Aspec Engineering specialises in addressing complex materials handling challenges. ABHR learns how the company recently helped find the right dust control solution for a critical alumina shiploading project.
For more than 55 years, Queensland Alumina Limited (QAL) has been one of the world’s leaders in alumina production.
The producer was looking to improve its operations, specifically when it came to dust control. Alumina dust is made up of very fine particles that are easily caught by the wind.
Adam Mayers, principal mechanical engineer at Aspec Engineering, said the site was looking for ways to improve upon its infrastructure, which is why QAL contracted ASPEC to find technologies that could help reduce dust emissions.
“They contacted us to help come up with a concept that would eliminate dust during ship loading, without increasing loading on the existing wharf,” he told ABHR.
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“Our first step was to try and identify the root causes. The existing shiploader used air slide conveyors on a boom that ‘luffed’ from horizontal to near vertical. When this happened – usually during a vessel hatch change – it compromised the conveyor seal, allowing alumina to escape and resulting in dust emissions.
“If a ship had five hatches that needed to be visited three times each, you could be looking at up to 15 potential events.
“The conveyors and transfer chutes were also prone to entraining excess air, which when combined with the belt cleaners, allowed alumina product to bypass containment measures and be released as dust.
“Inconsistent feed control to the shiploader from upstream storage sheds exacerbated the dust generation by overwhelming existing materials handling and dust collection systems.”
Aspec Engineering began exploring the market, looking for technologies that could handle the task. One of the first steps in its process was challenging the assumptions and criteria involved.
The engineering team soon found that a luffing motion wasn’t needed to load the vessels. Instead, the new infrastructure would use a ‘slewing’ method. This eliminated the need to lift the boom to the same extent for the hatch change and meant that the conveyor seal and the landward end of the boom could be maintained continuously, keeping the material contained.
In addition, several advanced dust control features were included in the new infrastructure, including enhanced ‘airslide’ or ‘air-gravity’ conveyors that utilise low-pressure air to fluidise alumina. This facilitates sealed downhill flow with no moving parts.
A Cleveland Cascade loading chute was also incorporated to maintain consistent slow flow speed through a sequence of inclined cones within a dust containment shroud, preventing air entrainment and dust generation.
Belt cleaning processes, including primary, secondary, and ‘air knife’ cleaners, were improved at the tripper discharge point onto the shiploader. Self-cleaning dust collectors also generate negative pressure within the system to prevent dust from escaping.
Mayers said one of the main goals of the project was to ensure the upgrade could be completed without affecting production or requiring major wharf upgrades.
“One of the big challenges was the age of the wharf,” he said. “New machinery tends to be heavier due to modern design standards, but the wharf couldn’t accommodate heavier wheel loads without major changes.”
“Changing the design to a slewing shiploader meant we didn’t need a large tower to facilitate the luffing range, which reduced a lot of weight. It was also not as tall, which was important for keeping the wind loads down through a lower profile.”
“We also helped come up with an innovative risk-based approach to prioritise repairs to the wharf. This helped solve any interface issues and meant the wharf was ready to receive the Shiploader when needed.”
The detailed design and supply of the shiploader and upstream dust control upgrades was awarded to Reel Alesa, a specialist Alumina materials handling supplier.
Following design, fabrication, off-site erection and pre-commissioning, the machine was transported to the QAL site via heavy lift vessel and delivered, fully assembled, in November 2023 for tie in works and commissioning.
The offshore fabrication and full assembly of the shiploader helped to minimise disruptions to berth operations. Stringent third-party quality inspections were essential to rectify defects identified prior to delivery to the site.
“During the inspection, we identified issues with the quality of the fabrication and painting, so we brought in welding and paint experts to find solutions before the shiploader arrived on site,” Mayers said.
In December 2023, the machine commenced full operations with negligible dust emissions.
Mayers said the project was a significant success.
“Throughout the design process, there was a lot of focus on simplification, to ensure the machine was easy to operate and maintain,” he said.
“QAL appreciated our support. We were with them throughout the entire process, offering our technical expertise. We even went to the United Arab Emirates at short notice to inspect the machine and address any issues before it was delivered to site.”
These kinds of projects are an everyday occurrence for Aspec Engineering. The company has spent the past 20 years offering its engineering support to vital bulk-handling infrastructure. It has also been involved with the design and supply of shiploaders across Australia, supporting the major mining companies.
Over the decades, Aspec Engineering has developed a core team of experts with a deep knowledge of the industry.
Mayers said this depth of knowledge allows Aspec Engineering to react quickly and draw upon a vast network to solve client needs quickly and efficiently.
“Aspec Engineering has a low turnover of staff – the people in the company have been with us for years and understand the specific issues that can arise on bulk handling projects,” he said.
“Speed is really important in the industry, as avoiding downtime is ultra critical, particularly in tight shutdown situations. We often find out about a problem in the morning and can have a solution by the afternoon. Part of this comes from our close relationship we have with our clients – we know their assets and we have the tools and knowledge needed to get started quickly.
“Aspec Engineering specialises in solving problems that are difficult and unique. We have a lean team that focuses on interesting value-adding ideas and hope to continue to do this work for another 20 years.”