Ash can be produced from the combustion of fuels, such as coal, plus the incineration of waste materials such as sewage sludge and medical waste. All of these different ashes have their own particular handling characteristics. Some are sticky; others, such as wood ash, can be associated with burning embers, sparking, etc. Ash can be produced in different forms; fine such as fly ash or coarse such as bottom ash which can include large clinkers well suited to be handled by the Macawber Ash Breaker. We have the experience and technology to address the special requirements associated with handling ash.
Many fuels are now burned in fluid bed combustors. Most industrial applications operate at atmospheric or low pressures. Flue gases can be cleaned by adding certain types of additives such as limestone which absorb the sulfur dioxide during the combustion process. Also, many of FBCs use sand in the bed. We have used our Sandpumps® to inject the sand into the bed as replenishment is required. Most combustion applications involve Macawber Denseveyors® for handling coal and limestone, the Ashveyor®, multi-pick-point system for handling ash, and the Controlveyor for the injection of fuel and sorbent materials into fluid bed combustors.
Macawber has installed many systems over the years in power utility plants where most fly ash is produced in economizers, air heaters and electrostatic precipitators (ESPs). The application is virtually the same as industrial plants except the number of pick-up points is greater.
Traditionally, vacuum systems, and to a lesser extend positive pressure dilute phase systems, have been used. Today, many users have switched to dense phase technology due to advantages such as:
* Lower energy consumption – sometimes up to 50% less than for vacuum systems
* Minimal pipe wear and the benefit of using regular schedule 40 carbon steel pipe
* Reduced maintenance due to lower wear and tear to flow control valves.
Macawber has a proven track record of supplying high-pressure gasifiers where the scope of supply is feeding systems and ash removal systems. Examples are coal burning combustion processes operating at high pressures of 300-450 psig (20-30 barg). Often the ash or coal fines are reinjected into lower pressure fluid bed combustors.
Other application examples include long-distance transfer of fly ash, fuel feed and pressure let-down systems for gasifiers.