Technical and economic evaluation for clean heating using straw in rural area based on principle of value engineering

The proportion of clean heating in northern China is low, especially bulk coal is widely used in winter in some areas. The emission amount of air pollutants is large, so it is urgent to promote clean heating. By the end of 2016, the total heating area of urban and rural buildings in northern China was about 20.6 billion m3, of which the heating area of rural buildings was 6.5 billion m3. Heating energy mainly includes coal, natural gas, electric energy, geothermal energy, biomass energy, solar energy, industrial waste heat and so on. Among them, coal-fired heating area accounts for about 83% of the total heating area. About 400 million tons of standard coals are consumed annually, of which 200 million tons of standard coals are bulk coals mainly distributed in rural areas. In rural areas, the total usage amount of bulk coal is large, burning season is concentrated, the discharge is dispersed, and without purification measures, so the pollutant discharge is serious. China is rich in crop straw, with theoretical resources exceeding 900 million tons, and among them still about 200 million tons are not effectively utilized. The rural straw clean heating can build distributed clean hearing system in rural areas by collecting local raw materials, processing and transforming on the spot, and consuming nearby. This model could reduce open-air burning of rural straw, provide clean heat, and realize directly replacement of coal burning in terminal consumption link. The rural straw clean heating has a great development space. Heating using straw could promote straw comprehensive utilization, and also promote clean heating in rural areas in northern China. Based on investigation and summary of present situation of straw clean heating technology, this paper puts forward a typical rural straw clean heating model with good application prospects, establishes the functional evaluation index system, and evaluates the technical economy of seven typical models by using the value engineering principle and the analytic hierarchy process. The results show that, without considering the external conditions such as resource endowment, transportation, physical geography and level of economic and social development, the corresponding value coefficients of CHP(combined heat and power) heating, pyrolysis cogeneration household heating, bundle-fired boiler central heating, pyrolysis cogeneration central heating, briquette fuel household heating, bundle-fired boiler household heating and briquette fuel central heating are 1.062, 1.050, 1.005, 0.990, 0.973, 0.965, 0.956, respectively. Overall, cogeneration, pyrolysis, bundle-fired and other technologies show relatively good economy for clean heating of rural straw. This study can provide important reference for guiding R&D and application of straw clean heating technology in rural area.