Plasma–fuel systems for clean coal technologies

Abstract

This paper presents plasma technology for pulverised-coal ignition and improving energy efficiency of power stations. Plasma–fuel systems (PFS) were developed to accomplish this technology. PFS are a combination of pulverised-coal burners with arc plasmatrons. The main idea of the technology using PFS is to replace the traditionally used fuel oil for flame stabilisation and starting coal-fired boilers with the products of plasma chemically treated pulverised-coal. The coal–air mixture is fed into the PFS where the plasmatron induces heating, devolatilisation and gasification of the coal particles and partial oxidation of the char carbon. As a result, a highly reactive two-component fuel (mixture of combustible gases and partially oxidised char particles) is formed at the exit of the PFS. At the entry to the furnace, this highly reactive two-component fuel is easily ignited. PFS increase the efficiency of coal ignition and combustion, eliminate fuel oil expenditure for boiler start-up and flame stabilisation and decrease unburned carbon, nitrogen oxides (NOx), sulfur oxides (SOx) and vanadium (V) oxide emissions. PFS have been tested at 30 coal-fired power stations and steam coals of all ranks were used. The volatile content of steam coals varied from 4 to 50%; ash from 15 to 56%; and heat of combustion from 6700 to 25 000 kJ/kg.