The safety implication of low heating rate pyrolysis of coal/biomass blends in pulverised fuel boilers

Abstract

Abstract Low heating rate pyrolysis of coal/biomass blends may lead to accidental fires in fuel handling units (e.g. pulverisers) of typical pulverised fuel (PF) boilers. To investigate this phenomenon, blends of biomass and coal were pyrolysed at temperatures between 150 and 700°C in a static batch reactor at heating rates from 5 to 80 K/min. Compositions of the pyrolysis gases were determined under various heating regimes using standard analytical instruments. The major components of the volatile matter were identified as CO, CO2, H2, CH4, C2H6 and C3H8 as well as a low concentration of other hydrocarbon gases. Results obtained from this investigation indicated that as the pyrolysis temperature increased the percentage mass of solid char fell while gas and tar product rose. Blends of coals and biomass showed lower pyrolysis temperature than typical coals. This can be partly attributed to the thermal degradation of cellulosic contents of biomass which occur at lower temperatures. The heating rate was found to have a small effect on the product yield especially at temperatures between 500 and 700°C.