US1390677A - Evaporating apparatus - Google Patents

Description

W. L. DE BAUFRE.

EVAPORATING APPARATUS.

APPLICMION HLED MAR13,1917.

'Patented sept. 13,1921.

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Specification ot Letten Patent. Patelited Sept. 13, 1921.

Application led Hatch 13, 1917. Serial No. 154,584.

To all whom it may concern Be it known that I, WILLIAM L. DE BAUFRE, a citizen of the United States, residing at Anna olis, in the lcounty of Anne Arundel and tate of Maryland, have invented a new and useful Evaporating Apparatus, of which the following is a specilcation.

My invention relates to apparatusv for evaporating and concentrating solutions and for recoverin the products of distillation by condensation, and has for its object the arranging and proportoning the several parts of such ap aratus so asto secure the most economicaf) and efficient operation, especially in those systems employing vapor com ressors for regenerative working.

ith the foregoing and other objects in view, my invention consists of the novel construction, combination'and arrangement of parts as hereinafter specifically described and illustrated in the drawings wherein is shown4 the preferred embodiment of my invention, but it is understood that changes, variations and modifications can be resorted to which come within the scope of the claims hereunto appended.

In the drawings of the herein described embodiment of my invention, Figure 1 shows a sectional view in elevation of my improved evaporating apparatus' Fig. 2 is a sectional View taken through Al of Fig. 1..

In the evaporating apparatus as shown in the two figures, the evaporator shells l and 3 constitute evaporating chambers, and within them are located the condensing chambers 2 and 4 respectively. The latter are illustrated as composed of helical coils of tubing connected to headers at top and bottom. The condenser shell 5 contains a similar condensing chamber 6, the reheater shell 7 a similar condensing cham er 8, and the heat exchanger shell 9 a similar cooling chamber 10.- Eleven and 12 are va or compressors of the ty e shown more in detail in i 3, 4 and 5. I'lhe numbers 15, 16, 17, 18 and 19 refer to devices for removing liquids from the several evaporatin and condensing chambers as will be exp ained later.

The plant is represented as having two effects onl shellV 1 with coils 2 bein Vthe first effect, andy shell 3 with coils 4 ing the second effect. While this number of Y effects is sufficient to illustrate the operation of the apparatus, any number of additional effects may be added between the second effect (shell 3) and the condenser (shell 5)'.

The primar va or is suf lied b main 20 through valvespQl' `and 52pm they steam nozzles 12 and 14 of vapor compressors 11 and 13 respectively, through valve 23 directly to the condensing chamber 2 of the first effect, through valve 2 4 directly to the condensing chamber 4 of the second effect, and to such additional effects, pumps, etc., as ma be required. Valves 25 and 26 control t e lsupply of secondary vapor from the evaporating chambers to the vapor compressors 11 and 13. and valves 27 and 28 control the discharge therefrom of the commingled primary and secondar vapors to the coils 2. A b -pass not s own could readily be provided to convey these cammingled va ors to the coils 4 of the second effect. alves 29 and 30 control the dischar e of vapor from shells 1 and- 3 respective y. Valve 3l controls the flow of vapor from the shell 1 of the first effect into the coils 4 of the second effect. Valve 32 'is a vapor by-pass from the first to the effects following the second and to the condenser. Through valve 33, vapor is supplied the coils 8 of the preheater.

From pipe 34 the liquid resulting from the condensation of vapor within coils 8, is drained away either b a valve manually operated or automatica ly by a trap such as indicated by 1%'18 and 19 for discharging the liquid forme in the condensing chambers 2, 4 and 6, respectively. Upon these indicate by the liquld level the roper working of the float or bucket wit in the trap. At the tops of these traps are connected :the air cocks 35, 36 and 37 to discharge the non-condensable gases which collect just above the liquid within them. The liquid is discharged by these traps through drain main 38 to the coils 10 of the heat exchanger and thence through pipe 39 to a storage tank not Shown or to waste. The non-condensable gases may 'also be discharged through coils 10 by connections'such as 40 from air cock 35 to drain main 38. By this means the heat in the non-condensable gases and the saturated vapor commingled with them is conserved, as wellias the heat in the` condensed vapor. It would be impractical to discharge these gases with the condensed steam without. dlschargin a considerable amount of vapor. If it is esired to operate traps are mounted age glasses at the side to fio the condenser and last effects at less than. l;

pumps to remove both the liquid and condensable gases under a vacuum.

Circulating water flows through shell 5 -over coil 6 of the condenser, the rate of flow being controlled by valve 41 and the circulating water pump not shown. This circulating water 1s discharged through pipe 42. In the case of evaporating apparatus intended primarily for the production of fresh water, the raw water to be fed through valve 43 may be taken from pipe 42. In any case, the rate of feed of the liquid to be evaporated is controlled by valve 43 and a feed pump not shown. Passing through the shell 9 of the heat exchanger and the shell 7 of the preheater, the solution enters the first effect through pipe 44.

The partially evaporated liquid passes from shell 1 through pipe 45 to trap 15 from which itis automatically discharged through pipe 47 to shell 3 of the second effect. Pipe 46 serves to equalize the pressures within trap 15 and within shell 1. .A gage glass on the trap 15 indicates by the liquid level the proper Working of the bucket or fioat within the trap to maintain the proper liquid level within shell l. From the second effect the liquid not evaporated therein is similarly discharged through pipe 50 to the succeeding effect or to a storage tank or to waste, by trap 16 with supply pipe 48 and equalizing pipe 49. The valves 51 and 52 are provided for draining the shells 1 and 3 respectively.

Bale 53 within shell 1 prevents columns of liquid being projected into the vapor space due to the boiling within the 'coils 2 below it. The vapor -produced is caused by pan 55 to pass to the circumference of the shell, and from the circumference the vapor must pass to the vapor pipe through a number of perforated openings staggered in two or more concentric cylinders 59. The moisture separated thereby drips down into pan 55 and is conveyed by pipe 57 either without the shell or to within the solution as shown. Within shell 3, the submerged baiile 54, separator 60, pan 56 and pipe 58 perform similar functions.

Upon shells 1 and 3 are mounted safety valves 61 and 62 so disposed that the escaping vapor does not pass through the separators for removing moisture from the va or before it reaches the vapor pipes. On s ell 1 there` is also shown a 4vacuum break'valve 63 to prevent the pressure within the shell becoming much less than atmospheric. A similar valve can be provided on-shell 3.

To the float 64 is attached the valves 65 and 66, the former to throttle the `-feed and the latter to discharge at first vapor and then liquid should the latter rise abnormally. The pipe 67 conveys the liquid-discharged to waste or to a storage tank.

Upon the top of the preheater an autoneeds?? matic device 68 is mounted to discharge noncondensable gases collecting therein.

Pressure gages may be provided as at 69l and 70 to aid in the proper operation of the apparatus.`

Referring to Fig. 1, during normal operation of the system, primary vapor is supplied through main 2O at a pressure slight higher than that for which the vapor compressors 11 and 13 are designed to operate. By throttling either manually by the valves 21 and 22 or automatically by reducing valves, the pressure is reduced to that for which the De Laval nozzles in the vapor compressors are designed. This reductlon in pressure near the compressors dries the primary vapor and may somewhat superheat it if the drop in pressure is sufficient, thus improving the action of the compressor. Y

With valves 25, 26, 27, 28 and 29 open, secondary vapor is drawn from shell 1, compressed, and forced at a higher pressure and temperature into coils 2 commingled with the expanded primary vapor from the De Laval nozzles 12 and 14. Within the coils 2, the commingled vapors are condensed, the resulting liquid trickling down through the coiled tubes to the trap 17 into which the non-condensable gases are also driven by the flow of the vapor. It is particularly desirable when vapor compressors are used, to so arrange the condensing chamber of the evaporator to produce a definite and rather high velocity over the condensing surface of the vapors to be condensed in order to attain a high rate of heat transfer. Also, the noncondensable gases, which are ordinarily denser than condensable vapor of the same pressure and temperature, should be driven downward by the How ofv vapor. Both of these objects are obtained by the arrangement of heating surface shown in Fig. 1.

The vertical coiled tube in transmitting heat vto the liquid within the coils form a column of mingled liquid and vapor less dense than the solid mass of liquid near the shell. This difference in specific gravity results in a flow up within the coil and down outside of it, with a conse uent improvement in heat transfer from t e outside surface of the coil to the solution. This also is particularly advantageous when vapor compressors are employed.

The columns of mingled liquid and vapor bubbles are prevented from being projected into the vapor space by the baffle 53 placed just above the coils. The va or bubbles are separated to a great extent rom the liquid and escape under the edges of the bale to the vapor space above. The pank 55 delects the rising vapor to the circumference of the shell, and to reach the vapor pipe the vapor must pass in a number of small streams through the holes or slits in the cylinders 59. The holes or slits are staggered 1n order to deflect the streams and thus'separate the moisture which drips into pan 55 and is conveyed by pipe 57 to within the solution. The pipe57 may be arran ed to convey the moisture without the shel It is very desirable that the vapor to be compressed by this form of compressor be free from moisture, as is accom lished by the means described.

Witli valves 24 and 32 closed, a part of the vapor produced in shell 1 passes through valves 29 and 31 into the condensing chamber 4 of the second effect, where it is condensed by imparting its latent heat through the surface ofcoils 4 to the li uid Within shell 3. Of the total uantity o secondary vapor roduced in she 1 1, from one-half to four-fi ths will be compressed by the vapor i compressors and discharged into coils 2 to be there condensed with the primary vapor, whilel the remainder of the secondary vapor asses to the coils 4 of the second effect. gVith the same temperature difference between vapor within the coils and liquid outside of them in the second effect as in the first effect, it is evident that there should be only one-half to one-fifth the condensing surface in the second effect as in the first effect.

The vapor produced in shell 3 by the condensation of secondary vapor from shell 1, passes through valve 30 to the coils 6 constituting the condensingchamber of the condenser having the shell 5. A continuous flow of circulating water is maintained through within the condensinigr shell 5 by regulating the valve 41 and the circulating water pump not shown.

Durin normal operation, the liquid resulting rom condensation of the vapor chamber 2 of the first removed by the trap greatest importance effect, is automatcal 17; and, what is of t e l 1n an evaporator operated by a vapor compressor, the non-condensable gases are continuously discharged from directly over the liquid surface where they collect. This latter is accomplished throu h the cock 35, which is representedv as of t e hand o rated type, but an automatic device may providedl which will allow gas with but very little vapor to escape. Similar traps 18 and 19 with cocks condensed vapor and -non-condensable gases from condensing chambers 4 and 6 respectively.

The condensed va r escapes at a temperature approaching t at of the vapor from which it is formed. Passing throu h drain pipe 38 to the coils 10 of the eat exchanger, it is cooled `by the incoming feed before being discharged by pipe 39. In some installations it may be desirable to keep separate the condensate from the first eect,

36 and 37 remove the shutting off point. This heating causes a separation o much of the contained gases, 4.and these are automatically removed by the device-68, or provision for their escape may be made by a manually operated cock at 68. The removal of the gases before theyenter the evaporator shell improves the performance ofthe vapor compressors which would otherwise have to remove them.

Entering the shell 1, the heated liquid boils by reason vof the further addition of heat from the coils 2. The partially evaporated liquid passes through pipe 45 to the trap 15 from which it is automatically discharged through 'Ipipe 47 to the shell 3 of the second effect. he liquid in pipe 45 is denser than the mixture of liquid and vapor bubbles within the shell 1. Consequently, the li uid level in 15 will be lower than the sur ace of the solution in the shell. The heating surface is most efficacious when the level Within the shell stands just about the top of the heating surface, the solution level in the trap 15 and attached gage glass then being from 0 to .10 inchesv lower. In an evaporator employing a vapor compressor, therefore, the most efficient operation is obtained by maintaining the apparent liquid level as indicated by an external gage glass attached to the shell, from 0 to 10 inches Vbelow the -top of the coils.

cording to the concentration desired at pipe 50 The advantages of providing two or more vapor compressors are set forth in Patent N o. 1,361,843 issued Dec. 14, 1920, filed September 16, 1916, for a single effect plant. These advantages also apply to a multiple effect) plant as herein described. Thus assume the'evaporator working at its maximum capacity with all vapor compressors in operation. The effect of shutting off one vapor compressor not only reduces the capacity but also increases the efficiency. This becomes evident when we consider that one ejector reduces the heat to be transferred by the fixed heating surface in the evaporator. Consequently, the temf increase of efficiency at reduced capacities perature difference between'the solution and.

- sors in parallel for a given capacity the vapor in the heating space is reduced with a corresponding reduction in the range of compression required in the vapor compressor. With reduced range of compresincreases theeliciency ofevaporation with the remaining vapor compressors in operation. By providing `several vapor compreswith a given multiple'effect plant, there is thus vobtained a iexibility of operation with an not available when a sin le vapor com ressor only is provided. xperiment `s ows that with a single vapor compressor, the capacity of lthe evaporator may be reduced by reducing the initial steam pressure but the eiiiciencydoes not increase.

above, are intended to take care of certain abnormal conditions. Thus, it may be necessary at times to operate at a greater capacity than possible with both compressors workin with rated primary vapor pressure. Wile a slight increase in capacity may be obtained by opening valves 21 and 22 wide the 'primary vapo-r suppl a much larger increase may be obtaine by opening valve 23 to by-pass the ejectors with primary vapor to the con'- densing chamber 2 of the first effect. A greater temperature difference can then be obtainedin the several effects with a conse.

quent increase incapacity but at poorer economy. Instead.v of opening valve 23,

valve 24 may be opened to admit primary vapor to condensing chamber 4 and thus inprime. Connecting the sa ety valve so that crease-the capacity of the effects succeeding the first, obtaining the desired increase in capacity without as great a reduction in economy.

Should for any reason valve 31 be closed during the operation of the plant, the pressure within shell 1 might reach a dangerous point unless safety valve 61 opens to discharge the excess vapor. The sudden opening of a safety valve, more especially of theu popping typ'e, causes a very rapid boiling of the liquid with a conse uent tendency to the large quantity' of vvapor iovv'in'gl to -it does. not` by-pass the separator t rough which the vapor leaving the evaporator must pass, reduces theelfect of. primingl This is especially advantageouswhen ejectors are used, as it prevents a large amount'l of the impure aliquid-beingvcarried over into the condensing space to contaminate the condensed vaportherein. y c

If the trap 15 should 'become-defective and allow the liquid level to risewithin shell 1, the float 64 will also rise when the liquid reaches it, thereby throttling the feed at 65 and at the same time opening an overfiow valve 66. The escape of vapor from pipe 63 will first serve as a Warning, the liquid later escaping being discharged through pipe 67 to a storage tank orto waste as the case maIy be. v

f the attempt is made to start up the evaporator with valves 25, 26 and 29 open, a vacuum will be produced within the shell. The vacuum break valve 63 will relieve this vacuum and thusprevent the collapse of a shell not designed sufficiently strong to stand the external pressure.

Pressure gages at 69, 70 and elsewhere serve in properly operating the apparatus.

Having thus described my invention, I claim and-desire to secure by Letters Patent', the following:

1. A plurality of vapor compressors in combination with a multiple effect evaporat- Various other devices,` not referred to ing plant, each effect of said plant 'containing a condensing chamber and an evaporating chamber, thesaid vapor compressors being connected in parallel to withdraw vapor from the evaporatingl chamber of the first effect andto discharge the said vapor compressed and commingled with the primary operating vapor .into the condensing cham ber of the said first effect, passages being provided for discharging vapor from the evaporating chamber of each eiect into the condensing chamber of the succeeding eect and from the evaporating chamber of the last effect, and valves being provided to reduce the number of vapor compressors in operation.

2. A lurality rof vapor compressors in combination With an evaporator contalnlng condensing and evaporating chambers, the .said compressors being connected in parallel to vWithdraw vapor from the said evaporating chamber and to discharge the said vapor number of vapor compressors in operation,

and means of preheatin the liquid fed to the said evaporating cham r by the condensation of' vapor from the said condensing chamber.

3. In an evaporating apparatus comprising a vapor compressor containing a De Laval nozzle incombination with an evaporator containing condensing and evaporating chambers, means of giving Warning of an abnormal rise of liquid in the said evapo rating chamber by automatically discharging vapor therefrom.

WiLLiAM L. DE BAUFRE.

v'Witnesses H. ASTURT, I WIN'rmorCoBn.

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