Prevention and safety measures for coke oven gas explosion accident

In the coking system, coke oven gas is a valuable secondary energy source and has a wide range of uses. It can be used as a gas for coke oven heating, as well as a fuel for heating in various industrial furnaces in the metallurgical industry. It is also a fuel gas for living in thousands of households. The correct use of gas can benefit the society. However, in the operation and maintenance of gas facilities, if there is a lack of safety knowledge, contrary to objective laws, there is a danger of causing a gas explosion accident. This article introduces the safety knowledge of coke oven gas and introduces the prevention and safety measures for gas explosion accidents for your reference.
1. What are the characteristics of coke oven gas ? The calorific value of the coke oven gas is as high as 17564~18819kJ/m 3 , and the fluctuation of the calorific value of the gas is small, which is convenient for adjustment operation. Compared with the gas with low calorific value, the gas consumption is small and the amount of exhaust gas is small.
2. Coke oven gas contains more hydrogen, reaching 54 to 59%, with less incombustible components, faster burning speed and shorter flame.
3. Coke oven gas contains many carbon-hydrogenated materials, which can be decomposed into graphite at high temperature, which is easy to hang on the burner and affects combustion.
4. When the coke oven gas is mixed with air to a certain ratio, it can form an explosive gas and explode in case of fire. The composition causing the explosion ranges from 5 to 30%.
5. When the coke oven gas is dirty, the gas pipeline and pipe fittings are easily blocked by tar and naphthalene. The condensate in the gas will also corrode the pipes and pipes, which will increase the difficulty of operation and maintenance.
Second, the prevention and safety measures of the gas explosion accident
(1) Hazardous characteristics of coke oven gas <br> Gas explosion accidents are extremely destructive, and carelessness and carelessness in work can cause gas explosion accidents. To this end, coking workers should understand the characteristics of gas, and understand the safety common sense of preventing and dealing with gas accidents. The dangerous characteristics of various gas are shown in Table 1.
Table 1 Hazard characteristics of various gases
Gas type Spontaneous ignition point °C Gas specific gravity (air is 1) Explosion limit (% by volume) Main ingredient
Lower limit Upper limit
Coke oven gas 600 0.45 5 30 Hydrogen, methane
Blast furnace gas 600 0.9 to 1.1 30 75 Carbon monoxide
Producer gas 610 0.8 to 0.9 20 75 Carbon monoxide
natural gas 650 0.5 to 0.7 3 15 Methane
It can be seen from Table 1 that the lower limit of explosion of coke oven gas and natural gas is low and the explosion risk is high. The main ingredients are hydrogen and methane, and the risk of poisoning is small. The main component of blast furnace gas and producer gas is carbon monoxide, which is highly toxic and colorless and odorless. The risk of poisoning is high, the lower explosion limit is high, and the risk of explosion is small. Therefore, coke oven gas is mainly to prevent gas explosion accidents.
( 2) Safe operation of gas <br> From the dangerous characteristics of gas, it is known that an explosion may occur only when the gas reaches the explosion limit. So, under what circumstances does the gas easily reach the explosion limit? There are three main situations:
1. The gas system, especially the negative pressure system, enters the air, and the oxygen content of the gas rises to reach the explosion limit;
2. The gas pipeline equipment leaks and reaches the explosion limit indoors or in the container;
3. Improper heating or violation of safety technical operating procedures, the explosion limit is reached in the furnace.
In the above three cases, the safety precautions that the gas easily reaches the explosion limit are the key to preventing the gas from reaching the explosion limit and prohibiting the open flame during operation. The safety measures for gas operation should be as follows:
(1) Gas pipeline equipment maintains positive pressure operation to prevent air from entering the gas system. When the equipment stops production and it is difficult to maintain positive pressure, the gas source should be cut off and the gas inside the equipment should be purged.
(2) The negative pressure system in front of the blower should be kept tight.
Maintain the water seal height of the condensate drainer, and adjust the pressure of the coke oven collector flap to prevent the negative pressure system from drawing in air.
(3) Purge the gas inside the gas replacement facility, apply steam or nitrogen, and prohibit the fire source during the purging process.
(4) When it is found that there is gas smell in the room, the door and window should be opened to ventilate, do not switch the electric gate, and prohibit all sparks. If the gas leak is not detected, it can be tested with a gas alarm. If the conditions are not available, you can use soapy water to apply the valve, gland, flange interface, union, etc., and there is a bubble to indicate air leakage. It should be handled in a timely manner, and it should not be sloppy.
(5) For gas stoves with furnaces, the following safety measures should be taken before ignition:
1 Check that the valve of the gas burner is indeed in the closed state before it can be ignited. Otherwise, the gas enthalpy enters the furnace before ignition. If the explosion limit is reached, an explosion will occur when the ignition occurs. For example, when the steaming boiler of a coking plant in a city is igniting the oven, the furnace is not careful to check the gas valve. Two of the six burner valves have a certain opening degree. Before the ignition, the gas has entered the furnace, and the explosion occurs when the furnace is fired. Five people were slightly injured and the boiler was blown up. In addition, considering that some valves are affected by scouring corrosion for a long time, the tightness is reduced or the air leakage is caused by the lack of debris and deposits. Therefore, the operator must carefully check before the ignition to determine that there is no gas in the furnace to ignite.
2 The operator must follow the ignition system of the first ignition and the valve to send the gas. To achieve "fire and other gas", never "gas and other fire." For example, on March 15, 1982, when a tar distillation kettle of a steel coking plant was ignited, the worker Zhu first opened the gas, and then clamped the fire with a pair of pliers to cause an explosion. In addition, the burners with many burners should be ignited by the ignition one by one. It is forbidden to ignite one burner first, then open other burners to hook fire.
3 If the ignition does not ignite, or if it is extinguished after ignition, the second ignition is prohibited. The valve should be closed immediately, the gas in the furnace should be drained and then re-ignited according to the operating regulations. Because at this time, explosive gas has formed in the furnace. For example, on July 10, 1985, the crude benzene tube furnace of a steel coking plant suddenly turned off due to the sudden drop in gas pressure. The workers on duty did not close the gas valve in time. When the gas pressure rose, the gas entered the furnace and formed an explosive gas. .
(III) Safety inspection measures for gas <br> In gas explosion accidents, the most occurred during maintenance. According to the statistics of "Coking Accidents 150", in the 21 accidents involving gas explosions, there were 15 accidents, accounting for 71.43%. Therefore, safety measures in gas overhaul are very important. Gas safety maintenance includes several conditions such as overhauling, plugging, pumping blinds and hot work on gas pipeline equipment. Now they are introduced as follows:
1. In the maintenance of safety inspection measures on gas pipeline equipment, open flames shall be strictly prohibited. In addition, copper tools should also be used. When there is no copper tool, the surface of the steel tool should be covered with butter. In areas where it is impossible to eliminate open flames, it is necessary to prevent gas leaks. For example, in the basement of the coke oven, the open flame cannot be extinguished, and the gas leakage is not allowed during the inspection. The Coking Safety Regulations stipulate that it is forbidden to use gas to block blind plates in the flue corridors and basements.
2. Safety measures for fire on gas pipeline equipment (1) On the gas pipeline of the operation, the welding and gas pipeline equipment can be stopped without production, without cleaning and replacement, with positive pressure. The safety conditions are: 1 The gas oxygen content is less than 1%, and no explosive gas is formed in the equipment. 2 positive pressure welding, air will not enter the equipment, it is impossible to form explosive gas. The leaked gas may burn, but the oxygen concentration in the equipment is low and will not temper. 3 Although the welding temperature is high, the gas is flowing and does not heat up to a dangerous level. 4 Repair welding should be carried out under the condition that the gas leakage is reduced after plugging, and there is no danger of gas equipment explosion.
(2) The safest way to fire on equipment that has been shut down is to fill the equipment with water vapor and then ignite. If the above conditions are not met, the following safety precautions must be taken: 1 separate the gas system connected to it with a blind plate; 2 reduce the gas concentration in the equipment to 0.5% with inert gas. The analysis and inspection work shall be carried out within half an hour before the fire.
(3) In the gas area, the fire should be separated from the connection of the gas pipe and the gas pipe. Use a blind plate to block the pipe valve or separate it;
2When the fire is welded to the pipeline, the site should be wetted with water, and the ventilated or covered outlet should be carefully checked for flammable components, and try to stay away from it;
3 All fire points must be confirmed and confirmed by the safety guards on site;
4 Before the fire, the joint warranty should be done to ensure the implementation of the joint guarantee system, fire equipment should be placed on site.
(4) Method of accident handling 1. When the gas pipeline equipment for leaking gas accidents leaks due to damage or corrosion, temporary emergency plugging measures may be taken, mainly including:
(1) Plugging with a tapered wooden wedge, suitable for holes, plugging with wooden wedges and asbestos, suitable for breaking.
(2) Punch, suitable for plugging cracks in pipelines.
The method is to make a ring-shaped steel plate which is close to the pipe and cover the crack of the pipe, and the rubber pad is filled inside, and the outer part is fixed by the clamp and repaired.
(3) Plugging with an adhesive. Such as epoxy resin, high pressure curing agent, etc.
(4) For emergency plugging, copper tools must be used. It is forbidden to use fire and wear gas masks.
2. When the fire treatment facility is on fire, the correct treatment can quickly extinguish the fire, and the handling of the error may result in an explosion. The main points of gas fire extinguishing are: 1 reduce the gas pressure and reduce the fire. For gas pipes with a diameter of lOOmm or less, the valve can be directly shut down to extinguish the fire. Fire on pipeline equipment with a diameter of 150mm or more. It is forbidden to suddenly close the gate threshold or water seal to prevent tempering and explosion. The valve should be gradually closed to reduce the gas pressure. The minimum pressure should not be less than lOPa (10mm water column). 2 A large amount of water vapor (or nitrogen) is introduced, and the vapor concentration is over 35%. 3 Water protection surrounding equipment is not burned red, burned out.

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