Desulfurized ash resource utilization process

Abstract

The invention discloses a desulfurization ash resource utilization process which comprises the following steps: performing magnetic separation on desulfurization ash, and mixing with water to obtain first desulfurization ash slurry; adding a mixed solution of sodium acetate and hydrochloric acid, reacting to obtain second desulfurized fly ash slurry with acidic pH, and collecting CO2 generated in the reaction process; introducing air to oxidize the second desulfurized fly ash slurry at the temperature of 60-80 DEG C, and stirring to react to obtain third desulfurized fly ash slurry; performing solid-liquid separation on the third desulfurized fly ash slurry to obtain solid calcium sulfate and a mixed solution of calcium acetate and sodium chloride; adding sodium carbonate into the mixed solution of calcium acetate and sodium chloride, and performing solid-liquid separation after reaction to obtain solid calcium carbonate and the mixed solution of calcium acetate and sodium chloride; a mixed solution of calcium acetate and sodium chloride is collected and circularly used for preparing the first desulfurized fly ash slurry. According to the method, the resource utilization process of the desulfurized fly ash is optimized, generation of harmful gases such as sulfur dioxide and ammonia gas is avoided, and valuable calcium sulfate and calcium carbonate products are obtained.

Description

Technical Field

[0001] This invention relates to the field of desulfurization ash resource utilization technology, and more specifically, to a desulfurization ash resource utilization process. Background Technology

[0002] The steel industry generates a large amount of flue gas during processes such as coking and sintering. To control flue gas emissions, semi-dry / dry desulfurization technology is commonly used for sintering flue gas desulfurization. While this technology offers advantages such as low investment and high desulfurization efficiency, it also produces a large amount of desulfurization ash during the process. The main components of this ash are CaSO3·1 / 2H2O, CaSO4·2H2O, CaCO3, and unreacted Ca(OH)2. Due to the large annual production of desulfurization ash in steel plants, its disposal faces the following challenges: Firstly, desulfurization ash storage sites occupy large areas, and many temporary storage sites lack environmental protection measures to prevent scattering, runoff, and leakage, posing significant environmental risks. Secondly, the cost of desulfurization ash disposal is high, and the final disposal channels are unstable. In the long run, this will inevitably affect the normal operation of desulfurization equipment and may even hinder the company's green and sustainable development.

[0003] Significant progress has been made in flue gas desulfurization in the steel industry, but the generation and stockpiling of desulfurization ash continue to rise. Therefore, promoting theoretical and technological research on the resource utilization of sintering desulfurization ash has become an urgent issue for the industry. Currently, the comprehensive utilization of desulfurization ash has expanded to multiple fields, including cement retarder preparation, oxidation treatment, acidic soil improvement, slag powder additives, aerated concrete blocks, and filler materials. However, the unstable composition and properties of desulfurization ash, the potential for secondary pollution from heavy metals, and excessively high chloride ion content limit its large-scale industrial application.

[0004] Chinese Patent Application No. 201911010028.2 discloses a method for the resource utilization of desulfurization ash. The method includes the following steps: (1) Desulfurization ash is conveyed into a high-temperature reactor by pneumatic conveying, and then a reaction gas is introduced into the reactor. The reaction gas is a mixture of coal gas and air, and the oxygen content of the mixture after combustion is controlled at 5-10%. The desulfurization ash is subjected to an oxidation roasting reaction in the high-temperature reactor. The oxidation roasting temperature is controlled at 800-1000℃ until the calcium sulfite in the desulfurization ash is oxidized into calcium sulfate and the calcium carbonate is decomposed into calcium oxide; (2) The reaction product obtained in step (1) is sent into a reaction tank for water washing. The water / ash ratio is >20. After thorough stirring, calcium oxide solution and wet stone are obtained by solid-liquid separation; (3) The calcium hydroxide solution generated in step (2) is added to calcium oxide to prepare a desulfurization slurry that can be used for desulfurization in the slurry injection system; (4) The wet stone generated in step (2) is processed by dehydration and drying to obtain industrial stone. This technology uses oxygen to oxidize and roast desulfurization ash, ultimately yielding only industrial-grade crude silica products. However, it does not further recover and utilize sulfate ions from the desulfurization ash, resulting in a low recovery rate. Furthermore, the calcination process of this technology is energy-intensive and emits carbon dioxide, polluting the environment.

[0005] Chinese patent CN 104096707 B discloses a method for the resource utilization of semi-dry desulfurization ash, including the following steps: (1) oxidizing the semi-dry desulfurization ash to fully convert CaSO3 in it into CaSO4; (2) adding water to prepare the oxidized desulfurization ash into a desulfurization ash slurry, and then charging CO2 into the desulfurization ash slurry to fully react with Ca(OH)2 in the desulfurization ash slurry to generate CaCO3, wherein the molar ratio of the charged CO2 to Ca(OH)2 is 1.2~1.5:1; (3) adding NH4HCO3 to the slurry obtained in step (2) at a molar ratio of NH4HCO3 to calcium of 1.2~1.5:1, and adjusting the pH to 7~9 to fully convert the sulfur-containing calcium into calcium carbonate precipitate; (4) performing solid-liquid separation on the slurry obtained in step (3) to obtain solid calcium carbonate and ammonium sulfate solution, then calcining the solid calcium carbonate to obtain calcium oxide, and purifying the solid ammonium sulfate from the ammonium sulfate solution. This technology uses a method of first introducing carbon dioxide and then adding ammonium bicarbonate to obtain solid calcium carbonate and ammonium sulfate solution. However, the ammonia and carbon dioxide generated are not effectively treated or recovered, which may lead to the emission of these gases and have a negative impact on the environment. In addition, the ammonia and carbon dioxide generated in the process will increase raw material losses and waste treatment costs, thereby increasing the overall production cost.

[0006] Chinese patent CN115156240B discloses a method for the resource utilization of desulfurization ash, which includes the following steps: (1) mixing desulfurization ash with water and wet screening to obtain a first desulfurization ash slurry; (2) adding oxidant H2O2 to the first desulfurization ash slurry, and reacting to form a second desulfurization ash slurry; (3) adding excess ammonium carbonate to the second desulfurization ash slurry, and introducing a mixture of oxygen and carbon dioxide, and stopping the reaction when the pH value of the system drops to 7-8 to obtain a third desulfurization ash slurry, and collecting and recycling the ammonia and carbon dioxide produced by the decomposition of ammonium carbonate during this process; (4) performing solid-liquid separation on the third desulfurization ash slurry to obtain solid calcium carbonate and ammonium sulfate solution; (5) obtaining pure calcium carbonate product by drying and magnetic separation of solid calcium carbonate, and obtaining ammonium sulfate product by distillation purification of ammonium sulfate solution. This method uses the method of adding oxidant first, then adding ammonium carbonate, and finally introducing a mixture of oxygen and carbon dioxide to obtain solid calcium carbonate and ammonium sulfate solution. Although this technology enables the recycling of ammonia and carbon dioxide, other volatile organic compounds (VOCs) or other environmental pollutants may still be generated during the reaction process, requiring efficient treatment facilities to manage and control environmental risks, which increases the complexity of the process operation to some extent. Furthermore, this technology consumes a large amount of oxidants (such as hydrogen peroxide) and ammonium carbonate, significantly increasing raw material costs. Summary of the Invention

[0007] In view of the shortcomings of existing technologies, such as low desulfurization ash recovery efficiency, high processing cost, and difficulty in controlling ammonia composition, the purpose of this invention is to provide a desulfurization ash resource utilization process, which optimizes the desulfurization ash resource utilization process, avoids the generation of harmful gases such as sulfur dioxide and ammonia, and significantly reduces the oxidation cost of calcium sulfite, which is conducive to environmental protection and sustainable resource utilization.

[0008] This invention provides a process for the resource utilization of desulfurization ash, comprising the following steps:

[0009] S1, the desulfurization ash is subjected to magnetic separation, and then the magnetically separated desulfurization ash is mixed with water to obtain the first desulfurization ash slurry;

[0010] S2, a mixed solution of sodium acetate and hydrochloric acid is added to the first desulfurization slurry. After the reaction, a second desulfurization slurry with an acidic pH is obtained, and the CO2 generated during the reaction is collected.

[0011] S3, the second desulfurization slurry is oxidized by air at a temperature of 60~80℃, and the third desulfurization slurry is obtained after stirring and reaction;

[0012] S4, the third desulfurization slurry is subjected to solid-liquid separation to obtain solid calcium sulfate and a mixed solution of calcium acetate and sodium chloride;

[0013] S5, sodium carbonate is added to a mixed solution of calcium acetate and sodium chloride. After the reaction is complete, solid-liquid separation is performed to obtain solid calcium carbonate and a mixed solution of calcium acetate and sodium chloride.

[0014] S6, collect the mixed solution of calcium acetate and sodium chloride, and add hydrochloric acid to the mixed solution of sodium acetate and sodium chloride to replace water and return it to step S1 to mix with desulfurization ash to prepare the first desulfurization ash slurry.

[0015] Preferably, in step S1:

[0016] The desulfurization ash is selected from the desulfurization ash generated by semi-dry / dry desulfurization technology for sintering flue gas in steel production.

[0017] The magnetic field strength for the magnetic separation process is 10000~20000 Gs;

[0018] The solid-liquid mass ratio of the first desulfurization slurry is 1:(4~9).

[0019] Preferably, the desulfurization ash contains 53-57% CaSO3, 19-23% CaCO3, and 6-8% Ca(OH)2.

[0020] In step S1, controlling the magnetic field strength within the range of 10,000 to 20,000 Gs ensures sufficient magnetic field strength to remove the main metallic slag from the desulfurization ash, thereby improving the purity and whiteness of the subsequent finished calcium carbonate product. Furthermore, dissolving the magnetically separated desulfurization ash in water forms the first desulfurization ash slurry. Controlling the solid-liquid mass ratio of the first desulfurization ash slurry within the range of 1:(4~9) helps to ensure thorough mixing with subsequent reaction raw materials and facilitates subsequent air oxidation of calcium sulfite in the slurry. If the solid-liquid mass ratio of the first desulfurization ash slurry is lower than 1:9, it will reduce the single-batch processing capacity and increase the subsequent separation load. If the solid-liquid mass ratio of the first desulfurization ash slurry is higher than 1:4, the slurry viscosity will significantly increase, the gas-liquid contact area will decrease, and the mass transfer resistance will increase, leading to a significant decrease in calcium sulfite oxidation efficiency.

[0021] Preferably, in step S2:

[0022] In the mixed solution of sodium acetate and hydrochloric acid, the molar ratio of sodium acetate to hydrochloric acid is 1:1;

[0023] The volume ratio of the sodium acetate and hydrochloric acid mixture to the first desulfurization slurry is 1:1.3 to 1:2.5.

[0024] Preferably, in step S2, the pH of the second desulfurization slurry is 4.0 to 5.0.

[0025] In step S2, sodium acetate and hydrochloric acid in the mixed solution of sodium acetate and hydrochloric acid are added to the first desulfurization slurry in the same molar ratio, and the amount of both added is controlled within the above volume ratio range. This allows the calcium carbonate and Ca(OH)2 in the slurry to react completely. After the reaction is complete, the pH value of the slurry reaches 4.0 to 5.0. At the same time, calcium sulfite does not decompose to produce SO2, and the CO2 produced by the reaction enters the gas collection device.

[0026] The specific reaction in step S2 is as follows:

[0027] CH3COONa + HCl = CH3COOH + NaCl

[0028] 2CH3COOH+CaCO3=Ca(CH3COO)2+H2O+CO2↑

[0029] 2CH3COOH+Ca(OH)2=Ca(CH3COO)2+2H2O

[0030] Preferably, in step S3:

[0031] The oxidation time is 2-4 hours, and the stirring speed is 500-1000 r / min;

[0032] The air is dispersed and bubbled through the gas plate and enters the second desulfurization slurry, and the air flow rate is 50-200 L / h.

[0033] In step S3, the air dispersed and bubbled into the slurry through the air plate helps to increase the contact area between the air and the second desulfurization slurry, thereby facilitating the oxidation of calcium sulfite. During the air oxidation process, if the oxidation temperature is below 60°C, the oxidation rate and the final oxidation rate will decrease significantly. If the oxidation temperature is above 80°C, the oxidation rate will not increase significantly, but the energy consumption cost will increase substantially. If the oxidation time is less than 2 hours, the oxidation reaction will be insufficient. If the oxidation time is more than 4 hours, the oxidation rate will not increase significantly, and the time and energy consumption cost will increase.

[0034] The specific reaction in step S3 is as follows:

[0035] 2CaSO3 + O2 = 2CaSO4

[0036] Preferably, in step S4:

[0037] The solid-liquid separation is performed using a vacuum filtration device;

[0038] The purity of the solid calcium sulfate is ≥95%.

[0039] Preferably, in step S5:

[0040] Sodium carbonate is added to a mixed solution of calcium acetate and sodium chloride at a molar ratio of sodium carbonate to Ca ions of 1:1.

[0041] The purity of the solid calcium carbonate is ≥98%, and the whiteness is ≥89.

[0042] The specific reaction in step S5 is as follows:

[0043] Ca(CH3COO)2+Na2CO3=CaCO3↓+2CH3COONa

[0044] In step S5, sodium carbonate is added to a mixed solution of calcium acetate and sodium chloride, and the amount of sodium carbonate added is controlled so that calcium ions and carbonate ions react fully to form calcium carbonate. After the reaction is completed, high-purity and high-whiteness solid calcium carbonate is obtained by solid-liquid separation.

[0045] Preferably, in step S6, hydrochloric acid is added to the mixed solution of calcium acetate and sodium chloride at a molar ratio of hydrochloric acid to acetate of 1:1.

[0046] In step S6, the mixed solution of sodium acetate and sodium chloride can be collected, added with hydrochloric acid, and repeatedly added to the reaction system for recycling. After a certain number of cycles, the sodium chloride in the solution can be evaporated and crystallized out for continued recycling. This can improve the utilization rate of raw materials in the reaction system, reduce the consumption of raw materials, and save costs.

[0047] In the method of this invention, the desulfurization ash produced by the semi-dry / dry desulfurization technology in steel production is prone to being mixed with metal slags such as iron, iron oxide, and iron(III) oxide, affecting the purity and quality grade of the final calcium sulfate and calcium carbonate products. If the desulfurization ash is directly prepared into a slurry for reaction, the unreacted metal slag will remain in the calcium sulfate product, reducing the purity and quality grade of the calcium sulfate product. In addition, the reacted metal slag will generate non-ferrous metal ions that enter the subsequent mixed solution of calcium acetate and sodium chloride, thereby reducing the purity and whiteness of the finished calcium carbonate product. Therefore, in step S1 of this invention, the desulfurization ash is first subjected to magnetic separation to remove the metal slag with magnetic properties, which can remove the main metal slag in the desulfurization ash, thereby improving the purity of the finished calcium sulfate product and the purity and whiteness of the calcium carbonate product.

[0048] Furthermore, the desulfurization ash generated during the semi-dry / dry desulfurization process mainly consists of CaSO3, CaCO3, and unreacted Ca(OH)2. The presence of calcium carbonate and Ca(OH)2 results in a high pH in the desulfurization ash slurry, affecting the subsequent reaction of calcium sulfite with oxygen in the air. Therefore, this invention innovatively employs the following process: First, the magnetically separated desulfurization ash is mixed with water to obtain a first desulfurization ash slurry. A mixed solution of sodium acetate and hydrochloric acid is added to the first desulfurization ash slurry to react and adjust the pH, allowing CaCO3 and Ca(OH)2 to react and generate free calcium ions without producing sulfur dioxide. The generated CO2 is collected and treated as a byproduct. At this point, the first desulfurization ash slurry only contains solid CaSO3 and CaSO4, reducing the impact of CaCO3 on the subsequent oxidation of calcium sulfite, thereby improving the purity of the finished calcium sulfate product. The second desulfurization slurry is oxidized by air at a certain temperature. After stirring and reacting, solid-liquid separation is obtained to get solid calcium sulfate and a mixed solution of calcium acetate and sodium chloride. Sodium carbonate is added to the mixed solution of calcium acetate and sodium chloride to obtain solid calcium carbonate and a mixed solution of sodium acetate and sodium chloride. The mixed solution of sodium acetate and sodium chloride can be collected and repeatedly added to the reaction system for recycling. After a certain number of cycles, the sodium chloride in the solution is evaporated and crystallized out, and then it can be recycled again. This can improve the raw material utilization rate of the reaction system, reduce raw material consumption, and save costs.

[0049] The desulfurization ash resource utilization process provided by this invention has the following beneficial effects:

[0050] 1. This invention removes metal slag from desulfurization ash through magnetic separation, effectively reducing the impact of metal impurities on calcium sulfate and calcium carbonate products, thereby improving the purity and recovery rate of calcium sulfate products, as well as the purity and whiteness of calcium carbonate products.

[0051] 2. This invention uses a mixed solution of sodium acetate and hydrochloric acid to adjust the pH value of the first desulfurization slurry, while removing solid CaCO3 and Ca(OH)2. During the oxidation process, air is dispersed and bubbled into the slurry through the gas plate, thereby improving the oxidation efficiency of calcium sulfite.

[0052] 3. This invention optimizes the process of desulfurization ash resource utilization, avoids the generation of harmful gases such as sulfur dioxide and ammonia, and significantly reduces the oxidation cost of calcium sulfite, which is conducive to environmental protection and sustainable resource utilization.

[0053] 4. This invention integrates the processes of magnetic separation, chemical conditioning and reaction treatment, which improves production efficiency and reduces operational complexity. By collecting and recycling the mixed solution of sodium acetate and sodium chloride, the consumption of raw materials is reduced, the utilization rate of raw materials in the reaction system is improved, and production costs are saved.

[0054] 5. The process of this invention is simple and easy to operate, with high resource utilization, producing high value-added products such as calcium sulfate and calcium carbonate, resulting in high economic benefits and easy industrial application. Attached Figure Description

[0055] Figure 1 This is a schematic diagram of the process flow for the resource utilization of desulfurization ash in this invention;

[0056] Figure 2 This is the XRD pattern of calcium sulfate prepared in Example 1 of this invention;

[0057] Figure 3 This is the XRD pattern of calcium carbonate prepared in Example 1 of this invention;

[0058] Figure 4 Here is a SEM image of the calcium sulfate prepared in Example 1 of this invention;

[0059] Figure 5 This is a SEM image of the calcium carbonate prepared in Example 1 of this invention. Detailed Implementation

[0060] To better understand the above-described technical solutions of the present invention, the technical solutions of the present invention are further described below in conjunction with the accompanying drawings and embodiments. The following embodiments are merely illustrative of one aspect of the present invention and are not intended to limit the scope of the present invention. The present invention can be employed under various conditions as long as it does not depart from the spirit of the present invention and achieves its objectives.

[0061] The desulfurization ash in the following examples is selected from the desulfurization ash produced by the semi-dry / dry desulfurization technology of Nanjing Meishan Iron & Steel Co., Ltd. of Baowu Group for desulfurization of sintering flue gas in steel production. The content of CaSO3 is 53-57%, the content of CaCO3 is 19-23%, and the content of Ca(OH)2 is 6-8%.

[0062] Example 1

[0063] Combination Figure 1 As shown, the desulfurization ash resource utilization process in this embodiment is as follows:

[0064] (1) Take 100g of desulfurization ash and perform magnetic separation on the desulfurization ash under a magnetic field strength of 12000Gs to remove the metal slag with magnetic materials;

[0065] (2) The desulfurized ash after magnetic separation is mixed with water to obtain the first desulfurized ash slurry with a solid-liquid mass ratio of 1:9;

[0066] (3) Add a mixed solution of sodium acetate and hydrochloric acid to the first desulfurization slurry, wherein both sodium acetate and hydrochloric acid are 1 mol and the volume ratio of the mixed solution of sodium acetate and hydrochloric acid to the first desulfurization slurry is 1:2.1. This amount can make the CaCO3 and Ca(OH)2 in the desulfurization ash react completely. The CO2 produced by the reaction enters the gas collection device. After the reaction, the second desulfurization slurry with a pH value of 4.82 is obtained.

[0067] (4) The second desulfurization slurry is oxidized by passing air through it at 60°C. The air is dispersed and bubbled into the second desulfurization slurry through the gas plate stone. The air flow rate is 60L / h. The reaction is stirred for 2h at a stirring speed of 500r / min. The reaction yields the third desulfurization slurry. In this process, calcium sulfite reacts with oxygen in the air and is oxidized to produce calcium sulfate.

[0068] (5) The third desulfurization slurry after the reaction is separated into solid and liquid by a vacuum filter to obtain a mixed solution of solid calcium sulfate and calcium acetate and sodium chloride;

[0069] (6) Sodium carbonate is added to a mixed solution of calcium acetate and sodium chloride at a molar ratio of sodium carbonate to Ca ions of 1:1. After the reaction is completed, a vacuum filter is used to separate the solid and liquid to obtain solid calcium carbonate and a mixed solution of sodium acetate and sodium chloride.

[0070] (7) The mixed solution of sodium acetate and sodium chloride can be recycled for step (2).

[0071] In this embodiment, the final product yielded 56.5g of calcium sulfate with a purity of 95% and 45.1g of calcium carbonate with a purity of 98% and a whiteness of 93.2.

[0072] Figure 2 This is the XRD pattern of the calcium sulfate product prepared in this embodiment. Figure 4 The image shows the SEM image of the calcium sulfate product. As can be seen from the image, the diffraction peaks of the oxidized product calcium sulfate show a good correspondence with the standard diffraction peaks of calcium sulfate dihydrate (CaSO4·2H2O, PDF#70-0982), indicating that calcium sulfite is mainly converted into the calcium sulfate dihydrate phase after oxidation. Most of the calcium sulfate particles exhibit an irregular short columnar morphology, with varying sizes ranging from 5 to 10 μm. There are also some irregular calcium sulfate particles, which are relatively dispersed.

[0073] Figure 3 The image shown is the XRD pattern of the calcium carbonate product prepared in this embodiment. Figure 5 The image shows the SEM image of the calcium carbonate product. As can be seen from the image, the calcium carbonate product is a stable calcite crystal form. No obvious impurity peaks are found in the spectrum, indicating that the calcium carbonate product has high purity, an extremely smooth surface, and a uniform particle size distribution.

[0074] Example 2

[0075] Combination Figure 1 As shown, the desulfurization ash resource utilization process in this embodiment is as follows:

[0076] (1) Take 100g of desulfurization ash and perform magnetic separation on the desulfurization ash under a magnetic field strength of 12000Gs to remove the metal slag with magnetic materials;

[0077] (2) Add hydrochloric acid to the mixed solution of sodium acetate and sodium chloride recovered in step (7) at a molar ratio of 1:1, and then mix it with the desulfurized ash after magnetic separation to obtain the first desulfurized ash slurry with a solid-liquid mass ratio of 1:9.

[0078] (3) Add a mixed solution of sodium acetate and hydrochloric acid to the first desulfurization slurry, wherein both sodium acetate and hydrochloric acid are 1 mol and the volume ratio of the mixed solution of sodium acetate and hydrochloric acid to the first desulfurization slurry is 1:2.2. This amount can make the CaCO3 and Ca(OH)2 in the desulfurization ash react completely. The CO2 produced by the reaction enters the gas collection device. After the reaction, the first desulfurization slurry is used to obtain the second desulfurization slurry with a pH value of 4.80.

[0079] (4) The second desulfurization slurry is oxidized by passing air through it at 60°C. The air is dispersed and bubbled into the second desulfurization slurry through the gas plate stone. The air flow rate is 60L / h. The reaction is stirred for 2h at a stirring speed of 500r / min. The reaction yields the third desulfurization slurry. In this process, calcium sulfite reacts with oxygen in the air and is oxidized to produce calcium sulfate.

[0080] (5) The third desulfurization slurry after the reaction is separated into solid and liquid by a vacuum filter to obtain a mixed solution of solid calcium sulfate and calcium acetate and sodium chloride;

[0081] (6) Sodium carbonate is added to a mixed solution of calcium acetate and sodium chloride at a molar ratio of sodium carbonate to Ca ions of 1:1. After the reaction is completed, a vacuum filter is used to separate the solid and liquid to obtain solid calcium carbonate and a mixed solution of sodium acetate and sodium chloride.

[0082] (7) The mixed solution of sodium acetate and sodium chloride can be recycled for step (2).

[0083] In this embodiment, the final product yielded 55.1g of calcium sulfate with a purity of 96% and 46.8g of calcium carbonate with a purity of 98% and a whiteness of 89.5.

[0084] Example 3

[0085] Combination Figure 1 As shown, the desulfurization ash resource utilization process in this embodiment is as follows:

[0086] (1) Take 100g of desulfurization ash and perform magnetic separation on the desulfurization ash under a magnetic field strength of 12000Gs to remove the metal slag with magnetic materials;

[0087] (2) The desulfurized ash after magnetic separation is mixed with water to obtain a first desulfurized ash slurry with a solid-liquid mass ratio of 1:6;

[0088] (3) Add a mixed solution of sodium acetate and hydrochloric acid to the first desulfurization slurry, wherein both sodium acetate and hydrochloric acid are 1 mol and the volume ratio of the mixed solution of sodium acetate and hydrochloric acid to the first desulfurization slurry is 1:1.9. This amount can make the CaCO3 and Ca(OH)2 in the desulfurization ash react completely. The CO2 produced by the reaction enters the gas collection device. After the reaction, the second desulfurization slurry with a pH value of 4.61 is obtained.

[0089] (4) The second desulfurization slurry is oxidized by passing air through it at 60°C. The air is dispersed and bubbled into the second desulfurization slurry through the gas plate stone. The air flow rate is 90L / h. The reaction is stirred for 2h at a stirring speed of 500r / min. The reaction yields the third desulfurization slurry. In this process, calcium sulfite reacts with oxygen in the air and is oxidized to produce calcium sulfate.

[0090] (5) The third desulfurization slurry after the reaction is separated into solid and liquid by a vacuum filter to obtain a mixed solution of solid calcium sulfate and calcium acetate and sodium chloride;

[0091] (6) Sodium carbonate is added to a mixed solution of calcium acetate and sodium chloride at a molar ratio of sodium carbonate to Ca ions of 1:1. After the reaction is completed, a vacuum filter is used to separate the solid and liquid to obtain solid calcium carbonate and a mixed solution of sodium acetate and sodium chloride.

[0092] (7) The mixed solution of sodium acetate and sodium chloride can be recycled for step (2).

[0093] In this embodiment, the final product yielded 52.9g of calcium sulfate with a purity of 96% and 48.6g of calcium carbonate with a purity of 98% and a whiteness of 90.4.

[0094] Example 4

[0095] Combination Figure 1 As shown, the desulfurization ash resource utilization process in this embodiment is as follows:

[0096] (1) Take 100g of desulfurization ash and perform magnetic separation on the desulfurization ash under a magnetic field strength of 12000Gs to remove the metal slag with magnetic materials;

[0097] (2) The desulfurized ash after magnetic separation is mixed with water to obtain a first desulfurized ash slurry with a solid-liquid mass ratio of 1:4;

[0098] (3) Add a mixed solution of sodium acetate and hydrochloric acid to the first desulfurization slurry, wherein both sodium acetate and hydrochloric acid are 1 mol and the volume ratio of the mixed solution of sodium acetate and hydrochloric acid to the first desulfurization slurry is 1:1.6. This amount can make the CaCO3 and Ca(OH)2 in the desulfurization ash react completely. The CO2 produced by the reaction enters the gas collection device. After the reaction, the second desulfurization slurry with a pH value of 4.48 is obtained.

[0099] (4) The second desulfurization slurry is oxidized by passing air through it at 60°C. The air is dispersed and bubbled into the second desulfurization slurry through the gas plate stone. The air flow rate is 90L / h. The reaction is stirred for 2h at a stirring speed of 500r / min. The reaction yields the third desulfurization slurry. In this process, calcium sulfite reacts with oxygen in the air and is oxidized to produce calcium sulfate.

[0100] (5) The third desulfurization slurry after the reaction is separated into solid and liquid by a vacuum filter to obtain a mixed solution of solid calcium sulfate and calcium acetate and sodium chloride;

[0101] (6) Sodium carbonate is added to a mixed solution of calcium acetate and sodium chloride at a molar ratio of sodium carbonate to Ca ions of 1:1. After the reaction is completed, a vacuum filter is used to separate the solid and liquid to obtain solid calcium carbonate and a mixed solution of sodium acetate and sodium chloride.

[0102] (7) The mixed solution of sodium acetate and sodium chloride can be recycled for step (2).

[0103] In this embodiment, the final product yielded 57.6g of calcium sulfate with a purity of 96% and 48.1g of calcium carbonate with a purity of 98% and a whiteness of 90.3.

[0104] Example 5

[0105] Combination Figure 1 As shown, the desulfurization ash resource utilization process in this embodiment is as follows:

[0106] (1) Take 100g of desulfurization ash and perform magnetic separation on the desulfurization ash under a magnetic field strength of 20000Gs to remove the metal slag with magnetic materials;

[0107] (2) The desulfurized ash after magnetic separation is mixed with water to obtain a first desulfurized ash slurry with a solid-liquid mass ratio of 1:4;

[0108] (3) Add a mixed solution of sodium acetate and hydrochloric acid to the first desulfurization slurry, wherein both sodium acetate and hydrochloric acid are 1 mol and the volume ratio of the mixed solution of sodium acetate and hydrochloric acid to the first desulfurization slurry is 1:1.3. This amount can make the CaCO3 and Ca(OH)2 in the desulfurization ash react completely. The CO2 produced by the reaction enters the gas collection device. After the reaction, a second desulfurization slurry with a pH value of 5.0 is obtained.

[0109] (4) The second desulfurization slurry is oxidized by passing air through it at 80°C. The air is dispersed and bubbled into the second desulfurization slurry through the gas plate. The air flow rate is 50L / h. The reaction is stirred for 4h at a stirring speed of 1000r / min. The reaction yields the third desulfurization slurry. In this process, calcium sulfite reacts with oxygen in the air and is oxidized to produce calcium sulfate.

[0110] (5) The third desulfurization slurry after the reaction is separated into solid and liquid by a vacuum filter to obtain a mixed solution of solid calcium sulfate and calcium acetate and sodium chloride;

[0111] (6) Sodium carbonate is added to a mixed solution of calcium acetate and sodium chloride at a molar ratio of sodium carbonate to Ca ions of 1:1. After the reaction is completed, a vacuum filter is used to separate the solid and liquid to obtain solid calcium carbonate and a mixed solution of sodium acetate and sodium chloride.

[0112] (7) The mixed solution of sodium acetate and sodium chloride can be recycled for step (2).

[0113] In this embodiment, the final product yielded 57.4g of calcium sulfate with a purity of 96% and 48.9g of calcium carbonate with a purity of 98% and a whiteness of 90.2.

[0114] Example 6

[0115] Combination Figure 1 As shown, the desulfurization ash resource utilization process in this embodiment is as follows:

[0116] (1) Take 100g of desulfurization ash and perform magnetic separation on the desulfurization ash under a magnetic field strength of 10000Gs to remove the metal slag with magnetic materials.

[0117] (2) The desulfurized ash after magnetic separation is mixed with water to obtain the first desulfurized ash slurry with a solid-liquid mass ratio of 1:9;

[0118] (3) Add a mixed solution of sodium acetate and hydrochloric acid to the first desulfurization slurry, wherein both sodium acetate and hydrochloric acid are 1 mol and the volume ratio of the mixed solution of sodium acetate and hydrochloric acid to the first desulfurization slurry is 1:2.5. This amount can make the CaCO3 and Ca(OH)2 in the desulfurization ash react completely. The CO2 produced by the reaction enters the gas collection device. After the reaction, the second desulfurization slurry with a pH value of 4.0 is obtained.

[0119] (4) The second desulfurization slurry is oxidized by passing air through it at 70°C. The air is dispersed and bubbled into the second desulfurization slurry through the gas plate. The air flow rate is 200 L / h. The reaction is stirred for 3 hours at a stirring speed of 500 r / min. The reaction yields the third desulfurization slurry. In this process, calcium sulfite reacts with oxygen in the air and is oxidized to produce calcium sulfate.

[0120] (5) The third desulfurization slurry after the reaction is separated into solid and liquid by a vacuum filter to obtain a mixed solution of solid calcium sulfate and calcium acetate and sodium chloride;

[0121] (6) Sodium carbonate is added to a mixed solution of calcium acetate and sodium chloride at a molar ratio of sodium carbonate to Ca ions of 1:1. After the reaction is completed, a vacuum filter is used to separate the solid and liquid to obtain solid calcium carbonate and a mixed solution of sodium acetate and sodium chloride.

[0122] (7) The mixed solution of sodium acetate and sodium chloride can be recycled for step (2).

[0123] In this embodiment, the final product yielded 53.4 g of calcium sulfate with a purity of 95% and 47.1 g of calcium carbonate with a purity of 98% and a whiteness of 89.2.

[0124] Comparative Example 1

[0125] This comparative example uses the method of Example 1, the difference being that in step (1), the desulfurization ash was not magnetically separated in a magnetic field; the final product obtained was 53.6g of calcium sulfate with a purity of 89%; and 46.1g of calcium carbonate with a purity of 94% and a whiteness of 76.9.

[0126] Comparative Example 2

[0127] This comparative example uses the method of Example 1, the difference being that in step (3), the mixed solution of sodium acetate and sodium chloride contains 0.5 mol of sodium acetate and 0.8 mol of sodium chloride, respectively. After the first desulfurization slurry is added and reacted completely, a second desulfurization slurry with a pH of 5.21 is obtained. The other conditions are the same, and 31.4 g of calcium sulfate is finally obtained. Calcium sulfite is not completely oxidized. The calcium carbonate product is 30.1 g, with a whiteness of 72.7.

[0128] Comparative Example 3

[0129] This comparative example uses the method of Example 1, the difference being that in step (4), the oxidation temperature is 50℃, and the other conditions are the same, ultimately yielding 29.8g of calcium sulfate, while calcium sulfite was not completely oxidized. The calcium carbonate product is 45.7g, with a whiteness of 65.4.

[0130] Comparative Example 4

[0131] This comparative example uses the method of Example 1, except that in step (4), the stirring reaction time is 1.5 h, and the other conditions are the same. 39.8 g of calcium sulfate was finally obtained, and the calcium sulfite was not completely oxidized. 46.1 g of calcium carbonate was produced, with a whiteness of 63.7.

[0132] Those skilled in the art should recognize that the above embodiments are merely illustrative of the present invention and are not intended to limit the present invention. Any variations or modifications to the above embodiments that are within the spirit and essence of the present invention will fall within the scope of the claims of the present invention.

Claims

1. A process for the resource utilization of desulfurization ash, characterized in that: Includes the following steps: S1, the desulfurization ash is subjected to magnetic separation, and then the magnetically separated desulfurization ash is mixed with water to obtain the first desulfurization ash slurry; S2, a mixed solution of sodium acetate and hydrochloric acid is added to the first desulfurization slurry. After the reaction, a second desulfurization slurry with an acidic pH is obtained, and the CO2 generated during the reaction is collected. S3, the second desulfurization slurry is oxidized by air at a temperature of 60~80℃, and the third desulfurization slurry is obtained after stirring and reaction; S4, the third desulfurization slurry is subjected to solid-liquid separation to obtain solid calcium sulfate and a mixed solution of calcium acetate and sodium chloride; S5, sodium carbonate is added to a mixed solution of calcium acetate and sodium chloride. After the reaction is complete, solid-liquid separation is performed to obtain solid calcium carbonate and a mixed solution of calcium acetate and sodium chloride. S6, collect the mixed solution of calcium acetate and sodium chloride, and add hydrochloric acid to the mixed solution of sodium acetate and sodium chloride to replace water and return it to step S1 to mix with desulfurization ash to prepare the first desulfurization ash slurry.

2. The desulfurization ash resource utilization process according to claim 1, characterized in that: In step S1: The desulfurization ash is selected from the desulfurization ash generated by semi-dry / dry desulfurization technology for sintering flue gas in steel production. The magnetic field strength for the magnetic separation process is 10000~20000 Gs; The solid-liquid mass ratio of the first desulfurization slurry is 1:(4~9).

3. The desulfurization ash resource utilization process according to claim 2, characterized in that: The desulfurization ash contains 53-57% CaSO3, 19-23% CaCO3, and 6-8% Ca(OH)2.

4. The desulfurization ash resource utilization process according to claim 1, characterized in that: In step S2: In the mixed solution of sodium acetate and hydrochloric acid, the molar ratio of sodium acetate to hydrochloric acid is 1:1; The volume ratio of the sodium acetate and hydrochloric acid mixture to the first desulfurization slurry is 1:1.3 to 1:2.

5.

5. The desulfurization ash resource utilization process according to claim 1, characterized in that: In step S2, the pH of the second desulfurization slurry is 4.0 to 5.

0.

6. The desulfurization ash resource utilization process according to claim 1, characterized in that: In step S3: The oxidation time is 2-4 hours, and the stirring speed is 500-1000 r / min; The air is dispersed and bubbled through the gas plate and enters the second desulfurization slurry, and the air flow rate is 50-200 L / h.

7. The desulfurization ash resource utilization process according to claim 1, characterized in that: In step S4: The solid-liquid separation is performed using a vacuum filtration device; The purity of the solid calcium sulfate is ≥95%.

8. The desulfurization ash resource utilization process according to claim 1, characterized in that: In step S5: Sodium carbonate is added to a mixed solution of calcium acetate and sodium chloride at a molar ratio of sodium carbonate to Ca ions of 1:

1. The purity of the solid calcium carbonate is ≥98%, and the whiteness is ≥89.

9. The desulfurization ash resource utilization process according to claim 1, characterized in that: In step S6, hydrochloric acid is added to the mixed solution of calcium acetate and sodium chloride at a molar ratio of hydrochloric acid to acetate of 1:1.

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