Petlyuk Arrangement Research Articles

Sustainable Process Design for Acetone Purification Produced via Dehydrogenation of 2-Propanol

Acetone purification is one of the most critical stages of its production process, because a large amount of energy is required. Due to this high energy consumption, the process turns out to be not very sustainable and not friendly to the environment. In this sense, the development of intensified alternatives that minimize energy consumption in this process is of utmost importance. Besides, the safest possible processes are sought, so it is necessary that the control properties of these novel processes be studied at an early design stage. This work proposes two new intensified systems for the purification of acetone; the intensified schemes are a thermally coupled distillation system with a side rectifier and a Petlyuk arrangement. The results indicate that in this type of systems where interconnection flows are used, the magnitudes of these flows have a direct impact on energy consumption, because lower values of interconnection flows as in the case of the thermally coupled system achieve a reduction, whereas higher values as in the case of the Petlyuk system have a negative impact. As for the control properties, the intensified schemes present better values of the condition number with respect to the conventional design, because the interconnection flows reduce the disturbance of the manipulable variables. On the other hand, if the feed is disturbed, the interconnection flows generate an increase in the disturbance in the system, obtaining that the conventional system presents the best values. Therefore, making a balance between the studied designs and looking for a system that presents the best sustainability indicators, the thermally coupled system obtains the best results with a 25.92% energy saving and CO2 emission reduction with respect to the conventional system and acceptable values for the control and safety indexes.

Energy Analysis and Remixing Effect of Thermal Coupling Petlyuk Column for Natural Gas Liquid (NGL) Fractionation Train

In this work, a non-conventional distillation sequence with thermal coupling (Petlyuk Column) was presented as a technique to perform the separation of the NGL consist of ethane, propane, butane or other higher alkanes. The improvements were investigated through the energy analysis and remixing effect. From the result obtained, it was found that the Petlyuk arrangement consumes less amount of energy and able to reduce the remixing effects as compared to the conventional column sequencing. The Petlyuk arrangement saved about 44.49% and 12.83% in terms of cooling and heating duty, respectively. The overall annual energy saving shown by this arrangement is 39.22%. This arrangement proved to be able to prevent the remixing effect occurrence that contributes to thermal and separation inefficiency. The desired separation efficiency also obtained by this arrangement as all the product specifications are met. The ability in avoiding remixing effect by the Petlyuk column permits a significant reduction in CO2 emission with an average of 29.43 % of each equipment involved. Hence, it can be concluded that the Petlyuk arrangement model is a better alternative to be implemented in the NGL fractionation train.

Robust Initialization of Rigorous Process Simulations of Multiple Dividing Wall Columns via Vmin Diagrams

Dividing Wall Columns (DWCs) allow the separation of a ternary mixture in one column shell by applying a vertical partition wall, yielding a reduction of operational and capital costs of up to 30%. Multiple DWC (mDWC), the consequent advancement of standard DWC, makes use of more than one partitioning wall, allowing the separation of quaternary or even higher mixtures in one column shell accompanied by a further reduction of energy consumption. Since no dedicated models for these columns are available in commercial process simulators, thermodynamic consistent flowsheets have to be designed and implemented. The thermally fully coupled Petlyuk arrangement is one important example. However, the initial convergence of these substituting flowsheets is demanding, since a large number of meaningful initial guesses have to be provided. A promising method for generating these first estimates are minimum vapor (Vmin) diagrams. All internal flows can be extracted from these diagrams and used for robust initialization of the simulation. The goal of this work is to present the Vmin method in a comprehensive way in order to initialize mDWC simulations to predict the separation of four component mixtures. Additionally, the adaptation of the diagram to configurations different than Petlyuk arrangements for mDWC is evaluated and a systematic procedure to obtain them is presented. In the end, an example of a converging simulation is given, which was obtained with the values from the Vmin diagram.

Evaluation of various heat pump assisted direct, indirect, Petlyuk and side stripper sequences for three-product separations

In this paper, various configurations of vapor recompression and bottom flashing systems were developed. The systems were developed based on direct sequence, indirect sequence, Petlyuk and side stripper designs. This research was performed with three main aims. First aim was to investigate possibility of enhancing energy and economic performance of complex three-product distillation systems via implementation of vapor recompression and bottom flashing. Second aim was to shed light on differences in potentials of vapor recompression and bottom flashing systems in energy and costs savings of three-product distillation schemes. Third aim was to name the best configuration of three-product separation schemes from economic and energy points of view. Twelve configurations were designed. Energy and costs requirements of each configuration were evaluated and compared to each other. Based on the presented results, implementation of vapor recompression and bottom flashing systems can lead to better economic performance of complex three-product distillation systems. In case study presented in this work, application of vapor recompression and bottom flashing enhanced performance of direct sequence, indirect sequence, Petlyuk and side stripper designs. Equivalent work requirements of base direct sequence separation system was 5.59 MW. Based on the obtained results, considering energy requirements, Side stripper and Petlyuk arrangements are the best options for separation of the three-product system with equivalent work savings of 27.6 and 23.5%, respectively. Considering equivalent mechanical work of the systems, the highest savings was obtained in Side stripper with VRC heat pump (71.3% saving). It is shown that the most economically attractive configuration is Petlyuk with bottom flashing with total annual costs (TAC) saving of 43.4% (compared to 9.58 mUSD/year TAC of the base case), while the best performances of vapor recompression systems were obtained on Petlyuk and side stripper designs with TAC savings of 37.4 and 31.0%, respectively.

Simplifying and synthesizing practical four-product dividing wall column configurations

The fully thermally coupled distillation column for four components mixture separation is shown to be energy efficient compared to conventional distillation column sequence. However, it has not been implemented in practice as the form of four-product dividing wall column (FPDWC) because inherent three pairs of vapor and liquid splits increase the complexity and operation difficulty of this equipment. Thus it is necessary to reduce the vapor and liquid split number in order to promote its industrial application. In the present work, three heuristics were proposed to simplify the internal structure of FPDWC, which could be used separately or simultaneously. In order to provide a criterion for energy requirement comparison, minimum vapor flow diagram (Vmin) was employed and shown to be an effective tool to analyze the feasibility of each simplified configuration. Compared to the complex Petlyuk arrangement, these derived practical configurations use less partition walls without energy penalty. To summarize, a flowchart was developed to synthesize configuration with least design and operation effort by employing the proposed heuristics. Two industrial mixtures were taken as examples to validate its effectiveness.

Alternative Petlyuk Distillation Configurations for the Separation of Four-Component Mixtures

The Petlyuk configuration represents an attractive alternative to the simple distillation column sequences because of its potential in energy saving. This point was extensively discussed for three-component mixtures. Moving to quaternary mixtures the complexity of the Petlyuk configuration represents the main barrier of its possible implementation in the industrial practice. In the present work, a set of new alternative distillation configurations to the four-component Petlyuk is presented. A hydrocarbon and an alcohol mixture are considered to prove their applicability. The total annual cost, together with the thermodynamic efficiency and the carbon dioxide emissions, are considered as comparison index between the Petlyuk and the alternative configurations. The results obtained proved that for the cases considered at least one of the alternative configurations showed a better or at least the same performance of the Petlyuk arrangement. For this reason, the new configurations are worth of consideration wh...

Control structure selection for four-product Petlyuk column

Direct material coupling between column sections in distillation leads to energy efficient systems like the Petlyuk column but with more difficult control problems compared to conventional multicomponent distillation sequences. A control study of a four-product extended Petlyuk column operating close to minimum energy is reported here. We study the “ideal” case with all steady state degrees of freedom available for control, including the vapor split valves, which is required to achieve minimum energy under all conditions. Four decentralized control structures are proposed and tested against a wide range of disturbances. This work demonstrates also the use of the graphical Vmin tool which can be used to visualize the minimum boilup requirement for Petlyuk arrangements.

Optimum design of Petlyuk and divided-wall distillation systems using a shortcut model

An optimization approach for fully thermally coupled distillation systems for the separation of ternary mixtures is presented. The thermally coupled schemes considered here can be implemented in the form of the original Petlyuk arrangement (with an external prefractionator) or the modified Kaibel arrangement (in the form of a divided-wall column). The approach uses a shortcut design method that allows the system to be modeled as a nonlinear programming problem. Given the practical interest in divided-wall column arrangements, special attention is given in this work to this type of structure. Several cases of study are presented to show the applicability of the proposed approach.

New Heat-Integrated Distillation Configurations for Petlyuk Arrangements

The Petlyuk arrangement has been proved to require the minimum energy consumption for multicomponent distillation that is an advantage for saving both energy and capital costs. On the other hand, the Petlyuk arrangement contains a maximum number of thermal couplings that is a disadvantage for the operability due to the harsh pressure constraints in terms of vapour transfers. This paper presents the synthesis of new distillation configuration with a reduced number of thermal couplings than the Petlyuk arrangement. Starting from the same separation sequence for the Petlyuk arrangement, a strategy taking advantage of simultaneous thermal coupling and heat integration achieves new distillation configuration for any n-component mixture. Compared to the Petlyuk arrangement, the new distillation configuration has the same number of columns, as well as the same number of column sections with only one condenser and one reboiler, while it has reduced the number of vapour transfers between columns. As a consequence, it has the potential to have the similar minimum energy consumption and capital investment, but improved operability than the Petlyuk arrangement. A simple procedure is formulated which generates the new distillation configuration systematically. It is shown that the new distillation configurations produce distinct thermodynamically equivalent structures due to the inherent different mass and heat transfers than the original Petlyuk arrangements. The new distillation configurations provide new alternatives when looking for the optimal distillation system with respect to both steady-state and dynamic performance.

A New Method for Synthesis of Thermodynamically Equivalent Structures for Petlyuk Arrangements

The Petlyuk arrangement is the mostly studied thermally coupled configuration due to its minimum energy requirement for multicomponent distillation. In this paper, a new method for synthesis of thermodynamically equivalent structures (TES) for the Petlyuk arrangement is presented. The total number of the possible TESs is theoretically calculated with a derived formula a priori. Then, a simple procedure is formulated which generates all of the TESs step-by-step. It is shown that the new method can systematically produce all the known TESs as well as the missing ones for the Petlyuk arrangement of any n-component mixture. It is found that, for any n-component mixture, the Petlyuk arrangement can produce a unique thermodynamically equivalent side column structure by simultaneously moving all of its movable column sections. It constitutes a new mechanism to derive the satellite column superstructure with one reboiler and one condenser. Finally, it is concluded that the Petlyuk arrangement is a superstructure that incorporates all of the known structures as its substructures.

Minimum Energy Consumption in Multicomponent Distillation. 3. More Than Three Products and Generalized Petlyuk Arrangements

We consider separation of ideal multicomponent mixtures with constant relative volatilities and constant molar flows and at constant pressure. The exact analytical solution of minimum energy in a generalized Petlyuk arrangement for separation of N-component feed into M products has been derived. Interestingly, the minimum-energy solution in a complex integrated Petlyuk arrangement is equal to the most difficult split between any pair of the products, as if each single split was to be carried out in an ordinary two-product column. This extends the results for the three-product Petlyuk arrangement from part 2 of the series to a generalized arrangement with any number of products and feed components. The solution is very simple to visualize in the Vmin diagram (part 1 of the series), simply as the highest peak. In addition, we obtain detailed flow rates and component distribution inside the arrangement. We also conjecture that the minimum energy requirement for the generalized extended Petlyuk arrangement is...

Minimum Energy Consumption in Multicomponent Distillation. 2. Three-Product Petlyuk Arrangements

We show that the minimum energy requirement for separation of a multicomponent mixture in a three-product Petlyuk arrangement is equal to the minimum energy for the most difficult of the two separations (top/middle or middle/bottom product) in a conventional single column. In the Vmin diagram (part 1 of this series), this is simply the highest peak. These results are based on an analytical solution for columns with an infinite number of stages, assuming constant relative volatilities and constant molar flows. The previous analytical results for the Petlyuk column are extended to include nonsharp separations, multicomponent feeds, and any feed quality.

Complex distillation arrangements: Extending the petlyuk ideas

The task of separating a multicomponent mixture into streams enriched in the respective constituents is commonly carried out in vonventional distillation columns arranged in series. However, due to the scrutiny of tighter requirements for energy and cost efficiency, current research aims at alternative column arrangements that offer savings in both operational (energy) and capital costs. Among these are the Petlyuk or dividing wall column, in which three components are separated in a single shell using only one reboiler and one condenser. In this paper we extend the Petlyuk ideas to separations of four components, although extensions to more components is straightforward. We provide a general definition of Petlyuk arrangements and discuss alternative structures from the literature. Following this overview we consider the arrangements which allows for implementation in a single shell using dividing walls or vertical partitions.