JP2017519750A - Method for stabilizing crude acrylonitrile and its storage tank - Google Patents

Abstract

A method of maintaining storage of crude acrylonitrile in a crude tank is provided. The method includes conveying crude acrylonitrile to a crude tank, adding to the crude acrylonitrile in the crude tank an amount of acid effective to maintain the pH below a target pH, and the crude acrylonitrile in the crude tank. Maintaining the temperature below the target temperature. [Selection] Figure 2

Description

  The present disclosure relates to an improved process for producing acrylonitrile and methacrylonitrile. Specifically, the present disclosure relates to the operation of a crude acrylonitrile tank.

  Acrylonitrile is an important general chemical used primarily as a monomer for the manufacture of various polymer materials such as polymers for acrylic fibers used in textile products and resins such as ABS and SAN resins. Acrylonitrile is produced in an amount of over 4 million tons annually worldwide. The most commonly used method for the production of olefinic unsaturated nitriles such as acrylonitrile or methacrylonitrile is the production of acrylonitrile using air or other oxygen molecular source as oxidant in an ammoxidation reactor. A suitable hydrocarbon such as propylene or propane for production or isobutylene for production of methacrylonitrile is reacted in the presence of ammonia. Such an oxidation reaction, also commonly referred to as an ammoxidation reaction, uses a solid, particulate heterogeneous catalyst in a fluidized catalyst bed to provide an acceptable conversion and yield of the desired acrylonitrile or methacrylonitrile. Catalyze ammoxidation reaction. Such an ammoxidation reaction generally produces other products such as acetonitrile, hydrogen cyanide (HCN) and other by-products in addition to the production of olefinically unsaturated nitriles. Methods for catalytic oxidation of hydrocarbons to acrylonitrile are disclosed, for example, in U.S. Pat. Nos. 4,503,001, 4,767,878, 4,863,891 and 5,093,299. All of these patents are incorporated herein by reference.

  It is important that acrylonitrile products meet specifications including the maximum amount of certain chemical impurities, as well as predetermined amounts of water and polymerization inhibitors. Control of the water and polymer content of the acrylonitrile product is important for the stability of the acrylonitrile product. In general, the amount of water in the acrylonitrile product and the amount of monomethyl ether hydroquinone or hydroquinone methyl ether (hereinafter “MEHQ”) polymerization inhibitor must be maintained within a specified level or range. MEHQ polymerization inhibitors require a certain amount of water to function and to suppress unwanted polymerization of acrylonitrile products. Acrylonitrile products that do not contain a certain amount of water and inhibitors are highly reactive, so specifications such as shipping specifications between the United States and nations usually contain the minimum amount of water and inhibitors in the shipping acrylonitrile product. Need to be. Since excess water and inhibitor make the desired subsequent reaction of acrylonitrile slow and difficult, specifications usually also list the maximum water and inhibitor content. Typically, acrylonitrile product specifications list maximum amounts for specific impurities such as hydrogen cyanide, acetonitrile and acetone.

  Sometimes it may be necessary to introduce unrefined or non-standard products into the holding tank. In such cases, it may be necessary to use the crude acrylonitrile tank as an unrefined or non-standard product holding tank.

US Pat. No. 4,503,001 U.S. Pat. No. 4,767,878 US Pat. No. 4,863,891 US Pat. No. 5,093,299

  Although the manufacture of acrylonitrile / methacrylonitrile has been performed commercially for many years, there are still areas where improvements can provide significant advantages. Usually, the crude acrylonitrile from the recovery tower contains acrylonitrile, cyanide and water and is therefore not particularly stable. Thus, crude acrylonitrile may be prone to polymerization reactions and loss of acrylonitrile product. It would be useful to reduce or eliminate polymerization reactions and loss of acrylonitrile product by having a method and apparatus that provides more effective crude acrylonitrile tank operation than conventional methods and apparatus.

  The foregoing and other aspects, features, and advantages of the present disclosure will become apparent when the following detailed description of the exemplary embodiments is read in conjunction with the accompanying drawings.

  Accordingly, aspects of the present disclosure provide a safe, effective and cost effective method and apparatus that overcomes or reduces the disadvantages of conventional methods and apparatus.

  A method of maintaining storage of crude acrylonitrile in a crude tank is provided. The method includes conveying crude acrylonitrile to a crude tank, adding to the crude acrylonitrile in the crude tank an amount of an acid effective to maintain the pH below the target pH, and the crude acrylonitrile in the crude tank. Maintaining the temperature below the target temperature.

  In another aspect, a method of preparing a crude tank that receives crude acrylonitrile includes adding an amount of water to the crude tank effective to absorb organisms under the floating roof of the crude tank, and the water in the crude tank. Maintaining the temperature at about 25 ° C. or less and acidifying the water to a pH of 4 or less.

  In another aspect, the crude acrylonitrile storage tank is configured to remove the crude acrylonitrile from the crude acrylonitrile storage tank and a plurality of temperature sensors configured to detect different height temperatures in the crude acrylonitrile storage tank. And a plurality of removal points. The tank includes a pH sensor configured to detect the pH of the crude acrylonitrile in the crude acrylonitrile storage tank, and a cooler configured to cool the recirculation flow drawn from the removal location of the crude acrylonitrile storage tank. And a return line configured to return at least a portion of the recycle stream to the crude acrylonitrile storage tank.

  The foregoing and other aspects, features, and advantages of the present disclosure will become apparent when the following detailed description of the exemplary embodiments is read in conjunction with the accompanying drawings.

  The exemplary embodiments of the present disclosure and their advantages can be more fully understood by reference to the following description, taken in conjunction with the accompanying drawings, in which like features are indicated by like reference numerals, and in which:

FIG. 4 is a schematic flow diagram of an embodiment applied to the manufacture of acrylonitrile products according to aspects of the present disclosure. FIG. 3 is a flow diagram of a method according to aspects of the present disclosure.

  For storage of crude acrylonitrile, it is important to monitor and control both temperature and pH. In this aspect, the method includes detecting a plurality of liquid temperatures at different heights of the crude tank. The method includes the steps of circulating a recirculation flow drawn from a crude tank outflow height, cooling the recirculation flow, and at least a portion of the recirculation flow when the detected temperature is outside a predetermined temperature range. Returning to the tank.

  The methods described herein require less time and steps to release the acrylonitrile product to the final product store than conventional systems and methods. Laboratories and factory labor can be reduced in analyzing samples and adjusting operating parameters to produce acrylonitrile products within specifications. Another advantage is that the number and / or capacity of rundown tanks can be reduced from the number and / or capacity of rundown tanks required in conventional systems and methods. Another advantage is that faster detection of substandard acrylonitrile products for chemical impurities can take corrective action and reduce the amount of acrylonitrile products that re-pass through part (s) of the system. It can be reduced with respect to the amount required in the system and method.

  In the following, reference will be made to the method and the apparatus for carrying it out with reference to the figures.

  As shown in FIG. 1, the apparatus 10 includes a tank 12. Tank 12 may be configured to receive a crude acrylonitrile product stream 14 via line 16. Crude acrylonitrile product stream 14 may be conveyed to tank 12 from a recovery tower or other container (not shown). Crude acrylonitrile product stream 14 may be conveyed into tank 12 at location 18 via line 16. The temperature sensors 20, 22, 24, 26 and 28 may be configured to measure the temperature of the liquid in the tank 12 at corresponding vertical heights 30, 32, 34, 36 and 38 of the liquid in the tank 12. it can. The crude acrylonitrile product in the tank 12 can be carried out of the tank 12 via the conduit 40. The top vapor 110 can be transported from the tank 12 via a pipe 112 to a scrubber (not shown).

  Crude acrylonitrile product can be conveyed from tank 12 via lines 82, 84, 86 and / or 88. Valves 92, 94, 96 and 98 can correspond to lines 82, 84, 86 and 88, respectively. The nozzles 102, 104, 106 and 108 can correspond to the conduits 82, 84, 86 and 88, respectively. The nozzles 102, 104, 106 and 108 may have a vertical height in the tank 12 corresponding to the vertical heights 32, 34, 36 and 38 of the liquid in the tank 12, respectively. The distance between nozzles in a series of nozzles can be the same. Therefore, the distance between the nozzle 102 and the nozzle 104 is the same as the distance between the nozzle 104 and the nozzle 106, and the other can be the same. In one aspect, the distance between successive nozzles can be about 2 to about 12 feet, in another aspect about 5 to about 12 feet, and in another aspect about 8 to about 12 feet. It can be 12 feet, and in another aspect about 10 feet. Although FIG. 1 shows the vertical height of the nozzle 100 lower than the vertical height 30, the nozzle 100 may have the same or almost the same vertical height as the vertical height 30.

  Line 46 can carry the crude acrylonitrile product to heat exchanger or cooler 54, for example, to the tube side of inlet 56 of cooler 54. The cooler 54 can be configured to cool the crude acrylonitrile product through heat transfer using a cooling fluid 58 such as cooling water introduced to the shell side of the inlet 60 of the cooler 54. The cooling fluid 58 can be discharged from the outlet 62 of the cooler 54.

  The crude acrylonitrile product can be cooled in the cooler 54 and then discharged from the outlet 64 and conveyed from the cooler 54 via line 66 as a cooled acrylonitrile product stream 78. For example, an acid 68 such as glycolic acid or acetic acid and combinations thereof can be conveyed through line 70 and added to the crude acrylonitrile product in line 66 at junction 74. The acid 68 can be pumped from the acid source 76 through the conduit 70 by the pump 72. In one embodiment, acid 68 can be added to the cooled acrylonitrile product stream 78 to maintain the pH of the liquid in tank 12 within a predetermined pH range. The cooled acrylonitrile product can be returned to tank 12 through line 80 and nozzle 100.

  In one aspect, the controller 11 corresponds to the temperature of the liquid measured by the temperature sensors 20, 22, 24, 26 and / or 28 and measurement parameters such as the vertical height 30, 32, 34, 36 and / or 38. Can be configured to process one or more signals. The controller 11 can be configured to determine whether the measurement parameter is above or below a predetermined parameter range. One skilled in the art, according to the present disclosure, this measurement parameter can be any suitable parameter useful for operation of the tank 12, such as, for example, a temperature measured by a temperature sensor of a predetermined vertical height. You will recognize it. The controller 11 adjusts the operation of one or more devices via a communication line or wireless communication (not shown in FIG. 1) when the measured parameter is below or above a predetermined parameter range. Can be configured to. For example, the controller 11 may control one or more nozzles 100, 102, 104, 106 and / or by controlling the operation of the cooler 54 and the operation of a valve such as 92, 94, 96 and / or 98, for example. The amount of crude acrylonitrile product conveyed through 108 can be adjusted.

  In one embodiment, the liquid in tank 12 and / or the liquid in tank 12 is localized by recirculating the cooled acrylonitrile product, allowing the liquid in tank 12 to cool, and mixing with the liquid in tank 12. The temperature of the region can be maintained within a predetermined temperature range. In one aspect, the controller 11 is returned to the tank 12 via the line 66, the amount of liquid drawn from the tank 12 via the line 40, the amount of crude acrylonitrile product cooled in the cooler 54, and the line 66. It can be configured to control the amount of crude acrylonitrile product (after cooling). In this embodiment, recirculation is effective to bring the temperature in the crude tank to about 25 ° C. or less. In a related embodiment, the temperature is measured from 1 to about 5 locations, and in another embodiment, the temperature is measured from 2 to about 4 locations. In one aspect, the method is effective to provide a rotation rate of about 50 to about 150 hours, and in another aspect, effective to provide a rotation rate of about 75 to about 125 hours. In embodiments, it is effective to provide a turnover rate of about 75 to about 80 hours, and in another embodiment is effective to provide a turnover rate of about 100 to about 105 hours.

  In one aspect, the controller 11 is configured to process one or more signals corresponding to the pH of the liquid in the tank 12 and / or the pH of the liquid drawn from the tank 12 via line 40. can do. In this aspect, the pH meter 116 can be configured to measure the pH of the crude acrylonitrile product in the tank 12 at location 120 and communicate a signal corresponding to the measured pH to the controller 11 or the flow controller 118. . Controller 11 or flow controller 118 can be configured to process information from the pH meter to control the flow of acid 68 to junction 74. In one aspect, the controller 11 or the flow controller 118 is adapted to adjust at least one operating parameter related to the flow of acid 68 to the junction 74 when the pH measured at location 120 is outside a predetermined pH. Can be configured. In one aspect, the controller 11 can be configured to control the operation of the flow controller 118. In one aspect, the controller 11 can include a flow controller 118. Controller 11 and / or flow controller 118 can include a processor. The processor of controller 11 and / or flow controller 118 may include a memory configured to receive and store predetermined conditions or parameters. The predetermined condition or parameter may be a desired pH value or pH range of the liquid at location 120.

  In one aspect, the controller 11 and / or the flow controller 118 receives a signal corresponding to the pH measured by the pH meter 116 at a predetermined frequency, such as about every 6 hours, and the measured signal is within a predetermined pH range. It can be configured to determine whether or not. In one aspect, the predetermined pH range can be about 2.5 to 4.5, and in another embodiment about 3 to about 4. In one aspect, if the measured pH is greater than or nearing about 4.5, the controller 11 and / or the flow controller 118 may open the valve 119 corresponding to the flow controller 118 at a junction. More acid 68 is added at 74 and can therefore be adjusted to add more acid to tank 12. If the pH measured at position 120 is about 2.5 or approaching it, controller 11 and / or flow controller 118 may open valve 119 corresponding to flow controller 118 with acid 68 applied at junction 74. Can be adjusted to reduce the amount of acid 68 added to the tank 12.

  As shown in FIG. 1, the effluent 41 in the conduit 40 can be withdrawn from the bottom of the tank 12 at a position 43. The position 43 can have a vertical height of zero or nearly zero with respect to the overall height of the tank 12. In one aspect, the ratio of length to diameter of the crude acrylonitrile storage tank is from about 0.5 to about 1.5, in another aspect from about 0.75 to about 1.25, in another aspect About 0.9 to about 1.1.

  FIG. 2 shows a flow diagram of a method 300 according to aspects of the present disclosure. The method 300 can be performed using the apparatus 10 shown in FIG. Step 301 can include detecting a first liquid temperature at a first height of the crude tank. Step 302 can include detecting a second liquid temperature at a second height of the crude tank. Step 303 may include circulating a recirculation flow drawn from the crude tank outflow height. Step 304 can include cooling the recycle stream. Step 305 can include returning at least a first portion of the recirculation flow to a first return height when the detected first temperature is outside the predetermined temperature range. The method 300 can include returning at least a second portion of the recirculation flow to a second return height when the detected second temperature is outside the predetermined temperature range. In one aspect, at least the first return height or the second return height is higher than the outflow height of the crude tank.

  In one aspect, a method is provided for preparing an empty crude tank that receives a crude acrylonitrile product stream, such as crude acrylonitrile product stream 14. In one aspect, the method includes adding to the crude tank an amount of water effective to absorb the organisms under the floating roof of the crude tank. The absorption of the organism is effective in preventing the loss of the organism from the crude tank.

  In another aspect, the start-up method is about 6% by weight or more in an empty crude tank, in another aspect from about 6 to about 15%, in another aspect, about 6 to float the floating roof of the tank. Filling with about 10%, in another embodiment about 6 to about 8% water, may be included. This method circulates water in a cooler, such as cooler 54, for example, so that the target temperature of the liquid in the tank is for example 25 ° C. or less, in another embodiment about 20 ° C. or less, In embodiments, about 18 ° C. or less, in other embodiments about 15 ° C. or less, in other embodiments about 10 ° C. or less, in other embodiments from about 1 to about 10 ° C., in other embodiments A step of about 5 to about 10 ° C can be included. The method can include adding acid to the circulating water to bring the pH of the liquid in the tank to about 4 or less, and in another embodiment from about 3 to about 4. In this embodiment, the acid is added to the water after the water temperature reaches 25 ° C. or below. In another embodiment, the crude acrylonitrile is added to the crude tank when the crude tank is at 25 ° C. or less and the pH is about 4 or less.

  In embodiments where crude acrylonitrile is present in the tank, the method can include sampling the pH of the liquid periodically, such as every 6 hours, and adding additional acid when the pH exceeds about 4.5. . The method can include circulating the crude acrylonitrile product through a cooler, such as cooler 54, to maintain a temperature of less than 18 degrees Celsius.

  In one aspect, a method can be provided that addresses the need to introduce unrefined or substandard products into the holding tank. In such cases, it may be necessary to use the crude acrylonitrile tank as an unrefined or non-standard product holding tank. In one aspect, tank temperature and pH are monitored to avoid or reduce chemical reactions within the tank.

  In one aspect, two separate tanks 12 can be operated in sequence or simultaneously.

  In the foregoing specification, the disclosure has been described with reference to several preferred embodiments thereof, and numerous details have been set forth for purposes of illustration, but those skilled in the art will recognize the present disclosure without departing from the basic principles of the disclosure. It will be apparent that further embodiments of the disclosure are possible and that some of the details described herein may be varied significantly. It should be understood that the features of the present disclosure may be modified, altered, changed or substituted without departing from the spirit or scope of the disclosure and the claims. For example, the dimensions, number, size and shape of various components can be varied to suit a particular application. Accordingly, the specific embodiments illustrated and described herein are for illustrative purposes only.

Claims (33)

A method of maintaining storage of crude acrylonitrile in a crude tank, comprising:
Conveying the crude acrylonitrile to the crude tank;
Adding to the crude acrylonitrile in the crude tank an amount of acid effective to maintain a pH below a target pH;
Maintaining the temperature of the crude acrylonitrile in the crude tank below a target temperature;
A method comprising the steps of: The crude acrylonitrile includes acrylonitrile, water and HCN,
The method of claim 1. The target pH is about 4.5 or less,
The method of claim 1. The target pH is about 2.5 to about 4.5.
The method of claim 1. The pH is measured at one place or two or more places.
The method of claim 1. Acid is added when the pH is increased by about 0.1 to about 0.5 pH units;
The method of claim 5. The acid is selected from the group consisting of organic acids, sulfuric acid and mixtures thereof.
The method of claim 1. The organic acid is selected from the group consisting of acetic acid, glycolic acid and mixtures thereof.
The method of claim 7. The temperature of the crude acrylonitrile in the crude tank is measured at one or more measurement points,
The method of claim 1. The temperature of the crude acrylonitrile in the crude tank is measured at 1 to about 5 measurement locations,
The method of claim 1. Each measurement location is at a different tank height,
The method of claim 9. The temperature of the crude acrylonitrile in the crude tank is maintained using a recycle stream;
The method of claim 1. The recirculation flow is removed from the crude tank at one or more removed locations.
The method of claim 12. The recycle stream is removed from the crude tank at about 1 to about 5 removal points.
The method of claim 13. The recycle stream is cooled using a heat exchanger;
The method of claim 12. The recirculation flow is returned to the crude tank at one or two or more locations different from the removal locations.
The method of claim 12. The recycle stream is effective to maintain the temperature of the crude acrylonitrile in the crude tank at about 25 ° C. or less.
The method of claim 12. Acid is added to the crude acrylonitrile in the crude tank using the recycle stream.
The method of claim 12. The recirculation is effective to provide a rotation rate of about 50 to about 150 hours;
The method of claim 12. A method of preparing a crude tank for receiving crude acrylonitrile, comprising:
Adding an amount of water to the crude tank effective to absorb organisms under the floating roof of the crude tank;
Maintaining the temperature of the water in the crude tank at about 25 ° C. or less;
A method comprising the steps of: The water is added to the crude tank at about 6 to about 15 volume percent of the crude tank.
The method of claim 20. The temperature of the water in the crude tank is maintained using a recirculation system;
The method of claim 20. The recycle stream is cooled using a heat exchanger;
The method of claim 22. The water is maintained at a temperature of about 1 to about 10 ° C.
The method of claim 20. Acid is added to the crude tank when the water in the crude tank is at or below about 25 ° C.
The method of claim 20. The pH of the water is about 3 to about 4.
The method of claim 20. The crude acrylonitrile is added to the crude tank when the crude tank is at or below about 25 ° C. and the pH is 4 or less;
The method of claim 20. A crude acrylonitrile storage tank,
One or more temperature sensors configured to detect different height temperatures in the crude acrylonitrile storage tank;
One or more removal locations configured to remove crude acrylonitrile from the crude acrylonitrile storage tank;
A pH sensor configured to detect the pH of the crude acrylonitrile in the crude acrylonitrile storage tank;
A return line configured to return at least a portion of the recycle stream to the crude acrylonitrile storage tank;
A crude acrylonitrile storage tank comprising: Further comprising a cooler configured to cool a recycle stream drawn from the one or more removal points of the crude acrylonitrile storage tank;
The crude acrylonitrile storage tank according to claim 28. A controller configured to receive a signal corresponding to the pH detected by the pH sensor from the pH sensor and further configured to regulate an acid flow to the tank;
The crude acrylonitrile storage tank according to claim 28. The controller is configured to receive a signal corresponding to the temperature detected by the temperature sensor from the temperature sensor and configured to adjust a flow rate of the recirculation flow.
The crude acrylonitrile storage tank according to claim 30. Further comprising an inlet for adding acid to the recycle stream;
The crude acrylonitrile storage tank according to claim 28. The crude acrylonitrile storage tank has a length to diameter ratio of about 0.5 to about 1.5.
The crude acrylonitrile storage tank according to claim 28.

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