The application of bag filter has been more than 100 ye […]
The application of bag filter has been more than 100 years old. Its biggest advantage is high dust removal efficiency (up to 99.99%), discharge concentration can reach below 10mg/m3, and the classification efficiency is also very high, below 2.5μm. Fine particulate matter also has good capture efficiency and is therefore widely used. However, after years of operation, the bag filter has also exposed some problems, such as easy damage to the filter bag, condensation, high running resistance, failure of cleaning, and poor ash discharge. There are many factors that cause problems in the operation of the bag filter. In addition to the factors of the dust collector itself, improper operation and management are also important reasons for problems in operation. In this paper, the problems that often occur in the current bag filter are analyzed and discussed.
The advancement of the bag filter is mainly reflected in the innovation of the filter material and the change of the cleaning method. The filter bag is the heart of the bag filter. The maintenance cost of the filter bag is the largest in the maintenance cost of the dust collector. Up to 70% of the maintenance cost. The filter bag is the most critical factor in determining the performance of the precipitator. The main factors causing damage to the filter bag are: high temperature burnout, corrosion, mechanical damage, installation quality, product quality, operation, management and many other reasons.
High temperature damage to the filter bag is fatal. For example, a pulverized coal drying kiln in Heilongjiang, because the pulverized coal particles are very fine and very sticky after drying, the cleaning is not ideal, so that a large amount of dried coal powder remains on the surface of the filter bag, and the dried coal powder has a very burning point. Low, when the high-temperature flue gas enters the dust collector, it will quickly ignite the coal powder on the surface of the filter bag, causing the filter bag and skeleton of the entire dust collector to be burned. It can be seen from Fig. 1 that a large amount of dried coal powder remains on the surface of the filter bag, and the box is also burned from the upper left corner.
In addition to the high temperature burnout, the damage of Mars in the smoke to the filter bag is also very serious. In the production process, such as coke oven, drying kiln, chain furnace, cupola, electric furnace, blast furnace, mixed iron furnace, etc., a large number of Mars will be mixed into the flue gas, such as the treatment of Mars is not timely, especially the dust layer on the surface of the filter bag. When thin, Mars will burn through the filter bag to form an irregular round hole (Figure 2). However, when the dust layer on the surface of the filter bag is thick, Mars will not directly burn the filter bag, which will cause a deep color baking mark on the surface of the filter bag.
Another damage to the filter bag by high-temperature flue gas is high temperature shrinkage. Although the temperature of use of each filter material is different, when the flue gas temperature exceeds its use temperature, if the warp shrinkage rate is too large, the filter bag will be in length. The size in the direction is shortened, and the bottom of the bag is held against the skeleton and damaged by force. If the latitudinal heat shrinkage of the filter bag is too large, the filter bag will be reduced in radial size, and the filter bag will be tightly hung on the skeleton, and even the skeleton may not be pulled out. Therefore, the filter bag is always under stress, causing the filter bag to shrink, deform, become brittle, accelerate the strength loss, and shorten the life of the filter bag. Since the filter bag is tightly hooped on the skeleton after being deformed, the filter bag is difficult to be deformed during the cleaning, which is not advantageous for the spray cleaning, resulting in high resistance of the filter bag.
After the high-temperature dust is collected into the ash bucket, if it cannot be discharged in time, the dust will accumulate in the ash bucket for a long time, causing the temperature inside the ash bucket to rise continuously. The filter bag will become brittle and hard when it is baked at high temperature for a long time. Burnt, especially the flammable substances contained in the dust, will burn in the hopper and burn the filter bag.