EP1087194A1 - Bath vaporiser-condensor and corresponding air distillation device - Google Patents

Abstract

The vaporization passages are subdivided by separation bars (15, 16) into at least two superimposed vaporization regions (13A-13C) where each is entirely open at top and bottom. Each vaporization region includes a liquid recirculation corridor (14A-14C) and, at its top end, means (16B, 16C) of allowing liquid to overflow to the next region down. Vaporizer-condenser bath with at least one exchanger body (5) made of a stack of parallel plates (8), closing bars (9) and corrugated bracings (10) which define a series of vaporization passages (11) open at the bottom and the top and a series of condensation passages (12). Each region has a separate bath and the top of each lower and intermediate region is spaced vertically by the separation bars which support the next bath up. The exchanger body contains means of feeding liquid to the top region and means of extracting vapor from each intermediate level between two regions. The means of extracting vapour comprise openings (27) defined in the side closing bars (9). The lower separation bar (15) of each region is connected at one end to a side closing bar and the overflow operates that the other end. The recirculating corridor is placed inside the vaporization passage, in particular between the vaporization region and the side closing bar. Each lower separation bar only extends over part of the vaporization passage and the overflow is made possible using a retention bar inside the vaporization passage. The vaporization passages are not interconnected and the liquid is fed equally to each vaporization passage, or the vaporization passages are connected using a lateral channel extending the width of the vaporizer-condenser. The lateral channel acts as the overflow and provides means of recirculating the liquid. Air distillation unit containing such a vaporizer-condenser to vaporize liquid oxygen by condensing nitrogen.

Description

The present invention relates to a vaporizer-condenser bath, of the type comprising at least one body exchanger which includes a stack of plates parallel, closing bars and spacer waves which define a series of vaporization passages fully open at their lower end and upper end and a series of passages from condensation.

The invention applies in particular to main vaporizers-condensers of air distillation, which vaporizes liquid oxygen under low pressure (typically slightly higher than the atmospheric pressure) by medium nitrogen condensation pressure (typically 5 to 6 at absolute bars), and it will be explained below in this app.

Bath vaporizers / condensers operate in thermosyphon. The bottom-up circulation of oxygen is vaporizing is ensured by the hydrostatic pressure due to the height of the liquid oxygen bath and the lightening of the liquid that vaporizes.

For safety reasons, the oxygen flow recirculating liquid must be several times greater than the flow of vaporized oxygen. For this reason, we impose that the height of the liquid oxygen bath is approximately equal to the height of the exchanger, that is to say that it is almost completely submerged in the liquid.

If you want to reduce the temperature difference between the fluid that condenses and one that vaporizes, in order to decrease the pressure of the heating nitrogen and therefore the compression energy of the treated air, it is necessary to increase the heat exchange surface. As the dimensions exchangers are limited by space available at the bottom of the distillation column pressure, the height of the exchanger must be increased.

However, such an increase in height increases the hydrostatic pressure of the liquid at the bottom, i.e. at the entrance, spray passages. This creates in the lower part of the exchanger a region containing free liquid sub-cooled and neutralizes at least partially the beneficial effect of increasing the exchange surface.

The invention aims to improve the efficiency of the vaporizer-condenser with a relatively construction simplified.

To this end, the invention relates to a vaporizer-condenser of the aforementioned type, characterized in that the spray passages are subdivided by bars of separation into at least two vaporization regions superimposed each of which is fully open to its lower end and at its upper end each spray region being provided with a recirculation of the liquid and, at its upper end, means for overflowing the liquid in a region of underlying vaporization, so as to create in each vaporization region a separate partial height bath or other baths and immersing this region on substantially over its entire height, in that the end upper of each lower spray region and intermediate is spaced vertically from the bar separation which supports the immediately upper bath, and in that the vaporizer-condenser comprises on the one hand means for supplying liquid to the region of superior vaporization, and secondly means steam outlet at each intermediate level between two spray regions.

The invention also relates to an apparatus for air distillation comprising a vaporizer-condenser main as defined above, intended to vaporize liquid oxygen by nitrogen condensation.

• la Figure 1 représente schématiquement une partie d'un appareil de distillation d'air suivant l'invention, en coupe verticale dans un passage de vaporisation du vaporiseur-condenseur principal;
• la Figure 2 est une vue analogue de l'appareil de distillation, prise en coupe verticale dans un passage de condensation du vaporiseur-condenseur principal;
• la Figure 3 est une vue analogue à la Figure 1 d'une variante ;
• la Figure 4 est une vue en perspective d'une autre variante ;
• les Figures 5 et 6 sont des vues analogues à la Figure 1, prises en coupe respectivement suivant les lignes V-V- et VI-VI de la Figure 4 ;
• la Figure 7 est une vue analogue à la Figure 4 d'encore une autre variante ; et
• les Figures 8 et 9 sont des vues analogues à la Figure 1, prises en coupe respectivement suivant les lignes VIII-VIII et IX-IX de la Figure 7.

Examples of embodiments of the invention will now be described with reference to the attached drawing, in which:

• Figure 1 schematically shows part of an air distillation apparatus according to the invention, in vertical section in a vaporization passage of the main vaporizer-condenser;
• Figure 2 is a similar view of the distillation apparatus, taken in vertical section in a condensation passage of the main vaporizer-condenser;
• Figure 3 is a view similar to Figure 1 of a variant;
• Figure 4 is a perspective view of another variant;
• Figures 5 and 6 are views similar to Figure 1, taken in section respectively along the lines VV- and VI-VI of Figure 4;
• Figure 7 is a view similar to Figure 4 of yet another variant; and
• Figures 8 and 9 are views similar to Figure 1, taken in section respectively along the lines VIII-VIII and IX-IX of Figure 7.

The air distillation apparatus 1 shown partially in Figures 1 and 2 is a double column distillation consisting of a distillation column medium pressure 2 surmounted by a distillation column low pressure 3. The nitrogen at the top of column 2, which operates at 5 to 6 bar absolute, is linked heat exchange in the main evaporator-condenser 4 of the device with the liquid oxygen produced in the tank of the column 3. The operating pressure of the latter is slightly higher than atmospheric pressure. More specifically, the vaporizer-condenser 4 is intended to vaporize the bottom column tank liquid oxygen pressure by condensation of nitrogen gas at the top of the medium pressure column.

The vaporizer-condenser 4 is fixed in the shell of the low pressure column 3, in the tank thereof, with a free space between this shell and him on all its around. It consists of a single exchanger body 5 of the brazed plate type, and of two semi-cylindrical boxes 6 and 7 welded to this body. The body exchanger 5, of generally parallelepiped shape, is consisting of a stack of rectangular plates vertical 8 aluminum, all identical, of bars peripheral closure 9 represented by simple lines thick, dividing bars which will be described more far, and of spacer waves 10, for example of corrugated sheet perforated. The whole is brazed in the oven in one surgery. On the body 5 are welded the two boxes 6 and 7, namely an upper side box 6 for nitrogen input gas and a lower side box 7 of nitrogen outlet liquid. Of course, an exit from "incondensables" (not shown) is provided in box 7.

Each pair of adjacent plates 8 delimits a passage of generally flat shape. These passages are alternately oxygen vaporization passages 11 (Figure 1) and nitrogen condensation passages 12 (Figure 2). Bars 9 close the periphery of these passages, with the exception of entry / exit openings for fluids.

Thus, the passages 11 are closed laterally on most of their height and totally open to their upper and lower ends.

On the contrary, passages 12 are closed on all their periphery except for a side window upper nitrogen gas inlet, which leads to the box 6, and a lower side outlet window liquid nitrogen, onto which the box 7 opens.

Each spray passage 8 (Figure 1) is subdivided into several superimposed spray regions, three in this example, namely a region of lower vaporization 13A, a vaporization region intermediate 13B and an upper vaporization region 13C. Each region 13A to 13C is substantially totally immersed in a liquid oxygen bath and is defined by a wave with vertical generators, of rectangular shape, respectively 10A to 10C.

The wave 10A of the lower region 13A extends over most of the horizontal width of the passage. By hand and on the other side of this wave, a recirculation duct 14A of liquid is delimited between the wave and the closing bar 9 adjacent.

Intermediate region 13B is located above and at a certain vertical distance from a dividing bar horizontal bottom 15B which extends from a bar 9 (that on the right in Figure 1) at a location spaced from the opposite bar 9. Region 13B starts from bar 9 on the right and ends at a distance from a retaining bar vertical 16B from the left end of the bar 15B. The 10B wave is arranged in the space defined by the bars 15B and 16B. The upper edge of this wave is substantially at the top end of the bar 16B, while its lower edge delimits with the bar 15B a free space 17B for source supply. In the horizontal direction, wave 10B starts from bar 9 on the right and ends a short distance from bar 16B, delimiting with it a liquid recirculation space 14B.

Bar 15B is spaced vertically from the edge upper 10A wave. This defines between regions 13A and 13B a free space 19 which extends over the entire width of the exchanger body and which is connected to a free space of liquid descent 18B existing between bar 9 on the left and bar 16B.

The upper vaporization region 13C has the same structure as region 13B, but reversed left / right, with a 13C lower dividing bar, a lateral restraint 16C and free spaces 17C supply and 14C recirculation delimited by the wave 10C. Bar 15C is spaced vertically from the edge higher of the 10B wave, which defines between regions 13B and 13C a free space 21 which extends over the entire width of the exchanger body. This space 21 is connected to a free descent space 18C demarcated between bar 16C and bar 9 on the right.

Above and remote from region 13C is located, in the upper end region of the passage of vaporization, a supply spillway 23 constituted by a horizontal lower bar 24 and a short bar vertical lateral 25. Bar 24 starts from bar 9 of right, and bar 25 connects to the left end of the bar 24 and is substantially perpendicular to the bar 16B. This defines a feed descent 26 between the bar 25 and bar 9 on the left.

The closing bar 9 on the right defines a window 27 between regions 13A and 13B and between region 13C and the overflow 23. The closing bar 9 on the left defines a similar window 27 between regions 13B and 13C.

The waves 10 of the condensation passages 12 have vertical generators over most of the height of these passages, and are extended above and below by waves distribution slants that open into the windows side nitrogen inlet / outlet, in a conventional manner.

In operation, a mass of liquid oxygen to constant level is collected in the tank of column 3. Sa free surface is substantially at the edge top of the 10A wave, so this one is substantially completely immersed in a lower bath 28A partial height liquid oxygen.

The liquid oxygen produced by column 3 is distributed substantially uniformly across all spillways 23, as shown by the arrow F on the Figure 1.

This liquid falls by overflow in the region 13C, where it forms an upper bath 28C of partial height. Liquid oxygen undergoes partial vaporization in this region. Excess liquid overflows into space 18C over the bar 16C and falls in the region 13B, while that the vaporized oxygen escapes from the exchanger body in column 3, essentially via the upper window 27.

Likewise, in region 13B, liquid oxygen forms an intermediate bath 28B of partial height. The partial vaporization of oxygen in region 13B causes the formation of gaseous oxygen which escapes from the exchanger body via intermediate window 27 and pass so in column 3 while the excess liquid overflows in the descent 18B, above the bar 16B, and reaches the lower bath 28A.

Partial vaporization of oxygen in this bath lower form of gaseous oxygen which escapes into the column 3 via window 27 below, while the excess liquid overflows and recirculates itself in the bath 22A via the downpipes 14A.

In each bath, the partial vaporization of oxygen causes a circulation of liquid by effect of thermosiphon, with recirculation via spaces 14A, 14B and 14C.

In the condensation passages 12 (Figure 2), conventionally, the nitrogen gas from the head of the column 2 enters via the upper box 6, then descends gradually condensing over the entire height of the body exchanger. Liquid nitrogen is collected at the base and returns, via the lower box 7, in column 2.

In the example in Figure 1, only the regions of lower vaporization 13A of the different passages of vaporization communicate with each other, via the lower bath 28A. The other spray regions are isolated from homologous regions of the other passages. This makes it necessary a dispenser ensuring uniform distribution of the liquid between the different passages at the top of the vaporizer-condenser, by appropriate means known per se and not represented.

• le déverseur 23 est supprimé ;
• les barres 16B et 16C sont supprimées, et les ondes 10A à 10C s'étendent sur toute la largeur des passages 11 ;
• la fenêtre 27 supérieure de la Figure 1 est supprimée, et des fenêtres 27 sont prévues à droite et à gauche dans les barres de fermeture 9 entre les régions 13A et 13B et entre les régions 13B et 13C ;
• sur toute l'épaisseur, perpendiculairement au dessin, du corps d'échangeur ont été ajoutées :
  • à droite du corps 5, une goulotte supérieure 29C qui recueille tout le liquide qui déborde de la région 13C, et dont la partie inférieure communique avec l'espace 17C via une fenêtre supplémentaire 30C de la barre 9 de droite ;
  • une goulotte intermédiaire 31, qui coiffe la précédente et recueille tout le liquide qui déborde de celle-ci. La partie inférieure de la goulotte 31 communique avec la fenêtre 27 de droite située entre les régions 13B et 13C ; et
  • à gauche du corps 5, une goulotte inférieure 29B qui recueille tout le liquide qui déborde de la région 13B et dont la partie inférieure communique avec l'espace 17B via une fenêtre supplémentaire 30B de la barre 9 de gauche.

In the example of FIG. 3, on the contrary, means are provided for making all the regions 13B communicate on the one hand, all the regions 13C on the other hand. For this, the vaporizer-condenser is modified as follows:

• the overflow 23 is eliminated;
• the bars 16B and 16C are eliminated, and the waves 10A to 10C extend over the entire width of the passages 11;
• the upper window 27 of FIG. 1 is deleted, and windows 27 are provided on the right and on the left in the closing bars 9 between the regions 13A and 13B and between the regions 13B and 13C;
• over the entire thickness, perpendicular to the drawing, of the exchanger body have been added:
  • to the right of the body 5, an upper chute 29C which collects all the liquid which overflows from the region 13C, and the lower part of which communicates with the space 17C via an additional window 30C of the bar 9 on the right;
  • an intermediate chute 31, which covers the previous one and collects all the liquid which overflows from the latter. The lower part of the chute 31 communicates with the window 27 on the right situated between the regions 13B and 13C; and
  • to the left of the body 5, a lower chute 29B which collects all the liquid which overflows from the region 13B and the lower part of which communicates with the space 17B via an additional window 30B of the bar 9 on the left.

Thus, in operation, liquid oxygen can fall directly on the exchanger body, as shown schematically by the arrow F in Figure 3. It forms the bath higher 28C by spreading across all regions 13C via the chute 29C. From there, the liquid overflows into the chute 31 for supplying the intermediate bath 28B and distributes among all regions 13B via chute 29B. From there, the liquid overflows into the lower bath 28A.

The gaseous oxygen resulting from the vaporization passes in column 3 via the two lower windows 27 and via the two upper windows 27, and also by the upper opening of the passages 11, over the entire width of these.

In the embodiment of Figures 4 to 6, the side face 32 of the vaporizer-condenser, consisting of slices of plates and closing bars 9, east devoid of opening and accessories. this allows back-to-back two identical vaporizers-condensers.

• la boíte 7 de sortie d'azote liquide ;
• une rangée horizontale de fenêtres 27, toutes identiques, de débordement d'oxygène liquide et d'évacuation d'oxygène gazeux vaporisé de la région inférieure 13A ;
• une boíte semi-cylindrique 33 d'alimentation de toutes les régions intermédiaires 13B et de mélange de liquide, s'étendant sur toute l'épaisseur du vaporiseur-condenseur ;
• une rangée de fenêtres constituée, dans la partie gauche (en considérant la Figure 4) de l'épaisseur du vaporiseur-condenseur, de fenêtres 27 d'évacuation d'oxygène gazeux vaporisé dans la région 13B, et, dans la partie droite de ladite épaisseur, de fenêtres 127 d'évacuation d'oxygène gazeux et de débordement d'oxygène liquide. Ces fenêtres 27 et 127 ont leurs extrémités supérieures au même niveau, tandis que les fenêtres 127 ont une hauteur supérieure ;
• une boíte semi-cylindrique 34 d'alimentation en liquide de toutes les régions supérieures 13C. Cette boíte s'étend sur toute l'épaisseur du vaporiseur-condenseur ;
• la boíte 6 d'entrée d'azote gazeux; et
• une boíte semi-cylindrique 35 de débordement de liquide de toutes les régions supérieures 13C. Cette boíte ne s'étend que sur la partie gauche de l'épaisseur du vaporiseur-condenseur.

On the opposite side are provided from bottom to top:

• the liquid nitrogen outlet box 7;
• a horizontal row of windows 27, all identical, of overflow of liquid oxygen and evacuation of vaporized gaseous oxygen from the lower region 13A;
• a semi-cylindrical box 33 for supplying all the intermediate regions 13B and for mixing the liquid, extending over the entire thickness of the vaporizer-condenser;
• a row of windows consisting, in the left part (considering FIG. 4) of the thickness of the vaporizer-condenser, of windows 27 for evacuating gaseous oxygen vaporized in the region 13B, and, in the right part of said thickness, of windows 127 for evacuation of gaseous oxygen and for overflow of liquid oxygen. These windows 27 and 127 have their upper ends at the same level, while the windows 127 have a higher height;
• a semi-cylindrical box 34 for supplying liquid to all the upper regions 13C. This box extends over the entire thickness of the vaporizer-condenser;
• box 6 of nitrogen gas inlet; and
• a semi-cylindrical box 35 of liquid overflow from all the upper regions 13C. This box extends only on the left side of the thickness of the vaporizer-condenser.

A pipe 36 for supplying liquid to the vaporizer-condenser ends up in box 34, near the end right of it, and a liquid supply pipe 37 from region 13B connects box 35 to box 33, near the left end of it.

As can be seen in Figures 5 and 6, the region 13A spans the entire width of each passage of vaporization 11, while each region 13B, 13C starts from the bar 9 on the left (in Figures 5 and 6) and leaves free a recirculation space 14B, 14C between itself and bar 9 on the right. Windows 27 and 127 are located just below the dividing bars 15B and 15C. The lower windows 27 extend down to upper level of region 13A, and windows 127 to the upper level of region 13B.

The lower generator of the box 33 is at the level of the bar 15B, that of the box 34 at the level of the bar 15C (Figure 6), and that of the box 35 substantially at the upper level of region 13C. Likewise that in Figure 3, the latter is fully open towards the top, like regions 13A and 13B.

A section of horizontal bar 38, forming a baffle, is provided halfway up each box 33 and 34 and level of the lower edge of the corresponding wave 10B, 10C.

In operation, the upper regions 13C are supplied from source via hose 36 and box 34. Level equalization in all 13C regions, as well that mixing the recirculating liquid with fresh liquid, take place at the top of this region and via box 34.

The liquid which overflows from the 13C regions passes, via the box 35 and the pipe 37, in the box 33, where it mixture with the liquid which recirculates in each region 13B.

The liquid which overflows from the regions 13B crosses the lower part of windows 127 and falls directly into the lower bath 28A (Figure 6).

We note that, in regions 13B and 13C, the liquid supply and the overflow take place in opposite locations in the thickness direction of the vaporizer-condenser. This promotes mixing of the liquid recirculating with fresh liquid, reducing risks of local concentration of pollutants. The mixture is further favored by the presence of bars 38.

The variant of Figures 7 to 9 corresponds for the essential to the previous one, after deleting the floor intermediate 13B. In such a simplified embodiment, the pipe 37 and box 35 are replaced by a simple notch 135 in the left side of the wall liquid retaining upper, and it is no longer necessary to make two types of windows: windows 27, only necessary for the lower floor, have all the same height and serve both to overflow liquid oxygen and the evacuation of gaseous oxygen.

Claims (18)

Bath-type vaporizer-condenser comprising at least one exchanger body (5) which comprises a stack of parallel plates (8), closing bars (9) and spacer waves (10) which define a series of spray passages (11) fully open to their lower end and at their upper end and a series of condensation passages (12), characterized in that the spray passages are subdivided by dividing bars (15, 16) in at least two regions of superimposed vaporization (13A to 13C) each of which is fully open at its lower end and at its upper end, each spray region being provided with a liquid recirculation corridor (14A to 14C) and, at its upper end, means (16B, 16C; 29B, 29C; 27, 35, 127) of liquid overflow in a region underlying vaporization (27), so as to create in each spray region a bath (28A to 28C) in height partial separate from the other bath (s) and immersing this region over substantially its entire height, in that the upper end of each spray region lower (13A) and intermediate (13B) is spaced vertically from the dividing bar (15B, 15C) which supports the immediately superior bath, and in that the exchanger body (5) comprises on the one hand means supplying liquid to the spray region upper (13C), and secondly means (27; 27, 127) steam outlet at each intermediate level between two spray regions (13A-13B, 13B-13C). Vaporizer-condenser according to claim 1, characterized in that said means for evacuating steam include openings (27; 27, 127) steam outlet defined by the closing bars lateral (9) at each intermediate level between two spray regions (13A-13B, 13B-13C). Vaporizer-condenser according to claim 1 or 2, characterized in that the dividing bar lower (15B, 15C) of each spray region is connected at one end to a side closing bar (9) of the spray passage (11), and in that the means overflow are provided on the opposite side of this passage. Vaporizer-condenser according to any one claims 1 to 3, characterized in that the passage recirculation (14A to 14C) is located inside the spray passage (1), in particular between the region of spray (13A to 13C) and a side closing bar (9) of this passage. Vaporizer-condenser according to any one claims 1 to 4, characterized in that each bar separator (15B, 15C) extends only over one part of the width of the spray passage (11), and what the means of overflow from at least one region of vaporization (13B, 13C) are formed by a retaining bar (16B, 16C), inside the spray passage, which forms an overflow. Vaporizer-condenser according to any one claims 1 to 5, characterized in that the regions intermediate (13B) or higher (13C) spray each spray passage (11) does not communicate with those of the other spray passages, and that said liquid supply means are adapted for distribute the liquid substantially uniformly between the different spray passages (11). Vaporizer-condenser according to any one claims 1 to 5, characterized in that at least one intermediate (13B) or upper (13C) region communicates with a region homologous to all the other passages of vaporization via a side channel (29B, 29C; 33) which extends over the thickness of the vaporizer-condenser (1). Vaporizer-condenser according to claim 7, characterized in that said lateral channel (29B, 29C) forms a liquid recirculation chute. Vaporizer-condenser according to claim 7 or 8, characterized in that said lateral channel (29B, 29C) forms the overflow means. Vaporizer-condenser according to any one claims 1 to 4, characterized in that the means overflow comprise a duct (37) lateral to the body exchanger (5) which connects a high point of a region of vaporization (13C) at a low point in the region of underlying vaporization (13B). Vaporizer-condenser according to any one of claims 1 to 10, characterized in that, for at least at least one vaporization region (13B, 13C), the means for overflow (35, 127) start from an opposite location, in the thickness direction of the heat exchanger body (5), at a point bottom liquid supply from this region. Vaporizer-condenser according to any one of claims 1 to 10, characterized in that, for at least at least one vaporization region (13B, 13C), the means for overflow (16B, 16C; 29B) are located opposite this region, across the width of the passage, relative to the feeding location (18C, 26; 31) of this region in liquid. Vaporizer-condenser according to any one claims 1 to 12, characterized in that, at the upper end of at least one vaporization region (13A, 13B), the side bars (9) of the passageways vaporization (11) define a row of windows (27, 127) evacuation of vaporized fluid, part of which at less also forms said overflow means. Vaporizer-condenser according to claim 13, characterized in that said part (127) of the row windows higher than others windows in this row. Vaporizer-condenser according to any one claims 1 to 14, comprising at least three regions vaporization (13A to 13C), characterized in that the overflow means (16B, 16C; 29B, 29C) are located alternately on one side and the other of the passage of vaporization (11). Vaporizer-condenser according to any one claims 1 to 14, characterized in that the means overflow (27, 35, 127) are all on the same side spray passages (11), the opposite side face (32) of the exchanger body (5) being planar. Vaporizer-condenser according to claim 16, characterized in that it comprises two exchanger bodies (5) joined by their flat lateral faces (32). Air distillation apparatus, comprising a vaporizer-condenser for vaporizing liquid oxygen by nitrogen condensation, characterized in that the vaporizer-condenser (1) conforms to any one of claims 1 to 17.

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