Under normal circumstances, although the dust removal efficiency of the cyclone can reach more than 90%, the following problems still exist:

(1) The recovered fine-grain ammonium sulphate forms a scale layer on the inner wall of the dust collector, the fan and the air duct due to the easy moisture absorbing knot, and the thickness of the scale layer in the dust remover can reach 50 mm or more, which not only increases the resistance of the system, but also reduces the dust removal efficiency. The decline, and the wet sulfur ammonium corrosion of the steel plate is extremely serious, so the maintenance work of the dust removal system equipment is greatly increased.

(2) Because the quality of fine-grain ammonium sulfate recovered in the precipitator is difficult to meet the requirements of national standards, it can only be treated as an external product or recycled to the ammonium sulfate mother liquor.

2 Dust collector structure

In view of the problems existing in the cyclone dust removal process, since 1998, the wet dust removal process has been used to purify the exhaust gas discharged from the ammonium sulfate dryer.

The guide baffle in the wet scrubber makes the exhaust gas of the dryer contact with water when passing through the passage leading to the partition plate and the horizontal plane, and dissolves the fine-grained ammonium sulfate entrained in the water to purify the exhaust gas. In order to ensure that the resistance of the exhaust gas is not significantly increased, the pressure of the exhaust gas discharge port of the dryer is generally controlled to zero or a slight positive pressure, so that the fan after the dust remover can be taken, and the exhaust gas purification process is simplified.

The wet dust collector is synthesized from the body, the exhaust gas inlet and outlet, the drain pipe water inlet, the overflow pipe and the level gauge. The distance between the guiding partition and the water surface in the crucible body is determined according to the following principle. It is necessary to ensure that the exhaust gas can fully contact with water when passing through the exhaust gas to achieve the effect of water film dust removal, and the resistance of the exhaust gas passage is not significantly increased. An exhaust pipe that is upright is connected to the exhaust gas discharge port, and the suction force of the exhaust pipe is used to resist the resistance of the dust remover. The water supply port on the drain pipe is used when the sulfuric acid crystal deposition layer of the water drainer is used, so that it can be smoothly discharged into the sulfur ammonium mother liquor tank.

3 The effect of wet dust removal system

The above-mentioned improved half-year production practice shows that the dust removal effect of the wet dust removal system is good. The fine-grained ammonium sulfate in the exhaust gas of the ammonium sulfate dryer is almost completely absorbed by water, and the steel structure and the cement member near the exhaust gas discharge port are not corroded. When the bubbling bed is in normal operation, the pressure of the exhaust gas discharge port is 50-100Pa, the moisture index of the product ammonium sulfate is qualified, the drying operation is about 2h per shift, and the ammonium sulfate is produced 3~4t. When using the cyclone, each shift needs to be discharged. 30-80kg of waste ammonium sulphate, after switching to the wet dust collector, it is only necessary to put the water in the wet dust collector into the ammonium sulfate mother liquor tank every 4 days, and re-inject the water into the dust collector, the operation is extremely simple. After using the wet dust removal process for half a year, when the wind blind panel was opened, it was found that the thickness of the sulphur ammonium scale layer on the inner wall of the pipe was only 1-2 mm, and the cleaning work was very simple.

4 Conclusion

In summary, the production practice shows that the use of a wet scrubber instead of a cyclone to purify the exhaust gas from the ammonium sulfate mixed bed dryer simplifies the process and reduces the energy consumption. In operation, as long as the exhaust gas from the dryer remains in the micro Positive pressure will not adversely affect the normal operation of the fluidized bed.

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