engleski

Experimental investigation of syngas composition variation along updraft fixed bed gasifier

Fixed bed gasification represents a convenient pathway for exploiting lignocellulose since it can be carried outon a small scale, while current technology is robust and fairly simple. Updraft gasifier is characterized by higherefficiency and isflexible towards feedstock, compared to the downdraft gasifier. The hydrogen to carbonmonoxide ratio is the decisive parameter for determining syngas quality. Present contribution for thefirst timereports the evolution of the syngas composition at different heights of the reactive biomass bed in a pilot plantoperating in a continuous mode, i.e. 20–30 kg/h of biomass feed. This was achieved by probing syngas streamsdirectly from the core and analysing it onsite to measure the content of hydrogen, carbon monoxide, carbondioxide, light hydrocarbons, nitrogen and oxygen, whilst the tar content was analysed offline. The addition ofsteam deeply affected the evolution of the chemical species and thermal profile. The syngas chemical compo-sition was related to the thermal profile provided by in bed measurements of six thermocouples at the samelocations. In the tests, almond shells were gasified with air or air and superheated steam mixture at equivalenceratio of 0.20 ± 0.01 and various steam to biomass ratios between 0 and 0.16 kg/kg. Addition of steam sta-bilized thermal profile inside the gasifier below 900 °C, improved the production of hydrogen up to 37.5 g/kg ofbiomass and the cold gas efficiency up to 72.5%. The use of steam positively affected the molar ratio of hydrogento carbon monoxide that reached a steady value of 0.77 during the gasification operated at steam to biomassratio of 0.11 kg/kg, versus the value of 0.46 measured in the corresponding test operated only with air. On theother hand, steam addition increased tar production up to 163 g/kg in air/steam gasification compared to the137 g/kg with air gasification. Obtained data of the syngas composition along the bed height provide insight intothe underlying physical and chemical phenomena and can be further used for the improvement and validation ofgasification mathematical models.

Updraft gasification ; Syngas composition ; Almond shells ; Lignocellulosic feedstock ; Water gas shift

nije evidentirano