Hydrofluoric Acid (HF) Alkylation Units
Olefins (C3-C4) from the FCC unit are combined with isobutane (i-C4) and are first treated with a mol sieve bed to remove water. Concentrated HF is then mixed in and fed to the reactor. The alkylation reaction is a result of combining the olefins with the isobutane to form the alkylate product consisting of high octane value products which are later blended into the gasoline pool.
The HF and alkylate product are separated by a settler and the HF is recovered for re-use in the reactor. The reactor hydrocarbons are separated by the main fractionator where the isobutane is recycled to the reactor, alkylate is drawn off the bottom and an n-butane product stream is separated and treated with caustic (KOH).
Most of the overheads consist of HF acid fumes and propane gas. They are then cooled and the HF is separated. Propane is further treated through the propane splitter to remove any dissolved HF and finally treated with alumina to remove fluorinated organics, and then caustic (KOH) to neutralize any remaining acid. Effective separation is a critical component of an efficient, reliable and safe H2SO4 alkylation process.
HF Alkylation Unit Requirements
- Equipment reliability and minimized corrosion to meet 4-6 year refinery turn around schedule
- Meet product specs for high octane value alkylate and caustic free propane and n-butane
- Low acid makeup costs by minimizing acid dilution from wet feedstocks
- Maintain high levels of safety by avoiding any equipment failures that could lead to fugitive emissions of HF
HF Alkylation Challenges and Solutions
| Challenge | Solution | Shop Pall Product |
|---|---|---|
Bed FoulingMeeting product specifications due to bed fouling and associated channeling |
| High efficiency AquaSep® XS and PhaseSep® EL liquid/liquid coalescers reliably meet ‘clear and bright’ product specification and sodium levels downstream |
Corrosion and PluggingProtecting fractionator towers from corrosion and plugging. KO pots, mesh pads and cyclonic devices may not effectively remove emulsified water, caustic or acid droplets and fine solids. |
| High efficiency PhaseSep® EL Liquid/Liquid coalescers reliably remove HF acid carryover from the acid settler and is made with Hastelloy hardware to withstand severe HF service. |
Control acid makeup costs
|
| High efficiency AquaSep XS or PhaseSep ® EL Liquid/Liqud coalescers remove free water that can overload sieves, allowing acid dilution |
HF Alkylation Process Flow Diagram
Key Application/Filter Recommendations For Hydrofluoric Acid (HF) Alkylation Units
| Application | Pall Product | Customer Benefits |
|---|---|---|
1, 3, 5, 7, 9. Pre-filtration prior to liquid/liquid coalescer | Ultipleat® High Flow or Profile® Coreless PPS filter | Lower operating costs by improving the life of the liquid/liquid coalescer |
2. Feed water (or caustic) removal | AquaSep XS liquid/liquid coalescer | Prevent dilution of HF acid catalyst and potential for corrosion–extend mol sieve life |
4. Water removal from propane | PhaseSep® EL liquid/liquid coalescers | Ensure propane meets purity spec/prevent dilution of KOH |
6. Water removal from n-butane | PhaseSep® EL liquid/liquid coalescers | Ensure n-butane meets purity spec/prevent dilution of KOH |
8. HF acid removal after reactor HF acid settler | PhaseSep® EL liquid/liquid coalescers | Reduce corrosion and potential fouling of trays in the isobutane stripper |
10. Water removal from olefin regenerant from mol sieve | PhaseSep® EL liquid/liquid coalescers | Allow re-use of olefin |
For fast track upgrades, NO CAPEX: | Pall-Fit filter and coalescer retrofits | Enable a move to Pall quality without changing your existing filter housing |
| Pall filter and coalescer housing rentals | Enable a technology upgrade for rapid problem resolution. |
To learn more about our Liquid/Liquid Coalescers, watch our short video below or contact one of our experts on the form provided.
Video - How Pall coalescers help effective liquid separation and particle removal
For more information on improving the efficiency of your processes, contact our team of filtration experts.
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HF Alkylation
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