Studies of Fuel Blend Properties in Boilers and Simulation Rigs to Increase Biomass and Biowaste Materials Used for Cofiring in Pulverised Coal Fired Boilers
Project Number 238
This project seeks to develop an integrated package of measures, which will allow to develop methodologies to allow operators of large coal fired Utility boilers to increase the use of diverse biomass fuels co-fired in existing boilers, thus reducing emissions of greenhouse gases.
Although co-firing of biomass and bio-wastes has been practised in a number of plants, the practice is not widespread, a recent survey showed that only 29 out of 353 power plants surveyed employed any form of co-firing, less than 2 % of the potential level of waste co-incineration envisagable under the German Clean Air Act.
Barriers to substantially increased co-firing arise from a number of technical, economic and emission related factors. A critical technical factor identified is the effect of the co-fired fuel on slagging, fouling and deposition in the system, resulting effects on heat transfer and subsequent effects on clean up systems and final emissions. There are no models or techniques at the moment which allow an operator of a large utility boiler to ascertain whether particular form of biomass material or waste can be successfully co-fired without causing serious damage to the various heat transfer surfaces via slagging, fouling or deposition. This arises because the ash from these materials acts in a different way to those from coal and indeed when such materials are used in blends with coal totally unexpected results can occur, extending these effects to the final clean-up systems. This often limits the quantities of materials which can be co-fired with coal and results in a substantive barrier to their utilisation.
Technically the proposal seeks to develop and extend an integrated approach to dealing with these problems by a co-operative work programme between a number of Universities, a major research laboratory and a group of utlity operators, who wish to increase their use of co-firing.
The core of the work involves the use of several laboratory and pilot scale rigs, which provide different experimental information concerning the behaviour of the fuel blends in different temperature/ residence time/ atmospheres/ particle dynamic situations as representative as possible to those occurring in real large utility boilers. Complimentary modelling work will be undertaken so as to be better able to describe the processes occurring both in the rigs and in large boilers. The new methodologies which will be derived, arising from the integrated approach and complimentary nature of the information obtained will enable an increased level of substitution via co-firing, whilst allowing more utility plants to use co-firing.
The project is carried out from January 2003 to June 2005 by an international consortium consisting of ten partners (Utilities, University and Research Institutes, VGB PowerTech).