Would you believe that petroleum engineers can use physics and chemistry to break apart various hydrocarbon chain-like molcules into gasoline-size molecules? It's kinda like rearranging Legos with each piece representing a CH4 (methane) molecule.
Watch the video and read below to discover the cutting-edge science of hydrocarbon molecular rearranging inside one of today's state-of-the-art refineries. And because the refining process uses water and air, they also employ cool technologies to address environmental concerns.
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The first major step (shown in another video) in refining crude oil is fractional distillation where they heat the crude and literally “boil off” the different hydrocarbon chains. This causes the vertical separation of the different hydrocarbon molecules in the tower.
But because fractional distillation only produces about 20% gasoline from the crude, petroleum engineers get techy by using some sophisticated combinations of physic and chemistry in a process called “cracking”.
Cracking is the process of breaking apart longer hydrocarbon molecular chains into smaller pieces. The process breaks or cracks the heavier, higher boiling-point petroleum fractions into more valuable products such as gasoline and diesel fuel. Though that may sound simple, it’s far from it. In fact, they use several different sophisticated methods of cracking hydrocarbon molecules in a modern refinery.
The first is thermal cracking that they do inside a unit called a “coker” where they subject the hydrocarbons to extreme heat and pressure. Coking is a severe method of thermal cracking used to upgrade heavy residuals into lighter products or distillates. Coking produces straight-run gasoline (naphtha) and various middle-distillate fractions used as catalytic cracking feedstock. The process so completely reduces hydrogen that the residue is a form of carbon called “coke.”
Another form of cracking is hydrocracking. A hydrocracking unit, or hydrocracker, takes heavier and higher boiling range molecules and cracks the heavy molecules into distillate and gasoline using hydrogen and a catalyst.
When you’re ready to crack into more layers of refining science, click on the “Learn More” tab below. Also, don’t miss exploring the other videos and lesson activities on our website that complete the rest of the crude oil refining and transportation story.
Plus, take a moment and check out the jazzed petroleum industry careers video on the right and the link to “Careers for Petroleum Engineers” below. Then, click the link of our educational partner here to discover bonus info about refining and transporting crude oil.
Then there’s fluid catalytic cracking. This is a chemical process that uses a catalyst to create new, smaller molecules from larger molecules to make gasoline and distillate fuels. After the gas oil is cracked through contact with the catalyst, the resulting fluid is processed in fractionators that separate it based on various boiling points into several products, including butane and lighter hydrocarbons such as gasoline.
If you’ve studied chemistry, you probably know that catalysts are materials that help either speed up a reaction or make a reaction more selective, or change the conditions that a chemical reaction will occur under, such as different pressures and temperatures. Some catalysts that they use in refineries can contain specific metals such as platinum.
The opposite of cracking or breaking apart longer hydrocarbon molecule chains is actually taking smaller molecules and putting molecules back together. They perform this fancy feat in a poly-gasoline unit that is a reactor that takes small molecules and combines them together to make gasoline. It also produces propylene that can be used to in making plastics. Without his plastic hardhat and glasses, Robert can’t be a wantabe engineer at the refinery.
Environmental Concerns
If you’ve ever seen a refinery, you can’t help but notice the steam coming off their various towers. Mostly it’s used to cool down some of their intense heating operations. But they also boil it to turn it into steam that’s then used as a heating medium. Most of the water in the refinery either it disappears into the clouds as water vapor, or it’s discharged into a watercourse.
What? Into a watercourse? Okay, that’s reason for concern, right?
Pine Bend solves this potential environmental problem by recycling much of its water. A wastewater treatment plant occupies a corner of their property and treats over 3.5 million gallons of water every day. The refinery transports the water back through the refinery to cool different reactions and then treats it yet again. Eventually, they discharge some of the water back into the adjacent Mississippi River… after it’s been treated in the treatment plant that separates out any residual oil in gravity separators. They also chemically remove any oil. Before discharging the water, it finally goes through a series of bio-basins where bacteria digest all the material in the water.
Lastly, it’s tested for several different parameters including oil, suspended solids and different metals. They even perform a toxicity test where small water fleas and other aquatic species are put in the water that have to survive for a specified amount of time.
The environmental protection methods Pine Bend Refinery practices don’t end at their property boundary. Project Green Fleet is one example. This program started in 2005 and has modified over 4,000 diesel vehicles to reduce their emissions. The Pine Bend Refinery is a founding sponsor of this project and contributed one million dollars to help the project succeed. And succeed it has. The efforts of Project Green Fleet to retrofit vehicles had the same impact on emissions as removing 750,000 cars from the road each year! In 2008, the Environmental Protection Agency awarded the project their Clean Air Excellence Award.
Blue and green-winged teal depend on the shallow waters in wetlands for their habitat.
The Pine Bend Refinery also partnered with Ducks Unlimited in the mid-1990’s to protect wetland habitat in Minnesota. Since then, their contributions have helped Ducks Unlimited restore over 6,000 acres of shallow lake habitat, preserve over 200 acres of grasslands, and manage more than 36,000 acres of wild rice on over 100 lakes in northern Minnesota.
There is no denying that oil refineries can have negative impacts on the health of the environment. That’s why it’s so important that individual refineries do all they can to creatively manage these impacts and safeguard the environment around their operations. The Pine Bend Refinery is spending $750 million over the next several years to lessen their emissions even further. They will likely maintain their role as a leader, not only in refining technology, but also in how refineries can protect the environment.
• Gasoline used in automobiles boils mainly between 30° and 200° C (85° and 390° F)
• One barrel of oil accounts for about 19.15 gallons of gasoline, 9.21 gallons of diesel, 3.82 gallons of jet fuel, 1.75 gallons of heating oil and about 7.3 gallons for other petrochemical products like tar, asphalt and bitumen.
• Crude oil was first pumped from the ground in Sichuan, China 2,500 years ago. Too bad they didn't know how to refine it.
• In 2006, the EPA mandated that diesel fuel refiners reduce the sulfur content of their fuel by 97% because sulfur gas compounds are a major source of air pollution.