Influence of heat transfer across the wall of dividing wall columns on energy demand

Abstract

The implementation of a vertical dividing wall (DW) into a distillation column is a well-known concept which can result in considerable energy savings for the separation of multicomponent mixtures. It is commonly known that heat streams across the DW, which are present due to temperature differences between both sides, may either increase or decrease the energy demand for a certain separation task. However, no work has been published so far which explains the maximum influence on energy demand. This article derives the maximum extent to which the minimum energy demand for a given column design can change due to heat transfer across the DW. Additionally, it is illustrated how energy-efficient column operation can be assured even if the total amount of transferred heat is unknown. These results show that the phenomenon of heat transfer across the DW can be handled very well with a suitable control strategy.Within this work, an EQ model based on the well-known MESH equations is used. 24 For the solution of the model equations, the software Aspen Custom Modeler (ACM) by Aspen Technology, is applied. ACM is an equation-oriented simulation tool and is thus especially suited for the Figure 2. Material streams being used in Eqs. 1 and 2.

A Comprehensive Analysis on the Reactive Dividing‐Wall Column, its Minimum Energy Demand, and Energy‐Saving Potential

“…The advantages can only be realized in practice if a safe and stable operation is possible. As has been demonstrated, e.g., by Buck et al [13] and Ehlers et al [38], the nonreactive DWC can be controlled and operated very well. Preliminary studies by the authors of this article indicate for the RDWC that fluctuations in the vapor split and in the amount of component E can be handled by temperature control maintaining the desired CS E .…”

“…It has to be pointed out that the above-mentioned energysaving potential can only be realized when operating the DWC correctly. As Ehlers et al [38] demonstrate, a wrong operation of the DWC can lead to a much higher vapor demand in comparison to the conventional column sequences. This is due to a strong effect of the vapor split (VS) at the bottom and liquid split (LS) at the top of the dividing wall on the split of the components in the prefractionator.…”

Experimental operation of a reactive dividing wall column and comparison with simulation results

“…The value of the vapor split can be of very high importance in order to reach energy efficient column operation. Simulation‐based research studies showing the huge impact of the vapor split on the energy efficient operation of dividing wall columns are published by Fidkowski and Krolikowski, Halvorsen and Skogestad, and Ehlers et al In a recently published paper, Schröder et al show this strong influence for RDWCs as well. In reality, however, the vapor split can hardly be measured directly.…”

Dividing wall column: Improving thermal efficiency, energy savings and economic performance

“…Jing et al [17] have proposed a heat transfer model of DWC, in which, the additional virtual intermediate heat exchangers are placed between the prefractionator and the main column, and thus the heat transfer process among the virtual intermediate heat exchangers will produce the thermal-coupled effect. Through a simple thought experiment and simulation study [18], it is concluded that the change in minimum energy demand of DWC cannot be more than the amount of heat which is transferred across the dividing wall.…”