No abstract

Bentonite is the most commonly used binder for iron ore pellets. However, due to its high alumina and silica content, the slag volume and energy consumption are increased. The aim of the present work is to identify the CSL (sodium ligninsulfonate added CaCO3) as an alternative binder in iron ore pelletization. FTIR and zeta potential tests verified that sodium ligninsulfonate (SL) reacted with magnetite mainly through ligand exchange, hydrogen bond and electrostatic interaction. Compared with SL, CSL has more active sites and stronger adsorbability. The strength of CSL preheated and roasted pellets was determined by TG and SEM. CaCO3 as a fluxing agent develops oxide bridging and bonding between the magnetite grains, forming more slag, reducing porosity and improving the compressive strength of roasted pellets. The experimental results show that it is feasible to add CaCO3 in SL as binder in pellet production.

The reactor was started up under the neutral condition. The pH value in the reactor was gradually lowered down. At pH 7.0, the average COD removal efficiency the biogas yield and the methane content of the UASB reactor were steady at 93% above, 25L·d-1and 54%, respectively. During the period of the pH value lowered from 7.0 to 5.5, the average of the COD removal efficiency, the biogas yield and the methane content of the UASB reactor were 83.1%, 19.6L/d and 47.7%, respectively. At pH 5.5, the operating condition of UASB reactor began to recover from the 76thday, and on the 84thday, the COD removal efficiency, biogas yield and the methane content recovered to 80.5%, 17.1L/d and 47.9%, respectively.