US3503433A - Controlled recompression evaporator with regulated heating,feed and discharge - Google Patents

Description

March 31, 1970 P. RIVA ET AL 3,503,433

CONTROLLED RECOMPRESSION EVAPORATOR WITH REGULATED HEATING, FEED AND DISCHARGE Filed Sept. 7. 1966 6 Sheets-Sheet 2 Q N m \w 5% Q a a (3% "k & a v Q Q) F /'g. 6 Relay INVENTORS ATTORNEYj ow on" iii NQQ CONTROLLED RECOMPRESSION EVAPORATOR WITH REGULATED HEATING, FEED AND DISCHARGE 6 Sheets-Sheet 5 Filed Sept. 7, 1966 33k .85 n m m sea. :33 mm M 3: fimhwfii MAM v xstw W Mn m wt km W0 L wmwfim A m QM M m am 1M a w i a E @m Wm A N. m f Q i a MWMNH R v u QM: 8% vi mi TM HQ u i w M v d w a i R i i Q H M March 31, 1970 P. RIVA ET AL 3,

CONTROLLED RECOMPRESSION EVAPORATOR WITH REGULATED HEATING, FEED AND DISCHARGE 6 Sheets-Sheet 4 Filed Sept. '7, 1966 v2.33 wwwotfi m W M sa i g a $1 i A H N m l 5 a m W a L W Fli 1|. ll lllllllllll llll IE-K 2235 WQ Q OMHP QUE d m U 358 s: 855 NW INVENTORS BY WM lwm w ATTORNEYS March 31, 1970 p, RIVA ET AL 3,503,433

CONTROLLED RECOMPRESSION EVAPORATOR WITH REGULATED HEATING, FEED AND DISCHARGE Filed Sept. 7, 1966 6 Sheets-Sheet 5 64 6 ig/1 66 T T I level level rule r! ranlut L6/suF/a2 H46 INVENTORS BY M 1, M

ATTORNEY March 31, 1970 P. RIVA ETAL 3,503,433

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INVENTORS ATTORNEYS United States Patent 3,503,433 CONTROLLED RECOMPRESSION EVAPORA- TOR WITH REGULATED HEATING, FEED AND DISCHARGE Pietro Riva, Via De Amicis 15, and Guido Riva, Via Cavour 5, both of Soresina, Cremona, Italy Filed Sept. 7, 1966, Ser. No. 577,726 Claims priority, application Italy, Apr. 13, 1966, 16,7 46/ 66 Int. Cl. B01d 1/06, 1/28, 3/42 U.S. Cl. 15944 'Claims ABSTRACT OF THE DISCLOSURE The present invention relates to mechanical thermocompression evaporators for aqueous solutions.

Mechanical thermocompression evaporators are already known requiring, during running, the operators assistance and supervision.

Mechanical thermocompression evaporators are also known, in which the supply of auxiliary heat during running is automatically adjusted and is moreover provided with devices which automatically close down the evap orator if the flow of feed liquid is accidentally interrupted, or if the vapour compressor is working below certain pre' determined temperatures.

However, though an evaporator thus equipped assumes semi-automatic characteristics, the various delicate presetting operations for the pre-heating, running and Stop ping of the evaporator, have instead remained entrusted to the manual intervention and judgement of the operator.

The true distillation is normally preceded by a pre heating and starting phase of the evaporator. Said phase which, as it will be seen later on, implies a succession of operations and has a duration varying from two to three hours.

This means that if the preheating and starting of the evaporator begin when the plant activity starts, the distillate production will only start after two or three hours with the result that, should the distillate be produced at the beginning of the factory activity, as required in almost all cases, it will be necessary for the operator appointed to the control of the evaporator, to intervene two or three hours before in order that he may carry out the aforesaid pre-heating and starting operations.

Similarly, very often plant schedules require that the evaporator should not be stopped at the ceasing of the normal plant activity, but that it should continue its output still for a further fixed period (night hours).

It is obvious that under these circumstances, the opera tor is obliged in both cases, to go to the factory before and after his working day in order to set at Work and halt the evaporator, this thing clearly representing an inconvenience.

Among the other things, the starting phase which follows the pre-heating one, requires a certain technical competence from the operator who has been appointed to it.

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Also for this reason, the automation of the evaporator has become an exigency specially felt by those industries having shortage or even lack of a qualified person to be appointed to the control of such a machine.

It is therefore an object of the present invention to overcome the above disadvantages.

.Accordingly, the present invention comprises, in a suitable way for use with a mechanical thermocompression evaporator, an apparatus including means apt to automatically and successively control: the feeding of an aqueous solution inside the evaporator, pre-heating of the solution, setting out of the compressor, running of the evaporator under steady state conditions and its stopping as well as means responsive to possible abnormalities in the operating conditions of the evaporator, and shut it out at the same time.

Moreover, the invention also includes a mechanical thermocompression evaporator equipped with said ap paratus.

In order to have the invention fully understood, one embodiment of it will now be described with reference to the here enclosed drawings, wherein:

FIG. 1 shows the hydraulic system of a mechanical thermocompression evaporator wherein the principal component parts and the elements controlled by the automation apparatus of the following figures, are represented;

FIG. 2 shows the electric system of the power circuit for the apparatus according to the present invention;

FIG. 3 shows the electric system of the control circuit for the apparatus according to the present invention;

FIG. 4 shows the electric system for the alarm and signal apparatus (Q.A.) that in FIG. 2 is represented in block;

FIG. 5 shows the relay electronic system for the thermostat shown in FIGURE 2;

FIG. 6 shows the relay electronic system for the vacuum gauge L represented in FIGURE 2;

FIG. 7 shows the programme cycle for the apparatus according to this invention.

Particular reference will now be made to FIGURE 1 of the drawings in which, as shown, the following have been indicated: a vapour tank A, a condenser-evaporator B, a heating chamber D, a distillate heat exchanger E, a concentrate heat exchanger H, a vapour compressor I, a suction piping N of the compressor, an automatic feeder G3 and a pressure reduction tank G4 for the liquid in question.

In the above mentioned hydraulic system of FIGURE 1, the members relating to the control automatic apparatus of the evaporator, are the following: a minimum level magnetic contact G1; a float contact G2 indicating the lack of the liquid fed; a group R1 of heating electric resistors energized both during the pre-heating and the steady state operation or working running of the evaporator; a group R2 of heating electrical resistors energized only in the pre-heating phase; a group R3 of heating electrical resistors energised directly in the preheating phase and switched into circuit with the automatic control device for the auxiliary heating during the steady state operation (we point out that, for simplicity of drawing, groups R1, R2 and R3 of electrical resistors have been schematically represented by a sole element in FIGURES 1 and 2 in the annexed drawings, however this must not be considered in a restrictive sense); a vacuum gauge L connected with said automation; a vacuum state value V to stop the evaporator in case of excessive vacuum; a motor M for driving the compressor; an inlet electrovalve EVl for the liquid in question; a motorized valve EV2 in the vapour compressor by-pass; a compressor purge electrovalve EV3; a concentrate discharge electrovalve EV4; a thermostat K with electrical contacts for maximum values related to the compression temperature.

The path of the fiuid is clearly indicated with the arrows represented in FIGURE 1 and, moreover, the working of such hydraulic system will be explained below.

Now, with particular reference to FIGURES 2 to 6, we shall shortly describe the power and the control circuits, while, for a correct interpretation of said circuits, we suggest the reading of the drawings together with the detailed explanation of the working of said apparatus which will be given later on.

POWER CIRCUIT (FIGURE 2) The power circuit substantially comprises the threephase line RST, provided with a general switch 20, which line feeds the primary winding 21 of a three-winding transformer whose secondary winding 22 feeds the alarm apparatus Q.A. (FIGURE 4) and whose secondary winding 23 feeds the control circuit shown in FIGURE 3.

The power circuit comprises, moreover, a working motor M of compressor I, this motor, being controlled through a contactor 24 (see FIGURE 3) whose main contacts 24 24 and 24 (shown in FIGURE 2) are respectively connected with the three phases of motor M before the protective thermal relay Q; a group R1 of resistors connected with the three-phase branch line RS by means of main contacts 25 and 25 of a contactor 25 (shown in FIGURE 3); a group R2 of resistors connected with the threephase branch line RT by contacts 26 and 26 of a contactor 26 (shown in FIGURE 3); and a group R of resistances connected with the three-phase branch line ST by contacts 27 and 27 of a contactor 27 (shown in FIGURE 3) during the evaporator pre-heating phase, and by contacts 28 and 28 of a contactor 28 (shown in FIGURE 3) during the steady condition phase.

We point out that during the steady condition phase, group R3 of resistors is connected indirectly to the threephase line by the electronic relay 29 shown in FIGURE 2 and represented in FIGURE 6 in detail, as it will be more clearly explained in the specification of the cited FIGURE 6. We insist again upon the fact that groups R1, R2 and R3 of resistors have been indicated in FIG- URE 2 by a single resistor element for drawing evidence.

As it may be noted in FIGURE 2, both for motor M circuit and for heating resistors circuit R1, R2 and R3, 21 protection by means of common fuses has been realized.

CONTROL CIRCUIT The control circuit, represented in FIGURE 3 in detail, is fedthrough conductors 41 and 42-by the secondary winding 23 of the three-phase transformer previously cited and shown in FIGURE 2.

The control circuit, whose function is to control the evaporator whole working cycle, as it will be explained later on, is represented as a functional diagram and is substantially formed by common electromagnetic relays shown with numbers 30 to 37 and by timers T1, T2 and T3 whose working will be described later on. Besides the aforesaid elements and contaactors 24 to 28, the control circuit also comprises a particular cyclic relay 43 which is operated by timer T3, as represented in FIG- URE 3 by a dash line, this cyclic relay being apt to successively close its four independent contacts, with a certain fixed program.

We do not describe in detail the control circuit represented in FIGURE 3, owing to the fact that a technician of the field is in a position to read such a functional diagram, while the direct reading of the drawing can be affected together with the reading of the working detailed explanation of the apparatus, in order to correctly understand the worlging of the control circuit itself.

4 ALARM CIRCUIT In FIGURE 4 of the annexed drawings, it has been represented, in detail, the alarm circuit indicated in FIG- URE 2 by Q.A.

As already stated, the alarm circuit is fed by the secondary winding 22 of the three-winding transformer and it substantially comprises common electromagnetic relays 38, 39 and 40 and the alarm lamps 44 to 49 respectively for the excessive vacuum 44 overload of motor 45, inactive system 46, lack of water 47, plant in the heating phase 48 and in the running phase 49 connected in the way clearly represented by FIGURE 4 itself.

Moreover the alarm circuit comprises the contacts connected with the vacuum state V and the float contact G2 of tank G4 for the reduction of the pressure of the unevaporated liquid.

Also for the alarm circuit of FIGURE 4 please refer to its description which will be made together with the detailed description of the apparatus.

FIGURE 5 illustrates the diagram of the electronic relay of thermostat K, which electronic relay has been represented in FIGURE 2 by block 50.

As it appears from FIGURE 2, the electronic relay 50 is fed, with a 24V tension, by the secondary winding 22 of the three-winding transformer and is controlled by thermostat K which represents the two contacts 51 and 52 apt to be short circuited by the liquid of thermostat K.

In FIGURE 5 thermostat K has been represented under the form of a switch whose movable contact 53 has the function of the liquid of thermostat K.

As shown in FIGURE 5, the electronic relay 50 comprises a common rectifying circuit 54 with a smoothing capacitor which feeds, through a transistor 56, an electromagnetic relay 57 whose function will be explained later on and whose auxiliary contact 57 is also represented in the functional diagram of FIGURE 3. In parallel with relay 57, there is a diode 58 apt to protect transistor 56 from the reverse overvoltage.

In FIGURE 5, the transistor 56 has its collector connected to the coil of relay 57, its emitter directly connected to one end of rectifier 54, and its connecting base is connected to the other end of rectifier 5.4 through a resistor 59 and a movable contact 53 which contact 53 together with the fixed contacts 51 and 52 represent, in their whole, thermostat K of FIGURE 2.

The electronic relay has the function to protect the contacts 51, 52, 53 with which thermostat K is provided; in fact, said contacts could not absorb the exciting current of the coil of relay 57 and therefore it is advisable to amplify through transistor 56, the small current which interests the thermostat contact as shown in the diagram of FIGURE 5, in order to have a current with a value sufficient to energize the relay 57.

Now we are going to describe FIGURE 6 representing the electronic diagram of a second electronic relay indicated in FIGURE 2 with 29, which is controlled by level meter or vacuum gauge L.

Also this circuit is a transistor common circuit, at whose input there are: a rectifier 60 connected through conductors 71 and 71 to auxiliary contacts 28 and 28 respectively, of electromagnetic switch 28 a levelling capacitor 61 connected in parallel to the rectifier itself; and a relay 62 operated by level meter or vacuum gage L (FIGURE 2) which in FIGURE 6 has been represented with movable contact 65, this latter contact being able to connect either with maximum value contact 63 or with minimum value contact 64.

The maximum value contact 63 and minimum value contact 64 are respectively connected with the base of transistors 66 and 67 which are apt to amplify not only the current signal passing through the contacts of level meter L, but also to realize a memory in order to maintain relay 62 energized till when the maximum value contact 63 is closed.

More exactly the electronic relay of FIGURE 6 has the function of protecting the contacts of level meter L; besides, it must have relay 62 energized at the same moment in which contact 64 closes with contact 65 of the level meter L; keeping it excited also after that such a contact has been opened, while it will be only de-energized when contact 63 is closed with contact 65.

In order to keep relay 62 energized also after the opening of the minimum value contact of level meter L, a holding contact 62 is utilized, as it is shown in FIG- URE 6.

Instead, when the maximum value contact of level meter L is closed, transistor 66 is brought into conduction state and therefore the ends of the coils of relay 62 are practically short-circuited in such a way that, since there is no more tension on the coil of the relay 62, this latter one de-energizes.

We point out that such short-circuit cannot cause any damage to the apparatus because the current is limited by a high resistor -68 in series with relay 62 itself.

Moreover in FIGURE 6 it has been represented the auxiliary contact 62 of relay 62 in order to connect conductors 69 and 70 of FIGURE 2 and an auxiliary contact 62 this latter connecting the conductors 71 and 72 of FIGURE 2, in consequence of the energizing of relay 62.

In the diagram of FIGURE 7, the programming cycle is shown in the sequence of the phases following one another automatically during the working of the previously described apparatus. The various phases have been indicated with numerical reference from 101 to 108 arranged according to a horizontal axis, while, according to a vertical axis, we have indicated the symbols of the various elements which are set in action during the evaporator cycle; more exactly we have indicated with ON the energized condition for each element and with OFF their de-energized condition.

To better understand the working of the evaporator, we shall summarize, hereunder, the various situations of elements in the single phases and, afterwards, we shall explain the detailed working of the apparatus.

Phases of inactivity of the evaporator (101) EV1de-energized and closed EV2de-energized and open EV3de-energized and open Mstationary EV4-de-energized and closed Pro-setting of the pro-heating (102) O-electrical switch of appropriate pre-set programming gives a start to said cycle closing contact 0 (FIGURE 3). More precisely:

EV1is energized and opened allowing the entrance into the evaporator of the unevaporated liquid in question EV2is energized and closed EV3-is de-energized and remains open Mstationary EV4de-energized and closed When the unevaporated liquid in question reaches such a level as to have covered the heating resistances, the preheating phase takes place by means of G1.

Pre-heating phase (103) EV1-energizes and remains open EV2de-energized and remains closed EV3de-energized and open 6 Mstationary R1on R2on R3on (directly) EV4de-energized and closed When the vapour compressor I has reached the work temperature indicated by the maximum electrical control of the thermometer K, the pre-set starting phase takes place.

Pre-set starting phase (104) EV1-energizes and remains open EV2--self-energizing, it opens EV3self-energizing, it closes Mstationary R1on R2on R3-on (directly) EV4-de-energized and closed Starting phase (105) When EV2 is completely open:

The evaporator remains for a certain time in the above described conditions and then begins the intermittent closure of the valve EV2.

On the complete closure of EV2, and after a certain predetermined interval, the running phase (106) begins.

Steady state running phase (106) EV1--still energized and open EV2de-energized and closed EV3energized and closed Mrunning R1on (auxiliary steady state heat) R2is off R3-is switched into circuit with the automatic vacuum regulation apparatus (29) EV4-energized and open The steady state running phase is prolonged up to the time per-set on the clock of the switch 0;

On opening the contract of electric switch 0 the next phase (107) is commenced.

Pre'setting of stopping (107) In this phase, the opening of EV2 is started while the other members remain in the position of the running phase (106).

Stopping (108) When EV2 is completely open, the following takes place:

EVl-de-energized and closes the flow of feed liquid EV2de-energized and remains open EV3de-energizes and opens Mst0ps R1-c-uts out R2remains off R3-cuts out EV4-de-energizes and closes The detailed functioning of the apparatus above described is more fully described below.

Pre-setting of the pre-heating phase On the closure of the contact 0 (FIGURE 2) of the programmed switch 0, the auxiliary relay 3-6 and successively the relay 30 are energized.

The relay 30 thus energized, closes its self-feeding contact 30 and closes another of its contacts 30 permitting opening of the electrovalve EV1, and at the same time puts the servomotor of the bypass valve EV2 into action.

The energization of EV2 takes place, provided that the relay 33 (having rest contact 33) which is under the control of the thermometer K, be de-energized. In fact, relay 33 is controlled by contact 57 of relay 57, (see FIGURES 3 and 5) which energizes at the closure of contact 53 (FIGURE 5).

The energization follows of relay 37 which gives voltage to the remaining portion of the control circuit (make contacts 37 and 37 The energization of the relay happens only when the unevaporated liquid of the evaporator reaches G1 which excites, in its turn, relay 31 (make contact 31 but it is necessary that no intervention conditions for the alarms exist.

More precisely it is necessary that the following be deenergized (see FIGURES 4):

(a) the relay 38of the excessive vacuum alarm-rest contact 38 (b) the relay 39of the overloading motor alarm-rest contact 39 (c) the relay 40of the lack of feed liquid alarm-rest contact 40 Pre-heating phase The following contactors are simultaneously energized:

25energizing the group of heating resistors R1 26energizing the group of resistors R2 27energizing the group of resistors R3.

The contactors 26 and 27 come into action because the relay 35 is in a de-energized position (rest contact 35 At this moment the unevaporated liquid contained in the evaporator is heated up to boiling.

The vapour that develops is gathered in the tank A, and EV2 being closed in advance, the vapour itself is obliged to run, through the piping N, into the compressor I and heat it.

When the fluid of the thermometer K connects contacts 51, 52 (the contact 53 is closed, see FIGURE 5) the relative relay 57 is energized which relay by means of its contact 57 energizes the relay 33.

The contact 33 of the relay 33 makes the by-pass valve EV2 open by means of its servomotor and at the same time, by means of the contact 33 prevents the possibility of re-closure of EV2.

Starting phase When EV2 is completely open, the limit contact FC closes and the auxiliary relay 32 is energized.

A contact 32 of said relay puts the motor M into motion by means of the contactor 24, provided that the relay 33 is energized (make contact 33 Simultaneously, on account of the fact that the relay 34 is de-energized, the control is given to the time lag device T1, whose contact T1 closing after a predetermined time, can energize the relay 34, whose contact 34 takes the feed away from the time lag device T1.

Another contact of the relay 34, that is the contact 34 gives the control to the cyclic interrupter T3-43, which makes the electro-valve EV2 close with a cycle of fixed intermittence.

A third auxiliary contact 34 does not allow a rapid opening of EV2.

When the by-pass EV2 is again completely closed, the limit contact FC2 is closed.

The limit contact FC2, gives the control to the time lag device T2, provided that 24 is energized and 35 deenergized (make contact 24 and rest contact 35 The device T2, after a predetermined time, closes its contact T2 and the relay 35 is energized, its contacts operating as follows:

The make contact 35 self-feeds the relay itself.

The make-contact 35 energizes the concentrate discharge electrovalve EV4 and also the contact 28, which switches by means of contacts 28 and 28 the group R3 of resistors into circuit with the electronic relay 29 for the vacuum regulation control.

Rest contact 35 de-energizes the contactors 26 and 27 cutting out the resistor group H2, by means of make contacts 26 and 26 and the direct feed of the resistor group R3 with the make contacts 27 and 27 The rest contact 35 de-energizes the device T2. At this point, the evaporator is in the steady state running condition.

Pre-setting for the stopping When the programmed switch 0 indicates the predetermined stop time, it opens its contact 0 and consequently it de-energizes the relay 36 which, through its auxiliary rest contact 36 gives the opening command to the by-pass valve EV2.

The contacts 15/2 and 15/3 simultaneously prevent the closure of EV2.

Simultaneously, the make contacts 36 and 36 hinder the closing of EV2.

From the instant that 0 opens, the relay 30 remains energized in consequence of its self-feeding 30 till the valve EV2 is completely open.

This condition of the relay 30 is possible because the limit contact FCI excites the relay 32, Which in its turn opens the relative rest contact 32 taking the feed from the relay 30 itself.

Stopping With the stopping of the feed to 30, the contact 30 is opened, which provokes the interruption of the whole control circuit.

As a consequence of this, the following takes place:

the electrovalve EVl de-energizing, closes the electrovalve EV2 remains in the open position the electrovalve EV3 de-energizin g, opens the contactor 24 de-energizes and stops the motor M and compressor I the contactor 25 of the group of resistors R1 is deenergized the contactor 26 of the group of resistors R2 is deenergized the contactor 28 for the group of resistors R3, switched into circuit with the automatic vacuum regulation apparatus 43, is de-energized the electrovalve EV4, de-energizing, closes.

ANOMALIES IN RUNNING (a) if during running, a condition of excess vacuum in the evaporator arises, the contact of the vacuum state device V energizes the relay 38 (FIGURE 4) which, by means of its contact 38, de-energizes the relay 37 of the general panel. The relative contacts 37 and 37 opening interrupt the feed to the control circuit, stopping the evaporator. In the meantime, 38, closes its contact 38 which makes the signal lamp 53 light, indicating the cause of stopping of the evaporator due to excessive vacuum;

(b) if, during running, for any reasons, the vapour compressor overloads the motor M which operates it, the thermal protection relays Q of the contactor 24 intervene.

The action of Q closes contact Q and relay 39 is energized, which relay 39, by means of the auxiliary contact 39 opens the relay 37 thereby taking away the voltage from the evaporator control circuit. Simultaneously the relay 39 closes its contact 39 and the signal lamp 45, which indicates stopping of the evaporator because of overloading of the motor M of the compressor 1, is simultaneously lit;

(0) if during running, the flow of unevaporated liquid in question should accidentally come to a stop, the float contact G2 closes, exciting the relay 40.

This by means of its contact 40 de-energizes 37 thus taking away the voltage from the control circuit. The evaporator stops working and lights the relative lamp 47 indicating stoppage because of lack of feed liquid. On the basis of the light signals, the operator knows the cause of the evaporator stoppage and obviously makes provision to eliminate it.

Before putting the evaporator back into service, however, he must push the push button of the alarm cancel device P.S.

Operating in this way he takes the cycle back to the programming starting position.

As stated above, it is also an object of the present invention to provide a mechanical thermocompression evaporator incorporating the above described apparatus.

Variations may be brought to the apparatus object of the present invention without, for that, going beyond the protective field of the invention itself.

In particular, instead of electric resistors for pre-heating and heating under steady state conditions of the unevaporated liquid, coils may be used inside which low-pressure vapour flows, whose flux is controlled by electrovalves connected with the same organs controlling, in the above described form of execution, the insertion of the resistors.

Description of the working of the apparatus By the programmed switch 0, the evaporator working period is established by fixing the starting and end hour of the working cycle which comprises the phases indicated by reference numbers 102 to 107 in FIGURE 7.

When contact 1 of the programmed switch closes (FIGURE 3), relay 36 is energized, which relay sets into work its own auxiliary contacts, of which:

36 disconnects the opening circuit of valve EV 36 closes the closing circuit of valve EV 36 pre-sets the insertion of the cyclic relay 43;

36 (FIGURE 4) determines the switching-otf of the lamp 46 signalling the evaporator inactivity;

36 determines the energization of relay 30, which closes its self-feeding contact 30 and its contact 30 for energizing the closing circuit of valve EV at the same time, the auxiliary contact 30 (FIGURE 4) pre-sets the lighting of the signal lamps 48 and 49.

Therefore the valve EV2 closes and the evaporator preheating phase takes place. At the same time that EV2 closes, valve EV1 opens, this latter valve allowing the flow of the liquid to treat.

The liquid starts fiowing into the heating exchangers E and H, then it rises to the heating chamber D, successively entering the condensator-evaporator B till reaching the level fixed by G3. One moment before the water reaches said level, the minimum level magnetic contact G1 (FIGURE 1) is set in work, said contact G1 (FIG- URE l) inserting relay 31 (FIGURE 3) which, in its turn closes the self feeding contact 31 it closes contact 31 which makes relay 37 energize, while contact 31 (FIG. 4) closes to pre-set the lamp 47 insertion when the liquid to be treated in G4 lacks.

The energization of relay 37 causes the closing of auxiliary contacts 37 and 37 which supply voltage to the remaining portion of the circuit of FIGURE 3 finding itself on the right of said contacts. At the same time, also contact 37 determining the. switching on of lamp 48, closes.

By closing contacts 37 and 37 the feeding of the remaining part of the circuit of FIGURE 3 causes the energization of contactors 25, 26 and 27, said contactors closing the respective contacts 25 25 26 26 and 27 27 (FIGURE 2), these latter directly inserting the heating elements R1, R2 and R3, supposing that the main switch 20 be closed. During the preheating phaseEV2 being closed-the vapor produced passes all through a vapor compressor to heat this latter and pre-set it to working. The pre-heating phase lasts until a temperature fixed by thermostat K is reached. When said temperature is reached,

thermostat K closes its contacts 51, 52 (FIGURE 2), i.e. with reference to FIGURE 5, the movable contact 53 connects the fixed contacts 51 and 52, and, through the electronic relay 50, it causes the energization of the electro-magnetic relay 57 (FIGURE 5), which closes its own contact 57 (FIGURES 3 and 5) and this latter causes, in its turn, the energization of relay 33. The energization of relay 33 causes the opening of contact 33 of the closing circuit of EV2 and, at the same time, the closing of contact 33 of the opening circuit of EV simultaneously also contact 33 closes, said contact pre-setting the circuit of FIGURE 3 for the energization of 24, T1 and 34 and at the same time it determines the closing of EV The open- 1ng of EV causes the closing of limit contact FC and the opening of limit contact FC The phase starts with the opening of EV2. The closing of FCI causes the energization of relay 32 whose auxiliary contact 32 determines the feeding of contactor 24 which closes its contacts 24 24 and 24 (FIG. 2) for feeding motor M, and then the working of compressor I (FIGURE 2.) that simultaneously-through the auxiliary contact 24 (FIG. 3) determines the energization of timer T1. After a prefixed period of time, timer T1 closes its contact T1 which energizes the relay 34 which, with its own contact 34 de-energizes T1, while contact 34 sets in motion the timer T3 which drives the cyclic relay 43 for a closing at programmed intervals of valve EV to gradually bring ompressor I to its steady state conditions.

The contactor 24 energization determines; moreover, the closing of contact 24 which pre-sets timer T2 for the start when contact FC is closed by the closing of valve EV Now we are passing to the steady state conditions. Similarly we have the closing of contact 24 for the selfenergization of both contactor 24 and relay 34 previously energized at closing of contact T1 Timer T2 is then set in motion and after a certain period of time it closes its contact T2 which determines the energization of relay 35 which is self-energized with 35 and which, by the auxiliary contact 35 causes the energization and the opening of valve EV for the discharge of the concentrate and the energization of contactor 28 which, with its own contacts 28 and 28 (FIGURE 2) switches the heating element R3 on the electronic relay 29 controlled by the vacuum gauge L for the auxiliary heating during the phase of steady state conditions. At the same time the auxiliary contact 35 opens, and contactors 26 and 27, which disconnect elements R2 and R3, de-energize; the auxiliary contact 28 (FIG. 4) makes lamp 48 switch off and the auxiliary contact 28 makes lamp 49 switch on in FIGURE 4. At this point, we enter the phase of steady state conditions. During the steady state conditions, there may be the auxiliary heating of the heating element R3 controlled by the vacuum gauge L through the electronic relay 29.

During the steady state conditions of the evaporator, the distillation of the liquid to be treated takes place. At the fixed hour of the stopping, the programmed switch 0 opens its contact 0 de-energizing the relay 36 (FIG. 3) which causes the opening of valve EV2. When EV2 opens, also contact FC2 opens and there is the closing of contact FCl which energizes the relay 32 whose auxiliary contact 32 Opens and causes the de-energization of relay 30 which opens its auxiliary contact 30 taking off the feeding to the whole circuit and consequently the evaporator stops working. The evaporator remains in the rest position for the whole fixed period and the successive day, at the fixed hour, the switch 0 closes its contact 0 again making the evaporator start a new working cycle.

What is claimed is:

1. An apparatus for the complete automation of a mechanical thermocompression evaporator comprising in combination:

(a) an electrical motor for operating the evaporator compressor, which is connected with a suitable power source;

(b) a first immersion heating means of the aqueous solution to be treated directly inserted in either phase of the pre-heating and running-under-steady-state conditions of the evaporator; a second immersion heating means of the said aqueous solution energized directly during the pre-heating phase of the evaporator; and a third immersion heating means of the said aqueous solution, directly energized during the preheating phase of the evaporator, and indirectly energized through an automatic controlling device for auxiliary heating during the running of the evaporator under steady state conditions;

() an electric circuit for automatically controlling various working phases of the evaporator, said circuit having a first, electro-valve for controlling the flow of aqueous feed solution to be treated in the evaporator; a programmed switch whose closing controls the energization and opening of the first mentioned electrovalve, in order to start the evaporator working cycle;

a second compressor by pass electro-valve; means to control the energization and closing of the second compressor by pass electrovalve depending on the evaporator temperature, during the pre-heating phase; means adapted to set the said compressor motor in motion during the starting phase; and a number of timer means acting in sequence and adapted to control a cyclic switch in order to determine the cyclic closing and opening of the second mentioned electrovalve, according to an already fixed sequence, during said starting phase;

a third compressor dump electro-valve; means adapted to energize and close the third electrovalve during the evaporator pre-setting of starting and pre-setting of stopping phases;

a fourth valve for the discharge of the concentrate; means adapted to energize and keep the fourth cited electro-valve opening during the workingunder-the-steady-state conditions for the discharge of the concentrate itself; the control circuit also comprising: means controlling the direct insertion of the three said heating means during the pre-heating phase as a function of the minimum allowed level of fluid in the evaporator; means adapted to connect the third, said heating means on the automatic control device of the auxiliary heating and to disconnect the second heating means during the working phase under steady state conditions, the said programmed switch causing the evaporator working cycle to start and stop in fixed periods;

(d) said apparatus, moreover, comprising safety means adapted to signal abnormal stops and running anomalies of the compressor, simultaneously stopping the working of the compressor itself.

2. An apparatus according to claim 1, characterized in that said first, second and third heating means are electric resistors.

3. An apparatus according to claim 1 characterized in that said first second and third heating means, are pipe coils inside which low pressure vapour flows.

4. An apparatus according to claim 1, characterized in that the automatic control device of the auxiliary heating comprises a contact vacuum gauge connected with the dome of the evaporator and is provided with minimum and maximum value contacts to operate an electronic relay which indirectly connects and disconnects the said third heating means as a function of the vacuum reached in the dome of the evaporator itself.

5. An apparatus according to claim 1, characterized in that said means for the control of the energization and closing of the second electro-valve as a function of the temperature and level of the fluid reached in the evaporator during the pre-heating phase, comprise a minimum level magnetic contact connected with a float directly operated to the aqueous solution to be treated, and a first auxiliary contact of a relay operated by the closing of electric contacts of a contact thermostat sensing the compressor temperature, the closing of the last relay also allowing the energization of further relay means adapted to control the connection of the said heating means.

6. An apparatus according to claim 1, characterized in that the timer means are adapted to control the cyclic opening of the said second electro-valve during the starting phase and comprises a first timer which, when closing its contact after a fixed time, energizes a relay which, in its turn, operates the said timer of the cyclic switch thus effecting the closing of the second electro-valve with the fixed intermittance cycle.

7. An apparatus according to claim 1, characterized in that the means adapted to connect the third heating means on the automatic control device of the auxiliary heating and to disconnect the said second heating means during the phase under steady state conditions, comprise relay means controlled by a further timer operated by an offlimit contact at the closing of the second electro-valve and after that this latter one has effected the fixed intermittance cycle, the last cited timer causing, moreover, the opening of the previously cited fourth valve.

8. An apparatus according to claim 1, characterized in that it comprises a first safety means adapted to signal an excessive vacuum inside the dome of the evaporator, the said safety means being constituted of a vacuum state inserted in the said dome, this vacuum state acting on a relay whose operation depends on the vacuum state itself, to break the energizing and stop the running of the evaporator, said vacuum state Causing also the lighting of a corresponding signalling lamp.

9. An apparatus according to claim 1, characterized in that it comprises a second safety means adapted to signal a motor overload, substantially constituted by a thermic relay inserted on the energizing phases of the motor, to break the energizing itself, said thermic relay causing through an auxiliary contact-the energizing of a further relay which acts to deenergize the control circuit and to stop the evaporator, lighting, at the same time, a signalling lamp.

10. An apparatus according to claim 1, characterized in that it comprises a third safety means adapted to signal, during the run under the steady state conditions, the lack of the fluid to treat, said third safety means comprising a contact operated by a float placed on the tank for the reduction of the evaporator pressure, the closing of said contact causing the energization of a further relay which deenergizes the cited control circuit thus stopping the evaporator and lighting, at the same time, a signalling lamp.

References Cited UNITED STATES PATENTS 2,073,825 3/1937 Beck et al 15944 3,192,130 6/1965 Potthurst 159--24 X FOREIGN PATENTS 1,350,074 4/1902 France.

1,387,120 4/ 1902 France.

NORMAN YUDKOFF, Primary Examiner J. SOFER, Assistant Examiner US. Cl. X.R.

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