bluuebunny/crossref_metadata_2025 huggingface dataset:
Integration, Commissioning and Operation of Solar Steam Generator 4 at Kimberlina
Authors: Morton Andrew F. , Keneipp Dan , Altasserre Antoine
Published: March 2012

AREVA Solar, Inc. constructed, commissioned and operated the first-of-its-kind Once Through Solar Steam Generator (OTSG SSG), SSG4 at the Kimberlina Solar Thermal Power Station. The construction and commissioning of SSG4 was completed in September 2010, culminating in the successful execution of a series of performance tests. This was the first SSG that AREVA Solar, Inc. designed, manufactured and constructed to comply with ASME Section I, and registered with the National Board. SSG4 is the first in its class that produces high-pressure, superheated steam in a once through configuration. Some aspects of the system presented unique commissioning and operational challenges that are not commonly found in conventional fired boilers. These include: i) the use of a first-in-class model predictive control (MPC) system; ii) a steam integration system to blend steam from the once-through superheated SSG4 and the previous-generation, saturated steam SSGs; iii) a steam handling system that delivers the steam to a turbine generator or to a dump condenser; iv) precision optical tracking that is required for optimal boiler performance; v) 1310ft (400 meter) long boiler tube bundle. Unique for field erected boilers, the SSG4 tube bundle was welded at grade. After being inspected, the receiver and tube bundle support structure was placed over the bundles, secured and the entire receiver structure, with boiler tubes, was hoisted to its operating position, 60ft (18m) above grade. Following final connections of feedwater and steam piping, the boiler was inspected by Hartford Steam Boiler Insurance Company, which included hydrostatic test pressurization to 2002.5 psi (13.8MPa), and the stamps were applied to the boiler nameplate (see Figure 1 for a photo of the SSG4 boiler nameplate). Commissioning included standard boiler flushing and tube cleaning program and a comprehensive set of pre-operational tests. There were additional requirements that are unique to Compact Linear Fresnel Reflector (CLFR) solar thermal systems such as reflector alignment and tuning. These and other commissioning activities were scheduled around a constraint unique to solar systems — the availability of sunlight. A comprehensive set of procedures was followed to enable safe and successful integration and commissioning of the model predictive control system. Upon completion of commissioning, the plant was turned over to operations for continued testing. Stable superheated steam delivery was achieved within one week of Mechanical Completion, and Acceptance Testing was completed two weeks later at levels that exceeded the guarantee. This paper will describe the details of the integration, construction and commissioning milestones, distinctive aspects of commissioning solar thermal systems, and organization of the commissioning team to achieve success.
Effects on Boiler Efficiency Standards of Pulverizing Coal
Authors: Lang Fred D. , Golightly Tim , Rodgers David A. T. , Canning Tom
Published: March 2012

This paper examines the effects of particle size on the calorific value of hydrocarbons, shedding light on the thermodynamics of pulverizing coal in a commercial power plant. Both laboratory testing results and energy balances around an actual pulverizer are presented. Although tacitly known to any power plant engineer, efficient combustion is seen in two parts: preparation of the material’s surface/mass ratio, and then its combustion with the proper air/fuel mix and associated mechanics. This work attempts to put a thermodynamic face on the first part. A theory is presented which demonstrates that a hydrocarbon’s surface/mass ratio affects its potential to release its full chemical energy. This theory has been generally supported in this work by laboratory testing of pure substances; however this testing was not conclusive and should be repeated. If an optimum surface/mass is not achieved, unburned combustibles will result — and this regardless of subsequent air/fuel mixtures and/or burner sophistications. This work is suggests that a unique optimum surface/mass ratio exists for each hydrocarbon substance (and coal Rank); that once its full potential is reached, a higher ratio provides no further benefit. Since surface tension describes a material’s free energy, an aspect of surface tension, termed hydrogen bonding free energy, was shown to relate to the A¨calorific value penalty associated with non-optimum surface/mass ratio. A correlation was developed relating surface/mass ratio to observed an A¨calorific value penalty and hydrogen bonding free energy. This correlation’s form may be applied to coal if supported with additional research. The impetus for this work was the ASME Performance Test Code 4’s allowance of pulverizer shaft power to influence boiler efficiency’s “credit” term, thus affecting efficiency. It was demonstrated that surface/ mass affects calorific value and thus efficiency. However, there is no observable difference between grinding a hydrocarbon to a given surface/mass ratio, versus manufactured spheres. Although laboratory preparation of coal samples should emulate pulverizer action, this work suggests that a renewed and careful review of laboratory procedures is required. Recommendations are provided for critique and debate.
Flow Accelerated Corrosion in Steam Condensate Piping and Valves: Problems Faced and Actions Taken
Authors: Upreti K. C. , Bontha Sai Vamsidhar
Published: March 2012

Flow accelerated corrosion (FAC) is a combined form of erosion, corrosion and Cavitation. This is prominent in steam condensate lines which results in fast reduction of thickness in piping, piping components and valves. It is estimated that this problem is faced by majority of plants. There has been an increased emphasis on correcting these problems due to fatal accidents that occurred in 1986, 1995, 1996 and 2004 at various locations around the world. [3] After commissioning of the plant, Steam condensate system erosion/corrosion problem started appearing within one year of operation. To ensure uninterrupted plant running on line sealing was done and monitoring was done by proper thickness checking. These on line sealing points were replaced during available opportunity. In some cases plant shutdown was taken to replace leaking piping components & these incidents resulted into revenue loss to company. Aggressive inspection programs were taken up for thickness measurement on condensate lines and as a proactive measure, elbows were encapsulated with higher size elbows, reducers by on line welding/furmaniting with special clamps. Similarly gate and globe valves in condensate service also started failing as a result of erosion of body seat rings. Globe valves installed on bypass lines of control valves were found passing. Once these valves were operated for maintenance of control valves they could not be closed. In some cases valve body developed leak due to high velocity erosion. Various studies conducted for replacing these components by higher schedule fittings & pipes but it did not improve the situation except for slight increase in life of these components. Velocities were calculated at various locations and higher velocity, condensate impingement/cavitation was found as root cause of problems. This problem was solved by various methods like using higher metallurgy P11, P22 material, line size increase with increase in control valve sizing, lay out changes etc. This helped in improving reliability of condensate system and reducing risk associated with failure of piping. This paper presents a variety of cases where single-phase and two-phase steam flows, caused erosion-corrosion damage mainly at turn points of elbows and valves. It was observed that the presence, even of a small amount of the vapor phase can significantly increase the velocity of the condensate. This paper describes the mechanism of failures by study of the failed components, operating conditions & piping lay out. In this study velocity of steam /condensate at reducing section was found to be very high. Other various contributing factors like control valve / piping sizing, metallurgical requirements, effectiveness of steam traps, flow velocity and valve design (globe & gate) were also studied. The main causes of the failures are discussed and recommendations are provided to rectify the root cause of the problems & avoid similar problems in the future.
Steam Turbine Modernizations at Operating Fossil Power Plants: An Approach to Maximize Efficiency and Optimize Coal Power Plants
Authors: Smiarowski Michael W.
Published: March 2012

In 2010, according to the International Energy Agency, coal fired power plants provided 49% of U.S. electricity — far higher than its 31.2% share of electric generating capacity — due to coal plants being run at higher capacity rates. This was due to the stable costs associated with coal as compared with the volatility of the natural gas markets. The remaining coal plants, which represents over 200GW of capacity, will likely require significant investment in air quality control systems (AQCS) and efficiency upgrades to survive. One of the fastest and most cost effective means to achieve greater energy efficiency and add capacity is through modernization of the steam turbine components. In many cases, modernized turbines can be manufactured and ready for installation in less than two years. Coal plants that will continue to operate for the next 20 or more years will likely have to have AQCS, which can consume up to 30% parasitic load (i.e. carbon capture). This load loss can be recovered in part through modernizing the original steam turbine with the latest technology. This paper will provide a commentary on trends and observations on the direction coal plants are taking and provide industry goals. An example of a steam turbine modernization will be discussed and the benefits it provides, such as improvement in performance, availability, reliability, life extension, and reduced life cycle costs. Opinions will be presented on the dynamic nature of the market.
An Integrated Performance Monitoring and Solar Tracking System for Utility Scale PV Plants
Authors: Sadineni Suresh B. , Realmuto Jonathan D. , Boehm Robert F.
Published: March 2012

Monitoring of photovoltaic (PV) systems is essential for achieving reliable and, maximum yield from solar PV plants. This paper proposes PV plant hierarchy, and a novel near real-time monitoring system combined with a solar tracking controller for utility scale PV installations. Currently, most PV installations employ monitoring at the inverter level, lacking sufficient resolution. Furthermore, the solar tracking and performance monitoring systems are isolated from one another. The proposed design increases monitoring resolution, allowing PV malfunctions to be addressed immediately, effectively optimizing a plant’s power generation. Moreover, the tracker control and monitoring are fused into an inclusive hardware design. Incorporating state-of-the-art electronic sensors, coupled with wireless communication protocols, the resulting system is a robust, accurate sensor and control network. Accessible through the internet, the system will provide a way to monitor and control multiple installations from a centralized location. The collected data enables efficient maintenance scheduling, and long-term performance analysis for utility scale PV plants. The developed system includes string level power measurement sensors, sun tracking actuators, a network of microprocessors and a central processing unit (CPU) for application in utility-scale central inverter PV plants. The basic designs and feasibility of the system are presented in this paper.
Aerodynamic Performance Assessment of Part-Span Connector of Last Stage Bucket of Low Pressure Steam Turbine
Authors: Mistry Hiteshkumar , Santhanakrishnan Manisekaran , Liu John , Stein Alexander , Dey Subhrajit , Slepski Jonathon
Published: March 2012

Modern steam turbines often utilize very long last stage buckets (LSB’s) in their low-pressure sections to improve efficiency. Some of these LSB’s can range in the order of 5 feet long. These long buckets (aka “blades”) are typically supported at their tip by a tip-shroud and near the mid span by a part span shroud or part span connector (PSC). The PSC is a structural element that connects all the rotor blades, generally at the mid span. It is primarily designed to address various structural issues, often with little attention to its aerodynamic effects. The objective of the current work is to quantify the impact of PSC on aerodynamic performance of the last stage of a LP steam turbine by using detailed CFD analyses. A commercial CFD solver, ANSYS CFX™, is used to solve the last stage domain by setting steam as the working fluid with linear variation of specific heat ratio with temperature. A tetrahedral grid with prismatic layers near the solid walls is generated using ANSYS WORKBENCH™. The results show a cylindrical PSC reduces the efficiency of the last stage by 0.32 pts, of which 0.20 pts is due to the fillet attaching the PSC to the blade. The results also show insignificant interaction of the PSC with the bucket tip aerodynamics. The work presents a detailed flow field analysis and shows the impact of PSC geometry on the aerodynamic performance of last stage of steam turbine. Present work is useful to turbine designer for trade-off studies of performance and reliability of LSB design with or without PSC.
Study on the Steady and Unsteady Aerodynamic Performance of a Radial Inflow Turbine With Small Partial Admission in a Miniature ORC System
Authors: Li Ping , Chen Jianhui , Zhang Di , Xie Yonghui
Published: March 2012

There is a great deal of residual heat under 350 °C being released into environment, without being used efficiently. Compared to the Rankine cycle with water as its working substance, it is effective to utilize Organic Rankine Cycle (ORC) to recover these waste heats. In the threshold of this paper, a miniature ORC system is proposed, and maximum efficiency of the system is achieved by means of optimal working substance. Moreover, numerical simulation of the partial admission (ε = 0.267) high rotational speed radial inflow turbine, which is the key unit in the system, is fulfilled. At the operating rotational speed of 60000 rpm and the proposed thermodynamic parameters, steady and unsteady flow field in the turbine are investigated with R11 as working fluid. The detailed parameters, such as axial force of rotor, power generated and thermal efficiency of the radial turbine, are analyzed. In addition, the unsteady flow pressure is integrated around the rotor blade profile to provide the unsteady aerodynamic blade force. And subsequently frequencies of unsteady disturbances and excitation force factors are obtained by spectrum analysis, which are of key importance for blade response analysis. The generation, development and dissipation process of the secondary flows, passage vortex and leakage vortex are observed in the flow channel. The results reveal that the partial admission greatly influences the parameters distributions in the flow field and the losses of radial turbine mainly occur at the frontier of the passage in the vicinity of blade root. As is discussed in the analysis of excitation force factor, the radial turbine is safe in the operation. The results discussed in this paper are beneficial for the sequent optimization and manufacture of the miniature turbine.
Numerical Sensitivity Studies on Nucleation of Droplets in Steam Turbine
Authors: Sriram A. T. , Mistry Hiteshkumar , Moraga Francisco , Dey Subhrajit
Published: March 2012

This work presents the results of canonical test cases that highlight the importance of nucleation bulk surface tension factor (NBTF) on CFD predictions for condensing flows in steam turbines. Numerical simulations are carried out on nozzle and cascade geometries to explore modeling effects on the condensation of water vapor. The recent Euler-Euler approach [10] for modeling homogeneous condensation provides better results than the equilibrium assumption. Modeling of the nucleation rate plays a significant role in the non-equilibrium approach and it depends on the free surface energy of each droplet. NBTF is introduced in the classical homogeneous condensation nucleation rate expression to control the intensity of the homogeneous condensation event [3, 10]. It is observed that the NBTF controls the location of the condensation front, degree of super cooling, wetness fraction and droplet size. In addition, no unique value of NBTF is found in the range of simulations to match the experimental observations. Finally, by increasing the value of NBTF from 0.7 to 1.0 for a particular nozzle case, the location of condensation front is shown to be delayed by 60 mm and super cooling increased by 20%. This in turn will affect quantities such as the flow angle, pressure at the blade row exit and the thermodynamic loss which are relevant for the turbine designer.
Interdependence of Renewable and Conventional Fossil Power Generation
Authors: Arnold John L. , Bisbee Laney H. , Pratt Jim
Published: March 2012

The current economic climate and energy policies are forcing significant change on the bulk of the US power generation fleet. Specifically, the rapid increase in renewable power generation and in environmental requirements will have a direct impact on the conventional fossil-fuel fired power plants. The likely outcome will be the shuttering of smaller coal generating units, older boilers, and units where environmental-related capital investment is not economically viable. Many of the surviving plants will face the addition of environmental-related equipment and a change in operation from base-loaded to more cyclical duty. While some coal plants will continue to operate as base-load generation due to the specific energy market served, it is forecast that much of the US coal fleet will in some way be required to balance the intermittent and variable production characteristics of renewable generation when those sources (wind, solar, hydro) are not available. As the renewable portfolio standards are currently estimated to range from 15–33% (1) of a utilities annual generation, this balancing role is critical to match the electricity demands of the US market. The resultant increase in cycling of the existing fossil fleet that will occur when this balancing occurs is expected to have extremely deleterious effects on the fleet of aging plants. Specifically, the impact will be felt in the areas of serviceability of the critical systems, emissions of fossil plants, and operational efficiencies. This paper is intended to identify some of the major issues that are expected to occur to the existing conventional fossil-fuel fleet as the renewable generation increases. These issues include the degradation in serviceability and reliability in light of increased cyclic operation, reductions in plant thermal efficiency, and impact on plant emissions.
Development of a Compact Primary Heat Exchanger for a Molten Salt Reactor
Authors: Lippy Matthew , Pierson Mark
Published: March 2012

The first Molten Salt Reactor (MSR) was designed and tested at Oak Ridge National Laboratory (ORNL) in the 1960’s, but recent technological advancements now allow for new components, such as heat exchangers, to be created for the next generation of MSR’s and molten salt-cooled reactors. The primary (fuel salt-to-secondary salt) heat exchanger (PHX) design has been largely ignored up to this point; however, it is shown here that modern compact heat exchangers have the potential to make dramatic improvements over traditional shell-and-tube designs. Compact heat exchangers provide a higher effectiveness and more efficient use of material that offer a more cost-effective alternative to the massive, more expensive heat exchangers planned for the MSR. While this paper focuses on the application of compact heat exchangers on a Molten Salt Reactor, many of the analyses and results are similarly applicable to other fluid-to-fluid heat exchangers. The heat exchanger design in this study seeks to find a middle-ground between the dependable shell-and-tube design and the ultra-efficient, ultra-compact designs such as the Printed Circuit Heat Exchanger being developed today. Complex channel geometries and micro-scale dimensions in modern compact heat exchangers do not allow routine maintenance to be performed by standard procedures, so extended surfaces will be omitted and hydraulic diameters will be kept in the minichannel regime (minimum channel dimension between 200 μm and 3 mm) to allow for high-frequency eddy current inspection methods to be developed. Rather than using a “checkerboard” channel pattern, which requires complex header designs among other design challenges, row composition is homogeneous, and the borders between adjoining channels are removed to provide high aspect ratio rectangular channel cross-sections. Various plant layouts of smaller heat exchanger banks in a “modular” design are introduced, and the feasibility of casting such modules is assumed to be possible for the purposes of this research. FLUENT was used within ANSYS Workbench to find optimized heat transfer and hydrodynamic performance for straight-channel designs with two molten salts acting in pure counter-flow. Limiting the pressure drop to roughly that of ORNL’s Molten Salt Breeder Reactor’s shell-and-tube design, the compact heat exchanger design of interest in this study will lessen volume requirements, lower fuel salt volume, and decrease material usage. Compact heat exchangers have shown commercial feasibility in several industries but have yet to be assimilated into the nuclear industry. This intermediately-sized compact minichannel heat exchanger demonstrates that such a heat exchanger is viable for further testing. The original design of the MSR was an engineering marvel over 60 years ago, but several of its key components, namely the intermediate heat exchanger, must be updated in order for the MSR to reach its full potential.
A Probabilistic Gas Touched Length Analysis
Authors: Skelonis Carl D. , Shelton M. Brett , Burney Glenn T.
Published: March 2012

Field measurements of the steamside oxide thickness for high temperature (> 850F) boiler tubing subject to the accumulation of creep damage often are made to support deterministic assessments of the remaining life. Most often, these inspections are undertaken to understand the condition of the tubing at some particular location along a circuit, often as a result of a tube failure. The life assessment is based on relationships that have been developed between oxide growth kinetics and temperature. Unfortunately, because of variability in the oxide-temperature relationships reflecting different original data sets, and because of the inherent uncertainty in materials properties where heat-specific test data is not available, there typically exists a broad range of uncertainty in the deterministic assessment results. Large utility-type boilers typically contain a number of high temperature sections, including various stages of superheat and reheat, each of which will contain miles of tubing. Since the temperature derived from an oxide thickness measurement is relevant only to the specific location where the measurement was made, the deterministically derived life calculation is also specific to that location. As a result, the attempt to draw conclusions regarding the condition of an entire superheater or reheater section from measurements made at only one or two locations in those sections is fraught with difficulties. It is for this reason that the Probabilistic Gas Touched Length Analysis model has been developed. This model makes it possible to calculate creep damage accumulation/remaining life at any point along the steam path. Oxide thickness data and operating data are the primary operating inputs into the model, which performs heat transfer calculations at user-defined locations along the length of the tube circuit. The model applies statistical methods to evaluate variations in operating conditions as well as in physical and mechanical properties using a Monte Carlo simulation to generate values for the probability of failure at selected locations. This paper will discuss the limitations of the existing approach to estimating the remaining life of high temperature boiler tubing and present the underpinning theory of the gas touched length analysis model. A case study showing the analysis results is included.
Woody Biomass Co-Firing in Pulverized Coal Fired Boilers
Authors: Raatikka Luther M.
Published: March 2012

With legislation requiring utilities to produce a significant fraction of their electrical energy with renewable fuel supplies, it is anticipated that cofiring biomass in large utility boilers will become increasingly popular. Boilers that are designed to burn pulverized coal (PC) can typically burn woody biomass at up to 5% of the rated heat input. An 800 MW PC-fired unit could, therefore, produce up to 40 MW of renewable energy with biomass co-firing. The generating plant may experience a net capacity de-rating whenever biomass is co-fired. This potential reduction in net plant output may be attributed to reduced boiler efficiency and additional auxiliary power requirements. Biomass fuel handling related auxiliary power requirements are dependent upon the form in which biomass is delivered to the plant. Preparation of woody biomass for co-firing in large PC-fired boilers is typically performed onsite with hammer mills or by off-site processing. For an 800 MW unit, onsite fuel size reduction will usually result in an incremental increase in auxiliary power of 3–4 MW, whereas the use of pre-processed biomass such as wood pellets will require a minimal increase in parasitic load. However, delivered fuel costs for raw wood requiring onsite processing are at least 60% lower than that of densified biomass on a heat input basis. This paper includes an economic comparison of co-firing woody biomass that is processed onsite by direct injection vs. co-firing densified woody biomass by co-milling in a large PC-fired boiler. This comparison will consider delivered fuel costs, capital costs, CO2 emissions and impacts upon boiler efficiency and net heat rate.
Co-Firing Coal, Biomass and Waste Fuels in Circulating Fluidized Bed Boilers to Reduce CO2 Emissions
Authors: Hancharik Ronald
Published: March 2012

The combustion of CO2 neutral solid fuels like biomass and waste-based fuels with circulating fluidized bed (CFB) boiler designs has become an accepted way to generate electric power and process steam to reduce global CO2 emissions (i.e. reduce “carbon footprint”) and hence to reduce the potential impact on climate change. In the European Union, for example, there is a co-combustion directive to encourage the use of biomass and waste as energy sources with the co-firing of coal. Quite often biomass and waste combustion in CFB’s have unique technical challenges when compared to fossil fuels. The technical challenges of firing these CO2 neutral fuels do impact CFB boiler design and may impact plant lifecycle and reliability when compared to coal. Among these are combustion bed agglomeration, furnace and heating surface slagging, and new forms of corrosion potential. However, when co-firing these CO2 neutral fuels with coal, these challenges can be tempered in a positive way through inherent changes in the flue gas chemistry and other design considerations. Co-firing makes sense. In addition to reducing the carbon footprint of a boiler project through use of biomass and waste, these energy sources can have a significant positive impact on plant financials owing to low cost supply. However these fuels can have wide variations in availability and energy content over the course of the many years of a boiler’s life. As such, maintaining coal as a supplemental fuel or back-up fuel also provides significant benefit in terms of guaranteeing the energy input supply and thereby securing plant availability. This benefit can help lower project financial risk and improve financial attractiveness and viability. This paper describes this type of boiler, its design considerations and operating history. Highlighted herein is the operating facility in Pori, Finland, commissioned in 2008, which is a 60 MWe CFB boiler burning peat, biomass and recycled waste fuel (RDF) with coal as a back-up fuel. Other facilities with similar design and with operating history of over 10 years are included as reference.
Equilibrium and Kinetics Analysis of NOx Reduction From Biogas Combustion
Authors: Chavero Jorge , Harrold Duff , Marbach Timothy
Published: March 2012

The undeveloped potential generation capacity of landfills, wastewater digesters and food digesters is estimated at 600 MW in California and 3,000 MW in the United States. California’s 2000 dairies have the potential to produce an estimated 40 million cubic feet of biogas per day, representing a potential generation capacity of about 140 MW. One of the most significant challenges facing the combustion of digester biogas is high NOx emissions. Sulfur in the biogas poisons post-combustion catalysts, rendering them ineffective for reducing NOx emissions. To address this challenge, an integrated pollution capture and microwave system has been developed to reduce NOx emissions from biogas engines. The feasibility of reburning the captured NOx was assessed and the effect of various operating parameters, including temperature, pressure, and reactant composition were determined using chemical equilibrium and kinetic modeling.
Implementation and Validation of a Generic Real-Time Hydroelectric Plant Simulator
Authors: Galindo-Garci´a Iva´n F. , Rodriguez-Lozano Sau´l
Published: March 2012

A generic real-time hydroelectric plant simulator has been implemented and validated. The simulator has the capability to run entirely in a simulation mode or to use actual control components running in parallel with simulated components. This flexibility results in a wide range of applicability, for example, it may be used for training of I&C personnel, tuning of turbine governors or testing the performance of actual control equipment. A further important feature of the simulator is its generic nature. A user-friendly interface is employed to parameterize any particular hydroelectric unit that uses a Pelton, Kaplan, or Francis turbine. The simulator includes mathematical models for the major systems in a hydroelectric plant, namely, hydraulic system (dam, water conduits, and turbine), electric generation (synchronous generator and excitation system) and power system (electrical grid). The simulator has been implemented on a GNU/Linux operative system with a Fedora Core 6 distribution and within a complete simulation environment, which includes real-time conditions management, graphical interfaces to operate the simulator, databases to store variables, and post-processing tools to visualize results. For control equipment testing applications an I/O data system is employed for the interaction between the simulator and the control equipment being tested. Comprehensive tests have been conducted and results compared with available plant data as validation. Three hydroelectric plants have been selected for tests: a 55 MW Pelton turbine plant, a 105 MW Kaplan turbine plant, and a 180 MW Francis turbine plant. A wide range of tests can be simulated, for example: turbine startup, disturbances in turbine speed or load, load rejection, electrical or mechanical trips, etc. Comparisons between calculations and plant data show in general relatively good agreement. A few selected tests are presented.
Physics-Based Common Cause Failure Modeling in Probabilistic Risk Analysis: A Mechanistic Perspective
Authors: Mohaghegh Zahra , Modarres Mohammad , Christou Aris
Published: March 2012

The modeling of dependent failures, specifically Common Cause Failures (CCFs), is one of the most important topics in Probabilistic Risk Analysis (PRA). Currently, CCFs are treated using parametric methods, which are based on historical failure events. Instead of utilizing these existing data-driven approaches, this paper proposes using physics-based CCF modeling which refers to the incorporation of underlying physical failure mechanisms into risk models so that the root causes of dependencies can be “explicitly” included. This requires building a theoretical foundation for the integration of Probabilistic Physics-Of-Failure (PPOF) models into PRA in a way that the interactions of failure mechanisms and, ultimately, the dependencies between the multiple component failures are depicted. To achieve this goal, this paper highlights the following methodological steps (1) modeling the individual failure mechanisms (e.g. fatigue and wear) of two dependent components, (2) applying a mechanistic approach to deterministically model the interactions of their failure mechanisms, (3) utilizing probabilistic sciences (e.g. uncertainty modeling, Bayesian analysis) in order to make the model of interactions probabilistic, and (4) developing appropriate modeling techniques to link the physics-based CCF models to the system-level PRA. The proposed approach is beneficial for (a) reducing CCF occurrence in currently operating plants and (b) modeling CCFs for plants in the design stage.
Comparison Between Air Blows and Gas Blows for Cleaning Power Plant Fuel Gas Piping Systems
Authors: Phung Hoc , Jones Gary , Smith Norman K.
Published: March 2012

Gas blows have been quite commonly used in the power industry for cleaning fuel gas lines during the plant commissioning process, but this practice is being seriously evaluated and reconsidered by regulatory agencies and public safety organizations due to the fire and explosion hazards, and recent accidents and loss of life. This article merely captures the recent practices at Pacific Gas and Electric Company in the construction of power plants. It is not intended to reflect industry practices.
Numerical Simulation and Experimental Validation of Gas-Liquid Flow Characteristics in Dual-Contact-Flow Absorption Tower
Authors: Zhang Yafei , Li Na , Zhou Qulan , Hui Shi’en , Zhao Qinxin
Published: March 2012

A mathematic model of gas-liquid flow in the dual-contact-flow absorption tower is established and some valuable theoretical and numerical simulation results are also obtained. The numerical results show that the velocity and density of liquid droplets are spatially nonuniform and the maximum density of liquid droplets appears at the top of the liquid bed. Therefore the mass and heat transfer there are significantly intense. However, once the gas or liquid velocity is so high that the liquid droplets carried away from the absorption tower can not be neglected, the heat transfer quantity will drop sharply, thus there may generate the heat transfer deterioration. Although liquid droplets consist of broken droplets of different sizes, almost all the active droplets possess the same maximum jetting height. Moreover, in most cases the theoretical analysis and numerical simulation of the actual bed height agree well with the experimental results. Besides, the gas velocity can only lead to changing of the fallback characteristic, while it has little effect on the bed height. In addition, the limit diameter of droplets increases obviously with the gas velocity, while it has little relevance with liquid jetting velocity.
Effect of Elbows on Stability of Water-Based TiO2 Nanofluids Under Laminar Flow Conditions
Authors: Yang Junhong , Cheng Dapeng , Di Qianqian , Zhu Jialing , Zhang Junhong
Published: March 2012

The aim of this paper is to study the effect of flow conditions on nanoparticle fraction suspending in base fluid, using water-based TiO2 nanofluids under laminar flow conditions as an example. With the same initial concentration of nanoparticle (about 0.5% mass fraction), significant deterioration of stability is observed and the deterioration depends on the flow conditions (Reynolds number 500–2000, circulating time). The nanoparticle fraction in nanofluids flowing through bend tube with multi elbows is obviously lower than straight tube with fewer elbows, especially for that at higher Reynolds number. After 8 h, compared with the initial concentration (about 0.5% mass fraction), the relative concentration of nanofluids is 71.5% and 68.5% at Re = 500, for straight tube and bend tube, respectively. Whereas, that is 96.9% and 89.3% at Re = 2000 for straight tube and bend tube, respectively. Sample of nanoparticles in base fluid flowing through bend tube obviously appears the agglomeration (shown in TEM images), larger particle size (measured by laser particle size analyzer) compared with that flowing through straight tube. Moreover, the precipitation of particles can be apparently observed at the out curvature of elbows. These results imply that higher nanoparticle fraction can be maintained for nanofluids at higher Reynolds number and fewer elbows. It maybe helpful for better understanding heat transfer behavior of nanofluids.
An Investigation on Co-Combustion Behaviors of Hydrothermally Treated Municipal Solid Waste With Coal Using a Drop Tube Reactor
Authors: Lu Liang , Jin Yuqi , Nakamura Masato R. , Castaldi Marco J. , Yoshikawa Kunio
Published: March 2012

This work aims at demonstrating the feasibility of replacing Indonesian coal (INC) with hydrothermally treated municipal solid waste (MSWH) in co-combustion with high ash Indian coal (IC). Combustion behaviors of MSWH, INC and their blends with IC were tested in a laboratory-scale drop tube reactor (DTR). The combustion efficiency and emissions such as CO, NO for a series of tests performed under a range of temperatures and air conditions were evaluated and the main results derived from this study can be concluded as the followings: the combustion efficiency of IC is increased by blending both MSWH and INC and CO emission is reduced in the meanwhile with the temperature rising. With regards to NO emission, the blending of MSWH leads to the increase of NO emission whereas the blending of INC results in either the increase or decrease of NO emission compared with IC only combustion depending on the temperature. The combustion behaviors of IC-MSWH blend are comparable to that of the IC-INC blend indicating it is possible for MSWH to become a good substitute for INC in the co-combustion with IC. The CO emission falls while the NO emission rises with the increase of the excess air in the case of IC-MSWH blend at 900 °C and the highest combustion efficiency is obtained at the excess air of 1.9. The existence of moisture in the co-combustion system of IC-MSWH blend can slightly improve the combustion efficiency, reduce CO emission and increase NO emission. The results of this work are expected to be a good instruction for the application of MSWH for co-combustion with coal.
Effect of Header on Latent Heat Recovery Heat Exchanger
Authors: Osakabe Masahiro
Published: March 2012

The most part of energy losses in heat & power system is due to the heat released by the exhaust gas to atmosphere. The exhaust gas consists of non-condensable gas and steam with sensible and latent heat. As a lot of latent heat is included in the exhaust gas, its recovery is very important to improve the system efficiency. Based on the previous basic studies, a thermal hydraulic prediction method for latent heat recovery exchangers was proposed. Two kinds of compact heat exchanger with staggered banks of large and small diameter tubes were designed and fabricated based on the prediction method. In the calculations varying the various parameters, approximately the same heat recovery rate was obtained with both the heat exchangers. The more compactness was obtained with the small tubes at a desired heat recovery rate. The pressure loss in gas side was slightly smaller and that in water side was significantly larger incase of the small tube. By adapting the single header instead of conventional multi header, the pressure loss in the water side could be significantly reduced but the reduction rate of heat recovery was only between 40 to 10%.
Power Generation by Low Condition Heat Generator Combined With Advanced Oxy-Fuel Combustion LNG Gas Turbine Power Plant
Authors: Oshima Kanji , Uchiyama Yohji
Published: March 2012

We propose a novel concept for power generation that involves the combination of a low-condition heat generator (LCHG), such as a light water nuclear reactor or a biomass combustion boiler, with an advanced closed-cycle oxy-fuel combustion gas turbine—a type of complex and efficient oxyfuel gas turbine plant, in accordance with our previous studies in combination with a simple oxy-fuel gas turbine plant. In this study, a LCHG is designed to heat water to saturated steam of a few MPa, to assist in the generation of the main working fluids, instead of a compressor used in the advanced oxy-fuel gas turbine. This saturated steam can have a lower pressure and temperature than those of an existing nuclear power plant or biomass-fired power plant. We estimated plant performances from a heat balance model based on a conceptual design of a plant for different gas turbine inlet pressures of 2.5–6.5 MPa and temperatures of 1300 and 1500°C, taking into account the work to produce O2 and capture CO2. While the net power generating efficiencies of a reference advanced oxy-fuel gas turbine plant are estimated to be about 52.0% and 56.0% at 1300 and 1500°C, respectively, and conventional steam power generation is assumed to have an efficiency of about 35% or less for pressures of 2.5–6.5 MPa, the proposed hybrid plant achieved 42.8–44.7% at 1300°C and 47.8–49.2% for 1500°C. In the proposed plant, the power output contributed by a LCHG may be obtained by subtracting the LNG contribution from the whole net power output. Even supposing that the generation efficiency of the LNG system in the proposed plant remains equal to that of the reference plant (56.0% at 1500°C), some components used in the reference plant are omitted by installation of the LCHG. The efficiency of LCHG system can be estimated 37.4% for 6.5 MPa and 33.2% for 2.5 MPa, even though the LHCG system may be regarded as consisting of fewer plant facilities than a conventional LCHG power plant.
Experimental Study on a Cascade Flapping Wing Hydroelectric Power Generator
Authors: Abiru Hisanori , Yoshitake Akira
Published: March 2012

In this paper, a hydroelectric power generator that can extract the water flow energy from the hydroelastic response of an elastically supported rectangular wing is experimentally investigated. An electric motor is used to excite pitching oscillations of the wing. The wing and the electric motor are supported by leaf springs that are designed to function both as a linear guide for the sway oscillations and as elastic elements. The wing mass in the sway direction necessary to achieve a hydroelastic response is obtained by utilizing a mechanical snubber mechanism. The load to generate electricity is provided equivalently by magnetic dampers. In a previous paper, the power generation rate and the efficiency of a single-wing model were examined through experiments, and the feasibility of a flapping wing hydroelectric power generator was verified. In this paper, the influence of neighboring wings is examined by using two experimental apparatuses with the intention of achieving a practical cascade-wing generator. Tests showed that a cascade moving in-phase with neighboring wings with smaller gaps between the wings has a higher rate of electric power generation.
Hybrid Wind Power System to Absorb Power Fluctuation by Battery Energy Storage System
Authors: Takahashi Masaya , Oohara Shinya , Hoshino Naoki , Suzuki Kazuo , Hashimoto Tadashi , Mitani Katsura
Published: March 2012

As more and more wind turbines and farms are constructed in Japan, utility companies have introduced a grid code, which is effective in controlling the grid frequency. We designed a hybrid system by combining charge/discharge properties of lead-acid batteries with long life, and a power control of wind turbines to ensure the code. We also constructed a wind farm with this system in Shiura, Japan, which went into operation in January 2010. This system showed reduction in wind farm power fluctuation, and that battery capacity can be maintained for 17 years.
Stress Corrosion Cracking of Low-Pressure Steam Turbine Rotor
Authors: Yan Liang , Nakajima Kazuyoshi , Inagaki Shuichi , Arimura Masao , Hosoi Shigeo
Published: March 2012

Corrosion cracks were found at the bottom of the first hook of the L-4 stage of a low-pressure steam turbine rotor after about 230,000 hours operation with about 300 times of starts and stops of a thermal power plant. They developed in the circumferential direction, showing a groove line on the bottom surface of the first hook. Cross sectional observation showed that they had branched and blunted shapes, and X-ray cartography analysis results showed that they filled with corrosion products, and sulfur concentration was detected. In order to verify that they were caused by stress corrosion cracking (SCC), bent-beam stress-corrosion tests with four-point loaded specimens (ASTM G40 method) were performed in a 0.25wt%H2SO4+NH4OH solution with a pH controlled at 9.8 to simulate the corrosion environment of the steam turbine, and the test temperature was set at 80°C. After 6,000-hour and 10,000-hour tests, the cross sections of SCC specimens were inspected with a scanning electron microscope (SEM). Branched and blunted cracks were observed and the crack shapes were similar to those of the corrosion cracks occurred in the steam turbine. Sulfur concentration was also observed in the blunted cracks of the specimens by X-ray cartography analysis. Based on the test results, it can be assumed that the corrosion cracks developed from stress corrosion cracking (SCC) in the low-pressure steam turbine. It is thus necessary to periodically inspect not only the L-1, 2 stages of the wet and corrosion zone, but also the L-3, 4 stages of dry and salt zone in low-pressure steam turbines.
Auto Tuning Algorithm for Vigilance Parameter in the Adaptive Resonance Theory Model and its Application to Fault Diagnosis System of Thermal Power Plants
Authors: Sekiai Takaaki , Kusumi Naohiro , Hori Yoshinari , Shimizu Satoru , Fukai Masayuki
Published: March 2012

In order to operate thermal power plants safely, early detection of equipment failure signs is one of the most important issues. To detect the signs before an alarm is issued in the existing monitoring system, we developed a fault diagnosis system based on the Adaptive Resonance Theory (ART). The vigilance parameter, which is a design parameter in the ART model, was shown to influence the diagnosis accuracy. Fixing the value of the vigilance parameter also had problems: we needed to use time-consuming trial and error, and we needed to have empirical knowledge of the parameter tuning. In this paper, using simulations we demonstrated the relationship between the vigilance parameter and diagnosis accuracy. Furthermore, to overcome the problems of the vigilance parameter tuning, we have proposed an auto tuning algorithm to make the parameter the optimum value. The performance of the proposed algorithm was evaluated in several case studies using gas turbine plant data. The effectiveness of the proposed algorithm was confirmed by the obtained results.