Domestic waste incineration fly ash modification method, concrete and preparation of concrete

Abstract

The invention discloses a household garbage incineration fly ash modification method, concrete and preparation of modified fly ash concrete. The fly ash modification method comprises the steps that household garbage incineration fly ash is washed with water; pickling the fly ash; washing the fly ash again; the fly ash is soaked in water to obtain a mixed solution A, and calcium oxide and sodium aluminate are added into the mixed solution A to obtain a mixture B; and carrying out filter pressing on the mixture B, drying, adding calcined magnesium-aluminum hydrotalcite into the mixture B, and carrying out ball milling to obtain the modified household garbage fly ash. The modified fly ash prepared by the method is used as a raw material for preparing the concrete and the modified fly ash concrete. Through water washing, acid pickling, calcium hydroxide and sodium aluminate, and addition of calcined magnesium-aluminum hydrotalcite, high-alumina cement and mineral powder, the content of free and cured Cl <-> in fly ash can be effectively reduced, and the Cl <-> curing capacity of the concrete is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of concrete production, and in particular to a method for modifying fly ash from the incineration of domestic waste, concrete, and concrete preparation. Background Art

[0002] Municipal solid waste incineration fly ash is a solid waste generated after the incineration of municipal solid waste. Its main components include sodium chloride, potassium chloride, basic calcium chloride (CaClOH), activated carbon (later used to adsorb dioxins), calcium carbonate, anhydrous calcium sulfate, dioxins, etc. As shown in Chinese patents CN202311326459.6 and CN201911031919.6, after multiple water washing, drying, ball milling and other processing steps, the waste incineration fly ash can be used as an admixture in the production of concrete or as a raw material in the production of cement. However, even after multiple water washings, some water-soluble Cl- still exists in the waste incineration fly ash, which increases the risk of concrete corrosion to steel bars and limits the large-scale application of waste incineration fly ash in concrete. Summary of the Invention

[0003] In view of the defects in the prior art, the present application provides a method for modifying fly ash from the incineration of domestic waste and the preparation of concrete thereof, so as to solve the problems raised by the above background technology.

[0004] In order to achieve the purpose of the above invention, the technical solution provided by the present invention is as follows:

[0005] A method for modifying and treating fly ash from incineration of domestic waste comprises the following steps:

[0006] Step 1: Wash the fly ash from the incineration of domestic waste and dehydrate the washed fly ash to preliminarily remove water-soluble Cl- in the fly ash;

[0007] Step 2: Pickling the fly ash obtained in step 1 and dehydrating the pickled fly ash to remove acid-soluble chloride ions in the fly ash;

[0008] Step 3: Wash the fly ash obtained in step 2 again, and dehydrate the washed fly ash after a period of reaction;

[0009] Step 4: Soak the fly ash obtained in step 3 in water to obtain a mixed solution A, add calcium oxide and sodium aluminate to the mixed solution A, or add calcium hydroxide and sodium aluminate to the mixed solution A, and dehydrate the mixed solution A after a period of reaction to obtain a mixture B;

[0010] Step 5: filter-press and dry the mixture B, add the calcined magnesium-aluminum hydrotalcite to the mixture B, and then ball-mill the mixture. After ball-milling for a period of time, the modified domestic waste incineration fly ash is obtained.

[0011] In one embodiment, the weight ratio of water to ash during water washing in step 1 is 2.5-3.5:1. After the fly ash and water are uniformly stirred, a filter press dehydrator is used to dehydrate the washed fly ash.

[0012] In one embodiment, in step 2, the fly ash obtained in step 1 is pickled with dilute hydrochloric acid or dilute nitric acid. When dilute nitric acid is used for pickling, the liquid-to-solid weight ratio of the dilute hydrochloric acid to the fly ash obtained in step 1 is 1:1.8-2.2. After the dilute hydrochloric acid and the fly ash obtained in step 1 are uniformly stirred, the fly ash is dehydrated using an acid-resistant filter press dehydrator.

[0013] In one embodiment, the dilute hydrochloric acid is prepared by mixing 1 part of concentrated hydrochloric acid with 2.5-3.5 parts of water in a volume ratio.

[0014] In one embodiment, the weight ratio of water to ash during washing in step three is 2.5-3.5:1. After the fly ash and water are evenly stirred and reacted for 8-12 minutes, the washed fly ash is dehydrated using a filter press dehydrator.

[0015] In one embodiment, the mass ratio of water to fly ash obtained in step 3 in mixed solution A is 3:0.8-1.2. If calcium hydroxide and sodium aluminate are added to mixed solution A, the mass of calcium hydroxide and sodium aluminate is 0.5-1.5% of the mass of the fly ash obtained in step 3, and the mass ratio of calcium hydroxide to sodium aluminate is 1:1.1. After a period of reaction, mixed solution A is dehydrated using a filter press dehydrator to obtain mixture B. If calcium oxide and sodium aluminate are added to mixed solution A, the mass of calcium oxide and sodium aluminate is 0.5-1.5% of the mass of the fly ash obtained in step 3, and the mass ratio of calcium oxide to sodium aluminate is 1:1.5. After a period of reaction, mixed solution A is dehydrated using a filter press dehydrator to obtain mixture B.

[0016] In one embodiment, the mass of the calcined magnesium aluminum hydrotalcite in step 4 is 0.8-1.2% of the mass of mixture B.

[0017] The present application also provides a concrete comprising the following raw materials by weight: 27-32 parts of cement, 11-13 parts of blast furnace slag powder, 6-9 parts of fly ash, 70-80 parts of fine aggregate, 2-5 parts of modified fly ash, 94-101 parts of coarse aggregate, 0.4-0.5 parts of water reducer and 15-16 parts of water; wherein the cement is high-aluminum cement, the blast furnace slag powder is high-aluminum blast furnace slag powder, and the modified fly ash is produced by the above-mentioned fly ash modification treatment method.

[0018] In one embodiment, the cement is P·O42.5 ordinary Portland cement, the sum of the mass of tricalcium aluminate and tetracalcium aluminoferrite in the cement is greater than 25% of the mass of the cement; the chemical composition content of alumina in the blast furnace slag powder is greater than 17%, the specific surface area of ​​the blast furnace slag powder is ≥400 m2 / kg, and the 28-day activity index of the blast furnace slag powder is ≥95%; the 45 μm sieve residue of the coarse aggregate is ≤45%, the 28-day strength activity index of the fly ash is ≥70%, the particle size range of the coarse aggregate is 5-25 mm, and the fine aggregate and coarse aggregate are in a dry state; the water reducer is a polycarboxylic acid series or a naphthalene series, and the water reducing rate of the water reducer is ≥14%.

[0019] The present application also provides a method for preparing concrete, comprising weighing, by weight, 27-32 parts of cement, 11-13 parts of blast furnace slag powder, 6-9 parts of fly ash, 70-80 parts of fine aggregate, 2-5 parts of modified fly ash, 94-101 parts of coarse aggregate, 0.4-0.5 parts of a water reducer, and 15-16 parts of water, wherein the cement is high-aluminum cement, the blast furnace slag powder is high-aluminum blast furnace slag powder, and the modified fly ash is prepared by the fly ash modification treatment method according to any one of claims 1 to 7;

[0020] The modified fly ash is mixed evenly with silicate cement, mineral powder, fly ash, sand and gravel, and then water and a water reducing agent are added and mixed to prepare the modified fly ash concrete.

[0021] Compared with the prior art, this application has at least the following beneficial effects:

[0022] The present invention not only removes water-soluble Cl- in fly ash from waste incineration by water washing, but also removes part of acid-soluble Cl- in fly ash by acid washing. The acid washing also removes heavy metal ions in fly ash, thereby achieving the purpose of reducing fly ash.

[0023] The calcium oxide / calcium hydroxide and sodium aluminate added to the mixed solution A can effectively react with the soluble Cl- in the fly ash to form Friedel's salt (3CaO·Al2O3·CaCl2·10H2O) and Kuzel's salt (3CaO·Al2O3·1 / 2CaSO4·1 / 2CaCl2·11H2O), converting free Cl- into solidified Cl-. Compared with the multiple water washing process in the prior art, this method removes Cl- more thoroughly and uses relatively less water.

[0024] In the fly ash modification method, magnesium-aluminum hydrotalcite is added to the fly ash and then ball milled. The magnesium-aluminum hydrotalcite is a layered double metal hydroxide that can effectively form a bond with the remaining free Cl- in the fly ash to form Mg-Al-CLDHS with Cl- as the interlayer anion, thereby converting the free state into a solidified state. The magnesium-aluminum hydrotalcite that does not participate in the solidification can also combine with dissolved Cl- and externally penetrated Cl- during the service life of the concrete, thereby improving the concrete's resistance to chloride ion corrosion. High-aluminum cement and mineral powder are used in the raw materials and production method of the concrete. The high-aluminum cement and mineral powder can react with Cl- to form Friedel's salt and Kuzel's salt, effectively improving the Cl- solidification ability of the cementitious material system.

[0025] The present application effectively reduces the free and solidified Cl- content in fly ash through water washing, acid washing, calcium hydroxide or calcium oxide + sodium aluminate, and the addition of calcined magnesium-aluminum hydrotalcite, high-aluminum cement and mineral powder, and improves the Cl- solidification ability of concrete, thereby reducing the impact of Cl- on steel bars and making it possible to dispose of fly ash from municipal solid waste incineration on a large scale in concrete. DETAILED DESCRIPTION

[0026] To make the objectives, technical solutions, and advantages of the present invention more clearly understood, the present invention is described below by way of specific embodiments. However, it should be understood that these descriptions are merely illustrative and are not intended to limit the scope of the present invention. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion of the present invention.

[0027] The terms used in this disclosure are for the purpose of describing specific embodiments only and are not intended to limit the disclosure. As used in this disclosure and the appended claims, the singular forms "a," "an," "the," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should also be understood that the term "and / or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items.

[0028] It should be understood that although the terms first, second, third, etc. may be used in this disclosure to describe various information, such information should not be limited to these terms and should not be understood to indicate or imply relative importance. These terms are only used to distinguish information of the same type from each other. For example, first information may also be referred to as second information, and similarly, second information may also be referred to as first information without departing from the scope of this disclosure. Depending on the context, the word "if" as used herein may be interpreted as "at the time of" or "when" or "in response to determining."

[0029] In the description of the present invention, unless otherwise specified and limited, it should be noted that the terms "installed", "connected" and "connected" should be understood in a broad sense. For example, it can be a mechanical connection or the internal communication between two components. It can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to the specific circumstances.

[0030] In order to better understand the technical solution of the present invention, the present invention is described in detail below with reference to embodiments and comparative examples.

[0031] Example 1:

[0032] A method for modifying fly ash from incineration of domestic waste comprises the following steps:

[0033] Step 1: Wash the fly ash from the incineration of domestic waste with a water-ash ratio of 3:1, stir it evenly, and then use a filter press dehydrator to dehydrate it;

[0034] Step 2: The fly ash obtained in step 1 is pickled using dilute hydrochloric acid (1:3), wherein the liquid-solid weight ratio of the dilute hydrochloric acid to the fly ash obtained in step 1 is 1:1, and after being stirred evenly, the fly ash is dehydrated using an acid-resistant filter press dehydrator;

[0035] Step 3: Wash the fly ash obtained in step 2 with water at a water-ash ratio of 3:1, stir evenly, react for 10 minutes, and then dehydrate using a filter press dehydrator;

[0036] In step 4, the fly ash obtained in step 3 is immersed in water at a water-to-ash ratio of 3:1. The mass of calcium hydroxide and sodium aluminate is 1% of the mass of the fly ash obtained in step 3. Then, Ca(OH)2 and NaAlO2 are continuously added at a mass ratio of 1:1.1. The fly ash is then dehydrated using a filter press dehydrator.

[0037] Step 5: The fly ash obtained in step 4 is subjected to filter pressing treatment, and then dehydrated and dried, and then 1% of magnesium aluminum hydrotalcite is added and ball milled to obtain modified fly ash.

[0038] A method for preparing modified fly ash concrete comprises the following steps:

[0039] According to weight, weigh 32 parts of high-alumina Portland cement, 11 parts of high-alumina blast furnace slag powder, 6 parts of fly ash, 80 parts of fine aggregate, 5 parts of fly ash prepared by the modified fly ash modification method described above, 94 parts of coarse aggregate, 0.5 parts of water reducer and 16 parts of water;

[0040] Mixing water and a water reducing agent uniformly to obtain a first mixed solution;

[0041] The powder and aggregate were added into a mixer, mixed for 1 minute, and then the first mixed solution was added, followed by further mixing for 3 minutes to obtain modified fly ash concrete;

[0042] The water-soluble and acid-soluble Cl- contents in 28-day hardened concrete were tested according to JGJ / T322-2013 "Technical Specifications for the Detection of Cl- Content in Concrete".

[0043] Example 2:

[0044] A method for modifying fly ash from incineration of domestic waste comprises the following steps:

[0045] Step 1: Wash the fly ash from the incineration of domestic waste with a water-ash ratio of 3:1, stir it evenly, and then use a filter press dehydrator to dehydrate it;

[0046] Step 2: The fly ash obtained in step 1 is pickled using dilute hydrochloric acid (1:3), wherein the liquid-solid weight ratio of the dilute hydrochloric acid to the fly ash obtained in step 1 is 1:1, and after being stirred evenly, the fly ash is dehydrated using an acid-resistant filter press dehydrator;

[0047] Step 3: Wash the fly ash obtained in step 2 with water at a water-ash ratio of 3:1, stir it evenly, and then use a filter press dehydrator to dehydrate it;

[0048] Step 4: Soak the fly ash obtained in step 3 in water at a water-to-ash ratio of 3:1. The mass of calcium hydroxide and sodium aluminate is 1% of the mass of the fly ash obtained in step 3. Then, continuously add Ca(OH)2 and NaAlO2 at a mass ratio of 1:1.1 and stir. Dehydrate the mixture using a filter press dehydrator.

[0049] Step 5: The fly ash obtained in step 4 is subjected to filter pressing treatment, and then dehydrated and dried, and then 1% of magnesium aluminum hydrotalcite calcined at 450° C. for 4 hours is added and ball milled to obtain modified fly ash.

[0050] A method for preparing modified fly ash concrete comprises the following steps:

[0051] According to weight, weigh 32 parts of high-aluminum Portland cement, 11 parts of high-aluminum blast furnace slag powder, 6 parts of fly ash, 80 parts of fine aggregate, 5 parts of modified fly ash, 94 parts of coarse aggregate, 0.5 parts of water reducer and 16 parts of water;

[0052] Mixing water and a water reducing agent uniformly to obtain a first mixed solution;

[0053] The powder and aggregate were added into a mixer, mixed for 1 minute, and then the first mixed solution was added, followed by further mixing for 3 minutes to obtain modified fly ash concrete;

[0054] The water-soluble and acid-soluble Cl- contents in 28-day hardened concrete were tested according to JGJ / T322-2013 "Technical Specifications for the Detection of Cl- Content in Concrete".

[0055] Comparative Example 1:

[0056] A method for modifying fly ash from incineration of domestic waste comprises the following steps:

[0057] Step 1: Wash the fly ash from the incineration of domestic waste with a water-ash ratio of 3:1, stir it evenly, and then use a filter press dehydrator to dehydrate it;

[0058] Step 2: The fly ash obtained in step 1 is pickled using dilute hydrochloric acid (1:3), the first mixed solution is stirred evenly, and then dehydrated using an acid-resistant filter press dehydrator;

[0059] Step 3: Wash the fly ash obtained in step 2 with water at a water-ash ratio of 3:1, stir it evenly, and then use a filter press dehydrator to dehydrate it;

[0060] Step 4: Repeat step 3. Then perform dehydration, drying and ball milling to obtain detoxified fly ash.

[0061] A preparation method of modified fly ash concrete comprises the following steps:

[0062] According to weight, weigh 32 parts of ordinary Portland cement, 11 parts of ordinary blast furnace slag powder, 6 parts of fly ash, 80 parts of fine aggregate, 5 parts of detoxified fly ash, 94 parts of coarse aggregate, 0.5 parts of water reducer and 16 parts of water;

[0063] Mixing water and a water reducing agent uniformly to obtain a first mixed solution;

[0064] The powder and aggregate were added into a mixer, mixed for 1 minute, and then the first mixed solution was added, followed by further mixing for 3 minutes to obtain modified fly ash concrete.

[0065] The water-soluble and acid-soluble Cl- contents in 28-day hardened concrete were tested according to JGJ / T322-2013 "Technical Specifications for the Detection of Cl- Content in Concrete".

[0066] The comparison of chloride ion content in the concrete prepared in Example 1, Example 2 and Comparative Example 1 is shown in Table 1.

[0067] Table 1 Chloride ion content in concrete

[0068]

[0069] It can be seen from Table 1 that the acid-soluble Cl in the concrete produced in Example 1, Example 2 and Comparative Example 1 -The content of water-soluble Cl in the concrete produced in Example 1 and Example 2 is basically the same. - The content of water-soluble Cl in the concrete produced in Comparative Example 1 is significantly lower than that in - The water-soluble Cl in the concrete produced in Example 2 was obtained by adding calcined magnesium-aluminum hydrotalcite to the fly ash and then ball-milling. - The content of water-soluble Cl in the concrete produced by Example 1, which is obtained by adding magnesium-aluminum hydrotalcite to fly ash and then ball-milling, is significantly lower than that in the concrete produced by Example 1. - content.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to preferred embodiments, ordinary technicians in the field should understand that the specific implementation methods of the invention can still be modified or some technical features can be replaced by equivalents without departing from the spirit of the technical solutions of the present invention. They should all be included in the scope of the technical solutions for which protection is sought in the present invention.

Claims

1. A method for modifying fly ash from incineration of domestic waste, characterized in that: The following steps are involved: Step 1: Wash the fly ash from the incineration of domestic waste and dehydrate the washed fly ash; Step 2: pickling the fly ash obtained in step 1 and dehydrating the pickled fly ash; Step 3: Wash the fly ash obtained in step 2 again, and dehydrate the washed fly ash after a period of reaction; Step 4: Soak the fly ash obtained in step 3 in water to obtain a mixed solution A, add calcium oxide and sodium aluminate to the mixed solution A, or add calcium hydroxide and sodium aluminate to the mixed solution A, and dehydrate the mixed solution A after a period of reaction to obtain a mixture B; Step 5: filter-press and dry the mixture B, add the calcined magnesium-aluminum hydrotalcite to the mixture B, and then ball-mill the mixture. After ball-milling for a period of time, the modified domestic waste fly ash is obtained.

2. The fly ash modification method according to claim 1, characterized in that: The weight ratio of water to ash during water washing in step 1 is 2.5-3.5:

1. After the fly ash and water are evenly mixed, a filter press dehydrator is used to dehydrate the washed fly ash.

3. The fly ash modification method according to claim 1, characterized in that: In step 2, the fly ash obtained in step 1 is pickled with dilute hydrochloric acid, the liquid-solid weight ratio of the dilute hydrochloric acid to the fly ash obtained in step 1 being 1:1.8-2.

2. After the dilute hydrochloric acid and the fly ash obtained in step 1 are uniformly stirred, the fly ash is dehydrated with an acid-resistant filter press dehydrator.

4. The fly ash modification method according to claim 3, characterized in that: The dilute hydrochloric acid is prepared by mixing 1 part of concentrated hydrochloric acid with 2.5-3.5 parts of water in a volume ratio.

5. The fly ash modification method according to claim 1, characterized in that: The weight ratio of water to ash during water washing in step 3 is 2.5-3.5:

1. After the fly ash and water are evenly stirred and reacted for 8-12 minutes, the washed fly ash is dehydrated using a filter press dehydrator.

6. The fly ash modification method according to claim 1, characterized in that: In step 4, the mass ratio of water in the mixed solution A to the fly ash obtained in step 3 is 3:0.8-1.

2. If calcium hydroxide and sodium aluminate are added to the mixed solution A, the mass of the calcium hydroxide and sodium aluminate is 0.5-1.5% of the mass of the fly ash obtained in step 3, and the mass ratio of calcium hydroxide and sodium aluminate is 1:1.

1. After a period of reaction, the mixed solution A is dehydrated using a filter press dehydrator to obtain a mixture B. If calcium oxide and sodium aluminate are added to the mixed solution A, the mass of the calcium oxide and sodium aluminate is 0.5-1.5% of the mass of the fly ash obtained in step 3, and the mass ratio of calcium oxide and sodium aluminate is 1:1.

5. After a period of reaction, the mixed solution A is dehydrated using a filter press dehydrator to obtain a mixture B.

7. The fly ash modification method according to claim 1, characterized in that: The mass of the calcined magnesium aluminum hydrotalcite in step 4 is 0.8-1.2% of the mass of the mixture B.

8. A concrete, characterized in that: The method comprises the following raw materials by weight: 27-32 parts of cement, 11-13 parts of blast furnace slag powder, 6-9 parts of fly ash, 70-80 parts of fine aggregate, 2-5 parts of modified fly ash, 94-101 parts of coarse aggregate, 0.4-0.5 parts of water reducer and 15-16 parts of water; wherein the cement is high-aluminum cement, the blast furnace slag powder is high-aluminum blast furnace slag powder, and the modified fly ash is produced by the fly ash modification method according to any one of claims 1 to 7.

9. The concrete according to claim 8, characterized in that: The cement is P·O42.5 ordinary Portland cement, and the sum of the mass of tricalcium aluminate and tetracalcium aluminoferrite in the cement is greater than 25% of the mass of the cement; the chemical composition content of aluminum oxide in the blast furnace slag powder is greater than 17%, the specific surface area of ​​the blast furnace slag powder is ≥400m2 / kg, and the 28-day activity index of the blast furnace slag powder is ≥95%; the 45μm sieve residue of the coarse aggregate is ≤45%, the 28-day strength activity index of the fly ash is ≥70%, the particle size range of the coarse aggregate is 5-25mm, and the fine aggregate and the coarse aggregate are in a dry state; the water reducer is a polycarboxylic acid series or a naphthalene series, and the water reduction rate of the water reducer is ≥14%.

10. A method for preparing modified fly ash concrete, characterized in that: The following steps are involved: Weigh by weight: 27-32 parts of cement, 11-13 parts of blast furnace slag powder, 6-9 parts of fly ash, 70-80 parts of fine aggregate, 2-5 parts of modified fly ash, 94-101 parts of coarse aggregate, 0.4-0.5 parts of water reducer and 15-16 parts of water, wherein the cement is high-aluminum cement, the blast furnace slag powder is high-aluminum blast furnace slag powder, and the modified fly ash is prepared by the fly ash modification method according to any one of claims 1 to 7; The modified fly ash is mixed evenly with silicate cement, mineral powder, fly ash, sand and gravel, and then water and a water reducing agent are added and mixed to obtain the modified fly ash concrete.

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