MechChem Africa

thyssenkrupp tkIS Facor Power CFBC boiler“The thyssenkrupp brand is well known in Africa for its ‘pit-to-port’ mining and materials handling solutions and its turnkey cement plants, but the Industrial Solutions business area among others also combines leading know-how in the fields of chemicals, fertilisers, oil & gas and electrolysis. It also has a long and successful history in developing and supplying sugar plants, boiler installations and power plants, especially in India” begins Jacques Steyn, tkIS GM for Materials Handling.

Spanning the comprehensive range of plant solutions and equipment is the company’s service offering, with the thyssenkrupp Industrial Solutions Service Centre in Chloorkop at its heart. Originally equipped with the capacity to manufacture and refurbish the largest Polysius-branded HPGRs (high-pressure grind rolls) in the thyssenkrupp range, the facility has CNC vertical and horizontal machining centres capable of handling 100 t components – “and we have just improved and refurbished an HPGR for a diamond mine in Gauteng,” says Lamprecht.

Today, all of the thyssenkrupp Industrial Solutions’ business lines are supported through the Service Centre, as well as through field and onsite presences. “Refurbishments, new and replacement parts and wear part manufacturing, fabrication and machining for any of our equipment offerings can be done locally and quickly through our Service Centre,” he continues. “We hold and manufacture spares, support the field services teams and are available 24/7 for breakdowns, shut-downs and product support.

“We also offer technical training and we can take full responsibility for plant uptime via customised integrated asset management (IAM) contracts, through which we can operate and maintain industrial plants and/or equipment” he assures.

“We provide services that cut across all of the pit-to-port, cement, process plant and power equipment solutions that we offer,” adds Steyn. “Our integrated service offering makes us unique in that a huge variety of industrial plant equipment can be serviced from a single source,” he says.

Power solutions for emerging markets

Power and Energy is a recent introduction to thyssenkrupp Industrial Solutions’ sub-Saharan African product offering. “Globally, this is a strong division in its own right,” says Wilfred Barkhuizen, GM for Minerals Processing, Power and Energy, adding that, in India, thyssenkrupp has over 200 installations.

“The offering includes three core technologies: coal-based circulating fluidised-bed combustion (CFBC) plants of between 20 and 150 MW per unit; biomass boiler installations for the likes of renewable power plants including the sugar and pulp & paper industries; and waste recovery plants for industrial energy users wishing to reduce the specific energy associated with their production processes,” he tells MechTech.

The core application for the biomass technology in India lies primarily in the sugar industry, which uses large amounts of steam for the extraction process and, from the cane residue, produces a dry waste product called bagasse, which is an ideal fuel for thermal plants.

Cold-cyclone CFBC technology first entered thyssenkrupp through a collaboration in the late eighties with Deutsche Babcock Germany and thyssenkrupp Industries India (tkII). The technology was widely adopted for captive power generation/co-generation application and, in India to date, thyssenkrupp has over 55 CFBC boilers commissioned and 15 in various stages of execution.

“Most utility-scale power stations in South Africa use pulverised coal to ensure complete and efficient combustion. CFBC power stations operate at lower combustion temperatures and can use much lower quality coal, including discard coal that is normally regarded as unusable,” says Barkhuizen.

How does it work? Instead of being pulverised, the coal is simply crushed to a size of less than 8.0 mm. It is then fed onto a fluidised bed on the boiler floor. Air is blown up into the bed from below, which suspends and agitates the fuel, resulting in large fuel particles circulating in the bed. Smaller particles are blown into the furnace and are captured with a cyclonic filter at the furnace outlet, before being recirculated back to the fluidised bed. “Generally speaking with low quality coal, the carbon is unreactive and the ash fusion temperature is low. In a fluidised bed, the airflow removes the surface ash, the circulating action ensures a high residence time for combustion of unreactive coals and the relatively low bed temperature prevents ash from fusing,” Barkhuizen explains.

 “These are conventional sub-critical tower type boilers with superheaters upstream of the cyclones and a fluidised bed at the bottom. They use normal balance of plant items, such as water treatment systems, conveyors, crushers, flue gas treatment (bag filters, for example) and normal steam turbine generators,” he tells MechTech.

Barkhuizen continues: “India has the same coal problems as we have, with high levels of discard coal from its mines. In South Africa, high quality fuel is used most frequently, so coal producers end up with large stockpiles of discard coal, which cannot be sold.

“But this discard fuel is ideal for use in CFBC plants. Our estimations suggest that most coalmines could meet their own power requirement by burning discard coal, which, since the coal is already mined, is a very low-cost fuel that offers an exceptional business case for power plant installations,” he says.

But are the emissions a problem? “No!” responds Barkhuizen. “Because of the lower combustion temperatures, along with the addition of lime to the fluidised bed, SOx and NOx emissions are significantly reduced. SOx is entrapped in solid ash waste in the form of gypsum, while thermal NOx is reduced due the lower combustion temperature. Emissions from our CFBC plants are acknowledged to be below World Bank standards,” he explains.

Due to their simplicity and the packaged nature of the solutions, the investment costs for installing a thyssenkrupp CFBC plant are significantly lower compared to conventional solutions. “I think it is fair to say that these solutions come in at a fraction of the cost of pulverised-coal equivalents. We estimate the costs at between US$1.8 to $2.4-million per megawatt installed,” he says.

“The second problem with big grid connected plants is the distribution infrastructure. If a coalmine, sugar plant or steel mill installs a captive CFBC plant to take care of its local needs, it is very economical to install the infrastructure to supply the surrounding communities. This has been a common model in India and is ideal for overcoming weak grid issues across Africa,” he continues.

“As well as the capex being low, the opex is very low. The fuel used is less expensive or ‘free’ and the less sophisticated nature of the plant makes it easier and less complex to maintain when compared to the large power plants. And we can install a plant, from signing the contract to producing power, in 24 months,” he assures.

Service is key

Power plants are designed to operate 24/7 for 30 to 40 years, so servicing of the plant itself and the balance of plant equipment becomes vital if the full benefits are to be realised. “Through our asset management, service centres, field services offering and part manufacture and supply, we are ready to take on full IAM responsibility by operating and maintaining power plants at every level,” says Ruben Lamprecht, Services GM.

“We can do shut-downs, revamps and full plant-wide asset management, which is the best way to establish the reliable power supply needed for African industrial growth,” he adds.

“For us in South Africa, the Power and Energy business is new and exciting. Africa does not always need the R100-million shiploader or the R130-billion power station. Sometimes a simple conveyor on the end of jetty is perfectly adequate, or a 50 MW power plant burning biomass or waste coal.

“Our power offering, as well as our balance of plant, mining, cement and materials handling solutions are all custom-engineered to fit the purpose and scale of the intended application. We believe that this approach and the solutions we offer are ideally suited to the emerging economies in Africa,” Steyn concludes.

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