A process for preparing belite-sulfoaluminate cement using industrial waste as an auxiliary raw material

Abstract

The present invention discloses a process for preparing belite-sulfoaluminate cement by using industrial waste as an auxiliary raw material. 80-100 parts of limestone are used as the main raw material, and 20-30 parts of fly ash, 10-15 parts of industrial gypsum, 10-15 parts of aluminum-containing sludge, and 5-10 parts of steel slag are used as auxiliary raw materials. It is prepared through two-stage reactions of hydrothermal reaction and calcination sintering. Through the improvement of the composition, content of raw materials and the process, on the premise of ensuring the mechanical properties of the cement, the emission of waste gas can be effectively treated, and the energy consumption in the production process is reduced; on the other hand, a biomass powder preparation system is coupled to co-pyrolyze biomass powder with cement raw materials, further reducing the generation of waste gas such as carbon dioxide and nitrogen oxides and the treatment cost; it has good application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of cement production, and particularly relates to a process for preparing belite-sulfoaluminate cement by using industrial waste as an auxiliary raw material. Background Art

[0002] Cement clinker is the most widely used building material in modern industrial construction; with the improvement of China's infrastructure construction, the consumption of cement is extremely large. Cement is usually divided into Portland cement, sulfoaluminate cement, aluminate cement, slag Portland cement, etc. Although the production process of cement is relatively mature in the prior art, cement production is a high-energy-consuming and high-pollution-emission industry. In the face of the global demand for environmental protection and energy conservation, the requirements for production enterprises to improve production efficiency and reduce waste emissions are becoming increasingly stringent, which is also the basic requirement for enterprises to survive without being abandoned by the industry.

[0003] The emission of CO2 in the cement production process is also huge and its proportion is very high. Now more and more enterprises have done a lot of research in this regard. Among them, belite-sulfoaluminate cement has been studied more at present. Its process has the advantages of low energy consumption and low emissions, and some industrial wastes, such as steel slag, electrolytic manganese slag, slag, etc. can be used as part of the raw materials for belite-sulfoaluminate cement; precisely because the production volume of cement can correspond to a relatively large discharge of solid waste, such a process can not only effectively save costs, but also help relieve the pressure of solid waste treatment in steel mills, which is a win-win process.

[0004] Patent document CN105060744A discloses a method for preparing belite sulfoaluminate cement with low carbon and green characteristics, which uses industrial waste residue and industrial gypsum as raw materials, uses bauxite or tailing bauxite as a corrective material, mixes them, adds water for grinding, forms, then conducts hydrothermal reaction, and then crushes,

[0005] calcines, grinds, and obtains belite sulfoaluminate cement with main components of and β-C2S.

[0006] Patent document CN111233357A discloses an industrial production method for preparing high-quality sulfoaluminate cement clinker and recovering high-concentration SO2 tail gas to co-produce sulfuric acid with all raw materials from industrial solid waste, adopting sorting, grinding and homogenization technology to stabilize chemical components and carbon-sulfur regulation gas-solid phase equilibrium technology; it has the advantages of low raw material cost, high product added value, and good economic and environmental benefits.

[0007] Patent document CN103964713A discloses a method for preparing belite sulphoaluminate cement clinker by using fly ash, bayer red mud, desulphurization gypsum, limestone and bauxite. And an appropriate amount of natural gypsum and Portland cement clinker are incorporated into the clinker to make belite sulphoaluminate cement. Through reasonable batching, the former two replace part of the aluminous raw materials in the belite sulphoaluminate cement raw materials, and the desulphurization gypsum replaces the traditional raw material natural gypsum to co-fire the cement clinker. Its characteristics are that the alkali and rare metals in the red mud can be used to carry out high-temperature solidification or activation on the clinker minerals to improve the hydration activity of the clinker minerals; when preparing cement, an appropriate amount of Portland cement clinker is introduced into the belite sulphoaluminate cement clinker as a performance regulating component, and the hydrated calcium silicate gel hydrated from Portland cement and the ettringite hydrated from belite sulphoaluminate intersect and interpenetrate with each other, making the structure of the cement stone more dense, thereby improving the early strength and the later strength growth rate of the cement.

[0008] The non-patent document "Research on Preparation of Belite-Sulphoaluminate Cement by Coordinating Electrolytic Manganese Residue and Barium Residue", author He Weilong, proposed to prepare belite-sulphoaluminate cement by using electrolytic manganese residue system barium residue, limestone and bauxite; "Research on Preparation and Hydration Characteristics of Waste-Based Belite-Sulphoaluminate Cement", author Sun Cunyong, studied the preparation of belite-sulphoaluminate cement by using materials such as coal gangue, carbide slag, steel slag and gypsum dihydrate. The prepared BSAC has a relatively fast setting time, as well as relatively high early strength and later strength; it has obvious advantages in energy conservation and emission reduction, and the CO2 emission reduction is as high as 55%.

[0009] The non-patent document "Firing Belite-Sulphoaluminate Cement with Fly Ash", author Shen Yanming, studied that fly ash raw material 2 with a low Al2O3 content can be calcined into belite-sulphoaluminate cement with C2S as the main minerals through appropriate batching design, and the more appropriate sintering temperature is 1250 °C.

[0010] Although there have been many studies in this regard, due to the composition of solid waste and impurity factors, the performance of cement clinker is greatly affected; and there is still much room for improvement in aspects such as waste gas and waste solids. Summary of the Invention

[0011] In view of the existing needs and deficiencies in the prior art, the present invention provides a method for preparing belite-sulphoaluminate cement by using industrial waste as an auxiliary raw material and its preparation process. The cement prepared by the present invention has excellent mechanical properties, effectively reduces the treatment of industrial waste and the production cost of cement, and the emissions of waste gas and waste solids are very low, having good enterprise production value; on the other hand, a biomass powder preparation system is coupled to carry out co-pyrolysis of biomass powder and cement raw materials, further reducing the generation and treatment cost of waste gas such as carbon dioxide and nitrogen oxides; it has good application prospects.

[0012] To solve the above technical problems and achieve the above technical effects, the present invention is implemented through the following technical solutions.

[0013] A process for preparing belite-sulfoaluminate cement using industrial waste as an auxiliary raw material, comprising the following steps:

[0014] (1) By weight, 80-100 parts of limestone are used as the main raw material, 20-30 parts of fly ash, 10-15 parts of industrial gypsum, 10-15 parts of aluminum-containing sludge, and 5-10 parts of steel slag are used as auxiliary raw materials, and they are pretreated.

[0015] (2) Pour the above raw materials into a reaction kettle, add 400-500 parts of water, start stirring, and add 10-20 parts of alkaline substances during the stirring process, and continue stirring until evenly dispersed to form a dispersion.

[0016] (3) Heat the above dispersion to 120-150 °C, increase the pressure in the reaction kettle to 0.2-0.3 MPa, and react under the above conditions for 3-5 h; after the reaction is completed, use a gas pipeline to introduce the gas in the reaction kettle into the next batch of dispersion.

[0017] (4) Filter the reaction solution in step (3), store and collect the filtrate, dry the filtered solid components at 60-70 °C, and then mix them with biomass fuel powder and send them into a pyrolysis furnace for co-pyrolysis; the pyrolysis furnace is coupled with a biomass powder preparation system.

[0018] (5) Put the decomposed solid components into a sintering reactor, heat them at a heating rate of 5 °C / min to 700-800 °C and hold for 1-2 h; continue to heat to 1050-1100 °C and calcine for 60-90 min.

[0019] (6) Turn off the power, introduce the gas in the pyrolysis furnace and the sintering reactor into the filtrate in step (4) through a pipeline for drying the solid components, and continue to introduce the tail gas into the filtrate in step (4) for adsorption, analyze the composition of the filtrate and recycle and reuse it.

[0020] (7) Mix the solid components, raw gypsum, and limestone in step (6) according to the weight ratio of (83-85):(7-10):(4-5), and use a ball mill to grind them until the residue on a 200-mesh square-hole sieve is less than 3% to obtain belite-sulfoaluminate cement.

[0021] Further, the process of the present application further includes step (8): adding sodium hydroxide and / or potassium hydroxide to the filtrate in step (4). Reasonably adding sodium hydroxide and / or potassium hydroxide to the filtrate according to the adsorption situation of the waste gas can adsorb and treat the waste gas to the greatest extent.

[0022] Further, in step (1), the industrial gypsum is one or more of desulfurized gypsum and phosphogypsum; the aluminum-containing sludge is aluminum-containing sludge from anodic oxidation or electrolytic aluminum plants; the steel slag is steel slag from steel-making enterprises.

[0023] Further, the pretreatment step in step (1) is: ball-milling the steel slag in a ball mill to a particle size of 0.05 - 0.10 mm; putting limestone, fly ash, industrial gypsum, and aluminum-containing sludge into a stirring and crushing device simultaneously and stirring until no large particles are observed.

[0024] In the existing process, the raw materials need to be broken into powders with suitable particle sizes before the calcination step, and usually, the raw materials need to be dried before ball-milling and / or crushing, which inevitably consumes a large amount of heat energy. The pretreatment step in the present application does not require drying all the raw materials, and such an improvement in the pretreatment step can greatly reduce energy consumption. This is because fly ash, industrial gypsum, and aluminum-containing sludge are easy to refine their particles by stirring; and the technical solution of the present application is not a calcination step but a hydrothermal step in the subsequent steps, so whether the raw materials are dry does not affect.

[0025] Further, the temperature in the pyrolysis furnace is 600 - 700 °C.

[0026] The present application has conducted a large amount of research on the raw material ratio. Finally, it is considered that 80 - 100 parts of limestone are used as the main raw material, 20 - 30 parts of fly ash, 10 - 15 parts of industrial gypsum, 10 - 15 parts of aluminum-containing sludge, and 5 - 10 parts of steel slag are used as auxiliary raw materials to produce cement; the amount of solid waste is increased as much as possible without affecting the mechanical properties, thus reducing the amount of limestone used. Such a beneficial effect is that the proportion of limestone used is reduced, and the corresponding carbon dioxide emissions are also reduced, which can avoid the pressure of carbon dioxide waste gas treatment.

[0027] Further, in step (2), the alkaline substance is selected from one or more of sodium hydroxide, potassium hydroxide, and sodium bicarbonate.

[0028] Adding an alkaline substance in step (2) can, on the one hand, improve the dissolution and dispersion of large-particle raw materials; on the other hand, the dispersion liquid is alkaline, and this dispersion liquid can be used as an adsorption of the gas after the reaction in the reaction kettle, which can effectively reduce the emission of gases such as carbon dioxide. And the dispersion liquid that adsorbs the gas can then be used as the raw material for the next reaction.

[0029] Further, in step (4), the pyrolysis furnace is coupled with a biomass powder preparation system, and the biomass powder is co-pyrolyzed into one or more of powdery peanut shells, straws, sawdust, wood chips, and bamboo chips.

[0030] Further, the biomass powder preparation system includes a feeding system, a crushing system, a separator, a dust collector, a storage chamber, a powder feeding system, a mixing system, and a powder outlet.

[0031] In step (6) of the present application, the gas in the sintering reactor is introduced into step (4) through a pipeline to dry the solid components. On the one hand, the alkaline substances in the filtered solid components can be used to react with waste gases such as carbon dioxide to be fixed; on the other hand, the waste heat of the gas after the sintering reaction can also be used to dry the filtered solid components; the unabsorbed and fixed tail gas is further introduced into the filtrate of step (4) for adsorption. The waste gas is effectively fixed and reused, which is beneficial to reducing the energy consumption of the production process.

[0032] Further, the 3d compressive strength of the belite-sulfoaluminate cement is 35 - 38 MPa, the 7d compressive strength is 40 - 45 MPa, and the 28d compressive strength is 70 - 75 MPa.

[0033] In the present application, through the optimization and improvement of the process steps, the waste gas generated in the production process of cement clinker can be adsorbed and treated in a simple manner; and the temperature of the calcination process is effectively reduced, and the consumption of heat is avoided as much as possible, which can greatly reduce the energy consumption; the calcination temperature adopted in the present application is between 1050 and 1100 °C, which is a low-energy consumption and green cement clinker production process.

[0034] The applicant found in the research process that although solid waste can be used as an auxiliary raw material to produce belite-sulfoaluminate clinker, different solid wastes still have obvious effects on the mechanical properties of cement; through the creative work of the applicant, fly ash, industrial gypsum, aluminum-containing sludge, and steel slag are selected as auxiliary raw materials, and adjustments are made to the improvement of the process, and finally the improvement of the mechanical properties of belite-sulfoaluminate cement is achieved, which is also the most basic guarantee for the utilization of solid waste.

[0035] Compared with the prior art, the technical solution of the present application has the following beneficial effects:

[0036] (1) The present application uses fly ash, industrial gypsum, aluminum-containing sludge, and steel slag as auxiliary raw materials, which can effectively and largely treat industrial solid waste while producing cement, can save the production cost of cement and also reduce the treatment cost of solid waste generating enterprises, achieving a win-win result.

[0037] (2) The applicant has carried out a creative screening of the types of existing solid wastes and, in combination with the improvement of the process, ensured that the utilization of solid wastes will not affect the mechanical properties of cement; the belite-sulfoaluminate cement prepared by the technical solution of the present invention has excellent early strength and will not show the phenomenon of strength retrogression. The 3-day compressive strength is 35-38 MPa, the 7-day compressive strength is 40-45 MPa, and the 28-day compressive strength is 70-75 MPa.

[0038] (3) During the production process of belite-sulfoaluminate cement in this application, a pyrolysis furnace is coupled with a biomass powder preparation system, which can effectively provide biomass powder to enter the pyrolysis furnace and realize continuous powder supply; moreover, the gas generated during the pyrolysis of biomass powder can react with carbon dioxide, quickly consume the carbon dioxide decomposed from the cement raw materials, and promote the rightward shift of the reaction equilibrium. This in-situ autocatalytic effect can effectively reduce the decomposition temperature of calcium carbonate; in addition, through this reaction process, it can also effectively reduce the decomposition temperature of raw meal in the traditional cement manufacturing process, avoid the generation of nitrogen oxides at high temperatures, and can effectively convert carbon dioxide into carbon monoxide, reducing carbon emissions.

[0039] (4) Through the creative improvement of the process in the technical solution of this application, on the one hand, it can effectively reduce energy consumption and the raw materials do not need excessive drying; and through the improvement of the process, the calcination temperature is greatly reduced. Compared with the existing 1200-1300 °C, the calcination temperature of the process in this application is only 1050-1100 °C; in addition, the waste gases such as carbon dioxide generated during the process of this application do not require additional treatment steps, and only the steps required by the technical solution of this application are used for cooperation in treatment, which can simply achieve the emission of waste gases and fix and convert carbon dioxide gas into production raw materials. Description of the Drawings

[0040] Figure 1 It is a schematic structural diagram of a biomass combustion system; in which there are a feeding system 1, a pulverizing system 2, a separator 3, a dust collector 4, a storage chamber 5, a powder feeding system 6, a mixing system 7, a plurality of powder outlets 8, a pyrolysis furnace 9, and an air inlet pipeline 10. Detailed Embodiments

[0041] To make the original intention, technical solution and technical effect of the embodiments of the present invention clearer, the technical solution will be clearly and completely described below in conjunction with the embodiments; obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0042] In the following embodiments, a pyrolysis furnace 9 is coupled with a biomass powder preparation system. The biomass powder preparation system includes a feeding system 1, a pulverizing system 2, a separator 3, a dust collector 4, a storage chamber 5, a powder feeding system 6, a mixing system 7, multiple powder outlets 8, and an air inlet pipeline 10. Biomass raw materials 1 enter the feeding system 1, and then the switch is turned on to enable them to enter the pulverizing system 2 to form powder. The powdered biomass then passes through a conveying pipeline and is sent to the separator 3 and the dust collector 4. The processed biomass powder enters the storage chamber 5 and is sent to the mixing system 7 through the powder feeding system 6, where it converges with the air inlet pipeline 10. The biomass powder can be sent to the powder outlet 8 by using wind power and finally enter the pyrolysis furnace 9. This system is coupled to the pyrolysis furnace, which can avoid manually adding biomass powder to the pyrolysis furnace and improve production efficiency.

[0043] Example 1

[0044] A process for preparing belite-sulfoaluminate cement using industrial waste as an auxiliary raw material includes the following steps:

[0045] (1) By weight, 80 parts of limestone are used as the main raw material, 20 parts of fly ash, 10 parts of desulfurized gypsum, 10 parts of aluminum-containing sludge, and 5 parts of steel slag are used as auxiliary raw materials, and they are pretreated. The specific pretreatment steps are as follows: The steel slag is ball-milled in a ball mill to a particle size of 0.05 mm; the limestone, fly ash, desulfurized gypsum, and aluminum-containing sludge are simultaneously put into a stirring and crushing device and stirred until no large particles are observed.

[0046] (2) Pour the above raw materials into a reaction kettle, add 400 parts of water, start stirring, and add 20 parts of potassium hydroxide during the stirring process. Continue stirring until evenly dispersed to form a dispersion.

[0047] (3) Heat the above dispersion to 120 °C and increase the pressure in the reaction kettle to 0.2 MPa. React under the above conditions for 5 h; after the reaction is completed, use a gas pipeline to introduce the gas in the reaction kettle into the next batch of dispersion.

[0048] (4) Filter the reaction solution in step (3), store and collect the filtrate, dry the filtered solid components at 60 °C, and then mix them with biomass fuel powder and send them into a pyrolysis furnace for co-pyrolysis; the pyrolysis furnace is coupled with a biomass powder preparation system, and the temperature in the pyrolysis furnace is 600;

[0049] (5) Put the dried solid components into a sintering reactor, heat them at a heating rate of 5 °C / min to 700 °C and hold for 2 h; continue to heat to 1050 °C and calcine for 90 min;

[0050] (6) Turn off the power supply, and pass the gas in the pyrolysis furnace and the sintering reactor through a pipeline into the solid components for drying in step (4), and continue to pass the tail gas into the filtrate in step (4) for adsorption, analyze the composition of the filtrate, and recycle and reuse it;

[0051] (7) Mix the solid components, raw gypsum, and limestone in step (6) according to the weight ratio of 83:7:4, and grind them with a ball mill until the residue on a 200-mesh square-hole sieve is less than 3%, to obtain belite-sulfoaluminate cement.

[0052] Example 2

[0053] A process for preparing belite-sulfoaluminate cement using industrial waste as an auxiliary raw material, comprising the following steps:

[0054] (1) By weight, use 100 parts of limestone as the main raw material, 30 parts of fly ash, 15 parts of phosphogypsum, 15 parts of aluminum-containing sludge, and 1020 parts of steel slag as auxiliary raw materials, and perform pretreatment on them; the specific steps of pretreatment are: place the steel slag in a ball mill and grind it to a particle size of 0.10 mm; put the limestone, fly ash, phosphogypsum, and aluminum-containing sludge into a stirring and crushing device at the same time, and stir until no large particles are observed.

[0055] (2) Pour the above raw materials into a reaction kettle, add 500 parts of water, start stirring, add 10 parts of sodium hydroxide during the stirring process, and continue to stir until evenly dispersed to form a dispersion;

[0056] (3) Heat the above dispersion to 150 °C, raise the pressure in the reaction kettle to 0.3 MPa, and react under the above conditions for 3 h; after the reaction is completed, pass the gas in the reaction kettle into the next batch of dispersion through a gas pipeline;

[0057] (4) Filter the reaction solution in step (3), store and collect the filtrate, dry the filtered solid components at 70 °C, and then mix them with biomass fuel powder and send them into a pyrolysis furnace for co-pyrolysis; the pyrolysis furnace is coupled with a biomass powder preparation system, and the temperature in the pyrolysis furnace is 700 °C;

[0058] (5) Put the dried solid components into a sintering reactor, heat them at a heating rate of 5 °C / min to 800 °C and hold for 1 h; continue to heat to 1100 °C and calcine for 60 min;

[0059] (6) Turn off the power supply, and pass the gas in the pyrolysis furnace and the sintering reactor through a pipeline into the solid components for drying in step (4), and continue to pass the tail gas into the filtrate in step (4) for adsorption, analyze the composition of the filtrate, and recycle and reuse it;

[0060] (7) Mix the solid components, raw gypsum, and limestone in step (6) according to the weight ratio of 84:8:5, and grind them using a ball mill until the residue on a 200-mesh square-hole sieve is less than 3% to obtain belite-sulfoaluminate cement.

[0061] Example 3

[0062] A process for preparing belite-sulfoaluminate cement using industrial waste as an auxiliary raw material includes the following steps:

[0063] (1) By weight, use 90 parts of limestone as the main raw material, 25 parts of fly ash, 12 parts of phosphogypsum, 12 parts of aluminum-containing sludge, and 7 parts of steel slag as auxiliary raw materials, and perform pretreatment on them; the specific pretreatment steps are: place the steel slag in a ball mill and grind it to a particle size of 0.08 mm; put the limestone, fly ash, phosphogypsum, and aluminum-containing sludge into a stirring and crushing device at the same time and stir until no large particles are observed.

[0064] (2) Pour the above raw materials into a reaction kettle, add 450 parts of water, start stirring, add 15 parts of sodium bicarbonate during the stirring process, and continue stirring until evenly dispersed to form a dispersion.

[0065] (3) Heat the above dispersion to 130 °C and raise the pressure in the reaction kettle to 0.25 MPa, and react under the above conditions for 4 h; after the reaction is completed, pass the gas in the reaction kettle into the dispersion of the next batch through a gas pipeline.

[0066] (4) Filter the reaction solution in step (3), store and collect the filtrate, dry the filtered solid components at 65 °C, and then mix them with biomass fuel powder and send them into a pyrolysis furnace for co-pyrolysis; the pyrolysis furnace is coupled with a biomass powder preparation system, and the temperature in the pyrolysis furnace is 650 °C.

[0067] (5) Put the dried solid components into a sintering reactor, heat them at a heating rate of 5 °C / min to 740 °C and hold for 1.5 h; continue to heat to 1070 °C and calcine for 70 min.

[0068] (6) Turn off the power, pass the gas in the sintering reactor through a pipeline into the filtrate in step (4) for adsorbing the solid components for drying, and continue to pass the tail gas into the filtrate in step (4) for adsorption, analyze the composition of the filtrate, and recycle and reuse it.

[0069] (7) Mix the solid components, raw gypsum, and limestone in step (6) according to the weight ratio of 85:10:5, and grind them using a ball mill until the residue on a 200-mesh square-hole sieve is less than 3% to obtain belite-sulfoaluminate cement.

[0070] Example 4

[0071] A process for preparing belite - sulphoaluminate cement using industrial waste as an auxiliary raw material, comprising the following steps:

[0072] (1) By weight, 85 parts of limestone are used as the main raw material, 27 parts of fly ash, 14 parts of phosphogypsum, 11 parts of aluminium - containing sludge and 6 parts of steel slag are used as auxiliary raw materials, and they are pretreated; the specific pretreatment steps are: the steel slag is ball - milled in a ball mill to a particle size of 0.07 mm; the limestone, fly ash, phosphogypsum and aluminium - containing sludge are simultaneously put into a stirring and crushing device and stirred until no large particles are observed.

[0073] (2) Pour the above raw materials into a reaction kettle, add 460 parts of water, start stirring, add 15 parts of sodium bicarbonate during the stirring process, and continue stirring until evenly dispersed to form a dispersion liquid;

[0074] (3) Heat the above dispersion liquid to 140 °C and raise the pressure in the reaction kettle to 0.27 MPa, and react under the above conditions for 4 h; after the reaction is completed, the gas in the reaction kettle is introduced into the dispersion liquid of the next batch through a gas pipeline;

[0075] (4) Filter the reaction liquid in step (3), store and collect the filtrate, dry the solid component after filtration at 65 °C, and then mix it with biomass fuel powder and send it into a pyrolysis furnace for co - pyrolysis; the pyrolysis furnace is coupled with a biomass powder preparation system; the temperature in the pyrolysis furnace is 660 °C

[0076] (5) Put the dried solid component into a sintering reactor, heat it at a heating rate of 5 °C / min to 780 °C and keep it warm for 1.2 h; continue to heat it to 1060 °C and calcine it for 75 min;

[0077] (6) Turn off the power, pass the gas in the sintering reactor through a pipeline into the filtrate in step (4) for drying the solid component, and continue to pass the tail gas into the filtrate in step (4) for adsorption, analyze the composition of the filtrate and recycle and reuse it;

[0078] (7) Mix the solid component, gypsum and limestone in step (6) according to a ratio of 84:9:4 by weight, and use a ball mill to grind it until the residue on a 200 - mesh square - hole sieve is less than 3%, to obtain belite - sulphoaluminate cement.

[0079] XRD characterization was carried out on the belite - sulphoaluminate cement clinker prepared in Examples 1 - 4. According to the XRD patterns, the phases of the belite - sulphoaluminate cement clinker prepared in this application include alite, belite, aluminate, and a small amount of ferrite phase was also found.

[0080] The belite-sulfoaluminate cement prepared in Examples 1-4 was subjected to mechanical tests. The cement was mixed with water and stirred evenly (water-binder ratio 0.4) to make specimens of 30×30×30 mm, and cured in a curing box at 25±2 °C and relative humidity greater than 93% for 1 day. After demolding, its mechanical properties were measured according to the standard of "Test Method for Strength of Cement Mortar (IS Method)" GB / T 17671—1999, and the data were recorded in Table 1.

[0081] Table 1

[0082]

[0083] According to the data in Table 1, it can be seen that the belite-sulfoaluminate cement prepared by the present invention has high early strength, the 3-day compressive strength reaches 36 MPa, and there is no phenomenon of strength retrogression; the 28-day compressive strength is between 70 and 75 MPa. Thus, it can be seen that the belite-sulfoaluminate cement of this application has excellent mechanical properties.

[0084] The above description is only the preferred embodiments of this application and the explanation of the technical principles applied. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to the technical solutions formed by the specific combination of the above technical features, and should also cover reasonable modifications that can be made by those skilled in the art without departing from the inventive concept.

Claims

1. A process for preparing belite-sulfoaluminate cement using industrial waste as an auxiliary raw material, characterized in that, It includes the following steps: (1) Taking 80 - 100 parts by weight of limestone as the main raw material, 20 - 30 parts of fly ash, 10 - 15 parts of industrial gypsum, 10 - 15 parts of aluminum - containing sludge, and 5 - 10 parts of steel slag as auxiliary raw materials, and performing pretreatment on them; (2) Pouring the above - mentioned raw materials into a reaction kettle, adding 400 - 500 parts of water, starting stirring, adding 10 - 20 parts of alkaline substances during the stirring process, and continuously stirring until evenly dispersed to form a dispersion; (3) Heating the above - mentioned dispersion to 120 - 150 °C, raising the pressure in the reaction kettle to 0.2 - 0.3 MPa, and reacting under the above conditions for 3 - 5 h; after the reaction, introducing the gas in the reaction kettle into the next batch of dispersion through a gas pipeline; (4) Filtering the reaction solution in step (3), storing and collecting the filtrate, drying the solid component after filtration at 60 - 70 °C, and then mixing it with biomass fuel powder and feeding it into a pyrolysis furnace for co - pyrolysis; the pyrolysis furnace is coupled with a biomass powder preparation system; (5) Putting the decomposed solid component into a sintering reactor, heating it at a heating rate of 5 °C / min to 700 - 800 °C and holding for 1 - 2 h; continuing to heat to 1050 - 1100 °C and calcining for 60 - 90 min; (6) Shutting off the power supply, introducing the gas in the pyrolysis furnace and the sintering reactor into the filtrate in step (4) through a pipeline for adsorbing the gas used to dry the solid component, and then analyzing the composition of the filtrate and recycling and reusing it; (7) Mixing the solid component, raw gypsum, and limestone in step (6) according to the ratio of (83 - 85):(7 - 10):(4 - 5) by weight, and grinding them with a ball mill until the residue on a 200 - mesh square - hole sieve is less than 3% to obtain belite - sulphoaluminate cement; It further includes step (8): adding sodium hydroxide and / or potassium hydroxide to the filtrate in step (4); In step (2), the alkaline substances are selected from one or more of sodium hydroxide, potassium hydroxide, and sodium bicarbonate; In step (4), the co - pyrolyzed biomass powder is one or more of powdered peanut shells, straws, sawdust, wood chips, and bamboo chips; The biomass powder preparation system includes a feeding system, a crushing system, a separator, a dust collector, a storage chamber, a powder feeding system, a mixing system, and a powder outlet; The 3 - day compressive strength of the belite - sulphoaluminate cement is 35 - 38 MPa, the 7 - day compressive strength is 40 - 45 MPa, and the 28 - day compressive strength is 70 - 75 MPa.

2. The process for preparing belite-sulfoaluminate cement according to claim 1, characterized in that, In step (1), the industrial gypsum is one or more of desulfurized gypsum and phosphogypsum; the aluminum - containing sludge is aluminum - containing sludge from anodic oxidation or electrolytic aluminum plants; the steel slag is steel slag from steel - making enterprises.

3. The process for preparing belite-sulfoaluminate cement according to claim 1, characterized in that, The pretreatment step in step (1) is: ball - milling the steel slag in a ball mill until the particle size is 0.05 - 0.10 mm; putting the limestone, fly ash, industrial gypsum, and aluminum - containing sludge into a stirring and crushing device at the same time and stirring until no large particles are observed.

4. The process for preparing belite-sulfoaluminate cement according to claim 1, characterized in that, The temperature in the pyrolysis furnace is 600 - 700 °C.

5. A belite-sulfoaluminate cement, characterized in that, Prepared by using the process described in any one of claims 1 - 4; The 3-day compressive strength of the belite-calcium sulfoaluminate cement is 35 to 38 MPa, the 7-day compressive strength is 40 to 45 MPa, and the 28-day compressive strength is 70 to 75 MPa.

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