Discontinuous phenomena in bioreactor and membrane reactor systems

2019 ◽  
Vol 12 (04) ◽  
pp. 1950046
Author(s):  
Hany A. Hosham
Keyword(s):  
Residence Time ◽  
Membrane Reactor ◽  
Biomass Concentration ◽  
Discontinuous Flow ◽  
Recycle Ratio ◽  
Existence And Stability ◽  
Discontinuous Bifurcation ◽  
Reactor Models ◽  
Stability Issues ◽  
Solid Liquid

In this work, we analyze the existence of discontinuous bifurcation and stability issues in discontinuous flow of bioreactor and membrane reactor models with or without recycle. The reaction is assumed to be governed by certain types of discontinuities in Monod growth kinetics curve leading to discontinuous dynamical system. The criteria for the existence and stability of steady-states of these models are established. More generally, our analysis highlights the presence of several types of bifurcation depending upon the effect of the dilution factor (residence time), biomass concentration and solid-liquid-gas separator efficiency. As well, we present bifurcation conditions defining the dynamics near steady-state branches on the border, providing a possible framework for existing of saddle-node, nonsmooth fold, persistence and grazing-sliding scenarios. It is shown that the critical values of residence time dependence upon recycle ratio, decay rate and existence of discontinuity surface. Further, the performance of the reactor at largest residence times will be discussed. In addition, numerical simulations to illustrate and confirm the results will be carried out.

Aerosol Synthesis of Nano and Micro-Scale Zero Valent Nickel Particles From Oxide Precursors

2010 ◽  
Author(s):  
Haytham Soliman ◽  
Jonathan Phillips ◽  
Claudia Luhrs ◽  
Hugo Zea ◽  
Zayd C. Leseman
Keyword(s):  
Particle Size ◽  
Metal Oxide ◽  
Residence Time ◽  
Rapid Expansion ◽  
Metal Particles ◽  
Micro Scale ◽  
Nickel Particles ◽  
Solid Liquid ◽  
Urea Decomposition ◽  
Reduction Of Oxides

In this work a novel aerosol method, derived from the batch Reduction/Expansion Synthesis (RES) method, for production of nano / micro-scale metal particles from oxides and hydroxides is presented. In the Aersosol-RES (A-RES) method, an aerosol, consisting of a physical mixture of urea and metal oxide or hydroxides, is passed through a heated oven (1000 °C) with a residence time of the order of 1 second, producing pure (zero valent) metal particles. It appears that the process is flexible regarding metal or alloy identity, allows control of particle size and can be readily scaled to very large throughput. Current work is focused on creating nanoparticles of metal and metal alloy using this method. Although this is primarily a report on observations, some key elements of the chemistry are clear. In particular, the reducing species produced by urea decomposition are the primary agents responsible for reduction of oxides and hydroxides to metal. It is also likely that the rapid expansion that takes place when solid/liquid urea decomposes to form gas species influences the final morphology of the particles.

Performance and membrane foulant in the pilot operation of a novel biofilm-membrane reactor

2002 ◽  
Vol 2 (2) ◽  
pp. 177-183
Author(s):  
K. Kimura ◽  
Y. Watanabe
Keyword(s):  
Membrane Fouling ◽  
Membrane Reactor ◽  
Pilot Scale ◽  
Ammonia Nitrogen ◽  
Manganese Concentration ◽  
Membrane Cleaning ◽  
Chemical Washing ◽  
Pre Treatment ◽  
Solid Liquid ◽  
Solid Liquid Separation

We have developed a novel biofilm-membrane reactor (BMR) in which a nitrifying biofilm is fixed on the surface of a rotating membrane disk. With this reactor, both strict solid-liquid separation and oxidation of ammonia nitrogen can be simultaneously performed. Based on the results obtained in previous bench-scale experiments, a pilot-scale study was conducted using river water at a water purification plant. The results obtained in the pilot study can be summarized as follows. (1) By implementation of pre-treatment (coagulation and sedimentation) and simple membrane cleaning (sponge cleaning), the filter run could be continued for 17 months without any chemical washing. (2) Sufficient nitrification was observed when water temperature was high. Deterioration in nitrification efficiency during winter was reduced by the addition of phosphorus. (3) In addition to nitrification, biological oxidation of AOC and manganese can be expected with the BMR. In this study, both AOC and manganese concentration in the permeate decreased to a level less than 10 μg/L. (4) Irreversible membrane fouling, which was thought to be mainly caused by manganese, became significant as the operation period became longer.

A BIOLOGICAL TREATMENT OF INDUSTRIAL WASTEWATERS: CONTOIS KINETICS

2015 ◽  
Vol 56 (4) ◽  
pp. 397-415 ◽  
Author(s):  
RUBAYYI T. ALQAHTANI ◽  
MARK I. NELSON ◽  
ANNETTE L. WORTHY
Keyword(s):  
Steady State ◽  
Residence Time ◽  
Continuous Flow ◽  
Biological Treatment ◽  
Membrane Bioreactor ◽  
Industrial Wastewaters ◽  
Steady State Operation ◽  
Recycle Ratio ◽  
Steady State Solutions ◽  
Bioreactor Performance

This paper analyses the steady-state operation of a generalized bioreactor model that encompasses a continuous-flow bioreactor and an idealized continuous-flow membrane bioreactor as limiting cases. A biodegradation of organic materials is modelled using Contois growth kinetics. The bioreactor performance is analysed by finding the steady-state solutions of the model and determining their stability as a function of the dimensionless residence time. We show that an effective recycle parameter improves the performance of the bioreactor at moderate values of the dimensionless residence time. However, at sufficiently large values of the dimensionless residence time, the performance of the bioreactor is independent of the recycle ratio.

Miniaturized Tubular Cooling Crystallizer With Solid-Liquid Flow for Process Development

2018 ◽  
Author(s):  
Mira Schmalenberg ◽  
Lukas Hohmann ◽  
Norbert Kockmann
Keyword(s):  
Residence Time ◽  
Mass Flow ◽  
Modular Design ◽  
Process Development ◽  
Test System ◽  
Successful Operation ◽  
Liquid Suspension ◽  
Axial Temperature ◽  
Inner Diameter ◽  
Solid Liquid

Production of fine chemicals and pharmaceuticals often includes solid-liquid suspension flow. For continuous cooling a tubular crystallizer was designed based on the coiled flow inverter (CFI) concept, providing a narrow residence time distribution (RTD) of the liquid phase. Counter-current cooling allows for a smooth adjustment of the axial temperature profile. Successful operation of up to 50 g min−1 in a prototype with 4 mm inner diameter was scaled down to a tube-in-tube CFI crystallizer (CFIC) with an inner diameter of 1.6 mm and varying length from 7.8 to 54.6 m. This leads to a significantly lower consumption of chemicals in process development with lower total mass flow rates of 15–20 g min−1. Due to modular design, mean residence time (3.8 to 6.9 min) and mean cooling rate (0.6 to 1.4 K·min−1) were varied at constant mass flow rate. Crystallization growth rate and yield are analyzed with the L-alanine/water test system and seed crystals of 125–180 μm.

scholarly journals Stability and Performance Analysis of Bioethanol Production with Delay and Growth Inhibition in a Continuous Bioreactor with Recycle

Processes ◽  
2021 ◽  
Vol 9 (3) ◽  
pp. 461
Author(s):  
Rubayyi T. Alqahtani ◽  
Samir Kumar Bhowmik ◽  
Abdelhamid Ajbar ◽  
Mourad Boumaza
Keyword(s):  
Residence Time ◽  
Ethanol Concentration ◽  
Substrate Inhibition ◽  
Substantial Effect ◽  
Feed Concentration ◽  
Dynamic Simulations ◽  
Continuous Bioreactor ◽  
Proposed Model ◽  
Recycle Ratio ◽  
And Performance

This paper proposes and analyzes a mathematical model for the production of bioethanol in a continuous bioreactor with recycling. The kinetics correspond to the use of Saccharomyces bayanus for the fermentation of sugars found in wastewater from soft drinks. The proposed model considers product growth latency, which was experimentally found in batch studies of ethanol production. Furthermore, the inhibition effect of ethanol is expressed by a modified version of the classical Andrew’s model for substrate inhibition. The proposed model consists of only three ordinary differential equations containing a minimal number of operating parameters, which include the bioreactor residence time, glucose feed concentration, recycle ratio and the fraction of biomass removed from the reactor by the flow. The positivity and the boundedness of solutions of the model were confirmed under reasonable restrictions of parameters. The stability analysis showed that there is a value of residence time at which an exchange of stability occurs between the trivial washout and non-washout solutions. This critical value depends only on the substrate feed concentration, biomass death rate, recycle ratio and purge fraction. Dynamic simulations of the model were carried out for substrate concentration in the range of 100–250 g/L, commonly used for the production of ethanol. An inverse response due to the inhibition effects of ethanol was observed in the time evolution of substrate and biomass concentrations. Parametric studies showed that ethanol concentration increases with the recycle ratio, with the inverse of residence time and with the inverse of purge fraction. The effect of ethanol latency has, on the other hand, a substantial effect on ethanol concentration. Despite its unstructured nature and the fact that some parameters such as temperature and acidity were not taken into consideration, the proposed model managed to provide useful results on the bioreactor-settler stability and the effect of key parameters on its dynamic behavior, which could pave the way for future optimization studies.

scholarly journals Novel Module-Based Design Algorithm for Intensified Membrane Reactor Systems

Processes ◽  
2021 ◽  
Vol 9 (12) ◽  
pp. 2165
Author(s):  
Brent A. Bishop ◽  
Fernando V. Lima
Keyword(s):  
Membrane Reactor ◽  
Degrees Of Freedom ◽  
Membrane Reactors ◽  
Design Approach ◽  
Computational Time ◽  
Design Algorithm ◽  
Module Design ◽  
Design Heuristics ◽  
Reactor Models ◽  
And Control

The growing interest in intensified process units that improve efficiency by combining several phenomena into one unit, has led to a loss in degrees of freedom when addressing the control scheme of these units. Previous work demonstrated that a novel module-based design approach to membrane reactors could improve the operability index of membrane reactor systems. This approach sought to decouple the phenomena to regain some degrees of freedom for the control system. However, the computational time to determine such an optimal module design made this class of design problems intractable to solve in a reasonable amount of time. This work proposes a set of design heuristics for a new module-based design approach for membrane reactors. These heuristics are used in combination with a genetic algorithm formulation to produce a novel, two-staged algorithm for the design and control of membrane reactor systems. This algorithm is developed in Python and uses rigorous membrane reactor models built in AVEVA Process Simulation. The proposed algorithm solves the original non-polynomial (NP) complexity problem in polynomial time (P), while still being able to find the optimal designs discovered in previous work through exhaustive methods.

Solid suspension and gas dispersion in gas-solid-liquid agitated systems

2010 ◽  
Vol 64 (2) ◽  
Author(s):  
Anna Kiełbus-Rąpała ◽  
Joanna Karcz
Keyword(s):  
Residence Time ◽  
Experimental Studies ◽  
Gas Bubbles ◽  
High Energy ◽  
Gas Velocity ◽  
Solids Concentration ◽  
Three Phase ◽  
Phase Systems ◽  
Superficial Gas Velocity ◽  
Solid Liquid

AbstractThe aim of the research work was to investigate the effect of superficial gas velocity and solids concentration on the critical agitator speed, gas hold-up and averaged residence time of gas bubbles in an agitated gas-solid-liquid system. Experimental studies were conducted in a vessel of the inner diameter of 0.634 m. Different high-speed impellers: Rushton and Smith turbines, A 315 and HE 3 impellers, were used for agitation. The measurements were conducted in systems with different physical parameters of the continuous phase. Liquid phases were: distilled water (coalescing system) or aqueous solutions of NaCl (non-coalescing systems). The experiments were carried out at five different values of solids concentration and gas flow rate. Experimental analysis of the conditions of gas bubbles dispersion and particles suspension in the vessel with a flat bottom and four standard baffles showed that both gas and solid phases strongly affected the critical agitation speed necessary to produce a three-phase system. On the basis of experimental studies, the critical agitator speed for all agitators working in the gas-solid-liquid systems was found. An increase of superficial gas velocity caused a significant increase of the gas hold-up in both coalescing and non-coalescing three-phase systems. The type of the impeller strongly affected the parameters considered in this work. Low values of the critical impeller speed together with the relatively short average gas bubbles residence time tR in three phase systems were characteristic for the A 315 impeller. Radial flow Rushton and Smith turbines are high-energy consuming impellers but they enable to maintain longer gas bubbles residence time and to obtain higher values of the gas hold-up in the three-phase systems. Empirical correlations were proposed for the critical agitator speed, mean specific energy dissipated and the gas hold-up prediction. Its parameters were fitted using experimental data.

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