Research Of Thermal Coupling In Column Tray Based On Rigorous Model Of Dividing Wall Column

Distillation is the most popular separation operation in chemical industry, while it also accounts for the most energy consumption in a process. The emergence of divided wall column (DWC) provided an integrated way to improve the energy efficiency of a process, but there is still a significant effort from both academia and industry to avoid its unnecessary energy loss. However, in most of the existing studies published about DWCs, the heat transfer between both sides of the wall was neglected. Therefore, the DWCs taking into account the heat transfer across the dividing wall still exist great modification and improvement room in energy consumption and economic benefit. This is the main issue of this paper.This paper aims to establish the rigorous equilibrium stage model considering thermal-coupled effect, based on which the heat transfer process is taken into account. The study indicates that, in BTX system, the heat coupling processes between different stages, among of which the feed stage is regarded as a boundary, have different effects on the reboiler duty of DWC considering the heat transfer across the wall. This effect may be positive or negative. By changing the composition of toluene (T) of different trays, the reasonable explanations for the changes of reboiler heat duty and energy consumption are as follows:1. The heat transfer above the feed stage is not benefit to energy conservation, which increases the total heat duty of the reboiler, thus it should be avoided as possible; however, the heat transfer below the feed stage is benefit to energy conservation, which decreases the total heat duty of the reboiler, thus it should be implemented as possible within the engineering permissible range.2. The heat transfer between the both sides of dividing wall has a great influence on the concentration of middle component toluene (T).Decreasing the middle component distribution towards the bottom and top of DWC,that is,reducing the remixing of middle component to save energy, which is consistent with the principle of energy saving of dividing wall column.3. Take an example of benzene separation process of 100000 tons/year. By avoiding the heat transfer above the feed stage and exchanging heat below the feed tray,3300 ton stream can be saved in a year according to the simulation results.Rigorous equilibrium stage model considering thermal-coupled effect is established in this paper. While the further studies on the form and space of heat coupling are still needed to be more consistent with industrial practice. Meanwhile, the impact of nonlinear dynamic simulation on the entire model is not considered. Therefore the future research might focus on the form of heat coupling and dynamic models.