Boiler Cleaning Using ISB (Intelligent Soot Blowing) System Integration: Recent Developments and Case Study

Ash and slag deposits in coal fired boilers contribute to boiler in-efficiency, capacity reductions, and overheated tubes, which lead to tube failures. Typical on-line cleaning systems are not automated and do not optimize the removal of ash and slag deposits. The paper describes the development and implementation of an Intelligent Sootblowing (ISB) system which monitors data such as heat transfer rate and pendant weight and operates the boiler cleaning devises in an automatic mode. The system operates cleaning equipment to only clean what needs to be cleaned, thus reducing tube erosion and clinker formation. The Intelligent Sootblowing (ISB) system uses the process data, algorithms, thermodynamic models, and ash weight to derive a supervisory sequence control to initiate most effective sootblowing device, when and where necessary. Unique strain gage ash weight measurement feedback is utilized in the system. The system is modular and built with an Open Architecture off the shelf components. It comprises PLC Panels, Data Acquisition Panels and HMI (Human Machine Interface) / EWS (Engineering Work Station) using distributed controls architecture. This system also supports industry standard communication protocols, which provides seamless integration between the ISB system and the plant’s DCS. This protocol can be Ethernet, Modbus, Modbus TCP, DH+ or Serial. The Case Studies will describe existing installations where the integrated system controls the entire boiler cleaning system. One installation is in Texas for an 850 MW, supercritical Combustion Engineering tangential fired pulverized coal unit. The boiler burns Texas lignite coal with as much as 15% Powder River Basin coal blended. The soot blowing system consists of 50 retractable soot blowers and 8 water cannons plus air heater cleaners. Testing for this unit was supervised by EPRI. A second installation is in Louisiana where the system improved overall plant efficiency as much as 1% with a resulting high return on investment. Improvements also included improved heat rate, boiler efficiency, a reduction in spray flow and a reduction in soot blowing events.Copyright © 2010 by ASME