复合制冷循环间接空冷系统状态分析与运行优化

发布时间：2018-05-03 00:38

本文选题：蒸汽动力循环 + 复间冷系统　；参考：《浙江大学》2014年博士论文

【摘要】：我国发电用一次能源以煤炭为主,主要分布于东北、华北、西北等“三北”地区,而这些地区水资源都紧缺,为解决以燃煤为主的蒸汽动力循环电站一次能源和水资源分布地理结构上的矛盾,空冷技术得到广泛应用。但传统空冷技术因冷却风温度和风量的变化幅值、频率都难以准确预报,进而导致空冷系统很难长时间维持在设计工况下工作,从而降低了其运行经济性。针对传统空冷技术的缺陷,复合制冷循环间接空气冷却系统(复间冷系统)被提出用作蒸汽动力循环电站的排汽冷却。针对复间冷系统的应用问题,本文主要进行了以下几方面工作：基于蒸汽动力循环和复合制冷循环的耦合关联及其制冷循环和朗肯循环的工作过程分析,本文通过环保性能、参数匹配、做功能力3轮严格比较筛选,作为自然物质的氨,从十多种单质制冷介质中脱颖而出,成为现阶段蒸汽动力循环电站复间冷系统制冷、做功和环保性能俱佳的首选介质。为对环境气温大幅度、高频率、随机性变化给复间冷系统运行经济性影响作出定量评估,本文采用虚拟复间冷与直冷的对比分析法,构建了复间冷机组运行于环境高温时段的热经济性转捩温度与环境气温的定量关联,继而以年累计输出电量最大为目标拟定了复间冷机组最佳设计背压的优选算法,同时提出厂址敏感性系数的定义及确定方法,揭示了厂址所在地环境气温分布对复间冷机组经济性的影响。基于复间冷系统的能量转化和传递过程机理,构建了整个复间冷系统的变工况模型。它们包括：仅工作于环境高温时段的制冷循环与汽轮机排汽压力互动的变工况计算模型,可实时定量给出压缩机功耗、环境气温、翅片通道入口迎面风速、排汽热负荷等主要影响因素对汽轮机排汽压力的影响；仅工作于环境低温时段的朗肯循环的变工况计算模型的主导变量选用膨胀机的输出功率,其主要影响因素有汽轮机排汽压力、工质过热度、环境气温、迎面风速、排汽热负荷等。基于复间冷系统运行于高温时段和低温时段的最佳真空特性,拟定了相应的复间冷机组最佳排汽真空和年累计发电量的实时算法,进而采用全生命周期法对比评估了虚拟复间冷机组和同地同型直冷机组的全生命周期环境排放和成本,可望为未来全面评估复间冷机组的经济、环境、社会效益奠定基础。为检验复间冷系统应用于汽轮机排汽冷却的可行性、有效性和可实施性,本文为此设计了复间冷制冷循环模拟试验系统。该系统通过冷凝/蒸发器串接耦合模拟排汽装置与制冷机,初步验证了复间冷制冷循环降低排汽冷凝温度的有效性；基于多因素的正交试验结果,获得环境气温、排汽热负荷与迎面风速对排汽冷凝温度的影响规律。为改善复间冷系统空冷散热器(空冷器)运行过程中因灰垢积聚而降低的传热性能,本文设计了一种以压缩空气代替高压除盐水的干式吹扫装置,提出了吹扫效果评价方法以定量评价灰垢热阻对排汽冷凝温度的影响。在某600MW直冷机组空冷器现场实验表明干式吹扫装置节能节水效果明显；并以空冷器运行期内因灰垢积聚和干式吹扫产生的经济损失之和最小为原则,提出一种空冷器清洁度优化管理模型,确定干式吹扫最佳清洗周期。
[Abstract]:The primary energy of power generation in China is mainly coal, which is mainly distributed in Northeast, North China, northwest and other "Three North" areas, and the water resources are scarce in these areas. The air cooling technology is widely used to solve the contradiction between the primary energy and the distribution of water resources in the steam power cycle power plant, which is the main steam power cycle. However, the variation amplitude and frequency of wind temperature and air volume are difficult to predict accurately, which leads to the difficulty of maintaining the air cooling system working in the design condition for a long time, thus reducing its operating economy. In view of the defects of the traditional air cooling technology, the compound refrigeration cycle indirect air cooling system (complex intercooling system) is proposed as a steam power cycle electricity. The exhaust of the station is cooled.
In view of the application of complex intercooling system, the following works are carried out in this paper.
Based on the coupling relation of steam power cycle and compound refrigeration cycle and the working process analysis of the refrigeration cycle and the Rankine cycle, this paper strictly compares the environmental performance, the parameter matching and the work ability 3 rounds. As the ammonia of the natural material, it stands out from the more than 10 kinds of refrigerating medium and becomes the steam power cycle power station at the present stage. The complex medium cooling system is the preferred medium for refrigeration, good work and environmental protection.
In order to make a quantitative assessment of the economic impact of the complex intercooling system operating on a large scale, high frequency and randomness, a quantitative correlation between the transition temperature of a complex intercooled unit and the ambient temperature is established by the comparative analysis of virtual intercooling and direct cooling. The optimization algorithm for the best design back pressure of the complex intercooled unit is formulated as the target of the maximum quantity of electricity. At the same time, the definition and determination method of the sensitivity coefficient of the site are put forward, and the influence of the ambient air temperature distribution on the economy of the complex intercooled unit is revealed.
Based on the mechanism of the energy conversion and transfer process of the intercooled system, a variable working model of the whole complex intercooled system is constructed. They include the variable working model of the interaction between the refrigeration cycle and the steam turbine exhaust pressure working in the high temperature period of the environment. The power consumption, ambient temperature, and the entrance to the inlet of the fin channel can be given in real time. The influence of main factors such as speed, exhaust heat load and other factors on steam turbine exhaust pressure; the leading variable of the variable working condition calculation model of the Rankine cycle working in the ambient low temperature period selects the output power of the expander. The main influencing factors are steam turbine exhaust pressure, overheating of working fluid, ambient air temperature, front wind speed, exhaust heat load and so on.
Based on the optimum vacuum characteristics of the intercooling system running at high temperature and low temperature period, the corresponding real-time algorithm for the optimal exhaust vacuum and annual accumulative power generation of a complex intercooled unit is proposed. The whole life cycle environment emission and cost of the virtual complex cooling unit and the same type direct cooling unit are compared and evaluated by the full life cycle method. It is hoped that it will lay a foundation for the comprehensive assessment of the economic, environmental and social benefits of the secondary cooling units in the future.
In order to test the feasibility, effectiveness and feasibility of the application of the complex intercooling system to the steam turbine exhaust cooling, this paper designed a cycle simulation test system for the complex intercooling refrigeration cycle. This system has verified the effectiveness of the reduction of the exhaust condensing temperature by the cascade coupling of condensing / evaporator coupling and the refrigerating machine. Based on the orthogonal test results of multiple factors, the effects of ambient temperature, exhaust heat load and head-on wind speed on exhaust condensing temperature are obtained.
In order to improve the heat transfer performance of air cooled radiator (air cooler) in the operation process of air cooled radiator (air cooler), a dry sweeping device with compressed air instead of high pressure desalting water is designed in this paper. The effect of blowing effect evaluation method is put forward to evaluate the effect of gray scale thermal resistance on the condensing temperature of exhaust gas. In a 600MW direct cooling unit The field experiment of air cooler shows that the effect of energy saving and water saving is obvious in the dry cleaning device, and the optimization management model of air cooler cleanliness is put forward in the operation period of air cooler, and the optimum cleaning period of dry sweeping is determined.

【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TM621

【参考文献】