JP6363936B2 - Pollutant removal method - Google Patents

Description

  The present invention relates to a method for removing pollutants (harmful substances) such as toxic substances, radioactive substances, and bacteria.

  For example, in highway tunnels, walls and lamps are regularly cleaned and repaired. However, toxic substances (pollutants) such as black glaze, NOx dust, SOx dust, PM dust, and dioxin derived from automobile exhaust gas are used. ) Is regarded as a problem. That is, dust and treated water generated during cleaning may contaminate the environment such as air, water, and soil, and may impair the health of decontamination workers and surrounding residents. Therefore, in Patent Document 1, a dry ice pellet that does not cause secondary contamination is used as a blast medium (projection material), and a moving work section surrounded by a cover that covers the blast nozzle (injection nozzle) and the injection region is provided. The negative pressure of the pollutant is prevented from spreading.

  Also, for example, in nuclear power plants and nuclear fuel reprocessing plants, dust and treated water generated when decontaminating radioactive materials (contaminants) such as radioactive waste and buildings have an environment such as air, water, and soil. There is a risk of contamination and the health of decontamination workers and local residents. Therefore, in Patent Document 2, dry ice pellets that do not cause secondary contamination are used as blast media (projection material), a moving work chamber that is surrounded by a blocking wall and accommodates a blast gun (injection nozzle), and a hood that covers the injection area. And the expansion of the contamination is prevented by sucking the contaminant in the hood under a negative pressure.

  By making the work section including the spray nozzle for dry ice pellets movable as in Patent Documents 1 and 2, the entire tunnel interior, the interior of the nuclear power plant, and the like can be efficiently decontaminated. However, in such a case, even if you try to extend the dry ice pellet supply hose to extend the movement range of the work section, the dry ice pellets ejected from the nozzle gradually become smaller as the transport distance becomes longer, and eventually the injection nozzle This causes a phenomenon in which the pellets are no longer sprayed and the peeling function is lost. Dry ice pellets supplied to the injection nozzle through a synthetic resin supply hose are physically scraped by contact (and friction) between the pellets or by contact (and friction) between the inner surface of the supply hose and the pellets. It is considered that the temperature gradually decreases as a result of repeated adhesion and detachment from the inner surface of the supply hose, or progress of sublimation before injection due to a temperature rise accompanying the generation of frictional heat. Further, if the temperature rises while the compressed air flows through the air supply hose, it is assumed that heat is transferred to the dry ice pellets during mixing to promote sublimation of the dry ice pellets and hence a reduction in impact energy. As a result of these synergistic effects, the distance that dry ice pellets can be conveyed by the supply hose is generally less than 10 m.

  By the way, it often occurs when the radius of the tunnel of the expressway reaches 10 m or more, or when the movement distance in the primary building is required 10 m or more. In such a case, the decontamination work cannot be continued unless the pellet and compressed air supply sources (at least a part thereof) are moved in the tunnel or the building together with the moving work section in addition to the injection nozzle. Decreases and decontamination costs increase.

Japanese Patent Laid-Open No. 10-337667 JP2013-210210A

  The subject of this invention is providing the contaminant removal method which can extend the supply hose for supplying a dry ice pellet to an injection nozzle long, and can improve the efficiency of a decontamination operation | work.

Means for Solving the Problems and Effects of the Invention

In order to solve the above problems, the pollutant removal method of the present invention is:
The dry ice pellets supplied via the pellet supply hose and the compressed air supplied via the air supply hose are mixed by an injection nozzle and sprayed onto the contaminated surface to which the contaminant has adhered, and the contaminant is injected into the contaminated surface. In the pollutant removal method that peels off from and captures and recovers the peeled contaminants,
The dry ice pellets are added with a curing agent that increases the hardness of the dry ice pellets and has volatility at room temperature,
In the middle of the air flow path between the compressed air supply source and the air supply hose, a coolant that cools the compressed air passing through the air flow path to 0 ° C. or less is mixed in an inert gas state,
When the dry ice pellets and compressed air are sprayed from the spray nozzle onto the contaminated surface, the hardener is a volatile gas and the coolant is an inert gas. The material and the dry ice pellet are recovered together with sublimated carbon dioxide.

  In this way, the hardness of the dry ice pellets is increased by the addition of the curing agent, and the compressed air is cooled to 0 ° C. or less by mixing the coolant, so that it is mixed with the compressed air and injected by the injection nozzle through the pellet supply hose. The dry ice pellets are less likely to be broken (hard to be scraped) over the entire interval until the temperature rises, and the temperature rise is suppressed, so that sublimation before injection (strictly speaking, before pollutant removal) does not proceed easily. As a result, the pellet supply hose (and the air supply hose) can be extended long (for example, up to about 100 m or more) to secure a wide work area, and the efficiency of the decontamination work can be improved.

  In the present invention, the “pollutant” may contaminate the environment such as air, water, and soil, such as toxic substances, radioactive substances, and bacteria, or may impair the health of decontamination workers and the surrounding residents. A harmful substance in general. For example, in highway tunnels, it is mainly a toxic substance such as black glaze, NOx dust, SOx dust, PM dust, dioxin. In nuclear power plants, nuclear fuel reprocessing plants and their surrounding areas, they are mainly radioactive materials such as cesium and plutonium.

  The trapping device is, for example, a planar nonwoven fabric air filter, and one and the other of the activated carbon layer and the zeolite layer downstream in series, and the contaminant removal that passed through one and the other of the air filter, the activated carbon layer and the zeolite layer. Exhaust air afterwards.

  Curing agents are alcohols such as ethyl alcohol and methyl alcohol. Powdered (powdered) dry ice obtained by cutting a dry ice block (ie, dry ice powder) or powdered carbon dioxide solidified. When (snowy) dry ice (that is, dry ice snow) is pressed and formed into dry ice pellets, it is added by spraying.

  By spraying alcohol as a hardener when molding dry ice pellets, the hardness of the pellets can be increased uniformly. The curing agent includes aromatic alcohol (for example, benzyl alcohol, salicyl alcohol), alicyclic alcohol (for example, cyclohexanol, cyclooctanol) and the like in addition to ethyl alcohol and methyl alcohol.

  The dry ice pellet is prepared so that the Mohs hardness after adding the curing agent is 2.5 to 3.

  The addition of a curing agent improves the Mohs hardness of the dry ice pellets to 2.5-3, so that even if the pellet supply hose is extended, contact between the pellets (and friction) and contact with the inner surface of the supply hose (and friction) ) Pellets that are resistant to breakage and are difficult to cut. The Mohs hardness of the dry ice pellets to which the hardener is added is harder than gypsum (Mohs hardness 2) and comparable to calcite (Mohs hardness 3). If the Mohs hardness is less than 2.5, the dry ice pellets may become smaller before jetting due to contact between the pellets or contact with the inner surface of the supply hose, and impact energy may be insufficient. On the other hand, if the Mohs hardness exceeds 3, the impact energy increases and the contaminated surface may be damaged.

  The coolant is nitrogen gas, carbon dioxide or a rare gas, and is mixed into the compressed air flowing through the air flow path when the compressed air is injected from the injection nozzle onto the contaminated surface.

  Mixing of coolant in the air flow path makes it easier for the compressed air to maintain a low temperature (below 0 ° C) even in the air supply hose following the air flow path, reducing the impact energy of the dry ice pellets injected from the injection nozzle Can be suppressed. In addition to nitrogen gas and carbon dioxide, the coolant includes rare gases, that is, helium, neon, argon, krypton, xenon, and radon.

  The compressed air is adjusted so that the temperature when the coolant is mixed is 0 ° C. to −10 ° C.

  By setting the temperature of the compressed air to 0 ° C. to −10 ° C. between the compressed air supply source and the air supply hose by mixing the coolant (that is, upstream of the air supply hose), the pellet supply hose ( And even if the air supply hose) is extended for a long time, the temperature of the compressed air is kept low, and a reduction in impact energy of the dry ice pellets injected from the injection nozzle can be suppressed. If the temperature of the compressed air exceeds 0 ° C. upstream of the air supply hose, the sublimation of the dry ice pellet proceeds before the collision with the contaminated surface, and the impact energy of the dry ice pellet may be reduced. On the other hand, when the temperature of the compressed air is lower than −10 ° C. on the upstream side of the air supply hose, the air supply hose is frozen and the quality deteriorates and is easily damaged.

The schematic diagram which shows the example which applied the contaminant removal method which concerns on this invention to the decontamination in a tunnel. The schematic diagram which shows the example which applied the contaminant removal method which concerns on this invention to decontamination in a nuclear power plant building. Explanatory drawing which expands and shows the supply area which is a principal part common to FIG. 1 and FIG. Explanatory drawing which expands and shows the principal part of a capture device. Explanatory drawing which shows the modification of FIG.

  Hereinafter, embodiments of the present invention will be described with reference to examples shown in the drawings. FIG. 1 is a schematic view illustrating decontamination in a tunnel as an application example of the pollutant removal method according to the present invention. The pollutant removal apparatus 1 shown in the conceptual diagram of FIG. 1 includes a pellet supply unit 21 that supplies dry ice pellets DP that is sprayed onto the wall surface PS (contamination surface) of the tunnel TN to which the contaminant RM has adhered, and is gripped by an operator. And a spray nozzle 24 (spray gun) that sprays the dry ice pellet DP onto the wall surface PS. Further, the pollutant removing device 1 is located in the booth 3 with the bellows opening / closing type covering the space around the wall surface PS on which the dry ice pellet DP is jetted so that the pollutant RM is not scattered. The negative pressure suction part 4 (suction port) for sucking the pollutant RM peeled off from the wall surface PS is connected to the negative pressure suction part 4 via a bellows-type telescopic hose 6 as a communication means. The trapping device 5 that captures the pollutant RM in the process of collecting the pollutant RM sucked by the unit 4 and transferred via the hose 6 in the trapping unit 72 (filter device) and passing it together with air is provided. Further, the contaminant removing device 1 includes a negative pressure pump 8 (suction pump) as a negative pressure generating device that generates a negative pressure that acts on the negative pressure suction unit 4.

  The pollutant removing device 1 decontaminates the wall surface PS contaminated with a pollutant RM that is a toxic substance such as black candy, NOx dust, SOx dust, and the like. For example, an operator holding the injection nozzle 24 gets on the lifting platform 101 of the movable work platform 100, and the dry ice pellet DP is injected from the injection nozzle 24 onto the wall surface PS. The entire lifting work table 101 and a part of the wall surface PS to be decontaminated are isolated in the booth 3. The pellet supply unit 21, the capture device 5, the negative pressure pump 8, and the like are arranged outside the tunnel TN.

  In this contaminant removal apparatus 1, the dry ice pellet DP supplied through the pellet supply hose 21a and the compressed air supplied through the air supply hose 22a are mixed by the injection nozzle 24, and the contaminant RM adheres. The pollutant RM is peeled off from the wall PS by spraying on the wall PS, and the peeled pollutant RM is captured by the capture device 5 and collected. The pellet supply hose 21a and the air supply hose 22a are made of hard or soft synthetic resin. A fixed pipe (metal pipe such as cast iron pipe, stainless steel pipe, copper pipe) of the air flow path 13 is connected in series and in a straight line from the air compressor 11 and the air dryer 12 which are supply sources of compressed air to the pellet supply unit 21. The pellet supply unit 21 is connected to the air supply hose 22a. Accordingly, the compressed air is supplied from the air compressor 11 to the injection nozzle 24 via the air dryer 12, the air flow path 13, and the air supply hose 22a.

  The trap 5 is sucked from the booth 3 by the negative pressure pump 8 and the mass difference from the solid fragments such as wall concrete from the air containing the pollutant RM and the carbon dioxide etc. from which the dry ice pellet DP sublimated. Is provided with a separation chamber 71 that is separated by a trapping portion 72 (filter device) for adsorbing and capturing the contaminant RM and the like on the downstream side thereof. In the embodiment, the negative pressure pump 8 is provided between the separation chamber 71 and the capture unit 72, but the negative pressure pump 8 may be provided in front of the separation chamber 71 or behind the capture unit 72. Further, the separation chamber 71 may be provided with a separation device such as a cyclone to separate solids.

  As shown in FIG. 4, the capture unit 72 (filter device) downstream of the separation chamber 71 includes a HEPA filter 72a that is a planar nonwoven fabric air filter, an activated carbon layer 72b downstream thereof, and a zeolite layer 72c downstream thereof. Are arranged in series in the vertical direction. A connection pipe 73 having a predetermined length is connected between the HEPA filter 72a and the activated carbon layer 72b and between the activated carbon layer 72b and the zeolite layer 72c. The air sucked by the negative pressure pump 8 and introduced into the capture unit 72 passes through the HEPA filter 72a → the activated carbon layer 72b → the zeolite layer 72c. ) And the like are selectively adsorbed and collected, so that air after passing through them can be discharged into the atmosphere. In addition, you may make it pass through in order of HEPA filter 72a-> zeolite layer 72c-> activated carbon layer 72b.

  The above-mentioned HEPA filter (high efficiency particulate air filter) 72a is a filter paper-like fiber layer having a fiber diameter of 1 μm or less, and even a particle having a particle diameter of 0.1 μm has a dust collection rate of 99.99% or more. Therefore, by using the HEPA filter 72a as the non-woven air filter, fine solids (for example, dust, dust, soil particles, non-sublimated dry ice, etc.), and in some cases, predetermined radioactive contaminants can be captured. there is a possibility. Further, the activated carbon layer 72b and the zeolite layer 72c adsorb and capture radioactive contaminants such as cesium 134 and 137, for example. Activated carbon is a porous carbonaceous material having a high adsorbing ability, and zeolite (also called zeolite) is a molecular sieve having a gas selective adsorptive property. Nitrogen gas can be captured within a certain range.

  A sensor 74 for measuring the residual radiation dose is provided on the outlet side of the zeolite layer 72c, and the switching controller 75 controls the two switching valves based on the measured value of the sensor 74. That is, when the measured value of the residual radiation dose by the sensor 74 is within the allowable range, the switching controller 75 opens the outlet-side first switching valve 76 and discharges the air after passing into the atmosphere (the circulation-side first valve). The two switching valve 77 is closed). On the other hand, when the measured value is out of the permissible range, the switching controller 75 closes the outlet-side first switching valve 76 and opens the circulation-side second switching valve 77 to allow the air after passing through the separation chamber 71 and the negative pressure. It circulates to the HEPA filter 72a, the activated carbon layer 72b, and the zeolite layer 72c via the pump 8 (see FIGS. 1 and 2).

  As described above, the pollutant RM is peeled off from the wall surface PS by the impact energy at the time of spraying the dry ice pellet DP, and all or most of the dry ice pellet DP is sublimated into a gas. Can be done.

  Next, FIG. 2 is a schematic view illustrating the decontamination inside the nuclear power plant as an application example of the pollutant removal method according to the present invention. In the pollutant removal apparatus 1 shown in the conceptual diagram of FIG. 2, the dry ice pellet DP is jetted onto the wall surface PS (contaminated surface) of the primary building BL to which the radioactive pollutant RM has adhered. That is, this contaminant removal apparatus 1 decontaminates the wall surface PS contaminated with radioactive contaminants RM such as cesium and plutonium. For example, a remotely operated spray nozzle 24 is mounted on the lifting work table 201 of the movable unmanned traveling vehicle 200, and the dry ice pellet DP is sprayed from the spray nozzle 24 to the wall surface PS. The entire lifting work table 201 and a part of the wall surface PS to be decontaminated are isolated in the booth 3. The pellet supply unit 21, the capture device 5, the negative pressure pump 8, etc. are arranged outside the nuclear power plant building BL, and decontaminate the nuclear power building BL unattended for safety.

  FIG. 3 is an explanatory diagram showing an enlargement of a supply area which is a main part common to FIGS. 1 and 2. As shown in FIG. 3, when the liquid carbon dioxide 31 contained in the cylinder is blown into the cylinder 32 while being adiabatically expanded, it is solidified into a powdery form (snowy form) (freezing point (sublimation point) −78.5 ° C.) and the powder. When the dry ice snow D1 is pressed and hardened by the piston 33, a rod-shaped dry ice D2 is formed. When this rod-shaped dry ice D2 is cut with a cutter 34, a cylindrical dry ice pellet DP is formed. When the powdered dry ice snow D1 is pressed and hardened, the ethyl alcohol AL is uniformly added to the dry ice pellets DP by spraying the ethyl alcohol AL into the cylinder 32.

  By adding ethyl alcohol AL to the dry ice pellet DP, the ordinary dry ice pellet DP has a Mohs hardness of 1.5 (harder than talc and softer than gypsum) to 2 (same as gypsum). Hardens from 2.5 (harder than gypsum and softer than calcite) to 3 (similar to calcite). By adding ethyl alcohol AL as a curing agent and injecting dry ice pellets DP with increased hardness from the injection nozzle 24, the pellet supply hose 22a does not change shape (becomes small or cracks) during conveyance, and impact Energy reduction is suppressed. Further, when blasting the dry ice pellet DP, ethyl alcohol AL is volatile at room temperature and is adsorbed by the activated carbon layer 72b and the zeolite layer 72c, so that secondary contamination does not occur.

  Since the dry ice pellet DP is formed in a predetermined shape (for example, a short-axis columnar shape having a diameter of 2 to 3 mm and a length of 2 to 6 mm) such as a columnar shape or a prismatic shape, the dry ice pellet DP is used as it is in the pellet supply unit 21. It puts into the pellet hopper 21b. Due to the venturi effect of the compressed air supplied to the injection nozzle 24, the dry ice pellet DP in the pellet hopper 21b is sucked, supplied to the injection nozzle 24 via the pellet supply hose 21a, and injected in a state of being mixed with the compressed air. Injected from the nozzle 24.

  In an inert gas state, nitrogen gas 35 obtained by evaporating liquid nitrogen (boiling point−195.8 ° C.) in a cylinder in an air flow path 13 (metal pipe line) between the air dryer 12 and the pellet supply unit 21 is used. When mixed, the compressed air passing through the air flow path 13 is cooled to 0 ° C. or lower (specifically, 0 ° C. to −10 ° C.). Thus, by mixing the nitrogen gas 35 into the air flow path 13 as a coolant, a decrease in impact energy of the dry ice pellet DP can be suppressed. Further, when the dry ice pellet DP is blasted, the nitrogen gas 35 is in an inert gas state and is adsorbed by the activated carbon layer 72b and the zeolite layer 72c, so that secondary contamination does not occur.

  Thus, ethyl alcohol AL is added as a hardener to the dry ice pellet DP, and nitrogen gas 35 is mixed as a cooling agent into the compressed air, thereby suppressing a reduction in impact energy of the dry ice pellet DP, The pellet supply hose 21a (and the air supply hose 22a) can be extended to, for example, about 100 m. As a result, the air compressor 11, the air dryer 12, the air flow path 13 and the like are installed outside the tunnel TN and the nuclear power plant building BL, and the pellet supply hose 21a, the air supply hose 22a, the injection nozzle 24 and the like are installed in the tunnel TN and the nuclear power plant building BL. Since it only needs to move inside, decontamination work efficiency is dramatically improved.

  FIG. 5 is an explanatory view showing a modification of FIG. As shown in FIG. 5, a dry ice powder D1 ′ in the form of a powder (powder) obtained by cutting a prismatic (for example, 100 mm × 100 mm × 130 mm, weight about 2 kg) dry ice block DB with a cutting blade 30 Is introduced into the cylinder 32, and the powdery dry ice powder D1 ′ is pressed and hardened by the piston 33 to form a rod-shaped dry ice D2. When this rod-shaped dry ice D2 is cut with a cutter 34, a cylindrical dry ice pellet DP is formed. When the powdered dry ice powder D <b> 1 ′ is pressed and hardened, the ethyl alcohol AL is uniformly added to the dry ice pellets DP by spraying the ethyl alcohol AL into the cylinder 32.

  Specifically, the cutting blade 30 is disposed so as to protrude upward from a slit 301a formed in the placement portion 301 on which the dry ice block DB is placed, and is pressed against the bottom surface of the dry ice block DB. The dry ice block DB rotates about the drive shaft 303 of the holder 302 on the rotary sliding surface 301b formed on the mounting portion 301, and is cut by the cutting blade 30 to generate powdery dry ice powder D1 ′. Is done. Powdered dry ice powder D <b> 1 ′ is introduced from the funnel-shaped hopper 304 into the cylinder 32 through the powder hose 305. The hopper 304 is formed in an inverted conical shape in which the cross section gradually decreases from the trumpet-shaped opening 304 a located below the cutting blade 30 toward the lower part.

  Also in FIG. 5, dry ice pellets DP (ordinary Mohs hardness is 1.5 to 2), with the addition of ethyl alcohol AL, Mohs hardness 2.5 (harder than gypsum and softer than calcite) to 3 (similar to calcite) ) To cure. Moreover, in FIG. 5, since ethyl alcohol AL is sprayed (added) when the dry ice powder D1 ′ obtained by shaving the dry ice block DB having a uniform hardness is pressed and hardened again, Ethyl alcohol AL tends to be uniformly distributed in the dry ice pellet DP. Therefore, the dry ice pellet DP having a Mohs hardness of 2.5 to 3 is obtained as compared with the case where the dry ice pellet DP is formed from the powdery dry ice snow D1 obtained by adiabatic expansion of the liquid carbon dioxide 31 as shown in FIG. Therefore, the amount of ethyl alcohol AL added can be reduced (for example, about 20 to 50%).

  In FIG. 2, parts having the same functions as those in FIG. Similarly, in FIG. 5, parts having the same functions as those in FIG.

  In addition, these embodiments can be appropriately combined and implemented within a range that does not cause technical contradiction. Further, the present invention is not limited to the radioactive substances and toxic substances described above, and can be widely applied to apparatuses and methods for removing pollutants that pollute the environment such as air, water, and soil.

Based on the above description, it is possible to grasp the above-described contaminant removal apparatus as a novel invention. For example,
The dry ice pellets supplied via the pellet supply hose and the compressed air supplied via the air supply hose are mixed, sprayed onto the contaminated surface to which the contaminant has adhered, and the contaminant is peeled off from the contaminated surface. An injection nozzle;
A booth covering the spray nozzle and the space around the contaminated surface;
A negative pressure suction part which is located in the booth and sucks contaminants peeled off from the contaminated surface;
A capture device for capturing contaminants sucked from the negative pressure suction part;
A negative pressure generating device for generating a negative pressure acting on the negative pressure suction part,
In the manufacturing process of the dry ice pellets, an addition means for increasing the hardness of the dry ice pellets and adding a curing agent having volatility at room temperature is provided,
Mixing means for mixing a coolant for cooling the compressed air passing through the air flow path to 0 ° C. or less in an inert gas state in the middle of the air flow path between the compressed air supply source and the air supply hose. Is provided,
When the dry ice pellets and compressed air are sprayed from the spray nozzle onto the contaminated surface, the hardener is a volatile gas and the coolant is an inert gas. It is a pollutant removal device in which the substance and the dry ice pellet are collected by the capture device together with sublimated carbon dioxide.

1 Pollutant removal device 3 Booth 4 Suction port (negative pressure suction part)
5 Capturing device 6 Hose 8 Negative pressure pump (negative pressure generator)
11 Air compressor (Compressed air supply source)
12 Air dryer (Compressed air supply source)
13 Air flow path 21 Pellet supply part 21a Pellet supply hose 22a Air supply hose 24 Injection nozzle (injection gun)
31 Liquid carbon dioxide 35 Nitrogen gas (cooling agent)
72 Capture unit (filter device)
TN Tunnel BL Nuclear power plant PS Wall surface (contaminated surface)
RM pollutant (toxic substance; radioactive substance)
AL ethyl alcohol (curing agent)
DP Dry ice pellet DB Dry ice block

Claims (6)

The dry ice pellets supplied via the pellet supply hose and the compressed air supplied via the air supply hose are mixed by an injection nozzle and sprayed onto the contaminated surface to which the contaminant has adhered, and the contaminant is injected into the contaminated surface. In the pollutant removal method that peels off from and captures and recovers the peeled contaminants,
The dry ice pellets are added with a curing agent that increases the hardness of the dry ice pellets and has volatility at room temperature,
In the middle of the air flow path between the compressed air supply source and the air supply hose, a coolant that cools the compressed air passing through the air flow path to 0 ° C. or less is mixed in an inert gas state,
When the dry ice pellets and compressed air are sprayed from the spray nozzle onto the contaminated surface, the hardener is a volatile gas and the coolant is an inert gas. A pollutant removal method, wherein the substance and the dry ice pellet are recovered together with sublimated carbon dioxide.   The curing agent is an alcohol such as ethyl alcohol or methyl alcohol, and is added by spraying when powdered dry ice obtained by cutting a dry ice block is pressed and formed into the dry ice pellets. The pollutant removal method according to claim 1.   The hardener is an alcohol such as ethyl alcohol and methyl alcohol, and is added by spraying when powdered dry ice in which liquid carbon dioxide is solidified is pressed and formed into the dry ice pellets. The described contaminant removal method.   The pollutant removal method according to any one of claims 1 to 3, wherein the dry ice pellet is prepared such that the Mohs hardness after the addition of the curing agent is 2.5 to 3.   5. The coolant according to claim 1, wherein the coolant is nitrogen gas, carbon dioxide, or a rare gas, and is mixed into the compressed air flowing through the air flow path when the compressed air is sprayed from the spray nozzle onto the contaminated surface. The method for removing contaminants according to claim 1.   The pollutant removal method according to any one of claims 1 to 5, wherein the compressed air is adjusted so that a temperature when the coolant is mixed is 0 ° C to -10 ° C.

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