Heaters refractory dry out procedure

[Abu noor]

I need guidelines for heaters refractory dry out. How much temperature should be maximum and minimum? which media we can use inside the coil (steam, nitrogen, oil….etc)or without media?

[Nasir Hussain]

Refractory dry out is the process to remove moisture from the refractory by applying controlled heat. The dry-out procedure and maximum temperature limit are provided by the vendor. But general
NOTE:
Heating rate, heating steps, and maximum heating temperature are provided by the relevant vendor. So follow his instructions for the safe and successfully dry out.
1. Temperature is usually monitored at the exit of the radiation section (heater arch). Initially pilot burners are light up and further burners are light up as per heating rate.
2. Normal heating rate is 20~25 C/hr ( as per vendor guidelines).
3. Heating is carried out in steps, Step1: Heat up to ~125 C and hold for 24 hours, Step2: heat up to 290~325 C and then hold for 24 hours. Step3: Further heat up to ~550 C and hold for 24 hours.
4.After completion of heating steps, the refractory is cooled down at the rate of ~40~55 C/hr.

A typical refractor dries out trend is attached.

Media Inside the tubes
For hydrotreating or hydrocracking units, normally Nitrogen is being used because reactor dry out is also completed.

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