INCREASE OF COMBUSTION EFFICIENCY OF ORGANIC FUELS IN COMBINED STEAM AND GAS POWER PLANTS

Abstract

Ukraine's thermal energy is in critical condition due to the wear of technological equipment and huge emissions of harmful substances to the atmosphere, while the combined power system of the state is characterized by a significant shortage of maneuver capacity. Combustion of organic fuel in existing boiler units, manufactured in the middle of the last century, is inefficient due to the formation of nitrogen oxides. The reaction of their formation is endothermic, which leads to decrease of flue gas temperature, causing decrease of efficiency of the entire power unit. In order to correct the existing situation, it is proposed in this article while retrofitting existing TPPs, which will have to be implemented, use combined steam and gas power plants, where traditional steam method of electricity generation is combined with gas generation. It is shown that the gas unit of the power plant can work on low-quality coal gasification products. It is expedient to carry out gasification in the additional furnace, where a part of the powdered coal is supplied, the additional furnace itself consists of two-walls and compressed air enters the space between the walls for heating and formation of the gas turbine working environment. At this stage, the excess air ratio is slightly less than the stoichiometric amount required for complete combustion. In order to increase the efficiency of combustion in the main and additional furnaces oxygen enriched air is used. To enrich the air with oxygen, it is reasonable to use membrane technologies that provide two to three times higher oxygen content compared to currently used combustion technologies. As far as oxygen-enriched fraction is used in the combustion process, it reduces the amount of so-called atmospheric nitrogen oxides. The nitrogen fraction is utilized in the gas cycle of electricity generation. Such a combined steam and gas power plant has a much larger range of power variations, that is, it is more maneuverable, the speed of power ascension increases – it becomes more mobile, and due to the use of membrane air separation technologies, the amount of formed nitrogen oxides is reduced. The temperature of the flue gases increases which improves the efficiency factor, as well as the amount of flue gases at the flue outlet is reduced.