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EP0149666A1 - Systeme de distillation a membrane thermique - Google Patents

Systeme de distillation a membrane thermique

Info

Publication number
EP0149666A1
EP0149666A1 EP84902854A EP84902854A EP0149666A1 EP 0149666 A1 EP0149666 A1 EP 0149666A1 EP 84902854 A EP84902854 A EP 84902854A EP 84902854 A EP84902854 A EP 84902854A EP 0149666 A1 EP0149666 A1 EP 0149666A1
Authority
EP
European Patent Office
Prior art keywords
membrane
hydrophobic
liquid layer
distillation system
membranes
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP84902854A
Other languages
German (de)
English (en)
Inventor
Dah Yu Cheng
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
International Power Technology Inc
Original Assignee
International Power Technology Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by International Power Technology Inc filed Critical International Power Technology Inc
Publication of EP0149666A1 publication Critical patent/EP0149666A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/36—Pervaporation; Membrane distillation; Liquid permeation
    • B01D61/364—Membrane distillation

Definitions

  • This invention relates to distillation purifi- cation systems and more particularly to distillation systems using hydrophobic membranes to desalinate water.
  • the distillation process has long been recognized as a means for purifying a chemical substance from a mixture of chemical substances. Early methods involved boiling the mixture and condensing out the substance to be purified. However, it has more recently been recognized that the ability of certain membranes to selectively pass the vapor phase of water while retarding the transport of the liquid phase will eliminate the need for violent boiling and use less energy to achieve distillation.
  • Evaporation of water requires: (1) that the water to be extracted or purified has a lower evaporation temperature than the remaining species in the mixture and (2) a coordinated heat input and removal process to extract water by evaporation and condensation. In this manner, large amounts of energy are transported by means of latent heat, although the temperature gradient between evaporation and condensation required to drive the process is usually very small.
  • the evaporation temperature of a substance in a mixture is higher than that of the pure substance at the same ambient pressure. This temperature difference is called "evaporation temperature elevation.”
  • a minimum temperature difference between that of the evaporating mixture and condensing or "pure” liquid ( T ) must be maintained in order to proceed with mass transport. At a value smaller than T MTK ⁇ ' mass transport can actually be reversed even if the condensing surface temperature is lower than the mixture solution temperature.
  • Evaporation temperature is also a function of partial vapor pressure. At temperatures below normal boiling point, evaporation can be continued by lowering the ambient pressure in the chamber.
  • a multiple-stage flash evaporator is designed to recognize these factors, and make the distillation process energy efficient.
  • the cooling necessary for condensation is done by a liquid, such as the feed water brine, which absorbs the latent heat of condensation from chamber to chamber through a non- permeable heat transfer surface in the form of a tube or radiator.
  • the chamber is selected so that each chamber has its own equilibrium chamber pressure. Chamber pressure is selected and controlled so that the coolant always has a temperature lower than the evaporating solution plus T M IN*
  • the latent heat of condensation becomes a regenerative heat source for the incoming brine, before any additional heat input is required.
  • the brine solution is then further heated to eventually become the evaporating solution.
  • the temperature of the evaporating solution open to the chamber continues to drop from chamber to chamber as pure vapor is evaporated.
  • the number of stages or chambers of the evaporator is selected in order to balance out or optimize the pressure/temperature profile and flow rates in addition to the operating and capital costs. Generally, the larger the number of stages, the lower the energy costs will be. The temperature difference of the condensing surface and evaporating liquid becomes smaller with increasing number of stages, hence one trades off energy costs for capital costs.
  • the number of stages is bound by ⁇ ⁇ the TM,, ⁇ I.,, . and TM complement ⁇ IN. ⁇ is a function of the mixture concentration.
  • FIG. 1 is a cross-sectional representation of one embodiment of a thermal membrane distillation system of the present invention
  • FIG. 2 depicts a cross-sectional depiction of a "stacked" thermal membrane distillation system of the present invention
  • FIG. 3 illustrates a spiral wound distillation system corresponding to the linear system of FIG. 1;
  • FIG. 4 illustrates a spiral wound thermal membrane distillation system, again, of a stacked configuration.
  • the present invention deals with a thermal membrane distillation system whereby a product liquid layer is separated from a brine liquid layer by a microporous, hydrophobic membrane and the product liquid layer is also separated from a coolant liquid layer by a barrier.
  • the product liquid is formed by condensing vapor from a brine which has passed through the hydrophobic membrane as a result of a temperature gradient across it.
  • the heat of condensation is transferred to a coolant liquid through a fluid impervious barrier whereby a counter flow relationship is established between the brine and coolant.
  • the membrane distillation system can be conformed into a spiral configuration.
  • FIG. 1 a counter flow thermal membrane distillation system is shown whereby the hot distilland or brine is shown flowing from side 7 to side 6 within space 2 being bounded on its top surface by microporous hydrophobic membrane 1. Above the membrane is located distillate or fresh water, which is produced by vapor migration through the membrane and condensation within space 3 due primarily to low temperature impervious barrier 4. The temperature of barrier 4 is maintained by coolant within space 5 which travels from surface 6 to surface 7, counter currently with the distilland within area 2.
  • the structure depicted above incorporating a hydrophobic microporous membrane represents a significant advantage over conventional multiple-staged flash evaporator systems. In a multiple staging condition liquids contact both sides of the membrane sealing off individual pores to form microporous chambers.
  • a vapor gap is established between the distilland and distillate whereby heat is employed to warm the distilland providing for evaporation across the vapor gap and condensation at a surface remote from the body of distilland liquid.
  • a vigorous heating of the distalland can cause impurities to travel the vapor gap and contaminate the distillate.
  • this can be significantly prevented by increasing the physical dimension of the vapor gap, any increase in such dimension greatly reduces distillation efficiency.
  • the distilland and distillate surfaces can be separated by the mere thickness of the membrane itself, while virtually eliminating contamination across the membrane.
  • thermal membrane distillation system of the present invention differs from prior art multi-staged flash evaporators in that the prior art devices are generally composed of multiple discrete stages where the present system is of a continuous design. As a result, it is necessary to design the counter-flow system so that the hydrophobic membrane is capable of transferring substantially pure water vapor from the distilland throughout the entire linear length of the system where local temperature and pressure conditions vary throughout. In designing such a system, it is recognized that the high temperature end (side 7 of FIG. 1) characteristically encloses distilland and product liquid of relatively high vapor pressures.
  • the thermal membrane distillation system of the present invention will function as long as the temperature gradient along the outer surface of the membrane is minimal. That is, (T-.-T 7 )/L is minimal where T.. is the temperature at which the hot distilland enters the system (side 7) and T_ is the temperature at which it exits (side 6). L is the linear length of the membrane. In other words, the temperature gradient across the membrane should be very large in comparison to that along the membrane. Ideally, the flow parameters are chosen so that the vapor mass transfer of the pure water across the membrane is at least five times greater than the vapor mass transfer due to the temperature gradient along the surface of the membrane.
  • the present invention be configured in the form of the spiral such as that shown in FIG. 3. More speci ⁇ fically, heated distilland enters the system within channel 14 at the center of the spiral and winds its way radially outward within channel 13. In a counter- flow relationship, coolant enters channel 11 at the radial extremity of the spiral and proceeds to travel inwardly as shown in the figure. The resultant fresh distillate then collects within channel 12 and is withdrawn from the spiral in a manner similar to that depicted in FIG. 1. As in FIG. 1, the distillate and coolant are separated by impervious barrier 15 while the hot brine and pure product are in turn separated by microporous membrane 16.
  • FIG. 2 whereby a composite structure is illustrated providing for an improved distillation scheme.
  • a center channel 23 is provided for housing the hot brine which is bounded on each side by hydrophobic microporous membranes 22 and 24.
  • a counter current flow arrangement is established between the hot brine within channel 23 and the cooling liquid in channels 27 and 28 which are separated from the distillate or condensate products within channels 21 and 25 by impervious partitions 20 and 26, respectively. Further, by forming symmetrical pairs, an adiabatic system is achieved.
  • a hydrophobic membrane separating a distilland within space 23, such as salt water, and a distillate located within spaces 21 and 25, such as fresh water. It is the nature of the hydrophobic membrane to possess pores across the body thereof. Due to the properties of the non-wetting hydrophobic material at low pressures, liquid is prevented from entering the pores of the hydrophobic membrane. Initially, neither the distilland nor distillate penetrates within the gaseous region of the pores. In fact, two convex-shaped liquid-vapor surfaces are found to exist at each end of the various pores.
  • distillation apparatus typically after several days, the vapor barrier across the pores of the hydrophobic material is destroyed due to water-logging, and hence the distillation process through the membrane ceases.
  • the distilland liquid-vapor interface migrates in a direction toward the distillate side until eventually it intersects the liquid-vapor interface on the distillate side of the membrane. This destroys the gaseous barrier needed for the distillation process to occur. It has been determined that this liquid migration can be substantially eliminated by providing a hydrophilic layer which is essentially non-porous onto the hydrophobic microporous membrane adjacent to the distilland side of said membrane.
  • the maximum pore diameter of the hydrophobic membrane is intended to be less than approximately 0.5 microns.
  • Fluoro-substituted vinyl polymers which are suitably hydrophobic are ideal materials for the microporous hydrophobic membranes.
  • Polytetrafluoro-ethylene is the most hydrophobic polymeric material known.
  • a plurality of composite microporous membranes can be arranged in a multi-staged cell configuration.
  • the main advantage of multiple—staged cell configurations is the conservation of heat energy.
  • the heat rejected from one stage is used to provide the temperature gradient across another stage. The optimum number of stages is reached when the operating
  • the membrane multi-stage evaporator of the present invention can be made more energy efficient by using, as cooling fluid, cold brine which is gradually heated while passing counter current to the hot brine used as the distilland.
  • cooling fluid is partially heated before being used, itself, as hot brine solution within chamber 23 of FIG. 2.
  • Another incidental utility in practicing the claimed invention is the removal of low boiling temperature trace substances from the distilland.
  • low boiling temperature components tend to evaporate right along with the low boiling temperature distillate.
  • the distillate becomes contaminated. It is common to have low temperature boiling contaminants in the ground waters, particularly in areas proximate urban areas and these potentially toxic chemicals cannot be removed by ordinary water distillation plants.
  • the membrane thermal distillation system of the present invention the incoming liquid is heated by the condensing distillate causing the low boiling temperature contaminants to bubble off as the liquid reaches the distilland heater. At that point, the various contaminants can be vented from the system before the liquid becomes the distilland in contact with the membrane.
  • PR n x l- T 2 T l- 4
  • n is a factor which expe imentally accounts for heat and mass transfer loss due to the inefficiencies influenced by the choice of flow rate, type of membrane and heat transfer coefficient of the channel flow.
  • T-. is the hot solution temperature.
  • T is the discharge solution temperature.
  • T. is the coolant temperature at exit. It was discovered that if the convection system's performance ratio (PR) is greater than 10, substantially pure vapor could be added to the brine liquid will tend to increase the performance ratio without needing additional heat transfer surface area.
  • OMPI OMPI
  • One method would be to configure the evaporator in a vertical mode, somewhat as shown by the figure's orientation itself. In this way, additional pressure can be imposed upon the upstream end of the hot brine in order to increase the solution boiling temperature which would consequently increase the efficiency of the system.
  • Yet another means of increasing efficiency is to provide a structure as shown in FIG. 4.
  • hot brine enters the system at the geometric center of the spiral as shown as area 70.
  • the brine progresses through the spiral between membrane pairs 74 and 75.
  • Rejected brine exits the system at the radial extremity of the spiral following channel 73, while fresh water distillate similarly is withdrawn from areas 71 and 72 at the radial extremity.
  • Coolant is caused to flow in a counter current fashion beginning at the radial extremity and progressing inwardly within areas 76, 77, 78, etc. operating in much the same manner as the counter current flow arrangement of FIG. 2.
  • Example 1 A countercurrent heat exchanger was made as depicted in Fig. 1. The cell had the following dimensions: Channel width 5"
  • brine entered the cell at a temperature of 190°F and entered the heater at 180.9°F.
  • Example 2 The cell of Example 1 was again used in the manner disclosed in practicing this invention. In doing so, four different cases were generated as follows:
  • thermal membrane distillation system can be used in any environment now occupied by prior distillation systems employed today.

Landscapes

  • Engineering & Computer Science (AREA)
  • Water Supply & Treatment (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Separation Using Semi-Permeable Membranes (AREA)
  • Vaporization, Distillation, Condensation, Sublimation, And Cold Traps (AREA)

Abstract

Système de distillation à membrane thermique dans lequel une couche d'un produit liquide dans l'espace (3) est séparée d'une couche de saumure liquide dans l'espace (2) à l'aide d'une membrane microporeuse hydrophobe (1) et la couche de produit liquide est également séparée d'une couche de liquide refroidisseur dans l'espace (5) à l'aide d'une barrière (4). Le produit liquide est formé en condensant la vapeur dégagée par une saumure ayant traversée la membrane hydrophobe (1) à la suite d'un gradient thermique au travers de la membrane. La chaleur de condensation est transférée dans un liquide refroidisseur par l'intermédiaire d'une barrière (4) imperméable au fluide, une relation de contre-courant s'établissant entre la saumure et le refroidisseur. Dans un mode préféré de réalisation, le système de distillation à membrane peut avoir une configuration en spirale.
EP84902854A 1983-07-05 1984-07-02 Systeme de distillation a membrane thermique Withdrawn EP0149666A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US51094283A 1983-07-05 1983-07-05
US510942 1983-07-05

Publications (1)

Publication Number Publication Date
EP0149666A1 true EP0149666A1 (fr) 1985-07-31

Family

ID=24032830

Family Applications (1)

Application Number Title Priority Date Filing Date
EP84902854A Withdrawn EP0149666A1 (fr) 1983-07-05 1984-07-02 Systeme de distillation a membrane thermique

Country Status (3)

Country Link
EP (1) EP0149666A1 (fr)
JP (1) JPS60501746A (fr)
WO (1) WO1985000532A1 (fr)

Families Citing this family (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5938928A (en) * 1991-08-01 1999-08-17 Nonap Pty. Ltd. Osmotic distillation process using a membrane laminate
US6112908A (en) * 1998-02-11 2000-09-05 Rentiers Machinery Pty, Ltd. Membrane laminates and methods for their preparation
CN110526313B (zh) * 2019-09-12 2024-06-04 北京中科瑞升资源环境技术有限公司 膜脱氨组件和膜脱氨设备
US10787872B1 (en) 2019-10-11 2020-09-29 Halliburton Energy Services, Inc. Graphene oxide coated membranes to increase the density of water base fluids
US10689268B1 (en) 2019-10-11 2020-06-23 Halliburton Energy Services, Inc. Coated porous substrates for oil and gas or chemical processing wastewater treatment
US10919781B1 (en) 2019-10-11 2021-02-16 Halliburton Energy Services, Inc. Coated porous substrates for fracking water treatment
WO2021071509A1 (fr) 2019-10-11 2021-04-15 Halliburton Energy Services, Inc. Traitement de fluides récupérés à partir d'opérations de puits à l'aide d'une membrane revêtue d'oxyde de graphène
JP2024520428A (ja) * 2021-05-28 2024-05-24 ダイアリティ インコーポレイテッド 脱気ユニット

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3340186A (en) * 1964-05-14 1967-09-05 Research Corp Recovery of demineralized water from saline waters
DE1642833A1 (de) * 1967-03-16 1971-04-29 Yves Henderyckx Verfahren und Vorrichtung zum Abtrennen eines oder mehrerer Bestandteile aus einer Loesung
US4265713A (en) * 1979-02-14 1981-05-05 International Power Technology, Inc. Method and apparatus for distillation
EP0039197A1 (fr) * 1980-04-25 1981-11-04 W.L. GORE & ASSOCIATES, INC. Appareil de distillation

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO8500532A1 *

Also Published As

Publication number Publication date
JPS60501746A (ja) 1985-10-17
WO1985000532A1 (fr) 1985-02-14

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Inventor name: CHENG, DAH, YU