A mechanism investigation of synergy behaviour variations during blended char co-gasification of biomass and different rank coals

Gasification is a well proven thermal conversion technology that has been used to convert solid fuel into gaseous fuel. There are different types of conventional feedstocks such as coal and biomass that have been gasified in either individual or blended form. The advantage of co-gasification over typical gasification is the ability to obtain the desired product gas composition by varying the blending ratio and feedstock. Furthermore, it is applicable for many feedstocks such as sewage sludge, black liquor, glycerol, and municipal solid waste. These feedstocks have good thermophysical properties, however, gasification of these feedstocks is difficult using a conventional technique, thus highlighting the need for co-gasification. Recently, the effect of feedstock type and their blending for syngas production have attracted interest among researchers especially when feedstocks are non-conventional. Several review articles have been published on gasification of individual coal and biomass. However, no review that exhaustively dealt with the catalytic co-gasification of a different kind of conventional and non-conventional feedstock. The feedstock type and blending ratio of feedstock are the most important parameters that affect the co-gasification process. The objective of the current paper is therefore to review the effect of feedstock type and their blending ratio on syngas quality, co-gasification performance, and tar formation for catalytic co-gasification of both conventional and non-conventional feedstocks. This review highlights the need for research and development in co-gasification and also provides the research gap for further research to develop a state of art technologies.

Effect of various blended fuels on syngas quality and performance in catalytic co-gasification: A review

Co-gasification of coal and biomass: Synergy, characterization and reactivity of the residual char.

Catalytic gasification is a method for converting carbon feeds to usable products such as hydrogen, carbon monoxide, and methane. This review summarizes the research on potassium, sodium, calcium, magnesium, and heavy metal catalysts, the interactions between these catalysts and other species in typical feeds, and gasifier design considerations. Phase behaviour is a critical element in the performance of a gasification catalyst – the active phase of the catalyst must be thermodynamically favoured. Formation of stable but inactive forms and/or highly volatile forms of the catalyst are detrimental. Given that real feeds are complex and the conditions in a gasifier not uniform, laboratory results must be carefully translated to the larger scale.

Catalysts for gasification: a review

A review on reactivity characteristics and synergy behavior of biomass and coal Co-gasification

Synergetic and inhibition effects in carbon dioxide gasification of blends of coals and biomass fuels of Indian origin.

Gasification of solid fuels such as coals, lignite and biomasses has been studied using isothermal and non-isothermal thermogravimetric analysis (TG) with CO2 as gasifying agent. Non-isothermal TG of three Indian coals (two bituminous and one sub-bituminous coal), one lignite and two biomass fuels (Casuarina and empty fruit bunches) at a constant heating rate of 20 °C min−1 in the temperature range from 25 to 1200 °C showed a clear separation of DTG peaks associated with pyrolysis and CO2 gasification. Based on these studies, isothermal TG experiments were conducted in the temperature range from 900 to 1100 °C for coals and from 800 to 1000 °C for biomass fuels. These results show that the CO2 gasification rate follows coal rank for the three coals and the lignite. The two biomasses have significantly higher reactivities than the three coals. The higher reactivity of one coal is attributed to the presence of calcium-containing minerals in its inorganic matter. The kinetic parameters for each fuel were extracted from the isothermal TG results using the volumetric reaction model for the coals and a zeroth-order model for biomass fuels. Biomass and lignite are found to have a much higher reactivity index and much lower conversion time than the three coals under identical conditions.

Evaluation of CO2 gasification kinetics for low-rank Indian coals and biomass fuels

CO2 capture from coal-fired power plants is necessary for continued use of coal as a fuel. Proven CO2 capture techniques such as amine absorption and oxyfuel combustion entail significant energy penalty leading to considerable decrease in the net thermal efficiency of the power plant. Recent studies of high-ash Indian coals show that CO2 has sufficient reactivity for coal gasification in temperature ranges of interest to IGCC. Against this background, we analyse in the present study, a new power plant layout which uses part of the sequestered flue gas stream for high-pressure gasification of the coal within the framework of an IGCC power plant with CO2 capture. Detailed thermodynamic calculations of the new plant layout, referred to here as Oxy-RFG-IGCC-CC, using commercial power plant simulation software show that the optimized Oxy-RFG-IGCC-CC plant with CO2 capture produces power at an overall thermal efficiency of 34.2%, which is nearly the same as that of current generation of pulverized coal boiler-based power plants without CO2 capture or that of a conventional IGCC with post-combustion capture. The proposed simpler layout is also 1.9% more efficient than a comparable CO2-capture-enabled IGCC plant that uses steam for coal gasification.

V. Satyam Naidu

Papers

Synergetic and inhibition effects in carbon dioxide gasification of blends of coals and biomass fuels of Indian origin.

Evaluation of CO2 gasification kinetics for low-rank Indian coals and biomass fuels

Improving efficiency of CCS-enabled IGCC power plant through the use of recycle flue gas for coal gasification