Quantitative Risk Assessment for Process Design Modification and Maintenance Optimization in Refineries and Petrochemical Plants

Quantitative risk assessment is methodology based on calculating probabilities and frequencies of sequential events using Boolean algebra, and it is normally used to perform safety assessments for complex interacting systems. Although quantitative risk assessment has been commonly used in aerospace and nuclear industries, it can also be used for quantifying economic risk and for estimating possibilities of potential production losses in a petrochemical or a manufacturing plant. In developing quantitative risk assessment models for petrochemical plants, component failures as well as human (operator) errors are taken into consideration in developing the plant's fault‐tree logic, in which is used to predict probabilities of future plant upsets. This paper shows how the quantitative risk assessment can be used to rank the economic importance of the production units in a refinery for prioritizing maintenance activities. In addition, two case studies are compared to demonstrate how a quantitative risk assessment model can be used as an invaluable tool in process design optimization. The quantitative risk assessment methodology developed in this work relates production losses to the performance of the major components and the process design. This application of the quantitative risk assessment provides a basis for the risk‐informed decision‐making and optimizing allocation of plant resources in support of plant operation and maintenance activities.     

Recent developments in the organization goals conformance using ontology

Organizational goals serve as the most important achievement target in every organization. Even though some researchers have developed the concept of the organization goals, but structuring the organization goals model is always questionable by the way it is being used. In this paper, we propose ontology to develop a unified model for the organization goals structure. We review the recent literature on the organization modelling and ontology development as an effort to evaluate the organization goals using a metrics for the achievement of the organization goals. We suggest that the metrics is important to identify the relevant organization data in relation to the organization goals conformance. In order to achieve this purpose, we investigate various associated concepts and organize the literature based on the organization goals, organization ontology and metrics model. We observe our proposed models are important for domain experts and entrepreneurs to evaluate the relevant organization data and to assist them in decision making. In summary, the contribution of this survey may serve as a first step in understanding the evaluation of the organization data for the achievement of the organization goals.     

The Feasibility of Lab-scale Cyclic CO2 Injection in Fractured Porous Media

A comprehensive analysis of the CO₂ Huff-n-Puff process with application to representative light oil system contained within a fractured porous media is present in this article. To accomplish this work, a simulation model representative of the laboratory experimental model was built and constrained under similar laboratory conditions. Six sets of CO₂ Huff-n-Puff experiments were conducted at injection pressures of 1723–10342 kPa; moreover, additional sensitivity analysis was performed on the 5170 and 6894 kPa conditions for different permeability and porosity. Results of this study demonstrate that cyclic injection of CO₂ under miscible conditions performs more favorably than under immiscible injection conditions.     

Engulfment Behavior of Inclusions in High-Carbon Steel: Theoretical and Experimental Investigation

Previous studies on inclusions behavior at the front of the solidifying steel shell have mainly focused on low-carbon steels. However, with the increasing applications of high-carbon steel in recent years because of its superior properties, it is crucial to understand this behavior in high-carbon steel. Most of the high-carbon steels are deoxidized by silicon, calcium treated, and contain higher sulfur percentage. Also, higher carbon content has a determining influence on the viscosity and surface tension, which will affect the inclusion behavior. In this study, we have investigated the engulfment behaviors of inclusions in front of the solidifying interface in high-carbon steels using concentric solidification method. The critical velocity of the growing shell, at which the particle is engulfed in the solidifying shell, instead of being pushed by this shell, was determined. The inclusion identified in this study is a bi-component form of CaO-SiO₂-based oxide and CaS. It was revealed that engulfment behavior is strongly affected by convection of liquid steel that originates from carbon push out in high-carbon steels. This study provides new crucial information to produce high-carbon steel with fewer inclusions, which opens new application pathways for this emerging grade of steel.     

Application of a new hybrid neuro-evolutionary system for day-ahead price forecasting of electricity markets

In this paper, a new forecast strategy is proposed for day-ahead prediction of electricity prices, which are so valuable for both producers and consumers in the new competitive electric power markets. However, electricity price has a nonlinear, volatile and time dependent behavior owning many outliers. Our forecast strategy is composed of a preprocessor and a Hybrid Neuro-Evolutionary System (HNES). Preprocessor selects the input features of the HNES according to MRMR (Maximum Relevance Minimum Redundancy) principal. The HNES is composed of three Neural Networks (NN) and Evolutionary Algorithms (EA) in a cascaded structure with a new data flow among its building blocks. The effectiveness of the whole proposed method is demonstrated by means of real data of the PJM and Spanish electricity markets. Also, the proposed price forecast strategy is compared with some of the most recent techniques in the area.     

Effect of dimethyl formamide in the synthesis of linear low density polyethylene on branched and molecular structure

In this research work, effect of dimethyl formamide (DMF) as an external electron donor in gas phase ethylene/1‐butene copolymerization process in the presence of Ziegler–Natta catalyst has been investigated. Different experiments were performed using TiCl₄/MgCl₂ as catalyst, triethyl aluminum as cocatalyst and in the presence of various amounts of DMF as an external electron donor. Then, effect of DMF on various parameters such as catalyst activity, molecular weight, and short chain branching content of the samples has been studied. The results showed that the more the ratio of DMF/Ti, the lower the catalyst activity. Moreover, the curves relating molecular weight and short chain branching content of the samples to the ratio of DMF/Ti passed through an extremum point at about DMF/Ti = 0.25. A justification for the occurrence of the extremum point has been proposed in this research work, and some analysis methods are adopted to confirm the suggested justification. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci 123: 1267–1272, 2012     

The effect of ginger on diabetic nephropathy,plasma antioxidant capacity and lipid peroxidation in rats

Oxidative stress is a major factor in the pathogenesis of diabetic complications. We studied the effects of ginger powder on nephropathy induced by diabetes, and measured changes in plasma antioxidant capacity and lipid peroxidation.