Method for reinforcing biogenic contaminated soil using co2 mineralization

Abstract

The application discloses a life source pollution soil reinforcement method using CO2 mineralization, converts gaseous CO2 into injectable carbon alkali liquid, changes the soil water chemical environment through the carbon alkali liquid, generates carbonate precipitate in the soil pores with the calcium source liquid injected into the soil, forms calcium cement between the particles, and further realizes in-situ reinforcement of the life source pollution soil. The application can adjust the life source pollution soil environment from an acidic environment to a weak alkaline environment, inhibits degradation of the pollution material, converts the exogenous CO2 through different chemical phase states from a gas phase to a dissolved water phase and then to a mineral phase, achieves the effect of CO2 mineralization in the life source pollution soil, and plays a role in in-situ reinforcement of the life source pollution soil.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of environmental engineering geology, and particularly relates to a household source pollution soil reinforcement method using CO2 mineralization. BACKGROUND

[0002] The main components of the household source pollution fluid are soluble organic acids, soluble monosaccharides, amino acids and other organic matters, and contain inorganic matters such as Na + , K + , Ca 2+ , CO3 2- , SO4 2- , Cl - and a small amount of heavy metal ions. The seepage and degradation of the household source pollution fluid in the soil body will change the mineral composition and structure of the soil body, and then affect the physical and mechanical properties of the soil body, cause cumulative deformation of the soil body, and lead to a series of geological disasters and engineering problems such as uneven ground settlement, foundation deformation and slope instability. Therefore, it is necessary to explore a method for in-situ reinforcement of household source pollution soil.

[0003] The CO2 mineralization technology is a technology for geological storage and utilization of CO2, which is achieved by reacting gaseous CO2 with alkaline Ca 2+ or Mg 2+ to generate carbonated products. In addition, the household source pollution matter degrades in the soil body, gradually converts the soil body environment into an acidic environment, and releases CO2. Therefore, adjusting the soil body environment of the household source pollution soil to be weakly alkaline is beneficial to inhibit the degradation of the household source pollution matter, reduce the emission of greenhouse gases, and promote the mineralization of exogenous CO2 in the soil body, thereby achieving the effect of reinforcing the household source pollution soil.

[0004] The existing soil reinforcement technology does not have a reinforcement method for such household source pollution soil which is easy to degrade, has unstable composition and structure, and releases greenhouse gases. The widely used CO2 mineralization technology, such as directly introducing CO2 into the stratum or soil body to react with mineral matter and embed CO2 into the mineral structure, has difficulty in storing the mineralization products in the household source pollution soil, cannot change the characteristics of the household source pollution matter that continuously degrades, cannot solve the problem of unstable composition and structure of the household source pollution soil, and cannot achieve the purpose of reinforcing the household source pollution soil and reducing the generation of greenhouse gases. SUMMARY

[0005] The present application provides a household source pollution soil reinforcement method using CO2 mineralization, which can adjust the household source pollution soil body environment from an acidic environment to a weakly alkaline environment, inhibit the degradation of the pollution matter, achieve the effect of CO2 mineralization in the household source pollution soil, and play a role in in-situ reinforcement of the household source pollution soil.

[0006] To achieve the above object, the application provides a life source pollution soil reinforcement method using CO2 mineralization, comprising the following steps:

[0007] The gaseous CO2 is converted into injectable carbon alkali solution, and after the soil water chemical environment is changed by the carbon alkali solution, the carbon alkali solution and the calcium source solution injected into the soil generate carbonate precipitates in the soil pores and form calcareous cement between the particles, thereby realizing in-situ reinforcement of the life source pollution soil.

[0008] As a further scheme of the application, the exogenous CO2 undergoes different chemical phase changes, wherein the process of generating carbon alkali solution by reacting with CO2 is that the gaseous CO2 is converted into injectable carbon alkali solution in the dissolved water phase by absorbing CO2 with an alkaline solution; wherein the alkaline solution includes but is not limited to metahydroxyaluminate, ammonium salt and soda ash, and the reaction formula is as follows:

[0009]

[0010] After the obtained carbon alkali solution is filtered and injected into the life source pollution soil, the soil water chemical field is adjusted, the pH environment of the soil is adjusted from acidic to weak alkaline, and the carbon alkali solution is converted into mineral phase by reacting with the calcium source solution injected into the soil to generate carbonate precipitates; wherein the calcium source solution includes but is not limited to calcium chloride, and the concentration of the calcium source solution is consistent with that of the carbon alkali solution, and the reaction formula is as follows:

[0011]

[0012] As a further scheme of the application, the reinforcement method comprises the following specific steps:

[0013] 1) The alkaline solution is placed in a reaction device with a stirrer and a pressure gauge, and CO2 in a CO2 cylinder is introduced into the reaction device;

[0014] 2) When the amount of introduced CO2 reaches 50% of the amount of the alkaline solution, the introduction of CO2 is stopped, the stirrer is turned on, and the reaction is ended when the pressure value is stable and no more precipitates are generated;

[0015] 3) The solution after reaction is filtered by using a multi-stage filter assembly to obtain clear carbon alkali solution;

[0016] 4) The carbon alkali solution is injected into a carbon alkali solution storage tank, and the calcium source solution is injected into a calcium source solution storage tank, the gas inlet ends of the carbon alkali solution storage tank and the calcium source solution storage tank are connected with a CO2 filter and a gas pressure control box, the gas pressure control box is connected with an air compressor, and the liquid outlet ends of the carbon alkali solution storage tank and the calcium source solution storage tank are connected with a rotary jet drilling machine;

[0017] 5) After the site is leveled, a plurality of rotary jet injection hole sites, monitoring wells and sampling areas are arranged;

[0018] 6) start the air compressor and filter out CO2 in the air through the CO2 filter, control the injection speed through the air pressure control box, drill with the rotary jet drill, inject the carbon alkali solution into the soil and stir;

[0019] 7) after the carbon alkali solution injection is completed, the calcium source solution is injected, and the drill rod is lifted and the reverse stirring is performed;

[0020] 8) after the drill rod lifting is completed, the rotary jet drill is moved to the next rotary jet injection hole position, and steps 5)-6) are repeated until all the rotary jet injection hole positions and the peripheral soil are treated;

[0021] 9) after the injection is completed, the resistivity and CO2 monitoring instrument is placed in the monitoring well, the conductivity of the reinforced area is detected, and the detection data before the site is repaired is compared, and the diffusion and migration of the CO2 mineralization solution is analyzed;

[0022] 10) after the injection is completed, the reinforced sample is taken out from the sampling area, and the control sample is taken from the non-injection area, and the effect of the CO2 mineralization and reinforcement of the life source contaminated soil is detected.

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

[0024] As a further scheme of the present application: the rotary jet injection hole arrangement mode is a triangle, the distance between adjacent rotary jet injection holes is 2-2.5 m, and the area within 1-1.5 m from the rotary jet injection hole is set as a sampling area, and the monitoring well is arranged at the center position of the triangle distribution.

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

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

[0027] 1) The present application uses CO2 to prepare a carbon alkali solution, which can effectively improve the acidic environment of life source contaminated soil after being injected into the soil, inhibit the further degradation of the contaminant, slow down the damage of the life source contaminant to the soil structure, and reduce the CO2 generated by the degradation of the contaminant.

[0028] 2) By adding a calcium source solution to the life source contaminated soil, calcium carbonate precipitates are generated after the reaction of the calcium source solution and the carbon alkali solution, which can effectively increase the strength of the soil and repair the damage to the soil structure caused by the life source contaminant.

[0029] 3) The present application finally converts the exogenous CO2 into calcium carbonate precipitates and stores them in the soil, which provides an effective way for carbon sequestration using life source contaminated soil.

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

[0031] Figure 1 The specific step implementation structure diagram of the reinforcement method of the present application.

[0032] Figure 2 For Figure 1 The schematic diagram of the replaceable filter membrane and the detachable fixing clamp at A.

[0033] Figure 3 The position schematic diagram of the rotary jet injection hole, monitoring well and sampling area proposed by the present application.

[0034] In the figure: 1, CO2 gas cylinder, 2, gas valve, 3, stirrer, 4, pressure gauge, 5, reaction device, 6, control valve one, 7, support frame, 8, primary vacuum filter, 9, control valve two, 10, control valve three, 11, secondary vacuum filter, 12, vacuum pump two, 13, valve two, 14, vacuum pump one, 15, valve one, 16, carbon alkali liquid storage tank, 17, gas valve one, 18, CO2 filter, 19, air pressure control box, 20, air compressor, 21, liquid outlet valve one, 22, gas valve two, 23, calcium source liquid storage tank, 24, liquid outlet valve two, 25, rotary jet drilling machine, 26, rotary jet injection hole, 27, resistivity and CO2 monitoring instrument, 28, monitoring well, 29, sampling area, 30, surface soil, 31, soil to be treated, 32, replaceable filter membrane, 33, detachable fixing frame. DETAILED DESCRIPTION

[0035] The present application will be further described below through examples.

[0036] As Figure 1 and Figure 3 shown, a life source contaminated soil reinforcement method using CO2 mineralization, converts gaseous CO2 into injectable carbon alkali liquid, changes the soil water chemical environment through the carbon alkali liquid, and generates carbonate precipitates in the soil pores with the calcium source liquid injected into the soil, and forms calcium cement between the particles, thereby realizing the in-situ reinforcement of life source contaminated soil.

[0037] Further, the exogenous CO2 undergoes different chemical phase changes, wherein the process of generating carbon alkali liquid by reacting with CO2 is to absorb CO2 by an alkaline solution to convert gaseous CO2 into injectable carbon alkali liquid in the dissolved water phase; wherein the alkaline solution includes but is not limited to metaborate, ammonium salt, soda ash, and the reaction formula is as follows:

[0038]

[0039] The transformed carbon alkali liquid is filtered and injected into the life source contaminated soil, the water chemical field of the soil is adjusted, the pH environment of the soil is adjusted from acidity to weak alkalinity, and then the carbon alkali liquid is reacted with the calcium source liquid injected into the soil to be transformed into a mineral phase to generate carbonate precipitate; wherein the calcium source liquid includes but is not limited to calcium chloride, and the concentration is consistent with that of the carbon alkali liquid, and the reaction formula is as follows:

[0040]

[0041] The system device used in the implementation process of the reinforcing method includes a carbon alkali liquid preparation device, a mineralization liquid injection device and a sampling monitoring device;

[0042] The carbon alkali liquid preparation device includes a CO2 gas cylinder 1, a multi-stage filter assembly and a reaction device 5, the CO2 gas cylinder 1 is connected with the reaction device 5 through a gas valve 2, the reaction device 5 is connected with a stirrer 3 and a pressure gauge 4, and the reaction device 5 is connected with the mineralization liquid injection device through the multi-stage filter assembly; the multi-stage filter assembly and the reaction device 5 are fixed through a support frame 7, the gas valve 2 is used for controlling the gas inlet amount, cooperating with the stirrer 3 to fully react in the reaction device 5, and then filtering through the multi-stage filter assembly 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, a gas pressure control box 19, a CO2 filter 18 and a rotary jet drill 25, the air compressor 20 is connected with the gas pressure control box 19, the gas pressure control box 19 is connected in parallel with the carbon alkali liquid storage tank 16 and the calcium source liquid storage tank 23 through the CO2 filter 18, the carbon alkali liquid storage tank 16 is connected with the multi-stage filter assembly, and the carbon alkali liquid storage tank 16 and the calcium source liquid storage tank 23 are jointly connected with the rotary jet drill 25; wherein the CO2 filter 18 is filled with a solution capable of adsorbing CO2, including but not limited to sodium hydroxide solution;

[0044] The sampling monitoring device includes a monitoring well 28 and a resistivity and CO2 monitoring instrument 27, the monitoring well 28 is arranged according to the rotary jet injection hole site 26, and a sampling area 29 is arranged around each rotary jet injection hole site 26.

[0045] In order to ensure the filtering effect of the multi-stage filter device, as shown in Figure 1 and Figure 2 , the multi-stage filter device includes a first-stage vacuum filter 8 and a second-stage vacuum filter 11, the first-stage vacuum filter 8 and the second-stage vacuum filter 11 are each divided into an upper part and a lower part, a replaceable filter membrane 32 is arranged between the upper part and the lower part, and the upper part and the lower part are fixed through a detachable fixing frame 33;

[0046] The first-stage vacuum filter 8 and the second-stage vacuum filter 11 are respectively connected with a vacuum pump one 14 and a vacuum pump two 12 through a valve one 15 and a valve two 13 in the upper part;

[0047] The upper inlet end of the first-stage vacuum filter 8 is connected with the liquid outlet of the reaction device 5, the liquid outlet of the reaction device 5 is provided with a control valve 1, the lower outlet end of the first-stage vacuum filter 8 is connected with the upper inlet end of the second-stage vacuum filter 11, the lower outlet end of the first-stage vacuum filter 8 is provided with a control valve 2, the lower outlet end of the second-stage vacuum filter 11 is connected with 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.

[0048] The pore size of the replaceable filter membrane 32 of the first-stage vacuum filter 8 is greater than that of the replaceable filter membrane 32 of the second-stage vacuum filter 11. The pore size of the replaceable filter membrane 32 of the first-stage vacuum filter 8 can be 1 μm, and the pore size of the replaceable filter membrane 32 of the second-stage vacuum filter 11 is between 0.2 μm and 0.45 μm, which ensures the effective removal of the oxygen alumina particles generated in the reaction and maintains the fluidity of the solution.

[0049] When the construction is performed on different soil types, the carbon alkali liquid storage tank 16 and the calcium source liquid storage tank 23 can be connected with the CO2 filter 18 and the rotary jet drilling machine 25 as needed to ensure the effect. The connecting ends of the carbon alkali liquid storage tank 16 and the calcium source liquid storage tank 23 and the CO2 filter 18 are respectively provided with a gas valve 1 and a gas valve 2, and the connecting ends of the carbon alkali liquid storage tank 16 and the calcium source liquid storage tank 23 and the rotary jet drilling machine 25 are respectively provided with a liquid outlet valve 1 and a liquid outlet valve 2.

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

[0051] 1) Put the alkaline solution (such as metashite) into the reaction device 5 provided with a stirrer 5 and a pressure gauge 4, and introduce CO2 in the CO2 cylinder 1 into the reaction device 5;

[0052] Further, the prepared carbon alkali liquid has a solubility lower than 1 mol / L, and the specific concentration should be determined according to the pH and soil strength of the life source pollution soil to be treated and other soil engineering property parameters. The concentrations of all the reagents used can be adjusted.

[0053] 2) When the amount of substance of the introduced CO2 reaches 50% of the amount of substance of the alkaline solution, the introduction of CO2 is stopped, the stirrer 3 is turned on, and the reaction is ended when the pressure gauge 4 shows a stable value and no more precipitate is generated;

[0054] The amount-of-substance ratio of metashite to CO2 is 2:1, and the clear carbon alkali liquid is obtained after multi-stage filtration, and the by-product is aluminum hydroxide. If the amount of substance of the introduced CO2 exceeds the standard ratio, the prepared carbon alkali liquid needs to be treated in a water bath at 60℃.

[0055] 3) The solution after the reaction is filtered by using a multi-stage filtration assembly to obtain the clear carbon alkali liquid;

[0056] Specifically: open the reaction device 5 liquid outlet control valve 6, close the first-stage vacuum filter 8 liquid outlet control valve 2 9, open the vacuum pump 1 4 and valve 1 5, so that the reaction suspension enters the first-stage vacuum filter 8 for first-stage filtration, and the first-stage vacuum filter 8 can select a replaceable filter membrane 32 with a pore size of 1 μm;

[0057] After the first-stage filtration is completed, the vacuum pump 1 4, valve 1 5 and control valve 3 10 are closed, the control valve 2 9 is opened, the vacuum pump 2 1 2 and valve 2 1 3 are opened, so that the first-stage filtered solution enters the second-stage vacuum filter 1 1 for second-stage filtration, and the second-stage vacuum filter 1 1 can select a replaceable filter membrane 32 with a pore size of 0.2 μm to 0.45 μm;

[0058] After the second-stage filtration is completed, the vacuum pump 2 1 2 and valve 2 1 3 are closed, and the control valve 3 1 0 is opened, so that the clear carbon alkali solution is discharged;

[0059] 4) The carbon alkali solution is injected into the carbon alkali solution storage tank 1 6, and the calcium source solution is injected into the calcium source solution storage tank 2 3. The gas inlet ends of the carbon alkali solution storage tank 1 6 and the calcium source solution storage tank 2 3 are connected to the CO 2 filter 1 8 and the gas pressure control box 1 9. The gas pressure control box 1 9 is connected to the air compressor 2 0. The liquid outlet ends of the carbon alkali solution storage tank 1 6 and the calcium source solution storage tank 2 3 are connected to the rotary jet drill 2 5.

[0060] 5) After the site is leveled, a plurality of rotary jet injection hole sites 2 6, monitoring wells 2 8 and sampling areas 2 9 are arranged;

[0061] Further, the rotary jet injection hole sites 2 6 are arranged in a triangular shape, the distance between adjacent rotary jet injection hole sites 2 6 is 2-2.5 m, the area 1-1.5 m away from the rotary jet injection hole sites 2 6 is set as the sampling area 2 9, and the monitoring well 2 8 is arranged at the center position of the triangular shape; Figure 3 As shown in the figure, the rotary jet injection hole sites 2 6 are distributed in a triangular shape, the monitoring well 2 8 is located at the center position of the triangular distribution, and the sampling area 2 9 is located 1-1.5 m away from the rotary jet injection hole sites 2 6;

[0062] 6) The air compressor 2 0 is started, and the CO 2 in the air is filtered out through the CO 2 filter 1 8. The injection speed is controlled through the gas pressure control box 1 9. The rotary jet drill 2 5 drills into the soil and stirs the carbon alkali solution;

[0063] The drilling speed of the drill is 0.5-1 m / min, the injection speed of the carbon alkali solution is 20-50 L / min, and the rotation speed is 1 0-1 5 r / min;

[0064] 7) After the carbon alkali solution is injected, the calcium source solution is injected, and the drill pipe is lifted and stirred in the opposite direction;

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

[0066] The drilling speed, injection speed of carbon alkali solution, rotation speed, and drill lifting speed of the rotary jet drilling machine 25 can be adjusted according to the properties of the life source pollution soil to be treated.

[0067] 8) After the drill rod lifting is completed, the rotary jet drilling machine 25 is moved to the next rotary jet injection hole site 26, and steps 5)-6) are repeated until all the rotary jet injection hole sites 26 and the peripheral soil are treated.

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

[0069] 9) After the injection is completed, the resistivity and CO2 monitoring instrument 27 is placed in the monitoring well 28, and the electrical conductivity of the reinforced area is detected at 12 h, 24 h, 36 h, 48 h, and 72 h after the injection is completed, and compared with the detection data before the site is repaired, so as to analyze the diffusion and migration of the CO2 mineralization solution.

[0070] 10) After the injection is completed, the reinforced sample is taken out from the sampling area 29 at 12 h, 24 h, 36 h, 48 h, and 72 h, and the control sample is taken out from the non-injection area, and the calcium carbonate content, pH, unconfined compressive strength, triaxial compression, and other tests are performed to detect the effect of the CO2 mineralization reinforced life source pollution soil.

Claims

1. A method for reinforcing biogenic contaminated soil using CO2 mineralization, characterized by, The application relates to a method for in-situ reinforcement of life-source contaminated soil. The gaseous CO2 is converted into injectable carbon alkali liquid, the water chemical environment of the soil is changed by the carbon alkali liquid, the carbonate precipitate is generated in the soil pores by the carbon alkali liquid and the calcium source liquid injected into the soil, and the calcareous cement is formed between the particles, so that the life-source contaminated soil is in-situ reinforced. The gaseous CO2 undergoes different chemical phase changes, wherein the process of generating the carbon alkali liquid by reacting with the CO2 is that the gaseous CO2 is converted into the injectable carbon alkali liquid in the dissolved water phase by absorbing the CO2 through the alkaline solution; wherein the alkaline solution is a metahydroxyaluminate, an ammonium salt or pure alkali, and the reaction formula is as follows: ； After the obtained carbon alkali liquid is filtered and injected into the life-source contaminated soil, the water chemical field of the soil is adjusted, the pH environment of the soil is adjusted from acidity to weak alkalinity, and the carbon alkali liquid is converted into a mineral phase by reacting with the calcium source liquid injected into the soil to generate carbonate precipitate; wherein the calcium source liquid is calcium chloride, the concentration of the calcium source liquid is consistent with that of the carbon alkali liquid, and the reaction formula is as follows: ； The specific steps of the reinforcement method are as follows: 1) the alkaline solution is placed into a reaction device (5) provided with a stirrer (3) and a pressure gauge (4), and the CO2 in a CO2 cylinder (1) is introduced into the reaction device (5); 2) when the amount of substance of the introduced CO2 reaches 50% of the amount of substance of the alkaline solution, the introduction of the CO2 is stopped, the stirrer (3) is opened, and the reaction is ended when the pressure gauge (4) shows a stable value and no more precipitate is generated; 3) the solution after the reaction is filtered by using a multistage filtering assembly to obtain the clear carbon alkali liquid; 4) the carbon alkali liquid is injected into a carbon alkali liquid storage tank (16), and the calcium source liquid is injected into a calcium source liquid storage tank (23); the gas inlet ends of the carbon alkali liquid storage tank (16) and the calcium source liquid storage tank (23) are connected with a CO2 filter (18) and a gas pressure control box (19), the gas pressure control box (19) is connected with an air compressor (20), and the liquid outlet ends of the carbon alkali liquid storage tank (16) and the calcium source liquid storage tank (23) are connected with a rotary jet drilling machine (25); 5) after the site is leveled, a plurality of rotary jet injection hole positions (26), monitoring wells (28) and sampling areas (29) are arranged; 6) the air compressor (20) is started, the CO2 in the air is filtered through the CO2 filter (18), the injection speed is controlled through the gas pressure control box (19), the rotary jet drilling machine (25) is drilled, the carbon alkali liquid is injected into the soil and stirred; 7) after the injection of the carbon alkali liquid is completed, the calcium source liquid is injected, and the drill rod is lifted and stirred in the reverse direction; 8) after the lifting of the drill rod is completed, the rotary jet drilling machine (25) is moved to the next rotary jet injection hole position (26), and the steps 5) to 6) are repeated until all the rotary jet injection hole positions (26) and the surrounding soil are treated; 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 detected, and the detection data before the site is repaired are compared to analyze the diffusion and migration of the CO2 mineralized liquid; 10) after the injection is completed, the samples after the reinforcement are taken from the sampling areas (29), the contrast samples are taken from the non-injection areas, and the effect of the CO2 mineralized reinforced life-source contaminated soil is detected.

2. The method for reinforcing biogenic contaminated soil using CO2 mineralization according to claim 1, characterized in that, The obtained carbon alkali liquid has a solubility lower than 1 mol / L.

3. The method for reinforcing biogenic contaminated soil using CO2 mineralization according to claim 1, characterized in that, The rotational jet injection hole site (26) is arranged in a triangular shape, and the distance between adjacent rotational jet injection hole sites (26) is 2-2.5 m. A sampling area (29) is arranged at a distance of 1-1.5 m from the rotational jet injection hole site (26), and a monitoring well (28) is arranged at the center of the triangular distribution.

4. The method for reinforcing biogenic contaminated soil using CO2 mineralization according to claim 1, wherein The injection volume of the carbon alkali solution and the calcium source solution into the soil (31) is 1-1.5 times the pore volume of the soil.

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