A high pressure homogenizer is a type of mixer that works by forcing material through a narrow and confined space in order to create a mixture that is consistent and even. In addition to high pressure, the use of multiple forces such as turbulence and cavitation is employed in order to achieve an even distribution of the contents of a solution. The pump creates an environment in which the material to be processed is subjected to pressure while passing through a narrow space that is located between the valve seat and the valve. Both turbulence and mixing are caused when the force of the pressure and the movement through the valve are combined. Homogenizers are essential to the production and quality of products in the chemical industry, as well as the beverage and pharmaceutical industries.

Homogenizers Used in the Milk Manufacturing ProcessThe past:

In the early 1900s, Auguste Gaulin invented a piece of machinery that could homogenize milkThis invention marked the beginning of the development of homogenizersThe apparatus consisted of a positive displacement pump with three pistons and capillary tubes attached to the dischargeA concave valve was located downstream of the capillary tubes, and this is where the milk droplet jet would make contact

Diagrammatic Representation of Gaulin's Homogenizer

The capillary tubes of the homogenizer were eventually replaced with a single, smaller tube as a result of subsequent developments in the engineering of homogenizers. The tube had a slight opening in it, and this was where the homogenization process took place, so this was the most important feature.

Theories and fundamentals of homogenizers are covered in Chapter 2.

Throughout the years, numerous hypotheses and theories concerning the method of homogenization that involves the utilization of high pressure have been developed. The globule disruption by turbulence theory and the cavitation theory are currently the two most prominent theories that have survived. These two remaining theories both provide excellent illustrations of the various forces that can exert an influence on the homogenization process.

According to the cavitation theory, changes in pressure during homogenization result in the formation of bubbles or cavities within a liquid. The imploding and collapsing of the bubbles generates kinetic energy that surrounds the particles in the liquid, which in turn creates high-velocity jets that shatter the particles. Cavitation is produced when bubbles in a liquid undergo the process of imploding and collapsing, which creates turbulence in the liquid. An emulsion is a mixture of two or more liquids that, under normal circumstances, cannot be mixed together because of the phase separation that occurs between the liquids. A number of different physical mechanisms, including surface tension, polarity or repulsion, and viscosity, are responsible for bringing about this liquid-to-liquid phase separation.

The use of emulsions

A mixture that is composed of solid particles that settle down but are unable to be completely dissolved in the mixture is called a suspension. The solid particles are able to be distinguished from the dispersed particles in a homogenous solution as a result of their significantly larger size, which is approximately hundreds to thousands of times greater than that of the dispersed particles. Non-homogeneous mixtures that can be dispersed in liquids and have particles that are one hundred times larger than those found in solutions make up suspensions. Homogenization is one of its primary functions, and one of its primary functions is to supply the force necessary to combine suspensions with a solution.

Put in suspension

When one is familiar with the different kinds of heterogeneous mixtures that can be processed by a homogenizer, it is easy to understand how a high pressure homogenizer functions. The dispersed components are first broken or subdivided into smaller particles through the action of a homogenizer, and then these smaller particles are distributed evenly throughout the mixture.

The homogenization process takes place inside the homogenizer valve, which is the primary part of the apparatus. In an earlier explanation, it was mentioned that the initial high pressure homogenizer valve consisted of an assembly that included a capillary tube and a concave valve. The fluid pressure was reduced inside the capillary tube, which resulted in the creation of kinetic energy. The fluid jet had an impact with the concave valve, which served in that capacity. In more recent designs, the capillary tube has been replaced with a seat that is designed to mate with the valve at an appropriate clearance in order to create a small gap that can be used to throttle flow. While the fluid is contained within this gap, it is subjected to the appropriate flow conditions for homogenization, which is accomplished using a variety of different physical principles. However, in the presence of a disruption, such as acceleration caused by a rotor-stator or deflection caused by an impact ring, different velocities develop as a result of the fluid's internal friction. These different velocities result in different outcomes. The velocity of the fluid is equal to zero at the boundary layer, also known as the layer that is located between the high pressure homogenizer surface and the fluid.

When a large particle or droplet becomes trapped between fluid layers moving at different speeds, High pressure homogenizer goes through a process known as shearing. The shear forces cause large particles and droplets to be broken down into smaller pieces of varying sizes.

Shearing of Fluids

Cavitation occurs whenever a fluid is subjected to a significant decrease in pressure. As the fluid moves through the high pressure homogenizer valve, the pressure of the fluid is transformed into kinetic energy. When there is a significant enough drop in pressure, the vapor pressure of the fluid inside the homogenizer rises to a level that is higher than the absolute pressure. Because of this, it is possible for brief cavities to form from relatively small pockets of vapor.

Turbulence is the final physical principle that contributes to the homogenization process. When the fluid's speed increases to a certain point, it develops turbulence. The high velocity causes the fluid to behave in an erratic manner throughout. The eddies that are produced contribute to the fragmentation of the particles, making them smaller.

turbulent eddies of turbulence

The design of the high pressure homogenizer valve and the properties of the fluid, such as temperature, pressure, composition, and viscosity, determine the degree to which each individual physical effect contributes to the process of homogenizing the substance. Nevertheless, the results of the vast majority of investigations and experiments point to the turbulence effect as the primary mechanism responsible for producing homogenization.

There are other mechanisms that can also produce shearing, cavitation, and turbulence effects in addition to a  valve. Although the other types of homogenizers operate in a different way than the first type, they still accomplish the same goal.

Homogenizer Operating at High Pressure

A high-pressure pump and a homogenization valve are the two components that make up high-pressure homogenizers, which are also known as piston homogenizers. A positive displacement reciprocating type pump was chosen for the high-pressure pump because this type of pump is inherently suitable for viscous fluids and maintains its efficiency even when subjected to varying degrees of flow and pressure. Homogenizers that operate at high pressure typically have three or more pistons and plungers.