How should the LNG tank be purged and cooled before it is first filled with the medium?

It is necessary to verify that all pipeline installations meet the requirements of the PID. It is necessary to ensure that all pipelines are protected with nitrogen, and that their dew point and oxygen content are within specified limits. It is necessary to confirm that all pressure safety valves are in operation. It is necessary to ensure that all instruments are functioning properly. It is also necessary to confirm that the flare system is operational. . . Basic requirements include, for example: 1. Drying: The inner tank should be dried to a maximum dew point temperature of -20°C, while the perlite-filled space can reach -8°C. 2. Displacement: Use N2 for displacement. The O2 content can reach up to 9%. 3. Cooling: BOG gas is used, with a cooling rate of 3°C per hour, up to 5°C per hour, and a maximum temperature difference between adjacent thermocouples of 30°C. When loading LNG for the first time, there should be a very strict set of procedures to follow.

It’s quite complicated. I have files in both Chinese and English for the test drive, but unfortunately I can’t give them to you, haha! Simply put, it involves nitrogen displacement, LNG displacement, pre-cooling, and unloading from the ship! Among them, the nitrogen displacement takes the longest time! These driving documents will be provided to you by the Patent Chamber!

Determination of the emptying time for LNG storage tanks. Technical exchange forum for storage and transportation engineering – bastaro2008-5-6 0 / 2942008-5-6 19:54 by bastaro. Pre-cooling technology for LNG vaporization plants. Article sharing section (organized) – bastaro2007-8-31 0 / 13612007-8-31 14:21 by bastaro. This post was last edited by bastaro on 2009-2-23 13:58

I read the post on floor 4, which was about the pre-cooling process for LNG regasification plants. In my opinion, what the poster is asking about is likely the pre-cooling strategy for large storage tanks located by the sea, used to receive imported LNG – there is a significant difference between the two!

:If that’s the case, then why look for solutions online? The costs associated with pre-cooling and replacement are likely to be in the hundreds of thousands; it’s therefore necessary to spend a few tens of thousands to hire an expert team to conduct a feasibility study.

Requirements for drying the storage tanks used at LNG receiving stations (capacity: 165,000 cubic meters): For the inner tanks, the dew point should be below -20 degrees Celsius and the oxygen content should be less than 4%; for the circumferential spaces, the dew point should be below -10 degrees Celsius with an oxygen content of less than 4%; for the bottom insulation layer, the dew point should not exceed 20 degrees Celsius and the oxygen content should remain below 4%. For pump wells and pipelines, the dew point must be below -20 degrees Celsius and the oxygen content should be less than 4%. The nitrogen used for drying must have a purity of over 99%, with a dew point of below -60 degrees Celsius. For cooling the LNG storage tanks in our project, liquid LNG is used (with sprinklers installed at the top); once complete cooling is achieved, the temperature across all thermometers at the bottom of the inner tanks should be below -150 degrees Celsius. The maximum cooling rate is 5°C per hour, while the desired cooling rate is 3°C per hour. The maximum allowable temperature difference between any two adjacent thermometers is 30°C, and the maximum allowable temperature difference between any two distinct thermometers is 50°C. The volume of LNG required to achieve complete cooling is approximately 960 tons. The estimated time required is around 38 hours. The desired LNG supply rate is approximately 40–75 M3/h　　

When we replaced the ethylene tank, the oxygen content was less than 1% and the dew point was below minus 20 degrees Celsius; approximately 160 tons of ethylene were burned! Upstairs, is the oxygen level at 4% already below the lower limit of the combustion range?

The explosive limit of methane is 5–15%.