Abstract:For all experiments, the concentrations of ethanol in the feed liquid, bottoms liquid, and permeate vapor condensate were determined using a gas chromatograph (GC, Agilent 6890) equipped with a Flame Ionization Detector (FID) with DI water dilution, as necessary, for the concentration to be in the calibrated range. Ethanol and water were quantitated in the feed vapor and retentate vapor condensates using a thermal conductivity detector (TCD) on the same GC using anhydrous 1-propanol (Sigma Aldrich) as a diluen… Show more
“…Peer-reviewed literature on syngas fermentation has mostly focused on the maximum achieved ethanol concentration in the fermentation broth, which is critical for process economics to distill ethanol (Vane et al, 2012). However, knowledge about maximum ethanol production rates is equally important, but remains underreported (Gaddy et al, 2007;Kundiyana et al, 2010;Richter et al, 2013b;Wang et al, 2013).…”
Syngas fermentation is an anaerobic bioprocess that could become industrially relevant as a biorefinery platform for sustainable production of fuels and chemicals. An important prerequisite for commercialization is adequate performance of the biocatalyst (i.e., sufficiently high production rate, titer, selectivity, yield, and stability of the fermentation). Here, we compared the performance of three potential candidate Clostridium strains in syngas-to-ethanol conversion: Clostridium ljungdahlii PETC, C. ljungdahlii ERI-2, and Clostridium autoethanogenum JA1-1. Experiments were conducted in a two-stage, continuously fed syngas-fermentation system that had been optimized for stable ethanol production. The two C. ljungdahlii strains performed similar to each other but different from C. autoethanogenum. When the pH value was lowered from 5.5 to 4.5 to induce solventogenesis, the cell-specific carbon monoxide and hydrogen consumption (similar rate for all strains at pH 5.5), severely decreased in JA1-1, but hardly in PETC and ERI-2. Ethanol production in strains PETC and ERI-2 remained relatively stable while the rate of acetate production decreased, resulting in a high ethanol/acetate ratio, but lower overall productivities. With JA1-1, lowering the pH severely lowered rates of both ethanol and acetate production; and as a consequence, no pronounced shift to solventogenesis was observed. The highest overall ethanol production rate of 0.301 g · L(-1) · h(-1) was achieved with PETC at pH 4.5 with a corresponding 19 g/L (1.9% w/v) ethanol concentration and a 5.5:1 ethanol/acetate molar ratio. A comparison of the genes relevant for ethanol metabolism revealed differences between C. ljungdahlii and C. autoethanogenum that, however, did not conclusively explain the different phenotypes.
“…Peer-reviewed literature on syngas fermentation has mostly focused on the maximum achieved ethanol concentration in the fermentation broth, which is critical for process economics to distill ethanol (Vane et al, 2012). However, knowledge about maximum ethanol production rates is equally important, but remains underreported (Gaddy et al, 2007;Kundiyana et al, 2010;Richter et al, 2013b;Wang et al, 2013).…”
Syngas fermentation is an anaerobic bioprocess that could become industrially relevant as a biorefinery platform for sustainable production of fuels and chemicals. An important prerequisite for commercialization is adequate performance of the biocatalyst (i.e., sufficiently high production rate, titer, selectivity, yield, and stability of the fermentation). Here, we compared the performance of three potential candidate Clostridium strains in syngas-to-ethanol conversion: Clostridium ljungdahlii PETC, C. ljungdahlii ERI-2, and Clostridium autoethanogenum JA1-1. Experiments were conducted in a two-stage, continuously fed syngas-fermentation system that had been optimized for stable ethanol production. The two C. ljungdahlii strains performed similar to each other but different from C. autoethanogenum. When the pH value was lowered from 5.5 to 4.5 to induce solventogenesis, the cell-specific carbon monoxide and hydrogen consumption (similar rate for all strains at pH 5.5), severely decreased in JA1-1, but hardly in PETC and ERI-2. Ethanol production in strains PETC and ERI-2 remained relatively stable while the rate of acetate production decreased, resulting in a high ethanol/acetate ratio, but lower overall productivities. With JA1-1, lowering the pH severely lowered rates of both ethanol and acetate production; and as a consequence, no pronounced shift to solventogenesis was observed. The highest overall ethanol production rate of 0.301 g · L(-1) · h(-1) was achieved with PETC at pH 4.5 with a corresponding 19 g/L (1.9% w/v) ethanol concentration and a 5.5:1 ethanol/acetate molar ratio. A comparison of the genes relevant for ethanol metabolism revealed differences between C. ljungdahlii and C. autoethanogenum that, however, did not conclusively explain the different phenotypes.
“…The subject of this paper is one such synergistic hybrid, termed Membrane Assisted Vapor Stripping (MAVS), combining distillation‐based vapor stripping and membrane‐based vapor permeation in a manner that significantly reduces energy usage for the recovery of volatile solvents and biofuels from water . A schematic diagram of a ‘2nd generation’ MAVS process is shown in Fig.…”
Section: Introductionmentioning
confidence: 99%
“…In our previous publications on the subject, we have described the general theory behind MAVS processes, simulation predictions for performance and initial cost estimates, energy demand, and experimental verifications for ethanol/water, 1‐butanol/water, and acetone/1‐butanol/ethanol/water (ABE/water) systems . In this paper, we evaluate the effect of a variety of process variables and membrane performance/unit cost characteristics on energy usage and the overall separation cost for MAVS systems.…”
BACKGROUND
Alcohols, including ethanol and butanol, are receiving increased attention as renewable liquid biofuels. Alcohol concentrations may be low in a biological process due to product inhibition and, for non‐starch feedstocks, limited substrate concentrations. The result is high separation energy demand by conventional distillation scenarios, despite favorable vapor–liquid equilibrium and, for butanol, partial miscibility with water. A hybrid vapor stripping–vapor permeation process, termed membrane assisted vapor stripping (MAVS), incorporating a fractional condensation step was found to be at least 65% more energy efficient than conventional distillation approaches. The effect of process design, component performance, and capacity changes on the energy usage and processing cost of MAVS systems for separating ethanol, 1‐butanol, and acetone/butanol/ethanol (ABE) mixtures from water was studied.
RESULTS
For the recovery of 1‐butanol from a 1 wt% aqueous solution, the 99.5 wt% 1‐butanol product contained 7.0 times as much heating value energy as the MAVS process required to recover and dry it. The calculated cost to perform this separation was 0.126 US$ kg−1‐product (0.102 US$ L−1) for a heating value cost of 3.69 US$ GJ−1, far below the current values for crude oil and conventionally‐produced ethanol. Energy (electricity, natural gas) was 23% of this cost. The largest capital cost item was the compressor on the overhead vapor stream from the stripping column. Capital costs for membranes/modules was the 6th highest cost category, representing only 4% of the capital cost. A 10‐fold increase in membrane cost caused the cost of production to increase 38%.
CONCLUSION
Hybrid MAVS processes are an energy‐ and cost‐efficient means to recover alcohols from water. Despite recent fluctuations, fossil fuel costs are projected to increase. Thus processes utilizing mechanical energy to recapture and transfer thermal energy, including MAVS, should have a greater cost advantage in the future. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.
“…Although the alcoholic-water mixture provides a high osmotic pressure but the separation of ethanol-water, the mixture is energy intensive especially when ethanol concentration is lower than 5% by weight [46,47]. Therefore, it is clear that the development of DS regeneration process is significantly desirable to make the FO technologies more competitive and attractive compared to other methods.…”
In hot regions like the Middle East, the road asphalt pavement experience many fluctuations in their temperature profile that provides the large dark surface area with intensive heat absorption capacity, which warms the roads up to 75°C or more in summer. This phenomenon is negatively affecting the performance and urban heating. On the other hand, the most amount of water available (about 97%) is low-quality water or seawater, which needs to be treated in an efficient way to cope with the dramatic increase on demand of clean water due to population growth and agriculture requirements. Several techniques have been used for water desalination and most are thermally based techniques. Therefore, they are consuming high energy per water desalinating volume.The aim of this study is to design a novel heat harvesting system combined with a membrane based unit, to produce clean water from impure water. The heat will be harvested from the roads and buildings, by a low-grade system through Forward Osmosis (FO) unit. The diluted draw solution (SD) will be regenerated at low operating temperature, while the road and building's roofs surfaces are cooled and maintained at a lower temperature.The proposed technology will save energy and enhance microclimate conditions as well. The innovative DS regeneration system was simulated by HYSYS V8.8 and the results show a 1.17 m 3 /hr of treated water can be recovered for each one-m 2 . The quality of water depends on the amount of heat harvested and, consequently the surface temperature. Potable water is achievable only when the surface temperature is higher than 70°C and, therefore a trim heater is recommended for the winter season otherwise, the water will be used for non-drinking applications. Although the required Capex for this technology is around $13778/m 2 , but the payback is two years.
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