Studies of Phenolic-Compound Decomposition under Synthane Gasifier Conditions

摘要

Phenolic effluents are produced in varying quantities during the gasification of coal. Process operating conditions such as temperature, vapor residence time, reaction environment, coal heating rate and gas-solid contacting determine observed production patterns. More specifically, phenolic compounds are very susceptible to thermal and catalytic cracking in the typical gasification environment. The present experimental program was conducted to determine the pattern of phenolic compound decomposition under typical Synthane PDU gasification conditions. Bench-scale experiments were conducted at atmospheric pressure in a steam/synthesis gas atmosphere to study homogenous gas phase ortho-cresol decomposition characteristics, and quantify phenol decomposition in the presence of gasifier solids. Major conclusions drawn from this study regarding the decomposition characteristics of phenols are: (1) phenols typically formed during coal gasification decompose via successive dealkylation of higher phenol homologues; (2) the rate limiting step in the decomposition of phenols during coal gasification is decomposition of the compound phenol; (3) the presence of char solids in the Synthane PDU, and for that matter other gasification processes, enhances phenol decomposition rates by 2 to 3 orders of magnitude over those seen during homogeneous gas-phase reaction under typical gasifier thermal conditions; and (4) methane content of the reaction gas is stable under conditions conducive to achieving substantial levels of phenolic compound decomposition.