Vapor is
bubbled
through liquid
to help cool and
recondense it
Removing vapor from
tank causes liquid heel
to boil into vapor
Liquid line is valved closed
during vapor recovery.
Four Way Valve Position 2
Vapor Line
Vapor Line
Liquid Line
(3.8 to 4.5 bars). A good rule of thumb is not to operate
beyond the point at which the inlet pressure is one-
fourth the discharge pressure. Some liquids are so
expensive that further recovery may be profitable, but
care should be taken that the ratio of absolute discharge
pressure to absolute inlet pressure never exceeds 7 to
1. Further excavation of very high value products would
require a Corken two-stage gas compressor.
Invariably, there is some liquid remaining in the tank
after the liquid transfer operation. This liquid “heel”
must be vaporized before it can be recovered, so
do not expect the pressure to drop immediately.
Actually, more vapor will be recovered during the first
few minutes while this liquid is being vaporized than
during the same period of time later in the operation.
Remember that more than half of the economically
recoverable product is usually recovered during the
first hour of operation on properly sized equipment.
1.3 Compressor
Construction Features
The Corken liquid transfer-vapor recovery compressor
is a vertical single-stage, single-acting reciprocating
compressor designed to handle flammable gases
like LPG and toxic gases such as ammonia. Corken
compressors can handle these potentially dangerous
gases because the LPG/NH
3
is confined in the
compression chamber and isolated from the crankcase
and the atmosphere. A typical liquid transfer-vapor
recovery compressor package is shown in figure 1.3A.
Figure 1.3A: 107-style compressor mounting.
Corken gas compressors are mounted on oil lubricated
crankcases remaining at atmospheric pressure. Crankshafts
are supported by heavy-duty roller bearings and the
connecting rods ride the crankshaft on journal bearings.
With the exception of the small size model 91 compressor,
all compressor crankcases are lubricated by an automotive
type oil pressure system. An automatically reversible gear
Figure 1.2A: Residual vapor recovery.
6
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