Bagasse Fired Boiler Control

Uganda

Power

Power, Boiler Control, Sugar Processing

Control system for a Bagasse fired boiler and power generation facility. Boiler drum-level control is critical. Too low a level may expose boiler tubes, which overheat and damage them. Too high a level may interfere with separating moisture from steam, which reduces boiler efficiency and carries moisture into the process or turbine. The controller must maintain a constant steam load.

The Kinyara Sugar Works in Uganda engaged Thorne International Boilers to convert an existing incinerator to a boiler fired by Bagasse.  Bagasse is a biomass fuel produced as a by-product of sugar production and it provides enough energy to meet the needs of a typical sugar mill with energy to spare. As discussed previously boiler control is critical and Thorne International needed sophisticated, integrated control technology to manage this vital plant component. It required a highly available system that could provide sophisticated drum level control and would be expandable to enable the inclusion of additional boilers in the future.

We designed, implemented and commissioned a solution based on Siemens PCS7 DCS system.  The control system had five variable speed drives connected via a Profibus DP network and around 400 hardwired I/O.

Our solution was designed with high availability with a dual redundant PCS7 server and AS S7-400 Series Controllers with simplex remote I/O based on a redundant Profibus network.  In addition there were two operator workstations and an engineering workstation providing trending, navigation, faceplates, alarming etc. These workstations enable the operator to survey the process extremely easily, and rapidly navigate between different views of the plant. 

This system provides complex three element drum level control and is designed to deliver as much steam flow as the plant demands. The PCS7 system maintains the Drum Level at an operator enterable set point and this is used to derive the Feed Water Flow. The three Element Feed Water Control is a cascade control system utilising feed forward and feed back algorithms.

This project is the first phase of an on-going scheme to bring all the boilers into a single redundant control system.