Liquid ammonia, as an important industrial raw material, is typically stored and transported using dedicated liquid ammonia storage tanks. Because liquid ammonia leaks can cause serious harm to the environment and human health, extra caution is required during use. Icing in liquid ammonia storage tanks is a common but easily overlooked problem. So why do liquid ammonia storage tanks freeze? Is icing dangerous? Is it a normal phenomenon? The following will provide detailed answers.
I. Reasons for Icing in Liquid Ammonia Storage Tanks
(I) Pipeline Icing
Icing in the pipeline between the liquid ammonia regulating valve and the evaporator is mainly due to the large amount of heat absorbed during the vaporization process of liquid ammonia, causing a rapid drop in ambient temperature. When liquid ammonia moves from a low-temperature environment to a normal-temperature environment, its saturated vapor pressure is greater than atmospheric pressure. The liquid ammonia will rapidly vaporize and absorb heat from the surrounding environment to meet the latent heat of vaporization. This causes water molecules in the air to condense and freeze on the surface of the pipeline, which is a normal phenomenon.
(II) Icing on the Pressure Gauge at the Bottle Neck
For cryogenic liquid ammonia tanks that have undergone long-term transportation, the connection between the top level gauge and the tank body may become loose. When not in use, this loosening may not be noticeable, but once in use, ammonia leakage can lead to significant icing. This not only indicates a potential leak of liquid ammonia but may also trigger a fire or other accidents, causing personal injury or environmental pollution, requiring the cylinder to be sent for repair immediately.
(III) Icing Inside the Tank
Icing inside the tank is mainly due to heat exchange between the inner and outer liner of the liquid ammonia tank and the condensation of moisture in the air. Slight frost is normal, but severe frost requires attention, as it may indicate damage to the tank. In this case, immediate repairs should be carried out, and the tank should be taken out of service.
II. Preventive Measures for Icing in Liquid Ammonia Storage Tanks
Icing in liquid ammonia storage tanks not only affects the normal operation of the equipment but may also cause safety hazards. Therefore, daily prevention of icing in liquid ammonia storage tanks is crucial and can be approached from the following aspects:
(I) Optimizing the Heating System
By optimizing the automatic adjustment performance of the liquid ammonia evaporator heater, ensure that the hot coal of the liquid ammonia evaporator operates at a stable temperature. This can effectively prevent the liquid ammonia evaporator from tripping and the hot coal temperature from dropping too low, thereby reducing the occurrence of icing.
(II) Alarm and Interlock System Installation
An alarm and interlock system should be installed in the liquid ammonia evaporator heater. If the liquid ammonia evaporator trips, the system should immediately sound an alarm to alert operators. Simultaneously, the interlock system should automatically close the inlet and outlet valves of the liquid ammonia evaporator to prevent a large amount of unheated liquid ammonia from flowing directly into the buffer tank, thus avoiding icing due to heat absorption during vaporization.
(III) Regular Maintenance and Cleaning
Regularly clean and drain the liquid ammonia storage tank to ensure internal cleanliness. Simultaneously, properly adjust the ammonia inlet regulating valve of the liquid ammonia evaporator at normal pressure to mitigate icing caused by throttling expansion.
Icing in liquid ammonia storage tanks is a serious issue. While some icing is normal, severe icing may indicate equipment damage or improper operation. Optimizing the heating system, installing alarm and interlock systems, and conducting regular maintenance and cleaning can effectively prevent icing in liquid ammonia storage tanks, ensuring safe equipment operation.
Luoyang Hongchang Industry and Trade Co., Ltd. has extensive experience in the production, filling, and transportation of liquid ammonia, ammonia water, hydrogen peroxide, and other products. We consistently adhere to strict safety regulations to ensure the safety of our products during transportation and use. If you have any related needs, please feel free to contact us; we will provide you with professional services and solutions.
