Overview
Tank blanketing in a nut shell
What is tank blanketing?
Tank blanketing with nitrogen means to cover a liquid with gas to protect the tanks and the medium. But how does tank blanketing work and who needs it?
Tank blanketing with valves (inerting) is indispensable in many industries, including pharmaceuticals, biotechnology, (petro)chemical, food and beverage production. Not only fuels, but also various chemicals, bulk materials, vapours, gases or dusts can form an explosive mixture in combination with atmospheric oxygen or in interaction with other substances and must be protected from these dangerous reactions during storage.
A case study of tank blanketing valves
104 tank blanketing valves for the first refinery financed with private funds in Zhejiang Province
This purchase order arrived at Mankenberg GmbH -the German valve manufacturer- at the end of 2018. The first stage of this newly built oil refinery comprises 104 partly very huge fuel tanks which have to be inerted with nitrogen. It was an unusual project for the German company. The refinery was built on an artificially created group of islands about 300 km air-line distance southeast of Shanghai. For this purpose, 42 hectares of artificial land were dredged. The refinery complex is operated by Zhejiang Petroleum and Chemical Co.
Tank blanketing with nitrogen
Tank blanketing with nitrogen is a very relevant topic because industrial nitrogen is the most commonly used inert gas. Other possible and frequently used gases are for ex. carbon dioxide or noble gases such as argon. Nitrogen is filled into a tank as an inert gas to displace existing oxygen and to thus prevent, besides other things, unwanted oxidation. Even though industrial nitrogen is cheaper than argon, it is still an expensive material in general. Therefore, the pressure range as well as the constant regulation of the gas are important parameters in any tank farm that works with fixed tank roofs. The floating roof storage tanks, on the other hand, have different requirements.
Tank blanketing valves and their crucial features
Tank blanketing valves – the key factor
Tank blanketing valves need to be of high accuracy, because this is the most important factor in tank farms. The key point in blanketing a liquid is to maintain the column of nitrogen in the vapour space. For this purpose, the vapour space must be pressurized or covered with nitrogen gas. The vapour gas pressure must be precisely maintained to ensure proper blanketing for safety. The pressure requirement is low because higher pressures do not significantly improve results. Increasing the blanketing pressure will cause more gas loss (typical blanketing pressure between 5 – 25 mbar).
Sweet or bitter? Tank blanketing for NFC juice
By the skillful use of pressure control valves, which regulate the inert gas pressure in a tank within a precisely defined scope (up to 5 mbar), many tank plant operators follow a very simple principle. Small set pressure → low nitrogen flow → reduced loss of the expensive gas whilst the protective function is maintained!