The Thermogravimeric Analysis On Black Liquor From NSSC And Study On Combustion Character In Fluidized Bed

Wastewater from pulp and paper mills comes first in the pollution of the industry water, and the black liquor is regarded as the most harmful contaminant. Neutral Sulfite Semi-Chemical Pulp(NSSC) is the primary craft of making chipboard paper, the black liquor from which has the characteristic of low organic matter and heat-value. Consequently, the heavy oil has to be used as auxiliary fuel in a conventional alkali recovery boiler to sustain stable combustion. Depending on the advantage of FBC technology in disposing of low heat-value waste, an attempt has been made to displace the conventional alkali recovery boiler by FBC, which not only can dispose the NSSC black liquor efficiently, but also reduce the investment and operating expenses. The thermogravimetric analysis and the combustion characteristic of NSSC black liquor are investigated in the paper.Based on the thermogravimetric analysis of dry basis black liquor, the pyrolysis discipline has been studied under nitrogen atmosphere condition at different heating rate in the temperature range of 25～800℃. At the same time, the kinetics of pyrolysis reaction has been carried out, and kinetics parameters, such as the apparent activation energy E and frequency factor A, are figured out accordingly. By comparison of the thermogravimetric analysis of dry basis black liquor, the differences between nitrogen and air atmosphere are studied.The combustion test of black liquor was carried out in fluidized bed to investigate the influence of different temperature and alkali metal salt on bed agglomeration at temperature. Alumina powder mixed with black liquor in different proportion was burnt in fluidized bed to study the alumina on bed material agglomeration.At last, the author put forward using zeolite as bed material at high temperatures from 860℃to 900℃. It is concluded that zeolite is a promising bed material for alkali recovery.