Plasma-Assisted Biomass Gasification with Focus on Carbon Conversion and Reaction Kinetics Compared to Thermal Gasification

Abstract

Compared to conventional allothermal gasification of solid fuels (e.g., biomass, charcoal, lignite, etc.), plasma-assisted gasification offers an efficient method for applying energy to the gasification process to increase the flexibility of operation conditions and to increase the reaction kinetics. In particular, non-thermal plasmas (NTP) are promising, in which thermal equilibrium is not reached and electrons have a substantially higher mean energy than gas molecules. Thus, it is generally assumed that in NTP the supplied energy is utilized more efficiently for generating free radicals initiating gasification reactions than thermal plasma processes. In order to investigate this hypothesis, we compared purely thermal to non-thermal plasma-assisted gasification of biomass in steam in a drop tube reactor at atmospheric pressure. The NTP was provided by means of gliding arcs between two electrodes aligned in the inlet steam flow with an electric power of about 1 kW. Reaction yields and rates were evaluated using measured gas temperatures by the optical technique. The first experimental results show that the non-thermal plasma not only promotes the carbon conversion of the fuel particles, but also accelerates the reaction kinetics. The carbon conversion is increased by nearly 10% using wood powder as the fuel. With charcoal powder, more than 3% are converted into syngas.

Investigation of Non-Thermal Plasma Assisted Charcoal Gasification for Production of Hydrogen-Rich Syngas

“…The plasma generator supplies totally 0.9 kW power into the reaction. The measured operating current amplitude lying between 0.4 and 0.7 A shows clearly non-thermal characteristics, s. [15]. The drop tube reactor has around 0.1 m in diameter and 4 m in length.…”

“…10 kV between a gap distance of electrodes of around 2 mm. In the upper part of the window zone, in which two rectangular quartz glasses are installed, the generated fluctuating plasma arc can be observed and measured optically [14][15], in which the results showed no substantial deviations in gas temperature between NTP and thermal cases.…”

“…The test-rig is explicitly described in a previous publication [15]. Figure 1 presents a general overview of the used test facility.…”

Overview of Electric Field Applications in Energy and Process Engineering

“…Recent work on plasma gasification of biomass can be found in Ref. [106] which is also part of this special issue.…”

“…Biomass pyrolysis and gasification using plasma is a relatively new technique and only few laboratory investigations using biomass feedstock have been reported in the literature [104][105][106]. In comparison to coal, biomass has a large H/C ratio, a higher volatile content and a low ash content which favors a better product yield from plasma pyrolysis [104].…”