STEEL INDUSTRY

Air assisted atomizers selection guide

How do you choose a pneumatic atomizer? What are the things to know to make the right choice?

Air assisted atomizers selection guide

How do you choose a pneumatic atomizer? What are the things to know to make the right choice?

Choosing a pneumatic atomizer may seem a complicated task, in which many factors are taken into account. We have developed a scheme that will guide you step by step in your choice of a pneumatic atomizer.

Below we list the technical characteristics of a pneumatic atomizer to help and support you in your choice. We are always available for personalized advice and help you find the right nozzle for your needs.

What is a pneumatic atomizer

The term “atomization” is generally used to indicate the separation of a liquid volume which leads to the formation of a dispersion (more or less fine) of liquid particles (drops).

The term atomization refers to a very deep fragmentation (up to the level of the atoms) of the liquid. A device used for the atomization of liquid (ie the disintegration of the liquid into drops) is called an “atomizer”. The atomization of a liquid using a compressible fluid such as air, steam, or gas is called two-phase, double fluid, or pneumatic atomization.

Applications of pneumatic atomizers

Pros and cons of systems with hydraulic or pneumatic atomizers

SYSTEM WITH
HYDRAULIC ATOMIZERS

Several industrial processes need the atomizing of liquids into fine and very fine droplets.
This result might be achieved through a purely hydraulic nozzle, with the liquid being fed at high pressure through a very small orifice, but the process would originate two main problems:

1- Requiring costly investments and a complicated layout;
2- Originating plugging problems because of the small orifice dimensions.

SYSTEM WITH
AIR-ASSISTED ATOMIZERS

In most industrial processes, fine liquid atomization is obtained utilizing air-assisted atomizers, where compressed air supplies the required energy to break the liquid and throw the droplets at a given distance from the atomizer.

An air atomizing system has however two inherent limitations:
1- The narrow inside passages require adequate filtering of air and liquid;
2- The high-speed jet will only produce narrow-angle sprays. To overcome this inconvenience multiple orifice atomizers are used to produce diverging sprays with better droplet distribution.

Types of pneumatic atomizers

Many industrial processes require using finely atomized droplets and the techniques to produce finely
atomized sprays have been largely improved in recent years with new types of atomizers being developed.

CLASSIC
ATOMIZERS

Classic atomizers are devices producing an atomized spray with the assistance of compressed air, where the liquid is broken into droplets when its outer surface is subjected to shear action from the high-speed airflow..

ULTRASONIC
ATOMIZERS

Ultrasonic atomizers operate on a very sophisticated process which is based on two steps:
1 In the first one tiny water jets are injected into a high-speed airflow which provides a first break up and atomization of the fluid.
2 In the second step the two-phase flow, air-entraining liquid droplets, goes through a field of sound waves which produce a further breakup and a lower droplet dimension.

AIR ACTUATED
ATOMIZERS

Air actuated atomizers bodies contain an air actuated cylinder that controls the spray operation using a needle, opening or closing the water inlet in the liquid nozzle. Normally the air used for atomizing the liquid flows continuously, while the air to the actuator is used to start and stop the atomizing cycles.

SPECIAL
ATOMIZERS

In many industries bi-phase water-air atomizers are manly, but not only, used to suppress and cool fumes. In these situations, it is very important to have products that give a homogenous distribution of the nebulized jet that interacts with the gaseous phase and to have the possibility to work with a wide range of pressures, both for water and air.

Operating principles of pneumatic atomizers

The set-up can be designed in two different ways to obtain the following actions
Air and liquid are mixed up in a mixing chamber inside the atomizer and then they are ejected through the orifice as a spray.
Air and liquid are ejected from the atomizer through different orifices, and the spray is generated by the impact of the two jets.

EXTERNAL MIX
SET-UPS

 

The two fluids are sprayed by separate orifices and the mixing caused by their impact occurs outside the nozzle, so the pressure values can be easily adjusted independently of each other and their flow rates easily controlled. External mixing allows to atomize viscous liquids or containing solids in suspension. External mixing units are built only in the pressure type, and can generate only a flat jet.

INTERNAL MIX
SET-UPS

The atomizer unit is designed so that the two fluids are mixed inside and the resulting atomized flow is sprayed by the orifice, or orifices, of the nozzle. In this group of atomizers, the variation of the flow or pressure values of one of the fluids causes variations in the flow of the other fluid. The increase in air flow rate will cause a decrease in the flow rate of the liquid with finer drops, and vice versa.

How to choose a pneumatic atomizer

Our Technical Department has developed a simple infographic that can help our customers choose a pneumatic sprayer:

STEP 1

To choose a pneumatic atomizer you need to:
– Define the goal, what you want to achieve with this tool;
– Identify your resources, that is, know the plant;

STEP 2 | 3

– Before proceeding, it useful to verify if the same result can also be achieved with a hydraulic atomizer: if so, choose one: -> the guide to the choice of hydraulic nozzles is available at this link;
– If a hydraulic pump is available, proceed to step 4, if not, decide how to supply the liquid: by gravity or by suction;

STEP 4

Define the properties of the air available: the flow rate and the system air pressure;

STEP 5

Define the properties of the jet you are looking for: distribution, flow rate and angle of the jet;

STEP 6

Choose between internal or external mixing: if the viscosity of the liquid is high, we recommend external mixing. Conversely, if the viscosity is normal, we recommend internal mixing.

STEP 7

Define the controls and accessories of the atomizer