Modeling and Economic Assessment of Integrated Gasification with Sorbent CO2 Capture
Creators: name: Esmaili Darki, Ehsan
Publisher: name: Graduate Studies
Year: 2014
Subjects: subject: Energy
subject: Engineering--Chemical
subject: Engineering--Mechanical
subject: Gasification
subject: CO2 Capture
subject: Process Modeling
subject: Economic Assessment
subject: Computational Fluid Dynamics (CFD)

description: Uncertainty in the price of conventional energy sources, such as oil and natural gas, along with increasing evidence of climate change have rekindled great interest in the development of processes that can produce clean synthetic gasses (hydrogen and carbon monoxide). In this context, gasification of carbonaceous solids followed by syngas conversion processes have taken a center stage. In the first part of this study, two approaches for simulation of coal gasification process in a bubbling fluidized bed reactor are studied. The first method is an equilibrium model based on minimization of Gibbs free energy which predicts the thermodynamic limits of the product gas composition for an air-blown coal gasifier. The thermodynamic equilibrium model is further modified by introducing an approach temperature which corresponds to the deviation from equilibrium condition. The major components in produced gas, H2, H2O, CH4, CO, CO2, and N2 have been determined and compared with the pure equilibrium modeling as well as the experimental data. In the second approach, an Eulerian-Eulerian computational fluid dynamics (CFD) simulation has been developed to predict the hydrodynamic behavior of the fluidization regime in the gasifier. The predicted hydrodynamic parameters from the CFD simulation are integrated into the kinetics of gasification chemical reactions taking place in the bubble, cloud and emulsion phases. The comparison of the predicted results with experimental measurements showed that most of the predicted molar gas compositions in the produced gas were within 15% of the experimental data. The model was further used to predict the performance of the gasifier at different operating conditions. In the second part of the study, an Integrated Gasification Combined Cycle with in-situ CO2 capture using lime (IGCC-SCC) has been developed in order to assess the application of gasification process in power generation industry. Aspen Plus is used to simulate the detailed heat and material balance of the process. The base case was defined with 3000 tons of coal feed per day in order to compare the overall performance results of the proposed process with industrial gasification coal-to-power processes. Furthermore, a high level economic model is prepared in order to evaluate the economic viability of IGCC-SCC plant in comparison to GE Energy and Shell Convective gasification processes for converting coal to power with the same feed coal capacity in U.S. Total capital cost (CAPEX) of the IGCC-SCC facility is estimated to be USD 1,082,869,813 with an annual operating cost (OPEX) of USD $ 187,818,045. An indicative Internal Rate of Return (IRR) and Payback Period (PP) of the IGCC-SCC plant is compared with the IRR and PP of the same size GE Energy and Shell Convective facilities. An after tax IRR of 14.4 % which translates to 9.1 years of Payback Period is estimated for the IGCC-SCC plant. A sensitivity analysis is also conducted on the economic results in order to identify the relative importance of the key economic variables driving the project returns, and to quantify the impact of changes in the assumed values on the IGCC-SCC economics.