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A detailed kinetic model for the hydrothermal decomposition (HTD) of sewage sludge was developed based on an explicit reaction scheme considering exact intermediates including protein, saccharide, NH4(+)-N and acetic acid. The parameters were estimated by a series of kinetic data at a temperature range of 180-300°C. This modeling framework is capable of revealing stoichiometric relationships between different components by determining the conversion coefficients and identifying the reaction behaviors by determining rate constants and activation energies. The modeling work shows that protein and saccharide are the primary intermediates in the initial stage of HTD resulting from the fast reduction of biomass. The oxidation processes of macromolecular products to acetic acid are highly dependent on reaction temperature and dramatically restrained when temperature is below 220°C. Overall, this detailed model is meaningful for process simulation and kinetic analysis., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

The CO2 gasification properties and kinetics of three biomass chars (WS-char, RL-char and PS-char) and anthracite char (AC-char) were investigated by thermogravimetric analysis method. Three nth-order representative gas-solid reaction models, random pore model (RPM), volume reaction model (VM) and unreacted core model (URCM) were employed to describe the reactive behavior of chars. Results show that gasification reactivity order of different chars from high to low was WS-char, PS-char, RL-char and AC-char. In addition, the chemical components as well as physical structures of four chars were systematically tested. It was found that gasification properties of char were determined by carbonaceous structure. It was concluded from kinetics analysis that RPM model was the best model for describing the reactivities of biomass chars and VM was the model that best fitted the gasification process of anthracite char. The activation energies obtained for the biomass and anthracite char samples lie in the range of 236.4-284.9 kJ/mol., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

As a renewable, carbon-neutral raw material, the application of biomass in steel production is conducive to reducing greenhouse gas emissions and achieving green and sustainable development in the steel industry. The heating and reduction process of a rotary hearth furnace was simulated under laboratory conditions to roast and reduce biochar carbon-bearing pellets with coke powder and anthracite carbon-bearing pellets as a comparison. This was conducted to investigate the impact of biochar as a reducing agent on the direct reduction in carbon-bearing pellets. Under various reduction temperatures, carbon/oxygen ratios, and reduction times, tests were conducted on the compressive strength and metallization rate of carbon-bearing pellets made using typical binder bentonite. Results show that with the increase in reduction temperature, the metallization rate of pellets increases, while the compressive strength initially decreases and then increases, reaching the lowest point at 900 °C and 1000 °C. When the ratio of carbon to oxygen is between 0.7 and 0.9 and the reduction time is between 15 and 25 min, carbon-bearing pellets meet the requirements of both the metallization rate and the strength, with the metallization rate above 80%. However, severe volume swelling and low strength were observed in biochar carbon-bearing pellets at 900 °C and 1000 °C, which negatively impacted multi-layered charging and heat transfer efficiency in the blast furnace. Therefore, a novel laboratory-prepared binder was introduced in the preparation process of biochar carbon-bearing pellets at an appropriate addition ratio of 5–8%. Without producing any swelling concerns, the inclusion of this binder considerably improved the compression strength and metallization rate of the pellets, enabling them to fulfill the standards for raw materials in the blast furnace. [ABSTRACT FROM AUTHOR]

Hydrothermal carbonization (HTC) technology was used to carbonize and improve biomass raw material to obtain hydrochar. The effects of HTC temperature and holding time on the yield, composition, structure, combustion behavior, and safety of hydrochar were studied systematically. In addition, the results show that with the increase in HTC temperature and the prolongation of holding time, the yield of hydrochar gradually reduces, the fixed carbon content of hydrochar increases, the volatile content decreases, and a large number of ash and alkali metals enter the liquid phase and are removed. Further, the analysis of the combustion properties and the structure of hydrochar can be observed in that, as the HTC process promotes the occurrence of polymerization reactions, the specific surface area gradually reduces, the degree of carbon ordering increases, and the combustion curve moves toward the high-temperature zone and gradually approaches bituminous coal. Since biomass hydrochar has the characteristic of being carbon neutral, blast furnace injection hydrochar can reduce CO2 emissions, and every 1 kg/tHM of biomass hydrochar can reduce CO2 emissions by 1.95 kg/tHM. [ABSTRACT FROM AUTHOR]

It is critical for the iron and steel industry to achieve green transformation and development by effectively utilizing abundant biomass resources in blast furnace ironmaking. In this paper, four types of typical biomass were carbonized and upgraded using the hydrothermal carbonization (HTC) method, and the metallurgical performance of the prepared hydrochar for blast furnace injection was systematically tested. The results show that HTC treatment could remove volatile matter and dissolved mineral elements in biomass so that the hydrochar had the characteristics of high fixed carbon and low ash and alkali metal content. Moreover, the hydrochar had good grindability and excellent combustion performance, which meet the requirements of blast furnace injection. Finally, the metallurgical performance of blended coal and wood chip hydrochar was examined. It was observed that when the ratio of hydrochar was less than 15%, it would not affect the blast furnace injection, and the potential safety hazard caused by the explosive hydrochar could be resolved by mixing hydrochar with anthracite. The application of hydrochar in blast furnace injection could not only alleviate the current energy shortage situation, but also be of great significance to realize the "carbon peak" of the steel industry. [ABSTRACT FROM AUTHOR]

• The life cycle assessment of blast furnace ironmaking process is put forward. • The impact of biomass and fossil fuel use on process emissions is investigated. • Adding 108.6 kg of biomass hydrochar can reduce CO 2 emissions by 408.95 kg. • The use of biomass fuels has the most significant impact on human health. The impact of the iron and steel production process on the ecological environment cannot be ignored. This study aims to assess the impact of life cycle assessment on the traditional fossil fuel blast furnace ironmaking process and the biomass hydrochar blast furnace ironmaking process. The Simapro v9.0 software is used to comprehensively evaluate the life cycle impacts of biomass hydrochar in the blast furnace ironmaking process. The results show that the life cycle impact categories of the blast furnace ironmaking process mainly include global warming, non-renewable energy and respiratory inorganics. The global warming impact of the ironmaking process using hydrochar is 2054.00 kg CO 2 eq, which is 420.61 kg CO 2 eq less than that of traditional blast furnace ironmaking process. The global warming impact is mainly reflected in the emission of CO 2 gas, and the main source is the generation of blast furnace gas and the use of sinter. The respiratory inorganics impact is mainly manifested in the emission of nitrogen oxides, sulfur oxides and particulates, which mainly comes from the mining of iron ore and the production of sinter. The non-renewable energy impact mainly comes from the coal resources, and the use of other renewable energy such as biomass energy is an important way to reduce the impact. Therefore, biomass hydrochar used in the metallurgical process is more suitable for sustainable development of the ecological environment. [ABSTRACT FROM AUTHOR]

The non-isothermal thermogravimetric method was applied to petroleum coke (PC), corncob char (CC) and their blends with the different mass ratios under CO 2 atmosphere. The results show that CC with highly developed pore structure, high content of alkali metals and low degree of order had more reactivity than that of PC. The gasification reactivity of PC could be effectively improved by blending with CC. Meanwhile, there was obviously synergetic effect for the co-gasification of PC and CC. With the increase of mass ratio of CC, the synergetic effect first increased and then decreased. The synergetic effect was most obvious when CC mass ratio was 20%. Three n th-order representative gas-solid models: volume reaction model (VM), random pore model (RPM) and unreaction core model (URCM) were used to interpret the carbon conversion data. The overall fitting result of the RPM was slightly better than that of the VM and URCM. Furthermore, the synergetic effect between PC and CC was observed from the kinetics data calculated by RPM. The activation energy determined for PC and CC gasification was 203.2 kJ/mol and 243.3 kJ/mol, respectively, whereas, the lowest activation energy for their blends was 197.8 kJ/mol when CC ratio was 20%. [ABSTRACT FROM AUTHOR]

The thermal decomposition behavior of Shenhua bituminous coal (SB), Rice husk (RH), Pine sawdust (PS) and their blend during combustion were investigated by using the thermal analysis method. The apparent kinetic parameters of combustion process were estimated by fitting the experimental data to the double parallel reactions n th order rate model. The results showed that the combustion characteristics of the two kinds of biomass residues with low degree of order are higher than that of bituminous coal. For blend of bituminous coal with biomass residues, the ignition performance could be improved by increasing content of biomass residues, but the comprehensive combustion characteristics first decreases and then increases, with its lowest value occurring at addition content of 60%. Meanwhile, through comparison between theoretically calculated and experimentally measured data, it is concluded that there’s a synergistic effect during combustion process of biomass and coal blend. Through kinetic analysis, it is found that the combustion processes of coal, biomass and their blends could be well represented by the double parallel reactions n th order rate model, and for the two stages in combustion, with an increase of biomass content both activation energies first decrease and then increase. Both stage activation energies of the RH blend have lowest value when RH ratio of 60% (first stage 140.2 kJ/mol, second stage 136.9 kJ/mol), but for the SP blend the first stage lowest activation energies was PS ratio of 20% with a value of 143.1 kJ/mol and the second stage’s was a PS ratio 40% with a value of 143.9 kJ/mol. [ABSTRACT FROM AUTHOR]

The combustion behaviors of biomass, coal and their blends were studied by thermogravimetric analysis. Combustion parameters such as ignition, burnout, peak rate, ignition index, and combustibility index were analyzed. The kinetic parameters were optimized based on experimental results by a double parallel reactions random pore model (DRPM) proposed in this paper. The results show that the combustion characteristic temperature of the biomass is lower and maximum rate of combustion is higher than that of anthracite coal. With the increase of biomass content, ignition temperature and burnout temperature of blends tended to decrease, while the ignition index and combustibility index increased. Compared with the original RPM model, the DRPM model could not only describe the combustion process with a single peak rate, but also the combustion of biomass-coal blends with two rate peaks. The combustion activation energies of blends were extracted by DRPM model in the present study. [ABSTRACT FROM AUTHOR]

Hydrothermal carbonization (HTC) technology upgrades combustible waste (CW) to high-quality fuel known as hydrochar. However, there is a research gap regarding the application limit of hydrochar instead of fossil fuels in blast furnaces. In this study, the physical, chemical, and metallurgical properties of hydrochar were thoroughly analyzed. The results showed that gross calorific value, grindability, ignition temperature, explosivity, combustion and gasification all improved by HTC process compared with the waste feedstocks. Moreover, the HTC process can effectively remove harmful elements (K, Na, Cl, and S) from feedstocks into liquid and gas phase without adding other reagents, reducing harmful effects in the blast furnace. Removal rates by HTC were >80% for alkali metals and >73.9% for Cl (reaching 98.18% for polyvinyl chloride hydrochar). The environmental benefit calculation shows that the CO 2 emission reduction of replacing bituminous coal with 40% HTC-treated maize straw can reach 94.7 kg/tHM. The annual CO 2 reduction can reach 1.7 × 107 kg and the annual coal reduction is 1.5 × 107 kg of a blast furnace. The results showed that hydrochar is a clean energy source compared with fossil fuel alternatives and meets the blast furnace injection requirements. [Display omitted] • HTC process can improve the metallurgical properties of plastic and biomass feedstock. • The harmful elements of plastic and biomass feedstock was efficiently removed into liquid and gas phase by HTC. • Hydrochar as an alternative fuel for ironmaking can achieve CO 2 reduction 94.7 kg/tHM ideally. [ABSTRACT FROM AUTHOR]

• The effect of pyrolysis temperature on the characteristics of biochar was studied. • The coal rank of biochar increases with the increase of pyrolysis temperature. • As the pyrolysis temperature increases, the combustibility and reactivity decrease. • The Coats-Redfern model was used to clarify the mechanism of chemical reaction. As a carbon–neutral fuel, biomass plays a prominent role in replacing fossil fuels. The objective of this research is to uncover the influence of pyrolysis temperature on the metallurgical properties of biochar, as well as to provide a theoretical reference for the preparation of biochar suitable for blast furnace injection. The metallurgical properties of biochar have been systematically studied through the comparative analysis of the physical and chemical properties of biochar. The results show that pyrolysis technology can effectively improve the fuel performance of biomass. As the pyrolysis temperature increases, the fuel performance of biochar increases, the carbonization degree gradually increases, and the combustion performance and reactivity gradually weaken, approaching carbonaceous materials. The Coats-Redfern kinetic equation is used for the kinetic fitting of the combustion process of biochar, and has achieved good results. This clarifies the speed control link in the combustion process of biochar. [ABSTRACT FROM AUTHOR]

In this paper, a co-hydrothermal carbonization (co-HTC) process of biomass and polyvinyl chloride (PVC) is proposed. The feasibility of applying the product to blast furnace injection was verified, and the effects of different temperatures, liquid–solid ratios and holding times on the characteristics of the co-HTC products of pine and PVC were studied. After co-HTC, the fixed carbon and HHV increased to varying degrees, while the H/C and O/C atomic ratios decreased. Compared with single HTC, co-HTC significantly improved the removal efficiency of the alkali metals and organic chlorine up to 94.46% and 95.61%, respectively. Moreover, a physicochemical characteristic analysis was performed, and it showed that the order degree of the hydrochar carbonaceous structure increased and that C O and C C decreased and increased, respectively. Moreover, the physicochemical characteristic analysis showed that the corresponding combustion characteristics deteriorated. The density functional theory calculation showed that in HTC, the elimination order of the Cl atoms at the four sites followed 2-1-3-4. Moreover, the substitution was found to be more likely to occur in the region of sites 3–4. [ABSTRACT FROM AUTHOR]

• The feasibility of using biomass energy to make iron with a high proportion of blast furnaces is being studied. • The combustion characteristics of anthracite can be improved effectively by mixing with biomass hydrochar. • The physical and chemical properties of anthracite and biomass hydrochar were studied systematically. • The obvious synergistic effect in the later stage of the co-combustion process of mixed coals. • The performance of the RPM model is obvious better than that of the URCM model. Under the energy saving and emission reduction pressure, biomass has attracted much attention from metallurgical workers because of the renewability and zero CO 2 emission characteristics. In this paper, the physical and chemical properties of biomass residue hydrochar (BRC) and Yangjing pingding anthracite (YAC) were systematically studied by X-ray diffraction, scanning electron microscope and Raman spectroscopy. Moreover, the combustion characteristics and mechanism of biomass residue (BR), BRC, YAC, and the mixtures of BRC and YAC were studied by thermogravimetric analysis experiments. The results show that BR has a high volatile content of 82.26% and contains a large amount of alkali metals, but BRC has a low alkali metal content. The carbon atom sequence degree and graphitization degree of BRC are lower than that of YAC. The BRC particles also have a well-developed pore structure, and the reactivity of BRC is higher than that of YAC. The addition of BRC to YAC can improve the combustion performance of YAC. There is an obvious synergistic effect in the combustion process of the mixed sample. The kinetic model was used to fit the combustion reaction, and it was found that the random pore model (RPM) showed a more accurate fitting result. When the ratio of BRC is 60%, the activation energy of the mixed sample is 38.5 kJ/mol, which has superior combustion characteristics in raceway of blast furnace. [ABSTRACT FROM AUTHOR]

• HPC has shown better caking and fluid properties, 95 % and 35.48 mm. • The suitable addition ratio of HPC in blending coking is 15 wt%. • The vitrinite content and mean vitrinite reflectance of HPC are 95% and 0.352, respectively. • Cold strength of the coke decreases with HPC augmentation when its content is higher than 20 wt%. This study aimed to effectively utilize low-rank coal and biomass residue in the coking process. Hypercoal was produced through co-thermal extraction, and its performance as a component in the coking process was investigated. The effects of the amount of hypercoal extracted from 80 wt% low-rank coal and 20 wt% biomass residue on the coke strength and structure were investigated. Raman spectroscopy, optical microscopy, and scanning electron microscopy were used to analyze the carbonaceous, optical, and pore structures of the hypercoal coke. The optimal ratio of the coal blend contained 15 wt% hypercoal, with compressive and drum strengths of 7.76 MPa and 86 %, respectively. The vitrinite content and average maximum vitrinite reflectance of the hypercoal were 95 % and 0.352, respectively. High vitrinite contents in hypercoal contribute to the formation of mosaics within the coke, which can improve its cold strength. Moreover, the evolution of the hypercoal coke structure at various addition ratios was explored. [ABSTRACT FROM AUTHOR]

This study aimed to effectively utilize low-rank coal and biomass residue in the coking process. The gasification performance of cokes prepared from the modified coal was investigated, meanwhile the structural characteristics of different cokes were analyzed by Raman spectroscopy, X-ray diffraction and infrared spectroscopy. The results showed that solvent thermal extraction process could dramatically remove the ash content and gradually enhance the caking performance and carbon content for low-rank coal. The ash content, carbon content, penetration distance, and caking index of modified coal were 0.86 wt%, 78.18 wt%, 35.48 mm, and 95%, respectively. Structural analysis results showed that the order degree and graphitization degree of BIOC-HPC coke were superior to those of coking coal coke, and the overall compactness of BIOC-HPC coke was improved. Compared with the coking coal coke, the gasification performance of coke could be improved by adding modified coal; the optimal addition ratio of the modified coal in coal blending for coking was between 10 wt% to 15 wt%. The gasification kinetic analysis indicated that the RPM model was the optimal model for simulating the gasification process of modified coal coke, and the activation energy was between 211.36 kJ/mol and 228.81 kJ/mol. • The influence of BIOC-HPC content on gasification performance of BIOC-HPC coke was investigated. • The optimal gasification property could be found in the coke with 10–15 wt% BIOC-HPC addition. • The random pore model could predict the gasification process of BIOC-HPC coke well. • Low-rank coal and biomass treated by co-thermal extraction had greater application potential in coking. [ABSTRACT FROM AUTHOR]