A design of on-line computer-aided system of distillation column based on a simple startup algorithm.

Yasuoka, Hiroaki; Nakanishi, Eiji; Kunugita, Eiichi

doi:10.1252/kakoronbunshu.11.337

Cited by 14 publications

(30 citation statements)

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“…A numerical criterion is used. This criterion is based on a characteristic function M T (Yasuoka et al, 1987) defi ned as the T (Yasuoka et al, 1987) defi ned as the T difference between tray temperature in the column at each time during the start-up and the tray temperature at steady state. However, the resulting start-up time values depend on the allowed error value (here, 10 -4 ).…”

Section: Resultsmentioning

confidence: 99%

Strategies for Starting Up Azeotropic Distillation Columns with Multiple Steady States

Benz¹,

Francesconi²,

Scenna³

2004

Can J Chem Eng

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T here are several works analysing multiple solutions in ideal, azeotropic and/or reactive distillation columns. Jacobsen and Skogestadt (1991), Cairns and Furzer (1990), Bekiaris et al., (1993Bekiaris et al., ( , 1996, Gani and Jørgensen (1994), Hauan et al. (1995), Kienle and Marquardt (1991), Scenna (1997), andMohl et al. (1999), among others, have considered their origins, the hysteresis curve behaviour or the infl uence of different variables upon them. Jacobsen and Skogestad (1995) analysed the operability and instability of binary distillation column with multiple steady state output during continuous operation. They stated that hysteresis may be experienced during the actual operation. Furthermore, Kienle et al. (1995) and Koggersbøl et al. (1996) confi rmed the existence of multiple steady states in an experimental way when separating a binary mixture.As regard to azeotropic distillation operations, Güttinger et al. (1997) found two stable steady states caused by the vapour-liquid equilibrium for the ternary homogeneous methanol-methyl butyratetoluene system in an industrial pilot column. Besides, Dorn et al. (1998) verifi ed the existence of a third unstable steady state and studied the transient behavior of that azeotropic column. Also, Lee et al. (1999) found periodic oscillations and a limit cycle (sustained oscillations) while analysing the dynamic behaviour of the open-loop column. Bossen et al. (1993) found four steady states for the dehydration of ethanol with benzene by dynamic simulation. Moreover, by means of a dynamic experiment, Müller and Marquardt (1997) verifi ed both the existence of multiple steady states in a heterogeneous azeotropic distillation (ethanol dehydration with cyclohexane as entrainer) and the hysteresis behaviour due to multiple steady states. On the other hand, Chien et al. (1999) analysed the dynamic behaviour of another heterogeneous azeotropic column (isopropyl alcohol-cyclohexane-water). They found three branches of steady states. The lowest and highest solutions were stable and the intermediate one was unstable. Besides, a bifurcation analysis showed that different operating regions could be placed in an operating variable diagram (heat duty vs. refl ux). These operating zones of the column (and different steady states) were characterised by the ratios of entrainment to other components and their potential azeotropes. Chien et al. (1999) suggested a particular desirable start-up strategy, but they did not develop it. Later, Chien et al. (2000) developed a suitable operating procedure for reaching the desirable high-purity steady state. Gani and Jorgensen (1994) proposed that the displacement of the internal composition front could be the cause of the possible connection between multiplicity and operability. Here we will show that * Author to whom correspondence may be addressed. E-mail address: sbenz@frro.utn.edu.ar The operability of azeotropic distillation columns with multiplicity is analysed during start-up by dynamic simulation. Different steady states can...

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Section: Resultsmentioning

confidence: 99%

Strategies for Starting Up Azeotropic Distillation Columns with Multiple Steady States

Benz¹,

Francesconi²,

Scenna³

2004

Can J Chem Eng

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show abstract

“…20 A numerical criterion that indicates the temperature deviation in every plate belonging to both columns is used to determine the time rigorously required by the train to get the steady state. The characteristic function then can be defined as the difference between the tray temperature within the column at each time and the steady-state tray temperature.…”

Section: Open-loop Start-up Timementioning

confidence: 99%

Startup of Homogeneous Azeotropic Distillation Sequences with Multiple Steady States

Scenna

Benz

Rodríguez

et al. 2005

Ind. Eng. Chem. Res.

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The operability of an azeotropic sequence, which consists of an azeotropic distillation column with multiple steady states and an entrainer recovery column with the corresponding recycle stream, is analyzed by dynamic simulation during its startup. The goal is to study the effect of the recycle stream on the start-up performance. The well-known benzene-heptane-acetone (BHA) system is studied. Given open-loop (manual) start-up strategies, the way in which the system reaches different steady states by applying different start-up configurations and/or policies can be observed through the temperature profile evolutions. These are generated using different initial charges in one or both columns, and by applying different schedules for the evolution of the operative variables. Indeed, a partition of the start-up policy space yielding different solutions is achieved. Therefore, it is possible to identify a set of critical values for the supervision of the startup. Based on these results, very simple closed-loop start-up policies, using a simple PI controller, are analyzed. The study shows that the desired steady state can always be obtained by providing a minimum benzene flow rate, which has to be maintained during the startup. Thus, a methodology that uses dynamic simulation to search systematically suitable start-up procedures is presented. An adequate start-up operation mode (minimizing start-up time) is determined for the BHA system. Moreover, this start-up strategy is also applied to another well-known system with multiplicity: the methanol-methylbutyrate-toluene (MMT) case. In this example, the start-up time is also reduced to a minimum, in comparison with all the other policies explored.

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“…The trays are hydraulically sealed and the column is shifted from the total reflux conditions to the required reflux rate. Then, as the column reaches the neighbourhood of the desired steady state (third phase), different start-up control schemes have been proposed in the literature (Yasuoka et al, 1987;Ganguly and Saraf, 1993;Han and Park, 1999;Klein et al, 2000) in order to reduce the start-up time and the waste product.…”

Section: Background On Start-up Operationmentioning

confidence: 99%

“…Also, the quantitative indicator for determining optimal switching time proposed by Yasuoka et al (1987) is adopted here for computing the start-up time. Then, the characteristic function M T defined as the difference between the tray temperature within the column during the start-up and the state during the steady state operation is used here to determine the start-up parameters.…”

Section: Computing the Start-up Timementioning

confidence: 99%

An Extensive Analysis on the Start‐up of a Simple Distillation Column with Multiple Steady States

Benz¹,

Scenna²

2002

Can J Chem Eng

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The impact of start‐up procedures on the behaviour of simple distillation columns with multiple steady states is analyzed. A well‐known system with hysteresis is studied in this paper and transient responses for a binary distillation column yielding different steady states during the start‐up operation are shown. Several dynamic simulation results showing an interesting behaviour are presented. Through the examination of the profile evolutions corresponding to given start‐up policies, it can be seen how the column arrives to different steady states. It is shown that it is possible to identify a set of critical values for the start‐up supervision. Also, guidelines of general validity are achieved with the aim of finding the appropriate start‐up policy to obtain the desired solution.

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A design of on-line computer-aided system of distillation column based on a simple startup algorithm.

Cited by 14 publications

References 0 publications

Strategies for Starting Up Azeotropic Distillation Columns with Multiple Steady States

Strategies for Starting Up Azeotropic Distillation Columns with Multiple Steady States

Startup of Homogeneous Azeotropic Distillation Sequences with Multiple Steady States

An Extensive Analysis on the Start‐up of a Simple Distillation Column with Multiple Steady States

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