JPS63286697A - Rotary hearth type elevator type furnace - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention is applicable to molded products such as bricks, ceramics, fine ceramics, and ferrous and non-ferrous metals, or powder products that are handled by being filled into heat-resistant containers. This invention relates to a rotary hearth type elevator type furnace for heat treating.

<Conventional technology> Conventional furnace equipment can be roughly divided into (1) intermittent operation furnaces and (2)
There is a continuously operating furnace.

(1) Heat treatment of intermittent operation furnace products When the heat treatment conditions such as acid, treatment temperature, treatment time, etc. are changed each time the operation is performed, generally Fig. 6 (a)
, (b), the Carvel type furnace shown in FIGS. 7(a) and 7(b), or the elevator type furnace shown in FIG. 8, intermittent operation furnaces are used.

Each time these furnaces are operated, the products to be heat-treated are loaded onto a trolley and charged into the furnace at a low temperature close to room temperature, and the temperature of the furnace body and the trolley is raised by the combustion heat of fuel, etc., and preheated. ,
It is heated, soaked, and further cooled to complete a predetermined heat treatment operation, that is, operations are performed according to a series of programs to complete a single operation.

Intermittent operation furnaces have the following advantages:

(8) Heat treatment conditions can be changed each time the operation is performed.

(B) Therefore, a wide variety of products can be easily heat treated.

(C) The furnace can be operated and stopped freely, making it suitable for heat treatment of small quantities of products.

(D) Maintenance is easy when the furnace body is stopped.

However, it has the following drawbacks.

(b) Each time the furnace is operated, a large amount of heat is absorbed by raising the temperature of the furnace body and cart, and most of it is discarded as lost heat.

In addition, a part of the fuel combustion heat supplied to the furnace, the product and the furnace body,
Either it is consumed to raise the temperature of the trolley, etc., or the rest becomes waste gas at a temperature roughly equal to the temperature inside the furnace and is discarded into the atmosphere through the flue and chimney. Incidentally, the waste heat may be recovered during the exhaust gas path to preheat the air or as another heat source, or the amount of heat is only a small amount. That is, the above-mentioned waste heat loss is extremely large, and the thermal efficiency is extremely low.

([1)-Since the operation is repeated every time, the operating rate of the furnace equipment is poor, that is, the productivity is low.

(c) - Is it easy to automatically program the operation such as controlling the temperature inside the furnace each time, or is it extremely complicated to automate the process including charging and extracting the product into the furnace?

(:) The lifespan of the furnace body is short due to the frequent repetition of heating and cooling of the furnace body.

(2) Continuously Operating Furnace When the heat treatment conditions are subject to few changes and operation under approximately the same conditions continues for a relatively long period of time, a continuous operating furnace is usually used. As a representative example, Figure 9 (
a), (b), and (c) are tunnel type trapezoidal furnaces, No. 1 O
Figure (al (b) shows a rotary hearth type furnace, Figure 11 (a), (
b) shows a roller hearth type furnace. Figure 9(a),(b)
), (c) The tunnel type furnace shown in (c) is preheated from the furnace entrance;
? Each furnace chamber is arranged and connected in the order of heating/soaking zone and cooling zone, and consists of tunnel-shaped furnace chambers that communicate with each other so that products placed on a trolley can freely pass through the furnace. There is. The high-temperature gas in the furnace generated in the fuel combustion area of the heating and soaking zone flows to the preheating (iF) side and is disposed of into the atmosphere from near the furnace inlet through the flue and chimney. The processed products are charged from the furnace inlet, are preheated, heated, and soaked while being transferred to the preheating zone, heating/soaking zone, and are further cooled while being transferred to the cooling zone. It is cooled by air etc. and extracted from the furnace outlet.
Predetermined heat treatment operations are completed, and these operations are carried out continuously by continuously charging carts from the furnace inlet. In addition, in the above-mentioned continuous operation, 1. Normally, the temperature inside the furnace is completed in advance to an atmosphere suitable for the target heat treatment conditions at the beginning of the operation, or regular operation is started as soon as the temperature increase is predicted. .

This tunnel type furnace has the following main advantages.

(A) The fuel combustion heat supplied in the heating and soaking zone is effectively used to preheat the product in the preheating zone, and the air used for cooling the product is recovered in the cooling zone and used as preheated air for fuel combustion. The degree of effective use of heat is extremely high. In addition, the heat absorbed by the furnace body is only at the initial stage of operation, and there is no loss of heat absorbed by the furnace body during subsequent continuous operation. Therefore, thermal efficiency is extremely good.

(B) Automatic control of furnace temperature, etc. and charging of products into the furnace.
Automation of extraction allows easy and stable operation maintenance.

(C) It is easy to maintain stable heat treatment conditions, and the heat treatment effect on the product is constant, resulting in improved quality and yield.

(D) Productivity is very high due to continuous operation.

(E) The frequency of heating and cooling of the furnace body is reduced, thus extending the life of the furnace body.

However, it has the following drawbacks.

(a) A common drawback of continuous operation type furnaces is that they are not responsive to changes in heat treatment conditions, that is, they are difficult to respond to changes in furnace temperature and reductions in product throughput.

(b) In the case of tunnel type trapezoidal furnaces shown in Figure 9 (a), (b), and (C), it is difficult to adjust the pressure balance near the boundary between the end of the soaking zone and the cooling zone, and Furnace gas tends to flow in and out between the two. As a result, problems such as atmospheric disturbance and increased heat loss arise. In addition, since it is difficult to completely seal between the furnace carriage and the furnace body, gas in the furnace or cold air under the carriage tends to flow in and out between the inside of the furnace and the lower part of the carriage, resulting in uneven temperature distribution within the furnace and heat loss. 5. Abnormal damage under the bogie may occur. A further disadvantage is that it requires an operation to return the cart extracted from the furnace outlet, which is farthest from the furnace entrance, to the entrance side.

(c) In the case of the roller hearth type furnace shown in Figures 11(a) and (b), it is possible to heat the product from the top and bottom, and the temperature distribution is uniform or at a temperature of 1100 to 1200'c or more. There are many problems such as the material used, strength and arrangement of the hearth rollers in terms of temperature, and they are significantly restricted by conditions such as the width of the furnace interior, the heat treatment temperature, and the size, shape, and weight of the product. Further, depending on the size and shape of the product, a tray may be required, which has the disadvantage of requiring a tray return operation outside the furnace.

(d) In the case of the rotary hearth type furnace shown in Figure 1O (a) and (b), the tunnel type furnace shown in Figure 9 (a), (b), and (C) is made into an annular shape, and the furnace entrance is The charged product is transferred to the furnace outlet adjacent to the inlet and extracted by one rotation of the rotary hearth, which is very convenient for transferring the product inside the furnace, but the temperature distribution inside the furnace tends to be extremely uneven. It has its drawbacks. Furthermore, when molded products such as bricks are stacked high on a hearth and heat treated, loading and extracting the products into the furnace becomes difficult. The present invention aims to improve the many drawbacks of the conventional intermittent operation type furnace and continuous operation type furnace at once. It is an object of the present invention to provide a rotary hearth type elevator-type furnace that has improved various characteristics fE such as productivity, energy saving, labor saving, etc., which can correspond to a large or small processing amount.

<Means for Solving the Problems> The rotary hearth type elevator type furnace according to the present invention has a plurality of independent furnace chambers and a product loading/unloading work area arranged in a ring shape, and a plurality of independent furnace chambers and a product loading/unloading area. Each of the product loading/unloading stations is provided with a hearth board which can be raised and lowered and which moves sequentially along the annular arrangement direction.

Function> First, the product to be heat treated is loaded onto the hearth board in the product loading work area, which has been raised to the same height as the hearth in the furnace room. Next, the hearth board in the workplace loaded with products and the hearth board in each furnace room are simultaneously lowered to a predetermined position, and then each of those hearth boards is moved to the adjacent furnace room or work area, Raise each hearth plate to the hearth level again. When heat-treating a product, for example, the product transferred from the workplace is stored in a preheating chamber and preheated for a predetermined period of time. Also, during the preheating time, the next product to be charged is loaded onto the hearth plate in the product loading workshop, and the product waits until the next charging time. Thereafter, the product, which has been preheated by repeating the same operations as described above, is transferred to a heating chamber and a soaking chamber, and then sequentially transferred to a first cooling chamber and a second cooling chamber, where heat treatment is performed respectively. Completes the entire process of preheating, heating, soaking and cooling. The products cooled in the second cooling room in the final process are unloaded from the hearth board in the product unloading workshop.

<Example> An example of the present invention will be described below with reference to the drawings. An example of the main structure is shown in the heat treatment temperature curve in FIG. 4 and in FIGS. 1 to 5, and the outline thereof will be explained. In addition, FIG. 1 is a w-w' plane sectional view of FIG. 2, FIG. 2 is a xx' cross-sectional view of FIG. 1, and FIG. 3 is a Y-Y' and z-
Cross-sectional view cut in the direction of the z′ arrow and arranged in series, No. 5
The figure shows a cross-sectional view of the bottom of the furnace chamber.

(1) Furnace chamber and workshop As shown in the heat treatment temperature curve shown in FIG. 4 and the corresponding FIG. 3 and FIG. Furnace chambers 1 are arranged so as to be located in the center of the furnace, and each furnace chamber 1, which has an independent cooling chamber from the inlet side, includes a preheating chamber 1a, a heating chamber 1b, a soaking chamber 1c, a first cooling chamber 1d, and a second cooling chamber 1e. A group of furnace chambers arranged in sequence, and a product loading work area 3 where products M to be charged into the furnace chamber L are loaded onto a hearth board 2.
Then, a product unloading work area 4 where the product M extracted from the second cooling room 1e at the end of the furnace chamber group 1 is unloaded from the hearth board 2, a product preparatory work area 5, etc. are arranged around a circumference with a predetermined dimension R as a radius. They are arranged on the work deck 6 along the same line and at the same interval P.

(2) Hearth board, rotating hearth frame, rotating device, and lifting device Immediately below the aforementioned work deck 6, the furnace chamber group 1, product loading work area 3, and product unloading work area 4 are arranged at equal intervals on a concentric circumference. , a rotary hearth frame 7 with annular wheels 8 in which an equal number of hearth plates 2 are set, and a pedestal 9 for supporting these are provided. A rotating device 10 is installed on the pedestal 9 to integrate the hearth plate 2 and the rotary hearth frame 7 and rotate the hearth plate 2 around the center of the circumference of the arrangement. There is. Further, this pedestal 9 is horizontally supported by a plurality of elevating devices 11, such as hydraulic lifters, which are installed to raise and lower the pedestal 9. However, the hearth board 2
The lifting device 11 is used to lower the top of the product M loaded thereon to a height where it does not touch the lower part of the work deck 6 below the furnace chamber 1, and the rotary hearth frame 7 is freely rotated by the rotating device 10. (See Figure 3).

(3) Structure of the furnace chamber (A) Each furnace chamber 1, for example, the preheating chamber 1a, the heating chamber 1b, the soaking chamber 1c, the first cooling chamber 1d, and the second cooling chamber 1e has a steel case with fireproof material and heat insulation on the inner surface. It has a cylindrical or box-like shape consisting of side walls and ceiling lined with wood, etc., and the bottom of the furnace chamber is lined with product M.
The furnace chamber 1 is opened so that the product M can be charged into or extracted from the furnace chamber 1 by raising and lowering a pedestal 9 that supports the hearth board 2 loaded with the products M. In addition, a heat-resistant para-kink 12 and a sand seal 13 or a water seal are provided at the bottom of the furnace chamber l so that when the product M is stored in the furnace chamber l, a heat-resistant para-kink 12 and a sand seal 13 are installed so that the product M can be completely sealed between the lower surface of the furnace chamber l and the upper surface of the hearth plate 2. A double sealing device 14 such as a seal is provided (see FIG. 5).

(B) A soaking chamber 1c located at the center of the furnace chamber group is equipped with a fuel combustion burner 15 at a position so as to uniformize the temperature distribution in the furnace. In addition, the soaking chamber 1c and the heating chamber 1b are sufficiently insulated so that the high-temperature furnace gas generated in the soaking chamber 1c is introduced into the heating chamber 1b adjacent to the entrance side of the soaking chamber 1c and reused. They are communicated by a flue 16.

(C) In the heating chamber 1b, the product must be sufficiently and uniformly preheated 119 before being transferred to the scorching chamber 1c. The means for this is first to recycle the gas in the furnace introduced from the scorching chamber 1c, but it is also equipped with a high-speed jet blowing device 17 for the high-temperature gas recovered in the first cooling chamber 1d. Aim for forced stirring and waste heat recovery. Further, the high-speed jet blower 17 is used in combination with an auxiliary burner for fuel combustion, and can further raise the temperature inside the furnace chamber as necessary. The heating chamber 1b and the preheating chamber 1a are provided with a sufficiently insulated flue 16 so that the furnace gas in the heating chamber 1b is further introduced into the preheating chamber 1a adjacent to the entrance side of the heating chamber for reuse.
It is communicated with.

(D) In the preheating chamber 1a, the waste gas introduced from the heating chamber 1b is used to sufficiently and uniformly preheat (and dry) the product before being transferred to the heating chamber 1b. Equipped with a heat-resistant fan 18 for forced stirring. The waste gas in the preheating chamber 1a is discharged into the atmosphere from a flue 16 at the end of the furnace chamber through a chimney 19, or a combustion air preheating device 19'' is further installed in the waste gas path to recover waste heat. It can also happen.

(E) In the cooling chamber, the high temperature product extracted from the soaking chamber 1c is cooled to a predetermined temperature, or the first cooling chamber 1d (high temperature side) and the second cooling chamber are used to match the cooling temperature of the product. 1e
They are installed separately on the low-temperature side, and both use a cooling method using air blowing. That is, in the case of this example, as shown in FIG. 3, first, fresh air preheated by a combustion air preheating device 19'' installed in the waste gas path of the preheating chamber 1a is sent to the second cooling chamber 1e. The waste air is blown into the furnace chamber, and the waste air is then blown into the first cooling chamber 1d to cool the respective products.In this way, the products are cooled, but at this time, the high temperature is increased by heat exchange with the products. The heated exhaust air (air) is sent to the above-mentioned soaking chamber lc and heating chamber 1b and used as fuel combustion air, or as a high-speed jet stream for forced stirring of the gas in the furnace in the heating chamber 1b. When blowing cooling air into the first cooling chamber ld and the second cooling chamber 1e, the temperature of the blown air can be adjusted by mixing outside air (cold air).

(4) Structure of the hearth board The hearth board 2 conforms to the bottom shape and dimensions of each furnace chamber l, that is, the preheating chamber 1a, the heating chamber lb, the soaking chamber 1c, the first cooling chamber 1d, and the second cooling chamber le. It is a steel frame made of steel, etc., with a combination of refractory and heat insulating materials, and is set in an easily removable manner on a rotating hearth frame 7 with wheels 8, and can be used as a spare hearth board. It has a structure that can be easily replaced (see Figure 5). (5) Work area on the work deck Product loading work area 3 where products M are loaded onto the hearth board 2 on the work deck 6-11, product unloading. A workshop 4 and a product preparatory workshop 5 are provided, where the products are stored in a furnace chamber and the above-mentioned operations are performed during heating and cooling operations.

(6) Heat insulation and sealing device for the furnace chamber and under the hearth plate When the heated product in the furnace chamber is lowered to the bottom of the furnace chamber together with the hearth plate 2,
In order to prevent the temperature of the product from dropping due to outside air under the furnace room,
It is equipped with a heat insulating/sealing device 20 that is linked to the vertical movement of the hearth board 2. In this example, a case is shown in which a heat insulating plate and a heat insulating sheet with good heat insulating properties are used, and the heat insulating sheets are installed along the circumference and inscribed circle connecting each furnace room and the work area, respectively, over the entire circumference.

(7) Atmosphere in each furnace chamber Usually, each furnace chamber heat-treats products in an oxidizing atmosphere. However, by creating a non-oxidizing atmosphere in each furnace chamber for preheating, heating, and soaking,
In addition, nitrogen gas or a non-oxidizing atmosphere gas from the furnace chamber is recovered and used as a cooling medium in the cooling chamber to adjust the temperature to an appropriate temperature, thereby creating a non-oxidizing atmosphere in the entire furnace chamber or a part of it. It is also possible to heat treat the finished product.

In this case, it is advisable to use a heat exchanger to indirectly preheat the combustion air using waste gas from a cooling chamber or the like.

(8) In this example, the furnace chamber includes a preheating chamber, a heating chamber,
Although we have described the case where each of the soaking chamber, first cooling chamber, and second cooling chamber is provided, it is not necessary to have all of these furnace chambers. For example, it is not necessary to have all of these furnace chambers. A single chamber or a combination of several of these chambers may be used.

Next, the operating method of this embodiment will be explained based on FIGS. 1 to 5.

(1) First, the cradle 9 of the hearth plate 2 and the rotating hearth frame 7
When the elevating device 11 is operated to raise the product M to be heat-treated in the product vXa workshop 3, the product M is placed on the hearth board 2-
J:, and waits until the time for charging into the preheating chamber 1a.

(2) The lifting device 11 is operated according to a program in which the charging time is set in advance to lower the pedestal 9, and then the rotating device 10 is driven to move the rotary hearth frame 7 to 1 pitch, that is, the product It rotates from the center of the loading work area 3 to the center of the preheating chamber 1a. Subsequently, with the center of the hearth board 2 aligned with the center of the preheating chamber 1a, the lifting/lowering fill is operated to raise the pedestal 9, and the product M on the hearth board 2 is stored in the preheating chamber la.

(3) Preheat the product for the time set in the program with the product stored in the furnace chamber l. Also, the next product to be charged is loaded on the hearth board 2 at the product loading work area 3 on the inlet side of the furnace chamber 1 during the same period, and the product waits until the charging time as described in (1) above.

(4) Hereafter, by repeating the same operations as above (1), (2), and (3), the preheated product is heated in the heating chamber 1b,
The product is transferred to the soaking chamber 1c, and then sequentially transferred to the first cooling chamber 1d and the second cooling chamber 1e, where heat treatment is performed respectively, thereby completing all steps of preheating, heating, soaking, and cooling.

(5) The product cooled in the second cooling chamber 1e in the final step reaches the product unloading work area 4 on the furnace outlet side and is unloaded from above the hearth board 2.

(6) All operations from below can be performed automatically according to a preset program.

(7) Also, heating chamber lb, soaking chamber 1c and first cooling chamber 1
d. Temperature control of the second cooling chamber 1e, fuel combustion control, etc. are automatically performed according to a program <Effects of the Invention> With the above configuration, the present invention has the following unique effects. That is, (1) High operability and productivity.

(a) Since it has afE as a continuous furnace, each furnace chamber is independent, so each furnace chamber is charged with the product,
Various conditions such as heat treatment temperature and furnace atmosphere can be changed, allowing heat treatment operations for a wide variety of products.

(b) In step 1 of adjusting the product charging fee for each batch,
Able to respond immediately to changes in production volume.

(C) Since the furnace chambers are independent, there is no radiant heat exchange between each furnace chamber or heat exchange due to the inflow and outflow of gas in the furnace, and as a result, the heat loss that would occur in a continuous furnace can be suppressed, and the temperature rise in the furnace chamber jI31 is reduced. , the operability and controllability of cooling etc. will be improved.

(d) Improving the uniform heating and cooling of the product by making the temperature distribution in the furnace structurally and operationally uniform through independent furnace chambers and strengthening the sealing between the furnace chamber and the hearth, and as described in item (c) above. Due to improvements in temperature raising, holding, and cooling performance, it is possible to shorten heat treatment time compared to conventional furnaces, and from this aspect as well, operability and productivity are improved.

(2) It is an energy-saving furnace.

(a) By flowing the fuel combustion gas stepwise from the soaking chamber to the heating chamber and preheating chamber, it can be effectively used for preheating and heating charged products.

(b) Product cooling air (hot air) in the cooling chamber can be recovered and effectively used as fuel combustion air or recirculated hot air.

(3) It is a labor-saving furnace.

(a) Since the inlet hearth plate dynamically returns to the entrance origin by the rotational drive of the hearth frame, there is no need to return the hearth plate.

(b) Furnace temperature, combustion control, hearth board (product) transfer, etc. can be easily and completely automatically performed according to a program.

(4) Improving product quality and yield.

As the heat treatment temperature of products becomes more uniform, both product quality and yield improve.

(5) Easy maintenance.

(a) Since the furnace is an independent furnace chamber, local repairs are extremely easy.

(b) Since the hearth plate is easy to attach and detach, even if the hearth plate refractory, which is the most easily damaged, is damaged, it can be simply replaced with a spare hearth plate, and there is no need to stop the heat treatment operation at all.

[Brief explanation of drawings]

1 shows an embodiment of the present invention, FIG. 2 is a sectional view taken along line W-w' in FIG. 2, FIG. -Y' and z-z'' cross-sectional views cut in the direction of the arrows and arranged in series, Figure 4 is a heat treatment temperature curve diagram in each furnace, Figure 5 is a sectional view of the bottom of the furnace chamber, Figure 6 (a
), (b) to FIG. 11(a), (b) show conventional examples, and FIG. (b) is a cross-sectional view and longitudinal cross-sectional view of a Carvel type furnace, Figure 8 is a vertical cross-sectional view of an elevator type furnace, and Figures 9 (a), (b), and (C) are a longitudinal cross-sectional view of a tunnel type trapezoidal furnace. Cross-sectional view, vertical cross-sectional view, heat treatment temperature curve diagram, Figure 1O (a)
, (b) is a cross-sectional view and a vertical cross-sectional view of a rotary hearth type furnace.
Figures (a) and (b) are longitudinal cross-sectional views of a roller hearth type furnace;
It is a xx' cross-sectional view. ■... Furnace room, 2... Hearth board, 3... Product loading work area, 4... Product unloading work area, lO... Rotating device, I
I... Lifting device.

Claims (1)

[Claims] A hearth which has a plurality of independent furnace chambers and product loading/unloading workplaces arranged in a ring shape, is movable up and down to each of the furnace chambers and the product loading/unloading workplaces, and moves sequentially along the annular arrangement direction. A rotary hearth type elevator type furnace characterized by the provision of a panel.