Coal gasification ash planting soil, and application and preparation method thereof

Abstract

The present application belongs to the field of comprehensive utilization and treatment of industrial solid waste, and provides a coal gasification ash planting soil, application and preparation method thereof. The planting soil comprises coal gasification fine slag, fly ash and loess, and optional coal gasification coarse slag. According to weight parts, the planting soil comprises 42.5% of coal gasification coarse slag, 42.5% of coal gasification fine slag, 5% of fly ash and 10% of loess, or 70% of coal gasification fine slag, 10% of fly ash and 20% of loess. The present application can be used for large batch treatment of coal gasification ash discharged by a coal water slurry gasification device, and is suitable for large-scale planting and disposal of waste slag.

Description

Technical Field

[0001] This invention belongs to the field of comprehensive utilization and treatment of industrial solid waste, specifically relating to a planting soil based on coal gasification ash. Background Technology

[0002] Coal gasification ash, including coarse and fine coal gasification ash, is a byproduct of coal consumption. Currently, the main methods for treating coal gasification ash are stockpiling and landfilling. However, stockpiling coal gasification ash requires large amounts of land and can generate dust storms. Furthermore, the leachate from coal gasification ash can pollute soil and water resources.

[0003] Currently, many universities and research institutions in China are actively seeking technologies for the resource utilization of coal gasification ash. However, current research mainly focuses on small-scale basic research in the laboratory stage, and large-scale engineering application technologies are not mature enough or lacking. All existing technologies are unable to process the large quantities of stockpiled coal gasification ash in the short term. Therefore, more research and exploration are needed on the utilization and treatment of coal gasification ash. Summary of the Invention

[0004] Based on previous research, the inventors of this application discovered that using coal gasification ash as the main component to prepare planting soil can enable the planted plants to grow effectively.

[0005] In a first aspect, the present invention provides a coal gasification ash planting soil, comprising coal gasification fine slag, fly ash and loess, and optionally coal gasification coarse slag, wherein, by weight, the coarse slag comprises 42.5%, the fine slag comprises 42.5%, the fly ash comprises 5%, and the loess comprises 10%, or the fine slag comprises 70%, the fly ash comprises 10%, and the loess comprises 20%.

[0006] In a preferred embodiment, the coarse coal gasification slag, fine coal gasification slag, and fly ash are respectively subjected to particle size screening and acid washing treatment. More preferably, the pH value of the treated coarse coal gasification slag, fine coal gasification slag, and fly ash is 6.5 to 7.5.

[0007] In a preferred embodiment, the coarse coal gasification slag has a particle size of less than 8 mm and a loss on ignition of 15% to 25%; the fine coal gasification slag has a loss on ignition of 35% to 48%; the fly ash has a particle size of less than 8 mm; and the loess has a particle size of 0.05 mm to 2 mm.

[0008] In a second aspect, a method for planting crops is provided, comprising planting crops using the coal gasification ash planting soil of the present invention.

[0009] In a third aspect, the present invention provides the application of the coal gasification ash residue planting soil for crop cultivation.

[0010] In a preferred embodiment, the crop is a radish, tomato, etc.

[0011] In a fourth aspect, a method for preparing the planting soil of the present invention is provided, comprising the following steps:

[0012] 1) Processing of various raw materials;

[0013] 2) Mix and prepare the processed raw materials;

[0014] 3) Adjust the moisture content of the planting soil to 50-60%, preferably 55%.

[0015] Preferably, step 1) is performed as follows:

[0016] (1) Particle size treatment of raw materials: Select coarse coal gasification slag with a loss on ignition of 15% to 25% and fine coal gasification slag with a loss on ignition of 35% to 48%, and retain particles with a particle size of less than 8 mm in coal gasification ash or fly ash by screening; perform particle size separation on loess, and retain medium and fine particles with a particle size of 0.05 mm to 2 mm in loess particles;

[0017] (2) pH treatment of raw materials: The pH value of raw materials is adjusted to 6.5-7.5 by spraying coal gasification ash and fly ash with a weak acid solution or by diluting with water and drainage; preferably, the weak acid solution is selected from ammonium chloride solution and ammonium sulfate solution;

[0018] (3) Moisture content treatment of raw materials: The gasification ash, fly ash and loess with high moisture content after spraying are dried; preferably, by sun-drying or baking, such as drying at 105-110℃; more preferably, the moisture content of the raw materials after treatment is 10%-15%.

[0019] In a preferred embodiment, step 2) is as follows:

[0020] Weigh each of the above-treated components according to the required weight and mix them thoroughly using a mixing device.

[0021] This invention combines coal gasification ash, fly ash, and loess to prepare planting soil. The preparation method is easy to operate and low in cost. It can be used for large-scale processing of coal gasification ash emitted from coal-water slurry gasification devices and is suitable for large-scale planting and waste disposal. Attached Figure Description

[0022] Figure 1 The radishes grown in Example 1 (left side) and Comparative Example 1 (right side) of the present invention are compared. Detailed Implementation

[0023] The coal gasification ash residue described in this invention includes coarse coal gasification ash residue and fine coal gasification ash residue.

[0024] Coal gasification coarse slag refers to the molten slag produced during the partial oxidation reaction of coal water slurry and oxygen at high temperature to generate crude coal gas in the coal water slurry gasification process. After being chilled and solidified, the molten slag is retrieved from the slag pool and transported out of the coal water slurry gasification unit using equipment such as belt conveyors or bucket elevators. Its loss on ignition is 15%–25%. The particle size distribution of the coal gasification coarse slag can be: 20–2 mm accounting for 40–45%, 2–0.5 mm accounting for 20–25%, 0.5–0.25 mm accounting for 8–12%, 0.25–0.075 mm accounting for 5–10%, 0.075–0.005 mm accounting for 5–7%, and particles smaller than 0.005 mm accounting for 1–21%. In this invention, it is necessary to screen and retain particles smaller than 8 mm.

[0025] Coal gasification fine slag refers to the fine ash residue separated from the bottom of the settling tank after the black water from the quench chamber of the gasifier and the black water from the bottom of the washing tower settles in a coal-water slurry gasification unit. This ash is then dewatered by equipment such as a vacuum filter and a horizontal screw press before being transported out of the gasification unit. The loss on ignition is 35%–48%. The particle size distribution of coal gasification fine slag is as follows: 0.25–0.075 mm accounts for 30–40%, 0.075–0.005 mm accounts for 45–55%, and less than 0.005 mm accounts for 5–25%. For example, 0.25–0.075 mm accounts for 33.9%, 0.075–0.005 mm accounts for 51.3%, and less than 0.005 mm accounts for 14.8%.

[0026] Loss on ignition (LOI) refers to the percentage of mass lost after burning at a certain high temperature for a sufficient duration relative to the original sample mass. LOI is related to carbon content; generally, a higher LOI indicates a higher carbon content. Comparative studies on planting effects show that coarse and fine slag within the LOI range selected in this invention are more conducive to plant growth.

[0027] Fly ash refers to the powdery solid waste discharged from coal-fired power plants after coal combustion and melting. In this invention, it is necessary to screen and retain particles smaller than 8 mm.

[0028] The loess selected in this invention is medium and fine particles with a particle size of 0.05mm to 2mm. Medium and fine particles of soil contain a high amount of calcium ions, which is beneficial to the growth of plant roots.

[0029] In this invention, unless otherwise specified, "%" represents the percentage content by mass.

[0030] In this invention, alkaline hydrolysate nitrogen (available nitrogen) is detected by alkaline hydrolysis diffusion method; available phosphorus is detected by 0.5 mol·L⁻¹. -1 Determination by NaHCO3 solution extraction colorimetric method; available potassium was determined using 1 mol·L⁻¹ -1 The NH4OAC extraction flame spectrophotometric method was used to determine the moisture content. Soil content was determined using a soil drill and oven drying method.

[0031] In this invention, the pH values ​​of the coarse coal gasification slag, fine coal gasification slag, and fly ash are measured using a pH meter. The above substances are dispersed in water at a water-to-soil ratio of 5:1, and after standing, the clear leachate is taken for testing.

[0032] For tests not explicitly described, use conventional techniques in the field.

[0033] The technical solution of the present invention will be described in detail below with reference to specific embodiments. Those skilled in the art should understand that the following embodiments are for illustrative purposes only and not for limiting the present invention.

[0034] The coarse coal gasification slag used in the following examples is taken from the ash residue discharged from the coal-water slurry gasification unit of Guoneng Baotou Coal Chemical Co., Ltd., and is the ash residue scooped from the slag pool in the coal-water slurry gasification unit. The fine coal gasification slag is taken from the sediment at the bottom of the settling tank of the coal-water slurry gasification unit of Guoneng Baotou Coal Chemical Co., Ltd., and is the sediment separated from the bottom of the settling tank after the black water exiting the quench chamber of the gasifier and the black water exiting the bottom of the washing tower has settled, and has undergone preliminary dewatering by a screw press. The fly ash is taken from the fly ash discharged from the coal-fired boiler of Guoneng Baotou Coal Chemical Co., Ltd. The loess is taken from about 1 meter underground around the coal gasification ash and slag yard of Guoneng Baotou Coal Chemical Co., Ltd., with a specific gravity of 2.67.

[0035] Example 1:

[0036] The soil for planting radishes was prepared by mixing 42.5% coarse coal gasification slag, 42.5% fine coal gasification slag, 5% fly ash, and 10% loess.

[0037] Preparation process:

[0038] (1) The coarse coal gasification slag, fine coal gasification slag, fly ash and loess are subjected to particle size treatment. The loss on ignition of the coarse coal gasification slag is 15% to 25%, the loss on ignition of the fine coal gasification slag is 35% to 48%, the coarse coal gasification slag, fine coal gasification slag and fly ash retain particles smaller than 8 mm, and the loess retains medium and fine particles of 0.05 mm to 2 mm.

[0039] (2) The pH values ​​of the coarse coal gasification slag, fine coal gasification slag, and fly ash were adjusted by diluting them with water and draining water to achieve a pH value of 6.5–7.5.

[0040] (3) The coarse coal gasification slag, fine coal gasification slag, fly ash and loess are dried at 105-110℃ until their respective moisture content is 10%-15%;

[0041] (4) Weigh the dried coal gasification coarse slag, coal gasification fine slag, fly ash and loess according to the above weight, mix them evenly, and add water to adjust the moisture content to 55%.

[0042] Planting:

[0043] Radish seedlings were planted using conventional methods, and samples were collected and analyzed 60 days later.

[0044] result:

[0045] 1) Physicochemical properties of planting soil:

[0046] The physicochemical properties of the planting soil were analyzed, and the results are shown in Table 1. It can be seen that the planting soil prepared in this invention is rich in nitrogen, phosphorus and potassium, which can meet the needs of plant growth.

[0047] Table 1: Physicochemical properties of the prepared planting soil

[0048]

[0049] 2) Radish growth status:

[0050] The length and weight of the harvested radishes were measured, and the results are shown in Table 2.

[0051] Table 2: Growth of radishes grown in potting soil (60 days)

[0052] Length of a single radish (cm) Weight of a single radish (g) 30～40 200～300g

[0053] 3) Detection of heavy metal and inorganic content

[0054] Further testing was conducted on the heavy metal and inorganic matter content of the cultivated radishes, and the results are shown in Table 3. Comparison with the "National Food Safety Standard Limits for Contaminants in Food" in Table 4 shows that the radishes grown using the soil of this invention fully comply with the limits for heavy metals and inorganic matter, and there are no food safety issues.

[0055] Table 3: Results of heavy metal and inorganic matter content in radishes grown in planting soil

[0056] Testing items Test result mg / kg Total arsenic Not detected cadmium Not detected chromium 0.035 lead Not detected Total Mercury Not detected

[0057] Table 4: National Food Safety Standards for Maximum Levels of Contaminants in Food (Excerpt from GB2762-2017)

[0058]

[0059] Comparative Example 1:

[0060] All materials in Example 1 were replaced with an equal weight of loess, i.e., loess accounted for 100% of the mix. The test results are shown in Tables 5 and 6.

[0061] Table 5: Physicochemical Properties of Loess for Planting

[0062]

[0063] Table 6: Growth of radishes grown in loess soil (60 days)

[0064] Length of a single radish (cm) Weight of a single radish (g) 10～22 80～180g

[0065] Comparative Example 2:

[0066] Similar to the materials used in Example 1, only the soil composition for planting in Example 1 was adjusted to 35% coarse coal gasification slag, 35% fine coal gasification slag, 10% fly ash, and 20% loess. The test results are shown in Tables 7 and 8.

[0067] Table 7: Physical and chemical properties of soil used for planting in Comparative Example 2

[0068]

[0069] Table 8: Growth of radishes grown in the same soil as in Example 2 (60 days)

[0070] Length of a single radish (cm) Weight of a single radish (g) 20～30 150～200g

[0071] The results from Example 1 and Comparative Example 1, Comparative Example 2, and Figure 1 It can be seen that the planting soil of this invention can not only improve the water physical properties of local loess and increase the water holding capacity of the soil, but also increase the organic matter content of local loess. The available nitrogen, available phosphorus and available potassium are all significantly increased. The planting soil prepared by this invention has a significant promoting effect on plant growth and can be used as planting soil.

[0072] Example 2:

[0073] A planting soil mixture consisting of 70% coal gasification slag, 10% fly ash, and 20% loess was prepared and used for tomato cultivation. The selection and processing of the planting soil raw materials were the same as in Example 1. The tomato cultivation method was consistent with conventional methods. Local loess soil was used as a control, and tomatoes were harvested at the same maturity stage.

[0074] The results are shown in Tables 9-11. As can be seen, compared to local loess soil, the planting soil of this invention allows tomato plants to grow taller and have deeper roots within the same timeframe, enabling the plants to absorb more nutrients and resulting in heavier individual tomatoes. Furthermore, the heavy metal and inorganic matter content of the fruits grown using the planting soil of this invention meets food safety requirements.

[0075] Table 9: Effects of planting soil and local loess on the growth of tomato seedlings and fruits in Example 2

[0076]

[0077] Table 10: Physicochemical Properties of Prepared Planting Soil

[0078]

[0079] Table 11: Test results of heavy metal and inorganic matter content in tomato fruits grown in the prepared planting soil.

[0080]

[0081]

Claims

1. A planting soil made from coal gasification ash residue, wherein, By weight, the coal gasification ash planting soil comprises 42.5% coarse coal gasification slag, 42.5% fine coal gasification slag, 5% fly ash, and 10% loess, or the coal gasification ash planting soil comprises 70% fine coal gasification slag, 10% fly ash, and 20% loess; The coarse coal gasification slag, fine coal gasification slag, and fly ash are respectively subjected to particle size screening and acid washing treatment; The particle size of the coal gasification coarse slag is less than 8 mm, and the loss on ignition of the coal gasification coarse slag is 15%~25%; The loss on ignition of the coal gasification slag is 35%~48%; The fly ash has a particle size of less than 8 mm, and the loess has a particle size of 0.05 mm to 2 mm. The pH value of the treated coal gasification coarse slag, coal gasification fine slag, and fly ash is 6.5~7.

5.

2. A method for planting a crop, comprising planting the crop using the coal gasification ash planting soil as described in claim 1.

3. The application of the coal gasification ash planting soil as described in claim 1, for crop cultivation.

4. The method for preparing planting soil from coal gasification ash as described in claim 1, comprising the following steps: 1) Raw material processing; 2) Mix and prepare the processed raw materials; 3) Adjust the moisture content of the planting soil to 50-60%; The process of step 1) is as follows: (1) Particle size treatment of raw materials: Select coal gasification coarse slag with a loss on ignition of 15%~25% and coal gasification fine slag with a loss on ignition of 35%~48%, and retain particles with a particle size of less than 8mm in the coal gasification coarse slag, coal gasification fine slag and fly ash by screening; perform particle size separation on loess, and retain medium and fine particles with a particle size of 0.05mm~2mm in the loess particles; (2) pH treatment of raw materials: The pH value of raw materials is adjusted to 6.5~7.5 by spraying the coarse slag, fine slag and fly ash of coal gasification with a weak acid solution or by diluting with water and drainage. (3) Moisture content treatment of raw materials: The coarse slag, fine slag, fly ash and loess with high moisture content after spraying are dried. Step 2) is as follows: Weigh each of the above-treated components according to the required weight and mix them evenly.

5. The preparation method according to claim 4, wherein, In step 3), the moisture content is adjusted to 55%.

6. The preparation method according to claim 4, wherein, In step 1), during the raw material pH treatment, the weak acid solution is selected from ammonium chloride solution and ammonium sulfate solution.

7. The preparation method according to claim 4 or 6, wherein, In step 1), the moisture content of the raw materials is treated by sun-drying or drying at 105~110℃.

8. The preparation method according to claim 4 or 6, wherein, In step 1), the moisture content of the raw materials is reduced to 10%~15% after treatment.

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