| Dyeing sludge has a complicated composition, including dyes, sizing agent, surfactant, etc., and is quite difficult to be dealt with, resulting serious environmental pollution. The disposal of dyeing sludge has hindered the development of the printing and dyeing enterprises. In the other hand, dyeing sludge contains a great amount of organic components and fiber materials, consequently having a relative high heating value. The sludge drying-incineration technology can completely utilize the effective components and realize the reduction, harmlessness and recycling of sludge during disposal dyeing sludge, thus having a brilliant future in waste treatment and disposal.With the support of 2012 Jiangsu Province Environmental Protection Research Program (2012033), this work proposed the process of integrated desulfurization in drying-incineration furnace, according to the development and status of sludge treatment and disposal technology. Firstly, the optimal conditioning scheme was obtained using cationic polyacrylamide (CPAM), lime and aluminum sulfate as conditioner and pneumatic pressure filtration device operating at 1.6 MPa as dewatering machine. The result shows that the optimal conditioning order is aluminum sulfate, lime, CPAM with an adding interval of 5 min. Besides, the optimal dosage is 9% of aluminum sulfate,12% of lime and 0.125% of CPAM. After dewatering, the moisture content of sludge cake is around 50% using the optimal condition.Secondly, this work studied the drying characteristics of conditioned dyeing sludge by monitoring the variation of moisture content of sludge with drying time. The result shows the sludge drying process was divided into three stages as preheating, constant drying rate period and the falling drying rate period. The falling drying rate period lasted the longest time. Drying temperature and particle size are the two main factors affecting the drying characteristics and the drying temperature has the greatest influence. When the drying temperature increased from 90℃ to 150℃ and the particle size decreased from 5-6 mm to 2-3 mm, the drying rate was increased quickly, resulting in the reduction of drying time. The predicted value from Page model was quite close to experimental value with a root mean square error less than 0.01318.Lastly, this work taken the thermogravimetric analysis and combustion in circulating fluidized bed to studied the co-combustion characteristics of dyeing siudge. The result shows that the combustion process included fuel drying, combustion and volatilizing of volatiles, combustion and volatilizing of organic matters with high boiling point, combustion of fixed carbon and residues. Every stage has its reaction order as 2.5,3,0.5 and 0.5. Co-combustion of the conditioned sludge with coal could improve the burnout characteristics and reduce the ignition temperature. The comprehensive combustion performance was the best when the blending ratio was around 10%～15%. Keeping the fuel feeding rate constant, the furnace temperature was dropped 5.12℃, the boiler output was decreased 0.68 t/h; the thermal efficiency was decreased 0.78 percent and the HCl mission was increased by 3.33 percent if the ratio of dyeing sludge to coal was increased by 1 percent. However, the desulfurization efficiency was increase by 1.72 percent and the NOx emission was reduced by 1.93 percent. In order to ensure the stable operation of circulating fluidized bed, the ratio of dyeing sludge to coal was better to be lower than 20%. The heavy metal content in the fly ash and furnace slag kept increasing with the ratio of dyeing sludge to coal, but not exceeded the pollution emission standard in the range studied in this work.This work proposed the process of integrated desulfurization in drying-incineration furnace, according to the development and status of sludge treatment and disposal technology. The result has a great referential value for dyeing sludge recycling. |
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