A calcium-based composite material for synergistically immobilizing sulfur, nitrogen and heavy metals, and a preparation method and application thereof
Patent Information
- Application Number
- CN202610805833.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-06-05
- Publication Date
- 2026-08-21
AI Technical Summary
而低阶煤与市政污泥共热解技术更能实现两类固废的协同处置与能量互补，但该共热解过程仍面临严峻的环保问题：高温热解会释放SO2、H2S等含硫气态污染物，同时体系中的有机氮主要以HCN、NH3、NOx等形式进入气相；热解残渣中的重金属易发生迁移与溶出，若未做稳定化处理直接排放，会对周边环境造成二次污染
本发明提供的钙基复合材料以固废为原料，用于在低阶煤与污泥共热解中协同固硫控氮固化重金属。其中，电石渣主要成分为Ca(OH)2，石灰除尘灰中CaO含量也很高，两者与钢渣混合形成的复合材料具有较高碱性，适合作为固硫控氮的添加剂，石灰除尘灰用于煤燃烧时可显著提高固硫效率，其固硫性能优异。本发明的钙基复合材料利用工业废渣制备，成本低廉，符合资源化利用理念，制备得到的钙基复合材料与低阶煤、污泥共混热解过程中能显著降低SO2、H2S等含硫气体排放，其中的钙化合物与硫氧化物反应生成稳定的CaSO4或CaS，避免硫以气态形式释放。钙基复合材料中的碱性位点有利于含氮官能团的裂解及重排，促进燃料氮向NH3路径转化，并抑制HCN、NOx等含氮污染物的生成。进一步地，在碱性条件下，部分含氮中间体更易发生加氢或重排反应生成 NH3，从而提高氮向氨的转化比例。同时钙基物质高温下与煤污泥中的重金属共同熔融或反应，形成不易溶出的固体富集相，提高重金属在残渣中的固定率，最终将污染物留存在固相，从而实现“固硫、控氮、固化重金属”的协同效果。
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of solid waste resource utilization and environmental protection technology, and more specifically relates to a calcium-based composite material for synergistic sulfur fixation, nitrogen control and heavy metal solidification, its preparation method and application. Background Technology
[0002] Low-rank coal is a type of coal resource with high volatile matter content and relatively low calorific value. The combustion and pyrolysis of low-rank coal generate large amounts of smoke, dust, and sulfur- and nitrogen-containing gaseous pollutants. On the other hand, sludge produced after wastewater treatment contains abundant organic matter, sulfur and nitrogen elements, and various heavy metals. How to efficiently and cleanly utilize solid waste resources such as low-rank coal and sludge is currently a research hotspot. Compared to traditional sludge incineration technology, sludge pyrolysis technology under an anaerobic / anoxic reducing atmosphere can significantly reduce dioxins and NOxes at the source. x The generation of oxidized pollutants such as SO2 is significantly reduced, as is the amount of hazardous fly ash, resulting in less pressure on secondary pollution control and greater economic feasibility. This technology is considered a highly efficient and clean approach for the harmless treatment and resource utilization of sludge. Furthermore, the co-pyrolysis technology of low-rank coal and municipal sludge can achieve synergistic treatment and energy complementarity between the two types of solid waste. However, this co-pyrolysis process still faces serious environmental challenges: high-temperature pyrolysis releases sulfur-containing gaseous pollutants such as SO2 and H2S, while the organic nitrogen in the system is mainly in the form of HCN, NH3, and NO. x Heavy metals in pyrolysis residues are easily released into the gas phase in various forms; if they are discharged directly without stabilization treatment, they will cause secondary pollution to the surrounding environment.
[0003] Traditional calcium-based sulfur fixatives primarily use limestone and lime as raw materials. Their sulfur fixation mechanism involves the reaction of calcium oxide with sulfur in coal combustion to produce calcium sulfate and calcium sulfite. However, these sulfur fixatives have significant technical limitations: at high temperatures (above 800℃), calcium sulfate and calcium sulfite decompose and release sulfur dioxide, leading to a decrease in sulfur fixation efficiency. More importantly, existing calcium-based sulfur fixatives lack the ability to promote nitrogen-directed ammonia conversion; instead, they inhibit ammonia formation and promote the release of highly toxic nitrogen-containing pollutants (HCN). Their single inorganic calcium component cannot provide a suitable alkaline environment and catalytic conditions for nitrogen to convert to NH3, and they also hinder the deamination reaction of nitrogen-containing compounds, significantly reducing ammonia conversion efficiency and making it difficult to achieve nitrogen resource recovery and utilization. This contradicts the need for nitrogen-directed resource utilization in the co-pyrolysis of low-rank coal and sludge.
[0004] Furthermore, existing sulfur-fixing agents are not ideal for solidifying heavy metals. During the co-pyrolysis of low-rank coal and sludge, the migration and transformation of heavy metals such as copper, arsenic, lead, and chromium are complex and require specialized technical control. Traditional calcium-based sulfur-fixing agents lack an effective solidification mechanism for heavy metals, making it difficult to meet environmental protection requirements.
[0005] To address the aforementioned issues, it is necessary to develop novel solid additives to synergistically control pollutant emissions during pyrolysis. Therefore, how to provide a calcium-based composite material that can synergistically fix sulfur, control nitrogen, and stabilize heavy metals during coal-sludge pyrolysis has become a pressing problem for those skilled in the art. Summary of the Invention
[0006] The purpose of this invention is to develop a calcium-based composite material for synergistic sulfur fixation, nitrogen control, and heavy metal solidification, as well as its preparation method and application, to solve the problems existing in the prior art and simultaneously achieve efficient sulfur fixation, nitrogen-directed ammonia conversion, and heavy metal solidification during the co-pyrolysis of low-rank coal and sludge.
[0007] To achieve the above objectives, the present invention provides the following solution: One of the technical solutions of the present invention is to provide a calcium-based composite material for synergistic sulfur fixation, nitrogen control and solidification of heavy metals, wherein the calcium-based composite material comprises lime dust (C), carbide slag (D) and steel slag (G) in a mass ratio of 3~5:3~5:1~4.
[0008] Furthermore, the mass ratio of the lime dust, carbide slag, and steel slag is 4:4:2.
[0009] Furthermore, the lime dust has a CaO content ≥70wt%, an Fe2O3 content ≥2wt%, and a particle size ≤0.2mm.
[0010] Furthermore, the carbide slag has a Ca(OH)2 content ≥80wt%, a moisture content ≥10wt%, and a particle size ≤80 mesh.
[0011] Furthermore, the steel slag has a CaO content ≥10wt%, an Fe2O3 content ≥50wt%, and a particle size ≤80 mesh.
[0012] Lime dust provides a highly active calcium source, carbide slag provides a high proportion of Ca(OH)2 active phase, and steel slag provides Fe / Mg / Si mineral framework and heavy metal fixation sites; when the three are compounded in this proportion, they can balance the supply of active Ca, structural stability and heavy metal fixation capacity.
[0013] The second technical solution of this invention provides a method for preparing the above-mentioned calcium-based composite material for synergistic sulfur fixation, nitrogen control, and heavy metal solidification, comprising the following steps: Lime dust, carbide slag, and steel slag were crushed and sieved separately, mixed, ball-milled, and dried to obtain the calcium-based composite material for synergistic sulfur fixation, nitrogen control, and heavy metal solidification.
[0014] Furthermore, the pulverization and sieving process involves passing the material through an 80-mesh sieve.
[0015] Furthermore, the ball milling process is solvent-free dry milling, with a milling time of 2 hours and a rotation speed of 300 r / min.
[0016] Solvent-free dry grinding ensures that the material composition is not diluted.
[0017] Furthermore, the drying temperature is 100-110°C.
[0018] The purpose of drying is to remove free water from the product.
[0019] The third technical solution of the present invention is to provide an application of the above-mentioned calcium-based composite material for synergistic sulfur fixation, nitrogen control, and heavy metal solidification in the co-pyrolysis of low-rank coal and sludge.
[0020] Fourth technical solution of the present invention: A method for co-pyrolyzing low-rank coal and sludge, comprising: The calcium-based composite material for synergistic sulfur fixation, nitrogen control, and heavy metal solidification was added to a mixture of low-rank coal and sludge. After thorough mixing, the mixture was pyrolyzed and carbonized, and the pyrolysis semi-coke, gaseous products, and solid products were collected.
[0021] Furthermore, the amount of the calcium-based composite material for synergistic sulfur fixation, nitrogen control, and heavy metal curing is 1-10 wt% of the dry basis mass of the mixture.
[0022] Furthermore, the pyrolysis carbonization temperature is 700-900℃, and the time is 30-90 min.
[0023] Optionally, the pyrolysis carbonization temperature is 800℃ and the time is 60min.
[0024] The method for co-pyrolysis of low-rank coal and sludge provided by this invention is a method for synergistic sulfur fixation, nitrogen control, and heavy metal solidification in sludge pyrolysis using calcium-based composite materials. The calcium-based composite material used can fix sulfur in the mixture in a stable state in the pyrolysis semi-coke; release nitrogen in the mixture into the gas phase in the form of ammonia, which is then collected and processed; and convert the heavy metal elements in the mixture into a more stable form and solidify them in the solid phase.
[0025] The present invention discloses the following technical effects: The calcium-based composite material provided by this invention uses solid waste as raw material for synergistic sulfur fixation, nitrogen control, and heavy metal solidification during the co-pyrolysis of low-rank coal and sludge. The main component of carbide slag is Ca(OH)2, and lime dust also has a high CaO content. The composite material formed by mixing these two materials with steel slag has high alkalinity, making it suitable as an additive for sulfur fixation and nitrogen control. Lime dust significantly improves sulfur fixation efficiency when used in coal combustion, exhibiting excellent sulfur fixation performance. This calcium-based composite material is prepared using industrial waste residue, resulting in low cost and conforming to the concept of resource utilization. During the co-pyrolysis of the prepared calcium-based composite material with low-rank coal and sludge, it significantly reduces the emission of sulfur-containing gases such as SO2 and H2S. The calcium compounds react with sulfur oxides to generate stable CaSO4 or CaS, preventing the release of sulfur in gaseous form. The alkaline sites in the calcium-based composite material facilitate the cracking and rearrangement of nitrogen-containing functional groups, promoting the conversion of fuel nitrogen to NH3 and inhibiting HCN and NO. x This leads to the formation of nitrogen-containing pollutants. Furthermore, under alkaline conditions, some nitrogen-containing intermediates are more likely to undergo hydrogenation or rearrangement reactions to generate NH3, thereby increasing the conversion ratio of nitrogen to ammonia. Simultaneously, calcium-based substances co-melt or react with heavy metals in coal sludge at high temperatures, forming a solid enriched phase that is difficult to dissolve, increasing the fixation rate of heavy metals in the residue, and ultimately retaining pollutants in the solid phase, thus achieving a synergistic effect of "sulfur fixation, nitrogen control, and heavy metal solidification." Attached Figure Description
[0026] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a schematic diagram of the process for preparing calcium-based composite materials according to the present invention and their further application in the co-pyrolysis of low-rank coal and sludge.
[0027] Figure 2 This diagram illustrates the effects of directional nitrogen-ammonia conversion in different groups.
[0028] Figure 3 The images show the curing effect of sulfur in different groups.
[0029] Figure 4 The effect of adding heavy metal fixation to different groups of calcium-based composite materials.
[0030] Figure 5 Add images showing the effect of heavy metal fixation to the comparative samples of different groups. Detailed Implementation
[0031] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.
[0032] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.
[0033] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.
[0034] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.
[0035] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.
[0036] Unless otherwise specified, all raw materials and reagents involved in the specific embodiments of this invention are commercially available products.
[0037] In the specific embodiments of the present invention, the three raw materials used—lime dust, carbide slag, and steel slag—are all untreated industrial wastes.
[0038] The lime dust was provided by a steel company in Shanxi Province. The particle size was 80 mesh, and the main components were: CaO ≥ 70 wt% and Fe2O3 ≥ 2 wt%.
[0039] The calcium carbide slag was provided by a certain calcium carbide chemical company in Shanxi Province. It was the undersize material that passed through an 80-mesh sieve, and its main components were: Ca(OH)2 ≥ 80wt% and water content ≥ 10wt%.
[0040] The steel slag was provided by a group company in Taiyuan. The particle size was 80 mesh, and the main components were: CaO ≥ 10wt% and Fe2O3 ≥ 50wt%.
[0041] Unless otherwise specified, room temperature and normal temperature in the specific embodiments of this invention refer to 20-30℃.
[0042] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.
[0043] Example 1 The preparation steps of calcium-based composite materials for synergistic sulfur fixation, nitrogen control, and heavy metal solidification include: Three types of calcium-containing solid wastes—lime dust, carbide slag, and steel slag—were crushed and screened separately to achieve a particle size ≤80 mesh. They were then mixed in a mass ratio of 4:4:2 and subjected to ball milling (solvent-free dry milling, milling time 2 hours, speed 300 r / min). After ball milling, the mixture was thoroughly dried at 105℃ to remove free moisture from the raw materials, yielding a calcium-based composite material.
[0044] Example 2 The only difference from Example 1 is that the mass ratio of the raw materials is 5:3:2.
[0045] Example 3 The only difference from Example 1 is that the mass ratio of the raw materials is 3:3:4.
[0046] Comparative Example 1 The difference from Example 1 is that the raw materials for the calcium-based composite material are lime dust and carbide slag in a mass ratio of 1:1.
[0047] Comparative Example 2 The difference from Example 1 is that the raw materials for the calcium-based composite material are carbide slag and steel slag in a mass ratio of 2:1.
[0048] Comparative Example 3 The difference from Example 1 is that the raw materials for the calcium-based composite material are lime dust and steel slag in a mass ratio of 2:1.
[0049] Comparative Example 4 The difference compared to Example 1 is that the mass ratio of lime dust, carbide slag and steel slag in the calcium-based composite material is 2:2:6.
[0050] Test case The calcium-based composite materials prepared in the examples and comparative examples were used for co-pyrolysis of low-rank coal and sludge, and the steps are as follows: Calcium-based composite material was added to a mixture of low-rank coal (dry basis, 50 wt%) and sludge (dry basis, 50 wt%), with the addition amounts shown in Table 1. After grinding and vibration mixing, the mixture was subjected to anaerobic pyrolysis in a tubular furnace at 800 °C for 60 min. The pyrolysis semi-coke, gaseous products, and solid products were collected.
[0051] Among them, the low-rank coal is selected from Xinjiang fine coal in China, whose main components are quartz and kaolinite; The sludge was selected from domestic sewage sludge from Taiyuan Municipal Wastewater Treatment Plant, and its main components are quartz, calcite and a small amount of carbon.
[0052] The calcium-based composite material without the addition of calcium was used as a blank control group, denoted as S5L5-800 (in S5L5-800, S5 is the dry basis percentage of sludge in the mixture of 50wt%; L5 is the dry basis percentage of low-rank coal in the mixture of 50wt%; 800 is the pyrolysis temperature).
[0053] Figure 1 This is a schematic diagram of the process for preparing calcium-based composite materials according to the present invention and their further application in the co-pyrolysis of low-rank coal and sludge.
[0054] Table 1 The instantaneous change in ammonia content in pyrolysis flue gas was measured using a Fourier transform infrared (FTIR) flue gas analyzer. The vertical axis represents the instantaneous ammonia production, such as... Figure 2 As shown.
[0055] Figure 2 The graph shows the effect of directional ammonia conversion of nitrogen in different groups (the coordinates represent the changes in S content in the pyrolysis semi-coke of different groups, and the higher the S content, the better the sulfur fixation effect).
[0056] The sulfur content in pyrolysis semi-coke is measured using an elemental analyzer. The vertical axis represents the sulfur content in the same mass of pyrolysis semi-coke. Figure 3 As shown.
[0057] Figure 3 The graph shows the sulfur solidification effect in different groups (the coordinates represent the changes in S content in the pyrolysis semi-coke of different groups, and the higher the S content, the better the sulfur solidification effect).
[0058] The changes in the speciation of heavy metals in different groups of pyrolysis semi-coke after continuous extraction by BCR were studied. F4 represents the stable residual state; a higher concentration of F4 indicates better correlation of solidified heavy metals. Figure 4 , Figure 5 As shown.
[0059] Figure 4 The graph shows the effect of adding calcium-based composite materials of different groups on the fixation of heavy metals (Pb, As, Cr and Cu). The coordinates represent the changes in the occurrence form of heavy metals in pyrolysis semi-coke and mixed raw materials of different groups. F4 is the most stable in the residual state. The higher the F4 content, the better the effect of solidifying heavy metals.
[0060] Figure 5The graph shows the effect of adding heavy metals (Pb, As, Cr and Cu) to the comparative samples of different groups (the coordinates represent the changes in the occurrence form of heavy metals in the pyrolysis semi-coke of different groups, F4 is the most stable in the residue state, and the higher the F4 content, the better the effect of solidifying heavy metals).
[0061] Depend on Figures 2-5 It can be seen that the addition of a certain amount of calcium-based composite material from Example 1 to the pyrolysis semi-coke has a significant effect on fixing sulfur; the residual content of heavy metal elements (taking copper, arsenic, lead, and chromium as examples) in the semi-coke is greater than that in the raw materials, indicating that the addition of calcium-based composite material from Example 1 can effectively fix heavy metals; and the release of NH3 in the gaseous nitrogen-containing products is 10 times greater than that without the addition of calcium-based composite material.
[0062] The residual content of heavy metal elements (taking copper, arsenic, lead, and chromium as examples) in the semi-coke after adding the calcium-based composite material of Example 2 was higher than that in the raw material, indicating that the addition of the calcium-based composite material of Example 2 can effectively fix heavy metals; and the release of NH3 in the gaseous nitrogen-containing products increased by 30 times compared with the case without the addition of calcium-based composite material.
[0063] The residual content of heavy metal elements (taking copper, arsenic, lead, and chromium as examples) in the semi-coke after adding the calcium-based composite material of Example 3 was higher than the residual content (F4) of heavy metal elements in the raw material, indicating that the addition of the calcium-based composite material of Example 3 can effectively fix heavy metals.
[0064] In summary, the calcium-based composite material provided by this invention can effectively capture and fix sulfur-containing gases such as SO2 and H2S, while releasing fuel nitrogen in the form of NH3, significantly reducing NO. x This method can eliminate HCN emissions and stably solidify heavy metal ions in the solid phase. It has a positive promoting effect on achieving efficient and clean utilization of sludge and coal resources.
[0065] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.
[0066] 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 calcium-based composite material for synergistically immobilizing sulfur, nitrogen, and heavy metals, characterized by, The calcium-based composite material comprises lime dust, carbide slag, and steel slag in a mass ratio of 3~5:3~5:1~4.
2. The calcium-based composite material as described in claim 1, characterized in that, The mass ratio of the lime dust, carbide slag, and steel slag is 4:4:
2.
3. The calcium-based composite material as described in claim 1, characterized in that, The lime dust contains ≥70wt% CaO, ≥2wt% Fe2O3, and has a particle size ≤80 mesh.
4. The calcium-based composite material as described in claim 1, characterized in that, The carbide slag has a Ca(OH)2 content ≥80wt%, a moisture content ≥10wt%, and a particle size ≤80 mesh.
5. The calcium-based composite material as described in claim 1, characterized in that, The steel slag has a CaO content ≥10wt%, an Fe2O3 content ≥50wt%, and a particle size ≤80 mesh.
6. The method for preparing the calcium-based composite material as described in claim 1, characterized in that, step... include: Lime dust, carbide slag, and steel slag were crushed and sieved separately, mixed, ball-milled, and dried to obtain the calcium-based composite material for synergistic sulfur fixation, nitrogen control, and heavy metal solidification.
7. The preparation method according to claim 6, characterized in that, The pulverization and sieving process involves passing the material through an 80-mesh sieve. And / or, the ball milling process is solvent-free dry milling, with a milling time of 2 hours and a rotation speed of 300 r / min; And / or, the drying temperature is 100-110°C.
8. The application of a calcium-based composite material for synergistic sulfur fixation, nitrogen control, and heavy metal solidification as described in any one of claims 1-5 in the co-pyrolysis of low-rank coal and sludge.
9. A method for co-pyrolyzing low-rank coal and sludge, characterized in that, include: The calcium-based composite material for synergistic sulfur fixation, nitrogen control, and heavy metal solidification as described in any one of claims 1-5 is added to a mixture of low-rank coal and sludge, thoroughly mixed, and then subjected to pyrolysis and carbonization. The pyrolysis semi-coke, gaseous products, and solid products are collected.
10. The method as described in claim 9, characterized in that, The amount of the calcium-based composite material for synergistic sulfur fixation, nitrogen control, and heavy metal solidification is 1-10 wt% of the dry basis of the mixture. And / or, the pyrolysis carbonization temperature is 700-900℃ and the time is 30-90min.