The Port of Seward has completed a conveyor system upgrade for its coal handling operations that has increased throughput by an estimated 20 percent, allowing Alaska’s largest coal producer to better compete for international customers.
By installing the new EVO™ Conveyor Load Zone from Martin Engineering, the terminal has increased the average load rate for the entire ship-loading process from 700 mt/h to 858 mt/h. The terminal has gone from an absolute maximum of 18,000 mt/d with dry coal and optimal loading conditions, to more than 20,000 mt/d on average – including operations in poor weather and less than ideal operating conditions.
With throughput increased, ship-loading times are being reduced, driving down costs and making the exported coal more affordable to overseas customers. “Basically, we should be able to knock one day off our loading time for each ship,” observed Steve Denton, VP of Business Development for Usibelli Coal Mines (UCM). “Over the course of a million tons per year, that’s a major savings for our customers, as they’ll be able to enjoy better FOB prices. It also saves us tremendously on the cost of ship demurrage, which helps us to pay for the cost of the conveyor investment,” Denton said.
The Port of Seward: a critical link
Since 1985, the Port of Seward has shipped over 16 million metric tons (mmt) of coal, all of it originating at the Usibelli mine 400 miles to the north, which currently exports more than 45 percent of its annual production. UCM and its affiliate Aurora Energy Services, LLC (AES), operator of the Seward coal terminal, have no doubt that the port plays a key role in their future. As one of Alaska’s few year-round ice-free harbours, Seward is also the southern terminus of the state-owned Alaska Railroad. It offers terminal facilities – owned by the railroad and operated by AES – with the ship-loading resources to feed the expanding international export market.
A major obstacle to expansion was the port facility’s aging infrastructure, which had seen few improvements prior to 1999. Upgrades began that year when Alaska Railroad purchased the terminal, but despite best efforts, by 2008 the facility had become a logistical bottleneck, and with its occasional dust clouds, also a source of complaint.
The issues
One of the issues was the ship-loader itself. With a view to expanding Usibelli’s export market-share, AES began taking steps to increase throughput at the Port facility, but initial efforts to reach 2,000 mt/h proved almost entirely unsuccessful. “Working with what we had, we could only reach 600-700 mt/h,” saidAES Terminal General Foreman Vic Stoltz. “We made some improvements and got up to a steady run rate of 750 mt/h. But as we did, there were still some major issues with coal backing up in the chute.”
Even as some gains were realized, AES found that with higher-speed operation, dust became an increasing problem. Constructed in a less environmentally-sensitive era, the shiploader design was not adequate to contain fugitive material, allowing airborne coal dust to generate negative attention and threaten community relations.
Combining solutions
The need to increase throughput capacity at Seward while protecting the region’s air quality and natural splendour led AES to investigate new conveyor technology from Martin Engineering. AES first sent bucket-sized samples of the typical conveyed material to Martin’s R&D centre in Illinois. After testing the coal to determine its flow properties, the company’s specialists used Discrete Element Method modelling to design a chute capable of properly handling the coal. “When we got back the computer models, we saw that we were able to pass 1500 mt/h and still control dust, all while keeping within our capital budget,” said Stoltz.
A few months later, Martin Engineering followed up with an environmental audit while AES was loading a ship, suggesting improvements to the process. AES decided to implement several significant modifications, including a new EVO-equipped shiploading chute. “We knew that we had to do something about the environmental and production issues that were being caused by this one chute,” said Stoltz. “When our management realized that we could increase throughput, increase safety and reduce our environmental impact all at once, they were completely in favour of implementing the suggested upgrades.”
A new conveyor architecture
The new transfer point makes use of Martin® Inertial Flow™ Transfer Technology, and the entire chute is custom-engineered and modelled in 3-D to provide the optimum design for the material and flow rate required. The ‘hood’ controls the flow of material from the discharging conveyor, maintaining a coherent material stream and minimizing induced air. A smooth loading chute (spoon) places the stream of coal onto the ship-loader’s boom conveyor at the proper speed and angle with minimal impact, reducing material degradation, belt abrasion and the expulsion of airborne dust. By controlling the flow of material, this engineered transfer chute helps eliminate blockages, shape the load and contain fugitive material.
Martin Engineering supplied other redesigned components to contain material and improve serviceability. Belt support cradles were installed under the drop chute to absorb impact and stabilize the belt line and prevent spillage. AES also mounted EVO External Wearliner on the load zone’s existing skirtboard for improved sealing. Because it is attached from the outside, it is easier to install, inspect and adjust than conventional seals, without requiring confined space entry.
