1、 Overview

The low-pressure pulse long bag dust collector is a specially developed advanced pulse bag dust collector based on the spray pulse dust removal technology to meet the needs of high air volume purification. It not only has the strong dust cleaning ability, high dust removal efficiency, and low emission concentration of the spray pulse dust collector, but also has the characteristics of stability, reliability, low air consumption, and small footprint, especially suitable for processing high air volume flue gas. The series of low-voltage pulse bag filters have been applied worldwide and widely promoted in China, widely used for high air volume flue gas purification in industries such as metallurgy, machinery, chemical engineering, and building materials.

2、 Working principle

The low-pressure pulse long bag dust collector is mainly composed of an upper box, a middle box, an ash hopper, an ash unloading system, and a control system, and adopts a lower intake chamber structure. Adopting an offline dust cleaning control system.

The dusty flue gas enters the ash hopper through the lower part of the middle box through the air inlet. Some larger dust particles directly fall into the ash hopper due to inertial collision, natural settling, etc., while other dust particles rise with the airflow and enter various bag chambers. After filtering through the filter bag, the dust is trapped on the outer surface of the filter bag, and the purified gas is discharged into the atmosphere through the bag mouth, upper box, and air outlet by the induced draft fan from inside the filter bag. The dust in the ash hopper is periodically or continuously discharged from the conveying system. As the filtration process continues, the accumulation of dust on the outer surface of the filter bag increases, leading to a gradual increase in the resistance of the dust collector itself. When the resistance reaches a certain value, the PLC dust cleaning control system sends a signal to first close the offline valve of the first bag chamber to cut off the filtered airflow in that chamber. Then, the electromagnetic pulse valve is opened to compress the air sequentially through the air bag, pulse valve, and nozzle on the spray pipe, and spray it into the filter bag in a very short time (0.005-0.1 seconds). Compressed air rapidly expands inside the filter bag, causing high-frequency vibration and deformation of the filter bag. In addition, the reverse airflow causes the dust cake attached to the outside of the filter bag to deform and fall off. After fully considering the settling time of dust (to ensure that the fallen dust can effectively fall into the ash hopper), the offline valve is opened, and the filter bag in this bag chamber returns to the filtering state, while the next bag chamber enters the cleaning state. This process continues until the last bag chamber is cleaned, which is a cleaning cycle. The low-voltage pulse long bag dust collector is composed of multiple independent bag chambers, each of which is cleaned in sequence without interfering with each other, achieving long-term continuous operation. The above dust cleaning process is automatically controlled by the PLC dust cleaning control system, which is divided into two types: timed and fixed resistance. The choice can be determined according to the user's requirements.

3、 Characteristics

1. This dust collector adopts offline cleaning pulse jet cleaning technology, which overcomes the shortcomings of conventional pulse dust collectors and chamber back blowing dust collectors. It has strong cleaning ability, high dust removal efficiency, low emission concentration, low air leakage rate, low energy consumption, low steel consumption, small footprint, stable and reliable operation, and good economic benefits. Suitable for the purification of dusty gases and material recovery in metallurgy, building materials, cement, machinery, chemical, power, and light industry industries.

2. Due to the use of offline dust cleaning pulse blowing, the goal of thorough dust cleaning can be achieved with just one blow, which extends the cleaning cycle and reduces the energy consumption of dust cleaning. The compressed air consumption can be greatly reduced. At the same time, the fatigue level of the filter bag and pulse valve is correspondingly reduced, thereby doubling the service life of the filter bag and valve plate.

3. The maintenance and bag replacement can be carried out in separate rooms without stopping the system fan and under normal operating conditions of the system. The filter bag mouth adopts an elastic expansion ring, which has good sealing performance and is firm and reliable. The filter bag cage bone adopts a circular shape, which reduces the friction between the bag and the cage bone, prolongs the life of the bag, and facilitates the unloading of the bag.

4. Adopting the upper bag extraction method, after extracting the skeleton during bag replacement, the dirty bags are put into the lower ash hopper of the box and removed from the manhole, improving the operating conditions for bag replacement.

5. The box adopts an airtight design with good sealing performance. The inspection door uses excellent sealing materials, and during the manufacturing process, kerosene is used for leak detection, resulting in a very low air leakage rate.

6. The layout of the inlet and outlet air ducts is compact, with low airflow resistance.

4、 Series design

1. Low voltage pulse long bag dust collectors are arranged in rows on a chamber by chamber basis, and are divided into two different arrangements based on the different arrangements of filter bags and filtration areas in each chamber, namely single arrangement and double arrangement. The size of the filter bag is 158X6000. The pulse blowing pressure can be low pressure (0.2-0.3Mpa) or high pressure (0.4-0.5Mpa), which can be selected by the user. If the user has special requirements, special specifications can also be designed according to the user's on-site requirements.

2. The inlet dust concentration of the dust collector is generally allowed to be below 50g/Nm3. If there are special requirements, they can be designed according to user requirements.

3. The dust concentration at the outlet of the dust collector is generally allowed to be below 50mg/Nm3. If there are higher requirements, they can be designed according to actual requirements.

5、 Selection of dust collector

1. Selection of filtering speed

The filtration speed is a key factor in selecting a dust collector, which should be determined based on factors such as the properties of smoke or dust, application scenarios, dust particle size, viscosity, gas temperature, moisture content, dust concentration, and different filter media. When the dust particle size is fine, the temperature and humidity are high, the concentration is high, and the viscosity is high, it is advisable to choose a low value. Such as ≤ 1m/min; On the contrary, a high value can be selected, generally not exceeding 1.5m/min. When the dust concentration requirement at the outlet of the dust collector is below 30mg/Nm3, 0.6-0.8m/min should be selected. When selecting the filtration speed, the net filtration air velocity should not exceed the above value when reducing the filtration area of one room (during dust cleaning).   

2. Selection of filter materials

It should be considered based on the temperature, moisture content, acid and alkali properties, viscosity, concentration, and abrasion resistance of the dust containing gas. Generally, when the moisture content is low and there is no acidity, the selection is based on the temperature of the dusty gas. At room temperature or ≤ 130 ° C, polyester needle punched felt with a density of 500-550g/m2 is commonly used. When the temperature is below 250 ° C, choose aramid Nomex needle punched felt, 800g/m2 fiberglass needle punched felt, 800g/m2 weft double fiberglass fabric, or FMS high-temperature filter material (glass fiber material cannot be used for fluorine-containing gases). When the moisture content is high and the dust concentration is high, it is advisable to use waterproof, oil proof filter media (also known as anti condensation filter media) or membrane filter media (the base fabric should be a needle punched felt that has undergone waterproof treatment). When the dusty gas contains acid or alkali and the gas temperature is ≤ 190 ° C, Ryton polyphenylene sulfide needle punched felt is often used. When the gas temperature is ≤ 240 ° C and the acid and alkali resistance requirements are not too high, P84 (polyimide) needle punched felt should be selected. When the dusty gas is flammable and explosive, use anti-static polyester needle punched felt. When the dusty gas has a certain amount of moisture and is also flammable and explosive, use waterproof, oil proof, anti-static (three proof) polyester needle punched felt.