This study applied oxygen-enrichment conditions to remove tar (the main problem in biomass gasification) and increase gasification efficiency. Experiments on oxygen-enrichment conditions were conducted at oxygen concentrations of 21%, 25%, 30%, and 35% in oxidants. This was expected to increase the partial oxidation reaction in gasification reactions, thus leading to thermal decomposition of tar in producer gas. The decomposed tar was expected to be converted into syngas or combustible gases in the producer gas. The results were as follows: Tar-reduction efficiency was 72.46% at 30% oxygen enrichment compared to the standard 21% enrichment condition. In addition, the concentrations of syngas and combustible gases in the producer gas tended to increase. Therefore, the 30% oxygen-enrichment condition was optimal, resulting in 78.00% for cold gas efficiency and 80.24% for carbon conversion efficiency. The application of oxygen enrichment into the lab-scale gasification system clearly reduced the concentration of tar and tended to increase some indexes of gasification efficiency, thus suggesting the usefulness of this technique in large-scale biomass gasification operations.

One of the problems commonly encountered during the gasification process for biomass is the agglomeration of residue associated with low efficiency, which occurs due to the use of low-quality fuels containing ash and alkali and alkaline earth metallic (AAEM) compounds. In this study, the empty fruit bunch (EFB), which is a byproduct of the palm oil industry that could potentially be used as fuel, was pretreated by washing with both tap water and a nitric acid solution (0.1 wt %) for different washing times to try to resolve this problem. The washing process decreased the ash content from 5.9 wt % to 1.5 wt % when all the washing pretreatments were employed, and over 80 wt % of the AAEM compounds, such as potassium (K), magnesium (Mg), calcium (Ca), and sodium (Na), were removed. Additionally, scanning electron microscopy (SEM) with X-ray diffraction (XRD) was used to identify the composition and surface characteristics of the agglomerations produced during gasification. The proportion of agglomeration measured in washed EFB decreased by over half compared to the agglomeration produced by unwashed EFB, regardless of the type of washing solution used. Previous research has shown that syngas yields of approximately 70% can be achieved at a temperature range of 900 to 1000 °C. Thus, washed EFBs were applied to a bubbling fluidized bed reactor (BFB), and the optimum experimental conditions (temperature and equivalence ratio, ER) were chosen as 900 °C and ER = 0.6. The syngas yield of the washed EFB gasification was higher than that of the unwashed EFB. Additionally, agglomeration was reduced from 8.7 wt % to 1.3 wt %.

Gaining energy independence by utilizing new and renewable energy resources has become imperative for Korea. Energy recovery from Korean municipal solid waste (MSW) could be a promising option to resolve the issue, as Korean MSW is highly recyclable due to its systematic separation, collection and volume-based waste disposal system. In this study, gasification experiments were conducted on Korean municipal waste-derived solid fuel (SRF) using a fixed bed reactor by varying the equivalence ratio (ER) to assess the viability of syngas production. Experiments were also conducted on coal and biomass under similar conditions to compare the experimental results, as the gasification applicability of coal and biomass are long-established. Experimental results showed that Korean SRF could be used to recover energy in form of syngas. In particular, 50.94% cold gas efficiency and 54.66% carbon conversion ratio with a lower heating value of 12.57 MJ/Nm3 can be achieved by gasifying the SRF at 0.4 ER and 900 °C. However, compared to coal and biomass, the syngas efficiency of Korean SRF was less, which can be resolved by operating the gasification processes at high temperatures. If proper research and development activities are conducted on Korean SRF, it could be a good substitute for fossil fuels in the future.

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