【作者】 曹君；

【导师】 沈本贤；

【作者基本信息】 华东理工大学 ， 化学工艺， 2012， 博士

【摘要】 本文基于分子管理的理念,在石脑油固定床吸附分离工艺的基础上研究开发了石脑油模拟移动床(SMB)吸附分离工艺。通过模拟移动床吸附分离工艺,上海石化(SPC)直馏石脑油在分子水平上被分离为富含正构烷烃分子的脱溶剂脱附油和富含非正构烷烃分子的脱溶剂吸余油,实现了石脑油作为原料的乙烯裂解过程和催化重整过程目的产物收率的双目标优化,提高了石脑油的利用效率,并推进了石脑油资源分子管理工艺技术的提高和发展。本文首先构建了一种测定正构烷烃在5A分子筛上液相吸附真实吸附量的方法,并设计了应用于实际带压工况下的双阀门液相真实吸附量测定装置。与文献中通常采用的浓度差法测得的结果比较,本方法测得的液相吸附真实吸附量更为准确,为液相模拟移动床工艺提供了基础数据。随后,本文考察了正构烷烃在5A分子筛上的静态吸/脱附过程,结果表明,正戊烷为模拟移动床工艺较为合适的液相脱附剂。由不同碳数差的正构烷烃在5A分子筛上的双组分吸附相图表明,当正构烷烃碳数接近时,短链正构烷烃由于其较小的空间体积较易满足进入孔道的空间要求,因此短链正构烷烃可以优先进入分子筛孔道内并占据吸附位。而当不同正构烷烃碳数相差较大时,长链正构烷烃优先占据吸附位。进而,本文以不同非正构烷烃组分作为溶剂,考察了石脑油中不同非正构烷烃组分对正构烷烃在5A分子筛上液相吸附动力学特性的影响,并由动力学模型和阿仑尼乌斯模型对实验数据进行拟合得到相应的液相表观吸附扩散系数与表观吸附活化能。由结果可知,各溶剂对正构烷烃在5A分子筛上的液相吸附扩散速率的影响大小顺序为：芳香烃>环烷烃>异构烷烃。本文还设计了应用于实际带压工况下的双阀门液相吸附动力学实验装置,获得了对带压工况下烃类液相吸附动力学特性的认知,充实了应用基础理论的成果。在此基础上,本文研究了上海石化(SPC)石脑油模拟移动床高效分离优化的工艺条件,结果表明：操作温度170℃,石脑油进料流速5ml/min,正戊烷脱附剂进料流速20ml/min,脱附油出口流速10ml/min,循环流速15ml/min,切换时间900s为优化条件。脱附剂回收过程中,脱附油塔(D-D塔)的优化塔板数为6块,回流比0.2；吸余油塔(R-D塔)的优化塔板数为22块,回流比为0.29。在此工艺条件下,制取的脱溶剂脱附油中正构烷烃含量为98%左右,脱溶剂吸余油中非正构烷烃含量为92%左右。与原料石脑油相比,SMB脱溶剂脱附油作为乙烯裂解原料使乙烯收率提高约17个百分点,SMB脱溶剂吸余油的芳烃潜含量和研究法辛烷值分别提高了约10个单位和20个单位,显著提高了石脑油的综合利用价值,并实现了工艺技术的连续化,具有自主知识产权。与固定床气相吸附分离工艺相比,SMB工艺具有操作温度低；液相连续操作、年处理量高；石脑油中正构烷烃在5A分子筛上平衡吸附量高；装置结构紧凑、占地面积小等优势。最后本文对基于分子管理的石脑油模拟移动床吸附分离工艺热集成和固定床气相吸附分离工艺热集成方案效果进行比较,结果显示,与热集成SMB工艺方案Ⅰ相比,热集成SMB工艺方案Ⅱ可节约能耗约77%；与热集成固定床工艺方案相比,热集成SMB工艺方案Ⅱ可节约能耗约9%。同时本文还使用Microsoft Visual Basic语言分别编写了两种工艺的设计软件。更多还原

【Abstract】 With molecule-scale management idea, a simulated moving bed (SMB) technology was developed and researched based on the previous fixed bed technology. Through SMB technology, SPC naphtha was separated into de-solvent extract oil (DEO) in which the content of normal paraffins was high and de-solvent raffinate oil (DRO) in which the content of non-normal paraffins was high. By this way. multi-object optimization on the ethylene cracking process and the catalytic reforming process with naphtha as the feed was achieved, the utilization efficiency of naphtha was increased and the level of molecule-scale management technology was developed to a new stage.An approach for determining the absolute liquid adsorption capacity of normal paraffins on 5A molecular sieves was designed, which was called "Inert-component method" in this paper. The wetting capacity of the sieves was firstly measured by using an inert component as the solution, in the next step when the sieves were immerged in the solution with n-paraffin as the solute and inert component as the solvent, the decreasing amount of the solution was called total adsorption capacity, then the absolute adsorption capacity was the difference between the total adsorption capacity and the wetting capacity. With this method, the absolute adsorption capacities of different normal paraffins on 5A sieves were determined, and it was found that the result from this method was more accurate than what’s reported in literatures. With the increase of carbon number or decrease of adsorption temperature, the absolute adsorption capacity of n-paraffin on 5A sieves increased. The isotherm curves of n-paraffins on 5A sieves at different temperatures fit the Langmuir isotherm model. This experiment provided support for SMB technology.The investigation on the static adsorption/desorption process of n-paraffins on 5A sieves showed that n-pentane was the suitable desorbent for SMB. The phase diagrams of different normal paraffins on 5A sieves showed that with small difference of carbon number, the normal paraffin with less chain number would enter the adsorption pore easier, while with large difference of carbon number, the normal paraffin with more chain number would preferentially be adsorbed. Classic composition of naphtha could be divided into four groups, which were normal paraffins group, iso-paraffins group, cyclo-paraffins group and aromatics group. The influence of each non-normal paraffins group on the adsorption kinetics of normal paraffins on 5A sieves was investigated, and the result was fitted with the kinetics model and Arrhenius model. The result showed that the sequence of the influence on the adsorption rate was aromatics>cyclo-paraffins>iso-paraffins. Through the discussion on the adsorption mechanism, it was found that the aromatic solvent molecules were expected to be preferentially adsorbed on the external surface, forming an adsorbed layer which may act like a barrier to the diffusion of the sorbate molecules into the zeolite pores.For SPC naphtha, the optimal operation conditions were the operation temperature of 170℃, the flow rate of naphtha of 5ml/min, the flow rate of n-pentane of 20ml/min, the flow rate of extract oil of 10ml/min and the switch time of 900s. For the desorbent recycle process, the optimized conditions for D-D tower were 6 plates and the reflux ratio was 0.2, while the optimized conditions for R-D tower were 22 plates and the reflux ratio was 0.29. From the coupled technology of SMB with solvent recycle process, the n-paraffins content in DEO reached 98% and the non-normal paraffins content in DRO reached 92%. Compared with naphtha, with DEO as the feed for ethylene cracking process, the ethylene yield increased by 17%; while the aromatics potential content and octane number of DRO increased by 10 units and 20 units respectively. This technology improved the utilization efficiency of naphtha, accomplished the continuous operation and had the own property right. Compared with fixed bed technology. SMB technology had the advantages like lower temperature, liquid phase operation, higher handling capacity, higher adsorption capacity and smaller floor area.In the end, the heat integration for fixed bed and simulated moving bed technology was calculated, the result showed that the SMB heat-integration projectⅡcould save the energy cost by 9% as compared with the fixed bed technology, and by 77% as compared with the SMB heat-integration projectⅠ. And Microsoft Visual Basic language was used to make the two softwares for the two technologies.更多还原