Preparation process of multi-solid-waste low-carbon cementing material based on suspension calcination

Abstract

The invention discloses a preparation process of a multi-solid-waste low-carbon cementing material based on suspension calcination. The preparation process comprises the following steps: S1, grinding coal gangue; s2, the coal gangue and the regenerated micro powder are mixed into a dispersing agent according to a specific proportion, a mixture A is obtained for standby application, and the dispersing agent accounts for 0.2%-1% of the sum of the mass of the coal gangue and the mass of the regenerated micro powder; the mass ratio of the regenerated micro powder to the coal gangue is (1: 1.5)-(1: 5), and the specific value is adjusted according to the calorific value of the coal gangue; s3, the mixture A obtained in the S2 is fed into a suspension calcining system and passes through a five-stage suspension preheating cylinder, a suspension calcining kiln, a three-stage suspension cooling cylinder, a second-stage fluidized bed and a sleeve type water-cooling spiral conveyor, a high-activity mixture B is obtained, and finally the high-activity mixture B is fed into a finished product bin. And the mixture of the two can be used as a high-activity auxiliary cementing material to replace part of cement clinker, so that the low-carbon development of the cement industry is promoted.

Description

Technical Field

[0001] The present invention belongs to the technical field of low-carbon gelling system preparation, and more specifically, the present invention relates to a process for preparing multi-solid waste low-carbon gelling material based on suspension calcination. Background Art

[0002] Gangue, a solid waste generated during coal mining and washing, represents my country's largest industrial solid waste, with the largest annual output and the most storage sites. According to incomplete statistics, the cumulative amount of gangue stored in my country currently exceeds 6 billion tons, but its comprehensive utilization rate is less than 30%. Gangue is primarily used as roadbed material, underground backfill, and ecological restoration, with a small amount used in the production of construction materials and chemical raw materials.

[0003] In the construction materials industry, gangue is commonly calcined at high temperatures to produce highly active metakaolin, which is used to prepare auxiliary cementitious materials. The activity of calcined gangue is directly related to the calcination temperature. Furthermore, the dehydroxylation temperatures of the mineral components within the gangue vary: kaolinite has a dehydroxylation temperature of 300-750°C, illite has a dehydroxylation temperature of 450-700°C, montmorillonite has a dehydroxylation temperature of 650-900°C, and muscovite has a dehydroxylation temperature of 650-900°C. When the temperature exceeds the dehydroxylation temperature, new dense crystal structures are formed, and the activity decreases. Existing gangue calcination and activation technologies can be divided into two categories, depending on the dispersion state of the gangue material in the hot air flow: bulk activation calcination and suspended activation calcination. Pile-state calcination generally uses granular or lumpy gangue, which is placed in a pile in the calcination kiln. However, due to the low thermal conductivity of the gangue material, a large temperature difference occurs between the inside and outside of the material during the calcination process, resulting in overburning on the outside and underburning on the inside, seriously affecting the quality and activity of the product. Grinding the gangue into powder and calcining it in a suspended state can increase the heat transfer efficiency between the materials, increase the speed of the gangue dehydroxylation reaction, and effectively avoid the phenomenon of overburning on the outside and underburning on the inside of the calcined gangue product. However, gangue often contains a large amount of combustible substances, which will release a certain amount of heat at high temperatures. The combustion temperature range of combustible materials is wide, with the combustion temperature range of gangue being 350-600℃ and the intense combustion temperature range of gangue being 450-550℃. When using suspended preheating decomposition technology, unstable combustion and uneven temperature distribution can occur within the calciner, leading to unstable calcined product quality. Furthermore, the gangue combusts and releases heat within the preheater system, causing problems such as scaling and blockage. Therefore, it is necessary to develop an efficient gangue suspended calcination method and process system to address the issues of efficient and stable combustion within the calciner and scaling and blockage in the preheater system, thereby enabling large-scale resource utilization of gangue in the building materials sector.

[0004] With the advancement of urbanization, the emission and stockpiling of construction waste, another major solid waste material, is increasing. Approximately 50% of this is waste concrete, which is crushed and screened to produce recycled coarse and fine aggregate, which is currently being widely utilized as a resource. However, the production process of recycled coarse and fine aggregate also produces approximately 20% to 35% recycled fine powder. When used to replace cement or mineral admixtures of the same particle size range, this powder is not efficiently utilized due to its low activity and high water requirement, resulting in significant resource waste. Recycled micropowders primarily consist of inert components such as silica and calcium carbonate, a hydration product, CSH gel, and a small amount of unhydrated minerals. High-temperature calcination is one of the primary pathways for recycled micropowder activation. The dehydrated phase of CSH gel after high-temperature treatment at 400°C and 650°C exhibits significant hydration activity. Inert components such as calcium carbonate decompose at temperatures exceeding 800°C, and silica melts at over 1600°C, both of which exhibit relatively low hydration activity. However, high fineness allows for full filling and nucleation effects, promoting cement clinker hydration. The resourceful utilization of recycled micropowders is urgent. In addition to studying the impact of its mineral composition on hydration activity, developing efficient activation processes and synergizing with other industrial solid wastes are key avenues for its high-value utilization.

[0005] Patent CN 111847468 A discloses a method for producing high-whiteness calcined kaolin through multi-stage suspended calcination of coal-based kaolin. The method employs a "segmented precise control" calcination method to segment the "dehydration-dehydroxylation-decarbonization" process of the coal-based kaolin. This effectively solves the problem of incomplete combustion of organic matter during the calcination of coal-based kaolin, in which the partial pressure of oxygen in the system is reduced due to water discharge.

[0006] Patent CN201610228875.6 discloses a decarbonization process for coal-bearing kaolin, proposing to remove and recover carbon impurities in coal-bearing kaolin by crushing, grading, re-selection, crushing of intermediate density products of re-selection, or grinding and flotation operations, ultimately obtaining kaolin of higher purity. However, there are problems such as complex process, low efficiency, and poor product quality.

[0007] Patent CN106186770B discloses a method for activating regenerated micropowders, which is calcined and ball-milled at 200-500℃, 600-700℃, and 800-1000℃ to obtain a micropowder with a specific surface area greater than 400m 2 / kg of activated regenerated micropowder. Although high temperature treatment is one of the effective means to enhance the activity of regenerated micropowder, the high energy consumption caused by the treatment process requires the coordination of cement kiln production system to achieve it.

[0008] Patent CN116217162A discloses the feasibility of using metakaolin and recycled micropowder as composite cementitious materials. However, the simultaneous addition of slag and the activation of low-activity metakaolin and recycled micropowder by adjusting the alkalinity of the system have an adverse effect on the later volume stability of concrete. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to address the problem of crusting and blockage in the combustion system and unstable product quality caused by the high calorific value of coal gangue during activation. A low-carbon cementitious material with multiple solid wastes is prepared through a suspended calcination kiln process. To address the problem of material accumulation, a scheme of coordinated calcination with a recycled micropowder composite system is provided, which can absorb the heat generated during the coal gangue calcination process and activate the recycled micropowder at the same time, thereby improving the hydration activity of the composite cementitious system.

[0010] In order to achieve the above object, the technical solution adopted by the present invention is:

[0011] A process for preparing a multi-solid waste low-carbon gelling material based on suspended calcination comprises the following steps:

[0012] S1, grinding the coal gangue;

[0013] S2. Adding a specific proportion of coal gangue and recycled micropowder to a dispersant and mixing to obtain a mixture A for standby use, wherein the dispersant accounts for 0.2 to 1% of the sum of the mass of the coal gangue and the recycled micropowder; the mass ratio of the recycled micropowder to the coal gangue is 1:1.5 to 1:5, and the specific value is adjusted according to the calorific value of the coal gangue;

[0014] S3. The mixture A obtained in S2 is sent to the suspension calcination system, and passes through a five-stage suspension preheating cylinder, a suspension calcination kiln, a three-stage suspension cooling cylinder, a two-stage fluidized bed, and a sleeve-type water-cooled screw conveyor to obtain a highly active mixture B, which is finally sent to the finished product warehouse.

[0015] Through the above technical solution:

[0016] The inert substances CaCO3 and SiO2 in the regenerated micropowder will not decompose or release heat within the calcination temperature range of coal gangue, while the main hydration products gradually lose structural water after heating, which is an endothermic process. Therefore, the regenerated micropowder can form a dilute phase suspension with coal gangue, avoiding the impact of coal gangue heat release on production safety and product quality stability.

[0017] The active Al2O3 in the metakaolin formed after the gangue is calcined in S2 will react with the CaCO3 in the regenerated micropowder as shown in the following formula (1). The two react in equimolar amounts to generate a relatively stable hydration product, hydrated monocarbonate calcium aluminate.

[0018]

[0019] Among them, A represents Al2O3, represents CaCO3, CH represents Ca(OH)2, and H represents H2O. It stands for hydrated calcium aluminate monocarbonate.

[0020] The specific qualities of calcined clay and recycled fine powder are determined based on the Al₂O₃ content in the calcined clay and the CaCO₃ content in the recycled fine powder. However, the production batching is not strictly limited to equimolar quantities of the two. This is because a small amount of excess Al₂O₃ can form ettringite, while a small amount of excess CaCO₃ can act as a filler and nucleation agent. Compared to cementitious materials such as fly ash and slag, calcined gangue has a higher pozzolanic activity. Recycled fine powder contains a large amount of CaCO₃ and a small amount of unhydrated products. The hydration products CH₂ and CSH after grinding can also play a nucleation role, promoting the formation of cement hydration products and improving the early performance of cement-based materials.

[0021] Furthermore, in S3, the mixture A is sent to the first-stage cyclone preheating cylinder, dispersed and suspended in the air flow under the action of the air flow to achieve preheating, and then transported to the second-stage cyclone preheating cylinder from the bottom discharge port, and passes through the third-stage, fourth-stage, and fifth-stage cyclone preheating cylinders and their connecting pipes in the same manner to complete heat exchange and achieve sufficient preheating; then it enters the suspension calcining kiln through the discharge port of the fifth-stage cyclone preheating cylinder, and is calcined and decomposed in a high-temperature gas environment. By adjusting the temperature range in the calcining kiln, mixtures B with different reaction activities can be prepared.

[0022] Furthermore, in S2, the dispersant is a mixture of one or more of powdered polyphosphate, polyvinyl alcohol, saponin powder, triethanolamine, and ethylene glycol in different proportions.

[0023] Furthermore, the fineness of the coal gangue in S1 is 80 μm sieve residue ≤ 10%, the content of kaolin in the coal gangue is 20% to 90%, the mass proportions of the main components in the coal gangue are SiO2: 30% to 60%, Al2O3: 30% to 55%, Fe2O3: 0% to 20%, and the calorific value of the coal gangue is 2.0 to 6.3 MJ / kg;

[0024] The fineness of the regenerated micropowder in S2 is 80μm sieve residue ≤10%, and the mass proportions of the main chemical components in the regenerated micropowder are SiO2: 10%~60%, CaO: 20%~60%, and Al2O3: 0%~20%.

[0025] Furthermore, the internal temperature field of the suspension calcining kiln in S3 is stable within the range of 500 to 1000°C.

[0026] Furthermore, the suspension calcining kiln system uses gas fuel, and the gas fuel is selected according to the calorific value of the gangue and the components of the mixture A. When the calorific value of the gangue is 2.0-4.0 MJ / kg, or the mass ratio of the regenerated micropowder to the gangue is 1:1.5-1:3, any fuel is preferred; when the calorific value of the gangue is 4.0-6.3 MJ / kg, or the mass ratio of the regenerated micropowder to the gangue is 1:3-1:5, medium and low calorific value fuels are preferred.

[0027] Furthermore, gas fuels include high calorific value fuels (>15.07MJ / Nm 3 ), medium calorific value fuel (6.28~15.07MJ / Nm 3 ) and low calorific value fuels (<6.28MJ / Nm 3 ; High calorific value gas fuel is natural gas, and medium and low calorific value gas fuels include blast furnace coke oven gas, coal biomass gasification gas, petrochemical smelting exhaust gas, landfill gas and coal mine gas, etc.

[0028] Furthermore, the waste heat in the suspension calcining kiln in S3 can be recycled into the preheating system.

[0029] Furthermore, in S3, the internal temperature of each stage of the five-stage cyclone preheating cylinder is controlled by adjusting the air inlet volume and the feed volume. The outlet temperatures of the first, second, third, fourth, and fifth stage preheating cylinders are 50-100°C, 100-250°C, 250-400°C, 400-500°C, and 500-600°C, respectively. The residence time of the material in the suspension preheating cylinder is 5-15 minutes, and the wind speed is 15-25 m / s.

[0030] The volume of the cyclone preheating cylinder and the cyclone cooling cylinder in the suspension calcining system is the same, and the volume of the suspension calcining kiln is 3 to 5 times that of the cyclone preheating cylinder and the cyclone cooling cylinder.

[0031] Furthermore, the residence time of the mixture A in the suspension calcining kiln is 30 to 240 minutes, the wind speed is 15 to 25 m / s, and the O2 content at the outlet of the suspension calcining kiln is controlled to be ≥3.5% and the CO content is ≤0.5% by controlling the air intake and fuel intake. The feed amount of the mixture A is less than 50% of the volume of the preheating cylinder, and the interval between two feeds is controlled to be 10 to 30 minutes.

[0032] Furthermore, by adjusting the air inlet volume, the outlet temperature of the first-stage cyclone cooling tube is controlled at 400-500°C; the outlet temperature of the second-stage cyclone cooling tube is controlled at 300-400°C, and the outlet temperature of the third-stage cyclone cooling tube is controlled at 100-300°C; the residence time of the material in each level of cyclone cooling tube is 5-15 minutes, the wind speed is 15-25m / s, and the O2 content at the outlet of each level of cyclone cooling tube is ≥3.5%, and the CO content is ≤0.5%.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] (1) The present invention simultaneously realizes the thermal activation treatment of coal gangue and recycled micropowder, and the mixture of the two can be used as a highly active auxiliary cementitious material to replace part of the cement clinker, which is conducive to promoting the low-carbon development of the cement industry.

[0035] (2) Since the combustible components in the gangue will burn and release a large amount of heat during the preheating process, the present invention uses a multi-stage cyclone preheating system to achieve the purpose of precise zone temperature control and gradient preheating. At the same time, the regenerated micropowder and the gangue are subjected to suspended calcination together. On the one hand, the energy diffusion released by the high-temperature calorific value of the gangue is diluted, and the heat release of the gangue in the preheating system is avoided, which increases the temperature of the flue gas at the outlet of the preheating furnace and causes an increase in the heat consumption of the system, and also reduces the risk of crusting and blockage of the preheating furnace. On the other hand, the heat generated by the combustion of the combustible components of the gangue is used to achieve thermal activation treatment of the regenerated micropowder.

[0036] (3) The composite effect of metakaolin and recycled micropowder can improve the comprehensive performance of cement-based materials. Even due to the commonly used composite systems such as fly ash and mineral powder, the present invention can achieve uniform dispersion of coal gangue and recycled micropowder in a suspended state, effectively avoiding the problem of fluctuations in the performance of cement-based materials caused by uneven mixing during application. DETAILED DESCRIPTION

[0037] 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. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0038] In the examples, two different sources of coal gangue and a type of recycled micropowder were used to collaboratively produce a multi-solid waste low-carbon cementitious material, and concrete of conventional strength grade was prepared. The performance of the concrete prepared was compared with that of the cementitious material formed by ordinary cement clinker.

[0039] Calorimeter testing revealed that the fineness of coal gangue M1 was 5.1% on an 80 μm sieve, the moisture content was 2.7%, and the calorific value was 3.2 MJ / kg. The fineness of coal gangue M2 was 4.3% on an 80 μm sieve, the moisture content was 1.8%, and the calorific value was 4.7 MJ / kg. The fineness of the recycled micropowder was 3.4% on an 80 μm sieve. The chemical compositions of the different raw materials are listed in Table 1.

[0040] Table 1 Chemical composition of each component

[0041]

[0042]

[0043] Comparative Example 1

[0044] Comparative Example 1 uses 95% cement clinker and 5% gypsum to form a cementitious material. The concrete mix design is shown in Table 2. The water-binder ratio is 0.45, the coarse aggregate is 5-25mm basalt that meets the continuous gradation, and the fine aggregate is river sand with a fineness modulus of 2.6-2.9. The prepared concrete has a 28-day compressive strength of 43.2MPa and a chloride ion permeability coefficient of 4.1×10 -12 m 2 / s.

[0045] Table 2 Concrete mix ratio (kg / m 3 )

[0046]

[0047] Example 1

[0048] The regenerated micro powder and the coal gangue M1 powder were mixed uniformly at a mass ratio of 1:2, and a powdered dispersant accounting for 0.4% of the sum of the mass of the coal gangue and the regenerated micro powder was added. The ratio of polyphosphate to triethanolamine was 8:2 to form a mixture A. The feed amount was 30% of the volume of the preheating cylinder, the interval between two feeds was controlled at 20 minutes, the temperature in the suspension calcination kiln was controlled at (700±10)℃, the calcination time was 60 minutes, and the fuel used was high calorific value fuel natural gas; the outlet temperatures of the first, second, third, fourth and fifth preheating cylinders were controlled at (100±10)℃, (200±10)℃, (300±10)℃, (400±10)℃ and (500±10)℃ respectively, and the material residence time in the kiln was 10 minutes respectively. By adjusting the gas flow rate, the O2 content at the outlet of each level of preheating system was controlled at 100±10℃, (200±10)℃, (300±10)℃, (400±10)℃ and (500±10)℃ respectively. The outlet temperature of the first-stage cyclone cooling tube is controlled at (450±10)℃; the outlet temperature of the second-stage cyclone cooling tube is controlled at (350±10)℃, and the outlet temperature of the third-stage cyclone cooling tube is controlled at (200±10)℃; the residence time of the material in each level of cyclone cooling system is 10min respectively; the outlet O2 content of the three-stage cyclone cooling system is controlled at (4±0.5)%; finally, it is further cooled to (50±5)℃ by a sleeve-type water-cooled screw conveyor and then sent to the finished product warehouse and bagged.

[0049] The chemical composition of the obtained finished mixture B is mainly metakaolin, calcium carbonate, silicon dioxide and calcium oxide, with a 45μm sieve residue of 3.1% and a specific surface area of ​​3.54m2 / g. The cementitious material is prepared with a mass ratio of mixture B, cement clinker and gypsum of 30:65:5. The total amount of cementitious material, the amount of coarse and fine aggregates and the amount of water in the concrete mix design are the same as those in the comparative example. The prepared concrete has a 28d compressive strength of 45.3MPa and a chloride ion permeability coefficient of 3.7×10 -12 m 2 / s.

[0050] Example 2

[0051] The regenerated micro powder and the coal gangue M2 powder were mixed uniformly at a mass ratio of 1:2, and a powdered dispersant accounting for 0.4% of the total mass of the coal gangue and the regenerated micro powder was added. The ratio of polyphosphate to triethanolamine was 8:2 to form a mixture A. The feed amount was 30% of the volume of the preheating cylinder, and the interval between two feeds was controlled at 20 minutes. The temperature in the suspension calcining kiln was controlled at (650±10)℃, the calcination time was 60 minutes, and the fuel used was blast furnace coke oven gas with medium and low calorific value. The outlet temperatures of the first, second, third, fourth and fifth preheating cylinders were controlled at (100±10)℃, (200±10)℃, (300±10)℃, (400±10)℃ and (500±10)℃ respectively. The residence time of the material in the cyclone preheating cylinder was 10 minutes respectively. By adjusting the gas flow rate, the outlet of each level of preheating system was controlled at (650±10)℃, (200±10)℃, (300±10)℃, (400±10)℃ and (500±10)℃ respectively. The O2 content is controlled at (5±0.5)%, and the CO content is controlled below 0.4%; the outlet temperature of the first-stage cyclone cooling cylinder is controlled at (450±10)℃; the outlet temperature of the second-stage cyclone cooling cylinder is controlled at (350±10)℃, and the outlet temperature of the third-stage cyclone cooling cylinder is controlled at (200±10)℃; the residence time of the material in each level of cyclone cooling system is 10 minutes respectively; the O2 content at the outlet of the three-stage cyclone cooling system is controlled at (4±0.5)%; finally, it is further cooled to (50±5)℃ by a sleeve-type water-cooled screw conveyor and then sent to the finished product warehouse and bagged.

[0052] The chemical composition of the obtained finished mixture B is mainly metakaolin, calcium carbonate, silicon dioxide and calcium oxide, with a 45μm sieve residue of 3.4% and a specific surface area of ​​3.54m 2 / g, the cementitious material was prepared with the mass ratio of mixture B, cement clinker and gypsum being 30:65:5. The total amount of cementitious material, the amount of coarse and fine aggregates and the amount of water in the concrete mix design were the same as those in the comparative example. The prepared concrete had a 28d compressive strength of 49.5 MPa and a chloride ion permeability coefficient of 2.8×10 -12 m 2 / s.

[0053] Example 3

[0054] Regenerated micropowder and coal gangue M1 powder were uniformly mixed in a mass ratio of 1:2, and a powdered dispersant accounting for 0.5% of the total mass of coal gangue and regenerated micropowder was added. The ratio of polyphosphate to triethanolamine was 8:2 to form mixture A. The feed amount was 30% of the preheating tube volume, the interval between two feeds was controlled at 20 minutes, the temperature in the suspension calcining kiln was controlled at (700±10)℃, the calcination time was 60 minutes, and the fuel used was high calorific value fuel natural gas. The outlet temperatures of the first, second, third, fourth and fifth cyclone preheating tubes were controlled at (100±10)℃, (200±10)℃, (300±10)℃, (400±10)℃ and (500±10)℃, respectively. The material residence time in the cyclone preheating tubes was 10 minutes. By adjusting the gas flow rate, the O2 at the outlet of each preheating system was controlled at 100±10℃, (200±10)℃, (300±10)℃, (400±10)℃ and (500±10)℃, respectively. 2 content is controlled at (5±0.5)%, CO content is controlled below 0.4%; the outlet temperature of the first-stage cyclone cooling cylinder is controlled at (450±10)℃; the outlet temperature of the second-stage cyclone cooling cylinder is controlled at (350±10)℃, and the outlet temperature of the third-stage cyclone cooling cylinder is controlled at (200±10)℃; the residence time of the material in each level of cyclone cooling system is 10min respectively; the O2 content at the outlet of the three-stage cyclone cooling system is controlled at (4±0.5)%; finally, it is further cooled to (50±5)℃ by a sleeve-type water-cooled screw conveyor and then sent to the finished product warehouse and bagged.

[0055] The chemical composition of the obtained finished mixture B is mainly metakaolin, calcium carbonate, silicon dioxide and calcium oxide, with a 45μm sieve residue of 3.4% and a specific surface area of ​​3.54m 2 / g, the cementitious material was prepared with the mass ratio of mixture B, cement clinker and gypsum being 45:50:5. The total amount of cementitious material, the amount of coarse and fine aggregates and the amount of water in the concrete mix design were the same as those in the comparative example. The prepared concrete had a 28d compressive strength of 48.1 MPa and a chloride ion permeability coefficient of 3.0×10 -12 m 2 / s.

[0056] Example 4

[0057] The regenerated micro powder and the coal gangue M1 powder were mixed uniformly at a mass ratio of 1:4, and a powdered dispersant accounting for 0.5% of the total mass of the coal gangue and the regenerated micro powder was added. The ratio of polyphosphate to triethanolamine was 8:2 to form a mixture A. The feed amount was 30% of the volume of the preheating cylinder, the interval between two feeds was controlled at 20 minutes, the temperature in the suspension calcining kiln was controlled at (700±10)℃, the calcination time was 60 minutes, and the fuel used was blast furnace coke oven gas with medium and low calorific value. The outlet temperatures of the first, second, third, fourth and fifth preheating cylinders were controlled at (100±10)℃, (200±10)℃, (300±10)℃, (400±10)℃ and (500±10)℃ respectively. The residence time of the materials in the kiln was 10 minutes respectively. By adjusting the gas flow rate, the O2 The content is controlled at (5±0.5)%, and the CO content is controlled below 0.4%; the outlet temperature of the first-stage cyclone cooling cylinder is controlled at (450±10)℃; the outlet temperature of the second-stage cyclone cooling cylinder is controlled at (350±10)℃, and the outlet temperature of the third-stage cyclone cooling cylinder is controlled at (200±10)℃; the residence time of the material in each level of cyclone cooling system is 10 minutes respectively; the O2 content at the outlet of the three-stage cyclone cooling system is controlled at (4±0.5)%; finally, it is further cooled to (50±5)℃ by a sleeve-type water-cooled screw conveyor and then sent to the finished product warehouse and bagged.

[0058] The chemical composition of the obtained finished mixture B is mainly metakaolin, calcium carbonate, silicon dioxide and calcium oxide, with a 45μm sieve residue of 3.4% and a specific surface area of ​​3.54m 2 / g, the cementitious material was prepared with the mass ratio of mixture B, limestone powder, cement clinker and gypsum being 30:15:50:5. The total amount of cementitious material, the amount of coarse and fine aggregates and the amount of water in the concrete mix design were the same as those in the comparative example. The prepared concrete had a 28d compressive strength of 46.6 MPa and a chloride ion permeability coefficient of 3.4×10 -12 m 2 / s.

[0059] For ease of comparison, the production process parameters of the multi-solid waste low-carbon cementitious materials and the properties of the prepared concrete in the comparative example and the example are listed in Table 3. Comparative Example 1 is a concrete prepared using ordinary Portland cement, while the examples all use the cementitious material prepared by this patent to replace part of the cement to prepare concrete. In Examples 1 and 2, the mass ratio of recycled micropowder to coal gangue in Mixture A is 1:2. The calorific value of the coal gangue used in Example 2 is higher than that in Example 1. Therefore, Example 2 uses medium-low calorific value fuel, while Example 1 uses high calorific value fuel. The mass ratio of Mixture B replacing cement clinker is 30%. However, the 28d compressive strength of the concrete prepared in Example 2 is higher than that in Example 1, and the chloride ion permeability coefficient is also slightly lower. From this, it can be inferred that the cementitious material prepared in Example 2 is more active.

[0060] Example 1, Example 3 and Example 4 all use the same coal gangue, and the mixture B prepared by Example 1 and Example 3 is the same. However, in the concrete preparation process, the proportion of clinker replaced by Example 3 is 45%, which is higher than 30% of Example 1, resulting in higher 28d compressive strength and lower chloride ion permeability coefficient. That is, the increase in the replacement rate of composite cementitious materials is beneficial to improving the comprehensive performance of concrete.

[0061] The difference between Example 1 and Example 4 lies in the mass ratio of recycled micropowder and coal gangue in mixture A. In Example 4, the mass ratio of recycled micropowder and coal gangue is 1:4, and the proportion of coal gangue is higher than that in Example 1, resulting in a higher overall calorific value. Therefore, medium and low calorific value fuels are used, and when preparing concrete, in order to make the cement clinker replacement rate in the two examples the same, Example 4 is supplemented with 15% limestone powder. The comprehensive performance of the concrete finally prepared is slightly higher than that of Example 1. The comparison between the two is to illustrate the controllability of the cementitious material components.

[0062] Table 3 Production process parameters and performance results of each embodiment

[0063]

[0064]

[0065] Working principle and method

[0066] The above is an exemplary description of the present invention. Obviously, the specific implementation of the present invention is not limited to the above-mentioned method. As long as various non-substantial improvements are made using the method concept and technical solution of the present invention, or the concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the scope of protection of the present invention.

Claims

1. A process for preparing low-carbon cementitious materials from multiple solid wastes based on suspended calcination, characterized in that: The following steps are involved: S1, grinding the coal gangue; S2. Add a specific proportion of coal gangue and regenerated micro powder into a dispersant and mix to obtain a mixture A for standby use, wherein the dispersant accounts for 0.2 to 1% of the sum of the mass of the coal gangue and the regenerated micro powder; the mass ratio of the regenerated micro powder to the coal gangue is 1:1.5 to 1:5; S3. The mixture A obtained in S2 is sent to the suspension calcination system, and passes through a five-stage suspension preheating cylinder, a suspension calcination kiln, a three-stage suspension cooling cylinder, a two-stage fluidized bed, and a sleeve-type water-cooled screw conveyor to obtain a high-activity mixture B, which is finally sent to the finished product warehouse.

2. The process for preparing low-carbon cementitious materials from multiple solid wastes based on suspended calcination according to claim 1, characterized in that: In S2, the dispersant is a mixture of one or more of powdered polyphosphate, polyvinyl alcohol, saponin powder, triethanolamine, and ethylene glycol in different proportions.

3. The process for preparing low-carbon cementitious materials from multiple solid wastes based on suspended calcination according to claim 1, characterized in that: The fineness of the coal gangue in S1 is 80μm sieve residue ≤10%, the content of kaolin in the coal gangue is 20% to 90%, the mass proportion of the main components in the coal gangue is SiO2: 30% to 60%, Al2O3: 30% to 55%, Fe2O3: 0% to 20%, and the calorific value of the coal gangue is 2.0 to 6.3MJ / kg; The fineness of the regenerated micropowder in S2 is 80μm sieve residue ≤10%, and the mass proportions of the main chemical components in the regenerated micropowder are SiO2: 10%~60%, CaO: 20%~60%, and Al2O3: 0%~20%.

4. The process for preparing low-carbon cementitious materials from multiple solid wastes based on suspended calcination according to claim 1, characterized in that: The internal temperature field of the suspended calcining kiln in S3 is stable within the range of 500-1000℃.

5. The process for preparing low-carbon cementitious materials from multiple solid wastes based on suspended calcination according to claim 1, characterized in that: The suspension calcining kiln system uses gas fuel, which is selected according to the calorific value of the gangue and the components of the mixture A. When the calorific value of the gangue is 2.0-4.0 MJ / kg, or the mass ratio of the regenerated micropowder to the gangue is 1:1.5-1:3, any fuel is preferred; when the calorific value of the gangue is 4.0-6.3 MJ / kg, or the mass ratio of the regenerated micropowder to the gangue is 1:3-1:5, medium and low calorific value fuels are preferred.

6. The process for preparing low-carbon cementitious materials from multiple solid wastes based on suspended calcination according to claim 5, characterized in that: Gas fuels include high calorific value fuels (>15.07MJ / Nm 3 ), medium calorific value fuel (6.28~15.07MJ / Nm 3 ) and low calorific value fuels (<6.28MJ / Nm 3 ; High calorific value gas fuel is natural gas, and medium and low calorific value gas fuels include blast furnace coke oven gas, coal biomass gasification gas, petrochemical smelting exhaust gas, landfill gas and coal mine gas.

7. The process for preparing low-carbon cementitious materials from multiple solid wastes based on suspended calcination according to claim 1, characterized in that: The waste heat in the suspension calcining kiln in S3 can be recycled into the preheating system.

8. The process for preparing low-carbon cementitious materials from multiple solid wastes based on suspended calcination according to claim 1, characterized in that: In S3, the five-stage cyclone preheating cylinder controls the internal temperature of each stage of the preheating cylinder by adjusting the air intake and feed amount. The outlet temperatures of the first, second, third, fourth and fifth stage preheating cylinders are 50-100°C, 100-250°C, 250-400°C, 400-500°C and 500-600°C respectively. The residence time of the material in the suspension preheating cylinder is 5-15 minutes, and the wind speed is 15-25m / s.

9. The process for preparing low-carbon cementitious materials from multiple solid wastes based on suspended calcination according to claim 1, characterized in that: The residence time of mixture A in the suspension calcining kiln is 30 to 240 minutes, the wind speed is 15 to 25 m / s, and the O2 content at the outlet of the suspension calcining kiln is controlled to be ≥3.5%, and the CO content is ≤0.5% by controlling the air intake and fuel intake. The feed amount of mixture A is less than 50% of the volume of the preheating cylinder, and the interval between two feeds is controlled to be 10 to 30 minutes.

10. The process for preparing low-carbon cementitious materials from multiple solid wastes based on suspended calcination according to claim 1, characterized in that: The outlet temperature of the first-stage cyclone cooling cylinder is controlled at 400-500°C; the outlet temperature of the second-stage cyclone cooling cylinder is controlled at 300-400°C, and the outlet temperature of the third-stage cyclone cooling cylinder is controlled at 100-300°C; the residence time of the material in each level of cyclone cooling cylinder is 5-15 minutes, the wind speed is 15-25m / s, and the O2 content at the outlet of each level of cyclone cooling cylinder is ≥3.5%, and the CO content is ≤0.5%.

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