焦化汽(柴)油加氢精制装置生产国Ⅴ柴油的实践与优化

随着车用柴油的排放标准日益严格,炼油厂面临着柴油质量升级问题,主要指标是降低硫含量(≤10%)、提高十六烷值(≥49%)、降低稠环芳烃含量(≤11%)。惠州炼化2.0Mt/a焦化汽(柴)油加氢精制装置生产的精制柴油占全部柴油产量的40%左右,其硫含量偏高(40μg/g左右),改用柴油深度加氢脱硫催化剂FHUDS-6,以生产国Ⅴ标准柴油。对使用该催化剂的满负荷标定数据进行分析。加氢精制反应器第一、二床层装填再生后的精制剂FH-40C,第三床层装填催化剂FHUDS-6。装置标定结果表明,FHUDS-6催化剂具有良好的加氢脱硫活性和稳定性,在氢分压7.6MPa、氢油体积比590、加氢保护反应器反应床层平均温度332.7℃、加氢精制反应器反应床层平均温度365℃、加氢保护反应器空速1.746h-1、加氢精制反应器空速1.931h-1的条件下,柴油中硫的质量分数为5.2μg/g,十六烷值为54.8,产品质量满足国Ⅴ柴油排放标准要求。     

标准催化剂公司加氢催化剂在惠州炼化高压加氢裂化装置的应用

中海油惠州炼化高压加氢裂化装置处理能力为4000kt/a,采用先进的壳牌专利工艺技术,是目前国内单套处理能力最大的加氢裂化装置,加工原料主要是常减压减二、减三线蜡油和焦化蜡油。该装置选用标准催化剂公司开发的保护剂Opti Trap[Medellion]、Opti Trap[Macro Ring]、Opti Trap[Ring]、Opti Trap[Filter Lobe]、Max Trap[Ni,V]VGO、加氢精制催化剂DN-3551、深度脱氮催化剂Z-503和加氢裂化催化剂Z-3723。从催化剂床层压降、反应温度(催化剂活性)、催化剂选择性、产品收率和产品性质等方面分析催化剂使用性能,结果表明:保护剂较强的容垢能力和级配装填技术,为主催化剂充分发挥性能提供了条件;加氢精制催化剂DN-3551以及深度脱氮催化剂Z-503具有较强的脱硫、脱氮和芳烃饱和能力;加氢裂化催化剂Z-3723具有较高的裂化活性和选择性。     

汽油脱硫醇装置固定床床层压降增大的原因及对策

长庆石化汽油精制装置,采用的是无碱Ⅱ型脱硫醇工艺,现设置3台汽油脱硫醇固定床反应器,固定床反应器床层压降增大给装置的正常运转带来困难,影响装置的加工量,严重时会造成精制汽油硫醇硫含量超标,博士试验不合格。导致床层压降增大的原因主要有:汽油携带碱液进入固定床反应器,盐类和杂质在催化剂表面的累积,以及加工量波动对床层的扰动。总结出采用碱液洗涤降低床层压降的方法:通过对碱液和固定床反应器的强化控制,以及平稳汽油的进料流量,使床层压降降低,产品质量合格。提出了推迟固定床床层压降增大、延长使用时间的3条建议:更换一个容积更大的(为80.8m3)预碱洗沉降罐;在纤维膜预碱洗罐出口增加2台液-液聚结分离器,以脱除汽油中携带的碱液和水分,减少对后路反应器的影响;将3台固定床反应器的压力显示接入DCS系统,进行实时监控。     

重整装置预加氢单元压降增大原因分析及对策

九江分公司催化重整装置由于用氢流程的安排、预加氢增压机能力、原料杂质、系统的含铁物质等原因．预加氢反应系统存在压降上升过快现象,影响了装置长周期稳定运行。由重整原料油氯含量相对较高引起的铵盐沉积．预加氢反应器入口处的低压操作（1．70～1．75MPa）和气油体积比的低限操作（100）加速了催化剂的生焦积炭,这些因素不仅影响装置的处理量,而且引起重整系统压力上升,致使重整反应深度降低、产氢减少．成为限制重整装置稳定运行的瓶颈。通过对反应器顶部催化剂床层的“撇头”、氮气吹扫处理,再对空冷器E106和水冷器E107进行热水冲洗,并在反应器顶部装填级配剂后,预加氢反应系统总压降由0．48MPa降至0．2MPa．     

焦化汽柴油加氢装置反应器撇头原因分析与对策

惠州炼化汽柴油加氢精制装置设计加工延迟焦化汽柴油,为提高乙烯裂解原料品质,降低柴油产品中的硫、氮含量,该装置保持着苛刻的反应条件。针对该装置一反一床层压差连续两次快速上升的现象进行分析,进料中携带的焦粉和金属离子是该装置频繁撇头的主要原因,其中焦粉来自上游延迟焦化装置,金属离子主要为钠离子,脱硫联合装置含碱液和二硫化物的反抽提溶剂进入加氢精制装置原料罐,随装置原料进入反应器,被床层顶部的保护剂吸附,且吸附量逐渐增加,最终使床层顶部催化剂板结,导致一反一床层压差持续上升。通过平稳上游装置操作,减少焦粉夹带,调整含碱二硫化物油走向,避免钠离子污染,彻底清理装置原料罐区,抬高原料抽出口高度,加氢装置内自动反冲洗,以及强化罐区沉降脱水等措施,改善原料质量,该装置实现了连续三年超负荷平稳运行。     

固定床反应器催化剂装填方案的优化

脱砷反应器压降升高会严重影响压缩机的安全运行,同时也制约了装置的加工量。分析认为,压降升高的主要原因是床层空隙率减小,而空隙率减小的主要原因是床层杂质增多,堵塞了颗粒间的空隙。阐述了级配剂和除垢篮在抑制压降升高方面的作用,提出级配剂加除垢篮的组合装填方案,有效解决了固定床反应器的压降问题,使撇头周期达到9个月,并对装填方案的进一步优化提出建议。     

纳米颗粒的流化特征及滞后现象研究

为研究纳米颗粒的流化特征以及滞后现象,通过实验考察SiO_2、Al_2O_3和TiO_2纳米颗粒的流化行为,详细比较了在纳米颗粒流化过程中正向和反向的流化状态及床层压降之间的差异.结果表明:在稳定流化状态下,3种纳米颗粒的床层压降和流化状态有所差异,SiO_2表现为聚团散式流态化,Al_2O_3和TiO_2表现为聚团鼓泡流态化;3种纳米颗粒的正向流化均出现了显著滞后,在正向流化过程中床层压降和膨胀高度波动较大,而反向流化时相对平稳;通过设计"正-反-正"流化实验,发现二次正向流化曲线与反向流化曲线几乎重合,没有出现滞后现象,说明初始床层纳米颗粒的堆积结构和内聚力是引起流化滞后的原因.     

低直径比柱状颗粒固定床化学链燃烧的数值分析

随机固定床化学链燃烧氧化反应非常复杂，固定床中载氧体结构对床层内的流场和化学反应均有较大的影响，而流场与化学反应之间又相互影响。利用数值方法对低直径比实心圆柱和开孔圆柱两种载氧体颗粒的固定床的径向孔隙率、流动压降、传质传热以及反应特性进行分析。结果表明，采用开孔圆柱载氧体的固定床，由于其径向孔隙率较大，流动压降更小，组分以及反应产生的热量能够在整个床层内迅速传递。开孔圆柱结构载氧体能够显著地改善颗粒的内扩散现象，使得床层达到最大温升和Cu转化为CuO的时间大大缩短。     

外加磁场对磁流化床烟气脱硫过程的影响

研究了磁流化床脱硫过程中外加磁场对流化状态、脱硫效率和脱硫产物特性的影响,并分析了磁场强化脱硫的机理.结果表明:随着磁场的增强,磁流化床经历了3个阶段.在鼓泡流化状态下,床层压降不稳定,脱硫效率低;在磁稳流化状态下,床层压降小,脱硫效率快速提高;在磁聚状态下,床层压降较大,脱硫效率提高.兼顾脱硫效率和能源消耗两方面的要求,在磁稳流化状态下进行烟气脱硫是适宜的.此外,对脱硫产物微观形貌和化合物成分的分析表明:磁场改变了铁磁颗粒表面脱硫产物的附着方式,并促进了S(IV)的氧化,提高了SO2的吸收速率,从而提高了磁流化床的脱硫效率.     

炉内布置隔墙水冷壁的循环流化床锅炉床压偏差原因及分析

为了改善细颗粒燃料在循环流化床中的燃烧环境,提出热风送粉方式对其进行加热和混合,针对某新建电厂480 t/h循环流化床锅炉炉膛隔墙水冷壁两侧床层压降存在偏差的问题,通过实际的测量计算,结合运行数据及布风板结构特点,运用布风板稳定运行的基本原理,合理解释了床层压降偏差产生与消除的机理,讨论了布风板在设计上以及运行操作上存在的问题.     

Effects of catalyst separation in stratified-bed autothermal reforming of methanol

An investigation of the effect of catalyst separation in stratified autothermal reforming was conducted. A reactor containing two catalyst beds - a platinum group metal monolith followed by a pelletized copper-based steam reforming catalyst - was investigated under four different configurations corresponding to different distances between the catalyst beds. Heat shields were utilized in some trials to promote reactant mixing and increase radial heat transfer through the reactor. Reactor performance, as measured by conversion, hydrogen yield, and selectivity was quantified for each configuration. Results confirm that the reaction is heat transfer limited, with the short-distance, high-temperature configuration corresponding to an improved reactor performance. This was indicated by a 4–5% drop in methanol conversion as well as in the hydrogen yield and selectivity upon the addition of spacing between the catalysts. Visual inspection of the catalyst revealed suspected signs of potential degradation due to high temperatures, indicating the need for longer-duration experiments to determine the long-term effects of sustained high temperatures on catalyst performance.     

Numerical simulation of effect of catalyst wire-mesh pressure drop characteristics on flow distribution in catalytic parallel plate steam reformer

Steam reforming of hydrocarbons using a catalytic plate-type-heat-exchanger (CPHE) reformer is an attractive method of producing hydrogen for a fuel cell-based micro combined-heat-and-power system. In this study the flow distribution in a CPHE reformer, which uses a coated wire-mesh catalyst, is considered to investigate the effect of catalyst wire-mesh pressure drop characteristics on flow distribution in the CPHE reformer. Flow distribution in a CPHE reformer is rarely uniform due to inlet and exhaust manifold design. Poorly-designed manifolds may lead to severe flow maldistribution, flow reversal in some of the CPHE reformer channels and increased overall pressure drop. Excessive flow maldistribution can significantly reduce the CPHE reformer performance. Detailed three-dimensional models are used to investigate the flow distribution at three different catalyst wire-mesh pressure drop coefficients and at five different flow rates. Experiments are performed on a single CPHE reformer channel to evaluate the pressure drop characteristics of the catalyst wire-mesh in the current CPHE reformer design. The results are used in the numerical model where the catalyst zone is simulated as domains with momentum source to account for the pressure drop. The numerical model is verified experimentally, numerical and experimental results are found to be in good agreement. The study shows that severe flow maldistribution exists in the current reformer stack. At nominal load some channels in the CPHE reformer receive up to four times the average mass flow, while other channels have reversed flow. Flow maldistribution and flow reversal can be improved significantly by increasing the pressure drop characteristics of the catalyst wire-mesh.     

固体催化剂装填技术及设备进展

随着催化反应器的大型化及科技水平的发展,固体催化剂的装填技术和设备越来越成为催化剂工程化开发的重要内容。催化剂装填质量的好坏,直接影响到装置的技术经济指标。更重要的是,如果催化剂装填疏密不均,很容易造成物料"短路"或床层下陷,从而导致反应器内物料和温度分布不均匀,物料与催化剂接触时间不均匀,反应器压力降不均匀,影响产品质量和催化剂寿命。催化剂装填技术的核心,就是要在装填过程中实现催化剂的均匀装填,提高装填密度和装填效率。目前,工业上大多数固体催化剂的装填已实现了由人工到机械的转化,甚至实现了自动化,而且许多工业催化剂实现了密相装填。国外许多公司都开发了专有的密相装填技术,国内在催化剂密相装填设备和技术开发上也取得了可喜的进展。不过,催化剂装填的许多科学和技术问题仍有待解决,如催化剂装填的均匀化和高密度化仍需提高,催化剂装填过程中的颗粒破损和压力降增大问题还没有得到很好解决等。     

Desiccant solar air conditioning in tropical climates: I—Dynamic experimental and numerical studies of silicagel and activated alumina

This paper presents a dynamic study of moist air dehumidification in view of its use in an air conditioning process by evaporative cooling in tropical climates. A special device has been built to study dehumidification of tropical-like inlet air, through a fixed compact bed of silicagel and activated alumina. The compact desiccant storage is composed of two parallel beds to reduce the pressure drop. A good agreement is obtained for our experiment, and the computed amount of cycled water from the numerical model in the adiabatic process. This analytical model is used to simulate a complete air conditioning open cycle operating with hot and humid air.     

Thermal performance and pressure drop of rock beds with large storage materials

In air-based solar heating systems, the fan power needed to overcome friction loss in rock beds can reduce the benefit of the system. The system performance of rock beds with large-sized storage materials that have comparably low friction loss is studied. A theoretical model of the heat transfer process within the rock bed is developed for large storage materials. In this model, the temperature within the materials is assumed to be distributed quadratically and symmetrically at their center. The relationship between the model parameter and the air flow rate was derived from experimental measurements for some large materials as well as the pressure drop through the bed. The energy performance of heat pump solar systems with rock beds of various storage materials are studied by the computer simulation under Japanese winter weather conditions. It is concluded that the possibility exists for some large-sized storage materials to have almost the same performance as small-sized materials for heat pump solar systems.     

Pressure drop in cyclone separator at high pressure

For the design of pressurized circulating fluidized beds, experiments were conducted in a small cyclone with 120 mm in diameter and 300 mm in height at high pressures and at atmospheric temperatures. Influence of air leakage from the stand pipe into the cyclone was specially focused. A semi-empirical model was developed for the prediction of the pressure drop of the cyclone separator at different operate pressures with the effect of air leakage and inlet solid loading. The operate pressure, air leakage and inlet solid loading act as significant roles in cyclone pressure drop. The pressure drop increases with the increasing of pressure and decreases with the increasing of the flow rate of air leakage from the standpipe and with the increasing of the inlet solid loading.     

A review on packed bed solar energy storage systems

Because of intermittent nature of solar energy, storage is required for uninterrupted supply in order to match the needs. Packed beds are generally used for storage of thermal energy from solar air heaters. A packed bed is a volume of porus media obtained by packing particles of selected material into a container. A number of studies carried out on packed beds for their performance analysis were reported in the literature. These studies included the design of packed beds, materials used for storage, heat transfer enhancement, flow phenomenon and pressure drop through packed beds. This paper presents an extensive review on the research carried out on packed beds. Based on the literature review, it is concluded that most of the studies carried out are on rocks and pebbles as packing material. A very few studies were conducted on large sized packing materials. Further no study has been reported so far on medium sized storage elements in packed beds.     

Analogy between pressure drop and heat transfer in liquid–solid circulating fluidized beds

An analogy was found between the frictional pressure drop and the heat transfer in liquid–solid circulating fluidized beds. This investigation is based on the predicting correlations for the particle holdup, the heat transfer coefficient, and the pressure drop, which were all developed by the authors. When the heat transfer coefficients were expressed in terms of the modified j‐factor, then a close mutual relationship was observed between the modified j‐factor and the friction factor of the pressure drop due to liquid and particle flow. A correlation to express this mutual relationship was derived, which consists of the density ratio of particle to liquid and the non‐dimensional riser diameter. The heat transfer coefficient predicted from the derived correlation agreed well with the experimental data by the authors, and with existing data. © 2009 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20246     

Degradation analysis of dead-ended anode PEM fuel cell at the low and high thermal and pressure conditions

In this study, it is demonstrated that operation of dead-ended anode fuel cell at high temperature and pressure reduce the durability of membrane electrode assembly. In such a way that after 9000 degradation cycles, the maximum power density under H₂/O₂ gas feed mode for the aged MEA at high temperature and pressure is dropped by 38.8%. While the maximum power density drop is 27.1% for the aged MEA at low temperature and pressure. Comparison of the electrochemical impedance spectroscopy responses of MEAs shows that during aging process, the charge transfer resistance increase rate is more at higher temperature and pressure. This suggests the more severe destruction of catalyst layer at higher temperature and pressure and is in agreement with the obtained values of electrochemical surface area from the cyclic voltammetry test. In addition, the transmission electron microscopy and scanning electron microscopy images show the further degradation of cathode catalyst layer and more sever Pt agglomeration at higher temperature and pressure.