Efficient handling of cement in marine export terminals

Cement and clinker trade faces a downward trend, due to the economic crisis and because of the recent investment boom in the cement industry, with new production capacities in former import countries and corresponding lower imports.

In a new market report, OneStone Consulting has analysed the situation [1] and how this will develop by 2013. The cement surplus situation leads to an export excess capacity in such a way that more countries and traders are increasingly looking for exports, while imports decline and no new significant import capacities are needed. Accordingly, in the short to medium term, export facilities will be expanded and modernized to cope with new requirement, and to make export terminals more efficient and competitive.

This article will strive to illustrate the actual cement trade situation and highlight the available cement export design options.

Cement imports and exports

In 2009, the worldwide cement and clinker trade accounted for 138 million tons per year (Mta), including 93 Mta (67 per cent) of cement and 45 Mta (33 per cent) of clinker, 85 per cent of which (around 108 Mta) is seaborne trade (using waterways).

Of the Seaborne trade 66 per cent is for cement. Compared to 2008, the cement trade decreased by 21.5 per cent while clinker trade decreased by 8.5 per cent [1]. The large decline in cement trade has not only to do with the economic crisis, and the declining cement demand in established markets such as North America and Europe, it is also caused by the large capacity expansion programs in other cement import countries such as Nigeria, UAE or Vietnam. Moreover, in the coming years, with large new clinker and cement capacity becoming operational, the situation will even become worse.

Figure 1 shows how the exports, imports and export excess capacity have developed until 2009 and how they are forecasted until 2013. The figure clearly shows that the export excess capacity has increased from five Mta in 2007 to 19 Mta in 2009. The excess capacity defines the extra export volumes that are offered to market, which cannot be balanced by imports. The excess capacity is only a part of the cement surplus capacities in the individual markets. Excess capacities have especially developed in the Far East and Europe, and they will further develop in the Far East, Middle East, Northern Africa and Europe. The main boom is in the Middle East and Northern Africa in such countries as Egypt, Turkey, Pakistan, Iran, Saudi Arabia and UAE. Most of the countries are looking for additional exports to Africa, with new or modernized cement export facilities.

Terminal design options

In the relevant export countries, the majority of cement plants are located inland, so bulk cement has to be transported mainly by trucks to the export terminals. Such a terminal will provide several docking stations for the road tankers, from which cement is pneumatically discharged and blown into the storage facility (Figure 2). Nevertheless, efficient export terminals will need a certain planning and realisation time, which depends on several parameters including the proposed service life of the terminal, ship sizes and deep water requirements and the equipment and storage facilities used. Furthermore, local conditions such as labour costs and environmental constraints also have an influence. For cement storage, several options are available such as flat storage facilities, steel silos, central cone concrete silos and dome silos. Each silo type has its advantages and disadvantages. Flat storage systems, such as warehouse buildings and multiple steel silos, are a low investment cost solution with short construction times; a central cone silo system allows a minimum footprint and low operating costs, while dome systems become more economical with larger capacities, and especially offer less foundation work. As a matter of fact, depending on the service life of the terminal, throughput and required handling rates for planned ship sizes, the focus can be either on low capital costs or on low operational and shipping costs, i.e. the specific handling costs per tonne of cement.

There are basically two concepts of loading cement ships. For direct loading with capacities up to 450 t/h for single lines, screw pumps can be used to transport the cement from a silo discharge over distances of up to 500m directly into the cargo holds, via an installed piping on the cement tanker. On-board cranes carry flexible hoses, for the connection of the shore and ship pipes (Figure 3). Compressors at the terminal or on-board the cement carrier can provide compressed air for pneumatic transportation. By a computerized pipe distribution system, with motor actuated two-way valves, the cement can be directed into selected holds.
Alternatively, an on-deck distribution system with fluid slides or horizontal screw conveyors is also possible.

For indirect cement loading, mechanical ship loaders are used (Figure 4). Such loaders consist of an intermediate bin; a loading arm, with pneumatic or mechanical transport; and a telescopic loading spout, to compensate the different ship drafts and to convey the cement into the ships holds. The loading arm can be slewed in a horizontal direction.

Depending on the distance from the storage silo to the bin of the ship loader, screw pumps or fluid slides are typically used to feed ship loaders. Transport distances up to 500m can only economically be fulfilled with screw pumps. Fluid slides are mainly used at the loading arm, vertical screws for bin feeding and horizontal screws as alternative to fluid slides. Loading capacities range from 100 t/h for single lines, up to 1,200 t/h for two or more lines.
 

Practical example

Holcim (Deutschland) AG operates a new export terminal at Brunsbüttel, at the Kiel Canal, some 25km away from the Lägerdorf production plant in Northern Germany. Before the terminal installation, Holcim could only carry out cement exports from that site by direct ship loading from silo vehicles, with the drawback of relatively long ship loading times. The new terminal (Figure 5) was designed for an annul throughput of 0.6 Mta. The millionth tonne of cement had just passed through within three years.

Joe Harder, OneStone Consulting Group GmbH, Buxtehude, Germany
Edition: Edition 45

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