Although the Chinese government encourages
using clean fuels for heating, many households in remote areas still
rely on coal as their energy, especially in the Qinghai Tibet Plateau.
An updraft coal heating stove was modified to preheat secondary air.
The performance of the modified stove was studied compared with a
baseline stove. The temperatures in the combustion chamber and near
the chimney exit are measured, and the undiluted exhaust concentrations
of CO, NO
x
, and SO2 are obtained.
The results indicated that the temperatures and exhaust gas concentrations
varied periodically with the coal addition. The oxygen concentration
in the flue gas for the modified stove is higher than that for the
baseline stove, and the O2 concentration was decreased
with the increase in fuel feed rate. The CO concentration peaked 5–15
min after fuel addition and descended quickly toward a baseline with
the higher fuel feed rates. It remained almost unchanged at the beginning
and then slightly increased when the combustion began to fade with
a lower fuel feed rate for the modified stove. The NO
x
emission for the modified stove is generally lower
than that for the baseline stove. The NO
x
formation during coal combustion mainly comes from prompt NO and
fuel NO, while the SO2 emission is mainly related to the
sulfur element in the raw coal in the present work. The modified stove
is effective in reducing NO
x
and SO2 emissions. However, the CO emission of the modified stove
is higher than that of the baseline stove, especially at the end of
the batch.