Design, Modeling and Analysis of a Continuous Process for Hydrogenation of Diene based Polymers using a Static Mixer Reactor

Hydrogenated nitrile butadiene rubber (HNBR) which is known for its excellent elastomeric properties and mechanical retention properties after long time exposure to heat, oil and air is produced by the catalytic hydrogenation of nitrile butadiene rubber (NBR). Hydrogenation of NBR is carried out preferably in solution via homogeneous catalysis. As yet, it is being commercially produced in a semi-batch process where gaseous hydrogen continuously flows into a batch of reactant polymer. Several catalysts have been exploited successfully for the hydrogenation of NBR in organic solvents, which include palladium, rhodium, ruthenium, iridium and osmium complexes. Owing to the drawbacks of batch production (such as time taken for charging and discharging the reactants/products, heating and cooling, reactor clean up), and the huge demand for HNBR, a continuous process is proposed where potential time saving is possible in addition to the high turn over of the product. Numerical investigation of the HNBR production in a plug flow reactor and a continuous stirred tank reactor showed that a reactor with plug flow behavior would be economical and efficient. A static mixer (SM) reactor with open-curve blade internal geometry is designed based on the simulation and hydrodynamic results. The SM reactor was designed with 24 mixing elements, 3.81 cm ID and 90 cm length. The reactor has a jacket in which steam is used to heat the polymer solution. The hydrodynamics in the SM reactor (open-flat blade structure) with air-water system showed that plug flow could be achieved even under laminar flow conditions (Reh < 20). For a constant mean residence time, the Peclet number was varying such that it is 4.7 times the number of mixing elements (ne) used in the SM reactor. Empirical correlations were developed for gas hold up (εG) and overall mass transfer coefficient (KLa). The mass transfer experiments showed that high KLa, 4 to 6 times compared to that of the conventional reactors could be achieved in the SM reactor at particular operating conditions. Very important information on the Peclet number, liquid hold were obtained from the hydrodynamic experiments conducted with the actual working fluids (hydrogen, polymer solutions) in the SM reactor. The superficial gas velocity had an adverse effect on both Peclet number and liquid hold up. The viscosity of the polymer solution also had a marginal negative effect on the Peclet number while a positive effect on the liquid hold up. The hydrogenation performance with the homogeneous catalyst OsHCl(CO)(O2)(PCy3)2 was performed in the continuous process with SM reactor. Complete hydrogenation of NBR was possible in a single pass. The effect of mean residence time, catalyst and polymer concentration on the final degree of hydrogenation was studied. The minimum catalyst required to achieve degree of hydrogenation over 97% was empirically found and an empirical correlation was developed for degree of hydrogenation as a function of operating conditions and parameters. Hydrogenation in the SM reactor is modeled by using plug flow with axial dispersion model that is coupled with the concentrations of carbon-carbon double bond, hydrogen and osmium catalyst. The model involves coupled, non-linear partial differential equations with different dimensionless parameters. The proposed model was verified with the experimental results obtained from the hydrogenation and hydrodynamic experiments. The model could satisfactorily predict the degree of hydrogenation obtained from experimental results at various operating conditions. In general, the designed continuous process with SM reactor performed well and was an effective method of manufacturing HNBR on a continuous basis. The designed system is amicable to the industrial operating conditions and promises to be highly efficient and economic process for production of HNBR

Performance of polyacrylamide and poly(acrylamide/sodium acrylate) hydrogel-coated mesh for separation of oil/water mixtures

The final publication is available at Elsevier via https://dx.doi.org/10.1016/j.jwpe.2018.09.009 © 2018. This manuscript version is made available under the CC-BY-NC-ND 4.0 license https://creativecommons.org/licenses/by-nc-nd/4.0/Hydrogels are widely used as a coagulant in water treatment in addition to using in tissue engineering due to their high water absorption capacity and biocompatibility. Our research objective is to synthesize a reinforced membrane made using hydrogels targeted for the separation of water from oil-water mixtures. The reinforced hydrogel is synthesized by graft polymerization of water-soluble polymer such as polyacrylamide (PAM) homo-polymer and poly (Na-Ac/AM) copolymer reinforcing on a thin-fine metallic mesh. Different factors such as the mesh size, the percentage of coated-hydrogel, swelling index are varied to study their effect on the separation efficiency. The morphology of the reinforced hydrogel was analyzed by using scanning electron microscopy. In the case of hydrogels made from copolymers, the effect of the corresponding concentration of the copolymer on the separation efficiency is studied. Oil-water mixtures of 5/95 and 10/90 oil/water % were chosen based on typical compostion found in industrial wastewater. The wettability of water and oil on the PAM- hydrogel coated mesh was evaluated using the contact angle measurements obtained at ambient temperature. It was found that PAM polymer and Na-Ac/AM copolymer hydrogel coated meshes are super-hydrophilic in an air-solid-liquid three phases with both contact angles in oil and water less than 15°. Underwater contact angles for the four different sizes of meshes based on PAM coated mesh are observed to be greater than 90°. This indicates the oleophobic properties of the coated mesh under the water and oil cannot penetrate through the coated mesh while the water alone is absorbed through it. The difference in the water flow or separation time becomes smaller with increasing the mesh’s pore size up to 80 μm, while separation time was higher for 200 μm mesh as more hydrogel was blocking the pores. In contrast, the separation time is faster with the copolymer due to the higher swelling capacity of the copolymer. Therefore, under-water oleo-phobic properties of the PAM coated meshes make it a promising candidate for separation of oil/water emulsions with more than 95% separation efficiency

Molecular Simulations of Low-Shrinkage Dental Resins Containing Methacryl-Based Polyhedral Oligomeric Silsesquioxane (POSS)

Nanocomposites of methacrylate-based polyhedral oligomeric silsesquioxane (POSS) are used as resins in dentistry to fill dental cavities. In this article, molecular dynamics simulations (MDS) are used to study and understand the interactions of monofunctional and multifunctional methacrylate groups on hybrid resins containing POSS additives for dental applications. These interactions are further related to the structural properties of the nanocomposites, which in turn affect their macro-properties that are important, especially when used for specific uses such as dental resins. For monofunctional methacrylate, nanocomposite of methacryl isobutyl POSS (MIPOSS) and for multifunctional methacrylate, methacryl POSS (MAPOSS) are used in this study. Molecular dynamic simulations (MDS) are performed on both MIPOSS and MAPOSS systems by varying the amount of POSS. On a weight percent basis, 1%, 3%, 5%, and 10% POSS are added to the resin. Density calculations, stress&ndash;strain, and powder diffraction simulations are used to evaluate the macro-properties of these nanocomposites and compare them with the experimental findings reported in the literature. The observations from the simulation results when compared to the experimental results show that MDS can be efficiently used to design, analyze, and simulate new nanocomposites of POSS

Performance Evaluation of Nonacosan-10-ol-Based Polyethylene Packaging Material Using Molecular Dynamics Simulations

Packaging material has a significant role in maintaining or altering the shelf life of different products. Polymer materials are extensively used as packaging materials for different perishable and non-perishable products both during transportation and storage. This article aims at developing a new polymer composite which can be used as packaging material. This new composite addresses the challenge of controlling oxygen diffusion rates during the storage of perishable goods such as vegetables, meat and produce, etc. The proposed new composite primarily consists of nonacosan-10-ol and polyethylene. Molecular dynamics simulations (MDS) are performed by mixing 5.2%, 17.1%, 29.2%, 40.8% and 45.2% (wt/wt) of nonacosan-10-ol to amorphous polyethylene. Mechanical properties such as Young’s modulus/glass transition temperature, and gas transport properties such as diffusion coefficient and diffusion volume are estimated from the MDS and diffusion related simulations consisting of different oxygen concentrations in polyethylene-alone system and polyethylene- nonacosan-10-ol blends. The impact of adding different weight percent of nonacosan-10-ol to polyethylene is quantitatively assessed and optimal composition of the proposed additive is suggested corresponding to minimal oxygen diffusion rate, high elastic modulus and good thermal stability

Molecular Simulations of Low-Shrinkage Dental Resins Containing Methacryl-Based Polyhedral Oligomeric Silsesquioxane (POSS)

Nanocomposites of methacrylate-based polyhedral oligomeric silsesquioxane (POSS) are used as resins in dentistry to fill dental cavities. In this article, molecular dynamics simulations (MDS) are used to study and understand the interactions of monofunctional and multifunctional methacrylate groups on hybrid resins containing POSS additives for dental applications. These interactions are further related to the structural properties of the nanocomposites, which in turn affect their macro-properties that are important, especially when used for specific uses such as dental resins. For monofunctional methacrylate, nanocomposite of methacryl isobutyl POSS (MIPOSS) and for multifunctional methacrylate, methacryl POSS (MAPOSS) are used in this study. Molecular dynamic simulations (MDS) are performed on both MIPOSS and MAPOSS systems by varying the amount of POSS. On a weight percent basis, 1%, 3%, 5%, and 10% POSS are added to the resin. Density calculations, stress–strain, and powder diffraction simulations are used to evaluate the macro-properties of these nanocomposites and compare them with the experimental findings reported in the literature. The observations from the simulation results when compared to the experimental results show that MDS can be efficiently used to design, analyze, and simulate new nanocomposites of POSS

Compensator for constant relative stability in process control systems

Process control systems are designed for a closed-loop peak magnitude of 2dB, which corresponds to a damping coefficient () of 0.5 approximately. With this specified constraint, the designer should choose and/or design the loop components to maintain a constant relative stability. However, the manipulative variable in almost all chemical processes will be the flow rate of a process stream. Since the gains and the time constants of the process will be functions of the manipulative variable, a constant relative stability cannot be maintained. Up to now, this problem has been overcome either by selecting proper control valve flow characteristics or by gain scheduling of controller parameters. Nevertheless, if a wrong control valve selection is made then one has to account for huge loss in controllability or eventually it may lead to an unstable control system. To overcome these problems, a compensator device that can bring back the relative stability of the control system was proposed. This compensator is similar to a dynamic nonlinear controller that has both online and offline information on several factors related to the control system. The design and analysis of the proposed compensator is discussed in this article. Finally, the performance of the compensator is validated by applying it to a two-tank blending process. It has been observed that by using a compensator in the process control system, the relative stability could be brought back to a great extent despite the effects of changes in manipulative flow rate

A Data Size Reduction Approach Applicable in Process Control System of Oil and Gas Plants

In oil and gas plants, the cost of devices applicable for supervising and controlling systems directly depends on the transmission and storage systems, which are related to the data size of process variables. In this paper, process variables frequency-domain and statistical analysis results have been studied to infer if there exists any possibility to reduce data size of the process variables without loss of any necessary information. Although automatic control is not applicable in a shutdown condition, for generalization of the obtained results, unscheduled shutdown data has also been analyzed and studied. The main goal of this paper is to develop an applicable algorithm for oil and gas plants to decrease the data size in controlling and monitoring systems, based on well-known and powerful mathematical techniques. The results show that it is possible to reduce the size of data dramatically (more than 99% for controlling, and more than 55% for monitoring purposes in comparison with existing methods), without loss of vital information and performance quality

Mechanical Properties and Diffusion Studies in Wax–Cellulose Nanocomposite Packaging Material

This article focuses on the study related to the estimation of packaging material properties of cellulose–wax nanocomposite using molecular dynamics simulation (MDS). Cellulose based packaging material is gaining lot of importance due to its good material properties and low cost. Cellulose with small amount of plant-derived wax (nonacosane-10-ol and nonacosane-5,10-diol) offers higher mechanical strength and modulus of elasticity compared to the conventional synthetic polymer materials. In this article, in addition to the estimation of mechanical properties, the thermal stability of the proposed ecofriendly cellulose–wax composite is evaluated by estimating the glass transition temperature which essentially provides critical information on the glassy state and rubbery state of this biopolymer. The glass transition temperature of this composite changes significantly compared to that of pure cellulose (which also suffers from poor mechanical strength). Transport properties such as diffusion volume and diffusion coefficient of oxygen, nitrogen, and water are estimated using the results obtained from MDS. The diffusion coefficients of these species within the cellulose–wax composite are analyzed using the diffusion volume and interaction energies of these constituents with the wax and cellulose

Numerical Simulation of Dispersion Patterns and Air Emissions for Optimal Location of New Industries Accounting for Environmental Risks

One of the main reasons for air pollution is industrial plants releasing huge amounts of air pollutants in the form of gas emissions. The different chemical pollutants and their corresponding levels present in these emissions, and their proximity to the industrial source, have serious effects on the nearby ecosystems. Some of the industrial nuisances include noise, smoke, dirt, dust, odor and noxious gases, which have to be minimized (if possible, eliminated), especially if the location is desired to be used as a community site. When choosing locations at which to build either new industrial plants or new community sites, software can be used to assess both the short-term and long-term concentration profiles of the various detrimental air pollutants. In this study, the AERMOD model was used to find an optimal location to build a new plant in Toledo, Ohio, USA. Simulations were performed to study the pollutant emissions and their dispersion patterns for four different geographic locations situated away from an existing plant in this region. The AERMOD model, along with the IRAP-h View model, which is approved by the US Environmental Protection Agency (EPA), has been successfully used to assess the fate and transport of pollutants from the proposed new industrial plants. The hazard quotients from the analysis of the results for these four different geographic locations were assessed. The highest total non-cancer hazard indices of 18.7 and 13.2 were obtained for fisher adult and fisher child, respectively, in one of the four locations. The acute inhalation quotient risk was less than the target hazard index of 0.25 for all the four locations. With respect to the concentrations of several chemicals of potential concern (COPC), such as soil, produce, beef, chicken, milk and pork, the fourth location (farthest east) recorded the minimum range values compared to the other three locations

Optimal Configuration of Gas Solid Separation Equipment Using Mixed Integer Nonlinear Programming

The separation of solid particles from gas-solid process streams is an important unit operation in many chemical processes. Out of the many different types of separation equipment that are used for gas-solid separation, cyclone separators are widely used for their operational flexibility, efficiency and capital cost. This study focused on the design of an optimal configuration for several cyclones used in a fertilizer plant. The granulation step in the fertilizer plant leads to using different size cyclones and a different number of cyclones in series or parallel or a mix of both arrangements. A Mixed Integer Nonlinear Programming (MINLP) model is formulated to find the best cyclone arrangement with the optimal number of cyclones and dimensions from several combinations of 1D3D and 2D2D cyclones arranged in parallel-series for a high volume and heavy loading of solid particles. The objective function was to minimize the total cost, including the operating cost and the capital cost. The results indicated that a maximum of 90% efficiency is achieved with a parallel-series arrangement of 1D3D and 2D2D cyclones to be an optimal configuration for the maximum reduction in pollution level