Importance

Loading Importance Indicators...

Abstract

In the drying of solvents-containing material in a vacuum concentrator and which involves condensation of evolved solvents in a cold trap, simplified and inexpensive flow blocking devices are provided intervening an outlet of the cold trap and an inlet to the vacuum pump with which the concentrator is evacuated. The flow blocking practiced allows cryopumping effect to ensue between the concentrator and cold trap such being the agency by which solvent vapor outflows from the concentrator and is recovered by condensation thereof in the cold trap. Near complete solvent recovery can be achieved and carryover of solvent to the vacuum pump is reduced to insignificant measure. In one form, flow blocking is attained by use of a simple pressure differential valve. This valve will stay closed as long as absolute pressure differential acting on the valve is a desired value, such as one corresponding to difference of condition of vacuum at pump inlet and at the upstream end of the valve, such differential being one at which cryopumping conditions exist. If the differential is greater, the valve will open to reconnect system flow to the vacuum pump which continues until cryopumping condition is again achieved when the valve will again close. Flow blocking also readily can be provided with a solenoid operated valve, the solenoid being controlled by a pressure differential switch sensing condition of vacuum at the pump inlet and at a location upstream in the system. When the differential of vacuum conditions sensed is as desired, the switch is closed maintaining a signal to the valve keeping it closed allowing cryopumping of solvent to occur. When the sensed differential is greater than desired, the switch opens, the signal terminates and the valve opens to connect the system to the vacuum pump.

Loading the Abstract Image...

First Claim