Safe operation of liquid ammonia tank area
Author: Source: Date: 2018-10-08 15:23:05
Liquid ammonia is widely used as an important chemical raw material. As the scale of industrial production continues to expand, the storage scale of liquid ammonia has also expanded. Since liquid ammonia is a toxic, flammable and explosive medium, several liquid ammonia leaks and poisoning accidents have occurred in recent years, causing casualties and economic losses. Therefore, ensuring the safe operation of the liquid ammonia tank area has become a serious concern question.
1 Introduction to liquid ammonia
Liquid ammonia, also known as anhydrous ammonia, is a colorless liquid with a special pungent odor. As an important chemical raw material, ammonia is widely used. For transportation and storage convenience, gaseous ammonia is usually pressurized or Cooling gives liquid ammonia. Liquid ammonia is widely used in industry, and it is corrosive and volatile, so the accident rate is quite high. Liquid ammonia volatilizes to produce ammonia, which is a toxic, flammable, and explosive gas.
2 Liquid ammonia tank area safety facilities and operation
The tank area is a centralized storage area for liquid ammonia, ensuring its safe operation is the top priority for ensuring enterprise safety. Our years of management experience in the liquid ammonia tank area, the liquid ammonia tank area should have the following safety facilities.
2.1 The liquid ammonia storage tank should be equipped with a fireproof embankment. The effective volume in the embankment should be 60% of the maximum storage tank volume. If the ammonia storage tank leaks, the liquid ammonia will not spread around, which provides convenient conditions for the accident treatment. The launching system shall be provided with two channels of rainwater and production sewage, which are normally closed and, in some cases, selectively opened as required.
2.2 Liquid ammonia storage tank design should meet the specifications. Liquid ammonia storage tank should be equipped with liquid level gauge, pressure gauge, safety valve and thermometer.
2.3 The safe filling capacity of liquid ammonia storage tank shall not exceed 85% of the storage tank volume. In normal production, the liquid ammonia storage tank shall be controlled at a lower liquid level, generally controlled within 30% of the safe filling capacity. In order to avoid the expansion and rise of the ambient temperature during storage, the tank may be over-pressured.
2.4 Outdoor liquid ammonia tank area should be equipped with accidental spray water and drainage facilities. In this way, in the case of a large amount of leakage in the storage tank, the leakage of liquid ammonia can be absorbed by the fire water to reduce environmental pollution. The drainage should be provided with two passages, a rainwater system and a production sewage system.
2.5 In order to prevent over-pressure of the storage tank caused by summer sun exposure, the outer wall of the spherical tank should be brushed with cool plastic to reduce the radiant heat of the sunlight and reduce the conduction heat, so that the storage tank can survive the hot summer. At the same time, the integrity of the pipeline to keep cold is also an effective measure to protect the pipeline.
2.6 In order to ensure that the storage tank is not overfilled, the tank liquid level display should be set to be high to remind the operator that the tank filling has reached the safety permit limit.
2.7 A flammable gas alarm device should be installed near the liquid ammonia tank area and the liquid ammonia pump. When the ammonia concentration is close to 10% of the lower explosion limit, an alarm signal should be issued.
2.8 Storage tanks and pipelines should have static electricity discharge facilities, and regular inspection by professionals. When liquid ammonia is transported, a large amount of static charge will be generated due to the friction between liquid ammonia and the pipeline. If the charge is not conducted through the grounding device, the charge will accumulate on the storage tank to form a high potential. When this potential reaches a certain gap discharge potential, an electric spark may cause a fire or explosion accident.
2.9 The spherical tank opening should adopt the principle of minimization to ensure the overall strength of the spherical tank is optimal; the wind direction indicator should be set at the height of the tank area. When there is a large amount of ammonia leakage accident, the personnel should evacuate upwards; the storage tank and pipeline should be measured regularly. Wall thickness to grasp the thinning of the equipment.
2.10 Accident tanks and accident pumps shall be provided in the liquid ammonia tank area. The minimum storage capacity of the accident tank shall not be less than 1/4 of the maximum tank capacity. At the same time, the operation post shall formulate corresponding accident plans, equip relevant protective equipment, and establish a management system for equipment, distribution and use.
3. Tips for operation
3.1 The pipeline equipment is purged before being put into use and replaced with nitrogen. In particular, there is no possibility of water, otherwise liquid ammonia will generate a large amount of heat of dissolution in contact with water, which is extremely dangerous.
3.2 Anti-corrosion and cold preservation of pipelines is the key to the long-term safe operation of liquid ammonia pipelines. Anti-corrosion can effectively reduce the corrosion and thinning of pipelines, while cold preservation can avoid the formation of condensed water on the outer wall of the pipeline during the wet season in summer, so that the anti-corrosion effect can be more effectively improved.
3.3 Regularly measuring the wall thickness of the pipeline equipment can enable the management personnel to dynamically understand the corrosion and thinning of the equipment pipeline and formulate countermeasures in a timely manner. However, after each thickness measurement, each time the thickness is measured, the anti-corrosion and cold preservation should be restored in time to avoid the thickening point becoming a new corrosion thinning. At the same time, the selection of measuring points should be representative in order to fully reflect the corrosion thinning state of the system.
3.4 System gaskets should be replaced periodically and recorded. Storage tanks shall be regularly verified by professional departments as required.
3.5 Liquid ammonia discharge should be discharged to the torch line through the closed pipeline. When the liquid ammonia pipeline needs to be fired, the liquid ammonia must be drained cleanly, and then purged with nitrogen, then rinsed with water. When the flushing water is neutral, it is regarded as Rinse well. If it is necessary to purge the pipeline water with nitrogen, it can be applied.
Liquid ammonia is a dangerous chemical that is increasingly valued by all parties. The design and operation of this system must take into account fire prevention, explosion prevention, poisoning prevention and environmental pollution.
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