Effects of Catalysts on Pyrolysis of Tannery Sludge

摘要

Six inorganic compounds, Na_2CO_3, Na_2SO_4, NaCI, K_2CO_3, K_2SO_4, KCl have been investigated with regard to their catalytic effects on pyrolysis of tannery sludge by thermal analysis experiments. The influence of catalyst categories and dosage on sludge pyrolysis were studied by the comparison and analysis of the TG ( thermogravimetry ) and DTG(derivative thermogravimetry) curves derived from tests of differential thermal balance of untreated sludge and sludge respectively mixed with six inorganic compounds of certain scale. The results show that the catalytic effect of the sodium compounds follow the order of Na_2CO_3>Na_2SO_4>NaCl, while the potassium compounds follow K_2CO_3>K_2SO_4>KCl, which both coincide with their basicity, and the two carbonates are more efficient as pyrolytic catalysts And all the six additives lowered the pyrolysis temperature of tannery sludge of which K_2CO_3 was most efficient and increased the maximum loss rate most, whereas Na_2CO_3 made the highest conversion of sludge pyrolysis. As the dosage of Na_2CO_3and K_2CO_3 increased, the pyrolysis temperatures decreases and the maximum weight loss rate increases, but the conversion rate of sludge pyrolysis decreases, considering these two factors, 5%wt is chosen as the optimal dosage of the catalysts.