What is the difference between a decanter and a separator?


The Difference Between a Decanter and a Separator


When it comes to the separation of fluids and materials, two common devices that often come to mind are decanters and separators. These tools are widely used in various industries ranging from chemical engineering to food processing. While both decanters and separators serve the purpose of separating substances, they differ in their working principles and specific applications. In this article, we will delve deeper into the differences between decanters and separators, exploring their functionalities, designs, and applications in various industries.

The Functionality of a Decanter

Decanters are devices designed to separate substances by density or viscosity differences. They are commonly used to separate liquid-liquid or liquid-solid mixtures. Decanters operate on the principle of gravity separation, utilizing centrifugal forces. One distinguishing feature of decanters is their conical shape. These devices consist of a rotating bowl mounted horizontally, with a screw conveyor within the bowl.

Decanters function by feeding a mixture into the bowl, where the solid or denser liquid settles against the inner walls due to centrifugal forces. Simultaneously, the screw conveyor transports the settled materials towards one end of the bowl, known as the conical section. As the conveyor rotates, it gradually moves the settled materials, or sediment, towards the discharge end of the bowl. The clarified liquid, which is less dense, remains above the sediment and overflows at the opposite end, known as the liquid discharge section.

With its ability to handle high solid concentrations and separate mixtures efficiently, decanters find applications in various industries. They are commonly used in wastewater treatment plants to separate sludge and liquid, in oil refineries to remove solid impurities from crude oil, and in food processing to clarify juices and oils, among other applications.

The Functionality of a Separator

Separators, on the other hand, are devices used for the separation of fluid mixtures, primarily in industrial processes. Unlike decanters, separators operate based on the differences in specific gravity between the components of a mixture, regardless of their viscosity. Separators are commonly used to separate liquids from gases, solids from gases, and immiscible liquid-liquid mixtures.

The functionality of separators is based on the principle of mechanical separation. These devices typically consist of a vessel with internals such as baffles, coalescers, and filters. The mixture enters the separator and undergoes various stages of separation to achieve the desired degree of purity. In the case of liquid-gas separation, the mixture is introduced into the vessel, and the gas rises to the top due to its lower density. The separated gas is then discharged, while the liquid phase is collected at the bottom.

Separators are widely used in industries such as oil and gas, pharmaceuticals, and chemical processing. In oil refineries and natural gas processing plants, separators play a crucial role in separating oil and gas from the produced fluid, allowing for further processing and refining. In the pharmaceutical industry, separators are utilized to separate and purify active pharmaceutical ingredients (APIs) from their reaction mixtures.

The Design and Components of a Decanter

Decanters have a relatively simple design compared to separators. They consist of three main components: a rotating bowl, a screw conveyor, and a drive system. The bowl, usually made of stainless steel, is the key component responsible for the separation process. The screw conveyor, also known as an auger, rotates within the bowl, transporting the settled material towards the discharge end. The drive system ensures the rotation of the bowl and screw conveyor.

Decanters also include additional features, such as adjustable discharge plates, variable speed drives, and various control mechanisms. The adjustable discharge plates allow operators to control the quantity and quality of the separated solids and liquids. Variable speed drives enable the adjustment of the screw conveyor's rotational speed, facilitating the optimization of the separation process. Control mechanisms, such as level sensors and automated valves, ensure the efficient operation of decanters.

The Design and Components of a Separator

Separators are more complex in design compared to decanters, as they require various internal components to achieve efficient separation. The main components of a separator include an inlet section, an outlet section, baffles, coalescers, filters, and a control system. The inlet section allows the mixture to enter the separator, while the outlet section collects the separated phases.

Baffles are essential components within separators, responsible for enhancing the separation process. They create a tortuous path for the mixture, promoting the separation of different phases by extending the residence time within the separator. Coalescers, on the other hand, are used to combine small droplets within a liquid phase to form larger droplets, aiding in their separation. Filters may also be incorporated into separators to capture solid particles and impurities from the mixture.

The control system of a separator ensures the efficient operation of the device. It includes various instruments such as level sensors, pressure gauges, and flow meters, allowing operators to monitor and maintain optimal operating conditions. Automated valves and control algorithms may also be employed to regulate the flow rates and pressures within the separator, improving the overall efficiency of the separation process.

Applications of Decanters and Separators in Different Industries

Decanters and separators find applications in numerous industries, contributing to the efficient separation of substances. Some of the key industries where decanters are commonly employed include wastewater treatment, mineral processing, and food and beverage production.

In wastewater treatment plants, decanters are used to separate sludge from the liquid phase. Sludge, which contains solid particles and microorganisms, settles at the bottom of the decanter, while clarified liquid is discharged. This process helps in the removal of pollutants from the wastewater, allowing for cleaner water to be released back into the environment.

In mineral processing, decanters are utilized for the separation of various valuable minerals from slurries. The feed mixture, which contains solid particles and liquids, is fed into the decanter, and the heavier minerals settle at the bottom due to centrifugal forces. The separated minerals are then collected, while clarified liquid is discharged.

In the food and beverage industry, decanters are commonly used for the separation of liquids such as juices, wines, and oils. By separating solids and impurities from these liquids, decanters ensure a higher level of purity and improve the quality of the final products.

Separators, on the other hand, are extensively utilized in industries such as oil and gas, pharmaceuticals, and chemical processing. In the oil and gas industry, separators play a critical role in separating oil, gas, and water from the produced fluid. This separation allows for the recovery of valuable hydrocarbons and facilitates the removal of impurities from the gas stream.

In the pharmaceutical industry, separators are employed in the purification of APIs and the removal of impurities from reaction mixtures. Separators aid in achieving the desired level of purity for pharmaceutical products, ensuring their quality and efficacy.


In conclusion, while decanters and separators serve the purpose of separating substances, they differ in their working principles, designs, and applications. Decanters rely on gravity separation and centrifugal forces to separate materials based on density or viscosity differences. They find applications in industries such as wastewater treatment, mineral processing, and food production. Separators, on the other hand, utilize mechanical separation based on differences in specific gravity to separate substances. They are widely employed in industries such as oil and gas, pharmaceuticals, and chemical processing. Both decanters and separators play crucial roles in various industries, enabling efficient and effective separation processes.


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