(73d) Mathematical Modeling of a Transient 1D Entrained-Flow Texaco Gasifier Using Aspen Custom Modeler

Coal-fired integrated gasification combined cycle (IGCC) power plants produce synthesis gas that is subsequently converted into electricity through combustion in a gas turbine. Several mathematical models have been developed to study the processes taking place inside the gasifier. Such models range from simple one-dimensional steady-state models to sophisticated transient three dimensional CFD-based models that incorporate turbulence effects in the reactor. The practical operation of the gasifier is dynamic in nature but most one dimensional and some higher dimensional models are often steady state and although many higher order CFD based models are dynamic in nature, they are too complicated with many process parameters to be used directly in design and scale-up studies. Thus lower dimensional models are still useful in these types of studies.

In the current study, a one dimensional transient model for the entrained flow GE/Texaco type gasifier is developed using Aspen Custom Modeler ®, which is an equation-based industrial simulator for creating, editing and re-using models of process units.

The current model is based on mass, momentum and energy balances for the solid and gas phases that exist in the gasifier. The chemical reactions considered in the model are the devolatilization/pyrolysis, gasification and combustion, and homogeneous gas-gas reactions. This highly nonlinear system of equation is solved using the inbuilt Newton-based non-linear solvers.

The results to be presented are the transient and steady state solutions to our model equations giving the velocity, concentration (mass fractions), and temperature profiles in the gasifier. Parametric studies results for which the effect of the process parameters on the performance of the gasifier is investigated would be presented for different types of coals. Comparisons of the current model results to available Texaco pilot plant data and other published models will also be made.