2024 AIChE Annual Meeting

(373ab) Industrial Volatile Organic Compound (VOC) Capture Performance Evaluation Via Dynamic Simulation, MILP Scheduling and Economic Analysis

Authors

Gerogiorgis, D. - Presenter, University of Edinburgh
Tzanakopoulou, V. E., University of Edinburgh
Pollitt, M., GlaxoSmithKline (GSK)
Castro-Rodriguez, D., University of Newcastle upon Tyne.
ABSTRACT

Volatile Organic Compounds (VOC) are in the heart of primary pharmaceutical manufacturing, as solvents for reactions and separations. The release of VOC emissions is strictly regulated, due to their serious repercussions for climate, ecosystems, and human health (UK Department of Environment, Food and Rural Affairs, 2023). While it has become customary to measure environmental footprint of processes in terms of CO2 emissions, it is vital to start including VOCs in these metrics for pharmaceutical and chemical industries. Solvent substitution is rarely a realistic option due to the risk associated with regulatory re-approval of established medicine lines.

End-of-pipe VOC emission capture systems emerge as reliable and environmentally-responsible solutions to this problem. Gas effluent mitigation via adsorption is an established VOC abatement technique due to its ability to filter large volume streams with low pollutant concentrations at high energy efficiency. However, activated carbon beds are irregularly and quickly saturated due to feed variability from manufacturing campaigns, thus prompting frequent and costly adsorbent material regeneration outsourcing. Dynamic modelling and Mixed Integer Linear Programming (MILP) are key to the digital transformation of the manufacturing industries towards increased system monitoring, predictability, and efficiency maximisation at an even lower cost (Akbar & Irohara, 2018).

A validated non-isothermal, multicomponent adsorption model using the Langmuir Isotherm for equilibrium and the Linear Driving Force model for gas-solid mass transport is first used to examine multicomponent VOC mixture breakthrough (Tzanakopoulou et al., 2023; 2024). Three binary VOC trace mixtures (hexane-acetone, hexane-dichloromethane, hexane-toluene) are examined for four different bed lengths (0.25, 0.50, 0.75, 1 m) and six different superficial velocities (0.1, 0.2, 0.3, 0.5, 0.7, 0.9 m s-1). Dynamic simulations reveal preferential adsorption of acetone and toluene over hexane, and hexane over dichloromethane, as well as breakthrough onset patterns on coconut derived activated carbon. Temperature rise is minimal in all cases due to the trace concentrations examined, while pressure drops become significant at longer column lengths and higher flow rates, as expected by Ergun’s equation. Moreover, a key breakthrough onset metric is introduced (onset time per unit column length), indicating different bed operation regimes based on multicomponent mixture composition.

Mixed-Integer Linear programming is the established state of art for batch production scheduling. This work also presents the development and application of an MILP case study in a pharmaceutical industry example, using cloud software, CProS (Misra et al., 2022). Specifically, the MILP algorithm finds the optimal production schedule for a 16-task and 35-state state-task-network (STN) with the objective of makespan minimisation. The problem is solved for five different VOC mixture emission scenarios, informed by gPROMS dynamic simulation metrics. In each of the five problems, adsorption task duration is mixture-specific and dependent on breakthrough onset calculations. Finally, an economic evaluation of the adsorption process is performed based on industrial data to assess the operational expenditure associated with different mixture feed, bed and market condition scenaria.

LITERATURE REFERENCES

  1. Akbar, M., Irohara, T. (2018). Scheduling for sustainable manufacturing: A review. Journal of Cleaner Production, 205, 866-883.
  2. Belkhir, L., Elmeligi, A. (2019). Carbon footprint of the global pharmaceutical industry and relative impact of its major players. Journal of Cleaner Production, 214, 185-194.
  3. Department of Environment, Food and Rural Affairs, UK Government. (2023). Emissions of air pollutants in the UK – non-methane volatile organic compounds (nmvocs) - gov.Uk. Retrieved 11 September 2023 from https://www.gov.uk/government/statistics/emissions-of-air-pollutants/emissions-of-air-pollutants-in-the-uk-non-methane-volatile-organic-compounds-nmvocs
  4. Misra, S., Buttazoni, L. R., Avadiappan, V., Lee, H. J., Yang, M., Maravelias, C. T. (2022). CProS: A web-based application for chemical production scheduling. Computers & Chemical Engineering, 164: 107895.
  5. Tzanakopoulou, V.E., Pollitt, M., Castro-Rodriguez, D., Costa, A., Gerogiorgis, D. I. (2023). Dynamic modelling, simulation and theoretical performance analysis of volatile organic compound (VOC) abatement systems in the pharma industry. Computers & Chemical Engineering, 174: 108248.
  6. Tzanakopoulou, V.E., Pollitt, M., Castro-Rodriguez, D., Gerogiorgis, D.I. (2024). Dynamic modelling and simulation of multicomponent Volatile Organic Compound (VOC) abatement systems. Industrial & Engineering Chemistry Research (in press).
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