Under the background of implementing environmental protection and energy saving in an all-round way, upgrading the dust removal technology of blast furnace gas and strengthening the dust removal effect of blast furnace gas have become the inevitable trend of modernization construction and development of related industries. With the continuous innovation and application of blast furnace gas dedusting technology, its dedusting and purification technology has developed from wet dedusting to dry dedusting (including bag dedusting, electrostatic dedusting, etc.). Based on this, taking bag dust removal technology as an example, starting with its related overview, the application of bag dust removal technology in blast furnace gas dust removal is analyzed, and the existing problems are put forward.
1. Overview of bag dust removal technology
Under the background of implementing environmental protection construction and resource-saving construction in an all-round way, bag dust removal technology has achieved certain development results, and its equipment technology, automatic control technology, product services, system accessories, special fiber filter material have been improved to varying degrees.
2. Application Mechanism of bag Dust Removal Technology in Blast Furnace Gas Dust Removal
2.1. Collection of filter material for bag filter
When the bag filter technology is applied to purify and remove the dust in blast furnace gas, the filter material in the bag filter will collect the dust particles through inertial collision effect, electrostatic effect, screening effect, diffusion effect and gravity sedimentation effect.
For example, when the larger particles of dust in the blast furnace are under the action of airflow and close to the fiber trap of bag filter, they flow rapidly. The larger particles will deviate from the airflow track under the action of inertia force and move forward along the original trajectory, and collide with the trapping fibers, which will be solid under the effect of trapping fiber filter. Now the dust particles are filtered. At the same time, when the airflow passes through the filter material of bag filter, the electrostatic effect is formed under the action of friction force, which makes the dust particles charged, and the dust particles are adsorbed and trapped under the action of potential difference and Coulomb force.
2.2. Collection of Dust Layer in Bag Dust Collector
Usually, the filter bags of bag filter are made of fibers. During purification and filtration, dust particles will form "bridging phenomenon" in the voids of the filter material net, which will reduce the pore size of the filter material net and gradually form a dust layer. Because the diameter of dust particles in the dust layer is smaller than the diameter of filter material fibers to a certain extent, the filter and interception of the dust layer appear, and the dust removal effect of bag filter is improved.
2.3. Purification and removal of blast furnace gas dust by bag filter.
Usually, the particle size distribution of smoke and dust in blast furnace gas is from small to large. Therefore, in the process of bag filter operation, the airflow containing dust particles will pass through the filter material of the bag filter. In this process, the larger dust particles will be left in the filter material or on the surface of the filter material net by gravity, while the smaller dust particles (less than the filter cloth void) will be forced to impact, screen or leave in the filter material table. The surface is left in the void of the filter cloth by Brownian motion. With the continuous accumulation of dust particles captured by filter materials, a dust layer will be formed on the surface of the filter bag, and to a certain extent, it will become the "filter membrane" of the filter bag to enhance the purification and dust removal effect of the bag filter.
3. Application of bag dedusting technology in blast furnace gas dedusting
3.1. Overview of Application
The bag dust removal system is mainly composed of back-blowing ash removal system, control system, semi-clean gas pipeline system, semi-clean gas safety temperature system, ash conveying and ash unloading system, etc. It is used to realize the purification and dust removal of blast furnace gas.
3.2. Application of Bag Dust Collection System
3.2.1.Application of Back-blown Soot Cleaning System
In the bag dust removal system, the back-blown ash removal system can be divided into two categories: the pressurized back-blown ash removal system and the nitrogen pulse back-blown ash removal system. The pressurized back-blown ash removal system is an internal filter mode. When the dusty gas flows outward through the filter bag of the bag filter, the airflow will change direction under the action of the back-blown ash removal system, realizing the airflow from outward to inward, thus achieving the purpose of dust removal through the collection of the filter bag. The nitrogen pulse back-blown dust cleaning system is to flow the gas containing dust particles from the bottom to the outside surface of the filter bag. While strengthening the role of the dust layer, the dust accumulation on the outside surface of the filter bag can be cleaned by means of the pulse valve. In order to maximize the role of the back-blowing ash-cleaning system, a specific analysis should be made according to the specific situation in its application.
3.2.2. Application of Differential Pressure Detection System
In the application process of the bag filter, it is very important to ensure the safety and stability of its differential pressure detection system. Usually, the pressure difference detection points are mostly distributed in the gas inlet and outlet pipes and the clean gas chamber of the box body. The scientificity and rationality of the system installation is the key to ensure the accuracy and accuracy of differential pressure signal detection, and the detection accuracy is the key means to improve the quality of dust collector maintenance, as well as an important way to improve the service life of filter bags, improve system quality and reduce energy consumption.
3.2.3. Application of Semi-clean Gas Safety Temperature Control System
In the process of blast furnace smelting in iron and steel enterprises, the gas produced by blast furnace equipment will become "semi-clean gas" under the action of gravity purification and dust removal. At the same time, semi-clean gas enters the bag filter bag through the blind valve, butterfly valve of dust collector and semi-clean gas pipeline for dust removal. Usually, when semi-clean gas enters the dust collector tube, the gas temperature will change to a certain extent, that is, heating up. With the increase of temperature, the airflow will destroy the filter bag in the dust collector and burn the filter bag. Therefore, in order to ensure the safety of temperature, it is necessary to install a semi-clean gas safety temperature control system for temperature control.
3.2.4. Other Application Strategies
In order to ensure the full play of the role of bag filter and reduce energy consumption in operation. In the application process, it is necessary to scientifically select the valve of the dust collector box to ensure the safety and tightness of the system and avoid gas leakage in the process of dust removal. Usually, when the pressure of the system network changes and has adverse effects on butterfly valves, the straight plate dust butterfly valves or through the installation of dust clearing holes can be used to strengthen the butterfly valves.
4. Concluding remarks
In industrial smelting, it is of great significance to improve the utilization rate of blast furnace gas resources, reduce the environmental pollution of blast furnace gas, improve the economic efficiency of enterprises, and promote the sustainable competitive development of enterprises.
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