Vapor recovery systems are generally used to prevent pollution of the environment and to recover valuable product. Two basic types of vapor recovery systems may be encountered. One is designed to gather toxic wastes that would pollute the atmosphere but are not valuable enough to warrant full recovery. In this type system, the vapors are generally gathered and incinerated. If incineration will not meet government disposal standards, the vapors are generally compressed and condensed into a liquid and sent to a liquid disposal system.
The vapor recovery systems that are typically used with refrigerated storage tanks are generally integrated with the product refrigeration systems. In these types of systems, the vapors are generally compressed, condensed, and put back into the tank with the fill stream.
Vapor recovery systems on atmospheric pressure, ambient temperature storage tanks do not normally require a refrigeration system to condense the vapors. They are generally compressed through one stage of compression, condensed in either an air cooled or water cooled exchanger, and then put back into the tank. Fig. 6-20 provides the flow schematic of this system.