Engineers at Algaeventure Systems(Marysville, Ohio; www.algaevs.com) have developed a system for separating liquids from solids and semi solids at very low energies. Originally targeted at harvesting and dewatering microalgae where the technology could remove a major cost barrier, the separation system can be used for a host of applications, including drying food-waste effluent, coal fines, hog manure, anaerobicdigester effluent and others.For example, Algaeventure’s system is capable of producing 1.0 kg/h of product cake from a concentrated (11 g/L) algal feed solution at an energy cost of $2.76/ton. Company tests indicate that, using a centrifuge, the same feed stream produced only 0.05 kg/h of product cake at an energy cost of $2,718/ ton.The technology consists of a polyester based membrane screen moving on a conveyor belt system that comes in contact with a capillary belt moving in the opposite direc-tion (diagram). “You’re basically ‘painting’a moving screen with the algae mixture,”explains Ross Youngs, Algaeventure CEO,“and using a surface-tension differential to pull out the water.”
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| Algaeventure System [source : www.che.com] |
After being gravity-fed onto the membrane, algae material passes over a capillarybelt that pulls water from the screened algae by capillary action. The dried algae are then scraped off the membrane as a flaky solid.The capillary belt is made from a proprietary combination of natural and synthetic fibers. Small-scale laboratory models have recently become commercially available,and slightly larger, prototype models arebeing used at partner sites. Algaeventure recently received a grant of close to $6 million from the U.S. Dept. of Energy’s (Wash-ington, D.C; www.energy.gov) ARPA-E (Advanced Research Projects Agency-Energy)program to develop the technology. Youngs says his company hopes to build productionmodels with throughputs 300% higher than the prototype.
