Cement, Energy and Environment

Actions Burner Nozzle Inspection and Maintenance HAG Coating Dislodgement and Temperature Stabilization Frequent occurrences of ash and unburned coal at the HAG (Hot Air Generator) discharge area indicated inefficiencies in coal combustion. A thorough observation revealed that draft variations were higher than acceptable limits. While the HAG zone typically operates under negative draft, occasional positive draft shifts led to the dislodgement of coating fragments, disrupting the combustion process. Internal inspections also revealed ash ring formation, which had closed off 50% of the HAG zone. The Hot Air Generator (HAG) experienced challenges in maintaining consistent operating temperatures due to variations in coal mill output and the dislodgement of internal coatings. These issues were traced back to coal mill outlet temperatures, where volatile matter (VM) and moisture content were not being controlled within optimal limits. The fine coal moisture content, along with residue measurements at 90 microns and 212 microns, was found to be inconsistent, contributing to fluctuating temperatures. To address this, the plant introduced rigorous monitoring of volatile matter and moisture levels, ensuring that VM stayed below 2.75%. A systematic reduction of false air entry into the system was also implemented, with teams promptly arresting any leakages as they were detected. Additionally, PID (Proportional-Integral-Derivative) control loops were applied to regulate HAG temperatures more precisely. This optimization significantly reduced temperature variability, contributing to overall process stability and energy efficiency improvements. Reference - Figure 4.1 & 4.2 A detailed inspection of the coal burner nozzles uncovered blockages and wear issues. Maintenance teams undertook cleaning and refurbishment of the nozzles, removing the jams and performing necessary wear build-up repairs. The nozzle cleaning drastically improved the uniformity of coal combustion, ensuring that heat transfer was more efficient. This, in turn, stabilized the draft conditions and reduced instances of coating dislodgement, which had previously caused temperature fluctuations in the burning zone. Reference - Figure 3.1 & 3.2 Figure 2.2 Figure 3.1 Figure 3.2 18