Boron removal in purifying metallurgical grade silicon by CaO-SiO_2 slag refining

Boron removal from metallurgical grade silicon （MG-Si） using a calcium silicate slag was studied. The results show that it is impossible basically to remove boron using a pure SiO2 refining. The oxidizing ability of CaO-SiO2 slag for boron removal was characterized by establishing the thermodynamic relationship between the distribution coefficient of boron （LB） and the activities of SiO2 and CaO. The experimental results show that the distribution coefficient and the removal efficiency of boron are greatly improved with the increase of CaO proportion in the slag. The maximal value of LB reaches 1.57 with a slag composition of 60%CaO-40%SiO2 （mass fraction）. The boron content in the refined silicon is reduced from 18×10^-6 to 1.8×10^-6 using slag refining at 1600 ℃ for 3 h with a CaO-SiO2/MG-Si ratio of 2.5, and the removal efficiency of boron reaches 90%.

Boron removal from metallurgical silicon using CaO-SiO_2-CaF_2 slags

The removal of boron from metallurgical silicon in slag system of CaO-SiO2-10%CaF2 was investigated. The partition coefficient of boron （LB） between slag and silicon phase was studied under different conditions of slag basicity （CaO/SiO2 ratio）, temperature, mass ratio of slag to silicon and gas blowing. The results show that LB has a maximum value of 4.61 when the CaO/SiO2 mass ratio is around 2 at l 873 K. The logarithm of LB is linear to the reciprocal of temperatures in the range of 1 773-1 973 K. LB increases with the increase of mass ratio of slag to silicon, but it does not increase markedly when the ratio excesses 3. Gas blowing can sionificantlv increase the removal of boron, and LR increases with the increase of water vapor content.

Phase conversion and removal of impurities during oxygen-rich alkali conversion of high titanium slag

In order to achieve high-efficiency alkali conversion and impurity removal of high titanium slag under the condition of low alkali concentration,a new way of oxygen-rich alkali conversion in KOH solution was proposed.The conversion law of element occurrence state and the influence of the conversion conditions on the titanium conversion rate and removal rate of silicon and aluminum were studied.The results showed that the KOH solution converted the titanium oxide in high titanium slag into whisker-like potassium titanate.Silicon and aluminum elements were dissolved into the solution.Under the following conditions,KOH concentration of 6 mol/L,conversion temperature of 260℃,initial oxygen partial pressure of 2 MPa,liquid−solid ratio of 35 mL/g,conversion time of 4 h,and high titanium slag particle size of 48−74μm,the conversion rate of titanium was 97.0%,and the removal rates of silicon and aluminum were 90.2%and 76.2%,respectively.Oxygen-rich alkali conversion product was converted to rutile with a TiO_(2) grade of 99.1%by acid hydrolysis conversion.

PHOSPHORUS REMOVAL USING STEEL SLAG

Steel slag is a byproduct produced in large amounts in the steel-making process. It is an important resource that can be effectively utilized. An experiment was described in which steel slag was tested as an adsorbent for the removal of phosphorus from waste water. Phosphorus removal depended on the amount of steel slag added, the pH value, the contact time, and the initial concentration. Under laboratory conditions when the added slag was 7.5g/L, the contact time 2h, and the pH value was equivalent to 6.5, over 99% of the phosphorus was removed; the experimental data on steel slag adsorption of phosphorus in the water fitted the Freundlich isotherm model. Steel slag was found to be very effective in adsorbing phosphorus.

Mechanisms of phosphate removal from aqueous solution by blast furnace slag and steel furnace slag

We report the adsorption of phosphate and discuss the mechanisms of phosphate removal from aqueous solution by burst furnace slag (BFS) and steel furnace slag (SFS). The results show that the adsorption of phosphate on the slag was rapid and the majority of adsorption was completed in 5~10 min. The adsorption capacity of phosphate by the slag was reduced dramatically by acid treatment. The relative contribution of adsorption to the total removal of phosphate was 26%~28%. Phosphate adsorption on BFS and SFS follows the Freundlich isotherm, with the related constants of k 6.372 and 1/n 1.739 for BFS, and of k 1.705 and 1/n 1.718 for SFS. The pH and Ca2+ concentration were decreased with the addition of phosphate, suggesting the formation of calcium phosphate precipitation. At pH 2.93 and 6.93, phosphate was desorbed by about 36%~43% and 9%~11%, respectively. These results indicate that the P adsorption on the slag is not completely reversible and that the bond between the slag particles and adsorbed phosphate is strong. The X-ray diffraction (XRD) patterns of BFS and SFS before and after phosphate adsorption verify the formation of phosphate salts (CaHPO4·2H2O) after adsorption process. We conclude that the removal of phosphate by BFS and SFS is related to the formation of phosphate calcium precipitation and the adsorption on hydroxylated oxides. The results show that BFS and SFS removed phosphate nearly 100%, indicating they are promising adsorbents for the phosphate removal in wastewater treatment and pollution control.

Experimental study on sulfur removal from ladle furnace refining slag in hot state by blowing Air

In view of the present problem of sulfur enrichment in the metallurgical recycling process of ladle furnace （LF） refining slag, a simple and efficient method of removing sulfur from this slag was proposed. The proposed method is compatible with current steelmaking processes. Sulfur removal from LF refining slag for SPHC steel （manufactured at a certain steel plant in China） by blowing air in the hot state was studied by using hot-state experiments in a laboratory. The FactSage software, a carbon/sulfur analyzer, and scanning electron micros- copy in conjunction with energy-dispersive X-ray spectroscopy were used to test and analyze the sulfur removal effect and to investigate factors influencing sulfur removal rate. The results show that sulfur ions in LF refining slag can be oxidized into SO2 by O2 at high tempera- ture by blowing air into molten slag; SO2 production was observed to reach a maximum with a small amount of blown O2 when the tem- perature exceeded 1350℃. At 1370℃ and 1400℃, experimental LF refining slag is in the liquid state and exhibits good fluidity; under these conditions, the sulfur removal effect by blowing air is greater than 90wt% after 60 min. High temperature and large air flow rate are benefi- cial for removing sulfur from LF refining slag; compared with air flow rate, temperature has a greater strongly influences on the sulfur re- moval.

Smelting chlorination method applied to removal of copper from copper slags

In order to reasonably utilize the iron resources of copper slags, the smelting chlorination process was used to remove copper from copper slags. Higher holding temperature and O2 flow rate are beneficial to increasing copper removal rate. However,the Cu2O mode is formed by the reaction of surplus O2 and CuCl with O2 flow rate increasing over 0.4 L/min, causing CuCl volatilization rate and copper removal rate to decrease. The resulting copper removal rate of 84.34% is obtained under the optimum conditions of holding temperature of 1573 K, residence time of 10 min, Ca Cl2 addition amount of 0.1(mass ratio of CaCl2 and the copper slag) and oxygen flow rate of 0.4 L/min. The efficient removal of copper from copper slags through chlorination is feasible.

赤泥-钢渣基免烧陶粒的制备及除磷特性研究

针对传统烧结陶粒制备过程中成本高、能耗大的缺点,以赤泥和钢渣为主要原料,通过免烧工艺制备出了具有磷吸附性能的陶粒。以解体率为其力学性能指标,通过正交实验确定了陶粒的最佳质量配比(赤泥、钢渣质量比4:3、稻壳灰添加量10%、石膏添加量4%、水泥添加量10%),最佳制备工况下的陶粒解体率为3.90%;所制作陶粒无重金属浸出风险,属于环境友好型材料。陶粒对水中磷的吸附特性实验结果表明,陶粒在酸性溶液中具有最佳的除磷效果;对于初始磷浓度为20 mg/L的溶液,设置30 g/L的陶粒投加量,除磷率可达96.40%;陶粒吸附过程遵循准二级动力学模型和Langmuir等温吸附模型,最大理论吸附量为0.99 mg/g;磷与陶粒表面的CO_(3)^(2-)、Ca^(2+)、Fe^(3+)、Al^(3+)发生离子交换和磷酸盐共沉淀反应,是水中的磷去除的机理,沉淀物质主要由Ca_(3)(PO_(4))_(2)、FePO_(4)、AlPO_(4)组成。

秸秆-钢渣混合填料对低C/N比污水脱氮研究

为探讨作物秸秆和钢渣对低C/N比污水脱氮的影响,本研究分别以空白(CK)、小麦秸秆(W组)、水稻秸秆(R组)、小麦秸秆+钢渣(WF组)、水稻秸秆+钢渣(RF组)、钢渣(F)为填料,在厌氧循环系统中对C/N比为0.23~0.93的污水进行处理,探究6种不同的填料-系统对NO3-N的去除效果。结果表明:W组、R组、WF组和RF组的NO_(3)^(-)-N去除率分别为94.99%、86.70%、98.75%和94.70%;相比于WF组和RF组填料系统,纯秸秆填料系统(W组和R组)对污水中NO_(3)^(-)-N的去除速度更快,但在处理过程中的可溶性有机碳(DOC)浓度更高;WF组和RF组钢渣中含铁化合物的释放及转化会消耗有机质,因此其DOC浓度保持在较低水平,避免了因DOC浓度过高而引起的二次污染问题。综合考虑,小麦秸秆+钢渣混合填料在脱氮过程中能够在保持高效脱氮的同时避免出水二次污染问题,更适用于低C/N比污水的脱氮。

Study on the removal of Hg^0 from flue gas by coal dry powder gasification coarse slag

The prevention and treatment of mercury in coal-fired power plants has always been the focus and difficulty.How to control the pollution of mercury to human body and ecological environment quickly and effectively is a hot research topic nowadays.As a low cost and potential adsorbent,there is a huge space for the development of coal dry powder gasification coarse slag.In this paper,Mercury osmotic tubes are heated by water bath tank as mercury source,and the scavenging effect of adsorbent on Mercury monomer under different influence conditions is explored.The adsorbent plays an important role in adsorption of mercury monomer because of its special active sites on the surface.The reason is that the adsorbent surface is rich in carboxyl group,hydroxyl functional group,combined with mercury to form complexes.This shows that chemical adsorption facilitates the adsorption process.

Isolation and Identification of Phosphate-accumulating Strain PAO3-1 and Its Phosphorus Removal Characteristics

A phosphate-accumulating bacteria strain PAO3-1 was isolated from biological phosphorus removal sludge supplied with sodium acetate as carbon source under stable performance. This strain has good enhanced biological phosphorus removal effect on normal activated sludge system. Phosphorus removal ratio was raised form 44% with no added strain to more than 82% with strain strengthening biological phosphorus removal. It is identified to be Alcaligenes sp. according to its morphology, biochemical characteristics and 16S rDNA sequence analysis. The cell of strain PAO3-1 is straight bacilli form, 0.4×1.1μm, no flagellum, gram negative and special aerobiotic. The optimal temperature and pH for growth are 32℃-37℃ and 5.5-9.5, respectively. The shape of slant clone is feathery. The phosphate accumulating rate of strain PAO3-1 was 8.1mgP/g cell·h, and 14.3 mgP/g cell·h when in phosphate-starving situation, which was 76.5% higher than that in non-starving situation. Its phosphate release rate of log course in anaerobic phase and in culture without phosphorus was 7.6mgP/g cell·h, while in stable course the rate was 6.1mgP/g cell·h. The rate in stable course was 19.7% lower than that in log course.

Synthesis of (Ca, Mg)-α′-Sialon-AlN-BN powders from boron-rich blast furnace slag by microwave carbothermal reduction-nitridation

(Ca, Mg)-α′-Sialon-AlN-BN powders were synthesized by the carbothermal reduction and nitridation (CRN) method using boron-rich slag, one of the intermediate products from pyrometallurgy separation of pageit, as the staring material. The influences of synthesis temperature and holding time on the phase composition and microstructure during the microwave CRN were studied by XRD, SEM and EDS. The comparison between two heating techniques, conventional and microwave heating, on the synthesized powder was presented as well. The experimental results revealed that the phase compositions and microstructures of the synthesized products were greatly affected by the synthesis temperature and holding time. With an increase in the synthesis temperature or holding time, the relative amount of α′-Sialon increased and α′-Sialon became the main crystalline phase at 1400 °C for 6 h. The synthesized products also contained AlN, BN and a small amount of β-SiC. Elongated α′-Sialon grains, short rod AlN grains, aggregate nanoscale BN grains were observed in the synthesized powders. The reaction temperature of microwave heating method was reduced by 80 °C, the reaction time was shortened by 2 h, and more elongated α′-Sialon grains with large aspect ratio were observed.

一株锰氧化细菌AL-6与柚子皮生物炭耦合修复电解锰渣场污染地下水特性研究

为了研究电解锰渣场污染地下水中复杂废水的修复问题,以农业废弃物柚子皮为原材料制成生物炭作为菌株Acinetobacter baumannii AL-6固定化载体(MBC),得到菌株生物炭耦合体系(MBC)。探究了该耦合体系对含锰、氨氮以及高钙镁离子复合废水的综合处理能力,同时构建序批式间歇反应器(SBR)以探究其在废水处理中的应用潜力。实验结果表明,MBC在48 h内去除了98.46%的锰。与2个独立的实验组(生物炭组,菌株AL-6组)相比,MBC对锰的去除具有良好的协同作用。MBC对锰的平均去除率为15.87 mg/(L·h),是菌株AL-6组的1.09倍,生物炭组的14.33倍。此外,MBC对氨氮的最大去除率为71.92%,对钙镁离子也有一定的去除效果,分别为41.46%和26.95%。在SBR中,MBC能去除90.1%的锰和85.44%的氨氮。结果表明,微生物固定化具有巨大的应用潜力,可用于处理电解锰渣复合污染废水。

Removal Rate of Phosphorus by Different Constructed Wetland Substrates

[ Objective] The study aimed to discuss the removal rate of phosphorus by different constructed wetland substrates. [ Methed] Based on static experiments, we analyzed the removal rate and characteristics of phosphorus by different constructed wetland substrates like steel slag, cin- der slag, shale, boiler slag, soil and gravel. [ Result~ The maximum adsorption of phosphorus by various substrates showed as follows, steel slag 〉 cinder slag 〉 shale 〉 boiler slag 〉 soil 〉 gravel. When the initial concentration of phosphorus was 5 mg/L, the removal rate of phosphorus by the steel slag, cinder slag, shale, boiler slag, soil and gravel was 99.76%, 85.8%, 71.2%, 63.0%, 46.8% and 11.7% respectively. It is suggested that shale and boiler slag can be used as the substrate of subsurface-flow constructed wetlands; cinder slag can be chosen as a renewable sub- strate for intensifying phosphorus removal; steel slag could be used at the end of subsurface-flow constructed wetlands for treating TP in outflows. [Concluslon] The research could provide theoretical references for choosing a suitable substrate for constructed wetlands to remove phosphorus in future.

Effect of TiO2 Addition on Slag Resistance of Lightweight Corundum-spinel Castables

Five lightweight castables containing different TiO2 additions were prepared by using porous corundum - spinel （ MgAl2O4 ） ceramics as aggregate. Corrosion of the lightweight cstables by ladle slag was conducted using a static crucible test. The effect of the TiO2 addition on the slag resistances of the lightweight corundum -spinel castables was investigated through SEM, EDS and Fact- Sage@ software, etc. h was found that TiO2 additi,ve t,vmoted the sintering degree of the castables, deereased the average pore .size, the apparent porosity, and the contact area between the casmbles and slag, and then en- hanced the corrosion resistance. However, TiO2 additive decreased the viscosity of the penetrated .slag simultane- ously, and then deteriorated the penetration resistance.

Corrosion of Magnesia-chrome Brick by Smelting Reduction Slag with Iron Bath

Effects of FeO content （0, 5%, 10%, and 15% in mass, respectively ） in lab-synthesized smelting redttc- tion slag with iron bath and test temperature （1 450, 1 500, 1550, anti 1 600 ℃ ） on corrosion am,amount and microstructure of fused rebonded magnesia - chrome brick with 26.02 massqc of Cr2O3 were researched by rotary cylinder method. The results show that ： （ 1 ） the corro- sion amolult of magnesia -chrome brick by slag without FeO is higher than that by the slag with 5% FeO, and the vorrosion amount increases when FeO content increa- ses from 5% to 15% ; （2） the test temperature is one of the important factors affecting the slag corrosion resist- ance of magnesia - chrome brick, and the corrosion of smelting reduction slag to brick increases with the temperature rising.

柠檬酸-赤泥联用高效脱除电解锰渣氨氮的工艺及机理研究

电解锰渣中氨氮限制了其资源化利用,柠檬酸酸-赤泥联用可高效彻底脱除电解锰渣中氨氮。本文研究处理剂用量、反应时间和浸取方式等工艺条件对电解锰渣中氨氮剩余浓度的影响,通过XRD和XPS等技术表征物质变化,探讨氨氮脱除机理。结果表明,柠檬酸浸出工序是柠檬酸用量25%、液固比为5:1条件下机械振荡浸出30min;赤泥深度脱除工序是电解锰渣与赤泥质量比为1:0.5、室温浸取5h,电解锰渣中氨氮残存浓度降至1mg/L左右。浸出液中的铵根离子与柠檬酸反应最终生成柠檬酸铁铵稳定于浸出液中。赤泥中的碱性物质与残存氨氮反应,氨氮以气体形态脱除。

铝粉还原污酸中砷新工艺研究

由于硫化精矿中砷含量越来越高,致使烟气处理过程产生的污酸中砷含量也越来越高,同时污酸中含有铜、铁等有价金属。目前污酸除砷方法多以除砷为目的,形成的含砷渣属于危废,还需要二次处理。本研究研发了还原除砷新工艺,首先向污酸中加入硫化砷渣进行脱铜预处理并回收铜,然后用铝粉还原脱铜后液中的砷回收砷,最后向脱砷液中加入硫酸钾回收铝,还原后液回收还原剂后采用两段中和法处理。试验研究结果表明,在加入铜离子摩尔量1.1倍的硫化砷渣、反应温度85℃、反应时间3 h的条件下,污酸中的铜含量由2000 mg/L降至196 mg/L,硫化铜渣返熔炼配料系统;在还原温度70℃、还原时间2 h,还原剂用量1.8倍的条件下,砷的还原率大于96%,还原后液中的砷含量低于300 mg/L,得到的砷渣品位大于95%,可用于后续制备高品位单质砷;在硫酸钾用量1.1倍、反应温度常温、反应时间2 h的条件下,溶液含铝3.6 g/L,得到的明矾可达到《工业硫酸铝钾》(HG/T2565—2007)一等品标准。该方法除砷效果好,且能将污酸中的砷转变为具有经济价值的砷产品,还不会产生硫化氢气体,具有应用推广价值。

煤气化炉渣免烧陶粒的制备及其在反硝化滤池中的应用

煤气化炉渣是煤气化过程中产生的固体废弃物。大量的炉渣堆积不仅造成了资源的浪费,而且增加了企业的运营成本,对当地环境造成危害。以内蒙古地区的煤气化炉渣为主要原料,加入水泥、生石灰、CaSO_(4)等,通过免烧结的方式制备陶粒。在制气炉渣、水泥、生石灰、CaSO4质量比为70∶30∶2.5∶5的条件下制得的陶粒性能最优越,比表面积可达51.7 m^(2)/g,堆积密度为809 kg/m^(3),颗粒破碎强度为6.61 MPa。将该陶粒用作反硝化生物滤池填料,相比于普通市售陶粒挂膜速度更快;在水力停留时间(HRT)为12 h时,化学需氧量(COD)由300 mg/L下降至60 mg/L以下,COD去除率在80%以上;硝态氮(NO_(3)^(-)-N)由60 mg/L下降至2 mg/L以下,NO_(3)^(-)-N去除率在95%以上。利用煤气化炉渣制备免烧结陶粒实现了煤气化炉渣的资源化利用,同时为污水反硝化处理提供了一种新的填料。

页岩-钢渣组合填料湿地强化脱氮除磷研究

以城市污水A／O工艺出水为处理对象，运用页岩和钢渣物化除磷、调控进水碳氮比和氮素氧化性等技术手段，在中试规模上研究了页岩和钢渣组合填料湿地的脱氮除磷效能及影响因素．结果表明，当COD面积负荷率、TN面积负荷率、TP面积负荷率、HRT（水力停留时间）分别为6．5～20．7g·（m^2·d）^-1、2．57～8．22g·（m^2·d）^-1、0．41～1．32g·（m^2·d）^-1、0．5～1．6d时，①氨氮、亚硝态氮和硝态氮的去除率分别为85.8％、56．3％和18．6％，TN去除率为58．0％，TN面积负荷去除率为3．58g·（m^2·d）^-1，TN反应动力学常数为0．31m·d^-1，TN面积负荷去除率随进水TN负荷的增加而线性增加．②TP去除率为90．4％，TP面积负荷去除率为0．89g·（m^2·d）^-1，TP反应动力学常数为0．86m·d^-1，TP面积负荷去除率随进水TP负荷的增加而线性增加．③水温、HRT、氮素组分、C／N等因素对湿地系统的脱氮除磷效率有显著影响．TN面积负荷去除率随HRT、COD／TN值的增加而幂函数增加．TN面积负荷去除率随水温、（NO2^- -N＋NO3^- -N）／TN值的增加而呈指数函数增加．