Experimental Study of Hydrodynamic Characteristics and CO2 Absorption in Producer Gas Using CaO-sand Mixture in a Bubbling Fluidized Bed Reactor

Abstract

Producer gas, from biomass gasification process can be used to generate power as an alternative to fossil fuel. Carbon dioxide (CO2) content in the producer gas is acts as a diluent gas resulted in low heating value. We used limestone (which is of rather wide occurrence in Malaysia) that consisted mainly of the mineral calcite (calcium oxide, CaO) as calcium based sorbent to absorb CO2 in the producer gas. Removing the CO2 from the producer gas will improved its heating value. In this paper, the first step was to study the behavior of CaO-sand mixtures in a cold model experiment. The effects of the CaO-sand mixtures, the CaO particle sizes, the volume flow rate and the pressure of air intake were investigated experimentally. Then, the hot model experimental was conducted to investigate CO2 absorption at the optimum condition obtained from the cold model experiment resulted. The CaO percentages of 50 and 40 in sand were found to have a good fluidization at all air pressures (200-600 kNm-2). In addition to that, the 1000 micron particle size of the CaO-sand mixture and the volume flow rate of air between 0.00025- 0.00092 m3s-1 were also found to give a good fluidization. In the hot model experiment, the best CO2 absorption occurred at 50 percent CaO mixture with simulated gas pressure of 300 kNm-2 and the volume flow rate of 0.00075 m3s-1 at 650-750°C in a bubbling fluidized bed reactor (BFBR).