H rice husk-fired CFB boiler

08

Steam raising (boiler operation/design)

overall heat transfer coefficient of each component. Model performance predictions are compared to cases available in the literature. Also presented are results from parametric studies.

Burning low volatile coals in utility boilers with high efficiency and clean envlronment

99/99585

Zhou, J. Proc. Annu. Int Pittsburgh Coal Conf, 1997, 14, (8) 71-87. Low grade coals contain lower volatile matters (VM), such as anthracites and semi-anthracites as well as lean coals, while the moisture and ash contents are sometimes high. The conventional pulverized coal boilers and burners can not burn such fuel well due to the difficulties of the ignition, flame stability and carbon conversion. The boilers burning such fuels have a lower efficiency, and high unburned carbon in the fly ash. The boiler load turn down range is poor while the minimum load without oil support is high. Under the government energy policy of most developing countries, the utility industry is requested to burn more low VM coals. The enhanced ignition and flame stabilization and longer residence time in the furnace are the key technological points to successfully burn such fuels. The down-shot firing with w-shape flame furnace plus low VM burner can meet the requirements. The environmental concerns in burning low VM coals are more serious compared to the case of burning high grade coals (bituminous) by the same type furnace. Its NO, emission level is much higher than bituminous. The available technologies for De-NO, during the combustion stage are too sensitive to the coal quality, and are still under development, and improving. At the current stage, most of the down-shot firing with w-shape furnaces world wide are 300-350 MW in capacity. The fuels as fired are most likely blended fuels by anthracites and lean coals. Under development are more larger capacity down-shot w-flame furnaces. Performance of operated down-shot units in China is good.

Co-firing straw and coal in a 150~MW. utility boiler: in situ measurements

99100588

Hansen, P. F. B. et al. Fuel Process. Technology, 1998, 54, (l-3) 207-225. At a 150-MW, PF-boiler unit reconstructed for co-firing straw and coal a 2year demonstration programme is carried. As a part of the demonstration program, a comprehensive in situ measurement campaign was conducted during the spring of 1996 in collaboration with the Technical University of Denmark. Six sample positions have been established between the upper part of the furnace and the economizer. The study included in situ sampling of deposits on water/air-cooled probes, sampling of fly ash, flue gas and gas phase alkali metal compounds, and aerosols as well as temperature measurements. At all operating conditions material balance closures were carried out.

Combustion of sponge iron plant wastes - char and fly ash in FBC boilers

99100587

Rajavel, M. et al. Proc. Int. Conf. F&d. Bed Combust., 1997, 14, (2), 801806. Large quantities of waste materials are generated by coal based sponge iron plants in the form of kiln char and fly ash. This material has very little fuel value because it contains a large percentage of ash and it is almost free of volatiles. Wide size range of the kiln rejects makes it practically impossible to burn in conventional firing. However, it is realized that if the char, fly ash and a considerable quantity of coal fines, separated in the coal preparation plant, can be utilized, the overall economy of the sponge iron plant is likely to be greatly enhanced. The only possible way to use these fuels is by fluidized bed combustion. Tests were conducted with these fuels in bubbling fluidized bed combustion test facilities in Tiruchirapalli, India. This paper discusses the findings which were subsequently used to design large size FBC boilers and highlights the experience gained with the above waste fuels.

99lOO589 Design of a 110 MWth CFB boiler firing RdF, rejects, sewage sludge, wood waste and coal Rosenauer, G.et al. Proc. Int. Conf. Fluid. Bed Combust., 1997, 14, (2). 795-799. The plant, which will be built in Austria, will be started up in the fall of 1998 and is in the design stage. The objective of the plant is to burn various fuels to overcome the challenges of waste fuel utilization. The main fuel to be burnt will be refuse derived fuel (RdF). Additional fuels will be rejects, sewage sludge, wood waste, and coal. The design of the plant is based on the Lurgi (CFB) circulating fluidized bed technology. The boiler system and the fuel feeding systems will be supplied by Austrian Energy. 99/00590 A diffusion layer model for steam condensation within the AP800 containment Herranz, L. E. et al. Nuclear Engineering and Design, 1998, 183, (l/2), 133150. In case of a postulated accident, steam condensation plays a key role in removing heat from the atmosphere of the Westinghouse AP600 containment. A model of steam condensation on containment surfaces under anticipated accident conditions is presented and validated against an extensive and sound database. Based on the diffusion layer theory and on the use of the heat/mass transfer analogy, one can deal with large temperature gradients across the gaseous boundary layer under high mass flux circumstances. The thermal resistance of the condensate film, as well as its wavy structure, have also been considered in this model. The model has shown a good response to the influence of primary variables in steam condensation (i.e. subcooling, non-condensable concentration and pressure), providing a mechanistic explanation for effects such as the presence of light non-condensable gas in the gaseous mixture. In addition, the model has been contrasted against correlations used in safety analysis and occasionally to Dehbi’s database. This cross-comparison has pointed out several shortcomings in the use of these correlations and has extended the model validation to other databases. 99ioo591

inn;tlpg

ENEL and Ansaldo experience in designjng, and operating reburn systems In large oll-flred

Cenci, V. et al. EC (Am. Sot. Mechanical Eng.), 1997, 5, (l), 661-669. Within its generating park, a comprehensive modification program has been conducted by the Italian Electricity Company (ENEL S.P.A.), together with Ansaldo Energia, in order to comply with the new air quality standards for fossil fuel-fired power stations. The two companies have developed and implemented innovative technologies for ‘in-furnace’ NO, control, which have been applied both in Italy and abroad, on boilers of any kind and for different fuels: oil, gas and coal. Among all the combustion modification technologies, reburning has proven to be so effective that, in most cases (oil and gas-fired units), it permits to reach NO., values lower than 200 mg/Nm2 avoiding the installation of SCR. This paper outlines the technical knowledge available for the design of reburn systems for retrofit application and describes the main results obtained when this technology was applied in 320 and 660 MWe oil-fired units.

Experience of heat pipe with hydrogen oxidation means in coal combustion boiler

99100592

Lin, B. and Chen, E. Proc. Annu. Int. Pittsburgh Coal Conf., 1997, 14, (2). 41-47. In a pulverized coal-fired boiler a high reliability heat pipe air preheater(HPAPH) with oxidation hydrogen removal technology was used. Operation data show consistent heat transfer performance, stable hot air temperatures and little air leakage, with the deterioration of heat-transfer capacity less than 10% in three years. 200 KW of draft fan power is saved, resulting in an annual saving of 1.40 million kWh.

Experience with combustion tuning and fuel system modifications to inexpensively reduce NO. emissions from eleven coal-fired tangential boilers 99ioo593

99lOO588 Commercial development of the Battelle/FERCO biomass gasification process - Initial operation of the McNeil gaslfier Paisley, M. A. et al. Making Bus. Biomass Energy, Environ., Chemical, Fibers Mater., Proc. Biomass Conf. Am., 3rd, 1997, (l), 579-588. Edited by Overend, R. P. and Chornet. E. The emphasis on .renewable energy supplies has increased due to restructuring in the utility industry. To meet this need, the US Department of Energy (DOE) has focused on a number of high efficiency power generation technologies that can effectively utilize biomass. One of these promising power generation technologies is biomass gasification coupled with either a gas turbine in a combined cycle system or a fuel cell. The gasification of biomass from renewable energy crops can efficiently and economically produce a renewable source of a clean gaseous fuel suitable for use in these high efficiency power systems or as a substitute fuel in other combustion devices such as kilns, boilers, or other natural gas fired equipment. Discussed in this paper is the development and first commercial-scale application at the Burlington Electric Department’s McNeil Station of the Battelle/FERCO high-throughput gasification process for gas turbine based power generation systems. Projected process economics for a gas turbine combined cycle plant are presented. A description of the McNeil gasification plant and results of the initial operation are discussed along with results of recent development efforts at Battelle. Also included are additional development plans for the McNeil gasification plant and current commercialization activities.

58

Fuel and Energy Abstracts

January 1999

Mazzi, E. A. and Haythornthwaite, S. M. EC (Am. Sot. Mechanical Eng.), 1997, 5, (1) 219-229. Discussed are commercially available, low-cost options to achieve NO, compliance on pulverized coal-fired tangential boilers which require 5-50% reductions, Often, NO, reductions and economic benefits can be achieved simultaneously. Actual performance data are presented based on direct experience applying combustion tuning and fuel system modifications on 11 coal-fired, dry-bottom tangential boilers in the USA. Several low-cost options are presented, some of which are generally unknown to electricity combustion tuning efforts fall short of utility engineers. Frequently, required NO, reduction goals because it is not known how to inexpensively overcome common limiting factors (e.g. unburnt carbon. slagging). In order to overcome these factors important limiting factors are described, including low-cost methods. 99ioo594

E’,rboiler

Experimental research on rice husk combustion in and the design of a 35TIH rice husk-fired CFB

Guanyi, C. et al. Proc. fnt. Conf. Fluid. Bed Combust., 1997, 14, (1) 175181. On a cold model bed of inner diameter 120 mm, the fluidization and transportation properties of rice husk have been studied. The ignition and combustion characteristics of rice husk mixed with coal were studied in a l-

08 Steam raising (boiler operation/design) MW experimental circulating fluidized bed (CFB) system. Drawn on the basis of these experiments, the conclusions are found to be very useful for the design of a 35tonne/h CFB boiler firing this biomass fuel.

economizer, an air heater suitable for ammonia applications, dynamic classifiers, and, for the TFS 2000 firing system, a multi-zone secondary air flow control system utilized.

Experimental stud and design considerations for co-firing paper mill sludge in E FB boiler

New ferritic steels increase the thermal efficiency 99/09601 of steam turbines

99ioo595

Xiaodong, L. et al. Proc. Inf. Conf. Fluid. Bed Cornbust., 1997,14, (l), 159164. In a circulating fluidized bed pilot facility, experimental studies have been done on co-firing paper mill sludge and coal. The effects of water content, bed temperature, sludge size, fluidizing velocity, on combustion and emissions are studied. Bed temperature and sludge feed size have very important effects on incineration and emissions. Too small a size of sludge, although it can reduce incineration time, will reduce the agglomeration capacity of sludge and be difficult to keep high combustion efficiency. The experimental and pilot results provided a reasonable design basis for the first paper mill sludge to co-fire 220 tons/h in a CFB boiler in China.

FLASHGRAN-an efficient way for utilization of 99100596 furnace wastes from fluidized bed boilers Smolka, W. et al. -.*

Proc. Anna Inr. Pittsburgh Coal Conf., 1997, 14, (26), Sl-

IL.

An efficient method to use waste ashes from fluidized bed boilers, FLASHGRAN (fluidized bed ash granulation), is described. Topics discussed include: fluidized bed boiler ash characterization; and technology to produce granulated product and use fluidized bed boiler ash. Disadvantages associated with ash storage are eliminated by granulated product properties and are used in the mining industry as a component in hydraulic filling.

Fiextech CFB boilers for southeast Asian and Chinese coals

99100597

Tanca, M. C. and Schaker, Y. Proc. Annu. Int. Pittsburgh Coal Conf., 1997, 14, (26), 22-38. The circulating fluidized bed (CFB) technology, with the rapid expansion of electric power in south-east Asia and China, meets the needs of local utilities and independent power producers (IPPs) alike. This paper will discuss how the ABB-Combustion Engineering FLEXTECH CFB technology can meet these growing electric poker nee&. The locally available coals of China and south-east Asia and how they are readily suited for firing in the FLEXTECH CFB technology will be discussed. Detailed discussions will include the characteristics of-each coal, expected local emission levels, and the operational characteristics of the FLEXTECH designs while firing the various coals. Proposed FLEXTECH CFB solutions for electric generation from 50 to 250 MW of power are then illustrated in detail.

99l09596 wood

Gasifier

boiler for solid fuels,

particularly

for

Herlt. C. and Haker. D. Ger. DE 19.646.525 (Cl. ClOJ3/06).,I 10 Jun 1998. Appl.’ 19,646,525, 25 Ott 1996; 8 pp. (In be&an) In combustion of solid fuels (especially large pieces of wood) a furnace has a fuel- and gasification space wiih a pear-shaped cross section converging at the bottom in the middle of the vertical line. A slit-containing grate is extended over l/5-1/3 of the vertical line length. Above the grate, primary air inlets are located on both sides at 0.4-0.6 of the maximum height of the fuel- and gasification space. Slit-shaped combustion nozzles are placed below the grate. The combustion space is divided to’ an upper (precombustion + mixing) chamber and a lower after-combustion chamber by means of an inclined wall. Both kidney-shaped chambers are continuously widened in the flow direction. A preheater is provided for secondary air. Uniform combustion, a suitable mixing of secondary air, and stable combustion at optimum temperatures and residence times are provided by the heating furnace.

Incineration of a biomass sludge in a bubbling ;::05gg North, B. C. and Eleftheriades, C. M. Proc. fnt. Conf. Fluid. Bed Cornbust., 1997, 14, (l), l-6. A multinational food company based in Estcourt, Natal, South Africa approached the CSIR requesting a fluidized bed combustion zone for a 26ton/h boiler. Two desien reouirements emereed from the clients needs: additional plant steam &d disposal of 12 ton$h of coffee grounds sludge containing ~87% water. The dual purpose of the FB posed a considerable challenge. Coffee sludge, although combustible, contains insufficient energy to evaporate its own water and maintain the bed at operating temperaturk (900”). Coal therefore had to be co-fired as a support fuel. Additional fuel was required in order to produce the full rated capacity of 26 tons/h steam. Calculation and tests were carried out to optimize FBC.

The integration of low NO,, control technologies at 99100600 the Southern Energy, Inc. Birchwood Power Facility

Lauber, J. A. et al. Proc. Annu. Inr. Pittsburgh Coal Conf., 1997, 14, (9), 17-28. The paper describes the integration of both in-furnace and post-combustion NO, control technologies into the overall boiler design. Operational data depicting boiler outlet NO,, stack NO, and loss on ignition (LOI) are presented across the design load range from 32% to 100% boiler output. The description, arrangement, design parameters and operation of the NO, control equipment are discussed. Novel design features include a split

Mayer, K. H. and Bakker, W. T. PWR (Am. Sot. Mechanical Eng.), 1996, 30, (2), 333-346. The way has been paved for fossil-fired power stations to be operated at turbine steam inlet temperatures of up to around 600” and high supercritical steam pressures with a distinct improvement in thermal efficiency by the further development of ferritic high-temperature-resistant 9-11% steels. This is a significant contribution towards reducing the environmental impact of SO*, NO, and CO2 emissions and to a more economical utilization of fossil fuels. Advances in the development of these steels are primarily attributable to joint research projects undertaken by the manufacturers and operators of power stations in Japan (EPDC), in the USA (EPRI) and in Europe (COST 501). The report gives details on the results achieved under EPRI Research Project RP 140 3-15/23 on the creep behaviour of modified 9%CrMo cast steel used in the manufacture of steam turbines for coal-fired power plants. Great benefits are also offered by the modified 9%CrMo cast steel as regards improving the useful life and thermal efficiency of existing power plants.

control NO. Industrial cyclone boiler

99100602

using natural

gas reburn on an

Farzan, H. et al. PWR (Am. Sot. Mechanical Eng.), 1996, 30, (2), 835-845. In order to comply with the New York State regulations adopted in conformance with the Title I of the Clean Air Act Amendments (CAAA) of 1990, Eastman Kodak Company’s cyclone boiler has been retrofitted with the gas reburn technology to reduce NO, emissions. At the peak load, the ozone non-attainment required NO, reduction from baseline levels necessary to meet the presumptive limit for cyclone boilers in this regulation is 56%. Equipment installation for the gas reburn system was performed in a September 1995 outage. Boiler No.43’~ maximum continuous rating (MCR) is 550,000 lb per h of steam flow. Because of the compact boiler design, there is insufficient furnace residence time to use coal or oil as the reburn fuel, thus making it a prime candidate for gas reburn. Kodak currently has four cyclone boilers. Contingent upon successful completion of this gas reburn project, modification of Kodak’s other cyclone boilers to include reburn technology will be considered. The paper will describe B fuzzy logic control of heat exchange between flue gases and steam; and SO2 concentration prediction in the fluidized-bed coal combustion.

Performance evaluation of a 1 MW oil shale circulating fluidized bed boiler pilot plant

99l90603

Tardin, P. R. et al. Proc. Inr. Conf. Fluid. Bed Cornbust., 1997.14, (Z), 779784. The performance of a circulating fluidized bed boiler pilot plant, located at Sao Mateus do Sul, PR, Brazil is analysed in this work. The boiler was designed to burn oil shale fines, producing 1 t/h of superheated steam at 3200 kPa and 350”. Thirty-nine tests were performed and they indicated the boiler technological feasibility, with a pdrformance close io other steam generators. Negative pressures were obtained along the combustor. Runs carried out usine oil shale onlv or shale oil sludee combustion Y oresented L efficiencies higher than runs wiih limestone addition. Carbon content in the bottom ash was lower than in the fly ash. The flue gas sensible heat loss was predominant, followed by the heat losses due to incomplete combustion and to sensible heat in the solid refuse. Runs with limestone addition showed, in general, an input-output overall efficiency higher than those burning only oil shale. The increase in the Ca/S molar ratio up to 1.80 improved sulfur removal. The use of a more efficient cyclone, the introduction of additional heat exchange area in the air pre-heater and reduction of the heat exchange surface area in the combustor riser could increase the boiler efficiency and the overall performance.

Reburning using biomass for NO, control 99100604 Adams, B. R. and Harding, N. S. Fuel Process. Technology, 1998,54, (l-3), 249-261. Examined in this study is the use of wood reburning for NO, reduction in a cyclone-fired boiler. Reburning is an in-furnace NO, control technology that uses fuel injected above the main firing system to reduce NO formed in the main heat release zone. Bench and pilot-scale work done over the past several years suggests that, under the right conditions, NO, reduction up to 60% is possible using reburning. The practical implementation of reburning technology depends on the ability to contact the reburning fuel with NO formed in the cyclone barrel at the optimum stoichiometry for the maximum time. Thus, reburning effectiveness in practical systems is determined by the performance of the mixing system. This paper describes the results of a computer modelling study of the TVA Ailen Station Unit No. 2 to evaluate various reburning fuel injection and overfire air injection designs and estimate the NO, reduction potential using wood as a reburning fuel. Results of this study showed the best mixing was obtained using opposed fired reburning injectors located as close to the cyclone barrels as possible with opposed-wall overfire air injectors at as high a velocity as pressure drop constraints allow. Under these conditions, NO, reduction of ~45% is expected. When the wood carrier air is replaced by fuel gas, the expected NO, reduction increases to ~55%.

Fuel and Energy Abstracts January 1999 59