Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
  • B01J19/0006—Controlling or regulating processes
  • B01J19/0013—Controlling the temperature of the process
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
  • C07C51/16—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation
  • C07C51/21—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen
  • C07C51/255—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen of compounds containing six-membered aromatic rings without ring-splitting
  • C07C51/265—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen of compounds containing six-membered aromatic rings without ring-splitting having alkyl side chains which are oxidised to carboxyl groups
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
  • C07C51/42—Separation; Purification; Stabilisation; Use of additives
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
  • B01J2219/00002—Chemical plants
  • B01J2219/00004—Scale aspects
  • B01J2219/00006—Large-scale industrial plants
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P20/00—Technologies relating to chemical industry
  • Y02P20/50—Improvements relating to the production of bulk chemicals

Definitions

• This invention relates to systems and methods to recover heat and scrub the off- gas from oxidation reactors in a process to produce aromatic carboxylic acids.
• Purified terephthalic acid can be produced in a two stage process.
• crude terephthalic acid CTA
• CTA crude terephthalic acid
• the reaction temperature is in the range of about 150-210° C.
• the oxidation is typically carried out in one, two or three vessels in series, and multiple reactors can be used in parallel for each step.
• Reactor vessels are typically agitated vessels, where the agitation is achieved by a combination of mechanical agitation, and the agitation effect of the air being added.
• the second stage of the production process is the purification of the CTA by catalytic hydrogenation in aqueous solution.
• CTA is dissolved in water at high pressure (70-90 barA) and high temperature (275 - 290° C), and hydrogenated over a fixed bed catalyst of palladium supported on carbon.
• the resulting solution is cooled as it passes through a series of four to six crystallizers, where the purified terephthalic acid (PTA) is crystallized with most of the impurities and by-products, such as paratoluic acid, remaining in solution.
• PTA purified terephthalic acid
• the resulting slurry (at a temperature of 140-160° C) is then fed to a suitable continuous solid liquid separation device(s), such as a decanter centrifuge, rotary pressure or vacuum filter, etc where the PTA is separated from the purification mother liquor stream and then dried.
• a suitable continuous solid liquid separation device(s) such as a decanter centrifuge, rotary pressure or vacuum filter, etc where the PTA is separated from the purification mother liquor stream and then dried.
• FIG. 1 illustrates one approach to reacting paraxylene to produce the crude CTA, where two oxidation reactors in series are used.
• the primary oxidation reactor includes paraxylene, aqueous acetic acid, a catalyst, and air and is operated at a reaction temperature of about 200° C at 16 barA.
• the slurry from the primary oxidation reactor is transported to a secondary oxidation reactor, where the slurry is reacted with air at about 187° C and 12 barA to convert more of the reactants to CTA.
• Each of the primary and secondary oxidation reactors has separate off gas systems to recover heat and to scrub the vapor.
• a compressor (not shown) can be used to boost the pressure of the off-gas from secondary oxidation heat recovery system to feed upstream of a single vapor scrubbing system to reduce duplicated components, such as the secondary oxidation reactor off-gas vapor scrubber system.
• this approach requires capital expenditure for the compressor.
• embodiments of this disclosure include systems, methods for the production of terephthalic acid, and the like.
• One exemplary system among others includes a primary oxidation reactor, wherein the primary oxidation reactor is operated at pressure of about 12 to 18 barA and a temperature of about 180 to 210° C, wherein the primary oxidation reactor is in communication with a primary heat recovery system, wherein the primary heat recovery system is in communication with a vapor scrubbing system; and a secondary oxidation reactor, wherein the secondary oxidation reactor is operated at less than 2 bar below the primary oxidation reactor pressure and a temperature of about 5 - 15° C below the primary oxidation reactor temperature, wherein a slurry produced in the primary oxidation reactor is transferred to the secondary oxidation reactor, wherein the secondary oxidation reactor is in communication with a secondary heat recovery system, wherein the secondary heat recovery system is in communication with the vapor scrubbing system.
• One exemplary method for the production of terephthalic acid includes: providing a primary oxidation reactor, wherein the primary oxidation reactor is in communication with a primary heat recovery system, wherein the primary heat recovery system is in communication with a vapor scrubbing system; providing a secondary oxidation reactor, wherein the secondary oxidation reactor is in communication with a secondary heat recovery system, wherein the secondary heat recovery system is in communication with the vapor scrubbing system; introducing paraxylene, acetic acid, a catalyst, and air to the primary oxidation reactor; operating the primary oxidation reactor at pressure of about 12 to 18 barA and a temperature of about 180 to 210° C to produce a first slurry; introducing the first slurry produced in the primary oxidation reactor to the secondary oxidation reactor; and operating the secondary oxidation reactor at less than 2 bar below the primary oxidation reactor pressure and a temperature of about 5 - 15° C below the primary oxidation reactor temperature to produce a second s
• FIG. 1 illustrates a schematic block diagram of part of a process for the production of terephthalic acid.
• FIG. 2 illustrates a schematic block diagram of part of an improved process for the production of terephthalic acid.
• Embodiments of the present disclosure will employ, unless otherwise indicated, techniques of chemistry, chemical engineering, chemical recycling, and the like, which are within the skill of the art. Such techniques are explained fully in the literature.
• Embodiments of the present disclosure include systems for the production of terephthalic acid, methods for processing terephthalic acid, and the like. Embodiments of the systems and methods of the present disclosure are advantageous in that they reduce capital expenditures since certain systems and components are needed to process terephthalic acid. For example, in comparison to one system a vapor scrubbing system can be eliminated, while in comparison to another system a vapor compression system can be eliminated.
• CTA crude terephthalic acid
• the air used for oxidation contains molecular oxygen that can be enriched or depleted in comparison with atmospheric air, prior to feeding to an oxidation reactor.
• the resulting slurry of CTA from the oxidation reactor(s), comprising CTA, oxidation catalyst, reaction intermediates and by products, including color compounds, is typically fed to more than one vessel, usually referred to as crystallizers, to reduce the pressure and temperature of the process stream.
• the CTA solid is separated from the oxidation process mother liquor and, optionally, dried from the oxidation solvent.
• the CTA solid is then mixed with water to form the CTA purification feed stream, prior to purification of the CTA in the second stage of the purified terephthalic acid (PTA)
• the CTA purification process/system can include a number of stages including, but not limited to, CTA re-slurrying stage, slurry heating and CTA dissolution stage, catalytic hydrogenation stage, crystallization stage, filtration stage, solvent recovery stage, drying stage, a mother liquor stream treatment stage, a mother liquor solid treatment stage, and the like.
• FIG. 2 illustrates an embodiment of a portion of a system for the production of CTA.
• the system includes a primary oxidation reactor and a secondary oxidation reactor.
• the primary oxidation reactor and the secondary oxidation reactor are used to form terephthalic acid by an oxidation reaction including paraxylene, acetic acid, a catalyst (e.g., cobalt and/or manganese compounds or other heavy metals such as vanadium, chromium, iron,
• a catalyst e.g., cobalt and/or manganese compounds or other heavy metals such as vanadium, chromium, iron,
• molybdenum a lanthanide such as cerium, zirconium, hafnium and/or nickel and an oxidation promoter
• air a lanthanide such as cerium, zirconium, hafnium and/or nickel and an oxidation promoter
• the relative weight percentage in the liquid phase of each component used is about 10 to 25 of paraxylene, about 74 to 90 of aqueous acetic acid, about 0.1 to 1 of catalyst, and the air flow is greater than about 4.5 times the paraxylene mass flow (for normal atmospheric air, without oxygen enrichment or depletion).
• the initial oxidation occurs in the primary oxidation reactor and produces an off gas (also referred to as "primary off gas”) and a slurry (also referred to as “primary slurry") including the reactants, reaction intermediates and products, is transferred (e.g., flowed or otherwise moved) to the secondary oxidation reactor.
• an off gas also referred to as "primary off gas”
• a slurry also referred to as "primary slurry”
• an off gas also referred to as a "secondary off gas”
• the secondary slurry is further processed to produce purified terephthalic acid.
• the primary off-gas is communicated (e.g., flowed or otherwise transferred using a pipe or transfer structure) to a primary heat recovery system, while the secondary off gas is communicated to a secondary heat recover system.
• the primary and secondary heat recovery systems remove heat from the off gas and produce steam, by exchanging heat with water or steam as the heat accepting fluid and a condensate stream, as a liquid.
• the residual off-gas from each of the primary heat recovery system and the secondary heat recovery system is communicated to the vapor scrubbing system.
• the vapor scrubbing system processes the residual off-gas streams to produce a liquid and vapor that can be further processed.
• the primary oxidation reactor can be operated at a pressure of about 12 to 18 barA and in one embodiment at about 16 barA, while the temperature of the primary oxidant reactor can be about 180 to 210° C and in one embodiment about 200° C.
• the secondary oxidation reactor can be operated at less than 2 bar below the primary oxidation reactor pressure and greater than 1 bar below the primary oxidation reactor pressure, and a temperature of about 5-15° C below the primary oxidation reactor temperature or in one embodiment about 192° C (when the primary oxidation reactor is about 200° C).
• the residual off-gas flowing from the primary heat recovery system can be combined with off-gas flowing from the secondary heat recovery system to flow to a single vapor scrubbing system.
• the pressure drop through the primary heat recovery system must also be increased.
• a benefit of increasing the pressure drop through the primary heat recovery system is the significant increase in the heat transfer coefficient for the heat exchangers in the primary heat recovery system. This reduces the size of the heat exchangers, thereby reducing capital costs in the primary heat recovery system. As the heat recovery systems are typically constructed from expensive corrosion-resistant material, such as titanium, the reduction in capital cost is significant.
• each of the primary and secondary oxidation reactors can be a vessel that is constructed of or lined with a corrosion-resistant material, such as titanium. Because the oxidation reaction is conducted at an elevated pressure, each oxidation reactor can be constructed to withstand the high pressures used for the oxidation reaction. In addition, the contents of the oxidation reactor are agitated to optimize the oxidation reaction and also to maintain the solid reaction product in suspension. Agitation comprises specific fluid mixing configurations and the oxidation reactor can be equipped with one or more mechanical agitators.
• Crude terephthalic acid which is the solid reaction product produced by the oxidation reaction, leaves both oxidation reactors along an outlet line, for example, in the form of an oxidation reaction slurry that comprises a mixture of crude terephthalic acid, water, acetic acid, catalyst metals, oxidation reaction intermediates, and reaction byproducts.
• the primary heat recovery system includes at least one condenser, where each condenser condenses a portion of the off-gas and raises steam.
• the primary off gas is communicated into a gas line that delivers the primary off gas to a series of condensers.
• a first condenser produces a first pressure of steam (e.g., at about 145°C and 4.5 barA)
• the second condenser produces a second pressure of steam (e.g., at about 130°C and 3 barA)
• the third condenser produces a third pressure of steam (e.g., at about 100°C and 1 barA).
• Other embodiments can include more or less than three condensers that can be operated at temperatures and pressures that are appropriate for the number of condensers.
• the secondary heat recovery system can include at least one heat exchanger that transfers heat to a heat transfer fluid.
• the heat exchanger acts as a condenser and condenses a portion of the off-gas and raises steam.
• the steam can be utilized elsewhere in the process and also to generate power.
• the initial heat exchanger acting as a condenser can generate steam at about 130° C and about 3 barA.
• the vapor scrubbing system operates at about 40-50°C and about 9-15 barA and includes optionally a system to degas the condensate from one or both of the primary and secondary heat recovery systems, a system to recover volatile organics (e.g., methyl acetate, paraxylene, etc.), and a system to retain the liquids used for scrubbing within the vapor scrubbing system and venting residual gases.
• the components of the scrubbing system are known in the art.
• the scrubbing liquid can include acetic acid and water, and a combination thereof.
• the vapor scrubbing system comprises at least one scrubbing zone.
• an embodiment of the method of producing CTA including using a system for processing terephthalic acid as described herein that includes a primary and a secondary oxidation reactor.
• eactants such as paraxylene, acetic acid, a catalyst, and air are introduced to the primary oxidation reactor.
• the primary reactor can be operated at a pressure of about 12 to 18 barA and a temperature of about 180 to 210° C (or at other temperatures or pressure described herein) to produce a primary slurry.
• the primary slurry is introduced to the secondary oxidation reactor.
• the secondary oxidation reactor is operated at less than 2 bar below the primary oxidation reactor pressure and a temperature of about 5 - 15° C below the primary oxidation reactor temperature (or at other temperatures or pressure described herein) to produce a secondary slurry.
• a primary off gas from the primary oxidation reactor is produced during the oxidation reaction.
• the primary off gas is flowed to the primary heat recovery system to produce a treated primary off gas.
• the treated primary off gas is flowed to the vapor scrubbing system, where the treated primary off gas is scrubbed.
• a secondary off gas from the secondary oxidation reactor is produced during the oxidation reaction.
• the secondary off gas is flowed to the secondary heat recovery system to produce a treated secondary off gas.
• the treated secondary off gas is flowed to the vapor scrubbing system, where the treated secondary off gas is scrubbed.
• the primary heat recovery system removes heat from the primary off-gas by heat interchange using one or more heat exchangers. As the off-gas flows through each heat exchanger the temperature of the off-gas is reduced and a primary condensate as a separate liquid phase is formed and comprises volatile organic and aqueous components, such as acetic acid, paraxylene, reaction intermediates and water. The primary condensate liquid is collected and can be recycled to the oxidation reactor, purged to remove by-products and water or returned elsewhere in the production process, as required.
• the secondary heat recovery system removes heat from the secondary off-gas by heat interchange using one or more heat exchangers. As the off-gas flows through each heat exchanger the temperature of the off-gas is reduced and a secondary condensate as a separate liquid phase is formed and comprises volatile organic and aqueous components, such as acetic acid, reaction intermediates and water. The secondary condensate liquid is collected and can be recycled to the oxidation reactor, purged to remove by-products and water or
• the treated primary off-gas is scrubbed in a vapor scrubber with the scrubbed treated primary off gas flowing to a power recovery system to beneficially recover work, for example using a turbine to reduce the pressure of the gas.
• the treated secondary off-gas flows to a separate vapor scrubber and is subsequently vented to atmosphere.
• FIG. 2 is an improved embodiment to utilize the scrubbed, treated
• FIG. 2 may not include all of the various components used in each system, method, or process.
• one or more fluid pumps can be used to cause the streams to flow through the system or process at one or more flow rates and at one or more pressures.
• ratios, concentrations, amounts, and other numerical data may be expressed herein in a range format. It is to be understood that such a range format is used for convenience and brevity, and thus, should be interpreted in a flexible manner to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited.
• a concentration range of "about 0.1 % to about 5%” should be interpreted to include not only the explicitly recited concentration of about 0.1 wt% to about 5 wt%, but also the individual concentrations (e.g., 1 %, 2%, 3%, and 4%) and the sub-ranges (e.g., 0.5%, 1.1 %, 2.2%, 3.3%, and 4.4%) within the indicated range.
• the term “about” can include ⁇ 1 %, ⁇ 2%, ⁇ 3%, ⁇ 4%, +5%, ⁇ 8%, or ⁇ 10%, of the numerical value(s) being modified.
• the phrase "about 'x' to 'y'" includes “about 'x' to about 'y'".

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• 2010
  • 2010-12-15 CN CN201080056879.1A patent/CN102652122B/zh active Active
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