US3165455A

US3165455A - Distilling arrangement

Info

Publication number: US3165455A
Application number: US29684A
Authority: US
Inventors: Rose Werner; Kolenda Herbert
Original assignee: GEA Luftkuehler GmbH
Current assignee: GEA Luftkuehler GmbH
Priority date: 1959-05-21
Filing date: 1960-05-17
Publication date: 1965-01-12
Anticipated expiration: 1982-01-12
Also published as: DE1091084B; GB916620A

Description

Jan. 12; 1965 w. ROSE ETAL 3,1

DISTILLING ARRANGEMET Filed May 17. 1960 3 Sheets-Sheet 1 FIG] mlm-wmq 5 Jan. 12, 1965 w. ROSE ETAL DISTILLING ARRANGEMET 3 Sheets-Sheet 3 Filed May 17. 1960 3 1:. H. HCQDF mcmuc d wr/nvmes United States Patent 3,165,455 DISTILLENG ARRANGEMENT Werner Rose, Bochurn, and Herbert Kolenda, Essen, Germany, assignors to GEA-Luftkuhler-Gesellschaft m.b.H., Bochum, Germany Filed May 17, 1969, Ser. No. 29,684 Claims priority, application Germany, May 21, 1959,

Claims. ci. 202 is9 ture which does not condense in the spiral tube-chiefly the inert carrier gas or any other inert gas componentsare drawn off at the lower end of the spiral tube. The spiral tube is therefore connected to the head of the column in condenser-fashion.

This known column head condenser is open to the objection that, due to the considerable differences in temperature of the atmosphere, the drop in temperature available for the condensation is subject to strong fluctuations so that the cooling efiiciency of the condenser is dependent to a great extent upon the actual air temperature. Moreover, the cooling effect is also strongly influenced by the strength of the actual air movement so that this air-cooled condenser-regarded as a whole-possesses such a low degree of efficiency that it cannot come into question for use in practice. The great dependency of the cooling effect upon the actual temperature and movement of the atmosphere would lead to a very variable quality and quantity of the product separated by the condenser and consequently 'to technically and economically prohibitive fluctuations in the operation of the entire rectifying or distilling column. In rectifying or distilling media with a relatively high setting point such a condenser would beentircly useless, because it would not be possible to avoid with certainty dropping below the setting point at which these media become viscous or thick so that they can no longer flow downwards under the action of gravity. 7 i

For this reason air-cooled condensers have not been introduced in practice for the head product of distilling or rectifying columns but condensers cooled with water or other liquids (for example a mixture of 27% diphenyl and 73% diphenyloxide) have been given preference, particularly in large-scale plants, as these enable better degrees of efflciency to be attained owing to the possibilities of better regulation. In order to avoid too strong under-cooling of the condensing mediumwhich is particularly important in the case of easily setting mediait is, however, frequently necessary in the case of watercooled condensers to preheat the cooling liquid so as to avoid uneconomical and inadmissible undercooling of the condensate. Another objection to these liquid-cooled condensers is that even slight leakages in the cooling tube cause a pollution of the product so that the cooling liquidfor example water-under high pressure mixes with the condensed product and possibly reacts chemically therewith with the result that the product becomes useless. To exclude this danger, extensive safety measures are generally necessary which consist for example in erecting the liquid-cooled condenser adjacent the column. As, however, such a rectifying column only operates when a portion of the product precipitated in the con- "ice 'denser flows back over the exchange plates or trays of the rectifier column, such an arrangement requires pumps which feed back a portion of the condensate through special return conduits onto the uppermost exchange plate or tray. With the usual height of such rectifier columns, which often amounts to 30 to 50 meters, extensive additional arrangements are necessary which result in an increase of the initial and working costs of the plant. Moreover the vaporous product passing out from the head of the column must in this case be deflected several times if necessary which, particularly in the case of plants operating under high vacuum, leads to serious flow losses due to the high flow velocities required by the large specific volumes of the vapor.

In spite of these disadvantages connected with the use of liquid-cooled condensers for the product from rectifying and distilling columns, these have hitherto been accepted because with air-cooled condensers operation meeting the economic and technical requirements could not be attained.

It is the object of the invention to overcome these disadvantages which hitherto obstructed the use of aircooled condensers and condensers connected up in condenser-like fashion for the head product of distilling or rectifying columns.

The invention provides a distilling arrangement including an air-cooled condenser for the head product of a distlling or rectifying column with condenser tubes connected to the column head, the condenser comprising at least one jacket composed of condenser elements with upright ribbed tubes surrounding the head with lateral clearance and forming in horizontal section an equilateral polygon, and at least one propeller blower arranged above the column head in the projection of the polygon for producing a current of cooling air brushing against the condenser elements and regulatable in strength and if necessary in direction.

By this means it is possible, while providing a compact and space-saving distilling arrangement and without appreciably increasing the constructional height of the column, to accommodate in the region of the head of the column an air-cooled condenser with high cooling capacity, the operation of which can also be regulated, in the event of atmospheric temperatures fluctuating considerably, so that a constant quality of the head product is always ensured.

The polygonal arrangement of the condenser elements surrounding the head of the column firstly offers the advantage that the upper part of the column can be used as carrier structure for the condenser elements so that foundations and staging, particularly adjacent the column, are not required for supporting the condenser. In

addition, by this arrangement long conduits for the vapors to be condensed and for deflecting these, are avoided with the result that flow losses caused thereby are eliminated.

By regulation of the strength and/or the direction of the stream of cooling air, which can be effected for example by throttling or deflecting devices, a regulation of the number of rotations or reversing the direction of the propeller blower, or by adjusting the propeller blades, the cooling capacity of the condenser can be adapted to j the temperature of condensation of the actual head product so that any undesirable or impermissible under-cooling of the condensate, for example dropping below the setting point or the freezing point temperature in the case of solidifying media, is reliably avoided. In this manner even large fluctuations inthe atmospheric temperature or wind velocity can be easily compensated without affecting the quality of the head product of the column.

In the case of slight fluctuations in temperature which 7 are to be expected and when working media which do not congeal, it is as a rule sufficientif the cooling air current brushing over the condenser elements is merely adjustable in strength yet retains its direction permanently. Moreover an arrangement of this kind is so designed that the propeller blower or blowers socks or suck the cooling air through the condenser elements or the space left between the condenser elements and the head of the column and blows or blow it upwards into the atmosphere.

In'cases when particularly low external temperatures are to be expected as well as when distilling for rectifying easily congealable media, it is on the other hand more advisable to. provide also possibilities of reversing the direction 'of flow of the cooling air current so as to effect, in the case of particularly low external temperatures, a preheating of the cooling air on the outer wall of the head of the column before this air brushes against the outer side of the ribbed tubes of thecondenser elements. Another possibility, in the case 'of media with a relatively high congealing point, of reliably excluding any inadmissible undercooling of the condensate, consistsin that an arrangement is provided which enables the condenser to be switched "overpartly or entirely to boiling components of the head product takes place in the region of the height of the condenser elements, which results in relieving the condensers and enables the production of a very pure condensate.

Another advantage of the condenser proposed according to the invention consists in that the arrangement of the condenser elements in the form of one or more jackets surrounding the column head enables large heat-extogether with the inert carrier gas or any other inert components of the gas. In addition, in the case of an aircooled condenser, the pumping ofthecooling medium on the column head, which is necessary in the caseof a liquid cooler arranged in the region of the column head, as well as thepurnps and conduits required therefor, are dispensed with, which results in a considerable reduction in the initial and running costs of the plant. Finally, in the case of an air-cooledcondenser, no measures are necessaryto protect the cooling medium against the danger of freezing in the event of extremely low I atmospherictemperatures, as i'n'thecase of liquid coolers.

, ticularly low atmospheric temperatures is prevented by e the hot air curtain produced by the column.

changing surfaces to be accommodated in a very small space so that it presents no dilficulties to completely condense the large quantities of vapor produced in recti fying or distilling columns with high throughput capacity. 7

The arrangement of the condenser elements in the region of the column head also has an advantageous effect in that, in addition to the cooling air current produced by the propeller blower or blowers, the natural air move ment in the region of the column head is also utilized for cooling the condenser tubes.

The number of sides of the polygon formed by the condenser elements can Vary and is dependent upon the number of condenser elements actually required, that is the necessary cooling output of the condensers. Thus,

'forexample, "in the case of larger cooling outputs, the

condenser elements can form in cross-section a prefer ably equilateral octagon or decagon, whereas in the'case of lower outputs or several condenser jackets arranged one within the other, polygons with a smaller number of sides are preferable. also produces a very stable construction in itself which,

due to its advantageous adaptations to the cross-sectional.

shape of the column. head, enables 'it to be connected The polygonal circular shape.

to the column head by means of relatively simple and light structural elements in such a manner that it is I capable of withstanding the strongest stresses, such as trating through leaky points would be directly sucked off Regarded as a whole,the condenser proposed according to the .inventionis, as compared to the previously known constructions, characterized by the possibility of much better regulationand a considerably higher-degree of efiiciency, while the initial andrunning costs of the plant are far lower and the reliability of operation is 1 much greater.

In a preferred form of the distilling'a'rrangement, the condenser elements of each jacket are similar to each other and arranged in substantially vertical, planes, Thus a uniform distribution of the heat-exchangingsurfaces over-"the peripheryof the column head is attained so that, independently of the actual direction of the. wind, the natural air movement can be utilized to a uniform extent for additionally cooling the condenser tubes. By the arrangement of the condenser elements in substantially vertical planes, a better utilization of the total cross-section of the ribbed tubes for the condensatioriprocess is attained, as compared with aninclined arrangement. Moreover, such vertical arrangementof the condenser elements adapts itself better to the column head which is mostly of cylindrical construction: r

As a rule it is advisable to connect the upper end chambers of the condenser elements to a common circular conduit constructed as a distribution conduit and which is connected'with the head of the column by means of several connection pieces distributed at substantially uniform distances apart around the peripery. thereof. The con condenser'element'sonone half of the'periphery of the column head being subjected to a particularly intensive natural impingement of air.

A particularly simple construction is produced by fixing the condenser elements to the upper annular conduit in suspended arrangement, the connection pieces being constructed as carrier elementsfor the upper annular conduit and condenser elements fixed thereon.

The lower end chambers of the condenser elements are preferably also connected up to a common annular conduit which in turn is connected to a suction device and can beselectively connected up witha return conduit leading to the column head and a discharge conduit for the finished product. s

In cases where it is a question of obtaining particularly large throughput outputs, it is advisable to provide two or more radially spaced condenser jackets'surrounding each other as well as the head of the column, which jackets form in horizontal section geometrically similar polygons. Between the'condenser jackets surrounding each 'other devices for moistening the cooling air'are preferablyprovided inorder to reduce the temperature of the cooling.

air to its moisture temperature after it has flowed through the first condenser jacket. By this means the cooling air admitted to the next following condenser jacket has about the same temperature as the air sucked out of the atmosphere and flowing through the first condenser jacket. The air moistening device preferably consist of spraying nozzles distributed at substantially uniform distances apart over the cross-section of the current of cooling air in opposite direction to the flow of air.

Whereas the lower end chambers of the condenser elements are hermetically joined to the outer wall of the head of the column by a shell, it isadvisable to connect the upper end chambers of the condenser elements to a second shell covering the end face of the head of the column with clearance and provided with apertures for the arrangement of propeller blowers. A particularly advantageous form of construction is obtained by constructing the upper shell as a prismatic hood, the air apertures provided in the upper substantially horizontal end face of which are lined with casings serving as intake passage, blower housing or diffuser. In order to enable the strength and/ or direction of the cooling air current to be changed in the desired manner, propeller blowers which are variable in speed and/or reversible in direction of rotation are provided. Instead of using several propeller blowers distributed over the end face of the upper shell which is advisable in many instancesonly a single propeller blower may be arranged coaxially to the head of the column, the speed of which blower is regulatable preferably infinitely.

A preferred embodiment of the invention will now be described by way of example and with reference to th accompanying drawings, in which:

FIG. 1 is a side elevational view of a distilling arrangement embodying the invention;

FIG. 2 is a section taken on line IIII of FIG. 1;

FIG. 3 is a top plan view, on a reduced scale, of FIG. 2, and

FIG. 4 is a section, on a reduced scale, taken on line IV-IV of FIG. 2.

FIGS. 1 and 2 show a distilling arrangement including a rectifying column having a head 1 which may have a diameter of, for example, 3 to 5 meters and a height of, for example, 20 to 50 meters. Exchange plates or trays 2, only one of which is shown in FIG. 4, are arranged one above the other inside the column and constructed in a known manner.

Above the uppermost exchange plate or tray, not shown in the drawings, the head 1 of the column is provided with several laterally projecting connection pieces 3 preferably arranged at uniform distances apart around the periphery thereof, which connection pieces are equipped with regulating and shut-off elements 4 which can be operated independently of each other. The connection pieces 3 carry an upper annular conduit 5 constructed as a distribution conduit, which, in plan view (FIG. 3) forms an equilateral polygon, namely an equilateral polygon, namely an equilateral hexagon. The upper end chambers 7 of

condenser elements

8 and 8a are connected up to the annular conduit 5 by a number of branch connection pieces 6 corresponding to the number of sides of the polygon, which condenser elements form two condenser jackets encircling the head of the column with different clearances. The condenser jackets, like the upper annual conduit 5, are in the shape of an equilateral polygonwhich in the example illustrated in the drawings is an equilateral hexagonand arranged in relation to each other in similar geometrical fashion and coaxially to the longitudinal axis of the column head 1. The distance between the inner and outer condenser jackets is about three times as great as the distance between the inner condenser jacket and the periphery of the column head 1.

Lower end chambers 9 of the

condenser elements

8 and 8a are connected to a common lower annular conduit 11 by means of connection conduits of considerably smaller cross-section than the connection pieces 6, said lower annular conduit 11 being connected up with an exhausting device for the inert carrier gas and other inert components of the gas, which device is not shown in the drawings, and can also be selectively connected up with a return conduit leading to the column head 1 and a discharge conduit for the finished product, which conduit is likewise not shown in the drawings.

The connection pieces 3 for the upper annular conduit 5 are at the same time constructed as carrier elements so that the

condenser elements

8 and 8a fixed in suspended arrangement on the upper annular conduit 5 are carried by the connection pieces 3.

Below the lower end chambers 9 and the lower annular conduit 11 a substantially horizontal platform 12 is provided the inner edge of which extending up to the periphery of the column head 1 is mounted in brackets 13. The platform 12 is also held in position by inclined struts 14 which are fixed in brackets 15 provided on the column head 1. The platform 12, in the example illustrated in the drawings, is in plan view polygonal corresponding to the arrangement of the

condenser elements

8 and 8a and projects on all sides beyond the periphery of the outer condenser jacket formed by the condenser elements 8. In this outer zone the platform 12 is constructed as a Working platform and provided with a guard railing 16.

In the form of construction illustrated in the drawings, the

condenser elements

8 and 8a are, in addition to being suspended on the upper annular conduit 5, supported by substantially T-shaped supports 17 resting on the platform 12.

The platform 12 also carries a prismatic sheet-metal shell 18 corresponding with the inner condenser jacket as regards shape and dimensions and having the form of an equilateral polygon in cross-section like the condenser jacket, as can be seen from FIG. 3. The polygonal shell 18 is provided in the region of the condenser elements 8a of the inner condenser jacket with apertures of a size corresponding with the surface area of these elements, which apertures are covered by the condenser element-s 8a arranged in front of them. The upper end of this polygonal sheet-metal shell 18 is closed by a substantially horizontal sheet-metal end plate 19, which, in the example illustrated in the drawings, is provided with four symmetrically arranged apertures 20 for accommodating propeller blowers 21. The upper part of the shell 18 and the plate 19 thus form a prismatic hood enclosing the end face 1a of the column head 1 with clearance. The end plate 19 of this shell is, as can be seen from FIG. 2, supported against the end face 111 of the column head by a prop 22 arranged coaxially to the longitudinal axis of the column head 1.

The apertures 20 in the upper end plate 19 of the condenser shell are lined with casings 23 which serve as blower housings and also form short suction passages or diifusors.

The propeller blowers 21 are driven in constant direction by variable speed motors 24 so that they suck cooling air through the double jacket of the

condenser elements

8 and 8a in the direction x into the space between the inner condenser jacket and the periphery of the column head 1 and blow it upwards into the atmosphere in the direction 2: The propeller blowers 21 are arranged in the outer region of the upper end plate 19 of the condenser shell so that they ensure a uniform brushing of the cooling air over all

condenser elements

8 and 8a distributed around the periphery of the column head 1, with a relatively low loss of flow. As the shell composed of the end plate 19 and the polygonal wall 18 is completely closed except for the appertures for accommodating the condenser elements 8a and the propeller blowers 21, and also the platform 12, at least in the region located within the polygonal wall 18, is of closed construction and hemetically connected to the external periphery of the only through the condenser elements 8 and 2a The

condenser elements

8 and 8a consist in a known manner of end chambers land 9 connected-'by a relatively large number of ribbed tubes arranged parallel to one another and at a distance apart. In the form of construction illustrated in the drawings, the condenser elements 8 and Sa have only a single row of ribbed tubes in the direction of flow x of the cooling air. However, condenser elements with two or possibly more rows of tubes arranged 'one behind the other in the direction of flow at of the cooling'air might also be used.

. Between the inner and outer jackets formed by the

condenser elements

8 and 8a thereis'an air moistening device, as can be seen'from FIGS. 2 and .4. This air moistening device consists of a plurality of spraying nozzles 25 arranged at uniformdistances apart and-distributed over the cross-sectional area of the cooling air stream.

These spraying nozzles 25 point in theopposite direction to the flow x of the cooling air current and cause a reduction of the cooling air temperature to its moist temperature between the inner and outer condenser jackets. Spraying liquid, preferably water, is fed through feed conduits provided with regulating devices, not shown in the drawings.

The end plate 19 ofthe condenser shell is also constructed as a workingplattorm like the outer portion of the platform 12 and for this purpose is provided with a guard rail or railing 26.

- Instead of four propeller blowers 21 arranged substantially symmetrically to the longitudinal axis of the column head 1, a larger or smaller number of propeller blowers may be provided when necessary. In the case where only one propeller blower with a suitably large output is provided, the space between the upper end plate 19 of the shell and the end face In of the column head 1 must be made correspondingly large. In this case the blower may be driven through the intermediary of a-suitable gearing by a variable speed motor arranged for example on the end face 1a of the column head.

The vapors collecting above the uppermost exchange plateor tray of the column head 1 are fed through the connection pieces 3, the upper annular conduit 5, the branch connection pieces 6 and the upper end chambers 7 to the condenser elements 8 where they are condensed by the air brushing against the outer side of the condenser tubes. The condensate flows through the lower end chambers 9 and the

connection conduits

10 and 10a into the lower annular conduit 11 whence it is either returned into the column head 1 or drawn off as finished product. Hereby it is possible to work both under vacuum and also under pressures exceeding atmospheric pressure.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

We claim: I I

l. A distilling arrangement comprising, in combination, an elongated distilling column having an upper end portion in which the vaporized head product collects; air cooled condenser means comprising at least one jacket composed of aplurality of groups of finned tubular condenser elements spaced from each other and surrounding said upper end portion of said column spaced therefrom and having each an upper end located at a higher elevation than the lower end thereof and a length which is only a small fraction of that of said column; means connected to the upper ends of a plurality of said condenser elements and to the upper end of said column for carrying said condenser elements on said upper end .of'said column and for connecting the" interior of said upper end of said column in parallel with the interior of said condenser elements so that the vaporized head product may pass through saidscondenser elements to condense therein, whereby the condensate will flow in downward direction through said element s; means connecting the lowenen-ds'offsaid'condenser elements in parallel to each other; and air circulating means located in the region of saidupper end portion of said column and within the area between said column and said jacket for circulating air between said condenser' elements and through the space between the latter and said upper end portion ofsaid column. V t

2 A distilling arrangement as set forth-in claim 1 in which said condenser'ele'ments are arranged substan tially verticalJ I. a t 3.A distilling arrangement comprising, in combination, an elongated distiliing column having ahead at its upper and in which the vaporized head product collec'ts; air cooled condenser means comprising at least onejaclret composed of a plurality of groups of finned tubular, substantially vertically extending condenser elements, spaced from each other and surrounding said head of said column spaced therefrom and each having a length which is'only a small. fraction of that of said column; means connected to the upper ends of said condenser elements and to the'head of the columnfor carrying said condenser elements on said head and forconnecting the'interior ofsaid head in' parallel with the interior of said condenser elements so that the vaporized head, product may pass throu-gh said' condenser elements to condense therein, whereby the condensate. will flow in downward direction through said elements,- said means comprising an annular distributor'conduit disposed above and communicating with the upper ends of said condenser elementsand a plurality ofsuostantially uniformly distributed connecting pieces connecting said distributor conduit with saidhead; meansconnecting the lower ends of said condenser elements in parallel to each other; and air circulating means located above said head and within the cross-sectional area defined by saidjacket for circulating air between said condenser elements and through the space between the latter and said head.

4. A distilling arrangement comprising, in combination, an elongated distilling column having a head atits upper end in which the vaporized head pro-duct collects; a shell structure surrounding said head of said column and having a top wall, an-annular bottom wall engaging said head. and closingsaid shell at its lower end, and a plurality of side walls extending between 'said top and;

bottorn -walls spaced'fro m said head and each formed with anaperture; air cooled condenser meansgcomprising a plurality of groups of finned tubular condenser-elements each having an upper end and a lower end and arranged ad acent to and outside of said apertures and forming together a jacket surrounding said head spaced therefrom and also surrounding said shell structure, each of said condenser elements having a length which is. onlyv a small fraction o'f-that of said columng'means connected to the upper ends of said condenser elements and to said head for carrymgsaid condenser'elements on said head and for connecting the interior of said head in parallel with the interior of said condenser elements so that the vaporized head product may pass through said condenser elements to condense therein, whereby the condensate will flow-in downward direction through said elements; means connecting .the lower ends of said condenser elements in parallel 'to each other and having. at least one common delivery end for the condensate; andat least one blower mounted in an opening formed insaid top wall of said shell structure for circulating cooling air through said apertures so as to'force that cooling airto flow about said condenser elements and'tlirough the space between the latter and said head. 7 r r 5. An arrangement as set forth in claim 1, wherein said jacket forms in horizontal section an equilateral polygon and said air circulating means comprises at least one blower disposed above said upper end portion of said column head.

6. An arrangement as set forth in claim 5, wherein said blower is reversible.

7. A distilling arrangement as set forth in claim 1, wherein said condenser means comprises a plurality of concentric jackets spaced from each other and forming in horizontal section geometrically similar polygons.

8. A distilling arrangement as set forth in claim 7, further comprising means disposed between said jackets for moistening the cooling air.

9. A distilling arrangement as set forth in claim 8, wherein said moistening means comprises spray nozzles which are regularly distributed between the jackets for discharging a liquid in a direction counter to the flow of cooling air.

10. An arrangement as set forth in claim 3, further comprising valve means in said connection pieces for regulating the flow of head product theret hrough.

References Cited in the file of this patent UNITED STATES PATENTS Hawkes J an. 8, Wittemann Feb. 26, Bleicken Dec. 27, Keath Mar. 29, Pugh June 16, Hines Feb. 23, Kessel Oct. 25, McGovern June 25, Larrecq June 18, Hunter Sept. 21, Morse Apr. 23, Stanley Mar. 4, Rollins et al Apr. 1, Stutz June 16, Buehler Nov. 10, Sweeney et a1 June 19,

FOREIGN PATENTS Sweden Nov. 1, Austria Apr. 15,

Claims

1. A DISTILLING ARRANGEMENT COMPRISING, IN COMBINATION, AN ELONGATED DISTILLING COLUMN HAVING AN UPPER END PORTION IN WHICH THE VAPORIZED HEAD PRODUCT COLLECTS; AIR COOLED CONDENSER MEANS COMPRISING AT LEAST ONE JACKET COMPOSED OF A PLURALITY OF GROUPS OF FINNED TUBULAR CONDENSER ELEMENTS SPACED FROM EACH OTHER AND SURROUNDING SAID UPPER END PORTION OF SAID COLUMN SPACED THEREFROM AND HAVING EACH AN UPPER END LOCATED AT A HIGHER ELEVATION THAN THE LOWER END THEREOF AND A LENGTH WHICH IS ONLY A SMALL FRACTION OF THAT OF SAID COLUMN; MEANS CONNECTED TO THE UPPER ENDS OF A PLURALITY OF SAID CONDENSER ELEMENTS AND TO THE UPPER END OF SAID COLUMN FOR CARRYING SAID CONDENSER ELEMENTS ON SAID UPPER END OF SAID COLUMN AND FOR CONNECTING THE INTERIOR OF SAID UPPER END OF SAID COLUMN IN PARALLEL WITH THE INTERIOR OF SAID CONDENSER ELEMENTS SO THAT THE VAPORIZED HEAD PRODUCT MAY PASS THROUGH SAID CONDENSER ELEMENTS TO CONDENSE THEREIN, WHEREBY THE CONDENSATE WILL FLOW IN DOWNWARD DIRECTION THROUGH SAID ELEMENTS; MEANS CONNECTING THE LOWER ENDS OF SAID CONDENSER ELEMENTS IN PARALLEL TO EACH OTHER; AND AIR CIRCULATING MEANS LOCATED IN THE REGION OF SAID UPPER END PORTION OF SAID COLUMN AND WITHIN THE AREA BETWEEN SAID COLUMN AND SAID JACKET FOR CIRCULATING AIR BETWEEN SAID CONDENSER ELEMENTS AND THROUGHT THE SPACE BETWEEN THE LATTER AND SAID UPPER END PORTION OF SAID COLUMN.