CFD Simulation and Optimization of Winpak-based Modular Catalytic Structured Packing

Abstract

A recently designed packing sheet Winpak was assembled with catalysts in a modular catalytic structured packing (MCSP) column. A combined mesoscale−microscale methodology was used to analyze and determine the pressure drop mechanism in the MCSP. The proposed methodology differentiates the pressure drop into six different principles, which was determined and compared using computational fluid dynamics (CFD). The three major causes are gas flow confluence and diffluence through the packing windows, the sudden change in the effective gas channel area and the wall effect. Inspired by constructal theory, the height of packing sheets loaded with catalysts was reduced, which resulted in a less abrupt gas channel contraction and expansion at the packing layer junction and more favorable for the undisturbed gas flow. The optimized overall pressure drop was reconstructed in Fluent and was validated by both dry and irrigated packing experiments. Furthermore, irrigated packing experiments were also conducted. Result comparisons reveal that the proposed optimization method is reliable and accurate. This methodology is shown to be significant in the optimization of Winpak-based MCSP. INTRODUCTIONProcess intensification is a critical method for achieving energy conservation and emissions reduction. Resource consumption and pollution can be reduced and high efficiency, sustainability and flexibility can be achieved. The combination of different unit operations is a logical method to approach process intensification. For instance, a distillation column can be integrated with a reactor, which is known as a catalytic distillation column. Catalytic distillation packing plays a significant role in a catalytic distillation column. Its structure, amount and installation method affect the pressure drop, liquid holdup and mass transfer. The most frequently used packing type is modular catalytic structured packing (MCSP), such as bale packing, 1,2 Katapak 3,4 and Multipak. 5,6 In general, catalytic distillation processes that produce esters, 7 acetal 8 and gasoline additive 9 use one or more prereactors before the catalytic distillation column, which ensures that the conversion rate of reactants in the prereactor(s) is at least 80%. Therefore, because of the good selectivity of the catalyst (e.g., MTBE, 10 TAME, 11 ethyl acetate 12 ), the catalytic distillation column is limited by the flux capacity rather than by the reaction.The primary structure of an MCSP is built from conventional corrugated sheets or sheets with flutes, embossments, perforations, grooves, lances, etc. In this case, the flux capacity of an MCSP is dependent on the geometry and arrangement of the corrugated sheet: the lower the packing layer pressure drop, the larger the column flux capacity. Researchers have analyzed the effects of packing on the pressure drop through the column. From the perspective of packing performance under specific operating conditions, Olujić1 3 proposed the Delft overall performance model, which predicted the hydraulic and separation perform...

Hydraulic performance of Winpak‐C modular catalytic structured packing

“…The estimated parameters in Equations (17)(18)(19) can be regressed as F 1 ¼ 1:726, F 2 ¼ 0:386, G ¼ 0.29, K 1 ¼ 0:343, and K 2 ¼ 1:120. As shown in Figure 9, the models for the liquid holdup presented above fit the experimental data very closely.…”

“…Katapak‐S licensed by Sulzer and Multipak from Montz. Based on previously developed types of MCSP, a newly‐developed highly efficient structured catalytic packing, named Winpak‐C (C stands for catalytic), is presented in this paper. Catalyst bags filled with ion exchange resins are arranged in layers between metal corrugated sheets with diversion windows (called “Winpak,” shown in Figure ), forming an element of Winpak‐C.…”

Liquid Distribution and Local Hydrodynamics of Winpak: A Multiscale Method

“…Winpak is a novel structured packing invented by our research group based on a multibaffled plate . Experiments have been set up to procure empirical correlations for hydrodynamic behavior at pilot scale. − The CFD method has also been used in single-phase simulations for optimizing pack structure in order to reduce dry pressure drop. , Nevertheless, deep insight into the liquid distribution and the two-phase flow pattern inside the novel packing is still deficient. Therefore, based on previous research by our group, a novel multiscale method was developed and applied to investigate the liquid distribution and local hydrodynamics within a 350Y-type Winpak.…”

Experimental Investigation of Liquid Axial and Radial Dispersion in Winpak Modular Catalytic Structured Packing

“…5−7 Modern structured catalytic column internals have played a significant role in expending the fields of application of reactive distillation and extending its use to new applications. 1,8,9 The selection of appropriate column internals for specific catalytic distillation processes is an essential design element. 10 The application of modular catalytic structured packing (MCSP), for example, Multipak, 6,11 Katapak-SP 12,13 is development tendency.…”

“…24 A new MCSP named Winpak-C was also introduced in the previous work. 1 The separation element is composed of Winpak packing sheets, and the reaction element also contains Winpak packing sheets (Figure 1). As computational power has improved, CFD has played an increasingly important role in the study of MSCPs.…”