Application 1070 Photograph of an RBR reactor holding liquid prior treatment (dark blue) and after treatment (colourless, clear)

Decolourization of product residues

In the manufacture of liquid products, they may be coloured with appealing and brand-building colourants. During changes of batches, downtimes, or other regular day-to-day operations, coloured product residues are washed out of the process line. These are ideally recycled to minimize waste and maximize utility. For this, however, they need to undergo decolourization. Below we present a customer story in which the SpinChem RBR technoloy was deployed to decolourize viscous product residues.

The basis of the decolourization relies on the use of a rotating bed reactor (RBR) loaded with an adsorbent that is capable of binding and thereby removing the dissolved dye. The study commenced by screening for the most suitable adsorbent resin and the resin loading volumes needed for effective treatment. This was followed by investigations into the effects of processing temperature and stirring speed (see Figure 1).


Figure 1. Effect of temperature (left) and stirring speed (right) on decolourization progress in viscous media.


These findings indicate that an increase in temperature accelerates rate limiting internal diffusion phenonmena and thus positively effects processing speed. At the same time, we see a significant improvement when increasing the stirring speed from 400 to 600 rpm, but no further improvement beyond that. This, likewise, can be attributed to the fact, that above 600 rpm external mass transfer is not anymore rate limiting, but internal pore diffusion is.

Final laboratory tests were performed at optimized process conditions and treated an actual samples from customer storage tanks rather than model solutions of individual dyes. Photographes from the real test at laboratory scale are provided below in Figure 2 and 3.


Figure 2. Figure 2. Photographes of the liquid sample from the storage tank prior treatment with the RBR technology (left) and after processing (right).


Figure 3. The RBR filled with solid adsorbent prior treatment (left) and after processing (right).


With this, it was demonstrated that 100% removal of the visible colourant from the process fluid was possible. This constitutes another prime example for the straightforward deployment and highly effective use of the rotating bed reactor and how it helps to contribute to a more circular economy.

If you wonder how the RBR technology can simplify or add value to your overall process line, reach out to us!

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