This is only a simple overview and further instruction will be needed to completely understand all aspects of a petroleum refinery.
How Refinery Work?
A petroleum refinery is a chemical plant that processes crude oil and produces several valuable products. A refinery contains many different types of units that perform a variety of different operations. The main goal is to take the undesirable components of the crude oil and upgrade them into more valuable products. Gasoline, diesel, and jet fuel are among the most valuable products, whereas fuel oils and lubricants are sometimes sold at a loss. Below is a list describing the different types of units found in a refinery, followed by a system overview from the beginning of the refining process to the end.
Refining Process Overview
The crude oil first enters the desalter to remove any salts that may corrode the processing units. From there, the desalted crude enters the atmospheric distillation unit. The separated components are as follows: light distillates, kerosene, light gas oil (diesel), heavy gas oil (fuel oils), and atmospheric residue.
The light distillates enter the light ends unit, where they are further separated into several more distinct components. The methane and ethane is captured and burned to provide heat for other processes. Propane and butane are first hydrotreated before being sold as LPG. The light straight run naphtha is sent to the gasoline blending pool and the heavy straight run naphtha is hydrotreated and then sent to the catalytic reform to produce high octane gasoline.
The straight run kerosene is hydrotreated before being sold as a final product, which is mostly jet fuel. The straight run diesel is also hydrotreated before being sold to the public.
Hydrotreating the diesel remains extremely important due to the increasing governmental restriction on its sulfur content. The heavy gas oil is either sold as low grade fuel oil or more often it is upgraded using fluid catalytic cracking to produce more desirable products.
The atmospheric residue is sent to vacuum distillation. The light vacuum gas oil is further refined using a visbreaker and then sold as a fuel oil. The heavy vacuum gas oil is hydrocracked to produce gasoline and other products. The vacuum residue is sent to a deasphalter, producing asphalt and a deasphalted oil, which is further treated to produce fuel oils, or to a coker.
Finally, various processes, such as the fluid catalytic cracker and coker provide the feedstocks for the alkylater.
What are the important units in a refinery?
These units take an incoming stream and separate it into different components. No chemical reactions occur in these units.
Ions in the crude oil will corrode the pipes in the refinery and may deactivate the catalysts. It is important to remove these salts from the crude before any other processes are started. The process involves forcing water into the crude oil feed stream. This pulls out the salts and prevents corrosion.
The distillation is performed at atmospheric pressures. The outputs of the distillation unit include light ends, kerosene, diesel, heavy gas oil, and atmospheric residue.
This unit distills the atmospheric residue and produces light vacuum gas oil, heavy vacuum gas oil, and vacuum residue. The distillation occurs because the pressure inside of the unit is decreased to nearly zero, allowing the components
Light Ends Unit:
Light Ends Unit:
of the atmospheric residue to boil at a lower temperature.The light ends unit consists of many different fractionators that separate the different components of the light ends fraction from atmospheric distillation.
The separated components consist of methane and ethane, which are used for fuel to heat operations throughout the refinery; propane and butane, which are mixed and compressed to be sold as Liquid Petroleum Gas (LPG); light straight run (lsr) naphtha (C5 and C6), which is used in gasoline pools; and heavy straight run (hsr) naphtha, which is used as a feed stock for the catalytic reformer.
This unit takes the vacuum residue and pulls out all of the heavy particles leaving heavy gas oil that can be further refined or used as fuel oil, and asphalt, which is used in paving.
This unit precipitates long n-paraffins out of heavy vacuum gas oil creating lubricating oils that will withstand low temperatures without solidifying
These units add the final touches before the product can be sold. Some chemical reactions may
occur, but none that significantly alter the final product. Blending: These units take a variety of streams and mix them to meet certain criteria and compositions.
Hydrotreater: Most crude oils today have a high sulfur content. Sulfur is a strong pollutant and must be removed to meet emission standards. Also, sulfur can deactivate catalysts in further refining units. Sulfur is removed by pumping hydrogen gas into any stream. The hydrogen reacts with a molecule and extracts the sulfur to produce hydrogen sulfide.
These units change the composition of input streams through chemical reactions. In the reactors,
a low grade product is converted into a higher grade product.
Catalytic Reformer: This unit takes HSR naphtha and unsaturates the hydrocarbons to produce aromatic rings and other various olefins. These aromatic rings and olefins are used in premium gasolines because of their high octane numbers.
This unit transforms heavy gas oil into light distillates, such as gasoline and LPG, as well as light cycle oil. The unit utilizes a catalyst to take long chain hydrocarbons and break (crack) them into shorter, more valuable hydrocarbons
This unit performs the same operation as the catalytic cracker, but uses hydrogen gas instead of a catalyst to break long hydrocarbon chains into shorter ones. Also, the feedstock is light vacuum gas oil and the products are light and middle distillates.
This unit uses heat to break larger molecules into smaller ones, but is rarely used today.
This unit employs a mild version of thermal cracking to convert vacuum residue into light and middle distillates, fuel oil, and coke or heavy gas oil into slightly lighter fuel oil.
This unit converts short olefins (ethylene, propylene, and butenes) and isobutane chains into branched C7 and C8 chains via strong acids and heat.
This unit uses a very severe version of thermal cracking to convert vacuum residue into light and middle distillates, as well as coke.
This has only been a simple overview and further instruction will be needed to completely understand all aspects of a petroleum refinery.