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It is common practice in chemical engineering to design processes sequentially. The type of product desired determines the choice of the feed materials that are introduced into the reactor networks. These in turn lead into the separation networks. The flows of heat and work are the final part of the sequence to be considered, with the application of heat exchanger networks, and any deficiency or excess in these flows is usually compensated for with the use of utilities. Although the ongoing research into reactor, separation, and heat exchanger optimization is of indubitable value, an aspect that is often overlooked in conventional research is the question: How do changes to one of the elements in the sequence affect the others? Most process designers do not address such matters until the next optimization of the sequence begins. The result of this sequential approach to design is that processes may contain a few very efficient units, but may also have others that are highly inefficient. A graphical technique that incorporates the flows of heat and work into the design of the process at a very early stage is proposed. The technique can be used to prepare flow sheets that represent a synthesized version of the elements that make up the complete process, rendering each component highly efficient. This new design tool uses the thermodynamic properties of enthalpy (representative of process heat requirements) and Gibbs free energy (representative of process work requirements) to develop process flow sheets that operate as close to reversibly as possible, and can be used as a foundation for more detailed refinements to achieve the best possible result. A case was described in a previous paper in which the graphical technique was applied to gasification. The application of the technique to the production of syngas by the steam reforming of natural gas is detailed. We show that the steam reforming process can be operated with increased reversibility and can actually consume carbon dioxide, thus representing a process with a carbon efficiency of greater than 100%, if the way in which all the process units interact with one another is used to utmost advantage. © 2013 American Institute of Chemical Engineers AIChE J, 59: 3714-3729, 2013 [ABSTRACT FROM AUTHOR]

Abstract: The application of attainable regions (AR) to batch reactor configurations is presented. In this work, we consider the problem of constructing an equivalent batch structure given an AR generated for a continuous system from a specified feed composition and associated kinetics. The authors show that by the appropriate transformation, results developed from a continuous AR may be used to form a related batch structure, and thus improvement of batch reactor structures is also possible by use of the attainable region. [Copyright &y& Elsevier]

The article discusses the use of the attainable region (AR) approach in teaching reaction engineering. It is a research technique utilized to optimize reactor networks. Undergraduates and graduate students are introduced to reactor network optimization using the AR approach without the need for calculations. An isothermal reaction network with a constant density and is in liquid phase is discussed in order to illustrate the AR approach.

The article discusses a graphical technique in choosing a chemical reactor configuration based on optimizing residence time. The authors inform that the application of gas-phase continuously stirred tank reactors (CSTR) for chemical reactions can be used in industry under certain circumstances although the common usage is a plug flow reactor. They provide seven steps of a graphical technique in assessing CSTR.

In this work, a graphical method of identifying opportunitiesforimproving the production rate from batch reactors is presented. Onthe basis of this approach, a modification to the standard procedureof batch operation is also developed. It is found that by modifyingthe initial concentration of the batch, overall production performancemay be improved. This may be achieved in practice by retaining a fractionof the final product volume and mixing with fresh feed material forthe next batch cycle. This result is counterintuitive to the normalmethod of batch operation. Arguments demonstrating how the graphicalmethod may be used to gain insight into alternative methods of operationare also briefly discussed. As such, the bypassing of feed may alsobe used to improve production rate for exit concentrations not associatedwith the optimal concentration. The graphical approach also allowsoptimization of batches where only experimental data are given. Themethod is demonstrated through several industrial examples and issuccessfully shown to improve over the standard method of batch operation. [ABSTRACT FROM AUTHOR]

This paper describes a technique that can be used to analyze the reactions that take place in a reactor via mass balances, a graphical representation and interpretation of basic thermodynamic principles. This allows for the chemical species taking part in the reactions being considered, to create lines that define attainable boundaries in a GH plot. The end result is an attainable area that satisfies the conditions for an attainable region in a GH plot. The simultaneous methanol synthesis from syngas with the Water Gas Shift (WGS) reaction is used to illustrate this approach. Considering the investigation, one can readily see that at higher temperatures the reaction was not feasible thermodynamically at 1bar, but at increased pressure the reaction could again become favorable and thermodynamically feasible. This paper also shows that the introduction of either water or CO2, or both, to the feed opens up the mass balance region, resulting in WGS activity and generating more reaction path alternatives. Again, the change in Gibbs free energy across the reactor and the reaction pathways leading to product are interlinked. [ABSTRACT FROM AUTHOR]

The Flory distribution that is often observed in Fischer–Tropsch (FT) reactors could be described by reaction equilibrium between species. Furthermore, it has been suggested that vapour–liquid equilibrium (VLE) exists in the reactor and this could cause the two-alpha product distribution that is often observed experimentally. Simultaneous reaction and VLE lead us to ask the question: can we not describe the FT reaction as a reactive distillation system? In this paper we develop a mathematical model to describe the behaviour and performance of an FT reactor by considering the dynamic interaction between reaction and VLE. The model results show that the rate of formation of component hydrocarbons is dependent on either the reaction rate or stripping rate, depending on which one is rate-limiting. Furthermore we show that at steady state, the rate of formation of hydrocarbons is proportional to the stripping rate. We conducted an experiment which showed a reaction rate increment when the reactor was switched from CSTR to batch mode. The CO rate increases because reactant stripping was limiting the reaction rate. Modelling an FT reactor as a reactive distillation column is also consistent with the two-alpha positive deviation product distribution observed experimentally and industrially. [ABSTRACT FROM AUTHOR]

A series of experiments were performed to investigate and compare the heat transfer characteristics of a catalyst bed during the Fischer−Tropsch synthesis (FTS) reaction and heating without the reaction. A Co/TiO2catalyst was used in a relatively large internal diameter (ID) tubular reactor. In the first set of experiments, the bed was run under typical low-temperature FTS conditions, while in the second set an inert gas was fed to the bed and a heater with variable heat output was used along the center axis of the catalytic bed to generate the temperature profile. The two-dimensional (radial and axial) temperature profiles in the bed in both cases were measured for varying flow rates and reactor wall temperatures. Simple radial heat transfer models were derived for these two sets of experiments, and the effective thermal conductivity coefficients of the catalyst bed were estimated. Comparisons of the results showed that there were considerable differences between the values of the coefficients and in the shape of the temperature profiles in the reaction and nonreaction cases. This suggests that the liquid formed during the reaction may play an important role in affecting the heat transfer characteristics of the catalyst bed. [ABSTRACT FROM AUTHOR]