The ISB system utilizes feedback from four sources: heat flux sensors (SmartSensor), strain gages (SmartGauge), thermodynamic model (SmartConvection), and boiler parameters such as steam and gas temperatures, spray flow and draft pressures. Heat flux sensors are able to measure the cleanliness of different section of the water wall and inform the ISB system when and where to clean. In the case of water cannon cleaning, thermal impact data from heat flux sensors can be used to adjust the cleaning speed and water pressure of water cannon for optimizing the cleaning process.
The convection pass is monitored with thermodynamic models and direct reading from strain gages. Thermodynamic models use steam temperatures, pressure, and flow rates to measure the effectiveness of heat transfer in a section of the steam generating components in the convection pass. This can be expressed in terms of cleanliness or as a fouling factor. The cleanliness factors of different steam generation banks are input to the ISB system to optimize sootblowers operation for different heating surfaces.
Strain gages are mounted on the hanger rods of the superheater for reheater pendants. The weight change on the strain gages can be used to identify the clinker build-up and slagging condition. In addition, the amount of ash removed is measured by the weight change. Thus individual blower operation and effectiveness can be monitored. This measurement forms the basis for effectiveness measurements for individual soot blowers and leads to the ability to optimize the frequency of blower operation.
Various elements of Intelligent Soot Blowing (ISB) system are combined to operate the cleaning equipment. The Sensor/Gauge Interface Module provides the ISB algorithms that determine the cleanliness states of various boiler components. This interface derives priority tables that determine which soot blowers are most effective and which should be operated to achieve desired steam conditions. For the furnace the interface determines water cleaning speed and pressure. The Interface receives information from the heat flux sensors in the furnace, the strain gages in the superheater and reheater sections, and from the thermodynamic model. In addition, the interface serves as a monitor of other plant conditions, such as steam temperature, unit load, spray flows, draft pressure and other pertinent cycle parameters. The output of the ISB algorithm logic is the operation of the cleaning equipment. This may be water cannons, retractable soot blowers, and other cleaning devices.
The algorithms that balance the performance of sections of the boiler drive the control of the boiler cleaning equipment. Modern control systems utilize Programmable Logic Controllers (PLCs) to direct the equipment operation. Operator interface is provided by using PC and Windows based applications. Open system architecture supports all standard communications protocols including Ethernet, Modbus, DH+, Profibus, etc. OPC (OLE for Process Control) server is also utilized for the communication. All these features allow an easy integration with other systems such as DCS and PI historian. Typical system integration for the ISB system is shown in the graph on the left side.