GB2111852A

GB2111852A - Gas-liquid contacting apparatus

Info

Publication number: GB2111852A
Application number: GB08234414A
Authority: GB
Inventors: Tomoyoshi Nakano; Bunji Kinno; Shinkichi Nozawa
Original assignee: Toyo Engineering Corp
Current assignee: Toyo Engineering Corp
Priority date: 1981-12-04
Filing date: 1982-12-02
Publication date: 1983-07-13
Also published as: JPS5898101A; IT8224596A1; IT1154624B; IT8224596A0; DE3244521A1

Abstract

The apparatus enables significant reduction of tower height by providing an outer shell (1) in the shape of a sphere or a vertical cylinder having closed ends. This apparatus comprises, inside the outer shell (1) at least one partition (2,3,4,5) positioned vertically within the outer shell, the partition(s) dividing the shell interior into at least two separate spaces (e.g. 15,16,17,18). Gas-liquid contacting means (20,21,22) are mounted in the spaces, and there are openings (25, 30, 31, 32) for introducing a gas and/or a liquid into the spaces, and openings (26, 33, 34, 35) for withdrawing a gas and/or a liquid from the spaces. Gas passage(s) (27, 28) and/or liquid passage(s) connect the spaces in a series, parallel or series- parallel manner, depending on the function to which the apparatus is put. <IMAGE>

Description

SPECIFICATION Gas-liquid contacting apparatus This invention relates to an improved gas-liquid contacting apparatus.

Gas-liquid contacting apparatuses, such as absorption towers, regeneration towers, distillation columns and the like, are intended to fulfil their functions on the premise that a liquid to be treated is allowed to flow downward from the top under the influence of gravity. Accordingly, it is regarded as the best practice to construct them in the form of high towers, if no limitation is placed on the tower height. However, high towers are problematic from the viewpoint of earthquake-proof design. Moreover, in the case of a so-called modular plant which is constructed at a place other than the site of operation, shipped in sections, and reassembled at the site of operation, tower-like structures have their centers of gravity at high levels and hence encounter difficulties in shipment.Thus, it is believed to be desirable that such a plant is constructed from modules having a height of 30 meters or less. For these reasons, if high performance is required, it is necessary to divide a tower into a plurality of sections, arrange them properly, and modify the gas and liquid flow rates so as to conform to the arrangement. However, the contruction of a plurality of individual towers is inevitably disadvantageous because of the increased costs and the greater installed space requirements It is therefore desirable to provide a gas-liquid contacting apparatus of reduced tower height, which can bear comparison with high towers in equipment efficiency, construction costs and installed space requirements.

According to the present invention, there is provided a gas-liquid contacting apparatus comprising an outer shell in the shape of a sphere, or a vertical cylinder having closed ends and a cylinder height-todiameter ratio of not greater than 7; at least one partition positioned vertically within said outer shell thus forming in the shell at least two spaces separated thereby; gas-liquid contacting means mounted in each of said spaces; openings for introducing a gas and/or a liquid into the said spaces; openings for withdrawing a gas and/or a liquid from the said spaces; and a gas passage and/or a liquid passage connecting said spaces in a series, parallel or series-parallel manner.

The said inlets and/or the said outlets may be formed in the upper, middle and/or lower parts of each of the spaces according to the purposes for which they and the apparatus are utilized. The present gas-liquid contacting apparatus makes it possible to determine and vary the cross-sectional areas of the spaces and change the arrangement thereof, thus tailoring the apparatus giving due consideration to the operating conditions in the respective spaces.

The invention will now be described in more detail by way of example with reference to the accompanying drawings in which: Figure 1 is a schematic illustration, in longitudinal section (a) and in cross section (b), of an exemplary gas-liquid contacting apparatus embodying the present invention, which has a spherical outer shell; Figure2 is a schematic illustration, in longitudinal section (a) and in cross section (b), of another exemplary gas-liquid contacting apparatus embodying the invention, which has an outer shell in the shape of a vertical cylinder having closed ends; Figure 3 (a) and (b) are schematic cross-sectional views illustrating some exemplary arrangements of partitions in the gas-liquid contacting apparatus according to the present invention;; Figure 4 is a schematic view illustrating the combined use of an absorption tower (I) and a regeneration tower (II), both constructed in accordance with the present invention; and Figure 5 is a schematic view of a rectifying column constructed in accordance with the present invention.

The gas-liquid contacting apparatus embodying the present invention may be used in applications involving the exchange or transfer of heat or mass between a liquid and a gas, and specific examples of such applications include gas absorption, stripping, rectification, extractive rectification, humidification, heating, cooling and the like.

The gas-liquid contacting means of the present apparatus can be any of the conventional means, such as packed beds, column plates, spray devices and the like, that are commonly used for gas-liquid contacting. The spaces having gas-liquid contacting means mounted therein may be connected in a series, parallel or series-parallel manner for gas flow or liquid flow, or both. However, it is preferable that at least one pair of these spaces be connected in series for gas flow or liquid flow, or both.

The outer shell of the apparatus embodying the present invention is in the shape of a sphere, or a vertical cylinder having closed ends and a cylinder height-to-diameter ratio of not greater than 7 and preferably not greater than 5. Generally speaking, where the apparatus is to be operated under either high pressure or subatmospheric pressure, the outer shell constitutes a pressure-resistant shell common to all the spaces. Thus, a spherical outer shell is preferred because the amount of pressure-resistant material required for the construction thereof is minimized. Where the apparatus is to be operated under only slight pressure, an outer shell having the shape of a vertical cylinder is preferred because of the ease of construction.

Preferred embodiments of the present invention are now described with reference to the accompanying drawings.

Figure 1 illustrates an exemplary gas-liquid contacting apparatus including a spherical outer shell, and Figure 2 illustrates another exemplary gas-liquid contacting apparatus including an outer shell in the shape of a vertical cylinder having closed ends. In the apparatus of Figure 1, the internal space of an outer shell 1 is divided by partitions 2, 3, 4 and 5 into a space 15 of annular cross section, spaces 16 and 17 of fan-shaped cross section, and a space 18 of circular cross section. In the apparatus of Figure 2, the internal space of an outer shell 1 is divided by partitions 3, 4 and 5 into spaces 16 and 17 of fan-shaped cross section and a space 18 of circular cross section.In both apparatuses of Figures 1 and 2, convertional gas-liquid contacting means 20, 21 and 22 (for example, packed beds, column plates, spray devices and the like) are mounted in the spaces 16, 17 and 18 defined within the outer shell 1.

A gas inlet 25 is formed at the bottom of the space 16, and a gas outlet 26 at the top of the space 17. A gas passage 27 is provided to connect the spaces 16 and 18 in series, and a gas passage 28 to connect the spaces 18 and 17 in series. The upper and lower ends of each gas passage correspond to a gas outlet and a gas inlet for the respective spaces it connects. In addition, liquid inlets 30,31 and 32 and liquid outlets 33,34 and 35 are formed at the top and bottom of the spaces 16, 17 and 18, respectively. In the illustrated embodiments, the spaces 16,17 and 18 are connected in series for gas flow and in parallel for liquid flow. However, it is to be understood that, according to the need, these spaces may be connected in any of various well-known manners.By way of example, they may be connected in series for both gas and liquid flow, or two of them may be connected in parallel and then connected in series with the remaining one. It is also to be understood that, although the gas passages 27 and 28 extend through the gas-liquid contacting means in the illustrated embodiments, they may be disposed outside the outer shell 1. Moreover, where the spaces are connected in series for liquid flow, each liquid passage comprises a flow channel for conducting a liquid from the bottom of one space to a liquid inlet formed at the top of another space, and a pump is installed in the flow channel.

The annular space 15 in the apparatus of Figure 1 can be utilized, for example, to receive a mist separator for the gas withdrawn from the gas outlet 26. Alternatively, where a gas or liquid inlet/outlet pipe extending through the outer shell is to be installed in the middle part of a space, the space 15 can be used to receive a bent pipe portion of the pipe for stress relief, as described hereafter, for example.

In the illustrated embodiments, the internal space of the outer shell 1 is divided into 3 sections by the partitions 2, 3, 4 and 5, but the present invention is not limited thereto. Depending on the intended purpose, the internal space of the outer shell 1 can be divided in various ways such as those illustrated in Figure 3. As is evident from these examples, the optimum cross-sectional area of each space for the intended purpose can be determined by varying the diameter of a concentric partition or partitions and the arrangement partition or partitions and the arrangement of radial partitions. Moreover, if there exist considerable pressure differences between the spaces, it is desirable to divide the internal space of the outer shell 1 by using concentric partitions alone to the exclusion of radial ones.

As described above, a gas passage or passages may be disposed either in the respective spaces or outside the outer shell 1. Alternatively, a gas passage can be established in the following manner: In the apparatus of Figure 1, for example, the space 18 may be used as a gas passage. To this end, an opening (corresponding to a gas outlet for the space 16) is formed in the uppermost part of the partition 3 so as to communicate with the space 16, and an opening (corresponding to a gas inlet for the space 17) is formed in the lowermost part of the partition 3 so as to communicate with the space 17.Thus, the gas that has passed through the space 16 from bottom to top is introduced into the space 18 through the opening formed in the uppermost part of the partition 3, allowed to flow downward through the space 18, and then introduced into the bottom of the space 17 through the opening formed in the lowermost part of the partition 3.

Figure 4 illustrates an embodiment involving the combined use of an absorption tower (I) and a regeneration tower (II), both constructed in accordance with the present invention. In the spherical absorption tower (I) which is operated under high pressure, a high-pressure gas containing a componentto be absorbed is introduced through a gas outlet 25 into a space 16 and then passed through a gas-liquid contacting means 20, where it is brought into contact with an absorbing medium introduced through a liquid inlet 30.Subsequently, the gas is conducted through a gas passage 27 into a space 17 to bring it into contact with an absorbing medium introduced through a liquid inlet 32, and then conducted through a gas passage 28 into a space 18 to bring it into contact with an absorbing medium introduced through a liquid inlet 31, whereby essentially all of the component to be absorbed is removed from the gas. The gas withdrawn from the space 18 is conducted through the gas passage 29 into a space 15, where the mist contained therein is separated. Thereafter, the gas is discharged out of the system by way of a gas outlet 26.The absorbing medium withdrawn from the liquid outlets 33,34 and 35 of the respective spaces is reduced to atmospheric pressure by means of a reducing valve 50, and then coated through a line 40 into the spaces 16' and 17' of a regeneration tower (11) having the shape of a vertical cylinder. While flowing downward through the gas-liquid contacting means 20' and 21' mounted in the respective spaces, the absorbing medium releases the absorbed gas component (which is discharged out of the system by way of a gas outlet 26'). Subsequently, the absorbing medium is withdrawn from the liquid outlets 33' and 35' of the respective spaces and pressurized by means of a pump 51. Then, a portion of the absorbing medium is conducted through a line 42, depressurized again, and introduced into a space 18' for further regeneration, while the rest is conducted through a line 43 and recycled to the spaces 16 and 17 byway of the liquid inlets 30 and 32. The absorbing medium withdrawn from the space 18' is pressurized by means of a pump 52, conducted through a line 44, and introduced into the space 18 by way of the liquid inlet 31. In accordance with this embodiment, the recycled absorbing medium can also be subjected to efficient multistage regeneration and intermediate extraction.

Figure 5 illustrated a rectifying column constructed in accordance with the present invention, in which the internal space is divided in substantially the same manner as in Figure 1. Gas-liquid contacting means 21,20 and 22 correspond, in that order, to the upper, middle and lower sections of a single prior-art rectifying column. In the case of rectification involving the existence of temperature differences between the spaces, it is preferable to provide the partitions with conventional stress-absorbing means (bellows 90 and 91 in this embodiment) for relieving thermal stresses caused by a difference in thermal expansion between expansion between the partitions and the outer shell, and to make the partitions themselves of heat insulating material. In the apparatus of Figure 5, a preheated feed material in the form of liquid, vapor or a mixture thereof is supplied through a line 47.The liquid fraction of the feed material is combined with the intermediate liquid reflux which has flowed downward through the gas-liquid contacting means 21 mounted in a space 17 and has been conveyed from a liquid outlet 35' by means of a pump 52'. Then, the combined liquid flows downward through the gas-liquid contacting means 20 mounted in a space 16, where it undergoes rectification by countercurrent contact with the vapor conducted from the top of the gas-liquid contaction means 22 of a space 18 by way of a gas passage 28'. During this process, a vaporous or liquid side stream product is withdrawn from an outlet 48 having a bent pipe portion 49 for stress relief in the space 15.The liquid that has fallen to the bottom of the space 16 and has become less rich in low-boiling components is withdrawn from a liquid outlet 33' and conveyed to the top of the gas-liquid contacting means 22 of the space 18 by means of a pump 51 '. While flowing downward through the gas-liquid contacting means 22, the liquid undergoes rectification again by contact with the vapor supplied from a heater 80 through a vapor inlet 25'.

The liquid that has fallen to the bottom of the space 18 is withdrawn from a liquid outlet 34' and introduced into the heater 80, where it is heated to boiling by a heat source supplied through a line 63 and discharged through a line 64. The resulting vapor is supplied through the vapor inlet 25' to the gas-liquid contacting means 22, whereby the above-described rectification takes place. A portion of the liquid obtained from the space 18 is withdrawn from an outlet 45 as a high-boiling product.

On the other hand, the vapor that has risen above the gas-liquid contacting means 20 mounted in the space 16 is conducted through a passage 27' and introduced into the space 17 below the gas-liquid contacting means 21. While flowing upward through the gas-liquid contacting means 21, the vapor undergoes rectification by countercurrent contact with the liquid reflux flowing downward from the top. The vapor that has risen to the top of the gas-liquid contacting means 21 and has become richer in low-boiling components as a result of the rectification is passed through the cooling tubes 71 of a condenser 70 and indirectly cooled by cooling water supplied through a line 61 and discharged through a line 62.The resulting condensate is collected in a reservoir 72 and then allowed to flow downward through the gas-liquid contacting means 21, where this liquid reflux contacts the upward-flowing vapor to effect the above-described rectification. A portion of the liquid collected in the reservoir 72 is withdrawn from an outlet 46 as a low-boiling product.

The rectification process described above is only illustrative and any of the well-known rectification processes can be carried out in the apparatus of the present invention. As occasion arises, the so-called extractive distillation (i.e., a rectification process in which a selected liquid highly miscible with some components of the feed material and poorly miscible with other components thereof is added at any desired point along any one of the gas-liquid contacting means 20, 21 and 22) can also be carried out in the apparatus of the present invention. Where the apparatus of the present invention is utilized as a rectifying means, the mode of using the partitioned spaces must be determined with consideration of temperature differences therebetween. In the abovedescribed embodiments, the central space 18 is allotted to the hottest section.However, the preferred arrangement may vary according to the size of the apparatus, the magnitude of the temperature differences, and the like.

In the prior art, gas-liquid contacting apparatuses such as absorption towers, regeneration towers, distillation columns and the like tended to have an unduly large tower height. The present invention makes it possible to reduce the tower height of such gas-liquid contacting apparatuses without causing any decrease in equipment efficiency. As a result, the whole plant can be reduced in height, thus permitting the modular design to be applied to a greater variety of plants. The present invention is also effective in providing a countermeasure against earthquakes. Furthermore, since the tower height can be reduced without causing any increase in the number of towers, it is possible to control the increase in installed space requirements and, in addition, curtail the amount of pressure-resistant material required for the construction of highpressure towers.

Claims

1. A gas-liquid contacting apparatus comprising an outer shell in the shape of a sphere, or a vertical cylinder having closed ends and a cylinder height-todiameter ratio of not greater than 7; at least one partition positioned vertically within said outer shell thus forming in the shell at least two spaces separated thereby; gas-liquid contacting means mounted in each of said spaces; openings for introducing a gas and/or a liquid into the said spaces; openings for withdrawing a gas and/or a liquid from the said spaces; and a gas passage and/or a liquid passage connecting said spaces in a series, parallel or series-parallel manner.

2. A gas-liquiding contacting apparatus as claimed in claim 1, wherein the gas-liquid contacting means is selected from packed beds, column plates and spray devices.

3. A gas-liquid contacting apparatus as claimed in claim 1 or claim 2, comprising at least one pair of the spaces connected in series by a gas passage and/or a liquid passage.

4. A gas-liquid contacting apparatus as claimed in any of claims 1 to 3, wherein the outer shell is a vertical cylinder having closed ends and a cylinder height-to-diameter ratio of not greater than 5.

5. A gas-liquid contacting apparatus as claimed in any of claims 1 to 4, wherein stress absorbing means is disposed between the outer shell and the or a partition therein.

6. A gas-liquid contacting apparatus as claimed in any of claims 1 to 5, wherein the partitions provide a plurality of gas-liquid contacting spaces and a further space, and a mist separator is provided in the latter space.

7. A gas-liquid contacting apparatus as claimed in any of the preceding claims, for use as a rectifying column.

8. A gas-liquid contacting apparatus as claimed in any of claims 1 to 6, for use as an absorption tower.

9. A gas liquid contacting apparatus as claimed in claim 8, combined with a further apparatus as claimed in any of claims 1 to 6, the latter apparatus serving as a regeneration tower.

10. A gas-liquid contacting apparatus as claimed in any of the preceding claims, wherein the said vertical partitions comprise a combination of cylin dricai and radial partitions which divide the shell into spaces of circular or annular or part-annular shape in horizontal cross-section.

11. Gas liquid contacting apparatuses substantially as herein described with reference to and as shown in the accompanying drawings.