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How to Spot Damage in Modern Lime Kilns Using Thermal Surveys

The mineral lime is important in many areas of the economy, including construction, civil engineering, water treatment and steel production. It is produced by heating limestone to a temperature above 900 °C .

Vertical twin shaft parallel flow regenerative lime kilns are energy efficient and offer high throughput so they are the preferred method of production in most regions. However, the process is arduous, and damage to the interior refractory structures can occur without obvious indications. A thermal survey using an infrared imager can help guide operational decisions by detecting refractory damage at an early stage.

Safely inserted via access ports during kiln switch over, a high-definition borescope thermal imager can provide detailed data on the state of refractories and reveal signs of wear and hotspots. This information can then be used to make the decision to continue operations or plan for repairs.

Figure 1. shows two images from Port 3 of the kiln, the image on the left is a monochrome palette that can reveal fine details of refractories with hot spots showing white. The image on the right has a rainbow palette applied, with blue being the cold end of the range. The images show some build-up of deposits, but no damage to the structure is evident.

Christopher Leonard - Lime Kiln Blog

Figure 1. Monochrome palette (left), rainbow palette (right) 

Figure 2. shows two images from Port 7 of the kiln. Displaced refractory arch bricks are clearly evident. The image to the left has a sunspot isotherm palette applied to highlight the areas above a specified level. The image on the right has a rainbow palette applied which clearly shows the temperature ‘leakage’ from the inside of the kiln due to the damaged refractories. 

The thermal survey gave the operator enough data and confidence to continue operations while planning for a repair maintaining critical plant uptime.  

A thermal survey using a borescope thermal imager can provide a powerful tool to help you gain essential insight into thermal processes and keep operations running smoothly. 

Christopher Leonard - Lime Kiln Blog

Figure 2. Sunspot isotherm palette (left) and rainbow palette (right)
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