Chapter 5 - Liquefaction: Thermal Breakdown in the Liquid Phase

Abstract

This chapter deals with the process of liquefaction, which is the thermal breakdown in the liquid phase. During the liquefaction process, materials extracted by the solvent and those detached from the solid coal matrix by the rupture of covalent bonds are released into the liquid phase. The chapter presents an outline of the general trends to be expected from coal liquefaction experiments and examines how the interplay between reaction chemistry and reactor design can affect observations made during bench scale experiments. For any given coal, the extractable material content prior to the covalent bond rupture stage is variable. It depends on the solvent used for extraction and the temperature. Based on this understanding, this chapter presents a conceptual integration of sample characterization with reactor design. The chapter also presents a review of methods for liquid product characterization. The integration of product characterization with reactor design leads to attempt a unified understanding of successive thermally driven events that bring about thermal breakdown in pyrolysis and liquefaction.