Gasification chemical reactions during

Figure 5.1.28 Main chemical reactions during pyrolysis, gasification, and combustion of coal.

The chemical reactions taking place during the gasification of coal are well known. Some of these are listed in Table 3. 

So far, only single reversible chemical reactions were considered. In practice, often multiple reversible chemical reactions take place, for example in the case of coal gasification or the steam-reforming process. During the calculation only the set of independent reactions has to be considered, this means only the reactions which cannot be obtained by linear combinations from the already selected reversible chemical reactions. 

A discussion of this reaction provides a detailed insight as to what happens during gasification by carbon dioxide and steam. Chemical reactions, within molecular-sized space, differ from chemical reactions without space restrictions. 

If any thermodynamic assessment involving coal is intended, it is necessary to define its heat of formation. In particular, temperature calculation during the modeling of gasification or pyrolysis is extremely sensitive to consistent enthalpy calculation. The problem is that normally only clearly defined substances such as carbon (graphite) can be consistently treated in chemical reaction systems. Therefore, coal must be theoretically decomposed to its elements and a correctly assigned standard enthalpy of formation is required. 

During steam-coal gasification, two consecutive chemical processes take place [30, The first process, the pyrolysis reaction... 

Unlike the catalytic reaction discussed above, gas-solid reactions involve the solid particle as well as the gas in the reaction. Typical examples of industrial applications include spent FCC catalyst regeneration, calcination, coal combustion, gasification, and silicon chlorination. Owing to the solid particle involvement in the reaction, significant changes in the chemical compositions and physical properties of the particles occur during the reaction. Particles reduce in size and/ or increase in porosity in some reactions like coal combustion, whereas particles increase in size and/or decrease in porosity in other reactions such as limestone sulfation. As a result, the particle properties vary unlike those particle properties in catalytic reactions. However, as with catalytic reactions, gas-solid reactions take place on the particle surface as gas reactant adsorbs to the surface. 

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