Hui An

Fabrication of CaO-based sorbents for CO2 capture by a mixing method

Three types of sorbent were fabricated using various calcium and support precursors via a simple mixing method, in order to develop highly effective, durable, and cheap CaO-based sorbents suitable for CO(2) capture. The sorption performance and morphology of the sorbents were measured in a thermogravimetric analyzer and a scanning electron microscopy, respectively. The experimental results indicate that cement is a promising low-cost support precursor for contributing to the enhancement of cyclic CO(2) sorption capacity, especially when organometallic calcium precursors were used. A sorbent (with 75% CaO content) made from calcium l-lactate hydrate and cement showed the highest CO(2) sorption capacity of 0.36 g of CO(2)/g of sorbent and its capacity decreased only slightly after 70 cycles of carbonation and calcination.

Investigation on coal seam gas formation of multi-coalbed reservoir in Bide-Santang Basin Southwest China

This paper presents a comprehensive study on the geological characteristics of a multi-coalbed reservoir using coal cores collected from well drilling tests in Bide-Santang Basin, China. The study focuses on the investigation of the coalbed methane (CBM)-bearing property, porosity and permeability, sealability of capping rocks, and groundwater characteristics in coal seams, providing the experimental information on the control function of sequence strata for the coalbed methane. This reservoir is comprised of a large number of coalbeds and exhibits many distinctive geological characteristics of a CBM reservoir, such as high CBM content, complex vertical volatility of CBM content, vertical discontinuous distribution of porosity and permeability, strong sealing capping property and many vertical water-bearing systems, etc. The investigation shows that the unattached multiple superposed CBM-bearing system (UMSCS), which formed the unique multi-coalbed CBM reservoir, can be identified in the study area. Depending on the development scale of vertically unattached CBM-bearing coal seams, the CBM reservoir in the study area can be classified as simple UMSCS and complex UMSCS. The former, typically appearing in Zhuzang syncline and Agong syncline, exhibits the continuity of geological reservoir-forming characteristics in terms of less coal seams, much weaker sealability of capping rocks, higher CBM content, and many vertical water-bearing systems. The latter, typically represented by Shuigonghe syncline and Santang syncline, shows the continuity of geological reservoir-forming characteristics with a large number of coal seams, strong sealing capping property, and reasonably high CBM content. For simple UMSCS reservoirs, a sublevel exploitation method should be adopted for CBM exploitation in order to minimize the effect caused by larger variation of the reservoir energy in different systems. For complex UMSCS reservoirs, one effective way for CBM exploitation is to fracture virtual reservoir (mainly key sandstone member) to depressurize it uniformly and thus achieve large-scale discharging and mining in several adjacent CBM-bearing subsystems.

Effect of addition of weak acids on CO2 desorption from rich amine solvents

Experiments were conducted to study the effect of addition of four weak acids (adipic, suberic, phthalic and sebacic acids) on the regeneration of three types of CO2-loaded rich solvents (Monoethanolamine (MEA), Diethanolamine (DEA) and Methyldiethanolamine (MDEA)). It was found that CO2 could be released faster and in a larger quantity when the amount of acid added to the solvent was increased while other desorption conditions were maintained unchanged. Adipic acid appeared to be more effective than phthalic, suberic and sebacic acids in enhancing solvent regeneration rate. Among the three amines investigated, MEA had the highest CO2 desorption rate, while DEA saved the most energy. The effect of adipic acid residue in the MEA solvent on CO2 absorption was also investigated. The residue acid reduced the absorption capacity of the MEA solvent significantly when the solvent concentration was low and slightly when the concentration was high.

Modeling anisotropic permeability of coal and its effects on coalbed methane reservoir simulation

In this study, an alternative permeability model was developed and compared with data from laboratory investigations. The model was further applied for reservoir simulation with several cases in order to evaluate the effects of the anisotropic permeability variation on the CO2-sequestration and CO2- sequestration enhanced coalbed methane (CO2-ECBM) recovery. The permeability model developed in this study is based on a discontinuum medium approach, in which coal is treated as a discontinuum medium containing anisotropic matrixes and cleats. The permeability variations and anisotropic permeability ratios under isotropic net stresses were tested with relatively large coal samples. The simulations show good agreements with the experimental data, revealing that the developed model is superior for describing stressand sorption-induced permeability variations in coals compared with models using constant values for stress-dependent parameters. The results from reservoir simulation incorporating the developed permeability model show the anisotropic permeability exhibit significant effect on CO2-ECBM recovery.