Multi-source solid waste-dredged sediment geopolymer recycling method based on response surface optimization

Abstract

The invention provides a multi-source solid waste-dredged sediment geopolymer recycling method based on response surface optimization, raw materials of a multi-source solid waste-dredged sediment geopolymer comprise a cementing material and an alkali activator solution, the cementing material comprises multi-source solid waste and dredged sediment, and moreover, the alkali activator solution is added into the multi-source solid waste-dredged sediment geopolymer. Water required by the multisource solid waste-dredged sediment geopolymer is provided by an alkali activator solution; the mix proportion of the multisource solid waste-dredged sediment geopolymer is determined after being optimized by a response surface method, and the method comprises the following steps: fitting test results and establishing a response surface equation by taking the dredged sediment mixing amount, the Na2O concentration of an alkali activator solution and the modulus of an alkali activator as main variable parameters and taking the compressive property of the geopolymer as a response value; according to the performance requirements of recycling products, the expected value of the compression resistance is combined, optimization parameters are obtained through a single-target optimization model, the multi-source solid waste-dredged sediment geopolymer is prepared according to the obtained optimized proportion, and resource utilization of the multi-source solid waste-dredged sediment geopolymer is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of dredged sludge disposal and utilization, and in particular to a multi-source solid waste-dredged sludge geopolymer resource utilization method based on response surface optimization. Background Art

[0002] Due to the needs of comprehensive water environment management, waterway maintenance and port construction, it is necessary to dredge rivers, lakes and seas, which produces a large amount of dredged sediment. Through the resource utilization of dredged sediment, green building materials and other products can be obtained, which has generated certain economic benefits and has become one of the key research directions in this field.

[0003] Generally speaking, the dredged sludge needs to be solidified to achieve resource utilization. At present, cement clinker is mostly used as a curing agent. However, the production of cement is a high-energy consumption and high-carbon dioxide emission process. It is one of the main sources of anthropogenic carbon dioxide emissions. The carbon dioxide emissions during its manufacturing process are as high as 0.95 tons of CO2-eq / ton; in addition, the strength of the solidified product obtained by the existing cement solidification technology is reduced, and a large amount of cement is required to obtain the ideal strength. For example, CN 105130289 A discloses a method for preparing unburned bricks using dredged sludge aggregates, using dredged sludge ceramsite as dredged sludge aggregates, cement, quicklime, gypsum and fly ash as cementitious materials, and then through batching, water addition and stirring, mixture aging, brick pressing machine pressing and molding, product maintenance, the finished dredged sludge unburned bricks are obtained.

[0004] In comparison, geopolymer is a green and low-carbon cementitious material with good mechanical properties. Compared with traditional cement, the production energy consumption of geopolymer can be reduced by 70%, and carbon emissions can be reduced by 60% to 80%. Moreover, the raw materials of geopolymer are widely available. Multi-source solid wastes such as fly ash, slag, and steel slag can all be used as geopolymer raw materials, which can replace cement for dredging sludge resource utilization; and geopolymer also has the advantage of high early strength, and its 7d compressive strength is usually much higher than that of traditional cement.

[0005] In summary, the resource utilization of dredged mud using cement as a curing agent faces the problems of high carbon emissions and low strength of the solidified product. At the same time, geopolymer materials have the advantages of low carbon emissions and high strength. Dredged mud and multi-source solid wastes such as fly ash, slag, and steel slag have the ability to act as geopolymer cementitious materials. Therefore, the resource utilization of multi-source solid waste-dredged mud geopolymer is a green and low-carbon way to utilize dredged mud resources. Summary of the invention

[0006] In view of the growing demand for green, low-carbon and high-compressive strength dredged mud resource utilization, the present invention provides a multi-source solid waste-dredged mud geopolymer resource utilization method based on response surface optimization, which can reduce carbon emissions in the process of dredged mud resource utilization and turn waste into treasure, making it easy to promote and use.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] One of the purposes of the present invention is to provide a multi-source solid waste-dredged mud geopolymer resource recovery method based on response surface optimization, the resource recovery method comprising the following steps:

[0009] (1) The raw materials of multi-source solid waste-dredged sludge geopolymer include a gelling material and an alkaline activator solution, wherein the gelling material includes multi-source solid waste and dredged sludge;

[0010] Based on the response surface optimization theory, the main variables and the response quantity are selected, wherein the main variables include the amount of dredged sediment, the Na2O concentration of the alkali activator solution and the modulus of the alkali activator, and the response quantity is the compressive strength, and the range of the main variables is set respectively;

[0011] (2) Based on the range of the main variable set in step (1), several groups of slurry mix ratios of multi-source solid waste-dredged sediment geopolymer are set according to the central composite design principle, and the resulting slurry is poured, cured, and subjected to compressive strength tests in sequence to obtain corresponding response quantities;

[0012] (3) Based on the main variables and response quantities corresponding to the several groups of slurry mix ratio tests in step (2), a quadratic model is fitted to obtain a quadratic multivariate regression fitting equation and perform a significance test;

[0013] (4) Based on the quadratic multivariate regression fitting equation described in step (3), the compressive strength requirement of the target resource recovery product is taken as the expected function to solve the optimal slurry mix ratio of the main variable that meets the expected value of the response quantity.

[0014] It should be noted that the dredged sludge dosage in the present invention refers to the mass percentage of the dredged sludge relative to the cementitious material.

[0015] In the resource utilization method of the present invention, the raw materials of multi-source solid waste-dredged sludge geopolymer include gelling material and alkaline activator solution, the gelling material includes multi-source solid waste and dredged sludge, and the water required for the multi-source solid waste-dredged sludge geopolymer is provided by the alkaline activator solution; the mix ratio of the multi-source solid waste-dredged sludge geopolymer is determined after optimization by the response surface method, comprising the following steps: taking the dredged sludge dosage, the Na2O concentration of the alkaline activator solution, and the alkaline activator modulus as the main variable parameters, and taking the compressive performance of the geopolymer as the response value, fitting the test results and establishing a response surface equation; according to the performance requirements of the resource product and the expected value of the compressive performance, obtaining the optimization parameters through a single-objective optimization model, and preparing the multi-source solid waste-dredged sludge geopolymer according to the obtained optimized mix ratio, and realizing its resource utilization.

[0016] The present invention adopts dredged sludge and multi-source solid waste as raw materials of geopolymer, which can solve the problem of difficult disposal of large amounts of dredged sludge generated in dredging projects, reduce the amount of cement used in the process of resource utilization, reduce carbon emissions in the process of dredged sludge resource utilization, and ensure the high strength of resource products, thereby realizing green and low-carbon resource utilization of dredged sludge.

[0017] As a preferred technical solution of the present invention, the slurry is prepared according to the optimal slurry mix ratio described in step (4), and the obtained slurry is poured, cured, and subjected to a compressive strength test in sequence according to the method described in step (2) to obtain a test compressive strength;

[0018] Relative to the expected compressive strength corresponding to the optimal slurry mix ratio, if the error of the test compressive strength is within 10%, the test compressive strength is basically consistent with the expected compressive strength, and the optimal slurry mix ratio does not need to be adjusted and optimized; otherwise, return to step (1) and adjust the range setting of the main variable, and re-solve the optimal slurry mix ratio of the main variable that meets the expected value of the response quantity.

[0019] As a preferred technical solution of the present invention, in step (1), the dredged sludge includes any one of lake dredged sludge, river dredged sludge, waterway dredged sludge or port dredged sludge.

[0020] As a preferred technical solution of the present invention, in step (1), the multi-source solid waste includes any one of fly ash, slag, steel slag, volcanic ash, red mud or incineration fly ash.

[0021] As a preferred technical solution of the present invention, in step (1), the multi-source solid waste is a combination of fly ash and slag, and the mass ratio of fly ash to slag is a:(1-a), wherein a is 0.65 to 0.75, for example, the mass ratio of fly ash to slag is 0.65:0.35, 0.68:0.32, 0.7:0.3, 0.72:0.28 or 0.75:0.25, etc.

[0022] As a preferred technical solution of the present invention, in step (1), the alkaline activator in the alkaline activator solution includes sodium silicate and caustic alkali, and the caustic alkali includes sodium hydroxide and / or potassium hydroxide.

[0023] As a preferred technical solution of the present invention, the range setting of the main variable in step (1) includes: the dredged mud dosage is 30-80wt%, for example, 30wt%, 35wt%, 40wt%, 45wt%, 50wt%, 55wt%, 60wt%, 65wt%, 70wt%, 75wt% or 80wt%, etc., preferably 40-60wt%, the Na2O concentration of the alkaline activator solution is 2-10wt%, for example, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%, etc., preferably 4-8wt%, and the alkaline activator modulus is 1.0-2.0, for example, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9 or 2.0, etc., preferably 1.2-1.8.

[0024] As a preferred technical solution of the present invention, the step (2) of sequentially casting, curing and compressive strength testing the obtained slurry includes: casting several groups of obtained slurries into 150mm×150mm×150mm cubic test blocks, curing them in a constant temperature and humidity standard curing box to the age of 7d, and performing compressive strength testing using a universal testing machine.

[0025] As a preferred technical solution of the present invention, in step (3), the quadratic multivariate regression fitting equation is:

[0026] y=α0+α1x1+α2x2+α3x3+α4x1x2+α5x1x3+α6x2x3+α7x1 2 +α8x2 2 +α9x3 2 ;

[0027] Among them, y is the compressive strength as the response, x1 is the dredged sludge dosage as one of the main variables, x2 is the Na2O concentration of the alkali activator solution as one of the main variables, x3 is the alkali activator modulus as one of the main variables, α i is the polynomial coefficient of the fitted regression equation, α i The specific value of is obtained through the response surface experiment in the above steps.

[0028] As a preferred technical solution of the present invention, in step (3), the significance test includes a P value test. If the P value is less than 0.001, the fitting is significant and the fitting result is valid. Otherwise, return to step (1) and adjust the range setting of the main variable to re-solve the optimal slurry mix ratio of the main variable that meets the expected value of the response.

[0029] Compared with the prior art solutions, the present invention has at least the following beneficial effects:

[0030] (1) In the resource utilization method of the present invention, the raw materials of the multi-source solid waste-dredged sludge geopolymer include a cementitious material and an alkaline activator solution, the cementitious material includes multi-source solid waste and dredged sludge, and the water required for the multi-source solid waste-dredged sludge geopolymer is provided by the alkaline activator solution; the mix ratio of the multi-source solid waste-dredged sludge geopolymer is determined by optimization by the response surface method, comprising the following steps: taking the dredged sludge dosage, the Na2O concentration of the alkaline activator solution, and the alkaline activator modulus as the main variable parameters, and taking the compressive performance of the geopolymer as the response value, fitting the test results and establishing a response surface equation; according to the performance requirements of the resource product and the expected value of the compressive performance, obtaining the optimization parameters through a single-objective optimization model, and preparing the multi-source solid waste-dredged sludge geopolymer according to the obtained optimized mix ratio, and realizing its resource utilization;

[0031] (2) The present invention uses dredged sludge and multi-source solid waste as raw materials for geopolymers, which can solve the problem of difficult disposal of large amounts of dredged sludge generated in dredging projects, reduce the amount of cement used in the process of resource utilization, reduce carbon emissions in the process of dredged sludge resource utilization, and ensure the high strength of resource products, thereby realizing green and low-carbon resource utilization of dredged sludge. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a response surface analysis result diagram of the resource utilization method described in Example 1 of the present invention. DETAILED DESCRIPTION

[0033] The technical solution of the present invention is further described below with reference to the accompanying drawings and through specific implementation methods.

[0034] To better illustrate the present invention and facilitate understanding of the technical solution of the present invention, typical but non-limiting embodiments of the present invention are as follows:

[0035] The present invention provides a multi-source solid waste-dredged sludge geopolymer resource utilization method based on response surface optimization, wherein the resource utilization method obtains an optimal slurry mix ratio of the multi-source solid waste-dredged sludge geopolymer based on the response surface optimization method, and prepares a multi-source solid waste-dredged sludge geopolymer resource product, such as unburned bricks, according to the obtained optimal slurry mix ratio. The present invention is further described in detail below in conjunction with an embodiment.

[0036] Example 1

[0037] This embodiment provides a multi-source solid waste-dredged mud geopolymer resource recovery method based on response surface optimization, and the resource recovery method comprises the following steps:

[0038] (1) The raw materials of multi-source solid waste-dredged sludge geopolymer include a cementitious material and an alkaline activator solution, wherein the cementitious material includes multi-source solid waste (fly ash and slag powder mixed in a mass ratio of 7:3) and dredged sludge, wherein the dredged sludge after dehydration and drying is crushed by rolling, and then crushed into fine powder by a ball mill for use as dredged sludge; water, sodium silicate and sodium hydroxide are mixed to prepare an alkaline activator solution, and the mass ratio of water to cementitious material is controlled to be 0.3, which is used to provide the water required in the preparation process of multi-source solid waste-dredged sludge geopolymer;

[0039] Based on the response surface optimization theory, the main variables and response quantities are selected. The main variables are the dredged sludge dosage, the Na2O concentration of the alkali activator solution and the alkali activator modulus. The response quantity is the compressive strength. The ranges of the main variables are set respectively. The dredged sludge dosage is 33.2-66.8wt%, the Na2O concentration of the alkali activator solution is 2.64-9.36%, and the alkali activator modulus is 1.0-2.0. A three-factor five-level response surface experiment is established. The specific design is shown in Table 1.

[0040] Table 1

[0041]

[0042]

[0043] (2) Based on the range of the main variable set in step (1), 20 groups of slurry mix ratios of multi-source solid waste-dredged sludge geopolymers were set according to the central composite design principle, and the obtained slurry was rapidly stirred for 2 min using a mixer, and the mixer speed was set to 500 r / min. The stirred slurry was poured into a mold for unfired bricks and cast into 150 mm × 150 mm × 150 mm cubic test blocks. The blocks were placed in a constant temperature box and maintained at 55 °C for 24 h to allow the slurry to be fixed. The demoulding blanks were placed under natural conditions for curing for 7 days to obtain unfired brick test blocks of multi-source solid waste-dredged sludge geopolymers. The compressive strength was tested using a universal testing machine to obtain the corresponding response. The specific design combination and test results are shown in Table 2.

[0044] Table 2

[0045]

[0046]

[0047] (3) Based on the values ​​of the main variables and the response in step (2), the response surface analysis was performed with the dredged sediment dosage (x1), the Na2O concentration of the alkali activator solution (x2), and the alkali activator modulus (x3) as the main variables and the 7d compressive strength (y) as the response. Figure 1As shown), the quadratic model is fitted to obtain the quadratic multiple regression fitting equation

[0048] y=–127.44+0.86x1+22.87x2+79.65x3-0.11x1x2+0.05x1x3–2.95x2x3

[0049] –0.005x1 2 –0.83x2 2 –24.42x3 2 ;

[0050] The fitting results were tested to ensure the significance of the model. The variance test included standard deviation and correlation coefficient R. 2 , P value test, the results are shown in Table 3.

[0051] Table 3

[0052] Response volume Standard Deviation <![CDATA[Correlation coefficient R 2 > P-value test Compressive strength(MPa) 3.22 0.9192 <0.001

[0053] (4) Based on the quadratic multivariate regression fitting equation described in step (3), the compressive strength (15.0 MPa) of the load-bearing solid blocks with strength grade MU15.0 in GB / T 8239-2014 "Ordinary Concrete Small Blocks" was taken as the expected value, and the optimal slurry mix ratio was calculated by response surface model: dredged sludge content 62 wt%, Na2O concentration 7.3 wt%, and modulus 1.3.

[0054] The slurry was prepared according to the optimal slurry mix ratio, and the obtained slurry was poured, cured, and tested for compressive strength in sequence according to the method described in step (2), and the experimental 7d compressive strength was 16.1 MPa; relative to the expected 7d compressive strength corresponding to the optimal slurry mix ratio, the experimental 7d compressive strength deviated from the theoretical value by 1.1 MPa, and the error was within 10%. The experimental compressive strength was basically consistent with the expected compressive strength, so the optimal slurry mix ratio did not need to be adjusted and optimized, which proved the credibility of the response surface optimization results.

[0055] Finally, a geopolymer slurry was prepared with a dredged mud dosage of 62wt%, a Na2O concentration of 7.3wt% and a modulus of 1.3, and poured into a brick-making mold and placed in a constant temperature box for 24 hours of constant temperature curing at 55°C to allow the slurry to take shape. The demolded blanks were placed under natural conditions for curing for 7 days to obtain unfired bricks prepared based on multi-source solid waste-dredged mud geopolymers.

[0056] In the resource utilization method of the present invention, the raw materials of multi-source solid waste-dredged sludge geopolymer include gelling material and alkaline activator solution, the gelling material includes multi-source solid waste and dredged sludge, and the water required for the multi-source solid waste-dredged sludge geopolymer is provided by the alkaline activator solution; the mix ratio of the multi-source solid waste-dredged sludge geopolymer is determined after optimization by the response surface method, comprising the following steps: taking the dredged sludge dosage, the Na2O concentration of the alkaline activator solution, and the alkaline activator modulus as the main variable parameters, and taking the compressive performance of the geopolymer as the response value, fitting the test results and establishing a response surface equation; according to the performance requirements of the resource product and the expected value of the compressive performance, obtaining the optimization parameters through a single-objective optimization model, and preparing the multi-source solid waste-dredged sludge geopolymer according to the obtained optimized mix ratio, and realizing its resource utilization.

[0057] The present invention adopts dredged sludge and multi-source solid waste as raw materials of geopolymer, which can solve the problem of difficult disposal of large amounts of dredged sludge generated in dredging projects, reduce the amount of cement used in the process of resource utilization, reduce carbon emissions in the process of dredged sludge resource utilization, and ensure the high strength of resource products, thereby realizing green and low-carbon resource utilization of dredged sludge.

[0058] The present invention illustrates the detailed structural features of the present invention through the above embodiments, but the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the components selected by the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0059] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0060] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0061] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A multi-source solid waste-dredged mud geopolymer resource utilization method based on response surface optimization, characterized in that: The resource utilization method comprises the following steps: (1) The raw materials of multi-source solid waste-dredged sludge geopolymer include a gelling material and an alkaline activator solution, wherein the gelling material includes multi-source solid waste and dredged sludge; Based on the response surface optimization theory, the main variables and the response quantity are selected, wherein the main variables include the amount of dredged sediment, the Na2O concentration of the alkali activator solution and the modulus of the alkali activator, and the response quantity is the compressive strength, and the ranges of the main variables are set respectively; (2) Based on the range of the main variable set in step (1), several groups of slurry mix ratios of multi-source solid waste-dredged sediment geopolymer are set according to the central composite design principle, and the obtained slurries are poured, cured, and tested for compressive strength in turn to obtain corresponding response quantities; (3) Based on the main variables and response quantities corresponding to the several groups of slurry mix ratio tests in step (2), a quadratic model is fitted to obtain a quadratic multivariate regression fitting equation and perform a significance test; (4) Based on the quadratic multivariate regression fitting equation described in step (3), the compressive strength requirement of the target resource recovery product is taken as the expected function to solve the optimal slurry mix ratio of the main variable that meets the expected value of the response quantity.

2. The resource recovery method according to claim 1, characterized in that: The resource recovery method further comprises: preparing slurry according to the optimal slurry mix ratio described in step (4), and sequentially performing pouring, curing, and compressive strength testing on the obtained slurry according to the method described in step (2) to obtain a test compressive strength; Relative to the expected compressive strength corresponding to the optimal slurry mix ratio, if the error of the test compressive strength is within 10%, the test compressive strength is basically consistent with the expected compressive strength, and the optimal slurry mix ratio does not need to be adjusted and optimized; otherwise, return to step (1) and adjust the range setting of the main variable, and re-solve the optimal slurry mix ratio of the main variable that meets the expected value of the response quantity.

3. The resource recovery method according to claim 1 or 2, characterized in that: In step (1), the dredged sludge includes any one of lake dredged sludge, river dredged sludge, waterway dredged sludge or port dredged sludge.

4. The resource recovery method according to claim 1 or 2, characterized in that: In step (1), the multi-source solid waste includes any one of fly ash, slag, steel slag, volcanic ash, red mud or incineration fly ash.

5. The resource recovery method according to claim 4, characterized in that: In step (1), the multi-source solid waste is a combination of fly ash and slag, and the mass ratio of fly ash to slag is a:(1-a), wherein a is 0.65 to 0.

75.

6. The resource recovery method according to claim 1 or 2, characterized in that: In step (1), the alkaline activator in the alkaline activator solution includes sodium silicate and caustic alkali, and the caustic alkali includes sodium hydroxide and / or potassium hydroxide.

7. The resource recovery method according to claim 1 or 2, characterized in that: The range setting of the main variable in step (1) includes: the dredged sludge dosage is 30-80wt%, the Na2O concentration of the alkaline activator solution is 2-10wt%, and the alkaline activator modulus is 1.0-2.

0.

8. The resource recovery method according to claim 1 or 2, characterized in that: The step (2) of sequentially casting, curing, and compressive strength testing the obtained slurry includes: casting several groups of obtained slurries into 150mm×150mm×150mm cubic test blocks, curing them in a constant temperature and humidity standard curing box to the age of 7 days, and performing compressive strength testing using a universal testing machine.

9. The resource recovery method according to claim 1 or 2, characterized in that: In step (3), the quadratic multivariate regression fitting equation is: y=α0+α1x1+α2x2+α3x3+α4x1x2+α5x1x3+α6x2x3+α7x1 2 +α8x2 2 +α9x3 2 ; Among them, y is the compressive strength as the response, x1 is the dredged sludge dosage as one of the main variables, x2 is the Na2O concentration of the alkali activator solution as one of the main variables, x3 is the alkali activator modulus as one of the main variables, α i are the polynomial coefficients of the fitted regression equation.

10. The resource recovery method according to claim 1 or 2, characterized in that: In step (3), the significance test includes a P value test. If the P value is less than 0.001, the fitting is significant and the fitting result is valid. Otherwise, return to step (1) and adjust the range setting of the main variable to re-solve the optimal slurry mix ratio of the main variable that meets the expected value of the response.

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