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Evaluation and integrated upgrade of the existing Savannah ash handling system to improve plant reliability, availability, operational efficiency and maintainability — addressing wear, blockages, pressure issues and operational difficulties identified during a detailed on-site assessment.
RULA evaluated the existing Savannah ash handling system and engineered an integrated upgrade — redesigned pneumatic conveying, modified pressure vessels, a vented surge hopper, new screw conveyors with automatic capacity control, an isolable ash cruncher and a redesigned silo discharge — to deliver a more robust, maintenance-friendly plant capable of responding automatically to varying boiler and ash-production conditions.
Rather than simply increasing equipment capacity or adding additional power, RULA’s approach focused on improving the fundamental operation of the system. The upgraded design was developed around three key principles:
The overall philosophy was to create an ash handling plant capable of responding automatically to changing operating conditions while reducing operator and maintenance intervention.
The existing pneumatic conveying philosophy was reviewed and redesigned to improve conveying efficiency. The upgraded system uses vessel level indication and timing controls to determine the conveying sequence, allowing pressure vessels to fill more effectively before conveying. This reduces unnecessary conveying cycles and helps lower conveying velocities, resulting in:
The conveying pipeline routing was redesigned to create a more direct and efficient material flow path. The revised arrangement reduces the number of bends and eliminates potential dead areas where ash could accumulate or settle. Long-radius ceramic-lined bends were incorporated into the design to provide improved wear resistance and extended service life.
Selected pressure vessels were modified and increased in capacity to improve system performance and reduce the number of conveying cycles.
The ESP Field 1 vessels were increased to approximately 800 litres, while the MDC vessels were increased to approximately 1.7 m³.
A vented surge hopper was incorporated above the MDC pressure vessels to accommodate sudden increases in ash production. The hopper was designed with steep wall angles to promote reliable material flow and minimise material hang-up, providing additional protection during periods where ash production suddenly increases and preventing downstream equipment from becoming overloaded.
The blower air supply system was improved to provide better control of conveying air. A controlled blow-off arrangement allows excess air to be safely released between conveying sequences rather than continuously forcing air through the conveying pipeline. This assists in:
The vessel agitation arrangement was reviewed to provide more controlled material flow into the conveying pipeline. A fixed nozzle arrangement assists with material agitation and discharge, while a flip-flap arrangement provides additional control of conveying line pressure. The objective is to achieve reliable vessel discharge without introducing excessive uncontrolled air into the system.
The ash handling system was upgraded with three new screw conveyors per unit. The screw conveyors were designed with similar configurations and lengths to improve component interchangeability and simplify maintenance. The first screw conveyor can be equipped with a Variable Speed Drive (VSD), allowing its speed to be adjusted according to downstream conditions. Additional monitoring at the discharge of the third screw provides early warning of increased material flow.
The upgraded system incorporates level and proximity monitoring to identify increases in ash production before downstream equipment becomes overloaded. Signals from the surge hopper and screw conveyor discharge can automatically:
This provides an additional layer of protection against material build-up and equipment overloading.
A dedicated ash cruncher can be installed between the second and third screw conveyors. The cruncher breaks down bulky bagasse ash and unburned material before it reaches downstream equipment. A bypass arrangement allows continued operation when the cruncher is not required or needs to be isolated for maintenance.
The silo discharge arrangement was redesigned to improve material flow and reduce the possibility of silo blockages. The proposed arrangement incorporates a vented, inclined live-bottom system, discharging through a rotary feeder to the ash conditioner, providing more controlled and reliable discharge of material from the silo.
RULA evaluates existing bulk materials handling plant and engineers integrated, maintenance-friendly upgrades.