GB2145012A - Gas/liquid contact apparatus - Google Patents
Gas/liquid contact apparatus Download PDFInfo
- Publication number
- GB2145012A GB2145012A GB08322008A GB8322008A GB2145012A GB 2145012 A GB2145012 A GB 2145012A GB 08322008 A GB08322008 A GB 08322008A GB 8322008 A GB8322008 A GB 8322008A GB 2145012 A GB2145012 A GB 2145012A
- Authority
- GB
- United Kingdom
- Prior art keywords
- gas
- liquid
- contact
- trays
- discharge devices
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
- B01D3/14—Fractional distillation or use of a fractionation or rectification column
- B01D3/16—Fractionating columns in which vapour bubbles through liquid
- B01D3/22—Fractionating columns in which vapour bubbles through liquid with horizontal sieve plates or grids; Construction of sieve plates or grids
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
- B01D3/14—Fractional distillation or use of a fractionation or rectification column
- B01D3/16—Fractionating columns in which vapour bubbles through liquid
- B01D3/163—Plates with valves
Landscapes
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Physical Or Chemical Processes And Apparatus (AREA)
- Vaporization, Distillation, Condensation, Sublimation, And Cold Traps (AREA)
Abstract
A vertical gas/liquid contact column encloses horizontal trays 7 vertically spaced from one another, each provided with openings 8 for downward flow of liquid, and each having at least one discharge device 9 for upward flowing gas which substantially fully extends above the tray 7 and is provided with an open lower inlet end and pressure reducing means 16 and an outlet opening 13 arranged near the next upper contact tray, the outlet openings 13 being so arranged that during operation gas from a discharge device 9 of a contact tray 7 flows in a horizontal direction to the open lower inlet end of a discharge device 9 of the next upper contact tray 7. <IMAGE>
Description
SPECIFICATION
Gas/liquid contact apparatus
The present invention relates to an apparatus for contacting a liquid with a gas for heat or mass transfer and to a gas/liquid contact process employing such an apparatus. More in particular the invention relates to a gas/liquid contact apparatus, suitable for stable operation at a wide range of liquid- and gas loads.
The term gas as used hereinafter in the specification and the claims is to be understood invariably to include vapour.
Gas/liquid contact apparatuses are suitably employed in processes like distillation, absorption and stripping. A well known type of gas/liquid contact apparatus comprises a normally vertically extending column having a plurality of horizontal trays arranged in the column one above the other, each of the trays being provided with openings for the passage of upward flowing gas and with one or more socalled downcomers for downward transfer of liquid from the upper side of a given tray to a point below said tray. Examples of trays which may be utilized in such apparatuses are grid trays, sieve trays and valve trays, the latter being sieve trays provided with valves displaceably arranged above the openings in the trays.
During operation of a column of the above known type, layers of liquid are formed on top of the contact trays, while gas is introduced into said liquid layers via the tray openings and forms a froth layer above the contact trays. The liquid layers are in fact broken up by the gasflow into small segments which are intensively mixed with the gas, thereby effecting an exchange of matter or heat between the liquid phase and the gas phase. Above the froth the gas separates itself from the liquid and enters via the openings in the next upper contact tray into a further contact zone for contact with a further quantity of liquid. The liquid flows in horizontal direction away from the perforated part of the relevant tray and is subsequently collected into the downcomers, which downcomers are normally in the form of downwardly extending troughlike elements.
At or near the lower ends of said elements discharge openings are provided, through which the liquid can enter into a lower positioned gas/liquid contact zone.
The maximum allowable capacity of the contact trays for handling gas and liquid flows is of primary importance in designing a gas/liquid contact column of the above type, since it determines the minimum possible diameter of the column and therefore the major part of the manufacturing costs. For a constant liquid rate, excessive increase of the gas rate will result in liquid entrainment and finally flood ing of the column, i.e. the phenomenon that the contact spaces and finally the whole column is filled with froth so that a proper separation between the liquid phase and the gas phase is no longer possible. At the floodpoint it is difficult to obtain a net downward flow of liquid, and the liquid introduced into the column will leave the column entrained by the outflowing-gas.Flooding may also occur if the liquid rate is excessively increased while the gas rate is maintained at a constant level.
Excessive liquid flow can overtax the capacity of the liquid downcomers, with the ultimate results of increased liquid hold up, increased pressure drop, and finally flooding of the column.
Apart from a maximum allowable capacity, the minimum allowable capacity also sets requirements to the contact trays-and column design. The minimum allowable capacity of a column is determined by the need for effective dispersion and contact between the two fluid phases in the column. The types of contact trays differ in their ability to permit low flows of gas and liquid. Sieve plates can operate at only reduced gas flow down to a point where liquid drains through the tray openings. Valve trays on the other hand can be operated at very low gas rates because of valve closing. Similarly, there are minimum liquid flowrates below which good liquid distribution over the contact trays is not possible.
In view of the ever increasing demand for apparatuses which can be operated at a wide range of fluid loads, many proposals have been made for columns which can handle high loads of liquid and/or gas. In practice a large variety of contact trays are applied, always however based on the basic embodiment of contact trays with openings for upward flowing gas and downcomers for countercurrently, downward flowing liquid. When considering gas/liquid contact columns it should always be taken into account that the column shell itself forms a major contribution to the total column manufacturing costs. It is therefore of major importance to design columns with a diameter and a height as small as possible at the required operating conditions.
The object of the present invention is to provide an improved gas/liquid contact apparatus which is in particular suitable for extremely high gas throughputs at high liquid to gas flowrates.
The gas/liquid contact apparatus according to the invention thereto comprises a normally substantially vertically extending column enclosing a plurality of substantially horizontal contact trays vertically spaced apart from one another, the contact trays being each provided with openings for downward flow of liquid and having each at least one discharge device for upward flowing gas, the discharge devices each substantially fully extend above the accompanying contact tray, are provided with open lower inlet ends and pressure drop means and have an outlet opening arranged near the next upper contact tray, wherein the outlet openings are so arranged that during operation gas from a discharge device of a contact tray flows in substantially horizontal direction to the open lower inlet end of a discharge device of a next upper contact tray.
Contrary to the known perforated tray gas/liquid contacting devices, the now proposed gas/liquid contact apparatus is provided with contact trays having openings for downward flowing liquid and separate discharge devices for transfer of gas in upward direction through said apparatus. During operation of the proposed apparatus, gas is flowing from a discharge device of a contact tray along the lower side of a next upper contact tray into a discharge device of said upper tray, and so on, while liquid flows in the form of thin curtains of small droplets via the openings in the trays through the gas mass flowing along the lower sides of the trays. Upon flowing of the liquid through the gas, liquid and gas are intensively mixed with one another, thereby effecting transfer of heat or matter between the fluid phases.Since the liquid has already been divided into thin curtains of liquid droplets, passing through the openings in the contact trays prior to contact with the gas, the gas velocity can be kept relatively low compared to conventional gas/liquid contact systems in which the liquid needs first to be broken -up by the gasflow. Since the gas is forced to flow along the lower sides of the contact trays, the lower part of the contact spaces between the trays can be fully used as settling zones in which liquid is collected and gas entrained by the liquid can escape from the latter.
The proposed apparatus enables the application of columns having a smaller diameter at a given liquid- and gas load and therefore being cheaper, than possible when using the conventional downcomer type equipment.
The apparatus according to the invention is particularly suitable for gastreating operations in which large quantities of treating liquid are required for treating relatively minor amounts of gas.
In order to reduce entrainment of liquid by gas flowing into the gas discharge devices, the lower ends of said devices preferably extend slightly below the lower sides of the contact trays so that liquid creeping along the contact trays is prevented from entering into the gas discharge devices. The rate of extension should be rather moderate in order to
prevent hampering of the gasflow. A suitable distance between the lower end of the gas discharge devices and the accompanying contact trays is chosen in the range of up to
about 10 cm. The gas discharge devices may
have any suitable configuration in vertical
cross section. In a preferred embodiment of the invention the gas discharge devices in vertical cross section substantially taper in upward direction, to increase the available space above the trays for gas/liquid contact without reducing the gas inlet opening.The gas inlet openings of the gas discharge devices are suitably chosen as wide as possible for further reducing liquid entrainment by the incoming gasflow. Instead of wide inlet openings for minimizing liquid entrainment in the gas discharge devices, liquid separating means may be arranged at or near the gas inlet openings. The liquid separating means may be formed by gridlike structures, such as demister mats.
The pressure drop means may form an integral part of the outlet openings in the gas discharge devices. In a more preferred embodiment of the invention the pressure drop means are separate from the outlet openings of the gas discharge devices and are arranged inside said devices upstream of the outlet openings. In this manner the outlet openings may be chosen relatively large so that the gas can smoothly flow out of the outlet openings and along the liquid films from the openings in the next upper contact tray. The separate pressure drop means may be formed by perforated plates inside the gas discharge devices substantially above the inlets, so that the gas can freely enter into the gas discharge devices.
In a suitable embodiment of the present invention, the pressure drop means in the gas discharge devices are variable with the gasflow, so that the pressure drop over said devices can be kept substantially constant and
independent of the gasflow. A constant pressure drop over the gas discharge devices in its turn means the ability to keep the liquid on the active tray areas at a substantially constant level. The application of variable pressure drop means therefore enables a more stable operation of the proposed column especially at large fluctuations of the gas load. The variable pressure drop means may be formed
by perforated plates inside the gas discharge
devices, wherein said plates are provided with openings and means for varying the area of said openings depending on the gasload.
These latter means may be formed for
example by valves or flaps actuated by the
gasflow.
To provide a large gas/liquid contact area
and sufficient liquid settling zone above the
contact trays, the outlet openings of the gas
discharge devices are preferably arranged at
or near the upper ends of the gas discharge
devices. In a preferred embodiment according
to the invention the outlet openings are ar
ranged in the upper endparts of the sidewalls
of the gas discharge devices. This arrange
ment enables a horizontal outflow of the gas
in the desired direction i.e. towards the
shower of liquid droplets issuing from the
perforations in the contact trays. A further
advantage of side openings over top-openings
resides in the reduced risk of liquid flow from
a next upper contact tray into the gas dis
charge devices.
To minimize the risk of liquid flow into the
gas discharge devices via the gas outlet open
ings, the contact trays may suitably be pro
vided with separate liquid height restricting
means formed by overflow weirs with the
upper ends thereof arranged below the outlet
openings of the gas discharge devices. The
overflow weirs may be for example formed by
open ended tubular elements vertically
mounted over openings in the active parts of the contact trays.
To further promote stable operation of the
column over a wide range of liquid loads and
especially at low liquid loads the contact trays
are suitably provided with means for control
ling the minimum liquid height on the trays.
These minimum liquid level controlling means
may suitably be formed by valves arranged
below the tray openings, and closing said openings when the liquid on the trays has reached its minimum level. In another suitable embodiment of the minimum liquid level controlling means, the tray openings are provided with capped chimneys extending above the trays and having a height corresponding with the required minimum liquid level.
The present invention will now be further elucidated by way of example only with reference to the accompanying drawings in which
Figure 1 shows a vertical cross-section of a gas/liquid contact apparatus according to the invention, and
Figure 2 shows cross-section ll-ll of Figure
1.
The shown apparatus comprises a normally vertically extending column (1) having a top gas outlet means 2, an upper liquid inlet means 3, a bottom liquid outlet means 4 and a lower gas inlet means 5. The interior of the column is divided into a plurality of compartments 6 for gas/liquid contact by means of a plurality of substantially horizontal contact trays 7, vertically spaced apart from one another. The contact trays 7 are provided with openings 8 having substantially the same cross-sectional area and being substantially uniformly distributed over the active parts of the contact trays, i.e. those parts below which an intense mixture of gas and liquid is formed during operation of the column. Each of the contact trays is further provided with a gas discharge device 9 running along a segment of the contact tray.The gas discharge devices 9 nearly fully extend above the adjoining contact trays 7 and are formed by upwarding tapering sidewalls 10 and a topwall 11. The sidewalls 10 have their lower ends arranged slightly below the lower sides of the contact trays thereby forming skirts 12 preventing inflow of liquid creeping along the contact trays into the gas discharge devices during operation of the column. The upper parts of the discharge devices are provided with gas outlet openings 13 running along substantially the full length of the discharge devices.
The topwalls 11 are preferably arranged slightly below the next upper contact trays thereby forming a space 14 which can be
used for gas/liquid contact. The interior of each gas discharge device 9 is provided with pressure drop means consisting of a plate 15 extending from wall to wall of the device and being provided with one or more relatively small openings 16 for the passage of gas. In order to maintain during operation the pressure drop over the openings 16 substantially constant, independent of the gas flow rate, obstructions 17 in the form of for example valves, are movably arranged in the openings
16. Instead of valves any other type of movable obstructions, such as flaps hingedly secured to the plate 15, can be applied.
The operation of the column, shown in the
Figures, will now be discussed with reference to a process for treating gas by means of a liquid treating medium.
Gas to be treated is introduced into the lower part of the column via gas inlet 5, while a liquid treating medium is supplied via the upper liquid inlet 3. The liquid is collected on the contact trays 7 and flows via the openings 8 in said trays in downward direction towards the bottom liquid outlet 4. Simultaneously the gas flows through the column in upward direction and is transferred between sequential contacting zones via the gas discharge devices 9. Upon flowing along the contact trays 7 the gas is intimately contacted with liquid flowing in the form of showers from the openings 8 of the contact trays. During the gas/liquid contact contaminants in the gas are extracted by the liquid treating medium.
The height of the liquid layers formed on the contact trays should be sufficient to allow coalescence of the liquid droplets and escape of gas from the liquid below the formed froth of gas and liquid. This liquid height is determined by the total pressure drop over the contact tray i.e. the pressure drop of the gas in the gas discharge devices plus the pressure drop of the liquid over the tray openings. At a given pressure drop of the gas the number and size of the openings in the contact trays should be so determined that during operation these openings give rise to a pressure drop of the liquid which is sufficient to maintain the minimum height of the liquid layers on the contact trays. In the shown embodiment the pressure drop of the gas is substantially independent of the gasflowrate owing to the presence of the variable obstructions 17 in the gas discharge devices 9.Since the openings 16 in the plates 15 are provided with adjustable obstructions 17, the pressure drop can be maintained at a substantially constant level independent of the gasload in the column. A substantially constant pressure drop of the gas promotes stability of the liquid level on the contact trays.
The gas outlet openings in the gas discharge devices 9 are arranged near the lower sides of the next upper contact trays thereby allowing large fluctuations of the liquid level on the trays without the risk of liquid entering into the discharge devices. The lower ends of the gas discharge devices are chosen relatively large to avoid excessive liquid entrainment of the gas leaving the contact zones via the gas discharge devices. A pressure drop is imposed to the gas flow upon passing the pressure drop means 15. 16. Since the gas discharge devices are substantially arranged above the respective contact trays, the whole zone on the next lower trays below said discharge devices can be effectively used for gas/liquid contact.
It should be noted that the contact trays can be provided with a plurality of gas discharge devices, instead of with one as shown in the Figures for the sake of simplicity. The configuration of the gas discharge devices on a contact tray may be suitably chosen the same as the configuration of downcomer means in conventional tray designs for gas/liquid contact columns.
Finally, it is remarked that the invention is not restricted to gas discharge devices having outlet openings arranged in the sidewalls thereof. In an equally suitable arrangement the gas discharge devices have open upper ends and are provided with non-perforated ceilings arranged substantially above the sidewalls thereby leaving a space forming a lateral gas outlet opening.
Claims (14)
1. Gas/liquid contact apparatus comprising a normally substantially vertically extending column enclosing a plurality of substantially horizontal contact trays vertically spaced apart from one another, the contact trays being each provided with openings for downward flow of liquid, and having each at least one discharge device for upward flowing gas, the discharge devices each substantially fully extend above the accompanying contact tray, are provided with open lower inlet ends and pressure drop means and have an outlet opening arranged near the next upper contact tray, wherein the outlet openings are so arranged that during operation gas from a discharge device of a contact tray flows in substantially horizontal direction to the open lower inlet end of a discharge device of a next upper contact tray.
2. Gas/liquid contact apparatus as claimed in claim 1, wherein the discharge devices have their lower ends arranged at a distance of at most about 10 cm below the accompanying contact trays.
3. Gas/liquid contact apparatus as claimed in claim 1 or 2, wherein the discharge devices each substantially taper in upward direction.
4. Gas/liquid contact apparatus as claimed in any one of the claims 1-3, wherein the discharge devices provided with close topwalls arranged slightly below the next upper contact trays.
5. Gas/liquid contact apparatus as claimed in any one of the claims 1-4, wherein the pressure drop means are variable with the gas load in the discharge devices.
6. Gas/liquid contact apparatus as claimed in claim 5, wherein the pressure drop means are formed by plates in the discharge devices, said plates being provided with passages variable in cross-section.
7. Gas/liquid contact apparatus as claimed in any one of the claims 1-6, wherein means are arranged at or near the inlets of the discharge devices for liquid impingement.
8. Gas/liquid contact apparatus as claimed in claim 7, wherein the liquid impingement means are formed by grid like structures extending over substantially the full cross-sections of the discharge devices.
9. Gas/liquid contact apparatus as claimed in any one of the claims 1-8, wherein the contact trays are further provided with liquid height restricting means formed by overflow weirs having their upper ends arranged below the outlet openings of the gas discharge devices.
10. Gas/liquid contact apparatus as claimed in any of the claims 1-9, wherein the contact trays are further provided with means for controlling the minimum liquid height on the contact trays.
11. Gas/liquid contact apparatus as claimed in claim 10, wherein the minimum liquid height controlling means are formed by valve means extending below the openings in the contact trays.
12. Gas/liquid contact apparatus as claimed in claim 10, wherein the minimum liquid height controlling means are formed by capped chimneys arranged substantially above the openings in the contact trays.
13. Gas/liquid contact apparatus substantially as described with particular reference to the accompanying drawings.
14. Process for contacting a gas with a liquid in which process a column is used as claimed in any one of the preceding claims.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08322008A GB2145012A (en) | 1983-08-16 | 1983-08-16 | Gas/liquid contact apparatus |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08322008A GB2145012A (en) | 1983-08-16 | 1983-08-16 | Gas/liquid contact apparatus |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB8322008D0 GB8322008D0 (en) | 1983-09-21 |
| GB2145012A true GB2145012A (en) | 1985-03-20 |
Family
ID=10547362
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08322008A Withdrawn GB2145012A (en) | 1983-08-16 | 1983-08-16 | Gas/liquid contact apparatus |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2145012A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0266458A1 (en) * | 1986-11-03 | 1988-05-11 | Koch Engineering Company Inc | Gas liquid contact tray and method of use |
| US4820455A (en) * | 1987-08-13 | 1989-04-11 | Fractionation Research, Inc. | Apparatus for redistribution of vapor and liquid in a packed column |
| CN103100291A (en) * | 2013-02-19 | 2013-05-15 | 天津派瑞环境工程技术有限公司 | Gas-liquid mass transfer device |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115888154B (en) * | 2022-09-09 | 2023-09-05 | 江苏省特种设备安全监督检验研究院盐城分院 | Tetrahydrofuran high pressure rectifying column |
| CN116474403B (en) * | 2023-05-16 | 2024-01-23 | 江苏竣业过程机械设备有限公司 | Height-adjustable cross-flow type tray multi-effect recovery tower |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB989341A (en) * | 1960-08-02 | 1965-04-14 | Shell Int Research | Process for the separation of mixtures by means of distillation or absorption |
| GB1566191A (en) * | 1976-01-23 | 1980-04-30 | Union Carbide Corp | Liquid-liquid contacting tray |
-
1983
- 1983-08-16 GB GB08322008A patent/GB2145012A/en not_active Withdrawn
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB989341A (en) * | 1960-08-02 | 1965-04-14 | Shell Int Research | Process for the separation of mixtures by means of distillation or absorption |
| GB1566191A (en) * | 1976-01-23 | 1980-04-30 | Union Carbide Corp | Liquid-liquid contacting tray |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0266458A1 (en) * | 1986-11-03 | 1988-05-11 | Koch Engineering Company Inc | Gas liquid contact tray and method of use |
| US4820455A (en) * | 1987-08-13 | 1989-04-11 | Fractionation Research, Inc. | Apparatus for redistribution of vapor and liquid in a packed column |
| CN103100291A (en) * | 2013-02-19 | 2013-05-15 | 天津派瑞环境工程技术有限公司 | Gas-liquid mass transfer device |
Also Published As
| Publication number | Publication date |
|---|---|
| GB8322008D0 (en) | 1983-09-21 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |