Liquid nitrogen preparation generators are mainly divided into two mainstream technical types: air separation cryogenic liquefaction nitrogen generator and PSA nitrogen liquefaction generator. The two types of equipment have significant differences in working principle, structural configuration and operating energy consumption. Energy consumption is the core index to measure the operating cost of liquid nitrogen production equipment, and analyzing the energy consumption difference is of great significance for industrial enterprises to select economical and applicable liquid nitrogen preparation equipment. Cryogenic liquefaction equipment is traditional large-scale liquid nitrogen production equipment, while PSA liquefaction equipment is new small and medium-sized energy-saving liquid nitrogen preparation equipment, which are applicable to different production scale scenarios.
The cryogenic air separation liquid nitrogen generator has high single-unit output but high comprehensive energy consumption. Its working principle is to compress and cool air to ultra-low temperature through multi-stage compression and heat exchange, realize air liquefaction, and separate liquid nitrogen through fractionation. The equipment has complex structure, including air compression system, refrigeration system, heat exchange system and fractionation tower system, with large startup power and long preheating time. The average energy consumption of industrial operation is 0.8-2 kWh per liter of liquid nitrogen, which is suitable for large-scale liquid nitrogen continuous production with daily output of more than 10 tons, and the unit energy consumption can be reduced only under full-load long-term operation.
The PSA liquid nitrogen generator has obvious energy-saving advantages in small and medium-scale production scenarios. It first uses pressure swing adsorption technology to produce high-purity gaseous nitrogen, and then adopts micro-low-temperature liquefaction technology to liquefy gaseous nitrogen into liquid nitrogen. The equipment has a simple structure, fast startup and no long preheating process. The average operating energy consumption is 0.4-0.6 kWh per liter of liquid nitrogen, which is nearly 40% lower than that of traditional cryogenic equipment. For enterprises with intermittent liquid nitrogen demand and small daily consumption (less than 5 tons), PSA liquefaction equipment can avoid energy waste caused by idle operation of large cryogenic equipment, with lower comprehensive operating cost and higher energy utilization efficiency.
In terms of comprehensive energy consumption evaluation, large-scale continuous production scenarios are suitable for cryogenic liquefaction equipment to obtain scale energy efficiency advantages, while small-batch and intermittent production scenarios are more suitable for PSA liquefaction generators. In addition, the maintenance energy consumption and loss of PSA equipment are lower, with lower failure rate of supporting systems, which further reduces the long-term comprehensive energy consumption cost of liquid nitrogen production, and has higher economic applicability for most small and medium-sized industrial enterprises.
