Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D9/00—Crystallisation
  • B01D9/0018—Evaporation of components of the mixture to be separated
  • B01D9/0022—Evaporation of components of the mixture to be separated by reducing pressure

Definitions

• the present invention relates to an adiabatic cooling crystallization method and apparatus for organic compounds.
• the present invention relates to a method and apparatus suitable for obtaining paraxylene crystals.
• the present inventor considered mixed xylene (m-xylene + o-xylene + ethylbenzene + p-xylene system), which is a raw material in typical p-xylene production in petrochemical industrial processes, and after isomerization reaction. It is effective to perform crystallization operation using propane (or propylene, ethylene, carbon dioxide, ammonia, etc.) as a refrigerant in eutectic multi-component systems such as mixed xylene (m xylene + o xylene + p xylene). I found out that there was.
• the P-xylene in the eutectic multicomponent system is cooled to about -30 ° C to -60 ° C.
• the crystallization tank is equipped with a cooling chamfering mechanism, and the refrigerant from the jacket is compressed with a compressor and condensed, for example, under a high pressure of 20 atm.
• a circulating refrigerant system is required.
• the crystallization tank which only increases the power cost of the compressor, must be equipped with a cooling surface scraping mechanism that requires complicated and frequent maintenance. Bulky.
• Patent Document 1 a form using a heat pump is also conceivable. It is difficult to say that the system does not necessarily meet the cost of the equipment.
• Patent Document 1 Japanese Patent Laid-Open No. 4 327542
• a main object of the present invention is to provide an adiabatic cooling type crystallization method and apparatus for an organic compound capable of reducing operating costs (including maintenance costs) and equipment costs.
• Another object is to provide a method and apparatus suitable for crystallization of p-xylene.
• the present invention that has solved the above problems is as follows.
• It is composed of a plurality of operation stages by combining a crystallization tank that performs adiabatic cooling and evaporation of the refrigerant and a corresponding absorption condenser for the mixed solution of the target organic compound including the refrigerant,
• Each of the evaporation vapors in each crystal tank is pressurized by a compressor to a pressure higher than the operating pressure of each crystal tank, and led to the corresponding absorption condenser in the stage,
• Each of the absorption condensers is cooled and condensed while contacting the mixed solution of the organic compound and the pressurized evaporation vapor,
• the condensate in the first stage is led to the corresponding crystal tank in the first stage, and the crystal slurry extracted in the first stage obtains crystals by solid-liquid separation, and the separated mother liquor is in the next stage.
• the condensate in the next stage is guided to the crystallization tank in the corresponding next stage for crystallization operation, and the crystal slurry extracted in the next stage is led to the crystallization tank in the previous stage.
• the heat of crystallization is substantially taken away by the evaporation of only the refrigerant liquid component. And crystals are deposited.
• the evaporation vapor is pressurized by the compressor above the operating pressure of the crystallization tank and led to an absorption condenser for condensation.
• the reason why the vaporizer is pressurized to a pressure higher than the operating pressure of the crystallization tank by a compressor is to secure a temperature difference for condensation by pressurization by a compressor as in a general refrigeration cycle.
• Absorption condensers come in contact with a mixed solution of organic compounds with low vapor pressure, resulting in an increase in boiling point and an increase in the temperature at which absorption and condensation can occur. Therefore, it is sufficient that the degree of pressurization required is small and the input energy of the external force necessary for condensation is small.
• the condensate in the absorption condenser can be continuously crystallized by introducing it into the crystallization tank.
• propane is used as the refrigerant
• the crystallization tank is at normal pressure, for example, and the absorption condenser is, for example, about 8 atm due to pressurization by a compressor.
• the crystal slurry produced in the crystallization tank is extracted and separated into a crystal component and a mother liquor by solid-liquid separation means, and the crystal component is purified as it is by a purification means if necessary to be commercialized.
• a purification means if necessary to be commercialized.
• there are no limitations on the facilities and processes for solid-liquid separation and examples include a centrifugal separator, a filter, a melt purification tower, a piston type or screw type washing tower, and the like.
• a crystallization operation can be performed without using a crystallization tank as a pressure vessel.
• the compressor and the absorption condenser are the minimum, it is necessary to use an expensive heat pump equipment configuration as in the prior art. It is economical.
• a plurality of operation stages are configured by a combination of a crystal tank and an absorption condenser. From the viewpoint of gas-liquid flow, it can also be said that the crystal tanks are arranged in series.
• a single crystallization tank (crystal can) is used for cooling crystallization to the lowest temperature to obtain the recovery rate of the target component, and a plurality of crystallization tanks (crystal cans) are arranged in series to determine the operating temperature.
• the cost of the latter apparatus configuration is higher when the cost of the apparatus itself and the required energy are comprehensively judged. It was found to reduce.
• a structure consisting of a plurality of operation stages by combining a crystal tank that performs adiabatic cooling and evaporation of the refrigerant with a mixed solution of the target organic compound including the refrigerant, and an absorption condenser corresponding thereto;
• Each vaporizer in each crystal tank is pressurized by a compressor above the operating pressure of each crystal tank and led to the corresponding absorption condenser in the stage,
• each of the absorption condensers means for condensing by cooling while bringing the mixed solution of the organic compound and the pressurized evaporation vapor into contact with each other;
• the condensate in the next stage is guided to the crystallization tank in the corresponding next stage for crystallization operation, and the crystal slurry extracted from the crystallization tank force in the next stage is provided with means for guiding it to the crystallization tank in the previous stage. ;
• cooling can be performed without installing an apparatus for scoring crystals precipitated on the cooling surface, which is unavoidable in the cooling crystallization facility,
• the required amount of utility energy for cooling (freezing) can be reduced, thereby reducing operating costs and equipment costs.
• it is suitable for crystallization of p-xylene.
• crystallization tanks crystal cans
• the cost of the apparatus itself and the required energy are combined. Judging from the point of view, it becomes an economical system configuration.
• Fig. 1 shows a basic embodiment, which is composed of two operation stages by a combination of a crystal tank and an absorption condenser, and includes an absorption condenser 10A, 10B, a crystal tank 20A, 20B. And a compressor 30 and a solid-liquid separation means 40.
• the mixed solution 1 of the target organic compound containing the refrigerant (the target liquid for the crystallization operation.
• the liquid of the eutectic multicomponent mixture containing p-xylene and its isomer) is absorbed in the first (first stage). It is led to the condenser 10A where it absorbs refrigerant vapor (eg propane) and condenses it into a homogeneous refrigerant mixture.
• refrigerant vapor eg propane
• the homogeneous refrigerant mixture from the absorption condenser 10A is introduced into the first (first stage) crystal tank 20A through the temporary storage tank 11A through the pipe 61A, and the refrigerant containing the refrigerant is condensed in the first crystal tank 20A. Adiabatic cooling and evaporation of the refrigerant are performed on the liquid.
• the crystal slurry generated by this operation is extracted from the first crystal tank 20A by the pump 62A, and separated into the crystal fraction stream Cr and the mother liquor stream Mo by the solid-liquid separation means 40 such as a centrifuge or a liquid cyclone. .
• the evaporation vapor in the first crystal tank 20A passes through the pipe line 63, is pressurized by the compressor 30 to a pressure higher than the operating pressure of the first crystal tank 20A, and is guided to the first absorption condenser 10A.
• the cooling medium 2 for example, chilled water tower cooling water, refrigeration, etc.
• the mixed solution mixed liquid 1 of the organic compound and the pressurized evaporation vapor. It is cooled by the cold heat of the machine brine, etc.) to absorb and condense, and this absorbed condensate is led to the first crystal tank 20A.
• the first crystallization tank 20A if the adiabatic cooling and evaporation operation of the refrigerant liquid component is performed on the target organic compound mixed liquid containing the refrigerant liquid component, the heat of crystallization is accompanied by the evaporation of the refrigerant liquid component. Is taken away and crystals are deposited.
• the vaporizer is pressurized by the compressor 30 to a pressure higher than the operating pressure of the first crystallization tank 20A and led to the first absorption condenser 10A for absorption condensation.
• the reason why the compressor 30 is provided to pressurize the evaporation vapor is that the first crystal tank 20A and the first crystal tank 20A are used for recondensing the refrigerant at a temperature much higher than the operating temperature of the first crystal tank 20A. 1
• the temperature difference from the absorption condenser 10 A is secured by pressurizing with the compressor 30.
• propane is used as the refrigerant.
• pressure by the compressor 30 causes, for example, About 8 atm.
• the crystal slurry generated in the first crystallization tank 20A is extracted and separated by the solid-liquid separation means 40 into the crystal fraction stream Cr and the mother liquor stream Mo, and the crystal fraction stream Cr is left as it is, if necessary by a purification means or a washing means. Purify and increase the purity and commercialize.
• the mother liquor flow Mo is led to the second (next stage) absorption condenser 10B via the pipe line 64 to perform absorption condensation.
• the homogeneous refrigerant mixture from the second absorption condenser 10B is introduced into the second (next stage) crystal tank 20B through the temporary storage tank 11B via the pipeline 61B, and the refrigerant is supplied to the second crystal tank 20B.
• Adiabatic cooling and evaporation of the refrigerant are performed on the condensate.
• the crystal slurry generated by this operation is also extracted from the second crystallization tank 20B by the pump 62B and separated into a concentrated slurry and a clarified fraction by a solid-liquid separation means 50 such as a centrifugal separator or a liquid cyclone.
• the concentrated slurry is supplied to the first crystal tank 20A.
• the refrigerant discharged from the system in the state of being dissolved in the clarified liquid in the solid-liquid separation means 50 is recovered by a downstream distillation column (not shown), or is made into a refrigerant gas in the suc- sion part of the compressor 30 as a make-up. Can be supplied as 1A.
• the evaporation vapor in the second crystallization tank 20B is pressurized together with the evaporation vapor in the first crystallization tank 20A by the compressor 30 to a pressure higher than the operating pressure of the first crystallization tank 20A, and the first absorption. Lead to condenser 10A for absorption condensation.
• the crystallization operation can be performed without using the first crystallization vessel 20A and the second crystallization vessel 20B as a high pressure resistant vessel. Since the first crystallization tank 20A, the second crystallization tank 20B, the compressor 30, the first absorption condenser 10A, and the second absorption condenser 10B are sufficient, the expensive heat pump equipment configuration as in the prior art is sufficient. It is economical in terms of overall system and operating costs.
• crystal tanks crystal cans
• cooling crystallization is performed under the condition of gradually lowering the operating temperature
• the cost of the apparatus itself and the required energy are comprehensive. Judging from the point of view, it becomes an economical system configuration.
• FIG. 2 shows a second embodiment with three operation stages, showing an example of a three-stage configuration.
• the equipment configuration at the third stage is denoted by the symbol “C”.
• cyclohexane is produced by hydrogenating benzene.
• This operation is continuously performed under the equipment configuration according to the present invention.
• the benzene crystals and the separated mother liquor are depropanated, mixed with the raw materials, and fed back.
• the mixed liquid system of benzene and cyclohexane is a eutectic system in the entire concentration range.
• the pure benzene has a crystallization point of 5.5 ° C and cyclohexane has a crystallization point of 5.7 ° C.
• the filtrate which is a mixed xylene solution of propane
• the filtrate is supplied to the absorption condenser 10B, while being contact-mixed with a vapor pressurized to 0.2 to 0.7 MPa through the crystallization tank 20A and 20B force compressor 30. Condensed at about 30 ° C.
• the resulting condensate is a mixed xylene solution with a propane concentration of 10 to 30%, and this is led to a second crystallization tank 20B operated at -20 to -5 ° C under normal pressure for crystallization. planned.
• the obtained crystal slurry is supplied to the hydrocyclone 50, the concentrated slurry is discharged to the first crystal tank 20A, the clarified liquid is discharged out of the system, and the propane that is discharged out of the system in a state dissolved in the clarified liquid is discharged.
• the makeup was supplied to the compressor 30 suction section.
• the paraxylene concentration in the clarified liquid was 60-70%.
• FIG. 1 is a flow sheet of a basic embodiment.
• FIG. 2 is a flow sheet according to another embodiment.

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• Chemical & Material Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

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Citations (4)

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• 2005
  • 2005-03-30 JP JP2005100175A patent/JP4666594B2/ja not_active Expired - Fee Related
• 2006
  • 2006-03-07 WO PCT/JP2006/304332 patent/WO2006112188A1/ja active Application Filing
  • 2006-03-21 TW TW095109549A patent/TW200633768A/zh unknown

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