New Application of Clean Energy Heating in South China—— Successful Operation of Waste Heat Recovery Heating in Yaxi Town, Zunyi, Guizhou

Yaxi town in Zunyi is the old revolutionary town in Guizhou Province, and one of the "four famous towns in the north of Guizhou". Yaxi town has won many honors, such as the National Key Town, the Most Charming Town in China, the Best Case Award for Development and Innovation of the Town with Chinese Characteristics, Top 1000 Towns with Comprehensive National Strength, the Provincial Model Town, the Provincial Ecological Town and the Provincial Demonstration Town.

It is located in the upper reaches of the Yangtze River. From mid November to mid March of next year, the local temperature is around 1-10 ℃ all the year round. In the past, the traditional heating methods used by local residents were mainly domestic air conditioning, gas and natural gas, etc., which had high energy consumption, poor effect and low security. In order to further improve people's livelihood, deepen energy conservation and emission reduction, strengthen environmental protection, contribute green energy, and improve operation efficiency, Zunyi Yaxi power plant uses the waste heat of the power plant to provide heat sources for nearby residents and enterprises. As the first central heating project in Guizhou Province, the Phase I central heating project in "Sihengshuian" residential quarter in Yaxi Town, Bozhou District, Zunyi City, was officially completed and put into operation.

In traditional power production, some energy must be discarded as waste heat (cooling tower, flue gas and other ways to release to the natural environment). Through the transformation of combined heat and power, it captures some or all of the by-products used for heating. Hot water used to heat living areas is called "combined heat and power district heating"(CHPDH). Compared with the traditional single-generator, the fuel efficiency of CHP can reach 80% at most. Using the waste heat generated in operation is equivalent to obtaining additional benefits and reducing the cost of emissions. Through the technical transformation of waste heat recovery and heat pump technology, on the premise of not increasing the capacity of the unit and the amount of coal burning, the simultaneous improvement of thermal efficiency, heating capacity, energy conservation and environmental protection effect has been realized.

With rich experience in the application of cogeneration project, Accessen was invited to participate in the initial design of the whole project and the scheme evaluation of the heat exchange part.  Accessen had many field visits and technical exchanges for the project conditions for this project. As a pilot project of central heating in the south, the total construction area of Sihengshuian project is about 270000㎡. The heat source adopts the primary network steam delivered by Yaxi power plant as the industrial steam. The maximum temperature and pressure of the steam can reach 350 ℃ and 2.5MPa respectively. It is different from the traditional water –water plate heat exchanger in the north. In order to overcome the special requirements of high temperature, high pressure and water quality of steam in the project, Accessen provided the on-demand heat solution. We provided the design scheme of replacing the traditional water-water plate heat exchanger unit with the steam-water plate& shell heat exchanger unit, which was used to meet the heating demand of 180000㎡ for residents and businesses in four buildings (18 floors in each building). Plate and shell heat exchanger unit of Accessen is not only resistant to high temperature and high pressure, but also has lower energy consumption and better heat exchange effect compared with traditional tube heat exchanger. The user chose our on-demand heat solution, and then the heating cost of local residents was greatly reduced, the quality of life was improved, and the power plant would obtain better economic benefits, providing a better guarantee for environmental protection.