Analysis of the statement on mill outlet temperature:

Points in favor of higher mill outlet temperature (up to 100 – VM):

• Improved combustion: Higher temperature leads to better evaporation of moisture and volatile matter in the coal,resulting in more efficient combustion and less unburned carbon in the fly ash.
• Reduced mill rejects and current: Lower temperatures can cause larger particles, leading to higher rejects and increased power consumption.
• Decreased clinkering: Higher temperature melts ash components more effectively, reducing clinker formation and associated problems.
• Optimized air ratio: Maintaining the proper proportion of } primary air (PA) and secondary air (SA) is crucial for combustion efficiency. Higher temperature allows for adjustments to air ratio without risking fire in bowl mills.

Risks and precautions for high mill outlet temperature:

• Fire risk: While the risk of fire is lower in bowl mills compared to ball mills, exceeding the limit (100 – VM) can still lead to ignition. Careful monitoring and control of temperature are essential.
• Increased NOx emissions: Higher temperatures can contribute to higher NOx formation, which requires consideration for environmental regulations.
• APH performance: As mentioned, cold air in the mill can negatively impact APH performance. Ensure adequate preheater temperature to avoid this issue.
• ESP temperature and SPM: High inlet ESP temperature can increase particulate matter (SPM) emissions. Monitor ESP temperature and adjust air flows if necessary.

Overall recommendation:

Running the mill at a higher outlet temperature, up to the recommended limit (100 – VM), can offer several benefits in terms of combustion efficiency, mill performance, and clinker reduction. However, careful monitoring and control are crucial to mitigate fire risk, NOx emissions, and potential impacts on APH and ESP performance. It’s essential to maintain all equipment at their rated parameters to ensure optimal techno-environmental efficiency and minimize losses.

Additional thoughts:

• Consider implementing online monitoring and control systems for mill parameters to maintain optimal operating conditions.
• Regular maintenance and optimization of the milling system and related equipment can further improve performance and minimize risks.
• Consult with plant engineers and specialists to determine the most suitable operating parameters for your specific context and equipment.

I hope this analysis helps you make informed decisions regarding mill outlet temperature and operation. Please let me know if you have any further questions.