A Simplified Model for the Prediction of the Erosion of a Metal Screen for Sand Control

In oil drilling processes,sand production in the oil layer is a common issue,generally mitigated by means of sand control screens.To prevent or reduce the risk of damage of these screens and to improve the related service life,it is necessary to investigate the related erosion dynamics.In this study,a screen mesh model based on the flow field similarity theory is proposed to overcome the otherwise too complex geometric structure of this type of equipment.Such model is optimized using experimental data.The predicted results are in good agreement with the measured values,and the error is less than 15%.The results also show that the simplified geometric screen model and the optimized Zhang et al.erosion model have high reliability;therefore,they could effective be used to select underground screen meshes and improve the design of production process.

Removal of heavy metals through adsorption using sand

The removal of four heavy metals i.e. Pb, Cr, Cu, and Zn from their aqueous solutions, using ordinary sand as an adsorbent, was studied at 20℃. The amount of metal adsorbed to form monolayer on sand(a_m), obtained from Langmuir isotherm, exhibited the preference of metals for sand in the order Pb>Cr>Cu>Zn. The heavy metal-sand adsorption phenomena can be illustrated on the basis of the interaction between surface functional group of silicates (sand) and the metal ions. It is deduced that sand can be used as a low cost adsorbent for the removal of heavy metal from wastewater (containing low conc. of metals), especially in the developing countries.

低品位脉石英热压浸出工艺动力学研究

为解决低品位脉石英中杂质元素含量高的问题,采用湖北蕲春灵虬山脉石英为原料,研究了液固比、反应时间和反应温度对杂质去除效果的影响。结果表明,经过热压浸出工艺提纯后,石英砂SiO_(2)含量(质量分数,下同)由97.766%增至99.974%,主要金属元素杂质的去除率显著提高。阿弗拉米动力模型表明,杂质去除过程受内扩散和化学反应共同控制。研究结果为优化脉石英的提纯工艺提供了理论依据和实践指导。

复杂内腔铝合金件液态模锻试验研究

目的为拓宽液态模锻技术的应用范围,实现具有复杂内腔结构件的高性能短流程成形制造,开展了使用砂芯的液态模锻技术试验研究。方法以具有复杂内腔的新能源汽车铝合金空气弹簧顶座为对象,利用广州和德装备制造公司生产的卧式液态模锻机,对比研究不同砂芯、涂料及液锻加压制度对黏砂缺陷的影响作用。结果普通砂芯在液锻中容易被压溃或产生黏砂缺陷;在苏铸砂芯的基础上自行配制HDSC01液锻砂芯,配合HDCoating03专用涂料,采用阶梯加压方法进行液态模锻,所得液锻件内表面光洁无黏砂、尺寸精确。结论液态模锻可以使用砂芯进行复杂内腔结构件的高性能精密成形,但工艺控制不当,容易出现黏砂缺陷。阶梯加压、使用专用砂芯和专用涂料是防止黏砂的有效途径。

重型商用车平衡轴支架铁型覆砂铸造工艺设计与优化

以某重型商用车平衡轴支架为研究对象,根据平衡轴支架的结构特点与质量要求,初步设计了平衡轴支架的铁型覆砂铸造工艺方案并进行样件试制。样件剖切结果发现在平衡轴根部厚大区域出现了较为严重的缩孔缩松缺陷。利用AnyCasting软件对平衡轴支架铸件的充型与凝固过程进行模拟仿真,仿真结果预测的铸件缩孔缩松位置与实际情况相一致。基于平衡轴支架充型与凝固过程及铸件缺陷产生原因的分析,对初始铸造工艺方案进行优化。优化后的仿真结果显示平衡轴支架铸件的缩孔缩松缺陷已基本消除。根据优化后的铸造工艺方案再次进行样件试制,样件剖切结果表明原平衡轴根部厚大区域的缩孔缩松缺陷已完全消除,平衡轴支架铸件内部质量满足要求。

回转体类铝合金“金属型+砂型”“双型”重力铸造成型工艺开发

针对公司铝合金铸件重力铸造工艺研制存在的诸多问题,以及公司现阶段树脂型(芯)砂尚未具备旧砂再生的现状,并结合机加工序对铝合金表面质量提升的要求,借鉴行业内铝合金金属型铸造的经验,开发了适用于回转体形状特征的“金属型+砂型”“双型”铝合金铸件重力铸造成型工艺,该工艺不仅大幅度降低了回转体类铝合金铸件的铝砂比,而且也明显地提升了铸件质量和生产效率,该创新工艺是公司在现阶段条件下回转体类铝合金铸件重力铸造工艺研制和批产的最佳途径。

铁型覆砂铸造工艺在轨道交通电机机座类铸件上的应用

分析电机机座类铸件结构特点与技术要求,选其中一种电机机座铸件为例,根据铁型覆砂工艺特点确定半封闭式浇注系统,分析该铸件铁型覆砂工艺设计及砂芯设计要点,采用有限元软件对铁型覆砂铸造工艺方案进行验证及优化,经生产实践表明,该电机机座铸件铁型覆砂铸造工艺方案可行,铁砂比为1∶6,工艺出品率为90.8%,产品合格率为95%。经济效率显著,已实现批量生产。

铁型覆砂灰铸铁件氮气孔缺陷分析与改善措施

针对铁型覆砂铸造工艺生产灰铸铁件时产生的氮气孔缺陷,通过使用EDS能谱仪对氮气孔缺陷进行定性和定量分析,并结合铸件生产工艺对氮气孔的形成原因进行分析,通过在原材料上更换覆膜砂、提高新砂加入量、分开管理壳型线和铁型线回用砂,生产工艺上采取增加排气塞和提高铁型温度、固化时间、浇注温度等措施降低缺陷风险。改进后的工艺连续生产超过10万件产品,未再出现氮气孔缺陷。

Experimental confirmation of physical metal penetration generation and press casting production considering molten metal's pressure control

This paper presents a technique for controlling the pressure of a molten metal when using a new type of iron casting method called sand mold press casting to realize high productivity and obtain high-quality products.The past test results using this method showed a casting yield of 90% to 95%,while conventional methods only show a casting yield of 60% to 70%.Although the press casting method does not require a sprue cup or runner channel casting defects such as metal penetration are often caused by the high pressure in the high-velocity pressing part of this casting process.Therefore,we proposed a pressure control method with a mathematical model of molten metal pressure,and with it we achieved experimental confirmation of the successful production of brake drums at different pressing temperatures.Results show that the proposed pressing control method can realize sound,penetration-free casting production.However,the theoretical analysis and design of this pressing process had not previously been studied sufficiently,and therefore this paper presents the theoretical design algorithm for the process as well as its experimental confirmation.

Recycling of waste foundry sands by chemical washing method

This study aims to remove the metals(inorganic and heavy metals) in waste foundry sand(WFS)via chemical washing method. Washed waste foundry sand(WWFS) samples were obtained by using triptych washing successively with 5 M HCl, 5 M H_2SO_4 and 5 M NaOH solutions. Analysis on functional groups,micropores, heavy metals,and inorganic components of WFS and WWFS was carried out by using FT-IR, SEM and XRF. Results show that the concentration values of some inorganic components such as Ca, Fe, Mg, S were decreased, and the maximum removal percentage of these inorganic components are 47%, 19%, 32%, and 8%,respectively. The concentration values for each of the heavy metals of WWFS are below of limit values given in App-3 List of Regulation on General Principles of Waste Management. The removal percentages of Pb, As and Zn elements are 100%, 71%, and 40%, respectively. The findings of this research suggest that WWFS can be used in more applications due to its ability to remove heavy metals and some other inorganic components.

防砂管金属丝编织过滤网堵塞-冲蚀破坏微观损伤机理研究

为了探明防砂管金属丝编织过滤网在防砂生产过程中的破坏机理,采用全尺寸防砂筛管冲蚀模拟装置,实验研究了一定含砂浓度条件下生产压差对筛网堵塞-冲蚀破坏的影响规律和微观损伤机制。结果表明:生产压差越大筛网防砂失效的时间越短,防砂失效时的筛网质量损失百分比临界值为0.45%,超过该临界值后挡砂失效;筛网多数过流孔被砂粒堵塞,导致含砂流体过流速度分布不均,造成筛网局部冲蚀破坏,形成破坏“热点”;SEM/EDS微观分析发现,编织网金属丝迎流外表面并未发生明显冲蚀损伤,而金属丝泄流面冲蚀损伤严重,认为堵塞滞留在编织网孔处的砂粒在流体压差的作用下会以较高的动能和一定的角度弹射撞击到编织网泄流面邻近金属丝隆起阻挡高速砂粒流动的区域、造成金属丝磨损、切削损伤,建议通过控制生产压差来降低编织网泄流侧的冲蚀程度,通过改变编织孔网三维结构来改善筛网的抗冲蚀破坏能力。本文研究结果对防砂筛管冲蚀破坏原因分析和长效防砂筛管设计有一定指导意义。

Diversity and Chemical Composition of Weeds in Sand-Filled Mangrove Forest at Eagle Island, Niger Delta, Nigeria

Mangroves are habitat specific and grow mainly in swampy soil, but due to anthropogenic activities (e.g. sand mining) other species had encroached into their habitat. It is thus hypothesized that change in species diversity will lead to change in soil chemistry. In a 40 m × 90 m plot, diversity index (H) and importance value (Iv) of weed were estimated. Soil and weed samples were collected and analyzed for total hydrocarbon content (THC), Zinc (Zn), Lead (Pb) and Cadmium (Cd). All samples were analyzed with atomic absorption spectrophotometric method using the HACH DR 890 calorimeter (wavelength 420 nm). The result shows that swampy soils were more acidic (3.1 - 3.5) than sandy soils (4.2 - 4.7). Swampy soil was also more saline and thus has higher conductivity (8320 - 9880 μS/cm) than sandy soil (4320 - 5650 μS/cm). Mangrove swamp had higher total organic carbon (TOC) (2.25% - 3.41%) than sandy soil (0.12% - 0.21%). There was a significant difference in THC and heavy metals in soil (F8,63 = 2.04, P < 0.05), but there was no significant difference in THC and heavy metals in plant species (F8,63 = 247.0, P > 0.05). Concentration of THC and heavy metal was higher in plant than in soil. Reissantia indica, an aquatic weed, had the highest concentration of THC in root soil. A total of fifteen (15) weed species were identified, out of which Mariscus longibracteatus had the highest diversity (-0.366) followed by Mariscus ligularis (-0.339) and Paspalum vaginatum (-0.270). Similarly, M. longibracteatus had the highest importance value in the study site (Iv = 58.24). This result implies that the presence of weed species in mangrove forest is an indicator of human disturbance of the ecosystem. It also means that the weeds were bioaccumulating THC and heavy metals present in the soil.

Comparative Study of Gold Concentration by Elutriation from Different Precious Metal Bearing Ores

Conventional methods for precious metals gravimetric concentration involve equipment such as shaking tables, centrifuging concentrators, jigs, trommels, or a combination of those. A less commonly used technique is elutriation, which represents an efficient, safe and low-cost method of separation. The goal of the present investigation was to make a comparative study of gold concentration by elutriation from different precious metal bearing ores: an oxide ore, a mineral consisting of a sulfide matrix, a mineral in which the precious metals are free and disseminated and a slimy and clayey black sand material. The best recoveries of precious metals by elutriation were attained for the free disseminated ore and for the black sands, obtaining gold recoveries of 70% and 96% respectively, with appreciable ratios of concentration as well.

离心铸造原理分类及应用

离心铸造按回转轴方向分为立式离心铸造和卧式离心铸造,按使用模具分为模具离心铸造、砂型离心铸造及特种型离心铸造等。该文对不同类型离心铸造原理及其特点与不足进行分析,探究铸造过程中的缺陷及应对方法,确保离心铸造技术可以更加稳定的使用。

白云岩砂改良煤矸石基质对黑麦草生长及重金属淋溶影响

煤矸石是煤炭生产过程中产生的固体废弃物。植被恢复是减少煤矸石堆场重金属淋溶迁移的主要途径,而露天煤矸石基质改良是植被恢复的基础。通过盆栽和野外堆场小区黑麦草种植试验以及淋溶试验,探究白云岩砂改良煤矸石基质对黑麦草生长和重金属淋溶的调控效应。结果表明:在添加10%~30%白云岩砂的煤矸石基质上黑麦草的地上部生物量和叶绿素含量均出现显著的增加,黑麦草植株对氮和磷的吸收量也明显的增加。同时,添加10%~30%白云岩砂的煤矸石基质中有效态Mn、Cd和Zn质量分数均出现显著性降低,且煤矸石基质渗透水中Fe、Mn、Cd和Zn质量分数也出现显著性的下降;特别是煤矸石中添加20%~30%白云岩砂时,煤矸石基质中有效态Fe和Mn质量分数及其渗透水Fe和Mn质量浓度均出现明显的降低。在煤矸石中添加适量白云岩砂有利于降低煤矸石基质中重金属的生物有效性和水溶态重金属的质量浓度,从而明显减少煤矸石基质中Fe、Mn淋溶迁移对水环境质量的影响。

半咸水宁夏沙湖沉积物中重金属的分布特征、潜在生态风险及来源解析

为揭示和明确半咸水湖泊湿地的重金属污染状况,以宁夏沙湖为例,于2018年4月(春)、7月(夏)、10月(秋)、2019年1月(冬),对沙湖湿地9个采样点沉积物中有机质(OM)、总氮(TN)、总磷(TP)、硝态氮(NO_(3)^(−)-N)、全盐和6种对环境影响较大的有毒有害重金属(As、Pb、Hg、Cd、Cr、Cu)的含量进行了定量分析并运用多种手段进行风险评估.结果表明,人类活动密集区(湖心、鸟岛和2号桥)沉积物中OM和营养盐含量高于其他区域.全盐含量在夏季最高,冬季最低;OM、TN和TP含量在夏季最高,春季最低;NO_(3)^(−)-N含量在秋季含量最高,冬季最低.宁夏沙湖沉积物中As、Pb、Hg、Cd、Cr、Cu含量分别在8.83—13.55 mg·kg^(−1),16.61—21.71 mg·kg^(−1),0.02—0.08 mg·kg^(−1),0.02—0.46 mg·kg^(−1),51.16—66.54 mg·kg^(−1),14.67—24.42 mg·kg^(−1)之间,其中Pb和Cd含量均超过背景值.6种重金属单因子污染指数均小于1,地累积指数(Igeo)均小于0,表明宁夏沙湖沉积物质量状况良好,其中Cr、As和Pb单因子污染指数和Igeo指数较大,空间分布为假日酒店、湖心相对较高,需在今后监测工作中重点关注.潜在重金属生态风险为中等污染,仅Hg和Cd出现强和中等的生态危害程度,表明宁夏沙湖沉积物重金属生态风险主要由Hg和Cd造成,生态风险较高的区域主要位于假日酒店、湖心等区域.相关性分析和主成分分析揭示Pb、Cd、Cr、Cu、OM、TN、TP具有相似的污染来源,主要来源是人为来源和自然来源.本研究将为半咸水湖泊重金属污染状况及潜在生态风险提供数据支撑,也将为水环境污染防控提供科学依据.

组合铸造工艺在生产中的应用

对磁选机轴承端盖砂型铸造生产中产生的气孔缺陷类型、形成机理进行了分析,使用金属型-砂型组合铸造工艺方案并进行工艺设计。生产实践证明,改进后的铸造工艺不但明显改善了气孔质量缺陷,而且使产品合格率及生产效率都得到极大提高。

铁型覆砂球墨铸铁曲轴冷隔缺陷的工艺改进

针对铁型覆砂曲轴下箱冷隔缺陷进行了分析,认为铁液浇注温度低、浇注速度慢、浇注时断流、浇注系统设计不合理等是形成冷隔缺陷的原因。通过设计浇注包“U”型浇包嘴,包衬改用保温材料,改进浇口杯与浇口窝形状,减少球化剂、孕育剂的加入量,提高浇注温度等措施减少缺陷。改进后铸件冷隔废品率由0.27%降低到0.1%以下。

多孔隙金属筛管热采防砂性能评价试验研究

多孔隙金属筛管主体挡砂层采用抗高温、耐腐蚀性能优良的金属研制而成,因其特殊的三维立体孔隙结构,筛管具有较强的通透性和过流能力,目前在常规冷采开发油气田适用性良好。为进一步评价筛管在稠油热采条件下的适应性,开展了多轮次蒸汽吞吐防砂模拟试验,模拟筛管在经过多轮次蒸汽吞吐过程中的防砂效果变化情况,分析在多轮次注采过程中筛管内外的压力、温度、出砂量和出砂粒径的变化规律。试验结果表明,经过16个轮次的高温蒸汽吞吐(蒸汽温度350℃、注入压力17 MPa)试验,筛管出砂质量分数在1.86×10^(-7)%~6.63×10^(-6)%之间,出砂粒径中值略小于筛管挡砂精度,渗透率保持能力在85.7%左右,筛管整体过流能力和抗堵塞性能保持率良好。试验结果充分证明了筛管在稠油热采油藏开发方面具有良好的防砂效果和过流性能,可为稠油热采工况下油气田防砂完井提供技术参考。