DE68904186T2 - CONDENSER / EVAPORATOR. - Google Patents

Description

The present invention relates to a condenser/evaporator as described in the preamble of claim 1 .

Such a condenser/evaporator is known from US-A-4,606,745.

Many condenser/evaporators for use with a double rectification column in a cryogenic air separation plant as disclosed in JP-A-56-56592 are so-called plate-fin heat exchangers, each of which uses many parallel partitions to divide the condenser/evaporator into two kinds of chambers, namely, oxygen chambers each as first fluid chambers and nitrogen chambers each as second fluid chambers, which are alternately arranged adjacent to each other. In each oxygen chamber of such a cold plate condenser/evaporator, many vertical evaporation channels are formed by vertically arranging heat exchanger plates, each evaporation channel being open at the top and bottom, the bottom opening serving as an inlet for introducing liquid oxygen and the top opening serving as an outlet for a mixture of gaseous and liquid oxygen. When the entire condenser/evaporator is immersed in liquid oxygen present in the lower space in the upper column of a double rectification column, it is filled with liquid oxygen and the liquid oxygen in this chamber is subjected to heat exchange with gaseous nitrogen in the adjacent nitrogen chamber, whereby part of the liquid oxygen is evaporated into bubbles of gaseous oxygen and in the evaporation channel The liquid oxygen forms a circulating flow inside and outside the condenser/evaporator due to the rising force of the gaseous oxygen and the density difference due to the mixture of gas and liquid.

The nitrogen chamber is a chamber which is completely closed and in which vertical heat exchanger plates are arranged like in the oxygen chamber to form many vertical condensing channels; it is connected to the lower column of the double rectification column through headers provided upstream and downstream of the condensing channels. The gaseous nitrogen in the upper part of the lower column is passed as a downward flow into the condensing channels from the upper header to undergo heat exchange with the liquid nitrogen in the adjacent evaporation channel in the condensing channels. The condensed liquid nitrogen is discharged from the lower header.

When the conventional condenser/evaporator is immersed in liquid nitrogen in the lower part of the space at the bottom of the upper column, the pressure in the head of the liquid increases to the boiling point (about 1ºC/m). The condenser/evaporator has a higher boiling point in the lower part than in the higher part, which accordingly reduces the difference between the boiling temperature of oxygen and the condensation temperature of nitrogen.

Normally the difference between the temperature on the nitrogen side of the condenser/evaporator and that on the oxygen side is 1 to 2ºC in the upper part of the condenser/evaporator, so that the mentioned increase in the boiling point of the liquid oxygen leads to a significant problem in the efficiency of the condenser/evaporator.

In other words, in order to ensure the proper operation of the lower column at 5 kgf/cm²G (kgf is the weight of a mass of 1 kg and G is a gauge pressure), it is necessary to make the condenser/evaporator about 2 meters high or shorter; since vertically extending the condenser/evaporator increases the liquid depth of the liquid oxygen and thereby increases the boiling pressure, the operating pressure of the lower column should be increased to improve the efficiency, so it is necessary to increase the number of condensers/evaporators to be arranged, increasing the diameter of the upper column while keeping the height of each condenser/evaporator unchanged, which makes the construction of the double rectification column difficult.

The increase in boiling point due to the liquid oxygen's liquid depth affects the operating pressure of the lower column. That is, the operating pressure of the lower column determines the condensation temperature of saturated gaseous nitrogen in the upper region of this column; lowering this condensation temperature requires lowering the liquid oxygen temperature.

Since the power of an air separation plant is mainly realized in compressing the output air or increasing the pressure to the lower column level, further reducing the lower column pressure can reduce electricity costs.

However, in the conventional structure in which a condenser/evaporator is immersed in liquid oxygen, the reduction in the pressure of the lower column is limited by the amount of increase in the boiling point of the liquid oxygen by a liquid head.

In addition, the performance of the condenser/evaporator cannot be fully achieved unless liquid oxygen is present in the space at the bottom of the lower column where the condenser/evaporator is installed. Therefore, until the condenser/evaporator is immersed in the liquid oxygen, sufficient condensed liquid is not produced by liquid nitrogen serving as the reflux liquid of the lower column, nor is a rising vapor of the upper column sufficiently produced by evaporating the liquid oxygen. As a result, the rectification operation does not start, requiring a useless waiting time (start-up time) and resulting in increased power loss. In addition, safety measures for an emergency become an important issue.

The liquid oxygen rising in the evaporation channel in the bottom area of the oxygen chamber should be heated to the boiling point temperature by conventional heat transfer with low heat transfer coefficient, which reduces the heat transfer efficiency of this channel. Since the nitrogen chamber has vertically formed condensing channels on the condensing side and gaseous nitrogen flows downward while being condensed, the amount of liquid nitrogen in the downstream area of these condensing channels increases and the condensed nitrogen becomes a thick liquid film covering the heat transfer surface of the condensing channels. This film serves as a thermal resistance layer, which reduces the heat transfer efficiency.

From US-A-4,606,745 a condenser/evaporator is already known in which first fluid chambers and second fluid chambers are alternately formed by a plurality of vertical subdivisions and in which a liquid in the first fluid chambers is subjected to heat exchange with a fluid in the second fluid chambers. This condenser/evaporator comprises a plurality of heat exchanger plates arranged in multiple up/down stages in the first fluid chambers to form a plurality of liquid channels open at one end, and a plurality of liquid tanks communicating with the liquid channels and provided in multiple up/down stages on one side of the other end of the liquid channels, the liquid tanks being open at the top and a liquid being introduced into the liquid channels for heat exchange while being supplied to the liquid tanks in each stage.

The condenser/evaporator disclosed in US-A-4,606,745 has a condenser block which is saturated with liquid oxygen. Therefore, a large cylindrical vessel is required to store the large amount of liquid sufficient to saturated the stage sections of the condenser block with liquid oxygen.

A similar structure of a condenser/evaporator is known from JP-A-60/253 782. This condenser/evaporator also requires a large amount of liquid, which must be stored in order to saturate the stage parts of the condenser block with liquid oxygen.

It is an object of the invention to provide a condenser/evaporator with significantly reduced circulating amount of liquid oxygen flowing into the lower region of the column and an oxygen pump or a thermosiphon reboiler in order to reduce the equipment cost and the operating cost and to improve the heat exchange efficiency.

The condenser/evaporator according to the invention is characterized in that

- several liquid receivers for receiving a liquid flowing downwards from the open ends of the liquid channels are arranged separately from the liquid containers in multiple up/down stages; and

- a liquid return channel is provided to return liquid from the liquid receivers to the liquid containers.

The condenser/evaporator of the present invention does not require a large amount of liquid to be immersed in the stages of the condenser blocks, but separately comprises a plurality of box-shaped liquid tanks and liquid receivers in multiple up/down stages at both ends of the condenser block. Therefore, the condenser/evaporator of the present invention requires a much smaller amount of liquid to be stored in the liquid tanks and liquid receivers than in the cited documents.

Embodiments of the invention are disclosed in subclaims 2 to 14.

The invention will be described in more detail with reference to the accompanying drawings, in which:

Figures 1 and 2 illustrate a first embodiment of the invention, the former being a cross-section through an oxygen chamber of a condenser/evaporator and the latter being a cross-section taken along line 2-2 in Figure 1;

Fig. 3 is a cross-section through an oxygen chamber of a condenser/evaporator according to a second embodiment;

Figures 4 and 5 illustrate a third embodiment, the former being a longitudinal section illustrating an oxygen chamber and a liquid return chamber of a condenser/evaporator and the latter being a lateral cross section through the condenser/evaporator;

Figures 6 to 9 illustrate a fourth embodiment of a condenser/evaporator according to the invention, wherein the upper part of Figure 6 is a cross-section along the line 6-6 in Figure 7 and the lower part of Figure 6 is a cross-section along the line 7-7, and Figure 7 is a sectional plan view of an oxygen chamber, Figure 8 is a partial section from the left, and Figure 9 is a partial section from the right;

Figures 10 and 11 illustrate a fifth embodiment of the invention, the former being a cross-section through an oxygen chamber of a condenser/evaporator and the latter being a side view of a condenser/evaporator block;

Figs. 12 and 13 illustrate an example in which the condenser/evaporator of the fifth embodiment is incorporated in a rectifier, the former being a sectional plan view and the latter being a perspective view of the essential portion; and

Fig. 14 to 18 illustrate a sixth embodiment of a condenser/evaporator according to the invention, wherein Fig. 14 is a sectional front view of an oxygen chamber of a condenser/evaporator, Fig. 15 is a sectional front view of a nitrogen chamber, Fig. 16 is a partial sectional view, Fig. 17 is a partial sectional front view and Fig. 18 is a sectional plan view.

The invention will be described with reference to the accompanying drawings in a case where the liquid to be evaporated is liquid oxygen and the fluid to be condensed is nitrogen gas. Since the same reference numerals are assigned to identical elements in the individual embodiments in the following description of the drawings, the repeated description is omitted. The flow of liquid is indicated by solid arrows and the flow of gas by dashed arrows.

Figures 1 and 2 illustrate the first embodiment of the invention, the former showing an oxygen chamber serving as a first fluid chamber and the latter showing a cross-section taken along line 2-2 in Figure 1.

A condenser/evaporator 50 has a plurality of oxygen chambers 56 as first fluid chambers and a plurality of nitrogen chambers 57 as second fluid chambers, which are alternately formed by a plurality of vertical parallel partitions 55 secured by upper and lower inclined rods 51 and 52 and left and right rods 53 and 54. An inlet header 58 for dispersively introducing nitrogen gas GN into the nitrogen chambers 57 is provided at the top of the oxygen chambers 56 and the nitrogen chambers 57, and an outlet header 59 for collectively discharging liquid nitrogen Ln condensed in the chambers 57 is provided at the bottom of the chambers 56 and 57. The individual nitrogen chambers 57 are defined by the partitions 55 and the side bars 53 and 54 which are present on the respective sides of the partitions.

The individual oxygen chambers 56 are defined by the partitions 55 and the upper and lower inclined bars 51 and 52. Heat exchanger plates 60 are arranged in multiple up/down stages within each oxygen chamber 56, to form a plurality of liquid channels 61. Although one plate at each stage may be used for the heat exchanger plates 60 dividing adjacent partitions 55 in an up/down manner, a corrugated heat exchanger fin is normally used. The liquid channels 61 are inclined so as to rise from one end of each oxygen chamber 56 to the other end. That is, the liquid channels 61 have an increasing inclination from one end on the side of the liquid tanks to the other, open end. A plurality of liquid tanks 63 connected to the liquid channels 61 are arranged in multiple up/down stages on the side of an inlet 62 provided in the lower parts of the channels 61. In addition, a plurality of liquid receivers 65 communicating with the liquid channels 61 are arranged in multiple up/down stages on the side of an outlet 64 arranged in the upper parts of the liquid channels 61 corresponding to the liquid containers 63 except for the liquid channel 61 in the last stage.

The liquid tanks 63 are box-shaped and open at the top and communicate with the oxygen chambers 56 at the open side so that a plurality of up/down liquid passages 61 communicate with one liquid tank 63. A liquid distribution device 68 comprising a connecting pipe 66 and a distributor 67 is connected to each liquid tank 63. Liquid oxygen LO is supplied to each liquid tank 63 from this liquid distribution device 68. Since each liquid tank 63 is open at the top, pressure is applied to the gas of the associated oxygen chamber 56 and the height of the liquid in each liquid chamber 63 is small, which reduces the influence of the pressure of the liquid head on the liquid oxygen LO. This prevents the boiling point from being raised due to the pressure of the liquid head. Because the liquid oxygen LO rises in height, the condensation temperature of gaseous nitrogen GN is lowered to lower the operating pressure of the lower column, and the power consumption of the outlet air compressor can be significantly reduced.

The liquid receivers 65 are box-shaped and open at the top, almost like the liquid containers 63. The liquid receivers 65 are open to the side of the oxygen chambers 56, so that several up/down liquid channels 61 are connected to one liquid receiver 65. The liquid receivers 65 and the liquid containers 63 are each provided as a block for several liquid channels 61. A liquid receiver 65 is connected to the associated liquid container 63 at a level one block lower via a liquid return line 69 which connects the bottom areas of the two. Liquid oxygen LO, which has flowed out of the liquid container 63 arranged above through the liquid channel 61 and has not been evaporated in this liquid channel 61, returns via this line 69 to the liquid container 63 in the next lower stage.

The liquid nitrogen LO to be introduced into the oxygen chambers 56 thus formed is supplied to the individual liquid containers 63 via the distributor 67. The liquid oxygen LO in each liquid container 63 flows into the associated liquid channel 61 and undergoes heat exchange with gaseous nitrogen GN flowing through the adjacent nitrogen chamber 67 via the heat exchanger plates 60 and the partitions 55. As a result, part of the liquid oxygen is evaporated into bubbles of gaseous oxygen GO. After these bubbles are evaporated in the liquid channel 61 together with the liquid oxygen LO have risen in this channel, they separate from the liquid oxygen LO in the outlet 64 and continue to rise. Meanwhile, liquid oxygen LO which has not been vaporized in the liquid channel 61 falls from the outlet 64 and is received by the liquid receiver 65 and flows via the liquid return line 69 into the liquid tank 63 arranged one block lower. The amount of liquid oxygen LO flowing through the liquid line 61 is about 6 times or even more than the amount of vaporized liquid oxygen in order to prevent concentration and precipitation of acetylene.

Liquid oxygen LO flows into each liquid passage 61 while flowing out of the liquid receivers 65 sequentially via the liquid return lines 69 for the lower liquid tanks 63, and further flows downward by repeating the vaporization and downward flow. The liquid oxygen LO which has not yet vaporized in the lowermost liquid passage 61 flows out of the outlet 64 downstream of the condenser/evaporator 50 and remains in the liquid tank in the bottom portion of the upper column of the double rectification column. A portion of the liquid oxygen LO is taken out as a product as required, and the remaining portion is moved upward by a liquid oxygen pump or a thermosiphon reboiler or the like and is circulated again to each liquid tank 63 via the liquid distribution device 68 after concentrated acetylene is removed via an acetylene adsorber. The circulated liquid oxygen LO is part of excess liquid oxygen LO supplied to the oxygen chambers 56 to prevent precipitation of a hydrocarbon compound such as acetylene in each channel. Since the amount of this liquid oxygen is only that of the liquid oxygen LO supplied from the lowest liquid channel 61 of the oxygen chamber 56, as stated above, the circulation quantity stated above must be very small.

The inclination angle of each liquid passage 61 is appropriately selected depending on the depth of the liquid container 63 to be connected and the length of the liquid passage 61. Although the liquid passage 61 can be arranged horizontally, inclining the liquid passage 61 facilitates bubbles of gaseous oxygen GO resulting from evaporation to flow out due to the flow force and can increase the heat transfer rate by promoting the flow of the liquid oxygen LO. The inclination of each liquid passage 61 in the vertical direction is appropriately set in such a way that the liquid oxygen LO is entrained by the gaseous oxygen GO; if this inclination is too large, it is difficult for the flow force of the gaseous oxygen GO to cause the liquid oxygen LO to entrain.

According to the above embodiment, forming the liquid passages 61 with inclination allows the flow force of the bubbles of the vaporized gaseous oxygen GO to cause the liquid oxygen LO to move and discharge the gas from the outlet 64. Accordingly, the liquid oxygen LO is vaporized with good efficiency and no vaporized gaseous oxygen GO remains, so that the heat exchange efficiency of the condenser/evaporator 50 can be improved. The amount of liquid oxygen LO flowing in each liquid passage 61 can be adjusted by adjusting the liquid height in the liquid tank 63 or adjusting the length, inclination or opening area of the liquid passage 61.

The liquid return pipes 69 may be spout-shaped and open-topped, and there may be a plurality of them depending on the amount of liquid. Furthermore, by providing a nitrogen chamber on each outer side of the condenser/evaporator 50 and by arranging a spout-shaped liquid return pipe in close contact with the outer wall of the nitrogen chamber, nitrogen gas can perform heat exchange with the liquid nitrogen in that area to evaporate the latter.

The liquid distribution device 68 may be formed by providing an overflow pipe or weir of the proper height for each liquid tank 63 to cause the liquid oxygen LO to flow sequentially from the overflow pipe or weir into the liquid tanks 63 in lower stages, instead of providing the distributor 67 and the connecting pipes 66. Alternatively, the distributor 67 and the liquid tanks 63 may be formed integrally with a connecting hole of a predetermined diameter to establish a connection between the distributor 67 and each liquid tank 63 so that the liquid oxygen LO can be supplied to each liquid tank via the connecting hole. Furthermore, a predetermined amount of liquid oxygen LO can be supplied to each liquid tank 63 by arranging a liquid adjustment mechanism in the upper portion of the manifold 67, or by adjusting the diameter or location of the connecting pipe 66 or the connecting hole or the overflow pipe, and further adjusting the height of the overflow pipe or the weir.

As described above, liquid oxygen LO which has not been evaporated in the liquid channel 61 is discharged from the liquid receiver 65 at the outlet 64 of this liquid passage without flowing downward out of the condenser/evaporator 50 as from the outlet 64; and then it is returned to the liquid tank 63 at the inlet 62 from the liquid receiver 65, which significantly reduces the amount of liquid oxygen flowing downward. That is, in order to prevent precipitation of acetylene, more excess liquid oxygen LO which has undergone vaporization should be supplied to the liquid tank 63 or the liquid receiver 65 at this stage and allowed to flow downward. Accordingly, it is possible to make the conveying means such as the liquid oxygen pump or the thermosiphon boiler compact for raising the liquid oxygen LO from the bottom of the upper column of the rectifier via the condenser/evaporator 50, which can significantly reduce the running power cost by lowering the discharge pressure of the outlet air compressor, as well as reducing the equipment cost and the running cost of the conveying means.

Fig. 3 illustrates the second embodiment of the invention.

An oxygen chamber 56 in this condenser/evaporator 70 has, as in the previous embodiment, a plurality of liquid passages 61 formed in multiple up/down stages. Liquid tanks 63 and liquid receivers 65 are arranged in a plurality of stages at the two ends of each liquid passage 61. Moreover, a liquid tank 71 and a liquid receiver 72 for supplying liquid oxygen LO are arranged in the block of the liquid passage 61 in the uppermost stage. The liquid receiver 65 of each stage below the liquid receiver 72 has a bottom 65a connected to the liquid passage 61 which is connected to the upper portion of the liquid tank 63 below the liquid tank 63 which introduces the liquid oxygen LO flowing downward into the liquid receiver 65 into the liquid channel 61. In addition, a liquid return line 69 connects the liquid receiver 65 to the liquid tank 63 which corresponds to the block of each liquid channel 61.

Accordingly, the liquid oxygen LO flowing downward from the rectifying section of the upper column of the double rectifying column, or the liquid oxygen LO supplied from the bottom of the upper column in circulation by the liquid oxygen pump or the thermosiphon reboiler, etc., is first supplied to the uppermost liquid receiver 72 and then flows through the uppermost liquid passage block 61 into the uppermost liquid tank 71. Meanwhile, the gaseous oxygen GO which has been vaporized while flowing down through the liquid passage 61 rises upward from the liquid receiver 72 against the flow of the liquid through this liquid passage 61, or flows downward together with the liquid to the liquid tank 71, and is separated to rise from this liquid tank 71. The liquid oxygen LO in the uppermost liquid container 71 flows downwards via the distributor 67 and the connecting line 66 into the lower liquid containers 63 and enters the respective liquid channels 61.

The liquid oxygen LO which has not been vaporized in the liquid channels 61 is received in each liquid receiver 65 at the outlet 64, and a part of the liquid oxygen flows from the liquid receiver 65 into the liquid channel 61 which communicates with the upper end of the lower liquid container 63 and flows due to the inclination of this channel 61 downward to enter the lower liquid tank 63. Gaseous oxygen GO which has been vaporized during the downward flow flows into the liquid tank 63 together with the liquid oxygen LO and is separated to rise therefrom. A part of the liquid oxygen LO received by the liquid receiver 65 flows into the liquid channel 61 to be introduced into the lower liquid tank 63; the other parts are circulated back to the original liquid tank 63 via the liquid return line 69. The liquid oxygen LO between the liquid tank 63 and the liquid receiver 65 corresponding to the block of the lowermost liquid channel 61 circulates in a path which starts from the liquid tank 63 and returns thereto via the liquid channel 61, the liquid receiver 65 and the liquid return line 69 while a part of it is vaporized. The liquid oxygen LO supplied in excess to prevent precipitation of acetylene overflows via this liquid tank 63 or the liquid receiver 65 in the lowest stage and flows to the bottom of the upper column.

By introducing a part of the liquid oxygen LO returning from the liquid receiver 65 to the liquid tank 63 into the liquid passage 61 communicating with the upper portion of the lower liquid tank 63, it is possible to prevent precipitation of acetylene with a small amount of excess liquid oxygen, in addition to the effects of the above embodiment.

Otherwise, if the liquid receiver 65 is not present, the liquid oxygen LO flows into each liquid channel 61 connected to the liquid container 63, depending on the liquid level in the liquid container 63, so that only a small amount of liquid oxygen LO flows into the liquid channel 61 which communicates with the upper part of the liquid container 63. This may cause the bubbles of gaseous oxygen GO to flow backwards without flowing together with the liquid through the liquid channel 61 to the outlet 64. When this counterflow phenomenon occurs, the liquid oxygen LO may not reach the outlet 64 of the liquid channel 61, thereby forming a dry region in the channel where acetylene may precipitate. Now, if the bottom of the liquid receiver 65 is connected to the liquid passage 61 on the upper side of the lower stage liquid tank 63 as in this embodiment, liquid oxygen LO can be introduced into the liquid passage 61 in which the dry region could be formed, so as to prevent the interior of this liquid passage 61 from drying out and hence the precipitation of acetylene. Moreover, in this structure, this liquid passage 61 serves the same purpose as the liquid return passage 69 to supply liquid oxygen LO to successively lower stages, thereby eliminating the need for the separate arrangement of the liquid return passage 69. The number of liquid passages used to return liquid can be appropriately set depending on the amount to be processed or the like.

Figures 4 and 5 illustrate the third embodiment in which a liquid return chamber serving as a liquid return line is formed next to an oxygen chamber. The oxygen chamber 56 of this condenser/evaporator 80 has, as in the two previous embodiments, heat exchanger plates 60 which are arranged in a plurality of stages so as to form a plurality of liquid passages 61 in a chamber formed by partitions 55 and inclined rods 51 and 52, with liquid containers 63 having their top open end disposed on the side of an inlet 62 and liquid receivers 65 having their top open end disposed on the side of an outlet 64 provided in the plurality of stages at the both ends of each liquid passage 61. In the region of the heat exchanger plate where a bottom plate 63a of the liquid container 63 and a bottom plate 65a of the liquid receiver 65 are connected, a plate thicker than the usual heat exchanger plate or a partition rod 81 is arranged to improve the connection between both bottom plates 63a and 65a and to reduce liquid leakage at this connection portion.

Furthermore, outside the outermost oxygen chamber 56, a side plate 82 is mounted, and a liquid return chamber 83 is formed between the side plate 82 and the partitions 55 defining the oxygen chamber 56. As shown in the lower half of Fig. 4, this liquid return chamber 83 has a plurality of partition bars 84 connecting the bottom plate 63a of the liquid container 63 and the bottom plate 65a of the liquid receiver 65 corresponding to each block. The upper and lower partition bars 84, the side plate 82, and the partitions 55 define liquid return channels 85 corresponding to the liquid container 63 and the liquid receiver 65.

The liquid return channel 85 thus formed serves, like the liquid return channel 69 in the previous embodiment, to allow the liquid oxygen LO to flow from the liquid receiver 65 to the liquid container 63 can flow; it should preferably be located so that it does not adjoin the nitrogen chamber 57 so as not to cause liquid oxygen LO to be vaporized in the liquid return channel 85 to impede the flow of the liquid; this is because of the above-mentioned problem of precipitation of a hydrocarbon compound, particularly in the case of liquid oxygen LO.

According to the description of this embodiment, it is therefore preferable that the liquid return chamber 83 is arranged outside the oxygen chamber 56 at the very outside or between the oxygen chambers 56. Therefore, when the nitrogen chamber 57 at the position indicated by "A" in Fig. 5 serves as the liquid return chamber thus formed, it is preferable for the oxygen chambers 56 to be located on both sides of the liquid return chamber. The liquid return chamber 83 may be located adjacent to the nitrogen chamber 57. In this case, the width of the channel should be set in consideration of the flow resistance by the bubbles of the vaporized gaseous oxygen GO.

Although it is preferred to avoid, as far as possible, installing anything that increases the flow resistance in the liquid return line 85, a grooved rib or spacer with low flow resistance may be installed to increase structural strength.

A plurality of liquid return chambers 83 may be provided, for example, on both sides or in the middle depending on the flow rate of the liquid oxygen LO, and they may be combined with the mentioned liquid return lines or the like.

According to this embodiment, the two ends of the two sides of the condenser/evaporator 80 in such a manner as to form both side walls of the liquid tank 63 and the liquid receiver 65. On one side of the liquid tank 63, a liquid supply pipe 86 as liquid distribution means is mounted adjacent to one side plate 82, and a communication hole 87 for each liquid tank 63 is bored therein. The liquid supply pipe 86 and the communication hole 87 may be provided on the side of the liquid receiver 65 to supply liquid oxygen LO to each liquid receiver 65. A weir 88 is cut in the side wall of the end portion of the liquid receiver 65 to allow a predetermined amount of liquid oxygen LO to flow downward to prevent precipitation of a hydrocarbon compound such as acetylene and to adjust the amount of liquid in each block to a constant value.

Since the condenser/evaporator 80 is formed in the above-mentioned manner, the individual fluid chambers 56 and 57 or the liquid return passage 85 and the liquid tank 63 or the liquid receiver 65 can be simply and integrally formed by, for example, aluminum brazing, which prevents pipes, drains or the like from being exposed. The device can therefore be easily handled.

The condenser/evaporator 90 shown in Figs. 6 to 9 has an oxygen chamber 56 in which a first liquid channel 61a slopes upwards from one side of the condenser/evaporator to the other side, and it has a second liquid channel 61b which slopes in the opposite direction to that of the first liquid channel 61a, i.e. from the other side of the condenser/evaporator to the one side. The first liquid channels 6la which slope to the right in Fig. 6 are collectively on one side (upper half in Fig. 7) of the condenser/evaporator 90 in the width direction (upward direction in Fig. 7), and the second liquid channels 61b rising to the right in Fig. 6 are arranged together on the other side (lower half in Fig. 7). These liquid channels 61a and 61b are normally made by inclining a corrugated heat exchange fin. Partition bars 81 slightly thicker than the heat exchange plate are arranged at appropriate intervals in a part of the liquid channels 61a and 61b to define channel blocks.

A plurality of liquid tanks 63 and liquid receivers 65 communicating with the liquid channels 61a and 61b are arranged in multiple up/down stages in the end portion of the thus formed oxygen chamber 56. The liquid tanks 63 and liquid receivers 65 are provided for a plurality of liquid channels 61a and 61b in the vertical direction for one channel block, and are formed by a single bottom plate 91 bent to be located at a predetermined position and a wall plate 92 mounted to enclose the three sides of the bottom plate 91. The liquid containers 63 and the liquid receivers 65 are connected to each other on the surface of the bottom plate 91, with the mounting height of the plate 91 corresponding to the liquid receiver 65 being higher than the height corresponding to the liquid container 63, allowing liquid oxygen LO to flow down from the liquid receiver 65 into the liquid container 63 at the same stage.

The liquid oxygen LO to be introduced into the oxygen chamber 56 thus formed is supplied to the liquid container 63 on the side of the first liquid channel 61a via the connecting hole 87 from the liquid supply line 86 and flows into this channel 61a to undergo heat exchange with gaseous nitrogen GN in the adjacent nitrogen chamber 57 so that a part of the liquid oxygen is evaporated to gaseous oxygen GO. The unevaporated liquid oxygen LO flows out of the outlet of the first liquid channel 61a together with the gaseous oxygen GO and flows into the liquid receiver 65 in the end region of this channel 61a. The liquid oxygen flowing into the liquid receiver 65 flows down via the bottom plate 91 into the liquid tank 63 of the adjacent second liquid channel 61b to be introduced from the liquid tank 63 into this channel 61b. At this time, a part of the liquid oxygen LO overflows the weir 88 downwards to the liquid tank 63 or to the liquid receiver 65 in a lower stage or in the lower region of the condenser/evaporator 90.

That is, liquid oxygen LO supplied to the liquid tank 63 via the liquid supply line 86 is introduced from the liquid tank 63 into the first liquid channel 61a, reaches the liquid receiver 65 while being partially evaporated, flows down from the liquid receiver 65 into the liquid tank 63 of the second liquid channel 61b to be introduced into this channel 61b. Then, it returns from the liquid receiver 65 of the second liquid channel 61b to the original liquid tank 63 and circulates along this path. Accordingly, the amount of liquid oxygen LO corresponding to the amount evaporated in the individual channels 61a and 61b and the amount flowing over the weir 88 is supplied to the liquid tank 63 from the liquid supply line 86. When the liquid oxygen LO is supplied via the liquid channels 61a and 61b circulates through the liquid receiver 65 and the liquid tank 63 in the same stage while being partially evaporated in these channels 61a and 61b, it is possible that the amount of liquid oxygen flowing downward in the condenser/evaporator 90 may be significantly reduced.

Although in this embodiment, each of the upper and lower liquid containers 63 and liquid receivers 65 has the same size and adjacent liquid containers 63 and liquid receivers 65 are connected to each other via the bottom plate 91, the sizes of the liquid containers 63 and liquid receivers 65 may be changed along the up/down direction, or the liquid containers 63 and liquid receivers 65 may be formed as independent boxes, both of which are connected to each other via spouts or pipes serving as connecting channels for liquid supply.

Figs. 10 and 11 illustrate the fifth embodiment in which a plurality of condenser/evaporator blocks are integrally arranged to form a condenser/evaporator.

A plurality of liquid tanks 63 are arranged in multiple up/down stages between individual condenser/evaporator blocks 100a, 100b, 100c and 100d of this condenser/evaporator 100. In Fig. 10, the liquid tank 63 serves as one for supplying liquid to the condenser/evaporator block arranged to the left with respect to the liquid tank 63, and serves as a liquid receiver for the condenser/evaporator block arranged to the right thereof, as well as serving as a liquid supply channel. A distributor 67 is connected to each liquid tank. via a connecting line 66 so that liquid oxygen LO, as present in a liquid oxygen receiver 101 arranged in the upper region of the condenser/evaporator 100, is supplied to each liquid container 63 via the connection to the line 66.

The liquid oxygen LO to be introduced into the oxygen chamber 56 thus formed is supplied to each liquid tank 63 from the distributor 67 and flows into each liquid passage 61. Liquid oxygen LO which has not been evaporated in the liquid passage 61 flows out from the associated outlet 64 accompanied by gaseous oxygen GO and flows down into the liquid tanks 63 arranged between the adjacent condenser/evaporator blocks 100a, 100b, 100c and 100d in the next stage. Most of the liquid oxygen LO flowing down into the liquid tanks 63 flows with the liquid oxygen LO supplied from the manifold 67 into the liquid passage 61 of the condenser/evaporator blocks 100a, 100b, 100c and 100d in the next stage, although a part of it overflows below the condenser/evaporator 100.

As described above, the liquid oxygen LO, while being partially evaporated in the liquid channels 61 of the individual condenser/evaporator blocks 100a, 100b, 100c and 100d, flows into the individual liquid channels 61 of the condenser/evaporator block of the next stage. When the condenser/evaporator blocks 100a, 100b, 100c and 100d are arranged linearly, the liquid oxygen LO flowing out of the last liquid channel 61 of the condenser/evaporator blocks 100a, 100b, 100c and 100d in the last stage can be recycled and returned to the condenser/evaporator blocks 100a, 100b, 100c and 100d of the first stage by connecting spouts or pipes between the liquid receivers provided at the outlets 64 of the individual liquid channels 61 of the condenser/evaporator blocks 100a, 100b, 100c and 100d of the last stage and the liquid containers of the condenser/evaporator blocks 100a, 100b, 100c and 100d of the first stage.

Accordingly, as described above, excess liquid oxygen LO supplied to and discharged from each liquid channel 61 is sequentially supplied to the adjacent liquid channels 61 of the condenser/evaporator blocks 100a, 100b, 100c and 100d in the same stage, thereby significantly reducing the amount of liquid oxygen flowing downward from the condenser/evaporator 100.

By dividing the condenser/evaporator 100 into a plurality of condenser/evaporator blocks 100a, 100b, 100c and 100d to shorten each liquid passage 61, separation of evaporated gaseous oxygen GO from liquid oxygen LO can be carried out with good effect, thereby improving the heat exchange efficiency.

Although in this embodiment the liquid tanks 63 of the individual condenser/evaporator blocks 100a, 100b, 100c and 100d have the same height and the same size and a liquid is supplied to the condenser/evaporator blocks 100a, 100b, 100c and 100d sequentially in the next stage, the vertical heights or the sizes of the individual liquid tanks 63 may be changed. More specifically, as shown in Fig. 11, if the weirs of the upper liquid tanks 63 overhang the lower liquid tanks 63 to cause overflowing liquid oxygen LO to flow down from the weir directly to the bottom of the upper column, the concentration of acetylene. In addition, liquid tanks and liquid receivers may be provided on either side of each of the condenser/evaporator blocks 100a, 100b, 100c and 100d and may be connected to one another via spouts or pipes serving as liquid supply channels.

Figs. 12 and 13 illustrate an embodiment in which a condenser/evaporator 100 having the above structure is installed in a cylindrical vessel, e.g., a rectifier bottom.

In this condenser/evaporator 100, four condenser/evaporator blocks 100a, 100b, 100c and 100d constructed in substantially the same manner as in the above embodiment are arranged on the same circumference in an upper column 102 of the rectifier, and they are connected to each other via wide nozzles 103 serving as liquid supply channels. Liquid oxygen LO flowing out from the outlet 64 of the liquid channel 61 of each condenser/evaporator block 100a, 100b, 100c and 100d is received by the liquid receiver 65 and is then supplied through the nozzle 103 to the liquid tank 63 of each of the next-stage condenser/evaporator blocks 100a, 100b, 100c and 100d. A weir 88 is cut into the side wall of the liquid tank 63 so that excess liquid oxygen LO supplied to the liquid tank flows down over this weir 88 into the liquid tank 63 in the next stage. Therefore, the liquid oxygen LO supplied via a connecting line 66 from a distributor 67 flows counterclockwise in Fig. 12 while being partially evaporated in the condenser/evaporator blocks 100a, 100b, 100c and 100d and partially flows as liquid oxygen sequentially over lower liquid tanks 63. in the condenser/evaporator 100 to prevent the precipitation of a hydrocarbon compound.

Gaseous nitrogen GN for heat exchange with the liquid oxygen LO is introduced into the nitrogen chamber 57 via a gaseous nitrogen riser 104 and a distribution line 105 in the middle region of the upper column 102 through an inlet header 58 at the top of each of the condenser/evaporator blocks 100a, 100b, 100c and 100d and is then condensed and discharged to the outside from an outlet header (not shown).

Arranging the condenser/evaporator blocks 100a, 100b, 100c and 100d on the same circumference can facilitate circulation of the liquid oxygen LO. Since the condenser/evaporator blocks 100a, 100b, 100c and 100d have the same structure, assembly can be easily performed.

Figs. 14 to 18 illustrate the sixth embodiment of this invention. This condenser/evaporator 100 has a preferable structure such that heat exchange plates 60 are arranged up and down in multiple stages as described above to form liquid channels 61. A nitrogen chamber 57 is formed by partitions 55 adjacent to an oxygen chamber 56 which is designed to introduce liquid nitrogen LO into the channels 61 from the liquid tank 63 located on one side thereof. Each nitrogen chamber 57 is enclosed by inclined bars 51 and 52 and side bars 53 and 54, and has heat exchanger plates 111 like corrugated fins arranged thereon to form many condensing channels 112 as gas channels open on both sides, with a gas guide channel 113 and an exhaust channel 114 being provided on respective sides of the condensing channels 112.

In order to discharge liquid nitrogen LN condensed in a condensing passage 112 to the outside, this passage 112 has a suitable downward inclination with respect to the horizontal direction and extends from the gas guiding passage 113 to the exhaust passage 114. An inlet header 58 and an exhaust header 59 are connected to the gas guiding passage 113 and the exhaust passage 114, respectively, on the two sides of the nitrogen chamber 57, to charge gaseous nitrogen GN into the chamber 57 and to discharge liquid nitrogen LN condensed in the condensing passage 112.

The gaseous nitrogen GN is introduced into the individual condensing channels 112 via the inlet head 58 and the gas guide channel 113. The gaseous nitrogen GN introduced into the condensing channels 112 undergoes a heat exchange with liquid oxygen LO in the adjacent oxygen chamber 56 and is condensed into liquid nitrogen LN. This liquid nitrogen LN then flows downward to the outlet channel 114 due to the downward inclination of the condensing channels 112 and is discharged from the outlet channel 114 via the outlet head 59. Uncondensed gas GX in the gaseous nitrogen GN is discharged via a blow-out nozzle 115 provided in the upper region of the outlet channel 114.

Since many downwardly inclined condensing channels 112 are formed in the nitrogen chamber 57 to introduce gaseous nitrogen GN from one end of each condensing channel 112 and to discharge it from the other end, the amounts of nitrogen gas to be introduced into each condensing channel 112 as formed in the up/down direction in the nitrogen chamber 57 can be the same, and the amount of nitrogen to be condensed in the channels 112 can be substantially the same from the uppermost to the lowermost condensing channel 112.

The heat transfer coefficient across a film in the vertical direction of the condenser/evaporator 110 can therefore be set to essentially the same value everywhere.

Accordingly, sufficient heat exchange with the liquid oxygen LO is possible in the lower region of the oxygen chamber 56, thereby achieving the maximum heat exchange efficiency in condensation/evaporation. Specifically, in large and tall condensers/compressors, the condensing channel 112 can be significantly shortened compared with the prior art, and the liquid film of liquid nitrogen LN formed in each condensing channel 112 near the outlet channel 114 can be thinner, which minimizes the reduction in heat exchange efficiency. In addition, since the cross section and the opening area of the condensing channel 112 can be increased, the condensation amount and the fluid resistance per area of the condensing channel can be reduced, thereby further improving the heat exchange efficiency. Moreover, when a liquid dropper, which is a protruding portion of the heat exchanger plate 111, is in a part of the open end of the condensing channel 112 opened into the outlet channel 114, the liquid nitrogen LN flowing downward from the upper condensing channel 112 can be guided into the outlet channel 114, thereby preventing the upper end of the lower condensing channel 114 from being sealed by a liquid film.

The gas guide channel 113 and the gas outlet channel 114 may be provided with a reinforcing part if necessary to improve the pressure resistance characteristics; the material and the location should be selected taking into account the following: achieving a low flow resistance for gas or liquid, uniform Gas distribution, liquid outlet properties, etc.

The oxygen chamber 56 may have a structure similar to that of the previous embodiments, and the liquid supply mechanism and the liquid return mechanism are not limited to those shown in Figs. 14 to 18, but may be replaced by those used in the previous embodiments.

Forming the oxygen chamber 56 and the nitrogen chamber 57 in the above manner can minimize the increase in the boiling point of liquid oxygen LO due to the pressure of the liquid head on the oxygen chambers 56 side, as well as a deterioration in the heat exchange characteristic due to an increase in the thickness of the liquid film on the nitrogen chamber 57 side. Accordingly, the entire heat exchange area of the condenser/evaporator 110 can be used for the boiling and condensation by heat transfer with high heat exchange efficiency. Since the heat exchange characteristic in the up/down direction can be set to substantially the same value, the height of the condenser/evaporator 10 can be freely adjusted, so that the capacity can be increased by increasing the height, resulting in a large double rectification column without increasing the diameter of the vessel in which the condenser/evaporator is arranged. In addition, since the heat exchange characteristic is improved, the temperature difference between the fluid on the condensation side and the fluid on the evaporation side can be reduced, thereby lowering the pressure in the lower column or the power consumption of a compressor for compressing output air.

Claims (13)

1. Condenser/evaporator in which first fluid chambers (56) and second fluid chambers (57) are alternately formed by a plurality of vertical partitions (55), and a liquid in the first fluid chambers (56) is brought to heat exchange with a fluid in the second fluid chambers (57), with a plurality of heat exchanger plates (60) arranged in multiple up/down stages in the first fluid chambers (56) to form a plurality of liquid channels (61) having an open end (64) and a plurality of liquid containers (63) communicating with the liquid channels (61) and formed in multiple up/down stages on the side of the other end of the liquid channels (61), the liquid containers (63) being open at the top and liquid being introduced into the liquid channels (61) for heat exchange while it is supplied to the liquid containers (63) in each stage, characterized in that a plurality of liquid receivers (65) for receiving a liquid flowing downward from the open ends (64) of the liquid channels (61) are arranged separately from the liquid containers (63) in multiple up/down stages, and that a liquid return channel (69, 85, 105) is provided to return liquid in the liquid receivers (65) to the liquid containers (63). 2. Condenser/evaporator according to claim 1, characterized in that the liquid channels (61) have an upward slope which runs from one end on the side of the liquid containers (63) to the tip at the other end on the open side. 3. Condenser/evaporator according to claim 2, characterized in that the liquid containers (63) and receivers (65) are provided for several liquid channels (61) which are arranged successively in the up/down direction as a channel block. 4. Condenser/evaporator according to one of claims 1, 2 or 3, characterized in that a plurality of dividing rods (81) are arranged parallel to the heat exchanger plates (60) for predetermined intervals of the heat exchanger plates (60) arranged in the first fluid chambers (56) to divide the liquid channels (61) into channel blocks, with a plurality of channels (61) in the vertical direction, wherein liquid containers (63) and/or liquid receivers (65) are provided for each of the channel blocks, and bottom plates (63a, 65a) of the liquid containers (63) and/or the liquid receiver (65) are connected to end portions of the dividing rods (81). 5. Condenser/evaporator according to one of claims 3 or 4, characterized in that a liquid channel (69) arranged in an upper region of each channel block serves as a return channel to return liquid from the liquid receivers (65) to the liquid containers (63). 6. Condenser/evaporator according to claim 5, characterized in that the return channel is a line (69) or a spout (103) with an upwardly open part in order to connect the liquid receivers (65) and the liquid containers (63) to one another. 7. Condenser/evaporator according to one of claims 5 or 6, characterized in that the return channel is formed between the first fluid chambers (56), or in a region adjacent to the outside of a first Fluid chamber (56), whereby a channel is defined by arranging a dividing rod (61) to establish a connection between the bottom plate (65a) of the liquid receiver (65) and that (63a) of the liquid container (63). 8. Condenser/evaporator according to one of claims 1 to 7, characterized in that a liquid supply line (86) is arranged along the liquid containers (63) and/or the liquid receivers (65) which are present in multiple up/down stages, and that this liquid supply line (86) is connected to the liquid containers (63) and/or the liquid receivers (65) via liquid supply holes (67) which are formed in side walls of the liquid containers (63) and/or the liquid receivers (65). 9. A condenser/evaporator according to claim 1, characterized in that a plurality of heat exchanger plates (60) are arranged in multiple up/down stages in the first fluid chambers (56) to form first liquid channels (61a) having an upward inclination from one end of the condenser/evaporator to the other end thereof, and to form second liquid channels (61b) having an upward inclination from said other end of the condenser/evaporator to the one end thereof in the direction opposite to the inclination of the first liquid channels (61a), a plurality of liquid containers (63) communicating with individual liquid channels and open at the top are provided in multiple up/down stages in lower end regions of the first and second liquid channels (61a, 61b), a plurality of liquid receivers (65) communicating with individual liquid channels and open at the top are provided in multiple up/down stages in upper end regions of the first and second liquid channels (61a, 61b) are arranged, and that a liquid flowing downward in the liquid receivers (65) from one end of the liquid channels (61a, 61b) is supplied to the liquid containers (63) of the other liquid channels (61a, 61b). 10. Condenser/evaporator according to claim 9, characterized in that the first liquid channels (61a) and the second liquid channels (61b) are divided into a first group of liquid channels and a second group of liquid channels. 11. Condenser/evaporator according to claim 1, characterized by - a plurality of condenser/evaporator blocks (100a- - 100d) for introducing a liquid into the liquid channels (61), while the liquid is supplied to the liquid containers (63) in individual stages to undergo heat exchange with a fluid in the second fluid chambers; - a plurality of liquid containers (63) for each block, communicating with individual liquid channels (61) and arranged in multiple up/down stages at the other end of the liquid channels (61) to receive a liquid flowing downward from one end of the liquid channels (61); and - a liquid supply channel which allows the liquid to flow from the liquid receiver (65) of one block to the liquid container (63) of another condenser/evaporator block (100a - 100d). 12. Condenser/evaporator according to claim 11, characterized in that the condenser/evaporator blocks (100a - 100d) are arranged on the same circumference. 13. Condenser/evaporator according to claim 1, characterized in that several heat exchanger plates are arranged in the second Fluid chambers (57) are arranged in such a manner that they are inclined downwards with respect to the flow direction of a gaseous fluid to thereby form a plurality of gas channels, and that a gas guide channel is arranged near the inlet side of the gas channels and that an outlet channel is arranged near the outlet side of the gas channels. l4. Condenser/evaporator according to claim 1, characterized in that outlet channels for vaporized gas and non-vaporized liquid are arranged close to the outlet end (64) of the liquid channels (61) on the open side.