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[Display omitted] • Using green clean biomass (green carbon) instead of traditional fossil energy to efficiently reduce iron-containing raw materials. • The reduction behavior of two kinds of C/O iron ore powder-green carbon composite briquettes under different conditions was analyzed. • Green carbon has excellent reducibility and can reduce iron-containing raw materials to metallic iron in a reducing-free atmosphere. The metallurgical industry is a key sector for carbon emissions, and in recent years, there has been widespread attention on the use of biomass resources as a green, renewable, and carbon–neutral energy source material for low carbon ironmaking processes. The waste wood after hydrothermal-pyrolysis carbonization has the characteristics of low content of harmful elements and high content of fixed carbon. In this study, the waste wood after hydrothermal-pyrolysis two-step carbonization treatment was used as a reducing agent for the reduction of iron ore to prepare iron ore powder- green carbon composite briquettes (ICCB) with two carbon–oxygen ratios. The study investigated the effects of reduction behavior and reaction temperature on the reduction performance of the ICCB. The results indicate that with the increase in reaction temperature, the volume of the ICCB gradually contracts, leading to a reduction in mass. The shrinkage rate of the ICCB during self-reduction at 1200℃ is significantly higher than during co-reduction, and the shrinkage effect of the C/O 0.5 ICCB is more pronounced than that of the C/O 0.8 ICCB. Due to the excessive carbon content in the C/O 0.8 ICCB, the carbon cannot be fully consumed during the reaction process, resulting in consistently low compressive strength of the ICCB, with a compressive strength of 12 N after reduction at 1200℃. In contrast, the iron phase in the C/O 0.5 ICCB gradually recrystallizes during the reduction process, ultimately yielding plastic iron briquettes with compressive strengths exceeding 3000 N after different reaction behaviors at 1200℃. In summary, reducing the carbon-to-oxygen ratio and increasing the reaction temperature contribute to the volume contraction and enhanced compressive strength of the ICCB during the reduction process. [ABSTRACT FROM AUTHOR]

[Display omitted] • This study presents environmental sustainability of pelletized watermelon peel waste biofuel treated with H 2 SO 4. • Proximate analysis, calorific value and physicochemical parameters of the treated and untreated briquettes samples were accessed before and after delignification. • Eco-friendliness and the presence of Potential Toxic Elements (PTEs) were evaluated using EDXRF. • Machine leaning models were developed to model the physical and combustion characteristics of the bio-briquette. As the world faces the challenges of climate change and diminishing fossil fuel reserves, researchers and scientists have increasingly explored the use of plant waste as a viable biofuel source. Among the various plant waste materials, watermelon peel waste, which is typically discarded during processing of beverages or consumption, has gained attention due to its high cellulose content. This study focuses on comparing the properties and environmental sustainability of watermelon peel waste biofuel treated with H 2 SO 4 to raw watermelon peel waste biofuel. From a sustainable energy perspective, maximizing the amount of energy recovered from solid bio-fuel is a critical consideration. Thus, the adaptive neuro-fuzzy inference system (ANFIS) was developed in this study to predict the calorific value (a significant indicator of the energy values) of both H 2 SO 4 -treated and raw watermelon waste briquettes while providing useful insights into the effect of the H 2 SO 4 treatment on the energy value of the briquette. The results indicate that the watermelon peel waste treated with acid performed better compared to the untreated sample. It exhibited a higher mean fixed carbon content and calorific value of 22.70 ± 0.16 % and 14.62 ± 0.21 MJ/kg, respectively. Additionally, the treated sample showed a significantly lower mean ash content of 11.20 ± 0.13 %. The EDXRF analysis revealed that the treated samples had reduced proportions of Nickel, Sulfur, and Arsenic, along with a higher carbon count. The FTIR analysis confirmed surface modification in the acid-treated watermelon peel waste (ATWB) through a decrease in lignin content (8.41 ± 0.014 wt%). It also identified a shift in the C-O vibrational stretch from 1021 cm−1 in the untreated watermelon peel waste (UWB) sample to 1028 cm−1 in the ATWB. Moreover, the SEM micrographs displayed a well-packed surface, indicating a reduction in fiber diameter (porosity) in the treated sample. The recorded RMSE, MAD, MAE, and MAPE values of the model are 0.1427, 0.0883, 0.1246 and 1.2313 at the training phases and 0.1581, 0.0997, 0.1484, and 1.9011 at the testing. The regression plot of calorific value with a R2-value of 0.9065, depicts a strong positive linear relationship between the predicted and real values. This outcome of the study suggests an improvement in thermal energy release and enhanced combustibility while the ANFIS model's ability to optimize energy values aligns with the objective of developing eco-friendly bio-briquettes. [ABSTRACT FROM AUTHOR]

[Display omitted] • Coal derivatives were viable substitutes for raw coals to produce HyperCoal. • Thermal extraction transformed coal into HyperCoal based on hydrogen-carbon ratios, while coal derivatives showed distinct behavior. • Coal derivatives extracts exhibited higher compressive strength, suitable as HPCBs binders. • A clean and efficient coal utilization route to prepare HPCB from DCLR thermal extract was established. • This study expands bituminous coals utilization and explores more raw materials for HPCB. In this study, the thermal extraction of various coal and derivatives by N-methylpyrrolidone was systematically compared and the extract was used as binder to prepare hot-pressed coal briquettes (HPCBs). The results demonstrate the effectiveness of thermal extraction in converting coal to HyperCoal, and the conversion yields varied from 12 to 71%. While the extraction tends to have a linear relationship with hydrogen-carbon ratio of raw coals, this relationship was not directly observed for derivatives due to inherent changes occurring during production. Proximate analysis of the extract reveals a reduction in ash content to below 1% while an increase in volatile matter by more than 8%. XPS and FTIR spectra demonstrate the high efficiency of thermal extraction in extracting hydrocarbons, but poor for compounds such as alcohols, phenols, ethers, and carboxylic acids. The extracts, rich in hydrocarbons, exhibited excellent thermoplasticity, making them suitable binders for HPCBs preparation. Among the extracts, coal derivatives exhibited higher compressive strength compared to coals. Consequently, the extract derived from direct coal liquefaction residue with the highest compressive strength was selected for preparing HPCB. Furthermore, we investigated the application characteristics of the HPCB and identified its great potential for use in COREX melting-reduction ironmaking. The preparation of HPCB is vital for expanding the utilization of bituminous coals while reducing dependence on lump coal and coking coal resources. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Wheat and maize straw, wood branch and their briquettes and charcoals were tested. • EFs of OC were averagely 3.2 times higher than EC while K (K+) and Cl (Cl−) were comparable in PM 2.5. • Levoglucosan dominated the total saccharides with EFs of 0.03–110.41 mg kg−1. • Charcoals showed over 90% emission reduction efficiency compared to raw fuels. Abstract In this study, maize straw, wheat straw, and wood branches and their processed products (i.e., briquettes and charcoals) were used to investigate the emission factors (EFs) of PM 2.5 components and the influence of form changing. The EFs of organic carbon (OC) was 241 ± 39.7 to 3920 ± 792 mg kg−1; OC was the largest contributor in PM 2.5. The EFs of PM 2.5 , OC and elemental carbon (EC) demonstrated that charcoal was the most efficient in reducing PM 2.5 and carbonaceous fraction emissions, followed by briquettes compared with raw fuels in residential burning use. Among cations, K+ had the highest EF, whereas Cl− has the highest EF among anions; the presence of both K+ and Cl− was attributable to high abundance in biomass. Cl, K, S, and Na (in descending order) contributed more than 95% of total elements with high EFs; the other elements, particularly heavy metals, had very low EFs. The EFs of total polycyclic aromatic hydrocarbons (PAHs) and saccharides were in the following order of magnitude: raw fuels > briquettes > charcoals. PAHs with four rings (i.e., pyrenes) dominated the total PAHs in PM 2.5−, whereas among saccharides, levoglucosan had the largest EFs (0.03–110.41 mg kg−1). Briquettes, with simple process and reasonable cost, demonstrated a good ability in decreasing PM 2.5 emission with potential of 53% (765,000–427,000 t year−1), and their emission reduction potential were much higher for straws than for branches. Charcoals demonstrated considerable emission reduction potential for straw (93.7% averagely for PM 2.5 and compositions) and comparable for wood branches (80% averagely) while its complex process and high cost should be considered. More than 600,000 t of PM 2.5 and thousands of tons of PAHs and saccharides are estimated to be eliminated annually if all raw biomass fuels are processed through carbonization. Considering the efficiency–cost ratios, biomass briquetting may aid clean heating in rural areas, in addition to the "natural gas and electricity replacement strategy," in China and other countries facing similar problems. [ABSTRACT FROM AUTHOR]

Highlights • Outbursts were fabricated due to the rate of gas decompression. • Coal briquettes and CO 2 were used by a designed experimental apparatus. • Major energy of outbursts is from the free state gas in coal briquettes. • Evolution of outbursts was observed and analysed. Abstract The coal and gas outburst has become a worldwide challenge and is still not fully understood. In this study, an experimental investigation was carried out for outburst evolution. Coal briquettes were fabricated based on less than 0.6 mm pulverized coal particles of Tunliu Coal Mine. CO 2 was used to simulate outbursts by saturating coal briquettes in varying gas pressures (0.2, 0.4 and 0.6 MPa). The outbursts of coal briquettes were induced when rapid gas decompression was performed. The results indicate the outbursts depend on the gas pressure, water content and the rate of gas decompression. The differential pressure between the gas inside and outside the coal briquette is essential to outbursts and varies for different water contents while other parameters affect the initiation and intensity of outbursts as well. The higher gas pressure the more intense outburst occurs. It is worth noting that low rate of gas decompression cannot activate any outburst in the experiments even for a high gas pressure. The water content affects the outburst strongly. The critical minimum gas pressure in the coal briquettes with high water content becomes much higher than that in the coal briquettes with low water content. The major energy of the outbursts in the experiments is the expansion energy of the free state gas inside the coal briquettes. This study clearly demonstrates the progressive fragmentation of outbursts due to gas decompression. [ABSTRACT FROM AUTHOR]

[Display omitted] • This research converts pine flower biomass waste into biobriquettes. • Biobriquettes from pine flower generally conform to the standards of several countries. • Biobriquettes have potential applications in bioenergy products. • Increased use of biobriquettes can help reduce reliance on forest wood for charcoal production. • There is a potential future market of biobriquettes from pine flower for household needs. Pine-flower biomass waste is abundant, but its utilization is still lacking. This research converts pine-flower waste into biobriquettes by using pine resin adhesive. This study aims to identify the effect of pine resin adhesive concentration and the effect of grain size on the quality of the resulting biobriquettes. The production of biobriquettes begins by processing pine flower waste into biochar using the pyrolysis method at 400 °C. Biochar from pinecones was ground and sieved into sizes (250, 500, and 750 µm). Then proximate analysis (moisture content, ash content, volatile matter, fixed carbon), and heating value were performed. Making biobriquettes using pine resin adhesive with different concentrations (5, 10, and 15%) of the total mixture According to the results, the ideal grain size was 750 m, the adhesive concentration was 15%, and the moisture content, ash content, volatile matter content, fixed carbon content, and heating value were all respectively 2.23%, 4.51%, 30.23%, 70.04%, and 23.34 MJ/kg, and the longest flame was also determined to be 0.0250 g/sec. All of them comply with universally accepted biobriquette standards (Indonesian National Standard 01–6235–2000), Japanese, English, and ISO 17225. Biobriquettes have potential applications in bioenergy products. Investigation of the economic feasibility of biobriquette production seen from Profit on Sales is 26.43%, Rate on Investment is 34.00%, Pay Out Time is 2.47 years, and Break Event Point is 49.22%. [ABSTRACT FROM AUTHOR]

• The double-sided molding method for making coal briquette was proposed. • Influences of initial particle size on density of the briquette were analyzed. • Segmented fractal characteristics were found in fragment size distribution of briquette. • Vertical distributions of the breakage energy of the briquette were obtained. Using the reconstituted coal briquette to replace tectonic coal is a forced choice for many experimental studies on the mechanism of coal and gas outbursts. The molding method and initial particle size are two important factors affecting the properties of the soil-like coal briquette. In this study, tectonic coal particles with five different initial sizes were compressed into coal briquettes using three different molding methods. Each coal briquette was evenly divided into five parts along the vertical direction and each subunit was fragmented by a drop hammer to test the firmness. The results show that the briquette density first increases and then decreases with the rise of initial particle size. Briquettes obtained by the traditional one-sided molding method possess the lowest density. The fragment size distributions of the briquettes and the original tectonic coal have segmented and non-segmented fractal characteristics, respectively, which are mainly related to the initial particle size distribution of the coal powder used for making briquettes. Combining the vertical distribution laws of the surface work, Protodyakonov coefficients, and fractal dimension of the briquettes, it is determined that the coal briquettes obtained by the double-sided molding method are soft in the middle and possess a relatively symmetric structure. The surface work and Protodyakonov coefficients of the briquettes (9.03 ± 2.27 J/m2 and 0.10 ± 0.02, respectively) are comparable to those of the in-situ tectonic coal with the highest outburst risk. [ABSTRACT FROM AUTHOR]

• A high value-added method of recovering coke breeze was proposed. • Coal tar pitch was used as a binder without heating. • The optimal production conditions of the product were determined. • The excellent effect of trimethylbenzene on coal tar pitch was confirmed. As a solid waste fuel, coke breeze was recycled with coal tar pitch as the binder to produce a metallurgical coke substitute in this study. Coal tar pitch, with no binding at room temperature, must be heated to a molten state to be used as a binder. Here, the activation of trimethylbenzene on its binding was found. In this study, the trimethylbenzene activation on coal tar pitch, the effects of trimethylbenzene dosage and operational conditions on the compressive strength of formed coke products, performances of products and their microstructures were investigated. Trimethylbenzene combined with the coal tar pitch to form new organic compounds, increasing its viscosity and binding by adding more associative and free functional groups. The activated pitch, with higher aromatic ring activity, had an excellent binding performance at room temperature. Furthermore, adding trimethylbenzene can increase the apparent density and reduce the porosity of the briquettes. The compressive strengths of green briquette, devolatilized briquette and the product were significantly increased using trimethylbenzene as an activator. A formed coke product with 35.07 MPa of compressive strength was obtained, meeting the Chinese secondary metallurgical coke standard. The optimum coal tar pitch and trimethylbenzene dosages were 13% and 2.5%, respectively. And the operation conditions were briquetting at 45 MPa, devolatilization at 370 °C for 25 min and carbonization at 1100 °C for 30 min. This study provides an efficient way of recycling coke breeze resources. And it offers an essential research reference for recycling-related solid wastes. [ABSTRACT FROM AUTHOR]

Ultra-small biomass gasification and power generation systems are a promising technology for disaster areas in developed countries and non-electrified rural areas of developing countries. The gasification characteristics of carbonized wood pellets and carbonized wood briquettes without or with 1 wt% sea salt were tested in a pilot-scale updraft fixed-bed gasifier. The results showed that the carbon balance during gasification was easily achieved, and most of the chlorine in the carbonized briquettes with sea salt remained in the residual char and fly ash after gasification. Inorganic chlorine in the solid fuel was transformed into organic chlorine combined with carbon matrix after heat treatment in the gasifier. Syngas with a low heating value higher than 4 MJ·m −3 could be continuously obtained when the system reached a stable condition, which enabled power generation using a gas engine. A combination of several secondary tar removal processes was adopted for the syngas purification. The tar content in the syngas after the gas cleaning for 425 °C-carbonized pellet, 425 °C-carbonized briquette, 475 °C-carbonized briquette, and 475 °C-carbonized briquette with sea salt was 0.98, 0.26, 1.4, and 0.2 g·Nm −3 , respectively. During the stable stage, 425 °C-carbonized pellet showed the highest cold gas efficiency (CGE) of 45.6% and carbon conversion efficiency (CCE) of 57.8%, respectively, with an equivalence ratio (ER) of 0.24. A lower carbonization temperature showed a higher CGE and CCE. The residual char and fly ash after gasification could be considered for reuse as feedstock to further improve the overall process efficiency. The maximum output power was 23 kW at an air flow rate of 40 Nm 3 /h during the gasification of carbonized pellets, and the corresponding overall power generation efficiency of the engine using the syngas was about 27.8%. For 475 °C carbonized briquette, the maximum output power was 18 kW at an air flow rate of 40 Nm 3 /h, and the corresponding overall power generation efficiency of the engine using the syngas was about 25.5%. [ABSTRACT FROM AUTHOR]

A laboratory-scale shaft furnace was used for the pyrolysis of the lignite briquette together with thermogravimetric analysis to study the intrinsic pyrolysis kinetics under two different heating rates, 10 °C/min and 100 °C/min. Apart from coal conversion rate, the tar yield, quality and radical concentration in char were also measured to explore the difference between lignite briquette and the respective pulverised powder. Additionally, a 1-D model coupled with the chemical percolation devolatilisation (CPD) code was developed to quantitatively understand heat transfer using temperature dependent parameters; product distribution and yields, and the pyrolysis mechanism. It was discovered that heat transfer was the limiting factor for pyrolysis of the lignite briquette, which subsequently lowered the heating rate and led to increased cross-linking and decreased tar production compared to a coal particle. Simultaneously, the primary tar also underwent internal cracking and even deoxygenation to decompose into light aromatics and gases inside the briquette char matrix. Providing a hot gas environment was found to facilitate the cracking of tar species compared to a slow heating rate where tar is released at a lower temperature. The changes in radical concentration in the solid material were linked to the structural changes predicted by the CPD model including bridge-breaking, tar release and cross-linking phenomena. [ABSTRACT FROM AUTHOR]

This study reports the briquetting and carbonization processes of naturally grown algae biomass collected from regional lakes. After drying them in air and chopping them into small pieces (∼2.5 × 2.5 cm), three different briquetting pressures (e.g., 2, 3, and 5 tons/cm 2 ) were applied to form algae briquettes with 3–5% moisture content. Three major investigations were performed on the prepared samples. The first test was to investigate the briquettes’ handleability, in which the algae briquettes were dropped 100 times from a height of 1.524 m to resemble a handling mechanism. The second test was conducted on the samples to resolve the residual strength of the briquettes before and after the carbonization process at 800 °C. Ignition points of the algae briquettes were reviewed in the third analysis. Test results showed that briquettes under 2, 3, and 5 tons/cm 2 of pressure had density values of 1303, 1423, and 1553 kg/m 3 , respectively. Drop tests demonstrated that the weight contractions of the briquettes were reduced from 10.2% to 2.1%, when the pressure was intensified from 2 to 5 tons. Ignition temperatures for the non-carbonized briquettes under 2, 3, and 5 tons/cm 2 were 492, 510, and 520 °C, respectively; however, after carbonization, these temperatures were reduced to 474, 487, and 492 °C, respectively. Compression strength tests for the non-carbonized briquettes under 2, 3, and 5 tons/cm 2 resulted in 22.1, 29.2, and 33.5 MPa, respectively. These test outcomes can be suitable for future guidance of an algae-based biomass and fuel system for reducing environmental impacts. [ABSTRACT FROM AUTHOR]

• This study evaluates the effects of alkali pre-treatment on the fuel properties of bio-briquettes produced from Celosia argentea. • The physicochemical parameters and combustion characteristics of Celosia argentea briquettes samples were accessed before and after delignification. • Eco-friendly nature and the presence of Potential Toxic Elements were evaluated using EDXRF. • Morphological restructuring and bond orientation of the briquette samples were monitored using SEM and FTIR. • Machine leaning models were developed and adopted to evaluate the physical and combustion characteristics of the solid biofuel. This study produced and compared the combustion properties of alkaline treated Celosia argentea (TCAB) and untreated Celosia argentea (UCAB) waste bio-briquettes using starch as binder. Heat energy of TCAB and UCAB were determined. Potential toxic elements, surface modification and bond orientation of briquettes were monitored using EDXRF, SEM and FTIR, respectively. Levenberg-Marquardt Back-Propagation based Artificial Neural Network (LMBP-ANN) and Fuzzy C-means Clustered Adaptive Neuro-Fuzzy Inference System (FCM-ANFIS) models were adopted for the bio-briquettes. Calorific values of 11.38 ± 0.20 MJ/Kg (UCAB) and 12.79 ± 0.25 MJ/Kg (TCAB) at p < 0.05 were recorded. EDXRF showed percentage reduction in Pb content of TCAB (1.425 %) as against 3.253 % in UCAB. FTIR recorded a C O stretch difference of 4 cm−1, while SEM shows morphological restructuring. FCM-ANFIS outperformed LMBP-ANN with root mean square error (RMSE), mean absolute percentage error (MAPE), mean absolute deviation (MAD) and R2-values of 0.0748, 2.4756, 0.0687 and 0.9323, respectively at the testing phase for heat content, suggesting strong agreement between the experimental data and predicted values. The study shows that alkaline pretreatment enhanced the combustion properties and eco-friendliness of the solid-biofuel. [ABSTRACT FROM AUTHOR]

The influences of pyrolysis temperature and phosphorus additives on physico-chemical quality and combustion property of bio-char briquettes were investigated in this research. Bio-char briquettes were obtained from directly pyrolysis of maize straw briquettes. Pyrolysis temperature were from room temperature to 250–650 °C with a heating rate 10 °C/min. Combustion tests were performed in a thermal-gravimetric analyzer. Results showed that with the increased pyrolysis temperature, volume density decreased initially and subsequently turned flat. While durability rating and mass yield sustained to decline. The optimal pyrolysis temperature was estimated to be 550 °C, gave the higher heating value 21.05 MJ/kg, energy-mass co-benefit (EMCI) 8.14. The volumetric energy densities were mainly in the range of 10–14 GJ/m 3 . Combustion feature of bio-char acquired at 250 °C was significantly different. Both the index S and D i at the first stage were obviously higher; the S was improved by addition of Ca(H 2 PO 4 ) 2 at a suitable pyrolysis temperature. The E generally showed increasing trend with enhanced pyrolysis temperature. In the same pyrolysis temperature, the sequence of E from high to low is: E MS , E MS-CPM and E MS-ADP . The performance of NH 4 H 2 PO 4 on combustion characteristics was worst. [ABSTRACT FROM AUTHOR]

The constant increase in the use of biomass fuels has raised prices of the most common commercial products and consequently seeking for new alternative biomass resources for thermal conversion, like some industrial and agricultural wastes, becomes an interesting issue. To this aim, thirteen alternative raw biomass samples were analyzed and compared with briquette, wood pellets, and charcoal. Their proximate, ultimate and calorimetric analysis and physical properties data have been considered. In the same way gaseous emissions, ash composition, deposition and corrosion tendencies were evaluated. In addition to these intrinsic and environmental parameters, a general economic study, based on our previously obtained data, has been developed. Some of the selected samples, like almond shell and especially olive stone, seem to be optimum biomass resources to use instead of wood pellets, charcoal or briquettes in grate boilers, while some others require pretreatment to improve their characteristics and make them suitable alternatives to be considered in a short term future. [ABSTRACT FROM AUTHOR]

Binders can be employed to improve the particle adhesion, compressive strength, abrasion resistance and energy content of densified biomass, such as briquettes. They may also reduce the energy cost of producing such briquettes, by reducing the compaction pressure, conditioning temperature and the wear on production equipment. This study explored and compared the effects of three different binders, including starch, enhanced treated biosolids and microalgae, on density, durability, energy content and combustion characteristics of fuel briquettes produced from blends of rice husks, corn cobs and bagasse, in a multilevel factorial design experiment. Briquettes had relaxed unit densities of 1.9–3.3 times the loose biomass bulk density, and were stronger than briquettes from the individual materials, with an average unconfined compressive strength of 125 kPa. An unconfined compressive strength of 175 kPa was achieved for a 2:4:1 blend of rice husks, corn cobs and bagasse with the microalgae binder at a compaction pressure of 31 MPa. Statistical analysis of the results showed that the addition of biosolids and microalgae binders significantly improved briquette density, while the addition of starch reduced briquette density, and biosolids reduced briquette strength. Of all the briquettes produced with the three binders, those containing the microalgae binder were found to be most durable, with a higher energy value, slower mass loss during briquette combustion, and a higher afterglow time. Since microalgae may be grown using CO 2 from biomass combustion, discovery of their advantages as a binder in briquetting is particularly welcome. [ABSTRACT FROM AUTHOR]

End-face combustion experiments were conducted on cylindrical bio-coke (BIC), i.e., a highly densified biomass briquette, to investigate whether quasi-one-dimensional steady combustion can be attained in 400-K air flow, as measured by a steady regression rate. In the experiment, it was found that the average regression rate in the first 0.01 m of BIC was relatively small after ignition, whereas after the first 0.01 m, the average regression rate became almost steady and much larger than that in the first 0.01 m. This suggests that before the steady regression period is reached, a non-negligible unstable regression rate phase exists. To investigate this transient combustion phase, one-dimensional numerical calculations were conducted, and the time-dependent regression rate and temperature distribution were computed. The mechanisms controlling transient combustion and the effects of volatile and moisture contents on transient combustion behavior were examined. The results show that a transient combustion period exists before steady combustion is achieved. This transient combustion period decreases as volatile content increases, and moisture content has a similar effect on transient combustion as volatile content. The phenomenon can be explained by the different final steady temperature distribution and evolution rate from the initial temperature distribution to the final steady temperature distribution. [ABSTRACT FROM AUTHOR]

• Briquetting showed obvious influence on sludge pyrolysis. • Mechanical performance of cylindrical-shaped biochar decreased with the increase of activation temperature. • CO 2 -activated biochar showed higher adsorption capacity than steam-activated biochar. • Both physical and chemical adsorptions played important role in methylene blue adsorption. • The maximum adsorption capacity of 513.81 and 419.29 mg/g could be achieved by the CO 2 and steam-activated biochar. Sludge briquettes were prepared through briquetting (under the pressure of 25 MPa) of half-dried sewage sludge with moisture content of 30 wt%, and the cylindrical-shaped biochar (CSB) was obtained by subsequent pyrolysis (600 °C) and CO 2 /steam activation (650–950 °C). Briquetting process showed great influence on the pyrolysis of sewage sludge. The temperature range for the organic decomposition increased from 150 to 500 °C for the sludge without briquetting to 150–700 °C for the sludge briquette. The mechanical performance of CSBs was greatly influenced by activation temperature. The axial compressive strength of the CO 2 /steam activated CSBs were in the range of 17.8–22.2 kg·cm‑2 at the activation temperature of 650 °C and 800 °C, but dropped markedly when the activation temperature increased to 950 °C. CSBs were negatively charged and rich in oxygen/nitrogen-containing functional groups like –OH, –COOH, amines and amides, and the specific surface area of the optimal steam and CO 2 -activated CSB were 123.2 and 113.5 m2·g‑1, respectively. The prepared CSBs were applied in methylene blue (MB) adsorption, and the maximum adsorption capacity of 513.81 and 419.29 mg·g‑1 could be achieved by the CO 2 and steam-activated CSB, respectively. Both physical and chemical adsorptions played important role in the MB adsorption. Finally, the regeneration test showed that optimal samples of the CO 2 and steam-activated CSB still retained around 90 % of its original adsorption capacity after three cycles of adsorption-regeneration tests, but the mechanical performance dropped by 58.1 % and 47.8 %, respectively. [ABSTRACT FROM AUTHOR]

[Display omitted] • Densified fuel does not significantly degrade environmental performances of the stove. • The cylindrical geometry is preferable to the cubic one. • Briquette compaction is a key parameter for combustion conditions. • Briquette composition has an impact: avoid bark and biomass of "waste" type. A panel of twenty commercial briquettes representative of the French market was set up with the different actors of the French densified log industry. The selected briquettes were characterized via the determination of their water and ash content, their ultimate and elemental composition and their heating value. Pollutant emission factors during the combustion of the briquettes were evaluated in real conditions in a domestic stove with natural draught. Gaseous pollutants like CO, CO 2 , NOx, SO 2 and THC (Total HydroCarbons) were monitored. Particulate emissions in mass (TSP) and number (PM 2.5) were also measured. Briquettes characterizations showed that the majority of the data determined in laboratory are in agreement with the one announced by the producers. Moreover several briquettes are in agreement with limitation established by the EN ISO 17225 standard. Combustion tests showed that the use of densified fuel instead of traditional log does not lead to a significant degradation of the environmental performances of the stove. Some briquettes present emission factors close to the one measured with traditional wood log. Several recommendations concerning briquettes characteristics were drawn from this study. [ABSTRACT FROM AUTHOR]

In order to increase the usage of semi-soft coking coal and the productivity in cokemaking, a novel process of charging only briquettes into a conventional slot-type coke oven was studied from the viewpoint of productivity, coke quality and coke pushing. Coal briquette charging process can increase the productivity and coke quality compared to powder charging. Larger size briquettes made from coal blends having lower caking property are favorable from the viewpoint of enhancing productivity. Pushing performance of coke cake generated from coal briquette charging process depends on the experimental conditions and in some cases still leaves rooms for improvement. Larger size briquettes are favorable from the viewpoint of making coke cake structure rigid enough for normal pushing. [ABSTRACT FROM AUTHOR]

Biomass is nowadays a very important alternative to energy consumption, since it provides less environmental harms. Briquettes come as an option since they include logistical and efficiency advantages. This study aimed to characterize Leucaena leucocephala (leucena) and Gonoacantha piptadenia (pau-jacaré) biomass, to define their energy potential and verify the briquettes’ moisture content and the mechanical resistance. Six treatments were provided: 2 species and three different moisture contents (10%, 12% and 15%). Fifteen briquettes were produced for each treatment. The results showed that moisture content changes the stability of the briquettes. The pau-jacaré showed a better performance, in every aspect analyzed, superior chemical characteristics (ash content of 1.83%), higher heating value (18,956 kJ kg −1 ) and better mechanical resistance (0.5255 MPa). However, both species provided fine results toward this proposal. Therefore, they can be used in every moisture content tested here, offering satisfactory results for bioenergy. [ABSTRACT FROM AUTHOR]

• Ultrafine Ca(OH) 2 combined with microwave was proposed for coal pretreatment. • Around 70% of total sulfur was fixed in coal ash by the combined treatment. • Effects of coal particle size and employed alkalis on sulfur fixation was studied. • A continuous pretreatment system was developed for practical utilization. • Briquette made from treated coal achieved a sulfur fixation rate of 74.97%. Sulfur fixation technology for raw coal can reduce SO 2 emission during coal combustion. A method combining microwave irradiation and ultrafine Ca(OH) 2 slurry was proposed, where raw coal was pulverized to mix with the slurry, and then treated by microwave irradiation. For anthracite coal (sulfur content = 1.90 wt%) with particle size distributed in the range of 75–180 μm, the treatment fixed 67.98 % of the sulfur in coal ash. Results prove that there is a synergy between microwave irradiation and ultrafine Ca(OH) 2 for coal pretreatment, and finer coal particles had higher fixation rate. Under the same treatment condition, the sulfur fixation rate was increased to 74.68 % by adding 1 mol/L NaOH. Applying more NaOH or less Ca(OH) 2 both made the fixation rate decrease. The combined treatment was also applied to bituminous coal (sulfur content = 0.79 wt%), and a fixation rate of 87.93 % was obtained. A continuous pretreatment system was developed for practical utilization of the method. Coal treated by the system was made into honeycomb briquette and burnt in a domestic coal stove, where a sulfur fixation rate of 74.97 % was obtained, compared to that of 4.55 % from untreated coal briquette. [ABSTRACT FROM AUTHOR]

Anthracite briquettes were developed using mainly waste anthracite fines, plant byproducts of rice hulls and rice hull ash and silicon metal powder as an ecofriendly fuel and as an alternative to conventional coke used in a cupola furnace. Si metal powder reacts with anthracite to form SiC, which provides high mechanical strength to an anthracite briquette when it is exposed to a high temperature in the cupola furnace. Rice hull and rice hull ash, which are agricultural byproducts with high SiO 2 content were investigated as partial substitutes for silicon as the former are inexpensive relative to silicon metal. The formation of SiC was investigated under different conditions using X-ray diffraction and transmission electron microscopy. In addition, unconfined compressive strength of the briquettes was measured when the rice hull or ash substituted Si powder partially or completely. When anthracite briquettes prepared with elemental Si powder and either rice hull ash or rice hull powder were pyrolyzed at 1400 °C for 2 h, SiC formed and the briquettes showed high mechanical strength in the range of 2000–4000 kPa, which is enough to keep their structural integrity in a cupola furnace. [ABSTRACT FROM AUTHOR]

Isothermal drying behaviors of the municipal sewage sludge briquettes were investigated based on a laboratory-scale hot air forced convective dryer at 1.5 m s −1 air speed. The influences of drying temperatures (60–180 °C) and lignite as a typical additive with 10% dosage on the drying kinetics of the sewage sludge were highlighted. A considerable shrinkage and cracking of the sewage sludge briquettes presented in the drying process, and there were many hollow cavities formed in the final drying stages. The average drying rates of the sewage sludge/lignite blend in the whole falling rate periods were higher than that of the raw sewage sludge. The Midilli models gave good agreement between experimental and predicted moisture ratios of the raw sewage sludge or sewage sludge/lignite blend with the highest R 2 . The apparent activation energies of the raw sewage sludge or sewage sludge/lignite blend in the first falling rate periods were higher than that in the second falling rate periods. Adding lignite could obviously improve the drying behavior of the sewage sludge briquettes over 120 °C. [ABSTRACT FROM AUTHOR]

• Hydrolysis lignin and lignin chars, pyrolyzed were co-carbonized with coking coal. • L1200 did not have joint interface with coke structure after co-carbonization. • The coke structure near the HLIG and L450 briquette was found to be highly porous. • Voids were formed between the coke and the structure of the chars, L600 and L1200. • Voids were related to dilation and contraction of the chars in the coking process. The utilization of bio-based side streams in metallurgical coke making promotes two major factors in the mitigation of climate impact in the steel industry. Circular economy as the waste material from biorefinery industry is utilized as a raw material in the steel industry, and mitigation of the production of fossil-based CO 2 emissions. In this work, lignin from the hydrolysis process was used in a briquetted form as part of the raw material blend in metallurgical coke making. For the experiments and analyses, lignin briquettes were pyrolyzed at 450, 600 and 1200 °C, while one sample was left non-pyrolyzed. In the co-carbonization of briquetted lignin, lignin chars and bituminous coal, the focus was to evaluate the interaction between char and coal in the carbonization. This was studied by thermogravimetric analysis (TGA), optical dilatometry, and light optical microscopy. The results suggested that the interaction between the coal and lignin reduced when the pyrolysis temperature of the briquettes, prior to co-carbonization, was elevated. This was due to the decrease of overlapping of the pyrolysis rates of chars and coking coal. Combined with the dilation and shrinking behaviour of the chars, presented in this paper, separate char and coke structures were formed in the final coke in co-carbonization. [ABSTRACT FROM AUTHOR]

• SWOT factors for biomass briquettes in Africa are identified. • Analytic Hierarchy Process method is integrated into the SWOT factors. • Empirical data is retrieved from three sectors. • Strategies for utilizing sawdust biomass briquettes in the three sectors are given. Due to environmental pollution caused by the excessive use of fossil fuels, developing countries are under considerable pressure to find sources of renewable and clean energy with limited financial resources and inadequate technological capacity. Bioenergy from briquetting sawdust, an organic waste by-product of the lumber industry, is one source of renewable and clean energy that is inexpensive to produce and does not require sophisticated technology. Since Madagascar's main industry is lumber, this study therefore set out to identify the key factors affecting the production and use of biomass sawdust briquettes in that country by integrating strengths, weaknesses, opportunities, threats (SWOT) analysis with a multi-criteria decision-making technique known as analytic hierarchy process (AHP). The results indicate that the most critical SWOT factors are lack of knowledge about biomass briquettes, lack of government support, political instability, social acceptance of biomass briquettes, focusing more on other types of renewable energy, and fossil fuel incentives. Suggestions are offered for how to promote the production and use of sawdust briquettes by overcoming critical weaknesses and coping with threats revealed in this study, including providing financial subsidies and tax breaks in Africa. [ABSTRACT FROM AUTHOR]

• PM 2.5 EFs of semi-coke briquette reduced efficiently relative to raw coals. • Semi-coke briquette mitigated the induced oxidative stress and cell membrane damage. • Organic carbon and specific heavy metals were contributed to cytotoxicity. Coal combustion emits large amounts of PM 2.5 (particulate matter with a diameter of ≤ 2.5 μm), and the emissions from different coal types differ. Clean fuels are essential in reducing PM 2.5 emissions and their respiratory effects on human. This study compared PM 2.5 emissions and their chemical components from four types of coal (i.e., bituminous raw-coal chunk, semi-coke briquette, anthracite, and bituminous briquette). The bioreactivies triggered by PM 2.5 exposure to human alveolar epithelial (A549) cells were compared, and the emission factors (EFs) of bioreactivies were calculated. The PM 2.5 EFs of semi-coke briquettes were reduced efficiently compared with those of raw-coal chunk, and their chemical profiles also differed. The contribution of total carbon and metals (i.e., S, Cl, Zn, and Pb) was higher for semi-coke briquette relative to raw-coal chunk, which may be due to the concentration effect of the semi-coke briquette preparation process. The production of lactate dehydrogenase (LDH) and reactive oxygen species (ROS) was higher for semi-coke briquette relative to raw-coal chunk at the PM 2.5 exposure dose of 100 μg mL−1. The EFs of LDH and ROS for semi-coke briquette, anthracite, and bituminous briquette were substantially lower than those for raw-coal chunk, which verified the effects of clean coal on oxidative stress and cytotoxicity. Organic carbon and specific heavy metals (i.e., Cu, Fe, Ni, Zn, Pb, and Cr) were significantly correlated with cell membrane damage and oxidative stress. This study clarifies potential adverse effects of PM 2.5 emissions from the combustion of various coal types and highlights the necessity of adopting clean coal to reduce PM 2.5 emissions and cytotoxicity. [ABSTRACT FROM AUTHOR]

This paper describes attempts to produce blast furnace coke from Victorian brown coals. The attempted method involves combining a coal-derived binder with the original brown coal or its commercial products, briquettes. Briquetting of these mixtures gave composites that were then carbonized to form coke-like materials. Products were characterized by bulk density, helium density, compressive strength, reactivity, surface area, scanning electron microscopy and X-ray diffraction analysis. It was found that the products have sufficient compressive hardness to be used as coke but are still too reactive to be used in a blast furnace. [ABSTRACT FROM AUTHOR]

Aiming at the general problem that both for the production of foundry coke made by anthracite pulverized coal and furnace coke made by tamped coke in the coke oven, namely the shrinkage problem for large-size briquette and tamped coke in the pyrolysis process, a mass and volume integrated measuring device was used to study the shrinkage process of large-sized briquettes (volume equals 10 3 cm 3 ) under constant temperature (450 °C, 550 °C, 650 °C and 850 °C). The briquette shrinkage kinetic model was also established according to the regulation of mass loss and volume shrinkage, where the volume shrink calculation method of tamped coal cakes (13,280 mm × 500 mm × 4300 mm) was also obtained. Three conclusions were drawn in this study: 1. In the process of the carbonization, the dehydration and degassing reaction before 450 °C as well as polycondensation reaction at 650 °C were the main reason causing the briquette shrinkage, the decomposition reaction at 550 °C came second, while the hydrogen evolution reaction after 850 °C has the least effect on briquette volume shrinkage. There were three main reasons causing the shrinkage of large-size briquette: the decrease of coal volume caused by the volatilization of moisture and volatiles, the decrease of coal volume caused by the pyrolysis reaction and the density increase of briquette caused by the decrease of coal volume. 2. The briquette shrinkage kinetic model was represented as follows: d V t /d t = V 0 [(1 − x )d β /d t − A 0 e − E / RT (1 − x ) n β ]; There was a positive correlation between the volume changing parameter β and the density of briquette, and the volume changing parameter increased with the reaction; the shrinkage reaction was divided into three stages; with the reaction went on, the reaction order and reaction rate constant decreased, the pre-exponential factor increased and the activation energy decreased firstly and increased then. 3. The shrinkage of the tamped coal cakes from the large-scale chamber was counted in the calculated unit whose thickness was 100 mm. The shrinkage velocity of the tamped coal cakes in carbonization chamber was obtained by weighted calculating the shrinkage parameters of each volume unit at different temperatures. The shrink regulations of the tamped coal cakes in the carbonization chambers, which were in agreement with industrial production, were approximately the same as those of the large-sized briquettes. However, the shrinkage rate curve of the tamped coal cake in the carbonization chamber was gentler than that of the large-sized briquette, as a result of the large temperature gradient of different coal in carbonization chamber. [ABSTRACT FROM AUTHOR]

In this work partial briquetting is employed as a means of biomass densification to allow for biomass inclusion in coking coal blends. The effect of increasing the bulk density was evaluated by comparison with direct addition. Two briquettes of different composition were studied. The influence of the briquettes on the Gieseler plasticity of the coals was determined. It was found that the effect of the binder was not enough to compensate for the decrease in plasticity produced by the inert components of the briquettes. Carbonizations were carried out in a movable wall oven of 17 kg capacity and the quality of the cokes produced was tested by evaluating their mechanical strength, coke reactivity to CO 2 and post-reaction strength. In addition, the porosity and ash chemistry of the cokes was determined and an attempt was made to establish a relation between these results and the quality of the cokes. Coke quality results suggest that 10–15 wt.% of briquettes containing biomass can be included in coking blends. [ABSTRACT FROM AUTHOR]

• Constructed a radial vibration mechanical model for CO 2 gas explosion; • First designed and then carried out radial vibration laboratory testing of a briquette under a CO 2 gas explosion; • Creatively analyzed each stage of the life cycle under a CO 2 gas explosion, quantitatively studied the radial vibration parameters of each stage, and solved the problem of differentiating the life cycle stages. CO 2 gas explosion is an important technology for coal seam permeability enhancement and fracturing, but the stage division of its life cycle is unclear, and research on the use of radial vibration characteristic parameters for stage division is lacking. To more accurately divide each stage of the life cycle and analyse the characteristics of each stage, a radial vibration mechanical model of CO 2 gas explosion was constructed. A novel radial vibration laboratory test of a briquette under CO 2 gas explosion was designed and conducted, and the characteristic parameters, such as the explosion radial vibration signal waveform, peak acceleration, velocity, and peak energy, were quantitatively analysed. The results show that there were three stages in the life cycle of a coal briquette under the action of a CO 2 gas explosion. The first stage, from 0 to 1.507 ms, was the stress wave action stage, in which the peak acceleration and peak energy around the blasthole were 25.460 g and 9.480 × 1012 (m/s)2, respectively. The second stage, from 1.507 ms to 9.282 ms, was the CO 2 gas explosion energy storage stage, in which the peak acceleration and peak energy around the blasthole were 1.478 g and 5.524 × 107 (m/s)2, respectively. The third stage, from 9.282 ms to 12.606 ms, was the CO 2 splitting stage, in which the peak acceleration and peak energy around the blasthole were 6.527 g and 1.470 × 109 (m/s)2, respectively. The research results analysed after the CO 2 gas explosion verify the promotion of gas splitting in the second and third stages, explain the evolution mechanism of radial vibration in each stage of CO 2 explosion, and provide a theoretical basis for the optimal design of CO 2 explosion technology. [ABSTRACT FROM AUTHOR]

[Display omitted] • Volatile matter (VM) showed a nonlinear effect on the EFs of PM 2.5. • The difference between PM 2.5 EFs and VM was related to tar oxidation from stage 1. • Char reaction in the whole coal combustion process lengthened with the coal maturity. • Compared with SO 2 , correlation between NOx and VM was more significantly (R = 0.92, p < 0.01). To evaluate the influence of geological maturity on coal combustion pollutant emissions, six chunk coals and corresponding briquettes (volatile matter [VM] content from 8.0% to 39.9%) were selected for simulated residential combustion in a carefully designed chamber, and the formation mechanism involved was investigated. VM was revealed to have a nonlinear effect on the emission factors (EFs) of particulate matter with an aerodynamic diameter of <2.5 μm (PM 2.5), polycyclic aromatic hydrocarbons (PAHs), elemental carbon (EC), and organic carbon (OC), with the highest EFs observed in VM of 15.8% and 26.8%. Coal tar yield and air-supply from VM combustion in its initial stage was found to be a key factor influencing PM 2.5 and PAH emissions when compared with the char combustion and burnout stages. The highest PM 2.5 and PAH EFs were observed in coal with 15.8% VM. Additionally, significant amounts of hydrogen cyanide (HCN) were detected at stage 1 and were released as volatile-N through the pyrolysis of coal-N. N 2 O and NO x were also emitted through homogeneous gas-phase HCN reactions. However, only a small proportion of NO x was produced, indicating that the contribution of VM to HCN and N 2 O emissions is greater than that of NO x. In the char reaction stage (stage 2), char-N reacted with O 2 to form large amounts of NO, and the reaction length of the entire coal combustion process exhibited a positive relationship with coal maturity (correlation coefficient 0.69, p < 0.05), suggesting that the contribution of NO from char-N to overall NO emissions increased with the coal's geological maturity due to the increase in coal-N retention in char. Furthermore, coal briquetting was found to decrease the EFs of pollutants, which may be explained by an increase in MCE (modified combustion efficiency) and the conversion from coal tar to carbon and hydrogen. This study elucidated the effects of geological maturity on pollutant emissions from coal combustion and examined relevant underlying mechanism. These data can serve as the foundation for a clean coal project in China or other counties concerned with coal combustion emissions. [ABSTRACT FROM AUTHOR]

Scientific research often require application of samples with repeatable properties. This demand is difficult to fulfill especially in case of experiments concerning coals. Therefore, a necessity occurs to use a material which stands for coal and is characterized with properties similar to coal. Authors of this article suggest, in required situations, the use of coal briquette as a research material. Huge advantage of coal briquettes application is the fact that in many aspects their properties are similar to the structurally deformed coal (altered coal) which presence, according to recent research, is closely related to areas of increased outburst risk. Authors have conducted studies of mechanical and gaseous properties of coal briquettes. The experimental part of the presented studies included the preparation of coal briquettes of a various porosity (from 13.5% to 33%) and determination of their mechanical parameters: uniaxial compressive strength and Protodiakonov coefficient as well as determination of their gaseous parameters: desorption intensity and adsorption capacity. The properties of coal briquettes were analyzed and referenced to the properties of normal coal and altered coal, characterized by mechanical and gaseous properties specific for coals that are hazardous and prone to outbursts. Dependences between the determined uniaxial compressive strength Rc and porosity, Protodiakonov coefficient f and porosity as well as the relationship between Rc and f for the studied coal briquettes were expressed mathematically. Threshold value of f (equal to 0.3), introduced for Polish outburst prevention, corresponded to 18.5% porosity of coal briquette. Changeover of coal briquette's porosity provides a prospect of obtaining a coal material which have Rc and f parameters typical for coals occurring in natural conditions. Coal briquette of experimentally determined porosity may replicate the mechanical properties of normal or altered coal. Adsorption capacity of different coal samples (briquette, normal, altered) depended on the coal microstructure and the grinding level of coal. The relationship between the 2 min desorption intensity and the methane saturation pressure for different coal samples (briquette, normal, altered) showed that if the grains constituting the grain fraction were larger the amounts of methane desorbed (for the studied time interval) were smaller. A correlation between coal briquette's porosity and amount of methane released during 2 min desorption test was not found. Grinding level of coal material creates a new distribution of grain size and it determines diffusion and seepage rate of gas releasing from the inside area of the pores. It was shown in this work that mechanical and gaseous properties of coal briquettes predispose them to conduct representative outburst research. A proper method of coal material preparation for the briquetting process is a key point for future properties of coal briquettes. [ABSTRACT FROM AUTHOR]

Highlights: [•] Coke is an expensive fuel that consumes 20% of the coal’s fuel value when produced. [•] Bindered anthracite bricks is a fuel alternative that require only a mild drying step. [•] 8tons of anthracite bricks were tested in 2 full scale demonstrations. [•] Our material perform similar to coke at full scale. [•] Less fuel is required when using anthracite bricks due to the efficient combustion. [ABSTRACT FROM AUTHOR]

Highlights: [•] Coal and gas mini-outburst initial conditions were analyzed. [•] Coal briquettes and three different gases: CO2, CH4 and N2 were used. [•] Briquettes saturated with CH4 were the least prone to undergoing outbursts. [•] All analyzed factors together were responsible for mini-outburst initiation. [ABSTRACT FROM AUTHOR]

Highlights: [•] Glycerin-biomass briquette fuels were studied. [•] Energy used during processes was compared to HV of the briquette. [•] Actual HV and correlated HV were compared and found to be within 5%. [•] Relationship of total HV was a function of mass fraction of its compositions. [ABSTRACT FROM AUTHOR]

Highlights: [•] LDPE is proposed as a robust, cost-effective binding agent for beneficiating low-grade coal fines into briquettes. [•] Interaction effects between southern Indiana coal and LDPE are noted via TGA/DSC. [•] Addition of LDPE increases flame temperatures and assists ignition of blends. [•] Addition of LDPE increases combustion efficiency of coal under identical operating conditions. [ABSTRACT FROM AUTHOR]

Abstract: This work focuses on the manufacture of briquettes by using carbon-containing wastes from steelmaking as fillers and binders for use in coke ovens to produce metallurgical coke. Coal-tar sludges from the tar decanter of a by-products coking plant were employed individually as a binder or combined with other wastes, such as oils from the steel rolling mills and deposits from the coke oven gas pipelines. Another objective of this study was to use alternative low-cost fillers such as the coal generated after routine cleaning operations in the coal stockyards, so as to reduce the overall cost of briquette manufacture. Carbon briquettes with different formulations produced by a roll-press machine were tested in a semipilot movable wall oven by adding them to a coking blend at a ratio of 10wt%. The quality of the cokes produced was assessed by measuring of their reactivity towards CO2 and mechanical resistance before and after gasification with CO2. In general, the coke quality parameters did not show any significant deterioration as a result of the addition of carbon briquettes when the amount and the nature of the binder and the particle size of the filler were optimized. Partial briquetting of the charge enabled cokes to be produced according to the specific requirements of blast furnace. [Copyright &y& Elsevier]

[Display omitted] • A novel organic binder starch grafted acrylamide with bentonite dispersed is synthesized. • Excellent grafting efficiency with enhanced bonding performance for composite binder. • The binder has a good thermal stability and cold crushing strength. • Briquette formed have excellent water resistance index along with binding properties. In the present investigation, a novel composite binder which aids in forming coke briquettes from industrial waste coke dust were synthesized in one pot setup. The composite binder enables efficient utilization of the coke fines by their reformulation into coke briquettes. The novel binder has been characterized by scanning electron microscopy, Fourier transform infrared spectrophotometry, X-ray diffraction, X-ray photonic spectroscopy and nuclear magnetic resonance spectrometry to understand the grafting efficiency and bentonite as filler incorporation. The composite binder with a secondary filler (bentonite) and a secondary binder (ordinary Portland cement) was mixed in definite proportion to obtain the compound binder. The coke briquette was made from coke fines and compound binder in a fixed ratio confers to high thermal stability with improved cold compressive strength. The high-temperature study indicates that the characteristics of coke briquette resemble that of coke used in submerged arc furnaces for ferroalloy production. [ABSTRACT FROM AUTHOR]

Abstract: The seepage of gas through coal and in particular through coal briquettes has already been a quite well known phenomenon. This also refers to its influence on certain initial conditions of coal and gas outbursts such as threshold values of so called gas stresses. In turn a detailed research on the influence of sorption processes on these conditions has been neglected until now. There is, however, an opinion that (fast) desorption is crucial for rock and gas outburst initiation and continuance, although many examples contradict such a thesis. The goal of the studies described here was to investigate a part of this ambiguity, namely the influence of sorption processes on gas stresses leading to coal and gas outbursts carried out in laboratory conditions. A series of laboratory experiments concerning provoking coal and gas outbursts was conducted. Coal briquettes and two gases: nitrogen and carbon dioxide were used. The experimental data was computed out into the gas stresses and the most important information was extracted. The obtained results showed that in experiments with nitrogen slightly higher gas stresses and thus more intensive provoking were needed in order to initiate outburst than in experiments with carbon dioxide. It indicates that sorption may be the factor that promotes outbursts. Comparative analysis implied also that for a given level of gas stresses the more sorptive the gas was, the longer it took to initiate an outburst. Moreover, in the experiments with nitrogen the global maximum of gas stresses occurred deeper inside of the briquette for any given time than in experiments with carbon dioxide. All the found differences were weak, though easily noticeable. [Copyright &y& Elsevier]

Abstract: This paper compares the spontaneous combustion of two Victorian brown coals and a Pakistan lignite with that of products of the same coals which have been dried, mainly by the mechanical thermal expression technique (MTE) in which aqueous slurries of the materials are heated (125 or 200°C) and pressed (5–15MPa). Samples of briquettes obtained by steam heating and pressing from a similar Victorian coal have also been studied. The amount of residual moisture in the dried samples had the largest effect on Tcrit values. The inorganic content of the samples varied and may also have contributed to the changes. Tcrit increased with increasing particle size for the dried coals and MTE samples. There was no obvious correlation between Tcrit and pore volume. [Copyright &y& Elsevier]

• The deformation characteristics of briquette/raw coal was discussed. • The adsorption characteristics of coal to different gases were studied. • Analysis of macroscopic damage and failure characteristics of coal. In order to clarify the characteristics of gas-bearing coal adsorption-instantaneous pressure relief deformation, and reveal the mechanism of the effect of gas desorption on the outburst. Through the gas-bearing coal adsorption-instantaneous pressure relief test system, the adsorption-instantaneous pressure relief test using briquette/raw coal samples was used to conduct a comprehensive comparison and analysis of the deformation characteristics of the two coal samples. Studying the damage of coal with different adsorption characteristics gases under the condition of adsorption-instantaneous pressure relief, and use strain gauges to monitor the microscopic deformation of the coal, and analysis of the adsorption of briquette/raw coal at constant pressure-instantaneous similarities and differences of deformation characteristics during pressure relief. "The results showed that under the same test conditions of adsorption equilibrium pressure, the degree of crushing of coal samples after instantaneous pressure relief is CO 2 > CH 4 > N 2. At the moment of instantaneous pressure relief, the strain of the raw coal/briquette suddenly decreases, characterized by swelling deformation. Under the same temperature and pressure conditions, the expansion energy of CO 2 is the highest, followed by CH 4 and N 2. Due to the raw coal has not completely destroyed the joints, only elastic deformation occurs, and the strain rises rapidly within a short period of time, resulting in shrinkage deformation. However, during the instantaneous pressure relief of the briquette, swelling and deformation occurred, and the coal was destroyed. The research results have certain significance for the exploration of coal and gas outburst mechanism. [ABSTRACT FROM AUTHOR]

• The micropores of BC-5 ℃/min was greater than other BC. • The mechanical strength of BC-5 ℃/min was close to RC. • Heating rate primarily affects the longitudinal conjugation and condensation of the briquette. • The aromatic rings gradually shortened, and their aromaticity values increased with increase in the heating rate. Briquette coal (BC) is the material produced from coal and gas outburst experiments. Preparing BC via the heating and pressure method can improve its low mechanical strength in physical simulation tests and gas outbursts while increasing experimental reliability. However, the influence of heating rate on the mechanical properties and microstructure of BC and the reasons underlying the evolution of its mechanical strength analyzed in terms of carbon molecular structure still need to be further studied. In this study, we developed an experimental system to prepare BC. The influence of the pore and carbon molecular structure on the BC uniaxial compressive strength was examined via a rock mechanics test system, scanning electron microscopy, nuclear magnetic resonance, specific surface area analysis, X-ray diffraction, and Fourier transform infrared spectroscopy. The results indicated that when the heating rate was increased from 3 to 6 °C/min, the briquette structure changed from looser smooth sheets to rough agglomerates of coal. The pore types observed after four different heating treatments (3, 4, 5, and 6 °C/min) on briquette samples were primarily micropores and mesopores. At 5 ℃/min, the number of micropores in the briquette sample were significantly higher than that observed in other samples. All samples exhibited similar adsorption curves as those of inverted "S"-type coal samples, which can be regarded as a combination of Type IV isotherms. With increasing heating rates, the L a and L c first increased and then decreased, with a decrease in A ar /A al , whereas H al /H and CH 2 /CH 3 increased. The strength of coal samples under the increasing heating rates were 5.62, 6.43, 7.07, and 5.99 MPa, respectively. The heating rate of 5 ℃/min was found to be the appropriate heating rate for briquette preparation. These results can provide an excellent alternative raw material required for large-scale physical simulation experiments for the prevention and control of coal and gas outbursts. [ABSTRACT FROM AUTHOR]

[Display omitted] • Lignin provides strength to anthracite briquettes during pyrolysis. • We studied the binding mechanism by Raman and briquettes strength. • Rate of briquette strength gain is similar to G and D Raman bands area rate change. • Similar activation energies were found using strength data and Raman band area. • Formation of polyaromatics from lignin pyrolysis is suggested as binding mechanism. As alternative fuel for the partial replacement of coke in foundry operations, our research team has engineered anthracite briquettes that use lignin in its binder formulation. To understand the mechanism by which lignin provides strength to the briquettes, in this study we characterized the progressive increase in mechanical strength of lignin-containing anthracite briquettes following progressively longer pyrolysis. We compared these results with the progressive change of the Raman signal of lignin that was pyrolized under the same conditions. The rate of strength gain by the anthracite briquettes increased linearly with the pyrolysis time up to a point, and this rate is described by an Arrhenius-like plot, which exhibited an apparent activation energy of 33.6 kJ/mol. We analyze the D and G bands from the Raman signal of pyrolyzed lignin, after isolating these bands via deconvolution. The D band area increased and the G band area decreased with the pyrolysis time up to a point. We correlated both the rate of D-band growth and G-band diminishment with pyrolysis time in Arrhenius-like plots; and these two bands exhibited apparent activation energies of 51.9 and 43.2 kJ/mol respectively. In light of the similar activating energy values obtained during the increase of strength of the anthracite briquette and the formation of a polyaromatic structure using Raman signal, we discerned that the mechanism by which the pyrolyzed lignin strengthened the briquettes was via the creation of poly aromatic structures that connected the grains of anthracite into this rigid network. This network provided resistance to fracture when the briquettes were subjected to the unconfined compressive strength (UCS) test. [ABSTRACT FROM AUTHOR]

• The mechanical properties of briquette coal are significantly influenced by heat treatment. • The surface microstructure and fracture structure in the briquette coals are different under various heating temperatures. • The heating temperature affects the shape and diameter distribution of pores in the briquette coals. Coal and gas outburst disasters mainly occur in geological structure belts, whose outburst coals are cataclastic, granular, or mylonitic microstructures, and their texture is loose, with mostly broken grain and pieces, so that it they hardly meet the laboratory specimen requirements. Consequently, briquettes are usually prepared at room temperature to study the mechanisms of coal and gas outburst in coal mines. In the present study, we employed a novel method of heating on briquette coal samples to investigate the effect of heating temperature on the strength and pore and fracture structure of briquette coals, and to determine the suitable heating temperature for briquette forming processes. A rock mechanics test system, MTS-815, scanning electron microscopy, nuclear magnetic resonance, and specific surface area and aperture analyzer measurements were used to analyze the mechanical parameters, morphology, and pore size distribution of briquette coal samples at different heating temperatures. The results indicate that the uniaxial compressive strength and elastic modulus of briquette coal first increased and then decreased. The pore size distribution and morphology of the briquette coal samples changed after heating. The smooth intact lamellar shape changed to a rough fractured lamellar shape, and the pores changed from unobvious micropores to observable mesopores and macropores. With an increase in the heating temperature, the transverse relaxation time spectra of the briquette coal samples decreased gradually, and both the porosity of the mesopores and macropores first increased, decreased, and then increased again. The pore diameter distributions of the five tested briquette coal samples had similar pore structures, excluding the sample heated to 600 °C. With an increase in heating temperature, pore volume, specific surface area, and average pore diameter of the briquette coal samples first decreased and then increased. The present study provides a novel method that can be applied in physical simulations aimed at preventing future disasters caused by coal and gas outburst in coal mines. [ABSTRACT FROM AUTHOR]

Abstract: Substance liable to self heat and spontaneously ignite under storage or transportation conditions can be a serious fire hazard in several industries. In order to estimate if, under specific storage conditions, a substance will dangerously self heat up to ignition, it is necessary to have knowledge of several thermochemical properties of the substance itself. Among this properties, one of the most relevant is the overall activation energy of the exothermic reactions that are responsible of the internal heat generation. In this short communication it will be discussed the possibility to retrieve the value of the overall activation energy from oven heating experiments conducted at temperature below the critical temperature of the sample, taking as an example a set of experimental data retrieved for commercially available charcoal briquettes. [Copyright &y& Elsevier]

This paper determines the effect of compaction process parameters such as compressive stress, process temperature and biomass moisture content on the density of the resulting briquette, its compressive strength, Young's modulus, relaxation, process energy consumption, and the work needed for densification. The research material was pine sawdust from the forests of Puszcza Zielonka located in the west-central region of Poland which was dried to the moisture content of 20% and 10%. It was subjected to the loading–unloading process and the triaxial compression process, and the resulting briquette was subjected to axial compression and shear. The values of the friction coefficient of sawdust against steel – the material of the compaction assembly elements – were determined. The experimental research made it possible to determine the best values for the compaction process parameters in order to obtain the optimal properties of briquettes, taking into account their transport and storage as well as application as an biofuel. The highest strength of the briquette was obtained for the compressive stress of 150 MPa, temperature of 150 °C and sawdust moisture content of 10%. The research enabled the creation of the numerical model for the compaction process using the Drucker-Prager-Cap model. The simulation model and its experimental verification made it possible to reflect the characteristics of changes in compaction force, energy consumption and density, which makes it useful in the context of simulating the compaction process without the need to perform experiments. It also enables the formulation of guidelines for newly developed designs of compaction machinery working units. [ABSTRACT FROM AUTHOR]

• Charcoal-based briquettes prepared using bio-tar as a binder were proposed. • Charcoal improved the combustion characteristics of semi-coke. • Addition of bio-tar enhanced the physical stability of charcoal-based briquettes. • Effects of bio-tar addition on pollutant emission were controlled by hydrated lime. In this study, charcoal-based briquettes prepared using bio-tar as a binder are proposed as a substitute for conventional coal in rural China; furthermore, the fuel properties of the blends of charcoal, semi-coke, and bio-tar and the co-densification and pollutant emission characteristics of charcoal-based briquettes are investigated. The addition of charcoal improved the heating value and combustion index; however, the addition of a small amount of bio-tar did not have any significant effect on the fuel properties of the charcoal and semi-coke blend. The blending of charcoal and semi-coke with a mass ratio of 1:1 increased the integrated combustion characteristics from 7.73 × 10−12 (only semi-coke) to 16.92 × 10−12 K−3min−2. Results of the co-densification experiments suggest that the bio-tar effectively improved the physical stability of charcoal-based briquette. By increasing the addition of bio-tar from 0 to 9 wt% at the densification temperature of 20 °C, the strength compaction and drop resistance increased by 8.6% and 13.9%, respectively. Increasing the densification temperature from 20 to 50 °C resulted in negative effects on mechanical strength. Pollutant emissions were observed during the ignition, stable combustion, and burnout phases of the stove. The bio-tar addition had distinct negative influences, increasing the total suspended particle and VOC emissions, which could be effectively weakened or eliminated by adding 3 wt% of hydrated lime. Herein, the applied chain and technical chain of charcoal-based briquettes are summarized. The study provides technical support for the industrial application of charcoal-based briquettes in rural China, with replication potential elsewhere. [ABSTRACT FROM AUTHOR]

• Free radical (R•) variation of anthracite briquette during pyrolysis was studied. • Adding AS binder could inhibits the rapid polycondensation of R• in anthracite. • The content and arrangement of different carbon types affect the variation of R•. • Better match of R• variation in components and rearrangement of R• improve M 40. The variation in behavior of free radicals during the pyrolysis and co-pyrolysis of anthracite and coal-based binder (AS) was determined by Electron paramagnetic resonance (EPR). Besides, Thermogravimetry (TG) and Carbon-13 nuclear magnetic resonance (13C NMR) were also applied to investigate the nature of pyrolysis and structural characterization of the coal samples. The results indicated that the induced effect of free radical existed in the co-pyrolysis of anthracite and AS, such that the free radical concentration (Ng) of AS carbonized briquette (ASB) at 300–500 °C is far higher than the additive value of Ng when anthracite and AS are separately carbonized. When the temperature exceeds 500 °C, the timely release of AS free radicals could combine with the aromatic free radicals of anthracite, leading to a slight decrease in the Ng value of ASB. Due to the limited combination, the rapid polycondensation of aromatic free radicals in anthracite was inhibited and more number of short side-chains and cross-links were generated in ASB. These effects delay the major polycondensation process of ASB to a higher temperature compared with other samples. As a result, the Ng value of ASB drops significantly above 700 °C and the line shape of it transforms closer to the Lorentz line shape. The lapping of free radical variation in anthracite and binder would broaden the temperature range for bonding-polymerization, which makes the free radicals of the blend components to rearrange and to form strong carbon–carbon bonds. Thus, the mechanical strength (M 40) of carbonized briquette would be improved. [ABSTRACT FROM AUTHOR]

• Thermoplastics and sawdust are densified for the production of a solid fuel. • Hot-extrusion is recommended to achieve the well mixture of plastics and biomass. • LLDPE/sawdust briquettes have higher water resistance than PP/sawdust ones. • PP/sawdust briquettes have higher stability to mechanical damage. • A solid fuel with energy density at > 18 GJ/m3 is produced with 10% of plastics. Thermoplastics, linear low-density polyethylene (LLDPE) and polypropylene (PP), were used as binders for the briquetting of sawdust. A novel hot-extrusion method (at 200 °C for 3 min) was developed to achieve the mixing of plastics and sawdust. The durability of briquettes containing 0–10% w/w plastic and produced under different pressures (150–300 kN) was investigated by laboratory and outdoor tests. Results from drop and tumble tests suggested that the use of plastics significantly enhances the strength of briquettes and the stability improves with the increase of plastic content. An outdoor weather test was conducted for two weeks with cumulative rainfall of > 50 mm to test the weather-resistance of briquettes. The briquettes prepared at 300 kN with 10% of PP showed superior durability to weather exposure with 100% survival rate to mechanical damage and an increase of moisture content at ~ 8% in post-exposure testing. The binding mechanisms and effect of plastics on briquettes are discussed. Moreover, the addition of plastics at 10% and densifying at 300 kN could produce solid fuels with heating values > 18 GJ/m3 which is comparable to coal and suitable to be used for co-firing existing coal-fired boilers. Collectively, results of this study recommend co-briquetting of waste plastics and lignocellulosic biomass to produce solid fuels with high durability, hydrophobicity, and moderate to high heating values; and as a solution to waste plastic management. [ABSTRACT FROM AUTHOR]

• Effect of hydrothermal temperature and WS/DW ratio on HWV yield is studied by RSM. • HWV yield decreases to 68.8% at 230 °C and increases to 72.4% at 260 °C. • Hydrogen bonds and lignin play the bonding roles in the briquetted hydrochar. • Lignin plays the bonding role in the carbonized briquette (CB). • Energy density and tensile strength of CB-230 is up to 26.4GJ/m3 and 2.56 MPa. Low conversion efficiency and simplex derived product with low added value of biomass waste resource have become prevalent challenges. A novel route for the preparation of hydrothermal wood vinegar (HWV) and briquette fuels by hydrothermal treatment process from wood sawdust (WS) has been developed. The interactive effect of the hydrothermal temperature and the ratio of WS to deionized water on the yield of HWV was studied by response surface methodology, and the results indicate that hydrothermal temperature played the dominant role during the treatment process. The yield of HWV decreases from 70.6% to 68.8% when the treatment temperature increases from 200 °C to 230 °C, and then increases to 72.4% at 260 °C. The chemical constituents in HWV were formed by the hydrolysis and conversion of hemicelluloses before 200 °C, and celluloses and lignins at 200–260 °C. The size of WS particles became smaller after the hydrothermal treatment at 200–260 °C and abundant functional groups are retained on the surface of hydrochar. However, there is nearly no obvious change in the functional groups on the surface of the briquetted hydrochar with increasing temperature. Hydrogen bonds between celluloses and lignins acted as binder are responsible for the high tensile strength of the briquetted hydrochar. The energy density (24.6 GJ/m3) of the hydrochar briquette prepared at 230 °C (24.6 GJ/m3) is significantly higher than that prepared from WS (18.6 GJ/m3). The energy density of the hydrochar briquette was further improved to 26.4 GJ/m3 by carbonization process at 400 °C. Lignin played the bonding role between carbon particles in carbonized briquette. [ABSTRACT FROM AUTHOR]