Multistage Liquefaction Process

The overhead liquid product is fractionated into light and heavy liquids and the residue is de-ashed by treatment with a solvent that promotes the settling of an under-flow stream that contains, essentially, all of the ash that occurred in the original coal feed. 

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In preceding sections, fundamental coal chemistry, liquefaction mechanisms, solvent and catalyst characteristics were summarized briefly. In the following three sections, the roles and improvements in solvents and catalysts in multistage liquefaction processes are reviewed in more detail on the basis of recent progress in this area. 

A multistage liquefaction process consisting of deashing, hydrogen-transfer liquefaction, catalytic depolymerization with FeS2, catalytic hydro-... 

The multistage liquefaction process (Figure 19.17) involves the liquefaction of crushed, dried coal which is slurried with an aromatic recycle solvent and the whole is then charged to a reactor at 415°C-440°C (VSOT-STST) at approximately 2000 psi. An expanded bed reactor system is employed to circumvent the problems that arise through reactor plugging, catalyst deactivation, and inequitable liquid distribution. 

Multistage coal liquefaction has been proposed to consist of the following stages, as shown in Fig. 1 [this scheme is the basis for promising processes... 

Extremely thermostable amylases and pullulanases, active above 100 °C and stable/active at acidic pH values wiU significantly improve the industrial starch bioconversion processes of liquefaction, saccharification, and isomerization. The lack of enzymes with these characteristics means that the bioconversion of starch to glucose and fructose must be carried out in a multistage process (step 1 pH 6.0 to 6.5, 95 to 105 °C step 2 pH 4.5, 60 to 62 °C step 3 pH 7.0 to 8.5, 55 to 60 °C),... 

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