方解石、白云石中Ca,Mg元素在碳酸溶液中的化学动力学

查明碳酸盐矿物中方解石、白云石与CO2、水相互作用规律能够为提高煤储层导流能力提供实验支撑。以沁水盆地余吾、寺河矿为研究背景,在不同温度、不同p H值条件下,进行单一方解石、白云石与碳酸溶液的化学动力学实验,通过原子吸收光谱仪(AAS)、能谱仪(EDS)、X射线衍射(XRD)、扫描电镜(SEM)等测试手段,探讨了Ca~(2+),Mg~(2+)在反应液中的溶出规律以及固态元素变化规律、晶体变化、表面结构变化,建立了方解石、白云石的反应动力学模型。研究结果表明:方解石中Ca~(2+)溶出量比白云石大,白云石中Ca~(2+)溶出量比Mg~(2+)大,Ca~(2+),Mg~(2+)含量均随反应时间先增大后减小,并伴随震荡现象;各离子含量均随p H值减小而增大,随反应温度升高而减小,Mg~(2+)含量受温度影响较小;固相物质中钙元素、镁元素含量均为先减小后增大,晶体特征峰强度也均有先减弱再增强的趋势;建立的化学动力学模型反映出温度越高,反应级数越大,浓度对化学反应影响越大;p H值越小,反应活化能越小,反应速率越大。

Chemical kinetics of Ca/Mg elements from calcite/dolomite in carbonic acid solution

This paper provides an experimental support for increasing the flow conductivity of coal reservoir by identifying the interaction characteristics between CO2，water and calcite/dolomite.Under the research background on Yuwu and Sihe Mines in Qinshui Basin，with the chemical dynamical experiment between carbonic acid solution and calcite/dolomite，based on the experimental tests of atomic absorption spectrometric analysis (AAS)，energy spectrum analysis(EDS)，X-ray diffraction analysis (XRD) and scanning electron microscope (SEM)，the study investigated the releasing rule of Ca2+/Mg2+ in reaction solution，solid state element change rule，crystal variation and surface structure change，established the reaction kinetics model of calcite and dolomite.The results show that the dissolved quantity of Ca2+ in calcite is more than that of dolomite，and the dissolved quantity of Ca2+ in dolomite is more than that of Mg2+.The contents of Ca2+ and Mg2+ increase first and then decrease with reaction time and the data fluctuate greatly.The ion contents increase with decreasing pH value，and decrease with increasing temperature，but it has little influence on the content of Mg2+.The contents of calcium and magnesium in solid phase decrease first then increase，and the intensity of characteristic peaks of crystal reduces first then enhances.The established chemical kinetics model shows that the higher the temperature，the lager the reaction order，and the concentration has a great influence on chemical reaction.When pH value is low，or apparent activation energy is low，the reaction increases.