Feed Impurity Research Articles

Unraveling the alternative process configurations for more environmentally friendly Maleic Anhydride production

This study aims to propose and evaluate alternative configurations for producing maleic anhydride (MA) through the n-butane oxidation pathway to enhance overall environmental friendliness. Seven alternative configurations, which vary in the number of non-adiabatic reactors and heat exchange methods, as well as the stripping agents used for recovering MA in the purification section, are rigorously designed and comprehensively compared. Among the proposed configurations, we have found that the one utilizing single reactor with co-current cooling and water as the stripping agent (Scheme 2) shows the most promise. It has an optimal yield of 70.0 %, an energy efficiency of 97.52 %, and exergy efficiency of 44.92 %. A cradle-to-gate life cycle impact assessment determines a Global Warming Potential (GWP) of 0.091 kg-CO2eq/kg-MA from this scheme. In contrast, a techno-economic evaluation determines a minimum required selling price (MRSP) of 0.965 USD/kg-MA from this scheme. All these indicators are superior compared to those documented in the existing literature, suggesting a higher level of environmental friendliness. Subsequently, a suitable control strategy is proposed for the optimized Scheme 2 and evaluated by rejecting various kinds of feed disturbances (i.e., ± 10 % change in feed flowrate, ± 5 % change in molten salt flowrate, 1 % and 2 % of i-butane as feed impurity, and catalyst deactivation up to 40 %). Enhanced controllability is achieved by regulating the flowrate ratio between the flashed liquid and the n-butane (FL/NBU), which promptly indicates the reaction conversion during production. Based on the findings, we have concluded that overall environmental friendliness can be significantly enhanced with moderate modifications in the process configuration, which are easily feasible in the industry.

Experimental and influencing factors of corn stalk pulling force

The harvesting of straw by the flail knife type straw cutting device will cause loose contacts between straw roots and soil, affecting the straw feed's impurity content. In this study, a theoretical analysis of the straw cutting process was conducted to explore the factors influencing the root-soil disturbance. A pulling force test device was designed to test the pulling force of the corn stalk. The response surface method was used to study the effects of various factors on the straw pulling force under different conditions of draft angles (20°, 30°, 40°), soil moisture content (15.23%, 17.62%, 20.47%), and different straw root diameters. The test results showed that the straw pulling force was directly proportional to the straw root diameter and inversely proportional to the soil moisture content. The straw pulling force decreased first and then increased with the increase of the draft angle. According to the established second-order regression model, when the draft angle was 28.5°, the soil moisture content was 20.47%, the root diameter was 22 mm, the minimum pulling force of straw was 189.635N. The test results can provide a reference for the design of straw feed harvester.

Low‐density polyethylene tubular reactor control using neural Wiener model predictive control

AbstractLow‐density polyethylene (LDPE) is a valued commodity plastic with versatile applications. However, controlling the LDPE polymerization reactor is a challenging task due to its nonlinear behavior and multivariable process and operates in a board operating region. This work aims to develop and explore the neural Wiener MPC (NWMPC) application in controlling the LDPE tubular reactor process. The motivation for NWMPC development originates from its advantage in terms of lower development effort, time, resource, and computational costs compared to nonlinear MPC (NMPC) using the first principle model (FPM). In order to develop the LDPE tubular reactor model, the Aspen Plus and Aspen Dynamic software are used to simulate the process in steady‐state and dynamic form. The neural Wiener (NW) model identification is performed using state space and neural network model identification using Matlab software. The identification result shows the ability of the NW model to identify the nonlinear LDPE tubular reactor process successfully. Furthermore, the NWMPC has outperformed the state space MPC (SSMPC) in controlling grade transition, feed pressure loss, feed impurity disturbance, and heat of polymerization change during the online closed‐loop performance tests. These results signify the ability of NWMPC to handle practical LDPE tubular reactor control scenarios.

Impact of hybrid CO2-CO feeds on methanol synthesis over In2O3-based catalysts

Catalysts for CO2-to-methanol are typically evaluated in a single-pass regime using pure CO2streams. In a practical process however, CO shall be present as a feed impurity or as a recycled byproduct. Herein, the sensitivity to CO was evaluated on In2O3 catalysts in bulk, supported, or metal-promoted forms, using cycle experiments with variable CO2 and CO contents at H2/(CO + CO2) = 4. The methanol productivity was decreased (−20-−40 %) on all catalysts except In2O3/monoclinic-ZrO2, the activity of which was boosted by 10 %. In-depth characterization of the catalysts uncovered controlled formation of oxygen vacancies and resistance to sintering as the main reasons for the activation of the latter and an interplay of CO/H2O-induced sintering and CO inhibition as the origin of performance loss. Focusing on the most representative systems, operation protocols were explored to maximize their methanol yield. We emphasize that assessment with hybrid CO2-CO feeds is key for the design of industrially-viable catalysts for sustainable methanol production.

Protecting effect of mass transport during electrochemical reduction of oxygenated carbon dioxide feedstocks

This work elucidates fundamental transport and kinetic phenomena underlying oxygen gas feed impurity behavior during CO2electroreduction.

Estimator Based Inferential Control of an Ideal Quaternary Endothermic Reactive Distillation with Feed-Forward and Recurrent Neural Networks

Abstract A feed-forward neural network (FNN) and a layered recurrent neural network (LRNN) based two composition estimators, respectively, are designed for the purpose of tight product purity control for an ideal, quaternary, hypothetical, kinetically controlled, reactive distillation (RD) column. The output variables of the considered control structure i.e. the compositions, are estimated using the chosen tray temperatures as inputs to the estimators. The performances of the estimators in the control of the column for the servo, regulatory, feed impurity disturbances and catalyst deactivation are studied. The estimator based control is found to be effective for the on-spec product purity control. One-to-one relation between the number of tray temperature measurements and their sensitivity to the accuracy of estimation is observed. Overall, the performance of LRNN is found to be superior over the FNN for the throughput manipulations tested for the more number of inputs to estimator.

Coupling Solvent Extraction Units to Cyclic Adsorption Units

The possibility of regenerating the solvent of extraction units by cyclic adsorption was analyzed. This combination seems convenient when extraction is performed with a high solvent-to-impurity ratio, making other choices of solvent regeneration, typically distillation, unattractive. To our knowledge, the proposed regeneration scheme has not been considered before in the open literature. Basic relations were developed for continuous and discontinuous extraction/adsorption combinations. One example, deacidification of plant oil with alcohol, was studied in detail using separate experiments for measuring process parameters and simulation for predicting performance at different conditions. An activated carbon adsorbent was regenerated by thermal swing, making cyclic operation possible. When extracting the acid with methanol in a spray column, feed = 4 L min−1, solvent = 80 L min−1, feed impurity level 140 mmol L−1, and extract concentration 7.6 mmol L−1, the raffinate reaches a purity of 1.2 mmol L−1, the solvent being regenerated cyclically in the adsorber (364 kg) to an average of 0.7 mmol L−1. Regeneration of the solvent by cyclic adsorption had a low heat duty. Values of 174 kJ per litre of solvent compared well with the high values for vaporization of the whole extract phase (1011 kJ L−1).

Neural Network to Understand Process Capability and Process Intermediates Acceptance Criteria in Monoclonal Antibody Production Process

In today’s competitive environment, it is crucial for biopharmaceutical companies to have a robust R&D pipeline and reliable manufacturing processes. To ensure success in drug manufacturing, regulatory agencies often mandate appropriate acceptance criteria for process intermediates to increase the likelihood of the drugs meeting the final release specification. When setting acceptance criteria for process intermediates, it is important to first understand process capability, or the impurity clearance of each process step. However, this process involves either challenging experimentation or an estimation method that might not be comprehensive. In this study, we propose the use of neural network to understand process capability. This approach not only will be able to delineate the relationship between the feed and product impurity level for a specific step but will also be able to define the acceptance criteria for the feed (or product from previous process step) impurity level based on a predetermined product impurity level. These acceptance criteria will enable us to determine whether or not to forward process the step based on the feed impurity level. Process impurity data are a combination of actual data collected from actual manufacturing lots and simulated data. Impurity clearance for a specific step is estimated using a conventional method and a neural network, a method that we propose in this study. Since impurity clearance is usually dependent on the input impurity level, using neural network to estimate process capability and ultimately to define process intermediates acceptance criteria has been shown to be more useful than the conventional method.

Process optimization of an industrial acetic acid dehydration progress via heterogeneous azeotropic distillation

Abstract The simulated process model of the HAc dehydration process under actual overloaded condition was conducted by amending the model of standard condition in our previous work using the process data collected from actual production. Based on the actual process model, the operation optimization analysis of each plant (HAc dehydration column, decanter and NPA recycle column) was conducted using Residue Curve Maps (RCMs), sensitivity analysis and software optimization module. Based on the optimized parameters, the influence of feed impurity MA and the temperature of decanter on the separating effect and energy consumption of the whole process were analyzed. Then the whole process operation optimizing strategy was proposed with the objective that the total reboiler duty QTotal of C-1 and C-3 reaches the minimum value, keeping C-1 and C-3 at their optimized separation parameters obtained above, connecting all the broken recycle and connection streams, and using the temperature of D-1 as operation variable. The optimization result shows that the total reboiler duty QTotal of the whole process can reach the minimum value of 128.32 × 106 kJ·h− 1 when the temperature of decanter is 352.35 K, and it can save 5.94 × 106 kJ·h− 1, about 2.56 t·h− 1 low-pressure saturated vapor.

Influence of Sulfuric Acid on the Performance of Ruthenium-based Catalysts in the Liquid-Phase Hydrogenation of Levulinic Acid to γ-Valerolactone.

The presence of biogenic or process‐derived impurities poses a major problem on the efficient catalytic hydrogenation of biomass‐derived levulinic acid to γ‐valerolactone; hence, studies on their influence on catalyst stability are now required. Herein, the influence of sulfuric acid as feed impurity on the performance of Ru‐based heterogeneous catalysts, including Ru/ZrO2 and mono‐ and bimetallic Ru‐on‐carbon catalysts in dioxane as solvent, was investigated. The carbon‐supported Ru catalysts proved to be very sensitive to minor amounts of sulfuric acid. In stark contrast, Ru/ZrO2 showed a remarkable stability in the presence of the same impurity, which is attributed to the sulfate‐ion adsorption capacity of the support. Preferential sulfate adsorption onto the surface of ZrO2 effectively protects the Ru active phase from deactivation by sulfur poisoning. A simple catalyst regeneration strategy was effective in removing adsorbed impurities, allowing efficient catalyst recycling.

Systematic approach for targeting interplant hydrogen networks

This study proposes a systematic method for targeting the interplant hydrogen network with direct and purification reuse/recycle schemes. The generalized Improved Problem Table is proposed to locate the flowrate targets of individual and interplant hydrogen networks. The constructed limiting composite curves and optimal hydrogen supply lines are utilized to illustrate the insights of the proposed approach. The generalized Improved Problem Table incorporated with mass balance equations is applied to determine the optimal targets (i.e. the optimal flowrates of hydrogen utility and product of the purifier, optimal feed impurity of purifier) of hydrogen network with purification reuse/recycle. Two scenarios of interplant hydrogen integration with direct reuse/recycle are investigated. The case study shows that the conservation ratio of the flowrate of hydrogen utility in Scenario 2 is greater than or equal to that in Scenario 1 and that with purification reuse/recycle scheme is increased sharply. Meanwhile the optimal feed impurity of purifier is greater than or equal to the pinch impurity with direct reuse/recycle scheme. The energy performance evaluation shows that interplant hydrogen integration offers an impressive way to reduce the equivalent energy consumption.

Robust fault diagnosis for an exothermic semi-batch polymerization reactor under open-loop

An independent radial basis function neural network (RBFNN) is developed and employed here for an online diagnosis of actuator and sensor faults. In this research, a robust fault detection and isolation scheme is developed for an open-loop exothermic semi-batch polymerization reactor described by Chylla–Haase. The independent RBFNN is employed here for online diagnosis of faults when the system is subjected to system uncertainties and disturbances. Two different techniques to employ RBFNNs are investigated. Firstly, an independent neural network (NN) is used to model the reactor dynamics and generate residuals. Secondly, an additional RBFNN is developed as a classifier to isolate faults from the generated residuals. Three sensor faults and one actuator fault are simulated on the reactor. Moreover, many practical disturbances and system uncertainties, such as monomer feed rate, fouling factor, impurity factor, ambient temperature and measurement noise, are modelled. The simulation results are presented to illustrate the effectiveness and robustness of the proposed method.

Investigation of the Energy-Saving Design of an Industrial 1,4-Dioxane Dehydration Process with Light Feed Impurity

In this work, several energy-saving designs of an industrial 1,4-dioxane dehydration process with small amounts of triethylamine (TEA) impurity were compared. The original process contains a preconcentrator column to remove TEA and two other columns operated at different pressures by pressure-swing distillation to separate the remaining azeotrope-containing mixture. To save on the operating costs of this process, two alternative designs were investigated. The first combines the condenser of a high-pressure column with the reboiler of a low-pressure column. The second design uses a completely different method for this separation by heterogeneous azeotropic distillation. This second design can further be thermally coupled into a dividing-wall column with only one column shell. It was found that significant savings in the operating costs (49.09%) and in the total annual cost (43.31%) can be realized by using this second design as compared to the original process. The proposed method uses the light impurity a...

Optimization of a ligand immobilization and azide group endcapping concept via “Click-Chemistry” for the preparation of adsorbents for antibody purification

This report describes and compares different strategies to deactivate (endcap) epoxide groups and azide groups on bio-chromatographic support surfaces, before and after ligand attachment. Adsorbents possessing epoxide groups were deactivated using acidic hydrolysis or were endcapped with 2-mercaptoethanol or 2-ethanolamine. The influence of surface-bound 2-ethanolamine was demonstrated for the triazine-type affinity adsorbent B14-2LP-FractoAIMs-1, which was tested in combination with the weak anion exchange material 3-aminoquinuclidine-FractoAIMs-3 (AQ-FA3). Azide groups were modified with 2-propargylalcohol using Click-Chemistry. Besides the conventional one-pot Click reaction, an alternative approach was introduced. This optimized Click protocol was employed (i) for the preparation of the weak anion exchange material AdQ-triazole-Fractogel (AdQ-TRZ-FG) and (ii) for the endcapping of residual azide groups with 3-propargyl alcohol. Using the new Click reaction protocol the ligand immobilization rate was doubled from 250 to 500 μmol/g dry adsorbent. Furthermore, the modified support surface was proven to be inert towards the binding of immunoglobulin G (IgG) as well as feed impurities. A thorough evaluation of modified surfaces and adsorbents was performed with dynamic binding experiments using cell culture supernatant containing monoclonal human immunoglobulin G (h-IgG-1). Besides SDS-Page, a recently introduced Protein A – size exclusion HPLC method (PSEC-HPLC) [1] was used to visualize the feed impurity composition and the IgG content of all collected sample fractions in simple PSEC-Plots. A surprising outcome of this study was the irreversible binding of IgG to azide modified surfaces. It was found that organic azide compounds, e.g. 1-azide-3-(2-propen-1-yloxy)-2-propanol (AGE-N3) promote antibody aggregation to a slightly higher extent than the inorganic sodium azide. The possibility that the Hofmeister Series of salt anions may be applicable to predict the properties of the corresponding organic compounds is discussed.

Ultra-purification of ionic liquids by melt crystallization

Ionic liquids (ILs) have received a great deal of attention in the field of engineering during the last decade due to their unique properties. ILs are a very important new class of non-volatile solvents ( T m < 100 °C) in (bio)catalysis applicable to many ionic, polar and non-polar structure groups and as efficient electrolytes [Wasserscheid, P., and Welton, T., 2003, Ionic Liquids in Synthesis (Wiley–VCH, Weinheim, Germany)]. The applications range from electrochemistry, sensors, analysis, and separation techniques to catalysis and reaction engineering. Given their growing importance, it is vital to develop low cost production methods for ionic liquids including efficient techniques for purification and ultra-purification. This paper will present results of purification and ultra-purification of EMIM-chloride and EMIM-bromide (EMIM, 1- ethyl-3- methyl- imidazolium) by melt crystallization. Different techniques for purification are discussed including zone melting, layer crystallization and dry sweating in lab scale [König, A. and Wasserscheid, P., Ultra Purification of Ionic Liquids by Melt Crystallization, Proceedings of the 13th International Workshop on Industrial Crystallization BIWIC 2006, September 13–15, 2006, Delft, The Netherlands, pp. 79–84] and layer crystallization for static and dynamic crystallization conditions in pilot scale. In the case of EMIM-chloride, segregation coefficients are in the range of 0.05 < k seg < 0.6 depending on crystallization rate, yield, feed impurity concentration and techniques used. The crystallization behavior of purified ionic liquids is discussed in detail relative to those of organic substances with similar melting points. Purification potential of EMIM-chloride is discussed with respect to different crystallization techniques and different scales used for crystallization. The excellent purification results of EMIM-chloride suggest melt crystallization techniques offer purification potential for other ionic liquids, creating a new innovative class of solvents and reactants. Melt crystallization can be used as a very efficient method to purify ionic liquids at different scales from 0.5 g up to 1000 kg with purity of w IL > 99.99 % .

Design and Control of an Acetic Acid Dehydration Column with p-Xylene or m-Xylene Feed Impurity. 2. Bifurcation Analysis and Control

In the production of terephthalic acid and isophthalic acid, a tiny amount of one reactant p-xylene or m-xylene may exist in the unreacted acetic acid, which needs to be purified for reuse by a dehydration column. In our previous study (Huang et al.1), it was found that the feed tray location is extremely important for optimizing the operating and the total annual costs. In this paper, the optimal designed processes with and without feed impurity will be further studied in terms of their bifurcation behavior and control. Three cases (one without feed impurity, one with feed impurity and side stream, and one with feed impurity but without side stream) will be studied. In this study, bifurcations due to output multiplicity are observed in two of the cases which have feed impurity but not in the case without. In each bifurcation case, the optimal base case is located on an unstable branch. The overall control at this unstable operating point is thus proposed to deal with disturbance from throughput or feed c...

Design and Control of Acetic Acid Dehydration Column with p-Xylene or m-Xylene Feed Impurity. 1. Importance of Feed Tray Location on the Process Design

In the production of aromatic acids, such as terephthalic acid and isophthalic acid, tiny amounts of reactant p-xylene or m-xylene may also enter into the acetic acid dehydration column through the feed stream. In this work, the process design flow sheets both with and without these tiny impurities are considered. For the case with one of these tiny impurities in the feed stream in combination with a high-purity specification for the bottom stream, a side stream is necessary to purge the impurity; otherwise, accumulation of the impurity will occur inside the column. If only the optimum side stream location and its flow rate are considered in the optimization search, it is found that the total annual cost and the operating cost of this acetic acid dehydration column become much higher by just adding a tiny amount of p-xylene or m-xylene in the feed stream, compared to the no-impurity case. With careful reselection of the feed tray location, significant total annual cost and energy savings for the operation...

Influence of Feed Impurity on the Design and Operation of an Industrial Acetic Acid Dehydration Column

In this work, the design and operation of an industrial column for acetic acid dehydration via heterogeneous azeotropic distillation is investigated. Multiple column feed streams from various parts of the upstream process are fed into this column. The feed components besides acetic acid and water also contain small amounts of methyl acetate and another component. For proprietary reasons, this component will not be specified in this paper. This component during normal operation will not leave the column system through either a top decanter aqueous outlet stream or a column bottom stream. The accumulation of this component inside the column system is illustrated via rigorous dynamic simulation. A side stream is proposed to solve the accumulation problem of this component. The appropriate side-stream location and its flow rate are determined in this paper by total annual cost analysis. There is a great influence of this small feed impurity on the design and operation of the column. With the same purity specifications on both the top and bottom products, the column system with feed impurity requires much larger total annual cost and operating cost in comparison with the design of the no feed impurity case. A very simple overall control strategy is proposed for the column system with feed impurity and continuous side-stream draw-off. Because the optimal flow rate of the side stream is quite small, an alternative operating strategy in industry is to periodically purge out this impurity through the side stream. A practical automatic purging strategy is thus proposed in the paper. This automatic purging strategy does not rely on any online composition measurement but just needs information on some tray temperature measurements. Closed-loop dynamic simulation demonstrates that the proposed purging strategy can successfully keep the column under normal operation with both the top and bottom product purities at their specifications.

Metal zeolites for transalkylation of toluene and heavy aromatics

The fabrication and modification of metal zeolite catalysts for the conversion of heavy aromatics were investigated. The catalytic performances for various metal-free 12-MR zeolites were evaluated in terms of conversion, product yields, benzene purity and reaction network analyses using transalkylation of toluene and 1,3,5-trimethylbenzene as the test reaction. The effects of metal content, feed impurity, and steaming treatment on the catalytic performances of Pt/mordenite zeolites prepared by different metal incorporation methods were also examined. A sulfuration technique for fine tuning the catalytic activity of the metal catalyst while sustaining desirable stability and performance was developed and its application for transalkylation of heavy aromatics was illustrated by Pt/ZSM-12 catalyst.

Effect of Feed Impurity on the Design and Control of a Ternary Two-Recycle Process

This paper studies both the steady-state design aspects and the dynamic controllability aspects of processes in which a fresh feed stream contains significant impurities. The ternary process with t...