The Idea of the Process

In the steam gasification process coal is converted into synthesis gas, typically composed of 25-30% of hydrogen, 30-60% of carbon monoxide, 5-15% of carbon dioxide, 2-30% of steam, and 0-5% of methane (Smolinski, 2007). Carbon monoxide is further converted into CO2 in the water-gas shift reaction (WGS) and in the Boudouard reaction, during which CO is converted into amorphous carbon and CO2. The idea of hydrogen-rich gas production in the process of steam gasification of coal applied in the study was to use Fe2O3 as an oxygen transfer compound to enhance the conversion rates of CO to CO2 and CaO to absorb the produced CO2. Simultaneous addition of Fe2O3 and CaO was proved to result in a high content of hydrogen in the product gas (Hauserman, 1994; Hacker et al., 2000; Lin et al., 2002a,b; Hacker, 2003; Kuramoto et al., 2003; Lin et al., 2003; Cox, 2004; Takenaka et al., 2004a,b; Lin et al., 2005a,b; Mondal et al., 2005; Urasaki et al., 2005; Smolinski and Stanczyk, 2006). The reactions of the process of steam gasification of coal to hydrogen-rich gas are presented in Table 17.1. The heats of the reactions were calculated for the temperature range of 873-1173 K using HSC Chemistry ver.3.0.

Table 17.1 The main reactions and the heats of reactions AH (kJ/mol) in the process of steam gasification of coal in a temperature range of 873-1173 K.

Reactions

ÀH873

ÀH973

ÀH1073

ÀH1173

c+h2°ÎB)=c°ÎB)+h2ÎB)

135,663

135,753

135,742

135,620

c°ÎB)+H2°ÎB)=C°2ÎB)+H2ÎB)

-35,734

-34,703

-33,707

-32,750

2C0(S)=C02(S)+C

-171,397

-170,455

-169,449

-168,370

CH4(B)+H20(B)=C0(B)+3H2(B)

223,967

225,360

226,355

226,999

CH4(B)+C°2ÎB)=2COÎB)+2H2ÎB)

259,701

260,063

260,062

259,748

C+2H2(B)=CH4(B)

-88,304

-89,607

-90,613

-91.379

Fe2°3+C0(e)=2Fe0+C°2(B)

-0,554

-3,522

-4,751

-4,650

Fe2°3+C=C°(e)+2Fe°

170,843

166,934

164,698

163,719

Fe2°3+H2iB)=2Fe°+H2°iB)

35,180

31,181

28,956

28,100

Ca°+ H20(B)=Ca(0H)2

-98,163

-96,080

-94,025

-92,003

Ca0+C02(g)=CaC°3

-172,091

-170,466

-168,698

-166,786

Ca(0H)2+C02(B)=CaC03+H20(B)

-73,928

-74,386

-74,673

-74,783

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