RU2575118C2 - Obtaining dicarboxylic acid by method of self-activated oxidative destruction - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to method for obtaining aromatic dicarboxylic acid, which includes (a) oxidation of aromatic compound in, at least, one oxidation installation with obtaining exhaust gas, formed in oxidation installation, and product, formed in oxidation installation, which represents aromatic dicarboxylic acid; (b) direct or indirect supply of, at least, part of said exhaust gas, formed in oxidation installation, into thermal oxidation destruction (TOD), where said TOD device represents installation of regenerative thermal oxidation; and (c) oxidation in said TOD device of, at least, said part of exhaust gas, formed in oxidation installation, where at set mode of said TOD device operation, at least, 60% of quantity of fuel, supplied into said TOD device, is supplied from said exhaust gas, formed in oxidation installation, or from products of reaction of said exhaust gas, formed in oxidation device. In particular invention relates to method for obtaining terephthalic acid, which includes (a) oxidation of paraxylene in, at least, one oxidation installation with obtaining exhaust gas, formed in oxidation installation, and product, formed in oxidation installation, which represents terephthalic acid; (b) direct or indirect supply of, at least, part of said exhaust gas, formed in oxidation installation, into device for thermal oxidation destruction (TOD), where said TOD device represents installation for regenerative thermal oxidation; and (c) oxidation in said TOD device of, at least, said part of exhaust gas, formed in oxidation installation, where, at least, part of said exhaust gas, formed in oxidation installation, which is oxidised in said TOD device, contains acetic acid in quantity, smaller than 0.005 kg/kg of said aromatic compound, supplied into said oxidation installation and contains carbon monoxide in quantity smaller than 0.45 kg/kg of said aromatic compound, supplied into said oxidation installation, and at set mode of said TOD device operation, at least, 70% of quantity of fuel, supplied into said device for thermal oxidative destruction, is supplied from said exhaust gas, formed in oxidation installation, and, at least, 90 mol.% of carbon-containing compound, present in, at least, said part of said exhaust gas, formed in oxidation installation, which is introduced into said TOD device, is oxidised in said TOD to carbon dioxide. With application of exhaust gas more energy is generated on shaft than it is required for bringing main compressor into action in order to obtain compressed air, even at preferable, relatively low temperatures of oxidation method.

EFFECT: invention provides better extraction of contained energy and work on shaft from exhaust gas after carrying out reactions of xylene oxidation and simultaneously minimised consumption for processing waste water.

31 cl, 1 dwg

Description

State of the art

As you know, most of the evaporated solvent from the exhaust gas after the reaction is extracted by passing it through at least one cooling, absorption and / or distillation unit, and a liquid regenerated solvent is obtained. In the General case, it is necessary to maximize the extraction from the exhaust gas of the gas vapor of compounds containing at least one hydrocarbyl bond, which in the present description are called "hydrocarbyl compounds", "volatile organic compounds" and "VOC".

As is known, at least one distillation unit is used to remove excess water from the regenerated solvent, in large quantities generated together with the product during partial oxidation of para-xylene. Various schemes are known for using the energy obtained from the partial oxidation of p-xylene as a source of at least a portion of the energy required for the operation of a distillation plant.

The term "water produced by the preparation of terephthalic acid (TPA)" is defined in the present description as 0.340 kg of water / kg of starting p-xylene (pX) of commercial purity. The indicated amount is obtained from the expected TPA formation from p-xylene according to the following stoichiometry: pX + 3O ₂ gives TPA + 2H ₂ O. Despite the fact that commercial quantities of p-xylene are present, some impurities are present and that a small amount of p-xylene does not completely oxidized and / or excessively oxidized, in modern plants p-xylene of commercial purity is obtained, containing a very low amount of impurities, which is suitable for converting it with a very high yield into crude TPA and / or purified TPA. The total TPA yield as a solid, crude and / or purified TPA, is preferably at least about 96, or 97, or 98, or 99 mol%. by weight of the source of commercial p-xylene, divided by the molecular weight of 106.16 grams per mole. The mass fraction of p-xylene in the starting commercial-grade p-xylene is preferably at least about 0.990; or 0.995; or 0.997; or 0.998.

It is also known that, together with the extraction of the evaporated solvent from a portion of the exhaust gas, using various combinations, energy is recovered, both thermal energy and mechanical work transmitted to the shaft. A known method of energy recovery is to use at least a portion of the exhaust gas to heat the boiling liquid, for example, water or pentane, to produce steam. This steam is used to transfer heat to another consumer, or the steam pressure is reduced in the expander, usually in a turboexpander, in order to produce power transmitted to the shaft. The energy recovered in a turboexpander can be converted directly into mechanical work, such as driving a compressor that supplies compressed air, or other moving mechanisms, or converting it into electricity by rotating an electric generator associated with a power distribution and consumption system.

Another known method of energy recovery is to pass at least a portion of the off-gas containing molecular nitrogen through a turboexpander. The energy recovered in a turboexpander can be converted directly into mechanical work, such as driving a compressor that supplies compressed air, or other moving mechanisms, or converting it into electricity by rotating an electric generator associated with a power distribution and consumption system.

It is also known that a significant portion of the water in the form of steam contained in the exhaust gas is sent to a thermal oxidative degradation (TOD) plant, where pollutants in the form of harmful gases and VOC, for example, carbon monoxide, acetic acid, methyl acetate, p-xylene and methyl bromide is converted to more environmentally friendly waste, such as water vapor and carbon dioxide. Some conversion systems describe the removal from the oxidation reactor of p-xylene of “water generated in the reaction method” as steam by treatment in a thermal degradation apparatus in order to remove harmful pollutants.

SUMMARY OF THE INVENTION

The present inventors have discovered preferred embodiments of the present invention that are not known in the art. Embodiments of the present invention allow significant recovery of the power supplied to the shaft from the off-gas from the oxidation reaction gas, which is carried out in a particular reaction medium, in the form of recovered electric energy or energy for direct mechanical use, and / or recuperation by removing water vapor in an amount exceeding the amount of water generated during TPA production and / or due to a self-sustaining (self-activating) method WKE TOD. In some embodiments, the implementation of the present invention may even offer a combined method of obtaining according to the scheme pX-TPA-PET, in which liquid wastewater practically does not form.

In a preferred embodiment, the present invention provides for the passage of substantially all of the off-gas generated in the oxidation reaction, including off-gas from both primary and secondary oxidation reactors, in which both p-xylene and m-xylene are used as starting material through a common distillation system for extracting the solvent, and then carrying out the processing stage by overheating and processing in a 2-stage turboexpander, including intermediate heating, so as to produce There is more power transferred to the shaft. The specified configuration allows the export of electricity, in addition to its consumption used in the method of air compressors and used in the method of pumps for supplying liquids and suspensions. Flash vapor obtained from condensate in turboexpander heaters is used in another TPA production process. After the turboexpander, part of the water vapor from the off-gas after the oxidation reaction is condensed in order to obtain liquid water, which is used in various methods; and the remaining amount of water vapor is left in the exhaust gas, which is sent to the installation for carrying out the TOD method. To heat the exhaust gas, direct combustion of fuel is optionally used, rather than steam heating, in order to ensure the necessary overheating inside the turboexpander. The pressure at the outlet of the turboexpander is optionally reduced by recompression of the offgas after it has passed through a condenser device and a liquid trap.

In addition, in other aspects of the method of the present invention, the following embodiments of the present invention are preferred:

Sufficient energy fuel potential is stored in the exhaust gas, so that it is heated in a TOD, preferably in a regenerative thermal oxidation (RTO) plant, in order to reduce the amount of environmental pollutants, preferably to a large extent, and more preferably, is completely carried out by self-heating without adding fuel that is not present in the exhaust gas after the reaction. Even more preferably, methyl acetate (MeOAc), which is a known by-product of the oxidation of p-xylene in acetic acid, is the source of a substantial portion of the indicated energy potential of the fuel. The inventors have found how to keep methyl acetate formation low enough that the significant capital and operating costs required to separate methyl acetate and acetic acid by hydrolysis become unjustified compared to the amount of purchased fuel added to RTO.

Condensed water is often generated from water vapor that is contained in the surrounding atmosphere, in compression systems that feed air from the surrounding atmosphere to the oxidation reactors to produce TPA, and said water is potentially contaminated with lubricants and hydraulic lock fluids. The specified condensed water from the environment, preferably, is not sent immediately to the waste water treatment plant, but is introduced into the process fluids used in the TPA production method, for example, used as scrubber water, cooling water, irrigation water, or as process water, for example, as make-up water for a cooling tower.

After the removal and / or thermal degradation of the VOC contained in the exhaust gas, in many regions, hydrogen bromide must be removed from a similarly treated exhaust gas before being discharged into the environment. Such gas purification is often carried out by purifying the gas with water to form a bromine salt, for example, by using an aqueous solution of sodium hydroxide and sodium bisulfite to wash the gas, and sodium bromide is formed. The inventors of the present invention have found that washing water, which is used to control the content of dissolved solids in the scrubber liquid, can not be sent to liquid wastewater, but can be successfully used as process water, for example, make-up water for a cooling tower.

The method for producing polyethylene terephthalate (PET) is also accompanied by the formation of water during the course of the PET formation reaction, and this water is often contaminated with various VOC compounds, for example, ethylene glycol, acetic aldehyde and various dioxolanes. At least a portion of the contaminated water from the PET production method is preferably treated in a common combined plant together with the water generated by the production of TPA in a neighboring TPA synthesis plant. To carry out the treatment, said contaminated water after PET synthesis is preferably either left in the vapor form in which it leaves the specified PET synthesis unit, or it is converted into the vapor form using at least a portion of the heat energy released in said adjacent unit TPA synthesis. More preferably, the water from the PET synthesis method is treated in a common combined TOD unit together with the water generated in the synthesis of TPA.

Both independently and in various combinations, the methods of carrying out the present invention disclosed in this description allow the development of a plant for the conversion of p-xylene to TPA, which gives a very low, practically zero amount of liquid wastewater that requires treatment in order to protect the environment per unit of TPA produced. In addition, the present invention allows the development of a pX-TPA-PET chain conversion plant providing a very low, practically zero amount of liquid wastewater that requires treatment to protect the environment per unit of PET produced.

Brief Description of the Drawings

Figure 1 shows exemplary embodiments of the present invention.

Detailed Description of Preferred Embodiments of the Present Invention

The present invention can be combined with the methods disclosed in US patent applications No. 20070293699 and No. 20060047158 (the entire contents of which are incorporated herein by reference), with the aim of preparing the preferred medium for the primary oxidation reaction, method and development of plants for converting p-xylene to TPA These disclosed descriptions include numerous preferred mechanical devices and conditions for the primary oxidation process, and the process modes, in particular, include temperatures and temperature gradients, pressures and pressure gradients, flow rates, compositions and gradients, mixing and contact and distribution times. Used in the present description, the terms "oxidizable compound", "solvent", "oxidizing agent", "reaction medium" and "hydrocarbyl radical" are given according to the above links.

More preferred are embodiments of the present invention in which at least a portion of the off-gas from the secondary oxidation reaction medium is combined with at least a portion of the off-gas from the primary oxidation reaction medium prior to treatment in solvent extraction and / or dehydration units. It is the secondary reaction medium that receives most of the aromatic substance stream from the upstream oxidation reactor, which may be the primary oxidation reaction medium and / or another secondary reaction medium. See U.S. Patent Application No. 20070155985 and No. 20070208191 for a secondary oxidation reactor that is optimized to further react with incoming liquid phase aromatics, including preferred ranges of process parameters, including temperature, pressure, flows, compositions, mixing, and contacting and distribution times, which are balanced taking into account various costs, including, in particular, excessive oxidation of the substrate, product and solvent. In the present description, this type of secondary oxidation reactor is referred to as a “subsequent oxidation reactor”. See also, in US applications No. 20070208190 and No. 20070219393, a description of a secondary oxidation reactor optimized for further reaction using a solid-phase aromatic compound, including preferred ranges of process parameters, including temperatures, pressures, flows, compositions, mixing and times contacting and distribution, which are balanced taking into account various costs, including, in particular, excessive oxidation of the substrate, product and solvent. In the present description, this type of secondary oxidation reactor is referred to as a “cleavage reactor”.

In the case when it is necessary to generate energy, in particular, shaft power, by burning (oxidative combustion) of compounds, in particular compounds including hydrocarbyl bonds (fuels), the temperature in the method of said combustion is often raised as much as mechanically feasible in order to maximize energy recovery, in accordance with the known principles of thermodynamics. On the other hand, when conducting incomplete catalytic oxidation with the formation of a chemical product, the temperature and pressure of the reaction medium are usually set so as to control the final yields, degree of conversion and purity of the product. The catalytic oxidation methods of the present invention proceed quite quickly, so that great care must be taken to maintain a suitable concentration of dissolved molecular oxygen in the liquid phase, and this leads to the preference given to higher pressures in the system in order to create a higher partial pressure molecular oxygen in the gas phase.

Despite these general preferred options regarding a higher temperature for better energy recovery and a higher pressure to increase the purity of the product as TPA, the present inventors have found that it is preferable to carry out the process, at least for a portion of the primary oxidation reaction medium, with the following moderate pressure and temperature values, even from the point of view of recovering more power on the shaft, and removing more waste water in vapor form. It is preferable to carry out the method, at least for a portion of the primary oxidation reaction medium at a pressure of less than about 12, 10, 8, 7 bar absolute pressure. It is preferable to carry out the method, at least for a portion of the medium of the primary oxidation reaction at a pressure of at least about 2, or 3, or 4, or 5 bar absolute pressure. It is preferable to carry out the method, at least for a portion of the medium of the primary oxidation reaction at a temperature of less than about 200, or 190, or 180, or 170 ° C. It is preferable to carry out the method, at least for a portion of the primary oxidation reaction medium at a temperature of at least about 120, or 130, or 140, or 150 ° C, or 155 ° C, or 160 ° C. The authors of the present invention have found that it is preferable to generate maximum volumes and masses of steam at the outlet of the gas leaving the reaction medium, while observing the energy balance required to obtain preferred values for the reaction temperatures and pressures. Unfortunately, generating more steam increases the difficulties associated with the release of liquids and solids from the exhaust gas leaving the reaction medium. The specified increase in the amount of exhaust gas leads to an increase in the diameters and volumes of pipelines and sizes of technological equipment that processes the exhaust gas after the reaction, which is undesirable; the foregoing relates in particular to a solvent recovery and / or dehydration unit. Exhaust gas is released from the oxidation reaction medium of the present invention, which is corrosive enough to require the use of unusually expensive materials, often containing titanium, in constructions, which is undesirable. The increased vapor stream leaving the reaction medium is significantly depleted both in mass and volume during processing in the solvent extraction and / or dehydration unit, which is undesirable, with most of the hydrocarbyl component of the solvent being regenerated. However, the inventors of the present invention have found that an increased amount of solvent vapor generated in the exhaust gas after the reaction can be partially stored as an increased amount of steam, mainly including water, which leaves the solvent extraction and / or dehydration unit and enters the exhaust gas turboexpander, which often provides a general economic advantage for recovering shaft power, which, as it turned out unexpectedly, outweighs the increase in other operating costs and increases capital expenditures. In one embodiment of the present invention, the hydrocarbyl-depleted exhaust gas generated after the solvent recovery column contains at least 10, or 15, or 20, or 30, or 35, or 40, or 45, or 50 wt%. water vapor from the total flow of hydrocarbyl-depleted exhaust gas. In the method of implementing the present invention, the hydrocarbyl-depleted exhaust gas formed after the solvent recovery column contains less than 4, or 3, or 2, or 1% of the mass. acetic acid by weight of the hydrocarbyl-depleted exhaust gas stream.

The vaporous compounds in the off-gas from the reaction are water vapor plus VOC. Non-condensable gaseous compounds in the off-gas from the reaction gas include molecular nitrogen, molecular oxygen, carbon monoxide, carbon dioxide and molecular hydrogen. Using various aspects of the present invention, the inventors have found that it is possible and preferable as follows to carry out a partial oxidation of p-xylene with increased amounts of vaporous compounds in the exhaust gas after the reaction. The vaporous compounds in the exhaust gas after the reaction are preferably at least about 0.67; or 0.72; or 0.75; or 0.77 kg / kg of exhaust gas after the reaction. The vaporous compounds in the exhaust gas after the reaction are preferably at least about 12.4; or 13.2; or 13.8; or 14.2 kg / kg p-xylene fed to the appropriate oxidation reaction medium.

In an attempt to obtain the indicated significant amounts of steam in the exhaust gas after the reaction, the inventors of the present invention have found that it is preferable to substantially reduce environmental losses and intentional heat removal from the oxidation reaction medium of the present invention through conductive, insulating, boundary surfaces, despite the fact that such an oxidation reaction is highly exothermic and requires significant cooling. It is preferable to insulate so that at least about 70, or 90, or 95, or 99% of the exposed, exposed surface of the reactors and / or pipelines containing at least a portion of the oxidation reaction medium is coated a layer of insulating substance, the thickness of which is at least about 0.01, or 0.02, or 0.04, or 0.08 m. Loss of thermal energy through open, exposed to the environment surfaces of pipelines and / or vessels, containing, by necks least a portion of oxidation reaction medium preferably constitute less than about 40, or 20, or 10, or 5 watts / kg p-xylene fed to corresponding oxidation reaction medium. It is preferable to limit the cooling of at least part of the oxidation reaction medium by means of cooling liquids, in particular by means of water and air, through conductive, insulating, boundary heat exchange surfaces so that the removal of thermal energy is less than about 100, or 10, or 0.1 or 0.01 watts / kg of p-xylene fed to the appropriate oxidation reaction medium.

In an attempt to produce significant amounts of steam in the off-gas from the reaction, the inventors also found that the starting materials fed to the oxidation reaction medium should preferably be as hot as practicable, again despite the fact that such an oxidation reaction is highly exothermic and requires strong cooling. The flow of oxidizing agent supplied to at least one oxidation reaction medium is predominantly compressed air, which is minimally cooled after leaving the final compression stage. At least about 50, or 70, or 90, or 99% of the mass. said compressed air that enters the oxidation reaction medium preferably has a temperature of at least about 60, 70, 80, 90 ° C. At least about 50, or 70, or 90, or 99% of the mass. the specified compressed air that enters the oxidation reaction medium preferably has a temperature at least equal to the temperature at the outlet of the corresponding compressor minus 40, or 20, or 10, or 5 ° C. The insulation is preferably carried out in such a way that at least about 50, or 70, or 90, or 95% of the exposed, exposed surface of the pipelines, vessels and control devices for delivering said compressed air is coated with an insulation layer with a thickness at least equal to approximately 0.005; or 0.01; or 0.02; or 0.04 m.

The solvent is preferably recovered from the exhaust gas after the reaction in at least one solvent extraction and / or dehydration unit, and then returned to the oxidation reaction medium at a temperature that exceeds the ambient temperature and is approximately equal to the temperature of the corresponding reaction medium. Thus, hydrocarbyl compounds are preferably condensed from the off-gas after the reaction, subjected to appropriate dehydration and returned to the reaction medium a little colder than the off-gas. More preferably, said hot regenerated solvent is supplied together with a limited amount of additionally introduced heat energy via conductive, insulating, heat exchange boundary surfaces. As indicated in the present description, this result is achieved due to the corresponding limitation of the amount of thermal energy removed in these installations, the extraction of solvent and / or dehydration. At least about 40, or 60, or 80, or 90% of the mass. the specified regenerated solvent is preferably fed into the oxidation reaction medium with a temperature of less than about 200, or 190, or 180, or 170 ° C, because it is preferable not to transfer thermal energy to the regenerated solvent at a temperature higher than the temperature of the primary oxidation reaction medium. At least about 40, or 60, or 80, or 90% of the mass. the specified regenerated solvent is preferably fed into the oxidation reaction medium with a temperature at least approximately equal to the temperature of the gas leaving the reaction minus less than about 80, or 40, or 20, or 10 ° C. Preferably, at least about 40, or 60, or 80, or 90% of the mass. the specified regenerated solvent is fed into the environment of the oxidation reaction with a temperature of at least equal to approximately 60, or 90, or 120, or 140 ° C. At least about 40, or 80, or 90, or 98% of the total amount of thermal energy to the solvent extraction and / or dehydration units is preferably supplied directly to the incoming gas stream after the reaction without transferring thermal energy through conductive, insulating, boundary heat transfer surfaces. Preferably, at least about 40, or 60, or 80, or 90% of the mass. of said regenerated solvent leaves the solvent extraction and / or dehydration unit at a temperature at least close to the temperature of the corresponding gas leaving the reaction minus less than about 80, or 40, or 20 or 10 ° C, and at the same time it undergoes processing in the specified installation using thermal energy supplied through conductive, insulating, boundary surfaces of heat transfer in an amount of less than about 100, or 30, or 10, or 3 kcal / kg of regenerated solvent, and about n enters the corresponding reaction medium with the amount of thermal energy transferred by means of conductive, insulating, boundary heat exchange surfaces of less than approximately 100, or 30, or 10, or 3 kcal / kg of the regenerated solvent. The insulation is preferably carried out in such a way that at least about 70, or 90, or 95, or 99% of the exposed, exposed surface area of the vessels and / or pipes containing at least a portion of the regenerated solvent is coated with an insulating material with a thickness of at least about 0.01; or 0.02; or 0.04; or 0.08 m.

The solvent used in the filtration, which is collected after filtration and washing with solid TPA, is mainly returned to the oxidation reaction medium heated to a high temperature, which ensures the transfer of thermal energy through conductive, insulating, boundary heat transfer surfaces. The solvent used in the filtration is a solvent after mechanical separation and / or washing of the solid TPA when it is isolated from the suspension. A method of obtaining a solvent used in filtration is the filtration and washing of a TPA suspension by any method known in the filtration technology, however, the authors of the present invention consider all other mechanical separation methods known from the technical field to obtain a solvent used in filtration; for example, sedimentation, the use of centrifuges, hydrocyclones, etc.

Before returning it to the environment of the oxidation reaction, preferably at least about 40, or 60, or 70, or 80% of the mass. said solvent used in the filtration is cooled to a temperature of less than about 100, or 80, or 70, or 60 ° C. This procedure can successfully reduce the solubility of TPA in suspension, and successfully reduces the corrosion ability of the solvent used in the filtration, so that for the design of pipelines, reactors, pumps, and other technological and control equipment, including storage tanks and the processing of the solvent used in the filtration less expensive materials may be used. Suitable structural materials for the specified cooled solvent used in the filtration are various metals and alloys with moderate corrosion resistance, such as stainless steels or duplex steel, as an alternative to titanium and other, more expensive metals and alloys with high corrosion resistance .

However, more preferably, at least about 40, or 60, or 70, or 80% of the mass. the specified solvent used for filtration is fed into the oxidation reaction medium with an inlet temperature of at least about 60, or 90, or 120, or 140 ° C. Preferably, solar energy, heat energy from the off-gas and / or heat energy from steam condensing at a pressure of less than about 60, or 20, or 8, or 4 bar absolute pressure are used so as to heat about 40, or 60, or 70 , or 80% of the mass. the specified solvent used for filtration, at least to a temperature of about 10, or 20, or 40, or 60 ° C before introducing it into the oxidation reaction medium. The specified thermal energy is preferably transferred to the solvent used in the filtration through conductive, insulating, boundary heat exchange surfaces.

p-Xylene is preferably fed into the oxidation reaction medium heated to a high temperature. Preferably, at least about 40, or 60, or 70, or 80% of the mass. the specified source of p-xylene is fed into the reaction medium with an inlet temperature equal to at least about 60, or 90, or 120, or 140 ° C. Mostly, solar energy, heat energy from the exhaust gas and / or heat energy from steam condensing at a pressure of less than about 60, or 20, or 8, or 4 bar absolute pressure are used to heat about 40, or 60, or 70, or 80% of the mass. the specified p-xylene, before introducing its oxidation reaction medium, at least about 10, or 20, or 40, or 60 ° C higher than the temperature at which it is stored in the warehouse, and / or ambient temperature. Preferably, said heat energy is transferred to p-xylene via conductive, insulating, heat exchange boundary surfaces.

Alone or in combination, higher temperatures for the supply of compressed air, the regenerated solvent used in filtering the solvent and / or p-xylene, require an increased liquid flow to be fed to the oxidation reactor in order to maintain the energy balance in the reactor and to provide preferred operating temperatures and pressures . Together with hotter starting materials, more reaction heat is removed in the form of latent heat of evaporation of the solvent, and does not lead to noticeable heating of the starting materials, and an increased amount of incoming liquid solvent leaves the oxidation reactor in the form of solvent vapor in the exhaust gas after the reaction. The supply of increased quantities of the initial liquid solvent requires more expensive pumps, pipelines and devices and control systems, along with an increase in pump capacity, which is undesirable.

When compressing the ambient air, if you do not use drying methods other than cooling, an increase in temperature due to the refusal to use an end cooler often leads to an increase in the amount of water vapor entering the oxidation method. Such added water should ultimately be separated and removed from the oxidation process along with the water formed upon receipt of the TPA in order to maintain the desired solvent composition. In addition, when such added water is finally removed either in the form of steam, or liquid, or solid, this method is often accompanied by a loss of mass of purchased carbon-containing compounds, and, finally, as is known from the art, the amount increases waste water. Thus, such additional water vapor entering together with compressed atmospheric air can be considered doubly undesirable, since it potentially causes a loss of carbon and an increase in the amount of wastewater.

However, in an attempt to use the inventions described herein to remove an increased amount of water in the form of steam and to use the corresponding limited amounts of VOC as a combustible fuel in the TOD, the inventors of the present invention found a general beneficial effect if a predetermined amount of water vapor was stored in compressed atmospheric air, which is used as the initial oxidizing agent. Thus, preferably at least about 70, or 80, or 90, or 95% of the mass. the oxidizing agent, which is fed to at least one oxidation reaction medium of the present invention, contains at least about 0.01; or 0.03; or 0.04; or 0.05 kg of water per kilogram of p-xylene supplied to the corresponding oxidation reaction medium, and less than about 0.12; or 0.10; or 0.08; or 0.07 kg of water / kg of p-xylene supplied to an appropriate oxidation reaction medium.

At the outlet of the oxidation reaction medium, more preferably, the primary oxidation reaction medium, at least part of the exhaust gas is mainly used to create a certain amount of work on the shaft using one or more turboexpanders. Installing a turboexpander, or simply a turboexpander, includes one or more processing steps in a turboexpander, carried out in series, which are optionally provided with one or more devices for intermediate heating. The off-gas leaving the stage with the lowest pressure in the turboexpander until it enters the further steps of the process is referred to herein as off-gas after the turboexpander. At least one processing step in the turboexpander is preferably arranged so that it is mechanically connected to at least one compression step for supplying the oxidizing agent from the ambient air. Such communication is conveniently carried out by means of a rotating mechanical shaft and / or gearbox.

To maximize the power on the shaft, it is necessary to minimize the pressure drop and decrease the thermal energy of the exhaust gas before it enters the turboexpander. However, the requirements to reduce pressure and heat energy required to remove the solvent and remove the appropriate amount of water in the solvent extraction and / or dehydration unit compete with each other. In addition, the capital cost requirements for solvent recovery and / or dehydration plants increase significantly at reduced pressures, which are preferred at the outlet of the turboexpander, since in this case the volumes of exhaust gas become extremely large.

As indicated in the present description, the authors of the present invention have found combinations of parameters that provide and maintain a balance of the flow rate of pressure and thermal energy transmitted by the exhaust gas after the reaction of the solvent extraction and / or dehydration unit, in relation to the recovery of the shaft power transmitted by the exhaust gas in the installation turboexpander. Discovered features and corresponding descriptions of a preferred solvent recovery and / or dehydration plant are described herein. Before discussing them, preferred aspects regarding the installation of a turboexpander will be considered.

Attention should be paid to the preferred pressure ranges that relate to flows at the inlet of the processing stages in the turboexpander. The pressure at the outlet of the exhaust gas from the solvent recovery and / or dehydration unit is preferably reduced by less than about 2, or 1, or 0.5, or 0.2 bar of static pressure, which is estimated at the point where the reaction exhaust gas is generated near the upper surface of the reaction medium. Preferably, the loss of hydrodynamic pressure from friction in the auxiliary heating device supplying thermal energy to the exhaust gas between the outlet of the solvent extraction and / or dehydration unit and the inlet of the turboexpander is less than about 32,000, or 16,000, or 8000, or 4000 Pa. Preferably, the pressure of the exhaust gas at the inlet of the first processing stage in the turboexpander decreases by less than about 2, or 1, or 0.5, or 0.2 bar of static pressure, which is estimated at the place where the reaction exhaust gas is formed near the upper surface of the reaction Wednesday. Preferably, the inlet pressure of at least one processing step in the turboexpander is at least about 2, or 3, or 4, or 5 bar absolute pressure. Preferably, the inlet pressure of the first processing step in the turboexpander is less than about 12, or 10, or 8, or 7 bar absolute pressure. Preferably, the total loss of hydrodynamic pressure from friction in any interstage pipelines and process steps, such as heat exchangers, between the entrance to the first processing stage in the turboexpander and the outlet of the last stage is less than approximately 64,000, or 32,000 or 16,000, or 8000 Pa.

Although it is necessary to minimize the distance from the outlet of the exhaust gas from the solvent extraction and / or dehydration unit to the inlet of the turboexpander in order to minimize the loss of thermal energy through insulation and the loss of pressure energy caused by the loss of hydrodynamic pressure due to friction, the authors of the present invention found that it is preferable to locate the outlet of the exhaust gas into the turboexpander at a distance of less than about 40, or 30, or 20, or 10 m, which is measured upward from a given etki. The above maximizes the re-conversion of the hydrostatic pressure of the exhaust gas into a static pressure at the inlet of the turboexpander, since the height of the rise of the exhaust gas leaving the solvent extraction and / or dehydration unit can be more than 50 m above the indicated mark.

In order to recover more power on the shaft, it is preferable to minimize the supporting pressure in the turboexpander. The reduced maintenance pressure helps to achieve maximum recovery of shaft power in the turboexpander by maximizing the ratio of decompression and off-gas volume. However, the exhaust gas after the turboexpander of the present invention must meet other conflicting requirements. At the very least, the pressure necessary for pumping through pipelines, through control devices and systems, and various equipment, which often includes cooling devices, devices for carrying out processing in accordance with environmental requirements, must be provided before the waste is released into the environment. The production of exhaust gas after a turboexpander with lower pressure values causes significant difficulties associated with the design and capital costs during the indicated final steps of the method. Greater pressure for the off-gas after the turboexpander is recommended to facilitate condensation of the preferred amounts of water and VOC, especially when developing methods where, predominantly, “almost” all the water vapor from the leaving expander is condensed. At lower pressure values, condensing the corresponding parts of water vapor and VOC in the exhaust gas after a turboexpander is difficult or practically impossible if technical coolants with temperatures close to ambient temperature are used, and the cooling of technical coolants is undesirable due to high thermal loads. In addition, the required physical size for heat exchangers is reduced if more pressure remains in the exhaust gas after the turboexpander due to better heat transfer coefficients, better temperature difference compared to the temperature of any selected source of technical coolants, better control of speeds, pressure drop and flow distribution inside specified heat exchangers. Even after most of the condensation has occurred, or after almost complete removal of water vapor and VOC, lower pressures for the exhaust gas after the turboexpander still mean larger sizes for downstream pipelines, control devices and systems and other equipment. In addition, when designing some methods, it is preferable to use the exhaust gas after the expander or the exhaust gas of the condenser to transfer the obtained TPA powder, and this may cause an additional need for increased support pressure in the turboexpander.

In accordance with one aspect of the present invention, the inventors have found that the disclosed structures for exhaust gas pipelines, control devices and systems, heat exchangers, TOD devices, and scrubber devices allow the following preferred conditions to be created for the pressure of the exhaust gas at the outlet of the turboexpander. The pressure of the exhaust gas after the turboexpander is preferably less than about 0.9; or 0.6; or 0.4; or 0.3 bar gauge pressure. The exhaust gas pressure after the turboexpander is preferably at least about 0.05, or 0.10, or 0.15, or 0.20 bar gauge, and, in accordance with this aspect, sufficient pressure energy is provided for so that the exhaust gas after the turboexpander can pass through these pipelines, control systems and devices, and equipment that includes an exhaust gas condenser, a device for trapping fog from condensate, a TOD, a scrubber device, but does not include a step of repeated harvest before discharge into the environment.

According to another aspect of the present invention, it is preferable to further minimize the maintenance pressure in the turboexpander by minimizing the use of downstream pressure, as mentioned above, as well as carrying out the recompression step of the exhaust gas of the condenser of the heat exchanger, where at least about 10, or 20, or 40, or 80% of the mass. water vapor weight present in the exhaust gas after the turboexpander is removed in the form of liquid water. The inventors of the present invention have found that even if water vapor is discharged into the environment according to the inventions described herein, the effective removal of water vapor from the exhaust gas according to the present invention allows a recompression step to be carried out for the remaining exhaust gas, which requires substantially less energy than the increase in power required for greater decompression in the upstream turbo expander. In addition, it is more preferable to place the device for separating the condensate between the condenser for the exhaust gas and the entrance to the recompression unit. (See the description and designations for condenser exhaust gas and condensate trap exhaust gas here). When using off-gas recompression, it is preferable to re-compress the condenser off-gas, more preferably, re-compress the condensate trap off-gas by at least about 0.05; or 0.1; or 0.2; or 0.3 bar. When using off-gas recompression, it is preferable to re-compress the condenser off-gas, more preferably, re-compress the condensate trap off-gas by less than about 0.9; or 0.8; or 0.6 bar. When using off-gas recompression, the pressure of the off-gas leaving the stage with the lowest pressure in the turboexpander is preferably less than about 0.3; or 0.2; or 0.1; or 0.0 bar gauge pressure. When using off-gas recompression, the pressure of the off-gas leaving the stage with the lowest pressure in the turboexpander is preferably at least about -0.9; or -0.6; or -0.4; or -0.3 bar gauge pressure. When using off-gas recompression, it is preferable to arrange at least one recompression step in such a way that it is mechanically connected to at least one processing step in a turboexpander and / or at least one compression step for feeding oxidizing agent from atmospheric air. Such communication is conveniently carried out by means of a rotating mechanical shaft and / or gearbox.

You should now pay attention to the preferred temperature at the inlet of the exhaust gas to the turboexpander installation or, if it is not necessarily present, at the inlet of the exhaust gas preheater, which is placed after the solvent extraction and / or dehydration unit and before the said turboexpander installation. The temperature at the inlet of the first processing stage in the turboexpander is preferably at least about 110, or 120, or 130, or 135 ° C, which is measured in front of any exhaust gas preheater device, optionally placed before the first installation of the turboexpander. The inlet temperature of the first treatment stage in the turboexpander is preferably less than about 190, or 175, or 165, or 155 ° C, which is measured before any exhaust gas preheater device, optionally placed before the first turboexpander installation. The temperature reduction, which is estimated from the point where the exhaust gas after the reaction is formed near the upper surface of the reaction medium, to the point where the exhaust gas enters the first turboexpander unit, is preferably less than 50, or 40, or 30, or 25 ° C while the temperature is measured in front of any device for preheating the exhaust gas, optionally placed before the first installation of the turboexpander.

Although condensing turboexpanders that operate at or below the dew point temperature of a working fluid are well known in the art, certain components of the exhaust gas of the present invention cause excessive erosion and corrosion of many structural materials when used in a turboexpander operating at temperature too close to the dew point of the exhaust gas. The corrosion components are believed to be carboxylic acids and / or bromine in combination with water and / or molecular oxygen.

Thus, it is preferable to operate at the outlet temperature of at least one processing stage in a turboexpander, which is at least about 5, or 10, or 20, or 25 ° C higher than the local temperature of the dew point of the exhaust gas. More preferably, the specified temperature margin, compared with the dew point, is maintained at the outlet of all processing steps in a turboexpander. Similar temperatures are achieved in various ways, including limiting mechanical efficiency. turboexpander, adding thermal energy to the exhaust gas between the outlet of the solvent extraction and / or dehydration unit and the outlet of the turboexpander, and / or limiting the pressure reduction during processing in the turboexpander.

However, after the dew point temperature was effectively avoided, the inventors of the present invention found that in terms of capital costs and operating costs, it is often undesirable to carry out the present invention with too much overheating of the exhaust gas after the turboexpander. Thus, it is preferable to operate at the outlet temperature of at least one processing stage in a turboexpander and at the inlet to the exhaust gas condenser, which is less than about 150, or 120, or 90, or 60 ° C higher than the local dew point temperature .

A less efficient turboexpander requires less thermal energy needed to ensure that the temperature at the outlet of the turboexpander remains in the temperature range specified with respect to the dew point. In the case when less enthalpy is extracted from the working fluid and converted into mechanical energy, the temperature at the outlet of the turboexpander, respectively, will be higher. Depending on the relative costs of thermal energy and the cost of electricity, improving the mechanical efficiency turbines can be harmful or useful for cost optimization. The authors of the present invention have found that in the case where the price per unit of heat input is less than about 0.3 of the cost of electricity expressed in the same units, it is preferable to maximize the mechanical efficiency turboexpander and the use of an additional supply of thermal energy in order to provide the required dew point temperature range at the outlet of the turboexpander. This is less efficient than can be achieved in the cycle of generating electric energy, in particular, it is at least about 0.5 for the ratio of mechanical energy at the output to the thermal energy at the inlet, so that the supply of thermal energy for the exhaust gas may be unreasonable compared to the energy achieved on the shaft. However, the problem of preventing the onset of dew point means that the increasing supply of thermal energy can be combined with improved turboexpander efficiency and / or increased increased decompression in it in order to achieve a noticeable overall improvement in energy recovery. Thus, preferably, mechanical efficiency the turboexpander used in the present invention is at least about 65, or 75, or 80, or 85% of the maximum shaft work output that can be achieved with ideal, isentropic expansion of the off-gas working fluid.

In order to increase the output of mechanical energy from the turboexpander, in particular from the point of view of maintaining the outlet temperature in a preferred temperature range with respect to the dew point temperature, while using a highly efficient turboexpander, it is preferable to transfer the following amounts of thermal energy to the exhaust gas in the interval between the exit from the extraction unit solvent and / or dehydration and entrance to the turboexpander and / or at one of the intermediate stages in a multistage turboexpander: according to at least about 100, or 200, or 300, or 350 watts / kg p-xylene fed to the appropriate oxidation reaction medium; less than about 1000, or 800, or 600, or 500 watts / kg p-xylene fed to the appropriate oxidation reaction medium; at least about 10, or 20, or 30, or 40 watts / kg of exhaust gas after the turboexpander; less than about 100, or 90, or 80, or 70 watts / kg of exhaust gas after the turboexpander; from incoming heat energy, the temperature of the exhaust gas rises by at least about 10, or 20, or 40, or 60 ° C; and from the incoming heat energy, the temperature of the exhaust gas rises by less than about 250, or 200, or 150, or 100 ° C.

Such amounts of thermal energy are supplied through heat exchangers, including conductive, insulating, heat exchange boundary surfaces, which preferably comprise various corrosion-resistant metals and metal alloys known in the art. Preferably, thermal energy is supplied together with the hot working fluid, more preferably due to condensation of the vapor to form part of the liquid aqueous condensate. In addition, the inventors of the present invention have found that it is preferable to form at least a portion of the flash vapor from the condensate with a lower vapor pressure generated in the exhaust gas heat exchanger, to use at least a portion of the flash steam to at least in at least one heat exchange unit elsewhere in the TPA production process, for example, to heat a portion of xylene, a regenerated solvent used to filter the solvent, solid TP A and / or exhaust gas.

Such amounts of thermal energy, optionally, come from the oxidation of fuel by molecular oxygen and the direct association of the resulting hot reaction products with the exhaust gas. These hot reaction products are fed to the point between the exit from the solvent extraction and / or dehydration unit and the inlet to the turboexpander and / or to the intermediate stage of the multi-stage turboexpander. Preferably, said fuel contains hydrocarbyl bonds. More preferably, said fuel is alcohol, acetate and / or hydrocarbon. Even more preferably, said fuel advantageously includes methanol, ethanol, methane, propane, butane and / or diesel fuel. Most preferably, said fuel comprises at least about 50, or 70, or 90, or 95% of the mass. methane.

Part of the compressed atmospheric air is preferably supplied for the oxidation of said fuel, since the exhaust gas from the solvent extraction and / or dehydration unit is often relatively depleted in molecular oxygen and enriched in water vapor. More preferably, at least about 50, or 70, or 90, or 100% of the mass. a stoichiometric amount of molecular oxygen comes from a source of compressed atmospheric air, which is fed into the oxidation reaction zone of said fuel. The stoichiometric amount of molecular oxygen is the minimum amount required to completely convert the incoming fuel into water and carbon dioxide. Even more preferably, less than at least about 300, or 200, or 150, or 120% of the mass. A stoichiometric amount of molecular oxygen is supplied in the form of compressed atmospheric air, which is supplied to the oxidation reaction zone of said fuel. Preferably, the peak temperature for oxidizing said fuel is at least about 300, or 400, or 600, or 800 ° C. Advantageously, to accelerate the oxidation of at least about 10, or 50, or 80, or 95% of the mass. the specified fuel oxidation catalyst is not used. Preferably, at least about 10, or 50, or 80, or 95% of the mass. The VOC in the off-gas leaving the solvent recovery and / or dehydration unit does not burn before it leaves the last stage of processing in a turboexpander.

In addition to increasing the temperature and pressure at the inlet to the turboexpander, the inventors of the present invention have found that the parameters disclosed herein are also preferable for increasing the mass of water vapor reaching the inlet of at least one turbo expander unit. These compositions provide the parameters disclosed in the present description that allow you to develop and make up the primary medium of the oxidation reaction, solvent extraction and / or dehydration plants and pipelines connecting them. Preferably, the composition of the exhaust gas entering at least one processing step in a turboexpander contains at least about 3.0; or 3.3; or 3.5; or 3.6 kg of water per kilogram of p-xylene supplied to the corresponding oxidation reaction medium. Preferably, the exhaust gas entering at least one processing step in a turboexpander includes at least about 0.38; or 0.42; or 0.44; or 0.46 kg of water per kilogram of off-gas produced in the same place. Preferably, the mass flow of exhaust gas at the inlet of at least one processing step in a turboexpander is at least about 6.9; or 7.3; or 7.6; or 7.8 kg / kg p-xylene fed to an appropriate oxidation reaction medium.

Attention should again be paid to the solvent recovery and / or dehydration unit. In the General case, it is necessary to maximize the recovery from the gas after the reaction of the vaporous compounds containing at least one hydrocarbyl bond, which in the present description are referred to as "volatile organic compounds" and "VOC". If you do not remove them from the exhaust gas, then these compounds enter the environment, which is undesirable, and it is more preferable to convert most of them into water vapor and carbon dioxide in TOD. Although the outflow from TOD is safer from an environmental point of view, the loss of VOC in the solvent recovery and / or dehydration unit remains operational costs.

In particular, in the General case, it is necessary to limit the loss of p-xylene, acetic acid and methyl acetate in the exhaust gas that enters the TOD. Various mechanical devices in the solvent recovery and / or dehydration unit influence this minimization of losses, however, ultimately, the separation is controlled by thermodynamics and energy consumption in the solvent recovery and / or dehydration unit. In general, higher energy costs can provide lower VOC losses. Such energy costs result in lower temperatures and / or higher reflux ratios in the solvent recovery and / or dehydration unit.

However, the inventors of the present invention have found that a deliberate increase in the loss of volatile organic compounds in excess of the practical minimum leads to an improvement in the overall economics of the process by integrating with the fuel requirements for the TOD and recovering the shaft power in the turboexpander.

Thus, it is preferable to control energy recovery and energy loss in at least one solvent extraction and / or dehydration unit, in which the off-gas is treated as described herein. The temperature of at least about 40, or 60, or 80, or 90% of the mass. the exhaust gas leaving the solvent recovery and / or dehydration unit is preferably reduced to less than about 50, or 40, or 30, or 25 ° C, and the temperature is measured at the point where the exhaust gas after the reaction is formed near the upper surface of the reaction medium . Advantageously, at least about 70, or 90, or 95, or 99% of the exposed surface of the pipelines, reactors and systems and the control device, including the solvent extraction and / or dehydration unit, are insulated with an insulating material, the thickness of which is at least about 0.01, or 0.02, or 0.04, or 0.08 meters, despite the large amounts of heat energy that are ultimately released into the environment after the turboexpander. Heat losses through open, exposed surfaces of pipelines and / or reactors, including a solvent recovery and / or dehydration unit, are preferably less than about 40, or 20, or 10, or 5 watts / kg of p-xylene supplied into the appropriate oxidation reaction medium.

It is preferable to limit the recovery of thermal energy in such a way that less than about 1000, or 100, or 1, or 0.1 W of thermal energy per kilogram of p-xylene supplied to the corresponding oxidation reaction medium is recovered from the liquids used in the method through conductive insulating, boundary heat transfer surfaces located in the place where the gas leaving the reaction is formed near the upper surface of the reaction medium, and so far at least about 80, or 90, or 95, or 99% of the mass. The molecular nitrogen contained in the reaction gas will not pass through the turboexpander. Some designs known for recovering energy from off-gas from a reaction gas include condensing and recovering a solvent by extracting heat energy through conductive, insulating, heat-exchange boundary surfaces to heat and / or evaporate process fluids before the off-gas passes through a turboexpander . Process fluids are then used to recover shaft power and / or transfer thermal energy to other stages. Examples of technical fluids used for heat transfer and / or cooling include liquid water and / or steam, light liquid hydrocarbons and / or steam, and / or air.

The solvent recovery and / or dehydration unit preferably operates without the addition of auxiliary compounds for azeotropic separation. Examples of azeotropic distillation adjuvants include n-butyl acetate and / or n-propyl acetate. The solvent recovery and / or dehydration unit preferably works in such a way that the total amount of azeotropic distillation aid added is less than about 0.1; or 0.01; or 0.001; or 0.0001 kg / kg of solvent recovered from the off-gas from the reaction.

The solvent recovery and / or dehydration unit of the present invention preferably includes a highly efficient distillation unit that processes at least about 80, or 90, or 95, or 99% of the mass. non-condensable gases and / or molecular nitrogen present in the exhaust gas after the reaction. The specified distillation installation preferably includes at least about 20, or 25, or 30, or 35 ideal stages of separation. The loss of hydrodynamic pressure from the friction of the exhaust gas in said distillation unit is preferably less than about 60, or 40, or 20, or 10 kPa. The design of any distillation trays used should advantageously provide a small pressure reduction that is less than about 1200, or 900, or 700, or 500 Pa per tray, although this undesirably limits the range of variation of the parameters of these trays in the operating method . It is more preferable to use a structured packing known in the art, despite the need for expensive corrosion-resistant alloys, and despite the potential flammability of some metals containing titanium. The specified distillation installation is preferably constructed using at least two different diameters for the reactor, with a maximum horizontal diameter of the upper section of less than about 1.0; or 0.96; or 0.92; or 0.90 of the maximum horizontal diameter measured at a height mark of approximately 4 m in the lower part of the reactor, while the plant processes at least about 80, or 90, or 95, or 99% of the mass. molecular nitrogen contained in the exhaust gas after the reaction.

Preferably, after exiting the turboexpander, at least a portion of the off-gas is cooled in at least one heat exchanger, which is referred to herein as an off-gas condenser, to form a liquid, which is called reflux in this description and which mainly contains water , and at least a portion of said liquid is directed to said solvent recovery and / or dehydration unit. The various preferred ranges of temperature, pressure and / or composition at the inlet of the off-gas condenser are preferably the same as those at the outlet from the final processing stage in the turboexpander. The loss of hydrodynamic pressure from the friction of the exhaust gas in said off-gas condenser is preferably less than about 16, or 12, or 8, or 4 kPa. If the exhaust gas recompression step is not carried out, the excess pressure of the exhaust gas at the outlet of said exhaust gas condenser is preferably at least about 0.02; or 0.08; or 0.12; or 0.16 bar. If the exhaust gas recompression step is not carried out, then the excess pressure of the exhaust gas at the outlet of said exhaust gas condenser is preferably less than about 0.6; or 0.5; or 0.4; or 0.3 bar. If an optional off-gas recompression step is carried out, the excess pressure of the off-gas at the outlet of said off-gas condenser is preferably at least about -0.8; or -0.7; or -0.6; or -0.5 bar. If an optional off-gas recompression step is carried out, the excess pressure of the off-gas at the outlet of said off-gas condenser is preferably less than about 0.1; or 0.0; or -0.1; or -0.2 bar. The temperature of the exhaust gas at the outlet of said exhaust gas condenser is preferably at least about 30, or 40, or 50, or 60 ° C. The temperature of the exhaust gas at the outlet of said exhaust gas condenser is preferably less than about 110, or 100, or 90, or 80 ° C. The temperature of the exhaust gas at the outlet of said exhaust gas condenser is preferably reduced by at least about 10, or 20, or 30, or 35 ° C, compared with the temperature at the outlet of the turboexpander. The temperature of the exhaust gas at the outlet of said exhaust gas condenser is preferably reduced by less than about 100, or 80, or 70, or 60 ° C, compared with the temperature at the outlet of the turboexpander. In said off-gas condenser, preferably, an amount of thermal energy is recovered which is less than about 3100, or 2900, or 2700, or 2500 watts / kg of p-xylene supplied to the corresponding oxidation reaction medium. Preferably, at least about 1600, or 1800, or 2000, or 2100 watts of heat energy per kilogram of p-xylene fed to the corresponding oxidation reaction medium is recovered in said off-gas condenser.

The amount of reflux and temperature are selected and controlled in such a way as to maximize the amount of water vapor entering the turboexpander, while minimizing the loss of VOC in the exhaust gas that leaves the condenser. The reflux stream directed to the solvent recovery and / or dehydration unit preferably contains at least about 7.0; or 8.0; or 8.5; or 9.0 kg of liquid water per kilogram of water formed upon receipt of TPA in oxidation reactors that are serviced by said solvent extraction and / or dehydration unit. The reflux stream directed to the solvent recovery and / or dehydration unit preferably contains less than about 12.0 or 11.0, or 10.5; or 10.0 kg of liquid water per kilogram of water formed upon receipt of TPA in oxidation reactors that are serviced by said solvent extraction and / or dehydration unit. The reflux stream directed to the solvent recovery and / or dehydration unit preferably contains at least about 0.70; or 0.75; or 0.79; or 0.82 kg of liquid water per kilogram of water vapor leaving the solvent recovery and / or dehydration unit. The reflux stream directed to the solvent recovery and / or dehydration unit preferably contains less than about 0.98 *; or 0.96; or 0.92; or 0.90 kg of liquid water per kilogram of water vapor leaving the solvent recovery and / or dehydration unit. (* If optional direct combustion of the fuel is used, more water is generated by the combustion of the fuel.) The reflux temperature supplied to the solvent recovery and / or dehydration unit is preferably at least about 40, or 50, or 55, or 60 ° C. The temperature of the reflux supplied to the solvent recovery and / or dehydration unit is preferably reduced to less than 40, or 30, or 20, or 10 ° C, compared with the temperature of the water vapor in the off-gas leaving the condenser.

The authors of the present invention note that the placement of the exhaust gas condenser with such a low pressure, according to the present invention, significantly increases the volume of exhaust gas at the inlet and outlet of the condenser. If pipelines of an unusually large diameter are not used, then the flow rates and hydrodynamic pressure decrease too actively. Thus, the off-gas pipelines between the outlet of the turboexpander and the inlet of the off-gas condenser should preferably have a diameter of at least about 1.2; or 1.5; or 1.8; or 2.1 m, which is quite a lot for pressure pipelines used in the methods, which are made of various expensive, corrosion-resistant metals and metal alloys. To reduce the diameter and cost of pipelines, the reduced velocity of the exhaust gas in the pipelines between the outlet of the turboexpander and the inlet of the exhaust gas condenser should preferably be at least about 30, or 40, or 50, or 60 m / s. Such unusually high speeds in the pipelines cause erosion, especially in the case of a corrosive gas leaving the process at a temperature close to the dew point temperature, so strict control of the dew point temperature is required. At the outlet of the off-gas condenser, the presence of a certain amount of liquid droplets increases the likelihood of erosion and corrosion, and it is preferable to limit the reduced velocity in said pipelines to a value less than about 30, or 25, or 20, or 15 m / s, until the off-gas falls into a condensate trap designed to remove liquid, as disclosed in the present description.

The authors of the present invention also note that, according to the present invention, the operation of the off-gas condenser at low pressure forces the use of a lower temperature during the process in order to condense a given amount of reflux. The lower temperatures of the method are limited by approaching the temperature of the cooling liquid, and lower pressures of the method lead to a decrease in the film heat transfer coefficient during the process. All these factors lead to an increase in the area of conductive, insulating, boundary surfaces of heat transfer, which, as a rule, contain various expensive, corrosion-resistant metals and metal alloys.

The design difficulties and costs of the off-gas condenser of the present invention are further increased when, in accordance with some aspects of the present invention, it is desired to release the preferred amounts of water vapor into the environment. Removing a predetermined amount of water vapor requires special control over the amount of energy removed in the off-gas condenser, even when new or non-clogged conductive, insulating, boundary heat exchange surfaces are used, they work with low mass transfer values and / or energy costs, obtaining TPA with reduced performance, and with variable refrigerant temperatures, which is often observed, for example, due to daily and seasonal changes in environmental conditions.

Particularly difficult to control the operation of the exhaust gas condenser is that most of the water supply systems in the cooling tower contain large amounts of dissolved solids, the concentration of which increases significantly with adiabatic cooling using ambient air. In the case where the flow of such cooling water is controlled so as to control the temperature in the flue gas condenser, the temperature of the cooling water at the outlet increases. If the temperature of such cooling water rises too high, then part of the dissolved substances precipitate. Unfortunately, under similar deposits, pitting quickly attacks many corrosion-resistant metal alloys, forming holes. In this regard, the authors of the present invention have found the following preferred embodiments of the exhaust gas condenser of the present invention. As used herein, the term “condenser exhaust gas” is an exhaust gas, at least a portion of which has been treated in at least one exhaust gas condenser.

Said flue gas condenser producing liquid water is predominantly air-cooled, while the surrounding air is in contact with conductive, insulating, boundary heat exchange surfaces containing said flue gas. In order to organize the movement of the air flow through the conductive, insulating, boundary heat exchange surfaces containing said exhaust gas, pressure fans are preferably used. Preferably, the fan speed, the inclination of the fan blades, the ventilation grilles for controlling the air flow and / or other means for controlling the air flow and / or air temperature are used in order to control the degree of cooling of the exhaust gas depending on at least one process parameter ; for example, the temperature and / or pressure of the condenser exhaust gas; temperature and / or flow rate of the liquid used in the condenser; chemical composition or condenser exhaust gas or condensate, which is determined by any operational analytical method, for example, using infrared methods for analyzing the chemical composition.

More preferably, said liquid water-producing off-gas condenser includes cooling water in contact with conductive, insulating, heat exchange boundary surfaces containing said off-gas. Preferably, the cooling water flow rate, the cooling water inlet temperature and / or the cooling water outlet temperature are used to control the degree of cooling of the exhaust gas depending on at least one process parameter, for example, the temperature and / or pressure of the condenser exhaust gas ; temperature and / or flow rate of the liquid used in the condenser; chemical composition or condenser exhaust gas or condensate, which is determined by any operational analytical method, for example, using infrared methods for analyzing the chemical composition. Preferably, at least a portion of the cooling water leaving the specified water-cooled heat exchanger has a temperature of at least about 50, or 60, or 70, or 80 ° C. Preferably, said cooling water is water cooled by direct contact with the surrounding atmosphere. More preferably, said cooling water is “closed loop cooling water”. Preferably, said closed loop cooling water contains a reduced total dissolved solids (TDS), for example, deionized water or steam condensate. Preferably, at least a portion of the heat is removed from said cooling water in a closed loop in a heat exchanger that includes process cooling water, which is cooled by direct contact with the surrounding atmosphere. Preferably, at least a portion of the heat is removed from said cooling water in a closed loop in a plate heat exchanger.

Optionally, at least a portion of the conductive, insulating, boundary surface of the heat transfer is sometimes removed from the duty cycle depending on at least one process parameter, for example, the temperature and / or pressure of the condenser exhaust gas; temperature and / or flow rate of the liquid used in the condenser; chemical composition or condenser exhaust gas or condensate, which is determined by any operational analytical method, for example, using infrared methods for analyzing the chemical composition. The specified part of the surface is removed from the duty cycle, blocking its contact with the exhaust gas stream and / or the flow of technical coolant.

An alternative way to control the amount of energy removed in the off-gas condenser is to provide a bypass for a portion of the off-gas after the turboexpander to bypass said capacitor, as disclosed in US Pat. No. 6,040,551, the entire contents of which are incorporated herein by reference. However, this bypassing of gas creates new problems, despite the fact that it allows you to regulate and control the extraction of energy. Firstly, such bypassing directly affects the material balance, as well as the energy balance, since it is not easy to condense the solvent vapor in the exhaust gas passing through the bypass line. If too much or too little gas is directed to the bypass line, then an attempt to satisfy the energy balance causes a violation of the water balance in the solvent extraction system and leads to the fact that the regenerated solvent becomes too wet or too dry; the amount of VOC sent to the environment and / or to the TOD also changes. Secondly, it is necessary to combine again the condenser exhaust gas and the exhaust gas that has passed through the bypass line in order to process in a common device designed to remove environmentally harmful components. However, such a combination causes problems since when mixing a colder liquid-saturated gas stream with a warmer liquid-saturated gas, aerosol fog is typically formed. Such an aerosol is dangerous from the point of view of pitting corrosion in pipelines and inside the equipment, since the aerosol tends to collect in the form of droplets on colder and / or less turbulent surfaces. The rapid removal of such an aerosol from a method that uses high speeds is difficult to achieve by limiting the pressure drop and / or adding thermal energy, despite the fact that with increasing separation time, such fog easily coalesces with the formation of rain from liquid droplets.

Thus, the present inventors have found the following preferred embodiments of the present invention. At the outlet of the turboexpander, at least a portion of the off-gas through the bypass line passes at least one off-gas condenser to form a “bypass off-gas”, using one or more of the following preferred aspects. Preferably, said bypass exhaust gas is cooled by less than about 60, or 50, or 30, or 10 ° C in a heat exchanger including conductive, insulating, heat exchange boundary surfaces before combining it with the exhaust gas leaving the exhaust gas condenser, which enters the TOD and / or is released into the environment. Preferably, the specified bypass exhaust gas is at least about 1, or 2, or 4, or 8% of the mass. from the mass of all exhaust gas leaving the turboexpander. Preferably, the specified bypass exhaust gas is less than about 50, or 40, or 30, or 20% of the mass. from the mass of all exhaust gas leaving the turboexpander. The volumetric flow rate of said bypass exhaust gas is preferably used to control the degree of cooling of the exhaust gas depending on at least one process parameter, for example, the temperature and / or pressure of the condenser exhaust gas; temperature and / or flow rate of the liquid used in the condenser; chemical composition or condenser exhaust gas or condensate, which is determined by any operational analytical method, for example, using infrared methods for analyzing the chemical composition. Said bypass exhaust gas, before being released into the environment, is preferably combined with at least a portion of the exhaust gas exiting the exhaust gas condenser, thereby forming a “mixed exhaust gas”. A "condensate trap", in which at least one of the following design features is used, preferably processes at least a portion of the condenser exhaust gas, thereby producing a "condensate trap exhaust gas". Preferably, at least about 10, 50, 98, 99.9% of the mass. the liquid entering the specified condensate trap is separated and removed with a content of less than about 50, or 95, or 99, or 99.8% of the mass. molecular nitrogen present in the exhaust gas from an opening located at the bottom of said condensate trap at a distance of less than 80, or 60, or 40, or 10% of the height of said condensate trap. At least a portion of said condensate trap is preferably located lower than at least one off-gas condenser supplying said condensate trap with a multiphase gas and liquid flow. Liquid water leaves said condensate trap from an opening, preferably located below the inlet level for the stream coming from the off-gas condenser. The reduced vertical velocity of the exhaust gas in said condensate trap is preferably less than about 4, or 3, or 2, or 1 m / s in the plane of the largest horizontal diameter. The reduced horizontal velocity of the exhaust gas in said condensate trap is preferably less than about 6, or 5, or 4, or 3 m / s in the plane of the largest vertical diameter. The average residence time of the exhaust gas in said condensate trap is preferably less than about 20, or 13, or 8, or 5 seconds. The average residence time of the exhaust gas in said condensate trap is preferably at least about 0.5; or 1.0; or 1.5; or 2.0 sec. The average residence time of the liquid inside said condensate trap is preferably at least about 0.5; or 2, or 4, or 8 minutes. The average residence time of the liquid inside said condensate trap is preferably less than about 60, or 48, or 24, or 12 minutes. Preferably, at least one reflective surface for separating the liquid, which is different from the boundary surfaces serving to maintain pressure, is located within said condensate trap. Preferably, the area of the solid surface in contact with the exhaust gas that passes through the condensate trap is at least about 0.0005, or 0.001, or 0.002, or 0.004 m ² / kg of exhaust gas that leaves the condensate trap. Preferably, at least a portion of the exhaust gas that passes through said condensate trap is in contact with at least about 0.001, or 0.005, or 0.01, or 0.02 square meters of the non-pressurized insulating solid surface area a kilogram of p-xylene fed to the appropriate oxidation reaction medium. Preferably, at least about 70, or 80, or 90% liquid droplets, the size of which is at least less than about 500, or 200, or 75, or 25 μm, are present in the exhaust gas that is fed to the condensate trap is removed from the exhaust gas passing through the condensate trap. The inventors of the present invention have found that these various preferred design features of a condensate trap are preferred for a condensate trap in which a condenser exhaust gas is treated, with or without bypass exhaust gas.

Preferably, at least a portion of the bypass off-gas is processed in a TOD, which also processes at least a portion of the off-gas that exits the off-gas condenser. More preferably, before being fed to the TOD, at least a portion of the bypass off-gas is combined with at least a portion of the off-gas passed through the condenser to form a mixed off-gas stream. Most preferably, thermal energy is added in order to raise the temperature of said mixed exhaust gas before introducing it into the TOD device. The specified heating reduces the formation of condensate in the pipelines of the exhaust gas, reactors and other vessel vessels and, thus, minimizes the cost of structural materials. Said heat energy may be added to all or part of said mixed exhaust gas stream, to a specified bypass exhaust gas stream, or to a specified exhaust gas stream exiting the condenser. The temperature of said mixed off-gas is preferably at least about 10, or 20, or 40, or 60 ° C higher than the temperature of the off-gas discharged from said off-gas condenser.

The inventors have found that, in accordance with this aspect, it is preferable to add thermal energy to the exhaust gas after it has been treated in a condensate trap, even without using a bypass exhaust gas. The flue gas condenser and the condensate trap are preferably positioned in such a way as to strike a balance between the cost of pumping cooling water to a greater height, the cost of high structures and supporting elements, and the conditions for ensuring the necessary level of height in order to allow gravity of the condensed liquid to flow into the condenser and / or through a flue gas condenser and / or condensate trap. The height of the lowest cooled surface in at least one off-gas condenser is less than about 50, or 30, or 20, or 10 meters above the ground. The height of the highest cooled surface in at least one flue gas condenser is at least about 6, or 9, or 12, or 15 meters above the ground. The level of liquid storage for the condensate trap inside the condensate trap is preferably at least about 0.5, or 1, or 2, or 3 m above the earth's surface at that location. The level of liquid storage for the condensate trap inside the condensate trap is preferably less than about 20, or 15, or 10, or 5 meters above the ground.

In combination with improved energy recovery from the exhaust gas turboexpander and / or TOD self-heating, as disclosed herein, the inventors of the present invention unexpectedly found the benefits of maintaining an increased amount of water vapor in the discharged exhaust gas, despite the large VOC losses that often accompany this increased amount of water vapor. Thus, the inventors of the present invention disclose the following preferred embodiments of a “removable water vapor” that is present in the condenser exhaust gas, the condensate trap exhaust gas and / or the exhaust gas at the inlet to the TOD. The water vapor to be removed is preferably less than about 400, or 300, or 250, or 200% by weight of the water formed upon receipt of the TPA. The above allows at the same time to avoid excessive consumption of the heat of the oxidation reaction to the evaporation of liquid water during the energy cycle of the turboexpander, as well as subsequent capital costs and operating costs for processing in TOD, and at the same time to avoid a concomitant increase in the reflux rate to the solvent extraction and / or dehydration unit. Removed water vapor, preferably, is at least about 100, or 110, or 130, or 150% of the mass. from the mass of water formed upon receipt of TPA. In order to avoid a situation where excessive dehydration of the regenerated solvent system occurs and thereby the oxidation reaction conditions are violated, this description discusses preferred sources of such an amount of water that exceeds the amount of water generated during TPA production.

The water vapor to be removed, in addition to the amount of water that was formed during the production of TPA, preferably contains at least a portion of the water that has entered the process together with the supply of an oxidizing agent, more preferably compressed atmospheric air. This description describes the preferred amount of water vapor supplied with compressed air. The water vapor to be removed, in addition to the amount of water that was formed during the production of TPA, preferably contains at least a portion of the water that was formed from the excessive oxidation of aromatic compounds and the solvent. The steam to be removed preferably includes at least about 0.05; or 0.10; or 0.15 kg of water, which was formed during excessive oxidation of aromatic compounds and solvent per kilogram of p-xylene supplied to the corresponding oxidation reaction medium. The steam to be removed preferably includes less than about 0.05; or 0.04; or 0.03 kg of water, which was formed during excessive oxidation of aromatic compounds and solvent per kilogram of p-xylene supplied to the corresponding oxidation reaction medium.

The water vapor to be removed, in addition to the amount of water that was formed when the TPA was prepared, preferably includes water that was formed when the steam was injected under pressure (at least 50, 90, 95, 99% by weight of water, at least about 110, or 140, or 180, or 220 ° C) into a process stream comprising a liquid solvent. Preferred embodiments of the present invention include steam as a source of thermal energy and as a medium for flushing pipes, holes and equipment. The water vapor to be removed, in addition to the amount of water that was formed during the production of TPA, preferably includes at least a portion of the water that is used to clean the ventilation pipes, through which the gas is subsequently released into the environment. The water vapor to be removed, in addition to the amount of water that was formed when the TPA was prepared, preferably includes at least a portion of the water that is used as an aid for azeotropic separation in the solvent purification and / or catalyst recovery method disclosed in US Pat. Nos. 4,939,297 and No. 7351396 and US patent application No. 2005-0038288.

The water vapor to be removed, in addition to the amount of water that was formed during TPA production, preferably includes at least part of the water that was formed during fuel oxidation, if it is optionally used to heat the exhaust gas in the gap from the outlet of the solvent recovery unit and / or dehydration to the outlet of the turboexpander.

The water vapor to be removed, in addition to the amount of water that was generated during the production of TPA, preferably includes at least a portion of the water that comes from the adjacent PET production method and which is introduced into the TPA production process at the point in front of the TOD outlet, more preferably , before entering the TOD. The specified method for producing PET is preferably located so that the minimum horizontal distance from the specified TPA method is less than approximately 1800, 900, 300, 100 meters. In said method for producing PET, preferably at least a portion of the PET is produced using a TPA product from said method for producing TPA. At least a portion of said TPA product is preferably introduced into the reaction medium of said adjoining method for producing PET for less than about 72, or 24, or 12, or 4 hours after it has been prepared from para-xylene, para-toluyl aldehyde and / or para-toluic acid. Water coming from said PET production process is preferably at least about 0.02; or 0.2; or 0.3; or 0.4 kg / kg of water generated upon receipt of TPA. Water coming from said PET production process is preferably less than about 1.1; or 0.9; or 0.7; or 0.6 kg / kg of water generated upon receipt of TPA.

TOD is preferably self-activated by oxidizing the compounds contained in the exhaust gas, including carbon monoxide and VOC, in particular by oxidizing methyl acetate. The fuel content of the exhaust gas is preferably at least about 60, 70, 80, 90% of the total amount of fuel entering the TOD. The fuel content is estimated as the heat of oxidation reactions, which lead to the formation of products in the vapor phase, including water vapor and gaseous carbon dioxide. The fuel content in the exhaust gas is preferably less than about 160, or 140, or 120, or 110% of the minimum fuel content necessary for the TOD to operate without the use of condenser devices, for example, for noticeably heating air or other gas / steam and / or noticeable or latent heating of water or another liquid, either directly by mixing the masses, or indirectly by insulating the conductive heat transfer surfaces.

It is expedient and even predominantly used as fuel in TOD to use methyl acetate contained in the exhaust gas, in accordance with the following description. Methyl acetate is a known by-product of the liquid phase oxidation of p-xylene in the preparation of TPA in acetic acid. A technique is known in the art for the separation of methyl acetate, followed by its hydrolysis with water to extract acetic acid as a solvent, and waste is generated in the form of methanol as a by-product. The inventors of the present invention have found that an effective TPA synthesis system, as shown, for example, in US Pat. No. 20070293699 and US 20070208191 (the entire contents of which are incorporated herein by reference), is suitable for reducing the overall rate of methyl acetate formation. CO as a component of the exhaust gas has a relatively low calorific value, and the exhaust gas often contains a relatively small amount of MeBr and acetic acid. Methyl acetate is a fuel suitable for use in TOD in order to achieve the required temperatures and to efficiently decompose pollutants, including methyl acetate. If the fuel content in the exhaust gas is too low, then auxiliary fuels, such as methane, methanol, diesel fuel, must be supplied to the TOD in order to ensure the required temperatures and achieve efficient decomposition of pollutants.

The present inventors have found the following preferred ranges for the methyl acetate content in the condensate trap exhaust gas, i.e. ranges that balance the energy potential of methyl acetate in TOD and the capital and operating costs necessary to further reduce methyl acetate formation and / or recovery of acetic acid from it by separation and hydrolysis. The methyl acetate content in the exhaust gas of the condensate trap and / or in the exhaust gas entering the TOD is preferably at least about 0.003; or 0.005; or 0.007; or 0.008 kg / kg p-xylene fed to an appropriate oxidation reaction medium. The methyl acetate content in the exhaust gas of the condensate trap and / or in the exhaust gas entering the TOD is preferably less than about 0.030; or 0.025; or 0.020; or 0.015 kg / kg p-xylene fed to the appropriate oxidation reaction medium. Methyl acetate preferably comprises at least about 20, or 30, or 40, or 50% of the total amount of fuel entering the TOD. In another embodiment of the present invention, the content of methyl acetate and / or methanol in the exhaust gas of the condensate trap and / or in the exhaust gas entering the TOD is preferably less than about 0.030; or 0.025; or 0.020; or 0.015 kg / kg p-xylene fed to the appropriate oxidation reaction medium. Preferably, methyl acetate is at least about 20, or 30, or 40, or 50% of the total amount of fuel entering the TOD.

The content of acetic acid in the exhaust gas of the condensate trap and / or in the exhaust gas entering the TOD is preferably less than about 0.005; or 0.004; or 0.003; or 0.002 kg / kg p-xylene fed to the appropriate oxidation reaction medium. The carbon monoxide content in the exhaust gas of the condensate trap and / or in the exhaust gas entering the TOD is preferably less than about 0.45; or 0.40; or 0.35, or 0.30 mol%, which is evaluated in terms of only dry, non-condensable gaseous compounds.

However, it is undesirable to waste too much energy in TOD, both the combustible fuel contained in the exhaust gas and the added fuel. Therefore, the total combustion energy released in the TOD is preferably less than 600, or 500, or 450, or 400 kJ per kilogram of p-xylene supplied to the corresponding oxidation reaction medium. Said small amount of the required calorific value is achieved in various ways due to efficient thermal integration between the hot treated off-gas at the exit of the TOD and the non-treated off-gas at the entrance to the specified TOD, as is known in the art.

The supply of heat obtained by combustion is controlled appropriately by operational methods and using the composition of the exhaust gas, as indicated in the present description. TOD preferably operates at a peak internal temperature of at least about 200, or 400, or 600, or 800 ° C. Preferably, at least about 94, or 96, or 98, or 99 mol%. carbon-containing compounds in the exhaust gas entering the TOD, before leaving the TOD, is oxidized to CO ₂ . Most preferably, the TOD unit, in all embodiments disclosed herein, is a regenerative thermal oxidation (RTO) unit.

After the removal and / or decomposition of carbon monoxide and pollutants in the form of VOC in the exhaust gas after the oxidation reaction, significant removal of bromine from the treated exhaust gas is required in many places. Said bromine reduction is often accomplished by wet cleaning the treated exhaust gas from TOD, for example, by liquid cleaning the exhaust gas using an aqueous solution of sodium hydroxide and sodium bisulfite to form sodium bromide salt. Over time, the concentration of various salts accumulates in the water used for purification, and it is necessary to discharge wastewater and recharge with cleaner water. Preferably, said water used to feed the off-gas scrubber is filtered water. More preferably, said water used to feed the off-gas scrubber is demineralized water, deionized water and / or steam condensate.

The inventors of the present invention have found that these effluents after washing the scrubber, which are mainly water, are successfully used as process water, for example, make-up water for a cooling tower. Thus, it is preferable to use at least about 0.01 or 0.05 kg of wastewater after washing the off-gas scrubber per kilogram of p-xylene supplied to the appropriate oxidation reaction medium as process water, rather than sending said water after the scrubber to the wastewater treatment unit and / or directly to the environment. In another embodiment of the present invention, any aqueous waste obtained from production plants including an oxidation reaction medium can be used as process water in a ratio of from 0.01 to 0.05 kg of wastewater per kilogram of p-xylene fed to the corresponding reaction medium oxidation, instead of sending process water to the wastewater treatment unit and / or directly to the environment.

An alternative and more preferred embodiment of the present invention provides for combining the oxidation reaction of the exhaust gas, including both primary and secondary oxidation reactors as its sources, for the purpose of processing in a common combined solvent extraction and / or dehydration unit, turboexpander unit, condenser, trap condensate, TOD and / or scrubber to remove bromine.

From the point of view of energy recovery, it is undesirable that the working pressures and temperatures of the secondary reaction media often differ significantly (sometimes even significantly higher) from the primary reaction medium and / or from each other. The simple expansion of higher-pressure off-gases from the reaction through a throttle valve to convert the higher-pressure off-gas to the lower-pressure off-gas is usually accompanied by significant dispersion of entropy, resulting in a loss of the ability to subsequently generate energy on the shaft. However, the present invention can successfully maintain the enthalpy in the combined exhaust gases at the inlet to the turboexpander, and the combined exhaust gas flows are advantageously mixed with CO and VOC with energy potential before being sent to the TOD.

Preferably, the exhaust gas is treated from at least two different reaction media in a common combined solvent recovery and / or dehydration unit, turboexpander unit, condenser, condensate trap unit, TOD and / or bromine scrubber. Preferably, at least a portion of these different reaction media is horizontally separated from each other by less than about 1000, or 500, or 300, or 150 meters. "Integration of the method" means that the starting materials or product streams from two different methods / plants are combined and processed using at least one piece of common equipment selected from the group consisting of a turboexpander, condenser, condensate trap, TOD and / or a scrubber to remove bromine.

In the formation of the off-gas mixture, preferably, the total amount of off-gas in the mixture that comes from the secondary oxidation reaction medium is much less than the total amount of off-gas in the mixture which comes from the primary oxidation reaction medium. In mixtures of primary and secondary off-gas, the off-gas generated in the secondary oxidation reaction media is preferably less than about 20, or 10, or 5, or 2% of the mass. from the mass of the combined exhaust gas and contains less than approximately 20, or 10, or 5, or 2% of the mass. from the amount of molecular nitrogen in the combined exhaust gas. In mixtures of primary and secondary off-gas, the off-gas generated in the secondary reaction oxidation media is preferably at least about 0.1; or 0.2; or 0.4; or 0.8% of the mass. by weight of the combined exhaust gas and contains less than about 0.1; or 0.2; or 0.4; or 0.8% of the mass. from the amount of molecular nitrogen in the combined exhaust gas.

Preferably, at least about 40, or 60, or 80, or 90% of the mass. the exhaust gas after the reaction of the at least one medium of the secondary oxidation reaction is combined with at least 40, or 60, or 80, or 90% of the mass. exhaust gas after the reaction from the primary oxidation reaction medium for processing in a common combined solvent extraction and / or dehydration unit, turboexpander, condenser, condensate trap, TOD and / or bromine scrubber. Preferably, at least a portion of the off-gas from said secondary medium is formed at a temperature of at least about 160, or 175, or 190, or 200 ° C. Preferably, at least a portion of the exhaust gas from said secondary medium is formed at a temperature of less than about 250, or 240, or 230, or 220 ° C. At least a portion of the off-gas from said secondary medium is preferably formed at a pressure of at least about 7, or 10, or 13, or 16 bar absolute pressure. At least a portion of the exhaust gas from said secondary medium is preferably formed at a pressure of less than about 40, or 34, or 28, or 24 bar absolute pressure.

At least a portion of the off-gas from the reaction from at least two different secondary oxidation reaction media is preferably combined with each other and at least a portion of the off-gas from the primary oxidation reaction to process in a common a combined solvent recovery and / or dehydration unit, turboexpander, condenser, condensate trap, TOD and / or bromine scrubber. Preferably, at least a portion of the off-gas from at least one secondary medium is formed at a temperature that is less than about 20, or 15, or 10, or 5 ° C higher than the temperature of a portion of said off-gas from said primary reaction medium oxidation. Preferably, at least a portion of the off-gas from one secondary medium is formed at a temperature that is at least about 10, or 15, or 25, or 35 ° C higher than the temperature of a portion of said off-gas from said primary oxidation reaction medium and / or portions of said off-gas from another secondary oxidation reaction medium. Preferably, at least a portion of said off-gas from one secondary medium is formed at a temperature that is less than about 20, or 15, or 10, or 5 ° C. different from the temperature of another portion of said off-gas from another secondary oxidation reaction medium. Preferably, at least one of said exhaust gases from the reaction comes from a secondary oxidation reaction medium that is horizontally removed from a portion of said primary reaction medium of less than about 60, or 20, or 8, or 2 m. Preferably, at least one of these reaction exhaust gases comes from a secondary oxidation reaction medium that is horizontally removed from a portion of said primary reaction medium by at least about 4, or 8, or 16, or 32 m.

Preferably, the treatment is at least about 40, or 60, or 80, or 90% of the mass. molecular nitrogen in the exhaust gas after the reaction of at least one medium of a secondary oxidation reaction, which combine with at least 40, or 60, or 80, or 90% of the mass. molecular nitrogen in the exhaust gas after the reaction from the primary oxidation reaction medium in a common combined solvent extraction and / or dehydration unit, turboexpander, condenser, condensate trap, TOD and / or bromine scrubber.

The present invention is preferred for a process for producing crude TPA, wherein the total impurity content of the monobasic carboxylic acid is at least about 1000, or 2000, or 4000, or 6000 parts per million (ppm); for a method for producing purified TPA, where the total impurity content of the monobasic carboxylic acid is less than about 1000, or 500, or 300, or 200 ppm; and for the method of simultaneously producing both crude and purified TPA in any ratio. The impurities of the monobasic carboxylic acid are mainly benzoic acid, para-toluic acid and 4-carboxybenzaldehyde.

The present invention is more preferable to obtain purified TPA with a colorimetric b value of less than about 4.0, or 3.5, or 3.0, or 2.5 units of exponent b in the Lab model. The colorimetric value b in this specification refers to one of the color indicators that is measured using a spectral instrument such as a Hunter Ultrascan XE instrument (Hunter Associates Laboratory, Inc., 11491 Sunset Hills Road, Reston, VA 20190-5280, www.hunterlab.com ), in reflection mode. Positive values express the degree of yellowness (or a measure of absorption of blue), while negative values express a degree of blueness (or a measure of absorption of yellow).

The embodiments described herein relate to methods for converting m-xylene (mX) to isophthalic acid (IPA) for all aspects described herein by replacing the meta-derivatives with para-derivatives, for example, m-xylene with p-xylene, isophthalic acids with terephthalic acid, meta-toluic acid, para-toluic acid and 3-carboxaldehyde 4-carboxaldehyde. This supplement applies to all methods for obtaining IPA separately. The specified addition is also applicable in partially and / or fully combined methods for producing both TPA and IPA.

Aspects of the present invention relating to combining exhaust gas from a reaction from various reaction media to treat at least one solvent extraction and / or dehydration unit, turboexpander, condenser, condensate trap, TOD and / or bromine scrubber, also applicable to all aspects when the predominant aromatic compound in at least one reaction medium is a para-substituted compound and the predominant aromatic compound in at least one th other reaction medium is meta- substituted compound. All aspects of the present invention regarding the regenerated solvent are also applicable when at least a portion of the solvent recovered from the exhaust gas after the reaction during the oxidation of one of the xylenes is subsequently used for 72, or 48, or 24, or 12 hours in a reaction medium in which another xylene is oxidized. All aspects of the present invention relating to the solvent filtrate are also applicable when at least a portion of the solvent filtrate formed during the isolation of the solid product, which is mainly one aromatic dicarboxylic acid, is subsequently used for 72, 48, 24, 12 hours in a reaction medium in which the oxidation of another xylene is carried out. (Despite the fact that whenever possible and often it is preferable to try to preserve one filtrate from getting Co / Mn / Br and even heavy aromatic impurities from another isolated filtrate, they mainly do not make any efforts to separate components such as water, vinegar acid and benzoic acid.)

Preferably, at least a portion of the solvent filtrate (para-filtrate) from the method in which the predominant aromatic compounds are para-substituted compounds and a portion of the solvent filtrate (meta-filtrate) from the method in which the predominant aromatic compounds are meta are processed - substituted, in a solvent purification and / or catalyst recovery unit, wherein at least one pipeline, a pressure vessel and / or rotating assemblies located therein are shared. Suitable filtrate purification plants are disclosed in US Pat. Nos. 4,939,297, 7,351,396 and US Patent Application No. 2005-0038288 (the entire contents of which are incorporated herein by reference). At least a portion of the para-filtrate and meta-filtrate together, more preferably, are fed at the same time, compared with the case when they are involved in the method sequentially. At least a portion of the purified filtrate and / or at least a portion of the regenerated catalyst from the process is preferably used subsequently to create at least a portion of the oxidation reaction medium and subsequently participates in the formation of a portion of the para-filtrate or meta-filtrate more preferably involved in the formation of a portion of both filtrates. Preferably, at least about 10, or 40, or 80, or 98% of the mass. aromatic impurities removed from the para-filtrate in the specified method of purification of the solvent filtrate and / or extraction of the catalyst are physically combined with at least about 10, or 40, or 80, or 98% of the mass. aromatic impurities removed from the meta-filtrate in the specified method.

All aspects of the present invention relating to compressed air for supplying an oxidizing agent are applicable when a part of the compressed air from the compressor is separated in order to provide an oxidizing agent to at least one oxidation reaction medium where the predominant aromatic compound is a para-substituted compound , and at least one other oxidation reaction medium, wherein the predominant aromatic compound is a meta-substituted compound.

All aspects of the present invention related to the condensate formed in the intercooler when the oxidant is supplied are applicable when at least a part of the condensate formed in the intercooler when the oxidant is supplied is divided into the part that is used at least , in one step of the process, where the predominant aromatic compound is a para-substituted compound, and another part that is used in at least one other step of the process, where the prevailing aromatic The female compound is a meta-substituted compound.

In one embodiment of the present invention, preferably a smaller scale method for producing IPA is located adjacent to a large scale method for producing TPA. When the exhaust gas from at least one reaction medium where the meta-substituted compound predominates is combined with the exhaust gas from at least one reaction medium where the para-substituted compound predominates, then preferably the exhaust gas generated from the environment where the meta-substituted compound predominates is less than about 50, or 40, or 30, or 20% of the mass. from the mass of the combined exhaust gas and contains less than about 50, or 40, or 30, or 20% of the mass. from the amount of molecular nitrogen in the combined exhaust gas.

When the exhaust gas from at least one reaction medium where the meta-substituted compound predominates is combined with the exhaust gas from at least one reaction medium where the para-substituted compound predominates, then preferably the exhaust gas generated from environments where the meta-substituted compound predominates is at least about 0.5; or 1.0; or 1.5; or 2.0% of the mass. by weight of the combined exhaust gas and contains less than about 0.5; or 1.0; or 1.5; or 2.0% of the mass. from the amount of molecular nitrogen in the combined exhaust gas.

When the atmospheric air compressor feeds the oxidizing agent into at least one reaction medium where the meta-substituted compound predominates and at least one reaction medium where the para-substituted compound predominates, then preferably the reaction medium where the predominant meta-substituted compound, receive less than approximately 50, or 40, or 30, or 20% of the mass. from the total mass flow of the oxidizing agent from said atmospheric air compressor. When the atmospheric air compressor feeds the oxidizing agent into at least one reaction medium where the meta-substituted compound predominates and at least one reaction medium where the para-substituted compound predominates, then preferably the reaction medium where the predominant a meta-substituted compound give at least about 0.5; or 1.0; or 1.5; or 2.0% of the mass. from the total mass flow of the oxidizing agent from said atmospheric air compressor.

More preferably, said IPA and TPA production processes are adjacent to at least one adjacent PET production process. IPA obtained in the specified adjacent method preferably includes at least about 0.5; or 1.0; or 1.5; or 2.0% of the mass. all of the dicarboxylic acid sent to the adjacent PET production process. Preferably, the IPA obtained in the specified adjacent method is less than about 16, or 12, or 8, or 4% of the mass. from all of the dicarboxylic acid sent to the adjacent PET production process.

In another embodiment of the present invention, whether or not adjacent to IPA and TPA production, it is more preferable that at least a portion of the IPA supplied from the primary reaction medium and predominantly containing meta-substituted compounds is sent to the medium the reaction of obtaining PET without purification of the specified IPA by dissolving, selective hydroprocessing and reprecipitation to remove 3-CBA and / or colored impurities.

In one embodiment of the invention, said IPA directed to the PET production reaction medium is preferably either crude IPA obtained directly from the primary oxidation reaction medium, which is a predominantly meta-substituted compound, or IPA after additional oxidation that forms in the medium secondary reaction, the average temperature of which during the reaction is less than about 24, 16, 12, 8 ° C higher than the temperature of the specified medium of the primary reaction. Preferably, said crude IPA and / or IPA after further oxidation contains at least about 20, or 80, or 160, or 320 wt. ppm 3-CBA; less than about 3000, or 2400, or 1800, or 1200 wt. ppm 3-CBA; at least about 2, or 4, or 8, or 16 wt. ppm 2.6-DCF; and less than about 160, or 120, or 80, or 60 wt. ppm 2,6-DCF.

In another embodiment of the invention, said IPA directed to the PET production reaction is preferably a vaporized IPA obtained in a secondary reaction medium, the average temperature of the reaction being at least about 16, or 24, or 30, or 36 ° C higher than the temperature of said primary reaction medium, and less than about 80, or 70, or 60, or 50 ° C higher than the temperature of said primary reaction medium. Said evaporated IPA preferably contains at least about 10, or 40, or 60, or 80 wt. ppm 3-CBA; less than about 1000, or 800, or 500, or 300 wt. ppm 3-CBA; at least about 2, or 4, or 6, or 8 wt. ppm 2.6-DCF; and less than about 120, or 80, or 60, or 40 wt. ppm 2,6-DCF.

Another aspect of the present invention relates to the ability to better dispose of water from the surrounding atmosphere, which condenses and is removed in a method for compressing atmospheric air to supply an oxidizing agent, rather than storing it as steam. A compressor for supplying compressed atmospheric air often includes multi-stage compression systems in which at least one intermediate cooler is used to remove heat generated by compression and to make the method more thermodynamically and mechanically efficient. In such systems, as a rule, condensed water is formed in the interstage coolers, and said water is usually separated from the air before being supplied to the next compression stage. Since such condensate formed in the intermediate cooler during the supply of the oxidizing agent may be contaminated with lubricants and / or hydraulic lock liquids, this condensate is usually sent to a wastewater treatment device, which can simply be an oil separator, although sometimes biological or other devices are used in this device cleaning technology.

The authors of the present invention have identified the following best options for using the condensate formed in the intermediate refrigerator when the oxidizing agent is supplied, while reducing the cost of wastewater treatment and reducing the cost of buying and / or cleaning tap water. At least a portion of the condensate formed in the intercooler when the oxidizing agent is fed is preferably fed to the TPA production process and / or the neighboring PET production process, more preferably at least one of the following process steps: solvent and / or dehydration upon receipt of TPA, in particular in the form of reflux, as described in this description. A solvent filtrate purification system for producing TPA, in particular as an azeotropic separation aid, in the recovery of catalyst components to produce TPA, more preferably containing isopropyl acetate, according to the references provided herein. Method for purification of TPA by selective catalytic hydrogenation of crude TPA. A scrubber in a line connecting the surrounding reactor to the receiving reactor or a container for storing TPA or PET.

At least a portion of the condensate formed in the intercooler when the oxidant is supplied is preferably sent to at least one process water preparation system, more preferably for the formation of the following systems, and most preferably for use in processes for producing TPA and / or an adjacent PET production method: A water cooling system, more preferably a water cooling system in a cooling tower, where the water is cooled by direct contact with air. Filtered water system. A system of deionized and / or demineralized water. Water extinguishing system.

The amount of condensate formed in the intercooler when the oxidant is supplied varies depending on the humidity of the air, the temperature of the refrigerant, the feed rate of p-xylene and the excess of molecular oxygen in the exhaust gas after the reaction, both for a short period of time and on average. Accordingly, preferred methods of use described herein include at least about 0.01; or 0.02; or 0.04; or 0.08 kg of condensate formed in the intermediate refrigerator when the oxidizing agent is supplied per kilogram of p-xylene supplied to the corresponding oxidation reaction medium.

In general, water vapor is preferably continuously removed by introducing it into various stages of the process; nevertheless, irregularities in the production method inevitably occur, and, in addition, equipment is maintained that lead to the formation of a temporary excess of liquid wastewater. For example, opening a reactor to inspect or repair it during a process shutdown is often accompanied by thorough washing with water or steam treatment, in order to remove almost all solvent, substrate and product; and the amount of such water generated during a process violation may be too large compared to the amount required for maintenance. Preferably, at least one storage tank for liquid wastewater is provided, and said liquid wastewater is subsequently returned to at least one step of the process and then removed as water vapor, as described herein. Such a liquid wastewater storage tank is preferably provided with effective insulation so as to control the release of VOC into the environment. The volume of such a storage tank is preferably at least about 50, or 100, or 200, or 400 cubic meters. The volume of such a storage tank is preferably less than about 12000, or 9000, or 6000, or 3000 cubic meters.

By combining various aspects related to the removal of water in vapor form into the environment, more preferably after treatment in TOD, along with the use of condensate formed in the intercooler when the oxidizing agent is fed and / or the water used in the scrubber to remove bromine, the disclosed embodiments of the present invention for use in the method and / or for use as process water, preferably, less than about 400, or 350, or 300, or 250, or 200, or 100, , 50, or 20 grams of liquid wastewater per kilogram of solid TPA product obtained. These operating parameters are preferably maintained substantially continuously for extended periods of time. These small amounts of liquid wastewater are preferably obtained for at least 60, or 80, or 90, or 95% of the time in a continuous 24-hour period. These small amounts of liquid wastewater are preferably obtained over an average period of time that is at least about 4, or 16, or 64, or 254 days. A PET synthesis unit also produces water in a process for converting at least a portion of TPA into PET, and this water is often contaminated with various VOC compounds, for example, ethylene glycol, acetaldehyde and various dioxolanes. At least a portion of the contaminated water after receiving the PET is preferably subjected to treatment in a common combined plant together with the water after receiving the TPA, which comes from a neighboring TPA receiving plant. Preferably, said contaminated water after receiving PET is left in the form of steam leaving said PET unit for processing, or it is converted to vapor form using at least a portion of the thermal energy from said adjacent TPA unit.

In another embodiment of the present invention, the amount of water generated as a by-product or added to the oxidation method, which is released from the specified installation into the environment in the form of steam, is at least 0.3; or 0.4; or 0.49 kg / kg of aromatic compound. In the present description, an apparatus for producing a product may include wastewater treatment.

More preferably, at least a portion of the evaporated water generated during the production of PET by reactions in a nearby PET synthesis unit is treated together with at least a portion of the evaporated water generated by the production of TPA, generally combined TOD, and even more preferably, in RTO, according to any and / or all embodiments of the present invention disclosed herein relating to the treatment of exhaust gas from an oxidation reaction medium. Preferably, at least a portion of the oxidation reaction medium in which the TPA is formed is positioned such that the minimum horizontal distance from said PET synthesis unit is less than about 1800, or 900, or 300, or 100 meters. At least a portion of the TPA is preferably introduced into the reaction medium of said adjacent PET synthesis unit after less than about 72, or 24, or 12, or 4 hours after it has been prepared from para-xylene. Preferably, at least about 40, or 60, or 70, or 80% of the mass is treated. off-gas from said adjacent PET synthesis plant in a common TOD, and more preferably in an RTO, together with at least about 40, or 60, or 70, or 80% of the mass. exhaust gas after the reaction of at least one medium of the primary oxidation reaction. The treatment is preferably subjected to at least about 40, or 60, or 70, or 80% of the mass. water generated during the production of TPA, which comes from the TPA production unit, in general, combined TOD, and more preferably in RTO, together with at least about 40, or 60, or 70, or 80% of the mass. water generated during the production of PET, which comes from the specified located next to the installation for the production of PET.

Preferably, a typical wastewater stream from said adjacent PET production unit combined with a normal wastewater stream from said TPA production unit is less than about 400, or 200, or 100, or 50 g of liquid wastewater per kilogram of produced PET. If the amount of TPA obtained in the specified installation receiving TPA, more than 10% of the mass. differs from the amount of TPA consumed in the adjacent PET production unit, then the liquid wastewater stream from the specified unit is proportionally divided depending on the ratio of its use in the specified PET unit, the specified value is summed with the liquid wastewater stream from the specified unit PET and divided by the amount of PET received.

Claims (31)

1. The method of obtaining aromatic dicarboxylic acid, including:
(a) oxidizing the aromatic compound in at least one oxidation unit to produce off-gas formed in the oxidation unit and a product formed in the oxidation unit, which is aromatic dicarboxylic acid;
(b) directly or indirectly supplying at least a portion of said exhaust gas generated in an oxidation unit to a thermal oxidative degradation (TOD) device, wherein said TOD device is a regenerative thermal oxidation unit; and
(c) oxidizing in said TOD device at least a portion of the off-gas generated in the oxidation unit, where at steady state operation of said TOD device, at least 60% of the amount of fuel supplied to said TOD device comes from said off-gas generated in the oxidation unit, or from the reaction products of said off-gas generated in the oxidation unit. 2. The method according to p. 1, where at a steady state operation of the specified TOD device, at least 70% of the amount of fuel supplied to the specified device thermal oxidative degradation, comes from the specified exhaust gas generated in the oxidation unit. 3. The method according to p. 1, where at a steady state operation of the specified TOD device, at least 90 mol%. carbon-containing compounds present in at least a portion of said off-gas generated in an oxidation unit that is introduced into said TOD device is oxidized in said TOD to carbon dioxide. 4. The method according to p. 1, where at least the specified part of the specified exhaust gas generated in the oxidation unit, which is oxidized in the specified TOD device, contains methyl acetate and / or methanol in an amount of at least 0.003 kg / kg of said aromatic compound entering the specified oxidation unit and less than 0.030 kg / kg of said aromatic compound entering the specified oxidation unit. 5. The method according to p. 1, where at least the specified portion of the specified exhaust gas generated in the oxidation unit, which is oxidized in the specified TOD device, contains acetic acid in an amount of less than 0.005 kg / kg of the specified aromatic compounds entering the specified oxidation unit. 6. The method of claim 1, wherein at least said portion of said off-gas generated in an oxidation unit that is oxidized in said TOD device contains carbon monoxide in an amount of less than 0.45 kg / kg of said aromatic compound into said oxidation unit. 7. The method according to p. 1, where at least the specified portion of the specified exhaust gas generated in the oxidation unit, which is oxidized in the specified TOD device, contains methyl acetate in an amount of at least 0.005 kg / kg of the specified aromatic compounds entering the specified oxidation unit and less than 0.020 kg / kg of the specified aromatic compound entering the specified oxidation unit. 8. The method of claim 4, wherein said methyl acetate present in at least a portion of said off-gas formed in an oxidation unit that is oxidized in said TOD device is a by-product of said oxidation step (a). 9. The method according to p. 4, where the methyl acetate is practically not removed, or does not undergo conversion, or is not hydrolyzed after solvent extraction or in the solvent extraction method and prior to processing in the said TOD device, so that almost all methyl acetate leaving the indicated solvent extraction step arrives at the specified TOD device. 10. The method according to claim 1 or 4, which further comprises treating the offgas generated in the TOD that leaves the TOD device in a scrubber to remove bromine, thereby producing offgas purified from bromine. 11. The method of claim 10, further comprising recovering the hydrocarbyl compounds from said off-gas formed in the oxidation unit in a solvent extraction system, thereby producing off-gas depleted in hydrocarbon compounds. 12. The method of claim 11, further comprising heating at least a portion of said exhaust gas depleted in hydrocarbyl compounds using a thermal heating system, wherein a heated exhaust gas stream is obtained. 13. The method according to p. 12, which further includes passing at least part of the specified stream of heated exhaust gas through at least one turboexpander, while generating work and receiving the exhaust gas after the turboexpander. 14. The method according to p. 13, which further includes cooling the specified exhaust gas after the turboexpander in the condenser for the exhaust gas, while the water vapor present in the exhaust gas after the turboexpander is condensed and an outflow from the condenser is formed, which is a condenser exhaust gas and a condensed liquid . 15. The method of claim 14, further comprising transmitting at least a portion of said outflow from the condenser through a liquid separation device, wherein said outflow from the condenser is separated into exhaust gas from the condensate trap and the separated liquid. 16. The method of claim 15, further comprising recompressing at least a portion of said exhaust gas from the condensate trap in the exhaust gas compressor. 17. The method according to claim 1 or 4, which further comprises thermal oxidative degradation (TOD) of at least a portion of said exhaust gas from the condensate trap in the TOD device, thereby producing exhaust gas after the TOD. 18. The method according to p. 1 or 4, where the specified aromatic compound is para-xylene. 19. The method according to p. 1 or 4, where the specified oxidation unit is a bubble column reactor. 20. A method of obtaining terephthalic acid, including:
(a) oxidizing para-xylene in at least one oxidation unit to produce off-gas formed in the oxidation unit and a product formed in the oxidation unit, which is terephthalic acid;
(b) directly or indirectly supplying at least a portion of said exhaust gas generated in an oxidation unit to a thermal oxidative degradation (TOD) device, wherein said TOD device is a regenerative thermal oxidation unit; and
(c) oxidizing in said TOD device at least a portion of said off-gas generated in an oxidation unit, where at least a portion of said off-gas generated in an oxidizing apparatus that is oxidized in said TOD comprises acetic acid in an amount of less than 0.005 kg / kg of the specified aromatic compound entering the specified oxidation unit and contains carbon monoxide in the amount of less than 0.45 kg / kg of the specified aromatic compound entering the specified mouth posing the oxidation, and at steady state operation of said TOD device at least 70% of the quantity of fuel supplied into said apparatus heat oxidative degradation is supplied from said exhaust gas generated in the oxidation unit, and at least 90 mol%. carbon-containing compounds present in at least a portion of said off-gas generated in an oxidation unit that is introduced into said TOD device is oxidized in said TOD to carbon dioxide. 21. The method according to p. 20, where at least the specified portion of the specified exhaust gas generated in the oxidation unit, which is oxidized in the specified TOD device, contains methyl acetate and / or methanol in an amount of at least 0.003 kg / kg of said para-xylene entering the specified oxidation unit, and less than 0.030 kg / kg of the specified para-xylene entering the specified oxidation unit. 22. The method according to p. 20, where at least the specified portion of the specified exhaust gas generated in the oxidation unit, which is oxidized in the specified TOD device, contains methyl acetate in an amount of at least 0.005 kg / kg of the specified aromatic compounds entering the specified oxidation unit and less than 0.020 kg / kg of the specified aromatic compound entering the specified oxidation unit. 23. The method of claim 21, wherein said methyl acetate present in at least a portion of said off-gas formed in an oxidation unit that is oxidized in said TOD device is a by-product of said oxidation step (a). 24. The method according to p. 21, where the methyl acetate is practically not removed, or does not undergo conversion, or is not hydrolyzed after extraction of the solvent or in the method of solvent extraction and before processing in the specified TOD device, so that almost all methyl acetate leaving the specified stage of solvent extraction arrives at the specified TOD device. 25. The method according to p. 20, which further comprises treating the exhaust gas generated in the TOD leaving the specified TOD device in a scrubber to remove bromine, whereby the exhaust gas purified from bromine is obtained. 26. The method of claim 25, further comprising recovering the hydrocarbyl compounds from said off-gas generated in the oxidation unit in a solvent extraction system, thereby producing off-gas depleted in hydrocarbyl compounds. 27. The method according to p. 26, which further includes heating at least a portion of the specified exhaust gas depleted in hydrocarbon compounds using a thermal heating system, while receiving a stream of heated exhaust gas. 28. The method according to p. 27, which further includes passing at least part of the specified stream of heated exhaust gas through at least one turboexpander, while generating work and receiving the exhaust gas after the turboexpander. 29. The method according to p. 28, which further includes cooling the specified exhaust gas after the turboexpander in the condenser for the exhaust gas, while the water vapor present in the exhaust gas after the turboexpander is condensed and an outflow from the condenser is formed, which is the condenser exhaust gas and a condensed liquid . 30. The method according to p. 29, which further includes passing at least a portion of said outflow from the condenser through a liquid separation device, wherein said outflow from the condenser is separated into exhaust gas from the condensate trap and the separated liquid. 31. The method of claim 30, further comprising recompressing at least a portion of said exhaust gas from the condensate trap in the exhaust gas compressor.

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