Pyrolysis of Denim Jeans Waste: Pyrolytic Product Modification by the Addition of Sodium Carbonate

Abstract

Quickly changing fashion trends generate tremendous amounts of textile waste globally. The inhomogeneity and complicated nature of textile waste make its recycling challenging. Hence, it is urgent to develop a feasible method to extract value from textile waste. Pyrolysis is an effective waste-to-energy option to processing waste feedstocks having an inhomogeneous and complicated nature. Herein, pyrolysis of denim jeans waste (DJW; a textile waste surrogate) was performed in a continuous flow pyrolyser. The effects of adding sodium carbonate (Na₂CO₃; feedstock/Na₂CO₃ = 10, weight basis) to the DJW pyrolysis on the yield and composition of pyrolysates were explored. For the DJW pyrolysis, using Na₂CO₃ as an additive increased the yields of gas and solid phase pyrolysates and decreased the yield of liquid phase pyrolysate. The highest yield of the gas phase pyrolysate was 34.1 wt% at 800 °C in the presence of Na₂CO₃. The addition of Na₂CO₃ could increase the contents of combustible gases such as H₂ and CO in the gas phase pyrolysate in comparison with the DJW pyrolysis without Na₂CO₃. The maximum yield of the liquid phase pyrolysate obtained with Na₂CO₃ was 62.5 wt% at 400 °C. The composition of the liquid phase pyrolysate indicated that the Na₂CO₃ additive decreased the contents of organic acids, which potentially improve its fuel property by reducing acid value. The results indicated that Na₂CO₃ can be a potential additive to pyrolysis to enhance energy recovery from DJW.

Keywords: synthetic fiber; thermochemical conversion process; waste recycling; waste treatment; waste-to-energy.

Figure 1

Mass balance of pyrolysate made from DJW without Na₂CO₃ as a function of pyrolysis temperature. Average values of triplicate are reported with and standard deviations of the average values of 3–4%.

Figure 2

Product distribution of the gas phase pyrolysate made from DJW without Na₂CO₃ as a function of pyrolysis temperature. Average values of triplicate are reported with and standard deviations of the average values of 3–4%.

Figure 3

The yield of pyrolysates made from DJW with and without Na₂CO₃ at varied pyrolysis temperatures: (a) gas phase pyrolysate, (b) liquid phase pyrolysate, and (c) solid phase pyrolysate. Average values of triplicate are reported with standard deviations given as error bars.

Figure 4

Non-condensable gas yields obtained by the pyrolysis of DJW with and without Na₂CO₃ at varied pyrolysis temperatures. Average values of triplicate are reported with standard deviations given as error bars.

Figure 5

Product distributions of the liquid phase pyrolysates of DJW with and without Na₂CO₃ at varied pyrolysis temperatures. Average values of triplicate are reported with standard deviations given as error bars.