Marie-Noëlle Dumont

Mathematical modelling and design of an advanced once-through heat recovery steam generator

The once-through heat recovery steam generator (HRSG) design is ideally matched to very high temperature and pressure, well into the supercritical range. Moreover this type of boiler is structurally simpler than a conventional one, since no drum is required. In a conventional design, each tube plays a well-defined role: water preheating, vaporisation, superheating. Empirical equations are available to predict the average heat transfer coefficient for each region. For once-through applications, this is no more the case and mathematical models have to be adapted to account for the disappearance of the conventional economiser, boiler and superheater. General equations have to be used for each tube of the boiler, and the actual heat transfer condition in each tube has to be identified. The mathematical complexity as well as the number of equations is increased. A thermodynamic model has been selected and implemented to suit very high pressure (up to 240 bar), sub- and supercritical steam properties. Model use is illustrated by two case studies: a 180 bar once-through boiler (OTB) and a conventional boiler superheater and reheater.

Computer-Aided Design of Redundant Sensor Networks

Abstract A systematic method to design sensor networks able to identify key process parameters with a required precision at a minimal cost is presented. The procedure is based on a linearised model, derived automatically from a rigorous non-linear data reconciliation model. A genetic algorithm is used to select the sensor types and locations.

OPERATION OF A STEAM PRODUCTION NETWORK WITH VARIABLE DEMANDS MODELLING AND OPTIMIZATION UNDER UNCERTAINTY

Abstract The results of a collaborative study on the operation of a steam production network are presented in this paper. An overdesigned utility network is first modelled, based on plant measurements, where the network equipment is modelled through sets of conventional processing blocks. Data reconciliation methods are applied to determine design parameters, as turbine efficiencies, pump efficiencies etc. A multiperiod optimization framework is then employed to determine network operation and energy management schedules for variable demand levels and for uncertain process parameters.

Assessing the environmental potential of carbon dioxide utilization: A graphical targeting approach

Abstract Carbon Capture and Utilization (CCU) has the potential to reduce both greenhouse gas emissions and fossil fuel use. However, the conversion of CO 2 is intrinsically difficult due to its low energetic state. Thus, a positive environmental effect of a CO 2 -consuming reaction cannot be taken for granted. In this work, we therefore present a graphical method to identify promising reaction schemes using CO 2 as a feedstock. Reactant mixtures leading to minimal life-cycle greenhouse gas (GHG) emissions are determined. The optimal reaction schemes strongly depend on the reactants global warming potential (GWP); in the case of CCU, the future GWP values of CO2 and H 2 are particularly critical and subject to major uncertainty today. The graphical method therefore provides GWP targets for CO 2 capture and H 2 production technologies. The method is demonstrated for the production of methanol. Five optimal reaction schemes are identified depending on the GWP values of CO 2 and H 2 . Thus, four threshold relations for the GWP of CO 2 and H 2 are derived showing directly under which conditions the utilization of CO 2 as a feedstock is environmentally preferential.

Adaptation and testing of data reconciliation software for CAPE-OPEN compliance

Abstract The experience gained in the development of a CAPE-OPEN 1.0 thermo socket for the BELSIM-VALI software is presented. VALI is a data validation and reconciliation software that provides consistent mass and energy balances, reliable and accurate Key Performance Indicators and soft sensors. It is not a simulation software per definition, but rather a powerful equation based software that is used online, to monitor and manage the operations of different processes. VALI has its own thermodynamic database of chemical compounds (> 800 fluids, > 650 solids) and methods. After demands of our clients it was decided to make VALI compliant with other thermodynamic packages via a CAPE-OPEN 1.0 thermo socket. The source code of the VALI physical property modules had to be modified, to call the Material Object components instead of built-in thermodynamic functions (thermo socket). In the user interface, we had to develop a CAPE-OPEN thermo plugs viewer to allow the selection of a CAPE-OPEN thermo plug from our Graphical User Interface (GUI). Several case studies were analysed, with performance comparison between the native thermodynamic model, and properties obtained from several CAPE-OPEN thermoplugs. We will particularly analyse here the modelling of a gas liquefaction system and a distillation case study.

Recent Evolutions and Trends in the Use of Computer Aided Chemical Engineering for Educational Purposes at the University of Liège

Abstract The present paper addresses the evolution and perspectives in the teaching of CAPE methods in the Department of Chemical Engineering at the University of Liege. The transition that happened in the 90ies with the arrival of commercial software is highlighted, as the learning outcomes evolved from the ability of building programs to solve chemical engineering problems towards the ability to use complex commercial software and to understand their limitations. Moreover, CAPE methods were extended to non-dedicated CAPE courses, which is illustrated here by the goals and challenges of their use in courses like “Reactor Engineering” and “Life Cycle Analysis”. It was observed that students sometimes assume that CAPE softwares provide straightforward and trustworthy solutions without the need of understanding their mathematical bases and assumptions. Thus, solutions to make students aware of these limitations are proposed, including the creation of an integrated project focussing on complex multi-disciplinary issues, evidencing the need for critical input from the operator.