Operation experience of ammonium sulfate production in spray saturator

Thread Content

The operating experience of spray saturators to produce ammonium sulfate has been improved (Coking Plant of Taigang Group Linfen Iron and Steel Co., Ltd., Linfen 041000) The ammonium sulfate section of the secondary chemical production workshop of Linfen Iron and Steel Co., Ltd. of Taigang Group adopts the spray saturator production process. The gas from the desulfurization section enters the saturator through the preheater. It is divided into two streams in the upper section of the saturator and enters the annular chamber. After being sprayed by the circulating mother liquid, the gas is synthesized into one stream and enters the back chamber to be sprayed by the mother liquid. Then it enters the acid remover in the saturator to separate the acid mist entrained in the gas. The gas is finally sent to the final cooling benzene washing section. The mother liquor in the upper part of the lower section of the saturator is pumped to the annular chamber for spraying by a circulating pump. The circulating mother liquor flows from the central down pipe to the bottom of the lower section of the saturator, and the bottom slurry is sent to the crystallization tank using a crystallization pump. The mother liquor overflowing from the full flow port of the saturator goes into the full flow tank, and is sent to the back chamber of the saturator with a small mother liquor pump for spraying. When replenishing water and adding acid, the excess mother liquor passes through the full flow tank to the mother liquor storage tank, and then is pumped to the saturator with small mother liquor. After the slurry in the crystallization tank is initially dehydrated by the centrifuge, the ammonium sulfate crystal is sent to the fluidized bed dryer by a conveyor. The air blower heats the air through the heater and enters the two air chambers of the main machine. The moisture in the upper chamber is discharged into the atmosphere through the dust collector and the induced draft fan. 1 Causes and solutions for increased resistance in the gas system 1.1 Causes and solutions for high resistance in the preheater In order to prevent the mother liquor from entering the preheater, the large mother liquor was pumped into the spray pipe of the front room and a blind plate was blocked during commissioning. However, after 3 to 5 months of use, the resistance of the preheater still increased from 500Pa to 3000Pa, so the saturator was forced to be used for maintenance. When dismantling the preheater for maintenance, the large mother liquid pump was turned on with the saturator inlet open, and it was found that liquid splashed outward from the nozzle of the annular chamber. During normal production, the mother liquid would splash into the gas inlet pipe and enter the preheater. In this regard, the directions of the two nozzles closest to the gas inlet of the annular chamber are reversed, that is, the gas is changed from counter-flow to downstream, and the nozzles are bent down at a certain angle to avoid collision with the liquid sprayed by the second nozzle. After the transformation, the resistance of the preheater has stabilized at 500-1000Pa, and the ammonia content of the gas behind the preheater has remained at 30-58 mg/m3. 1.2 The instantaneous amount of scarred gas in the gas pipeline at the outlet of the saturator sometimes exceeds the design capacity of the saturator (35,000 m3/h) and reaches 40,000 m3/h, and the saturator is not operating normally, causing the full flow pipe to be blocked. The mother liquid is brought into the gas outlet pipe, causing scarring in the pipeline, and the resistance reaches 4 kPa, forcing the saturator to be shut down for maintenance. In this regard, a system of adding acid every other day has been formulated, that is, adding acid once every 2 days. After discharging until the crystal ratio is the minimum, add acid to 7% to 8%, cycle for 0.5 to 1.0 hours, open the flushing water door one by one for flushing, and the excess mother liquor enters the mother liquor storage tank. By controlling the gas temperature after the preheater, the mother liquor in the mother liquor storage tank can be pumped into the mother liquor circulation system for digestion in one day. Open two DN400 inspection holes at the two elbows of the gas pipeline at the outlet of the saturator. When the resistance of the saturator is found to increase, open the inspection holes for inspection and flushing. After taking the above measures, the saturator resistance can be stabilized at 1~2kPa. 2 Causes and treatments for flying materials at the induced draft fan outlet when ammonium sulfate is discharged 2.1 The automatic discharge valve of the cyclone separator does not work. The lower part of the cyclone separator is equipped with an automatic discharge valve. In this regard, the automatic discharge valve was removed and replaced with an "8" blind plate, and the accumulated material in the cyclone separator was regularly released during discharging. 2.2 The screen surface of the fluidized bed dryer is scabbed and clogged. Since the material after drying by the centrifuge contains high moisture, the screen surface of the fluidized bed dryer is prone to scabbing and clogging, which causes the induced draft fan to increase the suction force of the system behind the dryer and cause flying materials. Regularly clean the fluidized bed drying machine. After manually removing the accumulated material on the screen surface and bottom plate, open the manhole on the bottom plate, rinse the screen surface with an appropriate amount of industrial water, and the water flows out from the manhole. In order to ensure that the inside of the dryer is dry when discharging materials, turn on the induced draft fan, air supply fan and air heater after flushing, and use hot air to dry the inside of the dryer. In addition, in the regular maintenance of the saturator, the annular chamber nozzle gasket is listed as a maintenance item. Since the nozzle gasket of the annular chamber of the saturator is made of acid-resistant rubber plates, it can easily be damaged when the outlet of the large mother liquor pump is flushed. If the pressure of the mother liquid at the nozzle of the annular chamber is not guaranteed, the ammonia content in the gas after the saturator will exceed the standard. In order to ensure the flow rate of the small mother liquor pump, the nozzle core in the back chamber of the saturator is removed, which solves the problem of frequent blockage of the nozzle in the back chamber and difficulty in ensuring the flow rate of the small mother liquor pump.