Stripping absorption module

Abstract

In a process, a portion of a liquid mixture flow is vaporized to produce a vapor and a depleted flow of liquid. The vapor is introduced to a brine which is adapted to exothermically absorb one or more components therefrom, and heat is withdrawn, to produce at least a flow of heat and a flow of brine which is enriched in the one or more components. The heat previously withdrawn is transferred, to drive the vaporization. This transfer can be associated with the change of a working fluid from a gaseous into a liquid gate. In this case, the heat withdrawal involves the change of the working fluid from the liquid to the gaseous state. In the liquid state, the working thud flows only by one or more of gravity, convection and wicking. In the gaseous state, the working fluid flows only by one or more of diffusion and convection.

Claims

1. Process for use with a flow of a liquid mixture that is separable by vaporization into a flow of vapor and a depleted flow of liquid, the process comprising: a vaporization step, wherein a portion of said liquid mixture flow is vaporized to produce said flow of vapor and said depleted flow of liquid; an absorption step, wherein (i) the flow of vapor is introduced to a flow of brine which is adapted to exothermically absorb one or more components from the vapor and (ii) heat is withdrawn, to produce at least a flow of heat and a flow of brine which is enriched in the one or more components; and a heat transfer step, wherein the heat withdrawn in the absorption step is transferred, to drive the vaporization in the vaporization step, wherein the transfer of heat to drive the vaporization is associated with the phase change of a working fluid from a gaseous state into a liquid state; the withdrawal of heat in the absorption step involves the phase change of the working fluid from the liquid state into the gaseous state; in the liquid state, the working fluid flows only by one or more of gravity, convection and wicking; and in the gaseous state, the working fluid flows only by one or more of diffusion and convection.

2. A process according to claim 1, wherein one or more heat pipes are used to withdraw the heat for the absorption and to drive the vaporization.

3. A process according to claim 2, wherein the one or more heat pipes are stacked such that the one or more heat pipes operate in use as a packed vaporization column in the vaporization and as a packed absorption column in the course of vaporization.

4. A process according to claim 1, wherein the flow of vapor is in substantial vapor-liquid equilibrium with the liquid mixture.

5. A process according to claim 1, wherein, in use, the temperature of the depleted flow of liquid is lower than the temperature of the liquid mixture.

6. A process according to claim 1, wherein substantially all of the heat withdrawn from the absorption results in vaporization.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic view of a stripping/absorption module according to an exemplary embodiment of the invention;

(2) FIG. 2 is a schematic view of the module of FIG. 1 in an exemplary use;

(3) FIG. 3 is a view, similar to FIG. 2, of another exemplary use of the structure of FIG. 1;

(4) FIG. 4 is a another schematic view showing another exemplary use of the structure of FIG. 1;

(5) FIG. 5 is a schematic view of an ethanol production facility employing two modules according to FIG. 1;

(6) FIG. 6 is a simplified schematic view of the ethanol production facility of FIG. 5 in combination with a simplified view of the structure of FIG. 4;

(7) FIG. 7 is a schematic view of an alternate embodiment of the module of FIG. 1:

(8) FIG. 8 is a schematic view of a yet further embodiment of the module of FIG. 1;

(9) FIG. 9 is a cross-sectional view of a yet further embodiment of the module of FIG. 1; and

(10) FIG. 10 is a schematic view of another embodiment of the invention.

DETAILED DESCRIPTION

(11) A stripping/absorption module (SAM) is shown in FIG. 1 in schematic form and designated with general reference numeral 20.

(12) This module comprises: a vessel 21, a pair of bulkheads 22,24, a plurality of heat pipes 24 and a pair of distributors 28,30.

(13) Vessel 21 is a robust vessel, suitable for operation at reduced pressures, for example, 30 Torr.

(14) The pair of bulkheads comprises a first bulkhead 22 and a second bulkhead 24. The first bulkhead 22 extends upwardly from the base of the vessel and terminates beneath the top of the vessel. The second bulkhead 24 is disposed in spaced relation from the first, extends downwardly from the to of the vessel and terminates above the base. Through this arrangement, first 32 and second 34 voids are defined interiorly of the vessel, which are coupled to one another by a conduit 35 defined by the space between the bulkheads 22,24.

(15) The vessel is punctuated by a plurality of ports 36-44, one lower port 36,38 at the base of each void, one upper port 40,42 adjacent the top of each void and one uppermost port 44 proximal the top of the second void 34.

(16) The plurality of heat pipes 26 extend from the first void 32 to the second void 34 and are for carrying heat from the second void 34 to the first void 32. The heat pipes 26 are of conventional construction and as such are not described herein in detail.

(17) The pair of distributors 28,30 extend one each from the upper ports 40,42 of the first and second voids 32, 34 and are adapted for wetting the heat pipes 26.

(18) From this, it should be understood that the major functional features of the illustrated SAM are: first void 32; second void 34; the conduit 35 connecting the first and second voids; the lower ports 36,38; the upper ports 40,42; the uppermost port 44; the heat pipes 26; and the distributors 28,30

(19) FIG. 2, which is a schematic embodiment of an exemplary separator apparatus for use with a flow of a mixed liquid that is separable by vaporization into a flow of vapor and a depleted flow of liquid, shows the manner in which such major functional features operate in use.

(20) Herein, it will be seen that the module 20 is shown along with a secondary absorber 46 and a desorption apparatus 48.

(21) Turning first to the module 20, it will be understood that the first void 32 forms a first volume. This is where the flow of mixed liquid is received and partially vaporized into the aforementioned flows of vapor and depleted flow of liquid. The manner in which vaporization is carried out is described below, in the description relating to the heat pipes.

(22) The lower port 42 at the base of the first volume defines a first liquid passage by which said depleted flow of liquid leaves the first volume 32.

(23) The conduit 35 defines a vapor passage by which said flow of vapor leaves the first volume 32.

(24) The second void 34 defines a second volume to which the vapor passage 35 leads.

(25) The uppermost port 44 defines a vent.

(26) The distributors 28,30 and heat pipes 26 together define heat and mass transfer apparatus and heat movement apparatus. The heat and mass transfer apparatus: (i) receives flow of brine adapted to exothermically absorb one or more components from the vapor; (ii) introduces the flow of brine to the vapor (i.e. the brine is sprayed or dropped into the second volume 34 onto the heat pipes 24); and (iii) withdraws heat from the second volume, to produce at least a flow of heat and a flow of brine which is enriched in the one or more components. The heat movement apparatus transfers the flow of heat to the first volume 32 to provide for said separation, and as such, each of the heat pipes 26 has a heat receiving part disposed in the second volume and a heat delivering part disposed in the first volume.

(27) The brine can be, for example, only, LiBr solution having a lithium bromide mass concentration between 40% to 70%, preferably between 45% to 65%. However, any absorbent fluid known in the art would be suitable.

(28) The lower port 38 at the base of the second volume 34 defines a second liquid passage by which the flow of brine which is enriched in the one or more components leaves the second volume 34.

(29) By virtue of use of the heat pipes, it will be understood that: that the transfer of heat into the first volume is associated with the phase change of a working fluid, in this case, water, from a gaseous state into a liquid state; the withdrawal of the heat from the second volume involves the vaporization of the working fluid from the liquid state into the gaseous state; the working fluid in the liquid state flows only by one or more of gravity and wicking; and the working fluid in this gaseous state flows only by one or more of diffusion and convection. Working fluids other than water can and would be used depending upon the application: ammonia and commercial refrigerant fluids are but two examples. The choice of working fluid is a matter of routine to persons of ordinary skill and as such is not described herein.

(30) The heat pipes 26 are stacked such that that portion of the heat pipes disposed in the first volume 32 operate in use as a packed evaporation column and that portion of the heat pipes disposed in the second volume 34 operate in use as a packed absorption column.

(31) Accordingly: the vapor leaving the first volume 32 is in substantial vapor-liquid equilibrium with the mixed liquid entering the first volume 32; at least a substantial portion of the vapor is absorbed in the second volume 34, with the balance leaving the second volume via the vent 44.

(32) The secondary absorber 46: (i) receives the balance of the vapor, i.e. that portion not absorbed in the SAM; and (ii) introduces the balance of the vapor to a secondary flow of brine which is adapted to exothermically absorb the one or more components. This produces a diluted brine and also produces a gas stream composed of non-absorbable gases and any non-absorbed absorbables, the latter being vacated from the secondary absorber along arrow 50.

(33) The desorption apparatus 48, i.e. a boiler or a distillation apparatus, receives the flow of brine produced by the heat and mass transfer apparatus and the diluted brine produced by the secondary absorber 46 and produces: the flow of brine 52 adapted to exothermically absorb at least one or more components from the vapor; and the secondary flow of brine 54; and a product stream 56.

(34) FIG. 3 shows a variation of the structure of FIG. 2, for use in circumstances wherein the pressures in the first volume and second volume are reduced in comparison to atmospheric pressure, in this application, at least the majority of the enriched vapor is absorbed in the second volume and a vacuum pump 58 provides for the non-condensables and any unabsorbed condensables in the vapor to be voided from the apparatus.

(35) Turning now to FIG. 4, same will be understood to show in schematic form a plant that could be usefully used for concentrating apple juice. This plant is generally similar to the structure of FIG. 3, i.e. In that it includes a SAM 20, a secondary absorber 46 and a vacuum pump 58, but the desorption apparatus 48 has, rather than a distillation device, a two-stage desorber [since the purpose in this application is not to fractionate the mixed liquid but merely to concentrate the juice.] The two-stage desorber includes a number of economizers 60, to advantageously pass heat between various parts of the process, a pair of boilers 62 and variety of pumps 64. Predictions have been made in respect of the operation of this system, the values being set forth on Table 1, below.

(36) TABLE-US-00001 TABLE 1 Flow rate lb/hr Stream Water LiBr Total Temp C. % LiBr 1 100 0 100 30 0 2 60 0 60 30 0 3 40 0 40 30 0 .sup.4A 80 120 200 165 60 .sup.4B 80 120 200 70 60 .sup.5A 40 120 240 55 50 .sup.5B 40 120 240 85 50 6 98 120 218 90 54.2 7 18.7 0 18.7 30 0 8 21.3 0 21.3 105 0 9 25.6 0 25.6 178 0 10 As required <30

(37) The predicted energy input (in the form of 125 psig steam) fed via stream 12, is 557 Btu/lb water evaporated. This contrasts favorably to simple evaporation efficiency [about 1000 Btu/lb]. At the same time, the facility is predicted to be relatively inexpensive to construct and operate, as will be evidence to persons of ordinary skill in the art on review of the schematic.

(38) Turning now to FIG. 5 same will be understood to show in schematic form an ethanol production facility and will be seen to include: as corn milling facility 66, a cooking/liquefaction facility 68 and a saccharification facility 70; these are all substantially conventional, in that they take corn and create therefrom a feedstock suitable for fermentation; a yeast conditioning facility 72, for producing a flow of water, enzymes and yeast; a continuous stirred tank reactor (CSTR) 76: to which the fedstock, water, etc., are fed, in which fermentation continuously takes place and from which a bleed stream 115 is drawn; a SAM device 70, coupled to the CSTR to: withdraw a flow of the fermentation broth on a continuous basis, preferentially remove alcohol from the withdrawn broth to produce an enriched alcohol (brine) flow 104 and a remainder flow 131; and return the remainder flow 131 to the CSTR 76; a batch tank 78, which receives and ferments the bleed stream 135 in hatches a second SAM device 20 coupled to receive the product from the batch tank 78 and produce (i) a stream of whole stillage from which ethanol has been substantially removed and (ii) brine enriched in ethanol a stillage processor 79 a secondary absorber 46, for absorbing the remainder of the absorbables not taken up by the SAM devices 20; a vent scrubber 74 for extracting trace alcohol from, inter alia, the batch tank 78 and the secondary absorber 46 and diverting same back to the cooking facility 68, before exhausting non-condensables to atmosphere via stream 142 3 desorbers 84,82,80, arranged to create a three-stage desorber, to regenerate the brine, produce a concentrated ethanol stream; and produce a recycle water stream; a condenser 90 and receiver 92, for condensing the recycle water stream and returning same to the corn milling facility 68; a rectifier/dehydration facility 86; economizers 60 and pumps 64, for passing flows between the various elements; and ethanol product storage facility 88.

(39) Predicted operating conditions for various of the flows are indicated in Table 2.

(40) TABLE-US-00002 FERMENTATION TRAIN Stream Mass flow rate lb/hr percent percent Temperature Stream name # water sugars DGS ethanol total ethanol sugars Degrees C. Mash fed to main fermentor 137 224,400 66,000 37,620 0 328,020 0 20 30 Beer feed to SAM1 132 211,455 5,610 37,620 18,117 272,802 7 2 30 Beer recycled from SAM1 131 198,511 5,610 37,620 6,039 247,780 2 2 28 Main fermentor bleed 135 211,455 5,610 37,620 18,117 272,802 7 2 30 Fully fermented beer 136 211,455 0 37,620 20,922 269,997 8 0 32 BRINE TRAIN Stream Mass flow rate lb/hr Stream Composition Temperature Stream name # LiBr Water Ethanol Total % LiBr % Water % Ethanol Degrees C. SAM1 vapours 99a 0 12,944.63 12,078.00 25,022.63 0 51.73 48.27 30 SAM2 vapours 99b 0 19,927.34 20,922.00 40,849.34 0 48.78 51.22 30 Feed to Secondary Absorber 100 133,028 121,558 33,000 287,586 50 42 11.47 55 Product from Secondary Absorber 101 133,028 128,787 33,803 295,618 45 44 11.43 45 Strong Brine to SAM1 103 66,514 44,343 0 110,857 60 40 0 70 Strong Brine to SAM2 104 66,514 44,343 0 110,857 60 40 0 70 Low Pressure Desorber Product 107 133,028 88,686 0 221,714 60 40 0 95 High Pressure Desorber Poduct 112 133,028 105,799 3,426 242,254 55 44 1.41 260 Mid Pressure Desorber Product 113 133,028 118,271 15,898 267,197 50 44 6 175 Ethanol Laden Condensate 117 0 12,472 12,472 24,944 0 50 50 202 Mid Pressure Vapor 118 0 10,516 17,905 28,421 0 37 63 138 Ethanol Product as vapor 163 0 134 33,000 33,134 0 0 100 ambient

(41) Persons of ordinary skill in the art will readily understand the operation of the device in consideration of the flows and the schematic. Accordingly, for brevity, a detailed item-by-item description is neither requited nor provided.

(42) However, Table 2 is notable at least for the following: product streams fed to the rectifier 86 are of concentrations suitable for conventional processing by pervaporation or molecular sieve techniques; calculations suggest that high quality heat requirements, i.e., fuel-generated heat, for the high pressure desorber 84, are 4,717 btu/gallon ethanol produced [up to the rectifier 86], this contrasts favorably to common ethanol production facilities, wherein heat requirements up to rectification can reach as high as 18,000 btu/gallon the broth withdrawn from CSTR 76 has a temperature of about 30 C. and the remainder broth has a temperature of about 28 C.; this arrangement is advantageous, in that the broth is never elevated in temperature above about 30 C. [or supercooled], which would harm the live yeast.

(43) Again, the facility is predicted to be relatively inexpensive to construct, as will be evident to persons of ordinary skill.

(44) Without intending to be bound by theory, it is believed that the advantageous energy and construction cost requirements flow in part from: the pressure in the first volume 34 and the temperature of the mixed liquid entering the first volume 32 are such that substantially all of the heat transferred to the first volume 32 results in evaporation of the mixed liquid; the remainder broth has a temperature lower than that of the withdrawn broth, thereby reducing chilling loads on the CSTR; the use of multiple-effect desorption; and the relatively modest refrigeration loads associated with the vaporization [which, in areas where very cold cooling water is not available in abundance, i.e., as is commonly the case, must be provided by mechanical means]

(45) FIG. 6 shows a simplified variation of the FIG. 5 structure, with further detail in respect of an advantageous method for stillage processing, utilizing a SAM according to the invention.

(46) Briefly, CSTR 76 receives feedstocks 96 and produces strong beer 98 which is fed to a SAM apparatus 20. Weak beer 100 passes back from this SAM to CSTR 76. A bleed stream 104 passes to batch tank 78. Strong beer 102 from batch tank 78 is fed to its own SAM 20. Whole stillage 108 from batch tank 78 is centrifuged 110 to produce wet cake 112 and thin stillage 114, the latter being sent to yet another SAM 20, to produce syrup 116 which, along with cake 112, is dried in a DDGS dryer 118. Dilute brine 120 produced by each of the SAMS is fed to still 94 for regeneration. Although still 94 shows all of the diluted brines converging, it should be understood that still apparatus 94 could have two trains, thereby to keep separate brine streams relatively higher concentration in ethanol and brine streams relatively barren of ethanol.

(47) The predicted utility in respect of the aforementioned prophetic examples has been verified experimentally.

(48) Experimental Results

(49) Twenty heat pipes, each 7.0 in length and 0.25 in diameter, were mounted horizontally, one above the other, to form an array about 10.0 in height. This assembly was sandwiched between transparent sheets of acrylic. Two separate, side-by-side chambers [an evaporator chamber and an absorber chamber] were formed between the sheets, with the heat pipes passing through both chamber. A 0.5 ID hose was used to connect the top part of the evaporator chamber to the bottom of the absorber chamber. At the top of each chamber, a crude liquid distributor was provided. At the top of each chamber, a 2 liter flask, vented to atmosphere was provided, and coupled to the liquid distributor of that chamber via a flow control valve. At the bottom of each chamber, a liquid exit port was provided, coupled to a collection flask. A vent at the top of the absorber chamber was coupled a standard laboratory vacuum pump with two lines of defense protecting it from water and ethanol vapours.

(50) The first defense measure was a secondary absorber comprised of a flask partly filled with a strong cool LiBr solution. Gases en route to the vacuum pump were forced to bubble through the solution in the flask, stripping them of absorbable components. The second stage of defense was a liquid nitrogen cold trap.

(51) Two runs were made. In each run, measured amounts of brine were provided in the bubbler tank and absorber-coupled flask and a measured amount of beer was provided in the evaporator-coupled flask; the flow control valves were opened; and temperature and pressure measurements were made as the liquids traversed the unit. Readings were terminated when one or both of the feed flasks had been drained.

(52) TABLE-US-00003 TABLE 3 Run 1 Time Beer Beer Brine Brine System Elapsed Input Output Input Output Pressure (min) C. C. C. C. mmHg 1 26 24 49 23 41.7 2 27 27 60 42 37.2 3 27 27 62 48 33 4 27 27 63 52 29.1 5 27 27 64 52 27.7 6 27 28 64 55 27.7 7 27 29 65 53 28.6 8 27 31 66 56 28

(53) TABLE-US-00004 Bubbler starting weight 1303 g ending weight 1304 g Cold trap starting weight 0 Ending weight 0 Beer starting weight 83 g ethanol + 952 g water = 1035 g (8% EtOH) ending weight 70 g ethanol + 931 g water = 1000 g (7% EtOH) Brine starting weight 701 g water + 1052 g LiBr = 1753 g (60% LiBr) Ending weight 13 g ethanol + 713 g H.sub.20 + 1052 LiBr = 1778 (59% LiBr)

(54) This test confirmed that the SAM can preferentially remove ethanol from an ethanol-water mixture and simultaneously cool the ethanol water mixture. It also indicated that a secondary absorber is a useful way to remove residual water and ethanol vapors from the vacuum train. The heat transfer coefficient for the device in this ran was calculated as 33 BTU/hr/ft.sup.2/ F.

(55) TABLE-US-00005 TABLE 4 Run 2 Time Beer Beer Brine Brine System Elapsed Input Output Input Output Pressure (min) C. C. C. C. mmHg 1 35 22 50 37 20 2 36 25 63 44 25 3 36 27 68 49 25 4 36 27 69 52 30 5 36 27 71 53 30 6 37 30 72 55 30 7 37 30 72 55 40 8 36 30 72 54 42 9 37 31 72 53 40 10 37 31 72 53 40 11 37 31 73 53 40 12 36 31 73 52 40 13 36 32 73 53 40 14 36 33 76 58 40 15 36 33 77 60 45 16 35 34 78 61 43 17 34 34 78 63 43 18 34 34 79 64 45

(56) TABLE-US-00006 Bubbler starting weight 1303 g ending weight 1304 g Cold trap starting weight 0 Ending weight 16.5 g ethanol + 16.5 g water = 33 g (50% EtOH) Beer starting weight 481 g ethanol + 1236 g water = 1717 (28% EtOH) ending weight 307 g ethanol + 1154 g water = 1462 g (21% EtOH) Brine starting weight 1239 g water + 1859 LiBr = 3098 g (60% LiBr) Ending weight 115 g EtOH + 1293 g H.sub.2O + 1859 g LiBr = 3267 (43% LiBr)

(57) This test also confirmed that the SAM device can preferentially remove ethanol from an ethanol-water mixture and simultaneously coot the ethanol water mixture. The heat transfer coefficient for the device in this run was calculated as 70 BTU/hr/ft.sup.2/ F. As the liquid distribution system in the test apparatus left unwetted much of the heat pipe surface area, this performance is viewed as relatively favourable. A more thorough liquid distribution can be expected to bring the coefficient in line with published values for commercial systems, which typically exceed 150 BTU/hr/ft.sup.2/ F.

(58) Whereas FIG. 1 shows a schematic SAM, it will be evident to persons of ordinary skill in the art that changes can be made.

(59) FIG. 7 shows one such possibility, namely, an arrangement wherein the heat pipes 26 are arranged parallel to a common axis X-X and the structure is adapted for pivotal movement about a horizontal axis Y-Y which is orientated normally to the common axis. It is contemplated that this arrangement could be used to periodically expedite clearance of liquid from the heat-delivering parts of the pipes.

(60) FIG. 8 shows another possibility, wherein the first volume 32 is defined by one or more first voids 32A, the second volume 34 is defined by one or more second voids 34A, each of the one or more first voids 32A and each of the one or more second voids 34A are defined by a respective vessel 130; and piping 132 defines the vapor passage 36. It is contemplated that this embodiment may have some usefulness in terms of reduced construction costs, as well as heat transfer efficiency [shorter heat pipes are normally better]. Discrete vessels render it possible to create substantial pressure differentials between the absorption and vaporization operations, and commensurate greater temperature differentials. A greater temperature differential would result in higher heat transfer through the heat pipes; this could have advantage in terms of capital costs, i.e. fewer heat pipes and smaller vessels.

(61) However, it should be understood that small pressure differentials could be created even within a SAM device of the type shown schematically in FIG. 1, by the interposition, for example, of a pump or fan in the vapor passage.

(62) FIG. 9 shows yet another possible SAM structure, wherein the vessel 21 is defined by a horizontally-orientated cylindrical vessel, the vapor passage 35 [indicated by arrows A] is defined by external piping (not shown) and the first volume 32 and second volume 34 are separated from one another by a vertical bifurcating wall 140. The wall is defined by upper 142 and lower 144 ridges extending interiorly from the tubular wall of the vessel 21. A rubber 148 sheet spans between the ridges 142 and 144 and is sandwiched between steel sheets 146 and 150 which are secured to one another by upper 156 and 152 lower webs. The rubber sheet 148 is perforated with holes to permit the heat pipes 26 to be passed therethrough in substantially hermetically sealed relation; the steel sheets 146,150 have corresponding holes, of larger diameter, to permit free passage of the heat pipes. Without intending to be bound by theory, this arrangement is believed to be advantageous from the standpoint of relatively low construction costs and simplicity in terms of maintenance; for maintenance, the operator would merely be required to remove one end of the vessel, and slide the entire heat pipe assembly out horizontally. Various bearings or rollers (not shown), could also be employed, if desired, to further simply construction. Further, whereas a single bifurcating wall is shown, the vessel could be segmented by two walls, each having heat pipes formed therethrough, to produce a structure having similar functionality to that shown in FIG. 8. In this two wall embodiment (not shown) the heat pipes could be angled, so that drop flow could travel back and forth in the chamber.

(63) Further, whereas specific operating conditions are delineated in the description relating to FIGS. 4 and 5, it will be understood that wide variations are possible.

(64) For example, in the context of an ethanol production facility, wherein the viability of the yeast is to be maintained on a continuous fermentation basis, at least the following ranges are contemplated to have utility: the broth withdrawn from the fermentation arrangement can have a temperature of about 28-32 C. and an ethanol concentration of about 4-10%; the remainder broth can have a temperature of about 2-4 C. lower than that of the withdrawn broth and have an ethanol concentration of about 2-4% less than that of the withdrawn broth; and the pressure in the first volume can be about 30-100 Torr.

(65) As well, whereas the structure of FIG. 5 is indicated to be useful for ethanol production, persons of ordinary skill in the art will readily recognize that the structure could be readily modified for handling other separations, notably but not limited to butanol and methanol. Indeed, the general structure of FIG. 5 could be useful for any catabolic reaction having a catabolic inhibitor capable of removal by absorption. Further, whereas the description references continuous production, it should be understood that this is not strictly necessary. In a batch ethanol operation, broth could be withdrawn from the batch tank while the fermentation is underway and passed through a SAM device, to withdraw ethanol. Removing ethanol from the batch would take stress off the yeast and could decrease cycle time and increase yield. As well, whereas in the context of ethanol and a LiBr brine, the thermodynamics are such that ethanol is withdrawn preferentially, i.e. at a higher concentration than the bulk, this is not strictly required for usefulness. In the context of an aqueous system, for example, wherein water and another component are being withdrawn, there could be occasions where it was acceptable that water was withdrawn in preference to the other component, and make-up water was added to balance flows. In this further regard, it should be understood that in this specification and the appended claims, liquid mixture means a liquid with another material mixed together, the other material may be liquid, such as alcohol, but this is not necessarily the case, as evidenced from, inter alia, the apple juice concentrator example.

(66) Further, whereas the secondary absorbers are shown in series with the SAM devices, it will be appreciated that this is not necessary. Secondary absorbers could be deployed in parallel, or omitted altogether in some situations.

(67) Additionally, whereas the distributors are illustrated schematically as perforated pipes, but it will be understood that sprayers or distribution trays, such as used in packed columns, could be used. The particular form of distributor chosen will vary, inter alia, with the geometry of the reactor and is a matter of routine for persons of ordinary skill.

(68) As yet another option, not shown, the structure of FIG. 5 could usefully be used as an adjunct to a conventional dry-mill corn ethanol plant. In plants of this type, the bottoms of the beer columns are typically sent to centrifuges, for the production of DDGS and other co-products. These bottoms contain unfermented C5 and C6 fermentable sugars, primarily cellulose and hemi-cellulose, which are difficult to process. Diversion of this bottoms stream to the structure of FIG. 5, for pre-treatment, hydrolization and fermentation, allows additional ethanol to be extracted from the original can feedstock, and this incremental ethanol production is carried out in circumstances that obtain the general benefits in energy efficiency previously mentioned. Without intending to be bound by theory, it is believed that this modification to an existing plant in this way can increase ethanol yield per bushel of corn; on a per bushel of corn basis, increase revenue from ethanol sales that substantially offset losses in revenue from decreased sales of DDGS and other co-products; increase production capacity of the main plant (in that fermentation residence time can be reduced in the main plant, since unfermented sugars will be captured in the add-on plant); and generally increase revenues that offset increases in costs.

(69) As another option, the SAM device could be replaced with a conventional liquid-liquid heat exchanger. FIG. 10 shows a tube 204 and shell 202 heat exchanger configured for this purpose. In this case, the flow of mixed liquid 242 would enter a manifold 206 on one side of the heat exchanger and travel through tubes 204 to manifold 208. During this travel, the mixed liquid, would be partially vaporized into a flow of vapor 230 and a depleted flow of liquid 234. The flow of vapor 230 is directed back into the shell 202, at 232. An entrainment separator 210 ensures that only vapor is directed to the shell 202. Strong brine 226 is introduced into the shell such that vapor 232 is introduced to the brine 226. Absorption of the vapor 232 occurs, as in the case of the earlier-described embodiments, producing a brine enriched in ethanol which exits the shell at 228. Gases 236 leaving the shell pass to an entrainment separator 222, to return any entrained brine to the shell at 238, and a vacuum pump 224 draws non-condensables from the shell to exit at 240. A blower 220 is used to create a pressure differential in the vapor flows between 230 and 232, to account for pressure drop in the system. This alternative could have some advantage in terms of capital costs. However, the vapor 230 is in substantial vapor-liquid equilibrium with the depleted flow 234, i.e. higher water content, which has disadvantage in terms of operating costs.

(70) Yet further variations on all the above would be readily appreciated by persons of ordinary skill in the art. Accordingly, the invention should be understood as limited only by the accompanying claims, purposively construed.