The carbonation characteristics of K2CO3/Al2O3 supported sorbent for CO2 capture was investigated with thermogravimetric apparatus(TGA),X-ray diffraction(XRD),scanning electron microscopy analysis(SEM)and N2 adsorptio...The carbonation characteristics of K2CO3/Al2O3 supported sorbent for CO2 capture was investigated with thermogravimetric apparatus(TGA),X-ray diffraction(XRD),scanning electron microscopy analysis(SEM)and N2 adsorption.The results showed that the carbonation rate of K2CO3 before being loaded on Al2O3 was slow.However,the K2CO3/Al2O3supported sorbent showed excellent carbonation performance.The difference in carbonation behavior between K2CO3and K2CO3/Al2O3supported sorbent was analyzed from the microscopic view.The analytical reagent K2CO3 sample was of monoclinic crystal structure and could react quickly with H2O in the experimental carbonation environment to produce K2CO3·1.5H2O,which was unfavorable to carbonation reaction.When K2CO3was loaded on Al2O3,the surface area and porosity of the sorbent was improved greatly.So the carbonation properties of the K2CO3/Al2O3 supported sorbent was also improved.展开更多
Indirect CO2 mineral sequestration that involves two separate steps,with acetic acid as the recycling medium,was limited by a crystallization conversion of only 20% in the second gas-liquid reactive crystallization st...Indirect CO2 mineral sequestration that involves two separate steps,with acetic acid as the recycling medium,was limited by a crystallization conversion of only 20% in the second gas-liquid reactive crystallization step.In this paper,the second carbonation step was greatly improved by coupling reactive crystallization and solvent extraction with the introduction of an organic solvent,tributyl phosphate(TBP),to the process.The effect of the initial concentration of calcium acetate in the aqueous solution on the crystallization conversion was studied experimentally.The obtained calcium conversion was above 40%,which was one time higher than that reported in the literature.Based on the mechanism discussion and thermodynamic equilibrium calculation analysis,it can be concluded that adding TBP to the step can consume the produced acetic acid,and it is in favor of the precipitation of calcium carbonate.While the challenge presented by the strong interaction between calcium ions and acetate ions for further improving crystallization conversion cannot be solved only by the addition of TBP.展开更多
The structure identification and carbonation characteristics of several potassium-based supported sorbents for CO2 capture were investigated with TGA,XRD,XRF,SEM and N2 adsorption method.Potassium-based sorbents were ...The structure identification and carbonation characteristics of several potassium-based supported sorbents for CO2 capture were investigated with TGA,XRD,XRF,SEM and N2 adsorption method.Potassium-based sorbents were prepared by impregnation with potassium carbonate on supports,such as cocoanut activated charcoal(AC1),coal active carbon(AC2),silica gel(SG)and diatomite(DT)using the iso-volume impregnation method.The results showed that the K2CO3 loading amounts of AC1,AC2,SG and DT were 24.1%,22.5%,21.7% and 19.1% respectively.The surface area and pore volume of K2CO3/AC1 and K2CO3/AC2 were larger than others.In contrast,those of K2CO3/DT were small.For K2CO3/SG,pore volume was large but surface area was small.K2CO3/AC1 and K2CO3/AC2 showed excellent carbonation capacity.However,the carbonation capacities of K2CO3/SG and K2CO3/DT were low.The difference in carbonation capacity of those sorbents were attributed to the difference in pore structure,leading to different supported sorbents.展开更多
Four kinds of Ca-based sorbents were prepared by calcination and hydration reactions using different precursors： calcium hydroxide, calcium carbonate, calcium acetate monohydrate and calcium oxide. The CO2 absorption...Four kinds of Ca-based sorbents were prepared by calcination and hydration reactions using different precursors： calcium hydroxide, calcium carbonate, calcium acetate monohydrate and calcium oxide. The CO2 absorption capacity of those sorbents was investigated in a fixed-bed reactor in the temperature range of 350-650 ℃. It was found that all of those sorbents showed higher capacity for CO2 absorption when the operating temperature higher than 450 ℃. The CaAc2-CaO sorbent showed the highest CO2 absorption capacity of 299 mg.g-1. The mor- phology of those sorbents was examined by scanning electron microscope （SEM）, and the changes of composition before and after carbonation were also determined by X-ray diffraction （XRD）. Results indicated that those sorbents have the similar chemical compositions and crystalline phases before carbonation reaction [mainly Ca（OH）2], and CaCO3 is the main component after carbonation reaction. The SEM morphology shows clearly that the sorbent pores were filled with reaction products after carbonation reaction, and became much denser than before. The N2 adsorption-desorption isotherms indicated that the CaAc2-CaO and CaCO3-CaO sorbents have higher specific surface area. lar2er oore volume and anoropriate pore size distribution than that of CaO-CaO and Ca（OH）2-CaO.展开更多
The co-removal of CO_(2)while removing SO_(2)and NOxfrom industrial flue gas has great potential of carbon emission reduction but related research is lacking.In this study,a wet scrubbing process with various urea sol...The co-removal of CO_(2)while removing SO_(2)and NOxfrom industrial flue gas has great potential of carbon emission reduction but related research is lacking.In this study,a wet scrubbing process with various urea solutions for desulfurization and denitrification was explored for the possibility of CO_(2)absorption.The results showed that the urea-additive solutions were efficient for NOxand SO_(2)abatement,but delivered<10%CO_(2)absorption efficiency.The addition of Ca(OH)_(2)dramatically enhanced the CO_(2)absorption,remained the desulfurization efficiency,unfortunately restricted the denitrification efficiency.Among various operating parameters,pH of solution played a determining role during the absorption.The contradictory pH demands of CO_(2)absorption and denitrification were observed and discussed in detail.A higher pH of solution than 10 was favorable for CO_(2)absorption,while the oxidizing of NO to NO_(2),NO_(2)^(-)or NO_(3)^(-)by NaClO_(2)was inhibited in this condition.When7<pH<10,it was favorable for the conversion and absorption of NO and NOx.However,the conversion of HCO_(3)^(-)to CO_(3)^(2-)was significantly inhibited,hence preventing the absorption of CO_(2).Large part of Ca(OH)_(2)became CaCO_(3)with a finer particle size,which covered the unreacted Ca(OH)_(2)surface after the reaction.Kinetic analysis showed that the CO_(2)absorption in urea-NaClO_(2)-Ca(OH)_(2)absorbent was controlled by chemical reaction in early stage,then by ash layer diffusion in later stage.展开更多
文摘The carbonation characteristics of K2CO3/Al2O3 supported sorbent for CO2 capture was investigated with thermogravimetric apparatus(TGA),X-ray diffraction(XRD),scanning electron microscopy analysis(SEM)and N2 adsorption.The results showed that the carbonation rate of K2CO3 before being loaded on Al2O3 was slow.However,the K2CO3/Al2O3supported sorbent showed excellent carbonation performance.The difference in carbonation behavior between K2CO3and K2CO3/Al2O3supported sorbent was analyzed from the microscopic view.The analytical reagent K2CO3 sample was of monoclinic crystal structure and could react quickly with H2O in the experimental carbonation environment to produce K2CO3·1.5H2O,which was unfavorable to carbonation reaction.When K2CO3was loaded on Al2O3,the surface area and porosity of the sorbent was improved greatly.So the carbonation properties of the K2CO3/Al2O3 supported sorbent was also improved.
文摘Indirect CO2 mineral sequestration that involves two separate steps,with acetic acid as the recycling medium,was limited by a crystallization conversion of only 20% in the second gas-liquid reactive crystallization step.In this paper,the second carbonation step was greatly improved by coupling reactive crystallization and solvent extraction with the introduction of an organic solvent,tributyl phosphate(TBP),to the process.The effect of the initial concentration of calcium acetate in the aqueous solution on the crystallization conversion was studied experimentally.The obtained calcium conversion was above 40%,which was one time higher than that reported in the literature.Based on the mechanism discussion and thermodynamic equilibrium calculation analysis,it can be concluded that adding TBP to the step can consume the produced acetic acid,and it is in favor of the precipitation of calcium carbonate.While the challenge presented by the strong interaction between calcium ions and acetate ions for further improving crystallization conversion cannot be solved only by the addition of TBP.
文摘The structure identification and carbonation characteristics of several potassium-based supported sorbents for CO2 capture were investigated with TGA,XRD,XRF,SEM and N2 adsorption method.Potassium-based sorbents were prepared by impregnation with potassium carbonate on supports,such as cocoanut activated charcoal(AC1),coal active carbon(AC2),silica gel(SG)and diatomite(DT)using the iso-volume impregnation method.The results showed that the K2CO3 loading amounts of AC1,AC2,SG and DT were 24.1%,22.5%,21.7% and 19.1% respectively.The surface area and pore volume of K2CO3/AC1 and K2CO3/AC2 were larger than others.In contrast,those of K2CO3/DT were small.For K2CO3/SG,pore volume was large but surface area was small.K2CO3/AC1 and K2CO3/AC2 showed excellent carbonation capacity.However,the carbonation capacities of K2CO3/SG and K2CO3/DT were low.The difference in carbonation capacity of those sorbents were attributed to the difference in pore structure,leading to different supported sorbents.
基金Supported by the National Natural Science Foundation of China （21006053）, the Fundamental Research Funds for the Central Universities （65010551） and Special Projects of Environmental Protection （2009ZX07208）.
文摘Four kinds of Ca-based sorbents were prepared by calcination and hydration reactions using different precursors： calcium hydroxide, calcium carbonate, calcium acetate monohydrate and calcium oxide. The CO2 absorption capacity of those sorbents was investigated in a fixed-bed reactor in the temperature range of 350-650 ℃. It was found that all of those sorbents showed higher capacity for CO2 absorption when the operating temperature higher than 450 ℃. The CaAc2-CaO sorbent showed the highest CO2 absorption capacity of 299 mg.g-1. The mor- phology of those sorbents was examined by scanning electron microscope （SEM）, and the changes of composition before and after carbonation were also determined by X-ray diffraction （XRD）. Results indicated that those sorbents have the similar chemical compositions and crystalline phases before carbonation reaction [mainly Ca（OH）2], and CaCO3 is the main component after carbonation reaction. The SEM morphology shows clearly that the sorbent pores were filled with reaction products after carbonation reaction, and became much denser than before. The N2 adsorption-desorption isotherms indicated that the CaAc2-CaO and CaCO3-CaO sorbents have higher specific surface area. lar2er oore volume and anoropriate pore size distribution than that of CaO-CaO and Ca（OH）2-CaO.
基金supported by the National Key Research and Development Plan of China (Nos.2019YFC0214300 and 2020YFF0408886)the Central Public-interest Scientific Institution Basal Research Fund of China (Nos.PM-zx703-202104059,PM-zx703-202104-087,and PM-zx703-202204-159)the Project of Science and Technology Program of Guangzhou,China (No.202102020135)。
文摘The co-removal of CO_(2)while removing SO_(2)and NOxfrom industrial flue gas has great potential of carbon emission reduction but related research is lacking.In this study,a wet scrubbing process with various urea solutions for desulfurization and denitrification was explored for the possibility of CO_(2)absorption.The results showed that the urea-additive solutions were efficient for NOxand SO_(2)abatement,but delivered<10%CO_(2)absorption efficiency.The addition of Ca(OH)_(2)dramatically enhanced the CO_(2)absorption,remained the desulfurization efficiency,unfortunately restricted the denitrification efficiency.Among various operating parameters,pH of solution played a determining role during the absorption.The contradictory pH demands of CO_(2)absorption and denitrification were observed and discussed in detail.A higher pH of solution than 10 was favorable for CO_(2)absorption,while the oxidizing of NO to NO_(2),NO_(2)^(-)or NO_(3)^(-)by NaClO_(2)was inhibited in this condition.When7<pH<10,it was favorable for the conversion and absorption of NO and NOx.However,the conversion of HCO_(3)^(-)to CO_(3)^(2-)was significantly inhibited,hence preventing the absorption of CO_(2).Large part of Ca(OH)_(2)became CaCO_(3)with a finer particle size,which covered the unreacted Ca(OH)_(2)surface after the reaction.Kinetic analysis showed that the CO_(2)absorption in urea-NaClO_(2)-Ca(OH)_(2)absorbent was controlled by chemical reaction in early stage,then by ash layer diffusion in later stage.
