Research On The Characteristics Of Flint Calcination And The Preparation Of Ceramic Proppant

With the advance in hydraulic fracturing technology, the requirements for ceramic proppant performance gradually have increased, so we need a kind of low-density but high-strength ceramic proppant to meet the requirements. At present, the main raw material for making low-density but high-strength ceramic proppant is high-grade bauxite. Because its price is more expensive and its reserve becomes less, we need to find a new material to replace it in making ceramic proppant. In this paper, we used flint clay in making low-density but high-strength ceramic proppant, and researched its phase composition, micro-structure and physical properties.The experiment used METTLER TOLEDO comprehensive thermal to analyze the flint clay material. The result showed that the flint consists of two phases in the calcination process: dewatering phase and transformation of product after dewatering. Calcination temperature between 30℃ and 100℃ is the volatilization of free water; calcination temperature between 450℃ and 800℃ is the drawing off of structural water; the calcination temperature between 950℃ and 1050℃, 1050℃ and 1300℃ undergone phase changes. Below 950℃, the phase of calcined flint clay is mainly metakaolin;between 950℃ and 1050℃, the phase of calcined flint clay becomes silica-alumina spinel and some mullite; when the calcination temperature reaches 1150℃, the phase of calcined flint clay changes into mullite.With flint clay as raw material, the experiment sintered low density high strength ceramic proppant at temperature between 1420℃ and 1540℃ and analyazed the influence of sintering temperature on the properties of the proppant. The results showed that 20/40 mesh proppant ceramic sintering 1480℃ has the best property with a bulk density of 1.57g/cm3, apparent density of 2.73g/cm3 and a broken rate of 4.88% at 52 MPa closed pressure. As the temperature increases, mullite grows up and forms interpenetrating network structure, while cristobalite phase evenly distributes in the skeleton structure formed of mullite and when there is the right amount of liquid, it will facilitate the completion of sintering and make the structure more compact.With flint clay and potassium feldspar as raw materials,the experiment sintered the ceramic proppant at 1350℃ and analyzed the effects of potassium feldspar powder amount to proppant properties..The results showed that the ceramic proppant with feldspar powder added amount of between 10wt% to 20wt% has better property. Potassium feldspar powder dosage 15wt%, the 20/40 mesh proppant property ceramic sintering at 1350℃ is the best, with a bulk density of 1.56g/cm3, apparent density of 2.72g/cm3 and broken rate of 8.74% at 52 MPa closed pressure. During sintering, feldspar glass phase softening and decomposition of feldspar reduced sintering temperature of the proppant, while the glass phase is generated in favor of mutual diffusion of Al2O3 and SiO2 and promoting the formation and growth of mullite. When the amount of potassium feldspar is too much, it will generate a lot of liquid and reduces the property of ceramic proppant.