Friday, 13 November 2020

What Everyone Ought To Know About Petroleum Refining Process? (#petroleumIndustry)(#ipumusings)(#chemicalengineering)

What Everyone Ought To Know About Petroleum Refining Process? 

What Everyone Ought To Know About Petroleum Refining Process? (#petroleumIndustry)(#ipumusings)(#chemicalengineering)


Petroleum is a fossil fuel which is formed when large quantities of organic matter are deposited as sediments. Refining is the process of removing impurities or unwanted elements from a substance. Hence, the process to transform crude oil, extracted from the earth, into useful products like petrol, LPG, diesel oil, kerosene, etc. is known as Petroleum refining. Petroleum Industry generated enormous revenue of $3.3 trillion in the year 2019. Petroleum Refining is one of the most integral parts of the Petroleum Industry.

Refining Process

The refining process of Petroleum takes place in 3 basic steps:

1. Physical Separation

2. Chemical Catalytic conversion process

3. Thermal Chemical conversion process 

What Everyone Ought To Know About Petroleum Refining Process? (#petroleumIndustry)(#ipumusings)(#chemicalengineering)

Physical Separation

It is the most basic and important step in the refining process which includes separating the products based on their physical properties. Physical separation techniques include:

Crude Distillation: 

Crude oil distillation or fractionation refers to the separation of products due to difference in boiling point in an atmospheric distillation column. The fractions obtained have a specific range of boiling points and can be classified in order of decreasing volatility into gases, light products, middle products, gas oil, and residue. Before entering into the atmospheric distillation column, heated crude oil is mixed with washing water. This is known as desalting and is done to remove undesirable impurities before distillation. The desalted crude is fed to a vertical distillation column just above the bottom. The heavier products like oil or asphalt residue settle at the bottom while the rest products turn into vapour. At successively higher points on the tower, various other products like lubricating oil, gasoline etc. are obtained after condensation via natural convection at low temperatures.

What Everyone Ought To Know About Petroleum Refining Process? (#petroleumIndustry)(#ipumusings)(#chemicalengineering)
*The yields quoted here depend on feed composition and properties.
In this case, the feed API was 26.3

Solvent deasphalting:

This process involves the selective separation of carbon from heavy petroleum fraction such as vacuum residue. It is a molecular process in which oil is mixed with paraffinic solvents and precipitating out solution asphaltenes and other residue heavy components. It is an effective separation technique as deasphalted oil has low sulphur and metal contents and relatively high hydrogen deasphalted oil products which are used to increase light oil production in cracking units.

Solvent extraction:
It is used to remove aromatics components from lube oil feedstock, by dissolving them in a single-phase and then removing them. This is done to improve viscosity, enhance resistance to oxidation, improve colour and reduce the formation of gum.

Solvent Dewaxing:
It involves 3 steps: First, the feedstock is dissolved in a solvent and then chilled, crystallizing the high molecular weight paraffin. Second, the crystallized wax is removed from the solvent. Third, the solvent is recovered from the wax cake. The extracted and dewaxed oil is called lube oil.     

Chemical catalytic conversion process:

It involves converting different fractions into products and other resources through catalysts.

Catalytic reforming:
In this process, low octane naphtha (C6-C10) are retransformed into aromatics and isoparaffins components by using a catalyst. The produced reformate has a high octane number and is used as a gasoline blending component.

Hydrotreating is a hydrogenation process used to clean petroleum fractions from impurities such as nitrogen, sulphur, oxygen and metals. The catalyst depends on the type of impurity and the intensity of cleansing.  

Catalytic Hydrocracking:
It serves up two purposes: First, converting high molecular weight fractions into light products with the help of cracking in the presence of hydrogen. Second, Removing feed containments such as nitrogen sulphur and metals from atmospheric residues and vacuum gas oils. A dual-function catalyst is used which fulfils both requirements.

Catalytic cracking:
Catalytic cracking is used to convert vacuum gas oil, a heavy fraction, to high octane gasoline. Types of catalytic cracking include fluid catalytic cracking and hydrocracking. The catalyst used is a zeolite.

It is the conversion of C3-C5 olefins with isobutane to highly branched C5-C12 isoparaffins which is an important gasoline blending component. It is an acid-catalyzed reaction in which the catalyst used is mainly either sulphuric acid or hydrofluoric acid.

Isomerisation refers to changing the molecular arrangement of compounds without adding or removing anything from the original molecule. In the refining process, light naphtha having low octane number hydrocarbons are transformed into a branched product with the same carbon number.

Thermal Chemical Conversion Processes
These processes involve the upgrading process for vacuum residue

Delayed Cooking:
This process is used to convert residual streams from atmospheric and vacuum distillation into valuable products or intermediates such as LPG, diesel, etc. The vacuum residue is first heated and then fed to large drums. A large column of steam is injected to delay the cooking and finally, coke is deposited on the walls of the drums and the rest of the products are separated by distillation.

In this process, coke is burned to provide the heat required for thermal cracking. This process of thermal cracking gasifies most of the coke into fuel gas.

Visbreaking is a thermal cracking process done through two ways: Coil and Soaker visbreaking. In coil visbreaking, the feedstock is sent to coil heated furnace where thermal cracking takes place. Then the thermal cracking reaction is stopped and products are sent to a fraction for separation. In soaker visbreaking, Thermal cracking takes place in a soaker drum placed after the furnace. In both cases, the products are gases, gas oil, gasoline and other unconverted residues.

All the above steps give a brief overview of the journey of Petroleum from crude petroleum to useful products.

• Fundamentals of Petroleum Refining Book, 2010, Authors: Mohamed A. Fahim, Taher  A. Alsahhaf and Amal Elkilani

The petroleum industry, Nicholas P. Cheremisinoff, Paul Rosenfeld, in Handbook of  Pollution Prevention and Cleaner Production - Best Practices in The Petroleum Industry, 2009

• SOLVENT DEASPHALTING (SDA), 2018, (weblink

• Refining Operations and the Sources of Pollution, Nicholas P. Cheremisinoff PhD, Motasem B. Haddadin, in Beyond Compliance, 2006

• Hydrocarbons from Petroleum, James G. Speight PhD, DSc, in Handbook of Industrial Hydrocarbon Processes, 2011

• Catalysts for Hydrogenations, Dehydrogenations and Metathesis, Guido Busca, in Heterogeneous Catalytic Materials, 2014

• Catalytic Cracking Processes, James G. Speight, in Heavy Oil Recovery and Upgrading, 2019

Nafis D.A., Detrick K.A., Mehlberg R.L. (2014) Alkylation in Petroleum Processing. In: Treese S., Jones D., Pujado P. (eds) Handbook of Petroleum Processing. Springer, Cham

• Refining Operations and the Sources of Pollution, Nicholas P. Cheremisinoff Ph.D., Motasem B. Haddadin, in Beyond Compliance, 2006

• Delayed Coking, weblink, 2020

Visbreaking Processes, Dr Semih Eser,2018

About Author:
Dravya Malik is pursuing his BTech/MTech in Chemical Engineering at University School of Chemical Technology, GGSIP University, Dwarka, Delhi. He wants to do his specialization in petroleum engineering.

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