Method for treating waste incineration fly ash through metallurgical sintering

Abstract

The invention discloses a method for treating waste incineration fly ash through metallurgical sintering, which comprises the following steps: (1) uniformly mixing waste fly ash, a binder, a stabilizer, an iron-containing granulation material and a proper amount of water, and preparing iron-containing pellets through pelletizing equipment; (2) mixing the obtained iron-containing pellets with iron ore powder, a flux, fuel, return mine and the like to prepare a sintering mixture; (3) paving the sintered mixture on a sintering machine for sintering to prepare sintered ore meeting smelting requirements; and (4) finally feeding the obtained sintered ore as an ironmaking raw material into a blast furnace for iron and steel smelting. After sintering treatment, the quality of the obtained sintered ore meets the production requirement, pollution to the environment is avoided, potential hazards caused by the waste incineration fly ash are effectively eliminated, and harmless treatment of the fly ash is achieved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of harmless disposal and resource utilization of solid waste, and mainly relates to a method for disposing waste fly ash by metallurgical sintering. BACKGROUND

[0002] Harmless disposal and resource utilization of hazardous solid waste is an important part of "comprehensively strengthening ecological environment protection, winning the battle against pollution prevention, improving ecological civilization, and building a beautiful China", and has great strategic significance. Domestic waste incineration fly ash, as a typical hazardous solid waste, is mainly derived from the residual materials collected in the domestic waste incineration flue gas purification system and heat recovery system, which is enriched with high concentrations of heavy metals, chlorides, and organic pollutants such as dioxin and furan. If not disposed properly, it will cause serious pollution to the air, water, soil, and other surrounding environments. Safe disposal of domestic waste incineration fly ash has become an urgent environmental problem. At present, the main methods for treating waste incineration fly ash include landfill, solidification, high-temperature melting, etc. Landfill is to pretreat the waste incineration fly ash and meet the requirements of the national standard (GB16889-2008) before landfill. Common pretreatment technologies include fly ash chelation stabilization, solvent extraction, melting solidification, and chemical agent treatment, etc. These methods can greatly reduce the leaching rate of heavy metals in fly ash and reduce the toxicity of fly ash. However, landfill construction costs are high, cannot reduce the volume, and cannot be resourceized. At present, it is not a long-term solution in the domestic situation. The solidification method mainly uses cement and concrete solidification, which has the advantages of low cost, easy operation, and mature technology, but the heavy metal leaching problem is serious. High-temperature melting can achieve fly ash volume reduction, pyrolysis of dioxin and other organic matter, separation and extraction of valuable metals, and resource utilization of molten slag as building material aggregate, but it requires additional construction of a high-temperature melting furnace, which has high investment and operation costs. Therefore, it is necessary to seek a safe disposal method for waste incineration fly ash with low treatment cost, high comprehensive utilization rate, and strong treatment capacity.

[0003] China has become the world's largest steel smelting country, and the smelting equipment, process, and technology have reached the world's advanced level. While attaching importance to the development of steel product varieties and quality improvement, more attention is paid to the development and application of energy-saving and emission-reduction technologies. Under the background of the new era, metallurgical enterprises have taken on the important mission of synergistically disposing solid waste. Metallurgical sintering process has the characteristics of high temperature, good kinetic conditions, and advanced environmental protection equipment, so it has inherent advantages in the harmless disposal and resource utilization of waste incineration fly ash. However, the addition of fly ash changes the composition of sintering raw materials, which will affect the sintering process and the quality of sintered ore. The introduction of alkali metals, chlorine, and heavy metals also has an unclear impact on the sintering process. Therefore, it is necessary to study the impact of waste incineration fly ash on the sintering process and the metallurgical properties of sintered ore to achieve the purpose of harmless disposal and resource utilization of waste incineration fly ash, while ensuring the quality of sintered ore and the smooth operation of the sintering process.

[0004] Based on the above, the present application provides a method for disposing waste incineration fly ash by metallurgical sintering, which combines waste incineration fly ash with blast furnace ironmaking process, utilizes chemical reactions between waste incineration fly ash and various raw materials in the blast furnace for ironmaking to realize decomposition of dioxins in waste incineration fly ash, migration of harmful elements such as heavy metals from waste fly ash to sinter, and comprehensive utilization of fly ash, which has important significance for environmental protection. The present discovery has theoretical and practical significance for realizing safe disposal of waste incineration fly ash, improving the efficiency of sintering process for treating waste incineration fly ash, and ensuring the quality of sinter. SUMMARY

[0005] The present application aims at the problems of high toxicity of heavy metals in waste incineration fly ash, high cost of existing disposal methods, and low resource utilization rate, and provides a method for disposing waste fly ash by metallurgical sintering.

[0006] The method for disposing waste incineration fly ash by metallurgical sintering provided by the present application uses waste incineration fly ash as raw material, and the process steps are as follows: 1. Mixing of raw materials Mixing of raw materials: mix 2% to 16% of waste fly ash, 2% to 6% of binder, 0 to 2% of stabilizing agent, and the rest of iron-containing granulation material with an appropriate amount of water, and use balling equipment to make 4 to 14 mm iron-containing material pellets; wherein the granulation material is a mixture of any of iron ore powder, blast furnace gas ash, converter dust and mud, sulfuric acid residue, limestone, and slaked lime; 2. Sintering of mixed materials Sintering of mixed materials: mix the iron-containing material pellets obtained by mixing of raw materials with iron ore powder, flux, fuel, returned ore, and a wetting amount of water to obtain sintering mixed materials; 3. Sintering Sintering: place the obtained sintering mixed materials on the sintering machine trolley for sintering, detect the performance indicators of sinter, and utilize it as sinter.

[0007] Compared with the prior art, the present application has the following advantages: (1) the metallurgical sintering process is combined with waste incineration fly ash disposal, realizing harmless and resourceful integrated treatment of fly ash, and at the same time, the performance of the mixed material granulation is improved, and the green comprehensive utilization of metal elements in fly ash is promoted; (2) through granulation treatment of fly ash, the flowability and formability of the particles are greatly improved, dust pollution is reduced, material storage and transportation are facilitated, and the environmental friendliness and operability of the overall process are improved; (3) fly ash granulation significantly improves the permeability of the sintered mixture and the metallurgical performance of the sinter, improves the technical index and resource utilization efficiency of the smelting process, and has the advantages of low cost and simple process; (4) the method adopts sub-melting point temperature sintering technology to realize particle densification under the condition of incomplete melting, effectively fix the heavy metals in fly ash, and the heavy metal leaching rate meets the environmental protection standard, ensuring environmental safety. BRIEF DESCRIPTION OF DRAWINGS

[0008] Figure 1 is a process flow chart of the present application DETAILED DESCRIPTION

[0009] The present application will be described in detail below in conjunction with examples, but the scope of protection of the present application is not limited to the following examples.

[0010] The main chemical composition (mass percentage) of the waste incineration fly ash used in the following examples is 7.21% SiO2, 1.42% Al2O3, 40.62% CaO, 0.52% MgO, 4.14% K2O, 0.04% Cr2O3, 0.53% ZnO, 0.24% PbO, and 9.12% Na2O.

[0011] Example 1 (1) The weight ratio of the granulation material according to the mass percentage is 15.5% iron ore powder, 20% blast furnace gas ash, 22% converter dust mud, 25% sulfuric acid slag, 2% limestone, 4.5% calcium hydroxide, 5% fly ash, 4% binder, 0.5% stabilizing agent, and an appropriate amount of water is mixed uniformly, and 5-12mm pellets are made by using a pelletizing device, and are cured at room temperature for 10 hours; (2) The iron ore powder 73.2%, quicklime 5%, limestone 1%, coal powder 4.2%, returned ore 15%, rolled steel skin 1%, and the pellets prepared in step (1) 8% are mixed uniformly to obtain a sintering mixture; (3) The sintering mixture in step (2) is laid on the sintering machine trolley for sintering, and the performance indexes of the sinter are detected. Among them, the thickness of the laid material layer is 600mm, and the sintering ignition temperature is 1080°C.

[0012] The sintering test shows that, compared with the sintered ore without adding the waste incineration fly ash, the sintered ore drum strength index is increased by 0.6 percentage points, the yield is increased by 0.6 percentage points, and the sintered ore low-temperature reduction disintegration rate is decreased by 2.8 percentage points.

[0013] Example Two (1) 25% of blast furnace gas ash, 25% of converter dust, 30% of sulfuric acid residue, 5% of limestone powder, 2.7% of slaked lime, 3% of waste fly ash, 3.5% of binder, 0.3% of stabilizing agent, and an appropriate amount of water are mixed according to the mass percentage, and then 5-8 mm pellets are prepared by using a pelletizing device and cured at room temperature for 20 hours; (2) Sintering mixture: 63.0% of iron ore powder, 4.2% of slaked lime, 2% of limestone, 3.8% of coal powder, 12% of return fines, and 15% of the pellets prepared in step (1) are mixed to obtain a sintering mixture; (3) The sintering mixture in step (2) is laid on the sintering machine trolley for sintering, and various performance indicators of the sintered ore are detected. Among them, the layer thickness of the laid material is 650 mm, and the sintering ignition temperature is 1120°C.

[0014] The sintering test shows that the various metallurgical properties of the sintered ore are not lower than the properties of the sintered ore without adding the waste fly ash, or are better, among which the drum strength index is increased by 1.5 percentage points, the yield is increased by 1.11 percentage points, the sintered ore low-temperature reduction disintegration rate is decreased by 0.52 percentage points, and the reduction degree is increased by 1.10 percentage points.

[0015] Example Three (1) 70% of iron ore powder, 9% of blast furnace gas ash, 3% of slaked lime, 15% of waste fly ash, 3% of binder, and an appropriate amount of water are mixed according to the mass percentage, and then 5-12 mm pellets are prepared by using a pelletizing device and cured at room temperature for 20 hours to obtain a stable particle structure; (2) 67.8% of iron ore powder, 4.5% of quicklime, 1% of limestone, 1.5% of calcined dolomite, 4.2% of coal powder, 10% of return fines, 1% of rolled steel skin, and 10% of the pellets prepared in step (1) are mixed to obtain a sintering mixture; (3) The sintering mixture in step (2) is laid on the sintering machine trolley for sintering, and various performance indicators of the sintered ore are detected. Among them, the layer thickness of the laid material is 700 mm, and the sintering ignition temperature is 1100°C.

[0016] The sintering test shows that, compared with the sintered ore without adding the waste incineration fly ash, the sintered ore drum strength index is increased by 0.1 percentage points, the yield is increased by 1.6 percentage points, the sintered ore low-temperature reduction disintegration rate is decreased by 1.3 percentage points, and the reduction degree is increased by 2.28 percentage points.

[0017] The high-temperature sintering technology adopted by the application provides sufficient diffusion energy for fly ash particles under conditions of significantly lower energy consumption than the melting method, thereby eliminating most or even all pores in the crystal, and enabling the pressed fly ash preform to be converted into a dense and hard sintered body at a temperature lower than the melting point of the fly ash, thus meeting the performance requirements of sintered ore. After high-temperature sintering of the fly ash, the heavy metal elements therein will undergo reduction or oxidation reactions and be fixed by the dense particle structure, making it difficult to escape.

Claims

1. A method for treating waste incineration fly ash by metallurgical sintering, characterized in that: The steps include: Step 1: uniformly mix fly ash, a binder, a stabilizer, an iron-containing pelletizing material, and an appropriate amount of water, and prepare iron-containing pellets with a particle size of 4 to 14 mm through a pelletizing device; wherein the pelletizing material is a mixture of any of iron ore powder, converter dust, sulfuric acid slag, limestone, blast furnace gas ash, and slaked lime; Step 2: Mixing the iron-containing pellets obtained in step 1 with iron ore powder, fuel, flux, return ore, and an appropriate amount of water to obtain a sintering mixture; Step 3: Spread the sintered mixture obtained in step 2 on the sintering machine trolley for sintering, test the various performance indicators of the sintered ore, obtain the sintered ore, and put it into the blast furnace for smelting.

2. The method for treating waste incineration fly ash by metallurgical sintering according to claim 1, characterized in that: In the step 1, the weight ratio of the granulated materials is: iron ore powder 0% to 80%, blast furnace gas ash 0% to 40%, converter dust sludge 0% to 40%, sulfate slag 0% to 40%, garbage fly ash 2% to 16%, binder 2% to 6%, and stabilizer 0% to 2%.

3. The method for treating waste incineration fly ash by metallurgical sintering according to claim 1, characterized in that: In step 2, the iron ore powder is concentrate powder, and the flux is quicklime, dolomite or limestone.

4. The method for treating waste incineration fly ash by metallurgical sintering according to claim 1, characterized in that: In step 2, the fuel is coal powder or coke powder, and the returned ore is hot returned ore or cold returned ore.

5. The method for treating waste incineration fly ash by metallurgical sintering according to claim 1, characterized in that: In step 2, the weight ratio of each material is: iron-containing pellets are 2% to 16%, iron ore powder is 20% to 70%, quicklime is 1% to 8%, limestone is 1% to 9%, coke powder is 2% to 5%, return ore is 10% to 20%, and other iron-containing materials are 0% to 20%.

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