1. Introduction
Currently, there are about 203 Millions households in Europe,
mostly equipped with a single heating system (boilers). A signifi-
cant part of heating units is clearly obsolete and need immediate
replacement [1]. The heat production with old-fashioned boilers
can cause serious health and ecological problems. Pollution of
environment by household heating boilers that are fired with coal
and is called low emission. The combustion process in such appliances
frequently runs without appropriate supervision, which results
in excessive emission of substances that are hazardous to
humans and the environment. Effects of that emission are clearly
visible in urban agglomerations, where a huge number of such
boilers operate within relatively small areas. Flue gas from such
small heating units is usually released to the atmosphere by means
of stacks that are of low height and as such do not distribute the
pollutants over larger areas. The resulting air pollution is comparable
with that generated by the industry. During winter, the
emission of hazardous substances is often a dominant factor of
urban air pollution. The problem of low emission can be resolved in
several ways. One of the promising ideas is using of more efficient
heating units. When considering pollutants emission, higher effi-
ciency of the boiler advantages in two ways. First of all, less fuel is
used for producing the same effect. Additionally, better combustion
means less carbon monoxide in the flue gases which indicates less
pollutants emitted to atmosphere.
The technology of small-scale coal-fired (biomass-fired) boilers
with retort burners appeared on the domestic market in mid 90's.