关键词: 垃圾焚烧发电厂, 直接空冷, ITD优化, 变工况运行

Abstract: Direct air-cooled condenser(DACC) system poses great advantage on water-saving compared to wet cooling system. However, lower efficiency and higher initial investment remain critical bottleneck issues that need to be addressed. A scale of 2×750 t/d municipal solid waste incineration (MSWI) power plant with 45 MW turbine and generator unit in Central Asia was taken as an example, combined with thermal calculation, off-design conditions operation, and the maximum annual net power generation profit and profit of the whole life cycle method, initial temperature difference(ITD, namely the difference between the condensate temperature corresponding to exhaust pressure of the turbine and the design environment temperature) optimization, main design parameters selection and optimization method for DACC of waste incineration power plants were formed, in order to achieve the dual goals of harmless treatment of waste incineration and increase the net profit of the whole life cycle of waste incineration. Optimal ITD value of this project was obtained as 18.97 ℃ (design ambient temperature 35 ℃ and exhaust pressure 15 kPa), face velocity was 2.00-2.25 m/s and heat transfer area was approximately 3.15×105 m2. The research results showed that the increase rate of heat transfer area was sharply varied with the design ambient temperature and exhaust pressure when the design ambient temperature was higher than a certain value. And it also revealed that electricity sales price was one of the important factors of ITD and when it was at a higher level, it could increase the heat transfer area of condenser (that is, by choosing a smaller ITD value) to get maximum annual net profit and net profit of whole lifecycle. And the ITD value increased with the rise of the bundle price which was a significant ITD sensitive factor. Face velocity had a great influence on the heat transfer area and power consumption of fans and there was an optimal face velocity(2.00-2.25 m/s) to achieve maximum annual net profit. Compared with thermal power plants, ITD of MSWI plants was lower, and the design ambient temperature should be determined more closely in combination with typical annual meteorological parameters through ITD optimization and the design ambient temperature method for DACC recommended in DL/T 5339—2018 Code for Hydraulic Design of Fossil Fired Power Plant .

Key words: municipal solid waste incineration power plant, direct air-cooled condenser, ITD optimization, off-design conditions operation