Packing for mass transfer equipment

Abstract

The packing for mass transfer equipment comprises flat and to-be-corrugated sheets having perforation in the shape of hexagons with width a and height h, where a<h, and the perforation vertex angle β varies between 60° and 90°. The corrugated perforated sheets have no perforation or covered perforation areas. Adjacent corrugated sheets are symmetrical relative to the flat sheet between them. This invention for mass transfer equipment helps lengthen the path and residence time of dispersed phase droplets in the packing, consequently increasing the heat and mass transfer coefficients and intensifying the renewal of phase contact surface.

Description

[0001] PACKING FOR MASS TRANSFER EQUIPMENT TECHNICAL FIELD OF THE INVENTION

[0002] The invention belongs to packing contactors that are used in heat and mass transfer processes of countercurrent packed columns. This primarily includes the processes of liquid-liquid interaction (liquid-liquid extraction) and the processes of gas-liquid interaction (fractionation, absorption, distillation, heat exchange in scrubbers by mixing). The invention may be used in oil and gas processing, petrochemical, gas chemical, and other industries.

[0003] BACKGROUND

[0004] Liquid-liquid extraction processes are widely used in refining and petrochemical industry. In particular, liquid-liquid extraction processes are used when producing lubrication oils, recovering aromatic hydrocarbons from petroleum fractions and by-product cokes, in removal of sulfur compounds (hydrogen sulfide, mercaptans) from petroleum products. Liquid-liquid extraction is also used for recovery of valuable organic substances, such as acetic acid, formic acid, glycerin, etc. (Treybal R. Liquid-liquid extraction [Zhidkostnaya ekstraktsiya] / R. Treybal. - Moscow: Khimiya Publ. - 1966. - 724 p.). In oil and gas industry, the liquid-liquid extraction processes, as well as fractionation and absorption processes, usually take place in column-type equipment fitted with various contactors, mostly packing-type ones. (Skoblo A. I. Refining and Petrochemical Processes and Equipment [Protsessy i apparaty neftegazopererabotki i neftekhimii] / A. I. Skoblo, Yu. K. Molokanov, A. I. Vladimirov, V. A. Schelkunov - Moscow: Nedra Publ., 2000. - 676 p.) Packing contactors usually include either random packings (Raschig rings, Pall rings, Intalox saddles) or structured packings, such as SMV / SMVP made by Sulzer. (Rauber, J. Design practice for packed liquid liquid extraction columns / J. Rauber. - Sulzer Chemtech Ltd. - 12 p.). In view of the above, improving the structural design of packing contactors is a relevant objective in chemical technology, both for liquidliquid extraction processes and for fractionation and absorption processes.

[0005] There is a structured packing for column equipment that consists of layered contactors. The contactor has two expandable parts, each of which consists of two film-holding surfaces (perforated and expanded sheets).

[0006] The parts are connected together with a lock (utility model patent RU 87636, IPC B01D3 / 18, B01J19 / 32 filed on September 17, 2008 and published on October 20, 2009). Deficiencies of this utility model are as follows:

[0007] 1) The film-holding surfaces have a lot of free space between them where the mass transfer phases have hardly any contact. This results in a decline of general holding capacity of the packing in terms of the dispersed phase and in a reduction of residence time of the dispersed phase droplets, which eventually causes lower efficiency of the mass transfer;

[0008] 2) Individual contactors are difficult to manufacture and install inside mass transfer equipment.

[0009] There is a packing for mass transfer equipment that consists of vertical filmholding elements, made of mesh or perforated and expanded sheets, and of horizontal turbulizing elements inside a casing (utility model RU 82133, IPC B01D3 / 28, filed on September 17, 2008, published on April 20, 2009).

[0010] Deficiencies of this utility model are as follows:

[0011] 1) High flow resistance in the packing in case of countercurrent flow of phases that is due to horizontal turbulizing elements. This might result in flooding of the column at high load;

[0012] 2) Extra turbulizing elements (in addition to vertical film-holding elements) require more metal in fabrication of this structure;

[0013] 3) Absence of sharp edges in the packing results in low efficiency of droplet breakup. Droplets move primarily as a film, which causes a reduction of average driving force of the mass transfer process.

[0014] A product that is the closest to the invention described herein in terms of its technical substance and achieved result is the structured counterflow packing for extraction column that consists of alternating vertical and parallel flat perforated and corrugated perforated sheets which are adjacent and interconnected with horizontal studs. The perforation is diamond-shaped with sides b and h where b < h (invention patent RU 2640525, IPC B01D3 / 20, B01D3 / 28, filed on June 8, 2017, published on January 9, 2018). Deficiencies of this invention are as follows:

[0015] 1) Low residence time of the dispersed phase droplets, which is due to the fact that in reality the droplets move almost in a straight line without changing their trajectory. This results in a lower holding capacity in terms of the dispersed phase, ultimately reducing the efficiency of mass transfer.

[0016] 2) The use of corrugated perforated and expanded sheets leads only to higher intensity of droplet breakup against the packing elements without, however, the reverse process of coalescence. In this case, there is almost no renewal of the contact surface, which might result in diffusion resistance of the mass transfer process.

[0017] SUMMARY OF THE INVENTION

[0018] The invention process had the following objectives:

[0019] - creating such a flow structure of the dispersed phase that in addition to film flow of the dispersed phase the droplets would break up, thus increasing the phase contact area and, as a result, making the mass transfer more efficient;

[0020] - creating such a flow structure of the dispersed phase that in addition to breakup of droplets they would coalesce. This will help equalize the substance concentration in each drop, thus increasing the average driving force of mass transfer process;

[0021] - lengthening the path and residence time of the dispersed phase droplets to increase breakup efficiency;

[0022] - improving the intensity of mass transfer process by increasing the heat and mass transfer rate as a result of additional turbulence of the flow and formation of local eddies when the phases go through the packing.

[0023] These objectives are achieved with the packing for mass transfer equipment that consists of alternating vertical and parallel flat perforated and expanded and corrugated perforated and expanded sheets which are adjacent and interconnected with horizontal studs; the perforation of flat and to-be-corrugated sheets has the shape of a hexagon with width a and height h, where a<h, and the perforation vertex angle 0 varies between 60° and 90°; the corrugated perforated and expanded sheets have areas without perforation or with covered perforation; adjacent corrugated sheets are symmetrical relative to the flat sheet between them, and the phases enter the equipment one of the following ways:

[0024] 1) for liquid-liquid systems, with the dispersed phase density being less than the continuous phase density, the dispersed phase enters via the bottom part of the packing and the continuous phase enters via the top part of the packing;

[0025] 2) for liquid-liquid systems, with the dispersed phase density being more than the continuous phase density, the dispersed phase enters via the top part of the packing and the continuous phase enters via the bottom part of the packing;

[0026] 3) for gas-liquid systems, the liquid phase enters via the top part of the packing and the gas phase enters via the bottom part of the packing.

[0027] In order to lengthen the path and residence time of the dispersed phase droplets, increase the turbulization of flows, it is practical to make the packing for mass transfer equipment with corrugated perforated and expanded sheets that have areas without perforation; before corrugation such sheets should be perforated in certain areas, with the non-perforated areas forming multiple strips. For fabrication of the perforated and expanded sheets, it is practical to use sheets with thickness of up to 1 mm (to reduce steel consumption), the perforation elements should be made so that their width is within 3-5 mm, height is within 8-15 mm. It is practical to make a bridge with width of up to 1.5 mm between adjacent perforation elements.

[0028] It is rational to make the packing for mass transfer equipment by corrugation of perforated and expanded sheets with some areas covered; plates should be electric resistance welded onto the corrugated perforated and expanded sheets for longer path and residence time of the dispersed phase droplets and improved turbulization of the flows. The plates should be placed in pairs on the opposite sides of corrugated perforated and expanded sheets; the plates should be secured to perforated sheets and to each other by electric resistance welding. This will result in greater stability of the plates both during corrugation of the perforated and expanded sheets and during further operation of the packing. Before corrugation of the perforated and expanded sheets for the mass transfer equipment packing, it is practical to use electric resistance welding to attach pairs of thin plates on the opposite sides of the corrugated perforated and expanded sheets, which will increase the turbulization level of mass transfer flows. It is practical to make the plates with thickness of no more than 0.5 mm to provide for subsequent corrugation.

[0029] LIST OF THE DRAWINGS

[0030] The invention is illustrated with Figures 1-12 which show the embodiment of the packing for mass transfer equipment:

[0031] Figure 1 shows a general view of the counterflow packing with corrugated perforated and expanded sheets that have non-perforated areas;

[0032] Figure 2 shows a general view of the counterflow packing with corrugated perforated and expanded sheets and plates for partial covering of perforation;

[0033] Figure 3 shows a fragment of a flat perforated and expanded sheet;

[0034] Figure 4 shows a perforation element;

[0035] Figure 5 shows a fragment of a perforated and expanded sheet with partial perforation;

[0036] Figure 6 shows fabrication stages of a corrugated perforated and expanded sheet with partial perforation;

[0037] Figure 7 shows fabrication stages of a corrugated perforated and expanded sheet with plates welded onto it;

[0038] Figure 8 shows the plate with its basic geometrical dimensions;

[0039] Figure 9 shows an isometric view of a corrugated perforated and expanded sheet with welded plates;

[0040] Figure 10 shows fabrication stages of a corrugated perforated and expanded sheet with plates;

[0041] Figure 11 schematically shows the circulation of flows in the packing;

[0042] Figure 12 shows the trajectory of a droplet in the packing.

[0043] Figures 1-12 show items with the following reference numbers:

[0044] 1 — flat perforated and expanded sheet; 2, 5 — corrugated perforated and expanded sheets;

[0045] 3 — areas without perforation;

[0046] 4 — sheet bracing areas;

[0047] 6 — plates;

[0048] 7 — perforation elements;

[0049] 8 — bridges;

[0050] 9 — perforated and expanded sheet with partial perforation;

[0051] 10 — folding lines;

[0052] 11 — corrugated perforated and expanded sheet with no perforation or covered perforation areas;

[0053] 12-13 — flows;

[0054] 14 — trajectory;

[0055] 15 — droplet breakdown area;

[0056] 16 — droplet coalescence area.

[0057] BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 shows a general view of the counterflow packing with corrugated perforated and expanded sheets that have non-perforated areas. The packing for mass transfer equipment consists of alternating flat perforated and expanded sheets 1 and corrugated perforated and expanded sheets 2 with non-perforated areas 3 that are installed vertically and parallel to each other with some free channels and are interconnected with horizontal studs (not shown in the Figure) in sheet bracing areas 4 to make the structure stiff. Adjacent corrugated perforated and expanded sheets 2 with non-perforated areas 3 are symmetrical relative to flat perforated and expanded sheet 1 between them.

[0059] Figure 2 shows a general view of the counterflow packing with corrugated perforated and expanded sheets and plates for partial covering of perforation. The packing for mass transfer equipment consists of alternating flat perforated and expanded sheets 1 and of corrugated perforated and expanded sheets 5 that are installed vertically and parallel to each other with some free channels and are interconnected with horizontal studs (not shown in the Figure) in sheet bracing areas 4 to make the structure stiff, and of plates 6 for partial covering of perforation that are placed in pairs on the opposite sides of corrugated perforated and expanded sheet 5. Adjacent corrugated perforated and expanded sheets 5 are symmetrical relative to flat perforated and expanded sheet 1 between them.

[0060] Figure 3 shows a fragment of a flat perforated and expanded sheet. The flat perforated and expanded sheet comprises many perforation elements 7, which form the space for the travel of the continuous and the dispersed phases, and bridges 8, which are found between adjacent perforation elements 7, facilitate breakdown of the dispersed phase droplets and serve as the film-holding surfaces.

[0061] Figure 4 shows a perforation element. Dimensions of perforation elements 7 may vary within the following values: perforation width a is 3 to 5 mm, perforation height h is 8 to 15 mm, perforation vertex angle 0 is 60° to 90°.

[0062] Figure 5 shows a fragment of a perforated and expanded sheet with partial perforation. Perforated and expanded sheet with partial perforation 9 comprises many perforation elements 7, bridges 8, and non-perforated areas 3 represented by multiple strips. Perforated and expanded sheet with partial perforation 9 is subjected to corrugation.

[0063] Figure 6 shows fabrication stages of a corrugated perforated and expanded sheet with partial perforation. Corrugated perforated and expanded sheet 2 with nonperforated areas 3 is made by corrugation of perforated and expanded sheet with partial perforation 9 so that the strips of non-perforated areas 3 do not fall within the corrugation vertices and undergo practically no deformation. The corrugation pattern is based on folding lines 10.

[0064] Figure 7 shows fabrication stages of a corrugated perforated and expanded sheet with plates welded onto it. For fabrication of the packing for mass transfer equipment by welding plates 6 onto corrugated perforated and expanded sheet 5, this plate is first made by corrugating flat perforated and expanded sheet 1. Then plates 6 are welded onto this corrugated perforated and expanded sheet 5 on its opposite sides in pairs. Figure 8 shows the plate with its basic geometrical dimensions. Width b’ of plate 6 shall be enough for the plate to stay away from the corrugation vertex, while the plate thickness x’ shall not exceed 0.5 mm.

[0065] Figure 9 shows an isometric view of a corrugated perforated and expanded sheet with welded plates (perforation is not shown for clarity). Plates 6 are welded in pairs onto corrugated perforated and expanded sheet 5 in a staggered pattern for a more even distribution of the dispersed phase droplets and for a more even distribution of the continuous phase velocities within the packed space. As shown in Figure 9, the width of plates 6 shall not exceed the distance between any adjacent corrugation bends.

[0066] Figure 10 shows fabrication stages of a corrugated perforated and expanded sheet with plates. At the first stage, pairs of plates 6 are welded onto flat perforated and expanded sheet 1 in a staggered pattern. Plates 6 are welded in pairs onto the opposite sides of flat perforated and expanded sheet 1. Then this structure is corrugated with folding lines 10 in mind, producing the structure which has already been described in Figure 9 (corrugated perforated and expanded sheet 5 with welded plates 6).

[0067] Figure 11 schematically shows the circulation of flows in the packing. Regardless of its fabrication method, the packing for mass transfer equipment includes flat perforated and expanded sheets 1 and corrugated perforated and expanded sheets with no perforation or covered perforation areas 11 that may be fabricated in various ways: using corrugated perforated and expanded sheets 2 with non-perforated areas 3 (Figure 6) as well as using corrugated perforated and expanded sheets 5 with welded plates 6 (Figure 9). In this case the phase contact is arranged so that the light phase is dispersed and the heavy phase is continuous. The heavier continuous phase travels in flow 12 from the top to the bottom of the packing and the lighter dispersed phase travels in flow 13 as droplets from the top to the bottom along trajectory 14. The dispersed phase droplets consecutively travel in flow 13 through droplet breakdown area 15, which is formed by bridges and sharp edges of perforation elements, and through droplet coalescence area 16, which is formed at the surface of non-perforated / non-covered areas and also where dispersed phase flows 13 directed towards each other meet at the surface of flat corrugated and expanded sheets 1.

[0068] If the dispersed phase is heavier, it shall enter at the top of the packing, while the lighter continuous phase shall enter at the bottom of the packing. However, in this case the packing itself shall be flipped symmetrically to Figure 11 in horizontal plane.

[0069] The intensity of droplet breakdown increases due to sharp edges on the surface of the packing that form when the sheet is perforated. This increases the phase contact area as small droplets with great specific contact area form on the packing surface in addition to thin film. Droplet breakdown will be the most intensive if the packing material repels the dispersed phase.

[0070] Greater intensity of droplet coalescence, in addition to breakdown, is caused by the flows directed towards each other joining together at a certain droplet speed and creating larger droplets. Moreover, droplets will coalesce before non- perforated / non-covered areas in the flow direction of dispersed phase. The coalescence process will help equalize the substance concentration in each drop, thus increasing the average driving force of mass transfer process. The contact surface will renew with greater intensity due to multiple instances of droplet breakdown and coalescence. Moreover, the trajectory of phases promotes the formation of local eddies resulting in greater mass and heat transfer coefficients.

[0071] Figure 12 shows the trajectory of a droplet in the packing. This shows how a droplet of dispersed phase moves in the 100 mm high packing comprising flat perforated and expanded sheets 1 and corrugated perforated and expanded sheets with no perforation or covered perforation areas 11. Trajectory 14 describes how the droplet moves. Better efficiency of mass transfer is guaranteed by the packing that makes the dispersed phase droplets move along trajectory 14 with longer path and residence time, thus increasing the contact duration.

[0072] Example 1. Let us review the trajectory of liquid in the packing with 100 mm bed height. Corrugation height is 10 mm, corrugation vertex angle is 52.5°. Figure 12 shows the trajectory of a droplet in the packing. According to calculation, this droplet trajectory is 43% longer than the straight trajectory the droplet would have (moving vertically upward).

[0073] In conclusion, the invention helps lengthen the path and residence time of dispersed phase droplets in the packing, consequently increasing the heat and mass transfer coefficients and intensifying the renewal of phase contact surface, which will help improve the fractionation efficiency, including when the packing material repels the dispersed phase.

Claims

CLAIMS OF THE INVENTION1. The packing for mass transfer equipment that consists of alternating vertical and parallel flat perforated and expanded and corrugated perforated and expanded sheets which are adjacent and interconnected with horizontal studs; that is characterized by perforation of flat and to-be-corrugated sheets which has the shape of a hexagon with width a and height h, where a<h, and the perforation vertex angle P varying between 60° and 90°; the corrugated perforated and expanded sheets have areas without perforation or with covered perforation; adjacent corrugated sheets are symmetrical relative to the flat sheet between them, and the phases enter the equipment one of the following ways:1) for liquid-liquid systems, with the dispersed phase density being less than the continuous phase density, the dispersed phase enters via the bottom part of the packing and the continuous phase enters via the top part of the packing;2) for liquid-liquid systems, with the dispersed phase density being more than the continuous phase density, the dispersed phase enters via the top part of the packing and the continuous phase enters via the bottom part of the packing;3) for gas-liquid systems, the liquid phase enters via the top part of the packing and the gas phase enters via the bottom part of the packing.

2. The packing for mass transfer equipment according to claim 1 wherein the fabrication of corrugated perforated and expanded sheets with non-perforated areas provides for partial perforation of the sheets before corrugation, with the nonperforated areas forming multiple strips.

3. The packing for mass transfer equipment according to claim 1 wherein the fabrication of corrugated perforated and expanded sheets with covered areas provides for electric resistance welding of plates onto the corrugated perforated and expanded sheets.

4. The packing for mass transfer equipment according to claim 1 wherein thin plates will be electric resistance welded in pairs on the opposite sides of perforated and expanded sheets before corrugation of said perforated and expanded sheets.

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