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1.
采用连续稳态MSMPR反应结晶器,结合聚结-破裂生死函数粒数衡算模型对六氨氯化镁的结晶动力学进行了研究。通过改变传统破裂生死函数的表达形式,摆脱了等体积破裂假设限制,从而提出了改进后的二元随机聚结-破裂生死函数模型。在采用该模型对产品的粒度分布(PSD)数据进行离散变化求解后,获得了六氨氯化镁的结晶动力学参数。 相似文献
2.
采用反应结晶法制备了六氨氯化镁,研究了各种操作条件对六氨氯化镁晶体粒度分布的影响,确定了晶体粒度分布的控制因素。结果表明:采用连续反应得到的六氨氯化镁平均粒径大于间歇反应,反应器两侧同时加料时的粒径大于一侧加料的粒径;适当提高搅拌转速,可以提高产品的平均粒径,降低加料速率和减少搅拌时间均可以提高平均粒径,晶种的加入可以使粒度分布更加均匀。 相似文献
3.
溶液结晶是一项重要的工业操作,被广泛用于各个领域.针对扑热息痛-乙醇体系,结合计算流体动力学、结晶动力学和粒数衡算模型建立了CFD-PBM耦合模型,模拟搅拌结晶器中的间歇冷却结晶过程.与实验进行对比表明,模拟结果和实验结果有较好的一致性.探究晶种加入、破碎过程、搅拌速度和降温速率对粒度分布的影响,得出如下结论:适当加入晶种可以避免新晶体成核造成的高过饱和度,从而获得具有平均粒径大、颗粒数多的粒度分布;采用合适的破碎模型,考虑更为全面的结晶动力学模型,能够提高产品粒度分布的预测能力;随着搅拌速度增大,颗粒数增加,颗粒的平均粒径减小;线性降温速率减小,产生的颗粒数减少,但颗粒的平均粒径增大. 相似文献
4.
地塞米松磷酸钠的反应结晶动力学 总被引:1,自引:0,他引:1
利用连续稳态法在混合悬浮混合产品排除(MSMPR)结晶器中研究了地塞米松磷酸钠反应结晶动力学。以粒数密度衡算方程为基础,由实验得到的晶体粒度分布数据,采用非线性最优化方法直接进行参数估计,确定了地塞米松磷酸钠晶体的成核和生长速率方程.动力学方程的分析结果表明,地塞米松磷酸钠晶体生长速率与粒度相关,合适的过饱和度、悬浮密度和温度是得到理想地塞米松磷酸钠晶体的关键因素. 相似文献
5.
《天津科技大学学报》2017,(1)
通过实验方法研究饱和氢氧化钙溶液与CO_2反应结晶生成碳酸钙沉淀的过程.研究不同操作条件对体积传质系数、反应结晶速率以及产品最终粒度分布的影响.实验结果表明:气液体积传质系数随着搅拌速率与气体流量的增加而增加;反应结晶速率随着搅拌速率、气体流量与CO_2体积分数的增加而增加;而晶体平均尺寸随着搅拌速率和CO_2体积分数的增加而降低;气体流量对晶体的粒度分布无显著影响.碳酸钙晶体同时存在生长与聚并现象. 相似文献
6.
物理场在蔗糖结晶过程中的作用研究 总被引:1,自引:1,他引:1
利用工业结晶过程的粒数恒算原理进行分析后指出,制糖工业结晶过程中的晶体粒度分布明显受到过饱和精液物理场的影响。本论文通过一套可检测晶体生长速率和计算物理场的连续结晶系统证实了这一学术观点。由此可知,为了使得晶体群获得良好的粒度分布,就应该重视结晶设备中精液物理场的作用。 相似文献
7.
《天津科技大学学报》2017,(3)
在实验的基础上建立理想混合假设下Ca(OH)_2–H_2O–CO_2系统气液反应结晶模型.此模型包含气液物理吸收与化学吸收模型、结晶动力学模型以及气泡与晶体的粒数群体平衡模型.为解决模型刚性问题,采用高阶矩量分类法对粒数群体平衡模型进行矩变换并离散,采用高阶向后差分算法对方程组进行求解.通过实验数据对结晶动力学模型中的未知参数进行回归,得到与实验结果高度相符的反应结晶模型,为深入了解气液反应结晶机理提供理论依据. 相似文献
8.
多级连续闪蒸结晶过程的模拟与分析 总被引:1,自引:0,他引:1
文中基于物料衡算方程、热量衡算方程、粒数衡算方程、溶解度方程和结晶动力学方程建立了多级连续闪蒸结晶器的数学模型。对于模型中非线性方程组的求解,提出了以结晶内浓度为迭代变量的新迭代算法,该算法初值易确定并具有良好的稳健性和收敛速度,计算结果与文献报道值符合良好。在此基础上以一个KNO3三级连续闪蒸结晶过程为例考察了首级结晶器的温度和停留时间以及进料浓度对结晶产品粒度分布的影响。 相似文献
9.
工业蒸发结晶是一个复杂的多相传热与传质过程,其传热传质规律直接决定着晶体的成核和生长,并最终决定产品的粒度分布。根据双步结晶理论,对蒸发结晶的成核和生长动力学进行分析,建立了成核和生长的理论模型。该模型准确描述了蒸发结晶的生长规律,对其中参数的求取和分析可以确定结晶的控制步骤。研究以氯碱工业中烧碱提纯单元NaCl蒸发结晶为例,通过对模型参数的求取,分析NaCl蒸发结晶过程的控制步骤。结果显示,在高温和低流速下,NaCl结晶受扩散过程控制。从而以扩散控制理论为基础,建立了NaCl蒸发结晶的传质传热模型。综合考虑了温度、流速、过饱和度、晶体粒度对结晶粒度分布的影响规律,建立了涵盖各个参数的数学模型。结合粒数衡算,进行了模型计算,得到结晶粒度与操作参数的关系。模型计算结果与实际结果吻合良好,表明该模型可以很好地表示蒸发结晶过程中各操作参数对结晶粒度分布的影响规律。 相似文献
10.
用MSMPR结晶器对谷氨酸从工业发酵液中连续等电点结晶的动力学进行了研究。 在假设△L定律适用于MSMPR结晶过程的前提下,测量了晶体的粒数密度n和晶体平均粒度 L之间的关系。在多组实验中1n(n·Lμm)和 L之间在L>40 μm范围内存在良好的直线关系, 说明谷氨酸结晶过程符合△L定律,在L<40 μm范围内,ln(n·Lμm)值和L之间关系不符合 △L定律,对其原因在文中作了讨论。根据1n(n·Lμm)-L直线在坐标轴上的截距及其斜率所计 算出的晶核粒数密度n°和晶体生长速率G之间的关系推导出结晶过程的成核速率B°。最后从 1n(n°·Lμm)与1n(G·hμm-1)之间的直线关系再推导出谷氨酸从发酵液中连续等电点结晶在 10℃情况下的成核速率B°-晶体生长速率G之间的动力学表达式:B°=8.65×107G0.27。 相似文献
11.
Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness. 相似文献
12.
Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women's language from these perspectives: pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women's language, more attention should be paid to language use in social context. What's more, the linguistic phenomena in a speaking community can be understood more thoroughly. 相似文献
13.
Wuthering Heights, Emily Bronte's only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well. 相似文献
14.
The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation. 相似文献
15.
理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。 相似文献
16.
As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death. 相似文献
17.
Miao Maosheng 《华南师范大学学报(自然科学版)》2014,(6)
正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula- 相似文献
18.
Yang Weitao 《华南师范大学学报(自然科学版)》2014,46(6):137-138
We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re- 相似文献
19.
Bernard Kirtman 《华南师范大学学报(自然科学版)》2014,(6)
正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that 相似文献
20.
《上海师范大学学报(自然科学版)》2014,(5):550
<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with 相似文献