Pneumatic conveying and material properties of dust Profile

First, dust
Solid material called elementary solid particles, dispersed in the air for a certain time called solid particles of dust. International Organization for Standardization,

particle size less than 75 microns is defined as powered roller conveyor dust suspended solids.
1 generates
The production process of the solid material for mechanical crushing, grinding dust is generated. Such as: coal crushing.
Metal smelting or heating of the object, the physical and chemical processes of sublimation or vapor in the air condenses to form tiny particles or oxidation. Such as: coal or

coke oven coke pushing process.
Or incomplete combustion of organic matter combustion, emissions species contains a lot of tiny dust particles and smoke. Such as: coal spontaneous combustion or inadequate

supply of oxygen and other reasons can not fully burn, smoke exhaust material contains various forms of dust.
In the powder material mixing, transfer, screening, packaging and discharging the production process, a large number of dust particles escape from the device and so the gap.
(2) the nature of
(1) invasive
Dust invasive means of solid particles in contact with the cleansing liquid, the liquid surface of the infiltration of dust skate roller conveyor particles. This phenomenon performance liquid on the

surface of dust particles the size of the force. Usually the degree of infiltration of water on the dust particles of dust into the hydrophilic and hydrophobic categories.
(2) explosive
Reaches a certain concentration of industrial dust in the air to meet fire, discharge, temperature and friction effects, explosion may occur, a phenomenon called dust explosion.
(3) Abrasion resistance
Abrasive dust usually refers to the degree of abrasion of the device, wear dust with its own hardness and shape of the hardness, surface roughness of the large abrasive dust.
3 Classification
(A) by nature
Inorganic dust include: mineral dust (such as sand, coal); metal dust (such as iron, tin, lead and their compounds); artificial inorganic dust (such as silicon carbide, cement,

glass fibers).
Organic dust: Includes vegetable dusts (such as wood, tobacco, flour); animal dust (eg skins, skin, hair); artificial organic dusts (such as explosives, organic dyes, plastics,

chemical fiber).
Mixed dust, dust of the various mixtures (such as metal grinding, abrasive dust, metals and mixtures thereof).
(2) according to particle size classification
Dust: particle diameter greater than 10 microns, the electrostatic air to accelerate sedimentation, non-proliferation.
Sand and Fog: Dust particle diameter is between 10-0.1 microns in static air at constant speed landing, not spread.
Dust: particle diameter of 0.1 and 0.001 microns, because of its size is close to the air molecules, by the collision of air molecules showed Brownian motion, almost no

settlement or very slow and tortuous descent. Since dust particles of different sizes, the length of the residence time in the air is different, the processing side

Different method.
Second, the material properties
Pneumatic conveying system design, the material particle characteristics determine whether to adopt the pneumatic conveying and pneumatic conveying in what form. Material

properties including particle size and distribution, shape, density, hardness, brittleness, compressibility, permeability, viscosity, separation, explosive and electrostatic

Effects, etc..
1 particle shape
The shape of the suspended particles have a greater impact speed. The same kind of spherical particles of suspended material in the maximum speed, a variety of other irregularly

shaped particles suspended speed is smaller. Suspension rate is small, in the same transport gas velocity, the material will be deposited on the bottom of the tube, by the

movement of materials between the push

Or stationary. Polygonal particle friction, surface bumps and more particles tend to smoke and melt.
(2) Bulk density
The bulk density of the material the greater the energy consumption for transporting the greater. Such as the use of air power to transport, requires enhanced conveying

velocity. Gas velocity is too low, will inevitably result in the deposition of the bottom of the tube material, the residual amount of increase in transport Hou.
3 moisture
Increase the moisture content of materials, in addition to adhesion and prone to clogging pipes, but also affect the device transport capacity. For example, when the gas

conveying the water content of 0-3% of clay, each increase of 1% moisture, transport capacity is reduced by 15%. Generally use pneumatic conveying of material moisture content

of 6% to

Under high pressure to send a maximum moisture content of the material does not exceed 4%. Typically, the material from the vacuum blower can be compared using a slightly higher

moisture content of pressure-feeding. Water content, the material is difficult to produce static electricity, sticking down.
4 hygroscopicity
It is easy to agglomerate material is hygroscopic, it will affect the amount of transmission capacity and residual materials. Pneumatic conveying the greatest difficulty lies in

ashes, ashes contact with the atmosphere 1-2 hours hygroscopic sticky.
5 of viscous
The viscous material will directly affect the accumulation of material in the pipeline, thus affecting the normal transport. Sometimes sticky particles can cause serious

problems arise pipe blockage.
6 Wear
The physical characteristics of the material wear of the pipeline has a direct relationship between the amount of the wear degree of the material and conveying stone learning

function of speed.
7 compressibility
The compressibility of the material implies a material density of the gas and the material deposit and the relationship between permeability, which directly affects the material

movement in the pipeline, especially at high feed rate and under conditions of low-speed transport.