Method for preparing coal gangue-based active cementing material through pellet sintering

Abstract

The invention discloses a method for preparing a coal gangue-based active cementing material by pellet sintering, which comprises the following steps: S1, respectively crushing and finely grinding coal gangue, other solid wastes and fuel to obtain finely ground raw materials; s2, proportioning the finely ground raw materials according to a set proportion, adding water, and uniformly mixing to obtain a mixture; s3, pelletizing the mixture to obtain green pellets, screening the green pellets, using the green pellets with qualified particle sizes for subsequent sintering decarburization and activation, crushing the green pellets with unqualified particle sizes, and returning to the step S2; s4, material distribution is carried out on a belt type sintering machine trolley, then ignition, heat preservation, air draft sintering and cooling are carried out, decarburization and activation are carried out on the coal gangue, and finished ore is obtained; and S5, crushing and finely grinding the finished ore to obtain the active cementing material. The coal gangue is decarbonized and activated in a pellet sintering mode to prepare the cementing material, and the pellet sintering has the advantages that when the performance of the cementing material is similar, the utilization coefficient of pellet sintering is higher than that of conventional pelletizing sintering, the treatment capacity of solid waste is larger, and the utilization rate of the pellet sintering is higher. The air permeability of a material layer of green pellets prepared by pelletizing is superior to that of raw material particles prepared by conventional pelletizing, so that the vertical sintering speed is increased.

Description

Technical Field

[0001] The present invention relates to the technical field of comprehensive utilization of solid waste, and particularly to a method for preparing a coal gangue-based active cementitious material by pellet sintering. Background Art

[0002] Coal is the main energy source in China. Coal gangue is a solid waste generated during coal mining and washing processes. It is a black-gray rock with a lower carbon content and higher hardness than coal, which is associated with coal during the coal formation process. It accounts for about 15 - 20% of the coal production. The stockpile of coal gangue in China has exceeded 7 billion tons and is steadily increasing at a rate of 150 - 350 million tons per year. The large-scale stacking of coal gangue has brought very serious social, environmental, and economic problems. The main components of coal gangue are Al2O3 and SiO2, which are similar to those of building materials, and the market demand for building materials is large. Therefore, using coal gangue to prepare building materials (such as cementitious materials) can achieve the large-scale consumption and resource utilization of coal gangue. The key to using coal gangue to prepare cementitious materials is to adopt appropriate methods to increase its activity and reduce the residual carbon and loss on ignition in coal gangue.

[0003] Chinese Patent CN117760202A discloses a process and device for coupling coal gangue calcination activation with tunnel kiln brick-making equipment. The coal gangue is calcined in the tunnel kiln for 24 - 36 hours. Although this process is simple, it has a long calcination time, high energy consumption, and low output. Chinese Patent CN113429137B discloses a method for preparing geopolymers from coal gangue by microwave activation. The coal gangue powder is heat-insulated in a microwave processor for 1 - 6 hours. This process has a long calcination time, high energy consumption, low output, and it is extremely difficult and costly to scale up the microwave oven for large-scale industrial production. Therefore, the above two processes cannot handle a large amount of coal gangue on a large scale.

[0004] Chinese Patent CN110078401B discloses a process for preparing active admixtures by belt sintering of coal gangue, Chinese Patent CN113526883B discloses a fuel-free self-heating ultra-high bed decarbonization process for coal gangue, and Chinese Patent CN115448623B discloses a method for preparing cementitious materials by sintering and activating coal gangue. These methods all use sintering processes to decarbonize and activate coal gangue. These processes require the fixed carbon content of coal gangue to be 2% - 5%, which limits the use of coal gangue with a higher fixed carbon content in these processes; and these processes use a cylindrical granulator to granulate coal gangue, but the permeability of the material layer is poor during the suction sintering process of the granulation product, the sintering time is long, and the utilization coefficient is not high, making it difficult to consume a large amount of coal gangue and restricting the further application of these processes. Summary of the Invention

[0005] In view of the problems in the prior art of small gangue processing capacity, small applicable range of gangue, poor activation effect of gangue, and low sintering utilization coefficient of conventional granulation products, the purpose of the present invention is to provide a method for preparing gangue-based active cementitious materials by pellet sintering, broaden the range of available gangue, use pellet sintering to strengthen gangue decarbonization and activation, improve the permeability of the material layer, thereby improving the utilization coefficient and realizing high-value and large-scale utilization of gangue.

[0006] In order to achieve the above technical objectives, the technical solution of the present invention is:

[0007] The present invention provides a method for preparing a gangue-based active cementitious material by pellet sintering, comprising the following steps:

[0008] S1. crushing and fine-grinding coal gangue, other solid waste and fuel respectively to obtain finely ground raw materials;

[0009] S2, mixing the finely ground raw materials obtained in step S1 according to a set ratio, adding water and mixing well to obtain a mixture;

[0010] S3, pelletizing the mixed material obtained in step S2 to obtain green balls, screening the green balls, and using the green balls with qualified particle size for subsequent sintering, decarburization and activation, while the green balls with unqualified particle size are crushed, and the process returns to step S2;

[0011] S4, placing materials on the belt sintering machine trolley, then igniting, heat preservation, ventilation sintering and cooling, decarbonizing and activating the coal gangue to obtain finished ore;

[0012] S5, crushing and finely grinding the finished ore obtained in step S4 to obtain an active gelling material.

[0013] In a preferred solution, in step S1, the coal gangue is clay rock gangue, and the fixed carbon content of the coal gangue is 2% to 20%. This method is suitable for coal gangue with a fixed carbon content greater than 5%, thus broadening the scope of utilization of the coal gangue.

[0014] In a preferred embodiment, in step S1, the other solid wastes are divided into aluminosilicate-based solid wastes and calcium-based solid wastes, which can be divided into coal-fired boiler waste slag, mining tailings, engineering slag, and silt sludge according to their sources, including but not limited to fly ash, garbage incineration slag, iron tailings, red mud, steel slag, chromium slag, phosphorus slag, ferromanganese slag, carbide slag, desulfurized gypsum, construction excavation, subway excavation, river sludge, lake mud, and urban sludge. One or more.

[0015] Calcium-based solid waste decomposes at high temperature to produce reactive free calcium oxide, which reacts with aluminosilicate-based solid waste, aluminosilicates in coal gangue, and iron-containing minerals to form minerals such as tricalcium silicate (C3S), dicalcium silicate (C2S), tricalcium aluminate (C3A), and tetracalcium ferroaluminate (C4AF). These generated minerals have hydraulicity and are important components of active cementitious materials.

[0016] In a preferred embodiment, in step S1, the fuel is one or more of anthracite, bituminous coal, and semi-coke.

[0017] In a preferred embodiment, in step S1, the coal gangue, other solid waste, and fuel are crushed and finely ground to a particle size of -1 mm; more preferably, they are crushed and finely ground to a particle size of -0.5 mm.

[0018] In a preferred embodiment, in step S1, the crushing treatment is carried out using one or more of a jaw crusher, a pair-roll crusher, a cone crusher, a counterattack crusher, an impact crusher, and a hammer crusher;

[0019] The fine grinding treatment is carried out in the following three ways: wet ball milling with water followed by drying, high-pressure roller milling under natural moisture, and dry ball milling after drying; more preferably, high-pressure roller milling pretreatment under natural moisture is adopted.

[0020] The finer the raw materials, the smaller their particle size, the larger their specific surface area, the larger the contact area between components, and at the same time, the greater the free energy of surface particles, which enhances the reaction and diffusion ability. Therefore, the reaction rate is faster, and the decarbonization and activation effects are better. However, when the raw materials are ground to a certain extent, if further fine grinding is continued, the increase in the reaction rate is not obvious, while the output of the mill will be greatly reduced, and the power consumption for grinding will increase sharply. Therefore, it is necessary to make a comprehensive balance and control the raw material particle size within an appropriate range.

[0021] In a preferred embodiment, in step S2, the mass percentages (by dry weight) of coal gangue, other solid waste, and fuel are:

[0022] Coal gangue 50% - 100%, other solid waste 0% - 50%, fuel 0% - 7%;

[0023] More preferably, coal gangue 60% - 90%, other solid waste 10% - 40%, fuel 0% - 7%.

[0024] In a preferred embodiment, in step S2, 1% - 5% water is added to mix the raw materials evenly, and the fixed carbon content of the mixture is maintained at 2.0% - 10% (by dry weight). The addition amount of other solid waste is adjusted according to its output and product performance. If the fixed carbon content of the coal gangue is relatively high, the fuel can be not added, and the addition amount of other solid waste can be increased; if the fixed carbon content of the coal gangue is relatively low, fuel needs to be supplemented, and the addition amount of other solid waste can be reduced.

[0025] More preferably, the fixed carbon content of the mixture is maintained at 2% - 6.5% (by dry weight).

[0026] Coal gangue can not only serve as the matrix of silicon and aluminum in the cementitious material, but also play the role of fuel during the activation process due to the carbon it contains; other solid wastes play three roles: first, providing free calcium oxide to strengthen the activation effect of coal gangue; second, providing aluminosilicate as the matrix of the cementitious material; third, adjusting the fixed carbon content of the mixture. If the fixed carbon content in the mixture is too low, it may lead to decarbonization, and the material layer cannot burn or burns insufficiently during the activation process, resulting in low activity of the cementitious material; if the fixed carbon content is too high, it is easy to cause the temperature of the material layer to be too high, and a large amount of mullite phase is likely to be generated during the crystallization process, resulting in a decrease in the activity of the cementitious material.

[0027] In a preferred embodiment, in step S3, a disc pelletizer or a drum pelletizer is used for pelletizing. The moisture content of the green pellets produced is 7% - 15%, the average particle size of the qualified green pellets is 5 - 8 mm, and the green pellets have different sizes and inconsistent particle diameters. The air permeability resistance of the green pellet layer is 30 - 60 mmH2O. If the moisture content of the green pellets is too low, it is easy to cause poor pelletizing effect during the pelletizing process; if the moisture content of the green pellets is too high, on the one hand, it will cause the material to stick to the disc during the pelletizing process, and on the other hand, it will make the particle diameter of the green pellets too large, resulting in too fast sintering speed, high residual carbon in the finished ore, and low activity. An appropriate particle size of the green pellets can make the air permeability of the material layer moderate, and while having a high utilization coefficient, it can reduce the residual carbon content of the finished ore and improve its activity.

[0028] In a preferred embodiment, in step S4, during the feeding process, the particle size of the bottom layer material is 12 - 25 mm, the height of the bottom layer material is controlled to be 20 - 70 mm, and the total height of the material layer is controlled to be 800 - 2000 mm; the total height of the material layer is also the height of the bottom layer material + the height of the qualified green pellets. If the fixed carbon content of the coal gangue < 5%, the bottom layer material is the original crushed coal gangue; if the fixed carbon content of the coal gangue ≥ 5%, the bottom layer material is the crushed finished ore, which can play a role in protecting the grate bars. Using a high material layer and an ultra-high material layer for decarbonization and activation can utilize its self-heating effect, so that less fuel can be used to achieve the same or even better decarbonization and activation effects. However, the material layer should not be too high, as too high a material layer will lead to too large a material layer resistance and too slow a sintering speed.

[0029] In a preferred embodiment, in step S4, the ignition time is 2 - 5 min, the ignition temperature is 900 - 1150 °C, and the ignition negative pressure is 4 - 6 kPa; the holding temperature is 800 - 900 °C, and the holding time is 3 - 6 min; the negative pressure during the suction sintering is 7 - 18 kPa. By reasonably adjusting the above parameters, the sintering process can have a high utilization coefficient, and at the same time, the decarbonization and activation effects of the finished ore are good.

[0030] In a preferred embodiment, in step S4, the cooling time is 4 to 12 minutes, and the cooling negative pressure is 5 to 15 kPa to rapidly cool the finished ore. The main functions of rapid cooling are as follows: it can prevent the conversion of β-dicalcium silicate (C2S) to γ-dicalcium silicate (C2S), and prevent the decomposition of tricalcium silicate (C3S) into dicalcium silicate (C2S) and free calcium oxide, thereby obtaining higher hydraulicity; rapid cooling can prevent MgO from crystallizing in time and existing in the vitreous body, reducing its harm to the soundness of the cementitious material; rapid cooling can make tricalcium aluminate (C3A) mainly in the vitreous state, so the cementitious material has strong resistance to sulfate solution corrosion; rapid cooling can increase the vitreous content, and at the same time cause internal stress in the finished ore, which can significantly improve the grindability of the finished ore and reduce the fine grinding cost of the subsequent production of active cementitious materials from the finished ore.

[0031] In a preferred embodiment, in step S5, the properties of the obtained active cementitious material are as follows: the proportion of particles with a size of -0.08 mm is 97% to 99%, the loss on ignition is ≤3%, the residual carbon content is ≤3%, the specific surface area is 300 to 500 m 2 / kg, and the activity index is ≥75%.

[0032] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0033] (1) The fixed carbon content of the coal gangue applicable to the present invention is significantly expanded. The fixed carbon content of the coal gangue required by the prior art is 2% to 5%, and the suitable fixed carbon content range of the coal gangue of the present invention is expanded to 2% to 20%. After the available fixed carbon content range of the coal gangue is expanded, about 70% of the coal gangue can be used in the present invention. In addition, there are many types of other available solid wastes, wide sources, and large production volumes. Appropriate addition of other solid wastes can not only realize the disposal of other solid wastes, but also strengthen the activation of coal gangue. The present invention can realize the resource utilization of multiple solid wastes mainly composed of coal gangue.

[0034] (2) The present invention uses pellet sintering to decarbonize and activate coal gangue to prepare cementitious materials. Compared with conventional granulation sintering, the advantages of pellet sintering are as follows: when the properties of the cementitious material are similar, the utilization coefficient of pellet sintering is higher than that of conventional granulation sintering, and the treatment amount of solid waste is larger. This is because the permeability of the green pellets prepared by pelletizing is better than that of the raw material particles of conventional granulation, and the vertical sintering speed is increased. When the utilization coefficient is similar during the sintering process, the properties of the cementitious material prepared by pellet sintering are better than those of conventional granulation sintering. This is because the raw materials before pelletizing need to be crushed and finely ground to -1 mm, while the raw materials for granulation are required to be -8 mm. The finer the particles, the more conducive to the reaction between particles, thereby achieving more efficient decarbonization and activation.

[0035] (3) The present invention realizes the rapid cooling of the finished ore by increasing the cooling negative pressure and prolonging the on-machine cooling time. The functions of rapid cooling are as follows: First, it can avoid the reduction of effective minerals such as tricalcium silicate (C3S) and β-dicalcium silicate (C2S) during the cooling process. At the same time, MgO and tricalcium aluminate (C3A) are present in the vitreous body, which can improve the performance of the product cementitious material. Second, rapid cooling enables the formation of a large amount of amorphous glass phase, which can improve the grindability of the finished ore and reduce the grinding cost of preparing the cementitious material from the subsequent finished ore. Third, it avoids the slow cooling of the finished ore after unloading, which may damage the subsequent ore-breaking, fine-grinding equipment and conveyor belts. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the embodiments. Obviously, the drawings described below are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on the provided drawings.

[0037] Figure 1 It is the process flow chart of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0038] The following will clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present application.

[0039] The following will further describe the present application in detail with reference to the drawings and specific embodiments:

[0040] Embodiment 1

[0041] The gangue from a certain area is used, and its chemical composition is as follows: SiO2 56.10%, Al2O3 20.51%, CaO 0.50%, MgO 0.69%, fixed carbon 2.50%, LOI (loss on ignition) 12.44%.

[0042] The original gangue ore is crushed to -12 mm by a jaw crusher, and then the gangue is crushed and finely ground to -0.5 mm by a high-pressure roller mill.

[0043] The gangue powder is mixed with water and then fed into a disk pelletizer for pelletizing. The pelletizing time is 8 min. The moisture content of the green pellets is 8.5%, the average particle size of the green pellets is 8 mm, and the air permeability resistance of the green pellets is 55 mmH2O.

[0044] The belt sintering machine (with a material layer height of 900 mm) feeds materials through rollers, uses raw gangue with a size of 12 - 25 mm as the bedding material, and the thickness of the bedding material is 50 mm. Then, green pellets are fed. The ignition temperature is 1150 °C, the ignition time is 4 min, the ignition negative pressure is 6 kPa. After ignition, heat preservation is carried out, and heat preservation is carried out at 900 °C for 5 min. The sintering negative pressure is 11 kPa. After sintering, the exhaust negative pressure is adjusted to 15 kPa. After cooling for 5 min, the decarbonized gangue is unloaded and naturally cooled in the air. The sintering utilization coefficient is 1.69 t / (m 2 ·h).

[0045] After the decarbonized gangue is crushed to -1 mm by a jaw crusher, it is then dry-ground in a ball mill to a specific surface area of 450 m 2 / kg, and the proportion of particles with a size of -0.08 mm is 98%. Then, the gangue-based cementitious material can be obtained, with a loss on ignition of 2.82%, a residual carbon content of 1.13%, and an activity index of 80.15%.

[0046] Example 2

[0047] Using gangue from a certain area, its chemical composition is as follows: SiO2 38.70%, Al2O3 13.11%, CaO 5.45%, MgO 0.92%, fixed carbon 6.06%, LOI (loss on ignition) 23.55%.

[0048] The raw gangue is crushed to -12 mm by a jaw crusher, and then the gangue is crushed and finely ground to -0.5 mm by a high-pressure roller mill.

[0049] The gangue powder is mixed with water and then fed into a disc pelletizer for pelletizing. The pelletizing time is 8 min. The moisture content of the obtained green pellets is 14%, the average particle size of the green pellets is 6.5 mm, and the air permeability resistance of the green pellets is 48 mmH2O.

[0050] The belt sintering machine (with a material layer height of 900 mm) feeds materials through rollers, uses decarbonized gangue with a size of 12 - 25 mm as the bedding material, and the thickness of the bedding material is 50 mm. Then, green pellets are fed. The ignition temperature is 1150 °C, the ignition time is 2 min, the ignition negative pressure is 6 kPa. After ignition, heat preservation is carried out, and heat preservation is carried out at 900 °C for 2.5 min. The sintering negative pressure is 9 kPa. After sintering, the exhaust negative pressure is adjusted to 11 kPa. After cooling for 5 min, the decarbonized gangue is unloaded and naturally cooled in the air. The sintering utilization coefficient is 1.12 t / (m 2 ·h).

[0051] After the decarbonized gangue is crushed to -1 mm by a jaw crusher, it is then dry-ground in a ball mill to a specific surface area of 450 m 2 / kg, the proportion of -0.08mm particles is 98%, then the coal gangue-based cementitious material can be obtained, with a loss on ignition of 2.07%, a residual carbon content of 1.65%, and an activity index of 78.76%.

[0052] Example 3

[0053] Use the coal gangue from a certain area, and its chemical components are as follows: SiO2 38.70%, Al2O3 13.11%, CaO 5.45%, MgO 0.92%, fixed carbon 6.06%, LOI (loss on ignition) 23.55%.

[0054] The chemical components of the sludge are as follows: SiO2 0.70%, Al2O3 0.36%, CaO 42.78%, MgO 6.70%, LOI (loss on ignition) 42.41%.

[0055] Dry the sludge, use a jaw crusher to crush the raw coal gangue and sludge to -12mm, and then use a high-pressure roller mill to crush and finely grind the coal gangue and sludge to -0.5mm.

[0056] Mix the raw material powders according to the ratio of coal gangue:sludge = 90:10, add water and mix evenly, then send them into a disc pelletizer for pelletizing. The pelletizing time is 8min. The moisture content of the green pellets is 14%, the average particle size of the green pellets is 6mm, and the air permeability resistance of the green pellets is 50mmH2O.

[0057] The belt sintering machine (with a bed height of 900mm) is fed through rollers. Use decarbonized coal gangue of 12 - 25mm as the bottom layer material, with a bottom layer thickness of 50mm. Then feed the green pellets. The ignition temperature is 1150°C, the ignition time is 2min, the ignition negative pressure is 6kPa. After ignition, keep warm. Keep warm at 900°C for 2.5min, the sintering negative pressure is 9kPa. After sintering, adjust the exhaust negative pressure to 11kPa. After cooling for 5min, unload the decarbonized coal gangue and let it cool naturally in the air. The sintering utilization coefficient is 1.22t / (m 2 ·h).

[0058] After the decarbonized coal gangue is crushed to -1mm by a jaw crusher, then dry grind it in a ball mill to a specific surface area of 450m 2 / kg, the proportion of -0.08mm particles is 98%, then the coal gangue-based cementitious material can be obtained, with a loss on ignition of 2.05%, a residual carbon content of 1.03%, and an activity index of 82.39%.

[0059] Example 4

[0060] The coal gangue from a certain area was used, and its chemical composition was as follows: SiO2 55.78%, Al2O3 20.86%, CaO 0.56%, MgO 0.65%, fixed carbon 3.53%, and LOI (loss on ignition) 13.23%.

[0061] The chemical composition of desulfurized gypsum is as follows: SiO2 0.73%, Al2O3 0.32%, CaO 36.11%, MgO 1.56%, LOI (loss on ignition) 11.79%.

[0062] A jaw crusher is used to crush the coal gangue ore and desulfurized gypsum to -12mm, and then a high-pressure roller mill is used to crush and finely grind the coal gangue and sludge to -0.5mm.

[0063] The ingredients are prepared according to the ratio of coal gangue to desulfurized gypsum = 90:10, and after adding water and mixing, they are sent into a disc pelletizing machine for pelletizing. The pelletizing time is 8 minutes. The moisture content of the obtained green balls is 14%, the average particle size of the green balls is 6 mm, and the air permeability resistance of the green balls is 51 mmH2O.

[0064] The belt sintering machine (material layer height 2000mm) uses rollers to spread the material, using 12-25mm coal gangue as the base material, the base material thickness is 50mm, and then the raw balls are spread. The ignition temperature is 1100℃, the ignition time is 5min, the ignition negative pressure is 6kPa, and the ignition is completed. Keep warm at 900℃ for 6min, the sintering negative pressure is 13kPa, and the exhaust negative pressure is adjusted to 15kPa after sintering. After cooling for 6min, the decarbonized coal gangue is discharged and cooled naturally in the air. The sintering utilization factor is 1.45t / (m 2 h).

[0065] The decarbonized coal gangue is crushed to -1mm by a jaw crusher and then dry-ground in a ball mill to a specific surface area of ​​450m 2 / kg, -0.08mm particles account for 98%, and coal gangue-based cementitious materials can be obtained, with a loss on ignition of 1.92%, a residual carbon content of 0.89%, and an activity index of 86.15%.

[0066] Example 5

[0067] The coal gangue from a certain area was used, and its chemical composition was as follows: SiO2 56.10%, Al2O3 20.51%, CaO 0.50%, MgO 0.69%, fixed carbon 2.50%, and LOI (loss on ignition) 12.44%.

[0068] The chemical composition of desulfurized gypsum is as follows: SiO2 0.73%, Al2O3 0.32%, CaO 36.11%, MgO 1.56%, LOI (loss on ignition) 11.79%.

[0069] The fuel used is anthracite with a fixed carbon content of 81.27%.

[0070] The gangue ore, desulfurized gypsum and anthracite are crushed to -12mm by a double-roll crusher, and then the gangue, desulfurized gypsum and anthracite are crushed and finely ground to -0.5mm by a high-pressure roller mill.

[0071] The raw material powder is mixed according to the ratio of coal gangue: desulfurized gypsum: anthracite = 89:10:1, mixed with water and sent to the disc pelletizing machine for pelletizing. The pelletizing time is 8 minutes. The moisture content of the obtained green balls is 9%, the average particle size of the green balls is 5.5 mm, and the air permeability resistance of the green balls is 45 mmH2O.

[0072] The belt sintering machine (material layer height 1000mm) uses rollers to spread the material, using 12-25mm coal gangue as the base material, the base material thickness is 30mm, and then the raw balls are spread. The ignition temperature is 1150℃, the ignition time is 4min, the ignition negative pressure is 6kPa, and the ignition is completed. Keep warm at 900℃ for 5min, the sintering negative pressure is 12kPa, and the exhaust negative pressure is adjusted to 15kPa after sintering. After cooling for 5min, the decarbonized coal gangue is discharged and cooled naturally in the air. The sintering utilization factor is 1.46t / (m 2 h).

[0073] The decarbonized coal gangue is crushed to -1mm by a jaw crusher and then dry-ground in a ball mill to a specific surface area of ​​450m 2 / kg, -0.08mm particles account for 98%, and coal gangue-based cementitious materials can be obtained, with a loss on ignition of 1.73%, a residual carbon content of 0.85%, and an activity index of 82.61%.

[0074] Example 6

[0075] The coal gangue from a certain area was used, and its chemical composition was as follows: SiO2 55.78%, Al2O3 20.86%, CaO 0.56%, MgO 0.65%, fixed carbon 3.53%, and LOI (loss on ignition) 13.23%.

[0076] The chemical composition of fly ash is as follows: SiO2 50.16%, Al2O3 28.27%, CaO 3.50%, MgO 1.54%, LOI (loss on ignition) 4.40%.

[0077] The chemical composition of steel slag is as follows: SiO2 17.52%, Al2O3 2.98%, CaO 34.77%, MgO 7.99%, LOI (loss on ignition) -1.06%.

[0078] A jaw crusher is used to crush the gangue ore, fly ash and steel slag to -12mm, and then a high pressure roller mill is used to crush and finely grind the gangue, fly ash and steel slag to -0.5mm.

[0079] The raw material powder is mixed according to the ratio of coal gangue: fly ash: steel slag = 90:5:5, and after adding water and mixing, it is sent into a disc ball making machine for ball making. The ball making time is 8 minutes. The moisture content of the obtained green balls is 10%, the average particle size of the green balls is 6mm, and the air permeability resistance of the green balls is 52mmH2O.

[0080] The belt sintering machine (material layer height 950mm) uses rollers to spread the material, using 12-25mm coal gangue as the base material, the base material thickness is 40mm, and then the raw balls are spread. The ignition temperature is 1150℃, the ignition time is 4min, the ignition negative pressure is 6kPa, and the ignition is completed. Keep warm at 900℃ for 5min, the sintering negative pressure is 10kPa, and the exhaust negative pressure is adjusted to 14kPa after sintering. After cooling for 5min, the decarbonized coal gangue is discharged and cooled naturally in the air. The sintering utilization factor is 1.52t / (m 2 h).

[0081] The decarbonized coal gangue is crushed to -1mm by a jaw crusher and then dry-ground in a ball mill to a specific surface area of ​​450m 2 / kg, -0.08mm particles account for 98%, and coal gangue-based cementitious materials can be obtained, with a loss on ignition of 1.94%, a residual carbon content of 1.04%, and an activity index of 81.32%.

[0082] Example 7

[0083] The coal gangue from a certain area was used, and its chemical composition was as follows: SiO2 42.41%, Al2O3 14.28%, CaO 2.66%, MgO 0.89%, fixed carbon 12.15%, and LOI (loss on ignition) 29.15%.

[0084] The chemical composition of fly ash is as follows: SiO2 50.16%, Al2O3 28.27%, CaO 3.50%, MgO 1.54%, LOI (loss on ignition) 4.40%.

[0085] The chemical composition of desulfurized gypsum is as follows: SiO2 0.73%, Al2O3 0.32%, CaO 36.11%, MgO 1.56%, LOI (loss on ignition) 11.79%.

[0086] A jaw crusher is used to crush the gangue ore, fly ash and desulfurization gypsum to -12mm, and then a high-pressure roller mill is used to crush and finely grind the gangue, fly ash and desulfurization gypsum to -0.5mm.

[0087] The raw material powder is mixed according to the ratio of coal gangue: fly ash: desulfurized gypsum = 50:30:20, and after adding water and mixing, it is sent into a disc pelletizing machine for pelletizing. The pelletizing time is 8 minutes. The moisture content of the obtained green balls is 10%, the average particle size of the green balls is 5 mm, and the air permeability resistance of the green balls is 45 mmH2O.

[0088] The belt sintering machine (material layer height 900mm) uses rollers to spread the material, using 12-25mm decarbonized coal gangue as the base material, the base material thickness is 60mm, and then the raw balls are spread. The ignition temperature is 1100℃, the ignition time is 2min, the ignition negative pressure is 6kPa, and the heat preservation is carried out after the ignition is completed. The heat preservation is carried out at 900℃ for 2min, the sintering negative pressure is 9kPa, and the exhaust negative pressure is adjusted to 11kPa after the sintering is completed. After cooling for 5min, the decarbonized coal gangue is discharged and cooled naturally in the air. The sintering utilization coefficient is 1.34t / (m 2 h).

[0089] The decarbonized coal gangue is crushed to -1mm by a jaw crusher and then dry-ground in a ball mill to a specific surface area of ​​450m 2 / kg, -0.08mm particles account for 98%, and coal gangue-based cementitious materials can be obtained, with a loss on ignition of 2.16%, a residual carbon content of 1.12%, and an activity index of 87.32%.

[0090] Example 8

[0091] The coal gangue from a certain area was used, and its chemical composition was as follows: SiO2 34.79%, Al2O3 14.70%, CaO 1.83%, MgO 1.12%, fixed carbon 19.03%, and LOI (loss on ignition) 9.16%.

[0092] The chemical composition of the iron tailings is as follows: SiO2 41.97%, Al2O3 9.98%, CaO 10.90%, MgO 5.31%, LOI (loss on ignition) 5.56%.

[0093] The chemical composition of steel slag is as follows: SiO2 17.52%, Al2O3 2.98%, CaO 34.77%, MgO 7.99%, LOI (loss on ignition) -1.06%.

[0094] The gangue ore, iron tailings and steel slag are crushed to -12mm by a double-roll crusher, and then crushed and finely ground to -0.5mm by a high-pressure roller mill.

[0095] The raw material powder is proportioned according to coal gangue: iron tailings: steel slag = 50:40:10, mixed with water and then sent into a disc pelletizer for pelletizing. The pelletizing time is 8 min. The green pellets obtained have a moisture content of 11%, an average pellet size of 5 mm, and an air permeability resistance of 47 mmH2O.

[0096] The belt sintering machine (with a bed height of 900 mm) feeds the material through a roller, uses decarbonized coal gangue with a size of 12 - 25 mm as the bottom layer material, and the thickness of the bottom layer material is 70 mm. Then the green pellets are fed for material distribution. The ignition temperature is 1000 °C, the ignition time is 1.5 min, the ignition negative pressure is 6 kPa. After ignition, heat preservation is carried out, and heat preservation is carried out at 800 °C for 2 min. The sintering negative pressure is 9 kPa. After sintering, the exhaust negative pressure is adjusted to 11 kPa. After cooling for 5 min, the decarbonized coal gangue is unloaded and naturally cooled in the air. The sintering utilization coefficient is 1.31 t / (m 2 ·h).

[0097] After the decarbonized coal gangue is crushed to -1 mm by a jaw crusher, it is then dry - milled in a ball mill to a specific surface area of 450 m 2 / kg, and the proportion of particles with a size of -0.08 mm is 98%. Then the coal - gangue - based cementitious material can be obtained, with a loss on ignition of 2.25%, a residual carbon content of 1.24%, and an activity index of 85.43%.

[0098] Comparative Example 1

[0099] Coal gangue from a certain area is used, and its chemical composition is as follows: SiO2 56.10%, Al2O3 20.51%, CaO 0.50%, MgO 0.69%, fixed carbon 2.50%, LOI (loss on ignition) 12.44%.

[0100] The original coal - gangue ore is crushed to -8 mm by a jaw crusher.

[0101] The coal - gangue particles are mixed with water and then sent into a cylindrical pelletizer for pelletizing. The pelletizing time is 5 min. The moisture content of the green material obtained is 8.5%, the average pellet size is 5 mm, and the air permeability resistance of the green material is 50 mmH2O.

[0102] The belt sintering machine (with a bed height of 900 mm) feeds the material through a roller, uses the original gangue with a size of 12 - 25 mm as the bottom layer material, and the thickness of the bottom layer material is 50 mm. Then the green material is fed for material distribution. The ignition temperature is 1150 °C, the ignition time is 4 min, the ignition negative pressure is 6 kPa. After ignition, heat preservation is carried out, and heat preservation is carried out at 900 °C for 5 min. The sintering negative pressure is 11 kPa. After sintering, the exhaust negative pressure is adjusted to 15 kPa. After cooling for 5 min, the decarbonized coal gangue is unloaded and naturally cooled in the air. The sintering utilization coefficient is 1.05 t / (m 2 ·h).

[0103] The decarbonized coal gangue is crushed to -1mm by a jaw crusher and then dry-ground in a ball mill to a specific surface area of ​​450m 2 / kg, -0.08mm particles account for 98%, and coal gangue-based cementitious materials can be obtained, with a loss on ignition of 5.79%, a residual carbon content of 1.99%, and an activity index of 72.26%.

[0104] Comparative Example 2

[0105] The coal gangue from a certain area was used, and its chemical composition was as follows: SiO2 56.10%, Al2O3 20.51%, CaO 0.50%, MgO 0.69%, fixed carbon 2.50%, and LOI (loss on ignition) 12.44%.

[0106] A jaw crusher is used to crush the raw coal gangue to -12mm, and then a high pressure roller mill is used to crush and finely grind the coal gangue to -0.5mm.

[0107] The coal gangue powder was mixed with water and then sent to a disc pelletizing machine for pelletizing. The pelletizing time was 8 minutes. The moisture content of the obtained green balls was 8.5%, the average particle size of the green balls was 6 mm, and the air permeability resistance of the green balls was 56 mmH2O.

[0108] The belt sintering machine (material layer height 2200mm) uses rollers to spread the material, using 12-25mm raw gangue as the base material, the base material thickness is 50mm, and then the raw balls are spread. The ignition temperature is 1150℃, the ignition time is 4min, the ignition negative pressure is 6kPa, and the ignition is completed. Keep warm at 900℃ for 5min, the sintering negative pressure is 11kPa, and the exhaust negative pressure is adjusted to 15kPa after sintering. After cooling for 5min, the decarbonized coal gangue is discharged and cooled naturally in the air. The sintering utilization coefficient is 1.21t / (m 2 h).

[0109] The decarbonized coal gangue is crushed to -1mm by a jaw crusher and then dry-ground in a ball mill to a specific surface area of ​​450m 2 / kg, -0.08mm particles account for 98%, and coal gangue-based cementitious materials can be obtained, with a loss on ignition of 2.34%, a residual carbon content of 1.21%, and an activity index of 74.25%.

[0110] Comparative Example 3

[0111] The coal gangue from a certain area was used, and its chemical composition was as follows: SiO2 38.70%, Al2O3 13.11%, CaO 5.45%, MgO 0.92%, fixed carbon 6.06%, and LOI (loss on ignition) 23.55%.

[0112] A jaw crusher is used to crush the coal gangue ore to -8mm.

[0113] The coal gangue particles are mixed with water and then fed into a cylindrical granulator for granulation. The granulation time is 5 min. The moisture content of the green material obtained is 8.5%, the average particle size of the green balls is 6 mm, and the air permeability resistance of the green material is 41 mmH2O.

[0114] The belt sintering machine (with a material layer height of 900 mm) feeds the material through a roller, uses decarbonized coal gangue with a size of 12 - 25 mm as the bottom layer material, and the thickness of the bottom layer material is 50 mm. Then the green material is fed for ignition at a temperature of 1150 °C, an ignition time of 2 min, an ignition negative pressure of 6 kPa. After ignition, heat preservation is carried out at 900 °C for 2.5 min, the sintering negative pressure is 9 kPa. After sintering, the exhaust negative pressure is adjusted to 11 kPa. After cooling for 5 min, the decarbonized coal gangue is unloaded and naturally cooled in the air. The sintering utilization coefficient is 0.87 t / (m 2 ·h).

[0115] After the decarbonized coal gangue is crushed to -1 mm by a jaw crusher, it is then dry - milled in a ball mill to a specific surface area of 450 m 2 / kg, and the proportion of particles with a size of -0.08 mm is 98%. Then the coal gangue - based cementitious material can be obtained, with a loss on ignition of 2.50%, a residual carbon content of 2.02%, and an activity index of 78.48%.

[0116] Comparative Example 4

[0117] The coal gangue from a certain area is used, and its chemical composition is as follows: SiO2 38.70%, Al2O3 13.11%, CaO 5.45%, MgO 0.92%, fixed carbon 6.06%, LOI (loss on ignition) 23.55%.

[0118] The original coal gangue ore is crushed to -12 mm by a jaw crusher, and then the coal gangue is crushed and finely ground to -0.5 mm by a high - pressure roller mill.

[0119] The coal gangue powder is mixed with water and then fed into a disk pelletizer for pelletizing. The pelletizing time is 8 min. The moisture content of the green balls obtained is 14%, the average particle size of the green balls is 10 mm, and the air permeability resistance of the green balls is 64 mmH2O.

[0120] The belt sintering machine (with a material layer height of 900 mm) feeds the material through a roller, uses decarbonized coal gangue with a size of 12 - 25 mm as the bottom layer material, and the thickness of the bottom layer material is 50 mm. Then the green balls are fed for ignition at a temperature of 1150 °C, an ignition time of 2 min, an ignition negative pressure of 6 kPa. After ignition, heat preservation is carried out at 900 °C for 2.5 min, the sintering negative pressure is 9 kPa. After sintering, the exhaust negative pressure is adjusted to 11 kPa. After cooling for 5 min, the decarbonized coal gangue is unloaded and naturally cooled in the air. The sintering utilization coefficient is 1.56 t / (m2 h).

[0121] The decarbonized coal gangue is crushed to -1mm by a jaw crusher and then dry-ground in a ball mill to a specific surface area of ​​450m 2 / kg, -0.08mm particles account for 98%, and coal gangue-based cementitious materials can be obtained, with a loss on ignition of 5.63%, a residual carbon content of 3.78%, and an activity index of 52.14%.

[0122] Comparative Example 5

[0123] The coal gangue from a certain area was used, and its chemical composition was as follows: SiO2 55.78%, Al2O3 20.86%, CaO 0.56%, MgO 0.65%, fixed carbon 3.53%, and LOI (loss on ignition) 13.23%.

[0124] The chemical composition of desulfurized gypsum is as follows: SiO2 0.73%, Al2O3 0.32%, CaO 36.11%, MgO 1.56%, LOI (loss on ignition) 11.79%.

[0125] The desulfurized gypsum is dried, and the coal gangue ore and desulfurized gypsum are crushed to -12mm by a jaw crusher. Then, the coal gangue and sludge are crushed and finely ground to -0.5mm by a high-pressure roller mill.

[0126] The ingredients are prepared according to the ratio of coal gangue to desulfurized gypsum = 90:10, and after adding water and mixing, they are sent into a disc ball making machine for ball making. The ball making time is 8 minutes. The moisture content of the obtained green balls is 14%, the average particle size of the green balls is 6mm, and the air permeability resistance of the green balls is 50mmH2O.

[0127] The belt sintering machine (material layer height 1000mm) uses rollers to spread the material, using 12-25mm decarbonized coal gangue as the base material, with a base material thickness of 50mm, and then spreads the raw balls. The ignition temperature is 1100℃, the ignition time is 5min, and the ignition negative pressure is 6kPa. After the ignition is completed, it is kept warm at 900℃ for 6min, and the sintering negative pressure is 10kPa. After the sintering is completed, the decarbonized coal gangue is directly discharged and cooled naturally in the air. The sintering utilization factor is 1.43t / (m 2 h).

[0128] The decarbonized coal gangue is crushed to -1mm by a jaw crusher and then dry-ground in a ball mill to a specific surface area of ​​450m 2 / kg, -0.08mm particles account for 98%, and coal gangue-based cementitious materials can be obtained, with a loss on ignition of 1.92%, a residual carbon content of 0.89%, and an activity index of 66.52%.

[0129] It can be seen from Examples 1-8 and Comparative Examples 1-5 that, compared with conventional granulation, pellet sintering by finely grinding the raw materials can not only improve the sintering utilization coefficient, but also make the decarbonization and activation of coal gangue more sufficient, reduce the residual carbon content and loss on ignition, increase the activity index of the cementitious material, and the technology is applicable to a wide range of fixed carbon contents of coal gangue. Comparing Example 2 with Example 3, adding calcium-based solid waste can strengthen the activation of coal gangue and increase the activity index of the cementitious material. In Comparative Example 2, the bed height is too high, resulting in a decrease in the utilization coefficient and product activity; in Comparative Example 4, due to the too large green pellet size, the sintering speed is too fast, the loss on ignition and residual carbon of the finished cementitious material are high, and the activity is low; in Comparative Example 5, instead of rapid cooling, the sintered ore is directly unloaded and naturally cooled in the air, resulting in a decrease in the activity of the cementitious material.

[0130] The above content is only a specific implementation case of this application, rather than all application cases of this application. Any solution that follows the technical idea of this application and makes changes on the technical idea of this application is within the protection scope of the claims of this application.

Claims

1. A method for preparing a gangue-based active cementitious material by pellet sintering, characterized in that, It includes the following steps: S1. Crush and finely grind gangue, other solid wastes and fuel respectively to obtain the finely ground raw materials; S2. Mix the finely ground raw materials obtained in step S1 according to a set ratio and add water to mix evenly to obtain a mixture; S3. Pelletize the mixture obtained in step S2 to obtain green pellets, screen the green pellets, the green pellets with qualified particle size are used for subsequent sintering decarbonization and activation, and the green pellets with unqualified particle size are crushed and returned to step S2; S4. Charge the pallet of the belt sintering machine, then ignite, keep warm, carry out suction sintering and cooling to complete the decarbonization and activation of gangue and obtain the finished ore; S5. Crush and finely grind the finished ore obtained in step S4 to obtain an active cementitious material.

2. The method for preparing a gangue-based active cementitious material by pellet sintering according to claim 1, characterized in that, In step S1, the gangue is clay shale gangue, and the fixed carbon content of the gangue is 2% - 20%.

3. The method for preparing a gangue-based active cementitious material by pellet sintering according to claim 1, characterized in that, In step S1, the other solid wastes are divided into aluminosilicate-based solid wastes and calcium-based solid wastes, and can be classified into coal-fired boiler slag, mining tailings, engineering soil, silt and sludge according to the source, including but not limited to one or more of fly ash, waste incineration slag, iron tailings, red mud, steel slag, chromium slag, phosphorus slag, ferromanganese slag, carbide slag, desulfurized gypsum, building excavation soil, subway excavation soil, river sludge, lake sludge, urban sludge; The fuel is one or more of anthracite, bituminous coal and semi-coke.

4. The method for preparing a gangue-based active cementitious material by pellet sintering according to claim 1, characterized in that, In step S1, crush and finely grind gangue, other solid wastes and fuel to a particle size of -1 mm; more preferably, crush and finely grind to a particle size of -0.5 mm; The crushing treatment uses one or more of jaw crushers, roll crushers, cone crushers, impact crushers, impact crushers, hammer crushers; The fine grinding treatment adopts the following three methods: wet ball milling with water addition followed by drying, high-pressure roller milling under natural moisture, and dry ball milling after drying.

5. The method for preparing a gangue-based reactive cementitious material by pellet sintering according to claim 1, characterized in that, In step S2, the mass percentages (by dry weight) of gangue, other solid wastes and fuel are: Gangue 50% - 100%, other solid wastes 0% - 50%, fuel 0% - 7%. More preferably, gangue 60% - 90%, other solid wastes 10% - 40%, fuel 0% - 7%.

6. The method for preparing a gangue-based active cementitious material by pellet sintering according to claim 1, characterized in that, In step S2, the fixed carbon content of the mixture is maintained at 2.0% - 10%; more preferably, the fixed carbon content of the mixture is maintained at 2% - 6.5%.

7. The method for preparing a gangue-based active cementitious material by pellet sintering according to claim 1, characterized in that, In step S3, use a disk pelletizer or a cylindrical pelletizer to pelletize, the water content of the obtained green pellets is 7% - 15%, the average particle size of the qualified green pellets is 5 - 8 mm, and the green pellets have different sizes and inconsistent particle diameters, and the air permeability resistance of the green pellet layer is 30 - 60 mmH2O.

8. The method for preparing a gangue-based active cementitious material by pellet sintering according to claim 1, characterized in that, In step S4, during the charging process, the particle size of the bottom layer material is 12 - 25 mm, control the height of the bottom layer material to be 20 - 70 mm, and control the total height of the material layer to be 800 - 2000 mm; if the fixed carbon content of the gangue < 5%, the bottom layer material uses the original gangue after crushing; if the fixed carbon content of the gangue ≥ 5%, the bottom layer material uses the crushed finished ore, which can play a role in protecting the grate bars.

9. The method for preparing a gangue-based active cementitious material by pellet sintering according to claim 1, wherein In step S4, the ignition time is 2 - 5 min, the ignition temperature is 900 - 1150 °C, and the ignition negative pressure is 4 - 6 kPa; the heat preservation temperature is 800 - 900 °C, and the heat preservation time is 3 - 6 min; the negative pressure during exhaust sintering is 7 - 18 kPa; the cooling time is 4 - 12 min, and the cooling negative pressure is 5 - 15 kPa.

10. The method for preparing a gangue-based active cementitious material by pellet sintering according to claim 1, characterized in that, In step S5, the properties of the obtained active gelling material are as follows: the proportion of particles with a size of -0.08 mm is 97% to 99%, the loss on ignition is ≤ 3%, the residual carbon content is ≤ 3%, the specific surface area is 300 to 500 m 2 / kg, and the activity index is ≥ 75%.

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