【作者】 王斌；

【导师】 戴连奎；

【作者基本信息】 浙江大学 ， 控制科学与工程， 2015， 硕士

【摘要】 拉曼光谱分析技术以其分析速度快、对样品要求低、分析精度高等优点,越来越多的应用于在线分析领域。本文针对PX(对二甲苯)吸附分离装置的在线分析需求,采用了一种基于拉曼光谱解析的定量分析方法,并通过实验证明了该方法可以用于吸附分离装置中循环液与进料的定量分析；在原有的在线分析软件框架和在线分析仪硬件基础上,开发了一套专用的在线拉曼分析系统,并成功地将该系统应用于进料的在线分析中。本文主要研究内容包括：1)针对PX装置吸附塔循环液的在线分析问题,采用了一种基于拉曼光谱解析的定量分析方法。吸附塔循环液由甲苯MB、乙苯EB、对二甲苯PX、间二甲苯MX、邻二甲苯OX与(解吸剂)对二乙基苯PDEB组成。吸附工艺决定了循环液的物质成份变化范围宽、变化速度快,采用拉曼光谱进行分析最为合适。尽管循环液中的各个物质在680-880 cm-1谱段有着各自的拉曼特征峰,但这些特征峰相互重叠,无法直接采用特征峰面积与组分浓度建立分析模型。为此,本文采用了一种拉曼光谱解析的方法,将混合物光谱分解成各组分纯物质光谱的线性代数和,而分解系数反映了各组分在混合物中的浓度。为了证明该方法的有效性,我们配制了10个循环液的典型样品。实验分析结果表明,相对于混合物光谱在特征谱段的最大值,分解光谱的平均绝对偏差小于0.05；且各组分相对于PDEB的谱分解系数和相对浓度之间线性相关；对于组成未知的循环液测试样本,MB、EB、PX、MX、OX和PDEB的标准预测误差分别为0.30%、0.09%、0.56%、0.38%、0.37%、0.54%。由此可见,该方法可以用于吸附分离装置中循环液的定量分析,分析结果符合现场需求。2)基于上述分析方法,开发了一套针对PX吸附分离装置进料的在线拉曼分析系统。首先,通过配制若干有代表性的进料样本,建立了进料组成的定量分析模型；对于未知的进料测试样本,其组分EB、PX、MX和OX的标准预测误差分别为0.21%、0.12%、0.16%、0.22%,模型预测精度高。然后,编写了在线分析软件中的定量分析模块,结合已有的在线分析软件框架和在线分析硬件系统,研制了一套专门的在线拉曼分析系统。3)针对某石化厂的实际需求,成功地将上述系统应用于PX装置吸附塔进料组成的在线分析。截止目前,该系统已连续不间断运行1年以上。连续运行数据表明,该系统的重复性好,所测原始光谱在最大光强处的信噪比约为283：1,分析结果中EB、PX、MX和OX含量的重复性误差分别为0.03%、0.02%、0.05%和0.06%(标准差),极差分别为0.11%、0.10%、0.21%和0.22%。通过比对在线分析数据和人工离线采样分析数据,在线拉曼分析系统对EB、PX、MX和OX四种组分含量测量的标准预测误差分别为0.33%、0.11%、0.30%和0.20%。该系统分析精度高,且运行可靠,完全满足了厂家的日常生产需求。更多还原

【Abstract】 Raman spectral technology, with its fast speed of analysis, low sample requirements and high accuracy of prediction, has been increasingly used in the field of on-line analysis. To meet the need of a p-xylene (PX) adsorption separation process, this thesis applies a Raman spectral decomposition method to component analysis. The method has been proved that it can be used for the quantitative analysis of the circulating fluid and the feed of the PX separation process. Furthermore, an on-line analyzer for the feed is developed and has been successfully applied in an industrial PX unit. This thesis includes the following contents.1) A Raman spectral decomposition method for on-line quantitative analysis of circulating fluid in the above process is proposed. The components of circulating fluid includes methylbenzene (referred to as MB), ethylbenzene (EB), p-xylene, m-xylene (MX), o-xylene (OX), p-diethylbenzene (PDEB). Because of the wide change range of each component concentration in the circulating fluid, the Raman spectral technology is most appropriate for on-line analysis. Each component in the circulating fluid has its own special Raman peaks, but the Raman spectra of pure components overlap together. The common used method based on the peak area and concentration is no longer feasible; a recent method, indirect hard modeling, needs complex calculation. Therefore, this thesis proposes a Raman spectral decomposition algorithm. It is assumed that a spectrum of mixture can be decomposed into the sum of pure component spectra, whose decomposition coefficients are determined by each component concentration for the mixture. To verify the effectiveness of this algorithm,10 typical samples of circulating fluid are formulated. Experimental results draw the following three conclusions. First of all, a spectrum of mixture can be decomposed into the sum of pure component spectra and the average deviation of the error spectrum is less than 0.05 to the maximum of the original spectrum. Secondly, there exists linear relationship between relative decomposition coefficients and relative concentration to a reference component. Thirdly, the model built by the algorithm can precisely predict the composition concentration of testing samples. The standard errors of prediction (SEP) for the concentration of MB, EB, PX, MX, OX and PDEB are 0.30%,0.09%,0.56%,0.38%,0.37% and 0.54% respectively.2) An on-line Raman analysis system is developed for the feed of an adsorption separation process. The quantitative analysis model is built based on the above spectral decomposition algorithm, and the SEP for the concentration of EB, PX, MX and OX in the feed are 0.21%,0.12%,0.16% and 0.22% respectively. Then, a novel quantitative analysis module is developed based on the existing framework of on-line analysis software. Combined with the existing hardware system, an on-line Raman analysis system for the feed is developed.3) The above system has been applied to the on-line analysis for the feed of the separation process. The system has been working for more than 1 year. The running results show that the system has good repeatability, whose signal to noise ratio of the measured spectrum is about 283:1, and the standard errors of EB, PX, MX and OX are 0.03%,0.02%,0.05% and 0.06% respectively. Compared to the off-line gas chromatographic analysis data, the SEP of the on-line analyzer for the concentration of EB, PX, MX and OX are 0.33%、0.11%、0.30% and 0.20% respectively. The Raman system can meet the daily need of industrial processes because of its high reliability and accurate prediction.更多还原