Hao-Yeh Lee

Electric arc furnace dust as an alternative low-cost oxygen carrier for chemical looping combustion

The relative abundance and low cost of electric arc furnace dust (EAFD) make it a viable oxygen carrier for chemical looping combustion (CLC) system. Under a reducing agent, zinc ferrite (ZnFe2O4) phase in EAFD releases zinc vapor in a complex gas-solid reaction. In an effort to suppress the emission of zinc vapor, the reaction mechanism of ZnFe2O4 prepared as an oxygen carrier in a redox cycling test is primarily discussed, as well as the issue of coupling with an inert Al2O3 support. The study focused the investigation on redox cycling behavior and CO2 conversion in ZnFe2O4/Al2O3 and EAFD/Al2O3 systems using a thermogravimetric analyzer (TGA) and fixed-bed reactor (FxBR). In a lab-scaled semi-fluidized bed reactor (semi-FzBR) of EAFD/Al2O3 as an oxygen carrier system, a high CO gas yield approximately 0.98 after fifty redox cycles is also experimentally obtained. It can be anticipated that the use of EAFD/Al2O3 system as an oxygen carrier in a reversible CLC process could be economical and environmentally beneficial.

Design and control of diphenyl carbonate reactive distillation processes using arrangements with heat-integrated stages

Diphenyl carbonate is a very important precursor of polycarbonate. Therefore environmental friendly chemical routes and low-cost processes are necessary to cope with its demand. In this study, a new green route to produce diphenyl carbonate and methyl acetate from the reaction between phenyl acetate and dimethyl carbonate was adopted. Also, reactive distillation (RD) is the adopted process to do the reaction and separation simultaneously because this process can overcome chemical equilibrium limitations, obtain high selectivity, and can use the heat of reaction in distillation. The advantages of RD can increase the process efficiency and reduction of investments and operational costs. This study aims to design an RD process with heat-integrated stages that can further reduce the energy consumption in comparison with conventional RD technology. At the steady state, simulation and optimization techniques were combined to find the best design while at the dynamic state, the theoretical control properties at the open loop and the close loop performance were done to find the best control scheme and controller parameters.

Plantwide design for high-purity formic acid reactive distillation process with dividing wall column and external heat integration arrangements

We assessed eight configurations by implementing a dividing wall column (DWC) arrangement and an external heat integration (HI) arrangement for the reduction of energy consumption in the high-purity formic acid (FA) production process. At first, a patented high-purity FA production configuration was adopted and several main process variables were optimized. The optimal configuration was considered the base case for further investigation. The DWC arrangement was applied in the base case configuration to overcome the remixing phenomenon. Next, the external HI arrangement was implemented in those configurations. The simulation results showed that the non-reactive upper DWC between columns C2 and C3 with the HI configuration was the best configuration that provided 46.9% energy saving compared to base case configuration.

Design and control of diphenyl carbonate reactive distillation using a thermally coupled configuration

This study investigated the energy-saving design and control of diphenyl carbonate (DPC) reactive distillation (RD) process by using phenyl acetate (PA) and diethyl carbonate (DEC) through a thermally coupled arrangement. A thermally coupled arrangement eliminates the remixing effect and reduces the total energy. Two cases of DPC synthesis through RD configuration have been discussed in a previous study. However, a remixing effect can be observed between the RD and separation columns through composition profile analysis. To decrease the total heat duty, the remixing effect must be eliminated. This paper presents two cases of the proposed thermally coupled arrangement. After reducing the total heat duty through thermal coupling, the minimum TAC was determined in order to implement dynamic control. The product DPC as well as the byproduct EtAc was met the industrial specifications by temperature controller under the ± 10% throughput and −5%, −10% composition disturbances.

Process Simulation and Design of Acrylic Acid Production

This chapter investigated an integrated flowsheet with recycle streams for the production of acrylic acid. Many typical process units appeared in an integrated process were simulated using Aspen Plus. The simulated process units include a fluidized-bed reactor, cooler, flash drum, gas absorber, extraction tower, distillation column, and decanter. As compared to the designs in open literature, this proposed integrated flowsheet contains two important modifications. Firstly, more steam has been introduced into the reaction section as heat carrier to make the operating condition more realistic. Secondly, the separation section of the process has been improved by utilizing liquid–liquid extraction to save energy of a diluted mixture with large amounts of water.

Design and Simulation of Reactive Distillation Processes

Reactive distillation (RD) columns incorporate both separation and chemical reaction in a single unit. For systems such as etherification and esterification, they have economic advantages over conventional stand-alone configurations. In this chapter, process simulation for three distillation esterification processes of acetic acid to form methyl acetate (MeAc), butyl acetate (BuAc), and isopropyl acetate (IPAc) is demonstrated using Aspen Plus simulation software. These esterification processes consist of different azeotrope situations with phase equilibria. In simulating these processes, their thermodynamic and kinetic models are specified in Aspen Plus. The flowsheets for producing high-purity acetates consist of stripper, rectifier, reactive zone, and possibly a decanter. Besides, tray holdup has a profound effect on conversion, product compositions, and column composition profiles in RD. Thus, reaction holdup calculation is presented. Next, design procedures are presented where dominant design variables are used for optimizing the processes for minimum total annualized cost. For isopropyl acetate, a thermally coupled RD configuration is established.

Heat-Integrated Intensified Distillation Processes

Heat integration between vapor and liquid streams has been widely used in chemical and petrochemical plants for conventional distillation processes as an alternative to reduce the energy consumption. However, with the advances that have been proposed in intensified distillation processes in the last couple of decades, heat-integrated alternatives that are more attractive than the typical condenser–reboiler heat integration have also been proposed. Therefore, intensified distillation processes also need a new approach methodology to implement optimal locations and heat load in heat-integrated distillation. This chapter aims to cover the fundamentals, simulation and optimization approaches for heat-integrated intensified distillation processes for nonreactive and reactive systems. Conventional distillation can result in an intensified process if heat integration is allowed at locations other than the condenser and reboiler. Although thermally coupled distillation and Heat-Integrated Distillation (HIDiC) are already intensified processes, they can attain higher energy reduction by rearranging their heat load distribution. For reactive systems, at the location subject to heat integration, vapor–liquid equilibrium and reaction kinetic conditions are modified simultaneously, which results in a very challenging problem. Reactive system via multi-effect and thermally coupled configuration is also covered in this chapter for the methyl acetate hydrolysis and esterification of isopropyl alcohol. The applications of heat-integrated intensified distillation show feasible solutions with improved energy efficiency and total annual cost reduction for new designs.