Method for treating waste gas containing polycyclic aromatic hydrocarbons
A process for treating effluent gas containing polycyclic aromatic hydrocarbons includes a step of spray scrubbing with a mineral oil in order to trap the hydrocarbons, wherein the mineral oil includes a mixture of aromatic mineral oil and naphthenic mineral oil.
1. A process for treating effluent gas containing polycyclic aromatic hydrocarbons comprising a step of spray scrubbing with a mineral oil in order to trap said hydrocarbons, wherein the mineral oil comprises a mixture of aromatic mineral oil and naphthenic mineral oil.
2. The process as claimed in claim 1 , wherein the mixture comprises at least 20% by volume of aromatic mineral oil relative to the total volume of the mixture.
3. The process as claimed in claim 1 , wherein the mixture has a viscosity less than or equal to 150 mm 2 /s at 0° C. measured according to the ASTM D445 standard with an Ubbelohde viscometer with capillaries having a diameter of 0.88 mm.
4. The process as claimed in claim 1 , wherein the step of spray scrubbing comprises (i) loading the as aromatic mineral oil with polycyclic aromatic hydrocarbons whereby the aromatic mineral oil has a viscosity of greater than 150 mm 2 /s at 0° C. measured according to the ASTM D445 standard with an Ubbelohde viscometer with capillaries having a diameter of 0.88 mm, and (ii) adding the naphthenic mineral oil to the aromatic mineral oil thus loaded.
5. The process as claimed in claim 4 , wherein the naphthenic mineral oil is added in the form of a mixture of naphthenic mineral oil and aromatic mineral oil and wherein the addition is carried out by replacing a portion of the aromatic mineral oil loaded with polycyclic aromatic hydrocarbons with the same proportion by volume of the mixture of naphthenic mineral oil and aromatic mineral oil.
6. The process as claimed in claim 5 , wherein the mixture added contains at least 20% by volume of aromatic mineral oil relative to the total volume of the mixture.
7. The process as claimed in claim 1 , wherein the aromatic mineral oil has a vapor pressure of less than 1 Pa at 0° C.
8. The process as claimed in claim 1 , wherein the aromatic mineral oil is a xylene-based oil.
9. The process as claimed in claim 1 , wherein the naphthenic mineral oil has a viscosity less than or equal to 75 mm 2 /s at 0° C. measured according to the ASTM D445 standard with an Ubbelohde viscometer with capillaries having a diameter of 0.88 mm.
10. The process as claimed in claim 1 , wherein the naphthenic mineral oil has a vapor pressure of less than 1 Pa at 0° C.
11. The process as claimed in claim 1 , wherein the step of scrubbing the effluent gas is carried out by injecting mineral oil into an effluent gas stream travelling through a spray tower.
12. The process as claimed in claim 1 , further comprising circulating the mineral oil continuously between a recirculation tank that receives the mineral oil loaded with polycyclic aromatic hydrocarbons and at least one spray nozzle for spraying oil into an effluent gas stream.
13. The process as claimed in claim 12 , further comprising cooling the mineral oil over its path between the recirculation tank and the spray nozzle(s).
14. The process as claimed in claim 1 , wherein the effluent gas is produced by a chemical vapor infiltration or deposition process for the formation of a pyrolytic carbon deposit on substrates or for the densification of porous substrates by a pyrolytic carbon matrix.
15. The process as claimed in claim 2 , wherein the mixture comprises at least 30% by volume of aromatic mineral oil relative to the total volume of the mixture.
16. The process as claimed in claim 5 , wherein the addition is carried out by replacing between 20% and 35% of the volume of the aromatic mineral oil loaded with polycyclic aromatic hydrocarbons with the same proportion by volume of the mixture of naphthenic mineral oil and aromatic mineral oil.
17. The process as claimed in claim 7 , wherein the mixture added contains at least 30% by volume of aromatic mineral oil relative to the total volume of the mixture.
18. The process as claimed in claim 9 , wherein the naphthenic mineral oil has a viscosity less than or equal to 70 mm 2 /s at 0° C. measured according to the ASTM D445 standard with an Ubbelohde viscometer with capillaries having a diameter of 0.88 mm.
19. The process as claimed in claim 18 , wherein the naphthenic mineral oil has a viscosity less than or equal to 60 mm 2 /s at 0° C. measured according to the ASTM D445 standard with an Ubbelohde viscometer with capillaries having a diameter of 0.88 mm.