JP2007292379A - Manufacturing method and device of heat treated particle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat treatment furnace suitably used in manufacturing, in particular, foamed ceramic particles, by continuously performing batch treatment while utilizing the advantages of batch type heat treatment of a constant residence time, charging/recovering a particulate material as it is, and performing the heat treatment such as burning while keeping the advantages of the batch treatment, in a method of performing heat treatment on the particulate material by a medium fluidized bed. <P>SOLUTION: The particulate material is introduced to the medium fluidized bed in a reaction chamber, properly fluidized by the airflow applied within a range not scattering and not fusing/flocculating the treated particulate 6, and treated by heat while residing in the reaction chamber for a specific time. Then the heat treated particles are discharged to the outside of the medium fluidized bed in accompany with the airflow while increasing the airflow, and separated from the airflow by a separator 4 installed at a latter part of the fluidized bed to be recovered. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an improvement for continuous batch operation of a medium fluidized bed furnace capable of firing various powder materials, and a method and apparatus for producing heat treated particles, particularly high-performance fine artificial lightweight aggregate.

Conventional fluidized bed technology can be broadly divided into two types: batch type and continuous type. In the batch type, the mainstream is one in which the granular material to be treated is introduced into a fluidized bed container, and various treatments are performed to extract a treated product from the lower part or side surface of the container. As a special technique, there is a technique (see Patent Document 1) that promotes the discharge of target particles by lifting the lower layer in a piston manner after processing, but it is not general.
In the continuous type, the mainstream is one in which a fluidized bed container is provided with an outlet at the bottom or wall surface, one that uses overflow from the bed surface, or one that is constantly discharged to the top of the bed by an air flow.
Media fluidized bed using fluidized media (medium particles) is also used when the object is difficult to fluidize or when the heat medium effect or fluidization promotion is expected. In addition to conventional incinerators, expanded particles It is also applied to the manufacture of
However, for the continuation of the fluidized bed in which the object is a granular material, the medium particles are left in the layer and the target particles are sorted and collected, or after collecting both the target particles and the medium particles, the medium particles are sorted and collected. Must be returned to the fluidized bed. This selective collection of media particles is one of the factors that make it difficult to keep the batch fluidized bed continuous.

On the other hand, the apparatus for firing a foam differs depending on the foaming principle. In short-time foaming (in units of several seconds), there are an air flow layer and a material passing type medium fluidized bed (see Patent Document 3), and foaming for a long time ( In several minutes, rotary kilns are mainly used. Here, the short-expanded particles are mainly in the form of an ultra-light and low-strength balloon, and the long-expanded particles are slightly heavier and have a high-strength porous shape. In general, the longer the foaming time, the higher the independence of the bubbles and the easier it is to obtain a homogeneous foam. However, it is necessary to keep the particles in a molten state for a long time, and as the particles become finer, a fusing trouble is more likely to occur. Therefore, it has been difficult to produce a high-strength foam of 1 mm or less.
Japanese Patent Laid-Open No. 07-016457 JP 2004-293900 A JP 2001-278646 A

  The present invention has been studied in order to heat-treat a granular material by means of a medium fluidized bed, and makes it possible to continuously operate the batch while taking advantage of the batch-type heat treatment with a constant residence time. That is, the granular material can be input and recovered as it is, and heat treatment such as firing can be performed while maintaining the batch-type advantages. In particular, the present invention is to provide a method for producing heat-treated particles and an apparatus for producing heat-treated particles suitable for producing high-performance fine artificial lightweight aggregates.

In order to solve the above-mentioned problems, the present invention has the following configurations (1) to (10).
(1) The granular material is introduced into a medium fluidized bed in a reaction chamber formed by an air flow, the granular material is fluidized with the medium particles, heat treated to form heat treated particles, and then the air flow is increased. The heat treated particles are caused to be discharged from the medium fluidized bed along with the increased air flow, and the heat treated particles are recovered by a gas-solid separation device.
(2) The method for producing heat-treated particles according to (1), wherein an end time of the heat treatment is determined by an integrated temperature in which a temperature difference from a reference temperature is accumulated every unit time in the heat treatment.
(3) The fluidization state is any one of a uniform fluidization state and a bubble fluidization state, and the fluidization mode is at least one of a normal fluidized bed, a spouted bed, and a fluidized bed provided with external vibration. Or the manufacturing method of the heat-processed particle as described in (2).
(4) The method for producing heat-treated particles according to any one of (1) to (3), wherein the gas-solid separation device is a chamber, a filter, or a cyclone.
(5) The method for producing heat-treated particles according to any one of (1) to (4), wherein a flow rate of an air flow when the heat treatment is discharged out of the medium fluidized bed is increased stepwise or continuously.
(6) Of the above (1) to (5), volcanic glass, coal ash, incinerated ash, and various glasses for obtaining high-performance fine artificial lightweight aggregates are used as the main raw materials. The manufacturing method of the heat-processing particle | grains as described in any one.

(7) It has a reaction chamber filled with a fluid medium, an inlet for powdered material is provided in the reaction chamber, and a blower capable of changing the flow rate is provided at the bottom of the reaction chamber for dispersion An apparatus for producing heat-treated particles, characterized in that a hot air stream is fed into a reaction chamber through a vessel, and a separation device is provided following the reaction chamber.
(8) The heat treated particles according to (7), wherein the blower is provided separately for fluidizing the granular material and for discharging the heat treated particles out of the fluidized bed. Manufacturing equipment.
(9) The fluidized state of the granular material by the blower is a normal fluidized state, a fluidized state by a jet, a fluidized state in which a pulsation is added to an air flow, a swirl fluidized state, or external vibrations. The apparatus for producing heat-treated particles according to (7) or (8), wherein any one of fluidized states can be arbitrarily combined.
(10) The means according to (7) to (9), wherein the means for sending the airflow into the reaction chamber has control means for controlling the end point of the heat treatment by an integrated temperature that accumulates a temperature difference from a reference temperature every unit time. The manufacturing apparatus of the heat-processed particle baked granular material as described in any one.

The heat treatment in the present invention includes drying, firing, sintering, melting, chemical reaction, catalytic reaction, etc., as long as it produces a certain effect with heating, particularly for the production of high-performance fine artificial lightweight aggregates. Preferably used. In order to obtain lightweight aggregates, volcanic glass, coal ash, incinerated ash, and various glasses are used as raw materials.
In the present invention, medium particles are filled in the furnace body, and the medium particles are fluidized by an air flow blown into the furnace body to form a fluidized bed. The fluidized bed has good mixing properties of the powder material, high heat transfer due to particle collisions, in addition to the heat capacity effect of the fluidized medium, and has an excellent heat treatment effect. Naturally, in the fluidized state, the target particles should not be scattered, cause no fusion / aggregation, and should be set to a superficial velocity at which the mixed state of the target particles and the medium particles is maintained (no layer separation). is there. Due to the high particle shear effect of the fluidized bed and smooth fluidization due to fluidization of the medium, troubles of particle fusion can be prevented, and it is expected to sinter to particles of 1 mm or less, which has heretofore been difficult in the foam field. In general, the media particles have a specific gravity greater than that of the foam and the raw material particles, and thus fluidize around the dispersion plate at the bottom of the fluidized bed to prevent the raw material particles from staying between the disperser nozzles that are prone to fluidization failure. You can eliminate wearing problems. The object to be heat-treated can be arbitrarily held in the furnace for several minutes to several hours by the above-described fusion prevention technique. By inserting and immersing a temperature sensor such as a thermocouple in the fluidized bed, the product temperature can be measured in direct contact with the heat treatment target. In addition, since the temperature distribution in the layer is small, it is possible to treat the temperature data at several points in the layer as representative of the temperature of the product in the batch. This direct product temperature measurement is more accurate than a method of indirectly measuring the ambient temperature in other firing furnaces or the like. Rather than controlling under the heating conditions given from the outside, it is possible to cope with a control method based on a higher integrated temperature in which the end point of the heat treatment is determined each time from the temperature history of the current heat treated product.
The fluid medium is preferably alumina or mullite if it is heat-treated at 1000 ° C. or higher, and silica sand can be generally used if it is up to about 800 ° C. In addition, the shape of the fluid medium is desirably a spherical shape, and the size varies depending on the object to be processed, but is preferably in the range of 0.1 to 10 mm.

  In the case of a general continuous fluidized bed in which raw material supply and product recovery are always performed, the residence time distribution is generated in the product because the particles are nearly completely mixed. Among the foams whose specific gravity is proportional to product strength, the long-time foamed foam has a significant effect on the specific gravity of the product because the residence time significantly affects the specific gravity of the product. A product with a broad distribution containing low-strength particles of foam will be obtained. This excessively expanded particle becomes a defect in the secondary product, and also has a high risk of causing agglomeration trouble in the firing process. On the other hand, the mixing of heavy particles with insufficient foaming significantly impairs the weight reduction characteristics of the product. In general, in the field of lightweight concrete and mortar, a product with an unnecessary specific gravity distribution is not desired in order to carry out a thorough blending design in order to achieve both strength and lightness. For this reason, either a batch system with a constant residence time or a specific gravity separation between the inside and outside of the process is required. In any case, it is necessary to select and collect the product from the medium fluidized bed.

The air flow needs an air volume sufficient to fluidize the target particles and the medium particles together, and at the stage where the heat treatment is completed, the air flow is increased and the processed product (heat treated particles) is entrained in the increased air flow. It is necessary to produce an air volume necessary for separation from the fluidized medium by discharging it out of the particle layer (hereinafter referred to as an air sieve). Therefore, it is possible to switch the air volume with one blower, but it is preferable to provide a plurality of blowers with different air volumes and use them appropriately according to the timing. Wind sieving is a technology that separates powders by the difference in terminal speed at which each particle is discharged out of the bed by an updraft. Naturally, the particles to be discharged need to have a higher terminal velocity for reasons such as larger particle size and higher specific gravity than the remaining particles.
The fluidization state is either uniform fluidization or bubble fluidization. The bubble fluidization is a method in which air bubbles having a higher air volume than a uniform fluidization and bubbles having a stirring action are repeatedly generated, coalesced and broken.

The present invention was invented in order to combine batch-type high quality and continuous-type high productivity, and the following control method can also be employed for homogenization between batches. That is, in the present invention, the amount of heat until the completion of firing of the target particles to be used is set so as to be grasped as an integrated value (integrated temperature) of a temperature equal to or higher than the reference temperature. Switch to a sieve. When the air sieving is completed, the process proceeds to the next fluidized heat treatment stage. In this way, batch-type heat treatment is repeated as a continuous operation of the same furnace while maintaining homogeneity between batches.
There are two methods for setting the reference temperature: a method that is experimentally obtained from several preliminary experiments and a method that is theoretically obtained. In the theoretical case, the foaming technology estimated the viscosity at each temperature depending on the glass composition, and clarified the relationship between the reaction rate of the glass and the foaming agent in the bubble, the foaming gas generation rate, the bubble pressure and the viscosity of the glass. Above, we have to make an estimation formula. However, this requires advanced academic considerations and analysis. However, experimental calculation is desirable here from the viewpoint of being used at the manufacturing site. Preliminary verification tests are performed at the production site, and it is better to show the result of the product only with values such as time and temperature that can be measured directly rather than accurately measuring the specific heat of each material and analyzing it based on the calorific value. Convenient.
The present invention is characterized in that an integrated temperature obtained by accumulating such a temperature difference from the reference temperature per unit time is used as an index for determining the end time of the heat treatment. The unit time is usually 1 second, but depending on the granular material, the heat treatment time may be several tens of minutes. In such a case, the integrated temperature may be calculated with the unit time as 1 minute. Yes, any time can be set.

  In the conventional control, after confirming that the target temperature has been reached, the control is generally held for a certain period of time. For this reason, it has been impossible to correct the temperature history (the required time and temperature history up to the target temperature, the overshoot above the target temperature, and the temperature fluctuation while maintaining a constant temperature). In a foam in which the firing conditions severely affect the specific gravity and strength, such a difference in heating conditions between batches is undesirable. In the method for producing heat-treated particles of the present invention, an integrated temperature that accumulates the temperature difference from the reference temperature every second is introduced, and the firing is completed when the integrated temperature reaches a certain amount in each batch by computer control. Therefore, such differences in heating conditions can be unified from the viewpoint of integrated temperature, and quality fluctuations for each batch can be eliminated. The conventional control and the integrated temperature control are compared in FIG. 1, but the control is performed so that the area (integrated temperature) of the portion painted with a dotted line becomes equal. In the conventional control, if the control does not follow due to a difference in the charged amount or the start-up condition, the temperature is likely to fluctuate. This has resulted in the product quality being different even at the same set temperature.

  On the other hand, the integrated temperature control is corrected by automatically shortening the baking time if the temperature is more excessive than the set temperature. In addition, since it is judged that the temperature raising process also contributes to the firing, it is possible to finish the firing only by the temperature raising process without maintaining a constant temperature. However, the firing time can be shortened by several percent. Thereby, short-time high-temperature firing and long-term low-temperature firing are unified, and it is possible to flexibly cope with a case where the temperature rise is slow due to the start-up of the furnace or a case where the amount of preparation is small and the temperature rise is fast. Moreover, in the manufacturing method of the heat-treated particle | grains of this invention, since the temperature in a fluidized bed can be measured with a thermocouple, it is possible to measure a temperature history in detail.

  As shown in FIG. 2, the relationship between the integrated temperature and the specific gravity of the foam should be obtained in advance in a preliminary test. Here, the reference temperature serving as a threshold value is defined by raising and lowering the value so that the correlation between the integrated temperature and the specific gravity can be obtained most from a plurality of temperature histories. In particular, several types of approximate curves may be prepared and determined so that the R-square value is maximized. The most reliable, reproducible and simple approximation curve should be obtained at the production site. This approximate curve is input to a computer, and when a target foam specific gravity is input, a system for automatically calculating the necessary integrated temperature is obtained. Such integrated temperature control is a system that can be achieved because it is a fluidized bed in which a temperature sensor (thermocouple) can be inserted directly into the fluidized bed and accurate product temperature measurement is possible.

A separation means for separating and collecting the target particles and the medium particles flying along with the target particles from the air stream is provided at the subsequent stage of the fluidized bed furnace. As the separation means, various gas-solid separation means such as a large chamber, a filter, and a cyclone are used. In the separation means, the flow rate of the airflow may be changed according to the progress of the separation.
In a wind sieve, when fine particles (foam) and coarse particles (fluid medium) to be collected are used, the coarse particle jumping flux (kg / m ² s) is not only the superficial velocity (m / s) but also the fine particles. Is also strongly influenced by the pop-out flux (kg / m ² s). That is, if the flow of the ejected fine particles is seen from the coarse particles, it influences like a fluid, and the tendency of the coarse particles to jump out accompanying the flow of the fine particles increases. In addition, since the fine particles jump out more in the early stage of recovery with a high particle concentration, there is a high risk of accompanying coarse particles. Therefore, by controlling the air volume at the initial stage of recovery, controlling the mass flow rate of the fine particles to a certain low level, and gradually increasing the air volume to finally show high separation efficiency when this has decreased, It is important to prevent the particle mass flux from increasing. This makes it possible to reduce the entrainment scattering of the medium particles.

  As a heating method, not only a burner for blowing a normal fuel / oxygen source, but also an electric furnace, oxygen / air blowing into a combustible gas excess atmosphere, heavy oil spraying, etc., or a combination thereof may be used. It is also possible to cause two-stage combustion by injecting air or oxygen gas further in the fluidized bed portion after incomplete combustion with excess fuel from the hot stove at the bottom of the furnace. As a result, the air nozzle to be inserted into the fluidized bed does not require an ignited portion, the structure is simple, and consumption is suppressed by the nozzle cooling effect by the airflow. If high-concentration oxygen is blown into the two-stage combustion, the sensible heat of the combustion exhaust gas is reduced, so that it is possible to achieve a high-temperature fluidized bed exceeding 1200 ° C.

  A porous plate such as a dispersion plate used for a fluidized bed has a heat blocking effect. That is, when high-temperature gas is circulated through the perforated plate, the radiant heat of the high-temperature gas is reflected by the perforated plate, and heat can be transferred to the downstream side (upper part) only by convective heat transfer. Conversely, the temperature of the upstream portion rises due to the reflected radiant energy. This phenomenon is sometimes used to keep the combustion area warm and improve the thermal efficiency. However, when preheating is performed in a hot stove like fluidized bed firing and heat is supplied to the fluidized bed via a dispersion plate, The amount of heat supplied from is reduced. This phenomenon is remarkable in a temperature region of 800 ° C. or higher where radiant heat transfer is dominant over convective heat transfer. Therefore, in fluidized bed firing having a dispersion plate of 1000 ° C. or higher, first, two-stage heating in a hot air furnace and a fluidized bed must be employed.

As a method for charging the particles, it is desirable to input from the upper part of the fluidized bed. Those having a low risk of fusion can be blown from the lower part of the fluidized bed or before the dispersion plate. As for the position of the burner in the fluidized bed, it is desirable to insert the burner attached to the lower part of the dense layer of the fluidized medium as much as possible, although it depends on the degree of fusion adhesion.
Combustion on a free board where particles are not rich should be set to a temperature-retaining level.

Of course, the medium particles have a terminal velocity larger than that of the target particles. This is because, depending on the emergency stop or operating conditions, the medium particles and the target particles may be extracted in a mixed state and classified by a sieve or the like. The medium particles are generally higher in specific gravity and coarser. However, depending on the situation, it is necessary to make adjustments such as making mullite particles having a specific gravity lower than that of alumina and increasing the particle size accordingly. On the other hand, in order to obtain a good fluidization state, the fluidization start speed of the medium particles and the target particles should not be too different.
It should also be noted that the specific gravity and particle size of foamed materials differ greatly before and after foaming. When the amount of particles equivalent to the height of the stationary layer more than twice the tower diameter is fluidized, the particle layer and the air layer may be separated into a slugging fluidized state in which the piston moves. It becomes difficult to control the conversion. For foams and the like, the height of the stationary layer may double before and after foaming, so the raw material filling amount is preferably about the same as the tower diameter.

  In the present invention, the medium fluidized bed has an anti-fusing effect, and heat treatment with melting can be performed. Thereby, for example, it is easy to fire fine particles of 300 μm or less, which has been difficult in the field of lightweight aggregates, and commercialization of such fine particles with a single particle size is also possible. Temperature control is facilitated by the heat transfer characteristics of the medium particles and the inherent temperature uniformity of the fluidized bed. In addition, since the target particles can be fluidized and a sensor such as a thermocouple can be inserted there, the temperature of the target particles can be measured directly. This makes it possible to accurately measure the thermal history of the target powder. Batch firing is accompanied by a temperature history, but in addition to the above accurate thermal history measurement, the firing between batches can be made more uniform by controlling the integrated temperature above a certain temperature. Therefore, it is possible to provide an efficient heat treatment by exhibiting the characteristics of high productivity by the continuous heat treatment while having the advantage of high homogeneity due to the constant residence time in the batch in the heat treatment of the batch method. It is particularly effective for the production of high-performance fine artificial lightweight aggregates.

  Hereinafter, the present invention will be described with specific examples. FIG. 3 shows an example of an apparatus suitable for carrying out the present invention. In the figure, 1 is a hot blast furnace part for preheating and dispersing fluidized air, 2 is a concentrated layer part for forming a fluidized bed, and 3 is a free board part in which particles are repeatedly scattered and dropped from the surface of the layer. As a cylinder. 4 is a cyclone as a gas-solid separation device, and it is appropriate to connect between the cyclone 4 and the fluidized bed portion with a bellows 5 or the like that reduces thermal expansion and contraction of the device. The cooling layer 16 has not only a product cooling function but also a quality control function.

  As the firing furnace, (1) preheating period, (2) raw material charging / temperature recovery period, (3) fluidizing heat treatment period, and (4) wind sieving period are repeated in order. In the cooling layer, the (1) ′ input period is started in synchronization with the wind sieve period of (4), and thereafter (2) ′ cooling period, (3) ′ quality control period, and (4) ′ discharge period. Repeat. Here, the cooling time is adjusted so that the batch interval between the firing furnace and the cooling layer becomes equal. In addition, there are mechanisms that can take countermeasures at various locations to cope with emergency stops and non-standard products.

  The dense layer 2 of the baking furnace is charged with mullite medium particles 6 having a particle size of 1.0 to 0.5 mm. This is present to some extent depending on the raw material and the foam 7 to be added later and fluidization. Further, bubbles 8 are generated with fluidization. In the present invention, the flow rate of the hot air is set to 0.5 to 1.2 m / s (excess gas flux 0.3 to 0.9 m / s). More preferably, it is 0.9 m / s or less (excess gas flow velocity 0.7 m / s or less).

  12 is a dispersion plate, and 13 is a packed bed type disperser, which performs gas dispersion in order to fluidize the entire fluidized bed. Since the temperature of the fluidized bed is raised to 1100 ° C. or higher, it is difficult to use the disperser directly below the fluidized bed because of its heat resistance in the case of an integrally molded product of metal or various refractories. Therefore, the disperser 13 in the portion in direct contact with the particles employs a packed bed type disperser made of ceramic particles that can be replaced and has high heat resistance. Alumina balls with a diameter of 3-4 cm were filled. The dispersion plate 9 has a funnel-shaped extraction portion, and the fixed layer 13 is held by a shutter or the like indicated by 22. When the particles are discharged during an emergency stop or the like, the fixed layer particles 13, the medium particles 6, the raw materials and the expanded particles 7 can be recovered by opening the shutter 22. Moreover, if air is blown into the layer from this extraction pipe to make the air dispersion more uniform, or if this air volume is excessively increased, a jet fluidized bed with a strong upward flow can be formed in the center of the layer. .

  In the fluidizing heat treatment period, the air blown by the fluidizing blower 9 is adjusted by the flow meter 10 and burned by the burner 11, passed through the cone type gas disperser 12 and the packed bed type disperser 13, and then into the fluidized bed 2. Circulate. During the wind sieve period, the wind sieve blower 14 is also operated, and the foam 7 is transported from the fluidized bed 2 to the cyclone 4 where it is separated from the airflow and then dropped into the cooling layer 16 via the branch valve 15. The fluid is recovered from the recovery port 25 along the inclined dispersion plate 17 while fluidizing. The wind sieve blower 14 and the fluidizing blower 9 may be one that can change speed, or may be a plurality that can respond to changes in speed. In the preheating period in which the foam particles 7 do not exist so much in the layer, as long as the fluidization of the medium particles 6 can be maintained, the air volume of the burner 11 may be reduced to reduce the sensible heat takeout and improve the thermal efficiency.

  A heavy oil burner 18 is inserted into the layer, and temperature control is performed by a thermocouple 19 inserted in the medium particles 6 and the foam 7. The powder material is charged through a charging hopper 20 and from a charging nozzle 21. It is important to arrange the thermocouple 19 so as to be immersed in the fluidized bed portion in two states, that is, only the medium layer and the state in which the foam remains in the layer. The thermocouple inserted into the foam 7-layer part calculates the required integrated temperature after entering the heat treatment stage, checks the end point of the heat treatment, and instructs the blow sieve 14 for the result. Yes.

23 is a peephole for fluidization state observation. Reference numeral 24 denotes a pressure sensor probe, which can be measured with a differential pressure sensor. The fluidized bed is mainly used for judging the fluidized state in the bed.
The branch valve 15 is used to discharge unfoamed particles and wear powder that rarely scatter during the fluidization heat treatment period so as not to be introduced into the cooling layer. During the air sieve period, the cooling layer and the cyclone are connected. Let In addition, non-standard products can also be guided out of the product line when collecting wind sieves during an emergency stop.

  Although the cooling layer 16 may be in any fluidized state in the cooling process, it is desirable that the product be managed in a uniform fluidized state in order to perform simple specific gravity measurement of the foam and segregation of the fluid medium. . Here, from the section differential pressure of the cooling layer pressure sensor probe 24, ΔP (section pressure loss) ≈ρ (foam apparent density) × g (gravity acceleration) × ε (particle space ratio) / ΔL (section length) From the relationship, the apparent density of the foam fluidized in the section can be estimated. This enables real-time measurement of the degree of foaming of the product and in-line quality control. In addition, by measuring the differential pressure from the atmospheric pressure, the total amount of the recovered product can always be confirmed, and a decrease in yield due to a fusing problem and accumulation in the layer can be detected. Moreover, it is possible to settle and separate medium particles having a high specific gravity by uniform fluidization, and only the foam can be recovered from the plurality of outlets 25 having different heights. As a result, the medium particles mixed with the air sieve can be further removed, and the purity of the product can be increased.

  Although FIG. 3 shows a heating method using a burner, a heating method using an electric furnace may be adopted by arranging a tubular electric furnace in a fluidized bed furnace. When raw materials with low melting points such as waste glass are used, the firing temperature can be greatly reduced, and the choice of heating method based on the furnace material / structure, burner, etc. is expanded. In particular, in fluidized bed firing at 1000 ° C. or lower, firing is possible only by supplying high-temperature combustion gas from a hot air furnace below the fluidized bed.

Hereinafter, a specific Example is described about the example which manufactures a lightweight aggregate with the said apparatus.
As the packed bed type disperser 13, alumina balls (diameter 2-3 cm) were filled on the dispersion plate 12 and used inside the fluidized bed. The thermocouple 19 was measured mainly at two points, the lower part of the fluidized bed (upper part in the medium particle layer) and the middle of the fluidized bed (near the center of the foam particle layer).

(Combination of raw materials)
The following raw materials were mixed with a ribbon mixer, and the mixture was pulverized with a tube mill to an average particle size of 15 μm and granulated with 15 to 17 wt% added water. Later, after drying with a rotary dryer, the particles classified from 300 μm to 600 μm were coated so as to be coated with alumina powder (average particle size 1.1 μm) to obtain main raw material particles. The medium particles used were ITON CERATECH aluminum knight balls 0.5-1 mm standard products classified to 0.6-1 mm.
Anti-fluorite ground powder (average particle size 56μm) 100wt%
Bentonite 7.0wt%
Ultra fine SiC 0.4wt%

When the inside of the medium fluidized bed 6 reaches about 1050 ° C. (preheating period), the raw material particles are charged into the firing furnace 2 from the charging port 21. A fluidized state is maintained in the furnace together with the fluidized medium 6 and heating is performed (input / temperature recovery period).
In the meantime, the temperature is integrated from the time when the reference temperature is exceeded by a computer system connected to the thermocouple 19 in the material rich portion in the furnace (fluidization heat treatment period). When the integrated value reaches the target, the air sieve blower 14 is started to increase the air volume, the temperature is lowered, the sintering is stopped, and the sintered product is simultaneously air sieved and transferred to the cyclone 4 (wind sieve period). At this time, some of the fluid medium 6 moves to the cyclone 4 together with the sintered product.

In the stage where the wind sieve has broken down, in order to enter the next firing stage, a new powder material is introduced from the inlet 21 and the above firing process and wind sieve process are repeated. Thereby, batch type continuous operation is achieved.
The hot stove 1 is easily heated excessively by heat shielding, and the heat supply efficiency to the downstream is lowered, so the heavy oil supply amount is controlled so that it is always 1000 ° C. or lower. The superficial velocity of fluidization is 0.5 to 0.9 m / s.

  The wind sieve blower 14 is activated and raised to the target value over 1 minute from the start. The collection time is 2-3 minutes. The superficial velocity is about 2.6 m / s (at 1000 ° C.), and when combined with the fluidizing blower, a flow rate of about 3.5 m / s is obtained. This is lower than the final velocity 8.0 m / s of the medium particles (0.5-1 mm apparent specific gravity 3.75) at 1000 ° C., and the final velocity 3 of the foam (0.6-1 mm apparent specific gravity 0.8). Higher than 2 m / s.

(result)
Without causing particle fusion, a foam having a specific gravity of about 0.7 to 1.4 was obtained as shown in FIG. It has been demonstrated that the particle size can be fired in the same batch from 100 μm to approximately 1.2 mm. This is a product lineup that spans three types: No. 3 (0.6-1.2 mm), No. 4 (0.3-0.6 mm), No. 5 (0.15-0.3 mm). . Particles of 100 μm or less were discharged from the cyclone even during firing, and firing was insufficient.

An example of the temperature rise history is shown in FIG. As a result, although the temperature of the hot stove 1 is reduced from about 1100 ° C. to about 600 ° C. with a wind sieve, the temperature recovery is quick because the heat capacity is low. Although the temperature inside the layer is lowered to nearly 1000 ° C. by the air sieve, it is almost the same as the raw material input and is not fatal in the whole process.
When our No. 3 to No. 5 products were fired simultaneously, expanded particles of 1 mm or more remained in the layer, which was less than 10% of the total weight. Further, among the particles collected at that time, the mixed medium particles accounted for about 10% by weight. Most of them have been mixed into the recovered No. 3 product.
Therefore, when aiming at perfect separation with this technology, firing is centered on No. 4 (0.3-0.6 mm) and No. 5 (0.15-0.3 mm) against a fluid medium of 0.6-1 mm. In that case, it has been confirmed that both in-layer residuals and contamination can be reduced to 0.5 wt% or less.

(I) Verification of heating degree control A firing test was conducted with a bench furnace that was the predecessor of the pilot plant. Propane gas combustion and heater heating to the core tube were combined. FIG. 2 is a curve of various product specific gravity and accumulated temperature obtained in the aggregate firing by the fluidized bed bench furnace, and the error is only about 3%.

(II) Correspondence to various materials ・ Waste glass Waste glass (brown bottle glass) 95wt% Bentonite 5wt% SiC 0.3wt%, 840 ° C, 10 minutes hold, specific gravity 0.84, particle size 600-1200μm Particles could be fired. Here, the glass beads were fired only by heating with a hot stove.
-Coal fly ash Fly ash 70 wt% Waste glass 30 wt% Bentonite 5 wt% SiC 0.15 wt% A specific gravity of 1.29 and a particle size of 600-1200 µm could be fired at 1170 ° C for 20 minutes. Both the electric furnace and the air blowing method in an atmosphere with excess combustible gas were performed, and foam firing was confirmed.

  In the above embodiment, the production of the artificial lightweight aggregate has been described, but it can also be applied to a sintering process, a spheroidization / smoothing process by melting, and the like.

An example of an integrated temperature control method that determines the end point of firing based on an integrated value above a certain temperature Graph showing the correlation between accumulated temperature and product specific gravity Example apparatus for carrying out the present invention Graph showing the relationship between specific gravity and strength of products according to the present invention Temperature history of continuous batching by wind sieving process

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Hot-blast furnace part 2 Fluidized bed thick layer part 3 Free board part 4 Cyclone 5 Bellows 6 Media particle 7 Foam 8 Bubble 9 Fluidizing blower 10 Flowmeter 11 Burner 12 Cone type gas disperser 13 Packed bed type disperser 14 Wind sieve Blower 15 Branch valve 16 Cooling layer 17 Inclined dispersion plate 18 Heavy oil burner 19 Thermocouple 20 Input hopper 21 Input nozzle 22 Shutter 23 Peep hole 24 Pressure sensor probe

Claims (10)

The granular material is introduced into a medium fluidized bed in a reaction chamber formed by an air flow, the granular material is fluidized with the medium particles, heat treated to form heat treated particles, and then the air flow is increased to increase the heat treatment. A method for producing heat-treated particles, characterized in that the particles are entrained in the increased air flow and discharged out of the fluidized bed of the medium, and the heat-treated particles are recovered by gas-solid separation means. 2. The method for producing heat treated particles according to claim 1, wherein in the heat treatment, the heat treatment end time is determined by an integrated temperature obtained by accumulating a temperature difference from a reference temperature every unit time. The fluidization state is any one of a uniform fluidization state and a bubble fluidization state, and the fluidization mode is at least one of a normal fluidized bed, a spouted bed, and a fluidized bed provided with external vibration. A method for producing heat-treated particles. The method for producing heat-treated particles according to any one of claims 1 to 3, wherein the gas-solid separation means is any one or more of a chamber, a filter, and a cyclone. The method for producing heat-treated particles according to any one of claims 1 to 4, wherein a flow velocity of an air flow when discharging the heat-treated particles out of the medium fluidized bed is increased stepwise or continuously. The volcanic glass, coal ash, incineration ash, and various glasses for obtaining a high-performance fine artificial lightweight aggregate as the powder material are at least a main raw material. A method for producing heat-treated particles. It has a reaction chamber filled with a fluid medium, an inlet for powdered material is provided at the upper part of the reaction chamber, a blower capable of changing the flow rate is provided at the lower part of the reaction chamber, and a disperser is provided. An apparatus for producing heat-treated particles, characterized in that an air stream is fed into the reaction chamber through a separator and a separation device is provided following the reaction chamber. The apparatus for producing heat treated particles according to claim 7, wherein the blower is provided separately for fluidizing the powder particles and for discharging the heat treated particles out of the fluidized bed. The fluidized state of the granular material by the blower is a normal fluidized state, a fluidized state by a jet, a fluidized state in which a pulsation is added to an air current, a swirl fluidized state, or a fluidized state to which external vibration is applied, The apparatus for producing heat-treated particles according to claim 7 or 8, wherein any of the above can be arbitrarily combined. The means for sending the air stream into the reaction chamber has a control means for controlling an end point of the heat treatment by an integrated temperature obtained by accumulating a temperature difference from a reference temperature every unit time. Heat treatment particle manufacturing equipment.