What is Crude Oil Refining?
Written By: Souad LOUSDAD
Do you ever stop on the highway to get gas and ask yourself where does it come from?
Or buy a plastic cup of coffee and wonder how did it end up this way?
Well, the gas does not come up from the ground this way nor the plastic cup drops from the machine in that particular shape.
Actually, the primary resource is called “Crude Oil” or simply “Petroleum”.
Crude oil, also known as black gold is a thick dark brown flammable liquid, found in the upper strata of some regions of the Earth’s crust.
It is a complex mixture of hydrocarbons, mainly paraffins, naphthenes and aromatics along with trances of other chemicals and compounds.
In addition, small amounts of organic compounds containing sulfur, oxygen, nitrogen and metals such as vanadium, nickel, iron…
At a high level, the Crude Oil (even gas) value chain starts with exploration to discover resources, and then goes through development, production, processing, transportation/storage, refining, and marketing.
This value chain is normally grouped into the three areas of upstream, midstream, and downstream.
- Upstream: it is somehow the initiation of the process; it concentrates on finding wells, how good and how deeply to drill, how to operate wells in order to achieve the best incomes.
It includes then: exploration, drilling and production.
- Midstream: it primarily focuses on the transportation and storage of hydrocarbons and petroleum products via pipelines, tankers.
- Downstream: The final step, it means everything involved in turning crude oil into thousands of valuable finished products we use and depend on daily. It includes refining, petrochemicals, distribution and marketing.
a collection of Oil Refining Books, click here
When crude oil is extracted, it ranges in density from very light to very heavy and in color, from yellow to black.
Crude oil must pursue large series of processes in order to be shaped into more valuable products.
These series are encompassed in the global process of “Crude Oil Refining“.
Every oil refinery has its own specific processing scheme and design which is determined by the process equipment available, crude oil characteristics and quality, operating costs, and product demand. There are no refineries absolutely identical in their operations; the refinery is a complicated working environment with complex equipment and extensive piping networks.
Products are being produced on a continuous basis, meaning the system must be continuously monitored via pressure, temperature, vibration, or flow.
To ensure the systems are able to operate in a timely manner across the refinery or processing facility, a comprehensive and reliable communications system must be implemented also.
All processes with participation of aggressive substances occur in metallic equipment at temperatures from −196 °C to +1400 °C and pressures from vacuum to 1000 bar, let’s mention:
Crude Oil Distillation Unit – Vacuum Distillation Unit – Fluid Catalytic Unit – Isomerization Unit…
Oil refining industry produces a various range of products from crude oil, such as:
- Liquefied petroleum gas (LPG): is a group of hydrocarbon-based gases derived from crude oil refining or natural gas fractionation, including methane, ethane, propane, butane…
- Naphtha: is a flammable oil containing multiple hydrocarbons, obtained by the atmospheric distillation of petroleum.
- kerosene: or Kerosene-type jet fuel-based product is a light petroleum distillate that is used in space heaters, cook stoves and water heaters…
- lubricating oils: lubricant or lube, complex mixtures of petroleum hydrocarbons refined from crude oil used essentially to reduce some problems that might intrude on the surface of metals ( such as friction ).
- Asphalt (bitumen): It can be produced only from crude containing asphaltenic material.
- coke: is a solid carbon compounds formed from thermal conversion of petroleum.
read also Heavy Oil Recovery
All of these products and others must meet demanding specifications while the refinery stays within tight environmental constraints.
Petrochemical industry produces olefins and aromatics. Then, these chemicals are used for manufacturing solvents, polymers, paints, medicines, fertilizers, etc.
All the comfort life we are experiencing with the fancy products is linked to these materials.
There are five categories of general refinery processes and associated operations:
First of all, “Separation Processes” separate crude oil constituents into common boiling point fractions that are further processed until they end up as the desirable product that leave the refinery. They include principally “Atmospheric Distillation” and “Vacuum Distillation”.
Second, “Conversion Processes” where heavier molecules can be converted into lighter products for which there is higher demand. They include cracking, coking, visbreaking, alkylation and others
Third, as mentioned crude oil contains naturally contaminants such as sulfur, nitrogen and heavy metals, «Treating Processes», primarily hydrotreating remove these chemicals.
Following the treatment, blending and cooling processes, the liquids finally look like the fuels and products you are familiar with: gasoline, lubricants, kerosene … and petrochemical feedstock that are needed to create plastics like the cup of coffee you bought earlier, and many other products you use every day.
After that, « the feedstock and product handling » that consist of unloading, storage, blending and loading activities.
Finally,” Auxiliary facilities”, a wide assortment of processes and equipment not directly involved in the refining of crude oil, used in functions vital to the operation of the refinery.
Including Waste Water Treatment, Hydrogen Production, Sulfur Recovery Plant…
Shortly, crude oil refineries generally cover the five following processes: Separation, Conversion, Treating, feedstock and product handling and Auxiliary facilities.
Some books and articles sum it up all in three categories: Separation, Conversion and treating, for the main reason that those three processes end up producing the needed products.
The combination of numerous factors makes refinery equipment very vulnerable to a variety of phenomena that can lead to serious accidents, such as corrosion.
Also, despite their low concentrations, impurities such as sulfur, oxygen, nitrogen and iron are undesirable because they cause concerns in the processability of crude feedstock and they affect the quality of the produced products.
Then, as it is a piece of great working and continuous leading products nowadays, the refinery requires lots of discipline to maintain the best rate and to achieve its key objectives including return and investments, net profitability and cash flow, also to avoid any complications that might lead to shut it down or to slow down the production.
Resources:
– Petroleum refining (separation processes).
– Student’s Guide to Refining.
– Refining Crude Oil.
-Design of Distillation Column Control Systems.