Advanced Distillation Technologies for Solvent Recovery

Distillation is the process of separating a liquid mixture into its components by exploiting differences in volatility through partial evaporation and subsequent condensation. Every day, industrial production processes around the world generate thousands of tonnes of liquid mixtures composed of different components. The recovery of valuable liquids of high purity such as water and solvents from waste water or production processes, and their reuse within the process, saves on operating and waste disposal costs while providing significant environmental benefits through the conservation of energy and raw material resources. Where high mass transfer rates are required, distillation generally offers an economical and effective solution for separating liquid mixtures. It is particularly used where high purities must be achieved or where multi-component mixtures need to be separated. Today, the recovery of solvents and precipitates for repeated use within the process is carried out where energy requirements are extremely low or where energy can be effectively utilised in subsequent applications. In addition, the thermodynamic properties of the materials to be recovered, their integration into the overall production process and the desired facility capacity are among the key factors that play an important role in the selection of the distillation system to be used. Isopropanol Recovery The use of alcohols, particularly isopropanol, as a precipitation medium in the production of biopolymers such as pectin, carrageenan or xanthan is one of the methods frequently used to separate these polymers from water, biomass or other impurities. After precipitation and subsequent mechanical separation, isopropanol must be recovered from the waste material stream containing water. For such applications where there are large differences between the boiling temperatures at the bottom of the columns and the condensation temperatures of the vapours at the top, GEA offers a unique and patented distillation solution that provides energy savings. A split-column design is used for efficient heating of the rectification and stripping sections with Mechanical Vapour Recompression (MVR). Compared to an MVR-heated single-column system, this design approach achieves approximately 50% energy savings and requires no additional heating steam for normal operation.

Distillation plant with mechanical vapour recompression for solvent recovery from biopolymer production

Ethanol Separation

Ethanol is one of the most widely used organic solvents. Depending on specific requirements, GEA supplies distillation units for ethanol recovery to all operations, from small batch systems to highly efficient distillation plants. One of our areas of expertise is the design of plants where energy is optimally utilised, and in doing so we also take into account other units in the operating line; for example, the separated ethanol vapour is used to increase the concentration in waste streams through evaporation. Different plants with annual capacities ranging from 100 to 100,000 tonnes have been installed. In addition to separation, GEA also supplies additional purification and dehydration units for ethanol processing.

Recovery of High Boiling Point Solvents in Aqueous Solutions

The recovery and purification of high boiling point solvents in aqueous solutions is a challenging process and requires special expertise. The components are separated and purified in different process steps in a sequential manner according to their vapour pressures. The first step is the evaporation and purification of water in combined evaporation and distillation plants. In the second step, the solvent must be separated from the remaining mixture and purified in a rectification column. In the final step, the concentration of the waste stream is further increased in specially designed evaporation/rectification units to recover the remaining amount of valuable solvent and to reduce waste to a minimum. Mass Flow Diagram for Different Process Streams in a Solvent Recovery Plant for Aqueous Solutions High boiling point solvents such as DMAc (N,N-dimethylacetamide) or NMP (N-methyl-2-pyrrolidone) are used not only in wet-spinning processes for various synthetic fibres (acrylic fibre, artificial silk, aramid fibre, etc.) but also in capillary membranes in medical applications. In this process, the polymer is dissolved in solvent before spinning. After the spinning process, the solvent is separated from the fibre together with water. The solvent is highly diluted and contains fibre particles. Direct reuse is not possible. However, the disposal of contaminated solvent is not feasible for both ecological and economic reasons. Thanks to GEA's multi-effect distillation (MED) technology, manufacturers can recover solvents at high purities of up to 98% while also minimising energy consumption. Furthermore, the process water required for the precipitation step is recovered and can be recirculated. For over 100 years, GEA has been providing different plant designs and technologies to meet customer needs, taking into account specific project requirements. Multi-effect distillation technology has consistently been used as one of GEA's energy-saving solutions, in most cases in combination with mechanical vapour recompression or heat pump technology. Small batch systems and continuous single-column units complete our product portfolio. Our experienced engineering team is supported by our process technology and research and development centre, which utilises state-of-the-art tools and laboratories for testing as well as pilot operating facilities. İlker Damar - Sales Manager, Industrial Applications GEA Turkey Dipl. Ing. Ralf M. Leibig - Project Manager, Distillation Technologies GEA Germany