If CO2 shall be captured from the flue gases of coal fired power stations for subsequent dumping, a viable technology should be available also for retrofitting existing conventional pulverized coal fired power stations.
The objective is to investigate the potential for the use of recycled flue gases and oxygen injection in a large scale atmospheric coal burner designed to produce combustion products which are more suitable for treatment in carbon dioxide reduction processes.
The main issues associated with retrofit conversion of an existing coal-fired boiler were identified, including boiler start-up and change-over, retrofit changes to boiler configuration and equipment, and air leakage into the furnace. This last was found to be the most significant practical obstacle to successful oxygen/flue gas recirculation operation. Ultra low air ingress levels are needed to maintain CO2 concentrations high enough for efficient operation of the flue gas liquefaction process. Existing balanced draught boilers cannot deliver such low ingress levels unless they are modified to pressurised furnace operation, which would cause significant financial and technical repercussions. Overall thermal efficiency was predicted to fall from 37% for a conventional system to 23%, mainly because of the power consumption of the oxygen separation and CO2 liquefaction plants.
The combustion of fossil fuels is one of the main sources of global atmospheric pollution. Improvements in air quality have been achieved by using a combination of low NOx burners, catalysts, flue gas
desulphurisation and cleaner fuels. Looking forward towards a cleaner, less polluting environment, attention is now concentrated on reducing the emissions of gases which contribute to global warming.
The combustion of pulverised coal for large scale power generation will continue for the foreseeable future and this project will study the opportunities for reducing pollution from existing atmospheric systems. This project will examine the combustion of pulverised coal in an atmosphere of recycled flue gas with oxygen injection and measurements will be taken of efficiency, pollutants and suitability for installation in a wide variety of burner sizes in existing large scale boilers. Particular attention will be given to ensure that new pollutants, such as those produced by combustion at low temperature, are minimised.
The investigations will commence on small scale flames, a burner will be specifically developed using a combination of mathematical and physical modelling techniques. The performance of the small flame will be measured in detail and information obtained on the chemical species produced in both the near burner region and those emitted from the furnace outlet. Sufficient data will be gathered to ensure that the additional routines needed in the mathematical code will be validated and be used to scale up the burner to ten megawatts. This large scale burner will be evaluated on the combustion test facilities at Derby.
Funding SchemeCSC - Cost-sharing contracts