Energy Consumption Research On SCR Benitrification System In Large-scale Goal-fired Power Plants

NOX is serious pollutant to humans and environemtna, and it has gained more and more attention, just as SO2pollutant. Selective Catalytic Reduction (SCR) technology is widely used in coal-fired power plants for NOx removal. SCR denitrification system process inevitably increases the energy consumption of power plant. Therefore, the systematic research of energy consumption of SCR denitrification system is veru important and necessary to control the operating costs of the power plant and to reveal the mechanism between energy consumption and NOx pollutant emission.The energy consumption of denitrification system can be divided into two categories:the first is the energy consumption variations caused by the introducing of SCR system; another is additional energy consumption by SCR devices. According to the above analysis, this paper mainly studies the energy consumption of major devices of SCR denitrification system, such as diluted fan, induced fan, and establishes model of energy consumption for these devices. As the result of above study, the additional coal consumption of these devices are calculated and assessed. Secondly, through chemical reactions and energy balance of equipments, energy consumption model of ammonia, and steam consumption model of the ammonia evaporator are established. As the result of above study, additional coal consumption of steam model in the SCR denitrification system through the heat rate transformation coefficient method is established.SCR denitrification system can effectively remove the nitrogen oxides in coal-fired power plants. However, SCR system will definitely has some influence on the operation of boiler, such as inlet temperature distribution of the air preheater and the boiler efficiency. This paper studies the heat balance of the SCR system to identify the flue gas temperature variation derived from reaction heat, dilution air, radiation of reactor and flue, and leakage of air. In addition, the heat loss of flue gas and boiler efficiency is also re-calculated in this paper.Based on the above discussion,600MW unit and1000MW unit are selected as the case study to validate the proposed heat balance analysis of SCR system. From the case calculation, the additional coal consumption of steam is about0.03g/kWh, and on the BMCR conditions, the additional coal consumption of power equipments is about0.5g/kWh, temperature variation of flue gas is less than2℃for SCR system, and variation of heat loss of flue gas and boiler efficiency caused by the SCR system is less than0.05%.