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Thesubcritical steam gasification of coal was performed with acalcium-based CO2sorbent (Ca(OH)2) in a laboratory-scalebatch reactor to examine the gasification kinetics with respect tothe effects of partial pressure of steam and coal quality. The studywas intended to support the hydrogen production by a reaction-integratednovel gasification (HyPr-RING) process in which coal is gasified withsubcritical steam in a fluidized bed containing Ca(OH)2. Conducting subcritical steam gasification at 600–727 °Cand 3–20 MPa produced zero emissions of CO2becausethe rate of CO2sorption by Ca(OH)2was fasterthan that of CO2generation by gasification. The gasificationreaction mechanism was represented by a parallel first-order reactionmodel of the components of volatiles and char in coal. Hydrogen wasmainly produced via tar from volatiles. The optimal partial pressureof steam preferred for hydrogen generation was 3 MPa, rather than20 MPa. More volatiles in coal increased hydrogen yield in the gasification,a trend that could be estimated by analysis of its kinetics. [ABSTRACT FROM AUTHOR]

Abstract: A new hydrogen production process “HyPr-RING” (hydrogen production by reaction integrated novel gasification), in which high-pressure steam (HPS) gasifies organic materials with a CO2 sorbent (CaO) has been developed. In this study, the material balances of major elements such as sodium and magnesium, and trace elements such as arsenic, mercury and lead in coal in the HyPr-RING process at thermodynamic equilibrium were investigated using commercial simulation software package, and compared with those experimentally determined on the HPS gasification of coal with CaO at a temperature of 650°C and calcination of the solid residue collected after gasification at 900°C. The behaviors of sodium, magnesium and lead in the experiments were similar to those at equilibrium, whereas those of arsenic and mercury were different. Sodium and lead existed as solid-phase species after gasification, whereas they existed partly as gas-phase species after calcination. Magnesium existed as solid-phase species after gasification and calcination. After gasification, arsenic existed as gas-phase species at equilibrium, whereas solid-phase species were present in the experiments. After calcination, arsenic existed as solid-phase species at equilibrium and in the experiments. After gasification and calcination, mercury existed as gas-phase species at equilibrium, but part of the mercury remained in the solid residue collected in the experiments. [Copyright &y& Elsevier]

Pulverized Taiheiyo coal (Japanese subbituminous coal) was gasified with steam in the presence of CO2 sorbent (Ca(OH)2) under relatively high pressure (approximately 20 MPa; subcritical condition) using a tubing-bomb microreactor (TB reactor). The transient characteristics in the conversion of coal and the formation of gaseous products during the gasification were investigated. During initial heating period, 40–50 wt.% of the coal initially loaded was rapidly converted to gas or tar. In the presence of Ca(OH)2, the yield of gaseous products was apparently increased owing to the catalytic effects of Ca(OH)2 on coal gasification. No CO2 was observed in the produced gas at any soaking time in the gasification with Ca(OH)2, suggesting that CO2 sorption by Ca(OH)2 took place effectively under high-pressure conditions. A rigid agglomeration of char and CO2 sorbent was observed at relatively high temperature, which is attributed to the formation of melts of the CO2 sorbent. [Copyright &y& Elsevier]

Coal char was gasified using subcritical steam with/without a CO 2 sorbent (CaO) and/or a hydrogen separation membrane (palladium-23% silver) in a batch/semibatch autoclave reactor to investigate the kinetics in terms of the effect of hydrogen separation at 590-650 °C and 1.9-2.4 MPa in order to support a hydrogen production process of the HyPr-RING method. CO 2 sorption by CaO affects the production rate of H 2 but scarcely affected the carbon conversion to gas. Hydrogen separation promotes the hydrogen production in spite of the absence of CO 2 sorption. The effect of hydrogen separation on hydrogen yield and carbon conversion was higher than that of CO 2 sorption. A higher gasification temperature increased the hydrogen yield and carbon conversion. Using a first-order reaction form in parallel, the gasification reaction mechanism was explained for the components of the volatile matter and char in coal char. A higher reaction temperature results in an increase of the values of any kinetic constant for subcritical steam gasification of Adaro coal char with/without CaO and/or a hydrogen separation membrane. CO 2 sorption promoted hydrogen production due to the tar from volatiles with the catalytic effects of CaO, whereas hydrogen separation promoted hydrogen production due to char., Competing Interests: The authors declare no competing financial interest., (Copyright © 2019 American Chemical Society.)