Study of direct and indirect naphtha recycling to a resid FCC unit for maximum propylene production

To satisfy the increasing propylene demand, direct and indirect naphtha recycling schemes around an existing resid fluid catalytic cracking (FCC) unit were investigated. To this aim, light cracked naphtha (LCN), heavy cracked naphtha (HCN) and a PolyNaphtha (PN) oligomerisation product were cracked under a wide range of operating conditions over a commercial Y zeolite based equilibrium catalyst. Experimental data were acquired in three different units: a fixed bed bench scale unit, a fixed fluidised bed unit and an adiabatic circulating fluidised bed pilot plant. It was shown that FCC naphthas require high operating severities to crack, and that even then their conversion remains relatively moderate. Hence, direct recycling to the main riser does not seem a viable pathway to increase propylene product. Feeding FCC naphthas to a second reaction zone operating at high severity allows to increase the propylene yield in a significant manner. Increasing conversion, however, not only leads to higher LPG and propylene yields, but also results in very high dry gas yields. An alternative scheme was proposed, in which the olefinic C₄ and C₅ fractions are converted into a naphtha fraction through oligomerisation in a dedicated unit before being recracked in the secondary riser. As the highly olefinic oligomerised effluent mainly consist of dimerised and trimerised butenes and pentenes, this feed is more easily cracked and high conversions can be achieved. This indirect interconversion of butenes and pentenes into propylene therefore effectively allows to convert these butenes and pentenes into propylene, resulting in a significant increase in propylene yield. Each of the three main naphtha recycle options (directly to the main riser, directly to a secondary riser or indirectly via a light olefin oligomerisation unit) have been analysed and compared to a base case. In the evaluation of each of these schemes, all heat balance effects, both on the riser and the regenerator side, have been accounted for. The proposed process scheme with an indirect recycle via an oligomerisation unit enhances the already inherent flexibility of the FCC unit. The naphtha recycle can be turned on or off, the second reaction zone can be used to crack naphtha or to crack resid feed to maximise throughput, while the effluent of the oligomerisation unit can be recycled to the FCC unit for propylene production or hydrogenated and sent to gasoline and kerosene pool.     

Estimation of the Substrate Concentration Profiles in Petroleum Pipelines Containing Biofilms

In industrial systems, the formation of biofilms can cause many problems, such as an increase in the flow resistance of pipelines, energy losses in fluid transport and heat exchangers, product contamination, materials deterioration, and biocorrosion. As a result, biofilms contribute substantially to economic losses in the industry. Corrosion is particularly an issue in the petroleum industry and its implications range from down-hole completion through petroleum processing units. Much of this corrosion is attributed to microbial activities. This paper proposes a mathematical model for predicting substrate concentration for such microbial growth. Substrate concentrations in the system and near the biofilm surface are one of the parameters that has a great effect in determining the extent of the problems associated with biofilms. In this study, a convective-diffusion model under various flow conditions (stagnant, laminar, and turbulent) has been solved using the finite difference technique, employing the alternating direction implicit (ADI) method. The model assumes that a liquid containing substrate and bacteria is flowing in a pipeline with known concentrations at the inlet and then predicts the variation of the transient (as a function of time) substrate concentration along the pipeline and as a function of the pipe radius. The model is then used to predict and estimate the substrate concentration profiles on the biofilm surface under different environmental conditions. A parametric study was also conducted to study the effect of the different parameters influencing the substrate concentration profiles in the system and on the biofilm surface.     

模糊规划在炼油厂生产计划优化中的应用

生产计划的编制是炼油化工企业生产经营管理中的一个关键环节，然而由于市场变化的不确定性，使得企业的长远规划制定受到限制，笔者将模糊数学应用于炼厂生产计划的编制，通过模糊规划对炼油企业生产计划进行优化，使编得的生产计划在一定程度上反映市场的变化并使企业的生产效益最优，为企业管理决策者进行长期规划给予指导，给出了实例来说明该方法的可行性。     

我国钢铁行业清洁生产标准HJ/T189存在的问题与修订建议

2006年10月1日起实施的《清洁生产标准钢铁行业》(HJ/T189-2006)存在着一些不足之处,如不及时修订,将无法适应“十一五”期间钢铁工业的发展形势和清洁生产形势,在某种程度上还很容易对国内钢铁企业造成误导,而且会产生一些负面不良影响。根据目前我国钢铁工业的发展形势和国内外钢铁企业已经达到的实际清洁生产水平,就其存在的问题和今后的修订谈了一些看法。     

基于能力拍卖和多Agent的综合生产计划分布式建模及求解

把拍卖和市场理念引入到生产计划的求解过程中,结合多Agent理论,对大规模生产系统按生产单元建立分布式模型.各个生产单元看作相对独立核算的经济实体,其目标是实现自身利益最大化.当生产能力足够时,按照需求进行生产;当生产能力不足以完全满足需求时,紧缺生产资源的持有者按照单位能力获得最大收益的原则进行生产竞价与拍卖,实现了各个生产单元的分布式自主协商决策,并设计了求解算法.算例研究证明该方法的可操作性和求解的有效性.     

Line balancing in a just-in-time production environment: balancing multiple U-lines

The introduction of multiple, independent production lines has helped many firms to increase their production flexibility, provide for redundancy when equipment breaks down, reduce idle time and labor costs, and achieve many other benefits. This paper introduces and formalizes the multiple U-line balancing problem. Optimal solution methodologies are provided for Type I (minimize the number of stations for a given cycle time), Type II (minimize the cycle time for a given number of stations), and cost-minimization line-balancing problems. A branch-and-bound algorithm is also developed for the situation in which equipment requirements are dependent on the line configuration and the task assignment to stations. Computational results indicate that the greatest benefit of exploiting multiple lines occurs for smaller cycle-time problems that require higher output.     

苯乙烯类嵌段共聚物的生产及市场分析

介绍了苯乙烯类嵌段共聚物(SBC)的国内外生产和消费情况，分析了我国SBC的市场前景，提出了加大研发力度、提高SBC生产术、扩大生产规模、提高国内市场占有率，建设多功能装置等建议。     

《钢结构工程施工质量验收规范》修订简介

简要介绍《钢结构工程施工质量验收规范》(GB 5 0 2 0 5 - 2 0 0 1)的修订原则、方法以及对原规范进行修订中新增加的内容及要求 ,并进行了详细解释 ,以便于对新规范的理解     

企业实施精益生产的探讨

通过描述造成企业经济效益差的原因之一——浪费，提出了如何实施精益生产，消除企业浪费，以提高企业经济效益．     

宝浪油田宝北区块套管失效机理研究

为了深化宝浪油田的套损机理研究．提出了套管损坏因素新的分类方法。根据该新分类法,研究了宝北区块的套损机理。研究结果揭示了套损井的分布区域在主力油藏区域和主力油层;在构造顶部区域和油层顶部层段;为边缘注水井;集中在强度较低,变形量较大的煤层段和泥岩层段;在储层强度较低的射孔段。这些规律可以用有限元分析和实验结果合理地解释。