Composite rock-breaking of high-pressure CO_(2)jet&polycrystallinediamond-compact(PDC)cutter using a coupled SPH/FEM model

CO_(2) drilling is a promising underbalance drilling technology with great advantages,such as lower cutting force,intense cooling and excellent lubrication.However,in the underbalance drilling,the mechanism of the coupling CO_(2) jet and polycrystalline-diamond-compact(PDC)cutter are still unclear.Whereby,we established a coupled smoothed particle hydrodynamics/finite element method(SPH/FEM)model to simulate the composite rock-breaking of high-pressure CO_(2) jet&PDC cutter.Combined with the experimental research results,the mechanism of composite rock-breaking is studied from the perspectives of rock stress field,cutting force and jet field.The results show that the composite rock-breaking can effectively relieve the influence of vibration and shock on PDC cutter.Meanwhile,the high-pressure CO_(2) jet has a positive effect on carrying rock debris,which can effectively reduce the temperature rising and the thermal wear of the PDC cutter.In addition,the effects of CO_(2) jet parameters on composite rock-breaking were studied,such as jet impact velocity,nozzle diameter,jet injection angle and impact distance.The studies show that when the impact velocity of the CO_(2) jet is greater than 250 m/s,the CO_(2) jet could quickly break the rock.It is found that the optimal range of nozzle diameter is 1.5–2.5 mm,the best injection angle of CO_(2) jet is 60,the optimal impact distance is 10 times the nozzle diameter.The above studies could provide theoretical supports and technical guidance for composite rock-breaking,which is useful for the CO_(2) underbalance drilling and drill bit design.

Synthesis of layered double hydroxides/graphene oxide nanocomposite as a novel high-temperature CO_2 adsorbent

In this contribution, a novel high-temperature CO_2 adsorbent consisting of Mg-Al layered double hydroxide （LDH） and graphene oxide （GO） nanosheets was prepared and evaluated. The nanocomposite-type adsorbent was synthesized based on the electrostatically driven self-assembly between positively charged Mg-Al LDH single sheet and negatively charged GO monolayer. The characteristics of this novel adsorbent were investigated using XRD, FE-SEM, HRTEM, FT-IR, BET and TGA. The results showed that both the CO_2 adsorption capacity and the multi- cycle stability of LDH were increased with the addition of GO owing to the enhanced particle dispersion and stabilization. In particular, the absolute CO_2 capture capacity of LDH was increased by more than twice by adding 6.54 wt% GO as support. GO appeared to be especially effective for supporting LDH sheets. Moreover, the CO_2 capture capacity of the adsorbent could be further increased by doping with 15 wt% K_2CO_3. This work demonstrated a new approach for the preparation of LDH-based hybrid-type adsorbents for CO2 capture.

Tuned selectivity and enhanced activity of CO_(2) methanation over Ru catalysts by modified metal-carbonate interfaces

Carbonate-modified metal-support interfaces allow Ru/MnCO_(3) catalyst to exhibit over 99% selectivity,great specific activity and long-term anti-CO poisoning stability in atmospheric CO_(2) methanation.As a contrast,Ru/MnO catalyst with metal-oxide interfaces prefers reverse water-gas shift rather than methanation route,along with a remarkably lower activity and a less than 15% CH_(4) selectivity.The carbonatemodified interfaces are found to stabilize the Ru species and activate CO_(2) and H_(2) molecules.Ru-CO^(4) species are identified as the reaction intermediates steadily formed from CO_(2) dissociation,which show moderate adsorption strength and high reactivity in further hydrogenation to CH_(4),Furthermore,carbonates of Ru/MnCO_(3) are found to be consumed by hydrogenation to form CH_(4) and replenished by exchange with CO_(2),which are in a dynamic equilibrium during the reaction.Modification with surface carbonates is proved as an efficient strategy to endow metal-support interfaces of Ru-based catalysts with unique catalytic functions for selective CO_(2) hydrogenation.

The Chemical Principle of Green Coal Power

Coal is still a major source of energy, also a major source of SO_2, NOx and CO_2 emission though. Removal of SO_2 and NOx doubled the cost of power generation, and capture of CO_2 is equivalent to double the market price of power coal. The GCP （green coal power） is the power generated in coal-combustion with zero emission. The author indicates that it is possible to make coal-fired power plants emission free based on thermodynamic analysis and purposely designed experiments using SFG （simulated flue gases）. It is concluded in the study that all SO_2 and NOx in the post-combustion flue gas are reduced to inoffensive substances at temperature lower than 750 ℃ when contacting carbon and elemental sulfur is separated in succeeded cooling of flue gas at temperatures 200-400 ℃, and the ultrafine dusts are trapped in condensed water at temperature blow 100 ℃. Based on chemical engineering expertise the author is sure that the cost for removing acid gases is much lower than any clean coal technologies known to today. Instead of capture, the remained CO_2 is converted to CO in the second time contact with carbon at 900-950 ℃. CO is the raw material of chemical synthesis and, thus, CO_2 is stored in chemical products such as methanol, fertilizer, plastics, etc. The simple and low-cost processing allows GCP utilized in practice easily.

Ф73.02mm×5.51mm80S油管腐蚀失效原因分析

某油井80S油管在井下5个月开始发生腐蚀现象,并且井下深度越大,油管的腐蚀状况越严重。通过现场调查腐蚀环境,宏观观察样品腐蚀特点,并对样品进行化学成分分析和机械性能测试、电镜观察和分析腐蚀产物等,研究了各种腐蚀介质对80S油管的腐蚀行为,并探究了其外表面腐蚀失效的原因。结果表明,该80S油管所用的1Cr钢种无法抵抗高浓度的CO_(2)与Cl^(-)等多元共存的腐蚀环境,同时,井下高温加速该区域的阳极溶解,从而最终因腐蚀速度过快而发生油管早期失效,并提出减缓油管腐蚀失效的建议。

Synthesis,Structures of 2D Coordination Layers Metal-Organic Frameworks with Highly Selective CO_(2)Uptake

Main observation and conclusion By a strategy of fine-tuning of packing mode between the adjacent layers in a 2D net metal-organic frameworks(MOFs)through ligand changing,two 2D sql-type MOFs with highly selective CO_(2)uptake,CuHIN and CuHPB,were successfully synthesized.Compared with the precursor MOF-2,the fine-tuning structure of CuHIN shows selective adsorption of CO_(2)over N_(2)and CH_(4)with the CO_(2)uptake amounts as high as 4.7 wt%at 0.15 bar and at 298 K,and CO_(2)selectivity towards N_(2)and CH_(4)is 165.8 and 10.22 at 1 bar and at 298 K,respectively.In addition,for the 2D MOFs,the dynamic porous structure depends on the interaction of the adjacent layers.The suitable interaction is good for gliding smoothly and gas adsorption.

利用传感器进行呼吸作用释放CO_(2)的实验教学

以“利用传感器进行呼吸作用释放CO_(2)”实验为例,介绍了KD数字化实验系统的组成、CO_(2)传感器的使用方法以及传感器在其他实验中的应用,充分调动学生学习的积极性,引导其体会科技进步对科学发展的推动作用。

Long-term changes in the tree radial growth and intrinsic water-use efficiency of Chuanxi spruce(Picea likiangensis var.balfouriana) in southwestern China

Elevated CO_(2) level in the atmosphere is expected and intrinsic water-use efficiency(iWUE).Although current found the tree growth decline in water-limited area,it is st to improve the tree growth rates results inferring from tree rings unclear whether spruce trees in humid southwestern China benefit from the increasing 002.In this study,tree-ring width data were used to investigate the tree radial growth rate of Chuanxi spruce(Picea likiangensis var.balfouriana).Moreover,combining with the tree-ring carbon isotope date,we analyzed the physiological responses of Chuanxi spruce to rising CO_(2) concentrations in the atmosphere(C_(a))associated with climatic change in southwestern China.From 1851 to 2009,iWUE of Chuanxi spruce rose by approximately 30.4%,and the ratio of atmospheric CO_(2) to leaf in-tercellular CO_(2) concentration(C_(j)/C_(a))showed no significant trend in the study area.The result suggested that Chuanxi spruce used an active response strategy when C_(a) was significantly increased,iWUE showed a significant increasing trend in parallel with tree radial growth,indicating that the increasing iWUE resulted in an increase in radial growth.These results suggest that spruce forests in southwestern China have not shown declining trends under increasing Ca and climate change scenarios,in contrast to trees growing in water-limited areas.Therefore,spruce forests benefit from the increasing CO_(2) in the atmosphere in the humid areas of southwestern China.

Numerical Investigation on Convective Heat Transfer of Supercritical Carbon Dioxide in a Mini Tube Considering Entrance Effect

There are more and more researches on heat transfer characteristics and prediction of supercritical CO_(2).The method of adding adiabatic section before and after heating section is usually adopted in these researches to ensure that the fluid entering the heating section is no longer affected by boundary layer,but the appropriate length range of adiabatic section and the influence of entrance effect are not discussed.However,some studies show that the entrance effect would affect the heat transfer in mini tubes.This paper uses the commercial CFD code FLUENT 19.0 to numerically study the heat transfer of supercritical CO_(2) in a mini tube under different working conditions(such as Re_(in),P_(in),q_(w) and flow direction)and the lengths of the adiabatic section(l_(as)/d).The entrance effects on heat transfer is more pronounced when Re_(in) is within the transition state and wall heat flux is relatively high,the resulting heat transfer deterioration causes T_(w,x) and h_(w,x) to rise sharply.As the adiabatic section increases,the location at which the heat exchange deteriorates moves to the entrance of the heating section and eventually leaves.The buoyancy effect and flow acceleration effect caused by the sharp change of physical properties are analyzed,and the dimensionless velocity distribution at the inlet of the heating section in different adiabatic sections is compared.It is proved that the entrance effect has an influence on the convection heat transfer of supercritical CO_(2) in mini tubes.The interaction reflected by wall shear stress between boundary layer development and drastic changes in physical properties is the cause of heat transfer deterioration.