JP5818161B2 - Method for producing cement clinker, method for recovering radioactive cesium - Google Patents

Description

  The present invention relates to a method for producing a cement clinker and a method for recovering radioactive cesium from a production process of a cement clinker.

  Cement clinker is manufactured by firing cement raw materials such as limestone, clay, and silica in a kiln. In the production of such a cement clinker, dust in the kiln exhaust gas discharged from the kiln is also used as a cement raw material. For example, dust separated from the kiln exhaust gas discharged from the preheater by the dust collection facility, or bypass dust separated from the kiln exhaust gas by the desalination bypass facility provided between the kiln and the preheater is returned to the kiln. And used as a cement raw material (see Patent Document 1).

JP 2011-84425 A

  By the way, in recent years, there is a possibility that a large amount of waste and by-products containing radioactive cesium (hereinafter also referred to as Cs-containing materials) are generated around the nuclear power plant. For this reason, while utilizing Cs containing material effectively, it is calculated | required to collect | recover radioactive cesium efficiently. In the production of cement clinker, use of a Cs-containing material as a cement raw material or fuel has been studied.

  However, when such a Cs-containing material is used as a cement raw material or the like, the radioactive cesium is heated and vaporized in the kiln, so that the radioactive cesium is contained in the kiln exhaust gas. And after such kiln exhaust gas is discharged | emitted from a kiln, temperature falls. At this time, radioactive cesium in the kiln exhaust gas is deposited (attached) to the dust from the vaporized state.

  When dust containing such radioactive cesium is returned into the kiln as a cement raw material as described above, the radioactive cesium volatilizes from the dust and is contained again in the kiln exhaust gas. For this reason, if the cement clinker is continuously manufactured, the content of radioactive cesium in the kiln exhaust gas increases over time, and accordingly, the content of radioactive cesium in the dust returned to the kiln also increases over time. Will increase.

  Thus, when the content of radioactive cesium in kiln exhaust gas and dust increases, there is a risk that radioactive cesium will be contained in the manufactured cement clinker, and it is difficult to use a Cs-containing material as a cement raw material or the like. It becomes. Moreover, since the radioactive cesium adhering to dust is returned in a kiln with dust, it is difficult to collect | recover radioactive cesium efficiently.

  Accordingly, the present invention provides a method for producing a cement clinker and a method for recovering radioactive cesium that can effectively use waste containing radioactive cesium as a cement raw material and can efficiently recover radioactive cesium. The task is to do.

The method for producing a cement clinker according to the present invention forms a cement clinker by firing a cement raw material in a kiln, separates dust from the kiln exhaust gas discharged from the kiln, and supplies the dust as a cement raw material into the kiln. A method for producing a cement clinker, wherein the content of radioactive cesium in dust separated from the kiln exhaust gas is measured, and the amount of dust supplied into the kiln decreases as the content increases and performing adjustment of the supply amount.

  According to such a method, based on the measurement result of the content of radioactive cesium in the dust, by adjusting the supply amount of dust as a cement raw material, to the extent that no radioactive cesium is contained in the formed cement clinker, Dust can continue to be used as a cement raw material. For example, when the cement clinker is continuously manufactured, the content of radioactive cesium in the dust increases as described above.

  However, the amount of radioactive cesium supplied into the kiln is reduced by reducing the amount of dust supplied into the kiln as a raw material for cement according to the increase in the content of radioactive cesium. Can be maintained to the extent that it is not. That is, since the dust can be continuously used as the cement raw material while maintaining the state in which the radioactive cesium is not contained in the cement clinker, the Cs-containing material can be effectively used as the cement raw material or the like.

  Adjustment of the supply amount of dust as a cement raw material is preferably performed by collecting dust when the content of radioactive cesium in the dust exceeds a predetermined value.

  According to such a method, the content of radioactive cesium in the dust increases until it exceeds a predetermined value. That is, radioactive cesium can be accumulated in dust until the content of radioactive cesium exceeds a predetermined value. For this reason, radioactive cesium can be efficiently collect | recovered by collect | recovering such dust.

  It is preferable that adjustment of the supply amount of the dust as the cement raw material is performed on the dust separated from the kiln exhaust gas by either one or both of the electrostatic precipitator and the bag filter.

  According to such a method, dust (hereinafter also referred to as EP / Bag dust) separated from the kiln exhaust gas by one or both of an electrostatic precipitator and a bag filter is generally separated from relatively fine particles. Therefore, the surface area is large. Therefore, radioactive cesium is easy to adhere to EP / Bag dust. For this reason, the amount of radioactive cesium supplied to the kiln can be effectively adjusted by adjusting the supply amount of dust as a cement raw material to EP / Bag dust. Also, when the supply amount of dust as a cement raw material is adjusted by collecting EP / Bag dust, it is easy for radioactive cesium to adhere to EP / Bag dust, so collect EP / Bag dust. Thus, radioactive cesium can be efficiently recovered.

Method for recovering radioactive cesium according to the present invention, the cement material to form a fired at a kiln cement clinker, from kiln exhaust gas discharged from the kiln is separated dust content of radioactive cesium in said dust A method for recovering radioactive cesium that measures and recovers radioactive cesium from a manufacturing process of a cement clinker configured to reduce a supply amount of dust supplied into a kiln as a cement raw material in accordance with an increase in the content. The radioactive cesium content in the dust separated from the kiln exhaust gas is measured, and the dust is recovered when the content exceeds a predetermined value.

  According to such a method, the dust can be continuously used as a cement raw material until the content of radioactive cesium in the dust exceeds a predetermined value. For this reason, a Cs containing material can be effectively used as a cement raw material or the like. Moreover, the content of radioactive cesium in the dust increases until the content of radioactive cesium in the dust exceeds a predetermined value. That is, radioactive cesium can be accumulated in dust until the content of radioactive cesium exceeds a predetermined value. For this reason, radioactive cesium can be efficiently collect | recovered by collect | recovering this dust.

  The dust is preferably collected from the dust separated from the kiln exhaust gas by one or both of an electric dust collector and a bag filter.

  According to such a method, the EP / Bag dust is generally composed of relatively fine particles, and thus has a large surface area. Therefore, radioactive cesium is easy to adhere to EP / Bag dust. For this reason, the collection | recovery of dust is performed with respect to EP * Bag dust, and more radioactive cesium can be collect | recovered efficiently.

  As described above, according to the present invention, waste containing radioactive cesium can be effectively used as a cement raw material, and radioactive cesium can be efficiently recovered.

The block diagram which showed the outline of the manufacturing equipment of the cement clinker used with the manufacturing method of the cement clinker concerning this embodiment, and the collection | recovery method of radioactive cesium.

  Hereinafter, an embodiment of the present invention will be described with reference to FIG.

  The cement clinker production method (hereinafter referred to as production method) and the radioactive cesium recovery method (hereinafter referred to as recovery method) according to the present invention include radioactive cesium as a cement raw material and fuel used when producing cement clinker. It contains raw materials, fuels, wastes, etc. (hereinafter also referred to as Cs-containing materials). The Cs-containing material is not particularly limited, and includes soil containing radioactive cesium, sludge, rubble such as wood and plastics. Examples of radioactive cesium include those having a mass number of 134 or 137. Moreover, it does not specifically limit as a cement raw material, The raw material used when manufacturing a common cement can be used. For example, limestone, clay, silica stone and the like can be used as a cement raw material.

  The radioactive cesium in the Cs-containing material volatilizes when heated and precipitates when the temperature decreases. This property of radioactive cesium was confirmed by the following method. Specifically, 100 ppm of cesium chloride having substantially the same properties as radioactive cesium was added to a cement raw material calcined at 1000 ° C. and mixed uniformly. Two predetermined amounts of the resulting mixture were collected in platinum containers, one was capped and sealed, and the other was not capped and left open. The two containers were heated at 1450 ° C. for 30 minutes to fire the mixture, and then rapidly cooled to room temperature. Then, the cesium density | concentration was measured using ICP-MS with respect to each baked mixture. As a result of the measurement, the closed container had a cesium concentration of 50 ppm, whereas the open container had a concentration of 1 ppm or less. Thereby, it was recognized that radioactive cesium volatilizes by heating and precipitates when the temperature decreases.

  In the method for producing a cement clinker and the method for recovering radioactive cesium according to the present invention, a general cement clinker production facility can be used. For example, as shown in FIG. 1, the production facility 1 includes a kiln 2 for firing cement raw material to form a cement clinker, and a preheating facility 3 for preheating the cement raw material before being supplied to the kiln 2. , A storage facility 4 for storing cement raw material supplied to the preheating facility 3, a dust collecting facility 5 for separating dust from the kiln exhaust gas discharged from the kiln 2, and a raw material supply facility 6 for supplying cement raw material The ones provided are listed.

  The kiln 2 is not particularly limited, and for example, a dry kiln, a wet kiln, a lepole kiln, an SP kiln, an NSP kiln, a fluidized bed kiln, or the like can be used. As said preheating equipment 3, what is equipped with preheater 3a which preheats a cement raw material and calcining furnace 3b which calcines the preheated cement raw material can be used. The dust collection equipment 5 includes a sedimentation chamber 5a for separating dust having a relatively large particle size from the kiln exhaust gas, an electric dust collector 5b and a bag filter 5c for separating dust having a relatively small particle size from the kiln exhaust gas, The thing provided with the stabilizer 5d which adjusts the temperature of the kiln exhaust gas supplied to the electrical dust collector 5b can be used.

  In the manufacturing facility 1 as described above, the kiln exhaust gas is discharged from the kiln 2 and then passes through the preheating facility 3 (the calcining furnace 3b and the preheater 3a), thereby exchanging heat with the cement raw material to lower the temperature. To do. The temperature of the kiln exhaust gas discharged from the preheating facility 3 is not particularly limited, and is preferably 750 ° C. or higher and 850 ° C. or lower, for example.

  The kiln exhaust gas discharged from the preheating facility 3 (specifically, the preheater 3a) is sent to the dust collection facility 5. The temperature of the kiln exhaust gas immediately before being sent to the dust collection facility 5 (in this embodiment, the settling chamber 5a) is not particularly limited, but is preferably 400 ° C or lower, and 350 ° C or lower. Is more preferable.

  The kiln exhaust gas sent to the dust collection equipment 5 is first supplied to the settling chamber 5a. In the sedimentation chamber 5a, dust having a relatively large particle size is separated from the kiln exhaust gas. Specifically, in the sedimentation chamber 5a, it is preferable that dust having a particle size of 0.5 mm or more measured by a laser diffraction particle size distribution meter is separated from the kiln exhaust gas, and dust having a particle size of 0.1 mm or more. Is more preferably separated from the kiln exhaust gas.

  The kiln exhaust gas discharged from the settling chamber 5a is adjusted in temperature by passing through the stabilizer 5d, then sent to the electric dust collector 5b, and further sent to the bag filter 5c. The temperature of the kiln exhaust gas immediately before being sent to the electric dust collector 5b is not particularly limited, but is preferably 260 ° C. or lower, and more preferably 150 ° C. or lower. Further, the temperature of the kiln exhaust gas immediately before being sent to the electrostatic precipitator 5b is preferably 50 ° C. or higher, and more preferably 100 ° C. or higher.

  In the electric dust collector 5b and the bag filter 5c, dust having a relatively small particle size is separated from the kiln exhaust gas. Specifically, in the electrostatic precipitator 5b, dust having a particle size of 100 μm or more measured by a laser diffraction particle size distribution meter is preferably separated from the kiln exhaust gas, and dust of 1 μm or more is separated from the kiln exhaust gas. It is more preferable. In the bag filter 5c, dust having a particle size of 10 μm or more is preferably separated from the kiln exhaust gas, and more preferably 0.1 μm or more of dust is separated from the kiln exhaust gas.

  The dust separated by the dust collection equipment 5 (specifically, the sedimentation chamber 5a, the electric dust collector 5b, the bag filter 5c, and the stabilizer 5d) is sent to the storage equipment 4 and stored. The dust is supplied to the kiln 2 (specifically, after being supplied to the preheating facility 3) as a cement raw material together with the cement raw material supplied from the raw material supply facility 6 to the storage facility 4. That is, the dust in the kiln exhaust gas is discharged from the kiln 2 and then returned to the kiln 2 as a cement material. That is, in the method for producing a cement clinker and the method for recovering radioactive cesium according to the present invention, dust in the kiln exhaust gas is also used as a cement raw material.

  The kiln exhaust gas from which the dust has been separated by the dust collecting equipment 5 is discharged outside the manufacturing equipment 1 by an exhaust equipment (not shown) such as a chimney or a part thereof is sent to the raw material supply equipment 6 to obtain the cement raw material. It may be used for drying.

  When a cement clinker is produced in the production facility 1 as described above, if a Cs-containing material is used as a cement raw material or fuel, radioactive cesium is contained in the dust returned as the cement raw material. Specifically, when a Cs-containing material is used, radioactive cesium is vaporized in the kiln 2 and is discharged from the kiln 2 as a component of the kiln exhaust gas. The kiln exhaust gas is lowered in temperature through a route until it is discharged from the dust collection facility 5. As the temperature decreases, the volatilized radioactive cesium is deposited (attached) to the dust in the kiln exhaust gas. For this reason, radioactive cesium will contain in the dust supplied to a kiln as a cement raw material.

  In the method for producing cement clinker and the method for recovering radioactive cesium according to the present invention, the content of radioactive cesium in the dust is measured. The measurement of the content of radioactive cesium is preferably performed on the dust before being returned to the preheating facility 3 (specifically, the preheater 3a). For example, the measurement of the content of radioactive cesium is preferably performed on the dust separated from the kiln exhaust gas in the dust collection facility 5. In particular, it is preferable to measure the content of radioactive cesium with respect to dust separated by at least one of the settling chamber 5a, the electrostatic precipitator 5b, and the bag filter 5c.

  In particular, dust separated by the electrostatic precipitator 5b and the bag filter 5c (hereinafter also referred to as EP dust / Bag dust) has a relatively small particle size and therefore has a large surface area. For this reason, radioactive cesium becomes easy to adhere, it becomes possible to measure radioactive cesium at a high concentration, and to improve the measurement system. As the particle size of the dust to be measured for the content of radioactive cesium, the particle size measured with a laser diffraction particle size distribution meter is preferably 0.5 mm or less, and preferably 0.1 mm or less. More preferred.

  Here, as described above, radioactive cesium is contained in the dust separated from the kiln exhaust gas. For this reason, when such dust is supplied to the kiln 2 as a cement raw material, the radioactive cesium is vaporized again in the kiln 2. And the radioactive cesium volatilized from dust and the radioactive cesium volatilized from the Cs containing material used as a cement raw material will be discharged | emitted from the kiln 2 as a component of a kiln exhaust gas. For this reason, if manufacture of a cement clinker is performed continuously, content of radioactive cesium in kiln exhaust gas will increase. And the radioactive cesium in a kiln exhaust gas precipitates (attaches) to dust with the temperature fall of a kiln exhaust gas as mentioned above. For this reason, when the content of radioactive cesium in the kiln exhaust gas increases with time, the content of radioactive cesium in the dust separated from the kiln exhaust gas also increases with time.

  For this reason, in the method for producing cement clinker and the method for recovering radioactive cesium according to the present invention, based on the measurement result of the content of radioactive cesium in dust, the amount of dust supplied to the kiln as a cement raw material is Adjusted. Specifically, as described above, the content of radioactive cesium in the dust will be increased by continuous production of cement clinker. For this reason, the amount of radioactive cesium supplied into the kiln 2 is reduced to the extent that no radioactive cesium is contained in the cement clinker by reducing the amount of dust supplied as a cement raw material in accordance with the increase in the content of radioactive cesium. Can be maintained. That is, it is possible to continue using dust as a cement raw material while maintaining a state in which no radioactive cesium is contained in the cement clinker.

  The adjustment of the amount of dust supplied as a cement raw material is preferably performed for dust having a relatively small particle size. Since dust with a relatively small particle size has a large surface area, radioactive cesium tends to adhere to it. For this reason, such dust contains radioactive cesium in high concentration, and by adjusting the supply amount of such dust, the amount of radioactive cesium returned and supplied into the kiln 2 can be adjusted efficiently. Can do. The dust for adjusting the supply amount is preferably one having a particle size measured by a laser diffraction particle size distribution meter of 0.5 mm or less, more preferably one having a particle size of 0.1 mm or less.

  In addition, the adjustment of the dust supply amount is performed by adjusting the dust separated from the kiln exhaust gas, specifically, the dust separated from the kiln exhaust gas by at least one of the sedimentation chamber 5a, the electrostatic precipitator 5b, and the bag filter 5c. EP dust / Bag dust) is preferable. In particular, since EP dust and Bag dust have a relatively small particle size and a large surface area, radioactive cesium tends to adhere to them. For this reason, such dust contains radioactive cesium in high concentration, and by adjusting the supply amount of such dust, the amount of radioactive cesium returned and supplied into the kiln 2 can be adjusted efficiently. Can do.

  In the present embodiment, the manufacturing facility 1 further includes a measuring device A1 that measures the content of radioactive cesium in the dust. The measuring device A1 includes a sample seat A2 on which the separated dust is placed, and a supply amount adjusting means A3 that adjusts the amount of dust supplied to the storage facility 4. And it is comprised so that measurement of content of radioactive cesium may be performed with respect to the dust on a sample seat. The measuring device A1 is connected to the settling chamber 5a, the electrostatic precipitator 5b, the bag filter 5c, and the raw material supply facility 6.

  The adjustment of the amount of dust supplied into the kiln may be performed by collecting the dust when the content of radioactive cesium in the dust exceeds a predetermined value. Thereby, content of radioactive cesium in dust will increase until it exceeds a predetermined value. In other words, since radioactive cesium is accumulated in the dust, the radioactive cesium is efficiently recovered by collecting the dust. The dust to be collected is not particularly limited, and examples thereof include dust separated by the settling chamber 5a, the electric dust collector 5b, the bag filter 5c, and / or the stabilizer 5d, and dust generated by the desalting bypass. It is done. In particular, dust (EP dust / Bag dust) separated by either one or both of the electrostatic precipitator 5b and the bag filter 5c has a relatively small particle size and a large surface area, so that radioactive cesium is likely to adhere to the dust. . For this reason, such dust contains radioactive cesium in high concentration, and radioactive cesium can be efficiently recovered by recovering EP dust / Bag dust.

  As described above, according to the method for producing a cement clinker and the method for recovering radioactive cesium according to the present invention, waste containing radioactive cesium can be effectively used as a cement raw material, and the radioactive cesium can be efficiently used. It can be recovered.

  That is, according to the method for producing cement clinker and the method for recovering radioactive cesium according to the present invention, based on the measurement result of the content of radioactive cesium in the dust, by adjusting the amount of dust supplied as a cement raw material, Dust can be used as a cement raw material to the extent that radioactive cesium is not contained in the formed cement clinker.

  For example, when the cement clinker is continuously manufactured, the content of radioactive cesium in the dust increases as described above. However, the amount of radioactive cesium supplied into the kiln is reduced by reducing the amount of dust supplied into the kiln as a raw material for cement according to the increase in the content of radioactive cesium. Can be maintained to the extent that it is not. That is, since the dust can be continuously used as the cement raw material while maintaining the state in which the radioactive cesium is not contained in the cement clinker, the Cs-containing material can be effectively used as the cement raw material or the like.

  Moreover, when the radioactive cesium content exceeds a predetermined value, the radioactive cesium can be efficiently recovered by recovering the dust.

  Moreover, since radioactive cesium is easy to adhere to EP / Bag dust, the amount of radioactive material supplied to the kiln 2 is adjusted by adjusting the supply amount of dust as a cement raw material to EP / Bag dust. The amount of cesium can be adjusted effectively.

  Also, when the amount of dust supplied to the kiln 2 is adjusted by collecting EP / Bag dust, it is easy for radioactive cesium to adhere to the EP / Bag dust, so the EP / Bag dust is collected. By doing so, radioactive cesium can be efficiently recovered.

  The filling material supply method and the labor-saving track repair method according to the present invention are not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the present invention.

  DESCRIPTION OF SYMBOLS 1 ... Manufacturing equipment, 2 ... Kiln, 3 ... Preheating equipment, 3a ... Preheater, 3b ... Calcining furnace, 4 ... Storage equipment, 5 ... Dust collection equipment, 5a ... Settling chamber, 5b ... Electric dust collector, 5c ... Bug Filter, 5d ... Stabilizer, 6 ... Raw material supply equipment

Claims (5)

A cement raw material is fired in a kiln to form a cement clinker, and dust is separated from the kiln exhaust gas discharged from the kiln, and the dust is supplied to the kiln as a cement raw material.
The content of radioactive cesium in the dust separated from the kiln flue gas was measured, to make the adjustment of the supply amount so that the supply amount of the dust supplied to the kiln according to the increase of the content is reduced A method for producing a cement clinker.   2. The cement clinker according to claim 1, wherein the adjustment of the amount of dust supplied as a cement raw material is performed by collecting the dust when the content of radioactive cesium in the dust exceeds a predetermined value. Manufacturing method.   The adjustment of the supply amount of dust as a cement raw material is performed on dust separated from kiln exhaust gas by one or both of an electrostatic precipitator and a bag filter. The manufacturing method of the cement clinker of description. The cement material together and fired in a kiln to form cement clinker, from a kiln exhaust gas discharged from the kiln is separated dust by measuring the content of radioactive cesium in said dust, in response to the increase of the content of A method for recovering radioactive cesium that recovers radioactive cesium from a manufacturing process of a cement clinker configured to reduce the amount of dust supplied into a kiln as a cement raw material,
A method for recovering radioactive cesium, wherein the content of radioactive cesium in dust separated from the kiln exhaust gas is measured, and the dust is recovered when the content exceeds a predetermined value.   The method for recovering radioactive cesium according to claim 4, wherein the dust is collected from the dust separated from the kiln exhaust gas by one or both of an electrostatic precipitator and a bag filter.

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