Syngas and Hydrogen Applications
For synthesis-gas application the situation is somewhat different. In this case the moles of H2+CO per unit feedstock have to be optimized. The effect of the operating conditions on this maximum is illustrated in Figure 2-8.
The optimum along the abscissa is caused by the effect that at lower temperatures more carbon is converted into C02 and CH4, whereas the aim is to convert it as much as possible in CO. There is also a maximum along the ordinate. This is caused by the fact that by adding somewhat more steam less CH4 will be formed and some additional heat will be generated by the CO shift reaction.
The latter effects are small, but they are there. The result is that for a fixed heat loss and reactant composition and temperature, there is one point that yields the maximum amount of synthesis gas. The effect is of more importance to heavy oil gasification than for coal gasification, as the ash limitations for coal do not allow an operation at such low temperatures where these effects become relevant.
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