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.