Agribusiness & Food, Conveyors, Transfers, Chutes, Dust Control & Environment, Engineering, Logistics, Ports & Terminals

Bulk Talk: Observations of grain handling in South America

Rio Tinto’s Steve Davis discusses the many differences he observed visiting grain handling operations in Brazil and Argentina.

 


Brazil and Argentina are two major exporters of South American grain. The terminals visited in Brazil were in Barcarena, near Belém on the mouth of the Amazon River; and in Santos, near São Paulo on the east coast. Those in Argentina were in the San Lorenzo-Puerto General San Martín Port Complex and at Arroyo Seco, both on the Parana River near Rosario; and in the Port of Ingeniero White in Bahía Blanca on the South coast of Buenos Aires province.

All these port locations have several grain terminals in operation due to the quantities of export grain in season, limited location of suitable ports, and there being an open and competitive market for the service of receival and loading of grain to ships that has resisted consolidation. Many terminals are on land that is owned, or in some cases leased, by well-known international grain traders, who also operate the facilities.

Most of the terminals receive and store several types of grain. Some also receive and store soybean oil. Brazil exports approximately 50 million tonnes of wheat, corn, rice and soybean and smaller amounts of other grains. Argentina exports approximately 70 million tonnes of similar grains.

Like all agricultural producers, this tonnage is variable and affected mainly by weather. Other variables include political controls on land use and export duties. In a good year, during the main harvest the terminals operate 24/7 for many weeks on end. At other times the terminals may operate as little as two or three day shifts a week.

Transport to terminals

Grain is often transported to the terminals over long distances. Transport methods to the terminals include barges, rail and road vehicles. Travel of over 1,000 km to ports is not unusual for all three methods. All terminals can receive by road, some have road and rail feed or barge and road feed, and some have all three options.

From observation, it seems that well over 50 per cent of the grain is transported in by road. We were advised that the condition of the roads varies from little more than tracks to reasonable surfaced highways. Some of the larger terminals only have facilities to receive by road. Typical vehicles in Argentina are rigid trucks with dog trailers, although there are some B doubles and articulated semi-trailers. In Brazil, B doubles and semis were more common. The diversity in configuration and age of vehicles is large. There is a combination of farm owned and contract fleets. Road transport offers flexibility in capacity and destination necessary in the variable market.

Vehicles are marshalled in large areas to coordinate unloading of grains in sequence, either as an integral part of the terminal, or remote from terminals depending on space. Road access in and around the terminals is surprisingly poor and has arbitrary coordination. Bahia Blanca, for example, has a shared facility for marshalling trucks that has capacity for some 4,000 or more vehicle combinations that park before and after sampling.

Vehicles leave in batches to deliver grain to the terminals. This area is six kilometres from the port. On arrival, trucks are weighed and grain is sampled. Remote control probes with vacuum
conveying to the lab is typical. Grain is categorised immediately in site laboratories. If the grain is acceptable, the trucks then join queues to unload. Trucks are weighed again immediately after unloading. Independent truck drivers assess the delays at the port and head for the terminal with the shortest unloading time. Total unloading cycle time can be many hours.

Trucks are unloaded through rear discharge gates in the trays. As the truck, trailer combinations do not have tipping bodies, unloading is through truck tippers, also called unloading platforms. These tippers are not in common use in Australia, but are widely used through North and South America for bulk unloading. Truck combinations drive into the fully enclosed building containing the tipper platform, and the entire coupled combination tilts to an angle at which the grain flows from the rear gates. Cycle time is several minutes, and the tipper platform is drive through after unloading. Multiple tipper installations were common; one terminal visited had five in operation. Tipping platforms can be over 60 metres long and tip to approximately 35 degrees.


Drive through truck tippers in Argentina. Photo: Steve Davis

Barge transport requires additional transfer facilities from truck to barge at regional river terminals. Barge unloading at the main terminals required unloading facilities. Both loading and unloading facilities add cost to operate and maintain, but this allows grain traders to consolidate loads earlier in the logistics train. In Australia, US and Canada, regional rail hubs (elevators) provide similar consolidation of grain for transport. The transition to barge transport, with shorter road transport distances is ongoing. New barge unloading facilities were being, or had just been, built at several river terminals. Other terminals have been unloading barges for many years. Both vacuum and Siwertell type unloaders, and a few older grab cranes were in use. Direct transfer from barge to ship, as seen in some US and other ports, was not in use, as river currents are too high.


Grain barges on the Amazon River. Photo: Steve Davis

Rail transport requires transfer from truck to train and unloading to the terminals. The rail network in both Brazil and Argentina is relatively basic. All ports except Barcarena have rail connections, but there are few regional hubs for grain collection. Rail cars were top loaded and bottom discharge. Both loop and siding systems were in use for unloading with discontinuous single wagon unloading operation being the normal method. Santos has the best rail delivery set up, with about 50 per cent of grain delivered here by rail.

Direct loading from barge, truck or train to ship is usually possible in the terminal materials transfer configuration but only when topped up from storage. This was infrequent because there needs to be a ship being loaded at the same time and with the same grain type being delivered.

Grain terminal storage

Grain terminals generally have a variety of storages for grains and reflect expansion changes over time. Storage includes steel and concrete silos, rectangular bins, and several types of linear stockpiles (flat warehouses). More recent storage facilities seem to be all linear storage. Typical total storage capacities are from 100,000 tonnes through to 250,000 tonnes. All permanent storage was top filled and reclaimed by gravity discharge from below. Some sites had space for “overflow” storage in large plastic “sausage” bags. These were manually filled
and discharged.

Grain transfer around the terminals mostly uses a combination of bucket elevators and conventional troughing belt conveyors, with some other conveying systems noted. The older terminals, where expansions and changes have taken place have a web of conveying systems from unloading facilities to the different storages, often with ability to divert between storages. All conveyances are fully enclosed to keep the ever-present bird populations at bay.

Conveyance designs were conventional. Most conveying rates were relatively low, with the highest capacities at shiploading. The highest capacity for loading noted was 2,500 tonnes per hour.


Twin slewing, telescoping boom shiploader installation in Brazil. Photo: Steve Davis

Shiploading

Grain is loaded to seagoing vessels at the terminals. There are draft limits in all ports, either from river dredging or river mouth sandbars. This results in partial loading of Panamax size vessels, or smaller vessels being fully loaded in the river ports. Partial loads can be topped off at other ports that have less draft constraints, such as Bahía Blanca and Santos, even in Montevideo, where high tide draft is sufficient for Post-Panamax vessels. Rosario has a road bridge downstream of the grain terminals at the San Lorenzo-Puerto General San Martín Port Complex, that imposes additional clearance limitations.

The quantity of grain exported by the terminals varies from under one million tonnes to about 10 million tonnes. Some customers order mixed grain cargoes.

Terminals use belt conveyors to feed twin or triple gravity tube loading spouts, or twin or triple fixed, slewing and telescoping boom loaders. Some travelling luffing boom shiploaders are also in use.

Dust is always an issue when loading, and this is managed in several ways, without any direct application of surfactant to the grain. Boom loaders use telescopic shrouds that reach down into ships holds. Some of the spout loaders use a water spray curtain that captures dust that is blown away from the loading points. All seem to use a variation in tarpaulins to minimise the exposed hold opening. Loading ceases as soon as there is any sign of rain or snow. For Barcarena particularly, this means a significant extension in load time as there are many rain events.

Overall, the terminals visited were in good condition. The equipment was competent and fit for purpose. Construction and engineering is similar to Australia. There was good attention to health and safety, with good policies and reinforcement and historical accident and incident data. Dust extraction systems were evident, but design could have been better. Guarding and access was relatively good, considering the age of some of the facilities. There were obvious innovations to improve safe practice. The newer facilities showed best practice in health and safety.

There was little spillage evident, likely because that grain handling is well understood and consistent, and the varying rates of operation provide time for maintenance. Spillage is cleared quickly to avoid attracting pests.

In summary, there are many differences between these and Australian grain terminals and the way they are operated, with just a few similarities.

Steve Davis is the principal adviser – bulk materials process at Rio Tinto, based in Perth. Steve has worked in bulk handling for 30 years, for both resources companies and professional engineering firms, in Australia, South Africa, the Middle East and Canada. His experience encompasses such commodities as iron ore, coal, potash, phosphates, petcoke, sulphur, sands and grain.

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