A methodology for the analysis of distillation processes within rotating packed beds based on local temperature measurements

Self Cite

The impact of different sealing types and their wearing on the separation performance in distillation processes in rotating packed beds (RPB) has been investigated, which potentially causes bypass flows inside the unit. In the literature, a maximum separation performance is observed, which can have several possible explanations. Next to the theory that with increasing rotational speed a lower residence time counteracts the mass transfer intensification, one theory is that there are undetected bypasses from the casing of the unit to the eye of the rotor. Besides the effect of the maximum, the latter would indicate the fact that bypasses generally induce lower separation performance in RPBs. However, with a suitable sealing concept, higher separation performances could be achieved in the units. Therefore, the influence of bypass flows on the separation performance was investigated by installing different sealings in the RPB, which has not yet been discussed. For this purpose, two sealing types, a labyrinth and a floating ring sealing, were tested in two different RPBs of similar design. The results showed that the labyrinth sealing was less effective than the floating ring sealing in reducing the bypass mass flow. For the floating ring sealing, the separation performance dropped with increasing operation time due to abrasion and wearing. The results also showed that, in general, with increasing rotational speed, the tightness of the sealings is reduced, leading to the formation of bypass streams that reduce the separation performance of the plant. The study highlights the need for greater awareness of bypasses in RPBs especially concerning the separation performance and emphasizes the demand to develop more efficient and effective sealing systems that are ideally nonabrasive, require no additional fluids, and have higher tightness. These findings could call for re-evaluation of previous results, packing evaluations, and derived models.

Section: Materials and Methodologymentioning

confidence: 99%

Impact of Vapor Bypasses on Separation Performance of Rotating Packed Beds in Distillation

Pyka

Ressemann

Held

et al. 2023

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“…In the analysis, they divided the whole packing (metal foam) into four regions, including the casing, and characterized the mass transfer in these regions by using the number of transfer units (NTU) and the volumetric mass transfer rate. The data showed a relatively higher effect of changing rotational speed on the NTU values in the outer radius than the inner radius of packing …”

Section: Introductionmentioning

confidence: 86%

“…16 Furthermore, using the experimental technique developed for the online radial temperature measurements in the rotor of an RPB, Qammar et al 17 showed the effect of rotational speed on the separation efficiency of an empty rotor where the inner radius of the rotor seems to contribute more effectively to the separation than the outer radius of the rotor. Afterward, Ressemann et al 18 used a slightly modified and offline measurement technique and used data loggers to measure the radial temperature profile in an RPB. They presented a methodology for analyzing raw data under different assumptions and included the compensations of maldistribution.…”

Section: Mass Transfer Characterizationmentioning

confidence: 99%

“…The data showed a relatively higher effect of changing rotational speed on the NTU values in the outer radius than the inner radius of packing. 18 In this work, the experimental setup developed by Hampel et al 16 and Qammar et al 17 is further used with temperature measurements along the rotor's radius to characterize the mass transfer profile in the packing of an RPB as well as in the casing separately. This work aimed to understand the mass transfer contribution of different sections/zones in an RPB for different rotor configurations and not to achieve the maximum separation efficiency in an RPB.…”

Section: Mass Transfer Characterizationmentioning

confidence: 99%

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Radial Temperature Profile Measurements to Understand Mass Transfer in Rotating Packed Bed Distillation

Qammar,

Pyka,

Koop

et al. 2023

There is a considerable demand to understand the mass transfer fundamentals in rotating packed beds (RPB), especially for vapor-side controlled processes. An online measurement method allowing the determination of radial temperature profiles was developed to calculate the separation efficiency in the packing and casing via known VLE data. Furthermore, a radial separation efficiency profile was established to understand the nonuniformities in the separation performance of different packing parts that will eventually help optimize the packing design. Binary distillation experiments were carried out with an ethanol–water system in a packed and empty rotor. Investigations show that the radial separation efficiency achieved along the radius is a function of rotational speed and radial packing length, showing a maximum in the middle of the packed rotor under the operating and design conditions investigated. Furthermore, initial radial temperature profile measurements with an advanced Zickzack packing, developed by additive manufacturing, showed that the loss of separation efficiency due to radial liquid maldistribution in conventional RPB packings could be reduced with the proper packing design, enabling uniform liquid distribution.

“…They conducted the experiments in a single-rotor RPB (1R-RPB) containing a metal foam packing with a specific surface area of 2500 m 2 m –3 . The work motivated several other groups to study the separation of binary mixtures by distillation in 1R-RPBs under total reflux and atmospheric pressure. − In 2008 and 2010, Li et al , further advanced the RPB technology by using two 1R-RPBs for continuous distillation experiments. One 1R-RPB represented the enriching section, while the other 1R-RPB worked as the stripping section. , This setup allowed studying the influence of the reflux ratio on distillation in 1R-RPBs in order to operate the 1R-RPB in a continuous separation process. , Recently, Pyka et al showed the importance of using sealings in distillation experiments in 1R-RPBs.…”

Section: Introductionmentioning

confidence: 99%

Impact of Number of Rotors in Rotating Packed Beds on Separation Performance in Distillation

Pyka,

Backhaus,

Held

et al. 2023

Different configurations of a rotating packed bed (RPB) were used in a distillation study to comprehend the impact of the number of rotors on the separation performance of ethanol/1-propanol distillation at total reflux and atmospheric pressure. The separation performance of a single-rotor RPB (1R-RPB) was compared with that of a two-rotor RPB (2R-RPB). To achieve a uniform liquid distribution in the lower rotor of the 2R-RPB, a liquid collector and a rotating baffle distributor (RBD) were installed. The rotational speed (n rot ) was varied between 300 and 1200 rpm, and two different F-factors were investigated (F G = 1.3 Pa 0.5 and F G = 2.1 Pa 0.5 ). The pressure drop of each rotor in the different setups was nearly equal. Thus, neither the liquid collector, nor the RBD, nor the intermediate floor contributed significantly to the total pressure drop of the RPB. The separation performance of the lower rotor of the 2R-RPB was in fair agreement with the separation performance of the 1R-RPB at F G = 1.3 Pa 0.5 for all investigated n rot . This demonstrates that the separation performance in a 2R-RPB can ideally be twice as high as that of the 1R-RPB. However, there are separation performance losses compared to the ideal case. At F G = 2.1 Pa 0.5 and n rot = 900 rpm, the lower rotor of the 2R-RPB shows a separation performance loss of 36% compared to the 1R-RPB, which can be compensated for by increasing n rot to 1200 rpm. Therefore, this study provides a promising concept for numbering up rotors in RPB machines to enable separation tasks that could not be achieved in 1R-RPBs due to the limited separation performance.