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“HyPr-RING” is a new H2 production process using carbonaceous fuels in which the fuel is reacted with subcritical steam and a calcium-based CO2 sorbent. We investigated the applicability of this process to organic matter by examining the performance of the process with fuels of differing volatility. The gasification rate and relative contributions of the volatile and “char” components to H2 production were investigated by using dried sewage sludge with a high volatile component concentration, coal with an intermediate volatile component concentration, and coal char with a low volatile component concentration. During the initial thermal decomposition, carbon in the fuels rapidly decreased with time and was converted to carbonaceous gas of CH4 and C2H6 in addition to H2. The amount of the decrease depended on the volatile content in the fuels. Following this initial rapid stage, the residual carbon appeared to become charlike, even for the high volatile content fuel. The gasification rate became slow, and the gasification shifted to favor H2 production in a molar ratio of H2 to CH4 that approximated the equilibrium composition for a char and steam reaction. NaOH catalytically promoted H2 production even for the sludge.

The subcritical steam gasification of coal was performed with a calcium-based CO2 sorbent (Ca(OH)2) in a laboratory-scale batch reactor to examine the gasification kinetics with respect to the effects of partial pressure of steam and coal quality. The study was intended to support the hydrogen production by a reaction-integrated novel gasification (HyPr-RING) process in which coal is gasified with subcritical steam in a fluidized bed containing Ca(OH)2. Conducting subcritical steam gasification at 600–727 °C and 3–20 MPa produced zero emissions of CO2 because the rate of CO2 sorption by Ca(OH)2 was faster than that of CO2 generation by gasification. The gasification reaction mechanism was represented by a parallel first-order reaction model of the components of volatiles and char in coal. Hydrogen was mainly produced via tar from volatiles. The optimal partial pressure of steam preferred for hydrogen generation was 3 MPa, rather than 20 MPa. More volatiles in coal increased hydrogen yield in the gasification, a trend that could be estimated by analysis of its kinetics.

A laboratory-scale batch reactor was used to perform a limited number of experiments on the steam gasification of coal tar formed by pyrolyzing Taiheiyo coal at 873 K for 2 h in N 2 . The study was intended to support the HyPr-RING process in which coal is gasified with steam in a fluidized bed containing Ca-based CO 2 sorbent. H 2 is the desired product, while substantial amounts of CH 4 and small amounts of C 2 H 6 were also produced. The amounts were decreased but the molar ratio of CH 4 to H 2 in the product gases was increased with a decrease of the temperature. The predominant production occurs in the initial stage including the heating period. The behavior for tar is similar to that for coal, suggesting that CH 4 and H 2 production from coal should be caused by tar produced from coal in the initial stage and especially that H 2 production in the second stage should be by char from coal.

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