TW201544156A - Heads column overhead system - Google Patents

Abstract

An apparatus comprises a heads column and an overhead system. The heads column is configured to receive a crude nitriles feed stream. The heads column is configured to distill the crude nitriles feed stream under a partial vacuum and produce a heads column overhead stream comprising HCN at the top of the heads column, and a bottom liquid stream comprising acrylonitrile product at the bottom of the heads column. The heads column comprises a condenser that is configured to condense the heads column overhead stream. The apparatus comprises a glandless pump in the overhead system. The pump is configured to pump at least a portion of the heads column overhead stream as a reflux stream to the heads after the heads column overheard stream is condensed in the condenser.

Description

Head fraction tower top system Field of invention

The present invention relates to an improved process for the manufacture of acrylonitrile and methacrylonitrile. In particular, the present invention relates to an improved heads column overhead treatment of hydrogen cyanide (HCN).

Background of the invention

A variety of methods and systems are known for making acrylonitrile and methacrylonitrile; see, for example, U.S. Patent No. 6,107,509. As noted in U.S. Patent No. 6,107,509, the conventional method generally involves recovering and purifying the produced acrylonitrile by the following method after a completed hydrocarbon (selected from propane, propylene or isobutylene), direct reaction of ammonia and oxygen in the presence of a catalyst. /Methacrylonitrile: The reactor effluent containing acrylonitrile/methacrylonitrile is sent to a first column (quench) in which the reactor effluent is cooled using a first aqueous stream, and the cooled acrylonitrile is contained/ The methacrylonitrile effluent is passed to a second column (absorber) wherein the cooled effluent is contacted with a second aqueous stream to absorb acrylonitrile/methacrylonitrile into the second aqueous stream, which will contain acrylonitrile The second aqueous stream of /methacrylonitrile is transported from the second column to the first distillation column (recovery column) for separating the crude acrylonitrile/methacrylonitrile from the second aqueous stream, and will be separated The crude acrylonitrile/methacrylonitrile is sent to a second distillation column (heads column) to remove at least some impurities from the crude acrylonitrile/methacrylonitrile, and to deliver the partially purified acrylonitrile/methacrylonitrile to the first A tristillation column (product column) to give the product acrylonitrile/methacrylonitrile. Typical recovery and purification methods for acrylonitrile and methacrylonitrile are described in U.S. Patent Nos. 4,234,510; 3,885,928; 3,352,764; 3,198,750 and 3,044,966.

The acrylonitrile manufacturing process produces very toxic HCN by-products. in In order to minimize exposure of humans to HCN during operation or maintenance of the equipment, it is useful to have a low leakage risk for equipment that can handle HCN. One approach is to use gravity flow to eliminate the need for pumps in HCN service. However, in the acrylonitrile plant HCN column or heads column, contamination (especially tray fouling) is often a problem.

Summary of invention

Accordingly, an aspect of the present disclosure provides a safe, efficient, and cost effective method and apparatus that overcomes or reduces the disadvantages of conventional methods.

In one aspect, the apparatus comprises a heads column and an overhead system. The heads column is configured to accept a crude nitrile feed stream. The heads column is arranged to distill a crude nitrile feed stream while operating under partial vacuum, and to produce a heads stream stream comprising HCN at the top of the heads column and an acrylonitrile product at the bottom of the heads column. Bottom liquid stream. The overhead system comprises a condenser arranged to condense the overhead stream of the heads column. The device comprises a pump without a gasket. The pump is arranged to pump at least one after condensing the head column overhead stream in the condenser Part of the heads fraction tower top stream.

The above and other aspects, features, and advantages of the present disclosure are attached It will be apparent from the detailed description of the embodiments of the drawings that the description

1‧‧‧ crude nitrile feedstock

2‧‧‧ head fractionation tower top logistics

3‧‧‧Return Logistics

4‧‧‧Water flow

5‧‧‧HCN by-product logistics

6‧‧‧Condenser export logistics

7‧‧‧Contacts

8‧‧‧Controller, flow controller

9‧‧‧Valves, Control Valves

10‧‧‧ Equipment

12‧‧‧ heads tower

14‧‧‧Tower System

16‧‧‧Condenser

18‧‧‧No gasket pump, control pump

20‧‧‧ Temperature Controller

22‧‧‧ silo, condenser silo

25‧‧‧Valve, product valve

26‧‧‧Liquid Logistics

27‧‧‧Level controller

28‧‧‧Tray, top tray

30‧‧‧Top tray

32‧‧‧Intermediate tray

34‧‧‧ bottom

40‧‧‧Flow controller

68‧‧‧ Controller

200, 300‧‧‧ method

201-205, 301-305‧‧‧ steps

A more complete understanding of the exemplary embodiments of the invention and the advantages thereof, in which the A schematic flow diagram of one embodiment of various aspects of the present disclosure.

2 illustrates a flow chart of a method in accordance with aspects of the present disclosure.

FIG. 3 illustrates a flow chart of a method in accordance with aspects of the present disclosure.

4 is a schematic flow diagram of an alternate embodiment for the manufacture of acrylonitrile products in accordance with aspects of the present disclosure.

Detailed description

The recovered portion of the acrylonitrile plant produces a crude nitrile feed stream which is a mixture comprising acrylonitrile, HCN and water. The processing step in the purification of acrylonitrile is the removal of HCN by-products by distillation. The distillation column from which the HCN is removed from the crude nitrile feed stream is referred to as an HCN column, a heads column or a heads column drying column. Using this distillation column, HCN can be recovered as a high purity overhead product.

In the acrylonitrile plant HCN column or heads column, tray fouling is often a problem. It has been found that reducing the pressure in the HCN or heads column, for example, operating the HCN or heads column under partial vacuum, significantly reduces pollution And extend the execution time between the cleaning of the HCN tower or the heads column. However, operating a HCN column or a heads column under reduced pressure requires a lower condensation temperature and requires the use of a larger condenser. As a result, the condenser of the heads column designed for vacuum use is typically too large to be physically mounted on top of or near the top of the heads column. If the condenser is installed down into the support structure near the heads column, one (or more) pumps can be used to provide reflux to the heads column and/or to deliver HCN by-products to HCN users and/or HCN storage and/or Or disposal (disposal).

In an aspect of the disclosure, a gasketless pump (eg, magnetic A coupled pump and/or a pump that has no direct connection between the motor shaft and the impeller can be used in the overhead system of the heads column. By using a sealless pump, the risk of HCN leakage can be minimized because this type of pump does not have a leaky drive seal and there is no heat transfer from the motor to the pumped fluid.

The method and apparatus of the present disclosure are described in detail with reference to FIG.

Apparatus 10 is downstream of a recovery column (not shown in Figure 1) for the acrylonitrile manufacturing process. Apparatus 10 includes a heads column 12 and a top system 14. The heads column 12 is arranged to distill the crude nitrile feed stream 1 and produce a heads column overhead stream 2 comprising primarily HCN and traces of acrylonitrile and water. The crude nitrile feed stream 1 can comprise from about 82 to about 90 weight percent acrylonitrile, and from about 5 to about 13 weight percent HCN, with the balance of the composition being water. In this respect, the components that can cause contamination depend on the type of inhibitor used.

The overhead system 14 includes a condenser 16 that is configured to condense the heads column overhead stream 2. The overhead system 14 includes a pump 18 without a gasket. In one aspect, the heads column 12 can be configured to distill the crude nitrile while operating under partial vacuum. Class feed stream 1. In one aspect, the heads column 12 can be configured to distill the crude nitrile feed stream 1 while operating at a partial vacuum of 0.044-0.090 MPa absolute. In one embodiment, the heads column 12 distills the crude nitrile feed stream 1 under partial vacuum at a top pressure of about 0.075 MPa absolute. The fluid in the heads column 12 can be heated by a backup reboiler (not shown in Figure 1) which can be used to heat the fluid in the heads column 12 and the product column downstream of the heads column 12 ( The fluid in (not shown in Figure 1). Lean water can be used as a heat source for one (or more) reboilers.

The heads column 12 contains a plurality of trays. In one embodiment, The heads column 12 contains fifty-two (52)-seventy-two (72) trays. In one embodiment, the heads column 12 comprises sixty-two (62) trays. The heads column 12 can be configured to accept the crude nitrile feed stream 1 at the tray 28. In one embodiment, tray 28 can be the 42nd tray from the bottom of heads column 12. In an alternate embodiment, tray 28 can be the 38th tray from the bottom of heads column 12. In an alternate embodiment, tray 28 can be the 47th tray from the bottom of heads column 12, and heads column 12 can contain sixty-seven (67) trays. In one embodiment, the first to twentieth bottom trays of the heads column 12 are dried with an acrylonitrile product. In one embodiment, the 21st-42th tray from the bottom 34 of the heads column 12 removes and purifies the HCN. In one embodiment, the heads column 12 can be operated without a drying function. In one embodiment, the heads column 12 comprises forty (40) to sixty-five (65) trays. In one embodiment, the feed tray 28 can be between the 20th and 30th trays from the bottom of the heads column, including the 20th tray and the 30th tray.

The condenser 16 can be configured to accept cooled or frozen water (RW) Stream 4. The chilled water stream 4 may contain an antifreeze and the inlet temperature to the condenser 16 is between about -10 and 5 °C. In one aspect, the condenser 16 can be located near the heads column 12, but not at the top of the heads column 12. The condenser 16 (including suitable dimensions) can be configured to accommodate the lower temperatures required to operate the heads column 12 under partial vacuum. The lower temperature for operating the heads column 12 can range from -10 to +10 °C.

A gasketless pump 18 can be used to pump the main from the condenser 16 The condenser outlet stream 6 of HCN is to be included. The condenser outlet stream 6 can be separated at point 7 into a reflux stream 3 and an HCN byproduct stream 5. In one aspect, the HCN by-product stream 5 can be sent to an HCN user, HCN for storage or disposal.

The reflux stream 3 can be passed to the heads column 12. The system can utilize about 2 A reflux ratio of about 7, on the other hand, a reflux ratio of from about 2 to about 6.5, and on the other hand, a reflux ratio of from about 3 to about 6. In one aspect, the reflux stream 3 can be received in the top tray 30 of the heads column 12. In one embodiment, the top tray 30 of the heads column 12 can be the 62nd tray from the bottom of the heads column 12. In one aspect, the flow rate of the reflux stream 3 can be adjusted by a flow controller 8 provided as a regulating valve 9. The flow controller 8 can be controlled by the temperature controller 20. The temperature controller 20 can be located at an intermediate tray 32 below the heads column 12 of the top tray 30 of the heads column 12. In an aspect, the controller 68 can be configured to process one or more signals corresponding to the measured parameters (eg, the temperature measured by the temperature controller 20). The controller 68 can be arranged to determine whether the measured parameter is above or below a predetermined range of parameters, for example, the temperature measured by the temperature controller 20 is below or above a predetermined temperature range. If the measured parameter is below or above a predetermined parameter range, the controller 68 can be set to be via a communication line or Wireless communication (not shown in Figure 1) regulates the operation of one or more devices. For example, controller 68 may be configured to regulate the amount of reflux stream 3 flowing to heads column 12 when the temperature measured by temperature controller 20 is below or above a predetermined temperature range. Controller 68 may be arranged to control the operation of pump 18 and/or the operation of valve 9, such as the size of the opening of control valve 9. Those skilled in the art recognize that controller 68 or a similar controller may be located remote from flow controller 8 (as shown in FIG. 1) or may be located at flow controller 8 and include flow controller 8.

The condenser 16 can include a condenser bin 22 and level control 27. The level controller 27 can be configured to control the level of liquid condensed in the condenser bin 22. As shown in FIG. 1, the level controller 27 can be configured to control the level of liquid condensed in the condenser bin 22 by adjusting the opening of the product valve 25. As shown in FIG. 1, valve 25 can be located downstream of condenser 16. In one embodiment, the controller 68 can be configured to process signals corresponding to measurement parameters (eg, the level of liquid in the condenser bin 22 as measured by the level controller 27). The controller 68 can be arranged to determine whether the liquid level measured by the level controller 27 is above or below a predetermined liquid level range of the condenser bin 22. If the liquid level measured in the condenser bin 22 is above or below the predetermined liquid level range of the condenser bin 22, the controller 68 can be configured to communicate via a communication line or wirelessly (not shown in FIG. 1) Adjusting the operation of one or more devices. For example, controller 68 may be configured to adjust the size of the opening of valve 25 when the liquid level measured in condenser bin 22 is above or below a predetermined liquid level range of condenser bin 22. Those skilled in the art recognize that the controller 68 or similar controller can be located remotely from the level controller 27 (eg, Also shown in FIG. 1 or may be located at level controller 27 and include level controller 27.

A liquid stream 26 comprising acrylonitrile can be removed from the bottom of column 12 go with. Liquid stream 26 can be passed to the product column (not shown in Figure 1). Alternatively, liquid stream 26 can be passed to a drying column, such as a drying column in a 3-column purification system comprising a heads column, a drying column, and a product column.

Figure 4 is a side view of the present disclosure applied to the manufacture of acrylonitrile products. A schematic flow diagram of an alternate embodiment of a face. Figure 4 is similar to the schematic flow diagram shown in Figure 1. As shown in FIG. 4, flow controller 40 is in electronic communication with temperature controller 20 and valve 25. As shown in FIG. 4, the flow controller 8 is in electronic communication with the level controller 27 and the valve 9.

As in Figure 1, in Figure 4, the controller 68 can be set up in place One or more signals corresponding to the measured parameters (eg, the temperature measured by temperature controller 20). The controller 68 can be arranged to determine whether the measured parameter is above or below a predetermined range of parameters, for example, the temperature measured by the temperature controller 20 is below or above a predetermined temperature range. If the measured parameter is below or above a predetermined parameter range, the controller 68 can be configured to adjust the operation of one or more devices via a communication line or wireless communication (not shown in Figure 4). For example, controller 68 may be configured to regulate the amount of reflux stream 3 flowing to heads column 12 when the temperature measured by temperature controller 20 is below or above a predetermined temperature range. Controller 68 may be arranged to control the operation of pump 18 and/or the operation of valve 9 and/or the operation of valve 25, such as the size of the opening of control valve 9 and/or valve 25. By controlling the size of the opening of the valve 25, the controller 68 controls the flow through the valve 25 that would otherwise flow through the valve 9. Those skilled in the art recognize that Controller 68 or similar controller may be located remote from flow controller 8 and flow controller 40 (as shown in Figure 4), or may be located at flow controller 8 and/or flow controller 40 and include a flow controller 8 and/or flow controller 40.

As in FIG. 1, in FIG. 4, controller 68 may be arranged to process signals corresponding to measurement parameters (eg, the level of liquid in condenser bin 22 as measured by level controller 27). The controller 68 can be arranged to determine whether the liquid level measured by the level controller 27 is above or below a predetermined liquid level range of the condenser bin 22. If the measured parameter is below or above a predetermined parameter range, the controller 68 can be configured to adjust the operation of one or more devices via a communication line or wireless communication (not shown in Figure 4). For example, when the liquid level in the condenser bin 22 as measured by the level controller 27 is below or above a predetermined liquid level range, the controller 68 can be configured to regulate the reflux stream 3 to the heads column 12 The amount. Controller 68 may be arranged to control the operation of pump 18 and/or the operation of valve 9 and/or the operation of valve 25, such as the size of the opening of control valve 9 and/or valve 25. By controlling the size of the opening of the valve 9, the controller 68 controls the flow through the valve 9 that would otherwise flow through the valve 25. Those skilled in the art recognize that controller 68 or a similar controller may be located remote from flow controller 8 and flow controller 40 (as shown in Figure 4), or may be located at flow controller 8 and/or flow controller 40 and includes controller 8 and/or flow controller 40

FIG. 2 illustrates a flow chart of a method 200 in accordance with aspects of the present disclosure. Method 200 can be performed using the apparatus described above. In step 201, a crude nitrile feed stream is received in a heads column comprising a plurality of trays. In step 201, a tower from the 38th to the 47th tray at the bottom of the heads column The plate takes place in the heads column to accept the crude nitrile feed stream. In step 202, a crude nitrile feed stream is distilled in a heads column under partial vacuum to produce a heads stream stream comprising HCN at the top of the heads column and an acrylonitrile product at the bottom of the heads column. The bottom liquid stream. In step 203, a condensation heads overhead stream is produced in the condenser. In step 204, after condensing in the condenser, at least a portion of the heads column overhead stream is pumped as a reflux stream to the heads column and/or pumped to the HCN storage, HCN user or treatment using a pump. One. In step 205, a reflux stream is received in the heads column. As noted above, with respect to aspects of the present disclosure of the apparatus, in step 205, a reflux stream can be received in the heads column at the top tray of the heads column.

Method 200 can also include additional steps (not shown in Figure 2). For example, the method 200 can further include the step of determining the temperature of the fluid at a predetermined tray between the top tray of the heads column and the tray receiving the crude nitrile feed stream. The method 200 can also include the step of adjusting the flow rate of the reflux stream to the heads column to maintain the temperature of the fluid at the predetermined tray within a predetermined temperature range. The method 200 can also include the step of controlling the level of liquid condensed in the silo 22 of the condenser 16 to be within a predetermined level range, and the step can be performed by adjusting at least one valve located downstream of the condenser 16

FIG. 3 illustrates a flow chart of a method 300 in accordance with aspects of the present disclosure. Method 300 can be similar to method 200. In step 301, a crude nitrile feed stream is received in a heads column comprising a plurality of trays. In step 301, the accepting of the crude nitrile feed stream in the heads column can occur at the trays from the 38th to the 47th trays at the bottom of the heads column. In step 302, what happens in The crude nitrile feed stream is distilled in a heads column under partial vacuum to produce a HCN-containing heads overhead stream at the top of the heads column and a bottoms liquid stream comprising the acrylonitrile product at the bottom of the heads column. In step 303, a condensation heads overhead stream is produced in the condenser. In step 304, after condensing in the condenser, at least one of the at least a portion of the heads column overhead stream is sent as a reflux stream to the heads column and/or to the HCN storage, HCN user or treatment. Feeding at least a portion of the heads column overhead stream as a reflux stream to the heads column may or may not include pumping the reflux stream. In step 305, a reflux stream is received in the heads column. As noted above, with respect to aspects of the present disclosure of the apparatus, in step 305, receiving a reflux stream in the heads column can occur at the top tray of the heads column.

Method 300 can also include additional steps (not shown in Figure 3) Show). For example, method 300 can further include the steps of determining the temperature of the fluid at the first predetermined tray and the second predetermined tray, each of the first and second predetermined trays being located at the top tray of the heads column and receiving the crude nitrile feed stream Between the trays. The method 300 can also include adjusting a flow rate of the reflux stream to the heads column to maintain the temperature of the fluid at the first predetermined tray within a first predetermined temperature range, and adjusting the flow of the reflux stream to maintain the fluid at the second predetermined The step of the temperature at the tray being within a second predetermined temperature range. In one aspect, the first predetermined temperature range is lower than a temperature at which the fluid will begin to cause contamination at the first predetermined tray in the first predetermined temperature range. In one aspect, the second predetermined temperature range is lower than a temperature at which the fluid will begin to cause contamination at the second predetermined tray in the second predetermined temperature range. Method 300 can also include the condenser 16 The level of liquid condensed in the silo 22 is controlled within a predetermined range of liquid levels, and this step can be performed by adjusting at least one valve located downstream of the condenser 16.

Although the present disclosure has been described in connection with certain preferred embodiments thereof, and the details of the invention have been described, it will be apparent to those skilled in the art that And certain details described herein may vary significantly without departing from the basic principles of the disclosure. It is to be understood that the features of the present disclosure are susceptible to modifications, variations, alterations, and substitutions, without departing from the spirit and scope of the disclosure. For example, the size, number, size, and shape of the various components can be varied to suit a particular application. Accordingly, the specific embodiments illustrated and described herein are for illustrative purposes only.

1‧‧‧ crude nitrile feedstock

2‧‧‧ head fractionation tower top logistics

3‧‧‧Return Logistics

4‧‧‧Water flow

5‧‧‧HCN by-product logistics

6‧‧‧Condenser export logistics

7‧‧‧Contacts

8‧‧‧Controller, flow controller

9‧‧‧Valves, Control Valves

12‧‧‧ heads tower

14‧‧‧Tower System

16‧‧‧Condenser

18‧‧‧No gasket pump, control pump

20‧‧‧ Temperature Controller

22‧‧‧ silo, condenser silo

25‧‧‧Valve, product valve

26‧‧‧Liquid Logistics

27‧‧‧Level controller

28‧‧‧Tray, top tray

30‧‧‧Top tray

32‧‧‧Intermediate tray

34‧‧‧ bottom

68‧‧‧ Controller

Claims (32)

An apparatus comprising: a heads column disposed to receive a crude nitrile feed stream and a distillate crude nitrile feed stream, and to produce a headline overhead stream comprising HCN at the top of the heads column And a bottoms liquid stream comprising an acrylonitrile product at the bottom of the heads column; a top system comprising a condenser arranged to condense the top stream of the heads column; and a pump arranged to be condensed After condensing, at least a portion of the heads column overhead stream is pumped as a reflux stream to the heads column and/or pumped to at least one of HCN storage, HCN users or treatment; wherein the heads column is set to The crude nitrile feed stream is distilled under partial vacuum. The apparatus of claim 1, wherein the heads column is configured to distill a crude nitrile feed stream while operating at a partial vacuum of 0.044-0.090 MPa absolute. The apparatus of claim 1, wherein the heads column comprises a plurality of trays, the plurality of trays comprising 52-72 trays. The apparatus of claim 3, wherein the heads column comprises 62 trays. The apparatus of claim 3, wherein the heads column is configured to receive a reflux stream at a top tray of the heads column. The apparatus of claim 3, wherein the condenser is configured to receive a stream of frozen water for cooling the heads column overhead stream. The apparatus of claim 6, wherein the frozen water stream comprises an antifreeze. The apparatus of claim 3, wherein the chilled water stream has an inlet temperature in the condenser ranging from about -10 to 5 °C. The apparatus of claim 1 wherein the heads column is configured to accept a crude nitrile feed stream comprising from about 82 to about 90 weight percent acrylonitrile and from about 5 to about 13 weight percent HCN. The apparatus of claim 3, wherein the heads column is configured to accept a crude nitrile feed stream at a tray from the 38th tray to the 47th tray at the bottom of the heads column. The apparatus of claim 10, further comprising a temperature controller and a flow controller, wherein the temperature controller is disposed between the top tray located in the heads column and the tray receiving the crude nitrile feed stream The temperature of the fluid is determined at a predetermined tray, wherein the temperature controller is configured to control a flow controller configured to regulate a valve downstream of the condenser to control a flow of reflux stream to the heads column, wherein The temperature of the fluid at the predetermined tray is maintained within a predetermined temperature range. The apparatus of claim 10, wherein the condenser comprises a condenser silo and a liquid level controller, wherein the liquid level controller is configured to be controlled in the condenser silo by adjusting at least one valve located downstream of the condenser The level of the condensed liquid is within a predetermined liquid level range. The apparatus of claim 12, wherein said at least one valve downstream of the condenser is a return valve on a return line leading to the heads column and/or on a line leading to HCN storage, HCN user or disposal HCN product valve. The apparatus of claim 1, wherein the pump is a pump without a gasket. A method comprising: accepting a crude nitrile feed stream in a heads column comprising a plurality of trays; and distilling a crude nitrile feed stream in a heads column under partial vacuum to produce at the top of the heads column a heads stream stream comprising HCN and a bottoms liquid stream comprising an acrylonitrile product at the bottom of the heads column; condensing the heads column overhead stream in a condenser; and after condensing in the condenser, using a pump at least A portion of the condensed heads column overhead stream is pumped as a reflux stream to the heads column and/or pumped to at least one of HCN storage, HCN users, or disposal. The method of claim 15, wherein the distilling of the crude nitrile feed stream is carried out under partial vacuum having a top pressure in the range of from 0.044 to 0.090 MPa absolute. The method of claim 17, the method further comprising receiving a reflux stream in the heads column. The method of claim 17, wherein the reflux stream is received in the heads column at the top tray of the plurality of trays of the heads column. The method of claim 15, wherein the heads column is configured to accept a crude nitrile feed stream comprising from about 82 to about 90 weight percent acrylonitrile and from about 5 to about 13 weight percent HCN. The method of claim 17, wherein the crude nitrile feed stream is received at a tray from the 38th tray to the 47th tray at the bottom of the heads column. The method of claim 15, the method further comprising measuring the temperature of the fluid at a predetermined tray between the top tray of the heads column and the tray receiving the crude nitrile feed stream, and adjusting the flow to the heads column The flow of the reflux stream is maintained to maintain the temperature of the fluid at the predetermined tray within a predetermined temperature range. The method of claim 15, the method further comprising controlling the level of liquid condensed in the condenser bin to be within a predetermined liquid level range by adjusting at least one valve downstream of the condenser. A method comprising: accepting a crude nitrile feed stream in a heads column comprising a plurality of trays; and distilling a crude nitrile feed stream in a heads column under partial vacuum to produce at the top of the heads column a heads column stream comprising HCN and a bottoms liquid stream comprising an acrylonitrile product at the bottom of the heads column; condensing the heads column overhead stream in a condenser; and condensing at least a portion after condensing in the condenser The overhead stream overhead stream is sent to the heads column as a reflux stream and/or to at least one of HCN storage, HCN users or disposal; at the top tray of the heads column and receiving the crude nitrile feed stream The temperature of the fluid is measured at a predetermined tray between the trays, and the flow rate of the reflux stream to the heads column is adjusted to maintain the temperature of the fluid at the predetermined tray within a predetermined temperature range. The method of claim 23, wherein the distillation of the crude nitrile feed stream is The top pressure is under partial vacuum of 0.044-0.090 MPa absolute. The method of claim 23, the method further comprising receiving a reflux stream in the heads column. The method of claim 25, wherein the reflux stream is received in the heads column at the top tray of the plurality of trays of the heads column. The method of claim 23, wherein the heads column is configured to accept a crude nitrile feed stream comprising from about 82 to about 90 weight percent acrylonitrile and from about 5 to about 13 weight percent HCN. The method of claim 26, wherein the crude nitrile feed stream is received at a tray from the 38th tray to the 47th tray at the bottom of the heads column. The method of claim 23, wherein the predetermined temperature range is lower than a temperature at which the fluid will begin to cause contamination at the predetermined tray at the predetermined tray. The method of claim 23, wherein the determining the temperature of the fluid at the predetermined tray comprises determining the temperature of the fluid at the first predetermined tray and the second predetermined tray, and adjusting the flow rate of the reflux stream to the heads column And maintaining the temperature of the fluid at the first predetermined tray within a first predetermined temperature range and adjusting the flow rate of the reflux stream to the heads column to maintain the temperature of the fluid at the second predetermined tray at the second Within the predetermined temperature range. The method of claim 30, wherein the first predetermined temperature range is lower than a temperature at which the fluid will begin to cause contamination at the first predetermined tray at the first predetermined tray, wherein the second predetermined temperature range Lower than the temperature at which the second predetermined tray at the fluid will begin to cause contamination at the second predetermined tray. The method of claim 23, the method further comprising controlling the level of liquid condensed in the condenser bin to be within a predetermined liquid level range by adjusting at least one valve downstream of the condenser.