Numerical simulation of micro-mixing in gas–liquid and solid–liquid stirred tanks with the coupled CFD-E-model

The coupled CFD-E-model for multiphase micro-mixing was developed, and used to predict the micro-mixing effects on the parallel competing chemical reactions in semi-batch gas–liquid and solid–liquid stirred tanks. Based on the multiphase macro-flow field, the key parameters of the micro-mixing E-model were obtained with solving the Reynolds-averaged transport equations of mixture fraction and its variance at low computational costs. Compared with experimental data, the multiphase numerical method shows the satisfactory predicting ability. For the gas–liquid system, the segregated reaction zone is mainly near the feed point, and shrinks to the exit of feed-pipe when the feed position is closer to the impeller. Besides, surface feed requires more time to completely exhaust the added H⁺ solution than that of impeller region feed at the same operating condition. For the solid–liquid system, when the solid suspension cloud is formed at high solid holdups, the flow velocity in the clear liquid layer above the cloud is notably reduced and the reactions proceed slowly in this almost stagnant zone. Therefore, the segregation index in this case is larger than that in the dilute solid–liquid system.     

石化企业挥发性有机物无组织排放监测技术进展

无组织排放占石化企业挥发性有机物（VOCs）排放的主导地位,排放点多、面广、量大、分散、无规则,总体表现为大型面源或体积源,监测难度很大。本文评述了点、线和面(通量)等VOCs无组织排放监测技术及应用进展,总结了石化企业VOCs无组织排放监测存在的主要问题与难点,提出了石化企业VOCs无组织排放监测体系及适用监测技术。总体上,石化企业VOCs无组织排放监控存在排放清单质量不高、源头监测及溯源困难、排放烟羽及其迁移扩散途径无定形、厂界等开放空间难以封闭监测、常规监测的时间和空间覆盖有限等问题或技术难点,可复合应用点、线、面及通量监测技术,结合常规离线、实时在线、排放通量、移动快速响应等监测设计,构建覆盖排放与环境影响的多元化、网络化、立体化监控体系。未来石化企业VOCs无组织排放监控将向多层级、智能化和大数据应用发展。     

并联永磁同步风电机组小干扰稳定性分析

采用平均磁链定向控制多台永磁同步风电机组进而构造分频发电系统是未来陆上尤其是海上风电的汇集方案之一,但对该模式下多台风电机组间稳定性的研究鲜有文献涉及。针对此问题,基于特征值分析法,研究了平均磁链定向控制的永磁同步风电机组之间的小干扰稳定性。首先,基于高压大容量直驱式永磁同步风电机组的分频集电系统拓扑结构,建立了适用于小干扰稳定分析的风电系统的数学模型;其次,通过辨识振荡模态并分析模态参与因子确定了影响系统振荡的主控因素,通过绘制根轨迹分析了主控因素参数变化对系统振荡的影响,并发现系统振荡受发电机电感、电阻和直流电容参数的影响最大;最后,通过时域仿真验证了研究结论的正确性。     

不同催化剂对催化裂化柴油加氢裂化产品影响及预测

采用中国石油化工股份有限公司大连(抚顺)石油化工研究院研制的三种酸性依次提高,比表面积依次增大,加氢功能金属含量依次减少的催化剂,以芳烃含量较高的催化裂化柴油为原料进行了中试试验,在工艺条件相同的情况下,研究了上述三种不同类型催化剂对催化裂化柴油加氢裂化的产品分布、液体收率、氢耗和产品性质的影响规律。结果表明:在适宜的工艺条件下,采用酸性增强、比表面积增大和加氢金属含量减少的催化剂,加氢裂化产品中重石脑油收率和化学氢耗增加,柴油收率和液体收率减小,重石脑油抗爆指数可以达到84以上,柴油馏分十六烷指数可以达到35以上。以此数据建立六级总动力学模型,实现了加氢裂化装置液收和氢耗预估,以及石脑油馏分烷烃、环烷烃、芳烃和抗爆指数,柴油馏分烷烃、环烷烃、芳烃和十六烷指数率等产品性质的预测。通过对模型参数的调整,以及预测值与试验值的对比,较好地预测了不同催化剂对催化裂化柴油加氢裂化产品性质的影响,预测误差均在4%以内。     

加氢反应器空间利用率分析及提升技术开发

通过研究影响加氢反应器空间利用率的主要因素,从最大化提高加氢反应器空间利用率的角度出发,开发出提高加氢反应器空间利用率技术,包含提高反应器空间利用率的反应器内构件成套技术和优选异形齿球形催化剂技术。该技术在保障加氢反应器整体效能和运行周期的基础上,使加氢反应器空间利用率提高了10%~23%。其中,新型内构件成套技术,解决了物料分布不均、易出现局部热点的工程放大问题,使反应器空间利用率比传统技术提高5.3%~14.5%;优选的异形齿球形催化剂技术,能够使反应器空间利用率提高4.7%~8.5%,提高原料油加工量,经济效益十分显著。     

焙烧气氛和孔结构对加氢脱金属催化剂性能的影响

采用饱和浸渍法、在不同焙烧气氛（空气、氮气、水蒸气）下制备了三种加氢脱金属Mo-Ni催化剂,并考察了焙烧气氛对催化剂脱金属、脱硫和脱残碳的影响,研究结果表明：焙烧气氛对加氢脱金属反应的活性影响不大,而空气气氛下焙烧的催化剂表现出相对较高的加氢脱硫和脱残碳活性。进一步考察了氧化铝孔结构对催化剂加氢脱金属性能的影响,并结合数值模拟计算,发现最可几孔径为22 nm的催化剂更有利于加氢脱金属过程的反应-扩散平衡,从而表现出较高的加氢脱金属性能。     

D2H2 equilibration over γ-irradiated zeolites

D₂H₂ equilibrium was studied at 77 and 298 K over HY, AIHY, HZSM-5 and Al_xO_yHZSM-5 which had been γ-irradiated at 77 and/or 298 K. The exchange rate was found to be higher at the lower temperature regardless of the temperature of irradiation. Moreover, at 77 K the exchange rates were similar and more stable over the individual zeolites than at 298 K, thus indicating a common reaction path at 77 K. The exchange rate at 298 K depended on the zeolite type: it was more stable and higher over HZSM-5 than over HY, and extra-lattice Al increased both these properties on HY as well as on HZSM-5. The reaction mechanism is discussed in connection with the nature of defects generated by γ-irradiation.     

Influence of Ce3+ and Pt2+ ions on the reducibility and dispersion of Cu in copper-exchanged Y zeolites

The influence of small additions of Ce³⁺ and Pt²⁺ ions on the reducibility and dispersion of Cu in CuNaY zeolite was examined. The presence of Ce³⁺ ions in CuNaY zeolite during reduction by hydrogen increased the degree of Cu²⁺ reduction, forming Cu⁰ which occured as very small clusters. The addition of a small amount of platinum also increased the degree of reduction of Cu²⁺ ions, but the copper then formed large crystallites (20–30 nm). When Ce³⁺ and Pt²⁺ ions are present simultaneously, platinum has controlling influence on the reducibility and dispersion of Cu⁰.