When it comes to cleaning and emptying chemical recovery boilers, Valmet has the services required to do it swiftly and safely. If the recovery boiler cleaning process starts too quickly, the water being used in the washing process may cause an explosion when it comes into contact with the molten smelt. In the past, this potential threat has been avoided by waiting 15-35 hours to make sure the smelt bed is frozen and safe to clean. To speed up and improve this procedure, Valmet has developed the Smelt-X and Wash-X processes which change the way recovery boiler cleaning is executed.
The Smelt-X process has been specifically designed to alleviate the recovery boiler cleaning process. The bottom section of the recovery boiler furnace is heated during load reduction so that the whole smelt bed becomes molten, and the smelt is extracted from the floor to the dissolving tank using air-operated ejectors. Our custom designed ejectors for each furnace arrangement are made to extend from spouts to lowest point in floor for max extraction. This custom design is unique in the industry, and can’t be matched by our competitors. Our typical extraction time is 1-3 hours and smelt does not touch spouts during the extraction process. The Smelt-X process also allows for chemicals in the smelt bed to be recovered and the amount of strongly alkaline waste water is minimized resulting in savings in both make-up and neutralization chemicals. Due to these features, Smelt-X can be carried out safely in the middle of the operation cycle as well, and the operation can continue with the same spouts without any additional risk of spout failures during the rest of the cycle.
Other benefits include:
- faster cooling – boiler bank and superheater washing can begin sooner
- recovery of chemicals in the smelt bed
- minimisation of wash water volume and alkalinity
- savings in makeup chemicals for black liquor
- savings in neutralization chemicals in waste water plant
- faster floor cleaning for inspection and repairs
- safer floor cleaning – reduced need for mechanical cleaning and/or high pressure washing
- shorter mill shutdown – increase in pulp production
Valmet has also developed a washing service for recovery boilers called Wash-X in which the floor is washed simultaneously with the rest of the boiler using low pressure water sprays and mixing devices installed on the furnace floor. Once the super heaters are clean, the mixing devices are removed and floor is emptied of wash water using smelt ejectors.
The typical Wash-X arrangement for mixing devices and wash water sprays:
- 1 or 2 mixing devices in each spout (operated with pressurized air)
- 8 – 18 primary air port sp rays connected to feedwater or warm water system (depending on floor size)
- black liquor sprays (at least) in front wall (not shown here) spraying warm wash water
The Smelt-X and Wash-X services will save a huge amount of time for companies who need their recovery boiler systems cleaned. Our process will do no damage to your boiler and have you back operating at full strength much faster than any other process on the market. Please contact Mike Ward to arrange an in person meeting to discuss how our Smelt-X and Wash-X services can work for you.