Preventing of flooding phenomena on vacuum distillation trays column via controlling coking value factor
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Preventing of flooding phenomena on vacuum distillation trays column via controlling coking value factor Hossein Peiravan1 · Ali Reza Ilkhani1 · Mohammad Javad Sarraf2 Received: 26 February 2020 / Accepted: 30 August 2020 © Springer Nature Switzerland AG 2020
Abstract The occurrence of flooding phenomena (FP) on the vacuum distillation trays column (VDTC) is investigated on a refinery in the middle region of Iran. Accumulation of coke sediment that is occasionally observed in refinery processing using coal tar (CT) feeding is the main reason of the FP on VDTC. This usually occurs at the down-comer areas and the seal pans of the column. Quinolone insoluble (QI) and toluene insoluble (TI) parameters, two routine methods used to measure coke containing sediments, are employed to determine probable critical areas of FP at the down-comers and the seal pans of CT feed in this study. Analyzing the obtained results of QI and TI tests demonstrated that FP at the column is directly related to the quality of CT feeding. For instance, when the QI of the inlet CT in battery 1 increases from 0.56%W in the first sample to 6.5%W in the 25th sample, the vacuum pressure at the top of the distillation column is reduced from − 230 mbar to − 420 mbar. To prevent sediment accumulation of coke and the occurrence of FP, the CT feeds are centrifuged to reduce coke sedimentation at the down-comer areas and the seal pans of VDTC. Moreover, the seal pan trays are replaced by normal ones and all moveable valves with 25 mm diameter on trays 15 and higher in the column, where coke sediment accumulation is observed the most, are modified by installing wider fixed valve (40 mm diameter) trays. Graphic abstract
Keywords Flooding phenomena on distillation column · Coking value factor · Sediment accumulation of coke · Quinolone insoluble parameter · Toluene insoluble parameter
* Ali Reza Ilkhani, [email protected] | 1Department of Chemistry, Yazd Branch, Islamic Azad University, Yazd, Iran. 2Department of Chemical and Polymer Engineering, Faculty of Engineering, Yazd University, Yazd, Iran. SN Applied Sciences
(2020) 2:1670
| https://doi.org/10.1007/s42452-020-03470-y
Vol.:(0123456789)
Research Article
SN Applied Sciences
(2020) 2:1670
1 Introduction Flooding phenomena (FP) is an abnormal problem in the separation of products in refineries [1–3]. The FP occurs inside the distillation column when the volume of the stream of vapors that travel up and liquids flow down do not equalize and the balance of mass transfer on trays is disrupted. Vapor/liquid contact is facilitated in the trays of the distillation trays column (DTC). In other words, the equilibrium between liquid evaporation and vapor condensation is balanced using the trays [4, 5]. There is a simple rule that should be obeyed for the design of any distillation column; the stream vapors traveling upward and the liquids leaving downward from each tray of the column, must be equal. Any reasons that cause high liquid loads in trays will increase the risk of FP and negatively
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