(485f) Development of an Interactive Software Tool for Designing Industrial Solvent Recovery Processes

The chemical industry was reported to be the world’s second-largest manufacturing sector in 2017, and its production is projected to double by the year 2032 (United Nations Environment Programme 2019; Vlaeminck 2022). With production growth there is an increase in subsequent waste generation, that leads to many environmental concerns. One of the largest contributions to process waste is solvents, since they are used in most chemical operations as a reaction medium, for selective dissolution, extraction or dilution agents. Due to the typical single-use operations with no recovery and recycle, a sizable amount of solvent waste is generated. In addition, even more waste accumulates due to process inefficiencies such as inefficient mixing, or inappropriate process equipment. The three most common methods to handle solvent wastes are on-site disposal, off-site disposal, and incineration (J. Raymond, Stewart Slater, and J. Savelski 2010). All three of these methods pose great environmental risks, yet are commonplace, since all methods are easy to use for large-scale material disposal. One greener alternative to these methods is solvent recovery, which attempts to recycle the material back into the process rather than releasing it into the environment. However, solvent recovery is not typically used due to complications in achieving the required purity set by regulatory standards for pharmaceutical and chemical industries. Furthermore, solvent recovery requires additional separation infrastructure, demanding investments in an already established chemical plant. To this end, finding a simple approach to solvent recovery requires a multi-level framework aimed at achieving the required purity while keeping other aspects in mind such as capital needs, environmental benefits, and comparison to traditional disposal methods. Often times, professional engineers find this task daunting due to the multitude of recovery technologies available and no clear guidance system or tool to assist them in comparing multiple recovery options. If such a tool existed, professional engineers can easily access the different possible solvent recovery options and start a shift towards an environmentally friendly waste handling method rather than incineration, on-site disposal, or off-site disposal.

Thus, our team is working towards creating such a user-friendly tool by combining knowledge of chemical and solvent properties, separation techniques, plant design, modeling, simulation and optimization methods. As Figure 1A depicts, this tool will provide a greener alternative, but also give a process engineer the ability to recycle used solvent back into the plant, which is economically favorable to purchasing fresh solvent.

To account for the myriad of chemicals that can be found in waste streams, a robust framework is needed. The framework has a maximal process flow diagram which is broken into different stages of separations. Each stage is comprised of multiple technologies and is aimed at one area of separation. As a result, the process flow diagram develops a superstructure which gives a multitude of technology combination pathway options for any one solvent waste stream. By reviewing literature on existing separation techniques, we created four unique stages in the superstructure: Solid Removal, Recovery, Purification, and Refinement (Yenkie, Wu, and Maravelias 2017; Biegler 1997; Geankoplis 2003). Common and novel technologies are allocated to the different stages based on the components they can separate in terms of their physical and chemical properties. These properties are taken from a comprehensive chemical database which is developed using sources such as the Design Institute for Physical Properties (DIPPR) (“DIPPR” 2012). The coding environment, General Algebraic Modeling Systems (GAMS), is used to model the separation units and process flows as a multi-objective optimization problem, to maximize the solvent recovered while minimizing total cost and environmental footprints (Chea et al. 2020; Yenkie et al. 2016). To make the framework easily accessible, a Graphical User Interface (GUI) is created in MATLAB with the GAMS code operating in the back end. As Figure 1B depicts, the GUI communicates with the GAMS code and chemical database, finding the optimal technology pathway from the user inputs.

The GUI allows for a user to input components and parameters that model the waste stream being considered. Through the connection between MATLAB and GAMS, the solvent recovery process can be modeled in the GUI with the specific input parameters. After executing the code, economic, chemical, and environmental factors are displayed for the user to consider. The tool breaks the economic costs into an annualized cost breakdown, utility costs, consumable costs, labor costs, and overhead costs. The chemical factors report the purity level for each component recovered and the amount of solvent the selected pathway recovered. Lastly, the environmental factors report the environmental impact of the selected pathway against common waste handling methods. Thus, this tool provides an accessible option for engineers to develop a solvent recovery waste handling system for their chemical plant.