碳酸钙直接硫化反应产物层固态离子扩散机理研究

循环流化床富氧燃烧因其可对再循环烟气温度有效控制,被称为最有工业前景的控制温室气体技术之一。在该燃烧方式下,煤燃烧产生的SO2仍采用石灰石除掉,但该过程属于石灰石的直接硫化反应。此反应目前争议较多的为硫化反应产物层中的扩散物质种类问题。文中采用向石灰石中添加Na2CO3的方法,对其循环流化床富氧燃烧工况下的硫化特性进行研究,目的在于探讨硫化反应产物层中的扩散机理及添加剂对石灰石硫化反应的作用。结果表明Na2CO3对石灰石在富氧气氛下直接硫化反应具有明显的促进作用,而且随反应进行,这种促进作用相对更加显著。SEM分析表明经Na2CO3处理后的石灰石硫化后所形成的CaSO4产物层中CaSO4晶粒较原始石灰石硫化后所形成CaSO4晶粒小,且晶粒之间排列更不规则。Na2CO3的添加导致硫化产物层中缺陷浓度增加,从而加速了产物层中的离子扩散率,是使石灰石直接硫化的最终转化率和硫化速率升高的原因。这也给石灰石直接硫化反应产物层中固态离子扩散理论提供了进一步的依据。

Leaching behaviors of calcium and magnesium in ion-adsorption rare earth tailings with magnesium sulfate

The leaching behaviors of calcium and magnesium in the rare earth tailings leached with magnesium sulfate using deionized water,CaCl2 solution and lime water were investigated.Experimental data indicated that magnesium in the tailings was easy to be leached out since most of the magnesium was in the form of water-soluble phase.Most of calcium in the lime water was electrostatically adsorbed on the clay mineral of the tailings,and the water-soluble magnesium was also gradually converted into exchangeable phase because of back-adsorption of Mg2+on the clay mineral with increasing the pH values.When the liquid-to-solid ratio was 0.80,the contents of readily-available magnesium and calcium were 104.4−207.6 and 201.7−1426.3 mg/kg,respectively,which could meet the requirements for plants.These results suggest a promising route for the environmental remediation of ion-adsorption rare earth ore after in-situ leaching.

Reactive Crystallization of Calcium Sulfate Dihydrate from Acidic Wastewater and Lime

The present work focused on the recycle of the sulfate and the metal ions from acidic wastewater dis charged by nonferrous metallurgical industry. The effects of the temperature, the reactant concentration, the stirring speed and the metal ions on the reactive crystallization process of calcium sulfate between sulfuric acid and lime were systematically investigated. The morphology of the precipitated crystals evolved from plateletlike and nee dlelike shape to rodlike shape when the temperature was increased from 25 to 70 ℃. An increase in the agglom.

In-vitro degradation behavior of Mg alloy coated by fluorine doped hydroxyapatite and calcium deficient hydroxyapatite

Fluorine-doped hydroxyapatite(FHA) and calcium deficient hydroxyapatite(CDHA) were coated on the surface biodegradable magnesium alloy using electrochemical deposition(ED) technique. Coating characterization was investigated X-ray diffraction(XRD), Fourier-transformed infrared spectroscopy(FTIR), transmission electron microscopy(TEM), scanni electron microscopy(SEM) and energy dispersive X-ray spectroscopy(EDS). The result shows that nano-FHA coated samp presents nano needle-like structure, which is oriented perpendicular to the surface of the substrate with denser and more unifo layers compared to the nano-CDHA coated sample. The nano-FHA coating shows smaller crystallite size(65 nm) compared to t nano-CDHA coating(95 nm); however, CDHA presents thicker layer(19 μm in thickness) compared to the nano-FHA(15 μm thickness). The corrosion behaviour determined by polarization, immersion and hydrogen evolution tests indicates that the nano-FH and nano-CDHA coatings significantly decrease corrosion rate and induce passivation. The nano-FHA and nano-CDHA coatings c accelerate the formation of bone-like apatite layer and significantly decrease the dissolution rate as compared to the uncoated M alloy. The nano-FHA coating provides effective protection to Mg alloy and presents the highest corrosion resistance. Therefore, t nano-FHA coating on Mg alloy is suggested as a great candidate for orthopaedic applications.

Physicochemical properties of arsenic-bearing lime-ferrate sludge and its leaching behaviors

Physicochemical properties and leaching behaviors of two typical arsenic-bearing lime?ferrate sludges(ABLFS),waste acid residue(WAR)and calcium arsenate residue(CAR),are comprehensively described.The chemical composition,morphological features,phase composition and arsenic occurrence state of WAR and CAR are analyzed by ICP?AES,SEM?EDS,XRD,XPS and chemical phase analysis.The toxicity leaching test and three-stage BCR sequential extraction procedure are utilized to investigate arsenic leaching behaviors.The results show that the contents of arsenic in WAR and CAR are2.5%and21.2%and mainly present in the phases of arsenate and arsenic oxides dispersed uniformly or agglomerated in amorphous particles.The leaching concentrations of arsenic excess119and1063times of TCLP standard regulatory level with leaching rates of47.66%and50.15%for WAR and CAR,respectively.About90%of extracted arsenic is in the form of acid soluble and reducible,which is the reason of high arsenic leaching toxicity and environmental activity of ABLFS.This research provides comprehensive information on harmless disposal of ABLFS from industrial wastewater treatment of lime?ferrate process.

Limestone mechanical deformation behavior and failure mechanisms： a review

In this paper, several mechanical deformation curves of limestone are reviewed, and the effects of temperature, confining pressure, and fluid are discussed. Generally, Mohr–Coulomb is used for limestone brittle fracture. The characteristic of low temperature cataclastic flow and the conditions and constitutive equations of intracrystal plastic deformation such as dislocation creep,diffusion creep, and superplastic flow are discussed in detail. Specifically, from the macroscopic and microscopic view, inelastic compression deformation(shear-enhanced compaction) of large porosity limestone is elaborated.Compared with other mechanics models and strength equations, the dual porosity(macroporosity and microporosity) model is superior and more consistent with experimental data. Previous research has suffered from a shortage of high temperature and high pressure limestone research; we propose several suggestions to avoid this problem in the future:(1) fluid-rock interaction research;(2) mutual transition between natural conditions and laboratory research;(3) the uniform strength criterion forshear-enhanced compaction deformation;(4) test equipment; and(5) superplastic flow mechanism research.

The coupling of fluid flow and uplift since Late Cretaceous in Zoige area, western Sichuan

The uplift indicated by five AFT (apatite fission track) samples is more than 3400 m by multi-episodic uplift since Late Cretaceous in Zoige area; especially the processes of fast uplift in Late Cretaceous and Neogene have important influences on the stress of paleo-fluid. Based on field geology, macroscopic features of fracture, and geochemistry of fluid inclusions, we decipher the paleo-fluid process of episodic migration. In early uplift stage, the temperature of inclusions increased with the constant salinity, whilst both of them proportionally decreased in the mid-late stage, indicating the different tendency of heat-fluid warming and freshwater contamination at different time. Of particular importance are the features of episodic fluid flow, such as ESR ages, and features of multi-episodic migration that correspond well with the process of multi-episodic uplift. Thus, concerning the rock stress-strain behavior responding to uplift, we further discuss the spatio-temporal coupling effect of episodic migration and decompression in multi-episodic uplift, thereby to better understand petroleum geology in the region.