Refractory dry-out is the process to eliminate moisture from refractory materials. The refractory dry-out procedure is necessary after the installation of the refractory but before the operations start. This will help you from damage to the linings of the refractory. It needs careful planning and consideration.
What is Actually The Refractory Dryout Process?
This process is also known as the bake-out process. The refractory dry-out procedure is the process of removing chemical water and mechanical water from the refractory lining. Mechanical water is present in the refractory materials during the mixing process. While chemical water is the existing water content at the time of refractory manufacturing.
The refractory dry-out process evaporates the mechanical water and the chemical water is removed by the upper hold points that give them a very strong bond and maximum strength.
Why Refractory dry out is necessary for Boilers?
The refractory dry-out procedure is important to ensure proper drying and curing of the refractory in the boiler. The linings of the boiler are made from refractory materials. They should contain a hard surface with no moisture.
However, consistent manufacturing processes and usage of a furnace will lead to damage to the refractory lining and the possibility of moisture residue is there in the boiler. To remove this type of chemical or mechanical moisture, a dry-out process is necessary.
Pre-requisites For Boiler Refractory Dry Out Process
- Make sure that all the pre-commissioning checks are complete.
- Ensure the availability of tile according to the need of the supplier, and an adequate amount of wooden logs to the estimated sizes.
- Additionally, you should check the availability of the draft system and instrument that is necessary for boiler firing.
- Make your staff and operators ready for Refractory Dry Out Procedure.
- Check all the vent lines are open on the boiler drum and top superheater header throughout the process.
Boiler Refractory Dry Out Procedure
- First of all, you must cover all air and coal nozzles using bed material. This first step is necessary to avoid damage to nozzles while throwing wood logs into the furnace. Wood logs size must be in the range between 2 to 3”.Select the wood logs with optimum moisture because too wet or too dry woods are not suitable for the dry-out process.
- Secondly, you must confirm that the dry-out process is undergoing the natural draft. Fans are not necessary. Additionally, check all the suction and discharge chambers of the fan are kept open. After that, put the wood on the bed material. Spray the small amount of diesel on it. Now, it is time to fire the woods.
- Thirdly, check the temperature at the initial level. For the first few hours, the temperature should be slow at the rate of 25 degrees celsius. The next step will be raising the temperature of the boiler outlet flue gas up to 100 degrees Celsius for 8 to 10 hours. This temperature is necessary for soaking refractory inside the boiler. Original Equipment Manufacturer(OEM) gives the guidelines for this process so follow the same guidelines without any negligence.
- For the next step, raise the temperature to 250 degrees celsius for the next 6 to 8 hours. This step is necessary to soak the refractory inside the boiler. Finally, raise the boiler outlet flue gas temperature to 350 degrees celsius and hold for the next 8 to 10 hours for soaking the refractory inside the boiler.
- In the end, Stop the firing and allow the boiler to cool down naturally. After cooling down, inspect the refractory. Check whether the refractory has any damage or cracks or not. If you find any minor damages or cracks, then the boiler refractory repair procedure is done with the same quality refractory material.
Conclusion
The boiler refractory dry-out procedure is important as it properly dries the refractory and eliminates the moisture completely. It is necessary to note that refractory undergoes chemical changes during the initial level of heating. You have to make sure during this entire process that there must be free airflow over the refractory. Refractory dry-out will ensure the complete removal of moisture.
