An Official Journal of the American Society of Thermal and Fluids Engineers

Comprar $35.00 Check subscription Descargar registro MARC Agregar al Gestor de Citas

Descargar la cita en el formato EndNote Descargar la cita en el formato RefWorks Descargar la cita en el formato BibTex

CCSEM ANALYSIS OF MINERALS IN COAL AND THERMAL PERFORMANCE OF PC-FIRED BOILERS

SINOPSIS

Mineral matter in coal, during combustion, transforms into fly ash, and results in the build-up of ash deposits on heat transfer surfaces in PC-fired boilers. This paper presents a method to estimate the thermal performance of a pulverized-coal-fired boiler based on the detailed information on minerals in coal and a number of mathematical models. These models include transformation of minerals to ash, transportation of ash to heat transfer surfaces, stickiness of ash particles, and thermal properties of deposits.
The ash formation process determines the ash character, i.e., its particle size distribution and variation in chemistry. The ash formation model primarily considers two mechanisms for ash formation: coalescence of included mineral grains and fragmentation of excluded mineral grains during combustion. This detailed information on mineral types and its size distribution is obtained for a number of coals from the computer controlled scanning electron microscopy (CCSEM) technique.
The rate of ash deposition has been estimated using an ash transportation model, which accounts for different mechanisms including inertial impaction, thermophoresis, and Brownian motion as a function of ash particle size distribution. The viscosity of an ash particle derived from each mineral grain has been considered as a measure of stickiness of particles. The deposit structure has also been estimated from the ash deposit chemistry and temperature profiles within the deposit. The thermal performance has been estimated for a number of coals.