Current status and development of gas recovery technology and converter dust removal

There are more than 600 converters in China, and more than 500 of them are still using the traditional “OG” wet method. Whether it is from the perspective of increasing environmental protection requirements, comprehensive recycling, or from the aspects of energy conservation, cost reduction, and competitiveness of enterprises, technological transformation has to be carried out. Generally speaking, the traditional “OG” wet method will be phased out or rebuilt; although the new “OG” method has improved in environmental protection and energy conservation, the dust consumption is still high and should not be recommended; the dry method is the general direction of development. However, there are still many practical problems in the existing dry methods, such as transformation time, investment, maintenance costs, and unstable emissions. In particular, the requirements for converter equipment and automatic control chain are high, and small and medium-sized converters are generally not used. The use of semi-dry method to gradually develop into a true full-dry method should be a transformation and development direction of converter dust removal technology that is more in line with China's national conditions. The specific outlook is as follows:

Dust concentration

Dust concentration control standards are getting lower and lower, which is an inevitable trend. It is easier to achieve 20~50mg/Nm3 with the new “OG” method, especially the semi-dry gram method. Therefore, as long as the converter dust removal is technically modified, the dust concentration control requirement should be determined to be below 50 mg/Nm3, instead of only requiring the current level of 80-100 mg/Nm3. The final exhaust gas and coal dust concentration are controlled to fight recovering 10mg / Nm3 or less.

2. Gas recycling

At present, the average recovery amount of converter gas in China is 50Nm3/t, and the main technical reasons for low recovery are as follows: First, there is no automatic control and adjustment device for the differential pressure of the furnace mouth, or more is designed but can not operate normally; Second, the hood The sealing performance is not solved well; the third is that the system capacity is not enough, and a large amount of flue gas is burned outside the hood, which not only reduces the gas recovery, but also increases the amount of secondary flue gas and the treatment cost. Regardless of which method is developed, it is necessary to solve the control adjustment of the differential pressure of the furnace mouth and the sealing performance of the hood, and to ensure that the system capacity is slightly larger, so that the air combustion coefficient is controlled to 10% or even 5% or less, so that the steel gas per ton The recovery amount reaches a limit level of 100 Nm 3 /t or even 130 Nm 3 /t. Gas recovery should also consider some of the chemical raw materials to achieve low-carbon economic development.

3. Steam recycling

At present, the actual level of converter steam recovery is 50kg/t. By adopting appropriate technical measures and strengthening rational utilization, it is possible to recover 100kg/t or even 150kg/t. It is necessary to completely eliminate low-level applications such as release and bathing from the technical system.

4. Dust removal

The main reason for the high dust consumption of the converter at one time is that the "OG" system has a large innate resistance, reaching more than 20 kPa. The dry and wet electrostatic precipitator is used as a fine dust removal device , and the system layout is simplified, so that the total system resistance is reduced to 6~8 kPa. It can save 50% of electricity, that is, save 3~4kWh/t. For secondary dust removal, spray-assisted unpowered dust removal or low-resistance electric dust removal, stopping or reducing high energy consumption and high waste bag dust removal system can also significantly save electricity. The temperature at which the converter flue gas enters the dedusting system is currently 900 °C. Many studies at home and abroad have focused on using this part of the waste heat to produce steam to generate electricity or on the grid, and the new water supplemented is mainly consumed in high temperature flue gas cooling. At present, new wastewater is used to replenish new water, such as soft water system drainage and water seal drainage. From the perspective of development, the use of high-temperature flue gas to treat wastewater should be a promising direction before economic and reasonable use of flue gas waste heat.

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