Bag Filters types ,working principles & daily maintenance

 

• Dust collection equipment categories:

All of the air can be separated dust precipitator apparatus are referred to. Precipitator classification is as follows:

1, according to the principle of separation of dust from gases divided:

• Using gravity particles themselves: such as: settling chambers, 0625,2625 and the like.
• Particle motion using the inertial force: The louvered precipitator.
• Particles using a centrifugal force: as a cyclone dust collector: 0325,2305 like.
• Spray washed with water to effect particle: The foam precipitator.
• Using filtration material particle: As the bag filter, the particle filter layer (with some filtration material particles).
• An electric field of particle separation: The electrical precipitator.

2, also by dry and wet classification.

 

• Dust collection equipment efficiency:

Collection efficiency is a major parameter collecting performance characteristics, as well as primary factors in selecting role precipitator. It may represent the total collection efficiency of dust collection efficiency of the dust collection efficiency and the degree of dispersion in two forms.

1, the total collection efficiency:The weight ratio of precipitator dust is collected into the dust collector down with the weight of the dust. Expressed as a percentage, may be calculated by the weight method or concentration method.

⑴, efficient method to calculate the weight:Provided into the dust precipitator weight G1, the weight of collected dust from the precipitator hopper is G2, then this overall collection efficiency of the precipitator:

Where:h- The total collection efficiency%

G1– amount of dust into the dust collectorkg / h

G2– amount of dust collected by the precipitator

When the dust-laden gas through the filter bag, the mesh cloth is greater than the gas in the dust particles are separated from the gas retention, the mesh cloth typically is 10 to 20 microns, if raising the mesh 5 to 10 microns, Therefore, generally above 5 microns may be separated from dust. Then smaller than dust mesh filter cloth, dust-laden gas through the filter cloth to the filter cloth lost due to collision inertia force itself, and adhering to the intake side of the mesh surface. Since the lateral aspect of the dust accumulation, bridge phenomenon is generated between the fibers, so that the intake-side layer of cloth dust resistant film is formed after a few minutes of operation, the dust layer which is made of fine particles, but also acts to improve the filter cloth filtration, gas0.5Even micron0.1Micron dust filter can also be almost down.

 

(Ii) common bag filter:

In front of the bag filter bag requirements were introduced, and baghouse dust collection efficiency is good or bad with cleaning ability, wind speed, let’s introduce the bag filter in the cleaning method classification:

1, the automatic mechanical rapping bag filter formula:

Such a bag filter such as a cam driven mechanical means in groups alternately periodically rapping bag, while mechanically control related to the damper, so that the clean air blown into the bag the reverse, so that dust soon fall, Therefore, stable operation thereof, dust collecting efficiency can always be maintained at more than 98%, the wind speed of the filter is generally 2-3m / minWe factory mainly drying belt system uses:

Vibration cleaning should be considered in the selection of cleaning that is not on a short time, because if the cleaning time needed to occupy a substantial portion of the running time, the time to stop filtering braid will account for too much. It is designed to allow the bag to get the best able to produce “S”Shaped vibration frequency and amplitude of vibration, the dust falling down.

2, reverse flow cleaning bag filter formula:

There are two cases using the reverse flow cleaning of a filter bag for filtering the outside, the side bag cleaning metal gridlines like supporting the bag to maintain a certain tension, the use of this cleaning method, filter bags withstand buckling minimal. Do not use a cloth with blankets. Another is a dust bag medial layer, such cleaning requires a strong cloth between 11-45 kg, big difficulties hang the bag, the bag will be a little slack. When cleaning the knitted fabric bag may be fixed at the lower end is bent calendar harm, resulting in easy breakage of the filter cloth. In order to prevent the bag from collapsing after the cloth packed together, to hold up the bag to use the skeleton, can make dust falling down falls freely unhindered hopper. Blowback duration of less than one minute.

Cleaning backflush stream has several, some valves disposed in each compartment, with only a wind turbine backflushing; (air-cleaning bag filter is such that we use branch), each of some compartment has its own cleaning fan, some with the mobile device for plate-shaped or cylindrical bags one by one backflush (i.e. blown gas ring bag filter).

Improve the cleaning effect.

Cleaning process is a cleaning chamber from beginning to end, generally 3-10 seconds, from the end of the cleaning chamber to the first chamber of the second cleaning start cleaning interval. This time depends on the nature of the flue gas, selection of fixed size, fixed length may be a few minutes, tens of seconds set as short, cleaning cleaning interval can be divided into centralized and spaced uniformly spaced two kinds of cleaning, the so-called concentrated cleaning interval cleaning means from the first chamber to the last chamber after the end of a cleaning, are all chamber into the filter until the next start cleaning, spaced evenly cleaning the chamber after the end of the last cleaning, still the same interval the first time to start cleaning chamber, so a uniform cleaning process cleaning intervals are continuous. Starting from the cleaning chamber to the process of the first time interval between the start time in this chamber cleaning process, said cleaning cycle, cleaning cycle length depends on the length of the cleaning interval. Cleaning shortest interval not less than 15 seconds.

Compartment will cleaning chamber watched isolation device, which is a poppet valve and the valve plate, closing of the poppet valve requires time less than 2 seconds, preferably 1 second or less, may be more appropriate slow opening, and closing the valve plate after the valve plate the maximum clearance between the holes does not exceed0.8mm, Using compressed air to the pressure regulating valve is adjusted by the three-piece, and generally0.3MPa.

The system requires air leakage rate should be less than 30%:

Model Description:

P   P   D    C   32-4

 

production yield per unit

Box business red dust chamber row

Substituting the chamber of

No. Number of bags

number

(Four), I plant the injection pulse bag filter:

Characteristics of pulse jet bag filter is in the same dust collecting chamber, each row in turn jet dust bag, and still be filtered while collecting cleaning, i.e. a so-called line cleaning. This cleaning dust cleared under way, some will be trapped near the bag again. If a large gas capture dust concentration, this phenomenon is more serious, so the jet pulse cleaning bag filter application subject to certain restrictions.

Use points:It is noted that the main wind speed using a reasonable choice, and control the concentration of dust-containing gas temperature.

The wind speed is usually set to the level of dust concentration in the 1-3 m/Minute. Of course, the wind speed is also related with cloth material.

• Check the high pressure air pipe for leaks, is blocked, or pulse cleaning fan is working properly, the poppet valve is normal; Note 🙁 cycle to check a)
• Whether the discharge hopper with a product material, the conveying member is operating normally;
• If the new bag after changing precipitator, opened fan baffle opening not large opening, is lower than normal, the rapping system start to be delayed two hours;
• Fan baffle opening operation should be less than 40%.

4, stop Note:

• Ventilator or stop the shutter is closed;
• Let rapping cleaning system running for some time, in order to remove adsorbed on the dust bag
• To finally stop the delivery system;.

5, daily care and maintenance:

• Class gas tank in the sewage water once every 4 months while the cleaning of a water separator, mist should always check to ensure that the oil reservoir and the fuel injection situation;
• Inspection door seal is intact, the fixing bolts are loose;
• Check the bag, on the loose, aging, damaged bag processing, replaced.
• Solenoid valves, such as pulse valve malfunction, should be excluded, such as internal impurities, water, should be cleaned, the membrane damage should be replaced;
• Check the cleaning operation controller case (anti-hair, a pulse, a cylinder, etc.) the accuracy of the cycle;
• Periodically tank pressure switches, safety valves, pressure gauge to check whether it is normal, if the problem in time replacement;
• Periodically check air system, ash system operating conditions, and remove abnormal;
• Offline cleaning bag filter type, do not breathe source is shut down to ensure that the poppet valve in an open state;
• Delivery system apparatus according to the provisions oil changes, lubrication;

When operation of the bag filter, the delivery system can not be stopped, to prevent extrusion hopper filled with dust

⑵, collection efficiency calculated concentration method:Generally do not facilitate the calculation method of the weight, can be sampled at the point before the dust collector, according to the previous dust collector, the dust concentration of the gas, dust collection efficiency is calculated using the following equation:

 

Where:g₁– gas before the precipitator dust concentrationg / m3

g₂– gas concentration after the precipitator dustg / m3

hp =         × 100%   orhp =              × 100%   Where:hp- precipitator dispersion% h – precipitator overall efficiency% R1– The percentage of the set of particles into the precipitator total weight R2– in the precipitator dust collected, the set percentage by weight of particles R3– in the purge gas, the percentage by weight of particles of the group

R2 ×h R1

2, dispersion efficiency:Only the overall efficiency of the precipitator represented precipitator capacity is not enough, because the dust particles contained in the particle is composed of particles of different sizes, the ability to collect a variety of particles with different diameters precipitator is different such as: settling chambers as compared with the bag filter, although the former has a certain efficiency, but it is usually only collect particles above 50μm, the collection of fine particles is low, but the bag filter for particles of 1 ~ 5μm there is a high collection capacity. So not only consider the overall efficiency of the dust collector when the dust collector selection, but also in accordance with specific consideration of dispersion efficiency of the dust collector. The calculation is as follows:

• Bag Filter

A bag filter using natural fibers or inorganic fibers as a filter cloth, the filtered dust in the gas purification equipment, since the bag-shaped filter cloth are made, it is generally referred to as a bag filter. It is a fine dust collecting efficiency equipment, when properly used, may be0.5Micron dust collection of more than 99%, because of its high collection efficiency, reliable operation, less accidents, easy maintenance, small equipment costs, so widely used.

Where:hp- precipitator dispersion%

h – precipitator overall efficiency%

R₁– The percentage of the set of particles into the precipitator total weight

R₂– in the precipitator dust collected, the set percentage by weight of particles

• Bag filter works:

Since reverse flow of cleaning air through the bags must be re-cleaning is not filtered by the filter bag, so the use of reverse flow cleaning, in addition to have suspended part of the bag filter for cleaning, but also increases the overall filter Gas flow. This will increase the filtration rate, or to Cadogan bag.

3, pulse cleaning bag filter:

Pulse in the pulse cleaning bag cleaning side, there are fouling the bag side of the pulse, the pulse in the bag inside, the outside of the filter bag pulse.

Pulse cleaning according to certain time or a predetermined filter pressure drop, signaled by the control device, the control valve by a program control each pulse valves open and close, short ejected from respective orifices on the injection tube into the bag compressed air cleaning.

Cleaning bag filter between two pulses referred to the elapsed time interval. The pulse length of the interval can be adjusted according to the pressure drop to be maintained, typically about0.5-1Minute pulse cleaning and automatic control means performs a variety of different configurations.

Pulse cleaning process to accomplish three things:

• Normal filtration air flow stop;
• Vibration bag;
• Cause sufficient pressure within the bag, to ensure that gas from the clean side of the bag member to the fouling of the reverse flow side.

Each row of filter bag cleaning time is very short, usually about0.1Second, because of the low ratio of the filtration time and the cleaning time, almost the entire area of ​​the filter has been at work, so this dust collection bags pulsed high dust concentration can be processed gas.

Pulse cleaning bag filter type is an efficient bag filter, the use of4.5-7kg / m2Pulse of compressed air blowing mode, width and pulse period can be adjusted so that the filter bag to maintain good state. Therefore, a high filtration velocity of about 3-6 m / min.

Size can be reduced because, while no moving parts, the bag against mechanical forces, long bag life.

The main drawback:Complex pulse controller, to high technology, high concentration of cement, high humidity, dust is not ideal.

(C), or factory air box pulse bag filter:

Features air box pulse bag filter is employed for cleaning compartment in turn, a so-called off-line cleaning. When a cleaning chamber for injection, filtered air flow cut off, avoiding the secondary cleaning dust flying. This dust collector can trap dust concentrations up to 1000g / Nm3gas.

advantage:Cleaning rooms and is being filtered room without disturbing each other, to achieve a long-term continuous operation

The gas temperature in the cloth material allows selection between the maximum temperature and dew point, to prevent condensation, the general requirements above the dew point temperature filter claim 15 ℃.