Bio-Hydrogen Production in Packed Bed Continuous Plug Flow Reactor—CFD-Multiphase Modelling (original) (raw)
Related papers
Mathematical modelling and optimization of hydrogen continuous production in a fixed bed bioreactor
Chemical Engineering Science, 2002
The purpose of this paper is to investigate, both theoretically and experimentally, hydrogen production from agro-industrial by-products using a continuous bioreactor packed with a mixture of spongy and glass beads and inoculated with Enterobacter aerogenes. Replicated series of experimental runs were performed to study the e ects of residence time on hydrogen evolution rate and to characterize the critical conditions for the wash out, as a function of the inlet glucose concentration and of the uid superÿcial velocity. A further series of experimental runs was focused on the e ects of both residence time and inlet glucose concentration over hydrogen productivity. A kinetic model of the process was developed and showed good agreement with experimental data, thus representing a potential tool to design a large-scale fermenter. In fact, the model was applied to the optimal design of a bioreactor suitable of feeding a phosphoric acid fuel cell of a target power. ?
A novel approach of modeling continuous dark hydrogen fermentation
Bioresource Technology, 2018
In this study a novel modeling approach for describing fermentative hydrogen production in a continuous stirred tank reactor (CSTR) was developed, using the Aquasim modeling platform. This model accounts for the key metabolic reactions taking place in a fermentative hydrogen producing reactor, using fixed stoichiometry but different reaction rates. Biomass yields are determined based on bioenergetics. The model is capable of describing very well the variation in the distribution of metabolic products for a wide range of hydraulic retention times (HRT). The modeling approach is demonstrated using the experimental data obtained from a CSTR, fed with Food Industry Waste (FIW), operating at different HRTs. The kinetic parameters were estimated through fitting to the experimental results. Hydrogen and total biogas production rates were predicted very well by the model, validating the basic assumptions regarding the implicated stoichiometric biochemical reactions and their kinetic rates.
Effect of Organic Loading on Hydrogen in A Continuous Bio-hydrogen Production Reactor
This experiment used a continuous stirred tank reactor (CSTR) with brown sugar water as the fermentation substrate, and sewage sludge as the initiation of reaction. Hydrogen production reached a stable level under conditions of an intake of pH 7.0+0.1, an oxidation-reduction potential (ORP) of -420mV, a temperature of (35 ± 1) ℃ and a hydraulic retention time (HRT) of 6 hours. (Hydrogen was the main component from the ethanol-type fermentation). We were able to focus on the impact of changing the organic load on Hydrogen production by keeping all other parameters consistent. At the same time, the microorganisms were allowed to maintain high activity by regulating the pH level. Results showed that when the organic load increased from 12 kg/m³-d to 32 kg/m³-d, the biogas and hydrogen production rates continuously increased. When the organic load was 32 kg/m³-d ,it reached a maximum production rate of 18.6L/d and a hydrogen production rate of 6.4L/d. Compared with the initial 12kg/m ³-d , gas production improved by 89% and 87%,respectively. During system operation, lowering the intake pH to 5.85 resulted in the inhibition of microbial activity of anaerobic fermentation, resulting in a decline of rate of hydrogen production and the ORP increased to-328mV. Under these conditions, the reactor could maintain a high hydrogen production rate of ethanol-type fermentation by adding a certain amount of NaOH in the reactor to regulate the pH level.
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.
Catalysts
Dark fermentation is a hydrogen generating process carried out by anaerobic spore-forming bacteria that metabolize carbon sources producing gas and short-chain acids. The process can be controlled, and the hydrogen harvested if bacteria are grown in a reactor with favorable conditions. In this work, bacteria selected from natural sources were grown with a defined culture media, while pH was monitored, with the aim of relating the amount of generated hydrogen to the increase in hydron ion concentration. Therefore, a model based on the acid-base species mass balance is proposed and solved to estimate the lag phase time and measure the hydrogen production efficiency and kinetics. Hydrogen production in a stirred batch reactor was performed for 150–200 h, at given operating conditions using a previously defined growth media, to validate the model. Using the proposed model, the cumulated moles of produced hydrogen correlate well with those predicted from the pH curve. Hence, the modified...
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.
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.
Biological hydrogen production in suspended and attached growth anaerobic reactor systems
International Journal of Hydrogen Energy, 2006
Biological production of hydrogen gas has received increasing interest from the international community during the last decade. Most studies on biological fermentative hydrogen production from carbohydrates using mixed cultures have been conducted in conventional continuous stirred tank reactors (CSTR) under mesophilic conditions. Investigations on hydrogen production in reactor systems with attached microbial growth have recently come up as well as investigations on hydrogen production in the thermophilic temperature range. The present study examines and compares the biological fermentative production of hydrogen from glucose in a continuous stirred tank type bioreactor (CSTR) and an upflow anaerobic sludge blanket bioreactor (UASB) at various hydraulic retention times (2-12 h HRT) under mesophilic conditions (35 • C). Also the biohydrogen production from glucose in the CSTR at mesophilic and thermophilic (55 • C) temperature range was studied and compared. From the CSTR experiments it was found that thermophilic conditions combine high hydrogen production rate with low production of microbial mass, thus giving a specific hydrogen production rate as high as 104 mmole H 2 /h/l/g VSS at 6 h retention time compared to a specific hydrogen production rate of 12 mmole H 2 /h/l/g VSS under mesophilic conditions. On the other hand, the UASB reactor configuration is more stable than the CSTR regarding hydrogen production, pH, glucose consumption and microbial by-products (e.g. volatile fatty acids, alcohols etc.) at the HRTs tested. Moreover, the hydrogen production rate in the UASB reactor was significantly higher compared to that of the CSTR at low retention times (19.05 and 8.42 mmole H 2 /h/l, respectively at 2 h HRT) while hydrogen yield (mmole H 2 /mmole glucose consumed) was higher in the CSTR reactor at all HRT tested. This implies that there is a trade-off between technical efficiency (based on hydrogen yield) and economic efficiency (based on hydrogen production rate) when the attached (UASB) and suspended (CSTR) growth configurations are compared. ᭧