Cembreak Lump Breaker

grinds ash and slag in power stations

Crushing and grinding ash and slag is an essential part of process and plant reliability in power stations. Agglomerated material can constitute up to 5% of the total, resulting in process breakdowns and rising costs. There is consequently a demand for reliable, tailored solutions such as the Cembreak lump breaker supplied by Telschig.

Around 1,200 tonnes of waste are burned per day in the modern EnBW Stuttgart-Münster waste incineration plant for energy generation. The Cembreak lump breaker is an important component in the system of the three huge waste incineration boilers, the oversize pipework and kilometres of cable. It grinds the residual slag from the boilers, to keep the plant system flowing smoothly.

Ash or slag is generated as combustion residue in the huge waste or coal boilers of the power stations. This is generally moved by pneumatic conveyors to slag silos or ash hoppers when it has cooled down, and processed from there. "As the slag or ash cakes onto the boiler wall and flakes off, lumps of up to around 300mm in size are created which block the conveyors and can obstruct the discharging of bulk transport vehicles. This results in wasted time and unnecessary cost", explains Silke Franz, project engineer at Telschig Verfahrenstechnik GmbH. The proportion of slag or ash from waste incineration or coal boilers in power stations can be up to 5%. To keep material moving smoothly, the maximum grain size must be around 10 mm, which must not be exceeded.

In the Stuttgart-Münster waste incineration plant Telschig installed a twin-shaft "CEMBREAK-TD” unit with screen insert below the ash collecting container. It can be used up to a product temperature of 400°C, and it grinds all slag agglomerations over 150mm in size to an output size of 10 mm. To avoid having to pass all this material through the grinder with the associated unnecessary wear, Telschig staff installed a screening grate in the main flow upstream of the grinding processor to separate out the agglomerations that require grinding.

The processor’s tools driven by the two shafts grind the large lumps with a low level of noise and absolutely vibration-free, since the CEMBREAK-TD operates at low revolutions. The ground product from the grinding processor is fed back into the main flow via a downpipe. This principle enables the CEMBREAK-TD to avoid blockages in the bulk transport vehicles when they are discharging, ensuring a high level of process and plant reliability.

"The essence of efficient lump crushing is adapting the particular technical configuration to the particular problem on site", explains Silke Franz. This requires an extensive range of technical configuration options to choose from, and experience to match. Telschig Verfahrenstechnik GmbH for example offers single-shaft lump breakers as well as twin-shaft models. The parameters governing which lump breaker to use are principally the throughput, input grain size, grain spectrum and product temperature. One uniform factor is that grinding and any screening takes place in one process stage. In the case of highly complex applications or with new unknown products, Telschig also offers its customers the option of conducting trials in its in-house development centre to establish a basis for designing optimum configurations. "Money well spent for the customer", comments Silke Franz, "because lump crushers are critical interfaces between the raw material and processing". Suboptimal plant at these interfaces often gives rise to delays and additional cost, and can soon amount to many times the development cost.

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