Ammonia replacement method for maintenance of liquid ammonia tank

Abstract

The invention provides an ammonia replacement method for maintenance of a liquid ammonia tank. The ammonia replacement method for maintenance of the liquid ammonia tank comprises the following steps that (1) when the liquid level in the liquid ammonia tank is reduced to the lowest liquid level, a connector between the liquid ammonia tank and the outside is closed, water is injected into the liquid ammonia tank for dilution, when the water level in the liquid ammonia tank reaches 3.8 m, the water is continued to be injected, a blow-down door at the bottom of the liquid ammonia tank is opened, and the water is discharged to a trench, when the concentration of ammonia discharged to the trench from the blow-down door is 0 ppm, water injection is stopped, and the water in the liquid ammonia tank is completely discharged; and (2) a blind plate is additionally arranged at a flange for isolation, a manhole door of the ammonia tank is opened, the ammonia tank is ventilated, when the oxygen content is 18%-23% and the ammonia concentration is 0 ppm, ventilation is stopped, and a maintainer is allowed to enter the tank for maintenance work. According to the ammonia replacement method for maintenance of the liquid ammonia tank, the ammonia in the liquid ammonia tank is absorbed by using cheap water, so that a large amount of cost is saved, and the replacement period is shortened; and water injection, water drainage, blind plate isolation and ventilation are adopted, so that the ammonia-free environment in the liquid ammonia tank is ensured, and the safety guarantee is improved.

Description

technical field [0001] The invention relates to the technical field of liquid ammonia tank maintenance, in particular to an ammonia replacement method for liquid ammonia tank maintenance. Background technique [0002] Liquid ammonia is stored in the liquid ammonia tank, and the liquid ammonia tank needs to be shut down for maintenance after a certain period of operation, including wall thickness measurement, hardness measurement, non-destructive testing, etc. In addition, when the liquid ammonia tank has flange leakage defects, it also needs to be shut down for maintenance. Because ammonia cannot be mixed with air, the explosive limit of the ammonia concentration in the air is 16% to 25%, and the mixture of ammonia and air reaches the explosive limit, which is very prone to combustion and explosion, resulting in production accidents and safety accidents. Therefore, on the one hand, the liquid ammonia tank is required to be completely replaced by ammonia gas before it is shu...

AI Technical Summary

Problems solved by technology

However, when the water is finally drained, some ammonia gas is likely to volatilize in the liquid ammonia tank, and maintenance personnel will have adverse effects on their bodies when they work in a confined space for a long time

Moreover, during the irrigation process, due to the dissolution of ammonia gas, the pressure inside the tank is low, and negative pressure is very easy to occur, and the liquid ammonia tank has the risk of negative pressure instability.