Visbreaker: Difference between revisions

Latest revision as of 03:44, 13 February 2025

Visbreaker[edit]

Diagram of a visbreaker unit

A visbreaker is a type of chemical engineering process unit used in petroleum refineries to reduce the viscosity of heavy residual oils. The primary purpose of a visbreaker is to break down large hydrocarbon molecules into smaller, more valuable products such as fuel oil and gasoline. This process is a form of mild thermal cracking.

Process Description[edit]

The visbreaking process involves heating the heavy residual oil feedstock to a high temperature, typically between 450°C and 500°C, in a furnace. The heated oil is then passed through a soaking drum where the thermal cracking reactions occur. The residence time in the soaking drum is carefully controlled to achieve the desired level of cracking without producing excessive amounts of coke.

The cracked products are then rapidly quenched to stop the cracking reactions. The resulting mixture is separated into different fractions using a fractionating column. The main products of the visbreaking process include:

Types of Visbreaking[edit]

There are two main types of visbreaking processes:

Furnace Visbreaking: In this type, the cracking reactions occur primarily in the furnace tubes. The feedstock is heated to a high temperature and then immediately quenched.

Soaker Visbreaking: In this type, the feedstock is heated to a lower temperature and then held in a soaking drum for a longer period to allow the cracking reactions to occur.

Advantages and Disadvantages[edit]

The visbreaking process offers several advantages:

Increased Yield: It increases the yield of valuable lighter products from heavy residual oils.
Reduced Viscosity: It reduces the viscosity of the residual oil, making it easier to handle and transport.
Lower Operating Costs: Compared to other cracking processes, visbreaking is relatively simple and has lower operating costs.

However, there are also some disadvantages:

Limited Conversion: The conversion of heavy molecules to lighter products is limited compared to more severe cracking processes like fluid catalytic cracking.
Coke Formation: There is a risk of coke formation, which can foul equipment and reduce efficiency.

Applications[edit]

Visbreakers are commonly used in refineries to process heavy residual oils that are not suitable for further processing in other units. The products from visbreaking can be used as feedstock for other refining processes or blended into finished products.

Related Pages[edit]

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-'''Visbreaking''' is a thermal [[cracking]] process used in [[oil refinery|oil refineries]] to reduce the viscosity of heavy residual oils, making them more suitable for further processing or sale as fuel oils. The process involves the mild cracking of these heavy oils at temperatures between 450°C and 500°C in the presence of a short residence time to produce a mixture of lighter oils, gas, and coke. The term "visbreaking" is derived from "viscosity breaking," reflecting the process's primary goal of reducing the oil's viscosity.
+== Visbreaker ==
-==Process Overview==
+[[File:Visbreaker.png|thumb|right|Diagram of a visbreaker unit]]
-Visbreaking is conducted in a so-called visbreaker unit, which typically operates in one of two modes: the soaker mode or the furnace mode. In the soaker mode, the feedstock is held at the cracking temperature in a soaker drum for a period to allow the cracking reactions to proceed. In the furnace mode, the feedstock is rapidly heated in a furnace then immediately quenched to stop the cracking reactions. The choice between these modes depends on the desired product quality and refinery configuration.
-The main reactions occurring during visbreaking are thermal cracking reactions, where large hydrocarbon molecules are broken down into smaller ones. This process reduces the molecular weight of the residue, thereby decreasing its viscosity and making it easier to handle and process. However, visbreaking is a relatively mild form of thermal cracking, designed to minimize the production of undesirable by-products like coke and dry gas.
+A '''visbreaker''' is a type of [[chemical engineering]] process unit used in [[petroleum refineries]] to reduce the [[viscosity]] of heavy residual oils. The primary purpose of a visbreaker is to break down large hydrocarbon molecules into smaller, more valuable products such as [[fuel oil]] and [[gasoline]]. This process is a form of mild thermal [[cracking (chemistry)|cracking]].
-==Products==
+== Process Description ==
-The primary products of visbreaking are:
-* Lighter oils, which can be blended into fuel oils or further processed in other refinery units.
-* Tar, which has reduced viscosity and can be used as a feedstock for other processes or sold as a fuel oil component.
-* Gases, including methane, ethane, propane, and butenes, which can be used as refinery fuel or feedstock for petrochemical processes.
-* A small amount of coke, which deposits on the reactor surfaces and must be periodically removed.
-==Applications==
+The visbreaking process involves heating the heavy residual oil feedstock to a high temperature, typically between 450°C and 500°C, in a furnace. The heated oil is then passed through a soaking drum where the thermal cracking reactions occur. The residence time in the soaking drum is carefully controlled to achieve the desired level of cracking without producing excessive amounts of [[coke (fuel)|coke]].
-Visbreaking is primarily used to reduce the viscosity of heavy fuel oils, making them easier to transport and use. It also increases the yield of more valuable light and middle distillates from heavy crude oil fractions, improving overall refinery economics. Additionally, visbreaking can serve as a feed pretreatment step for more severe cracking processes, such as [[fluid catalytic cracking]] (FCC) or [[hydrocracking]], by reducing feedstock viscosity and coking tendencies.
-==Environmental and Safety Considerations==
+The cracked products are then rapidly quenched to stop the cracking reactions. The resulting mixture is separated into different fractions using a [[fractionating column]]. The main products of the visbreaking process include:
-The visbreaking process involves high temperatures and potentially hazardous materials. It requires careful control and monitoring to prevent equipment fouling and to ensure the safety of operations. Additionally, the gases produced can contain sulfur and nitrogen compounds, which must be treated to meet environmental regulations regarding emissions.
-==See Also==
+* [[Gasoline]]
-* [[Oil refinery]]
+* [[Diesel fuel]]
-* [[Thermal cracking]]
+* [[Fuel oil]]
+* [[Gas (fuel)|Gas]]
+== Types of Visbreaking ==
+There are two main types of visbreaking processes:
+* '''Furnace Visbreaking''': In this type, the cracking reactions occur primarily in the furnace tubes. The feedstock is heated to a high temperature and then immediately quenched.
+* '''Soaker Visbreaking''': In this type, the feedstock is heated to a lower temperature and then held in a soaking drum for a longer period to allow the cracking reactions to occur.
+== Advantages and Disadvantages ==
+The visbreaking process offers several advantages:
+* '''Increased Yield''': It increases the yield of valuable lighter products from heavy residual oils.
+* '''Reduced Viscosity''': It reduces the viscosity of the residual oil, making it easier to handle and transport.
+* '''Lower Operating Costs''': Compared to other cracking processes, visbreaking is relatively simple and has lower operating costs.
+However, there are also some disadvantages:
+* '''Limited Conversion''': The conversion of heavy molecules to lighter products is limited compared to more severe cracking processes like [[fluid catalytic cracking]].
+* '''Coke Formation''': There is a risk of coke formation, which can foul equipment and reduce efficiency.
+== Applications ==
+Visbreakers are commonly used in [[refineries]] to process heavy residual oils that are not suitable for further processing in other units. The products from visbreaking can be used as feedstock for other refining processes or blended into finished products.
+== Related Pages ==
+* [[Petroleum refining processes]]
+* [[Cracking (chemistry)]]
 * [[Fluid catalytic cracking]]
-* [[Hydrocracking]]
+* [[Coking (chemistry)]]
-* [[Petroleum product]]
-==References==
+[[Category:Petroleum refining]]
-<references/>
-[[Category:Oil refining]]
 [[Category:Chemical processes]]
-{{Energy-stub}}