This sinter plant, owned by the Saint-Gobain Pont-à-Mousson group, was part of a steel work which produced ductile iron pipe and fittings for water and sewage networks. Simply speaking, the sinter plant turns iron ore into sinter, which is the optimal product for the blast furnace. Sinter is made by burning a mix of iron ore powder, fluxes and recycled substances from the steel plant to create an open-grained, consistent substance. The process, called sintering, causes the constituent materials to fuse to make a single porous mass with little change in the chemical properties of the ingredients.
The Saint-Gobain sinter plant, which opened in 1967 and was mothballed in 2018 (although to my knowledge it has not beed operational since) is the last operational sinter plant in the French region of “La Lorraine”. It has a capacity of 660000 tonnes of sinter iron which roughly corresponds to 375000 tonnes of ductile iron.
The raw materials (limestone, raw iron ore, coke etc) required for the sintering process were brought in by train and stored in large storage bins. The raw materials stored in the individual bins are precisely dosed onto a conveyor belt and are transferred to the mixer where the various ingredients are mixed into a highly homegeneous “sinter” mix. Following the mixing, this raw mix is charged into the granulator where granulation to the required grain size is carried out. This process of mixing and granulating is performed around the clock in order to ensure a continuous supply of sintered ore to the blast furnace. The “granulation” ensures that the next step, the actual sintering process, is performed as optimally as possible. The granulated iron ore is then placed on a sintering machine.
In a typical sintering machine, the sintering grate is a continuous chain of large length and width, formed by the union of a series of pallet cars which make the sintering strand. Each pallet car passes below a charging hopper where it is charged firstly by material of coarse particles in a layer having thickness of 30mm to 60 mm which forms the hearth layer composed mainly of return sinter. the hearth layer protects the steel grates from over-heating during the sintering process. A second layer of smaller particles is charged over the hearth layer and levelled. Then the pallet car passes below an initialising furnace, where the combustible ignition takes place on the surface of the charge mix. At the same time, the mix is subjected to a down draught suction through the sinter charge. Due to the down draught suction, air is drawn through the moving bed causing the fuel to burn.
As the pallet car continues the process and the combustion progresses in the direction of the gas flow. In this way the sintering process takes place. The combustion process does not happen simultaneously in the whole thickness of the bed but happens as a horizontal layer which moves vertically through the bed. At the end of the machine, the sintered material in the form of cake is discharged into the hot sinter crusher. Here the sinter cake is crushed to a pre-determined maximum particle size. From here the sinter is discharged not a sinter cooler. When its temperature drops below 120°C, it was transported on conveyor belts to the ore yard, from where it was dispatched to the blast furnaces of the region.