JP2000070678A - Method and apparatus for treating 14c-containing graphite - Google Patents

Abstract

PROBLEM TO BE SOLVED: To fix only 14C-containing graphite while reducing the vol. of fixed graphite without fixing all of graphite as is conventional in the treatment of 14C-containing graphite. SOLUTION: A furnace 11 burning introduced graphite containing 14C, a means 17 separating a combustion gas component 13 into an N2/O2 component 15, an isotope component (14CO2, 12CO2, 13CO2) 16, a methane forming apparatus 18 adding H2 to this CO2 isotope component to convert the isotope component to 14CH4, 12CH4, 13CH4 and H2O, a condenser 20 cooling the reaction component 19 such as the CH4 isotope components formed by the reaction in the methane forming apparatus, unreacted H2, formed H2O or the like to remove formed H2O, a means 23 separating a 14CH4/H2 component 21 and a 12CH4/13CH4 component 22 from the reaction product after the removal of H2O, a means 24 further separating the separated components into a 14CH4 component and a H2 component, a carbon solidifying means 25 for separated 14CH4 and a combuster 26 burning the isotope components to discharge them out of the system are provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for treating graphite containing ^14C .

[0002]

In a conventional, graphite used as a core material or the like of a nuclear power, has been treated as waste without being reused because it contains ¹⁴ C, for example ¹⁴
Graphite containing C is solidified as it is with cement or the like and buried underground.

[0003]

The ratio of ¹⁴ C of radioactive isotope in graphite used as a core material is 7.4 ×.
10 ^-5 %, and the balance was 98.90 with ¹² C as a stable compound.
%, ¹³ C is 1.10%. For this reason, the proportion of radioisotopes in the prior art cement solid is very small, but the amount of cement solid relative to the amount of radioisotope is very large. Inevitably, the conventional technology requires a space for burying a large amount of solidified cement, but in the current situation, there is a problem that it is difficult to secure a large space for the buried space.

[0004] The present invention has been made in view of the above problems, immobilized only ¹⁴ C, without immobilization of the conventional all graphite as the graphite processing method containing ¹⁴ C-achieving volume reduction of the fixed graphite And a processing device.

[0005]

Means for Solving the Problems According to the invention of claim 1 which solves the above-mentioned problems, graphite containing ¹⁴ C is burned, and the combustion gas is mixed with N ₂ and O ₂ components and ¹⁴ CO ₂ and ¹² CO _2. , ¹³ CO ₂
Separated from the combustion gas into the components, the ¹⁴ CO ₂ , ¹² CO ₂ , ¹³ C
By treating the O ₂ component, a carbon compound consisting of ¹² C and ¹³ C
Isotope separated into a carbon compound composed of ¹⁴ C, characterized by solidifying the carbon compound consisting of the ¹⁴ C.

A second aspect of the present invention is characterized in that, in the first aspect, the carbon compound comprises one of carbon dioxide (CO ₂ ), carbon monoxide (CO) and methane (CH ₄ ). .

[0007] The invention of claim 3 is to burn graphite containing ¹⁴ C and convert the combustion gas into N ₂ and O ₂ components and ¹⁴ CO ₂ and ¹² CO ₂ .
CO _2, ¹³ CO ₂ and the combustion gas separated into the components, the ¹⁴ C
Hydrogen is added to O ₂ , ¹² CO ₂ , and ¹³ CO ₂ components to form ¹⁴ CH.
_{It is characterized in that it is a 4} , ¹² CH ₄ , ¹³ CH ₄ component, then isotope-separated into a ¹⁴ CH ₄ component and a ¹² CH ₄ , ¹³ CH ₄ component, and the separated ¹⁴ CH ₄ component is solidified.

According to the invention of claim 4, the graphite containing ¹⁴ C is burned, and the combustion gas is converted into N ₂ and O ₂ components and ¹⁴ CO ₂ and ¹² CO ₂ .
CO _2, ¹³ CO ₂ and the combustion gas separated into the components, the ¹⁴ C
Add hydrogen to O ₂ , ¹² CO ₂ , and ¹³ CO ₂ components to add ¹⁴ C
O, ¹² CO, ¹³ CO components, then ¹⁴ CO components and ¹² C
It is characterized by being separated into O and ¹³ CO components and solidifying the separated ¹⁴ CO components.

According to the invention of claim 5, the graphite containing ¹⁴ C is burned, and the combustion gas is mixed with N ₂ and O ₂ components and ¹⁴ CO ₂ and ¹² CO ₂ .
CO _2, ¹³ CO ₂ and the combustion gas separated into the components, the ¹⁴ C
O ₂ , ¹² CO ₂ , and ¹³ CO ₂ components are combined with ¹⁴ CO ₂ components and ¹² CO
Isotope separated into ₂ , ¹³ CO ₂ components, and the separated ¹⁴ C
It is characterized by solidifying the O ₂ component.

The invention of claim 6 is characterized in that in claim 1 to 5, the solidification of the carbon compound comprising ¹⁴ C is carried out by plasma treatment.

The invention of claim 7 is characterized in that, in claims 1 to 5, the graphite containing ¹⁴ C is graphite used as a core material of a nuclear reactor.

[0012] The invention of claim 8 provides a combustion furnace for burning the graphite containing ¹⁴ C to be introduced, and converting the combustion gas components generated in the combustion furnace into N ₂ and O ₂ components and ¹⁴ CO ₂ , ¹² C
A combustion gas separating means for separating gas into O ₂ and ¹³ CO ₂ components, and adding H ₂ to the CO ₂ isotope component to form ¹⁴ CH ₄ , ¹² CO ₂
A methane generator for converting into CH ₄ and ¹³ CH ₄ components, and ¹⁴ CH ₄ and ¹² C produced by the reaction in the methane generator.
The H ₄ and ¹³ CH ₄ components are combined with the ¹⁴ CH ₄ component and the ¹² CH ₄ and ¹³ C
It is characterized by comprising isotope separating means for isotopically separating the H ₄ component and carbon solidifying means for solidifying the separated ¹⁴ CH ₄ .

A ninth aspect of the present invention is characterized in that, in the eighth aspect, there is provided a combustor for combusting the above-mentioned isotope-separated ¹² CH ₄ and ¹³ CH ₄ components and discharging the same out of the system.

The invention of claim 10 is introduced.¹⁴C
And a combustion furnace for burning graphite containing
The combustion gas component_Two, O_TwoIngredients¹⁴CO_Two,¹²CO
_Two, ¹³CO_TwoCombustion gas separation means for separating gas into components
When,¹⁴CO_Two,¹²CO_Two,¹³CO_TwoAdd hydrogen to the components
hand¹⁴CO,¹²CO,¹³CO component and H_TwoC to convert to O
An O-shift converter and the converted CO isotope component
Unreacted CO_TwoCO / CO separated into isotopes_TwoIsolated hand
Step and the separated¹⁴CO,¹²CO,¹³CO component¹²C
O,¹³CO component and¹⁴Isotope separation for isotopic separation with CO
Means and the separated¹⁴Carbon solidifying means for solidifying CO;
It is characterized by having.

[0015] The invention of claim 11 is based on claim 10.
And the above isotopes were separated¹²CO, ¹³Burning CO components
And a combustor for discharging to the outside of the system.

The invention of claim 12 is the invention of claims 8 to 11.
Wherein the carbon solidifying means immobilizes carbon by plasma treatment.

The invention of claim 13 is introduced.¹⁴C
And a combustion furnace for burning graphite containing
The combustion gas component_Two, O_TwoIngredients¹⁴CO_Two,¹²CO
_Two, ¹³CO_TwoCombustion gas separation means for separating gas into components
And the¹⁴CO_Two,¹²CO_Two,¹³CO_TwoIngredients¹²CO_Two,
¹³CO_TwoIngredients¹⁴CO_TwoAnd pressure swing adsorption method
Means for separating isotopes, and¹⁴CO_TwoFix
And a carbon solidifying device for converting the solidified carbon.

The invention of claim 14 is introduced.¹⁴C
And a combustion furnace for burning graphite containing
The combustion gas component_Two, O_TwoIngredients¹⁴CO_Two,¹²CO
_Two, ¹³CO_TwoCombustion gas separation means for separating gas into components
And the¹⁴CO_Two,¹²CO_Two,¹³CO_TwoIngredients¹²CO_Two,
¹³CO_TwoIngredients¹⁴CO_TwoCryogenic separation means for separating into
The separated¹⁴CO_TwoAnd a carbon solidifying device for solidifying
It is characterized by doing.

The invention of claim 15 is the invention according to claim 13 or 14, wherein the carbon solidifying device is capable of converting the ¹⁴ CO ₂ into an aqueous solution containing quicklime (CaO) or slaked lime (Ca (OH) ₂ ).
And solidified as calcium carbonate (CaCO ₃ ).

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described, but the present invention is not limited thereto.

The method for treating graphite containing ¹⁴ C according to the present invention comprises:
Burning a graphite containing ¹⁴ C, the combustion gas burned gas separated into N _2, O ₂ component and _{^{14 CO 2, 12 CO 2,}} 13 CO 2 component, the _{^{14 CO 2, 12 CO 2,}} 13 CO It processes the _two components, ¹² C, ¹³ isotopically separated into carbon compounds comprising a C and carbon compound consisting of ¹⁴ C, a method of solidifying a carbon compound composed of the ¹⁴ C. As a result, carbon such as graphite containing ¹⁴ C can be safely separated from a stable compound (a carbon compound composed of ¹² C and ¹³ C) and immobilized as ¹⁴ C to reduce the volume. Here, as a method for separating carbon dioxide generated by combustion, the carbon compound is any one of carbon dioxide, carbon monoxide and methane.

[First Embodiment] <First Graphite Treatment Containing ¹⁴ C> The first treatment method is as follows.
N ₂ and O ₂ components from the combustion gas generated by combustion and ¹⁴
The combustion gas is separated into CO ₂ , ¹² CO ₂ and ¹³ CO ₂ components,
Hydrogen is added to the separated ¹⁴ CO ₂ , ¹² CO ₂ , and ¹³ CO ₂ components, and ¹⁴ CH is added according to the following reaction formula (1) of “Chemical formula 1”.
_4, ¹² CH _4, ¹³ and CH ₄ component, then these ¹⁴ C
H ₄ component and ¹² CH ₄ and ¹³ CH ₄ components are isotope-separated,
This is a method of solidifying only the ¹⁴ CH ₄ component.

[0023]

Embedded image CO ₂ + 3H ₂ → CH ₄ + 2H ₂ O (1)

The first processing method will be described with reference to FIG.
The configuration of the device will be described. Of the present invention¹⁴Graphite treatment containing C
Equipment is introduced¹⁴Graphite containing C (graphite
G) Combustion furnace 11 for burning 10 and combustion gas components
(N_Two, O_Two, CO_Two) Is cooled to, for example, 100 ° C. or less.
Cooler 14 and the car in the cooled combustion gas component 13
After removing fine particles such as bon (C) with the filter 12
And N_Two, O_TwoComponent 15 and CO_TwoIsotopic component (¹⁴C
O_Two, ¹²CO_Two,¹³CO_TwoCombustion that separates gas into 16)
Gas separation means 17; _TwoH isotope component 16_Two
Is added, and the methane isotope formation
Minutes (¹⁴CH_Four,¹²CH_Four,¹³CH_Four) And H_TwoConvert to O
Methane generator 18 and the methane generator 18
CH generated by the reaction_FourIsotopic component, unreacted H_Two,
Generated, H_TwoThe reaction component 19 such as O was cooled and produced.
H_TwoA condenser 20 for removing O;_TwoAfter removing O
From component 19¹⁴CH_Four, H_TwoComponent 21 and ¹²CH_Four,¹³
CH_FourIsotope separation means 23 for isotope separation with component 22
And the separated¹⁴CH_Four, H_TwoIngredient 21¹⁴C
H_FourAnd H_TwoSeparates into components¹⁴CH _Four/ H_TwoSeparation means 2
4 and the separated¹⁴CH_FourIs fixed by plasma treatment or the like.
The carbon solidification means 25 to be¹²CH
_Four,¹³CH_FourCombustor that burns component 22 and discharges it out of the system
26.

Here, the combustion furnace 11 burns graphite with an oxidizing agent containing oxygen, and burns at a low temperature by controlling the supply amount of the oxidizing agent. This low-temperature combustion refers to combustion in a temperature range of about 400 to 700 ° C., and efficient and stable combustion can be performed by adding a combustion catalyst. By using a combustion catalyst, it becomes possible to perform graphite combustion at a low temperature of 500 ° C. In addition, since the control of the combustion furnace 11 is performed with the oxidizing agent to be introduced, it is not necessary to install a heat exchange tube or the like inside the combustion furnace 11, and as a result, the safety of the components of the combustion furnace is improved, The risk of secondary contamination such as leakage of radioactivity to the outside is greatly reduced.

The method of charging the graphite 10 into the combustion furnace 11 varies depending on the type of the combustion furnace, but the present invention is not limited thereto. For example, the graphite is crushed and charged into the combustion furnace by gas transfer. And a method of directly charging the graphite 10 can be appropriately selected.

The above-mentioned combustion gas separation means 17
(N_Two, O_Two,¹⁴CO_Two,¹²CO_Two, ¹³CO_TwoComponent) 1
3 for N_Two, O_TwoComponent 14 and¹⁴CO_Two,¹²CO_Two,¹³C
O_TwoComponent 15 is separated into
It is performed by the contact method or the temperature swing adsorption method.
You.

The pressure swing adsorption method uses an adsorbent to adsorb easily adsorbed components under high-pressure or normal-pressure conditions to take out easily adsorbed components, and to separate and recover the easily adsorbed components adsorbed under low-pressure conditions. Is a physical gas separation method that regenerates by pressure, and is a pressure swing method (Pressure-wing Adsorption: PSA)
(Jun Izumi "Utilization of Zeolite Adsorbent for Pressure Swing Method (PSA)", "Zeolite" Vol.
9 No. 2, 1992, pp. 60-68).

For example, when the target substance is adsorbed at atmospheric pressure as the above-mentioned adsorption pressure, for example, 0.1 torr to 380 torr,
The adsorbed substance can be desorbed by reducing the pressure to preferably 1 torr to 100 torr. As the adsorbent used in the above-mentioned adsorption method, the lattice structure of the adsorbent has gas permeation holes of 3 to 10 ° and is, for example, a zeolite-based adsorbent having a cation of Na, Ca, K, etc. Zeolites, Na-A-type zeolites, Na-KA-type zeolites, Na-X-type zeolites, etc.), but the present invention is not limited to these.

In the temperature swing adsorption method, after a target substance is adsorbed on an adsorbent at room temperature, the temperature is adjusted to, for example, 50 to 3 times.
This is a method in which the adsorbed substance is desorbed by raising the temperature to 00 ° C. As a heating means, a method of flowing inert gas hot air into the adsorbent, a method of heating the periphery of the adsorbent, a method of induction heating, and the like can be appropriately used.

FIG. 2 shows the pressure swing adsorption method (PSA).
1 shows an outline of the adsorption step. As shown in FIGS. 2A and 2B, the pressure swing adsorption device has a first adsorption tower 31 and a second adsorption tower 32, and the first and second adsorption towers 31,
Gases (A, B, C) 34 separated from the blower 33 from the line L ₁ are introduced into the blower 32 by switching valves. In addition, the first and second adsorption towers 3
Lines L _{2, which} are sucked through the vacuum pump 35 and lead to the surge tank 36, are formed in the first and the _second 32.

Here, the adsorption towers 31 and 32 are filled with the above-mentioned zeolite-based adsorbent, and a gas component 34 containing a target gas is introduced into the adsorbent to form the target gas. Is selectively adsorbed, or a gas other than the target gas is selectively adsorbed.

Here, the blower 33 converts the gas component 34 containing the target gas into the first and second adsorption towers 31, 32.
To be introduced. The vacuum pump 35 guides the adsorption tower to a reduced pressure to desorb the gas selectively adsorbed on the adsorbent. The surge tank 36 temporarily stores the gas separated by the adsorption tower.

Here, in FIGS. 2A and 2B, of the gas components 34 to be introduced, A is assumed to be an easily adsorbed component.
The case where B and C are hardly adsorbed components will be described. First, the gas components (A, B, C) 34 are guided to the first adsorption tower 31 by the blower 33. In “Step 1” shown in FIG. 2A, the first adsorption tower 31 performs adsorption, and selectively adsorbs A in the introduced gas 34. On the other hand, in the second adsorption tower 32, the A adsorbed by the suction of the vacuum pump 35
The desorption is done. Further, in “Step 2” shown in FIG. 2B, the second adsorption tower 32 performs adsorption, and the first adsorption tower 32 performs adsorption.
In the adsorption tower 31, desorption is performed. By switching from “step 1” to “step 2”, the first and second adsorption towers 31,
The adsorption step and the desorption step of 32 are reversed. In the adsorption step, the component A, which is an easily adsorbed component, is selectively adsorbed, and the hardly adsorbed components, B and C, exit the first and second adsorption towers 31 and 32 without being adsorbed. Line L ₃
Is discharged from On the other hand, in the desorption step, the adsorbed A component can be desorbed by putting the adsorption tower under a reduced pressure. The desorbed A component-rich gas is sucked through the vacuum pump 35 and temporarily stored in the surge tank 36. Thereby, the A gas component can be separated from the B and C gas components. When the gas can be separated by this adsorption method and the separation efficiency is improved, the gas can be separated by constructing in multiple stages.

In the present invention, the pressure swing adsorption method (P
SA) in the combustion gas separation means 17
3 is used to separate the methane isotope into ¹⁴ CH ₄ and ¹² CH ₄ , ¹³ CH ₄ components, in addition to being used to separate 3 into N ₂ and O ₂ components 15 and CO ₂ isotope components 16 The pressure swing adsorption method is also used in the means 23 and the ¹⁴ CH ₄ / H ₂ separation means 24, respectively.

Here, the adsorbent of the combustion gas separating means 17 by the pressure swing adsorption method (PSA) is Ca-X
It is preferable to use a zeolite type or the like as the adsorbent. Pressure swing adsorption method (PS
As the adsorbent according to A), it is preferable to use Na-A type zeolite type or the like as the adsorbent. ¹⁴ CH ₄ / H ₂
As the adsorbent of the separation means 24 by the pressure swing adsorption method (PSA), it is preferable to use a heat-treated Na-A type zeolite type or the like as the adsorbent.

The carbon solidifying means 25 is composed of ¹⁴ CH ₄ / H
_{2 The} ¹⁴ CH ₄ separated from the separation device 24 is converted into ¹⁴ C and immobilized. For example, ¹⁴ C is deposited by a plasma decomposition method or the like. The carbon solidifying means 25 generates plasma by an external power supply, dissociates ¹⁴ CH ₄ into ¹⁴ C and H ₂ by the energy of the plasma, and deposits the dissociated ¹⁴ C on a substrate installed in the apparatus. By doing so, only ¹⁴ C is immobilized.

FIG. 3 shows a graph of C using the isotope separation device 23.
H_FourIsotope component¹⁴CH_FourIngredients¹²CH_Four,¹³CH_FourSuccess
As an example of a multi-stage device separated into two parts, an outline of a seven-stage device
Abbreviated. The device of FIG. 3 is shown in FIG.¹⁴CH_FourIngredients
¹²CH_Four,¹³CH_FourSeparation test results with components (speed separation type
Adsorption: by Na-A type zeolite system (pore diameter: 4 mm)
,¹⁴CH_FourIngredients¹²CH_Four,¹³CH_FourSeparation effect from components
Assuming that the rate is 90%, the seven-stage separation devices 23-1 to 23-7 are used.
Was constructed to perform separation. The separation devices 23-1 to 23-23
-7, the first separator 23-1 has a suction capacity of 200 kg.
The adhesive is supplied to the remaining separation devices 23-2 to 23-7 with 200.
kg of adsorbent, each filled with H_Two： 2680Nm^Three
/ D,¹²CH_Four,¹³CH_Four： 1866Nm ^Three/ D,¹⁴C
H_Four: 1.38E-03Nm^Three/ D to the first adsorption device
And separated.

As shown in FIG. 3, when a velocity separation type PSA device is used using Na-A type zeolite as an adsorbent, ¹⁴ CH ₄ having a low diffusion rate passes without being adsorbed.
On the other hand since the ¹² CH _4, ¹³ CH ₄ component easily adsorbed faster diffusion rate in the ¹⁴ CH ₄ concentration side, the separation device of the first stage
¹⁴ CH ₄ is 1.38 × 10 ^-4 (1.38E-04), the second stage separator is ¹⁴ CH ₄ is 1.38 × 10 ^-5 (1.38E-05), the third stage separator is ¹⁴ CH ₄ is concentrated to 1.38 × 10 ⁻⁶ (1.38E-06), while the ¹² CH ₄ and ¹³ CH ₄ component concentration side
^{The 12} CH ₄ and ¹³ CH ₄ components are concentrated.

In the apparatus shown in FIG. 1, the results of separation by the respective separating means when 1000 kg / d of graphite 10 is charged into the combustion furnace are shown in Tables 1 and 2 below.

[0041]

[Table 1]

[0042]

[Table 2]

Isotope separation means 2 for separating CH ₄ isotopes
3 used a multi-stage separation device as described above. As shown in Table 1 and Table 2, ¹⁴ C
Was separated from the stabilized ¹² CH ₄ and ¹³ CH ₄ components at a rate of 99.99%, and only ¹⁴ C could be immobilized. As a result, it has become possible to reduce the amount of graphite to be fixed on a large scale as compared with the related art.

[0044] ^{_{Incidentally, 14 CH 4 / H 2 H}} 2 separated from the separator 24 is used as of H ₂ for addition to the methane generation device 18 (in the figure, marks of *). As shown in "Table 1", since the H ₂ separated is approximately about 1/4 H ₂ amount to be introduced into the methanation apparatus 18, it is possible to effectively utilize.

[Second Embodiment] <Second Graphite Treatment Containing ^14C > The second treatment method is as follows.
N ₂ and O ₂ components from the combustion gas generated by combustion and ¹⁴
The combustion gas is separated into CO ₂ , ¹² CO ₂ and ¹³ CO ₂ components,
Hydrogen is added to the separated ¹⁴ CO ₂ , ¹² CO ₂ , and ¹³ CO ₂ components to obtain a CO isotope ( ¹⁴ CO, ¹² CO, ¹³ CO) by the following reaction formula (2) of “Chemical formula 2”. Then, the ¹⁴ CO component is separated into ¹² CO and ¹³ CO components, and only the ¹⁴ CO component is solidified.

[0046]

Embedded image CO ₂ + H ₂ → CO + H ₂ O (1)

Referring to FIG. 5, the second processing method is performed.
The configuration of the device will be described. Of the present invention¹⁴Graphite treatment containing C
Equipment is introduced¹⁴Graphite containing C (graphite
G) Combustion furnace 11 for burning 10 and combustion gas components
(N_Two, O_Two, CO_Two) Is cooled to, for example, 100 ° C. or less.
Cooler 14 and the car in the cooled combustion gas component 13
After removing fine particles such as bon (C) with the filter 12
And N_Two, O_TwoComponent 15 and CO_TwoIsotopic component (¹⁴C
O_Two,¹²CO_Two,¹³CO_TwoCombustion that separates gas into 16)
Gas separating means 17 and the CO_TwoH isotope component 16_TwoTo
Is added, and the CO isotope component (
¹⁴CO,¹²CO,¹³CO) and H_TwoCO to convert to O
Shift converter 40 and the CO shift converter 40
Converted CO isotope component, unreacted CO_Two, Generate
H_TwoThe reaction component 41 such as O is cooled to produce H_TwoO
And a condenser 42 for removing H_TwoThe above reaction components after removing O
41 to CO isotope, unreacted H_TwoUnreacted with component 43
CO_TwoIsotope, H_TwoCO / C separated into O component 44
O_TwoSeparation means 45 and the separated CO isotope component 43
Further¹²CO,¹³CO component, unreacted H_TwoComponent 46 and
¹⁴Isotope separation means 47 for isotope separation into CO and separation
The said¹⁴CO¹⁴C to convert carbon to carbon
A carbon monoxide reduction device 48, which is a
Released¹²CO,¹³CO component and unreacted H_TwoIngredient 46
Unreacted H_Two/ H that separates _TwoSeparation means 49;
separated¹²CO,¹³Combustion that burns CO and discharges it out of the system
And a container 50.

The CO ₂ isotope and the H ₂ O component 44 separated by the CO / CO ₂ separation means 45 are returned to the CO shift converter 40, reacted again, and treated in a closed system. To prevent discharge to the public and improve safety.

[0049] Further, ¹⁴ CO / H ₂ separation device 49 H ₂ separated from are also reused as of H ₂ for addition to the CO shift converter 40 (in the figure, marks of *).

In the present embodiment, as in the first embodiment, the combustion gas 13 is divided into N ₂ and O ₂ components 15 and CO ₂ isotope components 1 by the combustion gas separation means 17.
And CO / CO separating CO and CO ₂ isotopes in addition to using the pressure swing adsorption method to separate
₍₂₎ Separation means 45, CO isotopes of ¹⁴ CO, ¹² CO, ¹³ CO
Isotope separation means 47 and ¹² CO and H ₂
The above-mentioned pressure swing adsorption method is also used in the ¹³ CO / H ₂ separation means 49 for separating into the ¹³ CO / H ₂ .

Here, the adsorbent of the combustion gas separation means 17 by the pressure swing adsorption method (PSA) is Ca-X
It is preferable to use a zeolite type or the like as the adsorbent. As the adsorbent of the CO / CO ₂ separation means 45, Na
-KA type zeolite type or the like is used as an adsorbent,
preferable. As the adsorbent of the isotope separation means 47 by the pressure swing adsorption method (PSA), it is preferable to use Na-A type zeolite type or the like as the adsorbent. ¹² CO,
¹³ CO / H ₂ separation means 49 pressure swing adsorption method (PS
As the adsorbent according to A), it is preferable to use a Na-X type zeolite type or the like as the adsorbent.

The carbon monoxide reduction device 48 converts the separated ¹⁴ CO into ¹⁴ C. As in the first embodiment, the carbon monoxide reducing device 48 is designed to deposit ¹⁴ C by a plasma decomposition method or the like. However, the present invention is not limited to this.

In the apparatus shown in FIG. 5, the results of separation by the respective separating means when 1000 kg / d of graphite 10 is charged into the combustion furnace are shown in Tables 3 and 4 below.

[0054]

[Table 3]

[0055]

[Table 4]

As shown in Tables 3 and 4, the amount of ¹⁴ C present in the graphite was reduced by 99.99% to ¹² C of the stabilized product.
Separated from the O and ¹³ CO components, only ¹⁴ C could be immobilized. As a result, it has become possible to reduce the amount of graphite to be fixed on a large scale as compared with the related art.

The conversion of CO ₂ to CO in the CO shift converter 40 of the present embodiment does not involve an exothermic reaction as in the methane generator 17 of the first embodiment. Reliability is further improved.

[Third Embodiment] <Third Embodiment¹⁴Graphite treatment containing C> The third treatment method is as follows:
¹⁴Combustion of graphite containing C_Two, O_TwoSuccess
Minutes and¹⁴CO_Two,¹²CO_Two,¹³CO_TwoIngredients and combustion gas content
Release,¹⁴CO_Two,¹²CO _Two,¹³CO_TwoIngredients¹⁴CO_Two
Ingredients¹²CO_Two,¹³CO_TwoComponent and isotope-separated¹⁴
CO_TwoIs a method of solidifying the components.
As in the first embodiment, the pressure swing adsorption method
Is what you do.

With reference to FIG. 6, the configuration of an apparatus for performing the third processing method will be described. The apparatus for treating graphite containing ¹⁴ C according to the present invention comprises a combustion furnace 11 for burning the introduced graphite (graphite) 10 containing ¹⁴ C and a combustion gas component (N ₂ , O ₂ , CO ₂ ) of, for example, 100%. After the filter 12 removes fine particles such as carbon (C) in the cooled combustion gas component 13, the N ₂ and O ₂ components 15 and the CO ₂ isotope component ( ¹⁴ C) are removed.
O ₂ , ¹² CO ₂ , ¹³ CO ₂ ) 16 and a combustion gas separating means 17 for separating the CO ₂ isotope component 16 into ¹⁴ CO 2.
₂ and ¹² CO _2, ¹³ to the CO ₂ component and isotope separation means 61 for separating by pressure swing adsorption, said it separated the ¹⁴ C
O ₂ to ¹⁴ are those having a carbon solidifying device 62 solidifying.

In this embodiment, as in the first embodiment, the combustion gas 13 is divided into N ₂ and O ₂ components 15 and CO ₂ isotope components 1 by the combustion gas separation means 17.
In addition to using the pressure swing adsorption method for separating CO ₂ and CO ₆ , the isotope separation means 62 for separating CO ₂ isotope into ¹⁴ CO ₂ and ¹² CO ₂ and ¹³ CO ₂ components also has the above-mentioned pressure swing adsorption. Method is used.

Here, the adsorbent of the combustion gas separating means 17 by the pressure swing adsorption method (PSA) is Ca-X
It is preferable to use a zeolite type or the like as the adsorbent. Pressure swing adsorption method (PS
As the adsorbent according to A), it is preferable to use Na-A type zeolite type or the like as the adsorbent.

In the apparatus shown in FIG. 6, the results of separation by each separation means when 1000 kg / d of graphite 10 is charged into the combustion furnace are shown in Table 5 below.

[0063]

[Table 5]

As shown in "Table 5", it is present in graphite.
¹⁴ C was added at a rate of 99.99% to the stabilized ¹² CH ₄ , ¹³ CH
Separated from the _four components, only ¹⁴ C could be immobilized. As a result, it has become possible to reduce the amount of graphite to be fixed on a large scale as compared with the related art.

[Fourth Embodiment] <Fourth Graphite Treatment Containing ¹⁴ C> A fourth treatment method is as follows.
^The graphite containing ¹⁴ C is burned, the graphite containing ¹⁴ C is burned, and the combustion gas is divided into N ₂ and O ₂ components and ¹⁴ CO ₂ and ¹² C.
The combustion gas is separated into O ₂ and ¹³ CO ₂ components, and the ¹⁴ CO ₂ ,
¹² CO ₂ , ¹³ CO ₂ component is converted to ¹⁴ CO ₂ component and ¹² CO ₂ , ¹³
Isotope separated into a CO ₂ component, a method for solidifying the ¹⁴ CO ₂ component.

Referring to FIG. 7, the fourth processing method is performed.
The configuration of the device will be described. Of the present invention¹⁴Graphite treatment containing C
Equipment is introduced¹⁴Graphite containing C (graphite
G) Combustion furnace 11 for burning 10 and combustion gas components
(N_Two, O_Two, CO_Two) Is cooled to, for example, 100 ° C. or less.
Cooler 14 and the car in the cooled combustion gas component 13
After removing fine particles such as bon (C) with the filter 12
And N_Two, O_TwoComponent 15 and CO_TwoIsotopic component (¹⁴C
O_Two,¹²CO_Two,¹³CO_TwoCombustion that separates gas into 16)
Gas separation means 17;_TwoIsotope component 16¹⁴C
O_TwoWhen¹²CO _Two,¹³CO_TwoCryogenic separation hand to separate into components
Step 63 and the separated¹⁴CO_TwoTo¹⁴Solidified carbon solidification
Device 62.

Here, the cryogenic separation means 63 is CO 2
₍₂ ) A method in which isotopes are compressed and cooled to form a liquid mixture, which is distilled and separated into each isotope component, whereby the ¹⁴ CO ₂ component is separated from the ¹² CO ₂ and ¹³ CO ₂ components.

The above-mentioned carbon solidifying device 62 includes quick lime (Ca
O) and hydrated lime (Ca (OH) in an aqueous solution containing ₂₎ ¹⁴ CO
₂ means that it is solidified as calcium carbonate (CaCO ₃ ) by blowing.

[0069] According to the present embodiment, it is present in graphite.
¹⁴ C was added at a rate of 99.99% to the stabilized ¹² CH ₄ , ¹³ CH
Separated from the _four components, only ¹⁴ C could be immobilized. As a result, it has become possible to reduce the amount of graphite to be fixed on a large scale as compared with the related art.

[0070]

As described above, according to the present invention,
Burning a graphite containing ¹⁴ C, the combustion gas burned gas separated into N _2, O ₂ component and _{^{14 CO 2, 12 CO 2,}} 13 CO 2 component, the _{^{14 CO 2, 12 CO 2,}} 13 CO processes the _two components, ¹² C, ¹³ isotopically separated into carbon compounds comprising a C and carbon compound consisting of ¹⁴ C, since the solidified carbon compound consisting of the ¹⁴ C, ¹⁴ C-present in the graphite at a rate of 99.99% is separated from the ¹² C, ¹³ C carbon component of the stabilizing compound, ¹⁴
Only C can be immobilized. As a result, it is possible to reduce the amount of graphite to be immobilized on a large scale as compared with the related art.

According to [Claim 2], since the carbon compound is any one of carbon dioxide (CO ₂ ), carbon monoxide (CO) and methane (CH ₄ ), ¹⁴ C can be immobilized by isotopically separating (CO ₂ ), carbon monoxide (CO) or methane (CH ₄ ).

According to [claim 3], graphite containing ¹⁴ C is burned, and the combustion gas is mixed with N ₂ and O ₂ components and ¹⁴ CO ₂ and ¹² CO ₂ .
CO _2, ¹³ CO ₂ and the combustion gas separated into the components, the ¹⁴ C
Hydrogen is added to O ₂ , ¹² CO ₂ , and ¹³ CO ₂ components to form ¹⁴ CH.
₄ , ¹² CH ₄ and ¹³ CH ₄ components, and then isotope-separated into ¹⁴ CH ₄ components and ¹² CH ₄ and ¹³ CH ₄ components, and the separated ¹⁴ CH ₄ components are solidified, so that they are present in graphite. Do ¹⁴
C is separated in the form of CH ₄ , and is separated from the ¹² CH ₄ and ¹³ CH ₄ components of the stabilizer at a rate of 99.99%, so that only ¹⁴ C can be immobilized.

According to [claim 4], graphite containing ¹⁴ C is burned, and the combustion gas is divided into N ₂ and O ₂ components and ¹⁴ CO ₂ and ¹² CO ₂ .
CO _2, ¹³ CO ₂ and the combustion gas separated into the components, the ¹⁴ C
Add hydrogen to O ₂ , ¹² CO ₂ , and ¹³ CO ₂ components to add ¹⁴ C
O, ¹² CO, ¹³ CO components, then ¹⁴ CO components and ¹² C
Since it is separated into O and ¹³ CO components and the separated ¹⁴ CO component is solidified, the ¹⁴ C present in the graphite is separated in the form of CO, and 99.9% of the stabilized ¹² CO, Separated from the ¹³ CO component, only ¹⁴ C can be immobilized.

According to claim 5, graphite containing ¹⁴ C is burned, and the combustion gas is mixed with N ₂ and O ₂ components and ¹⁴ CO ₂ and ¹² CO ₂ .
CO _2, ¹³ CO ₂ and the combustion gas separated into the components, the ¹⁴ C
O ₂ , ¹² CO ₂ , and ¹³ CO ₂ components are combined with ¹⁴ CO ₂ components and ¹² CO
Isotope separated into ₂ , ¹³ CO ₂ components, and the separated ¹⁴ C
Since the O ₂ component is solidified, the ¹⁴ C present in the graphite is reduced to CO
₂₎ and 99.9% of the stabilized ¹² CO
Separated from the ₂ , ¹³ CO ₂ component, only ¹⁴ C can be immobilized.

According to [claim 6], in claim 1 to 5, only the ^14C can be immobilized by solidifying the carbon compound comprising ^14C by a plasma treatment.

According to [claim 7], in the case where the graphite containing ^14C is graphite used as a core material of a nuclear reactor, the graphite used in nuclear power generation may be used. Only harmful ¹⁴ C can be immobilized. As a result, it is possible to reduce the amount of graphite to be cement-solidified to one-millionth of the volume of what has been conventionally solidified as cement, and it is not necessary to secure a large-capacity burying space.

According to [claim 8], a combustion furnace for burning the introduced graphite containing ¹⁴ C, and the combustion gas components generated in the combustion furnace are converted into N ₂ and O ₂ components and ¹⁴ CO ₂ , ¹² C
A combustion gas separating means for separating gas into O ₂ and ¹³ CO ₂ components, and adding H ₂ to the CO ₂ isotope component to form ¹⁴ CH ₄ , ¹² CO ₂
A methane generator for converting into CH ₄ and ¹³ CH ₄ components, and ¹⁴ CH ₄ and ¹² C produced by the reaction in the methane generator.
The H ₄ and ¹³ CH ₄ components are combined with the ¹⁴ CH ₄ component and the ¹² CH ₄ and ¹³ C
Since it is provided with an isotope separating means for isotope separation into H ₄ components and a carbon solidifying means for solidifying the separated ¹⁴ CH ₄ , ¹⁴ C present in graphite is separated in the form of CH _4. , 9
At a rate of 9.99%, it is separated from the ¹² CH ₄ and ¹³ CH ₄ components of the stabilizer, and only ¹⁴ C can be immobilized.

According to [claim 9], in claim 8, a combustor for burning the isotope-separated ¹² CH ₄ and ¹³ CH ₄ components and discharging the same to the outside of the system is provided. Becomes possible.

According to [claim 10], it is introduced¹⁴C
And a combustion furnace for burning graphite containing
The combustion gas component_Two, O_TwoIngredients¹⁴CO_Two,¹²CO
_Two, ¹³CO_TwoCombustion gas separation means for separating gas into components
When,¹⁴CO_Two,¹²CO_Two,¹³CO_TwoAdd hydrogen to the components
hand¹⁴CO,¹²CO,¹³CO component and H_TwoC to convert to O
An O-shift converter and the converted CO isotope component
Unreacted CO_TwoCO / CO separated into isotopes_TwoIsolated hand
Step and the separated¹⁴CO,¹²CO,¹³CO component¹²C
O,¹³CO component and¹⁴Isotope separation for isotopic separation with CO
Means and the separated¹⁴Carbon solidifying means for solidifying CO;
So it is present in graphite¹⁴C is divided in the form of CO
Release, 99.99% of the stabilized material¹²CO,¹³CO production
Separated from the minute,¹⁴Only C can be fixed
You.

According to claim 11, according to claim 10,
And the above isotopes were separated¹²CO, ¹³Burning CO components
Equipped with a combustor that discharges out of the system for efficient processing
Becomes possible.

According to [Claim 12], Claims 8 to 11
In the above, since the carbon solidifying means immobilizes carbon by plasma treatment, ¹⁴ C can be immobilized efficiently.

According to [claim 13], it is introduced¹⁴
Combustion furnace for burning graphite containing C and generated in the combustion furnace
The combustion gas component_Two, O_TwoIngredients¹⁴CO_Two,¹²C
O_Two,¹³CO_TwoCombustion gas separation means for separating gas into components
And the¹⁴CO_Two,¹²CO_Two, ¹³CO_TwoIngredients¹²CO_Two,
¹³CO_TwoIngredients¹⁴CO_TwoAnd pressure swing adsorption method
Means for separating isotopes, and¹⁴CO_TwoFix
And a carbon solidification device that converts
To¹⁴C to CO_TwoSeparated in the form of, stable at a rate of 99.99%
Fancy¹²CO_Two,¹³CO_TwoSeparated from the components,¹⁴C's
Only immobilization.

According to [claim 14], it is introduced¹⁴C
And a combustion furnace for burning graphite containing
The combustion gas component_Two, O_TwoIngredients¹⁴CO_Two,¹²CO
_Two, ¹³CO_TwoCombustion gas separation means for separating gas into components
And the¹⁴CO_Two,¹²CO_Two,¹³CO_TwoIngredients¹²CO_Two,
¹³CO_TwoIngredients¹⁴CO_TwoCryogenic separation means for separating into
The separated¹⁴CO_TwoAnd a carbon solidifying device for solidifying
So it is present in graphite¹⁴C to CO_TwoIsolated in the form of
And 99.99% of the stabilized material¹²CO_Two,¹³CO_Two
Separated from the components,¹⁴Only C can be fixed
You.

[0084] According to claim 15, claim 13 or in 14, the carbon solidifying device quicklime (CaO) or hydrated lime (Ca (OH) ₂₎ above in an aqueous solution containing ¹⁴ CO ₂
By blowing calcium carbonate (CaCO ₃ )
¹⁴ C can be solidified.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a graphite processing apparatus according to a first embodiment.

FIG. 2 is a schematic diagram of a pressure swing adsorption device.

FIG. 3 is an isotope separation mass balance diagram according to the first embodiment.

FIG. 4 is a graph showing the results of a CH ₄ isotope separation test.

FIG. 5 is a schematic diagram of a graphite processing apparatus according to a second embodiment.

FIG. 6 is a schematic diagram of a graphite processing apparatus according to a third embodiment.

FIG. 7 is a schematic diagram of a graphite processing apparatus according to a fourth embodiment.

[Description of Signs] 10 Graphite (graphite) 11 Combustion furnace 12 Filter 13 Combustion gas component (N ₂ , O ₂ , CO ₂ ) 14 Cooler 15 N ₂ , O ₂ component 16 CO ₂ isotope component 17 Combustion gas separation means Reference Signs List 18 methane generator 19 reaction component 20 condenser 21 ¹⁴ CH ₄ , H ₂ component 22 ¹² CH ₄ , ¹³ CH ₄ component 23 isotope separation means 24 ¹⁴ CH ₄ / H ₂ separation means 25 carbon solidification means 26 combustor 31 1 adsorption tower 32 second adsorption tower 33 blower 34 gas (A, B, C) 35 vacuum pump 36 surge tank 40 CO shift converter 41 reaction component 42 condenser 43 CO isotope, unreacted H ₂ component 44 CO ₂ isotope, H ₂ O component 45 CO / CO ₂ separation means 46 ¹² CO, ¹³ CO component and unreacted H ₂ components 47 isotope separation means 48 carbon monoxide reducing instrumentation 49 CO / H ₂ separation means 50 combustor 61 isotope separation means 62 carbon solidifying device 63 the cryogenic separation unit

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yuichi Fujioka 5-717-1, Fukahori-cho, Nagasaki-city, Nagasaki Prefecture Inside the Nagasaki Research Laboratory, Sanishi Heavy Industries Co., Ltd. No. 1 In the Nagasaki Research Laboratory, Mitsubishi Heavy Industries, Ltd. (72) Inventor Kajiji Kawamoto 5-717-1, Fukahori-cho, Nagasaki City, Nagasaki Prefecture In the Nagasaki Research Laboratory, Mitsubishi Heavy Industries, Ltd. (72) Inventor Kenji Hashiba Kobe, Hyogo Prefecture 1-1-1 Wadazakicho, Hyogo-ku Mitsubishi Heavy Industries, Ltd.Kobe Shipyard (72) Inventor Shinichi Kataoka 2-5-1 Marunouchi, Chiyoda-ku, Tokyo Sanishi Heavy Industries, Ltd. (72) Inventor Toshihiko Setoguchi Nagasaki 5717-1, Fukabori-cho, Nagasaki-shi, Nagasaki F-term (reference) in Nagasaki Research Laboratory, Mitsubishi Heavy Industries, Ltd. 4D012 BA02 CB16 CD03 CD05 CD06 CD07 CH01 CH02 CH05

Claims (15)

[Claims] (1)¹⁴Combustion of graphite containing C
To N_Two, O_TwoIngredients ¹⁴CO_Two,¹²CO_Two,¹³CO_Twocomponent
And the combustion gas is separated¹⁴CO_Two,¹²CO_Two,¹³CO_Two
Process the ingredients,¹²C,¹³A carbon compound consisting of C¹⁴C
And a carbon compound consisting of¹⁴Consists of C
A graphite treatment method comprising solidifying a carbon compound. 2. The graphite treatment method according to claim 1, wherein the carbon compound comprises one of carbon dioxide (CO ₂ ), carbon monoxide (CO) and methane (CH ₄ ). (3)¹⁴Combustion of graphite containing C
To N_Two, O_TwoIngredients ¹⁴CO_Two,¹²CO_Two,¹³CO_Twocomponent
And the combustion gas is separated¹⁴CO_Two,¹²CO_Two,¹³CO_Two
Add hydrogen to the components¹⁴CH_Four,¹²CH_Four,¹³CH_FourSuccess
Minutes and then¹⁴CH_FourIngredients¹²CH_Four,¹³CH_Fourcomponent
And isotope-separated into¹⁴CH_FourSolidifies the ingredients
A graphite treatment method. (4)¹⁴Combustion of graphite containing C
To N_Two, O_TwoIngredients ¹⁴CO_Two,¹²CO_Two,¹³CO_Twocomponent
And the combustion gas is separated¹⁴CO_Two,¹²CO_Two,¹³CO_Two
Add hydrogen to the components¹⁴CO,¹²CO,¹³CO component and
And then¹⁴CO component and¹²CO,¹³Separated from CO component
And the separated¹⁴Characterized by solidifying the CO component
Graphite treatment method. Claim 5.¹⁴Combustion of graphite containing C
To N_Two, O_TwoIngredients ¹⁴CO_Two,¹²CO_Two,¹³CO_Twocomponent
And the combustion gas is separated¹⁴CO_Two,¹²CO_Two,¹³CO_Two
Ingredients¹⁴CO_TwoIngredients¹²CO_Two,¹³CO_TwoSame as component
Body separated, the separated¹⁴CO_TwoTo solidify the ingredients
Characteristic graphite treatment method. 6. The graphite processing method according to claim 1, wherein the solidification of the carbon compound comprising ¹⁴ C is performed by plasma processing. 7. The method for treating graphite used in a nuclear power plant according to claim 1, wherein the graphite containing ¹⁴ C is graphite used as a core material of a nuclear reactor. 8. Introduced¹⁴Burns graphite containing C
And a combustion gas component generated by the combustion furnace_Two, O_TwoIngredients
¹⁴CO_Two,¹²CO_Two, ¹³CO_TwoFuel that separates gas into components
Combustion gas separation means;_TwoH isotope component_TwoAnd add¹⁴CH_Four,¹²CH
_Four,¹³CH_FourA methane generator for converting into components, and a product produced by a reaction in the methane generator¹⁴CH_Four,¹²
CH_Four,¹³CH_FourIngredients¹⁴CH_FourIngredients¹²CH_Four,¹³
CH_FourAn isotope separation means for separating isotopes into components,¹⁴CH_FourMeans for solidifying carbon
A graphite processing apparatus, comprising: 9. The graphite processing apparatus according to claim 8, further comprising a combustor for burning the isotope-separated ¹² CH ₄ and ¹³ CH ₄ components and discharging the same out of the system. 10. Introduced¹⁴Combustion of graphite containing C
And a combustion gas component generated by the combustion furnace_Two, O_TwoIngredients
¹⁴CO_Two,¹²CO_Two, ¹³CO_TwoFuel that separates gas into components
Combustion gas separation means;¹⁴ CO_Two,¹²CO_Two,¹³CO_TwoAdd hydrogen to the components¹⁴
CO,¹²CO,¹³CO component and H_TwoCO to convert to O
And the unconverted CO and the converted CO isotope component_TwoIsotope and
CO / CO separated into _TwoSeparating means, and the separated¹⁴CO,¹²CO,¹³CO component¹²CO,¹³
CO component and¹⁴Isotope separation means for isotope separation into CO
And the separated¹⁴And carbon solidifying means for solidifying CO.
A graphite processing apparatus. 11. The graphite processing apparatus according to claim 10, further comprising a combustor for burning the isotope-separated ¹² CO and ¹³ CO components and discharging the same to the outside of the system. 12. The graphite processing apparatus according to claim 8, wherein the carbon solidifying means fixes carbon by plasma processing. 13. Introduced¹⁴Combustion of graphite containing C
And a combustion gas component generated by the combustion furnace_Two, O_TwoIngredients
¹⁴CO_Two,¹²CO_Two, ¹³CO_TwoFuel that separates gas into components
Burning gas separation means;¹⁴CO_Two,¹²CO_Two,¹³CO_TwoIngredients¹²CO_Two,¹³C
O_TwoIngredients¹⁴CO_TwoSeparation by pressure swing adsorption method
Isotope separating means, and the separated¹⁴CO_TwoAnd a carbon solidifying device for solidifying
A graphite processing apparatus. 14. Introduced¹⁴Combustion of graphite containing C
And a combustion gas component generated by the combustion furnace_Two, O_TwoIngredients
¹⁴CO_Two,¹²CO_Two, ¹³CO_TwoFuel that separates gas into components
Burning gas separation means;¹⁴CO_Two,¹²CO_Two,¹³CO_TwoIngredients¹²CO_Two,¹³C
O_TwoIngredients¹⁴CO_TwoCryogenic separation means for separating the¹⁴CO_TwoAnd a carbon solidifying device for solidifying
A graphite processing apparatus. 15. The method according to claim 13 or 14, wherein the carbon solidifying device comprises quick lime (CaO) or slaked lime (Ca).
A graphite processing apparatus characterized in that the above ¹⁴ CO ₂ is blown into an aqueous solution containing (OH) ₂ ) and solidified as calcium carbonate (CaCO ₃ ).