Common problems in bag filters application

Bag Dust Collectors often have some problems in the actual use process, which not only affects the use effect, but also increases the maintenance cost and even affects the normal production of cement enterprises. This paper proposes corresponding solutions to the problems existing in the application of bag filter in cement plant.

1.1 problems

1) After the factory has eliminated the wet rotary kiln, it is planned to change the Φ3.0m×12m raw material mill to the open road high-fine cement mill. According to the technical transformation plan, the new bag filter for the cement grinding tail needs to be placed on the roof of the mill, while the hopper volume of the LTMC96-6 bag filter is 42m? Once the hopper is blocked, the load will exceed 100t. More than the safe carrying capacity of the mill. If the mill column and foundation are reinforced according to the original design plan, the cement mill production time will be postponed for more than 3 months, and the cement sales season will be missed.

2) The load increased by the accumulation of ash in the snow and the roof of the mill is not considered.

3) If you consider the dust removal problem of the grinding head, you need to set the grinding head dust collector, which will further increase the roof load of the mill.

1.2 Measures taken

1) The bag ash hopper is designed as a double ash hopper structure. After the transformation, the volume of the ash bucket is 28m?, which causes the possible load on the top of the mill to drop by one-third when the ash bucket is blocked. In addition, the compartmental damper valve is changed to a double-layer Flap Valve, thus reducing two motors ( Screw Conveyor and split wheel Feeder), reducing the installed power by 6kW. After the calculation of the civil engineering technicians, this reduces the amount of civil construction work of the mill column, and only needs to be framed structure on the roof of the mill.

2) It is clearly stipulated in the post operation rules that the inspection personnel check the ash pipe of the grinding bag filter every hour (feel the temperature change of the ash pipe by hand), and do a good job record, find the blockage (under ash) When the temperature of the pipe drops significantly, it should be inspected and treated in time to prevent the maximum load of the dust collector from appearing and ensure the safety of the mill. In winter snow weather, the thickness of the roof of the mill must be kept no more than 100mm during the day. Arrange personnel to clean up at any time.

3) In order not to set the bag filter in the cement grinding head, connect the dust removing pipe of the grinding head to the inlet pipe of the cement grinding bag filter, and set the regulating valve so that the grinding head can be operated under micro-negative pressure.

1.3 effect

After adopting the above measures, the load on the top of the mill is reduced, the workload of the civil construction of the mill is reduced, and the construction period of the technical renovation is greatly shortened, so that the cement mill is put into production in advance.

2 Optimization of the top filter of cement storage

2.1 problems

Four Φ12m×30m cement storages in a factory are arranged side by side. The grinding cement is sent to the cement storage by the air conveying chute (hereinafter referred to as the first chute) and the cement storage side hoist to the top of the cement storage tank, and then transported to the cement storage by the air conveying chute (hereinafter referred to as the secondary chute). The cement dedusting system has five Bag Filters, which are respectively provided with a swinging mechanical vibrating bag dust collector on the lower part of the cement storage elevator and a reverse blow bag dust collector on the top of each cement storage. Due to the unreasonable design and arrangement of the bag filter, not only the dust removal equipment is more, the maintenance cost is increased, and the dust removal effect is poor.

2.2 Problem Analysis

1) Since the top filter is ashless, in order to prevent the filter bag from falling into the cement store, a safety net of 40mm × 40mm is installed in the lower part of the dust collector. Once in the rainy season, the cleaned cement ash is easy to arch on the net, blocking the mesh, so that the dust removal of the dust collector is reduced, and the dust in the cement storage is increased.

2) Due to the weak dust removal and dust removal of the swinging mechanical vibrating bag dust collector and the reverse blow bag, the filter bag often has thick ash accumulation, and the moisture content of the air and cement in the rainy season is large, and the bag dust collector is easy to dew. The filter bag is knotted, and the dust removal resistance is greatly increased, which affects the dust removal effect.

2.3 Measures taken

1) In order to simplify the dust collection process, the ventilating port of the first chute is directly connected to the hoist by using Φ300mm pipe to fully utilize the pulling effect of the hoist chain bucket and the negative pressure in the hoisting machine to collect dust. Introduce a duct from the top of the hoist to the top of the adjacent cement storement, and ensure the micro-negative operation of the hoist by pumping air through the cement store. Remove the rocking mechanical vibrating bag dust collector.

2) Replace 2 sets of LFX (II) 4-16 bag filter to replace 4 cement bag top bag dust collectors. The dust collector is placed on the top of the low-grade cement storage as much as possible, and an integrated dust removal scheme is adopted. At the top of the cement storehouse, use a duct to connect to the adjacent cement storehouse and set up a regulating valve. Due to the low roof height of the roof, only two-stage and three-stage bag cages (top beams) can be used. When a cement storage is in stock, the bag filter is operated to adjust the valves of the library and the library air pipe, so that the feed cement storage and the library connected to the hoist form a negative pressure, and the entire dust removal system enters the working condition. According to the dust situation of each dust-generating point, the opening degree of the air-tube valve is appropriately adjusted to achieve the best overall dust-removing effect.

3) Change the size of the anti-drop bag net to 60mm×60mm. At the same time, install the vibrator on the channel steel connected to the top bag filter of the cement storehouse, and ask the post to vibrate once a day for 30s.

2.4 effect

1) Reconstruction and application for more than 2 years (the filter bag has not been replaced), the dust removal effect is good, the post environment is obviously improved (see Table 1), and the bag dust discharge at the outlet of the bag is up to standard (27.6mg/m, standard). Since 5 sets of dust removal equipment were changed to 2 sets, the installed power of the dust removal fan was reduced from the original 23.5kW to 15kW, and the annual electricity saving cost was 19635 yuan (electricity fee was 0.55 yuan/kWh, the fan operating efficiency was 70%, and the bag dust collector was running 6000h). ).

2) There are many ways to solve the problem of lower bagging due to the roof, such as ash hoppers and multi-stage bag cages. For multi-stage bag cages, full consideration should be given to the ease of handling, such as the use of wire clamps.

3 clinker chain bucket machine storage dust collector technical transformation

3.1 problems

A LNGM4-16 Pulse Bag Dust Collector was installed at the discharge port of clinker bucket machine of a factory. Since the application, the dust collection effect is not good, and the dust of the bucket machine discharge platform is piled up. The post personnel removed the filter bag in the single bag filter, causing the dust at the outlet of the dust collector to exceed the standard seriously; and the dust concentration in the post was as high as 127.5mg/m?. It not only seriously affects the physical health of the post personnel, but also increases the workload of post sanitation cleaning, and accelerates the wear of the chain fighting machine equipment, and the equipment failure increases significantly.

3.2 Problem Analysis

1) Since the temperature of the exhaust gas at the bucket machine is not fully considered and the temperature difference is large, the dust removal fan is of a common type, which reduces the actual ventilation capacity of the fan and affects the dust removal effect.

2) The setting of the dust removal point is unreasonable, as shown in Figure 2a. Since the difference between the two chain bucket machines is as high as 2.8 m, when the material falls onto the lower bucket machine, the generated dust diffuses outside the cover through the gaps and holes in the cover wall, polluting the environment. The dust removal point is actually a negative pressure area, and there is almost no dust.

3) The clinker bucket machine cutting chute section size is too large, the angle is vertical, causing the dust to increase, increasing the load of the precipitator.

3.3 Measures taken

1) Change the dust removal fan to the boiler fan; change the original needle felt filter material of the bag filter to Nomex high temperature filter material.

2) Set the blanking point at the front end of the suction point.

3) Redesign the clinker cutting chute according to the maximum conveying capacity of clinker, reduce its size, reduce the amount of dust in the dust hood, and reduce the load of the bag filter. The angle of the chute cannot be changed due to the influence of the site.

3.4 effects and experience

1) According to the site estimate, the newly added dust removal capacity of LNGM4-16 bag filter is about 0.8~1.2t/h.

2) If the site conditions permit, the vertical chain bucket cutting chute with high drop will be installed obliquely, or the baffle can be set in the cutting chute, which can reduce the amount of dust and reduce the material to the chain bucket. Impact, extending the life of the chain bucket.

3) After the transformation, the environment at the discharge port of the chain bucket machine is obviously improved. Not only the discharge concentration of the dust collector is up to the national standard, but also the dust concentration of the post is up to the standard. Although it occurs in the summer clinker red material phenomenon, due to the use of Nomex high temperature filter material, the bag filter has been operating normally for more than 2 years. With the improvement of the post environment, it is not necessary to clear the ash every shift, the labor intensity of the post personnel is greatly reduced, the wear of the chain bucket machine and the like is reduced, and the operation rate of the equipment is improved.

4 Powder Coal Ash Dust Optimization

4.1 Problems and analysis

In order to reduce the cost of cement production, a factory needs to add fly ash to the cement mill system. The fly ash storage can be arranged on the cement grinding tail, that is, on both sides of the grinding room, to be close to the grinding tail hoist and the principle of the behavior of the fly ash conveying vehicle. To this end, there are two options: Option 1 is an independent dust removal scheme: the LFX4-16 bag filter is used to remove dust from the fly ash storage top and the fly ash conveying chute. Due to the large selection of the dust collector, the power of the fan is large, the length of the dust removal duct is long, and there are many bend tubes, which is not conducive to dust removal.

The second scheme is to use the cement grinding tail negative pressure to connect the tail of the fly ash conveying chute with the Φ250mm air duct to the upper part of the cement grinding tail cover, and use the grinding tail WDMC128-7 bag filter to remove dust; in order to facilitate the cement grinding maintenance, The dust-removing air duct is flanged and air-conditioning valve is provided (to avoid the dust in the chute, the air volume should not be too large). The fly ash storage top dust collector only undertakes the dust removal of the fly ash storage. The LFX4-8 bag filter is used (see Table 3 for technical performance parameters), and the ash hopper is eliminated. The dust collector case is directly installed on the top of the library. The load on the top of the fly ash store is reduced, and the height of the dust collector is also reduced, and the wind hazard is reduced; a 50 mm×50 mm anti-drop wire mesh is installed in the lower part of the box body. After comprehensive consideration, the final option 2 is selected. After the transformation, the operation was normal, but after 2 months, the dust ash appeared on the top of the fly ash store. The driver of the fly ash also reported that the ash storage time increased by 1/3 to 1/2.

4.2 Measures taken

1) Since the fly ash store is a steel plate storehouse, it is easy to dew in the rain and snow weather storehouse, and the fly ash is easy to appear on the anti-drop bag net of the dust collector. When the fly ash is dry on sunny days, the fly ash that prevents the net on the bag from falling off is easy to fall off, the ventilation is improved, and the dust removal effect is improved. To this end, the operating procedures were revised, and the post personnel were required to use the hammer to tap the bayonet of the fly ash storage top dust collector bracket several times a week (rain and snow Tianqin tapping).

2) Because fly ash is difficult to control, it is also susceptible to water content. It is required to strictly control the position of the fly ash storage in the warehouse (not less than 6m) in actual operation. In the event of blockage, the small spiral gate should be closed before the compressed air is blown to prevent the dust from being washed.

4.3 effects and experience

1) By optimizing the dust removal process design, the process flow is simplified, which not only facilitates actual production, reduces maintenance workload, but also reduces the selection of dust collectors, saving investment and operating costs.

2) Since the top of the fly ash storage is an independent dust collector, the dust removal effect is good when the fly ash is discharged from the warehouse and stored in the warehouse. In the case of the dust collector preventing the bag net slab, it was planned to install the vibrator cleaning. Considering that the fly ash storage top dust collector is open-air arrangement, in order to prevent the vibration of the vibrator from cracking and seeping water, it is finally cleaned by manual tapping. The program is also conducive to regular inspection of the fly ash store.

5 Optimization of air intake mode of cement grinding bag dust collector

5.1 problems

A Φ3m×11m closed-circuit cement grinding tail bag dust collector of a factory adopts the top layout process of the mill.

During the use process, the bag dust collector often has great resistance, especially in winter. The dust inlet of the dust collector needs manual tapping or manual cleaning of the ash, but still feels poor ventilation and affects the normal operation of the cement mill.

5.2 Problem Analysis

1) The dust removal equipment manufactured by the environmental protection equipment factory often has fixed air inlets and air outlets. However, due to the limitation of the installation position of the dust collector in actual production, the dust removal pipe network has many elbows and long air ducts, which affects the dust removal system. Ventilation.

2) Although the air inlet pipe of the precipitator is insulated during installation, the blockage phenomenon often occurs. Due to the large resistance of the original designed pipe network system and the blockage, the ventilation capacity of the bag filter is greatly reduced ( The measured average value) is much lower than the nameplate value and affects the cement mill ventilation.

3) When the air inlet pipe is blocked, it is often necessary to disassemble the air inlet pipe flange. According to statistics, at least one flange cleaning elbow should be removed each year. Repeated disassembly and assembly, resulting in air leakage in the duct flange, not only reduced the ventilation of the cement mill, but also increased condensation and blockage at the inlet pipe bend, forming a vicious circle.

5.3 Measures taken

1) Contact the dust removal equipment manufacturer, change the air inlet of the bag filter from the horn to the rectangular box, and change the 90° bend of the inlet pipe into the inclined pipe to directly enter, which not only reduces the resistance of the inlet pipe, but also saves The air duct is easy to install and also reduces the winter blockage of the 90° elbow.

2) In order to make the dusty exhaust gas evenly enter the bag filter, a baffle is arranged in the rectangular air inlet, which not only reduces the dust scouring of the air inlet passage, but also reduces the system resistance, and also facilitates the dusty exhaust gas in the bag filter. The chamber is evenly distributed to avoid the flushing of the dusty waste gas to the partial filter bag, which improves the service life of the filter bag.

5.4 effect

The problem of blockage of the air inlet pipe disappeared, and the cement mill ventilation was significantly improved, which not only improved the production quality of the cement mill, but also improved the dust of the cement grinding head.

6 bag duster weld seam and upper board problem

6.1 Problems and analysis

1) At the beginning of the use of the pulse bag dust collector equipped with a slag dryer in a factory, it was found that the concentration of the exported dust exceeded the standard. When entering the dust collector, no damage to the filter bag was found, but it was found that a small number of filter bags were not perpendicular enough and skewed. Shortly after adjusting the verticality of the filter bag, the skew problem occurred again. The main reason is that the flatness of the upper plate with a thickness of 4 mm is not enough. In addition to the welding deformation and the stepping of the person when the filter bag is installed, there is a gap between the filter bag and the upper plate, which causes a short circuit of the dust.

2) Because the flue gas of the dryer is corrosive and the temperature changes greatly, it will easily cause condensation in the bag filter after a period of use, causing corrosion of the dust collector. In particular, there is no insulation on the top of the bag filter, and the weld on the upper plate is likely to corrode first, causing a short circuit of the dusty exhaust gas.

3) In order to reduce power consumption, some operators immediately cut off the air source and electric heating equipment after the bag filter is shut down, causing the dust on the filter bag to be cleaned in time, which easily causes the filter bag to get wet and increases the operation of the bag filter. Resistance also affects the next startup.

6.2 Measures taken

1) For the manufacturing problem of the upper flower board, the dust collector manufacturing enterprise is required to use the steel plate with a thickness of 6 mm to make the upper flower board, and the spacing of the flower board holes and the processing size are required to be accurate, and the welding of the upper flower board should pay attention to avoid deformation to maintain the flatness; When installing and replacing the Dust Filter Bag, the wooden board should be placed on the pedal to reduce the deformation of the upper plate caused by human factors, ensure the verticality of the filter bag installation, and reduce the wear of the bag bottom collision.

2) For the problem of fast corrosion of the upper plate, the weld inspection should be strengthened when welding the filter bag chamber and the upper casing weld. The kerosene penetration test is used on site, and the weld or the air hole should be repaired in time to ensure the weld. The airtightness of the upper case should be brushed before leaving the factory, especially the weld. At the same time, the upper tank of the bag filter adopts the same thickness as the filter bag chamber. The filter bag inspection door should not only use anti-aging seals, but also heat treatment.

3) For bag dust collectors with heating equipment, the electric heating equipment should be turned on 2~4 hours before starting. After the shutdown

Do not stop the heat equipment immediately. The equipment should be cleaned after the ash is completed and the ash bucket is drained.

6.3 effect

1) After the upper plate steel plate is thickened, the deformation is obviously improved, ensuring the verticality of the filter bag installation. After the upper case is insulated, the condensation phenomenon in the dust collector is reduced, and the corrosion problem of the upper plate is improved. The corrosion of the upper plate weld is not observed in the past 6 years, which improves the service life of the bag filter.

2) Although the corrosion of the bag filter is closely related to the bag dust collector insulation and air leakage, it is also very relevant to the production process management. In the actual production operation, the operation process of the dryer should be stabilized as much as possible to create conditions for the normal use of the dust collector.