CFD某油田碳质泥岩层钻井坍塌原因分析及对策研究

CFD某油田2h井水平段着陆前钻遇碳质泥岩层发生坍塌,影响钻井时效,为满足该油田后续钻井需求,针对性开展坍塌原因分析和对策研究.综合分析钻井液性能与井壁坍塌的关联性、坍塌掉块的层理结构和黏土矿物组分,确定钻井液密度低、封堵性能和抑制性能不足是碳质泥岩层坍塌的主要因素.从力学对策方面,基于强度各向异性模型建立了井斜与坍塌...     

碳基及碳基复合材料吸附剂对VOCs吸附性能研究进展

针对不同的碳基吸附材料(活性炭、生物质碳、碳纳米管和碳硅复合材料),分别从吸附材料结构参数、有机废气分子性质、水蒸气含量及吸附温度等因素对VOCs吸附性能的影响进行综述.简单介绍了其原理、特点及应用水平,并指出碳基吸附剂结构参数和吸附过程中的操作参数对吸附量的影响,提出了碳基吸附剂在VOCs吸附工艺中的发展前景.在不断...     

A review of effects of silver,lead, sulfide and carbonaceous matter on gold cyanidation and mechanistic interpretation

Despite the wealth of published data on the beneficial or detrimental effects of silver, lead, sulfide, and carbonaceous matter on the rate of gold cyanidation at an anode or by dissolved oxygen, the lack of comparative studies on relative effects has hampered rationalisation of the role of these activators or passivators of gold. In the present study, the published rate data per unit surface area of gold, silver, and gold–silver alloys based on electrochemical or chemical dissolution of rotating discs or foils of constant surface area in aerated cyanide solutions at ambient temperatures are analysed on the basis of the Levich equation. The current status of the reaction mechanism is also reviewed and updated on the basis of species distribution and potential–pH diagrams, stoichiometric factors, and interim chemical species of gold(I), silver(I), and lead(II). The anodic peak potentials of reported voltammograms closely follow the potential–pH lines of Au(I)/Au(0) and Pb(II)/Pb(0) couples. Despite the formation of stable complexes between lead(II), nitrate, and hydroxide ions, the total calculated soluble lead(II) in alkaline solutions of pH range 10–11 saturated with lead hydroxide is shown to be < 0.1 g/m³. A comparison of the reported diffusion coefficients of cyanide ions and dissolved oxygen with the values based on the Levich plots of reported rates reveals the rate-controlling stoichiometric M/CN or M/O₂ molar ratios. The difference between some of these ratios and the generally accepted ratios of M/CN = 1/2 and M/O₂ = 1/0.5 or 1/0.25 based on the formation of M(CN)₂⁻, H₂O₂ or OH⁻ in the overall cyanidation reaction is attributed to the oxidation of cyanide to cyanate and passivation due to the formation of gold hydroxides/oxides. The alloyed or dissolved silver and lead eliminate passivation due to the involvement of mixed hydroxo–cyano complexes of silver and lead ions in the surface reaction. Gold dissolution by oxygen in cyanide-rich solutions is limited by oxygen diffusion, but enhanced by the presence of a low concentration of sodium sulfide due to the involvement of hydrosulfide ion in the surface reaction. However, excess lead or sulfide retards gold cyanidation due to surface blockage by metallic lead, lead hydroxide, or due to passivation by Au₂S/S. Even low concentrations of hydrosulfide passivate gold–silver alloys due to the formation of Ag₂S. This can be eliminated by adding stoichiometric quantities of lead(II) to precipitate sulfide as PbS. Large stoichiometric ratios of O₂/M for the cyanidation of graphite coated gold appears to be a result of the enhanced oxidation of cyanide by oxygen or hydrogen peroxide, leading to a cyanide deficiency at the surface and passivation of gold by hydroxide/oxide. The presence of excess cyanide or lead(II) does not override this effect.     

Influence of carbonaceous materials on the interactions among (Al2O3-C)/Fe system with temperature and soaking time

It has practical significance for improving the service life of Al₂O₃-C refractories and reducing its influence on steel quality to reveal the reaction mechanism among (Al₂O₃-C)/Fe system under high temperature. The influence of carbonaceous materials on the interactions among (Al₂O₃-C)/Fe system with temperature and soaking time were studied using thermalgravity method in this paper in order to get a better understanding on the reaction mechanism among (Al₂O₃-C)/Fe system. The weight loss of (Al₂O₃-C)/Fe samples and the formation of Al₂O₃ crystal whiskers along with the change of aluminium and carbon content in iron indicates the mechanism of the effects of carbonaceous materials on the reactions among (Al₂O₃-C)/Fe system under high temperature. The result showed that the aluminium pickup of iron was not only due to the dissolution of Al₂O₃ in molten iron but mostly due to the carbothermic reduction of Al₂O₃ and carbonaceous materials in the presence of molten iron.     

Hydrogen by glycerol steam reforming on a nickel–alumina catalyst: Deactivation processes and regeneration

Hydrogen energy has attracted considerable attention because of its efficiency and environmental benefits, and the increasing demand requires finding renewable sources of raw materials to produce it. Glycerol, by-product of biodiesel production and coming from renewable raw materials, could be a bio-renewable substrate to produce hydrogen. The glycerol steam reforming to obtain hydrogen was evaluated using a 5.1 wt% Ni impregnated on Al₂O₃ catalyst, characterized by nitrogen adsorption, XRD, and FTIR. Deactivation processes were analyzed in successive cycles of reaction at 700 °C, atmospheric pressure, 5 h⁻¹ WHSV, and 3:1 water:glycerol molar ratio, during 12 h. Between reaction cycles, regenerating took place using a He/Air stream. Hydrogen was the main product on the fresh catalyst, following by CO and CH₄; during reaction, carbonaceous deposits deactivated catalyst, decreasing H₂ and increasing both CO and CH₄. Carbonaceous deposits were characterized by TPO, showing a main peak centered at 690 °C; the carbon content reached 11.9%.     

Carbon support hydrogenation in Pd/C catalysts during reductive thermal treatment

The resistance of the Pd/C samples towards hydrogenation of the carbon support was studied in the temperature-programmed and isothermal regimes. Carbonaceous graphite-like material Sibunit was used as a carbon support. Pristine Sibunit was additionally graphitized via high temperature treatment (1900 °C) in an inert atmosphere. Both initial and graphitized supports were subjected to oxidative treatment in order to increase the amount of surface functional oxygen-containing groups. Palladium (1 wt%) was supported using an aqueous solution of H₂PdCl₄. All the samples were characterized by a low-temperature adsorption of nitrogen, transmission electron microscopy, and Raman spectroscopy. The graphitization procedure was found to decrease significantly the specific surface area of the support, while the oxidative treatment affects this parameter negligibly. Testing the Pd-containing samples in a hydrogen flow revealed the following order in accordance with amount of methane released: Pd/iSib » Pd/iSib-ox > Pd/gSib > Pd/gSib-ox.     

液态高铅渣直接还原试验研究

以豫光氧气底吹炉所产高铅渣为原料,配入碳质还原剂,在高温熔融态下还原高铅渣中的铅,并对还原过程进行了系统研究。结果表明,最佳还原条件为:还原温度1 150℃、还原时间1 h、还原剂率3.5%。在上述条件下,高铅渣还原进行得较彻底,渣含铅可降到3%左右。     

多晶硅中杂质元素B、P的来源分析

为达到太阳能级多晶硅产品的要求,去除杂质元素B、P,以多晶硅生产为例,分析了各环节脱除B、P的效果,以及采用矿热炉生产工业硅过程中B、P的来源和去向。结果表明,工业硅生产过程中消耗的炭素材料是B、P的主要来源;选用低B、P的优质还原剂和经过处理的炭素电极,才能保证工业硅产品,满足后续多晶硅提纯工艺的要求。     

Effect of surface carbon on the hydrogen evolution reactivity of tungsten carbide (WC) and Pt-modified WC electrocatalysts

Tungsten carbide (WC) has been previously identified as both an electrocatalyst and a support for several types of electrochemical reactions. The synthesis of WC often leads to excess surface carbon that can greatly affect its electrocatalytic activity. This work will evaluate the effect of surface carbon on WC both as a catalyst and as a support for monolayer (ML) amounts of platinum (Pt). WC thin films with no surface carbon, along with those with 1, 2, 3, or 4 equivalent ML of surface carbon, were synthesized. The hydrogen evolution reaction (HER) activity was used as a probe to test the effect of surface carbon on the electrochemical activity of WC and 1 ML Pt on WC (Pt/WC) using linear sweep voltammogram (LSV) in 0.5 M sulfuric acid. The HER activity of WC was relatively unaffected for very small amounts of surface carbon but decreased when several MLs or more of surface carbon was present. Pt/WC without surface carbon was found to have slightly higher HER activity as compared to Pt deposited on WC with surface carbon.     

Synthesis of confinement structure of Sn/C-C (MWCNTs) composite anode materials for lithium ion battery by carbothermal reduction

A composite anode material was prepared with confined tin into multiwall carbon nanotube by carbothermal reduction. The morphology and structure of Sn/C (nature graphite) and Sn/C-C (nature graphite + multiwall carbon nanotube) were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). It was revealed that the additive of MWCNT was a crucial factor to improve Sn /C composite anodes for cyclability and reversible capacity. Volume changes and morphological changes in Sn can be reduced by encasing MWCNT in a carbonaceous material that has sufficient flexibility to act as a buffer. Electrochemical performance test shows that the charge capacity of the Sn/C-C (NG + MWCNT) electrode in the fiftieth cycle was 400 mAh/g, which was higher than that of the Sn/C (NG) electrode. After 50 cycles, the retention of the Sn/C-C electrode and the Sn/C electrode was 80% and 63%, respectively.