Patent Application
20230233987
The present invention relates to a CO2 separation and recover method and a CO2 separation and recovery device in cement production exhaust gas.
Priority is claimed on Japanese Patent Application Nos. 2020-97644 and 2020-97645, filed Jun. 4, 2020, and Japanese Patent Application No. 2020-101457, filed Jun. 11, 2020, which are incorporated herein by reference.
In various combustion facilities such as thermal power generation or the like, in order to reduce greenhouse gas, it is made effort to reduce CO2 that is generated and exhausted by combustion. Particularly, since most of energy which is necessary for a social activity is obtained by fossil fuel such as coal, petroleum, natural gas and the like and an amount of CO2 generated from the foil fuel is stupendous, it is effective to reduce CO2 originated from the energy for suppressing global warming.
As a technique for reducing CO2 in combustion exhaust gas, conventionally, for example, the methanation method described in Patent Literature 1 is known. That is a method to obtain methane by separating carbon dioxide contained in the combustion exhaust gas to react with hydrogen. In this methanation method, a step of absorbing carbon dioxide in the combustion exhaust gas by bringing the combustion exhaust gas into contact with a carbon dioxide absorber, a step of taking out gas mainly having carbon dioxide by heating the carbon dioxide absorber that absorbed carbon dioxide, a step of removing sulfur compound in the gas by adding a first amount of hydrogen to the gas mainly having carbon dioxide and then throwing into a desulfurizer which is filled with desulfurizing agent, and a step of converting into methane by adding a second amount of hydrogen to the gas after the step of removing sulfur to convert by methanation reaction through methanation catalyst.
In this methanation method, carbon dioxide to which hydrogen is added passes through the desulfurizer that is filled with desulfurizing agent to remove sulfur compound in the gas.
However, since the exhaust gas (cement production exhaust gas) of the cement facility includes a large amount of oxides other than the sulfur compound, for example, even if the desulfurizer as described in Patent Literature 1 is used, it is not possible to appropriately dispose the cement production exhaust gas.
The present invention is achieved in consideration of the above circumstances, and has an object to provide a CO2 separation and recover method and a CO2 separation and recover device in cement production exhaust gas which can dispose the cement production exhaust gas appropriately.
A CO2 separation and recover method in cement production exhaust gas according to the present invention removes an acidic component and a harmful component, before separating and recovering CO2 by bringing exhaust gas from a cement production facility into contact with a CO2 absorption material.
Here, the acidic components such as SOx, NOx, halogen and the like and the harmful components such as H2O, dusts and the like may influence the CO2 absorption material to deteriorate CO2 absorbing ability. Moreover, there is a possibility that dusts (mainly powder of cement raw material) included in the cement production exhaust gas adhere in pipes of the device and generates scales to increase pressure loss of the pipes, and decrease a gas amount which can be disposed in a CO2 separation and recover device.
In the present invention, by removing the acidic component and the harmful component before separating and recovering the exhaust gas from the cement production facility, it is possible to suppress the deterioration of the absorbing ability of the CO2 absorption material. Accordingly, CO2 can be efficiently recovered from the cement production exhaust gas.
A CO2 separation and recover device in cement production exhaust gas of the present invention includes a cement production facility that is provided with a harmful component removal unit that removes an acidic component and a harmful component from exhaust gas from the cement production facility, and a CO2 separation and recover unit that separates and recovers CO2 by bringing the exhaust from which the acidic component and the harmful component are removed into contact with a CO2 absorption material.
According to the present invention, it is possible to suppress deterioration of absorbing ability of CO2 absorption material by removing an acidic component and a harmful component appropriately from CO2 in exhaust gas of a cement production facility.
An embodiment of a CO2 separation and recover method in cement production exhaust gas and a CO2 separation and recover device in cement production exhaust gas of the present invention will be explained below referring drawings.
This embodiment is an example of removing an acidic component and a harmful component appropriately from CO2 in the cement production exhaust gas, then generating methane to utilize the methane as a part of fossil fuel or an entire alternative fuel to the cement production facility.
A CO2 utilizing system 100 is provided with a cement production facility 50 and an exhaust gas treatment facility 30 used by connected to the cement production facility 50 as shown in
The cement production facility 50 is provided with, as the whole is shown in
The cement burning kiln 5 is a lateral cylindrical rotary kiln which is slightly inclined, rotated around an axis to send the cement materials supplied in a kiln tail part 5a from the preheater 3 to a kiln front part 5b, and heats and burns to generate cement clinker at about 1450° C. by a burner 8 at the kiln front part 5b while sending. The generated cement clinker is sent out from the kiln front part 5b to the cooler 6. To the burner 8, a fuel supply line 15 supplying fuel containing fossil fuel such as coal, petroleum and the like is connected. Other than the fuel supply line 15, in order to enlarge the heat energy, a supplying system (not illustrated) of an alternative heat source such as waste plastic, waste tires and the like is also provided. The cement clinker is cooled in the cooler 6 to a prescribed temperature, then sent to a finishing step.
The preheater 3 is configured so that a plurality (four in an example shown in
The calcination furnace 4 has a burner 41 therein, and burns fuel such as coal or the like supplied from a fuel supply line 42, thereby calcining the cement material sent from the upper cyclone 13, and supplying the calcined cement material to the lowermost cyclone 13 through a riser duct 25 together with the exhaust gas generated by the calcination. The cement material is supplied from the lowermost cyclone 13 to the kiln tail part 5a of the cement burning kiln 5. The riser duct 25 sends the exhaust gas from the kiln tail part 5a of the cement burning kiln 5 to the lowermost cyclone 13, and the exhaust gas occurs in the calcination furnace 4 is also supplied to the cyclone 13 through the riser duct 25. Therefore, the exhaust gas of the cement burning kiln 5 and the exhaust gas from the calcination furnace 4 go together thorough the preheater 3 from the lower side to the upper side and then are introduced into the material mill/dryer 2 passing through an exhaust pipe 9.
The material mill/dryer 2 carries out pulverization and drying of the cement material simultaneously by introducing the exhaust gas from the calcination furnace 4 and the cement burning kiln 5. To the material mill/dryer 2, an exhaust gas treatment line 12 having a dust collector 10, a chimney 11 and the like is connected.
The exhaust gas treatment facility 30 is provided with an exhaust gas collection line 311 collecting the exhaust gas occurred in the cement burning kiln 5 and the calcination furnace 4 before discharged from the chimney 11 a methanation device 31 separating and recovering CO2 from the exhaust gas sent from the exhaust gas collection line 311 and adding hydrogen to the separated and recovered CO2 to generate methane, and a methane supply device 32 supplying 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 treatment line 12 of the cement production facility 50, and collects a part of the exhaust gas generated during cement burning. Since it is the exhaust gas is generated by burning of cement, an exhaust gas due to combustion of fuel such as coal is partially included, but it contains a large amount of exhaust gas originated from lime stone.
The methanation device 31 is provided with a CO2 separation/recover device 310 that separates and recovers CO2 from the exhaust gas, a hydrogen mixing unit 316 that supplies and mixes hydrogen to CO2 separated and recovered by the CO2 separation/recover device 310 and a methane production part 317 that generates methane from CO2 in which hydrogen is mixed.
As shown in
Since the exhaust gas sent from the exhaust gas collection line 311 is combustion exhaust gas of fossil fuel such as coal, petroleum coke, heavy oil or the like, waste plastic, waste tires and the like, CO2 is contained at about 20% or more for example, and the other gas than CO2, an acidic component, and a harmful component are contained. Therefore, the harmful component removal unit 312 removes the acidic component (for example, acidification gas such as nitrogen oxides [NOx] or sulfur oxides [SOx]) and the harmful component (H2O, dusts and the like) from the exhaust gas, and is provided with a scrubber that is filled with an aqueous NaOH and the like, a dehumidifier, an electrostatic precipitator, and the like. By removing the acidic component and the harmful component, halogen is also removed with NOx, an absorption material (CO2 absorption material) of amine compound used for the next separation and recover of CO2 is prevented from deteriorating, and the deterioration of the absorbing ability is suppressed.
As a method of desulfurization (SOx removal method), a wet lime-gypsum method, magnesium hydroxide method, and a soda absorption method are known. These are methods of absorbing SOx in alkaline solution; and there is a coalash utilizing method as a dry method. As methods of treating desulfurization (removal of SOx) and denitration (removal of NOx) simultaneously, there are an activated carbon method that is a dry method, and an electron beam method. As the denitration method, there are a catalytic reduction method (SCR method) and a non-catalytic reduction process as dry methods; and an oxidation absorbing method, an oxidation reduction method, and an equimolar absorption method as wet methods.
Since a suspension preheater unit works as a desulfurizing unit, in the exhaust gas from the cement production facility, there are many cases in which SOX is several-ten ppm, generally.
Here, it seems that by an influence of impurities on the absorption material for CO2 separation and recover, affinity between amine compound and impurity compound does not largely differ in either a chemical absorption method and a physical absorption method. In recover of CO2 by the CO2 separation/recover unit 313, SOx in the exhaust gas is combined with the amine compound in the absorption material and impedes the CO2 absorbing ability of the amine compound, so that the absorption rate is largely decreased as time passes. As described above, the amine compound has strong basicity, and other than SOx, NOx and halogen such as Cl, F and the like tend to be absorbed by the CO2 absorption material.
A Ni catalyst which is broadly used as a catalyst for methanation deteriorates a yield of the methanation under the sulfur compound mixed in H2 since the sulfur compound reacts on a surface of the Ni catalyst and covers the surface, so that it is necessary to be removed in the harmful component removal unit 312. Similarly, NOx and halogen such as Cl, F and the like may be adhered to the surface of the Ni catalyst and deteriorate the yield of the methanation, so that it is necessary to be removed in the harmful component removal unit 312.
In the present embodiment, any of the above-described methods may be used for desulfurization (removal of SOx) and denitration (removal of NOx). For example, in the present embodiment, any of the above-described desulfurization methods and any of the above-described denitration methods are used to remove the acidification gas such as the nitrogen oxides (NOx), the sulfur oxides (SOx), and the like.
The CO2 separation/recover unit 313 is made of a standard CO2 recover device, and is provided with a CO2 absorption material (a liquid absorption material in which an amine compound is dissolved in water, a solid absorption material in which an amine compound is supported on a porous material, and the like) that absorbs CO2 in the exhaust gas when the exhaust gas in which the harmful matters are removed comes into contact therewith. Then, by heating the CO2 absorption material that has absorbed CO2 and the like, CO2 is taken out from the CO2 absorption material and recovered. The CO2 separation/recover unit 313 discharges the exhaust gas after removing CO2 to the exterior. The compression unit 314 compresses the recovered CO2 by applying a pressure of 0.1 MPa or more, preferably 0.5 to 1.0 MPa. The dehumidification unit 315 removes moisture contained in CO2 by cooling the compressed CO2. This dehumidification is carried out in order to remove moisture before methanation since the moisture affects the oxidation of a Ni-based catalyst in the methanation device.
The hydrogen mixing unit 316 supplies hydrogen (for example, hydrogen gas) to the dehumidified CO2, mixes, and compresses it. The hydrogen produced by artificial light synthesis using renewable energy, decomposition of water, or the like can be utilized. The amount of hydrogen added by the hydrogen mixing unit 316 is appropriately set so that methane can be easily produced from CO2 in which hydrogen is mixed.
The methane production unit 317 generates methane from CO2 in which hydrogen is mixed. The methane production unit 317 is composed of a general methane production apparatus, provided with a plurality of reactors (not illustrated) filled with a catalyst exhibiting activity in methanation, and produces methane by supplying and reacting CO2 in which hydrogen is mixed with these reactors. For example, Ni, Pt, Pd, and Cu are used as a hydrogenation catalyst; in the methanation catalyst, particularly, Ni and Ni alloy on which Al2O3, Cr2O3, SiO2, MgAl2O4, TiO2, ZrO2 or the like are supported.
Conditions for a general methanation reaction (CO2+4H2→2H2O) have a temperature of 200° C. to 700° C., preferably 200° C. to 350° C., and a pressure of 0.1 to 3 MPa, and it is reacted in multiple stage in order to improve the reaction yield of methane.
As shown in
A method of reducing CO2 in the exhaust gas of the cement production facility 50 and effectively utilizing it using the above-described CO2 utilizing system will be explained with the flowchart shown in
In the cement production facility 50, the powdery cement material obtained by milling and drying lime stone, clay, silica stone, iron material and the like as the cement material is preheated; the preheated cement material is subjected to the calcination and then burned, and cooled, so that the cement clinker is produced. The exhaust gas occurred in the cement burning kiln 5 and the calcination furnace 4 during the production of the cement clinker goes through the preheater 3 from the lower side to the upper side, passes through the exhaust pipe 9 to be introduced into the material mill/drier 2 for drying the cement material, then is discharged from the chimney 11 via the dust collector 10.
In this process of producing cement, a part of the exhaust gas occurred when the cement is burned is collected to the exhaust gas collection line 311 of the methanation device 31 between the dust collector 10 and the chimney 11 of the exhaust gas treatment line 12. Next, the harmful component removal unit 312 removes the acidic component and the harmful component from the exhaust gas (harmful component removal step). In the harmful component removal unit 312, nitrogen oxides (NOx), sulfur oxides (SOx), halogen, H2O, dusts and the like are removed. Then, CO2 is taken out from the exhaust gas by the CO2 separation/recover unit 313 and separated/recovered. At this time, the exhaust gas from which CO2 is removed is discharged outside.
Next, the compression unit 314 compresses the recovered CO2 to be 0.1 MPa or more by applying a pressure of 0.5 to 1.0 MPa, and then moisture included in CO2 is removed by the dehumidification unit 315. Then, by the hydrogen mixing unit 316, hydrogen is supplied to the dehumidified CO2 and mixed with it, then pressurized. Then, by the methane production unit 317, methane is generated from CO2 in which hydrogen is mixed.
The methane generated in this manner is stored in the tank 322 of the methane supply device 32. The methane stored in the tank 322 is supplied to the cement burning kiln 5 and the calcination furnace 4 via the methane supply line 323. In the cement burning kiln 5, fossil fuel such as petroleum, coal of the like is supplied from the fuel supply line 15, however, some of the fossil fuel can be substituted with methane by supplying methane, and the fossil fuel can be reduced. Similarly, in the calcination furnace 4, some of the fuel such as coal is substituted with methane, so that fossil fuel can be reduced.
In the present embodiment, before separation and recover of the exhaust gas from the cement production facility 50, by removing the acidic components such as SOx, NOx, halogen and the like, and the harmful components such as H2O, dusts and the like contained in CO2 of the cement production exhaust gas, the deterioration of the absorption ability of the CO2 absorption material can be suppressed. Accordingly, CO2 can be efficiently recovered from the cement production exhaust gas. The CO2 absorption material also can be maintained to have stable performance for a long time. By converting CO2 appropriately treated to methane, CO2 discharged from the cement production facility 50 can be reduced; and by using the methane as the alternative fuel for the cement burning kiln 5 and the calcination furnace 4, the methane can be effectively utilized. Notably, since methane substitutes for the fossil fuel such as coal and petroleum being the major cause of the global warming, the usage of the fossil fuel is decreased to reduce CO2 derived from energy, and the reduction effect of the greenhouse gas can be improved.
The present invention is not limited to the above-described embodiments and various modifications may be made without departing from the scope of the present invention.
For example, although the generated methane is supplied to both the cement burning kiln 5 and the calcination furnace 4, it is possible to supply to either one of them.
Moreover, although the methane is generated using the exhaust gas from both the cement burning kiln 5 and the calcination furnace 4, it is possible to apply to a cement production facility having no calcination furnace; in this case, methane is generated from exhaust gas from a cement burning kiln.
Acidic components and harmful components is appropriately removed from CO2 in exhaust gas of a cement production facility and deterioration of absorption ability of a CO2 absorption material can be suppressed.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2020-097644 | Jun 2020 | JP | national |
| 2020-097645 | Jun 2020 | JP | national |
| 2020-101457 | Jun 2020 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2021/020405 | 5/28/2021 | WO |
