MEMBRANE TECHNOLOGY MODULE MEMBRANE

INTRODUCTION [1] feed module retentate permeate In order to apply membranes on a technical scale, large membrane areas are normally required. The smallest unit into which the membrane area is packed is called a module. The module is the central part of a membrane installation. The simplest design is one in which single module is used. feed module retentate permeate Fig 1. Schematic drawing single module design: Permeate : the fraction of the feed passed Retentate: the fraction of the feed retained

INTRODUCTION [2] 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. Configuration Diameter (mm) Tubular Capillary Hollow fiber 10.0 0.5 – 10.0 < 0.5

Surface area per volume (m2/m3) INTRODUCTION [3] 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) 5 0.5 0.05 360 3600 36000 The choice of module configuration, is based on : [1] Economic consideration [2] Others : Ease of cleaning, maintenance, and operation Compactness of the systems Scale The possibility of membrane replacement

PLATE-AND-FRAME MODULE [1] Permeate Membrane Spacer Retentate 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 [2] Fig 3. Schematic flow path in plate-and-frame module. Membrane Spacer Feed Permeate Retentate Spacer material is used to improve mass transfer and to reduce concentration polarization.

Fig 4. Schematic flow path of SPIRAL-WOUND MODULE This module in fact a plate-and-frame systems wrapped around a central collection pipe. The packing density of this module (300-1000 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 [1] INSIDE-OUT OUTSIDE-IN 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 [2] 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. Feed Permeate Retentate Feed Permeate Retentate (a) (b) Fig 6. Schematic drawing of capillary module (a) inside-out, (b) outside-in

HOLLOW FIBERS MODULES [1] 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 30.000 m2/m3 WHEN is used ? The feed stream is relatively clean Fig 7. Schematic drawing of hollow fiber module Seawater desalination, but very effective pretreatment is required

HOLLOW FIBERS MODULES [2] 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 HOLLOW FIBERS MODULES [2] Fig 8. membrane for separation gas

HOLLOW FIBERS MODULES [3]

COMPARISON OF MODULE CONFIGURATIONS Tubular Plate-and-frame Spiral-wound Capillary Hollow fiber Packing density Low Very high Investment High Fouling tendency Cleaning Good Poor Membrane replacement Yes/no Yes No

SYSTEMS DESIGN – CROSS FLOW FILTRATION [1] 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 (a) (b) (c) (d) Co-current Counter-current Cross-flow Perfect mixing

SYSTEMS DESIGN – CROSS FLOW FILTRATION [2] Co current flow Cross flow Counter 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 Recirculation pump (b) Recirculation system

SYSTEMS DESIGN – HYBRID DEAD-END/CROSS FLOW SYSTEM [1] Permeate Feed A B Dead-end system The high recovery, the feed is completely passing the membrane. A tremendous flux decline is obtained. Cross flow system 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.

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 (a) Permeate Feed Retentate Two-stage membrane process

SYSTEMS DESIGN – CASCADE Permeate Feed Retentate Permeate Feed Retentate (b) Three-stage membrane process

EXAMPLES of SYSTEMS DESIGN : ULTRAPURE WATER [1] 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. UV Well water tap Activated carbon RO Drain Mixed-bed Ion exchange Microfiltratin ultrafiltration Permeate Storage Fig 9. flow diagram for an ultrapure water production system

EXAMPLES of SYSTEMS DESIGN : ULTRAPURE WATER [2] Pretreatment is also necessary and depends on the quality of the source 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 [1] Feed (seawater) Pretreatment RO systems High-performance RO membranes exhibit a salt rejection > 99%. To improve the quality further, a two-stage (or multi-stage) system is often used. PURE WATER

EXAMPLES of SYSTEMS DESIGN : DESALINATION OF SEAWATER [2]

EXAMPLES of SYSTEMS DESIGN : OTHERS

ECONOMICS Installation cost The capital cost The operating cost 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 cost The operating cost Membrane modules Cost of piping, pumps, electronics, vessel Pretreatment and post-treatment Power requirement Membrane replacement Labour and maintenance

Membrane performance characterized by PROCESS PARAMETER [1] Retention Membrane performance characterized by Permeation Schematic drawing of a membrane system : feed module retentate permeate cf qf cr qr cp qp Where: cf : feed concentration qf : feed flow rate cr : retentate concentration qr : retentae flow rate cp : permeate concentration qp : permeate flow rate

PROCESS PARAMETER [1] Recovery 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.

PROCESS PARAMETER [2] Volume Reduction In batch operation, the volume reduction is defined : Retention Which is solute is retained by the membrane

TERIMA KASIH