FLY ASH RESEARCH PAVES WAY TO EVEN GREENER CEMENT

South Africa’s pioneering role in the use of fly ash in cement production opens the door for the country to reduce its carbon emissions while retaining a strong and innovative cement sector.

This is according to Hannes Meyer, cementitious executive at South African construction materials leader AfriSam, who says the local sector has already made great strides in reducing its carbon footprint. By incorporating fly ash – as well as ground granulated blast furnace slag (GGBFS) – in its cements, AfriSam reduced its carbon emissions per tonne of cement by over 30% between 2000 and 2018.

There are other environmental benefits from using more fly ash, including a reduction in the amount of coal ash that power stations must dump on surface. About two-thirds of the ash produced worldwide still ends up in ash ponds or landfill sites, says Meyer. Fly ash comprises the fine particles of coal ash that rise with flue gases from burning coal, and is usually removed by electrostatic precipitators or bag filters.

“Fly ash extends the volume of cement while adding valuable cementitious qualities to the final product,” Meyer says. “This on its own reduces the amount of energy-intensive clinker that must be produced – thereby economising on the energy our plants must consume.”

More than that, he says, the use of fly ash can also replace the traditional non-renewable products in the manufacture of clinker. These include limestone and shale, which have to be mined at considerable cost. AfriSam has been researching this area for some time, with exciting results.

“The use of fly ash in clinker production means less carbon dioxide is produced,” he says. “Usually, calcium carbonate in the limestone must first be converted to calcium oxide, and this generates carbon dioxide. The calcium in ash, however, has already been converted in calcium oxide and silicate form.”

Meyer highlights the strategic importance of this kind of research and development for the future of the South African economy. He urges that revenues from the government’s recent carbon tax be carefully channelled into incentivising this kind of innovation in the market.

“The carbon tax needs to play a supportive role in gearing up the economy for a low-carbon future,” he says. “This is in fact vital to off-set the negative impact that the tax could have on the cement sector’s global competitiveness and its capacity to retain or create jobs.”

The danger of the tax rising to unsustainable levels in future was that local clinker manufacturing facilities could be moved offshore to untaxed jurisdictions. The cheaper clinker would then be imported, and the number of jobs required to produce cement locally would drop significantly.

HIGH SPEED TRAFFIC DOORS FROM APEX CONTAIN DUST

Efficient processes rely on a predominantly dust-free environment in industrial minerals processing plants. By containing and reducing the ingress of dust, companies experience higher levels of productivity and lower levels of maintenance and downtime. Many such facilities have realised the benefits of installing high speed fold-up or roll-up traffic doors from Apex Strip Curtains & Doors.

In a particular application at a cement production plant, the installation of high speed doors provided the optimal solution in reducing dust deposits. Wim Dessing, sales executive at Apex Strip Curtains & Doors explains that the cement plant was experiencing an issue with the dust deposited by the incoming coal deliveries.

“A rail line runs alongside the plant and when the coal tipper stops at the siding to offload coal, a large amount of dust was filtering into the surrounding atmosphere. This dust was then carried by the air currents into the plant, Dessing says. Coal dust is very abrasive and ensuing problems included the unwanted coal dust causing damage to equipment resulting in increased unplanned stoppages with negative effects on product integrity and quality.

The locality and operation called for doors that would offer wind-resistance and that would effectively contain the dust. The solution provided was the installation of two Apex high speed fold-up Traffic doors. These are constructed from strong self-extinguishing Class 2 fabric, and in this instance the doors are 4.7 metres high, with a combined width of 5.5 metres.

In another application, it was necessary to facilitate access into the product processing area while still preventing the ingress of contaminants from outside. At this customer, materials handling equipment needs to occasionally move in and out, and the installation of Apex high speed doors has facilitated the process but still allowed the doorway to remain closed for most of the time.

High speed traffic doors are the perfect option where doors need to be opened for short periods of time to allow the passage of vehicles. The doors in this particular application are activated by a manually operated push button, allowing fast and easy entrance and exit of the coal tippers.

Dessing says that not only have the Apex Traffic doors contributed to a cleaner working environment at the plant, but they do not in any way interfere in the coal offloading process. The doors were seamlessly integrated into the tipper offloading area and to date they have operated faultlessly and have met the required client expectations.

E AND I ZAMBIA SHOWCASES LOCAL PROJECT CAPACITY ON COPPERBELT

Experienced local electrical control and instrumentation specialist E and I Zambia has successfully completed a large project on a new process plant for one of Zambia’s leading copper miners.

The contract included the installation of six electrical substations, 20 transformers, five 1,250 kVA diesel generators for backup power and a 950 metre overland conveyor. Almost 250 kilometres of cable was pulled and nearly 15 kilometres of cable racking was constructed.

Also completed were six earth mat rings, 12 mast lights and a range of general plant earthing and lighting installations around the plant, as well as the fitting and termination of instruments. E and I Zambia conducted the work between January 2019 and April 2020, in close collaboration with both a leading design house and the end-client. According to projects manager Dave Opperman, the company has a sound track record in the country, having been active on the Copperbelt and beyond since 2002.

“The experience of our team on site, the quality of our artisans and the training of workers ensured that the quality of this job was world-class,” Opperman says. “While prioritising safety and quality, we were still able to adapt to the inevitable fine-tuning of project parameters and schedules, and to deliver on the client’s timelines.”

The safety standards were well reflected in the achievement of 395 Lost-Time Injury Free (LTIF) days. This was done despite a busy site – peak manpower grew to over 270 employees and subcontractors – in a project that consumed almost 590,000 manhours. Almost all the staffing on the project was local.

“Being so well-established in Zambia, we have a solid database of skilled artisans that we can draw upon for large projects like this one,” he says. “The country has a good foundation of these trades, and we can select the most suitable profile of skills to match the project.”

A close relationship with trade unions – maintained by regular consultation – ensured that no labour issues arose that could disrupt the project, he says.

“The company maintains a comprehensive collective agreement with labour, and our collaboration means that the unions understand what the success of the project demands,” Opperman says. “This creates a win-win relationship that allows the smooth running of projects – a vital factor in the meeting of strict deadlines.”

He notes that the company is also able to optimise its local procurement through its network of reliable suppliers, while maintaining a strong cross-border supply chain for large and specialised equipment and components from South Africa.

In line with quality standards, each phase of the project involved the sign-off of both in-house and external quality control officers. This ensured that all work was done in accordance with engineering designs and industry standard specifications before being certified ready for use.

Enhancing its local expertise and experience, E and I Zambia is able to draw on the extensive technical capacity of South Africa-based EnI Electrical, an operating entity within Zest WEG.

GETTING THE MOST FROM TREATING MINE EFFLUENT

Treating effluent on mines often makes use of reverse osmosis (RO) technology, but low recoveries can raise costs substantially; continuous counter current ion exchange can provide a fit-for-purpose solution.

This is according to Vincent Ridgard, process engineer at Multotec Process Equipment, who notes that RO was initially designed to remove monovalent salt molecules from sea water.

“However, wastewater on mines also includes divalent and trivalent elements, which cause scaling of membranes in RO systems,” Ridgard says. “This means that when a standalone RO plant is utilised to treat these waters, it is operated at lower recoveries to enhance the lifespan of the membranes.”

This results in large volumes of highly concentrated brine streams, he says, which are either recirculated within the system or require very expensive effluent treatment systems. To address these challenges, Multotec offers niche technologies that are suited to treat divalent and trivalent elements in water on mines.

“Through our close partnership with Clean TeQ Water in Australia, we offer mines across Africa a continuous counter current ion exchange technology,” he says. “This uses resin which is more selective to extracting larger molecules.”

As a result, these systems achieve high recoveries of over 90%, so that process water can be re-used within the mine’s process circuits or discharged safely to the environment. The resin-based chemistry removes target species, selectively extracting contaminants through exchanging ionic functional groups that are engineered on the resin beads.

Ridgard notes that, while these scientific principles are well accepted, there has previously not been a suitable technology to truly unlock the significant potential of resin chemistry. Clean TeQ’s ‘moving bed’ solution – supplied to the African market by Multotec – is therefore a game changer.

In contrast to the conventional fixed-bed systems, the use of resin transfer mechanisms allows the continuous ionic filtration (CIF) to handle up to 150 ppm of solids, whereas conventional systems need a 100% clean liquor. Total suspended solids (TSS) and total dissolved solids (TDS) can therefore be simultaneously removed.

It also optimises the inventory of resin, a significant cost contributor to the overall plant, and provides high water recoveries. Other benefits include its low power consumption and its ability to recover valuable trace metals as a by-product.

TRAVEL RESTRICTIONS NO CHALLENGE FOR TECHNOLOGY IMPLEMENTATION SAYS SANDVIK

Despite the travel restriction difficulties associated with COVID-19, Sandvik Mining & Rock Technology has found novel and innovative solutions to overcoming these challenges which has ensured the company maintains its leading position in the fields of both automation and digitalisation.

Considering Sandvik Mining & Rock Technology first introduced automation solutions into its product offering some 15 years ago, and digital technologies 10 years ago – the company has been leading the way in helping the mining industry adopt and embrace the modernisation revolution.

“The African mining industry has traditionally shied away from embracing new technologies, but COVID-19 has been the push factor in accelerating the necessity to adopt change, and this has happened rapidly as mines have had to learn to operate remotely and with limited resources owing to COVID-19,” starts Simon Andrews, Sandvik Mining & Rock Technology Vice President for Sales in Southern Africa.

The adoption of new technologies however is no longer the primary objective. Finding ways to implement them remotely has now become the primary focus, Andrews continues.

With the philosophy of working towards finding a solution for any challenge, Sandvik Mining & Technology has done just that, and introduced a headset which enables it to walk and talk anyone through the process of commissioning a machine and associated software without having ever seen it before. “This offering removes all barriers associated with the inability to connect physically on the ground and is a mechanism of training in itself,” says Niel McCoy, Automation Business Development Manager for Sandvik Mining & Rock Technology.

Coupled with this new skill set and offering is Sandvik Mining & Rock Technology’s ability to better utilise its highly skilled personnel. “Our top level experts within the business are no longer time restricted by travel and are able to utilise their skills set across multiple mines on a more frequent basis, something we had never considered in the past but is an exercise already reaping great success,” McCoy points out.

As a result of the company’s efforts in ensuring digital technologies and the implementation thereof remain a top agenda for clients – regardless of remote working conditions, lockdown restrictions, etc., Sandvik has established a new communication repertoire with its clients. “Never before have we communicated so effectively or as frequently with our clients as we do now. We know more about our sites now than we ever did before, which naturally provides us with the ability to better assist our clients in any areas that we can contribute towards and give input on,” Andrews concludes.

CONCOR’S EXPERTISE PAVES SA’S RENEWABLE FUTURE

Concor is completing its 10th wind farm project where the majority was constructed as an engineering, procurement and construction (EPC) contractor, highlighting its niche expertise and capability in this segment.

According to Concor contracts director Joe Nell, the company has been especially busy during the fourth round of the Renewable Energy Independent Power Producer Procurement (REIPPP) programme.

“We were awarded five projects during this last round, and were able to successfully implement four of them at the same time,” says Nell. “This performance is testament to our highly skilled and experienced teams on the ground, and our strong balance sheet to apply all necessary resources to each project’s particular demands.”

He highlights the tight timeframes in these projects, which were capable of delivering power to the national grid within two years of the project agreement being signed off. In most projects, Concor met a schedule of just 16 to 17 months, which included an initial four-month design phase.

The company’s contracts began with one of the country’s first wind farms – the 60-turbine project at Jeffreys Bay. More projects followed near Noupoort, De Aar and Loeriesfontein – often remote and with challenging conditions related to geology or weather. Four projects were then run concurrently – Perdekraal East in the Witzenberg district, Excelsior near Swellendam, Golden Valley near Cookhouse and Kangnas near Springbok.

“The most recent wind farm is Roggeveld, in the mountains between Matjiesfontein and Sutherland, where cold conditions and snowfalls forced the site’s closure on numerous occasions,” says Nell. “This created its own challenges which added to the experience of our teams.”

The wind farms that Concor has constructed now contribute over 1,000 MW of electricity to South Africa’s grid capacity. Nell says the company’s success in these projects has been based on its corporate values: care, trust, delivery, agility and teamwork.

ANOTHER WIND FARM SUCCESS FOR CONCOR

Concor has put its stamp of experience and quality on another renewable energy project – this time the Roggeveld Wind Farm in the Karoo, 40 km north of Matjiesfontein. This project won the Civil Engineering category in Construction World’s Best Projects 2020. It also received a Highly Commended Award in the AfriSam Innovation in Sustainable Construction category.

The 47-turbine, 147 MW project has been developed by Red Rocket under government’s REIPPPP initiative, and constructed by EPC contractor Nordex Energy South Africa. Concor successfully completed the civil balance of plant work, including turbine bases spread over a construction footprint of 40 hectares.

Among the challenges was the area’s topography, with the highest point at 1 485 metres above sea level and the site offices a full 200 metres lower. Greg Oosthuizen, Concor’s project manager, notes that the wind farm is also in an environmentally sensitive area, with strict compliance standards applied to all construction activities.

Accessing the sites for the wind turbine bases and hard stands was over difficult terrain, and required the construction of 34 km of access roadway. The blasting, excavation and cleaning of each site was followed with the pouring of blinding and installation of levelling legs. About 2000 tonnes of steel reinforcing was used.

Then came the final installation of the levelling template, with corrugated sleeves in the foundation for anchoring the concrete towers, which are grouted into the foundation once assembled. Shuttering could then be installed, preparing the base for the readymix pour. Some 25 000 m3 of readymix was used, supplied from Concor’s own on-site batch plant.

Oosthuizen points out, however, that the batch plant presented logistical challenges of its own. It was some distance from the actual wind farm project, and about 12 km from the nearest turbine base.

“We operated ten readymix trucks on the project, and carefully managed efficiencies at the batch plant to reduce the turnaround time of these vehicles,” he says. “We also had to adjust the pumping rate when pouring the readymix at the bases.”

He emphasises that there was little room for error in base construction, especially regarding the tolerances for the levelling template. While different teams were working simultaneously on the base construction, it was viewed as one activity.

“We found that open communication between the teams was critical, and we relied on the Daily Safe Task Instructions to ensure that everyone was aligned with what was required,” he says.

Roggeveld Wind Farm will contribute 555 000 MWh a year of clean energy to the national grid, and its location in a wind channel with high wind speeds will make it one of the most energy efficient of South Africa’s wind farms built to date. With hub heights of 100 metres and rotor diameters of 130 metres, 40 of the wind turbines are 3,15 MW capacity while seven are 3 MW.

BENEFITS OF DRY-TYPE TRANSFORMERS EMBRACED IN AFRICA

The steady uptake of dry-type transformers in the African market is being driven by the range of advantages offered by this technology, argues David Claassen, managing director of dry-type transformer specialist Trafo Power Solutions.

“We have seen wider application of dry-type transformers in Africa, as they move from niche products to more universal use,” says Claassen. “The reasons are not hard to find, and include safety, reliability and low installation costs.”

A key differentiator is that the electrical core and coils in a dry-type unit are cooled by normal air ventilation. By contrast, liquid-filled transformers are cooled by oil, silicone or other liquid. The risk of this liquid spilling is one of the main factors behind the increased use of dry-type transformers. The latter has higher levels of safety and does not present an environmental hazard.

“This makes dry-type units more suitable for indoor use, and also for underground and marine applications,” he says. “At the same time, they are also resilient enough for hostile outdoor environments.”

To insulate the windings and protect them from dirt, moisture, corrosive fumes and conductive dust, special treatment techniques are applied. Depending on the application, one of three main types of insulation is used: open-wound, vacuum pressure impregnated (VPI) or cast coil.

Among their safety benefits is their low fire hazard, with their transformer insulation made up of epoxy resin and eco-friendly quartz powder, the winding is flame-retardant. This also means it will not generate toxic gases when arcing occurs. The cost implication is that costly fire extinguishing equipment is rendered unnecessary.

“When locations are remote, as they often are in African applications, the installation of dry-type transformers makes good sense,” Claassen says. “This is because they are reliable and need little maintenance, while being easier and more economical to install.”

Without the risk of oil spillage, no concrete bund wall or significant civils works is required – saving time and money. Using only air for cooling, liquid testing is not required. At the same time, the smooth coil surface eliminates the build-up of heavy dirt. Designed to meet Class E2 environmental requirements, the units resist condensation and heavy pollution.

“In terms of high reliability, cast resin transformers typically have a service life of over 25 years and the failure rate has been shown to be very low,” concludes Claassen.

CHRYSO SOUTHERN AFRICA LEADS WITH FIBRE SOLUTIONS

CHRYSO Southern Africa offers outstanding solutions when it comes to fibre reinforced concrete. A mutually beneficial partnership with Oxyfibre has resulted in world class products being available locally, supported by expert fibre technology development and consultancy capabilities. 

Izak Louw, general manager at Oxyfibre, says that CHRYSO’s presence and established infrastructure in Southern Africa made them the partner of choice for making Adfil fibres available in Southern Africa.

CHRYSO® EasyFinish, as a macro fibre, optimises speed of construction by eliminating the need for costly placement of rebar and ensuring adequate cover to reinforcement. Added benefits include smooth surface finishes, maximum bond, greater tensile strength per fibre for enhanced residual flexural strength and toughness in the concrete. 

For micro fibre applications, CHRYSO® Fibrin XTserves as alternative to crack control mesh. The use of micro fibres in concrete product manufacturing has proved to enhance the surface properties and durability, significantly reducing the occurrence of plastic shrinkage and plastic settlement cracking.

Recent projects where these fibres have been used include the placing of 7000 m2 of concrete in very thick surface beds and several large warehouse floors. Other applications have been in coastal defence structures and shotcrete in the Western Cape, as well as for the construction of floors in the farming and food processing industries where harsh chemicals and other deleterious substances could potentially affect the concrete. All these projects reported noticeable cost and time savings. 

Louw says that ongoing research has resulted in new fibre solutions that will be available shortly. These include Ignis, a micro fibre specifically designed for its fire protection benefits, and a macro fibre that will address problem areas in the precast industry.

Fibre technology is used extensively in readymix concrete, but the ease of transport, storage and handling of these fibres also makes them ideal for smaller projects and on-site mixing.

The CHRYSO Southern Africa / Oxyfibre partnership has created a win-win solution for all stakeholders providing concrete reinforcement solutions for construction projects to be undertaken safely and rapidly with reduced waste and reduced impact on the environment.

KEEPING POWER STATION PUMPS UP TO SPEED

Integrated Pump Technology is keeping the submersible pumps at a large Limpopo power station’s process drain sumps in optimal condition through high quality maintenance.

The stainless steel Faggiolati pumps were initially supplied by Integrated Pump Technology, which locally represents the Italy-based original equipment manufacturer (OEM). The pumps were carefully specified to perform optimally in high temperatures of up to 70⁰ C. They pump water that reports to the sump from a number of the power station’s sub-systems, including the turbine hall hot drains and the condensate polishing plant.

“When the pumps are swopped out for maintenance, they are brought to our well-equipped workshop in Jet Park for a comprehensive strip quotation and fault report,” says Fred Slabbert, workshop manager at Integrated Pump Technology. “We assess the complete pump, including checks on oil, wear levels, insulation, bearing lubrication and electrical cables.”

An important aspect to consider is the wear on the impeller, says Slabbert, as this directly affects the pump’s efficiency and ability to reach its duty point. The pumps are required to move 100 m3 per hour at a head of 45 metres. To speed up turnaround times on maintenance, the company keeps special repair kits in stock from Faggiolati Pumps.

“With our experience in maintaining and repairing Faggiolati pumps – among other pump brands – we make sure that all work is done to OEM standards,” says Slabbert. “This includes extensive testing capability, with a test tank that can accommodate motors up to 150 kW in power.”

After the repairs on these units, a representative of the end-customer is present at the Integrated Pump Technology workshop to witness the final tests and receive the test certificate. This testing includes the 1,5 bar pressure test on pump seals, and confirmation that there is no water infiltration in the oil.

“The pumps are then subject to full-curve testing in the tank, witnessed by the end-customer,” he says. “We have always had positive efficiency results on the Faggiolati pumps in these tests, proving our technical capability to meet OEM standards.”