Hollow Fibre Membrane Module (1)

Hollow Fibre Membrane Module

By, • Shweta Singh-1402011 • Pranali Trivedi-1402012 • Gaurav Nikam-1402022 • Disha Ravipati-1402025 • Harmit Pandya-1402028 • Amish Chovatiya1402030

What is a membrane? • Membrane filters or “membranes” are microporous plastic films with specific pore size ratings. Also known as screen, sieve or microporous filters, membranes retain particles or microorganisms larger than their pore size primarily by surface capture.[1]

Membrane Module • The practical equipment where the actual membrane based separation occurs is known as membrane modules. • In order to apply membranes on a technical scale, large membrane areas are required.[2]

Why is it required? • Industrial membrane plants often require hundreds to thousands of square metres of membrane to perform the separation required on a useful scale. • From an overall cost standpoint, not only is the cost of membranes per unit area important, but also the cost of the containment vessel into which they are mounted. • Basically the problem is how one can pack the most area of membranes into the least volume, to minimise the cost of the containment vessel

Classification • Based on structure: Mainly two types of membrane configuration are there 1. Flat 2. Tubular

Plate-and-frame and spiral wound involve flat membrane. Tubular and hollow fibre are based on tubular membrane configuration.[2]

• Based on functioning: 1. Self-contained type. The most common module type for UF and RO membranes is the self-contained (or housed) membrane module where feed water is pumped through the housing. All feed, concentrate, and filtrate piping connections are integral to the module.[4]   2. Open immersion type. The open immersion type modules are placed into the feed water tank with the membrane exposed. [4]

HFM Introduction • Hollow fibre membranes (HFMs) are a class of artificial membranes containing a semipermeable barrier in the form of a hollow fibre. • Each filament is very narrow in diameter and very flexible. •  Dimensions: 50-μm internal diameter and 100- to 200-μm outer diameter.

Phase Inversion

Fibre Formation • All man made fiber spinning process are based on three general steps. These steps are: • ❶ Conversion of a polymer into a liquid or spinning solution, also called a dope. • ❷ Extruding the solution through a spinneret to from a filament or fiber. • ❸ Solidifying the fiber by coagulation, evaporation or cooling.[5]

Materials The molecular weights of fiber forming polymers must be high enough for achieving good mechanical and thermal stability, and at the same time, low enough for dissolving or melting for extruding into fibers.

Fabrication Of HFM • Melt spinning,  in which a thermoplastic polymer is melted and extruded through a spinneret into air and subsequently cooled. [5,6] • Dry spinning,  in which a polymer is dissolved in an appropriate solvent and extruded through a spinneret into air.[5,6] • Wet spinning,  in which a polymer is dissolved and extruded directly into a coagulant (usually water)[5,6]

Melt Spinning

Dry Spinning

Wet Spinning

HFM module manufacture • The earliest reports of hollow fiber module designs come from the patents of [7], i. Dow ii. DuPont •. The modern method for module formation is given by[7]: i. Generon

Module Structure • Hollow-fibre modules are characteristically 4-8 inch (10-20 cm) in diameter and 3-5 (1.0-1.6 m) feet long. • Hollow-fibre membrane modules are formed in 2 basic geometries[8]: (a) shell-side feed design (b) bore-side feed design

Shell-side feed design • In the shell-side feed design, a loop or closed bundle of fibres is contained in a pressure vessel. • The system is pressurised from the shell side, and the permeate passes through the fibre wall and exits through the open fibre ends. • Because the fibre wall must support considerable hydrostatic pressure, the fibres usually have small diameters and thick walls [2,8].

Bore-side feed design • In the bore-side feed design, the fibres are open at both ends and the feed is circulated through the bore (annulus area) of the fibres. • To minimise pressure drop inside the fibres, the diameter are usually larger than those of the fine fibres used in the shell-side feed design [2,8]. 

Regeneration

Air scouring • The injection of air causes high turbulence on the fibres leading to the removal of solids from the membrane surface. • Thus the cake layer is removed from the fibres [9].

Forward flush • Water enters through the feed inlet and leaves through the reject outlet. • Thus the solid are taken away with it regenerating the membrane module [9].

Backflush • Permeate enters through the permeate outlet and leaves through the reject outlet. • Thus the solid are taken away with it regenerating the membrane module. • The loss of permeate during backflushing is very low and hardly affects the net permeate flow [9]. 

Backflush with Air scouring • Simultaneous combination of backflush and air scouring [9].

Electric Field • By applying an electric field across a membrane, charged particles or molecules will migrate in the direction of the electric field. • Electrical cleaning can be applied without interrupting the process and the electric field is applied at certain time intervals [9].

Advantages •  Hold up volume of hollow fiber module is the highest, followed by plate and frame, spiral wound, tubular, and rotating disc/cylinder module. • The single greatest advantage of hollow-fibre modules is the ability to pack a very large membrane area into a single module. • For example, in an 8-inch diameter, 40-inch long spiral-wound module would contain about 20 - 40 m 2of membrane area. The equivalent hollow-fibre module filled with fibres of 100mm diameter, will contain approximately 600 m 2 of membrane area. • The investment is low.[2,8]

Disadvantages • Hollow fiber modules are very susceptible to fouling and are difficult to clean. • Pretreatment of the feed stream is most important in hollow fiber systems. • A fiber inner diameter variation leads to a flow rate variation that can dramatically reduce module performance[2,8].

Application • • • • • • • •

Waste water treatment process. Drinking water treatment process. Hollow Fiber Dialyser. Membrane oxygenator. Artificial Lungs. Artificial Kidney. Pervaporation of liquids. Gas seperation.

References 1. http://www.advantecmfs.com/catalog/filt/membrane.pdf 2. Mulder, M. (1996) Basic Principles of Membrane Technology. 2nd edn. Dordrecht: Kluwer Academic Publishers. 3. http:// www.separationprocesses.com/Membrane/MT_Chp04a.ht m 4. https:// www.asahi-kasei.co.jp/membrane/microza/en/kiso/kiso_7. html 5. http://textilestudycenter.com/melt-spinning-dry-spinnin g-and-wet-spinning-method / 6. Vandekar V. (2015) Manufacturing of Hollow Fiber Membrane. International Journal of Science and Research (IJSR), 4(9), pp. 1990-1993.

7. Norfamilabinti Che Mat, Yuecun Lou and G Glenn Lipscomb (2014) Hollow fiber membrane modules. Current Opinion in Chemical Engineering, 4, pp. 1824. 8. Baker, R. (2004) Membrane Technology and Applications. 2nd edn. Chichester: John Wiley and Sons, Ltd. 9. https://www.youtube.com/watch?v=K24eK7IdVRg

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