Optimization study of incineration in a incinerator with a vertical radiation shaft.

An extensive series of experimental tests were carried out at the Sheffield municipal solid
waste incinerator plant (30 MW) from September 1988 to July 1989 to investigate the
influence of the design and operating parameters on the performance of the incinerator
which burns domestic and commercial wastes (500 ton/day).
The following measurements were made around the plant: temperature measurements,
pressure measurements, flue gas composition analysis and determination of physical and
chemical properties of Sheffield refuse. Several other miscellaneous measurements were
also made to monitor the effect of variation of operating parameters on the performance
characteristics of the incinerator.
A combustion model of Essenhigh type was then employed to model the combustion
processes inside the solid refuse bed on top of the travelling grate. In addition a mathematical model of the finite difference type (FLUENT) was used to predict the three
dimensional reacting flows (gaseous phase) within the incinerator geometry. Experimental measurements of gas composition, temperature and exit velocity were compared with
model predictions. Modelling results were generally in good agreement with measurements.
As a result of the test data and the mathematical modelling of the whole process, suggestions for design improvements for the Sheffield municipal solid waste incinerator were
made which will substantially increase the efficiency, reduce emissions of pollutants and
reduce the maintenance costs at the plant. These are: a) replacing the existing secondary
air system with secondary air nozzles and the use of more secondary air (up to 20 % of
total air) in order to generate turbulence in the high intensity combustion zone where
it is most needed and b) introducing a baffle into the main stream inside the radiation
shaft in order to lower the gas temperatures entering the precipitator and to remove the
existing recirculation zone in the shaft.