SOLTEQ®
EQUIPMENT FOR ENGINEERING EDUCATION
EXPERIMENTAL MANUAL
MEMBRANE TEST UNIT MODEL: TR 14
SOLUTION ENGINEERING SDN. BHD. NO.3, JALAN TPK 2/4, TAMAN PERINDUSTRIAN KINRARA, 47100 PUCHONG, SELANGOR DARUL EHSAN, MALAYSIA. TEL: 603-80758000 FAX: 603-80755784 E-MAIL:
[email protected] WEBSITE: www.solution.com.my 054-0310-TR
SOLTEQ® MEMBRANE TEST UNIT (Model: TR 14)_______________________________________________
Table of Contents List of Figures………………………………………………………………………………………… . i 1.0 INTRODUCTION…………………………………………………………………………………1 2.0 DESCRIPTION AND ASSEMBLY 2.1 Membrane and membrane housing……………………………………………………… 5 2.2 Pumps……………………………………………………………………………………… . 5 2.3 Tanks and Cooling/Heating System………………………………………………………6 2.4 Water Flow Meter………………………………………………………………………… .. 6 3.0 SUMMARY OF THEORY……………………………………………………………………… 7 4.0 OPERATING PROCEDURES 4.1 General Start-Up Procedures...………………………………………………………….11 4.2 General Shut-Down Procedures………………………………………..…………..……11 5.0 EXPERIMENT PROCEDURES 5.1 Membrane Characteristic Study ...……………………………………………………….12 6.0 SAFETY PRECAUTIONS AND MAINTENANCE…………………………..….………….....13 6.1 Safety Precautions………………………………………………………………………….13 6.2 Maintenance…………………………………………………………………………………13 7.0 REFERENCES……………………………………………………………………………………14 APPENDICES
SOLTEQ® MEMBRANE TEST UNIT (Model: TR 14)_______________________________________________
List of Figures Page Figure 1
Process Schematic Diagram
2
Figure 2
A classification of major types of membrane processes
3
Figure 3
A typical crossflow operation includes recirculation loop
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Figure 4
Tubular (multichannel) type of microfilter
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Figure 5
Concentration polarization at a membrane surface. C w is the solute concentration at the membrane surface and C b is the bulk-solute concentration
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Figure 6
Typical dependence of membrane flux.
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SOLTEQ® MEMBRANE TEST UNIT (Model: TR 14)________________________________________________
1.0
INTRODUCTION
New chemical separation techniques such as membrane separations are becoming increasingly popular as it provides effective separation without the use of heating energy as in distillation processes. Heat sensitive materials can be separated or concentrated by virtue of their molecular weights. The Membrane Test Unit (Model: TR 14) is specially designed to allow students and researchers to carry out the membrane processes that are widely used in biotechnology and process industries — the Reverse Osmosis (RO), Nanofiltration (NF), and Ultrafiltration (UF). The process diagram is illustrated in Figure 1. Ultrafiltration and microfiltration membranes are usually specified in terms of their "molecular weight cut-off" (MWCO), whereas the nanofiltration and reverse osmosis membranes are specified in terms of their “percentage rejection of salts”. Polymeric membranes are widely used and supplied in the form of modules that give membrane areas in the range of 1 - 20 m2. The membranes that are supplied with the model TR 14 unit is classified as tubular type (Figure 2), which is widely used and have turbulent flow conditions. The system is in a cross flow configuration where the feed solution is pumped parallel to the membrane at a velocity in the range of 1 - 8 ms-1 with a pressure difference of 0.1 - 0.5 MPa across the membrane. Liquid permeates through the membrane and feed emerges in a more concentrated form on exit from module.
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SOLTEQ® MEMBRANE TEST UNIT (Model: TR 14)________________________________________________
Figure 1: Process Schematic Diagram
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SOLTEQ® MEMBRANE TEST UNIT (Model: TR 14)________________________________________________
Figure 2: A classification of major types of membrane processes
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SOLTEQ® MEMBRANE TEST UNIT (Model: TR 14)________________________________________________
The advantages of cross-flow membrane separations are a) Higher overall liquid removal rate is achieved by preventing solid buildup on membrane surface. b) The concentrate (retentate) remains in a mobile form suitable for further processing. c) The solute content of the concentrate may be varied over a wide range. d) It may be possible to fractionate solutes of different sizes.
CLEANING SOLUTION RETUM
CIRCULATION SOLUTION TANK
FEED
FEED TANK
TI
RECIRCULATION PUMP
SUSPENSION RECIRCULATION
PI
PI
FI BANK OF CROSSFLOW FILTERS
FILTRATE
FI PI TI
FLOW INDICATOR PRESSURE INDICATOR TEMPERATURE INDICATOR
DRAIN/BLEED CONCENTRATED SUSPENSION
VALVE
Figure 3: A typical crossflow operation includes recirculation loop
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SOLTEQ® MEMBRANE TEST UNIT (Model: TR 14)________________________________________________
2.0
DESCRIPTION AND ASSEMBLY 2.1
Membrane and Membrane Housing
The P.C.I Single-tube Tester is designed for the economical, quick, initial evaluation of membrane types and processes for separation and concentration at laboratory scale prior to more detailed test work. It may be fitted with samples of any of PCI’s wide range of tubular reverse osmosis, nanofiltration and ultrafiltration membranes. Simply constructed in 316 stainless steel, the module has termination points allowing easy connection by flexible or welded couplings to existing equipment. The open channel, highly turbulent flow design allows a wide variety of process fluid to be concentrated. It also allows simple clean-in-place techniques to be entirely effective. The TR 14 unit is supplied with membrane: i)
Membrane 1: AFC 99 (Polyamide Film)
ii)
Membrane 2: AFC40 (Polyamide Film)
iii)
Membrane 3: CA 202 (Cellulose acetate)
iv)
Membrane 4: FP 100 (PVDF)
The FP 100 PVDF membrane is rated with apparent retention character of 100000 MWCO and CA 202 is 2000 MWCO. In addition, the AFC40 has 60% CaCl 2 rejection and the AFC99 is rated with 99% NaCl rejection.
2.2
Pump
2.2.1
CAT Triple Plunger Pump - Model 241
The CAT Triple Plunger pump is used to pump the liquid from the feed tank into the membrane module. Specifications: Maximum flow rate : Working pressure range : Max. fluid temperature : Max. speed : Max. horsepower :
13 liter/min. 7-85 bar 71 °C 1725 RPM 3.0 HP
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SOLTEQ® MEMBRANE TEST UNIT (Model: TR 14)________________________________________________
A CPC 7002 Pressure regulator is also installed to regulate the operating pressure of the feed system. Specifications: Pressure regulated : 7-70 bar Allowable flowrates : 3.8 - 38 liter/min. 2.3
Tanks and Cooling/Heating System
The TR 14 unit is supplied with a feed tank and a product tank, both having maximum capacity of 15 liters. The feed and product tanks are made of stainless steel for corrosion and chemical resistance. The retentate line is equipped with a unit of thermostat as heat exchanger.
2.4
Water Flow Meter
The TR 14 unit is supplied with a Hedland turbine flow meter.
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SOLTEQ® MEMBRANE TEST UNIT (Model: TR 14)________________________________________________
3.0
SUMMARY OF THEORY
Membrane separation technology has evolved from a small-scale laboratory technique to a largescale industrial process during the past 30 years. A classification of major types of membrane processes is given in Figure 4. Numerous theoretical models for ultrafiltration, nanofiltration, and reverse osmosis have been proposed along with the identification of new factors controlling flux or mass transfer through membranes. The basic operating patterns are best outlined in terms of the hydrodynamic resistance resulting from the buildup of deposited materials on the membrane surface.
Figure 4: Tubular (multichannel) type of microfilter
The flux, J will be given by: J=
1 dV Am dt
=
∆Ρ ∆Ρ = v[Rm + (αVCb / Am )] v ( R m + Rc )
(1)
For most biological materials, α is a variable depending on the applied pressure and time (the compressible deposit), so that the expression requires a numerical solution. A useful method for the effects of cross-flow removal of depositing materials is to write:
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SOLTEQ® MEMBRANE TEST UNIT (Model: TR 14)________________________________________________
J=
∆Ρ v (Rm + Rd − Rr )
(2)
Removal of solute by cross-flow is sometimes assumed constant, and equal to the convective particle transport at steady state (J ss C b ), which can be obtained experimentally or from an appropriate model. In many situations however, steady state of filtration is seldom achieved. In such cases, it is possible to describe the time dependence of filtration by introducing an efficiency factor β, representing the fraction of filtered material remaining deposit rather than being swept along by the bulk flow. This gives: Rc =
βαVCb Am
, Where 0 < β < 1
(3)
Although deposition also occurs during ultrafiltration, an equally important factor controlling flux is concentration polarization. (Figure 5)
Figure 5. Concentration polarization at a membrane surface. C w is the solute concentration at the membrane surface and C b , is the bulk-solute concentration.
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SOLTEQ® MEMBRANE TEST UNIT (Model: TR 14)________________________________________________
Typical operating patterns of ultrafiltration are shown in Figure 6c.
Figure 6. Typical dependence of membrane flux. (a) Applied pressure difference, (b) Solute concentration, (c) Cross-flow velocity
Solution containing macromolecular gel-forming solute will form a gel on the surface of the membrane. The gel formation will contribute to formation of dynamic membranes. The mechanism is as follows: Due to convective flux through the membrane a concentration of the solution at the surface C w increases and eventually reaches a gel formation concentration C g (Figure 6b). The flux, J through the membrane depends on a concentration according to the relationship: J = k .In
Cw Cb
(4)
Combining Equations (1) and (4),
In
Cw ∆P = Cb v(R m + R p )k
(5)
As long as concentration C w is less than C g , C w will increase with pressure, but the moment C w equals C g , an increase in ∆Ρ brings about an increase of the layer resistance R p , and the flux will no longer vary with pressure (Figure 7a). Assuming no fouling effect, the membrane resistance R m can be calculated from the flux equation below: J=
∆Ρ v.Rm
(6)
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SOLTEQ® MEMBRANE TEST UNIT (Model: TR 14)________________________________________________
The slope obtained from the plot of flux, J versus ∆Ρ is equal to
1 v.R m
The retention of any solute can be expressed by the rejection coefficient, R. R =
1n(C f / C0 )
(7)
1n (V0 / V f )
Where, C f is final macrosolute concentration in the retentate C 0 is initial macrosolute concentration V0 is initial volume V f is final retentate volume This expression assumes complete mixing of retentate seldom accomplished due to concentration polarization. The apparent rejection coefficient depends on factors affecting polarization including UF rate and mixing. For material entirely rejected, the rejection coefficient is 1 (100% rejection); for freely permeable material it is zero. Rejection is a function of molecular size and shape. Nominal cut-off levels, defined with model solute, are convenient indicators. Fractional rejection by membranes with low MW cut-off spans a narrower range of molecular size than by more open membranes. For maximum retention of a solute, select a membrane with nominal cut-off well below the MW of the species. Many biological macromolecules tend to aggregate so that effective size 3may be much larger that the “native” molecule, causing increased rejection. Degree of hydration, counter ions and steric effects can cause molecules with similar molecular weights to exhibit very different retention behavior.
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SOLTEQ® MEMBRANE TEST UNIT (Model: TR 14)________________________________________________
4.0
OPERATING PROCEDURES 4.1
General Start-Up Procedures 1. Ensure all valves are initially closed. 2. Prepare a sodium chloride solution by adding 100 gram of sodium chloride into 20 liter of water. 3. Fill up the feed tank with the salt solution prepared in step 2. The feed shall always be maintained at room temperature. 4. Turn on the power for the control panel. Check that all sensors and indicators are functioning properly. 5. Switch on thermostat and make sure the thermo oil level is above the coil inside thermostat. Check that thermostat connections are properly fitted. Note: Adjust the temperature at the thermostat to maintain feed temperature. 6. The unit is now ready for experiments.
4.2
General Shut-Down Procedures 1. Switch off the plunger pump (P2). 2. Close valve V2. 3. Drain all liquid in the feed tank and product tank by opening valves V3 and V4. 4. Flush all the piping with clean water. Close V3 and V4, fill the clean water to feed tank until 90% full. 5. Run the system with the clean water until the feed tank is nearly empty (this is for cleaning purpose).
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SOLTEQ® MEMBRANE TEST UNIT (Model: TR 14)________________________________________________
5.0
EXPERIMENT PROCEDURES 5.1
Membrane Characteristic Study Objective: In this experiment, students will perform a characteristic study on 4 different types of membranes. This experiment requires approximately 100 gram of sodium chloride. Procedures: 1. Perform the general start-up procedures as described in Section 4.1. 2. Start the experiment for Membrane 1. Open valves V2, V5, V7, V11 and V15. 3.
To set the maximum working pressure at 20 bars, switch on the plunger pump (P1) and slowly close valve V5. Observe pressure value at pressure gauge and adjust the pressure regulator to 20 bars. Note: Use a proper wrench to turn the adjusting screw at the pressure regulator (PR1) by turning clockwise to increase pressure and counterclockwise to reduce pressure. Warning: Do not operate pump in dry condition. Make sure V2 is opened.
4.
Open valve V5. Then, set membrane maximum inlet pressure to 18 bars for Membrane 1 by adjusting the retentate control valve (V15).
5.
Allow the system to run for 5 minutes. Start collecting sample from permeate sampling port and weigh the sample using digital weighing balance. Record the weight of permeates every 1 minute for 10 minutes. Note: To collect sample, open valve V19 and simultaneously close valve V11.
6.
Repeat the step 1 to 5 for Membrane 2, 3 and 4. Open and close the respective sets of valves and adjust the membrane maximum inlet pressure for every membrane. Retentate Membrane Open Valves Sampling Membrane control maximum inlet (Step 2) Valves valve pressure (bar) V2, V5, V7, Open V19 and 1 V15 18 V11 and V15. close V11 V2, V5, V8, Open V20 and 2 V16 12 V12 and V16. close V12 V2, V5, V9, Open V21 and 3 V17 10 V13 and V17. close V13 V2, V5, V10, Open V22 and 4 V18 8.5 V14 and V18. close V14
7.
Plot the graph of permeate weight versus time. 12
SOLTEQ® MEMBRANE TEST UNIT (Model: TR 14)________________________________________________
6.0
SAFETY PRECAUTION AND MAINTENANCE 6.1
Safety Precautions 1. Never operate the pump when there is no liquid in the pipeline. It will cause serious damage to the pump. 2. High voltages exist and are accessible in the control panel. Return the unit to your supplier for any servicing. 3. The system should not be subjected to shock, sudden impact, vibration, additional load, or permanent external action of aggressive vapors. 4. Never splash water to the control panel. This will cause body injury and damage to the equipment. 5. Never use your bare hand to test the AC Power Supply. It may cause hazardous injury. 6. Leaking couplings or fittings should be carefully retightened. Replace any gaskets or seals if necessary.
6.2
Maintenance 1. Always check and rectify any leak. 2. After each experiment, drain off any liquids from the feed tank and product tank. Make sure that the feed tank, product tank and piping are cleaned properly by flushing the system with water until no traces of chemical are detected. 3. Dispose all liquids immediately after each experiment. Do not leave any solution or waste in the tanks over a long period of time. 4. Wipe off any spillage from the unit immediately. 5. Check the lubricant oil level in the pump motor. Refill if the level is reduced below the red spot
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SOLTEQ® MEMBRANE TEST UNIT (Model: TR 14)________________________________________________
7.0
REFERENCES
Warren L. McCabe, Julian C. Smith, Peter Harriott, “Unit Operations of Chemical Engineering”, 5th Edition, McGraw Hill, 1993 Christi J. Geankoplis, “Transport Processes and Unit Operations”, 3rd Edition, Prentice Hall International Edition, 1995 Perry, R.H., Green, D.W. and Maloney, J.O., “Perry’s Chemical Engineering Handbook”, 6th Edition, McGraw Hill, 1984
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SOLTEQ® MEMBRANE TEST UNIT (Model: TR 14)________________________________________________
APPENDICES
SOLTEQ® MEMBRANE TEST UNIT (Model: TR 14)________________________________________________
APPENDIX A SAMPLE TABLE FOR EXPERIMENT
Time (min) 1 2 3 4 5 6 7 8 9 10
Weight of Permeates (g) Membrane 1
Membrane 2
Membrane 3
Membrane 4
SOLTEQ® MEMBRANE TEST UNIT (Model: TR 14)________________________________________________
APPENDIX B SAMPLE EXPERIMENTAL RESULT Weight of Permeates (g) Time (min) 1 2 3 4 5 6 7 8 9 10
Membrane 1
Membrane 2
Membrane 3
Membrane 4
13.58
36.22
26.43
70.37
39.32
100.33
48.12
142.36
63.82
192.31
89.02
235.42
117.62
280.17
155.49
328.53
229.29
376.81
259.69
425.51
83.9 149.3 207.4 268.3 329.9 391.5 459.1 514.1 575.4 638.5
214.5 398.9 560.7 728.6 894.5 1058.9 1237.3 1381.8 1542.3 1704.1
SOLTEQ® MEMBRANE TEST UNIT (Model: TR 14)________________________________________________
APPENDIX C
