Effect of the air flows ratio on energy behavior and NOx emissions from a top‑lit updraft biomass cookstove

Abstract

ABSTRACT: Biomass as an energy source for three-stone cookfres is commonly used for cooking and heating rural and isolated house holds in developing countries; therefore, indoor air quality decreases. In this work, the efect of the air fows ratio (combustion air/gasifcation air, CA/GA: 2.8, 3.0, and 3.2), and the start type, cold (CS), and hot (HS), on the energy behavior and emissions from a forced-draft top-lit updraft (TLUD) cookstove, using wood pellets as fuel, is studied. Furthermore, the gasifcation process was thermodynamically characterized. The TLUD cookstove assessment was carried out following a modifed water boiling test (WBT). The highest thermal efciency of the cookstove was 26.74%. The lowest specifc CO, NOx, and total suspended particle matter (TSPM) emissions were 1.8 g/MJd, 106 mg/MJd, and 78.32 mg/MJd, respectively; this was attributed to a proper mixture between the producer gas and the combustion air. The gasifcation process showed a better energy yield under the hot start due to the preheating induced in the cookstove reactor. The optimal values of the producer gas heating value (LHVpg), cold gas efciency (CGE), and the biochar yield (Ychar) were 3.53 MJ/Nm3, 58.61%, and 12.49%, respectively. Here, an opposite efect was found for the air fows ratios assessed. The cookstove behavior improved as the mixture between CA and GA was suitable, achieving the maximum at CA/GA =3.0. However, the NOx emissions increased with the increment of CA/GA ratios (from 2.8 to 3.2). Therefore, future works must address the NOx emission reduction without penalizing performance or permanent emissions from the TLUD cookstoves.