Method and system for preparing ball carbonate calcium from waste incineration fly ash

Abstract

The present application belongs to the technical field of solid waste resource utilization, and relates to a method and system for preparing ball spar type calcium carbonate from waste incineration fly ash. Ammonium chloride is used as a leaching agent, and waste incineration fly ash is placed in a leaching agent solution for leaching, and then solid-liquid separation is performed to obtain a calcium solution. The calcium solution is subjected to carbonation reaction with an alkaline compound, sodium dodecyl benzene sulfonate and carbon dioxide under the conditions of a pressure of 0.5-0.7 MPa and a temperature of 25-180 DEG C for 60-90 min, and ball spar type calcium carbonate is obtained. The present application can prepare high-quality ball spar type calcium carbonate with high conversion rate, reduces the risk of fly ash, and realizes carbon dioxide mineralization, so as to realize waste treatment with waste and green production.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of solid waste resource utilization, and relates to a method and system for preparing vaterite-type calcium carbonate from waste incineration fly ash. BACKGROUND

[0002] The information disclosed in this Background section is only for the purpose of increasing the understanding of the general background of the application and does not necessarily constitute an admission or a recognition that the information forms part of the prior art that is already known in any country in the world.

[0003] Waste incineration fly ash (referred to as fly ash) has the characteristics of high salt content, and contains heavy metals and dioxins and other toxic substances, so it is classified as hazardous waste. At present, the main disposal method of fly ash is safe landfill, but the water-soluble salt, heavy metal pollution and the toxicity of dioxins have not been completely eliminated. From the composition of fly ash, the content of calcium is also relatively high compared with other components, so calcium is a potential resource with high utilization value.

[0004] Calcium carbonate products are mainly used as fillers and additives, so fly ash can be used as a raw material for producing calcium carbonate products. The crystal forms of calcium carbonate include calcite, aragonite and vaterite. In the research, it is found that vaterite has the characteristics of large specific surface area, good dispersibility, uniform spherical size distribution, etc. The filling performance of vaterite is obviously better than that of other two crystal forms of calcium carbonate for improving the product flowability and gloss of products such as ink, plastic, paper and paint. However, compared with other crystal forms, the thermodynamic performance of vaterite is unstable, and it belongs to a metastable crystal structure. During the preparation process, it is easy to be converted into calcite or aragonite with more stable crystal structure, so it is difficult to obtain high-quality vaterite-type calcium carbonate. At the same time, the main morphology of vaterite-type calcium carbonate is spherical, and there are also disc-shaped, flaky, hexagonal and lens-shaped morphologies. Therefore, although fly ash can be used as a raw material for producing calcium carbonate products, due to the high impurities in fly ash and the instability of vaterite-type calcium carbonate, it is difficult to obtain high-quality vaterite-type calcium carbonate with high efficiency. SUMMARY

[0005] In order to solve the problems in the prior art, the present application aims to provide a method and system for preparing vaterite-type calcium carbonate from waste incineration fly ash. The present application provides a new method for resource utilization of fly ash, which can prepare high-quality vaterite-type calcium carbonate with high conversion rate. The present application not only reduces the risk of fly ash, but also realizes the mineralization of carbon dioxide, so as to realize waste treatment with waste and green production.

[0006] In order to achieve the above-mentioned purpose, the technical scheme of the present application is as follows:

[0007] In a first aspect, a method for preparing vaterite-type calcium carbonate from waste incineration fly ash comprises the following steps:

[0008] Using ammonium chloride as a leaching agent, the waste incineration fly ash is placed in a leaching agent solution for leaching, and then solid-liquid separation is performed to obtain a calcium solution;

[0009] The calcium solution is reacted with an alkaline compound, sodium dodecylbenzenesulfonate and carbon dioxide under a pressure of 0.5 to 0.7 MPa and a temperature of 25 to 180° C. for 60 to 90 minutes to obtain the product.

[0010] The present invention selects ammonium chloride as a leaching agent. During the leaching process, ammonium ions in the leachate allow the reaction system to have a certain buffering capacity. When the ammonium chloride solution leaches fly ash, the entire leaching system is alkaline with a pH value of 8 to 9. A small amount of other metal ions in the fly ash are leached out, but most of them remain in the fly ash residue. Therefore, the ammonium chloride solution has selectivity for calcium-containing components in the fly ash, thereby improving not only the leaching efficiency but also the calcium ion content in the calcium solution, thereby providing a basis for preparing vaterite-type calcium carbonate from fly ash with a high conversion rate.

[0011] At present, carbonation method (or carbonization method) is one of the main methods for preparing vaterite calcium carbonate. Its essence is to use CO2 gas to dissolve in alkaline solution to obtain CO3 2- With Ca in solution 2+ The precipitation reaction produces calcium carbonate. The solubility rate and dispersion of CO2 gas in water are low. Therefore, the yield and efficiency of preparing vaterite calcium carbonate by this method are low. In order to increase the mass transfer rate and dispersion of CO2 gas in the solution, the method generally adopted at present is to add a gas disperser (or gas distributor) for bubbling. However, in any case, the calcium ion concentration directly affects the CO3 2- Therefore, carbonation usually requires a lower concentration of Ca 2+ However, in order to improve the conversion rate of fly ash into vaterite-type calcium carbonate when leaching calcium ions from fly ash, the calcium ion content in the calcium solution must be increased. Therefore, the use of the existing carbonation method is not conducive to achieving the purpose of preparing vaterite-type calcium carbonate with a high conversion rate of fly ash.

[0012] The present invention changes the pressure of the reaction system to make the reaction system under high pressure conditions; at the same time, the present invention adopts sodium dodecylbenzenesulfonate as a crystal form control agent, which can react with Ca 2+Strong electrostatic interaction exists between them, a strong Ca-O bond can be formed, the growth of some specific crystal faces is inhibited, and the concentration is greater, the inhibition effect is more obvious, therefore, the cooperation of high pressure condition and sodium dodecyl benzene sulfonate in the reaction process can not only prepare the vaterite type calcium carbonate by using the calcium solution with high calcium concentration, but also is beneficial to the preparation of the vaterite type calcium carbonate from the fly ash with high conversion, and the prepared vaterite type calcium carbonate has the high-quality characteristics of high calcium carbonate content, high whiteness, few black spots and the like, and is beneficial to further improving the value of the vaterite type calcium carbonate.

[0013] In addition, since the leaching system is alkaline, the prepared calcium solution is also alkaline, and therefore, the addition amount of the alkaline compound can be greatly reduced in the subsequent carbonation process, so that the cost is saved.

[0014] On the other hand, a system for preparing vaterite type calcium carbonate from waste incineration fly ash is used to realize the above method, comprising:

[0015] A leaching device is arranged to leach the waste incineration fly ash in the leaching agent solution;

[0016] A first solid-liquid separation device is arranged to perform solid-liquid separation on the material after the leaching device;

[0017] A high-pressure reaction device is arranged to perform carbonation reaction on the calcium solution obtained from the solid-liquid separation device, the alkaline compound, sodium dodecyl benzene sulfonate and carbon dioxide.

[0018] The beneficial effects of the present application are:

[0019] (1) The present application can selectively leach the calcium in the fly ash by selecting ammonium chloride as the leaching agent, so that the calcium ions in the fly ash are efficiently leached to obtain a calcium solution with high concentration, and then under high pressure condition, sodium dodecyl benzene sulfonate is used as a crystal type control agent to make the calcium efficiently converted into high-quality vaterite type calcium carbonate.

[0020] (2) The method provided by the present application not only realizes the resource utilization of waste incineration fly ash, but also uniformly introduces carbon dioxide in the carbonation stage to obtain uniformly distributed vaterite type calcium carbonate, realizes the mineralization of carbon dioxide, and the obtained vaterite type calcium carbonate has the advantages of high calcium carbonate content, high whiteness, few black spots and the like.

[0021] (3) The method has low energy consumption and material consumption, high CO2 mineralization efficiency, simple process, recovered chloride salt, and the leaching solution and leaching residue after carbonation are treated to realize waste-free experiment, easy to realize industrial production, can realize high-value utilization of solid waste, has good environmental benefits and broad market prospect. BRIEF DESCRIPTION OF DRAWINGS

[0022] The accompanying drawings, which form a part of this specification, are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification. The embodiments of the application, together with its

[0023] Figure 1 Flow chart for preparation of aragonite-type calcium carbonate from waste incineration fly ash in an embodiment of the present application;

[0024] Figure 2 Mineral composition chart for calcium carbonate product prepared in an embodiment of the present application;

[0025] Figure 3 Surface morphology chart for calcium carbonate product prepared in Example 1 of the present application;

[0026] Figure 4 Surface morphology chart for calcium carbonate product prepared in Example 2 of the present application;

[0027] Figure 5 Surface morphology chart for calcium carbonate product prepared in Example 3 of the present application;

[0028] Figure 6 Surface morphology chart for calcium carbonate product prepared in Example 4 of the present application;

[0029] Figure 7 Surface morphology chart for calcium carbonate product prepared in Example 5 of the present application. DETAILED DESCRIPTION

[0030] It should be noted that the following detailed description is exemplary in nature and is intended to provide further description of the application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0031] It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments in accordance with the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or groups thereof.

[0032] In view of the problem that it is difficult to efficiently prepare high-quality aragonite-type calcium carbonate using fly ash in the prior art, the present application provides a method and system for preparing aragonite-type calcium carbonate from waste incineration fly ash.

[0033] In a typical embodiment of the present application, a method for preparing aragonite-type calcium carbonate from waste incineration fly ash is provided, comprising the following steps:

[0034] The waste incineration fly ash is immersed in the leaching agent solution by taking ammonium chloride as the leaching agent, and then a calcium solution is obtained through solid-liquid separation.

[0035] The calcium solution is subjected to carbonation reaction with an alkaline compound, sodium dodecyl benzene sulfonate and carbon dioxide under the conditions of a pressure of 0.5-0.7 MPa and a temperature of 25-180 DEG C for 60-90 min.

[0036] In some embodiments, the liquid-solid ratio of the leaching agent solution to the waste incineration fly ash is 10-60 mL / g, and the concentration of the leaching agent solution is 1-5 mol / L. Specifically, the liquid-solid ratio is 30-50 mL / g. Specifically, the concentration of the leaching agent solution is 1-2 mol / L. Studies show that the effect of leaching calcium ions is better under the conditions.

[0037] In some embodiments, the leaching temperature is 25-85 DEG C, and the leaching time is 20-140 min. Specifically, the leaching temperature is preferably 25-45 DEG C. Specifically, the leaching time is 60-80 min. Studies show that the effect of leaching calcium ions is better under the conditions.

[0038] In some embodiments, the pH of the leaching system is 8-9. Under the conditions, the selectivity of leaching calcium is improved.

[0039] In some embodiments, the leaching is followed by standing and precipitation, and then the calcium solution and the ash residue are obtained through solid-liquid separation. Specifically, the ash residue is dried, ground and then filled after being solidified and stabilized.

[0040] In some embodiments, the concentration of calcium ions in the calcium solution is 4000-8000 mg / L, preferably 4500-7500 mg / L.

[0041] The alkaline compound in the application is a compound that is alkaline after being dissolved in water, which can be inorganic or organic. In some embodiments, the alkaline compound is ammonia, caustic soda or triethanolamine. Preferably, it is ammonia. The mass concentration of the ammonia in the application is 5-25%, preferably 20-25%. Specifically, the volume ratio of the calcium solution to the ammonia is 50:3-5.

[0042] In some embodiments, the volume ratio of the calcium solution to the mass of sodium dodecyl benzene sulfonate is 50 mL:0.05-0.15 g.

[0043] In some embodiments, the temperature of the carbonation reaction is 80-100 DEG C.

[0044] In some embodiments, solid-liquid separation is performed after the carbonation reaction, and the dried solid after the separation is the ball-shaped calcite type calcium carbonate.

[0045] In some embodiments, solid-liquid separation is performed after the carbonation reaction, sodium sulfide is added to the separated liquid and mixed uniformly to obtain a turbid liquid, and the turbid liquid is filtered, and the filtered liquid is evaporated and crystallized to recover.

[0046] Another embodiment of the present application provides a system for preparing ball-shaped aragonite type calcium carbonate from waste incineration fly ash, which is used to implement the above method, and comprises:

[0047] A leaching device is arranged to leach the waste incineration fly ash in a leaching agent solution.

[0048] A first solid-liquid separation device is arranged to perform solid-liquid separation on the material after the leaching device.

[0049] A high-pressure reaction device is arranged to perform carbonation reaction on the calcium solution obtained from the solid-liquid separation device, an alkaline compound, sodium dodecyl benzene sulfonate and carbon dioxide.

[0050] In some embodiments, a second solid-liquid separation device is further arranged to perform solid-liquid separation on the material after the high-pressure reaction device.

[0051] In some embodiments, a post-processing device is further arranged to further process the liquid output from the second solid-liquid separation device.

[0052] In order to enable those skilled in the art to more clearly understand the technical solutions of the present application, the technical solutions of the present application will be described in detail below with specific embodiments.

[0053] The composition of the fly ash used in the following embodiments is shown in Table 1.

[0054] Table 1 Composition of original fly ash

[0055]

[0056] Example 1

[0057] A method for preparing ball-shaped aragonite type calcium carbonate from waste incineration fly ash, as shown in Figure 1 The steps are as follows:

[0058] (1) Dry the domestic waste incineration fly ash in an oven at 105°C.

[0059] (2) Leach the domestic waste incineration fly ash with 1 mol / L ammonium chloride solution, the leaching time is 60 min, the leaching liquid-solid ratio is 50 mL / g, the pH is 8.5, the leaching temperature is 45°C, place it on a magnetic stirrer, the stirring speed is 400 r / min, conduct the leaching experiment, and obtain a mixture.

[0060] (3) The mixture is allowed to stand and precipitate, and then solid-liquid separation is performed to obtain a calcium-rich solution and ash residue.

[0061] (4) The ash residue is dried, ground, and then solidified and stabilized before being landfilled.

[0062] (5) 50 mL of the calcium-rich solution (calcium ion concentration: 4725.76 mg / L) is placed in a high-pressure reaction kettle, the experimental temperature is 80°C, the experimental time is 80 min, the rotation speed is 400 r / min, 4 mL of 25% ammonia water is added, pure CO2 is introduced, the pressure in the kettle is 0.6 MPa, and 0.1 g of a crystal form control agent, sodium dodecyl benzene sulfonate, is added. The lid of the high-pressure reaction kettle is tightened, and carbonation experiment is performed to obtain a turbid solution containing calcium carbonate.

[0063] (6) The turbid solution is taken out, and the solid and liquid in the turbid solution are separated using a suction filtration device. The obtained white solid is placed in an oven for drying, and the white solid is a calcium carbonate sample, as shown in FIG. 2. Figure 2 、 3

[0064] (7) 5% Na2S is added to the leaching solution after carbonation, and the leaching solution and 5% Na2S are mixed according to a ratio of 4:1 to react for 3 h on a magnetic stirrer to fully mix and obtain a turbid solution.

[0065] (8) The turbid solution is filtered to obtain a clear liquid, and whether the heavy metal concentration of the clear liquid meets the “GB 8978-1996 Integrated Wastewater Discharge Standard” is detected. The leaching solution contains a large amount of chloride salt components, which are evaporated and crystallized for recovery.

[0066] Example 2

[0067] A method for preparing aragonite-type calcium carbonate from waste incineration fly ash, as shown in FIG. 3, includes the following steps: Figure 1

[0068] (1) The waste incineration fly ash is dried in an oven at 105°C.

[0069] (2) The waste incineration fly ash is leached with 1 mol / L ammonium chloride solution, the leaching time is 60 min, the leaching liquid to solid ratio is 40 mL / g, the pH is 8.5, and the leaching temperature is 25°C. The mixture is placed on a magnetic stirrer and stirred at a rotation speed of 400 r / min to perform leaching experiment and obtain a mixture.

[0070] (3) The mixture is allowed to stand and precipitate, and then solid-liquid separation is performed to obtain a calcium-rich solution and ash residue.

[0071] ​​(4) The ash is dried, ground, and solidified and stabilized before landfill.

[0072] (5) 50 mL of the calcium-rich solution (calcium ion concentration of 5574.4 mg / L) is placed in a high-pressure reaction kettle, the experimental temperature is 100°C, the experimental time is 80 min, the rotation speed is 400 r / min, 4 mL of 25% ammonia water is added, pure CO2 is introduced, the pressure in the kettle is 0.6 MPa, and 0.1 g of crystal control agent sodium dodecyl benzene sulfonate is added, the lid of the high-pressure reaction kettle is tightened, carbonation experiment is carried out, and a turbid liquid containing calcium carbonate is obtained.

[0073] (6) The turbid liquid is taken out, and the solid and liquid in the turbid liquid are separated by using a suction filtration device. The obtained white solid is placed in an oven for drying, and the white solid is a calcium carbonate sample, as shown in FIG. 2. Figure 2 、 4

[0074] (7) 5% Na2S is added to the leaching solution after carbonation, and the mixture is reacted according to the ratio of leaching solution: 5% Na2S = 4:1, and is placed on a magnetic stirrer for reaction for 3 h to make it fully mixed and uniform, and a turbid liquid is obtained.

[0075] (8) The turbid liquid is filtered to obtain a clear liquid, and whether the heavy metal concentration meets the “GB 8978-1996 Integrated Wastewater Discharge Standard” is detected, and then it is discharged. There are a large amount of chloride salt components in the leaching solution, and they are evaporated and crystallized for recovery.

[0076] Example 3

[0077] A method for preparing aragonite-type calcium carbonate from waste incineration fly ash, as shown in FIG. 3, includes the following steps: Figure 1

[0078] (1) The waste incineration fly ash is dried in an oven at 105°C.

[0079] (2) The waste incineration fly ash is leached with 1 mol / L ammonium chloride solution, the leaching time is 80 min, the leaching liquid-solid ratio is 40 mL / g, the pH is 8.5, and the leaching temperature is 25°C. The mixture is placed on a magnetic stirrer and stirred at a rotation speed of 400 r / min to carry out leaching experiment, and a mixture is obtained.

[0080] (3) The mixture is allowed to stand and precipitate, and then solid-liquid separation is performed to obtain a calcium-rich solution and ash.

[0081] (4) The ash is dried, ground, and solidified and stabilized before landfill.

[0082] ​​(5) Put 50 mL of the calcium-rich solution (calcium ion concentration of 5670.4 mg / L) into a high-pressure reaction kettle, the experimental temperature is 80°C, the experimental time is 90 min, the rotation speed is 400 r / min, 4 mL of 25% ammonia water is added, pure CO2 is introduced, the pressure in the kettle is 0.6 MPa, and 0.1 g of crystal control agent sodium dodecyl benzene sulfonate is added, the lid of the high-pressure reaction kettle is tightened, and the carbonation experiment is carried out to obtain a turbid liquid containing calcium carbonate.

[0083] (6) The turbid liquid is taken out, and the solid and liquid in the turbid liquid are separated by using a suction filtration device, and the obtained white solid is placed in an oven for drying, that is, the white solid is a calcium carbonate sample, as shown in Figure 2 、 5 .

[0084] (7) 5% Na2S is added to the leaching solution after carbonation, and the mixture is reacted according to the ratio of leaching solution: 5% Na2S = 4:1, and is placed on a magnetic stirrer for reaction for 3 h to make it fully mixed and uniform, to obtain a turbid liquid.

[0085] (8) The turbid liquid is filtered to obtain a clear liquid, and whether the heavy metal concentration meets the “GB 8978-1996 Integrated Wastewater Discharge Standard” is detected, and then it is discharged, and a large amount of chloride salt components in the leaching solution are evaporated and crystallized for recovery.

[0086] Example 4

[0087] A method for preparing aragonite-type calcium carbonate from waste incineration fly ash, as shown in Figure 1 , the steps are as follows:

[0088] (1) The domestic waste incineration fly ash is dried in an oven at 105°C.

[0089] (2) The domestic waste incineration fly ash is leached with 1 mol / L of ammonium chloride solution, the leaching time is 70 min, the leaching liquid-solid ratio is 30 mL / g, the pH is 8.5, and the leaching temperature is 35°C, and it is placed on a magnetic stirrer with a rotation speed of 400 r / min for stirring, to carry out the leaching experiment, to obtain a mixture.

[0090] (3) The mixture is allowed to stand and precipitate, and then solid-liquid separation is carried out to obtain a calcium-rich solution and an ash residue.

[0091] (4) The ash residue is dried, ground, and solidified and stabilized for landfill.

[0092] (5) Put 50 mL of the calcium-rich solution (calcium ion concentration of 7449.6 mg / L) into a high-pressure reaction kettle, the experimental temperature is 90°C, the experimental time is 100 min, the rotation speed is 400 r / min, 4 mL of 25% ammonia water is added, pure CO2 is introduced, the pressure in the kettle is 0.6 MPa, and 0.1 g of crystal control agent sodium dodecyl benzene sulfonate is added, the lid of the high-pressure reaction kettle is tightened, and the carbonation experiment is carried out to obtain a turbid liquid containing calcium carbonate.

[0093] (6) The turbid liquid is taken out, and the solid and liquid in the turbid liquid are separated by using a suction filtration device. The obtained white solid is placed in an oven for drying, and the white solid is a calcium carbonate sample, as shown in Figure 2 、 6 .

[0094] (7) 5% Na2S is added to the leaching solution after carbonation, and the mixture is reacted according to the ratio of leaching solution: 5% Na2S = 4:1, and is placed on a magnetic stirrer for reaction for 3 h to make it fully mixed and uniform, and a turbid liquid is obtained.

[0095] (8) The turbid liquid is filtered to obtain a clear liquid, and whether the heavy metal concentration meets the “GB 8978-1996 Integrated Wastewater Discharge Standard” is detected, and then it is discharged. There are a large amount of chloride salt components in the leaching solution, and they are evaporated and crystallized for recovery.

[0096] Example 5

[0097] A method for preparing aragonite-type calcium carbonate from waste incineration fly ash, as shown in Figure 1 , the steps are as follows:

[0098] (1) Dry the domestic waste incineration fly ash in an oven at 105°C.

[0099] (2) The domestic waste incineration fly ash is leached with 1 mol / L of ammonium chloride solution, the leaching time is 60 min, the leaching liquid-solid ratio is 50 mL / g, the pH is 8.5, and the leaching temperature is 45°C. It is placed on a magnetic stirrer with a rotation speed of 400 r / min for stirring to carry out leaching experiment, and a mixture is obtained.

[0100] (3) The mixture is allowed to stand and precipitate, and then solid-liquid separation is carried out to obtain a calcium-rich solution and an ash residue.

[0101] (4) The ash residue is dried, ground, and solidified and stabilized for landfill.

[0102] (5) Put 50 mL of the calcium-rich solution (calcium ion concentration of 4725.76 mg / L) into a high-pressure reaction kettle, the experimental temperature is 80°C, the experimental time is 90 min, the rotation speed is 400 r / min, 4 mL of 25% ammonia water is added, pure CO2 is introduced, the pressure in the kettle is 0.6 MPa, and 0.1 g of crystalline form control agent serine is added, the lid of the high-pressure reaction kettle is tightened, the carbonation experiment is carried out, and a turbid liquid containing calcium carbonate is obtained.

[0103] (6) The turbid liquid is taken out, the solid and the liquid in the turbid liquid are separated by using a suction filtration device, and the obtained white solid is placed in an oven for drying, that is, the white solid is a calcium carbonate sample, as shown in Figure 2 、 7 .

[0104] (7) 5% Na2S is added to the leaching liquid after carbonation, and the mixture is reacted according to the ratio of leaching liquid: 5% Na2S = 4:1, and is placed on a magnetic stirrer for 3 h to make it fully mixed and uniform, and a turbid liquid is obtained.

[0105] (8) The turbid liquid is filtered to obtain a clear liquid, and whether the heavy metal concentration meets the “GB8978-1996 Comprehensive Discharge Standard for Sewage” is detected, and then it is discharged, a large amount of chloride salt component is contained in the leaching liquid, and is evaporated and crystallized for recovery.

[0106] After detecting examples 1, 2, 3, 4 and 5, the obtained data are as follows:

[0107] Table 2 Experimental data table of examples 1, 2, 3, 4 and 5

[0108]

[0109] In the calcium carbonate in example 4, the content of vaterite is 95%, and the content of calcite is 5%. This is mainly due to the fact that the time is too long (100 min), and the unstable vaterite type calcium carbonate develops into calcite. In the calcium carbonate of example 5, the content of calcite is 41.25%, the content of aragonite is 35.61%, and the content of vaterite is 23.14%.

[0110] Table 3 Calcium carbonate index data table of example samples

[0111]

[0112] As can be known from Table 2, utilizing sodium chloride solution to leach the calcium ion leaching rate in the fly ash can reach 92.3%, illustrates that most calcium-containing component has been leached in the solution in the fly ash, and the carbonation rate of solution has also reached 96.87%, and the purity of calcium carbonate is also very high.In conjunction with Table 2 and Table 3, it can be seen that this method can prepare high-quality vaterite type calcium carbonate efficiently, the leaching rate of calcium ion is all more than 85% in the fly ash, the content of calcium carbonate is all much greater than the requirement in " GB 8978-1996 " more than 98%, other indexes of calcium carbonate all meet the standard in " GB 8978-1996 ", so this method can make standard-compliant vaterite type calcium carbonate.

[0113] Depend on Figure 2 It can be seen that the crystal form of the calcium carbonate samples of Examples 1 to 4 is vaterite, and only a small amount of calcite is present in Example 4, but the crystal form of the sample is still mainly vaterite. Since the crystal form control agent added in Example 5 was changed, calcium carbonate mainly composed of calcite and aragonite appeared. Figure 7 It can be seen that in Example 5, cubic calcite and needle-shaped aragonite are the main components. Figure 3 It can be seen that the vaterite type calcium carbonate of Example 1 is mainly in the shape of a disc, and there are some hexagonal columns, which is consistent with the Figure 2 The XRD patterns of the vaterite type calcium carbonate are consistent, and the vaterite type calcium carbonate has disc shape and hexagonal shape. The calcium carbonate of Example 2 is the most common spherical vaterite type calcium carbonate, such as Figure 4 shown. Figure 5 It can be seen that the sample of Example 3 is mainly flake-shaped vaterite-type calcium carbonate. Figure 2 It shows that the calcium carbonate sample in Example 4 is mainly composed of vaterite and calcite. Figure 6 Spherical vaterite calcium carbonate and cubic calcite calcium carbonate can be seen; Figure 2 and Figure 3 In summary, the preparation of vaterite-type calcium carbonate from waste incineration fly ash is feasible and has high purity.

[0114] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for preparing vaterite-type calcium carbonate from waste incineration fly ash, characterized in that: The steps include: Using ammonium chloride as a leaching agent, the waste incineration fly ash is placed in a leaching agent solution for leaching, and then solid-liquid separation is performed to obtain a calcium solution; The calcium solution is reacted with an alkaline compound, sodium dodecylbenzenesulfonate and carbon dioxide under a pressure of 0.5-0.7 MPa and a temperature of 25-180° C. for 60-90 min to obtain the product; The calcium ion concentration in the calcium solution is 4000-8000 mg / L, and the mass ratio of the volume of the calcium solution to the sodium dodecylbenzenesulfonate is 50 mL: 0.05-0.15 g; During leaching, the liquid-to-solid ratio of the leaching agent solution to the waste incineration fly ash is 10-60 mL / g, and the concentration of the leaching agent solution is 1-5 mol / L; The immersion temperature is 25~85℃, and the immersion time is 20~140 min; The pH of the leaching system is 8~9.

2. The method according to claim 1, wherein: During leaching, the liquid-to-solid ratio is 30~50 mL / g.

3. The method according to claim 1, wherein: The concentration of the extractant solution is 1~2 mol / L.

4. The method according to claim 1, wherein: The extraction temperature is 25~45 ℃.

5. The method according to claim 1, wherein: The extraction time is 60~80 min.

6. The method according to claim 1, wherein: After leaching, the mixture is allowed to settle and then solid-liquid separation is performed to obtain calcium solution and ash.

7. The method according to claim 6, wherein: The ash is dried, ground, solidified and stabilized before being landfilled.

8. The method according to claim 1, wherein: The alkaline compound is ammonia water, caustic soda or triethanolamine.

9. The method according to claim 1, wherein: After the carbonation reaction, solid-liquid separation is carried out, and the separated solid is dried to obtain vaterite-type calcium carbonate.

10. The method according to claim 1, wherein: After the carbonation reaction, solid-liquid separation is performed, sodium sulfide is added to the separated liquid and mixed evenly to obtain a turbid liquid, the turbid liquid is filtered, and the filtered liquid is evaporated and crystallized for recovery.

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