Power

Dry Bottom Ash Extraction and Cooling System

Environmental regulations demand ever greater efforts from energy utilities to reduce the polluting load from power generation. Since 1980 MAGALDI provides technologies for the safe and environmentally friendly handling and transportation of raw materials and ash in the coal fired power plants worldwide.

The patented MAC (Magaldi Ash Cooler) Dry Bottom Ash System, is a unique system for dry extraction, cooling and handling of bottom ash from pulverized coal-fired boilers.

With almost a hundred of systems installed worldwide, the MAC Dry Bottom Ash system is the world's leading dry bottom ash handling system for utility boilers.

The success of the MAC system can be attributed to the following benefits over traditional wet bottom ash system

• Eliminates water usage in cooling and conveying bottom ash

• Reduces carbon content in bottom ash

• Captures heat energy from ash and returns to boiler

• Provides for potential sale of dry, low carbon ash

• Reduces operational and maintenance costs compared to conventional wet systems

• Fully automatic system from boiler throat to storage silo

The Mac system has been installed in both new boiler and retrofit projects on many different boiler types and makes in a wide range of operating conditions.

The main component of the MAC system is the MAC extractor, which is designed to operate in harsh conditions including exposure to high temperature and shock loads caused by the fall of large clinkers.

The MAC extractor is connected to the boiler throat through a refractory-lined hopper or a transition chute, which provides a volume for temporary ash storage. The hopper is available with bottom doors which can be closed to isolate the MAC extractor and for ash storage. The hopper or transition chute is connected to the boiler throat by a high temperature mechanical seal that allows for boiler expansion.

The key element of the MAC extractor is the Magaldi Superbelt steel belt conveyor, which receives and extracts bottom ash falling from the boiler. The Superbelt is enclosed inside the sealing casing of the Mac extractor.

During the conveying of ash on the Magaldi Superbelt, ash is cooled by a small, controlled amount of ambient air that flows by natural draft into the MAC casing through inlet valves. In addition the air provides oxygen to the unburned ash allowing a more complete combustion and return of heat to the boiler. Data from existing installations indicate reverse air flow does not disturb the combustion process and does not influence NOx formation.

From the MAC extractor, the cooled ash is discharged onto a crusher, which reduces the large ash clinkers to a size suitable for conveying to a silo. Any ash fines that fall on the MAC casing floor are swept off by the spill chain, a small scraper conveyor installed under the Magaldi Superbelt.

Features:

Since the ash is delivered dry, there are several different possibilities for the configuration of the equipment located downstream the primary crusher. The mostly applied configurations are described below.

1. From the crusher, the bottom ash is discharged through an ash conditioner into an existing ash conveying system, or into a truck or pit. This kind of configuration could be particularly attractive for retrofits, replacing the existing wet bottom ash extractor by a MAC extractor, while the existing downstream conveying system could be maintained. In that way, all benefits of primary extraction by the MAC system are obtained with a minimum cost for installation of new equipment.

2. A dry mechanical transport to a silo can be provided by a Magaldi Postcooler. The Magaldi Postcooler is a steel belt conveyor inside a sealed casing, providing a significant further cooling of the ash during conveying, with the dependability of the Magaldi technologies.

3. By the installation of a second crushing stage after the primary crusher, the ash size is fine enough to enable the transportation by a pneumatic vacuum system. With this configuration, the system can be fitted even in very restricted spaces.

4. If the dry bottom ash is pulverized by mills to a very fine size, it can be mixed with the fly ash. This can lead to a simplification of the overall ash handling system and increased ash sales revenues. In this configuration, usually a Magaldi Postcooler is used to transport the ash from the crusher to the pulverizers, followed by pneumatic conveying to the fly ash silo.

Further different configurations are possible. The integration of the MAC system with other ash handling systems, e.g. for economizer ash, is also possible. This can lead to a further simplification of the overall ash handling system.

Performance:

The MAC system is characterized by the following benefits for the overall boiler performance:

High dependability and safety

The MAC system has a proven, much higher dependability than other bottom ash handling systems, which can result in an increased boiler availability:

• In the entire operating experience of all installed MAC systems, not a single instance of Magaldi Superbelt failure leading to a forced boiler outage has occurred

• The MAC system is able to withstand to the impact of the biggest ash clinkers that can fall from the boiler, and there is no risk of sudden failure

• The MAC system is absolutely safe, because all moving parts are inside the casing and no manual intervention is required during operation. The casing itself is sealed and maintains a low temperature

No water-related problems

By not using any water for the ash processing, a series of operational and environmental problems are eliminated by the MAC system:

• no fresh water consumption and no waste water production

• no need for dewatering bins, ponds or waste water treatment

• no pumps, no heat exchangers, no pH-control

• no corrosion, no risk of ice formation

• no safety problems due to hot water splashing or vapor explosions

• no problems with environmental regulation regarding water pollution

Low operation & maintenance requirements

• Wear of the Magaldi Superbelt is negligible, because there is no relative motion between the belt and the ash.

• The MAC extractor design ensures that any ash clinker that can pass through the boiler throat, is transferred to the crusher

• Maintenance demand is extremely low, and all regular activities can be carried out with the system in operation

• Thanks to its special control system, the MAC system can be operated fully automatically

• Power consumption is very low, because no water has to be moved, only dry ash

Heat recovery from the ash to the boiler

In solid-fuel fired boilers, a significant amount of energy is contained in the bottom ash. In a wet bottom ash system, this energy is completely lost because the ash is quenched. In the MAC system, on the other hand, the cooling air takes up the heat from the ash and provides oxygen for postcombustion:

• A burn-out of more than 75% of unburned carbon is generally achieved in the MAC system

• In total, up to 90% of all heat contained in the bottom ash is recovered by the cooling air before it flows up into the boiler

• This heat recovery reduces the heat and fuel losses from the boiler, which can contribute to an increased boiler efficiency

• In the same time, it has been proven that the amount of cooling air used in the MAC system (typically less than 1% of total boiler combustion air) does not have any adverse effect on the boiler operation

Delivery of dry ash

The bottom ash is delivered dry, which offers the following benefits

• The configuration of the downstream processing equipment can be greatly customized

• Dry ash has much better sales opportunities than wet ash

• After pulverization, dry bottom ash can be mixed with fly ash, leading to increased ash sales revenues and simplified ash management

Fields of Application:

• The MAC systems are applied in almost a hundred installations worldwide of which more than half consisting of retrofits, substituting Water Impounded Hoppers and Submerged Scraper Conveyors (SSC) systems

• Total installed capacity of boilers with MAC systems: more than 21,000 MWe

• Cumulative operational experience: more than 2,5 millions

• Total quantity of dry bottom ash extracted till date: more than 12 millions

• MAC systems fit under boilers made by:

- ABB/CE (ALSTOM)

- ANSALDO

- Babcock Borsig Power

- B&W

- C.E.

- Dongfang Boiler

- Dürr-Werke

- EVT

- Foster Wheeler

- F. TOSI

- Harbin Boiler

- IHI

- MHI

- KHI

- RAFAKO

- SES

- VKW

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Power

Dry Fly Ash Handling

In the last years the respect for the environment has become the main target for many power plants in the world. At the present time all the efforts are focused on the emission reduction (CO2, NOx, SOx, particulates, etc.) and on the valorisation of the ash considered as a waste till few years ago.

These problems are amplified for the power plants provided with solid fuel fired boilers. Besides, some years ago, there have been effected international standards that regulate the possible uses of the ash as a constituent of cements (ENV 197-1) and concretes (UNI-EN 450). In this way the ash is not a waste anymore, but it can be considered as a source of useful by-products if it respects the limits specified in the above mentioned standards.

In order to reduce these environmental impacts and to make ash usable in cements or concretes, MAGALDI has developed and patented a system able to extract, cool and recycle into the combustion chamber, the ash coming from solid fuel fired boilers. This new system combines the MAC® (Magaldi Ash Cooler) System and its development, called MAR® (Magaldi Ash Recycling) System, resulting in an integrated MAC® + MAR® System.

The MAC® System allows to extract, convey and cool the bottom ash of a solid fuel fired boiler in a completely “dry” way, while the MAR® System recycles into the combustion chamber the dry bottom ash mixed with high unburned content fly ash.

Particularly, the main targets of this new integrated system are:

1. Dry extraction of bottom ash with no use of water for ash cooling and conveying

2. Bottom ash elimination through the recycling into the combustion chamber

3. UBC reduction in the fly ash ■

Power

Dry Mill Rejects Handling

The MAGALDI MRS is a patented steel belt conveying system designed to handle in a dry way mill rejects from the coal mills to a storage silo based upon the well proven dependable MAGALDI Superbelt. The MRS is the first, fully dependable, mechanical mill rejects conveying system.

No more water is required, avoiding all environmental problems associated with a wet system ; no more plugging problems may occur, as could happen in pneumatic conveying systems.

The well proven Magaldi Superbelt features allow to handle any quantity of mill rejects with a fraction of energy required by traditional systems.

FLUIMAC system

The patented FLUIMAC system is an innovative system for the dry handling of bed ash from Fluidized Bed Combustion (FBC) boilers. The FLUIMAC system is characterized by low operation & maintenance requirements, long life of the equipment & parts, no usage of water in the ash processing at all. In addition, with the FLUIMAC system it is possible to increase the boiler efficiency by heat recovery from the ash.

"Flat Back" Coal Feeder

The MAGALDI "Flat Back" Coal Feeder is an efficient, cost effective method of reclaiming stockpiles and feeding material.

Eliminate Costly Civil Work and Site Preparation

• In-ground hoppers, grids, tunnels and underground belt systems are no longer needed.

• It requires only solid, level ground conditions for installation.

• Material forms its own surge hopper, eliminating expensive fabricated upper hoppers and structures.

Versatile and Efficient

• "Flat Back" hopper less design allows material to be pushed by dozers or vertically discharged from front-end loaders, trucks, clam shell buckets and excavators directly onto the integral drag conveyor.

• Rugged machine frame design for dependable performance and availability.

• Mobility options include skid, wheel, crawler or railroad wheel mounting to match any reclaim condition.

• Available with rotary pick breaker for stockpile applications requiring size reduction and feeding from one unit.

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Foundry

Dependable handling of bulk materials is important to ensure the highest productivity in many industries.

It is difficult for traditional conveyors to withstand the high temperature, the heavy weight, the abrasiveness or the sharp edges of diverse bulk materials. Conventional conveyors often cause production losses due to unforeseen failures, require excessive maintenance and are noisy and dusty.

During the last 40 years, hundreds of successful installations confirm that the Magaldi Superbelt conveyor (in its different configurations) is the dependable and environmentally friendly solution for these problems.

The Magaldi Group supplies a wide range of equipment to different industrial sectors based on the Magaldi Superbelt technology. All applications of the Magaldi Superbelt distinguish themselves from competing technologies by:

• Unchallenged dependability

• High temperature operating ability

• Impact resistance

• Low wear, long life

• Low operational & maintenance costs

• Safe and clean working environment

• Cost-effective retrofitting

Features:

The Magaldi Superbelt is made up of a steel mesh belt, which carries partially overlapping steel pans forming a virtually sealed belt conveyor.

The patented method of connecting the pans to the belt leaves all components free to thermally expand in any direction, without permanent deformation. As a result, the Magaldi Superbelt withstands temperatures higher than any other known competitive conveyor.

The Conveyor

The Magaldi Superbelt is supported by carrying idlers across the entire width, in order to withstand heavy mechanical loads. In impact areas the idlers can be closely spaced or mounted on a shock absorber frame.

The driving force is transmitted by friction between the head pulley and the belt, while a pneumatic take-up device on the tail pulley supplies a constant tension.

Since there is no relative motion between the belt and the material transported on it, the wear of the Magaldi Superbelt is negligible.

Superbelt N

The Superbelt "N" type conveyor is used for horizontal and inclined transportation (up to 28°) of bulk materials as cement clinker, lime, magnesium oxide, lead, zinc and manganese sinter, foundry sand, pellets, chips. It is generally used in place of rubber belt conveyors, drag chain conveyors and vibrating conveyors.

Superbelt E

The "E" type is a conveyor belt provided with transversal cleats for conveying bulk materials up to 55° inclination. It is used in place of corrugated side walls rubber belt conveyors, bucket elevators and deep pan conveyors.

Superbelt P

The Magaldi Superbelt P type has been designed to withstand very high mechanical impacts caused by heavy material weighing hundreds of kilograms.

The Superbelt "P" type conveyor is used for horizontal and inclined transportation (up to 35°) of heavy pieces such as castings, sprues, forgings, scraps, crop ends.

It is generally used in foundries for transportation of castings at the outlet of Didion drums, shake-outs or vibradrums.

It can resist to the shock loads generated by hammers, air cannons or manipulators during the sprue removal operation.

Superbelt PR

The Magaldi Superbelt PR type has been designed to facilitate the sorting operation in foundries.

Its design without sidewalls, allows the operators to drag the castings over the lateral chutes during the sorting operation.

It is mainly used at the outlet of the shotblasting, either continuous or batch.

Thanks to the Superbelt smooth and noiseless operation, the equipment can be used as a moving worktable, chipping and grinding of the castings can be safely done directly on the belt, without the need of lifting each single casting to place it on the lateral worktables.

Superbelt PZ

Some applications may require a completely flat surface of the belt. For these types of condition Magaldi has developed a special version of the Superbelt P type that maintains all the properties of the original one with the addition of an extra feature consisting of a belt surface without steps in the overlapping area of the pans.

Applications with robot or where the precise and repeatable position of the casting is required.

Casting sorting and degating, especially with automatic or semi-automatic systems (SUPERBELT PZ).

Performance:

Dependability

Undoubtedly the best feature of the Magaldi Superbelt is its dependability. Unlike other conveyors, the Magaldi Superbelt cannot fail suddenly and keeps on running even in emergency conditions.

A rubber belt can be burned by hot material or can be cut by a sharp piece, in an apron conveyor a chain can suddenly break, whereas none of similar events can affect the Magaldi Superbelt.

Even if the belt gets damaged locally, it continues to operate without danger of unexpected failure until the next maintenance outage.

High temperature operating ability

The Magaldi Superbelt withstands higher temperatures than any other conveyors because all its components are made of steel and are free to expand in any direction, without distortion. Pans and mesh steel quality are selected to meet any specific requirement.

Impact resistance

The Magaldi Superbelt has a natural elasticity and is supported by idlers across its entire width, which gives it a great ability to absorb mechanical impacts. In impact areas, the idlers are closely spaced so that the impact is distributed over a large area.

Low wear, long life

• Wear of the Magaldi Superbelt is negligible, because there is no relative motion between the belt and the material transported on it, and there are no internal moving parts subject to friction.

• As a result, even in the heaviest applications the average expected life of the Magaldi Superbelt is 10 years.

Low operational & maintenance costs

• The Magaldi Superbelt has no chains, wheels or sprockets so the only points requiring lubrication are the drive and tail pulley bearings. Idlers and rollers are life lubricated.

• Replacement of idlers is easy and quick, just like in rubber belt conveyors.

• The Magaldi Superbelt requires less power than apron conveyors or drag chain conveyors.

• The Magaldi Superbelt lasts longer than other conveyors.

Safe and clean working environment

• The overlapping belt pans fit so tightly that there is no clearance between adjacent plates, so no leakage of fines occurs.

• The Magaldi Superbelt runs smoothly, with a noise level normally under 65 dB.

Cost-effective retrofitting

The concept of the Magaldi Superbelt is similar to traditional belt conveyors in most cases, which allows retrofitting.

The carrying idlers and return rollers can be fitted on existing frames of rubber belts or apron conveyors, turning old equipment into a much more dependable Magaldi Superbelt conveyor.

Fields of Application:

• Casting Cooling

• Casting sorting

• Sprue removal (degating)

• Shotblast loading and unloading

• Mold Conveying

• Furnace Feeding

• Sprue Crusher feeding

• Hot sand transportation

• Lead sinter conveying & cooling

• Replacement of the SBC rubber belt in Disamatic or Loramatic molding lines (SUPERBELT PZ).

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Cement / Clinker

Transport and conveying systems are an essential part of a modern industrial plant. The failure of a rubber belt conveyor or the need to re-adjust a pan conveyor imply an unacceptable loss of production and reduces the overall efficiency of the plant. MAGALDI has been providing for 40 years reliable solution for the safe handling of raw materials and high temperature clinker.

Hot Clinker Conveying

Dependable handling of bulk materials is important to ensure the highest productivity in many industries.

It is difficult for traditional conveyors to withstand the high temperature, the heavy weight, the abrasiveness or the sharp edges of diverse bulk materials. Conventional conveyors often cause production losses due to unforeseen failures, require excessive maintenance and are noisy and dusty.

During the last 40 years, hundreds of successful installations confirm that the Magaldi Superbelt conveyor (in its different configurations) is the dependable and environmentally friendly solution for these problems.

The Magaldi Group supplies a wide range of equipment to different industrial sectors based on the Magaldi Superbelt technology. All applications of the Magaldi Superbelt distinguish themselves from competing technologies by:

• Unchallenged dependability

• High temperature operating ability

• Impact resistance

• Low wear, long life

• Low operational & maintenance costs

• Safe and clean working environment

• Cost-effective retrofitting

The Magaldi Ecobelt is a patented conveyor whose main feature is the ability of handling bulk materials in an enclosed steel casing, which guarantees a total environmental protection.

The technical characteristics of the Magaldi Ecobelt are unique for its capability of handling hot, dusty and abrasive bulk materials of any lump size without limitation of temperature and hardness and with inclination ability up to 45°.

The Magaldi Ecobelt Conveyor is based on the well known technology of the Magaldi Superbelt, a steel belt conveyor with hundreds of worldwide references.

The Magaldi Ecomag/Ecobelt basically consists of a Magaldi Superbelt contained in a steel casing. Their exclusive features include:

• Low wear and a long life, because there is no relative movement between the belt and the material transported on it.

• High dependability, because there is no risk of sudden, unexpected failure.

• Easy maintenance, since all rollers’ bearings are located outside of the casing.

• No dispersion of dust or gas into the ambient, ensuring a clean & safe working environment, thanks to the completely enclosed casing.

• High temperature resistance, allowing the extraction and conveying of very hot materials.

• Impact resistance, for a easy transportation of heavy pieces.

• Low noise level and low power usage.

Features:

The Magaldi Superbelt is totally enclosed in a steel casing but all the rotating components are left outside in order to allow their maintenance while the conveyor is operating.

Moreover the Magaldi Ecobelt is provided with a number of “dragging buckets” that collect the fine particles accumulated at the bottom of the casing and then bring them back on the carrying side of the belt.

The Magaldi Superbelt cannot break suddenly; this guarantees the continuing operation of the conveyor and of all the equipment connected to it even under the most extreme operating conditions such as material high temperature and abrasiveness.

For these reasons the Magaldi Ecobelt conveyor is the ideal component for the MAC Systems (Magaldi Ash Cooler). In this application it is positioned downstream the primary crusher and thanks to the counter-flowing stream of air, it becomes an air-ash heat exchanger.

The Magaldi Ecomag-Ecobelt can be designed for:

• conveying capacities from 1 to 250 m3/h,

• available belt widths from 300 to 1200 mm

• inclinations up to 45°.

Volumetric and Gravimetric Dosing

Magaldi has developed a reliable belt feeder for handling hot and abrasive materials.

The operation is similar to traditional belt feeders installed under hoppers with the benefit of a higher resistance to shock loads given by the sturdiness of the Magaldi Superbelt.

This type of feeder can be easily transformed in a weighing feeder by mean of load cells.

In this case the entire conveyor is supported by a load cell at one end and pivots at the other end.

The actual feed rate is determined by integrating the belt speed, which is taken from a tachometer and the weight signal which is given by the load cells.

The controller compares the actual feed rate with the desired feed rate and it adjusts the belt speed in order to deliver an uniform feed rate.

This unit is capable of handling material up to 600°C. The weighing cell is protected by the radiant heat of the transported material.

Silos Loading

Magaldi Tsubaki chain bucket elevators cover most of the requirements for the vertical transport of bulk materials handled in the cement and power industry in the most reliable and economical way.

The Magaldi Tsubaki chain bucket elevators are a synthesis of state of the art technology and quality engineering and are available in a variety of types ad sizes to meet every requirement for conveying capacity and height.

Spillage Recovering

In many plants more than 80% of the material dispersed into the factory comes from conveyors spillage. Nowadays it is becoming ever more important to remove such spillage in order to avoid environmental pollution and to reduce operating costs.

The Magaldi Spill chain solves this problems: applied under the head section of the conveyor, it recovers the material scraped by the cleaning systems installed on the return path of the belt.

While for some sticky or toxic material, or for a complete cleaning of the unit, the Magaldi Spill-chain can be applied over the entire length of the Conveyor.

Magaldi Industrie manufactures four different types of Spill-chain, in order to cover all client needs.

Coal Yard Reclaiming

(see above)

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