Combustion of solid biomass under fixed bed conditions is a common technique to generate heat and power in both small and large scale grate furnaces (domestic boilers, stoves, district heating plan ...

High temperature aerosol formation and emission minimisation during combustion of wood pellets

This paper presents and discusses measurements of local flame temperature, local gas species concentrations and incident wall heat fluxes obtained in a 250 MWe residual fuel-oil front fired utility boiler. The work is aimed at improving knowledge of the efficiency of the thermal processes involved in large industrial boilers and covers three different operating conditions, which include load and air-fuel ratio variations. The measurements were made using special design probes through the ports available for inspection of the boiler. Local gas temperatures varied between 1650°C in the centre of the flames attached to the burners to around 1100°C close to the boiler nose, with maximum variations in the plane of the burners between the front and rear walls of about 200°C. The levels of CO were as high as 2% close to the ash pit and reach 1% near the boiler nose, suggesting some limitations in the process of fuel burnout and CO oxidation. Wall incident total heat fluxes varied between 200 k W/m2 and ...

Temperature, Species and Heat Transfer Characteristics of A 250 MWe Utility Boiler

This paper describes the use of digitally-compensated thermocouples to characterise the time-resolved behaviour of the temperature field in turbulent non-premixed jet flames for Re?2×104, including the transport of heat and the related temperature dissipation. The experimental procedures used are analysed, including the thermocouple time constant determination and the numerical derivative compensation method, and assessments of accuracy are provided for the cross-correlation techniques used in order to estimate high-order temperature statistics in the flames studied. The results quantify the influence of the spatial resolution of the measuring systems on the accuracy of correlation values, regarding the characteristics scales of the flames studied, and demonstrate the applicability of fine-wire thermocouples to characterise the turbulent transport and the dissipation of temperature in non-premixed jet flames.

Temperature and related statistics in turbulent jet flames

Experiments are conducted on a laboratory-scale fixed bed combustor This article discusses some of the data analysis methodologies that define the onset of steady state conditions, which are widely reported in the literature but poorly defined The effects of using different methods to determine the onset of the steady state performance, and to correct thermocouple data so as to account for radiative effects, are also presented Results show that using a combination of CO and NO emissions with free-board temperatures (at multiple axial positions) is more effective than other emissions, using temperatures (only) or the fuel burning rate (kg m–2 s–1) An important indicator is to analyze the percentile deviation of temperatures and emissions, compared to only using the time evolution of these variables To characterize the significance of correcting thermocouple data for radiative (wall) losses, two numerical models (aspirated and bare bead) were compared Radiative effects on thermocouples were fo

Methodologies for processing fixed bed combustor data

On the stabilization of flames on multijet industrial burners

This paper presents a review of the capabilities of probe techniques for combustion diagnostic and outlines the most significant sources of error inherent to their use. The emphasis of the search is on measurements of temperature and on those of major species and ion concentrations in combusting environments, and attention is focused to elucidate the importance of probe measurements to improve understanding of turbulent combustion.

A. L. N. Moreira

Papers

Probe Measurements of Scalar Properties in Reacting Flows