Summary:

The research is focused on energy sorrel as a fuel for local low-power heating systems with output up to 100 kW. Sorrel is perennial plant surviving in its location nearly 18 years which is very good from the point of crop expenses. It is a robust plant with height of about 2 m in second year of plantation. Dry phytomass is energetically rich fuel with total heating value 17.5 – 18.0 MJ*kg^-1 at the average yield of 10 tons per hectare. An experimental combustion of pure sorrel and its blends were done with boiler VERNER A25 – a hot water boiler for pellets. 11 different sorrel fuels consisting of 5 primary kinds were tested during the experiment: sorrel (Rumex tianshanicus x Rumex patientia), Phalaroides arundinacea, Canabis sativa, pine-bark, sorrel (Rumex tianshanicus x Rumex patientia), brown coal. Based on collected data it is possible to obtain an overview of these fuels and their emission properties. Satisfactory values of CO concentration are possible to gain partly by choosing appropriate combustion device and its settings and partly by mixing with other types of fuel. In the case of sorrel the combination of both has been shown very useful. It is very hard to combust sorrel only, and its testing proves unsatisfactory results. But if we combust blend of sorrel and canary grass 1:1 in the same device, the results are somewhat better. The best results can be reached if we burn this blend in more suitable device. By this way it is even possible to fulfil the emission limits. However, if we burn only pure sorrel in another burner, the emissions are very dissatisfactory again. Another possibility of how to burn sorrel effectively is to combine it with brow coal. On the basis of received results, fuel containing 10 to 20 % of coal can be recommended. From point of view of ash properties pure sorrel appears a problematic fuel. During our experiment ash accumulation in combustion chamber was observed. Unburnt fuel blocked air intakes which caused burning deterioration and increase of CO emissions. All above mentioned facts indicate that sorrel burning is possible if we fulfil all demands required for this fuel. Combustion of pure sorrel in any device without special settings means in many cases non effective use of fuel and bad emissions.