Abstract
The processing of large quantities of water in biorefining processes can lead to immense costs for heating, evaporation, and wastewater disposal. These costs may prohibit the exploitation of alternative products, e.g., xylooligosaccharides from straw, which are regarded as too costly. A new counter-current extractions method is proposed that aims at low solvent (water) consumption, as well as high yields and extract concentrations. This process was evaluated with suspension extraction experiments with steam pretreated wheat straw and the process window analysis based on a mass balance for a washing and a leaching scenario. The latter was conducted with two other suspension extraction processes as a comparison. The equilibration time was found to be well below 10 min. While the suspension extraction with and without recycling need to be designed to achieve a high yield or a high concentration and low solvent consumption, the proposed extraction method can reach all three simultaneously. Thus, this new process is evaluated as a potential method to spare water and downstream costs and allow new processing pathways in second-generation biorefineries.
Highlights
Solid–liquid extractions play an essential role in biorefining processes
We propose a new continuous counter-current, solid–liquid extraction process based on two or more stages of suspension extraction in stirred tanks and mechanical dewatering devices, for example, screw presses
The solute mass transport rate from the particle interior to the particle outside is of great importance in an extraction process
Summary
Solid–liquid extractions play an essential role in biorefining processes. They can be applied to remove the substrate’s contaminants or gain a product after (pre-) treatment. In both applications, solvent consumption, most often water, is a significant concern. Low water consumption will not allow a high extraction yield. Processing large quantities of water leads to space-consuming vessels, pumping capacity demand, heat demand to reach the process temperature and evaporation of dilute streams, and high wastewater costs. This work proposes a new counter-current, solid–liquid extraction process that aims to reach high extractions yields, high extract concentrations, low solvent consumption, and small space demand
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