09 Combustion (burners, combustion systems)

99100605 Research on structure model of coal ash melt and its effect on ash deposition Xiong, Y. ef al. Proc. Annu. Int. Pittsburgh Coal Conf., 1997, 14, (14), 2Y- 34. In a utility boiler, sintering and melting of coal ash is a key process of ash deposition. Coal ash melt structure characteristics is the determining factor in deposit growth and strength development. as well as the removability of ash deposits. This paper introduces the polymerization and structure model of coal ash melt. A structure property index NBO/T (non-bridging oxygen per tetrahedral co-ordinated cation), which is used for assessing the density point of aluminosilicate melts, is studied from about 70 coals used in utility boilers. It is found that some lignite and some coals from the Shengfu- Dongsheng coal field in Erdos basin in north-west China have similar NBOi T characteristics compared with coals from western America because of the similar inorganic geochemical conditions. But NBOiT is not suitable for differentiating the difference between some bituminous coals in China, where there is a lack of alkali and alkaline earth elements, and so NBOiT equals zero. For overcoming this defect, a new index PIM based on structure is put forward. PIM takes account of the roles and contribution of each element of bulk composition in melt structure, it stands for the coulomb strength of ash melt structure based on unit analysis. In this paper, the relationship between physical-chemical property such as fusion point and viscosity-temperature characteristics are analysed from data of aluminosilicates and coal ash used in power stations. The unreasonableness of b/a, which is widely used for predicting slagging propensity, and the mechanism of slag removability under low load condition of utility boilers are also discussed in this paper.

99100606 Role of various system parameters in furnace dynamic responses following a master fuel trip Rathi, J. S. and Phan. T. Q. EC (Am. Sac. Mechanical Erg.), 1997, 5, (l), 553-566. In the event of a master fuel trip (MFT) the draft system of a fossil boiler may experience catastrophic negative pressure excursions. Potential for such pressure excursions increases significantly if the draft system is retrofitted with flue gas desulfurization (FGD) equipment. The magnitude of negative pressure following a sudden load reduction or a MFT depends on a number of design and operating features of a plant such as: type of fuel, fuel valve closing time, ID fan damper stroke time, ID fan damper maximum opening position, and the kicker circuit parameters. Using PC- TRAX, a state-of-the-art dynamic simulation computer code, extensive analysis studies have been made for more than half a dozen fossil plants using coal, oil or natural gas as fuel. The size of the units investigated ranged from 150-1300 MW. This paper presents the main results of this study particularly with regard to the influence of those plant design parameters which significantly affect the severity of the consequences of a MFT.

99100607 Status and demonstration of the B&W DRB-42 burner developed for B&W’s advanced coal-fired low-emission boiler system Sivy, J. L. Am. Sot. Mechanical Eng., 1997, 5, (l), 205-211. Babcock & Wilcox has been under contract to the U.S. Department of Energy’s (DOE) Federal Energy Technology Center (FETC) in Pittsburgh to develop a low-emission boiler system (LEBS) under their combustion 2000 programme since 1992. To develop an advanced generating plant design, ready for commercial deployment in the year 2000, which achieves extremely low emissions and high efficiency at a cost of electricity (COE) at or below the COE of a commercial PC plant meeting new source performance standards (NSPS) is the objective of the LEBS programme. To meet these challenging goals B&W has coupled advanced environmental control technologies, capable of achieving emissions of SO,, NO, and particulate far below current NSPS, with an advanced boiler, equipped with improved combustion and heat transfer subsystems. Phases I through III have now been completed and B&W is anticipating demonstration of these technologies in Phase IV. Phase I, completed in 1994, considered a variety of potential advanced technologies and techniques for the control of emissions, and boiler design options to select the combination that would meet the performance goals with the greatest potential for low cost. Detailed system designs were developed and validated through subsystem testing which resolved nearly all uncertainties and provided the basis for a commercial generating unit (CGU) design during phase II. The design and cost estimate for (1) a proof-of-concept test facility and (2) the commercial generating unit were developed and evaluated against the program goals in phase III. While further development, particularly focused on integration of the subsystems, is needed during phase IV, efforts are underway to begin commercial deployment of key components and subsystems as retrofit technologies. One of the components successfully developed during the combustion 2000 program which has promising retrofit potential is B&W’s new ultra low-NO, DRB-4Z burner. This paper describes the unique development approach which led to the design of B&W’s new ultra low- NO, DRB-42 burner including its performance during subsystem testing at B&W’s clean environment development facility (CEDF) located at the Alliance Research Center. Described will be B&W’s plans for demonstra- tion of the DRB-4Z burner in phase IV and at a utility site.

99100606 Study of ashes from municipal wastes incinerated in classical grate boilers and FBC units-solidification of MWIR with FBC coal ashes for disposal Blondin. J. et al. Proc. Int. Cmf. Nttitl. Bed Comhust., lYY7, 14. (2). X07- 817. Due to its ability to meet environmental regulations, FBC is now widely used to burn low quality coals. The technology is also promising for a number of other fuels, especially those having high chloride contents. The characteristics of any fuel depend strongly on the combustion technique and temperature. FBC ashes would thus be expected to be substantially different from grate incinerator ashes. This study looks at the character- istics of ashes (MWIR) from municipal waste\, originated from various cities in Europe, and incinerated in FBC and classical grate furnace facilities. Also provided is information on the heavy metal contents and leaching characteristics of the various MWI reridues. All the rchults are examined in light of possible utilization strategies and landfill regulations regarding the potential for co-disposal of incinerator ashes with coal derived residues from FBC boilers to render the monolith\ lncrt and resistant against hazardous events that may occur during ultimate and definitive storage.

99100609 A sulfur capture model for circulating fluidized- bed boilers Mattisson, T. and Lyngfelt, A. Chenricul Eng. Sci., IYYX. 53. (fl), I Ih.i- 1173. Presented was a sulfur capture model that incorporated detailed laboratory data of limestone reactivity together with boiler data of particle-size distribution as well as residence times for the various particle sizes. The reactivity of limestone as a function of conversion was described hy an exponential decay approximation; a total of four constants were used to describe the rate as a function of particle size and conversion. The residence time for the different particle sizes and the particle-\ize distribution were determined from data of three utility circulating fluidized-bed boilers (CFBB) with thermal outputs of 12. 40, and I65 MW. The model was validated by sulfur and calcium analysis of sieved fly- ash and bed-ash samples, in which the degree of sorbent conversion as a function of particle size was determined The key factors that determined sulfur capture efficiency were: (1) the sorbent particle size distribution, (2) the residence time of each particle size, and (3) the reactivity as a function of conversion for each particle size. The model predicted the average sorbent conversion well for all three boilers, and the results followed the general trends in conversion level for each unit. However. the conversion was generally underpredicted by the model.

09 COMBUSTION

Burners, combustion systems

99100610 Ammonium sulfate-containing combustion ash treatment method Kubo, Y. et al. Jpn. Kokai Tokkyo Koho JP 10 146,576 198 146,576] (Cl. B09B3/00), 2 Jun 1998, Appl. 96/323,602, 19 Nov 1996; 7 pp. (In Japanese) In this method (NH4)$04 is decomposed to separate and recover NH? and fix SO4 residue as sulfates by kneading combustion ash with an alkaline substance and water in half-dry state. Methods using CaO, Ca(OH)2, and limestone as the alkaline. substance together with coal ash and/or cement and comprising a process of heating at specified temperature are also claimed. Recovered NH1 may be recycled for NO, removal, SO2 neutralization, etc., and gypsum is produced as a by-product. The methods are carried out without discharging wastewater and generating pollutants.

99iOO611 Analysis of accelerants and fire debris using aroma detection technology Barshick, S.-A. J. Forensic Sci., 1998, 43, (2). 284-293. This work investigates the utility of electronic aroma detection technologies for the detection and identification of ignitable liquid accelerants and their residues in suspected arson debris. Through the analysis of ‘known’ accelerants and residues, a trained neural network was developed for classifying fire debris samples. Three ‘unknown’ items taken from actual fire debris that had contained the fuels, kerosene, gasoline and diesel fuel, were classified using this neural network. One item, taken from the area known to have contained diesel fuel, was correctly identified as diesel fuel residue every time. For the other two ‘unknown’ items, variations in sample composition were shown to influence the sensor response. This manifested itself in inconsistent fingerprint patterns and incorrect classifications by the neural network. Sorbent sampling prior to aroma detection was demon- strated to reduce these problems and allowed improved neural network classification of the remaining items which were identified as gasoline and kerosene residues.

60 Fuel and Energy Abstracts January 1999