NEUMATIC TRANSPORT

Bulk material pneumatic transport consist in solids transport through a pipeline, do it by gas under pressure, usually air.

Pneumatic transport is a solid bulk transport system widely used in solid handling facilities that include storage, transport, dosing and weighing.

Pneumatic transport can be used in different types of industry and fields of production, such as: the industry of processing of minerals and other similar products such as cement, chemistry, agri-food, plastics industry, pharmaceutical industry, cosmetic, etc.

The performance of a pneumatic transport depends mainly on the design of the transport line, as well as the equipment selected for its execution. SOTECMA has extensive experience in this type of transport, including manufacturing many of the components used.

For a correct design of a pneumatic transport line, knowledge of the product and each and every one of its characteristics is fundamental. Granulometry, density, humidity, abrasivity, etc.

From these data, and knowledge of the transport line, the basic characteristics of transport will be decided:

• In vacuum or pressure
• In diluted phase or dense phase
• Applicable capacity range: from 1 kg to 50 tons per hour
• Possible distance range: up to 500 meters

SOTECMA designs and installs pneumatic transports, both suction or pressure (in dense or diluted phase). Providing engineering, elements or the complete installation.

The most common method in continuous pneumatic transport is the diluted phase. Transport in the diluted phase is characterized by a series of advantages such as high speed, low pressures, as well as a very low air / material ratio. In contrast, dense phase transport operates at a lower speed and higher pressure. It will be used especially for the transport of fragile or abrasive materials.

The different pneumatic transport systems

Depending on the pressure of the gas used to transport, the system is classified in three groups:

• Low pressure transport, do it in positive pressure or in negative pression (depression), the ranges would be from -50 mbar to 50 mbar
• Medium pressure transport. Like low pressure, can also be carried out with positive or negative pressure. Ranges between 50 mbar to 800 mbar for pressure transport and from -900 mbar to -50 mbar for depression transport.
• High pressure transport, it can only be done under pressure and the range used is from 1 bar to 6 bars.

Pneumatic transportation system components

Pneumatic transport system is made up of 4 elements or zones:

Pressure generating equipment

It is the main element of the pneumatic transport system, it is responsible to supply the energy needed to flow the gas, and therefore the solid to be transported. The machines used for this are fans, blowers and compressors, the choice depends on the transport type designed.

Solid feeder

This device feeds the solid flow in the transport line. In the feeding point, the power transmission ne did it. when the bulk material is in contact to the gas flow. The choice of the feeder type It is very important, the connection to the pipeline should be sealed. The feeders can be rotary valves, propellers, venturis, screws conveyors, etc.

Transport elements

Consists on pipes and auxiliary elements through the gas and solid mixture will flows. The choice, is depends on the solid capacity, transport pressure, bulk material abrasiveness, possible chemical attacks, etc. Special care must be taken in curves, bifurcations and any element that implies a change of direction or intersection in the transport line.

Solid-gas separation zone

Once the transport has been carried out, it is required to separate the solid from the gas. The subject is to recovery the bulk material from the gas, to recycle the gas in the transport process if is needed, and to avoid the dust emissions to the atmosphere. The equipment used for this applications are filters and cyclones.

Pneumtic transport types

Considering the degree of concentration of the solid against the transport gas, a pneumatic transport system can be classified into:

• Dense phase transport is when the ratio between the solid mass and the gas mass is bigger than 15. In this transport type, the solid flow in packages or batch at low speed. Then the abrasiveness to the pipe decrease. On the other hand, like the concentration of solid is high, a smaller section of pipe is needed for the same solid flow.
• Diluted phase transport is when the solid concentration ratio in the gas is below 15. The transport speed is bigger, thereby pipe section is bigger to the dense phase type, for the same mass flow. It is used to low flow capacities and for products that cannot be subjected to high pressure.

SOTECMA has long experience, especially in high pressure pneumatic system, by propellers; and in medium pressure system by blowers. Both in pressurized and depressed types. Mainly, working together with high precision dosing and weighting additives applications.

Pneumatic transport by propeller is the most modern solution to the bulk material transport, distribution and general movement in the industry.

Transport is carried out by batch, by medium working pressures, between 2 – 3 bars, and high solid concentrations, then reducing the speed and decreasing the wear.

Other important characteristics are the limited space occupied, easy and minimal maintenance, use flexibility, limited air consumption and minimal noise.