Method for sintering of waste incineration fly ash and sludge in cooperation with iron ore

Abstract

The present application relates to the field of solid waste treatment, and particularly relates to a method for sintering of waste incineration fly ash and sludge in cooperation with iron ore. The method comprises the following steps: mixing waste incineration fly ash and sludge according to a preset ratio, and performing cooperative dewatering and dechlorination treatment to obtain filter residue; performing heat treatment on the filter residue to decompose organic matter in the filter residue, and obtaining heat treatment products; replacing part of the quicklime with the heat treatment products as a sintering flux, and performing batching with the iron ore, the remaining quicklime and the coke powder to obtain a mixture; and sequentially performing first mixing, second granulation, material distribution, ignition, sintering, cooling and screening treatment to obtain sintered ore. The present application constructs an efficient and reliable resource disposal path for fly ash and sludge by using the complete technical chain of dewatering and dechlorination of waste incineration fly ash and municipal sludge according to a specific ratio, high-temperature heat treatment, and using the heat treatment products to replace part of the quicklime to participate in iron ore sintering.

Description

Technical Field

[0001] This invention relates to the field of solid waste treatment, specifically to a method for co-sintering iron ore with waste incineration fly ash and sludge. Background Technology

[0002] With the rapid advancement of urbanization in my country, the generation of municipal solid waste continues to grow, among which the treatment and disposal of incineration fly ash and municipal sludge are particularly urgent. As a byproduct of the incineration process, incineration fly ash contains high concentrations of persistent organic pollutants such as soluble chlorides and dioxins, as well as various heavy metals such as zinc, lead, copper, and cadmium. Therefore, it is generally classified as hazardous waste, and its safe disposal faces high technical barriers and significant costs. Meanwhile, municipal sludge, an inevitable product of wastewater treatment, is produced in extremely large quantities, with an initial moisture content typically exceeding 96%. This high moisture content makes deep dehydration extremely difficult, severely restricting subsequent resource utilization. Currently, the treatment of these two types of solid waste still largely relies on traditional methods such as landfill, which not only occupies a large amount of valuable land resources but also poses a risk of secondary environmental hazards due to pollutant leaching. Although the industry recognizes that co-processing fly ash and sludge may be more technically and economically feasible—for example, utilizing the calcium-rich components in fly ash to improve sludge dewatering performance and simultaneously using sludge as a medium to promote chlorine removal from fly ash—current technological explorations mostly remain at the level of simple physical mixing or single pretreatment stages, failing to form a complete and efficient end-to-end resource utilization technology system. In particular, how to safely, economically, and effectively integrate the co-processed products into large-scale industrial production, such as replacing some raw materials directly in metallurgical processes, remains a key unsolved problem. The core issue lies in the lack of a systematic approach that can organically link the three key stages of co-processing dewatering and dechlorination of fly ash and sludge, subsequent thermal treatment purification, and final use as a flux substitute in the sintering process, while precisely controlling the process parameters at each stage, thereby truly achieving a seamless transformation from hazardous waste to high-value metallurgical raw materials. Summary of the Invention

[0003] The purpose of this invention is to provide a method for co-sintering iron ore with fly ash and sludge from waste incineration, in order to solve the problem in the prior art that fly ash and sludge are difficult to co-efficiently utilize as resources, and at the same time achieve harmless disposal and enhanced sintering process.

[0004] To achieve the above objectives, the following technical solution is adopted.

[0005] A method for co-sintering waste incineration fly ash and sludge with iron ore includes the following steps:

[0006] The fly ash from waste incineration and sludge are mixed in a preset ratio and then subjected to synergistic dehydration and dechlorination treatment to obtain filter residue.

[0007] The filter residue is subjected to heat treatment to decompose the organic matter in the filter residue, promote the volatilization of heavy metals and the decomposition of dioxins, and obtain the heat-treated product.

[0008] The heat-treated product is used to replace part of the quicklime as a sintering flux, and is then mixed with iron ore, residual quicklime, and coke powder to obtain a mixture.

[0009] The mixture is subjected to a series of processes, including primary mixing, secondary granulation, feeding, ignition, sintering, cooling, and screening, to obtain sintered ore.

[0010] Optionally, the wet basis ratio of the waste incineration fly ash to sludge is 20:100 to 30:100.

[0011] Optionally, the temperature of the heat treatment is 1000°C to 1200°C.

[0012] Optionally, the mass percentage content of CaO in the heat-treated product is 55.02% to 66.58%.

[0013] Optionally, the basicity of the heat-treated product is 3.50 to 5.41.

[0014] Optionally, the heat-treated product replaces quicklime by a mass ratio of 5% to 20%.

[0015] Optionally, the heat-treated product accounts for 0.43% to 1.71% of the mass percentage of the sintering feedstock.

[0016] Optionally, the sintering temperature of the sintering step is 1300℃ to 1400℃, the moisture content of the mixture is 7.50% to 9.0% by mass, and the coke powder content in the ingredients is 2.7% to 3.9% by mass.

[0017] Optionally, the ingredients also include dolomite and recycled ore; the mass percentage of dolomite in the ingredients is 3.83% to 4.71%, and the mass percentage of recycled ore in the ingredients is 18.03%.

[0018] Optionally, the sintering rate of the sintering step is from 22.67 mm / min to 23.94 mm / min, the drum strength of the resulting sinter is from 61.3% to 64.4%, and the utilization coefficient is from 1.24 t / (m²·h) to 1.31 t / (m²·h).

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] This invention successfully constructs an efficient and reliable co-resource utilization pathway for fly ash and sludge by synergistically dehydrating and dechlorinating fly ash and sludge in a specific ratio, subjecting the resulting filter residue to high-temperature heat treatment, and utilizing the heat treatment product to replace part of the quicklime in iron ore sintering. The method first utilizes the complementary properties of fly ash and sludge components to significantly reduce the moisture and chlorine content of the mixed filter residue, laying the material foundation for subsequent utilization. Subsequently, through a precisely controlled heat treatment process, organic pollutants and dioxins are effectively decomposed, and most heavy metals (such as Pb, Cd, and Cu) are released at a high volatility, achieving the harmlessness and chemical stability of the filter residue. Finally, the obtained heat treatment product is partially recycled as a sintering flux in the sintering process, not only realizing the resource recycling of solid waste but also positively impacting the quality and yield indicators of the sintered ore due to its specific calcium and silicon composition. Specifically, the wet-base ratio of fly ash to sludge is crucial for achieving effective synergistic dehydration and dechlorination and obtaining filter residue with a suitable calcium-silicon ratio; the heat treatment temperature range is essential for ensuring organic matter decomposition, dioxin destruction, and efficient volatilization of heavy metals; the CaO content and alkalinity range of the heat-treated product are material guarantees for its successful replacement of some quicklime as an effective flux; the replacement ratio of the heat-treated product and its proportion in the batching are the optimized operating range for maximizing solid waste disposal while ensuring the quality of sintered ore; the sintering process parameters and the achieved sintered ore quality indicators demonstrate the significant effect of this method in optimizing the process (such as improving sintering speed, drum strength, and utilization coefficient); and the specific ratio of introduced dolomite and recycled ore further optimizes the overall composition of the sintering mixture, helping to maintain the stability of the sintering process and the performance of the final product. In summary, the various technical features of this invention are interconnected and synergistic, jointly achieving multiple beneficial effects such as the harmlessness and resource utilization of fly ash and sludge, and the enhancement of the sintering process. Attached Figure Description

[0021] Figure 1 This is a flowchart illustrating the steps of an embodiment of the present invention: co-sintering of waste incineration fly ash and sludge with iron ore. Detailed Implementation

[0022] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0023] The following detailed description is exemplary and intended to provide further detailed explanation of the invention. Unless otherwise specified, all technical terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. The terminology used in this invention is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention.

[0024] Example 1

[0025] like Figure 1 As shown, the fly ash samples from waste incineration plants involved in this invention are derived from typical grate-fired waste-to-energy plants. After sampling and homogenization, they are sealed and stored to ensure the stability of their properties. The sludge involved in this invention is taken from municipal sludge from a city wastewater treatment plant with a daily treatment capacity of 15,000 tons. The initial moisture content of this sludge is approximately 96%, exhibiting typical high moisture characteristics.

[0026] The core of this invention lies in providing a complete method for co-treating waste incineration fly ash and municipal sludge, and applying the final product to iron ore sintering. This method systematically solves the problem of treating the two solid wastes separately and creatively transforms them into useful resources in the sintering process.

[0027] First, a co-treatment process of dewatering and dechlorination of waste incineration fly ash and municipal sludge is performed. The two materials are mixed according to a preset wet-basis mass ratio. This ratio is crucial; extensive experimental verification has shown that an optimal synergistic effect is achieved when the wet-basis ratio of fly ash to sludge is between 20:100 and 30:100. At this ratio, the calcium components in the fly ash effectively promote the release of bound water from the sludge, significantly improving its dewatering performance. Simultaneously, the physicochemical environment of the sludge provides an efficient removal pathway for the high content of soluble chloride salts in the fly ash, primarily sodium chloride and potassium chloride. This co-treatment process ultimately produces a filter residue with significantly reduced moisture and chloride content. This filter residue serves as the base material for subsequent treatments. Its composition varies depending on the fly ash addition ratio, but it retains abundant calcium from the fly ash and silicon, aluminum, and other components from the sludge, giving the filter residue a calcium-silicon ratio characteristic suitable as a potential flux.

[0028] The obtained filter residue is then subjected to heat treatment. The purpose of heat treatment is multifaceted: first, to decompose any remaining organic pollutants in the filter residue; second, to promote the volatilization and removal of heavy metals present in various forms in the filter residue, such as zinc, lead, copper, and cadmium; and third, to ensure the decomposition and destruction of highly toxic dioxins, achieving a decomposition rate of 98%. The key control parameter for achieving these objectives is the heat treatment temperature. The heat treatment temperature range determined in this invention is 1000°C to 1200°C. Within this temperature range, not only can the effective removal of the aforementioned harmful components be guaranteed, but the filter residue can also undergo the necessary phase transformation, forming a chemically stable product suitable for subsequent metallurgical applications. The heat treatment process is typically carried out in a dedicated high-temperature furnace, accompanied by an appropriate holding time to ensure thorough treatment.

[0029] The solid product obtained after high-temperature heat treatment is called the heat-treated product. Chemical analysis of this product shows that its calcium oxide (CaO) content is consistently between 55.02% and 66.58% by mass. Simultaneously, the basicity of this heat-treated product, usually expressed as the mass ratio of CaO to SiO2, ranges from 3.50 to 5.41. These two key chemical indicators suggest that the heat-treated product has a high calcium content and suitable basicity, and its properties are quite similar to quicklime, a flux commonly used in steel sintering. Therefore, it has the potential to partially replace quicklime in sintering.

[0030] The process then moves to the batching stage of applying the heat-treated product to iron ore sintering. In traditional sintering batches, quicklime is used as an alkaline flux to adjust the alkalinity of the sintering mixture and reacts with acidic gangue components in the iron ore during sintering to generate low-melting-point compounds, promoting liquid phase formation and thus ensuring the strength of the sinter. In this invention, the aforementioned heat-treated product is used to replace a portion of the quicklime. The replacement ratio, by mass, is defined as the percentage of the mass of the heat-treated product to the total mass of the heat-treated product and quicklime. Through systematic sintering cup experiments and performance tests, a preferred replacement ratio range of 5% to 20% was determined. Correspondingly, the mass percentage of this heat-treated product added to the total sintering batch ranges from 0.43% to 1.71%. In addition to the heat-treated product and a portion of the quicklime, the complete sintering batch also includes iron ore as the main iron-containing raw material, coke powder as fuel, dolomite for further adjusting alkalinity, and return ore as a nucleating agent in the sintering process. In this batch, the mass percentage of dolomite in the ingredients is typically controlled between 3.83% and 4.71%, while the proportion of recycled ore is fixed at 18.03%. Coke powder, as a fuel to provide heat, is included in the batch at a ratio ranging from 2.7% to 3.9%.

[0031] After batching, all raw materials are thoroughly mixed once to ensure uniform composition. A second granulation process follows, where water is added and the mixture is rolled in a disc granulator or mixing drum to adhere fine powder to coarser core particles, forming a sintered mixture with a specific particle size distribution. This is crucial for ensuring the permeability of the sintered material layer. During this process, the mixture needs to be adjusted to a suitable moisture content range, typically 7.50% to 9.0%, to facilitate granulation and subsequent ignition and sintering.

[0032] After granulation, the mixture is evenly spread onto the sintering machine trolley via a feeding system, forming a material layer of a certain thickness. Then, an ignition furnace ignites the surface of the material layer, with the ignition temperature typically controlled within the range of approximately 1300 to 1400 degrees Celsius. After ignition, as the sintering process proceeds automatically downwards, the combustion front, i.e., the sintering flame front, passes through the material layer from top to bottom. This process is called sintering. The sintering rate, i.e., the rate at which the combustion front descends, is an important process indicator. In this invention, this rate is maintained at an optimal level of 22.67 mm / min to 23.94 mm / min. A higher sintering rate generally means better production efficiency.

[0033] After the sintering process is completed, the resulting hot sintered ore cake needs to be cooled, usually by forced air cooling, to reduce its temperature to a level suitable for subsequent processing and transportation. The cooled sintered ore cake is then crushed and screened to obtain finished sintered ore blocks that meet the requirements of blast furnace smelting and return ore that needs to be returned to the sintering process.

[0034] To verify the technical effects of the present invention, particularly to determine the optimal ratio of fly ash to sludge and the optimal proportion of heat treatment products replacing quicklime, a series of embodiments and comparative experiments were conducted. All embodiments and comparative examples were based on the same raw materials, only changing the two key variables: the wet-based ratio of fly ash to sludge and the replacement ratio of heat treatment products, while keeping the return ore ratio at 18.03% and the coke powder ratio at 3.3% constant to ensure a fair comparison.

[0035] Example 1

[0036] The fly ash in the filter residue was mixed with sludge in a wet ratio of 25:100. The proportion of quicklime replaced by heat treatment products was 5%. The composition of the mixed residue was 68.08% iron ore, 6.14% quicklime, 4.02% dolomite, 0.43% heat treatment products, 3.3% coke powder, and 18.03% recycled ore. The sintering speed was 23.45 mm / min, the yield was 77.33%, the drum strength was 62.3%, and the utilization coefficient was 1.25 t / (m²). 2 ·h).

[0037] Example 2

[0038] The fly ash in the filter residue was mixed with sludge in a wet ratio of 20:100. The proportion of quicklime replaced by heat treatment products was 10%. The composition of the mixed residue was 67.78% iron ore, 5.81% quicklime, 4.22% dolomite, 0.86% heat treatment products, 3.3% coke powder, and 18.03% recycled ore. The sintering speed was 23.24 mm / min, the yield was 77.12%, the drum strength was 63.1%, and the utilization coefficient was 1.24 t / (m²). 2 ·h).

[0039] Example 3

[0040] The fly ash in the filter residue was mixed with sludge in a wet ratio of 30:100. The proportion of quicklime replaced by heat treatment products was 15%. The composition of the mixed residue was 67.38% iron ore, 5.49% quicklime, 4.52% dolomite, 1.28% heat treatment products, 3.3% coke powder, and 18.03% recycled ore. The sintering speed was 23.94 mm / min, the yield was 77.93%, the drum strength was 64.4%, and the utilization coefficient was 1.31 t / (m²). 2 ·h).

[0041] Example 4

[0042] The fly ash in the filter residue was mixed with sludge in a wet ratio of 25:100. The proportion of quicklime replaced by heat treatment products was 20%. The composition of the mixed residue included 67.08% iron ore, 5.17% quicklime, 4.71% dolomite, 1.71% heat treatment products, 3.3% coke powder, and 18.03% recycled ore. The sintering speed was 22.67 mm / min, the yield was 76.08%, the drum strength was 61.1%, and the utilization coefficient was 1.22 t / (m²). 2 ·h).

[0043] Comparison Example 1

[0044] The fly ash to sludge wet-based ratio in the filter residue was 30:100. The proportion of quicklime replaced by heat treatment products was 0%. The mixed iron ore content was 68.38%, quicklime 6.46%, dolomite 3.83%, coke powder 3.3%, and recycled ore 18.03%. The sintering speed was 23.67 mm / min, the yield was 77.97%, the drum strength was 61.3%, and the utilization coefficient was 1.24 t / (m²). 2 ·h).

[0045] Comparison Example 2

[0046] The fly ash in the filter residue was mixed with sludge in a wet ratio of 35:100. The proportion of quicklime replaced by heat treatment products was 15%. The composition of the mixed residue was 67.38% iron ore, 5.49% quicklime, 4.52% dolomite, 1.28% heat treatment products, 3.3% coke powder, and 18.03% recycled ore. The sintering speed was 22.58 mm / min, the yield was 76.21%, the drum strength was 62.3%, and the utilization coefficient was 1.23 t / (m²). 2 ·h).

[0047] Comparison Example 3

[0048] The fly ash in the filter residue was mixed with sludge in a wet-based ratio of 15:100. The proportion of quicklime replaced by heat-treated products was 15%. The composition of the mixed residue was 67.38% iron ore, 5.49% quicklime, 4.52% dolomite, 1.28% heat-treated products, 3.3% coke powder, and 18.03% recycled ore. The sintering speed was 22.46 mm / min, the yield was 76.25%, the drum strength was 62.7%, and the utilization coefficient was 1.23 t / (m²). 2 ·h).

[0049] As can be seen from Examples 1-4 and Comparative Examples 1-3, by selecting a suitable fly ash sludge ratio and a suitable proportion of heat treatment products to replace quicklime, the yield rate does not change significantly, but the sintering speed, drum strength and utilization coefficient are improved, and the quality of sintered ore is also improved, which has significant economic and environmental benefits.

[0050] A comprehensive analysis of the above embodiments and comparative examples clearly demonstrates that strictly controlling the wet basis ratio of waste incineration fly ash to municipal sludge between 20:100 and 30:100, while simultaneously controlling the proportion of heat treatment products replacing quicklime within 5% to 20%, is key to achieving efficient and synergistic resource utilization of fly ash and sludge, while also ensuring and even improving the quality indicators of sintered ore. Within this optimized parameter range, as shown in Examples 1 to 3, not only can these two types of solid waste be effectively disposed of and treated, achieving their harmlessness and resource utilization, but high-quality sintered ore with high sintering speed, good drum strength, and ideal utilization coefficient can also be obtained, demonstrating significant economic and environmental benefits.

[0051] As is known from common technical knowledge, this invention can be implemented through other embodiments that do not depart from its spirit or essential characteristics. Therefore, the disclosed embodiments described above are merely illustrative in all respects and are not the only ones. All modifications within the scope of this invention or its equivalents are included in this invention.

Claims

1. A method for co-sintering iron ore with waste incineration fly ash and sludge, characterized in that, Includes the following steps: Waste incineration fly ash and sludge are mixed in a preset ratio and then subjected to synergistic dehydration and dechlorination treatment to obtain filter residue; the wet basis ratio of the waste incineration fly ash and sludge is 20:100 to 30:

100. The filter residue is subjected to heat treatment at a temperature of 1000°C to 1200°C to decompose the organic matter in the filter residue, promote the volatilization of heavy metals and the decomposition of dioxins, and obtain a heat-treated product; the mass percentage content of CaO in the heat-treated product is 55.02% to 66.58%; the basicity of the heat-treated product is 3.50 to 5.

41. The heat-treated product is used to replace part of the quicklime as a sintering flux, and is then batched with iron ore, residual quicklime, and coke powder to obtain a mixture. The heat-treated product replaces 5% to 20% of the quicklime by mass; the heat-treated product constitutes 0.43% to 1.71% of the sintering mixture by mass. The mixture also includes dolomite and recycled ore; the dolomite constitutes 3.83% to 4.71% of the mixture by mass, and the recycled ore constitutes 18.03% of the mixture by mass. The mixture is subjected to a first mixing, a second granulation, a feeding, ignition, sintering, cooling and screening processes to obtain sintered ore; wherein the sintering temperature of the sintering step is 1300℃ to 1400℃, the moisture content of the mixture is 7.50% to 9.0% by mass, and the coke powder content in the batch is 2.7% to 3.9% by mass.

2. The method for co-sintering iron ore with waste incineration fly ash and sludge according to claim 1, characterized in that: The sintering rate of the sintering step is from 22.67 mm / min to 23.94 mm / min, the drum strength of the resulting sinter is from 61.3% to 64.4%, and the utilization coefficient is from 1.24 t / (m²·h) to 1.31 t / (m²·h).

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