by Bruks Siwertell, Sweden

Tomorrow's import terminals will have higher degrees of integration and digital technology, enabling dynamic speed adjustment for the just-in-time arrivals of ships through to a host of automated systems; a critical part will be highly efficient unloading systems to match, explains Bruks Siwertell President, Per Karlsson.

Dramatic increases in populations, often with a tendency to cluster around ports, will drive change across the globe. Not only will we see higher levels of integration and the use of digitalisation and automated systems within the port environment, but also, we are likely to see a shift in the use of technology. We will not be able to meet demand without change.

Tomorrow's ports will look different. Some historic but wasteful practices will have had their day, stepping aside to make way for better ones. Ports will employ smarter systems that deliver accurate real-time data enabling ships to dynamically adjust their speed, potentially slow-steaming, so they no longer burn more fuel only to wait at anchor for a spot on the jetty.

With these smart systems, terminals will also be able to facilitate the full integration of intermodal services that connect to the port, for example, truck and rail wagons ready to meet a vessel being unloaded. In fact, we are already seeing a clear market trend for new cement, fertiliser and grain projects looking to build up capacity on the jetty, and within the terminal.

This maximises the speed at which material can be discharged from a vessel and then transferred to an onward receiving system, minimizing the time any dry bulk material spends in storage. Not only is this efficient, but the faster the terminal moves material on from storage, or bypasses it altogether, the quicker its financial turn-over.

Growth of four billion

Today's world population is about seven billion, but the United Nations (UN) estimates that by 2100 it will rise to around eleven billion. This is a huge increase, not only in terms of predicted demand for basic needs like food and power, but also for the raw materials to build infrastructures. For grain alone, which equates to about 600 million metric tonnes-per-year in international seaborne trade, demand is expected to increase at about 1.5 to 2 percent per year. However, in 2017, the annual increase was as high as seven percent.

Meeting this demand will also come at a time when 28 countries have declared a climate emergency. Never has there been more environmental scrutiny on bulk handling practices and the industry as a whole.

It stands to reason that grab unloaders will become less common in ports in the future. The dust emissions and their high degree of spillage, which can be up to two percent of a load, will make them unacceptable, particularly for powdery cargoes and delicate materials that are likely to degrade with heavy handling.

Dry bulk handling equipment has a long service life, especially mechanical systems such as chain, chain and bucket and screw-type unloaders, so dry bulk handling operators must make prudent choices now. These decisions will influence a terminal's long-term profitability, capacity, utilisation and environmental impact. All factors that need to be considered.

With this in mind, the highest performing equipment should become standard. We would argue that Siwertell unloaders should take this position, and for good reason.

Not every piece of equipment can unload every material, but some are far less suitable than others. For example, bucket chain unloaders are not used for grain handling, mainly due to their very high weight, which has a negative impact on cost. The unloader itself is also not completely enclosed in the transfer between the vertical and horizontal conveyor, and because of that dust can escape. This type of unloader is mostly used for high-capacity coal unloading.

Chain unloaders are enclosed; however, they have some fundamental drawbacks for some materials. Similar to pneumatic unloaders, they lack the capability of withstanding any digging forces because of their weak steel structures, making them unsuitable for any compacted bulk. This is the main reason why chain unloaders are not used for materials such as coal, and neither pneumatics nor chain unloaders are used for fertilisers and soya meal, where digging forces are needed for efficient unloading. If these are used, they require extremely extensive assistance from payloaders and excavators.

Handling multiple materials

Siwertell screw-type unloaders are the only enclosed systems on the market that have the capability of handling many different kinds of bulk materials, including highly volatile commodities such as sulfur. Throughout the world, Siwertell unloader installations handle more than 45 different bulk materials including coal, biomass pellets, salt, cement, all different kinds of grain and soya meals as well as all variations of fertiliser.

They are also capable of unloading at very high capacities, regardless of bulk material type. High-capacity mega-terminals served by Siwertell screw-type ship unloaders include an installation in Liverpool, in the UK, which has a rated capacity of 1,800t/h for handling grain, and achieves an average capacity of 70 percent when unloading 75,000 dwt vessels, and transfer terminals on the Amazon River in Brazil unloading soya beans from barges at between 1,500 and 1,700t/h at an average efficiency of 75 percent.

For other materials, a Siwertell cement unloader in Texas, in the US, has a rated capacity of 1,500t/h, and two unloaders at the Ha Tinh steel plant in Vietnam, each have a capacity of 2,400t/h when handling thermal and metallurgical coal. Both of these were ground-breaking for their time; the former set the highest cement-handling rates on the market in 2006 and the latter is the first installation of dedicated Siwertell coal unloaders for the steel industry.

We believe that Siwertell unloaders can meet all types of requirements from any client in the world and we claim that our screw-type unloader is much more efficient and environmentally friendly than any other unloading system available on the market.

Grain handling is an arena where Siwertell competes well with traditional unloading systems such as pneumatics. Both are totally enclosed, which means no dust or cargo spillage, but the comparison ends there. Siwertell systems offer significantly higher capacities, efficiencies and lower power consumption demands, positively impacting the environment.

Being gentle with grain

They also deliver additional benefits. The unloading velocity of Siwertell unloaders is only 10 percent of that offered by pneumatic unloaders, which translates into far fewer collisions between material particles in the conveyor, dramatically reducing degradation rates. This is especially important for sensitive materials such as soya beans, corn, alumina, wood pellets and other similar materials.

An unloader must use a light touch when handling commodities like grain, because of the production of powdery fragments, smaller than the grain particles themselves, known as fines.

Fines are problematic for many types of cargo, but in grain handling they can make the grain more difficult to aerate and increase spoilage rates and dust emissions.

Fines also have to be removed before milling; therefore, their presence has a significant knock-on effect on grain processing as a whole. A high level of fines in a grain shipment can also mean that the quality of the shipment is downgraded.

Efficiency of cargo reach

Cargo degradation is one drawback of pneumatics, another is hold reach. Siwertell screw-type unloaders can reach into all corners of a vessel's hold. This is because of the range of movement in the horizontal conveyor and the pendulum capability of the vertical arm, which also means that assistance from payloaders is kept to a minimum.

In contrast, a pneumatic unloader has a very limited reach into a hold, as the vertical arm can only be operated within the area of the hold opening. There are pneumatic unloaders that have the capability for some pendulum movement, but this type of unloader still has limitations relating to very low or no digging force capability.

Today, most grain is unloaded from vessels up to 60,000 dwt, and there is a considerable difference in the need for payloader assistance between a pneumatic and Siwertell screw-type unloader. For example, with grain that has an angle of repose of around 45 degrees, in a 60,000 dwt fully loaded vessel, the assistance of a payloader is close to 18 percent or about 11,000 metric tons when using a pneumatic unloader due to its movement limitations. In comparison, under the same conditions, a Siwertell unloader uses less than five percent payloader assistance, and in barges with horizontal walls, the need for a payloader will be below two percent.

Siwertell unloaders also have different inlet devices, depending on material, which can work at full capacity as long as they are submerged at about one meter into the cargo.

For a pneumatic unloader to reach even close to an efficiency rate equivalent to a Siwertell unloader, it must depend entirely on the effective assistance of payloaders. However, high payloader utilisation rates have a negative impact on total running costs as well as on the environment, and they bring far higher levels of grain breakages because of the double-handling.

Furthermore, pneumatic unloaders enjoy maximum capacity at the start of an operation. Once the hollow pipes are extended to reach deeper into the hold, power consumption increases because of the increasing distance from the pump. There is also an avalanche effect when air leaks into the suction pipe, temporarily, dropping unloading capacity to a very low level.

This is normally not considered when comparing power consumption and unloading efficiency with a screw-type unloader. For a Siwertell unloader, the unloading distance is same throughout the entire unloading process, efficiency rates and capacities remain consistent, and the effective inlet feeder eliminates the impact of cargo avalanches within the hold when working at these very high capacities.

When we talk about average capacity, this always includes all movements between the different holds down to a machine clean level, sweeping excluded. For example, a performance test carried out with two Siwertell unloaders, each with a rated capacity of 2,200t/h, on a 80,000 dwt vessel, fully loaded with coal, produced an average capacity above 77 percent; the time it took to completely unload the vessel, sweeping excluded.

In addition to this, it is widely accepted that if the rated capacity increases, it is more difficult to keep a high average capacity because of the larger differences between the clean-up capacity and the rated capacity.

We do see claims that pneumatic unloaders operate at similar through-ship efficiencies, but these exclude all movements between the different holds, which translates into a far lower overall efficiency.

New port-mobile alternatives

For some operators who potentially share terminals or jetty spaces, large, fixed installations are not suitable. In these instances, the alternative does not have to be a traditional pneumatic system, with its associated drawbacks; a new unloader is available, the Siwertell port-mobile unloader. It is particularly well-suited to grain handling and combines all the benefits of a Siwertell unloader into a mobile form.

The port-mobile unloader offers a higher efficiency than a pneumatic unloader, requires much less payloader assistance, and has lower operational costs because of reduced power consumption demands, which in turn lowers their environmental impact. It is also safer, quieter and has lower maintenance requirements.

In addition, higher capacities and efficiencies offer the port operator the possibility of benefitting from higher annual volumes and freeing up jetty space, which could, in turn, improve the port's utilisation rate and its profitability.

Terminals of tomorrow

In the future, terminals will have to meet higher annual volumes because of increased populations, and the utilisation rates of ports will have to improve. The only way to achieve this is to increase unloading rates and/or improve unloading efficiencies and the most cost-efficient way is to design a terminal with one or two high-capacity unloaders.

They have to be very efficient and minimise vessel unloading times and maximise the operational profits of the terminal, whilst also ensuring no material is wasted through spillage, negatively impacting the environment and profitability.

Siwertell unloaders have a capacity range from 150t/h to 3,000t/h, all with market-leading efficiencies, regardless of the material handled. In comparison, pneumatic unloaders are restricted to about 600 to 800t/h with one pipe when handling grain.

The pneumatic unloader works well in ports with a low annual intake, however if an existing or new port terminal needs to expand this cannot be an alternative. High-volume terminals will need high-capacity efficient systems to reduce operational costs to a minimum and lower environmental impact.

If we move away from food, increasing human populations will also require more energy. The global shift towards biomass to mitigate some of the effects of burning fossil fuels will also see a huge spike in demand. However, biomass pellets only have about three quarters the calorific value of coal, so far greater volumes need to be burned for the same energy generation.

Today, pellets are unloaded by either grab, pneumatic or screw-type unloaders. The pellets are very dusty and sensitive to degradation, making them unsuitable for handling with grabs because of the environmental impact. Pneumatic unloaders are restricted in capacity and have a high rate of material degradation because of the velocity of material flow in the unloader.

A Siwertell unloader can offer a continuous rated biomass handling capacity up to 2,000t/h. Today's industry standard rate for unloading pellets in the UK – Europe's leading biofuel user – is 1,200t/h. This is based on five Siwertell unloaders previously delivered to the country, which handle 70 percent of the total annual wood pellet imports in the UK. We are already discussing the use of these higher capacity biomass unloaders with operators.

Today's need for high-capacity, efficient unloading is even more urgent, and we encourage operators to make informed choices and not rely on traditional approaches to deliver the extraordinary needs of tomorrow.

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