STUDIES OF A TWO-STAGE CYCLONIC COMBUSTION SYSTEM TO SIMULATE THE TIME TEMPERATURE HISTORY FOUND IN LARGE UTILITY BOILERS WHEN FIRING SOLID FUELS

摘要

This paper describes a work programme designed to evolve a 100kW simulator for large utility boilers, based on replicating the time temperature history of the large dry bottomed utility Boiler in a much smaller, portable unit. The rationale behind the work is the increased use of biomass/coal blends in Utility Boilers and necessity of obtaining cheaply, quickly and economically information on slagging and fouling propensities in different parts of the boiler. A further problem is that many materials being considered for use as co-firing fuels have site specific licenses for use, and hence can only be utilized on that site, thus requiring site tests. The evolved solution comprises a two stage cyclone combustion system, which because of the cyclonic flows can produce similar time temperature histories with a much smaller unit and allow the possibility of investigating slagging and fouling in critical boiler areas. The design is based on a first stage inverted cyclone combustor operated fuel rich to simulate the first stage of Low NOx burners, followed by a second stage cyclone combustor where secondary air is added to complete the combustion process. Slag and deposits are collected from a number of areas of the system and are analyzed in the laboratories of Cardiff University for a wide range of physical, morphological and chemical properties. These results are then compared to deposits and slags collected from full size Utility boilers to calibrate the system and ensure that results obtained are representative of those found industrially. The paper will discuss the development of the system and how it can be matched to different boiler systems