What are the key criteria for evaluating alternative solvents in plant design?

1 Solvent properties

The first criterion to consider is the physical and chemical properties of the solvent, such as density, viscosity, boiling point, polarity, solubility, acidity, and reactivity. These properties affect how the solvent interacts with the solute, the process equipment, and the surrounding environment. You want to select a solvent that has the desired properties for your process objectives, such as high selectivity, low toxicity, low volatility, and high stability.

2 Solvent availability

The second criterion to consider is the availability of the solvent, both in terms of quantity and quality. You want to ensure that the solvent you choose is readily accessible, reliable, and consistent in its specifications. You also want to avoid using solvents that are scarce, expensive, or subject to regulatory restrictions. You may want to explore the possibility of using renewable or bio-based solvents, such as ethanol, glycerol, or ionic liquids, that can reduce your dependence on fossil fuels and lower your carbon footprint.

3 Solvent recovery

The third criterion to consider is the recovery of the solvent, both in terms of feasibility and efficiency. You want to minimize the loss of solvent in your process and maximize its reuse or recycling. This can help you save costs, reduce waste, and improve environmental performance. You may need to design a solvent recovery system that can separate, purify, and regenerate the solvent from the process stream. You may also want to consider using solvents that can be easily recovered by simple methods, such as distillation, crystallization, or phase separation.

4 Solvent compatibility

The fourth criterion to consider is the compatibility of the solvent with the other components of your process, such as the reactants, products, catalysts, and equipment materials. You want to avoid using solvents that can cause undesired side reactions, degradation, corrosion, or fouling. You may need to test the compatibility of the solvent with the other components under different conditions, such as temperature, pressure, and pH. You may also want to consider using solvents that can enhance the performance of your process, such as by increasing the reaction rate, yield, or selectivity.

5 Solvent safety

The fifth criterion to consider is the safety of the solvent, both in terms of human health and fire hazards. You want to avoid using solvents that are toxic, carcinogenic, flammable, or explosive. You may need to assess the potential exposure, risk, and mitigation measures of the solvent in your process. You may also want to consider using solvents that have low toxicity, low flammability, and low explosiveness, such as water, supercritical fluids, or deep eutectic solvents.

6 Solvent evaluation methods

The sixth criterion to consider is the methods for evaluating the alternative solvents in plant design. You want to use a systematic and comprehensive approach that can compare the solvents based on multiple criteria and identify the best option for your process. You may use various methods, such as screening tools, simulation models, experimental tests, or multi-criteria decision analysis. You may also want to consider using methods that can incorporate the principles of process integration and intensification, such as by minimizing energy and material consumption, maximizing process integration, and optimizing process configuration.

7 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?