09-11-2023 | Posted by Joaquín Martí
Many substances are stored at low temperatures to maintain them in a liquid state, either because they need to be used in that form or because that greatly reduces the volume requirements for storage at atmospheric pressure. The storage is normally characterized as cryogenic when the temperatures must be kept below -150 °C.
Typical liquids that are stored at low temperatures are ammonia (-33 ºC), propane (-42 °C), ethane (-89 °C), methane or natural gas (-162 °C), oxygen (-183 °C), nitrogen (-196 °C), hydrogen (-253 °C), and helium (-269 °C). The temperatures quoted are the liquefaction temperatures at atmospheric pressure.
All those chemicals are key in many applications. For example, natural gas is used in power generation, residential and commercial heating, transportation, and industrial processes, both as an energy source and as feedstock for producing chemicals, fertilisers, and plastics.
Liquid nitrogen is widely used for cryopreservation, cryosurgery, cryogenic cooling, and as a coolant for superconductors; it is also employed in the food industry for freezing and chilling. Ammonia’s uses include the production of fertilisers and explosives, refrigeration and cooling, cleaning, and the production of multiple chemicals. And so on.
Principia has worked on the design of storage tanks for many of those substances, perhaps particularly in tanks for storing liquefied natural gas (LNG) but also in many of the rest.
Their requirements vary depending on the storage temperature and the reactivity of the material concerned: while substances like nitrogen or helium do not pose special reactivity issues, hydrocarbons, oxygen, and hydrogen are clearly more problematic.
The worldwide storage capacity demanded by some of those substances may undergo drastic changes over relatively short times. Take the global capacity for storage of LNG, which has increased by almost an order of magnitude over the last 30 years and has led to Principia participating in over 70 projects of LNG tanks all over the world.
At the other end, liquid helium is practically only used for cooling superconductors and carrying out low-temperature research but, even then, we have been involved in the ITER facilities. Also, hydrogen is a crucial raw material for the synthesis of ammonia, methanol, and as a reducing agent in oil refining and the metal processing industries; however, it is its potential role in the energy industry that is receiving a lot of attention in recent times, even if the realities still lag far behind the future expectations. A recent post dealt with some of the advantages offered by hydrogen in the energy field and some of the challenges faced by its production, storage, and distribution.
There is practically no industry or technical field that has not been strongly affected by simulation in recent decades. But in the case of tanks for cryogenic storage of liquids, it would have been impossible to build them with anything near the level of safety that we demand from them.