What is an oil refinery, and how many types of oil refinery do you know? Of what importance is petroleum refining to diverse economic growth? This article will shed more light on several areas of petroleum refining as well as the capacities of different components of an oil refinery.
What is an oil refinery?
An oil refinery or petroleum refinery is an industrial process plant purposely built for transformation and refining of crude oil into more useful products such as gasoline, diesel fuel, heating oil, kerosene, liquefied petroleum gas, jet fuel, asphalt base, heating oil, and fuel oils.
It is an industrial site consisting of several buildings and machinery for manufacturing petroleum products such as petrol, diesel, kerosene, and the likes. Although each refinery has its unique features, it is a massive structure with different components, including the processing and distillation units.
Also, it consists of other structures such as storage facilities where refiners store crude oil and refined petroleum products. A complex structure usually built on several acres of land, an oil refinery runs 24 hours a day and 365 days a year. Running a refinery does not only require employing several people to monitor different plant units but also demands enough workforce to cope with its continuous operations.
Crude oil in its raw state is of little or no value until we take it through the refining processes and transform it into various usable products.
Top Four Types of Oil Refinery
There are four types of refineries – topping, hydro-skimming, conversion, and deep conversion refineries. Depending on the market a refiner is aiming at, each refinery has its unique design to ensure their production conforms to their host country’s set standards.
Topping Oil Refinery
Topping refinery is a processing plant with a simple configuration. Constructed primarily for preparing raw materials for manufacturing petrochemicals and industrial fuels, a topping refinery serves better in areas where there are less refining regulations.
Topping refineries comprise facilities such as tanks, distillation units, gas, light hydrocarbons recovery facilities, and other necessary utility systems.
However, they produce high volumes of poorly-refined oil because they lack the required processing units to reduce sulfur levels. Also, their outputs are usually limited to domestic markets.
Hydro-skimming Oil Refinery
Hydro-skimming refineries refine better than topping refineries because of the addition of hydrotreating and reforming units to the basic configuration that makes up a topping refinery.
A refining plant with more capabilities, hydro skimming plants can produce refined products from little feedstocks as well as high octane gasoline. Also, it can produce naphtha as well as hydrogen as by-products. The addition of a few other functional units such as hydro-treating, hydro-cracking, and a few others to hydro-skimming refineries make them more efficient than topping refineries.
However, hydro-skimming plants may not deliver high-quality petroleum products as most of their outputs are usually residual fuels. Also, their low-quality output remains a challenge because more consumers are shying away from sulfur-filled petroleum products.
Conversion Oil Refineries
Also known as cracking refineries, conversion refineries are refining plants that have all basic units that make up both topping and hydro-skimming refineries as well as gas oil conversion units. Also, additional units such as Olefin conversion plant and coking units are what makes them more efficient than hydro-skimming plants.
Furthermore, it has an additional beneficial feature which is reductions in the production of residual fuels. In other words, conversion oil refining plant produces lighter fuels such as gasoline, jet fuel, and diesel. It worth mentioning that light products are more profitable and environmentally friendly.
Deep Conversion Refineries
A Deep Conversion refinery is a combination os all components of a conversion refinery, and an additional unit known as the coking unit. The cooking unit makes it possible to treat and convert extremely heavy crude oil fractions into lighter products.
Understanding Crude Oil Refining
A refinery is a well-organized processing plant where the reformation of crude oil into various useful products takes place. Crude oil refining, on the other hand, is the process of breaking down all the organic matters in crude and separating them for further reformation.
There are stages and processes involved in crude oil refining – distillation, cracking, and treatment.
The Distillation Stage
The distillation stage involves the boiling of crude at two boiling points known as Atmospheric and Vacuum distillation.
Also known as topping refining, atmospheric distillation involves heating of crude oil at the bottom of a column. The column is usually 60 meters high, and the standard heating degree at this stage is between 350 to 400°C. The essence of the heating is to enable vaporization while the residuals remain at the bottom as the heat drops. At this stage of distillation, refiners can obtain methane, light gas, propane, kerosene, gas, and fuel oils.
Vacuum distillation, on the other hand, involves heating of the bottoms that refiners transfer from atmospheric distillation units (ADU) into vacuum distillation units for further processing. Extracting more petroleum products from the remains of the heated oil requires heating the bottoms to a lesser degree within the VDU. A typical vacuum distillation may produce gas oils, lubricating oil, and heavy oil for propane deasphalting.
The Conversion Stage
This process involves the use of catalysts to speed up chemical reactions when breaking down heavy molecules into smaller ones. It entails the conversion of large hydrocarbons into lighter products such as petrol and light fuel oil.
At a boiling point of 500°C, the catalyst cracking or conversion process can convert 75% of the heavy products into gas, gasoline, and diesel.
Treating Stage
The treating stage involves removing non-environment-friendly contents from the finished products. As part of refiners’ effort at improving air quality, they ensure the removal of air contaminants such as sulfur from the finished products.
Importance of Storage Tanks in Crude Oil Refinery
Storage tanks are essential to crude oil refining, and there is no way we can over-emphasize its usefulness. Their usefulness is immeasurable because, without them, there will be no place to store crude oil or finished products. They do not only vary in shapes but also in sizes.
Also, every refinery has multiple storage tanks to prevent product contamination. In other words, they provide a separate storage tank for each product to avoid product contamination.