4S-SERIES PRESSURE EXCHANGER ENERGY RECOVERY DEVICES
Energy Recovery, Inc.
5
ERI Document Number 80022-01-04
is transferred directly to a portion of the incoming raw seawater at up to 97% efficiency. This
pressurized seawater stream (D), which is nearly equal in volume and pressure to the reject
stream, passes through a booster pump (not the main high-pressure pump) to add the small
amount of pressure lost to friction in the PX unit, the membranes and the associated piping. The
booster pump also serves to drive the flow of the high-pressure stream through the PX unit (G
and D). Fully pressurized seawater then merges with the high-pressure pump discharge to feed
the membranes.
4.2 PX Energy Recovery Devices in SWRO Systems
The PX energy recovery device fundamentally changes the way an SWRO system operates. The
issues presented in this and the following sections should be taken into consideration when
designing an SWRO system. In addition, engineers at Energy Recovery, Inc. are available for
design consultation and review of process and instrument diagrams.
Example flow rates and pressures for an SWRO system with one PX-90S are listed in Table 4-1
below with reference to Figure 4-2. In an SWRO system with an ERI energy recovery device
Figure 4-2. Typical Flow Path of an SWRO System with a PX Unit
Figure 4-1. Flow Path through a PX Unit
Table 4-1. Example Flow Rates and Pressures
High Pressure side
Sealed Area
High-pressure seawater
going to booster pump
High-pressure brine reject
from SWRO membranes
Low-pressure seawater
inlet from seawater
Low-pressure brine
reject to drain
Seawater
Reject Water
Liquid Plug
Rotor Rotation
G
D
B
H
Low Pressure side
B
PX Booster Pump
Main High
Pressure Pump
Seawater Supply
Pump
Permeate
Pressure Exchanger
Device or PX Unit
Array
F
H
G
I
E
A
C
D
Membranes