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 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 . 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) CaCO3 + Q (heat)  CaO + CO2 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. Very much simplified

VORTEX FINDERS (DIP TUBES, IMMERSION TUBES) Cyclone with vortex finder - Steel alloy or ceramic 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 . 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 a low 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 speed of the attack on the steel and ceramic vortex finders varies from kiln to kiln and cyclone to cyclone

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 !!! The speed of the attack on the steel and ceramic vortex finders varies from kiln to kiln and cyclone to cyclone

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 Build-up sticks less easily to the ceramic vortex finder

VORTEX FINDERS (DIP TUBES, IMMERSION TUBES) XX Group cement plant in Switzerland Photo taken after 19 months. Damaged below roof 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 Shock – forunately this is not so often. Usually this (chemical) process occurs slowly. Build-up sticks less easily to the CVF.

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 28 vortex finders installed in Europe and Africa. Most of the customers will leave them there until they fall down. Very few block the cyclone and in 90% of cases the cyclone roof is fully protected.

CERAMIC VORTEX FINDERS The development continues …………………

CERAMIC VORTEX FINDERS INSTALLATIONS IN NEW INDUSTRIES : Power plants – CFB boilers Alumina industry – due to heavy abrasion