Any boiler burning anything other than natural gas will produce build up and require boiler deslagging. Oil, coal, biomass, and waste fuels all create ash, which accumulates on the outside of the boiler as slag.
Boiler deslagging is a method of removing these pollutants, which typically result in the reduction of harmful emissions, mitigating the likelihood of catastrophic damages, and bolstering boiler efficiency.
Today, there are several popular methods for keeping your boilers clean. These boiler cleaning methods can be separated into two general categories: offline boiler deslagging and and online cleaning. While offline boiler deslagging requires a scheduled shutdown, online cleaning can be completed while the facility is still operational. Continue reading to learn more about the different techniques of boiler deslagging.
What Is Boiler Slag?
Slag is the formation of partially fused, molten, or re-solidified deposits that are exposed to radiant heat. Slag forms on the walls of the furnace as well as on other surfaces. Over time, a base deposit of slag may formulate on the tubes of the boiler. This base deposit may start by the gradual accumulation of particles with extremely low melting-point constituents or from fine ash.
Once this base deposit thickens, the temperature on the outside face rises above the temperature of the tube surface. Eventually, the melting point of the ash constituents is exceeded, and the deposit turns into molten. Over time this process becomes self-accelerating with the impinging ash particles being trapped by the molten slag.
Online Boiler Deslagging Techniques
Online boiler deslagging is designed to function intermittently or continuously while the plant is still in use. These techniques use equipment installed onsite and becomes an important part of the system.
Industries tasked with handling and storing bulk particulate and granular materials have been increasingly using acoustic cleaning. With the acoustic cleaning setup, built-in speakers or horns create waves of sound that dislodge particulate. In boiler systems, these waves are used to loosen up dry ash buildup.
Unlike a water jet or a blower, this type of boiler deslagging doesn't need to be aimed and directed. Instead, acoustic deslagging cleans the entire volume. While acoustic cleaning may not have a major effect on molten ash buildup in boilers, it's highly effective at dislodging dry deposits.
Soot blowers are designed to shoot jets of concentrated and compressed water, steam, or air at slag. Soot blowers will erode and eliminate deposits. Due to the fact soot blowers have been in existence since the 1930s, the majority of boilers and plants have some variation of a blower system.
Although the effectiveness varies, air-driven or steam-driven soot blowers are used to remove slag deposits and ash from tube surfaces externally. If the areas are swept too clean by soot blowing, it can cause corrosion and localized erosion in specific areas.
This common problem can be overcome through the installation of shields on the tubes adjacent to sootblowers. Even then, the slag formation may not be able to be reached through conventional cleaning techniques.
Offline Boiler Deslagging Methods
As a more thorough method of boiler deslagging, offline cleaning typically happens during periods of planned outages. While the most common offline techniques for deslagging include picks and jackhammers, there are several other more cutting edge techniques used today.
Water Lance Boiler Deslagging
With a water lance system, a high-pressure jet of water is streamed at boiler buildup. These highly focused jets of water will strip off the toughest and most stubborn slag deposits. Essentially, water lance deslagging is similar to an amped up industrial-grade pressure washer. The primary drawback of water lance boiler deslagging is it may induce moisture into the boiler.
Contact Applied Technologies of New York
Choosing whether to use online boiler deslagging or offline boiler deslagging is a relatively important and big decision. While online methods may seem like the best choice, they can affect operation and be a significant capital investment.
For instance, a water-based soot blower may cause steam levels in the boiler to increase, which would bolster the stress on the induced fan. As a result, it's important to have a thorough site assessment conducted before choosing any boiler deslagging method. Regardless of the boiler deslagging method you choose, it's imperative to choose a contractor with the proper licenses to perform the job.
Fill out the form below for a free consultation to learn which boiler deslagging method is best for your facility. Or you can contact us directly to discuss any inquiries you may.