Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
  • B01F23/00—Mixing according to the phases to be mixed, e.g. dispersing or emulsifying
  • B01F23/20—Mixing gases with liquids
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
  • B01F23/00—Mixing according to the phases to be mixed, e.g. dispersing or emulsifying
  • B01F23/20—Mixing gases with liquids
  • B01F23/21—Mixing gases with liquids by introducing liquids into gaseous media
  • B01F23/213—Mixing gases with liquids by introducing liquids into gaseous media by spraying or atomising of the liquids
  • B01F23/2132—Mixing gases with liquids by introducing liquids into gaseous media by spraying or atomising of the liquids using nozzles
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
  • B01F25/00—Flow mixers; Mixers for falling materials, e.g. solid particles
  • B01F25/30—Injector mixers
  • B01F25/31—Injector mixers in conduits or tubes through which the main component flows
  • B01F25/313—Injector mixers in conduits or tubes through which the main component flows wherein additional components are introduced in the centre of the conduit
  • B01F25/3131—Injector mixers in conduits or tubes through which the main component flows wherein additional components are introduced in the centre of the conduit with additional mixing means other than injector mixers, e.g. screens, baffles or rotating elements
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
  • B01F25/00—Flow mixers; Mixers for falling materials, e.g. solid particles
  • B01F25/30—Injector mixers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
  • B01F25/00—Flow mixers; Mixers for falling materials, e.g. solid particles
  • B01F2025/91—Direction of flow or arrangement of feed and discharge openings
  • B01F2025/916—Turbulent flow, i.e. every point of the flow moves in a random direction and intermixes
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
  • B01F25/00—Flow mixers; Mixers for falling materials, e.g. solid particles
  • B01F25/40—Static mixers
  • B01F25/42—Static mixers in which the mixing is affected by moving the components jointly in changing directions, e.g. in tubes provided with baffles or obstructions

Definitions

• the invention relates to a method and a device for producing a homogeneous mixture of a vaporous aromatic hydrocarbon and an oxygen-containing gas for catalytic gas phase reactions, in particular a homogeneous
• Phthalic anhydride (PA) is an important intermediate for the production of synthetic resins 15, phthalate,
• PSA Phthalocyanine dyes and other fine chemicals.
• PSA is mainly produced from o-xylene and mainly by gas phase oxidation of o-xylene with air as an oxidant.
• plants for carrying out such a PSA manufacturing process consist essentially of the functional units for the production of the o-xylene vapor-air mixture, the reactor for the implementation of the o-xylene vapor-air mixture and a device for PSA separation and processing.
• reaction by catalytic gas phase oxidation mostly takes place on V 2 Os-containing catalysts.
• o-xylene is evaporated, mixed with an excess of air and passed at 340 ° C to 440 ° C over the catalyst in the tubes of a tube bundle reactor.
• the catalyst consists, for example, of a mixture of V 2 0 5 and Ti0 2 with promoters on ceramic bodies, such as porcelain or SiC balls or rings, for example 6 x 6 mm in size.
• Ceramic bodies such as porcelain or SiC balls or rings, for example 6 x 6 mm in size.
• Large reactors have 10,000 to 40,000 tubes in the tube bundle.
• reaction conditions in the tubes Due to inhomogeneities in the loading, the reaction conditions in the tubes also differ. This results in an increased amount of by-products which reduce the yields and which have to be separated from the PSA and disposed of in later cleaning stages. 0
• DE-A 1 793 453 discloses a process for producing a homogeneous mixture of vaporous o-xylene and air for the catalytic oxidation to phthalic anhydride.
• an o-xylene stream is sprayed into drops with a diameter of less than 1 mm, for example in a size of predominantly less than 0.3 mm, and introduced into an air stream preheated above the boiling point of o-xylene.
• This airflow is turbulent; a Reynolds number above 200,000 is recommended.
• the dwell time from the o-xylene injection to the reactor must be at least 0.2 seconds in order to obtain a homogeneous gas mixture and thus an even exposure to all tubes.
• the raw materials can be more or less contaminated.
• the air can contain, inter alia, N0 X , H 2 S, sulfur oxides such as S0 2 , NH 3 and their salts, for example with C0 2 , which can lead to narrowing of one or more nozzles.
• Corrosion particles can also change the drop size and shape of the atomized o-xylene jet. Similar effects arise from erosion of the nozzles in long-term operation.
• the o-xylene can also contain m- and p-xylene, toluene, ethylbenzene, isopropylbenzene, nonane and small amounts of styrene. Such compounds can affect the surface tension of the Q o-xylene.
• Drops can occur that fly farther than the aforementioned drops with a size of, for example, predominantly below 0.3 mm. These can wet the wall of the reaction tube and form a liquid film there. Another difficulty is that it is not possible in practice to install the nozzles used to atomize the o-xylene stream in such a way that no drops of the atomized o-xylene stream come into contact with the wall of the guide tube.
• the method according to DE-A 1 793 453 can also lead to unintentional, negatively acting changes in the set parameters, such as pressure and temperature and the amount of air.
• admixtures containing air and o-xylene can be added and the drops of the atomized o-xylene stream can touch the pipe wall. In this respect, the above-mentioned method is still in need of improvement.
• a vaporous aromatic hydrocarbon such as o-xylene and / or naphthalene
• an oxygen-containing gas in particular air
• the invention solves the above-mentioned problems in that, in a generic method, the atomization of the liquid aromatic hydrocarbon takes place by using a nozzle to form a hollow atomizing cone, preferably a swirl nozzle.
• the atomizing hollow cone can initially be a coherent film made of the liquid hydrocarbon, which at greater distance from the swirl nozzle tears into small pieces that contract to form individual drops with a diameter of less than 1 mm due to interfacial forces.
• the present invention therefore relates to a method for
• a homogeneous mixture of a vaporous aromatic hydrocarbon, such as o-xylene and / or naphthalene and an oxygen-containing gas, such as air, for catalytic gas phase reactions whereby the liquid aromatic hydrocarbon is atomized into drops with a diameter of less than 1 mm and in an oxygen-containing gas stream preheated above the boiling point of the aromatic hydrocarbon is injected, the process being characterized in that the liquid aromatic hydrocarbon is atomized by means of nozzles to form a hollow cone, preferably by means of swirl nozzles.
• the method according to the invention enables the generation of a very homogeneous, streak-free mixture of gaseous oxygen, preferably in air or another gas containing oxygen, and a hydrocarbon vapor.
• the process according to the invention is preferably used in the production of carboxylic acids or carboxylic anhydrides by catalytic gas-phase oxidation of aromatic hydrocarbons, such as xylenes, in particular o-xylene and / or naphthalene, in fixed bed reactors.
• aromatic hydrocarbons such as xylenes, in particular o-xylene and / or naphthalene
• PSA phthalic anhydride
• the hollow atomizing cone preferably has an opening angle of 30 ° to 70 °.
• the atomizing hollow cone particularly preferably has an opening angle of approximately 60 °.
• the axis of the hollow atomizing cone lies in the direction of flow of the oxygen-containing gas, that is to say approximately the air, but can deviate from this by up to 30 °.
• a further measure for this can in particular be to maintain a certain distance, approximately one third of the pipe radius, from the wall. It is preferable to use several nozzles, approximately 2 to 6, preferably 4 to 6, at approximately equal intervals.
• swirl nozzles are preferably used to atomize the liquid hydrocarbon.
• These swirl nozzles which are also referred to as hollow cone nozzles, preferably have a guide body with oblique inflow surfaces in front of the outlet opening, which impart swirl or rotation about the flow axis to the liquid to be atomized.
• Swirl nozzles of this type are known for other uses, such as rapid impulse transmission in water jet pumps, injection condensers, etc. (cf. Grassmann "Physical principles of process engineering", Verlag Sauerators (1970), pages 355 and 805).
• hollow cone nozzles are particularly preferred in the method according to the invention, full cone nozzles or slot nozzles can also be used in other embodiments of the invention.
• the liquid hydrocarbon stream is atomized into drops with a diameter of less than 1 mm, preferably less than 0.8 mm. Most preferably, the liquid stream is atomized into drops of 0.02 to 0.2 mm.
• the swirl nozzles used to form the hollow atomizing cone with an opening angle of 30 ° to 70 ° are advantageously in ⁇
• the nozzle outlet openings are directed in the direction of the gas flow.
• the axis of the hollow cone can deviate from the direction of flow of the gas by up to 30 °. It can thereby be achieved that fewer drops of the hollow cone touch the wall.
• Axial hollow cone nozzles of the type KS 1 (Lechler, Metzingen, Germany) are particularly suitable for the purposes of the method according to the invention. Such nozzles enable generation
• drops of 0.8 to 1 mm can fly 50 to 100 cm until they evaporate completely, touching and wetting the wall.
• thermoplates of this type are used in Germany, for example, produced by the companies BUCO, Geesthacht or DEG, Gelsenmün. Droplets of hydrocarbon that hit the heated pipe cannot deposit as a liquid film, but are evaporated immediately. This finally creates the desired mixture of hydrocarbon vapor and air, for example.
• the pipe gap of the double jacket pipe can be heated with high pressure steam, preferably with water steam of approx. 20 bar with a temperature of 214 ° C.
• the above-mentioned thermoplates can have a particularly narrow pipe gap.
• Thermo sheet metal tubes are relatively simple and therefore more cost-effective. Intensive heating can prevent cold spots in the thermo sheet. 5
• the steam-air mixture is then passed through a mixing device in accordance with a further advantageous process variant.
• Static mixers are preferably used as the mixing device. These are baffles attached in the flow-through tube, which divide the flow to be mixed several times and bring it back together, as a result of which the homogenization 5 takes place completely. Static mixers of this type are manufactured, for example, by Sulzer, Winterthur, Switzerland. Static mixers are also described in German patent applications DE 25 250 20 AI, DE 196 223 051 AI and DE 196 23 105 AI.
• the present invention also relates to a device for producing a homogeneous mixture of a vaporous aromatic hydrocarbon and an oxygen-containing gas with gas channels for a preheated, oxygen-containing gas stream, an atomization device opening into the gas channels for a stream of a liquid aromatic hydrocarbon , which is characterized in that the atomizing device has swirl nozzles, and that the gas channels have walls, at least downstream of the swirl nozzles, which can be heated at least to the boiling point of the hydrocarbon.
• the gas channels preferably comprise a heatable tube, in particular a double-jacket tube or a tube made of thermoplate.
• a static mixer is particularly preferably arranged downstream of the swirl nozzles in the gas channels.
• the temperature on the hot tube wall is set so that 5 to 50% by weight of the liquid hydrocarbon, in particular 5 to 40% by weight, particularly preferably 5 to 30% by weight, meet the tube wall and can be evaporated there, the exact Proportion depends on the contamination of the raw materials, the shape of the hollow cone and the change in the nozzle (erosion) during operation.
• further functional units may be about connect for the production of PSA, for example, 0 t he reactor for reacting the o-xylene to PSA, and the device for PSA separation and PSA obtain pure, as known from the prior art are.
• FIG. 10 In the figure of the drawing is a device 10 for generating a homogeneous mixture of vaporous o-xylene and / or
• the device has gas channels 11 which bring a preheated air flow (symbolized by arrow 12 in the figure).
• the gas channels 11 are designed as a tube in the example shown.
• a 5 atomizing device 13 is provided in the tube 11, which consists of supply lines 14 for liquid o-xylene and swirl nozzles 15 arranged at the end of the lines.
• the feed lines 14 are fed by a supply pipe (not shown) concentrically surrounding the pipe 11.
• the swirl nozzles 15 produce a hollow cone 16 made of liquid o-xylene, which disintegrates into the finest drops with an average diameter between 0.02 and 0.2 mm.
• a static mixer 17 is arranged in the tube 11, through which the steam / air mixture is passed. Downstream of the swirl nozzles 15, the tube 11 is designed as a heatable double-jacket tube 18. The tube is heated with steam to a temperature above the boiling point of o-xylene. Atomized o-xylene droplets falling on the
• the tube 11 opens into a tube bundle reactor in which phthalic anhydride is produced by catalytic gas phase oxidation of the o-xylene.
• the device for o-xylene evaporation in a plant for the production of PSA consisted of a vertical thermoplate with a diameter of 1200 mm.
• the oxidizing air which had been preheated to 200 ° C. using a preheater, was passed through this to the reactor.
• the pressure was approximately 1.5 bar absolute.
• the air was charged with o-xylene with a load of 100 g per Nm 3 .
• the air was sucked in from the environment without any special purification, only through an air filter.
• the thermoplate was heated to 214 ° C with 20 bar steam.
• the o-xylene was injected via 6 swirl nozzles, which were attached to a rim 600 mm in diameter and whose axis was pointing vertically upwards. These were axial hollow cone nozzles (KS 1 type 216.324 made of steel, Lechler company). The admission pressure was 8 bar. Static mixers were installed in the horizontal pipe section at a distance of 4.5 m behind the nozzles.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Accessories For Mixers (AREA)
• Hydrogen, Water And Hydrids (AREA)

Applications Claiming Priority (3)

Publications (2)

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ID=7934237

Family Applications (1)

Country Status (13)

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• 1999
  • 1999-12-23 DE DE19962616A patent/DE19962616A1/de not_active Withdrawn
• 2000
  • 2000-12-15 MY MYPI20005923A patent/MY125936A/en unknown
  • 2000-12-21 TW TW089127515A patent/TW581710B/zh not_active IP Right Cessation
  • 2000-12-22 AU AU21720/01A patent/AU2172001A/en not_active Abandoned
  • 2000-12-22 MX MXPA02005852A patent/MXPA02005852A/es active IP Right Grant
  • 2000-12-22 KR KR1020027008183A patent/KR100655339B1/ko not_active IP Right Cessation
  • 2000-12-22 AT AT00985245T patent/ATE262372T1/de not_active IP Right Cessation
  • 2000-12-22 JP JP2001548206A patent/JP4669184B2/ja not_active Expired - Fee Related
  • 2000-12-22 WO PCT/EP2000/013165 patent/WO2001047622A1/fr active IP Right Grant
  • 2000-12-22 ES ES00985245T patent/ES2218265T3/es not_active Expired - Lifetime
  • 2000-12-22 DE DE50005821T patent/DE50005821D1/de not_active Expired - Lifetime
  • 2000-12-22 CN CNB00817394XA patent/CN1174793C/zh not_active Expired - Fee Related
  • 2000-12-22 US US10/168,953 patent/US20030013931A1/en not_active Abandoned
  • 2000-12-22 EP EP00985245A patent/EP1239944B1/fr not_active Expired - Lifetime

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