Spectroscopy Uses in the Petrochemical and Refining Industry

Oil and Energy Companies Stock Investment Concept

Spectroscopy is an industry-proven tool for the real-time monitoring of reaction conditions and subsequent grading of finished petrochemical products in a refinery. Both Near Infrared (NIR) spectroscopy, Ultraviolet and Visible (UV-VIS) wavelength spectroscopy is utilized for inline and at-line measurements. Guided Wave has developed an infographic which describes the typical locations process analyzers can be installed in a refinery.

Real-Time Analyzers for Targeted Petrochemical Production 

Refinery Analyzer Locations Map

To stay competitive in today’s market, refineries are actively searching for alternative markets to serve. One example of this is the Crude-To-Chemical movement, in which excess middleweight hydrocarbon compounds such as Naptha (after purification) are repurposed into useful prepolymers and other useful petrochemical compounds for sale. To accurately monitor this new process the analyzer has to quickly switch to the proper set of calibrations. The ability of the Guided Wave NIRO Full Spectrum Analyzer to instantly switch between chemometric calibrations make it an industry-leading choice for the dynamic Crude-To-Chemical market.

How Does Spectroscopy Works?

NIRS or Near-Infrared Spectroscopy is the process of transmitting light through a sample, portions of the light are absorbed by various compounds in the sample, with the remaining transmitted light being sent to either a Dispersive Grating spectrometer (DG-NIR) or a Fourier transforms spectrometer for analysis. For practical purposes, the difference between FT-NIR and DG-NIR analyzers only lies in the underlying technology. Both methods produce comparable readings which a technician or area manager can use to make informed decisions. The spectrometer measures the difference between the pure spectrum of the light source and the light which passed through the sample, resulting in an absorbance spectrum. By varying the known concentration of specific chemicals between samples a calibration curve can be generated using chemometrics.

What is NIR Spectroscopy used for in the Petrochemical Industry

Near-Infrared (NIR) spectroscopy is used to monitor the hydrocarbon composition of various streams in the Petrochemical and Refining Industries. As shown in the above infographic, a sample interface can be installed in each processing stage of a refinery to provide real-time data and actionable information. At each stage of the refinery, NIR spectroscopy is used to monitor specific traits such as the Research Octane Rating, Benzene content, and Butane content.

What is Fuel Blending?

According to (https://www.eia.gov/todayinenergy/detail.php?id=26092) fuel blending is the process of mixing different fractions of crude oil distillations to produce specific grades of gasoline or diesel fuel. Additionally, various amounts of ethanol, a common biofuel additive for gasoline, and other additives can be included in the blending process. By homogenizing the various chemicals together the desired octane rating or required emission standards for the fuel can be achieved. 

Simple Blending Block Diagram with Guided Wave's NIR-O (DG-NIR) Analyzer

Why monitor Fuel Blending with NIR Spectroscopy?

Near-Infrared Spectroscopy or NIRS has been successfully installed in oil refineries for years. NIR spectroscopy can be used to detect multiple parameters of interest in only a matter of seconds. The real-time information provided by monitoring the fuel blending process with NIR provides refineries with enormous cost savings. Further advantages of real-time fuel blending monitoring with NIR are:

  • Short response times and fast quality control
  • Improved product quality and process optimization
  • Reduced investment, analysis, and maintenance costs
  • Accurate and precise measuring results
  • Lower cost per sample point than FT-NIR

What Parameters of The Fuel Blending Process can be Measured in Real-Time with a NIR Spectrometer?

NIR spectroscopy can simultaneously measure octane numbers, volatility (RVP, vapor-to-liquid ratio), aromatics content, olefins, oxygen, benzene, distillation parameters, ethanol, MTBE, ETBE and other properties throughout the refinery. Many of these parameters require time-consuming, expensive and cumbersome reference methods based on multi-dimensional GC, test engines for octane number evaluation, or distillations. Spectroscopy provides a more economical solution than gas chromatographs.

The Octane number rating of a gasoline is an indication of how the gasoline will perform under various engine conditions. Two different ratings are included: Research Octane Number (RON) and Motor Octane Number (MON). Finished gasoline must meet certain Octane number specifications. Thus refineries control this parameter during production and must certify that gasoline meets specification before it is released. NIR Spectroscopy can help ensure proper Octane levels avoiding the delay of an engine knock test.

Benzene is a naturally occurring compound in crude oil. However, Benzene is targeted for reduction in the refining process as it is highly toxic and a regulatory target of many emissions standards. For the Mobile Source Air Toxics (MSAT) gasoline fuel program, beginning January 1, 2011, refiners subject to EPA regulations, must meet an annual average gasoline benzene content standard of 0.62 volume percent (vol%) for all of their gasoline, both reformulated and conventional blends. Near-Infrared Spectroscopy can be used to monitor the benzene levels during blending or at the Reformater without the sample conditioning requires of a Gas Chromatograph.

Why use NIR for inline monitoring of Reformate after Catalytic Cracking?

Hydrocarbons in PIONA

Naptha and other heavy petrochemical products can be broken down into lighter or shorter hydrocarbon changes by being passed through a series of Crackers. During this process, NIR spectroscopy can be used to monitor the PIONA (Paraffins, Isoparaffins, Olefins, Napthenes, Aromatics) content of the Reformate. For complex mixtures, it may only be possible to monitor PONA with NIR, which considers the total concentration of Paraffins, Olefins, Napthenes, and Aromatics.

Why use NIR Spectroscopy for inline monitoring of Isomerization unit?

Isomerization is similar to catalytic reforming in that the hydrocarbon molecules are rearranged, but, unlike catalytic reforming, isomerization is primarily used to convert normal paraffins to isoparaffins in a single pass process. Near-Infrared spectroscopy can be used during the conversion to monitor catalyst efficiency and ensure that the process is limited by equilibrium. Alternatively, the isomerization unit can be used used to convert linear n-butane into iso-butane for use in the alky unit.

Why use NIR for inline monitoring of Biodiesel properties?

An important characteristic of fatty oil feedstock analysis is the iodine value (IV). NIR Spectroscopy can measure the unsaturated fatty acid content which indicates the ease of oxidation or the drying capacity of the finished product.

The Cetane number of diesel fuel is a measurement of the ignition properties and is an important specification that must be met during fuel production. The traditional laboratory method for Cetane number determination is the knock engine method in which the fuel is burned and its combustion characteristics compared to known standards. This method is time and labor-intensive and provides no ability for real-time control of production. NIR Spectroscopy can be used for real-time inline monitoring of Cetane number.

The Cloud Point of diesel fuel is the temperature below which wax forms. As the wax begins to condense out of solution, the opacity of the fuel decreases and begins to appear cloudy. The Cloud Point is a critical parameter for end customers as the presence of solidified waxes can clog fuel filters and negatively impact engine performance in their automobiles. NIR Spectroscopy can be used as an inline alternative to traditional testing methods where a fuel sample is cooled to the cloud point and the temperature is measured.

What is Visible Spectroscopy used for in the Petrochemical Industry?

The color of fuel for identification and tax purposes is routinely measured with UV/VIS Spectroscopy. Guided Wave manufactures a series of photometers for determining the color of fuel according to different standards.

 APHA/Pt-CoASTMSayboltTurbidityGardener
Range0-5000.5 to 7-16 to 201 to 6 haze, NTU 0-10001-18
Lightest013011
Darkest5008-16618
ASTM METHODD1209D1500, D1524D156, D6045D4176D1544, D6166
Typical ConfigurationAPHA ANALYZER
30 or 50 mm SST Probe
(Depends on high, low, or full scale range)
ASTM Analyzer
5mm Flow Cell
Saybolt Analyzer
20 or 50 mm SST Probe
Turbidity Analyzer
Turbidity Probe
5 mm Flow Cell

APHA Fuel Color Scale

APHA Color Scale

APHA is sometimes referred to as the Platinum- Cobalt (Pt/Co) or Hazen scale. The APHA color scale is a common method of comparison of the intensity of yellow-tinted samples to assess the quality of liquids that are clear to yellowish in color. Due to this APHA can be also referred to as a “yellowness index”. Discover how real-time monitoring of APHA color either on-line or in a laboratory setting using a photometer.

ASTM Fuel Color Scale

ASTM color as defined by ASTM D1500 and ASTM D1524 describes the color measurement method for fuels including lubricating oils, heating oils, diesel fuels, and petroleum waxes. The lowest value of 0.5 is a light yellow, 2 is yellow, 5 is orange, and 8 is a deep red. ASTM color measured by a photometer is an important finished petroleum product quality measurement for many refinery and petrochemical processes.

Saybolt Fuel Color Scale

Saybolt color scale

Saybolt color as defined by ASTM D156 and ASTMD6045 is primarily used in characterizing fuels including automobile and aviation gasoline, jet fuel, diesel fuel, and other petroleum products. The Saybolt color scale begins with a score of 30 for barely perceivable yellow and then decreases to –16 for a definite yellow. Guided Wave manufacturers cost-effective, explosion-proof, field-ready Saybolt Color monitors.

Alongside the measurement of Color, Turbidity is a property of interest for monitoring the quality of fuel. Guided Wave has engineered a Color and Turbidity monitor, directly compliant with ASTM method D4176.

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