ARM Cement Ltd is one of East Africa's leading cement manufacturers. The Kaloleni plant near Mombasa has chosen HGH's KILNSCAN system for monitoring rotary kiln mantle temperature. Featuring a 140˚ angle of view (FoV), the KILNSCAN Mantle Scanner system is adapted to installation requirements to accommodate a distance of only 10 meters between the rotary kiln and the mantle scanner. Thanks to its unrivaled 140˚ viewing angle in cases where the distance between the rotary kiln and the mantle scanner is very short and/or the length of the rotary kiln is very long, it eliminates the need for more than one Mantle Scanner and therefore the need for additional infrastructure (tower, etc.).
ARM's Contribution to Kenya's Economic Goals
ARM Cement Ltd is Kenya's second largest cement producer and has a capacity of 1 million tonnes/year in the country. It has two facilities at Athi River, a few kilometers outside Nairobi, and at Kaloleni, north of Mombasa. By completing the "Vision 2030" development program, Kenya aims to become the center of regional trade and significant economic growth is predicted in this region. This development process includes local infrastructure improvements such as the construction of new terminals at the Port of Mombasa, which will double the port's container handling capacity by 2020.
ARM plans to increase its annual production capacity to approximately 5 million tons in the next six years by building new facilities in Tanzania and increasing capacity in Rwanda in order to meet the increasing demand in the region. The company produces Portland Pozzolana Cement and Ordinary Portland Cement and is committed to offering the product with the best quality-price ratio. ARM is one of the few cement companies in the region to produce its own high-quality clinker, providing greater control over production costs, process efficiency and product quality.
Kaloleni Cement Plant Installation
ARM needed complete process control to accurately and reliably monitor the 45-meter rotary kiln at the Kaloleni facility, ensure no interruptions in production due to hot spots, and control the combustion process. Although the oven is relatively small, this project was difficult because the scanner had to be installed very close to the rotary kiln – less than 10 meters away. To measure the temperature at the rotary kiln mantle surface with a single sensor, a system with a scanning angle greater than 130˚ had to be installed.
HGH Infrared Systems' KILNSCAN thermal scanner with 140˚ field of view offers a simple and effective solution for such challenging configurations. In such close proximity to the rotary kiln, two conventional scanners with a 90˚ field of view were required to provide full thermal monitoring from the preheating tower to the cooler inlet. Of course, the use of two systems means additional costs and installation complexity. In cases where the Kaloleni furnace had a fairly large slope with the ground, the scanner had to be positioned accordingly. This ensures that the line of sight is parallel to the shell's axis of rotation. The simple operation of a single system becomes more complex when multiple sensors need to be aligned; The scanners must be aligned together so that the measurement line is unique and intact. Additionally, image straightening and compositing must also be performed for accurate scale temperature representation.
With a 140˚ wide viewing angle, KILNSCAN perfectly meets the need for a cost-effective thermal monitoring system adapted to the limited space between the scanner tower and the rotary kiln.
Flexibility in Complex Cement Plant Configurations
Such complex projects are not uncommon. KILNSCAN has already proven its flexibility to adapt to more challenging configurations. Below are two such examples:
Lafarge, UK: In the UK, HGH supplied Lafarge with a system to monitor a 110 meter long furnace. This oven operates inside a building. Again, the thermal scanners had to be positioned very close to the rotary kiln. In this configuration, HGH proposed a system based on three KILNSCANs, each with a 140˚ field of view, to be able to monitor the entire furnace. In this particular case, in addition to geometric constraints, the installed equipment also had to adapt to high ambient temperatures of up to 50 ˚C.
Tasek, Malaysia: The installation for Tasek in Malaysia is also an example of a complex configuration. In addition to the tower housing the Mantle Scanner being close to the rotary kiln, the scanner line of sight is blocked by several poles and pillars. In order to display a thermal map without shadow areas, a special configuration with three KILNSCAN scanners had to be designed. In this particular case, the wide-angle scanners are aligned to overlap in the line of sight. The thermal image is reconstructed by combining data from three scanners, eliminating on-screen shadows for rotary kiln mantle temperature monitoring.
Cement Plants Complex Configuration: Wide Angle on Specified Features
Being able to scan the entire rotary kiln is not the only challenge. More than 1000 KILNSCANs are in use worldwide and in all projects where HGH is involved, the main concern is to obtain reliable indicators of refractory bricks and kiln shell condition and clinker quality. This was also the case for ARM Cement. Oven shell maintenance is an important parameter that affects production costs. Considering that an unplanned stoppage of the rotary kiln can cause several days of production loss, it is very important to choose a reliable and high-performance thermal scanner.
The first important parameter is spatial resolution, which is the smallest hotspot size that the scanner can detect. Delayed warning may occur when using low resolution scanners because the maximum temperature values are averaged in the thermal map created by such scanners. As a result, alarm thresholds do not provide early enough warning to prevent oven shell deterioration. KILNSCAN offers imaging at single brick resolution, enabling rapid and effective intervention to rebuild the lining (such as cooling the shell locally or changing burner settings) and preventing unplanned kiln shutdown. When a few bricks are missing, such actions become useless, resulting in inevitable unplanned kiln stoppage, costly repairs and reduced life of the brick lining due to thermal shock. In addition to high spatial resolution, KILNSCAN has a thermal sensitivity of better than 0.05 ˚C. This means that the slightest temperature rise will be detected immediately and the configurable alarm system will alert the control room of any emergency. This way, maintenance operators can intervene quickly before irreversible damage occurs.
In the three case studies detailed above, the scanners installed have a 140˚ field of view, which is unique on the market and very useful to adapt to any configuration. Of course, this wide-angle scanning is achieved without sacrificing high spatial resolution and thermal sensitivity.
KILNSCAN also offers another unique advanced function – Thermal Warp calculation. This involves calculating the kiln deterioration of the shell resulting from temperature changes and provides information about the cyclic overloads and associated stresses experienced by the shell, tires and roller stations. This type of thermal degradation in the furnace provides information about the process within the furnace: coatings, unburned material push, flame adjustment, etc.
CONCLUSION
ARM Cement Ltd expressed their satisfaction following the commissioning of their new thermal monitoring system. With the widest field of view on the market (140˚), KILNSCAN displays the full thermal map of the shell in real time, with high accuracy and reliable output. Today, KILNSCAN is a leader in the mantle scanner industry in terms of spatial resolution and thermal sensitivity. Advanced and unique software features provide unmatched monitoring and enable facilities to achieve a good return on their investment for years to come.
