Dry Bag Cleaning Technology of Blast Furnace Gas

China’s blast furnace gas dry bag dedusting technology after 30 years of application and development, has become increasingly mature, and in many small and medium-sized blast furnace to promote the use of. At the same time, in recent years, China’s filter material has also made great progress, fiber and ultra-fine glass fiber composite high-temperature needle felt filter media not only improve strength, longer life, and the use of temperature, can withstand 260 degrees Celsius High temperature, blast furnace gas dry dust bag laid a solid foundation, combined with PLC automation control system, so that nitrogen pulse jet cleaning and unloading ash, ash can be automatically controlled according to the program, effectively promote the blast furnace gas dry Dust bag technology to enhance the level.
The successful use of medium and small blast furnace dry bag filter has laid a foundation for the use of dry bag filter in large blast furnace. However, the large amount of blast furnace gas, such as the use of small and medium-sized blast furnace dry dust box size specifications, to achieve the same filtration efficiency, is bound to be doubled to increase the number of boxes, resulting in the entire dry dust collector failure, Covers an area greatly increased. Taking this design idea, its reliability is reduced, far can not meet the needs of large-scale blast furnace, affecting its normal operation, leading to energy imbalance, resulting in huge losses.
In order to remove the obstacles of dry blast furnace dust removal, Ruifan company in the dry dust removal process, equipment, key accessories, ash delivery system and other aspects of the system do in-depth study, through a large number of arguments to increase the single box filter area, Diameter of the box (diameter of 5.2 meters) into the blast furnace gas dry dust collector, and the use of 6 m diameter box for dry dust removal system in large blast furnace application and promotion laid the foundation.

Economic Analysis of Large – scale Blast Furnace Dry Method Dust Removal

Baosteel 4 blast furnace effective volume of 2200 cubic meters, is a deep hearth furnace chunky blast furnace blast furnace gas, the average amount of 380,000 cubic meters / hour, blast furnace top pressure of 0.18 MPa, blast furnace gas purification using wet Two – stage venturi system. In 2005, the blast furnace launched a dry bag dedusting system, has more than two years of stable operation, the technical indicators have met or exceeded the design standards, a domestic blast furnace with more than 2000 cubic meters of dry gas with the first dust.
Blast furnace gas dust removal system by the wet dust to dry bag, the blast furnace production stable, dust removal system is stable and meet the needs of the actual working conditions. Compared with the wet method, the dry dust removal increases the annual power generation capacity of TRT by 21.56 million kWh, increases the heat recovery temperature of blast furnace gas by 100 degrees Celsius, and increases the utilization rate of pressure by 60 percent. At the same time, due to reduce the number of blast furnace repair wind which can increase annual production of 7,700 tons, 6188 tons of carbon dioxide emissions per year. To 2200 cubic meters of Baotou Iron and Steel blast furnace, for example, the dry dust removal system put into operation, can significantly save the turbid water ring water, saving maintenance costs, saving 60 tons of new water / year. At the same time, the way of dust removal, so that the thermal efficiency of dry dust greatly improved, dry dust for supporting the TRT residual pressure power generation system can double the generating capacity of about 6,000 kilowatt hours, the gas can also increase the theoretical combustion temperature.

Optimization of equipment to ensure a large blast furnace dry dust anterograde

Bag is the “heart” of the dry bag filter, its performance will directly affect the life of the dust collector, dust removal effect and overall performance. After the experiment of different materials and different ratio of bag in China, combined with the experience of dry blast furnace gas bag dedusting in the past, the final selection of high temperature, bending resistance, good tensile properties of needle felt filter media In Baotou large blast furnace bag filter.
There are many kinds of valves in dry dust remover, such as butterfly valve, flapper valve, ball valve and bell valve. The blast furnace gas temperature is high (150 ℃ ~ 260 ℃) and high pressure (0.2MPa ~ 0.25MPa) , A large amount of dust in the waste gas, requiring valve with good sealing performance, rigidity and reliability, and high temperature resistance, wear resistance and strength.
There are still many problems in butterfly valve, flapper valve, ash discharging valve in the current dust catcher system. For example, the butterfly valve in the normal temperature of the opening and closing is very flexible, but encountered high temperature (greater than 300 degrees Celsius) will be stuck or lax problem; flapper valve appeared to run half the valve plate can not move, resulting in a large number of gas Leakage problems; seal easy to wear and leakage problems; ash valve appears easy to wear, the service life is not long and so on. Therefore, the dry dust removal system should focus on the choice of the valve to consider the following questions:
First, the choice of three-eccentric butterfly valve, sealing Vice oblique, large cone angle structure, the inner wall of high temperature and wear resistant coating. The structure of the valve starting torque is small, the flow resistance is small, anti-erosion ability. Seal of the valve body with high-strength hard alloy surfacing, valve plate sealing with multi-level or “S” -type seal, may be appropriate to extend the life, to achieve a good sealing effect.
Second, the board valve to remove the traditional valve plate off the body, instead of mechanical limit directly drive the valve off the body, the valve plate and seat gap uniform, smooth friction-free operation; electric drive, screw nut clamping mechanism , Fully enclosed frame structure, compact electric device, easy installation and operation, and the screw nut clamping torque, to help seal the valve; screw nut designed to be closed to prevent dust into the valve plate guide rails Form instead of on the lower part of the valve box fouling caused by the valve plate running failure; the use of special silicone rubber, silicone rubber in the fine metal fibers can significantly improve the tensile strength of the seal ring to extend the life of the ring .
Third, the selection of the ball valve body using cast steel processing shape, the surface of the ball plated carbide, single-seat streamlined channel, the use of sealing body with adjustable spring function, and spraying the internal wear-resistant materials, thus greatly improving the use of life.
Fourth, dry bag filter gas main and branch pipes are equipped with corrugated compensator. The blast furnace gas contains sulfur ions, chloride ions, etc., in the dry bag after dust, because the gas temperature drops below the dew point when the temperature of liquid gas deposition attached to the pipeline, dissolved and enriched gas sulfur, Chloride ion, etc., on the compensator of stainless steel band to produce serious corrosion, and even cause the corrugated compensator leakage, resulting in dry dust collector system can not work properly.
In the ash transfer process, dry dust removal machinery there is a bad sealing, failure and more problems, the use of pneumatic conveying is the development trend. Currently used positive pressure pneumatic conveying in Baotou No. 4 blast furnace dust on the effect is better, run more than 2 years without problems, and in some dust on the elbow, three easy to wear problems, the service life is short. Therefore, the gas-solid ratio of pneumatic conveying, pipeline size, transmission gas pressure and other parameters also need further study. The use of storage pump dense phase ash will be a development direction.
The anti – corrosion problem of coal gas system is one of the main problems to be solved in dry blast furnace. Blast furnace gas contains many corrosive components, when the cold or when the cold wall, the gas in the water out of sulfur ions, chloride ions, dry dust removal system corrugated compensator strong. Now part of the system using special materials, but expensive.
The use of dry dust, gas collection under the fine dust particles, light weight, good mobility, improper handling and transportation during storage, easy to produce secondary flying pollution of the environment; dust, zinc and other metal elements are more difficult to return to sintering . Therefore, the separation of iron, zinc and other components in the dust, the recovery and recovery of other metals in the dust, the secondary use of dust and so on are the subjects to be studied.