US3360442A - Multi-stage flash evaporator - Google Patents

Multi-stage flash evaporator Download PDF

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US3360442A
US3360442A US420642A US42064264A US3360442A US 3360442 A US3360442 A US 3360442A US 420642 A US420642 A US 420642A US 42064264 A US42064264 A US 42064264A US 3360442 A US3360442 A US 3360442A
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chambers
succession
liquid
chamber
evaporator
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Starmer Roy
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Applied Research and Engineering Ltd
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Applied Research and Engineering Ltd
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    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01DSEPARATION
    • B01D3/00Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
    • B01D3/06Flash distillation
    • B01D3/065Multiple-effect flash distillation (more than two traps)

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  • a multi-stage flash evaporator in which a succession of ilash chambers are interconnected by barks, and including means for supplying heated liquid to the rst chamber in the succession, means for condensing vapors produced in the successive chambers, and for maintaining the chambers in the succession at successively decreasing vapor pressures.
  • the arrangement is such that the vapor pressure differences between chambers at the beginning of the succession are larger than the vapor pressure differences between chambers later in the succession.
  • the liquid tends, by reason of the vapor pressure differences between the chambers, to rise from one chamber to the next.
  • the invention relates to apparatus for the evaporation of liquids in distillation plants and more specifically relates to improvements in multi-stage Hash evaporators.
  • a plurality of orifices connect the chambers together and, although a small fraction of the liquid is vapourised in each chamber, the majority ow through the orifices between the stages which are maintained as successively decreasing vapour pressures.
  • the vapour pressure difference between stages at the high temperature end is, or may be, greater than the pressure difference between stages at the low temperature end.
  • the invention provides a multi-stage liash evaporator in which there is a succession of flash chambers interconnected by orifices, means for supplying heated liquid to the first chamber in the succession, means for condensing vapours produced in the successive chambers and for maintaining the chambers in the succession at successively decreasing vapour pressures, with the vapour pressure differences between chambers at the beginning of the succession larger than the vapour pressure diierences between chambers later in the succession, and in which the chambers at the beginning of the succession are at progressively higher levels whereby the liquid is caused, by the vapour pressure diiferences between the chambers, to rise from one chamber to the next.
  • the said chambers at the beginning of the succession are arranged in step-like form, the static head of liquid threby being gradually and constantly increased.
  • the chambers later in the succession are arranged in two (or more) tiers, one above the other, the circulation of liquid progressing from the initial chambers through the top tier of chambers and then through the lower tier of chambers.
  • the chambers later in ice the succession are arranged at progressively lower levels.
  • the chambers may be arranged in step-like form, the static head of liquid thereby being gradually and constantly, decreased.
  • the chambers later in the succession are either all at the same height or the rst of these chambers are at the same height and the remainder at progressively lower levels.
  • the circulation of liquid is preferably assisted by means of a pump.
  • the invention also provides the method of evaporating a liquid which comprises the steps of passing the liquid through a succession of chambers, maintaining the vapour pressure in the chambers at successively decreasing values along the succession, the dilierences in pressure between successive stages at the beginning of the succession being greater than the pressure differences between successive chambers later in the succession, and utilising the greater pressure dilerences to lift the liquid between stages at the beginning of the succession.
  • the flow of the liquid between chambers later in the succession may be downward.
  • FIGURE l is a diagrammatic view of a first form of evaporator
  • FIGURE 2 is a diagrammatic view of a second form of evaporator.
  • the evaporator comprises a circuit through which a liquid (e.g. brine) is continuously circulated.
  • the circuit comprises a heater 10, a control valve 9, a succession of heat evaporation stages or chambers 11, a pump 12 and a tube system 13 for heat recovery.
  • Brine is fed into the evaporator through a pipe 20 and is passed by the pump 12 through the tube system 13 where it is heated and then to the heater 10.
  • the brine then ows into the chamber 14 at the high temperature end of the evaporator and thence through a series ofticians 17, through the chambers to a chamber 15 at the low temperature end of the evaporator.
  • the chamber 15 is cooled by externally supplied heat transfer means 16.
  • Erosion around the orifices 17 is dependent on the velocity of flow therethrough. Hence, if the velocity of flow is reduced, the rate of erosion is also reduced. However, the velocity of flow through the orifices is dependent on the pressure di'erences on opposite sides thereof. These differences are, in turn, dependent on the level of the liquid on the opposite sides and the pressure dilierences between pairsv of chambers, which diterences are greater at the high temperature end than at the low temperature end of the succession.
  • the initial chambers are arranged in step-like form one above the other to cause the liquid to rise from one chamber to the next.
  • the pressure difference across the orifice is reduced which 'not only reduces the velocity of flow and hence the rate of erosion of the orifices over this portion of the evaporator, but also greatly assists the action of the pump.
  • FIGURE 2 the circuit is identical to the circuit described above except for the arrangement of the chambers later in the succession which in this case are in step-like form one below the other.
  • the references of FIGURE 2 correspond to those of FIGURE l.
  • This table is for operation of the apparatus for water.
  • Column 1 gives the values of various characteristics of the ow of water across an inter-stage orifice when the general temperature is 250 F. (i.e. at the higher temperature end of the evaporator) and the stage temperature drop per chamber is F.
  • Column 2 gives the modied values when the pressure difference between the stages is utilized to lift the water a given distance between the stages. It will be noticed that the velocity of the water through the orifices is considerably reduced.
  • Column 3 gives the values when the general temperature is changed to 100 F. (i.e. at the low temperature end of the evaporator and the stages are at the same height).
  • column 4 gives the modified values when the ow is assisted by the arrangement of the chamber as in FIGURE 2 where the pressure between stages is used to lift the water between stages. It will be seen that although the size of the pedal required for the circumstances of column 2 is greater than that required for the circumstances of column l, this is more than off-set by the saving in orifice area at the low temperature end of the evaporator as shown in column 4 with regard to column 3.
  • a multi-stage llash evaporator in which there is a succession of ilash chambers interconnected by barks, means for supplying heated liquid for distillation to the first chamber in the succession, means comprising a condenser tube arranged in the upper section of said chambers and through which said liquid ows for condensing vapours produced in the successive chambers and for maintaining the chambers in the succession at successively decreasing vapour pressures, with the vapour pressure differences between chambers at the beginning of the succession larger than the vapour pressure differences between chambers later in the succession, and in which said succession of chambers comprise a rst group and a second group connected together, the first group comprising a plurality of chambers arranged in step-wise form one above the other, the second group comprising a plurality of chambers arranged in step-wise form and in a downwardly inclined path one below the other to the last chamber.

Description

United States Patent O ABSTRACT OF THE DISCLOSURE A multi-stage flash evaporator in which a succession of ilash chambers are interconnected by orices, and including means for supplying heated liquid to the rst chamber in the succession, means for condensing vapors produced in the successive chambers, and for maintaining the chambers in the succession at successively decreasing vapor pressures. The arrangement is such that the vapor pressure differences between chambers at the beginning of the succession are larger than the vapor pressure differences between chambers later in the succession. There are at least two chambers at the beginning of the succession of which the second, or in other words the chamber with the lower vapor pressure, is at a higher level than the first chamber, or in other words the chamber with the higher vapor pressure. Thus, the liquid tends, by reason of the vapor pressure differences between the chambers, to rise from one chamber to the next.
The invention relates to apparatus for the evaporation of liquids in distillation plants and more specifically relates to improvements in multi-stage Hash evaporators.
In multi-stage flash evaporators a liquid to be evaporated in continuously circulated from one stage (usually the last) through a tube heat exchanger and a heater into another stage (usually the irst) of a series of ilash chambers through which the liquid then iiows in succession, a proportion of the liquid being evaporated in each chamber and the vapour being condensed by heat exchange with the liquid in the heat exchanger. A plurality of orifices connect the chambers together and, although a small fraction of the liquid is vapourised in each chamber, the majority ow through the orifices between the stages which are maintained as successively decreasing vapour pressures. The vapour pressure difference between stages at the high temperature end is, or may be, greater than the pressure difference between stages at the low temperature end.
The invention provides a multi-stage liash evaporator in which there is a succession of flash chambers interconnected by orifices, means for supplying heated liquid to the first chamber in the succession, means for condensing vapours produced in the successive chambers and for maintaining the chambers in the succession at successively decreasing vapour pressures, with the vapour pressure differences between chambers at the beginning of the succession larger than the vapour pressure diierences between chambers later in the succession, and in which the chambers at the beginning of the succession are at progressively higher levels whereby the liquid is caused, by the vapour pressure diiferences between the chambers, to rise from one chamber to the next.
Preferably the said chambers at the beginning of the succession are arranged in step-like form, the static head of liquid threby being gradually and constantly increased.
In one form of the invention the chambers later in the succession are arranged in two (or more) tiers, one above the other, the circulation of liquid progressing from the initial chambers through the top tier of chambers and then through the lower tier of chambers.
In another form of the invention the chambers later in ice the succession are arranged at progressively lower levels. In this form the chambers may be arranged in step-like form, the static head of liquid thereby being gradually and constantly, decreased.
In yet another form, the chambers later in the succession are either all at the same height or the rst of these chambers are at the same height and the remainder at progressively lower levels.
The circulation of liquid is preferably assisted by means of a pump.
The invention also provides the method of evaporating a liquid which comprises the steps of passing the liquid through a succession of chambers, maintaining the vapour pressure in the chambers at successively decreasing values along the succession, the dilierences in pressure between successive stages at the beginning of the succession being greater than the pressure differences between successive chambers later in the succession, and utilising the greater pressure dilerences to lift the liquid between stages at the beginning of the succession.
The flow of the liquid between chambers later in the succession may be downward.
By way of example two forms of ash evaporator in accordance with the invention will now be described with reference to the accompanying drawings in which:
FIGURE l is a diagrammatic view of a first form of evaporator, and
FIGURE 2 is a diagrammatic view of a second form of evaporator.
Referring to FIGURE l, the evaporator comprises a circuit through which a liquid (e.g. brine) is continuously circulated. The circuit comprises a heater 10, a control valve 9, a succession of heat evaporation stages or chambers 11, a pump 12 and a tube system 13 for heat recovery. Brine is fed into the evaporator through a pipe 20 and is passed by the pump 12 through the tube system 13 where it is heated and then to the heater 10. The brine then ows into the chamber 14 at the high temperature end of the evaporator and thence through a series of orices 17, through the chambers to a chamber 15 at the low temperature end of the evaporator. The chamber 15 is cooled by externally supplied heat transfer means 16. As the vapor pressures of successive chambers are lower the liquid flashes as it enters a chamber and the flash distillate is condensed in the tubes 13 and is collected in pans 21. The lblowdown is pumped from the apparatus at 22 by a pump 24. The distillate is pumped from the apparatus at 23 by a pump 25.
Erosion around the orifices 17 is dependent on the velocity of flow therethrough. Hence, if the velocity of flow is reduced, the rate of erosion is also reduced. However, the velocity of flow through the orifices is dependent on the pressure di'erences on opposite sides thereof. These differences are, in turn, dependent on the level of the liquid on the opposite sides and the pressure dilierences between pairsv of chambers, which diterences are greater at the high temperature end than at the low temperature end of the succession.
It will be seen from FIGURE 1 that the initial chambers are arranged in step-like form one above the other to cause the liquid to rise from one chamber to the next. In this way the pressure difference across the orifice is reduced which 'not only reduces the velocity of flow and hence the rate of erosion of the orifices over this portion of the evaporator, but also greatly assists the action of the pump.
Referring to FIGURE 2, the circuit is identical to the circuit described above except for the arrangement of the chambers later in the succession which in this case are in step-like form one below the other. The references of FIGURE 2 correspond to those of FIGURE l.
For further explanation of apparatus in accordance with the invention, the following table is included:
This table is for operation of the apparatus for water. Column 1 gives the values of various characteristics of the ow of water across an inter-stage orifice when the general temperature is 250 F. (i.e. at the higher temperature end of the evaporator) and the stage temperature drop per chamber is F. Column 2 gives the modied values when the pressure difference between the stages is utilized to lift the water a given distance between the stages. It will be noticed that the velocity of the water through the orifices is considerably reduced. Column 3 gives the values when the general temperature is changed to 100 F. (i.e. at the low temperature end of the evaporator and the stages are at the same height). Finally column 4 gives the modified values when the ow is assisted by the arrangement of the chamber as in FIGURE 2 where the pressure between stages is used to lift the water between stages. It will be seen that although the size of the orice required for the circumstances of column 2 is greater than that required for the circumstances of column l, this is more than off-set by the saving in orifice area at the low temperature end of the evaporator as shown in column 4 with regard to column 3.
I claim:
1. A multi-stage llash evaporator in which there is a succession of ilash chambers interconnected by orices, means for supplying heated liquid for distillation to the first chamber in the succession, means comprising a condenser tube arranged in the upper section of said chambers and through which said liquid ows for condensing vapours produced in the successive chambers and for maintaining the chambers in the succession at successively decreasing vapour pressures, with the vapour pressure differences between chambers at the beginning of the succession larger than the vapour pressure differences between chambers later in the succession, and in which said succession of chambers comprise a rst group and a second group connected together, the first group comprising a plurality of chambers arranged in step-wise form one above the other, the second group comprising a plurality of chambers arranged in step-wise form and in a downwardly inclined path one below the other to the last chamber.
2. A multi-stage evaporator as claimed in claim 1 and including a heat exchanger for condensing the vapours produced in the succession of chambers and means for passing the liquid to be evaporated through the exchanger in heat exchange relation with the vapours and thence through a heater to the succession of chambers.
References Cited UNITED STATES PATENTS 1,782,959 ll/l930 Elliott 202--173 2,979,443 4/1961 Frankel 202-173 3,l05,020 9/1963 Silver et al. 202-173 X 3,119,752 l/l964 Checkovich 202-173 X 3,206,379 9/1965 Hill 202-173 X 3,219,552 ll/l965 Starmer et al 202-173 X 3,219,553 ll/l965 Hughes 202-173 OTHER REFERENCES Publication, Nat. Academy of Sciences, Proceedings of Symposium, Saline Water Conversion (1957) (pp. 92 and 93).
NORMAN YUDKOFF, Primary Examiner.
F. E. DRUMMOND, Assistant Examiner.

Claims (1)

1. A MULTI-STAGE FLASH EVAPORATOR IN WHICH THERE IS A SUCCESSION OF FLASH CHAMBERS INTERCONNECTED BY ORIFICES, MEANS FOR SUPPLYING HEATED LIQUID FOR DISTILLATION TO THE FIRST CHAMBER IN THE SUCCESSION, MEANS COMPRISING A CONDENSER TUBE ARRANGED IN THE UPPER SECTION OF SAID CHAMBERS AND THROUGH WHICH SAID LIQUID FLOWS FOR CONDENSING VAPOURS PRODUCED IN THE SUCCESSIVE CHAMBERS AND FOR MAINTAINING THE CHAMBERS IN THE SUCCESSION AT SUCCESSIVELY DECREASING VAPOUR PRESSURE WITH THE VAPOUR PRESSURE DIFFERENCES BETWEEN CHAMBERS AT THE BEGINNING OF THE SUCCESSION LARGER THAN THE VAPOUR PRESSURE DIFFERENCE BETWEEN CHAMBERS LATER IN THE SUCCESSION, AND IN WHICH SAID SUCCESSION OF CHAMBERS COMPRISE A FIRST GROUP AND A SECOND
US420642A 1964-12-23 1964-12-23 Multi-stage flash evaporator Expired - Lifetime US3360442A (en)

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3440146A (en) * 1966-05-02 1969-04-22 Johan A Louw Desalination method and apparatus with plural vaporization chambers containing shallow layers of liquid
US3515646A (en) * 1967-04-19 1970-06-02 Weir Westgarth Ltd Vertical multi-stage flash evaporator with separate horizontal condensing chamber
US4216856A (en) * 1975-04-25 1980-08-12 Dunlop Limited Reinforcement for elastomeric articles
WO1995007123A1 (en) * 1993-09-10 1995-03-16 Emerson Electric Co. Water purifier having a multi-level boiler tray
WO1995021672A1 (en) * 1994-02-14 1995-08-17 Manostat Corporation Solvent evaporator and method for solvent evaporation
US9440164B2 (en) 2011-09-14 2016-09-13 Aquasource Technologies Corporation System and method for water treatment

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1782959A (en) * 1923-03-27 1930-11-25 William S Elliott Distilling apparatus
US2979443A (en) * 1956-08-07 1961-04-11 Richardsons Westgarth & Co Multi-stage flash evaporator
US3105020A (en) * 1957-09-21 1963-09-24 G & J Weir Ltd Method and apparatus for the multistage flash distillation of a liquid
US3119752A (en) * 1959-01-30 1964-01-28 Singmaster & Breyer Recovery of fresh water from sea water
US3206379A (en) * 1962-05-31 1965-09-14 Robert H Hill Multi-stage convective distillation system
US3219553A (en) * 1961-01-17 1965-11-23 American Mach & Foundry Multi-stage flash type evaporators
US3219552A (en) * 1959-02-27 1965-11-23 Richardsons Westgarth & Co Plural condensing mediums for multistage flash evaporator

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1782959A (en) * 1923-03-27 1930-11-25 William S Elliott Distilling apparatus
US2979443A (en) * 1956-08-07 1961-04-11 Richardsons Westgarth & Co Multi-stage flash evaporator
US3105020A (en) * 1957-09-21 1963-09-24 G & J Weir Ltd Method and apparatus for the multistage flash distillation of a liquid
US3119752A (en) * 1959-01-30 1964-01-28 Singmaster & Breyer Recovery of fresh water from sea water
US3219552A (en) * 1959-02-27 1965-11-23 Richardsons Westgarth & Co Plural condensing mediums for multistage flash evaporator
US3219553A (en) * 1961-01-17 1965-11-23 American Mach & Foundry Multi-stage flash type evaporators
US3206379A (en) * 1962-05-31 1965-09-14 Robert H Hill Multi-stage convective distillation system

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3440146A (en) * 1966-05-02 1969-04-22 Johan A Louw Desalination method and apparatus with plural vaporization chambers containing shallow layers of liquid
US3515646A (en) * 1967-04-19 1970-06-02 Weir Westgarth Ltd Vertical multi-stage flash evaporator with separate horizontal condensing chamber
US4216856A (en) * 1975-04-25 1980-08-12 Dunlop Limited Reinforcement for elastomeric articles
WO1995007123A1 (en) * 1993-09-10 1995-03-16 Emerson Electric Co. Water purifier having a multi-level boiler tray
US5492602A (en) * 1993-09-10 1996-02-20 Emerson Electric Co. Water purifier having a multi-level boiler tray
WO1995021672A1 (en) * 1994-02-14 1995-08-17 Manostat Corporation Solvent evaporator and method for solvent evaporation
US9440164B2 (en) 2011-09-14 2016-09-13 Aquasource Technologies Corporation System and method for water treatment
US9440162B2 (en) 2011-09-14 2016-09-13 Aquasource Technologies Corporation System and method for water treatment
US9440163B2 (en) 2011-09-14 2016-09-13 Aquasource Technologies Corporation System and method for water treatment
US9527005B2 (en) 2011-09-14 2016-12-27 Aquasource Technologies Corporation System and method for water treatment
US10092851B2 (en) 2011-09-14 2018-10-09 Aquasource Technologies Corporation System and method for water treatment

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