Abstract:
Biomass is rapidly becoming an alternative fuel for conventional fossil fuel fired
boilers and furnaces in the manufacturing and service industry in Sri Lanka. In
majority of these boilers, there is no proper way to control the combustion process
to ensure higher performance. Existing costly solutions have not attracted
particularly the small scale boiler owners. In this background, the aim of this
research was to develop a low-cost control system to improve combustion
efficiency of small scale intermittently-fed biomass combustors. A lab-scale
biomass combustor was developed and a series of experiments were conducted by
attaching a single-pass water-tube heat exchanger to the combustor.
Microcontroller based controller was developed to control the forced draft fan
speed by analyzing the combustion patterns observed during experiments. The
heat output was measured using the heat gained by the flowing water. The gross
heat output and its time variation under varying fan speeds were observed by
maintaining the water flow through the heat exchanger at constant. Results showed
that the overall heat energy produced and its time variation depends on the fan
speed, and there is an optimal fail speed yielding the maximum gross rate of heat
output for a given batch of biomass. The technology developed in this research can
directly be incorporated to develop a low-cUst controller applicable for medium
and small scale intermittently-fed biomass boilers and combustors.
