Assessing the energy consumption of the chemical recovery of GVL from the biomass fractionation spent liquor

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Kemian tekniikan korkeakoulu | Master's thesis
Chemical Engineering
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Master's Programme in Chemical, Biochemical and Materials Engineering
This study was aimed to assess the energy consumption for GVL solvent recovery from spent liquor from a biomass fractionation process. To carry out the thermodynamic simulation study of main components such as GVL, furfural, CO2 and water has been selected. Selection of thermodynamic models was decided based on the model decision tree and literature sources. The process was divided into three steps where liquid-liquid extraction was carried out to separate water from the GVL, compression of CO2 was carried out for recycling and finally, vacuum distillation of GVL and furfural was carried out. In the beginning, sensitivity analysis for vacuum distillation was conducted where different operating parameters such as no. of theoretical stages, feed composition, reflux ratio effect on GVL and furfural separation was studied using UNIF-DMD method. It was found that feed composition and reflux ratio play a significant role in separation efficiency. In addition, increasing reflux ratio is energy intensive. Another simulation case study conducted adding stripping columns prior to the distillation column allows the majority of GVL removal. Therefore, it enables less energy requirement to distillate the GVL and furfural with better separation yield. During CO2 compression simulation, it was assumed no impurities such as water and GVL entered the compressor. Threes stage compression simulation using REFPROP (Reference fluid properties equation state developed by NIST) was carried out to pressurize CO2 at 7.5 MPa and at outlet temperature of 298K which therefore recycles back to the liquid-liquid extraction column. Finally, liquid-liquid extraction was simulated based on the correlated measured distribution coefficients published prior to this work. In the process, it was studied enabling three stages of the decanting. Each separation stages uses a correlation based on the measured LLE. The out-stream of extracting columns showed a satisfactory result of removing the water phase. The overall GVL recovery process of energy consumption calculated based on the GVL feed mass flow rate and the calculated energy consumption is 6088.52 kJkg-1 GVL in the feed. The calculated results show that the compressor is the highly energy-intensive unit in the process which consumes approximately ≈92% of the total energy and requires 5657.15 kJkg-1 GVL in feed.
Sixta, Herbert
Thesis advisor
Pokki, Juha-Pekka
biomass, thermodynamic model, GVL, furfural, chemical recovery, energy
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