Selection and Maintenance of Bag Type Dust Collector

Release time:

Jun 16,2012

With the increasing attention of the whole society to environmental protection and energy saving, how to improve the efficiency of dust control in cement production has become a consensus. This paper analyzes the working principle, selection method, factors affecting dust collection efficiency and improvement measures to improve dust collection efficiency, and puts forward the methods of use, maintenance and maintenance. 1 Structure and working principle The main components of the 1.1 (1) Box: mainly fixed filter bags and air circuit components, made into a fully enclosed form. When cleaning ash, compressed gas first enters the box and flushes into the inside of each filter bag. According to different specifications, the box is divided

With the increasing attention of the whole society to environmental protection and energy saving, how to improve the efficiency of dust control in cement production has become a consensus. This paper analyzes the working principle, selection method, factors affecting dust collection efficiency and improvement measures to improve dust collection efficiency, and puts forward the methods of use, maintenance and maintenance.

1 Structure and working principle

1.1 main components

(1) box: mainly fixed filter bag and gas path components, made into a fully enclosed form. When cleaning ash, compressed gas first enters the box and flushes into the inside of each filter bag. According to different specifications, the box is divided into several chambers, which are separated by steel plates and are not breathable.

(2) Bag room: In the lower part of the box, it is mainly used to accommodate the bag cage and filter bag, and form a filter space, where the flue gas purification is mainly carried out.

(3) Ash hopper: it is arranged in the lower part of the bag room. In addition to storing the collected dust, it is also used as the air inlet manifold (lower air inlet type). The dust-containing gas enters the ash hopper before entering the bag room. Due to the large volume of the ash hopper, the air flow speed is reduced. In addition, the change of the air flow direction makes the coarser dust particles separate here, conveying equipment such as screw conveyor or air chute is arranged in the ash hopper, and air lock equipment such as rotary unloader or flap valve is also arranged at the outlet, which can discharge ash continuously.

1.2 working principle

The filtering mechanism of the bag dust collector is the result of a comprehensive effect, such as gravity, inertial force, collision, electrostatic adsorption, screening and so on. When the gas containing smoke and dust enters the middle and upper part of the cone of the large ash hopper through the air inlet, the dust collides with the deflector, and the dust with coarser particles falls into the ash hopper under the impact by inertial force and gravity. The finer particles enter the box at a uniform speed with the air flow rising. After being filtered by the filter bag, the dust is blocked outside the cloth bag, and falls into the ash hopper after being cleared and discharged by the ash unloading system, the gas passes through the filter bag and becomes purified flue gas, enters the box body along the filter bag, and then is discharged into the atmosphere by the valve plate hole and the air outlet to achieve the purpose of dust removal.

With the filtration, the smoke and dust outside the filter bag gradually increase, so that the running resistance of the dust collector gradually increases. When the equipment resistance reaches a certain limit, the smoke and dust accumulated on the surface of the filter bag should be removed in time. Under the action of external force (mainly pulse compressed gas, back blowing gas, mechanical vibration, etc.), shaking and back blowing the filter bag will remove the smoke and dust attached to the surface of the filter bag, the filter bag is regenerated and repeated to realize continuous filtration to ensure continuous and stable operation of the equipment. The dust materials collected by all aspects of the production system and all kinds of dust collectors will be returned to the batching system for use as raw material batching.

2 Selection method

Determination of 2.1 Filtration Wind Speed

In actual selection, the filtering wind speed should be determined according to the working conditions, and then the filtering area and total filtering area should be calculated according to the following formula according to the amount of flue gas to be treated.

F net = Q/(60V) (1)

Where: F net-net filtration area, m2; Q-treated flue gas volume, m3/h; V-filtration wind speed, m3/min.

F total = F net ×(1 1/n) (2)

where: F total-total filtration area, m2;n-number of chambers.

Then select the dust collector with the corresponding filter area according to the total filter area.

Calculation of 2.2 air consumption

  Q1=nZSK/T (3)

In the formula: Q1-air consumption, m3/min; N-number of chambers; Z-number of pulse valves per chamber; S-gas volume per injection, 1.5in pulse valve S = 0.24 m3,2.5in pulse valve S = 0.79 m3;K-coefficient, in-plant system gas supply K = 1.5, separate compressor gas supply K = 2;T-ash cleaning cycle, min.

The size of the cleaning period T depends on the filtering wind speed, inlet concentration and other factors, and is determined by the actual measurement of the working conditions.

3 Factors that affect the efficiency of dust collection.

3.1 filter bag material

The selection and application of the filter bag material of the bag dust collector is the core technology of the bag dust collector, which plays a decisive role in the performance of the dust collector. Due to the environment of each dust collection point, the nature, temperature and technical requirements of the dust are different, different filter materials should be selected according to different conditions, and corresponding technical protection measures should be taken. The requirements for filter bag materials include the following technical properties: filter bag materials are suitable for different temperatures, good peeling, easy cleaning, good air permeability, low resistance, high filtration efficiency, high strength, and can withstand high-strength cleaning. Long life and suitable price.

3.2 filtration wind speed

Filtration wind speed is a very important parameter to determine the performance of the dust collector, and it is also an important parameter to measure the advanced nature of the bag dust collector. The filtering wind speed is closely related to the dust concentration, dust particle size, application, viscosity, gas temperature, moisture content and cleaning method. When the particle size of the dust is fine, the temperature and humidity are high, the concentration is large, and the viscosity is large, the filtering wind speed should be lower, otherwise the high value can be selected. If the filter wind speed is too large, it will increase the load of the filter bag and increase the filter resistance, resulting in a short service life and low efficiency of the filter bag.

3.3 air leakage

Air leakage directly affects the dust collection effect and life of the dust collector, and the air leakage rate is required to be less than 3%. Bag dust collector is generally negative pressure operation, such as air leakage is easy to form a small circuit short circuit. The dust collection system has insufficient air volume to form positive pressure dust. Air leakage will also reduce the system temperature, easy to form moisture paste bags, increase dust collection resistance, reduce dust collection effect.

3.4 insulation

Insulation is also a must for bag dust collectors. Insulation is to keep the gas, avoid moisture paste bag. Most filter bags are smeared and blocked by the phenomenon of paste bags, which is caused by low dust temperature and high humidity.

3.5 cleaning interval

If the cleaning time interval is too long, the dust attached to the filter bag cannot be eliminated in time, resulting in an increase in system resistance. Generally, the interval time is about 4s (which can be adjusted according to the actual production situation) blowing, the blowing time is 0.2s ~ 0.3s, and the time interval between chambers is about 30s.

3.6 ash discharge

The ash hopper cone is not smooth in ash discharge and excessive ash accumulation in the ash hopper will block the air inlet and cause poor ventilation.

3.7 leakage

The top of the dust collector and the surrounding walls have serious air leakage. When it rains, water will enter, causing paste bags or wet materials to form clumps to block the ash outlet of the cone.

4 Measures to improve dust collection efficiency

4.1 strengthen management

Dust collector is a host equipment in the cement process circulation system, its operation directly affects the output and quality of the kiln, mill, dryer and other hosts served. The synchronous operation rate and intact rate of equipment system and dust collector must be guaranteed.

4.2 strengthening seal

The dust collection system mainly includes the dust collector body and other equipment of the dust collection system, such as steel impeller feeder, inlet and outlet valves, conveying equipment and pipelines, inspection doors, etc. Strengthen the sealing of each inspection hole and door. It is best to use double-layer door for inspection door, and heat-resistant silicone rubber shall be used for sealing around the door. The sealing of conveying equipment should also be strengthened to reduce and eliminate air leakage. All joints of the shell shall be welded continuously, and there shall be no leakage or hole (air leakage is most likely at the door hole and the place where the ash is removed). Therefore, it is necessary to strengthen the inspection and spot inspection of the dust collection system, check the integrity and tightness of the dust collector air pipe, shell, upper plate and other parts, and repair welding shall be carried out in time if worn-out parts are found.

4.3 reduce the number of start-stop and inspection

The dust collector shall not be abnormal or shut down for a long time. Generally, do not open the inspection door for maintenance. Every time it is opened, the temperature drops sharply and condensation occurs during the startup or maintenance period, which seriously affects the life of the dust collector.

4.4 strengthen the heat preservation of dust collector

The thickness of the insulation layer should be reasonably selected according to the temperature. Some better protective layers such as thin steel plates should be selected on the outer surface to prolong the service life and insulation effect of the insulation layer. The external insulation measures adopted by the dust collector will reduce the heat loss of the shell. Especially before starting up in winter, the heating system of the dust collector itself should be turned on first, and the filter bag should be preheated for more than one hour before normal production.

4.5 strengthen dust management

When the production system for technical transformation, to take into account the supporting dust collection system. The inlet concentration, temperature and wind speed of the dust collector have certain technical requirements in the design. When the production system is modified, it may be necessary to increase the wind speed and dust volume. At this time, it is necessary to consider the capacity of the dust collector and the possible consequences, and try to match each other.

4.6 reduce bag breakage

The outlet end of the cloth bag is easy to break. When installing and replacing the cloth bag, the center line of the blowing port must be kept coincident with the center line of the filter bag, otherwise it will cause damage to the air outlet of the filter bag. Secondly, the bottom of the filter bag is easy to be damaged. The main reason for this phenomenon is that the skeleton is too long, it is not fixed well, the lower part is shaken greatly, and the filter bag and the filter bag are caused by mutual friction. Therefore, the filter bag is about 50mm ~ 100mm longer than the skeleton.

4.7 reduction of flue gas dust concentration

In the slag heating system, before the flue gas enters the bag dust collector, the pre-dust collection (primary dust collection) and the downdraft of the flue gas should be used as much as possible to capture the high temperature and larger particles of the discharged flue gas and reduce the dust concentration of the flue gas. In particular, high-temperature flue gas directly enters the filter bag, reducing the number of dust cleaning and anti-blowing times of the filter bag, prolonging the service life of the filter bag, and the lower air inlet can make large particles of dust naturally deposit without passing through the filter bag. In the transformation of dust collection should be retained without power settling chamber, it is a kind of non-power running equipment, no energy consumption, is an ideal way to cooperate.

5 Use, maintenance and maintenance

(1) The dust collector equipment shall be operated and maintained by special personnel, and operation records shall be made. Managers should fully grasp the principle, performance, structure, and operating conditions of the dust collector, and deal with problems in time to ensure the normal operation of the production system.

(2) The mechanical moving parts such as the reducer and the ash conveying device should be filled and changed according to the regulations. In particular, the piston of the cylinder should not be short of oil. It must be filled with oil regularly. If any abnormal phenomenon is found, it should be eliminated in time.

(3) Ash emission at the air port indicates that the filter bag has been damaged. During maintenance, stop the high-temperature fan and exhaust gas fan, and open the upper cover of the dust collector. If dust is found at the filter bag opening, it indicates that the filter bag has been damaged and must be replaced.

(4) The air filter of the compressed air system should be discharged regularly, the drain valve at the lowest point of the air bag should be discharged regularly, and the air storage tank should also be discharged regularly.

(5) the control valve to be responsible for maintenance, regular inspection, maintenance and replacement of the solenoid valve and pulse valve.

(6) If the sealing strip on the overhaul manhole door is damaged or aged, it should be replaced in time.

(7) When the process system is stopped, the dust collector and exhaust fan should be kept working for a period of time to remove moisture and dust in the equipment. It must be noted that when the dust collector stops working, the dust collector must be repeatedly cleared (manual cleaning can be used) to remove the dust from the filter bag l to prevent moisture and paste the bag.

(8) When the dust collector is working normally, the ash discharge device cannot stop working, otherwise the dust in the ash hopper will overflow into the bag room, forcing the dust collector to stop.