Method for preparing admixture through multi-parameter screening and grading pretreatment of sludge incineration ash

Abstract

The invention relates to the technical field of solid waste resource utilization, and discloses a method for preparing an admixture through multi-parameter screening and grading pretreatment of sludge incineration ash, which is used for testing the heavy metal leaching toxicity, the fineness (45-micron square hole sieve residue) and the strength activity index of the sludge incineration ash. And comprehensive analysis and judgment are carried out according to the parameters, and the sludge incineration ash is classified and graded, so that subsequent pretreatment and resource utilization are facilitated. According to the method for preparing the admixture through multi-parameter screening and grading pretreatment of the sludge incineration ash residues, the problem that resource utilization is difficult due to the fact that components of the sludge incineration ash residues are complex and wood property fluctuation is large is solved, resource utilization of the sludge incineration ash residues of any source and batch can be achieved, and the utilization rate of the sludge incineration ash residues is increased. The most convenient technology for pretreating and recycling the sludge incineration ash is achieved, the economic cost is optimized, and the utilization rate is maximized.

Description

Technical Field

[0001] The invention relates to the technical field of solid waste resource utilization, and in particular to a method for preparing an admixture by multi-parameter screening and grading pretreatment of sludge incineration ash. Background Art

[0002] The chemical composition of sludge incineration ash is mainly SiO2, Al2O3, CaO and Fe2O3, and contains a certain glass phase. It has potential cementing activity and can replace part of cement as an auxiliary cementing material for mortar and concrete, reducing the amount of cement to achieve the purpose of energy saving and carbon reduction. At present, some companies use sludge incineration ash to prepare mixed materials or admixtures. However, compared with commonly used auxiliary cementing materials such as fly ash and mineral powder, sewage sludge comes from a wide range of sources and contains harmful substances such as heavy metals and organic pollutants. In addition, various modifiers are added during the sludge dehydration process, and the sludge composition varies greatly at different times, resulting in large differences in the material properties of sludge incineration ash and unstable properties. There are still the following problems when using it directly for mortar and concrete: ① The composition of sludge incineration ash is complex and the material properties vary greatly, which affects the stability of the performance of mortar and concrete; ② The sludge incineration ash has less glass phase and lower activity; ③ The sludge incineration ash has a high phosphorus content, which leads to slow cement hydration reaction and abnormal cement setting time, affecting the engineering quality and safety of mortar and concrete; ④ The sludge incineration ash is enriched with a large amount of heavy metals such as Cd, Pb, Cr, and the porous structure aggravates the risk of heavy metal leaching, affecting environmental safety.

[0003] Since the fineness, water demand ratio, strength activity index and other properties of sludge incineration ash from different sewage treatment plants vary greatly, if targeted pretreatment is not carried out, it will cause waste of energy and resources. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing admixtures by multi-parameter screening and grading pretreatment of sludge incineration ash, so as to solve the problem raised in the above background technology that the sludge incineration ash from different sewage treatment plants has large differences in fineness, water demand ratio, strength activity index and other properties. If targeted pretreatment is not carried out, it will cause waste of energy and resources.

[0005] To achieve the above object, the present invention provides the following technical solution: a method for preparing admixtures by multi-parameter screening and grading pretreatment of sludge incineration ash, comprising the following steps:

[0006] S1. Test the leaching toxicity of heavy metals in sludge incineration ash;

[0007] S2. Test the fineness of sludge incineration ash (45μm square hole sieve residue);

[0008] S3. Test the strength activity index of sludge incineration ash;

[0009] S4. Based on the comprehensive analysis and judgment of the above parameters, the sludge incineration ash is classified and graded before pretreatment.

[0010] in,

[0011] When the heavy metal leaching toxicity in the sludge incineration ash is total mercury ≤0.02mg / L, total arsenic ≤0.6mg / L, total cadmium ≤0.1mg / L, total chromium ≤1.5mg / L, and total lead ≤2.0mg / L, proceed to steps S2-S4; otherwise, landfill disposal should be carried out in accordance with the provisions of GB 18598.

[0012] When the fineness of the sludge incineration ash (45μm square hole sieve residue) is ≤30% and the strength activity index is ≥70%, no pretreatment is required.

[0013] Preferably, when the fineness of the sludge incineration ash (45 μm square hole sieve residue) is ≤30% and the strength activity index is 60%≤<70%, it is compounded with fly ash in a certain proportion, and the proportion of the sludge incineration ash during compounding is 10%-30%.

[0014] Preferably, when the fineness of the sludge incineration ash (45 μm square hole sieve residue) is ≤30% and the strength activity index is <60%, a modifier needs to be added to improve the performance, and the dosage of the modifier is within 7%.

[0015] Preferably, when the fineness of the sludge incineration ash (residue on a 45 μm square sieve) is greater than 30% and less than or equal to 45%, and the strength activity index is 60%≤strength activity index<70%, the sludge incineration ash can be directly pre-treated by ball milling.

[0016] Preferably, when the fineness of the sludge incineration ash (45μm square hole sieve residue) is greater than 30% and less than or equal to 45%, or the fineness of the sludge incineration ash (45μm square hole sieve residue) is greater than 45%, and the strength activity index is less than 60%, ball milling pretreatment is carried out while adding the modifier, and the dosage of the modifier is within 5%.

[0017] Preferably, the moisture content of the sludge incineration ash should be less than 1%.

[0018] Preferably, the fly ash has a sieve residue of ≤30% passing a 45 μm square hole sieve, a water requirement ratio of ≤105%, a loss on ignition of ≤8%, a moisture content of ≤1.0%, a strength activity index of ≥70%, a stability qualification of ≤5.0%, and the radioactive specific activities of natural radionuclides radium-226, thorium-232, and potassium-40 in the fly ash simultaneously satisfy IRa≤1.0 and Iγ≤1.0.

[0019] Preferably, the modifier is one or more of lime, desulfurized gypsum, calcium hydroxide, desulfurized ash, etc.

[0020] Preferably, when the fineness of the sludge incineration ash (45 μm square hole sieve residue) is greater than 30% and less than or equal to 45%, and the intensity activity index is less than 60%, the ball milling pretreatment time is 10-15 minutes.

[0021] Preferably, when the fineness of the sludge incineration ash (45 μm square hole sieve residue) is greater than 45% and the strength activity index is less than 60%, the ball milling pretreatment time is 16-20 minutes.

[0022] Compared with the prior art, the invention has the following beneficial effects: the method for preparing admixtures by multi-parameter screening and grading pretreatment of sludge incineration ash is

[0023] 1. The method for preparing admixtures by multi-parameter screening and grading pretreatment of sludge incineration ash. The present invention first tests the heavy metal leaching toxicity of the sludge incineration ash. If it exceeds the standard, it is landfilled. If it is qualified, it can be used as a solid waste resource before subsequent testing for classification and grading.

[0024] 2. The method of preparing admixtures by multi-parameter screening and grading pretreatment of sludge incineration ash. The sludge incineration ash used as an admixture must meet the requirements of Class II fly ash standards. Since the fineness, water demand ratio, strength activity index and other properties of sludge incineration ash from different sewage treatment plants vary greatly, it is necessary to test its fineness and strength activity index before pretreatment, and carry out targeted pretreatment based on the test results, which can effectively avoid waste of energy and resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the test results of heavy metal toxicity leaching, fineness (45μm square hole sieve residue) and intensity activity index of sludge incineration ash;

[0026] Figure 2 This is a schematic diagram of the test results of the performance of sludge incineration ash admixture;

[0027] Figure 3 It is a schematic diagram of the test results of heavy metal toxicity leaching, fineness (45μm square hole sieve residue) and intensity activity index of sludge incineration ash;

[0028] Figure 4 This is a schematic diagram of the test results of the performance of sludge incineration ash admixture; DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. 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.

[0030] The present invention provides a technical solution: a method for preparing an admixture by multi-parameter screening and grading pretreatment of sludge incineration ash, comprising the following steps:

[0031] (1) Testing the leaching toxicity of heavy metals in sludge incineration ash;

[0032] (2) Test the fineness of sludge incineration ash (45 μm square hole sieve residue);

[0033] (3) Testing the strength activity index of sludge incineration ash;

[0034] (4) Based on the comprehensive analysis and judgment of the above parameters, the sludge incineration ash is classified and graded before pretreatment.

[0035] in,

[0036] When the heavy metal leaching toxicity of the sludge incineration ash is total mercury ≤ 0.02 mg / L, total arsenic ≤ 0.6 mg / L, total cadmium ≤ 0.1 mg / L, total chromium ≤ 1.5 mg / L, and total lead ≤ 2.0 mg / L, proceed to steps (2) to (5); otherwise, the sludge should be landfilled in accordance with the provisions of GB 18598.

[0037] Sludge incineration ash with fineness (45μm square hole sieve residue) ≤30% and strength activity index ≥70% has met the requirements of Class II fly ash and can be directly used without treatment;

[0038] For sludge incineration ash with fineness (45μm square hole sieve residue) ≤30%, 60%≤strength activity index <70%, the fineness meets the requirements, but the content of silicon-aluminum glass is relatively small, so it needs to be compounded with fly ash in a certain proportion to supplement the silicon-aluminum glass in the admixture;

[0039] For sludge incineration ash with fineness (45μm square hole sieve residue) ≤30% and strength activity index <60%, the fineness meets the requirements but the activity is low. This is because the P2O5 content in the sludge incineration ash is high, which affects the hydration process of the cementitious material system. Improving the activity by simply compounding or ball milling the fly ash cannot meet the activity requirements of Class II fly ash. Therefore, it is necessary to add a modifier to stimulate the activity, and to stimulate the activity by increasing the Ca2+ ions or SO42- in the system.

[0040] For sludge incineration ash whose fineness (45μm square hole sieve residue) is greater than 30% and less than or equal to 45%, and whose strength activity index is 60%≤<70%, this is because the particle size distribution of sludge incineration ash is large and the area of ​​hydration reaction is small. Therefore, the sludge incineration ash can be directly pre-treated by ball milling;

[0041] For sludge incineration ash with a fineness (45μm square hole sieve residue) greater than 30% and less than or equal to 45%, or sludge incineration ash with a fineness (45μm square hole sieve residue) greater than 45%, and a strength activity index less than 60%, the activity cannot be improved by simply increasing the reaction area through ball milling. Therefore, it is necessary to use a physical-chemical combined excitation method of adding modifiers and ball milling pretreatment for pretreatment.

[0042] Example 1

[0043] Sludge incineration ash produced at different times in a sewage treatment plant was selected for heavy metal leaching toxicity, fineness (45μm square hole sieve residue) and strength activity index testing. The fineness was tested in accordance with GB / T 1596-2017 "Fly ash used in cement and concrete", and the strength activity index was tested in accordance with GB / T 17671-2021 "Test method for strength of cement mortar (ISO method)". The test results are shown in Figure 1 .

[0044] From the test results, it can be seen that except for the heavy metal leaching toxicity of sample No. 1 which is unqualified, the heavy metal leaching toxicity of the other samples No. 2-4 does not exceed the standard and can be used as raw materials for resource utilization. According to the performance test results of samples No. 2-4, their fineness is ≤30%, but the strength activity index varies greatly. According to the technical solution of the present invention, samples 3 and 4 are respectively pre-treated by compounding with fly ash in proportion and adding modifiers. The performance of the admixtures prepared after pretreatment is as follows Figure 2 shown.

[0045] Depend on Figure 2 It can be seen that after compounding with fly ash, the strength activity index of sample No. 3 was increased to 72.0%, reaching the requirements of Class II fly ash; after adding modifier, the strength activity index of sample No. 4 increased from 45.2% to more than 70%, especially the sludge incineration ash with the addition of lime, calcium hydroxide and desulfurization ash, whose strength activity index can reach up to 76.7%.

[0046] Example 2

[0047] Sludge incineration ash produced at different times in a sewage treatment plant was selected for heavy metal leaching toxicity, fineness (45μm square hole sieve residue) and strength activity index testing. The fineness was tested in accordance with GB / T 1596-2017 "Fly ash used in cement and concrete", and the strength activity index was tested in accordance with GB / T 17671-2021 "Test method for strength of cement mortar (ISO method)". The test results are shown in Figure 3 .

[0048] From the test results, it can be seen that the heavy metal toxicity leaching of all samples is qualified and can be used as raw materials for resource utilization. The strength activity index of samples 1 and 2 is both above 60.0%, and only the fineness is not more than 45%. Ball milling pretreatment is used to improve their activity; the fineness of samples 3 and 4 is more than 30% and less than 45%, and the strength activity index is less than 60%. Modifiers are used for pretreatment and ball milling for 15 minutes; the fineness of samples 5 and 6 is more than 45%, and the strength activity index is less than 60%. Modifiers are used for pretreatment and ball milling for 20 minutes. The performance of the admixtures prepared after pretreatment is as follows: Figure 4 shown.

[0049] Depend on Figure 4 It can be seen that after 10 minutes of ball milling, the strength activity index of samples 1 and 2 is above 70.0%, reaching the requirements of Class II fly ash; after 15 minutes of ball milling, the fineness of samples 3 and 4 becomes smaller, and the strength activity index increases to nearly 75.0%; after 20 minutes of ball milling, the fineness of samples 5 and 6 becomes smaller, and the strength activity index increases to over 75.0%, both meeting the requirements of Class II fly ash.

[0050] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing admixtures by multi-parameter screening and grading pretreatment of sludge incineration ash, characterized in that: The following steps are involved: S1. Test the leaching toxicity of heavy metals in sludge incineration ash; S2. Test the fineness of sludge incineration ash (45μm square hole sieve residue); S3. Test the strength activity index of sludge incineration ash; S4. Based on the comprehensive analysis and judgment of the above parameters, the sludge incineration ash is classified and graded before pretreatment. in, When the heavy metal leaching toxicity in the sludge incineration ash is total mercury ≤0.02mg / L, total arsenic ≤0.6mg / L, total cadmium ≤0.1mg / L, total chromium ≤1.5mg / L, and total lead ≤2.0mg / L, proceed to steps S2-S4; otherwise, landfill disposal should be carried out in accordance with the provisions of GB 18598. When the fineness of the sludge incineration ash (45μm square hole sieve residue) is ≤30% and the strength activity index is ≥70%, no pretreatment is required.

2. The method for preparing admixtures by multi-parameter screening and grading pretreatment of sludge incineration ash according to claim 1, characterized in that: When the fineness of the sludge incineration ash (residue on a 45 μm square sieve) is ≤30% and the strength activity index is 60%≤<70%, the sludge incineration ash is compounded with fly ash in a certain proportion, wherein the proportion of the sludge incineration ash is 10%-30%.

3. The method for preparing admixtures by multi-parameter screening and grading pretreatment of sludge incineration ash according to claim 1, characterized in that: When the fineness of the sludge incineration ash (45 μm square hole sieve residue) is ≤30% and the strength activity index is <60%, a modifier needs to be added to improve the performance, and the dosage of the modifier is within 7%.

4. The method for preparing admixtures by multi-parameter screening and grading pretreatment of sludge incineration ash according to claim 1, characterized in that: When the fineness of the sludge incineration ash (residue on a 45 μm square sieve) is greater than 30% and less than or equal to 45%, and the strength activity index is 60%≤<70%, the sludge incineration ash can be directly pre-treated by ball milling.

5. The method for preparing admixtures by multi-parameter screening and grading pretreatment of sludge incineration ash according to claim 1, characterized in that: When the fineness of the sludge incineration ash (45μm square hole sieve residue) is greater than 30% and less than or equal to 45%, or the fineness of the sludge incineration ash (45μm square hole sieve residue) is greater than 45%, and the strength activity index is less than 60%, ball milling pretreatment is performed while adding a modifier, and the dosage of the modifier is within 5%.

6. The method for preparing admixtures by multi-parameter screening and grading pretreatment of sludge incineration ash according to claim 1, characterized in that: The moisture content of the sludge incineration ash must be less than 1%.

7. The method for preparing admixtures by multi-parameter screening and grading pretreatment of sludge incineration ash according to claim 1, characterized in that: The fly ash has a sieve residue of ≤30% passing a 45 μm square hole sieve, a water requirement ratio of ≤105%, a loss on ignition of ≤8%, a moisture content of ≤1.0%, a strength activity index of ≥70%, a stability qualification of ≤5.0%, and the radioactive specific activities of natural radionuclides radium-226, thorium-232, and potassium-40 in the fly ash simultaneously satisfy IRa≤1.0 and Iγ≤1.

0.

8. The method for preparing admixtures by multi-parameter screening and grading pretreatment of sludge incineration ash according to claim 1, characterized in that: The modifier is one or more of lime, desulfurized gypsum, calcium hydroxide, desulfurized ash, etc.

9. The method for preparing admixtures by multi-parameter screening and grading pretreatment of sludge incineration ash according to claim 1, characterized in that: When the fineness of the sludge incineration ash (45 μm square hole sieve residue) is greater than 30% and less than or equal to 45%, and the intensity activity index is less than 60%, the ball milling pretreatment time is 10-15 minutes.

10. The method for preparing admixtures by multi-parameter screening and grading pretreatment of sludge incineration ash according to claim 1, characterized in that: When the fineness of the sludge incineration ash (45 μm square hole sieve residue) is greater than 45% and the strength activity index is less than 60%, the ball milling pretreatment time is 16-20 minutes.

11. The admixture prepared after pretreatment according to any one of claims 1 to 10 is used as a replacement for fly ash in cement concrete building materials.

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