In-situ high temperature CO/HC gas sensors for optimization of the firewood combustion in low-power fireplaces Binayak Ojha, Navas Illyaskutty, Jens Knoblauch, MuthuRaman Balachandran and Heinz Kohler Institute for Sensor and Information Systems (ISIS), Karlsruhe University of Applied Sciences binayak.ojha@hs-karlsruhe.de, heinz.kohler@hs-karlsruhe.de Abstract In this paper, the combustion and emission situations of batch wise firewood fueled fireplaces is discussed. Difference in CO-emissions of a hand operated and automatically air stream controlled firewood combustion process is illustrated. An air stream control algorithm is introduced which directs all phases of the firing process: ignition, high temperature and burn out phase. The combustion air stream control concept is based on motor driven shutters combined with air mass stream sensors and on flue gas analysis by sensors for combustion temperature, residual oxygen concentration (ROC) and residual un- or partly combusted pyrolysis gas components (CO/HC) Different commercially available high temperature CO/HC sensors along with an indigenously developed metal oxide (MOG) sensor array are evaluated in batch firing experiments with reference to the data sampled by a HT- FTIR analysis system. Finally, the signal stability of the sensors was investigated by repeated exposure to CO/air gas mixtures. Keywords: Firewood combustion, Firing process control, Mixed potential gas sensors, Metal oxide gas sensors 1 Introduction Residential wood combustion is of widespread concern owing to its adverse impacts on air quality and human health, especially in the many developing countries where wood is regularly used for residential cooking and heating, however, also developed countries use wood as a cheap alternative for domestic heating mainly at the countryside. Considering Germany in particular, about 14 million low-power single room fireplaces are being operated. Even after the second version of the new German emission law (1 st BImSchV) for low-power firewood fueled fireplaces has come into effect in 2015, the upper emission limits for single-room fire appliances (1250mg/m 3 for CO and 40mg/m 3 for particulate matter (PM)) are still stipulated much higher than the typical emissions from heating oil burners (approximately 50 mg/m 3 CO). Under optimal conditions, combustion of wood/biomass results solely in the emission of water vapor and carbon dioxide (CO 2 ). However, under incomplete combustion conditions, numerous gaseous and aerosolized compounds are emitted from biofuels in addition to CO 2 and water. These toxic gas components include CO, partially oxidized hydrocarbons (HC), polycyclic aromatic HC (PAHs) and particulate matter (PM) [1]. A substantial reduction of those emissions is possible with proper automated heating strategies. The control of the air streams based on combustion temperature and residual oxygen concentration (ROC) is meanwhile the modern state of the art. However, our firing experiments conducted at various fireplaces have shown that it is essential not only to enable sufficient oxygen but also to avoid cooling effects in the post combustion chamber by excess air throughout the firing process. To approach the quality of the firing process to the level of complete combustion, control of combustion air streams must be optimized. This is possible at situations of high combustion kinetics, i.e. at high combustion temperatures, which is merely achieved in a relatively short phase of a firing process by means of optimal feeding with combustion air. These aspects indicate the necessity for a representative knowledge of the combustion situation at every time of the firing process by monitoring of combustion temperature, ROC and the evolved gas components [2]. In this paper, the combustion and emission situations of batch-wise firewood fueled fireplaces (stoves) are discussed and a new air stream control algorithm is introduced which directs all phases of a batch-wise firing process: ignition, high temperature and burn out phase [1]. The combustion air stream 18. GMA/ITG-Fachtagung Sensoren und Messsysteme 2016 118 DOI 10.5162/sensoren2016/2.2.2