MechChem Africa November-December 2024

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Steinmüller Africa’s locally manufactured boilers deliver efficient waste management, improved energy efficiency, and cost savings for pulp and paper, sugar, minerals processing and coal mining industries. Warwick Ham, Boiler Process Group Leader for Steinmüller Africa explains. Waste to energy boilers for industrial sectors

Left: Steinmüller Africa’s boilers are built to be environmentally friendly by turning industrial waste into energy. Right: Boilers are typically designed to operate for about 200 000 hours, with boiler tubes, essentially, the only parts that require repair or replacement.

W ith 60 years of expertise, Steinmüller Africa offers full-service boiler solutions, including fired boilers that capitalise on sustainable waste disposal to produce steam, which is a valuable energy source for processes using steam: to convert raw materials into products or to generate electricity for onsite use. As well as the large mining sector in South Africa, the pulp and paper and sugar industries also generate significant amounts of combustible waste that requires disposal. Fired boilers can be fuelled by the waste products they produce, and/or combined with fossil fuels such as gas, oil or coal to generate steam for use onsite. Pulp and paper plants process wood chips and use heat and chemicals to dis solve the lignin to extract the fibre needed for paper making. The remaining liquor can be thickened into a tar-like substance and burned in special boilers, heating the water passing through boiler tubes to generate steam. In the sugar industry, sugar cane is cut, heated and crushed to extract the juice, which is crystallised to yield sugar. This process results in high volumes of cellulose fibre waste, known as bagasse, with a high residual moisture content. The bagasse makes up approximately 30 to 40% of the sugarcane volume and can be burnt in spe cial bagasse boilers, generating the steam needed in the sugar making process. This ensures better energy efficiency and more environmentally friendly waste disposal. In addition, the mining industry gener ates waste during the process of sorting valuable mineral ore from the surrounding

rock, or the refining the mined ore to yield the target commodity. In the coal mining industry, for example, coal is washed to separate high quality and medium to low quality products. The finer coal dust and sulphur-rich coal are generally rejected and disposed of in large waste-coal dumps. Some of the coal rejected as ‘low quality’ can still be burned for energy production, however, in purpose designed boilers. Steam production plants can use this energy to power large fans used for mine ventilation, for example, reducing their grid-based elec tricity consumption. Alternatively, rejected coal can be sold to other industries as an addition to the sustainable disposal in fired boilers of other industrial wastes such as bagasse or fibrous wood waste. “Waste in these industries serves as the fuel to generate steam in a fired waste-to energy boiler, making these industries more energy efficient and sustainable,” comments Warwick Ham, Boiler Process Group Leader for Steinmüller Africa. “We can custom engi neer the most profitable solution based on the client’s waste source, steam, tempera ture and pressure requirements.” Maintenance and inspection Steinmüller Africa’s has also secured sev eral large contracts in South Africa for its maintenance and inspection services, which are highly specialised to ensure optimal per formance and longevity and best possible efficiency of in-service boilers. Boilers are typically designed to operate for about 200 000 hours, with boiler tubes, essentially, the only parts that require re pair or replacement. Due to large average

boiler sizes, Steinmüller Africa conducts its inspection and maintenance services at client sites, and brings all the necessary in spection technology and expertise, welding technology, cranes and equipment onto site. Boiler inspections and maintenance outages require carefully planned plant shutdowns, before which, very large boilers must cool slowly, which can take several days. Boiler inspections should occur ev ery 18 months to determine whether the boiler tubes are corroding – due to low quality water and erosion/corrosion; ash or heat damage; or excessive temperature exposure. Once inspection reports and engineering assessment of the root causes are performed, damaged tubes are replaced, giving the boiler a new lease on life. Typically, an outage schedule includes a first inspection for assessment at 18 months; a mini overhaul outage at three years; another inspection outage at the four-and-a-half-year mark; and a general overhaul outage at six years, where a de tailed inspection is carried out followed by the replacement and refurbishment of any worn components. In both the fabrication and repair of boilers, alloy steel materials having to be pre-heated to prevent cracking before be ing welded, held at temperature and cooled slowly as a post-weld heat treatment to ensure optimal integrity. This is highly specialised work. Steinmüller Africa ensures high-quality, sustainable solutions that meet standards in sub-Saharan Africa, solidifying its position as a leader in heat exchangers and all types and sizes of fired boilers. www.steinmullerafrica.com

48 ¦ MechChem Africa • November-December 2024