[Gasification] What is the process he is trying to describe?

[Tom Miles]

Steve,

The deep bed combustor you are using is reminiscent of the deep bed burning
studies that Ken Ragland and Mark Bryden did for whole trees in 1995-1996.
You'll find a paper published in Energy & Fuels (1996) on the subject which
describes the mechanisms and the dehydration, gasification and combustion
reactions involved. (See abstract and citation below).

In St. Petersburg (formerly Leningrad) professor Pomerantsev did extensive
studies of deep bed wood chip burning in the 1950s and 1960s. He designed
furnaces and boilers based on deep bed burning which were built through out
Russia. Working with Russian combustion engineers and boiler manufactures we
improved the Pomerantsev furnace as part of a USAID funded project
(2001-2005). Descriptions of the operation of the furnace are mostly in
Russian. 

The design of continuously fed furnaces based on deep bed principles is
problematic due to the very high temperatures that develop when you have a
heavy bed of carbon burning at the grate. It becomes a blast furnace
environment. The high cost of maintenance has meant that it has not been
used very often in this country.

Tom Miles   

Numerical Modeling of a Deep, Fixed Bed Combustor
Kenneth M. Bryden* and Kenneth W. Ragland
Department of Mechanical Engineering, University of Wisconsin Madison,
Madison, Wisconsin 53706 Energy & Fuels 1996, 10, 269-275
Received October 2, 1995. Revised Manuscript Received January 4, 1996X

Abstract:
A computational model to evaluate the anticipated performance
characteristics of a deep, fixed bed combustor/gasifier utilizing whole
trees as the source of fuel is presented. This combustor/gasifier is the
heat source for a proposed steam-driven electric power plant utilizing whole
trees as the source of fuel. In the simulation model presented, hardwood
logs 20 cm in diameter are burned in a 3.7 m deep fuel bed. Solid and gas
velocity and CO, CO2, H2O, hydrocarbon, and O2 profiles are calculated. This
deep bed combustor obtains high energy release rates per unit area due to
the high inlet air velocity and extended reaction zone. The lowest portion
of the overall bed is an oxidizing region and the remainder of the bed acts
as a gasification and drying region. The overfire air region completes the
combustion. Approximately 40% of the energy is released in the lower
oxidizing region. The wood consumption rate obtained from the computational
model is compared with test results obtained from full scale testing. The
wood consumption rate predicted by the model is 2630 kg/(m2 h) which matches
well the consumption rate of 2670 kg/(m2 h) observed during the 2 h test
period of the field test. This corresponds to a heat release rate of 9.6
MW/m2. The model is used to investigate the performance of the combustor
under a variety of load conditions, fuel sizes, and moisture conditions.

http://pubs.acs.org/cgi-bin/abstract.cgi/enfuem/1996/10/i02/abs/ef950193p.ht
ml


WTE Plant (Ken Ragland to the Bioenergy List Discussion August 2005
http://listserv.repp.org/pipermail/bioenergy_listserv.repp.org/2005-August/0
10128.html

Whole Tree Energy Power Plant (2005)
http://www.mrec.org/confer/2005_WholeTreeEnergy.pdf