The front of the cement kiln dust collector in a cement plant is generally equipped with equipment such as a humidification tower and a waste heat boiler. Acidic components and low-temperature condensation in the exhaust gas are the main reasons for the internal corrosion of the kiln tail dust collector.

In recent years, most factories have added SNCR denitrification device and cement kiln co-processing facility to the process system. The addition of these two process facilities has brought corrosive gas to the system, increased humidity, and aggravated the kiln tail dust collector. Internal corrosion affects the stable use of the system.

In short, air leakage and condensation on the body, escape of SNCR denitrification ammonia, and co-processing of solid waste in cement kilns are the main reasons for the internal corrosion of the kiln dust collector.

Air inlet:
The part of the pipe near the inlet of the dust collector is mainly large particle dust. After entering the dust collector, it is mainly impact and abrasion. Due to the fast flow rate here, there is no condensation and corrosion, so it is necessary to check the wear condition.

Middle box filter area:
The outside of the middle box of the dust collector is provided with an insulating layer. After the flue gas enters the middle box, the pipe diameter further increases, and the flow rate of the flue gas further decreases, and the dust with a relatively larger particle size also falls under the action of gravity. At this time, the flue gas The degree of abrasion to the equipment surface is reduced. At this time, the temperature of the flue gas is also slightly lower than that at the inlet.

Here, the quality of the external insulation layer of the middle box of the dust collector determines its corrosion status. If the thermal insulation layer here is intact and meets the thermal insulation requirements, the internal temperature will remain above the dew point of the flue gas, and there will be no condensed water at this time, so there is almost no acid-base corrosion. If the thermal insulation layer here is damaged, soaked in water, or the thermal insulation effect declines for a long time and the thermal insulation design requirements are not met, the internal temperature will be below the dew point of the flue gas, and condensed water will be generated at this time, local corrosion will occur, and the thermal insulation layer will fail. The larger the area and the more condensed water, the more serious the corrosion.

The anti-corrosion here can be started from two aspects: the external insulation layer of the middle box and the internal anti-corrosion coating.

Upper box clean air chamber：
As the flue gas is filtered through the cloth bag and enters the clean air chamber, the dust in the flue gas is stripped away and only gas remains. Due to the normal temperature air entering the filter bag, it will exchange heat with the flue gas in the clean air chamber, which will reduce the overall temperature of the flue gas in the clean air chamber, especially the temperature of the surface of the recoil pipe and the connection between the recoil pipe and the dust collector. It will be greatly reduced to form condensed water. The condensed water absorbs cement dust to produce lye, and absorbs sulfide in the flue gas to produce acid, which will cause acid-base corrosion. Here, acid-base corrosion is a serious part of the entire dust collector.

Therefore, the clean air chamber of the upper box is mainly used to prevent the acid and alkali corrosion of the condensate. It must meet the long-term resistance to acid and alkali corrosion at the same time, and has excellent permeability resistance and certain wear resistance.

1. Effective use of suitable anti-corrosion coatings is a good solution. A reasonable anti-corrosion coating can not only isolate the direct contact between air and water and the inner surface of the steel in the kiln dust collector, but also resist the erosion of corrosive gases such as ammonia water and ammonia compounds.

Suitable anti-corrosion coating materials available on the market include: lightweight glass ceramic anti-corrosion materials, epoxy phosphoric acid paint, modified epoxy coal tar pitch glass fiber reinforced plastic paint, glass flakes, etc. The protective film, blocking the key link in the corrosion. Conditional enterprises can use stainless steel for perforated plates, injection pipes, pulse injection elbows, access door covers, and clean room side panels.

2. The structure of the dust collector can be further optimized. The sealing performance of the dust collector mainly depends on the shell. The tightness of the housing is related to its manufacturing and installation process. All joints of the shell shall be continuously welded, and the welds shall be inspected by the kerosene penetration method.

3. The top of the dust collector is the concentrated part of gas accumulation and condensation, and it is also the most severely corroded area. In view of the easy leakage of air from the access door at the top of the low-clean air chamber structure, resulting in the problem of cold and hot condensation, we propose two solutions.

(1) The structure of the upper and lower door covers: the dust collector adopts a double-layer thermal insulation inspection door, the inspection door adopts an upper and a lower layer, and the sealing around the door frame adopts heat-resistant silicone rubber.

In this scheme, the flue structure of the original equipment does not need to be changed, and the equipment changes are less. Since the door cover is heavy, you can set up a simple drive on the top to replace the door cover.

(2) Heightening of the clean air chamber: the overall height of the top clean air chamber is increased to 4 meters (the initial height is 750mm), and an inspection door is set for each room on the top, and the replacement of the filter bag is completed inside the clean air chamber. The entire top can be insulated, with fewer air leakage points. At the same time, the flue gas circulates more slowly in the high-clean room, and the temperature is more uniform, avoiding condensation.

The cost of this solution is higher, and the entire top structure needs to be replaced. At the same time, because it is a closed space during maintenance, safety needs to be considered. At the same time, due to the exchange of hot and cold air, the blowing pipe of the dust collector is extremely prone to condensation. It is recommended that the elbow be replaced with stainless steel, and the porous plate should be replaced with 316L stainless steel as much as possible.