Introduction
In 2020, a large power generation company in Southeast Asia commissioned the production of a new 600MW Pulverized Coal (PC) Boiler at its plant. The company had a requirement to be able to burn the full range of its coal, which had proved challenging due to the high calcium content of the fuel. As a result, a new boiler had been built and commissioned by a reputable manufacturer.
Since the boiler has been in operation, the plant has suffered with a build-up of slagging on the tubes. The plant’s requirement to burn the full range of coal means that some ranges had to be burned at an increased temperature, which had been causing excessive slagging at the bottom of the boiler. To fix the problem, the build-up was being regularly blasted, which was time consuming and inefficient.

The Issue of Boiler Slagging

Pulverized Coal boilers experience slagging as the molten ash adheres to the surrounding substrates. This is also commonly referred to as slag. The amount of slag is primarily dependent on temperature and the types of coal being used and whether it is anthracite, bituminous coal, subbituminous coal, or lignite. Boilers will often slag in the upper sections of the furnace where the temperatures are higher near the superheat pendants, but slagging may also occur on the waterwalls. The build-up has a negative effect on boiler operation. The slag acts as an insulation to the tube substrate and this loss of heat transfer is detrimental to performance. When the slag builds up on the tubes, the heat transfer decreases lowering the temperature of the steam going to the superheated portion of the system, therefore decreasing the overall efficiency of the system. Finding a solution to excessive slagging can have tremendous benefits for a boiler operator’s bottom line.
The Solutions

In most cases there are two viable options to resolve the issue of slagging. A reactive method comprises of the installation and maintenance of the water cannons to regularly remove the fouling. However, whilst the cannons are effective at removing most of the build-up, parts of the cannon often need replacing due to the erosive effect of water running through them and the ash burning around them. This makes the installation of water cannons a time consuming and costly method. The other option available is to apply a ceramic coating alternative to reduce the build-up of slagging, which was the solution chosen by the plant in Southeast Asia. The properties and benefits of such a ceramic coating are discussed in more detail, below.
Anti-Slag and Fouling Properties of the Ceramic Coating Surface

Anti-slagging technology such as that offered by Integrated Global Solutions (IGS) bonds tightly to the boiler tube’s surface, creating a non-porous, non-wetting, non-reactive surface. The coating will significantly limit molten slags from bonding to the surface, reducing slag and fouling agglomerations. Waterwall furnace tubes and Superheater tubes can benefit from being protected with the coating. IGS has developed a series of ceramic coating formulations which are modified to match boiler environments.

Increase Heat Rate, Lower Furnace Gas Exit Temperatures (FGET)
Ceramic coatings can help increase heat absorption into boiler tubes by reducing the amount of slag or fouling on the OD surface of the tube, and by eliminating the formation of corrosion scales on the tube surface.
The coating itself exhibits high thermal conductivity and high emissivity, which means the coating layer will not insulate the tubes. A coated tube will have higher heat absorption compared to an uncoated scaled tube. It is possible to rebalance a boiler that is suffering from severe slagging or fouling. The lower FGET is possible by absorbing more heat into the waterwalls while achieving the same final steam temp (reduced fuel input, same final steam temp, reduced waste heat). It is even possible to help address boilers that have de-rated their MW output capacity due to superheater fouling.
Reduce Damage from Soot Blowers and Water Cannons
By significantly reducing the amount of slag or fouling on a tube’s surface, it is possible to significantly reduce the frequency at which soot blowers or water cannons are activated. As there will be less slag attached to the tubes, lowering heat absorption, there’s no need to continuously run the slag control equipment. When soot blowers or retractable lances remove slag and fouling, the tube itself will be thermally shocked due to the removal of the dirty insulating material, creating the potential for circumferential cracking or corrosion assisted fatigue (CAF) of the tube. Reducing soot blower usage inhibits this and slows the wasting of the tube’s surfaces.

The In-situ Application
The plant and the boiler manufacturer agreed that a ceramic coating would be the most efficient long-term solution to increase productivity and negate the requirement for water cannon blasting and the associated maintenance costs.
The contractor, IGS, mobilised a team to the plant in December 2021 to complete the application of the ceramic coating on 10% of the total surface area. After results testing for effectiveness, the remaining 90% would be coated. The work was carried out across four night shifts during a planned shutdown.
The Result
The ceramic coating will significantly reduce the amount of slag build-up throughout the boiler. The sensors coated with the IGS anti-slagging technology will be hotter due to the prevention of fouling inhibiting the heat transfer process. The plant is expected to see significant financial and carbon savings associated with reduced maintenance and increased efficiency.
IGS Comment
Pete Johnson, Director O&G – APAC at IGS, said:
“This project has been a great success for IGS. We have been able to fulfil the client’s requirements to help resolve the issues that they had been experiencing in relation to slagging and fouling within the boiler.
“The feedback we have received from the client has been very positive; they were particularly impressed with our professionalism, our communication channels, and our safety protocols.
“We are pleased with the results that we are initially seeing, and we’ll be working closely with the client moving forwards to monitor and maintain the performance of the boiler.”
For more information about anti-slagging solutions, visit: https://integratedglobal.com/services/boiler-deslagging/