Case Study 131: Conveyor System
Industry Sector: Energy Trash-to-Steam


Conveyor System for Trash to Steam Plant

Allen Bradley SLC 500

Staneco Corporation designed the controls for conveying fuel and ash at a trash to steam plant.  The fuel conveyors took fuel from the storage building to the generator building where it was conveyed over the top of the boilers. The stream of fuel was continuously moving through the conveyors. When a boiler demanded fuel, a signal from the plant DCS was sent to the PLC. The PLC then switched gates to send fuel to the particular boiler. If no boilers demanded fuel, the fuel was returned to the storage building and re-circulated.

The boilers used fluidized beds consisting of a mixture of fuel and sand to more efficiently burn the fuel.  Air was pumped into the boiler which made the fuel and sand combination act like a fluid when it was burning. The burned fuel and sand mixture was removed from the boiler, where the sand was separated from the fuel ash. The sand was then returned to the boiler mixed with fly ash, removed from the stack by precipitators, and sent to a storage bin. The ash was later conveyed to trucks at the truck loading station and sent to a landfill.

The control system ensured the boilers ran efficiently and optimally by precisely controlling the fuel needed. Down time was reduced since conveyer jams were minimized.