Infrared linescanner improves cement kiln performance.

A linescanner from infrared temperature measurement specialist Land Instruments International has improved the monitoring of kiln shell temperatures at a cement factory in Cameroon.

Mounted in a robust, air purged and cooled stainless steel enclosure at a distance of 27 metres from the kiln, the Landscan LSP 62 infrared linescanner continuously scans almost the entire 55-metre length, relaying a thermal map to the control room so that staff can adjust process variables accordingly.  It also gives immediate warning of worn or missing refractories in the kiln lining.

Monitoring was previously limited to manual checks using a hand-held Land Compac 3 infrared thermometer.  Only 20 metres of the kiln shell was accessible for checking in this way, but it took a full hour to take the readings at 1-metre intervals - which were then entered onto a PC for evaluation.

With the kiln operating at up to 500 degrees C and an ambient temperature of around 45 degrees C, collecting readings was an extremely difficult task for the operating and maintenance engineers.

The factory, which is operated by the Lafarge subsidiary CIMENCAM, is in Figuil, close to the border with Chad and 800 km from Yaounde, the Cameroon capital.  The semi-desert location was chosen because of the local availability of limestone and other raw materials and the proximity of the border with Chad, to which much of the 275 tonnes produced each day is exported.

Three metres in diameter and 9.10 metres in circumference, the kiln makes
4.5 revolutions per minute at a speed of 750 mm per second.  It is scanned through an angle of 80 degrees with a field of view of 100:1 (95% energy), and each revolution triggers an encoder that saves the completed scan and displays it in the control room alongside the live data from the next.

The Landscan LSP 62 is one of Land's LSP6 series of linescanners which, although they have many other industrial applications, were developed with monitoring the shell temperature of rotary kilns very much in mind.

Damage to the kiln shell and its lining due to excessively high temperatures and thermal shock results in high repair costs and irrecoverable loss of production.

The refractory-lined lower end of the kiln can be subjected to temperatures of up to 2,000 degrees C, not to mention the effects of abrasion from the product itself.  If the refractory is damaged, localised heating of the kiln shell may occur, creating a hot spot that, unchecked, will seriously damage and even warp the kiln.

But much of this can be avoided if - as now in Cameroon - the plant operator has a detailed knowledge of the degree to which the lining is worn (and therefore the likelihood of premature failure), along with the presence and magnitude of clinker-ring build-up.

Conversely, monitoring the condition of the kiln refractories and stopping production for relining or repair only when necessary may lead to an extended campaign life with associated cost savings.

An infrared linescanner contains a high precision thermometer module, a rotating mirror and associated electronics.  Linescanning heads are normally used to monitor the shell temperature of a cement kiln, scanning a section from a distance of around 30 to 40 metres.  Up to 1,000 measurements can be taken with a single scan - the equivalent of having the same number of conventional fixed infrared thermometers mounted in a line down the length of the kiln.

Output signals are transmitted to a PC containing data acquisition electronics and software, which displays a coloured thermal map representing the distribution of temperatures along the kiln shell, making the location of hot or cold spots very evident.  Cooling fans can then be positioned accordingly.

Central to the LSP6 concept is the scanner head, which can generate high speed temperature profiles at up to 100Hz in the measurement range 20 to 600°C with an accuracy of +/-3°C.  It also has a wide scan angle of 80° and a field of view of 100:1 (95% energy) maintained at all target distances.

Of the three versions offered, the LSP62 is the most appropriate for kiln applications, covering temperatures from 100 to 600 degrees C.  It is sufficiently compact to be installed where space is limited, and has a sapphire protection window for added durability.  A built-in Class 2 laser to define the scan plane and sighting angle is supplied as part of the package, making the initial set up quick and simple.

A complete range of mounting assemblies, water cooling and air purging options are also available - and the scanner head can be de-mounted for maintenance and put back in position without the need for realignment.

Completing the system is the new 19in rack mounted Landscan Control signal processor, which generates serial and Ethernet temperature data outputs that can interface to local process control or the new Landscan Configuration Professional and Landscan WCA software.

For further information please contact:

Tom McDougall
Land Instruments International
Infrared Temperature Measurement
Dronfield S18 1DJ, England
Tel: (01246) 417691
Fax: (01246) 410585
Email: infrared.sales@landinst.com
Internet: www.landinst.com