01505 Optimization of combustion by fuel testing in a NOx reduction test facility

01505 Optimization of combustion by fuel testing in a NOx reduction test facility

09 Combustion (burners, combustion systems) consists of an upper part and a lower part; the lower part has a gasification chamber. Powdered coal is...

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Combustion (burners,

combustion systems)

consists of an upper part and a lower part; the lower part has a gasification chamber. Powdered coal is supplied continuously into both parts along with garbage.

Monitoring of the combustion heat of fuel gas and excess air coefficient by flame electroconductlvity

gal01 501

Smirnov, M. A. et al. Stal’, 1997, (7), 76-78. (In Russian) Fuel gas combustion heat and excess air coefficient can be measured with a flame conductivity probe coupled to available instruments. The deviation for combustion heat measurements in the 3.7-7.2 MJ/m3 range is 54%.


Nitrogen transformations in coal during pyrolysis

Kelemen, S. R. et al. Energy Fuels, 1998, 12, (l), 159-173. The changes in organically bound nitrogen‘forms present in the tars and chars of coals after pyrolysis were identified and quantified using XPS. The results of these studies are presented in full. 98lOI 503

Numerical analysis of diffusion combustion of coalgasified fuel. (Effect of pressure on NO, formation)

Xu, Z. et al. JSME Int. J., Ser. B, 1997, 40, (3), 439-446. Laminar jet diffusion flames were numerically calculated, taking into account detailed chemical kinetics and multicomponent diffusion. Attention was given to the effect of pressure and the amounts of hydrocarbon contained in the fuel on the NO, formation processes and characteristics. In order to clearly distinguish between thermal NO, and fuel NO, originating from N2 in the air and fuel N, respectively, and to elucidate the effects of interaction between thermal NO, and fuel NO, together with nitrogencontaining species, nitrogen-containing species originating from N2 in air and fuel nitrogen and their reactions are distinguished in the computations. Higher pressure resulted in a decrease in the amount of fuel NO formed and an increase in the amount of thermal NO formed. The tendency of the decrease of the conversion rate of ammonia to fuel NO for high-pressure flames becomes more apparent when the fuel contains greater amounts of methane and the effect of the destruction of thermal NO by nitrogencontaining species becomes more apparent for high-pressure flames as thermal NO concentration becomes high.

Numerical modelling of pulverized coal combustion 98101504 in an oxygen-coal combustor for blast furnace -

Gue, Y. et al. Ranshao Kexue Yu Jishu, 1997,3, (3), 297-302. (In Chinese) The continuum-trajectory model was used for the numerical modelling of pulverized coal combustion in an oxygen-coal combustor. The proposed combustor can prolong the coal particle residence time and enhance coaloxygen mixing. Small particles, preheated and rapidly devolatized, may have volatile combustion in the combustor, while larger ones can only be preheated and no devolatilization and combustion of such particles will occur in the combustor.

Optimization of combustion by fuel testing in a NO. 98101505 reduction test facility

Hesselmann, G. J. Fuel, 1997, 76, (13), 1269-1275. A 160 kWth NO, reduction test facility (NRTF) was studied, obtaining combustion data for a wide range of coals. Parametric testing was undertaken under conditions of single-stage combustion. furnace air staging and natural gas reburning. From these tests, detailed information directly applicable to large utility furnaces on the effects of coal characteristics, excess air, stoichiometry and residence time on NO,, CO and unburnt loss is now available. There are considerable differences between coal types, but even coals of similar properties can display large variations in combustion performance. The differences between coals are reduced under advanced low-NO, combustion conditions. Comparison with large plant data supports the NRTF results, as for NO, the NRTF matched a large utility boiler in both absolute emission and coal effects.

Peculiarities of the slow combustion of a hydro98iOI 508 carbon in a ‘wall-less’ reactor with laser heating

Mantashyan, A. A. Combustion and Flame, 1997, 112, (l/2), 261-265. The paper studies the slow combustion of the simplest hydrocarbons in a ‘wall-less’ reactor with laser heating. In such a reactor, combustion proceeds in the laser beam, while the reactor’s wall is at room temperature and does not take part in the process. It has been shown that conversion of propane plus oxygen mixtures can be observed at temperatures above 800 K. The results obtained are described and reveal the role of heterogeneous factors in the chemistry of slow combustion and show ways to complete these processes with a high selectivity. 98iOI 507

The prediction of carbon aonversion efficiency in pulverized coal combustion

Sun, J.-K. and Hurt, R. Chemical Physical Processes Combust., 1997, 151154. The development and testing of a computationally efficient kinetics-based model for estimating the effects of coal switching on loss-on-ignition value in full-scale power stations is described.


Fuel and Energy Abstracts

March 1998

98iOI 508

The rates of production of CO and CO1 from the combustion of pulverized coal particles in a shock tube

Commissaris, F. A. C. M. et al. Combustion and Flame, 1997, 112, (l/2), 121-131. Experimental results for coal combustion in a shock tube are presented with a time-dependent model of the boundary layer of a single, burning char particle under similar conditions. The partial pressure of O2 in a shock tube was varied between 0 and 10 bar, with gas temperatures ranging from 1300 to 1850 K. Particle temperatures between 1500 and 2500 K were reached under these conditions. CO and CO* concentrations were measured as functions of time and together with the equations for a particle’s energy and mass, it was possible to determine reaction rates as a function of both the particle’s temperature and the partial pressure of OZ. Furthermore, the measurement of gaseous reaction products enables fundamental aspects of their formation to be studied. CO and CO2 production rates allowed kinetic data to be obtained, consistent with that from a mass balance on a particle. A comparison of these results with the results from an energy balance on a particle shows hardly any heat transfer from the homogeneous combustion zone to the particle. This heat transfer increases if the rate of the heterogeneous reaction is decreased. Modelling calculations verified results, showing that CO combustion takes place in a wide zone surrounding the particle. CO can be considered to be the only primary product of heterogeneous reaction at the temperatures considered. 98/U 509

Simulation of coal ash deposition on to a super-

heater tube

Yilmaz, S. and Cliffe, K. R. J. Institute of Energy, March 1997, 70, 17-23. Simulation of coal ash particle deposition on to a superheater tube under pulverized coal combustion conditions was conducted with Soda Lime Silica Glass (SLSG) particles. A small-scale furnace and an air-cooled probe representing a superheater tube was located in the duct section in the path of the flue gases. The deposition rate of particles was determined for various parameters. Deposition was found to start when the particle viscosity was less than 6.7 x 10’ Pa. The deposition rate increased with probe surface temperature, gas temperature and velocity; it also showed a complex dependence on particle size. For large particles, deposition was controlled by stickiness of the probe surface up to 700°C. Small particles, however showed no dependence on stickiness. Addition of 1% NaCl to SLSG raised the rate of deposition to 100%. The formation of crystalline phases reduced the deposition rate of SLSG particles when NaCl and CaCOx were added.

Soot in coal combustion systems 98/01510 Fletcher, T. H. et al. Prog. Energy Combust. Sci., 1997, 23, (3). 283-301. Details are provided of the types of experiments performed, the soot yields obtained, the size of the soot particles and agglomerates, the optical properties of soot, the relationship between coal-derived soot and soot from simple hydrocarbons, and attempts to model soot in coal flames. Spray stagnation flames 98/01511 Li, S. C. Prog. Energy Combust. Sci., 1997, 23, (4), 303-347. The authors discuss spray combustion in laminar stagnation flows. This review covers spray structures in counterflowing streams, spray counterflowing diffusion flames, spray two-stage flames in counterflowing configurations and spray combustion in jets impinging on surfaces. Its focus concerns droplet and spray characteristics and details of the flame structures. There are two qualitatively different types of spray structures. In one type of structure, some larger droplets are able to cross the stagnation plane and pass through the flames to execute underdamped oscillation in the counterflowing streams or to collide with the target wall in an impinging stream. This type of behaviour occurs if the strain rate of the flow field is high and droplets in the spray are large. In the other type of spray structure, all droplets vanish at a vaporization plane before the stagnation plane and fuel vapour burns in a reaction zone in the flame. This second type of behaviour occurs if the strain rate is relatively low and droplets are relatively small. The review then illustrates how the investigations on the former provide information concerning relative motion between two phases as well as droplet collision dynamics with target walls and how the studies on the latter play roles in understanding flame structure and flame chemistry of liquid fuels. 98lo1512

Status and development of combustion technology

Obernberger, I. VDI-Ber., 1997, 1319, 47-79. (In German) The properties of biomass fuels, their combustion, suitable emissions from the combustion equipment are discussed.



gal01513 Thermochemical protection in combustion systems Borodyanski, C. et al. Heat Mass Transfer Chemical Process Ind. Accid., Proc. Int., 1994 (Pub. 1995). 381-394. The paper presents an experimental investigation of cooling and heat protection of high temperature objects. The method is based on endothermal chemical reactions. The coolant is CH,,, which reacts endothermally with CO2 and H20, which are supplied as hot products by hydrocarbon fuel combustion and are also used for heating the tested objects. The cooled objects are a hollow tube and gas turbine blades. Significant wall temperature reduction, AT, of -150 K, compared with nitrogen cooling, was obtained for wall temperature, T,, 900 K. Cooling efficiency decreased due to the slow rate of the chemical reactions at lower temperatures. At higher temperatures the cooling rate remained constant