Of course, compliance with environmental standards is an important condition for the successful and safe operation of any production. Purification of air polluted by processed products is a basic requirement for mining, cement, chemical, milling, metallurgical and other areas, in the process of which a large amount of dust, soot and other microscopic pollutants.
But modern cleaning designs can effectively solve the problem of excessive dustiness. air: the design and operation of the bag filter is aimed precisely at removing the smallest particles of harmful suspensions. After installing this unit, all dust and dirt settle on the walls of the filter, and lighter and free air is released into the atmosphere.
In this material, we will consider the structure and principles of operation of the baghouse filter, learn about the methods of their self-regeneration and replacement, and also reveal the advantages and disadvantages of this purification design.
The content of the article:
- The need for air purification in production
- How does a bag filter work and how does it work?
-
The main types of filter bags
- # 1: Difference in Equipment Performance
- No. 2: Classification according to the type of installation of hoses
- No. 3: Varieties by material of manufacture
- No. 4: Classification by regeneration method
- Features of bag filter replacement
- Advantages and disadvantages of fixtures
- Conclusions and useful video on the topic
The need for air purification in production
The ecological crisis on the planet is getting worse every day. Manufacturing enterprises play an important role in this: leakage of chemicals, pollution of water bodies wastewater and dust emissions have an extremely negative effect on both the state of nature and health of people.
In addition to direct harm to workers and residents living near the production, dust damages the enterprise itself. Dust deposits have a detrimental effect on the operation of the equipment, worsens the condition ventilation system and heat exchangers. These factors can lead to a decrease in the quality of manufactured products and even increase its cost due to breakdowns and faster wear of the equipment used.
Dust suppression in enterprises is organized by different methods. In addition to trapping suspended matter with special filters, a fogging system can be used, due to which dirt particles settle together with microdroplets of water
That is why high-quality collection and neutralization of dust is an integral part of the entire technological process in production. The bag filter effectively copes with the tasks and protects not only nature and people, but also the equipment of the enterprise.
How does a bag filter work and how does it work?
Bag filter cleaning equipment can be used as part of internal ventilation, providing return of purified air back to the room, as well as a system of complete purification of air before it is released into the surrounding Wednesday.
The bag filter is a fairly simple structure, which consists of the main elements:
- housings for filter units;
- chambers for clean and dirty air;
- bunkers and supports;
- an intake valve through which the air mixture passes;
- cleaning sleeves or a set of sleeves that are located in the path of air passage;
- an outlet valve with a pressure regulator that allows the purified stream to pass through;
- filter regeneration system, which allows you to periodically clean the bag from dust.
The design of the device is designed to allow a sufficiently large amount of air or gas to pass through. The streams entrained by the inlet valve pass through the system, leaving particles of dust or soot contamination on the surface of the filter on a woven or non-woven base.
The diagram above clearly shows the structure of the bag filter and the direction of the flow of polluted and purified air through the air purification system
The filter can be single, however, complexes with a battery of sleeves, which more effectively purify the air, remain more effective. After the sleeve, the processed air is discharged through an outlet valve equipped with automatic pressure control.
In fact, the structure performs three main tasks:
- qualitatively cleans the air-gas mixture from pollutants;
- ensures the uniformity of the dust load;
- regulates the amount of air supplied for filtration.
Separation of fine particles in the exhaust air makes it possible to ensure the proper purity of the discharged stream. Unwanted suspended solids are held securely inside the sleeve, which cleans itself out during the regeneration phase.
The main types of filter bags
The selection of a suitable baghouse filter is based on the manufacturing process and the nature of the dust produced in the process. The main criteria on which to rely on when selecting this equipment are the performance of the installation and the depth of cleaning the incoming air. The rest of the parameters are individual: the degree of their importance depends on the production conditions.
For example, the choice of material from which the filter is made depends entirely on the characteristics of dust contaminants that arise during production.
# 1: Difference in Equipment Performance
Bag filters are divided into two main types: round and flat. The first type is designed for operation at enterprises with a high dust load and is capable of passing and purifying quite serious volumes of air: more than 100 thous. m3 in hour.
However, the operation of such powerful equipment requires additional compressed air supply to the system. Flow volumes can be up to 4000 liters per minute
Flat sleeves have a more modest performance, but also have a more compact design. Such cleaning systems are suitable for workshops with a low dust load.
No. 2: Classification according to the type of installation of hoses
By the type of installation, systems with bag filters can be vertical or horizontal. The latter remain more efficient as they allow more air or gas to pass through.
The flow path itself along the sleeve is quite long, so the pores of the filter material trap more contaminants.
Sleeves are also distinguished in shape: ellipsoidal, cylindrical, rectangular.
No. 3: Varieties by material of manufacture
The classification and principle of operation of the baghouse filter is also influenced by the material from which the filter element is made. It is often made from fabric.
The material from which the bag filter is made directly affects the wear resistance of the equipment. Certain fabrics are less prone to tearing and leakage, resulting in less frequent filter changes
It can be either natural cotton or wool, or synthetic materials:
- polyester;
- fiberglass;
- polyamide;
- meta-aramid;
- polytetrafluoroethylene;
- polyacrylonitrile, etc.
The choice of hose material is based on the type of production, characteristics of the filtered mixture, dispersion and properties of dust, aggressiveness of the medium.
Recently, nonwoven filters with a more homogeneous and fine-pored structure, which, due to the fibrous surface, retain more contaminants, have become especially popular.
No. 4: Classification by regeneration method
The filter recovery method can be considered another category of classification of these devices. Regeneration of the sleeve assembly is an important stage in the structure's operation, so it should be given special attention.
The most popular way to regenerate bag filters is by impulse blowing, as shown in the diagram above. However, this method of purification is not suitable for all types of industries.
In fact, regeneration is the process of cleaning the bag from accumulated dirt.
The procedure can be carried out by several methods, the choice of which depends on the nature of the dust:
- Vibration cleaning, in the process of which the sleeve or the battery of sleeves is intensively shaken, after which the dirt particles fall into a special hopper for subsequent removal. Dust is removed from it using a dust transport system: a screw or pneumatic conveyor, a rotary vestibule, a scraper chain, a slide or valve gate.
- Pulse Purge or Air Purge. The filter is subjected to impulse blowing or pneumatic cleaning by means of a backflow of air, which knocks out microparticles from the pores.
- Combined cleaning. A battery or a single sleeve undergoes combined cleaning, during which the filter is shaken and blown over by streams of clean air.
Vibration cleaning can take place not only automatically: the regeneration process is sometimes carried out manually thanks to a special handle and is called mechanical cleaning of the sleeve.
But most often the regeneration process is carried out automatically due to the work of pollution sensors, which react to the amount of collected litter and determine the pressure and capacity of the sleeve. If the pressure at the outlet of the structure drops, the sensor starts the purge process or the shaking mechanism.
Regeneration is systematic and can significantly extend the life of the baghouse. On average, the filter element can be used for up to three years.
With low dust load in a non-aggressive environment in a small production area, a complete the functioning of the bag filter can be up to five years, after which it will require its planned replacement.
Features of bag filter replacement
Like the installation, replacement of worn-out filters is carried out on the basis of project documentation and the conditions in which the cleaning device operates.
Many key factors are taken into account:
- dust load;
- dispersion of dust and its quality;
- characteristics of the working environment;
- the performance of the filter itself;
- place of installation;
- depth of mixture cleaning, etc.
If only one hose is out of order in the battery, you can cut off its operation without replacing it. For this, the filter is clogged at the tube sheet level. It is not necessary to remove the purge tube or frame.
The bag filter is replaced after it is completely worn out or the regeneration efficiency has decreased. If through holes are formed in the material, the replacement can be carried out much earlier than the due date.
If the unit requires a complete replacement, you must perform the following steps:
- Close the dampers at the entrance and exit to the compartment, if this is provided for by the design features of the system.
- Through the sight glass, remove the purge tube leading to the hose or battery being replaced.
- Remove the sleeve frame.
- Remove the sleeve from the structure. It can be lifted up the tube sheet or dropped into a dust bin. In the latter case, the filter will need to be removed from the compartment through the viewing window.
- Install the new sleeve upside-down. After connecting, fix the frame, run the purge pipe.
After the replacement measures, it is necessary to carry out a test run of the equipment to make sure it is working properly.
It is better to trust a replacement to a specialized company whose employees have the skills and experience in removing and installing bag filters.
We also have an article on our website with detailed instructions on changing the filter in the supply ventilation.
Advantages and disadvantages of fixtures
Like any other cleaning equipment and systems, for example, aspiration, the baghouse filter has its own peculiarities of operation, during which the characteristic advantages and disadvantages of the system are revealed.
The advantages of such a complex are much more than the flaws, therefore, bag filters are widely used in various fields of production.
The arrangement of a ventilation system with a baghouse filter is suitable not only for large-scale and complex production, for example, in the metallurgical industry. A similar air filtration system is appropriate in small workshops for the production of furniture, paving slabs and other things.
The indisputable advantages of bag filters include the following features:
- The design is universal, therefore it can be easily integrated into ventilation and purification systems of various industrial sectors.
- The bag filter complex can be easily integrated into the production line and is not very demanding in terms of the area required for its construction.
- The degree of purification of the gas-air mixture reaches 90-99%, which is an extremely high indicator for a dry purification system.
- Filtration occurs equally effectively both at extremely low air temperatures and in a heated room.
- The complex management is very simple and can be fully automated.
- The planned replacement of used bag filters is carried out every two to three years.
In addition to the advantages, the bag filter also has minor disadvantages. The main one is the need to supply compressed air in conditions of filtration of air volumes over 150 m3 in hour.
Filters may be required for certain types of production or aggressive operating conditions expensive materials such as fiberglass or meta-aramid, which are more resistant to wear and tear.
Other types of filters are also used in the ventilation system. We talked more about air and carbon filtration systems in the next article.
Conclusions and useful video on the topic
The structure and principle of operation of the purification system with a bag filter is clearly shown in the video below:
The bag testing process and the filter cleaning mechanism have been demonstrated by the cleaning equipment manufacturer:
A bag filter is one of the simplest and most effective methods of dry air purification from dust of various origins. The universal system can be successfully integrated into almost any technological process, during of which large volumes of filtration medium are formed, requiring maximum removal of unwanted suspensions. The sleeves are easy enough to replace and do not require complex or expensive maintenance. Therefore, the owners of production facilities should definitely take a closer look at this type of exhaust air purification.
Would you like to supplement the above material with useful information or tell about the peculiarities of applying filters based on personal experience? Write your comments and additions, ask questions to our experts - the feedback block is located below.
