Coal Swelling

Abstract

Coal swelling is a phenomenon associated with physical and morphological changes that occur when coal is steeped in a particular solvent. Coal may be considered as a cross-linked polymeric macromolecule that may allow particular solvent molecules to penetrate the flexible framework. Analysis of the changes to the coal and solvent during swelling can provide valuable structural information on the coal, and facilitate more efficient use of this coal. This chapter describes coal swelling from a phenomenological viewpoint. We discuss prior studies in this area and the models that have been used to describe the swelling behavior. We compare the behavior of raw coal against that which has been swelled in pyrolysis and liquefaction processes. We also study the changes in properties (thermal, pore, and surface effects), char properties that occur and demonstrate the utility of swelling as a technique to probe the coal structure. We discuss the relationship between swelling and structural parameters, and present an investigation of the swelling behaviors of eight Chinese coals.