POWER GENERATION

AOS Engineering Group has established itself as a key player in the Thermal Spray business in Pakistan. With a strong track record, the company actively provides specialized coating solutions to some of the largest coal-fired power plants across the nation. AOS's commitment to quality and technical proficiency makes them a trusted partner in maintaining the operational integrity of these vital energy-producing facilities. Our on-site surface protection minimizes downtime and maximizes reliability of your critical equipment.

Circulating Fluidize Bed Boiler

Circulating Fluidized Bed (CFB) boilers have become the first choice for power plant operators due to their advantages of high combustion efficiency, low emissions, and high fuel mix flexibility. CFB boilers produce steam by burning coal, biomass, or pre-treated industrial or urban waste. Many power plants use different types of coal with high ash content. High ash and sulfur content results in significant erosion and corrosion on the boiler tubes.

Boiler Tube Erosion is a major challenge for circulating fluidized bed combustion due to the circulation of hard particles within the boiler.

Recognizing that erosion and corrosion issues differ in every CFB boiler, AOS customizes its Thermal Spray solutions to each process to mitigate wastage and extend the lifespan of boiler tubes. Our thermal spray coatings,

• Increase Reliability of their CFB Boiler

• Increase Outage Cycles

• Reduce Mechanical Repairs

Pulverised Coal Fired Boiler

PC-Fired Boilers generate thermal energy by burning pulverized coal that is blown by a combustion air stream to the burners in the firebox. These coal burners are typically located on the front and rear walls or in each of the corners to be known as wall fired or corner fired burners, respectively

PC-fired boilers are prone to corrosion due to the presence of sulfur in the fuel. During combustion under reducing conditions (low oxygen), the sulfur combines with hydrogen and deposits on the tube surface, reacting with the iron in the tube material to form a scale of FeS. This cycle repeats as more H₂S deposits on the walls, causing significant tube thinning.

AOS Engineering's thermal spray cladding acts as a protective barrier against corrosive flue gases for boiler tubes by eliminating ash and slag buildup on furnace walls. This coating, combined with its high emissivity top coat, not only prevents boiler tube thinning but also enhances furnace performance through reduced slag buildup and improved heat transfer. It is highly protective against under-deposit corrosion, when Sulfur together with Sodium, Potassium and Vanadium Oxides form low-melting-temperature pyro-eutectic salts. Consequently, plants can also save on steam costs due to the reduced need for sootblowing on the waterwalls.

Typical Erosion/Corrosion areas in the Pulverized Coal Fired Boilers

1. Combustion area (Radiant zone).

2. Superheater platen ( wingwall).

3. Economizer & Superheater section ( Erosion due the spray of high pressure steam from sootblowers).

4. Sulfidation of waterwalls leading to the thinning of the tubes due to corrosion.