Substituição parcial de finos de antracito por carvões vegetais de eucalipto na pelota crua de minério de ferro em forno de grelha móvel

Abstract

The pelletizing and sintering industries of iron ore utilize as main process fuels: coal, coke, fuel oil (from petroleum) and natural gas. Despite the growing pressure from societies in general to reduce greenhouse gas emissions from fossil fuel combustion, there is still no legal restriction concerning the usage of fossil fuels in the Brazilian iron ore industry (Conama, 2007). This work was sponsored by Samarco Mineração, a Brazilian iron ore pelletizing producer, interested in developing alternatively, environmentally, and less polluting Technologies for its combustion process. Those would have a neutral and more sustainable CO2 emission, for partial substitution of anthracite fines in bulk. The company has utilised only coal (anthracite fines in bulk), coke, natural gas and oil in its pelletizing plants as process fuel. Tests were carried out to burn iron ore green pellets. The first test was the standard, utilizing only anthracite fines in bulk (10.17% of volatile content) and the following tests were realized with a dual mixture of anthracite fines in bulk (volatile content ranging from 10.17% to 12.3% %, according to each test) and charcoal (eucalyptus coal with volatile content varying from 9.37% to 25.98%, according to each test), in a laboratory scale travelling grate indurating machine. The tests had the target to replace a percentage by mass equivalent of the fixed carbon of the anthracite fines in bulk, partially, by the equivalent amount of fixed carbon of the charcoal for each test as a function of volatile content. Thus, keeping the fixed carbon content of the green pellets by 1.0% by mass, on the dry basis of the mixture (iron ore, bentonite, limestone and charcoal). The burned pellets, with the dual mixture of fuels, were compared to the standard pellets (produced only with anthracite fines in bulk). The comparasion between pellets was restricted to the physical properties of pellets, those properties considered more important for Samarco Mineração S.A. are: crushing strength, tumble index (retained at 6.3mm) and abrasion (pass through at 0.5mm). The results obtained show that when compared to the standard test, produced only with anthracite fines in bulk, there was success in replacing at least 10.0% of anthracite fines in bulk (volatile content of 10.17%), in percentage of fixed carbon, per charcoal from eucalyptus from charcoal repyrolysed (11.14% volatile content) and in a similar way 7.5% of the same anthracite fines in bulk, being replaced by eucalyptus from charcoal (volatile content of 25,98%). Metallurgical tests are necessary and should be carried (Swelling test, low-temperature disintegration test, reducibility and pressure drop) to confirm a partial substitution of anthracites in fines bulk per eucalyptus charcoal