Showing papers in "Journal of Energy Resources Technology-transactions of The Asme in 2011"

Experimental Visualization of Two-Phase Flow Inside an Electrical Submersible Pump Stage

Abstract: Dynamic multiphase flow behavior inside a mixed flow Electrical Submersible Pump (ESP) has been studied experimentally and theoretically for the first time. The overall objectives of this study are to determine the flow patterns and bubble behavior inside the ESP and to predict the operational conditions that cause surging. An experimental facility has been designed and constructed to enable flow pattern visualization inside the second stage of a real ESP. Special high speed instrumentation was selected to acquire visual flow dynamics and bubble size measurements inside the impeller channel. Experimental data was acquired utilizing two types of tests (surging test and bubble diameter measurement test) to completely evaluate the pump behavior at different operational conditions. A similarity analysis performed for single-phase flow inside the pump concluded that viscosity effects are negligible compared to the centrifugal field effects for rotational speeds higher than 600 rpm. Therefore, the two-phase flow tests were performed for rotational speeds of 600, 900, 1200, and 1500 rpm. Results showed formation of a large gas pocket at the pump intake during surging conditions.© 2009 ASME

Effects of Fuel Injection Timing in the Combustion of Biofuels in a Diesel Engine at Partial Loads

Abstract: Methyl and ethyl esters of vegetable oils have become an important source of renewable energy with convenient applications in compression-ignition (CI) engines. While the use of biofuels results in a reduction of CO, particulate matter, and unburned hydrocarbons in the emissions, the main disadvantage is the increase of nitrogen oxides (NOx ) emissions. The increase in NOx emissions is attributed to differences in chemical composition and physical properties of the biofuel, which in turn affect engine operational parameters such as injection delay and ignition characteristics. The effects of fuel injection timing, which can compensate for these changes, on the performance and emissions in a single cylinder air-cooled diesel engine at partial loads using canola methyl ester and its blends with diesel are presented in this study. The engine is a single cylinder, four stroke, naturally aspirated, CI engine with a displacement volume of 280 cm3 rated at 5 HP at 3600 rpm under a dynamometer load. It was equipped with a pressure sensor in the combustion chamber, a needle lift sensor in the fuel injector, and a crank angle sensor attached to the crankshaft. Additionally, the temperature of the exhaust gases was monitored using a thermocouple inside the exhaust pipe. Pollutant emissions were measured using an automotive exhaust gas analyzer. Advanced, manufacturer-specified standard, and delayed injection settings were applied by placing shims of different thicknesses under the injection pump, thus, altering the time at which the high-pressure fuel reached the combustion chamber. The start of injection was found to be insensitive to the use of biofuels in the engine. The late injection timing of the engine provided advantages in the CO and NO emissions with a small penalty in fuel consumption and thermal efficiency.

Thermodynamic Properties of Ionized Gases at High Temperatures

Abstract: Thermodynamic properties of ionized gases at high temperatures have been calculated by a new model based on local equilibrium conditions. Calculations have been done for nitrogen, oxygen, air, argon, and helium. The temperature range is 300–100,000 K. Thermodynamic properties include specific heat capacity, density, mole fraction of particles, and enthalpy. The model has been developed using statistical thermodynamics methods. Results have been compared with other researchers and the agreement is good. [DOI: 10.1115/1.4003881]

Modeling Two-Phase Flow Inside an Electrical Submersible Pump Stage

Abstract: Dynamic multiphase flow behavior inside a mixed flow Electrical Submersible Pump (ESP) has been studied experimentally and theoretically for the first time. The overall objectives of this study are to determine the flow patterns and bubble behavior inside the ESP and to predict the operational conditions that cause surging. The theoretical study includes a mechanistic model for the prediction of the flow behavior inside the pump. The model comprises a one-dimensional force balance to predict occurrence of the stagnant bubbles at the channel intake. This model depends on two important variables, namely the stagnant bubble size and the bubble drag coefficient. The bubble size has been measured and a physically based correlation is presented. A new correlation for the drag coefficient is proposed as a function of rotational speed and Reynolds number. The model enables the prediction of the operational envelope of the ESP, namely the transition to surging.Copyright © 2009 by ASME

Potential Benefits of Plug-In Hybrid Electric Vehicles for Consumers and Electric Power Utilities

Abstract: Plug-in hybrid electric vehicles (PHEVs) have the potential of substantially reducing petroleum consumption and vehicular CO2 emissions relative to conventional vehicles. The analysis presented in this article first ascertains the cost-effectiveness of PHEVs from the perspective of the consumer. Then, the potential effects of PHEVs to an electric utility are evaluated by analyzing a simplified hypothetical example. When evaluating the cost-effectiveness of a PHEV, the additional required premium is an important financial parameter to the consumer. An acceptable amount for the additional upfront costs will depend on the future costs of gasoline and the on-board battery pack. The need to replace the on-board battery pack during the assumed vehicle lifetime also affects the allowed premium. A simplified unit commitment and dispatch model was used to determine the costs of energy and the CO2 emissions associated with PHEVs for different charging scenarios. The results show that electricity can be used to charge PHEVs during off-peak hours without an increase in peak demand. In addition, the combined CO2 emissions from the vehicles and the electric generation facilities will be reduced, regardless of the charging strategy.

System Analysis of Thermochemical-Based Biorefineries for Coproduction of Hydrogen and Electricity

Abstract: Fuels derived from biomass feedstocks are a particularly attractive energy resource pathway given their inherent advantages of energy security via domestic fuel crop production and their renewable status. However, there are numerous questions regarding how to optimally produce, distribute, and utilize biofuels such that they are economically, energetically and environmentally sustainable. Comparative analyses of two conceptual 2000 tonslday thermochemical-based biorefineries are performed to explore the effects of emerging technologies on process efficiencies. System models of the biorefineries, created using ASPEN Plus ® , include all primary process steps required to convert a biomass feedstock into hydrogen, including gasification, gas cleanup and conditioning, hydrogen purification, and thermal integration. The biorefinery concepts studied herein are representative of "near-term" (approximately 2015) and "future" (approximately 2025) plants. The near-term plant design serves as a baseline concept and incorporates currently available commercial technologies for all nongasifier processes. Gasifier technology employed in these analyses is centered on directly heated, oxygen-blown, fluidized-bed systems that are pressurized to nearly 25 bars. The future plant design employs emerging gas cleaning and conditioning technologies for both tar and sulfur removal unit operations. A 25% increase in electric power production is observed for the future case over the baseline configuration due to the improved thermal integration while realizing an overall plant efficiency improvement of 2 percentage points. Exergy analysis reveals that the largest inefficiencies are associated with the (i) gasification, (ii) steam and power production, and (iii) gas cleanup and purification processes. Additional suggestions for improvements in the biorefinery plant for hydrogen production are given.

Revamping, Energy Efficiency, and Exergy Analysis of an Existing Upstream Gas Treatment Facility

Abstract: Surface oil and gas treatment facilities in service for decades are likely to be oversized due to the natural depletion of their reservoirs. Despite these plants might have been designed modularly, meaning they comprise multiple identical units serving the same task, such units operate often in conditions far from the design. This work analyzes the revamping options of an existing upstream gas facility, chosen because representative of a wide set of plants. It presents a flexible process simulation model, implemented in the HYSYS environment and dynamically linked to an Excel spreadsheet, which includes the performance maps of all turbomachineries and the main characteristics of the investigated modifications. The model may be used to run simulations for various gas input conditions and to predict the performance over 1 year of operation and for different possible future scenarios. The first objective is to assess economically the considered options, which shall be applied only if yielding short return times of the investment since the reservoir is mature. Moreover, all options are appreciated adopting a figure of merit, here defined, that compares the overall energy consumption to the one calculated with state-of-the-art technologies. In addition, exergy and environmental analyses are executed.

Mechanism and Kinetics of Pyrolysis of Coal With High Ash and Low Fixed Carbon Contents

Abstract: There are much coal with low content of volatile matter (Vad 50%), low heating caloric (∼10,000 kJ/kg) in China. It is very important to study pyrolysis performance of the coal to ensure high efficiency of utilization and low pollution emissions. In this paper, we study the pyrolysis reaction details of different types of this coal from different regions of China under different pyrolysis pressures, temperatures, particle sizes, and heating rates by thermo-gravimetry (TG) method. The pyrolysis characteristic temperatures and the characteristic index of volatilization matter released of coal gangue (CG) are obtained in this work. In addition, the detailed process of mechanism and kinetic parameters of pyrolysis are presented. The results show that many factors have an obvious influence on the pyrolysis reaction of the coal. The pyrolysis process of the coal is comprised of two stages. At the primary stage(t 560 °C), the pyrolysis reaction is governed by the tar-released reaction and the pyrolysis reaction order is 1.5. The high activation energy is also observed for the second stage pyrolysis process.

Technoeconomic Analysis of Microalgae Cofiring Process for Fossil Fuel-Fired Power Plants

Abstract: The concept of cofiring (algal biomass burned together with coal or natural gas in existing utility power boilers) includes the utilization of CO 2 from power plant for algal biomass culture and oxycombustion of using oxygen generated by biomass to enhance the combustion efficiency. As it reduces CO 2 emission by recycling it and uses less fossil fuel, there are concomitant benefits of reduced greenhouse gas (GHG) emissions. The byproducts (oxygen) of microalgal biomass can be mixed with air or recycled flue gas prior to combustion, which will have the benefits of lower nitrogen oxide concentration in flue gas, higher efficiency of combustion, and not too high temperature (avoided by available construction materials) resulting from coal combustion in pure oxygen. A technoeconomic analysis of microalgae cofiring process for fossil fuel-fired power plants is studied. A process with closed photobioreactor and artificial illumination is evaluated for microalgae cultivation, due to its simplicity with less influence from climate variations. The results from this process would contribute to further estimation of process performance and investment. Two case studies show that there are average savings about $0.264 million/MW/yr and $0.203 million/MW/yr for coal-fired and natural gas-fired power plants, respectively. These cost savings are economically attractive and demonstrate the promise of microalgae technology for reducing GHG emission from fossil fuel-fired power plants.

Sensitivity of Slug Flow Mechanistic Models on Slug Length

Abstract: Slug flow is one of the common flow patterns in gas and oil production and transportation. One of the closure relationships required by the multiphase flow mechanistic models is slug length correlation. There are several closure relationships proposed in the literature as function of pipe geometry, pipe diameter and inclination angle, and to a lesser extent to the flow rates and fluid properties. In this paper, we show that most of the frequently used mechanistic models are insensitive to slug length information. The only exception to this is identified as the Zhang et al. Unified model [1]. The unified model shows sensitivity at high gas flow rates, while displaying a negligible sensitivity at low gas flow rates. In conclusion, the slug length closure relationship is not crucial for pressure loss and holdup calculations. It can be speculated that the success of the unit cell slug flow modeling approach could be attributed to insensitivity of the models to slug length considering the highly probabilistic nature of the slug length.Copyright © 2009 by ASME

Transient Wax Gel Formation Model for Shut-In Subsea Pipelines

Abstract: Physics of wax gel formation during shut-in is analyzed and described over a cross-section of a typical subsea pipeline. Two regions are identified during this process: the liquid and gel regions. Phase transition is assumed to occur at the liquid-gel interface. Unsteady-state heat and mass transfer models are proposed for each region. Two diffusion streams are evaluated: the dissolved wax molecules moving from the pipe center toward the wall due to temperature gradient and subsequently concentration gradient and the wax molecules diffusing from the liquid-gel interface into the gel deposit. This model is essentially the modification of the model given by Bhat [1] which considered transient heat transfer and neglected mass transfer of wax molecules through the gel deposit and the model by Singh [2] which considered transient mass transfer of molecules with carbon numbers higher than the` critical carbon number (CCN) necessary for wax diffusion into gel deposit but did not consider transient heat transfer effects during the cooling process. This paper presents a transient-state formulation circumventing the limitations of these previous models and better represents the true cooling and gelation process occurring in a shut-in subsea pipeline filled with waxy crude.

An Advanced Power-Generation System With CO2 Recovery Integrating DME Fueled Chemical-Looping Combustion

Abstract: Dimethyl ether (DME) is a promising alternative fuel, but direct combustion of DME will result in extra energy penalty for CO2 separation. In this paper, an advanced power-generation system with CO2 recovery integrating DME fueled chemical-looping combustion is proposed. In the reduction reactor, DME is oxidized by Fe2O3 into CO2 and H2O, and Fe2O3 is reduced into FeO simultaneously. Since the endothermic reduction in Fe2O3 with DME requires relatively low-grade thermal energy around 180 degrees C, waste heat is used to provide the reaction heat. FeO is oxidized into Fe2O3 by air in the oxidation reactor, producing high-temperature flue gas to generate electricity through a thermal cycle. The gas production from the fuel reactor only consists of CO2 and H2O, so CO2 can be easily separated through condensing with no extra energy penalty. As a result, the thermal efficiency could be expected to be 58.6% at a turbine inlet temperature of 1288 degrees C. This proposed system may provide a new approach for high efficient use of DME in the industrial fields, and offer a possibility of chemical-looping combustion with inherent CO2 capture for the alternative fuel. [DOI: 10.1115/1.4003441]

Performance Analysis of a Novel Compact Flotation Unit

Abstract: The oil and gas industry produces large quantities of water as a by-product of petroleum production Discharge specification of produced water requires efficient management and sophisticated technology Conventional technologies such as those based on gravity separation, cyclonic separation method, filtration techniques, flotation technique, and natural gas/air sparge tube systems are used for treating produced water However, most, if not all, of these technologies require a large footprint This problem has created a challenge for the produced water industry, as well as for operators managing the offshore production facilities Responding to the challenge at hand, Siemens Water Technologies Corporation has developed a novel compact flotation unit (CFU) equipped with a dissolved gas flotation (DGF) pump for treating produced water The CFU has a small foot print and shorter residence time The DGF pump is equipped with a unique, dual-sided impeller, which pulls the blanket gas on one side and the produced water on the other Under applied backpressure, the gas entering the DGF pump dissolves in a portion of a recycled, cleaned water stream The dissolved gas generates bubbles due to the pressure drop when the mixture of produced water and gas passes through a special valve before entering the CFU The ratio of the inlet produced water flow rate to the DGF pump output rate plays an important role in optimum separation of oil droplets from the produced water Besides the above-mentioned ratio, generation of an adequate number and size of bubbles provides another critical key factor in efficient operation of the CFU system To validate our theoretical approach regarding the controlled forced vortex of the multiphase flow, we performed various tests in the shop facility of Siemens Water Technologies Corporation, as well as on a platform facility offshore Louisiana We used a response surface methodology technique to analyze the CFU performance data and to generate an optimum surface response for free oil and grease removal efficiency For optimizing the size of the piping and CFU dimensions, we used the rigorous yet simple principles of the constrained similitude The free oil removal efficiency results in the shop and field tests, for CFU without the use of packing material, were satisfactory Additionally, we found that CFU system tests resulted in the removal efficiency of water soluble oil (WSO) We did not expect this additional outcome as the CFU system was not designed to affect the removal of WSO

Experimental Evaluation of Separation Methods for a Riser Dilution Approach to Dual Density Drilling

Abstract: A dual gradient, deepwater drilling system based on dilution of riser mud requires economically separating the riser mud into a low density dilution fluid and a higher density drilling fluid. This study investigated the practicality of accomplishing this separation using hydrocyclones and centrifuges and examined the possible benefits and efficiency of each. The separation experiments were conducted using a laboratory centrifuge and 2 inch hydrocyclones. The laboratory centrifuge was able to separate the riser mud into near ideal densities for dilution and drilling fluid. However, the dense slurry retained in the centrifuge had lower emulsion stability than the feed stream. The hydrocyclones achieved much less contrast in density between the low and high density discharges, but consistently resulted in a beneficial increase in the stability of the mud emulsion in all of the flow streams and had more desirable rheological properties. A qualitative comparison indicates that the hydrocyclone separation system may offer a feasible and desirable alternative to centrifuge separation system.Copyright © 2009 by ASME

Computational Model of a Hybrid Pressurized Solid Oxide Fuel Cell Generator/Gas Turbine Power Plant

Abstract: A computational model of a hybrid pressurized solid oxide fuel cell (PSOFC) generatorl gas turbine power plant is developed using classical thermodynamic analysis in conjunction with electromechanical, fluid-mechanical, and heat transfer simulations in the fuel cell by a commercial software. The thermodynamic analysis is based on energy ,and exergy balances. A case study is reported in which the plant contains a Siemens-Westinghouse PSOFC generator and a Solar Turbines Mercury-50 gas turbine. Among the calculated quantities for a range of fuel cell current are the plant output power, first-law efficiency, and exergetic efficiency.

Advanced Deconvolution Technique for Analyzing Multirate Well Test Data

Abstract: Deconvolution allows the test analyst to estimate the constant-rate transient pressure response of a reservoir-well system, and assists us in system identification and parameter estimation. Unfortunately, deconvolution amplifies the noise contained in data. Often, we cannot identify the reservoir system from deconvolved results owing to solution instability caused by noise in measured data. We previously presented a deconvolution technique based on the fast Fourier transform that we applied to a single buildup or drawdown period. In this paper, we extend our previous work and apply the deconvolution technique based on the fast Fourier transform to arbitrarily changing rate profiles such as multirate tests. The deconvolution results, which represent a constant-rate pressure drawdown response spanning the entire duration of the test, can provide helpful insight into the correct reservoir description. We have improved our original deconvolution method in number of ways, particularly with the introduction of an iterative algorithm that produces stable deconvolution results. We demonstrate application of our deconvolution method to analysis of synthetic and field examples, including both flow and shut-in periods. Our deconvolution method can efficiently reproduce the characteristic responses of the reservoir-well system and increase our confidence in parameter estimates.