Infoscience

Poster

Methodology using process integration for identifying suitable Organic Rankine Cycles for waste heat valorisation

The identification of a suitable combined electricity production cycle depends on the heating and cooling requirements of the respective industrial process. Due to the large number of options an exhaustive enumeration of all the possibilities is not realistic. An optimisation based approach has to be adopted; it should be multi-objective and non-linear. The Methodology proposed is systematically generating a list of competing options, it follows the logic: - Analyse – Identifying heating and cooling requirements of the process. - Generate – Generation of options and scenarios how requirements can be satisfied. - Evaluate – Classify the generated options. During the different steps, several models are used. In order to identify the heating and cooling requirements of the process, Pinch analysis and the integration of the process have to be applied. The generation of the various options is done by a number of models. First an evolutionary algorithm fixes the decision variables for one option within the pre-defined constraints; a flow sheeting tool is used to calculate the thermodynamic states with the help of thermodynamic models. From the results, thermodynamic key performance indicators are calculated. A further model calculates the optimal thermal integration of the cycle configuration into the process; the results of this integration are used by sizing models to calculate the sizing of needed equipment. With the help of the sizes, cost models are used in order to calculate cost indicators and environmental models are used to calculate key environmental and LCA-indicators. With all the indicators related to every single configuration, the pareto-optimal solutions in regard to the pre-defined objectives are identified. As decision variables we identify the thermodynamic cycle configurations, in which the working fluid, fluid mixtures and compositions, multi stage or single stage cycles are proposed. In addition a second level of continuous decision variables, define the operating conditions for the selected cycle configuration. In addition to the objective function a set of performance indicators is proposed for the choice of the cycle as a decision support: 1. Quantitative indicators like efficiency (first and second principle), cost, CO2-equivalents, ozone depletion potential (ODP), LCA-Indicators 2. Qualitative criteria like flammability, toxicity

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