Working Principle
1. Bag Dust Collector
Bag dust collector uses bag filter cloth made of fiber woven fabric as the core filter element. When the dust-laden gas passes through the filter cloth in one direction, the dust particles with larger particle size are intercepted due to collision with the filter cloth fibers under the action of inertial force; while the dust particles with fine particle size (usually 1μm and below) will be impacted by gas molecules to produce Brownian motion and constantly change the direction of movement.
Since the gaps between the filter cloth fibers are smaller than the free path of the Brownian motion of gas molecules, these fine dust particles will collide with the fibers and separate. As the dust removal process continues, a large number of dust particles accumulate on the surface of the filter cloth fibers and gradually form a filter cake. The filter cake can further capture finer dust particles by means of screening and other mechanisms. Finally, the dust particles are trapped upstream of the filter cloth (dust-laden gas side), while the purified clean gas passes through the filter cloth and gathers downstream (clean gas side). When the dust particles on the filter cloth have accumulated to a certain extent, they are removed from the filter cloth by means of pneumatic cleaning or mechanical cleaning, and then collected and transported.
2. Electrostatic precipitator
The electrostatic precipitator applies high-voltage direct current between the positive and negative electrodes to build a high-voltage electric field that can ionize the gas. When the dust-laden gas enters the electric field, the dust particles will be charged (usually negatively charged) under the action of the electric field. Driven by the electric field force, the charged dust particles move toward the dust collecting electrode (positive electrode) with opposite polarity, and finally deposit on the surface of the dust collecting electrode, thereby separating the dust particles from the dust-laden gas. Subsequently, by vibrating the electrode, the dust deposited on the dust collecting electrode falls off and falls into the collecting hopper at the bottom of the dust collector for subsequent collection and transportation.
Advantages of electrostatic precipitator
1. High dust removal efficiency
Electrostatic precipitator can significantly improve the collection efficiency by extending the length of the electric field. When the dust in the flue gas is in a normal state, its collection efficiency can usually reach more than 99%; if an electrostatic precipitator with 4 or 5 electric fields is used, the dust removal efficiency can be further improved. However, as the operation time of the electrostatic precipitator increases, its dust removal efficiency will decrease to a certain extent due to factors such as electrode corrosion.
2. Small equipment resistance and low energy consumption
The energy consumption of the electrostatic precipitator mainly comes from equipment resistance loss, power supply device, heating and insulation, and vibration motor. Compared with other types of dust collectors, the resistance of the electrostatic precipitator is smaller, generally 200-300Pa, which is about 1/5 of the resistance of the bag dust collector. The lower energy consumption makes it rare for the electrostatic precipitator to replace wearing parts during operation, thereby greatly reducing operating costs.
3. Wide range of applications
The electrostatic precipitator can effectively capture ultrafine particles with a particle size of less than 0.1μm, and can handle high-temperature flue gas with a temperature of up to 300-400℃. When the various parameters of the flue gas are within a certain fluctuation range, the electrostatic precipitator can still maintain good capture performance.
Advantages of bag dust filter
As a dry and efficient dust removal device, bag filter uses bag filter elements made of fiber weaving to achieve efficient capture of solid particles in dusty gas. The dust removal process involves many factors, including bag material, weaving method, fiber density, and the diffusion, inertia, mass and electrostatic characteristics of dust. At the same time, the cleaning method also has an important influence on the dust removal effect. The filter cloth material is the key to the bag filter. The filter cloth with excellent performance not only needs to have a specific density and air permeability, but also has good corrosion resistance, heat resistance, wear resistance and high mechanical strength. At present, the heat resistance of fiber materials with excellent heat resistance can reach 250℃ - 350℃, and the service life of bags with strong wear resistance can be up to 4-5 years.
1. High dust removal efficiency
Bag filter can efficiently capture dust above 0.3μm and purify dusty gas to a concentration of 15mg/m³ or even lower.
2. Fewer ancillary equipment and lower investment cost
Compared with electrostatic precipitators, bag filters have fewer ancillary equipment and relatively lower technical requirements, which makes them have certain advantages in investment cost, especially suitable for projects with limited budgets.
3. Wide range of dust collection
Bag filters can effectively capture dust that is difficult to recover with electrostatic precipitators, and to a certain extent can also collect compounds such as nitrates and sulfides, expanding their application range in different industries.
4. Strong load adaptability
Bag filters have good adaptability to load changes and are particularly suitable for capturing fine and dry dust. At the same time, the collected dry dust is easy to handle and recycle, and has high economic value.
Precautions when selecting bag dust collectors
1. Reasonable selection of structural form
When selecting the structural form of bag dust collectors, priority should be given to types with high reliability, convenient maintenance, simple structure, and good bag changing working conditions. At present, most bag changing locations are in the clean air chamber. This design can effectively improve the bag changing working environment and reduce the work intensity and safety risks of operators.
2. Ensure the reliability of filter materials
Filter bags are made of rich and diverse materials. When selecting, the key is to ensure that the filter materials meet the system requirements in terms of operating temperature, oil resistance, acid and alkali resistance, oxidation resistance, and waterproofness. In order to further optimize the performance of the filter materials, it is sometimes necessary to perform special treatments such as calendering and singeing on the bags.
3. Determine the appropriate filtration wind speed
The filtration wind speed directly affects the service life of the filter bag. During the installation process, it is necessary to ensure that the surface of the bag cage, flower plate and its connecting parts are smooth to avoid damage to the filter bag; at the same time, it is necessary to ensure that there is a reliable seal between the filter bag and the flower plate, and the flower plate has sufficient flatness and rigidity to ensure the stable operation of the dust removal system.