USE OF EXPANDER-GENERATOR UNIT AT CHP OF METALLURGICAL PLANT FOR PRODUCING ELECTRIC POWER AND INCREASING EFFICIENCY OF COMPRESSOR

The ability of saving energy in the production of compressed air is one of the most energy-consuming production in which much of the used energy is lost. The proposed technical solution is based on the united use of two energy-saving technologies. The first of them is the use of technological pressure drop of transported natural gas which lost irrevocably when it is throttled at gas control stations. The second one is air cooling before the compressor sections to reduce compression work. A scheme of a combined steam blowing and heat power plant of a metal manufacturer is proposed. In addition to a power and heat generating turbine and a two-section air compressor with a steamturbine drive, a two-stage expander-generator unit (EGU) producing electricity and cold is used. The thermodynamics of gas expansion processes in the expander is considered, the choice of a two-stage scheme is founded. The cold produced in the EGU is used to lower the air temperature at the inlet to the first and second sections of the compressor, thus reducing fuel consumption for air compression. Using the proposed scheme allows to reduce fuel consumption to the compressor drive, to use the heat of compressed air to preheat the transported gas before the steps of the expander and to generate additional electric power. At the same time, fuel is not used to generate electricity, and the heat of the cooled air is not discharged into the environment, therefore the plant operation is characterized by high environmental performance. The procedure for calculating of fuel economy when using the proposed scheme is given. The assessment has shown that the use of this scheme allows, under given conditions of calculation, to reduce fuel consumption at the combined heat power and steam blowing plant by 11.2 thousand tons of fuel equivalent per year, which is 0.84 %. The generated electric power of the EGU will be 5.3 MW.

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