A flexible solution minimizing recycled fractions and start-up time, achieving the highest purity and FDA compliance.

What

At Polaris, we developed the Internal Reflux Distillation Column, a proprietary technology (covered through an international patent) that combines mass and heat transfer to efficiently separate and purify streams. Thanks to this innovative technology or through more traditional internals, such as trays or structured packing, Polaris can offer complete systems for batch or continuous distillation for different applications.

The proposed technologies are particularly efficient where a high quality distillate is required. Internal Reflux Column is specifically adopted in solvent recovery from complex mixtures, where the results of other available techniques are inadequate or result in an economically inconvenient recovery.

Our plants are versatile, allowing us to design the recovery process according to specific project requirements, on a case by case basis. We have successfully utilized internal reflux distillation for the following processes:

    • distillation at pressures less than, equal to, or more than atmospheric pressure
    • distillation under high vacuum
    • azeotropic distillation
    • extractive distillation
    • de-hydration by distillation with phase separation

For each of the above-mentioned processes, it is possible to fractionate with variable or constant internal reflux.

The plant configuration and the recovery method are established depending on the characteristics and quantities of the mixtures to be treated, and on quality specifications defined for the distilled products.

Why

Advantages of the technology

  1. Quick start-up: Steady-state operation is established as soon as the boiling vapors reach the column top, which is just a few minutes after the mixture starts boiling in the still. Conventional columns with external reflux, on the other hand, require a longer time to bring appreciable quantities of the product to specification, which does not occur until the moment of being totally refluxed.

  2. Minimization of recycled fractions: The Internal Reflux Distillation Column has no dead points or hold-up of distillate fractions, which could contaminate the next distillate fractions (like the external condenser, reflux accumulator, column distributor, or trays, etc.). This minimizes the transitory phases from one product to the next, and increases recovery yields.

    This is particularly impactful in an industry where challenges arise as a result of chemico-physical interactions and affinity between the compounds present in the mixture: the stronger the affinity, the more difficult the separation will be. Significant quantities of off-spec fractions are thus produced, reducing the recovery yield and the overall system net capacity, and increasing the costs of recovery.

    With the internal reflux column, it is possible to get selective separation of components of extremely complex mixtures, with similar chemico-physical characteristics, which are not economically separable otherwise.

  3. Reduced contamination: An automatic clean in place (CIP) cycle can be added by introducing steam in the column coils. This ensures that the very few tails of distillate product adhering to the column surface are physically evaporated and drained at the column bottom into a separate tank, which can be recycled. The overall quantities of “heads” and “tails” is thus significantly reduced – reaching levels that are less than 5 % of what remains after all other conventional distillation techniques.

    As this CIP does not produce waste water, the validation of the unit by the internal QHSE department, as well as by external agencies, is easier – in particular for multi-purpose units in pharmaceutical applications.

  4. Solvent Separation: The Internal Reflux Column can be designed for top-reactor (for organic synthesis) installation to separate solvents during distillation phases (even under a vacuum or during a reaction), remove solvents quantitatively and selectively based on their volatility, and leave only the solvents required by the process functionality inside the reactor. This result cannot be obtained with a simple condenser. Successful applications of the internal reflux column demonstrated an increased yield, quality, and production capacity.

  5. Reduced Waste Costs: The Polaris Internal Reflux Column can reduce the waste disposal costs of solvents and water mixtures, with a recovery otherwise not economically justified. In this case the system:

    • separates the organic solvents from water, producing mixtures that can be sold in the market as diluents or as fuel;
    • separates water with COD levels below regulated limits in order to send the same to public sewer or water collection;
    • minimizes the residual fraction of non-recovered mixtures to be disposed of by third parties.
  6. Heat Recovery: The cooling fluid that circulates in the column coils exits at a temperature close to the still temperature (at boiling point), which is an interesting thermal gradient that can be considered for heat recovery. On the other hand, especially in batch distillation systems, the heat recovery in a conventional column is usually not applicable due to a very low thermal gradient. This heat recovery decreases operating costs.

How?

Typical plant configuration

The plant is a multi-purpose rectification unit, which can be used for solvent recovery from several mixtures (mother liquors of synthesis processes, centrifugation, drying, etc.), is easy to operate, and is very flexible in use. The unit, in its more complete configuration, includes the still, the reboiler, the rectification column, condenser(s), a gravity phase separator, one vacuum pump (if under vacuum), related instrumentation, and a control system.

The plant is skid mounted and supplied as a packaged unit.

Polaris makes the preliminary process analysis in order to define and propose a balanced system configuration and method to recover products with optimized yields and quality, and at a better cost/benefit ratio.

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