US2388328A - Still - Google Patents

Description

Patented Nov. 6, 1945 zgaaszs x STILL George T. Jacocks, New Rochelle, N. Y., assignor to Heat Transfer Products, Inc., New York, N. Y., a corporation of New York Application May 14, 1942, Serial No. 442,934

(Cl. 2oz- 52) 7 Claims.

This invention relates to distillation, especially the distillation of water rendered impure by the presence of dissolved or suspended matter.

A principal object of this invention is the provision of a method of distilling water of the character stated whereby increased thermal elciency is obtained.

A further object of the invention is the provision of a method of the kind stated which in-l cludes an arrangement for utilizing available potential pressure of a cooling iluid.

A further object of the invention is the provision ora method oi the kind stated which is characterized by the formation of a minimum of deposit on heated surfaces in contact with impure water. f

A still further object of the invention is the provision of a method of the kind stated which is especially adaptable for use in conjunction with self-scaling tubes of my invention.

Other objects and advantages will appear as the description of a particular physical apparatus selected to illustrate the method or process progresses and the novel features will be particularly pointed out in the appended claims.

In describing the invention in detail, and a particular physical apparatus used in practicing the method, reference will be had to the accompanying drawing.

The drawing is a schematic view illustrating an arrangement of physical apparatus usable for practicing the method.

In the drawing numeral I designates an evaporator. Water which is impure either by reason of the presence of dissolved matter or suspended matter or both in given volume is placed in the evaporator Iand its top surface or upper level would be as at 2.

Within the evaporator is a suitable means for heating the water 3. This means may be any oi' the usual ordinary or well-known means but is preferably a bundle of tubes 4 through which a heating medium such as steam is passed. The heating of the water 3 in the evaporator I will produce a water vapor which ascends through the evaporator and through the slot 5 to a condenser 8 where it expands and ilows around the -tube bundle 1.

The tube bundle 1 has an inlet at 8 through which impure water is forced under pressure.

This impure water after circulating through the tube 'I exits by the pipe 9.

The impure water circulating through the tube 1 is of relatively low temperature and so heat exchange occurs between the water in the tube .1

and the water vapor surrounding the tube luwith the result that the water vapor is condensed ,to water which may be withdrawn in any suitable or appropriate manner as by the pipe III. The cooling water issuing from the tubes l by the pipe 9 passes to the heat exchange device II pipe I6 and so to the valve I1, and if this valve is open, to and through the pipe I3 to the given volume 3 oi' impure water in the evaporator I.

Whether or not water enters the evaporator I through the pipe I8 depends upon whether or not the valve Il is open or closed and the position of valve I1 is regulated by the float I9 in the float chamber 20 which is connected by the pipes 2 I and 22 to the evaporator. The connections oi' the oat chamber to the evaporator are such, therefore, that the level of the water 2Ia in the oat chamber is that of the level of the water 3 in the evaporator. If the level of the water 3 in the evaporator lowers then the iioat I9 will lower and cause the rod 22a, to lower and open the valve I1 to allow a further volume of impure water toflow into the given volume oi impure water in the evaporator.

As the formation of water vapor from a body oi impure water results in concentrating the impurity and so raising the boiling point and causing other objectionable results it is desirable to continuously remove a'. portion of the given volume 3 of impure water in the evaporator. In order to do this, there is provided a pipe outlet 23 connected substantially at the bottom of the evaporator which connects through the valve 24 with the pipe 25 so that an adjustment of valve 24 will allow a constant waste through the pipe 25 if it is desired.'

It is not possible, however, to so empty the evaporator 3 if the pressure therein is less than atmosphere so that at certain times. as will hereinafter appear, as the evaporator is operated it will not be possible to exhaust water through pipe 25. It may be done, however by equalizing the pressure between the inside of evaporator and atmosphere.

In the arrangement shown, a portion of the impure water 3 concentrated in evaporator I is withdrawn by means of pipe 26 which connects t o e head 21 of the heat exchanger II and sfaromnthis passes by means of the tubes of tube bundle I2 to the other head 28 and then by pipe 28 to the inlet valve 30 of a pump. This pump has a plunger 3| operated by motor 32 and when the plunger 3| is operated the concentrated impure water is withdrawn from the evaporator I and discharged as waste through the outlet 33 of the pump.

The portion of the cooling water passing through the condenser which will pass into the evaporator I wi11 be governed by the rate of removal of the concentrated impure water in evaporator I by means of the pump. It has been found in practice that a desirable relationship of the water volume is to remove from the evaporator at a constant rate in a given time, twice the volume of water vapor produced, measured as water, and to allow such a portion of the condenser cooling water to flow into the evaporator in some given time at a constant rate as will equal three times the volume of the water vapor produced measured as water. By regulating the operation thus, the impure water in the evaporator does not become objectionably concentrated and so therefore does not cause the objectionable results which would ilow from a too high concentration notable the undue rising of the boiling point and the undue deposition of sediment upon the heating coils 4.

The cooling 'water issuing from the tube bundle l by the pipe 9 is also allowed to flow into the pipe 3l and so to the inlet 35- of a water jet air eductor 36. The water passing through the eductor 36 creates a suction at the suction orice 31. This suction orifice 31 is connected by the pipe 38 to the condenser chamber 39 and so to the surface above the impure water 3 in the evaporator I.

The amount of vacuum created over the water in the evaporator may be controlled by controlling the amount of flow of water through the air eductor so that any desired partial vacuum may be created in the evaporator I. i

As the rate of flow or pressure of the impure water through the condenser may not be constant it is preferred to interpose a pump, preferably a centrifugal pump 40 in the pipe line 34 and to operate this pump through the connection II with the motor 32 so that a more constant and sufiicient pressure at all times willwbe maintained at the air eductor.

By the method set forth of producing distilled water, the vapor is produced at a lower temperature than if it had been produced at atmospheric pressure so that the amount of scale formation is reduced. This scale formation is further reduced by preventing the formation of a high c oncentration of impurity in the evaporator. It is further contemplated that the tubes forming the bundle 4 will be made in accordance with my Patent No. 2,274,066 granted February .24, 1942, because the method herein set forth is especially emcient in connection with the use of such tubes because the range of temperature between or-` dinary atmospheric temperature and vaporization temperature is less in a method such as herein set forth than in the ordinary method where vapor is produced at atmospheric pressure, consequently, in order to cause a flexing of tubes of the bundle 4 when made in accordance with my application herein before referred to a much smaller range of temperature is necessary to pass from a full straight tube to the completely curved tube or vice vensa so that a small change in temperature will cause the scale formed onthe tubes to be removed and then it may be washed out through the pipe 2B.

Not only does the heat exchanger I I enable me to preheat the fresh supplies of impure water which go into the evaporator and so increase thermal eillciency but the heat exchanger II also cools the heated impure water coming from the evaporator I to such an extent that ebullltion does not take place in the line to the pump andV so does not interfere with the volumetric eiiiciency of the pump. This is important. -because the pump including the plunger 3| is in effect a volumetric pump as it is depended upon to remove a definite volume of liquid from the evaporator I in a given time.

AlthoughfI have particularly described one of the physical embodiments of the idea and means underlying my invention and explained the principal and mode of operation thereof and my new and novel method as illustrated by one of the physical embodiments, nevertheless, I desire to have it understood that the form selected is merely illustrative but does not exhaust the Dossible physical embodiments of the idea and means underlying my invention or the different physical embodiments by which my method may be practiced.

What I claim is new and desire to secure by Letn ters Patent of the United States is:

1. The method of distilling water vapor from impure water which comprises subjecting the vapor to the cooling action of a fluid under pressure and then directing the fluid from a zone of low velocity to a zone of high velocity and by said velocity change creating a partial vacuum in the space receiving the water vapor.

2. The method of distilling .water vapor from impure water which comprises subjecting the vapor from a given volume of impure water to the cooling action of a further volume of impure water under pressure and then directing a' portion of said further volume of impure water into the given volume of impure water and directing another portion of the impure water from a zone of low velocity to a zone of high veloci-ty and by said velocity change creating a partial vacuum over the given volume.

3. The method of distilling water vapor from impure water which comprises subjecting the vapor from a given volume of impure water to the cooling action of a further volume of impure water under pressure and then directing a por-tion of said further volume of impure water into the given volume of impure water in amount substantially equal to three times the volume of the vapor distilled measured as water and directing another portion of the impure water from a zone of low velocity to a zone of high velocity and by said velocity change creating a partial vacuum over the given volume.

4. The method of distilling water vapor from impure water which comprises subjecting the vapor from a given volume of impure water to the cooling action of a further volume of impure water under pressure and then directing a portion of said further volume of impure water into the given volume of impure water in amount substantially equal to three times the volume of the vapor distilled measured as water and directing another portion of the impure water from a zone of low velocity to a zone of high velocity andby said velocity change creating a partial vacuum over the given volume and removing a volume of the given volume of impure water as aug `heated in the heat mented in an amount substantially equal to two times the volume of water vapor produced, meastherlvolume of impure water. then passing a portioniof the further volume of cooling impure water in heat exchange relation to a portion taken from the given volume of impure water whereby the portion of the given volume of impurewater is reduced in temperature below its ebuilition point and then directing another portion of the impure water from a zone of low velocity t a zone of high velocity and by said velocity change creating a partial vacuum over the given volume.

6. In a distillation apparatus, in combination; an evgaporator, including means for heating and adapted for .containing a given volume of impure water; a condenser, said condenser including means for receiving water vapor from the evaporator and for cooling said water evaporated by heat exchange relation with a further volume of impure water circulated under pressure; a pump; a motor for operating the pump; connections between the pump and the body of water in the evaporator whereby water in the evaporator may be withdrawn therefrom by the pump; `a heat exchange device interposed in the connections :between the pump and the water in the evaporator, said heat exchange device providing means for heat exchange between water pumped from the evaporator and cooling water issuing `from the condenser whereby the cooling water issuingy from the condenser is heated and the water pumped from the evaporator is reduced in temperature below its ebuilition point; means connecting the cooling water from the condenser through the heat exchange device 'to the evaporator whereby the cooling water after being exchange device may pass into the evaporator to replace that lost by evapo# v formation to a minimum,

ration; a water iet air eductor, connections between said eductor and the cooling water issuing from the vapor condenser, said connections including a pump interposed therein; a connection between said centrifugal pump and said motor whereby the centrifugal pump is operated to send water through the water iet air eductor and connection between the suction inlet of the water .iet air eductor and the space above the water in the evaporator whereby a' partial vacuum is created above the water in the evapora-tor whereby ebullition in the evaporator takes place at a temperature lower than what it would take place under ordinary atmospheric pressure and whereby any desired volume of water from the evaporator may be withdrawn by the pump and any desired volume may be replaced in the water evaporator by water from the volume of impure water used in cooling and means forregulating the Water level in the water evaporator.

'7. The method of recovering pure water from impure water which consists in heating the impure water under diminished pressure producing vapor, condensing the vapor by heat exchange with a further volume of impure water, con-tinuously removing impure water from the heating region and passing the impure water so removed in heat exchange relation with the further volumes of impure water and then adding the further volume of impure water to the heating region, diverting a por-tion of the further volume of impure water before passing in heat exchange relation and directing it from a zone of low velocity to a zone of high velocity and by said velocity change creating a partial vacuum above the heated impure water whereby evaporation occurs under reduced pressure, thereby reducing scale both because of the constant withdrawal of impure water from the heating region and because of the reduced temperature of evaporation and whereby the power further volume of impure water.

GEoReE T. J'Acocxs.

Images