LAUSR

Abstract The applications of liquid CO2 as a slurry fluid for solid carbon feedstock (coal and biomass sludge) and impacts on gasification performance have been investigated experimentally and analytically. CO2 for rheological control of solid fuel suspensions resulted in solids loading of nearly 66 weight% (wt%) closely matching the theoretical loading of 68 wt%. As a representative example, the measured viscosity for Illinois #6 coal slurry was found to be between 31 and 87 mPa-s using CO2 compared to 62–300 mPa-s using water for loadings between 50 and 66 wt% solids, respectively. Similarly, a viscosity reduction of nearly a factor of four was measured for a heavy oil sample from the Utica basin. The viscosity of the oil at 40 °C and 100 psi measured 10.25 Pa.s yet a 0.64 wt% CO2 yielded a viscosity of 2.42 Pa-s. The gasification performance investigation was done using ASPEN® Plus simulations to understand the impact of CO2 on Integrated Gasification Combined Cycle (IGCC) plant and the gasifier performance. The results show that co-feeding CO2 into the gasifier provides higher cold gas efficiency (CGE). The baseline cold gas efficiency using steam gasification (no CO2) of Powder River Basin (PRB) coal is 78.46% whereas two cases in which CO2 was added provided CGE values of 83.22 and 81.13%. These simulations were validated via a series of Drop Tube Reactor experiments and show good agreement. The carbon conversion during gasification at 1000 ℃ increased from ∼50% to ∼68% by addition of 30% CO2.