Presentation on theme: "MODULE MEMBRANE MEMBRANE TECHNOLOGY. INTRODUCTION  Fig 1. Schematic drawing single module design: feed module retentate permeate Permeate : the fraction."— Presentation transcript:
MODULE MEMBRANE MEMBRANE TECHNOLOGY
INTRODUCTION  Fig 1. Schematic drawing single module design: feed module retentate permeate Permeate : the fraction of the feed passedRetentate: the fraction of the feed retained
INTRODUCTION  A number of module design are possible and all are based on two types of membrane configuration: [a] Flat[b] Tubular - Plate and frame - Spiral wound - Tubular - Capillary - Hollow fiber The difference between the latter type as is shown in Table 1. ConfigurationDiameter (mm) Tubular Capillary Hollow fiber – 10.0 < 0.5
INTRODUCTION  The membrane surface area per volume is only a function of the dimensions of the tube. Tube radius (mm)Surface area per volume (m2/m3) The choice of module configuration, is based on :  Economic consideration  Others :Ease of cleaning, maintenance, and operation Compactness of the systems Scale The possibility of membrane replacement
PLATE-AND-FRAME MODULE  Permeate Membrane Spacer Retentate Membrane Permeate Feed Fig 2. Schematic drawing of a plate-and-frame module. Sets of two membranes are placed in a sandwich-like fashion with their feed sides facing each other. In each feed and permeate compartment thus obtained a suitable spacer is placed. The number of sets needed for a given membrane area furnished with sealing rings and two end plates then builds up to a plate-and-frame stack.
PLATE-AND-FRAME MODULE  Membrane Spacer Feed Permeate Retentate Fig 3. Schematic flow path in plate-and-frame module. Spacer material is used to improve mass transfer and to reduce concentration polarization.
SPIRAL-WOUND MODULE This module in fact a plate-and-frame systems wrapped around a central collection pipe. The packing density of this module ( m2/m3) Membrane and permeate-side spacer material are then glued along three edges to build a membrane envelope. The feed-side spacer separating the top layer of the two flat to build a membrane envelope. The feed flows axial through the cylindrical module parallel along the central pipe whereas the permeate flows radially towards the central pipe Fig 4. Schematic flow path of a spiral-wound module.
TUBULAR MODULES In contrast to capillaries and hollow fibers, tubular membranes are not self- supporting. Such membranes are placing inside a porous stainless steel, ceramic or plastic tube with the diameter of tube being, in general, more than 10 mm. The number of tubes put together in the module may vary. Fig 5. Schematic drawing of tubular module. The feed solution always flows through the centre of the tubes, while the permeate flows through the porous supporting tube into the module housing.
CAPILLARY MODULES  The capillary module consist of a large number of capillaries assembled together in a module. The free ends of the fibers are potted with agents such as epoxy resin, polyurethanes, or silicone rubber. Two types of module arrangement can be distinguish : INSIDE-OUT The feed solution passes through the bore of the capillary (lumen) whereas the permeate is collected on the outside of the capillaries OUTSIDE-IN The feed solution enters the module on the shell side of the capillarioes (external) and the permeate passes into the fiber bore
CAPILLARY MODULES  Feed Permeate Retentate Feed Permeate Retentate The choice between the two concepts is mainly based on the application where parameters such as pressure, pressure drop, type of membrane available, etc are important. A packing density of about 600 – 1200 m2/m3 is obtained with modules containing capillaries. Fig 6. Schematic drawing of capillary module (a) inside-out, (b) outside-in (a)(b)
HOLLOW FIBERS MODULES  The difference between the capillary module and the hollow fiber module is simply a matter of dimensions since the module concepts are the same. In this concept the fiber modules are arranged in a loop and are potted on one side, the permeate side. The hollow fiber module is the configuration with the highest packing density m2/m3 The feed stream is relatively clean Seawater desalination, but very effective pretreatment is required Fig 7. Schematic drawing of hollow fiber module
HOLLOW FIBERS MODULES  HOLLOW FIBER Outside -in Inside- out Gas separation Pervaporation To avoid high pressure losses inside the fiber and to attain high membrane area To avoid increase in permeate pressure within the fibers Fig 8. membrane for separation gas
HOLLOW FIBERS MODULES 
COMPARISON OF MODULE CONFIGURATIONS TubularPlate-and- frame Spiral-woundCapillaryHollow fiber Packing densityLowVery high InvestmentHighLow Fouling tendency LowVery high CleaningGoodPoor Membrane replacement Yes/noYesNo
SYSTEMS DESIGN – CROSS FLOW FILTRATION  To reduce concentration polarization and fouling as far as possible, the membrane process is generally operated in a cross flow mode. Various cross-flow operations can be distinguished : Feed Permeate Retentate Permeate Feed Permeate Retentate Feed Permeate Feed Permeate Feed Permeate Feed Permeate (a) (b) (c) (d) Co-current Counter-current Cross-flow Perfect mixing
SYSTEMS DESIGN – CROSS FLOW FILTRATION  Co current flow Cross flowCounter current flow Perfect mixing flow The worst The best Two basic methods can be used in a single stage or a multi stage, are: Feed pump (a) Single pass system Feed pump Recirculation pump (b) Recirculation system
SYSTEMS DESIGN – HYBRID DEAD-END/CROSS FLOW SYSTEM  Dead-end system Cross flow system The high recovery, the feed is completely passing the membrane. A tremendous flux decline is obtained. The recovery is much lower. Better fouling control. The hybrid dead-end/cross flow process may combine the advantages of both processes and this concept is very beneficial in microfiltration and ultrafiltration where back-flushing is possible and essential. Permeate Feed AB
SYSTEMS DESIGN – CASCADE Often the single-stage design does not results in the desired product quality and for this reason the retentate or permeate must be treated in a second stage. A combination of stages is called a CASCADE Permeate Feed Retentate Two-stage membrane process (a) Permeate Feed Retentate
SYSTEMS DESIGN – CASCADE Permeate FeedRetentate (b) Three-stage membrane process Permeate Feed Retentate
EXAMPLES of SYSTEMS DESIGN : ULTRAPURE WATER  UV Well water tap Activated carbon RO Drain Mixed-bed Ion exchange Microfiltratin ultrafiltration Permeate Storage In the ultrapure water production system, ions, bacteria, organics, and other colloidal impurities have to be removed. A single membrane process does not give a high quality product and a combination of separation processes (hybrid processing) is necessary. Fig 9. flow diagram for an ultrapure water production system
Pretreatment is also necessary and depends on the quality of the source water. EXAMPLES of SYSTEMS DESIGN : ULTRAPURE WATER  Specifications for ultrapure water Electrical resistance (MΩ.cm)>18 Number of particles (/ml)< 10 Bacteria count (/ml)< 0,01 TOC (ppb)< 20
EXAMPLES of SYSTEMS DESIGN : DESALINATION OF SEAWATER  High-performance RO membranes exhibit a salt rejection > 99%. To improve the quality further, a two-stage (or multi-stage) system is often used. Feed (seawater) Pretreatment RO systems PURE WATER
EXAMPLES of SYSTEMS DESIGN : DESALINATION OF SEAWATER 
EXAMPLES of SYSTEMS DESIGN : OTHERS
ECONOMICS Whether or not a membrane process or another separation process is used for a given separation is based entirely on economic considerations. In fact, the costs have to be calculated for every specific separation problem and for this reason the economics will only be considered very general. Installation cost The capital costThe operating cost Membrane modules Cost of piping, pumps, electronics, vessel Pretreatment and post-treatment Power requirement Membrane replacement Labour and maintenance
PROCESS PARAMETER  feed module retentate permeate c f q f c r q r c p q p Membrane performance characterized by Retention Permeation Schematic drawing of a membrane system : Where: c f : feed concentrationqf : feed flow rate cr : retentate concentrationqr : retentae flow rate cp : permeate concentrationqp : permeate flow rate
Recovery PROCESS PARAMETER  Is define as the fraction of the feed flow which pass through membrane. The recovery ranges from 0 to 1 and is a parameter of economic importance. Commercial membrane process are often designed with a recovery value as high as possible. Increasing recovery, the performance declines because the concentration of the less permeable component increases. In laboratory set up, the recovery usually approaches zero, which implies maximum separation performance.
Volume Reduction In batch operation, the volume reduction is defined : Retention Which is solute is retained by the membrane PROCESS PARAMETER