【作者】 汤建伟；

【导师】 钟本和；

【作者基本信息】 四川大学 ， 化学工艺， 2003， 博士

【摘要】 液固反应是矿物化学处理最常见的加工方法之一。在磷矿酸解反应过程中，随着矿物的溶解，将出现反应产物的扩散和结晶。当结晶过程在固体反应物颗粒表面进行时，有可能在该颗粒表面形成一层固态薄膜，包裹该颗粒表面，阻碍矿物的继续分解，减慢甚至终止矿物的溶解反应过程。 加快磷矿酸解液固反应的传统方法主要有两类：1)控制反应条件，使矿物颗粒表面的反应产物为粗大结晶以形成疏松可透性膜；2)降低固液表面能，增大颗粒表面润湿度。这些方法与磷矿酸解工艺条件相关性较高，技术局限性较大。 微波是频率在300MHz～300GHz的电磁波，其具有吸收性和穿透性。液体分子吸收微波后，随着微波能量场正负极性的不断变换而改变方向，从而使液体分子的电离程度、离子活度和向反应固态膜的渗透能力都得到提高。液体分子间的相互摩擦和搅拌将产生微波“热效应”和“非热效应”，影响反应产物的结晶过程，加快反应产物向液相主体的扩散速度，增大液体分子与磷矿粉颗粒的接触几率。 硫酸或磷酸分解磷矿是磷肥工业中最重要的液固分解反应。本研究从磷矿酸解液固反应入手，通过对比的方法，探讨常规的液固反应体系施加微波电磁场后，对分解反应的影响。 主要的研究工作包括：1)构思和建立了间歇式多模腔微波反应器实验装置和间歇式程控加热反应实验装置；2)开展了微波作用与否条件下，等温和非等温条件下的硫酸分解磷矿反应动力学研究；3)测定了微波电磁场对磷矿分解反应体系中的液相物质的影响；4)研究了微波和加热作用对溶液结晶过程的影响；5)利用³²P示踪剂，模拟了微波与加热作用对介质渗透的不同影响。 实验结果表明，在一定的条件下，微波能够促进磷矿酸解液固分解反应的进行，加快反应速率;提高反应体系液相物质的电导率，促进磷酸和硫酸的电离，同时能够提高磷矿矿浆的温度，促进水分蒸发;微波能够加快反应结晶的沉积析出，并具有细化、均化结晶的作用，但微波作用不会改变结晶晶习、晶格结构和晶体组成;微波作用提高了分子的活度和自由运动的分子数目，促进了磷酸分子或离子在多孔介质和分子筛中的渗透能力;微波不仅存在“热效应”，而且存在“非热效应”。 通过等温稳态反应实验数据，建立了微波作用与否条件下的等温稳态反应动力学模型，如（1）、（2）式所示。 微波::=1.99sxzo一’e，o‘，o‘RT〔l一（1一x）“，j{z+（YZ/6）〔z+（z一x）’‘3一z（z一x）2‘，〕}（z） YZ=4 .478X105一3.849X10，T+1.102X10T，一l.052XI0一’T3 加热::=0.32se，，，‘o爪丁[l一（1一x），‘，〕{z+（yZ/6）[1+（l一x）’‘，一z（1一x）’‘，〕}（z） YZ=2 .209 X 105一1.872X103T+5.29灯2一4.98X10一3T3式中:T为反应温度，K;t为反应时间，min;x为反应分解率，%;R为摩尔气体常数，8.314)/（mol·K）。 发现了微波作用对反应活化能和频率因子的同升效应，施加的微波场从抑制和促进反应两个方面影响着反应物系。在反应温度超过40℃后，微波化学反应速率将超过非微波化学反应速率;发现了微波对扩散系数的负效应。当反应温度超过70℃后，随着温度的继续升高，微波与对照条件下的有效扩散系数Dc‘/D‘比值逐渐下降，传质速率不断减慢。 、_、._。、_，<sub><sub><sup><sub>，、_，。.^，.，_，，一_二.，，^，，、_一:、^、一一_tdT}^、 通过微波和程序升温加热条件下的实验数据，发现升温速率洲毛舟}，与温 ^一‘认州‘件，‘”^”“““小”’““大似取相’认^“’^<sup>甲尸{dt)’刃^度T呈非线性关系，回归出升温速率方程。月一e子+‘（3）式中系数如（4）、（5）式所示。、，、rJ任一勺J了、尹r、a=一70 432.434e一仪’/，27’78一434.812w十0.857 wZ十69 312.488b^一0 .0932一0.2105w+0.00215 wZ一5.947 w3h，_<sub>、，一，、^、一一}dT}_<sub>，.、，六.、、山_.一_，，、，一。^一<sub><sub>，一甄甲消为井温遐率1二厂r!，入/mm;w刀佩淡切革，W;a，b刀勺佩淡怕熊切半 \u乙]w有关的系数。 随着时间的延长，温度呈升高趋势，但升温速率呈下降趋势;在每个微波功率下，其升温速率并不是一个常数，而是时间的函数。同时还推出了非等温条件 —n—下的硫酸分解磷矿反应动力学模型，如（6）式所示。 In{〔（l一z），一’一I〕八:一l)}=In（A/月。）·（E‘/R）一2 .325一0.4567（E‘瓜T）（6）（6）式中部分系数如（7）、（8）式所示。 A二1 .822 X 10‘e一/5·’‘o+1.838w一7.0 X 10一‘wZ一1.936 X 10一，切，一155.939（7） E二4.093 X 103e一/，，25‘一1.540 X 103切+ 11.337 wZ一2.611 x 10一2w3+8.069 X 10‘（8） P。=e‘，尹=。子+‘，五，二五+。R式中:n一2/3;E为反应活化能，J/mol;R为8.314J/（mol·K），其它系数含义同（4）、（5）式。 发现在升温速率相同的条件下，微波反应与程序升温反应存在较大差别。当微波辐射功率较低时，?更多还原

【Abstract】 Solid-liquid reaction is one of the most common methods for rock processing. With phosphate rock decomposing in the course of reaction, some resultants of reaction will diffuse and separate crystals out. The crystals may deposit on the surface of particles of solid reactant, coat the particles, form a layer of solid film and resist further reaction, if the crystallization happens on the surface of particles, which results in a decreasing reaction rate or even stopping reaction.Conventional measures for increasing the rate of solid-liquid reaction between phosphate rock and acid can be sorted into 2 aspects: one is adjusting reactive condition for larger size of crystal resultants to form a porous solid film; the other is decreasing solid-liquid interfacial tension for higher surface irrigation rate. Unfortunately, the measures have too strong correlation with raw material rock properties to extend over whole industry.Microwave, which has absorptivity and penetrativity, is the electromagnetic wave with 300 MHz ~ 300 GHz frequency. Liquid molecules will frequently change their direction with polar shift of microwave field, thus their ionization degree, ionic activity and permeability to solid film are spirited up, when they absorb microwave. The results in microwave "thermal effect" of friction and " non-thermal effect" of agitation among liquid molecules, disturb the crystal course of resultants of reaction, increase diffusion rate of resultants of reaction to liquid phase and contact probability between liquid molecule and particle of phosphate rock.It is the most important solid-liquid reaction that sulfuric acid orphosphoric acid decomposes phosphate rock in phosphate fertilizer production. By contrast with conventional reaction of acid decomposing phosphate rock, the influence of microwave on the reaction is discussed.Main research items include: 1) setting up a set of batch microwave reactor with multi-model cavity and a set of batch reactor by intelligent temperature control system; 2) researching isothermal and non-isothermal kinetic of sulfuric acid decomposing phosphate rock under the condition of microwave or not; 3) determining some properties of liquid reactant in acid -rock system with microwave enhancement; 4) discussing the influence of microwave heating and electric heating on crystal course; 5) simulating experiment of 32P tracer for distinguishing the permeability to solid film with/ without microwave irradiation.The results show that under a certain condition, microwave can prompt the decomposing reaction of acid-phosphate rock, accelerate reactive rate; improve electrical conductivity and ionization degree of liquid reactant sulfuric acid or phosphoric acid, raise the temperature of phosphate rock slurry and drive water evaporating; enhance crystal deposit of resultants of reaction, grain refining and homogenization, and keep original crystal habit, crystal structure and component; increase the activity of molecule and amount of free activated molecule, increase the permeability of phosphoric acid molecule and ion to porous solid media; microwave can also bring "thermal effect" and "non-thermal effect".Based on the data from the experiments of isothermal kinetic of sulfuric acid decomposing phosphate rock under the condition of microwave or not, 2 mathematic models were established: Microwave: Heating: Where, T rreactive temperature, K; t?reactive time, min; x ?percent conversion, % ; R-8. 314 J/(m ?K).Meanwhile, the homotropic effect between activation energy andpre-exponential factor was discovered under the action of microwave, dual control of microwave prompting and inhibiting action on reactive rate influences the acid-rock reactive system. When reactive temperature is more than 40℃, the reactive rate of acid decomposing phosphate rock with microwave is higher than that without one. After reactive temperature is more than 70℃ , the ratio of available diffusion coefficients with and without microw更多还原