湿法磷酸净化是食品级磷酸和高品质磷酸盐生产的核心技术，其中高效的萃取洗涤工艺和设备是湿法磷酸产业实现节能减排的关键。微化工系统由于其优越的传递和反应性能以及过程安全可控等优点，已成为化工过程强化的一个前沿方向。本文以MIBK为萃取剂的湿法磷酸净化过程为对象，开展了新型洗涤剂及新洗涤工艺的研究，利用μ-PIV平台研究了液液微分散和传递基本规律，在此基础上针对萃取和洗涤过程的特点，发明高效的微型萃取设备，为湿法磷酸净化全流程微型化奠定基础。发明了磷酸二氢铵盐及其饱和水溶液的新型洗涤剂，分别针对模拟体系和实际体系考察新洗涤剂对金属阳离子的去除能力。新型洗涤剂对铁离子分离系数较原纯水或磷酸水溶液洗涤剂对铁离子分离系数提高3~5倍，在大油水相比操作下单级也能实现95%以上除杂效率，达到食品级磷酸生产要求。搭建了μ-PIV和μ-LIF测量分析平台并建立了微尺度速度场和浓度场的测定方法。以微通道中液滴形成段滴内的流动为对象，系统考察了通道结构，通道浸润性以及相间传质过程对其产生的影响。研究了十字型通道中液滴形成的浓度场变化规律，揭示了通过液滴内部涡流强化传质的机理，并建立了预测传质强化因子的数学模型。设计了微槽型抗堵微通道，考察其在错流剪切和垂直流剪切条件下的液液两相流动和传质性能。在垂直流剪切下，发现破碎流动等新流型。在高流速条件下，微槽萃取单级Murphree效率在1s左右能达到95%以上，计算得到的总体积传质系数kLa范围在0.05-1.8 s-1，较萃取塔的高1-2个数量级。设计了微槽与微填充柱耦合的微化工系统，考察其在大油水相比的操作条件下传质性能并研究了微填充柱结构对传质强化的影响及其强化机理。新型微化工系统萃取Murphree效率均在92%以上，具有优良的操作弹性。提出氨气作为洗涤剂的气液洗涤新工艺。利用同轴环管通道研究了微尺度下氨气吸收的性能，发现在气泡形成毫秒时间内传质达30%以上。针对其传质分散耦合过程研究气泡形成段的动态表面张力。在此基础上设计了微型喷淋装置，考察了氨气对MIBK和正丁醇为溶剂的磷酸体系洗涤时金属离子脱除能力，MIBK体系的金属离子脱除动力学较快，洗涤效率大于98%。
Wet process phosphoric acid purification is the key technique for producing food grade phosphoric acid and high quality phosphate by far. New technologies and efficient equipments for extraction and stripping process are crucial for energy saving and emission reduction of the wet process phosphoric acid industry. Micro-structured chemical technology, which has advanges like excellent mass transfer performance, safety and controllable, is one of the most promissing methods for process intensification. In this dissertation, basing on the wet process phosphoric acid purification process with MIBK as the extratant, new detergents and technologies for stripping process were studies. Fundamental researches on the liquid/liquid flows and mass transfer characteristics in microdevices were carried out by using a μ-PIV system. Efficient extraction equipments were designed for the extraction and stripping process, aiming to achieve miniaturization of the whole wet process phosphoric acid purification.Monoammounium phosphate and its saturated water solution were chosen to be the new detergent for stripping. Their abilities for metal impurities removal were studied with both model and industrial system. The separation coefficient of ion impurity of the new detergent is 3~5 times of that of the current used detergent like water or dilute phosphoric acid. 95% of the metal impurities could be removed with only one stage even at the operation condition of high oil to water phase ratio, which was satisfied for food grade phosphoric acid production.Micro-PIV and μ-LIF systems were estabilished for studied the flow field and concentration profiles in the liquid-liquid microdispersion. Influence of the structure of microchannels, wetting properties and mass transfer process on the flow field inside a growing droplet were studied. Also, evolution of the concentration profile in the droplet produced by the cross-junction was analyzed. The fierce convection caused by the vortex inside the growing droplet was the reason for mass transfer intensification.The intensification factor for qualifying the mass transfer process could be predicted with a general mathematical model.Slit-like microchannels with anti-clogging ability were designed. Fundamentals on liquid/liquid flows and mass transfer charateristrics with the mode of cross-flow dispersion and perpendicular rupturing were studied. At the moded of perpendicular rupturing, new flow patterns like dispersed flow were observed. At high flow rate, Murphree efficiency can reach 95% within about 1 s. Overall volumetric mass transfer coefficient was at the range of 0.05 to 1.8 s-1, which wass 1~2 orders higher of that of a common extraction column.A combination micro-structured system of a slit-like microchannel and with a micro packed column was designed and used for high ratio extraction process. The mass transfer performance of this system and the mechanism of process intensification were studied. Murphree efficiency over 92% could be achieved at all operation condictions, indicating high operation flexibility of this system.A new stripping technique based on gas/liquid system by using ammonia as the detergent was developed. Absorption dynamics of ammonia was studied with a coaxial microchannel. During bubble formation which was about several millisecond, ore than 30% of ammonia was absorbed. The dynamic surface tension during bubble formation was also studied. A micro-spary device was designed and used for studying the ability of metal impurities removal of ammonia when applied to the phosphoric acid loaded MIBK or butanol solution. For the system of MIBK, the efficiency over 98% could be reached within a short period of time.
