The Role of NIR Process Analyzers in Refineries to Process Crude Oil into Useable Petrochemical Products

Refineries process crude oil into usable petroleum based chemicals. Process analyzers such as ATOM INSTRUMENT’s Flare Gas Analyzer, SOFRASER’s Thermoset Viscosity Analyzer, Guided Wave’s Near Infrared Spectrometer/Photometers, and in-situ sample interfaces are all necessary for real-time monitoring in a profitable modern refinery. By installing and calibrating these process analyzers, technicians and plant managers gain access to a wide range of actionable information in seconds. Thus enabling them to optimize operating conditions.

The infographic shown below outlines where different analyzers can be installed in a refinery and the various ASTM methods that they satisfy.

Refinery Analyzer Locations Map
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The refining process starts by taking the raw crude oil from the well and running it through an atmospheric distillation tower. As the fluid is heated it passes through various levels or trays inside of the tower. Different densities of hydrocarbon products are then separated, with the lightest hydrocarbon chains rising to the top of the column and the heaviest falling to the bottom.

Once the mixture of hydrocarbons found in the raw crude oil have been separated, they can be individually processed into different kinds of fossil fuel products. The lightest hydrocarbon chains such as methane, propane, and butane can be diverted to the distillation furnace and feed the fires that heat the distillation process or they can be processed for sale.

Any waste fuel from the distillation process is generally incinerated in a Flare Stack. High Sulfur levels cannot be safely incinerated in the Flare in accordance with US EPA CFR 60.18 subpart Ja. ATOM’s FGA-1000 Total Sulfur Analyzer can be used to measure %vol total sulfur according to the EPA standards to allow proper diversion of high sulfur content to an SRU safely, to be reused and/or re-purposed for other areas of the refinery.

Response curve for excitation of sulfur using a FGA-1000

Other middleweight products such as kerosene, gasoline, and naphtha can be sent to a fuel blender where an infinite number of grades or blends can be produced to meet the requirement of the end customer. In order to achieve the best possible margin, various analyzers can be installed inline to inspect the fuel blending process.

If a higher octane rating is required, light naphtha can be sent through the isomerization reactor. During a single pass through isomerization process, normal paraffins are converted to isoparaffins. Alternatively, the isomerization unit can be used to convert linear molecules (i.e. pentane) into higher-octane branched molecules for fuel blending. Also used to convert linear n-butane into iso-butane for use in the alky unit. During the isomerization process, Near-Infrared spectroscopy can be used to optimize catalyst conditions.

Additionally, naptha and other petroleum compounds can be converted to useful chemicals as part of the crude to chemical process. This often occurs in a series of Steam or Catalyst Cracking tanks. NIR can be used to monitor the PIONA (Paraffins, Isoparaffins, Olefins, Napthenes, Aromatics) and the Distillation curve during the cracking process. The Reformate or Platformate can then be feed into the fuel blender to adjust the cetane and octane values of the finished product.

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

Regulations such as the American Tier III, European Euro 6 or the Indian Bharat VI set quantitative limits on the permissible amount of Sulfur Dioxide (SOx), Nitrogen Oxide (NO) and Nitrogen Dioxide (NO2), commonly referred to as NOx that are released during combustion. Sulfur and Nitrogen levels are both controlled under these regulations due to the health and environmental impact. To ensure that the final product created at the refinery meets these regulatory requirements, spot inspections for the Total Sulfur and Total Nitrogen can be conducted with ATOM’s XT Series Laboratory Analyzer for Total Sulfur and Total Nitrogen. Refineries interested in being compliant with ASTM D5453 can utilize the real-time information provided by ATOM Instrument patented Ultraviolet Fluorescence Systems to determine the Total Sulfur in their fuels.

Refineries interested in maximizing profits commonly want to determine the Fuel Octane Numbers (i.e. RON, MON) with online near-infrared (NIR) spectroscopic analyzers such as Guided Wave’s NIR-O. Spectroscopy is a tool compliant with ASTM D6122 which enables refineries to blend expensive high octane feedstocks with less expensive low octane naphtha while maintaining required octane levels and minimizing costs.

Thermoset Kinematic Viscometer response curve as a function of amplitude and temperature

Viscosity is another important physical property in the refining of crude oil. During the fuel blending process, a heavy and high viscosity stream is mixed with a light and low viscosity stream to achieve the desired end product. The expected blend of petroleum products with the correct viscosity level can be achieved thanks to SOFRASER Thermoset-LT, which provides viscosity measurement at constant reference. The Thermoset- KV is the only online direct kinematic viscosity analyzer that is easily correlated with ASTM D445.

Unit operations producing or processing high viscosity streams (visbreaking), bottoms of atmospheric distillation, and vacuum distillation residues can be monitored by MIVI sensors or Thermoset analyzers for improved process control.

After the different grades of fuel have been appropriately blended, they can be sent by a pipeline to the terminal for shipment all around the world. At the down stream terminal, Fuel Identification by NIR spectroscopy ensures that the correct and in-specification petroleum products are loaded for shipment to the customer.

Further to the atmospheric and vacuum distillations, the heavier hydrocarbon chains present in the crude oil must undergo additional cracking and distillation and then be broken up into shorter chains through various cracking and breaking processes. During these processes, analyzers can provide real-time data for plant technicians to make informed decisions on how to achieve the best yield from these residue products. Benzene can be produced During catalysis of the heavy fuels. NIR Spectroscopy can be used to monitor Benzene levels in fuel.