Is Rollover Possible in an Ammonia Storage Tank?

This article demystifies the confusion surrounding a phenomenon known as rollover and explains that it is not possible in tanks containing pure ammonia.

Ammonia is one of the most produced chemicals by mass and serves primarily as a raw material in the fertilizer industry. In the past decade, ammonia has also been proposed as an alternative to fossil fuels and as a suitable carrier for hydrogen. In an effort to meet global decarbonization goals, the use of ammonia in this manner will likely increase significantly in the coming decades, and large ammonia tanks will be constructed to store this ubiquitous chemical.

When storing any hazardous chemical, safety is paramount. This article investigates “tank rollover,” a phenomenon in which a spontaneous and sudden migration of a substantial mass of liquid from the bottom of the tank to the surface occurs. During a rollover event, large quantities of gas are generated in a tank in a short period of time, causing rapid over-pressurization.

The potential for rollover in an ammonia storage tank became a concern after a loss-of-containment incident occurred in Lithuania in 1989. Confusing statements regarding this incident have been published and reported in the literature.

This article explains why rollover is not possible in tanks storing pure ammonia (less than 0.5% water) and describes another phenomenon — thermal overload — that can impact ammonia storage tanks. This article discusses the rollover and thermal overload phenomena, the different causes, and their prevention in design and operation.

Rollover vs. thermal overload...