JP7230885B2 - CO2 Utilization Method and CO2 Utilization System in Exhaust Gas from Cement Manufacturing - Google Patents

Description

The present invention relates to a method for producing methane from CO ₂ in cement production exhaust gas and a methanation device.

In various combustion facilities such as thermal power generation, efforts are being made to reduce CO ₂ generated and emitted by combustion in order to reduce greenhouse gases. In particular, most of the energy required for social activities is obtained from fossil fuels _such as coal, petroleum, and natural gas _. is effective in curbing global warming.

As a technique for reducing CO ₂ in flue gas, for example, a methanation method for obtaining methane by separating carbon dioxide contained in flue gas and reacting it with hydrogen, which is described in Patent Document 1, is known. there is In this methanation method, a step of contacting combustion exhaust gas with a carbon dioxide absorbent to absorb carbon dioxide in the combustion exhaust gas; and a step of removing sulfur compounds in the gas by passing a gas obtained by adding a first amount of hydrogen to a gas containing carbon dioxide as a main component through a desulfurizer filled with a desulfurizing agent, and sulfur compounds adding a second amount of hydrogen to the gas from the step of removing and converting it to methane by a methanation reaction over a methanation catalyst.
In this methanation method, sulfur compounds in the gas are removed by passing hydrogen-added carbon dioxide through a desulfurizer filled with a desulfurizing agent.

JP 2019-172595 A

However, since exhaust gas from cement equipment (cement production exhaust gas) contains many oxides other than sulfur compounds, for example, even if a desulfurizer as described in Patent Document 1 is used, cement production exhaust gas can be properly treated. It cannot be processed and methane cannot be produced adequately.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and aims to provide a method and a system for utilizing CO ₂ in exhaust gas from cement _production , which can appropriately treat exhaust gas from cement production to produce methane appropriately. aim.

The method of utilizing _CO2 in exhaust gas from cement production of the present invention is a method of utilizing _CO2 in exhaust gas from cement production in a _CO2 utilization system comprising a cement production facility and an exhaust gas treatment facility connected to the cement production facility. The cement raw material is calcined in the calcining furnace of the cement manufacturing facility, and the calcined cement raw material is calcined in the cement calcining kiln of the cement manufacturing facility, and then cement clinker is produced in the cooler of the cement manufacturing facility. In the cement clinker manufacturing process that is manufactured by cooling, and in the exhaust gas treatment facility, hydrogen is added to the exhaust gas from the cement manufacturing facility or the _CO2 separated and recovered from the exhaust gas to generate methane, and the generated methane is used as the cement. and an exhaust gas treatment step of supplying the fossil fuel to the calcining kiln and the calciner as a substitute fuel for part or all of the fossil fuel. In the exhaust gas treatment step, the exhaust gas generated in the cement firing kiln and the calcining furnace of the cement manufacturing facility is passed through a preheater for preheating the powdered cement raw material, and the cement raw material is dried by a dryer. in an exhaust gas collection line connected between the dust collector and the chimney after use in a step of collecting a part of exhaust gas; removing at least halogen , nitrogen oxides (NOx) and sulfur oxides (SOx) as acidic components from the collected exhaust gas, and removing at least H ₂ O and cement raw material powder as harmful components. removing, contacting the exhaust gas from which the acidic component and the harmful component have been removed with a _CO2 absorbent to separate and recover _CO2 , and adding hydrogen to the _CO2 after the step of removing the moisture. and connecting the generated methane to a fuel supply line for supplying the fossil fuel to the burners of the cement firing kiln and a fuel supply line for supplying the fossil fuel to the burners of the calciner, respectively. and supplying by a methane supply line connected to the methane supply line .

Here, acidic components such as SOx, NOx, and halogens and harmful components such as H ₂ O and dust contained in the exhaust gas from cement production may affect the CO ₂ absorbent and deteriorate its CO ₂ absorption capacity. Furthermore, the dust (mainly cement raw material powder) contained in the exhaust gas from cement manufacturing adheres to the inside of the equipment piping and forms scale, which increases the pressure loss in the piping and increases the amount of gas that can be processed by the _CO2 separation and recovery equipment. There is a risk that the
In contrast, in the present invention, the deterioration of the absorption capacity of the CO ₂ absorbent can be suppressed by removing the acidic component and the harmful component before separating and recovering the exhaust gas from the cement manufacturing facility. Therefore, CO ₂ can be efficiently recovered from the cement production exhaust gas. Therefore, the efficiency of methanation is also improved.

In this method of utilizing CO ₂ in exhaust gas from cement production, it is preferable to produce methane after removing moisture from the separated and recovered CO ₂ .
Since the reaction of methane is CO ₂ + 4H ₂ →CH ₄ + 2H ₂ O, if the separated and recovered CO ₂ contains a lot of water, the amount of H ₂ O on the right side of the reaction formula will increase, and methane will be produced. difficult to do. In the above embodiment, water is removed from the separated and recovered CO ₂ and hydrogen is added to produce methane. Therefore, the methane production reaction proceeds more easily, thereby improving the efficiency of methanation.

The cement manufacturing exhaust gas CO ₂ utilization system of the present invention includes a cement manufacturing facility, and hydrogen is added to the exhaust gas from the cement manufacturing facility or CO ₂ separated and recovered from the exhaust gas, which is connected to the cement manufacturing facility, to produce methane. an exhaust gas treatment facility that produces and supplies the produced methane as a substitute fuel for some or all of fossil fuels to the cement production facility;
The cement manufacturing equipment uses the exhaust gas generated in the cement firing kiln and the calcination furnace to dry the cement raw material through a preheater that preheats the powdered cement raw material with a dryer. The exhaust gas treatment equipment includes an exhaust gas collection line connected between the dust collector and the chimney, and the fossil fuel and alternative heat source combustion exhaust gas and limestone-derived exhaust gas sent from the exhaust gas collection line. and a methane supply device for supplying the produced methane to the cement manufacturing facility, wherein the methanation device separates and recovers _CO2 from the exhaust gas _. a CO ₂ separation and recovery device, a hydrogen mixing unit for supplying and mixing hydrogen gas with the CO ₂ separated and recovered by the CO ₂ separation and recovery device, a methane production unit for producing methane from the CO ₂ mixed with hydrogen, wherein the methane supply device comprises a tank that stores methane produced by the methanation device, and a methane supply that is connected to the tank and sends methane to the burners of the cement calcining kiln and the burners of the calciner. a line and a pump, and the CO ₂ separation and capture device includes: a harmful component removal unit for removing acidic components and harmful components from the exhaust gas collected by the exhaust gas collection line; A _CO2 separation and recovery unit that separates and recovers _CO2 by bringing the exhaust gas into contact with a _CO2 absorbent, a methane production unit that adds hydrogen to the separated and recovered _CO2 to produce methane, and the recovered _CO2. and a dehumidification section for removing moisture from the compressed _CO2 , wherein the acidic components are at least halogens , nitrogen oxides (NOx) and sulfur oxides (SOx), and the harmful The components are at least H ₂ O and cement raw material powder, and the methane supply line is a fuel supply line that supplies the fossil fuel to the burner of the cement firing kiln and the fossil fuel to the burner of the calciner. It is connected to each of the fuel supply lines that supply fuel .

According to the present invention, by appropriately removing harmful components from CO ₂ in the exhaust gas of cement manufacturing equipment, the deterioration of the absorption capacity of the CO ₂ absorbent is suppressed, and the cement manufacturing exhaust gas is appropriately treated to remove methane. It can be generated properly, which can reduce energy-derived _CO2 .

1 is a flow chart showing the procedure of a method for utilizing CO ₂ in exhaust gas from cement production according to one embodiment of the present invention. FIG. 2 is a diagram showing a simplified system for utilizing CO ₂ in exhaust gas from cement production according to the above embodiment. It is a block diagram showing a schematic configuration of a methanation apparatus of the above embodiment.

An embodiment of a method for producing methane from CO ₂ in exhaust gas from cement production and a methanation apparatus according to the present invention will be described below with reference to the drawings.
This embodiment produces methane after adequate removal of acidic and harmful components from _CO2 in cement production flue gas, and uses the methane as a partial or complete replacement fuel for fossil fuels to cement production facilities. This is an example of using it.

[Configuration of _CO2 utilization system]
The CO ₂ utilization system 100 includes, as shown in FIG. 2, a cement production facility 50 and an exhaust gas treatment facility 30 connected to the cement production facility 50 for use. In the present embodiment, the exhaust gas treatment equipment 30 adds hydrogen to the exhaust gas from the cement manufacturing equipment 50 or CO ₂ separated and recovered from the exhaust gas to generate methane, and the generated methane is supplied to the cement manufacturing equipment 50 as a fossil fuel. Supplied as a partial or complete alternative fuel.

[Configuration of cement manufacturing equipment]
As shown in FIG. 2, the cement production facility 50 includes a raw material storage 1 for individually storing limestone, clay, silica stone, iron raw materials, and the like as raw materials for cement, and a raw material mill and a dryer for pulverizing and drying the cement raw materials. 2, a preheater 3 for preheating the powdered cement raw material supplied through the raw material supply pipe 22 and obtained by the raw material mill, and a calcining furnace 4 for calcining the cement raw material preheated by the preheater 3. , a cement calcining kiln 5 for calcining calcined cement raw materials, a cooler 6 for cooling cement clinker after calcining in the cement calcining kiln 5, and the like.

The cement firing kiln 5 is a cylindrical rotary kiln that is horizontally oriented and slightly inclined. By rotating around its axis, the cement raw material supplied from the preheater 3 to the kiln bottom portion 5a is sent to the kiln front portion 5b. During the sending process, the cement clinker is generated by heating and firing at about 1450° C. by the burner 8 of the kiln front part 5b, and this cement clinker is sent to the cooler 6 from the kiln front part 5b. A fuel supply system 15 for supplying fossil fuels such as coal and oil is connected to the burner 8 . In addition to the fuel supply line 15, a supply system (not shown) for alternative heat sources such as waste plastics and waste tires is also provided to supplement thermal energy. After the cement clinker is cooled to a predetermined temperature by the cooler 6, it is sent to the finishing process.

As shown in FIG. 2, the preheater 3 is constructed by vertically connecting a plurality of (four) cyclones 13 for circulating the exhaust gas generated in the cement firing kiln 5. A calcination furnace 4 is connected between 13 and the cyclone 13 above it, and the cement raw material calcined by the combustion gas of the calcination furnace 4 is discharged from the bottom cyclone 13 to the kiln end of the cement firing kiln 5. It is adapted to supply to the section 5a.

The calcining furnace 4 has a burner 41 inside, and calcines the cement raw material sent from the upper cyclone 13 by burning fuel such as coal supplied from the fuel supply line 42, It is supplied to the lowermost cyclone 13 through the rising duct 25 together with the exhaust gas generated by the calcination. The raw material for cement is supplied to the kiln bottom 5a of the cement firing kiln 5 from the lowest cyclone 13 . On the other hand, the rising duct 25 feeds the exhaust gas from the kiln bottom 5a of the cement firing kiln 5 to the lowermost cyclone 13, and the exhaust gas generated in the calcination furnace 4 is also supplied to the cyclone 13 via this rising duct 25. be. Therefore, the exhaust gas from the cement firing kiln 5 and the exhaust gas from the calcining furnace 4 are integrally passed through the preheater 3 from the bottom to the top, and then introduced into the raw material mill and the dryer 2 through the exhaust pipe 9 .

The raw material mill and dryer 2 are adapted to pulverize and dry the cement raw material at the same time by introducing the exhaust gas from the calcination furnace 4 and the cement firing kiln 5 . An exhaust gas line 12 including a dust collector 10, a chimney 11 and the like is connected to the raw material mill and the dryer 2 .

[Configuration of exhaust gas treatment equipment]
The exhaust gas treatment equipment 30 includes an exhaust gas collection line 311 that collects the exhaust gas generated in the cement firing kiln 5 and the calcining furnace 4 before being discharged from the chimney 11, and CO from the exhaust gas sent from the exhaust gas collection line 311. ₂ is separated and recovered, and hydrogen is added to the separated and recovered CO ₂ to produce methane;
The flue gas collection line 311 is connected between the dust collector 10 and the chimney 11 in the flue gas line 12 of the cement production facility 50, and collects part of the flue gas generated during cement firing. Since it is an exhaust gas generated by firing cement, it contains a part of exhaust gas from combustion of fuel such as coal, but it also contains a large amount of exhaust gas derived from limestone.

(Configuration of methanation device)
The methanator 31 includes a _{CO 2 separation} and recovery device 310 that separates and recovers CO ₂ from the exhaust gas, a hydrogen mixing unit 316 that supplies and mixes hydrogen gas with the CO ₂ separated and recovered by the CO 2 separation and recovery device 310, and a methane production unit 317 that produces methane from CO ₂ mixed with hydrogen.

As shown in FIG. 3, the CO ₂ separation and capture device 310 includes a harmful component removal unit 312 that removes harmful components such as SOx and NOx from the exhaust gas collected by the exhaust gas collection line 311, and a A CO ₂ separation and recovery unit 313 that separates and recovers CO ₂ , a compression unit 314 that compresses the recovered CO ₂ , and a dehumidifying unit 315 that removes moisture from the compressed CO ₂ are provided.

Since the exhaust gas sent from the exhaust gas collection line 311 is combustion exhaust gas from fossil fuels such as coal, petroleum coke, and heavy oil, and waste plastics and waste tires, it contains about 20% of CO ₂ , and CO Gases other than ₂ , acidic components, and harmful components are included. Therefore, the harmful component removal unit 312 removes acidic components (for example, acidic gases such as nitrogen oxides (NOx) and sulfur oxides (SOx)) and harmful components from the exhaust gas, and is filled with an aqueous NaOH solution or the like. equipped with a scrubber, dehumidifier, electrostatic precipitator, etc. By removing these acidic components and harmful components, halogens are also removed together with NOx, preventing deterioration of the amine compound absorbent (CO ₂ absorbent) used in the subsequent CO ₂ separation and recovery, as well as lowering the absorption capacity. suppress

As desulfurization methods (SOx removal methods), a wet limestone gypsum method, a magnesium hydroxide method, and a soda absorption method are known. These are methods of absorbing SOx with an alkaline solution, and there is a method using coal ash as a dry method. In addition, as a method for simultaneously performing desulfurization (SOx removal) and denitrification (NOx removal), there are a dry activated carbon method and an electron beam method. As the denitrification method, dry methods include a catalytic reduction method (SCR method, etc.) and a non-catalytic reduction method, and wet methods include an oxidation-absorption method, an oxidation-reduction method, and an equimolar absorption method.

On the other hand, since the suspension preheater functions as a desulfurization device, SOx in the exhaust gas from the cement manufacturing facility is generally several tens of ppm or less in many cases.
Here, as for the effect of impurities on the absorbent for CO ₂ separation and recovery, it is considered that there is no great difference in the affinity between the amine compound and the impurity component in either the chemical absorption method or the physical adsorption method. In the recovery of CO ₂ by the CO ₂ separation recovery unit 313, SOx in the exhaust gas binds to the amine compound in the absorbent, inhibiting the CO2 absorption capacity of the amine compound, and the absorption rate significantly decreases over time. As such, amine compounds have strong basicity, and halogens other than SOx, such as NOx, Cl, and F, tend to be adsorbed by the _CO2 absorbent.

In addition, the Ni catalyst, which is widely used as a catalyst for methanation, has a sulfur compound that reacts on the surface of the Ni catalyst and covers the surface under the presence of sulfur compounds mixed in _H2 . It must be removed in section 312 . Similarly, halogens such as NOx, Cl, and F may adhere to the surface of the Ni catalyst and deteriorate the methanation yield.

In the present embodiment, the desulfurization (SOx removal) and denitrification (NOx removal) methods by the harmful component removal unit 312 may use any of the removal methods described above. For example, in the present embodiment, oxidizing gases such as nitrogen oxides (NOx) and sulfur oxides (SOx) are removed using one of the above desulfurization methods and one of the above denitrification methods.

The CO ₂ separation and recovery unit 313 consists of a general CO ₂ recovery device, and contains a CO ₂ absorbent that absorbs CO ₂ (a liquid absorbent in which an amine compound is dissolved in water, an amine compound in a porous material). A supported solid absorbent, etc.) is provided, and the exhaust gas from which harmful substances have been removed comes into contact with this, whereby CO ₂ in the exhaust gas is absorbed by the CO ₂ absorbent. Then, by heating the CO ₂ absorbent that has absorbed the CO ₂ , the _{CO 2 is} extracted and recovered from the CO 2 absorbent. Note that the CO ₂ separation/recovery unit 313 discharges the exhaust gas from which the CO ₂ has been removed to the outside. The compression unit 314 compresses the recovered CO ₂ by applying a pressure of 0.1 MPa or more, preferably 0.5 to 1.0 MPa. The dehumidifying section 315 removes moisture contained in the CO ₂ by cooling the compressed CO ₂ . This dehumidification removes moisture prior to methanation because it affects the oxidation of the Ni-based catalyst in the methanator.

The hydrogen mixing unit 316 supplies and mixes hydrogen gas with the dehumidified CO ₂ and pressurizes it. Hydrogen gas can be produced by artificial photosynthesis using renewable energy, decomposition of water, or the like. The addition of hydrogen by the hydrogen mixing unit 316 is appropriately set to a concentration that facilitates the production of methane from the hydrogen-mixed CO ₂ .
The methane production unit 317 produces methane from CO ₂ mixed with hydrogen. This methane production unit 317 consists of a general methane production apparatus, and catalysts showing activity in methanation (for example, Ni, Pt, Pd, and Cu are used as hydrogenation catalysts, but in methanation, Al ₂ O ₃ , Cr ₂ O ₃ , SiO ₂ , MgAl ₂ O ₄ , TiO ₂ , ZrO _{2 ,} etc. supported Ni and Ni alloys are used as catalysts). Methane is produced by supplying CO ₂ mixed with hydrogen to these reactors and reacting them. The conditions for the general methanation reaction (CO ₂ +4H ₂ →CH ₄ +2H ₂ O) are a temperature of 200° C. to 700° C., preferably 200° C. to 350° C., a pressure of 0.1 to 3 MPa, In order to improve the reaction yield of methane, the reaction is carried out in multiple stages.

(Configuration of methane supply device)
As shown in FIG. 2, the methane supply device 32 is connected to a tank (not shown) that stores the methane produced by the methanation device 31, and is connected to the tank to supply methane to the burner 8 and the calciner in the front part 5b of the kiln. A methane supply line 321 and pumps 322 and 323 are provided to each of the four burners 41 . The methane supply line 321 is the fuel supply line 15 that supplies fuel such as coal or petroleum to the burner 8 of the cement kiln 5, and the fuel supply line 42 that supplies fuel such as coal to the burner 41 of the calciner 4. It is connected to the. Thereby, each burner 8, 41 is supplied with methane together with fuel.

[How to utilize _CO2 ]
A method of reducing and effectively utilizing CO ₂ in the exhaust gas of the cement manufacturing facility 50 using the above-described CO ₂ utilization system 100 will be described along the flowchart shown in FIG.

In the cement manufacturing facility 50, cement raw materials such as limestone, clay, silica stone, iron raw materials, etc. are pulverized and dried to preheat powdered cement raw materials, and the preheated cement raw materials are calcined and then fired. Cement clinker is produced by cooling this. Exhaust gas generated in the cement kiln 5 and the calcining furnace 4 in the production of this cement clinker passes through the preheater 3 from the bottom to the top, and then passes through the exhaust pipe 9 and is introduced into the raw material mill and the dryer 2, where it is used as the raw material for cement. After being used for drying, it is discharged from the chimney 11 through the dust collector 10 .

In this cement production process, the flue gas collection unit 311 of the methanation device 31 collects part of the flue gas generated during cement firing from between the dust collector 10 and the chimney 11 of the flue gas treatment line 12 . Next, the harmful component removal section 312 removes acidic components and harmful components from the exhaust gas. In this harmful component removing section 312, nitrogen oxides (NOx), sulfur oxides (SOx), halogens, H ₂ O, dust, etc. are removed. Then, CO ₂ is extracted from the exhaust gas and separated and recovered by the CO ₂ separation and recovery unit 313 . At this time, exhaust gas from which CO ₂ has been removed is discharged to the outside.

Next, the compression section 314 applies a pressure of 0.1 MPa or more, preferably 0.5 to 1.0 MPa, to the collected CO ₂ to compress it, and the dehumidification section 315 removes water contained in the CO ₂ . Then, the hydrogen mixing unit 316 supplies and mixes hydrogen gas with the dehumidified CO ₂ and pressurizes it. Then, a methane production unit 317 produces methane from CO ₂ mixed with hydrogen.

The methane produced in this way is stored in the tank of the methane supply device 32 . Then, the methane stored in this tank is supplied to the cement burning kiln 5 and the calciner 4 through the methane supply line 321 . A fossil fuel such as petroleum or coal is supplied to the cement firing kiln 5 from a fuel supply line 15. By supplying methane, part of the fossil fuel can be replaced with methane. Fossil fuel can be reduced. Similarly, in the calcining furnace 4, some or all of the fuel such as coal is replaced with methane, so fossil fuel consumption can be reduced.

In the present embodiment, before separating and recovering the exhaust gas from the cement production facility 50, acidic components such as SOx, NOx, and halogens and harmful components such as H ₂ O and dust contained in CO ₂ of the cement production exhaust gas are removed. Thereby, deterioration of the absorption capacity of the CO ₂ absorbent can be suppressed. Therefore, CO ₂ can be efficiently recovered from the cement production exhaust gas. In addition, the _CO2 absorbent can also maintain stable performance for a long period of time. By converting properly treated CO ₂ to methane, CO ₂ emitted from the cement manufacturing facility 50 can be reduced, and this methane can be used as an alternative fuel for the cement firing kiln 5 and the calciner 4. By doing so, methane can be used effectively. In particular, since fossil fuels such as coal and petroleum, which are major causes of global warming, are replaced with limestone-derived methane, the use of fossil fuels can be reduced, energy-derived _CO2 can be reduced, and greenhouse gases can be reduced. You can increase the effect.
In addition, since moisture is removed from the separated and recovered CO ₂ and hydrogen is added thereto to produce methane, oxidation of the Ni-based catalyst in the methanation device 31 can be suppressed.

It should be noted that the present invention is not limited to the configurations of the above-described embodiments, and various modifications can be made to the detailed configurations without departing from the gist of the present invention.
For example, in the above embodiment, the dehumidification unit 315 removes moisture _contained in the CO ₂ by cooling the compressed CO _2. However, the present invention is not limited to this. Any method can be used as long as the moisture can be removed.

Moreover, although the produced methane is supplied to both the cement firing kiln 5 and the calcining furnace 4, it may be supplied to either one.
Furthermore, methane was generated using the exhaust gas from both the cement firing kiln 5 and the calcining furnace 4, but it is also possible to apply it to a cement manufacturing facility that does not have a calcining furnace. produces methane from exhaust gas.

1 Raw material storage 2 Raw material mill and dryer 3 Preheater 4 Temporary firing furnace 5 Cement firing kiln 5a Kiln bottom 5b Kiln front 6 Cooler 8 Burner 9 Exhaust pipe 10 Dust collector 11 Chimney 12 Exhaust gas line 13 Cyclone 15 Fuel supply line 22 Raw material supply pipe 25 Rising duct 30 Exhaust gas treatment equipment 31 Methanation device 310 CO ₂ separation and recovery device 311 Exhaust gas collection line 312 Harmful component removal unit 313 CO ₂ separation and recovery unit 314 Compression unit 315 Dehumidification unit 316 Hydrogen mixing unit 317 Methane production unit 32 Methane supply device 321 methane supply lines 322, 323 pump 41 burner 42 fuel supply line 50 cement manufacturing facility 100 CO ₂ utilization system

Claims (2)

A method of utilizing CO ₂ in cement production exhaust gas in a CO ₂ utilization system comprising cement production equipment and exhaust gas treatment equipment connected to the cement production equipment,
The cement raw material is calcined in the calcining furnace of the cement manufacturing facility, and the calcined cement raw material is calcined in the cement calcining kiln of the cement manufacturing facility, and then the cement clinker is cooled in the cooler of the cement manufacturing facility. a cement clinker manufacturing process to be manufactured;
In the exhaust gas treatment facility, hydrogen is added to the exhaust gas from the cement manufacturing facility or _CO2 separated and recovered from the exhaust gas to generate methane, and the generated methane is fed to the cement firing kiln and the calciner as a fossil fuel. and an exhaust gas treatment process for supplying as an alternative fuel for some or all of
The exhaust gas treatment step includes:
The exhaust gas generated in the cement calcining kiln and the calcining furnace of the cement manufacturing facility is passed through a preheater for preheating the powdered cement raw material, and after being used to dry the cement raw material with a dryer, a dust collector is used. collecting a portion of the flue gas , including the fossil fuel and alternative heat source flue gas and limestone-derived flue gas, in an flue gas collection line connected between the dust collector and the chimney before discharging from the chimney through process and
a step of removing at least halogen , nitrogen oxides (NOx) and sulfur oxides (SOx) as acidic components and removing at least H ₂ O and cement raw material powder as harmful components from the collected exhaust gas;
a step of contacting the exhaust gas from which the acidic component and the harmful component have been removed with a CO ₂ absorbent to separate and recover CO ₂ ;
compressing the separated and recovered CO ₂ to remove moisture;
adding hydrogen to the _CO2 to produce methane after said removing water;
A step of supplying the generated methane through a methane supply line connected to a fuel supply line for supplying the fossil fuel to the burners of the cement calcining kiln and a fuel supply line for supplying the fossil fuel to the burners of the calciner. and a method for utilizing CO ₂ in cement manufacturing exhaust gas. a cement manufacturing facility connected to the cement manufacturing facility, hydrogen is added to exhaust gas from the cement manufacturing facility or _CO2 separated and recovered from the exhaust gas to generate methane, and the generated methane is delivered to the cement manufacturing facility. and an exhaust gas treatment facility that supplies as an alternative fuel for some or all of the fossil fuels of
The cement manufacturing equipment uses the exhaust gas generated in the cement firing kiln and the calcination furnace to dry the cement raw material through a preheater that preheats the powdered cement raw material with a dryer. Eject from
The exhaust gas treatment equipment includes an exhaust gas collection line connected between the dust collector and the chimney, and the exhaust gas containing the combustion exhaust gas of the fossil fuel and the alternative heat source and the limestone-derived exhaust gas sent from the exhaust gas collection line. and a methanation device for producing methane from CO ₂ and a methane supply device for supplying the produced methane to the cement manufacturing facility,
The methanation device includes a _{CO 2 separation} and recovery device that separates and recovers CO 2 from exhaust gas, a hydrogen mixing unit that supplies and mixes hydrogen gas with the CO ₂ separated and recovered by the CO ₂ separation and recovery device, and a hydrogen mixing unit. a methane production unit that produces methane from the converted CO ₂ ,
The methane supply device includes a tank for storing methane produced by the methanation device, a methane supply line and a pump connected to the tank for sending methane to the burners of the cement calcining kiln and the burner of the calciner, respectively. and
The CO ₂ separation and capture device includes a harmful component removal unit that removes acidic components and harmful components from the exhaust gas collected in the collection line, and a CO 2 absorbent that converts the exhaust gas from which the acidic components and the harmful components have been removed into a CO ₂ absorbent. A CO ₂ separation and recovery unit that separates and recovers CO ₂ by contact, a compression unit that compresses the recovered CO ₂ , and a dehumidification unit that removes moisture from the compressed CO ₂ ,
the acidic components are at least halogen , nitrogen oxides (NOx) and sulfur oxides (SOx);
The harmful components are at least H ₂ O and cement raw material powder ,
The methane supply line is connected to a fuel supply line that supplies the fossil fuel to the burners of the cement calcining kiln and a fuel supply line that supplies the fossil fuel to the burners of the calciner. Characterized CO ₂ utilization system in cement production _exhaust gas.

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