Method for Removing Volatile Organic Compounds from Sponge by Using Supercritical or Subcritical Fluid

Abstract

Disclosed is a method of removing volatile organic compounds from sponges by using supercritical/subcritical fluid, The method includes the following steps: placing the sponge block to be treated in the extraction kettle; feeding the critical flow medium into the extraction kettle; performing extraction under the supercritical or subcritical conditions of the critical flow medium; releasing pressure to normal pressure after extraction; and separating to obtain devolatilized sponge. The volatile removal device used in the disclosure is a supercritical extraction equipment, which can adopt static extraction or dynamic extraction or a combination of the two. CO2 releases pressure in the separating kettle after contacting the sponge to be treated in the device for mass transfer for a certain period, when the static extraction devolatilization is carried out.

Claims

1. A method of removing volatile organic compounds from a sponge by supercritical/subcritical fluid, the method comprising: placing a sponge block to be treated in an extraction kettle; feeding a critical fluid medium into the extraction kettle; performing extraction under a supercritical condition or a subcritical condition of the critical fluid medium; releasing the pressure to normal pressure (atmosphere pressure) after the extraction is finished; and separating the sponge and the medium to obtain a devolatilized sponge.

2. The method of claim 1, wherein the critical fluid medium is a pure carbon dioxide or a modified carbon dioxide.

3. The method of claim 2, wherein the modified carbon dioxide is formed by adding a modifier to the pure carbon dioxide in a proportion.

4. The method of claim 3, wherein the modifier is ethanol or isopropanol.

5. The method of claim 4, wherein the modifier is added in an amount of 0.5 to 20 wt. % of the mass of the pure carbon dioxide.

6. The method of claim 1, wherein the supercritical conditions are: 31.1° C.≤temperature≤60° C., 7.39 MPa≤pressure≤25 MPa; the subcritical conditions are: 20° C.≤temperature≤31.1° C., 3 MPa≤pressure≤7.39 MPa.

7. The method of claim 1, wherein an extraction time is from 5 to 30 minutes.

8. The method of claim 1, wherein the extraction is static or dynamic or a combination thereof.

9. The method of claim 1, wherein a separated carbon dioxide gas is returned to the extraction kettle for recycling.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] FIG. 1 illustrates a process flow diagram of the present disclosure.

[0032] The reference characters in the drawing: 1—carbon dioxide storage tank; 2—condenser; 3—carbon dioxide intermediate storage tank; 4—CO.sub.2 pump; 5—entrainer storage tank; 6—entrainer pump; 7—extraction kettle; 8—separation kettle.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] The process of the disclosure is shown in FIG. 1, including successively connected carbon dioxide storage tank 1, condenser 2, carbon dioxide intermediate storage tank 3, carbon dioxide pump 4, extraction kettle 7 and separating kettle 6. The entrainer storage tank 5 is connected to the inlet of the extraction kettle 7 via the entrainer pump 6; and the inlet and outlet of each equipment are provided with valves.

[0034] The carbon dioxide is condensed by condenser and fed into carbon dioxide intermediate storage tank 3, and a refrigerant is fed into the jacket of the intermediate storage tank to keep low temperature in the tank. The carbon dioxide in the intermediate storage tank is metrically fed into the inlet of the extraction kettle 7 by the carbon dioxide pump 4. If the pure carbon dioxide is used as the critical flow medium, the valve of the entrainer storage tank 5 is closed. When the carbon dioxide needs to be modified, the valve of the entrainer storage tank is opened at the same time, and the entrainer is metrically fed into the inlet of the extraction kettle by entrainer pump 6. The top outlet of the extraction kettle is connected to the inlet of the separation kettle. The carbon dioxide separated by the separation kettle is returned to the intermediate storage tank for recycling.

[0035] The technical scheme of the disclosure is further illustrated by way of specific examples in conjunction with the process shown in FIG. 1, but the scope of the disclosure is not limited thereto:

EXAMPLE 1

[0036] Loading the untreated latex sponge block with size of 0.5 m*0.8 m*0.1 m into a devolatilization kettle with volume of 10 L. Dynamic extraction was performed for 30 minutes at a temperature of 30° C., a pressure of 6.0 MPa, and a CO.sub.2 flow rate of 100 kg/h. Then slowly release the pressure of CO.sub.2 to normal pressure to obtain the devolatilized latex sponge. And analyzing the content of the residual volatile organic compounds in the devolatilized latex sponge with HS-GC-MS and environmental chamber methods. The content of the total volatile organic compounds released in 24 hours was 35 μg/m.sup.3, in line with the relevant national standards. The total removal rate was greater than 99%, in which the release amount of styrene was 1,2 μg/m.sup.3, the content of 4-vinylcyclohexene was 1.0 ρg/m.sup.3, the release amount of 1,3-butadiene was 0.9 μg/m.sup.3, complying with European Union standard.

EXAMPLE 2

[0037] Loading the untreated latex sponge block with size of 0.5 m×0.8 m×0.1 m into a devolatilization kettle with volume of 10 L. Dynamic extraction was performed for 15 minutes at a temperature of 40° C., a pressure of 12 MPa, and a CO.sub.2 flow rate of 100 kg/h. Then slowly release the pressure of CO.sub.2 to normal pressure to obtain the devolatilized latex sponge. And analyzing the content of the residual volatile organic compounds in the devolatilized latex sponge with HS-GC-MS and environmental chamber methods. The content of the total volatile organic compounds released in 24 hours was 25 μg/m.sup.3, in line with the relevant national standards. The total removal rate was greater than 99%, in which the release amount of styrene was 0.4 μg/m.sup.3, the content of 4-vinylcyclohexene was 0.9 μg/m.sup.3, the release amount of 1,3-butadiene was 0.1 μg/m.sup.3, complying with European Union standard.

EXAMPLE 3

[0038] Loading the untreated latex sponge block with size of 0.5 m×0.8 m×0.1 m into a devolatilization kettle with volume of 10 L. Dynamic extraction was performed for 30 minutes at a temperature of 40° C., a pressure of 12 MPa, and a CO.sub.2 flow rate of 120 kg/h. Then slowly release the pressure of CO.sub.2 to normal pressure to obtain the devolatilized latex sponge. And analyzing the content of residual volatile organic compounds in the devolatilized latex sponge with HS-GC-MS and environmental chamber methods. The content of the total volatile organic compounds released in 24 hours was 18 μg/m.sup.3, in line with the relevant national standards. The total removal rate was greater than 99%, in which the release amount of styrene was 0.4 μg/m.sup.3, the content of 4-vinylcyclohexene was 0.6 μg/m.sup.3, no 1,3-butadiene was detected, complying with European Union standard.

EXAMPLE 4

[0039] Loading the untreated latex sponge block with size of 0.5 m×0.8 m×0.1 m into a devolatilization kettle with volume of 10 L. Dynamic extraction was performed for 30 minutes at a temperature of 45° C., a pressure of 12 MPa, and a CO.sub.2 flow rate of 120 kg/h. Then slowly release the pressure of CO.sub.2 to normal pressure to obtain the devolatilized latex sponge. And analyzing the content of residual volatile organic compounds in the devolatilization latex sponge with HS-GC-MS and environmental chamber methods. The content of the total volatile organic compounds released in 24 hours was 12 μg/m.sup.3, in line with the relevant national standards. The total removal rate was greater than 99%, in which the release amount of styrene was 0.2 μg/m.sup.3, the content of 4-vinylcyclohexene was 0.2 μg/m.sup.3, no 1,3-butadiene was detected, complying with European Union standard.

EXAMPLE 5

[0040] Loading the untreated latex sponge block with size of 0.5 m×0.8 m×0.1 m into a devolatilization kettle with volume of 10 L. Dynamic extraction was performed for 5 minutes at a temperature of 40° C., a pressure of 20 MPa, and a CO.sub.2 flow rate of 100 kg/h. Then slowly release the pressure of CO.sub.2 to normal pressure to obtain the devolatilized latex sponge. And analyzing the content of the residual volatile organic compounds in the devolatilized latex sponge with HS-GC-MS and environmental chamber methods. The content of the total volatile organic compounds released in 24 hours was 15 μg/m.sup.3, in line with the relevant national standards. The total removal rate was greater than 99%, in which the release amount of styrene was 0.5 μg/m.sup.3, the content of 4-vinylcyclohexene was 0.6 μg/m.sup.3, no 1,3-butadiene was detected, complying with European Union standard.

EXAMPLE 6

[0041] Loading the untreated latex sponge block with size of 0.5 m×0.8 m×0.1 m into a devolatilization kettle with volume of 10 L. Dynamic extraction was performed for 30 minutes at a temperature of 30° C., a pressure of 6 MPa, and a CO.sub.2 flow rate of 120 kg/h. Then slowly release the pressure of CO.sub.2 to normal pressure to obtain the devolatilized latex sponge. And analyzing the content of the residual volatile organic compounds in the devolatilized latex sponge with HS-GC-MS and environmental chamber methods. The content of the total volatile organic compounds released in 24 hours was 45 μg/m.sup.3, in line with the relevant national standards. The total removal rate was greater than 99%, in which the release amount of 2,4-toluenediamine was 2.0 μg/m.sup.3, the content of 4,4′-diaminodiphenylmethane was 1.8 μg/m.sup.3, complying with European Union standard.

EXAMPLE 7

[0042] Loading the untreated latex sponge block with size of 0.5 m×0.8 m×0.1 m into a devolatilization kettle with volume of 10 L. Dynamic extraction was performed for 15 minutes at a temperature of 40° C., a pressure of 12 MPa, and a CO.sub.2 flow rate of 100 kg/h. Then slowly release the pressure of CO.sub.2 to normal pressure to obtain the devolatilized latex sponge. And analyzing the content of the residual volatile organic compounds in the devolatilized latex sponge with HS-GC-MS and environmental chamber methods. The total volatile organic compounds released in 24 hours was 35 μg/m.sup.3, in line with the relevant national standards. The total removal rate was greater than 99%, in which the release amount of 2,4-toluenediamine was 1.2 μg/m.sup.3, the content of 4,4′-diaminodiphenylmethane was 1.0 μg/m.sup.3, complying with European Union standard.

EXAMPLE 8

[0043] Loading the untreated latex sponge block with size of 0.5 m×0.8 m×0.1 m into a devolatilization kettle with volume of 10 L. Dynamic extraction was performed for 30 minutes at a temperature of 40° C., a pressure of 12 MPa, and a CO.sub.2 flow rate of 120 kg/h. Then slowly release the pressure of CO.sub.2 to normal pressure to obtain the devolatilized latex sponge. And analyzing the content of the residual volatile organic compounds in the devolatilized latex sponge with HS-GC-MS and environmental chamber methods. The content of the total volatile organic compounds released in 24 hours was 29 μg/m.sup.3, in line with the relevant national standards. The total removal rate was greater than 99%, in which the release amount of 2,4-toluenediamine was 0.9 μg/m.sup.3, the content of 4,4′-diaminodiphenylmethane was 0.8 μg/m.sup.3, complying with European Union standard.

EXAMPLE 9

[0044] Loading the untreated latex sponge block with size of 0.5 m×0.8 m×0.1 m into a devolatilization kettle with volume of 10 L. Dynamic extraction was performed for 30 minutes at a temperature of 45° C., a pressure of 12 MPa, and a CO.sub.2 flow rate of 120 kg/h. Then slowly release the pressure of CO.sub.2 to normal pressure to obtain the devolatilized latex sponge. And analyzing the content of the residual volatile organic compounds in the devolatilized latex sponge with HS-GC-MS and environmental chamber methods. The content of the total volatile organic compounds released in 24 hours was 15 μg/m.sup.3, in line with the relevant national standards. The total removal rate was greater than 99%, in which the release amount of 2,4-toluenediamine releasing amount was 0.6 μg/m.sup.3, the content of 4,4′-diaminodiphenylmethane was 0.5 μg/m.sup.3, complying with European Union standard.

EXAMPLE 10

[0045] Loading the untreated latex sponge block with size of 0.5 m×0.8 m×0.1 m into a devolatilization kettle with volume of 10 L. Dynamic extraction for 5 minutes at a temperature of 40° C., a pressure of 20 MPa, and a CO.sub.2 flow rate of 100 kg/h. Then slowly release the pressure of CO.sub.2 to normal pressure to obtain the devolatilized latex sponge. And analyzing the content of the residual volatile organic compounds in the devolatilized latex sponge with HS-GC-MS and environmental chamber methods. The content of the total volatile organic compounds released in 24 hours was 25 μg/m.sup.3, in line with the relevant national standards. The total removal rate was greater than 99%, in which the release amount of 2,4-toluenediamine was 1.2 μg/m.sup.3, the content of 4,4′-diaminodiphenylmethane was 0.8 μg/m.sup.3, complying with European Union standard.

[0046] The foregoing description is merely illustrative of specific embodiments of the present disclosure, and is not intended to limit the technical features of the present disclosure. Any change or modification made in the field of the disclosure by a skilled person in the relevant field should be deemed as within the scope of the present disclosure.