Influence Of Dyeing-Printing Wastewater On The Combustion Of Coal Powders

Aimed at the problems of the coal resources shortage and environment pollution caused by the combustion of coal and the discharge of dyeing-printing wastewater, treated coal powders were prepared by dipping coal powders into dyeing-printing wastewater in this work, leading to the improvement of the combustion performance of coal powders by the effective composition of wastewater and the decrease of exhaust gas. And the Influencing factors and mechanism of dyeing-printing wastewater to coal powder and the effect of dyeing-printing wastewater on combustion performance were systematically studied.Effects of dyeing-printing wastewater on heat value and combustion efficiency of coal powders were studied. The experiment results showed that when the ratio of wastewater to coal powders was 4%, the heat value and combustion efficiency of coal combustion increased by 2.29 and 8%, respectively.Properties of coal samples including initial separation point of fugitive constituent, kindling point and activation energy were studied by thermogravimetric analysis (TG) and differential thermal analysis (DTG). It was found that when the ratio of wastewater to sample was 4%, the kindling point and activation energy of coal samples were reduced by 16-26℃and 30.60-33.77%, respectively.Effect of wastewater on exhaust gas of coal combustion was also studied in this thesis. The gases, including CO and NOx, escaping from thermal analyser were detected by KM940 fume analyser. The results showed that the addition of wastewater led to the decrease of Co and NOx contents released from the combustion by 27.94 and 20%, respectively. The mechanisms of improving combustion performance and reducing exhaust gas were investigated. The decomposition of the oxidants in wastewater during burning led to the occurrence of more activated oxygen needed in the combustion stage, which accelerated the decomposition of fugitive constituent and carbon granule, thus leading to the full combustion of coal powders. The Na+ in wastewater adsorbed on the surface of coal particles could exchange with humified acid salt, which could catalyze the rupture of chemical bonds in alkane hydrocarbon of fatty group of coal. The intermediate products of combustion Na2O could act as the carrier of oxygen, which could accelerate the transfer of oxygen and reduce the activation energy of coal combustion, thus leading to the improvement of combustion performance of coal powders and the reduction of exhaust gases.