Method for co-processing waste incineration fly ash through hot-state blast furnace slag

Abstract

The invention discloses a method for co-processing waste incineration fly ash through hot-state blast furnace slag, relates to the field of hazardous waste disposal and utilization, and provides the method for co-processing waste incineration fly ash through hot-state blast furnace slag by controlling the adding amount of the waste incineration fly ash and combining with a fluxing agent to reduce the melting temperature. The waste incineration fly ash and boron oxide are mixed, crushed, granulated and molded, and then are fed into a fly ash ladle melting tank together with molten blast furnace slag which is just discharged from a furnace to react for a certain time, and then water quenching is performed to prepare water quenching slag. The waste heat of the hot blast furnace slag is used for carrying out high-temperature treatment on the waste incineration fly ash, high Ca, Si and Al of the blast furnace slag have an excellent fixing effect on heavy metal components in the waste incineration fly ash, and therefore the heavy metal components in the incineration fly ash can be fixed into water-quenched slag. According to the method, valuable components in the solid waste are fully utilized, the additional value of solid waste products is increased, and the utilization way of the waste incineration fly ash is widened.

Description

Technical Field

[0001] The present invention relates to the field of hazardous waste disposal and utilization, and particularly to a method for co-disposing municipal solid waste incineration fly ash with hot blast furnace slag. Background Art

[0002] Municipal solid waste incineration fly ash is a harmful by-product generated during the process of municipal solid waste incineration power generation, mainly from flue gas purification equipment such as bag filters, as well as sediments at the bottom of flues and chimneys. Its composition is complex and diverse, including oxides of metals such as calcium, sodium, and potassium, and also contains heavy metal ions such as lead, cadmium, and mercury, as well as chlorides. Fly ash has the characteristics of high toxicity and high chlorine content, is difficult to treat, and has a high treatment cost.

[0003] Currently, the treatment methods of municipal solid waste incineration fly ash mainly include cement solidification and landfill, chemical agent stabilization technology, and heat treatment technology. However, these methods all have significant limitations. Cement solidification and landfill will cause a large increase in the volume of fly ash, occupying a large amount of land resources, and heavy metals are difficult to be stably fixed, with a risk of leaching. Chemical agent stabilization technology faces challenges in stabilizing multiple heavy metals and has weak stability for other pollutants. In heat treatment technology, the co-processing method in cement kilns is limited in its application scope because the chlorine component in municipal solid waste incineration fly ash is likely to corrode the kiln body and affect the quality of cement at the same time.

[0004] The co-disposal of municipal solid waste incineration fly ash faces two major challenges: one is to ensure that harmful substances in municipal solid waste incineration fly ash are fully fixed or removed to achieve harmlessness; the other is to minimize the impact on the original process. For example, although co-processing in cement kilns can decompose organic pollutants and solidify heavy metals, soluble chlorides (such as NaCl, KCl) in municipal solid waste incineration fly ash are difficult to be completely removed, which is likely to cause crusting, blockage, and corrosion in the kiln, and the water washing pretreatment cost is high and the process is complex, restricting its large-scale application. Other processes such as high-temperature melting and sintering have problems such as complex technology, difficult tail gas treatment, and possible generation of secondary fly ash. Therefore, developing an environmentally and economically feasible way for the resource utilization of municipal solid waste incineration fly ash is still an urgent problem to be solved currently. Summary of the Invention

[0005] In view of the above deficiencies of the prior art, the present invention provides a method for co-disposing municipal solid waste incineration fly ash with hot blast furnace slag. While increasing the consumption of municipal solid waste incineration fly ash, it effectively solidifies heavy metals, reduces the leaching toxicity of municipal solid waste incineration fly ash, and at the same time minimizes the impact on the original process and reduces the treatment cost of municipal solid waste incineration fly ash.

[0006] To achieve the above invention purpose, the technical solution adopted by the present invention is as follows:

[0007] Provide a method for co-disposing municipal solid waste incineration fly ash with hot blast furnace slag, which comprises the following steps:

[0008] S1: Ball mill the waste incineration fly ash and boric oxide together.

[0009] S2: Granulate and dry after ball milling to obtain mixed granules.

[0010] S3: Feed the molten blast furnace slag and the mixed granules into the fly ash encapsulation melting tank together, and wait for the reaction to obtain the melt.

[0011] S4: Treat the melt by the cold water slagging method to obtain water-quenched slag.

[0012] Furthermore, the contents of heavy metals Zn, Cu, Pb, and Cr in the waste incineration fly ash are 0-6.00%, 0-5.50%, 0-0.24%, and 0-1.00% respectively.

[0013] Furthermore, the mass ratio of the waste incineration fly ash to boric oxide is 10:1.

[0014] Furthermore, the particle size of the mixed granules is 1.0-3.0 mm.

[0015] Furthermore, the mass ratio of the mixed granules to the molten blast furnace slag is 1:10.0-10.3; and the melting reaction time of the mixed granules and the molten blast furnace slag is 7-10 min.

[0016] Furthermore, the molten blast furnace slag is the slag just out of the furnace at 1450-1550 °C.

[0017] Furthermore, the cold water slagging water pressure is 0.2-0.4 MPa, and the slagging water injection volume is 8-12 m 3 / t.

[0018] Furthermore, in step S1, the ball milling time is 10-15 min, and the particle size of the particles obtained by ball milling is ≤3 mm.

[0019] The beneficial effects of the present invention are as follows:

[0020] A method for co-disposing waste incineration fly ash with hot blast furnace slag proposed by the present invention reduces the melting temperature by controlling the fly ash addition amount and combining with a boric oxide fluxing agent. The waste incineration fly ash and boric oxide are mixed and crushed and then granulated and formed, and then fed into the fly ash encapsulation melting tank together with the just-out-of-the-furnace molten blast furnace slag and reacted for a certain time and then water-quenched to prepare water-quenched slag. The sensible heat of the blast furnace slag is used to melt and dispose of the fly ash. At the same time, the high Ca, Si, and Al in the blast furnace slag have excellent fixation effects on heavy metal components, and can fix the heavy metal components in the incineration fly ash into the water-quenched slag. This method makes full use of the valuable components in the solid waste, increases the added value of the solid waste product, and broadens the utilization path of the waste incineration fly ash.

[0021] The fly ash treatment method provided by the present invention has remarkable beneficial effects. Through an innovative co-disposal process, about 10% of the fly ash equivalent to the mass of blast furnace slag can be consumed in a single treatment, significantly improving the fly ash treatment efficiency. At the same time, relying on the large annual output of blast furnace slag resources in China and based on the advantages of large-scale treatment, large quantities and continuous disposal of fly ash can be achieved. The combination of the two forms a scale effect in the total amount of fly ash treatment, effectively solving the problems of fly ash accumulation and environmental pollution, reducing the treatment cost, creating significant economic and environmental benefits, and having extremely high industrial application value and market promotion potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 SEM diagram of the water-quenched slag prepared in Example 1;

[0023] Figure 2 XRD diagram of the water-quenched slag prepared in Example 1;

[0024] Figure 3 Infrared test comparison diagram of the water-quenched slag prepared with different preparation parameters in Example 6. DETAILED DESCRIPTION OF THE INVENTION

[0025] The following describes the specific embodiments of the present invention to facilitate those skilled in the art of the present technology to understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those of ordinary skill in the art of the present technology, as long as various changes are within the spirit and scope of the present invention defined and determined by the appended claims, these changes are obvious, and all inventions created using the concept of the present invention are within the scope of protection.

[0026] In the embodiments of the present invention, the waste incineration fly ash produced by a certain waste incineration plant is used. After testing, its main components are CaO, SiO2 and Al2O3. The typical heavy metals Zn, Cu, Pb and Cr are calculated as ZnO, CuO, PbO and Cr2O3, and their contents are 0 - 6.00%, 0 - 5.50%, 0 - 0.24% and 0 - 1.00% respectively.

[0027] Example 1

[0028] The following steps are used to treat the waste incineration fly ash:

[0029] S1: Ball-mill the waste incineration fly ash and boric oxide (analytical pure) in a mass ratio of 10:1; the ball-milling time is 10 - 15 min, and the particle size of the ball-milled particles is ≤ 3 mm.

[0030] S2: Granulate and dry after ball-milling to obtain mixed particles with a particle size of 1.0 - 3.0 mm;

[0031] S3: Feed the molten blast furnace slag discharged from the blast furnace slag tapping opening at 1450 - 1550 °C and the mixed particles into the fly ash encapsulation melting tank at a mass ratio of 10.0 - 10.3:1, and wait for 7 - 10 min for the reaction to obtain the melt;

[0032] S4: Use the cold water slagging method with a water pressure of 0.2 - 0.4 MPa and a slagging water injection volume of 8 - 12 m 3 / t to treat the melt to obtain granulated slag.

[0033] Perform SEM and XRD tests on the granulated slag. The SEM test is as Figure 1 shown, and the XRD test results are as Figure 2 shown. Among them Figure 1 the right side is Figure 1 an enlarged schematic diagram of the position boxed on the left side. Figure 1 The magnification on the left side is 500 times, Figure 1 the magnification on the right side is 2000 times. As can be seen from Figure 1 this, the surface of the reconstructed granulated slag is smooth and attached with flaky small particles, showing an amorphous dispersed state as a whole, with distinct edges and corners. Combining with Figure 2 the XRD analysis results, it can be known that the original crystal structure of the fly ash in the reconstructed granulated slag has changed, and an amorphous vitreous structure is basically formed, which can reduce the exposure of heavy metals in the granulated slag and further reduce the leaching concentration of heavy metals. Compared with the original blast furnace slag, the mineral phase composition of the reconstructed granulated slag is basically similar to that of industrial blast furnace slag, and no other obvious changes are found.

[0034] Example 2

[0035] The difference between this example and Example 1 is that in step S1, the mass ratio of the municipal solid waste incineration fly ash to boron oxide is 11:1.

[0036] Example 3

[0037] The difference between this example and Example 1 is that in step S1, the mass ratio of the municipal solid waste incineration fly ash to boron oxide is 9:1.

[0038] Example 4

[0039] The difference between this example and Example 1 is that in step S3, the mass ratio of the molten blast furnace slag to the mixed particles is 10.4:1.

[0040] Example 5

[0041] The difference between this example and Example 1 is that in step S3, the mass ratio of the molten blast furnace slag to the mixed particles is 9:1.

[0042] Example 6

[0043] The heavy metal content and leaching concentration in the water-quenched slag prepared in Examples 1 to 5 were detected, and the results were converted into the solid solution rate of heavy metals. where R F is the solid solution rate. c o is the concentration of heavy metal in the sample before melting, mg·kg -1 ; m o is the mass of the sample before melting, kg; c1 is the concentration of heavy metal in the molten product, mg·kg -1 ; m1 is the mass of the molten product, kg. The results are shown in Table 1 below;

[0044] Table 1

[0045]

[0046] As can be seen from Table 1, compared with the untreated municipal solid waste incineration fly ash, the leaching toxicity of typical heavy metals such as Zn, Cu, Pb, and Cr in the water-quenched slag prepared by the method of the present invention is significantly reduced, proving that the typical heavy metals in the municipal solid waste incineration fly ash can be fixed by the molten blast furnace slag.

[0047] Compared with Example 1, Example 2 reduced the dosage of boron oxide. In the obtained water-quenched slag, the solid solution rates of Zn, Cu, Pb, and Cr were all less than those in Example 1. This may be because the reduction of boron oxide led to the failure of some heavy metals in the municipal solid waste incineration fly ash to melt successfully, resulting in insufficient heat and the failure of the municipal solid waste incineration fly ash to be fixed by the molten blast furnace slag. Compared with Example 1, Example 3 increased the dosage of boron oxide, but there was no significant change in the heavy metal leaching toxicity and solid solution rate in the water-quenched slag, proving that when the mass ratio of municipal solid waste incineration fly ash to boron oxide is 10:1, the heavy metals can be completely melted. In order to control costs, the mass ratio of municipal solid waste incineration fly ash to boron oxide of 10:1 is the best.

[0048] Compared with Example 1, Example 4 reduced the amount of mixed particles. The leaching toxicity of heavy metals in the obtained water-quenched slag decreased equally, but the solid solution rate decreased; compared with Example 1, Example 5 increased the amount of mixed particles, but the heavy metal leaching toxicity and solid solution rate in the obtained water-quenched slag increased synchronously. This may be because too many mixed particles led to a too rapid temperature drop after contacting the molten blast furnace slag, and the heavy metals in the mixed particles failed to be completely melted and fixed by the blast furnace slag, resulting in a decrease in the heavy metal content in the water-quenched slag. Therefore, the mass ratio of molten blast furnace slag to mixed particles of 10.0 - 10.3:1 is the best.

[0049] The water-quenched slag prepared in Examples 1 to 5 was subjected to material infrared testing. Specifically: 2.0 mg of 200-mesh water-quenched slag and 200 mg of KBr were uniformly mixed, and then the mixture was pressed into a disk with a diameter of 13 mm. In the range of 4000 - 400 cm -1Record the samples within the range of 1 cm resolution -1 , and collect 20 scans for each sample. The test results are as follows Figure 3 shown. Combining with Table 1, it can be seen that the water-quenched slag prepared by the method of the present invention has a similar structure to the untreated industrial blast furnace slag, does not change the original material properties of the blast furnace slag, still has potential hydration activity, and meets the requirements for subsequent utilization of blast furnace slag as building materials.

Claims

1. A method for co - disposing of waste incineration fly ash with hot blast furnace slag, characterized in that, It includes the following steps: S1: Ball-mill the waste incineration fly ash together with boron oxide; S2: Granulate and dry after ball-milling to obtain mixed particles; S3: Feed the molten blast furnace slag and the mixed particles into a fly ash cladding furnace together and wait for the reaction to obtain a melt; S4: Treat the melt by the cold water slag quenching method to obtain water-quenched slag.

2. The method for co - disposing of waste incineration fly ash with hot blast furnace slag according to claim 1, wherein, The contents of heavy metals Zn, Cu, Pb, and Cr in the waste incineration fly ash are 0-6.00%, 0-5.50%, 0-0.24%, and 0-1.00% respectively.

3. The method for co-disposing municipal solid waste incineration fly ash with hot blast furnace slag according to claim 2, characterized in that The mass ratio of the waste incineration fly ash to boron oxide is 10:

1.

4. The method for co-disposing waste incineration fly ash with hot blast furnace slag according to claim 3, characterized in that The particle size of the mixed particles is 1.0-3.0 mm.

5. The method for co-disposing municipal solid waste incineration fly ash with hot blast furnace slag according to claim 4, wherein The mass ratio of the mixed particles to the molten blast furnace slag is 1:10.0-10.3; and the melting reaction time of the mixed particles and the molten blast furnace slag is 7-10 min.

6. The method for co - disposing of waste incineration fly ash with hot blast furnace slag according to claim 5, characterized in that, The molten blast furnace slag is the slag just out of the furnace at 1450-1550 °C.

7. The method for co-disposing waste incineration fly ash with hot blast furnace slag according to claim 6, characterized in that, The water pressure for slag granulation with cold water is 0.2 - 0.4 MPa, and the water spraying volume for slag granulation is 8 - 12 m 3 / t.

8. The method for co-disposing waste incineration fly ash with hot blast furnace slag according to claim 7, characterized in that, In step S1, the ball-milling time is 10-15 min, and the particle size of the particles obtained by ball-milling is ≤3 mm.

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