Design and operation of a pilot plant for sugar beet extract colorants removal using powdered activated carbon.

Abstract

During sugar beet processing, molasses is subjected to slow moving bed chromatography to extract high value betaine and recover more sucrose. The result is commonly a high color sugar beet extract. Sucrose recovery can be increased by recycling this extract from the chromatography system back into the crystallization unit. However, this is only economically viable after it undergoes color reduction. Feasibility pilot plant studies were undertaken on the use of a high surface area powdered activated carbon (PAC) and diatomaceous earth (DE) to adsorb color compounds from sugar beet extract. Color compounds associated with beet extract either are generated during processing or are natural colorants. Experiments were performed using a batch decolorization process to maximize color removal and determine an optimal distribution of PAC either as a body feed or a pre-coat in a filter. A target of 50% color removal was achieved using 4,000 ppm of PAC with a recommended distribution of 75% as pre-coat in the filter and 25% as body feed in the process feed tank. A 50/50 distribution of PAC also produced consistent rate of color removal. PAC performance was slightly better for native colorants to sugar beet than factory colorants. Addition of PAC did not lead to sucrose loss neither had any negative effect on the pH of beet extract.