Comparison of pea coal combustion in a novel burner with separated primary and secondary air with combustion in a typical retort burner

Coal peas are still an important fuel for heating residential and public buildings, especially in towns without heating and gas networks. Recently, there has been an increased interest in replacing heating devices with new automatic eco-pea coal boilers. For these reasons, the task of designing an eco-pea coal burner with lower CO, NOx and particulate matter emissions than in typical retort burners was undertaken. A burner in the ISA (Integrated in burner Secondary Air) technology was proposed, in which the combustion air was separated into primary and secondary air. The air distribution was made by using apertures controlled by cables. Primary air is fed to the bottom of the burner to the place where the fuel is located. This is where the pyrolysis of coal and its partial combustion take place. Secondary air is fed to the top of the burner, where the produced gases are burned off. In the ISA coal burner, combustion tests of two types of eco-pea coal were carried out. The first is out-of-class coal, and the second is certified eco-pea coal. The combustion was carried out in the Klimosz company's in-house laboratory, equipped with a test stand with a boiler, measuring and data recording equipment. The burner settings, i.e. fuel and air output, were the same. To compare the operation of the ISA burner, combustion tests were also carried out on a typical retort burner. In each case, combustion tests lasted several hours and the following parameters were measured: CO, NOx, O2, CO2, exhaust gas temperatures, excess air coefficient and particulates. The combustion process was also documented with photographs. The ISA burner turned out to be less emission-intensive than the retort burner. The ISA burner emitted eight times less CO in the flue gas than the retort burner. The ISA burner reduces NOX levels in the flue gas by more than 25%. The particulate matter emission from the ISA burner was at the level of the emission from the retort burner. Uncertified coal turned out to be coking, causing sinters on the furnace, hindering free combustion.