Types of High Pressure Homogenizers: An Overview

How are High Pressure Homogenizers are classified?

 

The Classification of High Pressure Homogenizers. High pressure homogenizers can be categorized based on various perspectives, including the power source, pressurization principle, and the design and structure of interaction chambers.

 

High pressure homogenizers: Classification

 

1. by energy source

 

Electric

 

Electric homogenizers are powered by an electric motor. This category of homogenizer can be further subdivided into two types: direct-drive and intensifier.

 

 

Electric high pressure homogenizer with intensifier

Direct-drive type: The motor drives the crankshaft to move the plunger back and forth, directly pressurizing the material. Multiple plungers in the crankshaft work together to produce constant pressure and a high flow rate; large quantities of materials are required to produce the constant pressure. To drive the crankshaft, the motor requires a multi-stage gear reduction mechanism, which makes the equipment large in size. The homogenizer with a crankshaft is suitable for large-scale production with low-pressure applications.

 

Intensifier type: In intensifier-type high pressure homogenizers, the motor drives the intensifier to pressurize the material through the interaction chamber. The intensifier system can provide higher pressure, thereby improving the performance of the homogenization process. The flow rate of the homogenizer with an intensifier is lower than it is for the homogenizer with a crankshaft, smaller amounts of materials are required, and the pressure is higher. It can be used for laboratory applications with small amounts sample, and for production applications with high pressure. When equipped with the diamond interaction chamber, the electric high pressure homogenizer with an intensifier falls into the category of high-end homogenizers. This type is widely used in biology, pharmaceutical, and nanotechnology laboratories. The traditional intensifier is hydraulic, and the new type of electric cylinder by linear actuator is emerged with more performance.

 

Hand Driven

 

Hand-driven high pressure homogenizer (Handgenizer1)

 

Handgenizer1: Hand driven homogenizers pressurize the material by manual power. The flow rate of a hand homogenizer is small, but it is portable and easy to assemble and disassemble. It requires very small amounts of materials, making it suitable for small-scale experiments. This type of device is capable of supporting biopharmaceutical laboratories’ research and development needs. The manual high-pressure homogenizer is also called the Handgenizer1.

 

Air Driven

 

The air driven homogenizer converts the pressure of compressed gas into hydraulic pressure. Therefore, it needs the support of a nitrogen cylinder or an air compressor. This homogenizer’s gas consumption and noise levels are high, and its maximum homogenization pressure is generally low. However, since there is no separate intensifier pump structure, its volume is small, and it is suitable for sites equipped with compressed nitrogen.

 

 

2. by principle and structure of the interaction chamber

 

The three-type principle of high pressure homogenization

 

First Generation: Impact Type

 

Cavitation nozzles: The main function of this nozzle is cavitation, which leads to the separation of the emulsion and thereby increases the particle size. Under the pressure of the homogenizer, the materials flow into the cavitation nozzle with a very small aperture at several times the speed of sound. Meanwhile, intense friction and collision take place between the particles and the metal valve parts. This friction reduces the service life of the equipment, and the collisions cause metallic particles to fall into the final products.

 

Impact valve: The impact valve and impact ring structure moderately reduce local wear and prolong the homogenization chamber’s service life by using tungsten alloy materials. The role of the impact valve is a combination of impact and cavitation. However, its basic principle is the collision of the material in the suspension with the structure of a high-hardness metal (such as tungsten alloy). Therefore, the impact valve still cannot solve the problem of metallic particle residue. By the first decade of the 20th century, most high pressure homogenizers have added impact valve component.

 

Second Generation: Interaction Type

 

Y-type interaction chamber: The Y-type interaction chamber, regarded as one of the most powerful homogenization chambers to date, has been used by several manufacturers in the USA. In these systems, the flow stream is split into two channels that are redirected over the same plane at right angles and propelled into a single flow stream. High pressure promotes a high speed at the crossover of the two flows, which results in high shear, turbulence, and cavitation over the single outbound flow stream. With the unique Y-type structure, the high-speed moving materials in the high-pressure solution collide with each other, in a process that greatly improves the service life of the chamber over those with more conventional designs. The use of diamond material prevents the formation of metal particle residue.

 

The Y-type interaction chamber is widely used in the preparation of pharmaceutical emulsions because it minimizes cavitation and produces exquisite, stable particle size and PDI (poly dispersity index) control ability. Genizer and Microfluidics Corp. are the main manufacturers of the diamond interaction chamber. At present, the Y-type diamond interaction chamber is mainly used in high-end nanotechnology, and it occupies more than 90% of the US pharmaceutical industry. Genizer’s temperature-controlled interaction chamber avoids temperature surges and enables working pressure of up to 60,000 psi.

 

Diamond Homogenizing Interaction chamber with cooling jacket

 

Low emulsification efficiency and metallic particle residue are two problems caused by homogenization chambers designed with the impact principle. When particles collide with internal metal components during the production of pharmaceutical injections, residual inert metallic particles generate. These metallic particles may gather and form larger particles. In pharmaceutical applications, this is a problem because large particles will lead to a decrease in capillary blood flow, which in turn will cause mechanical damage to tissues in the human body, causing acute or chronic inflammation. The interaction chamber solves the problems of particle residue and demulsification. However, the chamber’s internal structure means that when the products’ concentration and viscosity are high, the chamber is more prone to cause flow blocking than impact homogenizers are.

 

3. by principle of pressurization

 

The ultra-high pressure homogenizer needs a large thrust to push the piston in the cylinder to achieve high pressure levels. The rotating motor needs to reduce the speed, increase the torque, and convert the linear motion to obtain the linear reciprocating motion with high thrust. The principle of pressurization operates differently in direct-drive type and intensifier-type homogenizers.

 

Direct-drive type: The motor drives the crankshaft to move the plunger back and forth and directly pressurize the material. Multiple sets of plungers provide constant pressure, and the flow rate is high for this type of homogenizer. However, the minimum material requirements are also high, as is the amount of residual produced. The crankshaft driven by the motor needs a multi-stage gear reduction mechanism, which limits these homogenizers to only moderate efficiency and requires large unit dimensions. This homogenizer type is suitable for the food and chemical industries, as well as other applications that do not have high pressure requirements.

Internal structure of direct-drive type homogenizer

 

Intensifier type: The intensifier-type homogenizer is the result of the development of ultra-high pressure technology in recent years. One of its mechanisms involves the motor driving the oil pump to pressurize the material through the hydraulic system. The pressure provided by the hydraulic system is higher than in direct-drive homogenizers, while the volume and the minimum material requirement is smaller. The intensifier-type homogenizer can be applied to both laboratory and production homogenizers with high pressure. Hydraulic homogenizers are expensive, but the hydraulic intensifier can achieve low-frequency and high-thrust piston movement, which increases the machine’s service life and reduces its maintenance costs. Using parallel four-cylinder technology, stable pressure can be obtained without an accumulator, achieving ultra-high pressure of up to 45,000 psi.

Structural diagram of hydraulic type-quad pump with constant pressure

In the past, most high pressure homogenizers were the direct-drive type, but this type’s disadvantage is obvious. Its service life is short, and its wearing parts need frequent maintenance, especially those pressure-bearing parts when the pressure is above 100 MPa. Hydraulic homogenizers have a high manufacturing cost, but they also offer a long service life and lower maintenance costs for wearing parts.