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The amount of precipitate and residue affects the timing of fuel filter blockage. This study develops a model for fuel filter blocking based on the Precipitate Measurement. Firstly, a modification of ASTM D 7501 for the Cold Soak Filtration Test (CSFT) measured the amount of precipitate in B20 fuel with variations of soaking temperatures and monoglyceride content in biodiesel. Then, a modified ASTM D 2068 for a filter blocking test (FBT) was conducted to correlate the impurities in the B20 fuel and the clogging limit effects represented by the change of pressure difference and time to reach a pressure drop of 30 kPa. Biodiesel B20 samples were prepared by adding monopalmitin so that each had a monoglyceride value of 0.2%, 0.4%, 0.6%, and 0.8% before blending with petroleum diesel. The modified CSFT showed that the amount of B0 impurity was almost zero. However, the amount of the B20 sample precipitate retained on the filter was higher when a lower soaking temperature and higher monoglyceride content was used in the biodiesel. Similar results in the modified FBT showed that the more impurities, the faster the pressure drop achieved a level of 30 kPa. A much shorter time was needed to reach the pressure drop of 30 kPa for B20 fuel samples with the impurities present in both test powders and precipitate compared to those for the B20 fuel samples with a single type of impurity (either test powders or precipitate). The fuel filter clogging time could also be predicted using the graph of fuel filter clogging time vs. the precipitate weight of B20 fuel derived from the FBT test if the precipitate weight had already been determined by the precipitation test (modified CSFT). The simulation model using Ergun’s equation for the FBT of the B20 fuel could also show similar results to that of the FBT experiment, with the difference (averaged errors) ranging from 4.15% to 5.79%.

Simultaneous saccharification and fermentation (SSF) configuration offers efficient use of the reactor. In this configuration, both hydrolysis and fermentation processes are conducted simultaneously in a single bioreactor, and the overall processes may be accelerated. However, problems may arise if both processes have different optimum conditions, and therefore process optimization is required. This paper presents a mathematical model over SSF strategy implementation for producing xylitol from the hemicellulose component of lignocellulosic materials. The model comprises the hydrolysis of hemicellulose and the fermentation of hydrolysate into xylitol. The model was simulated for various process temperatures, prior hydrolysis time, and inoculum concentration. Simulation of the developed kinetics model shows that the optimum SSF temperature is 36 °C, whereas conducting prior hydrolysis at its optimum hydrolysis temperature will further shorten the processing time and increase the xylitol productivity. On the other hand, increasing the inoculum size will shorten the processing time further. For an initial xylan concentration of 100 g/L, the best condition is obtained by performing 21-hour prior hydrolysis at 60 °C, followed by SSF at 36 °C by adding 2.0 g/L inoculum, giving 46.27 g/L xylitol within 77 hours of total processing time. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).