Scale up studies for the simultaneous removal of colorants and protein from a refinery sugar liquor using powdered activated carbon - a pilot plant study

Authors: Lima, Isabel; JIMENEZ, ANA - Carboua International; Eggleston, Gillian; PABON, BENHUR - Carboua International; SARIR, EMMANUEL - Carboua International; THOMPSON, JACK - Lsr Refinery, Llc

Submitted to: International Sugar Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/30/2020
Publication Date: 7/5/2020
Citation: Lima, I.M., Jimenez, A.M., Eggleston, G., Pabon, B., Sarir, E., Thompson, J. 2020. Scale up studies for the simultaneous removal of colorants and protein from a refinery sugar liquor using powdered activated carbon - a pilot plant study. International Sugar Journal. 122(1459):488-495.

Interpretive Summary: Pilot plant studies were carried out to scale up laboratory results reporting on the ability of powder activated carbon (PAC) in removing multiple impurities from sugarcane refinery streams. Prior laboratory studies identified a set of ideal treatment conditions to remove colorant compounds, soluble and insoluble starch, and residual amylase from refinery liquors (syrups). The pilot plant includes a pre-coat tank, a filter unit with filter bag insert, as well as feed and product tanks. Feed tank temperature is maintained via indirect heat exchange coils. Clarified refined syrup, at 75 or 80°C was spiked with either 0.5 or 1 ppm of high temperature stable a-amylase and treated with powdered activated carbon (PAC) at doses of 250, 500, or 750 ppm on a Brix basis. PAC effectiveness to simultaneously remove various impurities was monitored over 45 min residence time to determine best performance conditions and confirm prior laboratory results. Amylase (protein) removal improved with PAC application rate, with an overall amylase percent removal (across residence times and amylase doses) of 81.8%, 84.8%, and 94.0% respectively for 250, 500, and 750 ppm of PAC at 75°C. Highest percent color removal of 37.9%, 42.5% and 55.1%, respectively for color compounds measured at pH 4, 7, and 9, occurred for 750 ppm PAC and 45 min residence time, across both syrup temperatures and amylase doses. A concomitant decrease in the indicator value (I.V.) of up to 21% at the 750 ppm PAC dose, was also observed. PAC was also able to decrease turbidity by 42% on average. The small-scale pilot plant unit can bridge laboratory data to larger scale studies and report valuable information prior to large-scale industrial trials.

Technical Abstract: Pilot plant studies were carried out to scale up laboratory results reporting on the ability of powder activated carbon (PAC) in removing multiple impurities from sugarcane refinery streams. Prior laboratory studies identified a set of ideal treatment conditions to remove colorant compounds, soluble and insoluble starch, and residual amylase from refinery liquors (syrups). The pilot plant includes a pre-coat tank, a filter unit with filter bag insert, as well as feed and product tanks. Feed tank temperature is maintained via indirect heat exchange coils. Clarified refined syrup, at 75 or 80°C was spiked with either 0.5 or 1 ppm of high temperature stable a-amylase and treated with powdered activated carbon (PAC) at doses of 250, 500, or 750 ppm on a Brix basis. PAC effectiveness to simultaneously remove various impurities was monitored over 45 min residence time to determine best performance conditions and confirm prior laboratory results. Amylase (protein) removal improved with PAC application rate, with an overall amylase percent removal (across residence times and amylase doses) of 81.8%, 84.8%, and 94.0% respectively for 250, 500, and 750 ppm of PAC at 75°C. Highest percent color removal of 37.9%, 42.5% and 55.1%, respectively for color compounds measured at pH 4, 7, and 9, occurred for 750 ppm PAC and 45 min residence time, across both syrup temperatures and amylase doses. A concomitant decrease in the indicator value (I.V.) of up to 21% at the 750 ppm PAC dose, was also observed. PAC was also able to decrease turbidity by 42% on average. The small-scale pilot plant unit can bridge laboratory data to larger scale studies and report valuable information prior to large-scale industrial trials.