Modified carbide slag, and preparation method and application thereof

Abstract

The application belongs to the technical field of atmospheric pollution purification, and discloses a modified carbide slag and a preparation method and application thereof. The preparation method comprises the following steps: (1) washing the carbide slag with distilled water, drying, and grinding; (2) placing the carbide slag treated in the step (1) in a metal solution to perform ultrasonic immersion, so as to obtain a carbide slag slurry; (3) placing the carbide slag slurry treated in the step (2) in a pre-freezing device to perform pre-freezing, then placing the carbide slag slurry in a vacuum drying machine to perform freeze-drying, grinding, and screening, so as to obtain the modified carbide slag. It can be seen that the modified carbide slag decarbonizer is prepared by using the industrial solid waste carbide slag as a raw material, adopting ultrasonic immersion combined with freeze-drying method, and the method is simple and easy to operate. The catalyst has low cost, realizes the sustainable development goal of waste treatment by waste, is easy to popularize and use, and has high application value.

Description

Technical Field

[0001] This invention belongs to the field of air pollution purification technology, and more specifically relates to a modified calcium carbide slag, its preparation method, and its application. Background Technology

[0002] With the increasingly evident trend of global warming, the greenhouse effect has garnered growing attention. Greenhouse gas emissions are a major cause of global warming, and human activities primarily emit greenhouse gases such as CO2 from the combustion of fossil fuels (coal, oil, and natural gas). Reducing CO2 emissions has become a top priority in mitigating the environmental damage caused by the greenhouse effect.

[0003] While CO2 emission reduction technologies are rapidly evolving, few are readily applicable to actual production and operation; most remain in the development stage. Alkali metal-based dry CO2 removal technology, with its advantages of low raw material costs, low reaction energy consumption, high recycling efficiency, no equipment corrosion, no secondary pollution, and no need to modify existing power plant equipment, has become a current research hotspot.

[0004] Calcium carbide slag is a waste residue generated from the production of polyvinyl chloride (PVC) in chlor-alkali plants. In fact, calcium carbide slag has the following advantages: small particle size, low hardness resulting in low pretreatment costs, simple composition, and a Ca(OH)2 content of over 95%. Calcium carbide slag can not only serve as an excellent raw material for CO2 removal but can also be used to produce high-value-added CaCO3 products.

[0005] Currently, the dry decarbonization of calcium carbide slag mainly adopts calcium recycling technology. The basic principle of this technology is that in a mineralization furnace at a temperature of 650-700℃, CaO reacts with CO2 in the flue gas to achieve CO2 fixation. The generated CaCO3 enters a calcination furnace at a temperature >900℃ for thermal decomposition. The required heat is provided by fuel in the O2 / CO2 ratio. After condensation, the tail gas becomes an airflow with a CO2 content higher than 95%. The CaO generated by calcination continues to enter the mineralization furnace to absorb CO2. This reaction is repeated in cycles. Once CaO is deactivated, it is discharged, and the calcium-based absorbent is replenished simultaneously.

[0006] Although the use of calcium carbide slag as a low-cost adsorbent for high-temperature CO2 capture has been widely studied, excessively high calcination temperatures often lead to a significant decrease in CO2 capture performance after sintering, limiting its application in calcium recycling technology. Furthermore, this method suffers from high operating costs, complex processes, and large project investments.

[0007] Therefore, how to provide a modified carbide slag and apply it to dry flue gas decarbonization to achieve a CO2 removal technology with high economic benefits and low energy consumption is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0008] To overcome the shortcomings and deficiencies of existing technologies, this invention provides a modified carbide slag, its preparation method, and its application. It has a large adsorption capacity, good decarbonization effect, low cost, and is simple and easy to operate, achieving the sustainable development goal of treating waste with waste and is easy to promote and use.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] A method for preparing modified carbide slag includes the following steps:

[0011] (1) Wash the carbide slag with distilled water, dry it, and grind it;

[0012] (2) Place the carbide slag treated in step (1) into a metal solution for ultrasonic impregnation to obtain carbide slag slurry;

[0013] (3) The carbide slag slurry treated in step (2) is placed in a pre-freezing device for pre-freezing, and then placed in a vacuum dryer for freeze drying, grinding, and sieving to obtain modified carbide slag.

[0014] Preferably, in step (2), the metal solution is one or more of the following: an alkaline solution and a metal ion solution, mixed in any proportion.

[0015] Preferably, the alkaline solution is one of KOH solution, KHCO3 solution, K2CO3 solution, and NaOH solution; the metal ion solution is one or more of copper, iron, zinc, manganese, cobalt, silver, sodium, calcium, chromium, cerium, and lanthanum.

[0016] The beneficial effect of the above technical solution is that it improves the decarburization efficiency of the material by loading metal ions.

[0017] Preferably, in step (2), the metal loading of the metal solution is 1~50wt%, and the solid-liquid ratio is 1:1~20.

[0018] The beneficial effects of the above technical solution are: optimizing the metal loading and solid-liquid ratio, and screening out the optimal metal loading and solid-liquid ratio for CO2 removal.

[0019] Preferably, in step (2), the immersion temperature is 10~50℃, the ultrasonic power is 200W~800W, the ultrasonic frequency is 20~60KHz, and the immersion time is 0.5~8h.

[0020] The beneficial effects of the above technical solution are: ultrasound improves the degree of metal dispersion and increases loading efficiency.

[0021] Preferably, in step (3), the pre-freezing temperature is -200~0℃ and the pre-freezing time is 0.5min~24h.

[0022] The beneficial effects of the above technical solution are: optimizing the pre-freezing temperature and time, adjusting the size of the generated ice crystals, and selecting the best pore structure and average pore size of the material.

[0023] Preferably, in step (3), the freeze-drying temperature is -120~-15℃, the vacuum degree is ≤10Pa, and the drying time is 5h~72h.

[0024] The beneficial effects of the above technical solution are: to completely sublimate the ice crystals generated by the material, to produce a directional pore structure, and to ensure that the material is fully dried.

[0025] The present invention also provides a modified carbide slag prepared according to the above method.

[0026] The present invention also provides an application of the above-mentioned modified carbide slag, wherein the modified carbide slag is used in dry flue gas decarbonization.

[0027] Preferably, the modified calcium carbide slag is applied to dry flue gas decarbonization. The application process is as follows: 1~30g of modified calcium carbide slag is added to the flue gas decarbonization equipment, the temperature is set to 0~900℃, the flue gas flow rate is 50~700mL / min, and the CO2 concentration is 1~15%, and decarbonization is carried out.

[0028] As can be seen from the above technical solution, compared with the prior art, the present invention provides a modified carbide slag, its preparation method and application, which has the following beneficial effects:

[0029] 1. The raw material of this invention is an inexpensive and readily available calcium-based material, and the preparation method is simple. Freeze-drying can better maintain the state and activity of carbide slag before freezing, and at the same time can protect the activity of the loaded metal to the greatest extent. After simple metal modification, CO2 removal can be achieved.

[0030] 2. Calcium-based decarburizing materials with high-strength pores and ice crystal morphology were prepared using a freeze-drying process. By changing the preparation conditions, the size and direction of ice crystal growth can be controlled, thereby adjusting the pore morphology, porosity, and pore size of the material to prepare decarburizing agents with directional pore structures.

[0031] 3. This invention uses industrial solid waste carbide slag as raw material and prepares a modified carbide slag decarbonizing agent by ultrasonic impregnation combined with freeze drying. The resulting modified carbide slag has a large adsorption capacity, good decarbonization effect, low cost, and is simple and easy to operate, thus achieving the sustainable development goal of treating waste with waste and is easy to promote and use. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0033] Figure 1 a and b are SEM images of the calcium carbide slag in Comparative Example 1 at different magnification ratios.

[0034] Figure 1 c and d are SEM images of the modified carbide slag of Comparative Example 2 at different magnification ratios.

[0035] Figure 1 e and f are SEM images of the modified carbide slag in Example 1 at different magnification ratios.

[0036] Figure 2 a, b, and c are EDS mapping analysis diagrams of the carbide slag obtained in Comparative Example 1, Comparative Example 2, and Example 1, respectively.

[0037] Figure 3 The above are surface element content analysis diagrams of the calcium carbide slag obtained in Comparative Example 1, Comparative Example 2, and Example 1.

[0038] Figure 4 a represents the CO2 removal rate of the carbide slag obtained in Comparative Examples 1, 2, and 1.

[0039] Figure 4 b represents the CO2 adsorption capacity of the carbide slag obtained in Comparative Examples 1, 2, and 1. Detailed Implementation

[0040] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example 1

[0041] A method for preparing modified carbide slag includes the following steps:

[0042] (1) Wash the carbide slag with distilled water, dry it, and grind it;

[0043] (2) Place the carbide slag treated in step (1) into a metal solution for ultrasonic impregnation to obtain carbide slag slurry;

[0044] (3) The carbide slag slurry treated in step (2) is placed in a pre-freezing device for pre-freezing, and then placed in a vacuum dryer for freeze drying, grinding, and sieving to obtain modified carbide slag, denoted as FD-KHCO3-CS.

[0045] In step (2), the metal solution is an alkaline solution; the alkaline solution is a KHCO3 solution.

[0046] In step (2), the metal loading of the metal solution is 20 wt%, and the solid-liquid ratio is 1:2.

[0047] In step (2), the immersion temperature is 25℃, the ultrasonic power is 800W, the ultrasonic frequency is 59KHz, and the immersion time is 0.5h.

[0048] In step (3), the pre-freezing temperature is -15℃ and the pre-freezing time is 12h.

[0049] In step (3), the freeze-drying temperature is -65℃, the vacuum degree is ≤5Pa, and the vacuum drying time is 12h.

[0050] A modified carbide slag was prepared by the above method.

[0051] The above-mentioned application of modified calcium carbide slag is that the modified calcium carbide slag is used in dry flue gas decarbonization.

[0052] The application process is as follows: 2g of modified calcium carbide slag is added to the flue gas decarbonization equipment, the temperature is set to 500℃, the flue gas flow rate is 100mL / min, and the CO2 concentration is 10%, and decarbonization is carried out.

[0053] Comparative Example 1

[0054] Unmodified carbide slag is denoted as CS and applied to dry flue gas decarbonization.

[0055] The application process is as follows: 2g of calcium carbide slag is added to the flue gas decarbonization equipment, the temperature is set to 500℃, the flue gas flow rate is 100mL / min, and the CO2 concentration is 10%, and decarbonization is carried out.

[0056] Comparative Example 2

[0057] A method for preparing modified carbide slag includes the following steps:

[0058] (1) Wash the carbide slag with distilled water, dry it, and grind it;

[0059] (2) Place the carbide slag treated in step (1) into a metal solution for ultrasonic impregnation to obtain carbide slag slurry;

[0060] (3) Place the carbide slag slurry treated in step (2) into a blower drying oven, grind and sieve to obtain modified carbide slag, denoted as KHCO3-CS.

[0061] In step (2), the metal solution is an alkaline solution; the alkaline solution is a KHCO3 solution.

[0062] In step (2), the metal loading of the metal solution is 20 wt%, and the solid-liquid ratio is 1:2.

[0063] In step (2), the immersion temperature is 25℃, the ultrasonic power is 800W, the ultrasonic frequency is 59KHz, and the immersion time is 0.5h.

[0064] In step (3), the drying temperature is 100℃ and the drying time is 12h.

[0065] A modified carbide slag was prepared by the above method.

[0066] The above-mentioned application of modified calcium carbide slag is that the modified calcium carbide slag is used in dry flue gas decarbonization.

[0067] The application process is as follows: 2g of modified calcium carbide slag is added to the flue gas decarbonization equipment, the temperature is set to 500℃, the flue gas flow rate is 100mL / min, and the CO2 concentration is 10%, and decarbonization is carried out.

[0068] In this invention, the cumulative CO2 adsorption capacity q per unit mass of adsorbent is calculated as follows:

[0069]

[0070] Where: C in - Imported CO2 concentration (%), C out - Outlet CO2 concentration (%), Q - Gas flow rate (mL / min), m - Mass of modified carbide slag (g), T - Reaction temperature (K), T0 - 273K.

[0071] Figure 1 (af) shows the microstructure of FD-KHCO3-CS in Example 1 and CS and KHCO3-CS in Comparative Examples 1 and 2. Figure 1 It can be seen that the microstructure of the carbide slag changed before and after modification. The unmodified carbide slag CS is in the form of blocky particles with a rough surface, layering, and tight arrangement; KHCO3-CS is in the form of flakes with a narrow slit structure and irregular shape, and is relatively compact overall; while FD-KHCO3-CS has a dense needle-like structure on its surface and is relatively loose.

[0072] From the high-magnification SEM images of KHCO3-CS and FD-KHCO3-CS ( Figure 1d and Figure 1 f) The material clearly exhibits layered and needle-like structures, and some of the constituent particles may have hollow structures. These special hollow layered structures are conducive to the capture and transport of CO2 molecules, and can expose more active sites, thereby improving the performance of the adsorbent.

[0073] Figure 2 Mapping analysis of FD-KHCO3-CS in Example 1 and CS and KHCO3-CS in Comparative Examples 1 and 2 is presented. From... Figure 2 As shown in b, the K content increased significantly after KHCO3 modification, indicating that K was successfully loaded onto the surface of the carbide slag. Meanwhile, after freeze-drying... Figure 2 The distribution of elements in c is also relatively uniform and loose, which is more conducive to the removal of CO2.

[0074] Figure 3 The analysis of various elemental contents on the surface of FD-KHCO3-CS in Example 1 and CS and KHCO3-CS in Comparative Examples 1 and 2 is presented. Compared with CS, the increase in O content in the unfreeze-dried KHCO3-CS was relatively small, while the O content in the freeze-dried FD-KHCO3-CS increased significantly. This indicates that freeze-drying can effectively increase the surface oxygen content of carbide slag, thereby improving its CO2 removal capacity.

[0075] Figure 4 The CO2 removal rate and CO2 adsorption capacity of FD-KHCO3-CS in Example 1 and CS and KHCO3-CS in Comparative Examples 1 and 2 are shown. Figure 4 In Comparative Example 1, the CO2 removal rate of CS remained at 30%, while the CO2 removal rate of KHCO3-CS prepared in Comparative Example 2 remained at 100% for 10 minutes, but the adsorption efficiency decreased significantly in subsequent reactions. In contrast, the CO2 removal rate of FD-KHCO3-CS prepared in Example 1 remained at 100% for 18 minutes, indicating that the FD-KHCO3-CS prepared by the freeze-drying method used in this invention can maintain a high adsorption efficiency for a longer period.

[0076] Figure 4 b shows the CO2 adsorption capacity of FD-KHCO3-CS in Example 1 and CS and KHCO3-CS in Comparative Examples 1 and 2. Figure 4The adsorption capacity of CS in Example b was only 0.1 mmol / g, while the adsorption capacity of KHCO3-CS prepared in Comparative Example 2 for CO2 was 2.51 mmol / g, which is 25 times higher than that of CS. Furthermore, the adsorption capacity of FD-KHCO3-CS prepared in Example 1 for CO2 was 4.93 mmol / g, which is 49 times higher than that of CS. This indicates that freeze-drying can significantly improve the CO2 adsorption capacity of carbide slag.

[0077] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. The solutions disclosed in the embodiments are described simply because they correspond to the methods disclosed in the embodiments; relevant parts can be found in the method section.

[0078] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing modified carbide slag, characterized in that, Includes the following steps: (1) Wash the carbide slag with distilled water, dry it, and grind it; (2) Place the carbide slag treated in step (1) into a metal solution for ultrasonic impregnation to obtain carbide slag slurry; (3) The calcium carbide slag slurry treated in step (2) is placed in a pre-freezing device for pre-freezing, and then placed in a vacuum dryer for freeze drying, grinding, and sieving to obtain modified calcium carbide slag. In step (2), the metal solution is one of KOH solution, KHCO3 solution, K2CO3 solution, and NaOH solution; In step (3), the pre-freezing temperature is -200~0℃, and the pre-freezing time is 0.5min~24h; In step (3), the freeze-drying temperature is -120~-15℃, the vacuum degree is ≤10Pa, and the drying time is 5h~72h.

2. The method for preparing modified carbide slag according to claim 1, characterized in that, In step (2), the metal loading of the metal solution is 1~50 wt%, and the solid-liquid ratio is 1:1~20.

3. The method for preparing modified carbide slag according to claim 1, characterized in that, In step (2), the immersion temperature is 10~50℃, the ultrasonic power is 200~800W, the ultrasonic frequency is 20~60KHz, and the immersion time is 0.5~8h.

4. A modified carbide slag prepared by the method according to any one of claims 1-3.

5. The application of the modified carbide slag according to claim 4, characterized in that, The modified calcium carbide slag is used in dry flue gas decarbonization.

6. The application of the modified carbide slag according to claim 5, characterized in that, The application process is as follows: 1~30g of modified calcium carbide slag is added to the flue gas decarbonization equipment, the temperature is set to 0~900℃, the flue gas flow rate is 50~700mL / min, and the CO2 concentration is 1~50%, and decarbonization is carried out.

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