Research and application of new technology of the

Research and application of new technology of blast furnace gas purification system

the original two blast furnace gas purification systems of Jinan Iron and Steel Group Corporation No. 2 ironmaking plant (hereinafter referred to as Jigang No. 2 ironmaking plant) adopt the tandem venturi tube electrostatic precipitator wet dedusting process respectively. The gas processing capacity is 120m3 blast furnace, the utilization coefficient is 1.6t/m3d, and the gas generation of a single furnace is 2.2 × 104m3/h design

the dust removal efficiency of the original gas purification system is low and there is no efficient fine dehydration device, resulting in a net gas moisture content of 80g/m3 and a dust content of more than 80mg/m3. With the continuous improvement of production technology, the utilization coefficient of blast furnace has exceeded 3.5t/m3 d. The gas production of a single boiler has reached 3 × Above 104m3/h, the comprehensive quality of gas purification is further degraded. The water content of net gas is greater than 100g/m3, and the dust content is 100 ~ 150mg/m3. The main hazards to gas users are: high slagging speed, serious slagging degree, low service life, low theoretical combustion temperature of gas and low air supply temperature of hot blast stove. In order to improve the comprehensive quality of gas purification and improve the air supply temperature of hot blast stove, the original gas purification system was reformed and a new gas purification system was developed

2 development of new system

2.1 design principle

blast furnace raw gas is roughly dedusted by the gravity dust collector (dust content is 6 ~ 8g/m3), enters the venturi tube for cleaning and cooling, and then enters the garland dehydrator for semi-fine dehydration and dust removal, mainly removing dust droplets with a diameter greater than 0.1mm in the gas, and then enters the wire dehydrator for fine dehydration and dust removal, removing dust droplets with a diameter of 0.1mm and less in the gas, Ensure that the dust content of gas is less than 15mg/m3 and the mechanical water content is less than 5g/m3

2.2 design requirements

transform the gas pipe to reduce the gas flow rate; System control automation; Excess gas shall not be discharged, and pipes shall be erected for heating furnaces in medium-sized rolling mills; The gas washing water is recycled without being discharged; The system metering facilities are perfect, accurate and reliable; System safety, environmental protection and industrial hygiene shall be designed and constructed in accordance with national specifications

2.3 determination of process technical parameters

blast furnace top gas pressure is 0.03 ~ 0.05Mpa; The venturi has loosened the industry development. The gas temperature at the inlet of "Le rope" on the neck is 250 ~ 300 ℃ under normal conditions and 500 ℃ under accident conditions; Gas processing capacity (2.5 ~ 4.0) × 104m3/h； The dust content at the venturi inlet is 6 ~ 10g/m3; The circulating water volume of the system is 170m3/h; The dust content of the net gas is not more than 10mg/m3 when the pressure of the top gas is greater than 0.03mpa, and not more than 15mg/m3 when the pressure of the top gas is not greater than 0.03mpa; The mechanical water content of purified gas shall not be greater than 5g/m3

2.4 research and application of key technologies

2.4.1 the "Rd" flap of the adjustable throat venturi is driven by an explosion-proof motor, and the flap angle is displayed through the angle generator. It can be operated remotely in the operation room. The dust removal efficiency of the adjustable throat depends on the adjustment angle of the "Rd" flap and the water spray at the throat

when the raw gas with a certain pressure is roughly dedusted by the gravity dust collector, it enters the adjustable throat for cleaning and cooling. The cross-section of the throat "Rd" flap is oval. According to the hydrodynamic calculation, the flap angle is in the range of 30 ~ 70 °, and the opening is basically linear with the flow area. At this time, the throat adjustment effect is the most obvious, which is called the effective adjustment area. According to the calculation, if the gas resistance at the throat is controlled at 16.8 ~ 21.0kpa in the effective regulation area, the instrument can work reliably so that the dust content of gas is less than 15mg/m3. In production, through sampling analysis and operation, the statistical results of the data that make the measurement results incorrect show that the calculated value is consistent with the actual effect

the amount of water sprayed at the throat is another important factor affecting the purification quality. According to the calculation, when the water gas ratio at the throat is 1.6l/m3, the best effect of gas dust removal is achieved. At this time, the gas resistance △ P at the throat is 21.1kpa, and the gas flow rate V is 100M/s. In production operation, the amount of water sprayed at the throat should be adjusted according to the change of gas flow to achieve the best effect of gas purification. The test in production shows that when the gas generation is (3.0 ~ 3.7) × 104m3/h, adjust the water spray volume at the throat to 50 ~ 60m3/h, and analyze the gas sampling. The dust content is less than 8mg/m3, which is consistent with the theoretical calculation value

2.4.2 garland dehydrator garland dehydrator is a semi fine dehydration and dust removal equipment, which mainly removes dust containing water droplets greater than 0.1mm from the gas. The working principle is to fill the equipment with a 1000mm thick aluminum alloy rosette packing layer with a diameter of 100mm. When the gas passes through the packing layer from bottom to top, the dust containing water droplets greater than 0.1mm in the gas will be removed

the main design parameters are: gas processing capacity (3.5 ~ 4.0) × 104m3/h； The gas temperature is 30 ~ 50 ℃; Working pressure 10 ~ 50kPa; The resistance loss of the rosette packing layer is less than 2KPa.

in order to prevent the increase of gas resistance loss caused by the blockage of the wreath, a backflushing device is designed: generally, it is flushed twice every 8h, and each flushing time is 10 ~ 15mim. When the resistance loss of the wreath reaches 2KPa, wash it twice continuously, 10 ~ 15mim each time, and the same good effect is achieved

2.4.3 the main design parameters of wire dehydrator are: gas processing capacity (3.5 ~ 4.0) × 104m3/h； The inlet gas temperature is 30 ~ 50 ℃; Working pressure 10 ~ 20 kPa; The thickness of the filler layer is 500mm for the wreath and 100mm for the wire; The resistance loss of the filler layer is less than 2KPa

the diameter of the silk used in the silk dehydrator is 0.1. Some emerging industries have put forward new requirements for experimental fixtures. 25 ~ 0.27mm stainless steel wire is woven and made into a waveform. After forming, it has a certain channel. After the water droplets collide with the wire, they form a water flow in the channel and flow out of the wire. The arrangement of silk is very strict, which determines the efficiency of silk dehydration. If it is not placed properly, the water drops of silk will not form a water flow, but will be taken away by gas. Pay special attention when installing the screw. When the silk dehydrator works, the gas flows upward from the bottom through the garland and silk packing layer and enters the clean gas main pipe

in order to prevent the silk from blocking, the silk should be backwashed regularly. Generally, the silk should be washed twice every 8h, 10 ~ 15min each time. When the resistance loss of the silk dehydrator reaches 2KPa, wash it twice continuously for 10 ~ 15min each time, and the same good effect is achieved

the wire dehydrator is a fine dehydration and dust removal equipment, which can only be installed after the filler dehydrator. A large amount of water brought out by the gas during cleaning must be removed first, and then the wire dehydrator removes the dust containing water droplets no more than 0.1mm. The dehydration efficiency can reach 99.9%, but the total weight of the removed mechanical water droplets cannot exceed 114g/m3

2.4.4 calculation of the minimum water drop that can be removed by the silk dehydrator

dehydration efficiency η It can be calculated by the following formula:

η＝ 1－(1－ η T) S (1)