Local furnace and industrial services company Dickinson Group retrofitted a 30 t brick-lined iron ladle with a modular precast refractory lined ladle in July for heavy minerals miner Tronox Namakwa Sands’ mineral sands openpit mine and concentration plants in Brand-se-Baai, 385 km north of Cape Town, Dickinson Group CEO Trevor Dickinson tells Engineering News.
The sizes of the precast modular blocks for the ladles were between 1.2 t and 1.6 t each, “which are the largest modular precast refractory components ever manufactured in South Africa”.
He explains that andalusite was used for the precast components, “which is a naturally occurring alumina silicate used mainly in the manufacturing of refractory products in the form of shapes, castings and monolithics”.
Additionally, Dickinson points out that the company has invested R8-million in its precast division facility in Vereeniging, Gauteng, to improve the quality and range of its products.
He says the facility has enabled the company to manufacture precast components that are considerably larger than the previous products it produced.
“We are increasing production capacity at the plant, owing to the increasing demand for precast products by industry.”
Dickinson says in 2011 the company was contemplating closing down its precast division, which was established in 1986, as it was becoming “increasingly unprofitable”.
However, in early 2012, Dickinson Group established a partnership with US-based Allied Mineral Products that specialises in manufacturing monolithic refractories.
“Allied is a global leader in the industry with manufacturing plants in the US, the Netherlands, India, China, Brazil and South Africa,” highlights Dickinson.
In December 2012, Allied invited Dickinson Group to visit its manufacturing plants and associate company American Precast Refractories facility, in Ohio.
“We were impressed with what we saw and decided to invest R8-million in upgrading our precast facility instead of closing the precast division,” Dickinson enthuses, adding that the precast division has since not only become a profitable part of the group’s operations but the facility will also be expanded from 500 m2 to 1 500 m2 by the end of this year.
Meanwhile, Dickinson Group precast divisional manager Willie Nicklin says precast refractory shapes are not mass produced, but purpose-made products for a specific application, and that precast components are easy to install.
Dickinson Group business development manager Wayne Law points out that one precast block replaces about 30 bricks.
“An iron ladle, for example, can require as many as 3 000 bricks to build; however, only eight precast blocks are required to build the ladle,” highlights Nicklin.
“Dickinson Group has also established an alliance with Canadian coke oven solutions provider Vanocur Refractories for the manufacture of the company’s big block solutions for coke ovens. The big block solution provides the benefit of significantly reducing the number of joints on the coke oven walls as 150 modules of the big blocks replaces more than 4 000 normal silica bricks.”
He further notes that there are, therefore, fewer joints on the furnace, which reduces the number of potential failure points.
Additionally, Nicklin states that a brick-lined ladle can take between four to six days to build, but “Dickinson Group can build a ladle in just four hours using precast technology”.
“Therefore, it significantly reduces downtime at an operation,” Law adds.
Further, Nicklin says using precast shapes for the furnaces has changed the nature of the operation from a bricklaying activity to a rigging operation, which is a “lesser-skilled activity”.
Law also points out that the company has replaced wooden moulds with polystyrene ones, which are easier to shape and fully recyclable.
“The company bought several new computer numerically controlled lathes, which cut polystyrene moulds to a recurring accuracy of 0.3 mm,” he adds.
Moreover, Dickinson says historically precast components were manufactured using pan mixers, “which mixes the refractory castable, without any significant intensity”.
“However, we have bought several high-intensity mixers, which reduces mixing times from between 18 to 25 minutes to just eight to ten minutes.”
He says the high-intensity mixers ensure a more homogenous mixing solution, which results in stronger components being produced.
“The new mixers have programmable water-dosage systems, which removes the need for water to be manually added to the mixing solution.”
The company also bought new dryers, with programmable temperature control units, which eliminates manual temperature monitoring.
Nicklin says the increased mechanisation of the company’s precast division “has ensured that the quality of the products have been significantly improved, as human error . . . has been removed”.
Precast components significantly reduce emissions that escape the furnace linings, owing to the tightly compounded nature of the components.
Dickinson says, with growing pressure from governments for industrial operators to reduce their carbon dioxide (CO2) emissions levels, precast components will become more popular because they can effectively contain CO2 emissions in industrial furnaces.
“This will greatly assist companies that operate large coking ovens, which are large CO2 emitters, to reduce their negative impact on the environment,” states Dickinson.
He points out that merchant producer of high-performance foundry coke Erie Coke Corporation, in Pennsylvania, in the US, was also at risk of being closed down by the US government, owing to the high emissions levels of its facility.
“However, in the last five years, the Pennsylvania facility has become a model for clean operations because using precast technologies have significantly reduced carbon emissions,” highlights Dickinson.
He believes that using precast shapes components at local operations, such as steel producer ArcelorMittal South Africa’s coking ovens, will greatly assist in reducing the CO2 pro-duced at the facilities.