Processing & Refining Crude Oil
Chevron’s Pascagoula Refinery processes 330,000 barrels (13.9 million gallons) of crude oil a day – an amount equivalent to the size of a football discipline coated to a depth of forty toes.
Operators management the refining processes utilizing hello-tech computers located in management centers situated throughout the refinery.
Hi-Tech Process Management
Using the latest digital technology to monitor and control the plants, operators run the process models 24 hours a day, 7 days every week. From control rooms positioned in each Operations space, operators use a pc-pushed process management system with console screens that show shade interactive graphics of the plants and actual-time data on the status of the plants. The process control system permits operators to “fine-tune” the processes and respond instantly to course of changes. With redundancy designed into the management system, safe operations are assured within the event of plant upset.
Refining’s Basic Steps
Most refineries, regardless of complexity, perform just a few primary steps in the refining process: DISTILLATION, CRACKING, TREATING and REFORMING. These processes happen in our primary working areas – Crude/Aromatics, Cracking I, RDS/Coker, Cracking II, and on the Sulfur Restoration Unit.
Fashionable distillation includes pumping oil by way of pipes in scorching furnaces and separating gentle hydrocarbon molecules from heavy ones in downstream distillation towers – the tall, narrow columns that give refineries their distinctive skylines.
The Pascagoula Refinery’s refining course of begins when crude oil is distilled in two large Crude Items which have three distillation columns, one that operates at close to atmospheric pressure, and two others that function at less than atmospheric pressure, i.e. a vacuum.
Click on on the image for
Distillation Column Diagram
Throughout this course of, the lightest supplies, like propane and butane, vaporize and rise to the highest of the primary atmospheric column. Medium weight supplies, together with gasoline, jet and diesel fuels, condense in the center. Heavy supplies, known as gasoline oils, condense in the lower portion of the atmospheric column. The heaviest tar-like material, known as residuum, is referred to as the “bottom of the barrel” because it never actually rises.
This distillation process is repeated in many different plants as the oil is additional refined to make various products.
In some instances, distillation columns are operated at less than atmospheric pressure (vacuum) to decrease the temperature at which a hydrocarbon mixture boils. This “vacuum distillation” (VDU) reduces the possibility of thermal decomposition (cracking) resulting from over heating the mixture.
As part of the 2003 Clear Fuels Mission, the Pascagoula Refinery added a brand new low-pressure vacuum column to the Crude I Unit and converted the RDS/Coker’s VDU into virginia natural gas bill a second vacuum column for the Crude II Unit. These and other distillation upgrades improved gas oil recovery and decreased residuum quantity.
Utilizing the latest pc management methods, refinery operators exactly control the temperatures within the distillation columns which are designed with pipes to withdraw the various sorts of products the place they condense. Merchandise from the top, middle and backside of the column travel through these pipes to completely different plants for additional refining.
For the reason that market establishes product value, our competitive edge will depend on how efficiently we can convert center distillate, gas oil and residuum into the best value products.
On the Pascagoula Refinery, we convert center distillate, gas oil and residuum into primarily gasoline, jet and diesel fuels by utilizing a series of processing plants that literally “crack” massive, heavy molecules into smaller, lighter ones.
Heat and catalysts are used to transform the heavier oils to lighter products using three “cracking” methods: fluid catalytic cracking (FCC), hydrocracking (Isomax), and coking (or thermal-cracking).
The Fluid Catalytic Cracker (FCC) makes use of excessive temperature and catalyst to crack 86,000 barrels (three.6 million gallons) every day of heavy fuel oil principally into gasoline. Hydrocracking uses catalysts to react gas oil and hydrogen below excessive stress and high temperature to make both jet gasoline and gasoline.
Additionally, about 58,000 barrels (2.Four million gallons) of lighter gasoline oil is transformed every day in two Isomax Units, utilizing this hydrocracking course of.
We mix a lot of the products from the FCC and the Isomaxes immediately into transportation fuels, i.e. gasoline, diesel and jet gasoline. We burn the lightest molecules as fuel for the refinery’s furnaces, thus conserving natural gas and minimizing waste.
Within the Delayed Coking Unit (Coker), 98,000 barrels a day of low-worth residuum is converted (using the coking, or thermal-cracking process) to high-value mild merchandise, producing petroleum coke virginia natural gas bill as a by-product. The big residuum molecules are cracked into smaller molecules when the residuum is held in a coke drum at a excessive temperature for a time period. Only stable coke remains and should be drilled from the coke drums.
Modifications to the refinery throughout its 2003 Clear Fuels Challenge increased residuum volume going to the Coker Unit. The challenge increased coke dealing with capacity and replaced the a hundred and fifty metric-ton coke drums with new 300 metric-ton drums to handle the elevated residuum volume.
The Coker typically produces greater than 6,000 tons a day of petroleum coke, which is bought for use as gas or in cement manufacturing.
While the cracking processes break most of the gasoline oil into gasoline and jet gas, they also break off some pieces which might be lighter than gasoline. Since Pascagoula Refinery’s major focus is on making transportation fuels, we recombine 14,800 barrels (622,000 gallons) each day of lighter elements in two Alkylation Units. This course of takes the small molecules and recombines them within the presence of sulfuric acid catalyst to transform them into high octane gasoline.
Three. Treating (Removing Impurities)
The merchandise from the Crude Units and the feeds to different models include some pure impurities, resembling sulfur and nitrogen. Utilizing a course of called hydrotreating (a milder model of hydrocracking), these impurities are removed to scale back air pollution when our fuels are used.
Because about 80 p.c of the crude oil processed by the Pascagoula Refinery is heavier oils which might be excessive in sulfur and nitrogen, various treating units throughout the refinery work to remove these impurities.
Within the RDS Unit’s six 1,000-ton reactors, sulfur and nitrogen are removed from FCC feed stream. The sulfur is transformed to hydrogen sulfide and despatched to the Sulfur Unit where it is converted into elemental sulfur. Nitrogen is transformed into ammonia which is removed from the method virginia natural gas bill by water-washing. Later, the water is treated to recuperate the ammonia as a pure product to be used within the manufacturing of fertilizer.
The RDS’s Unit predominant product, low sulfur vacuum fuel oil, is fed to the FCC (fluid catalytic cracker) Unit which then cracks it into excessive worth products similar to gasoline and diesel.
Octane rating is a key measurement of how well a gasoline performs in an car engine. A lot of the gasoline that comes from the Crude Units or from the Cracking Units does not have sufficient octane to burn properly in cars.
The gasoline process streams within the refinery that have a fairly low octane score are sent to a Reforming Unit the place their octane ranges are boosted. These reforming items make use of precious-steel catalysts – platinum and rhenium – and thereby get the title “rheniformers.” Within the reforming course of, hydrocarbon molecules are “reformed” into excessive octane gasoline elements. For example, methyl cyclohexane is reformed into toluene.
The reforming course of really removes hydrogen from low-octane gasoline. The hydrogen is used throughout the refinery in numerous cracking (hydrocracking) and treating (hydrotreating) models.
Our refinery operates three catalytic reformers, where we rearrange and alter 71,000 barrels (about 3 million gallons) of gasoline per day to provide it the high octane automobiles want.
A final and critical step is the mixing of our products. Gasoline, for instance, is blended from treated components made in several processing items. Blending and Shipping Area operators precisely mix these to make sure that the blend has the suitable octane stage, vapor strain rating and different necessary specifications. All products are blended in an identical trend.
High quality Control
Within the refinery’s modernly-geared up Laboratory, chemists and technicians conduct quality assurance tests on all completed products, together with checking gasoline for proper octane score. Techron® Chevron’s patented performance booster, is added to gasoline at the company’s marketing terminals, considered one of which is positioned at the Pascagoula Refinery.