CN114870421A

CN114870421A - Head fraction column pump cycle

Info

Publication number: CN114870421A
Application number: CN202210464254.3A
Authority: CN
Inventors: T.R.麦克唐奈; L.L.杰克逊; D.R.瓦纳; P.T.瓦赫滕多夫; J.R.库奇
Original assignee: Ineos Europe AG
Current assignee: Ineos Europe AG
Priority date: 2015-11-16
Filing date: 2015-11-16
Publication date: 2022-08-09
Also published as: WO2017087175A1; TR201806463T1; RU2721779C2; RU2018120739A; RU2018120739A3; CN106699599A

Abstract

The invention relates to head-end column pump-around. Specifically, a process and system for acrylonitrile and HCN recovery includes a heads column system that operates to reduce the heads column condenser duty and reduce equipment while maintaining desired purity and specifications with minimal increase in reboiler duty. In one aspect, the process includes providing a feed stream comprising acrylonitrile, HCN, and water to a head-end column; distilling the feed stream in a heads column to produce a heads column overhead stream comprising HCN and a bottoms liquid stream comprising acrylonitrile; removing a side stream from a side draw of a head-end column comprising water and organics; separating at least some of the water and organics from the side stream to provide an organic stream; returning the organic stream to the head-end column; and adjusting a ratio of an amount of the side stream removed from the side draw of the heads column to an amount of the organic stream returned to the heads column below the side draw to provide 500ppm or less HCN to the bottoms liquid stream.

Description

Head fraction column pump circulation

Technical Field

A process and system for acrylonitrile and HCN recovery is provided. More specifically, the heads column (heads column) system operates to reduce the head column condenser loading and reduce equipment requirements while maintaining the desired purity specification with minimal increase in reboiler loading.

Background

The acrylonitrile manufacturing process produces HCN. HCN must be removed from the acrylonitrile in this process in order to meet the final acrylonitrile specification. HCN can be a valuable by-product so that the process is expected to recover purified HCN. To minimize human exposure, the system is in place to remove HCN and reduce exposure to HCN during equipment operation or maintenance. In some aspects, the manufacturing system utilizes equipment that can handle HCN with low risk of leakage. For example, a system utilizing gravity flow helps eliminate the need for pumps in HCN processing. However, fouling (particularly of trays) is often a problem in acrylonitrile plants. The polymerization of HCN can be a problem in the production of acrylonitrile.

One important system for removing HCN in an acrylonitrile manufacturing process involves the use of a head-end column. Head-end column 30 includes a plurality of trays. In one embodiment, the top fraction column 30 includes between fifty (50) and seventy-five (75) trays, alternatively between fifty-five (55) and sixty-five (65) trays. In an embodiment, the head fraction column 30 includes sixty-two (62) trays, alternatively sixty (60) or sixty-five (65) trays. The heads column 30 can be configured to receive the crude nitrile feed stream 1 at tray 28. In the embodiment, the trays 28 can in each case be located, starting from the bottom of the top-fraction column 30, between the thirty-fifth and forty-eighth trays, preferably between forty and forty-fourth forty trays. The heads column 30 can be configured to remove the side stream 44 from a side draw (sidedraw) of the heads column, which includes water and organics located in each case between the fifteenth and twenty-eight trays, preferably between the eighteen and twenty-five trays, from the bottom of the heads column 30. In alternative embodiments, tray 28 can be the fourth twelve or thirty-eight trays from the bottom of head end column 12.

In an alternative embodiment, tray 28 can be the forty-seventh tray from the bottom of head end column 30, and head end column 30 can include sixty-seven trays. In the examples, the first to twenty bottom trays of the head end column 30 dry the acrylonitrile product. In the examples, HCN is removed and purified from the twenty first to forty second trays from the bottom of the top fraction column 30. In an embodiment, the head-end column 30 includes between forty (40) and sixty-five (65) trays. In an embodiment, and feed tray 28 may be between and include the twentieth and thirty-th trays from the bottom of the head fraction column.

In some designs, the head-end column includes two column sections stacked on top of each other. In this design, the bottom section is referred to as the drying column/section and comprises between 15 and 30 trays, preferably between 18 and 25, more preferably between 18 and 22. In another aspect, the head end column comprises trays 1 to 20, wherein tray 1 is the lowermost tray. The top column section is where the HCN is distilled overhead and is referred to as the head-end column/section or HCN column/section and, in one aspect, includes between 30 and 50 trays, preferably between 32 and 48, and more preferably between 38 and 48 trays. In another aspect, the column comprises trays 21 to 62, wherein tray 62 is the highest tray. These numbers may be different in different heads.

To help reduce fouling, conventional head-end drying columns operate at reduced pressure (vacuum) operation. This mode of operation dramatically reduces fouling and extends the operating time between cleanings of the HCN or heads column. Operation of the HCN or heads column at reduced pressure requires distillation at lower temperatures. The polymerization reaction rate to produce solids that foul process equipment is greatly reduced at lower temperatures. However, as a compromise, lower temperature distillation is required to provide lower condensation temperatures. This requires a chilled coolant, for example, a chilled ethylene-glycol-water mixture, commonly referred to as "brine". Brine may require a temperature of about 0 ℃ for the heads column condenser and about-10 ℃ at the discharge condenser.

Disclosure of Invention

A process for acrylonitrile recovery includes providing a feed stream comprising acrylonitrile, HCN, and water to a head-end column; distilling the feed stream in a heads column to produce a heads column overhead (overhead) stream comprising HCN and a bottoms liquid stream comprising acrylonitrile; removing a side stream from a side draw of a head-end column comprising water and organics; separating at least some of the water and organics from the side stream to provide an organic stream; returning the organic stream to the head-end column; and adjusting a ratio of an amount of the side stream removed from the side draw of the heads column to an amount of the organic stream returned to the heads column below the side draw to provide 500ppm or less HCN to the bottoms liquid stream.

A process for acrylonitrile recovery includes providing a feed stream comprising acrylonitrile, HCN, and water to a head-end column; distilling the feed stream in a heads column to produce a heads column overhead stream comprising HCN and a bottoms liquid stream comprising acrylonitrile; removing a side stream from a side draw of a head-end column comprising water and organics; separating at least some water and organics from the sidestream; and separating the organic material into at least two streams and returning the streams to at least two separate locations on the head-end column.

A process for operating a heads column includes providing a feed stream including acrylonitrile, HCN, and water to the heads column; distilling the feed stream in a heads column to produce a heads column overhead stream and passing the heads column overhead stream to a heads column condenser; removing a side stream comprising water and organics from a side draw of the head-end column and passing the side stream to a side stream heat exchanger to provide a cooled side stream; separating at least some water and organics from the cooled side stream; returning the organic stream to the head-end column; and adjusting the ratio of the amount of the side stream removed from the side draw of the heads column to the amount of the organic stream returned to the heads column below the side draw to provide a ratio of the thermal load in the condenser of the heads column to the thermal load in the side stream heat exchanger of about 2.5 or less.

A process for acrylonitrile recovery includes providing a feed stream comprising acrylonitrile, HCN, and water to a head-end column; distilling the feed stream in a heads column to produce a heads column overhead stream comprising HCN, a bottoms liquid stream comprising acrylonitrile, and a side stream from the heads column comprising water and organics; wherein the vapor/liquid molar ratio above the side draw of the column in the column is from about 0.25 to about 0.55 and the vapor/liquid ratio below the side draw of the column in the column is from about 0.50 to about 0.65.

A process for acrylonitrile recovery includes providing a feed stream comprising acrylonitrile, HCN, and water to a head-end column; distilling the feed stream in a heads column to produce a heads column overhead stream comprising HCN, a bottoms liquid stream comprising acrylonitrile, and a side stream from the heads column comprising water and organics; wherein the ratio of the molar vapor/liquid ratio above the side draw of the column in the column to the molar vapor/liquid ratio below the side draw of the column in the column is from about 0.40 to about 1.

A head-end column system comprising: a heads column configured to receive a feed stream comprising acrylonitrile, HCN, and water, and further configured to distill the feed stream in the heads column to produce a heads column overhead stream comprising HCN and a bottoms liquid stream comprising acrylonitrile; a sidedraw configured to remove a blend of water and organics from the head column and cool the blend of water and organics prior to entering the decanter; the decanter is configured to separate a blend of water and organics in the water stream and the organic stream; a splitter configured to receive the organic stream from the decanter and to divide the organic stream into at least two streams; at least one reflux line configured to convey one of the organic streams to the head-end column above the side-draw; and at least one reflux line configured to convey one of the organic streams to the head-end column below the side-draw.

Drawings

The above and other aspects, features and advantages of several methods of this process will become more apparent from the following drawings.

Fig. 1 shows a head-end column system.

FIG. 2 shows a head end column system with pump around (pump around).

Figure 3 shows another aspect of a head-end column system with pump-around.

Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings. Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help improve understanding of various aspects. Additionally, common but well-understood elements that are useful or necessary in a commercially feasible aspect are often not depicted in order to facilitate a less obstructed view of these various aspects.

Detailed Description

The following description is not to be taken in a limiting sense, but is made merely for the purpose of describing the general principles of exemplary embodiments. The scope of the invention should be determined with reference to the claims.

A process and apparatus includes a head-end column. The heads column receives a crude nitrile feed stream (which includes acrylonitrile, HCN, and water). The distillation in the heads column provides a head column overhead stream comprising Hydrogen Cyanide (HCN) at the top of the heads column and a head column bottoms liquid comprising acrylonitrile product at the bottom of the heads column. Column distillation results in the removal of both hydrogen cyanide and water from acrylonitrile.

The heads overhead stream is sent to a heads condenser where a portion is condensed using a coolant. Uncondensed vapor from the heads condenser is sent to the heads vent condenser where a portion is condensed using a coolant. The process includes combining two condensed liquid streams from the heads column condenser and the heads column vent condenser, and passing those streams to the heads column reflux pump. A portion of the combined liquid stream is returned to the top of the heads column as reflux and the remainder is used as product or disposed of.

The process includes removing all of the liquid fraction at the middle section of the head-end column and sending the fraction to a side-stream cooler and then to a decanter. Previously, the liquid fraction would first go to a heat exchanger where the cooler organic stream from the decanter would cool the entire liquid fraction stream. The entire liquid fraction stream will then proceed to a heads column decanter where phase separation occurs. The water phase from the water side of the decanter may go to a recovery column feed manifold. The acrylonitrile phase from the organic side of the decanter is returned to the head-end column.

In one aspect, the process includes providing a feed stream including acrylonitrile, HCN, and water to a head-end column. As shown in fig. 1, feed stream 34 enters head-end column 30 at an upper section of head-end column 30 at a head-end column feed stream inlet 36. The feed stream inlet 36 may correspond to any of the number of trays 40 to 45 of the head-end column 30 in one aspect, and the number of trays 42 of the head-end column 30 in another aspect. The feed stream 34 can include about 82 to about 90 weight percent acrylonitrile and about 5 to about 13 weight percent HCN.

The process includes distilling the feed stream 34 in the heads column 30 to produce a heads column overhead stream 51 including HCN and a bottoms liquid stream 58 including acrylonitrile. The process includes removing a side stream 46 from a side draw 44 of the head-end column 30. In an aspect, the sidedraw 44 is at an intermediate section of the head end column 30. In another aspect, the side draw 44 can correspond to any of the tray numbers 18 to 23 of the head column 30 (which includes 62 trays), and in another aspect, to the tray number 21 of the head column 30. The side stream 46 includes water and organics.

The side draw 44 is at a height in the column that allows for the withdrawal of the side stream 46, in one aspect the side stream 46 comprises from about 90 to about 95 weight percent acrylonitrile, and in another aspect from about 92 to about 93 weight percent acrylonitrile, and from about 5 to about 10 weight percent water, and in another aspect, from about 7 to about 8 percent water.

As shown in fig. 1, the process may include continuously removing a side stream 46 from the heads column 30 using a side stream pump 39. The process includes cooling side stream 46 to provide a cooled side stream 49. The process shown in fig. 1 includes passing a side stream 46 through the first heat exchanger 35 and the second heat exchanger 37. The process provides a cooled side stream 49, which cooled side stream 49 has a temperature of about 35 ℃ to about 45 ℃, and in another aspect about 38 ℃ to about 42 ℃, prior to entering decanter 33. Providing this cooled side stream 49 to decanter 33 improves the separation of water and organics.

Water and organic material are separated in a decanter 33. A pump (not shown) removes the aqueous phase 42 from the decanter 33. Organic stream 48 is removed from decanter 33 by organic stream pump 31. In decanter 33, one phase is primarily water (about 93%) and the other phase is acrylonitrile (about 95%). The aqueous phase is pumped from the water side of decanter 33 to the recovery column feed manifold (not shown). The acrylonitrile phase from the decanter 33 on the organic side is pumped back to the head-end column 30.

Decanter discharge stream 47 can be sent to a scrubber (not shown). The organic stream 48 is passed to a first heat exchanger 35 where it provides a cooled stream. Organic stream 48 enters head-end column 30 at organic stream inlet 54. The organic stream inlet 54 can be at an intermediate section of the head-end column 30. In this aspect, the organic stream inlet 54 is below the sidedraw 44.

In another aspect, the process includes passing the heads column overhead stream 51 to a heads column condenser 55. Head ends column overhead stream 51 is condensed in head ends column condenser 55 using condenser coolant stream 53. In this aspect, the condenser coolant flow 53 is antifreeze or chilled water. The condenser coolant stream 53 has a temperature of from about-10 c to about + 10 c, and in another aspect, from about-10 c to about + 5 c. Vapor/liquid stream 92 is sent to vapor/liquid separator 94. Uncondensed vapor 58 from vapor/liquid separator 94 is sent to head ends column vent condenser 90. Uncondensed vapor 58 is condensed in head ends column vent condenser 90 which is cooled by vent coolant stream 61. In this aspect, the discharge coolant flow 61 may be antifreeze or chilled water. The exhaust coolant stream 61 has a temperature of about-10 c to about + 10 c, and in another aspect, about-10 c to about + 5 c. The vapor/liquid stream 96 is sent to a second liquid/vapor separator 98.

In another aspect, the process includes combining the heads column condenser condensate 63 and the heads column vent condenser condensate 65 to form a combined condensate stream 67. The process also includes passing the combined condensate stream 67 to the top portion of the heads column 30 with a condensate pump 71. The process may include withdrawing a portion of the combined condensate stream 67 at a withdrawal port 74. The combined condensate stream 67 may be returned to the top portion of the heads column 30 at a heads column condensate inlet 76.

As shown in fig. 2, and similar to fig. 1, the process includes providing a feed stream including acrylonitrile, HCN, and water to a head-end column. As shown in fig. 2, feed stream 34 enters head-end column 30 at an upper section of head-end column 30 at head-end column feed stream inlet 36. In one aspect, the feed stream inlet 36 can correspond to any of the tray numbers 40 to 45 of the head ends column 30 (which includes 62 trays), and in one aspect, to the tray number 42 of the head ends column 30. The process includes distilling the feed stream 34 in the heads column 30 to produce a heads column overhead stream 51 including HCN and a bottoms liquid stream 58 including acrylonitrile. In this aspect, the bottoms liquid stream 58 comprises about 500ppm or less HCN, in another aspect, about 0 to about 500ppm HCN, in another aspect, about 1 to about 400ppm HCN, in another aspect, about 1 to about 250ppm HCN, and in another aspect, about 1 to about 100ppm HCN. The bottom liquid stream 58 can also comprise from about 0.1 to about 0.5 weight percent water, in another aspect from about 0.1 to about 0.25 weight percent water.

Head end column overhead stream 51 comprises about 100ppm or less acrylonitrile, in another aspect, about 0 to about 100ppm acrylonitrile, in another aspect, about 1 to about 90ppm acrylonitrile, in another aspect, about 5 to about 50ppm acrylonitrile, in another aspect, about 5 to about 25ppm acrylonitrile, and in another aspect, about 1 to about 10ppm acrylonitrile. The overhead column overhead stream 51 can include from about 0.25 to about 0.75 weight percent water, and in another aspect, from about 0.4 to about 0.6 weight percent water.

The process includes removing a side stream 46 from a side draw 44 of the head-end column 30. In an aspect, the sidedraw 44 is at an intermediate section of the head end column 30. In another aspect, the side draw 44 can correspond to any of the number of trays 18 to 23 of the heads column 30, and in one aspect, to the number of trays 21 of the heads column 30. The side stream 46 includes water and organics.

In one aspect, and unlike the process of FIG. 1, the process shown in FIG. 2 includes passing a side stream 46 to the heat exchanger 38. In this aspect, side stream 46 may flow to heat exchanger 38 using gravity feed. The process provides a cooled side stream 49 having a temperature of from about 35 ℃ to about 45 ℃ and in another aspect from about 38 ℃ to about 42 ℃ prior to entering decanter 33. In the aspect of the process shown in fig. 2, the process does not require a pump to transfer the side stream 46 to the heat exchanger 38, and only a single heat exchanger is required before entering the decanter 33.

In another aspect, water and organic material are separated in decanter 33. A pump (not shown) removes the aqueous phase 42 from the decanter 33. Organic stream 48 is removed from decanter 33 by organic stream pump 31. Unlike fig. 1, the process shown in fig. 2 includes passing the organic stream 48 to a splitter 71. The splitter divides the organic stream 48 into a first organic stream 73 and a second organic stream 75. In this aspect, splitter 71 provides from about 40 to about 60 weight percent of organic stream 48 to either first organic stream 73 or second organic stream 75.

In another aspect, the process includes returning the first organic stream 73 and the second organic stream 75 to the heads column 30 at two separate locations of the heads column 30. In this aspect, the process includes returning the first organic stream 73 to the first organic stream inlet 77 of the head column and the second organic stream 75 to the second organic stream inlet 79 of the head column. In one aspect, the process includes returning the first organic stream 73 to a first organic stream inlet 77 that is about 5 to about 1 tray above the sidedraw 44 of the head column 30, in another aspect, about 4 to about 1 tray, in another aspect, about 3 to about 1 tray, in another aspect, about 2 to about 1 tray, and in another aspect, about 1 tray above the sidedraw 44 of the head column 30. In another aspect, the process includes returning the second organic stream 75 to a second organic stream inlet 79 that is about 5 to about 1 tray, about 4 to about 1 tray, in another aspect, about 3 to about 1 tray, in another aspect, about 2 to about 1 tray, and in another aspect, about 1 tray below the sidedraw 44 of the head column 30.

In another aspect and unlike fig. 1, the process shown in fig. 2 includes passing a decanter vent stream 47 to the head-end column 30. In this aspect, decanter vent stream 47 can enter head ends column 30 at decanter vent stream inlet 81. The decanter vent stream inlet 81 may correspond to the same tray position on the head column as the sidedraw 44. Decanter discharge stream 47 may be used as an equilibrium line when liquid is removed from sidedraw 44.

A comparison of the thermal load between the processes of fig. 1 and 2 is as follows.

A comparison of the processes of fig. 1 and 2 shows that the condenser duty of the heads column is reduced by about 13% with the split stream return shown in fig. 2. This change in heat load translates into savings in refrigeration. This change in heat load is essentially transferred to the side stream heat exchanger 38, and the side stream heat exchanger 38 uses cooling water, which is a relatively inexpensive utility. Although the heat balance around the head-end column varies significantly due to process equipment and operating variations, the overall net variation in cooling and reboiler duty between fig. 1 and fig. 2 is small, expected to be 0.62% and 0.43%. In this aspect, the side stream heat exchanger 38 has a heat load of 3165kw or less, in another aspect, about 1410 to about 2350kw, and in another aspect, about 2350 to about 3165kw (based on 260 and 350kta acrylonitrile production). In another aspect, the ratio of the heat load in the head-end column condenser 55 to the heat load in the side stream heat exchanger 38 is about 4.7 or less, in another aspect about 2.5 or less, in another aspect about 2 to about 3, and in another aspect about 2.5 to about 4.7.

In one aspect, the process shown in FIG. 2 provides for the removal of one heat exchanger and pump, and the reduction of refrigeration utility requirements. Practical examples of this benefit may manifest during a fouling state. As the head-end column begins to foul, operation of the column tends to require more and more reflux to maintain the same purity specifications until finally the column must be shut down for cleaning. This results in a lower condenser duty associated with fouling conditions in the heads column, since the pump-around to tray 22 is a source of increased reflux.

In another aspect, the process includes operating the head-end column at a vapor/liquid molar ratio. In this aspect, the vapor/liquid molar ratio in the head-end column 30 above the sidedraw 44 is from about 0.25 to about 0.55, in another aspect from about 0.26 to about 0.51, in another aspect from 0.26 to about 0.48, in another aspect from about 0.45 to about 0.55, in another aspect from about 0.46 to about 0.51, and in another aspect from about 0.49 to about 0.51. In one aspect, the vapor/liquid molar ratio above the side draw of the process including the split return is from about 0.25 to about 0.50, and in another aspect, from about 0.26 to about 0.48. In another aspect, the vapor/liquid molar ratio above the side draw of the process including a single return is from about 0.49 to about 0.51.

The vapor/liquid molar ratio in head end column 30 below sidedraw 44 is from about 0.4 to about 1, in another aspect, from about 0.5 to about 0.65, in another aspect, from about 0.55 to about 0.65, in another aspect, from about 0.54 to 0.61, in another aspect, from about 0.56 to about 0.62, and in another aspect, from about 0.58 to about 0.61. The vapor/liquid molar ratio below the side draw of the process including the split return is from about 0.5 to about 0.65, on the one hand, and from about 0.54 to about 0.61, in another aspect. In another aspect, the vapor/liquid molar ratio below the side draw of the process including a single return is from about 0.58 to about 0.61.

In another aspect, the process includes operating the head-end column at a vapor/liquid molar ratio. In this aspect, the ratio of the vapor/liquid molar ratio above the sidedraw 44 in the head column 30 to the vapor/liquid molar ratio below the sidedraw 44 in the head column 30 is from about 0.4 to about 0.9, in another aspect, from about 0.44 to about 0.88, in another aspect, from about 0.75 to about 0.90, in another aspect, from about 0.77 to about 0.82, and in another aspect, from about 0.82 to about 0.87. In another aspect, the ratio of the vapor/liquid molar ratio above the sidedraw 44 in the heads column 30 to the vapor/liquid molar ratio below the sidedraw 44 in the heads column 30 in a process that includes a split return is from about 0.4 to about 0.85, and in another aspect, from about 0.44 to about 0.83. In another aspect, the ratio of the vapor/liquid molar ratio above the sidedraw 44 in the heads column 30 to the vapor/liquid molar ratio below the sidedraw 44 in the heads column 30 in a process comprising a single return is from about 0.8 to about 0.9, and in another aspect, from about 0.81 to about 0.83.

The vapor/liquid ratio in the head-end column 30 above the sidedraw 44 can be calculated as follows:

flow rate in the heads column overhead stream 51/(flow rate in feed stream 34) + (flow rate of the combined condensate stream 67 at the heads column inlet 76)

The vapor/liquid ratio in the head-end column 30 below the sidedraw 44 can be calculated as follows:

flow rate in the heads column overhead stream 51/flow rate of the second organic stream 75.

Fig. 3 is similar to fig. 1 except that fig. 3 includes an additional heat exchanger 99.

While the invention disclosed herein has been described by means of specific embodiments, examples and applications thereof, various modifications and changes may be made thereto by those skilled in the art without departing from the scope of the invention set forth in the claims.

Claims

1. A process for acrylonitrile recovery comprising:

providing a feed stream comprising acrylonitrile, HCN, and water to a head-end column;

distilling said feed stream in said heads column to produce a heads column overhead stream comprising HCN and a bottoms liquid stream comprising acrylonitrile;

removing a side stream from a side draw of the head-end column, the side stream comprising a blend of water and organics;

cooling the side stream in at least one heat exchanger to provide a cooled side stream;

separating at least some water and organics from the cooled side stream in a decanter to provide an organic stream and a water stream;

dividing said organic stream into at least two streams;

wherein one of the organic streams is returned to the head column above the side draw of the head column and one of the organic streams is returned below the side draw of the head column; and

wherein the ratio of the amount of side stream removed from the side draw of the heads column to the amount of organic stream returned to the heads column below the side draw is adjusted to provide the bottoms liquid stream comprising 500ppm or less HCN;

wherein the heads column overhead stream is passed to a heads column condenser; and

wherein a ratio of a heat load in the head-end column condenser to a heat load in the side-stream heat exchanger is about 4.7 or less.

2. The process of claim 1, wherein the organic stream returned to the heads column above the sidedraw is returned to the heads column from about 5 to about 1 tray above the sidedraw of the heads column.

3. The process of claim 1, wherein the organic stream returned to the heads column below the sidedraw is returned to the heads column from about 5 to about 1 tray below the sidedraw of the heads column.

4. The process of claim 1, wherein one of the two streams of the organic material returned to the heads column comprises from about 40 to about 60 wt% of the organics in the side stream.

5. The process of claim 1, wherein the side stream is cooled in at least two heat exchangers.

6. The process of claim 1, wherein the side stream is conveyed to the heat exchanger by gravity feed.

7. The process according to claim 1, wherein a discharge stream from the decanter is returned to the head-end column.

8. The process of claim 1, wherein the ratio of the heat load in the heads column condenser to the heat load in the side stream heat exchanger is about 2.5 or less.

9. The process of claim 1, wherein the overhead column overhead stream has 100ppm or less of acrylonitrile.

10. A process for acrylonitrile recovery comprising:

separating at least some water and organics from the cooled side stream in a decanter; and

dividing the organic matter into at least two streams; (ii) a

Wherein one of the organic streams is returned to the head column above the side draw of the head column and one of the organic streams is returned below the side draw of the head column;

11. The process of claim 10, wherein the organic stream returned to the heads column above the sidedraw is returned to the heads column from about 5 to about 1 tray above the sidedraw of the heads column.

12. The process of claim 10, wherein the organic stream returned to the heads column below the sidedraw is returned to the heads column from about 5 to about 1 tray below the sidedraw of the heads column.

13. The process of claim 12, wherein one of the two streams returned to the head-end column comprises about 40 to about 60 wt% of the organics in the side stream.

14. The process of claim 10, wherein the side stream is cooled in at least two heat exchangers.

15. The process of claim 14, wherein the side stream is conveyed to the heat exchanger by gravity feed.

16. The process according to claim 13, wherein a discharge stream from the decanter is returned to the heads column.

17. The process according to claim 10, wherein the heads column overhead stream is passed to a heads column condenser.

18. The process of claim 10, wherein the ratio of the heat load in the head-column condenser to the heat load in the side-stream heat exchanger is about 2.5 or less.

19. The process of claim 10, wherein the bottoms liquid stream has 500ppm or less HCN.

20. The process of claim 10, wherein the overhead column overhead stream has 100ppm or less of acrylonitrile.

21. The process according to claim 10, wherein the vapor/liquid molar ratio in the heads column above the side draw of the heads column is from about 0.25 to about 0.55 and the vapor/liquid molar ratio in the heads column below the side draw of the heads column is from about 0.50 to about 0.65.