HRSG Design, Operation and Maintenance Considerations” was Hot Topic Hour on March 7, 2013
HRSGs can pose unique operational challenges based on the application. For example, when used with gas turbine exhaust in combined cycle operations, rapid startup requirements and subsequent thermal stresses can cause more frequent tube failures; when used with heavy oil-fired engines or boilers, the carbon in the exhaust can cause fouling or coating of the tubes. In addition, the challenges or potential problems can change when operating conditions such as load on a power generator, heating demand, fuel used in the primary combustion process or even ambient conditions change. Since it is difficult for plant owners and operators to predict future operating requirements and conditions, a HRSG that can accommodate a wide variety of conditions while maintaining efficient, cost-effective operation can be valuable.
Four highly qualified speakers addressed the issues related to the design, installation, operation and maintenance of HRSGs for various applications; there were some differences of opinion evidenced. The increasing utilization of a bypass system was observed by one speaker. He pointed to Florida, Texas and most countries outside the U.S. as preferring the bypass system due to the need for cycling.
The problems and recommendation to avoid bypass were voiced by another speaker. The bypass dampers create a big maintenance problem. Many localities have air emission limits which make it difficult to meet NOx requirements if bypass is frequent.
John DiVitto, Business Development Manager and Melvin J. Albrecht, Technical Fellow at Babcock & Wilcox Power Generation Group, Inc., discussed advantages of vertical separators which provide enhanced fatigue tolerance through thinner pressure part components.
Ati Manay, PMP, P.E. Product Manager, SMART Clean at Clyde Bergemann, Inc/Power Group Americas reviewed the advantage of retractable soot blowers vs. the rotary design. The retractable sootblower can provide a cleaning radius up to eight feet. Maintenance costs are low and the unit is easy to service. The negative is that you need six feet of space outside the boiler. Scott Owings summarized the many components between the turbine and the HRSG including diffusers, diverters, expansion joints and silencers.
Landon Tessmer, Senior Sales and Proposal Engineer for Flexible Operation explained that the Once-Through Steam Generator (OTSG) is a drumless HRSG that is smaller, more flexible, and simpler than a traditional HRSG. The unit is designed with high-nickel alloy tubes that allow the OTSG to operate dry without the use of a bypass stack. With zero blowdown, OTSG water treatment is the primary operational concern to ensure the highest reliability and longest life.
Deron Johnston, Manager of Field Services at Vogt Power International Inc. reviewed design considerations for drum type HRSGs. He also described a new monitoring program. LCAMP™ (Life Consumption Assessment & Monitoring Program) is a set of computer software for assessing consumption and process for controlling the operations.
LCAMP™
Bios, Abstracts and Photos can be seen at: BIOS, ABSTRACTS, PHOTOS, 3-7-13.htm
The individual presentations are as follows: