Steam Generation Unit Research Articles

Use of continuous mercury monitors at coal-fired utilities

In December 2000, the U.S. Environmental Protection Agency (EPA) published a notice of its determination that regulation of coal-fired utilities for mercury is appropriate and necessary as part of the hazardous air pollutant emission regulation for electric utility steam-generating units. To aid in the determination of mercury emissions from these sources, on-line mercury semicontinuous emission monitors (Hg SCEMs) have been developed and tested in recent years. Although Hg SCEMs have shown promise during these previous tests, rigorous field or long-term testing has not been done. In the past year, commercially available and prototype Hg SCEMs have been used by the Energy and Environmental Research Center (EERC) and others at several power plants. As part of the EERC work, Hg SCEMs were operated at a range of conditions and locations. In addition, the Hg SCEMs were operated for up to 1 month. The use of Hg SCEMs at these plants allowed for near-real-time data to be collected under changing plant conditions, as well as during normal ranges of operating conditions. Mercury emission data were obtained from different plants with different configurations. The plant configurations incorporated various pollution control technologies, including selective catalytic reduction (SCR), selective noncatalytic reduction, ammonium sulfate injection for flue gas conditioning, and flue gas desulfurization (FGD). The particulate control devices included electrostatic precipitators (ESPs), a fabric filter (FF), and a venturi scrubber. The testing at these sites included the operation of Hg SCEMs before and after particulate control devices, in wet and dry stack conditions, and at high temperatures (343 °C). The results from these field measurements have provided data that have been evaluated to determine the reliability, variability, biases, and overall capability of Hg SCEMs for monitoring mercury at coal-fired utilities. Even under the best conditions, operation of Hg SCEMs is by no means simple. Their operation at high-dust-condition locations (i.e., prior to the particulate control device), wet stack conditions, and high temperatures has tested the ruggedness of the Hg SCEMs. As a result of this testing, some of the critical factors affecting accuracy, precision, and reliability have been made apparent. The overall capability of Hg SCEMs to produce near-real-time data (data every 5 min) was also evaluated under these conditions. The duration of the tests ranged from short-term periods (1–2 h) up to 1 month. Evaluation of the data over the longer-term tests shows the range of mercury emissions due to the variability of mercury in the coal and the normal range of operating parameters for the unit. The range of data is important when control strategies and managing emission inventories are considered. EPA has not determined what type of monitoring or testing requirements will be included in the upcoming electric utility mercury regulations. There is, of course, interest in requiring the use of Hg SCEMs. However, our research to date has shown that commercially available Hg SCEMs are not capable of operating unattended to produce reliable and accurate emission data.

FW to upgrade Spanish power plant

Foster Wheeler Iberia SA’s Energy Division is to upgrade Endesa’s four steam-generating units at the As Pontes power plant in La Coruna, Spain. This is a short news story only. Visit www.filtsep.com for the latest filtration industry news

FW to upgrade Spanish power plant

Foster Wheeler Iberia SA’s Energy Division is to upgrade Endesa’s four steam-generating units at the As Pontes power plant in La Coruna, Spain. This is a short news story only. Visit www.worldpumps.com for the latest pump industry news

Effects of flue gas constituents on mercury speciation

Beginning with the 1990 Clean Air Act Amendments, there has been considerable interest in mercury emissions from coal-fired power plants. This past year, the U.S. Environmental Protection Agency (EPA) issued both the Mercury Study Report to Congress and the Study of Hazardous Air Pollutant Emissions from Electric Utility Steam-Generating Units, which make clear that EPA views mercury in the environment as a serious issue and that coal-fired utilities are a major source of mercury. For the past 4 years, EPRI and the U.S. Department of Energy (DOE) have funded research on mercury measurement, control, and chemistry at the Energy and Environmental Research Center (EERC). The primary goal of bench-scale work was to determine what flue gas constituents affect mercury speciation, specifically how mercury speciation affects measurement methods and the ability of mercury sorbents to absorb mercury. A bench-scale test rig was designed and built to simulate flue gas conditions. The baseline simulated flue gas consisted of O 2, CO 2, H 2O, and N 2. Other flue gas constituents tested include SO 2, HCl, NO, NO 2, HF, Cl 2, and fly ash. The mercury was delivered to system as either elemental mercury (Hg 0) or mercury(II) chloride (HgCl 2) via temperature-controlled permeation tubes. EERC bench-scale data clearly show that the type of fly ash is important in determining mercury speciation in flue gas streams. Not surprisingly, there appear to be a number of interactions between various flue gas constituents that affect mercury speciation. Depending on concentration, there is clearly an interaction between NO–NO 2 and fly ash, and it is possible that the interaction may be related to the ratio of NO:NO 2. However, it has been shown that when NO–NO 2 is tested without fly ash, there is no conversion of Hg 0 to Hg 2+. Bench-scale tests clearly show that the chemistry of mercury is very complex and that more research is needed to understand what is occurring. However, it is equally clear that the development of effective mercury sorbents and the ability to accurately model mercury speciation are dependent on understanding mercury chemistry, thermodynamics, and kinetics.

Optimal Multiperiod Planning of Utility Systems Considering Discrete/Continuous Variance in Internal Energy Demand Based on Decomposition Method.

Optimal multiperiod planning methodology for utility systems is proposed considering internal energy demand, which is formulated as a mixed integer nonlinear programming (MINLP) problem. The problem is decomposed into two levels: the energy distribution network level as a mixed integer linear programming (MILP) problem, and the steam generation unit as a nonlinear programming (NLP) one. The internal steam demand is calculated from the first principle model, and the internal electricity demand is obtained from design data. For multiperiod operation with varying demand as a series of piecewise constant for utilities, the optimal configurations of utility pumps (UP) are determined. The objective function is comprised of the operational costs for each period, transition costs and switch costs between periods. Total cost obtained from the proposed planning methodology has been reduced by 2.34% compared with the planning result without considering switch costs between periods and 3.15–9.14% compared with the result by Lee et al. (1998).

Leak noise detection and characterisation using statistical features

Covariance Matrix based statistical features have been used to detect leak, identify noise source and characterise noise transmission off-line on data from PFR Steam Generator Units. The methods show promise in their ability to detect leak in actual Steam Generator Units from the noise data with very low S/N ratios. Further analysis of data have yielded useful information on the potential of acoustic leak detection system.

Operation experience of the BN-600 fast reactor

This paper presents the main operating experience of the BN-600 Power Unit, which has been under operation since 1980 as a part of the Beloyarsk Nuclear Power Plant situated in Zarechny town, Sverdlovsk Region, Russia. Theperformance of the core, the reactor, the fuel handling systems, the steam generator unit, the sodium and steam circuits, and the electrical equipment is highlighted. The technological procedures and the events which occurred, including sodium leaks, are also considered.

Prototype fast reactor steam generator unit pressure vessel repairs

The prototype fast reactor at Dounreay has experienced a number of unscheduled shutdowns due to leaking reheater and superheater shell welds. There was a need to determine the cracking mechanism and to design a general repair technique simultaneously. Detailed investigations revealed that the crack locations correlated with the positions of rectification welds made at the time of vessel manufacture. A creep crack growth mechanism was identified; this requires through wall residual stress for through cracks to develop. A repair technique has been devised and successfully applied to the sites of a number of leaks.MST/1788

Prototype fast reactor steam generator unit pressure vessel repairs

The prototype fast reactor at Dounreay has experienced a number of unscheduled shutdowns due to leaking reheater and superheater shell welds. There was a need to determine the cracking mechanism and to design a general repair technique simultaneously. Detailed investigations revealed that the crack locations correlated with the positions of rectification welds made at the time of vessel manufacture. A creep crack growth mechanism was identified; this requires through wall residual stress for through cracks to develop. A repair technique has been devised and successfully applied to the sites of a number of leaks.MST/1788

FAILURE FACTORS

THE Structural Integrity Centre (SIC) had its origins in the 1970s when major integrity issues arose on the UKAEA's plant in service, eg weld cracking in the prototype fast reactors (PFR) steam generator units, and safety concerns led to a rigorous assessment of the integrity of the civil pressurised water reactors (PWR) pressure vessel (the Marshall committee report). In both cases engineers and scientists from various disciplines throughout the authority were involved in the consideration and resolution of these issues, and it was demonstrated that assurance of plant integrity could no longer be provided by the plant designer or operator alone.

Finite element prediction of differential eddy current probe signals from Fe 3O 4 deposits in PWR steam generators

Finite element analysis techniques have been successfuly applied to the study of eddy current NDT phenomena in axisymmetric test geometries. Major applications of such computer code have related to the design of probes and the gaining of physical insight into just how electromagnetic fields interact with defects. This paper is concerned with an additional application of the code, namely to the simulation of practical testing situations which are too difficult and/or expensive to replicate in a laboratory environment. Numerical experiments are described which simulate the differential eddy current probe response to the build-up and chemical flushing of magnetite in the crevice gap of a PWR steam generator unit. The simulation results agree well with the only experimental data available to the authors and lead to the conclusion that conventional differential eddy current probes should be capable of characterizing crevice gap conditions with respect to the presence of magnetite.

Guidelines for Measurement of Combustion Inside the Furnace of a Steam Generation Unit

Some logical justifications on selection and operation of Flame ‘Scanner for measuring combustion inside the furnace of industrial steam generating unit have been considered from safety and efficiency point of view of a plant concerned. Application of the present techniques existing specially in power plant engineering have been discussed giving full details of its merits and demerits. Basic guidelines for modifications of existing techniques have been given.

Hall-Plate Measurements of Magnetite Buildup in Pressurized-Water Reactor Steam Generators

A variable reluctance probe using Hall plates as the sensing elements has been designed, constructed, and field tested in an attempt to provide a measuring technique for the detection of magnetite build. up in the crevice gap region of pressurized water reactor steam generator units. Experimental and theoretical modeling results show that such a probe is sensitive to crevice gap conditions and could possibly be used to determine the effectiveness of chemical flushing procedures.

Survey of Cyclic Load Capabilities of Fossil-Steam Generating Units

The current practice of placing large-size fossil and nuclear steam-generating units into commercial operation will continue unabated for at least the next 10 years. Such units, intended primarily for base-load operation, generally do not have large load-turndown and two-shift cycling capabilities. Consequently, a loss of operating flexibility is slowly being created with potential future problems for power system operation.

Design and Manufacturing Experience for the German Thorium High-Temperature Reactor 300-MW(e) Steam Generator

The six identical steam generator units for the 300-MW(e) Thorium High-Temperature Reactor in Germany deliver both main and reheat steam at conditions similar to fossil-fired plants. Typical design...

Prediction of Dynamic Voltages During Plant Startup by Computer Techniques

A gas-turbine package power plant was used to provide startup power for a 250-MW steam-generating unit. Performance of the excitation system during startup of large power-station auxiliary motors closely matched that previously calculated by a digital-computer program. Results of the computer study and full- scale verification tests are presented. These results verified that the digital-computer program used accurately simulated the dynamic characteristics of the excitation system, generator, and motor. Based on this verification, it was concluded that further computer studies could be utilized with confidence to predict voltage dips at critical locations in the power system.

Boiling Heat Transfer in Steam-Generating Units and Heat Exchangers

Boiling Heat Transfer in Steam-Generating Units and Heat Exchangers

Hydrogen Damage to No. 2 Boiler at Armstrong Power Station

This paper documents the history of hydrogen damage to a large central station steam-generating unit. The nature and extent of the damage are discussed, and the inspection techniques used to detect damaged areas are described. Boiler operation, chemistry of boiler water, feedwater treatment, and other influencing factors are also discussed.

Engineering the Eddystone Steam Generator for 5000-Psig, 1200-F Steam

Abstract This paper is presented as one of three describing the development of the Eddystone Station. Particular attention is given to the major engineering considerations in the design of the steam-generating unit. It includes a description of the unit and its control system with a review of the research program which was a necessary part of the project.

Bagasse-Burning in the Mexican Sugar Industry

Abstract Bagasse is the principal source of heat for the production of raw sugar. Early furnace designs were satisfactory from the standpoint of operation and steam output during the period when labor was plentiful and this by-product fuel was assigned little or no value. Rising costs of fuel, equipment, repairs, and wages, however, have altered this picture materially. Older plants consisted in a multiplicity of small boilers with refractory hearth-type furnaces. Operating efficiency was low, and steam output dropped during long periodic hearth-cleaning periods. These designs are definitely outmoded through the rapid advances which have been made during the past 10 years. Newer designs of steam-generating units now incorporate spreader stokers, water-cooled furnaces, bent-tube boilers, superheaters, air heaters, and bagacillo-return systems. They have more flexibility, greater capacity, higher efficiency, and are less subject to operational interruption. Many units of this type have now been in operation for considerable periods of time in practically all of the world’s raw-sugar-producing areas. It is the purpose of this paper to discuss, primarily, the operating characteristics of this new design as experienced with installations in Mexico. Comparative data also will be presented to stress normal operating differences between hearth-type and spreader-fired unit.