Should a liquid ammonia storage tank be equipped with insulation?
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This post was last edited by Douwan on 2017-12-13 at 15:47. Should a liquid ammonia storage tank be equipped with insulation? I’m very confused about this question. I remember that during the certification review last year, we had a liquid ammonia storage tank with a capacity of 110 cubic meters – it was a horizontal vessel. Its operating temperature ranged from -5 to 45°C, the design temperature was -10/50°C, the design pressure was 2.16 MPa, and the material used was Q345R. The technical data sheet specified the use of 50 mm thick polyurethane foam for insulation based on the requirements of the relevant engineering field. However, during the certification review, experts insisted that this material be removed from the drawings, stating that the equipment in question could not provide insulation. The reason given was that the temperature of liquid ammonia when it enters the storage tank is very low; if insulation were used, the equipment would need to be designed as a low-temperature device. So we invited the person in charge of the manufacturing process and the chief engineer to explain that it was possible to maintain the temperature within the range of -5~45°C during the production process, but it was all useless in the end. Later, I looked up other drawings – some showed liquid ammonia storage tanks and others liquid ammonia spherical tanks – and I noticed that insulation was provided in all of them. As a result, I became more and more confused... What I also didn’t understand was that regarding the parameters for liquid ammonia storage tanks, the low temperature is used to determine the appropriate materials, while the high temperature is used to determine the design pressure; after all, even at low temperatures, the stress level is low! Do the liquid ammonia storage tanks you have designed or encountered all come with insulation?
Why is the temperature very low in a liquid ammonia storage tank? What is the pressure? How low can the temperature go? The saturated vapor pressure (absolute pressure) of liquid ammonia is approximately 0.19 MPa at -20 degrees Celsius, and about 0.355 MPa at -5 degrees Celsius. How was your operating pressure of -5 degrees Celsius determined?
-5℃ is a parameter proposed by the process.
We don’t have insulation here; we use liquid ammonia spheres!
When liquid ammonia is being filled, the pressure is low; the temperature corresponding to this saturated vapor pressure is also low, below the design temperature of -10. If insulation is provided, the storage tank and liquid ammonia cannot absorb heat quickly and rise in temperature. The storage tank is at a temperature below -10 degrees, which contradicts the design temperature. To use polyurethane foam, the design temperature must be reduced. -Polyurethane foam cannot be used for the design temperature of 10.
What if it’s -19 degrees Celsius? Can polyurethane foam be set?
The liquid ammonia storage tanks designed and manufactured by our company do not require insulation
The liquid ammonia storage tanks designed and manufactured by our company do not require insulation
The liquid ammonia storage tanks designed and manufactured by our company do not require insulation
Liquid ammonia storage tanks are divided into vertical atmospheric-pressure tanks, spherical tanks, and horizontal tanks. Atmospheric storage tanks require almost no cooling, while spherical storage tanks are semi-cooled tanks with a design pressure of generally 7 bar. The horizontal storage tanks you mentioned are of the fully refrigerated type; they have a high design pressure, which results in a high flash point for ammonia as well as high temperatures, so insulation is not necessary.