Patent Publication Number: US-2006011535-A1

Title: Multi-tube separation membrane module

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a multiple tube type separation membrane module used to separate specific components from a fluid such as a solution, a mixed gas, and the like.  
      2. Description of the Related Art  
      Multiple tube type separation membrane modules as equipment for separating components in solutions or mixed gases are known. The separation membrane element used in the multiple tube type separation membrane module is made by composing a membrane of zeolite and the like having fine pores approximately as large as the molecules of substances to be separated around a porous tube.  
       FIG. 6  shows an example of a conventional multiple tube type separation membrane module. The multiple tube type separation membrane module has a cylindrical shell  1 , plurality of tubular separation membrane elements  3  extending in the cylindrical shell  1 , support plates  2   a  and  2   b  having plurality of opening for supporting the tubular separation membrane elements  3  and fixed to one end and the other end of the cylindrical shell  1 , covers  4   a  and  4   b  attached to the shell  1  so as to cover the support plates  2   a  and  2   b , and plurality of baffles  5  attached in the cylindrical shell  1  so as to support the tubular separation membrane elements  3 . The cylindrical shell  1  has a fluid inlet  6  in the vicinity of the support plate  2   a  and a fluid outlet  7  in the vicinity of the support plate  2   b . Each of the baffles  5  is formed in a partly cutout disc shape and has a role to move the fluid in the shell  1  from the fluid inlet  6  of the cylindrical shell  1  to the fluid outlet  7  directing the flow of the fluid perpendicularly to the tubular separation membrane elements  3 .  
      The covers  4   a  and  4   b  have outlets  8   a  and  8   b  for components permeating the membrane, respectively. When a fluid F 1  is supplied from the fluid inlet  6  as well as the insides of the covers  4   a  and  4   b  being sucked from the outlets  8   a  and  8   b  for membrane-permeable-components, the fluid F 2  from the fluid F 1  comes out through the tubular separation membrane elements  3  and flows out from the outlets  8   a  and  8   b , and the remaining fluid F 3  flows out from the outlet  7 . Since the multiple tube type separation membrane module densely holds the separation membrane elements  3  in the cylindrical shell  1 , a large total area of the separation membranes is provided in the shell and a large fluid processing capacity is available, although the shell is compact. However, the processing capabilities of the tubular separation membrane elements  3  are not fully effective, and the processing capacity of the multiple tube type separation membrane module is far less than what calculated as the sum of the processing capacity of the individual membrane elements  3 . It is contemplated that this is because (a) although the flow direction of fluid can be effectively regulated by the baffles, diffusion rate of membrane permeating components from the fluid to the surface of the tubular separation membrane is low due to the insufficient turbulence of the fluid in the vicinities of the tubular separation membrane resulting from the difficulty to sufficiently increase the flow velocity of the fluid with the buffles, and (b) the shell has a dead space to which the fluid is not distributed and the separation membranes in the dead space do not contribute to the separation.  
     SUMMARY OF THE INVENTION  
      Accordingly, an object of the present invention is to provide a multiple tube type separation membrane module which enables full use of the processing capacity of individual tubular separation membrane element in the module.  
      As a result of diligent studies in view of the above object, the inventors have conceived the present invention by discovering that the processing capacity of the multiple tube type separation membrane module having plurality of tubular separation membrane elements for separating membrane-permeable-components from a fluid is improved, when the tubular separation membrane elements are surrounded by tubular materials to form narrow spaces there-between, since the fluid passes through the spaces at a high speed promoting turbulence of the fluid in the vicinity of the tubular separation membrane elements as well as the fluid is uniformly distributed to the overall separation membranes.  
      That is, a multiple tube type separation membrane module of the present invention includes plurality of tubular separation membrane elements having sealed ends and open ends; outside pipes surrounding the tubular separation membrane elements with spaces formed therebetween and having first openings on the sealed ends side of the tubular separation membrane elements as well as second openings in the vicinities of the open ends of the tubular separation membrane elements; means for inlet communicating with the first openings of the outside pipes; first means for outlet communicating with the open ends of the tubular separation membrane elements; and second means for outlet communicating with the second openings of the outside pipes, wherein a fluid flowing from the first openings of the outside pipes through the means for inlet flows in the spaces between the tubular separation membrane elements and the outside pipes, components separated from the fluid by the tubular separation membrane elements flows out from the first means for outlet through the open ends of the tubular separation membrane elements, and the remaining fluid flows out from the second means for outlet.  
      A preferable example of the present invention is a multiple tube type separation membrane module having a shell provided with an outlet; first support plate fixed to an end of the shell; second support plate fixed to the other end of the shell; plurality of outside pipes supported by the first and second support plates and extending in the lengthwise direction of the shell; tubular separation membrane elements disposed in the respective outside pipes; first cover attached to the first support plate; and second cover attached to the second support plate, wherein the outside pipes have first openings formed on the first cover side through which a fluid flows as well as second openings formed on the second cover side through which the remaining fluid flows out after the completion of separation processing, the tubular separation membrane elements have sealed ends on the first cover side as well as open ends on the second cover side, and the spaces between the outside pipes and the tubular separation membrane elements are opened on the first cover side and sealed on the second cover side, thereby components separated by the tubular separation membrane elements from the fluid flowing from the first openings of the outside pipes into the spaces between the outside pipes and the tubular separation membrane elements flows out into the second cover from the open ends of the tubular separation membrane elements, and the remaining fluid flows out from the outlet of the shell through the second openings.  
      A partition may be attached to the first cover to form a first chamber and a second chamber on both sides of the partition. A fluid flowed into the first chamber may pass through the spaces between the outside pipes having first openings in the first chamber and the tubular separation membrane elements, flow out from the second openings of the outside pipes, flow into the outside pipes having first openings in the second chamber from the second openings, pass through the spaces between the outside pipes and the tubular separation membrane elements, and flow into the second chamber.  
      It is preferable that the sealed ends of the tubular separation membrane elements are fixed in the outside pipes keeping the spaces by pins disposed to either the outside pipes or the sealed ends. The inside diameter of the outside pipes is preferably 1.1 to 2 times the outside diameter of the tubular separation membrane elements.  
      It is preferable that the tubular separation membrane elements are hollow ceramic tubes around which separation membranes having fine pores approximately as large as molecules of substances to be separated are formed. The separation membranes are preferably composed of zeolite. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a longitudinal sectional view showing a multiple tube type separation membrane module according to an embodiment of the present invention;  
       FIG. 2  is an enlarged sectional view showing an outside pipe and a tubular separation membrane element in the multiple tube type separation membrane module shown in  FIG. 1 ;  
       FIG. 3  is an enlarged sectional view of the multiple tube type separation membrane module taken along the line B-B of  FIG. 2 ;  
       FIG. 4  is an enlarged sectional view of the multiple tube type separation membrane module taken along the line A-A of  FIG. 1 ;  
       FIG. 5  is a longitudinal sectional view of the multiple tube type separation membrane module according to another embodiment of the present invention;  
       FIG. 6  is a schematic longitudinal sectional view showing an example of a conventional multiple tube type separation membrane module; and  
       FIG. 7  is a schematic longitudinal sectional view showing another example of the conventional multiple tube type separation membrane module. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION  
       FIG. 1  shows a multiple tube type separation membrane module according to an embodiment of the present invention. The multiple tube type separation membrane module has a cylindrical shell  1 , plurality of outside pipes  13  extending in the longitudinal direction of the cylindrical shell  1 , support plates  2   a  and  2   b  fixed to one end and the other end of the cylindrical shell  1  to support the plurality of outside pipes  13 , tubular separation membrane elements  3  disposed in the outside pipes  13  in a longitudinal direction with spaces formed therebetween, and covers  4   a  and  4   b  attached to the cylindrical shell  1  so as to cover the support plates  2   a  and  2   b.    
      The cylindrical shell  1  has an outlet  7  projecting outward through which non-permeable fluid F 3  is discharged. The non-permeable fluid outlet  7  is disposed at a position near to the support plate  2   b  fixed to the other end of the cylindrical shell  1 . The cover  4   a  has an inlet  6  projecting outward through which fluid F 1  is supplied, and the cover  4   b  has an outlet  8  projecting outward through which membrane-permeable fluid F 2  (separated component) is discharged. Further, the covers  4   a  and  4   b  have flanges gastightly engaged with the support plates  2   a  and  2   b  fixed to both ends of the cylindrical shell  1 , respectively.  
      The support plate  2   a  fixed to the one end of the cylindrical shell  1  has plurality of openings  21   a , and the support plate  2   b  fixed to the other end of the cylindrical shell  1  has plurality of openings  21   b . Each of the openings  21   a  of the support plate  2   a  is correctly positioned to face the corresponding opening  21   b  of the support plate  2   b . The extreme ends  131  of the outside pipes  13  are fixed to the openings  21   a  of the support plate  2   a , and the rear ends  132  of the same outside pipes  13  are fixed to the openings  21   b  of the support plate  2   b  corresponding to the openings  21   a , thereby the outside pipes  13  are supported by the support plates  2   a  and  2   b . The outside pipes  13  have second openings (fluid passing ports)  133  at positions near to the support plate  2   b.    
       FIG. 2  shows the outside pipe  13  supported by the support plates  2   a  and  2   b  and the tubular separation membrane element  3 . The extreme end of the tubular separation membrane element  3  (on the cover  4   a  side) is arranged as a seal end  31 , and the rear end thereof (on the cover  4   b  side) is arranged as an open end  32 . The seal end  31  is sealed by a seal member  9 , and a seal  114  is applied between the seal end  31  and the seal member  9  to secure gas tightness. A fixing member  10  is fixed to the open end  32  of the tubular separation membrane element  3  with a seal  115 , and the fixing member  10  is threaded into the rear end  132  of the outside tube  13 .  
      Plurality of pins  34  are disposed on the inside surface of the outside pipe  13  at positions near to the support plate  2   a , and seal member  9  abutt on the extreme ends of the pins  34 . The pins  34  support the tubular separation membrane element  3  in which the seal member  9  is fitted. Note that the pins  34  may be disposed to the seal member  9 . Further, a spacer having an opening may be interposed between the inside surface of the outside pipe  13  and the seal member  9 . The tubular separation membrane element  3  supported by the pins  34  is free to slide in the outside pipe  13 . Accordingly, when a fluid F 1  having a high temperature flows into the outside tube  13 , the tubular separation membrane element  3  can be prevented from being cracked due to the difference of the thermal expansion between the outside pipe  13  and the tubular separation membrane element  3 .  
      The outside pipe  13  is fixed to the support plates  2   a  and  2   b  gastightly by welding. The support plate  2   b  is welded to the outside pipe  13  being cured to prevent the portion where the fixing member  10  is threaded into the outside pipe  13  from being deformed.  
      The outside pipe  13  may be provided with projections on the inside surface thereof. The projection can promote turbulence in the fluid F 1  flowing in the outside pipe  13 . The shape of the projection is not particularly limited, and the projection need not be formed integrally with the outside pipe  13 . For example, a spring having the same outside diameter as the inside diameter of the outside pipe  13  may be disposed in the lengthwise direction of the outside pipe  13  coaxially therewith.  
       FIG. 3  is an enlarged sectional view of the multiple tube type separation membrane module taken along the line B-B of  FIG. 2  and shows the outside pipe  13  and the tubular separation membrane element  3  in detail. The ratio of the inside diameter L of the outside pipe  13  to the outside diameter M of the tubular separation membrane element  3  is preferably 1.1 to 2.0 and more preferably 1.2 to 1.5. A ratio L/M very close to 1 is not preferable because pressure loss is excessively increased thereby. Further, an excessively large ratio L/M is not also preferable because the flow velocity of the fluid F 1  passing through the space between the outside pipe  13  and the tubular separation membrane element  3  is excessively reduced.  
       FIG. 4  is an enlarged sectional view of the multiple tube type separation membrane module taken along the line A-A of  FIG. 1  and shows the outside pipes  13  and the tubular separation membrane elements  3  uniformly disposed in the cylindrical shell  1 . Note that the numbers of the outside pipes  13  and the tubular separation membrane elements  3  shown in  FIG. 4  are less than the actual numbers of them to simplify illustration. Although the distances between the centers of the outside pipes  13  supported by the support plates  2   a  and  2   b  are not limited, they are preferably 1.2 to 2 times the outside diameter of the outside pipes  13  and more preferably 1.25 to 1.5 times the outside diameter in practical use.  
      As shown in  FIGS. 1 and 2 , the fluid F 1  supplied into the cylindrical shell  1  from the fluid inlet  6  passes through the spaces between the outside pipes  13  and the tubular separation membrane elements  3  and flows to the second openings  133 . At the same time, by sucking the inside of the cover  4   b  from the membrane permeable fluid outlet  8  thereof, the fluid F 2  permeates each tubular separation membrane element  3 , and cobines in the cover  4   b , then flows out from the membrane-permeable fluid outlet  8 . In contrast, the remaining fluid F 3  (non-permeable fluid), which does not permeate the tubular separation membrane elements  3 , flows out to the outside of the outside pipes  13  from the second openings  133 , combines in the cylindrical shell  1 , and flows out from the fluid outlet  7 .  
      Since the fluid F 1  passes through the spaces between the outside pipes  13  and the tubular separation membrane elements  3 , the flow velocity of the fluid F 1  is increased and the fluid in the vicinity of the tubular separation membrane element  3  is made turbulent, thereby the diffusion of a membrane permeable substances in the fluid F 1  to the vicinities of the tubular separation membrane elements  3  is accelerated. As a result, permeation rate of the fluid F 2  through the tubular separation membrane elements  3  is increased, and processing capabilities there of are improved consequently. When the fluid F 1  is a liquid, preferable flow velocity of the fluid F 1  in the spaces between the outside pipes  13  and the tubular separation membranes element  3  is 0.2 to 2 m/s. Since resistance occurs against the flow of the fluid F 1  passing through the spaces between the outside pipes  13  and the tubular separation membrane elements  3  by keeping the flow velocity of the fluid F 1  within the above range, the fluid flowed into the cover  4   a  is uniformly dispersed in the spaces between the outside pipes  13  and the tubular separation membrane elements  3  and flows therethrough. As a result, the entire area of the membranes contributes to cause the component to pass therethrough, thereby the processing capacity of the multiple tube type separation membrane module is improved in its entirety. When the fluid F 1  is a gas, preferable flow velocity of the fluid F 1  is 2 to 20 m/s.  
       FIG. 5  shows a multiple tube type separation membrane module of another embodiment of the present invention. Since the embodiment shown in  FIG. 5  is approximately the same as that shown in FIGS.  1  to  4  except that a partition  41  is disposed in a cover  4   a  having an inlet  6  of the fluid F l , only the difference between the embodiments will be explained below. The partition  41  is fixed in the cover  4   a  to longitudinally divide it into two portions. The partition  41  is fixed to cover  4   a  gastightly by welding. The seal  116  is sandwiched between the end  41   a  of the partition  41  and support plate  2   a  to secure gas tightness.  
      The side of fluid inlet  6  of the cover  4   a  is arranged as the first chamber  42  by the partition  41 , and the opposite side thereof is arranged as the second chamber  43 . A fluid outlet  7  extending outward is disposed to the second chamber  43  divided by the partition  41 . Outside pipes are composed of first outside pipes  13   a  whose extreme ends  131  are fixed to the first chamber  42  and second outside pipes  13   b  whose extreme ends  131  are fixed to the second chamber  43 .  
      The fluid F 1  supplied to the cylindrical shell  1  from the fluid inlet  6  passes through the spaces between the first outside pipes  13   a  and the tubular separation membrane elements  3  and flows to second openings  133   a  of the first outside pipes  13   a . At the same time, when the inside of cover  4   b  is vacuumed from membrane permeable fluid outlet  8  thereof, the insides of the tubular separation membrane elements  3 , which open in the cover  4   b , are also vacuumed likewise the embodiment shown in FIGS.  1  to  4 . Accordingly, substances, which has permeability to the separation membranes of the tubular separation membrane elements  3 , permeate the separation membranes and flows into the tubular separation membrane elements  3 . The fluid F 2  that permeated the tubular separation membrane elements  3  combines together in the cover  4   b  and flows out from the membrane-permeable fluid outlet  8 .  
      In contrast, the primarily processed fluid F 4 , which does not permeate the tubular separation membrane elements  3  in the first outside pipes  13   a , flows into the cylindrical shell  1  from the second openings  133   a  of the first outside pipes  13   a . The primarily processed fluid F 4 , which fills the cylindrical shell  1 , flows into the spaces between the outside pipes  13   b  and the tubular separation membrane elements  3  from second openings  133   b  of the second outside pipes  13   b  whose extreme ends  131  are fixed to the second chamber  43 , passes through the spaces therebetween, combines in the second chamber  43  of the cover  4   a , and flows out from the fluid outlet  7  disposed to the second chamber  43 .  
      When the multiple tube type separation membrane module shown in  FIG. 5  is used, even if the quantity of flow of the fluid F 1  is reduced to about one half that in the multiple tube type separation membrane module shown in FIGS.  1  to  4 , the fluid F 1  exhibits a relatively large flow velocity between the first and second outside pipes  13   a  and  13   b  and the tubular separation membrane elements  3 . Accordingly, it can be said that this multiple tube type separation membrane module is preferable when the fluid F 1  has a small quantity of flow.  
      In any of the multiple tube type separation membrane modules, it is preferable to use a tubular porous support member which is composed of ceramics or metal and around which a separation membrane composed of zeolite and the like are formed as the tubular separation membrane element  3 . When, for example, the fluid F 1  composed of water and ethanol is separated, a tubular separation membrane element composed of a tubular support member, which is composed of porous ceramics and around which an A type zeolite membrane is formed, can be used. In this case, water becomes to compose the fluid F 2  which permeates the tubular separation membrane element and ethanol becomes to compose the non-permeate fluid F 3 .  
     EXAMPLE 1  
      Tubular separation membrane elements  3  were made by forming zeolite membranes around tubular porous support members composed of α-alumina (length: 80 cm, outside diameter: 10 mm, inside diameter: 9 mm) , and a multiple tube type separation membrane module (length: 110 cm, outside diameter: 14 cm) similar to the embodiment shown in  FIGS. 1 and 4  was assembled using 25 pieces of the tubular separation membrane elements. Mixed vapor composed of water and ethanol (water:ethanol=0.05:0.95 (mass fraction)) was supplied to a cylindrical shell  1  of the multiple tube type separation membrane module. The mixed stream was supplied at a rate of 100 kg/h, the temperature of the mixed steam was 110° C. at a fluid inlet  6  and the pressure thereof was 300 kPa. When the mixed vapor was supplied and membrane-permeable fluid outlet  8  was sacked at 1.3 kPa, membrane-permeable fluid F 2  flowed out from the membrane-permeable fluid outlet  8 , and non-permeable fluid F 3  flowed out from fluid outlet  7 . The flow rate of water vapor as the membrane-permeable fluid F 2  was 1.8 kg/h at the membrane-permeable fluid outlet  8 .  
     COMPARATIVE EXAMPLE 1  
      Mixed stream composed of water and ethanol was separated likewise the Example 1 except that a multiple tube type separation membrane module (length: 110 cm, outside diameter: 14 cm, number of tubular separation membrane elements: 25) was assembled as shown in  FIG. 7 .  
      The multiple tube type separation membrane module shown in  FIG. 7  is approximately the same as the embodiment shown in  FIG. 6  except that the rear ends of plurality of tubular separation membrane elements  3  whose extreme ends are sealed are attached to the support plate  2   a  attached to an end of the shell  1  and to the support plate  2   b  attached to the other end of the shell  1  in a cantilever beam fashion. When the mixed stream composed of water and ethanol was supplied into the shell  1  from the inlet  6  as well as the insides of channel members  4   a  and  4   b  being sucked from membrane-permeable component outlets  8   a  and  8   b , water vapor in the mixed stream permeated the tubular separation membrane elements  3  as membrane-permeable fluid F 2  and flowed out from the outlets  8   a  and  8   b , and ethanol flowed out from outlet  7  as non-permeable fluid F 3 .  
      The flow-out rate of the water vapor as the membrane-permeable fluid F 2  was 0.8 kg/h at the membrane-permeable component outlets  8   a  and  8   b.    
     POSSIBLE INDUSTRIAL APPLICATION  
      The multiple tube type separation membrane module of the present invention separates membrane-permeable-components (membrane-permeable-fluid) from a fluid by the tubular separation membrane elements wherein the fluid is caused to pass through the narrow spaces formed by surrounding the tubular separation membrane elements with the surrounding members. With the above arrangement, since a fluid flow is improved and the contact state between the fluid and the tubular separation membrane element is improved, the processing capabilities of the respective tubular separation membrane elements can be effectively exhibited. Further, the flow velocity of the fluid which permeates the tubular separation membrane elements is increased by increasing the flow velocity of the fluid in the vicinities of the tubular separation membrane elements, thereby the processing capacity of the multiple tube type separation membrane module can be greatly improved in its entirety.