US 3249517 A
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Description (OCR text may contain errors)
APPARATUS FOR MULTI STAGE FLASH EVAPORATION Filed April l2, 1965 C. J. LOCKMAN May 3, 1966 5 Sheets-Sheet l ATTORNEY c. J. LocKMAN 3,249,517
May 3, 1966 APPARATUS FOR MULTI STAGE FLASH EVAPORATION 5 Sheets-Sheet 2 000000 ooo ATTORNE) v May 3, 1966 c. J. LocKMAN 3,249,517
APPARATUS FOR MULTI STAGE FLASH EVAPORATION Filed April l2, 1965 5 Sheets-Sheet 5 ATTORNE)I May 3, 1966 c. J. LocKMAN A 3,249,517
APPARATUS FOR MULTI STAGE FLASH EVAPORATION ATTORN E Y May 3, 1966 c. J. LocKMAN 3,249,517
APPARATUS FOR MULTI STAGE FLASH EVAPORATION Filed April 12, 1963 5 Sheets-Sheet 5 Tlc'- Tlc'jl- 200 200 MPO,? ran/[R V/l 200 l/PR TOPI/EA ff- ZZ BY ATTORNEY of the liquor.
3,249,517 APPARATUS FOR MULTI STAGE FLASH EVAPRATION Carl Johan Lockman, Rindogatan 14, Stockholm, Sweden Filed Apr. 12, 1963, Ser. No. 272,654 7 Ciaims. (Cl. 202-159) This invention relates to methods and apparatus in multi stage ash evaporation and is particularly concerned with such method and apparatus based on a new approach to multiple effect ash evaporation.
In all multi stage flash evaporators heretofore devised, the vapor generated at each effect is used to heat the ingoing feed by means of indirect heat exchangers. The vapor in the last effect is condensed in an indirect heat exchanger while preheating the feed liquor. The vapor from the next to the last effect preheats that liquor to a higher temperature and so on from effect to effect. The tempertaure of the liquor is, accordingly, raised step by step by the condensing of the steam or vapor resulting from the flashing from the last to the first effect in the evaporator. Finally, addition-al steam is supplied to heat the liquor further and to sufficient extent to cause it to flash in the first effect.
It will thus be seen that the principle behind the method and apparatus of the prior art is that of utilizing the heat from the vapor flashing from effect to effect to preheat the liquor to be ultimately returned to the system for flashing. Furthermore, this preheating is accomplished by the use of a series, often a large number, of indirect heat exchangers. The invention proceeds on quite a different basis and though accomplishing the same ends does so by following-different principles.
Multi stage flash evaporation in -accordance with the invention proceeds by directly condensing the vapor from each effect in, and by means of, the condensate from the succeeding effect. Thus it is the temperature of the condensate that is brought up by the ashing rather than that It is also done directly by means of direct heat exchange thus eliminating indirect heat exchangers.
yThe final hot condensate is then used to preheat the ingoing feed in a single, indirect heat exchanger.
Following the principles of the invention, flash evaporation maybe devised to carry out the method of the invention in a much more simple manner than required for the performance of prior art methods. Various forms of simplified apparatus may be employed, for all condensing heating surfaces for vapor generated during ashing are eliminated. Instead one central liquid to liquid indirect heat exchanger is used to recover the heat from the hot condensate.
It is, accordingly, the main object of the invention to introduce a new principle into the technique of multiple effect evaporation.
Another object is to provide a novel method in multiple effect evaporation.
Another object is to simplify and economize upon apparatus for effecting multiple effect evaporation.
Still another. object is to simplify and economize on the operation of multiple effect evaporators.
Further objects are to effect such economy of operation by reducing the power needed for the operation of multiple effect evaporators, by reducing friction losses, by reducing time needed for cleaning the -apparatus and by reducing maintenance work generally through simplification of construction.
More specific objects are to reduce the number of indirect heat exchangers to three, to substantially eliminate pumping losses, and to substantially eliminate automatic controls.
Further and more detailed objects of the invention VUnited States Patent O M Fatented May 3, 1966 ICC will in part be obvious and in part be pointed out as the description of the invention taken in conjunction with the accompanying drawing proceeds.
In that drawing:
FIG. l is a schematic View in most simplified form of a multiple stage ash evaporator employing the principle of the invention and for carrying out the method thereof.
FIG. 2 is a schematic elevational view of the presently preferred embodiment of the invention and for carrying out the method thereof wherein the arrangement is in the form of a vertical stack.y
FIG. 3 is an enlarged fragmentary vertical sectional view of one detailed form of construction employed in the schematic system of FIG. 2.
FIG. 4 is a horizontal section taken on line 4-4 of FIG. 3 and looking in the direction of the arrows.
FIG. 5 is an enlarged fragmentary section of the perforated plate as seen in FIG. 4, with one illustrative form of condensate distributor rods mounted therein.
FIG. 6 is a horizontal sectional view taken on line 64-6 of FIG. 5 and looking in the direction of the arrows.
FIG. 7 is a view similar to FIG. 3 showing a modified arrangement for transporting the condensate from effect to effect.
FIG. 8 is a schematic elevation of another embodiment of the invention.
FIG. 9 is a front elevation of a further modification of stack or column in accordance with the invention.
FIG. 10 is a section thereof on lie 10-10 of FIG. 11,
FIG. ll is a top plan View thereof.
Through in the description to follow with reference to the accompanying drawing, methods and various forms of apparatus will be described and are illustrated embodying the invention, it is to be understood that such are for illustrative and not limiting purposes.
In the basic arrangement illustrated schematicallyin FIG. l, a multi stage or multi effect evaporator is shown having only four effects,l illustrated by rectangles and carrying respectively the reference characters 1, 2, 3 and 4 to identify the effects as the first, second, etc. For
economical operation a considerably greater number of effects would be employed with less pressure and temperature change from effect to effect, but, purely for illustartive purposes, the showing of four effects as here is adequate.
Commencing then at the left hand side of FIG. 1, it is seen that the feed comes in through the conduit 5 while the final product is taken out through the conduit 6 at the opposite end of the system. As against the total flow of liquor in the system, however, the amount of product withdrawn is only a minor portion. Further than that, since a considerable portion of the liquid is recirculated, the makeup from the feed is likewise small in proportion.
As the feed enters theA circulating conduit system at 7, and assuming that it is spent liquor from a pulping operation though the invention is by no means limited to the evaporation of such material, the liquor would be introduced, for example, at a temperature of F., and would ifow into the heat exchanger 8 where it would be heated up in indirect heat exchange relation by the mixture of circulating condensate and condensed ashed vapors coming from the hottest effect of the system, thus being at the highest temperature. Assuming then that the mixture of condensate and flash vapors before entering the heat exchanger at 8 had a temperature of approximately 255 F. when entering the heat exchanger 8 through the conduit 9, the liquor would emerge from the heat exchanger through the conduit 10 at a temperature of approximately 250 F. and would right away be introduced into another indirect heat exchanger 11 where it would be further heated by live steam entering through the conduit 12 and flowing off as condensate through the conduit 13. The liquor, now raised to a temperature of approximately 275 F. is introduced into' the first effect through the pipe 14.
The liquor, indicated at Z, flashes in the first effect 1, with the vapors V forming in the vapor body and passing through the conduit 15 at a temperature of approximately 260 F. These hot vapors mix with the condensate pumped into the direct heat exchanger i6 through pipe 1'7 by pump 17a. The condensate in the heat exchanger 16 would already have been heated to high temperature in condensing vapors from previous fiashings. For the purpose of illustration this temperature could be `considered as being about 198 F. After condensate at that temperature was mixed with and condensed the vapor at 260 F., from the first effect, the resultant mixture would have the temperature of about 255 F. at which temperature it would flow through the conduit 9 by the action of the pump 9a into the heat exchanger 8.
Proceeding on down the system, liquor from effect 1 ows through the conduit 1S to the second effect, or flashing chamber 2, where vapors hash at about 200 F., and flow through the conduit 19 into the direct heat exchanger or mixer 20 at the next lower temperature down the line. Here again the ashed vapors mix with and are condensed by condensate pumped in by pump 2in in the conduit 21 at a temperature of approximately 148 F. Next, the liquor, l, from effect 2 fiows through the conduit 22 into effect 3, ashes at approximately- 150 F. and the flashed vapor flows through the conduit 23 into the next heat exchanger 24 where it mixes with condensate pumped in through the conduit 25 by pump 25a at the next lowery temperature, in this case approximately 98 F. The fiashing vapors heat this condensate approximately 50 F. in the course of giving up their heat and being condensed.
Finally, as here illustrated, liquor from the Vthird effect flows through the conduit 26 into the fourth effect, flashes therein at a temperature of approximately 100 F., the Vapor flows through the conduit 27 into the heat exchanger 2.8 and gives up its heat therein to heat the condensate, coming through the conduit 29, from its initial temperature of 90 F. to a resultant temperature of about 98 F.
The remaining liquor l from the fourth effect 4 flows outthrough the conduit 30, returns to the pump 31 and then is pumped around through the pipe section 32 back into the initial indirect heat exchanger 8. 'of passing through the pipe section 32 some of the liquor may be drawn oif as feedproduct through the pipe 6 and the remainder may be diluted by additional feed brought in through the pipe 5.
Considering next the condensate mixture emerging from the indirect heat exchanger 8, it loses substantial heat to the liquor in that heat exchanger to the extent that as it flows out through the return conduit 33, its temperature has dropped to approximately 110 F. This is still not low enough for use as a coolant starting again at the fourth stage. Accordingly, the condensate mixture is first introduced into a storage or overow tank 34 from the bottom of which it is pumped by the pump 35 into the third and nal indirect heat exchanger 36. Here it is further cooled in indirect heat exchange with cooling water flowing in through the pipe 37 and out through the pipe 38. This cooling results in dropping the temperature of the condensate from its arrival temperature of 110 F. to its leaving temperature of 90 F.
As a supply of condensate mixture builds up in the tank 34, the level of it will be controlled by a level responsive device, which, through the ,control line 39, controls the operation of a valve 40 positioned in a line 41 in communcation with the portion 42 of the conduit extending between the pump 35 and heat exchanger 36. Thus, depending upon the position of the valve 40, part of the condensate will be pumped out of the system through the conduit 41.
In the course It is apparent from the foregoing description of a simple illustrative basic embodiment of the invention that in spite of the fact that the evaporator is of a multi effect type, the use of indirect heat exchangers is reduced to three, and instead of the flashing vapors serving to heat the liquor circulating in the system, they heat the condensatev in direct heat exchange relationship and are mixed with it. When that mixture reaches its highest temperature it is utilized for heating liquor to a substantial extent in one step in a indirect heat exchanger.
Though in the descriptive embodiment of a basic system of the invention as broadly illustrated in FG. l, approximate temperatures have been given at the various stages it is to be understood that these are merely intended to indicate the general manner of operation of the system and are in no sense limiting, for the temperatures and temperature differentials, as well as pressures, will vary in regard to a number of factors in a manner well understood by those skilled in the art.
In FIG. 2 the new principle of the invention is shown as Iapplied to a multiple effect evaporator formed in a vertical column or stack. Here, eleven effects are iliustrated with a portionv being broken away to show that additional intermediate effects have been omitted to save space. Further, it is to be noted that the liquor at highest pressure and temperature is introduced into the bottom of the column and proceeds upwardly hashing as it goes, as will be described. The condensate, however, and the flashed vapors mixing with it, moves down through the column. The column as seen widens in its upward extent.
Starting then at the position where feed is introduced Vinto the system as was done in FfG. 1, the introduction here is through the pipe 45. There the feed joins with liquor returned after fiashing in the last effect through the pipe 46. The total composite liquor fed is pumped by means of the pump 47 through the indirect heat exchanger 48 where it is reheated in indirect heat exchange with hot condensate flowing from its last effect of the column through the pipe 49. The liquorso heated ows from the heat exchanger 4S up the pipe 50 and through the indirect heat exchanger 51 where it is additonally heated vby means of raw stream introducedat 52. The condensate from that steam flows off at 53 after passing the steam trap 54. Liquor thus heated ready for ashing is introduced into the first effe-ct through the side wall 55 of the vapor body.
The effects in FIG. 2 are designated by the letters A to M with A designating the first effect at the bottom and M the last effect at the top.y Effects, F, G, and H have been omitted to save space.
Referring now for detail to FIGS.V 3, 4, 5 and 6, which show one specific structure for enabling the liquor to flow upwardly and the condensate and condensed dashing vapors to iiow downwardly, the side walls of the vapor bodies, which may be parts of one continuous cylinder except where it enlarges outwardly as shown at 55 and 57 in FIG. 2, carry the reference character 55 as in FIG. 2. Considering then the lowermost effect in FIG. 3 as being the third effect up from the bottom in FIG. 2, and thus being effect C and, appreciating the structure of the effect C is common to all, it follpws that this is the only effect that needs to be described in detail.
The inner wall of the effect is formed with a bottom portion as an outwardly and downwardly inclined annulus S8 tightly joined with the wall 55 at 59 and terminating at its inner periphery in an upwardly extending cylindrical portion 60. At the upper end of the cylindrical portion 60 the wall extends upwardly and outwardly again in an annular portion 61 which, however, terminates in a short upturned cylindrical collar 62 at a position spaced radially inwardly from the side wall 55 leaving an annular passage 63 for the ow of flash vapor.
A circular plate 64 is secured at 65 in yleak-tight engagement with respect to the side wall 55 where the inclined bottom 58 of the next effect also joins that wall. This able this to take place.
plate 64, as seen in FIGS. 4-6, is provided from a position closely adjacent its outer periphery inwardly with a multitude of holes 66 therethrough forming a pattern of concentric rings. These holes 66 serve to allow condensate to flow down through the plate. They are advantageously equipped with distributor rods having shanks 67 of considerably less diameter than the holes 66, but having heads in the form of outwardly flaring cross shaped formations 68.' The lower portions of the inclined sides 69 of these formations 68 readily pass through the holes 66 but the upper larger portions thereof are larger than the holes so serve to mount the r'ods in place. Being madein the form of a cross, however, the heads 68, as best seen in FIG. 6, leave substantial passages 70 for condensate to flow down through the hole 66 and down theA outside of the rod 67. The purpose of these rods is to slow down the flow of condensate and distribute it all around the surface of the rods 67 to bring a large area of condensate into contact with the flashed vapors flowing up through the passage 63. Such vapors will, accordingly, condense, mix with the condensate, flow down the wall portion 61 into the cylinder 60 and then repeat the process of flowing down through the holes 66 in the lower plate 64 along its rods 67.
Before passing from this plate construction it is to be noted that the rings of holes do not continue all the way into the center of the plate but that, at its center portion, the plate has a single larger hole 75 therethrough to receive the-end of the pipe 76. This pipe extends up to above the normal level of the condensate within the cylv inder 60, as seen at 77, and is suitably capped at 78 to prevent liquid-from flowing down through it, but, at the same time, is open around the cap so that non-condensable gases can escape. Thus such gases nd their way up through the opening 75 in the next plate above and the next pipe 76 and so on out through the top of the system.
Though the liquor in the lowermost effect A is under the highest temperature and pressure, and accordingly has a tendency to flow from effect to effect up the stack, the temperature and pressure are not quite sufficient to en- Accordingly, provision is made for liquor to flow out from each effect through a large pipe 79 extending through the side wall 55. This pipe79 turns downwardly and is provided at the bottom with a chambered portion 80, which may be removable by means of a flange connection 8-1 if desired. A smaller upflow pipe 82 is centered with respect to the downwardly extending portion 83 of the pipe 79 and this pipe 82 extends up out of the pipe 79 to where it becomes the same as the end of the pipe 50 as seen in FIG. 2 and extends into the interior of the effect D.
At its bottom the pipe 82 terminates in a frusto-conical downwardly and inwardly inclined portion 84 which serves as a valve seat for a float member 85 of complementary frusto-conical contour. When, however, the float member 85 is dislodged upwardly from its seat, as shown in dotted lines in FIG. 3, such unseating being due to the level and pressure of the liquor 1 in the effect C, float 85 is unseated upwardly. This enables some of the liquid to flow up into the' pipe portion 82 and since the pressure on that liquor is reduced, due to communication of the pipe 82 with the vapor body of the next effect, the liquor flashes to a certain extent, creates a turbulence and builds up pressure of its own. This provides the necessary additional lift to cause the-liquor to flow up and into the next effect through the pipe section 50. Due to the flashing the liquor that flows in this manner is a two phase mixture which has its specic gravity somewhat reduced.
The same arrangement and operation prevails from effect to effect through the height of the stack. Liquor introduced through the pipe 50 into the last effect M will flash and, after such flashing, the remaining liquor will collect and will flow back down through the pipe 46.
If the level of the liquor collecting in the last effect is lupward flow of flashed vapors.
high enough, level control 86 will act through the control line 87 on the valve 8S to allow some of the liquor to flow off as product through the pipe line 89. The remaining liquor with additional feed returns to the heat exchanger 4S through the lpump 47 as already explained.
As regards the non-condensable gases they pass out of the system through the line 90 at the head of the stack and the vacuum pump 91. v
Condensate at its hottest stage coming down through the pipe 49 is pumped by the pump 93 through the heat exchanger 4S, in which it los-es a substantial portion of its heat while heating cold'liquor. Coming out-of the indirect heat exchanger 48 the condensate flows through the pipe 92, and is further cooled by passing through the indirect heat exchanger 94 where it is'cooled in indirect heat exchange withcooling water entering through the pipe 95 and flowing out through the pipe 96. The condensate continues up ythe pipe 92 and is reintroduced through the pipe section 92a into the domed top 94 of the uppermost effect M. The condensate then commences its return down'through the stack yas already fully described. g
A. somewhat modified construction of the effects and of the operating means for the same is shown in the fragmentary vertical section in FIG. 7. It is to be understood that the structural detail here shown is applicable to a multi stage vertically disposed evaporator as illustrated in FIG. 2 with the specific structures in FIG. 7 being alternatives to their counterparts in FIG. 3.
In the FIG. 7 construction, rather than place reliance upon the flashing of a portion of the liquor Ato cause it to flow from effect to effect of the stack, the flow is brought about positively. Considering then the specific details of one effect denoted CC and understanding that the other effects in FIG. 7 are just the same, the cylindrical side wall has a pipe 101 extending through the wall thereof at 102 for the purpose of introducing liquor into the chamber 103 for flashing. This chamber has a frusto conical outwardly and downwardly inclined bottom wall 104 joined to the side Wall 100 and a frusto conical upwardly and outwardly inclined top wall 105 terminating in the vertical cylindrical collar portion 106 spaced from the wall 100. This provides an annular passage for the A perfor-ated plate 108 substantially the same as the plate 64 in the FIG. 3 form is positioned above the upper edge of the wallO 106 and is secured tightly in place to the wall 100 along with the periphery of the bottom 104 of the next effect. This plate has rods 67 carried in its perforations in the manner as shown in FIGS. 5 and 6.
One minor difference in this construction is that the plate 108 has an off center aperture therethrough at 109 to receive the vent pipe 110 for the venting of the noncondensable gases. This pipe passes up off center through the bottom 104 of the next effect and through the top 105 of the same, and has a trap 111 at it's top the same as the pipe 76 of FIG. 3. y
The significant difference between this form and that of FIG. 3 is that instead of the condensate mixed with newly condensed vapor flowing downfrom effect to effect of its own accord, it is pumped' down. Thus in FIG. 7 the top 105 of each effect has a conduit 112 communicating through the center portion thereof with the receptacle for condensate formed by the walls 105 and 106. Wall 106 is spaced inwardly from Wall 100 to form an annular space 107. The conduit 112 extends out through the wall 100 to a pump113 from which another conduit 114, below the conduit 112, extends back in again through the wall 100 and communicates at 115 through the center of the bottom wall 104 of the effect in question. The pump 113 acts to pump condensate from the receptacle above the wall 105, through the conduit 112, downwardly through the pump and back inwardly through the conduit 114 discharging that condensate mixed with condensed vapors into the effect below.
There is one of these pumps for each effect and due to their presence the pressure difference between the effects is not determined by the geometry of the condensate tower, but can be positively determined by the pumps. Thus the liquor l in the bottom of each effect has sufficient of a pressure head behind it to cause it to flow out through the pipe 116 and up to the next effect where it is introduced for flashing throughthe wall 1116, as seen at 117. According to the arrangement of FlG. 7 then, the liquor is passed from effect to effect without reduction in specific gravity by going to two phase flow. However, more pumping, pump connections and pipe connections are needed.
The alternative illustrated somewhat schematically in FIG. 8 differs generally from the form of FIG. 2 in that the vapor bodies and the direct condensers are built in the form of two separate towers. Also the flow of liquor in the Vapor body tower is downward instead of up. This embodiment avoids any problem in the transfer of liquor from one effect to the next in that the liquor flows from a higher pressure effect to a lower pressure effect directly below it. The two phase transfer of liquor from one effect to the next is accordingly eliminated through the pumping horsepower is increased and vapor piping is also necessary.
The two towers shown in FIG. 8 are designated generally by the letters R and S. .Tower R is merely concerned with the condensing of the flash vapors and causing the mixture of condensate and cooling liquid to flow from effect to effect down through the tower. ln the course of that flow the mixture is heated more and more until it is taken off from the bottom of the tower at its highest temperature through the pipe 125. From that pipe the condensate is pumped by the pump 126 through the indirect heat exchanger 127 where it gives up its heat to the cool liquor entering through the pipe 128. The liquor when heated up returns through the pipe 129 with some of it being taken off as product, if desired, through the pipe 130 and the remainder continuing on upwardly.
At the position 131 fresh feed may be added as a result of the action of the level control 132 which. responds to the level indication given it through the line 133 and in turn acts to control the valve 134 thus allowing more or less fresh feed to be introduced as needed. The line 129 then contains heated recirculating liquor possibly mixed with some -amount of fresh feed. This mixture is heated further in an additional indirect heat exchanger 135 by means of live steam introduced at 136 and flowing out together, the stages of the liquor tower have been designated from effect to effect in FIG. 8 by the capital letters from A to G each carrying L (for liquor), as a sulllx. The related units in the :condensate tower lalso carry the letters from A to G, but in this instance with the sulllx C (for condensate). Similarly, the vapor lines connecting the vapor bodies of the liquor tower with the vapor chambers of the units of the condensate tower have been designated by the letters A to H carrying the suffix V (for vapor).
The liquor at the highest temperature and pressure in troduced at 139 into the vapor chamber 140, of the unit AL, collects in the bottom of the unit as indicated at l, after a certain portion of it flashes. The portion which flashes flows off through the vapor conduit AV communicating with the condensing unit AC of the condensate tower at the position 141. Here as in the previous forms the hot vapors come into contact with condensate flowing down rods 67 loosely carried in openings in a plate 64 all of the same general nature as the plate in FIGS. 3-6.
Again, where the plate 64 meets the cylindrical shell 142 of the tower at 143 it is tightly joined thereto as is the periphery of the portion 144 of the condensate receptacle. This condensate receptacle continues upwardly from the wall 144 in a reduced cylindrical portion 145 and then flares outwardly in an upwardly and outwardly directed frusto conical portion 146. In this instance the periphery of the portion 146 makes a tight joint with the shell at 147 since vapor is introduced from the side rather than from below. Thus condensate mixed with condensed vapor as a result of the condensing action in the unit BC collects in the receptacle formed by the walls 145, 144, until it passes through the holes in the plate 64 and comes into Contact with the vapor AV in the unit AC. The mixture of condensate and condensed vapor from the unit AC at the bottom of the stack merely collects in the cylindrical receptacle 148 from which it flows off through the pipe to give up its heat as described at the outset thereof.
Returning now to the liquor tower, each of the effects from AL down through GL in this tower has a perforated bottom 151i. Thus while a certain amount of the liquor introduced at 139 into the eect AL flashes and passes off through the conduit AV, the remainder, which is being continuously replenished, feeds` down through the `perforations in the bottom 151i. As it does so it flashes in the free area of the unit BL with the result that the flashed vapors pass off through the vapor conduit BV, enter the condensate receptacle BC and are condensed by the condensate flowing down the rods 67. therein as just described.
Again the liquor collecting in the bottom of the unit BL flows down through the perforations in its perforated bottom 150, flashes again in the unit CL where the temperature and pressure are still lower. This action repeats on down to the bottom of theA liquor tower S while at the Same time the vapors ilashand go over into the cornplementary units in condensate tower R. 'Ihese stages all being the same it is not necessary to repeat the description. v
The liquor collecting in the bottom chamber 151 of the liquor tower flows out through the pipe 152 and is pumped by the pump 15251 into the heat exchanger 127 where it reheated as already described. The condensate coming from the heat exchanger 127. after having given up its heat, and due to the action of the pump v126, flows through the line 153 into another indirect heat exchanger 154 where it is further cooled in contraflow relation with respectfto cooling water entering the heat exchanger at 155 and flowing out at 155a.
Since the volume of condensate present 'increases as time goes on, provision is made for drawing a portion of it off in response to the level of it in the ilnal receptacle 148. Thus a level control responsive to the condensate level in the receptacle 148 acts through the line 156 and control device 157 to control the opening and closing of the valve 158 in the run-off line 159. The line 159, as seen, is connected with the condensate return line 153 at a position where the condensate has been fully cooled. This condensate taken olf can of course be utilized for cooling in other activities. The remaining cooled condensate in the line 153 -is reintroduced into the head of the vapor tower at 154 where it becomes effective in the unit HC to commece the condensing of the ashed vapors, in this instance receiving the coolest of those vapors through the pipe HV from the bottom unit HL of the liquor tower.
One other point to note is that the vapor tower R, like the vapor towers of FIGS. 3 and 7, has vent pipes'160 in each effect for venting off the non-condensable gases. The composite non-condensable gases are taken off from the top of the effect HC throughpthe pipe 161, which pipe connects with a vacuum pump 162. While a vacuum is being pulled by this pump the non-condensable gases are taken off and either vented to atmosphere or are conducted away to be utilized elsewhere.
' effect directly below it. Again, however, flashing vapor vfrom the liquor is used to heat condensate in direct heat exchange relationship as against the prior art practice of heating liquor by such vapor in indirect heat exchange relationship. Finally, in this embodiment also the combined condensate and condensed vapors act in the one.
indirect heat exchanger 127 to give off their heat in the preheating of the liquor.
In FIGS. 9-11 there are shown the essentials of a further modification which, however, operates in the same manner as the modification of FIG. 8 and is nothing other than a vapor tower, generally the same as that of FIG. 8, but with the liquor tower wrapped around it at its midposition in a radially segmented, or compartm-ented, torus.
Considering first the aspects of the vapor tower, illustrated generally at 200, it, like the vapor tower of FIG. 8, is shown as having eight units which are coupled to eight units made up out of the compartments of the liquor containing torus. The vapor pipe from the hottest liquor unit opens into the condensing unit wherein the condensate present has been heated to the greatest extent. In FIGS. 9-l l, for convenience sake, Athe units of the vapor tower starting from the first effect, or the hottest end, have been designated respectively by the reference characters 201-208 inclusive. The torus, generally-indicated at 209, has its segments related to the units of the vapor tower respectively indicated by the characters 211-218 inclusive. The liquor in this system is under sufficient pressure that it will flow from each compartment under higher pressure into the vapor space of thenext liquor compartment where the pressure is lower. This is done by the same piping arrangement of the angled pipe 219 in each instance.
The pipes which lead the flashed vapors from the flashing chamber in the segmental liquor compartments to the condensing areas in the condensate tower to the extent that they are visible in the drawings are given numbers from 221-228 inclusive, the last'digits of their numbers corresponding respectively with the last digits of the numbers given to units of the vapor tower as well as to the numbers given liquor compartments. The pipe 221 has its upper end well above the level of the liquor in the compartment 21.1 the same as is shown for the pipe 223 in FIG. 10. The pipe 221 extends down through the bottom of that compartment and in through the side wall of the condensing unit 201, Thus the pipe 221 introduces flashed vapor into the annular portion surrounding the upper and lower frusto conical and annular partition walls 231 and 232. This vapor comes into contact with condensate flowing down rods 67 loosely carried in the holes in the bottom 64 of the cylindrical condensate collecting chamber 232. The rods 67 and bottom plate 64 are in cated inan exact showing. Pipe 228 extends upwardly from segment 218 into the vapor unit of the uppermost effect 208- as is seen in FIG. 9. Again provision for reheating liquor, cooling condensate, taking off product, adding feed, disposing of non-condensable gases etc., is made in conjunction with this embodiment in generally the same manner as in FIG. 8 so the detail of it need not be repeated. Furthermore, it is believed that the manner of operation of this embodiment has been made apparent from the description of the embodiment itself, particularly when taken in conjunction with the description of the prior embodiments.
Though in the foregoing, the presently preferred and several alternative forms of apparatus have been disclosed in order to show how the novel principle of the invention may be performed in terms of method as Well as in terms showing, or description. Those skilled in the art on consuitable manner comparable to that shown and described in FIG. 8. Similarly the pipe 222 conducts vapors from would be largely behind pipe 227. To enable it to be seen more readily it has been moved radially inwardly in the FIG. 10 showing. Similarly, in FIG. 9, pipe 227 has been moved out from behind pipe 22S where it would be losidering this disclosure might well devise variations and modifications embodying the principle of the invention without however departing from the spirit and scope thereof as set forth in the claims to follow.
Speaking more generally, since certain changes in carrying out the above method and in the constructions set forth, which embody the invention may be made without departing from its scope, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not yin a limiting sense.
Having described my invention what I claim as new and desire to secure by Letters Patent is:
1. In multiple effect evaporation apparatus, an assembly including means providing a series of stages for the flashing of liquor, said stages being disposed at different levels, means for moving unflashed liquor progressively upwardly from stage to stage, means including condensing stages for condensing vapors resulting from said flashing in direct contact heat exchange relationship with a cooling medium and in stages connected to corresponding flashing stages, means to move the resulting condensate in the condensing stages progessively downwardly, the means moving unflashed liquor progressively upwardly from stage to stage comprising means employing the pressure resulting from the flashing of liquor in a stage to move the liquor to the next higher stage, each of the condensing stages having a floor, said floors forming roofs disposed above the respective next lower flashing stages, each of' said floors having a plurality of passages therein for the flow of cooling condensate therethrough, and means for conducting flash vapors from each lower stage upwardly into contact with the floor thereabove adjacent the passages therein.
2. Apparatus as in claim 1, wherein said passages'are located adjacent the periphery of the floor, and the. means for conducting flash vapors is an annular means disposed beneath the floor below and adjacent the passages in the floor.
3. Apparatus as in claim 1, comprising means at each of said floors for enhancing the contact of flashed vapor with condensate flowing through the passages.
4. Apparatus as in claim 3, wherein said contact enhancing means comprises a plurality of rod-like members depending from the floor adjacent the passages therein whereby condensate flows through the passages to form films on the rod-like members.
5. Apparatus as in claim 4, wherein said floor has a plurality of holes therethrough, the rod-like members have enlarged heads, extend through the holes, and are supported by engagement of the heads with the upper surface of the floor, the holes and the rod-like members being of such configuration as to provide said condensate conducting passages therebetween.
6. Apparatus as in claim S, wherein a portion of the head of each rod-like member lies within its respective hole in the floor, such portion of the head being fluted.
'7.Apparatus as in claim 6, wherein the heads of th rod-like members are tapered to converge downwardly, the upper end of the head having a diameter larger than that of the hole in the oor.
7References Cited by the Examiner UNITED STATES PATENTS Ray et al 159-18 Follain.
Peebles 159-2 Christensen 159-18 X Crews 159-18 Chambers 159-24 X Lockman.
Lockman 159-20 Worthen et al 159-20 X Lockman et al 159-20 X Ramen 159-18 Bethon 159-20 X Badger. Nilan 159-2 X Silver 159-2 X Williams 159-18 X FOREIGN PATENTS 12/1960 Canada.
Germany. Great Britain.
OTHER REFERENCES Kuwait Chem. Engg., October 1956, pages 126, 128,
' NORMAN YUDKOFF, Primary Examiner.
I. SOFER, Assistant Examiner.