Characteristics of reaction and product microstructure during light calcination of magnesite in transport bed

A gas-heating laboratory transport bed was adopted to simulate the industrial transportbed reactor for flash calcination of magnesite, and a method based on TG analysis of a reacted sample was further developed to calculate the decomposition rate or conversion of its containing MgCO₃. The study investigated how the conversion and product reactivity as well as microstructure vary with reaction conditions including temperature, particle size and times of re-calcination for powder magnesite. Magnesite powder (<150 μm) calcination is a quick reaction that reaches 98% decomposition of its containing MgCO₃ in 1—2 s,corroborating the feasibility of magnesite flash-calcination in transport bed reactors. The coloration time given by the citric acid chromogenic method was 17—55 s and 294 s for the obtained products from transport and fixed beds, respectively. This proves the obviously higher activity and thus improved microstructure of the product from transport bed. During the calcination process, the MgO grain size of the product gradually increases, and the surface structure changes from loose and porous to dense and smooth. This structural change can be completed within a few seconds.     

六偏磷酸钠对菱镁矿与白云石浮选分离动力学的影响

以油酸钠为捕收剂，研究了六偏磷酸钠对菱镁矿和白云石浮选行为和浮选动力学特性的影响。结果表明：不添加六偏磷酸钠时两种矿物可浮性相近，分离困难；在矿浆pH值为9-11.5的区间里，添加适量的六偏磷酸钠，菱镁矿仍保持较好的可浮性和较高的浮游速度，而白云石的可浮性和浮游速度大幅降低，从而有利于两种矿物浮选分离。菱镁矿和白云石的浮选分别符合经典一级动力学模型和二级矩形分布模型。     

高温悬浮态下石灰石与菱镁矿热分解 特性比较及动力学研究

利用悬浮态高温炉,对比研究了菱镁矿及石灰石的热分解特性,探讨了其热解模型及动力学参数。结果表明:低温段(650~750℃)时,菱镁矿比石灰石易分解,达到一定高温后其分解速率相差不大;菱镁矿、石灰石在悬浮态下的热解机理均符合收缩核模型,其活化能分别为50 kJ/mol、79 kJ/mol;随着菱镁矿粒度的增大,其分解速率趋缓,分解表观活化能增大。     

CO2 sequestration by magnesite mineralisation through interaction of Mg-brine and CO2: integrated laboratory experiments and computerised geochemical modelling

ABSTRACT

Several Carbon Capture and Storage (CCS) techniques have been studied including injections of carbon dioxide (CO₂) into the mature and/or depleted hydrocarbon reservoirs and deep saline aquifers. This work aims to test storing CO₂ into the magnesium-rich evaporite strata and also into the stratigraphic intervals containing Mg-rich brines. The test simulates Mg-carbonation of the synthetic solution obtained from the Mg-evaporite mineral, bischofite – both experimentally in the laboratory condition and also through computerised geochemical simulation. The laboratory experiments, which resulted in the crystallisation of anhydrous magnesite, were analysed. The TOUGHREACT^TM, Geochemist’s Workbench^TM (GWB) and PHREEQC^TM software simulated the experiments as computerised geochemical model and tested the results for natural geological conditions. The geochemical simulations successfully demonstrate the immense CCS potential for the Mg-evaporite (as well as the sedimentary strata charged with Mg-evaporitic brine) at their subsurface geological occurrences at elevated pressure-temperature and high salinity.     

镁-铝类水滑石的摩擦性能

以菱镁矿为原料,通过化学分解--水热法合成镁铝类水滑石,利用月桂酸钠对合成样品进行表面改性,以提高类水滑石粉体在润滑介质中的分散性。月桂酸钠的最佳添加量占浆液质量5%。分别采用微振动(SRV)摩擦实验和四球摩擦实验表征改性类水滑石粉体的摩擦性能。结果表明:类水滑石粉体作为减摩材料,其合理的添加量为30g/L基础油。类水滑石粉体可显著降低摩擦副间的摩擦系数,是一种具有潜在应用价值的减摩材料。     

MgO对多孔堇青石材料组成结构的影响

以菱镁矿轻烧粉、废弃水口和硅灰为原料制备多孔堇青石材料,研究分析菱镁矿轻烧粉中氧化镁对制备多孔堇青石材料致密度、结晶相组成及显微结构的影响。用XRD法和SEM法表征多孔堇青石材料中的结晶相和显微结构。结果表明:利用高温固相反应烧结,可以制备出以堇青石为主晶相的多孔堇青石材料。但菱镁矿轻烧粉的过量引入会降低多孔堇青石材料的孔隙率,导致合成材料中镁橄榄石相增多。     

氯氧镁制品裂纹与预防

分析了氯氧镁制品产生裂纹的原因，提出了相应的预防措施。     

菱镁复合宝丽板的研制

采取综合措施以克服菱镁宝丽板返卤、变形、耐水性差的缺陷,即控制MgO/MgCl_2mol比5～8;采用磺酸盐类减水剂;掺加由有机聚合物和含Fe、Al、PO_4的无机盐组成的复合外加剂;严格控制养护环境的温湿度.文中还介绍了生产工艺、性能指标及投资效益.     

菱镁矿浮选尾矿直接合成同时制备镁橄榄石和镁砂研究

为了有效利用菱镁矿浮选尾矿废弃物,提出以其为原料,在不添加任何物质、不经过高压压制成型的条件下直接烧制同时制备优质镁橄榄石和烧结镁砂的技术路线,并在高温管式炉中对其可行性进行了实验研究。通过对不同反应温度和时间条件下制备的样品进行XRD和SEM-EDS表征和分析,确认新技术路线不仅可行,并且还具有反应速度快、产品质量优等优势。当反应温度为1400℃及以上时,原料中的SiO₂在数分钟之内全部转化,产物镁橄榄石和烧结镁砂晶体发育良好。研究结果对进一步开发菱镁矿浮选尾矿废弃物高效利用新技术提供有力支持。     

块状菱镁矿烧结初期方镁石颗粒致密化行为

采用高温电炉对块状菱镁矿进行煅烧,研究了块状菱镁矿烧结初期(1000~1300℃)方镁石颗粒致密化行为。结果表明:在烧结初期,方镁石颗粒致密化过程主要分为4个阶段:阶段一、颗粒表面正负离子极化,引力增加,颗粒间距减小;阶段二、颗粒间点接触,形成团聚;阶段三、颗粒间面接触,导致间隙减小;阶段四、形成烧结颈,团聚致密化程度增加。母盐假相颗粒对烧结致密化行为有重要影响,当温度在1150~1200℃区间时,假相颗粒的体积收缩,导致其比表面积和颗粒配位数降低,烧结致密化受到阻碍,出现缓滞现象,这与粉状菱镁矿烧结有显著区别。在匀速升温烧结过程中,不同的温度区间,烧结激活能不同,温度为1000~1110℃时,Q=412.368 k J/mol;温度为1110~1230℃时,Q=473.990 k J/mol;温度为1230~1300℃时,Q=385.266 k J/mol。块状菱镁矿烧结初期,随着温度的升高,方镁石颗粒烧结致密化速率先增加后减小。