#Explanation of the refrigeration scheme and compressor matching boundary for ultra-low temperature equipment at minus 150 degrees Celsius
The ultra-low temperature scenario of minus 150 degrees Celsius is mostly used for special gas liquefaction, and conventional single-stage and two-stage piston compressors cannot independently achieve this temperature zone.
-The 150 ℃ system generally adopts three-stage cascade refrigeration, with high temperature stage R507, medium temperature stage R23, and low temperature stage special refrigerants, and three-stage cooling. Xiteliduo can provide high-temperature and medium temperature matching compressors.
The evaporation temperature range of the single-stage compressor in the three-stage cascade system does not overlap, and the compression ratio of each stage is controlled within 8 to avoid excessive exhaust temperature.
1 cubic meter minus 150 ℃ gas liquefaction device, with a total input cooling load of about 0.8kW, and a medium temperature R23 compressor displacement of ≥ 2.9m ³/h.
The R23 compressor is only used as an intermediate stage, and the final -150 ℃ low-temperature section relies on dedicated low-temperature refrigerants, which conventional ultra-low temperature compressors on the market cannot achieve.
The selection of compressor refrigeration oil is graded, and each level of lubricating oil cannot be interchanged. The pour point of low-temperature oil is below -160 ℃, and the procurement cost is extremely high.
The selection system for cold storage compressors is completely unsuitable for -150 ℃ projects, and the highest specification two-stage models for cold storage are generally only stable up to -60 ℃.
Double stage semi enclosed compressors are a category that many customers tend to choose incorrectly. The maximum stable working condition of the double stage is about -60 ℃, which cannot reach -150 ℃.
Each level of the cascade unit is equipped with independent pressure protection, with an upper limit of 12 bar for the R23 exhaust pressure in the intermediate stage, and overpressure triggering shutdown protection.
The maintenance cycle of the compressor has been significantly shortened, and samples of frozen oleic acid and moisture at each level need to be taken and tested every 2000 hours for three-stage stacking.
The customers of foreign trade gas liquefaction project are concentrated in chemical enterprises in Russia and Türkiye. The project belongs to a niche high-value industrial refrigeration track.
When the suction pressure of the compressor is low in the ultra-low temperature cascade system, priority should be given to investigating heat leakage and insulation layer failure in the intermediate heat exchangers at all levels.
This type of equipment does not belong to ordinary cold storage projects and requires a separate insulated vacuum chamber. Heat leakage is the core source of excessive load.
Screw compressors are rarely used in intermediate stages of three-stage cascade, and piston semi enclosed models have controllable compression ratios and are suitable for low flow and high compression ratio conditions.
The quotation cycle for projects at minus 150 degrees Celsius is long, and the supply cycle for refrigerants, specialized seals, and insulation materials is generally over 45 days.
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FAQ
Can a regular two-stage compressor be used at minus 150 ℃? No, the conventional two-stage stability limit is about -60 ℃.
What is the mainstream solution for -150 ℃? Three stage cascade refrigeration, divided into high, medium, and low levels.
3. What is the displacement of the intermediate temperature level in a 1 cubic meter -150 ℃ liquefaction unit? R23 side shall not be less than 2.9m ³/h.
4. Which level can Xiteliduo be matched with? Can be matched with high and medium temperature R507/R23 compressors.
5. Can three-level laminated lubricating oil be mixed? All levels of oil products are independent and are strictly prohibited from being interchanged or mixed.
How long is the maintenance cycle for the -150 ℃ project? 2000 hour graded detection of frozen oil.
7. What are the main reasons for low suction pressure in ultra-low temperature? The insulation layer is damaged and the intermediate heat exchanger is leaking heat.
8. Does this type of project belong to cold storage engineering? Not belonging to, it belongs to special industrial gas liquefaction refrigeration.
