Safety technology for ironmaking production

2022-08-07
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Safety technology for ironmaking production

ironmaking is to mix iron ore or sintered pellets, manganese ore, limestone and coke in a certain proportion and send them to the silo, and then send them to the blast furnace. Hot air of about 1000 ℃ is blown from the lower part of the blast furnace to make the coke burn and produce a large amount of high-temperature raw gas, so as to heat the furnace charge and make it react chemically. The iron ore begins to soften at about 1100 ℃, and melts at 1400 ℃ to form molten iron and liquid slag, which are stored in the hearth in layers. After that, conduct iron tapping and slag tapping

the raw materials and fuels required for ironmaking production, the nature of the products and by-products produced, and the environmental conditions of production have brought a series of potential occupational hazards to ironmaking personnel. For example, a large amount of dust will be generated during the transportation, loading and unloading, crushing and screening of ore and coke, and the granulation and screening of sinter; In the iron tapping yard in front of the blast furnace, the equipment, facilities and pipelines are densely arranged, there are many types of operations, the personnel are concentrated, and the dangerous and harmful factors are most concentrated, such as the high-temperature radiation of the operation in front of the furnace, the iron tapping and slag tapping will produce a large amount of smoke and dust, and the molten iron and slag will explode when exposed to water; Injury caused by tapping machine and crane; The leakage of iron making plant gas can cause poisoning. Blast furnace gas and air can explode with great explosion power; Injecting bituminous coal powder may cause dust explosion; In addition, there is the noise in the iron making area, as well as the injury of machines, tools and vehicles. So many risk factors threaten the life safety and health of production personnel

2. main safety technology of iron making production

1) safety technology of blast furnace charging system

the charging system continuously feeds the blast furnace with billets according to the smelting requirements of the blast furnace. In recent years, the loading system includes the transportation, storage, discharging, transportation of raw materials and fuels, and furnace top loading. The loading system shall minimize the handling and transportation links, improve the mechanization and automation level, and make it operate safely

(1) transportation, storage and discharging system. Most of the raw materials and fuels of large and medium-sized blast furnaces are transported by belt conveyor, which is easier to automate and control dust than train transportation. The ore storage tank is not equipped with barriers or the barriers are incomplete, and there are no railings around, so people may fall into the tank when walking; The shape of the chute is improper, and there are dead corners, which need to be cleaned manually; The lining is worn and the working conditions are poor during maintenance; If the material gate fails, it is often manually poked. If the material suddenly collapses, it will often cause injury. The dust concentration during discharging is very high, especially when the belt conveyor and vibrating screen are used to screen the materials, the working environment is even worse. Therefore, the structure of the ore storage tank should be permanent and very strong. The shape of each groove shall be automatically and smoothly cut, and the inclination of the groove shall not be less than 50, so as to eliminate the phenomenon of manual poke. Metal ore tanks shall be equipped with vibrators. For reinforced concrete structure, wear-resistant lining plate shall be laid on the inner wall; The lining board for storing hot sinter shall be heat-resistant. The ore tank must be provided with a fence and railings around it, which shall be kept intact. The material trough shall be provided with a material level indicator, and the discharge port shall select a valve with flexible switch, preferably a hydraulic gate. Completely enclosed dust removal facilities shall be used for the discharge system

(2) raw material conveying system. Most blast furnaces adopt the charging method of hopper car inclined bridge. The hopper car must be equipped with two opposite entrances and exits and waterproof and dustproof measures. One side shall be provided with a qualified pedestrian ladder leading to the furnace top. The discharging direction of the discharge port must be consistent with the running direction of the belt conveyor, and the machine shall be equipped with an anti deviation and slipping device. The belt conveyor is easy to hurt people during operation, so it must be stopped before maintenance, refueling and cleaning

(3) top furnace charging system. Bell type charging is usually adopted for blast furnace. The bell type charging takes the big clock as the center, and is composed of big clock, hopper, big and small clock opening and closing driving equipment, probe, rotating cloth and other devices. Pressure equalizing and discharging device must be set for high-pressure operation. Do a good job of sealing between devices. Especially during high-pressure operation, poor sealing will not only cause the components of the device to be washed by gas. 4. The frame 1 of the waterproof coiled material tensile testing machine must be lubricated to shorten its service life, and even the big clock will fall into the furnace. The transmission mechanism is caused by the same step belt or the reduction unit. The opening and closing of the bell must comply with the safety procedures. Therefore, the relevant equipment must be interlocked to prevent human error

2) safety technology for water supply and power supply

blast furnace is a high-temperature smelting furnace for continuous production, and it is not allowed to cut off water and power during the process. Especially for large and medium-sized blast furnaces, reliable measures must be taken to ensure safe power and water supply

(1) safety technology of water supply system. The blast furnace body, tuyere, furnace bottom, shell, water slag, etc. must be supplied with water continuously. Once interrupted, the cooling equipment will be burned out and a major accident of shutdown will occur. In order to supply water safely, the following measures should be taken for large and medium-sized blast furnaces: the water supply system is equipped with a certain number of standby pumps; All pump stations are equipped with two-way power supply; A water tower for water supply shall be set to ensure water supply when the diesel pump is started; Set the return water tank to ensure that the circulating water supply is maintained without external water supply; A continuous filter is arranged on the water supply pipe of the furnace body and the tuyere; Steel pipes are used for water supply and drainage to prevent cracking

(2) power supply safety technology. For instruments and equipment that cannot be powered off, in case of power failure, personal and equipment safety shall be considered and necessary security emergency measures shall be set. Set special and standby diesel generator set

computers, instrument power supplies, emergency power supplies and communication signals are security loads. Each electrical room and operation room shall be equipped with fluorescent lamps with chromium batteries for emergency lighting

3) safety technology of pulverized coal injection system

in order to ensure that pulverized coal can be blown into the blast furnace without causing hot air to blow back into the injection system, the pressure of the injection tank should be determined according to the blast furnace tuyere pressure. Check valve and automatic shut-off valve shall be set between mixer and pulverized coal conveying pipeline. A check valve shall be installed on the branch pipe of the coal injection vent. As the pulverized coal is very fine, the coal storage time in the injection tank and the coal storage tank shall not exceed 8 ~ 12h when the injection is stopped. The pulverized coal flow rate must be greater than 18m/s. The inner wall of the tank shall be smooth with curve transition, and the pipe shall avoid right angle bending

in order to prevent strong destructive force caused by explosion, the injection tank and coal storage tank shall be provided with explosion relief holes

during blowing, the tuyere is coking due to poor furnace conditions or other reasons, or the coal gun is burnt out due to air leakage at the contact between the coal gun and the air duct. Both of these phenomena can lead to the burning out of the air duct. Therefore, the operation should be inspected frequently to find and deal with it as soon as possible

4) safe operation technology of blast furnace

(1) operation technology of blowing in. It is very important to start the furnace, and accidents will easily occur if it is not handled properly. The following work shall be done before furnace startup: Equipment Inspection and joint inspection; Prepare raw materials and fuels; Formulate oven drying curve and strictly implement it; Ensure accurate calculation and batching

(2) operation technology of boiler shutdown. During the shutdown process, the carbon monoxide concentration and temperature of the gas gradually increase, and the hydrogen concentration in the gas increases due to the decomposition of the water injected into the cleaning furnace during the shutdown. In order to prevent gas explosion accidents, the following work should be done: deal with the gas system to ensure that the steam of the system is unblocked; Prevent water leakage into the furnace. Before boiler shutdown, cut off the water supply of the damaged cooling equipment and replace the damaged air slag outlet; Use water to control the furnace top temperature between 400 ℃ ~ 500 ℃; During the shutdown process, the furnace condition shall be normal and no wind shutdown is allowed; The sprinkler must be set under the big clock. When it is set on the big clock, it is forbidden to switch it on and off

5) safety technology for blast furnace maintenance

blast furnace production is continuous, and any unplanned wind shutdown is an accident. Therefore, it is necessary to strengthen the maintenance of the equipment, shorten the air rest time as far as possible, and ensure the normal production of the blast furnace

in order to prevent gas poisoning and explosion, the following points should be paid attention to:

(1) before class I and class II gas operations, the personnel of the gas protection station must be notified, and at least 2 people are required to work. Before class I gas operation, the carbon monoxide content in the air must be tested and oxygen respirators must be worn

(2) when hot work is carried out on the gas pipeline, the hot work ticket must be obtained first and preventive measures must be taken

(3) when entering the container for operation, the concentration of carbon monoxide in the air should be checked first. During operation, in addition to good ventilation, it is also required to have a special person outside the container for supervision

3. preventive measures and technologies for iron making production accidents

the coal gas poisoning accident in iron making plant is the most serious, with many deaths, mostly occurring in front of the furnace and during maintenance operations. The main measures to prevent gas poisoning are to improve the intact rate of equipment and minimize gas leakage; Install gas alarms in places prone to gas leakage; During gas operation, gas operators shall wear portable gas alarm and assign special personnel to monitor

scalding accidents are also easy to occur in front of the furnace. The main preventive measures are to improve the equipment level and operators should wear protective clothing. Vehicle injury and machine tool injury accidents are also easy to occur in the raw material yard and in front of the furnace

for the bituminous coal dust preparation and injection system, when the volatile content of bituminous coal exceeds 10%, dust explosion accidents may occur. In order to prevent dust explosion, measures such as controlling the temperature of the coal mill and the oxygen content of the air in the coal mill and the coal collector are mainly taken. At present, China mostly adopts the method of injecting mixed coal to reduce the content of volatile matter

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