摘要
本文以节能减排理念为指导,对青岛市某热电厂热电联产系统生产过程中的能量分级利用状况进行全面分析,科学评定系统能量损失分布,为实施系统节能改造提供依据。通过能量利用分析得出,该热电厂在供暖季节的全厂总热效率较高,平均在74%以上,而在非供暖季节,全厂总热效率急剧下降,最低时只有42.1%。
本文主要运用热力学第一定律和第二定律,根据热电厂记录的运行数据,定量计算全年每个月份的各项主要热经济评价指标和热电厂主要用能部位的能量损失,获得能量损失的关键部位是冷源损失。其中,7月份冷源损失占总的能量的百分数为58.1%,12月份冷源损失占总的能量的百分数为23.8%。针对热电厂夏季凝汽器真空降低,导致发电量减少的问题,完成热电厂冷端系统内凝汽器和冷却塔技术改造方案的理论研究与节能经济性论证。凝汽器内换热铜管改为不锈钢多向扰流强化换热管,增强了换热管的换热效果和抗腐蚀能力。冷却塔内采用PVC "S"波点滴薄膜式填料装置,增加了淋水面积,增强了冷却塔的冷却效果。
基于热电厂原来的热电联产系统,设计了采用溴化锂吸收式制冷机组的热电冷联产系统方案。夏季利用热电厂供热机组的抽(排)汽为热源,制取7℃左右的冷媒水集中制冷,增加了夏季热负荷和热化发电量,提高了热电厂夏季的热经济性,同时又节省了空调用电,降低电网负荷的峰谷差,提高电网经济性。夏季若实施热电冷三联产,系统总热效率将达到79.6%,较原来7月份热电联产系统的总热效率提高36.5%,系统的-次能节约率为45.8%。
Based on the guidance of energy conservation and environmental protection ideas, a comprehensive analysis of energy cascade utilization is made. The analysis is about the combined heat and power (CHP) system in the production process of a thermal power plant in Qingdao City. The energy loss distribution of the CHP system is scientifically evaluated, which provides the basis for the energy saving and reformation of the system. Through the analysis of energy utilization, a conclusion is drawed that the total thermal efficiency of the whole thermal power plant is relatively high in the heating season, averagely more than 74%; however, not in the heating season, the total thermal efficiency of the whole plant declined sharply, with only 42.1% at the minimum.
According to the operation data recorded of the thermal power plant, the first and second laws of thermodynamics are used to quantitatively calculate the major thermal and economic indexs of the twelve months. The energy loss quantity of the main energy using site in the thermal power plant is also calculated. On the basis of these, the key energy loss site is found, which is in the cold-end. The cold-end energy loss is 58.1% of the total energy in July, and that is 23.8% of the total energy in December. In the condenser, stainless steel heat-transfer enhancement tubes with multidirectional turbulent flow takes the place of brass tubes, enhancing the heat transfer effectiveness and corrosion resistance. In the cooling tower, PVC "S" wave ripple splash packings are used, which increase splashing water area and enhance the cooling effect of cooling tower.
In summer, the generated power reduces at a result of lower condenser vacuum. In order to solve the problem, an improving technical program about the condenser and cooling tower in the cold end is proposed. The program's argumentation on energy saving and economic efficiency is studied. Based on the original cogeneration system, a combined cooling, heating and power (CCHP) system with the lithium bromide absorption chiller is designed. In summer, the CCHP system uses the extracting and exhausting steam of heating unit as heat source to make about 7℃coolant water in concentrated cooling district. This increases heat load and the power generation capacity in summer, also improves the thermal economy. At the same time, the air-conditioning electric power consumption is saved and the difference between peak and valley power load is reduced. Grid economy is improved meanwhile. If the CCHP system is applied in summer, the total thermal efficiency of the system will reaches 79.6%, which is increased by 36.5% in comparison of the CHP system in July. The primary energy saving rate reaches 45.8%.
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