Recycling Waste Bakelite As A Carbon Resource In Ironmaking
Bakelite is a 3-dimensional cross-linked network structured thermosetting polymer which is difficult to recycle after use. However, it contains high levels of carbon and CaCO3 that can be recovered for use as reductant and fluxing agent in ironmaking. In this work we report the use of postconsumer bakelite as reductant for the production of metallic iron from iron oxide in a horizontal tube furnace through the composite pellet approach.Gas emission studies were conducted by pyrolysing raw bakelite at different temperatures within the temperature range 1200-1600 °C in a horizontal tube furnace. Following this,composite pellets were then formed from mixtures of iron oxide and post-consumer bakelite.The iron oxide-bakelite composites were heated from room temperature to 1200 °C and then between 1200-1600 °C in a continuous stream of pure argon and the off gas was analysed continuously using an infrared (IR) gas analyser. Elemental analyses of samples of the reduced metal were performed chemically for its oxygen content using a LECO oxygen/nitrogen analyser. The extent of reduction after ten minutes was determined from the oxygen content. Gas emission studies revealed the emission of large volumes of the reductant gases CO and CH4along with CO2.It is further demonstrated that post-consumer bakelite is effective at reducing iron oxide to produce metallic iron.
Carbon/Slag Interactions between Coke/Rubber Blends and EAF Slag at 1 550°C
Using the sessile drop approach, interfacial reactions taking place in the slag/carbon region were investigated at 1550°C in a horizontal tube furnace under inert atmosphere (1 L/min Ar). In this study, waste rubber tyres were blended with metallurgical coke, already used as injectant in electric arc furnace (EAF) steelmaking, in different proportions. Off gas analyses and physicochemical properties of the slag have been evaluated and correlated with the carbon/slag interactions. The gaseous emissions from metallurgical coke showed lower concentrations in comparison to the emissions from the coke–rubber blends. With an increase of rubber in the blend, gaseous emissions were enhanced. Significant carbon/slag interactions occurred when coke/rubber blends were used, with associated iron oxide reductions within the slag phase. Higher gas entrapment in the slag was also observed when the rubber partially replaced the coke.High levels of gas generation leads to increased likelihood of convective transport of reactants and products from the carbonaceous material surface due to evolution of gases as a result of slag/carbon interactions. The oxides present in the ash partially dissolve the molten slag, modifying the slag composition. The results have been discussed and correlated with the hydrogen, ash and sulphur contents of the carbonaceous residues as well as with the dynamic changes in slag composition.This study highlights significant differences in the carbon/slag interactions of coke/rubber blends with EAF slag, compared to interaction of coke with the same slag.
Foaming of slags under dynamic conditions
Slag foaming under dynamic conditions has been studied in laboratory scale to examine the influence of properties commonly used to describe the foaminess and foam stability of slags under steady-state conditions. Synthetically produced slags with compositions relevant to tool steel and stainless steel production were studied through X-ray equipment in measurements simulating the dynamic conditions found in real processes. It is found that the dynamic systems display a more complex behavior than systems under steady state. Traditional theories for foaming do not seem to be valid for slag foaming under dynamic conditions. The foam displays a fluctuating behavior, which the presently available models are not able to take into account. The concept of a foaming index does not seem to be applicable, resulting in the need for alternative models.