Petroleum Refinery Alkylation Process

The SensoTech LiquiSonic® is an inline analytical system for determining the concentration of binary liquids directly in the production process.

The analyzer is mostly used for phase separation and reaction monitoring in refineries, with the sensor installation within the product stream, thus meaning an extremely fast measurement that responds immediately to process changes for optimum control.

Motor Fuel alkylation using liquid hydrofluoric (HF) or sulphuric acids (H2SO4) is a catalytic process used in petroleum refinery operations.  The purpose of the alkylation is to improve fuel properties to achieve higher octane for lower emissions which is an important key process in the petrochemical alkylation operations.

 

While the H2SO4 alkylation scores points with safety and environmental protection aspects, the HF alkylation typically shows efficient acid recycling. Olefins (butene, propene) and the isoalkanes from raw oil resulting from Fluid Catalytic Cracking (FCC) constitute the starting materials. Together with HF and/or H2SO4 as catalysts, high-grade alkylates are formed. Due to their high octane rating, few aromatic compounds, and comparably environmentally friendly properties, they are perfectly suitable for petrol blending from both an economic and an ecologic point of view.

The most important requirement for the alkylation system is the error-free operation, also in case of fluctuating educt composition and secondary components to prevent e.g. an “acid runaway”, which can occur when the acid strength goes below 85-87%. In this case, the reactions between the olefins and the iso-butane turn into reactions of olefins only, producing polymers known as “acid sludge, red oil or more commonly known as ASO (acid-soluble oil).  To prevent this economic extreme case, control of the acid, water, and ASO quantity is of particular importance.

 

Traditional sampling is potentially very dangerous, time-intensive and the results only arrive after some hours of Lab testing. Here the LiquiSonic® scores points with immediate inline analysis and data recording as well as increased system productivity and safety.

The robust LiquiSonic® measuring technology has set benchmarks in 3-component analysis for years. Using select specialty materials, effectively prevents corrosion, abrasion, and drift, even under difficult conditions. The LiquiSonic® immersion sensors can be easily installed directly into the pipeline and are ATEX-, IECEx- and FM-certified.

Possible installation locations include upstream and downstream of the acid separator, and at the alkylate outlet of the iso stripper. Despite difficult, corrosive process conditions, utilizing materials such as Hastelloy C-276 or Monel, long-term system stability is possible.

 

The LiquiSonic® controller is connected to the sonic velocity sensor and a density measuring device. In the main menu, the controller displays the concentration values of the HF/acid and the ASOS.

Concentration values, as well as other parameters, such as temperature, sonic velocity, and pressure, can be visualized at the LiquiSonic® controller in real-time.

Alkylation processes in petroleum refineries