Effect of Temperature and Steam to Biomass Ratio on NO and SO₂ Formation in Palm Kernel Shell Catalytic Steam Gasification with In-situ CO₂ Adsorption

The emissions of NO_x and SO_x has given considerable attention in last few decades due to the severe problems associated such as acid rain which has harmful effect on aquatic animal life, plant and infrastructure. The topic is more concerned in coal combustion/gasification which contains high sulphur and nitrogen content. Biomass contains less sulphur and nitrogen content and thus threat to environment is less compared to coal. Power plants using biomass combustion and co firing of biomass with coal are of great concerned in the recent years to generate electricity. Moreover, the threat to the global warming due to the use of fossil fuel also encouraged biomass as the substitute source of energy. Therefore, the present study highlights the emissions of NO and SO₂ from local biomass feedstock i.e. palm kernel shell under catalytic steam gasification with in situ CO₂ adsorbent in pilot scale fluidized bed gasification system. Two important variables i.e. temperature and steam to biomass are considered. Temperature is varied from 600 °C to 750 °C while steam to biomass ratio is varied in the range of 1.5 to 2.5 (wt/wt). The lower reactor temperature (600 °C) contributes to the lower concentration of NO and SO₂ i.e. < 70 ppm and < 120 ppm, respectively, at steam to biomass ratio of 2.0, adsorbent to biomass ratio of 1.0 and catalyst to biomass ratio of 0.1. By increasing steam to biomass ratio from 1.5 to 2.5, the NO and SO₂ formation is decreased, and achieved the minimum concentration of 20 ppm and 100 ppm, respectively, at temperature of 675 °C, adsorbent to biomass ratio of 1.0 and catalyst to biomass ratio of 0.1. The results are then discussed and compared with commercial biomass power plants.