Model Identification of Fluid-Fluid Reaction Systems

S. Srinivasan, J. Billeter and D. Bonvin
Ongoing project (since 2012)

Dynamic models are keys to analyze, monitor, control and optimize reaction systems. These models are often based on first principles and describe the evolution of the states (numbers of moles, temperature and volume) by means of conservation and constitutive equations. The models include information regarding the underlying reactions (stoichiometry and kinetics), the transfer of species between phases (mass-transfer rates), and the operation of the reactor (initial conditions, inlet and outlet flows, operational constraints). The identification of reaction and mass-transfer rates represents the main challenge in building first-principles models for reaction systems. If the identification task is performed globally in one step via a simultaneous approach, all the rate laws need to be postulated a priori, thereby leading to a combinatorial type of approach and possibly to a large amount of correlation between the various identified rate parameters. In contrast, if an incremental approach is used, the extents of reaction and mass transfer can be obtained in a first step, with the advantage that each rate process can be investigated individually in a second step.

Recent work has proposed a variation of the incremental approach that identifies reaction and mass-transfer rates from concentration measurements in gas-liquid reaction systems. This novel incremental approach proceeds in two steps: (i) computation of the extents of reaction and mass transfer from concentration measurements without explicit knowledge of the reaction and mass-transfer rate laws, and (ii) estimation of the rate parameters for each rate individually from the computed extents using the integral method.

The present project, which is concerned with the further development of the extent-based approach for the incremental identification of fluid-fluid reaction systems, proposes the following three directions:

The first research direction concerns the investigation of fluid-fluid reactions with reaction in both fluid phases. The case with reaction and accumulation in the film will also be considered.

As the identification approach is data-driven, the second research direction deals with the optimal exploitation of data processing. The minimum number of species that need to be measured to reconstruct the various extents will be determined, and practical ways of meeting the requirement on the number of measured species will be investigated.

The third research direction considers the use of computed extents for the identification of reaction and mass-transfer laws and corresponding parameters. One industrially relevant fluid-fluid systems will be investigated in simulation, with the objective of assessing the potential of the proposed incremental approach and comparing its accuracy and computational effort with simultaneous approaches.

Keywords

Kinetic identification; Simultaneous identification; Incremental identification; Fluid-fluid reaction systems; Gas-liquid reaction systems; Extent of reaction; Extent of mass transfer

Publications

Extent-based incremental identification of reaction systems – Minimal number of measurements for full state reconstruction

J. Billeter; S. Srinivasan; D. Bonvin

2012. 104th Annual Meeting of the American Institute of Chemical Engineers (AIChE) , Pittsburgh (USA) , October 28 - November 2, 2012.

Simultaneous or incremental identification of reaction systems ?

J. Billeter; S. Srinivasan; D. Bonvin

2012. 4th Chemistry Congress of the European Association for Chemical and Molecular Sciences (EuCheMS) , Prague (Czech Republic) , August 26-30, 2012.