Humidity control of steel for world’s largest independent steel trader
Stemcor is the world’s largest independent steel trader. Their new steel service store in the heart of the deep-sea port of Uusikaupunki, Finland specialises in flat steel products.
The 11,000 m3 Stemcor storage building includes a wide range of steel products, which is why humidity control is critical to ensure pristine product quality. The relative humidity (RH) of the store is managed throughout the year by Munters MX2700. An additional challenge was the immediate proximity of the sea and its corrosive salt-laden air. The storage building is kept constantly below 50% RH to prevent corrosion of steel or oxidation of metals. Research has demonstrated that above 50% RH the rate of oxidation of metals is greatly accelerated from 100-2000 times greater than oxidation rates at lower humidity levels.
Desiccant - the right solution
The effective solution was Munters MX2700 desiccant dehumidifier, which supplies dry air into the store on a four hourly air change, and has a drying capacity of 21kg / hr. The desiccant dehumidified store ensures the relative humidity is controlled constantly throughout the year, irrespective of fluctuating outdoor conditions.
Using dehumidification to store metal materials keeps the product quality high with less waste. When storing metal products like galvanized steel, cold surfaces can “sweat” causing metal parts to corrode. The thin layer of water vapour molecules that settle on the metal surfaces supply an electrolyte to the corrosion process. With the RH in the store kept below 50%, corrosion is almost impossible, whereas the corrosion rate explodes at levels above 60% RH.
Heating warehouses reduces the relative humidity by expanding the air and thus increasing the air’s ability to hold water. It is an expensive solution compared to desiccant dehumidification where energy consumption is typically 30-70% less and the root cause of the corrosive atmosphere (moisture) is removed.
How it works...
Air from the store is drawn though the MX2700 desiccant drying wheel (rotor) and the moist air is absorbed by the hygroscopic desiccant. The air leaves the rotor as dry air and is distributed at high level into the store to dissipate throughout the store.
In a separate regeneration sector, hot air is blown through the rotor to remove the accumulated moisture and the resulting wet air is blown away outside the building. The sustainable, environmentally friendly system works without Freon or compressors.
Munters MX2700 system was supplied with complete control. The regeneration of Munters drying wheel utilises LPG, as Stemcor wished to make use of surplus liquefied petroleum gas from the heating system used during steel processing. This matched customer requirements with the most energy efficient option. Other drying wheel regeneration options include electricity and steam. Munters MX2700 is one of the first liquid - gas reclamation dry-air systems operating in Finland.
Munters service specialists precisely commissioned and ensured correct start-up, and the experienced team helped calculate the energy consumption to provide the most energy efficient solution.