Abstract
European Union recommends reducing high quality biomass usage in energy sector. Low quality biomass causes problems with combustion. Literature analysis indicates that secondary air usage can reduce ash agglomeration. Secondary air is implemented in this research to reduce ash agglomeration and increase the combustion time, simultaneously monitoring the effects on flue gas composition in the residential low-capacity retort pellet boiler. Secondary air was implemented in rotary air dispensary device, which induced swirl of flames. Reference tests were conducted to have comprehensive data of improvements. Secondary air supply was tested from 27.5 % to 45 % of the total supplied air, by adjusting the primary air supply amounts, thus reducing the oxygen concentration in the flue gases. Lowest secondary air supply had the best results out of all tests, which resulted in 2.9 % of efficiency increase, while CO emissions were reduced by 4.7 times compared to the best scenario of reference tests and NOx emissions reduced 20 % compared to the same scenario. Secondary air implementation allowed the tests to last much longer than reference tests, since less airway blockage was occurring by ash agglomeration. This research indicates that low-quality biomass can be used in residential heating if proper technology is implemented in the pellet boiler, thus contributing in accordance with sustainable development goal 12: responsible consumption and production. Secondary air supply has a potential to reduce the ash slag formation, increase the combustion time and reduce the emissions produced.