Closed loop control of the multi-column solvent gradient purification process

A PID controller able to support the operator in the operation of the Multi-column Countercurrent Solvent Gradient Purification (MCSGP) process which is a continuous, countercurrent chromatographic process has been developed. As measurement, only the online UV signals at each column outlet are used. This guarantees a simple and cheap control implementation and a fast control action. Accordingly, the controller does not guarantee any purity or yield value, but simply that the withdrawn window of the product is centered in a specific region of the UV chromatogram where the purity specifications are expected to be satisfied. This can be determined by the operator based on the batch chromatogram selected for designing the MCSGP operating conditions. Thus the controller provides a reliable and efficient tool for the operator to run properly a MCSGP unit in combination with suitable offline analytics for the quantification of purity and yield. The applications are discussed involving the purification of a model protein and a peptide. It is shown that the developed controller is effective in driving the unit to steady state during start up and in keeping a stable steady state while rejecting external disturbances.     

Production of Ethanol from Sweet Sorghum Juice Using VHG Technology: A Simulation Case Study

The aims of this study were to develop the kinetic model and determine kinetic parameters describing ethanol production from sweet sorghum juice using very high gravity technology in the batch fermentation of Saccharomyces cerevisiae NP01. The obtained experimental data were tested with four different types of model, based on the experimental data, accounting for the substrate limitation, substrate inhibition, product inhibition, and the combination of those three effects, respectively. The optimization technique to find kinetic parameters was non-linear regression using Marquardt method performed through numerical procedure. The chosen model with its kinetic parameters obtained in the batch mode was validated and tested against the other independent experimental data in the small batch-scale and large-scale fermenter, in order to investigate the applicability and scale-up effect of the model, respectively. Then, the obtained model with its parameters was applied in the simulations of the continuous and fed-batch operations to examine the concentration profiles of fermentation components with the variations in operating parameters such as the dilution rate, feed-flow rate, start-up time, and feed concentration. The results indicated that the kinetic model (the substrate limitation with substrate and product inhibition effects) was suitable to describe ethanol fermentation. In the continuous mode, using the dilution rate of 0.01 h^?1, the maximum ethanol concentration obtained was, approximately, 90 g/l whereas the simulated results from the fed-batch operation revealed that the maximum ethanol concentration at quasi-steady state condition was, approximately, 96 g/l. The start-up time of 21 h was the fastest time to reach the steady-state and quasi-steady state for both the continuous and fed-batch modes, respectively.     

Leaching of Celestite in Sodium Hydroxide Solutions and Kinetic Modelling

In this study, the dissolution kinetics of celestite in solutions of sodium hydroxide was investigated by batch process. The results showed that the parameters which had the greatest effect on the dissolution of celestite in sodium hydroxide solutions were reaction temperature, the concentration of sodium hydroxide and stirring speed. It was determined that the dissolution rate increased with increased stirring speed, sodium hydroxide concentration, reaction time and temperature and decreased with increasing particle size and solid-liquid ratio. The leaching process fitted the shrinking core model with diffusion through the product layer model as the rate-determining step. The activation energy of the dissolution of celestite was calculated as 62.24?kJ/mol. A semi-empirical kinetic model was obtained for dissolution of celestite in sodium hydroxide solution.     

The Operable Modeling of Simultaneous Saccharification and Fermentation of Ethanol Production from Cellulose

An operable batch model of simultaneous saccharification and fermentation (SSF) for ethanol production from cellulose has been developed. The model includes four ordinary differential equations that describe the changes of cellobiose, glucose, yeast, and ethanol concentrations with respect to time. These equations were used to simulate the experimental data of the four main components in the SSF process of ethanol production from microcrystalline cellulose (Avicel PH101). The model parameters at 95% confidence intervals were determined by a MATLAB program based on the batch experimental data of the SSF. Both experimental data and model simulations showed that the cell growth was the rate-controlling step at the initial period in a series of reactions of cellulose to ethanol, and later, the conversion of cellulose to cellobiose controlled the process. The batch model was extended to the continuous and fed-batch operating models. For the continuous operation in the SSF, the ethanol productivities increased with increasing dilution rate, until a maximum value was attained, and rapidly decreased as the dilution rate approached the washout point. The model also predicted a relatively high ethanol mass for the fed-batch operation than the batch operation.     

Kinetic Modeling of Ethanol Production by Scheffersomyces stipitis from Xylose

This work focuses on the kinetics of ethanol production by Scheffersomyces stipitis on xylose with the development of a mathematical model considering the effect of substrate and product concentrations on growth rate. Experiments were carried out in batch and continuous modes, with substrate concentration varying from 7.2 to 145 g L^?1. Inhibitory effects on cell growth, substrate uptake, and ethanol production rates were found to be considerable. Kinetic parameters were obtained through linear and non-linear regression methods. Experiments in continuous mode were performed at different dilution rates to evaluate the inhibitory effect of ethanol. A mixed mathematical model which combined Andrews and Levenspiel's models, combining substrate and product inhibition, was used. A quasi-Newton routine was applied to obtain a more accurate fitting of kinetic parameters. The parameters such as cell to product factor (Y _P/X) and limiting cell yield (Y _X) were shown to be dependent on substrate concentration. The kinetic model fitted satisfactorily the experimental data.     

A semi-continuous laboratory-scale polymer enhanced ultrafiltration process for the recovery of cadmium and lead from aqueous effluents

A semi-continuous process of polymer enhanced ultrafiltration for removal of lead and cadmium has been elaborated. This operation mode would let a better coupling between industrial and laboratory-scale processes. Basically, it includes two stages: (1) metal retention, where we can obtain a permeate stream free of heavy metals; (2) polymer regeneration, where the polymer is regenerated in order to be reused in metal retention stage. In order to work in this way, a control system of permeate and feed stream flows has been installed in a batch laboratory-scale plant. In the first place, more suitable hydrodynamic operating parameters were obtained by ultrafiltration experiments. The influence of pH has been studied to fix the pH for metal retention and polymer regeneration experiments, and the operative polymer binding capacity has been determined to know the metal amount that can be treated. A mathematical model taking into account both conservation equations and competitive reactions which occur in the medium has been established. The development of this mathematical model (which is in good agreement with experimental data) enables to estimate design parameters to dimension pilot and industrial scale installations based on this process.     

A batch modelling approach to monitor a freeze-drying process using in-line Raman spectroscopy

Freeze-drying or lyophilisation is a batch wise industrial process used to remove water from solutions, hence stabilizing the solutes for distribution and storage. The objective of the present work was to outline a batch modelling approach to monitor a freeze-drying process in-line and in real-time using Raman spectroscopy. A 5% (w/v) d-mannitol solution was freeze-dried in this study as model. The monitoring of a freeze-drying process using Raman spectroscopy allows following the product behaviour and some process evolution aspects by detecting the changes of the solutes and solvent occurring during the process. Herewith, real-time solid-state characterization of the final product is also possible.The timely spectroscopic measurements allowed the differentiation between batches operated in normal process conditions and batches having deviations from the normal trajectory. Two strategies were employed to develop batch models: partial least squares (PLS) using the unfolded data and parallel factor analysis (PARAFAC). It was shown that both strategies were able to developed batch models using in-line Raman spectroscopy, allowing to monitor the evolution in real-time of new batches. However, the computational effort required to develop the PLS model and to evaluate new batches using this model is significant lower compared to the PARAFAC model. Moreover, PLS scores in the time mode can be computed for new batches, while using PARAFAC only the batch mode scores can be determined for new batches.     

Continuous process for the production of vinyl acetate‐ethylene emulsion copolymers

A lab‐scale experimental program was conducted to determine the feasibility of producing vinyl acetate‐ethylene (VAE) emulsion copolymers via a continuous reaction process, using poly(vinyl alcohol), or PVOH, as a protective colloid. A process configuration of multiple stirred‐tanks in series was utilized. Comparisons were made between continuous and batch processes with regard to final‐product properties. As expected, notable differences in the breadths of the particle‐size distributions obtained via the two processes were observed. However, these differences did not appreciably alter product performance in tile‐mortar applications (as measured by plywood‐to‐quarry‐tile adhesive strengths). Additionally, for the continuous process, in‐process and final‐product samples were compared to determine how polymer properties varied with conversion.     

Kinetics of ethanol fermentation with high biomass concentration considering the effect of temperature

A model of ethanol fermentation considering the effect of temperature was developed and validated. Experiments were performed in a temperature range from 28 to 40°C in continuous mode with total cell recycling using a tangential microfiltration system. The developed model considered substrate, product and biomass inhibition, as well as an active cell phase (viable) and an inactive (dead) phase. The kinetic parameters were described as functions of temperature.     

Estimation of Fundamental Kinetic Parameters of Polyhydroxybutyrate Fermentation Process of Azohydromonas australica Using Statistical Approach of Media Optimization

Polyhydroxybutyrate or PHB is a biodegradable and biocompatible thermoplastic with many interesting applications in medicine, food packaging, and tissue engineering materials. The present study deals with the enhanced production of PHB by Azohydromonas australica using sucrose and the estimation of fundamental kinetic parameters of PHB fermentation process. The preliminary culture growth inhibition studies were followed by statistical optimization of medium recipe using response surface methodology to increase the PHB production. Later on batch cultivation in a 7-L bioreactor was attempted using optimum concentration of medium components (process variables) obtained from statistical design to identify the batch growth and product kinetics parameters of PHB fermentation. A. australica exhibited a maximum biomass and PHB concentration of 8.71 and 6.24?g/L, respectively in bioreactor with an overall PHB production rate of 0.75?g/h. Bioreactor cultivation studies demonstrated that the specific biomass and PHB yield on sucrose was 0.37 and 0.29?g/g, respectively. The kinetic parameters obtained in the present investigation would be used in the development of a batch kinetic mathematical model for PHB production which will serve as launching pad for further process optimization studies, e.g., design of several bioreactor cultivation strategies to further enhance the biopolymer production.     

Comparison of standard and new generation hydrophobic interaction chromatography resins in the monoclonal antibody purification process

Recent efforts to improve hydrophobic interaction chromatography (HIC) for use in monoclonal antibody (mAb) purification have focused on two approaches: optimization of resin pore size to facilitate mAb mass transport, and use of novel hydrophobic charge induction (HCIC) mixed mode ligands that allow capture of mAbs under low salt conditions. We evaluated standard HIC and new generation HIC and HIC-related chromatography resins for mAb purification process efficiency and product quality both as isolated chromatography steps and in purification process trains. We find that HIC resins with optimized pore size have significantly improved binding capacity which can increase HIC purification unit operation efficiency. The HCIC Mercapto-Ethyl-Pyridine (MEP) resin, which shows a different salt impact trend and impurity resolution pattern from standard HIC resin, can not only capture mAb from crude CHO fermentation supernatant but also substantially enhance mAb purification process flow efficiency when serving as a polishing role.     

Continuous purification of a clotting factor IX concentrate and continuous regeneration by preparative annular chromatography

Preparative continuous annular chromatography, a method to separate proteins in a truly continuous manner, was investigated in an industrial environment. Plasma-derived clotting factor IX concentrate was used as model protein. Separation of vitronectin, a common impurity in commercial available factor IX concentrates, from factor IX was studied and compared to conventional packed bed chromatography in batch mode. As sorbent, Toyopearl DEAE 650M was used. Regeneration was performed simultaneously with the purification of factor IX in continuous mode. All required parameters applied for preparative annular chromatography such as feed flow-rate and elution flow-rate were first estimated from experiments on conventional batch columns. Then preparative annular chromatography and conventional packed beds were compared regarding enrichment, purity and productivity. Three different process scenarios, the optimal batch process,the preparative annular chromatography process and the batch process equivalent to the preparative annular chromatography process were investigated. The productivity of the optimal batch process was higher than that of the preparative annular chromatography and batch process equivalent to the preparative annular chromatography process. Therefore the throughput could not be increased by the use of the continuous chromatographic system.     

Reactive Distillation: An Attractive Alternative for the Synthesis of Unsaturated Polyester

Summary: Unsaturated polyester is traditionally produced in a batch wise operating reaction vessel connected to a distillation unit. An attractive alternative for the synthesis of unsaturated polyester is a reactive distillation. To value such alternative synthesis route reliable process models need to be developed. In this paper, the strategy is described for the development of the reactive distillation model. Essential parts of the reactive distillation model are kinetic and thermodynamic which are subsequently validated with the experimental data of the traditional batch process such as acid value of the polyester, weight of the distillate and glycol concentration in the distillate. We find that the models predict these important variables reliably. Unsaturated polyester production time is around 12 hours in the traditional batch process. However, the simulation study of the reactive distillation process shows that the total production time of unsaturated polyester in a continuous reactive distillation system is between 1.5 hours to 2 hours for the same product quality as during batch production. The equilibrium conversion is raised by 7% compared to the traditional batch process. The model demonstrated that reactive distillation has the potential to intensify the process by factor of 6 to 8 in comparison to the batch reactor.     

Scale-up of batch kinetic models

The scale-up of batch kinetic models was studied by examining the kinetic fitting results of batch esterification reactions completed in 75 mL and 5 L reactors. Different temperatures, amounts of catalysts, and amounts of initial starting reagents were used to completely characterize the reaction. A custom written Matlab toolbox called GUIPRO was used to fit first-principles kinetic models directly to in-line NIR and Raman spectroscopic data. Second-order kinetic models provided calibration-free estimates of kinetic and thermodynamic reaction parameters, time dependent concentration profiles, and pure component spectra of reagents and product. The estimated kinetic and thermodynamic parameters showed good agreement between small-scale and large-scale reactions. The accuracy of pure component spectra estimates was validated by comparison to collected NIR and Raman pure component spectra. The model estimated product concentrations were also validated by comparison to concentrations measured by off-line GC analysis. Based on the good agreement between kinetic and thermodynamic parameters and comparison between actual and estimated concentration and spectral profiles, it was concluded that the scale-up of batch kinetic models was successful.     

Biohydrogen Production Based on the Evaluation of Kinetic Parameters of a Mixed Microbial Culture Using Glucose and Fruit–Vegetable Waste as Feedstocks

Hydrogen (H₂) production from the organic fraction of solid waste such as fruit and vegetable waste (FVW) is a novel and feasible energy technology. Continuous application of this process would allow for the simultaneous treatment of organic residues and energy production. In this study, batch experiments were conducted using glucose as substrate, and data of H₂ production obtained were successfully adjusted by a logistic model. The kinetic parameters (μ _max?=?0.101 h^?1, K _s?=?2.56 g/L) of an H₂-producing microbial culture determined by the Monod and Haldane–Andrews growth models were used to establish the continuous culture conditions. This strategy led to a productive steady state in continuous culture. Once the steady state was reached in the continuous reactor, a maximum H₂ production of 700 mL was attained. The feasibility of producing H₂ from the FVW obtained from a local market in Mexico City was also evaluated using batch conditions. The effect of the initial FVW concentration on the H₂ production and waste organic material degradation was determined. The highest H₂ production rate (1.7 mmol/day), the highest cumulative H₂ volume (310 mL), and 25 % chemical oxygen demand (COD) removal were obtained with an initial substrate (FVW) concentration of 37 g COD/L. The lowest H₂ production rates were obtained with relatively low initial substrate concentrations of 5 and 11 g COD/L. The H₂ production rates with FVW were also characterized by the logistic model. Similar cumulative H₂ production was obtained when glucose and FVW were used as substrates.     

Adsorption of U (VI) ions from aqueous solution using silicon dioxide nanopowder

The adsorption kinetics for removal of uranium (V1) from aqueous solution using silicon dioxide nanopowder (nano-SiO₂) was investigated in batch and continuous techniques. Pseudo-first order and pseudo-second order were used to analyze the kinetics of batch experiments. In continuous technique the important parameters (initial concentration, flow rate and bed height) on the breakthrough curves were studied and the adsorption kinetics was analyzed using Thomas and Yoon and Nelson kinetic models. The comparison between the kinetic models was evaluated by the correlation coefficients (r²). The results indicated that the batch experiments fitted well with pseudo second-order kinetic model. The comparison of the experimental breakthrough curve to the breakthrough profile obtained from Thomas and Yoon and Nelson methods showed a satisfactory fit for silicon dioxide nanopowder.     

Continuous Preparation of Calcite,Aragonite and Vaterite,and of Magnesium‐Substituted Amorphous Calcium Carbonate (Mg‐ACC)

The three water‐free calcium carbonate polymorphs calcite, aragonite and vaterite were prepared from aqueous solutions without additives using standard laboratory equipment in a continuous process. Variation parameters were the way of mixing, the solution concentrations, and the reactor residence time. The samples were crystallographically and chemically pure, but a thorough elemental analysis revealed the presence of small amounts of sodium carbonate which was not detectable by X‐ray powder diffraction. The continuous process avoids the inherent variability of batch syntheses. By adapting the crystallization parameters, magnesium‐substituted amorphous calcium carbonate (molar ratio of Mg:Ca of 1:2.68) was prepared in this continuous process.     

Modeling the adsorption of U(VI) onto animal chitin using coupled mass transfer and surface complexation

This paper reports the development of a treatment system, using animal chitin as a passive biosorbent, for removing U(VI) from aqueous waste streams. An integral part of this system is a model that provides for the optimization of the treatment system through simulation of U(VI) removal efficiency based on the characteristics of the influent waste stream. The model accounts for changing solution matrix conditions through the coupling of surface complexation and mass transfer models. Complexation of U(VI) by chitin surface sites was modeled using FITEQL. Application of FITEQL in the “forward” mode provided the sorbed and aqueous phase concentrations needed for the mass transfer model. The mass transfer model was derived for both batch and continuously stirred tank reactor (CSTR) configurations using Fick's Law, reactor mass balances and rate law expressions. The coupled model was successfully validated using CSTR data at pH 6.5 and rate constants determined from batch sorption experiments. The CSTR configuration yields a steady-state, eighty percent U(VI) removal for 1 μM influent U(VI) with a solution-phase pH of 6.5 and 3.9 g l⁻¹ chitin.     

Reaction kinetics and mechanism for hydrothermal degradation and electrolysis of glucose for producing carboxylic acids

Electrolysis in subcritical water can convert biomass-derived saccharides into value-added chemicals and fuels without any additives. In this work, we aim to understand reaction behaviours of glucose under subcritical water degradation or electrochemical conditions for the purpose of developing a new method for producing useful carboxylic acids. Degradation of glucose was carried out using a continuous flow-type reactor in subcritical water at various operating conditions, and electrochemical reactions of their product solutions were conducted at identical conditions with a 500-mL batch autoclave. Gaseous products obtained were analyzed by gas chromatography-thermal conductivity detection (GC-TCD), and liquid products were analyzed by high-performance liquid chromatography (HPLC) and gas chromatography-flame ionization detection (GC-FID). The total organic carbon (TOC) in the aqueous product solution was determined by using a TOC analyzer. Based on the experimental results, a reaction pathway for glucose is proposed for subcritical water degradation and electrolysis.     

Highly efficient,economic, and recyclable glutathione decorated magnetically separable nanocomposite for uranium(VI) adsorption from aqueous solution

A green and environment-friendly magnetically separable nanocomposite, glutathione@magnetite was fabricated sonochemically through the functionalization of Fe₃O₄ by glutathione which was well characterized using Fourier-transform infrared spectroscopy, ultravoilet-visible spectroscopy, scanning electron microscope, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, thermogravimetric analysis, vibrating sample magnetometer, Brunauer-Emmett-Teller, and high-resolution transmission electron microscope. The parameters affecting adsorption including pH, temperature, contact time, initial adsorbate concentration, and adsorbent amount were optimized by batch experiments. The magnetic glutathione@magnetite was applied for the removal of uranium(VI) in water with maximum adsorption capacity found to be 333.33 mg/g in 120 min at a neutral pH at 25 °C showing high efficiency for U(VI) ions. Furthermore, adsorption results obtained from UV-vis spectroscopy were validated by inductively coupled plasma optical emission spectroscopy. The thermodynamic parameters, viz Gibbs free energy (ΔGº), standard enthalpy change (ΔHº), and standard entropy change (ΔSº) of the process were calculated using the Langmuir constants. The pseudo-second-order kinetics model is seen to be applicable for describing the uptake process using a kinetics test. Moreover, desorption studies reveals that glutathione@magnetite can be used repeatedly, and removal efficiency shows only a small decrease after six cycles. Thus, glutathione@magnetite acts as a potential adsorbent for the removal of U(VI) from the water with great adsorption performance.