Method for removing heavy metals in waste incineration fly ash

Abstract

The invention belongs to the technical field of waste incineration treatment, and discloses a method for removing heavy metals in waste incineration fly ash, which comprises the following steps: the waste incineration fly ash is sieved, and then placed in a magnetic separator for wet magnetic separation to separate out iron, and the magnetic separation process parameters are as follows: the magnetic field intensity is 11000-15000 GS, the ash-water ratio is 220-350 g / L, and the retention time is 2-4 min; in the waste incineration fly ash, the content of Fe2O3 is 1-4%, the content of carbon is 13-20%, the content of sulfur is 0.5-1.5%, and the loss on ignition is 16-25%. According to the method, the magnetic separation effect of iron in the fly ash can be improved in a targeted mode, and high-quality iron ore can be recycled.

Description

Technical Field

[0001] The invention belongs to the technical field of waste incineration treatment, and in particular relates to a method for removing heavy metals from waste incineration fly ash. Background Art

[0002] Waste incineration fly ash is the capture product of the flue gas purification system during the incineration and disposal of municipal domestic waste and the bottom ash settled at the bottom of the flue and chimney.

[0003] The main phase of fly ash is glass, accounting for 50% to 80%. The crystalline minerals contained are mullite, α-quartz, calcite, anorthite, calcium silicate, hematite and magnetite, as well as a small amount of unburned carbon. The chemical composition of fly ash varies greatly, which is related to the fuel type, combustion conditions and ash collection method.

[0004] Fly ash contains a large amount of heavy metal iron. In the prior art, when fly ash is treated for resource recovery and harmlessness, magnetic separation is often used to pre-treat the fly ash to remove magnetic substances in the fly ash (mainly hematite Fe2O3 and magnetite Fe3O4, most of which are hematite Fe2O3). However, the specific chemical composition and particle size distribution of fly ash have a great influence on the magnetic separation process. For example, the iron ore content in fly ash determines the content of magnetic substances in fly ash, and carbon, sulfur and other substances in fly ash easily react with iron ore to change the magnetic separation results. However, the existing magnetic separation process rarely starts from the properties of fly ash itself, and ignores the influence of fly ash properties on the magnetic separation process, resulting in...

[0005] In summary, providing a method for removing heavy metals from waste incineration fly ash can not only improve the magnetic separation effect of iron in fly ash in a targeted manner, but also recover higher quality iron ore, which is an urgent problem to be solved. Summary of the invention

[0006] The purpose of the present invention is to overcome the shortcomings of the existing technology and provide a method for removing heavy metals from waste incineration fly ash. The fly ash with specific iron ore content, sulfur content, carbon content, ignition loss and specific particle size composition is subjected to magnetic separation treatment, which can not only improve the magnetic separation effect of iron in the fly ash, but also recover iron ore with a higher iron grade.

[0007] To achieve the above object, the present invention adopts the following technical solutions: A method for removing heavy metals from waste incineration fly ash comprises the following steps: taking the waste incineration fly ash for sieving, and then placing it in a magnetic separator for wet magnetic separation to separate iron, wherein the magnetic separation process parameters are: magnetic field intensity of 11000-15000GS, ash-water ratio of 220-350g / L, and retention time of 2-4min.

[0008] The waste incineration fly ash has an Fe2O3 content of 1-4%, a carbon content of 13-20%, a sulfur content of 0.5-1.5%, and a loss on ignition of 16-25%.

[0009] Preferably, the Fe2O3 content in the waste incineration fly ash is 2.5%, the carbon content is 15%, the sulfur content is 1.0%, and the loss on ignition is 18%.

[0010] Preferably, the particle size of the sieved waste incineration fly ash is 50-200 μm.

[0011] More preferably, the particle size distribution of the waste incineration fly ash after screening is as follows: the particle size is 40-49μm, accounting for 4-7%, the particle size is 50-69μm, accounting for 16-24%, the particle size is 70-89μm, accounting for 13-18%, the particle size is 90-119μm, accounting for 22-30%, the particle size is 120-159μm, accounting for 12-20%, and the remaining particle size is 160-200μm.

[0012] Preferably, sodium glycine carbonate is also added to the material during the magnetic separation process, and the amount added is 0.5-3% of the mass of the fly ash.

[0013] Preferably, the waste incineration fly ash is calcined at 600-800°C and then subjected to magnetic separation, and the calcination time is 40-100 minutes.

[0014] The beneficial effects of the present invention are: (1) Magnetic separation of fly ash with specific iron ore content, sulfur content, carbon content, ignition loss and specific particle size composition can not only improve the magnetic separation effect of iron in fly ash, but also recover iron ore with higher iron grade.

[0015] (2) When the present invention performs wet magnetic separation on fly ash, sodium glycine carbonate is also added, which can not only adjust the pH of the fly ash slurry, but also reduce the influence of calcium and magnesium ions dissolved in the fly ash on the magnetic separation of iron ore. In addition, by adjusting the pH of the fly ash slurry, the sulfur content in the iron ore obtained by magnetic separation can be further reduced. DETAILED DESCRIPTION

[0016] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0017] Unless otherwise specified, the reagents involved in the embodiments of the present invention are all commercially available products and can be purchased through commercial channels. Example 1

[0018] The waste incineration fly ash used in this embodiment has a Fe2O3 content of 2.5%, a carbon content of 15%, a sulfur content of 1.0%, a loss on ignition of 18%, and a pH of 11-13.

[0019] The particle size distribution of the waste incineration fly ash after screening is as follows: 5% of the particles are in the range of 40-49μm, 20% of the particles are in the range of 50-69μm, 16% of the particles are in the range of 70-89μm, 26% of the particles are in the range of 90-119μm, 16% of the particles are in the range of 120-159μm, and the remaining particles are in the range of 160-200μm.

[0020] This embodiment provides a method for removing heavy metals from waste incineration fly ash, comprising the following steps: taking the waste incineration fly ash for sieving, and then placing it in a magnetic separator for wet magnetic separation to separate iron. The magnetic separation process parameters are: magnetic field intensity 13000 GS, ash-water ratio 280g / L, retention time 3min. Example 2

[0021] On the basis of Example 1, in this example, sodium glycine carbonate is further added to the material during the magnetic separation process, and the amount added is 1.8% of the fly ash mass. The specific method at this time is: The waste incineration fly ash was sieved and then placed in a magnetic separator. Sodium glycine carbonate was added for wet magnetic separation to separate the iron. The magnetic separation process parameters were: magnetic field intensity 13000 GS, ash-to-water ratio 280 g / L, and retention time 3 min. Example 3

[0022] Based on Example 1, this example performs a roasting pretreatment on the fly ash and then performs magnetic separation. The specific method is as follows: The fly ash from waste incineration was screened and then calcined at 700℃ for 70min. It was then placed in a magnetic separator for wet magnetic separation to separate iron. The magnetic separation process parameters were: magnetic field intensity 13000 GS, ash-to-water ratio 280g / L, and retention time 3min. Example 4

[0023] On the basis of Example 1, this example simultaneously performs roasting pretreatment on the fly ash and adds sodium glycine carbonate during the magnetic separation process. The specific method at this time is: The fly ash from waste incineration was sieved and then calcined at 700℃ for 70min. It was then placed in a magnetic separator and sodium glycine carbonate (1.8% of the fly ash mass) was added for wet magnetic separation to separate the iron. The magnetic separation process parameters were: magnetic field intensity 13000 GS, ash-to-water ratio 280g / L, and retention time 3min. Example 5

[0024] The waste incineration fly ash used in this embodiment has a Fe2O3 content of 1%, a carbon content of 20%, a sulfur content of 0.5%, a loss on ignition of 25%, and a pH of 11-13.

[0025] The particle size distribution of the waste incineration fly ash after screening is as follows: the particle size is 40-49μm, accounting for 4%, the particle size is 50-69μm, accounting for 16%, the particle size is 70-89μm, accounting for 13%, the particle size is 90-119μm, accounting for 22%, the particle size is 120-159μm, accounting for 12%, and the remaining particle size is 160-200μm.

[0026] This embodiment provides a method for removing heavy metals from waste incineration fly ash, comprising the following steps: The fly ash from waste incineration was sieved and then calcined at 600℃ for 100min. It was then placed in a magnetic separator and sodium glycine carbonate (0.5% of the fly ash mass) was added for wet magnetic separation to separate the iron. The magnetic separation process parameters were: magnetic field intensity 11000GS, ash-to-water ratio 220g / L, and retention time 4min. Example 6

[0027] The waste incineration fly ash used in this embodiment has a Fe2O3 content of 4%, a carbon content of 13%, a sulfur content of 1.5%, and a loss on ignition of 16. The pH of the waste incineration fly ash is 11-13.

[0028] The particle size distribution of the waste incineration fly ash after screening is as follows: the particle size is 40-49μm accounting for 7%, the particle size is 50-69μm accounting for 24%, the particle size is 70-89μm accounting for 18%, the particle size is 90-119μm accounting for 30%, the particle size is 120-159μm accounting for 20%, and the remaining particle size is 160-200μm.

[0029] This embodiment provides a method for removing heavy metals from waste incineration fly ash, comprising the following steps: The fly ash from waste incineration was sieved and then calcined at 800℃ for 40min. It was then placed in a magnetic separator and sodium glycine carbonate (3% of the fly ash mass) was added for wet magnetic separation to separate the iron. The magnetic separation process parameters were: magnetic field intensity 15000 GS, ash-water ratio 350g / L, and retention time 2min.

[0030] Comparative Example 1 The difference between this comparative example and Example 1 is that the Fe2O3 content in the fly ash is 0.6%, the carbon content is 10%, the sulfur content is 0.2%, and the loss on ignition is 14%.

[0031] Comparative Example 2 The difference between this comparative example and Example 1 is that the Fe2O3 content in the fly ash is 5%, the carbon content is 22%, the sulfur content is 2%, and the loss on ignition is 28%.

[0032] Comparative Example 3 The difference between this comparative example and Example 1 is that the particle size distribution of the waste incineration fly ash after screening is as follows: the particle size is 40-49μm, accounting for 2%, the particle size is 50-69μm, accounting for 20%, the particle size is 70-89μm, accounting for 16%, the particle size is 90-119μm, accounting for 26%, the particle size is 120-159μm, accounting for 16%, and the remaining particle size is 160-200μm.

[0033] Comparative Example 4 The difference between this comparative example and Example 1 is that the particle size distribution of the waste incineration fly ash after screening is as follows: the particle size is 40-49μm, accounting for 5%, the particle size is 50-69μm, accounting for 12%, the particle size is 70-89μm, accounting for 16%, the particle size is 90-119μm, accounting for 26%, the particle size is 120-159μm, accounting for 16%, and the remaining particle size is 160-200μm.

[0034] Comparative Example 5 The difference between this comparative example and Example 1 is that the particle size distribution of the waste incineration fly ash after screening is as follows: the particle size is 40-49μm, accounting for 5%, the particle size is 50-69μm, accounting for 20%, the particle size is 70-89μm, accounting for 10%, the particle size is 90-119μm, accounting for 26%, the particle size is 120-159μm, accounting for 16%, and the remaining particle size is 160-200μm.

[0035] Comparative Example 6 The difference between this comparative example and Example 1 is that the particle size distribution of the waste incineration fly ash after screening is as follows: the particle size is 40-49μm, accounting for 5%, the particle size is 50-69μm, accounting for 20%, the particle size is 70-89μm, accounting for 16%, the particle size is 90-119μm, accounting for 20%, the particle size is 120-159μm, accounting for 16%, and the remaining particle size is 160-200μm.

[0036] Comparative Example 7 The difference between this comparative example and Example 1 is that the particle size distribution of the waste incineration fly ash after screening is as follows: the particle size is 40-49μm, accounting for 5%, the particle size is 50-69μm, accounting for 20%, the particle size is 70-89μm, accounting for 16%, the particle size is 90-119μm, accounting for 26%, the particle size is 120-159μm, accounting for 10%, and the remaining particle size is 160-200μm.

[0037] Comparative Example 8 The difference between this comparative example and Example 1 is that the particle size distribution of the waste incineration fly ash after screening is as follows: the particle size is 40-49μm, accounting for 9%, the particle size is 50-69μm, accounting for 20%, the particle size is 70-89μm, accounting for 16%, the particle size is 90-119μm, accounting for 26%, the particle size is 120-159μm, accounting for 16%, and the remaining particle size is 160-200μm.

[0038] Comparative Example 9 The difference between this comparative example and Example 1 is that the particle size distribution of the waste incineration fly ash after screening is as follows: the particle size is 40-49μm, accounting for 5%, the particle size is 50-69μm, accounting for 27%, the particle size is 70-89μm, accounting for 16%, the particle size is 90-119μm, accounting for 26%, the particle size is 120-159μm, accounting for 16%, and the remaining particle size is 160-200μm.

[0039] Comparative Example 10 The difference between this comparative example and Example 1 is that the particle size distribution of the waste incineration fly ash after screening is as follows: the particle size is 40-49μm, accounting for 5%, the particle size is 50-69μm, accounting for 20%, the particle size is 70-89μm, accounting for 20%, the particle size is 90-119μm, accounting for 26%, the particle size is 120-159μm, accounting for 16%, and the remaining particle size is 160-200μm.

[0040] Comparative Example 11 The difference between this comparative example and Example 1 is that the particle size distribution of the waste incineration fly ash after screening is as follows: the particle size is 40-49μm, accounting for 5%, the particle size is 50-69μm, accounting for 20%, the particle size is 70-89μm, accounting for 16%, the particle size is 90-119μm, accounting for 33%, the particle size is 120-159μm, accounting for 16%, and the remaining particle size is 160-200μm.

[0041] Comparative Example 12 The difference between this comparative example and Example 1 is that the particle size distribution of the waste incineration fly ash after screening is as follows: the particle size is 40-49μm, accounting for 5%, the particle size is 50-69μm, accounting for 20%, the particle size is 70-89μm, accounting for 16%, the particle size is 90-119μm, accounting for 26%, the particle size is 120-159μm, accounting for 23%, and the remaining particle size is 160-200μm.

[0042] Comparative Example 13 The difference between this comparative example and Example 1 is that the magnetic field strength in the magnetic separation process is 10000 GS.

[0043] Comparative Example 14 The difference between this comparative example and Example 1 is that the magnetic field strength in the magnetic separation process is 16000 GS.

[0044] Comparative Example 15 The difference between this comparative example and Example 1 is that the ash-water ratio in the magnetic separation process is 200 g / L.

[0045] Comparative Example 16 The difference between this comparative example and Example 1 is that the ash-to-water ratio in the magnetic separation process is 370 g / L.

[0046] Comparative Example 17 The difference between this comparative example and Example 1 is that the retention time in the magnetic separation process is 1 min.

[0047] Comparative Example 18 The difference between this comparative example and Example 1 is that the retention time in the magnetic separation process is 6 minutes.

[0048] Comparative Example 19 The difference between this comparative example and Example 2 is that sodium glycine carbonate is replaced with sodium carbonate.

[0049] Comparative Example 20 The difference between this comparative example and Example 4 is that the calcination temperature of the waste incineration fly ash is 500°C.

[0050] Comparative Example 21 The difference between this comparative example and Example 4 is that the calcination temperature of the waste incineration fly ash is 900°C.

[0051] Comparative Example 22 The difference between this comparative example and Example 4 is that the calcination time of the waste incineration fly ash is 30 minutes.

[0052] Comparative Example 23 The difference between this comparative example and Example 4 is that the calcination time of the waste incineration fly ash is 110 min.

[0053] 1. Magnetic separation process results 1. Iron recovery rate and grade The waste combustion fly ash was wet magnetically separated by the methods of Examples 1-6 and Comparative Examples 1-23, and the iron ore obtained by magnetic separation was filtered, dried, weighed, and chemically analyzed. The results are shown in Table 1 below.

[0054] Table 1

[0055] As can be seen from Table 1, the Fe recovery rate of the fly ash magnetic separation in Examples 1-6 of the present invention is in the range of 70.7-86.7%, and the Fe grade is in the range of 46.9-65.4%, showing a good magnetic separation effect.

[0056] On the basis of Example 1, Example 2 added sodium glycine carbonate during the magnetic separation process, Example 3 performed calcination pretreatment on the fly ash, and Examples 4-6 simultaneously performed calcination pretreatment on the fly ash and added sodium glycine carbonate during the magnetic separation process. As a result, the Fe recovery rate and grade of the fly ash were improved.

[0057] Compared with Example 1, Comparative Examples 1-18 respectively changed the chemical composition, particle size distribution, magnetic field intensity, ash-water ratio, retention time and other magnetic separation process parameters in the fly ash; compared with Example 2, Comparative Example 19 replaced sodium glycine carbonate with sodium carbonate; compared with Example 4, Comparative Examples 20-23 changed the roasting temperature and time. As a result, the Fe recovery rate and grade of the fly ash in Comparative Examples 1-23 were reduced, indicating that these parameters would affect the magnetic separation effect.

[0058] 2. Sulfur content in magnetically separated iron ore The methods of Examples 1-6 and Comparative Example 19 were respectively used to carry out wet magnetic separation on the waste combustion fly ash. The iron ore obtained by magnetic separation was filtered, dried, weighed, and subjected to chemical composition analysis. The sulfur content in the magnetically separated iron ore was analyzed. The results are shown in Table 2 below.

[0059] Table 2

[0060] As can be seen from Table 2, Examples 2 and 4-6 of the present invention can significantly reduce the sulfur content in the iron obtained by the fly ash magnetic separation process, and obtain iron ore with higher quality.

[0061] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for removing heavy metals from waste incineration fly ash, characterized in that: The method comprises the following steps: taking the waste incineration fly ash for screening, and then placing it in a magnetic separator for wet magnetic separation to separate iron, and the magnetic separation process parameters are: magnetic field intensity 11000-15000 GS, ash-water ratio 220-350g / L, retention time 2-4min; The waste incineration fly ash has an Fe2O3 content of 1-4%, a carbon content of 13-20%, a sulfur content of 0.5-1.5%, and a loss on ignition of 16-25%.

2. The method according to claim 1, characterized in that: The waste incineration fly ash has an Fe2O3 content of 2.5%, a carbon content of 15%, a sulfur content of 1.0%, and a loss on ignition of 18%.

3. The method according to claim 1, characterized in that: The particle size of the sieved waste incineration fly ash is 50-200μm.

4. The method according to claim 1, characterized in that: During the magnetic separation process, sodium glycine carbonate is also added to the material in an amount of 0.5-3% of the fly ash mass.

5. The method according to claim 1, characterized in that: The waste incineration fly ash is calcined at 600-800°C and then subjected to magnetic separation, and the calcination time is 40-100 minutes.

6. The method according to claim 3, characterized in that: The particle size distribution of the waste incineration fly ash after screening is as follows: the particle size is 40-49μm, accounting for 4-7%, the particle size is 50-69μm, accounting for 16-24%, the particle size is 70-89μm, accounting for 13-18%, the particle size is 90-119μm, accounting for 22-30%, the particle size is 120-159μm, accounting for 12-20%, and the remaining particle size is 160-200μm.

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