Abstract
An improved flexible solar-aided power generation system (SAPG) for enhancing both selective catalytic reduction (SCR) de-NOx efficiency and coal-based energy efficiency of coal-fired power plants is proposed. In the proposed concept, the solar energy injection point is changed for different power plant loads, bringing about different benefits for coal-fired power generation. For partial/low load, solar energy is beneficially used to increase the flue gas temperature to guarantee the SCR de-NOx effectiveness as well as increase the boiler energy input by reheating the combustion air. For high power load, solar energy is used for saving steam bleeds from turbines by heating the feed water. A case study for a typical 1000 MW coal-fired power plant using the proposed concept has been performed and the results showed that, the SCR de-NOx efficiency of proposed SAPG could increase by 3.1% and 7.9% under medium load and low load conditions, respectively, as compared with the reference plant. The standard coal consumption rate of the proposed SAPG could decrease by 2.68 g/kWh, 4.05 g/kWh and 6.31 g/kWh for high, medium and low loads, respectively, with 0.040 USD/kWh of solar generated electricity cost. The proposed concept opens up a novel solar energy integration pattern in coal-fired power plants to improve the pollutant removal effectiveness and decrease the coal consumption of the power plant.
Highlights
Coal is the primary energy source for electricity production, and this will continue for a long period in the future [1]
The thermodynamic cycle and energy equilibrium of the proposed solar-aided power generation (SAPG) based on the case unit is simulated using the EBSILON Professional software, which is widely used for the design, evaluation and optimization of power plants [21,22]
The following observations are obtained from Table 7: (1) In the proposed SAPG, the total collected solar energy in all loads is 24.5 MWth; (2) the utilization of 24.5 MWth of solar energy varies in different load; and (3) the heat transfer area of all heat exchangers is not large, which is reasonable and practical in engineering
Summary
Coal is the primary energy source for electricity production, and this will continue for a long period in the future [1]. As the major emitters of NOx , SOx , dust and CO2 , coal-fired power plant have negative effects on the environment. Using environmentally-friendly alternative energy sources is an effective way to reduce pollutant emissions. As a good fossil fuel replacement, solar energy has attracted great attention amongst the R&D and industry communities. Its instability, relatively low intensity and high investment nature constrain the commercial application of solar thermal energy. Integrating solar energy into coal-fired power plants, normally referred to solar-aided power generation (SAPG), offers better performance and lower cost [2]. SAPG was first proposed by Zoschak and Wu in 1975 [3].
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