JP6572154B2 - Recovery method for refractory bricks for rotary kilns contaminated with radioactive materials - Google Patents

Description

  INDUSTRIAL APPLICABILITY The present invention is used for inspecting the permeability of radioactive material in a brick lined in a rotary kiln that heats waste containing radioactive material such as radioactive cesium and removes radioactive cesium from the waste. Regarding technology.

  In order to remove radioactive cesium taken into the soil, for example, in Patent Document 1, the soil contaminated with radioactive cesium is heated with a rotary kiln, the kiln exhaust gas is cooled to produce fine powder containing radioactive cesium, and the kiln exhaust gas is produced. The technology which collects the coarse powder inside, returns to a rotary kiln, and collects fine powder from kiln exhaust gas is described. By this technique, radioactive cesium is concentrated to a high concentration to reduce the volume, and the burden of intermediate storage or final disposal can be reduced, and a fired product with a reduced concentration of radioactive cesium can be obtained.

JP 2013-19734 A

  By the way, the rotary kiln is lined with fired refractory bricks such as magnesia-chromium, magnesia-spinel, magnesia-dolomite. In a rotary kiln that implements the technique of Patent Document 1 or the like, in order to inspect the penetration of radioactive materials into these refractory bricks, an operator needs to enter the rotary kiln and remove the refractory brick. The working environment is extremely bad, such as raw materials containing radioactive materials remaining inside. Therefore, there has been a demand for a method for safely collecting refractory bricks while avoiding the risk of exposure.

  Therefore, the present invention has been made in view of the above problems in the prior art, and in a rotary kiln that heats waste containing a radioactive substance such as radioactive cesium and removes radioactive cesium and the like from the waste. The purpose is to collect bricks more safely when inspecting the penetration of radioactive materials into the stretched bricks.

  In order to achieve the above object, the present invention provides a method for recovering a refractory brick for a rotary kiln contaminated with a radioactive substance, wherein the rotary kiln includes a hollow cylindrical metal shell and a brick lined on the metal shell. Brick inside the rotary kiln is extracted from the outside of the rotary kiln by core removal.

  According to the present invention, bricks lined on a metal shell can be collected without an operator entering the rotary kiln, so that the risk of exposure to the worker can be reduced.

  In the refractory brick recovery method, the diameter of the core is made smaller than the minimum side length of the brick, and a part of the metal shell is peeled off before the core is removed to confirm the position of the brick. The core removal can be performed so that the core removal hole fits in one brick. When the core punching hole straddles a plurality of bricks, the contact area between the bricks decreases, so there is a risk that the bricks will fall with a decrease in holding power, but according to the present invention, this is prevented. be able to.

  The core removal can be performed at a plurality of locations across the axial direction of the rotary kiln. Thereby, the permeation | transmission degree etc. of a radioactive substance can be test | inspected for every some area | region which differs in the axial direction of a rotary kiln.

  The core removal can be performed at a plurality of locations over the circumferential direction of the rotary kiln. By shifting the timing of core removal at a plurality of locations in the circumferential direction, it is possible to inspect the degree of penetration of the radioactive material into the inspection brick in a time series.

  As described above, according to the present invention, bricks can be collected more safely in a rotary kiln that heats waste containing a radioactive substance such as radioactive cesium and removes cesium and the like from the waste.

It is the schematic which shows an example of the removal apparatus of the radioactive cesium provided with the rotary kiln which implements this invention. The state which attached the mounting seat to the rotary kiln shown in FIG. 1 is shown, (a) is a front view, (b) is the sectional view on the AA line of (a), (c) is the BB line of (a). It is sectional drawing. The state which attached the core drill to the attachment seat shown in FIG. 2 is shown, (a) is a partially broken front view corresponding to FIG. 2 (b), and (b) is a partially broken side view. It is a figure for demonstrating the positional relationship of the drill part of a core drill, and the brick lined with a shell, Comprising: (a) is a fragmentary sectional view, (b) is opposite to the sticking surface of the brick of (a). It is a figure which shows the state which looked at the brick used as the object of core removal from the side surface. BRIEF DESCRIPTION OF THE DRAWINGS The whole rotary kiln which implements this invention is shown, (a) is a partial cross section front view, (b) is the sectional view on the AA line of (a).

  Next, an embodiment for carrying out the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows an example of a radioactive cesium removal apparatus equipped with a rotary kiln (hereinafter referred to as “kiln”) to which the method for recovering refractory bricks according to the present invention is applied. And the firing apparatus 7 and the exhaust gas treatment apparatus 10.

  The raw material blending device 2 stores a storage tank 3 for storing waste W such as soil contaminated with radioactive cesium and incinerated ash, and a calcium oxide source (hereinafter referred to as “CaO source”) such as limestone as a reaction accelerator. A storage tank 4 storing a chlorine source such as calcium chloride (hereinafter referred to as “Cl source”), and waste W, CaO source and Cl source stored in storage tanks 3 to 5 as reaction accelerators. A fixed-quantity feeder (not shown) for drawing and blending, and a storage tank 6 for storing the blended raw material M are provided.

  The firing device 7 is composed of a kiln (heating furnace) 8 and a cooler 9. The kiln 8 ejects fossil fuels such as a charging port 8 a to which the prepared raw material M from the raw material preparing device 2 is supplied and pulverized coal. And the burner 8b for baking the preparation raw material M etc. is provided.

  The exhaust gas treatment device 10 is disposed at the rear stage of the firing device 7, the cooling tower 11 for cooling the exhaust gas G discharged from the kiln 8, the cyclone 12 disposed at the rear stage of the cooling tower 11, the first dust collector 16, A second dust collector 17, a denitration device 18 that denitrates the exhaust gas G 4 from which dust such as concentrated cesium salt has been removed by the dust collectors 16 and 17, and a chimney 19 that exhausts the exhaust gas G 5 of the denitration device 18 out of the system. The

  In the raw material mixing apparatus 2 of the radioactive cesium removal apparatus 1 having the above-described configuration, the waste W contaminated with the radioactive cesium and the CaO source and the Cl source as reaction accelerators are drawn out from the storage tanks 3 to 5 and prepared. After obtaining the raw material M, it is thrown into the kiln 8 through the inlet 8a and fired at 1200 ° C. or higher and 1550 ° C. or lower to obtain a fired product B.

  On the other hand, the radioactive cesium contained in the waste W of the preparation raw material M reacts with chlorine generated from the Cl source in the kiln 8 to volatilize as cesium chloride and is contained in the exhaust gas G in the cooling tower. 11 is introduced.

  The exhaust gas G is rapidly cooled by the water sprayed from the water sprinkler 11a in the cooling tower 11, and the cesium chloride contained in the exhaust gas G becomes a solid cesium salt and adheres to the dust fine powder.

  Since the coarse dust C contained in the exhaust gas G1 of the cooling tower 11 has a low radioactive cesium concentration, it is classified by the cyclone 12 and returned to the rotary kiln 8.

  On the other hand, the exhaust gas G2 from the cyclone 12 containing the cesium salt is introduced into the first dust collector 16, and the dust D1 containing the solid concentrated cesium salt is recovered. The recovered dust D1 can be stored in a sealed container or the like after further volume reduction treatment by compression, washing, adsorption, etc., if necessary, and waste containing radioactive cesium can be stored outside. Volume can be reduced and stored without leakage.

  Since the exhaust gas G3 after recovering the concentrated cesium salt contains harmful gas such as acid gas, the second dust collector 17 is added to the exhaust gas G3 after adding a neutralizer N such as slaked lime from the neutralizer addition device. Thus, the dust D2 adsorbing acid gas or the like from the exhaust gas G3 is recovered.

The dust D2 collected by the second dust collector 17 is returned to the raw material preparation device 2 as a CaO source or a Cl source, added to the waste W, and reused. On the other hand, when NOx is contained in the exhaust gas G4 of the second dust collector 17, ammonia gas (NH ₃ ) is injected and removed by the denitration device 18. The cleaned exhaust gas G5 is exhausted outside the system through the chimney 19.

  As described above, according to the radioactive cesium removal device 1, dust D1 enriched with radioactive cesium is obtained by collecting dust from the exhaust gas G2, and volume reduction of the waste W contaminated with radioactive cesium is achieved. Can do.

  On the other hand, as described above, radioactive material penetrates and accumulates in the brick lined to the kiln 8, and the brick needs to be collected in order to inspect the penetration degree and the like. Hereinafter, the collection method of the firebrick for kilns contaminated with the radioactive substance which concerns on this invention is explained in full detail.

  FIG. 2 shows an example of a mounting seat for a core drill used in the present invention. The mounting seat 21 includes an upper plate 21a formed so as to have a concentric surface with the shell 8c of the kiln 8, and the upper plate 21a. A side plate 21b rising from the surface of the shell 8c and a through long hole 21c formed on the surface of the upper plate 21a for attaching a core drill are provided.

  The shell 8c is made of a steel plate, and is formed in a hollow cylindrical shape having an inner diameter of 1.3 m and a total length of 15 m as an example. Further, as shown in FIG. 3, a brick 8 d as a fired refractory brick such as magnesia-chromium, magnesia-spinel, magnesia-dolomite or the like is attached to the inner surface of the shell 8.

  Before attaching the mounting seat 21 having the above configuration to the shell 8c, a part of the shell 8c of the kiln 8 is peeled off, and the position of the brick 8d (hatching is applied only to the core removal target) as shown in FIG. Keep it. Thereafter, the mounting seat 21 is positioned at a desired position, and the lower end of the side plate 21b is welded and fixed to the shell 8c, whereby the mounting of the mounting seat 21 is completed.

  The core drill is attached to the attachment seat 21 attached as described above. The core drill 22 is attached by engaging the projecting portion 22b provided at the bottom of the attachment portion 22c of the core drill 22 with the through long hole 21c of the attachment seat 21, and then attaching the core drill 22 to the attachment seat 21 with bolts and nuts (not shown). ) Is performed by fixing through.

  As the core drill 22, for example, a diamond core drill manufactured by Shibuya Co., Ltd. can be used. Moreover, after engaging the convex part 22b and the penetration long hole 21c by making the length of the longitudinal direction of the convex part 22b of the core drill 22 shorter than the length of the longitudinal direction of the penetration long hole 21c of the attachment seat 21, The core drill 22 can be slid on the mounting seat 21, and the mounting position of the core drill 22 can be finely adjusted.

  In positioning of the mounting seat 21 and the core drill 22, as shown in FIG. 4, the drill diameter D of the core drill 22 is smaller than the minimum side L of the brick 8d lined on the shell 8c, and the core punching hole H has a plurality of bricks. It is preferable not to straddle 8d. In other words, as shown in FIG. 4B, the core hole H may be accommodated in the surface S on the opposite side to the affixing surface (contact surface with the shell 8c) of one brick 8d. preferable. Thereby, the contact area between the bricks 8d is reduced, the holding force is lowered, and the brick 8d can be prevented from falling. In addition, if it is not necessary to consider the fall of the brick 8d, the core can be removed across the plurality of bricks 8d.

  When the mounting of the mounting seat 21 and the core drill 22 is completed, the operator manually turns the handle (not shown) of the core drill 22 to move the drill portion 22a to the position indicated by the broken line in FIG. And the brick 8d is cored, and the cylindrical shell 8c and the brick 8d scraped off inside the drill portion 22a can be recovered.

  As described above, according to the present invention, the operator can collect the brick 8d from the outside of the shell 8c without entering the inside of the kiln 8, so that the penetration degree of the radioactive substance into the brick 8d is inspected. In this case, it is possible to reduce the risk of exposure to workers.

  In addition, the structure of the attachment seat 21 for attaching the core drill 22 and the fixing method of the attachment seat 21 and the core drill 22 in the said embodiment are only examples, and are not limited to the said structure.

  Next, the position where the core is removed will be described with reference to FIG.

  Core removal is performed at four locations along the axial direction of the shell 8c (FIG. 5A shows only the core removal hole H). The positions are, for example, 4.5 m, 7.5 m, 10.5 m, and 13.5 m from the raw material outlet end of the kiln 8, and the inner diameter of the shell 8c of the kiln 8 is D, respectively 3.5D, 5. The positions can be 8D, 8.1D, and 10.4D, and these positions are included in each region of the firing band, the detachable band, the detachable band, and the calcined band.

  The rotary kiln is generally roughly divided into a cooling zone, a firing zone, a removable zone, and a calcining zone from the raw material outlet end, and these regions are in the range of 0 to 1D, 1-5D, 5-10D, 10D <from the raw material outlet end. Since the temperature and the desorption state of the fired product differ depending on these regions, the degree of chloride penetration also varies. Therefore, it is desirable to core the bricks so that they can be collected in each area. However, since the cooling zone has a short region and it is often difficult to remove the core, this may be omitted.

  Further, the core removal is performed at four positions at 90 ° intervals in the circumferential direction of the shell 8c (only the core hole H is shown in FIG. 5 (b)), and a total of 16 positions are performed together with the axial direction. The interval between the circumferential angles at which the core is removed and the position of the core removal are merely examples and are not limited thereto.

  The timing for performing the core removal is, for example, four months in the axial direction in FIG. 5 and four in the circumferential direction at each location, one for each location in the circumferential direction, three months after the operation period. By analyzing the brick 8d by dividing the core into four parts in the same half year, the same year, and the second year, the brick 8d is analyzed in a plurality of different areas in the axial direction of the kiln 8 in a time series. The penetrance of radioactive material into 8d can be examined.

DESCRIPTION OF SYMBOLS 1 Radiocesium removal apparatus 2 Raw material preparation apparatus 3-6 Storage tank 7 Baking apparatus 8 Rotary kiln 8a Input port 8b Burner 8c Shell 8d Brick 9 Cooler 10 Exhaust gas treatment apparatus 11 Cooling tower 11a Sprinkler 12 Cyclone 16 1st dust collector 17 2nd dust collector 18 Denitration device 19 Chimney 21 Mounting seat 21a Upper plate 21b Side plate 21c Through long hole 22 Core drill 22a Drill portion 22b Convex portion 22c Mounting portion B Fired product C Coarse powder D Drill diameter D1, D2 Dust G, G1-G5 Exhaust gas H Core hole L Length M Preparation raw material N Neutralizing agent S Surface W opposite to the surface to be affixed (Waste contaminated with radioactive cesium)

Claims (4)

In a rotary kiln comprising a hollow cylindrical metal shell and a brick lined to the metal shell,
A method for recovering a refractory brick for a rotary kiln contaminated with a radioactive material, wherein the brick inside the rotary kiln is extracted from the outside of the rotary kiln by core removal. The diameter of the core is smaller than the minimum side length of the brick;
Before performing the core removal, peel off a part of the metal shell to confirm the position of the brick,
The method for recovering a refractory brick for a rotary kiln contaminated with a radioactive material according to claim 1, wherein the core is removed so that the core hole is accommodated in one brick.   The method for recovering refractory bricks for a rotary kiln contaminated with a radioactive material according to claim 1 or 2, wherein the core removal is performed at a plurality of locations along the axial direction of the rotary kiln.   The said core removal is performed in multiple places over the circumferential direction of the said rotary kiln, The collection method of the firebrick for rotary kilns contaminated with the radioactive material of Claim 1, 2, or 3 characterized by the above-mentioned.

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