Deep-condensation VOCs recovery system using air as refrigerant

1. A deep-condensation Volatile Organic Compounds (VOCs) recovery system using air as refrigerant, comprising a gaseous air purification system, an air liquefaction system, and a VOCs recovery cold box,

wherein the gaseous air purification system comprises an air filter, a cold dryer and an air purifier, and the air liquefaction system comprises an air compressor, an air storage tank, a turbo-expander and an air precooler, an outlet of the air filter being connected with an inlet of the air compressor, an outlet of the air compressor being connected with an inlet of the air storage tank,

wherein the VOCs recovery cold box comprises a VOCs precooler, a VOCs condenser, a gas-liquid separator, the air precooler, and the turbo-expander, and the interlayer of a shell of the VOCs recovery cold box is filled with a powder and vacuumized to achieve the purpose of heat insulation,

wherein a liquefied air serves as a cooling medium to condense VOCs in a VOCs gas, and during operation, air passes through the air filter to remove microparticles and impurities contained in the air, and

the filtered air is compressed by the air compressor and enters the air storage tank for storage.

2. The VOCs recovery system of claim 1 , wherein the outlet of the air storage tank is connected with an inlet of the cold dryer, an outlet of the cold dryer is connected with an inlet of the air purifier, and an outlet of the air purifier is connected with a hot air inlet of the air precooler in the VOCs recovery cold box.

3. The VOCs recovery system of claim 2 , wherein a hot air outlet of the air precooler is connected with an inlet of the turbo-expander, an outlet of the turbo-expander is connected with an air inlet of the VOCs condenser, and a air outlet of the VOCs condenser is connected with an cold air inlet of the air precooler, wherein the turbo-expander liquefies air from the air precooler and the liquified air enters the VOCs condenser for heat exchange with the VOCs gas prior to entering the air precooler for heat exchange with hot air from the air purifier.

4. The VOCs recovery system of claim 1 , wherein an outlet of the VOCs precooler is connected with an inlet of the VOCs condenser in the VOCs recovery cold box, and an outlet of the VOCs condenser is connected with an inlet of the gas-liquid separator, and

wherein the VOCs gas passes through the VOCs precooler to remove moisture in the VOCs gas and to form a dried VOCs gas, the dried VOCs gas enters the VOCs condenser in the VOCs recovery cold box and exchanges heat with the liquified air and the VOCs gas is condensed into a liquid state to form a gas-liquid mixture, which enters the gas-liquid separator to separate liquid from gas in the gas-liquid mixture.

5. The VOCs recovery system of claim 4 , wherein a gas outlet of the gas-liquid separator is connected with an inlet of the VOCs precooler; and a tail gas exiting the VOCs recovery cold box is subjected to heat exchange with the VOCs gas.

6. The VOCs recovery system of claim 4 , wherein the VOCs precooler is a fin plate partition-wall precooler having three channels, wherein a first channel and a second channel serve as passages for the VOCs gas and a third channel serves as a passage for the liquefied air, the third channel is a microchannel with a diameter smaller than 1 mm, the first and the second channels are wide-size channels.

7. The VOCs recovery system of claim 6 , wherein the VOCs gas in the VOCs precooler flows in a cross flow pattern relative to the liquefied air.

8. The VOCs recovery system of claim 2 , wherein the VOCs recovery system comprises a microchannel mixer, the gas exiting the gas-liquid separator enters the microchannel mixer to mix with the liquified air.