How to prevent potential hazards in the operation of high-purity ammonia storage tanks?

Liquid ammonia storage tank

Liquid ammonia is included in the list of hazardous chemicals due to its flammable, explosive, and toxic properties. According to the “Identification of Major Hazardous Sources of Hazardous Chemicals” (GB18218-2009), the critical ammonia storage volume greater than 10 tons*** constitutes a major source of hazard. All liquid ammonia storage tanks are classified as three types of pressure vessels. Now analyze the hazardous characteristics and hazards during the production and operation of the liquid ammonia storage tank, and propose some preventive and emergency measures to avoid accidents.

Hazard analysis of liquid ammonia storage tank during operation

The hazardous properties of ammonia

Ammonia is a colorless and transparent gas with a pungent odor, which is easily liquefied into liquid ammonia. Ammonia is lighter than air and easily soluble in water. Since liquid ammonia is easily volatile into ammonia gas, when ammonia and air are mixed to a certain ratio, it can be exposed to open flames, the maximum range is 15-27%, in the ambient air of the workshop ***** *The allowable concentration is 30mg/m3. Leaking ammonia gas can cause poisoning, irritation to the eyes, lung mucosa, or skin, and there is a danger of chemical cold burns.

Risk analysis of production and operation process

1. Ammonia level control
If the ammonia release rate is too fast, the liquid level operation control is too low, or other instrument control failures, etc., the synthetic high-pressure gas will escape into the liquid ammonia storage tank, resulting in overpressure in the storage tank and a large amount of ammonia leakage, which is extremely harmful. The control of the ammonia level is very critical.

2. Storage capacity
The storage capacity of the liquid ammonia storage tank exceeds 85% of the volume of the storage tank, and the pressure exceeds the control index range or the operation is performed in the liquid ammonia inverted tank. If the procedures and steps are not strictly followed in the operating regulations, overpressure leakage will occur***** *accident.

3. Liquid ammonia filling
When liquid ammonia is filled, overfilling is not performed in accordance with the regulations, and the blasting of the filling pipeline will cause leakage and poisoning accidents.

Hazard analysis of equipment and facilities

1. The design, inspection, and maintenance of liquid ammonia storage tanks are missing or not in place, and safety accessories such as level gauges, pressure gauges, and safety valves are defective or hidden, which may lead to tank leakage accidents.

2. In summer or when the temperature is high, the liquid ammonia storage tank is not equipped with awnings, fixed cooling spray water and other preventive facilities as required, which will cause overpressure leakage of the storage tank.

3. Damage or failure of lightning protection and anti-static facilities or grounding may cause electric shock to the storage tank.

4. The failure of production process alarms, interlocks, emergency pressure relief, combustible and toxic gas alarms and other devices will cause overpressure leakage accidents or enlargement of the storage tank.

Accident prevention measures

Preventive measures for production process operation

1. Strictly implement operating procedures
Pay attention to the operation of discharging ammonia in synthetic posts, control the liquid level of cold cross and ammonia separation, keep the liquid level stable within the range of 1/3 to 2/3, and prevent the liquid level from being too low or too high.

2. Strictly control the pressure of the liquid ammonia storage tank
The storage volume of liquid ammonia shall not exceed 85% of the storage tank volume. During normal production, the liquid ammonia storage tank should be controlled at a low level, generally within 30% of the safe filling volume, to avoid ammonia storage due to ambient temperature. Rising expansion and pressure increase will cause overpressure in the storage tank.

3. Precautions for liquid ammonia filling
The personnel who install ammonia should pass professional safety education and training before they can take up their posts. They should be familiar with the performance, characteristics, operation methods, accessory structure, working principle, hazardous characteristics of liquid ammonia and emergency treatment measures.

Before filling, the validity of the certificates such as tank physical examination verification, tanker use license, driver’s license, escort certificate, and transportation permit should be verified. The safety accessories should be complete and sensitive, and the inspection should be qualified; the pressure in the tanker before filling should be low. Less than 0.05 MPa; the performance of the ammonia connection pipeline should be inspected.

The personnel who install ammonia should strictly follow the operating procedures of the liquid ammonia storage tank, and pay attention to the filling volume not exceeding 85% of the storage tank volume when filling.

Personnel who install ammonia must wear gas masks and protective gloves; the site should be equipped with fire-fighting and gas protection equipment; during filling, they must not leave the site, and strengthen inspections of tank truck pressure, pipeline flanges for leaks, etc., tank truck gas Recycle it to the system accordingly and not discharge it at will. If there is any abnormal situation such as leakage, stop filling immediately, and take effective measures to prevent unexpected accidents.

Routine inspections of ammonia installation facilities, measures and procedures shall be carried out on a daily basis, and inspection and filling records shall be made.

Post time: Aug-31-2021