Classifications

• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01C—AMMONIA; CYANOGEN; COMPOUNDS THEREOF
  • C01C1/00—Ammonia; Compounds thereof
  • C01C1/24—Sulfates of ammonium
  • C01C1/242—Preparation from ammonia and sulfuric acid or sulfur trioxide
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C253/00—Preparation of carboxylic acid nitriles
  • C07C253/18—Preparation of carboxylic acid nitriles by reaction of ammonia or amines with compounds containing carbon-to-carbon multiple bonds other than in six-membered aromatic rings

Definitions

• Acrylonitrile is an important commodity chemical used mainly as monomer for the manufacture of a wide variety of polymeric materials such as polymers for acrylic fibers used in textiles, and in resins such as ABS and SAN resins. Worldwide, acrylonitrile is produced in amounts exceeding four million metric tons per year.
• the most commonly used process for manufacturing acrylonitrile or other olefinically unsaturated nitrile, such as methacrylonitrile, is to react a suitable hydrocarbon, such as propylene or propane for the manufacture of acrylonitrile, or isobutylene for the manufacture of methacrylonitrile, in an ammoxidation reactor in the presence of ammonia using air or other source of molecular oxygen as an oxidant.
• Such oxidation reactions also called ammoxidation reactions, typically use a solid, particulate, heterogeneous catalyst in a fluidized catalyst bed to catalyze the ammoxidation reaction and provide the desired acrylonitrile or methacrylonitrile in acceptable conversion and yield.
• ammoxidation reactions In addition to producing an olefinically unsaturated nitrile, such ammoxidation reactions also generally produce other products such as acetonitrile, hydrogen cyanide (HCN) and other co-products.
• HCN hydrogen cyanide
• the processes widely used in commercial practice for recovering the products of such hydrocarbon ammoxidation, such as the ammoxidation of propylene to form acrylonitrile generally comprise the steps of: a) contacting the effluent from an ammoxidation reactor in a quench tower or column with an aqueous quench liquid to cool the gaseous effluent; b) contacting the quenched gaseous effluent with water in an absorber, forming an aqueous solution comprising the ammoxidation products; c) subjecting the aqueous solution to a water extractive distillation in a distillation column, and d) removing a first overhead vapor stream comprising the unsaturated nitrile and some water from the top of the column, and collecting a liquid waste stream containing water and contaminants from the bottom of the column.
• Further purification of the olefinically unsaturated nitrile, such as acrylonitrile, may be accomplished by passing the overhead vapor stream to a second distillation column to remove at least some impurities from the acrylonitrile, and further distilling the partially purified acrylonitrile.
• the effluent from the ammoxidation reactor generally contains a certain amount of ammonia. Therefore, the quench liquid used in the quench column may also contain a strong mineral acid, such as sulfuric acid, to react with and thereby form a water soluble salt of ammonia, such as ammonium sulfate.
• the used or spent quench fluid containing the ammonium sulfate and other components is typically treated or disposed of in an environmentally safe manner.
• the ammonium sulfate concentration in quench bottoms is about 5-10% by weight.
• U.S. Patent 4,341,535 describes an ammonium sulfate recovery process for recovery of heavy organic material contained in liquid bottoms from a quench column.
• the patent describes a sulfate condenser, a vacuum flash drum, a condenser, first, second and third extractors to produce a lower phase in the third extractor containing approximately 1% heavy organic material and 99% liquid, the liquid containing 52% water and 48% ammonium sulfate.
• the patent indicates that this lower phase is withdrawn from the bottom of the third extractor and transferred to a crystalizer for removing water and forming crystallized ammonium sulfate suitable for use as a fertilizer.
• an aspect of the disclosure is to provide a safe, effective and cost
• a process for operating a quench column includes conveying a reactor effluent to a quench column and contacting the reactor effluent with water containing polymer in an effluent extraction zone to provide an extracted effluent stream.
• FIG. 1 is a schematic flow diagram of an embodiment in accordance with aspects of the disclosure as applied to the manufacture of acrylonitrile product.
• the ammonium sulfate concentration in quench columns bottoms is about 5-10% by weight. It has been found that a quench column bottoms stream having an ammonium sulfate concentration of about 5-10% by weight is not suitable for recovery of sulfur in a sulfur regeneration unit ("SAR") due to its high water content and low sulfur content.
• SAR sulfur regeneration unit
• a process includes providing an ammonium sulfate stream having a higher ammonium sulfate concentration.
• the process includes conveying a reactor effluent to a quench column.
• the reactor effluent includes an effluent from an ammoxidation reactor, such as for example, a reactor used for production of acrylonitrile.
• the reactor effluent typically includes acrylonitrile, ammonia and HCN.
• the process includes conveying sulfuric acid to the quench column to provide a quench column bottoms stream having about 10 weight percent or less polymer, in another aspect, 8 weight percent or less polymer, in another aspect, about 5 weight percent or less polymer, and in another aspect, about 2 weight percent or less polymer.
• polymer refers to a mixture of heavy organic material and a slight amount of light organics.
• Heavy organic material may include a mixture of different high boiling organic compounds having a high degree of nitrile substitution and also containing some oxygenated hydrocarbon groups.
• formula y -Mlx + Cl where y is a weight % of ammonium sulfate, x is a weight % polymer, Ml is 4.6 or less and CI is 45 or less defines an amount of ammonium sulfate and an amount of polymer in the quench column bottoms stream.
• Ml is 1.5 or less and CI is 30 or less.
• the process provides a quench column bottoms streams having about 10 to about 25 weight % ammonium sulfate and less than about 5 weight % polymer, in another aspect, about 15 to about 21 weight % ammonium sulfate and less than about 5 weight % polymer.
• the quench column bottoms stream has a pH of about 4.5 to about 6.0.
• the process may include conveying the quench column bottoms stream to a sulfate concentrator.
• the sulfate concentrator provides a concentrated bottoms stream having an ammonium sulfate concentration of about 35 weight % or more.
• the process includes conveying the quench column stream is conveyed to the sulfate concentrator at a flow rate of about about 200 to about 900 kg quench bottoms stream/metric ton of acrylonitnle produced/hour, in another aspect, a flow rate of about 240 to about 860 kg quench bottoms stream/metric ton of acrylonitnle produced/hour, in another aspect, a flow rate of about 300 to about 800 kg quench bottoms stream/metric ton of acrylonitnle produced/hour, and in another aspect, a flow rate of about 500 to about 600 kg quench bottoms stream/metric ton of acrylonitnle produced/hour.
• the sulfate concentrator has a heat load of about 0.15 to about 0.5 kW/kg of quench bottom stream sent to the sulfate concentrator, in another aspect, about 0.15 to about 0.3 kW/kg, and in another aspect, about 0.15 to about 0.2.
• the concentrated bottoms stream from the sulfate concentrator may be conveyed to a sulfur regeneration unit to generate at least one sulfur product form the concentrated quench column bottoms stream.
• a process for operating a quench column includes conveying a reactor effluent to a quench column and contacting the reactor effluent with water containing polymer in an effluent extraction zone to provide an extracted effluent stream.
• the process further includes contacting the extracted effluent stream with sulfuric acid in an acid contact zone and removing a first stream to provide a first quench column stream having about 10 weight percent or less polymer.
• formula y -Mlx + Cl where y is a weight % of ammonium sulfate, x is a weight % polymer, Ml is 4.6 or less and CI is 45 or less defines an amount of ammonium sulfate and an amount of polymer in the first stream. In a related aspect, Ml is 1.5 or less and CI is 30 or less.
• the process includes removing a second stream to provide a second quench column stream having more than about 10 weight percent polymer and less than about 5 weight percent ammonium sulfate.
• the process includes providing at least a portion of the water from an evaporator system.
• an evaporator system include a multistage evaporator, such as a four-stage evaporator.
• the water may include polymer.
• At least a portion of the second quench column stream is recycled to the effluent extraction zone.
• the extracted effluent stream is countercurrent to the sulfuric acid.
• a first quench column stream is removed above the effluent extraction zone. Adiabatic cooling may occur in the effluent extraction zone.
• a process may comprise controlling the amount of makeup water
• the process may comprise detecting the pH of the liquid bottoms of the quench column bottoms and controlling the flow of sulfuric acid to the quench column based on the detected pH of the liquid bottoms to obtain a quench column bottoms stream having a pH of about 4.5 - 6.0.
• the process may comprise determining the concentration of ammonium sulfate in the quench column bottoms stream based on the flow rate of sulfuric acid to the quench column and the flow rate of the quench column bottoms stream from or out of the quench column. In an aspect, the process may comprise adjusting the flow rate of sulfuric acid and/or makeup water conveyed to the quench column based upon the concentration of ammonium sulfate determined in the determining step to maintain the concentration of ammonium sulfate in the range of about 10 to about 25% by weight.
• the process may comprise treating the concentrated quench column bottoms stream (having an ammonium sulfate concentration of about 35-40% by weight) in a sulfur regeneration unit ("SAR") to obtain sulfuric acid.
• the process may comprise conveying sulfuric acid that is generated in the SAR back to the quench column to neutralize ammonia in reactor effluent.
• the process may comprise combining concentrated quench column
• Wastewater from an MMA unit may comprise at least about 40% by weight ammonium sulfate, sulfuric acid and water. It has been found that a combination of concentrated quench column bottoms stream with wastewater from an MMA unit may be more easily treated in an SAR than the concentrated quench column bottoms stream alone.
• the process may comprise adding sulfuric acid to a concentrated quench column bottoms to raise the sulfur content of the stream so that the stream may have a sufficiently high sulfur content operate an SAR without or with a reduced amount of sulfur from other source, such as wastewater from an MMA unit.
• the sulfuric acid added to concentrated quench bottoms may be sulfuric acid produced by the SAR.
• the ability to operate a SAR with such feed to the SAR may be particularly useful when another source of wastewater is not available, e.g., when an MMA unit is temporarily taken offline for service.
• quench column 10 comprises a first portion 28 and a second portion 30, wherein first portion 28 is located below the second portion 30.
• First portion 28 of the quench column 10 comprises an inlet 32 configured to receive a gas stream or reactor effluent 12, wherein the gas stream or reactor effluent 12 comprises acrylonitrile and ammonia.
• Second portion 30 of the quench column 10 comprises a multi-level spray system 34 that is configured to receive an aqueous stream or quench liquid 16, wherein the aqueous stream or quench liquid 16 comprises an acid 36.
• Acid 36 may be added via line 38 to quench liquid 16 at juncture 40.
• Acid 36 may be any suitable acid, e.g., sulfuric acid (such as 98% sulfuric acid).
• Quench liquid 16 may comprise effluent or quench column bottoms stream exiting bottom 42 of quench column 10 and through line 44.
• effluent or quench column bottoms stream may comprise a concentration of ammonium sulfate of about 45 % by weight or less, in another aspect, about 10 to about 25% by weight, and in another aspect, about 15 to about 21% by weight.
• Water may be added via line 46 to quench column 10 through inlet 48, or otherwise may be added to quench liquid 16 or elsewhere in the liquid recycle loop formed by streams 17, 44, and 65.
• Quench liquid 16 may be circulated through line 44 and back to lines 18, 20, 22, and 24, using pump 50.
• An exit stream 67 may be withdrawn as part of the quench column bottoms stream exiting through line 44, in order to maintain a relatively constant mass flow in the liquid recycle loop by offsetting the liquid added via lines 38 and 46.
• Exit stream 67 removes formed neutralization reaction products (e.g., ammonium sulfate) and is also useful for preventing the accumulation of unwanted products in the liquid recycle loop, such as corrosion products.
• Exit stream 67 may be drawn from line 44 at siphon point 52.
• Multi-level spray system 34 comprises at least a first spray bar 54, corresponding to line 18, and a second spray bar 56 corresponding to line 20. As shown in FIG. 1, multi-level spray system 34 also comprises spray bar 58, corresponding to line 22, and spray bar 60, corresponding to line 24. Spray bars 54, 56, 58, and 60 extend substantially across a diameter 62 of quench column 10. As shown, spray bar 54 is located below spray bar 56, and substantially parallel to spray bar 56. Spray bar 58 is located above spray bar 56, and below spray bar 60. Spray bar 58 is substantially parallel to spray bar 60.
• Spray bars may 54, 56, 58, and 60 may each comprise a series of spray arms (not shown in FIG. 1). Spray arms may extend substantially across diameter or chords of quench column 10 that are perpendicular to diameter 62 of quench column 10. Each spray arm may comprise two or more extenders (not shown in FIG. 1). Each extender may extend substantially perpendicular to its respective spray arm. Each extender may comprise a spray nozzle at an end of its respective extender, wherein each spray nozzle faces downward.
• each nozzle of spray system 34 may be configured to downwardly spray a hollow cone spray of the quench liquid 16, wherein each hollow cone spray defines a center equidistant from the walls of the hollow cone spray.
• the nozzles of each spray bar may be spaced so that a portion of a first hollow cone spray of quench liquid from a first nozzle of the first spray bar overlaps with a portion of a second hollow cone spray of quench liquid from a second nozzle of the first spray bar to provide an overlap of the quench liquid, having an overlap center.
• Cooled effluent gas comprising acrylonitrile (including co-products such as
• the quenched or cooled effluent gas comprising acrylonitrile (including co-products such as acetonitrile, hydrogen cyanide and impurities), after passing through mist eliminator 26, may exit quench column 10 as gas stream.
• the gas stream may be passed through conduit to an absorber column (not shown).
• controller 11 may be configured to process one or more signals
• Controller 11 may be configured to determine whether the measured parameter is above or below a predetermined parameter range.
• the measured parameter may any suitable parameter useful in operation of the quench column, e.g., a temperature measured by the temperature controller at a predetermined location, or a liquid level measured by a level controller (not shown in FIG. 1) in boot 45 of the quench column 10, or a flow controller (not shown in FIG. 1).
• Controller 11 may be configured to adjust operation of one or more devices via communication lines or wireless communications (not shown in FIG. 1) if the measured parameter is below or above a predetermined parameter range.
• controller 11 may be configured to adjust the amount of a stream conveyed to quench column 10, e.g., streams such as reactor effluent 12, water (conveyed through line 46 to quench column 10), and/or quench liquid 16 (including acid 36 conveyed through line 38).
• controller 11 may be configured to control operation of pump 50 and/or operation of other pumps and/or valves associated with the above streams or streams further discussed below in order to meet the predetermined range.
• controller 11 may be configured to control operation of valves or other controllers.
• controller 11 may be configured to control operation other device(s) such as a pump (not shown) associated with the flow of water to spray bars.
• controller 11 or a similar controller may be located remote from a temperature controller, a level controller, or flow controller (not shown in FIG. 1), or may be located at and comprise a temperature controller, a level controller, or a flow controller.
• effluent or quench column bottoms may include a concentration of ammonium sulfate of about 45% by weight or less.
• Exit stream 67 may remove formed neutralization reaction products (e.g., ammonium sulfate) and may be also useful for preventing the accumulation of unwanted products in the liquid recycle loop, such as corrosion products.
• Quench column bottoms exiting bottom 42 of quench column 10 may be drawn from line 44 at siphon point 52 to provide stream 67.
• stream 67 may have the same composition as quench column bottoms, including a concentration of ammonium sulfate of about 45% by weight or less, in another aspect, about 10 to about 25% by weight or less, and in another aspect, about 15 to about 21% by weight.
• concentrated quench bottoms streams may be combined with wastewater streams generated by another processing unit, e.g., a methyl methacrylate unit ("MMA").
• Wastewater streams from a methyl methacrylate unit may be combined with concentrated quench bottoms streams and the combined streams may be conveyed to SAR.
• Wastewater streams may include at least about 40% by weight ammonium sulfate, sulfuric acid and water.
• it has been found that a combination of concentrated quench column bottoms stream with wastewater from a methyl methacrylate unit may be more easily treated in an SAR than the concentrated quench column bottoms stream alone.
• the pH of quench column bottoms may be monitored by a pH sensor (not shown).
• a flow controller may be configured to receive a signal corresponding to the pH of quench column bottoms and control the flow of sulfuric acid 36 through line 38 based on the pH of quench column bottoms detected by the pH sensor.
• a flow controller may be configured to control the flow of sulfuric acid 36 to quench column 10 based on the detected pH of quench column bottoms to obtain a stream of quench column bottoms having a pH of about 4.5 - 6.0.
• a flow meter may be configured to detect the flow rate of sulfuric acid being added to quench liquid 16 that is conveyed to quench column 10.
• the flow meter may be a mass flow meter, including but not limited to a Coriolis-type mass flow meter.
• a portion of quench column bottoms may be recycled from the bottom of the quench column back to the quench column. It has been found that when the concentration of ammonium sulfate in this recycle stream has a concentration of about 22% by weight or more, plugging of nozzles spraying ammonium sulfate back into the quench column may occur.

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• 2014
  • 2014-09-30 CN CN201410810834.9A patent/CN104587818B/zh active Active
• 2015
  • 2015-09-01 WO PCT/US2015/047873 patent/WO2016053549A1/en active Application Filing
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