The release of compounds of K with producer gas during biomass gasification is known to play significant roles in fouling and high-temperature corrosion in boilers and high-temperature heat exchangers as well as blades in gas turbines that use producer gas as fuel. These phenomena are a major setback in the application of biomass fuel in combination with advanced process conditions. Updraft gasification provides gas filtering by the fuel bed with a gas cooling effect, conditions anticipated to create an avenue for K retention in the gasifier. The objective of this study was to determine the K retention potential of such gasifiers during wood gasification. Samples for the determination of the fate of K compounds included in the feedstock were collected from the generated producer gas using Teflon filters and gas wash bottles and also from wall deposits and ash residues. Analyses of samples were carried out using inductively coupled plasma–atomic emission spectrometry/mass spectrometry and X-ray diffraction methods. The finding was that about 99% of K was retained in the gasifier. K was found in the ash samples as a crystalline phase of K2Ca(CO3)2(s) (fairchildite). A possible reaction mechanism leading to the formation of K2Ca(CO3)2 is discussed in the paper. The 1% K understood as released, equivalent to 1200 ppbw content of K entrained in the producer gas stream, exceeds a known limit for application of the gas in conventional gas turbines. This would suggest application of the gas in an externally fired gas turbine system, where some limited K and other depositions in the heat exchanger can be relatively easy to handle.

Today the large scale introduction of biomass gasification is hampered by health, and environmental issues which present a major barrier in the deployment of this technology. The condensate in particular resulting from producer gas cooling before use in gas engines is highly toxic and carcinogenic which, if not adequately controlled, can lead to detrimental impacts on human health and the environment. The study was therefore aimed at assessment of pollution levels resulting from biomass gasification organic condensates. The study involved assessing the concentration of polycyclic aromatic hydrocarbons (PAHs) and BTEX (i.e. benzene, toluene, ethylbenzene and xylene) in the condensate deemed toxic and carcinogenic, mention their impact on human health and the environment as well as recommend measures aimed at minimizing pollution levels resulting from biomass gasification.The gasifier installation at Makerere University was run in downdraft mode using maize cobs as biomass fuel. The producer gas was cooled using a water cooled condenser connected to the exhaust pipe of the gasifier. The condensate was then transferred into sampling bottles made of opaque glass to minimize photochemical reactions in water samples and preserved in a cooler at 2 o C to 6 o C until the time for analysis to minimize volatilization and bacterial degradation of the hydrocarbons. The capillary gas chromatography with mass spectrometric detector (CGCMSD) was used to analyze the condensate for the selected hydrocarbons.The procedures involved preparation of PAHs and BTEX standard solutions using standard mixtures and internal standards, calibration of the CGCMSD, extraction of the aromatic hydrocarbons using hexane, performing a surrogate analysis to . Acenaphthylene, acenaphthene, fluorene, phenanthrene and anthracene were not detected in the condensate by the CGCMSD due to their concentration levels being below the detection limit of the CGCMSD. The concentrations of naphthalene and xylene were considerably high compared to the recommended permissible exposure limits thus posing risks on both human health and the environment. It is therefore important to treat the condensate before disposal to the environment. On the other hand, the concentrations of benzene, toluene and ethylbenzene were below the permissible exposure limit and therefore for this study, the liquid effluent was considered to meet the regulatory standards. The recommendations aimed at minimizing pollution levels during biomass gasification were also discussed.