Main safety technologies in iron production

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Main safety technologies in iron production 1) Safety technologies for the blast furnace charging system The charging system continuously supplies the raw materials required for blast furnace smelting. The charging system includes processes such as the transportation, storage, discharging, and conveying of raw fuel, as well as charging from the furnace top. The loading system should minimize loading, unloading, and transportation steps, enhance the level of mechanization and automation, and ensure its safe operation. (1) Conveying, storage, and discharging system. In large and medium-sized blast furnaces, raw materials and fuel are mostly transported by belt conveyors, which makes automation and dust control easier compared to train transportation. The ore storage tank lacks grills or has incomplete grills, and there are no railings around it; people walking nearby risk falling into the tank ； The material chute has an improper shape with dead corners that require manual cleaning ； The lining is worn out, and the working conditions during repairs are poor ； When the material gate fails, manual pushing of the material is often used; sudden collapse of the material can often cause injuries. The dust concentration is very high during discharging, especially when using a belt conveyor and a vibrating screen for sorting the material, making the working environment even worse. Therefore, the structure of the ore storage tank should be permanent and extremely sturdy. The shape of each groove should allow for smooth automatic feeding; the inclination angle of the grooves should be no less than 50° to eliminate the need for manual pushing of the material. Vibrators should be installed in the metal troughs. For reinforced concrete structures, wear-resistant lining plates should be installed on the inner walls ； The lining plate for storing hot sintered ore should be heat-resistant. Grills must be installed on the mine troughs, with railings around them, and they must remain in good condition. The feed trough should be equipped with a level indicator, and the discharge port should use valves with flexible operation; hydraulic gates are preferred. A completely enclosed dust removal system should be used for the discharge system. (2) Raw material conveying system. Most blast furnaces use a car bridge feeding method, and the feeding cars must be equipped with entrances and exits in opposite directions, as well as waterproof and dustproof measures. A walkway leading to the furnace top that meets the requirements should be provided on one side. The discharge direction of the discharge port must be consistent with the operating direction of the conveyor belt, and the machine should be equipped with devices to prevent deviation and slipping. Conveyor belts can easily injure people while in operation; therefore, maintenance, lubrication, and cleaning must be carried out only after the machine has been shut down. (3) Top furnace charging system. Chimney feeding is commonly used for charging blast furnaces. The bell-type charging system is centered around a large bell, and consists of components such as the large bell itself, hoppers, devices for opening and closing the large and small bells, probes, and rotating distributors. When operating under high pressure, a voltage equalizing and relief device must be installed. Ensure proper sealing between all devices; especially during high-pressure operations, poor sealing not only exposes the components of the devices to gas erosion and shortens their service life, but can also lead to accidents such as large components falling into the furnace. The opening and closing of the material hopper must follow safety procedures. To this end, the relevant devices must be interlocked to prevent human errors. 2) Safety technologies for water and power supply: A blast furnace is a high-temperature smelting furnace that operates on a continuous basis, and interruptions in water or power supply are not permitted. In particular, large and medium-sized blast furnaces must take reliable measures to ensure a stable supply of power and water. (1) Safety technologies for water supply systems. The blast furnace body, tuyeres, furnace bottom, casing, sludge water, etc., require continuous water supply; any interruption can damage the cooling equipment and lead to serious shutdowns. To ensure a secure water supply, large and medium-sized blast furnaces should take the following measures: the water supply system should be equipped with a certain number of backup pumps ； All pump stations are equipped with two power supplies ； Install a water tower to supply water, ensuring adequate water flow when the diesel pump starts ； Install a return water tank to ensure continuous water circulation in the absence of external water supply ； Continuous filters are installed on the furnace body and the water supply pipes for the tuyeres ； Steel pipes are used for water supply and drainage to prevent cracking. (2) Power supply safety technology. For instruments and equipment that cannot operate without power, in the event of a power outage, measures to ensure the safety of personnel and equipment must be put in place as necessary emergency safeguards. Install dedicated and backup diesel generator sets. Computers, instrument power supplies, emergency power supplies, and communication signals all constitute critical loads; each electrical room and control room should be equipped with chromium-cell fluorescent lamps for emergency lighting. 3) Safety technology for coal powder injection systems: The greatest hazard associated with blast furnace coal powder injection systems is the potential for explosions and fires. To ensure that coal powder can be blown into the blast furnace without hot air flowing back into the injection system, the pressure of the injection tank should be determined based on the pressure at the blast furnace tuyeres. Check valves and automatic shut-off valves should be installed between the mixer and the coal powder delivery pipeline. A check valve should be installed on the branch pipe of the coal injection nozzles. Due to the extremely fine nature of the coal powder, when injection is stopped, the coal stored in the injection tank and the coal storage tank should not remain there for more than 8–12 hours. The coal powder flow rate must be greater than 18 m/s. The inner wall of the tank should be smooth with smooth curve transitions, and pipes should avoid right-angle bends. To prevent the massive destructive force of explosions, blast vents should be provided on the injection tanks and coal storage tanks. During injection, coking of the tuyeres due to poor furnace conditions or other reasons, or damage to the coal gun caused by air leakage at the point where the coal gun meets the air duct, can both lead to damage of the air duct. Therefore, regular inspections should be carried out during operation to detect and address issues early. 4) Blast furnace safe operation techniques (1) Operation techniques for starting up the furnace. Starting up the furnace is extremely important; improper handling can easily lead to accidents. The following tasks should be carried out before starting the furnace: conduct equipment inspections, and carry out joint inspections ； Prepare the raw materials and fuel properly ； Develop a furnace heating curve and strictly follow it ； Ensure accurate calculation and batching. (2) Operating techniques for shutting down the furnace. During the shutdown process, the carbon monoxide concentration and temperature of the gas gradually increase; furthermore, the decomposition of the moisture injected into the furnace during shutdown leads to an increase in the hydrogen concentration in the gas. To prevent gas explosion accidents, the following measures should be taken: address the gas system to ensure smooth flow of vapor within it ； Strictly prevent water leakage into the furnace. Before shutting down the furnace, cut off the water supply to the damaged cooling equipment and replace the damaged slag outlet ； Use water injection to control the furnace top temperature between 400°C and 500°C ； During the shutdown process, it is necessary to maintain normal furnace conditions; shutting down the blast furnace is strictly prohibited ； The large water sprinkler must be installed under the big bell. When installed on a large clock, it is strictly prohibited to turn the clock on or off. 5) Safety technologies for blast furnace maintenance. Blast furnace production is continuous, and any unplanned shutdown constitutes an accident. Therefore, equipment maintenance work should be strengthened to minimize downtime and ensure the normal operation of the blast furnace. To prevent gas poisoning and explosions, the following points should be noted: (1) Before carrying out operations involving type 1 or type 2 gases, it is necessary to inform the personnel at the gas safety station, and at least two people should be involved in the work. Before working with certain types of gas, it is also necessary to check the carbon monoxide level in the air, and oxygen respirators must be worn. (2) When working on gas pipelines, a hot work permit must be obtained first, and preventive measures must be taken. (3) When entering a container for work, the carbon monoxide concentration in the air should be checked first. During the operation, in addition to ensuring good ventilation, it is also necessary to have someone outside the container monitoring the situation.