Process Intensification in Bio-Ethanol Production–Recent Developments in Membrane Separation

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.

Inter-integration membrane-reactive distillation for EL synthesis: Equipment development and experimental validating

Ethyl levulinate, one of main derivatives of levulinic acid (LA), is of significant potential as platform chemicals for bio-based materials. The esterification of LA was generally carried out in a conventional batch reactor or in a conventional reactive distillation column. However, traditional methods are hard to deal with equilibrium limited reactions and azeotropic issues. Therefore, the reactive-vapor permeation-distillation (R-VP-D) process, which integrated reaction, distillation and membrane dehydration into one single unit, is proposed in this paper and validated in the pilot-scale experiments. A comparative study is made between a pilot-scale RD column with and without vapor permeation membrane module. Owing to the water-selective membrane and the ingenious design of related apparatuses, the R-VP-D process reveal a superiority in LA conversion of 21.9% maximum higher than RD without VP process and removing of product water about 53.6% from VP module, which indicates its promising industrial application in process intensification field.

Simultaneous Investigation of PEMFC Performance and Water Content at Different Flow Rates and Relative Humidities

In order to prevent membrane dehydration and flooding in proton exchange membrane fuel cells (PEMFC), appropriate water management must be done. Therefore, accurate knowledge of the effects of various parameters on cell water content is needed. This knowledge helps to achieve optimum cell performance. The effects of both anode and cathode stoichiometry and relative humidity on single serpentine PEMFC performance and flow channel water content are surveyed experimentally. All tests conducted on transparent fuel cell with serpentine flow field channels and 25cm2 MEA active areas. Digital image processing is performed on the captured images of cathode channel to detect accumulated water at that side. The results indicate that there is a correlation between water content of cathode flow channels and cell performance. Increasing cathode water content causes membrane hydration which leads to better cell performance, but high water content causes flooding. It is concluded that both stoichiometry and relative humidity have significant effect on cell performance. Increasing reactant relative humidity improves water transport mechanisms within the cell, but fully humidified reactants may causes flooding. Although high stoichiometry rate prevents flooding and facilitate reactants transport within catalyst layer, high anode and cathode stoichiometry leads to membrane dehydration. Experimental observation shows that both stoichiometry and relative humidity have optimum value.

Operating Condition Optimization of PEMFC via Visualization Technique

Fuel cell water management has two conflicting requirements; too less water causing membrane dehydration and too much water causing liquid water flooding. Both phenomena resulting in significantly instability voltage performance because of imbalance water presence. Therefore, it is vital to analyze and understand the root cause of the problem hence a 96cm2 transparent fuel cell was analyzed experimentally. The fuel cell allows clear visualization of flow channels, thus making it practical to analyze the transportation of reactants and products behavior. The experimental analyses were conducted under different reactant flow rate and inlet humidification variations. Highest cell performance was obtained under both reactant inlets humidification with largest air flow rates. On the other hand, when fuel and air in dry conditions, relatively lower cell voltage was obtained. Meanwhile, stable voltage was obtained under anode humidified and cathode non-humidified conditions with correct air to fuel ratio. Images of liquid water and voltage behavior are presented graphically corresponding to the changes in performance.