Zenith Knowledge

Causes And Solutions Of Bag Failure Of Bag Filter

With the increasingly strict requirements of environmental protection, the demand for dust collectors is also growing, and the requirements are higher and higher. The filter bag is the core part of the bag filter, and the status of the filter bag directly determines the quality of the dedusting performance. The following analysis bag filter failure reasons and solutions.

The common position of bag damage of bag filter is the breakage of bag mouth, bag body, bottom and bag suture. Due to the difference of air intake mode, filter bag mode and ash cleaning mode, it will cause wear failure of filter bag for different reasons. The wear of filter bag can be divided into mechanical wear and air flow erosion.

1. Mechanical wear

During the installation of the project, the disordered stacking of the filter bags and the filter cages will often cause the deformation of the filter cages and the mechanical damage of the filter bags. However, the deformation of the flower plate or the deviation of the hole of the flower plate caused by the use conditions will cause the mechanical wear of the bag mouth to intensify. At the same time, if the filter cage is not vertical, it will cause the mechanical wear between the filter bag and the filter bag, which will cause the wear failure of the lower part of the filter bag, and it can be observed that the wear is on the outside of the filter bag. When the installation of the filter bag and the filter cage is too tight and loose, the mechanical wear is caused by the sharp expansion, contraction, distortion and stretching of the filter bag during the ash cleaning process. In particular, the rough processing of the filter cage caused by rust, welding scar, burr and other surface irregularities, will accelerate the wear and failure of the filter bag, such wear in the inside of the bag body.

2. Airflow erosion

The damage and failure caused by airflow erosion are mainly caused by the high-pressure airflow directly blowing to the upper part of the filter bag, the way of flue gas inlet, the excessive concentration of flue gas, the excessive filtration speed of flue gas and the excessive rising speed of flue gas. For example, the inclination of the filter cage caused by the installation and the deformation of the flower plate will not only bring about mechanical wear, but also cause the drift of the filter cage line and the air flow erosion. The high pressure of ash cleaning gas, the tilt of nozzle and the uneven distribution of air flow between nozzles are the common causes of the upper air scour. The scour caused by the way of flue gas inlet is mainly caused by the uneven distribution of air flow in the bag room caused by the air inlet, and the local air flow is too large, which causes the dust to impact the bag and accelerates the wear failure of the bag. Especially for the local gas velocity of abrasive gas is too large, the failure of filter bag is more frequent.

Chemical failure of filter bag caused by flue gas characteristics of bag filter. When the selection of filter material is not considered comprehensively, the filter bag will fail quickly. The failure of filter bag caused by chemical action is chemical failure, mainly hydrolysis reaction, oxidation corrosion and acid-base corrosion. Polyester, polypropylene and Nomex, which are commonly used in chemical fiber filter materials, are prone to hydrolysis reaction. After hydrolysis reaction, the tensile strength of the filter material fiber decreases, and it is easy to wear. The water leakage from the top of the precipitator and the condensation of flue gas generate water vapor, which makes the filter material send hydrolysis under high temperature environment. The higher the moisture content and temperature in the gas, the faster the hydrolysis.

Bag failure caused by high temperature flue gas of bag filter. High flue gas temperature can be divided into instantaneous high temperature and continuous operation high temperature. Too high temperature will cause irreversible failure of the filter bag, such as burning, oxidation corrosion, deflagration and high temperature shrinkage. It can be seen from the influencing factors of hydrolysis and oxidation corrosion process that when the flue gas continues to operate at high temperature, the hydrolysis and oxidation corrosion process will be accelerated. Therefore, it is necessary to cool down the flue gas in order to extend the life of the filter bag.

3. Burn bags

Each kind of filter bag has a corresponding upper limit of use temperature. When the temperature is higher than the upper limit, it will cause losses to the base cloth, film covering and sewing line of the filter bag. Therefore, for smoke with deflagration, we should prevent dust from entering Mars by setting up dust remover, cooling spray tower, and Mars capture device. At the same time, we should use antistatic filter bags or metal wire to prevent static electricity. In the case of flue gas temperature fluctuation due to process reasons, attention should be paid to the flue gas temperature at the inlet of the precipitator, and a high temperature alarm control system should be set up. When the flue gas temperature exceeds the set value, the flue gas temperature can be reduced by spray cooling and air suction valve cooling. According to the characteristics of process flue gas, it is an energy-saving and effective way to recover waste heat of flue gas and reduce the temperature of treated flue gas by means of heat exchanger and waste heat boiler.

4. High temperature shrinkage

When the flue gas temperature continues to use or the instantaneous temperature exceeds the normal use temperature of the filter bag, due to the temperature characteristics of the filter material fiber, the longitudinal and latitudinal thermal shrinkage will increase. When the thermal shrinkage is too large, the filter bag becomes smaller and tightly wrapped on the filter cage, which is easy to affect the cleaning effect and can not extract the filter cage from the filter bag. At the same time, in the vertical direction, the filter bag becomes shorter, which is easy to be broken by the top of the filter cage.