Method for preparing low-carbon cement from large-particle steel slag

Abstract

The invention belongs to the technical field of solid waste utilization, and particularly relates to a method for preparing low-carbon cement from large-particle steel slag, which comprises the following steps of: 1, arranging steel slag injection devices at a blanking articulated chute where a preheater is connected to a kiln tail smoke chamber and at a slope of the kiln tail smoke chamber; 2, during production, steel slag particles and a mixture of iron powder and high-pressure gas are synchronously input into the steel slag injection device; thirdly, iron powder and steel slag particles are mixed and fluidized at a feeding opening through high-pressure gas by the steel slag injection device; 4, spraying the mixed particles fluidized by the high-pressure gas into a blanking articulated chute and a kiln tail smoke chamber at a high speed by an impeller to scour the inner wall of the blanking articulated chute and the kiln tail smoke chamber; 5, continuously and uniformly mixing the mixed particles sprayed from the steel slag spraying device at a high speed with the raw material in a blanking chute and a kiln tail smoke chamber, and then calcining in a rotary kiln to obtain cement clinker; and 6, jointly grinding the cement clinker, gypsum and limestone, and adding a reinforcing grinding aid to obtain the low-carbon cement. Iron powder, steel slag and raw materials can be uniformly mixed, and the problem that the clinker quality is affected due to non-uniform mixing of steel slag coarse particles and the raw materials is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid waste utilization, and particularly relates to a method for preparing low-carbon cement from large-sized steel slag. Background Art

[0002] The cement industry is the main way for comprehensive utilization of steel slag. Most of the steel slag discharged from steel mills will be crushed and ground after discharge. However, since the steel slag itself is relatively hard, crushing and grinding will significantly increase the treatment difficulty, resulting in additional energy consumption and equipment wear, and increasing production costs and time costs. On the other hand, trivalent chromium exists in the untreated steel slag. If it is directly put into the cement kiln, it will react with the oxygen therein to generate hexavalent chromium. Hexavalent chromium is a highly toxic harmful substance and will reduce the late strength and durability of the cement. Therefore, how to directly use steel slag particles for cement production without spending costs on steel slag crushing and grinding while reducing the generation of hexavalent chromium from steel slag in the cement kiln has become one of the technical problems to be solved in the prior art. Another problem is how to quickly mix large-sized steel slag particles with raw meal and mix them evenly when adding them into the cement kiln. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for preparing low-carbon cement from large-sized steel slag, which is used to solve the technical problem that it is difficult in the prior art to directly use steel slag particles for cement production without crushing and grinding while reducing the generation of hexavalent chromium from steel slag in the cement kiln.

[0004] The method for preparing low-carbon cement from large-sized steel slag described above includes the following steps:

[0005] I. Steel slag injection devices are respectively arranged at the feeding chute connecting the preheater to the kiln tail flue gas chamber and the slope of the kiln tail flue gas chamber.

[0006] II. During the production of cement, steel slag particles are input into the steel slag input pipe of the steel slag injection device, and at the same time, a mixture of iron powder and high-pressure gas is synchronously input into the steel slag injection device by means of pneumatic conveying.

[0007] III. The steel slag injection device fluidizes and mixes the iron powder and steel slag particles at the feeding port through high-pressure gas, and then sprays them from the feeding port of the steel slag injection device to the feeding chute and the kiln tail flue gas chamber.

[0008] IV. The mixed particles composed of steel slag and iron powder are sprayed into the feeding chute and the kiln tail flue gas chamber at high speed, and after scouring the inner walls of both the feeding chute and the kiln tail flue gas chamber, they enter the cement kiln.

[0009] V. The mixed particles sprayed out from the steel slag injection device at high speed are continuously and evenly mixed in the feeding chute and the kiln tail flue gas chamber, and then enter the rotary kiln for calcination to obtain cement clinker.

[0010] 6. Cement clinker is ground together with gypsum and limestone, and a grinding aid for enhancement is added to obtain low-carbon cement.

[0011] Preferably, in step two, the high-pressure gas is a gas with a pressure of 0.2 - 0.8 MPa, which sucks iron powder with a particle size below 0.2 mm into the pipeline. After passing through the throat pipe, the high-pressure gas and the iron powder are mixed and enter the air inlet tank of the steel slag injection device; the steel slag input pipe allows steel slag particles to enter the feeding port.

[0012] Preferably, in step three, the pneumatically conveyed iron powder quickly contacts and mixes with steel slag particles through a number of ventilation holes in the tank top plate, fluidizes the steel slag particles, and forms mixed particles; under the combined action of the air flow and the rotating separation wheel, the mixed particles pass through the orientation sleeve, and are brought into the impeller and the blade baffle, and are ejected from the sandblasting outlet to the blanking chute and the kiln tail flue gas chamber.

[0013] Preferably, the particle size of the steel slag particles is between 0.1 - 2 mm. With respect to the quality of the raw meal, the dosage range of the steel slag particles is 2% - 13.4%, and the dosage range of the iron powder is 0.01% - 0.2%.

[0014] Preferably, this method further includes step six: cement clinker, gypsum, and admixture are jointly added to a ball mill, and a grinding aid for enhancement with a total mass of 0.01 - 0.15% calculated based on the effective solid content is added. After ball milling by the ball mill, the final low-carbon cement is obtained.

[0015] Preferably, the grinding aid for enhancement is a mixed solution of any one or more of diethanol monoisopropanolamine, monoethanol diisopropanolamine, triisopropanolamine, dihydroxyethyl ethylenediamine, and dihydroxypropyl ethylenediamine.

[0016] Preferably, the steel slag injection device includes a housing, an impeller, a steel slag input pipe, and an iron powder input structure. The impeller is installed in the housing through a rotating shaft connected to a motor. In the housing, a feeding structure sleeved outside the rotating shaft is also fixedly installed; the steel slag input pipe is vertically arranged, and the upper end is connected to an input structure such as a steel slag hopper or a silo. The lower end of the steel slag input pipe communicates with the feeding port in the feeding structure; the air outlet end of the iron powder input structure communicates with the air inlet tank in the feeding structure. The feeding port and the air inlet tank are arranged in the same direction as the rotating shaft, and are separated by a tank top plate. A number of ventilation holes are evenly arranged on the tank top plate.

[0017] Preferably, the impeller includes a disc-shaped blade baffle and a plurality of arc-shaped blades, and the plurality of arc-shaped blades are uniformly arranged circumferentially along the blade baffle; the rotating shaft is vertically fixed at the center of the blade baffle, and a separating wheel centered on the rotating shaft is also fixed at the center of the blade baffle. The separating wheel is provided with a plurality of through grooves evenly distributed circumferentially on the cylinder wall; a guiding sleeve sleeved outside the separating wheel is also fixed in the shell, and the guiding sleeve is provided with a notch as a material outlet; there is a certain gap between the guiding sleeve and the separating wheel, and between the separating wheel and the feeding structure.

[0018] Preferably, a sand blasting outlet for ejecting steel slag particles is provided on the installation side of the shell, and heat insulation layers are provided on the wall plates of the installation side for connecting and installing with the cement kiln.

[0019] Preferably, the iron powder input structure includes a throat pipe. The air inlet end of the throat pipe is connected to a high-pressure gas source through a high-pressure air pipe, and the other end is connected to the air inlet groove. The side of the throat pipe is connected to an iron powder feeding pipeline.

[0020] The advantages of the present invention are as follows: The present invention directly feeds coarse-grained steel slag into the kiln for calcining clinker, without grinding the steel slag into powder, avoiding the key problem of difficult grinding of steel slag; the improved steel slag spraying device can quickly and evenly mix the steel slag particles with the iron powder input with high-pressure gas, making the steel slag particles form a fluidized state, facilitating rapid passage through the guiding sleeve and being thrown out by the impeller, and accelerating the sand blasting efficiency; making the iron powder, steel slag and raw meal evenly mixed, avoiding the problem that uneven mixing of coarse steel slag particles and raw meal affects the quality of clinker. Since trivalent chromium in steel slag mainly undergoes an oxidation reaction to become hexavalent chromium during the solid-phase reaction stage in the transition zone, and this solution can quickly and evenly mix the input iron powder and steel slag particles through the improved steel slag spraying device, after being input into the rotary kiln, through the oxidation reaction of iron powder and oxygen, a locally oxygen-deficient state can be formed in the solid-phase reaction zone, especially a locally oxygen-deficient state on the surface of the clinker, avoiding the oxidation of heavy metal chromium into hexavalent chromium.

[0021] On the other hand, the high-speed ejected coarse steel slag particles can act as a grinding medium to continuously impact and brush the inner walls of the C5 feeding chute and the kiln tail flue gas chamber, avoiding the problem of material crusting often occurring at the kiln tail, ensuring the stable operation of the cement kiln and saving labor. In addition, since the flue gas temperature at the tail of the cement rotary kiln is higher than 800 °C, if the impeller and the rotating shaft are directly connected to the cement kiln, it will cause equipment damage. This solution can also continuously cool the sand blasting mechanism through the low temperature of the high-pressure gas by introducing high-pressure gas to transport iron powder, avoiding overheating damage. The clinker produced by this solution has the characteristics of low calcination temperature and low heat consumption, which can effectively reduce coal consumption and carbon emissions, but its strength and grindability are slightly lower than those of ordinary clinker, and the strength and grindability are optimized by adding specific grinding aids.

[0022] Explanation of the drawings

[0023] Figure 1 Schematic structural diagram of the cement kiln system adopted by the method for preparing low-carbon cement from large-particle steel slag according to the present invention.

[0024] Figure 2 is Figure 1 Schematic structural diagram of the steel slag injection device in the structure shown.

[0025] Figure 3 is Figure 2 Schematic structural diagram of the impeller in the structure shown.

[0026] Figure 4 XRD pattern of the low-carbon cement clinker obtained in Example 3 and Example 6 of the present invention.

[0027] Figure 5 XRD pattern of the low-carbon cement clinker obtained in Comparative Example 1 and Comparative Example 2 of the present invention.

[0028] Reference numerals in the figure include: 1 decomposition furnace, 2 rotary kiln, 3 kiln tail smoke chamber, 4 feeding chute, 5 steel slag injection device, 51 housing, 52 impeller, 521 blade baffle, 522 arc-shaped blade, 523 rotating shaft, 524 separating wheel, 525 feeding port, 526 air inlet groove, 527 groove top plate, 528 orientation sleeve, 529 material outlet, 53 sandblasting outlet, 54 steel slag input pipe, 55 heat insulation layer, 56 iron powder feeding pipe, 57 high-pressure gas pipe, 58 throat pipe. Detailed implementation manners

[0029] The following further elaborates in detail the specific implementation manners of the present invention by describing the embodiments in conjunction with the drawings, so as to help those skilled in the art have a more complete, accurate and in-depth understanding of the inventive concept and technical solution of the present invention.

[0030] As Figures 1 - 5 shown, the present invention provides a method for preparing low-carbon cement from large-particle steel slag, including the following steps.

[0031] I. Steel slag injection devices 5 are provided at both the feeding chute 4 connecting the preheater to the kiln tail smoke chamber 3 and the feeding end of the kiln tail smoke chamber 3.

[0032] In the cement production system, the kiln tail of the rotary kiln 2 is connected to the kiln tail smoke chamber 3, the bottom of the decomposition furnace 1 communicates with the kiln tail smoke chamber 3, and the C5 cyclone of the preheater also communicates with the kiln tail smoke chamber 3 through the feeding chute 4. The steel slag injection device 5 is pre-installed at the feeding chute 4 and the feeding end of the kiln tail smoke chamber 3.

[0033] II. During the production of cement, steel slag particles are input into the steel slag input pipe 54 of the steel slag injection device 5, and at the same time, a mixture of iron powder and high-pressure gas is synchronously input into the steel slag injection device 5 by means of pneumatic conveying.

[0034] In this step, the high-pressure gas is a gas with a pressure of 0.2 - 0.8 MPa. When it passes through the iron powder inlet of the throat pipe 58, it sucks in iron powder with a particle size below 0.2 mm into the pipeline. After the high-pressure gas and the iron powder pass through the throat pipe 58, they are mixed and enter the air inlet of the steel slag injection device 5. The air inlet leads to an air inlet groove 526 arranged in the same direction as the rotating shaft 523 of the impeller 52 of the steel slag injection device 5. The steel slag input pipe 54 leads to a feeding port 525 arranged in the same direction as the rotating shaft 523, allowing steel slag particles to enter the feeding port 525.

[0035] Thirdly, the steel slag injection device 5 mixes and fluidizes the iron powder, high-pressure gas and steel slag particles through the impeller 52, and then sprays them from the feeding port 525 of the steel slag injection device 5 to the blanking chute 4 and the kiln tail smoke chamber 3.

[0036] The air inlet groove 526 and the feeding port 525 are arranged in the same direction and are separated only by a groove top plate 527. A number of ventilation holes with apertures significantly larger than the iron powder are evenly provided on the groove top plate 527. Therefore, the iron powder transported by air can quickly contact and mix with the steel slag particles. In addition, a mixing runner that rotates with the rotating shaft 523 is provided outside the feeding port 525, so that the iron powder, high-pressure gas and steel slag particles can be mixed evenly, and the high-pressure gas can also fluidize the steel slag particles. The directional sleeve 528 arranged outside the mixing runner controls the spraying direction of the fluidized steel slag particles. After spraying out from the material outlet 529 of the directional sleeve 528, through the agitation of the blade baffle 521 and the arc-shaped blade 522, the fluidized steel slag particles are quickly sprayed from the sand blasting outlet 53 to the blanking chute 4 and the kiln tail smoke chamber 3. At the same time, during the high-speed rotation process, the impeller 52 continuously presses out air from the sand blasting outlet 53 through centrifugal force, and the generated negative pressure will also accelerate the flow of steel slag particles into the feeding port 525.

[0037] Fourthly, the mixed particles composed of steel slag and iron powder are sprayed into the blanking chute 4 and the kiln tail smoke chamber 3 at high speed, scour the inner walls of both the blanking chute 4 and the kiln tail smoke chamber 3, and then enter the cement kiln.

[0038] The steel slag particles mixed with iron powder and high-pressure gas continuously scour the inner walls of the blanking chute 4, the inner wall of the kiln tail smoke chamber 3 and other parts after being thrown out. In this way, while inputting the steel slag particles, it is also possible to clean the materials adhered to the inner wall of the equipment by the impact of the steel slag particles, and continuously prevent subsequent materials from adhering to the inner wall of the equipment, achieving the effect of preventing these parts from caking.

[0039] Fifthly, the mixed particles sprayed out from the steel slag injection device at high speed are continuously and evenly mixed in the blanking chute and the kiln tail smoke chamber, and then enter the rotary kiln 2 for calcination to obtain cement clinker.

[0040] After the fluidized steel slag particles are input into the feeding chute 4 and the kiln tail flue gas chamber 3, they will be evenly mixed with the raw meal under the action of gas impact and enter the rotary kiln 2. During the calcination of the raw meal in the rotary kiln 2, the iron powder mixed in the steel slag particles will be oxidized, thus forming a reducing atmosphere in the material. These iron powders are mixed in the steel slag particles, so they can prevent the trivalent chromium element in the steel slag particles from being oxidized into harmful hexavalent chromium. As the temperature of the steel slag particles rises, they gradually melt, react with the raw meal powder, and are completely converted into cement clinker.

[0041] In the resulting cement clinker, the content of C3S mineral is 50 - 65%, the content of C2S mineral is 10 - 25%, the content of C3A mineral is 0.5 - 7%, and the content of C4AF mineral is 13 - 22%, meeting the requirements of low-carbon cement clinker. Its characteristic is that the content of C4AF mineral is relatively high, and on the basis of reducing the carbon content of steel slag, carbon emissions can be further reduced.

[0042] Sixth, the cement clinker, gypsum, and admixture are jointly added to the ball mill, and a grinding aid and strength enhancer with a total mass of 0.01 - 0.15% (calculated according to the effective solid content) is added, and the final low-carbon cement clinker is obtained after ball milling by the ball mill.

[0043] The grinding aid and strength enhancer in this step is a mixed solution of any one or more of diethanol monoisopropanolamine, monoethanol diisopropanolamine, triisopropanolamine, dihydroxyethyl ethylenediamine, and dihydroxypropyl ethylenediamine. Adding a small amount of the grinding aid and strength enhancer can effectively improve the performance of the cement clinker, especially for the cement clinker added with steel slag particles, and the effect of improving performance is more obvious.

[0044] The specific implementation of the method is as follows:

[0045] Example 1

[0046] In this example, the particle size of the steel slag particles is between 0.1 and 2 mm. Relative to the mass of the raw meal, the dosage of the steel slag particles is 6.5%, the dosage of the iron powder is 0.1%, and no grinding aid and strength enhancer is added.

[0047] Example 2

[0048] In this example, the particle size of the steel slag particles is between 0.1 and 2 mm. Relative to the mass of the raw meal, the dosage of the steel slag particles is 6.5%, the dosage of the iron powder is 0.1%, and 0.01% of the grinding aid and strength enhancer is added.

[0049] Example 3

[0050] In this example, the particle size of the steel slag particles is between 0.1 and 2 mm. Relative to the mass of the raw meal, the dosage of the steel slag particles is 6.5%, the dosage of the iron powder is 0.1%, and 0.05% of the grinding aid and strength enhancer is added.

[0051] Example 4

[0052] In this embodiment, the particle size of the steel slag particles is between 0.1 and 2 mm. Based on the mass of the raw meal, the addition amount of the steel slag particles is 2.0%, the addition amount of the iron powder is 0.1%, and 0.15% of grinding aid and strength enhancer is added.

[0053] Example 5

[0054] In this embodiment, the particle size of the steel slag particles is between 0.1 and 2 mm. Based on the mass of the raw meal, the addition amount of the steel slag particles is 6.5%, the addition amount of the iron powder is 0.01%, and 0.05% of grinding aid and strength enhancer is added.

[0055] Example 6

[0056] In this embodiment, the particle size of the steel slag particles is between 0.1 and 2 mm. Based on the mass of the raw meal, the addition amount of the steel slag particles is 6.5%, the addition amount of the iron powder is 0.2%, and 0.05% of grinding aid and strength enhancer is added.

[0057] Example 7

[0058] In this embodiment, the particle size of the steel slag particles is between 0.1 and 2 mm. Based on the mass of the raw meal, the addition amount of the steel slag particles is 13.4%, the addition amount of the iron powder is 0.1%, and 0.08% of grinding aid and strength enhancer is added.

[0059] Examples 1 - 6 all use ordinary clinker, and Example 7 uses high - iron - phase clinker. The low - carbon cement raw material table based on the above examples is shown in Table 1.

[0060] Table 1: Low - carbon cement raw material table of examples

[0061] Example Clinker type Granule size of steel slag Dosage of steel slag Dosage of Fe powder Dosage of grinding aid and strength enhancer Example 1 Ordinary clinker 0.1 - 2 mm 6.5％ 0.1％ 0.01％ Example 2 Ordinary clinker 0.1 - 2 mm 6.5％ 0.1％ 0.05％ Example 3 Ordinary clinker 0.1 - 2 mm 6.5％ 0.1％ 0.15％ Example 4 Ordinary clinker 0.1 - 2 mm 2.0％ 0.1％ 0.05％ Example 5 Ordinary clinker 0.1 - 2 mm 6.5％ 0.01％ 0.05％ Example 6 Ordinary clinker 0.1 - 2 mm 6.5％ 0.2％ 0.05％ Example 7 Clinker with high iron phase 0.1 - 2 mm 13.4％ 0.1％ 0.08％

[0062] The clinkers fired in Examples 1 - 6 are the same (ordinary clinker). The difference is that the addition amounts of the grinding aid and strength enhancer added during the grinding of cement in Examples 1, 3 and Examples 2, 4 - 6 are different. The difference between Example 4 and Example 2 is the addition amount of steel slag. The differences between Examples 5 and 6 and Example 2 are the addition amounts of Fe powder. The clinker fired in Example 7 is high - iron - phase clinker (C4AF mineral content ≥ 17%).

[0063] To study the advantages and disadvantages of the low - carbon cement obtained by this method, a comparative example is also set for comparison. The cement grinding time of the examples and the comparative example is the same, and the addition amounts of the admixture and gypsum are the same. The following are the specific comparative examples.

[0064] Comparative Example 1

[0065] In this comparative example, the particle size of the steel slag particles is between 0.1 and 2 mm. Based on the quality of the raw meal, the dosage of the steel slag particles is 6.5%, the dosage of the iron powder is 0.1%, and no grinding aid and strength enhancer are added. Comparative example 1 is used for comparison with Examples 1 to 3.

[0066] Comparative example 2

[0067] In this comparative example, the particle size of the steel slag particles is between 0.1 and 2 mm. Based on the quality of the raw meal, the dosage of the steel slag particles is 13.4%, the dosage of the iron powder is 0.1%, and no grinding aid and strength enhancer are added. Comparative example 2 is used for comparison with Example 7.

[0068] Comparative example 3

[0069] In this comparative example, no steel slag particles, iron powder, or grinding aid and strength enhancer are added, and the iron-containing corrective raw material is iron tailings. Comparative example 3 is used for comparison with Examples 1 to 3.

[0070] Comparative example 4

[0071] In this comparative example, based on the quality of the raw meal, 0.05% of grinding aid and strength enhancer is added, but no steel slag particles or iron powder are added, and the iron-containing corrective raw material is iron tailings. Comparative example 4 is used for comparison with Example 2.

[0072] Comparative example 5

[0073] In this comparative example, the steel slag used is fine steel slag powder after crushing and grinding (residue on 75-μm sieve is 14%). Based on the quality of the raw meal, the dosage of the fine steel slag powder is 6.5%, the dosage of the iron powder is 0.1%, and no grinding aid and strength enhancer are added. Comparative example 5 is used for comparison with Examples 1 to 3.

[0074] Comparative example 6

[0075] In this comparative example, the particle size of the steel slag particles is between 0.1 and 2 mm. Based on the quality of the raw meal, the dosage of the steel slag particles is 6.5%, 0.05% of grinding aid and strength enhancer is added, but no iron powder is added. Comparative example 6 is used for comparison with Example 2.

[0076] The low-carbon cement raw material tables for the above comparative examples are shown in Table 2.

[0077] Table 2: Low-carbon cement raw material tables for comparative examples

[0078]

[0079]

[0080] As can be seen from Table 2, the difference between Comparative example 3 and Comparative example 4 is that 0.05% of strength enhancer is added in Comparative example 4, and the difference between Comparative example 5 and Comparative example 6 is that the steel slag used in Comparative example 5 is ground fine steel slag powder.

[0081] The properties of the low-carbon cement clinker prepared based on the above examples and comparative examples are shown in Table 3.

[0082] Table 3: Performance table of low-carbon cement prepared from examples and comparative examples

[0083]

[0084] By comparing the properties of the low-carbon cement obtained from the examples and comparative examples, it is found that:

[0085] 1. After adding 0.5% iron powder, the water-soluble hexavalent chromium content of the ordinary clinker fired from the coarse steel slag is significantly reduced, indicating that the iron powder plays a reducing role during the clinker firing process, creating a locally oxygen-deficient environment on the surface and inside of the clinker, thereby reducing the water-soluble hexavalent chromium content of the clinker.

[0086] 2. After adding the grinding aid and strength enhancer, the strength and grindability of the ordinary clinker and high-iron phase clinker fired from the coarse steel slag are significantly improved. The strength improvement effect is higher than that of the group without steel slag (Comparative Example 4). Especially for the high-iron phase clinker, the 3-day strength is increased by 4.8 MPa (21.5%), and the 28-day strength is increased by 17.5 MPa (36.0%).

[0087] Continue to analyze and compare the mineral contents of the low-carbon cement clinker obtained from some examples and comparative examples, and the results are shown in Table 4.

[0088] Table 4: Mineral content table of low-carbon cement clinker prepared from some examples and comparative examples

[0089]

[0090]

[0091] In order to better mix and fluidize the iron powder, high-pressure gas, and unground steel slag particles, the steel slag injection device 5 adopted in this method uses an impeller structure for injection and improves the feeding structure. The steel slag injection device 5 includes a housing 51, an impeller 52, a steel slag input pipe 54, and an iron powder input structure. The impeller 52 is installed in the housing 51 through a rotating shaft 523 connected to a motor. A feeding structure sleeved outside the rotating shaft is also fixedly installed in the housing 51. The steel slag input pipe 54 is vertically arranged, and the upper end is connected to an input structure such as a steel slag hopper or silo. The lower end of the steel slag input pipe 54 communicates with the feeding port 525 in the feeding structure. The air outlet end of the iron powder input structure communicates with the air inlet groove 526 in the feeding structure. The feeding port 525 and the air inlet groove 526 are arranged in the same direction as the rotating shaft 523. The feeding port 525 and the air inlet groove 526 are separated by a groove top plate 527, and a number of ventilation holes are evenly provided on the groove top plate 527.

[0092] The impeller 52 includes a disc-shaped blade baffle 521 and a number of arc-shaped blades 522. Each arc-shaped blade 522 is fixedly installed radially along the blade baffle 521, and multiple arc-shaped blades 522 are evenly arranged circumferentially along the blade baffle 521. The rotating shaft 523 is vertically fixed at the center of the blade baffle 521. A separating wheel 524 centered on the rotating shaft 523 is also fixed at the center of the blade baffle 521, and the separating wheel 524 is sleeved outside the feeding structure. The separating wheel 524 is provided with a number of through grooves evenly distributed circumferentially on the cylinder wall. A guiding sleeve 528 is also fixed inside the housing 51. The guiding sleeve 528 is sleeved outside the separating wheel 524 centered on the rotating shaft 523. The guiding sleeve 528 is provided with a notch as a material outlet 529. There is a certain gap between the guiding sleeve 528 and the separating wheel 524, and between the separating wheel 524 and the feeding structure.

[0093] The installation side of the housing 51 is used for fixedly connecting with the installation structure at the blanking chute 4 or the side wall of the kiln tail smoke chamber 3. The installation side is provided with a sand blasting outlet 53 for the steel slag particles to spray out. The wall plates of the installation side are all provided with a heat insulation layer 55, and the heat insulation layer 55 is used for connecting and installing with the cement kiln to prevent the high temperature of the cement kiln from being largely transferred to the inside of the housing 51 through the installation side.

[0094] The iron powder input structure includes a throat tube 58. The air inlet end of the throat tube 58 is connected to a high-pressure gas source through a high-pressure air pipe 57 to input high-pressure gas, and the other end is connected to the air inlet groove 526. The side of the throat tube 58 is connected to an iron powder feeding pipe 56. When the high-pressure gas passes through the throat tube 58, the high-speed air flow sucks the iron powder from the iron powder feeding pipe 56, mixes them, and then transports the iron powder to the air inlet groove 526 through pneumatic conveying.

[0095] The present invention has been described exemplarily above in conjunction with the accompanying drawings. Obviously, the specific implementation of the present invention is not limited by the above-mentioned manner. As long as various non-substantive improvements are made by adopting the inventive concept and technical solution of the present invention, or the inventive concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. A method for preparing low-carbon cement from large-particle steel slag, characterized in that: The following steps are involved:

1. A slag injection device is installed at the material discharge chute where the preheater is connected to the kiln tail smoke chamber and at the slope of the kiln tail smoke chamber; 2. In the process of producing cement, steel slag particles are input into the steel slag input pipe of the steel slag injection device, and a mixture of iron powder and high-pressure gas is simultaneously input into the steel slag injection device by pneumatic conveying; 3. The slag injection device uses high-pressure gas to mix and fluidize iron powder and slag particles at the feeding port, and then sprays the mixed particles into the discharge chute and the kiln tail smoke chamber through a high-speed rotating impeller; Fourth, the mixed particles composed of steel slag and iron powder are sprayed into the material chute and the kiln tail smoke chamber at high speed, and flush the inner walls of the material chute and the kiln tail smoke chamber before entering the cement kiln; 5. The mixed particles ejected at high speed from the slag injection device are continuously and evenly mixed in the material discharge chute and the kiln tail smoke chamber, and then enter the rotary kiln for calcination to obtain cement clinker; 6. Cement clinker is ground together with gypsum and limestone, and enhanced grinding aids are added to obtain low carbon cement.

2. The method for preparing low carbon cement from large-particle steel slag according to claim 1, characterized in that: In step 2, high-pressure gas with a pressure of 0.2-0.8MPa is used to suck iron powder with a particle size of less than 0.2mm into the pipeline. The high-pressure gas and iron powder are mixed after passing through the throat and enter the air inlet slot of the slag injection device; the slag input pipe allows the slag particles to enter the feeding port.

3. The method for preparing low carbon cement from large-particle steel slag according to claim 2, characterized in that: In step three, the pneumatically conveyed iron powder quickly contacts and mixes with the steel slag particles through several air holes on the top plate of the trough, so that the steel slag particles are fluidized and mixed particles are formed; the mixed particles pass through the directional sleeve under the combined action of the airflow and the rotating separation wheel, and are brought into the impeller and the blade baffle, and are sprayed out from the sandblasting outlet to the discharge chute and the kiln tail smoke chamber.

4. The method for preparing low carbon cement from large-particle steel slag according to claim 1, characterized in that: The particle size of the steel slag particles is between 0.1 and 2 mm. Relative to the mass of the raw material, the addition amount of the steel slag particles is in the range of 2% to 13.4%, and the addition amount of the iron powder is in the range of 0.01% to 0.2%.

5. The method for preparing low carbon cement from large-particle steel slag according to any one of claims 1 to 4, characterized in that: The method also includes step 6, adding cement clinker, gypsum and mixed materials into a ball mill, adding a grinding aid and enhancer calculated according to the effective solid content in an amount of 0.01-0.15% of the total mass, and obtaining the final low-carbon cement after ball milling.

6. The method for preparing low carbon cement from large-particle steel slag according to claim 5, characterized in that: The grinding aid enhancer is a mixed liquid of any one or more of diethanol monoisopropanolamine, monoethanol diisopropanolamine, triisopropanolamine, dihydroxyethyl ethylenediamine, and dihydroxypropyl ethylenediamine.

7. The method for preparing low carbon cement from large-particle steel slag according to claim 1, characterized in that: The slag injection device includes a shell, an impeller, a slag input pipe and an iron powder input structure. The impeller is installed in the shell through a rotating shaft connected to the motor, and a feeding structure sleeved outside the rotating shaft is also fixedly installed in the shell; the slag input pipe is vertically arranged, and the upper end is connected to an input structure such as a slag hopper or a silo, and the lower end of the slag input pipe is connected to a feeding port in the feeding structure; the air outlet end of the iron powder input structure is connected to an air inlet groove in the feeding structure, the feeding port and the air inlet groove are both arranged in the same direction as the rotating shaft, and the feeding port and the air inlet groove are separated by a groove top plate, and a plurality of air vents are evenly arranged on the groove top plate.

8. The method for preparing low carbon cement from large-particle steel slag according to claim 7, characterized in that: The impeller includes a disc-shaped blade baffle and a plurality of arc-shaped blades, and the plurality of arc-shaped blades are evenly arranged along the circumference of the blade baffle; the rotating shaft is vertically fixed at the center of the blade baffle, and a separation wheel centered on the rotating shaft is also fixed at the center of the blade baffle, and the separation wheel is provided with a plurality of through grooves evenly distributed along the circumference on the cylinder wall; a directional sleeve is also fixed inside the shell and is sleeved on the outside of the separation wheel, and the directional sleeve is provided with a notch as a material outlet; there is a certain gap between the directional sleeve and the separation wheel, and between the separation wheel and the feeding structure.

9. The method for preparing low carbon cement from large-particle steel slag according to claim 7, characterized in that: The installation side of the shell is provided with a sandblasting outlet for spraying out steel slag particles, and the wall panels on the installation side are all provided with a heat insulation layer, and the heat insulation layer is used for installation in connection with the cement kiln.

10. The method for preparing low carbon cement from large-particle steel slag according to claim 7, characterized in that: The iron powder input structure comprises a throat, an air inlet end of the throat is connected to a high-pressure air source through a high-pressure air pipe, and the other end is connected to the air inlet groove, and a side of the throat is connected to an iron powder feeding pipeline.

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