JPS6022273B2 - Continuous air flow firing furnace for powder and granular materials - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a vertical furnace with an empty column and horizontal structure for continuously heating and simulating powder and granular materials in an air stream.

BACKGROUND ART Various vertical furnaces have been developed and proposed for use in heating and firing granular materials such as firing artificial lightweight aggregates, limestone, and dolomite.

The present inventors have determined that when artificial lightweight aggregate is fired in a rotary kiln, there are problems in preventing fusion of the fired product, heat transfer mechanism of the furnace, thermal economy, etc. ``Continuous air flow firing method for powder and granular materials using a vertical furnace, which is large and easy to prevent fusion of fired materials, has excellent firing processing ability, and can obtain lightweight bones with a lighter specific gravity even with fine grains of 5 grains or less. '' (Tokuka Sho 55-75522, hereinafter referred to as ``First-to-Apply-Banpo'') was first proposed. The present invention relates to a vertical furnace with a hollow column structure used in this prior application.

As a vertical furnace used for conventional air flow firing of powder and granular materials, '1
} As shown in Publication No. 49-48076, this is a vertical furnace with a hollow column structure, which has a combustion chamber in the lower part of the furnace and slits that generate a swirling upward hot gas flow in the furnace, and the fired product is discharged from the lower part of the furnace. However, those operated in a batch manner, such as the furnace used in [2] Tokukan Sho 53-1121807, are equipped with a perforated plate in the lower part of the furnace to rectify the rising air flow, and the fired product is continuously overflowed and discharged. A vertical furnace with a structure (3! A structure in which a plurality of rectifying plates for upward air currents are installed in the furnace, causing the fired product to overflow and fall to the lower stage in order, forming a deposited layer of the fired product at the bottom of the furnace and discharging it. 4 - As shown in Tokuseki Sho 54-Satoshi No. 796, a gas jet jet nozzle is installed in the center of the lower part of the furnace, and an inverted cone-shaped perforated plate is installed around it to create an upward air current, and the fired product is discharged overflow. A vertical furnace with a structure of ``5'' is a furnace that does not have a porous rectifying plate in the furnace, and has a hollow column structure in which the fired products are allowed to fall sequentially to the bottom of the furnace, forming a deposited layer of fired products at the bottom of the furnace and then being discharged. There are also vertical furnaces.

These secondary technologies are those in which a fluidized bed, a warm bed, an improved spouted bed, a swirling spouted bed, a packed moving bed, etc. of powder and granular materials are formed in a furnace by an upward airflow of combustion gas, etc., and then heated and fired. However, no matter which type of vertical furnace is used, it is not possible to obtain satisfactory conditions for preventing the formation of fuzzy deposits on the fired product.

In both cases, the machine exhaust gas from the furnace is discharged at a high temperature that is approximately the same as or higher than the firing temperature, resulting in poor thermal efficiency. It was found that there is considerable room for improvement in this respect. The inventors of the present invention have conducted repeated research to achieve the above-mentioned problems, and as a result have found ``{1}
When heating and sintering powder by forming a mixed layer of powder and granules in the furnace, it is recommended to use a furnace with a shape that creates a far-flung and slow-flowing part of the rising air. A thin mixed layer is formed where the grains are concentrated and fast, and if fired in a furnace shaped so that the two mixed layers of the parentheses are formed successively above and below, the gas in the upward air flow will form in the upper and lower mixed layers. Temperature: A gradient occurs in the temperature of the material (powder and granules). ■ The dilute mixed layer is fired as the highest temperature zone, and the composite material passes through this highest temperature zone and is not deposited at the bottom of the furnace, but instead is created by an upward air flow. By using a furnace with a structure that allows it to be discharged from the bottom of the furnace while being suspended or floating, it is easy to adjust the temperature inside the furnace and prevent the fired materials from sticking to the inside of the furnace, thereby improving the thermal efficiency of the furnace and reducing the internal volume of the furnace. It was found that the firing capacity per hit can be improved.

The present invention is based on these findings, and is a vertical furnace of an air tower structure, which does not have a porous part for passing airflow inside the furnace or around the furnace arm, and which has a granular material inlet and a settling chamber. A large straight cylinder part and a small cylinder part are formed in the lower part of the furnace through an inverted conical part. This is a continuous air flow firing furnace for powder and granular materials, which is characterized by having an inlet for fuel, etc. in the furnace.

The air flow kiln according to the present invention is intended to be used for the firing of powder and granules that are likely to adhere to grains at high temperatures, such as lightweight aggregates, but it also has improved thermal efficiency and The purpose is also to improve the ability to exfoliate scales, and it can also be used for firing granular materials such as limestone and dolomite.

In the present invention, the mixed layer of powder and granular material and an updraft is a layer in which the powder and granular material are in contact with an updraft in a vertical furnace having a hollow column structure, excluding a packed bed of powder and granular material and a mere sedimentation layer. This refers to a layer in which powder and granules form a fluidized bed, spouted bed, etc. due to rising air currents, and the powder and granules float and circulate.

An example of the vertical air flow kiln of the open column slow construction according to the present invention is shown in FIG. , 3 is a powder inlet, 13 is a settling chamber, and 7 is an opening for feeding firing fuel, air, and/or combustion gas (hereinafter referred to as fuel, etc.) upward from the bottom of the furnace.

Reference numeral 9 denotes a large-diameter straight cylindrical portion, which is a small-diameter straight joint portion, and is continuous vertically via inverted conical portions 11 and 12 (here, the cylindrical portion is not limited to a circular cross section, but may have a polygonal cross section). (The inverted conical portion may also be an inverted pyramid shape.)

Therefore, the flow velocity of the ascending air current is slow in the large-diameter straight cylindrical portion 9.
It becomes faster at the small path node 10'. As mentioned above, in the large straight cylinder part, there is a mixed layer 4 with a high concentration of powder and granules (hereinafter referred to as the "dense mixed layer"), and in the straight cylinder part 4, there is a mixed layer 5 with a small concentration of powder and granules (hereinafter referred to as a dilute mixed layer). layers) are formed one after the other. In the mixed layers 4 and 5, which are continuously formed on the upper and lower sides, not only the amount of powder particles retained in the steady state during heating and firing is different, but also the "inverted conical part 1
Due to the squeezing effect of step 1, differences occur in the amount of floating, circulating, and flowing powder and granules in each of the upper and lower mixed layers and between each other.
In other words, the upper and lower layers as a whole are incompletely mixed. In general, the aforementioned Tokukan Sho 53-1121807 and Tokukan Sho 54-1687
The mixed layer of No. 96 and the like is characterized by complete mixing of the powder and granular material as a whole layer and uniform temperature throughout the layer. Therefore, if firing is performed using the furnace according to the present invention, the mixed layer 5 will now be the heating center (the firing,
(optimum temperature range for lightweight aggregate foaming), in mixed layers 4 and 5, as mentioned above, the powder and granules are incompletely mixed and there is a difference in retention amount, and there is also a difference in flow velocity, so the difference in heat transfer amount is This causes a temperature difference. In other words, although the mixed layer is a continuous and integrally formed mixed layer, a low-high temperature gradient is created in the height direction of the furnace and a steady state is formed.As a result, the temperature of the gas discharged from the mixed layer is In addition, the discharge of the fired product from the furnace of the present invention is due to incomplete mixing in the upper and lower layers as described above.
Although it is not an overflow discharge due to full-thickness complete moat such as No. 7, that is, stochastic discharge, it is discharged from the bottom of the furnace as described later, so the powder and granules as a whole have the effect of piston flow, that is, the phenomenon of extrusion flow is added. The fired product is then discharged. As a result, the residence time (amount) of the powder and granules in the furnace is relatively short, and the competition of anaerobic materials is reduced. Furthermore, the bale heating effect between the gas and the granules is large, so the furnace The competition ability per content mirror is improved. Next, in the furnace of the present invention, a settling chamber is provided in the upper part of the furnace, the diameter of which is larger than that of the large straight cylindrical part, and which allows most of the powder to settle, and a mixed layer is formed in the updraft where the flow velocity is far higher than that of the conventional technology. Since the powder and granules are fired in the same manner, the amount of powder and granules retained is small as a whole.In addition, in the mixed layer 5, the flow velocity is even faster, the powder and granules are thinner, and the rope azusa effect is large, which prevents the fusion phenomenon of the fired products. It can be reduced.

As a result, it is possible to fire and foam even highly fused particles by processing at a relatively high temperature without using an anti-fusing agent, and it is possible to obtain lightweight aggregate with a higher specific gravity. In addition, because the structure of the furnace allows it to be heated rapidly in a floating state, when using granules as a firing raw material, even if the granules do not have the strength required for firing in a rotary kiln, the granules can be heated rapidly. The surface is hardened in a short time and can be used without breaking and turning into powder.

It is necessary that the upward opening angle of the inverted conical portions 11 and 12 of the vertical furnace according to the present invention be 900 degrees or less.

This is because if it exceeds this range, the powder particles will accumulate or stagnate on the inner wall of the inverted conical portion, causing fusion. And for more certainty, it is desirable to set it to 600 or less. In Figure 1, 6a~
Reference numeral 6d is an inlet for fuel, etc. in the side wall, and is a burner used for forming the above-mentioned temperature gradient, adjusting the maximum temperature and the internal pressure of the discharge section. However, this inlet port is not limited to the vertical side wall of the small-diameter cylindrical portion 10, but may also be provided in the inverted conical portions 11, 12 and the cylindrical portion 9 depending on the firing conditions. Next, 8 in FIG. 1 is a fired product discharge port, and when granular material is fired using the furnace according to the present invention, the granular material supplied from the granular material inlet 3 stays in the mixed layer. The effect of the fuel falling and being discharged from the discharge port 8 at the bottom of the furnace will be explained.

The powder and granules supplied from the powder and granular material inlet 3 to the mixing bed 4 are fluidized, circulated, and suspended in the mixing layers 4 and 5, and remain in the mixed layers 4 and 5. Since a sedimentation chamber 13 is provided in the upper part of the granular material 9, some of the powder and granules carried by the upward airflow descend to the mixed layer and remain there (during the particle weight distribution of the powder and granules, there is no noise that exceeds the terminal velocity ut of the upward airflow). The fine powder is carried out of the furnace from the combustion gas outlet 2 by the rising air), and by feeding the powder and granules, the balance between the pressure loss of the rising air and the amount of retention in the mixed layer, that is, the balance expressed by the following equation. The crushed pieces fall down and are discharged from the furnace bottom 8 out of the furnace.

W (retention amount) = △P (mixed layer writing pressure) × A (furnace cross-sectional area) As a result, in the firing using the furnace of the present invention, it is possible to continuously feed the granular raw material and continuously discharge the fired product. .

In firing using the furnace according to the present invention, the average flow velocity of the rising air in the mixed layer is the flow start velocity of the powder (Umf
) According to the knowledge of the present inventors, the reason why the above operation is performed and the fired product can be discharged from the bottom of the furnace by descending through the mixed layer rather than being discharged overflow is due to the above-mentioned imbalance between pressure loss and retention amount. It is presumed that this is due to the difference in the flow velocity of the rising air between the furnace center and the furnace peripheral wall. In FIG. 1, reference numeral 4 denotes a port through which fuel, etc. is introduced upward from the bottom of the furnace, and serves as an upward airflow that supports the mixed layer, and also controls the temperature of the mixed layer 5 and the fired products that descend from the mixed layer. This is necessary to allow the particles to float and be discharged without being deposited.

According to the furnace according to the present invention, the large-diameter straight cylinder part and the small-diameter cylinder part are formed through the inverted conical part, and the rich mixed layer and the dilute mixed layer are vertically connected and formed, thereby reducing the temperature gradient. {2} It is not divided and provided in multiple stages like the multi-stage fluidized bed of the subordinate pot, but it is continuous and integrated; '3
'The powder and granular material as a whole has a piston flow, and the flow is countercurrent as a whole in relation to the updraft. ■ The fired material is not discharged overflow, but is discharged falling, passing through the highest gas overflow zone of the furnace. Factors such as the structure that discharges directly from the bottom and the provision of a settling chamber at the top of the furnace work together...
It is easy to stabilize the furnace temperature and other furnace conditions, and even fine particles with a grain size of 5 grains or less can be fired without using a kudzu adhesion prevention material, and lightweight aggregate with a lighter specific gravity can be obtained.
The internal fuel consumption is reduced, the output capacity per internal mirror of the 8 furnaces is improved, and ■ If the discharge of the fired product is by overflow discharge method, it will be possible to reduce the In contrast, in the case of the present invention, it is directly discharged from the bottom of the furnace to the outside of the furnace, so even if a fused lump is generated, it is automatically discharged, and its practical industrial value is great. be. Example: The inner diameter of the sedimentation chamber 13 is 200 ribs, the inner diameter of the straight part 9 is 13, the inner diameter of the straight cylinder part is 7 arms, the inverted conical part 8, the upward opening angle of the blade is 45 degrees, and the mixed layer is used. The total height of the tortoise and 5 is approximately 470 mm, and it is a shaped airflow firing furnace with 3 fuel inlet ports on the side wall and a fuel inlet port at the bottom. Table 1 shows the results of firing lightweight bones using a firing furnace having a shape and structure similar to the one shown in Fig. 1 and having a firing outlet.

Table 1 Note that the raw material used was granulated pulverized Komaki to a size of 1.2 to 3.3 mm.

Further, most of the fired product was discharged and recovered from the furnace lower part 8, and a portion was discharged from the furnace upper combustion gas discharge port 2 and collected by a cyclone (not shown). As is clear from Table 1, according to the present invention, the exhaust gas temperature (temperature at the top of the mixed layer 4) is lower than the firing temperature (the highest temperature of the mixed layer 5), and the base release per furnace content is 634 kg. /〆・Hr. By the way, rotary kilns produce 40 to 60 kg/8 marks, and other fluidized furnaces produce about 200 k9/mark. Hd is the degree of brightness. According to the present invention, the specific gravity is 1.0 without using the kudzu adhesion prevention material.
Thirty-five samples were obtained.

[Brief explanation of the drawing]

The figure is a vertical cross-sectional view schematically showing an example of a vertical airflow firing furnace according to the present invention, and in the figure, 2...combustion gas outlet, 3... powder and granular material inlet, 6a-- 6d...Side wall fuel inlet 7...Lower fuel inlet 8
...Fired product outlet, 9...Daiomo Naooribe, 1■...
...Small diameter straight cylindrical part "11, 12...Inverted conical part, 13...
...It is a settling chamber. Multi-7 diagrams

Claims (1)

[Scope of Claims] 1. A vertical furnace with a hollow column structure, without any porous parts in the furnace or on the furnace wall to allow air to pass through, which has a powder inlet and a settling chamber, and has a large space at the bottom thereof. A diameter straight cylindrical part and a small diameter cylindrical part are formed through an inverted conical part, and a fired product discharge port is provided in the inverted conical part at the bottom of the small diameter straight cylindrical part, and fuel etc. are supplied to the lower part of the furnace and the furnace wall. A continuous air flow firing furnace for powder and granular materials characterized by having an inlet. 2. The continuous air flow firing furnace for powder and granular material according to claim 1, wherein the upward opening angle of the inverted conical portion between the large diameter straight cylinder portion and the small diameter straight cylinder portion is 90 degrees or less. 3. The continuous air flow firing furnace for powder and granular material according to claim 1 or 2, wherein the large-diameter straight cylinder part and the small-diameter straight cylinder part are square cylinders. 4. The continuous air flow firing furnace for powder and granular material according to claim 1 or 2, wherein the inverted conical portion is in the shape of an inverted pyramid.