Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
  • F28F9/00—Casings; Header boxes; Auxiliary supports for elements; Auxiliary members within casings
  • F28F9/02—Header boxes; End plates
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D1/00—Evaporating
  • B01D1/06—Evaporators with vertical tubes
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
  • B01D3/14—Fractional distillation or use of a fractionation or rectification column
  • B01D3/32—Other features of fractionating columns ; Constructional details of fractionating columns not provided for in groups B01D3/16 - B01D3/30
  • B01D3/322—Reboiler specifications
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
  • F28D7/00—Heat-exchange apparatus having stationary tubular conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall
  • F28D7/16—Heat-exchange apparatus having stationary tubular conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall the conduits being arranged in parallel spaced relation
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
  • F28F9/00—Casings; Header boxes; Auxiliary supports for elements; Auxiliary members within casings
  • F28F9/02—Header boxes; End plates
  • F28F9/04—Arrangements for sealing elements into header boxes or end plates
  • F28F9/16—Arrangements for sealing elements into header boxes or end plates by permanent joints, e.g. by rolling
  • F28F9/18—Arrangements for sealing elements into header boxes or end plates by permanent joints, e.g. by rolling by welding

Definitions

• the present invention relates to a vertical multitubular heat exchanger and a distillation column system, and more particularly to a vertical multitubular heat exchanger that performs heat exchange by introducing a process fluid containing an easily polymerizable substance into a heat transfer tube.
• the present invention relates to a distillation column system using the vertical multitubular heat exchanger.
• Multi-tube heat exchangers that exchange heat between high-temperature fluid and low-temperature fluid are one of the widely used chemical devices in the chemical industry. Compared with other types of heat exchangers, multi-tube heat exchangers can be used under severe conditions and can be operated continuously for a long period of time, so they are characterized by high reliability. Hereinafter, an example of such a multitubular heat exchanger will be described with reference to FIG. FIG. 10 is a sectional view of a vertical multitubular heat exchanger.
• the vertical multitubular heat exchanger 120 has a tubular body 122 extending vertically and an upper part 124 and a lower part 126 of the tubular body 122.
• a plurality of transmissions in which the flat upper tube sheet 1 28 and the lower tube sheet 130 provided respectively and the outer periphery 1 32 at both ends are fixed to the upper tube sheet 1 28 and the lower tube sheet 130 are provided.
• a process fluid is introduced into the heat transfer pipe 13 4.
• a fluid for performing heat exchange with the process fluid introduced into the heat transfer tube 134 is supplied around the heat transfer tube 134.
• the vertical multitubular heat exchanger 120 is used as a condenser of a distillation column system (not shown). The case of use will be described.
• the process fluid to be distilled is vaporized and the resulting process gas is introduced into the heat transfer tubes 1 34 from the upper tube sheet 1 28 side, The process gas is cooled and condensed by the fluid supplied around the heat transfer tube 134, and then the process fluid comes out of the lower tube plate 130 side of the heat transfer tube 134 as a liquid.
• the process fluid is, for example, a methanol chlorane-containing liquid
• the polymer of the easily polymerizable substance is used as the upper tube sheet.
• the polymer adhering near the upper opening of the upper surface 1336 of the upper tube sheet 128 and the inner surface 138 of the heat transfer tube 134 grows as the operation time elapses.
• “growth” means that the attached polymer becomes larger due to further polymerization on the surface of the attached polymer.
• the heat transfer efficiency of the vertical multitubular heat exchanger 120 deteriorates, and as a result, the heat exchange rate and the separation efficiency of the vertical multitubular heat exchanger 120 decrease. I do. Since the polymer adheres to the entire upper surface 1336 of the upper tube sheet 128, the heat transfer efficiency is significantly reduced.
• An object of the present invention is to provide a vertical multitubular heat exchanger that can prevent clogging due to a polymer and can be operated continuously for a long time.
• An object of the present invention is to provide a distillation column system capable of continuous operation for a long period of time.
• the present invention relates to a vertical multi-tube heat exchanger for exchanging heat by introducing a process fluid containing an easily polymerizable substance into a heat transfer tube, and extending vertically.
• the upper tube sheet is characterized in that the upper surface is formed to be inclined, and at least one heat transfer tube is arranged near the lowest position on the upper surface of the upper tube sheet.
• the process fluid when cooling a high-temperature process fluid, the process fluid is introduced into the heat transfer tube from the upper tube sheet side. After exchanging heat with the low temperature fluid around the heat transfer tube, the fluid comes out from the lower tube sheet side of the heat transfer tube.
• the process fluid contains an easily polymerizable substance, if the process fluid stays for a long time on the upper surface of the upper tube sheet and the upper end of the heat transfer tube, polymerization of the easily polymerizable substance is likely to occur, and the polymer is easily removed. Easy to adhere to.
• the stagnation of the process fluid generated on the upper surface of the flat upper tube sheet of the conventional vertical multi-tube heat exchanger is realized. It can be qualitatively eliminated. Further, since at least one heat transfer tube is disposed near the lowest position on the upper surface of the upper tube sheet, the stagnation of the process fluid flowing downward can be more reliably prevented. Due to such a retention preventing effect, the polymerization of the easily polymerizable substance hardly occurs, and the adhesion of the polymer to the upper tube sheet and the heat transfer tube is prevented. Furthermore, even if the operation of the vertical multi-tube heat exchanger is continued, Product growth is prevented and the tubes are not clogged. As a result, the work of removing the polymer, which is frequently performed in the conventional vertical multi-tube heat exchanger, becomes unnecessary, and the long-term continuous operation of the vertical multi-tube heat exchanger becomes possible.
• the upper surface of the upper tube sheet is formed so as to be inclined so as to become lower from the outer portion toward the center portion, and more preferably, The upper surface of the upper tube sheet is inclined downward by 0.05 to 0.1 radian with respect to a plane including the outer edge of the upper tube sheet.
• the upper tube sheet of the vertical multi-tube heat exchanger thus configured is easy to manufacture.
• the angle of inclination of the upper surface of the upper tube sheet is preferably as large as possible from the viewpoint of preventing polymer adhesion, but should be smaller than 0.1 radian from the viewpoint of processing easiness and processing cost. Is preferred. Further, it has been clarified by the applicant's experiments that if the inclination angle is not less than 0.05 radian, the adhesion of the process fluid polymer on the upper surface of the upper tube sheet can be further prevented.
• the upper end of the heat transfer tube arranged near the lowest position of the upper tube sheet is configured not to protrude from the upper surface of the upper tube sheet.
• the process fluid on the upper surface of the upper tube sheet flows toward the lowest position of the upper tube sheet, and most of the process fluid is arranged near the lowest position. Also, since it flows into the heat transfer tubes, the adhesion of the polymer can be prevented over the entire surface of the upper tube sheet.
• the upper ends of all of the plurality of heat transfer tubes do not protrude from the upper surface of the upper tube sheet. According to the vertical multi-tube heat exchanger of the present invention configured as described above, the effect of preventing the process fluid from staying on the upper surface of the upper tube sheet is promoted.
• an upper end of the heat transfer tubes other than the heat transfer tubes arranged near the lowest position of the upper tube sheet may be configured to protrude upward.
• the connection strength between the upper tube sheet and the heat transfer tubes is increased. be able to. Therefore, even if the heat transfer tube is constantly subjected to the vibration caused by the inflow and outflow of both the process fluid and the extra-fluid fluid, the vibration caused by the pump or the compressor, and the direct pulsating flow from the rotary pump machine, It is possible to prevent a decrease in the sealing performance of the connection between the upper tube sheet and the lower tube sheet, and prevent the process fluid from leaking between them.
• the lower surface of the lower tube sheet is preferably formed to be inclined.
• the retention of the easily polymerizable substance in the lower tubesheet can be prevented.
• the lower surface of the lower tube sheet is inclined from the outer portion toward the center by 0.05 to 0.1 radian below a plane including the outer edge of the lower tube sheet. Is preferred. This is for the same reason as the upper tube sheet.
• the easily polymerizable substance is acrolein, methacrolein, acrylic acid, methacrylic acid, or an ester thereof.
• the process fluid preferably contains a polymerization inhibitor.
• the present invention also provides a distillation column system comprising: a distillation column for distilling a fluid containing an easily polymerizable substance; and a condenser connected to the top of the distillation column. It is a multi-tube heat exchanger.
• the distillation column system of the present invention configured as described above, since the above-mentioned vertical multitubular heat exchanger is employed for the condenser, the distillation column system can be continuously operated for a long time.
• the present invention is a distillation column system comprising: a distillation column for distilling a fluid containing an easily polymerizable substance; and a reboiler connected to the bottom of the distillation column. It is characterized by the vertical multi-tube heat exchanger described above.
• the distillation column system of the present invention configured as described above, since the above-mentioned vertical multi-tube heat exchanger is employed in the reboiler, the distillation column system can be continuously operated for a long time.
• the present invention provides a distillation column comprising: a distillation column for distilling a fluid containing an easily polymerizable substance; a condenser connected to the top of the distillation column; and a reboiler connected to the bottom of the distillation column.
• the system is characterized in that the condenser and the reboiler are the vertical multi-tube heat exchangers described above.
• the above-mentioned vertical multi-tube heat exchanger is used for the condenser and the reboiler, so that the distillation column system can be operated continuously for a long time. become.
• FIG. 1 is a vertical sectional view of a vertical multitubular heat exchanger according to a first embodiment of the present invention.
• FIG. 2 shows a modification of the top cover of the vertical multitubular heat exchanger of FIG.
• FIG. 3 is a view showing a modification of the top cover of the vertical multitubular heat exchanger of FIG.
• FIG. 4 is a diagram showing a modified example of the top cover of the vertical multitubular heat exchanger of FIG.
• FIG. 5 is a diagram showing a modification of the top cover of the vertical multitubular heat exchanger of FIG.
• FIG. 6 is a partially enlarged cross-sectional view of the vertical multitubular heat exchanger according to the first embodiment of the present invention.
• FIG. 7 is a diagram showing a modification of FIG.
• FIG. 8 is a partially enlarged cross-sectional view of a vertical multitubular heat exchanger according to the second embodiment of the present invention.
• FIG. 9 is a schematic diagram of a distillation column system including a vertical multitubular heat exchanger according to the present invention.
• FIG. 10 is a longitudinal sectional view of a conventional vertical multi-tube heat exchanger.
• FIG. 1 is a vertical sectional view of a vertical multitubular heat exchanger according to a first embodiment of the present invention.
• the vertical multitubular heat exchanger 1 has a tubular body 2 extending in the up-down direction.
• the cross-sectional shape of the tubular body 2 is preferably circular, but may be other shapes.
• the vertical multi-tube heat exchanger 1 is disposed on the upper tube sheet 8 and the lower tube sheet 10 provided on the upper part 4 and the lower part 6 of the tubular body 2, respectively, and on the upper tube sheet 8. It has a top lid 12 and a bottom lid 14 arranged below the lower tube sheet 10.
• the top lid 12 may have the shape as shown in FIG. 1 or the top lid 12 of the modified vertical multitubular heat exchangers 1 a to 1 d shown in FIGS. 2 to 5. It may have a shape of a to 12d.
• the attachment between the top cover 12 and the upper tube sheet 8 may be of a separate cover plate type as shown in FIG. 1, or may be a cover plate integrated type, tube plate integrated type, etc. (Not shown).
• the bottom cover 14 and the lower tube sheet 10 may be attached in a fixed tube sheet type as shown in Fig. 1, or with a floating head gland type, floating head split flange type, floating head pull-out type, etc. (Not shown).
• an upper space 16 is constituted by the top lid 12 and the upper tube sheet 8, and the tubular body 2, the upper tube sheet 8 and the lower tube sheet 10 define An intermediate space 18 is formed, and a lower space 20 is formed by the bottom cover 14 and the lower tube sheet 10.
• the top lid 12 has a top port 22 that communicates with the upper space 16, and the bottom lid 14 has a bottom port 24 that communicates with the lower space 20.
• outer ends 26 at both ends are fixed to the upper tube sheet 8 and the lower tube sheet 10, respectively, and communicate the upper space 16 with the lower space 20.
• Multiple Heat transfer tubes 28 are provided. As will be described later, since the process fluid is introduced into the heat transfer tube 28, the heat transfer tube 28 does not react with the easily polymerizable substance and does not modify the easily polymerizable substance.
• the heat transfer tube 28 is preferably formed of a material that does not cause corrosion of the heat transfer tube 28 itself and is easily welded. Therefore, the heat transfer tube 28 is formed of, for example, an austenitic steel tube, an austenitic ferrite steel tube, or a ferritic steel tube.
• the tubular body 2 has two ports 30 and 32 communicating with the intermediate space 18, and a fluid for performing heat exchange with the process fluid introduced into the heat transfer tube 28 is supplied through the port. — It accumulates in the intermediate space 18 through the ports 30 and 32 and flows therethrough.
• the intermediate space 18 may be a one-pass type having one chamber as shown in FIG. 1 or a two-pass type or a three-pass type in which the intermediate space 18 is partitioned into a plurality of chambers (see FIG. 1). (Not shown).
• a partition for forming a flow path may be provided in the intermediate space 18.
• the flow path in the intermediate space 18 may be formed by a long baffle plate 2 pass type, a split flow type, a double split flow type, You may comprise a split flow type etc.
• the upper surface 34 of the upper tube sheet 8 is inclined so as to become lower from the outer portion 36 to the center portion 38.
• the inclination angle S of the upper surface 34 with respect to the plane including the outer edge 40 of the upper surface 34 is preferably 0.05 to 0.1 radian, more preferably 0.06 to 0.04. Radian, more preferably 0.07 to 0.02 radian.
• the upper surface 34 of the upper tube sheet 8 is preferably subjected to a treatment such as a mechanical polishing such as a puff polishing or an electrolytic polishing, but such a treatment may not be performed.
• a lowermost heat transfer tube 28L is arranged near the lowest position of the upper surface 34 of the upper tube sheet 8, that is, in the center portion 38.
• the lower surface 42 of the lower tube sheet 10 is inclined so as to be lower from the outer portion 44 to the center portion 46.
• the inclination angle of the lower surface 42 with respect to the plane including the outer edge of the lower surface 42 is preferably selected from the same angle range as the upper surface 34 of the upper tube sheet 8 described above. Good.
• FIG. 6 is an enlarged cross-sectional view of a connection portion between the upper tube sheet 8 and the heat transfer tubes 28.
• the upper tube sheet 8 has a hole 50 that can be fitted with the heat transfer tube 28, and all the heat transfer tubes 28 have ii ⁇ 52 further thereon. It is positioned lower than the upper surface 34.
• the moss 50 is provided with several grooves 56, and after inserting and positioning the heat transfer tube 28 in the hole 50, the heat transfer tube 28 is expanded, so that the heat transfer tube 28 is formed. It is adapted to be fitted and fixed. Further, the upper end 52 of the heat transfer tube 28 is welded all around the upper tube sheet 8 so that a step does not occur between the upper tube sheet 8 and the upper end 52 of the heat transfer tube 28. The entire circumference welding between the heat transfer tube 28 and the upper tube sheet 8 also has the effect of increasing the airtightness between them.
• the heat transfer tube 28 is inserted into the hole 50 having a number of grooves 56 and expanded by expanding the heat transfer tube 28.
• the upper end of the heat transfer tube 28 may be cut or polished so that there is no step between the upper end 28 of the heat transfer tube 28 and the upper surface 34 of the upper tube plate 8. .
• methacrolein gas is introduced from the top port 22 of the vertical multitubular heat exchanger 1 into the upper space 16.
• a part of the introduced methacrolein gas comes into contact with the upper surface 34 of the upper tube sheet 8 and condenses, and the condensed methacrolein liquid rides on the upper surface 34 of the upper tube sheet 8.
• the upper surface 3 4 of the upper tube sheet 8 is inclined downward from the outer portion 36 to the center portion 38, and has been subjected to a smoothing process such as buffing.
• the methacrolein liquid on 4 flows downward along the upper surface 34 of the upper tube sheet 8, ie, toward the center portion 38, without staying on the upper surface 34 of the upper tube sheet 8.
• the methacrolein liquid flowing downward flows into the heat transfer tube 28 on the way to the center or the lowermost heat transfer tube 28L arranged near the center.
• the methacrolein liquid does not stay on the upper surface 34 of the upper tube sheet 8, so that the methacrolein polymer adheres to the upper surface 34 of the upper tube sheet 8 and the vicinity of the upper end 52 of the heat transfer tube 28. Is prevented.
• the stagnation is prevented so that the polymer does not grow.
• a flow path for the methanochlorine gas and the mechanochlorine liquid flowing in the heat transfer tube 28 is also secured.
• the methacrolein gas also condenses in the heat transfer tube 28.
• the methacrolein liquid generated by the condensation flows along the inner surface 58 of the heat transfer tube 28, as described above, the flow path of the methacrolein gas and the methacrolein solution flowing in the heat transfer tube 28 is secured. Therefore, the methacrolein liquid in the heat transfer tube 28 is propelled by the mesochlorine gas or the like flowing downward, and flows downward without staying on the inner surface 58 of the heat transfer tube 28.
• the methacrolein liquid comes out from the lower tube sheet 10 side of the heat transfer tube 28.
• Most of the methacrolein solution coming out of the heat transfer tubes falls due to gravity, but a part of the methacrolein solution adheres to the lower surface 42 of the lower tube sheet 10 due to surface tension.
• the methacrolein liquid adhering to the lower surface 42 of the lower tube sheet 10 flows downward, that is, toward the center without stagnation. , Finally, it falls.
• the vertical multitubular heat exchanger 1 Even if the operation of the vertical multitubular heat exchanger 1 is continued, the polymer does not grow and the heat transfer tubes 28 are not clogged. As a result, the operation of removing the polymer, which is frequently performed in the conventional vertical multi-tube heat exchanger, becomes unnecessary, and the vertical multi-tube heat exchanger can be operated continuously for a long time.
• the vertical multi-tube heat exchanger according to the second embodiment is similar to the vertical multi-tube heat exchanger according to the first embodiment, and heat transfer tubes other than the heat transfer tubes disposed at the center are formed. It is characterized by protruding from the upper surface of the upper tube sheet. Therefore, only the portions of the second embodiment that are different from the first embodiment will be described below, and descriptions of other common portions will be omitted.
• the same elements as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.
• FIG. 8 is an enlarged cross-sectional view of a connecting portion between an upper tube sheet and a heat transfer tube of the vertical multitubular heat exchanger according to the second embodiment.
• the upper end 52 L of the lowermost heat transfer tube 28 L is connected to the upper tube sheet 8 similarly to the first embodiment.
• the upper end 62 of the other heat transfer tube 60 protrudes from the upper surface 34 of the upper tube sheet 8.
• the upper tube sheet 8 and the heat transfer tubes 60 are welded all around so that the upper surface 34 of the upper tube sheet 8 and the ⁇ 62 of the heat transfer tubes 60 are connected smoothly. This Full circumference welding between the heat transfer tubes 60 and the upper tube sheet 8 also has the effect of increasing the airtightness between them.
• the connection strength between the upper tube sheet 8 and the heat transfer tubes 60 can be increased.
• the vertical multitubular heat exchanger always generates vibration due to the inflow and outflow of the process fluid or the fluid that exchanges heat with the process fluid, vibration caused by the pump or compressor, and direct pulsating flow from the rotary pump machine.
• the sealing performance of the connection between the heat transfer tube 60 and the upper tube sheet 8 can be prevented from deteriorating, and the process fluid can be prevented from leaking from between them.
• connection strength of the heat transfer tubes 60 around the lowermost heat transfer tube 28 L increases, the sealing performance of the connection between the lowermost heat transfer tube 28 L and the upper tube plate 8 is also prevented from deteriorating. Is stopped.
• a large number of thin heat transfer tubes 60 are required. The connection with the upper tube sheet 8 can be reliably performed.
• FIG. 9 is a schematic diagram of a distillation column system including a vertical multitubular heat exchanger according to an embodiment of the present invention.
• the distillation column system 70 has a distillation column 72 capable of distilling a substance containing an easily polymerizable substance, and the distillation column 72 has a supply pipe 76 connected to an intermediate portion 74 thereof. And a top tube 80 connected to the tower top 78 and a bottom tube 84 connected to the tower bottom 82.
• the top tube 80 of the distillation column 72 is connected to the top portion 88 of the vertical multitubular heat exchanger 86 which is an embodiment of the present invention and acts as a condenser.
• a distilling pipe 92 is connected to the bottom 90 of the condenser 86, and the distilling pipe 92 is branched into two, and one is connected to the upper part 94 of the distillation column 72. The other is connected to the outside.
• the bottom pipe 84 of the distillation column 72 is branched into two, One is connected to the bottom 98 of a vertical multi-tube heat exchanger 96 which is an embodiment of the present invention and acts as a reboiler, and the other is connected to the outside.
• a temperature control pipe 102 is connected to the top 100 of the reboiler 96, and the temperature control pipe 102 is connected to a lower portion 104 of the distillation column 72.
• the distillation column 72 is preferably a tray column (tray column) from the viewpoint of preventing polymerization of easily polymerizable substances and tower efficiency, but is composed of a packed tower, a wet wall tower, a spray tower, and the like. Is also good.
• a methacrolein-containing solution is prepared.
• the methacrolein-containing solution is obtained, for example, by contacting gas-containing rain-containing gas obtained by contact gas phase oxidation of isoptylene with a molecular oxygen-containing gas with water, and collecting methacrolein as an aqueous methacrolein solution. Can be obtained.
• the methacrolein-containing liquid is supplied from the supply pipe 76 to the distillation column 72.
• the polymerization inhibitor may be, for example, one or more selected from molecular oxygen-containing gas, hydroquinone, methoquinone, cresol, phenol, t-butylcatechol, diphenylamine, phenothiazine, methylene butyl, dimethyldithionate copper rubinate, getyl At least one selected from copper salt compounds such as copper dithiocarbamate, copper dibutyldithiocarbamate and copper salicylate, and manganese salt compounds such as manganese acetate; p-phenylene such as p-phenylenediamine Examples include amines, N-oxyl compounds such as 4-hydroxy 2,2,6,6-tetramethylpiperidinoxyl, ureas such as urea, and thioureas such as thiourea.
• polymerization inhibitors may be added alone or in combination of two or more.
• the polymerization inhibitor may be introduced directly into the distillation column 72 or may be dissolved in the feed solution, reflux solution or other solvent. Alternatively, it may be introduced from a liquid sending line (not shown).
• the polymerization inhibitor is a molecular oxygen-containing gas, it may be directly mixed into the easily polymerizable substance by bubbling or the like, or may be dissolved in a solvent and mixed indirectly. In publishing, it is preferable to supply the molecular oxygen-containing gas from the bottom portion 82 of the distillation column 72 and / or the reboiler 96.
• the liquid containing methacrolein supplied to the distillation column 72 is vaporized to form a rain gas at the outlet of the distillation column 72, and is passed from the top 78 of the distillation column 72 to the condenser 86 through the top tube 80. Sent to top port 22.
• methacrolein gas contains a polymerization inhibitor
• a part of the polymerization inhibitor is removed from methacrolein gas in the distillation column 72, so that methacrolein gas is methacrolein gas. May not contain a sufficient amount of polymerization inhibitor to prevent the polymerization of
• the methacrolein gas sent to the condenser 186 is condensed in the condenser 186 by the vertical multitubular heat exchanger of the present invention to become a methacrolein liquid.
• the methacrolein solution does not stay on the upper surface 34 of the upper tube sheet 8 of the condenser 86 and the heat transfer tubes 28, etc. Driving becomes possible. As a result, long-term continuous operation of the entire distillation column system 70 becomes possible.
• the mesychlorine-containing liquid taken out from the bottom portion 82 of the distillation column 72 flows from the bottom of the reboiler 96 upward.
• the temperature is adjusted by heating, and the methacrolein, whose temperature has been adjusted, passes through the temperature adjusting tube 102 and passes through the lower portion 104 of the distillation column 72. Is returned to.
• the methacrolein-containing liquid flows from bottom to top in the reboiler 96 without any stagnation, and the upper surface 34 of the upper tube sheet 8 of the reboiler 96 is filled with the methacrolein-containing liquid. As a result, almost no polymer adheres.
• the methacrolein-containing liquid does not stay on the upper surface 34 of the upper tube sheet 8 of the reboiler 96 or the lower surface 42 of the lower tube sheet 10 and the like.
• the adhesion of the polymer to the upper surface 34 of the upper tube sheet 8 and the lower surface 42 of the lower tube sheet 10 is prevented.
• long-term continuous operation of the reboiler 96 is possible without having to inspect the inside of the reboiler 96 at the start of restart, and long-term continuous operation of the entire distillation column system 70 is also possible. become.
• the upper surface 34 of the upper tube sheet 8 is inclined so as to be lower from the outer portion 36 toward the central portion 38, but the inclination is not limited thereto, and the inclination is deviated from the central portion. It may be lower toward the place, or there may be two or more lower places.
• the upper ends 52 of all the heat transfer tubes 28 do not protrude from the upper surface 34 of the upper tube plate 8 will be described.
• the lowermost heat transfer tubes 2 Although only the upper end 52 of 8 L does not protrude from the upper surface 34 of the upper tube sheet 8, the upper end 62 of the other heat transfer tubes 60 protrudes from the upper surface 34 of the upper tube sheet 8.
• the upper end 52 of all the heat transfer tubes 28 may be configured to protrude from the upper surface 34 of the upper tube plate 8, or some of the heat transfer tubes 2 near the bottom heat transfer tube 28L. 8 Do not project the upper end 5 2 of the upper tube sheet 8 from the upper surface 3 4 of the upper tube sheet 8.
• methacrylic acid-containing gas obtained by subjecting methacrolein to catalytic gas-phase oxidation with a molecular oxygen-containing gas is brought into contact with water to collect methacrylic acid as a methacrylic acid aqueous solution.
• An extract obtained by extracting methacrylic acid from an aqueous solution of methacrylic acid using an organic solvent as an extractant, or a fluid obtained by appropriately distilling this extract may be prepared as a methacrylic acid-containing liquid. .
• the easily polymerizable substance is, for example, an ester of methyric acid, acrylic acid, maleic acid or an ester thereof, styrene, or acrylonitrile.
• These easily polymerizable substances may further include a mixture with a high-boiling substance, a solvent, and by-products at the time of producing the easily polymerizable substance.
• acrylic acid and acrylate there may be mentioned a mixture of acetic acid, propionic acid, acrolein, maleic acid, water, formalin and the like, which are by-produced when acrylic acid is obtained by catalytic gas phase oxidation reaction. it can.
• methacrolein for example, a mixture of acetic acid, water, and the like generated when mesochlorin is obtained by a catalytic gas phase oxidation reaction can be mentioned.
• methacrylic acid and methacrylic acid ester a mixture of acrylic acid, acetic acid and the like generated when methacrylic acid is obtained by a catalytic gas phase oxidation reaction can be mentioned.
• the inclination direction of the lower surface 42 of the lower tube sheet 10 is inclined downward from the outer portion 44 to the center portion 46, but from the outer portion 44 to the center portion 4. It may be inclined upward toward 6.
• the vertical multitubular heat exchanger of the present invention is connected to a condenser 86 and a reboiler 96.
• the present invention is not limited to this, and may be used as other condensers, coolers, heaters, or evaporators.
• the vertical multi-tube heat exchanger of the present invention includes a baffle plate, a long baffle plate, a buffer plate, a partition body trunk flange, a trunk lid flange, a trunk nozzle, a floating skull which a general heat exchanger has. , Fixing rods and spacers, gas vent seats, drain vent seats, instrument seats, support legs, suspension fittings, liquid level gauge seats, expansion joint thermal expansion countermeasures, etc.
• the distillation column used in conjunction with Examples 1 to 4 and Comparative Examples 1 to 4 was common, and was equipped with a stainless steel (SUS304) sieve tray with an inner diameter of 0.15 m and a number of stages of 30. ing.
• SUS304 stainless steel
• the inclined surfaces of the upper tube sheet and the lower tube sheet of the condenser and the reboiler in Examples 1 to 4 are provided so as to become lower from the periphery of each tube sheet toward the center, and the inclination angles are respectively set.
• Examples 1 and 2 and Comparative Examples 1 and 2 Purification of a Methacrolein-Containing Liquid
• a methanol chlorane-containing liquid was supplied to a distillation column.
• the supplied methacrolein-containing liquid was composed of 93% by mass of methacrolein, 3% by mass of acetic acid, and 4% by mass of water, and the supply amount of the liquid containing methacrolein was 50 kg / hr. .
• Hydroquinone was added to the methacrolein-containing liquid at 200 ppm as a polymerization inhibitor, and rectification was performed while introducing air as a molecular oxygen-containing gas at 0.3% by volume based on the amount of steam generated by the reboiler.
• the distillation column has a top pressure of 101 kPa, a top temperature of 66 C, a bottom pressure of 104 kPa, and a bottom.
• the system was operated and operated at a temperature of 76 ° C and a reflux ratio of 3.
• Example 1 and Comparative Example 1 used a vertical multi-tube heat exchanger in which all the heat transfer tubes did not protrude from the upper surface of the upper tube sheet.
• Example 2 and Comparative Example 2 Vertical heat exchanger where only one heat transfer tube (equivalent to the bottom in Example 2) does not protrude from the upper surface of the upper tube sheet, and the other heat transfer tubes protrude from the upper surface of the upper tube plate. Vessel was used.
• the lower tube sheet in all of Examples 1 and 2 and Comparative Examples:! And 2, all the heat transfer tubes used had a shape protruding from the lower surface of the lower tube sheet.
• Example 1 after continuous operation for two weeks, the operation was stopped once, and a process fluid containing a methacrolein-containing liquid was extracted. Two days later, operation was resumed and continued for another six months. After that, the condenser, the upper tube sheet, the lower tube sheet and the heat transfer tubes of the reboiler were inspected, but no adhesion of methacrolein polymer was observed.
• a liquid containing methacrylic acid was supplied to the distillation column.
• the composition of the supplied methacrylic acid-containing liquid was 95% by mass of methacrylic acid, 2% by mass of acetic acid, and 3% by mass of acrylic acid, and the supply amount of the liquid containing methacrylic acid was 80 kg / hr. .
• Hydroquinone was added as a polymerization inhibitor to the acrylic acid-containing liquid at 20 Opm, and air as a molecular oxygen-containing gas was rectified at a rate of 0.3% by volume based on the amount of vapor generated by the reboiler. Went.
• the distillation column was operated and controlled at a top pressure of 8 kPa, a top temperature of 77 ° C, a bottom pressure of 10 kPa, a bottom temperature of 9.9 ° C, and a reflux ratio of 2.
• Example 3 and Comparative Example 3 a vertical multi-tube heat exchanger in which all the heat transfer tubes did not protrude from the upper surface of the upper tube sheet was used. 4), only one of the heat transfer tubes does not protrude from the upper surface of the upper tube sheet, and the other heat transfer tubes protrude from the upper surface of the upper tube sheet. It was used. Regarding the lower tube sheet, in all of Examples 3 and 4 and Comparative Examples 3 and 4, the type in which all the heat transfer tubes protruded from the lower surface of the lower tube sheet was used.
• Comparative Example 3 where operation was attempted in the same manner as in Example 3, the operation was stopped because the capacitor clogged three months after restarting operation and it was no longer possible to use it. did. Inspection of the upper surface of the upper tube sheet and the heat transfer tubes of the condenser revealed that the upper surface of the upper tube plate was entirely covered with a polymer, and almost all of the heat transfer tubes were blocked with polymer deposits. In the reboiler, about 5 kg of polymer adheres to the upper surface of the upper plate, and about 60% of the heat transfer tubes are closed with polymer. I was blocking. Further, some adhesion of the polymer was also observed on the lower surface of the lower tube sheet of the condenser and reboiler.
• Example 4 In Comparative Example 4 in which the operation was attempted in the same manner as in Example 4, the operation was stopped four months after the operation was resumed because the condenser was clogged and could no longer be used. Inspection of the upper surface of the upper tube sheet and the heat transfer tubes of the condenser revealed that the upper surface of the upper tube plate was entirely covered with a polymer, and almost all of the heat transfer tubes were blocked by polymer deposits. In the reboiler, about 6 kg of polymer adhered to the upper surface of the upper plate, and about 70% of the heat transfer tubes were blocked by the polymer. In addition, some polymer adhered to the lower surface of the lower tube sheet of the condenser and reboiler.

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