新一代高频隔离级联式中高压变频器的协调方式研究

新一代高频隔离级联式中高压变频器取消了传统的工频变压器的使用,并减少了全控型开关器件的数量,提高了系统的功率密度。在实际应用中常常存在负载不平衡以及电网不平衡等问题,因此提出了一种整流-逆变级双星型交错连接以及隔离级变换器的多绕组共铁芯变压器的新型结构方式,从系统协调的角度解决不平衡状况导致的直流电压不平衡的问题以及实现故障隔离。详细分析该结构拓扑的功率传输特性,最后,搭建仿真验证了所提结构的可行性。     

新一代高频隔离级联式中高压变频器的协调方式研究

新一代高频隔离级联式中高压变频器取消了传统的工频变压器的使用,并减少了全控型开关器件的数量,提高了系统的功率密度。在实际应用中常常存在负载不平衡以及电网不平衡等问题,因此提出了一种整流-逆变级双星型交错连接以及隔离级变换器的多绕组共铁芯变压器的新型结构方式,从系统协调的角度解决不平衡状况导致的直流电压不平衡的问题以及实现故障隔离。详细分析该结构拓扑的功率传输特性,最后,搭建仿真验证了所提结构的可行性。     

三相线电压级联式中高压整流器的研究

针对H桥级联变换器存在功率器件数量多、控制复杂等问题,提出一种三相线电压级联 整流器拓扑;分析了此拓扑的工作原理、电路等效模型及交流侧电流正弦化工作的开关管调制约 束条件;通过解析拓扑交流侧相桥臂电压的谐波成分,设计了基于单周期控制的移相载波PWM 调制策略及功率因数校正控制器;推导了拓扑直流侧电容电压的控制传递函数。 理论分析及实 验验证表明,此拓扑及其控制策略使开关管承受耐压有效降低,提高了交流侧功率因数,可作为 新一代中高压变换器整流级。     

某矿用隔爆型高压开关的使用及故障处理

目前国内煤矿井下普遍采用了PBG-630/6矿用隔爆型高压开关,为降低PBG-630/6矿用隔爆型高压开关的运行故障率,对其进行了工频耐压试验、高压电脑保护装置试验、三相6 k V通电试验以及综合保护整定,提高了矿用隔爆型高压开关高效运行时对工况的适应性。     

基于三电平转差矢量控制的矿用高压变频器研究

针对煤矿井下运输设备启动冲击大,运行效率低,电能浪费严重,设计了一种基于三电平转差矢量控制的矿用高压变频器,采用十二脉波整流电路和二极管箝位式逆变电路,并以载波同相层叠调制逆变电压波形,选择基于转差频率的矢量控制方案。通过搭建高压电机变频调速Simulink系统模型,对电机的调速性能进行分析。结果表明,电机可以迅速响应负载变化,并达到稳定状态,系统具有较高鲁棒性。     

电压前馈功率解耦控制策略下的Buck型复合式整流器研究

针对井下LED照明设备对低压直流供电可靠性的要求,采用Buck型复合式H桥拓扑对AC-DC变换器的整流级进行了设计,使整流级既可以参与单位功率因数整流,又能够实现对纹波扰动的抑制。文章详细分析了Buck型复合式H桥整流器的工作原理、电路等效模型,推导了实际被控量的开关状态函数,提出了一种电压前馈解耦控制策略,在此基础上对解耦电路的关键参数进行设计。最后通过仿真验证了控制策略和解耦电路参数的正确性。     

矿用本安型电源软开关电路的设计

针对矿用本安电源Buck变换器中开关器件在传统的硬开关高频模式下工作,存在器件温度升高及开关损耗等问题,提出了一种适用于矿用本安电源的Buck电路软开关,实现了其开关器件的软开通和关断。应用MATLAB仿真进行了验证,能够有效地降低开关损耗,保证了本安电源的安全运行。     

矿用级联准阻抗源DC-DC升压变换器

提出了一种新型的矿用级联准阻抗源DC-DC升压变换器,分析了其电路基本结构和工作原理,推导了电路的相关电压关系。该电路克服了传统Z源变换器电压增益小、器件应力大以及输入电流断续等问题。应用MATLAB/Simulink对电路进行了仿真,并在仿真结果的基础上以TMS320F28335为核心搭建出试验电路,理论分析与试验结果相符,验证了此DC-DC变换器的可行性和正确性。     

开关磁阻电机在矿用抽水机中的应用研究

针对传统矿用抽水机启动转矩小、耗能大、开关频繁程度小和运行可靠性差等问题,设计了一种基于四相8/6式开关磁阻电机(SRM)的抽水机叶轮控制系统,以320F2812PGFA高性能控制芯片为主控制器,采用DTC控制策略,配以单相桥式整流电路、检测电路、H桥功率驱动电路等,实现了基于SRM的无极调速。在实际的抽水机测试中,系统节能省电、可频繁开关、免维护运行,与水泵机械部件能够很好地配合。     

矿用多电平高压变频器的研究

 本文以矿用高压变频器系统为对象,研究了多电平高压变频器的系统组成、主电路拓扑、控制单元构成及旁路控制。设计了基于DSP和PLC的控制电路和主电路,通过系统调试验证了该系统的可靠性和实用性。     

川西坳陷雷口坡组常量元素特征及其意义

通过对川西坳陷丰卤1井雷口坡组岩屑样品的常量元素分析,研究K含量,w(FeO)/w(Fe₂O₃)值特征以及w(MnO)/w(FeO+ Fe₂O₃)值特征,发现雷口坡组K含量变化与深度成正比关系,K含量整体偏小,未能达到钾盐沉积的标志线;w(FeO)/w(Fe₂O₃)值整体小于1,反映出沉积环境为氧化环境,有着干燥、炎热的气候条件;极小的w(MnO)/w(FeO+ Fe₂O₃)值（<1）不仅反映了氧化的沉积环境和干热的气候条件,还反映了较浅的水体环境。干燥炎热的气候条件以及浅水的次级构造条件都指示着川西坳陷雷口坡组具备良好的钾盐沉积条件,最后建立w(FeO)-w(Fe₂O₃)-w(MnO)判别图,判别图包含3个区域,分别为湿冷深水区、干热浅水区以及湿冷浅水区,发现雷口坡组属于干热浅水区。     

淮北煤田芦岭矿区次生生物气地球化学证据及其生成途径

从煤储层甲烷碳氢同位素组成、甲烷与水的氢同位素值的定量关系、煤层气田产出水的来源3个方面探讨了淮北煤田芦岭矿区煤层气的成因,结果表明：煤层气组分中甲烷气占绝对优势（达97%以上）,且明显显示出极干气的特征;甲烷碳和氢同位素值范围分别为-67.6‰~-64.2‰,-206‰~-224‰,属于生物成因气的分布范围;甲烷氢同位素值（δD（CH4））和水氢同位素值（δD(H2 O)）定量关系表明,煤层甲烷气主要是二氧化碳还原作用生成的次生生物成因气;煤层水样品点同位素值均落在大气降水线附近,说明煤层水的主要来源为大气降水,符合生物成因气生成需有雨水补给的条件。综合3个方面定性和定量分析结果,并结合研究区构造-热演化史,认为现今淮北煤田芦岭矿区的煤层气主要为次生生物成因气。     

陆相盆地古气候变化与环境演化、聚煤作用

为了揭示陆相盆地古气候变化与沉积环境、聚煤作用耦合关系,应用同位素地球化学、煤岩学等理论和方法,进行了柴北缘中侏罗统大煤沟组上段(巴柔期)主采煤层煤岩组分、有机碳同位素组成(δ13CO)及其古气候意义研究。研究煤层(7号和F煤层)δ13CO值平均为-23.9‰,分别变化在-26.7‰~-21.6‰和-25.6‰~-22.9‰。根据沼泽、陆源碎屑体系交替演化特征和煤层有机碳δ13CO值变化规律,将大煤沟组上段划分为8个阶段并对应于1个长周期旋回(C1)和3个短周期旋回(C2)。认为低变质煤δ13CO值在反映古大气CO2同位素组成及其含量变化的同时,还记录了聚煤期(植物生长至泥炭化阶段末)古气候(温度和湿度)的变化:湿暖古气候有利于成煤植物对碳同位素分馏及贫13C腐殖质(镜质组前身)的形成,煤δ13CO值降低;干热古气候不利于植物对碳同位素的分馏,但有利于富集13C的惰质组(丝质体)形成,进而引起煤δ13CO值升高。从煤层δ13CO值所反映的气候变化与陆源碎屑体系废弃、复活及聚煤发生、终止关系角度提出了陆相盆地古气候与沉积环境、聚煤作用关系模型,指出在盆地构造活动、基底沉降较稳定和均匀的煤系沉积过程中,气候变化通过盆地和流域内径流深度(年平均降雨量减去年平均蒸发量)和植被发育演化控制了绝对湖平面变化、沉积物的产生和搬运(供给)速率,进而引起盆地内沼泽、陆源碎屑两种矛盾体系的交替与演化。     

A comparison of the predictability of batch flotation kinetic models

Batch flotation test data of a mixture of pyrite and calcite were used to compare regression parameters of four kinetic model structures. The work included the use of unoxidized or a mixture of partially oxidized pyrite (by microwave irradiation). The objective of floating oxidized pyrite was to have mineral particles with different floatability, closer to a real situation. The models considered include: single rate constant, distributed rate constants (i.e. rectangular and gamma distributions), and a recently introduced approach based on fractional calculus. Such models were selected due to their good tradeoff between simplicity and accuracy. The regressions were performed (1) taking all the data points and comparing the mean square error (MSE) and adjusted correlation factor $\left(R_{\mathit{Adj}}^2\right)$ as indicators of the goodness of fit; and (2) taking the first data points while neglecting the last ones (from 1 to 3) and observing the variability of the model parameters and the prediction of maximum recovery (R_∞). For the latter regression scheme, besides MSE and $R_{\mathit{Adj}}^2$, a predictive factor, E, was defined by subtracting the final measured recovery from the calculation obtained by the model. This allowed to measure the ability of each model to extrapolate the omitted points on the recovery vs. time curve.Results from this study showed that the single constant model had a satisfactory performance with the advantage of having the least parameters compared to the other structures. The gamma model was effective and robust. The rectangular model gave an acceptable goodness of fit but overestimated the maximum and final recovery. Finally, the fractional calculus approach gave the best goodness of fit, overall, but failed in predicting the maximum recovery, which occurred when the derivative order was greater than 1.     

Antimony Mobilization through Two Contrasting Gold Ore Processing Systems,New Zealand

Antimony, a toxic metalloid similar to arsenic, is present at variable levels in most gold-bearing rocks. Antimony is soluble in the surface environment, so antimony (Sb) mobilization in mine waters is an environmental issue around gold mines. The Reefton gold mine was originally developed in gold-bearing quartz veins; Sb concentrations were low (<100 mg/kg) compared to arsenic (As) concentrations (>1,000 mg/kg), and the mine waters had low dissolved Sb (<0.1 mg/L). A second stage of gold mineralization at Reefton involved brecciation and cataclasis of quartz veins and wall rocks, with addition of stibnite (Sb₂S₃). Processing of this ore has resulted in higher dissolved Sb in mine waters (0.1–1 mg/L), even after water treatment that removes most dissolved As (to 0.01 mg/L) by adsorption to suspended iron oxyhydroxide. Competition between As and Sb for adsorption sites on iron oxyhydroxide particles may have resulted in partial exclusion of the more weakly adsorbed Sb. The high rainfall (2,000 mm/year) at Reefton ensures adequate dilution of mine waters after discharge. The Macraes gold mine has no stibnite, and most Sb is in solid solution in the abundant arsenopyrite (Sb up to 2,000 mg/kg). Pit waters have both Sb and As dissolved up to 0.1 mg/L, partly because of evaporative concentration in a low-rainfall environment. Macraes tailings waters have high As (up to 3 mg/L) but negligible Sb (<0.001 mg/L). Reefton mine gold-bearing concentrate, containing stibnite, is transported 700 km to be processed by autoclave oxidation and cyanidation at the Macraes mine. This introduction of additional Sb to the Macraes site substantially increases the Sb content of the process stream periodically. Tailings from this process have up to 3 wt% Sb, dispersed through As-rich iron oxyhydroxides that are formed in the autoclave. The Sb-rich tailings are strongly diluted (approximately 100:1) by the Macraes tailings, and adsorption of Sb to iron oxyhydroxides in the tailings piles ensures that there has been no increase in the Sb content of the tailings water since the Reefton concentrate has been added at Macraes.     

郑庄-胡底煤层气地球化学特征及成因探讨

结合沁水盆地南部地质构造史和热演化过程,从甲烷碳同位素与煤岩镜质组反射率、甲烷碳与氢同位素、甲烷与水的氢同位素值定量关系3方面探讨了郑庄和胡底区块煤层气成因,结果表明:煤层气组分中,甲烷体积分数占绝对优势,为96.83%~98.55%,为极干燥气体;甲烷δ13C1和δD分别为-33.1‰~-30.8‰和-179.32‰~-160.53‰;煤层气主要为经次生改造的热解成因煤层气。煤层气δ13C1实测值与推测值-27.89‰相比明显偏轻,其原因是燕山期异常古地温阶段,横向地下水循环和竖向热液循环过程中流体优先溶解13CH4产生的甲烷碳同位素分馏作用的结果。15号煤抽采煤层气甲烷氢同位素值与伴生水氢同位素值定量关系表明,由于CO2还原次生生物作用造成3号煤和15号煤抽采煤层气甲烷δD的差异。     

Application of differential evolution algorithm and comparing its performance with literature to predict rock brittleness for excavatability

ABSTRACT

The aim of this study was to estimate brittleness of intact rock by applying differential evolution (DE) algorithm and then to compare the results obtained from the optimum model with literature. For this aim, several models including linear and nonlinear were developed for predicting the brittleness via DE algorithm using the dataset obtained from 48 tunnel cases around the world. Each model were developed using 80% of the dataset as training and 20% of the dataset as testing in random. After that, developed models are compared according to the coefficient of correlations (r ²), computer process unit (CPU), mean-squared error (MSE) and number of function evaluation (NFE) values to choose the best accurate one among them. It is found that the values r ², MSE, NFE and CPU ranged between 0.9385–0.9501, 8.2616–9.938, 7217–11,176 and 4.91–36.22, respectively, with the quadratic model (QM) indicating the best performance. It is concluded that the DE algorithm is itself very powerful tool for estimating the brittleness; however, the QM is superior especially for simulations in which computational time and optimisation is a critical.     

丙酸钙再燃的脱硝特性

在沉降炉实验台上系统地研究了丙酸钙的再燃脱硝特性。丙酸钙基本再燃可以取得与液化石油气相当的脱硝效率。实验结果表明：在973~1 323 K,丙酸钙基本再燃的脱硝效率与温度同步升高,最高为79.65%,此后进一步升高温度,效率提高不明显;为保证基本再燃较高的脱硝效率,烟气中初始氧浓度不宜超过5%,再燃比应在25%附近,同时停留时间应保证在0.7 s左右。单独喷氨气的选择性非催化还原能取得的最高脱硝效率为1 273 K时的85.34%,但“温度窗口”较窄,为1 215~1 341 K,适宜氨氮摩尔比为1.75~2.00。在先进再燃过程中,由于丙酸钙和氨气存在协同的脱硝作用,这两种试剂的所需加入量大大减少,当再燃比为19.83%,氨氮摩尔比为0.8时,其最高效率可达到93.37%,同时“温度窗口”拓宽为1 195~1 355 K,而且在2%~6%的氧浓度范围内,先进再燃均能保持较高的脱硝效率。     

On the mechanism of the flotation of oxides and silicates

The mechanism of flotation of oxide and silicate minerals was established long ago as being due to the electrostatic attraction between the charged surface and the charge of the collector. What is less well established is the mechanism of the charging of the mineral surface. Most researchers have postulated that the adsorption of H⁺ is the cause. However, the adsorption model and its derivatives (such as the amphoteric and multisite-adsorption models), do not successfully describe the data for the zeta potential as a function of pH. In particular, these adsorption models have the following features that are not observed: (i) they are symmetrical about the point of zero charge, whereas the data is asymmetrical, (ii) they have an inflection at the pK_a values, leading to an asymptotic approach to the point of zero charge, whereas such an inflection is not observed, and (iii) they only fit the data in its extremes, that is, when the pK_a values differ by orders of magnitude, or are very close to one another. An alternative mechanism of charging is proposed here that is based on the dissolution of ions from and deposition of ions onto the mineral surface. It is shown that this model (a) fits the data, (b) is consistent with the thermodynamic model for reversible interfaces, (c) is consistent with the thermodynamics of the overall reaction and its solubility, (d) indicates reasons for the ageing of surfaces and (e) displays the observed features of zeta potential measurements as a function of pH, that is, it is pseudo-Nernstian and asymmetrical in nature. Application of the proposed theory is discussed for the flotation of quartz and corundum.     

The impact of thiosulfate oxidation products on the oxidation of gold in ammonia thiosulfate solutions

The continued use of cyanide in the recovery of gold is being questioned due to environmental and public concerns. The present paper describes research into the gold thiosulfate leaching system, which is considered to be the most promising alternative to cyanide. The thiosulfate system is complicated by the homogeneous reaction between two of the reactants, copper(II) and thiosulfate. This reaction produces copper(I) and polythionates. It is generally accepted that oxygen addition is thus required in order to regenerate copper(II) from copper(I). Despite this, no one has previously studied the effect of oxygen addition on the kinetics of gold leaching in thiosulfate solutions. This paper presents a study on gold leaching in thiosulfate solutions containing oxygen. It will be shown that the leaching reaction is severely hindered as the reaction between thiosulfate and copper(II) occurs in the presence of oxygen. It is postulated that an intermediate product of the oxidation of thiosulfate by copper(II) in the presence of oxygen is responsible for the slow leaching kinetics. This effect was not observed when oxygen is excluded from the solution. Disulfite (S₂O₅²⁻) was identified as a possible cause of this effect, as experiments performed with the addition of disulfite also resulted in very low gold oxidation rates.