Gasification slag sand and preparation method thereof

Abstract

The invention provides gasified slag sand and a preparation method thereof, and solves the problem that the existing gasified slag cannot be directly applied to civil engineering due to overlarge crushing index, low density and overlarge alkali-silicon reaction expansion rate of the original slag. According to the technical key points, physical separation and mechanical grinding are adopted, so that the apparent density of the gasified slag is integrally improved, and the crushing value of the gasified slag is reduced; the carbide slag powder, the sodium hydroxide and the carbon dioxide are used for carrying out chemical modification treatment on the gasified slag, the alkali activity and the water absorption rate of the gasified slag are reduced through the treatment, and a certain carbon sequestration effect is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of civil engineering materials, and particularly relates to a gasification slag sand and a preparation method thereof. Background Art

[0002] Gasification slag is a solid residue discharged through the bottom slag discharge system after coal combustion in a gasification furnace during the coal gasification process in the coal chemical industry, also known as coal gasification slag or gasification coarse slag. Generally, about 20%-40% of gasification slag is discharged by using 1 ton of coal through the gasification process. As a coal clean utilization technology, the coal chemical industry has developed rapidly in China in recent years. The annual national discharge of gasification slag exceeds 50 million tons, and most of it is concentrated in large coal chemical industrial parks. Due to the relatively late start of the coal chemical industry, which has only developed rapidly in the past 10-20 years, the corresponding resource utilization ways of gasification slag are very scarce, and its comprehensive utilization rate is less than 30%. Most of them are treated by stacking in slag yards. The slag yard stacking not only occupies natural sites, but also generates corresponding stacking costs and ecological environment problems, which to a certain extent restricts the development and growth of the coal chemical industry. Actively developing bulk and resource utilization technologies for gasification slag is an important way to promote the healthy and sustainable development of the coal chemical industry and related industries, and has significant environmental protection significance.

[0003] The quantity of sand used in construction engineering is huge. Currently, a large amount of natural sand and manufactured sand in use both require the exploitation of natural resources and have a huge consumption, and the corresponding sand and stone quarrying has a significant impact on the environment. Gasification slag has good particle size distribution. Using gasification slag to replace natural sand or manufactured sand in civil engineering can largely consume gasification slag and reduce the consumption of natural resources such as natural sand. However, the indexes of as-received gasification slag in terms of crushing index, density, alkali-aggregate reaction, etc. are all lower than the current national standards, which severely restricts the practical engineering application of gasification slag sand.

[0004] In view of this, the present invention believes that it is necessary to develop a gasification slag sand that can be applied to civil engineering and a preparation method thereof. Summary of the Invention

[0005] The purpose of the present invention is to solve the problem that the original gasification slag has an excessive crushing index, low density, and excessive expansion rate of alkali-silica reaction, and thus cannot be directly applied to civil engineering, and to provide a gasification slag sand and a preparation method thereof. The gasification slag sand prepared by this method meets all the current national standards in terms of various performance indexes and is applicable to various civil engineering projects.

[0006] To achieve the above purpose, the specific technical solution provided by the present invention is as follows:

[0007] A preparation method of a gasification slag sand, which is characterized in that it includes the following steps:

[0008] S1. Dry the gasification slag (here referring to the original gasification slag) to a moisture content of less than 5% to ensure the operability of subsequent screening and grinding processes and improve the preparation efficiency of the target material.

[0009] S2. First, screen the gasification slag dried in S1 into three specifications according to particle size: ≥5 mm, less than 5 mm and greater than or equal to 1.18 mm, and <1.18 mm. Then remove the gasification slag particles of ≥5 mm, and store the gasification slag particles of less than 5 mm and greater than or equal to 1.18 mm and the gasification slag particles of <1.18 mm separately.

[0010] The purpose of removing the gasification slag particles of ≥5 mm in this application is to reduce the number of highly active particles in the gasification slag, reduce the difficulty of subsequent process disposal of the gasification slag, reduce the amount of modified materials added, and reduce the production cost of the gasification slag sand. Taking 1.18 mm as the screening limit is because the research team of this application found through the analysis of the gasification process of the gasifier and a large amount of experimental data that the porosity of the particles of 1.18 mm and above in the gasification slag is high, and a considerable part of them are vitreous bodies after water quenching, with certain alkali activity, which is the main reason for the excessive crushing index, low density and excessive alkali-silica reaction expansion rate of the gasification slag sand. Through screening, the gasification slag particles of less than 5 mm and greater than or equal to 1.18 mm are obtained, and subsequent modification treatment is carried out on the particles in this particle size range to eliminate defects.

[0011] S3. Grind the gasification slag particles of less than 5 mm and greater than or equal to 1.18 mm screened in S2, and the bulk density of the gasification slag particles after grinding ≥1420 kg / m 3 ; This operation aims to physically modify the porous particles in the gasification slag, reduce the crushing index of the gasification slag, and increase the density of the gasification slag; among them, the specific grinding means can be selected according to the situation. It can either use a vertical shaft impact crusher for 1 - 3 cycles or use a ball mill for grinding for 8 - 15 min, as long as the bulk density ≥1420 kg / m 3 can be achieved;

[0012] S4. Carry out modification treatment on the gasification slag obtained after grinding in S3. The specific modification operation is as follows:

[0013] S41. Mix the modification slurry into the gasification slag obtained in S3, stir evenly and then stand for 24 - 48 h;

[0014] Among them, the modification slurry is composed of carbide slag powder and water. If the alkali activity coefficient K of the gasification slag is greater than or equal to 0.42, sodium hydroxide needs to be mixed into the modification slurry and then added to the gasification slag for modification;

[0015] The alkali activity coefficient K of the gasification slag is calculated according to the following formula:

[0016]

[0017] In the formula, MgO, Na 2 O, SiO 2 、Al 2 O 3 are the mass percentages of magnesium oxide, sodium oxide, silicon dioxide, and aluminum oxide in the gasification slag, respectively;

[0018] The main mechanism of modification by the modified slurry includes the following two aspects:

[0019] ① Through the chemical reaction between the modified slurry and the gasification slag particles, the alkali activity of the gasification slag particles is reduced, and the gasification slag particles are passivated in terms of activity;

[0020] ② Through the wrapping effect of the modified slurry on the gasification slag particles, the pore characteristics of the gasification slag particles are further optimized, and the chemical reaction between the gasification slag particles and the environmental medium is slowed down.

[0021] The purpose of adding carbide slag powder to the above-mentioned modified slurry is to introduce calcium ions, adjust the calcium-silicon ratio of the gasification slag and the modified slurry system, and improve the stability of the chemical reaction products during the passivation process of the system. The purpose of adding sodium hydroxide to the modified slurry is to increase the alkalinity of the gasification slag-modified slurry system (in order to avoid introducing other ions and affecting the modification effect, sodium hydroxide is used here to increase the alkalinity), promote the degree and speed of the chemical reaction between the silicate and aluminate in the gasification slag and the carbide slag powder, and enhance the passivation modification effect of the gasification slag;

[0022] S42. Place the gasification slag after standing still in a sealed pressure environment (for example: use a sealed pressure mixer, the internal of which is a forced stirring mechanism, which can ensure that the maximum particle size of the subsequent gasification slag is less than 4.75 mm after continuous stirring for 5 - 10 min to meet the requirements of construction sand) and mechanically stir for 5 - 10 min, then introduce CO 2 gas and pressurize it to 0.6 - 1.2 Pa, and then continue to stir (the purpose of introducing CO 2 gas is to solve the problem of too high alkalinity after the modification of the gasification slag. At the same time, it can also achieve the technical effect of carbon fixation), and the stirring time is 30 - 120 min to ensure that the pH value of the gasification slag ≤ 7.5, improve the particle strength of the gasification slag, and fully disperse the agglomerated gasification slag.

[0023] S43. Dry the stirred gasification slag until the moisture content is lower than 5%;

[0024] S5. Mix the gasification slag modified in S4 evenly with the gasification slag particles smaller than 1.18 mm screened out in S2 to finally obtain gasification slag sand that meets the requirements of construction sand.

[0025] Furthermore, the dosages of the components in the modified slurry used in S41 are obtained through the following method:

[0026] Calcium carbide slag powder: w d = w g *(1 - α)β;

[0027] Among them, w d is the dosage of calcium carbide slag powder, in kg; w g is the mass of gasification slag to be modified, in kg; α is the water content of gasification slag, in %; β is the first proportionality coefficient, which is used to control the mass of calcium carbide slag powder in the modified slurry added according to different alkali activities of gasification slag. Its value is related to the alkali activity coefficient K of gasification slag. The specific value-taking method is as follows: when K ≥ 1, take 0.2; when 0.42 ≤ K < 1, take 0.12; when K < 0.42, take 0.02; the calculation method of the above calcium carbide slag powder dosage takes into account the net gasification slag content in the gasification slag excluding the water content.

[0028] Sodium hydroxide: w n = w d *γ;

[0029] Among them, w n is the dosage of sodium hydroxide, in kg; γ is the second proportionality coefficient, which is used to control the mass of sodium hydroxide in the modified slurry added according to different alkali activities of gasification slag. Its value is related to the alkali activity coefficient K of gasification slag. The specific value-taking method is as follows: when K ≥ 1, take 0.01; when 0.42 ≤ K < 1, take 0.04; when K < 0.42, take 0;

[0030] Water: w w = w d *δ + w g *(1 - α)*0.15;

[0031] Among them, w w is the dosage of water, in kg; δ is the third proportionality coefficient, which is used to control the consistency of the modified slurry. Its value is related to the specific surface area of calcium carbide slag powder. The specific value-taking method is as follows: when the specific surface area of calcium carbide slag powder is between 250 - 300 kg / m 3 take 0.45; when the specific surface area of calcium carbide slag powder is between 300 - 400 kg / m 3 take 0.5; when the specific surface area of calcium carbide slag powder is between 400 - 500 kg / m 3 take 0.6; the calculation method of the above water dosage takes into account the influence of calcium carbide slag powder with different fineness on the consistency of the modified slurry and the influence of the water content of gasification slag on the mixing uniformity of the modified material after adding the modified slurry to the gasification slag.

[0032] Further, the specific operation of S41 is as follows: First, put the gasification slag obtained in S3 into a blender. After turning on the blender, then put the modified slurry into the blender and continue to stir for 10 - 20 minutes to ensure uniform contact between the modified slurry and the gasification slag. After the stirring is completed, place the gasification slag in a material yard and let it stand for 24 - 48 hours to ensure that a chemical reaction occurs to a large extent between the modified slurry and the gasification slag;

[0033] Meanwhile, the present invention also provides the gasification slag sand obtained by the above - mentioned preparation method and its application as construction sand in civil engineering. The soundness mass loss rate of this gasification slag sand is ≤8%, the single - stage maximum crushing index is ≤30%, and the apparent density is ≥2500 kg / m 3 , and the expansion rate of the alkali - silica reaction in 14 days is less than 0.1%.

[0034] In addition, construction sand with the gasification slag sand obtained by the above - mentioned preparation method as the active ingredient is also provided.

[0035] A method for regulating the properties of raw gasification slag is characterized in that the raw gasification slag is treated by the same means as the above - mentioned preparation method.

[0036] Advantages of the present invention:

[0037] 1. Relying on the R & D experience and technical accumulation in the fields of civil engineering materials and resource utilization of industrial solid waste, starting from basic theoretical analysis and combining a large number of experimental studies, the present invention summarizes a series of research results, develops a kind of gasification slag sand and its preparation method. Using the preparation method of the present invention can improve the main technical indexes of gasification slag and prepare construction sand based on coal gasification slag with excellent technical indexes. The gasification slag sand prepared by the present invention is sufficient to replace the existing natural sand and machine - made sand, can largely consume industrial solid waste, reduce the consumption of natural sand and gravel, and utilize CO 2 industrial tail gas during the preparation process, having a certain carbon sequestration effect.

[0038] 2. The technical key points of the present invention include physical separation and mechanical grinding, which overall improve the apparent density of gasification slag and reduce the crushing value of gasification slag; chemical modification treatment of gasification slag with carbide slag powder, sodium hydroxide, and carbon dioxide reduces the alkali activity and water absorption rate of gasification slag and has a certain carbon sequestration effect. Combining the above - mentioned modification measures, the problems of insufficient performance of gasification slag as fine aggregate in terms of particle strength, density, water absorption rate, and alkali - aggregate reaction are solved. Specific embodiments

[0039] The following further describes the content of the present invention in detail with specific embodiments:

[0040] The present invention provides a modified gasification slag sand, and the preparation raw materials include gasification slag, carbide slag powder, sodium hydroxide and carbon dioxide; among them, the gasification slag is the main raw material, the carbide slag powder is the main modification material, and sodium hydroxide and carbon dioxide are auxiliary modification materials, and their main functions are to adjust the alkalinity and fix carbon to improve the modification effect.

[0041] The main purpose of the gasification slag sand preparation method proposed by the present invention is to improve the crushing index, density and alkali activity of the gasification slag, so that the prepared gasification slag sand meets the various technical indicators required for construction sand. The detailed descriptions of its specific implementation methods, characteristics and implementation effects are as described in the embodiments.

[0042] The sources of the series of raw materials used in the embodiments of the present invention include:

[0043] Gasification slag: sourced from the coal-to-liquid branch of the National Energy Group Ningxia Coal Industry Co., Ltd. To better reflect the applicability and effectiveness of the method described in the present invention, the physical and chemical performance indicators of the gasification slag raw materials specifically used in the embodiments are different. See each embodiment for details;

[0044] Carbide slag: sourced from Guodian Ningxia Yinglitingdong Coal-based Chemical Co., Ltd. To better reflect the applicability and effectiveness of the method described in the present invention, the physical and chemical performance indicators of the carbide slag raw materials specifically used in the specific embodiments are different. See each embodiment for details;

[0045] Sodium hydroxide: industrial pure sodium hydroxide flakes produced by Ningxia Sanhe Risheng Chemical Co., Ltd., with a purity ≥ 95%.

[0046] Carbon dioxide: sourced from the high-concentration carbon dioxide tail gas of the coal-to-liquid branch of the National Energy Group Ningxia Coal Industry Co., Ltd., with a concentration ≥ 90%.

[0047] Example 1: A gasification slag sand and its preparation method

[0048] The gasification slag raw material used in this example is numbered as gasification slag A, and its basic performance is shown in Table 1 and its chemical performance is shown in Table 2.

[0049] Table 1 Basic performance of the gasification slag raw material used in Example 1

[0050]

[0051] Table 2 Chemical composition (wt%) of the gasification slag raw material used in Example 1

[0052] <![CDATA[K 2 O]]> <![CDATA[Na 2 O]]> <![CDATA[SO 3 > <![CDATA[SiO 2 > <![CDATA[Fe 2 O 3 > <![CDATA[Al 2 O 3 > CaO MgO Loss Gasification slag A 1.64 1.12 0.68 38.16 4.23 16.99 8.75 1.23 3.67

[0053] Dry the gasification slag A, and the moisture content α of the dried gasification slag A is 4.8%.

[0054] The activity coefficient K of the gasification slag is calculated to be 1.23 according to Table 2 with reference to the following formula.

[0055]

[0056] Based on the K value calculated from the gasification slag selected in this case, the parameter β is selected as 0.2, and the parameter γ is selected as 0.01; according to the specific surface area of the carbide slag selected in this case, which is 260 kg / m 2 , the parameter δ is selected as 0.45.

[0057] Taking the amount of the original gasification slag to be modified as a reference, that is, assuming the amount of the original gasification slag is 1 kg of unit mass, the addition ratios of other raw materials are calculated.

[0058] The doping amount of the carbide slag powder is calculated to be 0.19 according to the following formula.

[0059] w d = w g *(1 - α)β

[0060] The doping amount of sodium hydroxide is calculated to be 0.002 according to the following formula.

[0061] w n = w d *γ;

[0062] The doping amount of water is calculated to be 0.23 according to the following formula.

[0063] w w = w d *δ + w g *(1 - α)*0.15;

[0064] Prepare the modified slurry according to the ratio of carbide slag powder : sodium hydroxide : water = 1 : 0.01 : 1.21;

[0065] Screen the dried gasification slag, first remove the particles of 5 mm and above, and then screen it into particles of 1.18 mm and above and particles of less than 1.18 mm. Put the particles of 1.18 mm and above into the grinder and grind for 15 min; put the ground gasification slag particles into the mixer, start the mixer and stir, and put the modified slurry into it according to the ratio of 1 : 0.42 and continue to stir for 10 min; after stirring, place the gasification slag in the material yard and let it stand for 24 h; after standing, put the gasification slag into the sealed pressure mixer, stir for 10 min, then introduce carbon dioxide gas and maintain the gas pressure at 0.6 Pa, continue to stir for 60 min, then unload and carry out drying treatment, and then mix it evenly with the particles of less than 1.18 mm, thus obtaining the gasification slag sand prepared by the present invention.

[0066] The basic properties of the gasification slag sand prepared in this example are shown in Table 3.

[0067] Table 3 Basic properties of the gasified slag sand after modification in Example 1

[0068]

[0069] *Quoted from the quality standard of Class I construction sand in the national standard GB / T 14684-2022 "Construction Sand".

[0070] Through this example, it can be seen that after the as-received gasified slag is processed by the preparation method provided by the present invention, the soundness, crushing index, density, void ratio and rapid alkali-silica reaction of the gasified slag have been significantly improved. Among them, the mass loss obtained from the soundness test of the gasified slag is reduced from 10.3% to 7%, meeting the quality standard of Class I sand; the single-stage maximum crushing index is reduced from 56% to 19%, with a decrease of 66%, meeting the quality standard of Class I sand; the apparent density and bulk density are increased from 2120 kg / m 3 and 1180 kg / m 3 to 2550 kg / m 3 and 1420 kg / m 3 respectively, and the void ratio is reduced from 56% to 40%, meeting the current quality standard of construction sand; the 14-day expansion rate obtained from the rapid alkali-silica reaction test is reduced from 0.16% to 0.09%, meeting the current quality standard of construction sand. The above results demonstrate the effectiveness of the present invention.

[0071] Example 2: Preparation of gasified slag sand from gasified slags with different physical and chemical properties and its preparation method

[0072] The gasified slag raw materials used in this example are numbered as gasified slag B, C, and D, and their basic properties are shown in Table 4 and chemical compositions are shown in Table 5.

[0073] Table 4 Basic properties of the gasified slag raw materials used in Example 1

[0074]

[0075] Table 5 Chemical compositions (wt%) of the gasified slag raw materials used in Example 1

[0076] <![CDATA[K 2 O]]> <![CDATA[Sodium 2 O]]> <![CDATA[SO 3 > <![CDATA[SiO 2 > <![CDATA[Fe 2 O 3 > <![CDATA[Al 2 O 3 > CaO MgO Loss Gasification slag B 0.44 0.05 0.28 47.78 2.93 13.63 16.15 2.57 4.73 Gasification slag C 1.03 0.58 0.1 51.53 7.49 25.05 10.35 2.51 0.71 Gasification slag D 0.75 0.79 0.98 56.66 6.18 7.36 15.08 0.74 3.36

[0077] Dry gasified slag B, gasified slag C, and gasified slag D. The moisture content α of the dried gasified slag is shown in Table 6.

[0078] According to Table 5, the activity coefficient K of the gasified slag is calculated by referring to the following formula and shown in Table 6.

[0079]

[0080] The values of parameter β and parameter γ selected according to the K value calculated from the gasification slag selected in this case are shown in Table 6;

[0081] The specific surface area of the carbide slag selected according to this case is 260 kg / m 2 , and the value of parameter δ selected is shown in Table 6.

[0082] Taking the amount of as-received gasification slag to be modified as a reference, that is, setting the amount of as-received gasification slag as 1 kg of unit mass, calculate the addition ratios of other raw materials.

[0083] The dosage of carbide slag powder is calculated according to the following formula, and the results are shown in Table 6.

[0084] w d = w g *(1 - α)β

[0085] The dosage of sodium hydroxide is calculated according to the following formula, and the results are shown in Table 6.

[0086] w n = w d *γ;

[0087] The dosage of water is calculated according to the following formula, and the results are shown in Table 6.

[0088] w w = w d *δ + w g *(1 - α)*0.15;

[0089] Table 6 Values of gasification slag modification parameters

[0090]

[0091] Prepare the modified slurry B in a mass ratio of carbide slag powder:sodium hydroxide:water of 1:0.038:1.66 for modifying the gasification slag B, and the ratio of gasification slag B to the modified slurry B is 1:0.32;

[0092] Prepare the modified slurry C in a mass ratio of carbide slag powder:sodium hydroxide:water of 1:0.01:1.26 for modifying the gasification slag C, and the ratio of gasification slag C to the modified slurry C is 1:0.43;

[0093] Prepare the modified slurry D in a mass ratio of carbide slag powder:sodium hydroxide:water of 1:0:8 for modifying the gasification slag D, and the ratio of gasification slag D to the modified slurry D is 1:0.18;

[0094] The dried gasification slag is screened. First, particles of 5 mm or more are removed, and then it is screened into particles of 1.18 mm or more and particles of less than 1.18 mm. The particles of 1.18 mm or more are put into a grinder and ground for 15 minutes; the ground gasification slag particles are put into a mixer, the mixer is started for stirring, and the modified slurry is added in the aforementioned proportion and stirring is continued for 10 minutes; after the stirring is completed, the gasification slag is placed in a material yard and left to stand for 24 hours; after standing, the gasification slag is put into a sealed pressure mixer, stirred for 10 minutes, then carbon dioxide gas is introduced and the gas pressure is maintained at 0.6 Pa, continuous stirring is carried out for 60 minutes, then discharged and dried, and then mixed evenly with the particles of less than 1.18 mm, thus obtaining the gasification slag sand prepared by the present invention.

[0095] The basic properties of the gasification slag sand prepared in this example are shown in Table 7.

[0096] Table 7 Basic properties of the gasification slag sand after modification and processing in Example 2

[0097]

[0098] Through this example, it can be seen that for the original gasification slag of different batches, after being processed by the preparation method provided by the present invention, the soundness, crushing index, density, void ratio and rapid alkali-silica reaction of the obtained gasification slag sand have been significantly improved, and all can meet the current quality standards for construction sand. It shows the effectiveness and universality of the present invention in improving the properties of gasification slag with different properties.

[0099] Example 3: Effective contribution of step S2 to the invention content

[0100] The gasification slag raw material used in this example is numbered as gasification slag A, and the basic properties and chemical properties are shown in Table 1 and Table 2 of Example 1.

[0101] The gasification slag A is dried, and the moisture content α of the dried gasification slag A is 4.8%.

[0102] According to Table 2 and referring to the following formula, the activity coefficient K of the gasification slag is calculated to be 1.23.

[0103]

[0104] Based on the K value calculated for the gasification slag selected in this example, the parameter β is selected as 0.2, and the parameter γ is selected as 0.01; based on the specific surface area of the carbide slag selected in this example being 260 kg / m 2 , the parameter δ is selected as 0.45.

[0105] Taking the amount of the original gasification slag to be modified as a reference, that is, assuming the amount of the original gasification slag is 1 kg of unit mass, the addition ratios of other raw materials are calculated.

[0106] The dosage of carbide slag powder is calculated according to the following formula as 0.19.

[0107] w d = w g *(1 - α)β

[0108] The dosage of sodium hydroxide is calculated according to the following formula as 0.002.

[0109] w n = w d *γ;

[0110] The dosage of water is calculated according to the following formula as 0.23.

[0111] w w = w d *δ + w g *(1 - α)*0.15;

[0112] Prepare the modified slurry according to the ratio of carbide slag powder∶sodium hydroxide∶water of 1∶0.01∶1.21;

[0113] Screen the dried gasification slag, first remove particles of 5 mm and above, and then put it into a grinding machine for grinding for 15 minutes; put the ground gasification slag particles into a mixer and start the mixer for stirring, and put the modified slurry according to the ratio of 1∶0.42 and continue stirring for 10 minutes; after stirring is completed, place the gasification slag in a material yard and let it stand for 24 hours; after standing is completed, put the gasification slag into a sealed pressure mixer, stir for 10 minutes, then introduce carbon dioxide gas and maintain the gas pressure at 0.6 Pa, continue stirring for 60 minutes, then unload and conduct drying treatment, thus obtaining the gasification slag sand prepared by the present invention.

[0114] The basic properties of the gasification slag sand prepared in this example are shown in Table 8.

[0115] Table 8 Basic properties of the gasification slag sand after modification in Example 3

[0116]

[0117] Through this example, the role played by steps S2 - S3 in the present invention can be seen. Compared with Example 1, without going through step S2, that is, after drying, the gasification slag only removes particles of 5 mm and above and is not further screened into particles of 1.18 mm and above and particles of less than 1.18 mm; the grinding efficiency and grinding effect of the gasification slag are both reduced, resulting in the crushing index of the prepared gasification slag sand being higher than the standard of Class I sand, and the apparent density, loose bulk density and void ratio do not meet the national standards for construction sand. At the same time, due to the lack of screening treatment, the quantity of gasification slag that needs to be modified and secondarily dried increases significantly, increasing the preparation cost of the gasification slag sand.

[0118] Example 4: Effective Contribution of Step S3 to the Invention Content

[0119] The gasification slag raw material used in this example is numbered as gasification slag A, and its basic properties and chemical properties are shown in Tables 1 and 2 of Example 1.

[0120] The gasification slag A is dried, and the moisture content α of the dried gasification slag A is 4.8%.

[0121] According to Table 2 and referring to the following formula, the activity coefficient K of the gasification slag is calculated to be 1.23.

[0122]

[0123] Based on the K value calculated from the gasification slag selected in this case, the parameter β is selected as 0.2, and the parameter γ is selected as 0.01; according to this case, the specific surface area of the carbide slag is 260 kg / m 2 , and the parameter δ is selected as 0.45.

[0124] Taking the amount of the original gasification slag to be modified as a reference, that is, assuming the amount of the original gasification slag is 1 kg of unit mass, the addition ratios of other raw materials are calculated.

[0125] The addition amount of the carbide slag powder is calculated to be 0.19 according to the following formula.

[0126] w d = w g *(1 - α)β

[0127] The addition amount of sodium hydroxide is calculated to be 0.002 according to the following formula.

[0128] w n = w d *γ;

[0129] The addition amount of water is calculated to be 0.23 according to the following formula.

[0130] w w = w d *δ + w g *(1 - α)*0.15;

[0131] The modified slurry is prepared in the ratio of carbide slag powder:sodium hydroxide:water = 1:0.01:1.21;

[0132] The dried gasification slag is screened. First, particles of 5 mm and above are removed, and then it is screened into particles of 1.18 mm and above and particles of less than 1.18 mm. The gasification slag particles of 1.18 mm and above are put into a grinder, and the grinding times are respectively selected as 5 min, 8 min, 10 min, 15 min, and 20 min; the ground gasification slag particles are put into a mixer and the mixer is started for stirring. The modified slurry is put in according to a ratio of 1∶0.42 and stirring continues for 10 min; after the stirring is completed, the gasification slag is placed in a material yard and left to stand for 24 h; after standing, the gasification slag is put into a sealed pressure mixer, stirred for 10 min, then carbon dioxide gas is introduced and the gas pressure is maintained at 0.6 Pa. After continuous stirring for 60 min, discharging is carried out and drying treatment is carried out, and then it is mixed evenly with particles of less than 1.18 mm, thus obtaining the gasification slag sand prepared by the present invention.

[0133] The basic properties of the gasification slag sand prepared in this example are shown in Table 9.

[0134] Table 9 Basic properties of the modified gasification slag sand in Example 4

[0135]

[0136] Through this example, it can be seen the role played by the grinding time of 8 - 15 min using a ball mill during grinding in step S3 in the present invention. The adjustment of the grinding time will cause a series of changes in the properties of the gasification slag. As the grinding time of the gasification slag is prolonged, the number of coarse particles decreases, and the fineness modulus, crushing index, and void ratio as a whole show a decreasing trend, while the apparent density and loose bulk density increase. Among them, when the grinding time is 5 min, due to the too short grinding time, the grinding effect of the particles is not good, and the crushing index, apparent density, loose bulk density, and void ratio do not reach the standard indexes of construction sand. At the same time, due to the too large coarse particles, the effect of the modification treatment in step S4 is not good, and the rapid alkali-aggregate reaction expansion rate of the gasification slag particles exceeds the standard limit value. When the grinding time is 8 min, the indexes of the gasification slag sand can meet the requirements of the construction sand standard, but the crushing index can only reach the standard of Class III construction sand. When the grinding time is 20 min, although the indexes of the gasification slag sand can meet the requirements of the construction sand standard, the too long grinding time results in the fineness modulus of the gasification slag sand being only 1.6, reaching the minimum fineness modulus of fine sand.

[0137] Example 5: Effective contribution of the modification treatment in step S4 to the invention content

[0138] The gasification slag raw material used in this example is numbered as gasification slag A, and the basic properties and chemical properties are shown in Tables 1 and 2 of Example 1. The values of steps S1 - S3 are the same as those in Example 1 and will not be elaborated here. The gasification slag obtained after grinding in step S3 is subjected to modification treatment.

[0139] Table 10 Parameter Values of Modified Gasification Slag

[0140] α(％) K β γ δ <![CDATA[w d > <![CDATA[w n > <![CDATA[w w > Modified gasification slag sand 1 4.8 1.23 0.2 0.01 0.45 0.19 0.002 0.23 Modified gasification slag sand 21 -- -- -- -- -- -- -- -- Modified gasification slag sand 22 -- -- -- -- 0.45 0.25 0.002 0.23 Modified gasification slag sand 23 -- -- -- -- 0.45 0.1 0.002 0.23 Modified gasification slag sand 24 -- -- -- -- 0.45 0.19 0.005 0.23 Modified gasification slag sand 25 -- -- -- -- 0.45 0.19 0 0.23 Modified gasification slag sand 26 -- -- -- -- 0.45 0.19 0.002 0.3 Modified gasification slag sand 27 -- -- -- -- 0.45 0.19 0.002 0.2

[0141] Among them, to reflect the modification effect of the modified slurry on the gasification slag, the performance verification was carried out with reference to the modification parameters in Table 10. Among them, Modification 1 is exactly the same as Example 1 and serves as the control group. For Modification 21, the slurry was not modified; in Modification 22, the dosage of carbide slag exceeded the method limit, and in Modification 23, the dosage of carbide slag was lower than the method limit; in Modification 24, the dosage of sodium hydroxide exceeded the method limit, and in Modification 25, the dosage of sodium hydroxide was lower than the method limit; in Modification 26, the dosage of water exceeded the method limit, and in Modification 27, the dosage of water was lower than the method limit.

[0142] Table 11 Dosage Ratio Values of Gasification Slag and Modified Slurry

[0143] Modified slurry Modification 1 Modification 21 Modification 22 Modification 23 Modification 24 Modification 25 Modification 26 Modification 27 Dosage ratio 1:0.43 -- 1:0.48 1:0.33 1:0.43 1:0.42 1:0.49 1:0.39

[0144] The dried gasification slag was screened. First, particles of 5 mm and above were removed, and then it was screened into particles of 1.18 mm and above and particles of less than 1.18 mm. The particles of 1.18 mm and above were put into a grinder and ground for 15 min; the ground gasification slag particles were put into a blender, the blender was started for stirring, and the modified slurry was added according to the ratio shown in Table 11 and stirring continued for 10 min; after stirring, the gasification slag was placed in a material yard and left to stand for 24 h; after standing, the gasification slag was put into a sealed pressure blender, stirred for 10 min, then carbon dioxide gas was introduced and the gas pressure was maintained at 0.6 Pa, and stirring continued for 60 min and then discharged and dried, and then it was mixed evenly with the particles of less than 1.18 mm, thus obtaining the gasification slag sand prepared by the present invention.

[0145] For Modification 28, other modification measures are the same as those in Example 1, but it did not go through step S42, that is, it did not go through CO 2 treatment. The basic properties of the gasification slag sand prepared in this example are shown in Table 12.

[0146] Table 12 Basic Properties of Modified Gasification Slag Sand after Modification in Example 5

[0147]

[0148] Through this implementation case, the role played by step S4 in the present invention can be seen. Compared with Example 1, for the gasification slag sand without S4 modification treatment, its crushing index and rapid alkali-silica reaction both exceed the limits. The construction sand commonly used in current construction projects is mainly natural sand and manufactured sand, and their main chemical compositions are both calcium carbonate or silicon dioxide, and their mineral compositions are mainly limestone or quartzite. While the gasification slag is mainly composed of silicate-aluminate and has certain alkali activity itself, thus the risk of triggering alkali-aggregate reaction is relatively high. The main purpose of modifying with step S4 of the present invention is to reduce the alkali activity of the gasification slag through technical means, and secondly, there is also the technical effect of particle shaping. Comparing the modified gasification slag sand 21 with the modified gasification slag sand 1, the test result of the rapid alkali-silica reaction of the modified gasification slag sand 21 is significantly higher than that of the modified gasification slag sand 1, which indicates the beneficial effect of step S4 of the present invention on reducing the alkali activity coefficient of the gasification slag. And comparing the modified gasification slag sands 22 - 27, it can also be found that too high or too low dosages of carbide slag and sodium hydroxide in the modifying material are not conducive to optimizing the alkali activity coefficient of the gasification slag. And when the powder dosage in the modifying material increases, it will also lead to too high consistency of the modified slurry, resulting in the inability of the modifying material to evenly wrap and penetrate the gasification slag particles, leading to abnormal physical parameters such as fineness modulus and density.

[0149] Comparing the modified gasification slag sand 28 with the modified gasification slag sand 1, it is found that the expansion rate obtained from the test of the rapid alkali-silica reaction of the modified gasification slag sand 28 is significantly higher than that of the modified gasification slag sand 1. This is mainly because the modified slurry is a high-alkaline slurry. Although this slurry can promote the chemical reaction of the gasification slag, the alkalinity of the whole system will be significantly increased. Without neutralizing modification with carbon dioxide, the risk of alkali-aggregate reaction of the gasification slag sand will be significantly aggravated.

[0150] In summary, it can be seen that preparing gasification slag sand by the method of the present invention can solve the problems of excessive crushing index, low density, and excessive expansion rate of alkali-silica reaction of the existing raw gasification slag. And the prepared gasification slag fully meets the quality standards of Class I construction sand in the national standard GB / T 14684 - 2022 "Construction Sand". It can not only largely consume industrial solid waste, reduce the consumption of natural sand and gravel, but also save various costs.

[0151] The above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of various equivalent modifications or substitutions, and these modifications or substitutions should all be covered within the protection scope of the present invention. In addition, the content of the present invention cannot be obtained through limited experiments, and the above limited number of implementation cases cannot fully characterize the beneficial effects of the content of the present invention. However, the beneficial effects of the present invention can still be verified through experiments. It should also be noted that each technical link for treating and modifying the gasification slag has a complementary and jointly optimized effect. Therefore, it is recommended to systematically adjust the modification parameters for gasification slags with different characteristics.

Claims

1. A method for preparing gasified slag sand, characterized in that: The following steps are involved: S1. Dry the gasified slag to a moisture content of less than 5%; S2. The gasified slag after drying in S1 is first screened into three specifications according to the particle size: ≥5mm, less than 5mm and greater than or equal to 1.18mm, and less than 1.18mm, then the gasified slag particles ≥5mm are removed, and the gasified slag particles less than 5mm and greater than or equal to 1.18mm and the gasified slag particles less than 1.18mm are stored separately; S3. Grind the gasified slag particles with a size less than 5 mm and greater than or equal to 1.18 mm screened out in S2, and the bulk density of the gasified slag particles after grinding is ≥1420kg / m 3 ; S4. The gasified slag obtained after grinding S3 is subjected to modification treatment, and the modification operation is specifically as follows: S41. The modified slurry is mixed into the gasified slag obtained in S3, stirred evenly and allowed to stand for 24-48h; Among them, the main components of the modified slurry are carbide slag powder and water; if the alkali activity coefficient K of the gasified slag is greater than or equal to 0.42, sodium hydroxide needs to be mixed into the modified slurry and then added into the gasified slag for modification; The gasification slag alkali activity coefficient K is calculated according to the following formula: In the formula, MgO, Na2O, SiO2, and Al2O3 are the mass percentages of magnesium oxide, sodium oxide, silicon dioxide, and aluminum oxide in the gasified slag, respectively; S42. The gasified slag after standing is placed in a sealed environment, mechanically stirred for 5-10 min, CO2 gas is introduced and pressurized to 0.6-1.2 Pa, and stirring is continued for 30-120 min; S43. The stirred gasified slag is dried to a moisture content of less than 5%; S5. Evenly mix the gasified slag modified by S4 and the gasified slag particles <1.18 mm screened by S2 to finally obtain gasified slag sand.

2. The method for preparing gasified slag sand according to claim 1, characterized in that: The amount of each component in the modified slurry used in S41 is obtained by the following method: Carbide slag powder: w d =w g *(1-α)β; Among them, w d is the amount of carbide slag powder; w g is the mass of gasified slag to be modified; α is the moisture content of gasified slag; β is the proportional coefficient 1, and its value is related to the alkali activity coefficient K of gasified slag. The specific value selection method is: when K≥1, take 0.2; when 0.42≤K<1, take 0.12; when K<0.42, take 0.02; Sodium hydroxide: w n =w d *γ; Among them, w n is the amount of sodium hydroxide; γ is the proportional coefficient 2, and its value is related to the alkali activity coefficient K of the gasification slag. The specific value selection method is: when K≥1, take 0.01; when 0.42≤K<1, take 0.04; when K<0.42, take 0; Water: w w = w d *δ + w g *(1 - α)*0.15; Among them, w w is the water dosage; δ is the proportional coefficient 3, and its value is related to the specific surface area of ​​carbide slag powder. The specific value method is: when the specific surface area of ​​carbide slag powder is 250-300kg / m 3 When the specific surface area of ​​carbide slag powder is between 300-400kg / m 3 When the specific surface area of ​​carbide slag powder is between 400-500kg / m 3 Between, take 0.

6.

3. The method for preparing gasified slag sand according to claim 1, characterized in that: The specific operation of S41 is as follows: The gasified slag obtained from S3 is first put into the mixer. After the mixer is turned on, the modified slurry is put into the mixer and continued to be stirred for 10-20 minutes. After the stirring is completed, the gasified slag is placed in the material yard and allowed to stand for 24-48 hours.

4. A gasified slag sand, characterized in that: The method is obtained by any one of claims 1 to 3.

5. The gasified slag sand according to claim 4, characterized in that: Solidity mass loss rate ≤8%, single-stage maximum crushing index ≤30%, apparent density ≥2500kg / m 3 The expansion rate of alkali silicate reaction after 14 days is less than 0.1%.

6. Use of the gasified slag sand obtained by the preparation method according to any one of claims 1 to 3 as construction sand in civil engineering.

7. A construction sand, characterized in that: The product is obtained by the preparation method described in any one of claims 1 to 3.

8. A method for regulating the properties of gasified slag, characterized in that: The gasified slag is treated by the same means as the preparation method described in any one of claims 1-3.

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