(651h) Framework for Economic Evaluation of Solvent Recovery Options

The concerns for environmental sustainability have increased with the rise in product demand in the chemical market. Chemical solvents have served as a valuable material in chemical processes for reaction, extraction, cleaning, and purification. These solvents can account for up to 90% of the process by mass and are often discarded after single use due to purification concerns. However, this practice is detrimental to the surrounding environment because toxic substances and emissions are released into the surrounding ecosystem. To date, reducing solvent waste release from chemical processes remains a challenge because of the convenience of using the existing infrastructure, such as direct disposal and incineration. The combined contribution of the current solvent usage rate and solvent disposal method, such as incineration, can release toxic chemicals to the environment [1], [2]. The US EPA has predicted that solvent emissions are expected to double by 2030 and reach 10 million metric tons of carbon dioxide equivalent [3]. The potential detrimental effects on the environment and safety considerations required the implementation and optimization of existing solvent recovery technologies to improve the greenness and overall sustainability of a given chemical process. Multiple unique greenness analysis methods were developed in the past decade to identify economic, environmental, and process efficiency indicators around specific processes [4]–[9]. Although these methods can eventually lead to sustainability and improve process efficiency and cost, there has not been an integrated method that accounts for factors concerning the environment, safety, and economics [1]. Three objectives were devised to accomplish this work. (1) Information on solvent waste and separation methods were collected in conjunction with industrial consultation about solvent recovery issues in current manufacturing practices. (2) A generalized solvent recovery framework was developed, which encompasses all the possible cases involving solvent recovery from a chemical waste stream to minimize cost, environmental impact, waste discharge, and encourage safe design and process operation. (3) The robustness of the solvent recovery framework was tested through a mathematical modeling approach in the General Algebraic Modeling Systems (GAMS) of various solvent recovery waste issues in the chemical industry.

Pfizer and Rowan University had carried out an investigation to recover and purify isopropanol (IPA) from the celecoxib process waste stream. The celecoxib process produces the API for an arthritis pain medicine known as Celebrex® [10]. The waste stream following the final purification stage in the pharmaceutical process contains a significant amount of recoverable IPA. However, the results of laboratory-scale distillation and extraction conducted at the plant site failed to reach the purity requirement.

In Figure 1, we developed the case-specific superstructure as a starting point for analyzing process efficiency, cost, and environmental impact of a solvent recovery pathway [11]. This superstructure includes a systematic representation of all the relevant technologies and flow streams in the IPA recovery paths. Mixed-integer non-linear programming (MINLP) problem was formulated and solved using the General Algebraic Modeling Systems (GAMS) with Branch-And-Reduce Optimization Navigator (BARON) as the solver. The optimized IPA recovery pathway from GAMS required the selection of pervaporation (PVP1) and ultrafiltration (UF2). Using a basis of 1000 kg/hr waste feed, this pathway will require a $524,000 annualized cost of operation and $0.14/kg solvent recovered. The continuous incineration of this waste stream requires an annualized cost of $8.1 million, which equates to $2/kg of solvent processed. All solvent recovery pathways are more economically viable than incineration because materials are being recovered and reused within the process.

We are in the process of solving additional case studies from other industrial sectors that will include economic evaluation, metrics from life cycle analysis with considerations for environmental impact associated with each recovery pathway. These case studies will be used to refine our existing solvent recovery framework, which can be translated into a computational tool that can optimize solvent recovery, reuse, and recycling in any solvent consuming industrial process.

References

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[9] E. J. Cavanagh, “A new software tool to environmentally and economically evaluate solvent recovery in the pharmaceutical industry,” 2014.

[10] C. S. Slater, M. Savelski, G. Hounsell, D. Pilipauskas, and F. Urbanski, “Green design alternatives for isopropanol recovery in the celecoxib process,” Clean Technologies and Environmental Policy, vol. 14, no. 4, pp. 687–698, Aug. 2012, doi: 10.1007/s10098-011-0433-6.

[11] J. Chea, A. Lehr, J. Stengel, M. J. Savelski, C. S. Slater, and K. Yenkie, “Evaluation of Solvent Recovery Options for Economic Feasibility through a Superstructure-Based Optimization Framework,” Industrial & Engineering Chemistry Research, Mar. 2020, doi: 10.1021/acs.iecr.9b06725.