Material conversion method

Abstract

A material conversion method includes a carbonation step in which a material is brought into contact with a carbon dioxide-containing fluid to carbonate the material, and determined carbonation treatment times in the carbonation step is based on a value A of time-series information obtained by subtracting information on the change over time of the amount of carbon dioxide absorption R absorbed in the carbonation step from information on the change over time of the amount of carbon dioxide emission Pa resulting from the use of energy consumed in the carbonation step. The carbonation time may be when the time-series information changes from a decrease to an increase T1, or from an increase to becoming zero T2. The amount of CO₂ emitted may take into account emission from the use of auxiliary materials, heavy metal elution inhibitors, and granulation steps.

Description

[Technical Field]

[0001] The present invention relates to a material conversion method. [Background of the Invention]

[0002] Conventionally, in order to reuse fly ash discharged from waste incineration facilities as a material, a carbonation process has been carried out to reduce the pH level and prevent the elution of heavy metals. As a carbonation treatment apparatus for material conversion that includes a carbonation process such as this, a cylinder with closed ends, a reaction vessel arranged so that the central axis of the cylinder is horizontal, and a stirrer having a rotary axis arranged along the central axis of the reaction vessel as disclosed in Patent Document 1 are known.

[0003] The carbonation treatment apparatus described in Patent Document 1 measures the carbon dioxide absorption of fly ash and terminates the supply of carbon dioxide gas when this absorption reaches a set value. Specifically, measure the amount of carbon acid gas supply to the carbonation process and the amount of carbon dioxide emission from the carbonation process, and terminate the supply of carbon dioxide gas when the difference between the measured carbon dioxide supply amount and the carbon dioxide emission amount reaches a set value greater than 0.

[0004] In addition, Patent Document 2 discloses a carbonation treatment method as a pre-treatment method for waste. The carbonation treatment method in Patent Document 2 measures the temperature of the waste according to the plane of the container body into which the waste to be carbonated is put, and adjusts the amount of carbon dioxide supplied to the container body based on the measurement results. [Prior Art Documents] [Patent Documents]

[0005] [Patent Document 1] Japan Unexamined Patent Publication No. 2002-224640 [Patent Document 2] Japan Unexamined Patent Publication No. 2017-217575 [Abstract of Invention] [Problems to be Solved by the Invention] Using the techniques disclosed in Patent Documents 1 and 2, it is possible to reduce carbon dioxide emissions in the carbonation process. In particular, in the carbonation treatment apparatus disclosed in Patent Document 1, since the carbon dioxide emissions can be suppressed below the carbon dioxide supply quantity in the carbonation treatment, it is thought that a state in which the carbon dioxide emissions and the absorption are offset or a state in which the carbon dioxide absorption exceeds the emissions can be achieved. However, even if the fly ash or other material to be treated is carbonated under the above conditions, it is necessary to use additional power for agitation, aggregation, steam curing, and other operations required for use. Therefore, when the amount of carbon dioxide generated when using these powers is included, and carbon dioxide emissions are often not sufficiently suppressed in the carbonation process. In other words, it is understood that the carbonation treatment by the carbonation treatment apparatus described in Patent Document 1 cannot reduce carbon dioxide sufficiently and that it is difficult to further improve the carbon dioxide emission suppression effect merely by increasing the carbon dioxide absorption efficiency. Therefore, there is room for improvement in the carbonation treatment of materials to be treated, such as fly ash.

[0007] Therefore, there is a demand for a material conversion method that includes carbonation treatment that can further improve the carbon dioxide emission suppression effect. [Means for Solving the Problems]

[0008] The characteristic feature of the material-production method of the present invention is that it is a material-production method including a carbonation process in which the material is brought into contact with a carbon dioxide-containing fluid to carbonate the material, and the carbonation process time in the carbonation process is determined based on the value of time-series information obtained by subtracting information on the change overtime of the amount of carbon dioxide absorbed in the carbonation process from information on the change over time of the amount of carbon dioxide emitted due to the use of energy consumed in the carbonation process, a time series information value obtained by subtracting time series information obtained by subtracting the time series information obtained by subtracting the time series information obtained by subtracting the time series information on the amount of carbon dioxide absorbed in the carbonation project from the time-variation information on carbonation emissions resultingfrom the use of energy consumed in the carbonation process.

[0009] According to this material conversion method, it is possible to carry out carbonation processing at a carbonation processing time determined based on the value of time-series information obtained by subtracting information on the change overtime of carbon dioxide absorption from information on the change overtime of carbon dioxide emissions resultingfrom energy use. Therefore, it is possible to reliably reduce carbon dioxide emissions by carrying out carbonation processing at a time with the lowest value of the time-series information as the carbonation processing time. As a result, a material conversion method having the present characteristics can appropriately achieve a state in which the amounts of carbon dioxide emission and absorption are offset or a state in which the amount of carbon dioxide absorption exceeds the amount of carbon dioxide emission.

[0010] Another feature is that the carbonation processing time in the carbonation process is set based on the value of time series information obtained by subtracting time-varying information on the amount of carbon dioxide absorption absorbed in the carbonation process from the sum of time-varying information on the amount of carbon dioxide emission caused by the auxiliary materials used in the carbonation process and time-varying information on the amount of carbon dioxide emission caused by the use of energy consumed in the carbonation process from the sum of time-varying information on the amount of carbon dioxide emission caused by the auxiliary materials used in the carbonation process and time-varying information on the amount of carbon dioxide emission caused by the use of energy consumed in the carbonation process.

[0011] According to this material conversion method, it is possible to carry out carbonation processing within a carbonation processing time determined based on the value of time-series information obtained by subtracting the time-series information on the change in the amount of carbon dioxide absorption from the sum of the time-series information on the change in the amount of carbon dioxide emission caused by auxiliary materials and the time-series information on the change in the amount of carbon dioxide emission caused by energy use. Therefore, it is possible to reliably reduce carbon dioxide emissions by carrying out carbonation processing at a time with the lowest value of the timeseries information as the carbonation processing time. As a result, a material conversion method having the present characteristics can appropriately achieve a state in which the amounts of carbon dioxide emission and absorption are offset or a state in which the amount of carbon dioxide absorption exceeds the amount of carbon dioxide emission.

[0012] Another feature is that the carbonation process includes a granulation process for the material to be treated, and the carbonation process time in the carbonation process is determined based on the value of the time series information added with the amount of carbon dioxide gas emissions resulting from the use of energy consumed in the granulation process.

[0013] According to this material conversion method, it is possible to carry out carbonation engineering at a carbonation processing time determined based on the value of time-series information obtained by adding carbonation gas emissions caused by the use of energy consumed in the granulation process. Therefore, it is possible to reliably reduce carbon dioxide emissions by carrying out carbonation processingat a time with the lowest value of the time-series information as the carbonation processing time.

[0014] Another feature is that the carbonation process time in the carbonation process is determined based on the value of the time series information to which the carbon dioxide gas emission amount due to the auxiliary material used in the granulation process is further added.

[0015] According to this material conversion method, it is possible to carry out carbonation processing at a carbonation processing time determined based on the value of time series information obtained by adding the amount of carbon dioxide emission caused by the auxiliary material used in the granulation process. Therefore, it is possible to reliably reduce carbon dioxide emissions by carrying out carbonation processing at a time with the lowest value of the time-series information as the carbonation processing time.

[0016] Another feature is that the carbonation process time is the elapsed time until the value of the time series information changes from decreasing to increasing or becomes 0 after changing to an increase.

[0017] As with this feature, if the carbonation process time is the elapsed time until the value of the time series information changes from decreasing to increasing, or from increasing to becoming 0, it is possible to reliably achieve a carbonation process in which the amounts of carbon dioxide emitted and absorbed are offset, or the amount of carbon dioxide absorbed exceeds the amount emitted.

[0018] Another feature is that the auxiliary material includes a heavy metal elution inhibitor, the carbonation process includes a heavy metal elution prevention process using the heavy metal elution inhibitor, and when a second elapsed time for reducing the amount of elution of the heavy metal in the elution prevention process to a regulated value or less is longer than a first elapsed time until the value of the time series information changes from decreasing to increasing or becomes 0 after changing to an increase, the carbonation process time is set to the second elapsed time.

[0019] According to this feature, by setting the second elapsed time for reducing the amount of heavy metal leachingto below the regulated value as the carbonation treatment time and executingthe heavy metal leaching prevention treatment, it is possible to reliably perform the heavy metal leaching prevention treatment in the carbonation process. Brief description of the Drawings

[0020] Fig. 1 is a schematic diagram showingthe equipment configuration of an incineration facility according to a first embodiment. Fig. 2 is a graph showing the time-dependent change information and time-series information trends in the carbonation process according to the first embodiment. Fig. 3 is a schematic diagram showingthe equipment configuration of an incineration facility according to a third embodiment. Fig. 4 is a graph showing the time-dependent change information and time-series information trends in the carbonation process and granulation process accordingto the third embodiment. [Detailed Description of Preferred Embodiments]

[0021] Hereinafter, the material conversion method according to the embodiment of the present invention will be described in detail, based on the drawings. It should be noted that the embodiments described below are merely examples for describing the present invention, and the present invention is not limited to these embodiments. Therefore, the present invention can be embodied in various forms without deviating from the spirit of the present invention.

[0022] In a material recovery method including a carbonation step, for example, a material to be treated that includes fly ash and water is brought into contact with a gas that contains carbon dioxide (an example of a carbon dioxide-containing fluid) to carbonate the fly ash. In addition, the object to be carbonated in the material recycling method of this embodiment may be any substance that can be carbonated and is not limited to fly ash. Furthermore, the object to be carbonated in the materialrecycling method of this embodiment is not limited to particles.

[0023] The object to be carbonated in the material conversion method of the present embodiment is a solid material. The solid material to be carbonated may be a product of a heat treatment. The heat treatment may be, for example, simple melting without pyrolysis, or pyrolysis. Pyrolysis may be for the purposes of incineration, calcination, gasification, or roasting. Materials to be pyrolysed include, for example, municipal waste, biomass, paper sludge, sewage sludge, cement raw materials, and steel raw materials. The solid to be carbonated may be products derived from these pyrolysed objects. Products produced by pyrolysis include incineration ash. Incineration ash includes bottom ash, fly ash, and the like. Incineration ash to be carbonated may be in the form of molten slag. The product of the thermal decomposition may be slag produced during the metal refining process.

[0024] First Embodiment: Fig. 1 shows a facility in which a carbonated waste is produced, in the form of a incineration equipment 100 having an incinerator 10 and other components. The incinerator 10 incinerates materials to be incinerated, such as waste, and discharges high-temperature exhaust gas.

[0025] The exhaust gas discharged from the incinerator 10 contains gases such as carbon dioxide, sulphur oxides, nitrogen oxides, and hydrogen chloride as well as solid matter such as fly ash. Fly ash usually contains components derived from the material to be incinerated as well as components derived from the alkaline agent, which will be described later. The fly ash usually contains a compound containing one or more elements selected from the group consisting of potassium, calcium, and magnesium. The fly ash that is carbonated in the carbonation treatment apparatus 40 and carbonated by the material conversion method of this embodiment may contain a compound containing one or more elements selected from the group consisting of sulphur, phosphorus, and silicon. The fly ash may contain at least one element selected from the group consisting of sodium, zinc, iron, aluminium, copper, and compounds thereof. Fly ash can also contain heavy metals such as lead and hexavalent chromium and compounds thereof.

[0026] Examples of the compound include oxides, hydroxides, carbides, carbonates, hydrogen carbonates, nitrides, nitrates, sulphides, sulphates, and halides. The carbonation treatment apparatus 40 in this embodiment is used to carbonate the fly ash and to suppress the elution of heavy metals when the fly ash after the carbonation treatment is buried in the ground. In some examples, fly ash with leaching of 0.3 mg / L or more is carbonated. In some examples, fly ash with a hexavalent chromium elution amount of 1.5 mg / L or more is carbonated.

[0027] The material conversion method can be implemented for any purpose and is not limited to any particular facility. For example, the method can be implemented on fly ash discharged from an incinerator 10, as described below. The incineration equipment 100 of this embodiment includes an incinerator 10, a temperature reducing tower 20, and a dust collection apparatus 30. The cooling tower 20 cools the exhaust gas discharged from the incinerator 10. The dust collector apparatus 30 is equipped with a bag filter that removes fly ash, which is a solid component, from the exhaust gas cooled in the cooling tower 20.

[0028] Furthermore, the incineration equipment 100 is equipped with a carbonation treatment apparatus 40, a water contact apparatus 50, and a control apparatus 60. Fly ash discharged from the incinerator 10 and then removed by the dust collector 30 is supplied to the carbonation treatment apparatus 40, where the fly ash is subjected to carbonation treatment. The carbonation treatment apparatus 40 is configured to add water to the stored fly ash to prepare a material to be treated, and as described below, carbonates the material to be treated while stirring it to produce a carbonated material. The water contact apparatus 50 receives some or all of the exhaust gas that has passed through the dust collector 30, brings the exhaust gas into contact with water to remove easily soluble gases in the water contact apparatus 50, and then supplies the exhaust gas to the carbonation treatment apparatus 40. The control apparatus 60 controls the operation of the incineration equipment 100.

[0029] In this way, the incineration equipment 100 is configured so that the carbon dioxide (CO2, carbon dioxide gas) contained in the exhaust gas from which the fly ash has been removed after passing through the dust collector 30 can be used for carbonation in the carbonation treatment apparatus 40. More specifically, the incineration equipment 100 is configured so that a portion or all of the exhaust gas that has passed through the dust collection apparatus 30 can be brought into contact with water in the water contact apparatus 50, whereby easily soluble gases can be removed before being supplied to the carbonation treatment apparatus 40. In the water contact apparatus 50, components that are easier to remove from the exhaust gas by contact with water than carbon dioxide such as hydrogen chloride, sulphur dioxide, and nitrogen dioxidecan be removed. In this embodiment, exhaust gas is supplied to the carbonation treatment apparatus 40 as a gas containing carbon dioxide, but the gas is not limited to exhaust gas and various types of gas can be used. For example, carbon dioxide gas with a purity of 99% by mass or more that is commercially available and sealed in a cylinder can be supplied to the carbonation treatment apparatus 40, or carbon dioxide contained in the air can be supplied.

[0030] The carbon dioxide used for the carbonation treatment in the carbonation treatment apparatus 40 may be introduced into the carbonation treatment apparatus 40 in a liquid or solid state. Liquefied carbon dioxide or carbonated water may be used for the carbonation treatment. Dry ice may be used for the carbonation process. Additionally, liquids or solids that generate carbon dioxide through thermal decomposition or chemical reaction (e.g., sodium bicarbonate and sodium carbonate) can also be used for carbonation. The carbonation process can be carried out without using a water contact apparatus 50 or the like by using highly pure carbon dioxide gas ,dry ice, etc. The carbonation process may be carried out without utilizing the water contact apparatus 50 even when using exhaust gas.

[0031] The carbonation treatment apparatus 40 includes a reaction vessel 41 having a storage space for storing the material to be treated, which contains fly ash and water. The carbonation treatment apparatus 40 may be an agitation apparatus that agitates the material to be treated in the reaction vessel 41 or maybe a curing apparatus that cures the material to be treated in the reaction vessel 41.

[0032] In the carbonation process, fly ash is supplied to the reaction vessel 41 as the material to be treated, and then water, auxiliary materials described below, and exhaust gas are supplied to the reaction vessel 41 and appropriately mixed.

[0033] In the embodiment of the method for material conversion including a carbonation step, in addition to the fly ash, water, and gas containing carbon dioxide, a heavy metal immobilising agent (an example of a heavy metal outflow inhibitor) is used as a secondary material. Examples of heavy metal immobilising agents that can be used include inorganic immobilising agents such as calcium compounds such as calcium silicate, calcium hydroxide, calcium oxide, and calcium carbonate; phosphate compounds such as calcium phosphate and hydroxyapatite; and iron compounds such as ferrous sulphate and ferrous chloride; and organic (chelating) immobilising agents including dithiocarbamic acid compounds.

[0034] Method of Determining Carbonation Treatment Time: Fig. 2 is a graph showing the time-dependent change information and the transition of time-series information in the carbonation process. A method for determining the carbonation processing time will be described with reference to Fig. 2. In Fig. 2, the amount of carbon dioxide emission derived from secondary materials is represented as P1, the change in the sum P of the carbon dioxide emission amount P1 and the carbon dioxide emission amount Pa due to power consumption overtime is represented as time-dependent change information, and the change in the amount of carbon dioxide absorption R by the carbonation process over time is represented as time-dependent change information. In Fig. 2, the change in the total amount A of carbon dioxide gas obtained by subtracting the amount of absorbed carbon dioxide gas R from the sum P of the amount of discharged carbon dioxidegas P1 and the amount of discharged carbon dioxide gas Pa is shown as the time-dependent change information. The carbonation processing time is determined based on a sum A, which is the value of time-series information obtained by subtracting the time-series information ofthe carbon dioxide absorption amountRfrom the sum P ofthe time-series information ofthe carbon dioxide emission amount P1 and the carbon dioxide emission amount Pa. The elapsed time T1 is the carbonation process time at which the value of the total amount of carbon dioxide A when the carbon dioxide absorption amount R is subtracted from the sum P of the carbon dioxide emission amount P1 and the carbon dioxide emission amount Pa is the lowest, and is also the carbonation process time at which the value of the time series information changes from decreasing to increasing. The elapsed timeT2 represents the carbonation process time at which the value of the time series information changes from decreasing to increasing, and the sum A becomes 0 when the carbon dioxide absorption amount R is subtracted from the sum P of the carbon dioxide emission amount P1 and the carbon dioxide emission amount Pa. At the elapsed time T3, the sum A turns positive, and the sum P of the carbon dioxide gas discharge amounts becomes larger than the carbon dioxide gas absorption amount R.

[0036] Here, the amount of carbon dioxide gas discharged in the carbonation process refers to the amount of carbon dioxide (CO2) generated due to the use of auxiliary materials used in the carbonation process and energy consumed in the carbonation process. Therefore, the amount of carbon dioxide gas emitted in the carbonation process does not include the amount of carbon dioxide gas emitted when producing the material to be carbonated target material (for example, the amount of carbon dioxide gas generated during garbage incineration using incinerator 10) or the amount of carbon dioxide gas introduced from the outside.

[0037] Amount of Carbon Dioxide Gas Discharged Due to the Amount of Secondary Materials Used in the Carbonation Process: First, the amount of carbon dioxide gas discharged P1 (see Fig. 2) due to the amount of secondary materials used in the carbonation process is calculated. Here, the auxiliary material used in the carbonation step is a heavy metal immobilising agent (heavy metal elution inhibitor). In this embodiment, ferrous sulphate is used as the heavy metal immobilising agent (heavy metal elution inhibitor).

[0038] [Specific Method of Calculating Carbon Dioxide Emission Amount P1 Originating from Secondary Materials] Carbon dioxide emission amount P1 originating from the secondary materials used in the carbonation process can be calculated for example, by the following formula (1). Formula (1): Carbon dioxide emission amount P1 [kg-CO2] = (Ferrous sulphate emission source unit (carbon dioxide emission amount in one batch [kg-CO2 / ton])) * (Amount of ferrous sulphate added in one batch [ton]).

[0039] (Amount of Carbon Dioxide Discharged Due to Use of Energy Consumed in the Carbonation Process) Next, the amount of carbon dioxide discharged Pa due to use of energy consumed in the carbonation process is calculated. Here, the energy consumed in the carbonation process refers to the power consumption used to operate various devices such as an agitator and a blower. Power consumption is calculated based on the specifications (rated current) of various devices such as mixers and conveyors, and the operating times of each device. The power consumption may be calculated based on the torque of the various devices, the frequency at the time of operation, etc.

[0040] Specific Method of Calculating Carbon Dioxide Emission Amount Over Time: The carbon dioxide emission amount overtime Pa can be calculated, for example, by Formula (2) below. Carbon dioxide emission Pa [kg-CO2] = (total power consumption per batch of various equipment used in the carbonation process [kWh]) x (carbon dioxide emission intensity (example: Kansai Electric Power Co., Inc.'s CO2 emission intensity in 2020): 0.308 kg-CO2 / kWh)... (2) Here, the equipment used in the carbonation process is, for example, a mixer, a cooling tower, a hydraulic pump, etc.

[0041] Amount of Carbon Dioxide Absorbed in Carbonation Process: Information on the change overtime in the amount of carbon dioxide absorbed R by the carbonation treatment of the object to be carbonated in the carbonation process is calculated, for example, by the following method.

[0042] Specific calculation method: The carbon dioxide gas absorption amount R is calculated from, for example, the total carbon amount, calcination loss, thermogravimetry, or other measured values, or from the weight increase caused by forcibly absorbing carbon dioxide gas. The calcination loss is a method for measuring the carbon dioxide gas absorption amount R by incinerating the carbonation target at, for example, 600° C. to reducethe weight of the carbonation target. Thermogravimetry is a method in which the temperature is changed according to a fixed program and the amount of carbon dioxide absorption R of a sample is measured as a function of the mass of the sample as a function of the temperature.

[0043] The control apparatus 60 calculates, for example, the operating conditions (operating time) under which (carbon dioxide gas emission amount P1 due to auxiliary materials) + (carbon dioxide gas emission amount overtime Pa) - (carbon dioxidegas absorption amount R) is minimised, and the carbonation processing time is determined based on this operating condition. These values may also be calculated in advance using the example shown in the previous paragraph, or may be calculated based on data obtained by batch operation.

[0044] In other words, the carbonation processing time in the carbonation process is set, for example, by the control apparatus 60 based on time series information obtained by subtracting the time-varying information of the carbon dioxide absorption amount R absorbed in the carbonation process from the sum P of the carbon dioxide emission amount P1 resulting from the amount of auxiliary materials used in the carbonation process and the time-varying information of the carbon dioxide emission amount Pa resulting from the use of energy consumed in the carbonation process.

[0045] Specifically, the carbonation processing time is the elapsed time T1 until the value of the time series information changes from decreasing to increasing, or the elapsed time until the value of the time series information related to the carbon dioxidegas exhaust volume changes from decreasing to increasing and then becomes 0 (the elapsed time is greater than T1 and less than T2).

[0046] According to the material conversion method including a carbonation process of this embodiment, carbonation processing can be performed within a carbonation processing time determined based on time series information obtained by subtracting the time-varying information of the carbon dioxide absorption amount R from the sum P of the carbon dioxide emission amount P1 due to the amount of auxiliary materials and the time-varying information of the carbon dioxide emission amount Pa. Therefore, by performing the carbonation process by setting, for example, the elapsed time T1 as the carbonation process time, the amount of carbon dioxide gas discharged can be reliably suppressed. As a result, the material conversion method including the carbonation process of this embodiment can properly achieve a state in which the amount of carbon dioxide emitted and absorbed is offset or the amount of carbon dioxide absorbed exceeds the amount emitted.

[0047] Furthermore, as in the material conversion method of this embodiment, if the carbonation process time is the elapsed time until the value of the time-series information changes from decreasing to increasing, or from increasing to becoming 0 (the elapsed time is greater than or equal to T1 and less than T2), a carbonation process in which the amount of carbon dioxide emitted and the amount of carbon dioxide absorbed are offset can be reliably achieved.

[0048] The carbonation step of the first embodiment includes a heavy metal elution inhibitor as a secondary material used in the carbonation step, and the carbonation step includes a treatment for preventing elution of heavy metals by the heavy metal elution inhibitor. In this case, in the carbonation process, it is sometimes considered more important to prevent the elution of heavy metals by the auxiliary materials than to prevent an increase in the amount of carbon dioxide gas discharged. Therefore, in the second embodiment, if the elapsed timeT4 (an example of a second elapsed time) required for the amount of leaching of heavy metals in the leaching prevention treatment to be below the regulated value is longer than the elapsed timeTI or more andT2 or less (an example of a first elapsed time), which is the elapsed time until the value of the time series information changes from a decrease to an increase or until it becomes 0 after changing to an increase, the carbonation treatment time is set to the elapsed time T4. The carbonation treatment time is set, for example, by using the control apparatus 60, in the same manner as in the first embodiment.

[0049] According to the method of the second embodiment, the second elapsed time (elapsed time T4) for reducing the amount of heavy metal leaching to below the regulated value is set as the carbonation treatment time, and the heavy metal leaching prevention treatment is performed, thereby making it possible to reliably perform the heavy metal leaching prevention treatment in the carbonation treatment. Third Embodiment: As shown in Fig. 3, in the third embodiment, the incineration equipment 100 further includes a granulation apparatus 70. In other words, in this embodiment, a granulation process can be added to the carbonation process for the material to be treated, such as fly ash. The granulation apparatus 70 performs a granulation process on the carbonated material transported from the carbonation treatment apparatus 40. The granulating apparatus 70 consists of, for example, a pelletiser. The other configurations are the same as that the first embodiment. Specifically, the carbonated material to be treated is removed from the bottom of the reaction vessel 41, transferred onto a conveyor (not shown), and the mixture is transported to the granulation apparatus 70 via a connecting passage.

[0051] The granulation process is carried out by mixing treatment and granulation treatment. In the mixing treatment, secondary materials such as a filler and a binder are added to the carbonated material to be treated, and the mixture is mixed while water is being added. The mixing process may be carried out in the reaction vessel 41, in the granulation apparatus 70, or in a mixing tank (not shown) provided in the connecting passage. Thereafter, a granulation process is carried out in the granulation apparatus 70.

[0052] Fig. 4 is a graph showing the amount of carbon dioxide gas discharged in the granulation process and the transition of time-dependent change information and time-series information in the carbonation process. A method for determining the carbonation treatment time will be described with reference to Fig. 4. In Fig. 4, the amount of carbon dioxide gas emitted due to the auxiliary materials used in the carbonation process is represented by P1, and the amount of carbon dioxide gas emitted overtime due to the power consumption used in the carbonation process is represented by Pa. In addition, the amount of carbon dioxide gas emission obtained by adding the amount of carbon dioxide gas emission due to the use of energy (e.g., power consumption) consumed in the granulation process to P1 is represented as P2, and the amount of carbon dioxide gas emission obtained by adding the amount of carbon dioxide gas emission due to the auxiliary materials used in the granulation process to P2 is represented as P3. The sum P of the carbon dioxide gas discharge amounts is calculated by adding any one of the carbon dioxide gas discharge amounts P1, P2, and P3 and Pa, and the change in the sum P of the carbon dioxide gas discharge amounts is represented as time-dependent change information. In addition, the change overtime in the amount of carbon dioxide gas absorbed R by the carbonation process is represented as time-dependent change information. The elapsed timesTI and T3 are the same as in the first embodiment, and the elapsed time T4 is the same as in the second embodiment.

[0053] Binders, fillers, and the like are used as auxiliary materials used in the granulation process. The amounts of these binders and fillers are also converted into the amounts of carbon dioxide gas derived from the raw materials. Specifically, it is the value obtained by multiplying the emission intensity of the binder and filler (kg-CO2 / kg) by the amount of binder and filler added (kg). Therefore, in the third embodiment, after the carbonation step, a granulation step is performed in which a binder and a filler are added to the carbonation treatment product and the carbonation treatment product is granulated. In addition, the carbon dioxide emission amount resulting from the use of energy consumed in the granulation process (the carbon dioxide emission amount included in P2) and the carbon dioxide emission amount resulting from the auxiliary materials used in the granulation process (the carbon dioxide emission amount included in P3) are both fixed values, and in both cases, the carbon dioxide emission amount is added to P1 as described above. Therefore, the elapsed time T2' is closer to the elapsed timeTI than the elapsed timeT2 in the first embodiment (Fig. 2). Therefore, from the viewpoint of reducing carbon dioxide gas emissions, the carbonation process time in this embodiment is preferably set to the elapsed time T1 until the sum A, which is the value of the time-series information, changes from a decrease to an increase, or to a time greater than T1 and less than T2'.

[0054] Fourth Embodiment: In the third embodiment, an example is shown in which a secondary material that generates carbon dioxide gas is used in the granulation process. However, the granulation process may be performed without adding a secondary material that generates carbon dioxidegas. In that case, as shown by the dotted line in the graph in Fig. 4, the elapsed time from when the value of the time series information begins to increase untilit becomes 0 will be longer than the elapsed timeT2' in the third embodiment and shorter than the elapsed time T2. Therefore, in the fourth embodiment, a time longer than the elapsed time T2' in the third embodiment can be determined as the carbonation treatment time.

[0055] Other Embodiments: (1) In the above embodiment, an example was shown in which a heavy metal elution inhibitor was added as an auxiliary material used in the carbonation process, but the carbonation process may be performed without adding a heavy metal elution inhibitor as an auxiliary material. In this case, in the material conversion method, the carbonation processing time in the carbonation process is determined based on the value of time series information obtained by subtracting the information on the change overtime of the amount of carbon dioxide absorbed in the carbonation process from the information on the change overtime of the amount of carbon dioxide emission caused by the use of energy consumed in the carbonation process.

[0056] (2) In the third embodiment, as shown in Fig. 4, an example is shown in which the carbonation process is stopped at elapsed time T1, or when the elapsed time is greater than T1 and less than T2', and then auxiliary materials to be used in the granulation process are added to the carbonation processed product, and the product is transitioned to the granulation process. Alternatively, the auxiliary materials used in the granulation process may be added to the carbonation treatment product before the carbonation process together with the auxiliary materials added in the carbonation process, and then the carbonation process and the granulation process may be carried out successively. In this case as well, from the viewpoint of reducing carbon dioxide gas emissions, it is preferable to determine the carbonation treatment time in the material conversion method to be greater than or equal to elapsed time T1 and less than or equal to T2' when transitioning from the carbonation step to the granulation step. [Industrial Applicability]

[0057] The present invention is widely applicable to material conversion methods including carbonation treatment. [Description of Reference Numerals] 10: Incinerator 20: Cooling tower 30: Dust collector 40: Carbonation treatment apparatus 60: Control apparatus 70: Granulation apparatus 100: Incineration equipment A, B: Time series information values (total amount of carbon dioxide) P: Sum of carbon dioxide emissions P1, P2: Amount of carbon dioxide gas emissions Pa, Pb: Amount of carbon dioxide gas emissions R: Amount of carbon dioxide gas absorption T1: Elapsed time (first elapsed time) T2, T2': Elapsed time (first elapsed time) T3: Elapsed time T4: Elapsed time (second elapsed time)

Claims

[Claim 1.]A material conversion method having a carbonation process in which a material to be treated is brought into contact with a carbon dioxide-containing fluid to carbonate the material,the carbonation process time being determined based on the value of time-series information obtained by subtracting information on the change over time of the amount of carbon dioxide absorption by the material to be treated in the carbonation process from information on the change over time of the amount of carbon dioxide emission resulting from the use of energy consumed in the carbonation process.[Claim 2.]The material conversion method according to claim 1, wherein the carbonation treatment time in the carbonation process is determined based on a value of time-series information obtained by subtracting information on the change overtime of the amount of carbon dioxide gasabsorbed by the treated material in the carbonation treatment from the sum of information on the change overtime of the amount of carbon dioxide gas emitted due to the auxiliary materials used in the carbonation process and information on the change over time of the amount of carbon dioxide gas emitted due to the use of energy consumed in the carbonation process.[Claim 3.]The material conversion method according to claim 1 or 2,further comprising a granulation process for the material to be treated, and determining the carbonation processing time in the carbonation process based on the value of the time series information to which is added the amount of carbon dioxide emissions resulting from the use of energy consumed in the granulation process.[Claim 4.]The material conversion method according to claim 3, wherein the carbonation process time in the carbonation step is determined based on the valueof the time series information to which the amount of carbon dioxidegas emitted due to auxiliary materials used in the granulation step is further added.[Claim 5.]The method according to claim 1 or 2, wherein the carbonation process time is the elapsed time until the value of the time-series information changes from a decrease to an increase, or from an increase to becoming 0.[Claim 6.]The method for converting materials into resources according to claim 3, wherein the carbonation process time is the elapsed time untilthe value of the time-series information changes from a decrease to an increase, or from an increase to becoming 0.[Claim 7.]The method for converting materials into resources according to claim 4, wherein the carbonation process time is the elapsed time untilthe value of the time-series information changes from a decrease to an increase, or from an increase to becoming 0.[Claim 8.]The material conversion method according to claim 2, wherein the secondary material contains a heavy metal elution inhibitor, the carbonation process includes a treatment for preventing elution of heavy metals by the heavy metal elution inhibitor, and when a second elapsed time for reducing the amount of elution of the heavy metalsin the elution prevention treatment to a regulated value or less in the elution prevention treatment is longer than a first elapsed time untilthe value of the time-series information changes from a decrease to an increase or until it changes to 0 after changing to an increase, the carbonation process time is set to the second elapsed time.

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