Design Of New Type Desiccant Wheel Dehumidification System Applied In Furnace-blast And Economic Analysis

Steel and iron industry is an important part of Chinese industry which characteristic is high-cost, high energy consumption and high pollution. Many energy-saving measures for production process of steel & iron industry are put forward and paid attention. But large amount of low grade thermal energy such as exhaust thermal energy of slag flushing water is ignored and few effective measures are taken to utilize it. A novel dehumidification method using two-stage desiccant wheel for blast furnace is put forward to overcome the shortcomings of lithium bromide absorption refrigerating dehumidification(LBARD) system such as huge energy consumption. Meanwhile, the desiccant wheel dehumidification and preheating(DWDP) system reactivates the desiccant wheel by taking full advantage of waste heat in the slag flushing water.Based on a steel plant in Nanjing, China, the technical feasibility of the new method was validated experimentally and demonstrated in detail under summer conditions. The result of the experiment shows that the humidity of the outlet process air could meet the requirement that less than 10 g/kg and the dehumidification efficiency is 46% under the standard condition.Physical and mathematic model of the rotary desiccant wheel were presented. A comparison between the simulation result and the experimental result from the reference and earlier experiment of this research was taken and the deviation of them was less than 10%. So the model is reliable to predict the dehumidification result. Then a comparison of dehumidification performance between the systems regenerated in parallel and in series which simulated by the model shows that the former has a better effect than the later one.The results indicate that moisture remove capacity reaches 8.7 g/kg which contributes to the improvement of steel production by 0.9% and coal is saved of about 2100 tons per year. Also the energy consumed by cooling tower of slag flushing water can be reduced 7.3%. All of these energy saved equates to 10.3 million RMB annually. A comparison of initial investment and operating cost between DWDP system and LBRAD system is carried out. The results show that the initial investment and operating cost of DWDP system is only 37% and 57% of present LBARD system, and the payback period is also shortened 66%.