Methods for treating persistent organic pollutants

Abstract

This invention provides a method for decomposing POPs (Potential Population Sulfites) while minimizing the impact on clinker quality, even when introducing the POPs from the front of the cement kiln. [Solution] This processing method uses a cement clinker manufacturing facility comprising a cement kiln, a kiln burner installed at the front of the kiln, a first pipe installed at the front of the kiln for blowing in the material to be processed, including POPs, and a clinker cooler connected to the front of the kiln for blowing in cooling air. When viewed in the direction of blowing from the kiln burner, the material to be processed is blown through the first pipe into a region sandwiched between a first position vertically below the axis of the kiln burner and a second position advanced 180° from the first position in the rotational direction of the cement kiln, with respect to the axis of the kiln burner.

Description

Technical Field

[0001] The present invention relates to a method for treating persistent organic pollutants.

Background Art

[0002] Persistent Organic Pollutants (POPs) are substances that are difficult to decompose in the environment, tend to accumulate in living organisms, have long-range mobility, and can harm the human body. Since there is concern about global pollution by POPs, the "Stockholm Convention on Persistent Organic Pollutants" (POPs Convention) has been adopted and came into force in May 2004.

[0003] POPs include dioxins, PCBs (polychlorinated biphenyls), DDT, and PFAS (perfluoroalkyl substances and polyfluoroalkyl compounds), etc. As a method for decomposing these substances, heat treatment at high temperatures is known to be effective.

[0004] The applicant of the present application has previously proposed a method for suppressing the generation of dioxins by subjecting the processed municipal solid waste obtained by fermenting municipal solid waste to heat treatment using a cement kiln (see Patent Document 1 below).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] The method described in Patent Document 1 involves separating the fermented municipal solid waste into coarse particles with a high calorific value containing a large amount of waste plastics, etc., and fine particles with a low calorific value. The coarse particles are then fed in through a kiln burner, and the fine particles are fed in from the rear of the kiln. According to this method, the coarse particles, which contain waste plastics, etc., can be burned at the high temperature inside the cement kiln by being fed in from the front, thereby suppressing the generation of POPs.

[0007] However, unlike fine particles introduced from the kiln burner, the coarse particles introduced from the kiln burner are introduced near the kiln hood, where the clinker cooler is connected and the clinker is cooled. This means that POPs contained in the coarse particles may be introduced into and adhere to the clinker, potentially degrading its quality.

[0008] In view of the above problems, the present invention aims to provide a method for decomposing POPs that can be introduced from the front of a cement kiln while suppressing the impact on the quality of the clinker. [Means for solving the problem]

[0009] The method for treating persistent organic pollutants according to the present invention is: A method using cement clinker manufacturing equipment, The aforementioned processing method is a method using cement clinker manufacturing equipment, The aforementioned cement clinker manufacturing facility is Cement kiln and, A kiln burner is installed at the front of the cement kiln and blows fuel into the cement kiln. A first pipe is installed in the front of the kiln and blows the material to be treated, which contains persistent organic pollutants, into the cement kiln. The kiln is connected to the front of the kiln and includes a clinker cooler into which cooling air is blown, The method is characterized in that, when viewed in the blowing direction of the kiln burner, the material to be processed is blown through the first pipe into a region sandwiched between a first position vertically below the axis of the kiln burner and a second position advanced 180° from the first position in the rotational direction of the cement kiln with respect to the axis of the kiln burner.

[0010] In this invention, "persistent organic pollutants" refers to substances known as POPs, which are defined in the POPs Convention. Typically, POPs include PFAS, dioxins, DDT, and PCBs. PFAS are organofluorine compounds belonging to POPs, and are a general term for perfluoroalkyl compounds and polyfluoroalkyl compounds. Typical PFAS include PFOS (perfluorooctanesulfonic acid), PFOA (perfluorooctanoic acid), PFHxS (perfluorohexanesulfonic acid), and PFNA (perfluorononanoic acid). In Japan, regulatory limits have been set for PFOS and PFOA. For example, in the United States, standard concentrations for PFHxS and PFNA in drinking water have also been set. Therefore, it is possible that regulatory limits for PFHxS and PFNA will also be set in Japan in the future.

[0011] As described above, in the treatment method according to the present invention, the material to be treated, which contains persistent organic pollutants, is introduced into the cement kiln through a first pipe installed at the front of the cement kiln.

[0012] According to the "Technical Considerations Regarding the Treatment of PFOS and PFOA-Containing Waste" (hereinafter abbreviated as "Ministry of the Environment document") published by the Ministry of the Environment in September 2022, examples of waste containing PFAS include fire extinguishing foam, containers that hold PFAS-containing materials, and cloths used to wipe up PFAS-containing washing water. Furthermore, since technologies for concentrating, separating, and recovering PFAS using activated carbon and anion exchange resins are known, waste materials such as activated carbon and resins used in these treatments are also considered to be PFAS-containing waste.

[0013] Furthermore, according to the above-mentioned Ministry of the Environment document, treatment at approximately 850°C or higher for 2 seconds or more is recommended for PFOS, and at approximately 1,000°C or higher for 2 seconds or more is recommended for PFOA. PFOS and PFOA are representative substances of the PFAS group, and this Ministry of the Environment document does not mention other substances. However, if we apply the strict standards among these, it can be inferred that treatment at approximately 1,000°C or higher for 2 seconds or more is recommended when treating PFAS. Also, even when considering the broader concept of POPs, it can be inferred that if a material containing POPs can be treated at approximately 1,000°C or higher for 2 seconds or more, decomposition of POPs is possible.

[0014] One possible method for processing materials containing POPs under the high-temperature environment described above is to use a general incinerator. However, processing at a general incinerator generates incineration residue (bottom ash, fly ash), which becomes secondary waste. This secondary waste is usually disposed of in landfills.

[0015] Another method for processing materials containing POPs under the high-temperature environment described above is to utilize the cement manufacturing process. In the cement manufacturing process, processing takes place at a high temperature of approximately 1,450°C, and the incineration residue is incorporated into the cement clinker, thus eliminating the generation of secondary waste. For this reason, it has traditionally been used in technologies to convert waste materials such as waste plastics and waste tires into raw materials.

[0016] In cement clinker manufacturing facilities, there are many areas (equipment and piping) that exhibit different temperatures, and the air velocity of the gas flowing through the equipment and piping also varies in some locations. Therefore, even when using the cement manufacturing process to process materials containing POPs, careful consideration is needed regarding which area of ​​the cement clinker manufacturing facility should be used to process the materials.

[0017] Examples of locations where materials to be processed can be introduced include the tail end of a cement kiln, the duct connected to the tail end (rising duct), and the calcination furnace. Compared to the front of the cement kiln, these locations offer greater flexibility in the area where materials can be introduced, making it possible to introduce, for example, large lumps of materials to be processed. Thus, in terms of relaxing the requirements regarding the packaging of the materials to be processed, one or more of the tail end, rising duct, and calcination furnace can be considered superior to the front of the kiln as locations for introducing materials to be processed.

[0018] On the other hand, the front of a cement kiln, where a kiln burner is installed, creates a higher temperature environment compared to the rear of the kiln, the rising duct, and the calcination furnace. Therefore, the front of the kiln has an advantage over the rear of the kiln, the rising duct, and the calcination furnace as a point for introducing materials to be processed, in that it can achieve high decomposition rates for recalcitrant substances such as POPs.

[0019] However, since the front of the kiln is close to the discharge outlet (clinker cooler) of cement clinker fired in the cement kiln, there is a possibility that POPs contained in the material being processed may adhere to the cement clinker, affecting its quality. According to the above Ministry of the Environment document, 5.0 μg / kg has been set as a reference value for management targets of PFOS and PFOA contained in the residue.

[0020] Through diligent research by the inventors, it has been discovered that by placing the POPs injection point within the region between a first position vertically below the axis of the kiln burner and a second position 180° from the first position in the rotational direction of the cement kiln, when viewed in the injection direction of the kiln burner, the concentration of PFOS and PFOA remaining in the clinker can be kept below the above-mentioned reference control value, even when a material containing extremely high concentrations of PFOS and PFOA is injected.

[0021] The reason for this is that, regarding the rotation direction of the cement kiln, the region between the first position and the second position corresponds to a region where the air (secondary air) that has been used for cooling the cement clinker and introduced into the cement kiln from the clinker cooler generates an upward air current. That is, by introducing the object to be processed into the above region, the object to be processed rides on the upward air current and floats in the cement kiln, and the time for being exposed to a high-temperature environment can be ensured before landing on the cement clinker. As a result, it is considered that the time for decomposing the POPs contained in the object to be processed can be ensured before landing on the cement clinker, particularly before landing on the cement clinker located near the clinker cooler.

[0022] The object to be processed is assumed to be any one of a solid, a slurry, or a liquid. Among these, when the object to be processed is a liquid or a slurry with a solid content of less than 20% by mass, as described above, it may be introduced from any location within the region sandwiched between the first position directly below the axis of the kiln burner and the second position advanced 180° in the rotation direction of the cement kiln from the first position based on the axis of the kiln burner. Examples of the liquid object to be processed include a foam fire extinguishing agent, a cleaning liquid after washing POPs, etc. Further, examples of the slurry object to be processed include activated carbon slurry.

[0023] On the other hand, when the object to be processed is a solid or a slurry with a solid content of 20% or more by mass, it is preferably introduced into the region sandwiched between the third position advanced 90° in the rotation direction of the cement kiln from the first position based on the axis of the kiln burner and the second position when viewed in the blowing direction of the kiln burner.

[0024] If the material to be processed is a solid or a slurry with a solid content of 20% or more by mass, it is likely to fall to the bottom of the cement kiln due to its own weight. In this case, by placing the material to be processed in the region between the third and second positions, which is relatively farther away (closer to the top) than the region between the first and second positions in the rotational direction of the cement kiln, the time it takes for the material to fall to the bottom of the cement kiln while being carried by the secondary airflow can be extended, even for materials with a high solid content.

[0025] In particular, when the material to be processed is solid, it is preferable that the material has a particle size that allows it to pass through a Φ30 mm sieve completely, from the viewpoint of increasing its buoyancy by secondary air. That is, before introducing the material into the cement kiln through the first piping, pre-treatment such as crushing may be performed on the material to be processed as necessary to reduce its particle size to a level that allows it to pass through a Φ30 mm sieve completely.

[0026] Examples of solid materials to be processed include those containing at least one of plastic resins and activated carbon. A specific example of a resin is the anion exchange resin used in the separation of POPs.

[0027] When the material to be processed is a slurry, it is acceptable to dilute the slurry with a liquid before introducing it into the cement kiln through the first piping, in order to reduce the solid content of the slurry. In this case, water is typically used as the liquid for dilution, but other liquids that have been conventionally introduced into cement kilns, such as waste oil or alkaline waste liquid, can also be used.

[0028] When viewed in a first direction that is parallel to the horizontal plane and perpendicular to the axis of the kiln burner, a first virtual line, which is a virtual extension of the axis of the kiln burner, and a second virtual line, which is a virtual extension of the axis of the first piping, may intersect at a position within a range of 5m to 25m from the tip of the kiln burner with respect to the direction of the axis of the kiln burner.

[0029] If the material to be processed is introduced from the first piping in such a way that the first and second virtual lines intersect within 5 meters of the tip of the kiln burner in the direction of the kiln burner's axis, the area of ​​the material being processed will be more frequently crossed by the flame formed by the kiln burner, potentially impairing the stability of the flame.

[0030] On the other hand, if the material to be processed is introduced from the first piping so that the first and second virtual lines intersect in an area more than 25m away from the tip of the kiln burner in the direction of the kiln burner's axis, there is a concern that the wind speed and airflow required to bring the material to the high-temperature environment created by the flame formed by the kiln burner will be excessive, leading to an increase in the cost of the material injection equipment.

[0031] The insertion length of the first pipe (the length protruding from the kiln hood) should preferably be 1 / 2 or less of the insertion length of the kiln burner. If the first pipe is installed close to the tip of the kiln burner, the surface area of ​​the pipe wall of the first pipe exposed to the high temperature of the flame formed by the kiln burner will increase, which may increase the degree of thermal wear of the first pipe.

[0032] Therefore, the kiln burner and the first piping are fixed to the downstream end face of the kiln hood, which is connected to the cement kiln, at the front of the kiln. When viewed in the first direction, it is preferable that the length of the first pipe protruding from the downstream end face in a direction parallel to the horizontal plane is 0.5 times or less the length of the kiln burner protruding from the downstream end face in a direction parallel to the horizontal plane.

[0033] In this case, the end of the first pipe will be closer to the kiln hood than the end of the kiln burner. If, in this case, the first and second virtual lines are to be crossed in an area more than 25m away from the tip of the kiln burner in the direction of the kiln burner's axis, the inclination angle of the first pipe will be close to horizontal. Furthermore, if the wind speed and volume of the gas (typically air) used to blow the material to be treated through the first pipe are below appropriate values, there is a possibility that it will fall towards the kiln hood rather than the tip of the kiln burner, making it difficult to expose the material to the high-temperature environment necessary for the decomposition of POPs.

[0034] The amount of persistent organic contaminants contained in the treated material to be added may be set to a value greater than 0 and 100 g / t-clinker or less per unit of raw material. More preferably, the amount of persistent organic contaminants contained in the treated material to be added is 60 g / t-clinker or less.

[0035] Furthermore, the ratio of the heat energy of the material to be processed to the total heat energy of the fuel and the material to be processed introduced into the cement kiln from the front of the kiln may be 30% or less. [Effects of the Invention]

[0036] The present invention provides a method for decomposing a target material containing POPs while suppressing the impact on clinker quality. [Brief explanation of the drawing]

[0037] [Figure 1] This is a schematic diagram showing one form of cement clinker manufacturing equipment used in implementing the method for treating persistent organic pollutants of the present invention. [Figure 2] Figure 1 is a schematic enlarged view of the area near the front of the kiln of the cement clinker manufacturing facility shown in Figure 1. [Figure 3] Figure 2 is a schematic plan view of the cement kiln 2 as seen from the kiln hood 21 side. [Figure 4] This diagram schematically illustrates only some of the elements extracted from Figure 3. [Figure 5] This diagram schematically shows the relationship between the installation positions of the kiln burner 8 and the first piping 20 when viewed from the kiln hood 21 to the cement kiln 2. [Figure 6] Figure 4 is a diagram overlaid with the assumed region where the axis of the first pipe 20 is located. [Modes for carrying out the invention]

[0038] Embodiments of the method for treating persistent organic pollutants according to the present invention (hereinafter abbreviated as "this treatment method") will be described below with reference to the drawings. The following drawings are schematic representations, and the dimensional ratios in the drawings do not necessarily match the actual dimensional ratios, nor do the dimensional ratios between the drawings necessarily match.

[0039] Figure 1 is a schematic diagram showing one configuration of a cement clinker manufacturing facility used in implementing this processing method. As shown in Figure 1, the cement clinker manufacturing facility 1 includes a cement kiln 2 with a kiln burner 8 installed on the kiln front 11 side.

[0040] In the example shown in Figure 1, the cement clinker manufacturing equipment 1 comprises an upper cyclone 3, a rising duct 4 connected to the bottom 12 of the cement kiln 2, a calcination furnace 5 including a calcination burner 7, and a bottom cyclone 6 connected to the calcination furnace 5.

[0041] The cement raw materials, preheated by passing through the upper cyclone 3 (which consists of one or more stages), are introduced into the calcination furnace 5. In the structure of the cement clinker manufacturing facility 1 illustrated in Figure 1, the cement raw materials introduced into the calcination furnace 5 are calcined as they rise along with the flow of kiln combustion gas rising in the rising duct 4. The calcined cement raw materials are then sent by gas to the bottom cyclone 6 for solid-gas separation.

[0042] In the cement clinker manufacturing facility 1 shown in Figure 1, the gas outlet of the bottom cyclone 6 is connected to the upper cyclone 3, and the gas obtained by solid-gas separation in the bottom cyclone 6 is sent to the upper cyclone 3 and used for preheating the cement raw materials. On the other hand, the solid outlet of the bottom cyclone 6 is connected to the kiln end 12 through the bottom raw material chute 14. As a result, the cement raw materials decarboxylated by the calcination furnace 5 are introduced into the kiln end 12 from the bottom raw material chute 14 and then sent into the cement kiln 2. These cement raw materials are then fired in the cement kiln 2 under high-temperature conditions created by the combustion of fuel (main fuel) such as coal by the kiln burner 8, and transformed into cement clinker. After that, the cement clinker is cooled in the clinker cooler 13 and discharged.

[0043] Although Figure 1 shows an example where the cement clinker manufacturing facility 1 includes a calcination furnace 5, whether or not to include a calcination furnace 5 is optional.

[0044] As shown in Figure 1, the cement clinker manufacturing facility 1 is equipped with a first pipe 20 on the front 11 side of the cement kiln 2. As shown in Figure 2, this first pipe 20 is provided for introducing a material to be treated P1 containing persistent organic contaminants into the cement kiln 2. The material to be treated P1 may be in any form, such as solid, liquid, or slurry. The material to be treated P1 is not limited to materials containing persistent organic contaminants (POPs) such as PFAS, but examples include foam fire extinguishing agents, activated carbon, and resins. An example of a resin is anion exchange resin used when separating POPs.

[0045] The persistent organic pollutants (POPs) contained in the treated material P1 are substances defined in the POPs Convention and typically include PFAS, dioxins, DDT, and PCBs. PFAS typically include PFOS, PFOA, PFHxS, and PFNA.

[0046] Figure 2 is a schematic enlarged view of the area near the kiln front section 11 shown in Figure 1. As shown in Figure 2, the kiln front section 11 is provided with a kiln hood 21 connected to the cement kiln 2.

[0047] As described above, cement raw materials are introduced into the cement kiln 2 from the bottom raw material chute 14 via the kiln end 12. The cement kiln 2 has a horizontal cylindrical shape that is slightly inclined downward toward the downstream side (towards the kiln hood 21), and burns the cement raw materials while rotating in a high-temperature environment formed by the flame generated by the kiln burner 8.

[0048] The kiln hood 21 is the part that surrounds the downstream end of the cement kiln 2. The lower part of the kiln hood 21 is connected to the clinker cooler 13. The kiln burner 8 and the first piping 20 are fixed to the downstream end face 21a of the kiln hood 21. A portion of the downstream end face 21a of the kiln hood 21 is typically a door-like structure that can be opened and closed, and is opened for repair work on the cement kiln 2 or for installation and replacement of the kiln burner 8 and the first piping 20.

[0049] The cement raw materials supplied to the inside of the cement kiln 2 are fired by the kiln burner 8 attached to the kiln hood 21, producing cement clinker. The cement clinker falls towards the clinker cooler 13 located below the kiln hood 21 and is cooled in the clinker cooler 13.

[0050] The fired cement clinker is at a temperature of over 1,000°C, typically around 1,200°C to 1,500°C. This cement clinker is cooled by room temperature (around 20°C to 30°C) cooling air A1 supplied from a cooling fan (not shown) connected to the clinker cooler 13. The cooled cement clinker is discharged from the outlet end of the clinker cooler 13 and stored in a clinker silo (not shown).

[0051] The cooling air A1 that flows into the clinker cooler 13 undergoes heat exchange with the high-temperature cement clinker and is then supplied to the cement kiln 2 as secondary air A2. This secondary air A2 is used as combustion air for the kiln burner 8.

[0052] In the following explanation, the XYZ coordinate system will be referred to as appropriate, where the vertical direction is the Z direction, the axial direction on the kiln hood 21 side of cement kiln 2 is the X direction, and the direction perpendicular to the X and Z directions is the Y direction. In the following explanation, when the positive and negative signs of a direction are distinguished, they will be written as "+X direction" and "-X direction," while when the positive and negative signs of a direction are not distinguished, they will simply be written as "X direction." The same applies to the Y and Z directions.

[0053] Figure 3 is a schematic plan view of the cement kiln 2 as seen from the kiln hood 21 side, i.e., in the +X direction. As described above, the cement kiln 2 has a horizontal cylindrical shape that slopes slightly downward toward the downstream side (kiln hood 21 side). Therefore, conversely, when viewing the cement kiln 2 from the downstream side (kiln hood 21 side) toward the upstream side, i.e., in the +X direction, it exhibits a slight upward slope. For this reason, when viewing the cement kiln 2 from the kiln hood 21 side, the position of the top of the cylindrical shape should be displaced in the Z direction. However, in Figure 3, for illustrative purposes, only the portion of the cement kiln 2 closer to the kiln hood 21 is shown.

[0054] As mentioned above, the cement raw materials become cement clinker during the firing process in cement kiln 2. In other words, depending on their location, cement raw materials and cement clinker will coexist within cement kiln 2. In Figure 3, for the sake of simplification of terminology, the cement raw materials and cement clinker being fired in cement kiln 2 are collectively indicated by reference numeral 35, and will be collectively referred to as "cement clinker 35" below.

[0055] As described above, the cement kiln 2 burns the cement raw materials inside while rotating. In the example in Figure 3, it is assumed that the rotation direction dr2 of the cement kiln 2 is clockwise when viewed from the downstream side to the upstream side (i.e., in the +X direction). In other words, the cement kiln 2 burns the cement clinker 35 while rotating clockwise around its axis 2c when viewed in the +X direction.

[0056] During firing, the cement clinker 35 remains on an inclined plane that is biased in the rotational direction dr2 from the vertically downward bottom surface of the cement kiln 2, due to the rotation of the cement kiln 2 and friction between the inner wall 2a of the cement kiln 22 and the cement clinker 35.

[0057] Figure 4 is a schematic diagram showing only some elements extracted from Figure 3. As described above, the cooling air A1 that flows into the clinker cooler 13 exchanges heat with the high-temperature cement clinker 35 and is then supplied to the cement kiln 2 as secondary air A2 and used as combustion air. In Figure 4, the flow of this secondary air A2 is schematically illustrated by a dashed line.

[0058] As shown in Figure 4, the secondary air A2 flowing into the cement kiln 2 from the clinker cooler 13 rises to a position (Z coordinate position) at approximately the same height as the axis 2c of the cement kiln 2, then rises further while swirling in the same direction as the rotation direction dr2 of the cement kiln 2, and then exhibits an airflow that descends.

[0059] The location where the first piping 20 is suitably installed in the cement clinker manufacturing facility 1 will be explained with reference to Figure 5. Figure 5 is a schematic diagram showing the relationship between the installation position of the kiln burner 8 and the installation position of the first piping 20 when the cement kiln 2 is viewed from the downstream end face 21a of the kiln hood 21. In other words, Figure 5 is a diagram showing the relationship between the installation positions of the kiln burner 8 and the first piping 20 when viewed in the direction of injection of the kiln burner 8 (viewed in the +X direction).

[0060] In the cement clinker manufacturing facility 1, the first pipe 20 is positioned such that its axis lies within the hatched area in Figure 5 when viewed in the direction of injection from the kiln burner 8. More specifically, when viewed in the direction of injection from the kiln burner 8, the axis of the first pipe 20 is located within the region between a first position ya1, which is vertically below the axis 8b of the kiln burner 8, and a second position ya2, which is 180° from the first position ya1 in the rotational direction dr2 of the cement kiln 2 with respect to the axis 8b.

[0061] In Figure 5, the third position ya3 is shown as the position obtained by advancing 90° in the rotational direction dr2 of the cement kiln 2 from the first position ya1 with respect to the axis 8b. For the sake of explanation, as shown in Figure 5, the region between the first position ya1 and the third position ya3 will be referred to as region PA1, and the region between the third position ya3 and the second position ya2 will be referred to as region PA2.

[0062] Using this notation, when viewed in the direction of injection from the kiln burner 8, the first pipe 20 is positioned such that its axis lies within region PA1 or region PA2. The effect of positioning the axis of the first pipe 20 in such a position will be explained with reference to Figure 6. Figure 6 is a drawing that follows Figure 4, with the hatched regions (PA1, PA2) from Figure 5 superimposed on it.

[0063] As described above with reference to Figure 4, the secondary air A2 flowing from the clinker cooler 13 towards the cement kiln 2 rises to a position (Z coordinate position) at approximately the same height as the axis 2c of the cement kiln 2, then rises further while swirling in the same direction as the rotation direction dr2 of the cement kiln 2, and then descends.

[0064] In other words, the region (PA1, PA2) where the axis of the first pipe 20 is located corresponds to the region where the airflow of the secondary air A2 exhibits an upward flow. Therefore, when the material to be treated P1 containing POPs is blown into the region (PA1, PA2) via the first pipe 20, the material to be treated P1 is more likely to float in the cement kiln 2, carried by the flow of the secondary air A2 that forms an upward flow. As a result, the material to be treated P1 is exposed to a high-temperature environment for a sufficient amount of time before it lands on the cement clinker 35. This ensures that the POPs contained in the material to be treated P1 are decomposed before it lands on the cement clinker 35.

[0065] From this viewpoint, in order to further enhance the buoyancy of the material to be treated P1, it is preferable that the material to be treated P1 has a particle size that can pass through a Φ30 mm sieve, more preferably a particle size that can pass through a Φ25 mm sieve, and particularly preferably a particle size that can pass through a Φ20 mm sieve. If the particle size of the material to be treated P1 is high before being introduced into the first pipe 20, it is preferable to perform pretreatment such as crushing to make the particle size finer.

[0066] When the material to be treated P1 is a liquid or a slurry with a relatively low solid content, regardless of whether it is blown into either region PA1 or region PA2 as shown in Figures 5 and 6, time can be ensured for the POPs contained in the material to be treated P1 to decompose before the material to be treated P1 lands on the cement clinker 35. A slurry with a relatively low solid content is preferably a slurry with a solid content of less than 20% by mass, more preferably a slurry with a solid content of less than 15% by mass, and particularly preferably a slurry with a solid content of less than 10% by mass.

[0067] On the other hand, if the material to be processed P1 is a solid or a slurry with a relatively high solid content, and if it is blown into region PA1 as shown in Figures 5 and 6, the weight of the material to be processed P1 may cause it to land in the cement clinker 35 without being carried by the flow of secondary air A2 that forms an updraft. In this case, the material to be processed P1 may land in the cement clinker 35 before the POPs contained in the material to be processed P1 are decomposed, and the cement clinker 35 and the material to be processed P1 with the undecomposed POPs may be sent to the clinker cooler 13 in a mixed state. Therefore, if the material to be processed P1 is a solid or a slurry with a relatively high solid content, it is preferable to blow it into region PA2, which is +Z to region PA1, i.e., vertically above.

[0068] A slurry with a relatively high solid content is preferably a slurry with a solid content of 20% or more by mass, more preferably a slurry with a solid content of 25% or more by mass, and particularly preferably a slurry with a solid content of 30% or more by mass.

[0069] Let's return to Figure 2 and continue the explanation. As shown in Figure 2, when viewed in a direction parallel to the horizontal plane (XY plane) and perpendicular to the axis of the kiln burner 8 (i.e., the Y direction), let Q1 be the intersection point of a line that is a virtual extension of the axis of the kiln burner 8 (first virtual line 8c) and a line that is a virtual extension of the axis of the first pipe 20 (second virtual line 20c). The Y direction corresponds to the "first direction". At this time, the distance d1 in the Y direction between point Q1 and the tip 8a of the kiln burner 8 is preferably in the range of 5m to 25m. The distance d1 is more preferably in the range of 7m to 22m, and particularly preferably in the range of 10m to 20m.

[0070] When the distance d1 is less than 5m, it corresponds to the case where the material to be treated P1 blown through the first pipe 20 passes near the tip 8a of the kiln burner 8. In this case, the material to be treated P1 blown through the first pipe 20 crosses the flame formed by the kiln burner 8 by a large distance, impairing the stability of the flame and potentially affecting the quality of the cement clinker 35.

[0071] On the other hand, when the distance d1 exceeds 25m, it corresponds to a case where the material to be treated P1 blown in through the first pipe 20 passes at a position extremely far from the tip 8a of the kiln burner 8. In order to introduce the material to be treated P1 at such a position and expose it to a high-temperature environment for the time required for the decomposition of POPs while it is suspended, the wind speed and air volume of the gas used when blowing the material to be treated P1 through the first pipe 20 must be extremely high. As a result, the cost of the blowing equipment becomes enormous.

[0072] In Figure 2, d2 represents the length of the kiln burner 8 protruding in the X direction from the downstream end face 21a of the kiln hood 21 (insertion length of the kiln burner 8), and d3 represents the length of the first pipe 20 protruding in the X direction from the downstream end face 21a of the kiln hood 21 (insertion length of the first pipe 20). In this case, the length d3 is preferably 0.5 times or less of the length d2, more preferably 0.4 times or less, and particularly preferably 0.3 times or less. Regarding the X coordinate, the tip of the first pipe 20 may be approximately equal to the downstream end face 21a of the kiln hood 21 (for example, the protruding length may be 10 cm or less).

[0073] This configuration allows the first pipe 20 itself to be moved away from the tip of the kiln burner 8 towards the downstream end face 21a of the kiln hood 21, thereby reducing the degree of heat loss caused by the flame formed by the kiln burner 8.

[0074] The following will be explained with reference to examples.

[0075] A reference example was provided using the actual cement clinker manufacturing equipment 1, where cement clinker was produced under normal operation without introducing the material to be processed P1. An example was also provided where the material to be processed P1, including POPs, was introduced from the front of the kiln 11 through the first piping 20.

[0076] In the examples, the target material P1 was a stock solution of a foam fire extinguishing agent containing PFAS, a type of POPs. The substances belonging to PFAS were PFOS and PFOA. More specifically, the concentration of PFOA contained in the foam fire extinguishing agent was 5.5 × 10⁻⁶. 3 The concentration of PFOS is 6.4 × 10⁻⁶ μg / kg. 7 The concentration was μg / kg. The amount of foam fire extinguishing agent to be injected was set to 10 kg / h, and the injection pressure was set to 0.35 MPa.

[0077] In this embodiment, the first pipe 20 into which the material to be processed P1 is introduced is a single pipe, and the installation position of the first pipe 20 is 1.5 m vertically above the kiln burner 8. The tip of the first pipe 20 is set to protrude 10 cm from the downstream end face 21a of the kiln hood 21. The direction in which the material to be processed P1 is introduced is set to a position 10 m away from the tip 8a of the kiln burner 8 on the axis of the kiln burner 8. That is, the distance d1 between the intersection point Q1 of the first virtual line 8c and the second virtual line 20c shown in Figure 2 and the tip 8a of the kiln burner 8 is set to 10 m.

[0078] Furthermore, the input direction of the first pipe 20 was set so that the input point for the material to be processed P1 would be in area PA1 as shown in Figure 5.

[0079] Table 1 shows the operating conditions for the examples and reference examples, and Table 2 shows the PFAS concentrations contained in the flue exhaust gas and cement clinker. As shown in Table 1, coal fuel and waste fuel (waste plastic) were blown into the kiln burner 8 from the kiln front 11 side.

[0080] [Table 1]

[0081] [Table 2]

[0082] As shown in Table 1, the input amount of the material to be treated P1 in the example was set to 10.0 kg / h. Also, as shown in Table 1, the input amount of cement raw materials was set so that the daily production of cement clinker was 4,500 tons. In other words, when the input amount of the material to be treated P1 in the example is converted to an amount per ton of cement clinker, it was 53 g / t-clinker per unit of raw material cost.

[0083] According to a document from the Ministry of the Environment, the reference management target value for exhaust gas, assuming a concentration of PFOS, PFOA, etc. in the waste (materials to be treated) of 10,000 mg / kg, is 60 ng / Nm³. 3 This is set (based on 10% oxygen). Furthermore, according to the same document, 5.0 μg / kg is set as a reference value for the management target of PFOS and PFOA contained in the residue.

[0084] According to Table 2, in the examples, it was confirmed that the control standards were met for both the PFAS concentration in the exhaust gas and the PFAS concentration in the residue (cement clinker).

[0085] In Table 2, the PFAS concentrations in the exhaust gas and the PFAS concentrations in the cement clinker were all measured using methods in accordance with the aforementioned "Ministry of the Environment document."

[0086] The exhaust gas is sent from the front of the kiln 11 through the cement kiln 2 to the rear of the kiln 12, then sent to the upper cyclone 3 side and discharged from the chimney. In other words, when the material to be processed P1 is introduced from the front of the kiln 11, it is gasified or atomized by passing through the high-temperature region formed by the kiln burner 8, and then exposed to a high-temperature environment for a sufficient amount of time while flowing through the cement kiln 2, resulting in the PFAS concentration in the exhaust gas falling below the control standard.

[0087] On the other hand, the reason why the PFAS concentration in the generated cement clinker was below the control standard is presumed to be that, as shown in Figures 5 and 6, when the liquid material P1 to be treated was introduced into area PA1, the rising airflow of secondary air A2 introduced from the clinker cooler 13 made it easier for the material to float upward within the cement kiln 2, and sufficient time was secured for the PFAS contained in the material P1 to decompose before it landed on the cement clinker located near the clinker cooler 13.

[0088] In the example, the amount of PFAS added to the treated material P1 was 53 g / t-clinker. However, considering that the concentration of PFAS remaining in the cement clinker was extremely low, it is presumed that even if the amount of PFAS added was 100 g / t-clinker, the concentration of PFAS remaining in the cement clinker could be kept within the limits of the control standards.

[0089] The above verification was conducted using PFOA and PFOS, because, at present, regulatory targets have only been set for PFOA and PFOS in Japan. POPs include PFAS other than PFOA and PFOS, as well as dioxins, DDT, and PCBs. While various types of POPs are expected to be accepted by cement clinker manufacturing facility 1 as the target material P1, by processing under the above temperature conditions, it is possible to decompose at least the PFOA and PFOS contained in the target material P1 within the limits that meet Japan's regulatory targets. Furthermore, given that it is subjected to extremely high temperatures, it is presumed that other PFAS, dioxins, DDT, and PCBs contained in the target material P1 can also be similarly decomposed. [Explanation of symbols]

[0090] 1: Cement clinker manufacturing equipment 2: Cement Kiln 2a: Inner wall of the cement kiln 2c: Axis of the cement kiln 3: Upper Cyclone 4: Rising Duct 5: Kiln 6: Bottom Cyclone 7: Grilling burner 8: Kilnburner 8b: Center of the kiln burner 8a: Tip of the kiln burner 8c: First virtual line 11: Front of the kiln 12: Kiln bottom 13: Klinka Cooler 14: Bottom raw material chute 20:First piping 20c: Second virtual line 21: Kilnhood 21a: Downstream end face of the kiln hood A1: Cooling air A2: Secondary air d1: The distance in the Y direction between intersection Q1 and the tip 8a of the kiln burner. dr2: Rotation direction of the cement kiln P1: Object to be processed Q1: The intersection of the first and second virtual lines when viewed in the Y direction. ya1: first position ya2: second position ya3: third position

Claims

1. A method for treating persistent organic pollutants, The aforementioned processing method is a method using cement clinker manufacturing equipment, The aforementioned cement clinker manufacturing facility is Cement kiln and, A kiln burner is installed at the front of the cement kiln and blows fuel into the cement kiln. A first pipe is installed in the front of the kiln and blows the material to be treated, which contains persistent organic pollutants, into the cement kiln. The kiln is connected to the front of the kiln and includes a clinker cooler into which cooling air is blown, A method for treating persistent organic pollutants, characterized in that, when viewed in the blowing direction of the kiln burner, the material to be treated is blown through the first pipe into a region sandwiched between a first position vertically below the axis of the kiln burner and a second position advanced 180° from the first position in the rotational direction of the cement kiln with respect to the axis of the kiln burner.

2. The method for treating persistent organic pollutants according to claim 1, characterized in that the substance to be treated is a liquid or a slurry having a solid content of less than 20% by mass.

3. The material to be processed is a solid, or a slurry having a solid content of 20% or more by mass. A method for treating persistent organic pollutants according to claim 1, characterized in that, when viewed in the direction of blowing from the kiln burner, the object to be treated is blown through the first pipe into a region between the second position and a third position which is advanced 90° from the first position in the rotational direction of the cement kiln with respect to the axis of the kiln burner.

4. A method for treating persistent organic pollutants according to any one of claims 1 to 3, characterized in that, when viewed in a first direction that is parallel to the horizontal plane and perpendicular to the direction of the axis of the kiln burner, a first virtual line that is a virtual extension of the axis of the kiln burner and a second virtual line that is a virtual extension of the axis of the first piping intersect at a position within a range of 5 m to 25 m from the tip of the kiln burner with respect to the direction of the axis of the kiln burner.

5. The kiln burner and the first piping are fixed to the downstream end face of the kiln hood, which is connected to the cement kiln, at the front of the kiln. A method for treating persistent organic pollutants according to any one of claims 1 to 3, characterized in that, when viewed in a first direction parallel to the horizontal plane and perpendicular to the axis of the kiln burner, the length of the first pipe protruding from the downstream end face in a direction parallel to the horizontal plane is 0.5 times or less the length of the kiln burner protruding from the downstream end face in a direction parallel to the horizontal plane.

6. The method for treating persistent organic pollutants according to claim 3, characterized in that the material to be treated is a solid with a particle size that can pass through a 30 mm diameter sieve.

7. The method for treating persistent organic pollutants according to claim 6, characterized in that the object to be treated comprises at least one of a plastic resin and activated carbon.

8. A method for treating persistent organic pollutants according to any one of claims 1 to 3, characterized in that the amount of persistent organic pollutants contained in the object to be treated is greater than 0 and 100 g / t-clinker or less per unit of raw material.

9. A method for treating persistent organic pollutants according to any one of claims 1 to 3, characterized in that the persistent organic pollutants contained in the object to be treated are substances belonging to PFAS.

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