| Abstract [eng] |
The rapid expansion of population worldwide increases energy demand and waste generation. Wastes and biomass are potential energy resources. Concerning sustainable development, appropriate methods for waste and biomass conversion are necessary. Lately, plasma technologies have drawn attention as a possible way for biomass and waste conversion into valuable intermediate products, such as synthesis gas, which could partially satisfy the growing energy demands. Nevertheless, plasma technologies are not yet fully developed and commercialized and therefore further research at the laboratory scale level is needed. Thus, this experimental research aimed to determine the ability to gasify biomass (wood pellets) to synthesis gas in the thermal air plasma environment. The influence of different material conversion parameters, including the power of the plasma torch and the plasma-forming gas flow rate on the biomass gasification process, were analyzed. Also, the evaluation of the plasma system performance was carried out. The experimental biomass gasification system was designed at the Plasma Processing Laboratory of the Lithuanian Energy Institute. The experimentations were performed using the 6 mm diameter wood pellets as the reference biomass feedstock. Air was used as a plasma-forming gas and the main gasifying agent. The gasification of the wood pellets was carried out at the plasma torch power of 40.5–54.9 kW, air flow rate of 10.18–18.18 kg/h and the feedstock flow rate of 20.73 kg/h (equivalence ration of 0.11–0.16). The quantification of the biomass gasification system in terms of the producer gas composition, the H2/CO ratio, the lower heating value (LHV), the carbon conversion efficiency (CCE), the energy conversion efficiency (ECE), and the specific energy requirement (SER) were performed. The highest H2 and CO concentrations in the producer gas were 26.6% and 33.35%, respectively, giving the H2/CO ratio of 0.8. The LHV of the produced synthesis gas varied from 7.62 MJ/Nm3 to 8.82 MJ/Nm3 , respectively. The CCE ranged from 85.3% to 97.2%, while the ECE was equal to 29.23–30.57%. The SER producing 1 mole of syngas from wood pellets varied from 165.47 kJ/mol to 195.61 kJ/mol, respectively. Summarily, the thermal arc air plasma was applied to convert biomass to syngas. The comparison of different flow rates of the gasifying agent at a constant feedstock ratio showed that the air flow rate did not make a significant difference in the biomass conversion process. The synthesis gas generation varied from 59.95% to 62.51%, while the H2/CO ratio ranged from 0.68 to 0.8. Moreover, this primarily experimental research shows promising results for successful application of the newly designed plasma gasifier. Further research is needed to optimize the conditions of biomass/wastes conversion process in air plasma and other plasma environments. |
