AUMUNDNEWS No. 5 // 2018

Products. Projects. Progress.

W E C O N V E Y Q U A L I T Y

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International Cement Review

Semi-turnkey: the flexible friend

In cement plant projects, the process systems such as kilns and mills are often separated from the transport and electrical equipment, as well as civil works, with the client or EPC contractor putting these elements out to tender in separate but clearly-linked packages. This gives the customer the flexibility to choose favoured suppliers or specific equipment and services. This is particularly relevant in terms of civil works and electrical controls, where local contractor experience of the site is a major advantage. For example, a semi-turnkey approach to a cement or

clinker transport system could include the feeders, silos, conveying systems and storage along with the associated structures, bridges and transfer towers. Of course the materials handling and storage systems provider must work closely with the process equipment supplier to develop a plant layout that is both economical and satisfies the client’s general demands and local site topography.

Contact: cement@aumund.deAUMUND Fördertechnik GmbHwww.aumund.com

Making the fit

Engineering-only solutions and local equipment manufacture

Raw material preparation

Semi-turnkey beyond thepyro-processing section

Maintaining operation in a challenging environment

Contents

Cementos Balbao, Spain (photo AUMUND)

Semi-turnkey: the flexible friendSemi-turnkey contracts help maximise the benefit of detailed know-how in materials handling systems design. At the same time, they allow clients, or EPC contractors, the flexibility to split responsibilities into discrete packages, taking maximum advantage of specific suppliers’ niche products or services.

n by Martin Dalbert, AUMUND Fördertechnik GmbH, Germany

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I n cement plant projects, the process systems such as kilns and mills are often

separated from the transport and electrical equipment, as well as civil works, with the client or EPC contractor putting these elements out to tender in separate but clearly-linked packages. This gives the customer the flexibility to choose favoured suppliers or specific equipment and services.

This is particularly relevant in terms of civil works and electrical controls, where local contractor experience of the site is a major advantage. For example, a semi-turnkey approach to a cement or clinker transport system could include the feeders, silos, conveying systems and storage along with the associated structures, bridges and transfer towers. Of course the materials handling and storage systems provider must work closely with the process equipment supplier to develop a plant layout that is both economical and satisfies the client’s general demands and local site topography.

Making the fitFor a typical modern cement facility, the process element within major plant development projects will most likely include crushing systems, mills and perhaps a new kiln. In these circumstances an EPC contractor or the major equipment supplier (particularly the kiln supplier) will lead the project, taking process and performance responsibility.

Once the major process plant is decided, the relative displacement of the major plant elements, raw material, raw meal, kiln, cooler, clinker storage, milling and dispatch must be shoehorned into the available space on site. This often demands some radical and novel materials handling solutions to move materials between the process sections to deliver the performance and reliability demanded in this industry.

As part of its semi-turnkey approach to materials handling, aumund delivers all the associated loading plans for the civil works design and any plant interfaces. In addition, the Germany-based company meets the instrumentation and electrical control demands and control philosophy, respecting the plant norms and standards.

With all semi-turnkey solutions clear battery limits are critical to exactly define the extent of supply and the specific responsibility of the EPC contractor. Such battery limits may be, for example, the outlet flange of an incoming belt conveyor and the inlet flange of a downstream storage silo. The contract may provide for the complete design not only of the materials handling equipment but also all of the associated structures, bridges, towers, access walkways, cladding, instrumentation, cable routing risers and trays plus support for any services routed along the bridges.

Close liaison with the EPC contractor is essential to ensure all related activities, especially control and power cabling, are provided with sufficient capacity

for the associated capital supplied by other specialist manufacturers. With the extensive use of 3D modelling, the compatibility of such software across the contractors supplying each section of the plant is critical in allowing effective sharing of data on a common platform, whilst respecting the individual manufacturer’s intellectual property (IP). Under the control of the EPC contractor, efficient document management is vital to ensure an effective engineering change permit system is rigorously managed and change data is distributed to the related contractors.

Engineering-only solutions and local equipment manufactureWhilst the semi-turnkey contract may include the complete supply of mechanical conveying systems plus the associated supporting structures, transfer chutes, silos and access systems, very often the supply part may be restricted to the conveying equipment with the associated structures given as an engineering-only order. In this way the structural part of all of the semi-turnkey contracts may be combined by the

Holcim’s Ste Genevieve plant, the largest kiln line in the US, ordered multiple semi-turnkey packages from aumund including a comprehensive clinker transport system ©

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This article was published in “INTERNATIONAL CEMENT REVIEW“ June 2018

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EPC contractor and let to a single favoured manufacturer to maximise the volume and, therefore, minimise the rate per kilo of the manufacturers and the associated freight.

Effective quality control is essential. With a single equipment manufacturer a close relationship and trust can be more easily established and associated management costs mitigated. aumund is well versed in this modus operandi and extends the option for the EPC contractor or client to arrange the local manufacture of some elements of the conveyor systems such as elevator buckets and casings. The clear purpose here being to minimise the cost without sacrificing quality. aumund ensures parts fabricated locally remain interchangeable and are no different to the same parts manufactured at its works in Germany.

Raw material preparationThere are cement plants with their peculiarities, particularly related to the sourcing of limestone and its transportation. Limestone is mostly quarried by blasting and runs through a primary crusher to reduce the size for economical onward transportation.

In this set-up the crusher is the key element and is generally purchased from a specialist supplier outside the

semi-turnkey contract system. However, once the crushed limestone and necessary additives required to adjust the kiln chemistry arrive at the cement plant, then the first semi-turnkey packaged may be assembled. This package includes the equipment to take the materials into the plant and enables tertiary crushing, automated storage and blending, conveying, elevating, silo storage for additives, and blending and milling of the raw meal prior to being finally blended in silos and raised again to the preheater tower inlet. This package may be subdivided, but in general the sections can be easily defined and the battery limits clearly specified, terminating to the inlet flange of the preheater intake cyclone.

aumund offers the key material handling plant at every stage of the process and in particular, the chain and belt elevators required to raise the raw

material and ground meal to silos. In addition, schade Lagertechnik GmbH (part of the aumund Group since 2001) can add its portal, semi-portal or circular storage systems, including chain-based bridge-type reclaimers, into the package to homogenise the limestone before going into the raw meal mill. In this part of the process, additives are blended into the limestone stream using weigh feeders. In the aumund package weigh feeder type DPB based on the apron or pan feeder concept offers a robust and reliable solution both for feeding and silo extraction. Based on the type KZB

Four aumund type KZB pan conveyors extract clinker from storage silos and transport it to four individual vertical mills at Holcim’s Ste Genevieve plant, USA

Cementos Balboa in Spain is another greenfield site where aumund supplied a package of elevators and conveyors for the complete plant, including the clinker transport and storage silo

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or BPB chain pan/plate concept but with a supporting roller at every chain pitch, the load on the conveyor can be measured accurately on a weigh rail and the throughput computed from the chain speed.

Semi-turnkey beyond the pyro-processing sectionFrom the raw meal, the preheater, precalciner, kiln, clinker cooler and crusher are generally combined into a single-source package, almost invariably under the direct control of the EPC contractor. However, the clinker section downstream from the cooler/crusher lends itself to a semi-turnkey package all the way to the finished cement mill bunkers, including the clinker storage silos.

The mechanical part of such a project will often be the lead element defining the materials handling routing, and the associated control and civil works. Over the last 95 years aumund has developed a wide range of pan conveyor designs. Moreover, the company’s bucket conveyor and bucket elevators provide the maximum flexibility in plant layout by giving the plant designer the option to select the most appropriate working angle and lift height, resulting in a compact installation without sacrificing either performance or reliability. With the latest aumund conveyor chains lift heights of 96m with a single lift are possible and a 60˚ working angle using the BZB bucket apron conveyor principle. This often eliminates the need for

any intermediate transfer point, leading to savings in structures, access provisions and control equipment. In addition, the aumund type SPB pivoting pan conveyor offers a compact solution for loading dissimilar materials to the mill bunkers or longitudinal clinker storage hall.

For Holcim’s Ste Genevieve plant on the Mississippi River, USA, these benefits were particularly interesting. In this facility, the world’s largest with a proven performance of 13,000tpd, aumund USA handled large sections of the raw meal plant and most of the clinker transport from the cooler/crusher through to the twin storage silos and onto the mills, as well as the vertical elevators for the mill recirculation and finished cement handling.

The clinker handling specifically included twin aumund type KZB steep-angle conveyors installed within a single gantry supported at high level from a clinker rejects silo. A diverter valve and two high level transfer conveyors distribute the clinker to either of the two identical storage silos or the rejects silo between. From the adjacent silos, four parallel A aumund type KZB conveyors transfer the

clinker to four identical vertical finished cement mills. Each clinker conveyor is fitted with drive control allowing the output rate to be directly controlled to suit the mill demand.

Gypsum is added directly to the KZB conveyors at low level using small individual silos, each equipped with aumund centrex® extractors plus weigh belt feeders. Using the combination of flow rate control on the main KZB conveyors and the gypsum addition, the overall feed rate and blend ratio can be continuously and automatically monitored.

The full EPC contract may be, and generally is, broken into many different semi-turnkey contracts, which each having to align with the adjacent parts as well as the electrical and instrumentation systems in a seamless and fully-integrated process.

At some point, the client must take over the plant operation and maintenance and, therefore, is involved in the selection of the semi-turnkey contracts.

Maintaining operation in a challenging environmentAny semi-turnkey installation within the cement industry must perform 24/7 and deliver the dependability required in this most aggressive of applications, often handling highly abrasive and hot materials such as cement clinker direct from the cooler. During a kiln flush accumulated dust and raw material may flow through the system uncontrollably and expose the ongoing conveyors to massive short-term overloads and very high spot material temperatures. aumund steel pan conveyors are able to handle material temperatures up to 700˚C for short periods where a conventional belt conveyor would be a clear fire risk.

Furthermore, aumund offers an ongoing inspection and preventative maintenance package designed to expose potential faults at an early stage and, by continuous condition monitoring, determine the

possible failure point. In this manner maintenance and refurbishment work may be planned into a regular outage period, avoiding uncontrolled failures with associated expensive kiln downtime.

Conceptual design, materials handling systems, structures and storages, instrumentation and control philosophy along with associated dust plant and similar equipment is part of the aumund semi-turnkey package, supported by a wealth of know-how. n

Multiple aumund pan weigh feeders type DPB for corrective additions materials supplied for integration into the raw meal handling package ©

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Four aumund pan conveyors type KZB deliver clinker to four vertical mills

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©Copyright Tradeship Publications Ltd 2018

This article was published in “INTERNATIONAL CEMENT REVIEW“ June 2018

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