Application of Sewage Heat Pump Technology in Miyun Wastewater Treatment Plant

Abstract: The sewage heat pump project of Tanzhou Sewage Treatment Plant in Miyun County introduces the advanced technology and equipment from northern Europe and adopts the urban water source without any treatment as the water source heat pump technology, which transforms the low-level energy in the wastewater through the heat exchanger and the heat pump unit Become a high energy heating, cooling, supply hot water. Keywords: sewage heat exchanger heat pump economy Application of sewage heat pump technology to Miyun Sewage Plant By Yang haijing and luk Abstract: The sewage heat pump project of Miyun sewage plant, introduced the Northern Europe advanced technology and equipment .Adopting the municipal sewage without any treatment as heat source and heat sink, is the innovative technic that can transfer the low temperature energy of sewage water to high temperature energy through heat pump system for heating, air conditioning and hot water supply. Key word: sewage heat exchange heat pump economical efficiency I. Project Overview The Tanzhou sewage treatment plant in Miyun County is located at the beautiful Chaobai River and is the only sewage centralized treatment point in Miyun County. It handles nearly 24,000 m3 of sewage daily in Miyun County. Sewage water quality is stable, perennial temperature is 13 oC-15 o C. The factory has about 10000m2 buildings (office buildings, factories, garages, etc.), the use of untreated urban sewage as a heat source for the factory heating and partial cooling (only the office needs Cooling), and also for domestic hot water use. It uses sewage as a heat source when heating, and uses sewage as a heat sink when cooling. Due to adequate sewage treatment plant sewage supply, extraction and emission of heat to meet the needs of heating and cooling. The project is Miyun County Tanzhou sewage treatment plant coal-fired boiler room renovation project. As the original coal-fired boilers cause some atmospheric pollution each year, in order to meet the demand of environmental protection in Beijing, the heating system has been decided to renovate the heating system and no longer use coal. Therefore, both the heat-supply water and the cold water Source heat pump system. Sewage treatment plant transformation is divided into two parts, part of the transformation of office buildings, the other part is the transformation of plant equipment, office buildings are installed to the cooling fan heat pipe, the installation of equipment plant is better thermal performance Steel string radiator. Second, the system principle and design In winter, the sewage temperature of about 12-15 â„ƒ after the heat exchanger heat exchanger temperature is about 7-10 â„ƒ, the system to extract heat from the sewage as a water source heat pump unit of low temperature heat source into the heat pump unit evaporator , Heat pump condenser water as circulating water heating system, water supply and return temperature of 50-45 â„ƒ. In summer, the sewage temperature is about 14-18 â„ƒ after the heat exchanger heat exchanger discharge temperature of 19-23 â„ƒ, sewage away the heat in the system as a water source heat pump cooling water, heat pump evaporator water as a cooling System circulating water, water supply and return temperature of 7-12 â„ƒ. The heat pump has a heat recovery function to ensure the supply of domestic hot water while operating in winter and summer. User-side water supply separately through the manifold to each monomer floor. System winter, summer conditions by switching the station system to achieve the valve system. Third, the project focus and difficulties 1, the sewage heat exchanger Untreated sewage as a source of water for heating and cooling, water source heat pump is a way, due to suspended solids in sewage, sediment more dirt, and sewage pH greater , Easily produce corrosion on the heat exchanger, scaling, clogging and other phenomena, thus seriously affecting the heat transfer efficiency. Through experimental tests, the kinetic viscosity of urban primary sewage (15 â„ƒ) is about 40 times higher than that of clear water (15 â„ƒ, 1.14 Ã— 10-6ãŽ¡ / s), ie 4.56 Ã— 10-5ãŽ¡ / s. Such high viscosity , Corrosive and suspended material on the heat exchanger material, surface roughness and internal structure design have put forward high requirements. According to the investigation of the domestic heat exchanger industry, at present, there are few heat exchangers in China which can meet such harsh working conditions and are suitable for the price. Therefore, the Nordic relevant expert group which is ultimately involved in the project, Time study to determine the material of the sewage heat exchanger, using a variety of new materials and surface treatment technology to solve the problems of corrosion, clogging and scaling. The heat exchanger components purchased in Finland, Sweden, Denmark and other countries, and ultimately assembled by molding in Malaysia. Since the project was in operation for three years, the heat exchanger did not show any corrosion, clogging and fouling phenomenon, which basically met the need of normal operation of the sewage heat pump system. This proved that this heat exchanger is more suitable for the domestic wastewater quality in China. 2, grille sewage before entering the sedimentation tank through a coarse grille, to intercept the larger particles in the sewage floating and suspended solids, blocking the grid by manual removal. Sewage from the sedimentation tank and then through a fine grid to intercept small particles of sewage floating objects and suspended solids, intercepted grid slag about half an hour automatically transferred to the garbage pond. After two grilles filter, the size of the particles in the sewage float and suspended solids have been basically blocked, and then enter the sewage heat exchanger, so you can avoid heat exchanger clogging. Fourth, the measured data analysis The water source heat pump system from January 10, 2003 put into normal operation, experienced the coldest winter in Beijing in recent years, fully tested the performance of sewage source heat pump units. The unit is in good working condition in summer. In order to more accurately analyze the economy of the sewage source heat pump, we arranged full-time staff to keep a continuous record of more than two months at the equipment operation site and record the data every two hours, including the number of meters, temperature and pressure. Fifth, the project advantages 1. Environmental sewage source heat pump is the use of raw sewage as a source of cold and heat, energy conversion heating air conditioning system. The heating system eliminates the need for coal, gas, oil and other boiler room system, there is no combustion process to reduce greenhouse gas emissions of CO2 and other air pollutants; cooling water tower eliminates the need to avoid the cooling tower noise and mold Pollution. Do not produce any waste, waste water, waste gas and dust, make the environment more beautiful. 2. Energy-saving sewage heat pump unit available sewage temperature in winter is 11-15 â„ƒ, the sewage temperature is higher than the ambient air temperature is a good low temperature heat source; summer sewage temperature is 17-21 â„ƒ, the sewage temperature is lower than the ambient air temperature, Is a better heat sink. This temperature characteristic allows the sewage heat pump to operate 20% more efficiently than conventional air-conditioning systems. 3. Capital Savings The system also integrates heating, air conditioning and domestic hot water supply. - Set of heat pump system can replace the original heating boilers, refrigeration and air conditioning and hot water heating three sets of devices or systems, thereby increasing the economy. 4. Stable sewage temperature is relatively stable, the scope of its fluctuations is much smaller than the air changes. Is a good heat pump heat source and air conditioning cold source, sewage temperature is more constant characteristics, making the heat pump operation more reliable and stable, but also to ensure the system's high efficiency and economy. There is no air source heat pump in winter defrost and other difficult issues. 5. High degree of automation According to the system features, we choose four compressors of the unit, the system based on load fluctuations, automatically select the compressor start and stop, improve system efficiency; high degree of automation, the operation without special duties; management relative Easy, low unit maintenance costs; life of up to 15 years. VI Conclusion 1, sewage - water source heat pump thermostat has a water-saving, energy saving, environmental protection features, is the use of urban sewage heating, cooling air conditioning new situation, in line with the world's urban wastewater reuse and urban water problems. The adoption of this technology in Miyun County is of great significance for promoting the smoke-free counties and green eco-friendly counties in Miyun. 2, the use of untreated urban sewage as the source water source heat pump system in Miyun County, Tanzhou sewage treatment plant application success, marking the application of sewage source heat pump technology in our country another great development.