WO2015183866A1

WO2015183866A1 - Separation of crude acetonitrile from acrylonitrile

Info

Publication number: WO2015183866A1
Application number: PCT/US2015/032538
Authority: WO
Inventors: Timothy Robert Mcdonel; Jay Robert COUCH; David Rudolph Wagner; Paul Trigg Wachtendorf
Original assignee: Ineos Europe Ag
Priority date: 2014-05-30
Filing date: 2015-05-27
Publication date: 2015-12-03
Also published as: EA201692317A1; CN104027994A; CN104027994B; EA033014B1; SA516380397B1

Abstract

An apparatus comprises a column comprising a top, middle and bottom sections. The middle section is configured to receive a first stream comprising acrylonitrile, HCN, acetonitrile, and water. The column is configured to distill the first stream, and produce from the first stream a second stream, the second stream comprising water that is substantially free of acetonitrile. The column is configured to produce a third stream in the top section of the column, the third stream comprising acrylonitrile, HCN, and a portion of the water from the first stream. The column comprises a crude acetonitrile concentration zone defined by a baffle and an interior facing wall of the column. The column is configured to produce in an upper volume of the zone a stream comprising water and acetonitrile that is substantially devoid of acrylonitrile and HCN.

Description

SEPARATION OF CRUDE ACETONITRILE FROM ACRYLONITRILE

FIELD OF THE INVENTION

[1] The invention relates to an improved apparatus and process for the manufacture of acrylonitrile and methacrylonitrile. In particular, the invention is relates to an improved apparatus and process for separation of acetonitrile from acrylonitrile.

BACKGROUND

[2] Various processes and systems for the manufacture of acrylonitrile and methacrylonitrile are known; see for example, U.S. Patent Nos. 3,399,120; 3,442,771; 5,703,268; 5,869,730; and 6,107,509. Conventional processes provide for separation of acrylonitrile from crude acetonitrile, which is a valuable co- product. Conventional processes for separation of acrylonitrile from crude acetonitrile typically involve using at least two columns - a first column and a second column. The first column, also referred to as a recovery column, is configured to substantially separate acrylonitrile and hydrogen cyanide (HCN) from acetonitrile.

[3] A conventional process for separation of acrylonitrile from crude acetonitrile is shown in FIG. 1. As shown in FIG. 1, feed stream 1 from an acrylonitrile absorber (not shown) is sent to first column 10. Feed stream 1 typically contains acrylonitrile, hydrogen cyanide (HCN), acetonitrile, and water. Water stream 2 that is substantially free of acetonitrile is recycled from at or near the bottom of second column 20 to an upper portion of first column 10 in order to facilitate the separation of acetonitrile from acrylonitrile and HCN by extractive distillation. Stream 3 containing acrylonitrile, HCN, and a portion of the water from feed 1 is removed from the top of first column 10. Liquid stream 4 containing water and acetonitrile is sent as feed from the bottom of first column 10 to second column 20. Vapor stream 5 from second column 20 is sent to first column 10 to provide the heat needed for distillation in first column 10. A crude acetonitrile stream 6 containing acetonitrile, water and small amounts of acrylonitrile and HCN is removed from the top of second column 20. The remaining water stream 7, which is substantially free of acrylonitrile, HCN, and acetonitrile and is not recycled as water stream 2 back to first column 10, is discharged from second column 20 at or near the bottom of second column 20.

[4] Another conventional process for separation of acrylonitrile from crude acetonitrile is shown in FIG. 2. As shown in FIG. 2, feed stream 101 from an acrylonitrile absorber (not shown) is sent to first column 110. Feed stream 101 typically contains acrylonitrile, hydrogen cyanide (HCN), acetonitrile, and water. Water stream 102 that is substantially free of acetonitrile is recycled from at or near the bottom of first column 110 to the top of first column 110 in order to facilitate the separation of acetonitrile from acrylonitrile and HCN by extractive distillation. The portion of stream 102 that is not recycled from the bottom to the top of first column 110 is discharged from column 110 as stream 107. Stream 103 containing acrylonitrile, HCN, and a portion of the water from feed stream 101 is removed from the top of first column 110. A vapor side stream 104 containing water and acetonitrile from first column 110 is sent as feed to second column 120. Liquid stream 105 containing water and a small amount of acetonitrile from second column 120 is sent to first column 110 for further stripping of acetonitrile. Crude acetonitrile stream 106 containing acetonitrile, water and small amounts of acrylonitrile and HCN is removed from the top of second column 120. Stream 108, which is water that is substantially free of acrylonitrile, HCN, and acetonitrile, is discharged from the bottom of second column 120.

[5] Conventional systems and methods that require two column systems are costly, and two column systems take up a considerable amount of plot space. Since there are two columns, conventional apparatuses and methods require two pressure vessels, including two shells, two sets of heads, two sets of structure, and interconnecting piping between the two vessels or columns, and two plots for the two vessels or columns. SUMMARY

[6] Accordingly, an aspect of the present disclosure is to provide a safe, efficient and cost effective, method and apparatus that overcomes or reduces the disadvantages of conventional methods and apparatuses.

[7] In an aspect, an apparatus is provided comprising a column comprising a top section, a middle section, and a bottom section. The middle section of the column is configured to receive a first stream, the first stream comprising a feed stream, the feed stream comprising acrylonitrile, hydrogen cyanide (HCN), acetonitrile, and water. The column is configured to distill the first stream, and produce from the first stream a second stream, the second stream comprising water that is substantially free of acetonitrile. The column is configured to recycle the second stream from the bottom section of the column to the top section of the column. The column is configured to produce a third stream in the top section of the single column, the third stream comprising acrylonitrile, HCN, and a portion of the water from the first stream. The column comprises a crude acetonitrile concentration zone defined by a baffle, the crude acetonitrile concentration zone located in the middle section of the column. The crude acetonitrile concentration zone comprises an upper volume and a lower volume. The column is configured to produce in the upper volume of the crude acetonitrile concentration zone a vapor stream, the vapor stream comprising water and acetonitrile that is substantially devoid of acrylonitrile and HCN. The crude acetonitrile concentration zone comprises an upper outlet in the upper volume, the upper outlet configured to allow the vapor stream comprising water and acetonitrile that is substantially devoid of acrylonitrile and HCN to flow out of the column.

[8] In another aspect, a process for separating acetonitrile from acrylonitrile includes providing a first stream that includes acrylonitrile, HCN, acetonitrile and water to a column, distilling the first stream in the column to produce a second stream that includes water and that is substantially free of acetonitrile, a third stream that includes acrylonitrile, HCN and water, and a fourth stream that includes water and acetonitrile and that is substantially free of acrylonitrile and HCN. In this aspect, the fourth stream has about 5 to about 18 weight % acetonitrile.

[9] The above and other aspects, features and advantages of the present disclosure will be apparent from the following detailed description of the illustrated embodiments thereof which are to be read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWINGS

[10] A more complete understanding of the exemplary embodiments of the present invention and the advantages thereof may be acquired by referring to the following description in consideration of the accompanying drawings, in which like reference numbers indicate like features and wherein:

[11] FIG. 1 is a schematic flow diagram of a conventional apparatus;

[12] FIG. 2 is a schematic flow diagram of another conventional apparatus;

[13] FIG. 3 is a schematic flow diagram of an embodiment in accordance with at least one aspect of the disclosure;

[14] FIG. 4 illustrates a flow diagram of a method in accordance with aspects of the disclosure.

DETAILED DESCRIPTION

[15] The process and apparatus of the present disclosure is described in detail with reference to FIG. 3.

[16] Apparatus 300 may be provided for separation of acrylonitrile from crude acetonitrile. As shown in FIG. 3, feed stream 301 from an acrylonitrile absorber (not shown) is sent to first column 310. Feed stream 301 typically contains acrylonitrile, hydrogen cyanide (HCN), acetonitrile, and water. Feed stream 301 may be the same as or similar to feed stream 1 shown in FIG. 1 and/or feed stream 101 shown in FIG. 2.

[17] In an aspect, apparatus 300 comprises a single column 310. Single column 310 comprises a top section 330, a middle section 340, and a bottom section 350. Middle section 340 of the single column 310 may be configured to receive a first or feed stream 301 , the first stream 301 comprising acrylonitrile, hydrogen cyanide (HCN), acetonitrile, and water. First stream 301 may be a stream from an acrylonitrile absorber (not shown). First stream 301 may be the same as or similar to feed stream 1 shown in FIG. 1 and/or feed stream 101 shown in FIG. 2.

[18] Single column 310 is configured to distill first stream 301, and produce from first stream 301 a second stream 302. Second stream 302 may comprise water that is substantially free of acetonitrile. As used herein, substantially free of acetonitrile means a stream having a weight % of acetonitrile of about 0.0001 or less, in another aspect, about 0.00005 or less, and in another aspect, about 0.00004 or less. Single column 310 may be configured to recycle second stream 302 from bottom section 350 to top section 330 of single column 310. Stream 302 may exit bottom section 350 through bottom outlet 410 as shown in FIG. 3, or exit near bottom section 350. The portion of stream 302 that is not recycled from bottom section 350 to top section 330 may be discharged from column 310 as stream 307. Stream 307 may comprise water that is substantially free of acrylonitrile, HCN, and acetonitrile. In one aspect, the column includes a top section and a middle section and a ratio of a diameter of the middle section to the top section is about 1.5 to about 2.5, in another aspect, about 1.75 to about 2.25, and in another aspect, about 1.8 to about 2.

[19] Single column 310 may be configured to produce third stream 303 in top section 330. Third stream 303 may comprise acrylonitrile, HCN, and a portion of the water from first stream 301. Single column 310 may comprise a crude acetonitrile concentration zone 342 defined by a baffle 344 and interior facing wall 346 of middle section 340. Crude acetonitrile concentration zone 342 may be located in middle section 340 of single column 310. Crude acetonitrile concentration zone 342 may comprise an upper volume 348 and a lower volume 352. Crude acetonitrile concentration zone 342 may be configured to produce in upper volume 348 a fourth stream 354. Fourth stream 354 may be a vapor stream that comprises water and acetonitrile that is substantially free of acrylonitrile and HCN. As used herein, substantially free of acrylonitrile means a stream having a weight % of acrylonitrile of about 0.02 or less, in another aspect, about 0.01 weight % or less, in another aspect, about 0.005 weight % or less, and in another aspect, about 0.001 weight % or less. As used herein, substantially free of HCN means a stream having a weight % of HCN of about 0.25 or less, in another aspect, about 0.2 weight % or less, and in another aspect, about 0.1 weight % or less. In another aspect, the fourth stream has about 5 to about 18 weight % acetonitrile, in another aspect, about 5 to about 15 weight %, and in another aspect, about 8 to about 12 weight %.

Crude acetonitrile concentration zone 342 comprises upper outlet 356. Upper outlet 356 may be configured to allow fourth stream 354 to flow out of upper volume 348 of crude acetonitrile concentration zone 342. Fourth stream 354 may flow out of single column 310 through conduit or line 358, which is in fluid communication with upper outlet 356. Fourth stream 354 may flow to heat exchanger 360, wherein vapor in fourth stream 354 is condensed to a liquid, and then exit heat exchanger 360 through conduit or line 362 as fifth stream 366. A portion of stream 366 may be recycled back to single column 310 via conduit or line 364. In this aspect, about 6 to about 12 weight % of the fourth stream is conveyed to an acetonitriles fractionator after further processing, in another aspect, about 7 to about 11 weight %, and in another aspect, about 8 to about 10 weight %. Stream 366 may be sent via conduit or line 368 to an apparatus (not shown) for further processing, e.g., separation of acetonitrile from other components in stream 366, such as water. The fifth stream has about 35 to about 78 weight % acetonitrile, in another aspect, about 35 to about 65 weight %, in another aspect, about 40 to about 60 weight %, and in another aspect, about 45 to about 55 weight %. [21] In an embodiment, crude acetonitrile concentration zone 342 may comprise a plurality of trays extending between baffle 344 and interior facing wall 346, with a bottom tray 370 located at lower volume 352, and a top tray 372 located at upper volume 348, and additional trays (not shown) between bottom tray 370 and top tray 372. The total number of trays in crude acetonitrile concentration zone 342 may be about 5 to about 40 trays, and in another aspect, about 10 to about 20 trays. In an embodiment, the number of trays in crude acetonitrile concentration zone 342 may be fifteen trays, with top tray 372 being the fifteenth tray. Line 364 may be in fluid communication with inlet 374 of crude acetonitrile concentration zone 342. Inlet 374 may be above top tray 372 of crude acetonitrile concentration zone 342. Inlet 374 may be below outlet 356 of upper volume 348.

[22] It has been discovered, surprisingly, that both recovery of acrylonitrile and acetonitrile fractionation may be sufficiently obtained in a single column in accordance with the embodiment shown in FIG. 3. In accordance with the disclosure, the second column that is required in conventional apparatus and methods can be eliminated, such as a second column 20 shown in FIG. 1, and column 120 shown in FIG. 3. By eliminating the need for a second column, there is also no need for a feed line to a second column, such the conduit or line for stream 4 shown in FIG. 1, or the conduit or line for side stream 104 shown in FIG. 2, or the need for associated flow controllers and valves.

[23] Crude acetonitrile concentration zone 342 may have bottom outlet 376 that is in fluid communication with conduit or line 378. Bottom outlet 376 may be placed in a location that allows substantially all of the liquid from tray 370 to be removed from single column 310. For example, outlet 376 may be located at a seal pan 383 associated with and below tray 370. Bottoms stream 380 from crude acetonitrile concentration zone 342 may exit from single column 310 through outlet 376 and then flow through line 378 for further processing and/or storage. Stream 382, which may be all of stream 380 or a portion thereof, may be returned to column 310 via conduit or line 384, which is fluid communication with inlet 386. Alternatively, bottoms stream 380 from crude acetonitrile concentration zone 342 may be ducted internally to a desired location of column 310, e.g., to tray 390 (as shown in FIG. 3) or tray 392, and eliminating lines 378 and 384, e.g., if there is no need to send bottoms stream 380 elsewhere.

[24] Column 310 may comprise a plurality of trays outside of crude acetonitrile concentration zone 342. As shown in FIG. 3, the plurality of trays outside of crude acetonitrile concentration zone 342 may include trays 388, 390, 392, 394, and 396. Tray 388 may be a bottom tray in bottom section 350. Trays 390, 392 and 394 may be middle trays in middle section 340. Tray 396 may be a top tray in section 330. Additional trays (not shown) may be provided between trays 388 and 390, trays 392 and 394, and trays 394 and 396. Trays outside of crude acetonitrile concentration zone 342 may extend across a full horizontal cross section of column 310, for example trays 388, 390, 392, which extend from side or interior facing wall 398 to side or interior facing wall 400, and tray 396 that extends from side or interior facing wall 402 to side or interior facing wall 404. Interior facing wall 400 may comprise interior facing wall 346. Additional trays outside of crude acetonitrile concentration zone 342 may extend across a partial horizontal cross section of column 310, for example tray 394, which extends across side 398 to baffle 344. The total number of trays in column 310 outside of crude acetonitrile concentration zone 342 may be between eighty and one- hundred trays. In an embodiment, the number of trays in column 310 outside of crude acetonitrile concentration zone 342 may be ninety trays. In an embodiment, tray 396 may be the ninetieth tray in column 310 located outside of crude acetonitrile concentration zone 342.

[25] As shown in FIG. 3, in an embodiment, the crude acetonitrile concentration zone comprises a first plurality of trays, the first plurality of trays extending between baffle 344 and the first interior facing wall 346. The trays of the first plurality of trays are located at different heights of the column, and each tray of the first plurality of trays comprises a horizontal plane extending across a cross section of crude acetonitrile concentration zone 342. Crude acetonitrile concentration zone 342 comprises bottom tray 370 in lower volume 352, top tray 372 in upper volume 348, and at least one tray (not shown) between the bottom tray and the top tray of the crude acetonitrile concentration zone. [26] As shown in FIG. 3, a lower recycle loop may be provided. The lower recycle loop may be configured to recycle at least a portion of a stream from the bottom outlet 376 of the crude acetonitrile concentration zone 342 to a middle inlet 386 of the middle section 340 of the column 310, the middle inlet 386 located below the crude acetonitrile concentration zone 342. At least a portion of the lower recycle loop may be located outside the column. Alternatively, the lower recycle loop may be located inside the column. In accordance with an aspect, apparatus 300 provides capability to either recycle stream 380 to column 310 via line 384, and/or to withdraw stream 380 via line 378 and send stream 380 elsewhere in the acrylonitrile plant.

[27] As shown in FIG. 3, the column may comprise a second plurality of trays, the second plurality of trays located outside the crude acetonitrile concentration zone 342, wherein trays of the second plurality of trays are located at different heights of the column, and each tray of the second plurality of trays comprises a horizontal plane extending across a cross section of the column.

[28] Those skilled in the art will recognize that in accordance with the disclosure, tray 394 may be the same tray as tray 372, wherein baffle 344 extends through the tray, rather than tray 394 being a separate tray from tray 372. In this alternative embodiment, the tray has a portion outside of crude acetonitrile concentration zone 342 and a separate portion in crude acetonitrile concentration zone 342. Additional trays in middle section 340 may have a portion outside of crude acetonitrile concentration zone 342, and a separate portion in crude acetonitrile concentration zone 342. In another embodiment, baffle 344 may comprise a series of baffle segments, wherein each baffle segment extends between pairs of trays of the first plurality of trays.

[29] Stream 301 may enter column 310 through inlet 408. Inlet 408 may be located between tray 394 and the tray (not shown) above tray 394. Tray 394 may be between the fifty-eighth to the sixty-eighth tray from bottom section 350. In an embodiment, tray 394 is the sixty-fourth tray from bottom section 350. [30] Inlet 386 of column 310 may be located between tray 370 and tray 390 in middle section 340. In an embodiment, tray 390 may be the twenty-fifth to the thirty- third tray from bottom section 350, and tray 392 may be the twenty-sixth to the thirty-fourth tray from bottom section 350. In an embodiment, tray 390 is the twenty-ninth tray from bottom section 350, and tray 392 is the thirtieth tray from bottom section 350.

[31] Inlet 406 of column 310 may be in fluid communication with stream 302. Inlet 406 may be located in top section 330 of column 310. Inlet 406 may be configured to receive stream 302 in column 310 above tray 396.

[32] Stream 366 may be a crude acetonitrile stream having acetonitrile and water and substantially devoid of acrylonitrile and HCN. Water that was part of stream 301 and which exits column 310 as stream 307 may be substantially free of acrylonitrile, HCN, and acetonitrile. Stream 307 may be discharged at or near bottom section 350 of column 310.

[33] In an aspect, flow controller 357 may be configured to adjust valve 359. In an aspect controller 68 may be configured to process one or more signals corresponding to a measured parameter. Controller 68 may be configured to determine whether the measured parameter is above or below a predetermined parameter range. Controller 68 may be configured to adjust operation of one or more devices via communication lines or wireless communications (not shown in FIG. 1) if the measured parameter is below or above a predetermined parameter range. For example, when a measured parameter is outside a predetermined parameter range, controller 68 may be configured to adjust the amount of flow through valves 359, 379, and/or 381, such as adjusting the size of the opening of the valves. Those skilled in the art will recognize that controller 68 or a similar controller may be located remote from flow controller 357 (as shown in FIG. 1), or may be located at and comprise flow controller 357.

[34] FIG. 4 illustrates a flow diagram of a method 400 in accordance with aspects of the disclosure. Method 400 may be carried out using apparatus shown in FIG. 3 as previously described. Step 401 comprises receiving a first stream in a middle section of a column, the first stream comprising acrylonitrile, hydrogen cyanide (HCN), acetonitrile, and water. Step 402 comprises distilling the first stream in the column and producing from the first stream a second stream, the second stream comprising water that is substantially free of acetonitrile. Step 403 comprises recycling the second stream from a bottom section of the column to a top section of the column. Step 404 comprises producing a third stream in the top section of the column, the third stream comprising acrylonitrile, HCN, and a portion of the water from the first stream. Step 405 comprises producing a fourth stream comprising water and acetonitrile that is substantially devoid of acrylonitrile and HCN in an upper volume of a crude acetonitrile concentration zone of the column, the crude acetonitrile concentration zone defined by a baffle and a first interior facing wall of the middle section of the column, the crude acetonitrile concentration zone located in the middle section of the column. Step 406 comprises allowing the fourth stream to flow out of the column.

[35] In one aspect, the process may utilize the following ratios. A ratio of a rate of the first stream to a rate of the second stream is about 1.9 to about 2.4, in another aspect, about 1.9 to about 2.3, and in another aspect, about 2.0 to about 2.2. A ratio of a rate of the first stream to a rate of the third stream is about 12 to about 15.5, in another aspect, about 12 to about 15, and in another aspect, about 12 to about 14. A rate of the first stream to a rate of the fifth stream conveyed to an acetonitriles fractionator is about 257 to about 315, in another aspect, about 260 to about 310, and in another aspect, about 275 to about 300.

[36] While in the foregoing specification this disclosure has been described in relation to certain preferred embodiments thereof, and many details have been set forth for purpose of illustration, it will be apparent to those skilled in the art that the disclosure is susceptible to additional embodiments and that certain of the details described herein can be varied considerably without departing from the basic principles of the disclosure. It should be understood that the features of the disclosure are susceptible to modification, alteration, changes or substitution without departing from the spirit and scope of the disclosure or from the scope of the claims. For example, the dimensions, number, size and shape of the various components may be altered to fit specific applications. Accordingly, the specific embodiments illustrated and described herein are for illustrative purposes only.

Claims

WE CLAIM:

1. An apparatus comprising:

a column comprising a top section, a middle section, and a bottom section, the middle section configured to receive a first stream, the first stream comprising acrylonitrile, hydrogen cyanide (HCN), acetonitrile, and water;

the column configured to distill the first stream and produce from the first stream a second stream, the second stream comprising water that is substantially free of acetonitrile;

the column configured to recycle the second stream from the bottom section to the top section of the column;

the column configured to produce a third stream in the top section of the column, the third stream comprising acrylonitrile, HCN, and a portion of the water from the first stream;

the column comprising a crude acetonitrile concentration zone defined by a baffle and a first interior facing wall of the middle section of the column, the crude acetonitrile concentration zone located in the middle section of the column, the crude acetonitrile concentration zone comprising an upper volume and a lower volume;

the column configured to produce in the upper volume of the crude acetonitrile concentration zone a fourth stream, the fourth stream comprising water and acetonitrile that is substantially devoid of acrylonitrile and HCN;

the crude acetonitrile concentration zone comprising an upper outlet in the upper volume, the upper outlet configured to allow the vapor stream comprising water and acetonitrile that is substantially devoid of acrylonitrile and HCN to flow out of the column.

2. The apparatus of claim 1 , further comprising a heat exchanger, the heat exchanger configured to receive and cool the fourth stream.

3. The apparatus of claim 2, further comprising an upper recycle loop, the upper recycle loop configured to recycle at least a portion of the fourth stream to the crude acetonitrile concentration zone after being cooled in the heat exchanger.

4. The apparatus of claim 3, wherein the crude acetonitrile concentration zone comprises an upper inlet in fluid communication with recycle loop, the upper inlet configured to receive from the recycle loop the portion of the fourth stream after being cooled in the heat exchanger.

5. The apparatus of claim 4, wherein the upper inlet is located below the upper outlet of the crude acetonitrile concentration zone.

6. The apparatus of claim 5, wherein the crude acetonitrile concentration zone comprises a first plurality of trays, the first plurality of trays extending between the baffle and the first interior facing wall, wherein the trays of the first plurality of trays are located at different heights of the column, and each tray of the first plurality of trays comprises a horizontal plane extending across a cross section of the crude acetonitrile concentration zone, wherein the crude acetonitrile concentration zone comprises a bottom tray in the lower volume, a top tray in the upper volume, and at least one tray between the bottom tray and the top tray of the crude acetonitrile concentration zone.

7. The apparatus of claim 6, trays wherein the total number of trays in the crude acetonitrile concentration zone is about 5 to about 40.

8. The apparatus of claim 6, wherein the total number of trays in the crude acetonitrile concentration zone is about 10 to about 20.

9. The apparatus of claim 6, wherein the upper inlet of the crude acetonitrile concentration zone is located above the top tray of the crude acetonitrile concentration zone.

10. The apparatus of claim 6, wherein the crude acetonitrile concentration zone comprises a bottom outlet located in the lower volume and below the bottom tray of the crude acetonitrile concentration zone.

11. The apparatus of claim 10, wherein a seal pan comprises the bottom outlet of the crude acetonitrile concentration zone, the seal pan configured to receive liquid from the bottom tray of the crude acetonitrile concentration zone.

12. The apparatus of claim 11, further comprising a lower recycle loop, the lower recycle loop configured to recycle at least a portion of a sixth stream from the bottom outlet of the crude acetonitrile concentration zone to a middle inlet of the middle section of the column, the middle inlet located below the crude acetonitrile concentration zone.

13. The apparatus of claim 12, wherein at least a portion of the lower recycle loop is located outside of the column.

14. The apparatus of claim 12, wherein the lower recycle loop is located inside the column.

15. The apparatus of claim 6, wherein the column comprises a second plurality of trays, the second plurality of trays located outside the crude acetonitrile concentration zone, wherein trays of the second plurality of trays are located at different heights of the column, and each tray of the second plurality of trays comprises a horizontal plane extending across a cross section of the column.

16. The apparatus of claim 15, wherein at least one tray of the second plurality of trays extends from a second interior facing wall to the baffle, wherein the second interior wall is separated from the crude acetonitrile concentration zone by the baffle.

17. The apparatus of claim 16, wherein the total number of the second plurality of trays is between eighty and one-hundred trays.

18. The apparatus of claim 16, wherein the total number of the second plurality of trays is ninety trays.

19. The apparatus of claim 6, wherein the baffle extends vertically through at least one tray, the at least one tray having a horizontal plane extending across a cross section of the crude acetonitrile zone, and a horizontal plane extending across a cross section of the column outside of the crude acetonitrile zone.

20. The apparatus of claim 19, wherein the column comprises a second plurality of trays, the second plurality of trays located outside the crude acetonitrile concentration zone, wherein trays of the second plurality of trays are located at different heights from each other, and each tray of the second plurality of trays comprises a horizontal plane extending across a cross section of the column.

21. The apparatus of claim 6, wherein the baffle comprises a series of baffle segments, wherein each baffle segment extends between pairs of trays of the first plurality of trays.

22. The apparatus of claim 21, wherein the column comprises a second plurality of trays, the second plurality of trays located outside the crude acetonitrile concentration zone, wherein trays of the second plurality of trays are located at different heights of the column, and each tray of the second plurality of trays comprises a horizontal plane extending across a cross section of the column.

23. The apparatus of claim 1, wherein a ratio of a diameter of the middle section to a diameter of the top section is about 1.5 to about 2.5.

24. A process for separating acetonitrile from acrylonitrile, the process comprising:

providing a first stream that includes acrylonitrile, HCN, acetonitrile and water to a column; and

distilling the first stream to produce a second stream that includes water and that is substantially free of acetonitrile, a third stream that includes acrylonitrile, HCN and water, and a fourth stream that includes water and acetonitrile and that is substantially free of acrylonitrile and HCN, wherein the fourth stream has about 5 to about 18 weight % acetonitrile.

25. The process of claim 24, wherein the fourth stream is cooled to produce a fifth stream having about 35 to about 78 weight % acetonitrile.

26. The process of claim 25, wherein about 6 weight % to about 12 weight % of the fourth stream is conveyed to the acetonitriles fractionator.

27. The process of claim 24, wherein a ratio of a rate of the first stream to a rate of the second stream is about 1.9 to about 2.4.

28. The process of claim 24, wherein a ratio of a rate of the first stream to a rate of the third stream is about 12 to about 15.5.

29. The process of claim 25, wherein a ratio of a rate of the first stream to a rate of the fifth stream conveyed to an acetonitriles fractionator is about 257 to about 315.

30. The process of claim 24, wherein the process is conducted in a single column.

31. The process of claim 30, wherein the first stream is provided to a middle section of the column.

32. The process of claim 31, wherein the middle section of the column includes a baffle and a first interior facing wall.

33. The process of claim 31, wherein the middle section includes from about 5 to about 40 trays.

34. The process of claim 33, wherein the middle section includes from about 10 to about 20 trays.

35. The process of claim 31, wherein the column includes a top section and a ratio of a diameter of the middle section to the top section is about 1.5 to about 2.5.