JP5108277B2 - Pre-firing method for honeycomb molded body and pre-firing system for honeycomb molded body - Google Patents

Description

  The present invention relates to a firing pretreatment method for a honeycomb formed body that is an unfired body of a honeycomb structure.

  Honeycomb structures are widely used for catalyst carriers, various filters, and the like. Recently, it has attracted attention as a diesel particulate filter (DPF) for capturing particulate matter discharged from a diesel engine.

  In general, the honeycomb structure is mainly composed of ceramics. To manufacture such a honeycomb structure, first, water and various additives such as a binder are added to a ceramic raw material to form a clay, and then extruded to form a honeycomb-shaped formed body (honeycomb forming). Body). If the honeycomb formed body is dried and then fired, a honeycomb structure can be manufactured.

  As a drying method of the honeycomb molded body, it is generated by a dielectric drying method using a high-frequency energy generated by passing an electric current between electrodes provided above and below the honeycomb molded body, or by a gas burner. A hot air drying method is known in which drying is carried out by introducing hot air that has been generated. However, recently, instead of these drying methods, or in combination with these drying methods, a drying method using microwaves (microwave drying method) having advantages such as a high drying speed has come to be performed. (For example, see Patent Documents 1 to 3).

  However, in such a microwave drying method, drying of the upper and lower ends and the outer peripheral portion of the honeycomb formed body is delayed from other parts in the drying process, and it is sometimes difficult to dry the entire honeycomb formed body at a uniform speed. there were. Since the honeycomb formed body shrinks due to evaporation of moisture, if the drying speed is not uniform, problems such as deformation and breakage are likely to occur. Furthermore, the partition walls (ribs) partitioning the cells are becoming thinner, and the honeycomb molded body with thinner partition walls is more likely to be deformed. Therefore, uniform drying speed has become a particularly important issue in recent years.

  On the other hand, it is necessary to remove the binder contained in the honeycomb formed body similarly to the moisture. Further, when removing (degreasing) the binder, it is required to process the honeycomb molded body quickly without causing deformation or the like.

As a degreasing method, a method of evaporating and thermally decomposing a binder in the molded body by heating the molded body is common (see, for example, Patent Documents 4 and 5). However, in the degreasing method in which the binder is evaporated and thermally decomposed by heating the honeycomb formed body, a large amount of decomposition gas (CO ₂ or the like) is generated due to the thermal decomposition of the organic binder, so that the burden on the environment is large. Further, there is a problem that a temperature difference is generated inside the honeycomb formed body due to rapid heat generation during the thermal decomposition of the binder, and problems such as deformation and breakage are likely to occur. In order to solve such a problem, it is sufficient to suppress the internal heat generation by slowing the temperature rising rate, but there is a disadvantage that the processing time becomes very long.
JP 2002-283329 A JP 2002-283330 A International Publication No. 2005/023503 Pamphlet Japanese Patent Publication No.59-27743 International Publication No. 2005/047207 Pamphlet

  The present invention has been made in view of such problems of the prior art, and the problem is that a honeycomb molded body can be formed in a shorter time while suppressing the occurrence of defects such as deformation and breakage. It is possible to pre-fire the honeycomb molded body in a shorter time while suppressing the occurrence of defects such as deformation and breakage, as well as the firing pre-treatment method of the honeycomb molded body that can be pre-fired. An object of the present invention is to provide a pre-fired treatment system for a honeycomb formed body that is excellent in safety and energy efficiency and is environmentally friendly. The present invention also provides a method for drying a honeycomb formed body and a drying apparatus for the honeycomb formed body that can be used in such a pre-fired treatment method and a pre-fired treatment system.

  As a result of intensive studies to achieve the above-mentioned problems, the present inventors have increased the temperature of the honeycomb formed body with superheated steam at a predetermined temperature, and then raised the temperature of the superheated steam to a predetermined temperature and held it. The present inventors have found that the above-described problems can be achieved and have completed the present invention. Further, as a result of intensive studies to solve the above problems, the present inventors have found that the above problems can be achieved by microwave heating and / or dielectric heating in a superheated steam atmosphere. It came to complete.

  That is, according to the present invention, the following honeycomb pre-fired pretreatment method and honeycomb pre-fired treatment system are provided.

[1] A method for pre-firing an unfired honeycomb formed body having a plurality of cells serving as fluid flow paths partitioned by partition walls, comprising a raw material composition containing a ceramic raw material, water, and a binder. The temperature of the superheated steam is increased by passing superheated steam, which is dry steam in a gaseous state obtained by further heating saturated steam (wet steam) at 100 to 150 ° C., through the cell and increasing the temperature of the honeycomb formed body. A firing pretreatment method for a honeycomb formed body, which includes a first step of maintaining the temperature of the superheated steam passed through the cell at a temperature of 200 ° C. or lower.

  [2] In the first step, after the temperature of the honeycomb formed body is raised and brought into an equilibrium state, the temperature of the superheated steam is maintained at a temperature not lower than the temperature of the superheated steam passed through the cell and not higher than 200 ° C. The firing pretreatment method for a honeycomb formed body according to [1].

  [3] The method [1] further including a second step of maintaining the honeycomb formed body in an atmosphere of superheated steam at a temperature equal to or higher than the temperature of the first step and not higher than 600 ° C. after the first step. ] Or the firing pretreatment method for a honeycomb formed body according to [2].

  [4] The firing pretreatment method for a honeycomb formed body according to [3], wherein the first step and the second step are continuously performed by a single processing apparatus.

  [5] The honeycomb molded body according to any one of [1] to [4], wherein in the first step and / or the second step, the honeycomb molded body is subjected to microwave heating and / or dielectric heating. Firing pretreatment method.

  [6] Ingredients derived from the binder and water generated in the pre-firing process step for carrying out the pre-firing method for honeycomb formed bodies according to any one of [3] to [5], water generated in the pre-firing process step A primary separation step of separating an exhaust gas containing a gas component containing a component derived from the binder and a liquid component containing the water, the separated liquid component into the water, and other than the water Firing a honeycomb formed body having a secondary separation step of separating the components into the above components, and a reuse step of heating the separated water to obtain superheated steam and supplying the obtained superheated steam to the pretreatment process of firing Pre-processing system.

  [7] The honeycomb molded body pretreatment system for firing according to [6], further including a deodorizing step of deodorizing at least part of the gas component.

[8] A method for pre-firing an unfired honeycomb formed body having a plurality of cells serving as fluid flow paths partitioned by partition walls, comprising a raw material composition containing a ceramic raw material, water, and a binder. Honeycomb in which the unfired honeycomb formed body is heated in a microwave and / or dielectrically heated in a treatment chamber in a superheated steam atmosphere, which is dry steam in a gaseous state in which saturated steam (wet steam) is further heated at 100 to 200 ° C. A method for drying the molded body.

  [9] The method for drying a honeycomb molded body according to [8], wherein superheated steam is allowed to flow from one end face of the unfired honeycomb molded body such that the flow rate at the outer peripheral portion is greater than the internal flow rate.

  [10] The method for drying a honeycomb formed body according to [8] or [9], wherein the water vapor discharged from the processing chamber is reheated to form superheated steam and flows again into the processing chamber.

[11] A processing chamber for drying an unfired honeycomb molded body inside, and dry steam in a gaseous state in which superheated steam is generated and saturated steam (wet steam) is further heated in the processing chamber at 100 to 200 ° C. A superheated steam generator for introducing a certain superheated steam, a superheated steam inlet disposed in the processing chamber, a high frequency generating electrode and / or a microwave disposed in the processing chamber are introduced into the processing chamber. An apparatus for drying a honeycomb formed body including a waveguide.

  According to the method for pre-firing the honeycomb formed body of the present invention, the honeycomb formed body can be pre-fired in a shorter time while suppressing the occurrence of defects such as deformation and breakage. Further, according to the method for drying a honeycomb formed body of the present invention, the honeycomb formed body can be dried in a shorter time while suppressing the occurrence of defects such as deformation and breakage.

  BEST MODE FOR CARRYING OUT THE INVENTION The best mode for carrying out the present invention will be described below, but the present invention is not limited to the following embodiment, and is based on the ordinary knowledge of those skilled in the art without departing from the gist of the present invention. It should be understood that modifications and improvements as appropriate to the following embodiments also fall within the scope of the present invention.

  One embodiment of a firing pretreatment method for a honeycomb formed body of the present invention is an unprocessed method comprising a plurality of cells serving as fluid flow paths defined by partition walls, each comprising a raw material composition containing a ceramic raw material, water, and a binder. This is a method of pre-firing the honeycomb formed body for firing, and after passing the superheated steam at 100 to 150 ° C. through the cell to raise the temperature of the honeycomb formed body, preferably after being brought into an equilibrium state, This is a method having a first step of maintaining the temperature at a temperature not lower than the temperature of superheated steam passed through the cell and not higher than 200 ° C. The details will be described below.

  The honeycomb formed body used as the object to be processed in the method for pre-fired honeycomb formed body of the present embodiment has a structure as shown in FIGS. 1 and 2, for example. That is, the honeycomb formed body 1 has a plurality of cells 3 that serve as fluid flow paths partitioned by the partition walls 2. Moreover, the honeycomb formed body 1 is usually configured by disposing an outer peripheral wall 4 so as to surround a plurality of cells 3. The cross-sectional shape orthogonal to the axial direction (flow channel direction) of the cell 3 is not limited, and a shape such as a quadrangle as shown in FIG. 1 or a circle as shown in FIG. 2 can be arbitrarily selected. it can.

  The honeycomb formed body is an unfired body constituted by a raw material composition containing a ceramic raw material, water, and a binder. Examples of the ceramic raw material include oxide ceramics such as alumina, mullite, zirconia, and cordierite; non-oxide ceramics such as silicon carbide, silicon nitride, and aluminum nitride. A silicon carbide / metal silicon composite material, a silicon carbide / graphite composite material, or the like can also be used.

  Examples of the binder include polyvinyl alcohol, polyethylene glycol, starch, methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl methyl cellulose, polyethylene oxide, sodium polyacrylate, polyacrylamide, polyvinyl butyral, ethyl cellulose, cellulose acetate, polyethylene, and ethylene. -Vinyl acetate copolymer, polypropylene, polystyrene, acrylic resin, polyamide resin, glycerin, polyethylene glycol, dibutyl phthalate and the like.

  In the firing pretreatment method for a honeycomb formed body of the present embodiment, first, superheated steam at a predetermined temperature is passed through a cell to bring the temperature of the honeycomb formed body into an equilibrium state. When the honeycomb formed body is heated using hot air or microwaves, the drying proceeds at the same time. Therefore, it is difficult to advance the drying at a uniform speed in each part of the honeycomb formed body. In contrast, in the pre-firing method for firing a honeycomb formed body according to the present embodiment, the temperature of the honeycomb formed body is brought into an equilibrium state using superheated steam. Can be in a state. Further, by passing the superheated steam through the cell, it is possible to achieve an equilibrium state quickly and evenly as compared with the case where the superheated steam is simply blown.

  The temperature of the superheated steam that passes through the cell is 100 to 150 ° C, preferably 110 to 130 ° C. If the temperature of the superheated water vapor that passes through the cell is less than 100 ° C., the product is heated, but most of the vapor is condensed, and the product is hygroscopically swollen, which tends to cause problems such as shape deformation. On the other hand, if the temperature exceeds 150 ° C., the drying proceeds, the drying cannot be performed at a uniform speed, and deformation or breakage is likely to occur. The optimum temperature of the superheated steam is not unambiguous and should be changed according to the type of ceramic and the type of binder. In general, it is preferable to measure a change in the amount of moisture in the product by passing superheated steam and set the temperature so that the rate of change is zero. Furthermore, in the initial stage of ventilation, the temperature difference between the product and the superheated steam is large, so in order to prevent condensation due to heating of the product, the temperature is set to about 20 ° C. higher than the temperature obtained under the above conditions. It is preferable.

  The time required for the superheated steam to pass through the cell, that is, the time required for the temperature of the honeycomb formed body to be in an equilibrium state varies depending on the shape and size of the honeycomb formed body to be processed, but is usually 10 to 600 seconds. It is preferably about 10 to 30 seconds. If the time for allowing the superheated steam to pass through the cell is too short, there may be a case where sufficient equilibrium is not achieved, and homogeneous drying may not be possible in the second step. On the other hand, if the time for allowing the superheated steam to pass through the cell is too long, a temperature difference will occur between the inlet side and the outlet side of the superheated steam until equilibrium is reached, resulting in partial drying and swelling. There are cases where homogeneous drying is not possible in the second step.

  In the firing pretreatment method of the honeycomb formed body of the present embodiment, after increasing the temperature of the honeycomb formed body, preferably after being in an equilibrium state, the temperature of the superheated steam passed through the cell is equal to or higher than the temperature of the superheated steam. The honeycomb formed body can be dried by raising the temperature to 200 ° C. or lower, preferably 100 to 200 ° C., and more preferably 120 to 150 ° C. Alternatively, the honeycomb formed body can also be dried by changing the temperature of the superheated steam in accordance with the progress of drying. In addition, it is preferable to start drying after the temperature of the honeycomb formed body is in an equilibrium state, because the drying rate can be made more uniform and the occurrence of defects such as deformation and breakage can be further suppressed. Moreover, by using superheated steam, it can be dried in a shorter time than using hot air. In addition, in the conventional humidity conditioning drying, it is necessary to control the two variables of temperature and humidity at the same time to advance the drying. However, only the temperature of the superheated steam needs to be controlled. For this reason, the firing pretreatment method of the honeycomb formed body of the present embodiment has an advantage that it is simpler than the conventional drying method.

  If the temperature of the superheated steam at the time of drying the honeycomb formed body is lower than the temperature of the superheated steam that has been passed through the cell, drying becomes difficult to proceed. On the other hand, if it exceeds 200 ° C., the drying proceeds rapidly, and the honeycomb formed body tends to be deformed or damaged.

  The time for raising the temperature of the superheated steam and holding it, that is, the time required for drying the honeycomb formed body varies depending on the shape, dimensions, moisture content, etc. of the honeycomb formed body as the object to be treated, but is usually 1 to 120. Minutes, preferably about 1 to 20 minutes. Note that it is preferable to heat and hold the superheated steam and to irradiate the honeycomb formed body with microwaves because drying can be performed more rapidly.

  Further, as a method of flowing superheated steam into the cells of the honeycomb formed body, for example, (1) the honeycomb formed body is placed vertically and forcibly heated from above or below the cell using a blower fan or the like. A method of sending water vapor, (2) A method of sucking superheated steam by installing an exhaust fan above or below the cell, and (3) Natural ventilation using convection (updraft) due to temperature difference of superheated steam Methods, etc. In addition, by using a baffle plate or the like and controlling the flow of superheated steam at the inlet or outlet of the cell, it is possible to control the amount of ventilation at each position in the honeycomb molded body and adjust the drying speed.

  In the firing pretreatment method for a honeycomb formed body of the present embodiment, after the first step, the honeycomb formed body is heated to an atmosphere of superheated steam that is equal to or higher than the temperature of the first step and is 600 ° C. or lower. It is preferable to further have a second step of holding. Thereby, the binder having a boiling point higher than that of water contained in the honeycomb formed body can be removed (degreasing). In addition to being removed by vaporization without being decomposed, the binder may be partially decomposed or removed, for example. When superheated steam is used for degreasing, abnormal heat generation unlike in the case where the binder is burned and removed is difficult to occur, and the honeycomb formed body is hardly damaged due to the abnormal heat generation.

  If the temperature of the superheated steam in the second step is lower than the temperature in the first step, the binder cannot be removed. On the other hand, if it exceeds 600 ° C., the ceramic raw material that is a constituent raw material may be denatured by water vapor, which may cause a problem in the subsequent firing step. Further, the binder is excessively removed, the honeycomb formed body becomes brittle, and the handling tends to be difficult. In addition, it is preferable that the temperature of the superheated steam in a 2nd process is 400 degrees C or less, and it is still more preferable that it is 300 degrees C or less.

  In the method for pre-firing the honeycomb formed body of the present embodiment, it is efficient to continuously perform the first step (drying step) and the second step (degreasing step) with one processing apparatus. This is preferable because it enables easy pre-firing treatment. FIG. 3 is a schematic diagram illustrating a configuration example of a continuous processing apparatus. The continuous processing apparatus 10 includes a processing chamber 7 having an outlet 6 through which superheated steam can be jetted and an exhaust port 9 through which gas generated inside can be discharged to the outside. Inside the processing chamber 7, there is provided conveying means such as a conveyor 5 that sequentially conveys the honeycomb formed body 1 that is to be processed. In addition, it is preferable to have a plurality of jet nozzles 6 in the processing chamber 7. Moreover, the temperature of the superheated water vapor for each area (zone (1) 11, zone (2) 12, and zone (3) 13) partitioned in the conveyance direction of the conveyor 5 may be individually adjustable. preferable.

  The honeycomb formed body 1 placed on the conveyor 5 sequentially passes through regions where superheated steam having different temperatures are ejected and filled with the progress in the processing chamber 7. At this time, if the temperature of the superheated steam in each region is set to the temperature in the first step and the second step, drying and degreasing of the honeycomb formed body can be efficiently performed in a series of flow operations. It can be carried out.

  The cell density, partition wall thickness, cell shape, dimensions, etc. of the honeycomb formed body to be pre-fired in the method for pre-firing honeycomb formed body of the present invention are not particularly limited. However, a honeycomb molded body with thin partition walls (for example, partition wall thickness: 150 μm or less) that is more likely to be deformed or the like, or a large-sized honeycomb molded body (for example, total channel length: 200) that is likely to have a difference in drying speed at each portion. ˜1000 mm, outer diameter: 150 to 600 mm) is particularly effective when pre-baking treatment.

  Next, an embodiment of a firing pretreatment system for a honeycomb formed body of the present invention will be described. FIG. 4 is a flowchart showing an embodiment of a pre-firing system for honeycomb formed bodies of the present invention. As shown in FIG. 4, the firing pretreatment system for a honeycomb formed body of the present embodiment includes a firing pretreatment process, a primary separation process, a secondary separation process, and a reuse process.

  The pre-firing treatment process is a process for carrying out the pre-firing method for a honeycomb formed body according to the embodiment of the present invention described so far. In this firing pretreatment step, the honeycomb formed body using superheated steam is dried and degreased. For this reason, in the baking pretreatment process, the exhaust gas containing the component derived from water and a binder is discharged | emitted. In addition, the “component derived from the binder” referred to in the present specification conceptually includes the binder itself in addition to the component generated by decomposition of the binder contained in the raw material composition constituting the honeycomb formed body. .

  The primary separation step is a step of separating the exhaust gas generated and discharged in the firing pretreatment step into a gas component containing a component derived from a binder and a liquid component containing water. In order to separate the exhaust gas into a gas component and a liquid component, a general condenser, a heat exchanger, or the like can be used. If a heat exchanger is used, the recovered heat can be used to heat water in a reuse process described later, which is preferable from the viewpoint of energy efficiency.

  Since degreasing is performed using superheated steam in the firing pretreatment step, the separated gas component contains a component derived from the binder in a high concentration. Therefore, this gas component can be reused as fuel gas or the like. In addition, when it is difficult to reuse a gas component, it is preferable to further provide a deodorizing step for deodorizing at least a part of the gas component. In this deodorizing step, a general deodorizing device can be used.

  The secondary separation step is a step of separating the liquid component separated in the primary separation step into water and other components other than water. In order to separate the liquid component into water and other components, for example, distillation, extraction, or the like may be performed. The other components separated are so-called vinegar and may be treated as waste, but can be reused as fuel or the like.

  A reuse process is a process of obtaining superheated steam by heating separated water using heating devices, such as a boiler, and supplying obtained superheated steam to a pre-firing process. Thus, in the pre-fired honeycomb molded body pretreatment system of the present embodiment, the exhaust gas generated by the pre-fired honeycomb molded body is not simply discarded, but is reused while taking out useful components, Dispose of only the remaining ingredients. For this reason, the system is excellent in energy efficiency and environmentally friendly. In addition, the superheated steam used in the pre-firing treatment process is stable and has no fear of ignition, like the inert gas. Therefore, the firing pretreatment system for the honeycomb formed body of the present embodiment is an extremely safe system.

  Next, an embodiment of a method for drying a honeycomb formed body of the present invention will be described with reference to the drawings. The method for drying a honeycomb formed body of the present invention can be used as the first step of the above-described pretreatment method for firing the honeycomb formed body of the present invention, whereby the entire unfired honeycomb formed body is uniformly dried. It becomes possible to make it.

  The method for drying a honeycomb formed body of the present embodiment is a non-fired honeycomb formed body having a plurality of cells serving as fluid flow paths partitioned by partition walls, which are made of a raw material composition containing a ceramic raw material, water, and a binder. Is a method of subjecting the unfired honeycomb formed body to microwave heating and / or dielectric heating in a processing chamber of a superheated steam atmosphere at 100 to 200 ° C.

  The honeycomb formed body used as the object to be processed in the method for drying the honeycomb formed body of the present embodiment is the same as the honeycomb formed body used as the object to be processed in the above-described firing pretreatment method for the honeycomb formed body of the present invention. Is preferred.

  FIG. 7 schematically shows a cross section perpendicular to the conveying direction of the honeycomb molded body of one embodiment of the drying apparatus for the honeycomb molded body of the present invention used for carrying out the method for drying the honeycomb molded body of the present invention. It is sectional drawing. FIG. 8 schematically shows a cross section parallel to the conveying direction of the honeycomb molded body of one embodiment of the drying apparatus for the honeycomb molded body of the present invention used for carrying out the method for drying the honeycomb molded body of the present invention. It is sectional drawing shown. In FIG. 8, the superheated steam generator and piping are omitted. The honeycomb molded body drying device 21 of the present embodiment includes a processing chamber 22 that dries the unfired honeycomb molded body 41 therein, and a superheated steam generator 23 that generates superheated steam and flows the superheated steam into the processing chamber 22. And a superheated steam inlet 25 disposed in the processing chamber 22 and a waveguide 26 for introducing a microwave disposed in the processing chamber 22 into the processing chamber 22. Then, the honeycomb formed body 41 placed on the transport pallet 24 is carried into the processing chamber 22 and dried. In this embodiment, the honeycomb formed bodies are transported in the processing chamber 22 in a single row, but may be transported in two or more rows. In the honeycomb molded body drying apparatus 21 of the present embodiment, the superheated steam inlet 25 is also provided at the lower portion of the transport pallet 24, and the cells of the honeycomb molded body 41 are transferred from one end surface (lower end surface) of the honeycomb molded body 41. Superheated steam can be introduced to allow it to pass. Further, the transport pallet 24 is formed to be transported from the carry-in entrance 29 toward the carry-out exit 30 by the belt conveyor 28. The drying device for the honeycomb formed body of the present embodiment is a continuous drying device in which the honeycomb formed body is conveyed by a belt conveyor, but the drying device for the honeycomb formed body of the present invention is not limited to such a continuous type. It may be a batch type in which one or a plurality of honeycomb formed bodies can be processed simultaneously.

  In the method for drying a honeycomb formed body of the present embodiment, the inside of the processing chamber 22 is set to a superheated steam atmosphere at 100 to 200 ° C. The temperature of the superheated steam atmosphere is preferably 110 to 170 ° C, more preferably 120 to 150 ° C. If the temperature of the superheated steam atmosphere is less than 100 ° C., the product is heated, but most of the vapor is condensed, and the product is hygroscopically swollen, which tends to cause problems such as shape deformation. If it exceeds 200 ° C., the drying proceeds rapidly, and the honeycomb formed body tends to be deformed or damaged. The superheated steam is generated by the superheated steam generator 23 and irradiated into the processing chamber 22 from the superheated steam inlet 25 through the superheated steam supply pipe (pipe). Here, the superheated steam refers to water vapor (dry steam) in a completely gaseous state by further heating saturated steam (wet steam) to a temperature equal to or higher than the boiling point.

  In the drying method of the honeycomb formed body of the present embodiment, the microwave for microwave heating the unfired honeycomb formed body 41 in the superheated steam atmosphere is introduced through the waveguide 26. The frequency of the microwave is preferably 900 to 30000 MHz, particularly preferably 900 to 3000 MHz.

  As described above, since the honeycomb molded body is dried by performing microwave heating in the superheated steam atmosphere, it is possible to increase the temperature rise of the outer peripheral portion of the honeycomb molded body, which has conventionally been slow in drying speed. It becomes possible to increase the drying speed of the outer peripheral portion, and it is possible to suppress deformation and breakage of the honeycomb formed body. In addition, by performing microwave heating in a superheated steam atmosphere, not only the outer peripheral part but also the internal temperature rise can be accelerated, and the temperature rise curve of the outer peripheral part and the internal part can be approximated. Thus, deformation and breakage of the honeycomb formed body can be further suppressed.

  In the method for drying a honeycomb formed body of the present embodiment, it is preferable to flow superheated steam from one end face of the unfired honeycomb formed body 41 so that the flow rate at the outer peripheral portion is larger than the internal flow rate. In the present embodiment, the honeycomb molded body 41 is formed so as to irradiate the lower end surface of the honeycomb molded body 41 with the superheated steam 41 when the honeycomb molded body 41 is placed on the transport pallet 24 and transported in the processing chamber 22. At this time, it is preferable that the flow rate of the superheated steam passing through the outer peripheral portion of the honeycomb formed body 41 is larger than the flow rate of the superheated steam passing through the inside. This makes it possible to increase the temperature rise of the outer peripheral portion of the honeycomb formed body, which has conventionally been slow in drying speed. Here, the outer peripheral portion of the honeycomb formed body refers to a region in a range of ½ of the distance from the outer periphery to the central axis from the outer periphery of the honeycomb formed body toward the central axis. In addition, the term “inside of the honeycomb formed body” refers to a region inside the outer peripheral portion (region in a range of ½ of the distance from the outer periphery to the central axis from the central axis toward the outer periphery).

  As a method for causing the superheated steam to flow from one end face of the honeycomb formed body 41, a “method of passing superheated steam into the cells of the honeycomb formed body described above, which was used in the pretreatment method for firing the honeycomb formed body of the present invention described above. It is preferable to be the same as "."

  In the method for drying a honeycomb formed body according to the present embodiment, it is preferable that the water vapor discharged from the processing chamber 22 is reheated to be superheated water vapor and flowed again into the processing chamber 22. As shown in FIG. 7, in the present embodiment, the water vapor discharged from the processing chamber 22 through the drain pipe 35 is sent to the mixer 27 through the water vapor recovery pipe 34. And it mixes with the saturated water vapor | steam supplied through the saturated water vapor | steam supply pipe | tube 32 with the mixer 27, sends mixed gas to the superheated steam generator 23, makes superheated steam with the superheated steam generator 23, and processes through the superheated steam supply pipe | tube 33 It is formed so as to flow again into the chamber 22. The liquid discharged through the drain pipe 35 is discharged from the drain discharge port 31 to the outside. The steam discharged from the processing chamber 22 may be sent to the superheated steam generator 23 without being mixed with the saturated steam. Thus, the amount of energy and water used can be reduced by reusing wastewater steam.

  FIG. 9 schematically shows a cross section perpendicular to the conveying direction of the honeycomb molded body of another embodiment of the drying apparatus for the honeycomb molded body of the present invention used for carrying out the method for drying the honeycomb molded body of the present invention. FIG. FIG. 10 schematically shows a cross section parallel to the conveyance direction of the honeycomb molded body of another embodiment of the drying apparatus for the honeycomb molded body of the present invention used for carrying out the method for drying the honeycomb molded body of the present invention. FIG. In addition, in FIG. 10, the superheated steam generator and piping are abbreviate | omitted. 9 and 10, the same constituent elements as those shown in FIGS. 7 and 8, which represent an embodiment of the above-described honeycomb molded body drying device of the present invention, are denoted by the same reference numerals. . The drying device for the honeycomb formed body of the present embodiment is a continuous drying device in which the honeycomb formed body is conveyed by a belt conveyor, but the drying device for the honeycomb formed body of the present invention is not limited to such a continuous type. It may be a batch type in which one or a plurality of honeycomb formed bodies can be processed simultaneously.

  The method for drying a honeycomb formed body of the present embodiment is the same as that of the above-described method for drying a honeycomb formed body of the present invention, and the unfired honeycomb formed body in the treatment chamber 22 in a superheated steam atmosphere at 100 to 200 ° C. 41 is dielectrically heated. In the honeycomb molded body drying apparatus 21 used in the present embodiment, high-frequency generating electrodes 51 used for dielectric heating are disposed on the upper and lower portions of the honeycomb molded body 41 instead of the waveguide. Thereby, the effect similar to the case of one Embodiment of the drying method of the honeycomb molded object of this invention using the microwave mentioned above can be acquired.

  The frequency of the high frequency used for dielectric heating is preferably 2 to 100 MHz, particularly preferably 10 to 50 MHz.

  Next, an embodiment of a drying apparatus for a honeycomb formed body of the present invention will be further described. As described above, the honeycomb molded body drying apparatus 21 of the present embodiment shown in FIGS. 7 and 8 includes the processing chamber 22 that dries the unfired honeycomb molded body 41 inside, and the processing chamber 22 that generates superheated steam. A superheated steam generator 23 for introducing superheated steam into the superheated steam, a superheated steam inlet 25 disposed in the processing chamber 22, and a microwave for introducing the microwave disposed in the processing chamber 22 into the processing chamber 22. A wave tube 26 is provided.

  The processing chamber 22 and the belt conveyor 28 are not particularly limited, and known processing chambers and belt conveyors used for drying and firing the honeycomb formed body can be used.

  The shape of the waveguide 26 can be appropriately determined according to the frequency of the microwave to be used.

  The shape of the superheated steam inlet 25 is not particularly limited, and may be a tip portion of the pipe, or a shape in which a hole is formed in the pipe and the superheated steam is irradiated from there. .

  The transport pallet 24 is not particularly limited, but, as shown in FIGS. 11A and 11B, a plurality of through holes 24a penetrating in the normal direction (the normal of the plate-shaped surface). It is preferable that it is a plate-shaped member formed. Here, FIG. 11 shows a state in which the flow rate adjusting plate is placed on the transport pallet, FIG. 11 (a) is a plan view, and FIG. 11 (b) is a cross-sectional view along XX ′ in FIG. It is. The material of the transport pallet is not particularly limited, and a fluororesin or the like can be used. Thus, by forming the through hole 24a, when the honeycomb formed body 41 is placed on the upper surface, superheated steam can be caused to flow into the honeycomb formed body 41 from the lower portion of the transport pallet 24, It becomes possible to dry the composition 41 more uniformly. Further, at this time, it is preferable to flow more superheated steam into the outer peripheral portion than the inside of the honeycomb formed body 41. For example, as shown in FIGS. It is preferable to arrange the flow rate adjusting plate 42 at a position corresponding to the inside of the honeycomb formed body 41. As a result, when the superheated steam is caused to flow into the honeycomb molded body 41 from the lower part of the transport pallet 24, the flow rate adjusting plate 42 prevents the superheated steam from flowing, and the amount of superheated steam flowing into the honeycomb molded body 41 is reduced. It becomes possible. Further, a relatively large amount of superheated steam can be passed through the outer peripheral portion of the honeycomb formed body 41. Thereby, the superheated steam can be caused to flow from one end face of the unfired honeycomb formed body 41 so that the flow rate of the outer peripheral portion is larger than the internal flow rate. The flow rate adjusting plate 42 is preferably in a mesh shape, but may be a plate-like member having no holes. The material of the flow rate adjusting plate 42 is not particularly limited, and fluorine resin or the like can be used.

  The superheated steam generator 23 is not particularly limited, and a known superheated steam generator can be used. For example, a superheated steam generator such as an induction heating system, a burner system, or an electric heater system can be used.

  In another embodiment of the honeycomb molded body drying apparatus of the present invention, as shown in FIGS. 9 and 10, an electrode 51 for high frequency generation used for dielectric heating instead of a waveguide is formed of the honeycomb molded body 41. It is arranged at the upper part and the lower part. Other components are the same as those in the embodiment of the drying apparatus for a honeycomb formed body of the present invention described above. The frequency of the high frequency generated between the electrodes 51 is preferably 2 to 100 MHz, and particularly preferably 10 to 50 MHz. Thereby, the effect similar to the case of one Embodiment of the drying method of the honeycomb molded object of this invention using the microwave mentioned above can be acquired.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples.

(Examples 1-8)
A honeycomb formed body 1 (outer diameter × channel length: 80 mm × 100 mm, cell density: 50 cells / cm ² , partition wall thickness, produced using a molding aid such as a ceramic raw material and a binder having an outer shape as shown in FIG. : 0.3 mm). The prepared honeycomb molded body was subjected to pre-firing treatment (drying) under the conditions shown in Table 1 using the continuous processing apparatus 10 having the configuration shown in FIG. Note that the lengths in the traveling direction of the zone (1) 11, the zone (2) 12, and the zone (3) 13 in the continuous processing apparatus 10 are 1.0 m, 1.0 m, and 1.0 m, respectively. Moreover, the feed rate in the continuous processing apparatus 10 was 0.33 m / min. Table 1 shows the mass of the honeycomb formed body before firing (initial mass (g)), the mass after treatment (g), and the mass reduction rate (%). Moreover, the graph which plotted the mass decreasing rate (%) with respect to superheated steam temperature (zone (2)) (degreeC) is shown in FIG. As shown in Table 1, it is clear that there is a difference in the speed of drying depending on the temperature of the superheated steam. It has been found that the higher the temperature of the superheated steam, the faster the drying rate.

(Comparative Examples 1-5)
While using hot air instead of superheated steam, the pre-baking treatment (drying) was performed in the same manner as in Examples 1 to 8 except that the conditions shown in Table 2 were used. Table 2 shows the mass of the honeycomb formed body before firing (initial mass (g)), the mass after treatment (g), and the mass reduction rate (%). As shown in Table 2, crispness was generated on the outer periphery of the product even when dried under any conditions.

(Examples 9 to 12)
A honeycomb formed body (dried body) that was dried under the same conditions as in Example 3 (outer diameter × channel length: 150 mm × 200 mm) was prepared except that the treatment time was 40 min. The prepared honeycomb formed body was pre-fired (degreased) under the conditions shown in Table 3. Table 3 shows the mass of the honeycomb formed body before firing (initial mass (g)), the mass after treatment (g), and the mass reduction rate (%). Moreover, the graph which plotted the mass decreasing rate (%) with respect to superheated steam temperature (degreeC) is shown in FIG. As shown in Table 3, under any condition, the mass of the honeycomb formed body after the treatment decreased, and the color changed from white to gray. Further, the honeycomb formed bodies obtained by processing under the conditions of Examples 9 and 10 were in a slightly fragile state and required some care in handling. On the other hand, the honeycomb formed bodies obtained by processing under the conditions of Examples 11 and 12 in which the processing temperature was lower than those of Examples 9 and 10 were hard enough to be handled.

(Example 13)
A honeycomb formed body (outer diameter × channel length: 113 mm × 210 mm, cell density: 93 cells / cm ² , partition wall thickness: outer shape as shown in FIG. 2 and formed using a ceramic raw material and a forming aid such as a binder. 0.1 mm) was prepared. The prepared honeycomb formed body was dried using the honeycomb formed body drying apparatus 21 having the configuration shown in FIGS. 7 and 8. Note that the superheated steam inlet 25 disposed at the lower part of the honeycomb formed body 41 was not used. Microwave with a frequency of 2.45 GHz was irradiated for 300 seconds at an output density of 5 kW / kg. The temperature of the superheated steam atmosphere in the processing chamber 22 was 130 ° C. The feed speed of the belt conveyor 28 was 0.32 m / min. With respect to the dried honeycomb formed body, the temperature change at the center point A (inside A) of the upper end surface and the position B (outer peripheral portion B) of 10 mm toward the center from the outermost periphery of the upper end surface was measured. The results are shown in FIG. In FIG. 13, the symbol A indicates the temperature change in the interior A, and the symbol B indicates the temperature change in the outer peripheral portion B.

(Comparative Example 6)
The honeycomb formed body was dried in the same manner as in Example 13 except that the inside of the processing chamber 22 was not changed to the superheated steam atmosphere. In the same manner as in Example 13, the temperature of the dried honeycomb formed body was measured. The results are shown in FIG. In FIG. 14, the symbol A indicates the temperature change in the interior A, and the symbol B indicates the temperature change in the outer peripheral portion B.

(Example 14)
A honeycomb formed body (outer diameter × channel length: 113 mm × 210 mm, cell density: 93 cells / cm ² , partition wall thickness: outer shape as shown in FIG. 2 and formed using a ceramic raw material and a forming aid such as a binder. 0.1 mm) was prepared. The prepared honeycomb formed body was dried using the honeycomb formed body drying apparatus 21 having the configuration shown in FIGS. 7 and 8. Note that the superheated steam inlet 25 disposed at the lower part of the honeycomb formed body 41 was not used. Microwave with a frequency of 2.45 GHz was irradiated for 100 seconds at an output density of 5 kW / kg. The temperature of the superheated steam atmosphere in the processing chamber 22 was 130 ° C. The feed speed of the belt conveyor 28 was 0.32 m / min. With respect to the honeycomb formed body after drying, the residual moisture content was measured at nine measurement positions at different heights from the lower end surface to the upper end surface at the respective positions corresponding to the inner part A and the outer peripheral part B. The results are shown in FIG.

(Comparative Example 7)
The honeycomb formed body was dried in the same manner as in Example 14 except that the inside of the processing chamber 22 was not changed to the superheated steam atmosphere. In the same manner as in Example 14, the residual moisture content was measured for the dried honeycomb formed body. The results are shown in FIG.

  From the results of Example 13 and Comparative Example 6, it can be seen that the temperature increase rate difference between the inner part A and the outer peripheral part B is within 30 seconds. Moreover, it turns out that the temperature rising time to 100 degreeC became about half. Moreover, it can be seen from the results of Example 14 and Comparative Example 7 that the moisture difference at positions corresponding to the interior A and the outer peripheral portion B could be reduced to half or less.

(Example 15)
A honeycomb formed body (outer diameter × channel length: 113 mm × 210 mm, cell density: 93 cells / cm ² , partition wall thickness: outer shape as shown in FIG. 2 and formed using a ceramic raw material and a forming aid such as a binder. 0.1 mm) was prepared. The prepared honeycomb molded body was dried using a honeycomb molded body drying apparatus 21 having a configuration shown in FIGS. 7 and 8 in which a shielding plate 43 as shown in FIG. 12 was disposed. Here, FIG. 12 is a plan view schematically showing a part of another embodiment of the drying apparatus for a honeycomb formed body of the present invention and the honeycomb formed body. The plate-shaped shielding plates 43 are erected on both sides of the conveyance path through which the honeycomb molded body is conveyed so as to sandwich the conveyance pallet 24 therebetween, and limit the incidence of microwaves to the honeycomb molded body 41 from the horizontal direction. I tried to do it. The material of the shielding plate 43 was aluminum. Note that the superheated steam inlet 25 disposed at the lower part of the honeycomb formed body 41 was not used. A microwave with a frequency of 2.45 GHz was irradiated for 200 seconds at an output density of 5 kW / kg. The temperature of the superheated steam atmosphere in the processing chamber 22 was 130 ° C. The feed speed of the belt conveyor 28 was 0.32 m / min. For the honeycomb formed body after drying, the residual moisture content was measured at five measurement positions at different heights from the position of 90 mm from the lower end surface to the upper end surface of each position corresponding to the inside A and the outer peripheral portion B. . The results are shown in FIG.

  From the result of Example 15, it can be seen that the moisture difference at the upper end can be improved from about 4% to 0.7% as compared with the result of Example 14. The upper end moisture difference means a difference in residual moisture at the same radial position between about 5 mm from the upper end of the honeycomb formed body and about 30 mm from the upper end. For example, the moisture difference indicated by the moisture difference D in FIG. 17 corresponds to the upper end moisture difference.

  According to the firing pretreatment method and firing pretreatment system of a honeycomb formed body of the present invention, a honeycomb formed body that is an unfired body of a honeycomb structure widely used for a catalyst carrier, various filters such as DPF, etc. It can process suitably.

[Fig. 3] Fig. 3 is a perspective view showing an example of a honeycomb formed body used in the method for pre-firing the honeycomb formed body of the present invention. FIG. 6 is a perspective view showing another example of a honeycomb formed body used in the firing pretreatment method for a honeycomb formed body of the present invention. It is a schematic diagram which shows the structural example of a continuous processing apparatus. It is a flow figure showing one embodiment of a firing pretreatment system of a honeycomb fabrication object of the present invention. It is the graph which plotted mass reduction rate (%) with respect to superheated steam temperature (zone (2)) (degreeC). It is the graph which plotted mass reduction rate (%) with respect to superheated steam temperature (degreeC). [Fig. 3] Fig. 3 is a cross-sectional view schematically showing a cross section perpendicular to the conveying direction of the honeycomb formed body of the embodiment of the drying apparatus for the honeycomb formed body of the present invention. [Fig. 3] Fig. 3 is a cross-sectional view schematically showing a cross section parallel to the conveying direction of the honeycomb molded body of one embodiment of the drying apparatus for the honeycomb molded body of the present invention. [Fig. 5] Fig. 5 is a cross-sectional view schematically showing a cross section perpendicular to a conveyance direction of a honeycomb formed body of another embodiment of the drying apparatus for a honeycomb formed body of the present invention. [Fig. 6] Fig. 6 is a cross-sectional view schematically showing a cross section parallel to the conveying direction of the honeycomb molded body of another embodiment of the drying apparatus for the honeycomb molded body of the present invention. FIG. 11A is a plan view, and FIG. 11B is a cross-sectional view taken along line X-X ′ in FIG. 11A. FIG. 5 is a plan view schematically showing a part of another embodiment of a drying apparatus for a honeycomb formed body of the present invention and a honeycomb formed body. 14 is a graph showing a temperature change of a honeycomb formed body during drying in Example 13. 10 is a graph showing a temperature change of a honeycomb formed body during drying in Comparative Example 6. 14 is a graph showing the residual moisture content of the honeycomb formed body after drying in Example 14. 10 is a graph showing a residual moisture content of a honeycomb formed body after drying in Comparative Example 7. 16 is a graph showing the residual moisture content of the honeycomb formed body after drying in Example 15.

Explanation of symbols

1: honeycomb formed body, 2: partition wall, 3: cell, 4: outer peripheral wall, 5: conveyor, 6: jet outlet, 7: processing chamber, 9: exhaust port, 10: continuous processing apparatus, 11: zone (1) , 12: Zone (2), 13: Zone (3), 21: Drying device for honeycomb formed body, 22: Processing chamber, 23: Superheated steam generator, 24: Transport pallet, 24a: Through hole, 25: Superheated steam Inlet, 26: Waveguide, 27: Mixer, 28: Belt conveyor, 29: Inlet, 30: Outlet, 31: Drain outlet, 32: Saturated steam supply pipe, 33: Superheated steam supply pipe, 34 : Water vapor collecting pipe, 35: drain pipe, 41: honeycomb formed body, 42: flow rate adjusting plate, 43: shielding plate, 51: electrode, D: moisture difference.

Claims (11)

A method of pre-fired an unfired honeycomb formed body having a plurality of cells serving as fluid flow paths partitioned by partition walls, comprising a raw material composition containing a ceramic raw material, water, and a binder,
After the superheated steam, which is a dry steam in a gaseous state obtained by further heating saturated steam (wet steam) at 100 to 150 ° C. , is passed through the cell to raise the temperature of the honeycomb formed body, the temperature of the superheated steam is changed, A firing pretreatment method for a honeycomb formed body, which includes a first step of maintaining the superheated steam passed through the cell at a temperature of 200 ° C. or higher. In the first step,
The honeycomb molded body according to claim 1, wherein after the temperature of the honeycomb molded body is raised and brought into an equilibrium state, the temperature of the superheated steam is maintained at a temperature not lower than the temperature of the superheated steam passed through the cell and not higher than 200 ° C. Pre-baking treatment method.   3. The method according to claim 1, further comprising a second step of maintaining the honeycomb formed body in an atmosphere of superheated steam having a temperature equal to or higher than the temperature of the first step and not higher than 600 ° C. after the first step. A firing pretreatment method for a honeycomb formed article as described.   The firing pretreatment method for a honeycomb formed body according to claim 3, wherein the first step and the second step are continuously carried out by a single processing apparatus. In the first step and / or the second step,
The firing pretreatment method for a honeycomb formed body according to any one of claims 1 to 4, wherein the honeycomb formed body is heated by microwave and / or dielectrically heated. A firing pretreatment step for carrying out the firing pretreatment method for a honeycomb formed body according to any one of claims 3 to 5,
A primary separation step of separating the exhaust gas containing the component derived from water and the binder generated in the firing pretreatment step into a gas component containing the component derived from the binder and a liquid component containing the water. ,
A secondary separation step of separating the separated liquid component into the water and other components other than the water, and heating the separated water to obtain superheated steam, and obtaining the superheated steam obtained before the firing Reuse process to supply to the processing process,
A firing pretreatment system for a honeycomb formed body.   The firing pretreatment system for a honeycomb formed body according to claim 6, further comprising a deodorizing step of deodorizing at least part of the gas component. A method of pre-fired an unfired honeycomb formed body having a plurality of cells serving as fluid flow paths partitioned by partition walls, comprising a raw material composition containing a ceramic raw material, water, and a binder,
Honeycomb molding in which the unfired honeycomb molded body is microwave-heated and / or dielectrically heated in a treatment chamber in a superheated steam atmosphere, which is dry steam in a gaseous state in which saturated steam (wet steam) is further heated at 100 to 200 ° C. How to dry the body.   The method for drying a honeycomb formed body according to claim 8, wherein superheated steam is caused to flow from one end face of the unfired honeycomb formed body so that the flow rate of the outer peripheral portion is larger than the internal flow rate.   The method for drying a honeycomb formed body according to claim 8 or 9, wherein the steam discharged from the processing chamber is reheated to be superheated steam, and then reflowed into the processing chamber. A treatment chamber for drying the unfired honeycomb molded body inside;
A superheated steam generator for generating superheated steam to flow superheated steam, which is dry steam in a gaseous state obtained by further heating saturated steam (wet steam) at 100 to 200 ° C., into the processing chamber;
A superheated steam inlet disposed in the processing chamber;
A drying apparatus for a honeycomb formed body, comprising: a high-frequency generating electrode disposed in the processing chamber and / or a waveguide for introducing a microwave into the processing chamber.

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