Modified coal gasification slag as well as preparation method and application thereof

Abstract

The invention provides modified coal gasification slag as well as a preparation method and application thereof. The preparation method comprises the following steps: S1) mixing straw and coal gasification slag, and performing steam explosion treatment to obtain first coal gasification slag; s2) mixing the first coal gasification slag with an acid solution, and performing first grinding to obtain first acidified coal gasification slag; s3) mixing the first acidified coal gasification slag with a chelating agent, and performing secondary grinding to obtain second coal gasification slag; and S4) mixing the second coal gasification slag with an adhesive to obtain the modified coal gasification slag. The method can solve the problem that in the prior art, solid waste is difficult to post-treat, and is suitable for the field of modified coal gasification slag preparation.

Description

Technical Field

[0001] The present invention relates to the field of modified coal gasification slag preparation, and in particular to modified coal gasification slag and a preparation method and application thereof. Background Art

[0002] In the coal gasification reaction, coal particles are rapidly decomposed by high-temperature reaction in the gasifier. In this process, a large amount of volatiles are generated in the furnace. As these substances continue to volatilize, the carbon gradually changes to a graphite structure and further generates coal coke. In this process, the gasifying agent (oxygen, water vapor) diffuses into the coal powder particles, a gasification reaction occurs and synthetic coal gas is generated. When the coal coke particles reach a critical fragmentation state, if the reaction continues, the coal coke particles will gradually crack, and after a variety of homogeneous and heterogeneous reactions, the mineral components therein will be transformed into molten slag-like substances. A part of the molten slag flows along the furnace wall to the furnace bottom in a molten state on the gasifier wall, and solidifies after condensation to form coarse slag particles. Because of its large particle size, it is called coal gasification coarse slag (CGCS); the other part diffuses out of the gasifier through the airflow and enters the subsequent purification process with the synthetic gas to form fine slag with smaller particle size. This gasification slag is called coal gasification fine slag (CGFS). Usually, depending on the process and equipment, coarse slag usually accounts for 60% to 80% and fine slag accounts for 20% to 40%.

[0003] At present, in the prior art, the disposal method of coal gasification slag is similar to that of other solid wastes. After being discharged from the coal chemical plant, it is uniformly transported to a landfill for landfill or dumping. This type of disposal method leads to a large waste of land resources, pollution of the ecological environment, threats to human health, and increased burdens on corporate governance. According to statistics, every one million tons of coal gasification slag piled up will lead to the occupation of 500 acres of land resources. Secondly, the particles of coal gasification slag are small, and the fine coal gasification slag is in the form of fly ash with a smaller particle size. Therefore, the storage of coal gasification slag is very likely to cause dust pollution. As the stacking time increases, the scope of influence will gradually expand, resulting in an increase in the regional PM10 value, which will then affect the respiratory tract and lungs of the human body and endanger human health. Therefore, the prior art lacks a treatment method that can reduce the harmfulness of coal gasification slag. Summary of the invention

[0004] The main purpose of the present invention is to provide a modified coal gasification slag and a preparation method and application thereof, so as to solve the problem in the prior art that coal gasification slag is difficult to post-process as solid waste.

[0005] In order to achieve the above-mentioned object, according to a first aspect of the present invention, a method for preparing modified coal gasification slag is provided, the preparation method comprising: S1) mixing straw and coal gasification slag, and performing steam explosion treatment to obtain first coal gasification slag; S2) mixing the first coal gasification slag with an acid solution and performing a first grinding to obtain a first acidified coal gasification slag; S3) mixing the first acidified coal gasification slag with a chelating agent and performing a second grinding to obtain a second coal gasification slag; S4) mixing the second coal gasification slag with a binder to obtain modified coal gasification slag.

[0006] Further, in S1), the coal gasification slag is coarse coal gasification slag; the particle size of the coarse coal gasification slag is 1-9 mm; preferably, the mass ratio of straw to coal gasification slag is 1:5-30; preferably, the pressure of the steam explosion treatment is 0.2-1.5 MPa; preferably, the temperature of the steam explosion treatment is 140-200°C; preferably, the time of the steam explosion treatment is 20-60 min; preferably, the length of the straw is 1-5 cm.

[0007] Further, in S2), the acid solution is an inorganic acid solution; preferably, the acid solution includes a phosphoric acid solution and / or a nitric acid solution; preferably, the concentration of hydrogen ions in the acid solution is 0.5-1 mol / L.

[0008] Further, in S3), the chelating agent includes a solution of one or more of the following compounds: ethylenediaminetetraacetic acid, aminotriacetic acid, diethylenetriaminepentaacetic acid or hydroxyethyldiaminetriacetic acid; preferably, the chelating agent is a solution of ethylenediaminetetraacetic acid, and preferably, the concentration of the solute in the solution of ethylenediaminetetraacetic acid is 1-2 mol / L.

[0009] Furthermore, the mass ratio of the first coal gasification slag to the acid solution is 1:0.01-0.03; preferably, the mass ratio of the first acidified coal gasification slag to the chelating agent is 1:0.05-0.1; preferably, the power of the first grinding is 400-600w; preferably, the power of the second grinding is 700-1000w; preferably, the time of the first grinding is 20-30min; preferably, the time of the second grinding is 5-10min.

[0010] Further, in S4), the binder includes fly ash; preferably, the mass ratio of fly ash to the second coal gasification slag is 1:0.2-0.3.

[0011] Furthermore, the specific surface area of ​​the modified coal gasification slag is 420-450m 2 / g; preferably, the pore volume of the modified coal gasification slag is 0.35-0.46cm 3 / g; preferably, the average pore size of the modified coal gasification slag is 2.0-2.55nm.

[0012] In order to achieve the above object, according to a second aspect of the present invention, there is provided a modified coal gasification slag, wherein the modified coal gasification slag is prepared by the above-mentioned method for preparing the modified coal gasification slag.

[0013] Furthermore, the specific surface area of ​​the modified coal gasification slag is 420-450m 2 / g; preferably, the pore volume of the modified coal gasification slag is 0.35-0.46cm 3 / g; preferably, the average pore size of the modified coal gasification slag is 2.0-2.55nm.

[0014] In order to achieve the above objectives, according to the third aspect of the present invention, there is provided a modified coal gasification slag prepared by the above-mentioned method for preparing modified coal gasification slag, or the use of the above-mentioned modified coal gasification slag in soil remediation.

[0015] By applying the technical solution of the present invention, straw and coal gasification slag are mixed and then subjected to steam explosion treatment, first ground using an inorganic acid solution (acid solution), then second ground using a chelating agent, and finally mixed with a binder to obtain modified coal gasification slag with improved performance. The coal gasification slag, which is solid waste in the prior art, is recycled, thereby reducing the harmfulness of the coal gasification slag. DETAILED DESCRIPTION

[0016] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below in conjunction with the embodiments.

[0017] As mentioned in the background technology, the method for treating harmful coal gasification slag in the prior art is landfill or dumping, which not only endangers environmental safety and human health, but also wastes a lot of land resources. Therefore, in the present application, the inventor attempts to develop a method for modifying coal gasification slag, that is, a method for preparing modified coal gasification slag, using straw and coal gasification crude slag for steam explosion treatment, and mixing with an acid solution to modify the discarded coal gasification slag, which not only improves the harmfulness of the coal gasification slag itself, but also avoids the harm caused by the method of treating the coal gasification slag in the prior art, and can also obtain a modified coal gasification slag with increased specific surface area, pore volume and moderate average pore size, which can be used in soil remediation and reconstruction. Based on this, a series of protection schemes of the present application are proposed.

[0018] In a first typical embodiment of the present application, a method for preparing modified coal gasification slag is provided, characterized in that the preparation method comprises: S1) mixing straw and coal gasification slag, and performing steam explosion treatment to obtain first coal gasification slag; S2) mixing the first coal gasification slag with an acid solution, and performing a first grinding to obtain a first acidified coal gasification slag; S3) mixing the first acidified coal gasification slag with a chelating agent, and performing a second grinding to obtain a second coal gasification slag; S4) mixing the second coal gasification slag with a binder to obtain modified coal gasification slag.

[0019] The solid waste gasification slag produced during the industrial coal gasification reaction is generally treated by uniformly transporting it to a landfill for landfill or dumping. This type of treatment will lead to a large waste of land resources, pollute the ecological environment, and threaten human health and increase the burden of corporate governance. This application uses the discarded gasification slag and straw as raw materials, and can prepare a modified gasification slag through the above-mentioned preparation method, which can avoid the harm caused by landfilling and dumping of a large amount of gasification slag, and can also be used for soil repair. In this application, the straw and the gasification slag are first mixed evenly and then steam-exploded. The active sites on the surface of the first gasification slag are increased, which is conducive to the subsequent mixing reaction with the acid solution and the chelating agent. Compared with steam-exploding the straw and the gasification slag and then mixing them, the prepared modified gasification coarse slag has a larger specific surface area.

[0020] At the same time, in the process of steam explosion treatment of straw and coal gasification slag, the straw fragments after explosion enter the coal gasification slag, which is beneficial to expand the pore volume of coal gasification slag to a certain extent. Steam explosion treatment breaks the dense crystalline structure of lignocellulose in straw, destroys the cell wall structure network of the material, and tears the tissue into bundles of cellulose, realizing the separation of cellulose, hemicellulose and lignin. Cellulose, hemicellulose and lignin are all organic matter, which can provide rich nutrition for soil, and cellulose, hemicellulose and lignin also have certain water retention capacity and active sites. Therefore, the modified coal gasification slag prepared by the present application has a stronger water retention capacity and can be applied to soil improvement.

[0021] The present application treats the first coal gasification slag obtained after steam explosion with acid, first uses an acid solution to make initial pores, and removes metal impurities in the coal gasification slag; then uses a chelating agent to chelate and remove the remaining metal impurities, further improving the effect of pore making; it can not only remove metal impurities in the coal gasification slag, but also improve the effect of pore making, and expand the pore volume range of the final modified coal gasification slag. Moreover, the P and N elements in the above acid solution are also beneficial to enrich the nutrients of the soil, which can make the ion types of the modified coal gasification slag richer, and is beneficial to adjust the anion and cation exchange capacity of the soil to be improved.

[0022] Through the preparation method of the present application, the raw material straw is first mixed with the coal gasification slag that is harmful to the environment and human body, and then subjected to blasting treatment and two-step acid treatment, a modified coal gasification slag with improved specific surface area, pore volume, and pore size can be obtained, which eliminates the harmfulness of the coal gasification slag and avoids the environmental damage and waste of land resources caused by landfill or dumping. The modified coal gasification slag prepared by the present application has a strong water retention capacity, can keep the soil moisture from being lost, and effectively improve the soil water retention performance and nutrient fertility. Compared with the soil remediation materials in the prior art, the present application effectively utilizes the waste resource coal gasification slag as raw material, the raw material cost is lower, it conforms to the green production concept, and the preparation method is simpler, which is conducive to industrialized scale-up production.

[0023] In a preferred embodiment, in S1), the particle size of the gasification coarse slag is 1-9 mm; preferably, the mass ratio of straw to gasification slag is 1:5-30, including but not limited to 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, 1:20, 1:25 or 1:300, more preferably 1:10-20; preferably, the steam for steam explosion treatment is saturated steam or supersaturated steam; preferably, the pressure of steam explosion treatment is 0.2-1.5 MPa, including but not limited to 0.2, 0.3, 0.4, 0.5, 0.6, 0.65, 0.7, 0.75, 0.8, 0.9, 1, 1.3 or 1.5 MPa, more preferably 0.5-0.8 MPa; preferably, the temperature of steam explosion treatment is 140- 200°C, including but not limited to 165°C, 166°C, 167°C, 168°C, 169°C, 170°C, 171°C, 172°C, 173°C, 174°C, 175°C, 176°C, 177°C, 178°C, 179°C or 180°C, more preferably 165-180°C; preferably, the steam explosion treatment time is 20-60min, including but not limited to 21, 22, 23 , 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 50 or 60 min; preferably, the length of the straw is 1-5 cm, including but not limited to 1, 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3, 4 or 5 cm, more preferably 1-3 cm. The steam explosion device used in this application includes but is not limited to WUPC-XT, and those skilled in the art can flexibly select and replace it according to actual conditions.

[0024] In a preferred embodiment, in S2), the acid solution is an inorganic acid solution; preferably, the acid solution includes a phosphoric acid solution and / or a nitric acid solution; preferably, the concentration of hydrogen ions in the acid solution is 0.5-1 mol / L, including but not limited to 0.5, 0.6, 0.7, 0.8, 0.9 or 1 mol / L.

[0025] In a preferred embodiment, in S3), the chelating agent comprises a solution of one or more of the following compounds: ethylenediaminetetraacetic acid, aminotriacetic acid, diethylenetriaminepentaacetic acid, hydroxyethyldiaminetriacetic acid; preferably, the chelating agent is a solution of ethylenediaminetetraacetic acid, and preferably, the concentration of the solute in the solution of ethylenediaminetetraacetic acid is 1-2 mol / L, including but not limited to 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9 or 2 mol / L.

[0026] In a preferred embodiment, the mass ratio of the first coal gasification slag to the acid solution is 1:0.01-0.03, including but not limited to 1:0.01, 1:0.015, 1:0.02, 1:0.025 or 1:0.03; preferably, the mass ratio of the first grinding mixture to the chelating agent is 1:0.05-0.1, including but not limited to 1:0.05, 1:0.06, 1:0.07, 1:0.08, 1:0.09 or 1:0.1; preferably, the first grinding is performed by a swing mill; preferably, the power of the first grinding is 400-600w, including but not limited to Not limited to 400, 450, 500, 550 or 600w; preferably, the second grinding is performed using a swing mill; preferably, the power of the second grinding is 700-1000w, including but not limited to 700, 750, 800, 850, 900, 950 or 1000w; preferably, the time of the first grinding is 20-30min, including but not limited to 20, 21, 22, 23, 24, 25, 26, 27, 28 or 29min; preferably, the time of the second grinding is 5-10min, including but not limited to 5, 6, 7, 8, 9 or 10min. The grinding device used in this application includes but is not limited to the swing mill DFY-1000D, and those skilled in the art can flexibly select and replace it according to the range and actual production conditions.

[0027] In a preferred embodiment, in S4), the binder includes fly ash; preferably, the mass ratio of fly ash to acidified coal gasification slag is 1:0.2-0.3, including but not limited to 1:0.2, 1:0.24, 1:0.25, 1:0.28 or 1:0.3.

[0028] The fly ash is used as a binder and mixed with the second coal gasification slag for bonding. After crushing, the modified coal gasification slag of the present application can be obtained. The fly ash contains rich organic matter, which is beneficial for bonding the components in the second acidified coal gasification and can also increase the organic matter of the modified coal gasification slag finally prepared.

[0029] The modified coal gasification slag prepared in the present application has a rich porous structure, a large specific surface area, and rich organic matter derived from straw and fly ash. Compared with the unmodified coal gasification slag, the modified coal gasification slag in the present application has improved adsorption sites, the number of loaded ions, etc. When used in soil remediation, it can help to prevent soil moisture from being lost and improve soil water retention and nutrient fertility.

[0030] In a preferred embodiment, the specific surface area of ​​the modified coal gasification slag is 420-450m 2 / g; preferably, the pore volume of the modified coal gasification slag is 0.35-0.46cm 3 / g; preferably, the average pore size of the modified coal gasification slag is 2.0-2.55nm.

[0031] In a second typical embodiment of the present application, a modified coal gasification slag is provided. The modified coal gasification slag is prepared by any of the above-mentioned methods for preparing modified coal gasification slag.

[0032] In a preferred embodiment, the specific surface area of ​​the modified coal gasification slag is 420-450m 2 / g; preferably, the pore volume of the modified coal gasification slag is 0.35-0.46cm 3 / g; preferably, the average pore size of the modified coal gasification slag is 2.0-2.55nm.

[0033] In a third typical embodiment of the present application, there is provided a modified coal gasification slag prepared by any of the above-mentioned methods for preparing the modified coal gasification slag, or an application of any of the above-mentioned modified coal gasification slag in soil improvement.

[0034] The beneficial effects of the present application will be further explained in detail below in conjunction with specific embodiments.

[0035] Example 1

[0036] Sources of raw materials for the examples of this application:

[0037] The coal gasification slag is taken from Shenhua Xinjiang Chemical Industry Co., Ltd. The coal gasification slag is the water-containing slag discharged from the slag lock bucket at the bottom of the gasifier after the slurry coal particles are melted, quenched and condensed under the high temperature and high pressure conditions of the gasifier.

[0038] The leaching experiment was carried out on the coal gasification slag according to the "Identification of Hazardous Waste Identification Standard Leaching Toxicity Identification" (GB 5085.3-2007), and the ecological disposal risk assessment was carried out on it. The results showed that the pollutants in the coal gasification slag used in the examples of the present application did not exceed the standard and could be used for soil improvement.

[0039] Fly ash was obtained from Huaxin Power Plant.

[0040] The preparation of modified coal gasification slag comprises the following steps:

[0041] (1) After the straw and coal gasification slag are evenly mixed, steam explosion treatment is performed;

[0042] The straw is 2-3 cm in length; the straw is wheat straw, and the coal gasification slag is coarse coal gasification slag;

[0043] The mass ratio of straw to coal gasification slag is 1:10; saturated steam treatment is used during steam explosion treatment;

[0044] The pressure of the steam explosion treatment is 0.8 MPa; the temperature of the steam explosion treatment is 170° C.; the time of the steam explosion treatment is 25 min, and the first coal gasification slag is obtained.

[0045] (2) The first coal gasification slag is subjected to a first grinding with a phosphoric acid solution having a concentration of 0.6 mol / L to obtain a first acidified coal gasification slag; the mass ratio of the first coal gasification slag to the phosphoric acid solution is 1:0.02; the power of the first grinding is 400 W, and the time is 30 min.

[0046] The first acidified coal gasification slag was mixed with a 1.5 mol / L ethylenediaminetetraacetic acid solution for second grinding to obtain a second coal gasification slag, the ratio of the second coal gasification slag to the ethylenediaminetetraacetic acid solution was 1:0.05; the power was 1000w. The second grinding time was 5min. The equipment for the first grinding and the second grinding was a 1000g swing high-speed mill (DFY-1000D).

[0047] (3) The second coal gasification slag is mixed with fly ash and crushed (crushed into small particles of 1-2 cm) to obtain modified coal gasification slag, and the mass ratio of the second coal gasification slag to the fly ash is 1:0.2.

[0048] Example 2

[0049] The preparation of modified coal gasification slag comprises the following steps:

[0050] (1) After the straw and coal gasification slag are evenly mixed, steam explosion treatment is performed;

[0051] The straw is 2-3 cm in length; the straw is wheat straw, and the coal gasification slag is coarse coal gasification slag;

[0052] The mass ratio of straw to coal gasification slag is 1:20; saturation is used during steam explosion treatment; the pressure of steam explosion treatment is 0.6 MPa; the temperature of steam explosion treatment is 180°C; the time of steam explosion treatment is 30 minutes, and the first coal gasification slag is obtained.

[0053] (2) The first coal gasification slag is subjected to a first grinding with a phosphoric acid solution having a concentration of 1 mol / L to obtain a first acidified coal gasification slag; the mass ratio of the first coal gasification slag to the phosphoric acid solution is 1:0.01; the power of the first grinding is 600 W, and the time is 25 min.

[0054] The first acidified coal gasification slag is mixed with an ethylenediaminetetraacetic acid solution with a concentration of 1.2 mol / L for a second grinding to obtain a second coal gasification slag; the mass ratio of the first acidified coal gasification slag to the ethylenediaminetetraacetic acid solution is 1:0.08; the power of the second grinding is 700 W and the time is 9 min.

[0055] (3) The second coal gasification slag is mixed with fly ash and crushed (crushed into small particles of 1-2 cm) to obtain modified coal gasification slag, and the mass ratio of the second coal gasification slag to the fly ash is 1:0.2.

[0056] Example 3

[0057] The preparation of modified coal gasification slag comprises the following steps:

[0058] (1) After the straw and coal gasification slag are evenly mixed, steam explosion treatment is performed;

[0059] The straw is 2-3 cm in length; the straw is wheat straw, and the coal gasification slag is coarse coal gasification slag;

[0060] The mass ratio of straw to coal gasification slag is 1:15; saturation is used during steam explosion treatment; the pressure of steam explosion treatment is 0.7 MPa; the temperature of steam explosion treatment is 175°C; the time of steam explosion treatment is 30 minutes, and the first coal gasification slag is obtained.

[0061] (2) The first coal gasification slag is subjected to a first grinding with a phosphoric acid solution having a concentration of 0.7 mol / L to obtain a first acidified coal gasification slag; the mass ratio of the first coal gasification slag to the phosphoric acid solution is 1:0.03; the power of the first grinding is 500 W, and the time is 25 min.

[0062] The first acidified coal gasification slag is mixed with an ethylenediaminetetraacetic acid solution with a concentration of 2 mol / L for a second grinding to obtain a second coal gasification slag; the mass ratio of the first acidified coal gasification slag to the ethylenediaminetetraacetic acid solution is 1:0.08; the power of the second grinding is 800 W and the time is 7 min.

[0063] (3) The second coal gasification slag is mixed with fly ash and crushed (crushed into small particles of 1-2 cm) to obtain modified coal gasification slag, and the mass ratio of the second coal gasification slag to the fly ash is 1:0.28.

[0064] Example 4

[0065] The preparation of modified coal gasification slag comprises the following steps:

[0066] (1) After the straw and coal gasification slag are evenly mixed, steam explosion treatment is performed;

[0067] The straw is 2-3 cm in length; the straw is wheat straw, and the coal gasification slag is coarse coal gasification slag;

[0068] The mass ratio of straw to coal gasification slag is 1:13; saturation is used during steam explosion treatment; the pressure of steam explosion treatment is 0.65 MPa; the temperature of steam explosion treatment is 168°C; the time of steam explosion treatment is 33 minutes, and the first coal gasification slag is obtained.

[0069] (2) The first coal gasification slag is subjected to a first grinding with a nitric acid solution having a concentration of 0.9 mol / L to obtain a first acidified coal gasification slag; the mass ratio of the first coal gasification slag to the phosphoric acid solution is 1:0.02; the power of the first grinding is 500 W, and the time is 26 min.

[0070] The first acidified coal gasification slag is mixed with an ethylenediaminetetraacetic acid solution with a concentration of 1.6 mol / L for a second grinding to obtain a second coal gasification slag; the mass ratio of the first grinding mixture to the ethylenediaminetetraacetic acid solution is 1:0.05; the power of the second grinding is 900 W and the time is 8 min.

[0071] (3) The second coal gasification slag is mixed with fly ash and crushed (crushed into small particles of 1-2 cm) to obtain modified coal gasification slag, and the mass ratio of the second coal gasification slag to the fly ash is 1:0.24.

[0072] Example 5

[0073] The difference between this embodiment and embodiment 1 is that the pressure of the steam explosion treatment is 0.4 MPa and the time is 45 min. The remaining steps are the same as those of embodiment 1.

[0074] Example 6

[0075] The difference between this embodiment and embodiment 1 is that the pressure of the steam explosion treatment is 0.9 MPa and the time is 20 min. The remaining steps are the same as those of embodiment 1.

[0076] Example 7

[0077] The difference between this embodiment and embodiment 1 is that the temperature of the steam explosion treatment is 160° C. The remaining steps are the same as those of embodiment 1.

[0078] Example 8

[0079] The difference between this embodiment and embodiment 1 is that the temperature of the steam explosion treatment is 200° C. The remaining steps are the same as those of embodiment 1.

[0080] Example 9

[0081] The difference between this embodiment and embodiment 1 is that the concentration of the acid solution is 0.4 mol / L and the concentration of the chelating agent is 2.5 mol / L.

[0082] Example 10

[0083] The difference between this embodiment and embodiment 1 is that the concentration of the acid solution is 1.5 mol / L and the concentration of the chelating agent is 0.5 mol / L.

[0084] Comparative Example 1

[0085] The only difference from Example 1 is that the wheat straw and the coal gasification slag are steam exploded separately, and then the steam explosion products are mixed and subsequently mixed with an acid solution, first ground, etc. (the subsequent treatment is the same as in Example 1).

[0086] Comparative Example 2

[0087] The only difference from Example 1 is that the first grinding is performed after mixing with the acid solution, the second grinding is performed without mixing with the chelating agent, and the product prepared by the first grinding is directly mixed with the binder (subsequent treatment is the same as in Example 1).

[0088] Comparative Example 3

[0089] The only difference from Example 1 is that the product is not mixed with the acid solution and the first grinding is not performed, but is directly mixed with the chelating agent for the second grinding, and the product prepared by the second grinding is directly mixed with the binder (subsequent treatment is the same as in Example 1).

[0090] Test Example 1

[0091] The specific surface area, pore volume and average pore diameter of the unmodified crude coal gasification slag, and the modified coal gasification slag prepared in Examples 1 to 10 and Comparative Examples 1 to 3 were tested.

[0092] Detection method:

[0093] Detection method of specific surface area and pore volume: The pore volume and surface area are calculated by measuring the amount of gas adsorbed on the sample surface using the BET (Brunauer-Emmett-Teller) method.

[0094] Method for calculating the average pore size: Based on the adsorption isotherm obtained by the BET method, the pore size distribution and the average pore size are calculated using the BJH (Barrett-Joyner-Halenda) method. Micropores are pores with a diameter less than 2 nm, mesopores are pores with a diameter ranging from 2 to 50 nm, and macropores are pores with a diameter greater than 50 nm. The pore size distribution of the sample is calculated using the DFT model.

[0095] The test results are shown in Table 1.

[0096] Table 1

[0097] Group <![CDATA[Specific surface area (m 2 / g)]]> <![CDATA[Pore volume (cm 3 / g)]]> Average pore size (nm) Coal gasification slag 107.9 0.143 3.87 Example 1 426.4 0.367 2.54 Example 2 435.8 0.385 2.33 Example 3 442.1 0.401 2.26 Example 4 431.7 0.379 2.47 Example 5 422.8 0.360 2.50 Example 6 423.2 0.348 2.55 Example 7 420.2 0.342 2.51 Example 8 421.5 0.359 2.52 Example 9 416.9 0.357 2.44 Example 10 418.3 0.371 2.71 Comparative Example 1 413.2 0.339 2.62 Comparative Example 2 406.6 0.331 2.59 Comparative Example 3 401.9 0.296 2.57

[0098] It can be seen from the results in Table 1 that the modified coal gasification slag prepared in the embodiment of the present application has large specific surface area and pore volume and moderate average pore size. When it is used as a soil conditioner, it is beneficial to improve the soil porosity, organic matter content, and increase the number of capillary pores. Increasing the capillary porosity is beneficial to improving the soil texture and improving the water retention capacity of the soil.

[0099] Embodiment 11

[0100] The modified coal gasification slag prepared in Example 1 was evenly mixed with the gray-brown desert soil taken out from the Hongshaquan No. 1 open-pit mine in a mass ratio of 10:100.

[0101] Comparative Example 4

[0102] The modified coal gasification slag prepared in Comparative Example 1 was evenly mixed with the gray-brown desert soil taken out from the Hongshaquan No. 1 open-pit mine in a mass ratio of 10:100.

[0103] Comparative Example 5

[0104] The modified coal gasification slag prepared in Comparative Example 2 was evenly mixed with the gray-brown desert soil taken out from the Hongshaquan No. 1 open-pit mine in a mass ratio of 10:100.

[0105] Comparative Example 6

[0106] The modified coal gasification slag prepared in Comparative Example 3 was evenly mixed with the gray-brown desert soil taken out from the Hongshaquan No. 1 open-pit mine in a mass ratio of 10:100.

[0107] Comparative Example 7

[0108] The unmodified crude coal gasification slag is evenly mixed with the gray-brown desert soil taken out from the Hongshaquan No. 1 open-pit mine in a mass ratio of 10:100.

[0109] Test Example 2

[0110] The water and fertilizer retention capacity of the modified soils in Example 11 and Comparative Examples 4 to 7 was evaluated. The results are shown in Table 2.

[0111] Test methods for evaluating water and fertilizer retention capacity:

[0112] The intermittent soil column leaching method was used to conduct penetration tests on different treatments of the improved materials, study the water and fertilizer retention mechanism of the improved materials, and comprehensively compare and analyze the water and fertilizer retention capacity of the modified coal gasification slag and pure soil, including the following steps:

[0113] (1) The soil was naturally air-dried, ground and passed through a 2mm sieve to remove plant and animal remains; prepare the soil to be tested. Select a plexiglass tube with a length of 40 cm and an inner diameter of 6 cm. The bottom of the glass column is connected to a liquid receiver, and a triangular bottle is placed under the receiver. The bottom of the glass column is a porous water-discharging glass plate, on which is a layer of filter screen with an aperture of 200 mesh, a layer of filter cloth is placed above the filter screen, and a 1cm thick quartz sand layer is placed above the filter cloth. The soil is filled into the soil column tube and compacted with a compactor to ensure that the soil is evenly distributed in the soil column. During this process, the bulk density of the soil column is the same as or close to the bulk density of natural soil. The compacted surface is roughened to ensure rough contact between the interfaces of each soil layer; a layer of quartz sand with a particle size of 40 mesh is laid on the surface soil (to prevent the soil layer from being disturbed when adding water), with a thickness of about 1 cm.

[0114] (2) Add 200 mL of distilled water in advance to make the soil moisture close to saturation, let it stand for 7 days, then add 200 mL of water to the leached soil column, water it once every 5 days, and water it 5 times in total; collect the leaching solution after leaching, take out the surface quartz sand after leaching, and measure the soil moisture content under different treatments. Take another soil sample for air drying. After the soil is air-dried, pass the soil sample through a 2 mm sieve and use it to measure the soil alkali-hydrolyzable nitrogen (AN) and available phosphorus (AP). The soil moisture content and nutrient indicators before and after leaching are used to comprehensively evaluate the soil water and fertilizer retention performance.

[0115] Among them, nutrient loss rate = (nutrient content before leaching - nutrient content after leaching) / nutrient content before leaching. The lower the nutrient loss rate, the better the nutrient retention effect.

[0116] Table 2

[0117] Group Soil moisture content (%) AP loss rate (%) AN loss rate (%) Pure gray brown desert soil 30.1 15.4 31.6 Embodiment 11 43.6 9.2 14.9 Comparative Example 4 42.8 10.3 16.2 Comparative Example 5 41.7 12.1 17.8 Comparative Example 6 42.3 11.6 16.9 Comparative Example 7 34.5 13.7 26.3

[0118] From the results in Table 2, it can be seen that the modified coal gasification slag prepared in the embodiment of the present application has a rich porous structure, a large specific surface area, and rich organic matter. In addition, the adsorption sites and the number of loaded ions of the treated coal gasification slag are changed. When the modified coal gasification slag prepared in the embodiment of the present application is applied to soil improvement, the soil moisture can be kept from being lost, and the soil water holding capacity and nutrient fertility can be effectively improved.

[0119] From the above description, it can be seen that the above-mentioned embodiments of the present invention achieve the following technical effects: by using the preparation method of the modified coal gasification slag of the present application, by mixing straw with the coal gasification crude slag, steam explosion treatment, two-step acidification treatment to form pores, and finally mixing with the binder fly ash, a modified coal gasification slag with increased specific surface area and pore volume and moderate pore size, containing organic matter of coal gasification crude slag, straw and fly ash, is prepared, and the coal gasification slag is modified by the preparation method of the present application, thereby avoiding the harm to the environment caused by the landfill or dumping of the coal gasification slag and the waste of land resources. And when the modified coal gasification slag prepared by the present application is used in soil remediation, it has good water and fertilizer retention capacity. Compared with the soil remediation materials in the prior art, the modified coal gasification slag in the present application can effectively utilize the discarded coal gasification crude slag, the raw material cost is low, and the preparation method is simple, which is conducive to industrialized scale-up production.

[0120] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing modified coal gasification slag, characterized in that: The preparation method comprises: S1) mixing the straw and the coal gasification slag and performing steam explosion treatment to obtain the first coal gasification slag; S2) mixing the first coal gasification slag with an acid solution and then performing a first grinding to obtain a first acidified coal gasification slag; S3) mixing the first acidified coal gasification slag with a chelating agent and then performing a second grinding to obtain a second coal gasification slag; S4) mixing the second coal gasification slag with a binder to obtain the modified coal gasification slag.

2. The preparation method according to claim 1, characterized in that: In said S1), said coal gasification slag is coal gasification coarse slag; The particle size of the coal gasification coarse slag is 1-9 mm; Preferably, the mass ratio of the straw to the coal gasification slag is 1:5-30; Preferably, the pressure of the steam explosion treatment is 0.2-1.5 MPa; Preferably, the temperature of the steam explosion treatment is 140-200°C; Preferably, the steam explosion treatment time is 20-60 min; Preferably, the length of the straw is 1-5 cm.

3. The preparation method according to claim 1, characterized in that: In the S2), the acid solution is an inorganic acid solution; Preferably, the acid solution comprises a phosphoric acid solution and / or a nitric acid solution; Preferably, the concentration of hydrogen ions in the acid solution is 0.5-1 mol / L.

4. The preparation method according to claim 1, characterized in that: In said S3), said chelating agent comprises a solution of one or more of the following compounds: ethylenediaminetetraacetic acid, aminotriacetic acid, diethylenetriaminepentaacetic acid or hydroxyethyldiaminetriacetic acid; Preferably, the chelating agent is a solution of ethylenediaminetetraacetic acid; Preferably, the concentration of the solute in the EDTA solution is 1-2 mol / L.

5. The preparation method according to claim 1, characterized in that: The mass ratio of the first coal gasification slag to the acid solution is 1:0.01-0.03; Preferably, the mass ratio of the first acidified coal gasification slag to the chelating agent is 1:0.05-0.1; Preferably, the first grinding is performed using an oscillating mill device; Preferably, the power of the first grinding is 400-600w; Preferably, the first grinding time is 20-30 min; Preferably, the second grinding is performed using an oscillating mill device; Preferably, the power of the second grinding is 700-1000w; Preferably, the second grinding time is 5-10 min.

6. The preparation method according to claim 1, characterized in that: In said S4), said binder comprises fly ash; Preferably, the mass ratio of the fly ash to the second coal gasification slag is 1:0.2-0.

3.

7. The preparation method according to claim 1, characterized in that: The specific surface area of ​​the modified coal gasification slag is 420-450m 2 / g; Preferably, the pore volume of the modified coal gasification slag is 0.35-0.46 cm 3 / g; Preferably, the average pore size of the modified coal gasification slag is 2.0-2.55 nm.

8. A modified coal gasification slag, characterized in that: The modified coal gasification slag is prepared by the method for preparing modified coal gasification slag according to any one of claims 1 to 7.

9. The modified coal gasification slag according to claim 8, characterized in that: The specific surface area of ​​the modified coal gasification slag is 420-450m 2 / g; Preferably, the pore volume of the modified coal gasification slag is 0.35-0.46 cm 3 / g; Preferably, the average pore size of the modified coal gasification slag is 2.0-2.55 nm.

10. Use of the modified coal gasification slag prepared by the method for preparing modified coal gasification slag according to any one of claims 1 to 7, or the modified coal gasification slag according to any one of claims 8 or 9 in soil remediation.