What Is a Blast Furnace?

The blast furnace uses steel plates as the shell, and the shell is lined with refractory bricks. The blast furnace body is divided into five parts: furnace throat, furnace body, furnace waist, furnace belly, and furnace hearth from top to bottom. Due to the good technical and economic indicators of blast furnace ironmaking, simple process, large production capacity, high labor production efficiency, and low energy consumption, the iron produced by this method accounts for most of the world's total iron output.

The emergence and development of China's blast furnace is an important contribution to human material life.

history

The oldest known blast furnace is the furnace of the Western Han Dynasty (1st century BC) in China. The discovery of cast iron unearthed in Chinese cultural relics in the 5th century BC shows that smelting was practical in this era. The inner wall of the initial furnace was covered with clay, which was used to refine the phosphorus-containing iron ore. The earliest melting pot in the west appeared in Sweden from 1150 to 1350. The melting pots of these two countries have developed by themselves and have not communicated with each other.

The modern blast furnace using charcoal appeared in 1709. Due to the reduction of charcoal production in Europe at the time, multipurpose felling of forests and the forced development of iron-making methods using charcoal led to the emergence of new technologies that greatly increased the efficiency of iron-making.

The first modern blast furnace in Japan was the Kashiwa Ohashi blast furnace. Designed by Oshima Takahata, Anzheng 4 years (1857) ignited on November 26, and the first iron output on December 1. This day is also commemorated as the Japan Iron and Steel Industry Memorial Day. ^[1]

1. Before stopping the furnace, the blast furnace and the gas system must be separated closely and reliably. When the furnace is stopped by the water extraction method, the cone valve on the furnace top bleed valve or bleed tube should be removed. The height of the material surface should be continuously measured during the period when the water is cut and the furnace is lowered. Avoid wind breaks. When wind breaks are necessary, stop the water first and ignite the top gas.

2. It is forbidden to open the bell when the water is shut down and the material is lowered. No water is allowed on the clock. Analyze the content of carbon dioxide and hydrogen in the gas at least once every 1 h. The hydrogen content must not exceed 6%.

3. There should be a special water pump for the furnace top, and the temperature of the furnace top should be maintained between 400 ~ 500 . The top of the furnace should be sprayed with uniform raindrops to prevent the water from flowing down the furnace wall and causing the furnace wall to collapse.

4. For large and medium repaired blast furnaces, when the material level drops to the level of the tuyere, the wind can be shut down and the furnace can be stopped. For the overhaul of blast furnace, open the residual iron holes in the bottom of the furnace (hearth) where the water temperature difference is large, and exhaust the residual iron. ^[2]

I. Prevention of Blast Furnace Nodulation Accidents

There are various reasons for blast furnace nodules. The basic cause is that the melted material re-condenses and adheres to the furnace wall and grows gradually. Preventive measures should be taken in advance to prevent the occurrence of blast furnace nodules.

1) Stable raw fuel quality

Raw fuel has poor quality and large powder content, which can easily lead to powder aggregation and induce nodules at the lower feed line. At the same time, when the powder aggregation layer goes down to the reflow zone, it is easy to cause poor gas permeability, and small collapses and small particles appear. Sliding rule phenomenon, improper control is easy to induce furnace cooling and other accidents, affecting the normal operation of blast furnace smelting. Poor quality of raw fuels can easily lead to abnormal furnace conditions and difficult-to-suspend materials, which raises the top temperature, cannot be effectively controlled, and can easily cause upper nodules. For this reason, in the production organization, the smelting scheme of the blast furnace should be determined according to the quality of the raw fuel, to ensure that the blast furnace is stable and forward, and to deal with small furnace condition fluctuations in advance to prevent large furnace condition abnormalities.

2) Prohibition of long-term low material line operation

Long-term low-feed line operation will break through the blast furnace and cause serious damage to the charging system. At the same time, the blast furnace thermal system may be disrupted, and the blast furnace temperature field may be disturbed, which may cause the furnace wall to thicken or even nodule. Different specific measures should be taken according to the specific reasons of the low feed line operation. For the insufficient loading capacity, an appropriate batch weight should be selected, and the loading capacity of the blast furnace should be increased by increasing the loading rate of the trolley to ensure the full line rate of the blast furnace. For the low material line caused by equipment failure, corresponding measures should be taken to adjust it. It should be noted that when the material line is rushed, a marginal loading system can be appropriately developed. According to the depth of the material line, the net coke is increased or the load is appropriately reduced to ensure that The temperature of the blast furnace is plentiful and the furnace condition is stable.

3) Handle edge accumulation in time

After the blast furnace adopts intensive smelting measures, when the charging system and the air supply system are not rematched in time, it is easy to cause edge accumulation. The specific performance is that the iron front is easy to be pressed, and it is sensitive to the improvement of the operation of the deairing furnace. The temperature difference between the upper and lower slags is large. Small chipping and sliding rule often occur, the feeding is uneven, and the air outlet work is uneven. For this reason, the edge accumulation should be handled in a timely manner, and the air supply system to increase the diameter of the tuyere, the operation of the blast furnace with appropriate strength, the development of the charging system at the edge, the slag making system to reduce the basicity of the slag, and the thermal system to determine the appropriate furnace temperature For adjustment, if necessary, use a furnace cleaning agent to clean the furnace or use the full-flip method to strongly develop the edge. Use high-temperature gas to flush the thick furnace wall.

4) Control the appropriate cooling intensity

The irrational cooling system of the blast furnace will also cause nodulation of the furnace wall. Therefore, appropriate cooling intensity should be determined for each part according to the actual operation of the blast furnace. For example, the cooling water of the furnace body should be properly controlled in the initial stage of the furnace. Strength to prevent the formation of nodules at this site, which in turn will cause the occurrence of vicious accidents such as blast furnace nodules.

5) Stable operation policy

There are many variables in blast furnace operation, and the blast furnace smelting process runs on a relatively stable basis. To this end, the blast furnace operator should meticulously implement the operating policy, unify the operation of each shift, reduce human operation fluctuations, keep the furnace temperature field stable and balanced, and prevent artificially caused furnace condition fluctuations, leading to blast furnace nodules.

6) Eliminate the thickness of the furnace wall in time

If the thickness of the furnace wall is not handled properly or is not handled in time, it will easily cause blast furnace nodules. Therefore, decisive measures should be taken to deal with the signs of thickening of the furnace wall in a timely manner. When the blast furnace is intensified to smelt, the marginal charging system or the operation measures to reduce the smelting intensity should be taken to prevent the occurrence of furnace conditions. Malignant nodule accident.

7) Reduce the large amount of additional materials into the furnace

Addition of low-melting compounds with large quantities into the furnace will cause nodules of blast furnace when conditions are met. For this reason, in the production organization, the production rhythm should be controlled, the maximum amount of additional materials should be determined, and the charge structure should be adjusted so that the production organization can run in an orderly manner to prevent the occurrence of blast furnace nodulation.

8) Reduce material changes in each process before iron

Each change of material before the iron process will bring different degrees of fluctuation to the blast furnace. When managing the production organization, you should try to organize the processes in a long-term perspective to keep the material unchanged for a certain period of time. After the material change, technical tracking should be done. Work with service to make advance judgment and prevent in advance the fluctuation of furnace condition caused by changing materials. The blast furnace nodulation accident is a comprehensive reflection of the abnormal furnace conditions. Avoiding small fluctuations in the furnace conditions will effectively prevent the foundation from occurring, and will also win the initiative of the blast furnace operation to achieve the expected effect of the blast furnace operation. ^[2]

I. Toxic hazard analysis

The toxic substance involved in the blast furnace project is mainly carbon monoxide. Carbon monoxide is mainly present in hot-blast stove operations and iron-out operations in front of furnaces. The harmful effects of carbon monoxide on the human body are as follows: carbon monoxide is inhaled through the respiratory tract, which is a choking gas, which mainly causes acute poisoning of the human body. Carbon monoxide enters the human body and combines with hemoglobin, resulting in hypoxia in the body. Patients experience headache, dizziness, nausea, and even death. Chronic harm is not obvious. Hazard level .

Second, safety inspection of anti-virus measures

1. The production equipment should be sealed and pipelined to prevent leakage and escape of toxic substances;

2. The mechanization, programming and automatic control of the production process prevent the operator from contacting or little contact with toxic substances, preventing poisoning accidents caused by misoperation;

3. Subject to technical and economic conditions, when there is still toxic substance dissipation and natural ventilation cannot meet the requirements, the necessary mechanical ventilation should be set to detoxify;

4. The discharged toxic gases, liquids and solids should be treated by corresponding purification devices to meet environmental protection emission standards;

5. Reliable accident handling devices and emergency protective devices must be provided for equipment and workplaces where toxic substance leakage may cause major accidents;

6. According to the nature of toxic substances, the characteristics of toxic operations and the protection requirements, accident cabinets, first aid boxes and personal protective equipment should be provided in toxic operating environments;

7. Ventilation and ventilation equipment and rescue appliances should be provided for the dangerous working environment of hypoxia and the causes of asphyxia and poisoning asphyxia.

8. In workplaces where there is a danger of hypoxia or suffocation, warning signs should be set up in prominent places. ^[2]

(1) The low-pressure long-bag pulse dust collector is used to remove the dust generated at the iron mouth, sand mouth, slag ditch, swing chute, iron ditch, etc. during tapping of the blast furnace; Using 100m ³ three electric fields

(1) Personnel transportation, storage and unloading system. Most of the raw materials and fuels of large and medium-sized blast furnaces are transported by belt conveyors, which is easier to automate and control dust than rail transportation. The storage tank is not paved or incomplete, and there are no railings around it. There is a danger of people falling into the tank when walking; the material tank is improperly shaped, there are dead corners, and manual cleaning is needed; the inner lining is worn, and the labor conditions during maintenance are poor ; Material gates are often used for artificial failure, such as sudden collapse of materials often causes injury. The dust concentration during discharging is very high, especially when using a belt conveyor and a vibrating screen to screen the material, the working environment is even worse. Therefore, the structure of the storage tank should be permanent and very strong. The shape of each slot should be automatically and smoothly discharged, and the inclination angle of the slot should not be less than 50 ° to eliminate the phenomenon of manual feeding. Metal mines should be installed with vibrators. In the reinforced concrete structure, the inner wall should be laid with wear-resistant lining; the lining board for storing hot sintered ore should be heat-resistant. A barrier must be set on the mine trough, and railings must be set up around it to keep it intact. The material tank should be equipped with a material level indicator, and the discharge port should be selected with a flexible switch, preferably a hydraulic gate. For the discharge system, a completely closed dust removal facility should be used.

(2) Raw material conveying system. Most blast furnaces use the loading method of the slanting bridge of the feeding car. The feeding car must be provided with two entrances and exits in opposite directions, and waterproof and dustproof measures must be provided. One side should be provided with a pedestrian ladder leading to the furnace roof. The discharge direction of the discharge port must be consistent with the running direction of the belt conveyor. The machine should be equipped with anti-sway and slip devices. The belt conveyor is easy to hurt when it is running, so it must be stopped, and then it can be repaired, refueled and cleaned.

(3) Top furnace charging system. Bell type charging is usually used. The bell type charging is centered on the big bell, and it is composed of big bell, hopper, big and small bell opening and closing driving equipment, feeler, rotating cloth and other devices. For high pressure operation, a pressure equalization and pressure relief device must be provided. Sealing the various devices, especially during high-pressure operation, the poor sealing will not only cause the components of the device to be flushed by gas, shorten the service life, and even accidents when the bell falls into the furnace. Material clocks must be opened and closed in accordance with safety procedures. For this reason, the related equipment must be chained to prevent human error. ^{[3] [3]}