不同粒径磷石膏的脱水动力学

为研究粒径对磷石膏脱水反应动力学的影响,测定了流动N₂气氛中,不同粒径磷石膏脱水反应的TG-DSC同步热分析数据。运用Flynn-wall-Ozawa法、Kissinger法和Satava-Sestak法相结合计算动力学参数,得出不同粒径（105～125μm、125～150μm、150～200μm和200～300μm）磷石膏脱水动力学模型,利用动力学方程对不同粒径磷石膏在相同条件下等温热分解进行预测,得出不同粒径、不同温度下磷石膏脱水率与时间的关系。结果表明：当磷石膏粒径由200～300μm减小到105～125μm时,磷石膏第一步脱水活化能从114.62kJ/mol减小到82.55kJ/mol,第二步脱水活化能由96.30kJ/mol减小到78.5kJ/mol。磷石膏脱水活化能随粒径的减小而减小,机理函数均符合Avrami-Erofeev方程。在相同的煅烧温度下,粒径小的磷石膏完全脱水所需时间缩短。     

磷石膏与纯石膏脱水反应的TG、DSC表征与分析

测试了磷石膏和纯石膏的脱水的TG、DTG、DSC对比分析二者的脱水特性。结果表明,磷石膏和纯石膏脱水的相似点是脱水都分为两步进行,为吸热反应,产物分别是Ca SO4·0.5H2O和Ca SO4;纯石膏脱水的起始反应温度和DTG峰值温度都低于磷石膏,失重率都高于磷石膏,说明磷石膏脱水要比纯石膏脱水相对困难一些;纯石膏较磷石膏脱水反应历程短,峰较尖锐,峰值温度略低;特征温度点随升温速率的增加而升高。     

磷石膏与纯石膏脱水反应的TG、DSC表征与分析

测试了磷石膏和纯石膏的脱水的TG、DTG、DSC对比分析二者的脱水特性。结果表明,磷石膏和纯石膏脱水的相似点是脱水都分为两步进行,为吸热反应,产物分别是Ca SO4·0.5H2O和Ca SO4;纯石膏脱水的起始反应温度和DTG峰值温度都低于磷石膏,失重率都高于磷石膏,说明磷石膏脱水要比纯石膏脱水相对困难一些;纯石膏较磷石膏脱水反应历程短,峰较尖锐,峰值温度略低;特征温度点随升温速率的增加而升高。     

磷石膏分解工业反应动力学的研究

为开发磷石膏分解新技术，在模拟工况操作特性的模拟试验装置中进行了磷石膏分解的工业反应动力学试验，研究了温度，气氛，停留时间，生料化学组成，焦炭等不同影响因素以及“还原气氛－氧化气氛”区对磷石膏生料分解反应动力学的作用规律。结果表明，在１０６０－１１００℃的弱还原气氛和１１００℃的弱氧化气氛中分别停留３－５ｍｉｎ，磷石膏生料的脱硫率可达９５％以上。对比水泥生料中ＣａＣＯ３的悬浮态分解结果可以预测在同     

不同气氛下磷石膏热脱水特性及动力学比较研究

为研究不同气氛对磷石膏热脱水特性及动力学影响,分别测定了动态空气气氛和N2气氛下,不同升温速率时磷石膏热脱水反应的TG-DTG-DTA同步热分析数据.采用Kissinger法、FWO峰值转化率近似相等法和FWO等转化率法分别计算了磷石膏的热脱水动力学参数.结果表明,两种气氛下,磷石膏的热脱水温度都随升温速率的加快而升高...     

石膏脱水热分解动力学研究

采用TG-DSC热分析法对石膏脱水反应过程进行了实验研究,结合热分析的TG曲线,利用普适积分法处理试验结果,通过对不同机理函数的拟合计算分析,判断出石膏脱水的总反应过程是由化学反应机理控制,确定反应级数模型是最佳机理函数,并求得其动力学基本参数:表观活化能=137.879 KJ/mol,指前因子=1.515×1016 S-1,所建立的数学模型预测结果和实验曲线相吻合,其误差最大不超过4.985%。     

磷石膏还原分解动力学研究

在分散态试验装置上,研究磷石膏生料在CO还原性气体介质中,反应温度对其分解率、脱硫率、分解速率及主副反应的影响规律,同时探讨了还原势对其还原分解过程的影响,研究结果对磷石膏分解炉的研究开发提供理论依据。     

在非等温条件下石膏和硼石膏的加热脱水动力学研究

Thermal dehydration of gypsum and borogypsum was investigated under nonisothermal conditions in air by using simultaneous thermogravimetric-differential thermal analyzer. Nonisothermal experiments were carried out at various linear heating rates. Kinetics of dehydration in the temperature range of 373-503 K were evaluated from the DTA (differential thermal analysis)-TGA (thermogravimetric analysis) data by means of Coats-Redfern,Kissinger and Doyle Equations. Values of the activation energy and the pre-exponential factor of the dehydration were calculated. The results of thermal experiments and kinetic parameters indicated that borogypsum is similar to gypsum from dehydration mechanism point of view although it consists of boron and small amount of alkali metal oxides.     

磷石膏在还原—氧化双气氛下的分解反应动力学研究

在分散态试验装置上，研究硫化钙及磷石膏还原分解产物在O2－N2的混合气体中的高温氧化特性，对磷石膏分解炉的研究开发有指导意义。     

钨酸锆前驱体脱水反应动力学

采用水热法合成了Zr W2O8的前驱体Zr W2O7(OH)2(H2O)2,并应用热重分析技术研究了其脱水反应。升温速率β=10℃/min,实验失重率为8.382%,与理论失重率8.452%基本吻合,脱水反应温度在173℃左右。应用非等温方法计算了钨酸锆前驱体脱水反应的动力学参数:表观活化能E=232.54 k J/mol;阿伦尼乌斯指前因子ln A=58.06。前驱体脱水为二级反应,动力学方程可以描述为:dα/dt=1025.21exp(-27.97×103/T)(1-α)2。     

The dehydration behavior and non-isothermal dehydration kinetics of donepezil hydrochloride monohydrate (Form I)

Powders of donepezil hydrochloride monohydrate (Form I) underwent isomorphic dehydration, losing 3% w/w water between 90% and 10% relative humidity (RH) without changing its powder X-ray pattern. Below 10% RH, additional dehydration occurred in conjunction with a reversible phase transition between the monohydrate state and a dehydrated state, with a 4.0% w/w loss to 0% RH. A combination of methods was used to understand the structural changes occurring during the desolvation process, including dynamic vapor sorption measurements, thermal analysis and powder X-ray diffraction. Form I showed the characteristics of the channel hydrate, whose non-isothermal dehydration behavior proceeds in two steps: (1) the loss of non-crystalline water adsorbed on the surface, and (2) the loss of one crystalline water in the channel. Dehydrated Form I is structurally similar to the monohydrate Form I. According to the heat of fusion and the crystal density criteria, the two crystal forms belonged to the univariant system, and the anhydrate (Form III) is stable. The dehydration kinetics was achieved from the TG-DTG curves by both the Achar method and the Coats-Redfern method with 15 frequently cited basic kinetic models. The dynamic dehydration processes for steps 1 and 2 were best expressed by the Zhuralev-Lesokin-Tempelman equation, suggesting a three-dimensional diffusion-controlled mechanism.     

生物乙醇催化脱水制乙烯的动力学研究

采用质量分数3%金属镧改性的HZSM-5分子筛催化剂,考察在较低的反应温度（200～300） ℃、固定床反应器内质量空速、催化剂粒径、反应温度以及反应物分压对乙醇转化率、产物收率和生成速率的影响,确定了乙醇脱水反应的动力学控制区域：质量空速≥20 h^-1,催化剂粒径≤0.7 mm。在此基础上,建立了生物乙醇催化脱水的动力学模型,拟合值和实验值吻合较好。     

磷石膏热分解制备二氧化硫和氧化钙研究

在氮气氛下研究了碳还原分解磷石膏制备二氧化硫和氧化钙的反应特性,用烟气分析仪分析析出的气体成分,用X射线衍射仪（XRD）分析热分解固体样品。考察了煤颗粒尺寸、原料配比和反应温度对磷石膏热分解的影响。得到磷石膏热分解制备二氧化硫和氧化钙的最佳条件：煤粒径小于150 μm,碳与硫酸钙物质的量比为0.8,反应温度为1 000 ℃。在此条件下,可以得到二氧化硫最大体积分数为12.5%的分解炉气,分解固体样品中氧化钙质量分数达到65.32%,可以用作水泥原料或二氧化碳吸收剂。     

热分析在磷石膏制酸反应研究中的应用

采用热分析方法研究磷石膏制酸过程中CaSO4与焦炭的反应进程。在TG-DTA热分析仪上研究原料配比(C与CaSO4摩尔比)对反应进程及反应温度的影响。通过比较化学反应的实际失重量与理论失重量,发现原料配比为0.4和0.5时,反应先生成CaS,且反应温度随原料配比增加而降低。当原料配比增至0.6时,反应先生成CaO、CO。反应产物的XRD表征也进一步证实分别生成了CaS和CaO,因此可以认为热分析方法用于磷石膏制酸反应研究是可行的。最后对反应机理进行了初步的探讨。     

Polyethyleneglycol catalytic dehydration kinetics in the liquid phase

Eleven representative polyethyleneglycol (25322–68–3) catalytic dehydration reactions have been studied in the liquid phase at atmospheric pressure. The aim of this research is to build a kinetic model representative of the polyethyleneglycol dehydration process. Three types of reaction take place simultaneously in the process: cyclisation, condensation and alcoholysis. Activation energies and frequency factors are given, and the relationships between kinetic parameters and chain length of reactants and products are discussed according to the reaction type.     

磷渣粉改性磷石膏实验研究

以磷建筑石膏为原料,研究磷渣粉对磷建筑石膏力学性能和微观性能的影响。采用抗折抗压试验机研究力学性能,SEM电镜研究微观形貌。结果表明：FDN减水剂添加量为1.5‰,改性磷渣粉掺量在10%~15%范围内时,磷石膏基制品抗折强度均达到7.0 MPa以上,抗压强度达到15.0 MPa以上,约为空白样的2倍,效果显著。通过SEM电镜分析磷建筑石膏水化前后微观形貌,结果表明,添加磷渣改性材料后,磷石膏水化晶体形貌从片状或条状改变成短柱状或中空管状结构,大大提高了磷石膏基材料性能指标,为磷石膏生产石膏砂浆提供了理论和技术支持。     

外掺料对磷石膏基胶凝材料力学及导热性能的影响

将磷石膏应用于建筑业,可以解决磷化工副产物堆积的问题。采用单因素实验,通过改变水灰质量比、粉煤灰掺量、生石灰掺量等条件来研究各因素对磷石膏基胶凝材料力学性能及保温性能的影响,借助X射线衍射（XRD）、X射线荧光光谱（XRF）、扫描电镜（SEM）等手段来分析磷石膏基胶凝材料的物化性质和形貌结构。结果表明,磷石膏基胶凝材料的导热系数和抗压强度都与水灰质量比呈负相关,在水灰质量比为0.250时胶凝材料的抗压强度最大、水灰质量比为0.550时胶凝材料的导热系数最小;粉煤灰在磷石膏基胶凝体系中除了提供胶凝性能外,还会被生石灰激发出活性,增强胶凝体系的综合性能,粉煤灰掺量为50%（质量分数）时胶凝体系的综合性能最佳;生石灰在磷石膏基胶凝体系中对杂质的吸附效果明显,生石灰掺量超过7%（质量分数）以后对胶凝体系的保温性能和力学性能的增强效果明显。     

Kinetics of the dehydration of lithium dihydrogenphosphate

Phosphate‐based lithium materials, such as lithium iron phosphate (known as lithium ferrophosphate, LiFePO₄, LFP), are among the safest materials for large‐scale lithium‐ion batteries due to the stability of the phosphate‐bound oxygen at elevated temperatures. LFP can be melt‐synthesized where the kinetics is faster, allowing for coarser and lower cost reactants. The most common lithium‐ and phosphate‐bearing reactants can react violently upon heat‐up and release a large volume of gaseous by‐product. Lithium metaphosphate (LiPO₃, LPO) can improve the processability and safety of the operation. In this work, we investigate the thermal decomposition of lithium dihydrogenphosphate (LiH₂PO₄, LHP) to LPO up to 400 °C. The decomposition was analyzed by isothermal and constant rate differential thermogravimetric (DTG) experiments. Activation energy profiles were estimated by an isoconversional model‐free approach and kinetic model fitting. Li₅H₄P₅O₁₇ (L2.5) was determined to be the most stable reaction intermediate and can be isolated at temperatures between 200 and 240 °C. The resulting reaction is comprised of 6 reactions, where the LHP is progressively polymerized by condensation reactions leading successively to L2.5, Li₃H₂P₃O₁₀ (L3), Li₄H₂P₄O₁₃ (L4), and LPO. The first reaction step (LHP → L2.5) was fitted with 3 reactions series/parallel describing the solid surface reaction, the viscous/liquid surface reaction, and the bulk reaction. Limiting the reaction temperature to 400 °C results in a solid product that can be advantageous if LPO is to be prepared in advance and dosed for LFP synthesis.     

磷石膏脱硅试验探索

研究磷石膏浮选脱硅工艺技术,通过预先分级与浮选脱出磷石膏中的二氧化硅。研究表明,磷石膏细度大于0.025mm (>500目);捕收剂为G609用量为260g/t,作用时间2min;Na_2CO_3用量为2kg/t,作用时间2min;可以得到最终产品的二水硫酸钙含量98%～99%,其他杂质含量1～2%,浮选精矿产率最高可达80%左右,综合产率60%以上。