Highly efficient treatment of textile dyeing sludge by CO₂ thermal plasma gasification

Textile dyeing sludge is complex hazardous material with increasing amount year by year, and the conventional treatment techniques are limited by many drawbacks such as water/soil contamination, incomplete degradation of hazardous organics or inefficient fixation of toxic heavy metals. This work reported the first example of thermal plasma gasification treatment of textile dyeing sludge in a homemade rotating arc plasma reactor, which not only significantly reduced the volume and eliminated the safety risk of textile dyeing sludge, but also produced valuable syngas that can be used for chemical industry. At a feed rate of 36 g/min and a CO₂ flow rate of 0.43 Nm³/h (14.08 g/min), the carbon conversion efficiency of gasification was 99.9%; and the energy conversion efficiency could reach 71.8%; and the lower heating value of syngas-rich produced gas was 8.91 MJ/Nm³. At the same time, the volume reduction ratio of sludge was 41.19% and the fixing efficiency of the heavy metals in solid products reached above 99%. Toxicity characteristic leaching procedure confirmed the solid products were harmless in a wide environmental pH range. The proposed method exhibits its great potential of simultaneously realizing harmless, minimization and reclamation of textile dyeing sludge and even other hazardous solid waste.