Abstract: In respond to the energy conservation and emission reduction policy，and to meet the local heating demand and adapt to the emerging profit model of flexible peak shaving for coal-fired power plants，a low-pressure cylinder zero-output transformation was taken on a 135 MW coal-fired unit in northern Shanxi Province.The low-pressure cylinder zero-output technology can realize thermo-electric decoupling in small and medium-sized coal-fired power units，and its performance on improving heating capacity and flexibility of the units was analyzed.The results show that low-pressure cylinder zero-output transformation makes small and medium-sized coal-fired power units safe and controllable since it can solve rotor blade water erosion，blade surging，heating of blast and freezing prevention of air-cooled island.The low-pressure cylinder zerooutput scheme is of prominent economic advantage，as it reduces the total investment by about 550 000 yuan，and increases the power generating capacity and income per heating season by about 70.23 million yuan，respectively.The conclusion can be used as a reference for the design of similar units.

Key words: heating transformation, low-pressure cylinder zero-output technology, thermo-electric decoupling, air cooling island, smooth shaft, energy saving and emission reduction, district heating, peak-load regulation