# Thread: What is the air velocity required to convey fine particle dextrose.

1. neufeneufeld Guest

## What is the air velocity required to convey fine particle dextrose.

I am new to pneumatic conveying, and have built an excel macro that calculates the air velocity for every section of the pipe based on its compressibility and the pressure drop through the pipe. I have also used a Rizk calculation to estimate the conveying velocity required to convey the dextrose, but even when multiplying the saltation velocity by 1.5, my calculations seem to underestimate the velocity required to handle dextrose. If anyone has any experience in handling dextrose that would be greatly appreciated.

Right now the rate is
242 lbs/min
5 Inch diameter pipe
Horizontal length 80 ft
Vertical length 40 ft
Dextrose particle size 45-150 microns
Air only length 180 ft
13 air bends
4 inch diameter pipe air only length

2. Dear neufeneufeld,

You used the Rizk equation to calculate the saltation velocity of dextrose.

Rizk equation:

SLR = 1/(10^(1.44*d+1.96) * {Vs/sqrt(gD)}^(1.1*d+2.5)

Here, a direct relationship is assumed between SLR and Vs.

d = particle size in mm = 0.1 mm
g = 9.81 m/sec2
D = pipe diameter in m = 0.128 m
Vs = calculated saltation velocity in m/sec

If SLR=0 then Vs=0
If SLR=0.5 then Vs=2
If SLR=1 then Vs=7
If SLR=5 then Vs=13
If SLR=10 then Vs=17
If SLR=20 then Vs=23
If SLR=30 then Vs=26
If SLR=40 then Vs=30
If SLR=50 then Vs=32

To use this formula for the calculation of the saltation velocity, you must know the pipe diameter, the particle diameter and the Solid Loading Ratio

Obviously, you know the SLR (mass flow dextrose / mass flow air)
Knowing the rate (242 lbs/min), you must also know the air mass flow.

The average particle size of the dextrose is approx. 100 micron.
The particle density is 1540 kg/m3
Resulting in a suspension velocity of approx. 1.8 m/sec
The air velocity at approx. atmospheric conditions is then estimated at approx. 8-10 m/sec.

Back to the Rizk equation.
It is hard to understand that, when the SLR changes from 50 to 20, the saltation velocity of the product drops from 32 m/sec to 23 m/sec.

If you give the used compressor and the conveying pressure of your installation, a calculation can be executed.

have a nice day

3. Registered User
Join Date
May 15
Posts
4

## What is Alumina bubble brick?

With the development of science and technology, new hollow materials made of glass, ceramic and carbon are widely used in the many science industries.
Refractory products made of hollow spheres have good high temperature resistance, good insulation properties, good thermal shock resistance and high strength. Since those materials have low bulk density and low thermal capacity, they can improve the thermal efficiency of high temperature furnaces, shorten the production cycle and significantly reduce the weight of the furnace. It can be directly used in the linings of high temperature furnaces.

Alumina bubble bricks can be used at 1800℃ for a long time. At high temperature, they have good chemical stability and corrosion resistance. But they can keep stable in a hydrogen atmosphere.