D. L. Keairns

Coal devolatilization studies in support of the Westinghouse fluidized-bed coal gasification process

Abstract Coal devolatilization studies were carried out with a pressurized laboratory fluidized-bed reactor. The tests showed the behaviour of caking and noncaking coals during rapid heating in a fluidized bed. Small samples of coal were injected into a hot bed of char; the off-gas was sampled and analysed; and the char and agglomerates produced were examined and characterized. Data obtained on the variation of gas evolution rates with time were used to predict the duration of the plastic or sticky phase during transition of the coal to char. All tests were conducted at 1.013 MPa (10 atm) pressure; bed temperature and coal particle size were varied.

Particle Attrition in Fluid-Bed Processes

Attrition mechanisms of sulfur sorbents in fluidized-bed combustion (FBC) processes are being studied to develop a comprehensive model and a consistent test to screen sorbents. Available characterization work on particle fracture is reviewed and models developed for thermal and kinetic stress mechanisms based on theoretical studies and test data. The models for each mechanism relate sorbent properties and design and operating parameters to sorbent attrition.

Momentum Dissipation of and Gas Entrainment into a Gas-Solid Two-Phase Jet in a Fluidized Bed

Gas velocity profiles in a gas-solid two-phase jet inside a fluidized bed were determined at five different horizontal planes perpendicular to jet direction using a pitot tube. The experiments were conducted at three nominal jet velocities (35, 48, and 63 m/s) and with solid loadings (weight of solid/weight of gas) ranging from 0 to 2.75. The velocity profiles were integrated graphically, and gas entrainment into a jet was found to occur primarily at the base of the jet. The gas velocity profiles in the jet and the gas entrainment into the jet are reported.

Large-scale fluidized bed physical model: methodology and results

Abstract Fluidized bed physical modeling principles are identified and applied to simulate a large-jetting fluidized bed. Physical (cold) model results from 30-cm and 3-m gasifier simulation units for initial bubble diameter, bubble frequency, gas leakage, bubble velocity, jet penetration depth and jet half-angle are correlated and compared with previous studies.

what's new in high temperature sulfur removal systems for fluidized-bed coal gasification

High temperature sulfur removal can be achieved with calcium-based sor-bents (e.g. dolomite) in fluidized-bed coal gasification systems now being developed for power generation. The use of dolomite offers the opportunity to meet environmental emission standards, to minimize energy losses, and to reduce electrical energy costs. In addition to removing sulfur from the low-Btu gas, the complete sulfur removal system must be integrated with the total power plant and environment to assure compatibility. Critical requirements for achieving commercial system include establishing criteria for ‘acceptable’ sorbents, establishing integrated sulfur removal/gasification process design parameters, predicting trace element release, predicting sorbent attrition, developing an economic regeneration and/or once through process option, developing a spent sorbent processing system, and establishing safe and reliable disposition options for spent sorbent. Design and operating parameters are being developed and potential proc...

Assessment of Fluidized Bed Oil Gasification for Power Generation

Fluidized bed gasification of high sulfur oil at atmospheric pressure for the production of a clean fuel gas has been evaluated technically and economically. The clean fuel gas with minimal sulfur and particulates is utilized for power generation in conventional fossil fuel fired boilers. The gasification occurs in g limestone bed. Hydrogen sulfide produced during the cracking and partial combustion of the oil is removed by the lime to yield a clean fuel gas and sulfided lime. The hot, low sulfur, low Btu, fuel gas is burned in a steam generator. The process can be operated as a once-through, throw-away limestone system or as a limestone regeneration/sulfur recovery system. The sulfided lime can be converted to calcium sulfate in an air-fluidized vessel, operating near 1500°F, for dry disposal in the once-through concept. The regeneration system converts the sulfur in the stone to SO2 in an air fluidized bed operating near 1900°F. The regenerated stone is circulated back to the gasifler and the SO2 rich s...