Brendon Hausberger

Producing Transportation Fuels with Less Work

New reaction chemistry may reduce the energy input and carbon dioxide emissions from processes that convert coal into liquid fuels.

Convex attainable region projections for reactor network synthesis

Abstract This paper develops a systematic procedure for constructing an attainable region (AR). The approach uses two dimensional ARs constructed in orthogonal subspaces to construct higher dimensional ARs. Our technique relies on previous algorithms that provide a practical assurance of the completeness of ARs in two dimensions, using only PFR and CSTR reactors and mixing. Here we build on a modification of this property by constructing 2D projections and their intersections that provide upper and lower bounds of the AR. These bounds are then improved by applying AR constructions sequentially to candidate regions in orthogonal subspaces. The approach is demonstrated on a well-known AR problem in three dimensions.

Novel separation system design using “moving triangles”

Abstract Shortcut design techniques have been employed in the initial design of traditional distillation systems. Current techniques are not useful in the design of novel or complex configurations however. We will show that by using column profile mapping “moving triangles” to model the behaviour of column sections (CS), any distillation configuration, no matter how complex, can be modelled and its behaviour more thoroughly understood. As an example, a thermally coupled column will be modelled using column profile maps. It is suggested that by gaining an understanding of the behaviour of the configuration quickly and easily, using column profile maps, time and money can be saved by avoiding poor initial decisions and designs.

An experimental simulation of distillation column concentration profiles using a batch apparatus

Abstract There has been a growing interest in the use of residue curves for the preliminary design and sequencing of distillation columns. Residue curves are used not only to predict composition changes in separation processes, but also to determine the feasibility of proposed separations, and flowsheet development (Chem. Eng. Sci. 33 (1977) 281). An experimental technique has been developed for the measurement of these residue curves. (Distillation & absorption ’97, Inst. Chem. Eng. 1 (1997) 187). It can be shown that the time-dependent composition profiles obtained in a modified form of this apparatus are mathematically equivalent to the position-dependent profiles in a continuous distillation column. Hence, it is possible to experimentally simulate a distillation column profile in a small batch apparatus using only small quantities of material. The modified apparatus consists of a still immersed in a heated oil bath so that a liquid feed is continuously supplied to the still. Samples of liquid are then analysed over time using a gas chromatograph. The results from an experimental system have been compared to available information and simulations to determine the accuracy of the apparatus. This technique has several advantages over working with distillation columns, firstly in the sample size required, and secondly in the ease of operation. The method allows quick and low-cost measurements of the concentration variables that model a distillation column. The information obtained this way could prove useful for the selection of feasible systems and for finding minimum reflux requirements. It could also be very valuable for screening of complex systems where only small amounts of material are available and simulations may be very difficult.

Recursive constant control policy algorithm for attainable regions analysis

Abstract This paper proposes an automated technique for attainable regions using recursive constant control (RCC) policy algorithm. This approach uses iterative application of constant control policies to approximate the optimal state varying control policy. The theory of this technique followed from the pioneering work of Feinberg [Feinberg, M. & Hildebrandt, D. (1997). Optimal reactor design from a geometric viewpoint: I Universal properties of the attainable region. Chemical Engineering Science, 52(10), 1637–1665; Feinberg, M. (2000a). Optimal reactor design from a geometric viewpoint II: Critical sidestream reactors. Chemical Engineering Science, 55, 2455–3565; Feinberg, M. (2000b). Optimal reactor design from a geometric viewpoint III: Critical CFSTRs. Chemical Engineering Science, 55, 3553–2479] that optimal control policies that govern combinations of fundamental processes, outline the structure that give access to the final extreme points that form the boundary of the attainable region. In this work, the RCC algorithm is formulated to approximate these control policies from which candidate attainable region (AR)’s are generated. Case studies with three and four-dimensional candidate regions are used for illustrations and resulting structures are discussed.

Automating reactor network synthesis: finding a candidate attainable region for the water–gas shift (WGS) reaction

Abstract We use the attainable region (AR) technique to generate reactor network synthesis solutions to the WGS reaction system that is overall adiabatic. We first do this using the conventional method, as described by Nicol et al. (Comp. Chem. Eng. 21 (1001) 1997, s35), to generate the candidate AR (ARc) for exothermic reversible reactions in three dimensions. We then numerically generate the ARc using the iso-state algorithm and find the region to be within a percent of that found using the classical AR technique. We further use a linear programming model to show that no substantial extension to the ARc is possible. These latter two methods are shown to be simple enough such that they could, in principle, be incorporated in automated software. Generating the ARc using reaction and mixing processes for the WGS reaction provides the user with a benchmark for what can be attained in this system.

Expanding the operating leaves in distillation column sections by distributed feed addition and sidestream withdrawal

Publisher Summary This chapter describes the process of the expansion of operating leaves in distillation column sections by distributed feed addition and sidestream withdrawal. The synthesis of feasible distillation columns for multi-component mixtures is a major objective in the field of distillation. Traditionally, distillation columns are divided into rectifying (above the feed point) and stripping sections (below the feed point). Recently, a methodology to model feed addition, by using the difference point equation, has been introduced. This chapter shows the way to apply this approach to distributed feed addition over several trays. It makes use of column profile maps to show that the operating leaf can be expanded passed the residue curve. The chapter also incorporates the work of Glasser by considering sidestream withdrawal, to get the fully extended region of the operating leaves. In this connection, the chapter analyzes the difference point equation for feed addition and sidestream removal.

Automating Reactor Network Synthesis: Finding a Candidate Attainable Region for Water-Gas Shift(WGS) Reaction

We use the Attainable Region (AR) technique to generate reactor network synthesis solutions to the WGS system. We first do this using the conventional method as described by Nicol et al. (1999) to generate the AR for exothermic reversible reactions. We then generate the AR using the new iso-state algorithm and show the answers are essentially the same. We further use a linear programming model to show that no substantial extension to the candidate AR is possible at the level of resolution of the grid. These latter two methods are shown to be simple enough such that they could, in principle, be incorporated in software and be implemented by users who have a fair understanding of reactor system design. Generating candidate regions will provide the users with benchmarks for what can be attained for the WGS system.

‘Costing’ distillation systems from residue curve based designs

Abstract At present, when carrying out initial scoping of a project, one of the best ways to do preliminary designs for complicated separation systems is to use residue curve maps. However, in order to compare the different possibilities one needs to do some preliminary costing. As one does not require very accurate costing at this stage, only wishing to eliminate expensive alternatives, one would like to be able to do this directly from the sketches on the residue curve maps. This paper presents methods by which this can be done. In this paper we have limited ourselves to systems with constant relative volatilities, constant molar overflow and the differential equation description of the distillation column. It is shown that, for the rectifying section, by using binary approximations based on the least volatile component, one can obtain reasonable estimates (within a factor of two) for the number of stages. This is done by noting that the changes in the least volatile component are the simplest in nature and using the sum of two binary approximations as the final approximation.

Finding candidates for multidimensional Attainable Regions

Publisher Summary This chapter resorts to finding candidates for multidimensional attainable regions. The Attainable Region is defined as the set of all physically realizable products from a reactor system. This chapter considers reactor systems where the only fundamental processes occurring are chemical reaction and mixing. A candidate attainable region (AR C ) is a region that is attainable but does not necessarily contain all realizable products. To ensure that the region is in fact attainable, a few necessary conditions must be met. First, its necessary that it only includes points that are attainable, such as the feed point. Second, it needs to be convex. Any concavities are filled—using mixing—provided the space obeys linear mixing and mixing in an allowed process. Third, the reaction vector along the boundary of the AR cannot point out of the region. If such a point exists, the region can be expanded by allowing that point to undergo reaction in a plug flow reactor (PFR). Fourth, no negative extension of a reaction vector in the compliment of the AR can intersect the AR boundary or the AR itself.