The HSS Approach to Mid-Pack Fouling Restoration without Hot End Layer Removal
Malaysia
Megawatt: 1000 MW
Air-Preheaters
Analysis / The Challenge
The proposed removal of hot end elements presents several challenges:
Standoff Distance Issue:
Creating a standoff distance of up to 1.5 meters between the restoration device and mid-pack elements could cause the water jet to spread out, reducing effectiveness. HSS approach to retaining the hot end layer becomes particularly advantageous. The HSS system utilises a focused, narrow water jet that is contained within the hot end elements. The flow with the patented technology ensures the water jet can penetrate the mid-pack layer effectively, overcoming the limitations posed by the increased standoff distance.
Hot End Cleanliness Concern:
Removing the hot end could leave it uncleaned by HSS’s comprehensive restoration, risking residual fouling.
Time Constraints:
The time required for removing and replacing elements (6 to 8 days) could be more effectively used for HSS restoration and drying.
Complete Fouling Removal and Drying:
Considering a Delta P of 29 mbar, thorough cleaning might require 3-4 days per APH. The saved time from not removing hot end elements can be reallocated to HSS cleaning and drying, ensuring complete fouling removal and efficient maintenance.
Mid-Pack Fouling Concerns at Unit 2:
By January 2024, the extent of blockage will likely have worsened, as indicated by the May 2023 inspection. Increased use of the inbuilt APH wash system pushing the fouling to the mid packs (same with hand jetting) and operational heat might have hardened the fouling, making the retention of the hot end layer crucial for effective HSS restoration.
Water Usage:
The restoration flow rate might reach 1,600 litres per minute per APH. Avoiding hot end layer removal allows more time for sequential restoration, optimising water use and minimising impact on water and effluent systems.
Outcome /Advantage
Fluid Mechanics Principle
The HSS system, grounded in fluid mechanics principles, uses a high-flow, optimally pressured water jet. This approach ensures maximum Newton force application without damaging the elements, which is crucial for effective cleaning.
Patented Technology
HSS's patented technology allows for effective penetration from the hot to cold end elements and vice versa. This technology is critical to addressing mid-pack fouling efficiently.
Retention of Hot End Elements
Keeping the hot end elements in place during cleaning ensures the water jet remains tightly focused. This prevents the fanning out of the water stream, allowing it to effectively penetrate through the mid-pack layer to the cold end layer.
All layers restored
Keeping the hot end means all three layers are completely restored and cleaned, especially the mid-pack layer.
Dual-Sided Restoration Cleaning
HSS conducts its restoration cleaning from both sides of the APH. This comprehensive approach ensures that all layers, including the challenging mid-packs, are effectively cleaned.
Reflection / Conclusion
Optimal Mid-Pack Fouling Restoration Strategy
The HSS approach to mid-pack fouling restoration at the Power Plant presents a compelling and technically superior solution compared to the initial proposal of hot-end layer removal. This method, refined through extensive experience and backed by patented technology, offers a holistic and efficient path to restoring the APH's functionality and efficiency.
Key Advantages of the HSS Approach:
-
Effective Fouling Penetration: By retaining the hot end elements, the HSS system ensures a tightly focused water jet, crucial for penetrating and effectively cleaning the mid-pack layer. This targeted approach overcomes the challenges posed by the increased standoff distance and potential for water jet dispersion.
-
Enhanced Cleaning Efficiency: Using fluid mechanics principles and high-flow, optimally pressured water jets guarantees a thorough restoration process, maximising Newton force application without risking damage to the APH elements.
-
Time and Resource Optimization: The sequential restoration strategy, potentially augmented by the seal removal option, increases cleaning pressure and efficiency. This approach significantly reduces the restoration time, aligning with the plant's operational constraints.
-
Comprehensive Layer Restoration: The HSS method ensures a complete restoration of the APH by cleaning all layers, including the often-neglected mid-packs. The dual-sided cleaning further enhances the thoroughness of the process.
-
Sustainable and Practical Solution: Avoiding removing and replacing hot-end elements conserves valuable resources and aligns with the plant’s environmental and operational goals.
Conclusion
In summary, the HSS method addresses the unique challenges at the Power Plant with a nuanced, effective, and sustainable approach. By leveraging its patented technology and strategic methodology, HSS ensures that the APH system is restored to its optimal operational state, thus enhancing the overall performance and efficiency of the plant. This solution not only tackles the immediate issue of mid-pack fouling but also contributes to the long-term maintenance and efficiency of the APH, ensuring the plant's operational goals are met and exceeded.
Method / HSS Intervention
Our solutions for this projects are:
Sequential APH Restoration Strategy
Given the anticipated severity of fouling in the mid-pack layer and the uncertain condition of the elements, a sequential restoration approach is recommended for Tuanku Muhriz Power Plant. This method is informed by our experience with Unit 1 in June 2022 and the following considerations
-
Resource Allocation: The extent of fouling necessitates the use of all available HSS pumps on a single APH at a time to ensure maximum cleaning efficacy.
-
Restoration Timeline: Based on the restoration of Unit 1, it is anticipated that each APH will require approximately 3 to 4 days for complete restoration. This duration allows for a meticulous cleaning process that thoroughly addresses the fouling.
-
Severity Assessment: Unit 2 is presumed to have more severe fouling than Unit 1 based on the observations and time elapsed since the Unit 1 restoration. This assumption underlines the need for a robust and comprehensive cleaning approach.
Seal Removal Option
During the restoration of Unit 1, it was observed that the seals could withstand only a specific range of pressure and flow. To enhance the cleaning effectiveness for Unit 2, HSS suggest considering the following strategy to enable increased pressure if there is concern about the mid-pack fouling from Tuanku Muhriz's May 2023 inspection (Note: HSS has never needed to have seals removed in four decades of HSS restoration of APH)
-
Pre-Restoration Seal Removal: Removing the seals before commencing the HSS restoration process will allow higher pressure and flow rates without damaging the seals.
-
Post-Restoration Seal Replacement: After HSS restoration, the seals will be replaced, ensuring the integrity of the APH system is maintained.
-
Enhanced Cleaning Efficiency: This modified approach uses a different pressure and flow setting that is hypothesised to be more effective in dislodging the mid-pack fouling, particularly if it has hardened over time.
-
Element Condition Consideration: The effectiveness of this approach will be contingent upon the condition of the elements. A thorough assessment before the restoration will ensure that the applied methods are suitable and will not cause undue stress to the system.