alternative fuels and substitute raw

materials, their handling and storage AUMUND GroupSaalhoffer Str. 17 47495 RHEINBERG Germany . www.aumund.com Author – Barry Woodbine.

Sustainability:

During recent years the Cement industry has suffered significant increases in operat-ing costs driven in particular by spiralling energy prices plus pressure from environ-mental lobbies to reduce dependence on fossil fuels and reduce CO2 emissions overall. Considering the production of a ton of conventional Portland cement generates almost a ton of CO2 and in terms of total greenhouse gas emissions for all Industries worldwide places cement second only to power in the scale of global polluters.

These factors have generated an increased awareness of alternative fuel possibilities for kiln firing and substitute raw material options for cement production, reflecting also an increased demand for blended ce-ments particularly including ground granu-lated blast furnace slag (GGBFS); for every ton of GGBFS included in the final blended cement the total CO2 production is reduced by around 800 Kg…

In addition, burning at kiln high tempera-tures has proven an effective solution for the disposal of waste materials, such as scrap vehicle tyres and sewage sludge, with a positive environmental impact and often the overall economics are enhanced by grants paid from central government creating a win-win-win argument for these new processes.

Whilst the processes behind the use of al-ternative fuels and substitute raw materials is well understood the range of materials involved is extensive and the varying han-dling characteristics of these materials, from light dry vine prunings through to filter press cake represents a considerable chal-lenge for the plant designer.

In general these materials are difficult to handle reliably varying from extremely free flowing to very sluggish and prone to bridg-ing and blockage and liable to agglomerate in storage. Granulated blast furnace slag for example is also extremely abrasive with wear rates some five times greater than clinker in comparable installations.

The Aumund Group, including B&W and Schade, recognise these challenges and have developed innovative solutions for many of these handling problems with spe-cial adaptations of existing designs tailored to suit the specific demands of these new applications. Combining the traditional strengths of the Aumund Group products with new concepts to improve plant design flexibility and reduce project costs Aumund offer fast track effective solutions allowing clients to capitalise on short term market positions and maximise plant profitability.

Market Conditions:

In today’s rapidly changing international market the ability to react quickly to market volatility and take advantage of short-term market positions is essential if operators are to maximise profitability and return on capital invested.

This is particularly true for alternative fuels such as for example Petroleum Coke which is traded internationally and subject to wide price swings changing the relative econom-ics of fuel mix.

Similarly materials such as Flue Gas De-Sulphurised Gypsum (FGD) Gypsum often known as Synthetic Gypsum is widely used in other industries and as such pricing is market driven and the relative economies of use vary accordingly.

With alternative fuels derived from waste materials, such as scrap tyres, the market is generally subsidised by government lev-ies which may be subject to policy change outside the control of the cement producer, thereby changing the relative economies of use.

Under these conditions the cement manu-facturer has a difficult calculation to make when evaluating the payback period of any new plant investments dedicated to the handling of alternative fuels or substitute materials and as such reduced installation cost and flexibility are key issues when making these decisions.

- 2 -

Plant Handling Solutions:

As noted previously in the preamble to this paper alternative fuels vary considerably in their handling characteristics ranging from the very light such as Pro-Fuel (waste pa-per and plastics) through to Pet-Coke de-rived from oil distillation.

Between there are a myriad of materials such as car fluff, carpet waste, tyre derived fuel (TDF), meat and bone meal (MBM), sawdust, refuse derived fuel (RDF), oil im-pregnated sawdust, wood chip, biomass, agricultural waste, oil seeds, chemical resi-dues (sludge), filer press cake and animal carcases to name but a few…

Whilst some fluid materials Cemfuel, chemical waste and similar liquids are de-livered by tanker the vast majority of these materials are delivered to the Cement Plant by conventional road tipping trucks.

The Samson surface feeder developed by B&W has particular benefits uniquely suited to the handling of alternative fuel materials in general but particularly where these are to be delivered to the plant by tipping truck.

As an example of the integration of han-dling equipment into the cement process plant the following project case study illus-trates examples of raw material, clinker, additions materials, finish cement plus solid fuel handling as a complete and integrated package.

This plant is located in central Spain where over recent years the rapid development of extensive road and rail infrastructure plus expansion of house and commercial build-ing has fuelled an unprecedented expan-sion of cement demand making the Span-ish market now the largest in Europe…

To satisfy this extra capacity from local production has demanded an extensive development of the indigenous cement in-dustry with the expansion of practically every existing facility plus the development of Greenfield sites almost unique in the present European market.

As a Greenfield site the designers enjoyed exception flexibility in the equipment layout and choice of handling solutions.

Figure 1

As illustrated in figure 1) the new plant of Cementos Balboa commissioned in 2006 is an excellent example including Belt-Bucket plus Chain-Bucket Elevators and Clinker Transports from the Aumund Group.

Figure 2

As illustrated in figure 2) an Aumund type BW-G belt-bucket elevator raises the raw meal to the pre-calciner tower.

- 3 -

Similarly the Aumund belt bucket elevators are used to raise the finished cement to silo storage using a combination of air-slides to convey the cement to the elevators and from the elevators to the silos, figure 3).

In addition Cementos Balboa decided to utilise the Samson feeder from B&W (part of the Aumund Group since 2002) for the intake of additions material, clinker and limestone delivered by tipping truck.

The Samson provides a buffer holding ca-pacity plus a controlled rate discharge to an Aumund BW-Z chain-bucket elevator.

The elevator discharges at high level to a storage building using a belt conveyor with travelling tripper to distribute the material in the defined storage sections. As illustrated in figure 4) the Samson may be installed on the surface eliminating the need for expen-sive deep pits and underground hoppers traditionally used in these applications.

Figure 3

Figure 5

As illustrated in the diagram figure 5) mate-rial is drawn into the Samson body in a controlled stream virtually eliminating any free fall and therefore substantially elimi-nating dust generation at source. As a re-sult dust extraction requirements are sig-nificantly reduced and often eliminated unless handling very dusty material such as clinker where typically 15,000 m3 per hour of extraction is generally installed, roughly one third of the normal filter size for a compatible deep pit arrangement.

Figure 4

With this plant arrangement not only are the associated civil works and dust control equipment costs much reduced, giving a more economical total project capital and operating costs, the surface mounting con-cept allows greater flexibility in equipment location and easy relocation should plant development demand.

- 4 -

- 5 -

In addition to the surface mounted Samson feeder as illustrated in figure 6) Cementos Balboa incorporated a second Samson feeder for the intake of coal from railcars.

This is the first such application utilising the Samson feeder principle for under rail in-stallation, figure 7).

As illustrated above (figure 7) the Samson receives the coal directly from hopper bot-tom railcars requiring the minimum excava-tion depth and thanks to the raised dis-charge provides a simplified transfer to the ongoing belt conveyor equipment.

As illustrated in figure 8) the Samson body and belt are actually wider than the typical railcar outlet and therefore the material flows freely into the Samson body with the absolute minimum of free fall.

Figure 6 Figure 9

Material Free-Falls

Displaced Air Stream

Figure 7

In a typical deep hopper (figure 9), whether receiving from road or rail, the material free falls into the hopper conical section allow-ing particulate separation and as such dust particles are freed from the bulk of the ma-terial flow.

As the material accumulates in the conical section of the hopper the material level rap-idly increases displacing air and causing air within the hopper body to be expelled at high velocity.

The freed dust particles from the incoming material stream are swept upwards by the fast moving air stream and ejected at the hopper inlet unless controlled by very high capacity dust extraction equipment.

Figure 8

With the Samson principle the free fall dis-tance is minimised reducing the level of particulate separation and material terminal velocity and therefore also the velocity of the displaced air is significantly reduced thereby significantly reducing dust genera-tion requiring less dust extraction in even the most environmentally sensitive location.

Whilst the Cementos Balboa project is an excellent example of the combination of Aumund Group products in a Greenfield cement plant project the bulk of the devel-opments in the Spanish market have been plant upgrades or extensions.

In addition projects to introduce alternative fuels or substitute raw materials with a view to reducing production costs and reducing the plant carbon footprint.

An early example at the Holcim Jerez (fig-ure 10) plant includes a Samson surface feeder and a Schade circular storage sys-tem to receive pet-coke from tipping trucks and provide an automated storage and re-claim system.

The pet-coke is raised by inclined belt con-veyor from the Samson discharge to the Shade radial stacking boom within the cir-cular storage dome, figure 11).

The pet-coke is reclaimed by the chain scraper boom to a central outlet and con-veyed out to the fuel bunkers and milling plant.

Another similar plant installed at the Car-boneras works of Holcim where both coal and pet-coke are received from tipping trucks and discharged in this case to open storage using a radial stacking boom as illustrated in figure 12).

Figure 12

In both of these projects surface installation was a major factor in the decision process by simplifying the installation requirements.

Figure 10

Figure 13

Also in both of these applications the fuel is delivered using tipping trucks from the local port facility (for Jerez using the port of Cadiz and at Carboneras the local jetty) with a truck frequency of less than 3 min-utes providing an average handling rate of around 500 tonnes per hour.

Figure 11

It is also interesting to note on both of these projects no dust extraction is in-stalled and the equipment operates practi-cally dust free…

By eliminating the need for dust extraction equipment not only is the plant capital cost reduced the long term maintenance and operational cost is also reduced.

- 6 -

The range of combustible materials suit-able for use as alternative fuels for the ce-ment kiln is expanding daily.

In the cement industry alternative fuels and substitute raw materials are frequently con-sidered together as a package as both are mechanisms by which the plant carbon footprint of the may be effectively reduced as part of an integrated strategy.

Going back to the Carboneras plant of Hol-cim; thereto alternative fuels are utilised to part substitute for coal and pet coke.

Illustrated above, figure 14) a Samson sur-face feeder housed within the building above receives impregnated sawdust direct from tipping trucks. The Samson design being the same in principle as the other units illustrated herein but in this case housed within a separate building to reduce pollution risk to an absolute minimum.

Whilst the handling characteristics of the wide range of alternative fuels as listed in above varies significantly the Samson sur-face feeder is able to receive, store and discharge virtually any combination.

For example a Samson surface feeder supplied to Cemex for their San Vicenti project handles both TDF and Sludge with a very similar machine supplied to Holcim for handling Pro-Fuel…

Returning again to the Holcim Carboneras plant here in addition a new blended ce-ment facility was installed to utilise granu-lated blast furnace slag, figure 15).

Of the various substitute raw materials util-ised within the cement process granulated blast furnace slag (GBFS) represents the largest volume by far with substation ratios of up to 85 %.

The raw GBFS material may be trans-ported by any conventional means but generally arrives at the cement plant in conventional road tipping trucks.

Figure 15

Figure 14

Illustrated figure 16), again at the Holcim plant in Carboneras (Spain), the GBFS is discharged to ground stockpile and trans-ferred by loading shovel to a Samson sur-face feeder providing a buffer holding ca-pacity and controlled feed rate to the mill bunker via an inclined belt conveyor.

Figure 16

GBFS is prone to agglomeration in storage and forms into large boulders which must be removed or crushed before reaching the mill bunker.

For this purpose the Samson may be sup-plied with a reject grill at the entry, as at Carboneras, or a screen at the discharge or an integral Sizer to control lump sizes.

- 7 -

Alternative Fuels:

The wide Apron-Belt design of the Samson makes it almost impervious to the material handling characteristics being equally suited to light and dry materials or to heavy, wet and sticky materials.

Figure 33

As illustrated above, figure 17), generally the belt width is greater than the material bed depth and therefore bridging and blockage is almost impossible.

Also, thanks to the wide apron-belt design the Samson receives material at low level and therefore may be surface mounted.

By avoiding the need for expensive and permanent concrete foundations with deep pits and underground hoppers the Samson solution offers significantly reduced project costs with the flexibility to locate the equipment to suit the plant requirements independent of ground conditions. By com-bining the flexibility of surface mounting combined with the ability to handle almost any material type makes the Samson par-ticularly suited for Alternative Fuel applica-tions.

Illustrated above (figure 19) the Samson receives tyre chip direct from tipping trucks and loading shovels and combined with a screw metering feeder and vertical elevator discharging to the pre-calciner.

Tyre chip is a notoriously difficult material to handle and store reliably… The equip-ment in the illustration above (figure 19 and 20) handles doubled chipped material which means the initial chipped material (single chipped) has been passed through the shredder a second time to reduce the average material size down to 100 mm ap-proximately.

Figure 02

Figure 19

Figure 17

Figure 20

Figure 18

- 8 -

All truck and most passenger car tyres con-tain steel wire to reinforce the tyre struc-ture. The steel wire is cut by the tyre shredder but if the shredder blades are worn the resulting chips have strands of wire extending from the rubber part. This is typical of the material seen and when stored the free wire tends to bind together creating significant handling problems.

As illustrated above (figure 21) a sample of typical double chip material, with a calorific value typically 25 % greater than coal; this material is a very cost effective alternative.

Illustrated above (figure 22) a Samson storage and feeder unit is installed at the Holcim Theodore plant in the USA handling single tyre chip with an effective holding capacity of 100 tons.

As illustrated opposite (figure 23) the Sam-son discharges to a belt conveyor installa-tion transferring material to the pre-calciner tower.

To control the Samson discharge rate down to around 5 tonnes per hour a weigh belt feeder with load cell mounted weigh idler, as illustrated in figure 24) is installed across the Samson discharge.

The weigh feeder extracts material from the Samson head chute and using a scalping drum feeds this material at a variable rate, controlled by varying the feeder belt speed, on demand from the plant process control system.

There are many other examples of the Samson equipment for handling a whole range of materials but always based on the same general design principle.

Shown above (25) the Samson receives Pro-Fuel (a mixture of waste paper and plastics) at Maerker Cement in Germany.

Figure 21 Figure 24

Figure 22

Figure 25

Figure 23

- 9 -

The material is prepared off site and deliv-ered to the plant using dedicated contain-ers mounted to tipping vehicles which dis-charge direct to the Samson entry see fig-ure 26) below.

To prevent wind blown material escaping from the Samson entry a large reverse jet filter unit is installed above the tipping point as illustrated below.

Sawdust and wood chip along with other forest products are also potential alterna-tive fuels, as illustrated in figure 28 below.

Either used directly of combined with com-bustible solvents to increase the calorific value this is an interesting alternative fuel where the supply logistics are viable.

Figure 29

In this application the Samson provides the ideal solution for handling this cohesive material discharging at a controlled rate to a drag chain conveyor to transfer the mate-rial to a storage silo.

Figure 26

These materials could be classified as Bio fuels such as Chicken Litter as handled by the Samson feeder equipment as illustrated below, figures 30) and 31).

Figure 30

Figure 27

Figure 31Figure 28

- 10 -

In this installation six Samson receiving units plus six Samson sub-screen feeders handle litter for this 38.5 mW. power plant handling some 450,000 tons annually.

As is illustrated above, figure 32, the Sam-son receiving unit takes the material from the tipping truck providing a buffer storage capacity and controlled feed rate to the fol-lowing disk screens.

Beneath the disk screens a Samson sub-screen feeder receives the graded material and the oversize is rejected.

Bio Fuels in general are an interesting sub-ject since in countries observing the Kyoto Protocol bio fuel is considered as a CO2 free fuel and therefore can effectively re-duce the cement plant CO2 generation.

Whilst not strictly an alternative fuel, filter press cake (sewage sludge) can earn use-ful revenue for the cement plant operator where this material may be effectively treated (incinerated) through the kiln.

Thanks to the high kiln temperature any potentially harmful bacteria etc. are effec-tively sterilised and the residue combined into the clinker.

The sludge may be received direct from tipping trucks to a Samson surface feeder as illustrated in figure 33) and discharged at a controlled rate using twin screw feeder as illustrated below, figure 34).

Disk Screen

Figure 32

Figure 34

In the application illustrated above the sludge is handled onwards from the screw metering feeder using a progressive cavity type pump. Once plasticized by the screws the sludge becomes semi fluid and may be pumped down a 150 mm nominal diameter pipeline reducing handling problems and eliminating spillage.

Where large volumes of sludge are to be processed the Samson solution may be utilised as a horizontal silo as illustrated below, figure 35.

Figure 35

Figure 33

In this operation sludge is delivered to the plant by tipping truck to be received by a standard Samson surface feeder as illus-trated opposite (figure 33) and then con-veyed to the storage units (35) using sim-ple belt or drag chain conveyors.

- 11 -

Although it is fair to say the European plants have lead the way in many respects these technologies are now being exported by the major cement producing groups to their subsidiaries and partners worldwide.

Even in coal and oil rich Indonesia cement producers are investing in alternative fuel solutions to reduce their CO2 footprint.

Not only for environmental reasons but also economical and social benefits in that there are abundant local resources of Biomass and other combustible materials that can-not be reused or recycled and are therefore ideal kiln fuels, displacing mainly coal.

Indonesia has been a Party to the United Nations Framework Convention on Climate Change since 1 August 1994 and the coun-try ratified the Kyoto Protocol on the 3rd of December 2004 opening the way forward for the establishment of certified carbon offset schemes.

In particular Indocement have embarked on a project for the introduction of alternative fuels utilising the Clean Development Mechanism (CDM) with the resulting Certified Emission Reductions or Carbon Credits to be purchased by Finland and the Netherlands from this project.

The CO2 emission reductions from this pro-ject are due to biofuels which are regarded as CO2 neutral. The CO2 emissions from alternative fuels which are not biofuels are also included in the project specification. Alternative fuel types such as rice husks, saw dust, plastics, paper, textiles, used tires, waste oil, industrial liquids and solid waste are all considered in this overall scheme.

The social benefits arising from these ac-tivities can be seen in increased employ-ment for the preparation of the material and reduced landfill or other potentially polluting disposal activities.

Indocement is the second largest cement producer in Indonesia. The Company has integrated cement operations with a total annual production capacity of 15.4 million tons of clinker.

The Company was established in 1985 and currently operates 12 plants, nine of which are located in Citeureup, Bogor, West Java; two in Palimanan, Cirebon, West Java; and one in Tarjun, Kotabaru, South Kalimantan. In 2001, Heidelberg Cement Group, one of the world’s leading cement producers, based in Germany and operating in 50 countries, assumed a controlling majority shareholding of the Company.

Figure 36

The unit shown here (figures 36 and 37) at Indocement during testing illustrated the wide apron-belt design where the material depth on the feeder is actually less than the belt width and therefore bridging and blockage is totally eliminated.

Figure 37

- 12 -

So in conclusion the subject of handling and storage of Alternative Fuels is a com-plex, made so by the nature and potential variety of the materials involved.

In addition the installation of new facilities for the intake, storage and handling of al-ternative fuels is generally problematic in regards to the obtaining of the necessary permissions to burn such fuels.

For certification often a trial period of at least one year is required during which time the flue gas emissions must be monitored for any substantial increase in noxious gases. In some markets, the UK for exam-ple, burning of such materials must result in a reduction in pollutants; it is not adequate to simply equal the pollutant level associ-ated with burning conventional fossil fu-els…

In addition the use of alternative fuels will change the kiln chemistry and whilst the effects are generally now well documented there are still variable factors with the more exotic fuels which could limit their use.

For these reasons operators are reluctant to invest heavily in new plant during the trial period but nevertheless some new plant is inevitably required.

In this situation the Samson Surface Feeder is particularly attractive in that the permanent and expensive underground civil works associated with traditional truck intake solutions are completely eliminated making the installation more flexible whilst reducing the project costs.

As can be seen in the preceding section and in the following pages the Samson so-lution is a universal solution suitable for handling a very wide range of materials with the same basic design of feeder.

Therefore the Samson represents a lower investment risk being adaptable to handling other alternative fuels types or for example additions materials in other parts of the plant should the particular alternative fuel project be abandoned…

Substitute Raw Materials

Cement production is both heavily energy intensive and a major greenhouse gas pol-luter generating roughly 1 ton of CO2 for every ton of Ordinary Portland Cement.

Traditional raw materials, limestone, clays and shale incur significant costs for mining, crushing and handling all of which are en-ergy intensive activities often involving sig-nificant truck haulage with associated envi-ronmental problems.

Materials such as Fly Ash, Flue Gas De-Sulphurised Gypsum and Granulated Blast Furnace Slag are all co-products of other industries and as such their use in Cement manufacture is environmentally positive.

As with Pet-Coke the economics surround-ing the use of these materials depends upon the logistics involved in the delivery to the cement plant but where the resource is within reason close by to the consumer the economics are generally favourable.

If we begin by addressing the use of Fly Ash which is a co-product of coal fired power stations and is generally land filled with perhaps 30% used in other industrial processes in the most developed econo-mies.

With impending or actual land fill taxes ap-plied in most developed countries nowa-days the cost of disposal is significant and additional alternative uses are actively pur-sued and encouraged.

High Carbon Fly ash contains a significant level of carbon which acts as a fuel and when injected into the raw meal raises the temperature in the primary stage of the pre-heater resulting in nearly 30% increase in calcinations of the raw feed and therefore a higher kiln feed rate and an overall 10% improvement in clinker production.

On this particular test the corresponding reduction in energy consumption was equivalent to around 4% representing a saving of over 90,000 Btu/ton of clinker.

- 13 -

Although for the test referred herein the intent was to maximize the use of fly ash in the raw mix, fluctuations in the chemistry of the other raw materials limited the average addition of fly ash to 6% of the raw mix.

The fly ash requires no grinding and may be blended directly into the raw meal or may be inter-ground depending on the suitability of the plant layout.

Generally fly ash is delivered to the plant in road tankers and discharged to silo storage pneumatically.

Onward handling may also be by pneu-matic systems but where the material has to be raised the Aumund BW-G vertical belt-bucket elevator (figure 38) has proven an economic alternative with much reduced energy demand.

Typically in a direct comparison the belt-bucket elevator has demonstrated a reduc-tion of 75% in energy consumption, as illus-trated in the graph, figure 39).

The Aumund BW-G elevator is extremely well established over many years as the leading elevator design in the cement in-dustry handling raw meal and finished ce-ment, where reliability is paramount.

Another co-product of the coal fired power plant is Flue Gas De-Sulphurised Gyp-sum or Synthetic Gypsum which may be used as a direct replacement for natural gypsum as an additions material.

Synthetic Gypsum is notoriously difficult to handle and will blind, block and bridge with the slightest provocation and is disinclined to flow reliably in chutes or from tapered or coned hoppers.

The material is generally delivered in tradi-tional tipping type trucks and may be handed easily on conventional belt con-veyors.

Illustrated in figure 40) a B&W ship loading unit, including a Samson feeder, receives material from tipping trucks and deliver di-rect to small vessels for coastal shipment.

Figure 38

Figure 40

As can be seen from the material in the vessel hold even when freshly loaded the natural repose angle is very high and after a short period of consolidation is near verti-cal and can even be undercut when after even short term storage in bulk.

Based on Handling Rate - 200 t.p.h.

Power kW

Belt Bucket Elevator

Pneumatic Handling

Important Operational and Maintenance Savings

20m

30m

40m

50m

60m

70m

80m

90m

0 50

100 150 200 250

Pneumatic

Mechanical

Lift Height The Samson is the ideal solution to receive the material and provide buffer storage since, thanks to the wide apron-belt con-struction, bridging and blockage are com-pletely eliminated. Figure 39

- 14 -

- 15 -

However, for high volume longer term stor-age the extraction of Synthetic Gypsum from storage silos is a real science and cer-tainly conventional hopper bottoms and feeders are totally unsuitable, figure 41).

One of the only viable and proven options to recover Synthetic Gypsum from storage silos is the Centrex type circular feeder system from Aumund, see figures 42 & 43).

For the large scale storage of Synthetic Gypsum the Schade Portal Reclaimer based on Chain Scraper technology is the definitive solution.

Figure 44 Figure 41

Illustrated in figure 44) a portal reclaimer is installed within a longitudinal storage build-ing and arranged to recover material from the storage to a collecting conveyor run-ning parallel to the building long axis.

In this installation, to minimise the building height, the reclaimer is supplied with a twin boom chain scraper arrangement as illus-trated more clearly in the drawing below.

Logarithmic Shaped Extractor

Arm

Figure 42

Figure 45

Figure 43 The two booms, see figure 45), are joined with a unique connection arrangement to ensure smooth transfer of material and al-lowing maximum recovery of the stockpile volume.

Normally, since Synthetic Gypsum is stored within a building the material is loaded to the stockpile by overhead tripper conveyor as illustrated in the drawing above.

The design if the Tripper Car is also critical to the performance of the plant and this equipment may be supplied by Schade within the overall package.

Grinding slag for cement replacement re-quires only about 25 percent of the energy needed to manufacture normal Portland cement.

Generally the material is delivered to the grinding contractor or cement plant by tip-ping truck either direct from the steel works or where this is not viable then via ship and then from the port to the plant by truck.

Illustrated in figure 46) the GBFS is deliv-ered direct from the adjacent steel work (Corus Port Talbot) and loaded to stockpile using the B&W Stormajor mobile radial boom stacker…

The Stormajor is an excellent alternative to conventional fixed plant for the storage of granulated blast furnace slag where the total volume does not justify the high in-vestment of a stacker/reclaimer system. In these applications the GBFS is generally recovered by loading shovel …

On first inspection the material may appear easy to handle; but it is not…

Slag is notoriously abrasive, it is cohesive and will agglomerate in blocks and blind and block in chutes and hoppers and re-quires specialised equipment at every stage of the handling process to achieve reliability in operation.

The exact nature of the material will vary from different origins but as an example some GBFS is around five times more abrasive than Clinker…

Whilst a conventional belt conveyor may be used to raise the material to the mill bunker level the plant could be made much more compact using vertical elevation and for the purpose the Aumund BW-Z central chain bucket elevator is the ideal solution.

Figure 46

Flexible Rubber Casing Panels

Figure 47

However, recognising the problems already identified in handling this material Aumund tailor their design for this market specifi-cally with the following special features: -

• Central Forged Chain. • Labyrinth Seals. • Pre-Lubrication. • Fully Lined Buckets. • Toothed Buckets at 10th pitch. • Flexible Rubber Casings. • Rubber Lined Boot Casing. • Rubber Lined Drive Casing.

These features have been developed through the Aumund R&D department spe-cifically to address the particular issues presented by this material.

- 16 -

The forged chain with integral labyrinth seal arrangement and pre-lubrication (see figure 50) has, under test in the laboratory, re-duced wear by some 60%, effectively more than doubling the standard chain life with-out seals and without pre-lubrication.

For the largest installations where high vol-umes are required the Schade stacker and reclaimer equipment is appropriate, as il-lustrated below at the cement plant of CCB Italcementi in Belgium, figures 51 & 52).

Figure 48

Figure 51 Fully Lined

Buckets The GBFS is delivered to outside stockpile using a travelling and luffing rail mounted boom stacker with tripper conveyor running parallel to the stockpile, see figure 54).

Figure 52

Central Forged Elevator Chain

As illustrated in figure 52) the GBFS is re-covered automatically from the stockpile by a single boom portal chain scraper re-claimer which discharges the material to a troughed belt conveyor running parallel to the stockpile on the opposite side to the tripper system supplying the boom stacker.

Figure 49

Figure 50

The stacker and reclaimer and controlled automatically to allow simultaneous stack-ing and reclaim but operating from different sections of the stockpile.

Since GBFS is liable to agglomerate in storage and form large lumps effective stockpile management is required to en-sure first in first out wherever possible.

- 17 -

As an alternative to the portal type design the circular storage system may also be applied to GBFS storage and reclaim as illustrated below, figure 53).

As with any other plant handling this mate-rial wear is an issue also with the chain scraper reclaimer and for these applica-tions the outboard bearing chain is a stan-dard requirement.

The scraper chain and shovels are carried on the extended chain bolt and roller as-sembly, outside the material stream, and thus wear is minimised and the equipment operates at a much lower noise level also, see figure 54).

After reclaim from storage generally the GBFS is dried and ground in a vertical mill and after grinding becomes known as GGBFS, ground granulated blast furnace slag…..

The ground material (GGBFS) behaves very similar to finished cement and may be handled in the same manner.

For this purpose the Aumund type BW-G vertical belt-bucket elevator is the ideal so-lution, see figure 55.

Figure 53

Outboard Ball Bearing

Roller

Figure 55

The Aumund belt-bucket elevator is the in-dustry standard solution in this sector and may be found principally handling the raw meal to the pre-calciner and at the finished cement silos, key points in the cement plant where continuous reliability is para-mount.

Figure 54

- 18 -

As with the central chain elevator the Au-mund type BW-G belt elevator has been the subject of continuous development over many years culminating in a design of un-doubted reliability operating in continuous process applications running 24/7.

Typical examples are shown in figures 1) and 2) handling raw meal and finished ce-ment but illustrated below in figure 56) is shown the same elevator design incorpo-rated into a grinding plant to raise the GGBFS to silo storage.

Also in this application the GGBFS is deliv-ered to the bucket elevator by air slide and distributed to the silos similarly.

The belt-bucket elevator represents a sig-nificant advantage compared to other alter-natives such as for example air-lifts where the power demand and wear rates are ex-cessive generating much higher operating costs.

In these applications the Aumund BW-G Belt-Bucket elevator is unquestionably an effective and reliable solution proven in many hundreds of references worldwide…

In parallel to the development of new proc-ess to suit these changing market condi-tions the traditional demands of handling the raw materials for cement production and cement clinker remain paramount and the key to reliability and availability in the production of cement; demanding close attention to every detail.

Clinker Storage:

The storage of hot cement clinker is fun-damental to the cement production process and involves some special design features not found in general storage silos.

Figure 57

Figure 56

Aumund offer purpose designed steel silos as illustrated above (57) complete will all associated input and output conveyor sys-tems including bridges, trestles and trans-fer towers either as a supply or engineering only package for local manufacture.

There are many alternative storage design themes based on concrete constructions such as illustrated below, figure 58).

Figure 58

Similarly there are many alternative solu-tions to recover the material from storage.

- 19 -

For example the classical storage structure design is illustrated below with three dis-charge conveyors based on the Aumund KZB design.

Using three conveyors around 60% of the total storage volume may be recovered wi-thout manual intervention.

For the recovery of the storage material Aumund offer another solution based upon the “Mole” or “Molex” automated reclaim system allowing almost the entire silo con-tents to be effectively recovered.

Both the Mole and Molex designs are based on a chain scraper conveyor princi-ple mounted to a slewing ring in the centre and carried on rails around the silo periph-ery with a travel drive system.

The central section of the stockpile, ap-proximately 40% of the total capacity, is recovered by gravity with the remainder recovered by the mole system.

The mole scrapes the clinker to the central discharge point and discharges to a single type KZB pan conveyor.

The original design “Mole” allows the com-plete chain scraper conveyor to be im-mersed in clinker requiring only a flat bot-tom silo design.

Figure 61

Figure 59

Illustrated in figure 61) the Mole terminates to a central column which also supports the input conveyor bridge above to minimise loadings on the building structure.

The lighter “Molex” design assumes the chain scraper conveyor will be stored in a garage formed by concrete sections into the silo structure and therefore protected from the direct clinker load above.

Figure 62

Figure 60

A typical garage design is illustrated above (figure 62) with the Molex stored within ready to recover material travelling to the right side direction.

- 20 -

The mole concept has significant advan-tages over a traditional design with gravity only discharge in that only one discharge tunnel is required and similarly only one discharge conveyor…

The illustration above (figure 63) shows a typical arrangement with the area coloured red to be recovered by the Mole.

Since the bulk of the storage is live and available for discharge the effective storage capacity is fully realised.

To give an idea of scale the picture below shows a machine under construction in our production plant at Rheinberg, figure 64).

The chain scraper conveyor is illustrated below (65) showing the scraper shovels designed to always recover material from one face of the stockpile.

Environmental Pollution:

Environment pollution by fugitive dust is a major issue influencing the design of all modern Clinker Transport and handling systems throughout the cement plant.

Figure 63

Figure 66

At the silo outlet Aumund have a solution for the metering of material to the extrac-tion conveyor system and the control of dust as illustrated in figure 66).

Figure 64 Material flows from the silo under gravity to the discharge gate which generally sits above a type KZB pan conveyor.

Figure 67

Figure 65 By rotating the clam-shell half-door ar-rangement, see figure 67), the flow from the silo may be isolated and since this function is motorised the discharge of the silo may be planned by remotely selecting the designed discharge pattern.

The load sectional area of the ongoing pan conveyor is controlled by an adjustable gate and therefore the flow rate may be set according to the process demands.

- 21 -

Introduction – Import/Exports:

With ever expanding demand for cement products in the Middle and Far East cou-pled with a relative stable market within Europe and cooling demand in the USA it is increasingly difficult to predict world trends for the trading of clinker and finished cement.

As we have discussed relative to alterna-tive fuels and substitute raw materials the effect of global awareness of environmental and atmospheric pollution plus obligations entered into by the major cement manufac-turers under the cement sustainability initia-tive further complicates the market.

Continued expansion in the Middle East in particular is likely to generate substantial clinker overcapacity in particular which could be available for export, political con-siderations permitting.

Similarly the production of clinker in low energy cost environments is attractive combined with local grinding plants, for ex-ample in Europe and the USA, is likely to lead to increased trading volumes.

To further complicate transportation re-quirements we must also consider the re-quirements for blended cements not only for environmental reasons but to recognise the importance of physical properties par-ticularly of slag cement in marine or high-way applications exposed to salt.

The result of these changing trading pat-terns is generating a demand for new ex-port and import facilities for seaborne car-goes plus plant intake facilities for materials delivered by road and rail.

However, the trade pattern is ever chang-ing and whilst investment in permanent new production plant can be justified it is not so easy to make a case for high in-vestment levels in new import/export facili-ties at ports and terminals often outside the direct control of the cement producer.

In this respect flexibility and fast track availability is essential of the operator is to realise trading opportunities with minimum investment risk.

For the export of both raw materials and clinker the Mobile Shiploader offers com-plete flexibility without sacrificing either per-formance or environmental pollution stan-dards.

Figure 68

The operation above (figure 68) is a typical example utilising a mobile Shiploader to export raw materials on a general cargo berth receiving direct from tipping trucks.

This berth is also shared with mobile har-bour cranes for container and general cargo handling making best use of the available quay space.

At this particular port in Italy three mobile Shiploader plus around a dozen mobile harbour cranes service the complete port complex eliminating the need for any fixed port infrastructure or permanent civil works.

Figure 69

- 22 -

Similarly in shown in figure 69) the equip-ment may be installed at inhospitable loca-tions in this case loading Olivine rock to ships up to Handymax size.

Mobile Shiploaders are often supplied complete with integral Samson feeder units (see figure 68) to accept material direct from tipping trucks allowing export of most dry bulk cargoes from truck to ship.

For the movement of raw materials and in particular aggregates on inland waterways barge traffic is a common solution.

The B&W Stormajor mobile barge loader illustrated in figure 70), operating in Russia, loads aggregates (mainly Gabbros) to barges typically of 5,000 DWT.

Around both Moscow and St. Petersburg there is a real shortage of suitable aggre-gates and therefore material must be brought in for concrete and road building.

Clearly barge traffic is both an economical and environmentally sound solution allow-ing large volumes of aggregates to be de-livered into the city with minimum impact on the already overloaded road infrastructure.

For the loading of these barges the Stor-major, with its cantilevered outloading boom, is an excellent solution allowing the barge to be moored in deep water away from the river bank using the boom out-reach to load and trim the cargo.

Loading rates to 1,500 tonnes per hour are practical and, thanks to the integral Sam-son feeder material may be received direct from tipping trucks eliminating the need double handling.

In addition to stockpiling and barge loading the Stormajor is also suitable for railcar loading (71) and when supplied with an in-tegral weighing system allows a known quantity of material to be loaded to each railcar eliminating expensive overloading…

Figure 71

Figure 70

As a fully mobile autonomous machine the mobile Shiploader and Stormajor offer real flexibility for dry bulk cargo exports and in particular for cement clinker which we shall explore in more detail later in this paper.

Figure 72

For every bulk export facility there is a cor-responding import facility and for this pur-pose the Eco-Hopper by Aumund is a flexi-ble solution for gear vessels and mobile harbour cranes alike… See the section of this paper dealing with Clinker imports….

- 23 -

Imported Clinker:

With spiralling energy costs and continually changing economics within the cement in-dustry worldwide there are geographical areas where clinker production may be economical but demand is slack and there-fore the excess clinker capacity may be exported to satellite grinding plants in other countries where clinker capacity is not available or cost prohibitive.

Often the clinker will be exported by road truck and ship to be imported by grab and then transferred to the grinding plant using a fleet of tipping trucks working on a merry-go-round principle.

Clinker imports are generally handled by geared vessels with on-board grab cranes able to discharge without the need for fixed shore-side equipment such as continuous ship unloaders.

Discharge by grab is notoriously dusty and a real environmental hazard if not properly managed using a dust controlled grab hop-per by Aumund as figure 73) below.

The “Eco-Hopper” comprises an inner and outer hopper with Flex-Baffles between al-lowing the material to flow freely into the hopper but constraining and back flow to minimise dust generation.

Figure 74

Air displaced by the falling material is evacuated from the hopper inner bowl by reverse jet dust filters mounted around the hopper periphery between the inner and outer garners.

Figure 73 The Eco-Hoppers as illustrated (figure 73) discharge direct to quayside belt conveyors using the Aumund control gate as featured previously, see figure 66). However, the hopper may discharge direct to trucks us-ing the Aumund dust controlled loading chute as illustrated below, figure 75).

Figure 75

- 24 -

Clinker for satellite grinding plants may be imported by ship and discharged at a local port direct to tipping trucks for transfer to the grinding plant, as shown in figure 76) in Portugal operated by TDCIM (Cimpor).

In this plant all of the clinker and additions materials (gypsum etcetera) intake is by Samson surface feeders discharging direct to vertical elevators for distribution to portal and dome type storage.

Illustrated above in figure 77), the dome storage facility uses twin Samson surface feeders, with side vehicle entry, providing a compact layout to reduce the total plant footprint.

In this and many similar installations the benefits of surface mounting are clear in reducing civil works costs plus providing flexibility in plant location almost independ-ent of ground conditions.

Particularly where equipment is located in a port environment by avoiding deep pits wa-ter ingress is not longer an issue…

Clinker Exports:

For the export of Cement Clinker the Au-mund Group offer a unique solution based on a fully developed Mobile Shiploader de-signed to operate on an existing berth without fixed port infrastructure.

Figure 76

Figure 78

Illustrated in figure 78) a Mobile Shiploader operates at the port of Gizan loading ves-sels typically to Handymax size receiving material from the inland cement plant of Southern Province Cement.

The clinker is transferred to the port on a fleet of tipping trucks and stored locally un-til a ship is chartered. The Shiploader will receive material either direct from the tip-ping trucks or form the local storage using large loading shovels.

Illustrated in figure 79) the integral Samson feeder is equipped with a full enclosure and integrated dust extraction to minimise pollu-tion at the loading point.

However, in any ship loading operation the bulk of the dust generated is always at the transfer from the boom conveyor to the vessel hold where a vertical free fall of around 20 metres may be expected.

Figure 19

Figure 77

Figure 79

- 25 -

To minimise dust pollution from the vessel hold this Shiploader is equipped with a dust controlled loading spout (fig 80) suspended from the boom head as illustrated below.

In addition the Shiploader is also supplied with full function powered travel facilities and an on-board diesel gen-set allowing the unit to operate autonomously without shore side electrical supplies.

Many other variations in specification are available with for example Twin Samson feeder units to boost the handling rate where truck only deliveries are required.

Or, as illustrated in figure 81), the Ship-loader may be combined with fixed local storage and railcar intake facilities offering the best of both fixed and mobile solutions.

For this operation at the Dammam export terminal of the Saudi Cement Company the Aumund Group provided a comprehensive package. This project included an under-rail hopper and feeder system to receive the clinker from bottom discharge railcars. Figure 80

From the rail hopper the clinker is con-veyed by KZB pan conveyor to a central chain type BW-Z vertical bucket elevator and from the elevator by belt conveyor to the Dome storage.

From the Dome Storage the Clinker is ex-tracted via Aumund Dust Controlled gates to a type KZB pan conveyor and via the bucket elevator to a belt conveyor system installed in a high level gantry crossing to the export berth around 500 metres distant.

At the berth the Clinker is delivered to the B&W Mobile Shiploader using a B&W re-versing shuttle belt conveyor of the “Kleen-Line” design to reduce spillage and dust generation. The reversing and travelling shuttle conveyor allows the Shiploader to move along the vessel for hold trimming and movements between holds.

In all of these applications the Mobile Ship-loader offers the client and the port opera-tor complete flexibility in operation and the option to easily relocate the equipment should conditions demand.

Even when combined with fixed machinery the Mobile Shiploader retains the flexibility to move the equipment off the quay when not required thus freeing the berth of other operations.

The use of mobile equipment generally simplifies the negotiations with the port and other local authorities to obtain the neces-sary permissions. And, since no fixed civil works are required this is a fast track solu-tion allowing clients to maximise the oppor-tunities offered by short term market posi-tions.

Figure 81

- 26 -

Packaged Solutions:

The detailed applications as described herein focus on the handling of Alternative Fuels and Materials addressing the particu-lar handling solutions developed for these specific applications and materials.

However, the individual conveying equip-ment supplied by the Aumund Group may be packaged together to deliver a complete installation, as described for Saudi Cement.

As illustrated above (figure 82) a complete new plant including Aumund Group prod-ucts for the complete Clinker transportation and storage. In addition to the handling machinery all associated structures, silos and conveyor galleries were also included to complete the total package as illustrated in figure 83) below.

Conclusion:

Whilst the core processes in the Cement plant remain the key to productivity and are fundamental to the industries materials handling demands there are other issues.

Figure 82

As we have discussed in this paper there are many and varied possibilities for the introduction of alternative fuels in the ce-ment manufacturing process each with its own peculiar difficulties for the handling systems designer considering the diverse behaviour of the materials involved.

The handling characteristics of these mate-rials are extremely varied and to achieve a reliable solution experience is the key fac-tor in selecting the appropriate handling equipment. The benefits may be substan-tial but the pitfalls are equally important…

Figure 83The Aumund Group can offer you the products and the experience you need to successfully implement the required han-dling solution to capitalise on the financial benefits offered by incorporating alternative fuels and substitute raw materials whilst minimising the total investment cost and, more importantly, the associated risks…

- 27 -

Our advice and expertise is freely available at any time so if you have a potential appli-cation call us early.

We are pleased to provide layout drawings and general specifications to help you inte-grate the key process plant and materials handling equipment into your scheme.

Retro-Fits and Upgrades:

In many long established plants individual items of machinery, feeders, elevators, conveyors etc. may be effectively life ex-pired requiring an ongoing investment in maintenance with the risk of unscheduled outages costing valuable production time.

In many circumstances it is possible to re-alise the detailed benefits of the Aumund design and legendary reliability within the casing of an existing machine.

Illustrated above, figure 84), a plate feeder is re-conditioned using genuine Aumund components returning the unit to original condition.

This is particularly true for Chain Bucket Elevators and Pan Conveyors where vari-ous levels of retro-fit is possible including chain, buckets, pans, drive and tension sta-tions.

Obviously each application must be indi-vidually evaluated but we remain ready to offer site surveys and proposals for the conversion of existing equipment where considered appropriate.

In addition to gaining long term reliability it is also frequently possible to upgrade the performance within reasonable parameters but even without an actual increase in han-dling rate the performance will be improved by reduction in unscheduled outages.

Figure 85

Illustrated above genuine Aumund spare parts give you peace of mind in the certain knowledge performance and reliability will not be compromised.

Figure 84 In addition; Schade also offer an upgrade and re-build facility to both increase the performance of existing equipment and for life-expired machinery to rebuild using proven Schade components and expertise.

Figure 86

For example the Reclaimer at Fujairah Cement in the U.A.E. (figure 86) was origi-nally supplied by MVT for a reclaim rate of 280 t.p.h. and a storage capacity of 36,000 tons. Schade were able to upgrade using new chains, harrows and drives to obtain a reclaim capacity of 400 t.p.h. and by ex-tending the rails to increase the storage capacity to 43,000 tons…

- 28 -