循环流化床中含钒石煤料球的焙烧特性试验研究

为避免传统提钒工艺所存在的问题,采用循环流化床钙法焙烧工艺,以添加钙基原料的石煤料球为焙烧原料,在热输入功率为1 MW的循环流化床燃烧试验台上进行了含钒石煤焙烧特性试验,研究了燃烧稳定性、燃烧效率、污染物排放特性、燃烧后灰渣特性和灰渣钒浸出特性.结果表明:在以烟煤为助燃燃料的条件下,石煤料球可以在1 MW循环流化床试验台上稳定焙烧运行,且燃烧效率较高;料球中的钙基添加剂有较好的脱硫作用,但对于高硫石煤,要达到国家污染物排放标准,必须采取尾部烟气脱硫措施;焙烧产物以飞灰为主,飞灰中V2O5浸出率接近70%,表明循环流化床对石煤中的钒矿物具有良好的焙烧氧化作用.     

流化床焙烧石煤料团提取V2O5

在小型流化床燃烧器上对含钒石煤料团进行焙烧,并对灰渣酸浸提钒;系统分析了焙烧温度、焙烧时间、流化风速、氧气含量(过量空气系数)和料团粒径等因素对焙烧成球率和转浸率的影响,获得了各种合理运行参数.结果表明:焙烧温度为930℃,焙烧时间为90～100 min,较低流化风速,粒径为0～6 mm时,可获得较高的焙烧成球率和钒转浸率.同时,可有效回收石煤中的热能,产气发电,实现含钒石煤的热-电-钒多联产.     

富钒石煤与生物质在CFBC试验台上的混烧实验

针对石煤富钒的特点,利用实验室规模的循环流化床燃烧装置(CFBC),进行了生物质与富钒石煤的混烧实验研究.以期通过富集钒和回收热量达到资源综合利用的目的.实验结果表明:所实验的富钒石煤容易着火,燃烧稳定,燃尽性好,包括与生物质混烧也是如此;经过燃烧后,石煤中的钒大部分转换为五氧化二钒,并在灰渣中富集;石煤颗粒尺度大小、燃烧温度对钒的迁移特性没有显著影响;通过向炉内加入石灰石进行炉内脱硫,当Ca/S摩尔比为3时,烟气中的二氧化硫排放浓度低于国标.     

钙化重构含钒钢渣微波酸浸提钒研究北大核心CSCD

以钒电池为代表的液流电池有望成为大规模储能应用的电池技术,得益于其循环寿命长、能效高、可独立调节功率和能量等诸多优点。钒作为钒电池电解液的核心元素,由于相对稀缺导致成本过高,制约着钒电池产业的发展。因此,拓展钒资源途径成为当前研究的重点。而绝大部分钒产量来自于钒钛磁铁矿冶炼得到的钒渣,实现钢渣高效提钒成为我国钒产业可持续发展的关键举措。本文使用含钒钢渣为原料,在温度为1000℃,时间为3 h,配钙比为8%的条件下进行焙烧,最后以焙烧渣作为浸出原料,通过单因素试验研究了浸出温度、液固比、浸出时间及硫酸浓度对钒元素浸出的影响。采用高锰酸钾-硫酸亚铁铵滴定法,计算不同因素下钒的浸出率,最终得出浸出效果的最优参数。结果表明,在浸出温度为90℃、液固比为10∶1 mL/g、浸出时间为60 min、硫酸浓度达到35%时,钒的浸出效果最好,浸出率高达80.25%。这为缓解钒资源缺口提供了新的思路,有助于降低钒电池产业生产成本,进而加快国家的电化学储能建设。     

掺钒TiO_2可见光催化氧化SO_2的动力学和机理

利用溶胶-凝胶法制备掺钒纳米TiO_2,研究其在可见光条件下对SO2气体的催化氧化效果。采用烟气分析仪和碘量法测定SO2的浓度。利用XRD、BET、TEM、SEM、XPS、UV对掺钒TiO_2进行表征;研究焙烧温度、时间以及掺杂量等制备条件,对TiO_2脱除SO2的影响效果,探讨光催化氧化SO2的机理。结果表明:有O2条件下,在焙烧温度为700℃,时间为3 h,掺钒量物质的量含量为1.0%时,制备的TiO_2光催化氧化性能最好,SO2的脱除效率大于97%,氧化产物为SO3;光照和催化剂是SO2氧化的必要条件;光氧化效率随初始浓度的增大而增大,光催化反应符合一级反应动力学,且包括吸附和表面反应两部分,其中吸附为速控步骤;钒的掺杂使TiO_2产生红移,增强可见光催化活性,提高SO2气体的氧化效率。     

应用流化床焙烧制备熟石膏的实验研究

利用小型电加热流化床试验台对脱硫石膏进行焙烧实验以制备熟石膏,试验发现,焙烧温度在110℃～130℃左右,停留时间约为70 min时,熟石膏的生成率最大.在此条件下最终成功制备了β型半水硫酸钙,经测试,其性能达到了建筑石膏的技术指标.决定熟石膏(半水硫酸钙)生成品质的因素除了焙烧温度外,还有焙烧时间.不同焙烧设备的焙烧时间和焙烧温度各不相同.     

提高钒渣中V_2O_5品位的基础研究

通过含碳球团高温还原法研究还原温度和还原时间对高硅、高铁低品位钒渣的金属化率及钒富集的影响.结果发现,还原时间为60 min、还原温度为1 400℃时效果最佳,Fe的金属化率达80％以上,同时,可将二次钒渣中V2O5的含量提高至46.50％.     

废旧磷酸铁锂电池电极材料的硫酸化焙烧-水浸新工艺北大核心CSCD

针对目前急需解决的废旧磷酸铁锂(LiFePO_(4))电池中有价金属的清洁高效提取问题,提出硫酸化焙烧脱氟-水浸新工艺。用TG-DSC和XRD表征确定了正负极片热处理的适宜条件为:空气气氛、温度575℃。采用正交实验和单因素实验研究了浓硫酸使用量、焙烧时间和温度。水浸液固比、温度及时间对正负极混合料粉末中Fe、P和Li元素浸出率和浸出液中F元素残存率的影响。确定了最优焙烧工艺条件为:浓硫酸使用量为理论用量的0.75倍、焙烧时间2.5 h、温度110℃;最优水浸工艺条件为:液固比4∶1(mL/g)、温度60℃、时间2 h。在此工艺条件下,P和Li的浸出率都达到100%,Fe元素的浸出率为98.85%,F元素在浸出液中的残存率仅为13.11%。     

钒电池五价钒溶液的电导性质

全钒氧化还原液流电池被认为是满足风能、太阳能等新能源最有可行性的大规模储能技术之一。钒电池电解液既是导电介质又是能量存储的关键材料,是钒电池储能与能量转化的核心。对钒电池电解液热力学性质的研究,有助于深入认识溶液的本质特性,对钒电池的容量、能量密度以及系统稳定性的提高均具有极大意义。采用电导法测量了温度范围在278.15~318.15 K,不同浓度的V(Ⅴ)硫酸水溶液三元体系的电导率,通过多项式拟合及外推法,将V(Ⅴ)+H2SO4+H2O三元体系的电导率外推得到V(Ⅴ)水溶液二元体系电导率,并计算了离子的极限摩尔电导率、Stocks半径、迁移数、扩散系数和溶液电导活化能等参数并讨论了浓度、温度对这些性质的影响规律。     

Study on the conductivities of V(Ⅴ) solution of vanadium flow battery

全钒氧化还原液流电池被认为是满足风能、太阳能等新能源最有可行性的大规模储能技术之一。钒电池电解液既是导电介质又是能量存储的关键材料,是钒电池储能与能量转化的核心。对钒电池电解液热力学性质的研究,有助于深入认识溶液的本质特性,对钒电池的容量、能量密度以及系统稳定性的提高均具有极大意义。采用电导法测量了温度范围在278.15~318.15 K,不同浓度的V(Ⅴ)硫酸水溶液三元体系的电导率,通过多项式拟合及外推法,将V(Ⅴ)+H₂SO₄+H₂O三元体系的电导率外推得到V(Ⅴ)水溶液二元体系电导率,并计算了离子的极限摩尔电导率、Stocks半径、迁移数、扩散系数和溶液电导活化能等参数并讨论了浓度、温度对这些性质的影响规律。     

Anti-precipitation effects of TiO2 and TiOSO4 on positive electrolyte of vanadium redox battery

In this study, the effects of TiO₂ and TiOSO₄ on the precipitation of the positive electrolyte of vanadium redox battery (VRB) systems were investigated. TiO₂ and TiOSO₄ were used as anti-precipitating agents for V(V) ions at 40 and 60 °C. The optimum amounts and electrochemical properties of additives were determined by electrochemical methods such as cyclic voltammetry and electrochemical impedance spectroscopy. The optimum amount of additives was identified as wt% 0.004 and 0.003 for TiO₂ and TiOSO₄, respectively. The structural features and composition of electrodes were investigated by scanning electron microscopic and energy-dispersive X-ray analysis. A plausible reaction mechanism was also proposed for redox reaction occurring on the positive electrode of a VRB. The concentration of V(V) ions in the additive including electrolyte were higher than that of blank solution at the end of the thermal precipitation tests. According to thermal and electrochemical studies, TiO₂ and TiOSO₄ can be useful additives for the positive electrolyte of a VRB.     

Graphite–carbon nanotube composite electrodes for all vanadium redox flow battery

The voltammetric behaviors of graphite (GP) and its composites with carbon nanotube (CNT) were studied in 5 M H₂SO₄ + 1 M VOSO₄ solution with cyclic voltammetry (CV), and the surface morphology of the composites was observed with scanning electron microscope (SEM). The results obtained from voltammetry show that the redox couples of V(IV)/V(V) and V(II)/V(III), as positive and negative electrodes of all vanadium flow liquid battery, respectively, have good reversibility but low current on the GP electrode, and the current can be improved by CNT. It is found from the observation of SEM that the CNT is dispersed evenly on the surface of sheet GP when they are mixed together. The best composition for the positive and the negative of all vanadium flow liquid battery determined by comparing voltammetric behavior of the composite electrodes with different content of CNT is 5:95 (w_CNT/w_GP) for both positive and negative electrodes. The activity of the composite electrode can be affected by the heat treatment of CNT. CNT treated at 200 °C gives better activity to the composite electrode.     

Study on the sodium oxidation properties of low-iron vanadium-titanium magnetite with high vanadium and titanium

In this work, the oxidation properties of low-iron vanadium-titanium magnetite with high vanadium and titanium in a laboratory muffle furnace was investigated. XRD, SEM, and TG-DSC method are employed to identify the main phases and chemical composition of the samples. The roasting time of 4h and Na₂CO₃/vanadium titanium magnetite mass ratio of 7.5:100 were determined. The results showed that the blank oxidation roasting temperature ranged from 593°C to 1035°C, the mixed oxidation roasting temperature of vanadium-titanium magnetite and Na₂CO₃ at the range of 204°C to 825°C, and the forming temperature of soluble vanadate at the range of 700°C to 825°C. When roasting temperature reached 1000°C, consolidation was started. When roasting temperature was 850°C, the roasting conversion efficiency, acid leaching efficiency and water leaching efficiency were 92.4%, 87%, and 85%, respectively.     

再燃过程中HCN对NOx还原的重要性

在降低ＮＯｘ排放的一系列方法中,燃料再燃是重要措施之一。通过对再燃区不同的空气过量系数和再燃温度条件下的数值计算,研究了天然气（ＣＨ４）作为再燃燃料时ＨＣＮ对ＮＯ再燃过程和再燃率的影响。再燃区模拟烟气成分为：ＣＯ２＝１６．８％,Ｏ２＝２％,ＮＯ＝０．１％和平衡气体Ｎ２。研究发现,再燃燃料中含氮组分的存在,以及再燃区的工况条件都对ＮＯｘ的再燃率有很大的影响。因此,在实施降低ＮＯｘ排放的再燃技术过程中     

NOx control through reburning

Reburning is a process whereby a hydrocarbon fuel is injected immediately downstream of the combustion zone to establish a fuel-rich zone in order to convert nitric oxide to HCN. The reburning fuel can be gaseous (e.g., natural gas), solid (e.g., coal char or wood) or liquid (e.g., residual oil). Typically, the amount of reburning fuel used is 10–30% of the total fuel. This technology is practiced commercially with nitric oxide reduction levels of 35–65%, depending on the type and scale of the boiler or combustion, the primary and reburning fuels and other variables. Current research and development are suggesting several advanced reburning concepts including injection of ammonia or urea aft of the reburning fuel injection. Nitric oxide reductions of over 90% are anticipated. In this mini-review, a review of reburning technologies, measurements and mechanisms is presented. Predictive methods for reburning are also discussed. Recent work on reburning, including development of a global reburning reaction rate, is summarized, and results of application of a comprehensive combustion model to reburning measurements are summarized.     

Effect of α- and γ-alumina on the precipitation of positive electrolyte in vanadium redox battery

In this study, the effect of α-alumina (α-Al₂O₃) and γ-alumina (γ-Al₂O₃) on the precipitation of the positive electrolyte, which is one of the most important problems in vanadium redox battery (VRB) systems, was investigated. α-Al₂O₃ and γ-Al₂O₃ were used as additive materials to improve the thermal stability of V(V) ion and the performance of VRB at high temperatures. Cyclic voltammetry and electrochemical impedance spectroscopy were used to determine the properties of positive electrolyte systems. The optimum amount of additives was identified as wt% 0.004 and 0.010 for α-Al₂O₃ and γ-Al₂O₃, respectively. The surface morphology and composition of electrodes were investigated by scanning electron microscopy and energy-dispersive X-ray analysis. A plausible reaction mechanism was also proposed for redox reaction occurring on the positive electrode of a VRB. The adsorption of V(V) ions to the electrode surface from the solution increased by the time additives were added into the system. γ-Al₂O₃ showed the best anti-precipitation effects for the V(V) ion at 40 °C and 60 °C in the precipitation tests. In the battery test, the discharge capacity of γ-Al₂O₃ with a positive electrolyte, was the highest at 87.2 mAh. According to thermal and electrochemical studies, γ-Al₂O₃ can be a useful additive for the positive electrolyte of a VRB.     

Nanostructured hydrogen storage materials prepared by high-energy reactive ball milling of magnesium and ferrovanadium

Hydrogen storage nanocomposites prepared by high energy reactive ball milling of magnesium and vanadium alloys in hydrogen (HRBM) are characterised by exceptionally fast hydrogenation rates and a significantly decreased hydride decomposition temperature. Replacement of vanadium in these materials with vanadium-rich Ferrovanadium (FeV, V80Fe20) is very cost efficient and is suggested as a durable way towards large scale applications of Mg-based hydrogen storage materials. The current work presents the results of the experimental study of Mg–(FeV) hydrogen storage nanocomposites prepared by HRBM of Mg powder and FeV (0–50 mol.%). The additives of FeV were shown to improve hydrogen sorption performance of Mg including facilitation of the hydrogenation during the HRBM and improvements of the dehydrogenation/re-hydrogenation kinetics. The improvements resemble the behaviour of pure vanadium metal, and the Mg–(FeV) nanocomposites exhibited a good stability of the hydrogen sorption performance during hydrogen absorption – desorption cycling at T = 350 °C caused by a stability of the cycling performance of the nanostructured FeV acting as a catalyst. Further improvement of the cycle stability including the increase of the reversible hydrogen storage capacity and acceleration of H₂ absorption kinetics during the cycling was observed for the composites containing carbon additives (activated carbon, graphite or multi-walled carbon nanotubes; 5 wt%), with the best performance achieved for activated carbon.     

Control of NO emission during coal reburning

In this study, two types of coals were used as the reburning fuel to investigate the influence of the reburning zone stoichiometry SR₂, the primary NO level and the particle size on NO reduction. For both coals, the NO reduction can reach as high as 60–70% in the tested SR₂ range of 0.7–1.1. No optimum reburning zone stoichiometry was observed in this study. The NO reduction decreases monotonically with the decrease of reburning zone stoichiometry. The effect of particle size is only obvious for larger particle sizes.     

对用烃类和氨为还原剂的脱硝技术的计算分析

采用Chemkin 4．0软件包中基状流反应器和Miller等人的化学动力学模型,对再燃、先进再燃、选择性非催化还原（SNCR）以及加入烃类的SNCR反应的原理进行了模拟计算和比较分析,研究了不同反应温度、再燃燃料比和停留时间对脱硝效率的影响。计算结果表明,先进再燃引入氨基还原剂,可以拓宽脱硝的有效温度区间,加快反应速率,提高脱硝效率约20％,优于常规再燃技术;SNCR反应中加入很少量烃类（烃／NO〈1）可以增加其有效的脱硝温度范围,加快脱硝反应速率,使完成脱硝反应所需时间缩短一半,在较低的反应温度下达到较高的脱硝效率;而先进再燃达到相当的脱硝率则需要消耗超过15％的再燃燃料。     

Modelling NOx emissions during staged combustion

Staged combustion has been accepted as an effective way to reduce NO_x emission. Based on the comparison of calculated results using Miller and Bowman's (1989, Progr. Energy Combust. Sci. 15 , 287) detailed elementary reaction model with experimental data, it is found effective to apply this model in the simulation of NO formation and destruction during staged combustion. Sensitivity analysis shows that C, CH, CH₂ and HCCO play an important role in NO destruction and reduction under fuel staging. NO generated in the primary zone can be reduced greatly by staged combustion. Besides the air–fuel ratio in the primary combustion zone, the combustion temperature in the reburning zone and the mass factor of the reburning fuel in the overall fuel, the main factors which affect NO destruction and reduction are the position where reburning is introduced and the types of reburning fuel. It is found that reburning cannot be introduced too close to the primary combustion zone. The reburning fuels that can effectively stimulate NO to HCN are H₂ and C₂H₄. Copyright © 1999 John Wiley & Sons, Ltd.