气化炉锥底出现铁渣环的原因及危害分析

根据某煤制烯烃项目德士古气化炉出现的异常情况,分析气化炉锥底出现铁渣环的原因和危害,提出相应改进措施。

回转窑冶炼腐泥镍矿石生产镍铁合金渣环形成机理

阐述了冶炼腐泥镍矿石过程中,在回转窑形成渣环的机理。窑壁温度高于原料,炉料进入炉床位置的温度最高。释放出的低MgO和高SiO2·FeO硅酸盐和再结晶的非化学当量蛇纹石形成一次熔体,含有很多Al2O3的细矿石经过Ostwald熟化熔化石灰石,形成二次熔体。因此,它进入炉床会造成降温沉积在炉壁上并形成炉结,增大粘着力。渣环粘着区的原料略向出口端移动会迅速减少粘着。这是因为Ostwald熟化造成颗粒长大,进入熔池的熔体量减少,少量沉积在炉壁上,形成炉结,局部形成渣环。细小的低MgO高FeO矿石的点缺陷比高MgO低FeO矿石多。前者与后者相比,熔点较低,扩散率较高,前者比后者形成渣环的可能性更大。

CO_2 capture by carbonated carbide slag seriflux after drying in calcium looping cycles

A new carbide slag （CS） seriflux utilization was proposed. The flue gas from a coal-fired plant was first bubbled into CS seriflux for CO2 capture. The obtained carbonated carbide slag seriflux （CCSS） was dried and utilized as a CO2 sorbent in the calcium looping cycles. The CO2 capture behavior of the dried CCSS and the raw CS was investigated in a dual fixed-bed reactor and a thermo- gravimetric analyzer. The effects of carbonation time, calcination temperature and carbonation temperature on CO2 capture performance of CCSS in the multiple carbonation/ calcination cycles were studied. The results show that the CO2 capture capacity of CCSS was higher than that of CS. Calcined at 950 ℃, CCSS shows better carbonation reactivity than CS, which benefits CO2 capture under severe calcination conditions. In the range of 700 to 725℃ for the carbonation, CCSS shows the optimal CO2 capture performance. The calcined CCSS shows better porous microstructure than the calcined CS. The calcined CCSS exhibits a larger surface area and pore volume in the cycles, which favors a higher CO2 capture capacity in the multiple cycles.

Effect of copper slag recovery on hydrometallurgical cut-off grades considering environmental aspects

Determining the hydrometallurgical cut-off grades specifies the destination of low grade materials and this is subjected to more benefits in mining. Copper production rate is considered as one of the fundamental issues in hydrometallurgical cut-off grades determination. Slags are remarked as one of the main sources of copper. It is not only regarded as a waste but also identified as another resource extracting base metals. Slags are characterized by copper high grade. Thus, slag copper recovery can be led to different cut-off grades and net present value(NPV). The current research scrutinizes the effect of slag recovery by both flotation and hydrometallurgical methods on the hydrometallurgical cut-off grades. For this purpose, the optimum cut-off grade algorithms of hydrometallurgical methods are developed by considering associated environmental parameters, incomes and also the costs. Then, their optimum amounts are calculated with NPV maximization as an objective function. The results indicate that considering slag copper recovery in the hydrometallurgical cut-off grade algorithms reduces the environmental costs caused by slag dumping and leads to more NPV by 9%.

Physicochemical and environmental characteristics of alkali leaching residue of wolframite and process for valuable metals recovery

Physicochemical and mineralogical characteristics of an alkali leaching residue of wolframite were studied by XRD,SEM−EDS,chemical phase analysis,mineral liberation analyzer(MLA),and TG−DSC methods.Batch leaching tests,toxicity characteristic leaching procedure(TCLP)tests and Chinese standard leaching tests(CSLT)were conducted to determine the environmental mobility of toxic elements.The results show that,due to the high contents of W,Fe,Mn,Sn,and Nb,the residue is with high resource value,but the content of a toxic element,As,is also high.The existing minerals of the investigated elements mainly occur as monomer particles,but it is difficult to extract these valuable metals by conventional acid leaching due to their mineral properties.The release of As increases over time in acidic environment.The leaching concentration of all investigated harmful elements through TCLP is within the limiting value,while the leaching concentration of As through CSLT exceeds the limiting value by more than 4 times,so the residue is classified as hazardous solid waste based on the Chinese standard.A process for valuable metals recovery from this residue was proposed.Preliminary experimental results indicated that the main valuable metals could be extracted effectively.

Separation of alumina and silica from metakaolinite by reduction roasting-alkaline leaching process: Effect of CaSO_(4) and CaO

Limestone(CaCO3),which could promote sulfur fixation,was added to coal gangue during roasting in a circulating fluidized bed(CFB)boiler.CaO and CaSO_(4) were the main Ca-bearing minerals while metakaolinite was the major Al-bearing mineral in CFB slag.The effect of CaSO_(4) and CaO on the separation of alumina and silica from metakaolinite by reduction roasting−alkaline leaching process was studied.Results showed that metakaolinite was completely converted into hercynite and silica solid solutions(i.e.,quartz and cristobalite solid solutions)by reduction roasting with hematite.More than 95%of silica in the reduced specimen was removed by alkaline leaching.The addition of CaSO_(4) and CaO remarkably decreased the separation efficiency of alumina and silica in metakaolinite,which could be attributed to the formation of Si-bearing minerals:(1)Fayalite and anorthite were formed during the reduction roasting process;(2)Fayalite was stable while anorthite was converted into sodalite and wollastonite during the alkaline leaching process.This study demonstrates that sulfur in coal gangue should be fixed by treating the exhaust gas instead of controlling the combustion process of CFB to achieve the comprehensive recovery of silica and alumina from the CFB slag.

Spontaneous separation of Pb from PbSO_(4)-coprecipitated jarosite using freeze-thaw cycling with thiourea

To separate Pb from PbSO_(4)-coprecipitated jarosite,a novel thiourea-induced freeze-thaw cycling(T-FTC)process was investigated.Results show that distributed PbSO_(4)particles are pressed and aggregated around the jarosite particles by T-FTC.Under the freezing-concentration effect of T-FTC,the reaction between PbSO_(4)and thiourea is also promoted,forming lead thiourea sulfate(Pb-tu).As the cycles of T-FTC increase,PbSO_(4)around jarosite disappears for the reaction of forming Pb-tu.After 12 cycles of T-FTC,a spontaneous separation is observed between Pb-tu and jarosite,i.e.,Pb-tu is separated into the upper layer while jarosite-rich phases remain in the lower layer.Due to this spontaneous separation,leaching toxicity of the jarosite coprecipitates is reduced by 73.7%.These results suggest that T-FTC process can achieve the separation of Pb from PbSO_(4)-coprecipitated jarosite and is a promising approach for removing and recovering metals from iron-rich jarosite residues.

Physicochemical and environmental properties of arsenic sulfide sludge from copper and lead-zinc smelter

Physicochemical properties of arsenic sulfide sludge(ASS) from copper smelter(ASS-I) and lead-zinc smelter(ASS-II) were examined by XRD, Raman spectroscopy, SEM-EDS, TG-DTA, XPS and chemical phase analysis method. The toxicity characteristic leaching procedure(TCLP), Chinese standard leaching tests(CSLT), three-stage sequential extraction procedure(BCR) and batch leaching experiments(BLE) were used to investigate the environmental stability. The ASSs from different smelters had obviously different physicochemical and environmental properties. The phase composition and micrograph analysis indicate that ASS-I mainly consists of super refined flocculent particles including amorphous arsenic sulfide adhered with amorphous sulfur and that ASS-II mainly consists of amorphous arsenic sulfide. The valence state of arsenic in both sludges is trivalent, but the valence composition of sulfur is quite different. The ASSs have thermal instability properties. The results of TCLP and CSLT indicate that the concentrations of As and Pd in the leaching solution exceed the standard limits. More than 5% and 90% of arsenic are in the form of acid soluble and oxidizable fractions, respectively, which explains the high arsenic leaching toxicity and environmental activity of ASS. This research provides comprehensive information for the disposal of ASS from copper and lead-zinc smelter.

Nitrogen Derivatives of Irrigation in Chihuahua＇s Parks with Wastewater Treatment Residuals

Since 2000 Chihuahua City has distribution system Waste Water Treatment （WTR）, watering city＇s green areas. The need to cover the growing demand for drinking water has encouraged the use of non-potable water where water quality is not an issue despite being used by 10 years ago, it is not known whether nitrogen compounds derived from WTR pose risks to the environment and public health. Therefore, in order to minimize health and environmental risks, this is needed to assess the impact and policy support for water use. The aim of this study is to determine the constitution and the concentration of nitrogen compounds through selection and characterization of park＇s representative. It＇s divided into physical properties and main parameters that affect nitrogen transformations. It was determined that sand was material that allowed more favorable oxidation and reduction of nitrate in soil and atmosphere, opposite of the clay, When used WTR, nitrates, nitrites and ammonia nitrogen were identified in the subsurface and NOx and N20 were identified in the atmosphere. When drinking water was used, none of these compounds was found. However, it was determined that despite having high concentrations of nitrates, the WTR was within the limits allowed by the Mexican standard for the use of WTR in public places.

Alkaline extraction characteristics of steelmaking slag batch in NH_4Cl solution under environmental pressure

In order to obtain better carbonation effect, extraction behavior of slag batch is necessary to study. Relevant parameters like selective extraction yield were originally discussed. The relationship between selective extraction yield and conversion ratio was systemically focused on. The results show that alkaline earth metal conversion ratio is changed with leaching time and NH4CI concentration by first order exponential, and the maximum conversion for calcium keeps about 68% at 120 min in 0.4 mol/L NH4C1 solution, while leaching temperature and particle size have a linear effect on conversion ratio. Selective extraction yield of calcium is more than 93%, and the value of Mg is less than 5%. Apparent layer bands of silicon and calcium appear in the surface area through morphology detection of slag after leaching, and the case for 38-75 μm slag batch is more obvious than 75 150 μm slag and slag with larger particle size when leaching in 0.4 mol/L NH4Cl solution for 90 rain at 60 ℃.

Durability of Concrete Made with Manganese Slag as Supplementary Cementitious Materials

This paper discusses mineral composition and pore microstructure characteristics of water-cooled manganese slag and its effects on durability of concrete. The Mn slag has an alveolate pore structure, and the ground Mn slag is characterized by multiangular shape which consists of a＇-C2S, C3M82, CaO.MnO-2SiOu and C2AS. Experimental results show that the Mn slag has potential hydraulic reactivity. Concrete made with Mn slag as supplementary cementitious materials （SCMs） exhibits very low strength loss and weight loss in the synthetic seawater corrosion and freezing-thawing cycle tests. The research provides useful reference for knowing about Mn slag and for applying Mn slag to improve the durability of concrete.

JMDJ211VC—03型分离机及应用前景浅析

本文着重介绍配有外环活塞排渣自动清洗结构的ＪＭＤＪ２１１ＶＣ－０３型喷咀分离机的结构特点、工作原理、主要技术参数及应用前景浅析。