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Application of air compressor supporting pulse bag filter

The pulse type bag filter uses high-voltage electricity to generate electrostatic suction and the resistance of the bag itself to absorb the dust particles in the flue gas into the bag, and then use the vibration force generated when the folds of the bag are unfolded to pass the collected particulate dust through Gravity falls into the hopper, which removes the dust. It is often said that the screw air compressor provides the air source for backflushing to the bag filter, realizes the pulse backflushing function of the equipment, and ensures the normal operation of the equipment.


The compressed air provided by the air compressor can help the bag filter to complete the green ash, generally requiring a pressure of more than 6 kg, no water and no oil! The dust in the pipeline is mainly caused by settlement, which may be caused by the unreasonable design of the pipeline and the low design wind speed! Of course, it may also be a foreign object that should not have entered! Determined according to the air consumption per unit time and the cleaning pressure requirements. If the air consumption of the pulse valve and the minimum interval time for cleaning are determined, it is easy to do. Generally speaking, the air consumption of the air compressor matched with the pulse bag filter = the air consumption of a single cleaning * the number of cleaning times per unit time. The pressure is generally selected as 0.8 MPa.


The calculation method of the compressed air consumption of the bag filter, the consumption of the pulse valve + the consumption of the poppet valve (according to the working mechanism, the gas consumption value), the compressed air consumption is used to submit to the owner for the selection of the air compressor system. The consumption of the poppet valve is very small under "online cleaning", and this post will not discuss the calculation; the main compressed air consumption is the gas used for cleaning the electromagnetic pulse valve, and the most common calculation formula: air consumption L=1.5*n* Q/T (where 1.5 is the margin, n is the total design number of pulse valves for a single dust collector, Q is the single injection air volume of a single valve, and T is the injection cycle) First of all, Q is the data of each pulse valve manufacturer. Different, the forum has seen that the single injection air volume of 3-inch submerged single valve is 250-300 liters (no injection pressure, diaphragm opening time), the manufacturer's sample book marked: 3-inch submerged valve 0.3-0.35 Under the injection pressure of MPa, the injection time is 0.1ms, and the single-valve injection air volume is 450 liters, or even 480 liters under the same conditions (the air bag design is sufficient); Secondly, there are some data on the T-injection cycle: It is directly written that the dust concentration at the inlet of the dust collector is estimated according to the number of minutes. Some books write the inverse calculation of the injection cycle T according to the resistance value of the dust collector. In the case of inverse calculation, the resistance is divided into clean filter bags and dust removal. The structural resistance of the filter bag is basically a fixed value (some recommend about 125Pa, and some are more than 300Pa); the other part of the resistance is the dust resistance adsorbed on the surface of the filter bag. The calculation formula is relatively simple, but there is almost no source for the parameter values. P resistance value = dust ratio resistance coefficient * filtration speed * filtration speed * flue gas dust concentration * cycle, I think this cycle can be used as the pulse valve injection cycle T, the system pressure difference reaches 1200Pa for spray cleaning, inverse calculation The period T is used as the pulse valve injection period to calculate the air consumption L of the electromagnetic pulse valve. It is difficult to obtain the value of the dust ratio resistance coefficient here. The value is different under different working conditions, and there is no basis for this value to be checked.


Regarding the choice of air compressor type: At present, most of the air compressors for dust collectors are piston air compressors or screw air compressors. If you choose an oil-free air compressor, it will be better. But no matter which air compressor you choose, it needs to be equipped with a tank, dryer and filter. These are used to remove oil and moisture from the gas. Although oil-free air compressors do not worry about oil content, they still contain water content, so post-processing equipment is also required. Therefore, most manufacturers currently do not support oil-free air compressors. Another reason is the high cost.


When choosing an air compressor for a pulse bag filter, pay attention to the following three aspects:

 

1. Select the corresponding compressor and supporting equipment according to the requirements of the pulse bag filter for the compressor gas. There are a few things to consider:

 

1.1 To reduce the oil content in the compressed gas, a degreasing purifier can be used. If the required treatment index is high, a multi-stage treatment can be used.

 

1.2 To reduce the water content in the compressed gas, matching water removal equipment can be used.

 

2. According to the production task of the pulse bag filter and the specific conditions of the workshop, the form of the compressor structure is selected, such as vertical, horizontal or angle.

 

3. According to the exhaust volume and exhaust pressure required in the production of the pulse bag filter, select the appropriate model from the corresponding compressor sample or product catalog. It should be noted that air compressor samples or


The exhaust volume listed in the product catalog is generally calculated according to the gas volume at 20°C and 101.33 kPa, the unit is m3/min, and the exhaust pressure is expressed in Pa (gauge pressure). When it is necessary to determine the performance parameters of the air compressor required for the production of the pulse bag filter, the following aspects should be considered:


3.1 Exhaust pressure. The higher the discharge pressure of the compressor, the more energy is consumed. The sum of the operating pressure, pipeline resistance loss and the pressure of the supporting equipment is set as the lower limit of the rated discharge pressure of the selected compressor. Under normal circumstances, the diameter of the gas pipeline should be selected to be larger to reduce the resistance loss and achieve the purpose of reducing energy consumption in long-term operation. Do not use a compressor with excessively high discharge pressure.


3.2 Exhaust volume. Calculate the actual total gas consumption and multiply it by a factor of 1.1 to 1.2, as the exhaust volume of the selected model of the pulse bag filter. If the selection is too low, it will not reach the specified value of the pulse bag filter; Also higher.


4. Consideration should be taken before purchasing to avoid problems found when the pulse bag filter is used.

 

Example calculation of the air volume of the air compressor matched with the pulse bag filter: the air consumption of the bag filter is related to the size of the pulse valve, the injection time interval (determined by the viscosity of the dust), the injection pressure, the pulse width and other factors. The dust collector has 96 valves, 8 air bags, and each air bag has 12 pulse valves. It is certain that your pulse valve is a 3" valve, and the dust collector should be a line spray.


If you set the time interval to 5 seconds, then 12 valves work in one minute, that is, 60/5=12, and the cycle period of the valve is 96/12=8 minutes, which is generally ok. In this case:

 

1. Air consumption is: 0.24X12=2.88m3/min.

 

2. 3 cubic meters of gas storage tank is enough, and there is also a gas storage bag.

 

3. 4.5 cubic meters of screw air compressor is enough.

 

The above time interval must refer to the nature of the dust, otherwise the difference will be large.

 

An example of calculating the air volume of an air compressor according to the pulse valve:

 

ASCO pulse valve injection calculates the air consumption formula required for injection. For example: 4 meters long bag, diameter 16cm, 12 filter bags to be cleared for each pulse valve, diameter * π (3. 14) * filter bag length 0.16 meters * 3.14 * 4 meters = 2.01 square meters, 2.01 square meters * 12 filter bags = 24 square meters (that is, the area to be cleaned by each pulse valve).


Generally, the air consumption required per square meter is usually set at 10~15nl/square meter in the industry (estimated according to the dust content and density of the dust), so it is estimated that the dust to be cleaned is general dust. 1 square meter requires 12nl (liters), 24 square meters * 12 liters = 288 liters. After that, we will find the corresponding table for the injection volume of the pulse valve. Generally, the recommended pulse width is 100~200 kiloseconds (ms), so we find the corresponding table for a 1.5-inch pulse valve. The pulse width is 150 kiloseconds and the injection volume is 6 kg pressure. 280 liters, so it can be suggested that customers use a 1.5-inch electromagnetic pulse valve with such a filter bag cleaning area is sufficient.


Calculation method of air bag volume. For example: the length of the air bag is 5 meters, the diameter is 40cm, and the volume is radius * radius * π * length, which is 0.2 * 0.2 * 3.14 * 5 = 0.628 cubic meters = 628 liters (the volume of the air bag, in the state of natural atmosphere ).


Volume * pressure (kg) = air consumption per pulse injection 628 liters * 5 kg = 3140 (the air volume given by the air compressor to the air bag each time) The consumption of each injection should not exceed the content of the air bag 50%, this is to ensure that the pulse valve can be supplied with sufficient air for the next injection.


Generally, it is recommended to use 8-inch air bag for 1.5 inches, 10-inch air bag for 2-inch pulse valve, and 12-inch air bag for 3-inch pulse valve (or above, 14-inch air bag is also available).


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