First, the concept of vacuum cleaner
In the National Terminology Standard for Heating, Ventilation and Air Conditioning (GN50 155—92-92), the specific meanings of several kinds of dust collectors are defined, and the extracts are as follows.
1, dust collector, which is used to capture and separate dust particles suspended in air or gas, is called dust collector.
2. The settling chamber is a kind of gravity dust removal device. Because the speed of dusty airflow entering a large space suddenly decreases, dust particles are separated from the gas under their own gravity. We call it gravity dust collector.
3, dry dust collector, do not use water or other liquids to capture and separate dust particles in air or gas.
4, inertial dust collector, with the help of various forms of baffle, forcing the airflow to change direction, using the inertia of dust particles to collide with the baffle to separate and capture dust particles.
5. Cyclone dust collector, a kind of dust collector, in which dust particles are separated and captured under the action of centrifugal force, when dust-laden airflow enters the cylinder in a tangential direction for spiral rotation.
6. Multi-tube (cyclone) dust collector, which is composed of several cyclone separators with smaller diameters in parallel, and has the same inlet and outlet and dust collecting hopper.
7. Bag filter uses fiber filter bags to collect dust, also called bag filter.
8, granular layer dust collector, with quartz sand, gravel and other granular materials as the filter layer dust collector.
9. Electrostatic precipitator is composed of corona electrode, dust collecting electrode and other parts. Under the action of high voltage electric field, the particles in dusty airflow are charged, attracted and trapped on the dust collecting electrode.
10, wet dust collector, through the contact and impact of dusty gas with droplets or liquid film. A device for separating dust particles from airflow.
1 1, water film dust collector. Dust-containing gas enters tangentially from the air inlet at the lower part of the cylinder, and then rotates and rises, so that dust particles are thrown to the inner wall of the cylinder by centrifugal force, and at the same time are adhered and trapped by the water film flowing downward along the inner wall of the cylinder and discharged from the lower cone.
12, horizontal cyclone water film dust collector, a kind of wet dust collector composed of horizontal inner and outer drums, uses the rotating dusty airflow to impact the water surface, forms a flowing water film inside the outer drum and generates a large amount of water mist, so that dust particles collide with water mist droplets and are captured by the water film under the action of centrifugal force.
13. Foam dust collector is a kind of dust removal equipment in which dusty airflow passes through the foam layer on the sieve plate from bottom to top at a certain flow rate.
14. pulse dust collector, which is a wet dust collector. After the dusty airflow enters the cylinder, it turns downward and impacts the liquid level. Some larger dust particles directly settle in the mud bucket, and then the dusty airflow passes through the S-shaped channel at high speed, which arouses a large number of sprays and droplets, so that the fine dust and water mist are fully mixed and contacted and captured.
15 venturi dust collector, which is composed of venturi and droplet separator. When the dusty gas passes through the throat at high speed, the droplets sprayed by the nozzle are further atomized and collide with the dust particles continuously. Then break through the gas film around the dust particles, so that the fine particles condense into dust-containing droplets with larger particle size, which are separated and trapped after entering the separator, and the dust-containing gas is purified, also known as Venturi scrubber.
[14] Sieve plate tower, there are several layers of sieve plates in the cylinder, and the gas passes through the liquid layer on the sieve plates from bottom to top, absorbing harmful substances through gas bubbling.
17, packed tower, the cylinder is filled with annular, corrugated or other shapes of packing, absorbent is sprayed down on the packing from the top of the tower, gas rises along the packing gap, and harmful substances are absorbed through gas-liquid contact.
18, air filter, equipment for filtering and purifying dusty air through filter materials.
19, automatic winding filter, air filter which uses drum filter material and can automatically wind and clean dust.
Vacuum cleaner is a device for cleaning and purifying dust surface by means of high vacuum suction nozzle.
⒇ technology of dust removal, collection and separation of solid particles such as dust in airflow.
2 1, mechanical division, e. dust removal by using ventilator and dust collector.
22, wet dust removal, hydraulic dust removal, steam dust removal and spray dust removal methods collectively.
23, hydraulic dust removal, using water mist to humidify materials, reduce the amount of dust, and promote dust condensation and settlement of dust removal methods.
24, combined dust removal, mechanical dust removal and hydraulic dust removal method.
25, dust removal system, generally refers to the local exhaust hood, duct, fan and dust collector, etc. Mechanical exhaust system to capture, transport and purify dusty air.
Botou He Peng Environmental Protection Machinery Co., Ltd. has developed into the largest production base of dust removal equipment in northern China, and all the products described above can be produced.
Second, the classification of dust collector
The classification methods of dust collectors are different and can be divided into many types, which are used for different dust and different working conditions.
(1) See table for classification according to the principle of dust removal force.
type
Dust removal power
Types of dust removal equipment
application area
Efficiency of different particle sizes/%
Dust particle size/micron
Dust concentration/(g/m3)
Temperature/℃
Yin force/Pa
50um
5um
1um
dry
gravity
Gravity dust filter
> 15
> 10
20
< 100
five
< 100
0.05
0. 1
3~ 10
99 100 100
>99>99>99
999999
Inertia force, diffusion force and adhesion force
Self-excited dust collector spray dust collector Venturi dust collector
100~0.05
< 100< 10< 100
98
98
98
(2) Classify the collected smoke according to its humidity.
Dry and wet dust collectors
Dust removal category
Smoke state
Dust collecting equipment
Dry dust removal
Dry dust
Gravity dust collector, inertial dust collector, dry dust collector, bag dust collector, cyclone dust collector.
Wet dust removal
muddy
Water film dust collector, foam dust collector, impact dust collector, Venturi dust collector, wesp.
(3) according to the classification of dust removal efficiency
Dust removal efficiency type dust collector
Dust removal category
Dust removal efficiency/%
Name of dust collector
Inefficient dust removal
95
Electrostatic precipitator, bag dust collector, Venturi dust collector, air filter.
(4) Classification by working state According to the working state of the dust collector in the dust removal system, the dust collector can also be divided into positive pressure dust collector and negative pressure dust collector. The working temperature is divided into normal temperature dust collector and high temperature dust collector. According to the size of the dust collector, it can also be divided into small dust collector, medium dust collector, large dust collector and super-large dust collector.
(5) According to the different dust removal mechanism and function of dust removal equipment, according to the Classification and Naming Method of Environmental Protection Equipment (HJ/T1-1996), dust collectors can be divided into the following seven types.
① Gravity and inertial dust removal devices include: gravity settling chamber and baffle dust collector.
(2) Cyclone dust removal devices include: single-barrel cyclone dust collector and multi-barrel cyclone dust collector.
(3) Wet dust collector includes spray dust collector, pulse dust collector, water film dust collector, foam dust collector, inclined grid dust collector and Venturi dust collector.
④ Filter layer dust collector includes: particle layer dust collector, porous material dust collector, paper filter and fiber filler filter.
⑤ Bag dust collector includes: mechanical vibration dust collector, electric vibration dust collector, chamber back-blowing dust collector, nozzle back-blowing dust collector, vibration dust collector and pulse jet dust collector.
⑥ Electrostatic precipitator includes plate electrostatic precipitator, tube electrostatic precipitator and wet electrostatic precipitator.
⑦ Combined dust collector includes: In order to improve the dust removal efficiency, it is often "coarse particle dust collector is set in the front stage and fine particle dust collector is set in the back stage".
In addition, with the increasingly strict air pollution control laws and regulations, the flue gas desulfurization function is sometimes added to the flue gas dust removal device, and the flue gas dust removal desulfurization device is derived.
Third, the choice of dust collector (selection index)
(1) handling air volume (q)
Treatment air volume refers to the amount of gas that can be purified by dust removal equipment in unit time. The unit is cubic meter per hour (m3/h) or standard cubic meter per hour (Nm3/h). This is one of the most important factors in the design of bag filter.
When designing or selecting a bag filter according to the air volume, it is generally not allowed to make the filter run beyond the specified air volume, otherwise the filter bag will be easily blocked, the service life will be shortened, the pressure loss will be greatly increased and the dust removal efficiency will be reduced; However, the air volume should not be too large, otherwise it will increase the equipment investment and occupied area. The reasonable selection of the amount of air to be treated is usually determined according to the process conditions and experience.
(2) Working temperature
For bag filter, its service temperature depends on two factors, the first is the maximum bearing temperature of filter material, and the second is that the gas temperature must be above the dew point temperature. At present, due to the wide selection of glass fiber filter media, its maximum service temperature can reach 280℃, and measures must be taken to cool the gas above this temperature and raise the gas temperature below the dew point temperature. For bag filter, the relationship between operating temperature and dust removal efficiency is not obvious, which is different from electrostatic precipitator. For electrostatic precipitator, the change of temperature will affect the specific resistance and dust removal efficiency of dust.
(3) Dust concentration at the entrance
That is, when designing or selecting a bag filter, the dust concentration at the inlet determined by the ash point process is another important factor next to the treatment air volume. Expressed in g/m3 or g/Nm3.
For bag filter, the dust concentration at the entrance will directly affect the following factors:
(1) pressure loss and cleaning cycle. With the increase of inlet concentration, the dust deposition rate on the same filtration area is fast, and the pressure loss increases accordingly, which leads to the need to increase the number of dust removal.
② Wear of filter bag and filter box. When dust has high abrasiveness, its wear can be considered to be proportional to the dust concentration.
③ Pre-dust removal is necessary. Pre-dust removal is to add a level of dust removal equipment before the entrance of the dust collector, also known as pre-dust removal.
④ Ash discharging capacity of the ash discharging device. The ash discharging capacity of the ash discharging device shall be based on the ability to discharge all collected dust, and the dust amount is equal to the dust concentration at the entrance multiplied by the treatment air volume.
⑤ Operation mode. Bag filter is divided into positive pressure and negative pressure operation modes. In order to reduce fan wear, positive pressure operation mode is not suitable for high inlet concentration.
(4) export dust concentration
The dust concentration at the outlet refers to the emission concentration of the dust collector, and its expression is the same as that at the inlet. The export dust concentration should meet the local environmental protection requirements or user requirements, and the discharge concentration of bag filter can generally reach below 50g/Nm3.
(5) Pressure loss
The pressure loss of bag filter refers to the pressure drop of gas from the inlet to the outlet of the filter, or resistance. The pressure loss of bag dust removal depends on the following three factors:
(1) Pressure loss of equipment structure.
⑵ Pressure loss of filter material. It is related to the properties of filter materials (such as porosity, etc.). ).
(3) Pressure loss of dust layer accumulated on the filter material.
(6) Operating pressure
The working pressure of bag filter is determined by the static pressure value of equipment and fans before and after the filter and their installation positions, which is also the design pressure resistance value of bag filter.
(7) filtration speed
Filtering speed is an important factor in the design and selection of bag filter, which is defined as the speed of filtering gas passing through the filter material or the ratio of air volume passing through the filter material to the area of the filter material. The unit is expressed in meters per minute.
When the filtration area of the bag filter is determined, the size of the treated air volume depends on the choice of filtration speed, and the formula is:
Q=v×s×60 (m3/h)
Where: q-the amount of treated air.
V— filtering wind speed (m/min)
S—— Total filtration area (m2)
Note: filtration area (m2) = treated air volume (m3/h)/ (filtration speed (m/min)x60)
The filtration speed of bag filter can be divided into total filtration speed and net filtration speed. The total filtration rate refers to the amount of treated air divided by the total filtration area of the bag filter, while the net filtration rate refers to the amount of treated air divided by the net filtration area of the bag filter.
In order to improve the dust removal effect and continuous working ability, the bag filter is divided into several chambers (or zones) in design, and each chamber has a main air valve to control whether the chamber is in the filtering state (online or offline). When a room is being cleaned or maintained, its main air valve must be closed and off-line. At this time, the processing air volume is completely borne by other rooms, and the total filtering area of other rooms is called net filtering area. That is to say, the net filtering area is equal to the total filtering area minus the number of clean rooms and maintenance rooms that must be maintained during operation.
(8) Length-diameter ratio of filter bag
The length-diameter ratio of filter bag refers to the ratio of the length to the diameter of filter bag. The length-diameter ratio of the filter bag is specified as follows:
Back blowing type-30 ~ 40
Mechanical shaking type-15 ~ 35
Pulse type-18 ~ 23