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P.T.C. System


DAVID Process

Example of treatment of a mixture of pollutants in industry

This innovative "One-pot" process consists in capturing gaseous pollutants in a physicochemical treatment whose liquid effluents are subsequently digested by the aerobic bio-purification process in the treatment plant.

(A)    Simultaneous process of absorption (capture) and organic chemical modification of Volatile Organic Compounds (organic and inorganic).
This operation is carried out in a single operation on a collection installation by physico-chemical washing.

(B)    The final destruction of the capture products after the simultaneous process of absorption and chemical modification
This ultimate operation (B) is carried out in a biological treatment plant.
The organic compounds present and formed During the condensation reaction are digested by the process of natural aerobic bio-purification of the purification plant.

The originality of the process resides firstly in the choice of the reagent which combines with the pollutants to be treated and secondly in the final natural destruction in the wastewater treatment plant that does not generate any new gaseous pollution.

The example below describes the treatment of a mixture of pollutants in a single operation

      • A gas scrubbing column joins the vents of three "pilot" reactors in chemical industry:
      • Reactor 1 - Synthesis of an Acid Chloride
      • Reactor 2 - Synthesis of methyl ethyl sulfide
      • Reactor 3 - Decarboxylation of an Acid


The gaseous and volatile pollutants are composed of:

  • 3.2 kg SO2 (sulfur dioxide) 50 mol
  • 1.9 kg HCl (hydrochloric acid) 52 moles
  • Traces of dichloroethane (solvent)
  • Traces of SOCl2 (thionyl chloride)
  • 0.3 kg CH3SH (methyl mercaptan) 6.3 moles
  • 2.9 kg C2H5SH (ethylmercaptan) 47 moles
  • 0.2 kg H2S (hydrogen sulphide) 5.9 moles
  • 2.6 kg CO2 (carbon dioxide) 59 moles
  • Possible traces of alcohols

The amounts of base and reagent are calculated on the basis of Spreadsheet and load sheets .

Equipment used :

  • Absorption column 500 liters (column + tank), Height: 3 m,
    base area: 0.28 m2 (diameter 60 cm), plate lining,
    mist eliminator at the air outlet.
  • Fluid circulation pump adjustable from 0 to 25 m3 / H.
  • Adjustable polluting effluent feed valve From 0 to 500 m3 / H.

Operating load for a batch operation:

  • Water: 150 L.
  • 30% potash: 68 kg
  • Pure reagent: 21 kg or 54 kg of solution at 40%

Standard equipment




The complementary water determined in the worksheet corresponding to 20 volumes of the pure reagent and then in order the calculated quantities of alkaline potassium solution and the 40% solution of the reagent are charged into the suction sheet.
The reaction medium displays a pH value of> 11.
The circulation pump is activated and then the gas flow valve is gradually released and controlled at the desired flow rate.
The end of reaction is determined and controlled by pH <9.
The operations took place over a period of 10 hours with a gas flow rate of 500 m3 / h.
The end of the reaction is controlled by pH-metry (about 8.5-9), and the absence of H2S and mercaptans checked with lead acetate paper and pH paper.

The clear, colorless and odorless reaction medium is then evacuated to the plant self-neutralization pit before being discharged to the network to be subjected to the aerobic bio-purification process in the purification plant.

Results on the unfiltered reaction medium before rejection:

      • PH = 8.3;
      • temperature <30 ° C;
      • COD: 287 mg / L;
      • BOD5: 670 mg /L.

The calculation of the operating costs for evaluating the economic potential of the process:

The flux calculation worksheet to determine the quantities of reagents:

In this test, it is clear that for the destruction of the sulfur compounds, treatment with bleach would revert 12 times more expensive than treatment with the PTC system.
Treatments with ClO2 or H2O2 are even more expensive.

This example of chemistry treatment includes:

  • Complete removal of sulfur compounds.
  • Decarbonation (complete elimination of CO2).
  • Complete removal of hydrochloric acid.
  • Complete removal of traces of thionyl chloride.
  • Complete removal of trace solvents.

See also the examples of the DAVID Process - Odors



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