JP2015117869A - Radiant heater and radiant heating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radiant heater and radiant heating method capable of heating a burning target object in a preset heat flux history while achieving cost reduction.SOLUTION: A radiant heater includes: a conveyor 3 conveying a burning target object 2; a radiation plate 4 arranged along the conveyor 3; and a heat source 5 heating the radiation plate 4, radiation materials 7 (a high radiation material 71 and a low radiation material 72) different in radiation factor are provided on a surface of the radiation plate 4 which surface faces a conveyance surface 34 of the conveyor 3 along at least either a longitudinal direction or a width direction of the conveyor 3.

Description

  The present invention relates to a radiant heating apparatus and a radiant heating method, and more particularly to a radiant heating apparatus and a radiant heating method capable of heating an object to be fired with an appropriate heat flux history while reducing costs.

  For example, baked foods such as rice crackers and cookies have different chemical and physical qualities depending on how they are baked. For example, depending on the heating temperature of the food, browning of the food (Maillard reaction), heat denaturation of the protein, gelation of starch, etc. occur, and evaporation and diffusion of water from the food may occur depending on the atmospheric humidity in the vicinity of the food. Changes, resulting in a change in the quality of the baked food.

  Therefore, in order to bake a food with an appropriate quality, it is necessary to change the heating power and the atmospheric humidity over the food with time from the start to the end of baking. Here, the physical quantity corresponding to the thermal power is the heat flux, and the food is baked with the desired quality by adjusting the thermal power to the food based on the appropriate heat flux history obtained by experiments (trial baking, etc.) and simulation. can do.

  As a rice cracker baking device for baking food with an appropriate heat flux history, each conveyor is equipped with a conveyor for conveying rice cracker dough and a plurality of gas burners arranged at intervals along the length of the conveyor. It is already known that the heating power of the rice cracker dough is changed with time from the start to the end of baking by adjusting the heating power of the burner (see Patent Document 1).

  In addition, as a heating method, a gas heater that heats a radiator with heat generated by burning fuel gas and heats industrial materials, foods, and the like with radiation heat from the surface of the radiator is already known (for example, Patent Documents). 2).

Japanese Patent No. 3372233 JP 2013-29217 A

  According to the baking apparatus described in Patent Document 1 described above, by adjusting the heating power of each gas burner arranged at an interval in the longitudinal direction of the conveyor in advance, The applied heat flux can be changed to an appropriate value from the start to the end of baking, and the food can be appropriately fired according to a predetermined heat flux history.

  However, in order to adjust the heating power of each gas burner, a heating power adjustment valve and piping are required for each gas burner, and an increase in cost is inevitable. In addition, a large amount of cost is required for maintenance and management of the plurality of valves and pipes. This problem also applies to the radiation type heating device described in Patent Document 2, and a valve and piping for adjusting the thermal power are required for each hermetic gas heater, so an increase in cost is inevitable.

  The present invention was devised in view of the above circumstances, and provides a radiant heating device and a radiant heating method capable of heating an object to be fired with a predetermined heat flux history while reducing costs. It is to provide.

  According to the present invention, in a radiant heating device comprising a conveyor for conveying an object to be fired, a radiating plate disposed along the conveyor, and a heat source for heating the radiating plate, the surface of the radiating plate Further, there is provided a radiant heating device characterized in that radiant materials having different emissivities are provided along at least one of the longitudinal direction and the width direction of the conveyor.

  The heat source may include a plurality of gas burners arranged at intervals in the longitudinal direction of the conveyor, and a thermal power adjusting means capable of simultaneously adjusting the thermal power of the plurality of gas burners.

  Further, a high radiation material may be provided at a position facing the gas burner, and a low radiation material having a lower emissivity than the high radiation material may be provided between the high radiation materials, and the gas burner A low radiation material may be provided at an opposing position, and a high radiation material having a higher radiation rate than the low radiation material may be provided between the low radiation materials.

  Furthermore, the high radiation material may be provided such that the area at both ends in the width direction is larger than the area at the center in the width direction.

  Further, according to the present invention, using a radiant heating device comprising a conveyor for conveying an object to be fired, a radiating plate disposed along the conveyor, and a heat source for heating the radiating plate, In a radiant heating method in which the object to be fired conveyed by a conveyor is heated by radiant heat from the radiation plate, the emissivity varies depending on the heat flux history necessary for firing the material to be fired on the surface of the radiation plate. By providing the radiant material, there is provided a radiant heating method characterized in that the heat flux radiated from the radiant plate to the object to be fired is changed at least in the longitudinal direction of the conveyor.

  According to the radiant heating device and the radiant heating method of the present invention, the radiating plate is disposed along the conveyor that conveys the object to be fired, and the radiating materials having different emissivities according to the location of the surface of the radiating plate are provided. By providing, the heat flux applied to the object to be fired from the radiation plate can be changed from the start to the end of the firing without adjusting the heating power of the heat source according to the location of the radiation plate. Therefore, it is possible to heat the object to be fired with a predetermined appropriate heat flux history while reducing the cost.

It is explanatory drawing which shows the radiation type heating apparatus which concerns on 1st embodiment of this invention, (a) is a sectional side view, (b) has shown the heat flux distribution map. It is a perspective view which shows the detail of the radiation type heating apparatus shown in FIG. It is explanatory drawing which shows arrangement | positioning of a radiation material, (a) is a top view, (b) has shown the heat flux distribution map. It is explanatory drawing which shows arrangement | positioning of the radiation material in the radiation type heating apparatus which concerns on 2nd embodiment of this invention, (a) is a top view, (b) has shown the heat flux distribution map. It is a top view which shows arrangement | positioning of the radiation material in the radiation type heating apparatus which concerns on other embodiment of this invention, (a) has shown 3rd embodiment, (b) has shown 4th embodiment.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values shown in the embodiments are merely examples for facilitating understanding of the invention, and do not limit the present invention unless otherwise specified. In the present specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals, and redundant description is omitted, and elements not directly related to the present invention are illustrated. Omitted.

  As shown in FIG. 1A, the radiation heating device 1 according to the first embodiment of the present invention includes a conveyor 3 that conveys an object to be fired 2, and a radiation plate 4 that is disposed along the conveyor 3. And a heat source 5 for heating the radiation plate 4. The to-be-baked object 2 is a concept including all the objects heat-processed in the field | areas of foodstuffs and industrial products, such as baked confectionery and other baked foods, such as a rice cracker and a cookie, the coated goods, ceramics, etc., for example.

  For example, as shown in FIG. 1A and FIG. 2, the conveyor 3 includes an endless belt 31 made of a wire mesh, a head pulley 32 and a tail pulley 33 around which the endless belt 31 is wound, and conveyance of the endless belt 31. And a support roller 35 that supports the lower surface of the surface 34.

  A plurality of support rollers 35 are arranged at intervals in the longitudinal direction of the transport surface 34 of the endless belt 31, and are not limited to the illustrated number. By rotating the head pulley 32 or the tail pulley 33 by driving means such as a motor, the endless belt 31 circulates, and the object to be fired 2 placed on the conveying surface 34 is conveyed. In addition, this conveyor 3 is a conveying apparatus which conveys the to-be-baked material 2, and is not limited to the structure shown in figure, The existing conveying apparatus can be used according to the to-be-baked object 2. FIG.

  The radiation plates 4 are respectively disposed above and below the conveyance surface 34 of the conveyor 3, and the heat sources 5 for heating the radiation plates 4 are also disposed above and below the conveyance surface 34 of the conveyor 3. Each heat source 5 is provided in a plurality of gas burners 51 arranged at intervals in the longitudinal direction of the conveying surface 34 of the conveyor 3 and a collective pipe 52 of these gas burners 51, and the heating power of each gas burner 51 can be adjusted simultaneously. A single heating power adjusting means (for example, an opening degree adjusting valve 53).

  The gas burner 51 is accommodated in a casing 54 formed in a substantially rectangular parallelepiped shape formed along the longitudinal direction of the conveyor 3, and the radiation plate 4 is provided on the surface of the casing 54 facing the conveyance surface 34 of the conveyor 3. It has been. The radiation plate 4 is heated by each gas burner 51 and irradiates the object to be fired 2 conveyed by the conveyor 3 with radiant heat. A plurality of gas burners 51 may be arranged at intervals in the width direction of the conveyor 3.

  In this embodiment, since the gas burner 51 is accommodated in the casing 54, the combustion gas of the gas burner 51 is not sprayed on the to-be-fired object 2, and the influence of the combustion gas on the to-be-fired object 2 is excluded. can do. Further, even when moisture is sprayed on the object to be fired 2, the thermal power of the gas burner 51 is not weakened, and the atmospheric humidity of the object to be fired 2 can be easily controlled. Moreover, the casing 54 arrange | positioned up and down so that the conveyance surface 34 of the conveyor 3 may be pinched | interposed in the housing | casing 6 with which the inlet 61 and the exit 62 were opened, and comprises the so-called continuous heating furnace.

  The heat source 5 is not limited to the illustrated configuration. For example, the heat source 5 may be disposed only above or below the conveyor 3 or may be disposed in the left-right direction. Further, instead of the gas burner 51, a so-called micro combustor may be used.

  Further, the heating power adjusting means is not necessarily required to be independent. That is, the casing 54 may be divided into heating regions including a plurality of gas burners 51, and the thermal power adjusting means may be arranged for each heating region. The heating region may be divided in the row direction along the longitudinal direction of the conveyor 3 or may be divided in the column direction along the width direction of the conveyor 3. Further, it is preferable that the number of sections of the heating area is smaller than the number of gas burners 51 or smaller than the number of rows or columns of the gas burners 51.

  On the surface of the radiation plate 4 facing the transport surface 34 of the conveyor 3, radiation materials 7 having different emissivities are provided along at least one of the longitudinal direction and the width direction of the conveyor 3. FIG. 1A shows an example in which a high radiation material 71 and a low radiation material 72 are provided in accordance with the location along the longitudinal direction of the conveyor 3. Specifically, a heat flux history for firing the object to be fired 2 with an appropriate quality is obtained in advance by experiments (prototype firing, etc.) and simulations, and radiation having different emissivities so as to match the heat flux history. A material 7 is disposed on the surface of the radiation plate 4. The radiation material 7 is arranged by being applied or pasted on the surface of the radiation plate 4.

  FIG. 1B shows an example of a heat flux history for firing the object to be fired 2 with an appropriate quality. For example, the high radiation material 71 is provided on the radiation plate 4 corresponding to the peak portion of the heat flux history curve 8, and the low radiation material 72 is provided on the radiation plate 4 corresponding to the valley portion of the heat flux history curve 8. Provided. At this time, the radiation material 7 (the high radiation material 71 and the low radiation material 72) is based not only on the arrangement position but also on the heat flux history curve 8 for the radiation rate, the length in the longitudinal direction, the area, the thickness, and the like. Are adjusted accordingly.

  As the high radiation material 71, for example, magnesium, iron oxide, gypsum, ceramic or the like having a radiation rate of about 0.8 to 0.9 is used. These high radiation materials 71 are disposed on the surface of the radiation plate 4 by being applied to the radiation plate 4. Moreover, as the low radiation material 72, for example, aluminum, stainless steel, copper or the like having a radiation rate of about 0.2 to 0.3 is used. When the low radiation material 72 is aluminum, stainless steel or the like, a plate-like material is welded to the radiation plate 4, and when the low radiation material 72 is copper, it is deposited on the radiation plate 4 to be disposed on the surface of the radiation plate 4. Is done.

  By using the radiant heating device 1 described above, the radiating plate 4 is provided with the radiating material 7 having different emissivities according to the heat flux history necessary for firing the object 2 to be fired on the surface of the radiating plate 4. The heat flux radiated to the workpiece 2 can be changed at least in the longitudinal direction of the conveyor 3.

  That is, since high radiation heat is radiated from the high radiation material 71 higher than that of the low radiation material 72, an appropriate heat flux history (in which the arrangement and radiation rate of the high radiation material 71 and the low radiation material 72 are obtained in advance) By setting according to FIG. 1 (b), an appropriate heat flux corresponding to the heat flux history can be applied to the object to be fired 2 conveyed by the conveyor 3 from the start to the end of the firing. it can.

  In addition, by using the above-described radiant heating device 1, it is not necessary to individually adjust the heating power for each gas burner 51, and valves and piping for individually adjusting the heating power of each gas burner 51 are omitted. Thus, the cost can be reduced, and a heating device that is simple and excellent in reliability and durability can be provided.

  Moreover, according to the radiation type heating device 1 described above, the high heat flux burner and the low heat flux burner can be arbitrarily changed without changing the internal structure of the heater (heating device) by changing the radiation rate of the heater surface. Can be changed.

  Furthermore, when a material such as stainless steel is used for the heating device, the emissivity is about 0.2 in the unused state, but it is known that the emissivity changes to about 0.5 as it is used as it is used. Yes. In the present embodiment, by performing the above-described radiation control, it is possible to avoid such transient characteristics of the radiation rate and to omit pretreatment such as oxidizing the material in advance.

  Here, Fig.3 (a) is a top view which shows arrangement | positioning of a radiation material, FIG.3 (b) has shown the heat flux distribution map. The heat flux distribution shown in the heat flux distribution diagram of FIG. 3B shows the heat flux along the direction of travel of the conveyor applied from the radiation plate 4 to the workpiece 2. As shown in FIG. 3A, in the present embodiment, a high radiation material 71 is provided at a position facing the gas burner 51, and the radiation rate between the high radiation materials 71 is lower than that of the high radiation material 71. A radiation material 72 is provided.

  With such a configuration, the high radiant material 71 is heated to a temperature higher than that of the low radiant material 72 by the gas burner 51, and therefore the high radiant material 71 is fired from the high radiant material 71 along the traveling direction of the conveyor 3, coupled with the difference in emissivity. The difference between the heat flux applied to the object 2 and the heat flux applied to the object to be fired from the low radiation material 72 can be increased as compared with the case where the high radiation material 71 and the low radiation material 72 are heated to the same temperature.

  Next, the radiant heating device 1 according to the second embodiment of the present invention will be described with reference to FIGS. 4 (a) and 4 (b). FIG. 4 is an explanatory view showing the arrangement of the radiant material in the radiant heating device according to the second embodiment of the present invention, wherein (a) is a plan view and (b) is a heat flux distribution diagram. The radiation heating device 1 according to the second embodiment is obtained by changing the arrangement of the high radiation material 71 and the low radiation material 72.

  Specifically, as shown in FIG. 4A, a low radiation material 72 is provided at a position facing the gas burner 51, and the radiation rate between the low radiation materials 72 is higher than that of the low radiation material 72. A radiation material 71 is provided. That is, the arrangement of the high radiation material 71 and the low radiation material 72 in the first embodiment is exchanged.

  With such a configuration, the low radiant material 72 is heated to a temperature higher than that of the high radiant material 71 by the gas burner 51. Therefore, considering the difference in emissivity, the low radiant material 72 is covered from the low radiant material 72 along the traveling direction of the conveyor 3. The difference between the heat flux applied to the baked product 2 and the heat flux applied from the high radiant material 71 to the baked product 2 may be made smaller than when the low radiant material 72 and the high radiant material 71 are heated to the same temperature. it can. Therefore, as shown in FIG. 4B, the heat flux distribution can be controlled uniformly. However, the heat flux distribution is not limited to being uniform, and one of the heat fluxes of the high radiation material 71 and the low radiation material 72 may be high.

  Next, a radiant heating device 1 according to another embodiment of the present invention will be described with reference to FIGS. 5 (a) and 5 (b). FIG. 5 is a plan view showing the arrangement of the radiant material in a radiant heating device according to another embodiment of the present invention, wherein (a) shows the third embodiment, and (b) shows the fourth embodiment. Yes.

  In the radiant heating device 1 according to the third embodiment shown in FIG. 5A, the high radiation material 71 is provided such that the area at both ends in the width direction is larger than the area at the center in the width direction. It is. For example, as shown in the drawing, a low radiation material 72 is provided in a substantially circular shape at a position facing the gas burner 51, and a high radiation material 71 is provided around the low radiation material 72, whereby the area of the high radiation material 71 at both ends in the width direction is provided. Can be increased. Here, the shape of the low radiation material 72 is not limited to a circular shape, and may be an elliptical shape or a rectangular shape.

  In general, the radiant heat of the radiating plate 4 tends to have a high temperature in the central portion in the width direction close to the gas burner 51 and low in both end portions in the width direction. Accordingly, in order to heat the object to be fired 2 at a uniform temperature over substantially the entire width direction of the conveyor 3, it is preferable to provide the low radiation material 72 in the high temperature region and provide the high radiation material 71 in the low temperature region. .

  The radiant heating device 1 according to the fourth embodiment shown in FIG. 5 (b) is obtained by forming a non-radiation material region 41 in which the radiant material 7 is not provided on a part of the radiation plate 4. Here, the non-radiation material region 41 is disposed between the low radiation material 72 and the high radiation material 71. In this way, the heat flux radiated to the object to be fired 2 can also be adjusted by forming a region where the radiation material 7 is not provided in a part of the radiation plate 4.

  The preferred embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the above-described embodiments, and various modifications within the scope of the claims. Needless to say, examples and modifications also belong to the technical scope of the present invention.

  For example, the arrangement of the high radiation material 71 and the low radiation material 72 on the upper and lower radiation plates 4 is not limited to the vertical symmetry, and when the material of the article to be fired 2 is different between the upper surface side and the lower surface side, the upper and lower asymmetrical shapes. The high radiation material 71 and the low radiation material 72 may be arranged so that

DESCRIPTION OF SYMBOLS 1 Radiation type heating apparatus 2 To-be-fired object 3 Conveyor 4 Radiation board 5 Heat source 6 Case 7 Radiant material 8 Heat flux history curve 31 Endless belt 32 Head pulley 33 Tail pulley 34 Conveyance surface 35 Support roller 41 Non-radiation material area 51 Gas burner 52 Collective piping 53 Opening control valve 54 Casing 61 Inlet 62 Outlet 71 High radiation material 72 Low radiation material

Claims (5)

In a radiant heating apparatus comprising: a conveyor that conveys an object to be fired; a radiation plate disposed along the conveyor; and a heat source that heats the radiation plate.
A radiation-type heating device, wherein a radiation material having a different radiation rate is provided on the surface of the radiation plate along at least one of a longitudinal direction and a width direction of the conveyor.   The heat source includes a plurality of gas burners arranged at intervals in the longitudinal direction of the conveyor, and a thermal power adjusting means capable of simultaneously adjusting the thermal power of the plurality of gas burners. The radiation type heating device described in 1.   A position where the high radiation material is provided at a position facing the gas burner and a low radiation material having a lower emissivity than the high radiation material is provided between the high radiation materials, or a position facing the gas burner The radiation heating according to claim 1 or 2, wherein a low radiation material is provided on the substrate and a high radiation material having a higher emissivity than the low radiation material is provided between the low radiation materials. apparatus.   The radiant heating device according to claim 3, wherein the high radiation material is provided such that an area at both end portions in the width direction is larger than an area at a center portion in the width direction. The said to-be-fired conveyed by the said conveyor using the radiation type heating apparatus provided with the conveyor which conveys to-be-fired material, the radiation plate arrange | positioned along this conveyor, and the heat source which heats this radiation plate In a radiation type radiation heating method of heating an object with radiation heat from the radiation plate,
By providing a radiation material having a different emissivity according to the heat flux history necessary for firing the object to be fired on the surface of the radiation plate, at least the heat flux radiated from the radiation plate to the object to be fired is A radiation type radiant heating method, characterized by being changed in the longitudinal direction of the conveyor.