Research On The Technology Of Waste Heat Depth Recovery Of Low Temperature Flue Gas Of District Heating Industrial Boiler

Energy is important in the development of human society. Currently, the world and China’s are facing shape energy form. There are large amounts of energy wasted in our production and life. Particularly industrial energy consumption is very great. Potential waste heat also is great to recover. Based on the situation that temperature of coal-fired industrial boilers flue gas is too high, this paper aims to solve the problem that heating surface is corroded when temperature of flue gas has dropped below the acid dew point. This paper plans to develop a set of heat exchanger using fluoroplastic as material of flue gas waste heat recovery system, to further reduce exhaust smoke temperature, and to improve energy efficiency and realize the purpose of energy saving and emission reduction.The characteristics of gas from coal-fired boiler are analyzed in this paper. In view of the problem of flue gas acid corrosion and fouling, the suitable way of waste heat recovery and where to use are chose. A plan of waste heat recovery is designed that chooses fluoroplastic to be the main material of heat exchanger. Through heating surface at the end of boiler, flue gas flows in the dust remover and most of the dust is removed. After the draft fan, flue gas comes to the tube bundle of heat exchanger, and heat the water inside the tube bundle. At the same time, the temperature of the flue gas is reduced to under the acid dew point. A lot of heat is recovered and the flue gas enters the desulfurization tower, and is let out through the chimney.Before the calculation of heat exchanger, according to the characteristics of fluoroplastic material, the feature of using fluoroplastic pipes as the main body of the heat exchanger is analyzed and designed. In order to give full play to the advantages of fluoroplastic material about the good performance in chemistry, stable performance of surface. Small diameter and thin wall and large number of the pipes is chose to make up for the defect of its poor thermal performance. According to the characteristics of the material, several limits are put forward to determine the basic structure and the way of heat transfer.Heat transfer calculation of fluoroplastic heat exchange is conducted. Temperature of the fluid of important export is determined by the limit of system and requirements of technology. Log mean temperature difference method is adopted to calculate the heat transfer amount, Log mean temperature difference and heat transfer coefficient on either side of the flue gas and water. Because heat transfer calculation formula about fluoroplastic pipes is unfamiliar, this paper selected a part of the tube bundle of heat exchanger to conduct simulated calculation, aim to get the heat transfer characteristics, and to compare with the results of calculation. The overall structure of the heat exchanger is designed. Finally, the heat transfer performance of heat exchanger and structure size is confirmed.