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Abstract: Gasification of biomass using high-temperature agents (air/steam) has been proven to have many features superior to those of conventional gasification using low-temperature agents. In this work, an experimental fixed-bed gasifier is utilized to investigate the gasification of biomass using high-temperature air up to 1473 K. A mathematical model has been formulated for the prediction of the main chemical and physical processes and is used to study the influence of temperature, oxygen concentration and flow rate of the feed gas. Predicted gas species concentration profiles and their maximum values are in reasonable agreements with the measurements. The results show that: (a) When the temperature of feed gas is increased, a higher gasification rate, a higher ignition front rate, and higher molar fractions of fuel gases (CO, H2 and C m H n ), thus a higher LHV are obtained. (b) Increased oxygen concentration leads to higher peak values of the fuel gas concentrations, a higher gasification rate, and a larger ignition front rate. (c) Based on the air temperature, two distinct ignition modes are identified: the reaction-controlled and convective-controlled modes. (d) A critical air temperature exists, above which further preheating is no longer efficient if the purpose is to maximise the yield of gaseous products. [Copyright &y& Elsevier]

• Integrated process to produce H 2 -rich syngas and MAC from lignin is proposed. • Gasification is more beneficial for hydrogen production than pyrolysis. • The maximum H 2 yield of proposed process is estimated to be 42.73 mol/kg-lignin. • MACs can be used for domestic wastewater treatment for phosphate recovery. An integrated process that includes the pyrolysis of FeSO 4 dry impregnated lignin and subsequent steam gasification of the produced biochar has been performed to produce H 2 -rich syngas and magnetic activated carbon. The results show that gasification is more beneficial for hydrogen production than pyrolysis. Increasing the pyrolysis temperature from 550 °C to 800 °C and iron loading from 4% to 8% not only promotes the extension decomposition of lignin but also induces the production of char, which is more effective for gasification. As a result, the syngas yield and H 2 volumetric percentage of both the pyrolysis and steam gasification processes are enhanced. The maximum overall H 2 yield and exergy efficiency for producing H 2 are estimated to be 42.73 mol/kg-lignin and 46.63%, respectively. Magnetic activated carbon materials produced from the proposed integrated process have a good porous property and high saturation magnetization value. Magnetic activated carbon that is produced from the same process that achieves a maximum H 2 yield is obtained and exhibits an approximate 70% total phosphate and 20% ammonia and nitrogen removal efficiency for treating real domestic wastewater. [ABSTRACT FROM AUTHOR]

In order to eliminate problems such as corrosion and ash deposition caused by alkalis, effects of the biomass composition and the pressure of syngas in the downstream process on condensation of alkalis in a wood steam/oxygen blown fluidized bed gasification process are investigated based on a model. This model is established by combining Aspen Plus with SimuSage. Aspen Plus is applied to predict the composition of major gas species formed by C, H, O, N, S and Cl, using empirical correlations to predict the yields of non-equilibrium substances. SimuSage is used to study the release and condensation of inorganics associated with the minor elements (Al, Ca, Fe, K, Mg, Na, P, Si and Ti) based on a customized thermodynamic database. Results show that carbonation reactions between alkalis and CO/CO 2 can be occurred during gas cooling, leading to form alkali carbonates in the condensed phase. The temperature window forming melts varies with the change of the downstream pressure of syngas and the elemental composition of biomass. As the syngas pressure in the downstream process decreases, the initial temperature of forming melts during gas cooling is reduced. For biomass lower in K/Cl ratio, the condensate with the largest mass formed during gas cooling is potassium chloride. The condensation rate of Cl increases with the decrease of the K/Cl ratio in biomass. [ABSTRACT FROM AUTHOR]

In a biomass gasification process, condensation of inorganic species can cause problems such as corrosion and deposition on the downstream equipment. In this work, in order to investigate the condensation of inorganics during the gas cooling step of the biomass gasification system, both experimental and modelling studies were conducted. Experiments were performed on a pilot-scale steam/oxygen blown fluidized bed gasification facility. A CO 2 cooled probe was located at the head of a filter to condense inorganic species. Five thermocouples were used to monitor the probe temperature profile. Deposits on the probe were characterized using scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS) to analyze the elemental composition of deposits. A process model based on the local chemical and phase equilibriums was developed using software SimuSage to predict both release and condensation of inorganics. A customized thermodynamic database extracted from the FactSage 7.1 was used during model calculations. Two cases including with and without addition of bed material were calculated. Results show that the identified elemental compositions of deposit under different gas cooling temperatures reasonably agree with the elemental compositions predicted by model calculations. This demonstrates that the established model and the customized thermodynamic data are valid. A large amount of carbon is identified in the deposit of low temperature probe sections, which may come from the condensed tar. Additionally, a temperature window is found, where melts are formed during gas cooling. [ABSTRACT FROM AUTHOR]

Polygeneration is a promising technology for enhancing the performance of traditional centralized district heating and cooling (DHC) systems since it enables the use of renewable energy sources and provides flexibility in supplying a range of value-added products. The main objective of this study is to evaluate how a reduction in heating, cooling and electricity loads would impact on the performance of a polygeneration DHC system based on waste gasification from thermodynamic, exergy, economic and environmental perspectives. To this end, system models considering hourly performance for a typical year of operation were established with either refuse derived fuel (RDF) or municipal solid waste (MSW) as feedstocks. The study reveals that with a decrease in heating, cooling and electricity loads the system, using RDF or MSW as the main fuel, is still capable of delivering energy services, but with reduced amounts of value-added products and less favourable overall system performance. For example, with RDF as the main fuel, when char, syngas, synthetic natural gas and hydrogen are produced with the gas turbine operating at 25% of its nominal value, with no heating and cooling supplies, the system thermodynamic efficiency is only 3.9%, as compared with 31.5% for the maximal heating, cooling and electricity supplies for the same group of value-added products. Nevertheless, under these conditions the system operation is still feasible and economically viable; specifically, annual revenues and discounted net cash flows are 6.4 and 11.1 mln USD, respectively. [ABSTRACT FROM AUTHOR]

Conventional district heating and cooling (DHC) systems are compelled to reduce their fossil fuel dependency while ensuring profitability as cooling and heating demands decline. One solution is to retrofit the system with a gasifier and product gas upgrading equipment so that the system will be able to diversify its fuel input, including biomass and waste resources, while simultaneously producing synthetic natural gas (SNG), synthetic gas (syngas) and char complementarily to heat, cold and electricity. The main objective of this study is to assess energetically and economically a polygeneration DHC system based on gasification of refuse derived fuels considering the following sub-product scenarios: char; char and syngas; char and SNG; and char, syngas and SNG. The results show that when char is the only sub-product of the modified DHC system, the investment payback is 3 years, the discounted net cash flow (DNCF) is 142 mln USD, and the system trigeneration efficiency is 83.6%. When other sub-products are supplied by the system, its performance reduces but the system DNCF increases, while the investment payback remains constant. [ABSTRACT FROM AUTHOR]

District heating and cooling (DHC) systems, modified or retrofitted with integration of gasifiers and gas upgrading equipment, represent promising alternatives to traditional approaches since various scenarios of products complementary to heat, cold, and electricity can be realized, namely: char only; char and syngas; char, synthetic natural gas (SNG) and hydrogen (H 2 ); and char, syngas, SNG and H 2 . This manuscript evaluates a polygeneration-enabled DHC system in detail (operation during a typical year) from exergetic and exergoeconomic perspectives. The base DHC system utilizes natural gas as fuel with a nominal capacity of 29 MW heat, 35 MW of cold, and 5 MW of electricity. The retrofit employs refuse derived fuel (RDF) as feedstock to an atmospheric gasifier with downstream gas clean-up, a gas turbine, and a heat recovery steam generator along with heat exchangers for integration with the base DHC system. The exergy analysis revealed that the polygeneration system presents adequate performance at all scenarios established. Among the sets of value-added products the combination of char and syngas is the most beneficial as the system efficiency reaches a value of ∼72%. The outcomes of the exergoeconomic analysis support the exergy results. The lower production costs for value-added products are achieved for the maximum simultaneous char and syngas production, with each of these costs estimated to be 6.1 USD/GJ. [ABSTRACT FROM AUTHOR]

Highlights: [•] An equation was developed for pressure drop prediction with shrinking effect. [•] Graphical representations of correlation constants were introduced. [•] This would provide a guide to select pellet size and designing a grate. [ABSTRACT FROM AUTHOR]

Catalytic tar removal from producer gas is critical for the economic feasibility of Municipal Solid Waste (MSW) gasification in the waste-to-energy(WtE) approach. Nickel- and noble-metal catalysts have the highest tar cracking activities, but they increase costs, use scarce materials, and generate dangerous byproducts. To overcome these drawbacks, naturally occurring materials should be used for tar cracking. In this paper, two nanomaterials, synthesized from oyster and mussel waste shells respectively, are used to clean syngas from MSW in a secondary tar cracking unit. We observed that they reform class 1 tar (heavy tars that condense at high temperatures at very low concentrations) into class 3 tar (light hydrocarbons that are not important in condensation) and benzene. Although both catalysts' composition and textural properties were identical, crystallite size and especially specific surface area variation was enough to generate a change in product selectivity. A larger crystallite size and SSA shows a soot yield reduction of 95% with respect to the non-catalytic case, simultaneously increasing the H 2 /CO at 1000 °C. • Two CaO rich catalysts doped with Sr were synthesized from oyster and mussels waste shells. • Both catalysts improve syngas H2:CO ratio, reduce class 1 tar and soot yield at high temperatures. • Soot reduction is accompanied by a class 5 tar reduction and by an increase in class 3 tar. • The crystallite size and specific surface area of the two catalysts directly affect the tar cracking product selectivity. • The syngas quality obtained using the oyster derived catalyst makes it ideal to use in tandem with Ni and noble-metal catalysts. [ABSTRACT FROM AUTHOR]

• MSW gasification was performed under air and steam in a fixed-bed gasifier. • Naphthalene is the most stable compound in secondary tar thermal cracking. • Corona plasma-aided thermal cracking achieved naphthalene complete removal at 800 °C. • With a fixed energy input, the SEI increased when temperature increased. • Corona and plasma cracking have a synergistic effect below 800 °C. Gasification has been proposed as a good solution for recovering energy from waste and biomass in the form of syngas. However, the presence of tar limits syngas applications. Tar model molecules have been removed by cold plasmas up to 400 ° C, but to avoid syngas cooling tar removal above 600 ° C is required. To investigate tar removal by cold plasma at higher temperatures, two sets of experiments were done, one to identify tar composition from MSW gasification, and a second one to crack in a nanosecond-pulsed corona plasma at high temperatures the most refractory tar compound found, naphthalene. In this paper, we report the first results of cold plasma for tar cracking at temperatures up to 1100 ° C, revealing that this tandem can remove naphthalene completely at 800 ° C, compared to the 1000 ° C needed in case of thermal cracking alone. The synergy between plasma and thermal cracking is driven by higher energy densities when temperatures increase. However, this synergy stops when thermal cracking reactions predominate. [ABSTRACT FROM AUTHOR]

• Different integration scenarios are proposed for DRI production using biosyngas. • Mature fluidised bed gasifiers (TRLs 9) are considered for producing biosyngas. • The novel biosyngas DRI route can compete with other existing and emerging routes. • Carbon negative is possible as up to 1.13 t CO 2 per t DRI can be captured and stored. Bioenergy with carbon capture and storage (CCS) in iron and steel production offers significant potential for CO 2 emission reduction and may even result in carbon-negative steel. With a strong ambition to reach net-zero emissions, some countries, such as Sweden, have recently proposed measures to incentivise bioenergy with CCS (BECCS), which opens a window of opportunities to enable the production of carbon-negative steel. One of the main potential applications of this route is to decarbonise the iron reduction processes that account for 85 % of the total CO 2 emission in the iron and steel plants. In this study, gasification is proposed to convert biomass into biosyngas to reduce iron ore directly. Different cases of integrating the biomass gasifier, Direct Reduced Iron (DRI) shaft furnace, and CCS are evaluated through process simulation work. Based on the result of the work, the proposed biosyngas DRI route has comparable energy demand compared to other DRI routes, such as the well-established coal gasification and natural gas DRI route. The proposed process can also capture 0.65–1.13 t of CO 2 per t DRI depending on the integration scenarios, which indicates a promising route to achieving carbon-negative steel production. [ABSTRACT FROM AUTHOR]

Pretreatment of biomass becomes more and more important due to the large scale application of biomass having low energy density. In this paper, steam exploded biomass pellets (Black pellets) and unpretreated biomass pellets (Gray pellets) were gasified with air and steam at an updraft HTAG (High Temperature Agent Gasification) unit. Decomposition characteristics of pellets were first analyzed with TGA (thermo gravimetric analysis). Early decomposition of hemicellulose and cellulose were seen with Black pellets around 241 °C and 367 °C respectively. Introducing CO2 led comparatively high mass loss rate with Black pellets. Gasification of Black pellets resulted in syngas with high CO and hydrocarbon contents while Gasification of Gray pellets resulted in high H2 content of syngas. LHV (lower heating value) of syngas was high around 7.3 MJ/Nm3 and 10.6 MJ/Nm3 with air gasification and steam gasification respectively. Even with significantly low syngas temperature with gasification of Black pellets, only slightly high total tar content was seen compared to that of Gray pellets gasification. Phenolic compounds dominated the tar composition. In general, steam gasification of Black pellets seems to be more feasible if syngas with high energy value is desired. If higher H2 yield is preferred, gasification of unpretreated pellets likely to be more attractive. [ABSTRACT FROM AUTHOR]

Highlights: [•] CaO shows a good capacity of CO2 adsorption at devolatilization stage of MSW. [•] CaO acted as a catalyst both in MSW devolatilization and char steam gasification. [•] Good dispersion and mobility of calcium in char were observed. [•] Catalytic mechanism during devolatilization and char gasification were discussed. [ABSTRACT FROM AUTHOR]

Highlight: [•] A thermodynamic analysis was conducted to evaluate the characteristics of the PGM. [•] Energy recovery using gas furnaces is suggested due to high total energy and exergy. [•] Gas turbines are not recommended due to high tar yield. [•] Increasing heat to the PGM is beneficial for cold gas energy and exergy efficiencies. [•] A small steam addition is beneficial for PGM energy and exergy efficiencies. [ABSTRACT FROM AUTHOR]

Abstract: Plasma gasification melting (PGM) is a promising gasification technology aiming at providing sustainable disposal for various wastes. In this work, an Euler–Euler multiphase model was developed to study the characteristics of air and steam gasification of municipal solid waste in a PGM reactor. The model is validated by measurement data from a demonstration PGM reactor. With this model, three groups of simulations were performed to study the influences of operating conditions. It is confirmed that injection of high temperature steam is important for increasing the cold gas efficiency and syngas lower-heating-value. The effect of steam injection is affected by steam feeding rate, air feeding rate and plasma power. Based on the simulated results, an optimal condition is suggested for air and steam gasification in the PGM reactor. [Copyright &y& Elsevier]

Abstract: Plasma Gasification Melting (PGM) is a novel gasification technology which offers a promising treatment of low-heating-value fuels like municipal solid waste (MSW), medical waste (MW) and other types of waste. By considering the differences in pyrolysis characteristics between cellulosic fractions and plastics in MSW, a semi-empirical model was developed to predict the performance of the PGM process. The measured results of MSW air and steam gasification in a PGM demo-reactor are demonstrated and compared with the model predicted results. Then, the effects of dimensionless operation parameters (ER, PER, and SAMR) are discussed. It was found that all three numbers have positive effects on system cold gas efficiency (CGE). The reasons can be attributed to promoted tar cracking by enhanced heat supply. The effects of PER and ASME on syngas LHV are also positive. The influence of ER on syngas pyrolysis can be divided into two parts. When 0.04

Abstract: A new waste-disposal technology named Plasma Gasification Melting (PGM) was developed. A pilot PGM reactor was constructed in northern Israel. The reactor is an updraft moving-bed gasifier, with plasma torches placed next to air nozzles to heat the incoming air to 6000°C. The inorganic substances of the feedstock are melted by the high-temperature air to form a vitrified slag in which undesirable materials such as heavy metals are trapped. The residual heat in the air supplies additional heat for the gasification process. A series of tests were conducted to study the performance of PGM gasification. The plasma power was varied from 2.88 to 3.12MJ/kg of municipal solid waste (MSW), and the equivalence ratio (ER) was varied from 0.08 to 0.12. For air and steam gasification, the maximum steam/MSW mass ratio reached 0.33. The composition of the syngas product was analyzed in all tests; the lower heating value (LHV) of the syngas varied from 6 to 7MJ/Nm3. For air gasification, the syngas LHV decreased with increasing ER, whereas the gas yield and energy efficiency increased with ER. When high-temperature steam was fed into the reactor, the overall gas yield was increased significantly, and the syngas LHV also increased slightly. The positive effect may be attributed to the steam reforming of tar. In air and steam gasification, the influence of increased ER on syngas LHV was negative, while the effect of increased plasma power was positive. The maximum energy efficiency of the tests reached 58%. The main energy loss was due to the formation of tar. [Copyright &y& Elsevier]

Primary fragmentation during rapid pyrolysis is considered to be the critical size reduction mechanism as it determines the particle size distribution and char conversion rates in the fixed bed gasifier. This study aims to investigate the primary fragmentation behavior of Refuse Derived Fuel (RDF) pellets during a rapid pyrolysis process. RDF pellets consisted of different blending ratios of cardboard and polyethylene (PE) were produced by a single-pellet densification process. Pyrolysis tests at temperature ranges of 500–700 °C were performed for each pellet type, and the number and particle size of the fragmented particles were analyzed. The results demonstrate that the different composition of RDF causes different particle binding mechanisms that behave differently during pyrolysis. Densification of cardboard particles can maintain the structure of the pellet char at higher temperatures compared to PE, due to the more stable lignin binding mechanism. A modified Fragmentation Ratio (FR) is introduced to quantify the degree of fragmentation. It is shown that a raise of the concentration of PE from 25 to 75 wt% increases the FR value by up to 4.2 times, whereas an increase in pyrolysis temperature from 500 to 700 °C only slightly changes the FR values. It can be concluded that the type of materials in the RDF pellet has a more dominating effect on the fragmentation compared to the pyrolysis temperature. Further, the volatile matter content of pellets shows a linear correlation with the FR value, whereas no clear relation is found in the case of the pellet's mechanical strength. • Fragmentation RDF pellets were examined during pyrolysis tests at 500–700 °C. • Effects of pyrolysis temperature and pellet compositions were investigated. • Pellets with high cardboard and low plastic contents are less fragmented. • Volatile matter content of pellets shows a linear relation with the fragmentation degree. [ABSTRACT FROM AUTHOR]