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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Automatisk bedömning av reglerkretsarsprestanda / Automatic Evaluation of Control Loop Performance

Holmqvist, Peter January 2005 (has links)
In this thesis, a computer program that in a simple way can calculate the performance of control loops at the refinery Preemraff Lysekil has been created. The computer program has been adapted to the environment at Preemraff Lysekil. Theories for evaluation has been studied in aspect of reliability and of automatic implementation. The evaluation has been carried out from data collected directly from control loops at the refinery and from simulated control loops with implemented errors. Among the studied methods are Harris index and Stattin´s oscillation index. According to the literature the Harris index is the most used for measure of control performance, but the results show that it does not work as a single measure at Preemraff Lysekil. However Stattin´s oscillation index works well and can be used for detection of oscillations. Statistic measures like variance, IAE, ISE and a method based on histogram are also studied. All the statistical measures are simple to implement and are rather accurate. Several tests on control loops has been carried out and it has been shown that it ís enough to use the method based on histograms and Stattins oscillation index to get a good picture of the performace of the control loops at Preemraff Lysekil. The work has resulted in a MATLAB tool that evaluates the control loops and can be run at any time. The tool first calculates Stattin´s oscillation index. The loops that are oscillating are marked. In the next step, the method based on histograms is used and a list with the worst performing loops at the top is created.
42

A Study of Adopting New Technology in Corporations from Individual and Organization Perspectives

Lee, Wen-Pin 05 January 2013 (has links)
Adopting new technologies enable enterprises to improve employees¡¦ performance and competitive advantages. The differences in natures of adopting processes of organizations and individuals need further clarify for better understandings regarding to their framework in adopting new technologies. This paper based on the Theory of Reasoned Action (TRA) and existed research to construct the relations amongst the effective factors which affect the adopting new technologies in either individual or organization perspectives. In the individual level, the constructed research framework indicated employees¡¦ e-Learning satisfaction could be measured by three major dimensions, the perceived e-Learning qualities, individual internal beliefs (usefulness and ease of use), and social influence. Eight proposed hypothesis were confirmed by Structured Equation Modeling analysis of 428 valid samples. Path analyses verified the original path in TRA, TAM, and D&M ISS Model. The perceived e-Learning qualities and social influence cause significantly influence to employees¡¦ e-Learning satisfaction in both directly and indirectly, which by way of individual internal beliefs, positive paths. The results also showed that perceived information quality, usefulness, system quality, social influence, ease of use, and than service quality positively affect employees¡¦ satisfaction of e-Learning in descend sequences. Where, in the organization level, decision framework of adopting new technology of oil refinery was composed by modified Delphi method and was verified by Analytic Network Process from the survey of 15 experts. The consistency opinions confirmed four inter-depended dimensions and seventeen criteria were included. The results suggested that process fitness, environmental fitness, actors¡¦ organizational fitness, and new technology characteristics are important dimensions of adopting new technology in descend sequences. On the other hand, economic feasibility, relative advantages, government, environment acceptance, and engineering feasibility are the top five important factors to be evaluated during the adopting process. The different natures of adopting processes of organizations and individuals cause their different framework in adopting new technologies. This paper concluded that new technology, actors¡¦, environmental characteristics are three interdepended dimensions which influence the adopting behavior no matter in individual or organization context. In organization level of oil refinery case, actors¡¦ characteristics consist not only of actors¡¦ organizational fitness but also process fitness, which is the most important dimension while adopting new technology. In final, the implications of findings were discussed and directions were also suggested for future research.
43

Assessment of Public Health Risks Associated with Petrochemical Emissions Surrounding an Oil Refinery

Pulster, Erin L. 01 January 2015 (has links)
Refinery operations have been associated with a wide variety of atmospheric emissions consisting of criteria air pollutants, volatile organic components, hazardous air pollutants as well as other pollutants. With approximately 100 oil refineries in the Wider Caribbean region (WCR), hydrocarbons in this region pose significant environmental and human health risks. One of the oldest and largest refineries in the WCR is the Isla Refineriá, which is located on the island of Curaçao, and has been the basis of historical debates and conflict between the public and the local government over the environmental and human health risks. This research aims to establish baseline levels of ambient petrochemical emissions in Curaçao, specifically polycyclic aromatic hydrocarbons (PAHs), inhalable particulate matter (PM10) and sulfur dioxide (SO2), and to evaluate through comparative literature analysis and recommended public health guidelines the potential health risks in Curaçao. In addition, source elucidation of PAHs was conducted using concentration profiles, distribution profiles, binary diagnostic ratios and factor analysis. Passive air samplers with polyurethane foam collection disks (PAS-PUFs) were deployed in 2011 (n=43) and in 2014 (n=30) to measure ambient PAH concentrations. Ambient PAH concentrations ranged from 1.2 ng/m3 in 2011 and 27.3 to 660.1 ng/m3 in 2014, demonstrating no temporal differences. However, there were highly significant spatial differences, with the samples downwind of the refinery having significantly higher ambient PAH concentrations than those upwind in 2014. Source elucidation revealed the ambient PAHs were dominated by petrogenic emission sources (i.e., refinery) in the 2011 and the 2014 downwind samples, whereas the 2014 upwind locations were equally influenced by both petrogenic (i.e., refinery) and pyrogenic (i.e., vehicle emissions) sources. Available hourly, daily and monthly PM10 and SO2 measurements were downloaded from June 2010 through December 2014 from two local air monitoring stations. Concentrations of both PM10 and SO2 in Curaçao are among the highest reported globally, demonstrating an increasing trend over time and exceed current public health guidelines recommended by local and international agencies. It is plausible that the residents of Curaçao may experience health effects often associated with PM10 and SO2, however the epidemiological evidence is inadequate to infer causality between health effects and long-term exposures. Using the USEPA’s risk analysis methodology the resulting cumulative lifetime cancer risk estimates from PAH inhalation were below the level of concern (1.0 x 10-4). In contrast, by evaluating the potency adjusted concentrations relative to the most toxic compound (benzo[a]pyrene), age class (children and adults) extrapolated and site specific risks indicated levels exceeding the upper bound acceptable risk (1.0 x 10-4) by almost two orders of magnitude suggesting the need for remediation.
44

Petroleum refinery scheduling with consideration for uncertainty

Hamisu, Aminu Alhaji 07 1900 (has links)
Scheduling refinery operation promises a big cut in logistics cost, maximizes efficiency, organizes allocation of material and resources, and ensures that production meets targets set by planning team. Obtaining accurate and reliable schedules for execution in refinery plants under different scenarios has been a serious challenge. This research was undertaken with the aim to develop robust methodologies and solution procedures to address refinery scheduling problems with uncertainties in process parameters. The research goal was achieved by first developing a methodology for short-term crude oil unloading and transfer, as an extension to a scheduling model reported by Lee et al. (1996). The extended model considers real life technical issues not captured in the original model and has shown to be more reliable through case studies. Uncertainties due to disruptive events and low inventory at the end of scheduling horizon were addressed. With the extended model, crude oil scheduling problem was formulated under receding horizon control framework to address demand uncertainty. This work proposed a strategy called fixed end horizon whose efficiency in terms of performance was investigated and found out to be better in comparison with an existing approach. In the main refinery production area, a novel scheduling model was developed. A large scale refinery problem was used as a case study to test the model with scheduling horizon discretized into a number of time periods of variable length. An equivalent formulation with equal interval lengths was also presented and compared with the variable length formulation. The results obtained clearly show the advantage of using variable timing. A methodology under self-optimizing control (SOC) framework was then developed to address uncertainty in problems involving mixed integer formulation. Through case study and scenarios, the approach has proven to be efficient in dealing with uncertainty in crude oil composition.
45

Bewertungsmodell für die Wertschöpfungstiefe der Erdölverarbeitung in der Mongolei

Dashdavaa, Altantsetseg 21 March 2014 (has links) (PDF)
Die Forschungsarbeit beschäftigte sich mit der Frage, ob es zielführend ist, die Mongolei durch Veredelung eigener Ölressourcen mit Mineralölprodukten zu versorgen. Die Mongolei ist ein Land mit großem mineralischen Rohstoffpotential, darunter auch Erdöl. Zurzeit wird der Bedarf an Mineralölprodukten ausschließlich durch Import gedeckt. Zur Untersuchung der technischen Machbarkeit einer Ölverarbeitungsindustrie wurden verschiedene Raffinieriekonzepte auf Basis des mongolischen Rohöls Tamsag erarbeitet. Anschließend wurde anhand einer Bewertungsmethode die gesamtwirtschaftliche Relevanz der Downstream-Industrie in der Mongolei geprüft. Im Ergebnis der Untersuchungen zeigte sich, dass eine Erdölindustrie für die Mongolei sinnvoll ist. Die Erdölveredelung, als neuer Wirtschaftszweig, würde Möglichkeiten wirtschaftlicher Entwicklung eröffnen und die Importabhängigkeit der strategisch wichtigen Mineralölprodukte vermeiden.
46

Biodegradation of Polycyclic Aromatic Hydrocarbons by Arthrobacter sp. UG50 Isolated from Petroleum Refinery Wastes

Koch, Elisabeth 21 November 2011 (has links)
North American petroleum refineries use landfarming to dispose of hydrocarbon-containing wastes for bioremediation by indigenous soil microorganisms. In this study, we isolated PAH-degrading bacteria from landfarm soil by enrichment with hydrocarbon-containing effluent. One isolate, Arthrobacter sp. UG50, was capable of using phenanthrene and anthracene as sole carbon sources. The strain degraded phenanthrene (200 mg/L) within 24 h in pure culture at high cell density (10e8 cells/mL). Anthracene (50 mg/L) was slowly degraded, with 29% degraded within 21 days. The strain could not use naphthalene, pyrene, chrysene or benzo(a)pyrene as sole carbon sources, but could degrade pyrene (50 mg/L) cometabolically when phenanthrene was provided. Anthracene degradation (50 mg/L) was enhanced by phenanthrene, with 100% degraded within 6 days. The addition of strain UG50 to petroleum sludge in baffled flasks increased total hydrocarbon degradation and degradation of low concentrations of fluorene, phenanthrene, pyrene and chrysene compared to flasks with limited aeration or containing sludge alone. / NOVA Chemicals and the Ontario Centres of Excellence
47

Refinery Power Distribution Reliability and Interruption

Nygren, Leif Unknown Date
No description available.
48

MODELING AND OPTIMIZATION OF CRUDE OIL DESALTING

Ilkhaani, Shahrokh 06 November 2014 (has links)
When first received by a refinery, the crude oil usually contains some water, mineral salts, and sediments. The salt appears in different forms, most often times it is dissolved in the formation water that comes with the crude i.e. in brine form, but it could also be present as solid crystals, water-insoluble particles of corrosion products or scale and metal-organic compounds such as prophyrins and naphthenates. The amount of salt in the crude can vary typically between 5 to 200 PTB depending on the crude source, API, viscosity and other properties of the crude. For the following reasons, it is of utmost importance to reduce the amount of salt in the crude before processing the crude in the Crude Distillation Unit and consequently downstream processing units of a refinery. 1. Salt causes corrosion in the equipment. 2. Salt fouls inside the equipment. The fouling problem not only negatively impacts the heat transfer rates in the exchangers and furnace tubes but also affects the hydraulics of the system by increasing the pressure drops and hence requiring more pumping power to the system. Salt also plugs the fractionator trays and causes reduced mass transfer i.e. reduced separation efficiency and therefore need for increased re-boiler/condenser duties. 3. The salt in the crude usually has a source of metallic compounds, which could cause poisoning of catalyst in hydrotreating and other refinery units. Until a few years ago, salt concentrations as high as 10 PTB (1 PTB = 1 lb salt per 1000 bbl crude) was acceptable for desalted crude; However, most of the refineries have adopted more stringent measures for salt content and recent specs only allow 1 PTB in the desalted crude. This would require many existing refineries to improve their desalting units to achieve the tighter salt spec. This study will focus on optimizing the salt removal efficiency of a desalting unit which currently has an existing single-stage desalter. By adding a second stage desalter, the required salt spec in the desalted crude will be met. Also, focus will be on improving the heat integration of the desalting process, and optimization of the desalting temperature to achieve the best operating conditions in the plant after revamp.
49

High Temperature Corrosion Of Steels Used In Petroleum Refinery Heaters

Sultan, Abdelrahman Saleh 01 July 2005 (has links) (PDF)
The oxidation of three different steels used in the construction of petroleum refineryheaters was investigated by using thermogravimetric analysis technique (TGA). C-5,P-11, and P-22 steel samples were tested in two different oxidizing environments / air and CO2+N2+H2O (that simulates the combustion products of natural gas) at two different temperatures / 450oC and 500oC. In air oxidation P-22 had the best oxidation resistance among the three steels at two temperatures. In CO2+N2+H2O environment,C-5 possessed better oxidation resistance than P-22 and P-11. Analyses of oxidation products by using optical microscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM) were carried out to correlate TGA results to oxide composition and morphology. Lower oxidation rate of P-22 in air was explained with reference to the formation of Cr-O phase. Analytical rate equations showed that all the steels obeyed parabolic rate equation during oxidation and no transition was observed
50

Refinery Power Distribution Reliability and Interruption

Nygren, Leif 11 1900 (has links)
In the refining industry, the cost of a power system interruption is dominated by an associated loss of production. Power distribution within a refinery includes a set of production units within a highly inter-dependent process, where the outage of a single unit affects the production of additional units. This thesis proposes a method to quantify the impact of this cascading effect, called the criticality enhancement function, in which a process reliability model is introduced to link electrical outage cut-sets with lost production. Power system criticality is analyzed using four different approaches to the calculation of annual expected impact from load point interruptions on a case study of the 125,000 barrel-per-day Petro-Canada Edmonton Refinery. This thesis demonstrates how employment of the proposed technique, with its marriage of electrical and process reliability models, enables the most accurate estimation of the impact of power system interruptions.

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