石灰低温烟气脱硫的研究

LQW TEMPERATURE FLUE GAS DESULFURIZATION WITH LIME

防治燃煤锅炉烟气中的SO_2,是中国环保工作的一项迫切任务.在多种烟气脱硫过程中,炉内喷钙工艺由于投资少、成本低等优点,受到了中国各界的广泛注意,但其脱硫效率较低,吸着剂的钙利用率不高,废吸着剂中还含有很多未反应的CaO,形成大量碱性含钙灰渣需要处置,故影响了其商业应用.作者为此进行了CaO低温吸硫的研究.采用的方法是在增湿器内使CaO与适当大小的水滴相撞,将CaO转化为有活性的Ca(OH)_2,加速它与SO_2的反应.在中试装置上(能力1000m^3/时烟气),用专门研制的双流体喷头进行多参数试验(喷水量、气/水比、停留时间)的结果为:在SO_21500ppm,Ca/S为1.5,停留时间为2.3、3.5、7.0S条件下,最佳脱硫率可达26.9%、32.0%、47.3%;而在SO_22500ppm,Ca/S为2.5,停留时间为7.0S条件下,最佳脱硫率可达69.1%.如与炉内喷钙脱硫合并计算,脱硫效率总和可达74%-85%.预计左工业装置上,由于增湿器可采用大的长径比结构并可安设多个喷头组成喷雾系统,吸着剂及水滴分布可较中试有所改善,脱硫效率可在上述水平上进一步提高.如再计及在除尘装置上处于附着状态的吸着剂继续进行的硫吸收,总的脱硫放率将达到新的水平.

One of the urgent tasks of China's environmental activists is to control flue gas SO_2 from coal-fired boilers. Many FGD technologies are available on the market, in which the Limestone Injection Technology, due to low capital and operational costs, has aroused much interest in China, but the commercial application is retarded because its SO_2 removal is still low, and the spent sorbent contains a lot of unreacted CaO which causes difficulty in disposal of the alkalinic ash and residue. Aiming at solving this problem, the authors conducted research on low temperature FGD with CaO. Water is nefulmized into droplets of appropriate sizes. They collide with CaO and convert the latter into Ca(OH)_2 which then react with SO_2. Parametric tests (injected water rate, residence time, air/water ratio) on pilot scale facility with specially designed twin fluid nozzle reveal sthat, at SO_2 concentration 1500 ppm, Ca/S=1.5, residence time 2.3, 3.5, and 7sec., the optimum SO_2 removal is 26.9, 32.0, 47.3% respectively; at SO_2 2500 ppm, Ca/S=2.5, residence time 7 sec., the optimum remoral rises to 69.1%. In combjnatio with in-boiler removal, the overall removal could reach 74-85%. In commercial installations where humidifier with larger height/diameter ratio and arrays of multiple spray nozzles could be installed, better distribution of sorbent and water droplets would be achieved resalting in better SO_2 removal than what has been achieved in this pilot test. Besides, considering the fact that sorbent collected by particulate control system continues to adsorb SO_2, it can be anticipated that the overall SO_2 removal would be even better. Further work will be conducted to verify this prediction.