ITV in Ouro Preto tests equipment to reduce iron ore moisture

Researchers at the Vale Institute of Technology (ITV) in Ouro Preto (Minas Gerais) are testing a technology that could reduce an impact that has burdened the production cost of the company’s main product for years: moisture. Today, Vale’s iron ore presents on average 9.5% moisture when loaded at the port. That means, taking as an example Valemax, the largest ore carrier in the world, that carries 400,000 t, carries 36,000 t of water moving from Brazil to the company’s main clients on the other side of the world.

The origin of the water in the ore is related to the mineral’s chemical content, but the wet mineral processing adds to the moisture. Processes such as flotation use water. Water represents greater insurance expenditures for the cargo loaded into the ship and, in some cases, may cause the interruption of a loading at the port.

TML (Transportable Moisture Limit), the international legislation, rules that the maximum limit for moisture is 10.45%, for example, for a given embarkation region of the iron ore. “When the moisture percentage goes beyond the TML in loading, the ship’s captain may suspend the operation. And then one has to run against the clock to do the ore blending on the yard and thus reduce moisture to resume loading. All this represents a loss of profit”, the company explains.

For over a decade, Vale has studied how to reduce moisture, but all solutions have been proven economically unfeasible. In the conventional method, it is possible to use industrial driers, but due to the large volumes of iron ore exported by the company, investment and operating costs do not make up for it. ITV has been developing a solution for the last two years, with the aim to reduce iron ore moisture down to 1% to 1.8%.

Instead of using industrial drying machines, the plan is to adapt the iron ore transfer chute as a drying chamber. The idea is to inject hot, dry air in the transfer chute from the bottom to the top while the ore is passing by, aimed at a moderate water removal. The equipment proposed uses dehumidifiers and heaters for atmospheric air treatment, which is injected in the transfer chute. There is a proposal to use a gas-driven system, which could be liquefied petroleum gas (LPG) or natural gas.

“In the tests we already carried out, we observed that the cost to reduce moisture using the new proposed system is much lower than by traditional drying and could be economically feasible.” In the transfer chute, the moisture reduction process lasts three seconds, which is the time the equipment takes to change the conveyor belt’s direction. “While it changes the conveyor belt’s direction, hot dry air will be blown over the iron ore.” The solution developed by ITV-MI will be subjected to an industrial-scale concept test, expected to be performed on February 2017.