大型燃煤机组供热改造技术的工程应用

  目的  集中供汽的普及促使许多大型燃煤电厂开展了一系列供热改造，如何经济合理地选择供热改造技术是行业和企业普遍关注和深入研究的重点。  方法  文章以某电厂350 MW抽凝机组实施中压蒸汽供热改造为例，通过供热改造技术方案比选、水力计算分析来确定改造的技术路线。  结果  分析结果表明压力匹配器方案受机组抽汽参数和运行工况的限制，在机组低负荷时引射效率过低；水力计算结果表明在极端工况下机组供汽温度偏低，通过设置双供汽母管降低散热损失的方法仍不能满足要求，因此采用减温减压器并设置掺混蒸汽的方式进行供热。  结论  供热改造技术方案应根据机组运行条件、各项技术的特点，对比节能效果、投资大小、系统复杂程度等多方面因素后确定。对于存在不满足供汽温度要求的情况，可采用设置双母管系统，低流量时只通过一根母管供汽，可降低散热损失约30%；如仍不能满足温度要求，则可采用高温蒸汽掺混方案提高供汽初温以保证供热的可靠性和安全性。

Engineering Application of Heating Transformation Technology for Large Coal-Fired Units

  Introduction  The popularity of centralized steam supply has prompted many large coal-fired power plants to carry out a series of heating transformation. How to choose the heating transformation technology economically and reasonably is the focus of the industry and enterprises.   Method  In this paper, a 350 MW extraction-condensing unit in a power plant was used to implement medium-pressure steam heating renovation as an example, and the technical route of the renovation was determined through the comparison and selection of heating renovation technical schemes and hydraulic calculation and analysis.   Result  The analysis results show that the injection efficiency of the pressure matcher scheme is too low at low load due to the limitations of steam extraction parameters and operating conditions of the unit; The hydraulic calculation results show that under extreme conditions, the steam supply temperature of the unit is low, and the method of reducing heat loss by setting double steam supply header still cannot meet the requirements. Therefore, the method of temperature and pressure reducer and setting mixed steam is used for heating.   Conclusion  The technical scheme for heating transformation shall be determined after comparing the energy-saving effect, investment size, system complexity, and other factors according to the operating conditions of the unit and the characteristics of various technologies. In case of failure to meet the requirements of steam supply temperature, a double header system can be set. When the flow was low, only one header was used for the steam supply, which can reduce the heat dissipation loss by about 30%. If it still cannot meet the temperature requirements, the high-temperature steam mixing scheme can be adopted to improve the initial temperature of the steam supply to ensure the reliability and safety of the heating.