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Ivar S Ertesvag - One of the best experts on this subject based on the ideXlab platform.

  • on the definition of Exergy efficiencies for petroleum systems application to offshore oil and gas processing
    Energy, 2014
    Co-Authors: Tuongvan Nguyen, Mari Voldsund, Ivar S Ertesvag, Brian Elmegaard, Signe Kjelstrup
    Abstract:

    Exergy-based efficiencies are measures of the thermodynamic perfection of systems and processes. A meaningful formulation of these performance criteria for petroleum systems is difficult because of (i) the high Chemical Exergy of hydrocarbons, (ii) the large variety of Chemical components, and (iii) the differences in operating conditions between facilities. This work focuses on offshore processing plants, considering four oil platforms that differ by their working conditions and designs. Several approaches from the scientific literature for similar processes are presented and applied to the four cases. They showed a low sensitivity to performance improvements, gave inconsistent results, or favoured facilities operating under certain conditions. We suggest an alternative formulation, called the component-by-component Exergy efficiency, which builds on the decomposition of the Exergy flows at the level of the Chemical compounds. It allows therefore for sound comparisons of separation systems, while it successfully evaluates their theoretical improvement potentials. The platform displaying the lowest efficiency (1.7%) is characterised by little pumping and compression works, at the opposite of the one displaying the highest performance (29.6%). A more realistic measure of the technical potential for improving these systems can be carried out by splitting further the Exergy destruction into its avoidable and unavoidable parts.

  • Exergy analysis of the oil and gas processing on a north sea oil platform a real production day
    Energy, 2013
    Co-Authors: Mari Voldsund, Ivar S Ertesvag, Signe Kjelstrup
    Abstract:

    We explore the applicability of Exergy analysis as an evaluation and monitoring tool for the oil and gas processing on an offshore platform. A real production day on a particular North Sea platform is analysed. A process flowsheet is simulated using measured process data. We distinguish between temperature based Exergy, pressure based Exergy and the mixing part of the Chemical Exergy. It is shown that physical Exergy in the material streams mainly is pressure based Exergy, and most Exergy destruction is related to decrease or increase in pressure. The sub-processes with most destructed Exergy are the production manifold (4600 kW), the recompression train (4150 kW) and the reinjection trains (10,400 kW). At this platform 260 kW separation work is done, where a considerable part is done in the compression trains in addition to in the separation train. The specific power consumption is 179 ± 3 kWh/Sm3 and the exergetic efficiency is 0.13 ± 0.02. We propose measures to decrease Exergy destruction, and that Exergy analysis should be taken into regular use by the oil and gas industry. This study serve as a showcase on how to do an exact analysis of an existing offshore platform using measured process data.

  • Exergy analysis of the oil and gas processing on a North Sea oil platform a real production day
    Energy, 2013
    Co-Authors: Mari Voldsund, Ivar S Ertesvag, Signe Kjelstrup
    Abstract:

    abstract We explore the applicability of Exergy analysis as an evaluation and monitoring tool for the oil and gasprocessing on an offshore platform. A real production day on a particular North Sea platform is analysed.A process flowsheet is simulated using measured process data. We distinguish between temperaturebased Exergy, pressure based Exergy and the mixing part of the Chemical Exergy. It is shown that physicalExergy in the material streams mainly is pressure based Exergy, and most Exergy destruction is related todecrease or increase in pressure. The sub-processes with most destructed Exergy are the productionmanifold (4600 kW), the recompression train (4150 kW) and the reinjection trains (10,400 kW). At thisplatform 260 kW separationwork is done, where a considerable part is done in the compression trains inaddition to in the separation train. The specific power consumption is 179 3 kWh/Sm 3 and the exer-getic efficiency is 0.13 0.02. We propose measures to decrease Exergy destruction, and that Exergyanalysis should be taken into regular use by the oil and gas industry. This study serve as a showcase onhow to do an exact analysis of an existing offshore platform using measured process data. 2013 Elsevier Ltd. All rights reserved.

  • Exergy evaluation of the arctic snohvit liquefied natural gas processing plant in northern norway significance of ambient temperature
    Energy & Fuels, 2012
    Co-Authors: Anne Rian, Ivar S Ertesvag
    Abstract:

    The first Arctic liquefied natural gas (LNG) plant was evaluated using the Exergy method. The well stream is separated into flows of tradable products, substances for deposit or reinjection, pollutants for capture, and discharged products. Some natural gas is used for fuel in the on-site combined heat and power (CHP) plant. The Exergy of the delivered products was 95.1% of the feed stream Exergy, as most of the hydrocarbons were flowing through the plant without Chemical change. The consumed Exergy was the thermomechanical Exergy of the feed stream, mainly as a result of its pressure, and the Chemical Exergy of the CHP fuel. The Exergy efficiency taken as the ratio of the desired Exergy change owing to separation, cooling, and compression to the consumed Exergy was 23.2%. Here, separation accounted for 1.9%, while compressed CO2 accounted for 0.7%. The separation Exergy was expressed as the total change of the mixing term of the Chemical Exergy across the processing plant. The Exergy losses were 37%, 52%,...

  • sensitivity of Chemical Exergy for atmospheric gases and gaseous fuels to variations in ambient conditions
    Energy Conversion and Management, 2007
    Co-Authors: Ivar S Ertesvag
    Abstract:

    Abstract The variations of Chemical Exergy with ambient temperature from −30 °C to 45 °C, pressure from 0.6 to 1.1 bar and relative humidity (RH) from 10% to 100% were investigated for gaseous fuels and atmospheric gases on the basis of Szargut’s model. It was found that the variations are significant. At ambient pressure of 1 atm and RH at 70%, the Chemical Exergy of hydrogen increased 0.7–0.8% per 10 °C of lower ambient temperature, while for methane, the increase was 0.25–0.30%. For other gaseous hydrocarbons, the increase was 0.08–0.20%. An error analysis verified that the uncertainties in the results were 2–3 orders of magnitude less than the results. It was shown that assuming the atmospheric mole fraction of water vapor constant when varying the temperature leads to unrealistic and even unphysical results, giving an opposite behavior of the model. Calculating the change of Chemical Exergy over certain processes showed that separation of air gases is potentially most efficient in cold climates, while water electrolysis to hydrogen is favorable in warmer climates. Combustion reactors and fuel cells are potentially most efficient in cold climates.

G Q Chen - One of the best experts on this subject based on the ideXlab platform.

  • Chemical Exergy based evaluation of water quality
    Ecological Modelling, 2007
    Co-Authors: G Q Chen
    Abstract:

    The thermodynamic concept of Chemical Exergy is introduced for water quality evaluation, to develop unified objective indicators in contrast to conventional indicators characteristic of subjectivity. While a quantity termed specific standard Chemical Exergy based on the global reference substances is used to evaluate the standard water quality, an indicator as specific relative Chemical Exergy with reference to a spectrum of substances associated with some specified water quality standard is developed for practical water quality evaluation, with related concepts of carrying deficit and carrying capacity well embodied in Exergy terms. Based on the data collected in the GEMS/WATER project, water qualities of 72 rivers and 24 lakes over the world are evaluated, as a detailed case study to illustrate the adaptability of the Chemical Exergy based indicators for water quality evaluation.

Jun Xiao - One of the best experts on this subject based on the ideXlab platform.

Farhad Gharagheizi - One of the best experts on this subject based on the ideXlab platform.

  • standard molar Chemical Exergy a new accurate model
    Energy, 2018
    Co-Authors: Farhad Gharagheizi, Poorandokht Ilanikashkouli, Ronald C Hedden
    Abstract:

    Abstract One of the key challenges in Exergy analysis is computation of the standard molar Chemical exergies of the compounds involved in the process or system. Here, we present a new, data-driven model for computation of the standard molar Chemical exergies of pure organic compounds composed of C, H, N, O, S, F, Cl, Br, I and Si. The model is obtained by considering the formation of a pure organic compound from its constituent elements. The compound's standard molar Chemical Exergy is related to its standard state enthalpy and entropy of formation, and to the standard molar Chemical exergies of its constituent elements. A database of 3148 pure organic compounds is used to develop correlations for the enthalpy and entropy of formation of an arbitrary organic compound based on a group contribution approach. Using these correlations, the standard molar Chemical Exergy of a given organic compound can be computed from our model. Comparison of model predictions with experimental data for 3148 compounds produces an average absolute relative deviation of only 0.3%. The new model provides a reasonable basis to estimate the standard molar Chemical exergies of various organic compounds when experimental data are not available.

  • A group contribution method for determination of the standard molar Chemical Exergy of organic compounds
    Energy, 2014
    Co-Authors: Farhad Gharagheizi, Poorandokht Ilani-kashkouli, Amir H. Mohammadi, Deresh Ramjugernath
    Abstract:

    Exergy analysis can be used to achieve the optimal conditions at which a system or a process can precede; as close as possible to the environmental conditions (with minimum loss of energy). In order to do such an analysis, the Chemical Exergy of each compound should be available. Since there are a limited number of organic compounds for which the Chemical Exergy values have been reported in the literature, it would be of great interest to have a reliable method for the estimation of this parameter. In this communication, a group contribution method is proposed for the prediction of the Chemical Exergy of pure organic compounds at the standard condition of 1 atm and 298.15 K for pressure and temperature respectively. In order to develop and validate the model, and also to evaluate its predictive capability, a dataset of 133 pure organic compounds composed of carbon, hydrogen, nitrogen, oxygen, and sulfur was used. The model proposed has a low average absolute relative deviation of 1.6% from literature data and indicates the reliability of the method. It can be used as a predictive tool for the estimation of the standard Chemical Exergy of pure organic compounds.

  • prediction of standard Chemical Exergy by a three descriptors qspr model
    Energy Conversion and Management, 2007
    Co-Authors: Farhad Gharagheizi, Mehdi Mehrpooya
    Abstract:

    A new quantitative structure–property relationship (QSPR) three parameter correlation (R2 = 0.9977) of standard Chemical Exergy for a diverse set of 134 organic substances was developed by application of a genetic algorithm search. The descriptors are all calculated directly from the molecular structure, and the approach given is applicable, in principle, to all organic substances of regular structure. The application of the genetic algorithm in comparison with stepwise multi-variate linear regression (MLR) shows some advantages in required time for solving and in precision.

Selçuk Bilgen - One of the best experts on this subject based on the ideXlab platform.

  • a new correlation for calculation of the Chemical Exergy of bio oils obtained from agricultural residues by using elementary analyses data
    Energy Sources Part A-recovery Utilization and Environmental Effects, 2016
    Co-Authors: Selçuk Bilgen, Ikbal Sarikaya, Lokman Murat Ayyildiz
    Abstract:

    ABSTRACTThe correlation proposed in this work has been compared statistically with a larger database of bio-oils taken from values in the literature. The correlation developed here uses only one formula used in the major constituents of elementary analyses. Seventy-nine data points have been used to derive this correlation. This correlation is valid for bio-oils having a broad range of elemental composition, that is C: 8.2–89.3%; H: 4.6–14.4%; O: 1.4–76.9%; N: 0.0–10.8%; and S: 0.0–1.8%. It presents an average absolute error of 1.21% and bias error of 0.59%, and thereby establishes its versatility.

  • Correlation for estimation of the Chemical availability (Exergy) from ultimate analysis of pyrolytic oils obtained from fast pyrolysis of biomass
    Energy Sources Part A: Recovery Utilization and Environmental Effects, 2016
    Co-Authors: Selçuk Bilgen
    Abstract:

    ABSTRACTThe purpose of this study is to evaluate the Chemical Exergy (ECH) of liquid products obtained from fast pyrolysis of biomass. I have calculated the Chemical Exergy values from a formula in literature and have developed a formula for estimating the Chemical Exergy of biomass from the higher heating value and their ultimate analysis values. The mean differences between these values range from –0.391% to 0.460%. The formula developed for estimating the Chemical Exergy of biomass from the higher heating value and their ultimate analyses had a correlation coefficient (R2 = 0.9999), and the prediction of this formula is good. The goal is to identify desirable attributes that may serve as the basis for decision-making for future biofuel options. Studies on the pyrolytic oils showed that the oils obtained from chestnut cupulae and maple fruit can be used as a renewable fuel and Chemical feedstock.

  • Investigation of the Chemical Exergy and Water Quality of the Galyan River, Trabzon, Turkey
    Energy Sources Part A: Recovery Utilization and Environmental Effects, 2014
    Co-Authors: Selçuk Bilgen, Volkan Numan Bulut
    Abstract:

    In this study, Exergy is considered as the confluence of energy, environment, and sustainable development. The basis for this treatment is the interdisciplinary character of Exergy and its relation to each of these disciplines. The primary objective of this study is to present a unified Exergy-based structure that provides useful insights and direction to those involved in Exergy, environment, and sustainable development for analyzing and addressing appropriately each of these areas using Exergy concepts. The thermodynamic concept of Chemical Exergy is introduced for water quality evaluation. In this study, physical and Chemical analyses were performed of the water samples taken from the determined three stations in the Galyan River that will feed the Atasu Dam, which is under construction in order to supply the drinking and using water necessary for Trabzon province.

  • The determination of the Chemical Exergy values of Indonesian biomass and biomass residues.
    Journal of Biobased Materials and Bioenergy, 2014
    Co-Authors: Selçuk Bilgen
    Abstract:

    This study aims to provide a comprehensive analysis of Indonesian biomass and biomass residues by considering the contributions of ecological goods and services using Exergy calculations, and utilizing a number of aggregate metrics that developed from Indonesian biomass and biomass residues consumption. In this regard, the Chemical Exergy values of eighteen kinds of biomass and biomass residues in Indonesia were calculated in this article. The goal is to identify desirable attributes that may serve as the basis for decision making for future biofuel options. Calculations showed that the Chemical composition of biomass and biomass residues influences strongly the Chemical Exergy values (e CH ). High proportions of oxygen, compared to carbon or hydrogen, generally reduce the Chemical Exergy of these biomass samples. In this paper, the calculated Exergy values of biomass and biomas residues will be useful for energy experts studied in biomass area and biomass-fired powerplants.

  • Calculation of higher and lower heating values and Chemical Exergy values of liquid products obtained from pyrolysis of hazelnut cupulae
    Energy, 2012
    Co-Authors: Selçuk Bilgen, Sedat Keleş, Kamil Kaygusuz
    Abstract:

    Abstract The purpose of this study is to evaluate the Chemical Exergy (eCH), the higher heating value (HHV) and the lower heating value (LHV) of liquid products obtained from catalytic fast pyrolysis of hazelnut cupulae. In this study, the first and the second law of fast pyrolysis products of a biomass sample investigated experimentally in fixed-bed reactor under various conditions have been done. Calculations showed that the Chemical composition of liquid products obtained from catalytic fast pyrolysis of hazelnut cupulae influences strongly eCH, HHV and LHV. High proportions of oxygen, compared to carbon or hydrogen, generally reduce eCH, HHV and LHV of these liquid products. Studies on the pyrolytic oil showed that the oil obtained from hazelnut cupulae can be used as a renewable fuel and Chemical feedstock. The Chemical Exergy value and the higher heating value of this oil are 35.72 MJ/kg and 35.70 MJ/kg, respectively.