We propose a modeling framework for stable simulation of multi-phase reactor systems operating at thermodynamic equilibrium. The model framework can be used to determine system characteristics, explore parameter sensitivity and test control system strategies. The thermodynamic equilibrium assumption and the use of reaction invariants make it computationally inexpensive. We show that the feedback control approach based on the overall inventories of the system can be effectively used for improved performance of such reactor systems. Two multi-phase reactor systems - the vapor recovery reactor used in carbothermic aluminum reduction and the gasification reactor used in IGCC are considered to demonstrate the efficacy of the proposed modeling and control approach. (C) 2011 Elsevier Ltd. All rights reserved.