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Abstract: In this work, the high temperature air/steam gasification (HTAG) technique has been tested for a fuel in pellet form made from waste material of woody and plastic origin. The feedstock was gasified in an updraft fixed bed reactor by mixtures of air and steam (102 Nm3/h, 4% to 82% steam) preheated to 1400 °C, a temperature well above the fluid temperature of the feedstock. The produced gas was analyzed with respect to composition, including a detailed characterization of the tar. Lower heating values up to 9.5 MJ/Nm3 and gas yields as high as 3.4 Nm3/kg were reported, indicating the process to be highly efficient for waste-to-energy applications. The composition of the tars, suggested extensive cracking as a result of the high temperatures of the outgoing gas. [Copyright &y& Elsevier]

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: 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]