Crude glycerin from storage is first heated to 194 degrees Fahrenheit on a plate heat exchanger, using energy recovered from the purified glycerin stream, plus live steam. After a safety filtration to protect the downstream processing steps from fouling by suspended materials, the hot and clean crude glycerin is carefully degassed before entering a chromatographic separator.
The chromatographic separator combines the sequential simulated moving bed technology with Ambersep BD50, a high-performance chromatographic separation resin from Rohm and Haas, to purify crude glycerin with a high salt composition.
Such a system has high productivity and consumes small quantities of water for the separation of the salt fraction from glycerin.
Due to the systematic recycling of the condensates produced during the reconcentration of the purified glycerin fraction, no source of freshwater is necessary for the operation of the chromatographic separator during normal operations.
The Ambersep BD50 glycerin purification system includes the option to concentrate and crystallize the salt fraction coming out of the separator. The raffinate stream contains the salts, other organic impurities (color and free fatty acids), and the minor fraction of glycerin not separated by the sequential simulated moving bed chromatography unit. The raffinate is processed in an evaporator/crystallizer unit, affording the recovery of the salts in a crystalline form and a “secondary glycerin” having a similar composition to the crude glycerin input. This solution avoids the production of effluents in the glycerin purification plant.
Depending on the required purity of the final glycerin, it is possible to produce a purified glycerin product with 99.5 percent purity or to add a polishing step employing an ion-exchange demineralization unit which enables the end-user to produce a high-quality glycerin product with 5 parts per million to 10 parts per million salt content.
The degree of polishing of the refined glycerin can be adjusted depending on the final application. One of the features of this process compared to the conventional distillation route is its low energy requirement. The Ambersep BD50 system does not require the vaporization of glycerin. Water is used for the chromatographic separation and therefore the energy consumption is essentially limited to the removal of water from the purified glycerin after purification.