Fluidized bed gasification of coal–oil and coal–water–oil slurries by oxygen–steam and oxygen–CO2 mixtures

Polish bituminous coal, German brown (subbituminous) coal and rapeseed oil were selected for preparation of coal–oil slurry (COS) and coal–oil in water slurry (COWS) with content of coal about 50 mass%. Laboratory, electrically heated gasifier with fluidized bed (FB) of sand particles was used for the coal slurries gasification with steam–O2 and CO2–O2 mixtures (ER = 0.19–0.23) at temperatures between 800 and 925 °C. FB gasification with mixtures of O2/CO2 (CO2/dry fuel mass ratio 1–2.4) can generate producer gas with LHV values about 8–10 MJ/m3. The heating value of the dry, N2-free producer gas from CO2–O2 gasification is lower in comparison with gasification by steam–O2 mixtures at comparable conditions. The heating value of the producer gas is influenced by a relatively high content of methane, ethylene and BTX compounds. The yield of heavier tar compounds (excluding BTX) is high, exceeding 20 g tar/kg of dry German coal based COS and exceeding 36 g/kg of fuel for Polish coal based COS. Cold gas efficiency is higher for fuel gas from gasification of COS based on the German, subbituminous coal. FB gasification (ER ≈ 0.2) of the COWS prepared from the Polish coal (contents of coal, water and oil 47, 40 and 12 mass% respectively) reduces tar yield approximately to an half (related to gasification of the corresponding COS slurry), but simultaneously moderately reduces the heating value (LHV) of the dry, nitrogen free producer gas.