US2788065A - Surface type evaporator employing channel switching for cleaning purposes - Google Patents

Description

April 9, I957 C. J. LOCKMAN SURFACE TYPE EVAPORATOR EMPLOYING CHANNEL Filed Aug. 14, 1950 SWITCHING FOR CLEANING PURPOSES 4 Sheets-Sheet l April 9, 1957 c. .1. LOCKMAN 2,788,065

SURFACE TYPE EVAPORAT OR EMPLOYING CHANNEL SWITCHING FOR CLEANING PURPOSES Filed Aug. 14, 1950 4 Sheets-Sheet 2- 456 42a 3 /4a I5 /4 56 4e. 45 46; ,M5 9 QB C. J. LOCKMAN SURFACE TYPE EVAPORATOR EMPLOYING CHANNEL SWITCHING FOR CLEANING PURPOSES April 9,1957

Filed Aug. 14, 195 0 4 Sheets-Sheet 3 April 9, 1957. c. J. LOCKMAN 2,738,065

SURFACE TYPE EVAPORATOR EMPLOYING CHANNEL SWITCHING FOR CLEANING PURPOSES 4 Sheets-Sheet 4 Filed Aug. 14, 1950 SURFACE TYPE EVAPGRATOR 'EMPLOYING CHANNEL SWITCHENG FOR CLEANING PURPOSES Application August :14, 1950, Serial :No. 179,256"

2 Claims. (Cl. 159-20) This invention relates to heat exchange apparatus of the surface type for'heating, evaporating and like-pun poses and to a method of'operat'ing the same, and is a continuation-in-part of my, copending application Serial No. 22,215 filed April 20, 1948, now'Patent No. 2,576,- 843.

More particularly the invention has for its object to provide an apparatus of this kind havingseparate'passages for conducting a vaporous heatin'gmedium and scale forming liquid in heat exchange relation, and in which the paths of the different fluids may be interchanged periodically during the operation in order that at least the substantial portion 'ofany. scale precipitated from .the liquid on the walls of the liquid-conveying passages during a given period may be'removed byj'the dissolving action of the vapors and more particularly of their condensate formed on the heating surfaces when thevapors are passed through the same passages during the succeeding period.

This method of removing scale by passing each of the fluids alternatively through the diiferent passages is ob'viously very expedient since it may be performed in practice without stopping the operation and the interchanging of the passages may be effected at shorter or longer inter: vals as desired in the actual case without disturbing the continuance of operation so that the cleaning may be timed to set in when the scale deposits are ,still' very moderate and relatively easy to dissolve.

For an effective cleaning action it isnecessa-ry to insure the flow of a sufiicient volume of. condensate over the whole scale-contaminated passage walls. If. however steam is caused to condense on.a more or less vertical heating surface, the highest part of. said surface ;will be flooded only by condensate deposited. on that part directly, while the lower part of the surfacewill. be flooded not only by the. condensate directly deposited thereon but also by the accumulatedcondensate running down from the higher parts. Consequently, in case .of relatively resistant scale deposits the cleaning action. on the heating surfacc will be insuificientin and adjacent to its highest zone but may be more or less acceptable in.its central zone and -rather satisfactory. in. and adjacent to its lowest zone. In thiszcase, however, the :practical value of the cleaning'rnethod isreduced toa great extent because the incompletely removed'scale deposits will increase continually and. sooner; or: :laterrneeessitate taking the apparatus out of operationlfora'more thorough cleaning 'by chemical or. mechanical me'anst-arrdtthisawill involve substantial excess cost.

It is an objectof the invention toprovide-means "for recirculating and distributing -=accumulat'ed:condensate, withdrawn from the heating ism-face, over the highest zone of :said surface 'so as to supplyto-all partszoffsaid heating surface-a quantity of condensatesufficient-for efiicient-cleaning.

ln practice it has :moreover .been found that not only the'heating surfaces but also other part'sf-sucli as conduits,

States Patent ice 1 switching valves and flash chambers, whichmay b66011.

nected to the heat exchanger, are liable to be contami-nated by scale in contact-with heated scale forming liquid.

A further object of the invention is to eliminate these drawbacks by causing circulating condensate to clean the said partsof the system exposed to the scale-contaminating action of the scale formi-ng liquid;

Anotherobject of the invention istoprovide means for distributing circulated condensate in a sub-divided state, for instance by means of spraying nozzles,- in order tofacilitate flooding and wetting-of the passage walls and other parts contaminated b-y scales-from the-liquid.

A still further object of the invention is to-circula te the condensate in quantities substantiallyexceeding-the qu antityformed by new condensation.

Still further objects will beapparent from the following description.

One embodimentof the invention will now bedescribed with reference to the accompanying drawings, inwhich":

Figure 1 shows a plant with a heat exchanger having means for circulating condensate.

Figure 2 is a section of the'same heat-exchanger taken along the line II-II in Figure l, with inlets and outlets for the two heat "exchanging fluids.

Figure 3 is'asection of the heatexchangertaken along the line Ill-III in Figure 1,

Figure 4*is a-section of the heat exchanger taken along the line lV-IV in Figure 1',

Figure -5 is a cross section of one embodiment ofa nozzle for distributing'the condensate, and

Figure 6 is a diagrammatical view illustrating a modification of the heat exchanging plant.

In all figures the same reference characters refer to the same parts.

Theheatexchanger'l comprises a plurality of parallel heat transmitting walls 2 of metal sheet and spaced at equal distances between two side. plates ,3. Together with the plates 3 and strips 4 the walls 2 form a system of'equally shaped parallel and vertical channels 12 and 1221. Above and beneath the ends of the strips 4 the wallsZ are extendedin a V-shaped configuration so that at the'topand'the bottom the walls terminate in oblique edges'5, 5a., 5b and-5c, respectively. Each channehfor example channel 12, is .closed along one of itsoblique bottom edges, for instance the left one 5a, by. means of a strip 6a, and in the same manner, the same channel is closed along oneof its top edges, for instance likewise the. left'one, 5c bymeans of a strip 6b, although, instead, the right top edge 5!) may be closed if desired. The adjacent channels 12:; are closed along the remaining bottom and'top edges 5, 5b, respectively. In this manner alternate channels will be open to alternate sides, and therearej thus formed'two groups of channels, one group being open to .one side, for instance the left one, and the other group being open .to the other side, for instance the right one. Covers 7, at both sides closed by the extended'side plates 3, enclose chambers 53', 8a, 8b, 3c, at the bottom and the top of the channels 12, 12a. The vleft- hand chambers 80, 8c connect the channels 121; off 'thegroup open to the left while the right-hand chambers "8,"8'b 'connectthechannels 12 of the group open tothc right; It is al'soclearly seen'thatthe right-handb ttom chamber8 communicates-with the right-hand top cha n- 361"81) through the channels 12 and that theileft -hand bottom; chamber 8a communicates with the leftkhand top chambersc-throughthe:chann e1 s 12 a; Y

The scale forming'liquidto be heatedymay jbe introducedinto the exchanger through-a -conduit"9, a valve 101 and an inta'lte ll' and then passesthrough-the channels '12 whereupon" it isi-withdrawn" through theirconduit" *13, 'acting'as-an outlet, a pipe- 45; a valve 14 and acondiiit 15. A vaporous heating medium may be introduced through a conduit 18, a valve 19a, a pipe 46a and an intake 13a into the channels 12a. From the channels 12a condensate may be withdrawn through the outlet 11, a valve 230, a conduit 20, a fioat chamber or vessel 21, a conduit 22, a valve 23, a pump 24, conduits 25, 26 and a discharge conduit 26a controlled by a throttle valve 27. The valve 27 is operated from the float 28 by means of a link system 29 so that the valve 27 will close when the level of thecondensate in the vessel 21 sinks while the valve will open when the said condensate level rises. From the vessel 21 condensate may also be passed to the conduit 26 directly through a by-pass conduit 30 and a valve 31.

Alternately, the paths of flow of the heated and heating media passing through the heat exchanger may be interchanged so that the liquid will be introduced to the channels 12a through the valve and withdrawn from said channels through the intake 13a, pipe 45a and valve 14a, while the vaporous heating medium will be introduced into the channels 12 through the valve 19, pipe 46 and conduit 13, acting as an inlet, the condensate formed being withdrawn through the valve 23. Interchanging of the passages may be effected periodically so that channels which are conveying liquid during a given period will be conveying vapor during the next period.

Condensate withdrawn from the heat exchanger is passed in circulation through the pump 24, conduits 25, 32 and valve 33 or through conduit 32a and valve 33a into a condensate distributing pipe 34 or 34a, respectively. The valves 33, 3311 are set so as to supply the condensate to that one of the pipes 34, 34a which is arranged in the top chamber 8a or do conveying the heating medium. The condensate distributing pipes are closed at their ends 35 and 35a, respectively, and provided with a number of nozzles 36 adapted to spread the condensate over the whole top part of the heating surfaces of the channels. Thus, during a given period condensate will be flooded over said surfaces of the channels 12 conveying the heating medium, so as to remove scale therefrom precipitated from the liquid during the preceding period when said channels were conveying liquid. Owing to the fact that the channels are directed vertically and their heating surfaces likewise are vertical and since the heating surfaces have a substantially uniform width from the top to the bottom, the condensate distributed over the top part of the surfaces will continue to flood all remaining parts of the heating surfaces while flowing downwardly, so that the whole surfaces will be cleaned completely and very effectively.

One embodiment of the nozzle is shown as an ex ample in Figure 5. The nozzle mainly consists of an insert 41 having internal screw-like guiding surfaces 44. which spread the condensate stream into a fine more or less conical spray projected through an aperture 41a. The nozzle insert 41 is threaded into the condensate distributing conduit here shown as the conduit 34. Of course, the nozzle may be constructed in many other ways without departing from the scope of the invention.

In many cases scale will deposit not only on the heating surfaces but also at other parts in contact with the scale forming liquid. Such parts are the valves and conduits at the top and bottom inlet and outlet end of the heat exchanger. Scale adhering to the valve stems for instance, may render the valves inoperative or prevent them from being closed tightly, and as a result thereof, there may arise a leakage of heating vapor to the liquid side of the system, such leakage being very detrimental to the operation of the apparatus. A continuously growing layer of scale on the walls of the conduits will soon reduce thecross-sectional area of the conduits so that the pressure necessary to force the fluids therethrough willincrease to a considerable degree. It will be understood that, for instance in the case of an evaporator com- 4 prising several evaporating stages with heat exchangers of the type now described, the capacity of such an evaporator will decrease considerably if the drop in pressure necessary for, forcing the vapor from one stage to the other is allowed to increase to any considerable degree.

The valves and conduits at the bottom end of the heat exchanger are thoroughly cleaned by the withdrawn condensate.

With the object of cleaning said valves and conduits at the top end of the heat exchanger there is provided conduits 44, 44a, branching off from the conduit 25 and communicating with distributing pipes 42, 42a, 43, 43a projecting into pipes 45, 45a, 46, 46a, respectively, and provided with nozzles 36 for spraying condensate in said pipes and on the valves 14, 14a, 19, 19a. Each conduit 44, 44a has a valve 47, 47a, respectively, so that the condensate may be conveyed through one or the other of said conduits as desired. Nozzles 36 are also provided for spraying condensate into the inlet and outlet pipings 13, 13a so as to clean scale from them. In the same manner, similar nozzles may be provided for spraying condensate on any part of the system contaminated by scales from the liquid.

In some cases it may be of advantage to circulate a quantity of condensate in excess of the quantity formed by new condensation in the heat exchanger. Thus, in starting the operation of the heat exchanger the condensate will be circulated and withdrawal of condensate will occur automatically as soon as the total quantity of the condensate is suflicient for causing the float 28 to open the valve 27.

Figure 6 illustrates a plant for evaporation of scale forming liquid with a heat exchanger 1 associated with flash chambers or steam separators 48, 43a for separating vapor from the liquid heated in said heat exchanger. The liquid to be heated is supplied through a conduit 49 by means of a pump 50 and may then be conveyed through either of the conduits 51, 51a into the heat exchanger 1 directly to the top of the heat exchanger through either of the conduits 69, 69a and indirectly to the bottom of the heat exchanger through either of the conduits 71, 71a, flash chambers 48, 48a conduits 58, 53a and float chambers 59, 59a and conduits 74, 74a. Control valves 52, 52a are provided in the conduits 51, 51a respective- 'ly, for interchanging the paths of the liquid. Heating vapor is supplied to the heat exchanger from a conduit 53, through a control valve 55 or 55a in a conduit 54 or 5411, respectively, through the flash chamber 48 or 481: and the pipe 13 or 1311 leading into the chamber 8!), respectively, of the heat exchanger. The liquid heated and vaporized in the heat exchanger is withdrawn therefrom through the pipe 13 or 131: and introduced into the flash chamber 48 or 48:: in which the vapor is separated from the heated liquid and escapes through a valve 56,,5 6a, respectively. The liquid collected in the chamber 48 or 4811 is recirculated through a pipe 58 or 5812, a float chamber 59 or 5911, conduits 74 or 74a, and introduced into the bottom chamber 8 or 8a of the heat exchanger.

In the position shown in Fig. 6 the liquid circulates through the path 13, 48, 58, 59 and heating vapor is supplied through the path 54a, 55a, 48a, 13a and condensate is withdrawn from the chamber 8a to the float chamber 59a acting substantially in the same manner as the float chamber 21 shown in Figure 1. During the cycle of operation now described the float chamber 59 is filled with liquid and the liquid level in the flash chamber 48 is sufficiently high to actuate the float 60, which by means of a link system 61 operates a valve 62 so that the supply of liquid to be heated in the heat exchanger will be controlled automatically in dependence of the level in the chamber 48. A desired quantity of heat treated liquid is withdrawn from the float chamber 59 through pipes 63, 64 controlled by a valve 65.

The valve 66 operated by the float 67 in the chamber 59 is open and a valve 68 in a circulation conduit 69 is closed.

The condensate in the chamber 59a is circulated through a pump 70a, the open valve 68a and the conduit 69a, the valve 52a being closed so that part of the condensate is reintroduced at the top of the heat exchanger through the chamber 80, while part of the condensate is introduced into the flash chamber 48a through conduit 71a and the spray nozzles 72a, 73a adapted to spray condensate into the pipe 13a and on the walls of the flash chamber 48a so as to dissolve any scales precipitated thereon. In the same manner similar nozzles may be provided to spray condensate on other parts contaminated by scales.

During the cycle of operation now described condensate will be discharged fromthe system through the valve 66a (controlled by the float 67a), conduit 64a and the open valve 65a.

The liquid is supplied to the system from the conduit 51 partly through the conduit 69 and the nozzles 36 in chamber 8b and partly through the conduit 71 and the nozzles 72, 73. This continuous passing of liquid through the condensate circulation conduits and nozzles prevent them from being clogged by solidifying liquor otherwise left therein during the cycle in which said conduits and nozzles do not convey condensate.

It should be understood that on interchanging the path of the heating vapor and the liquid to be heated the flash chamber 48 will instead by sprayed with the circulating condensate, and a portion of the liquid to be heated will now be supplied to chamber 48a through pipe 71a and nozzles 72a, 73a, thus preventing the latter from being clogged.

What I claim is:

1. In a heat exchange system having a heat exchanger apparatus with two passages for conducting a vaporous heating medium and a scale forming liquid in heat exchange relation, two separators each being connected to one of said passages respectively, each of said passages having an inlet and an outlet, a valved inlet connection for selectively conducting said heating medium to one or the other of said passages, a valved outlet connection for selectively discharging condensate from said heating medium from one or the other of said passages, a valved inlet connection for selectively conducting said scale forming liquid to the other or the one of said passages, outlet connections for discharging heated liquid and flash vapor from the other or the one of said passages into the respective separator chambers connected thereto, said valved inlet and outlet connections for said heating medium and said condensate and said valved inlet connection for said liquid being operable for interchanging the paths of flow of said heating medium and said liquid through said passages, draining means for receiving condensate discharged from one or the other of said passages, means for selectively circulating condensate from said draining means to the corresponding one or the other of said separator chambers and means for distributing such condensate on the internal walls of said corresponding chamber.

2. In a heat exchange system having a heat exchange apparatus providing two different passages for conducting a vaporous heating medium and a scale forming liquid in heat exchange relation, a supply conduit for scale forming liquid, a liquid supply connection between said supply conduit and each passage, valve means in each liquid supply connection, a discharge conduit for scale forming liquid, a liquid discharge connection between each passage and said discharge conduit, valve means in each liquid discharge connection, a supply conduit for vaporous heating medium, a heating medium supply connection between said heating medium supply conduit and each passage, valve means in each heating medium supply connection, a heating medium condensate discharge conduit, a condensate discharge connection between each passage and said condensate discharge conduit, valve means in each condensate discharge connection, a draining device connected to said condensate discharge con duit for receiving condensate therefrom, all of the above mentioned valve means being operable to selectively sup ply scale forming liquid to one or the other of said passages and heating medium to the other or the one of said passages, and to discharge concentrated liquid from one or the other of said passages and discharge condensate from the other or the one of said passages and means to circulate condensate from said draining device only over the Walls of the other of said passages and the liquid discharge valve and heating medium supply valve connected thereto during the present cycle of operation and only over the walls of the one of said passages and the liquid discharge valve and heating medium supply valve connected thereto during the next succeeding cycle of operation to dissolve scale deposited in said system by said liquid.

References Cited in the file of this patent UNITED STATES PATENTS 1,006,197 Frasch Oct. 17, 1911 1,464,798 Anderson Aug. 14, 1923 1,576,410 Connery Mar. 9, 1926 2,229,306 Prestage Jan. 21, 1941 2,439,208 Gloyer Apr. 6, 1948 2,488,598 Lockman Nov. 22, 1949 2,490,750 Grewin et a1 Dec. 6, 1949 2,490,759 Tyden Dec. 6, 1949 2,576,843 Lockman Mar. 27, 1951 2,647,570 Lockman Aug. 4, 1953 FOREIGN PATENTS 64,286 Denmark Feb. 11, 1946

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