Vacuum system design of a 10 ton/day class air liquefaction cold box for liquid air energy storage

Vacuum system design of a 10 ton/day class air liquefaction cold box for liquid air energy storage

A vacuum system is designed for thermal insulation of a 10 ton/day class air liquefaction cold box for liquid air energy storage. The vacuum system is composed of a turbomolecular pump, a backing pump and vacuum piping for the vacuum pumps. Theturbomolecular pump is in combination with the backing pump for pumping capacity. The vacuum piping is designed with systeminstallation conditions, such as distance from the cold box, connections to vacuum pumps and installation space. The capacity ofthe vacuum pump combination, namely pumping speed, is determined by analysis of the vacuum system, and pump-down time to1×10-5 mbar is estimated. Vacuum piping conductance, system pumping speed and outgassing rate are calculated for the pumpdown time with the ultimate pumping speed range of the vacuum pump combination of 1400 – 2300 l/s. Although the pump-downtime gets shorter by larger capacity vacuum pumps, it mainly depends on target vacuum degree and outgassing rate in the cold box. The pump-down time is estimated as 3 – 6 hours appropriate for cold box operation for the pumping speed range. Considering theoutgassing rate has uncertainty, the vacuum pump combination with pumping speed of 1900 l/s is chosen for the vacuum system,which is middle value of the pumping speed range.

A vacuum system is designed for thermal insulation of a 10 ton/day class air liquefaction cold box for liquid air energy storage. The vacuum system is composed of a turbomolecular pump, a backing pump and vacuum piping for the vacuum pumps. Theturbomolecular pump is in combination with the backing pump for pumping capacity. The vacuum piping is designed with systeminstallation conditions, such as distance from the cold box, connections to vacuum pumps and installation space. The capacity ofthe vacuum pump combination, namely pumping speed, is determined by analysis of the vacuum system, and pump-down time to1×10-5 mbar is estimated. Vacuum piping conductance, system pumping speed and outgassing rate are calculated for the pumpdown time with the ultimate pumping speed range of the vacuum pump combination of 1400 – 2300 l/s. Although the pump-downtime gets shorter by larger capacity vacuum pumps, it mainly depends on target vacuum degree and outgassing rate in the cold box. The pump-down time is estimated as 3 – 6 hours appropriate for cold box operation for the pumping speed range. Considering theoutgassing rate has uncertainty, the vacuum pump combination with pumping speed of 1900 l/s is chosen for the vacuum system,which is middle value of the pumping speed range.