EP2969091A1

EP2969091A1 - Method for carrying out a mass transfer process in a column

Info

Publication number: EP2969091A1
Application number: EP14708583.1A
Authority: EP
Inventors: Reiner GIESE; Stefan Hädicke; Egon SCHMIDT; Jürgen PASCHOLD; Christoph Grossmann; Florian SCHARF; Alexey Shilkin
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2013-03-11
Filing date: 2014-03-10
Publication date: 2016-01-20
Also published as: CN105228713A; WO2014139958A1; US9403103B2; US20140251138A1

Abstract

The invention relates to a method for carrying out a mass transfer process in a column (1) which comprises at least two separation trays (5), each separation tray (5) having an upper plate (7) and a lower plate (9), with a sluice (13) being formed between the plates (7, 9), and valves (11) that are designed such as to allow gas to flow through the separation tray (5), liquid from the upper plate (7) flowing into the sluice (13) when the gas flow is disrupted, and the liquid running off from the sluice (13) once the gas supply is re-established. The method comprises the following steps: (a) allowing gas issued through the valves (11) in the separation tray (5) to flow through a liquid that is present on the upper plate (7), the amount of gas being sufficiently large to prevent liquid from flowing back through the valve (11); (b) disrupting the gas supply such that the liquid flows into the sluice (13) through the valves (11); (c) continuing the gas supply, the valves (11) in the lower plate (9) being opened such that the liquid runs off from the sluice (13). The sluice (13) is dimensioned such that once the liquid has run off from the top plate (7) into the sluice (13) not more than 70% of the sluice (13) is filled with liquid. The invention also relates to a valve for carrying out said method.

Description

The invention relates to a method for carrying out a mass transfer process in a column, comprising at least two separating trays, wherein each separating tray comprises an upper tray and a lower tray, a lock is formed between the trays and valves are provided , which are designed so that a gas can flow through the separating tray, when interrupting the flow of gas liquid flows from the upper floor into the lock and when re-gas supply, the liquid flows from the lock. The invention further relates to a valve for carrying out a mass transfer process in which liquid standing on a floor is flowed through by a gas, when the gas supply is interrupted, the liquid flows into a lock and, when the gas supply is restarted, the liquid flows out of the lock, the valve a closure member adapted to close an opening in a lower bottom of the lock with the closure member in a first valve position; and the closure member is guided in a sleeve positioned between an upper floor and lower floor defining the lock in which openings are formed in the region of the lock and which projects beyond the upper floor and has an upper stop for the closing element.

Method for carrying out mass transfer processes, in which separating trays are used, which comprise an upper and a lower bottom, between which a lock is formed and valves are further provided, which are designed so that a gas can flow through the separating tray and the interruption of the Gas flow Liquid flows from the upper floor into the lock and with renewed gas supply from the lock onto the lower separating floor, are known, for example, from EP 2 033 698 A1, EP 2 027 901 A1 or RU 2 237 508 C1. The valves disclosed in these documents each comprise a closing element which comprises two valve disks which are connected to one another by a spacer web. In a first position of the closing element, an outlet opening is closed off from the valve with the lower valve disk, through which liquid can flow from the lower floor to the separating floor underneath. At the same time, the second valve disk is in a position that allows the liquid to flow from the upper floor into the lock. In a second position, the closing element is raised so that gas can flow through the lower opening in the valve first into the lock and then flow around the lower valve plate through openings in the valve housing through the lock in the direction of the upper floor, the gas on the Upper floor is passed through the liquid standing on the floor.

Disadvantage of the known from the prior art method is that the valves can block, so that the liquid does not flow out of the lock on renewed gas supply or an excessive gas pressure is necessary to open the valve. This can lead to a deterioration of the separation performance. It is therefore an object of the present invention to provide a process for carrying out a mass transfer process in a column which can be stably carried out without deteriorating the separation performance. The object is achieved by a method for carrying out a mass transfer process in a column comprising at least two separating trays, wherein each separating tray comprises an upper floor and a lower floor, a lock is formed between the floors and valves are provided which are designed such that a gas can flow through the separating tray, liquid flows from the upper floor into the lock in the event of interruption of the gas flow and the liquid flows out of the lock when the gas is supplied again, comprising the following steps:

(a) passing a liquid standing on the upper floor with a gas exiting through valves in the ground, the amount of the gas being so great that no liquid flows back through the valve,

(b) interrupting the gas supply so that the liquid enters the lock through the valves; (c) restarting the gas supply, with valves in the lower floor opening so that the liquid flows out of the lock, the lock being dimensioned, that after the liquid has drained from the upper floor into the lock, the lock is filled to a maximum of 70% with liquid.

For the purposes of the present invention, the term "gas" is to be understood as meaning all gaseous substances, in particular also steam.

By filling the lock to a maximum of 70% after draining the liquid from the upper floor, the best ratio of separation efficiency to throughput of a floor is obtained. This is due to the fact that the lock must be degassed during the filling process. In addition, liquid, which is located above the closing element, at the beginning of the re-gas supply into the column partially pushed back onto the upper floor. This leads to the back-mixing of the liquid and thus to a deterioration of the separation efficiency. The amount of liquid forced back to the top bottom by the closure member is reduced as the level decreases. It has been shown that when the lock is filled to a maximum of 70%, the amount of liquid which is forced onto the upper floor when the gas is supplied again is so small that the backmixing is negligible. In a preferred embodiment, the height of the liquid standing on the upper floor is at least 2 cm, preferably at least 4 cm, and at most 30% of the distance between two separating trays, ie the upper bottom of the lower separating tray and the lower tray of the upper separating tray. The height of the liquid standing on the upper floor is the height which the liquid occupies, if it does not flow through a gas becomes. By the minimum height of 4 cm, the residence time of the gas bubbles is so large that a sufficient approximation to the thermodynamic equilibrium between liquid and gas is achieved. The maximum height of non-gas-trapped liquid on the upper floor is about 30% of the distance between the upper floor of a lower shelf and the lower floor of an upper shelf, hereinafter referred to as floor space. The ground clearance depends on the gas load, in particular the entrainment of liquid by the gas as well as liquid properties, for example the foaming tendency. In general, the ground clearance is in a range between 0.25 and 0.9 m. With column diameters of more than 3 m, however, the height of the floor beams increases substantially and defines the ground clearance. In these cases, the height required by the statics of the support structure is added to the ground clearance. The minimum lock height can be calculated by the following equation:

H _s = - ^ -.

0.7

Hs are the lock height, WL is the specific liquid load, t is the contact time between liquid and gas. The specific liquid load WL is calculated as VL / A, where Vi_ is the liquid load in m ³ / h and A is the cross-sectional area of the column.

The determination of the contact time t and of the column diameter results from the thermodynamics and the fluid dynamics of the process carried out in the column. When determining these parameters, care must be taken that the empirical condition

0.04. 0.3 -TS

<Hs S

0.7 0.7 is satisfied. Here TS is the ground clearance.

In a preferred embodiment, with the valve open, the ratio of the open cross-sectional area on an upper tray to the cross-sectional area of the column is in the range of 0.02 to 0.2, preferably in the range of 0.05 to 0.15. This aperture ratio corresponds to a Ge - Speed at the gas outlet of the valve of up to 20 m / s. If the cross-sectional area is too large, fluctuations will occur at the closing element, with the liquid occasionally passing the closing element during the contact time with the gas and reaching the underlying separating bottom. This also leads to a backmixing and thus deterioration of the separation performance.

The opening ratio is also decisive for the function of the valve used. When lifting with a gas, a lifting force acts on the closing element, whereby the lifting element acts on the closing element. force is the product of the pressure difference and the area of the closing element. The lifting force counteract the gravity of the closing element and the gravity of the liquid above the closing element. The pressure difference on the closing element is composed of two parts. On the one hand the so-called dry pressure loss, ie the pressure loss of the soil, as well as the pressure loss, which is due to the liquid column above the valve. The dry pressure loss is a complex function of the geometry of the valve, its related to the column cross-section free cross-sectional area and the weight of the closing element. At an aperture ratio, ie a ratio of the open cross-sectional area on an upper tray to the cross-sectional area of the column in the range of 0.02 to 0.2, optimum operation of the column results.

When restarting the gas supply at the bottom of the column, the individual closing elements of the valves are raised. This results in a response time of a closing element, i. the time between the beginning of the movement of the closing element until reaching the upper end position, with an average vapor velocity at the inflow surface of the closing element of 10 to 15 m / s of about 0.2 to 0.4 s. The momentum of the gas flow acting on the following separating tray is correspondingly delayed by this time. For a large number of floors, this results in a noticeable delay in the switching time of the valves on the bottom shelf and the top shelf. With a separation plate number of 40, the minimum switching delay is, for example, 8 to 16 s. As a result, the contact time of the gas with the liquid on the upper trays is shortened by the delay time.

This effect can be counteracted by the opening ratio of the valves on the trays from the column bottom in the direction of the column head is continuously reduced. The maximum difference in the opening ratio of the upper separating tray and the lower separating tray is preferably 5%. By reducing the opening ratio, a higher lifting force and thus a faster response time of the valves on the separating trays in the upper region of the column are achieved.

At the beginning of the gas supply to the column acts on the closing element given by the pressure difference lifting force. Under the influence of this lifting force, the closing element moves upwards, thus opening openings in the lower bottom, through which the liquid can flow out of the lock. The liquid thus flows in countercurrent to the gas from the lock. This leads to limitations in the maximum gas velocity when entering the valve. The maximum gas velocity is influenced by the opening ratio of the lower soil. When a maximum allowable gas velocity is exceeded, which occurs at a too small opening ratio, the liquid is partially retained in the lock or possibly even entrained by the ascending gas flow to the upper floor. It is therefore preferred that, with the valve open, the ratio of the open cross-sectional area of the upper floor to the open cross-sectional area of the lower floor be at least the ratio of the open cross-sectional area to the cross-sectional area of the column divided by 0.8 and maximum 0.25. It is preferred if the ratio of the open cross-sectional area of the upper floor to the open cross-sectional area of the lower floor is at least the ratio of the open cross-sectional area to the cross-sectional area of the column divided by 0.5 and not more than 0.15. For the ratio of the open cross-sectional area of the upper floor to the open cross-sectional area of the lower floor, the following applies:

<^ <0.25,

0.8 a _u preferably applies to the ratio

^ <^ <0.2.

0.5 a _u

Here, φ = a ₀ / A, where a _{0 is} the open cross-sectional area of the upper bottom and A is the cross-sectional area of the column. a _u is the open cross-sectional area of the lower floor.

The mass transfer process carried out in the column is, for example, rectification, distillation, absorption or stripping (desorption). In the case of rectification or stripping, for example, it is possible to interrupt the gas supply by separating from the column by synchronized valves, preferably synchronized quick-closing valves, evaporator and condenser. In this way, the gas phase is trapped in the column. The built during the contact time of the gas with the liquid pressure difference between the bottom of the column and the top of the column is now equalized. Condensation of the vapors in the condenser creates a negative pressure. It is preferred that the supply of the heating medium is not interrupted in the evaporator. This causes the vapor pressure in the evaporator to increase. To avoid excessive pressure fluctuations and thus possible mechanical damage to the column internals, the gas is preferably intermediately stored in an external or in the evaporator integrated buffer tank. The volume of this buffer container depends on the time that the gas supply is interrupted in the column. In addition, the switching delay must be taken into account. The volume of the buffer container is preferably designed so that the maximum pressure in the buffer tank does not exceed twice the operating pressure at the bottom of the column.

To restart the gas supply, the synchronized valves on the evaporator and condenser are reopened. When opening the valves, on the one hand, a vapor stream from the column is formed in the condenser and, at the same time, high-pulse steam flows into the column from the buffer vessel due to the built-up pressure. The movement of the closing elements is thus triggered simultaneously from two directions, namely on the one hand

Outflow of the vapor from the column and on the other hand by the influx of steam fes in the column from the buffer tank. This has the advantage that the Ansprechzeitverzug is considerably reduced at the closing elements of the individual shelves.

If the mass transfer process carried out in the column is an absorption, the same procedure is used. In this case, however, the synchronized valves ensure that the pressure compensation and thus the overflow time are realized as quickly as possible.

At the beginning of the interruption of the gas supply, the closing elements fall due to their mass and the weight of the liquid above the closing elements in their lower end position and thus close the openings in the lower bottom. Since no more vapor flows through the valves, the liquid can now flow from the upper floor through the openings in the upper floor in the lock. Due to the pressure profile in the column, namely from the sump to the head decreasing pressure, corresponding to the pressure loss of the individual soils, a pressure equalization within the column is desired. The pressure difference acts when interrupting the gas supply initially as a driving force for a gas flow despite separate inlet and outlet. The pressure in the entire column begins to equalize. Due to the equalization of pressure, secondary vapors develop in the lower part of the column because the liquid contained therein is boiled with decreasing ambient pressure. Since the closing elements have already reached their lower end position, and the lower bottoms of each separating tray hydraulically seal, the pressure equalization within the column takes place abruptly. The increase in pressure below a floor due to the resulting secondary vapors moves a portion of the closing element upwards until the openings in the lower floor are released so far that gas can flow into the lock. Since the gas pressure and the gas velocity is not sufficiently high to keep the liquid on the lower floor in the lock, there is a risk that a portion of the liquid from the lock on the underlying separating bottom and from there into the underlying lock expires. This leads to the mixing of the liquids with different concentrations and thus to a significant reduction of the separation efficiency. In order to reduce the run-off of the liquid by ascending secondary vapors, it is preferable to additionally receive pressure compensation valves in each case in the lower bottom. The pressure equalizing valves allow secondary vapors to escape upwards. The cross-sectional area of the pressure compensation valves is chosen so that no liquid expires when opening the pressure compensation valves by ascending gases or vapors. The pressure compensating valves used can be constructed identically to any conventional movable valves which are known to the person skilled in the art. Suitable pressure compensating valves include, for example, a movable plate and lifting and lowering limitations. The lowering limit is the lower bottom and the stroke limitation limits the movement of the plate upwards. The movable plate is designed so that in the absence of gas or vapor flow, the lock hydraulically seals in the area of the pressure compensation valves. In order for only the pressure compensating valves to open in the event of a secondary flow to equalize the pressure, it is further preferred if the closing element of the pressure compensating valves has a low mass than the closing element of the valves through which the liquid outlet is to take place. As a result, when the pressure is equalized, the pressure compensating valves initially respond and the closing elements of the valves, which permit a liquid drainage, are in their lower position. stay. The stroke of the closing elements of the pressure compensation valves is dependent on the gas or vapor velocity and the flow of the liquid is excluded due to the small opening of the pressure compensation valves. After completion of the pressure equalization process, the moving plates of the pressure compensating valves resume their lower end position on the ground and hydraulically seal the lock.

It is preferable if the maximum outflow area of the pressure compensation valves is between 0.005 and 0.03 relative to the cross-sectional area of the column. A suitable valve for carrying out the mass transfer process, in which a liquid standing on a floor is flowed through by a gas, when the gas supply is interrupted, the liquid flows into a lock and the liquid flows out of the lock when the gas supply is restarted, comprises a closing element, the like is designed so that with the closing element in a first valve position, an opening in a lower bottom of the Schleuse is closable, and the closing element is guided in a sleeve which between a the

Sluice limiting upper bottom and lower bottom is positioned, in which in the region of the lock openings are formed and which projects beyond the upper bottom and having an upper stop for the closing element. The closure member includes a hood having a top plate and a downwardly extending edge, with circumferentially received apertures in the downwardly extending edge positioned so that the apertures at least partially overlap apertures in the sleeve above the top bottom when the valve is open, wherein with the valve open, the hood of the closing element abuts the upper stop on the sleeve, or wherein the closing element comprises a piston rod, an upper closing element and a lower closing element, wherein the upper and the lower closing element each in the form of a Valve plate are formed and the lower closing element has a larger diameter than the upper closing element and the sleeve in the lower region has a larger diameter than in the upper region, so that both the lower closing element and the upper closing element are guided in the sleeve, or wherein theupper and lower closing element in the form of a valve disc are formed, which are connected to a second, movable sleeve, wherein the sleeve is guided on an axis.

The advantage of the upper closure element designed as a hood is that, with the opening in the lower bottom closed in the first valve position, the liquid on the upper floor can flow unhindered through the openings in the sleeve above the upper floor into the lock. In addition, can be adjusted by the geometry of circumferentially received in the downwardly extending edge of the hood openings required for the lifting force of the closing element pressure difference. A maximization of the lifting force can be achieved if the upper stop for the hood at the upper end of the sleeve is formed by a solid plate.

If the upper closing element is designed in the form of a hood, the closing element in a first embodiment comprises an upper closing element and a lower closing element, the hood forming the upper closing element and the lower closing element staltet is that with the lower closing element in the first valve position, the opening in the lower bottom is closed. Preferably, the lower closing element is designed in the form of a valve disk. The upper and the lower closing element can in this case also be connected to one another by means of a sleeve guided on an axis.

In a second embodiment, the hood forms the closing element, wherein the hood is designed so that in the first valve position, the downwardly extending edge of the hood rests on an edge enclosing the opening in the lower bottom and thus closes the opening in the lower bottom, wherein the openings in the sleeve in the region of the lock are arranged such that the openings in the sleeve and the openings in the hood do not overlap in the first valve position. The fact that the openings in the sleeve and the openings in the hood do not overlap in the first valve position, the drain from the lock is closed. When the hood is in the second valve position, i. in the upper position, the openings are open so that gas can flow unhindered through the lock on the upper floor. Once the gas supply is interrupted, the hood returns to the first valve position, and through openings in the sleeve, the liquid can flow into the lock. Since the openings in the hood and the openings in the sleeve do not overlap, the liquid remains in the lock. As soon as the gas supply is restarted, the hood is lifted due to the pressure difference and the liquid can flow out of the lock through lower openings in the sleeve.

If the closing element is designed such that the upper and the lower closing element are respectively designed in the form of a valve disk and the lower closing element has a larger diameter than the upper closing element, it is preferred if the ratio of the diameter of the upper closing element to the diameter of the lower Closing element is in the range of 0.5 to 0.9. It is particularly preferred if the ratio of the diameter of the upper closing element to the diameter of the lower closing element is in the range of 0.6 to 0.85. Due to the design of the upper and lower closing element in the form of a valve disk, it is possible to optimally choose the distance between the individual valves for the mass transfer and regardless of the opening ratio of the lower base plate.

If the upper and the lower closing element are each designed in the form of a valve disk, which have a different diameter, it is also advantageous if the respective sleeves, in which the closing elements run correspond to the diameter of the closing elements and each have a stroke limitation at the upper end , At the lower end, the sleeves have a countersink limit to prevent the closure member from falling out of the sleeve. The lifting and lowering limits on the sleeve, which is designed in different diameters, are preferably designed in the form of folds against which the respective closing element abuts in the first and second valve position.

Advantage of the design of the closure member such that the upper and lower closure member are connected to a sleeve which runs on an axis is that the closure member is guided between its upper and its lower end position and can not tilt. The axle is preferably fastened above the upper stop of the closing element and below the lower stop of the closing element centered in the outer sleeve. This can be done in any manner known to those skilled in the art, for example by screwing. If the upper stop is designed as a hood on the sleeve, the upper attachment of the axle is preferably centered in the cover. Alternatively, it is also possible to provide spokes that converge at the center of the sleeve and where the axle is attached. This is possible both for the upper attachment and for the lower attachment. When the closing element, a piston rod, an upper closing element and a lower

Closing element comprises, regardless of whether the upper closing element is designed in the form of a valve plate or a hood, it is further preferred if the upper closing element and the lower closing element are each movably connected to the piston rod. The movable connection with the piston rod avoids that the closing element is tilted and blocked during opening or closing in the sleeve in which it is guided.

Embodiments of the invention are illustrated in the figures and will be explained in the following description.

1 shows a section of a column for carrying out a mass transfer process with two separating trays, wherein the closing elements are in the first, lower valve position,

Gas flow during the mass transfer process, while the closing element is in the second, upper closed position, for example on a valve,

FIG. 3 shows the beginning of the gas flow and the outflow of the liquid from the lock;

Figure 4 shows a valve with a closing element, in the upper closing element and the lower

Closing element are designed in different diameters,

FIG. 5 shows a valve with an upper closing element designed as a hood,

Figure 6 shows a valve with a closing element designed as a hood in a lower, first

Valve position,

7 shows the closing element designed as a hood in a second, upper valve position, FIG.

8 shows a valve with a closing element with an upper and a lower closing element, which are fastened to a sleeve guided on an axis, FIG. 9 shows a valve with a closing element, in which an upper and a lower closing element are fastened to a guided on an axis sleeve, wherein the upper closing element is designed in the form of a hood.

Figure 1 shows a section of a column for carrying out a mass transfer process with two shelves, wherein the closing elements of the valves are in a first, lower valve position.

A column 1 for a mass transfer process comprises a shell 3 and separating trays 5. The separating trays 5 are usually connected to the casing 3.

In a column 1 designed according to the invention for carrying out a mass transfer process, the separating trays 5 comprise an upper bottom 7, a lower bottom 9 and valves 11, through which gas can flow in countercurrent to a liquid.

Through the lower bottom 9 and the upper bottom 7 a lock 13 is limited.

During the performance of a mass transfer process, liquid is on the upper bottom 7 and is traversed by a gas flowing through the valves 1 1, flows through. As a result, a mass transfer process takes place between the liquid and the gas. After a predetermined period of time, the gas supply is interrupted. This causes the valves close 1 1 and the liquid flows from the upper floor 7 in the lock 13. After the entire liquid has flowed into the lock 13, the gas supply is restarted, the valves 1 1 open again, the liquid flows from the lock 13 to the upper floor 7 lying below the lock 13 of the underlying partition 5 and is again gas flows through. By this method, a back mixing of the liquid during operation is avoided. During operation, no liquid flows from a separating tray to an underlying separating tray.

In order to interrupt the gas supply, it is preferable to separate the gas by two quick-acting valves from the evaporator and from the condenser. After the separation of the gas flow, a pressure profile exists over the height of the column 1 corresponding to the pressure loss of the individual separating trays 5. This pressure difference acts as a driving force for a gas flow despite separate inlet and outlet. The pressure in the entire column begins to equalize. In the course of this pressure equalization, secondary vapors are formed in the lower region of the column 1, since the liquid contained therein is brought to boiling point as the ambient pressure falls. Since the closing elements 15 of the valves 1 1 are located during the pressure equalization in their first, lower valve position, they seal the lower bottom 9 hydraulically. The pressure difference and the resulting pressure equalization lead to a part of the closing elements 15 being moved upwards. After the pressure relief, the closing elements 15 fall back into the lower end position. While these closing elements 15 are raised, however, the sealing of the lower bottom 9 is no longer guaranteed and liquid may partially run on the underlying soil. This leads to a back mixing of the liquid and thus to a considerable reduction of the separation efficiency.

In order to avoid the drainage of the liquid, it is therefore advantageous to additionally provide pressure equalization valves 17. As pressure compensation valves while valves can be used, as used in conventional soils. Such valves usually have a movable plate and lifting and lowering limits. The movable plate of the pressure compensation valve 17 is designed so that it hydraulically seals the lock in the absence of gas flow. The pressure compensation valves 17 are preferably designed so that the movable plate has a lower mass than the closing element 15 of the valves 11, taking into account the dynamic pressure difference of a fluid column standing above the valve. During pressure equalization, the pressure compensation valves 17 respond before the closing elements 15 of the valves 11 are brought into motion. In this case, a stroke of the pressure compensating valves 17 which depends on the gas velocity sets in. A drain of the liquid through the same openings is thereby excluded.

After completion of the pressure equalization operation, the movable plates of the pressure compensating valves 17 again assume their lower end position on the ground.

It is preferred if the ratio of the maximum outflow area of the pressure compensation valves 15 to the cross-sectional area of the column is in the range of 0.5 to 3%.

FIG. 2 shows a gas flow during the mass transfer process as long as the closing element is in a second, upper valve position.

During the mass transfer process, for example, a distillation or absorption, liquid 19 is located on the upper bottom 7 of the separating tray 5. The closing element 15 of the valve 11 is located in a second, upper valve position. In this case, the closing element 15 is guided in a sleeve 21 which extends between the lower floor 9 and the upper floor 7. The sleeve 21 has at its lower end a first opening 23 through which gas can flow into the sleeve during the mass transfer process. The gas flow is shown here by arrows 25. In the area of the lock 13, the sleeve 21 has openings 27. The openings 27 are designed so that a lower closing element 29 of the closing element 15 is located at a position which allows the gas to exit below the lower closing element 29 from the openings 27 and above the lower closing element 29 again through the openings 27 in the Enter sleeve. The lower closing element 29 is preferably designed in the form of a valve disk.

According to the invention, the sleeve 21 protrudes beyond the upper bottom 7, wherein above the upper bottom 7 in the sleeve further openings 31 are located, through which the gas can flow into the liquid 19. In this case, the openings 31 are present above the upper floor 7 Preferably designed so that they are flush with their lower edge flush with the upper floor 7.

In the second valve position illustrated in FIG. 2, an upper closing element 33 of the closing element 15 is located above the openings 31 above the upper floor 7. As a result, the further openings 31 are released above the upper floor 7 and are not blocked by the upper closing element 33.

At the same time, the stroke of the closing element 15 is limited by the upper closing element 33, in that it abuts against a stroke limiter 35, preferably an edge on the sleeve 21. The closing element 15 is held by the gas flow in the second, upper valve position.

According to the invention, the opening ratio of the valve is between 2 and 20%, preferably between 5 and 15%, depending on the gas velocity, the opening ratio being the free cross-sectional area related to the column cross-section. With an opening ratio in the range between 2 and 20%, this corresponds to a speed at the gas outlet of the valve of up to 20 m / s. If the cross-sectional area is too large, fluctuations will occur at the closing element 15, whereby liquid may flow back from the upper floor 7 through the openings and reach the underlying floor. This leads to a backmixing and thus to a deterioration of the separation performance. For this reason, the opening ratio should be selected so that as far as possible no liquid can drain from the upper bottom 7 against the gas flow during the mass transfer process through the further openings 31.

After a given contact time, the gas supply is interrupted. Once the gas supply is interrupted, the closing element 15 falls in a first, lower valve position, as shown in Figure 1. As a result, the first opening 23 is closed, so that no more gas can flow into the sleeve 21. In order to avoid that the closing element 15 slips through the sleeve, located at the lower end of the sleeve 21 is a Senkbegrenzung 37. The Senkbegrenzung can be an annular edge on the sleeve 21, for example. However, any other possible countersink limit, which allows a tight closure of the valve in the first valve position, is possible. When the closure element 15 is in the first, lower valve position and thus no more gas can flow through the valve, the liquid 19 flows from the upper bottom 7 through the openings 31 above the upper bottom 7 in the sleeve and then through the openings 27 in the lock 13. Since the first opening 13 is closed by the lower closing element 29, the liquid remains in the lock thirteenth

As soon as the liquid of the upper trays 7 of all the separating trays 5 has drained into the respective traps 13, the gas supply can be restarted. This is shown by way of example in FIG. 3 on a valve. Due to the restarted gas supply, the closing element 15 is raised again into the second, upper valve position. As a result, the opening 23 is released. The cross-sectional area of the opening 23 is chosen so that the liquid from the lock 13 in countercurrent to the gas flow 25 through the valve on the underlying separating tray 5 can proceed. The opening ratio of the first opening 23 is chosen so that even at maximum gas velocity no liquid is retained in the lock 13 or even entrained on the upper floor.

An alternative embodiment of the valve 1 1 is shown in Figure 4.

In the embodiment shown in Figure 4, the valve has a closing element 15, in which the upper closing element 33 and the lower closing element 29 are each designed in the form of a plate and are designed in different diameters. In order to ensure the function of the valve 1 1, the lower closing element 29 is guided in a lower sleeve portion 39 and the upper closing element 33 in an upper sleeve portion 41. The diameter of the lower sleeve portion 39 preferably corresponds to the diameter of the lower closing element 29 and the diameter of the upper sleeve portion 41 to the diameter of the upper closing element 33. The lower closing element 29 and the upper closing element 33 are preferably designed in the form of moving plates. The plates are connected to each other with a piston rod 43. The piston rod 43 also connects the upper closing elements 33 and lower closing elements 29 of the closing element 15 shown in FIGS. 1 to 3. In order to avoid tilting, the upper closing element 33 and the lower closing element 29 are preferably connected to the piston rod 43 in a movable manner.

In order to ensure the function of the valve shown in FIG. 4, openings 45 are formed in the lower sleeve section 39, wherein the openings lie within the lock 13 and are designed such that the openings 45 terminate flush with the lower floor 9 at their lower edge , This ensures that the entire liquid standing on the lower bottom 9 can drain out of the lock 13 through the valve 11.

So that both gas and liquid can flow through the valve 11, wherein the flow corresponds to that shown in Figures 2 and 3, are located within the lock in the upper sleeve portion 41 more openings 47. Through the openings 47 can flow from bottom to top Gas from the lock 13 in the upper sleeve portion 41 to flow. From the upper sleeve portion 41, the gas then flows through openings 31 above the upper floor 7. In order to obtain a faster outflow of liquid from the upper bottom 7 in the lock 13, it is further preferred if, in addition to the openings 31 over the circumference of the upper sleeve portion 41 at the upper end face another opening 49 is located. When the closing element 15 is in the second, upper closed position, the further opening 49 is closed by the upper closing element 33. Once the gas supply has stopped det, and the closing element 15 is in the first, lower closed position, the further opening 49 is released, and the liquid, which is located above the upper sleeve portion 41, in addition to the openings 31 and the opening 49 in the lock 13th flow. As a result, the total opening of the valve is increased and the liquid can drain faster from the upper floor 7 in the lock 13.

An alternative embodiment of the valve 1 1 is shown in FIG.

In the embodiment shown in Figure 5, the sleeve 21 corresponds to the sleeve of the valve, as shown in Figures 2 and 3. In contrast to the embodiment illustrated in FIGS. 2 and 3, however, the upper closing element 33 is not formed in the form of a plate but in the form of a hood 51. The hood 51 is designed so that a peripheral edge 53 of the hood is designed so that the lower edge 55 of the peripheral edge 53 is at the level of the top of the upper floor 7 when the closing element 15 is in its second, upper valve position. So that the gas through the designed as a hood 51 upper

Closing member 33 and the openings 31 can flow into the liquid, 31 openings in the peripheral edge 53 are formed in the peripheral edge 53 at the level of the openings. Through the openings 57 in the peripheral edge 53, the gas can then flow through the upper closing element 33 and the openings 31 into the liquid. The openings 57 are designed, for example, in the form of a row of holes. Through the openings 57, the opening ratio of the valve can be adjusted easily. This can be varied by varying the number of the opening 57 or the size of the opening 57.

An alternative embodiment of a closing element designed as a hood is shown in FIGS. 6 and 7.

In contrast to the closing elements illustrated in FIGS. 1 to 5, the closing element illustrated in FIGS. 6 and 7 does not comprise an upper closing element 33 and a lower closing element 29, but comprises only one hood 59.

In Figure 6, designed as a hood closing element 59 is shown in a first, lower closed position and in Figure 7 in a second, upper closed position. The designed as a hood 59 closing element is guided in a sleeve 21. The sleeve 21 is dimensioned such that it projects beyond the upper floor 7 and below the lower floor 9. So that the closure element designed as a hood 59 is held in the sleeve 21, this has a stroke limiter 61 and a lowering limiter 63. The stroke limiter 61 and the lowering limiter 63 can be designed, for example, in the form of a fold on the sleeve 21. Alternatively, it is also possible to provide a ring which is formed on the sleeve 21. If the closing element formed as a hood 59 is in the first valve position, this is located on the lowering limiter 63. This is shown in FIG. When the closure element designed as a hood 59 is in the upper, second valve position, it rests against the stroke limiter 61. When the closing element designed as a hood 59 is in the first valve position, as shown in FIG. 6, no gas flows through the valve. As a result, liquid can drain from the upper floor 7 through an upper opening row 65 in the sleeve 21 into the lock 13. So that the entire liquid can drain from the upper floor 7 through the upper row of openings 65 into the lock 13, the individual openings of the upper row of openings 65 are designed so that they are flush with the upper floor 7.

Through the upper row of openings 65, the liquid first flows into the sleeve 21. By a second row of openings 67, the liquid then flows from the sleeve into the lock 13 from. A third row of openings 69 below the second row of openings 67 is closed in the first valve position shown in FIG. 6 by the closing element designed as a hood 59. As a result, the liquid is held in the lock 13 and can not drain out of the lock 13. Thus, the entire liquid can drain from the lock 13, as soon as the designed as a hood 59 closing element is in the upper, second valve position, close the openings of the third row of openings 69 preferably with its lower edge flush with the other bottom 9.

As long as a mass transfer process is carried out, the closure element designed as a hood 59 is in the upper, second valve position, as shown in FIG. In the upper, second valve position designed as a hood 59 closing element is held by the gas flow. For this purpose, the gas flows through the opening 23 in the sleeve 21 and pushes the hood designed as a shutter 59 up against the stroke limiter 61. So that the gas can flow through the upper row of openings 65 into the liquid, in the hood 71 is an opening row 71st educated. The row of openings 71 in the hood 59 is arranged so that in the second, upper valve position, the openings of the opening row cover 71 with the openings of the upper row of openings 65, so that the gas through the openings of the opening row 71 and the openings of the upper row of openings 65 can flow into the liquid on the upper floor 7. When the closure element designed as a hood 59 is in the lower, first valve position, the openings of the opening row 71 are closed by the sleeve 21. For this purpose, the third row of openings 69 is designed such that the row of openings 71 lies above the third row of openings 69 when the closing element designed as a hood 59 is in the first valve position.

The closure element designed as a hood 59 is preferably designed such that the height of the closing element designed as a hood 59 corresponds to the distance from the lowering limit 63 to the lower edge of the openings of the second row of openings 67. This is marked with the letter A. Furthermore, preferably the distance between the upper edge of the openings of the row of openings 71 in the hood 59 to the cover 73 of the hood 59 corresponds to the height of the openings of the second row of openings 67. Furthermore, it is advantageous if the cross-sectional area of the openings of the rows of openings 65, 67, 69 each correspond to the cross-sectional area of the sleeve 21.

In Figure 8, a valve is shown having a closure member with upper and lower closure members secured to a movable sleeve guided on an axis. The valve shown in FIG. 8 comprises an upper sleeve 75 fixed in the upper floor 7. The upper sleeve 75 extends so far into the lock 13 that the distance between the lower end of the upper sleeve 75 and the lower bottom 9 is maximally as large as the distance between the upper closing element 33 and the lower closing element 29 of the closing element 15. This distance is designated by the letter "B." It is preferred if the distance between the upper closing element 33 and the lower closing element 29 is slightly greater than the distance between the lower bottom 9 and the lower end of the sleeve 75, for example 5 to 10 mm larger.

The upper closing element 33 and the lower closing element 29 are designed in the embodiment shown here as a valve disk.

Above the upper bottom 7, openings 31 are formed in the upper sleeve 75 through which gas can flow during operation and at a position of the closing element 15 in the position shown here, liquid can drain from the upper floor 7 into the lock 13.

In order for gas to flow through the valve when the closure member 15 is in its upper position, it is further necessary that the overall length of the upper sleeve 75 be smaller than the distance between the upper closure member 33 and the lower closure member 29 lower position of the closing element 15, a distance "A" between the upper closing element 33 and the lower end of the upper sleeve 75 so that the liquid from the upper bottom 7 through the openings 31 in the upper sleeve 75 and from the upper sleeve 75 further into the For this purpose, the movement of the closing element 15 downwards is limited by a lower sleeve 77, which projects downward from the lower bottom 9 by the distance A. When the distance "B" between the lower bottom 9 and the lower end of the upper sleeve 75 is slightly larger than the distance between the upper closing element 33 and the lower closing element 29, it is advantageous if the u ntere sleeve by the difference further from the lower bottom protrudes downwards than the distance between see the upper closure member 33 and the lower end of the upper sleeve 75 is.

In the embodiment illustrated here, the upper closing element 33 and the lower closing element 29 are connected to one another by a sleeve 79. The sleeve 79 is guided on an axis 81. By guiding the sleeve 79 on the axis 81, tilting and locking of the closing element 15 is prevented.

The axis 81, on which the sleeve 79 is guided, is preferably fixed in the upper sleeve 75 and the lower sleeve 77. For this purpose, it is possible, for example, to provide spokes which converge in the cross-section center of the sleeve 75, 77. In the cross-sectional center, the axis 81 can then be attached, for example by screwing, as shown here. The spokes preferably serve simultaneously as the upper stop or lower stop for the closing element 15. An alternative embodiment for an on-axis guided closure member is shown in FIG.

In contrast to the closing element 15 shown in FIG. 8, in the closing element 15 shown in FIG. 9, the upper closing element 33 is designed in the form of a hood 85. In the hood 85 while openings 87 are formed through which the gas can flow into the liquid on the upper floor 7 when the closing element 15 is in its upper position. For this purpose, it is necessary that the openings 31 are formed in the upper sleeve 75 so that the openings 87 in the hood 85 are not closed when the closing element 15 is in its upper position.

LIST OF REFERENCE NUMBERS

I column 45 77 lower sleeve 3 jacket 79 sleeve 5 separating base 81 axis

7 upper floor 83 spoke

9 lower floor 85 hood

I I valve 50 87 opening

13 lock

15 closing element

17 pressure balance valve

19 liquid

21 sleeve

23 first opening

25 gas flow

27 opening

29 lower closing element

31 openings above the upper floor 7

33 upper closing element

35 stroke limitation

37 countersink limit

39 lower sleeve section

41 upper sleeve section

43 piston rod

45 openings in the lower sleeve portion 39

47 openings in the upper sleeve section

41

49 more openings

51 hood

53 peripheral edge

55 Lower edge of the circumferential edge

53

57 opening

59 hood

61 stroke limitation

63 countersink limit

65 upper opening row

67 second opening row

69 third row of openings

71 Opening row in the hood 59

73 Lid of the hood 59

75 upper sleeve

Claims

Patent claims

1. A method for carrying out a mass transfer process in a column (1), comprising at least two separating trays (5), each separating tray (5) comprising an upper tray (7) and a lower tray (9), and between the trays (7, 9) a lock (13) is formed, and valves (1 1) are provided, which are designed so that a gas can flow through the separating base (5), and if the gas flow is interrupted, liquid from the upper base (7) into the lock (13) flows and when the gas is supplied again the liquid drains out of the lock (13), comprising the following steps:

(a) Flowing through a liquid standing on the upper base (7) with a

gas escaping through valves (11) in the separating base (5), the amount of gas being so large that no liquid flows back through the valve (11),

(b) interrupting the gas supply so that the liquid flows through the valves (1 1) into the lock (13),

(c) Restarting the gas supply, with valves (1 1 ) in the lower base (9) opening so that the liquid drains out of the lock (13), the lock (13) being dimensioned such that the lock (13) After the liquid has drained from the upper base (7) into the lock (13), it is filled to a maximum of 70% with liquid.

2. The method according to claim 1, characterized in that the height of the liquid standing on the upper floor (7) is at least 2 cm and a maximum of 30% of the distance between two separating floors (5).

3. The method according to claim 1 or 2, characterized in that when the valve (1 1) is open, the ratio of the open cross-sectional area on an upper plate (7) to the cross-sectional area of the column (1) is in the range from 0.02 to 0.2 .

4. The method according to any one of claims 1 to 3, characterized in that when the valve (11) is open, the ratio of the open cross-sectional area of the upper base (7) to the open cross-sectional area of the lower base (9) is at least the ratio of the open cross-sectional area to the cross-sectional area of the Column divided by 0.7 corresponds to a maximum of 0.25.

5. Method according to one of claims 1 to 4, characterized in that additional pressure compensation valves (17) are accommodated in the lower base (9).

Method according to one of claims 1 to 5, characterized in that the mass transfer process is a distillation, a rectification, an absorption or a stripping.

Method according to one of claims 1 to 6, characterized in that when the gas supply is interrupted, the gas is temporarily stored in an external buffer container or a buffer container integrated into the evaporator.

Valve for carrying out a mass transfer process in which a gas flows through liquid standing on a separating base (5), when the gas supply is interrupted the liquid flows into a lock (13) and when the gas supply is restarted the liquid flows out of the lock (13). , wherein the valve (1 1) comprises a closing element (15), which is designed such that an opening (23) in a lower base (9) of the lock (13) can be closed with the closing element (15) in a first valve position , and the closing element (15) is guided in a sleeve (21) which is positioned between the upper floor (7) delimiting the lock (13) and the lower floor (9), in which openings ( 27) are formed and which protrudes beyond the upper base (7) and has a stroke limiter (35) for the closing element (15), characterized in that the closing element (15) has a hood (51; 59) with an upper plate (73 ) and a downwardly extending edge (53) and openings (57; 71), which are positioned so that the openings (57; 71) at least partially overlap with openings (31; 65) in the sleeve (21) above the upper base (7) when the valve (1 1) is opened, with the hood (51; 59) of the closing element resting on the upper stroke limiter (35; 61) on the sleeve (21) when the valve (1 1) is open, or that the closing element (15) has a piston rod (43), an upper closing element (33) and a lower closing element (29), the upper (33) and the lower (29) closing elements each being designed in the form of a valve plate and the lower closing element (29) having a larger diameter than the upper closing element (33) and the sleeve (21) has a larger diameter in the lower area than in the upper area, so that both the lower closing element (29) and the upper closing element (33) are guided in the sleeve, or the upper closing element ( 33) and the lower closing element (29) are connected to a sleeve (79), the sleeve (79) being guided on an axis (81).

9. Valve according to claim 8, characterized in that the ratio of the diameter of the upper closing element (33) to the diameter of the lower closing element (29) is in the range of 0.5 to 0.9.

10. Valve according to claim 8, characterized in that the closing element (15) comprises a piston rod (43), an upper closing element (33) and a lower closing element (29), the hood (51) forming the upper closing element (33). and the lower closing element (29) is designed such that the opening (23) in the lower base is closed with the lower closing element (29) in the first valve position.

1 1. Valve according to one of claims 8 to 10, characterized in that the upper closing element (33) and the lower closing element (29) are each movably connected to the piston rod (43).

12. Valve according to claim 8, characterized in that the hood (59) forms the closing element, the hood (59) being designed such that in the first valve position the downwardly extending edge of the hood (59) rests on one of the openings in the lower base enclosing edge rests as a lowering limiter (63) and thus closes the opening (23) in the lower base (9), the openings (69) in the sleeve (21) being arranged in the area of the lock in such a way that the openings ( 69) in the sleeve (21) and the openings (71) in the hood (59) do not overlap in the first valve position.