考虑稳定同位素浓度垂向变化的蒸发分馏模型

针对同位素水文中经常应用的瑞利分馏模型因建立在假定静止水体中的稳定同位素充分混合的基础上,而没有考虑水体同位素组成的垂向差别,从而与自然界的实际过程不甚吻合的缺憾,利用微元分析方法结合质量守恒定律、fick扩散定律、瑞利分馏原理,在考虑水体的稳定同位素组成的垂向差别,以及此差别引起的扩散作用的前提下,重新推导了静止水体在仅受蒸发作用下的同位素组成的微分方程模型,给出了其微分方程与相应的定解条件,并指出了模型应用中分层取样应注意的问题.该模型的建立使定量分析湖泊等水体的同位素组成有了更为精细的数学基础.     

大庆和辽河油浆窄馏分的性质及组成

以大庆和辽河油浆为研究对象 ,采用超临界流体萃取分馏技术将其切割成窄馏分 ,分析了油浆窄馏分的性质及组成随收率变化的规律。研究表明 ,随累积萃取收率的增加 ,大庆和辽河油浆窄馏分的密度、粘度、折光率、硫含量及芳碳率呈增大趋势 ,油浆窄馏分的相对分子质量分布较窄 ( 3 0 0～ 4 0 0 )。窄馏分中的金属含量没有被检出 ,表明超临界流体萃取分馏将重金属浓缩于萃取残余物中。大庆、辽河油浆分别在累积萃取收率达 70 %和 2 5 %后 ,窄馏分中的芳香分含量超过饱和分且迅速增加 ,而饱和分含量相应下降。两种油浆的胶质含量基本相同 ,且呈缓慢递增趋势。在相同累积收率时 ,辽河油浆窄馏分的芳碳率远大于大庆油浆窄馏分     

气体分馏装置丙烯精馏塔操作条件的优化

采用ASPEN PLUS流程模拟软件对气体分馏装置中丙烯塔的精馏过程进行计算机模拟。通过优化操作参数，使工艺条件得到优化，丙烯纯度达到99．6％以上。     

三元非共沸混合工质变组成容量控制空调系统可行性分析

采用由R32／R125／R134a组成的三元非共沸混合制冷剂作为循环制冷工质,分析了其分馏特性,并且对变组成理论制冷循环的性能进行了计算,探讨了一种采用三元非共沸混合制冷剂的通过改变组分组成达到容量控制的新型空调系统的可行性。     

常减压装置改炼轻质原油对装置能耗的影响

<正>常减压装置能耗主要与原油性质、产品方案、装置处理量及操作等因素有关。其中,原油性质对能耗的影响复杂,轻质原油气化率高,分馏系统拔出率高,工艺用能多,但可回收的热量也大。本文,笔者将通过一个实例来说明这个问题。一、工程实例中国化工山东昌邑石化有限公司     

常减压装置改炼轻质原油对装置能耗的影响

常减压装置能耗主要与原油性质、产品方案、装置处理量及操作等因素有关。其中,原油性质对能耗的影响复杂,轻质原油气化率高,分馏系统拔卅率高,工艺用能多,但可回收的热量也大。本文,笔者将通过一个实例来说明这个问题。     

Application of chemical fractionation and X-ray powder diffraction to study phosphorus speciation in sediments from Lake Hongfeng,China

Based on the techniques of sequential extraction and X-ray powder diffraction (XRD), the distribution characteristics of phosphorus speciation were investigated in 13 sediment samples from Lake Hongfeng, an important drinking water source for Guiyang with a typical karstic limestone environment. The total phosphorus (TP) concentrations in the sediments ranged from 973.36 to 2334.18 mg/kg with a mean concentration of 1635.87 mg/kg (dry weight), and it was evident that the phosphorus level in the sediments was high compared with other eutrophic lakes such as Lake Chaohu and Lake Xihu. The results of the two methods, sequential extraction and XRD, demonstrated the presence of different phosphorus species in the lake sediments. Being compatible with local geophysical characteristics, the results of sequential extraction techniques indicate that the average percentages of dissolved phosphorus (DP), aluminum-bound phosphorus (Al-P), iron-bound phosphorus (Fe-P), calcium-bound phosphorus (Ca-P) and organic phosphorus (OP) in the sediments were 0.40%, 7.06%, 5.07%, 45.48% and 38.49%, respectively. Notably, the concentrations of inorganic phosphorus (IP) were higher than those of OP, and the IP consisted primarily of Ca-P. The high concentrations of Ca-P may temporarily control the release of phosphorus from the sediments because it is a relatively stable, inert and non-bioavailable phosphorus fraction. The results of XRD analysis indicated that, among phosphorus species, AlPO₄ was found in all sediment samples at relatively high concentrations. Moreover, the TP concentrations in the sediments were high; thus the release potential and bioavailability of phosphorus in the sediments was important. Further statistical analyses of the results revealed significant correlations between phosphorus species in the sediments with two extractable principal components and four selectable cluster levels allowing interpretation of possible origins of phosphorus loading and transformation mechanisms of phosphorus species. Furthermore, available remediation measures were briefly assessed for the lake while considering its distinct environmental features.     

青海省拉脊山一带金矿硫同位素特征及矿质来源初探

通过对同位素样品的统计分析,阐述了拉脊山一带金矿硫同位素特征,对金矿硫源及同位素分馏进行了分析、解释,认为该区硫为内生硫、幔源硫,对金矿的物质来源进行了初步探讨,金最初与硫共生,且来自上地幔。     

催化裂化装置分馏框架配管设计浅析

对催化裂化装置中,分馏泠换框架的核心设备(油浆-原油换热器)配管设计的设计特点和注意事项进行了初步探讨。     

稻叶分段硅同位素组成及硅、钾、钠、钙、镁分布特征

 稳定性硅同位素在植物体内的组成模式对研究硅生物循环、植物硅积累的机理具有重大意义。通过水培试验,研究了成熟期水稻叶内硅同位素组成及Si、K、Na、Ca和Mg营养元素的分布情况。试验结果表明,将水稻叶沿长轴按叶鞘、叶片基段、叶片中段和叶片顶段4部分划分后,各段的Si质量分数和δ³⁰Si值都存在显著差异,并呈现从叶下部到上部逐渐增加的一致趋势。在测定的其它营养元素中,只有Ca在水稻叶中的分布与Si类似,K和Na在叶鞘中的质量分数高于叶片,Mg在叶不同部位质量分数没有显著差异。本试验中水稻叶不同部位δ³⁰Si值变化范围是-0.25%～0.23%,超出了目前已知陆生植物样品δ³⁰Si值的变化范围（-0.17%～0.25%）。试验结果显示了水稻叶内硅分布主要受蒸腾作用的影响,硅同位素在叶中的分馏属于同位素动力学分馏。