Particle emissions from pellets stoves and modern and old-type wood stoves

The purpose of this work is to characterise particle emissions from pellets stoves and modern and old-type residential wood stoves. The mass concentration of particulate material in the hot flue gas was 19e82 mg/MJ, roughly the same for wood stoves and pellets stoves, but the old-type wood stoves tended to emit even higher quantities. Furthermore, during combustion of wood logs the considerably higher emission of organic gaseous carbon indicates an additional contribution to the emission from secondarily formed condensable organic particles. The particle mass emitted was dominated by fine particles (<1 mm) in all cases. The fine particle maximum was displaced towards larger size during inefficient combustion, e.g. during the start-up phase. The number concentration of particles from wood stoves was 1.0$1014e6.0$1014 #/MJ, from pellets 3.0$1013e5.0$1013 #/MJ, and in all cases dominated by fine particles. Efficient combustion of pellets resulted mainly in inorganic particles, dominated by potassium sulphate and potassium chloride. Zinc, the second most frequent metal, and calcium showed the highest concentrations among the less volatile components. The lowest concentration detected was for cadmium, about 105 times lower than for potassium

Particle emission from combustion of oat grain and its potential reduction by addition

Second-rate cereals, unsuitable for food, can be used as fuel for small-scale production of heat and hot water. However, there are more problems related to cereals than to woody fuels. This work aims at characterising the particle emission from residential combustion of oat grain and its potential reduction by addition of limestone or kaolin with the fuel. Then, to a large extent, the potassium supplied by the fuel is expected to be found in coarse particles, leaving the boiler as bottom ash, instead of being emitted to the air in the form of submicron particles. Combustion experiments were performed on a residential boiler, using filter sampling and low-pressure impactors to measure the mass and number concentrations and size distributions of the emitted particles. The particles and the bottom ash were subsequently analysed for inorganic material. To check the combustion conditions and basic emissions from combustion of cereals, the flue gas was analysed with respect to gaseous O2, CO2, CO, NOx, TOC (total organic carbon), HCl and SO2. Furthermore, thermodynamic equilibrium analysis was used to support the experimental data. Finally, it is concluded that the particle emission can be lowered by supplying kaolin, while there was no effect of limestone. © 2008 Elsevier B.V. All rights reserve

A pronounced thymic B cell deficiency in the spontaneously diabetic BB rat.

Abstract In an attempt to elucidate the origin of the T cell lymphopenia and/or the beta-cell-specific autoimmunity observed in diabetes-prone Bio-Breeding (DP-BB) rats, a thymic cDNA library was subjected to differential screening with thymic cDNA probes of DP-BB rats and nonlymphopenic nondiabetic controls. This approach resulted in the identification of a prominent lack of thymic B cells in DP-BB rats. This deficiency is distinct from a less pronounced peripheral B cell deficiency of different timing. The thymic B cell defect is linked to the lymphopenia trait on chromosome 4 and thereby with susceptibility to diabetes in crosses involving the DP-BB rat. In conclusion, our data suggest that the contribution of thymic B cells to the (negative) selection of thymocytes is inadequate in DP-BB rats, thus providing a plausible explanation for at least some of the spontaneous autoimmune phenomena in this animal model.</jats:p

Properties of Particles in the Fly Ash of a Biofuel-Fired Circulating Fluidized Bed (CFB) Boiler

A quench/dilution probe was designed and used for sampling of particles and vapors in the flue gas upstream of the convective path in a circulating fluidized bed boiler. Downstream of the convective path, flue gas was sampled by a heated probe. The sampled gas was lead through low-pressure impactors for analysis of the mass size distribution of particles. The particles were analyzed for Cl, S, K, Na, Ca, Mg, P, Al, Fe, Ba, Mn, and Si. A series of tests was carried out to study minimization of problems originating from the alkali content in the fuel, including the effect of additives to the fuel, change of bed material, and co-combustion with sewage sludge. Particle concentration and composition were compared to deposit growth and composition on a deposit probe, which represents a superheater. Alkali chloride in the particles was compared to online measurements of gaseous alkali chlorides. The continuous mass deposition on the heat-transfer surface in the convective path was illustrated by calculation of the reduction of heat transfer by means of the temperature drop of the flue gas. Fine particles (1 μm) particles increased. These test cases also showed the lowest deposit growth on the superheater probe. The particles deposited in the convective path were mostly coarse ones. The most favorable case with respect to low deposits was co-combustion with sewage sludge

Properties of Particles in the Fly Ash of a Biofuel-Fired Circulating Fluidized Bed (CFB) Boiler

A quench/dilution probe was designed and used for sampling of particles and vapors in the flue gas upstream of the convective path in a circulating fluidized bed boiler. Downstream of the convective path, flue gas was sampled by a heated probe. The sampled gas was lead through low-pressure impactors for analysis of the mass size distribution of particles. The particles were analyzed for Cl, S, K, Na, Ca, Mg, P, Al, Fe, Ba, Mn, and Si. A series of tests was carried out to study minimization of problems originating from the alkali content in the fuel, including the effect of additives to the fuel, change of bed material, and co-combustion with sewage sludge. Particle concentration and composition were compared to deposit growth and composition on a deposit probe, which represents a superheater. Alkali chloride in the particles was compared to online measurements of gaseous alkali chlorides. The continuous mass deposition on the heat-transfer surface in the convective path was illustrated by calculation of the reduction of heat transfer by means of the temperature drop of the flue gas. Fine particles (1 μm) particles increased. These test cases also showed the lowest deposit growth on the superheater probe. The particles deposited in the convective path were mostly coarse ones. The most favorable case with respect to low deposits was co-combustion with sewage sludge