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水力空化对重油降粘改质的实验研究及装置大型化模拟研究

作者:优质期刊论文发表网  来源:www.yzqkw.com  发布时间:2019/9/29 14:24:51  

摘要:基于水力空化过程中产生的高温、高压、微射流及强大的剪切力等极端的物理条件,利用自主研发的一种水力空化装置对不同产地的重质原油进行空化处理,以改善重油的粘度,提高后续工艺中轻质油品的产出,实现对重质油品降粘改质的目的。

利用基于拉瓦尔喷管的水力空化发生装置对实验平台进行工艺流程的设计及操作步骤的安排,并在此基础上实现对不同产地重质原油的空化处理,探究水力空化作用对重油降粘改质的机理及空化装置的普适性。同时采用CFD数值模拟的方法,探寻大处理量需求下空化装置结构参数对空化强度的影响和最大空化强度下各结构的最佳参数值。对比分析优化后装置与原装置内部流场的变化及对不同油品空化效果的改变。本文就以下方面开展实验与数值模拟研究:

(1)利用流变仪、实沸点蒸馏等不同的分析测试手段,对经过拉瓦尔喷管空化处理的沙特重油及塔河原油进行分析,实验中探究了不同压力、不同循环处理次数对不同原油的降粘效果及轻质化机理,结果表明:在一定压力范围内,随着空化压力的增大,沙特原油和塔河原油粘度均随之先降低后趋于稳定,空化装置对于不同油品具有降粘普适性;空化处理次数对不同油品的降粘效果影响不大,且无论是空化压力的改变还是空化次数的增多,空化对于油品中S、N等杂原子含量均没有明显的影响;水力空化实现重油降粘的主要原因是空化作用改变了油品的结构,破坏了重油中稠环芳烃稳定的盘状芳环结构,使得减压渣油向蜡油转变,分子量减小;空化处理使得减压渣油中沥青质向胶质部分转化,胶体体系更加松散,增加了延迟焦化加工时的液体收率,提高了高附加值产品收率。

(2)采用正交实验的方法,在一定参数值范围内探究处理量为105t/a需求的空化装置的最优结构参数。结果表明:最佳的结构参数组合为入口直径100mm,收缩段长度90mm,扩张段锥角16°,扩张段长度160mm,其中扩张段长度对整个喷管空化效果的影响最大,入口直径的影响最小;同时在相同的模拟条件下对此结构下的空化装置进行模拟分析,发现其轴截面气含率高达41.76%,符合实验预期。

(3)基于CFD的方法,对比了实验装置优化前后空化强度的变化,研究了介质的粘度对装置空化效果的影响,结果表明:优化前的喷管更适用于粘度较低的油品处理,而优化后的喷管更适用于粘度较高的油品的处理;所处理介质的粘度对优化后喷管的空化效果有一定的影响,随着介质粘度的升高,喷管的空化强度先增大后减小,在介质粘度为200mm2/s左右时,可获得较好的空化效果;优化后喷管的处理量会更大,同时也能保证较高的空化强度,可为今后更高处理量需求的空化装置的设计奠定基础。

Based on the extreme physical conditionssuch as high temperature, high pressure, micro-jet and strong shear forceproduced in the process of hydraulic cavitation. Using an independent researchand development hydraulic cavitation device to treat heavy crude oil fromdifferent producing areas, in order to ameliorate the viscosity of heavy crudeoil, increase the output of light crude oil in follow-up process, and realizethe purpose of reducing viscosity and upgrading heavy crude oil.

Using a hydraulic cavitation generatorbased on laval nozzle to design the process flow and arrange the experimentalsteps. On this basis, realizing the cavitation treatment of heavy crude oilfrom different producing areas, and exploring the mechanism of hydrauliccavitation for viscosity reduction and upgrading of heavy crude oil and theuniversality of the cavitation device. At the same time, using the CFDnumerical simulation method to explore the influence of structural parameterson the cavitation strength and the optimum parameters of each structure underthe maximum cavitation strength. Comparing and analyzing the variation ofinternal flow field and cavitation intensity of different oil products byoptimized equipment and original equipment. In this paper, experimental andnumerical simulation studies are carried out on the following aspects:

(1) Using rheometer and real boiling pointdistillation to analyz Saudi heavy oil and Tahe crude oil treated by Laval nozzlecavitation. The effects of different pressure and treatment times on viscosityreduction and upgrading of crude oil were investigated. The results show that:Within a certain pressure range, with the increase of cavitation pressure, theviscosities of Saudi crude oil and Tahe crude oil decrease first and thenstabilize, and the cavitation device has the universality of viscosityreduction for different oil products; The number of cavitation treatments haslittle effect on the viscosity reduction of different oils, and no matter thechange of cavitation pressure or the increase of the number of cavitationtreatments, cavitation has no obvious effect on the content of S, N and otherheteroatoms in oils; The main reason for reducing viscosity of heavy oil byhydraulic cavitation is that cavitation changes the structure of oil products,destroys the stable disc-like aromatic ring structure of polycyclic aromatichydrocarbons in heavy oil, and makes vacuum residue change to wax oil, andreduces its molecular weight; Cavitation treatment makes asphaltene in vacuumresidue convert to gelatine, and the colloid system is looser, which increasesthe liquid yield during delayed coking and the yield of high value-addedproducts.

(2) Using the method of orthogonal experiment,the optimum structure parameters of the cavitation unit with an annual capacityof 105 tons are explored within a certain range of parameters. The results showthat: The optimum combination of structural parameters is 100 mm inletdiameter, 90 mm contraction length, 16 degree cone angle of expansion sectionand 160 mm expansion section length. The length of expansion section has thegreatest influence on the cavitation effect of the whole nozzle and the minimuminfluence on the inlet diameter; Simultaneously, under the same simulatedconditions, the cavitation device with this structure was simulated andanalyzed. It was found that the gas holdup of the axial section was as high as41.76%, which accorded with the experimental expectation.

(3) Based on CFD method, comparing thevariation of cavitation intensity before and after optimization of theexperimental device, and studying the effect of medium viscosity on thecavitation effect of the device. The results show that: The pre-optimizationnozzle is more suitable for the treatment of oil with lower viscosity, whilethe Optimized nozzle is more suitable for the treatment of oil with higherviscosity.

关键词:水力空化;拉瓦尔喷管;重质原油;降粘改质;大处理量空化装置

Hydrodynamic Cavitation; Laval Nozzle;Heavy Crude Oil; Viscosity Reduction and Upgrading; Large Capacity CavitationUnit

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