| Carbon black(CB) is a type of widely used carbon material that is primarily used as a rubber reinforcing agent, and its consumption in the rubber industry accounts for approximately 89.5% of the total production. The CB produced via the oil furnace method, which is the current primary production technology, accounts for more than 90% of the total output. However, the reaction temperature in this method is notably high, meaning that the energy consumption is quite large. In addition, the exhaust gas contains a large number of pollutant gases, such as NOx and SO2.Chemical looping technology is a new type of clean and efficient method for fuel conversion, it uses oxygen carriers(OCs) to transfer lattice oxygen to the fuel, and the target products are controlled by the lattice oxygen/fuel ratio. This technology has a wide application prospect. Therefore, carbon black production from coal tar via chemical looping pyrolysis(CLP) was systematically explored. The main research contents and results are as follows:Firstly, according to the principle of Gibbs free energy minimization, the reaction process was investigated by thermodynamic analysis. The influences of temperature and OC/tar ratio on the CB yield were studied. The results reveal that the Fe2O3 and CaSO4 are both suitable for CLP process. At 900℃, when the molar ratios of Fe2O3/tar and CaSO4/tar are 2 and 1.5 respectively, the CB yield is highest. When temperature exceeded 900℃, coal tar components more easily oxidized to gas and the CB yield declined.According to above theoretical parameters, the CLP experiments of coal tar were performed in a fluidized bed reactor with hematite and gypsum. The results show that, with an decreasing particle size, the CB yields increased, but the CB impurity content rised, hence the 0.5 mm particle size is appropriate. With temperature increasing, the qualities of two types of CBs both improved. Compared to CaSO4 CB, the yield of Fe2O3 CB is higher, the particle size is smaller and uniform, and the spatial structure is more developed. The two types of OCs both have an inhibitory effect on NOx, and Fe2O3 OC is more effective, but they are helpless to reduce SO2 emissions.Then the hematite/γ-Al2O3 and hematite/NiO composite OCs were prepared by mechanical mixing. TGA analyses show that the reactivity of Fe/Ni OC is best, the Fe/Al OC follows, NiO and γ-Al2O3 can both improve the OC activity. The CLP research indicates that the CB yield of Fe/Al OC is highest, and coal tar components were almost all involved in the reactions. Compared to Fe2O3 CB, the particle size of Fe/Al CB is much smaller, and the spatial structure is also improved. However, since NiO reactivity is too high, the overall reaction tended to chemical looping combustion(CLC) process. Therefore, the yield of Fe/Ni CB is even lower than that of hematite CB, and the CB particle is larger, structural property is also poor. Relative to the NiO, γ-Al2O3 is a kind of ideal additive.In order to investigate the multi-cycle performance of OCs, the experiments of OC/coal tar co-pyrolysis and OC regeneration were alternately conducted in a fluidized bed reactor. The reduced Fe/Al and Fe/Ni OCs after three-cycles were respectively investigated by the TGA-DSC apparatus. Results indicate that the addition of γ-Al2O3 can effectively inhibit carbon deposition, whereas the NiO promoted carbon deposition. According to the burning temperature, the carbon deposition on reduced OCs is mainly hard coke, a kind of carbon material like graphite. The XRD analyses show that under the lower OC/coal tar ratio, the Fe2O3 in compound OCs mainly converted into FeO and Fe, which achieved a deep reduction. The NiO has a certain synergistic effect that promotes the activity of Fe2O3. The SEM characterizations show that the sintering was alleviated due to γ-Al2O3 addition, which effectively kept a good reactivity of the Fe/Al OC. However, the Fe/Ni OC cracked after three-cycles, and a lot of cokes deposited in the cracks, the surface sintering was also serious.
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