JP2019107618A - Method for manufacturing modified fly ash, and apparatus for manufacturing modified fly ash - Google Patents

Abstract

To provide a method for manufacturing a modified fly ash which prevents occurrence of a fly ash that does not satisfy a desired quality from a supplied coal ash and can more efficiently manufacture a modified fly ash, and can more effectively be utilized as an admixture material of concrete, and an apparatus for manufacturing a modified fly ash.SOLUTION: A method for manufacturing a modified fly ash includes: a crushing step of crushing a coal ash so that the Blaine specific surface area is 4,500 cm/g to 10,000 cm/g to obtain a first fly ash; and a heating step of heating the first fly ash by an external heat type rotary kiln so that a percentage content of unburned carbon contained in the fly ash is 0.5 mass% or less.SELECTED DRAWING: Figure 2

Description

  The present invention is fly ash which is preferably used as an admixture material such as concrete by reforming coal ash which is poor in pozzolanic reactivity and contains a large amount of unburned carbon, which is discharged from a pulverized coal combustion boiler or the like. The present invention relates to a method of producing modified fly ash and a device for producing modified fly ash.

  Pulverized coal combustion boilers and the like of coal-fired power plants generate combustion exhaust gas including coal ash. Conventionally, it has been known that coal ash having a predetermined quality contained in the combustion exhaust gas is collected by an electrostatic precipitator or the like and used as fly ash for admixture materials such as concrete.

  However, according to a report by the Japan Coal Energy Center, although coal ash production in 2015 reached 12.72 million tons (electricity business: 9.34 million tons, general industry: 3.38 million tons) The amount effectively used for concrete admixtures was only about 154,000 tons (1.2% of the total amount generated). The reason for this is considered to be the problem of pozzolanic reactivity of generated coal ash and unburned carbon contained in coal ash.

When used effectively as an additive for concrete, etc., coal ash is required to have pozzolanic reactivity. Pozzolanic reactivity is the ability to form a hardened body by chemical reaction with Ca (OH) ₂ or the like generated by hydration reaction of Portland cement or the like. In JIS A 6201 “Fly ash for concrete” which is a product standard for fly ash for concrete, an activity index is defined as a quality item for the pozzolanic reactivity, and fly ash (on the basis of the activity index etc. Coal ash is classified into four types, from class I to class IV. Generally, fly ash that is effectively used as an additive for concrete, etc., has an activity index of at least III specified in JIS A 6201 "fly ash for concrete", that is, 80% or more at 28 days of age , 90% of the 91-day material is required.

  On the other hand, the problem with unburned carbon contained in coal ash is that, when coal ash containing a large amount of unburned carbon which is the unburned residue of pulverized coal is used as admixture material for concrete etc., the unburned carbon is added to concrete It adsorbs various admixtures to be used, increases the amount of the admixture used in the production of concrete, and in the case of a hardened concrete, unburned carbon floats on the surface to impair the appearance. In JIS A 6201 “Fly ash for concrete” of the above product standard, the unburned carbon content of fly ash (coal ash) is indirectly defined as ignition loss. In general, coal ash that is effectively used as an additive for concrete, etc. is stricter than 3 mass% or less, which is the ignition loss of class I of fly ash specified in JIS A 6201 "fly ash for concrete", 1 mass% or less is required.

  In relation to such a subject, for example, in Patent Document 1, the raw material fly ash is heated to 600 to 950 ° C. while being stirred and conveyed, self-combustion of unburned carbon is carried out, and then the above-mentioned stirring or Disclosed is a method for producing a modified fly ash characterized by rapid stirring and indirect quenching to 200 ° C. or lower and recovering as it is or by classification by sieving or simple classification by spiral spiral flow. .

JP 2008-126117 A

  However, in the method of Patent Document 1, the raw material fly ash is self-combusted to reduce the unburned carbon content, and the modified fly ash having a predetermined quality is recovered by classification etc. When ash is present in a high temperature environment, crystallization of the amorphous phase causing pozzolanic reactivity proceeds rapidly, and there is a problem that pozzolanic reactivity of fly ash after treatment is lowered. Therefore, a considerable amount of fly ash which does not meet the desired quality is generated among the supplied coal ash, and there is a problem that the efficiency is poor.

  The present invention has been made in view of such problems, and it is possible to suppress the generation of fly ash having less than the desired quality from supplied coal ash, and to more efficiently add concrete etc. It is an object of the present invention to provide a method of producing modified fly ash and a device for producing modified fly ash that can produce modified fly ash that can be effectively used.

  As a result of intensive investigations to achieve the above object, the present inventors self-combustible unburned carbon by a predetermined heat treatment if the supplied coal ash is crushed to a predetermined degree of powder. While reducing the heat treatment, a certain level of pozzolanic reactivity is maintained even after the heat treatment, and the occurrence of qualitatively incompatible fly ash is suppressed, and the reformed fly having the desired quality is more efficiently performed. It has been found that ash can be obtained, and the present invention has been completed.

That is, reforming fly ash production method of the present invention, the coal ash, a pulverizing step of the Blaine specific surface area to obtain a first fly ash was ground so as to 4500cm ² / g~10000cm ² / g, the outer And heating the first fly ash to a content of unburned carbon contained in the first fly ash of 0.5% by mass or less using a thermal rotary kiln.

  According to the method for producing modified fly ash of the present invention, by providing the grinding step for grinding the supplied coal ash to a predetermined powder degree, the unburned carbon in the heating step by the externally heated rotary kiln is obtained. The self-combustion reduction efficiency is enhanced. In addition, a certain level of pozzolanic reactivity is maintained in fly ash that has undergone a heating step with an externally heated rotary kiln. Therefore, it is possible to more efficiently produce the modified fly ash by suppressing the generation of fly ash that is incompatible with the quality from the supplied coal ash.

  In the method for producing a modified fly ash according to the present invention, a separation step of solid-gas separating second fly ash contained in the exhaust gas from the exhaust gas generated in the heating step, the first fly ash and the second fly Mixing the ash with the third fly ash to form a third fly ash, the third fly ash in the externally heated rotary kiln, the content of unburned carbon contained in the third fly ash is 0.5% by mass It is preferable to heat so that it may become the following. According to this, by providing the separation step, it is possible to recover fly ash contained in the exhaust gas as the second fly ash from the exhaust gas generated in the heating step, and in the subsequent mixing step, the crushing step is carried out Since the mixture is mixed with the first fly ash pulverized to a predetermined particle size and returned to the heating step, the recovery rate of the modified fly ash modified to have a desired quality is enhanced.

  Further, in the method for producing a modified fly ash according to the present invention, the first fly ash or the third fly ash to be subjected to the heating step before the heating step by the external heating rotary kiln is the fly ash It is preferable to have a preheating step of preheating in a non-self-combustible environment in which the unburned carbon contained therein is not self-combustion. According to this, by providing the preheating step, combustion by self-combustion of unburned carbon is promptly started immediately after the fly ash is supplied to the externally heated rotary kiln. In addition, since the combustion by unburned carbon by the self-combustion continues stably in the indirectly heated state of the externally heated rotary kiln, the high quality reformed fly ash from which the unburned carbon is sufficiently removed becomes more efficient. It can be manufactured well.

  Further, in the method for producing a modified fly ash according to the present invention, the temperature of the non-self-combustible environment in which the preheating step is performed is not included in the first fly ash or the third fly ash to be subjected to the preheating step. It is preferable to determine based on the amount of carbon fuel. According to this, it is possible to set the preheating temperature of the fly ash to an appropriate range. For example, when the amount of unburned carbon contained in the fly ash supplied to the external heating rotary kiln is high, the preheating temperature of the fly ash is used. It is possible to prevent the self-combustion phenomenon of unburned carbon from becoming active as the crystallization of the amorphous phase proceeds rapidly to lower the pozzolanic reactivity in the subsequent heating step by lowering it or the like.

  Further, in the method for producing reformed fly ash according to the present invention, at least one of the supply amount of the combustion gas supplied to the external heating rotary kiln and the oxygen concentration of the combustion gas in the heating step is subjected to the heating step. It is preferable to determine based on the amount of unburned carbons of said 1st fly ash or said 3rd fly ash. According to this, the unburned carbon contained in the fly ash can be more stably burned by self-combustion and reduced.

Further, in the method for producing reformed fly ash according to the present invention, at least one of the supply amount of the combustion gas and the oxygen concentration of the combustion gas is the unburned carbon of the first fly ash or the third fly ash. When the amount is C mol / min and the amount of oxygen of the combustion gas supplied in the heating step is O ₂ mol / min, the O ₂ / C molar ratio is determined to be 1 or more and 6 or less preferable. According to this, the unburned carbon contained in fly ash can be more stably burned by self-combustion and reduced.

Meanwhile, in order to achieve the above object, reforming fly ash production apparatus of the present invention, the supplied coal ash and pulverized to its Blaine specific surface area is 4500cm ² / g~10000cm ² / g The (1) A pulverizing device for obtaining fly ash, and an externally-heated rotary kiln for heating the first fly ash so that the content of unburned carbon contained in the first fly ash is 0.5% by mass or less It is characterized by

  According to the apparatus for producing modified fly ash of the present invention, by providing the pulverizing apparatus for pulverizing the supplied coal ash to a predetermined particle size, the unburned carbon in the heating step by the externally heated rotary kiln is obtained. The self-combustion reduction efficiency is enhanced. In addition, a certain level of pozzolanic reactivity is maintained in fly ash that has undergone a heating step with an externally heated rotary kiln. Therefore, it is possible to more efficiently produce the modified fly ash by suppressing the generation of fly ash that is incompatible with the quality from the supplied coal ash.

  In the apparatus for producing reformed fly ash according to the present invention, a separation apparatus for solidifying the second fly ash contained in the exhaust gas from the exhaust gas generated in the externally heated rotary kiln, the first fly ash, and the first fly ash And a mixer for mixing the second fly ash with the third fly ash, and in the externally heated rotary kiln, the third fly ash has a content of unburned carbon contained in the third fly ash of 0. It is preferable to heat so that it may be 5 mass% or less. According to this, by providing the separation device, the fly ash contained in the exhaust gas can be recovered as the second fly ash from the exhaust gas generated in the externally heated rotary kiln, and this can be collected by the mixing device subsequently Since the mixture is mixed with the first fly ash pulverized to a predetermined particle size by the pulverizing apparatus and returned to the externally heated rotary kiln, the recovery rate of the modified fly ash reformed to a desired quality is enhanced.

  Further, in the apparatus for producing a modified fly ash according to the present invention, unburned carbon contained in the fly ash does not self-burn in the first fly ash or the third fly ash supplied to the externally heated rotary kiln. It is preferable to have a preheating device for placing in a non-self-combustion environment. According to this, by providing the preheating device, self-combustion combustion of unburned carbon is promptly started immediately after the fly ash is supplied to the externally heated rotary kiln. In addition, since the combustion by unburned carbon by the self-combustion continues stably in the indirectly heated state of the externally heated rotary kiln, the high quality reformed fly ash from which the unburned carbon is sufficiently removed becomes more efficient. It can be manufactured well.

  In the apparatus for producing reformed fly ash according to the present invention, the apparatus for producing reformed fly ash further comprises a control means, the control means controls the preheating environment in the preheating apparatus, and Preferably, the heating environment in a thermal rotary kiln is controlled. According to this, by providing the control device, it becomes easy to appropriately control the preheating environment of the fly ash in the preheating device and the self-combustion environment of the fly ash in the externally heated rotary kiln. For example, when the amount of unburned carbon contained in fly ash supplied to the externally heated rotary kiln is high, the temperature setting by the preheating device may be lowered or the temperature setting by the externally heated rotary kiln may be decreased via the control device. In the heating step, it is possible to prevent the self-combustion phenomenon of unburned carbon from becoming active as the crystallization of the amorphous phase proceeds rapidly and the pozzolanic reactivity is lowered.

  The quality of the modified fly ash obtained by the method for producing modified fly ash or the apparatus for producing modified fly ash according to the present invention is that the unburned carbon content is 0.5% by mass or less, and the material is 28 days old Preferably, the activity index is 80% or more, and the 91-day-old activity index is 90% or more.

BRIEF DESCRIPTION OF THE DRAWINGS It is schematic structure explanatory drawing which shows one Embodiment of the manufacturing apparatus of the modification | reformation fly ash which concerns on this invention. It is a flowchart explaining the process performed with the apparatus shown in FIG. It is a schematic structure explanatory view showing another embodiment of the manufacturing device of the modification fly ash concerning the present invention. It is a flowchart explaining the process performed with the apparatus shown in FIG.

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

  FIG. 1 shows an embodiment of a device for producing a modified fly ash according to the present invention. In FIG. 1, solid arrows indicate the flow of coal ash or fly ash, dashed dotted arrows indicate the flow of control signals, and dashed arrows indicate the flow of gas.

  As shown in FIG. 1, the modified fly ash producing apparatus 1 comprises: a coal ash pulverizing apparatus 11 for pulverizing the supplied coal ash D1 so as to obtain a predetermined powder degree to obtain a first fly ash F1; The obtained first fly ash F1 and the second fly ash F2 recovered from the high temperature exhaust gas are mixed, and supplied from the fly ash mixing device 13 and the fly ash mixing device 13 that form the third fly ash F3. The externally heated rotary kiln 14 which heats the third fly ash F3 so that the content of unburned carbon contained in the third fly ash is 0.5% by mass or less, and the second fly ash F2 is recovered from the high temperature exhaust gas to fly fly ash. Solid-gas separation device 16 (in this embodiment, first solid-gas separation device 16a (for example, a cyclone type classifier or the like can be used) to be supplied to the mixing device 13) The second solid-gas separation device 16b (for example, it is possible to use a bag filter or the like.) In composed of two aircraft.) And a. Further, a fly ash classification device 12 is provided at a later stage of the coal ash grinding device 11, and the fly ash ground by the coal ash grinding device 11 is classified with a predetermined particle diameter as a classification point, and coarse powder fly ash D2 is again The coal ash grinding device 11 is returned to be crushed to constitute a closed circuit mill. This makes it more reliable that the first fly ash F1 has a predetermined particle size. In addition, as basic composition for enjoying the effect by this invention of reducing the content rate of the unburned carbon contained in fly ash effectively, it grind | pulverizes coal ash D1 so that it may become a predetermined particle size. The coal ash pulverizing device 11 may be constituted by the coal ash pulverizing device 11 and the externally heated rotary kiln 14 for heating the pulverized raw material fly ash, and the second fly ash F2 may be recovered from the high temperature exhaust gas. Although it is not essential to mix the first fly ash F1 with the first fly ash F1, the solid-gas separation device 16 for recovering the second fly ash F2 from the high temperature exhaust gas in the manufacturing apparatus 1 of this embodiment And a fly ash mixer 13 for mixing this with the first fly ash F1 to provide a reformer having a predetermined quality. Recovery rate of the shoe is further improved from. Below, this manufacturing apparatus 1 of this modification fly ash is only called "the manufacturing apparatus 1", and is demonstrated in more detail.

In the manufacturing apparatus 1, first, the coal ash crushing unit 11, the supplied coal ash D1, the Blaine specific surface area by pulverizing such that the 4500cm ² / g~10000cm ² / g, the first fly ash F1 obtain. Further, at that time, a fly ash classification device 12 is provided at a later stage of the coal ash pulverizing device 11, and it is made more sure that the first fly ash F1 has a predetermined particle size. The first fly ash F1 has an activity index of the finally obtained modified fly ash of at least III of JIS A 6201 "fly ash for concrete", that is, 80% or more at 28 days of age, The maximum particle diameter is preferably 100 μm or less from the viewpoint of 90% or more at the age of 91 days. By the maximum diameter of the first fly ash F1 to 100μm or less, the Blaine specific surface area, generally it is possible to ensure the scope of 4500cm ² / g~10000cm ² / g.

In general, coal ash supplied from pulverized coal-fired boilers such as coal-fired power plants and the like, low-grade coal ash requiring improvement in activity index generally has a brane specific surface area of 2000 cm ² / g to 4000 cm ² It is / g, and in the manufacturing apparatus 1 of this embodiment, the variation in the degree of powderiness between incoming lots can be narrowed by making the degree of powderiness constant for such coal ash. In addition, since the specific surface area of the fly ash to be subjected to the heating step is increased, the self-combustion of unburned carbon is also easily generated, so the heating temperature can be set lower. The unburned carbon content can be effectively reduced while preventing the occurrence of crystallization and suppressing the decrease in the activity index.

  Here, the brane specific surface area is an index that represents the fineness of the particle size of fly ash, and is the specific surface area measured based on the brane method whose measurement method is defined in JIS A 6201 "fly ash for concrete". Point to

The upper limit of the brane specific surface area of the first fly ash is preferably 10000 cm ² / g or less. When the brane specific surface area of the first fly ash becomes larger than 10000 cm ² / g, the ratio of the fly ash supplied to the externally heated rotary kiln 14 to be recovered as the modified fly ash decreases. Specifically, for example, in the embodiment shown in FIG. 1, of the fly ash F3 supplied to the externally heated rotary kiln 14, after being taken into the combustion exhaust gas, it is recovered as the second fly ash F2 by the solid-gas separator 16 The ratio ((amount of second fly ash collected) / (amount of third fly ash supplied to the external heating rotary kiln) × 100%) (hereinafter, this ratio is referred to as “recirculation ratio”) is It tends to increase, which in turn tends to lower the production efficiency of the modified fly ash.

  The circulation rate is preferably 20% to 40%. With this circulation rate, reformed fly ash can be produced with high energy efficiency without excessive use of energy for heating in the externally heated rotary kiln 14.

As the coal ash pulverizing apparatus 11 for obtaining a predetermined degree of powder, a general dry type pulverizing apparatus such as a ball mill, a roll mill, a roller mill (a vertical mill) and the like can be suitably used. Further, as a fly ash classification device 12 for separating fly ash having a predetermined particle diameter from fly ash crushed by the coal ash grinding device 11, for example, a cyclone type or louver type inertia classifier and a vibrating sieve device For example, a dry classifier generally used for classification of powders may be used.

  Next, in the manufacturing apparatus 1, the first fly ash F1 and the second fly ash F2 recovered from the high-temperature exhaust gas (HG2 + HG1) discharged from the externally heated rotary kiln 14 are mixed by the fly ash mixing device 13 After the third fly ash F3 is formed, it is continuously supplied to the externally heated rotary kiln 14. Here, the second fly ash F2 is mainly derived from the fact that the third fly ash F3 supplied to the external heating rotary kiln 14 is trapped by the high temperature exhaust gas HG2 and discharged from the external heating rotary kiln 14. It can be said that its fineness is substantially equal to that of the first fly ash F1.

  In the present embodiment, the first solid-gas separator 16a (for example, a cyclone type classifier or the like can be used) and the first solid-gas separator 16 as a configuration of the solid-gas separator 16 for collecting the second fly ash F2. Although equipped with two solid-gas separation devices of two solid-gas separation devices 16b (for example, a bag filter etc. can be used), it is possible to recover the second fly ash F2 from the high temperature exhaust gas (HG2 + HG1) If it exists, the number of machines which constitute solid-gas separation device 16 will not be restricted. For example, when the solid-gas separator 16 is one unit, the first solid-gas separator 16a of FIG. 1 may be omitted, and only the second solid-gas separator 16b may be provided. Bag filters are preferred.

  The mixing of the first fly ash F1 and the second fly ash F2 in the fly ash mixing device 13 may be performed by simply laminating the fly ash, etc., but the third fly ash F3 to be supplied to the externally heated rotary kiln 14 Preferably, the mixture is thoroughly mixed in the fly ash mixing device 13 in order to average out the quality of the mixture. Therefore, it is preferable that the container for fly ash provided in the fly ash mixing device 13 be provided with a rotor, such as a paddle or a ribbon, and a mixing and stirring mechanism, such as aeration using various exhaust gases.

  A predetermined amount of third fly ash F3 is supplied from the fly ash mixing device 13 to the externally heated rotary kiln 14. For the supply of the third fly ash F3, a general powder metering feeder such as a volumetric metering feeder or a gravimetric metering feeder can be used. The measurement value of the supply amount by the fly ash mixing device 13 may be used as a substitute for the supply amount measurement value of the third fly ash F3 by the fly ash measuring device M11 described later.

  The externally heated rotary kiln 14 is configured as an inclined generally cylindrical device. That is, a cylindrical inner cylindrical portion 14b rotatably disposed between the fly ash supply portion 14a, the fly ash discharge portion 14d, the fly ash supply portion 14a and the fly ash discharge portion 14d, and the inner cylindrical portion 14b And the cylindrical heating portion 14c having an outer diameter larger than that of the inner cylindrical portion 14b, and the inner cylindrical portion 14b extends from the fly ash supply portion 14a toward the fly ash discharge portion 14d by 0.5 to 0.5 mm. It slopes downward at 5.0%. In the heating portion 14c of the externally heated rotary kiln 14, a plurality of electric heating elements H are disposed so as to heat the inner cylindrical portion 14b from the outside. Then, the third fly ash F3 supplied to the fly ash supply unit 14a of the externally heated rotary kiln 14 moves from the fly ash supply unit 14a to the fly ash discharge unit 14d with the rotation of the inner cylindrical portion 14b, After receiving a heating process in the heating unit 14c for a predetermined time during the movement, the reformed fly ash F4 is discharged from the fly ash discharging unit 14d.

  The heating method of the heating portion 14c of the externally heated rotary kiln 14 is not limited as long as it is a method capable of controlling the calorific value such as a burner by fossil fuel other than the method using Joule heat by the electric heating element H .

  Further, in the embodiment shown in FIG. 1, the manufacturing apparatus 1 heats the combustion gas A1 containing a relatively large amount of oxygen to form the combustion gas A2, which is contained in the inner cylindrical portion 14b of the externally heated rotary kiln 14. I am trying to introduce it. Further, the heat exchanger 15 is provided to raise the temperature of the combustion gas A1, and in this heat exchanger 15, heat exchange occurs with the high temperature exhaust gas HG1 discharged from the heating portion 14c of the externally heated rotary kiln 14. Thus, the combustion gas A1 is heated to be 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 becomes the exhaust gas G1 and is exhausted from the heat exchanger 15. Exhaust of the exhaust gas G1, that is, supply of the high temperature exhaust gas HG1 to the heat exchanger 15 is performed by the second exhaust fan 19.

  The combustion gas A2 may be introduced into the inner cylindrical portion 14b of the externally heated rotary kiln 14 from the side of the fly ash discharge portion 14d so as to be countercurrent to the moving direction of the third fly ash F3. The device layout for recovering the second fly ash F2 from the high temperature exhaust gas HG2 may be introduced from the side of the fly ash supply unit 14a so that the third fly ash F3 moves in parallel with the moving direction. From this point, it is preferable to introduce the combustion gas A2 from the side of the fly ash discharge portion 14d as shown in the embodiment of FIG.

  On the other hand, the first exhaust fan 18 for exhausting the high temperature exhaust gas HG2 discharged from the inner cylindrical portion 14b of the external heat type rotary kiln 14 makes the inside of the system negative pressure by suction, and the heat exchanger 15 and the external heat type rotary kiln 14 The solid-gas separation device 16 is configured to prevent the gas from leaking to the outside from the path of the combustion gas A2 or the high-temperature exhaust gas HG2 including the inner cylindrical portion 14b, the solid-gas separation device 16, and the air pipes of various places. Adjust the exhaust gas G2 exhaust rate after the second fly ash F2 is recovered, that is, the flow rate of the combustion gas A2 flowing in the inner cylindrical portion 14b of the externally heated rotary kiln 14, and further use of the combustion gas A1 Adjust the amount.

  According to such a configuration of the externally heated rotary kiln 14, the ambient temperature in the inner cylindrical portion 14b is indirectly raised by the external heating in the heating portion 14c, so the third fly ash by overheating It is convenient to stably generate the combustion of unburned carbon contained in the third fly ash F3, while preventing the crystallization of the amorphous phase of F3 from rapidly advancing and reducing the pozzolanic reactivity. Good.

  The position at which the third fly ash F3 is introduced into the externally heated rotary kiln 14 is the end on the fly ash supply side of the inner cylindrical portion 14b in the embodiment shown in FIG. Then, it is also possible to optionally slide it to the center portion side of the inner cylindrical portion 14b by adding a structure such as a supply pipe which is extended and inserted into the inner cylindrical portion 14b. According to this, as the third fly ash F3 moves from the fly ash supply portion 14a to the fly ash discharge portion 14d, the adjustment of the time for which the heat treatment is performed, the temperature of the portion where the third fly ash F3 is charged, It can be selected arbitrarily.

  Further, in the embodiment shown in FIG. 1, the manufacturing apparatus 1 evaporates by heating the third fly ash F3, and is mercury contained in the high-temperature exhaust gas HG2 and discharged from the inner cylinder portion 14b. Is provided with a mercury recovery device 17 for separating mercury from high temperature exhaust gas (HG2 + HG1). As the mercury recovery device 17, for example, a gas adsorption device that adsorbs and removes mercury with an adsorbent may be used. Specifically, a cartridge type stationary phase adsorption apparatus, a continuous cross flow type bed transfer adsorption apparatus 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 metal or mercury reactive with mercury may be used. In particular, as the activated carbon used in the mercury recovery device 17, it is preferable to use activated carbon that has been subjected to a sulfur-adhered treatment adjusted for mercury adsorption. When the mercury recovery device 17 is provided, the temperature of the high-temperature exhaust gas (HG2 + HG1) supplied to the mercury recovery device 17 needs to be equal to or higher than the boiling point of mercury (360 ° C.), preferably 380-420 ° C.

  When the mercury recovery device 17 is provided, the high-temperature exhaust gas (HG2 + HG1) after mercury recovery is directly supplied to the solid-gas separation device 16b (for example, a bag filter or the like can be used). Since the filter cloth and the like may be thermally damaged, it is preferable to lower the temperature by mixing the cooling air CA into the high temperature exhaust gas (HG2 + HG1) as necessary.

  In a preferred embodiment of the present invention, as shown in FIG. 1, the manufacturing apparatus 1 may further include a control device 51 for performing various controls based on measurements by various measuring devices.

  Specifically, for example, a first thermometer T11 is provided in the inner cylindrical portion 14b for each of the regions where the respective outputs can be adjusted by the plurality of electric heating elements H heating the inner cylindrical portion 14b. The first thermometer T11 measures the temperature of the third fly ash F3 inside the inner cylindrical portion 14b, and transmits information on the temperature to the control device 51. A second thermometer T12 is provided near the outer surface of the inner cylindrical portion 14b at the central portion in the long axis direction of the inner cylindrical portion 14b. In this embodiment, the vicinity thereof is the highest temperature portion of the inner cylinder portion 14b, and the second thermometer T12 measures the temperature of the highest temperature portion of the inner cylinder portion 14b, and information about the temperature Are sent to the control device 51. A thermocouple may be used as the first thermometer T11 and the second thermometer T12, for example.

  The control device 51 can further transmit a control signal to the heating unit 14c of the external heating rotary kiln 14 to individually control the outputs of the plurality of electric heating elements H for heating the inner cylindrical portion 14b. ing. Thus, for example, based on the measurement results of the first thermometer T11 and the second thermometer T12, the controller 51 adjusts the individual outputs of the electric heating element H to optimize the heating state in the inner cylindrical portion 14b. Can be

  In addition, a third thermometer T13 is provided in a flue connecting the externally heated rotary kiln 14 and the first solid-gas separation device 16a. The third thermometer T13 measures the temperature of the high-temperature exhaust gas (HG2 + HG1) introduced to the first solid-gas separator 16a, and transmits information on the temperature to the control device 51. In addition, a fourth thermometer T14 is provided in the air supply pipe connecting the first solid-gas separator 16a and the mercury recovery device 17. The fourth thermometer T14 measures the temperature of the high-temperature exhaust gas (HG2 + HG1) discharged from the first solid-gas separator 16a, and transmits information on the temperature to the control device 51. Furthermore, a fifth thermometer T15 is provided in the air supply pipe connecting the mercury recovery device 17 and the second solid-gas separation device 16b. The fifth thermometer T15 measures the temperature of the high-temperature exhaust gas (HG2 + HG1) discharged from the mercury recovery device 17, and transmits information on the temperature to the control device 51. As the third thermometer T13, the fourth thermometer T14, and the fifth thermometer T15, for example, a thermocouple may be used as in the case of the first thermometer T11 and the second thermometer T12.

  Furthermore, a fly ash measuring device M11 is installed between the fly ash mixing device 13 and the fly ash supply portion 14a of the external heating rotary kiln 14. The fly ash measuring device M11 measures the supply amount (for example, the supply amount per hour) and the unburned carbon content of the third fly ash F3 continuously supplied to the fly ash supply portion 14a of the externally heated rotary kiln 14. And transmit the information to the control device 51.

  Further, a fly ash measuring device M12 is installed downstream of the fly ash discharge portion 14d of the externally heated rotary kiln 14. The fly ash measuring device M12 measures the amount of discharge (for example, the amount of discharge per hour) and the unburned carbon content of the modified fly ash F4 continuously discharged from the fly ash discharge portion 14d of the externally heated rotary kiln 14. And transmits the measurement result to the control device 51.

  In addition, a fly ash measuring device M13 is installed between the solid-gas separator 16 and the fly ash mixing device 13. The fly ash measuring device M13 is a supply amount of the second fly ash F2 collected by the solid-gas separation device 16 (the first solid-gas separation device 16a and the second solid-gas separation device 16b) and supplied to the fly ash mixing device 13. (For example, the supply amount per hour), that is, the recovery amount of the second fly ash F2 from the high temperature exhaust gas (HG2 + HG1) (for example, the recovery amount per time) is measured, and the measurement result is transmitted to the control device 51.

  As a fly ash measuring device included in the fly ash measuring device M11, the fly ash measuring device M12 and the fly ash measuring device M13, for example, a loss in weight type, a type combining a belt feeder and a load cell, or a powder flow rate A general powder measuring device such as a method using a meter may be used.

  Moreover, as a measuring device of the unburned carbon content rate which the fly ash measuring device M11 and the fly ash measuring device M12 have, for example, the thermal balance analyzer which can obtain the unburned carbon content indirectly from the ignition loss value Alternatively, an on-line compatible device such as a reflected light amount measuring device using a blue light emitter as a light source disclosed in JP-A-11-258155 may be used.

  Furthermore, the fly ash measuring device M11 and the fly ash measuring device M12 may have a function of measuring the particle size of fly ash. As an apparatus used for such particle size measurement, for example, an on-line particle size distribution measuring apparatus using a dry laser diffraction / scattering method is suitable.

  On the other hand, a combustion gas measuring device M14 is installed at the introduction portion of the combustion gas A2 of the externally heated rotary kiln 14. The combustion gas measuring device M14 measures the supply amount (for example, the supply amount per hour) and the oxygen concentration of the combustion gas A2 supplied into the inner cylindrical portion 14b of the externally heated rotary kiln 14, and controls the measurement result Send to 51

  As the combustion gas measuring device M14, for example, a flow meter for ordinary gases such as thermal type, Coriolis type, eddy type, ultrasonic type, etc., and magnetic type (magnetic wind type and magnetic force type) or oxygen electrochemistry An apparatus or the like may be used in which an oxygen concentration measuring apparatus of electrochemical type (zirconia system and electrode system) utilizing a specific oxidation reduction reaction is additionally provided.

  In the embodiment shown in FIG. 1, the control device 51 can also transmit a control signal for controlling the first exhaust fan 18. That is, as described above, the first exhaust fan 18 for exhausting the high temperature exhaust gas HG2 exhausted from the inner cylindrical portion 14b of the external heat type rotary kiln 14 is the second fly ash F2 recovered from the solid-gas separator 16 Adjust the exhaust gas volume of exhaust gas G2 after Further, the first exhaust fan 18 is a high temperature exhaust gas (HG1 + HG2) flowing into the solid-gas separation device 16 (the first solid-gas separation device 16a and the second solid-gas separation device 16b), and hence the inner cylinder of the externally heated rotary kiln 14. The flow rate of the combustion gas A2 flowing in the portion 14b is adjusted. The control device 51 can control these gas flow rates and the like by controlling the power supplied to the first exhaust fan 18 or the like.

  In the embodiment shown in FIG. 1, the control device 51 is also capable of transmitting control signals for controlling the individual flow control valves N provided at various places in the pneumatic conduit. That is, for example, based on the measurement values of the temperature by the third thermometer T13, the fourth thermometer T14, the fifth thermometer T15, etc., each of the air pipes is provided so as to have an optimum temperature range. The temperature of the exhaust gas flowing in the air supply pipe is adjusted by adjusting the opening degree of the individual flow rate adjusting valve N or adjusting the opening degree of the flow rate adjusting valve N for introducing the cooling air CA. be able to.

  In the embodiment shown in FIG. 1, for example, from the measurement value of the particle size of the third fly ash F3 by the fly ash measuring device M11, when the particle size of the third fly ash F3 is different from the target set value, the control device 51 The control signal is sent to the coal ash grinding device 11 and / or the fly ash classification device 12 to optimize the operation conditions of the grinding classification process. Specifically, the particle size of the third fly ash F3 may be adjusted by controlling the amount of pulverization per unit time of the coal ash pulverizer 11 or the classification point of the fly ash classifier 12 or the like.

Also, for example, when the particle size of the modified fly ash F4 by the fly ash measuring device M12 is different from the target set value, if the particle diameter of the third fly ash F3 by the fly ash measuring device M11 is normal Since there is a strong possibility of occurrence, a control signal may be sent from the control device 51 to the heating unit 14c of the external heating rotary kiln 14 to adjust the operating conditions of the heating process.

  In a preferred embodiment of the present invention, the above-described circulation rate, ie, (second fly ash, is determined based on the flow rate of fly ash at each site measured by fly ash measuring device M11, fly ash measuring device M12, fly ash measuring device M13, etc. Amount ratio of recovered F2) to (supplied amount of third fly ash F3 supplied to external heating rotary kiln 14), yield of modified fly ash, ie, (produced amount of modified fly ash F4) The amount ratio of (the supply amount of the third fly ash F3 supplied to the external heating rotary kiln 14) may be obtained. By using this amount ratio as an operation index, stable operation can be performed with the operating condition of the apparatus for producing reformed fly ash optimized.

  For example, when the circulation rate does not reach a value of 20 to 40%, the amount of energy used in the heating step can be further suppressed, so that the aeration amount of the combustion gas A2 can be adjusted, or the fineness of the first fly ash F1 You can adjust the

  Furthermore, if the sum of the circulation rate and the yield does not reach 100%, the recovery of the second fly ash F2 from the high temperature exhaust gas (HG2 + HG1) by the solid-gas separator 16 is insufficient, or the external heating rotary kiln 14 is It indicates that there is a problem in manufacturing operation such as the retention of the third fly ash F3 in the cylindrical portion 14b, etc., so that it is possible to know the abnormality of the operation state at an early stage. It is possible to prevent and minimize the decrease in the production efficiency of the modified fly ash F4.

  Further, when the unburned carbon content of the reformed fly ash F4 does not reach a predetermined value by the fly ash measuring device M12, the heating portion 14c of the external heating rotary kiln 14 is controlled accordingly and the inner cylindrical portion 14b The temperature distribution of the inside is adjusted, the rotational speed of the inner cylindrical portion 14b is controlled to adjust the time during which the third fly ash F3 is heated, the adjustment of the fineness of the first fly ash F1, and thus the third The fineness of the fly ash F3 may be adjusted, or the fly ash mixing device 13 may be controlled to adjust the amount of supply of the third fly ash F3 to the externally heated rotary kiln 14.

  In a preferred embodiment of the present invention, the supply amount and oxygen concentration of the combustion gas A2 supplied to the externally heated rotary kiln 14, that is, the oxygen supply amount per unit time, is the supply amount of the third fly ash supplied and unburned carbon It is preferable to determine based on the content rate, ie, the unburned carbon supply amount per unit time.

  In that case, when the oxygen supply amount needs to be increased in the amount ratio of the unburned carbon supply amount per unit time to the oxygen supply amount per unit time, the combustion gas A1 for which the atmosphere can be used The increase in the supply amount of combustion gas A2 formed by heating the inner cylinder of the externally-heated rotary kiln 14 accompanied by the increase in the supply amount of combustion gas A2 as the thermal energy required for heating combustion gas A2 increases. By the increase in the flow velocity of the combustion gas A2 in the portion 14b, the above-described circulation rate is increased, and the production efficiency of the reformed fly ash is reduced.

  Therefore, in order to secure the necessary amount of oxygen supply while suppressing the fluctuation of the flow velocity of the combustion gas A2 in the inner cylindrical portion 14b of the externally heated rotary kiln 14, a gas having an oxygen concentration higher than that of the normal atmosphere is prepared. It is preferable to use a plurality of gases with different oxygen concentrations in combination so that the amount of supplied combustion gas does not fluctuate even if it becomes necessary to increase the amount of supplied oxygen.

In a preferred embodiment of the present invention, the measured value of the supply amount of the third fly ash F3 supplied from the fly ash mixing device 13 to the externally heated rotary kiln 14 and the unburned carbon content, which are measured by the fly ash measuring device M11. The amount of unburned carbon of the third fly ash F3 supplied per minute to the heating step is C mol / min, and the measured value of the supplied amount of combustion gas A2 and oxygen concentration measured by the combustion gas measuring device M14 When the amount of oxygen of the combustion gas A2 supplied for 1 minute in the heating step is set to O ₂ mol / min, it is preferable that the O ₂ / C molar ratio is, for example, 1 or more and 6 or less . By setting the ratio of the oxygen concentration of the combustion gas to the amount of unburned carbon of the third fly ash in this range, the unburned carbon in the fly ash supplied to the heating step can be more efficiently self-combusted . In this case, the control device 51 may control, for example, the supply amount of the third fly ash F3 supplied from the fly ash mixing device 13 so as to optimize the O ₂ / C molar ratio.

  Next, the process performed by the manufacturing apparatus 1 will be described with further reference to the flowchart shown in FIG.

  First, the inner cylindrical portion 14b of the externally heated rotary kiln 14 is rotated to adjust the outputs of the individual electric heating elements H disposed in the heating portion 14c to heat the inside of the inner cylindrical portion 14b from the outside (FIG. 1) / STEP 01).

  Then, the second exhaust fan 19 is operated to introduce the high temperature exhaust gas HG1 generated by the heating unit 14c into the heat exchanger 15 (FIG. 2 / STEP 02). At the same time, the first exhaust fan 18 is operated to suck the combustion gas A1 into the heat exchanger 15 to obtain the combustion gas A2, and then the combustion gas A2 is continuously fed to the inner cylindrical portion 14b at a constant flow rate. I worry (Figure 2 / STEP 03).

  At this time, the control device 51 is individually installed in the heating portion 14 c of the external heating rotary kiln 14 so that the temperature inside the inner cylindrical portion 14 b of the external heating rotary kiln 14 is maintained at, for example, 600 ° C. to 900 ° C. Control the output of the electric heating element H. The heating condition of the fly ash by the externally heated rotary kiln 14 is 600 ° C. or higher in the above range, so the self-combustion of fly ash is sufficiently promoted and the unburned carbon is efficiently reduced, and the range is 900 Since the temperature is not higher than ° C., the crystallization of the amorphous phase of fly ash proceeds rapidly to prevent adverse effects such as reduction of pozzolanic reactivity.

Furthermore, the coal ash crushing unit 11, the supplied coal ash D1, the Blaine specific surface area is pulverized so as to 4500cm ² / g~10000cm ² / g (Fig. 2 / STEP04). At this time, the fly ash pulverized by the coal ash pulverizer 11 is sent to the fly ash classifier 12 and classified at a predetermined classification point (for example, 100 μm) to obtain the first fly ash F1 obtained as a predetermined powder. It can be made more reliable to have a degree.

  The obtained first fly ash F1 is sent to the furan ash mixing apparatus 13, mixed with the second fly ash F2, and the third fly ash F3 formed by the mixing is supplied to the fly ash supply portion 14a of the externally heated rotary kiln 14. Supply continuously (Fig. 2 / STEP 05). At this time, the amount of supply of the third fly ash F3 supplied to the fly ash supply unit 14a, the unburned carbon content, and the particle size are measured by the fly ash measuring device M11, and the measurement results are transmitted to the control device 51. .

  On the other hand, the amount and oxygen concentration of the combustion gas A2 supplied to the inner cylindrical portion 14b of the externally heated rotary kiln 14 are measured by the combustion gas measuring device M14, and the measurement result is transmitted to the control device 51.

Then, the control device 51 determines the inner cylinder of the externally heated rotary kiln 14 per unit time, which is obtained from the supply amount of the third fly ash F3 supplied to the inner cylinder portion 14b of the externally heated rotary kiln 14 and the unburned carbon content. The amount of oxygen O ₂ mol supplied to the inner cylindrical portion 14b of the externally heated rotary kiln 14 per unit time can be determined from the amount of unburned carbon C mol / min supplied to the portion 14b and the supply amount of the combustion gas A2 and the oxygen concentration. The O ₂ / C molar ratio, which is the ratio of 1 / min, is determined, and the O ₂ / C molar ratio is optimized (FIG. 2 / STEP 06).

Specifically, if the obtained O ₂ / C molar ratio does not satisfy the predetermined reference value, an operation of raising the O ₂ / C molar ratio is necessary. In this case, the externally heated rotary kiln 14 is used. The supply amount of the third fly ash F3 may be reduced, or the supply amount of the combustion gas A2 or the oxygen (O ₂ ) concentration may be increased. The operation of increasing the supply amount of the combustion gas A2 is directly linked to the increase of the flow velocity of the combustion gas in the inner cylinder portion 14b, and the heat balance in the inner cylinder portion 14b of the externally heated rotary kiln 14 is changed. Production efficiency of the quality fly ash F4 is greatly reduced. In order to suppress this decrease in production efficiency, the combustion gas A1 used usually is used so that the operation of raising the O ₂ / C molar ratio can be performed without greatly changing the supply amount of the combustion gas A2. It is preferable to separately prepare a combustion gas having a high oxygen concentration and use it as appropriate.

The target set value of the O ₂ / C molar ratio is preferably, for example, 1 or more and 6 or less. By setting the ratio of the oxygen concentration of the combustion gas to the amount of unburned carbon of the third fly ash in this range, the unburned carbon in the fly ash supplied to the heating step can be efficiently self-combusted. However, depending on the unburned carbon content of the third fly ash F3, the unburned carbon content allowed for the modified fly ash F4 and the like, values outside the above range may be selected depending on the case.

  When the recovery amount of the second fly ash F2 sent to the fly ash mixing device 13, ie, the circulation rate is stabilized, the unburned carbon content of the modified fly ash F4 is measured by the fly ash measuring device M12, and the measurement result is It is transmitted to the control device 51.

In addition, the control device 51 controls the particle size of the third fly ash F3 transmitted from the fly ash measuring device M11 to a target setting value, for example, a maximum particle diameter of 100 μm or less and a brain estimated from the particle size distribution. It is confirmed that the specific surface area is 4500 to 10000 cm ² / g. When the measured value is different from the target set value, the particle size of the third fly ash F3 is controlled by controlling the amount of crushing per unit time of the coal ash crushing device 11, the classification point of the fly ash classification device 12, or the like. Adjust (Fig. 2 / STEP 07).

  Furthermore, the control device 51 confirms that the unburned carbon content of the modified fly ash F4 transmitted from the fly ash measuring device M13 is 0.5% by mass or less. Then, when the unburned carbon content of the modified fly ash F4 is larger than 0.5 mass%, the output of the heating portion 14c of the externally heated rotary kiln 14 is controlled to raise the temperature in the inner cylindrical portion 14b. Or adjust the unburned carbon content of the modified fly ash F4 by controlling the rotational speed of the inner cylindrical portion 14b to prolong the time during which the third fly ash F3 is heat-treated (FIG. 2 / STEP 08) .

  Here, the lower limit value of the unburned carbon content of the modified fly ash F4 is not particularly limited. However, when the unburned carbon content is less than 0.1% by mass, the heating step is an overheated state. There is a possibility that the crystallization of the amorphous phase contained in the fly ash may proceed to produce the modified fly ash F4 having a low activity index. As described above, when the unburned carbon content of the reformed fly ash F 4 is excessively reduced, the control in the reverse direction to the above, that is, the temperature in the inner cylindrical portion 14 b of the external heating rotary kiln 14 is lowered. Alternatively, the time for which the third fly ash F3 is subjected to the heating step may be shortened.

  The controller 51 appropriately adjusts the outputs of the individual electric heating elements H in the heating portion 14c of the externally heated rotary kiln 14 so that the unburned carbon content of the modified fly ash F4 satisfies the target value. If the output of the electric heating element H is adjusted using only the unburned carbon content of the modified fly ash F4 by the fly ash measuring device M12 as an index, it tends to overheat, and the third fly ash F3 does not Crystallization of the crystalline phase may proceed rapidly to reduce pozzolanic reactivity. Therefore, the temperature of the third fly ash F3 in the inner cylinder portion 14b by the first thermometer T11 and the heating temperature of the inner cylinder portion 14b by the second thermometer T12 are controlled by adjusting the output of the electric heating element H. It is necessary to maintain the low temperature while the unburned carbon amount measurement value by the ash measurement device M12 satisfies the target set value. In particular, in the case of reforming coal ash D1 having a large unburned carbon content, the heating environment set by the third fly ash F3 because a large amount of thermal energy due to the combustion heat of the unburned carbon is added in the heating step. Since a higher temperature environment may occur, temperature monitoring and control of the third fly ash F3 in the inner cylindrical portion 14b by the first thermometer T11 becomes important. Specifically, it is important to monitor and control the temperature of the central portion even in the inner cylindrical portion 14b, and when the unburned carbon content of the third fly ash F3 is 2 to 4% by mass, the inner cylindrical portion 14b is The temperature of the third fly ash F3 by the first thermometer T11 installed at the center part is 850 ° C or less if it is 850 ° C or less, 5 to 7% by mass, or 800 ° C or less if it is 8 to 10% by mass Is preferred. Further, regardless of the unburned carbon content of the third fly ash F3, the temperature of the highest temperature portion of the inner cylinder portion 14b is preferably 900 ° C. or less.

  On the other hand, as described above, in the present embodiment, the solid-gas separation device 16 is installed on the exhaust side of the external heating rotary kiln 14, and the high temperature exhaust gas from the inner cylindrical portion 14b of the external heating rotary kiln 14 is installed by the first exhaust fan 18. The high temperature exhaust gas (HG2 + HG1) containing HG2 is introduced into the solid-gas separator 16 (FIG. 2 / STEP 09). Further, the second fly ash F2 contained in the high temperature exhaust gas HG2 from the inner cylindrical portion 14b is separated from the high temperature exhaust gas (HG2 + HG1) and supplied to the fly ash mixing device 13 (FIG. 2 / STEP 10). Then, the fly ash mixing device 13 mixes the supplied second fly ash F2 with the first fly ash F1 to produce the third fly ash F3 and is continued to the fly ash supply portion 14a of the externally-heated rotary kiln 14. Supply (Fig. 2 / STEP 05).

[Another embodiment]
Next, another embodiment of the method for producing modified fly ash according to the present invention and the device for producing modified fly ash will be described. The structural example of the manufacturing apparatus 2 of the modification | reformation fly ash for implementing another embodiment is shown in figure following FIG. 1 in FIG. 3, and the line | wire in the manufacturing apparatus 2 of this modification fly ash is shown in FIG. A flow chart for explaining the processing to be performed is illustrated along with FIG. It is to be noted that substantially the same parts as those of the embodiment described above are denoted by the same reference numerals, and the description thereof will be omitted.

  More specifically, in the embodiment described with reference to FIGS. 1 and 2, the third fly ash F3 supplied to the externally heated rotary kiln 14 is a mixture of the first fly ash F1 and the second fly ash F2. Although this thing was what, it is provided with the fly ash pre-heating apparatus 21 for preheating this 3rd fly ash F3 on the conditions which the unburned carbon contained in this does not self-combine. Below, this manufacturing apparatus 2 of this modification fly ash is only called "the manufacturing apparatus 2", and is demonstrated in more detail.

  As shown in FIG. 3, the modified fly ash manufacturing apparatus 2 is a first solid-gas separation apparatus 16 a (for example, the solid-gas separation apparatus 16 of the manufacturing apparatus 1 according to the embodiment shown in FIG. 1). It is possible to use a cyclone type classifier or the like) and a fly ash preheating device 21 for preheating a third fly ash F3 formed by mixing the first fly ash F1 and the second fly ash F2. ing.

  The solid-gas separation device 16 is installed on the exhaust side of the fly ash preheating device 21 and the high temperature exhaust gas (HG1 + HG2) extracted from the fly ash preheating device 21 by the first exhaust fan 18 is introduced into the solid-gas separation device 16 Thus, the second fly ash F2 contained in the high temperature exhaust gas (HG1 + HG2) from the fly ash preheater 21 is separated and recovered. Then, it is supplied to the fly ash preheating device 21 together with the first fly ash F1 obtained by the coal ash crushing device 11 and discharged from the fly ash classification device 12.

  If the 3rd fly ash F3 supplied to external heating type rotary kiln 14 is preheated as composition of fly ash preheating device 21, there is no restriction in particular in the composition, but a large amount of 3rd fly ash F3 is stabilized. From the viewpoint of preheating and continuously supplying it to the externally heated rotary kiln 14, for example, it is preferable to be composed of one or more cyclones. There is no particular limitation on the number (stages) of cyclones.

  In the embodiment shown in FIG. 3, the manufacturing apparatus 2 is provided with an apparatus configured of two stages of cyclones 21 a and 21 b as the fly ash preheating apparatus 21, and is discharged from the heating unit 4 c of the externally heated rotary kiln 14. The high-temperature exhaust gas (HG2 + HG1) where the high-temperature exhaust gas HG1 and the high-temperature exhaust gas HG2 discharged from the inner cylinder 4b join is introduced into the cyclone 21b from the gas introduction part of the cyclone 21b on the lower side, After heat exchange with the third fly ash F3 while being formed, the exhaust gas is exhausted from the upper gas discharge port of the cyclone 21b. Further, the high temperature exhaust gas (HG2 + HG1) discharged from the cyclone 21b is introduced into the cyclone 21a from the gas introduction part of the cyclone 21a on the upper side, and the third fly ash is formed in the cyclone 21a similarly to the cyclone 21b. After heat exchange with F3, the gas is exhausted from the upper gas outlet of the cyclone 21a.

  On the other hand, the third fly ash F3 is first introduced into the cyclone 21a on the upper side, heated by the high temperature exhaust gas (HG2 + HG1) in the cyclone 21a, and continuously from the lower fly ash outlet of the cyclone 21a. After being further heated by the high temperature exhaust gas (HG2 + HG1) in the cyclone 21b whose temperature is higher than that of the high temperature exhaust gas (HG2 + HG1) in the cyclone 21a, the third fly ash F3 is preheated. It is continuously supplied to the fly ash supply portion 14 a of the thermal rotary kiln 14.

  In a preferred embodiment of the present invention, the temperature environment of the preheating step performed in the fly ash preheating device 21 is the supply amount of the third fly ash F3 subjected to the preheating step by the fly ash preheating device 21 and unburned carbon It is preferable to determine based on the content rate, ie, the unburned carbon supply amount per unit time. In this case, for example, the temperature of the high-temperature exhaust gas (HG2 + HG1) introduced to the cyclone 21b such that the temperature of the third fly ash F3 preheated by the control device 51 becomes a predetermined temperature, the mixing amount of the cooling air CA And can be controlled.

  Further, the amount of the third fly ash F3 supplied to the fly ash preheating device 21 may be controlled by the supply amount of the first fly ash F1 supplied from the fly ash classification device 12 or the fly ash classification device 12 Between the fly ash introduction portion of the cyclone 21a on the upper side of the fly ash preheating device 21 and a mixing device (not shown) similar to the fly ash mixing device 13 shown in FIG. The supply amount from the mixing device 13 may be controlled.

  In the manufacturing apparatus 2 according to the embodiment shown in FIG. 3, a bag filter is used as the solid-gas separator 16 for recovering the second fly ash F2 contained in the high-temperature exhaust gas (HG2 + HG1) discharged from the fly ash preheating device 21. Is preferably usable.

  As shown in the embodiment of FIG. 3, the manufacturing device 2 may further include a mercury recovery device 17 for recovering mercury in the high-temperature exhaust gas (HG2 + HG1) discharged from the fly ash preheating device 21.

  When the mercury recovery device 17 is provided, if the high temperature, high temperature exhaust gas (HG2 + HG1) after mercury recovery is directly supplied to the solid-gas separation device 16, the filter cloth of the solid-gas separation device 16 is thermally damaged. It is preferable to mix the cooling air CA into the high temperature exhaust gas (HG2 + HG1) according to.

  Next, with reference to the flowchart shown in FIG. 4, the contents of the processing performed by the manufacturing apparatus 2, particularly, the contents related to the fly ash preheating device 21 will be described. In addition, the processing content regarding things other than the fly ash pre-heating apparatus 21 is the same as the manufacturing method of the modified fly ash performed with the manufacturing apparatus 1 demonstrated in the said FIG.1 and FIG.2.

  The combustion gas A2 is continuously supplied at a constant flow rate to the inner cylindrical portion 14b of the externally heated rotary kiln 14 similarly to STEP01 to STEP03 in FIG. 1 (FIG. 4 / STEP 11, STEP 12, STEP 13).

  Next, the high temperature exhaust gas (HG2 + HG1) from the externally heated rotary kiln 14 is supplied to the fly ash preheating device 21 and introduced from the gas introduction part of the cyclone 21b on the lower side, and the high temperature exhaust gas (HG2 + HG1) in the cyclone 21b Form a swirling flow). The high temperature exhaust gas (HG2 + HG1) discharged from the cyclone 21b on the lower side is subsequently introduced from the gas introduction portion of the cyclone 21a on the upper side, and likewise forms swirling flow by the high temperature exhaust gas (HG2 + HG1) in the cyclone 21a. Let it go (Fig. 4 / STEP 14). At this time, for example, the cooling air for controlling the temperature of the high temperature exhaust gas (HG2 + HG1) is controlled so that the temperature of the high temperature exhaust gas (HG2 + HG1) sent to the fly ash preheating device 21 maintains 600 ° C to 800 ° C. Control by mixing CA etc. In such a temperature range, since the range is 600 ° C. or higher, the introduced fly ash is sufficiently preheated, and since the range is 800 ° C. or less, the heating in the external heating rotary kiln 14 is continued The adverse effect of overheating in the process and the like can be prevented.

Furthermore, the coal ash crushing unit 11, similarly to the manufacturing apparatus 1 of the embodiment shown in FIG. 1, the supplied coal ash D1, so that the Blaine specific surface area is 4500cm ² / g~10000cm ² / g Pulverize (Fig. 4 / STEP 15). At this time, the fly ash pulverized by the coal ash pulverizer 11 is sent to the fly ash classifier 12 and classified at a predetermined classification point (for example, 100 μm) to obtain the first fly ash F1 obtained as a predetermined powder. It can be made more reliable to have a degree. The obtained first fly ash F1 is continuously supplied to the fly ash introduction portion of the cyclone 21a on the upper side of the preheating device 21 together with the second fly ash F2 recovered by the solid-gas separation device 16 (FIG. 4) / STEP 16).

  The third fly ash F3 preheated and discharged by the fly ash preheating device 21 is continuously supplied to the fly ash supply portion 14a of the external heat rotary kiln 14 (FIG. 4 / STEP 17). At this time, the supply amount of the third fly ash F3, the unburned carbon content, and the particle size are measured by the fly ash measuring device M11, and the measurement results are transmitted to the control device 51.

  When the supply amount of the third fly ash F3 from the fly ash preheater 21 to the externally heated rotary kiln 14 is stabilized, the temperature of the high temperature exhaust gas (HG2 + HG1) supplied to the fly ash preheater 21 by the third thermometer T13 is The measurement result is sent to the control device 51.

  The control device 51 adjusts the temperature of the high-temperature exhaust gas (HG2 + HG1) sent to the fly ash preheating device 21 so that the temperature of the third fly ash F3 supplied from the fly ash preheating device 21 becomes 450 to 650 ° C. Control. In this case, the temperature of the third fly ash F3 is the unburned carbon supply amount and the unburned carbon content of the third fly ash F3 measured by the fly ash measuring device M11, that is, the unburned carbon supply per unit time It is preferable to adjust according to the amount. That is, when the amount of unburned carbon to be contained is large (for example, when the amount of unburned carbon introduced to the fly ash preheating device 21 per unit time is large), the external heat is generated by the amount of heat due to the combustion of such unburned carbon. Heating of the third fly ash F3 in the inner cylinder portion 14b of the rotary kiln 14 becomes excessive, and the crystallization of the amorphous phase of the third fly ash F3 proceeds rapidly to reduce the pozzolanic reactivity. It will be about high temperature. Therefore, in particular, when the content of unburned carbon in the third fly ash F3 is high, and for example, the amount introduced into the fly ash preheating device 21 per hour is large, the fly ash preheating device 21 It is necessary to suppress that the temperature in the inner cylindrical portion 14b of the external heating rotary kiln 14 becomes excessively high by lowering the preheating temperature.

  Specifically, when the unburned carbon content of the third fly ash F3 is 2 to 4% by mass, the temperature of the third fly ash F3 is 550 ° C. to 650 ° C., 5 to 7% by mass In the case of 500 ° C. to 600 ° C. and 8 to 10% by mass, the temperature is preferably 450 ° C. to 550 ° C. When the preheating temperature of the third fly ash F3 supplied to the externally heated rotary kiln 14 exceeds 650 ° C., there is a possibility that the overheating in the heating step or the like in the externally heated rotary kiln 14 may cause adverse effects. On the other hand, when the preheating temperature of the third fly ash F3 supplied to the externally heated rotary kiln 14 is less than 450 ° C., the place where unburned carbon starts burning moves to the inside of the inner cylindrical portion 14b. As a result, it may not be possible to give the time necessary for the unburned carbon to burn and decrease due to self-combustion, and it may not be possible to obtain the modified fly ash F4 having a reduced unburned carbon content.

  In the preheating step in the fly ash preheating device 21, the third fly ash F3 is preheated to a temperature just before the contained unburned carbon causes self-combustion. The high temperature exhaust gas (HG2 + HG1) introduced into the preheating device 21 is the one that has undergone combustion, and oxygen is sufficiently reduced. Therefore, the preheating by the high temperature exhaust gas (HG2 + HG1) is suitable for making the environment in the preheating device 21 an environment in which the unburned carbon of the third fly ash F3 is not self-combustible. For example, in the non-self-combustible environment in the preheating device 21, the atmospheric oxygen concentration is preferably 9% by volume or less, more preferably 5% by volume or less.

  The steps (FIG. 4 / STEP 18 to STEP 22) after the third fly ash F3 has been supplied to the external heating rotary kiln 14 are the same as the steps STEP 26 to STEP 10 in FIG.

  Finally, test results when coal ash is treated using the manufacturing apparatus 1 and the manufacturing apparatus 2 described above will be described. In Tables 1 and 2 below, more specific specifications that are common to the manufacturing apparatus 1 and the manufacturing apparatus 2 or specific to the manufacturing apparatus 1 or 2 are shown.

  In the test, the test conditions were fixed except that the degree of grinding by the coal ash grinding device 11 provided in each apparatus was changed, or the grinding was not performed. In this case, the effect of the particle size (Brain specific surface area) of the first fly ash F1 is as follows: (1) Unburned carbon content of the modified fly ash F4, (2) Activity index of the modified fly ash F4, (3 2.) The circulation rate of the second fly ash F2 in the manufacturing apparatus 1 and (4) power consumption of the heating unit 14c were compared.

  In addition, the measurement of the brane specific surface area of the 1st fly ash F1 is based on the specific surface area test of JIS R 5201 "physical test method of cement", and the measurement of the unburned carbon content of the modified fly ash F4 is JIS. Measurement of the activity index of the modified fly ash F4 according to M 8819 "Coal and cokes-Elemental analysis method by instrumental analyzer" is described in Appendix C "Fly" of JIS A 6201 "Fly Ash for Concrete". It measured according to the test method of the flow value ratio with mortar of an ash, and activity index, respectively.

  Table 3 shows the test results by the manufacturing apparatus 1, and Table 4 shows the test results by the manufacturing apparatus 2.

As shown in Tables 3 and 4, the unburned carbon content of the modified fly ash F4 is 0.5 mass in all of the examples in which the Blaine specific surface area of the first fly ash F1 is 4500 cm ² / g or more. In Comparative Examples 1 and 2 in which the brane specific surface area of the first fly ash F1 was less than 4500 cm ² / g while it was less than 10%, the unburned carbon content of the modified fly ash F4 was 1.0 mass% It showed the above high value. Furthermore, in all the examples, the activity index of the modified fly ash F4 shows 80% or more of 28 days of material, and 90% or more of 91 days of material age, which is a problem with concrete admixtures etc. There was obtained a modified fly ash having a quality that can be utilized without.
In addition, compared to the comparative example, the power consumption of the heating unit 14c tends to decrease in the example, and it is clear that the example is more advantageous from the viewpoint of energy efficiency of the heating process.

1, 2 ... Production equipment for reforming fly ash, 11 ... Coal ash crushing device, 12 ... Fly ash classification device, 13 ... Fly ash mixing device, 14 ... External heat type rotary kiln, 14 a ... Fly ash supply part, 14 b ... inside Cylinder part 14c Heating part 14d Fly ash discharge part 15 Heat exchanger 16 Solid-gas separation device 16a First solid-gas separation device 16b Second solid-gas separation device 17 Mercury recovery 18: first exhaust fan 19: second exhaust fan 21: fly ash preheater 21a: upper cyclone, 21b: lower cyclone 51: controller, A1: combustion gas, A2: combustion gas, CA ... air for cooling, D1 ... coal ash, D2 ... coarse powder fly ash, F1 ... first fly ash, F2 ... second fly ash, F3 ... third fly ash, F4 ... breaks Fly ash, G1, G2: exhaust gas, H: electric heating element, HG1, HG2: high temperature exhaust gas, M11, M12, M13: fly ash measuring device, M14: combustion gas measuring device, N: flow control valve, T11: first Thermometer, T12: second thermometer, T13: third thermometer, T14: fourth thermometer, T15: fifth thermometer

Claims (10)

Coal ash, a pulverizing step of the Blaine specific surface area to obtain a first fly ash was ground so as to 4500cm ² / g~10000cm ² / g,
And heating the first fly ash so that the content of unburned carbon contained in the first fly ash is 0.5% by mass or less by an external heating rotary kiln. Method of quality fly ash. In the method for producing modified fly ash according to claim 1,
A separation step of solidifying / separating a second fly ash contained in the exhaust gas from the exhaust gas generated in the heating step; and a mixing step of mixing the first fly ash and the second fly ash to form a third fly ash Equipped with
Production of modified fly ash characterized in that the third fly ash is heated by the externally heated rotary kiln so that the content of unburned carbon contained in the third fly ash is 0.5% by mass or less. Method. In the method of producing modified fly ash according to claim 1 or 2,
Prior to the heating step by the externally heated rotary kiln, the first fly ash or the third fly ash to be subjected to the heating step is preheated in a non-self-combustible environment in which unburned carbon contained in the fly ash is not self-combustible A method for producing a modified fly ash comprising a preheating step. In the method for producing modified fly ash according to claim 3,
The temperature of the non-self-combustible environment in which the preheating step is performed is determined based on the amount of unburned carbon contained in the first fly ash or the third fly ash to be subjected to the preheating step. Method of quality fly ash. The method for producing modified fly ash according to any one of claims 1 to 4.
At least one of the supply 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 unburned of the first fly ash or the third fly ash to be subjected to the heating step. A method of producing a modified fly ash characterized by being determined based on the amount of carbon. In the method for producing modified fly ash according to claim 5,
At least one of the supply amount of the combustion gas and the oxygen concentration of the combustion gas sets the unburned carbon amount of the first fly ash or the third fly ash to C mol / min and supplies the combustion in the heating step. A method for producing a modified fly ash, wherein the O ₂ / C molar ratio is determined to be 1 or more and 6 or less when the oxygen amount of gas is O ₂ mol / min. The supplied coal ash, a crusher to which the Blaine specific surface area to obtain a first fly ash was ground so as to be 4500cm ² / g~10000cm ² / g,
An externally heated rotary kiln for heating the first fly ash so that the content of unburned carbon contained in the first fly ash is 0.5% by mass or less Ash production equipment. In the apparatus for producing modified fly ash according to claim 7,
A separator for solid-gas separating second fly ash contained in the exhaust gas from the exhaust gas generated in the externally heated rotary kiln;
A mixer for mixing the first fly ash and the second fly ash to form a third fly ash;
In the externally heated rotary kiln, the third fly ash is heated so that the content of unburned carbon contained in the third fly ash is 0.5% by mass or less. manufacturing device. In the apparatus for producing modified fly ash according to claim 7 or 8,
Providing a preheating device for placing the first fly ash or the third fly ash supplied to the externally heated rotary kiln in a non-self-combustible environment in which unburned carbon contained in the fly ash is not self-combustible Equipment for producing modified fly ash. The apparatus for producing modified fly ash according to any one of claims 7 to 9, wherein
The apparatus for producing the reformed fly ash further comprises a control means, the control means controlling the preheating environment in the preheating apparatus, and controlling the heating environment in the externally heated rotary kiln. Equipment for producing modified fly ash.

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