US3147598A

US3147598A - Apparatus for evaporating impure water

Info

Publication number: US3147598A
Application number: US154583A
Authority: US
Inventors: Joseph R Wilson
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1961-11-24
Filing date: 1961-11-24
Publication date: 1964-09-08
Anticipated expiration: 1981-09-08
Also published as: GB948721A

Description

P 8, 1964 J. R. WILISON 3,147,598

APPARATUS FOR EVAPORATING IMPURE. WATER Filed Nov. 24, 1961 3 Sheets-Sheet 1 MOISTURE AND DRY SALT SEPARATOR BOILER GRANULAR SALT /GENERATOR TURBINE COOLANT mg I CONDENSER CONDENSATE PUMP PURE WATER INVENTOR Joseph R. Wilson Sept. 8, 1964 Filed Nov.

REHEAT SECTION J. R. WILSON APPARATUS FOR EVAPORATING IMPURE WATER 1 CONDENSATE PUMP 3 Sheets-Sheet 2 MOISTURE Ann DRY SALT SEPARATOR GRANULAR SALT /' GENERATOR INVENTOR Joseph R. Wilson P 8, 1964 J. R. WILSON 3,147,598

APPARATUS FOR EVAPORATING IMPURE WATER Filed Nov. 24, 1961 3 Sheets-Sheet 5 SALINE WATER E REHEAT SETION J J --j: REHEAT SECTION REHEAT SECTION GENERATOR CONDENSER BOILER FEED PUMP PURE WATER ONDENSATE 42 c PUMP Fig; 3 3

United States Patent 3,147,598 Patented Sept. 8, 1964 3,1475% APPARATUS FOR EVAPORATBNG URE WATER Joseph R. Wilson, Pittsburgh, Pa, assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Filed Nov. 24, 1961, Ser. No. 154,583 4 Claims. (Cl. 60-64) This invention relates to evaporation of impure water and more particularly to the production of pure water from mineralized or otherwise impure water by direct contact of the impure water with superheated steam.

One of the objects of the invention is to provide apparatus of the above type wherein pressurized vapor formed by the heating of the impure water, together with pressurized steam for effecting the vaporization, is reheated and then employed to motivate a Steam turbine, so that useful power may be extracted therefrom before condensing the vapor for use, as required, in substantially pure water form.

A further object is to provide apparatus of the above type wherein the impure water is completely vaporized while in finely divided form in a high pressure chamber so that, when sea water is employed, the remaining impurities may be collected for use in pulverous dry salt form.

Yet another object of the invention is to provide apparatus of the above type wherein a plurality of evaporation chambers are arranged in cascade, each operating at the same or slightly lower pressure and having means for reheating the vapors formed in each of the chambers, so that the resulting vapor issuing from the last pressure chamber is still in a condition of sufliciently high pressure and superheat for employment as motive fluid in a steam turbine power plant, before condensation of the vapor and off take of the condensate in substantially pure water form for other use, as required.

A still further object of the invention is to provide a highly improved method of flash evaporating mineralized or otherwise impure water, such as sea water, and reheating the resulting vapor to a sufficiently high degree for employment in a steam turbine power plant, while collecting the saline impurities removed from the vapor in substantially dry pulverous form for useful purposes.

Briefly, in accordance with the invention, there is provided a substantially closed casing forming a flash vaporizing chamber, means including a nozzle for admitting saline or otherwise impure water into the chamber in a finely divided spray and means including a second nozzle for admitting superheated steam at high pressure into the chamber at a rate sufficient to completely vaporize the saline water by direct contact heat exchange. The casing is further provided with a lower convergent portion for collecting the finely divided salt particles that are removed from the saline water during vaporization so that, from time to time, or continuously, as desired, the substantially dry salt may be removed therefrom for useful purposes.

The resulting vapor formed in the vaporizing chamber is employed to motivate a steam turbine power plant before ultimate condensation. Before admission to the turbine, the vapor may be directed through a boiler wherein it is reheated to the degree most suitable to motivate the turbine. Means is further provided for directing some of the thus reheated vapor to the vaporizing chamber to continue the process of vaporizing the saline water. By proper regulation of the steam flow rate into the vaporizing chamber as well as regulation of the rate of admission of saline water into the chamber, complete vaporization of the saline water may be continuously maintained. If required, a suitable moisture separator may be interposed between the boiler and the vaporizing chambet to remove particles of unvaporized saline moisture, thereby to improve the degree of purification of the vapor. After expansion in the turbine with concomitant dissipation of superheat and high pressure, the substantially vitiated vapors are condensed in a suitable surface condenser to provide substantially pure water.

If desired, some of the thus condensed water may be returned to the boiler in a substantially closed loop for re-evaporation purposes.

The invention is susceptible of many modifications. For example, a plurality of casings may be employed and arranged in cascade. With this arrangement, impure water is admitted into each of the vaporizing chambers and the pressurized superheated vapor formed in the first chamber is further heated before admission to the succeeding chamber. Accordingly, the successively reheated vapor flow from one chamber to the next permits operatron of each successive chamber at nearly the same high pressure and temperature as the one immediately upstream thereof. The last vaporizing chamber in the series is subjected to the aggregate vapor flow from all of the vaporizing chambers preceding it. Hence, the vapor delivered from the last vaporizing chamber is at a sufficiently high pressure and condition of superheat for direct admission to the steam turbine, with attendant operating economies and increased yield of pure water.

The foregoing and other objects are effected by the invention as will be apparent from the following description taken in connection with the accompanying draw mgs, forming a part of this application, in which:

FIG. 1 is a schematic view illustrating apparatus for evaporating mineralized water such as sea water for providing substantially pure water and dry salt, in accordance with the invention;

FIG. 2 is a schematic view similar to FIG. 1 illustrating a second modification of the invention, and

FIG. 3 is a schematic view illustrating another embodiment wherein a plurality of vaporizing chambers of the type shown in FIG. 2 are staged or arranged in cascade to increase the yield of pure water and dry salt.

Referring to the drawings in detail, in FIG. 1 there is shown apparatus including :a closed casing 10 capable of withstanding high pressure and temperature and defining a water vaporizing chamber 11. i The upper portion of the casing 10 is provided with a suitable downwardly directed nozzle 12 to which impure water, such as sea water or otherwise mineralized water, is directed by a suitable conduit 13 having a pump 14 interposed therein to highly pressurize the water, so that it issues from the nozzle 12 into the chamber 11 as a finely divided or atomized spray.

In the lower portion of the casing 10 there is provided an upwardly directed second nozzle 15 for admitting steam in spray form into the evaporating chamber 11. Steam from a suitable source (not shown) is delivered to the nozzle 15 with a high degree of superheat and at a slightly lower pressure than the nozzle 12 by

conduit structure

16 and 17, and a suitable valve 18 may be interposed in the conduit 16 to control the steam flow rate therethrough.

The upper portion of the casing 10 is provided with a suitable moisture separating device 19 having its inlet in communication with the chamber 11 and its outlet connected to a blower 20 by a conduit 21. A boiler 23 of any suitable type is also provided having a heating coil structure 24 disposed therein which is connected at one end to the outlet of the blower 20 by a conduit 25 and at its other end to the steam spray nozzle 15 by a conduit 26. As illustrated, the conduit 26 is disposed in parallel arrangement with the steam supply conduit 16 so that as hereinafter to be described, steam may be ad- 3 mitted to the steam spray nozzle by the conduit 16 and/ or the conduit 25.

There is further provided a steam turbine power plant of any suitable well known type including a steam turbine 28 operatively connected to a suitable load such as an electric generator 29. The turbine 28 is of the condensing type and is further provided with a surface type condenser 30 having a coil structure 31 through which a suitable fluid coolant is passed, and equipped with a suitable pump 32 for pumping out the vapor condensed in the condenser 30, as well known in the art.

The turbine 28 is connected to the conduit 26 by a steam conduit 34 having a suitable valve 35 interposed therein, so that steam flow through the turbine 23 may be turned on or oil or otherwise regulated as desired during operation.

To initiate operation of the above described apparatus, the valve 35 is closed and the valve 18 is opened and a modest quantity of superheated steam is admitted to the vaporizing chamber 11 through the

conduits

16 and 17 and the spray nozzle 15. Flow of impure Water is then initiated by opening a suitable valve 37 in the impure make-up water conduit structure 13. The ensuing atomized water spray is intimately intermixed with the highly heated steam spray with resulting flash evaporation of the water spray. Hence, during operation, the internal walls of the chamber 11 are maintained in a substantially dry condition. By proper regulation of the steam admission valve 18 and the make-up water admission valve 37, a proper balance in the heat exchange may be obtained so that all of the impure water is flashed into steam and the resulting dry salt crystals fall by gravity to the bottom of the chamber 11, Where they are collected in a lower conical portion 39 in the casing 10, for subsequent removal through an outlet 40. The particle size of the salt crystals is directly proportional to the water spray droplet size, hence the salt collected in the conical portion 39 is pulverous or granular in character.

The vapor thus formed augments the volume of the steam admitted through the nozzle 15 and the two vapor mixtures, although still at a superheat, contain a lower degree of superheat. This steam mixture is directed through the moisture separating device 19 wherein any particles of unvaporized mixture are collected and returned to the chamber 11. The thus dried steam may then be pumped to its initial pressure by the blower 20 and directed through the heating coil structure 24 of the boiler, wherein it is reheated to the initial condition of superheat required. This steam is then again admitted to the evaporating chamber 11 and the rate of flow of the impure makeup water is increased accordingly by further opening the valve 37. This step further increases the quantity of vapor formed by the increased rate of evaporation of the impure Water.

The recirculation process is continued until the heating capacity of the boiler 23 is attained, at which time the steam supply through conduit 16 is interrupted by turning the valve 18 to the closed position, andthe valve 35 is opened to initiate flow of the highly pressurized and superheated steam to the turbine 28. By proper regulation of the

valves

35 and 37, sufficient steam is directed into the vaporizing chamber 11 by the nozzle 15 to completely flash vaporize the water sprayed thereinto by the nozzle 12, thereby increasing the volume of steam sufficiently to maintain the evaporation process and motivate the steam turbine 28. After expansion in the turbine 28, the thus vitiated steam is condensed in the condenser 30 and pumped therefrom by the pump 32 through a suitable conduit 42, for any desired useful purpose, in pure water form.

The salt collected in the conical portion 38 of the casing 10 may be continuously, or from time to time, removed through the outlet 40 for useful purposes as desired. Hence, in addition to the pure water obtained, a substantially pure salt derived from the process may d be sold commercially to enhance the economic aspects of the apparatus.

The amount of heat required to produce the pure water at the outlet 42, beyond that required to generate power in the turbine 28, is relatively smallabout 30 B.t.u.s per pound of pure water produced, so that the increased cost for fuel to operate the boiler 23 is very low. According to calculations of a preliminary nature, the operating cost of the fuel should be about 1 cent per thousand gallons of water.

From the above it will be seen that the system shown and described in connection with FIG. 1 provides three useful commodities at relatively loW cost, electric power, pure water and salt, in a highly simplified system.

In FIG. 2 there is shown a second embodiment showing another modification of the invention. This embodiment is similar in many aspects to that shown and described in connection with FIG. 1. Accordingly, Where similar structure is shown, the same references apply.

In this embodiment, the casing 18 may be substantially identical to that shown in the first embodiment and operates in substantially similar manner. It is employed in connection with a boiler 53 of the reheater type having an additional reheating section comprising a heating coil structure 54. This reheating coil structure 54 is connected at on end to the vapor conduit 21 from the evaporating chamber 11, and at its other end to the inlet of the turbine 28 by a conduit 55. Also, a portion of the condensate in pure water form is returned to a separate heat exchange portion 57 of the boiler 53 by a conduit 59 connected at its upstream end to the outlet of the condensate pump 32 in parallel with the pure water off take conduit 42. A suitable boiler feed pump 68 is interposed in conduit 59 for pressurizing the Water returned to the boiler portion 57 as feedwater. In the boiler portion 57, the water is converted into pressurized superheated steam and is thence delivered to the spray nozzle 15 by a suitable conduit 61.

In operation, highly pressurized superheated steam is sprayed into the evaporating chamber 11 by the steam spray nozzle 15, While impure make-up water at a slightly higher pressure is sprayed thereinto by the water spray nozzle 12. Here again the intermingling of the steam and water sprays evaporates the water by flashing, and the resulting vapor mixtureis thence directed through the moisture separator is and conduit 21 to the reheat section 54 of the boiler, wherein it is superheated to the required higher degree for motivating the turbine 28.

The steam is admitted to the turbine 28 by the conduit 55 and, after expansion, condensed in the surface condenser 30, and the resulting condensate is pumped therefrom by the condensate pump 32. A portion of the condensate in pure water form is removed from the system for other useful purposes through the conduit 42, while the remaining portion is returned to the boiler 53 as feedwater through conduit 59. During its flow through the conduit 59 the feedwater is pressurized to the degree required in the system by the boiler feed pump 60. Accordingly, the steam generated in the heat exchange portion 57 of the boiler is at high pressure and in a condition of high superheat.

As previously described in connection with the first embodiment, by proper regulation of the valve 37 in the impure make-up water conduit 13, proper balance may be obtained in the evaporating chamber 11 so that all of the incoming water spray is flash evaporated in a continuous process with the continuous formation of dry salt in granular form.

With the abOVe described arrangement no auxiliary supply of steam is required for vaporization of the impure water, since this steam is continuously provided bythe boiler 53.

FIG. 3 shows a modification of the arrangement shown in FIG. 2 employing a plurality of casings 10 having vaporizing chambers 11a, 11b, 11c, 11d, 11a and 11 arranged in cascade. In this embodiment, there is provided a boiler 63 having a plurality of

reheat sections

64, 65, 66, 67 and 68 for reheating the vapor formed in each of the vaporizing chambers 11a to 112, respectively. The impure water, after being pressurized by a suitable pump 69, is delivered to each of the vaporizing chambers lla to 11 by a plurality of branch conduits 13a to 139, respectively, connected in parallel with the outlet of the pump 69. Each of these conduits 13a-13f may be provided with a valve 72 for regulating the rate of flow of impure make-up water therethrough, as subsequently to be described, and the casings are interconnected in such a manner that the vapor formed in chamber 11a is directed through a conduit 74 to one end of the reheat section 64 and after passing therethrough with attendant reheating to a higher value, it is delivered therefrom to the steam spray nozzle 15 in chamber 11!) by a conduit 75.

In a similar manner, the vapor formed in chamber 11b is directed by a conduit 76 to its associated reheat section 65, and from the reheat section 65 to the chamber 11c by a conduit 77, etc. The steam supply for the first vaporizing chamber 11a is provided by the usual steam generator section 78 of the boiler 63 and directed to its associated steam spray nozzle 15 by a suitable conduit 79, while the vapor stream from the last vaporizing chamber 11 is delivered to the turbine 28 by a suitable conduit 80 to provide motive power thereto. The remaining portion of the system is substantially identical to that shown in FIG. 2 and includes the surface condenser 30 for condensing the vitiated steam exhausted from the turbine 28, a pump 32 for pumping the resulting condensate from the condenser 30 and the pump 60 for pumping a part of the condensate to the steam generating section 78 of the boiler as feedwater.

In operation, highly pressurized and superheated steam is delivered by the steam generating section 78 to the steam spray nozzle 15 of the first chamber 11a concomitantly with the spray of impure Water thereinto through the nozzle 12, with resultant flash evaporation of the impure water to augment the volume of vapor, so that the resulting vapor flow through the conduit 74 to the reheat section 64 is greater than the flow of steam through the steam spray nozzle 15 by the amount generated in complete vaporization of the incoming impure spray. The thus augmented and reheated vapor thence flows through conduit 75 to the steam spray nozzle 15 of chamber 11b to flash vaporize the impure water admitted thereto by its associated spray nozzle 12. The resulting vapor is again increased in this chamber by the amount formed by complete evaporation of the impure water sprayed thereinto and this augmented steam flow is delivered to the reheat section 65 by the conduit 76. In a similar manner, the vapor thus reheated in reheat section 65 is delivered to the vaporizing chamber 11:: by conduit 77, etc. Accordingly, in each of the successive evaporating chambers 11d, He and 11 the vapor flow is augmented until all of the thus generated vapor is delivered through the conduit 80 as motive fluid for the steam turbine 28.

In a manner similar to that described in connection with the embodiment shown in FIG. 2, a portion of the condensate is returned to the boiler 63 and the remainder is removed through conduit 42 in pure water form for other useful purposes. However, in this embodiment, the quantity of pure water formed is a considerably larger portion than that required as boiler feedwater. By way of example, by proper proportion and design of the apparatus, the quantity of pure water removed through conduit 42 may be on the order of two-thirds of the total capacity of the vaporizing chambers Ila-11f, inclusive, so that only one-third of the quantity of water produced is required to feed the boiler steam generating section 75. Also, since the quantity of superheated steam sprayed into the vaporizing chambers is progressively increased from one chamber to the next, each successive chamber is capable of vaporizing more impure water than its immediately adjacent upstream neighbor.

It will now be seen that the invention provides apparatus for evaporating mineralized or otherwise impure water with highly improved efiiciency. It will further be seen that the invention provides apparatus of highly simplified form for demineralizing water in which the minerals, such as salt, are precipitated in the evaporating chamber in fine granular form and in a dry state. The granular salt thus precipitated may be conveniently removed for sale or other useful purposes, thereby enhancing the economic value of the apparatus by providing a return on the investment that reduces the cost of producing the pure water.

With this arrangement, substantially all of the recoverable heat energy in the vapor is recovered in the turbine to provide useful power. Hence, in addition to the production of pure Water and granular salt, useful power may also be obtained to motivate an electric generator or the like. Since steam turbine power plants are usually employed by electric power generating utilities and, since pure feedwater is required from time to time to augment that employed in the system, as required to replace water'- lost from the system, this arrangement is highly desirable for such application.

While the invention has been shown in several forms, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various other changes and modifications without departing from the spirit thereof.

What is claimed is: 1. Apparatus for evaporating impure water comprising a closed casing forming a flash vaporizing chamber, means including a nozzle for admitting pressurized impure water into said chamber in a finely divided p y,

a boiler,

means for admitting pressurized superheated steam from said boiler into said chamber and into direct contact With the impure water spray at a rate sufficient to completely vaporize said impure water,

said casing having a portion disposed below said nozzle for collecting solid impurities removed from said impure water during vaporization,

said boiler having a reheater portion,

means for delivering the vapor from said chamber to said reheater,

said reheater heating said vapor to a superheated condition,

means including a steam turbine for extracting energy from the superheated vapor by expansion,

an external load driven by said turbine,

means for conducting at least a portion of the superheated vapor from said reheater to said turbine, means for condensing the vapor after expansion of the vapor,

means for returning a portion of the condensed vapor to said boiler,

and means for removing the remainder of the condensed vapor for other purposes. 2. Apparatus for evaporating impure water comprising a closed casing forming a flash vaporizing chamber, means including a first nozzle for admitting pressurized impure water into said chamber in a finely divided p y,

means including a second nozzle for admitting pressurized superheated steam into said chamber and into direct contact with the impure water spray at a rate suflicient to completely vaporize said impure water,

first conduit structure connected to said second nozzle for delivering steam thereto,

said casing having a portion disposed below said nozzles for collecting solid impurities removed from said impure water during vaporization,

a boiler having an inlet and an outlet,

means for delivering the vapor from said chamber to said boiler inlet including a blower for pressurizing the vapor,

said boiler being eflective to heat said vapor to a superheated condition,

a steam turbine for extracting energy from the superheated vapor by expansion,

an external load driven by said turbine,

second conduit structure connecting said boiler outlet jointly to said second nozzle and said turbine,

and means for condensing the vapor after expansion in said turbine.

3. Apparatus for evaporating mineralized water comprising,

means defining at least first, second and third closed flash vaporizing chambers,

each of said chambers having means for admitting pressurized mineralized water thereinto in a spray,

and means for admitting steam thereinto and into direct contact with the water spray at a rate sulficient to completely vaporize said mineralized water p y,

said chambers each having a lower portion for collecting solidified minerals removed from the water during vaporization;

a steam boiler having at least one steam reheating section and a steam generating section,

said steam generating section being connected to said steam admitting means of said first chamber,

conduit structure connecting the upper portion of said first chamber to said reheating section,

conduit structure connecting said reheating section to said steam admitting means of said second chamber,

means including conduit structure connecting the upper portion of said second chamber to said steam admitting means of said third chamber,

a power plant including a steam turbine and an external load driven thereby,

conduit structure connecting the upper portion of said third chamber to said steam turbine, means including a surface condenser connected to said turbine, and means for removing at least a portion of the condensed vapor from said condenser to provide a supply of pure water. 4. The method of operating a water evaporating system having at least first, second and third vaporizing 10 chambers and a steam turbine which comprises admitting pressurized mineralized water into each of said chambers in a finely divided spray, admitting superheated steam into said first chamber and into direct contact with the mineralized water spray at a rate suflicient to substantially flash said mineralized water spray into vapor and solidify the minerals in small particle form,

reheating said vapor, admitting said vapor to said second chamber to flash the mineralized water spray into vapor by direct contact, reheating the vapor generated in said second chamber, directing the reheated vapor from said second chamber to said third chamber to flash the mineralized 5 water spray into superheated vapor by direct contact, directing said superheated vapor through said steam turbine to motivate the latter, employing said turbine to drive an external load device,

and condensing the vapor passed through the turbine to provide pure water.

References Cited in the file of this patent UNITED STATES PATENTS 986,365 Corliss Mar. 7, 1911 2,328,892 Colgate et al. Sept. 7, 1943 2,515,013 Kruhmin July 11, 1950 2,636,555 Klepetko et al Apr. 28, 1953 2,947,689 Cain Aug. 2, 1960 3,032,482 Shoemaker May 1, 1962

Claims

4. THE METHOD OF OPERATING A WATER EVAPORATING SYSTEM HAVING AT LEAST FIRST, SECOND AND THIRD VAPORIZING CHAMBERS AND A STEAM TURBINE WHICH COMPRISES ADMITTING PRESSURIZED MINERALIZED WATER INTO EACH OF SAID CHAMBERS IN A FINELY DIVIDED SPRAY, ADMITTING SUPERHEATED STEAM INTO SAID FIRST CHAMBER AND INTO DIRECT CONTACT WITH THE MINERALIZED WATER SPRAY AT A RATE SUFFICIENT TO SUBSTANTIALLY FLASH SAID MINERALIZED WATER SPRAY INTO VAPOR AND SOLIDIFY THE MINERALS IN SMALL PARTICLE FORM, REHEATING SAID VAPOR, ADMITTING SAID VAPOR TO SAID SECOND CHAMBER TO FLASH THE MINERALIZED WATER SPRAY INTO VAPOR BY DIRECT CONTACT, REHEATING THE VAPOR GENERATED IN SAID SECOND CHAMBER, DIRECTING THE REHEATED VAPOR FROM SAID SECOND CHAMBER TO SAID THIRD CHAMBER TO FLASH THE MINERALIZED WATER SPRAY INTO SUPERHEATED VAPOR BY DIRECT CONTACT, DIRECTING SAID SUPERHEATED VAPOR THROUGH SAID STEAM TURBINE TO MOTIVATE THE LATTER, EMPLOYING SAID TURBINE TO DRIVE AN EXTERNAL LOAD DEVICE, AND CONDENSING THE VAPOR PASSED TROUGH THE TURBINE TO PROVIDE PURE WATER.