Table 1 The product yields of microwave pyrolysis sludge under different moisture content and operating conditions

Wastewater sludge in a petrochemical plant.

Moisture: 84.9 ± 1.20 wt%; Volatile solids: 9.4 ± 0.11 wt%; Ash: 5.6 ± 0.06 wt%; Combustibles^a: 62.9 ± 1.5 wt%; Ash^a:37.1 ± 0.85 wt%

Multimode-microwave oven; N₂;

400–800^d

Not reported

69–51^d

16.3–20.3^d

14.8–29.5^d

[6]

Wastewater sludge in a chemical plant.

Moisture: 32.6 ± 2.5 wt%; Volatile solids: 39.3 ± 1.8 wt%; Ash: 28.1 ± 1.3 wt%; Combustibles^a: 58.3 ± 2.7 wt%; Ash^a:41.7 ± 3.1 wt%

400–800^d

Not reported

65–42^d

16.2–23.8^d

8.3–37.7^d

Sludge in a wastewater treatment plant.

Moisture:78%; Ash^a: 42%;Volatile matter^a: 55%;

Multimode-microwave oven; Ar;

500–800^d

Not reported

40–36^d

45–18^d

15–46^d

[12]

Sludge in the wastewater treatment facility of a petrochemical plant.

Moisture: 84.9 ± 1.2 wt%; Solids: 15.1 ± 0.3 wt%; Volatile: solids^a: 62.9 ± 0.27 wt%; Ash^a: 37.5 ± 0.18 wt%;

Multimode-microwave oven; N₂;

400–800^d

Not reported

57–69^d

14–20^d

15–29^d

[24]

The dewatered high-ash sludge from. Industrial wastewater treatment plant

Moisture: 88.10 wt%; ash^a: 61.88 wt%; organic substance^a: 38.12 wt%; for ash analysis indicated that the contents of Si, Fe, and Al were more than 10.10 wt% and all existed in the form of oxides.

Self-made single-mode and linear adjustable microwave oven; N₂;

1131.7^b

SiC

78.3 ± 3.9

3.0 ± 0.7

17.0 ± 4.8

[29]

919.2^b

Graphite^c

84.3 ± 7.3

3.4 ± 0.7

10.8 ± 3.4

1003.5^b

Pyrolysis residues

82.5 ± 4.5

3.5 ± 0.6

12.1 ± 5.1

Sludge in the metropolitan wastewater treatment plant.

Moisture: 78 wt%; Ash^a:17.5 wt%;Volatile matter^a: 82.2 wt%; Fixed carbon^a: 0.3 wt%;

Modified microwave oven; Vacuum;

450–600^d

ZSM-5 SiC balls

62.3–33.0^d

16.5–28.0^d

Not reported

[34]

The remaining sludge in the 5 secondary sedimentation tank of a sewage treatment plant.

Moisture:84.3%; ash^a: 46.72%; organic substance^a: 50.42%; fixed carbon^a: 2.86%; C, H, N and S^a: 28.86 wt%, 7.35 wt%, 3.88 wt% and 0.89 wt%.

Single-mode and linear adjustable microwave oven; N₂;

500–900^d

Not reported

70.0 ± 3.4–60.0 ± 2.0^d

14.5 ± 0.7–14.4 ± 0.5^d

11.3 ± 0.6–23.5 ± 1.1^d

[35]

10 wt% CaO

65.2 ± 2.7–51.0 ± 0.8^d

15.5 ± 0.7–15.8 ± 0.6^d

17.1 ± 0.8–33.1 ± 1.6^d

10 wt% Fe₂O₃

70.2 ± 2.9–55.0 ± 1.4^d

11.5 ± 0.5–14.4 ± 0.6^d

15.1 ± 0.7–29.5 ± 0.8^d

Sludge in urban wastewater treatment plants.

Moisture: 80 wt%; Ash^a: 24.5%;Volatile matter^a: 75.5%;

Multimode-microwave oven; N₂;

490^c

Not reported

39.4

49.8

10.8

[36]

330–1200^d

77.3–32.6^d

18.3–7.2^d

4.4–60.2^d