Dust collector

The dust collector is divided into the following five categories according to its action principle;
(1) Mechanical dust collectors include gravity dust collectors, inertial dust collectors, centrifugal dust collectors, etc.
(2) Washing dust collectors include water bath dust collectors, foam dust collectors, venturi dust collectors, and water film dust collectors.
(3) Filter dust collectors include bag dust collectors and particle layer dust collectors, etc.
(4) Electrostatic precipitator.
(5) Magnetic dust collector.
Factors to be considered in the selection of dust collector equipment

1. Handling air volume (Q)
The treatment air volume refers to the volume of gas that the dust removal equipment can purify in a unit time. The unit is cubic meters per hour (m3/h) or standard cubic meters per hour (Nm3/h). It is one of the most important factors in the design of bag filter.
When designing or selecting a bag-type dust collector according to the air volume, it is generally not possible to operate the dust collector above the specified air volume. Otherwise, the filter bag is easily clogged, the life is shortened, the pressure loss is greatly increased, and the dust removal efficiency is also reduced; but it cannot be If the air volume is too large, it will increase equipment investment and floor space. Reasonable choice of treatment air volume is often determined based on process conditions and experience.
2. Use temperature
For bag filter, its operating temperature depends on two factors, the first is the highest withstand temperature of the filter material, and the second is the gas temperature must be above the dew point temperature. Due to the large selection of glass fiber filter materials, the maximum operating temperature can reach 280 ℃, the temperature must be taken to reduce the temperature of gas above this temperature, must be taken to raise the temperature of the gas below the dew point temperature. For bag dust collectors, the relationship between the use temperature and the dust removal efficiency is not obvious. This is different from electric dust removal. For the electric dust collector, the temperature change will affect the specific resistance of the dust and the dust removal efficiency.
3. Dust concentration at the entrance
That is, the inlet dust concentration is determined by the process of the dust point. When designing or selecting a bag-type dust collector, it is another important factor after the amount of air processed. Expressed in g/m3 or g/Nm3.
For bag dust collectors, the inlet dust concentration will directly affect the following factors:
⑴ Pressure loss and cleaning cycle. As the inlet concentration increases, the dust accumulation speed on the same filtering area is fast, and the pressure loss increases accordingly. As a result, the number of dust removal times has to be increased.
⑵Wear of filter bag and box body. In the case of dust with strong abrasiveness, the amount of wear can be considered proportional to the dust concentration.
⑶ Is it necessary to pre-collect dust? Pre-dust collection is to add a level of dust removal equipment in front of the dust collector entrance, also known as front-level dust removal.
⑷ Ash discharge capacity of the ash discharge device. The ash discharge capacity of the ash discharge device should be based on the ability to discharge all the collected dust. The amount of dust is equal to the inlet dust concentration times the treatment air volume.
⑸ Operation mode. The bag filter is divided into two operating modes: positive pressure and negative pressure. In order to reduce the wear of the fan, the positive pressure operation mode should not be used for the inlet with large concentration.
4. Dust concentration at the outlet
The dust concentration at the outlet refers to the discharge concentration of the dust collector, which is the same as the dust concentration at the entrance. The dust concentration at the outlet should be based on local environmental protection requirements or user requirements. The discharge concentration of the bag dust collector can generally reach 50 g /Nm3 or less.
5. Pressure loss
The pressure loss of bag-type dust removal refers to the pressure drop of gas from the dust collector inlet to the outlet, or resistance. The pressure loss of bag dust removal depends on the following three factors:
⑴ Pressure loss of equipment structure.
⑵ Pressure loss of filter material. Related to the nature of the filter material (such as porosity, etc.).
(3) Pressure loss of dust layer accumulated on filter material.
6. Operating pressure
The operating pressure of the bag dust collector is determined by the static pressure value of the device before and after the dust collector and the fan and its installation position. It is also the design pressure value of the bag dust collector.
7. Filtration speed
Filtration speed is an important factor in the design and selection of a bag filter. Its definition is the speed at which the filtered gas passes through the filter material, or the ratio of the air volume passing through the filter material and the filter material area. The unit is expressed in m/min.
The filter area of the bag filter is determined, then the size of the air volume depends on the selection of the filter speed, the formula is:
Q = v × s × 60 (m3/h)
In the formula: Q — handling air volume
v — filtering wind speed (m/min)
s — total filtration area (m2)
Note: Filtering area (m2)=Treatment air volume (m3/h)/(Filtering speed (m/min)x60)
The filtration speed of the bag filter is divided into the gross filtration speed and the net filtration speed. The so-called gross filtration speed refers to the treatment air volume divided by the total filtration area of the bag dust collector, and the net filtration speed refers to the treatment air volume divided by the bag dust collector Net filtration area.
In order to improve the cleaning effect and the ability to work continuously, the bag dust collector is divided into several rooms (or zones) in the design, and each room has a main air valve to control whether the room is in a filtering state or a filtering stop state (online or Offline). When cleaning or repairing a room, the main air valve must be closed and the filter is stopped (offline state). At this time, the treatment air volume is completely borne by the other room. The total filtering area of the other room is called the net filtering area. That is to say, the net filtration area is equal to the total filtration area minus the sum of the filtration areas of the number of cleaning rooms and maintenance rooms that must be maintained during operation.
8. The length-diameter ratio of the filter bag
The aspect ratio of the filter bag refers to the ratio of the length and diameter of the filter bag. The length-diameter ratio of the filter bag is as follows:
Anti-blowing type —30～40
Mechanical shaking type —15～35
Pulse type —18～23
New dust collector
Negative pressure blowback filter bag dust remover to control industrial boiler waste gas pollution. Practice has shown that the filter bag dust collector has a low investment, a small footprint, a large filtration area, stable working performance, high purification efficiency, reliable use, and the recovered dry smoke is convenient for comprehensive utilization, effectively protecting the environment and is a good performance , Can meet the requirements of the current environmental protection law, reliable and efficient dust removal device.
In order to effectively control the waste gas pollution of the boiler, based on a comprehensive investigation and research on the filter bag dust removal technology, the plant combines the characteristics of the horizontal quick-installed chain grate boiler, the operating characteristics, and according to the production requirements and on-site conditions, the design of the furnace should be negative The pressure blowback filter bag dust collector is set in the negative pressure zone of the induced draft fan of the boiler. The negative pressure is formed by the induced draft fan. The medium alkaline glass fiber filter material is used to resist the corrosion of SO2 in the flue gas.
(1)　Boiler flue gas emissions range from 12000m3/h to 14000m3/h.
(2) 　 After the boiler flue gas is exchanged in two stages of economizer and heat pipe exchanger, the flue gas temperature is controlled at 140℃～170℃.
(3)　Smoke emission concentration<200mg/m3, flue gas blackness (4)　Using the blowback valve to control the pipeline flue gas to ensure the filter bag cleaning operation under the condition that the boiler does not stop.
The negative pressure back-blowing bag filter basically controls the pollution, and the concentration of smoke and dust after purification is obviously lower than the national standard.
Overview and purification mechanism of negative pressure blowback filter bag dust collector
Schematic diagram of negative pressure blowback filter bag dust collector.
1—Air inlet; 2—Motor; 3—Screw conveyor; 4—Pool dust outlet; 5—Air flow distribution plate; 6—Dust collector; 7—Dust filter room; 8—Dust removal filter bag; 9 -Flower board; 10-outlet.
The boiler adopts Y5-48-6.37 centrifugal induced draft fan, with a flow rate of 12350m3/h, a pressure of 3942Pa, a rotational speed of 2900r/min, and a power of 22kW. It is used as the air induction device for the negative pressure blowback filter bag dust collector of the boiler. In order to ensure that the filter bag dust collector works normally or performs the filter bag cleaning operation under the condition that the boiler does not stop, the dust collector is grouped into 3 independent dust filter rooms. There are 22 filter bags installed in each room. The dust removal of the filter bags can be grouped or work in parallel. When one group of filter bags is cleaned, the other group of filter bags keeps working normally. The flue gas enters tangentially from the air inlet at the lower part of the dust collector.The flue gas moves forward along the negative pressure air channel in the dust collector.A part of the dust particles are settled in the dust collecting hopper due to gravity; the other part of the smoke gas is passed through the filter bag Retained in the filter bag, the purified gas is discharged through the induced draft fan, so as to achieve the purpose of removing smoke, purifying gas and protecting the atmospheric environment.
The purification mechanism of negative pressure back blowing filter bag dust collector: the negative pressure of the dust collector system is composed of the boiler induced draft fan, and the flue gas flows negatively. The filter bag dust collector has inertial collision, sieve filtering (contact retention), interception, accumulation and static electricity, and can filter coarse (≥10μm particle size) and fine (<5μm particle size is the most harmful to human body) particles The smoke and suspended fine dust can be effectively captured, which is its outstanding advantage.
Filter bag cleans dust, after the dust collector runs for a period of time, a certain thickness of smoke and dust adheres and accumulates on the surface of the filter bag, and the dust on the surface of the cloth bag is removed by controlling the blowback valve.
The filter bag dust collector is set in the negative pressure area of the induced draft fan, so that the dust removal system works under negative pressure, which is beneficial to prolong the service life of the induced draft fan and avoid being worn by smoke. In order to ensure the normal operation of the filter bag, bypass flue and valve are also set up for temporary use of the filter bag for the boiler maintenance oven and ignition.
The negative pressure blowback filter bag dust collector has a simple structure and a small footprint (within 30m2), which can be flexibly designed and arranged on site according to production needs.
The negative pressure blowback filter bag dust collector has a strong ability to purify dust-containing gas and can effectively control pollution.In particular, the concentration of smoke emission after purification is significantly lower than the national emission standard.It can be applied to small and medium-sized industrial boilers, and the dust removal efficiency can reach 98%. the above.
The production and operation cost of negative pressure back blowing filter bag dust collector is lower, and the energy consumption is lower than that of similar technologies.
Negative pressure back-blowing filter bag dust collector can effectively capture the smoke and suspended fine dust that are harmful to the human body with a particle size of ≥10μm and a particle size of <5μm, which plays a special role in purifying the atmospheric environment and protecting human health.
Reasonable choice of dust removal equipment in industry
According to foreign experience, there are three different levels of choice for dust removal equipment: dust is the first choice, that is, like various diseases, prevention is always more cost-effective than treatment, such as adding a flow slot during loading and unloading and belt transfer, it can be greatly reduced Dust or smoke generation and processing capacity; when dealing with bulk materials such as steel slag, local sealing is adopted to make the generated dust and smoke circulate and consume their kinetic energy, and most of the dust will naturally settle down. This type of mechanical dust prevention and dust removal is called non-powered dust removal abroad. Most of the dust in many occasions is suitable for non-powered dust removal; at least the pre-treatment of unpowered dust removal must be used first.
The second is to assist in the use of water spray mist or foam dust removal. On the one hand, direct spraying can make the dust particles wet, adhere to each other, agglomerate, and grow, and then easily separate from the atmosphere; on the other hand, for relatively high temperature flue gas, direct spraying can be used to achieve evaporative cooling with a small amount of water. Flue gas cooling, volume shrinkage, and reduced speed also facilitate dust removal. In the past textbooks and design manuals, it was said that spray dust removal is only suitable for processing dust of more than 50 m, and the dust removal efficiency is only 40-70%. Practical experience has proved that due to the advancement of spray technology, the dust can be removed by the spray system above 10?m close to 100%, and the dust above 1?m can also be removed 90-95%. For example, tundish turning over and steel slag treatment using spray dust removal have all achieved a high dust removal efficiency of 90-95%.
Therefore, from the perspective of reducing emissions and saving energy and reducing costs, we must first consider unpowered dust removal and direct spray dust removal. The third option is really a last resort: ventilation and dust removal. Because as long as you choose ventilation and dust removal, you must have high-energy fans and dust collectors, which is more difficult to save energy and reduce costs. When adopting the ventilation and dust removal system, the electric dust removal with low energy consumption must be considered first, and finally the cloth bag dust collector. Rethinking the actual selection order of our dust removal equipment according to this idea, we can find some issues that are worth improving: such as secondary dust removal in converters, dust removal in the blast furnace yard, dust removal in loading and unloading, and many other similar applications, the dust particles are 80% or even more than 90% It is more than 10?m, but almost all of China adopts ventilation and dust removal, and uses a bag filter to solve the problem of reducing emissions, but the operating costs are very high; the dust is also large when the converter LT method is not combusted. Some are coarse particles, but the inlet concentration of the electric dust collector is designed according to 70-100 grams per standard cubic meter, resulting in many electric fields and huge equipment. Of course, the unstable efficiency of some ESPs is also a practical problem that must be solved.
Dust collector-low pressure pulse blowing long bag dust collector
1. Dust collector, bag type dust collector, bag type dust collector
Product introduction:
Low pressure pulse jet long bag dust collector is a new type and high efficiency bag dust collector developed on the basis of summarizing various bag dust collectors. It adopts off-line low-pressure pulse jet cleaning technology to prevent dust reattachment and runaway problems, enhance the cleaning effect of the filter bag, increase the filtering speed, save the energy consumption of cleaning dust and extend the life of the filter bag. The dust collector adopts PLC programmable controller to automatically control the entire process of dust removal and ash delivery. Therefore, the dust collector is a large-scale dust removal device with large air volume, good dust removal effect, high dust removal efficiency, reliable operation, convenient maintenance, and small footprint.
2. Electrostatic precipitator, electric precipitator, electric precipitator; alkali recovery furnace electric precipitator
working principle:
The dust collector is mainly composed of ash hopper, filter room, air purifying room, bracket, poppet valve, spray cleaning device and so on. During work, the dusty gas enters the ash hopper from the air duct. Large particles of dust fall directly into the bottom of the ash hopper, and the smaller dust turns into the filter chamber upward with the airflow and is retained on the outer surface of the filter bag. The purified flue gas enters the bag and passes through the bag mouth and the air purification chamber The wind enters and exits, and is discharged from the exhaust port.
As the filtration continues, the dust on the outer surface of the filter bag continues to increase, and the resistance of the equipment increases. When the resistance of the equipment rises to a certain value, the dust removal operation should be performed to remove the dust accumulation on the surface of the filter bag.
Three, electric bag composite dust collector, electric bag dust collector, electric bag combined dust collector;
Performance characteristics:
1. Using low-pressure pulse injection technology, high dust removal efficiency and low energy consumption.
Use straight-through low-pressure pulse valve. The injection pressure is only 0.2 ~ 0.4MPa, the resistance is low, the opening and closing is fast, and the cleaning ability is strong. Because the cleaning effect is good and the cleaning cycle is long, the energy consumption of the blowback gas is reduced.
2. The pulse valve has long service life and good reliability.
Due to the low injection pressure (0.2 ~ 0.4MPa), the pressure of the pulse valve diaphragm and the impact force during opening and closing are low. At the same time, due to the longer cleaning cycle, the number of pulse valve openings is correspondingly reduced, thereby extending the service life of the pulse valve and improving the reliability of the pulse valve.
3. The equipment has low running resistance and good blowing effect.
The dust collector adopts the sub-chamber pulse back blowing offline cleaning method, which avoids the phenomenon that the dust is repeatedly absorbed, improves the effect of pulse spray cleaning, and reduces the resistance of the bag.
4. The filter bag is easy to assemble and disassemble, and the fixation is reliable
Using the upper pumping method, when the bag is changed, the filter bag skeleton is drawn from the air chamber of the dust collector, the dirty bag is put into the ash hopper, and the ash hopper is taken out through the hole, which improves the environment for bag change. The filter bag is fixed on the flower plate hole by the elastic expansion ring of the bag mouth, which is firmly fixed and has good sealing.
5. The air duct adopts the arrangement of collecting pipes and has a compact structure.
6. Adopting advanced PLC programmable controller dust collector to run the whole process.
The use of pressure difference or timing two control methods, high reliability and long service life, easy for users to operate and use.
Specifications and technical parameters: 1. RFDML low-pressure pulse blowing long bag dust collector, divided into RFDML390 and RFDML970