JP6948190B2 - Method of manufacturing modified fly ash and fly ash reformer - Google Patents

Description

The present invention provides a method for producing modified fly ash obtained by removing unburned carbon from fly ash containing unburned carbon discharged from a pulverized coal combustion boiler or the like, and unburned carbon from the supplied fly ash. Regarding a fly ash reformer for removing.

Coal ash (fly ash) generated from pulverized coal combustion boilers of coal-fired power plants is used as an admixture material for concrete. However, the amount of fly ash that is effectively used as an admixture for concrete is only about 1% of the total amount generated. One of the reasons for this is considered to be the problem of unburned carbon contained in fly ash.

When fly ash containing a large amount of unburned carbon is used as an admixture material for concrete, the unburned carbon adsorbs various admixtures added during the production of concrete, and the amount of admixtures added increases. .. Further, in a hardened concrete body in which fly ash containing a large amount of unburned carbon is used, unburned carbon is exposed on the surface of the hardened body, and the aesthetic appearance is spoiled.

Therefore, for example, in Patent Document 1, fly ash is supplied to an externally heated rotary kiln, and the supplied fly ash is heated by heat and combustion gas applied from a heating portion of the rotary kiln to generate unburned carbon contained in the fly ash. There is a known method of burning and removing.

Japanese Unexamined Patent Publication No. 2005-207627

According to the method using an externally heated rotary kiln as in Patent Document 1, the fly ash is indirectly and gently heated, so that the fly ash is coarsened by fusion of the fly ash particles due to overburning. It is possible to heat the fly ash to an appropriate temperature at which unburned carbon in the fly ash burns (self-combustion) while suppressing the burning.

However, since it takes time to heat the fly ash to a temperature at which unburned carbon starts combustion, there is a problem that the fly ash cannot be reformed stably and efficiently.

The present invention has been made in view of the above problems, and a method for producing a modified fly ash using an externally heated rotary kiln, which can stably and efficiently modify the fly ash, and a method for producing the modified fly ash. It is an object of the present invention to provide a fly ash reformer using an externally heated rotary kiln.

As a result of diligent studies to achieve the above object, the present inventors have obtained a high-quality modification in which unburned carbon is sufficiently burned and removed by supplying preheated fly ash to an externally heated rotary kiln. We have found that fly ash can be stably obtained, and have completed the present invention.

That is, in the method for producing a modified fly ash of the present invention, a preheating step of preheating the fly ash in a non-self-combustion environment in which the unburned carbon contained in the fly ash does not self-combustion and a fly ash that has undergone the preheating step are external. It is characterized by having a heating step of supplying the thermal rotary kiln together with combustion gas and heating the unburned carbon contained in the fly ash in a self-combustion environment.

According to the method for producing a modified fly ash of the present invention, a preheating step of preheating the fly ash in a non-self-combustion environment in which unburned carbon contained in the fly ash does not self-combustion and a fly ash that has undergone the preheating step are removed. Since it is equipped with a heating process that supplies the fly ash together with the combustion gas and heats the unburned carbon contained in the fly ash in a self-combustion environment, immediately after the fly ash is supplied to the externally heated rotary kiln, Combustion of unburned carbon starts immediately. In addition, since the combustion of unburned carbon continues stably in the indirect heating state of the externally heated rotary kiln, it is possible to efficiently obtain high-quality modified fly ash from which unburned carbon is sufficiently removed. can.

Further, in the method for producing a modified fly ash of the present invention, at least one of the amount of the combustion gas supplied to the externally heated rotary kiln in the heating step and the oxygen concentration of the combustion gas is subjected to the preheating step. It is preferably determined based on the amount of unburned carbon contained in the passed fly ash supplied to the externally heated rotary kiln. According to this, unburned carbon contained in fly ash can be burned more stably.

Further, in the method for producing a modified fly ash of the present invention, at least one of the amount of the combustion gas supplied to the externally heated rotary kiln and the oxygen concentration of the combustion gas in the heating step is subjected to the preheating step. The amount of unburned carbon contained in the passed fly ash supplied to the externally heated rotary kiln is C mol / min, and the _{amount of oxygen of the combustion gas supplied to the externally heated rotary kiln in the heating step is O 2 mol / min.} In this case, _{it is preferable that the O 2} / C molar ratio is determined to be 1 or more and 7 or less. According to this, the ratio of the amount of unburned carbon to the amount of oxygen required for its combustion can be set in an appropriate range, and even if the unburned carbon content of the fly ash supplied to the externally heated rotary kiln fluctuates, for example, The unburned carbon can be burned stably.

Further, in the method for producing a modified fly ash of the present invention, the temperature of the non-self-combustible environment in which the preheating step is performed is determined based on the content of unburned carbon contained in the fly ash provided in the preheating step. It is preferable to be done. According to this, the preheating temperature of the fly ash can be set in an appropriate range. For example, when the unburned carbon content of the fly ash supplied to the externally heated rotary kiln is high, the preheating temperature of the fly ash is lowered. Therefore, in the subsequent heating step, it is possible to prevent the fly ash particles from being excessively heated to the extent that they are fused to each other.

Further, in the method for producing a modified fly ash of the present invention, the maximum temperature of the non-self-combustion environment in which the preheating step is performed is lower than the maximum temperature of the self-combustion environment in which the heating step is performed, and the minimum temperature thereof is high. It is preferable that the temperature is lower than the minimum temperature of the self-combustion environment in which the heating step is performed.

Further, in the method for producing a modified fly ash of the present invention, the non-self-combustion environment in which the preheating step is performed is the environment for heating the fly ash to 450 ° C. to 650 ° C., and the heating step is performed. The self-combustion environment is preferably the environment for heating the fly ash that has undergone the preheating step to 600 ° C. to 900 ° C.

On the other hand, in order to achieve the above object, the fly ash reformer of the present invention includes a preheating device for preheating the supplied fly ash and the supplied fly ash in the preheating device. The first heating means for placing the unburned carbon in a non-self-combustible environment, the external heating type rotary kiln that heats the fly ash preheated and supplied by the preheating device, and the external heating type rotary kiln are preheated. The fly ash supplied is provided with a second heating means for placing the fly ash in a self-burning environment in which the unburned carbon contained in the fly ash self-burns.

According to the fly ash reformer of the present invention, a preheating device for preheating fly ash in a non-self-combustion environment in which unburned carbon contained in the fly ash does not self-combustion via a first heating means, and the preheating. Since the fly ash preheated and supplied by the apparatus is provided with an externally heated rotary kiln for heating the fly ash via a second heating means in a self-combustion environment in which the unburned carbon contained in the fly ash self-combusts. In the fly ash reforming process using this, combustion of unburned carbon starts immediately after the fly ash is supplied to the externally heated rotary kiln. In addition, since the combustion of unburned carbon continues stably in the indirect heating state of the externally heated rotary kiln, it is possible to efficiently obtain high-quality modified fly ash from which unburned carbon is sufficiently removed. can.

Further, in the fly ash reforming apparatus of the present invention, the apparatus further includes a control means, and the control means controls the non-self-combustion environment via the first heating means, and the second heating means. It is preferable that the self-combustion environment is controlled via the above. According to this, the control means can appropriately separate the non-self-combustion environment and the self-combustion environment, and can burn the unburned carbon contained in the fly ash more stably.

Further, in the fly ash reformer of the present invention, the control device is said to be non-self-combustible via the first heating means based on the content of unburned carbon contained in the fly ash supplied to the preheating device. It is preferable that the temperature of the environment is controlled. According to this, the preheating temperature of the fly ash can be set in an appropriate range. For example, when the unburned carbon content of the fly ash supplied to the externally heated rotary kiln is high, the preheating temperature of the fly ash is lowered. Therefore, in the subsequent heating step, it is possible to prevent the fly ash particles from being excessively heated to the extent that they are fused to each other.

Further, in the fly ash reformer of the present invention, the maximum temperature of the non-self-combustion environment in the preheating device is lower than the maximum temperature of the self-combustion environment in the external heating rotary kiln , and the minimum temperature is the outside. The environment is preferably lower than the minimum temperature of the self-combustion environment in the thermal rotary kiln.

Further, in the fly ash reformer of the present invention, the non-self-combustion environment in the preheating device is the environment for heating the supplied fly ash to 450 ° C. to 650 ° C., and the external heat type rotary kiln. The self-combustion environment in the above is preferably the environment for heating the preheated and supplied fly ash to 600 ° C. to 900 ° C.

Further, in the fly ash reformer of the present invention, it is preferable that the preheating device is composed of one or more cyclones. According to this, a large amount of fly ash can be stably preheated, and in addition, this can be continuously supplied to the externally heated rotary kiln.

It is a schematic block diagram which shows one Embodiment of the fly ash reformer which concerns on this invention. It is a flowchart explaining the process performed by the reformer shown in FIG.

Hereinafter, the fly ash reformer and the method for producing the modified fly ash according to the present invention will be described with reference to the drawings.

FIG. 1 shows an embodiment of a fly ash reformer according to the present invention. In FIG. 1, the solid line arrow indicates the fly ash flow, the alternate long and short dash line arrow indicates the control signal flow, and the broken line arrow indicates the gas flow.

As shown in FIG. 1, the fly ash reformer 1 (hereinafter referred to as “reformer 1”) includes a preheater 3 for preheating the supplied untreated fly ash F1 and a supplied preheated fly ash F3. It is equipped with an externally heated rotary kiln 4 for heating. In this embodiment, the solid air separating device 6 is installed on the exhaust side of the preheating device 3, and the exhaust gas G from the preheating device 3 is introduced into the solid air separating device 6 by the exhaust fan 7. The fly ash contained in the exhaust gas G from the above is separated to obtain the recovered fly ash F2. Then, in the ash supply device 2, the untreated fly ash F1 and the recovered fly ash F2 are mixed and supplied to the preheating device 3. This can prevent the fly ash from being released into the atmospheric environment.

The externally heated rotary kiln 4 is configured as an inclined substantially cylindrical device. That is, a cylindrical inner cylinder portion 4b and an inner cylinder portion 4b rotatably arranged between the fly ash supply portion 4a, the fly ash discharge portion 4d, and the fly ash supply portion 4a and the fly ash discharge portion 4d. Has a cylindrical heating portion 4c having an outer diameter larger than that of the inner cylinder portion 4b, and the inner cylinder portion 4b is 0.5 to 0.5 toward the fly ash discharge portion 4d from the fly ash supply portion 4a. It is inclined downward at 5.0%. A burner B is arranged in the heating portion 4c of the external heating type rotary kiln 4 so as to heat the inner cylinder portion 4b from the outside. Then, the preheated fly ash F3 supplied to the fly ash supply unit 4a of the external heat type rotary kiln 4 moves from the fly ash supply unit 4a to the fly ash discharge unit 4d as the inner cylinder portion 4b rotates. After undergoing heat treatment for a predetermined time during the movement, it becomes modified fly ash F4 and is discharged from the fly ash discharge unit 4d.

Further, in the embodiment shown in FIG. 1, the reformer 1 heats the combustion gas A1 containing a relatively large amount of oxygen to obtain the combustion gas A2, which is the inner cylinder of the burner B and the externally heated rotary kiln 4. It is introduced in the part 4b. Further, a heat exchanger 5 is provided to raise the temperature of the combustion gas A1, and in this heat exchanger 5, heat exchange occurs with the high temperature exhaust gas HG1 discharged from the heating unit 4c of the external heat type rotary kiln 4. The combustion gas A1 is heated to form a high-temperature combustion gas A2. On the other hand, the temperature of the high-temperature exhaust gas HG1 is lowered by heat exchange, and it becomes exhaust gas G by an exhaust fan (not shown) and is discharged from the heat exchanger 5. The combustion gas A2 may be introduced into the inner cylinder portion 4b from the fly ash discharge portion 4d side so as to be countercurrent with respect to the movement direction of the fly ash, or may be introduced with respect to the movement direction of the fly ash. It may be introduced from the fly ash supply unit 4a side so as to have a parallel flow. In the embodiment shown in FIG. 1, the combustion gas A2 is introduced from the fly ash discharge unit 4d side.

According to the configuration of such an externally heated rotary kiln, the gas phase temperature inside the inner cylinder is indirectly raised from the outside by the thermal power of a burner or the like, so that the fly ash is fused due to overfiring. It is convenient to stably continue the combustion of unburned carbon contained in fly ash while preventing coarse graining.

On the other hand, as the configuration of the preheating device 3, if the fly ash supplied to the external heating type rotary kiln 4 is preheated, the configuration is not particularly limited, but a large amount of fly ash is stably preheated, and this is used. From the viewpoint of being able to continuously supply the externally heated rotary kiln 4, it is preferable that the rotary kiln 4 is composed of, for example, one or more cyclones. There is no particular limitation on the radix (number of stages) of the cyclone.

In the embodiment shown in FIG. 1, two-stage cyclones 3a and 3b are provided, and the high-temperature exhaust gas HG1 discharged from the heating portion 4c of the external heat type rotary kiln 4 and the combustion gas A2 discharged from the inner cylinder portion 4b. (Hereinafter, the gas obtained by mixing the high-temperature exhaust gas HG1 discharged from the heating portion 4c of the external heating rotary kiln 4 flowing through the preheating device 3 and the combustion gas A2 discharged from the inner cylinder portion 4b is referred to as "high-temperature exhaust gas HG2". ), It is introduced into the cyclone 3b from the gas introduction part of the lower cyclone 3b, and after heat exchange with the fly ash while forming a swirling flow in the cyclone 3b, it is discharged from the upper gas discharge port of the cyclone 3b. I am trying to be done. Further, the high-temperature exhaust gas HG2 discharged from the cyclone 3b was introduced into the cyclone 3a from the gas introduction portion of the cyclone 3a on the upper stage side, and heat exchanged with the fly ash in the cyclone 3a while forming a swirling flow in the same manner as the cyclone 3b. Later, it is made to be discharged from the upper gas discharge port of the cyclone 3a. On the other hand, the fly ash (in this embodiment, the mixed ash of the untreated fly ash F1 before the treatment and the recovered fly ash F2 recovered by the solid air separating device 6) is first introduced into the upper cyclone 3a and then the cyclone. After being heated by the high-temperature exhaust gas HG2 in 3a, it is continuously introduced into the lower cyclone 3b from the lower fly ash discharge port of the cyclone 3a, and the high temperature in the cyclone 3b is higher than the high-temperature exhaust gas in the cyclone 3a. After being further heated by the exhaust gas HG2, it becomes a preheated fly ash F3 and is supplied to the fly ash supply unit 4a of the externally heated rotary kiln 4.

In the embodiment shown in FIG. 1, the position where the preheated fly ash F3 is introduced into the externally heated rotary kiln 4 is the end of the inner cylinder portion 4b on the fly ash supply side, but the fly ash supply portion 4a is used. By adding a structure such as a supply pipe that communicates and extends and is inserted into the inner cylinder portion 4b, it can be arbitrarily slid toward the central portion side of the inner cylinder portion 4b. According to this, it is possible to adjust the time for heat treatment as the preheated fly ash F3 moves from the fly ash supply unit 4a to the fly ash discharge unit 4d.

As shown in FIG. 1, the reformer 1 may further include a control device 11 for performing various controls based on measurements by various measuring devices.

Specifically, for example, in this embodiment, a first thermometer T1 is provided inside the inner cylinder portion 4b for each region in which each output can be adjusted by a plurality of burners B for heating the inner cylinder portion 4b. It is provided. The first thermometer T1 measures the temperature of the fly ash inside the inner cylinder portion 4b, and transmits information about the temperature to the control device 11. Further, a second thermometer T2 is installed near the outer surface of the inner cylinder portion 4b at the center portion in the major axis direction of the inner cylinder portion 4b. In this embodiment, this vicinity is the hottest part of the inner cylinder 4b, and the second thermometer T2 measures the temperature of the hottest part of the inner cylinder 4b, and information on the temperature. Is transmitted to the control device 11. As the first thermometer T1 and the second thermometer T2, for example, a thermocouple may be used.

The output of the burners B (s) for heating the inner cylinder portion 4b is controlled by the control device 11. Specifically, the control device 11 adjusts the output of each of the burners B based on the measurement results of the first thermometer T1 and the second thermometer T2 to optimize the heating state in the inner cylinder portion 4b.

Further, the third thermometer T3 provided in the gas pipe measures the temperature of the high-temperature exhaust gas HG2 introduced or discharged into the cyclones 3a and 3b, and transmits information on the temperature to the control device 11. Further, the fourth thermometer T4 provided in the transport path measures the temperature of the fly ash discharged from the cyclones 3a and 3b, and transmits information on the temperature to the control device 11. As the third thermometer T3 and the fourth thermometer T4, for example, a thermocouple may be used as in the case of the first thermometer T1 and the second thermometer T2.

Further, the control device 11 optimizes the temperature of the high-temperature exhaust gas HG2 to be introduced into the cyclone 3b so that the temperature of the preheated fly ash F3 becomes a predetermined temperature by adjusting the mixing amount of the cooling air CA, or preheats. In order to adjust and optimize the amount of fly ash processed by the device 3, information regarding the amount of fly ash supplied can be transmitted to the ash supply device 2.

On the other hand, between the ash supply device 2 and the preheating device 3, a fly ash measuring device for measuring the unburned carbon content of the mixed ash of the untreated fly ash F1 and the recovered fly ash F2 supplied to the preheating device 3. M1 is installed. The fly ash measuring device M1 measures the amount of unburned carbon in the fly ash supplied to the preheating device 3, and transmits information on the amount of unburned carbon to the control device 11.

Further, in order to measure the unburned carbon content of the modified fly ash F4 discharged from the fly ash discharge unit 4d of the externally heated rotary kiln 4, the modified fly ash F4 discharged from the fly ash discharge unit 4d is discharged. A fly ash measuring device M2 is installed on the route. The fly ash measuring device M2 measures the amount of unburned carbon in the produced modified fly ash F4, and transmits information on the amount of unburned carbon to the control device 11.

The fly ash measuring device M1 and the fly ash measuring device M2 are disclosed in, for example, a heat balance analyzer capable of indirectly obtaining the unburned carbon content from the ignition loss value, or JP-A-11-258155. An online compatible device such as a reflected light amount measuring device using the blue light emitter as a light source may be used.

Further, in this embodiment, the combustion gas measuring device M3 is installed in the introduction path of the combustion gas A2 introduced into the externally heated rotary kiln 4. The combustion gas measuring device M3 measures the flow rate (supply amount) and oxygen concentration of the combustion gas A2 supplied into the inner cylinder portion 4b of the externally heated rotary kiln 4, and sends information on the flow rate and oxygen concentration to the control device 11. Send.

Examples of the combustion gas measuring device M3 include a flow meter for ordinary gases such as a thermal type, a Koriori type, a vortex type, and an ultrasonic type, and a magnetic type (magnetic wind type and magnetic force type) or oxygen electrochemistry. An apparatus or the like equipped with an oxygen concentration measuring apparatus of an electrochemical type (zirconia method and an electrode method) utilizing a specific redox reaction may be used.

The amount of mixed ash supplied from the ash supply device 2 to the preheating device 3 can be controlled by the control device 11. Specifically, for example, based on the measurement results of the fly ash measuring device M1 and the combustion gas measuring device M3, the ratio of the oxygen concentration of the combustion gas to the unburned carbon amount of the mixed ash is controlled to be a predetermined value. The device 11 may determine the amount of fly ash supplied from the ash supply device 2.

As described above, the reformer 1 may further include a solid air separating device 6 for separating the fly ash contained in the high temperature exhaust gas HG2 as a configuration for treating the high temperature exhaust gas HG2 discharged from the preheating device 3. good. As the solid air separation device 6, for example, a bug filter or the like may be used. The recovered fly ash F2 recovered by the solid air separation device 6 is conveyed to the ash supply device 2 and mixed with the untreated fly ash F1 before the treatment to form a mixed ash.

Here, the exhaust fan 7 for exhausting the high-temperature exhaust gas HG2 discharged from the preheating device 3 adjusts the exhaust amount of the exhaust gas G from which the recovered fly ash F2 from the solid air separation device 6 has been removed. That is, the exhaust fan 7 captures the flow rate of the high-temperature exhaust gas HG2 flowing into the solid-air separation device 6, the flow rate of the high-temperature exhaust gas HG2 flowing inside the preheating device 3, and the inside of the inner cylinder portion 4b of the externally heated rotary kiln 4. The flow rate of the flowing combustion gas A2 is adjusted. The power supplied to the exhaust fan 7 (that is, the displacement by the exhaust fan 7) may be controlled by the control device 11.

As shown in FIG. 1, the reformer 1 may further include a mercury recovery device 8 that recovers mercury in the high-temperature exhaust gas HG2 discharged from the preheating device 3. As the mercury recovery device 8, for example, a gas adsorbent that adsorbs and removes mercury with an adsorbent may be used. Specifically, a cartridge type stationary phase adsorption device, a continuous cross-flow type layer transfer adsorption device, or the like may be used. As the adsorbent, an adsorption medium carrying sulfur or metal sulfide, activated carbon or activated carbon, or an adsorption medium carrying a metal or mercury that reacts with mercury may be used. As the activated carbon used in the mercury recovery device, it is particularly preferable to use activated carbon that has been subjected to a sulfur impregnation treatment adjusted for mercury adsorption. When the mercury recovery device 8 is provided, the temperature of the high-temperature exhaust gas HG2 discharged from the uppermost cyclone 3a needs to be equal to or higher than the boiling point of mercury (360 ° C.), and is preferably 380 to 420 ° C.

When the mercury recovery device 8 is provided, if the high-temperature high-temperature exhaust gas HG2 after mercury recovery is directly sent to the solid air separation device 6, the filter cloth of the solid air separation device 6 will be damaged, so if necessary. It is preferable to mix the cooling gas CA with the high temperature exhaust gas HG2.

Next, the process performed by the reformer 1 will be described with reference to FIGS. 1 and 2. Note that FIG. 2 is a flowchart showing the processing performed by the reformer 1.

First, the inner cylinder portion 4b of the external heating type rotary kiln 4 is rotated, the output of the burner B arranged in the heating portion 4c is adjusted, the inner cylinder portion 4b is heated from the outside, and the inside of the inner cylinder portion 4b is 600. Heat to ° C to 900 ° C (Fig. 2 / STEP01). At this time, the control device 11 is, for example, a burner arranged in the heating portion 4c of the external heating type rotary kiln 4 so that the temperature inside the inner cylinder portion 4b of the external heating type rotary kiln 4 is maintained at 600 ° C. to 900 ° C. B Control by adjusting the output of each.

Next, the high-temperature exhaust gas HG2 from the externally heated rotary kiln 4 is sent to the preheating device 3 and introduced from the gas introduction portion of the cyclone 3b on the lower stage side to form a swirling flow by the high-temperature exhaust gas HG2 in the cyclone 3b. .. Then, the high temperature exhaust gas HG2 discharged from the lower cyclone 3b is subsequently introduced from the gas introduction portion of the upper cyclone 3a to form a swirling flow by the high temperature exhaust gas HG2 in the cyclone 3a as well (FIG. 2). / STEP02). At this time, the control device 11 mixes, for example, a cooling gas CA for temperature adjustment with the high temperature exhaust gas HG2 so that the temperature of the high temperature exhaust gas HG2 sent to the preheating device 3 is maintained at 600 ° C. to 800 ° C. ,Control.

Further, the ash supply device 2 preheats the fly ash before the treatment (in this embodiment, the mixed ash of the untreated fly ash F1 before the treatment and the recovered fly ash F2 recovered by the solid air separation device 6) of the preheating device 3. It is continuously supplied to the cyclone 3a on the upper stage side (Fig. 2 / STEP03). At this time, the amount of unburned carbon in the fly ash supplied to the preheating device 3 (that is, the mixed ash of the untreated fly ash F1 and the recovered fly ash F2) is measured by the fly ash measuring device M1, and the measured value is controlled. It is transmitted to the device 11.

When the amount of the preheated fly ash F3 discharged from the preheating device 3 is stable, the temperature of the high temperature exhaust gas HG2 sent to the preheating device is measured by the third thermometer T3. Further, the temperature of the fly ash discharged from the lower fly ash discharge ports of the cyclones 3a and 3b of the preheating device 3 is measured by the fourth thermometer T4. Then, those measured values are transmitted to the control device 11.

The control device 11 controls the temperature of the high-temperature exhaust gas HG2 sent to the preheating device 3 so that the temperature of the preheating fly ash F3 discharged from the preheating device 3 becomes 450 to 650 ° C. In this case, the temperature of the preheated fly ash F3 depends on the unburned carbon content of the fly ash (that is, the mixed ash of the untreated fly ash F1 and the recovered fly ash F2) measured by the fly ash measuring device M1. It is preferable to adjust. When the amount of unburned carbon contained is large, the amount of heat generated by the combustion of the unburned carbon causes the fly ash in the externally heated rotary kiln to be overheated, resulting in a high temperature state in which the fly ash particles are fused to each other. Become. Therefore, especially when the content of unburned carbon in the fly ash is high, it is necessary to suppress the temperature in the externally heated rotary kiln from becoming excessively high by lowering the preheating temperature of the fly ash. Specifically, when the content of unburned carbon in the fly ash is 2 to 4% by mass, it is 550 ° C to 650 ° C, and when it is 5 to 7% by mass, it is 500 ° C to 600 ° C, 8 to 10% by mass. In the case of%, it is preferably 450 ° C. to 550 ° C. On the other hand, if the preheating temperature of the fly ash supplied to the externally heated rotary kiln is less than 450 ° C, the part where the unburned carbon starts burning moves to the inside of the externally heated rotary kiln. It may not be possible to give the time required for the unburned carbon to burn and burn, resulting in a high quality modified fly ash.

The heat treatment of fly ash by the preheating device 3 performs the preheating step in the present invention (FIG. 2 / STEP04). That is, in this preheating step, the fly ash is preheated to the temperature of the pre-stage in which the contained unburned carbon causes combustion (self-combustion). The high-temperature exhaust gas HG1 discharged from the externally heated rotary kiln 4 introduced into the preheating device 3 has reduced oxygen due to the combustion action of the burner B arranged in the heating portion 4c of the externally heated rotary kiln 4. There is. Further, the combustion gas A2 discharged from the inner cylinder portion 4b, which is also introduced into the preheating device 3, also has reduced oxygen due to the combustion action of unburned carbon in the fly ash. Therefore, it is convenient to make the environment in the cyclones 3a and 3b of the preheating device 3 such that the unburned carbon of fly ash does not burn (self-combustion). For example, in the non-self-combustion environment, the atmospheric oxygen concentration is preferably 9% by volume or less, and more preferably 5% by volume or less. Further, in this embodiment, the high-temperature exhaust gas HG2 introduced into the cyclones 3a and 3b of the preheating device 3 is described in the present invention as "the unburned carbon contained in the supplied fly ash does not self-combust. It can be said that it constitutes a "first heating means" for placing in a non-self-combustible environment. As the temperature range, as described above, it is preferable that the minimum temperature is 600 ° C. and the maximum temperature is 800 ° C. to maintain 600 ° C. to 800 ° C.

Next, the preheated fly ash F3 discharged from the preheating device 3 is continuously supplied to the externally heated rotary kiln 4 (FIG. 2 / STEP05).

The fly ash temperature heated in the externally heated rotary kiln 4 is measured by the first thermometer T1, and the measured value is transmitted to the control device 11. Further, the amount of unburned carbon in the modified fly ash F4 discharged from the externally heated rotary kiln 4 is measured by the fly ash measuring device M2, and the measured value is transmitted to the control device 11.

The control device 11 can appropriately adjust the output of the burner B of the externally heated rotary kiln 4 so that the amount of unburned carbon in the modified fly ash F4 is equal to or less than a predetermined value. When the output of the burner B is adjusted using only the unburned carbon content of the quality fly ash F4 as an index, the burner B tends to be over-fired, and the fly ash particles may be fused to each other. Therefore, in the adjustment of the output of the burner, the temperature of the fly ash in the inner cylinder portion 4b by the first thermometer T1 and the heating temperature of the inner cylinder portion 4b by the second thermometer T2 are not adjusted by the fly ash measuring device M2. It is necessary to maintain a low temperature while the measured carbon fuel content meets the target. In particular, when modifying fly ash having a high unburned carbon content, the fly ash may be present in an environment higher than a predetermined temperature because heating by the combustion heat of the unburned carbon is also added. Therefore, it is important to monitor and control the temperature of the fly ash in the inner cylinder portion 4b by the first thermometer T1. Specifically, temperature monitoring and control on the fly ash supply unit 4a side is important even in the inner cylinder portion 4b, and when the unburned carbon content of the fly ash is 2 to 4% by mass, the inner cylinder portion 4b When the temperature of the fly ash by the first thermometer T1 installed at the position closest to the fly ash supply unit 4a is 800 ° C. or less, 5 to 7% by mass, 775 ° C. or less, 8 to 10% by mass. The temperature is preferably 750 ° C. or lower. Further, regardless of the unburned carbon content of the fly ash, the temperature of the hottest portion of the inner cylinder portion 4b is preferably 900 ° C. or lower.

Further, the control device 11 includes the measurement result of the fly ash measuring device M1 (that is, the unburned carbon content of the mixed ash of the untreated fly ash F1 and the recovered fly ash F2) and the measurement result of the combustion gas measuring device M3 (that is, the measurement result of the combustion gas measuring device M3). That is, the drive of the exhaust fan 7 is controlled based on the flow rate and oxygen concentration of the combustion gas A2) to control the supply amount of the combustion gas A2 to the inner cylinder portion 4b of the externally heated rotary kiln 4, or to supply ash. The device 2 can be controlled to control the supply amount of the mixed ash of the untreated fly ash F1 and the recovered fly ash F2.

Specifically, first, the control device 11 first determines the inner cylinder portion per unit time based on _{the supply amount of the combustion gas A2 and the oxygen (O 2} ) concentration supplied to the inner cylinder portion 4b of the external heat type rotary kiln 4. The amount of oxygen (O ₂ ) supplied to 4b (mol / min) is calculated.

Next, the control device 11 determines the unburned carbon content of the preheated fly ash F3 supplied to the inner cylinder portion 4b (that is, the unburned carbon content of the mixed ash of the untreated fly ash F1 and the recovered fly ash F2). Based on the supply amount, the amount of unburned carbon (C) (mol / min) supplied to the inner cylinder portion 4b per unit time is calculated.

_{Then, the control device 11 controls the ash supply device 2 so that the molar ratio O 2} / C of the amount of oxygen and the amount of unburned carbon is 1 or more and 7 or less, and the preheating fly is supplied to the inner cylinder portion 4b. The supply amount of ash F3 (that is, mixed ash of untreated fly ash F1 and recovered fly ash F2) is adjusted. Further, the supply amount of the combustion gas A2 or the oxygen (O ₂ ) concentration may be adjusted. In order to stabilize the production amount of the modified fly ash F4, it is preferable to give priority to the control of the supply amount of the mixed ash of the fly ash F1 and F2 by the ash supply device 2.

Here, when _{an operation for increasing the O 2} / C molar ratio is required and the supply amount of the preheated fly ash F3 cannot be decreased, an operation for increasing the supply amount of the combustion gas A2 or the oxygen (O ₂ ) concentration is performed. However, the operation of increasing the supply amount of the combustion gas A2 is directly linked to the increase in the flow velocity of the combustion gas in the inner cylinder portion 4b, and the inside of the inner cylinder portion 4b of the external heating type rotary kiln and the cyclone 3a of the preheating device 3 The heat balance in 3b will be changed, and the production efficiency will be greatly reduced.

_{In order to suppress this decrease in production efficiency, the O 2} / C molar ratio can be increased without significantly changing the supply amount of the combustion gas A2, so that it is larger than the normally used combustion gas A1. It is preferable to prepare a combustion gas having a high oxygen concentration so that it can be used as appropriate.

The O ₂ / C molar ratio is based on the unburned carbon content of the mixed ash of the untreated fly ash F1 and the recovered fly ash F2, the unburned carbon content desired for the modified fly ash F4, and the like. A value other than 1 or more and 7 or less may be selected.

The heat treatment of fly ash by the external heat type rotary kiln 4 constitutes the heating step in the present invention (FIG. 2 / STEP06). That is, in this heating step, the unburned carbon contained in the fly ash is sufficiently burned down to become a modified fly ash. By adjusting the oxygen concentration of the combustion gas A2 introduced into the external heat type rotary kiln 4 to a relatively high value, the unburned carbon of fly ash burns in the environment inside the inner cylinder portion 4b of the external heat type rotary kiln 4 (self-combustion). ) Of course, it is possible to create an environment. For example, in the self-combustion environment, the atmospheric oxygen concentration is preferably 15% by volume or more, and more preferably 18% by volume or more. Further, in this embodiment, it is introduced into the inner cylinder portion 4b of the external heating type rotary kiln 4, and is heated by heat exchange in the heat exchanger 5 or indirect thermal power from the outside by the burner B. It can be said that the combustion gas A2 constitutes the "second heating means for placing the preheated and supplied fly ash in a self-combustion environment in which the unburned carbon contained in the fly ash self-combusts" in the present invention. .. As the temperature range, as described above, it is preferable to maintain 600 ° C. to 900 ° C. with a minimum temperature of 600 ° C. and a maximum temperature of 900 ° C.

On the other hand, as described above, in this embodiment, the solid air separating device 6 is installed on the exhaust side of the preheating device 3, and the high temperature exhaust gas HG2 from the preheating device 3 is introduced into the solid air separating device 6 by the exhaust fan 7. (Fig. 2 / STEP07). Further, the fly ash contained in the high temperature exhaust gas HG2 from the preheating device 3 is separated and recovered, and the recovered fly ash F2 is supplied to the ash supply device 2 (FIG. 2 / STEP08). Then, the ash supply device 2 mixes the supplied recovered fly ash F2 with the untreated fly ash F1 and supplies it to the preheating device 3 (FIG. 2 / STEP03).

According to the method for producing modified fly ash according to the present invention as described above, modified fly ash having a low unburned carbon content can be stably and efficiently obtained. Generally, the unburned carbon content of the modified fly ash used as an admixture for concrete is preferably 0.5% by mass or less, and more preferably 0.4% by mass or less.

Finally, the test results related to the treatment performed in the reformer 1 will be described.

As the test apparatus, the above-mentioned reformer 1 was used. Table 1 shows the details of the inner cylinder portion 4b and the heating portion 4c of the externally heated rotary kiln 4 of the reformer 1.

The test conditions (common) were as shown in Table 2.

In this reformer 1, (1) when the preheating device 3 is used (however, the fly ash F3 and the combustion gas A2 in the inner cylinder portion 4b are countercurrent) (Example 1). ), (2) When the fly ash F3 and the combustion gas A2 in the inner cylinder portion 4b are countercurrent without using the preheating device 3 (Comparative Example 1), (3) without using the preheating device 3. , The three conditions of the case where the fly ash F3 and the combustion gas A2 in the inner cylinder portion 4b flow in parallel (Comparative Example 2) were compared.

Table 3 shows the measured values of the temperature distribution of fly ash in the inner cylinder portion 4b and the results of the unburned carbon content of the modified fly ash F4.

As shown in Table 3, in Example 1, the fly ash in the inner cylinder portion 4b formed a symmetrical temperature distribution over the long axis direction of the inner cylinder portion 4b, whereas in Comparative Example 1, In No. 2, a temperature distribution having a higher temperature was formed on the discharge portion side. The temperature distribution of this comparative example indicates that the combustion of unburned carbon contained in fly ash is activated in the latter half of the heating process, and is sufficient from the start of combustion of unburned carbon to burning. It is considered that the unburned carbon content of the modified fly ash was not sufficiently reduced because a sufficient time could not be secured in the heating process. On the other hand, in the first embodiment, since the combustion of unburned carbon starts immediately when the fly ash is supplied into the inner cylinder portion 4b by passing through the preheating step, it is a limited time in the heating step. However, it was considered that the unburned carbon content could be sufficiently reduced.

1 ... reformer, 2 ... ash supply device, 3 ... preheater, 3a, 3b ... cyclone, 4 ... external heat type rotary kiln, 4a ... fly ash supply part, 4b ... inner cylinder part, 4c ... heating part, 4d ... Fly ash discharge unit, 5 ... heat exchanger, 6 ... solid air separator, 7 ... exhaust fan, 8 ... mercury recovery device, 11 ... control device, A1 ... combustion gas, A2 ... combustion gas, B ... burner, CA ... Cooling air, G ... Exhaust gas, HG1, HG2 ... High temperature exhaust gas, F1 ... Untreated fly ash, F2 ... Recovery fly ash, F3 ... Preheated fly ash, F4 ... Modified fly ash, M1, M2 ... Fly ash measuring device , M3 ... combustion gas measuring device, T1 ... first thermometer, T2 ... second thermometer, T3 ... third thermometer, T4 ... fourth thermometer.

Claims (9)

A preheating process in which the fly ash is preheated in a non-spontaneous environment in which the unburned carbon contained in the fly ash does not self-combust.
The fly ash that has undergone the preheating step is supplied to an externally heated rotary kiln together with combustion gas, and is provided with a heating step of heating in a self-combustion environment in which unburned carbon contained in the fly ash self-combustes.
The temperature of the non-combustible environment in which the preheating step is performed is based on the content of unburned carbon contained in the fly ash subjected to the preheating step. A method for producing modified fly ash, which is determined so that the amount of heat generated by combustion does not cause excessive heating to such a high temperature state that fusion of fly ash particles occurs. In the method for producing modified fly ash according to claim 1,
At least one of the amount of the combustion gas supplied to the externally heated rotary kiln and the oxygen concentration of the combustion gas in the heating step is the externally heated rotary kiln of unburned carbon contained in the fly ash that has undergone the preheating step. A method for producing modified fly ash, which is determined based on the amount of feed to. In the method for producing modified fly ash according to claim 2.
At least one of the amount of the combustion gas supplied to the externally heated rotary kiln and the oxygen concentration of the combustion gas in the heating step is the externally heated rotary kiln of unburned carbon contained in the fly ash that has undergone the preheating step. When the amount of combustion gas supplied to the externally heated rotary kiln in the heating step is O ₂ mol / min and the amount of oxygen supplied to the combustion gas is O 2 mol / min, the O ₂ / C molar ratio is 1 or more and 7 or less. A method for producing a modified fly ash, which is characterized in that it is determined to be. In the method for producing modified fly ash according to any one of claims 1 to 3.
The non-self-combustion environment in which the preheating step is performed has a maximum temperature lower than the maximum temperature of the self-combustion environment in which the heating step is performed, and the minimum temperature thereof is lower than the minimum temperature in the self-combustion environment in which the heating step is performed. A method for producing a modified fly ash, which is characterized by being. In the method for producing modified fly ash according to any one of claims 1 to 4.
The non-self-combustion environment in which the preheating step is performed is the environment for heating the fly ash to 450 ° C. to 650 ° C., and the self-combustion environment in which the heating step is performed is 600 ° C. for the fly ash that has undergone the preheating step. A method for producing a modified fly ash, which comprises the environment for heating to ~ 900 ° C. A preheating device that preheats the supplied fly ash,
In the preheating device, a first heating means for placing the supplied fly ash in a non-spontaneous environment in which the unburned carbon contained in the fly ash does not self-combust.
An externally heated rotary kiln that heats the fly ash that has been preheated and supplied by the preheating device.
In the external heating type rotary kiln, a second heating means for placing the preheated and supplied fly ash in a self-combustion environment in which unburned carbon contained in the fly ash self-combusts,
A control device for controlling the non-self-combustion environment via the first heating means and controlling the self-combustion environment via the second heating means is provided.
Based on the content of unburned carbon contained in the fly ash supplied to the preheating device, the temperature of the non-self-combustion environment is set by the control device via the first heating means, and the self-combustion environment in which the heating step is performed. The fly ash reforming apparatus, which is configured to control so as not to be excessively heated to a high temperature state where the fly ash particles are fused to each other due to the amount of heat generated by the combustion of the unburned carbon in the above. In the fly ash reformer according to claim 6,
The maximum temperature of the non-self-combustion environment in the preheating device is lower than the maximum temperature of the self-combustion environment in the external heating rotary kiln, and the minimum temperature thereof is lower than the minimum temperature of the self-combustion environment in the external heating rotary kiln. A fly ash reformer characterized by being an environment. In the fly ash reformer according to claim 6 or 7.
The non-self-combustion environment in the preheating device is the environment for heating the supplied fly ash to 450 ° C. to 650 ° C., and the self-combustion environment in the external heating type rotary kiln is preheated and supplied. A fly ash reformer comprising the environment for heating fly ash to 600 ° C. to 900 ° C. In the fly ash reformer according to any one of claims 6 to 8.
The preheating device is a fly ash reformer characterized in that it is composed of one or more cyclones.

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