The new stirrer-based solution is particularly suitable for treating large batches

The new stirrer-based solution is particularly suitable for treating large batches

New way to cut hot metal sulphur

The Siemens firm’s system involves a low maintenance design and use of a compact stirrer but does not entail separate procurement of expensive desulphurisation agents

01 September 2013

Simetal HM KR Desulf from Siemens Metals Technologies offers operators of iron and steel works a further type of plant for hot-metal desulphurisation. A mechanical stirrer handles the mixing of the bath. Low-quality burnt lime, which accumulates in the steel works anyway, can be used as the desulphurisation agent. It is therefore no longer necessary to buy in additional desulphurisation agents such as high-grade burnt lime, calcium carbide or magnesium separately. The new process is particularly suitable for treating large batches. Simetal HM KR Desulf adds a stirrer-based solution to the current Siemens portfolio of desulphurisation plants that run on the injection process.

Due to the use of sulphur-containing fuels in the blast-furnace process, hot metal always contains a certain amount of sulphur. Depending on the steel grade being produced, this amount has to be reduced to a defined level before the hot metal can be converted to high-grade steel in the converter. The necessary desulphurisation agents can either be blown into the bath with a lance or poured onto the bath and distributed with a mechanical stirrer. Which alternative is more economical for a steel works operator depends on many different variables, including the availability and quality of raw materials, the prices of desulphurisation agents and also individual conditions in the works.

Unlike in the injection process, the Simetal HM KR Desulf process involves placing the desulphurisation agent in the hot-metal bath with a mechanical stirrer. The system is based on a robust and low-maintenance design and is particularly suitable for large batches. As from a batch weight of about 150 tonnes, desulphurisation takes around 10 minutes and is thus faster than in the injection process. Final sulphur content values of 0.002 per cent can be achieved. Another advantage lies in process frugality with regard to the desulphurisation agents used. Reproducibly good results are possible even with low-grade burnt lime, which is frequently used as a by-product in steel works. Expensive desulphurisation agents, such as high-grade burnt lime or magnesium, or those that are difficult to handle, for example calcium carbide, no longer need to be procured separately.

Simetal HM KR Desulf is equipped with an integrated measuring lance for measuring the bath temperature and taking samples semi-automatically. Online measurement of the bath level ensures optimum positioning of the stirrer. Other special technical features of the new desulphurisation plant from Siemens are the compactness of the stirrer drive and the plant’s low-maintenance design. The transmission and material-conveying system to the screw feeder are designed in the shape of a Z, resulting in an extremely low mounting height. Value was also placed on ease of access to important components, which facilitates maintenance and boosts occupational safety.

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