US2097364A - Still - Google Patents

Description

Oct. 26, 1937. E, BRANSON 2,097,364

STILL File d Dec. 21, 1934 2 Sheets-Sheet 1 M INVENTOR WW5 VOWATTORNYS Oct. 26, 1937.

Filed Dec. 21, 1934 J. E. BRANSON STILL 2 Sheets-Sheet 2 t -20 l .50 I 5 :2 g

INVENTOR iryonums Patented Oct 26, 1937 @UNlTED STATES PATENT OFFICE STILL Application December 21, 1934 Serial No. 758,633

11 Claims.

This invention relates to the art of distillation and has particular reference to those industries where accuracy of distillation is of secondary or incidental, rather than of primary importance,

5 and where reliability and simplicity are requisite.

The utilization of the distillation apparatus of the present invention is characterized, for instance, in the dry cleaning industry, in which volatile, inflammable hydrocarbon solvents are used to effect the removal of oils, greases and dirt. The distillation of solvent of the type used in dry cleaning industry will therefore be used as an example of the use to which the apparatus of this invention may be applied.

In the dry cleaning industry, fabrics to be cleaned are immersed, agitated and treated in a solvent of the type exemplified by gasoline, naphtha. benzine, etc., and, during the process, dirt and foreign matter is removed from the fabrics and becomes entrained in the solvent. The solvent consequently must be clarified before further use. Moreover, in some dry cleaning processes, water is used in conjunction with the solvents as an additional fabric treating agent, and entrain-ed water further contaminates the dirty solvent. To ei fect clarification of the solvent the distillation process is quite generally used.

In an industry such as the dry cleaning, the clarification process is, obviously, a procedure of relatively minor importance so far as the entire business is concerned but, on the other hand, it is a necessary step and must be conducted by methods which are simple, reliable, occasion the most infrequent supervision and, lastly, which are utterly safe. In many industries such as the dry cleaning industry, where the operators are not given to close control of incidental operating problems, elaborate, complex or precisely ac-.

curate distillation apparatuses are not only unnecessary but definitely undesirable.

Since the conditions of distillation are practically constant, flexibility of control is unwarranted; but, since the material being distilled is inflammable and dangerous, safety and reliability are urgent requisites.

The expulsion of entrained water in the clarified solvent in the past has necessitated the use of elaborate moving-part mechanisms such as 50 float-operated valves, traps and the like; all of these necessitating frequent maintenance and adversely affecting the reliability of the apparatus. By a novel method, my invention'utilizes the natural difference in gravity between water 55 and solvent to accomplish the expulsion of the water. No moving parts are used to effect the removal.

To make the apparatus safe, after vaporization of the dirty solvent and condensation of the vapors, the temperature of the condensate is lowered to a safe working temperature by incorporating into the condenser a liquid cooler, oraftercooler. By means of the expulsion apparatus the water level of the condensate in the aftercooler is maintained constant and, as a result, the temperature of the clarified liquid remains substantially constant at a safe temperature below the danger point.

My-invention essentially comprises an evaporator, a preheater, adapted to transfer part of the heat from the vapors generated in the evaporator to the incoming dirty solvent, and an after-cooler condenser which condenses the balance of the vapors generated in the evaporator and further cools all of the distillation condensate in the after-cooler portion. In operation, the vapors are condensed as rapidly as they are generated. To obviate the necessity of high temperatures during operation, vacuum is maintained in the system. Under vacuum, the boiling point of the dirty liquid is lowered and vaporization takes place at a lower temperature. The flow of the vapors through the elements of the apparatus should be as short as possible since the resistance to flow reduces the vacuum.

Minimum resistance to gas passage is obtained by interconnection of the preheater and the condenser in parallel with one another and in series with the evaporator. Through this arrangement less heat is utilized to operate the apparatus. This method of connection makes possible a desirably compact structure.

It is therefore an object of this invention to produce a distillation apparatus which embodies the foregoing desirable characteristics and which is of a design particularly suitable for application to an industry such as the dry cleaning industry.

It is another object of this invention to provide in a distillation apparatus automatic means for discharging any water which may be contained in the clarified solvent.

It is a further object of this invention to produce a distillation apparatus which is completely and reliably automatic in operation.

It is a still further object of this invention to provide a vacuum distillation apparatus in which maximum vacuum maintenance is obtained by means of minimum resistance to flow.

It is a still further object of this invention to PIQViile a distillation apparatus which is operable economically and safely by the use of tap water such as is usually available, without the necessity of further cooling the clarified solvent after the solvent leaves the apparatus.

Other objects and further advantages will be more fully apparent from a description of the accompanying drawings, in which:

Figure 1 is a partially diagrammatic elevation of the apparatus, the preheater and the condenser having been separated from the evaporator for purposes of clarity of illustration.

Figure 2 is a fragmentary cross sectional view of the evaporator, showing the heating element.

Figure 3 is a perspective view of the assembled apparatus.

In the drawings, line 4 admits raw solvent to a preheater 5, of the counterfiow type. The preheater is of sufficient capacity to transfer at least the latent heat of vaporization of the gases to the incoming liquid and comprises a shell 6, fitted with end caps 'I-7, and tube sheets 8--8, which are spaced inwardly from the ends of, and pressure tightly attached to shell 6. Extending between the tube sheets 88 and expanded into borestherein are disposed a plurality of heat transfer tubes 9. Transversely embracing alternate parts of the tube bundle and disposed to cause the gases to take a circuitous path generally longitudinally of the tubes, are a plurality of bafiles I0.

An evaporator I I is connected to the preheater 5 by a vapor manifold I 2 and a liquid supply line I3. The evaporator I I comprises a shell I4 preferably closed at each end by dished heads. The evaporator is heated by a heating element generally indicated by I5. The heating element, which is disposed at the lower portion of the evaporator shell I4, comprises a plurality of tubes l6 held in the form of a tube bundle by tube sheets II-I I,- which are pressure tightly annexedto opposite steam boxes I 8-I8 extending from the evaporator shell and capped by end caps I9! 9.

The tubes I6 are of such length that the tube sheets I'I-I'I at the ends thereofdo not extend to the extremities of the steam boxes I8I8 but are spaced inwardly therefrom to form chambers generally indicated by 20. From one such chamher a steam condensate discharge line 2| is taken to a trap whereby, if desired, the steam condensate from the heater may be discharged back to the heating system or boiler.

From the top of the evaporator a vapor discharge line 22 is connected into the manifold I2. From the bottom of the evaporator a drain line 23 is taken to provide means whereby the evaporator I I may be drained. The liquid level in the evaporator is automatically controlled within predetermined limits by a liquid level controller 2 which is preferably of the fioat operated type.

Lines 25 and Z6 connect the liquid level controllers 24 to the evaporator and are taken at points above and below the liquid level desired to be maintained therein. The liquid level of the evaporator is visible through a sight glass 21. A vacuum gauge 28 indicates pressure conditions within the evaporator.

To the end of the vapor manifold I2 opposite the preheater 5 is connected a counterfiow type after-cooler condenser 29. This element of the apparatus, generally similar inconstruction to the preheater 5, is of a size suitable to condense part of the vapors from the evaporator and additionally cool all the distilled condensed liquid.

This element performs two functions, these being condensing of the vapors from the evaporator,

sired to be maintained in the element.

a plurality of tubes 33.

and cooling of these condensed vapors and the vapors condensed in the preheater 5. Otherwise stated, the condenser element is sufficient to remove from the vapors the latent heat of vaporization. By incorporating and making integral with the condenser a liquid cooler, that is to say, by making the condenser of elongated form, the lower part of the element serves as a liquid cooler while the upper part of the same element serves as a condenser, and the dividing line between,the two elements may be considered the liquid level de- This structure is particularly desirable in apparatus of the type being described inasmuch as the apparatus may be compacted and simplified.

This after-cooler condenser 29 comprises a shell 30 fitted with end caps 3 I3 I, tube sheets 3232 which are disposed inwardly from the ends of the shell 30 and into the bores of which are expanded Counterflow inlet and outlet coolant connections 34 and 35 are connected to the respective ends of the after-cooler condenser. A plurality of bailles 36 alternately oppositely embracing portions of the tube bundle are disposed from the shell 30 so as to cause the vapors and the liquid flowing therethrough to take a path generally longitudinally circuitous.

A steam operated air ejector 31 adapted to create vacuum in the apparatus prior to starting is connected to the condenser at the line 38. This point of connection is above the predetermined liquid level in the after-cooler condenser. To a T in the line 33 is connected the upper end of a riser leg or stand pipe 39, the lower end of the stand pipe being connected to the after-cooler at or near the bottom of the after-cooler or liquid chamber. Between the extremities of this riser leg is taken a discharge line 40 at a height corresponding to the height at which the liquid level in the after-cooler condenser is to be maintained. Line 40 is directly connected to a vacuum pump 4|. The ejection of air from the system, that is to'say, the air ejector 31, is controlled by the valves 42 and 43.

Vapors condensed in the preheater by the incoming raw liquid are passed to the after-cooler zone orportion of the condenser through a line 44 and, in the after-cooler, mix with the other condensate to be further cooled. If the material being clarified be inflammable and of a dangerous nature, the cooling capacity of the after-cooler should be sufficient so that with the evaporator operating at normal capacity and with cooling water at a normal temperature, for instance as high as F., the discharge temperature of the liquid will be safely within the critical or flash point temperature.

Line I3 in which is located a liquid level controller operated valve 44*, automatically passes partially heated raw liquid from the preheater 5 to the evaporator II in accordance with the rate of vapor generation in the evaporator so that the liquid level in the evaporator is maintained substantially constant. It is preferable that the automatically controlled valve 44 be by-passed for hand control, if necessary, as at 45.

A relief connection 46 is taken from the vapor or condenser zone of the condenser 28 to the preheater 5. This cross connection serves. to equalize the pressures within the twoelements and enables the preheater to, operate at maximum capacity.

It is preferable that the evaporator be heated by steam coils adapted to operate at comparatively low steam pressure. The main steam line to the apparatus is indicated by 41. From this line steam is applied to the ejector 31 which operates at comparatively high pressure through a line 48. A pressure reducing valve 49 is used to reduce the pressure in the main steam line 41, and line 59 connected to the reduced pressure steam supply supplies low pressure steam to the heating element [5. All of the Vapor and liquid connections in the apparatus should be pressure tight. Method of operation In putting the apparatus into operation, steam is admitted to the ejector 3'! by operation of valve 43; valve 42 is opened and vacuum is created in the system during the starting-up period. The vacuum created, which is preferably of the order of 20 to 25 inches of mercury, will draw raw liquid into the preheater through line 4, from which it will flow to the evaporator ll through line it until the liquid level control 24 operates valve 44a, to stop the flow at a predetermined level. Steam is admitted to the heating element I and the liquid in the evaporator is brought up to its boiling temperature. As the liquid approaches boiling temperature, the vacuum in the system is lowered, the condensate pump 4! is started, and coolant is admitted to the condenser through line 34. After the starting period, the ejector control valves 42 and 43 are closed unless it becomes necessary during operation to effect removal of air and non-condensable gases.

I-Iot vapors are liberated in the evaporator. These vapors rise upwardly to header manifold l2, and part pass to the preheater 5, the remainder passing to condenser 29. In the preheater 5 the hot gases heat the incoming cold, raw liquid. The vapors condensed in the preheater pass through line 44 to the after-cooler portion of condenser 29 wherethe liquid is further cooled. The line 46 equalizes the pressure in the preheater with that in the condenser so that as much heat as possible is transferred to incoming raw liquid in the preheater.

In the condenser 29 the gases are condensed and thereupon pass to the after-cooler zone, mix with the condensate from the preheater, and are further cooled by coolant admitted through line 34,

Any water accumulating in the condenser, either by mechanical carryover or by direct vaporization, being aheavy component, will settle to the bottom of the condensate chamber and as the level of the distilled liquid above builds up, the Water will be over-balanced and forced from the system through riser leg 39 and withdrawn through line 4 and the pump 4!. The liquid level in the condenser will not rise above the line 38, since any liquid rising to this point will overfiow through the line. Furthermore the connection of the stand pipe 39 to two outlets in the condenser 29 affords a relief connection to facil itate unrestrained flow through the gooseneck comprising the line 39 and the line 40.

As liquid is evaporated in the evaporator l I, the liquid level control 24 operates to open valve 44 admitting additional preheated raw liquid so that substantially constant liquid level is maintained therein.

Dirt and so-called heavy ends accumulating on the evaporator bottom are removed through the drain connection 23, at convenient periods.

In operation, since there is only one moving part, little or no maintenance is required other than to drain the separated foreign fractions from the evaporator at sufficiently frequent intervals to prevent undue accumulations.

Having described my invention, I claim:

1. In a still of the type described, an evaporator, a manifold adapted to receive the discharge from said evaporator, a preheater connected to one end of the manifold and adapted to heat incoming, undistilled liquid by means of the vapor discharged from the evaporator, an. integral condenser and liquid cooler connected to the other end of the manifold adapted to condense the remainder of the vapors not condensed in the preheater, a pressure equalizing connection between the preheater and the condenser, a condensate discharge line from the preheater to the liquid cooler, and means for constantly maintaining a predetermined liquid level within the liquid cooler.

2. In a vacuum distillation apparatus, including an evaporator, a preheater and a condenser, the preheater and the condenser being in parallel gas circuit connection, meansfor concurrently maintaining a volume of condensed liquid at'a predetermined level in the condenser and automatically expelling foreign fractional components of heavier gravity, comprising an outlet from the condenser at a level below said predetermined level, a riser leg connected to said outlet, a dis charge outlet connected to said riser leg at a level corresponding to the predetermined liquid level to be maintained in the condenser, and a relief connection taken from said discharge outlet connecting with the condenser, at a level above the said predetermined liquid level in the condenser. u

3. In a vacuumdistillation apparatus, in combination with an evaporator, a condenser adapted to condense part but not all of the gases from the evaporator, a preheater adapted to transmit at least the heat of vaporization from the balance of the gases to incoming undistilled liquid, the preheater and the condenser being in parallel gas circuit connection, conjointly to receive vapors from the evaporator, a liquid cooler integral with said condenser, and means for maintaining a liquid level therein, comprising a stand pipe having its terminals respectively connecting with the said liquid cooler and condenser at levels above and below the said liquid level to be maintained in said liquid cooler, and a discharge connection from said stand pipe at a height corresponding tothe height of the desired liquid level in the liquid cooler.

4. A still for purifying liquids such as dry cleaners solvent, wh chcomprises, an evaporator, a vapor manifold into which said evaporator discharges vapors, a preheater, atone extremity of said vapor manifold, adapted to condense a portion of the vapors from the evaporator by exchange of heat to raw incoming liquid flowing toward the evaporator through said preheater countercurrent in relation to said vapors, a condenser connected to said vapor manifold at its other extremity and adapted to condense the remaining portion of the vapors not condensed in said preheater, means to convey liquid condensed in the preheater to the condenser, means for equalizing the vapor pressure in the preheater and the condenser, and means for maintaining a substantial volume of liquid in said condenser for cooling, before it is discharged from said distilling apparatus.

5. In a vacuum distilling apparatus for removing impurities from liquids, a vapor manifold, an evaporator discharging vapors into said manifold intermediate its length, a preheater connected with said manifold at its one extremity,

for transferring heat from the vapor it receives to raw liquid to be purified, and a condenser connected with the other extremity of said manifold for condensing the remainder of the vapors discharged into said manifold not condensed. by said preheater, means for equalizing the pressure between said preheater and said condenser, means for transferring liquid condensed in said preheater to said condenser, and means for maintaining a substantial level of liquid condensate in the lower portion of said condenser, said means comprising an outlet at the lower extremity of said condenser, a gooseneck element rising from said outlet to the height at which the liquid level is desired to be maintained in said: condenser, and a relief connection from said gooseneck element to the condenser above the liquid level therein to be maintained.

6. In a vacuum distilling apparatus for removing impurities from liquids, a vapor manifold, an evaporator discharging vapors into said manifold intermediate its length, a preheater connected with said manifold at its one extremity and adapted to transfer heat from the vapor it receives to raw liquid to be purified, and a condenser, connected to the other extremity of said manifold for condensing the remainder of the vapors discharged into said manifold and not condensed by said preheater, means for equalizing the pressure between said preheater and said condenser, and means for transferring liquid condensed in said preheater to said condenser.

7. In a vacuum distillation apparatus, which includes an evaporator, a preheater and a con- .denser, a manifold adapted to receive vapors from the evaporator, the preheater and the condenser connected to said manifold in parallel relation to each other, means for continuously maintaining a predetermined volume of distilled condensed liquid in the condenser, comprising, a riser leg having terminals connecting with the condenser at elevations above and below a determined condensate discharge level to be maintained in the condenser, and a discharge outlet connecting with the said riser leg at a level intermediate the levels of the terminals of the,riser leg, controlling the discharge level maintained thereby in the condenser.

8. In a vacuum distillation apparatus, comprising, an evaporator, a preheater, a condenser, a vapor manifold adapted to receive vapors from the evaporator, connecting the preheater and the condenser in parallel gas circuit relation and means for maintaining a volume of condensed liquid at a predetermined level in said condenser, comprising, a conduit having its terminals-connecting with, said condenser at levels above and below said predetermined level, and a discharge outlet in said conduit intermediate its terminals and at the level of the liquid to be maintained in said condenser..

9.. A still for distilling liquid such as dry cleaners solvent which comprises, an evaporator, a condenser, a preheater, a vapor manifold adapted to receive vapors from said evaporator, the preheater and the condenser communicating in parallel with the manifold conjointly to receive vapors therefrom, means for passing raw liquid through the preheater, the preheater adapted to condense a portion of the vapors from the evaporator by exchange of heat to incoming raw liquid, means for conveying raw liquid from the preheater to the evaporator, the condenser adapted to condense vapors from the evaporator not condensed in the preheater, the preheater and the condenser additionally communicating with each other for passage of condensate from the, preheater to the condenser and for equalization of vapor pressure in the condenser and in the preheater, and means associated with the condenser for cooling liquid condensate before it is discharged from the distillation apparatus.

10. A distillation apparatus for distilling liquid such as dry cleaners solvent, which comprises, an evaporator, a heat exchange preheater in which a portion of the vapors from the evaporator are condensed by heat exchange with incoming solvent, a condenser adapted to condense vapors from the evaporator not condensed by the preheater, a vapor conduit adapted to receive vapors generated in the evaporator, the preheater and the condenser communicating in parallel with the conduit conjointly to receive vapors therefrom, and means associated with the condenser for effecting cooling of the liquid condensate before the liquid condensate is discharged from the distillation apparatus.

11. In a vacuum distillation apparatus, the combination comprising an evaporator, a condenser, a preheater, a vapor manifold adapted to receive vapors from said evaporator, the preheater and the condenser communicating in parallel with the manifold, conjointly to receive vapors therefrom, part of the vapors from the evaporator being passed to the preheater to heat incoming undistilled liquid, the remaining part of the vapors being passed to the condenser, means conveying condensate from the preheater to the condenser, and means for equalizing the vapor pressure between the condenser and in the preheater.

JAMES E. BRANSON.

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