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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]

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]

• 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