Proposed Separation Process Research Articles

Optimization of the bioethanol dehydration process using MgCl2 as mass separating agent

Ethanol derived from lignocellulosic sources is an important chemical that can have several uses such as biofuel that can be blended with gasoline, as sanitizer for the disinfection of surfaces, or as additive in the food, cosmetic and pharmaceutical industry. Nevertheless, its separation poses a challenge because it must be separated from water and this mixture forms an azeotrope. This research focuses on the ethanol dehydration using magnesium chloride (MgCl2) as a mass separating agent, which is an innocuous chemical used in the food industry to process Tofu. Therefore, it does not have any side effect, or it is not harmful for humans. Therefore, the use of this salt makes possible to use the purified ethanol as an additive in the food, cosmetic, or pharmaceutical industry. The proposed separation process is optimized using surrogate nonlinear models for the preconcentration and salt evaporation units. The results showed that using magnesium chloride dodecahydrate is a feasible alternative to bioethanol valorization.

A Technical Proton Pump for Industrial Biotechnology: Electrochemical pH-Swing Extraction of Succinic Acid

Industrial biotechnology established new routes for sustainable production of platform chemicals.[1] Succinic acid is a versatile building block for bio-based polymers and solvents.[2] Despite the progress made in up-stream development separation and product purification still account for up to 40% of total production costs.[3] The high separation costs originate from a mismatch between the optimal pH for fermentation and product recovery. While most bio-catalysts work best at neutral pH, acidic pH is advantageous for product recovery.[4] However, pH control by inorganic bases and acids comes with the drawback of producing large amounts of inorganic salt waste like gypsum.[5] Electrochemical separation methods have the potential to overcome the unsustainable production of salt waste and are thus regarded a more environmentally benign separation technology.[6] The integration of electrochemical separation methods showed great potential for overcoming the mismatch between fermentation pH and pH required for separation. With promising results reported for electrochemical unit operations applied for waste free product recovery from fermentation [7] integration of electrochemical unit operations into a complete downstream process sequence should be the next objective. [8]We recently proposed an electrochemical downstream concept applying electrochemical pH-swing extraction for the recovery of succinic acid from pH-neutral aqueous solutions followed by another pH-swing step for product stripping from the extractant and eventual product recovery by direct electrochemical pH-shift crystallization.[9,10] Thereby, generation of spatially separated regions of acidic and alkaline pH by water electrolysis is utilized to generate the pH-dependent driving force for reactive extraction of succinic acid by tri-n-octylamine. The acidic pH shifts the aqueous acid-base equilibrium towards the protonated succinic acid, which is then available for extraction.[4] Hydroxide ions simultaneously produced at the cathode create an alkaline catholyte, which can be used for pH control in succinic acid fermentation. The water electrolysis coupled to liquid-liquid extraction creates an integrated buffer-recycle between fermentation and product separation and overcomes the need for adding inorganic acids and bases for pH-control. In a second electrochemical pH-swing cell the alkaline solution produced by the cathodic reaction of a water electrolysis cell is used to strip the acid from the loaded extractant producing an aqueous solution with high succinic acid concentration. The anodic reaction of this second cell is eventually used to crystallize succinic acid from this mother liquor by the electrochemical pH-shift.[9] Recovery of solid succinic acid was achieved by a downstream process constituted of four electrochemical processing steps synergistically integrated into two electrochemical cells which did not require energy intensive evaporation of water.This contribution gives insights into experimental examples for succinic acid recovery via the proposed separation process and discusses opportunities for the design of membrane free cells, as separation selectivity is solely determined by liquid-liquid extraction. In extension to previous work [11] the dynamic modeling approach for electrochemical pH-swing electrolysis was extended to account for concentration dependent increase of ohmic losses and pH-dependent proton cross-over. The new model is used to identify good operational conditions with high current efficiencies. The model results are compared to experimental data recorded in a 100cm² electrolysis cell coupled to a lab-scale extraction column.

Process development for separation of lignin from OrganoCat lignocellulose fractionation using antisolvent precipitation

For the sustainable production of chemicals, lignocellulosic biomass can be fractionated into cellulose, hemicellulose and lignin, which can be subsequently converted into valuable intermediates. In the OrganoCat pulping process, lignin is separated from other fractionation products by in situ extraction into the organic solvent 2-methyltetrahydrofuran. However, a suitable concept for the subsequent separation of lignin from this solvent has not yet been identified. In this work, a technically feasible process for the separation of lignin from 2-methyltetrahydrofuran solutions using antisolvent precipitation is developed and evaluated based on lignin precipitation yield, solvent recovery and energy efficiency. For the determination of suitable antisolvents, an experimental solvent screening is performed. The conceptual process design is accomplished on the basis of lignin solubility measurements and process simulations. High lignin precipitation yields are achieved using n-hexane and n-pentane. An efficient process for lignin separation by combining solvent evaporation and precipitation using n-pentane is presented. The proposed separation process leads to lignin which can be separated by filtration and is characterized by low energy consumption and effective antisolvent recovery.

Energy-efficient separation process and control scheme for extractive distillation of ethanol-water using deep eutectic solvent

With the development and improvement of solvents (or entrainers), the extractive distillation process has been significantly enhanced, and the energy consumption of the separation process has been effectively reduced. In this work, the energy-efficient separation process for extractive distillation with deep eutectic solvent ChCl/Urea (1:2) is designed. The ethanol dehydration process is selected as a case study to evaluate the practical utility of this novel solvent in large-scale production. The multi-objective genetic algorithm is used to optimize the extractive distillation process, and the waste heat is recovered through the heat intensification strategy to achieve the optimal design. Five control schemes, which include proportional-integral (PI) and model predictive control strategies (MPC), are developed for the proposed separation process. According to the nonlinear relationship between manipulated variables and controlled variables, the improved control structures are designed to enhance the dynamic performance. Integral absolute error (IAE) and destroyed exergy are applied as evaluation criteria to test the controllability and energy efficiency of the system. The results show that both CS4 and MPC control schemes have good controllability, and the MPC control scheme displays better energy efficiency than the CS4 control scheme.

Theoretical Study of Moisture-Pretreated Lithium as Potential Material for Natural Gas Upgrading

For efficient natural gas upgrading at near ambient temperatures, moisture-pretreated lithium is proposed as a reactive adsorbent, and its separation performance was examined for selected gas mixtures (involving combination of CH4, CO2, O2, N2, and/or H2) by theoretical studies. For evaluating the proposed adsorbent, we used density functional theory calculations as well as temperature-programmed kinetic Monte Carlo calculations. Contributions of different mechanisms for the gas capture were examined, including diffusion, adsorption, and reaction. Among these mechanisms, reaction was found to be the dominant factor during the gas-capture process. In contrast to the conventional reactive adsorbents where gases directly react with adsorbents and thus are captured, the gas-capture mechanism herein follows the reaction between gases and species generated upon pre-exposure of lithium to moisture. The proposed separation process is thermodynamically favorable and would progress spontaneously. It is shown that f...

Optimization of extraction solvent-to-feed ratio: Aqueous ethanol mixture separation using [TDTHP][NTf2] ionic liquid

Separation of ethanol from its diluted aqueous solution by liquid–liquid extraction is modelled using ionic liquid tetradecyltrihexylphosphonium bis(trifluoromethylsulfonyl)imide as the extraction solvent. Based on the ternary phase equilibrium data, composition of the extract phase in counter-current separation equipment was computed showing a maximum in the ethanol-to-water mole ratio while the solvent-to-feed mole ratio was changing. Ethanol pre-concentration was further enhanced during the extraction solvent regeneration by ethanol (and water) stripping into inert gas. Final step of the proposed separation process was freeze-drying of the inert gas used for the extraction solvent regeneration. Temperature in the stripper was optimized for the minimum overall heat duty in the stripper and cooler/freezer. A simplified economic balance showed that operational expenditures connected with the proposed separation procedure attain only approximately 40% of those required for the ethanol separation by distillation.

Process Configurations and Simulations for a Novel Single-Column Cryogenic Air Separation Process

In this article, a novel single-column atmospheric cryogenic air separation process is proposed to reduce energy consumption through the implementation of thermal pump technique. Different from the conventional double-column cryogenic process, the new single-column distillation includes a nitrogen compressor acting as a thermal pump, which makes use of the latent thermal energy of the streams in the distillation column. To verify the validity of the proposed separation process, four typical configurations of the single-column processes are constructed and simulated on the ASPEN PLUS platform with the operation conditions: air flow rate at 50 000 N m3, inlet temperature of the distillation column at 87 K, and various nitrogen compression temperatures. The conventional double-column cryogenic air separation process is also simulated as the base to compare the energy consumptions between the conventional and the novel processes. On the basis of such a comparison, the novel single-column cryogenic air separat...

Modeling, simulation and control of an internally heat integrated pressure-swing distillation process for bioethanol separation

Abstract Ethanol produced from biomass is one of the most promising renewable fuels. However, most of the proposed separation methods use volatile organic compounds as solvents. Because such solvents are environmentally hazardous, new, efficient and sustainable ways of alcohol purification process ought to be developed. Ideally, no solvent should be required for the high purity purification of alcohol aqueous solutions. Therefore, in this work the modeling, simulation and control of an internally heat integrated pressure-swing distillation (IHIPSD) process to separate the ethanol/water azeotropic binary system into a high purity ethanol stream are addressed. By means of the proposed separation process, high-purity ethanol, suitable for use in the transportation sector, is obtained. Despite the high interaction between the column sections, the results show that the proposed separation process can be operated smoothly with an array of PI controllers. Moreover, the purity of ethanol is maintained with the control structure proposed in the face of upsets.

Entwicklung eines Extraktionsverfahrens zur Gewinnung von Technetium und Palladium aus der Abfallösung der Kernbrenstoffwiederaufbereitung: Teil 2: Selektivitätsuntersuchungen und Testung einer Laboranlage

The results of the investigation of extraction of Tc and Pd with tri-n-octylamin in CCl4, were given in Part 1. In this part the extraction isotherms with model solution, which simulates the waste solution, are studied and data for the selectivity of the proposed separation process are given. A flow scheme is proposed and the whole process is tested in a laboratory plant.