JP2021191731A - Method for utilizing co2 in cement production exhaust gas, and co2 utilization system - Google Patents

Abstract

To provide, in order to reduce energy-originated CO2, a method for utilizing CO2 in cement production exhaust gas in which non-fossil fuel derived CO2 in cement exhaust gas can be effectively utilized by methanation, and to provide a CO2 utilization system.SOLUTION: The method includes a methane production step in which hydrogen is added to CO2 in the exhaust gas from a cement production facility or CO2 separated and recovered from the exhaust gas to produce methane, and a methane consumption step in which the methane produced in the methane production step is used as an alternative fuel for some or all of the fossil fuels into the cement production facility, and in which the methane production step and the methane consumption step are repeated continuously.SELECTED DRAWING: Figure 1

Description

_{The present invention relates to a method for utilizing CO 2} originating from energy contained in the exhaust gas of a cement manufacturing facility while reducing it, and a CO ₂ utilization system.

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, since most of the energy required for social activities is obtained from fossil fuels such as coal, oil, and natural gas, _{the amount of CO 2} generated from this fossil fuel is enormous, and CO _{2 originating from this energy} Is effective in controlling global warming.

_{As a technique for reducing CO 2 in} combustion exhaust gas, for example, a methaneization method for obtaining methane by separating carbon dioxide contained in combustion exhaust gas described in Patent Document 1 and reacting with hydrogen has been known. There is. In this methanation method, a step of bringing the combustion exhaust gas into contact with a carbon dioxide absorber to absorb carbon dioxide in the combustion exhaust gas, and a gas containing carbon dioxide as a main component by heating the carbon dioxide absorber that has absorbed carbon dioxide. And the step of removing the sulfur compound in the gas by passing the gas obtained by adding the first amount of hydrogen to the gas containing carbon dioxide as the main component through a desulfurizing agent filled with a desulfurizing agent, and the sulfur compound. It includes a step of adding a second amount of hydrogen to the gas that has undergone the step of removing carbon dioxide and converting it into methane by a methanation reaction that has passed through a methanation catalyst.
By using this methanation method, the release of carbon dioxide from the combustion exhaust gas into the atmosphere is suppressed.

JP-A-2019-172595

However, while the method described in Patent Document 1 makes effective use of the emitted _{combustion gas by methaneization, it is released as CO 2} again when methane produced from the combustion gas derived from fossil fuel is burned. , It is hard to say that the amount _{of CO 2} originating from energy is reduced.

The present invention has been made in view of such circumstances, in order to reduce the CO ₂ from energy sources, cement production exhaust gas to the CO ₂ cement in the exhaust gas not from fossil fuels can be and methanation effective utilization The purpose is to provide a _{CO 2} utilization method and a CO _{2 utilization system.}

_{The CO 2} utilization method in the cement production exhaust gas of the present invention comprises a methane production step of adding hydrogen to _{CO 2} in the exhaust gas from the cement production facility _{or CO 2} separated and recovered from the exhaust gas to generate methane, and the methane. The methane production step is provided with a methane consumption step in which the methane produced in the production step is used as a substitute fuel for a part or all of the fossil fuel for the cement production facility, and the methane production step and the methane consumption step are continuously repeated.

In the present invention, by converting the CO ₂ separated recovered from CO ₂ and exhaust gas in the exhaust gas from the cement manufacturing facility to methane, it is possible to reduce the CO ₂ emissions from a cement manufacturing facility, the methane cement production facility _{CO 2} can be effectively utilized by circulating it as an alternative fuel for CO2, that is, by using it continuously and repeatedly. _{In particular, since more than half of the CO 2 in} the exhaust gas from the cement production facility is derived from limestone, _{methane is continuously produced from the CO 2 in} the exhaust gas and used as fuel, so that coal and petroleum are used. It is possible to reduce the use of fossil fuels such as CO ₂ from energy sources and enhance the effect of reducing greenhouse gases.

_{In this method of utilizing CO 2} in the cement manufacturing exhaust gas, the methane is burned in the cement manufacturing facility _{to the CO 2} in the exhaust gas used for producing the methane _{or the CO 2} separated and recovered from the exhaust gas. The generated CO _{2 will} also be included.
Therefore, the exhaust gas generated by burning methane in the cement manufacturing facility has a low content of nitrogen oxides (NOx) and sulfur oxides (SOx), and the exhaust gas can be made cleaner.

In CO ₂ reduction method of the cement production in the exhaust gas, the CO ₂ is the exhaust gas from the cement manufacturing facility may be brought into contact with the CO ₂ absorbing material is separated recovered CO _{2.
By using CO 2} separated and recovered from the exhaust gas, the concentration thereof can be increased to produce high-concentration methane, and methane can be used more effectively.

_{The CO 2} utilization system in the cement manufacturing exhaust gas of the present invention is a methane that produces methane by adding hydrogen to the CO _{2 in the exhaust gas from the cement manufacturing facility or the CO 2} separated and recovered from the exhaust gas to the cement manufacturing facility. The methaneization device includes a methane supply device that supplies the methane produced by the methaneization device as an alternative fuel for a part or all of the fossil fuel to the cement production facility, and the methaneization device is the methane supply device. It is connected to the cement manufacturing facility to which methane is supplied by.

In this CO ₂ abatement cement production in the exhaust gas, to be provided with a CO ₂ separation and recovery device exhaust gases into contact with the CO ₂ absorbent to separate and recover the CO ₂ from the cement manufacturing facility.

According to the present invention, since methane is continuously produced from _{CO 2} contained in the exhaust gas of a cement manufacturing facility and _{used as a fuel, CO 2} is effectively utilized to generate CO _{2 originating from energy.} It can be reduced and the greenhouse gas reduction effect can be enhanced.

It is a flowchart which shows the procedure _{of the CO 2} utilization method in the cement manufacturing exhaust gas which concerns on one Embodiment of this invention. It is a simplified view showing a CO ₂ utilization system of cement production in the exhaust gas of the above embodiments. It is a block diagram which shows the schematic structure of the methanation apparatus which constitutes _{the CO 2} utilization system in the cement manufacturing exhaust gas of the said embodiment.

_{Hereinafter, an embodiment of the CO 2} utilization method in the cement manufacturing exhaust gas and the CO ₂ utilization system in the cement manufacturing exhaust gas of the present invention will be described with reference to the drawings.
_{This embodiment is an example of continuously repeating the production of methane from CO 2} in the cement production exhaust gas and using it as fuel for a cement firing kiln and a calcining furnace in a cement manufacturing facility.

[ _{Configuration of CO 2} utilization system]
As _{shown in FIG. 2, the CO 2} utilization system 100 includes a cement manufacturing facility 50 and an exhaust gas treatment facility 30 connected to and used in the cement manufacturing facility 50. In the present embodiment, the exhaust gas treatment facility 30 _{adds hydrogen to the exhaust gas from the exhaust gas or CO 2} separated and recovered from the exhaust gas to generate methane, and the generated methane is used as fossil fuel for the cement production facility 50. Supplied as an alternative fuel in part or in whole.

[Structure of cement manufacturing equipment]
As shown in FIG. 2, the cement manufacturing facility 50 includes a raw material storage 1 for individually storing limestone, clay, silica stone, iron raw materials, etc. as cement raw materials, and a raw material mill and dryer for crushing and drying these cement raw materials. 2 and a preheater 3 that preheats the powdered cement raw material supplied through the raw material supply pipe 22 and obtained by this raw material mill, and a calcining furnace 4 that calcins the cement raw material preheated by the preheater 3. It is provided with a cement calcined kiln 5 for calcining a calcined cement raw material, a cooler 6 for cooling a cement clinker after being calcined by the cement calcined kiln 5, and the like.

The cement firing kiln 5 is a cylindrical rotary kiln that is slightly inclined sideways, and by rotating around the axis, the cement raw material supplied from the preheater 3 is sent to the kiln front portion 5b to the kiln tail portion 5a while being sent to the kiln front portion 5b. In the process of sending, the burner 8 of the front part 5b of the kiln heats and fires at about 1450 ° C. to generate a cement clinker, and the cement clinker is sent from the front part 5b of the kiln to the cooler 6. A fuel supply system 15 for supplying fossil fuels such as coal and petroleum is connected to the burner 8. In addition to the fuel supply line 15, a supply system (not shown) for an alternative heat source such as waste plastic or waste tire is also provided to supplement the heat energy. The cement clinker is cooled to a predetermined temperature by the cooler 6 and then sent to the finishing process.

As shown in FIG. 2, the preheater 3 is constructed by connecting a plurality of (four) cyclones 13 that circulate the exhaust gas generated in the cement firing kiln 5 in the vertical direction, and is the lowermost cyclone. A calcining furnace 4 is connected between 13 and the cyclone 13 above it, and the cement raw material calcined by the combustion gas of the calcining furnace 4 is transferred from the bottom cyclone 13 to the kiln tail of the cement firing kiln 5. It is designed to be supplied to the portion 5a.

The calcining furnace 4 has a burner 41 inside, and by burning fuel such as coal supplied from the fuel supply line 42, the cement raw material sent from the upper cyclone 13 is calcined. Together with the exhaust gas generated by the calcining, the exhaust gas is supplied to the lowermost cyclone 13 via the rising duct 25. The cement raw material is supplied from the lowermost cyclone 13 to the kiln tail portion 5a of the cement firing kiln 5. On the other hand, the rising duct 25 sends the exhaust gas from the kiln tail portion 5a of the cement firing kiln 5 to the lowermost cyclone 13, and the exhaust gas generated in the calcining furnace 4 is also supplied to the cyclone 13 through the rising duct 25. Ru. Therefore, the exhaust gas from the cement firing kiln 5 and the exhaust gas from the calcining furnace 4 are integrated and passed through the preheater 3 from the lower side to the upper side, and then introduced into the raw material mill and the dryer 2 through the exhaust pipe 9.

The raw material mill and the dryer 2 are adapted to simultaneously crush and dry the cement raw material by introducing the exhaust gas from the calcining 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.

[Composition of exhaust gas treatment equipment]
The exhaust gas treatment facility 30 includes an exhaust gas collection line 311 that collects exhaust gas generated in the cement firing kiln 5 and the calcination furnace 4 and before being discharged from the chimney 11, and CO from the exhaust gas sent from the exhaust gas collection line 311. _{It is provided with a methaneization device 31 that separates and recovers 2} and adds hydrogen to the separated and recovered CO 2 to generate methane, and a methane supply device 32 that supplies the generated methane to the cement production facility 50.
The exhaust gas collection line 311 is connected between the dust collector 10 and the chimney 11 in the exhaust gas line 12 of the cement manufacturing facility 50, and collects a part of the exhaust gas generated during cement firing. Since it is exhaust gas generated by cement firing, it includes some exhaust gas from combustion of fuel such as coal, but it also contains a large amount of exhaust gas derived from limestone.

(Composition of methanizer)
Methanation apparatus 31 includes a CO ₂ separation and recovery device 310 for separating and recovering CO ₂ from the exhaust gas, a hydrogen mixing section 316 for mixing by supplying a hydrogen gas into CO ₂ separated recovered by CO ₂ separation and recovery device 310, It includes a methane production unit 317 that produces methane from _{CO 2 mixed with hydrogen.}

As _{shown in FIG. 3, the CO 2} separation and recovery device 310 has a harmful component removing unit 312 that removes harmful components such as SOx and NOx from the exhaust gas collected by the exhaust gas collection line 311 and the exhaust gas from which the harmful components have been removed. a CO ₂ separation collector 313 for separating and recovering CO _2, includes a compression unit 314 for compressing the recovered CO _2, and dehumidifying unit 315 for removing moisture from the compressed CO _2, the.

When the exhaust gas sent from the exhaust gas collection line 311 is fossil fuel such as coal, petroleum coke, heavy oil, or combustion exhaust gas such as waste plastic and waste tire, CO ₂ is contained, for example, about 20%. , Contains gases other than _{CO 2 and harmful components.} Therefore, the harmful component removing unit 312 removes harmful components (for example, oxidizing gases such as nitrogen oxides (NOx) and sulfur oxides (SOx)) from the exhaust gas, and is a scrubber filled with an aqueous NaOH solution. To prepare for. By removing this harmful component, halogen is also removed together with NOx, so that deterioration of the absorbent material of the amine compound used in _{the next CO 2 separation and recovery is prevented.}

As will be described later, when methane is contained in a part of the fuel of the cement fired kiln 4, the content of the harmful component is reduced, but the harmful component is removed by the harmful component removing unit 312.

CO ₂ separation collector 313 is made common CO ₂ recovery apparatus, the inside absorbs CO ₂ CO ₂ absorbent (amine compound liquid absorbing material dissolved in water, the amine compound to the porous material A supported solid absorbent or the like) is provided, and the exhaust gas after the harmful substances are removed comes into contact with the solid absorbent, so that CO _{2 in} the exhaust gas is absorbed by the CO _{2 absorbent.} Then, such as by heating the CO ₂ absorbing material that has absorbed CO _2, is recovered by extraction of CO ₂ from the CO ₂ absorber. The CO ₂ separation / recovery unit 313 _{discharges the exhaust gas after 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. Dehumidifying unit 315, by cooling the compressed CO _2, removing the moisture contained in the CO _2. This dehumidification removes water before methanation because it affects the oxidation of the Ni-based catalyst in the methanization apparatus.

The hydrogen mixing unit 316 _{supplies hydrogen gas to the dehumidified CO 2} to mix and pressurize it. As the hydrogen gas, those produced by artificial photosynthesis using renewable energy, decomposition of water, etc. can be used. The addition of hydrogen by the hydrogen mixing unit 316 is appropriately set to a concentration at which methane can be easily produced from _{CO 2 mixed with hydrogen.}
The methane production unit 317 produces methane from _{CO 2 mixed with hydrogen.} The methane production unit 317 is composed of a general methane production apparatus, and catalysts that are active in methaneization (for example, Ni, Pt, Pd, and Cu are used as hydrogenation catalysts, but Al is particularly used in methaneization. It is equipped with a plurality of reactors (not shown) filled with ₂ O ₃ , Cr ₂ O ₃ , SiO ₂ , MgAl ₂ O ₄ , TIO ₂ , ZrO _{2 and other 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.

(Composition of methane supply device)
As shown in FIG. 2, the methane supply device 32 is connected to a tank (not shown) for storing methane produced by the methaneization device 31, and a burner 8 and a calcining furnace for methane in the front part 5b of the kiln. It is equipped with a methane supply line 321 and a pump 322, 323 to send to each of the burners 41 of 4. The methane supply line 321 is a fuel supply line 15 that supplies fuel such as coal or petroleum to the burner 8 of the cement firing kiln 5, and a fuel supply line 42 that supplies fuel such as coal to the burner 41 of the calcination furnace 4. It is connected to the. As a result, methane is supplied to each of the burners 8 and 41 together with the fuel.

In the cement manufacturing facility 50, a plurality of cement firing kilns 5 and calcining furnaces 4 are installed, but the methane supply device 32 is connected to the methaneization device 31 as shown in FIG. Methane is supplied to the cement firing kiln 5 and the calcining furnace 4. In other words, the exhaust gas sent to the methane conversion device 31 is the exhaust gas from the cement firing kiln 5 and the calcining furnace 4 to which methane is supplied by the methane supply device 32.

[How to utilize _{CO 2]
A method of reducing and effectively utilizing CO 2 in} the exhaust gas of the cement manufacturing equipment 50 by using _{the CO 2} utilization system 100 described above will be described with reference to the flowchart shown in FIG. _{In the CO 2} utilization method of the present embodiment, _{a methane production step of adding hydrogen to CO 2} separated and recovered from the exhaust gas from the cement production facility 50 to generate methane, and a methane production facility for producing methane in the methane production step. The methane consumption step of using a part or all of the fossil fuel for each of the 50 cement firing kilns 5 and the calcination furnace 4 as an alternative fuel is continuously repeated.

(Methane production process)
In the cement manufacturing facility 50, a powdery cement raw material obtained by crushing and drying limestone, clay, silica stone, iron raw material, etc. as a cement raw material is preheated, and the preheated cement raw material is calcined and then fired. Then, by cooling this, a cement clinker is manufactured. Exhaust gas generated in the cement firing kiln 5 and the calcining furnace 4 due to the production of this cement clinker is introduced into the raw material mill and the dryer 2 through the exhaust pipe 9 after passing through the preheater 3 from the lower side to the upper side, and is used as a cement raw material. After being used for drying, it is discharged from the chimney 11 via the dust collector 10.

In this cement manufacturing process, the exhaust gas collecting unit 311 of the methaneization apparatus 31 collects a part of the exhaust gas generated during cement firing from between the dust collector 10 and the chimney 11 of the exhaust gas treatment line 12. Next, the harmful component removing unit 312 removes the harmful component from the exhaust gas. Nitrogen oxides (NOx), sulfur oxides (SOx), halogens and the like are removed in the harmful component removing unit 312. Then, the CO ₂ separation and recovery unit 313 extracts CO ₂ from the exhaust gas and separates and recovers it. At this time, _{the exhaust gas from which CO 2} has been removed is discharged to the outside.

Next, the recovered CO ₂ is compressed by applying a pressure of 0.1 MPa or more, preferably 0.5 to 1.0 MPa by the compression unit 314, and the water contained in the _{CO 2 is removed by the dehumidifying unit 315.} Then, hydrogen gas is supplied to the _{dehumidified CO 2} by the hydrogen mixing unit 316, mixed, and pressurized. Then, the methane production unit 317 produces methane from _{CO 2 mixed with hydrogen.}

(Methane consumption process)
The methane thus produced is stored in the tank of the methane supply device 32. Then, the methane stored in this tank is supplied as a substitute fuel for a part or all of the fossil fuel to the cement firing kiln 5 and the calcining furnace 4 via the methane supply line 321. Fossil fuels such as petroleum and coal are supplied to the cement fired kiln 5 from the fuel supply line 15, and by supplying methane, part or all of the fossil fuel can be replaced with methane. Similarly, in the calcination furnace 4, fossil fuels can be reduced because part or all of the fuel such as coal is replaced with methane.

By supplying this methane to the cement firing kiln 5 and the calcining furnace 4 together with the fossil fuel, the exhaust gas includes the exhaust gas generated by the combustion of methane together with the fossil fuel, and the exhaust gas is the exhaust gas. It is sent to the methanizer 31 via the collection line 311 and similarly produced as methane and supplied to the cement firing kiln 5 and the calcination furnace 4.
In this way, in the cement manufacturing facility 50, a series of steps of generating methane from the exhaust gas and using the produced methane as a part of the cement manufacturing fuel is continuously repeated.

In the present embodiment, by converting the CO ₂ separated recovered from exhaust gas from a cement manufacturing facility 50 to methane, it is possible to reduce the CO ₂ emissions from cement production facility 50, the methane cement kiln 5 and the temporary _{CO 2} can be effectively utilized by circulating it as an alternative fuel for the incinerator 4, that is, by using it repeatedly. _{In particular, since more than half of CO 2 in} the exhaust gas from the cement production facility is derived from limestone _{, methane from the CO 2 in} the exhaust gas is continuously produced and used as fuel, so that coal or coal can be used. It is possible to reduce the use of fossil fuels such as petroleum, reduce CO ₂ originating from energy, and enhance the effect of reducing greenhouse gases.
_{Further, by using CO 2} separated and recovered from the exhaust gas, the concentration thereof can be increased to produce high-concentration methane, and methane can be used more effectively.

_{Further, the CO 2} of the exhaust gas generated by burning methane together with the fossil fuel in the cement firing kiln 5 and the calcining furnace 4 is a nitrogen oxide as compared with the exhaust gas generated by using only the fossil fuel containing no methane as fuel. Since the content of (NOx) and sulfur oxide (SOx) is low, the exhaust gas can be made cleaner. Therefore, even when a part of the exhaust gas is discharged to the atmosphere from the chimney 11 of the cement manufacturing facility 50, air pollution can be reduced, and deterioration of the catalyst and the like of the methanization apparatus 31 can be suppressed.

The present invention is not limited to the configuration of the above embodiment, and various changes can be made to the detailed configuration without departing from the spirit of the present invention.
_{For example, in the above embodiment, CO 2} is separated and recovered from the exhaust gas of the cement manufacturing equipment 50, but since the exhaust gas of the cement manufacturing equipment 50 contains CO _{2 at a} concentration of 20% or more, hydrogen is directly added to the exhaust gas. May produce methane.
Further, although the generated methane is supplied to both the cement firing kiln 5 and the calcining furnace 4, it may be supplied to either one.
Furthermore, although methane was generated using the exhaust gas from both the cement firing kiln 5 and the calcining furnace 4, it can also be applied to cement manufacturing equipment that does not have a calcining furnace. In that case, the cement firing kiln can be used. Produces methane from the exhaust gas of the kiln.

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 Methaneization device 310 CO ₂ Separation and recovery device 311 Exhaust gas collection line 312 Harmful component removal section 313 CO ₂ Separation and recovery section 314 Compression section 315 Dehumidifying section 316 Hydrogen mixing section 317 Methane production section 32 Methane supply device 321 Methane supply line 322 Pump 323 Pump 41 Burner 42 Fuel supply line 50 Cement production equipment 100 CO ₂ utilization system

Claims (4)

_{A methane production step of adding hydrogen to CO 2} in the exhaust gas from the cement manufacturing facility _{or CO 2} separated and recovered from the exhaust gas to generate methane, and the methane generated in the methane production step to the cement manufacturing facility. A method for utilizing _{CO 2} in cement production exhaust gas, which comprises a methane consumption step used as an alternative fuel for a part or all of fossil fuel, and continuously repeats the methane production step and the methane consumption step. The method for utilizing _{CO 2 in} cement manufacturing exhaust gas according to claim 1, wherein the CO _{2 is CO 2 obtained} by contacting the exhaust gas from the cement manufacturing facility with a CO ₂ absorbing material and separating and recovering the CO _{2. A methane conversion device that produces methane by adding hydrogen to CO 2} in the exhaust gas from the cement production facility _{or CO 2} separated and recovered from the exhaust gas, and the methane produced by the methaneization device are added to the cement production facility. A methane supply device for supplying a part or all of fossil fuel to the cement production facility as an alternative fuel is provided, and the methaneization device is connected to the cement production facility to which methane is supplied by the methane supply device. _{A CO 2} utilization system in cement production exhaust gas, which is characterized by being present. _{The CO 2} utilization system in cement manufacturing exhaust gas according to claim 3, further comprising _{a CO 2} separation and recovery device that separates and recovers _{CO 2} by bringing the exhaust gas from the cement manufacturing facility _{into contact with a CO 2 absorbing material.}

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