1.0 Process Specifications
1.1
Process
Description
An RO system produces clean water by using high pressure
(30-40 bar g) to force
water molecules through tight pore membranes. Most other molecules that are
present in the brine blowdown feed solution; protein,
lactose, fat and ash; are too
large to pass through the membranes and remain behind in
the retentate stream. By
pumping the feed solution through a number of RO stages in
series, it is possible to
concentrate the dissolved solids to a higher level, limited
by hardness scaling, while
producing a clean water permeate stream suitable for
re-use.
The Electromat 7x1
Electrodialysis (ED) system for demineralization of acid casein whey, quoted
separately requires approximately 110 m3/day of clean process water to be used
for brine make-up. The ED system will
produce approximately 120 m3/day of brine blowdown which contains the ash
removed from the whey plus small amounts of organics that either pass through
the membranes or enter the brine via cross-leak. By feeding the ED brine blow down through a
special design RO system, it is possible to recover up to 70% of the water to
be used a second time for brine make-up.
1.2
Mass Balance
Following is a
theoretical mass balance for the RO system based on the expected typical composition of the ED brine blowdown:
|
|
Brine Blowdown /RO Feed
|
RO Permeate
|
RO Retentate
|
|
Volume, m3/d
|
120
|
80
|
40
|
|
Total solids, w/w%
|
2.00
|
0.06
|
5.90
|
|
Lactose, w/w%
|
0.60
|
0.02
|
1.75
|
|
NPN, w/w%
|
0.20
|
0.01
|
0.60
|
|
Ash, w/w%
|
1.20
|
0.03
|
3.55
|
1.3
System Sizing
& Configuration
Based on processing
120 m3/day of ED brine blowdown of the above composition, reverse osmosis (RO)
system with two recirculating stages, each stage containing two membrane
vessels. The vessels in stage 1 will
each contain three, 8” x 40” membrane elements.
The vessels in stage 2 will each contain two, 8” x 40” membrane
elements. The total membrane area is 300
m2.
System configuration:
Number of Elements Membrane
Stage
No. Vessels per vessel Area (m2)
1 2 3 180
2 2 2 120
The RO system
operating parameters are:
System baseline Pressure: 30-40 bar g
Operating temperature range: 20-40 ºC.
The RO system will operate continuously for 20 hours per
day at a feed flow rate of
approximately 6.0 m3/h.
The system will be off-line for 3-4 hours per day for Clean-
in-Place (CIP).
Operating temperature: 35 ºC
Maximum
CIP temperature: 50 ºC
Feed
rate: 100 LPM typical
Water
recovery: 65-70%
Feed
solids: 2.0 % typical
Retentate
Solids: 6.4 % typical
Process
pH: 3.2 typical
Cleaning
pH: 2.0 - 11.5
2.0 Equipment Specifications
2.1 RO System to treat 120 m3/d of brine blow down:
The proposed RO System includes the following major
equipment items.
Feed Section
One (1) Feed/CIP Tank: 500 liter capacity, with
CIP spray ball and level
transmitter, 304 SS construction. (To be supplied by the
customer).
One (1) Feed Flow Control Valve: 2.5” 304 butterfly valve with pneumatic
actuator.
One (1) CIP Water Supply Valve: 2.0” 304 SS ball valve with pneumatic
actuator.
One (1) Feed Tank Drain Valve: Air-actuated butterfly valve, 2” size.
One (1) Level Transmitter: 2.0” clamp connection. Analog and digital output.
Feed Section,
One (1) Flow
Diverter Plate: 4 port x 2.5”, 304 SS,
clamp connections.
One (1) Feed Pump
#1: Fristam Model FPX-1742 centrifugal
pump, 316 SS wetted parts, 7.5 KW, 3 phase/50Hz/415V, TEFC motor.
One (1) Dual Sock
Filter Assembly: 2.5” size filter housings piped in parallel with 40u polypropylene
bag over a 316 SS basket, including four (4) manual butterfly valves.
One (1) Feed Magnetic Flowmeter: Size 2.5”, 0-35 m3/h.
One (1) High
Pressure Feed Pump: Sundyne SunFlo
P2EGS050 high pressure pump, Model
P2FGS, 316 SS wetted parts, 3 phase/50Hz/415V, 30 KW TEFC motor for VFD
regulation.
Three (3) Pressure Gauges: Sanitary
clamp connections, glycerin filled.
One (1) Temperature Indicator: -20-90 C range.
Recirculation Section:
Four
(4) Pressure Vessels: 8.0”, 304 SS
construction, with permeate end cap and anti-telescoping-devices (ATD’s). Sized to contain five, 40” long membrane
elements.
Ten
(10) Membrane Elements: GE Osmonics RO
membrane elements, 8” diameter x 40” long, full fit construction.
Two
(2) Recirculation Pump, high pressure
centrifugal pump, 11 kw, 3 phase/50Hz/415 TEFC motor.
One
(1) Cooling Heat Exchanger: Shell-in-tube style heat exchanger for
indirect removal of pumping induced heat using chilled water, SS-304.
One (1) RTD and
Temperature Transmitter: 0-100 ºC range.
One (1) Cooling
Water Control Valve: Size 2” ductile
iron control valve with pneumatic actuator.
Two (2) Stage
Flush Valves: 3” check valves to prevent
bypass flow during flushing.
Two
(2) Pressure Gauges: Sanitary clamp connections, glycerin filled.
Two (2) Temperature Indicator: -20-90 ºC range.
Permeate
Section:
Three
(3) Permeate Divert Valve: Size 2.5”
Butterfly valve with pneumatic actuator..
Two (2) Sample valves: ¼” 304 SS ball valve.
Two (2) Permeate Rota meters: for monitoring
permeate flow from the individual
stages, 0-250 LPM range.
Concentrate Section:
One
(1) Automatic back pressure
Valve: 1.5” SS angle type control valve
with pneumatic actuator and positioner.
One (1) Concentrate Sample Valve:
¼” 304 SS ball valve.
One (1) Concentrate
Magnetic Flowmeter: 1.5” size, 0-15
m3/h.
Two (2) Concentrate
Divert Valve: Size 1.5” Butterfly valve with pneumatic actuator.
Controls Section
The electrical control equipment required for the RO system
includes pump motor controls plus a PLC and operator interface.
The
skid-mounted control enclosure typically includes:
·
Allen-Bradley
PLC - SLC 5/03
·
Allen-Bradley
Panel View PV 900 operator interface
·
Necessary
switches and pushbuttons.
·
Pneumatic
controls: solenoid valves and I/P converters
·
Alarm beacon
and horn
·
PID analog control loops for tank level
control, feed flow control, feed/concentrate ratio control and temperature
control.
The motor
control enclosure includes:
·
One 45 KW
Variable Frequency Drive for control of the high-pressure pump.
·
Standard motor
starter for the feed pump (7.5 KW).
·
Soft motor
starters for the two recirculation pumps (11 KW).
·
One
transformer to provide 24 VAC control power to the PLC.
2.4 Electrical Requirement and Other Utilities
The RO
system will be designed for 415 VAC, 3 phase, 50 Hz electrical power. Power
consumption will be approximately 2750 KWH/day.
Approximate
consumption of other utilities:
·
Volume
of water required for flush and CIP: 15
m3/day @ 45 ºC
·
CIP
flush water rate: 500 lpm
·
Volume
of water required for cooling: 150 lpm
maximum at 10 ºC
·
Pump
seal water: 90 lph
·
Dry
instrument air: 5.5 bar g pressure
2.5 CIP
Procedure
The RO system is designed for automated clean-in-place with
manual addition of the
cleaning chemicals.
Typical cleaning steps for a RO system are as follows:
(1)
Product
flush out
(2)
Caustic
solution recirculation
(3)
Water
flush
(4)
Acid
solution recirculation
(5)
Water
flush
(6)
Enzyme
solution recirculation
(7)
Water
flush
(8)
Sanitizer
soak cycle
(9)
Water
flush
The
anticipated time for CIP is 3 hours.
Water
used for flushing and make-up of the CIP solutions must meet the following
quality requirements:
Iron <0.05 ppm
Manganese <0.02 ppm
Copper <0.05 ppm
Barium <0.10 ppm
Silicates <10 ppm
Aluminum <0.05 ppm
Total
hardness (CaCO3) <35 ppm
Chlorides <20 ppm
SP
(total plate count <1000/ml)
Yeast
& Mold <10
Coliform <10
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