DISTRIBUTION OF GAS AND LIQUID IN A CONTACT DEVICE

Abstract: The present invention relates to a contact device (1) comprising a structured packing (8) with a plurality of differently oriented packing layers (11-17), wherein the respective flow channels (18) through the packing layers (11-17) have a definite direction, placed between an inlet (3), located at the lower part (2) of the device, for an upwardly directed gas flow, and an outlet (4) at the upper part (5) thereof, for discharging the treated gas flow, as well as an inlet (6) at the upper part (5) of the device, for a downwardly directed liquid flow, and an outlet (7) in the lower part (2) thereof, for discharging the treated liquid flow. The important feature of the invention is that said inlet (3) for the gas flow opens out substantially on a level with the lower limiting surface (10) of the structured packing (8).

Description: Distribution of σas and liquid in a contact device The present invention relates to contact device, comprising a structured packing with a plurality of differently oriented packing layers, wherein the respective flow channels through the packing layers have a definite direction, placed between an inlet, located at the lower part of the contact device, for an upwardly-directed gas flow, and an outlet at the upper part thereof, for discharging the treated gas flow, as well as an inlet at the upper part thereof, for a downwardly- directed liquid flow, and an outlet at the lower part thereof, for discharging the treated liquid flow. From US 5139544, a contact device of the kind described above is previously known, which comprises a structured packing with a plurality of differently oriented packing layers. Liquid is introduced into the contact device directly from a liquid distributor, which is arranged at the top of the structured packing, into an upwardly directed flow passage of an upper packing layer, for achieving contact between gas and liquid within the upper packing layer and reducing the risk of formation of drops. The US document discloses a traditionally designed contact device, in which the gas flow is introduced from the side of the contact device, that is, perpendicular to the direction of flow in the contact device. To achieve a uniform gas distribution, the packing of contact devices, of prior art, is usually located far downstream of the inlet, such that a change in direction of the gas flow may occur and the flow become stabilised into a uniform distribution before the gas penetrates into the packing. However, the necessary distance from the inlet of the contact device to the packing is too large to be feasible in practice and normally, therefore, the packing is located closer to the inlet of the contact device than what is desirable. It has now proved that such a design results in poor gas distribution in the packing and that eddies are formed behind the inlet edge, resulting in an uneven gas distribution. If the liquid distribution in the packing in a contact device is uniform, but the distribution of the gas is non-uniform, or vice versa, there is a considerable risk that the distribution within the packing becomes poor, which may result in the formation of different paths of gas or liquid through the contact device. This leads to lower transfer of mass than expected. The object of the present invention is to improve the distribution of gas and liquid within the packing. This object is achieved according to the invention with a device of the kind described in the introductory part of this description, which is characterised in that an upper edge of the mentioned inlet for the gas flow opens out substantially on a level with the lower limiting surface of the structured packing. The structured packing is utilised as a gas distribution member, in that the pressure drop and the structure of the packing are connected with a definite position of the packing in the contact device, that is, the packing is placed on a level with the upper edge of the gas inlet into the contact device. By using a structured packing in the contact device, that is, a packing where the flow channels through the packing have a definite direction, and placing the packing such that the lower edge of the packing lies on a level with the upper edge of the gas inlet of the contact device, the distribution of the gas in the packing will be considerably improved, while at the same time the height of the contact device is reduced. The location together with the pressure drop of the packing contributes to prevent the formation of eddies behind the inlet edge, and, in addition, by directing the first layer in the packing such that the flow of the gas flow perpendicular to the main direction of the flow in the contact device is prevented, a very uniform gas distribution is achieved in the packing. To avoid disturbance of the distribution of the gas, a necessary supporting lattice is suitably placed at the packing, between the first and second packing layers. The first packing layer is preferably suspended below the supporting lattice and may therefore be easily replaced from below if a replacement is considered necessary. The invention will now be described in detail with reference to the accompanying drawing, wherein Figure 1 shows a schematic cross-section view of a contact device according to the present invention. Figure 1 of the drawing shows an essentially vertically arranged contact device 1, comprising an inlet 3, arranged at the lower part 2 of the contact device, essentially perpendicular to the contact device 1, for a gas flow directed up- wards through the contact device 1, and an outlet 4 at the upper part 5 thereof, for discharging the treated gas flow, as well as an inlet 6 at the upper part 5 of the contact device, for a liquid flow directed downwards through the contact device 1, and an outlet 7 at the lower part 2 thereof, for discharging the treated liquid flow. The expression contact device comprises, for example, a tower, a column or a scrubber for absorption, adsorption, desorption or distillation, etc. The contact device 1 comprises at least one structured packing 8 , which is placed between the inlet 3 and the outlet 4. An upper edge 9 of the inlet 3 for the gas flow opens out substantially on a level with the lower limiting surface 10 of the structured packing 8. In a known manner, the structured packing 8 may be formed from two corrugated plates or the like, arranged against each other, which between them form a number of flow channels 18. The packing 8 suitably comprises a plurality of packing layers 11-17, of which at least the lowermost packing layer 11 is arranged in such a t H > H 1 o π LΠ n o ri ω fD tr fD < 0 ) ri H- fD P> •

Claims: CLAIMS 1. A contact device (1) comprising a structured packing (8) with a plurality of differently oriented packing layers (11- 17), wherein the respective flow channels (18) through the packing layers (11-17) have a definite direction, placed between an inlet (3), located at the lower part (2) of the device, for an upwardly directed gas flow, and an outlet (4) at the upper part (5) thereof, for discharging the treated gas flow, as well as an inlet (6) at the upper part (5) of the device, for a downwardly directed liquid flow, and an outlet (7) in the lower part (2) thereof, for discharging the treated liquid flow, characterised in that an upper edge (9) of said inlet (3) for the gas flow opens out substantially on a level with the lower limiting surface (10) of the structured packing (8) . 2. A device according to claim 1, characterised in that at least the lowermost packing layer (11) is arranged in such a way that its flow channels (18) through the packing layer (11) extend in a plane essentially perpendicular to the direction of flow (19) of the incoming gas flow. 3. A device according to claim 2, characterised in that at least the lowermost packing layer (11) is supported essentially freely below a supporting lattice (20), which is located in the structured packing (8) . 4. A device according to claim 3, characterised in that the two lowermost packing layers (11, 12) are arranged in a similar manner, with the respective flow channels (18) located in a common plane.

Inventors: BJARNOE ODD E, KALTIN LARS, BJARNOE, ODD, E., KALTIN, LARS
Applicants: BJARNOE ODD E, FLAEKT AB, KALTIN LARS, ABB FLAEKT AKTIEBOLAG, BJARNOE, ODD, E., KALTIN, LARS
Application year: 1999
Main classification: B01J10
IPC codes: B01D3, B01D47, B01D53, B01J10, B01J19