Terttaliisa Lind

Ash Vaporization in Circulating Fluidized Bed Coal Combustion

ABSTRACT In this work, the vaporization of the ash forming constituents in circulating fluidized bed combustion (CFBC) in a full-scale 80 MWth unit was studied. Ash vaporization in CFBC was studied by measuring the fly ash aerosols in a full-scale boiler upstream of the electrostatic precipitator (ESP) at the flue gas temperature of 125°C. The fuel was a Venezuelan bituminous coal, and a limestone sorbent was used during the measurements. The fly ash number size distributions showed two distinct modes in the submicrometer size range, at particle diameters 0.02 and 0.3 μm. The concentration of the ultrafine 0.02-μm mode showed a large variation with time and it decreased as the measurements advanced. The concentration of the 0.02-μm mode was two orders of magnitude lower than in the submicrometer mode observed earlier in the bubbling FBC and up to three orders of magnitude lower than in the pulverized coal combustion. Scanning electron micrographs showed few ultrafine particles. The intermediate mode at 0....

On the determination of electrostatic precipitator efficiency by differential mobility analyzer

Abstract In order to determine penetration curve of the electrostatic precipitator (ESP) as a function of aerosol particle diameter in the range of 10–1000 nm measurement series were carried out in real scale power plant conditions. Differential mobility particle sizing (DMPS) system was used to measure the particle mobility distributions before and after ESP. MICRON -algorithm (constrained regularization) was used to invert mobility distribution to the corresponding number distributions. Penetration curve was calculated from the measured number distributions.

Aerosol formation in real scale pulverized coal combustion

Abstract Aerosol formation in pulverized coal combustion have been studied experimentally at the real scale power plant. Combustion aerosol mass and number size distributions have been determined, when burning bituminous coal from Poland. Mass size distributions have been measured by low pressure impactor and number distributions by differential electrical mobility (DMA) method.

A field study on the trace metal behaviour in atmospheric circulating fluidized-bed coal combustion

Trace element behaviour in atmospheric circulating fluidized-bed combustion (CFBC) of Venezuelan bituminous coal was studied by determining particle size distributions in the CFBC flue gas. The size distributions of calcium, iron, aluminium, and 21 trace elements, Sc, V, Cr, Mn, Co, Ni, Zn, Ga, As, Se, Sr, Cd, Sb, Cs, Ba, La, Ce, Sm, Lu, Pb, and Th, in the size range 0.01–70 μm, were determined by collecting aerosols with a low-pressure impactor-cyclone sampling train from the flue gases of an 80-MW(th) CFBC boiler upstream of the electrostatic precipitator. The collected samples were analyzed gravimetrically and with instrumental neutron activation analysis (INAA), particle-induced x-ray emission analysis (PIXE), and inductively coupled plasma mass spectrometry (ICP-MS). The number size distributions of the aerosols were determined with a differential electrical mobility method in the size range 0.01–0.8 μm. In the ultrafine particle mode, i.e., D p

Fly Ash Deposition Onto the Convective Heat Exchangers During Combustion of Willow in a Circulating Fluidized Bed Boiler

The deposition of fly ash onto the convective back pass in the CFBC of Swedish willow (Salix) between two soot-blowing periods was found to be 56–64%. The deposition was mainly determined by the particle size. The particle composition had no effect on the deposition. The deposition increased rapidly with increasing particle size. For example, it was found to be about 5% for the 1μm-sized particles and about 90% for the 10μm-sized particles. The elements which were mainly in the coarse fly ash fraction, Si, Al, Ca and P, were deposited most efficiently, whereas the deposition was smaller than average for K, S and Cl. Large amounts of K, S and Cl were found to be released during the combustion and were therefore found in the fine fly ash particle fraction.

Studies on Ash Species Release during the Pyrolysis of Solid Fuels with a Heated Grid Reactor

The release of alkalis (sodium and potassium) and five ash matrix elements (silicon, aluminium, iron, calcium and magnesium) during the pyrolysis of Polish coal, Pittsburgh #8 coal, peat and two wood chips was studied with a heated grid reactor using heating conditions relevant to fluidised bed combustion and gasification. Mineral particles or any other super micron fragments were found not to be released from any of the fuels during the pyrolysis. Less than 5 % of any of the elements studied were released from the fuels, with an exception of iron from wood chips. Some iron may have been released from the wood chips (less than 14 % from whole tree chips and less than 8 % from wood chips fuel fraction). Less than 1 % of iron was released from coals and peat.

Continuous method for pulverized coal combustion emission mass monitoring

Abstract A method for pulverized coal combustion aerosol mass concentration measurements with a dilution system and tapered element oscillating microbalance (TEOM) is introduced. The TEOM microbalance method gives continuous information about mass concentration variations in a minute scale time resolution. Particle upper size limit is chosen with a cyclone.

Ash Transformations in the Real-Scale Pulverized Coal Combustion of South African and Colombian Coals

In this work, the formation of ash particles in the combustion of South African Klein Kopie coal and a Colombian coal was studied by measuring the ash particle characteristics upstream of the electrostatic precipitator (ESP) at a 510 MWe pulverized coal fired power plant. We measured the ash particle mass size distributions in the size range 0.01-50 µm using low-pressure impactors and pre-cutter cyclones. Also, samples were collected for computer controlled scanning electron microscopy (CCSEM) with a cyclone with an aerodynamic cut-diameter of about 1 µm. The cyclone-collected samples were analyzed with standard CCSEM procedure by depositing the particles on a filter, and by embedding the particles in epoxy hence acquiring the cross-section analysis of the sample. All major mineral classes in both coals were found to undergo extensive coalescence during combustion. Iron, calcium and magnesium rich particles resulting from the decomposition of pyrite, calcite and dolomite were found to coalesce with quartz and aluminosilicate particles. The size distributions of the fly ash determined with CCSEM and low-pressure impactor-cyclone sampler were found to be similar.