On the problem of environmental safety in heat power engineering on the basis of solar-fuel technologies

Full text: The fuel-and-energy complex is the basic source of hotbed gases in Republic Uzbekistan. Present time there are 2 292 boiler-houses in the sector of heat power engineering. Its use as fuel about 86 % gas's volumes of total quantity. The 14,0 billion cubic meters of natural gas is spent for necessities of household sector per year. In Uzbekistan total gas production is 42,0 billion in cubic meters per year.The efficiency of existed boilers is low (75 %), that leads to the considerable over-expenditure of fuel. The operative equipment of boiler-houses of the centralized heat supply and the technological equipment at heat power engineering centrals on its technical characteristics don't respond to the modern economic and ecological requirements. When 1 ton of conditional fuel burns in boilers about 30 kg of polluting substances are thrown out to the atmosphere. Total emissions are over 100 million ton of hotbed gases for this sector. The heat supply of micro districts of Tashkent city is maintained from 147 boiler-houses of various capacities. Existing now in republic centralized heat supply systems are realized on the scheme of open water distribution, i.e. the systems of building's heating are attached directly to thermal networks through the mixing devices. The limitations of natural gas to objects of the heat power engineering system, predicted further increases of cost of natural gas predetermine the creation of the combined fuel-solar boiler-houses. The use of solar energy allows lowing fuel expenses. Earlier such projects have been realized in boiler-houses 'Vodnik', 'Mashinosozlar-2' in Tashkent city. For re-equipment of existing boiler-houses it is enough to execute two inserts in the pipeline of chemically cleaned water for connection geliofield which consists from solar water-heating collectors and intermediate heat exchangers. In Tashkent's existed geliofields solar energy is used for preheating water from 20 † 250 degrees till 40 † 500 degrees, and other stages the technological process of heating water is realized in boilers. The coefficient of replacement the geliotechnical part's producing in a solar-fuel boiler-house at given technological scheme is equal φ=(40-20)/(65-15)=0,4 in summer season. It is possible to increase the replacement of burned fuel in a boiler-house by energy produced in geliotechnical part. Necessary using solar energy at the stage of preparation of initial cold water before the chemical water purification block. This is also provided the most thermo neutral operating work of solar collectors in relation to the ambient temperature that decrease it's thermal losses. In this case the coefficient of replacement φ will be equal 0,6. The offered scheme also allows increasing the duration of the operation of gelio system in a boiler-house, which for the traditional scheme covers the period from April till October. At environmental conditions of March and November, when it is possible to heat up the heat-carrier in solar collectors until 20-250 degrees, it is probably switched to use the gelio system only for heating of initial water in the following heat exchanger. The further development of the combined solar-fuel technologies in heat supply systems has real prospects as for decreasing the burning of fuel volumes in boiler-houses and the improvement of ecological situation in republic. (authors)