柴油液相加氢固定床鼓泡反应器的混合传质特性及反应器模型

发布时间：2018-03-30 14:20

本文选题：液相加氢　切入点：固定床鼓泡反应器　出处：《浙江大学》2017年硕士论文

【摘要】：无循环上流式柴油液相加氢工艺是一种符合低硫柴油生产标准的新生工艺,该工艺不仅能够有效降低柴油中的硫含量,满足油品质量升级需要,同时能够节省大量设备及操作费用,在石化炼制工业展现出巨大的发展潜力。该工艺的核心是以预饱和的柴油进料,并由柴油中的溶解氢提供反应所需的氢气,消耗的氢气则通过多点注氢的方式不断地进行补充。快速有效地供氢是此工艺的关键。本文以无循环上流式柴油液相加氢工艺所使用的固定床鼓泡反应器作为研究对象,一方面通过测定工业条件下氢气在直馏柴油中的饱和溶解度,为无循环上流式柴油液相加氢工艺技术参数的确定提供依据;另一方面,则通过冷模实验的方法对固定床鼓泡反应器内传质和混合情况进行研究;在此基础上,建立反应器模型,以指导注氢点的设计及反应器的工程化放大。论文主要研究内容和成果包括:(1)利用取样闪蒸的方法测定了工业条件下氢气在直馏柴油中的溶解度,重点考察了氢气溶解度随操作温度和压力的变化规律,并提出了氢气在直馏柴油中溶解度的计算模型,模型计算结果与实验值的平均相对偏差在10%以内。同时,利用Aspen plus软件建立了氢气溶解度模拟计算流程,考察了H2S、NH3、CH4等杂质气体对氢气溶解的影响。结果发现升高操作温度和压力均有利于提高氢气在直馏柴油中的溶解度。杂质气体的存在会不同程度的抑制氢气的溶解,其中CH4气体的抑制作用最强,NH3次之,H2S最弱。(2)利用溶氧电极法考察了固定床鼓泡反应器内的气液传质系数随表观气速、表观液速、填料直径等参数的变化规律。在实验条件下,提高表观气液速均会使得气液传质系数增大,且表观液速的影响更为显著。而随填料直径增大,气液传质系数则表现出先减小后增大的趋势。通过对实验数据的分析,回归得到气液传质系数kLa的经验关联式,公式预测值与实验值的相对偏差在±20%以内。(3)利用电解质示踪法考察了固定床鼓泡反应器内的液相宏观停留时间分布随表观气速、表观液速及填料直径等参数的变化规律。结果表明,平均停留时间随表观液速的增大而减小,随表观气速的增大则没有明显变化。当填料直径较小时,平均停留时间随填料直径的增大而减小;而当填料直径较大时,继续增大填料直径则对平均停留时间无显著影响。基于不同条件下的停留时间分布,采用轴向扩散模型对反应器内返混程度进行计算,结果显示返混程度随表观液速的增大而减小,随表观气速的增大而增大,且液速对返混程度的影响比气速更为显著;返混程度随填料直径的增大先减小后增大。通过对多组实验数据的回归分析,提出了 Pe准数与气液两相雷诺数及填料直径的经验关联式,公式预测值与实验值的相对偏差在±20%以内。(4)基于实验测得的氢气溶解度及气液传质系数与返混程度计算关联式,结合无循环上流式柴油液相加氢工艺的操作特性,建立了固定床鼓泡反应器的数学模型。经验算,脱硫效率、脱氮率、总氢耗等模型计算值与文献值符合较好,误差在5%以内。在此基础上,使用该模型分析了入口流股温度、液相空速及氢分压对脱硫效率和反应器进出口温差的影响。结果显示:升高入口流股温度和降低液相空速都会使得脱硫效率增大,且当氢油比≥100 Nm3·m-3,入口流股温度≥360℃,液相空速LHSV≤2.0h-1时,继续升高流股温度或降低液相空速并不会对脱硫效率产生明显影响。同时,升高入口流股温度或降低液相空速均会使得反应器进出口温升增大。提高氢分压对脱硫效率无显著影响,但却会使得反应器进出口温差增大。按照单段床层温差不超过12℃,反应器进出口温差不超过20℃的原则,用该模型对注氢点的设计方法进行了讨论:总氢油比一定时,单点注氢和多点注氢都能够降低床层温升,然而同时也会降低脱硫效率,因此注氢点的设置需要综合考虑脱硫效率和床层温升两个因素;在本文研究范围内,若要保证较高的脱硫效率,中间补偿氢气与柴油的比例应小于20Nm3·m-3,并且补氢位置应选在靠近床层底部的位置。
[Abstract]:No upflow diesel liquid-phase hydrogenation technology is a new technology with a standard diesel production, this technology can not only effectively reduce the sulfur content in diesel oil, to meet the needs of upgrading the quality of oil, and can save a lot of equipment and operating costs, showing great potential in the petrochemical refining industry. The core of the process is the pre saturated oil feed, and the dissolved hydrogen in diesel oil provides the required for the reaction of hydrogen, the hydrogen consumption is continuously supplied by multi point injection of hydrogen. Hydrogen supply quickly and effectively is the key to this process. This paper in upflow liquid hydrogenation process using diesel the fixed bed bubble reactor as the research object, on the one hand, the saturated solubility determination of industrial conditions in hydrogen from straight-run diesel oil, identified as non upflow diesel liquid hydrogenation technology parameters. For basis; on the other hand, through the cold mold experiments of fixed bed bubble mass transfer and mixing in the reactor were studied; on this basis, the establishment of the reactor model, in order to guide the design of hydrogen injection point amplification and reactor engineering. The main research contents and results include: (1 under the condition of hydrogen solubility in industry) from straight-run diesel oil was determined by the method of sampling flash, focuses on the variation of hydrogen solubility with temperature and pressure, and put forward the calculation model of hydrogen solubility in straight run diesel, the average relative deviation of the model calculation results and the experimental value is less than 10%. At the same time that established the hydrogen solubility simulation flow by using Aspen plus software, the effects of H2S, NH3, CH4 and other impurities in the gas influence on hydrogen dissolved. The results showed that the increase of operating temperature and pressure are beneficial to the improvement of hydrogen gas in diesel oil In the presence of dissolved hydrogen solubility. Can inhibit different levels of impurities in the gas, in which the strongest inhibitory effect of CH4, NH3, H2S is the weakest. (2) investigated the gas-liquid mass transfer coefficient of fixed bed bubble reactor with the superficial gas velocity using oxygen electrode method, superficial liquid velocity changes. Law of filler diameter parameters. Under the experimental conditions, increase the apparent speed will increase the gas-liquid mass transfer coefficient, and the effect of apparent liquid velocity is more obvious. And with the filler diameter increases, the gas-liquid mass transfer coefficient showed the trend of increasing first. Through the analysis of experimental data, experience the correlation regression of the gas-liquid mass transfer coefficient kLa formula, predictive value and relative deviation of the experimental value is less than 20%. (3) investigated the fixed bed bubble reactor macro liquid residence time distribution with the superficial gas velocity using the electrolyte tracer method, superficial liquid velocity and filling Changes of material diameter parameters. The results showed that the average residence time increases with the superficial liquid velocity decreases with the increase of superficial gas velocity does not change significantly. When the filler diameter is small, the average residence time decreases with increasing filler diameter; when the filler diameter is bigger, increasing the diameter of the filling there is no significant effect on the average residence time. The residence time under different conditions based on the distribution, the axial backmixing degree of the reactor within the calculated diffusion model, results show that the mixing degree with the increase of superficial liquid velocity decreases, and increases with the increase of superficial gas velocity, and liquid velocity on the mixing degree the effect is more significant than the gas velocity; mixing with increasing filler diameter decreased and then increased. Through the regression of experimental data analysis, put forward the empirical correlation of Pe number and two-phase Reynolds number and the diameter of the filling, formula The relative deviation of predicted values and experimental values is less than 20%. (4) measured the hydrogen solubility and gas-liquid mass transfer coefficient and mixing formulas based on the operating characteristics of upflow diesel hydrogenation process, a fixed bed bubble reactor mathematical model of experience. And the desulfurization efficiency, nitrogen removal rate, the total hydrogen consumption model calculated values are in good agreement with the literature values, the error is less than 5%. On this basis, using the model to analyze the influence of entrance stream temperature, liquid space velocity and hydrogen partial pressure on the desulfurization efficiency and the temperature difference between inlet and outlet of the reactor. The results show that the increase of entrance stream temperature and reduce the liquid airspeed will make the desulfurization efficiency increases, and when the ratio of hydrogen to oil is more than 100 Nm3 - M-3, entrance stream temperature more than 360 DEG C, liquid phase space velocity of LHSV is less than or equal to 2.0h-1, to increase or reduce the stream temperature of liquid phase space velocity is not desulfurization efficiency of Ming Dynasty Significant impact. At the same time, increase or decrease the entrance stream temperature of liquid phase space velocity will make the reactor temperature rise of import and export increased. The hydrogen partial pressure had no significant effect on the desulfurization efficiency, but it will make the reactor temperature difference between inlet and outlet increases. According to the single bed temperature does not exceed 12 DEG C, the reactor inlet outlet temperature difference not more than 20 DEG C principle, using the model design method of hydrogen point are discussed: the total hydrogen oil ratio, single point and multi-point injection of hydrogen hydrogen injection can reduce the temperature rise of bed, but at the same time it will reduce the efficiency of desulfurization, so injection hydrogen point set needs to consider the desulfurization the efficiency and the bed temperature rise of two factors; in this study, to ensure high desulfurization efficiency, hydrogen gas and diesel intermediate compensation ratio should be less than 20Nm3 and M-3, and the hydrogen supply position should be selected in the near bed bottom position.

【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TE624

【参考文献】