IL32401A - Multipurpose continuous vacuum evaporator - Google Patents

Description

Multipurpose continuous vacuum evaporator INTERNATIONAL MACHINERY CORPORATION N.V. 0: 30703 This invention relates to equipment for concentrating food liquids by partial evaporation thereof to a desired extent under vacuum, allowing to handle either extremely heat sensitive juices or high viscosi-ty concentrates.

In many citrus producing regions tomatoes are also grown either on an equal basis or as a side-line. Due to the widely differing requirements for handling citrus juices and tomato paste, it has heretofor been necessary to provide distinct equipments for these two types of products , which means high investment and operation costs. Where citrus grooves and tomato fields are traditionally very large, these costs may be supported. This however is generally not the case in quite a number of countries.

The object of this invention is to provide a multipurpose continuous vacuum evaporator which can easily handle both low and high viscosity food products and which is particularly economical in price and operation.

Such a multi ur ose vacuum ting feed liquid up to about 25% solids, a rotary coil vacuum evaporator connected to the outlet of said system, and, in said connection, a selectively operated by-pass means. · Preferably, said combination further includes a rotary coil heat exchanger connected to the outl-et of said rotary coil vacuum evaporator.

As this novel vacuum evaporator is destined to handle a wide variety of products, it should be capable of maintaining the same qualitative and economical operation when running at less than full capacity .It is another object of this invention to. achieve this result by a special arrangement in aforementioned multistage system.

Preferably, said multistage system substantially consists in the combination of means supplying high temperature feed liquid under pressure, evaporator means operatively connected to , said liquid supplying means for receiving liquid therefrom at a high velocity and partially evaporating the liquid into a liquid and vapor mixture under suction pressure, vapor heating means operatively connected to said evaporator means for effecting said partial evaporation, separator means operatively connected to the evaporator means for recei ving the liquid and vapor mixture therefrom and separating the mixture into concentrated liquid and vapor, preheater means connected to the separator means for re> ceiving the vapor therefrom for elevating said feed liquid to said high temperature, said evaporator means comprising vertically disposed chamber means, a plurality of spaced heat transfer tubes mounted within said' ψ of the chamber means, expansion inlet means mounted in insulated relation above the upper end of the chamber means in communication with upper ends of the tubes, insulated liquid-vapor mixture outlet means mounted the below the chamber means in communication with/lower end of the tubes, and nozzle means connected to said inlet means for delivering liquid thereto at said high velocity .

To more clearly define the present invention, one preferred embodiment thereof is hereinafter described by way of example only, reference being made to the accompanying drawings, wherein: Figure 1 is a diagrammatic representation of the multipurpose vacuum evaporator according to this invention and Figure 2 is a schematic illustration of an apparatus according to Figure 1.

Referring to Figure 1, a multipurpose vacuum evaporator according to the invention consists in the combination of a multistage system A for concentrating feed liquid up to about 25% solids, of a rotary coil vacuum evaporator B for further concentrating the liquid to up to about 35% solids and of a by-pass means C between evaporators A -and B, a rotary coil heat exchanger D being generally provided at the outlet of evaporator B.

Such an arrangement is shown more in detail in Figure 2 , wherein arrows indicate the flow of liquid through the system. It will therefore be observed that a feed pump 12_ which receives feed liquid from some preheater L6 through which the feed liquid passes and ,is delivered b conduit 1Q_ to an intermediate stage preheater 2_0. The intermediate stage preheater 2_0 delivers the feed liquid to a conduit 2_2 which is connected to final stage preheater 2_4 through which the feed liquid passes. Conduit 2_5 therefore delivers the finally prehea ted feed liquid to an initial evaporator stage 2_8. The feed liquid is thereby partially evaporated into a liqui and vapor mixture under vacuum pressure delivered by outlet conduit _30 to an initial stage separator _32 to which •the outlet conduit _30 is tangentially connected adjacent the bottom-.. Tangentially connected adjacent the top of the separator _32_ is a vapor outlet conduit 34. which is connected to the intermediate stage preheater 20_ for supplying the vapor thereto for purposes of preheating the feed liquid passing therethrough by heat transfer between the vapor and the feed liquid. The initial sta separator 32. also delivers the concentrated liquid to an outlet conduit 3_6 connected to a transfer pump _3_8 whereby it is discharged under pressure sufficient to raise it to the top of the next stage evaporator. The transfer pump therefore withdraws the initially concentra ted liquid from the initial stage separator 3_2 and delivers it through conduit 40 to an intermediate stage evaporator.

At this point it should be appreciated that the construction of the evaporator of the initial stage 2_8 and intermediate stage 4_2 are similar. The initial stage evaporator however will necessarily operate under higher temperatures. The source of heat by means of which both the final reheater 24 and the initial sta e eva orator vely the liquid, differs from that of the other pre-heater and evaporators. Accordingly, a steam inLot conduit is provided for supplying steam or for that matter any externally heated fluid to the evaporator 2 8 and also by a conduit 4_6 supplies the final prehea-ter 2 4 . A condensate outlet 4j8 is provided for the final preheater 2M_, . while a condensate vent outlet 50 is provided for the evaporator of stage 2J3. - The intermediate stageevaporator on the other hand receive its source of heat by the vapor circulated through the intermediate s^age preheater 2Q_ conducted through the connecting passage 5_2 . The heating vapor enters the intermediate stage evaporator adjacent the bottom thereof and the non-condensible portions of the vapor passing through the intermediate stage evaporator are discharged out the vent outlet 5_4 to some vapor remova apparatus. Condensate is discharged from outlet 12 6 . The intermediate stage evaporator therefore delivers through outlet conduit 56_ its mixture of liquid and vapor resulting from the further evaporation of the initially concentrated liquid supplied thereto by conduit 4_0 . The vapor liquid mixture therefore is tangen-tially supplied by conduit 5_6 to the bottom portion of an intermediate stage separator 5_8 . Further concentrated liquid therefore , leaves the second stage separator 58 by a conduit i60 by being withdrawn under suction pressure of transfer pump 62_ . The further concentrated liquid is then fed through conduit 4 through a final evaporator stage £6 similar in construction to the intermediate stage. The additional vapor released by the second stage separator 5_8 is on the other hand 68 to the initial stage preheater _16 for initially preheating the feed liquid passing therethrough. Accordingly, the vapor circulated through the initial preheater 16 is delivered to the final stage evaporator by 70 the connecting conduit/for final evaporation of the concentrated liquid passing therethrough. A vent outlet 72 is therefore also provided for the non-condensible portion of the heating vapor passing upwardly through the final stage evaporator, similar to vent outlet _54 while condvensate is discharged from outlet 126. The outlet conduit 7_{+ therefore similarly delivers a vapor liquid mixture to the final stage separator 76 .

Finally concentrated liquid will be withdrawn from the final stage separator 7J3 by a conduit 7_8 and delivered to a flash cooling chamber j80 . The flash cooling chamber _80 is operated in a manner well known to those skilled in the rt, by means of high velocity high pressure steam entering conduit 82_ and passing through a Venturi device 84_ which is connected to the flash coo ling chamber 80 by means of passage 86_ . The finally con centrated liquid is thereby cooled within the flash cooling chamber _80 and withdrawn therefrom by a product pum 88 at a reduced temperature.

The final released vapor from the final stage separator 7_6 is delivered' by outlet vapor conduit j ) to a delivery conduit 9_2 to a condenser 9_4 . The condenser 9*4 therefore receives cooling medium by an inlet conduit 96 for circulation and discharge through outlet conduit 98. · The steam et produced by the device _84 may therefo discharge into the condenser 94 by a conduit 100 while under vacuum by pump 103.

The evaporators of each of the stages 2_8 , 4_2 and £6 consist of a vertically disposed cylindrical tank 104. The heating chamber 106 is enclosed within the walls of the tank 10 between an upper end plate 108 and a lower end plate 110. Preferably, a conical inlet chamber 117 defined by a removable conical head member 118 is formed above the upper end of the chamber 106 and insulated therefrom by a space insulating chamber 112 formed between plates 109 and 108 while a fluid insulating chamber 114 is disposed beneath the chamber 106 and is formed between plates 110 and 113. The foregoing arrangement is sufficient to provide a heat transfer barrier for loss of heat from the flowing fluid. A plurality of evaporating heat transfer ducts 116 are therefore mounted in parallel spaced relation to each other with the upper ends thereof in communication with the inlet chamber 117 and for conducting a downwardly flowing vapor liquid mixture to the outlet chamber 115 ♦ The inlet cha ber 117 is conically shaped for confining a liquid inlet spray delivered to the inlet chamber by means of nozzles 120. Alternately , the . conical inlet chamber may be replaced by an inlet chamber with a removable lid.

The outlet end of the evaporator disposed at the bottom thereof includes a removable bottom 124 in communication with the outlet 115 which is connected to the outlet conduit through which the liquid and vapor mix ture passes. It will therefore also be observed that connected to the heating chamber 10_6 adjacent the bottom thereof is the heating vapor inlet 52^ or 70, Also adja the bottom of the heating chamber is- a condensate outlet 126. It will therefore be apparent from the foregoing description of the evaporator structure that the fluid enters through nozzle 12.0 at a higher temperature than in chamber 1 7 and will therefore be converted into a vapor-liquid mixture entering the tubes 116 at a high vel city while the major evaporation and/or concentration occurs as the mixture flows through the tubes. The insulation for the inlet end provided by the chamber 112 is therefore necessary in connection with the cleaning action of the high velocity fluid mixture to prevent scaling and/or burning at the inlet ends of the tubes 116 ♦ The flow of fluids through the system may be traced by reference to the exemplary values of orange juice as the feed liquid. Accordingly, juice fed from the feed pump _12 may be delivered to conduit 11 at a temperature of 70°F. and preheated by the initial pre-heater 1_6 so as to deliver the juice .to conduit 18 at a temperature of 130°F. The juice subsequently preheated by intermediate preheater 20^ is delivered to conduit 2_2 at a temperature of 160°F., whereupon the final preheater 2_4 finally preheats the juice to a temperature of 200°F.' in conduit _26_. The preheating by the final preheater 2_4 i-s accomplished by supply thereto of steam at 212°F. The prehea^ted juice is then converted into a vapor liquid mixture by volumetric expansion after passing through nozzle 120 into the inlet chamber 117 under a reduced static pressure. The mixture enters the tubes 116 in the initial stage evaporator having evaporating heat transfer surfaces so that further heating and evapo-ration takes place. The mixture is then separated by to a lower pressure point in the next stage. The 180°F. vapor in conduit 34. is therefore supplied to the intermediate stage preheater 2 for raising the juice from 130° . to 160°F. after which it is withdrawn under vacuum as hereinbefore indicated. The 180°F. initially concentrated juice is thereafter further evaporated by the intermediate stage evaporator and after being supplied to the nozzle 120 thereof at the 180°F. temperature which is higher than the temperature corresponding to the vacuum in stage 42^. the intermediate stage separator 58 at the lower temperature of 150°F. Accordingly, the vapor leaving the separator 5_8 through conduit 6jJ at 150°F. may preheat initially the juice to raise it from 70°F. to 130°F. as hereinbefore indicated. The 150° further concentrated juice is then admitted to the final stage evaporator by a conduit 6_4 and finally separated by the separator 7j5 into a finally concentrated juice product at 95°F. The finally concentrated juice product therefore upon leaving the flash cooling chamber _80 is delivered by the product pump 88 at a temperature of 40°F. It will also be observed in Figure 2 that sight glasses 128 are provided in the intake conduits 3_6, _60 for the transfer pumps 3_8 and 6_2 and the intake conduits to the product de livery pump 8_8 for the purpose of" providing visual means for inspecting the progress of the feed liquid through th system.

Pump 8jB_ delivers product to conduit 130 leading into the shell of a vacuum evaporator 132 equipped with a rotary coil 134 wherein steam is admitted through hollow shaft 136. Condensate is discharged from said coil throu of a pump 1M_U , and sent into an afterheater 1*46 equipped with a rota ry ooil 1U8. Steam is delivered to the latter through hollow shaft 150 and condensate is discharged therefrom through hollow shaft 152.

• For the best economical use of the steam vapor coming from evaporator 132 , connection l'tO can be directed to the separator 3_2 ; bypassing the heat exchanger 20 if necessary, direct to the chamber 106.

The .end .product is evacuated., at the desired density and temperature, through conduit 15 for packaging or further processing. Should a cool end product be desired, a coolant may be "sent through coil 1^8 , instead of steam.

Should the above described equipment operate on less than maximum capacity, steam only would fill part of the initial evaporator stage 2_8, resulting in excessive heat transferjrate on part of the tube surface thereof and no heat transfer on the rest. To obviate this and according to one feature of this invention, a line 156 is provided which connects the bottom of evaporator 2_8 46 to a Venturi 158 mounted on conduit _JH+. The condensate outlet 50^ is connected to an open vent 160.

By this arrangement, air is drawn from the lower part of evaporator 2_8 through conduit 156 , with the aid of Venturi 158 , and re-introduced in evaporator 28 , via conduit 4_4 and preheater 2_4. This air reduces the heat transfer rate from the steam to the tube bundle in said evaporator, thereby reducing the temperature of the tube walls and, consequently, the heat transfer rate 1D the product. In this manner, the tube surface down to the level of conduit 156. When steam reaches said conduit the available supply of air is cut-off or at least markedly reduced, thus automatically adj the heat transfer · rate to that required to speed &vei?-aii of the tubes. V/hen the equipment operates ·©»- at full capacity , conduit 156 recirculates only steam, due to the fact that the air has been driven out through the vent 160.

In this manner, a very flexible and economical multipurpose evaporator is obtained. Not only is it here ith possible to easily switch from one product to anothe but the production rate may also be widely adjusted according to circumstances, without impairing the efficiency of the equipment.

It will be obvious to one skilled in the Art that numerous changes and modifications may be brought to the equipment described hereabove by way of example only, without departing from the scope of the invention as claimed .

Claims (8)

1. HAVING NOW particularly described and ascertained the nature of our said invention and in what manner the same is to be performed, we de lare that what we claim is:- 1. - Multipurpose continuous vacuum evaporator comprising the combination of a multistage system for concentrating feed liquid up to about 25% solids, a rotary coil vacuum evaporator connected to the outlet of said system and, in said connection, a selectively operated by-pass means.
2. 2. - Multipurpose continuous vacuum evaporator according to claim 1, wherein- a rotary coil heat exchanger is connected to the product outlet of said rotary coi u vacuum evaporator.
3. 3. - Multipurpose continuous vacuum evaporator according to claim 1, wherein said multistage system substantially consists in the combination of means supply ing high temperature feed liquid under pressure, evaporator means operatively connected to said liquid supplying means for receiving liquid therefrom at a high velocity and partially evaporating the liquid into a liquid and vapor mixture under suction pressure, vapor heating means operatively connected to said evaporator means for effecting said partial evaporation, separator means operativel connected to thejevaporator means for receiving the liquid and vapor mixture therefrom and separating the mixture in concentrated liquid and vapor, preheater means connected the separator means for receiving the vapor therefrom for elevating said feed liquid to said high temperature, said evaporator means comprising vertically disposed chamber means, a plurality of spaced heat transfer tubes mounted within said chamber means and extending beyond lower and ted in insulated relation above the upper end of the chamber means in communication with upper ends of the tubes, insulated liquid-vapor mixture outlet means mounted below the chamber means in communication with lower end of the tubes, and nozzle means connected to said inlet means for delivering liquid thereto at said high velocity .
4. 4. - Multipurpose continuous vacuum gvaporator according to claim 3,· wherein steam is fed to the initial evaporator means via a conduit and a prsheater means , the bottom region of said evaporator means being connected to said conduit, saidbottom region being further provided with a condensate outlet equipped with an open vent.
5. 5. - Multipurpose continuous vacuum evaporator according to claim 4, wherein the bottom region of said evaporator means is connected .to a. Venturi mounted in said conduit.
6. 6. - Multipurpose continuous vacuum evaporator according to claim 2 , wherein the coil of said heat exchanger is fed steam.
7. 7. - Multipurpose continuous vacuum evaporator according to claim 2 , wherein the coil of said heat exchanger is fed a coolant.
8. 8. - Multipurpose continuous vacuum evaporators substantially as described hereabove and illustrated in the appended drawings .