Crude oil is processed into useful fuel such as gasoline, petroleum naphtha, diesel fuel, lubricants, asphalt base, heating oil, and kerosene at petroleum refineries all over the world. The conversion of crude oil into useful end products requires many processes, such as hydrocracking, hydrotreating, distillation, and sulfur recovery. Refinery operators need to ensure safe operation while maximizing process efficiency to optimize final product quantity and quality. Refinery applications include:
Combustion Control and Boiler Safety
Oxygen control is needed for the combustion process. The unburned carbons in the form of carbon monoxide represent an explosion hazard which is both a safety concern and an indication of inefficient combustion. A well-controlled combustion process will also improve environmental control by reducing nitrogen oxide emissions.
Continuous Catalytic Regeneration
Continuous catalytic regeneration is part of the catalytic reforming process, where hydrogen and naphtha feeds are reacted to create desired end products. The catalyst used in the reaction is continuously flowing through the reactors and then regenerated. The efficiency of the regeneration process impacts the yield and quality of the end products.
Flare Control and Compliance
Monitoring and control of the flare stack performance is typically regulated and monitored by local and/or national government agencies. For example, in the United States, rules include monitoring and analysis requirements that make it necessary for refinery operators to quickly and accurately determine the heat values of flare stack gases. This is important because enough combustible material must be continuously present to achieve high combustion efficiencies.
Hydrogen Recycle/Separation
Catalytic reforming is a chemical process used to convert petroleum refinery heavy naphthas, having relatively low octane value, into high-octane liquid products called reformates. The catalyst used in the reforming process can be inactivated by hydrogen sulfide, so it is important to measure hydrogen sulfide concentrations and reduce catalyst replacement expenses. Moisture must also be measured, to reduce the formation of acids that can cause corrosion and damage to catalytic reformer units.
Moisture in Refinery Applications
Moisture applications include catalytic reforming, moisture in olefins, and moisture in natural gas.
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Catalytic reforming: Proper moisture balance in feedstocks and hydrogen recycle streams must be maintained to optimize product yield and catalyst life. Measurement reliability is greatly complicated by the presence of compressor oils and the high boiling point of hydrocarbons in the stream.
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Moisture in olefins: Ethylene polymerization catalysts are extremely sensitive to trace moisture which decreases catalyst activity and may turn the catalyst black, leading to discoloration of the virgin polymer. Accurate, reliable, and rapid sub-1 ppm moisture analysis is required.
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Moisture in natural gas: Natural gas is a common feedstock for the on-site production of hydrogen using steam methane reformers, and for the production of ethylene. Natural gas is also a common fuel used for process heaters within various refinery process units. Fast responding, accurate moisture readings are required to ensure the quality of the natural gas meets the process specifications.
Oxygen Measurements Monitoring in Vapor Headspaces
Oxygen measurement is typically carried out in the process line where the oil/water headspace is suctioned to one of two thermal oxidizers or flares. When oxygen level exceeds the safe limit of operation, a nitrogen purge of the tank headspace is initiated to keep oxygen at safe levels. By measuring the oxygen concentration in the headspace, nitrogen consumption can be optimized to keep the operating costs low while ensuring safe plant operation.
Hydrogen Sulfide in Refinery Fuel Gas
EPA regulation 40 CFR Part 60, sub part J, paragraph 60.105 requires the measurement of post-combustion hydrogen sulfide in refinery fuel gas as a measure of the sulfur dioxide released to atmosphere in the combustion process.
Sulfur Recovery Unit:
For more information about this section of the refinery, see our blog titled, “Sulfur Recovery and Tail Gas Treating Unit Analyzer Applications.”
For more information about this application click here to read the related industry brochure.