PLC Based Ash Handling Controls

Applied Synergistics recently received a patent for our intelligent ash control system. The system is designed around the same industry standard PLC¹s and PC based MMI that is used to control other plant processes. The system allows easy control, maintenance, and trending from the control room of a system that has traditionally been primarily controlled by local controls. It simplifies the interface with the operator by integrating boiler cleaning operations.

We have designed our ash handling controls based on the same principles used for the sootblower controls. For added flexibility, the ash handling controls can be directly integrated on the Cleaning Manager PC platform used for sootblower controls or can be standalone. Unlike previous ash handling controls, we have incorporated setup menus for definition of setpoints and sequences. We have also implemented an innovative ash handling control scheme that monitors the time to empty each hopper and adapts the emptying sequence to accommodate variations in fill rate.

The system also provides the platform for operating the ash system based on sensed need to convey ash rather than on a timed or sequential operation. This allows some intelligence to be injected into the process providing the opportunity to operate the boiler more efficiently and to reduce component wear.

Initially a system is set up to convey ash on a rotational basis based on previous plant experience. The system then uses available instrumentation including air flow and vacuum to determine the time required for an individual hopper to empty. The time between hopper conveying operations is varied to achieve consistent hopper ash levels for each operation. The result is the frequency of individual hopper conveying operations is determined by the ash loading not time.

Like ASI/BMS's intelligent sootblowing, this system can save the utility money and help achieve gains in plant efficiency.

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The ash handling system represents new technology and is the next logical step in auxiliary equipment control system design. First generation PLC or PC based control systems merely replicated relay and timer based control systems originally supplied. Device activation was based primarily upon timed cycles.

Second generation technology introduced demand based actuation using sensors or computer models to determine when to operate devices such as sootblowers or ash hopper gates. This new third generation adaptive technology takes the information from sensor based or model based technology a step further by "learning" the behavior of the process and not only actuating but modifying the performance of the control device as it learns to optimize the process.

Operational Features

• Remote control of ash dumping operations
• Dump based on determination of level of ash, rather than just based on time.
• Works with any manufacturer¹s system
• Industry standard hardware

Set-Up Features

• Based on setup tables on MMI, no programming or PLC code changes
• Manual and automatic parameters under operator control
• Event data and analog parameters trended so operation can be fine tuned

Integration

• Integrates with boiler cleaning operations
• Integrates directly with sootblower and water cannon controls
• Integrates with DCS

ASI/BMS's family of performance-based controls and optimization systems include: sootblower controls, ash controls, pneumatic sootblower controls upgrade, Furnace Cleanliness Module (furnace sootblowing optimization), Sootblowing Cleaning Expert (convection region sootblowing optimization) and Boiler Efficiency Module.

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