JP3721204B2 - Rice husk ash manufacturing method and manufacturing apparatus - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a method and apparatus for producing rice husk ash using a fluidized bed furnace.
[0002]
[Prior art]
When the rice husk is burned at an appropriate temperature of 600 to 900 ° C., amorphous ash containing 80% or more of silicon oxide (SiO ₂ ) and having high pozzolanic activity is obtained. When this amorphous ash is used as an admixture or as a substitute for cement in concrete and mortar, there are many advantages such as strength enhancement. For example, the Concrete Engineering Annual Report, 1993, Vol. It is already known by papers such as “Highly active rice husk ash manufacturing method and properties of concrete using the same” by No. 1 Sugita et al. And “Basic properties of mortar mixed with rice husk ash” by Harada et al.
[0003]
The quality of rice husk ash depends mainly on the pozzolanic activity and the amount of unburned carbon. That is, when the combustion temperature is too high, minerals such as cristobalite are generated and the pozzolanic activity decreases. If the combustion temperature is too low, or if the residence time in the furnace is too short, the amount of unburned carbon increases.
[0004]
When rice husk ash is used in concrete or mortar, if the pozzolanic activity of rice husk ash is low, for example, strength enhancement decreases. Moreover, when there is much amount of unburned carbon, it will be necessary to use a large amount of admixture in order to deteriorate the air entrainment property and reduce the effect of concrete admixtures, such as a water reducing agent. Use of a large amount of an admixture is not preferable in terms of physical properties and cost of the concrete, and also causes a problem of coloring the concrete surface.
[0005]
Therefore, when rice husk ash is used for concrete or mortar, it is necessary to minimize the amount of unburned carbon in rice husk ash while maintaining high pozzolanic activity. Conventionally, a fluidized bed type as one of the methods for producing rice husk ash has been disclosed, for example, as JP-A-60-36360.
[0006]
[Problems to be solved by the invention]
In such a conventional method, when the rice husk is directly charged into the fluidized bed and combusted, the flammable volatile components of the rice husk are ignited and burnt rapidly, so the rice husk inlet side in the furnace becomes locally hot. . When this local high temperature exceeds about 900 ° C., the ash that should be amorphous is crystallized, and the pozzolanic activity of the ash is lowered. Therefore, in order to keep the local high temperature within the allowable range, the amount of rice husk input is restricted, and the increase in the processing amount is not easy. On the other hand, the temperature is relatively low on the opposite side of the rice husk inlet, and the rice husk is not sufficiently burned, resulting in ash with a lot of unburned carbon, which is a quality problem.
[0007]
As a method for obtaining rice husk ash having high activity even at a high temperature, the “two-stage incineration method” is known, for example, from the literature such as Sugita. When this method is applied to a fluidized bed furnace, the quality of rice husk ash is thought to improve, but thermal loss increases, and a large amount of combustible gas is generated in the carbonization process of rice husk. The problem that it becomes difficult occurs.
[0008]
Accordingly, an object of the present invention is to solve the problems in the prior art in view of the above-described circumstances, and to efficiently treat large amounts of amorphous rice husk ash with low unburned carbon and high pozzolanic activity. It is in providing the manufacturing method and apparatus of this.
[0009]
[Means for Solving the Problems]
In order to achieve the above-described object, according to the present invention, a method for producing rice husk ash uses rice husks in a fluidized bed furnace as a heat source in a preceding stage of the fluidized bed furnace without directly contacting the combustion husks with the rice husks. Preheating is performed, and a combustible gas generated when the rice husk is preheated is introduced at a plurality of locations above the fluid medium in the fluidized bed furnace and burned to make the furnace temperature uniform .
[0010]
Further, according to the present invention, apparatus for producing chaff ash provided a preheating device for preheating the chaff without contacting the flue gas of the fluidized bed furnace in front of the fluidized bed furnace as a heat source directly to the combustion exhaust gas chaff In addition, a combustible gas combustion means for making the furnace temperature uniform by introducing a plurality of combustible gases generated when the rice husk is preheated by a preheating device into a fluidized bed furnace and burning them at a plurality of locations. It is characterized by providing .
[0011]
[Action]
According to the present invention, since the rice husk is pre-carbonized by preheating and the combustible gas is removed, rapid combustion of the rice husk does not occur in the fluidized bed furnace, and for this reason, localized in the furnace. Since high temperature part does not occur and crystallization of rice husk ash can be avoided, highly active ash can be obtained, and because the calorific value of rice husk from which combustible gas has been removed is low, Even if the input amount to the fluidized bed furnace is increased, the inside of the furnace does not become excessively hot. That is, the processing amount of rice husk ash can be increased. Furthermore, the most important feature is that an appropriate amount of the combustible gas generated by the preheating of the rice husk is introduced into an appropriate place in the fluidized bed furnace and burned, thereby providing a temperature range suitable for carbon combustion over a wide range in the furnace. As a result, the amount of unburned carbon can be reduced. Moreover, in order to effectively reuse the combustible gas generated by preheating and the combustion exhaust gas of the fluidized bed furnace as a heat source, effects such as improvement in thermal efficiency can be obtained.
[0012]
Other objects, features and advantages of the present invention will become apparent from the following detailed description of the present invention, taken in conjunction with the accompanying drawings.
[0013]
【Example】
1 and 2 of the drawings show an embodiment of a production apparatus for carrying out the rice husk ash production method of the present invention. As shown in the figure, the rice husk ash production apparatus uses a fluidized bed furnace 1 having a fluidized medium 16 heated by a heat source 20 and an exhaust gas provided in a preceding stage of the fluidized bed furnace 1 to preheat the rice husk from the hopper 3. A preheating device 2 as a heat source, a cyclone 5 connected to the fluidized bed furnace 1 so as to separate the burned rice husk ash and the exhaust gas, a combustion box 6 for burning excess combustible gas, and a combustion box 6 It is mainly comprised from the dust collector 7 connected.
[0014]
In such a rice husk ash production apparatus of the present invention, the fluid medium 16 in the fluidized bed furnace 1 is preliminarily brought up to a temperature at which the rice husks can self-combust by a heat source 20 using coal, heavy oil, kerosene, gas or the like as combustion means. The temperature is raised. As the heat source 20, an electric heater or the like can be used in addition to the coal, heavy oil, kerosene, gas and the like. In addition, fuel such as coal, heavy oil, kerosene, and gas, which are combustion means of the heat source 20, is supplied to the heat source 20 by an appropriate means such as a pump, and fluidized air is introduced into the fluidized bed furnace 1 by the blower 21. Supplied.
[0015]
The hopper 3 is filled with rice husk and is supplied to the preheating device 2 by a predetermined amount by a conveyor such as a rotating screw or other similar supply device and preheated to a required temperature. A heat pipe 22 is provided in the preheating device 2, and the exhaust gas separated from the husk ash and the exhaust gas is separated by the cyclone 5 in the cyclone 5 and supplied through the valve 9 to preheat. The rice husk in the apparatus 2 is preheated to a required temperature, for example, 300 to 500 ° C. This preheat temperature of the rice husk is measured by a thermometer 18. The rice husk preheated by the preheating device 2 is put into the fluidized bed furnace 1 by a predetermined amount by a supply device such as a screw conveyor.
[0016]
The input amount of the preheated rice husk fluidized bed furnace 1 is determined so that the value of the thermometer 17 for measuring the temperature in the fluidized bed furnace 1 such as a thermocouple is an appropriate temperature, for example, 600 to 900 ° C. Is preferred. In the fluidized bed furnace 1, the rice husk is burned by the fluid medium 16 heated in advance by the heat source 20 to become rice husk ash, and the rice husk ash generated by the combustion in the furnace is scattered from the top of the furnace together with the exhaust gas. The cyclone 5 is then separated into rice husk ash and exhaust gas, and the rice husk ash is recovered. The exhaust gas separated from the rice husk ash is sent to the heat pipe 22 of the preheating device 2 through the exhaust gas introduction valve 9 to preheat the rice husk in the preheating device 2. A part of the exhaust gas is sent from the surplus exhaust gas discharge valve 10 to the combustion box 6.
[0017]
Thus, the preheating of the rice husk in the preheating device 2 is performed by the indirect heating method in the illustrated embodiment, but can also be performed by the direct heating method in direct contact with the exhaust gas in addition to the indirect heating method. Since the generated combustible gas and the exhaust gas are mixed, it is difficult to use the combustible gas, and the indirect heating method is more advantageous from the viewpoint of controllability of the preheating temperature.
[0018]
Further, the combustible gas generated in the preheating device 2 is guided to a plurality of combustible gas introduction jackets 14 provided around the outside of the fluidized bed furnace 1 by the pump 19 through the combustible gas introduction valve 4. In addition, the flow rate is controlled by the combustible gas introduction valve 13 (FIG. 2), and it is introduced into the furnace and burned. The opening degree of the combustible gas introduction valve 13 is individually controlled so that the values of the in-furnace thermometers 17 for measuring the in-furnace temperature provided at several places in the furnace are uniform. Although the control of the combustible gas introduction valve 13 may be performed manually, it is preferable to perform automatic control in conjunction with the in-furnace thermometer 17.
[0019]
The surplus combustible gas in the preheating device 2 is sent to the combustion box 6 through the surplus combustible gas discharge valve 12 and the transport pipe 11, and after being combusted in the combustion box 6, it is mixed with the cooling air 8 and cooled. Then, it is discharged through a dust collector 7 such as a bag filter.
[0020]
In addition, when the temperature in the preheating device 2 rises excessively and the rice husk self-combusts, or when the concentration of the combustible gas enters an area where danger such as an explosion may occur, an inert gas is supplied. It is preferable to control the temperature or gas concentration by introducing an inert gas such as CO ₂ or N ₂ from the valve 15 for use.
[0021]
FIG. 3 shows an example of the temperature distribution in the fluidized bed furnace obtained from the illustrated embodiment of the present invention. For comparison, FIG. 4 shows an example of a fluidized bed furnace according to the prior art, and FIG. 5 shows an example of a temperature distribution in the fluidized bed furnace according to the prior art. In the figure, (1), (2), (3), etc. indicate temperature measurement positions. From FIG. 3 and FIG. 5, the conventional technology has a maximum temperature difference of 280 ° C. in the vertical direction and a maximum temperature of about 150 ° C. in the same horizontal plane. It is difficult to obtain active and low unburned carbon rice husk ash.
[0022]
On the other hand, in the present invention, the temperature difference in the vertical direction in the furnace is 60 ° C. at the maximum and about 20 ° C. in the same horizontal plane, which is an ideal condition for obtaining highly active and low unburned carbon rice husk ash. It is. In addition, the present invention provides a 30% increase in throughput compared to the prior art, and furthermore, the amount of unburned carbon in the obtained rice husk ash was 2.5 to 3.5% in the prior art. On the other hand, in the present invention, it was 2.0% or less, and a clear decrease in the amount of unburned carbon was observed.
[0023]
【The invention's effect】
As described above, according to the present invention, the temperature distribution in the furnace can be made uniform by a simple manufacturing method and manufacturing apparatus, and a high pozzolanic activity and low unburned carbon rice husk ash is produced in large quantities and extremely efficiently. It is clear that it can be manufactured and is superior and superior to the conventional technology in terms of thermal efficiency, quality of rice husk ash, throughput, etc. The high quality rice husk ash produced in this way has an appropriate particle size. In addition to being pulverized and used as a high-performance concrete admixture, etc., it can be used effectively as a hydraulic cement, a hardener, a molding material, etc. by utilizing its high pozzolanic activity.
[Brief description of the drawings]
FIG. 1 is a schematic view showing an embodiment of a production apparatus for carrying out the method for producing rice husk ash according to the present invention.
FIG. 2 is a partial cross-sectional view of the fluidized bed furnace portion of FIG.
FIG. 3 is a diagram showing an example of temperature distribution in the fluidized bed furnace when rice husk ash is produced using the production apparatus of FIG. 1;
FIG. 4 is a schematic diagram showing a manufacturing apparatus according to the prior art.
FIG. 5 is a diagram showing an example of temperature distribution in a fluidized bed furnace when rice husk ash is produced using a production apparatus according to the prior art.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Fluidized bed furnace 2 Preheating apparatus 3 Hopper 4 Flammable gas introduction valve 5 Cyclone 6 Combustion box 7 Dust collector 9 Exhaust gas introduction valve 10 Excess exhaust gas discharge valve 12 Surplus combustible gas discharge valve 13 For introducing combustible gas Valve 14 Flammable gas introduction jacket 15 Inert gas supply valve 16 Fluid medium 17 Furnace thermometer 18 Preheating device thermometer 19 Pump 20 Heat source 21 Blower 22 Heat pipe

Claims (2)

In the method for producing rice husk ash using a fluidized bed furnace,
Preheating the rice husk in the first stage of the fluidized bed furnace using the flue gas from the fluidized bed furnace as a heat source without bringing the flue gas into direct contact with the rice husk ,
A method for producing rice husk ash, characterized in that a combustible gas generated when the rice husk is preheated is introduced at a plurality of locations above the fluid medium in the fluidized bed furnace and burned to make the furnace temperature uniform . In rice husk ash production equipment using a fluidized bed furnace,
Combustible for generating a pre-stage in the flue gas as a heat source a combustion gas of the fluidized bed furnace of the fluidized bed furnace Rutotomoni provided preheating device for preheating the chaff without direct contact with the chaff, when the preheated chaff by the preheating device An apparatus for producing rice husk ash, comprising combustible gas combustion means for uniformizing the temperature in the furnace by introducing a plurality of gasses above the fluid medium in the fluidized bed furnace and burning them.

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