内蒙古油砂固体颗粒的矿物组成和亲疏水性特征

Mineral Composition and Hydrophilicity/Hydrophobicity of Solid Particles Isolated from Inner Mongolia Oil Sands

油砂是一种重要的非常规油气资源,由沥青、固体颗粒(包括粗颗粒和细颗粒)和水组成,其开发利用的关键在于提高其中沥青的提取效率。溶剂提取技术因其沥青提取效率高、环境友好等优点被认为有望取代现有水基提取技术。在溶剂提取过程中,主要存在沥青中固体颗粒残留率高和尾矿中有机溶剂回收效率低的问题,这与固体颗粒的组成结构和表面性质密切相关。因此,探明油砂中固体颗粒的矿物组成和表面性质(特别是亲疏水性)至关重要。中国内蒙古地区的油砂具有储量丰富、含油率高等特点,目前关于该地区油砂中固体颗粒的矿物组成和亲疏水性等特征尚不完全明确。本文对来自该地区油砂样品采用环己烷分离其中的沥青和固体颗粒,采用45μm标准筛分离固体颗粒中的细颗粒和粗颗粒,采用激光粒度分析仪、X射线衍射仪、比表面积及孔隙度分析仪、傅里叶变换红外光谱仪、有机元素分析仪、扫描电镜和能谱分析等多种手段对颗粒的矿物结构进行分析,采用表层浮选法和水蒸气吸附法对颗粒的亲疏水性进行评价。结果表明,油砂固体细颗粒和粗颗粒分别占总固体含量的53.4%和46.2%;固体细颗粒中含有蒙脱石、高岭石、伊利石、α-石英和钙长石等,粗颗粒中主要含有α-石英、钙长石及少量高岭石、伊利石和蒙脱石;细颗粒的沥青残留量、羟基含量均高于粗颗粒;细颗粒和粗颗粒的平均临界表面张力分别为>47.62mN/m和>45.55mN/m,单位面积水蒸气吸附量分别为1.27mg/m^(2)和0.41mg/m^(2),固体粗颗粒的疏水性稍高于细颗粒。因疏水性固体颗粒对油砂沥青的分离提取和有机溶剂的回收有不利影响,因此应在关注固体细颗粒的同时,加强对固体粗颗粒影响的研究。

BACKGROUND: Oil sand is an important unconventional oil and gas resource, which is composed of bitumen, solid particles(including coarse and fine particles) and water. The key to its development and utilization is to improve the extraction efficiency of bitumen. Solvent extraction technology is expected to replace the existing water-based extraction technology due to its high bitumen extraction efficiency and environmental friendliness. The high residue rate of solid particles in bitumen and low recovery efficiency of organic solvent in gangues are two main problems during solvent extraction, which is closely related to the composition, structure and surface properties of solid particles. Therefore, it is very important to understand the mineral composition and surface properties, especially hydrophilicity/hydrophobicity, of solid particles in oil sand. The oil sands in Inner Mongolia, China are characterized by abundant reserves and high oil content. At present, the mineral composition and hydrophilicity/hydrophobicity of solid particles in the oil sands in this area are not clear.OBJECTIVES: To investigate the mineral composition and hydrophilicity/hydrophobicity of solid particles isolated from Inner Mongolia oil sands.METHODS: Cyclohexane was adopted to separate the bitumen and solid particles from the oil sands. Fine particles and coarse particles were then separated using a 45μm standard sieve. The composition and structure of the particles were investigated by laser particle size analyzer, X-ray diffraction analyzer, specific surface area and porosity analyzer, Fourier transform infrared spectroscopy, organic element analyzer, scanning electron microscopy-energy dispersive X-ray spectrometry(SEM-EDX). The hydrophilicity/hydrophobicity of the particles was determined by film floatation and water vapor adsorption methods.RESULTS: The contents of fine particles and coarse particles in the oil sands were 53.4% and 46.2%, respectively. The fine particles contained montmorillonite, kaolinite, illite, α-quartz and anorthite, while the coarse particles contained α-quartz and anorthite with minor kaolinite, illite and montmorillonite. The contents of bitumen and hydroxyl group in the fine particles were higher than those in the coarse particles. The mean critical surface tensions for fine particles and coarse particles were >47.62 mN/m and >45.55 mN/m, respectively, and the average water vapor adsorptions per unit area were 1.27 mg/m^(2)and 0.41 mg/m^(2), respectively, indicating that the coarse particles were more hydrophobic than the fine particles.CONCLUSIONS: Regarding the adverse effects of hydrophobic solid particles on the separation and extraction of oil sand bitumen and the recovery of organic solvents, it is necessary to pay attention to fine solid particles and strengthen the research on the influence of coarse solid particles.