An Experimental Study On The Feasibility Assessment Of High Capacity Unit With The System Of Limestone Injection Into The Furnace

Currently, because of the short supply of coal and the extremely high cost of the low-sulfur coal, the high-sulphur coal is used frequently at one power plant with 660MW Unit. As a result of that, when high-sulphur coal is used or the FGD system is unavailable, the amount of SO2 discharged by this 660MW Unit can not satisfy the requirement of environmental protection. In terms of this situation, the most direct method to solve this problem is expanding the capacity of original FGD system. However, this method is quite uneconomical and time-consuming, so, in order to conserve money and time and gain much higher desulfurization efficiency. This thesis provides one efficient way to solve this problem: adding a limestone injection system in the boiler. So, my job was studying the feasibility of this method through field test in 220t/h boiler.Fifteen working conditions including distinct Ca/S, boiler load, and the injection height of desulfurizer were studied in 220t/h boiler. Furthermore, the concentration of SO2 and exhaust gas temperature at the exits of duster were tested in the field test. The finding showed that the optimum Ca/S was about 2 and the number of desulfurization efficiency was from 45% to 74%. In addition, whether the temperature field in boiler fitted using desulfurizer was assessed at this subject. The finding was that the optimum temperature area where the AG-2 desulfurizer can meet high desulfurization efficiency distributes at 42⁵0m height of furnace. And then, after analyzing in the laboratory, the finding illustrated that specific resistance increased dramatically at 125℃and the estimated value of fly ash increased approximately 4%. Finally, the performance of fly ash was assessed in this subject. The finding was that the quantity of SO₃ and F-CaO in fly ash probably cannot met the requirement of GB/T1596-2005.In conclusion, adding a limestone injection system in the 660MW Unit contributes to ease the pressure of the environmental protection. But the bad effects on the quality of fly ash and the efficiency of electrostatic precipitators can not be ignored, which demand to take some measure to improve.