Gelling material slurry based on flue gas desulfurization circulating fluidized bed power plant solid waste and preparation method thereof

Abstract

The invention relates to the technical field of cementitious material preparation, in particular to cementitious material slurry based on flue gas desulfurization circulating fluidized bed power plant solid waste and a preparation method of the cementitious material slurry. The cementing material slurry is prepared from the following raw materials in parts by mass: 100 parts of a first mixture, 20 to 30 parts of a second mixture and 130 to 150 parts of fly ash, the preparation method comprises the following steps: weighing a first mixture, a second mixture and fly ash in parts by weight, mixing the raw materials weighed in proportion, conveying the mixture into a high-speed slurry dispersion machine, spraying a dispersing agent, and dispersing to obtain the cementing material slurry based on the in-furnace desulfurization circulating fluidized bed power plant solid waste. The cementitious material provided by the invention is suitable for being used as a cementitious material of building materials such as premixed mortar, backfill materials, pavement base binders and the like. The raw materials are all dry solid waste, solid waste slurry and common raw materials discharged by a circulating fluidized bed boiler power plant, dehydration and drying are not needed, solid waste and waste water discharge of the power plant is reduced, and the method is green, low-carbon, environmentally friendly and remarkable in economic effect.

Description

Technical Field

[0001] The present invention relates to the technical field of gelling material preparation, and in particular to a gelling material slurry based on solid waste from a flue gas desulfurization circulating fluidized bed power plant and a preparation method thereof. Background Art

[0002] Circulating fluidized bed boiler coal-fired power generation technology is a clean coal-fired power generation technology with low combustion temperature, high efficiency, SO2 and NO x In terms of desulfurization technology, conventional circulating fluidized bed boiler coal-fired power generation industry mostly adopts the method of adding limestone desulfurizer into the furnace. Although this can control sulfur emissions to a certain extent, it brings new problems: the discharged ash is rich in aluminum silicate, CaO and SO3, which are generally water-absorbing, volcanic ash-active, self-hardening and expansive; what is more difficult is that the CaO and SO3 in traditional circulating fluidized bed boiler ash are mostly concentrated in lime and anhydrite. When used as a cementitious material, it is very easy to have poor stability problems, making it difficult to achieve effective resource utilization of a large amount of circulating fluidized bed boiler ash, resulting in resource waste and subsequent treatment difficulties.

[0003] To address these issues, many circulating fluidized bed (CFB) boiler power plants have abandoned in-furnace limestone desulfurization and sulfur fixation processes, opting for the same flue gas desulfurization (FGD) process used in conventional pulverized coal (CPB) boilers. This process involves minimal in-furnace desulfurization, with the majority of SO2 entering the flue gas desulfurization (FGD) system with the flue gas. This results in CaO and SO3 contents in the boiler flue ash and bottom ash similar to those of conventional fly ash. However, this process also produces desulfurization gypsum, in addition to fly ash and bottom ash. Currently, fly ash, bottom ash, and desulfurization gypsum from conventional CPB power plants can be directly sold to building materials manufacturers as raw materials. However, due to restrictions set by the national standard GB / T 1596, "Fly Ash for Cement and Concrete," CFB power plant fly ash and bottom ash are explicitly prohibited from being used as fly ash or its raw materials. Consequently, even though the chemical composition of CFB boiler ash from FGD is similar to that of fly ash, it remains difficult for the building materials market to fully realize its value.

[0004] At present, among the solid wastes produced by the flue gas desulfurization circulating fluidized bed boiler process, only the desulfurization gypsum has a slightly high resource utilization rate, while fly ash and bottom ash are still idle in large quantities and have not been effectively developed. Taking into account the cementitious potential contained in the coal powder combustion in power plant boilers and the flue gas desulfurization solid waste, it is urgent to design a cementitious material slurry that can fully rely on the existing raw materials and equipment of the circulating fluidized bed power plant and achieve efficient conversion of process solid waste. The fly ash, bottom ash and desulfurization waste slurry can be processed synergistically to transform them into a cementitious material slurry with practical value, thereby achieving the utilization of solid waste in circulating fluidized bed boiler power plants. In view of this, we propose a cementitious material slurry based on the solid waste of flue gas desulfurization circulating fluidized bed power plants and a preparation method thereof. Summary of the Invention

[0005] The purpose of the present invention is to solve the deficiencies mentioned in the above background technology and provide a gelling material slurry based on solid waste from flue gas desulfurization circulating fluidized bed power plants and a preparation method thereof.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] A cementitious material slurry based on solid waste from a flue gas desulfurization circulating fluidized bed power plant. Calculated by mass, the raw materials of the cementitious material slurry include 100 parts of a first mixture, 20-30 parts of a second mixture, and 130-150 parts of fly ash.

[0008] Preferably, the solid content of the gelling material is 67%±1%, and the residue on a 45 μm sieve is ≤30%.

[0009] Preferably, the raw materials of the components of the first mixture include 50 parts of limestone, 40 parts of carbide slag and 10 parts of flue gas desulfurization circulating fluidized bed boiler bottom ash in parts by mass.

[0010] Preferably, the second mixture has a solid content of 30%, and a dihydrate gypsum content in dry solids of ≥80%.

[0011] Preferably, the total mass percentage of the three oxides SiO2, Al2O3 and Fe2O3 in the fly ash is greater than 80%, the average particle size is 50 μm, and the 28-day strength activity index is greater than 85%.

[0012] Preferably, the mass percentage of CaO in the limestone is ≥52%, and the mass percentage of Ca(OH)2 in the carbide slag is ≥90%;

[0013] The total mass percentage of SiO2, Al2O3 and Fe2O3 in the flue gas desulfurization circulating fluidized bed boiler bottom ash is greater than 80%, the CaO content is 5%-6%, and the SO3 content is 2%-3%.

[0014] Preferably, based on parts by mass, 1 part of cementitious material slurry is mixed with 2 parts of standard sand to prepare cementitious material mortar, and the cementitious material mortar has a compressive strength of ≥10 MPa after standard curing for 28 days.

[0015] A method for preparing a gelling material slurry based on solid waste from a flue gas desulfurization circulating fluidized bed power plant, the specific steps of the preparation method are:

[0016] Step 1: Weighing the raw materials of each component of the first mixture according to the mass fraction of the materials and mixing them with water, and grinding them in a wet ball mill until the particle size is less than 45 μm and the solid content reaches 30%, thereby preparing a first mixture;

[0017] Step 2: transporting the first mixture to a flue gas desulfurization system of a circulating fluidized bed boiler power plant as a desulfurizer, and the mixture discharged after the flue gas desulfurization is the second mixture;

[0018] Step 3: After the pulverized coal is fully burned in the flue gas desulfurization circulating fluidized bed boiler, the dust-laden flue gas is collected by the dust collector as fly ash;

[0019] Step 4: Weigh the first mixture, the second mixture and fly ash according to their mass fractions;

[0020] Step 5: Mix the raw materials weighed according to the ratio and transfer them to a high-speed mixer;

[0021] Step 6: spraying a dispersant, stirring and dispersing, and obtaining a cementitious material slurry based on the solid waste of the in-furnace desulfurization circulating fluidized bed power plant.

[0022] Preferably, the amount of the dispersant is 0.5% of the total mass of the first mixture, the second mixture and the fly ash raw material; by mass percentage, the dispersant includes 45%-50% naphthalene sulfonate, 1%-2% cellulose ether, 3%-5% triethanolamine and the balance water.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. The present invention can fully utilize solid waste from flue gas desulfurization circulating fluidized bed power plants, improve resource utilization, and overcome the problem that fly ash and bottom ash from circulating fluidized bed boilers cannot be directly used as raw materials for building materials;

[0025] 2. The cementitious material prepared by the present invention does not require the addition of any type of cement, cement clinker, or strong alkali activator. The cementitious material slurry obtains its gelling properties based on a synergistic hydration reaction, and has green and low-carbon characteristics.

[0026] 3. Cementitious materials can be hydrated and hardened without using any cementitious materials or activators.

[0027] 4. The preparation of the cementitious material slurry of the present invention mainly involves a dispersion process without a grinding process. The added naphthalene sulfonate water reducer and triethanolamine can disperse fine particles, while the cellulose ether has a thickening effect, thereby ensuring that the cementitious material will not exude water, separate, or delaminate during transportation and storage.

[0028] 5. The cementitious material slurry prepared by the present invention can be directly used in the production of premixed mortar, backfill materials, and road base binders, with high strength, simple process, and low cost. DETAILED DESCRIPTION

[0029] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. In the absence of conflict, the embodiments in this application and the features in the embodiments can be combined with each other. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0030] The present invention describes the above technical solution in detail through the following embodiments:

[0031] Example 1

[0032] A cementitious material slurry is prepared based on the solid waste of a flue gas desulfurization circulating fluidized bed power plant. The purpose of the present invention is to provide a method for realizing the coordinated utilization of solid waste in the power plant process and to make full use of the existing equipment and raw materials of the power plant. There is a limestone / lime wet grinding system in the flue gas desulfurization circulating fluidized bed boiler coal-fired power plant, which is suitable for preparing cementitious material slurry. In addition, the desulfurization slurry produced by the desulfurization system has a solid content of about 30%, and generally needs to be concentrated / dehydrated to form a desulfurization gypsum cake with a solid content of more than 80%, and then transported for utilization. The cementitious material of the present invention is a slurry, and the preparation method of the present application can directly utilize the undehydrated desulfurization slurry, which will greatly reduce the cost of dehydration and wastewater treatment, disposal and reuse.

[0033] The cementitious material slurry is composed of a first mixture, a second mixture, and fly ash from a circulating fluidized bed boiler for flue gas desulfurization. In this embodiment, 100 parts of the first mixture, 20 parts of the second mixture, and 130 parts of fly ash from a circulating fluidized bed boiler are used, calculated by mass. The specific preparation method is as follows:

[0034] First, after the materials are dried, 50 parts of limestone, 40 parts of calcium carbide slag, and 10 parts of flue gas desulfurization circulating fluidized bed boiler bottom ash are mixed with water on a dry basis by weight, and ground in a wet ball mill until the particle size is less than 45 μm and the solid content reaches 30%. The prepared slurry is the first mixture; the flue gas desulfurization circulating fluidized bed boiler bottom ash in this application is the slag discharged after the coal powder is fully burned in the flue gas desulfurization circulating fluidized bed boiler, the large particles of material settle to the boiler hearth, and are cooled in a slag cooler.

[0035] Next, the first mixture is transported to the flue gas desulfurization system (FGD system) of the circulating fluidized bed boiler power plant as a desulfurizer. The mixture discharged after the flue gas desulfurization is the second mixture. The solid content of the second mixture is 30%, and the dihydrate gypsum content in the dry solid is ≥80%. It should be noted that one of the raw materials of the first mixture of the present invention is used as a component material of the cementitious material slurry, and the other is used as a desulfurizer and then desulfurized as a raw material for the second mixture of the cementitious material slurry. The second mixture is the product of the desulfurization of the first mixture, and its chemical composition has undergone significant changes compared with the first mixture, that is, the first mixture undergoes a chemical reaction to transform into the second mixture.

[0036] The first mixture, the second mixture, and fly ash are weighed according to the material mass, the raw materials weighed according to the proportion are mixed, and the mixture is conveyed to a 2000-liter high-speed mixer with an adjustable speed of 0 to 1440 rpm, with the speed in this embodiment being 1200 rpm. A dispersant, 0.5% by weight of the total mass of the raw materials, is simultaneously sprayed in, the dispersant comprising 50% of a naphthalene sulfonate, 2% of a cellulose ether, 4% of triethanolamine, and the balance being water to 100%, and stirring and dispersing is completed to obtain a gelling material slurry based on solid waste from an in-furnace desulfurization circulating fluidized bed boiler. The prepared gelling material slurry is stable and does not bleed water, has a solids content of 67%±1%, and a 45 μm sieve residue of ≤30%.

[0037] It is important to explain that the cementitious material of the present invention can be hydrated and hardened without using any cementitious material or activator. Its hydration and hardening mechanism is mainly based on the pozzolanic reaction, ettringite formation reaction and carbonoaluminate hydration reaction of calcium hydroxide in carbide slag, active aluminosilicate in fly ash / bottom ash of flue gas desulfurization circulating fluidized bed boiler, dihydrate gypsum in desulfurization products, and calcium carbonate in limestone powder. The specific reaction is as follows:

[0038] Pozzolanic reaction: Ca(OH)2+Al2O3+SiO2+H2O→CSH (calcium silicate hydrate)+CAH (calcium aluminate hydrate)+CASH (calcium aluminosilicate hydrate);

[0039] Ettringite formation reaction: Ca(OH)2+Al2O3+CaSO4·2H2O+H2O→AFt / AFm (hydrated calcium sulfoaluminate, ettringite);

[0040] Carbonate aluminate reaction: Ca(OH)2+Al2O3+CaCO3→Mc / Hc (hydrated calcium carbonate aluminate).

[0041] In summary, the traditional flue gas desulfurizer is limestone slurry, and the CO2 emission during the desulfurization process is relatively high; the carbide slag used in the present invention has a high Ca(OH)2 content and a desulfurization activity much higher than that of limestone, so it can replace limestone as a desulfurizer in large quantities.

[0042] In addition, the unreacted Ca(OH)2 enters the cementitious material slurry and is also an important raw material component for the pozzolanic reaction, the ettringite formation reaction and the carbonoaluminate hydration reaction; the bottom ash stays in the boiler for a long time, and the carbonate components present in the coal powder are easy to react with SO2 to undergo in-furnace desulfurization reaction. Therefore, the bottom ash of the present invention has relatively high CaO and SO3 contents. When used as a desulfurizer, the aluminosilicate adsorption capacity of the bottom ash is strong, and it will adsorb more SO2 and promote the desulfurization reaction; in addition, it can also provide gypsum crystal nuclei to promote the formation of dihydrate gypsum.

[0043] Example 2

[0044] The cementitious material slurry of this embodiment is composed of a first mixture, a second mixture and fly ash from a flue gas desulfurization circulating fluidized bed boiler. The only difference is that, by mass, it includes 100 parts of the first mixture, 20 parts of the second mixture and 135 parts of fly ash from the circulating fluidized bed boiler. The specific preparation method is as follows:

[0045] First, after the materials are dried, 50 parts of limestone, 40 parts of calcium carbide slag, and 10 parts of flue gas desulfurization circulating fluidized bed boiler bottom ash are mixed with water on a dry basis by weight, and ground in a wet ball mill until the particle size is less than 45 μm and the solid content reaches 30%. The prepared slurry is the first mixture; the flue gas desulfurization circulating fluidized bed boiler bottom ash in this application is the slag discharged after the coal powder is fully burned in the flue gas desulfurization circulating fluidized bed boiler, the large particles of material settle to the boiler hearth, and are cooled in a slag cooler.

[0046] Next, the first mixture is transported to the flue gas desulfurization system (FGD system) of the circulating fluidized bed boiler power plant as a desulfurizer. The mixture discharged after flue gas desulfurization is the second mixture. The second mixture has a solid content of 30%, and the dihydrate gypsum content in its dry solids is ≥80%.

[0047] The first mixture, the second mixture and fly ash are weighed according to the mass of the materials, the raw materials weighed according to the ratio are mixed, and conveyed to a 2000-liter capacity high-speed mixer with an adjustable speed of 0 to 1440 rpm. The speed in this embodiment is 1200 rpm.

[0048] Simultaneously, 0.5% of a dispersant accounting for the total mass of the raw materials is sprayed in, wherein the dispersant includes 50% of naphthalene sulfonate, 2% of cellulose ether, 4% of triethanolamine and the balance of water to 100%, and stirring and dispersion are completed to obtain a gelling material slurry based on in-furnace desulfurization circulating fluidized bed boiler solid waste.

[0049] The prepared cementitious material slurry is stable and does not bleed water; the solid content of the slurry is 67%±1%; and the residue on a 45μm sieve is ≤30%.

[0050] Example 3

[0051] The cementitious material slurry of this embodiment is composed of the first mixture, the second mixture and the fly ash of the circulating fluidized bed boiler of flue gas desulfurization. The only difference is that, by weight, it includes 100 parts of the first mixture, 20 parts of the second mixture and 140 parts of the fly ash of the circulating fluidized bed boiler. The preparation method is:

[0052] Example 4

[0053] The cementitious material slurry of this embodiment is composed of a first mixture, a second mixture and flue gas desulfurization circulating fluidized bed boiler fly ash, with the only difference being that, by mass, it includes 100 parts of the first mixture, 25 parts of the second mixture and 135 parts of circulating fluidized bed boiler fly ash.

[0054] Example 5

[0055] The cementitious material slurry of this embodiment is composed of a first mixture, a second mixture and flue gas desulfurization circulating fluidized bed boiler fly ash, with the only difference being that, by mass, it includes 100 parts of the first mixture, 25 parts of the second mixture and 140 parts of circulating fluidized bed boiler fly ash.

[0056] Example 6

[0057] The cementitious material slurry of this embodiment is composed of the first mixture, the second mixture and the fly ash of the flue gas desulfurization circulating fluidized bed boiler. The only difference is that, by weight, it includes 100 parts of the first mixture, 25 parts of the second mixture and 145 parts of the fly ash of the circulating fluidized bed boiler. The preparation method is:

[0058] Example 7

[0059] The cementitious material slurry of this embodiment is composed of a first mixture, a second mixture and flue gas desulfurization circulating fluidized bed boiler fly ash, and in terms of material mass, includes 100 parts of the first mixture, 30 parts of the second mixture and 140 parts of circulating fluidized bed boiler fly ash.

[0060] Example 8

[0061] The cementitious material slurry of this embodiment is composed of a first mixture, a second mixture and flue gas desulfurization circulating fluidized bed boiler fly ash, and in terms of material mass, includes 100 parts of the first mixture, 30 parts of the second mixture and 145 parts of circulating fluidized bed boiler fly ash.

[0062] Example 9

[0063] The cementitious material slurry of this embodiment is composed of a first mixture, a second mixture and flue gas desulfurization circulating fluidized bed boiler fly ash, and in terms of material mass, includes 100 parts of the first mixture, 30 parts of the second mixture and 150 parts of circulating fluidized bed boiler fly ash.

[0064] Table 1:

[0065]

[0066] The cementitious material slurries and their solid contents of Examples 1-9 are shown in Table 1.

[0067] The mechanical properties of cementitious mortar were tested with reference to GB / T 17671 “Test method for strength of cement mortar (ISO method)”. One part of cementitious mortar was mixed with two parts of standard sand according to the mass ratio. The 28-day compressive strength of the prepared cementitious mortar is shown in Table 2.

[0068] Table 2:

[0069]

[0070] As can be seen from Table 2, the prepared cementitious material slurry can be directly mixed with standard sand to prepare cement mortar without the need to add mixing water. The compressive strength of the mortar is greater than 10 MPa, and it has the potential to be directly used as a binder for premixed mortar, backfill material, and pavement base material with a grade of 10 MPa or below. It complies with GB / T 17671 "Test method for strength of cement mortar (ISO method)" for testing the mechanical properties of cementitious material slurry.

[0071] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations that come within the meaning and range of equivalents of the claims be embraced therein.

Claims

1. A cementitious material slurry based on solid waste from flue gas desulfurization circulating fluidized bed power plant, characterized in that: In terms of mass percentage, the raw materials of each component of the cementitious material slurry include 100 parts of the first mixture, 20-30 parts of the second mixture, and 130-150 parts of fly ash.

2. The cementitious material slurry based on solid waste from flue gas desulfurization circulating fluidized bed power plant according to claim 1, characterized in that: The solid content of the cementitious material is 67%±1%, and the residue on a 45 μm sieve is ≤30%.

3. The cementitious material slurry based on solid waste from flue gas desulfurization circulating fluidized bed power plant according to claim 2, characterized in that: In terms of weight, the raw materials of the first mixture components include 50 parts of limestone, 40 parts of carbide slag and 10 parts of flue gas desulfurization circulating fluidized bed boiler bottom ash.

4. The cementitious material slurry based on solid waste from flue gas desulfurization circulating fluidized bed power plant according to claim 2, characterized in that: The second mixture has a solid content of 30%, and a dihydrate gypsum content in dry solids of ≥80%.

5. The cementitious material slurry based on solid waste from flue gas desulfurization circulating fluidized bed power plant according to claim 2, characterized in that: The total mass percentage of the three oxides SiO2, Al2O3 and Fe2O3 in the fly ash is greater than 80%, the average particle size is 50 μm, and the 28-day strength activity index is greater than 85%.

6. The cementitious material slurry based on solid waste from flue gas desulfurization circulating fluidized bed power plant according to claim 3, characterized in that: The mass percentage of CaO in the limestone is ≥52%, and the mass percentage of Ca(OH)2 in the carbide slag is ≥90%; The total mass percentage of SiO2, Al2O3 and Fe2O3 in the flue gas desulfurization circulating fluidized bed boiler bottom ash is greater than 80%, the CaO content is 5%-6%, and the SO3 content is 2%-3%.

7. The cementitious material slurry based on solid waste from flue gas desulfurization circulating fluidized bed power plant according to claim 1, characterized in that: Calculated by weight, 1 part of cementitious material slurry is mixed with 2 parts of standard sand to prepare cementitious material mortar, and the cementitious material mortar has a standard compressive strength of ≥10MPa after 28 days of curing.

8. A method for preparing a cementitious material slurry based on solid waste from a flue gas desulfurization circulating fluidized bed power plant, which is applicable to the cementitious material slurry described in any one of claims 1 to 7, characterized in that: The specific steps of the preparation method are: Step 1: Weigh the raw materials of each component of the first mixture according to the mass fraction of the materials, mix them with water, and grind them in a wet ball mill until the particle size is less than 45 μm and the solid content reaches 30%, so as to prepare a first mixture; Step 2: transporting the first mixture to a flue gas desulfurization system of a circulating fluidized bed boiler power plant as a desulfurizer, and the mixture discharged after the flue gas desulfurization is the second mixture; Step 3: After the pulverized coal is fully burned in the flue gas desulfurization circulating fluidized bed boiler, the powder collected by the dust-containing flue gas through the dust collector is selected as fly ash; Step 4: weigh the first mixture, the second mixture and fly ash according to their mass fractions; Step 5: Mix the raw materials weighed according to the proportion and convey them into a high-speed mixer; Step six: spray the dispersant, stir and disperse, and obtain the cementitious material slurry based on the solid waste of the circulating fluidized bed power plant in the furnace desulfurization.

9. The method for preparing a cementitious material slurry based on solid waste from a flue gas desulfurization circulating fluidized bed power plant according to claim 8, characterized in that: The amount of the dispersant is 0.5% of the total mass of the first mixture, the second mixture and the fly ash raw material; In terms of mass percentage, the dispersant comprises 45%-50% of naphthalene sulfonate, 1%-2% of cellulose ether, 3%-5% of triethanolamine and the balance of water.

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