129- Discussion on the technical design of the olefin feed coalescer for the alkylation unit in the isooctane project
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This post was last edited by luoli519 on 2020-1-4 at 13:48. A few days ago, a colleague consulted us regarding the design of the olefin feed coalescer in an octane plant. In recent years, there have also been many companies in China that have adopted the Rumus process package for octane production in their oil refining and deep processing facilities. I am using this issue raised by my colleague as an opportunity to discuss it with everyone here, in order to learn from one another and improve.
The isooctane plant mentioned by this friend has a capacity of over 200,000 tons per year; it uses the process package provided by Lummus, a company under CBI, with the process design being carried out by a highly capable engineering company in China. This device primarily uses C4 olefins and C4 alkanes as its main raw materials.
This colleague said that part of their C4 feedstock comes from the etherified C4 fraction; due to the presence of alcohols such as methanol and tert-butanol, this C4 fraction is washed in reverse flow with deionized water through a wash tower to remove these alcohols, which in turn results in water being introduced into the C4 fraction. Before entering the reactor, the C4 fraction must pass through a liquid-liquid coalescer to remove water from the hydrocarbons.
In the Lummus process package, this hydrocarbon-water coalescer is referred to as the “Olefin Feed Coalescer”; its Chinese name is: Olefin Feed Coalescer. The corresponding operating parameter for this device is as follows: 1–Material composition: C4 hydrocarbons with a dispersed water content of 200 ppm ； Its composition is (wt%), propane 0.12, propylene 0.07, isobutane 43.36, n-butane 10.59, isobutylene 2.52, 1-butene 10.55, trans-2-butene 18.80, cis-2-butene 13.01, C5 components 0.82, and components with C6 or higher 0.05 ； 2-Material flow rate: 33,000 kg/h ； 3-Operating temperature: 13℃ ； 4-Operating pressure: 0.85 MPaG ； 5- Hydrocarbon phase density: 590 kg/m^3; 6- Water phase density: 1000 kg/m^3; 7- Hydrocarbon phase viscosity: 0.18 cp ； 8- Water phase viscosity: 1.2cp ； 9-Hydrocarbon phase surface tension: 13.3 dyne/cm ； 10- Surface tension of the aqueous phase: 73 dyne/cm.
Requirements specified in the Lummus process package: The water content dispersed in the hydrocarbon phase at the outlet of the 1-olefin feed coalescer must be below 10 ppm； 2-Operating maximum pressure difference: 0.034 MPa ； 3-Internal material: SS304 ； 4-Internal component replacement cycle: not less than 60 months ； 5-Shell material: CS; 6-Design pressure: 1.9 MPaG ； 7-Design temperature: 65℃ ； However, it requires steam purging at 1.0 MPaG@190°C ； 8-Operational flexibility: 60%-110% ； 9- Design standard: ASME; 10- The capacity of the water boots must be at least 1.1 m^3.
This post was last edited by luoli519 on 2023-9-27 09:36. Based on our understanding of the process flow for this project and our experience in designing liquid-liquid coagulators, our recommendations for the feed coagulator are as follows: 1–Since it is necessary to separate trace amounts of water, and considering the large volume of feed, a horizontal design would be more suitable； 2- Since it is necessary to coagulate and separate the trace amounts of inorganic water present in the organic phase, the coagulation element must adopt a two-stage structure of \"pre-coagulation + vane separation coagulation\" ； 3- Considering that the hydrocarbon liquid coming from the wash tower has not undergone thorough two-phase separation, the hydrocarbon phase is likely to contain large-sized agglomerates of inorganic water; therefore, two water boot structures should be installed on either side of the coalescing internals assembly – the former being used primarily for collecting and discharging these agglomerated water phases, while the latter is used for collecting the water agglomerates formed by the coalescing internals ； 4- The space distance between the oil and water outlets of the coalescer must be kept as large as possible.
This post was last edited by luoli519 on 2019-7-2 at 14:09. The diagram below shows the structure of the olefin feed coalescing separator, which was developed by our team using NOVEL’s precise dynamics separation calculation and configuration system platform; it is provided for your reference
This post was last edited by luoli519 on 2019-7-2 14:10. Liquid-liquid separation technology and its equipment are actually a simplified version of gas-liquid-liquid separation technology and its equipment. The image below shows our design for a new type of composite weir chamber-based gas-liquid-liquid three-phase separator, which can be used as a reference.
Friends who are interested can log in to Nuowei Company’s specialized network for separation technologies to learn more about the technical details.