In 2000 L. V. Technology introduced a new cyclone design (LVC), which has been successfully installed in more than 15 installations. The LVC cyclone is a high efficiency cyclone, which reduces the pressure loss considerably and thereby a reduction in fan power consumption is obtained. This reduction in pressure drop can be used to increase kiln capacity, when installed in preheaters.
Today L. V. Technology Public Company Limited performs a wide range of cement plant modifications and until now more than 500 orders have been placed for conversions. The modifications include ball mills and vertical mills as well as preheater, kiln and cooler upgrades.
The key words in this type of upgrades are pressure drop reducing modifications and obtaining proper combustion conditions in the calciner. The idea is to reuse the existing ID fan, where the reduced pressure drop over the preheater opens up for increased flow i.e. increased clinker production.
LV – Cyclone
LV Cyclone is different from other cyclone designs by the fact that:
- The inlet has been pulled as far away as possible from the cyclone portion.
- The conventional cylindrical portion of the cyclone has been substituted by a reverse conical portion.
- The top roof spirals downwards.
- The inner tube is extended.
Until now L. V. Technology has supplied more than 80 cyclones for de dusting of mills and classifiers, and recently L. V. Technology has commissioned kiln upgrades with the cyclones as top cyclones.
For preheater modifications this cyclone design can be used for 1st and 2nd stages in a 5 stage preheater and 1st stage in a 4 stage preheater. Installed as a top stage cyclone in a 5 stage preheater it can (recommended) be installed without refractory to reduce tower load.
The fundamental issues for obtaining proper combustion of the calciner fuel are fuel fineness and retention time. Mixing of fuel and combustion air is an essential part of the process which must take place to facilitate the combustion.
In case of a new calciner (new preheater), the retention time can be selected properly. In case of upgrading projects, the calciner volume can sometimes be increased to give improved retention time.
However mixing of the fuel and the combustion air is a most important factor.
Based on this fact L. V. Technology has developed a calciner mixing chamber, which can be installed on conventional In Line Calciner type of calciners.
Two different LV calciner mixing chamber designs had been tested via computer simulations of the gas flows (kiln exhaust gas and tertiary air), to evaluate the mixing process taking place.
The main differences between LV calciner mixing chamber design and other calciner manufacturers design are:
- The tertiary air duct enters the calciner without enlargement of the flow area i.e. with the full velocity.
- The tertiary air enters the mixing chamber fully tangential.
The effect of the LV designed calciner mixing chamber produces a better mixing of the kiln exhaust gas and the tertiary air,resulting in an improved degree of burn out of the calciner fuel within the same calciner retention time (volume).
This is an important effect to obtain – especially in the kiln upgrade projects, where the calciner volume cannot be increased as required.
NOx – Reduction
The concept of the LV calciner design (the mixing chamber) can be used in connection with NOx reduction projects also.
By introducing a reduction zone between the kiln and the calciner, it is possible to obtain a substantial reduction of NOx without increasing the kiln system operation cost.
The principle of the reduction is, that fuel which is normally fed into the bottom of the calciner above the entry of the teriary air,now is introduced between the kiln and the entry of the tertiary air. In this way a reducing zone is created which will allow the reduction of the Nox created in the kiln.
The temperature in the reduction zone is controlled by installing a material dividing gate, which can divide the material stream from the second lowest cyclone stage to the tertiary air duct and to the riser.
By introducing the NOx reduction zone a considerable level of CO is created, and it is therefore of outmost importance, that an optimal mixing is performed afterwards to secure a satisfactory degree of combustion of the fuel in the calciner.