Feasibility of measuring moisture content of green sand by a low frequency multiprobe detector based on dielectric characteristics

Green sand is a mixture of silica sand,bentonite,water and coal powder,and other additives.Moisture content is an important index to characterize the properties of green sand.Based on the dielectric characteristics of green sand and transmission line theory,a method for rapidly measuring the moisture content of green sand by means of a low frequency multiprobe detector was proposed.A system was constructed,where six detectors with different arrangements and probes were designed.The experimental results showed that the voltage difference of transmission line increases with the increasing frequency before 29 MHz while decreases after 35 MHz.A voltage difference platform occurs in the range of 29-35 MHz,which is suitable for measuring the moisture content due to its insensitivity to frequency.The electric field intensity gradually decreases with the increase of the probe depth,and the intensity of central probe is always greater than that of the edge probe.When the distance of the probe away from the sand sample surface is 80 mm,the electric field intensity of the edge probe is found to be very weak.The optimal excitation frequency for measuring the moisture content of green sand is 29-33 MHz.The optimal detector is the one with one center probe and three edge probes,and their lengths are 80 mm and 60 mm,respectively.The distance between the center and edge probes is 25 mm,and the diameter of probes is 5 mm.Taking the voltage difference of transmission line,bentonite content,coal powder content and compactability as parameters of the input layer,and the moisture content as a parameter of the output layer,a three-layer BP artificial neural network model for predicting the moisture content of green sand was constructed according to the experimental results at 33 MHz.The prediction error of the model is not higher than 3.3% when the moisture content of green sand is within the range of 3wt.%-7wt.%.

Optimization of green sand mould system using Taguchi based grey relational analysis

The strength of the mould cavity in sand casting is very much significant to attain high-quality castings. Optimization of green sand process parameters plays a vital role in minimizing casting defects. In the present research work, the effect of process parameters such as AFS grain fineness number, water, molasses, bentonite, fly ash, and ramming, and their levels on the resultant mould properties were investigated and optimized using Taguchi based grey relational analysis. The Taguchi L18 orthogonal array and analysis of variance(ANOVA) were used. The quality characteristics viz., green compression strength, permeability, bulk density, mould hardness and shatter index of green sand mould were optimized using grey relational grade, based on the experiments designed using Taguchi's Design of Experiments. ANOVA analysis indicated that water content is the most influential parameter followed by bentonite, and degree of ramming that contributes to the quality characteristics. The results are confirmed by calculating confidence intervals, which lies within the interval limits. Finally, microstructure observations and X-ray diffraction analysis have been performed for the optimal sand parametric combination. Results show that presence of maximum amount of SiO_2, which might be the reason for enhancement of the physical properties of the sand.

TECHNIQUES ABOUT DIRECT OPTIMIZING CONTROL OF GREEN SAND QUALITY

Green sand casting is still a main method in the world at present and it isvery significant to develop the technology of controlling green sand quality. A new concept, fromcontents test to contents control, is advanced. In order to realize the new idea, a new method toon-line test active clay and moisture of green sand - double powers energizing alternately (DPEA)method is put forwards. The principle of the new method is to energize standard sand sample with ACand DC powers and to test the electric parameters, and then, to calculate active clay and moistureof green sand by using artificial neural network (ANN). Based on this new method, a directoptimizing system for controlling green sand quality is developed. Techniques about testing andcontrolling methods, hardware and software are discussed.

The Study of Green Compression Strength of a Green Sand Mould Using Statistical Approach

The study of green compression strength of a green sand mould using statistical approach has been undertaken. Empirically generated data in National Metallurgical Development Centre, Jos Sand Testing Laboratory were used for the study. Coefficient of correlation, coefficients of determination and coefficient of multiple determinations were used to explain the relationship existing between the two independent variables of clay and moisture content and green compression strength, the dependent variable. The study showed that the coefficient of determination for Ys: X1 was 0.88 while the coefficient of correlation was 0.94, coefficient of determination for Ys: X2 was 0.90 while the coefficient of correlation was 0.95 and the coefficient of multiple determination was 0.72;these coefficients assisted tremendously in the study of green compression strength. A mathematical model was developed for the prediction of green compression strength;it was tested and proved to be a good estimation tool for estimating green compression strength values on the foundry shop floor. The study has clearly shown that statistical approach is a good tool for studying green compression strength of green sand moulds.

Nonlinear Constitutive Equation for Green Sand Considering the Tri-axial Compression Behavior

The compression characteristics of green sand were investigated experimentally, including the squeezing and yielding during deformation. An expression was developed for the transient compression modulus of sand during compression. Based on the hypothesis put forward of the compression state, the differential equation for the nonlinear constitutive equation was deduced by introducing a move-yield poten- tial function. The state constitutive equation under the tri-axial experiment is further studied according to the sand attributes, considering the differential form of Hooke’s law and the Mohr-Coulomb condition. The re- lated experiment data are applied to verify the proposed constitutive model of sand.

Defect elimination in green sand casting using simulation techniques:A case study

The Reynolds number of molten metal flowing mold cavity causes bulk turbulence and is the main cause of defects like shrinkage porosity and sand erosion.Machined housings with shrinkage porosity at critical bearing bores and surface made the casting useless.In old gating casting areas of perimeters 290mm and 264mm of transmission housing,Reynolds numbers were observed as 16307 and 13806,respectively using simulation software.Data were collected from experiments to change casting area perimeters from 785mm and 785mm along with the addition of overlap area.New Reynolds numbers at two locations were observed as 3705 and 3393,respectively.Molten metal pressure,velocity and temperature results were related for final shrinkage results of the components on full production.The purpose of the study is to reduce shrinkage and porosity defects in green sand casting part using MAGMAS simulation software.High outcome was the reduction of casting machining rejection in transmission housing casting from 5.8%0.7%with savings of approximately 0.13 million USD over the period of 14 months.Implications of this work include casting defects study and reduction in different grades and weight range.

Shrinkage Behaviour of Spheroidal Graphite Cast Iron in Green and Dry Sand Molds for the Benchmarking of Solidification Simulation

The effects of metallurgical and processing parameters on the formation of shrinkage cavities and porosities in spheroidal graphite cast iron have been studied, considering the parameters of carbon equivalent, inoculation, casting modulus, mold type (green or dry) and pouring temperature within specific ranges of these variables. Based on the orthogonal experiments, the metallurgical and processing parameters of the minimum casting shrinkage and the maximum casting shrinkage were obtained, and the effects of metallurgical and processing parameters on the formation of shrinkage cavities and porosities in spheroids graphite cast iron castings were discussed. Finally, two regression equations relating these variables to the formation of shrinkage porosity were derived based upon the orthogonal experiments conducted.

湿型粘土砂多参数集成检测方法与便携式检测装置开发

型砂质量是影响铸件质量的重要因素之一,型砂性能参数便携式检测装置尤其是多参数便携检测装置对于铸型质量控制具有重要作用。本文研制了一种基于单片机测试与控制的,可实现湿型粘土砂紧实率、含水量、透气性和湿压强度生产现场同步检测的便携检测装置。文中介绍了仪器工作原理、硬件组成、软件设计和实测结果。便携式检测装置与标准检测方法检测结果对比的相对误差为紧实率0.60%、含水量2.12%、透气性1.87%、湿压强度1.61%,检测时间小于2 min,证明便携式检测装置具有较高的测试精度和工作稳定性。

有机物对铸造粘土废旧砂再生质量的影响研究

铸造粘土废旧砂通常采用高温焙烧结合机械摩擦方法进行再生回用,为了得到高质量的再生砂,废旧砂再生过程中要求焙烧温度相对精确和稳定,但粘土废旧砂中存在的煤粉及有机树脂砂壳芯混入的有机物使焙烧温度出现巨大波动,特别是细颗粒废旧砂中的有机物,影响再生砂质量和再生效率。本文首先将粘土废旧砂进行100目筛分分级,研究100目筛上和100目筛下两种粒级废旧砂中有机物对燃烧速率的影响,然后确立废旧砂中有机物燃值贡献的计算公式,并通过实际生产测试,获得有机物燃值贡献阀值和废旧砂的再生最优投入量,为粘土废旧砂的高效率和高质量再生提供理论参考。

水分加入量对粘土湿型砂性能的影响

介绍了在混砂过程中水分对湿型粘土砂性能影响的试验方法:(1)通过采用不同含水量的回用砂,研究回用砂水分对型砂性能的影响;(2)通过采用不同的混砂水分加入量方案,研究水分加入量对型砂性能的影响。结果表明:(1)型砂各性能均随回用砂水分和混砂时间的不同而变化,也会随着混砂时水分加入量的不同而改变;(2)使用水分在1.8%的回用砂进行混砂,各性能指标达到峰值所需的混砂时间最短,混砂消耗的动能最少,混砂效率更高,更利于组织流水线生产。

致密气试油期间天然气回收工艺在川西北部文兴气区的应用及评价

川西北部文兴气区沙溪庙组气藏是典型的致密砂岩气藏,酸化和加砂压裂对提高气藏采收率具有良好效果,注入地层的酸化液和压裂支撑剂在试油期间与原料气混合,通常在试油排采阶段返排回地面直接点火燃烧,资源浪费的同时也有环境伤害的风险。针对传统排采方式在经济环保上的弊端,设计并应用“双分离+双除砂+多级节流+超音速脱水脱烃”放喷天然气回收工艺。该工艺在川西北部文兴气区应用效果表明,采用油管特殊丝扣替代传统钢管焊接,设备安装周期可缩短70%;工艺组合针对排采初期复杂地层返排物除砂、分离效果良好,脱水脱烃后气质达标从而实现成功回收;该放喷天然气回收设备设施能耗较低,是绿色低碳清洁效益开发的重要举措。该工艺在现区块应用过程中取得了较好的经济和社会效益,展现出了较好的推广应用价值。

混合湿型旧砂再生技术现状与展望

实现绿色铸造、清洁生产是当今铸造技术发展及研究的必然趋势。目前,环保要求日趋严格,铸造旧砂再生回用已得到业界的广泛认同与应用。介绍了几种典型湿型砂与树脂砂、无机砂混合砂的再生技术,指出了湿型砂混合砂再生技术的发展方向,提出了一些建议。

夹砂层土壤Green-Ampt入渗模型的改进与验证

对于土层夹砂结构,湿润锋穿过砂层上界面时,入渗率变为稳渗率。为确定各因素下夹砂层土壤的稳渗率,在Green-Ampt入渗模型基础上,引入导水度系数(小于1)来量化上层土壤的导水程度,建立了改进的夹砂层土壤Green-Ampt入渗模型。采用HYDRUS-1D软件,模拟了不同土壤质地、初始含水率、压力水头、砂层埋深和砂层厚度条件下的稳渗过程,根据模拟结果分析了夹砂层土壤的入渗规律及其影响因素,稳渗率主要受土壤质地、压力水头和砂层埋深的影响。在相同压力水头、初始含水率和砂层厚度下模拟获得不同砂层埋深的稳渗率,并采用改进的Green-Ampt入渗模型拟合,求得导水度系数和进水吸力值。分析发现导水度系数变化较小,为简化计算,取其平均值0.95。在此基础上,提出了由土壤物理特性参数进气值倒数估算进水吸力的计算公式。利用秦王川地区的夹砂层土壤积水入渗试验及已有文献资料验证所建模型的有效性,结果表明所建模型待定参数少,计算误差基本在5%以内,且试验设计较简单,可为农田水分管理及工程防渗技术提供理论依据。

抽水蓄能电站绿色施工技术

抽水蓄能电站建设发展迅猛,但在工程施工过程中存在高投入、高消耗、高污染、低效率等现象,迫切需采取措施推进绿色施工。为此,基于绿色施工的核心理念,介绍了近年来抽水蓄能电站绿色施工技术,包括抽水蓄能电站新坝型、绿色输水隧洞施工技术、绿色混凝土制备技术、绿色砂石加工技术、边坡生态修复技术、二氧化碳爆破技术及施工车辆电气化等,取得了良好效果。

混凝土废水处理系统的设计与应用

介绍了混凝土企业为了实现绿色生产,设计出一套废水处理系统,达到废水废浆零排放。该系统采用了一系列的物理处理技术,包括废水通过砂石分离设备进行固液分离、过滤、均质后,澄清的废液通过配浆处理重新应用于生产,悬浮液通过压滤设备压滤成饼,用于生产其他建筑材料,实现废水的循环利用,减少对环境的污染。

青海省茫崖市马海地区钾矿绿色勘查措施

青海省实施大量的盐湖钻探施工项目,要求实施绿色勘查。本文以青海省茫崖市马海地区钾矿勘查9号孔为例,根据现场实际施工情况,结合矿区矿区自然生态概况,合理规划了生活区和施工区的平面布置,分析了造成环境扰动的主要因素有项目临时道路修筑、车辆行驶、项目驻地建设、钻探工程施工等方面,同时制定了对应的绿色勘查措施。可为提高地质钻探从业者的绿色施工的意识、形成绿色勘查习惯,以及其他单位在风成砂覆盖区开展地质钻探施工时提供了可复制、可参考的绿色勘查经验。

基于改进沙猫群优化算法的绿色多式联运路径优化

为了解决整车多式联运物流过程中涉及的因素种类多,各方面成本难以平衡,且对节能减排要求较大的问题,综合考量运输成本、中转成本、风险成本、燃料消耗成本、碳排放成本和服务时效成本六个部分,并且加入对货运新能源车能耗排放的考虑,构建了一种绿色整车物流多式联运模型,该模型能够更好地反映出实际整车多式联运物流过程中的成本构成。为了更好地求出合理的配送方案,提出了一种混合沙猫群优化算法,在沙猫群优化算法的基础上,通过随机分布和Kmeans聚类算法优化初始沙猫的位置,并引入粒子协同机制和随机游走策略。通过与其它在基准函数中测试的算法进行比较,证明了所提算法在收敛精度和速度上都具有更好的性能。最后,将所提算法用于实际多式联运整车物流运输问题,实验结果表明,混合沙猫群优化算法在解决多式联运路径规划问题方面具有很大的优势。

陕西“三北”防护林体系建设历史论析

陕西省是“三北”防护林体系建设工程重点省份。1949年以来,全省大力开展防风治沙、植树造林,控制水土流失取得明显成效,为“三北”防护林体系建设规划提供了实践支撑。文中通过档案等相关材料的梳理,总结1949年到中共十一届三中全会召开期间陕西防沙治沙、绿化造林对全国的影响及其在“三北”防护林体系建设工程的提出、规划和实施中的重要贡献,对于全面认识总结“三北”防护林体系建设的历史价值有重要意义。

双碳目标下计及新能源接入的主动配电网协调优化

在碳达峰碳中和目标下,以新能源为主体的新型配电网运行提出了更高的要求,迫使配电网兼顾绿色低碳和经济高效两个方面效益。基于配电网的不确定性以及对环境和经济效益的影响,提出一种改进沙猫群算法。在改进沙猫群算法中,采用高破坏性多项式突变策略初始化种群,提高初始阶段解的质量,为全局搜索奠定基础;引入计数切换机制,帮助可行解跳出局部最优。为应对分布式发电的随机性问题,构建基于蒙特卡洛模拟和k-means聚类的分布式发电出力典型日场景生成方法。将改进沙猫群算法应用到主动配电网优化调度,以配电网运行成本作为目标函数,在IEEE 33总线测试系统中进行验证,结果表明:清洁能源的有效利用与经济效益的高低密切相关,能够提高调度精益化水平,平均成本为383.8万元,最终实现了绿色低碳和节约成本的目的。

广东省河道采砂管理问题与对策研究

随着经济社会高速发展,砂石资源供需矛盾加剧,影响社会结构稳定。为科学管理河道砂石资源,系统梳理了广东省河道采砂管理相关法规、制度建设,以及分级管理和创新管理模式的实施情况,归纳总结其在供需矛盾、制度更新及监管手段等方面存在的问题,并提出相应的发展对策。研究结果表明,广东省河道采砂管理需尽快完善相关配套制度,以匹配2019年修订的《广东省河道采砂管理条例》要求,建立基于信息化的全过程河道采砂智慧管理平台,严格落实河道采砂规划和计划,推广绿色替代砂源,加强上砂码头、堆砂场、洗砂场的规范化建设。