Supercritical water oxidation of organic matter such as PCBs and sludge

2.
4.
1.
4 Supercritical water chlorination of organic substances such as PCBs

Foreign researchers supercritical water oxidation treatment of PCBs PCB wastewater removal found influenced by temperature, process conditions at 550 deg.
] C or more, the rate of PCB destruction of PCB up to 99.
99%; with H ₂ O _{2 is} used as the oxidant for the reaction.
The research on two kinds of polychlorinated biphenyl compounds shows that the highest removal rate of 3-chlorobiphenyl in the sequencing batch reactor can reach 99.
999%, which is better than the reaction system using O ₂ as the oxidant.

.

In the flow reactor at a temperature of 400℃ and a pressure of 30MPa, more than 99% of 3-chlorobiphenyl compounds can be degraded within 10.

Modell et al.
used a continuous flow system to study the supercritical water oxidation of an organic wastewater with an organic carbon content between 27000 and 33000 mg/L
.

Wastewater contains 1,1,1-trichloroethane, hexachlorocyclohexane , methyl ethyl ketone , benzene, o-xylene , 2,2'-dinitrotoluene, DDT, PCB1234, PCB1254 and other toxic and harmful Pollutants

Swallow et al.
used a continuous flow reactor to study the supercritical water oxidation of chlorinated dibenzo P-dioxin and its precursors at 600～630℃ and 25.
6MPa.
The wastewater contained 0.
4～3mg/L Tetrachlorodibenzo-P-dioxin (TCDBD) and octachlorodibenzo-P-dioxin (OCDBD) and several possible precursor molecules of 1～50g/L (such as chlorobenzene, Phenol and anisole ), as a result, 99.
9% of OCDBD and TCDBD were destroyed
.

Table 2-5 summarizes the results of supercritical water oxidation treatment of organic substances other than phenol

Table 2-5 Supercritical water oxidation of some organics

① Tetrachlorodibenzofuran
.

② 2,3,7,8 tetrachlorodibenzo-P-dioxin
.

③ Octachlorodibenzofuran
.

④ Octachlorodibenzo-P-dioxin
.

2.

4.

The sludge treatment in the supercritical water environment is mainly to completely oxidize the organic matter into CO ₂ and water
.

Harlingen, Texas, USA, launched the primary operation line of a treatment plant that uses SCWO to treat municipal sludge

Shanableh et al.
studied the destruction of sludge in wastewater treatment plants under conditions close to supercritical and supercritical (300-400℃)
.

The total solid content (TS) of the sludge of the plant is 5%, and the total CODcr of the liquid-solid two-phase is 46500mg/L

Previous studies on wet oxidation treatment of sludge have shown that it is difficult to dispose of the sludge after it is converted into lower fatty acids
.

Dioxins are often generated during waste incineration .

In order to determine the main control parameters of the SCWO process for the treatment of urban sludge, the State Key Laboratory of Multiphase Flow in Power Engineering of Xi’an Jiaotong University used a self-built batch SCWO device to conduct research and discussion
.

The research results show that temperature has a significant effect on SCWO sludge, while pressure has no obvious effect, and residence time has a great effect on sludge oxidation