SYSTEM FOR THE CHEMICAL DECONTAMINATION OF CORROSIVE GASES

Abstract

The use of a composition including at least one acido-basic neutralising agent for decontaminating an atmosphere contaminated by a corrosive gas, the acido-basic neutralising agent having at least 2 pKa's and being characterised by: pKa 1≤pKa 2, pKa 1>2, pKa 2<12, 4<½ (pKa 1+pKa 2)<10 pKa 1, representing the smallest of the basic pKa's and pKa 2 representing the largest of the acidic pKa's. Also, a method for decontaminating an atmosphere contaminated by a corrosive gas comprising the spraying of the neutralising agent, and to a decontamination device.

Claims

1.-14. (canceled)

15. A composition comprising at least one acido-basic neutralising agent for decontaminating an atmosphere contaminated by a corrosive gas, said acido-basic neutralising agent having at least 2 pKa's, wherein: pKa 1≤pKa 2, pKa 1>2, pKa 2<12−4<½, and (pKa 1+pKa 2)<10, pKa 1 representing the smallest of the basic pKa's and pKa 2 represents the largest of the acidic pKa's.

16. The composition according to claim 15, wherein said acido-basic neutralising agent is an amphoteric agent.

17. The composition according to claim 16, wherein the amphoteric agent is selected from the group consisting of: an amino acid or a salt of an amino acid, a citric acid salt, a phosphoric acid salt, a pyrophosphoric acid salt, an ethylenediaminetetraacetic acid (EDTA) salt, complexed or free, an ascorbic acid salt, or a carbonate.

18. The composition according to claim 15, wherein said acido-basic neutralising agent is a mixture of at least one conjugate base of an acid and of at least one conjugate acid of a base.

19. The composition according to claim 18, wherein said conjugate acid and said conjugate base are present in an equimolar ratio.

20. The composition according to claim 15, wherein the conjugate base is an EDTA-aluminium disodium complex and the conjugate acid is boric acid.

21. The composition according to claim 16, wherein the composition contains two amphoteric agents, in particular an EDTA-aluminium disodium complex and sodium glutamate.

22. The composition according to claim 15, wherein said composition is in solution form or in solid form.

23. The composition according to claim 22, wherein said composition in solution form or in solid form is formulated as an aerosol.

24. The composition according to claim 22, wherein said composition in solution form is formulated as a foam.

25. The composition according to claim 15, wherein said composition is sprayed directly into the atmosphere contaminated by corrosive gases.

26. A method for decontaminating an atmosphere contaminated by a corrosive gas comprising the following steps: 1) spraying, directly into the contaminated atmosphere, a composition comprising at least one acido-basic neutralising agent for decontaminating an atmosphere contaminated by a corrosive gas, said acido-basic neutralising agent having at least 2 pKa's and wherein: pKa 1≤pKa 2, pKa 1>2, pKa 2<12−4<½, and (pKa 1+pKa 2)<10, pKa 1 representing the smallest of the basic pKa's and pKa 2 represents the largest of the acidic pKa's; then 2) checking the decontamination; 3) optionally repeating steps 1 and 2 until there is total decontamination; 4) recovering the solid or liquid residues; and 5) optionally rinsing the decontaminated zone to eliminate the residues of the composition.

27. A device for decontaminating an atmosphere contaminated by a corrosive gas, comprising: at least one means able to spray a composition comprising at least one acido-basic neutralising agent for decontaminating an atmosphere contaminated by a corrosive gas, said acido-basic neutralising agent having at least 2 pKa's and wherein: pKa 1≤pKa 2, pKa 1>2, pKa 2<12−4<½, and (pKa 1+pKa 2)<10, pKa 1 representing the smallest of the basic pKa's and pKa 2 represents the largest of the acidic pKa's; and at least one reservoir intended to receive said composition.

28. The device according to claim 27, wherein said at least one reservoir is connected to at least one circuit comprising a fluid, said at least one circuit being a circuit belonging to a fire extinguishing plant.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0162] FIG. 1 shows a device for decontaminating an atmosphere comprising sprinklers 1 connected to a water circuit 2, itself being connected via a valve 4 to a reservoir 3 able to receive a composition in aqueous form, said valve 4 being coupled to a gas detection system 5 via an automatic control unit 6, for automatic actuation.

[0163] FIG. 2 shows a device for decontaminating an atmosphere comprising sprinklers 1 connected to the water circuit 2, itself being connected via a valve 4 to a reservoir 3 able to receive a composition in solid form, by means of a valve 4 located at the junction of the reservoir 3 and the water circuit 2, said valve 4 being coupled to a gas detection system 5 via an automatic control unit 6, for automatic actuation.

[0164] FIG. 3 is a graph showing the change in the concentration in gaseous HCl (ppm) according to the volume (mL) sprayed of a composition comprising a EDTA-aluminium disodium complex and boric acid in an equimolar mixture at 0.1 mol/L.

[0165] FIG. 4 is a graph showing the change in the concentration in gaseous HCl (ppm) according to the volume (mL) sprayed of a composition comprising a EDTA-aluminium disodium complex and sodium glutamate in an equimolar mixture at 0.5 mol/L.

[0166] FIG. 5 is a graph showing the change in the concentration in gaseous NH.sub.3 (ppm) according to the volume (mL) sprayed of a composition comprising a EDTA-aluminium disodium complex and sodium glutamate in an equimolar mixture at 0.5 mol/L.

EXAMPLES

Example 1

[0167] An aqueous chemical-decontamination composition is prepared, comprising, as neutralising agent, the following mixture: [0168] a conjugate base of an acid: EDTA-aluminium disodium complex, the pKa of which is 5.87 at a concentration of 0.1 mol/L, and [0169] the conjugate acid of a base: boric acid the pKa of which is 9.28 at a concentration of 0.1 mol/L.

[0170] This composition is sprayed into an atmosphere contaminated by gaseous HCl, a corrosive acid, manually in an aerosol by a spray at a rate of approximately 175 mL/min and the carrier gas of which is compressed air.

[0171] After spraying the composition, the contaminated atmosphere was decontaminated and a contaminant content below the regulatory threshold (Average exposure value: 5 ppm) was obtained.

[0172] FIG. 3 shows the change in the concentration in Gaseous HCL according to the volume of the composition sprayed into the atmosphere.

[0173] The pH of the liquid residue that falls out is 4, i.e. little acidic and non-corrosive.

Example 2

[0174] An aqueous chemical-decontamination composition was prepared comprising, as neutralising agent, an amphoteric agent, sodium glutamate at a concentration of 1 mol/L and the pKa's of which are 4.15 and 9.58. This composition is sprayed into an atmosphere contaminated by a corrosive atmosphere, such as hydrogen chloride.

[0175] After spraying of the composition, the contaminated atmosphere was decontaminated and a level of contaminant below the regulatory threshold was obtained.

Example 3

[0176] An aqueous chemical decontamination composition is prepared comprising as a neutralising agent, the following mixture: [0177] a conjugate base of an acid: EDTA-aluminium disodium complex the pKa of which is 5.87 at a concentration of 0.5 mol/L, et [0178] the conjugate acid of a base: sodium glutamate the pKa of which is 9.67 at a concentration of 0.5 mol/L.

[0179] This composition is sprayed via a pump in an atmosphere contaminated by gaseous HCl, a corrosive acid, manually as aerosol by a spray rate of about 375 mL/min.

[0180] After spraying the composition, the contaminated atmosphere was decontaminated and a content in contaminant below the regulatory threshold (Average exposure value: 5 ppm) was obtained.

[0181] FIG. 4 shows the change in the concentration in Gaseous HCL according to the volume of the composition sprayed into the atmosphere.

[0182] The pH of the liquid residue that falls out is 7, i.e. a neutral and non-corrosive liquid.

Example 4

[0183] An aqueous chemical decontamination composition is prepared comprising as a neutralising agent, the following mixture: [0184] a conjugate base of an acid: EDTA-aluminium disodium complex the pKa of which is 5.87 at a concentration of 0.5 mol/L, and [0185] the conjugate acid of a base: sodium glutamate the pKa of which is 9.67 at a concentration of 0.5 mol/L.

[0186] This composition is sprayed via a pump in an atmosphere contaminated by gaseous NH.sub.3, a corrosive base, manually as aerosol by a spray rate of about 375 mL/min.

[0187] After spraying the composition, the contaminated atmosphere was decontaminated and a content in contaminant below the regulatory threshold (Average exposure value: 20 ppm) was obtained.

[0188] FIG. 5 shows the change in the concentration in gaseous NH.sub.3 according to the volume of the composition sprayed into the atmosphere.

[0189] The pH of the liquid residue that falls out is between 7 and 8, i.e. a neutral and non-corrosive liquid.