MASS TRANSFER COLUMN WITH CROSS FLOW OF LIQUID AND GAS (VAPOUR) PHASES OF PETON SYSTEM

Abstract

The invention relates to cross-flow packing heat and mass transfer column vessels, where rectifying separation of liquid-vapour mixtures, distillation of liquid-vapour mixtures, and absorptive separation of liquid-vapour mixtures occur, and may be used in oil-refining, petrochemical, chemical, gas, food, and other industries.

The proposed mass transfer column with cross flow of liquid and gas (vapour) phases of PETON system includes a shell, a feed nozzle, distillate and residue withdrawal nozzles, nozzles of injection and withdrawal of auxiliary flows, cross-flow packing sections separated heightwise by horizontal baffles having, successively, in the direction of gas (vapour) phase, in the normal shell cross section, a window for gas (vapour) flowing on the packing section inlet side and a continuous area on the packing section outlet side, which alternate on the horizontal baffles neighbouring by height, with liquid distributors between the packing adjacent sections and above the packing upper section, which consist of three successively mating parts: a horizontal leaf, a set of steps, and a blind pocket.

The invention allows achieving the objective of development of a highly efficient mass transfer column that allows for a dramatic variation of the liquid phase flow rates, which ensures a considerable extension of the vessel stable operation range as well as the possibility to use the contact devices with a different number of flows in one vessel.

Claims

1. A mass transfer column with cross flow of liquid and gas (vapour) phases of a PETON system including a shell, a feed nozzle, distillate vapor and residue withdrawal nozzles, nozzles of injection and withdrawal of auxiliary process gas (vapour) and liquid flows, cross-flow packing sections limited on the two opposite sides by continuous side walls and separated heightwise by horizontal baffles having, successively, in the direction of gas (vapour) phase, in normal cross section of the shell, a window for gas (vapour) flowing on the inlet side of the cross-flow packing section and a continuous area on the outlet side of the cross-flow packing section, which alternate on the horizontal baffles neighbouring by height, with liquid distributors between the adjacent sections of the cross-flow packing and above the upper section of the cross-flow packing, wherein it is a horizontal leaf tightly attached to two opposite continuous side walls with a bent-down edge and mated to a part B on the opposite side; wherein the part B is shaped as a set of steps, each step being made of two mating continuous end and perforated drain plates that are tightly attached to two opposite continuous side walls limiting the cross-flow packing section, the drain plate of a lower step being mated to a part C; wherein the part C is shaped as a blind pocket tightly attached to two opposite continuous side walls, with a bottom and a side, the upper edge of the blind pocket side being mated to the drain plate of the part B lower step; the opposite side of the blind pocket is mated to the shell and the bent-down edge of a part A horizontal leaf is lowered into part C with a gap relative to the blind pocket bottom; the upper step of part B is equipped with a vertical plate partially isolating the gas phase outflow from the packing layer of the cross-flow packing downstream section and the lower part of the packing layer of the cross-flow packing upstream section.

2. The mass transfer column as defined in claim 1, wherein the liquid distributor part B drain plates are positioned horizontally.

3. The mass transfer column as defined in claim 1, wherein the liquid distributor part B horizontal drain plates are of equal width.

4. The mass transfer column as defined in claim 1, wherein a width of the liquid distributor part B horizontal drain plates gradually increases from the lower step to the upper one.

5. The mass transfer column as defined in claim 1, wherein the liquid distributor part B drain plates are made inclined at an acute angle to the horizon from the lower step to the upper one.

6. The mass transfer column as defined in claim 1, wherein the liquid distributor part B inclined drain plates are of equal width.

7. The mass transfer column as defined in claim 1, wherein a width of the liquid distributor part B inclined drain plates gradually increases from the lower step to the upper one.

8. The mass transfer column as defined in claim 1, wherein the vertical plate is used to partially isolate the lower part of the packing layer of the cross-flow packing upstream section to the height that ensures the liquid phase flow rate corresponding to the maximum column reflux stream capacity via the liquid distributor.

9. The mass transfer column as defined in claim 1, wherein the gap between the bent-down edge of the part A horizontal leaf and the bottom of the part C blind pocket does not exceed half height of the part B lower step end plate, which ensures the liquid phase flow rate corresponding to the minimum column reflux stream capacity via the liquid distributor.

10. The mass transfer column as defined in claim 1, wherein the column is built symmetrically to the multi-flow one in terms of liquid and gas (vapour) phases.

11. The mass transfer column as defined in claim 10, wherein, in the multi-flow column the bottoms of blind pockets at two symmetrical opposite sections of cross-flow packings in the vertical set of cross-flow packing sections forming one flow are joined using a solid bridge that isolates the gas (vapour) phase supply channel.

12. The mass transfer column as defined in claim 11, wherein the gap between the bent-down edge of the part A horizontal leaf lowered into part C and the blind pocket bottom is equal to the height of 15-30% of the part B lower steps; the edge of the part A horizontal leaf is offset towards the part B upper step with a vertical plate by the value equal to the total length of 15-30% of the part B lower steps.

13. The mass transfer column as defined in claim 2, wherein the liquid distributor part B horizontal drain plates are of equal width.

14. The mass transfer column as defined in claim 2, wherein a width of the liquid distributor part B horizontal drain plates gradually increases from the lower step to the upper one.

15. The mass transfer column as defined in claim 5, wherein the liquid distributor part B inclined drain plates are of equal width.

16. The mass transfer column as defined in claim 5, wherein a width of the liquid distributor part B inclined drain plates gradually increases from the lower step to the upper one.

Description

LIST OF DRAWINGS

[0037] FIGS. 1 to 11 show the structural design of the claimed invention:

[0038] FIG. 1. General view of the mass transfer column with cross flow of liquid and gas (vapour) phases of PETON system

[0039] FIG. 2. Mass transfer column distributor

[0040] FIG. 3. The distributor operating principle at the liquid phase minimum design flow rate

[0041] FIG. 4. The distributor operating principle at the liquid phase operating flow rate

[0042] FIG. 5. The distributor operating principle at the liquid phase maximum design flow rate

[0043] FIG. 6. The distributor operating principle at the liquid phase over-maximum design flow rate

[0044] FIG. 7. Part B shaped as a set of steps, in which the liquid distributor drain plates are positioned horizontally, with equal width of the plates

[0045] FIG. 8. Part B shaped as a set of steps, in which the liquid distributor drain plates are positioned horizontally, with the width of plates gradually increasing from the lower step to the upper one

[0046] FIG. 9. Part B shaped as a set of steps, in which the liquid distributor drain plates are made inclined and positioned at an acute angle to the horizon from the lower step to the upper one, with equal width of the plates

[0047] FIG. 10. Part B shaped as a set of steps, in which the liquid distributor drain plates are made inclined and positioned at an acute angle to the horizon from the lower step to the upper one, with the width of plates gradually increasing from the lower step to the upper one

[0048] FIG. 11. Fragment of a double-flow option of the multi-flow column

[0049] FIG. 12 shows the distributor operating principle at offset of the horizontal leaf edge.

[0050] FIGS. 13 to 15 are the pictures of the test bench used in various hydrodynamic operating modes of the mass transfer packed column with the water-air system liquid distributor.

[0051] FIGS. 1 to 12 use the following legend:

[0052] 1. Column shell

[0053] 2. Cross-flow packing section

[0054] 3. Feed nozzle

[0055] 4. Distillate vapor withdrawal nozzle

[0056] 5. Residue withdrawal nozzle

[0057] 6. Reflux injection nozzle

[0058] 7. Reboiler vapour injection nozzle

[0059] 8. Part A of the liquid distributorhorizontal leaf with bent-down edge

[0060] 9. Part B of the liquid distributor shaped as a set of steps

[0061] 10. Part C of the liquid distributor shaped as a blind pocket with a bottom and a side

[0062] 11. Vertical plate

[0063] 12. Bridge

BRIEF DESCRIPTION OF DRAWINGS

[0064] The mass transfer column with cross flow of liquid and gas (vapour) phases of PETON system operates, for example in case of rectification of the initial hydrocarbon vapour-liquid mixture, as follows (FIG. 1). The feedstockhydrocarbon vapour-liquid mixtureis fed for fractionation to column shell 1 with cross-flow packing sections 2 through feed nozzle 3, while being separated in the column free space into liquid and vapour phases. Distillate in the vapour phase and residue in the liquid phase resulting from fractionation are removed from column shell 1 through nozzles 4 and 5 respectively. A part of distillate having been condensed in the cooler (not shown in FIG. 1) returns to column shell 1 via reflux injection nozzle 6 for liquid reflux of upper cross-flow packing section 2. A part of residue having been evaporated in the reboiler (not shown in FIG. 1) returns to column shell 1 via nozzle 7 for vapour reflux of lower cross-flow packing section 2. In cross-flow packing sections 2, mass transfer occurs between vertically descending liquid phase film streaming down packing 2 and horizontally passing vapour phase flow, in the course of which the liquid phase is enriched with high-boiling feedstock components and the vapour phase with low-boiling ones. The vapour phase goes through the entire vertical cross section of cross-flow packing section 2 and the liquid phase goes through the part of the horizontal cross section of cross-flow packing section 2 that is proportional to the liquid phase flow rate, which is possible due to the design of the liquid distributor consisting of three parts A, B and C: horizontal leaf with bent-down edge 8, set of steps 9 and blind pocket with bottom and side 10 respectively. The liquid phase flows from cross-flow packing upstream section 2 to horizontal leaf 8 of the liquid distributor and streams down along the bent-down edge to blind pocket with side 10 in the amount proportional to the liquid phase flow rate, thus forming the appropriate liquid phase level in pocket with side 10 mated to ascending set of steps 9, each step having perforated holes in its horizontal area, to allow for the liquid phase streaming down to cross-flow packing downstream section 2, which ensures reflux of the respective fragment of cross-flow packing downstream section 2 (FIG. 2). Therefore, part of fragments of cross-flow packing downstream section 2 located under the lower steps of set of steps 9 filled with liquid phase, is refluxed with liquid phase and participates in the mass transfer process, and the remaining part of fragments of cross-flow packing downstream section 2 located under the upper steps of set of steps 9 not filled with liquid phase is not refluxed with liquid phase and remains dry, not participating in the mass transfer process. During mass transfer column operation, as the liquid phase flow rate increases as per the process mode, the next upper steps of set of steps 9 are filled and the next fragments of cross-flow packing downstream section 2 switch over to the mass transfer mode. Such operation of the liquid distributor considerably extends the mass transfer column stable operation range.

[0065] At liquid phase minimum design flow rate, the mass transfer column operates on the first lower step of set of steps 9 with the liquid phase level that exceeds the differential pressure when the liquid phase flows through the perforated plate of the first lower step, which ensures the required liquid phase flow in the column to the final packing fragment of cross-flow packing downstream section 2 in the direction of vapour stream (FIG. 3).

[0066] At a certain operation mode with a given liquid phase flow rate, the mass transfer column operates at the liquid phase level that provides filling of the respective part of lower steps of set of steps 9, which ensures the required liquid phase flow in the column to the respective packing fragments of cross-flow packing downstream section 2 in the direction of vapour stream (FIG. 4).

[0067] At liquid phase maximum design flow rate, the mass transfer column operates in the mode, where the entire volume of liquid phase distributor is filled up to the space between the last upper step of set of steps 9 and horizontal leaf 8 is filled with liquid phase, which ensures the required liquid phase flow in the column to all packing fragments of cross-flow packing downstream section 2 in the direction of vapour stream (FIG. 5). If liquid phase actual flow rate exceeds the maximum design flow rate, the liquid distributor will overfill and the excessive liquid phase will overflow through vertical plate 11 from the cross-flow packing upstream section to the blind pocket of the cross-flow packing downstream section (FIG. 6).

[0068] Depending on the mass transfer column operational specifics, the drain plates of set of steps 9 with perforated holes can have equal length in case of uniform variation of the column liquid phase capacity (FIGS. 7 and 9) or have different length in case of the non-uniform variation of the column liquid phase capacity (FIGS. 8 and 10).

[0069] Depending on the mass transfer column operational specifics, the drain plates of set of steps 9 with perforated holes can be horizontal in case of discrete variation of the column liquid phase capacity (FIGS. 7 and 8) or be inclined at an acute angle to the horizon with the ability of almost indiscrete variation of the column liquid phase capacity (FIGS. 9 and 10) from the minimum value to the maximum one.

[0070] FIG. 11 shows a fragment of a double-flow option of the multi-flow column, where, to reduce the column hydraulic resistance, the column shell accommodates two parallel sets of cross-flow packing sections, where the blind pocket bottoms of two symmetrical cross-flow packing sections of the vertical set of cross-flow packing sections forming one flow are joined by solid bridge 12 isolating the vapour phase supply channel.

[0071] FIG. 12 shows a fragment of the reconstructed mass transfer column with an increased cross section of the cross-flow packing section, leading to offset of the distributor horizontal leaf edge deep into the inter-section space.

[0072] In case of absorption gas treatment with liquid absorbent, the mass transfer column with cross flow of liquid and gas (vapour) phases of PETON system operates in a similar manner.

[0073] The claimed invention is corroborated by the following embodiments.

[0074] Embodiment 1. In the continuous mass transfer column with a 100 % rated maximum flow rate of reflux stream in the column, the liquid distributors have a set of 10 steps with horizontal perforated drain plates; herewith, the liquid phase level on the perforated drain plate at the lower step equaling half height of the end plate of the lower step will ensure the minimum flow rate of reflux stream of at least 5%, which forms the range of stable operation of the mass transfer column in the range of at least 5-100%; and the vessel is capable of self-similar implementation of at least 11 process modes of reflux stream rate.

[0075] Embodiment 2. The batch mass transfer column separates a four-component reaction mixture comprising 10%, 20%, 30% and 40% (respectively) of various components at gradually increasing boiling temperature and with reflux ratio of 10 at withdrawal of each component. The liquid distributors have a set of three steps with horizontal perforated drain plates with equal width. During the batch mass transfer column operation, in case of stripping of the first component the first lower step of the liquid distributor will be in operation, in case of stripping of the second componenttwo lower steps of the liquid distributor, in case of stripping of the third componentall the three steps of the liquid distributor.

[0076] Embodiment 3. The batch mass transfer column separates a four-component reaction mixture comprising 20%, 10%, 30% and 40% (respectively) of various components at gradually increasing boiling temperature and with reflux ratio of 10 at withdrawal of each component. The liquid distributors have a set of three steps with horizontal perforated drain plates with equal width. During the batch mass transfer column operation, in case of stripping of the first component two lower step of the liquid distributor will be in operation, in case of stripping of the second componentonly one lower step, in case of stripping of the third componentall the three steps of the liquid distributor.

[0077] Embodiment 4. In the continuous mass transfer column with a 100% rated maximum flow rate of the reflux stream in the column, the liquid distributors have a set of 10 steps with horizontal perforated drain plates. During the column reconstruction, in order to increase the reflux flow rate up to 120%, the cross section of the cross-flow packing section was enlarged by 20%, therefore the number of steps of the liquid distributor was increased from 10 to 12, the bent-down edge of the part A horizontal leaf was raised above the blind pocket bottom to the height of two additional lower steps of part B and shifted towards the upper step of part B by the value equal to total length of two additional lower steps of part B. As a result of the described reconstruction, the liquid phase capacity of the mass transfer column increased up to 120% with a quite broad range of the column stable operation maintained from 20% to 100%.

[0078] Embodiment 5. On the full-scale bench 2000 mm high and 400 mm wide, operational hydrodynamics with the water-air system of the double-flow option fragment of multi-flow column was tested under the claimed invention, where, to reduce the column hydraulic resistance, the column shell accommodates two parallel sets of cross-flow packing sections, where the blind pocket bottoms of two symmetrical cross-flow packing sections of the vertical set of cross-flow packing sections forming the single flow are joined by solid bridge isolating the vapour phase supply channel. FIGS. 13 to 15 illustrate different stages of the study. FIG. 13 demonstrates operation of the double-flow column bottom part at the 80% liquid phase flow rate; FIG. 14 demonstrates operation of the double-flow column bottom part at the 50% liquid phase flow rate, FIG. 15 demonstrates the liquid distributor operation of one section of the double-flow column at the 90% liquid phase flow rate. The tests showed that the column stable operation range under the claimed invention is within 5% to 100%. The tests showed that the column stable operation range under the claimed invention is within 5% to 100%.

[0079] Therefore, the claimed invention allows achieving the objective of development of a highly efficient mass transfer column that allows for a dramatic variation of the liquid phase flow rates, which ensures a considerable extension of the vessel stable operation range well as the possibility to use the contact devices with a different number of flows in one vessel.