Mathematical modelling and optimization of hydrogen continuous production in a fixed bed bioreactor (original) (raw)
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Modeling and optimization of fermentative hydrogen production
Bioresource Technology, 2011
Biohydrogen is a sustainable energy resource due to its potentially higher efficiency of conversion to usable power, non-polluting nature and high energy density. The purpose of modeling and optimization is to improve, analyze and predict biohydrogen production. Biohydrogen production depends on a number of variables, including pH, temperature, substrate concentration and nutrient availability, among others. Mathematical modeling of several distinct processes such as kinetics of microbial growth and products formation, steady state behavior of organic substrate along with its utilization and inhibition have been presented. Present paper summarizes the experimental design methods used to investigate effects of various factors on fermentative hydrogen production, including one-factor-at-a-time design, full factorial and fractional factorial designs. Each design method is briefly outlined, followed by the introduction of its analysis. In addition, the applications of artificial neural network, genetic algorithm, principal component analysis and optimization process using desirability function have also been highlighted.
Bioprocess Engineering, 2000
Hydrogen bioproduction from agro-industrial residues by Enterobacter aerogenes in a continuous packed column has been investigated and a complete reactor characterization is presented. Experimental runs carried out at different residence time, liable of interest for industrial application, showed hydrogen yields ranging from 1.36 to 3.02 mmol H 2 mmol À1 glucose or, in other words, from 37.5% to 75% of the theoretical hydrogen yield. A simple kinetic model of cell growth, validated by experimental results and allowing the prediction of biomass concentration pro®le along the reactor and the optimization of super®cial velocity, is suggested. By applying the developed approach to the selected operative conditions, the identi®cation of the optimum super®cial velocity v 0,opt of about 2.2 cm h)1 corresponding to the maximum hydrogen evolution rate H 2gYmax , was performed.
Kinetics of two-stage fermentation process for the production of hydrogen
International Journal of Hydrogen Energy, 2008
Two-stage process described in the present work is a combination of dark and photofermentation in a sequential batch mode. In the first stage glucose is fermented to acetate, CO 2 and H 2 in an anaerobic dark fermentation by Enterobacter cloacae DM11. This is followed by a successive second stage where acetate is converted to H 2 and CO 2 in a photobioreactor by photosynthetic bacteria, Rhodobacter sphaeroides O.U. 001. The yield of hydrogen in the first stage was about 3:31 mol H 2 ðmol glucoseÞ À1 (approximately 82% of theoretical) and that in the second stage was about 1:521:72 mol H 2 ðmol acetic acidÞ À1 (approximately 37-43% of theoretical). The overall yield of hydrogen in two-stage process considering glucose as preliminary substrate was found to be higher compared to a single stage process. Monod model, with incorporation of substrate inhibition term, has been used to determine the growth kinetic parameters for the first stage. The values of maximum specific growth rate (m max Þ and K s (saturation constant) were 0:398 h À1 and 5:509 g l À1 , respectively, using glucose as substrate. The experimental substrate and biomass concentration profiles have good resemblance with those obtained by kinetic model predictions. A model based on logistic equation has been developed to describe the growth of R. sphaeroides O.U 001 in the second stage. Modified Gompertz equation was applied to estimate the hydrogen production potential, rate and lag phase time in a batch process for various initial concentration of glucose, based on the cumulative hydrogen production curves. Both the curve fitting and statistical analysis showed that the equation was suitable to describe the progress of cumulative hydrogen production.
Modelling of biohydrogen production in stirred fermenters by Computational Fluid Dynamics
Process Safety and Environmental Protection, 2019
A bioreactor for the production of hydrogen from the dark fermentation of organics is studied by a comprehensive modelling strategy. The bioreactor is a dual impeller vortex ingesting stirred tank working under batch and attached-growth conditions. Two geometrical configurations of the reactor are investigated: one devised to ensure an effective fluid dynamics behaviour and the other proposed to increase the hydrogen productivity. The turbulent gas-liquid fluid dynamics, the production and the recovery of H 2 from the liquid phase are predicted by the numerical solution of the two-phase Reynolds averaged Navier-Stokes equations and the species mass transport equations, including a simplified kinetic model for the fermentative hydrogen production found in literature and a local interphase mass transfer model for the hydrogen stripping from the aqueous to the gas phase. A simplified model for the description of the interfacial area in the context of the two-fluid model is also proposed. This work suggests a method for the predictive simulations of a complex biological process via numerical modelling based on Computational Fluid Dynamics. The main outcome of the proposed investigation method is a detailed estimation of the different relevant variables and their interaction on a local basis, providing a viable tool for the optimization and the scale-up of bioreactors.
DOAJ (DOAJ: Directory of Open Access Journals), 2013
In this work, we study the hydrogen production through a dark fermentation process by hydrogen forming bacteria consortium. In this sense, fermentation experiments are performed in a discontinuous reactor using glucose as the carbon source. Product and substrate profiles are measured in order to study the production of bio hydrogen. A kinetic model for the batch bioreactor that describes the production of all fermentation products, the growth of biomass and the consumption of substrates is developed. The model comprises fifteen differential equations and one algebraic equation. We formulate a parameter estimation problem for the bioreactor model. Fifteen input parameters are estimated taking account the experimental data obtained in the present work. The maximum hydrogen yield obtained was 2.68 mol H 2 /mol glucose and the highest hydrogen production rate observed was 1.61 l H 2 / l-day. Numerical results show good agreement between experimental data and simulated profiles.
International Journal of Hydrogen Energy, 2002
Desk studies were carried out to calculate the feasibility of hydrogen gas production by (hyper)thermophilic organisms in high rate bioreactors. One of the main problems to deal with is the requirement of a hydrogen gas pressure lower than 20; 000 Pa. Only under these conditions carbohydrates are converted into hydrogen gas, carbon dioxide and acetic acid. These conditions can be created by stripping the hydrogen gas with steam produced by evaporation of water at a large surface area created by packing material in an anaerobic trickling ÿlter. The steam production occurs at 70
2012
Simultaneous achievement of high volumetric productivities (HP ¼ 231.3 mmol H 2 /L/h) and high hydrogen yields (HY ¼ 3.55 mol H 2 /mol glucose) was obtained by increasing the temperature to 70 C and by reducing the total bioreactor system volume (V) to 5.74 L and increasing the degassed effluent recycle rate (F er) to 3.2 L/min, giving a V/F er value of 1.8 min. The bioprocess involved the recycling of degassed effluent at a high flow rate through a quasi-stationary fluidized granular bed. In this process the rate of physical removal of H 2 trapped in the bulk liquid phase surrounding the fluidized granules reduced the thermodynamic constraints preventing the simultaneous achievement of high HPs and high HYs in the anaerobic fluidized granular bed bioreactor. Energy balance analysis showed that with heat recycling the bioreactor system could achieve a net positive volumetric energy output of 11.76 W/L at an energy efficiency of 49.3%.
Continuous fermentative hydrogen production under various process conditions
Journal of Food Agriculture & Environment, 2010
The feasibility of continuous H 2 production from coffee drink manufacturing wastewater (CDMW) was tested in two different types of reactors: a completely-stirred tank reactor (CSTR) and an up-flow anaerobic sludge blanket reactor (UASBr). While the performance in CSTR was limited, it was significantly enhanced in UASBr. The maximum H 2 yield of 1.29 mol H 2 /mol hexose added was achieved at HRT of 6 h in UASBr operation. Non-hydrogenic, lactic acid was the dominant in CSTR, while butyric and caproic acids in UASBr. As caproic acid is generated by consuming acetic and butyric acids, all of which are related to H 2 production, the presence of caproic acid in the broth also indicates H 2 production, yielding 1.33 mol H 2 /glucose. It was speculated that the enhanced performance in UASBr was attributed to the high concentration of biomass over 60,000 mg VSS/L in the blanket zone, which provided insufficient substrate for indigenous lactic acid bacteria (LAB) to survive. The abundance of LAB in CDMW was confirmed by natural fermentation of CDMW. That is without the addition of external inoculum, CDMW was mainly fermented into lactic acid under mesophilic condition. For the first time ever, H 2 producing granules (HPG) with diameters of 2.1 mm were successfully formed by using actual waste as a substrate.
Revivability of fermentative hydrogen producing bioreactors
International Journal of Hydrogen Energy, 2011
In this study we investigated the revivability of a continuous biological hydrogen producing reactor after a period of feed interruption. Before the feed interruption, the hydrogen production yield was 1.36 mol H 2 /mol glucose with butyric acid and acetic acid as the main metabolic products. However, after feed interruption, butyric acid formation completely stopped and the hydrogen yield decreased to 0.29 mol H 2 /mol glucose. Lactic acid, ethanol and acetic acid became the main metabolites after restart up. Reduction of organic loading rate together with increasing the pH after the feed interruption resulted in an increase in the hydrogen yield to 0.7 mol H 2 /mol glucose. The microbial community dynamics showed complete elimination of Clostridium affiliated strains and predominance of Lactobacillus affiliated strains after the restart up of the reactor.