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Over the next few decades, defining an optimal response to the challenges of climate change and rising sea levels will be at the forefront of the dredging industry’s agenda.
Royal IHC’s Manager R&D, Erik van der Blom, is at the heart of a new philosophy regarding sustainability, which encompasses technology, innovation and a change of mindset.
The dredging industry faces a number of challenges linked to climate change over the coming years. While new opportunities are expected owing to rising sea levels, stricter emission regulations for exhaust gases will also play their part. The latter will have a significant impact on the design of dredging vessels and equipment and the type of fuels to be used.
There is a continuous search for more sustainable methods of dredging and ways to power vessels. In addition, the number of emission-controlled areas (ECAs) around the world is increasing and emission regulations regarding shipping are becoming tougher. The International Maritime Organisation (IMO) is also rolling out stricter regulations for sulphur and nitrogen emissions.
In the next few years, the maritime industry will face an increase in legislation regarding the reduction of CO2, particulate matter and black carbon. The effects of which are already being felt, because the majority of the world’s largest vessels use heavy fuel oil (HFO) for power.
“Emission regulations will impact on the design and operation of dredging equipment, and if you’re a vessel designer or owner, you need to start thinking ahead,” says van der Blom.
“That means considering where the vessel will be operating, what type of projects it will be involved with, and what emission regulations will be in place in the future. At the keel-laying stage, a vessel must already comply with new legislation. If companies only consider this aspect when the regulations are in place, it will be too late.”
The fuel of choice
As a designer and builder of dredging vessels, IHC is working to overcome these challenges.
For van der Blom, one of the first aspects to consider when designing a new dredger relates to the choice of fuel: “Emission regulations are closely tied to fuel, and fuel choice has an effect on the engine type and the layout of the vessel. However, it isn’t possible to merely switch engines. In fact, designing a vessel such as a trailing suction hopper dredger (TSHD) is a complex process with numerous variations. The choice that a dredging company makes regarding the engine has an effect on the arrangement of the vessel, the propulsion system and the control system.”
Liquefied natural gas (LNG) is quickly becoming one of the fuels of choice on board new vessels. LNG-fuelled ships eliminate sulphur oxide and particulate matter emissions, and significantly reduce the release of nitrogen emissions.
Dual-fuel engines, which operate through both diesel and LNG, are increasing in popularity because they provide greater flexibility. They enable dredging companies to operate the vessel in areas where LNG is not yet available and in a sustainable way in areas where LNG is accessible.
However, integrating LNG in a hopper dredger is a challenge. Storage of LNG requires three times the volume compared to diesel, which has a significant effect on a vessel’s design. Safety zones and additional safety measures around the LNG fuel system also increase complexity in the design process.
State-of-the-art dredgers
IHC has been continuously reducing the environmental impact of its vessels, including its TSHD’s. Two such ships – the Minerva and Scheldt River – were launched in December 2016 and January 2017 respectively. Both vessels were ordered by DEME in Spring 2015.
Minerva is the world’s first LNG-powered TSHD, which was an important milestone for the dredging industry. The 3,500 cubic meter dual-fuel vessel was issued a ‘Green Passport’ and a ‘Clean Design’ notation. Minerva is the culmination of IHC’s investigations into green solutions combined with DEME’s commitment to invest in sustainable dredging vessels. It represents a significant step forward in modern dredger design.
“We had to overcome the challenge of LNG storage and integration of the LNG fuel system on our new vessels,” says Van der Blom.
“An important design choice was where to situate the LNG storage tank. In one vessel, we positioned this in the aft ship just above the engines, and on another, we placed this in the fore ship underneath the accommodation. Safety zones around the LNG fuel system must also be taken into account.”
“It’s important to mention that sustainable product development is not all about switching to LNG, it’s much broader than that. For example, we’ve been optimising hull shapes for decades. On every new vessel, we try to further enhance the hull design. It’s an incremental improvement that results in hull shapes that are optimised for specific operations and sailing speeds.”
To further optimise fuel consumption and reduce emissions, the Minerva and Scheldt River are also equipped with new innovations. Both vessels feature an IHC-patented two-speed propulsion drive, which is a result of the company’s research into fuel saving and analysis of operational profiles. This technology ensures that fuel savings can be made when sailing at lower speeds.
“Our two-speed propulsion system is a result of analysing the operational profile of dredgers, and measuring the fuel and power consumption during different dredging cycles,” adds Van der Blom.
“As a result, we discovered that drive systems on board hopper dredgers are working in partial load conditions much more than we expected.”
“This is why our drive system can operate in two gears. For example, once a dredger sails inside a harbour it usually cannot sail at full speed. At this point, the crew can switch the gear of the propulsion system, enabling the engine to work at a better efficiency point and thereby saving fuel. In a way, it’s comparable to a gearbox on a vehicle.”
The Minerva and Scheldt River also feature a newly developed wing-shaped bow thruster tunnel, which improves maneuverability. This new shape is the outcome of extensive hydrodynamic analyses, using modern computational fluid dynamics (CFD) calculation techniques and improves the bow thruster performance when a vessel is travelling at a forward speed. The Scheldt River and Minerva are the first TSHD’s to benefit from the above innovations and both comply with international and local environmental regulations.
IHC has also designed the vessel Spartacus. This vessel will not only be the world’s largest cutter suction dredger (CSD), but also the first CSD to be powered by LNG. In addition, the environmentally-friendly Spartacus has other features such as a waste heat recovery system that converts heat from the exhaust gases to electrical energy.
The 15,000 cubic meter TSHD Bonny River also highlights IHC’s commitment to sustainability. The vessel’s hydrodynamic hull and dual-fuel engines ensure optimal fuel consumption, while the closed process water circuit minimises turbidity caused by overflowing during dredging operations. This enables the TSHD to dredge in environmentally sensitive areas.
A wealth of innovations
IHC remains focused on the future and other areas in which dredgers can be further optimised.
“Beyond the choice of fuel and vessel design, there are a number of exciting avenues for us to explore in enhancing the performance of a vessel,” continues Van der Blom.
“For example, through the implementation of intelligent control systems and automation.”
IHC’s focus on innovation has resulted in the development of its Eco Control Package. This makes use of three integrated controllers that manage the vessel and the dredging process at a high level.
The Eco Dredge Pump Controller regulates the speed of the dredge pump, and the Trail Speed Controller maintains a constant vessel speed while compensating for trail force and other external forces during dredging. The Visor Controller controls the visor of the draghead to ensure optimal production levels during loading operations. This combined approach ensures that suction production is maximised in all conditions and fuel consumption is minimised regardless of the disturbances that are acting on a vessel, for example wind, waves and varying soil conditions.
Such technology was fully utilised on the 5,500 cubic meter TSHD DCI Dredge XXI, which was specially designed by IHC for a project on the Hooghly River – a tributary of the Ganges River in West Bengal.
During sea trails on the North Sea, IHC tested the Eco Control Package during several loading cycles. Despite the disturbances acting on the vessel, the suction production levels remained constant. IHC was subsequently able to compare these results to measurements taken on board the DCI Dredge XX, a sister vessel working in similar conditions.
On board the DCI Dredge XXI, loading times were reduced by 15 per cent, which demonstrates how intelligent control systems can contribute directly to higher production levels.
“This shows clearly that by deploying intelligent control systems and managing data effectively, there are significant gains to be made by dredging companies,” adds Van der Blom.
Overcoming turbidity
IHC has also been looking into improving the overflow systems on board dredgers. These are designed to optimise the efficiency of the dredging process by draining excess water and leaving more weight available for the payload.
One of the problems with conventional overflow systems is that large pockets of air are sucked into the overflow and released underneath the vessel. This air – in turn – creates a much larger overflow plume, leading to higher turbidity in the water column. IHC’s patented Plumigator overflow limits the influx of air in the overflow, which contributes to a reduction of the plume.
Not only does the Plumigator overflow overcome turbidity and air beneath a dredger, it also reduces the risk of potential failures.
“There are no additional moving parts – unlike traditional environmental valves – and this reduces the risk of excessive wear,” says Van der Blom.
“The Plumigator overflow can also be integrated with new vessels or retrofitted.”
One of the unique advantages is that it helps operators work in a more environmentally friendly way. For example, by limiting the undesirable plume around the vessel, which is known to harm marine life.
“This demonstrates our commitment to reducing fuel consumption, efficient dredging and greener solutions,” adds Van der Blom.
“At IHC, we are able to make the most of the knowledge and expertise we have across the entire company.”
“For example, we use specific calculation tools to predict fuel consumption – even at the early design stage – which helps our customers to select the most optimal drive train for their vessel. At all times, our innovations are focused on generating high economic and ecological benefits, as well as reducing energy consumption, emissions, turbidity and operational costs.”
Engaging with the industry
IHC is also proactive in its engagement with the dredging market.
The company participated it the Dredging Today conference in Amsterdam.
“For me, the theme of the event – ‘changing climate, resilient business’ – aligns perfectly with what IHC is trying to achieve. Ultimately, we must all be conscious of the economic, social and environmental challenges that face the dredging industry. The feedback we received from the attendees was encouraging, and it was highly satisfying to receive recognition for our sustainable initiatives,” says Van der Blom.
With regards to climate change, there are opportunities for the dredging industry. At the Dredging Today conference, delegates were given a presentation by the Dutch Meteorological Institute concerning climate change and rising sea levels. This will affect urban areas and the dredging industry can play a role in protecting them. However, the challenge is two-fold. At the same time, the industry must continue its focus on developing sustainable equipment and initiatives.
As the maritime industry evolves, it will continue to demand cleaner, more effective and environmentally-friendly solutions from companies such as IHC.
“At IHC, we are delighted to contribute by developing innovative vessels that deliver the highest possible performance and loading capacity, while constantly working on the reduction of fuel consumption and emissions.”
via WMN