Sungwon Hwang

Production of butene and butadiene by oxidative dehydrogenation of butane over carbon nanomaterial catalysts

C4 alkenes are generally used to produce synthetic rubbers, plastics, and other important chemicals. Transition metal oxides are traditionally used as catalysts to produce C4 alkenes from n-butane by oxidative dehydrogenation (ODH). On the other hand, metal-free carbon nanomaterials are receiving much attention as catalysts for ODH due to their environmental benignity, corrosion resistance, and unique surface properties. In this work, a systematic methodology was designed to measure conversion of the reactants, selectivity to main products, and other catalytic performances of a set of carbon catalysts, including graphite and activated carbon. The experiments were carried out under a wide range of reaction conditions, and the reaction mechanism and kinetics were developed based on Marsvan Krevelen interpretation of the experimental results.

Optimum Reactor Design in Methanation Processes With Non-uniform Catalysts

A generic methodology is developed to design a heterogeneous catalytic reactor for methanation processes. For the optimization of a heterogeneous catalytic reactor, nonuniform catalyst pellets such as a layered catalyst are considered with respect to reaction type, reactor performance, and component distribution inside the catalyst. Heterogeneous uniform and nonuniform catalyst models were developed to analyze the effect of mass and heat transfer between both bulk phase and catalyst surface and inside a catalyst pellet. Then, concentration profiles of hydrogen and carbon monoxide in the catalyst pellet and along the reactor axis were obtained by analyzing simulation results. It was shown that the application of different types of nonuniform catalyst pellets at a certain number of separate zones within a reactor could produce higher catalyst performance than a reactor with uniform catalyst. Furthermore, it proved a significant decrease of catalyst deactivation behavior such as coking and sintering. Layered catalysts were optimized to maximize an overall reactor performance over the catalyst lifetime, achieving capital cost reduction characterized by reactor size, catalyst amount, and degree of catalyst deactivation. Last, temperature control throughout the reactor operating periods was strategically planned for a reactor operation with distribution of nonuniform catalyst pellets. This methodology can also be usefully applied to the design of heterogeneous catalytic reactors for other processes such as hydro-treating process and cracking process.

Process integration of solid oxide fuel cells with process utility systems

In the process industry, a utility system is one of the main energy consumption and pollution emission sources. Significant progresses have been made in the chemical industry to improve the efficiency and reduce the emissions of utility systems. However, few efforts have been made in investigating the possibility and strategy of incorporating new energy conversion devices such as fuel cells into industrial energy systems. The article presented focuses on systematic integration of fuel cells and industrial energy systems. A steady-state model of an indirect internal reforming solid oxide fuel cell (IIR-SOFC) system has been developed to estimate its thermodynamic and electrochemical properties and to optimise system performance. The model is then applied to the integration study of SOFCs into utility systems. Different process integration options are investigated and evaluated. Case studies show significant benefits of energy efficiency improvement and emission reductions by incorporating fuel cells into industrial utility systems.

A novel approach to the design and operation scheduling of heterogeneous catalytic reactors

A number of studies have been conducted to reduce the overall level of catalyst deactivation in heterogeneous catalytic reactors, and improve the performance of reactors, such as yield, conversion or selectivity. The methodology generally includes optimization of the following: (1) operating conditions of the reaction system, such as feed temperature, normal operating temperature, pressure, and composition of feed streams; (2) reactor design parameters, such as dimension of the reactor, side stream distribution along the axis of the reactor beds, the mixing ratio of inert catalyst at each bed; and (3) catalyst design parameters, such as the pore size distribution across the pellet, active material distribution, size and shape of the catalyst, etc. Few studies have examined optimization of the overall catalyst reactor performance throughout the catalyst lifetime, considering catalyst deactivation. Furthermore, little attention has been given to the impact of various configurations of reactor networks and scheduling of the reactor operation (i.e., online and offline-regeneration) on the overall reactor performance throughout the catalyst lifetime. Therefore, we developed a range of feasible sequences of reactors and scheduling of reactors for operation and regeneration, and compared the overall reactor performance of multiple cases. Furthermore, a superstructure of reactor networks was developed and optimized to determine the optimum reactor network that shows the maximum overall reactor performance. The operating schedule of each reactor in the network was considered further. Lastly, the methodology was illustrated using a case study of the MTO (methanol to olefin) process.

Application of simulated annealing (SA) to the synthesis of heterogeneous catalytic reactor

This paper reviews a practical application of the optimization algorithm to conceptual design of a heterogeneous catalytic reactor and catalyst and its synthesis. In particular, a simulated annealing (SA) algorithm is mainly used since it provides a reliable optimization solution without being trapped at local optimum points, which arise from nonconvexities and multiplicities in a complex reaction system. Furthermore, it allows a design engineer to evaluate multiple design options of reactor and catalyst systems which satisfy both user-specified objective functions and constraints. In the final stage of optimization, these generated solutions are fine-tuned by using deterministic optimization. To enhance the efficiency of optimization further, a profile-based synthesis is adopted for the optimization algorithm. Lastly, this research takes into account a number of factors for the synthesis of heterogeneous catalytic reactors such as reactor configuration, uniform and non-uniform catalyst type, and fundamental catalyst design parameters including shape and its definite dimensions.

A new approach to developing a conceptual topside process design for an offshore platform

This study introduces a new approach for the conceptual design of an offshore topside process, satisfying environmental standards, saving utility consumption, and consequently, maximizing economic profit. Twelve individual processes are modeled as a case study, based on sets of combinations between four topside process configurations and three individual production scenarios (i.e., peak oil, peak gas, and peak water) over the life cycle of an oil reservoir. Then, the simulation results of these models are analyzed based on economic profit. In particular, the simulation program is integrated with a mixed-integer non-linear programming algorithm to optimize the design and operating variables (e.g., operating pressures of the multi-stage separators) in order to maximize the economic profit of the platform. Lastly, an economic feasibility study is performed for the design of a profitable and eco-friendly offshore platform.

Tubular reactor design for the oxidative dehydrogenation of butene using computational fluid dynamics (CFD) modeling

Catalytic reactors have been essential for chemical engineering process, and different designs of reactors in multi-scales have been previously studied. Computational fluid dynamics (CFD) utilized in reactor designs have been gaining interest due to its cost-effective advantage in designing the actual reactors before its construction. In this work, butadiene synthesis via oxidative dehydrogenation (ODH) of n-butene using tubular reactor was used as a case study in the CFD model. The effects of coolant and reactor diameter were investigated in assessing the reactor performance. Based on the results of the CFD model, the conversion and selectivity were 86.5% and 59.5% respectively in a fixed bed reactor under adiabatic condition. When coolants were used in a tubular reactor, reactor temperature profiles showed that solar salt had lower temperature gradients inside the reactor than the cooling water. Furthermore, higher conversion (90.9%) and selectivity (90.5%) were observed for solar salt as compared to the cooling water (88.4% for conversion and 86.3% for selectivity). Meanwhile, reducing the reactor diameter resulted in smaller temperature gradients with higher conversion and selectivity.

Technology development for the reduction of NOx in flue gas from a burner-type vaporizer and its application

We developed a modified process of a submerged combustion vaporizer (SMV) to remove nitric oxides (NOx) efficiently from flue gas of the SMV at liquefied natural gas (LNG) terminals. For this, excess oxygen is injected into exhaust gas that contains NOx from SMV burner. Then, the mixed gas spreads into a hydrogen peroxide solution or water bath. We initially performed experiments of the modified system to estimate the effect of various process variables (temperature, excess O2 concentration, pH of water, residence time of flue gas in water tank, and H2O2 concentration) on NOx conversion, and developed a mathematical model of the system based on the experiment results. Lastly, we confirmed higher performance of the modified system and validated the feasibility for its field application.

Catalytic propane dehydrogenation: Advanced strategies for the analysis and design of moving bed reactors

A moving bed reactor (MBR) is one of the most innovative reactors that are commonly used in industry nowadays. However, the modeling and optimization of the reactor have been rarely performed at conceptual design stage due to its complexity of design, and it has resulted in increased capital and operating costs of the overall chemical processes. In this work, advanced strategies were introduced to model an MBR and its regenerator mathematically, incorporating catalyst deactivation, such as coke formation. Various reactor designs and operating parameters of the MBR were optimized to increase the overall reactor performance, such as conversion or selectivity of the main products across the reactor operating period. These optimization parameters include: (1) reactant flow inside a reactor, (2) various networks of MBRs, (3) temperature of the feed stream, (4) intermediate heating or cooling duties, (5) residence time of the catalyst or velocity of catalyst flow, and (6) flow rate of the fresh make-up catalyst. The propane dehydrogenation process was used as a case study, and the results showed the possibility of significant increase of reactor performance through optimization of the above parameters. For optimization, the simulated annealing (SA) algorithm was incorporated into the reactor modeling. This approach can be easily applied to other reaction processes in industry.