Posted by Rudy Wiratama in article, static mixer
A static mixer or a motionless mixer is a precision engineered device for the continuous mixing of fluid materials. Normally the fluids to be mixed are liquid, but static mixers can also be used to mix gas streams, disperse gas into liquid or blend immiscible liquids.
In industrial applications liquids and gases are moved through pipelines. The energy needed for this, in the form of pressure, is generated by a pump or compressor. Static mixers are very often fitted into these pipes and the components that need to be mixed or dispensed are added to the main flow directly before the mixer.
A Static mixers have a very wide range of application within various kinds of industries and are therefore very flexible. In general applications such as technical homogeneous mixing, extraction, washing, reacting, cooling, mixing of viscous media and heating are the most common. But of course other less common applications are also possible.
The type of mixer elements inside a static mixer have a number of corresponding characteristics. There are
a minimum of two elements in a static mixer and they are placed one behind the other as a string. The
mixing elements strand which is constructed like that gives an axial twist to the flow pattern, and each successive element has alternately a left and a right-hand twist. In addition each subsequent element is placed rotated by 90 degrees in comparison with its predecessor.
Static mixing with laminar flow
Following the laminar principle, the flow is repeatedly split into sub flows in a static mixer and subsequently brought together again. With the right pitch a balanced flow is created from outside to the inside and vice versa. This is how the medium is mixed, in a large amount of very thin layers, and the number of layers created determines the extent of the mixing.
Static mixers are an arrangement of mixing elements installed in a pipe or duct. They function without moving parts and are used to achieve specific mixing and dispersion in continuous processes.
Static mixing with turbulent flow
The mixing effect of a static mixer following the turbulent mixing principle is mainly achieved by internal rotation and shearing away the layers within the liquid. This happens at the point where the direction of the rotation is reversed. When small percentages of shearing are required then the pitch between two rotations can be accurately adjusted to achieve this. With this pitch the rotation process is slowed down which results in extra mixing. After this reversed rotation will also start more slowly.
Homogeneity of the mixture
The homogeneity of the mixture is best measured by determining the temperature deviations or the concentration differences behind the PRIMIX static mixer. This is expressed in the theory of probability as standard deviation measured against the average. In the diagram below it is clearly visible when the medium is homogeneous.
Applications include mixing two-component adhesives and sealant; waste water treatment and chemical processing. Static mixers can be used in the refinery and oil and gas markets as well, for example in bitumen processing or for desalting crude oil. In polymer production, static mixers can be used to facilitate polymerization reactions or for the admixing of liquid additives. Static mixer could be used for:
Liquid – Liquid mixing
Gas- Gas mixing
The overall system design of Static Mixer is dependent on many variables including the physical properties of fluids, mixer length, tube inner diameter, the number of elements and their geometrical design.