Patent Application
20180140966
The present invention relates to the field of gas/liquid contact columns, and more specifically to gas treatment, CO2 capture, dehydration or distillation units.
Gas treatment units and/or CO2 capture units using amine wash processes and/or distillation and/or dehydration units comprise columns for matter and/or heat exchange between a gas and a liquid, which can be liquid or gaseous fluid absorption and regeneration columns for example. These columns operate under counter-current or co-current gas/liquid flow conditions.
The columns used in these gas treatment and/or CO2 capture and/or distillation and/or dehydration units generally operate on the principle of matter and/or heat exchange between the gas and the fluid that circulate in the columns.
Standard distributors 2 used in absorption/regeneration or distillation columns generally consist of a collector/distributor tray equipped with chimneys 4 (also referred to as boxes) allowing passage of the gas through the tray. Under counter-current operating conditions, each chimney 4 allows passage of the gas from the lower part of the column to the upper part of column 1. Chimneys 4 project from one side of tray 2 and they are perpendicular thereto. Each chimney 4 consists of several walls, for example cylindrical (as shown in
In order to provide good operability of the column and compliance with the specifications relative to the products resulting from gas treatment for example, the column distribution system needs to ensure as homogeneous a gas and liquid phase distribution as possible.
An example of distributor trays according to the prior art more particularly intended to improve the gas distribution is disclosed for example in patent FR-2,936,717, where the gas rises in rectangular chimneys and flows through lateral holes/slots, the slots of two neighbouring profiles being offset by half a pitch. U.S. Pat. No. 5,464,573 discloses a device where fins allow the liquid to be collected and sent to boxes connected by a central collection channel, the gas flowing through the space between the boxes, then between the fins.
However, distributor trays according to the prior art can have not perfectly homogeneous gas feed rates, notably on the edges of such trays, all the more so since the diameter of the column is larger.
It can be noted that, generally speaking, gas distribution homogeneity is all the more difficult to obtain if the packing used as gas/liquid contactor is capacitive. What is referred to as capacity of a packing is the maximum amount of gas that can circulate without flooding the column in relation to a given liquid flow, i.e. without creating liquid accumulation in a part of the packing. The capacity of a packing depends on many factors (angle of the channels, shape of the elements, etc.), it is generally inversely proportional to the specific surface area thereof (also referred to as geometric surface area), which is the contact area per unit volume (expressed in m2/m3).
The present invention relates to a distributor tray allowing more homogeneous distribution of the gas velocities at the gas passage chimney outlet, notably in the case of large-diameter columns (diameter typically at least equal to 3 m), by using a dispersive material arranged within at least one of said chimneys for passage of said gas.
The invention relates to a distributor tray for a column intended for heat and/or matter exchange between a gas and a liquid, comprising at least one chimney projecting from the upper part of said tray for exclusive passage of said gas through said tray and at least one means for passage of said liquid through said tray, the inside of at least one of said chimneys for exclusive passage of said gas being provided with a material dispersive towards said gas.
According to an embodiment of the invention, said dispersive material can be uniformly distributed within said chimney in a longitudinal direction and in a transverse plane.
Advantageously, said dispersive material can be distributed over a thickness at least greater than 10 cm.
According to an embodiment of the invention, said dispersive material can be a random or structured packing.
According to a variant embodiment of the invention, said chimney for exclusive passage of said gas can be substantially parallelepipedic.
According to another variant embodiment of the invention, said chimney for exclusive passage of said gas can be substantially cylindrical.
Advantageously, all of said chimneys (4) for said exclusive passage of said gas can be provided with said gas dispersive material.
According to an embodiment of the invention, said liquid passage means can comprise a plurality of orifices and/or chimneys for passage of the liquid.
According to a variant embodiment of the invention, said liquid passage chimneys can project from the upper part of said tray and/or from the lower part of said tray.
According to an embodiment of the invention, said tray can comprise a plurality of liquid passage means uniformly distributed on said tray.
According to a variant embodiment of the invention, said liquid passage means can consist of downcorners arranged on the periphery of said tray.
Furthermore, the invention relates to a column intended for heat and/or matter exchange between a gas and a liquid, wherein the two fluids are contacted by means of at least one gas/liquid contactor, said column comprising at least one distributor tray according to the invention for distributing said fluids over said gas/liquid contactor.
According to an embodiment of the exchange column according to the invention, at least one distributor tray according to the invention can be arranged in the bottom of the column.
According to an embodiment of the exchange column of the invention, said column can comprise a plurality of sections, and each one of said sections can comprise a gas/liquid contactor and a distributor tray according to the invention.
Moreover, the invention relates to the use of an exchange column according to the invention for a gas treatment, CO2 capture, distillation, dehydration or air conversion method.
Other features and advantages of the method according to the invention will be clear from reading the description hereafter of embodiments given by way of non limitative example, with reference to the accompanying figures wherein:
The present invention relates to a distributor tray for a column intended for heat and/or matter exchange between a gas and a liquid, comprising at least one chimney projecting from the upper part of the tray for exclusive passage of the gas through said tray and at least one means allowing passage of the liquid through the tray. Conventionally, the distributor tray is substantially cylindrical. The upper part of the distributor tray is understood to be the part of the distributor tray oriented towards the top of the exchange column.
The distributor tray according to the invention is suited for counter-current flows in the heat and/or matter exchange column, the gas rising up through the exclusive gas passage chimneys and the liquid flowing down through the liquid passage means.
According to the invention, the chimneys enabling exclusive gas passage project from the upper part of the tray (and they are therefore oriented towards the top of the column). These chimneys allow, for columns operating under counter-current conditions, passage of the gas from the bottom of the tray (or lower part) to the top of the tray (or upper part).
According to the invention, chimneys for exclusive gas passage include at least one means for preventing liquid passage through the chimney. This means can be a cap, raised with respect to the chimney. Such a cap allows the gas to escape from the space contained between the cap and the chimney, but it prevents the liquid (flowing in through the top of the upper part of the tray since the distributor tray according to the invention operates under counter-current conditions) from entering the chimney.
Advantageously, exclusive gas passage chimneys have a substantially parallelepipedic and preferably rectangular shape. Indeed, such a geometry allows wide opening for gas passage, which enables pressure drops to be limited. Furthermore, when the distributor tray comprises several gas passage chimneys, they can be arranged parallel to one another. Alternatively, the exclusive gas passage chimneys have a substantially cylindrical shape.
According to the invention, the inside of at least one of said chimneys for exclusive gas passage is provided with a material dispersive towards gas, i.e. a material providing dispersion of the gas as it passes through the chimney, thus generating better distribution (in the sense of homogenization) of the gas as it leaves the chimney. Advantageously, all the chimneys of the distributor tray are provided with a dispersive material so as to promote homogenization of the gas stream downstream from the distributor tray.
Advantageously, the dispersive material is distributed within the exclusive gas passage chimney(s) uniformly in a longitudinal direction (the longitudinal direction is the direction of an axis going from the lower part of the tray to the upper part of the tray) and uniformly in a transverse plane. Dispersion of the gas passing through the chimney(s) is thus as homogeneous as possible, which provides a constant gas stream at the chimney(s) outlet over a section corresponding to the section of the chimney(s).
Advantageously, the dispersive material is uniformly distributed over a thickness of at least 10 cm along the longitudinal direction of the chimneys. The gas particles flowing through such dispersive material thicknesses are thus sufficiently dispersed to provide a homogeneous gas stream at the outlet of these chimneys. Advantageously, the dispersive material is uniformly distributed over the entire height of the exclusive gas passage chimneys.
Preferably, the dispersive material that is distributed within at least one exclusive gas passage chimney is a random or structured type packing, preferably of structured type. Indeed, a structured packing provides uniform density of the dispersive medium. A random packing is understood to be anarchic and random piles of unit elements with particular shapes, for example rings, spirals, etc. Heat and/or matter exchanges occur within these unit elements. They can be made of metal, ceramic, plastic or similar materials. Patent applications EP-1,478,457 and WO-2008/067,031 describe two examples of random packing unit elements. Random packing involves interesting qualities in terms of transfer efficiency, low pressure drop and ease of installation. The geometric surface area of the random packing can range between 70 and 250 m2/m3. A structured packing is understood to be piles of folded plates or sheets, corrugated and arranged in an organized manner in form of large blocks, as described notably in patent applications FR-2,913,353 (US-2010/0,213,625), U.S. Pat. No. 3,679,537 and U.S. Pat. No. 4,296,050. Heat and/or matter exchanges occur on these plates. Structured packings afford the advantage of providing a large geometric surface area for a given representative diameter. The geometric surface area of the structured packing can range between 100 and 500 m2/m3.
Advantageously, all the chimneys for said exclusive passage of said gas are provided with a gas dispersive material.
The liquid passage means enable the liquid to pass from the upper part of the tray to the lower part thereof.
According to an embodiment of the invention, notably in the case of an exchange column consisting of a plurality of sections, each section being made up of a gas/liquid contactor and a distributor tray, the means allowing passage of the liquid through the tray consist of a set of chimneys that can project on the upper side of the tray and/or the lower side of the tray. For the liquid to pass through the liquid passage chimneys and not through the exclusive gas passage chimneys, the liquid passage chimneys are advantageously less high than the gas passage chimneys. The liquid passage chimneys can be substantially cylindrical. According to another embodiment of the invention, the means allowing passage of the liquid through the tray consist of a set of orifices provided in the tray. According to another embodiment example (with an inter-bed configuration for example), the means allowing passage of the liquid through the tray comprise both chimneys and orifices. These liquid passage means are arranged between the exclusive gas passage chimneys. The number of liquid passage means is advantageously greater than the number of exclusive gas passage chimneys. The pitch of the liquid passage means can be triangular or square. In order to achieve good liquid delivery and good distribution of the liquid on the gas/liquid contactor, the liquid passage means are uniformly distributed over the tray, i.e. arranged over the entire surface of the tray, between the gas passage chimneys.
Alternatively, notably in the case of a distributor tray arranged in the exchange column bottom, the liquid passage means correspond to downcorners. The distributor tray downcorners are conventionally provided on the periphery of the tray for single-pass trays and they can be arranged on central sections for multi-pass trays, according to the column diameter.
According to a variant embodiment, not shown but as described in application EP-3,034,142 (US/2016-0,175,733), the distributor tray comprises at least two liquid collection and distribution levels, a part of the liquid from the upper level passing to the lower level prior to being delivered below the base of the tray, while another part of the liquid contained in the upper level is directly supplied to the base of the lower level. This configuration allows to improve liquid distribution in case of high liquid flow rates, notably in the case of a wide liquid flow rate variation range, while keeping reduced space requirement.
According to the non-limitative example of
According to another non-limitative example shown in
The invention also relates to a column for matter and/or heat exchange between two fluids, wherein two fluids are contacted by means of at least one gas/liquid contactor, the column comprising at least a first inlet for a liquid fluid, at least a second inlet for a gaseous fluid, at least a first outlet for a gaseous fluid and at least a second outlet for a liquid fluid. The column also comprises at least one distributor tray as described above, allowing homogeneous distribution of the gas onto the gas/liquid contactor.
According to an embodiment of the present invention, the column comprises a distributor tray as described above, arranged in the column bottom. Advantageously, the distributor in the column bottom is preceded by a gas phase pre-distribution device.
According to an embodiment of the invention, the column consists of several sections, each section comprising a gas/liquid contactor and a distributor tray as described above.
Advantageously, the gas/liquid contactor is a structured packing bed. Alternatively, the gas/liquid contactor is a random packing bed.
Preferably, the gas and the liquid flow through the column under counter-current conditions.
The column according to the invention can be used in gas treatment, CO2 capture (amine wash for example), distillation, dehydration or air conversion methods. Furthermore, the invention can be used with any solvent type.
In order to illustrate the advantages of the present invention, we compare hereafter the results obtained using an exchange column equipped according to the present invention with those obtained using a column of the prior art (i.e. without gas dispersive material in at least one exclusive gas passage chimney).
Thus, according to a first example, we consider a 3.76-m diameter exchange column. This column comprises a single distributor tray according to the invention, arranged in the bottom of the column. This tray comprises exclusive gas passage chimneys of rectangular shape, each chimney being topped by a cap, and each chimney being provided with a gas dispersive material in form of a structured packing. The main characteristics of the column according to the invention are detailed hereafter:
The performances, in terms of gas distribution, of this column according to the invention are compared with those of a column according to the prior art (i.e. without gas dispersive material in at least one exclusive gas passage chimney) having the same characteristics, except for the presence of a dispersive material in all the gas passage chimneys.
In a second invention implementation example, we consider an exchange column comprising a distributor tray according to the invention having the characteristics described in the above example, except that the column diameter is 7 m instead of 3.76 m. The performances, in terms of gas distribution, of this column according to the invention are compared with those of the 3.76-m diameter column according to the invention described in the first example. The results between the two columns are compared 5 cm upstream from the packing bed.
Thus, the distributor tray according to the invention enables more homogeneous distribution of the gas within an exchange column. Such an improvement can allow the height between the distributor tray and the gas/liquid contactor to be reduced without any risk of column flooding, even in the case of a large-diameter exchange column. The distributor tray according to the invention thus contributes to better contact between the gas and liquid phases, and therefore to better transfer.
| Number | Date | Country | Kind |
|---|---|---|---|
| 16/61.339 | Nov 2016 | FR | national |
