Leaching of vanadium from stone coal with sulfuric acid

The effects of roasting, mass ratio of H2SO4 to stone coal, leaching temperature, liquid-to-solid ratio, grinding fineness of stone coal, and two-stage counter-current leaching on the vanadium leaching ratio were studied. The results show that the vanadium leaching ratio of roasted stone coal through two-stage counter-current leaching can reach 65.1% at the mass ratio of H2SO4 to stone coal of 20%, leaching temperature of 95℃, leaching time of 30 h, liquid-to-solid ratio of 1.1 mL·g^-1, and grinding fineness of 0.1 mm, which can serve as an experimental basis for the production of vanadium from stone coal.

Extracting vanadium from stone-coal by oxygen pressure acid leaching and solvent extraction

Vanadium extraction from stone-coal was investigated by oxygen pressure acid leaching and solvent extraction.The mineralogy of the stone-coal from Tongren City of Guizhou Province,China,was investigated by various determination methods. The effects of leaching time,leaching temperature,leaching agent concentration,leaching L/S ratio,granularity of material,additive consumption were investigated based on the mineralogy.The results show that under the conditions of leaching time of 3-4 h, temperature of 150℃,sulfuric acid consumption of 25%?30%,ratio of liquid to solid of 1.2:1,the granularity less than 0.074 mm, additive consumption of 3%-5%,and oxygen pressure of 1.2 MPa,and the vanadium leaching rate can be more than 92%by the method of two-step pressurized acid leaching.The powdery V2O5 product with 99.52%in V2O5 content is obtained by the flowsheet of acid recovery,removing iron by reduction process,solvent extraction,precipitating vanadium with ammonium water,and pyrolysis from the stone-coal oxygen pressure acid-leaching solution.The total recovery efficiency of vanadium is above 85%,which is more than 20%higher than that obtained in the conventional process.Furthermore,the new process does not cause air pollution since no HCl or Cl2 is released by calcination of the raw material.

Leaching behavior of V,Pb,Cd,Cr,and As from stone coal waste rock with different particle sizes

This paper investigates the leaching behavior of heavy metals(V,Pb,Cd,Cr,and As) from stone coal waste rocks with various particle sizes using dynamic leaching experiments.The results show that the dissolved concentrations of V and As initially increased and then slightly decreased as time progressed and that the dissolved concentrations of Pb,Cd,and Cr were high in the early stage before decreasing.The particle size of the stone coal waste rocks strongly influenced the heavy metal concentration in the leaching solutions.The effects of the particle size of the stone coal waste rocks on the dissolved concentrations of V,Pb,and As decreased in the order fine fraction > medium fraction > coarse fraction,and the effects of particle size on the dissolved concentrations of Cr and Cd decreased in the order medium fraction > coarse fraction > fine fraction and coarse fraction > medium fraction > fine fraction,respectively.The quantities of heavy metals dissolved from the stone coal waste rock with fine particle sizes were observed to decrease in the order V(17104.36 μg/kg) > As(609.41 μg/kg) > Pb(469.24 μg/kg) > Cr(56.35 μg/kg) > Cd(27.52 μg/kg),and the dissolution rates decreased in the order As(2.96%) > Pb(0.93%) > V(0.35%) > Cd(0.25%) > Cr(0.01%).The specific surface area,pore size of the stone coal waste rocks,and chemical forms of heavy metals also influenced the release of heavy metals from the stone coal waste rocks.Kinetic analysis showed that the dissolution of heavy metals fundamentally agreed with the rate equation controlled by the shrinking core model.The results of this study are expected to serve as a reference for the evaluation of heavy metals contamination from stone coal waste rocks.

Acid leaching of vanadium from roasted residue of stone coal

Through leaching from residue directly and leaching after a roasting treatment,respectively,the experimental research on sulfuric leaching of vanadium from residue of stone coal that came from power generation was conducted.Factors which influence the leaching of vanadium such as concentration of sulfuric acid,leaching temperature,leaching time and liquid-to-solid ratio were investigated in both processes.In the process of direct leaching,to achieve a leaching rate of 74.49%,H2SO4 concentration of up to 5.4%,leaching temperature of 90℃and leaching time of 8 h were necessary reaction factors.The results show that after a roasting treatment at the optimum condition of 950℃at 1 h,76.88%vanadium can be leached under the experimental condition of 0.45% of H2SO4,30℃for 1 h with a liquid-to-solid ratio of 2 mL/g.Leaching after an oxidation roasting treatment is an efficient way to leach vanadium from the residue of stone coal,which has some advantages,such as high recovery,low economic cost and less impurities in leaching solution.

Calcified roasting-acid leaching process of vanadium from low-grade vanadium-containing stone coal

The low-grade vanadium-containing stone coal used in this experiment was collected from Wuxi Country, Chongqing City, China. The experiment focused on the vanadium recovery from roasted residue through optimizing the process conditions of an effective and environmentally-friendly technology, named calcified roasting-sulfuric acid leaching technology. By single-factor experiments and orthogonal experiments, the effects of roasting temperature, roasting time, sulfuric acid concentration and leaching time on the leaching ratio of vanadium were analyzed. The results showed that the leaching ratio of vanadium reached 85.5% under the proper technological conditions of roasting temperature=950℃, roasting time=4 h, 40% concentration of sulfuric acid and leaching time=6 h.

Mechanisms of aid-leaching reagent calcium fluoride in the extracting vanadium processes from stone coal

The mechanisms of aid-leaching reagent calcium fluoride in the extracting vanadium processes were researched by comparing the blank extraction with the extraction with calcium fluoride as aid-leaching reagent. The leaching experiments were carried out under the conditions of 95 ~C, 6 h, 1.5 ml.g-1, 15 vol % H2SO4, and 5 % calcium fluoride （mass ratio of CaF2 to stone coal）. The concentrations of hydrogen ion were adjusted from initial 1.82 and 4.79 mol.L-1 to the pH of 1.80 4- 0.05 by 200 g.L-1 lime milk, respectively. The solvent extraction experiments were carded out under the organic phase using 15 vol% D2EHPA, 5 vol% TBP, and 80 vol% sulfonated kerosene and O/A phase ratio of 1/4. The leaching rate of vanadium and six-stage countercurrent solvent extraction rate of vanadium can be remarkably improved from 66.71 to 92.97 % and 81.15 to 98.81%, respectively, when calcium fluoride was added as aid-leaching reagent. In the leaching process, fluorine can enhance the breakage of the structure of vanadium-bearing minerals. Meanwhile, fluoride ion can combine with iron ion to generate acid-insoluble iron fluoride hydrate （Fe2Fs.7H20） and consume all ferric ions and a portion of ferrous ions. In adjusting pH value process, the massive impurities are decreased to form KA1SO4 and FeA1Fs. In solvent extraction process, fluorine can prevent the formation of ferric hydroxide colloids and eliminate the formed unstable ferric hydroxide colloids and the silicon-containing colloids to promote the sufficient contact between the aqueous phase and the organic phase and the sufficient reaction.

Leaching vanadium by high concentration sulfuric acid from stone coal

An effectively new technology of extracting vanadium from stone coals by high concentration sulfuric acid was researched. The effect of the concentration of sulfuric acid,leaching temperature,leaching time and helper leaching agent on the extraction of vanadium was explored.The results show that the optimal conditions of extraction are as follows:the concentration of sulfuric acid is 6 mol/L,the ratio of liquid to solid is 3-1;the temperature is 90℃;the leaching time is 3-5 h,the diameter of the ore particle is less than 180μm,and the concentration of helper leaching agent R is 6%.Under these conditions,the extraction of vanadium can reach 95.86%.

Extraction of Alumina from Coal Fly Ash with Sulfuric Acid Leaching Method

Coarse γ-Al2O3 powder was prepared through acid leaching,solid-liquid separation,crystallizing and aluminum sulfate decomposing processes using coal fly ash and concentrated sulfuric acid as raw materials.The metallurgy level Al2O3 can be obtained by disposing coarse γ-Al2O3 powder with Bayer process.The optimum conditions of acid leaching process were determined by experiments.The extraction rate of Al2O3 can be stabilized at about 87% under these conditions.The thermodynamics and kinetics of sulfuric acid leaching process were studied with irreversible thermodynamics.

Application of response surface methodology(RSM) for optimization of leaching parameters for ash reduction from low-grade coal

Coal is the world's most abundant energy source because of its abundance and relatively low cost. Due to the scarcity in the supply of high-grade coal, it is necessary to use low-grade coal for fulfilling energy demands of modern civilization. However, due to its high ash and moisture content, low-grade coal exerts the substantial impact on their consumption like pyrolysis, liquefaction, gasification and combustion process. The present research aimed to develop the efficient technique for the production of clean coal by optimizing the operating parameters with the help of response surface methodology. The effect of three independent variables such as hydrofluoric acid(HF) concentration(10–20% by volume), temperature(60–100 °C), and time(90–180 min), for ash reduction from the low-grade coal was investigated. A quadratic model was proposed to correlate the independent variables for maximum ash reduction at the optimum process condition by using central composite design(CCD) method. The study reveals that HF concentration was the most effective parameter for ash reduction in comparison with time and temperature. It may be due to the higher F-statistics value for HF concentration, which effects to large extent of ash reduction. The characterization of coal was evaluated by Fourier transform infrared spectroscopy(FTIR) analysis and Field-emission scanning electron microscopy with energy-dispersive X-ray(FESEMEDX) analysis for confirmation of the ash reduction.

Effect of Calcium on the Vanadium Extraction from High Calcium Type Stone Coal

The high calcium type stone coal from Hubei province was leached by water and dilute acid separately after being roasted with different dosage of Na Cl. The water leaching rate of vanadium（WLRV） was low and only 26.8% of vanadium can be leached by water when 4% Na Cl was added, but the acid leaching rate of vanadium（ALRV） was relatively high. Calcium in the high calcium type stone coal is greatly superfl uous relative to vanadium, hence, the calcium reacts with vanadium to form Ca（VO3）2, Ca2V2O7 and Ca3（VO4）2orderly during the stone coal roasting process and high temperature is beneficial to the reactions between calcium and vanadium, which was validated by simulated reactions between pure calcium carbonate and vanadium pentoxide. These calcium vanadates are all water insoluble but acid soluble and this causes the low WLRV and relatively high ALRV. After calcium removal by HCl, the WLRV is highly enhanced and reaches about 50% when only 2% Na Cl was added. If the HCl content is too high, the stone coal is easily sintered and the formed glass structure can enwrap vanadium, which leads the WLRV to decline. Single water leaching process is not appropriate to extract vanadium from high calcium type stone coal.

Effect of vanadium occurrence state on the choice of extracting vanadium technology from stone coal

The extraction technology of vanadium from stone coal by means of no-salt-roasting and dilute acid solution leaching treatment has the advantages of low pollution, low investment, as well as high vanadium leaching efficiency, which makes it the best technology for extending application. In the present study, the effects of vanadium occurrence state in stone coal, roasting temperature and additive agent on the leaching efficiency of vanadium were studied. The results indicate that the effect of vanadium occurrence state on the extracting vanadium technology is obvious. If the vanadium component in stone coal existed in amorphous phase form, this type of stone coal can be treated by no-slat-roasting and dilute acid solution leaching technology; while the vanadium-bearing crystalline phase existed in stone coal, the roasting additive must be added to destroy this crystalline form so as to acquire high vanadium leaching rate.

Effects of the mineral phase and valence of vanadium on vanadium extraction from stone coal

The influence of roasting on the leaching rate and valence of vanadium was evaluated during vanadium extraction from stone coal. Vanadium in stone coal is hard to be leached and the leaching rate is less than 10% when the raw ore is leached by 4 moUL H2SO4 at 90℃ for 2 h. After the sample is roasted at 900℃ for 2 h, the leaching rate of vanadium reaches the maximum, and more than 70% of vanadium can be leached. The crystal of vanadium-bearing mica minerals decomposes and the Content of V（V） increases with the rise of roasting temperature from 600 to 900℃, therefore the leaching rate of vanadium increases significantly with the decomposition of the mica minerals. Some new phases, anorthite for example, form when the roasting temperature reaches 1000℃. A part of vanadium may be enwrapped in the sintered materials and newly formed phases, which may impede the oxidation of low valent vanadium and make the leaching rate of vanadium drop dramatically. The leaching rate of vanadium is not only determined by the valence state of vanadium but also controlled by the decomposition of vanadium-bearing minerals and the existence state of vanadium to a large extent.

A new process of extracting vanadium from stone coal

A new process of extracting vanadium from the stone coal vanadium ore in Fangshankou, Dtmhuang area of Gansu Province, China was introduced. Various leaching experiments were carried out, and the results show that the vanadium ore in Fangshankou is difficult to process due to its high consumption of acid and the high leaching rate of impurities. However, the leaching rate can be up to 80% and the content of V2O5 in the residue can be between 0.22%-0.25% in the process of ore fme grinding→oxidation roasting→mixing and ripening→aqueous leaching→P2O4 solvent extraction→sulfuric acid stripping→oxidation and precipitation→decomposition by heat. Also, the quality of flaky V205 produced by this process can meet the requirements of GB3283--87. The total leaching rate of vanadium is 70%. Also, three types of wastes are easy to treat. The vanadium extraction process is better in relation to the aspect of environmental protection than the sodium method.

Comparison of the mechanisms of microwave roasting and conventional roasting and of their effects on vanadium extraction from stone coal

Experiments comparing microwave blank roasting and conventional blank roasting for typical vanadium-bearing stone coal from Hubei Province in central China, in which vanadium is present in muscovite, were conducted to investigate the effects of roasting tempera- ture, roasting time, H2SO4 concentration, and leaching time on vanadium extraction. The results show that the vanadium leaching efficiency is 84% when the sample is roasted at 800℃ for 30 min by microwave irradiation and the H2SO4 concentration, liquid/solid ratio, leaching temperature, and leaching time are set as 20vo1%, 1.5：1 mL.g-1, 95℃, and 8 h, respectively. However, the vanadium leaching efficiency achieved for the sample subjected to conventional roasting at 900℃ for 60 min is just 71% under the same leaching conditions. Scanning electron microscopy （SEM） analysis shows that the microwave roasted samples contain more cracks and that the particles are more porous compared to the conventionally roasted samples. According to the results of X-ray diffraction （XRD） and Fourier-transform infrared （FTIR） analyses, neither of these roasting methods could completely destroy the mica lattice structure under the experimental conditions; however, both methods deformed the muscovite structure and facilitated the leaching process. Comparing with conventional roasting, microwave roasting causes a greater deformation of the mineral structure at a lower temperature for a shorter roasting time.

Effects of organic acids on dissolution of Fe and Mn from weathering coal gangue

Understanding the effects of organic acids(OA) on the transformation of Fe and Mn to surface water from the weathering coal gangue is of great bene?t to risk assessment and remediation strategies for contaminated water and soil. Based on the investigation on surface water in the central coal districts of the Guizhou Province, 18 water samples were collected for heavy metal analysis. The results indicated that the p H value of surface water is low(3.11–4.92), and Fe concentration(1.31–5.55 mg L^(-1)) and Mn concentration(1.90–5.71 mg L^(-1)) were, on average,10.86 and 34.33 times the limit of Surface Water Quality Standards, respectively. In order to evaluate the effects of the OA on the dissolution of Fe and Mn from the weathering coal gangue, column elution and batch leaching experiments were conducted. The results show that the low molecular weight of organic acids(LMWOAs, i.e., oxalic,tartaric, malic and citric acids) and fulvic acids signi?-cantly accelerated the dissolution of Fe and Mn; in addition, when the concentration of OA reached 25 mmol L^(-1),the concentrations of Fe, and Mn were 1.14–67.08 and1.11–2.32 times as high as those in 0.5 mmol L^(-1)OA,respectively. Furthermore, the migration of Fe and Mn was signi?cantly in?uenced by the p H and Eh, especially for Fe; the ion Mn was dissolved from the gangue more easily than the ion Fe in the column leaching, which was contrary to the results of batch leaching.

某低品位黏土型锂矿石的焙烧——无酸浸出试验研究

云南某低品位黏土型锂矿石含锂0.147%,为探究低能耗、环保的开发利用工艺,采用新型焙烧助剂ASH开展了低温焙烧—无酸浸出的提锂工艺研究,并结合XRD、SEM-EDS等分析手段阐述了反应机理。试验结果表明,在试样与ASH质量比为1∶0.3、焙烧温度为400℃、焙烧时间为1.0 h,去离子水浸出时间为2 h、浸出温度为70℃、液固比为5 m L/g条件下,锂浸出率为83.81%。机理分析显示,焙烧—浸出前后,样品中主要矿物相未发生变化,但衍射峰强度降低;经焙烧—浸出后,浸渣表面均匀分布着裂纹和空隙,Al、Si、Fe、Ti含量均有所降低。说明ASH与矿物发生反应,破坏了矿物的表面结构,生成了可溶性盐Li-ASH。与传统焙烧—浸出工艺相比,本研究所采用的提锂工艺焙烧温度低、浸出时无酸,降低了生产能耗、简化了工艺流程,对同类型低品位黏土型锂矿的绿色高效开发利用具有重要借鉴意义。

不同螯合剂对褐煤中金属离子浸出效果的实验研究

螯合剂种类的不同,其对金属离子浸出效果也存在差异,为分析螯合剂对贵州地区褐煤中金属离子的浸出效果,选取ASDA,DTPA,IDS和GLDA等共4种螯合剂,开展了浸出效果对比实验,利用电感耦合等离子体质谱仪(ICP)和扫描电子显微镜(SEM)对实验结果进行了表征。结果表明:螯合剂能够将煤体中矿物质解络为游离态,煤体表面孔隙呈现从微孔、小孔向大孔变化的趋势,煤体表面矿物质呈现颗粒数量减少、颗粒体积变小、颗粒形态圆润的特点;ASDA对该煤样中Mg,Al,Fe,Ca,Cu离子具有最佳浸出效果,DTPA对K,Pb离子具有最佳浸出效果。

煤气化细渣高炭组分超声强化酸浸法制备多孔材料

煤气化细渣是煤炭清洁高效利用的副产物之一,其资源化应用迫在眉睫。通过简单筛分得到固定碳含量高于60%的高炭组分,并以此为原料,采用超声酸浸法制备多孔材料。以核废水中放射性碘的吸附处理为应用背景,用碘吸附值表征多孔材料的吸附性能。结合SEM、BET、XRD和FT-IR等性质和结构分析方法,系统研究了超声时间、超声功率、酸浓度和温度对多孔材料碘吸附性能和组成结构的影响规律;并探讨了超声强化酸浸对残炭的组成结构的影响机制和灰成分的迁移转化规律,总结出超声强化酸浸作用机理。结果表明,煤气化细渣高炭组分在酸浓度为4 mol/L、酸浸温度为50℃、超声功率为210 W,超声时间1.5 h的条件下,所制备多孔材料的碘吸附性能最佳,为468.53 mg/g,比表面积达到474.97 m^(2)/g,且具有以介孔为主的丰富孔隙结构。各因素对多孔材料碘吸附性能影响的顺序为:超声时间>酸浓度>超声功率>酸浸温度。超声强化酸浸作用机理是超声空化和机械波作用一方面强化炭灰黏附颗粒的解离,使堵塞在气化细渣孔道内的灰颗粒脱附,增加孔隙结构的连通性;其次,会导致炭灰颗粒表面裂纹的产生,增强碳颗粒内部无机组分的可及性;第三,能够提高酸浸过程的传质速率,强化气化细渣中的无机组分的浸出效果。

煤气化渣除杂富铝制备聚合氯化铝实验研究

煤气化渣是煤气化工艺产生的固体废弃物,随着煤气化工艺的广泛推广与应用,大量煤气化渣的产生对生态环境造成威胁的同时也制约着煤化工行业的发展。为实现煤气化渣的资源化、工业化利用,以煤气化粗渣为研究对象,对其矿物赋存形态和化学组成进行分析,提出煤气化渣净化除杂-酸浸提铝制备聚合氯化铝(polyaluminum chloride,PAC)的总体构思。利用煤气化渣中各元素与酸溶液的反应活性差异,在低酸体系下浸出Fe^(2+),Ca^(2+)及少部分Al^(3+),再利用离子沉淀pH差异,将钙、铁与煤气化渣选择性分离,实现酸渣富铝。以富铝酸渣为原料,酸浸制备PAC前驱体。考察铝酸钙粉添加量、聚合温度、聚合时间对产品品质及絮凝效果的影响。结果表明:在60%理论耗酸量下,煤气化渣浸出Al^(3+),Fe^(2+),Ca^(2+),将反应液pH调至3.5,Al^(3+)选择性沉淀,固液分离后制备富铝渣,钙、铁的去除率可达84.06%和79.79%,Al_(2)O_(3)质量分数由原来的10.84%提升至14.38%;富铝酸渣添加酸后再次溶出,酸溶液中氧化铝质量浓度可达到28.4 g/L;按固液比为10 g∶100 mL向酸溶液添加铝酸钙粉,在80℃下聚合2.5 h,可获得符合GB/T 22627-2022要求的PAC产品;通过FTIR和XRD对PAC产品进行表征,表明生成的产品为PAC,将该产品应用于模拟废水中,去浊率高达92.90%。

低品位氧化铜原矿槽浸提铜工艺试验研究

试验采用原矿二级破碎-浓酸熟化-槽浸的流程,原矿破碎至粒径为5~10 mm后进行浓硫酸熟化,将熟化矿样直接用于浸出试验,在初始H_(2)SO_(4)浓度为100 g/L,液固比为1.5∶1,常温的条件下浸出24 h,Cu浸出率达到90%,浸出渣经水洗后洗液返回槽浸工序循环使用,Cu浸出率达到93%以上。槽浸浸出液即为CuSO_(4)溶液,可通过常规萃取-电解工艺得到最终产品阴极铜。试验结果表明:采用此工艺流程处理低品位氧化铜矿,Cu回收率达到93%以上。