VORTEX FINDERS (DIP TUBES, IMMERSION TUBES)

VORTEX FINDERS (DIP TUBES, IMMERSION TUBES)

VORTEX FINDERS (DIP TUBES, IMMERSION TUBES)

Cyclone with no vortex finder - Steel alloy or ceramic

Plan view

Section of cyclone

A cyclone is a device to separate the dust from the air. It does this very effectively. However a small portion of the air/dust mix escapes into the exit pipe

VORTEX FINDERS (DIP TUBES, IMMERSION TUBES)

THE NORMAL PROCESS IN A CEMENT CYCLONE (VERY SIMPLIFIED)

Cyclone with no vortex finder - Steel or ceramic

For the dust which escapes :

CaO + CO2 CaCO3 + Q (heat)

Energy lost +re-circulation and concentration of impurities. This leads to build-up.

CaCO3 + Q (heat) CaO + CO2

VORTEX FINDERS (DIP TUBES, IMMERSION TUBES)

Cyclone with vortex finder - Steel alloy or ceramic

The portion of the air/dust mix which escapes into the exit pipe is reduced

Which type to choose :

Upper cyclones (where the temperatures are below 700oC)

There are usually no problems here and you can easily use alow cost steel alloy tube : There are many suppliers

Lower cyclones (where the temperatures are above 700oC)

Steel alloy or ceramic vortex finders– We need to evaluate the advantages and disadvantages

THE EFFECTS OF ALTERNATIVE FUELS

Aggressive chemicals

– Certain chemicals attack the steel alloy vortex finder (chlorine, sulphur, CO)

– Other chemicals attack the ceramic vortex finder (alkalies).

Fluctuating temperatures (due to non-homogenous fuels and variable water content)

– If the normal temperature in the cyclone is 850 - 900oC and severe fluctuations occur then there is a big risk of overheating the steel alloy vortex finder.

– Too many fluctuating temperatures can cause failure due to thermal shock of the ceramic vortex finder elements

THE EFFECTS OF ALTERNATIVE FUELS

Aggressive chemicals– Certain chemicals can attack the steel alloy vortex finder (chlorine, sulphur, CO)– Other chemicals can attack the ceramic vortex finder (alkalies).

Fluctuating temperatures (due to non-homogenous fuels and variable water content)– If the normal temperature in the cyclone is 850oC and severe fluctuations occur then there is a risk of overheating the steel alloy vortex finder.– Too many fluctuating temperatures can cause failure due to thermal shock of the CVF

Under these conditions it is very difficult to estimate the lifetime of the vortex finder (steel alloy or ceramic)

The answer : Do a trial !!!

VORTEX FINDERS (DIP TUBES, IMMERSION TUBES)

THE STEEL ALLOY VORTEX FINDER

If the customer is satisfied with the lifetime (2 years or more) and there are no other problems then he will probably continue with the steel vortex finder.

If the plant engineers are dissatisfied there can be the following reasons :

• Lifetime : corrosion or heat can cause short lifetime• Build-up : causes the pressure drop to increase• Buckling : becomes so distorted the pressure drop increases- reduced efficiency• Abrasion : In some cases abrasion makes holes in the steel plates• Thickness : need to measure the steel thickness every shutdown• Sometimes difficult and time-consuming to remove and install (sometimes 3 – 7 days)• Often blocks the cyclone when pieces fall• Fallen steel segments damage the kiln lining, the cooler or the crusher

VORTEX FINDERS (DIP TUBES, IMMERSION TUBES)

XX Groupcement plant inSwitzerland

Photo taken after 19 months.

Damaged belowroof level after 27 months.

Re-installation to be January 2012

THE CERAMIC VORTEX FINDER

If the customer is satisfied with the lifetime (2 years or more) and there are no other problems then he will probably continue with the ceramic vortex finder.

If the plant engineers are dissatisfied there can be the following reasons :

• lifetime too short : due to thermal shock• lifetime too short : due to chemical deterioration of the precast elements • Occasionally blocks the cyclone when pieces fall

CERAMIC VORTEX FINDERS

About 3 years ago we did a full analysis of the ceramic vortex finder elements.

The analysis recommended that we stop using Silicon carbide (SiC) in the precast elements

The analysis recommended that we stop using steel alloy fibres in the precast elements

We did this and the lifetimes have definitely improved

CERAMIC VORTEX FINDERS

The development continues …………………

CERAMIC VORTEX FINDERS

INSTALLATIONS IN NEW INDUSTRIES :

Power plants – CFB boilers Alumina industry – due to heavy abrasion