LU81574A1 - DEVICE FOR EXTRACTING AND MIXING THE CONDENSATES OF THE EFFECTS OF A MULTI-EFFECT EVAPORATOR - Google Patents

Description

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The present invention relates to a new device for extracting and mixing condensates from the heating bodies of at least two effects of a multiple-effect evaporator, the pressure decreasing from the first to the last effect.

To date, it is known to associate an extraction means with each of the heating bodies concerned, these means being constituted by a duct carrying an extraction pump; the condensates extracted using these extraction means are then mixed, for example in a pan. mixed.

The cost price of these means <3 ′ extraction and their maintenance costs can therefore become significant if the number of heating bodies from which the condensate is to be extracted becomes high.

The object of the present invention is to reduce this cost price and these costs and to do this, it proposes a device which is characterized in that it comprises a reservoir into which open respective pipes. 15 .ment in relation to the part bottom of the heating bodies from which we want to extract condensate, this tank further comprising an extraction means.

Due to the pressure differences between the tank and the heating bodies, a column of water is created in the conduits which can extend into said heating bodies and it tends to be established between the surface 20 of the condensates present. in the tank and that of the water column, an equilibrium difference in height corresponding to the pressure difference existing between said tank and the heating body considered. The condensates produced in the heating bodies are therefore continuously eliminated so that this unevenness in balance is preserved.

It is also clear that the present invention no longer requires the use of as many extraction means as there are heating bodies; a single means is sufficient whatever the number of heating bodies from which we want to extract the condensates.

Advantageously, for each of the heating bodies from which the condensate is to be removed, the difference in level between the extraction point on the tank and the condensate removal point on the heating body is chosen so as to be at least equal to the pressure difference existing between the tank and the heating body in question, the extraction point being necessarily located below the sampling point.

Under these conditions, at equilibrium, the level of condensate in the heating bodies will not exceed that of the sampling point on the heating bodies. They will therefore not be cluttered with condensate and they will be able to function optimally.

According to a variant, all or part of the pipes open into the tank h0 at a level located below the extraction point. In the case I 2 'where all the pipes open below this point, the tank may be at the pressure of the heating body where the highest pressure prevails among the heating bodies from which the condensate is to be extracted, but it can also be at higher pressure.

According to another variant, only the pipe in relation to the highest pressure heating body opens into the tank at a level situated above the extraction point. In these conditions, there is communication between the tank and this heating body and the pressure prevailing in the first is equal to the pressure prevailing in the second. The condensate from this particular heating body flows, then by gravity into the tank and there is no formation of a liquid column in the pipe associated with this heating body.

Finally, all or part of the pipes can open into the tank at a level situated above the extraction point, the pipes 15a associated with a heating body having a pressure lower than that of the tank then being provided with means making unidirectional flow and preventing any migration of fluid and in particular vapor from the tank to the heating bodies. These means can be constituted by one-way valves.

These valves facilitate the formation of water columns in the pipes and thus balance in the tank-pipe-heater systems.

i These means can also be constituted by U-shaped tubes. It is quite certain that in these cases in which all or part of the pipes open into the tank at a level situated above the point of extraction, the pressure of the tank may be equal to or greater than that of the heating body where the highest pressure prevails among the heating bodies from which the condensate is to be removed.

According to one embodiment, the reservoir is brought to the pressure of the heating body where the highest pressure prevails among the heating bodies from which the condensate is to be extracted. This variant makes it possible to maintain a constant pressure in the tank, which is not always possible when the communication between said tank and the heating body in question is ensured by the pipe itself and especially if the latter is of low diameter.

An embodiment of the present invention is described below by way of example with reference to the appended drawing in which the single figure represents an evaporation installation consisting essentially of a four-effect evaporator of the falling-flow type. and provided with the device according to the invention.

More specifically, this installation includes a four kQ effect evaporator 1, 2, 3,! +, The liquid product to be concentrated arriving at the top of the first f /.

effect 1 through a conduit 5 * This product can be of any kind, such as for example a food product such as skim milk. The product from the "base of this effect 1 is then directed to the head A of the second effect 2, from the" base of this effect 2 to the head B of the third effect 3, from the base of this effect 3 to the head C of the 5 last effect V and finally from the base of this effect U to a storage tank or any place of use (not shown), respectively by a conduit 6 comprising an extraction pump 7, a conduit 8 comprising an extraction pump 9, a duct 10 comprising an extraction pump 11 and a duct 12 comprising an extraction pump 13 · In addition, in effects 1, 2, 3 U U of the evaporator-10 are respectively associated steam separators- liquid 1l ·, 15 »16, 17 * The vapor of evaporation created in effect 1 arrives by a conduit 18 in the separator it · from where it is directed by a conduit 19 in the body of heater 20 of the effect 2. In the same way, the evaporation vapor created in effects 2, 3, 1 · is respectively fed into the separators 15 "16," 15 1J by the conduits 21, 22, 23, then directed from these separators respectively into the heating body 2l · of effect 3 "the heating body 25 of effect l · and a condenser (not shown) by the conduits 26, 27, 28. The duct 26 carries the bypass the suction duct 29 of a steam thermocompressor 30, the discharge duct 31 of which opens into the heating body 32 of effect 1. It should be noted that the pressure prevailing in the heating bodies 20, ^ 2l ·, 25 and 32 is respectively P ^, P ^, P ^, PQ which are such that one has

Po> P,> P2> P3 *

Each of the heating bodies 20, 21 and 25 is provided at its lower part with a condensate collection pipe 33 ”31, 35” pipes which open out in a tank 36 provided at its base with a extraction duct 37 comprising an extraction pump 38. The pipe 33 associated with the heating body 20 ′ opens at the top of this tank 36, while the pipe 31 · associated with the heating body 21 · and the pipe 35 associated with the heating body 25 open into the tank at a level located below the point of extraction of this tank. The heating body 32 is also provided at its base with an 'extraction pipe 39 comprising an extraction pump the pipe 39 carrying a bypass pipe l ·! coming to join the pipe 37 * Finally, a pipe l · 2 connects the upper part of the tank 36 to the heating body 20 so that said tank is at all times at the pressure P-j.

35 The condensates produced in the heating body 20 therefore flow freely by gravity into said tank 36. The pressure P ^ in the heating body 21 · being lower than the pressure P1, the condensates present in the tank will rise in line 3l ·, and the condensates produced in the heating body 2l · are discharged in this same line 3l ·. The level of b0 condensates in line 3l · finally tends towards an equilibrium value B ^.

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The same is true in line 35 where the level of the condensate s tends towards an equilibrium value Rg situated above the level R ^ due to the fact that the pressure of the heating body 25 is lower than the pressure of the body heating 2b. Ultimately, if we call: 5 - H the difference in level between the level of the tank extraction point and the level and -H 'the difference in level between the level of the tank extraction point and the level Rg, the system evolves until reaching the equilibrium characterized by the following equations 10: H »P1 - P2 H '= P1 - P3

Then, the system behaves so as to always tend towards this balance. Thus, the condensates coming from the heating bodies 2b and 25 and 31 ....

15 qμi flow respectively in the pipes and 35 ”tend to raise the level of liquid in these pipes; but the system reacts immediately to oppose this rise in level and the supply of condensates from the heating bodies 2b, 25 is absorbed by the tank 36 and evacuated by the extraction circuit 37 ”38.

20 Of course, the spirit of the invention would not be altered in any way if | the lines 3¼ and 35 led into the tank 36 above the level of the extraction point of this tank. However, in this case, to facilitate the formation of the. column of liquid in said pipes, a one-way valve is arranged on each of them. Under these conditions, the vapor present in the reservoir 36 cannot at any time escape into the conduits 3 ^ · and 35 towards the heating bodies 2b and 25, thereby hampering the formation of the columns of liquid. The condensate coming from the heating bodies 2b and 25 will therefore flow respectively in the pipes 3 ^ and 35 until reaching there equilibrium levels as defined above, the valves opening and closing by so as to maintain these levels of equilibrium in the conduits 3 ^, 35 ·

In the installation shown above, the pipe 33 in which the condensates from the heating body 20 circulate, emerges at a level located above. above that of the extraction point and the pressure in the tank is then P1. However, if there is a one-way valve on this pipe 33 35 which prevents any migration of fluid from the tank to the heating body 20, or if this pipe 33 is unblocked in the tank 36 at a level located at - below the extraction point "it is then possible to have in said reservoir 36 a pressure greater than, for example PQ. Under these conditions, it will of course be necessary to create, between the tank 36 and the heating bodies 10, 20, 2b and 25, a sufficient elevation to allow the flow of condensates to the tank.

It should be noted that the condensates that form in effect 1 are discharged through line 39 and the extraction pump kO. A part of these condensates is mixed by means of the line Ul with the condensates coming from the reser-5 see 36, the remainder preferably being directed towards a boiler where all or part of the steam necessary for the operation of the thermocompressor 30 is produced. Of course, the line H1 could be eliminated without this affecting the operation of the installation.

The tank 36 could also be associated with the heating body 32, in which case all the condensates from the evaporator would be collected by a single extraction and mixing device.

The hot water extracted from the heating bodies of the effects of the evaporator, in accordance with the invention, finds different applications. It can for example be used to preheat the necessary air in a dryer by hot air coupled to one evaporator and in which the concentrate from said evaporator or any other concentrate is treated.

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Claims (4)

1. Device for extracting and mixing condensates from the heating body of at least two effects of a multiple-effect evaporator, the pressure decreasing from the first to the last effect, characterized in that it comprises a reservoir into which open pipes respectively in relation to the hasse portion of the heating bodies from which it is desired to extract the condensates, this tank further comprising an extraction means. 2. Extraction device according to claim 1, characterized in that, for each of the effects from which the condensate is to be extracted, the designation between the point of extraction on the tank and the point of sampling condensate on the heating body is chosen so as to be at least equal to the pressure difference existing between the tank and the heating body considered, the extraction point being located under the sampling point. 15 * "3 · Extraction device according to claim 1 or 2, characterized in that all or part of the pipes open into the tank at a level located below the extraction point. h. Device according to Claim 3, characterized in that only the line in relation to the highest pressure heating body 20 opens into the tank at a level situated above the extraction point, j 5 · Device according to the any one of claims 1 and 2, charac terized in that all or part of the pipes open into the tank at a level situated above the point of extraction, the pipes associated with the heating bodies m of pressure lower than that of the the tank then being provided with means making the flow unidirectional and preventing any migration of fluid and in particular of vapor from the tank to the heating bodies. 6. Device according to claim 5, characterized in that said means consist of unidirectional valves- T · Device according to claim 5, characterized in that said means consist of U-shaped tubes. 8. Device according to any one of the preceding claims, characterized in that the reservoir is brought to the pressure of the heating body where the highest pressure prevails among the heating bodies from which it is desired to extract the condensates. ΙΛλλλλρ