US3689366A

US3689366A - Flash distilling apparatus with buffer plates arrangement

Info

Publication number: US3689366A
Application number: US33852A
Authority: US
Inventors: Hiroyuki Satone
Original assignee: Hitachi Zosen Corp
Current assignee: Hitachi Zosen Corp
Priority date: 1969-05-01
Filing date: 1970-05-01
Publication date: 1972-09-05
Anticipated expiration: 1989-09-05
Also published as: GB1307717A; FR2052359A5; DE2020580A1; DE2020580B2

Abstract

A flash distilling apparatus utilizing high and low pressures and temperature differences characterized in that by positively imparting agitations to a stock solution flowing in a flash chamber portions of the stock solution existing in regions lying deep and having higher pressures than the saturated vapor pressure owing to their static pressures are forced to move to the vapor-liquid interface, thereby making it possible to utilize differences in the sensible heat of the solution due to pressure differences between flash chamber compartments for effective evaporation.

Description

p 5, 1972 HIROYUKI SATONE 6 3,689,366

FLASH DISTILLING APPARATUS WITH BUFFER PLATES ARRANGEMENT Filed May 1, 1970 5 Sheets-Sheet 1 PIC-3.1

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IN VEN T OR.

' ll/RO/UK/ J/ITO/Vf ATTORNEYS Sept. 5, 1972 Filed May 1. 1970 HIROYUKI SATONE 3,689,366

FLASH DISTILLING APPARATUS WITH BUFFER PLATES ARRANGEMENT 5 Sheets$heet 2 ma" A36 4 v M 7) Ma /49 AM /J4 INVENTOR.

ATTORNEYS FLASH DISTILLING APPARATUS WITH BUFFER PLATES ARRANGEMENT Filed May 1, 1970 Sept. 5, 1972 HIROYUKI SATONE 5 Sheets-Sheet 5 INVENTOR. 4/20 VZ/K/ 5/! 70/1/15 ATTORNEYS p 5, 1972 HIROYUKI SA'YTONE 3,689,366

FLASH DISTILLING APPARATUS WITH BUFFER PLATES ARRANGEMENT Filed May 1, 1970 5 Sheets-Sheet 4 'ATTOR NEYS p 1972 HIROYUKI SATONE 3,

FLASH DISTILLING APPARATUS WITH BUFFER PLATES ARRANGEMENT Filed May 1, 1970 5 Sheets-Sheet 5 FIG.6

AZ; /34 A96 INVENTOR.

////?O)(//F/ JATO/Vf ATTORNEYS United States Patent Office Patented Sept. 5, 1972 ABSTRACT OF THE DISCLOSURE A flash distilling apparatus utilizing high and low pressures and temperature differences characterized in that by positively imparting agitations to a stock solution flowing in a flash chamber portions of the stock solution existing in regions lying deep and having higher pressures than the saturated vapor pressure owing to their static pressures are forced to move to the vapor-liquid interface, thereby making it possible to utilize differences in the sensible heat of the solution due to pressure differences between flash chamber compartments for effective evaporation.

BACKGROUND OF THE INVENTION Among processes known heretofore, for evaporative recovery of a liquid from a solution are the immersed tube heating evaporation process and multi-stage flash process. Thus, evaporation by said flash process is effected on the principle that the vapor pressure in the flash chamber is lower than the saturated vapor pressure corresponding to the temperature of a solution entering the flash chamber. Therefore, as the temperature of the solution decreases, the pressure varies for decrease corresponding to the change in temperature, as shown in the following table.

TABLE OF SATURA'IED VAPORS.-(21-70 C.)

Thus, a change of :1 C. at a water vapor temperature of 70 exhibits a change of i125 .66 mm. H O at its saturation pressure P70, whereas a change of il C. at a water vapor temperature of 21 C. exhibits only a change of 1:16.32 mm. H O at its saturation pressure P21.

.Further, in evaporating the flowing solution in the flash chamber, it is possible to evaporate the top solution layer by utilizing the pressure difference between the pressure in the flash chamber and the saturation pressure corresponding to the temperature of the solution (excluding the pressure component resulting from boiling point raising depending upon the solution concentration) but as stages. Therefore, with water at 21 C. used, evaporation 7 becomes unable to proceed any further at a' depth of about 32.7 mm. below the surface when the temperature difference between compartments is 2 C. and at a depth of about 49.0 mm. when said temperature difference is 3 C. The lower the pressure, the shorter the distance from the surface where this suppression of evaporation due to static pressure takes place.

The present invention is intended to provide a distilling apparatus which prevents said phenomenon, i.e. the amount of evaporation decreasing due to the static pressure of a deep flowing solution, and which allows a difference in sensible heat resulting from a pressure difference between flash chamber compartments to be effectively utilized for evaporation.

SUMMARY OF THE INVENTION The present invention provides a flash distilling apparatus utilizing high and low pressures and temperature differences, characterized in that in order to decrease the degree of superheat of a stock solution, agitations are imparted to the stock solution, besides the evaporating action due to the internal energy of the stock solution thereby promoting evaporation.

By imparting agitations to the stock solution as described above, portions of the stock solution existing in regions lying in deep layers and having pressures higher than the saturation pressure as a result of their static pres sure, i.e. portions of the stock solution existing in regions where evaportion is to be suppressed by their static pressures are forced to move to the vapor-liquid interface, thereby eliminating or decreasing such suppression of evaporation to decrease the degree of superheat of the solution on the average even in deep layers, so that the difference in sensible heat resulting from a pressure difference between flash chamber compartments can be effectively utilized for evaporation.

As for means for imparting agitations to the stock solution, various methods are proposed including one in which agitation is effected by rotary agitating means, one in which agitation is effected by increasing the delivery pres sure of a booster pump or stock water feed pump and increasing flow resistance by buifer plates and one in which a great flow resistance is imparted to buffer plates by a difference in potential energy besides a difference in saturation pressure by providing a sufficient head (in particular, a difference in the level of stock solution) between places of installation of low pressure stage flash chambers and by increasing the delivery pressure of a stock solution feed pump.

In particular, in a case where buffer plates are curved and agitations are imparted by said curved buffer plates to a flowing stock solution in such a manner thatthe upper and lower layers of the stock solution change places with each other, to promote the evaporation of said stock solution, it is possible to decrease the degree of superheat in the flash chamber on the average without imparting a great flow resistance.

Further, in a case where in order to decrease the degree of superheat of a stock solution the flash chamber bottom surface or the like is inclined to increase the flow agitating action on the stock solution and promote evaporation, this inclined construction makes it possible to promote the flowability of the stock solution between said flash chamber compartments even if the amount of stock solution fed to the flash chamber is decreased. Thus, because of a small amount of stock solution with good flowability, it is possible to promote the agitating action on the stock solution, so that the difference in sensible heat of the aqueous solution due to the pressure difference between the flash chamber compartments can be effectively utilized for evaporation and the evaporating action can be promoted and the degree of superheat of .the stock solution can be decreased.

3. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary plan view showing a flash chamber bottom surface having special buffer plates;

FIG. 2 is an elevational view explanatory of the function of the buffer plates shown in FIG. 1;

FIG. 3 is a schematic elevational view of an apparatus according to the present invention having an inclined flash chamber bottom surface;

FIG. 4 is a schematic elevational view showing the modification of the arrangement shown in FIG. 3 into a multi-stage type;

FIG. 5 is a system diagram of an apparatus according to the present invention which is combined with a steam condenser and makes it possible to supply a stock SOllltlOil to a flash chamber without utilizing any pump;

FIG. 6 is a system diagram showing an arrangement wherein an apparatus according to the present invention having rotary agitating means is combined with a steam condenser;

FIG. 7 is a system diagram showing an arrangement wherein an apparatus according to the present invention having a booster pump and buffer plates is combined with a steam condenser; and

FIG. 8 is a system diagram showing the modification of the arrangement shown in FIG. 7 into a multi-stage e. typ DESCRIPTION OF THE PREFERRED EMBODIMENTS First embodiment FIGS. 1 and 2 show only the brine flow section, i.e. a region adjacent the bottom of the first stage flash chamber of an apparatus for converting sea water into fresh water by flash process. It is to be noted that the demister above the flash chamber, the condenser and circulating liquid heater, etc. are omitted since they are known per se and have nothing to do with the gist of the present invention.

The numeral 1 denotes a stock brine feed tube and the numeral 2 denotes a flash chamber surrounding wall. Brine 4 having undergone a process inside said flash chamber surrounding wall 2, i.e. in the chamber interior 3, will be transferred to the next process or discharged though conduits 5. The numeral'6 denotes a buffer plate for the flowing brine 4, such buffer plates being fixed to and projecting from a bottom surface 7 in a plurality of rows each comprising a plurality of buffer plates arranged widthwise. As shown in FIG. 1 the buffer plates 6 are arranged at an angle of about 45 degrees with the imaginary direction of flow of the brine 4 along a line which connects the feed tube 1 with the conduits 5, in such a manner that the rows of buffer plates stagger alternately with respect to each other. Further, each buffer plate 6 is outwardly curved in its cross-section so that the curved inner surface thereof forms a brine diverting surface 8, as shown in FIG. 2.

Therefore, the brine drained into the chamber interior 3 through the feed tube 1 will impinge against the respective diverting surfaces 8 of the buffer plates 6 in the first row and diverted in such a manner that lower streams flow around upwardly while upper streams downwardly, whereupon the brine is transferred to the second row of buffer plates 6, where it is again subjected to diversion in the manner described above. Thus, such diversion is repeated in each row.

Incidentally, the curved shape, angle and disposition of the buffer plates are not limited to those shown in the embodiment; they may, of course, be modified in various ways in accordance with the gist of the present invention depending upon the amount of flow of brine, the flash chamber size, and other factors so as to be most suitable forthe agitation of brine.

Second embodiment This embodiment is shown in FIG. 3, wherein the numeral 11 denotes a feed conduit for sea water which is a 4 stock material; 12 a stock sea water feed pump; 13, a stock sea water feed motor; and the numeral 14 denotes a conduit leading from said feed pump 12 to a condenser tube 16 in a flash chamber 15. The stock sea water passing through said condenser 16 is heated by vapor in the flash chamber 15. There is provided a conduit 17 which detours as it extends from the outlet of said condenser tube 16 to one end of the bottom of the flash chamber 15, and disposed in the route of this conduit 17 is a heater 18 for heating the stock brine moving through the conduit 17. The bottom surface 19 of said flash chamber is inclined so that the side thereof where said conduit 17 exists lies on a higher level. The bottom surface is provided with a plurality of buffer plates 20 agitating stock sea water.

Incidentally, the height of inclination h is so calculated as to assure suflicient agitation of said stock sea water to reduce the degree of superheat with due consideration of the physical environment of the stock sea water and flash chamber interior, the shape of the buffer plates 20- and other factors. The numeral 21 denotes a stock sea water reservoir provided at the inclined lower end portion of said bottom surface 19, and stock sea water which collects therein is discharged through a conduit 22, a flow-off pump 23 and a conduit 24. The numeral 25 denotes a motor for the flow-off pump. The vapor produced in said flash chamber 15 is condensed by said condenser tubes 16, collected in a fresh Water tray 26 and utilized as fresh water by being taken out through a conduit 27, a fresh water pump 28 and conduit 29. Further, the numeral 31 denotes a buffer plate installed in said fresh water tray 26.

Therefore, the stock sea water is moved to the side. of the conduit 17 and, after being heated by the heater 18, it is fed onto the bottom surface 19. The stock sea water, thus heated and fed onto the bottom surface 19, while being forced to move rapidly owing to the inclined construction thereof, evaporates while being sufficiently agitated to reduce its degree of superheat as a result of its impingement against the buffer plates 20. The vapor is then condensed by the condenser tube 16 into fresh water.

Third embodiment This embodiment is an application of the arrangement of the second embodiment to multi-stage flash process and is shown in FIG. 4. The function thereof is substantially the same as that of the embodiment shown in FIG. 3, and corresponding parts are indicated by like numerals with prime marks added thereto. The differences from the BIG. 3 embodiment are as follows. Stock sea water from a flash chamber 15' on the higher temperature side is fed to a flash chamber 15 by means of a booster pump 23', a booster pump motor 25' and connection conduits 22' and 24'. Further, in order to effectively utilize the sensible heat of the resulting fresh water on the higher temperature side, the fresh water is fed from'a. tray 26' on the higher temperature side to a fresh water tray 26 in a flash chamber 15 on the adjacent lower temperature side by means of a fresh water pump 28', a fresh water pump motor 30' and connection conduits 27' and 29'. The respective heights of inclination h, h' of the lflash chambers 15, 15', are calculated in accordance with the respective environmental conditions in the same manner as described above.

[[ncidentally, in the above mentioned embodiment the condenser tube 16 and fresh water tray 26 are inclined in conformity with the inclination h of the bottom surface 19 of the flash chamber 15 so as to make constant the conditions for vapor water separation of the vapor produced from every point on the flowing liquid surface in the flash chamber 15, so that the distances traveled by the vapors are made equal, but it is to be noted that there may be cases where the buffer plates 31 of the fresh water tray 26 are omitted and where the condenser tube 16 and fresh tray 26 are not inclined, depending upon the construction of the flash chamber 15, the degree of utilization of sensible heat on the fresh water side or the allowable concentration of fresh water.

Fourth embodiment In FIG. 5, the numeral 41 denotes a conduit for feeding sea water W which is a stock material and, a sluice valve .42 is placed somewhere between the ends thereof. The numeral 43 denotes the incondensable gas cooler of a distiller 46; 44, the condenser tube of said cooler 43, 45, a communication hole between the cooler 43 and a flash distiller 46 having a flash chamber bottom surface inclined as in the second embodiment; 47, the condenser tube of said distiller 46; 48, a fresh water tray; 49, a hot well for said fresh water tray 48; 50, a conduit leading from the hot well 49 to a fresh water pump 51; and the numeral 52 denotes a conduit leading from the pump 51 to a fresh water reservoir tank (not shown). The numeral 53 denotes a brine reservoir in said distiller 46 and 54 denotes a conduit for sea water leaving said distiller 46. Sea water passing through said conduit 54 passes through a condenser tube 56 and conduit 57 possessed by the incondensable gas cooler 55 and enters the condenser tube 59 of a steam turbine condenser 58'. The numeral 61 denotes a loop seal tube for return drain; 62, the hot Well of the steam turbine condenser 58; 63, a conduit leading from said hot well 62 to a condenser pump 64; and the numeral 65 denotes a conduit leading from the condenser pump 64 to the water feed system. During normal operation the sea water leaving the condenser 58 passes through conduits 66 and 67 and through a sluice valve 68 provided on the way and enters said flash distiller 46 and isspouted through a reduced pressure injection valve 69. Thus, it follows that the sea water heated to a higher temperature by being passed through the condenser tubes 47 and 59 is spouted into the distiller 46 in a high vacuum, part of said sea water being evaporated and condensed by the condenser 47 into fresh water the remainder being passed from the brine reservoir 53 through a conduit 70 and discharged through a conduit 72 from a brine discharge pump 71 serving also as a cooling water service pump for the condenser 58-. However, at the start when the degree of vacuum in the distiller 46 is low, or at the time when said distiller is not used, the sea water leavingthe condenser 58 passes from the conduit 66 through a'conduit 73 and through a sluice valve 74 provided on the way'and then directly through the conduit 70 and is finally discharged from the brine dis-' charge pump 71'through the conduit 72.

When the temperature of the sea water fed from said conduit 41 is low, in order not to cool the condensation water from the steam turbine atthe condenser 58 more than is necessary, means is provided for adjusting the temperature. That is to say, a conduit 75 is extended from the delivery side of the brine discharge pump 71 to somewhere between the ends of the conduit 57 connecting the condenser tube 56 of the cooler 55 with the condenser tube 59 of the condenser 58 to feed discharged sea water having a raised temperature thereby to raise the temperature of the cooling sea water, said feed being controlled by adjusting a regulator valve 76. The regulator valve 76 is adapted to be adjusted by a heat-sensitive conductor 77 which varies with the temperature of the condenser 58 output side sea water passing through the conduit 66.

The numeral 78 denotes a conduit branching from somewhere between the ends of said conduit 57; 79, a sea water discharge pump; and the numerl 80 denotes a conduit for discharge. It is made possible to discharge part of the cooling sea water through these members depending upon the amount of flow of the hot brine. The numeral 81 denotes a vacuum pump for the distiller and the numeral 82 denotes a conduit connecting said vacuum pump 81 with said cooler 43.

Further, the numeral 83 denotes a vacuum pump for the condenser and the numeral 84 denotes a conduit connecting said vacuum pump 83 with said cooler 55.

The numeral 85 denotes the surface of the sea, it being shown that the distiller 46, condenser 58, sea water feed conduit 41, etc. lie below or substantially below the level of said sea surface 85. Usually, by means of the high vacuum created at the time of the use of the distiller 46 rather than by means of a sea water feed pump, the sea water W will be spouted into the distiller 46 through the cooling tubes 47 and 59 of the distiller 46 and condenser 58. Further, in a case where the sea surface 85 is on a lower level (as when the tide is on the ebb) or where the head of the sea surface 85 and the head due to the vacuum in the flash chamber of the distiller 46 are not sufiicient as at the time of start or when the resistance in the cooling tube system is increased, the sea water W will be fed into the cooler 43 through a conduit 86, sea water feed pump 87, conduit 88 and sluice valve 89.

Incidentally, in the figure, an arrow 90 denotes the direction of inflow of the steam turbine exhaust. Further, the temperature and pressure (the degree of vacuum) values entered in the figure show one condition in the embodiment.

When the present apparatus is applied particularly in the manner shown in the fourth embodiment, it is possible to carry out the condensation of steam turbine exhaust and the conversion of sea water into fresh water at the same time, and the following advantages are obtained.

(1) The large amount of heat possessed by steam turbine exhaust can be utilized, so that the fuel cost for a plant for converting sea water into fresh water can be saved.

(2) Since the steam turbine condenser can also be used as a heater, the installation cost for a plant for providing fresh water can be decreased.

(3) As a result of the saving of said fuel and installation costs the cost price for converting sea Water into fresh water can be decreased and at the same time the overall plant efficiency can be increased.

Fifth embodiment FIG. 6 shows a concrete example of an application of single fiash process utilizing the heat of condensation of a generator steam turbine condenser to the conversion of sea Water into fresh water.

The numeral 101 denotes a conduit leading from a sea water intake port to a sea water feed pump 102; 103, a conduit leading from the pump 102 to a condenser tube 104 in a flash chamber 105; 106, a conduit leading to a condenser tube 108 in a steam turbine condenser 107; and the numeral 109 denotes an exhaust tube from the steam turbine. The numeral 110 denotes a tube for introducing sea Water from the condenser tube 108 into the flash chamber and the numeral 111 denotes condensation water in the steam turbine, which water is introduced into a fresh water tray 122 in the flash chamber 105 through a loop seal 112. The numeral 113 denotes fresh water, which is utilized by being taken out through a conduit 114, a fresh water pump 115 and a conduit 116. The numeral 117 denotes flashing brine raised in temperature by being passed through said

condenser tubes

104 and 108; the sensible heat difference with respect to the saturation temperature of the flash chamber 105 is utilized as latent heat of evaporation. The remaining brine is discharged through a conduit 118, a blow-off pump 119 and a discharge conduit 120. The numeral 127 denotes a vacuum pump, which discharges incondensable gases through a discharge conduit 126, thereby maintaining the interior of the flash chamber 105 in a predetermined degree of vacuum. Vanes 124, vane shaft 123 and electric motor 121 constitute a rotary agitating means. The numeral 125 denotes a seal box which keeps airtightness between the flash chamber 105 and the open air. The rotary agitating means serve to agitate the flashing brine 117 to decrease the degree of superheat.

Sixth embodiment In FIG. 7, the numeral 131 denotes a conduit from a sea water intake port; 132, a sea water feed pump; and the numeral 133 denotes a conduit leading from the pump to a. condenser tube 134 in a flash chamber 135. Stock sea water heated by being passed through the condenser tube 134 in the flash chamber 135 is passed through a conduit 136 and effects heat exchange in a condenser tube 138 in a steam turbine condenser 137. The numeral 139 denotes an exhaust tube from a steam turbine. The stock sea water further passes through a conduit 140 and is increased in pressure by a booster pump 151 and introduced into the flash chamber 135 through a conduit 152. The numeral 147 denotes flashing brine and the numeral 154 denotes a buffer plate for creating agitations by the flow of the flashing brine. By means of the aforesaid arrangement, the flashing brine 147 is forcibly fed into the flash chamber 135 by external force rather than by natural inflow due to pressure difference and forcibly agitated and flowed by the buffer plates 154 in the chamber, whereby the degree of superheat of the flashing brine 147 is removed. If the delivery pressure of the pump 132 is increased against the flow resistance in the delivery system sufliciently for agitation by the buffer plates 154, the booster pump 151 may, of course, be omitted. The exhaust from the steam turbine is condensed into Water as at 141 by the condenser tube 138, which water passes through the loop seal tube 142 into fresh water tray 153 and part of the water evaporates again and then, along with the flashing vapor from the stock sea water condenses again into water, which is utilized by being taken out through a conduit 144, fresh water pump 145 and conduit 146. The numeral 156 denotes a vacuum pump and the numeral 155 denotes a conduit for discharging the incondensable gases from the flash chamber 135. The remainder of the flashing brine is blown off through a conduit 148, pump 149 and conduit 150.

Seventh embodiment The eighth embodiment shown in FIG. 8 illustrates an example in which the present invention is applied to multistage flash process. The function is the same as in the embodirnent shown in FIG. 7, and the corresponding parts are indicated by like numerals, and prime marks are added thereto on the higher pressure side. In this embodiment, the flow of flashing brine 147 into a flash chamber 135 is effected not by natural inflow due to the difference in saturation pressure, but forcibly by a booster pump 151 and flashing brine 147 on the lower pressure side is forcibly agitated by buffer plates 154.

I claim:

1. Flash distilling apparatus including a flash chamber having a fiat bottom surface inclined in one direction; an inlet for a stock solution provided at the upper portion of said bottom surface; an outlet provided at the lower portion of said bottom surface; said inlet, outlet and inclination of the bottom surface establishing a normal direction of flow from the inlet downwardly across the bottom surface to the outlet; and means providing a plurality of controlled flow passages for the stock solution across said bottom surface which passages zig-zag in the direction of flow and in each of which passages the upper and'lower layers of the stock solution change places with each other, said means comprising buffer plates mounted on said bottom surface and arranged in a plurality of rows, each row extending generally transversely to said normal direction of flow and containing a plurality of said buffer plates arranged in generally parallel relationship to each other and obliquely to said normal direction of flow, each buffer plate having a diverting surface on the side thereof which receives the flow of the stock solution, said diverting surface having a flat lower portion extending upwardly from said bottom surface in inclined relation thereto and having a curved upper portion which extends above the normal level of the stock solution and over at least a part of said lower portion, the buffer plates in each successive row in said normal direction of flow being arranged obliquely opposite to the buffer plates in the next preceding row and positioned so that the diverting surfaces thereof each receive the flow of stock solution from the diverting surface of a buffer plate in such preceding row.

2. Flash distilling apparatus as set forth in claim 1 wherein said inlet and outlet each includes a plurality of openings, each opening being substantially aligned with one of said controlled flow passages.

References Cited UNITED STATES PATENTS 3,192,131 6/1965 Loebel et a1 202-173 3,192,132 6/1965 Loebel 202-173 3,360,442 12/1967 Starmer 202-173 3,395,085 7/1968 Kogan 202-173 3,398,059 8/1968 Cane et a1 202-173 3,412,558 11/1968 Starmer 203-DIG. 20 3,515,645 6/1970 Wetch 202-173 3,558,439 1/1971 Anderson 202-173 3,219,553 11/1965 Hughes 202-173 WILBUR L. BASCOMB, 111., Primary Examiner US. Cl. X.R.

202-173; 203-11, 88, 2, DIG. 16