Prihláste sa na odber noviniek
Probably none of the passenger rail carriers would be thrilled if you offered them to transport slag. However, this is completely different for rail freight hauliers. Transporting slag means a regular flow of raw material, which is related to the metallurgical industry, but in fact belongs to the building materials commodity. And, for ZSSK CARGO, slag means a volume of more than 350,000 tons of transported goods per year.
Steel making processes, just as any other industry, has its waste generated. In this case it is called slag. It is formed during the melting of liquid metals. The non-metallic components of the melt form a layer on its surface. These are metal oxides such as silica, silicates, iron oxides, calcium oxide and the like. Slag is produced in the production of both iron and steel and differs in lime content. Košice steelworks alone produce more than half a million tons of slag per year.
Someone’s Trash is Another One’s Treasure
If the slag was not used, huge heaps of this raw material would be formed around the iron and steel works. Fortunately, the slags have its use as a secondary raw material. And its largest consumers in Slovakia are cement producers. Coke ash and iron ore tailings are transformed into so-called slag granulate. It is produced by rapidly cooling liquid slag, which is poured into a stream of water. The granulate has good hydraulic properties and is added to cement. Granulated blast furnace slag thus finds its application in the production of Portland slag cements, blast furnace cements and hydraulic lime. Manufacturers of artificial aggregates value its strength, durability and environmental friendliness. And so, we encounter the slag that ZSSK CARGO brought to cement producers on a daily basis. It is part of the roads and highways we drive on, or parking lots at shopping malls, where we go to resupply our households. It has an environmental bonus too: slag replaces products mined in open quarries, thus helps to protect finite resources, and makes the most of the content in the raw materials necessary for the production of iron and steel.
The Advantage of the Network-Side Railway Carrier
ZSSK CARGO transports approximately 30,000 tons of slag every month from Haniska near Košice. It goes to customers in different parts of the country. As the only network-wide freight railway carrier in Slovakia, ZSSK CARGO can also provide services for this circular secondary use of raw materials. The slag is usually transported in high-volume hopper wagons with pneumatic control of side dampers of the Falls and Falns type. This allows the end customer to unload the load quickly and efficiently. It is possible to load more than 50 tons of cargo into a single wagon. On high demand, these wagons are complemented the standard Eas / Eanos open-top wagons.
Combination of Electric and Diesel Traction
The transport of slag from the east of Slovakia takes place to four main customers in the field of cement production.
One of them is a cement producer in Považie, in Horné Srnie. Unit trains pulled by electric locomotives run from Košice, through the Štrbská Pass to Žilina, where dual-system electric locomotives ZSSK CARGO take over the slag transport to the Trenčianska Teplá station. From here, the set is divided into several smaller local trains, which are gradually transported by Class 736 and 742 locomotives of the local depot to Horné Srnie. In Trenčianská Teplá, they again assemble an empty unit train for another run.
The second customer of the slag in Považie region is the cement plant in Ladce. Ladce station is an unoccupied tariff point, so here the electric locomotives shunt the train loaded with slag to a side rail. The station is regularly served by a local ZSSK CARGO shunting diesel train, which then brings the wagons to the siding for unloading and prepares the empties for return move either directly in the Ladce or in the Púchov station.
The longest route is that slag takes is the one from Košice to Záhorie. As with the Považie trains, the DC (Class 131) and AC (Class 240) locomotives change at the front of these trains. The advantage is the use of locomotives Class 363, which are able to operate under both voltage systems. This way, unit trains are powered by electricity for up to 500 km distant station of Zohor. Here, the traction for the last tens of kilometres changes from electric to diesel. Local ZSSK CARGO freight trains deliver loads to the customer in Rohožník, by Class 751 and 742 locomotives.
The last of the shipments is the shortest. It measures only 30 kilometres, but similarly to the transport of lime aggregates from the quarry to the processor under the lead of ZSSK CARGO, the transported volumes also significantly save the roads in the Gemer region. The wagons are pulled by diesel locomotives Class 751 and 752 since the beginning of their journey, and in Turňa nad Bodvou they set up wagons at the delivery point, from which the customer's shunting locomotive takes over to the siding.
The transport of secondary raw materials has a great potential on the railways. In the transformation of economies into a sustainable ones, the railway can play a major role in the transport of secondary raw materials, as is the case today in the transport of scrap, slag or wood chips. It can be similar with recycled glass, paper or plastic, but also in the transport of waste itself for its energy utilization. ZSSK CARGO is ready to accept these challenges and contribute to the fight against the climate crisis with an ecological transport for the emerging circular economy.
Photos: Lucia Knuteľová, David Galko, Marcel Baltiar
