Efficient desorption and reuse of collector from the flotation concentrate:A case study of scheelite

Flotation is the most common method to obtain concentrate through the selective adsorption of collectors on target minerals to make them hydrophobic and floatable.In the hydrometallurgy of concentrate,collectors adsorbed on concentrate can damage ion-exchange resin and increase the chemical oxygen demand(COD)value of wastewater.In this work,we proposed a new scheme,i.e.,desorbing the collectors from concentrate in ore dressing plant and reusing them in flotation flowsheet.Lead nitrate and benzohydroxamic acid(Pb-BHA)complex is a common collector in scheelite flotation.In this study,different physical(stirring or ultrasonic waves)and chemical(strong acid or alkali environment)methods for facilitating the desorption of Pb-BHA collector from scheelite concentrate were explored.Single-mineral desorption tests showed that under the condition of pulp pH 13 and ultrasonic treatment for 15 min,the highest desorption rates of Pb and BHA from the scheelite concentrate were 90.48%and 63.75%,respectively.Run-of-mine ore flotation tests revealed that the reuse of desorbed Pb and BHA reduced the collector dosage by 30%for BHA and 25%for Pb.The strong alkali environment broke the chemical bonds between Pb and BHA.The cavitation effect of ultrasonic waves effectively reduced the interaction intensity between Pb-BHA collector and scheelite surfaces.This method combining ultrasonic waves and strong alkali environment can effectively desorb the collectors from concentrate and provide“clean”scheelite concentrate for metallurgic plants;the reuse of desorbed collector in flotation flowsheet can reduce reagent cost for ore dressing plants.

Effects of temperature and age on physico-mechanical properties of cemented gravel sand backfills

Cemented backfill used in deep mines would inevitably be exposed to the ambient temperature of 20−60℃in the next few decades.In this paper,two types of cemented gravel sand backfills,cemented rod-mill sand backfill(CRB)and cemented gobi sand backfill(CGB),were prepared and cured at various temperatures(20,40,60℃)and ages(3,7,28 d),and the effects of temperature and age on the physico-mechanical properties of CRB and CGB were investigated based on laboratory tests.Results show that:1)the effects of temperature and age on the physico-mechanical properties of backfills mainly depend on the amount of hydration products and the refinement of cementation structures.The temperature has a more significant effect on thermal expansibility and ultrasonic performance at early ages.2)The facilitating effect of temperature and age on the compressive strength of CGB is higher than that on CRB.With the increase of temperature,the compressive failure modes changed from X-conjugate shear failure to tensile failure,and the integrity of specimens was significantly improved.3)Similarly,the shear performance of CGB is generally better than that of CRB.The temperature has a weaker effect on shear strength than age,but the shear deformation and shear plane morphology are closely related to temperature.

Evaluation of working fluids for organic Rankine cycles using group-contribution methods and second-law-based models

The group-contribution (GC) methods suffer from a limitation concerning to the prediction of process-related indexes, e.g., thermal efficiency. Recently developed analytical models for thermal efficiency of organic Rankine cycles (ORCs) provide a possibility of overcoming the limitation of the GC methods because these models formulate thermal efficiency as functions of key thermal properties. Using these analytical relations together with GC methods, more than 60 organic fluids are screened for medium-low temperature ORCs. The results indicate that the GC methods can estimate thermal properties with acceptable accuracy (mean relative errors are 4.45%-11.50%);the precision, however, is low because the relative errors can vary from less than 0.1% to 45.0%. By contrast, the GC-based estimation of thermal efficiency has better accuracy and precision. The relative errors in thermal efficiency have an arithmetic mean of about 2.9% and fall within the range of 0-24.0%. These findings suggest that the analytical equations provide not only a direct way of estimating thermal efficiency but an accurate and precise approach to evaluating working fluids and guiding computer-aided molecular design of new fluids for ORCs using GC methods.

Temperature effect on shear behavior of ore-backfill coupling specimens at various shear directions

Understanding the temperature effect on shear behavior of the ore-backfill coupling structure is critical for the safety and stability of backfill stope under the condition of high horizontal stress in deep mining.Direct shear tests were carried out on the cemented rod-mill sand backfill(CRB)and ore-CRB(OCRB)coupling specimens at various temperatures(20,40 and 60°C).The shear behavior and AE characteristic parameters of OCRB at different shear directions were compared and analyzed.The results show that the temperature effect on the shear performance of CRB mainly depends on the characteristics of microstructures and main mineral phases;the performance of CRB at 40°C is relatively good;the shear deformation of OCRB has one more“peak fluctuation stage”than CRB and has a good correlation with AE characteristic parameters.The temperature can positively or negatively impact the shear strength of OCRB,depending on the temperature and shear direction;the shear performance of OCRB along the axis direction(D1)is significantly better than that perpendicular to the axis direction(D2).The co-bearing capacity of the ore-backfill coupling structure(i.e.,stopes)is closely related to the ambient temperature and principal stress orientation.

基于微震多参数的大规模岩体垮塌前兆特征研究

微震监测技术能进行工程岩体失稳垮塌前兆特征的辨识和分析,对于地质灾害预警防控具有重要意义。本文基于已有室内岩石受压损伤破坏声发射实验规律,通过开展现场微震多参数定量分析,探究了柿竹园矿山6·21大爆破诱发山体滑移垮塌的前兆特征。大爆破诱发微震事件的b值和空间分形维数表现出下降趋势,b值急剧下降和分形维数降到最低可作为工程岩体失稳垮塌的前兆特征。此外,能量指数和累计视体积的变化可以分别表征应力和应变的变化。能量指数快速下降和累计视体积持续增加的组合特征反映了岩体的失稳状态。经过多个失稳破坏阶段后岩体发生最终的失稳垮塌。该案例表明微震监测能为工程岩体失稳垮塌的预警和防控提供重要信息,也为涉及爆破作业的诸多地质工程活动的安全监测提供了参考。

Physiological responses of people in working faces of deep underground mines

The research studied the influences of high temperature, high pressure, high humidity, noise and other harmful factors in mining conditions on the people health and safety, and investigated the impacts of confined environmental on human physiology factors, including temperature, humidity, noise, pressure,toxic and harmful gases in terms of environmental characteristics in underground mines and an artificial intelligence system for simulation of the environment in a confined space of deep mines. Our results show that the systolic pressure, diastolic pressure, mean pressure, heart rate, respiratory rate, typing test speed and memory level percentage are negatively correlated with temperature value, and positively correlated with humidity value; the human temperature and weight are positively correlated with temperature value, and negatively correlated with humidity value. This research lays the foundation for the study of interaction between the deep confined space environment and safety behavior.