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The SuperMAC® is a patented system for “dry” extraction, enhanced air cooling and mechanical handling of bottom ash from coal-fired boilers, burning high ash content coals (over 20÷30%, like Indian ones) or other low rank coals.
The SuperMAC® system is an improvement of the MAC® system, the world’s leading “dry” bottom ash handling system for utility and industrial boilers burning low-medium ash content coals. It is designed with further cooling capabilities and special system configuration to cool down effectively bottom ash, limiting cooling air generally in the range 1.0÷1.5% of the combustion air rate.
The SuperMAC® system’s very reliable operation is ensured by its construction and the use of the Magaldi Superbelt®, that allows safe receipt and transport of extremely hot, abrasive and dusty ashes, no matter if containing very big lumps. High temperatures and tear issues are resolved due to the patented method of connecting the pans to the mesh belt, that leaves all elements free to expand in any direction.
Ash cooling is carried out by air that enters the system through accurately sized inlet valves located along the conveyors. A certain amount of cooling air is forced to cross the belt and the ash layer, gaining an intimate contact between air and ash particles that maximizes the cooling process.
The SuperMAC® system improves the boiler efficiency better than the standard configuration of the MAC® system, thanks to a higher ash to cooling air ratio and a more effective heat exchange. Boiler efficiency improvement is calculated within the framework of ASME PTC4-1998.
The MAC® Magaldi Ash Cooler is a unique system for dry extraction, air cooling and mechanical handling of bottom ash from pulverized coal-fired boilers. With hundreds of installations worldwide since 1980s, the MAC® Magaldi Ash Cooler is the world’s leading dry bottom ash handling system for utility and industrial boilers, of any size and burning any kind of solid fuel.
The MAC® system’s very reliable operation is witnessed by millions of trouble-free operating hours. That is ensured by the MAC® construction and the use of the Magaldi Superbelt®, allowing safe collection and transport of extremely hot, abrasive and dusty ashes, no matter if containing very big lumps. High temperatures and tear issues are resolved thanks to the patented method of connecting the pans to the mesh belt, that leaves all elements free to expand in any direction. The Superbelt® damage-tolerant design eliminates any risk of sudden failures, otherwise always present, especially with hot and abrasive materials, in the case of conveyors using chains.
In the MAC® system, ash cooling is carried out by ambient air, naturally drawn into the system by the furnace negative pressure. That air recovers a significant amount of energy in the form of ash sensible heat, ash chemical energy from unburned particles, boiler radiation flux through the throat. The dry cooling process has been proven to have no negative effects on the main combustion.
The MAC® system, compared to conventional wet systems, can improve the boiler efficiency by a factor in the range 0.1÷0.6%, depending on coal properties and ash rates, calculated within the framework of ASME PTC4-1998.
The MAP® Magaldi Ash Postcombustor is a development of the MAC® system to extract, convey and cool bottom ash, and to enhance and control the postcombustion of unburnt particles on the steel belt in case of biomass / RDF co-combustion in pulverized coal-fired (PCF) boilers.
The option to apply biomass / RDF co-combustion (or co-firing) in PCF power plants can be strongly advantageous for environmental and energy aims. In case significant amounts of unburnt carbon should be extracted together with coal bottom ash, the MAP®system overcomes the limitations of conventional systems: water pollution, energy loss, particle floating in the water bath as well as fines suspended in the water.
The MAP® system aims at enhancing the oxidation of unburnt carbon fraction in “dry” bottom ash. It achieves the greatest advantages where the coarser biomass / RDF fraction (d > 1.0÷2.0 mm) does not have a residence time in the combustion chamber long enough to burn completely. That fraction, due to slower combustion kinetics, falls down in the bottom hopper, appreciably increasing the unburnt carbon content of bottom ash.
The MAP® system can be seen as a system integrated with the boiler, reducing the restrictions about co-fuel size distribution and mixing conditions.
The MAR® Magaldi Ash Recycling is an improvement of the MAC® system for “dry” extraction, cooling and handling of bottom ash from solid fuel fired boilers. That innovative process to recycle both “dry” bottom ash and economizer (ECO) ash in the combustion chamber aims at turning them into fly ash.
After the MAC® system, dry bottom ash along with ECO ash can be diverted to the MAR® system and then injected in the boiler through the coal pulverizers.
Dry bottom ash, extracted and cooled by the MAC® system, and ash from ECO hoppers are pneumatically conveyed and stored in small reception bins, located at the coal bunkers level. The finest particles, along with conveying air, are directly drafted into the combustion chamber or the flue gas ducts. Ash is extracted from the reception bins by tubular vibro-feeders and dosed to the coal mill feeding hoppers. Then ash is milled by coal pulverizers along with coal before being injected in the boiler through coal burners.
The MAR® system ensures the valorization both of bottom ash and ECO ash, turning a waste into a coal combustion product (CCP). Using CCPs, in cement or concrete production rather than disposing of them, conserves natural resources and reduces greenhouse gas emissions.
The MAS® Magaldi Ash System is a patented integrated “dry” mechanical system for handling all ash from solid fuel fired boilers, allowing a dependable and economical management for both fly and bottom ash.
The MAS® comprises 3 subsystems, as follows:
The MAS® properly addresses the demand of solid fuel fired power plants for sustainable practices in ash handling. Dry coal combustion products (CCPs) can directly contribute to achieve environmentally sound methods of disposal. Using CCPs, in cement or concrete production rather than disposing of them, conserves natural resources and reduces greenhouse gas emissions. Safe and beneficial use of dry ash should be viewed as a preferred alternative to ash ponds, avoiding the need for additional landfill space through sound technical and environmental management practices.
One single integrated mechanical ash transport and storage system is simpler, more efficient, and increases the market value of the ash. The result is the production of only fly ash, as coal combustion by-product.