JP2011213641A - Method for washing apparatus for producing bisphenol a - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for inexpensively washing an apparatus for producing bisphenol A with a reduced environmental load which efficiently removes the attachment of bisphenol A to an apparatus over the interior and enables maintenance of a cooling effect, inhibition of rising in pressure difference, and long-term continuous operation of a granulating column.SOLUTION: The method for washing an apparatus for producing bisphenol A which is used in producing bisphenol A in the form of a solid prill by bringing melt bisphenol A into contact with a cooling gas in a granulating column 1 comprises allowing dry ice particles to collide with the contact surface between the cooling gas and an apparatus constituted of the granulating column and/or peripheral equipment thereof.

Description

The present invention relates to a method for cleaning an apparatus to which bisphenol A is adhered. More specifically, it is a cleaning method for a bisphenol A production apparatus used for producing solid prill-shaped bisphenol A by bringing molten bisphenol A into contact with a cooling gas in the granulation tower, and the granulation tower is in contact with the cooling gas. The present invention also relates to a cleaning method for a bisphenol A manufacturing apparatus in which dry ice particles collide with a contact surface with an apparatus composed of peripheral devices.

Bisphenol A is generally distributed in the market as a spherical solid called prill having a diameter of about 1 to 3 mm. Prill is generally produced by bringing bisphenol A in a molten state into alternating contact with a cooling gas in a granulation tower and solidifying it. More specifically, the droplets of molten bisphenol A are dropped from an eye plate installed in the upper part of the granulation tower, and solidified by countercurrent contact with a gas such as nitrogen having a temperature lower than that of molten bisphenol A. In general, since the temperature of the gas used for cooling has risen, it is circulated and reused after being cooled by a heat exchanger. (See Patent Document 1)
Since the cooling gas used for solidification cooling of bisphenol A is in direct contact with molten bisphenol A in the granulation tower, it contains various organic vapors such as bisphenol A. When a gas containing such organic vapor is cooled by a heat exchanger, the saturated vapor pressure of the organic substance decreases, so the organic substance contained adheres to the heat transfer surface (surface) of the heat exchanger and heat The heat transfer efficiency of the exchanger decreases and the differential pressure increases. In such a case, it may be necessary to stop the plant and clean the heat exchanger each time, and continuous operation may be difficult. Methods for washing include a method of melting with steam, a method of dissolving in a solvent, and a method of mechanically scraping, but the former two are mixed with various organic substances such as bisphenol A, water, and solvent. There is a problem in terms of environment and cost that a large amount of waste liquid is generated, and the latter can only remove the surface of the heat exchanger transmission surface, so the shape of the heat exchanger is complicated or thick. Case It is difficult to remove organic substances adhering to the inside of the transmission surface.

  In Patent Literature 2, the organic vapor pressure at the temperature of the gas on the inlet side of the heat exchanger is supplied to the heat exchanger so that the organic vapor pressure at the surface temperature of the heat transfer surface of the heat exchanger is equal to or lower than the saturated vapor pressure of the organic substance. It is disclosed to reduce the adhesion of the heat exchanger surface of organic matter by controlling the supply amount and temperature of the refrigerant, but after the operation for a certain period by the method by this control, the operation is stopped, It is necessary to clean the heat transfer surface, and it has been desired to develop a cleaning method to enable continuous operation for a longer period.

Special Table 2002-534402 JP 2007-262021 A

  The object of the present invention is based on the above situation and is used as a cooling gas for molten bisphenol A liquid in a bisphenol A granulation tower, and a gas containing various organic substance vapors is cooled by a heat exchanger, When using again as a cooling gas for the molten bisphenol A liquid, the adhesion to the heat transfer surface of the heat exchanger, in particular the finned multi-tubular heat exchanger, is effectively removed over the inside, and the cooling effect is maintained. An object of the present invention is to provide an inexpensive and low environmental load cleaning method for a bisphenol A production apparatus that can suppress an increase in differential pressure and enable continuous operation of a granulation tower for a long period of time.

As a result of investigations for solving the above problems, the present inventors have made a bisphenol A production apparatus for use in producing solid prill-like bisphenol A by bringing molten bisphenol A into contact with a cooling gas in a granulation tower. The present inventors have found that the above-mentioned problems can be solved by causing dry ice particles to collide with a contact surface between a cooling gas and a device comprising a granulating tower and / or its peripheral equipment.

That is, the gist of the present invention is a cleaning method for a bisphenol A production apparatus used in producing a solid prill-like bisphenol A by bringing molten bisphenol A into contact with a cooling gas in a granulation tower. The present invention relates to a cleaning method for a bisphenol A production apparatus, characterized in that dry ice particles collide with a contact surface with a granulation tower and / or an apparatus comprising peripheral equipment.

  According to the present invention, the molten bisphenol A liquid is used as a cooling gas for the molten bisphenol A liquid in the granulation tower of bisphenol A, and after the gas containing various organic substance vapors is cooled by the heat exchanger, the molten bisphenol A is again used. In the equipment used when used as a liquid cooling gas, the heat exchanger, especially the finned multitubular heat exchanger, adheres to the heat transfer surface without producing a large amount of waste water or waste solvent. It is possible to efficiently remove and maintain the cooling effect and suppress the increase in the differential pressure. Also, by installing this removal method inside the granulation tower and carrying out without opening during operation, it is possible to remove organic substances adhering to the heat transfer surface of the heat exchanger without stopping the operation, and for a long time The continuous operation of the granulation tower becomes possible.

FIG. 2 is a diagram of a typical granulator used to make a bisphenol A melt into a solid prill. It is a typical figure of the side of a multi-tube heat exchanger with a fin. It is a typical figure of the upper surface of a multi-tube heat exchanger with a fin.

Hereinafter, the present invention will be described in detail. However, the description of the constituent elements described below is a representative example of embodiments of the present invention, and the present invention is not limited to these contents.
The method for cleaning a bisphenol A production apparatus of the present invention is, for example, by discharging a bisphenol A melt in the form of droplets from a nozzle arranged in the upper part of a granulation tower, and a countercurrent flow with a gas lower than the temperature of the melt. The molten liquid is made into a solid prill (granulated) by contacting, and the gas brought into contact with the molten liquid is extracted from the upper part of the granulation tower and then cooled by a heat exchanger, and the cooled gas is cooled to the tower of the granulation tower. The present invention can be applied to an apparatus that is supplied to the lower part and circulated.
There is no restriction | limiting in particular in molten bisphenol A concerning this invention, It can manufacture by the method shown below etc. as a typical method.

<Method for producing molten bisphenol A>
A reaction mixture containing bisphenol A is obtained by condensation reaction of a large excess of phenol and acetone in the presence of an acidic ion exchange resin or an acidic catalyst such as mineral acid such as hydrochloric acid or sulfuric acid, and unreacted acetone or phenol. A slurry solution containing adduct crystals of bisphenol A and phenol, called adduct crystals, is obtained from a solution obtained by removing and concentrating part of the generated water.
After the solid-liquid separation and taking out only the crystals, the adduct crystals can be heated and melted, and then the phenol can be distilled off.

The acidic catalyst used in this case is preferably an acidic ion exchange resin used as a catalyst for producing bisphenol A, and in particular, a styrene-divinylbenzene copolymer type acidic cation into which approximately the same number of sulfonic acid groups as the total number of benzene rings have been introduced. Exchange resins are preferred. Further, when the reaction is carried out using this catalyst, a mercaptan compound is preferably allowed to coexist as a promoter. This mercaptan means a compound having a thiol group in the molecule in a free form, and an alkyl mercaptan or an alkyl mercaptan having one or more substituents such as a carboxyl group, an amino group, and a hydroxyl group, such as mercaptocarboxylic acid, Aminoalkanethiol, mercapto alcohol, etc. can be used.

  Examples of such mercaptans include alkyl mercaptans such as methyl mercaptan and ethyl mercaptan, thiocarboxylic acids such as thioglycolic acid and β-mercaptopropionic acid, 2-aminoethanethiol, 2-pyridylethanethiol, 4- Examples include aminoalkanethiol such as pyridylethanethiol and mercapto alcohol such as mercaptoethanol.

  These mercaptans may be supplied to the reaction system simultaneously with the starting materials phenol and acetone as a co-catalyst. However, when a compound having a basic structure such as an amino group is used, the acid type ion exchange resin is used in advance. The reaction may be carried out by reacting a sulfonic acid group in the catalyst with a base such as an amino group of the promoter to immobilize the promoter on the catalyst and use it in the reaction. Moreover, these mercaptans may be used independently and may be used in combination of 2 or more type.

  When the reaction is carried out by adding a cocatalyst such as an alkyl mercaptan during the reaction, it is added in the range of 0.1 to 20 mol%, preferably 1 to 10 mol% with respect to the raw material acetone. Preferably, when the reaction is carried out by immobilizing a co-catalyst such as aminoalkanethiol, the co-catalyst is ion-bonded and immobilized on 1 to 50 mol% of the sulfonic acid group of the sulfonic acid type acidic ion exchange resin. Is preferred. If the amount of the cocatalyst used is too small, there is a problem that a practical reaction rate cannot be obtained. If the amount of the cocatalyst used is too large, the increase in activity corresponding to the amount used is unfamiliar and not economical.

  The molar ratio of phenol and acetone used in the reaction is not particularly limited, but phenol is preferably used in excess of the stoichiometric amount, and 3 to 30 mol, preferably 5 to 20 mol, per mol of acetone. Phenol is used. When the amount of phenol used per mole of acetone is less than 3 moles, the selectivity for bisphenol A is lowered, and when it is more than 30 moles, problems such as a reduction in reaction rate and enlargement of the apparatus occur.

  The condensation reaction of phenol and acetone in the above production method is not particularly limited in the reaction system, but phenol and acetone are continuously supplied to a reactor filled with an acid ion exchange resin having a promoter immobilized thereon. It is preferable to use a fixed bed continuous reaction system for reaction. At this time, the reaction may be carried out with one reactor, or two or more reactors may be arranged in series and / or in parallel.

The reaction temperature is usually 40 to 130 ° C., preferably 40 to 90 ° C. If the reaction temperature is less than 40 ° C., the reaction solution may solidify, which is not preferable. If the reaction temperature is higher than 130 ° C., the acidic group of the acidic ion exchange resin as a reaction catalyst is detached from the catalyst and bisphenol A is removed. Bisphenol A may be decomposed by mixing into the catalyst, or the catalyst may be decomposed at a high temperature to reduce the catalyst life.

The LHSV (liquid space velocity) of the raw material mixture is preferably passed through at 0.2 to 20 hr-1.
The reaction liquid containing bisphenol A produced in the reactor is supplied to a distillation column in order to remove unreacted acetone, a part of phenol, produced water and the like. At this time, the reaction solution may be filtered through a filter.

  There are no particular restrictions on the filter used at this time, but it is possible to use a cartridge filter made of glass fiber, a ceramic filter, a fired metal filter made of stainless steel, a membrane filter made of fluororesin, or the like. . Of these filters, it is preferable to use a filter that can capture particles of 30 microns or more.

By filtering the reaction solution, it is possible to remove catalyst residue and catalyst crushed material, and to suppress degradation of bisphenol A in the system and deterioration of hue.
Next, by distillation, unreacted acetone and phenol, water produced by the condensation reaction, mercaptan compounds used in the reaction, and the like are removed as necessary. Depending on the subsequent crystallization conditions, some or all of the material to be removed may be omitted.

When removing unreacted acetone or phenol, water produced by the condensation reaction, mercaptan compound used in the reaction, etc., the removal is usually performed by distillation under reduced pressure using one or two or more distillation towers.
This vacuum distillation is generally carried out under conditions of an absolute pressure of 5 to 100 kPa and a temperature of about 70 to 180 ° C. using a distillation column whose contact surface with the liquid is made of SUS304, SUS316, SUS316L or the like. If the temperature is too high, bisphenol A may be decomposed, which is not preferable.

The obtained distillate is sent to a crystallization tank to obtain bisphenol A or a 1: 1 adduct crystal (adduct crystal) of bisphenol A and phenol. Prior to crystallization, phenol, water, acetone, hydrocarbons such as C5 to C7, etc. may be added to the distillate to adjust the concentration and composition.
The liquid prepared by the above method is cooled to 40 to 70 ° C. to precipitate crystals, thereby obtaining a slurry liquid mainly composed of crystals and phenol. If the crystallization temperature is lower than 40 ° C., the phenol may solidify, and if it is 70 ° C. or higher, loss due to dissolution of bisphenol A in phenol increases, which is not preferable.
In this case, the cooling can be performed by using an external heat exchanger, or by supplying the crystallization adjustment liquid to a device under reduced pressure and using the latent heat of vaporization from the liquid, but is not limited thereto. Absent.

The slurry obtained by crystallization in this manner is separated into liquid components called crystals and mother liquor by known means such as filtration and centrifugation. There is no particular limitation on the method of filtration and centrifugation, but it is preferable to perform filtration and separation with an apparatus such as a vacuum type or pressure type belt filter or a rotary film evaporator.
Depending on the required quality of bisphenol A, the crystal obtained by the above filtration operation may be heated as necessary, or various phenol-containing solutions may be added and dissolved, and the crystallization operation may be repeated. There is no restriction | limiting in particular as a phenol containing solution to be used, For example, the phenol containing solution which exists in a process Specifically, recovered phenol, a crystallization mother liquid, the washing | cleaning phenol liquid of a crystal | crystallization etc. can be mentioned. Further, before recrystallization, the phenol solution in which the crystals are dissolved may be filtered and removed through a filter.

The crystallization mother liquor, which is the liquid component when filtered, is recycled to the reactor, or part or all of it is thermally decomposed by adding acid or alkali, and the resulting heavy components are removed from the system by distillation. Can do. From the remaining components, it is possible to recover only phenol by manipulating the conditions of the thermal decomposition treatment, or after recovering phenol and isopropenylphenol, the acidic components such as the sulfonic acid type acidic ion exchange resin are recovered. You may collect | recover as bisphenol by making it contact with a catalyst. Further, the 2,4 ′ isomer contained as an impurity may be converted to 4,4′bisphenol A and recovered by isomerizing a part or the whole before or after these operations.

When the separated crystals are bisphenol A crystals, the product bisphenol A can be used as it is. You may wash | clean with water, an organic solvent, etc. in order to remove the impurity of the crystal | crystallization surface as needed. In addition, if it is difficult to handle the crystal as it is, it may be prilled after being melted once.
When the separated crystals are 1: 1 adduct crystals of bisphenol A and phenol, bisphenol A is generally free from phenol by removing phenol from the crystals.
Get as a product. However, it is also possible to dissolve the adduct crystals and supply them as they are to the melt-process polycarbonate production process and use them as raw material monomers for polycarbonate.

As a method for removing phenol from a 1: 1 adduct crystal of bisphenol A and phenol, the adduct crystal that has been crystallized and separated is heated and melted to about 100 to 160 ° C. to form a liquid mixture, and then at an absolute pressure of 1 to 1 Most of the phenol is distilled off by a method such as various distillation operations (flash distillation, distillation using a thin-film evaporator such as a centrifugal type or a belt type) under a reduced pressure of about 10 kPa and a temperature of 150 to 200 ° C. This operation reduces the phenol concentration in the molten bisphenol A to a level of several wt%, but in order to further remove this residual phenol, the phenol is removed by steam stripping, etc., and finally the phenol content Is 100 wtppm or less, preferably 30 wtppm or less, more preferably 20 wtppm or less.

<Granulation method of melt of bisphenol A>
Hereinafter, a granulation method for making a melt of bisphenol A into a solid prill will be described in detail using the apparatus shown in FIG. 1 as a representative example.
The melt of bisphenol A is supplied to the granulation tower (1) via the line (101). The granulation tower (1) is not particularly limited as long as it is used for usual organic granulation. For example, a known granulation tower can be used. The structure of the granulation tower (1) is a structure having a vertically long cylindrical body having an inner volume of usually 1 to 2000 m3 and a lower end formed in a substantially inverted conical shape. Granulation tower (1
)) Is provided with a dropping nozzle (11), and the bisphenol A melt supplied via the line (101) forms droplets by the dropping nozzle (11), and the granulating tower ( 1) Fall inside. There are no particular restrictions on the dropping nozzle (11), and any known nozzle can be used. The nozzle diameter can be set according to the particle size of the granular material to be produced, the viscosity of the melt, etc. A nozzle having a perforated plate structure, a rotating nozzle using centrifugal force, or the like can be appropriately selected. In addition, droplet breakage and the like are improved by vibrating the nozzle as necessary.

The droplets of bisphenol A fall from the dropping nozzle (11) into the granulation tower in a shower shape.
At that time, it solidifies by countercurrent contact with the cooling gas introduced from the lower part of the granulation tower, and becomes a prill-like solid having a diameter of 1 to 2 mm. The produced prill of bisphenol A is discharged from the bottom of the granulation tower, and the gas heated for cooling is discharged from the top of the granulation tower, preferably from the center of the top. You may provide the well-known blockage | blocking prevention means as disclosed by Unexamined-Japanese-Patent No. 2002-306943 in the lower part of a granulation tower, for example. Thereby, it can prevent effectively that the inlet_port | entrance and the inside of a granular material discharge port (14) are obstruct | occluded with a lump.

As the cooling gas for the bisphenol A melt, a gas having a temperature lower than that of the bisphenol A melt is used, but an inert gas such as nitrogen gas or argon or air is preferable, and there is no risk of oxidation of bisphenol A or dust explosion. It is particularly preferable to use nitrogen which is economical and inexpensive. The gas used for cooling may be released to the atmosphere, but when nitrogen is used, it is recycled after cooling with a heat exchanger.

More specifically, the cooling gas extracted from the top of the granulation tower is supplied to the circulating gas blower after the fine bisphenol A powder accompanying the cooling gas is recovered and removed by a bag filter or the like. The bag filter that can be used is not particularly limited, and known ones such as a mechanical vibration type, a reverse air flow type, and a pulse jet type can be used. The gas from which the bisphenol A powder has been removed is supplied to a heat exchanger for gas cooling and cooled.

There is no particular limitation on the heat exchanger for gas cooling. For example, a well-known heat exchanger such as Shell & Tube type or plate type can be used, but a heat exchanger in which a plurality of tubes through which refrigerant flows is arranged in a row is inexpensive. It is preferable because a large amount of gas can be efficiently cooled. Further, in order to increase the heat transfer coefficient on the cooling gas side, it is preferable that the structure tube is provided with a plurality of fins or the like in a direction perpendicular to the tube axis so as to widen the heat transfer area. There is no particular limitation on the refrigerant used in the heat exchanger, and commonly used refrigerants such as water, ethylene glycol, and mixtures thereof can be used. However, in the case of bisphenol A, a low cooling temperature is not required. Cooling with water is possible.

When the cooling gas is circulated, bisphenol A and low boiling point impurities are present in the cooling gas as vapor equivalent to the vapor pressure, and these are the inner surface of the granulation tower, the inner surface of the piping through which the cooling gas flows, the gas Sublimation deposits and adheres to the heat transfer surface of the heat exchanger for cooling. In particular, the heat transfer surface of the heat exchanger for gas cooling has a problem that organic substances are likely to be deposited, and the cooling efficiency is lowered due to adhesion. The presence or absence of these deposits can be monitored and detected by installing a differential gauge because a differential pressure before and after the heat exchanger occurs due to precipitation and adhesion of organic crystals such as bisphenol A. .

<Dry ice blasting technology>
A blasting method that removes deposits due to friction by injecting abrasives (usually sand, baking soda, glass beads, metal powder, etc.) into the structure together with gas as a technology to remove the deposits on the structure. However, sand, baking soda, glass beads, metal powder, etc. are very hard and the structural material is soft, so the structural material may be deformed by blasting, or the abrasive itself There was a problem of remaining in the vicinity.

In recent years, dry ice blasting using dry ice as an abrasive has been used. This is because dry ice itself sublimes when it collides with the structural material, so that it does not deform the structural material by being injected at an appropriate injection speed, and adheres to the structure without leaving the abrasive itself. It is an excellent method that can remove the substances present.
In particular, in the case of a multi-tube heat exchanger in which tubes with fins attached perpendicularly to the tube axis are arranged in a row, the direction perpendicular to the tube axis as shown in FIG. Instead, it was found that osmotic effect was developed and osmotic force increased by blasting the tube up and down at an angle so that gas and dry ice escaped between the tubes. As shown in FIG. 2, the complex arrangement here means an arrangement in which a tube in the next column exists at the midpoint of a line connecting the centers of adjacent tube axes in a certain column. It is characterized by the distance (Lv) between the centers of the tube axes in the direction and the distance (Lh) between the rows perpendicular to it.

  That is, when the dry gas particles collide with the contact surface between the cooling gas and the heat exchanger and the dry ice particles, the direction in which the dry ice particles are sprayed drops the shadow of the locus on a plane perpendicular to the tube axis. The center of the tube axis forming the outermost surface of the heat exchanger and the direction connecting the center of the tube axis of the tube other than the outermost surface adjacent to the tube, or an angle of −15 ° to + 15 ° Is within the range, because the penetration effect is large and the dry ice penetrates not only to the side where the dry ice is jetted but also to the opposite side of the apparatus, and the deposits can be removed.

  On the other hand, in the horizontal direction parallel to the tube axis as shown in FIG. 3, blasting is performed on a plane perpendicular to the tube axis without changing the angle so that gas and dry ice can escape between the fins. It was revealed that the penetration effect was large and the penetration force was large when it was carried out. Thin fins are usually used for heat exchanger fins to improve heat exchange efficiency, and conventional abrasives sometimes deformed the fins. Excellent removal method that can remove not only the surface of the apparatus but also the bisphenol A crystals that are adhering to the inside of the pipe by using the penetration effect without causing deformation of the fins by spraying dry ice as an abrasive It turned out to be. In the dry ice blasting method defined in the present invention, the fluid gas for transferring the dry ice particles is not particularly limited, but air, nitrogen and the like are inexpensive and easily available. The dry ice particles have a particle size of about 0.5 to 5 mm, preferably 1 to 5 mm. The pressure of the dry ice particle transfer fluid is 0.2 to 0.8 MPa, preferably 0.3 to 0.5 MPa, relative pressure to the atmosphere. If the pressure is too low, the operation of the apparatus will be hindered, and the deposit removal effect will be low. On the other hand, if it is too high, it will cause problems such as damage to the heat exchanger such as fins and noise. As a dry ice spraying method, dry ice may be sprayed from one nozzle, but it may be sprayed from a number of nozzles at the same time, or it may be sprayed while moving one or more nozzles being sprayed. Alternatively, the structure itself such as a heat exchanger may be sprayed while being rotated or slid.

The line from the blasting device to the nozzle is not particularly limited and is generally various resin hoses, metal pipes, etc., but contamination caused by peeling of the inner wall of the pipe due to frictional collision between the dry ice moving in the pipe at high speed and the line From the viewpoint of static elimination of generated static electricity, metal piping is desirable. Stainless steel sanitary piping is the best.
A mechanism for supplying dry ice of a blasting apparatus to be used includes a rotary feeder, a vibration feeder, and the like, but a vibration feeder is more preferable from the viewpoint of preventing contamination due to scraps on the sliding portion.

The distance between the nozzle and the object when spraying the abrasive is preferably 10 to 100 cm, more preferably 25 to 75 cm. The supply amount of dry ice particles is preferably 1 to 30 kg / min, preferably 2 to 10 kg / min, and more preferably 2 to 5 kg / min. The continuous blasting time per time is 1 to 120 seconds, preferably 5 to 60 seconds. The spray speed of dry ice is 50 to 300 m / s, preferably 100 to 250 m / s. Since the kinetic energy of dry ice is proportional to the square of the ejection speed, the influence of the ejection speed is large. If it is too small, the deposit cannot be removed, and if it is too large, the object will be damaged. When the object is a multi-tube heat exchanger with fins, the fins are generally made of aluminum due to weight, price, ease of processing, etc., and the thickness is 0.5.
Since it is about ˜1.0 mm and is fragile, it is preferable to adjust the spray speed of dry ice to the above range. As for the size of the ejection nozzle, the size of the ejection port is 1 to 5 cm <2>, preferably 1.5 to 3 cm <2>. Most dry ice blasting systems are systems that control power with the gas supply pressure to the equipment, and ensure the above jetting speed, depending on the pipe diameter, shape, and length from the equipment to the nozzle. Above, if the jet outlet is larger than the above condition, the amount of jet gas becomes too large, which causes noise. On the other hand, if it is too small, the spot of the sprayed dry ice becomes small and the removal effect is reduced. Examples of organic substances attached to the heat transfer surface of the heat exchanger other than bisphenol A include propylphenol, butylphenol, isopropenylphenol, mesityloxylphenol, 2,2′-isomer of bisphenol A, and 2,2′-isomer of bisphenol A. Examples thereof include 4 ′ isomer, linear dimer of dianine, methyl bisphenol A, isopropenyl phenol, cyclic dimer of isopropenyl phenol, spiroindane, trisphenol, trisquiroman. These organic substances can also be removed together with the attached bisphenol A by the removal method of the present invention.

EXAMPLES Hereinafter, although an Example shows this invention in detail, this invention is not limited at all by the following example.
Using the same apparatus as shown in FIG. 1 and operating for 53 days, each example described below was performed using “C100” manufactured by ColdJet as a blasting apparatus.
As for the heat exchanger, a multi-tube heat exchanger with aluminum fins as shown in Figs. 2 and 3 is used, and fins are attached spirally at intervals of 2.5 mm perpendicular to the tube axis. The tubes are arranged in rows. Lv and Lh are 48 mm and 42 mm, respectively. That is, the line connecting the centers of the tube axes is a substantially regular triangle.

The operating conditions are as follows. 13 parts by weight of bisphenol A melt (temperature 169 ° C)
It is dropped into the granulation tower (1) from the dropping nozzle (11) at a rate of Hr, nitrogen gas is used as the cooling gas, and the flow rate of the cooling gas is adjusted by the valve (4) so as to be 70 parts by weight / Hr. While circulating. Further, while introducing nitrogen gas from the line (106), the circulating gas was purged from the line (105) so that the pressure in the granulation tower (1) was 2.5 kPa relative to atmospheric pressure. In addition, the temperature of water as the refrigerant of the heat exchanger (3) was adjusted so that the temperature of the cooling gas at the outlet (12) of the cooling gas was 70 ° C.

Example 1
From the tip of the blasting device through the line, from the tip of the nozzle with an inner diameter of 14 mm, nitrogen gas with a relative pressure of 0.3 MPa relative to the atmospheric pressure is used as the transfer fluid, and 3 mm diameter dry ice particles are injected at 2.1 kg / min, with a number of fins 50 cm ahead Deposits were removed by colliding dry ice with the tubular heat exchanger bundle for 10 seconds from the upstream side to the downstream side. At this time, blasting is performed so that the vertical angle is 30 ° downward so that gas and dry ice can escape through the gap between the tubes arranged in rows and columns with respect to the bundled multi-tube heat exchanger bundle surface. Went. However, the horizontal angle was set to 0 ° so that gas and dry ice could escape between adjacent fins. (The vertical angle and horizontal angle are the angles shown in FIGS. 2 and 3.)
As a result, the removal of deposits was confirmed in a circular shape with a diameter of about 20 cm on the upstream side, and the deposits were removed in a circular shape with a diameter of about 10 cm on the downstream side of the heat exchanger, confirming the penetration effect. At this time, in the part where the deposit on the downstream side is removed, the clearance between the fins is 1 mm on average due to the deposit.
What was about, has been improved to the original 2.5mm.

Example 2
In the same conditions and method as in Example 1, nitrogen gas with a relative pressure of 0.4 MPa relative to atmospheric pressure was used as the transfer fluid, the amount of dry ice sprayed was 3.5 kg / min, the spray time was 17 seconds, and the vertical angle was 30 ° upwards. Blasted as.
The result was almost the same as in Example 1, and the removal effect was confirmed on both the upstream side and the downstream side.

Example 3
Blasting was performed under the same conditions and method as in Example 2 with the vertical angle and horizontal angle both set to 0 °.
As a result, removal of the deposit was confirmed in a circular shape having a diameter of about 20 cm on the upstream side, but no penetration effect was observed, and removal of the deposit was not confirmed on the downstream side.

Example 4
Blasting was carried out under the same conditions and method as in Example 2 with the vertical angle being 30 ° downward and the horizontal angle being 45 °.
As a result, removal of the deposit was confirmed in a circular shape having a diameter of about 20 cm on the upstream side, but no penetration effect was observed, and removal of the deposit was not confirmed on the downstream side.

Comparative Example 1
Under the same conditions and method as in Example 2, the supply rate of dry ice was 0 kg / min, and only nitrogen was ejected from the blast apparatus for 20 seconds.
As a result, removal of deposits was not confirmed on both the upstream side and the downstream side.
The data of these examples and comparative examples are shown in Table 1.

  According to the present invention, adhesion of bisphenol A to the heat transfer surface of a heat exchanger, particularly a finned multi-tubular heat exchanger, can be efficiently removed without generating a large amount of waste water or waste solvent. It is possible to maintain the cooling effect and suppress the increase in the differential pressure. Also, by installing this removal method inside the granulation tower and carrying out without opening during operation, it is possible to remove organic substances adhering to the heat transfer surface of the heat exchanger without stopping the operation, and for a long time The continuous operation of the granulation tower becomes possible.

1: Granulation tower
2: Circulating gas blower
3: Heat exchanger
4: Valve
5: Bug filter
11: Dripping nozzle
12: Cooling gas outlet
13: Cooling gas inlet
14: Particulate outlet
21: Valve
22: Valve
31: Valve
32: Valve
33: Pump
34: Difference meter
105: Cooling gas (nitrogen) purge line
106: Cooling gas (nitrogen) inlet
107: Cooling water inlet
108: Cooling water 1: Vertical direction 2: Fin 3: Refrigerant flow path 4: Vertical angle 1: Horizontal direction 2: Fin tube 3: Refrigerant flow path 4: Refrigerant flow (dotted line)
5: Horizontal angle

Claims (3)

A cleaning method for a bisphenol A production apparatus used for producing solid prilled bisphenol A by bringing molten bisphenol A into contact with a cooling gas in a granulation tower, the granulating tower in contact with the cooling gas, and / or A cleaning method for a bisphenol A production apparatus, characterized in that dry ice particles collide with a contact surface with an apparatus comprising peripheral devices.   The device that contacts the cooling gas is a heat exchanger in which a plurality of tubes are arranged in a row, and the dry ice particles are sprayed when the contact surface between the cooling gas and the heat exchanger collides with the dry ice particles. The direction of the center of the tube axis that forms the outermost surface of the heat exchanger and the tube axis of a tube other than the outermost surface adjacent to the tube when the shadow of the trajectory falls on a plane perpendicular to the tube axis. 2. The cleaning method according to claim 1, wherein the cleaning method is in a range parallel to the direction in which the two are connected, or in the range of forming an angle of −15 ° to + 15 °.   3. The heat exchanger tube has a structure having a plurality of fins in a direction perpendicular to the tube axis, and a direction in which the dry ice particles are sprayed is on a plane perpendicular to the tube axis. Cleaning method.