Preliminary study on prevention and disposal of liquid ammonia leakage accident

2019-04-09 10:02:41

Liquid ammonia is widely used in the ice making and refrigeration industries due to its low cost. Take Qidong City, Jiangsu Province as an example. In more than 200 ice-making and refrigerating enterprises in six fishing ports along the coast and along the Yangtze River, ammonia refrigeration is adopted. The dangerous properties of liquid ammonia are also very obvious. It is very important for the grassroots brigade to do a good job in preventing and disposing of liquid ammonia leakage accidents. The author combines the investigation and practice of multiple liquid ammonia leakage and explosion accidents in recent years, and talks about prevention and disposal methods:

First, the fire risk of liquid ammonia. Liquid ammonia is a colorless and toxic gas with irritating odor. It is very soluble in water. The aqueous solution is alkaline and easy to liquefy. Generally, liquid ammonia can be used as a refrigerant. Contact with liquid ammonia can cause severe frostbite. The ammonia explosion limit is 15.7 to 27.4%. Therefore, ammonia gas mixed with air or oxygen will form an explosive mixture, and the storage container is also highly likely to explode when heated. Ammonia can attack wet skin, mucous membranes and eyes, causing severe cough, bronchospasm, acute pulmonary edema, and even blindness and suffocation.

Second, liquid ammonia leakage accident prevention measures. Ammonia is a Class B flammable gas. It is liquefied into liquid ammonia under appropriate pressure. It is generally stored in steel cylinders or storage tanks. In the storage, transportation and use, necessary fire prevention measures should be taken to prevent leakage and explosion accidents. First of all, the container for storing ammonia is a pressure vessel, which must be inspected regularly. The cylinder or storage tank should be placed in a cool and ventilated shed, away from fire, heat, direct sunlight, and fluorine, chlorine and acid that are in conflict with nature. Items are stored separately. Secondly, it is handled gently during handling to prevent damage to the cylinder and the bottle valve. The transport tanker should be filled with proper amount when transporting. It should not be over-pressed and transported. The transport vehicle should avoid the high temperature period to prevent exposure and protect it at the same time. Accessories valve and level gauge. In addition, in the ammonia refrigeration process, attention should be paid to the fire protection requirements of the ammonia compressor room. In the "Code for Fire Protection of Building Design", the ammonia compressor room is listed as a Class B fire hazard plant, and the first and second class fireproof grade buildings should be used. In the Design Code, there are also special design requirements for the ammonia compressor room. There should be sufficient pressure relief area. The electrical equipment should be considered according to the Q-2 (Zone 1) class explosion-proof requirements, and there is an emergency pressure relief device and can be used for rescue. A fire hydrant that sprays water mist. Equipped with the necessary gas mask, conditional air breathing apparatus.

Third, liquid ammonia leakage accident disposal measures. It is necessary to pay attention to five aspects: First, the warning zone is divided according to the scene situation, and the vehicles and personnel are generally parked in the direction of higher terrain and upper wind (or side wind). Second, the disposal personnel should take the necessary personal protective measures. When disposing of the leakage or related equipment, wear an insulated chemical protective suit and an air breathing apparatus. Wear cold clothing when in direct contact with liquid ammonia. You can also wear cotton trousers in an emergency, tighten the trousers and cover the mouth and nose with a wet mask. Third, all fire sources and flammable materials in the spill area should be quickly removed and ventilation should be strengthened. If the cylinder leaks, apply a non-sparking tool during disposal, and try to make the leak port up to prevent the liquefied gas from flowing a lot. When the valve closing and plugging measures are invalid, consider immersing the cylinder in water or dilute acid solution, or transferring it to an open area for decontamination. Fourth, the leakage of liquid ammonia should be dispersed by using misty water and flowering water. When handling, try to prevent leakage into the water, sewers or some control areas. Fifth, if there is a fire, apply misty water, flowering water, anti-solvent foam, sand or CO2 to save, and pay attention to cooling the container wall with a large amount of direct water. If possible, move the movable items out of the fire as soon as possible. If there is a danger sign such as the sound of the venting hole of the container becomes large or the wall of the container is discolored, it should be retracted immediately.

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