Effects of SO2 and pH Concentration on CO2 Adsorption Capacity in Coal Seams for CO2 Sequestration With Considerations for Flue Gas From Coal-Fired Power Plants

Carbon dioxide (CO2) has been used to replace coal seam gas for recovery enhancement and carbon sequestration. To better understand the alternations of coal seam in response to CO2 sequestration, the properties of four different coals before and after supercritical CO2 (ScCO2) exposure at 40 °C and 16 MPa were analyzed with Fourier Transform infrared spectroscopy (FTIR), low-pressure nitrogen, and CO2 adsorption methods. Further, high-pressure CO2 adsorption isotherms were performed at 40 °C using a gravimetric method. The results indicate that the density of functional groups and mineral matters on coal surface decreased after ScCO2 exposure, especially for low-rank coal. With ScCO2 exposure, only minimal changes in pore shape were observed for various rank coals. However, the micropore specific surface area (SSA) and pore volume increased while the values for mesopore decreased as determined by low-pressure N2 and CO2 adsorption. The combined effects of surface property and pore structure alterations lead to a higher CO2 adsorption capacity at lower pressures but lower CO2 adsorption capacity at higher pressures. Langmuir model fitting shows a decreasing trend in monolayer capacity after ScCO2 exposure, indicating an elimination of the adsorption sites. The results provide new insights for the long-term safety for the evaluation of CO2-enhanced coal seam gas recovery.

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CVD Synthesis, Functionalization and CO2 Adsorption Attributes of Multiwalled Carbon Nanotubes

Processes ◽

10.3390/pr7090634 ◽

2019 ◽

Vol 7 (9) ◽

pp. 634 ◽

Cited By ~ 3

Author(s):

Shazia Shukrullah ◽

Muhammad Yasin Naz ◽

Norani M. Mohamed ◽

Khalid A. Ibrahim ◽

Nasser M. AbdEl-Salam ◽

...

Keyword(s):

Carbon Dioxide ◽

Carbon Nanotubes ◽

Adsorption Capacity ◽

Multiwalled Carbon Nanotubes ◽

Functional Groups ◽

Co2 Adsorption ◽

Breakthrough Curves ◽

Multiwalled Carbon ◽

Amine Functionalized ◽

Co2 Adsorption Capacity

Carbon dioxide is one of the major greenhouse gases and a leading source of global warming. Several adsorbent materials are being tested for removal of carbon dioxide (CO2) from the atmosphere. The use of multiwalled carbon nanotubes (MWCNTs) as a CO2 adsorbent material is a relatively new research avenue. In this study, Fe2O3/Al2O3 composite catalyst was used to synthesize MWCNTs by cracking ethylene gas molecules in a fluidized bed chemical vapor deposition (CVD) chamber. These nanotubes were treated with H2SO4/HNO3 solution and functionalized with 3-aminopropyl-triethoxysilane (APTS). Chemical modification of nanotubes removed the endcaps and introduced some functional groups along the sidewalls at defected sites. The functionalization of nanotubes with amine introduced carboxylic groups on the tube surface. These functional groups significantly enhance the surface wettability, hydrophilicity and CO2 adsorption capacity of MWCNTs. The CO2 adsorption capacity of as-grown and amine-functionalized CNTs was computed by generating their breakthrough curves. BELSORP-mini equipment was used to generate CO2 breakthrough curves. The oxidation and functionalization of MWCNTs revealed significant improvement in their adsorption capacity. The highest CO2 adsorption of 129 cm3/g was achieved with amine-functionalized MWCNTs among all the tested samples.

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The Role of Coal Mechanical Characteristics on Reservoir Permeability Evolution and Its Effects on CO2 Sequestration and Enhanced Coalbed Methane Recovery

Geofluids ◽

10.1155/2020/8842309 ◽

2020 ◽

Vol 2020 ◽

pp. 1-28

Author(s):

Hao Han ◽

Shun Liang ◽

Yaowu Liang ◽

Xuehai Fu ◽

Junqiang Kang ◽

...

Keyword(s):

Elastic Modulus ◽

Coal Seam ◽

Coalbed Methane ◽

Co2 Sequestration ◽

Mechanical Characteristics ◽

Co2 Adsorption ◽

Co2 Injection ◽

Permeability Change ◽

Coal Seams ◽

Enhanced Coalbed Methane

Elastic modulus is an important parameter affecting the permeability change in the process of coalbed methane (CBM)/enhanced coalbed methane (ECBM) production, which will change with the variable gas content. Much research focuses on the constant value of elastic modulus; however, variable stiffness of coal during CO2 injection has been considered in this work. The coupled thermo-hydro-mechanical (THM) model is established and then validated by primary production data, as well as being applied in the prediction of CO2/N2-ECBM recovery. The results show that the harder coal seam is beneficial to primary production, while the softer coal seam results in greater CO2/N2-ECBM recovery and CO2 sequestration. N2 and CO2 mixture injection could be applied to balance early N2 breakthrough and pronounced matrix swelling induced by CO2 adsorption, and to prolong the process of effective CH4 recovery. Besides, reduction in stiffness of coal seam during CO2 injection would moderate the significant permeability loss induced by matrix swelling. With the increase of the weakening degree of coal seam stiffness, CO2 cumulative storage also shows an increasing trend. Neglecting the weakening effect of CO2 adsorption on coal seam stiffness could underestimate the injection capacity of CO2. Injection of hot CO2 could improve the permeability around injection well and then enhance CO2 cumulative storage and CBM recovery. Furthermore, compared with ECBM production, injection temperature is more favorable for CO2 storage, especially within hard coal seams. Care should be considered that significant permeability change is induced by mechanical characteristics alterations in deep burial coal seams in further study, especially for CO2-ECBM projects.

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