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CaribDA 2016 Conference & Exposition“Developing and Affording New Water Sources”
31st May – 3rd June 2016 in Trinidad
Regulation of double stage SWRO plant after improving the energy consumption using ERI technology. Case study: Las
Americas SWRO plant, Canary Islands
Julen Cabero, PhDSUEZ Treatment Solutions, SAU
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INTRODUCTION
3 GRAPHICS THAT SHOW THE EVOLUTION OF ENERGYEFFICIENCY IN DESALITATION PLANTS IN THE LAST 40 YEARS
� Evolution of the Technology
� Evolution of the Energy Recovery Devices in SWRO Plants
� Evolution of the Energy consumption
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Evolution of the desalinationtechnology
Figure 2: Capacity of installed desalted water by technology (2015) [*][*] Global Water Intelligence/IDA
Figure 1: Capacity of installed desalted water: Thermal vs membrane
processes (1980 – 2013) ) [*]
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Evolution of the Energy Recovery Devices in RO
1970 1980 1990 2000 2010 2015
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Evolution of SEC (Kwh/m3)
Figure 3: Evolution of the Specific Energy Consumption in seawater desalination plants (1970-2015)
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Description of Las Americas SWRO plant
Evolution of the installation from 1998 until 2015
� Increase the flowrate
� Improvement of the Energy Efficiency
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Location
Canary Islands, SpainLas Americas SWRO plant
30.000 m3/d
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Evolution of the Energy Efficiency in Las Americas SWRO plant
1998 Production: 10.000 m3/d(2 racks x 5.000 with Francis turbine. One stage of RO)
2000 Extension 1 - Production: 20.000 m3/d(4 racks x 5.000 with Francis turbine. One stage of RO)
2004 Extension 2 - Production: 30.000 m3/d(4 racks x 7.500 with pelton turbine. 2 stages of RO)
2015 Increase the Energy efficiency with new energy recovery devices system - 30.000 m3/d
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2015 -Revampingof the plant
The main modifications has been:
� Motors with more electrical efficiency
� Installation of frequency converters in the booster pumps
� Design and installation of a new energy recovery system based in ERI technology
TargetReduction of Energy Consumption: > 0,35 Kwh/m3
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From PELTON turbine
To ERI system
High pressure side
Low pressure side
Evolution of the Energy Efficiency device in Las Americas SWRO
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RO Building –Before: with Pelton turbines
1st Stage RO racks
High pressure pumps with pelton turbines
2nd Stage RO racks
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RO Building –After : with ERI
1st Stage RO racks
New area:� ERI devices,� Booster pumps� HPPs� instrumentation� regulating valves� modified piping
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Evolution of the Energy Efficiency device in Las Americas SWRO
From PELTON turbine To ERI system
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Operating Modes in the installation
One stage or Two stages
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2 operating modes
The plant can be operated with 2 modes:
� Working with one stage� Working with two stages
A B C
One Stage Close Open Close
Two Stages Open Close Open
Operating ModeValves
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Why is important a good regulating system?
� Potential problems
� How to avoid this potential problems
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Potential problems
If the regulation of the process is not correct, some problems could appear:
� Cavitation in the ERI booster pump. When the plant starts it has to be assured that there are not air in the circuit.
� Water Hammer problems in membranes. It´s important to regulate the start of the high pressure pump to avoid this important problem which could damage the membranes.
� Sudden stop of the ERI pump. The regulation system must be capable of stop the high pressure pump and all the process to avoid important problems in membranes.
� High flowrate of brine. The regulation of the system must allow stop the process when the brine flowrate is high to avoid problems in the ERI devices.
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Potential problems
If the regulation of the process is not correct, some problems could appear:
� Cavitation in the ERI devices. It´s necessary a pressure transmitter in the low pressure side of the ERI pipe to control that the pressure is not lower than minimum to avoid this problem
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How to avoid this Potential problems?
During the design of the plant special attention must be focus in the following issues:
� Instrumentation� Flow transmitters� Pressure transmitters
� Regulating valves
� Control loops
� Correct sequence of the control loops� Start-up of the process� Shut-down of the process.
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Basis of the regulation
� Alarms and Control System
� Control Loops
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Alarms and Control System
The control system includes alarms which warn about wrong operation:
� Low flowrate in the lowpressure inlet of the ERI
� Low flow rate in the impulsionof the ERI booster pump
� High leakage of ERIs
� High conversion of the system
High pressure side
Low pressure side
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Alarms and Control System
The control system includes alarms which warn about wrong operation:
� Low conversion of the system
� Problems with the protectionof motors and bearings of thepumps
High pressure side
Low pressure side
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Regulation – Control Loops (1/2)
3 types of control loops:
FIT
Pipe B
Flow Indicator Transmiter
Pipe A
Regulating valve
Set Point
Set Point
Pipe A
PIT
Pipe B
Regulating valve
Pressure Indicator Transmiter
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Regulation – Control Loops (2/2)
3 types of control loops:
Set PointFIT
Pipe B
Flow Indicator Transmiter
Pipe A
Pump with frequency converter
F/I
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Regulation of the RO –Mode 1
Reverse Osmosis system working
with One stage
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Before Star-up –Mode1
Operate manual valves:
� Close valves A and C
� Open valve B
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Schematic P&ID – Mode 1
1st STAGEPermeate
2nd STAGE
High Pressure
pump
Brine
Booster pump
Booster pump
Reject
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Step 1 – Pressurization of the circuit (Mode 1)
1st STAGEPermeate
2nd STAGE
High Pressure
pump
Brine
Booster pump
Booster pump
Reject
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Step 2 – Control Loop 1(Mode 1)
1st STAGEPermeate
2nd STAGE
High Pressure
pump
Brine
Booster pump
Booster pump
Reject
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1st STAGEPermeate
2nd STAGE
High Pressure
pump
Brine
Booster pump
Booster pump
Reject
Step 3 – Control Loop 2(Mode1)
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Step 4 –Control Loop 3(Mode 1)
1st STAGEPermeate
2nd STAGE
High Pressure
pump
Brine
Booster pump
Booster pump
Reject
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Important remarks
• Keep minimum pressure in the inlet of the pumps
• Adjust the opening percentage of the regulating valves
• Keep the minimum pressure in the ERI system. Due to the headlosses
• Keep minimum pressure in the ERI Booster outlet. To avoidoperation problems.
• Define perfectly the star-up ramp of the HPP. The increase ofpressure in the inlet of the membranes has to be progressive to avoid damages
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Regulation of the RO –Mode 2
Reverse Osmosis system working
with Two stages
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Before Star-up –Mode2
Operate manual valves:
� Close B
� Open valves A and C
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Schematic P&ID – Mode 2
1st STAGEPermeate
2nd STAGE
High Pressure
pump
Brine
Booster pump
Booster pump
Reject
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1st STAGEPermeate
2nd STAGE
High Pressure
pump
Brine
Booster pump
Booster pump
Reject
Step 1 – Pressurization of the circuit (Mode 2)
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1st STAGEPermeate
2nd STAGE
High Pressure
pump
Brine
Booster pump
Booster pump
Reject
Step 2 – Control Loop 1 (Mode 2)
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1st STAGEPermeate
2nd STAGE
High Pressure
pump
Brine
Booster pump
Booster pump
Reject
Step 3 – Control Loop 2 (Mode 2)
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1st STAGEPermeate
2nd STAGE
High Pressure
pump
Brine
Booster pump
Booster pump
Reject
Step 4 – Control Loop 3 (Mode 2)
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Permeate
2nd STAGE
High Pressure
pump
Brine
Booster pump
Booster pump
Reject
Step 5 – Control Loop 4 (Mode 2)
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1st STAGEPermeate
2nd STAGE
High Pressure
pump
Brine
Booster pump
Booster pump
Reject
Step 6 – Control of PITs
Control of the Differential Pressure
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Permeate
2nd STAGE
High Pressure
pump
Brine
Booster pump
Booster pump
Reject
Step 7 – Control Loop 5 (Mode 2)
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CONCLUSIONS
Regulation of double stage SWRO plant after improving the energy consumption using ERI technology.
Case study: Las Americas SWRO plant, Canary Islands
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CONCLUSIONS
� The improvement of the Energy Efficiency is not only a questionof changing electro-mechanical equipment (Energy recoverydevices, HPPs and booster pumps). Each plant must be studiedspecifically, and a dedicated regulation system is fundamentalin order to avoid problems during the life of the facility.
� Depending on the design of the RO and the operation modes ofthe plant, specific control loops must be implemented.Instrumentation, control valves and frequency converters arenecessary to design these control loops.
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CONCLUSIONS
� It´s important the design of the regulation during the normaloperation, but also the sequence of the control loops in othersituations as:
� Start-up of the RO� Shut-down of the RO� Flushing of the RO
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CONCLUSIONS
� Since September 2015 , LasAméricas SWRO plant is inoperation with the design andthe regulation system showed inthis presentation.
� The reduction of the energyconsumption is better thantarget. Depending the operationmode, it varies between 0,4and 0,5 Kwh/m 3
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ACKNOWLEGMENTS
Javier Iturriaga (Erection & Commisioning)Gerardo Cremer (Engineering)Javier Cuasante (Drawings)Manuel Fernandez (Execution)
The plant was built, erected an commissioned in 2015 by thefollowing team of SUEZ Degremont Spain :
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CaribDA 2016 Conference & Exposition“Developing and Affording New Water Sources”
31st May – 3rd June 2016 in Trinidad
Regulation of double stage SWRO plant after improving the energy consumption using ERI technology. Case study: Las
Americas SWRO plant, Canary Islands
Julen Cabero, PhDSUEZ Treatment Solutions, SAU