Investigation of coal agglomeration in a non-pressurized gasifier

Abstract

The gasification process is vital to various applications, such as the manufacture of products in the petrochemical industry, for example chemicals, diesel and petrol. The importance of gasification to the coal industry necessitates continuous research in order to achieve optimal operation. Continuous research ultimately results in the progress of the industry with regard to various factors, among others that of (a) environmentally cleaner operations which aim at protecting the green heritage, (b) effective material selection which leads to shorter residence times, and (c) the prolonged existence of equipment which in turn leads to stronger economical viability. The main objective of this Masters in Chemical Engineering was to investigate the agglomeration phenomenon which occurs inside the gasifier, causing problems such as pressure fluctuations, hindered bed permeability and possible downstream explosions. This research investigated the agglomeration phenomenon within a nitrogen atmosphere. Four South African coals were used during the experiments and the coal was cut into sample blocks of roughly 8cm3. The coal samples were subsequently pyrolized under various temperatures. After pyrolization, the samples were photographed. Once the coal samples had been pyrolized, the degree of agglomeration was determined by performing a rough break test. The four coal types agglomerated at different temperature ranges, to varying degrees. The higher both the vitrinite content and volatile matter of a coal type, the greater the tendency to agglomerate. An important finding in support of the literature is the greater the tendency of a coal type to agglomerate, the greater the force needed to break the bond which formed during pyrolysis. The novelty of this research is embedded firstly in the technique which this researcher developed for assessing coals, and secondly in the fact that this technique was aimed at screening coals to determine propensity for causing problems in a gasifier.