Living source polluted soil reinforcing method using CO2 mineralization

Abstract

The invention discloses a method for reinforcing living source polluted soil by using CO2 mineralization, which comprises the following steps of: converting gaseous CO2 into injectable carbon alkali liquor, changing a water chemical environment of a soil body through the carbon alkali liquor, generating carbonate with calcium source liquid injected into the soil body, precipitating the carbonate into pores of the soil body, and forming calcareous cement among particles, so as to realize in-situ reinforcement of the living source polluted soil. According to the method, the living source polluted soil body environment can be adjusted from the acid environment to the alkalescent environment, pollutant degradation is inhibited, exogenous CO2 is subjected to different chemical phase state conversion and is converted from a gas phase to a dissolved water phase and then to a mineral phase, the effect that CO2 is mineralized in the living source polluted soil is achieved, and the effect of reinforcing the living source polluted soil in situ is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental engineering geology and specifically relates to a method for utilizing CO 2 Methods for strengthening mineralized soil contaminated by domestic sources. Background Art

[0002] The main components of polluted fluids from living sources are soluble organic acids, soluble monosaccharides, amino acids and other organic substances, and contain Na + , K + , Ca 2+ , CO 3 2- 、SO 4 2- , Cl - Inorganic substances such as chlorine and a small amount of heavy metal ions, their seepage and degradation in the soil will change the mineral composition and structure of the soil and thus affect the physical and mechanical properties of the soil, causing cumulative deformation of the soil, leading to a series of geological disasters and engineering problems such as uneven surface settlement, foundation deformation, and slope instability. Therefore, it is very necessary to explore a method for in-situ reinforcement of soil contaminated by life sources.

[0003] CO 2 Mineralization technology is the process of converting gaseous CO 2 With alkaline Ca 2+ or Mg 2+ The carbonation product is a CO2 product with great application value and easy to realize. 2 In addition, pollutants from living sources degrade in the soil, gradually transforming the soil environment into an acidic environment and releasing CO 2 Therefore, adjusting the soil environment of the soil contaminated by life sources to a weak alkaline state is beneficial to inhibiting the degradation of life source pollutants, reducing greenhouse gas emissions, and promoting the exogenous CO 2 It mineralizes in the soil, thereby strengthening the soil contaminated by domestic sources.

[0004] The existing soil reinforcement technology does not have a reinforcement method for this kind of soil that is easily degraded, has unstable composition and structure, and releases greenhouse gases. 2 Mineralization technologies, such as direct conversion of CO 2 Passing into the ground or soil, it reacts chemically with minerals to convert CO 2 Embedded in the mineral structure, its mineralization products are difficult to exist in soil contaminated by domestic sources, cannot change the characteristics of continuous degradation of domestic pollutants, cannot solve the problem of unstable composition structure of soil contaminated by domestic sources, and cannot achieve the purpose of strengthening soil contaminated by domestic sources and slowing down the production of greenhouse gases. Summary of the invention

[0005] The object of the present invention is to provide a method for utilizing CO 2 The mineralized contaminated soil reinforcement method can adjust the soil environment from acidic to weakly alkaline, inhibit the degradation of pollutants, and achieve CO 2 It has the effect of mineralization in soil contaminated by domestic sources and plays the role of in-situ reinforcement of soil contaminated by domestic sources.

[0006] To achieve the above object, the present invention provides a method for utilizing CO 2 Mineralized domestic source contaminated soil reinforcement methods include:

[0007] The gaseous CO 2 It is converted into injectable carbon alkali solution. After the carbon alkali solution changes the water chemical environment of the soil, it generates carbonate precipitation in the pores of the soil with the calcium source solution injected into the soil, and forms calcareous cement between the particles, thereby realizing the in-situ reinforcement of soil contaminated by domestic sources.

[0008] As a further solution of the present invention: exogenous CO 2 undergoes different chemical phase changes, including CO 2 The process of generating carbon alkali solution is to react CO with alkaline solution. 2 Absorb gaseous CO 2 The converted dissolved water phase can be injected into a carbon alkali solution; wherein the alkaline solution includes but is not limited to aluminate, ammonium salt, and soda ash, and the reaction formula is as follows:

[0009]

[0010] After filtering the converted carbon alkali solution and injecting it into the soil contaminated by the living source, the soil water chemical field is adjusted to adjust the soil pH environment from acidic to weakly alkaline, and then react with the calcium source solution injected into the soil to transform into a mineral phase to generate carbonate precipitation; wherein the calcium source solution includes but is not limited to calcium chloride, and its concentration is consistent with that of the carbon alkali solution, and the reaction formula is as follows:

[0011]

[0012] As a further solution of the present invention: the specific steps of the reinforcement method are as follows:

[0013] 1) Place the alkaline solution into a reaction device equipped with a stirrer and a pressure gauge, and 2 CO in cylinders 2 Passing into a reaction device;

[0014] 2) When CO is introduced 2 When the amount of the substance reaches 50% of the amount of the alkaline solution, stop passing CO 2 , and turn on the agitator. The reaction ends when the pressure reading is stable and no more precipitation is generated;

[0015] 3) filtering the reaction solution using a multi-stage filtration assembly to obtain a clarified carbon alkali solution;

[0016] 4) injecting the carbon alkali solution into the carbon alkali solution storage tank, injecting the calcium source solution into the calcium source solution storage tank, and the carbon alkali solution storage tank and the calcium source solution storage tank are connected by CO 2 The filter is connected to the air pressure control box, the air pressure control box is connected to the air compressor, and the liquid outlets of the carbon alkali liquid storage tank and the calcium source liquid storage tank are connected to the rotary jet drilling rig;

[0017] 5) After leveling the site, arrange several jet injection holes, monitoring wells and sampling areas;

[0018] 6) Turn on the air compressor and pass the CO 2 Filters remove CO from the air 2 , the injection speed is controlled by the air pressure control box, the rotary jet drilling rig drills, and the carbon alkali solution is injected into the soil and stirred;

[0019] 7) After the injection of carbon alkali solution is completed, the calcium source solution is injected, and the drill pipe is lifted and reversely stirred;

[0020] 8) After the drill rod is lifted, the jet grouting drill is moved to the next jet grouting injection hole, and steps 5)-6) are repeated until all the jet grouting injection holes and the surrounding soil are processed;

[0021] 9) After injection, the resistivity and CO 2 The monitoring instrument is placed in the monitoring well to test the conductivity of the reinforced area and compare it with the test data before the site restoration to analyze the CO 2 Diffusion and migration of mineralized fluid;

[0022] 10) After the injection is completed, take out the reinforced sample from the sampling area, take a control sample from the non-injected area, and test the CO 2 The effect of mineralization on consolidation of soil contaminated by domestic sources.

[0023] As a further solution of the present invention: the solubility of the prepared carbon alkali solution is lower than 1 mol / L.

[0024] As a further solution of the present invention: the jet injection holes are arranged in a triangular pattern, the distance between adjacent jet injection holes is 2-2.5m, the area 1-1.5m away from the jet injection holes is set as a sampling area, and the monitoring well is arranged at the center of the triangular distribution.

[0025] As a further solution of the present invention, the injection volume of the carbon alkali solution and the calcium source solution into the soil of the to-be-treated layer is 1-1.5 times of the pore volume of the soil.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1) The present invention uses CO 2 Prepare carbon alkali solution and inject it into the soil, which can effectively improve the acidic environment of soil contaminated by living sources, inhibit the further degradation of pollutants, thereby slowing down the damage of living source pollutants to the soil structure and reducing the CO generated by the degradation of pollutants. 2 .

[0028] 2) By adding calcium source liquid to the soil contaminated by domestic sources, it reacts with carbon alkali liquid to form calcium carbonate precipitate, which can effectively increase the strength of the soil and repair the soil structure damage caused by domestic pollution.

[0029] 3) The present invention converts the exogenous CO 2 It is eventually converted into calcium carbonate precipitate and stored in the soil, providing an effective way to fix carbon using soil contaminated by domestic sources.

[0030] 4) The injection of the carbon alkali solution and the calcium source solution of the present invention can conveniently adjust the treatment depth of the soil contaminated by the living source, and is not limited to the treatment of shallow contaminated soil. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of the structure of implementing the specific steps of the reinforcement method of the present invention.

[0032] Figure 2 for Figure 1 Schematic diagram of the replaceable filter membrane and removable fixing clip at A.

[0033] Figure 3 This is a schematic diagram of the locations of the rotary jet injection holes, monitoring wells and sampling areas proposed in the present invention.

[0034] In the figure: 1. CO 2 Gas cylinder, 2. Gas valve, 3. Agitator, 4. Pressure gauge, 5. Reaction device, 6. Control valve 1, 7. Support frame, 8. Primary vacuum filter, 9. Control valve 2, 10. Control valve 3, 11. Secondary vacuum filter, 12. Vacuum pump 2, 13. Valve 2, 14. Vacuum pump 1, 15. Valve 1, 16. Carbon alkali liquid storage tank, 17. Gas valve 1, 18. CO 2 Filter, 19, air pressure control box, 20, air compressor, 21, liquid outlet valve 1, 22, air valve 2, 23, calcium source liquid storage tank, 24, liquid outlet valve 2, 25, jet drilling rig, 26, jet injection hole position, 27, resistivity and CO 2 Monitoring instrument, 28. Monitoring well, 29. Sampling area, 30. Topsoil, 31. Soil layer to be treated, 32. Replaceable filter membrane, 33. Removable fixing frame. DETAILED DESCRIPTION

[0035] The present invention will be further described below by way of examples.

[0036] like Figure 1 and Figure 3 As shown, a method using CO 2 Mineralized life source contaminated soil reinforcement method, gaseous CO 2 It is converted into injectable carbon alkali solution. After the carbon alkali solution changes the water chemical environment of the soil, it generates carbonate precipitation in the pores of the soil with the calcium source solution injected into the soil, and forms calcareous cement between the particles, thereby realizing the in-situ reinforcement of soil contaminated by domestic sources.

[0037] Furthermore, exogenous CO 2 undergoes different chemical phase changes, including CO 2 The process of generating carbon alkali solution is to react CO with alkaline solution. 2 Absorb gaseous CO 2 The converted dissolved water phase can be injected into a carbon alkali solution; wherein the alkaline solution includes but is not limited to aluminate, ammonium salt, and soda ash, and the reaction formula is as follows:

[0038]

[0039] After filtering the converted carbon alkali solution and injecting it into the soil contaminated by the living source, the soil water chemical field is adjusted to adjust the soil pH environment from acidic to weakly alkaline, and then react with the calcium source solution injected into the soil to transform into a mineral phase to generate carbonate precipitation; wherein the calcium source solution includes but is not limited to calcium chloride, and its concentration is consistent with that of the carbon alkali solution, and the reaction formula is as follows:

[0040]

[0041] The system devices used in the implementation process of the reinforcement method of the present invention include a carbon alkali solution preparation device, a mineralization solution injection device and a sampling monitoring device;

[0042] Carbon alkali solution preparation device includes CO 2 Gas cylinder 1, multi-stage filter assembly and reaction device 5, CO 2 The gas cylinder 1 is connected to the reaction device 5 through the gas valve 2, the reaction device 5 is connected to the stirrer 3 and the pressure gauge 4, and the reaction device 5 is connected to the mineralized liquid injection device through the multi-stage filtering component; the multi-stage filtering component and the reaction device 5 are fixed by the support frame 7, the gas valve 2 is used to control the intake amount, cooperate with the stirrer 3 to fully react in the reaction device 5, and then filter through the multi-stage filtering component to maintain the fluidity of the solution;

[0043] The mineralization liquid injection device includes a carbon alkali liquid storage tank 16, a calcium source liquid storage tank 23, an air compressor 20, an air pressure control box 19, a CO 2 The filter 18 and the jet grouting drill 25 are connected to the air compressor 20 and the air pressure control box 19. The air pressure control box 19 is connected to the air pressure control box 19 through the CO 2The filter 18 is connected in parallel to the carbon alkali liquid storage tank 16 and the calcium source liquid storage tank 23, the carbon alkali liquid storage tank 16 is connected to the multi-stage filter assembly, and the carbon alkali liquid storage tank 16 and the calcium source liquid storage tank 23 are connected to the rotary jet drilling rig 25; wherein the CO 2 The filter 18 is filled with a material capable of absorbing CO 2 solutions, including but not limited to sodium hydroxide solutions;

[0044] The sampling monitoring device includes monitoring well 28, resistivity and CO 2 The monitoring instrument 27 and the monitoring well 28 are arranged according to the rotary jet injection hole positions 26 , and a sampling area 29 is provided around each rotary jet injection hole position 26 .

[0045] In order to ensure the filtering effect of the multi-stage filtering device, such as Figure 1 and Figure 2 As shown, the multi-stage filtering device includes a primary vacuum filter 8 and a secondary vacuum filter 11, the primary vacuum filter 8 and the secondary vacuum filter 11 are both divided into an upper part and a lower part, a replaceable filter membrane 32 is placed between the upper part and the lower part, and the upper part and the lower part are fixed by a detachable fixing frame 33;

[0046] The first-stage vacuum filter 8 and the second-stage vacuum filter 11 are connected to the vacuum pump 1 14 and the vacuum pump 2 12 at the upper part through the valve 1 15 and the valve 2 13 respectively;

[0047] The upper inlet end of the first-stage vacuum filter 8 is connected to the liquid outlet of the reaction device 5, and the liquid outlet of the reaction device 5 is provided with a control valve 1 6. The lower outlet end of the first-stage vacuum filter 8 is connected to the upper inlet end of the second-stage vacuum filter 11, and the lower outlet end of the first-stage vacuum filter 8 is provided with a control valve 2 9. The lower outlet end of the second-stage vacuum filter 11 is connected to the carbon alkali liquid storage tank 16, and the lower outlet end of the second-stage vacuum filter 11 is provided with a control valve 3 10.

[0048] The pore size of the replaceable filter membrane 32 of the primary vacuum filter 8 is larger than the pore size of the replaceable filter membrane 32 of the secondary vacuum filter 11. The pore size of the replaceable filter membrane 32 of the primary vacuum filter 8 may be 1 μm, and the pore size of the replaceable filter membrane 32 of the secondary vacuum filter 11 may be between 0.2 μm and 0.45 μm, ensuring effective removal of the oxyalumina particles produced by the reaction and maintaining the fluidity of the solution.

[0049] When constructing for different soil types, in order to ensure the effect, the carbon alkali liquid storage tank 16, the calcium source liquid storage tank 23 and the CO 2 The connection ends of the filter 18 are respectively provided with an air valve 17 and an air valve 22, and the connection ends of the carbon alkali liquid storage tank 16, the calcium source liquid storage tank 23 and the rotary jet drilling rig 25 are respectively provided with a liquid outlet valve 1 21 and a liquid outlet valve 24.

[0050] The specific steps of the reinforcement method are as follows:

[0051] 1) Place an alkaline solution (such as aluminate) into a reaction device 5 equipped with a stirrer 5 and a pressure gauge 4, and add CO 2 CO in cylinder 1 2 Pass into reaction device 5;

[0052] Furthermore, the solubility of the prepared carbon alkali solution is lower than 1 mol / L, and the specific concentration used should be determined according to the geotechnical property parameters such as pH and soil strength of the domestic source contaminated soil to be treated, and the concentrations of all reagents used can be adjusted;

[0053] 2) When CO is introduced 2 When the amount of the substance reaches 50% of the amount of the alkaline solution, stop passing CO 2 , and turn on the agitator 3, and the reaction ends when the pressure gauge 4 shows a stable reading and no more precipitation is generated;

[0054] Aluminate and CO 2 The molar ratio of the substances is 2:1. After multi-stage filtration, a clear carbon alkali solution is obtained, and the by-product is aluminum hydroxide. 2 If the amount of the substance exceeds the standard ratio, the prepared carbon alkali solution needs to be treated in a water bath at 60°C;

[0055] 3) filtering the reaction solution using a multi-stage filtration assembly to obtain a clarified carbon alkali solution;

[0056] Specifically: open the liquid outlet control valve 6 of the reaction device 5, close the liquid outlet control valve 9 of the first-level vacuum filter 8, open the vacuum pump 14 and the valve 15, so that the suspension after the reaction enters the first-level vacuum filter 8 for primary filtration. The first-level vacuum filter 8 can select a replaceable filter membrane 32 with a pore size of 1 μm;

[0057] After the primary filtration is completed, close the vacuum pump 14, valve 15 and control valve 3 10, open the control valve 2 9, open the vacuum pump 2 12 and valve 2 13, and allow the primary filtered solution to enter the secondary vacuum filter 11 for secondary filtration. The secondary vacuum filter 11 can select a replaceable filter membrane 32 with a pore size between 0.2 μm and 0.45 μm;

[0058] After the secondary filtration is completed, close the vacuum pump 2 12 and valve 2 13, open the control valve 3 10, and the clarified carbon alkali solution can be discharged;

[0059] 4) injecting the carbon alkali solution into the carbon alkali solution storage tank 16, injecting the calcium source solution into the calcium source solution storage tank 23, and the air inlet ends of the carbon alkali solution storage tank 16 and the calcium source solution storage tank 23 are connected by CO 2The filter 18 is connected to the air pressure control box 19, the air pressure control box 19 is connected to the air compressor 20, and the liquid outlets of the carbon alkali liquid storage tank 16 and the calcium source liquid storage tank 23 are connected to the rotary jet drilling machine 25;

[0060] 5) After leveling the site, arrange several jet injection holes 26, monitoring wells 28 and sampling areas 29;

[0061] Furthermore, the jet injection holes 26 are arranged in a triangular pattern, the distance between adjacent jet injection holes 26 is 2-2.5 m, the area 1-1.5 m away from the jet injection holes 26 is set as the sampling area 29, and the monitoring well 28 is arranged at the center of the triangle; Figure 3 As shown, there are shown the rotary jet injection holes 26 distributed in a triangle, the monitoring well 28 located at the center of the triangle distribution, and the sampling area 29 located at a distance of 1-1.5m from the rotary jet injection holes 26;

[0062] 6) Turn on the air compressor 20 and pass the CO 2 Filter 18 removes CO from the air 2 , the injection speed is controlled by the air pressure control box 19, the rotary jet drilling rig 25 drills, injects the carbon alkali solution into the soil and stirs it;

[0063] The drilling speed of the drilling rig is 0.5-1m / min, the injection speed of carbon alkali solution is 20-50L / min, and the rotation speed is 10-15r / min;

[0064] 7) After the injection of carbon alkali solution is completed, the calcium source solution is injected, and the drill pipe is lifted and reversely stirred;

[0065] The injection speed of calcium source is 20-50L / min, and the drilling rod lifting speed is 0.5-1m / min;

[0066] The parameters of the jet-jet drilling rig 25 such as the drilling speed, the injection speed of the carbon alkali solution, the rotation speed, the drilling rig lifting speed, etc. can be adjusted according to the geotechnical properties of the domestic source contaminated soil to be treated;

[0067] 8) After the drill rod is lifted, the jet grouting drill 25 is moved to the next jet grouting injection hole 26, and steps 5)-6) are repeated until all the jet grouting injection holes 26 and the surrounding soil are processed;

[0068] Furthermore, the injection volume of the carbon alkali solution and the calcium source solution into the soil body of the to-be-treated layer 31 is 1-1.5 times the pore volume of the soil body;

[0069] 9) After injection, the resistivity and CO 2 The monitoring instrument 27 is placed in the monitoring well 28. After the injection is completed, the conductivity of the reinforced area is tested at 12h, 24h, 36h, 48h, and 72h. The conductivity is compared with the test data before the site restoration to analyze the CO2 Diffusion and migration of mineralized fluid;

[0070] 10) After 12h, 24h, 36h, 48h, and 72h after injection, the reinforced samples were taken from the sampling area 29, and the control samples were taken from the non-injected area to conduct tests such as calcium carbonate content, pH, unconfined compressive strength, and triaxial compression to detect CO 2 The effect of mineralization on consolidation of soil contaminated by domestic sources.

Claims

1. A method for consolidating soil contaminated by living sources using CO2 mineralization, characterized in that: include: The gaseous CO2 is converted into injectable carbon alkali solution. After the carbon alkali solution changes the water chemical environment of the soil, it reacts with the calcium source solution injected into the soil to generate carbonates that precipitate in the pores of the soil and form calcareous cement between the particles, thereby achieving in-situ reinforcement of soil contaminated by domestic sources.

2. The method for consolidating soil contaminated by living sources using CO2 mineralization according to claim 1 is characterized in that: Gaseous CO2 undergoes different chemical phase changes, wherein the process of reacting with CO2 to generate carbon alkali solution is to absorb CO2 through alkaline solution, and convert gaseous CO2 into dissolved water phase that can be injected into carbon alkali solution; wherein the alkaline solution includes but is not limited to aluminate, ammonium salt, soda ash, and the reaction formula is as follows: After filtering the converted carbon alkali solution and injecting it into the soil contaminated by the living source, the soil water chemical field is adjusted to adjust the soil pH environment from acidic to weakly alkaline, and then react with the calcium source solution injected into the soil to transform into a mineral phase to generate carbonate precipitation; wherein the calcium source solution includes but is not limited to calcium chloride, and its concentration is consistent with that of the carbon alkali solution, and the reaction formula is as follows:

3. The method for consolidating soil contaminated by living sources using CO2 mineralization according to claim 2 is characterized in that: The specific steps of the reinforcement method are as follows: 1) placing an alkaline solution into a reaction device (5) equipped with a stirrer (5) and a pressure gauge (4), and passing CO2 from a CO2 cylinder (1) into the reaction device (5); 2) When the amount of CO2 introduced reaches 50% of the amount of the alkaline solution, stop introducing CO2 and turn on the agitator (3). The reaction ends when the pressure gauge (4) shows a stable reading and no more precipitation is generated; 3) filtering the reaction solution using a multi-stage filtration assembly to obtain a clarified carbon alkali solution; 4) injecting the carbon alkali liquid into the carbon alkali liquid storage tank (16), injecting the calcium source liquid into the calcium source liquid storage tank (23), connecting the air inlet ends of the carbon alkali liquid storage tank (16) and the calcium source liquid storage tank (23) to the air pressure control box (19) through the CO2 filter (18), connecting the air pressure control box (19) to the air compressor (20), and connecting the liquid outlet ends of the carbon alkali liquid storage tank (16) and the calcium source liquid storage tank (23) to the rotary jet drilling machine (25); 5) After leveling the site, arrange a number of jet injection holes (26), monitoring wells (28) and sampling areas (29); 6) turning on the air compressor (20) and filtering out CO2 in the air through the CO2 filter (18), controlling the injection speed through the air pressure control box (19), drilling with the jet drilling rig (25), injecting the carbon alkali solution into the soil and stirring; 7) After the injection of carbon alkali solution is completed, the calcium source solution is injected, and the drill pipe is lifted and reversely stirred; 8) After the drill rod is lifted, the jet grouting drill (25) is moved to the next jet grouting injection hole (26), and steps 5)-6) are repeated until all the jet grouting injection holes (26) and the surrounding soil bodies are processed; 9) After the injection is completed, the resistivity and CO2 monitoring instrument (27) is placed in the monitoring well (28), the conductivity of the reinforced area is tested, and the test data is compared with the test data before the site restoration to analyze the diffusion and migration of the CO2 mineralized liquid; 10) After the injection is completed, the reinforced sample is taken from the sampling area (29), and a control sample is taken from the non-injected area to test the effect of CO2 mineralization on the reinforcement of domestic source contaminated soil.

4. The method for consolidating soil contaminated by living sources using CO2 mineralization according to claim 3 is characterized in that: The solubility of the prepared carbon alkali solution is lower than 1 mol / L.

5. The method for consolidating soil contaminated by living sources using CO2 mineralization according to claim 3 is characterized in that: The rotary jet injection holes (26) are arranged in a triangular pattern, the distance between adjacent rotary jet injection holes (26) is 2-2.5 m, the area 1-1.5 m away from the rotary jet injection holes (26) is set as a sampling area (29), and the monitoring well (28) is arranged at the center of the triangular distribution.

6. The method for consolidating soil contaminated by living sources using CO2 mineralization according to claim 3 is characterized in that: The volume of the carbon alkali solution and the calcium source solution injected into the soil body of the to-be-treated layer soil (31) is 1-1.5 times the pore volume of the soil body.

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