Pre-heating temperature induced flowability and wax deposition characteristics of crude oil adding wax inhibitors

This paper investigated the effects of pre-heating treatment temperatures(T_(pre))on the flowability and wax deposition characteristics of a typical waxy crude oil after adding wax inhibitors.It is found that there is little difference in wax precipitation exothermic characteristics of crude oils at different T_(pre),as well as the wax crystal solubility coefficient in the temperature range of 25-30℃.For the undoped crude oil,the flowability after wax precipitation gets much improved and the wax deposition is alleviated as T_(pre)increasing.At T_(pre)=50℃,the viscosity and wax deposition rate of crude oil adding wax inhibitors are higher than those of the undoped crude oil.When the T_(pre)increases to 60,70,and 80℃,the flowability of the doped crude oil are largely improved and the wax deposition is suppressed with the T_(pre)increase,but the wax content of wax deposit increases gradually.It is speculated that,on the one hand,the T_(pre)increase helps the dispersion of asphaltenes into smaller sizes,which facilitates the co-crystallization with paraffin waxes and generates more aggregated wax crystal flocs.This weakens the low-temperature gel structure and increases the solid concentration required for the crosslink to form the wax deposit.On the other hand,the decrease in viscosity increases the diffusion rate of wax molecules and accelerates the aging of wax deposits.The experimental results have important guiding significance for the pipeline transportation of doped crude oils.

特发性黄斑前膜手术前后脉络膜厚度分析

目的:研究特发性黄斑前膜手术前后膜脉络膜厚度的变化及视功能与脉络膜厚度的关系。方法:选取2016-01/2017-12于我院接受手术治疗的特发性黄斑前膜患者30例30眼进行临床研究,排除手术禁忌,采用25G玻璃体切割系统行标准三切口经睫状体平坦部玻璃体切除术联合剥除黄斑前膜及内界膜,观察术前、术后1wk,1、3mo患者的BCVA、黄斑中心凹脉络膜厚度,分析BCVA与脉络膜厚度的相关性。结果:术前的BCVA显著低于术后3mo(P=0.011),术后3mo BCVA与术前BCVA显著相关(r=0.610,P<0.01),术前术后不同时间的脉络膜厚度无差异(P=0.999)。手术前后BCVA与手术前后脉络膜厚度无线性相关关系。结论:特发性黄斑前膜手术前后脉络膜厚度无明显变化,患者视功能与脉络膜厚度也无明显相关性。

High molecular weight guar gum assisted settling of fine solids in diluted bitumen:Effect of solvents

As water-based extraction technologies for producing bitumen from oil sands have received increasing environmental concerns,developing non-aqueous extraction(NAE)technique is of both fundamental and practical importance.However,the relatively high concentration of fine solids trapped in the extracted bitumen presents an obstacle for pipeline transport as well as upgrading and refining downstream.This research attempts to provide a solution to fine solids removal without using synthetic additives or affecting bitumen recovery from NAE process.Herein,naturally hydrophilic additives(i.e.,water and high molecular weight guar gum(HGG)produced from Cyamopsiste tragonolobuosr L.Taup.)were introduced to promote the settling of fine solids suspended in bitumen-solvent solution,and the effects of solvents(i.e.,toluene,cyclohexane and their mixtures)were systematically investigated.Aggregate size distribution analyzed by the focused beam reflectance measurements confirmed that the addition of water and HGG could promote the agglomeration and settling of fine solids in all solvents studied.However,the size range and quantity of the agglomerates vary significantly with the solvent's aromatic character.Solvent mixtures demonstrate a superior performance on removing fine solids from bitumen over single solvent.Specifically,in a 3:2 toluene/cyclohexane mixture,the solid content was lowered from 0.66 wt%to 0.09 wt%.

Self-healing Hydrogelsand Underlying Reversible Intermolecular Interactions

Self-healing hydrogels have attracted growing attention over the past decade due to their biomimetic structure,biocompatibility,as well as enhanced lifespan and reliability,thereby have been widely used in various biomedical,electrical and environmental engineering applications.This feature article has reviewed our recent progress in self-healing hydrogels derived from mussel-inspired interactions,multiple hydrogen-bonding functional groups such as 2-ureido-4[1H]-pyrimidinohe(UPy),dynamic covalent bonds(eg,Schiff base reactions and boronic ester bonds).The underlying molecular basics of these interactions,hydrogel preparation principles,and corresponding performances and applications are introduced.The underlying reversible intermolecular interaction mechanisms in these hydrogels were investigated using nanomechanical techniques such as surface forces apparatus(SFA)and atomic force microscopy(AFM),providing fundamental insights into the self-healing mechanisms of the hydrogels.The remaining challenging issues and perspectives in this rapidly developing research area are also discussed.

Optimization of flow uniformity control device for six-stream continuous casting tundish

For a multistream tundish,the uniformity among the streams plays a significant role in the quality of molten steel.How to analyze the uniformity quantitatively and optimize structures of a multistream tundish is an important research content for a multistream tundish.A new approach was proposed to quantify the uniformity among the streams.And a physical study and a numerical study were carried out to optimize the structure of the diversion hole based on the prototype of a six-stream tundish in a steel plant.On the basis of average residence time,the uniformity of each flow was considered fully and then the optimal structure of the diversion hole was obtained by means of the comprehensive analysis of temperature field and velocity field.The results show that the optimum structural parameters adopted for diversion holes are height of 20 mm,angle of 15°and diameter of 80 mm.