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SAMPLING HF ALKYLATION

Monitoring HF Strength

In some refineries, hydrogen fluoride (HF) is used as a catalyst to convert olefins to high octane alkylate.

To achieve ideal operating conditions, however, acid strength and water content must be continuously monitored. Lower acid strengths are extremely dangerous and can lead to acid runaway. Low levels of water will result in poor alkylation conditions, while high levels will result in corrosion.

Whether the UOP or ConocoPhillips alkylation process is being used, optimization of the net consumption of HF acid is critical from both product quality and profitability standpoints.

Why Sample HF?

Sampling HF allows Operations to monitor the alkylation process which is directly affected by acid strength, water content and acid soluble oil (ASO) buildup. An accurate sampling program can ensure better efficiency, product quality and profitability.

What to Look for in the Sample

  • Water content
  • ASO (to prevent the buildup of ASO which also affects acid strength)

How to Safely Take HF Samples

  • BIAR Multi-Function Monel 400 inline sample valve with spring to close function, bellows seal (Hastelloy® C276), stuffing box as secondary containment. All wetted parts in Hastelloy or Monel.
  • BIAR Monel 400 Cylinder with bellows seal (Hastelloy C276)
  • Bayonet Adapter (for connecting BIAR Cylinder to the valve) Monel 400
  • Safety Plug (secondary containment) Monel/PTFE/SS316
BIAR Sampling System for HF Alkylation

BIAR Sample Cylinders are the industry's only sample cylinders available with bellows. When a sample valve is fitted with bellows seals, it offers the most effective protection against fugitive emissions.

We recommend installing the sample valve on a vertical pipeline or at a 90-degree angle on a horizontal pipeline to allow vapor space in the sample cylinder for product expansion. Consult this page to understand how BIAR COLUMBIA-LY sample cylinders provide sufficient vapor space to prevent the occurrence of excessive pressure from volumetric expansion.

This system differs from traditional sample panel systems which feature a cylinder with dip tube. It safer to use because there are fewer steps needed to take samples and there are no quick connects nor tubing needed. The system is designed to prevent outside moisture from influencing the sample.

Cutaway view of valve & sample cylinder

Hydrogen Fluoride

1) Description

Name: ...........................................................................................Hydrogen Fluoride

Chemical Formula: ...................................................................HF

CAS No: .........................................................................................7664-39-3

Other Names: .............................................................................Anhydrous hydrogen fluoride, Aqueous hydrogen fluoride, HF-A, Hydrofluoric acid

Uses: ..............................................................................................Industrial

Physical state: .............................................................................Colorless gas or fuming liquid (below 67°F)

Odor: ..............................................................................................Strong, irritating odor

Boiling Point: ...............................................................................19.4°C (67°F)

Freezing Point: ..............................................................................- 83°C (-118°F)

Flammability (solid, gas): .........................................................N/A

Vapor pressure: ...........................................................................783 mmHg

 

2) Hazards

Immediately Dangerous to Life or Health Concentrations (IDLH) NIOSH 1994.

H300: Fatal if swallowed
H310: Fatal in contact with skin
H314: Causes severe skin burns and eye damage
H330: Fatal if inhaled
 

Reactivity: Metals, water and steam. Corrosive to metal. Will attack glass and concrete.

Specific Hazards Related to Sampling: HF is an extremely reactive and corrosive chemical that can be fatal in small doses.
Great care must be exercised when handling it, and sampling HF safely has been a challenge for quite some time. When designing a system to sample HF, it is critical to consider the material from which the system will be constructed.
Materials such as Monel 400 and Hastelloy C276 offer better protection from corrosion from HF. Sampling systems must also be designed to ensure that no HF is allowed to escape into the atmosphere, and exposure risk is minimized. Sampling must be done in a totally enclosed environment to prevent any releases but also to prevent moisture from influencing the sample. Safe handling of HF in alkylation units are covered in RP-751 2.3.4.

 

CorrosiveAcute

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