High-temperature fermentation (HTF) of ethanol can reduce costs of cooling, sterilization, and related equipment compared to the costs of general ethanol fermentation. To realize HTF, however, there are various issues to be considered, such as the fermentation temperature upper limit for ethanol-producing thermotolerant yeast, the size of a fermenter that does not require cooling, and the effective temperature for suppressing microbial contamination. This study focused on these issues and also on downstream processes that exploit the advantages of HTF at temperatures exceeding 40 °C. The permissible size of a fermenter without cooling was estimated by simulating heat generation and heat dissipation. Fermentation productivity at high temperatures when using the thermotolerant yeast Kluyveromyces marxianus and the inhibitory effect of high temperatures on the growth of contaminant microorganisms were examined. After fermentation, the recovery and concentration of ethanol were performed by reduced-pressure distillation (RPD) and membrane separation. These experiments demonstrate that efficient HTF can reduce the amount of saccharifying enzymes in simultaneous saccharification and fermentation and can shorten the transition time from the saccharification step to the fermentation step in separate saccharification and fermentation, that RPD at fermentation temperatures enables a smooth connection to the HTF step and can be performed with a relatively weak vacuum, and that membrane separation can reduce the running cost compared to the cost of general distillation on a compact scale.
Ethanol is considered as a renewable transport fuels and demand is expected to grow. In this work, trends related to bio-ethanol production are described using Thailand as an example. Developments on high-temperature fermentation and membrane technologies are also explained. This study focuses on the application of membranes in ethanol recovery after fermentation. A preliminary simulation was performed to compare different process configurations to concentrate 10 wt% ethanol to 99.5 wt% using membranes. In addition to the significant energy reduction achieved by replacing azeotropic distillation with membrane dehydration, employing ethanol-selective membranes can further reduce energy demand. Silicalite membrane is a type of membrane showing one of the highest ethanol-selective permeation performances reported today. A silicalite membrane was applied to separate a bio-ethanol solution produced via high-temperature fermentation followed by a single distillation. The influence of contaminants in the bio-ethanol on the membrane properties and required further developments are also discussed.
The particle conversion during gasification of petroleum cokes in CO_2 gas was examined using a thermogravimetry analyzer and a captive particle imaging apparatus. The conversion of gasification of petroleum cokes was influenced by a temperature of environment. Using a petroleum coke was addel 1∿10wt%-K_2CO_3 as a catalysis of gasification, the relationship between the value of added catalysis and the kinetics of the gasification order of petroleum cokes was acquired. The petroleum coke added 3∿10wt%-K_2CO_3 was improved the kinetics of gasification order.
Waste woody biomass samples including poly(vinyl chloride) (PVC), which were mixed with metal hydroxides as additives, were carbonized at 500 °C to investigate the catalytic effect of the additives on pyrolysis products and to elucidate the mechanism of biomass carbonization. The results showed that the yield of char significantly increased, whereas tar evolution was suppressed by the influence of metal hydroxides, even with the coexistence of PVC. Moreover, the interaction behaviors between the biomass structure including PVC and metal hydroxides were further investigated. It was clarified that the dehydration reaction to form a cross-linked structure in biomass by the effect of metal ion and the neutralization reaction between PVC and metal hydroxides were simultaneously occurred during the carbonization. The presence of chlorine component, which is one of corrosive substances, was confirmed in char structure by chlorine analysis. Therefore, a flushing method with warm and cold water was applied, to investigate the possibility of chlorine removal. The results showed that flushing with warm water and cold water are both effective for the removal of chlorine component in the char. Finally, the new pyrolysis process of NaOH-mixed waste biomass materials, including proposed heat recovery facilities, can be suggested as an effective system of biomass utilization for energy savings and CO2 reduction.
