Gasification has been used in industry on a relatively limited scale for many years, but it is immerging as the premier unit operation in the energy and chemical industries. The switch from expensive and insecure petroleum to solid hydrocarbon sources (coal and biomass) is occurring due to the vast amount of domestic solid resources, national security and global warming issues. Gasification (or partial oxidation) is a vital component of “clean coal” technology. Sulfur and nitrogen emissions can be reduced, overall energy efficiency is increased and carbon dioxide recovery and sequestration are facilitated. Gasification units in an electric power generation plant produce a fuel gas for driving combustion turbines. Gasification units in a chemical plant generate synthesis gas, which can be used to produce a wide spectrum of chemical products. Future plants are predicted to be hybrid power/chemical plants with gasification as the key unit operation.

The widely used process simulator Aspen Plus offers a rigorous gasifier model that handles solids, so steady-state design and optimization studies of processes with gasifiers can be undertaken. However, at the present time these models cannot be exported into Aspen Dynamics. Dynamic simulations are essential for the development of stable and agile plantwide control structures for energy and chemical processes.

This paper presents a simple approximate method for achieving the objective of having a gasifier model that can be exported into Aspen Dynamics. The basic idea is to use a high molecular weight hydrocarbon that is present in the Aspen library as a pseudo fuel. This component should have the same 1:1 hydrogen-to-carbon ratio that is found in coal and biomass. For many plantwide dynamic studies, a rigorous high-fidelity dynamic model of the gasifier is not needed. The proposed approximate model captures the essential macro-scale thermal, flow, composition and pressure dynamics.