Method for producing silicate clinker by using coal gangue as tailings

Abstract

The invention belongs to the technical field of resource utilization of coal gangue, and provides a method for producing silicate clinker by using coal gangue as tailings. The preparation method comprises the following steps: mixing coal gangue with a modified solution, and grinding to obtain modified coal gangue powder; mixing and grinding limestone, clay, furnace slag and smelting waste residues to obtain a raw material, then adding the raw material into a preheater for preheating, feeding the preheated raw material into a decomposing furnace, and adding the modified coal gangue powder as tailings for combustion and decomposition to obtain an intermediate material; and feeding the intermediate material and bituminous coal into a rotary kiln, and calcining to obtain the silicate clinker. According to the method, the coal gangue is selected as the tailings, the silicate clinker with excellent performance is prepared, the compressive strength of the silicate clinker is improved, efficient resource utilization of the coal gangue is achieved, the production cost of the silicate clinker is reduced, in addition, potential safety hazards caused by blockage of a preheater are greatly reduced, and the method is suitable for industrial production. The method has important industrial application value and environmental protection significance.

Description

Technical Field

[0001] The present invention relates to the technical field of resource utilization of coal gangue, and particularly to a method for producing portland clinker by using coal gangue as secondary coal. Background Art

[0002] Coal gangue is a solid waste generated during coal mining and processing. According to its sources, it mainly includes heading gangue, mining gangue, and washing gangue. At present, the cumulative stockpile of coal gangue has reached a very high level and is still increasing annually. As the industrial solid waste with the largest emissions and stockpiles, coal gangue has a significant negative impact on the ecological environment. On the one hand, the large accumulation of coal gangue will lead to waste of land resources; on the other hand, under the action of weathering and leaching, coal gangue will release harmful substances, causing continuous pollution to soil and water bodies; in addition, the harmful gases and dust generated during the spontaneous combustion of coal gangue will also cause serious pollution to the atmospheric environment. In view of this, it is very necessary to promote the reduction and resource utilization of coal gangue.

[0003] At present, the main application way of coal gangue is as a part of raw material batching. Usually, it is incorporated into the raw material as an aluminous corrective material. However, since coal gangue will start to burn at a temperature of about 360°C, this means that the raw material containing coal gangue will undergo a combustion reaction in advance in the suspension state of the preheater and release a certain amount of heat. These heats will cause the raw material to form a liquid phase prematurely, which is extremely likely to lead to the blockage of the preheater. This situation not only brings greater safety risks but also greatly limits the addition ratio and actual usage of coal gangue in raw material batching.

[0004] The existing secondary coal used for producing portland clinker is bituminous coal. However, the cost of using bituminous coal as secondary coal is relatively high, while using coal gangue as secondary coal is beneficial to reducing production costs but is likely to cause incomplete combustion of pulverized coal and low carbonate decomposition rate.

[0005] Therefore, there is an urgent need to provide a method for resource utilization of coal gangue that can consume a large amount of coal gangue without causing blockage of the preheater. Summary of the Invention

[0006] In view of this, the present invention provides a method for producing portland clinker by using coal gangue as secondary coal, so as to solve the problems that when the existing coal gangue is used as raw material batching, it is impossible to consume a large amount of coal gangue and is extremely likely to cause blockage of the preheater, thus bringing greater safety risks.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] The present invention provides a method for producing portland clinker by using coal gangue as secondary coal, comprising the following steps:

[0009] 1) Mix gangue with a modified solution and grind to obtain modified gangue powder;

[0010] 2) Mix limestone, clay, slag and smelting waste slag, grind to obtain raw meal, then add the raw meal into a preheater for preheating, and after preheating, send it into a decomposition furnace and add the modified gangue powder obtained in step 1) as secondary coal for combustion decomposition to obtain intermediate materials;

[0011] 3) Feed the intermediate materials and bituminous coal into a rotary kiln for calcination to obtain portland clinker;

[0012] The modified solution is obtained by mixing sodium hypohalite, cerium nitrate, sodium citrate and water;

[0013] The mass ratio of the gangue to the modified solution is 100: 0.2 - 0.3.

[0014] Preferably, the mass ratio of sodium hypohalite, cerium nitrate and sodium citrate in the modified solution is 2 - 3: 0.5 - 1: 0.5 - 1; the mass concentration of the modified solution is 25 - 30%.

[0015] Preferably, in step 1), the Q of the gangue ar ≥12400 KJ / Kg, A ar ≤40%, V ar ≥10%, moisture content ≤1.5%, residue on 0.08mm square hole sieve ≤4%.

[0016] Preferably, in step 1), the grinding time is 20 - 30 min and the temperature is 70 - 100 °C; the content of particles with a particle size ≤0.08 mm in the modified gangue powder is 94 - 97%.

[0017] Preferably, in step 2), the mass ratio of limestone, clay, slag and smelting waste slag in the raw meal is 75 - 80: 10 - 15: 2 - 5: 2 - 5; the mass ratio of the raw meal to the modified gangue powder is 10 - 16: 0.5 - 1.

[0018] Preferably, in step 2), the slag includes an aluminous correction material, and the content of aluminum oxide in the aluminous correction material is 20 - 30%; the smelting waste slag includes an iron correction material, and the content of iron oxide in the iron correction material is 35 - 50%.

[0019] Preferably, in step 2), the preheating temperature is 300 - 550 °C and the time is 30 - 60 s.

[0020] Preferably, in step 2), the temperature for combustion decomposition in the decomposition furnace is 850 - 900 °C and the time is 10 - 20 min.

[0021] Preferably, the bituminous coal described in step 3) has a Q ar ≥ 21000 KJ / Kg, A ar ≤ 25%, V ar ≥ 20%, moisture content ≤ 1.5%, residue on 0.08 mm square hole sieve ≤ 10%; the content of particles with a particle size ≤ 0.08 mm in the bituminous coal is 95 - 97%; the mass ratio of the intermediate material to the bituminous coal is 30 - 32:1.

[0022] Preferably, the process conditions for calcination in the rotary kiln described in step 3) are: decomposition furnace outlet temperature: 750 - 850 °C, rotary kiln calcination temperature: 1400 - 1500 °C, calcination time: 30 - 35 min; primary air temperature: normal temperature; secondary air temperature: 950 - 1150 °C; tertiary air temperature: 800 - 900 °C.

[0023] Preferably, the basic chemical properties of the Portland clinker described in step 3) are: C 3 S + C 2 S ≥ 66%, CaO / SO 2 ≥ 2%, SO 3 ≤ 1.5%, LOSS ≤ 1.5%, insoluble matter ≤ 0.75%, MgO ≤ 5%, f-CaO ≤ 1.5%.

[0024] From the above technical solutions, it can be seen that compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] The present invention selects coal gangue as the tail coal. By modifying the coal gangue, the modified coal gangue burns more completely, has a higher burnout rate, and the actual calorific value is higher than the calorific value calculated by conventional industrial analysis. Trace elements such as sulfur and manganese in the coal gangue also play a positive role in assisting heat. After grinding the modified coal gangue to a certain fineness, it is transported to the decomposition furnace as fuel, replacing the bituminous coal used in the conventional Portland clinker preparation process, and preparing Portland clinker whose basic chemical properties and physical properties both meet the Portland clinker standard. At the same time, the compressive strength of the Portland clinker is also improved. This not only realizes the resource-efficient utilization of coal gangue, turning waste into treasure, but also significantly reduces the production cost of Portland clinker and improves economic benefits; in addition, the method of the present invention also greatly reduces the safety hazards caused by preheater blockage, providing a strong guarantee for the safe and stable operation of the production process, and having important industrial application value and environmental protection significance. Detailed Embodiments

[0026] The present invention provides a method for producing Portland clinker using coal gangue as the tail coal, including the following steps:

[0027] 1) Mix gangue with a modified solution, and grind to obtain modified gangue powder;

[0028] 2) Mix limestone, clay, slag and smelting waste slag, grind to obtain raw meal, then add the raw meal into a preheater for preheating, and after preheating, send it into a decomposing furnace and add the modified gangue powder obtained in step 1) as tail coal for combustion decomposition to obtain intermediate material;

[0029] 3) Feed the intermediate material and bituminous coal into a rotary kiln for calcination to obtain portland clinker;

[0030] The modified solution is obtained by mixing sodium hypohalite, cerium nitrate, sodium citrate and water; the mass ratio of the gangue to the modified solution is 100:0.2 - 0.3, preferably 100:0.22 - 0.28, further preferably 100:0.23 - 0.26, and more preferably 100:0.25.

[0031] In the present invention, the mass ratio of sodium hypohalite, cerium nitrate and sodium citrate in the modified solution is 2 - 3:0.5 - 1:0.5 - 1, preferably 2.2 - 2.9:0.55 - 0.9:0.55 - 0.9, further preferably 2.3 - 2.8:0.6 - 0.8:0.6 - 0.8, and more preferably 2.5:0.7:0.7; the mass concentration of the modified solution is 25 - 30%, preferably 25.3 - 28.5%, further preferably 26 - 28%, and more preferably 27%. The mass concentration of the modified solution refers to the concentration of the sum of the masses of sodium hypohalite, cerium nitrate and sodium citrate.

[0032] In the present invention, the Q of the gangue in step 1) ar ≥12400 KJ / Kg, preferably 12420 - 12430 KJ / Kg, further preferably 12450 - 12460 KJ / Kg, and more preferably 12470 - 12500 KJ / Kg; the A of the gangue ar ≤40%, preferably 38 - 39%, further preferably 36 - 37%, and more preferably 35%; the V of the gangue ar ≥10%, preferably 11 - 12%, further preferably 13 - 15%, and more preferably 16 - 18%; the moisture content of the gangue ≤1.5%, preferably 1.3 - 1.4%, and more preferably 1.1 - 1.2%; the residue on a 0.08 mm square hole sieve of the gangue ≤4%, preferably 3.5 - 3.8%, further preferably 3.0 - 3.2%, and more preferably 2.5 - 2.8%.

[0033] In the present invention, the gangue is preferably solid waste discharged during the coal mining process and the coal washing process; the temperature provided by the complete combustion of the gangue can reach 800 - 1000 °C.

[0034] In the present invention, the heat generated by the modified coal gangue powder in step 1) is mainly used for the decomposition of carbonate.

[0035] In the present invention, the grinding time in step 1) is 20 - 30 min, preferably 22 - 29 min, more preferably 23 - 26 min, and most preferably 25 min; the grinding temperature is 70 - 100 °C, preferably 75 - 95 °C, more preferably 80 - 90 °C, and most preferably 85 °C; the content of particles with a particle size ≤ 0.08 mm in the modified coal gangue powder is 94 - 97%, preferably 94.2 - 96.5%, more preferably 94.5 - 96%, and most preferably 95.5%.

[0036] In the present invention, the mass ratio of limestone, clay, slag and smelting waste slag in step 2) is 75 - 80:10 - 15:2 - 5:2 - 5, preferably 75.5 - 79:11 - 14:2.5 - 4.5:2.5 - 4.5, more preferably 76 - 78:11.5 - 13.5:2.8 - 4.0:2.8 - 4.0, and most preferably 77 - 77.5:12 - 12.5:3.0 - 3.5:3.0 - 3.5.

[0037] In the present invention, the content of particles with a particle size ≤ 0.2 mm in the raw meal in step 2) is ≥ 98.0%, preferably 98.2 - 98.3%, more preferably 98.4 - 98.5%, and most preferably 99.2 - 99.5%.

[0038] In the present invention, the mass ratio of the raw meal to the modified coal gangue powder in step 2) is 10 - 16:0.5 - 1, preferably 11 - 15:0.6 - 0.9, more preferably 12 - 14:0.65 - 0.8, and most preferably 13:0.7.

[0039] In the present invention, the slag in step 2) includes an aluminous correction material, and the content of aluminum oxide in the aluminous correction material is 20 - 30%, preferably 22 - 28%, more preferably 23 - 26%, and most preferably 25%; the smelting waste slag includes an iron correction material, and the content of iron oxide in the iron correction material is 35 - 50%, preferably 37 - 48%, more preferably 40 - 46%, and most preferably 42%.

[0040] In the present invention, the preheating temperature in step 2) is 300 - 550 °C, preferably 350 - 500 °C, more preferably 380 - 460 °C, and most preferably 400 - 420 °C; the preheating time is 30 - 60 s, preferably 35 - 55 s, more preferably 40 - 50 s, and most preferably 45 s.

[0041] In the present invention, the temperature for combustion and decomposition in the decomposition furnace in step 2) is 850 - 900 °C, preferably 855 - 890 °C, more preferably 860 - 880 °C, and even more preferably 865 - 870 °C; the time for combustion and decomposition in the decomposition furnace is 10 - 20 min, preferably 12 - 18 min, more preferably 13 - 16 min, and even more preferably 15 min.

[0042] In the present invention, the heat required for carbonate decomposition in the decomposition furnace is preferably 55 - 65% of the heat required for the formation of silicate clinker, more preferably 57 - 62%, and even more preferably 60%.

[0043] In the present invention, for the bituminous coal in step 3), Q ar ≥21000 KJ / Kg, preferably 21100 - 21150 KJ / Kg, more preferably 21200 - 21250 KJ / Kg, and even more preferably 21260 - 21300 KJ / Kg; for the bituminous coal, A ar ≤25%, preferably 23 - 24%, more preferably 21 - 22%, and even more preferably 20%; for the bituminous coal, V ar ≥20%, preferably 21 - 23%, more preferably 24 - 25%, and even more preferably 26 - 28%; the moisture content of the bituminous coal ≤1.5%, preferably 1.3 - 1.4%, more preferably 1.1 - 1.2%, and even more preferably 0.9 - 1.0%; the residue on a 0.08 mm square-hole sieve of the bituminous coal ≤10%, preferably 7 - 9%, more preferably 5 - 6%, and even more preferably 3 - 4%.

[0044] In the present invention, the function of the bituminous coal is to provide stable heat for the formation of the main mineral calcium silicate in the silicate clinker and maintain a stable temperature level in the rotary kiln.

[0045] In the present invention, in the bituminous coal in step 3), the content of particles with a particle size ≤0.08 mm is 95 - 97%, preferably 95.2 - 96.8%, more preferably 95.5 - 96.5%, and even more preferably 96%; the mass ratio of the intermediate material to the bituminous coal is 30 - 32:1, preferably 30.2 - 31.8:1, more preferably 30.5 - 31.5:1, and even more preferably 31:1.

[0046] In the present invention, the process conditions for calcination in the rotary kiln in step 3) are as follows: the temperature at the outlet of the decomposition furnace is 750 - 850 °C, preferably 760 - 830 °C, more preferably 780 - 820 °C, and even more preferably 790 - 800 °C; the calcination temperature in the rotary kiln is 1400 - 1500 °C, preferably 1420 - 1490 °C, more preferably 1430 - 1480 °C, and even more preferably 1450 - 1460 °C; the calcination time is 30 - 35 min, preferably 32 - 34 min, and even more preferably 33 min; the primary air temperature is normal temperature (20 ± 2 °C); the secondary air temperature is 950 - 1150 °C, preferably 960 - 1120 °C, more preferably 980 - 1100 °C, and even more preferably 1000 - 1050 °C; the tertiary air temperature is 800 - 900 °C, preferably 820 - 890 °C, more preferably 830 - 870 °C, and even more preferably 850 - 860 °C.

[0047] In the present invention, the basic chemical properties of the silicate clinker in step 3) are: C 3 S + C 2 S ≥ 66%, preferably 66.5 - 67.5%, more preferably 67.8 - 68.0%, and even more preferably 68.8 - 69.0%; CaO / SO 2 ≥ 2, preferably 2.2 - 2.35, more preferably 2.6 - 2.8, and even more preferably 2.9 - 3.0; SO 3 ≤ 1.5%, preferably 1.35 - 1.4%, more preferably 1.1 - 1.25%, and even more preferably 0.9 - 1.08%; LOSS ≤ 1.5%, preferably 1.35 - 1.45%, more preferably 0.60 - 1.25%, and even more preferably 0.38 - 0.50%; insoluble matter ≤ 0.75%, preferably 0.70 - 0.73%, more preferably 0.65 - 0.71%, and even more preferably 0.45 - 0.49%; MgO ≤ 5%, preferably 4.0 - 4.5%, more preferably 3.05 - 3.25%, and even more preferably 2.7 - 3.0%; f-CaO ≤ 1.5%, preferably 1.2 - 1.3%, more preferably 0.9 - 1.1%, and even more preferably 0.68 - 0.8%.

[0048] In the present invention, the main chemical components of the raw meal for preparing the silicate clinker preferably include CaO, SiO 2 、Al 2 O 3 and Fe 2 O 3 ; the silicate clinker is a hydraulic cementitious material mainly composed of calcium silicate minerals.

[0049] In the present invention, after the calcination in step 3), a cooling operation is preferably further included; the cooling is preferably carried out in a grate cooler.

[0050] In the present invention, the formation process of the silicate clinker in step 3) mainly includes the evaporation of free water, dehydration of clay raw materials, decomposition of carbonate, solid-phase reaction, formation and sintering of tricalcium silicate, and cooling steps of the clinker; wherein, the evaporation of free water, dehydration of clay raw materials and decomposition of carbonate are preferably completed in a preheater and a decomposition furnace; the solid-phase reaction, formation and sintering of tricalcium silicate are preferably completed in a rotary kiln; the cooling is preferably completed in a grate cooler.

[0051] In the present invention, the primary air temperature refers to the air temperature for conveying pulverized coal; the secondary air temperature refers to the air temperature when the air from the grate cooler after cooling the clinker enters the kiln; the tertiary air temperature refers to the air temperature when the air from the grate cooler after cooling the clinker enters the decomposition furnace.

[0052] In the present invention, the bituminous coal and coal gangue shall not be mixed with each other.

[0053] The technical solutions provided by the present invention will be described in detail below with reference to embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0054] Example 1

[0055] 1) Mix sodium hypohalite, cerium nitrate and sodium citrate according to a mass ratio of 3:1:1, and add distilled water to obtain a modified solution with a mass concentration of 30%, and set aside; then mix coal gangue (Q ar is 12400 KJ / Kg, A ar is 40%, V ar is 10%, moisture content is 1.5%, and the residue on a 0.08 mm square-hole sieve is 4%) with the above-mentioned modified solution according to a mass ratio of 100:0.25, and carry out grinding at a temperature of 80 °C. After grinding for 30 min, the content of particles with a particle size of 0.08 mm is 4% of the modified coal gangue powder;

[0056] 2) Mix limestone, clay, slag (the slag is an aluminous correction material with an alumina content of 25%) and smelting waste slag (the smelting waste slag is an iron correction material with an iron oxide content of 42%) according to a mass ratio of 77:12:3:3, and obtain raw meal with a content of 98% of particles with a particle size ≤ 0.2 mm after grinding. Then add the raw meal into a preheater and preheat it at a temperature of 300 °C. After preheating for 30 s, send it into a decomposition furnace and add the modified coal gangue powder obtained in step 1) as tail coal, and burn and decompose it at a temperature of 850 °C. After burning and decomposing for 10 minutes, an intermediate material is obtained, wherein the mass ratio of the raw meal to the modified coal gangue powder is 16:1;

[0057] 3) Feed the intermediate material obtained in step 2) and bituminous coal with a particle size ≤ 0.08 mm accounting for 96% (Q ar is 21000 KJ / Kg, A ar is 25%, V ar is 20%, moisture content is 1.5%, and the residue on a 0.08 mm square-hole sieve is 10%), that is, use bituminous coal with a residue on a 0.08 mm square-hole sieve of 4% and feed it into a rotary kiln for calcination according to a mass ratio of 30:1; among them, set the calcination process conditions as: the outlet temperature of the decomposition furnace: 800 °C, the calcination temperature in the rotary kiln: 1450 °C, the calcination time: 30 min; the primary air temperature: normal temperature (20 °C); the secondary air temperature: 1050 °C; the tertiary air temperature: 850 °C; after calcination, Portland clinker is obtained.

[0058] Example 2

[0059] 1) Mix sodium hypohalite, cerium nitrate and sodium citrate according to a mass ratio of 3:1:1, and add distilled water to obtain a modified solution with a mass concentration of 25%, and set aside; then mix coal gangue (Q ar is 12420 KJ / Kg, A ar is 38%, V ar is 11%, moisture content is 1.3%, and the residue on a 0.08 mm square-hole sieve is 3.5%) with the above-mentioned modified solution according to a mass ratio of 100:0.3, and carry out grinding at a temperature of 70 °C. After grinding for 30 min, modified coal gangue powder with a particle size of 0.08 mm accounting for 4% is obtained;

[0060] 2) Mix limestone, clay, slag (the slag is an aluminous correction material with an alumina content of 20%) and smelting waste slag (the smelting waste slag is an iron correction material with an iron oxide content of 35%) according to a mass ratio of 75:10:2:2, and obtain raw meal with a particle size ≤ 0.2 mm accounting for 98.5% through grinding. Then add the raw meal to a preheater and preheat it at a temperature of 300 °C. After preheating for 35 s, feed it into the decomposition furnace and add the modified coal gangue powder obtained in step 1) as tail coal, and burn and decompose it at a temperature of 850 °C. After burning and decomposing for 20 minutes, an intermediate material is obtained, among which, the mass ratio of the raw meal to the modified coal gangue powder is 16:1;

[0061] 3) Feed the intermediate material obtained in step 2) and bituminous coal with a particle size ≤ 0.08 mm accounting for 97% (Q ar is 21100 KJ / Kg, A ar is 23%, V arThe content is 21%, the moisture content is 1.3%, and the residue on a 0.08 mm square-hole sieve is 9%). That is, bituminous coal with a residue on a 0.08 mm square-hole sieve of 3% is fed into a rotary kiln for calcination according to a mass ratio of 30:1. Among them, the calcination process conditions are set as follows: the outlet temperature of the decomposition furnace: 850 °C, the calcination temperature in the rotary kiln: 1400 °C, the calcination time: 30 min; the primary air temperature: normal temperature (20 °C); the secondary air temperature: 950 °C; the tertiary air temperature: 800 °C; after calcination, Portland clinker is obtained.

[0062] Example 3

[0063] 1) Sodium hypohalite, cerium nitrate and sodium citrate are mixed according to a mass ratio of 3:1:1, and distilled water is added to obtain a modified solution with a mass concentration of 28%, which is reserved; then gangue (Q ar is 12460 KJ / Kg, A ar is 36%, V ar is 13%, the moisture content is 1.2%, and the residue on a 0.08 mm square-hole sieve is 3.2%) is mixed with the above-mentioned modified solution according to a mass ratio of 100:0.2, and grinding is carried out at a temperature of 90 °C. After grinding for 20 min, the content of particles with a particle size of 0.08 mm is 3.2% of the modified gangue powder;

[0064] 2) Limestone, clay, slag (the slag is an aluminous correction material with an alumina content of 30%) and smelting waste slag (the smelting waste slag is an iron correction material with an iron oxide content of 50%) are mixed according to a mass ratio of 80:15:5:5, and after grinding, the content of particles with a particle size ≤ 0.2 mm is 98.2% of the raw meal. Then the raw meal is added to a preheater and preheated at a temperature of 500 °C. After preheating for 30 s, it is fed into the decomposition furnace and the modified gangue powder obtained in step 1) is added as tail coal, and combustion decomposition is carried out until the temperature reaches 900 °C. After combustion decomposition for 10 minutes, an intermediate material is obtained. Among them, the mass ratio of the raw meal to the modified gangue powder is 16:1;

[0065] 3) The intermediate material obtained in step 2) and bituminous coal (Q ar is 21200 KJ / Kg, A ar is 20%, V ar is 26%, the moisture content is 1.1%, and the residue on a 0.08 mm square-hole sieve is 5%). That is, bituminous coal with a residue on a 0.08 mm square-hole sieve of 4% is fed into a rotary kiln for calcination according to a mass ratio of 30:1. Among them, the calcination process conditions are set as follows: the outlet temperature of the decomposition furnace: 750 °C, the calcination temperature in the rotary kiln: 1500 °C, the calcination time: 30 min; the primary air temperature: normal temperature (20 °C); the secondary air temperature: 1150 °C; the tertiary air temperature: 900 °C; after calcination, Portland clinker is obtained.

[0066] Comparative Example 1

[0067] The difference between this comparative example and Example 1 is only that: the tail coal in step 2) is replaced by Q ar is 21000 KJ / Kg, A ar is 25%, V ar is 20%, the moisture content is 1.5%, and the bituminous coal with a residue on a 0.08 mm square hole sieve of 10%.

[0068] Comparative Example 2

[0069] The difference between this comparative example and Example 2 is only that: the tail coal in step 2) is replaced by Q ar is 21100 KJ / Kg, A ar is 23%, V ar is 21%, the moisture content is 1.3%, and the bituminous coal with a residue on a 0.08 mm square hole sieve of 9%.

[0070] The properties of the silicate clinkers prepared in Examples 1 - 2 and Comparative Examples 1 - 2 were tested; among them, the basic chemical properties were tested according to the test standard of GB / T176; the initial setting time and final setting time were tested according to the test standard of GB / T1346; the soundness was tested according to the test standard or test method of GB / T1346. When the test cake had no bending cracks after boiling method test, it represented that the soundness was qualified; the compressive strength was tested according to the test standard of GB / T17671. The test results are shown in Table 1.

[0071] Table 1 Test Results of the Properties of Silicate Clinker

[0072]

[0073]

[0074] As can be seen from Table 1, the basic chemical properties and physical properties of the silicate clinker prepared in Examples 1-2 of the present invention all meet the standards of silicate cement clinker. Compared with the silicate clinker prepared in Comparative Examples 1-2, the free calcium content of the silicate clinker prepared in Examples 1-2 of the present invention has decreased, and both the 3-day compressive strength and the 28-day compressive strength have increased. The decrease in free calcium indicates that the clinker is more fully calcined and the formed petrographic structure is better, so the strength of the final product is higher. This shows that using the modified coal gangue as a substitute for bituminous coal in the conventional silicate clinker preparation process can not only ensure that the performance quality of the silicate clinker meets the existing national standards, but also effectively utilize the solid waste coal gangue, reduce the production cost of the silicate clinker, and effectively improve the compressive strength of the silicate clinker, thus enhancing the economic benefits of the enterprise. In addition, the method of the present invention greatly reduces the safety hazards caused by preheater blockage, provides a strong guarantee for the safe and stable operation of the production process, and has important industrial application value and environmental protection significance.

[0075] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for producing silicate clinker using coal gangue as tail coal, characterized in that: The steps include: 1) Mixing coal gangue with a modified solution and grinding them to obtain modified coal gangue powder; 2) limestone, clay, slag and smelting waste residue are mixed and ground to obtain raw material, and then the raw material is added to a preheater for preheating, and after preheating, it is sent to a decomposition furnace and the modified coal gangue powder obtained in step 1) is added as tail coal for combustion and decomposition to obtain an intermediate material; 3) sending the intermediate material and bituminous coal into a rotary kiln for calcination to obtain silicate clinker; The modified solution is obtained by mixing sodium hypohalite, cerium nitrate, sodium citrate and water; The mass ratio of the coal gangue to the modified solution is 100:0.2-0.

3.

2. A method for producing silicate clinker using coal gangue as tail coal according to claim 1, characterized in that: The mass ratio of sodium hypohalite, cerium nitrate and sodium citrate in the modified solution is 2-3:0.5-1:0.5-1; The mass concentration of the modified solution is 25-30%.

3. A method for producing silicate clinker using coal gangue as tail coal according to claim 2, characterized in that: Q of the gangue in step 1) ar ≥12400KJ / Kg, A ar ≤40%, V ar ≥10%, moisture ≤1.5%, 0.08mm square hole sieve residue ≤4%.

4. A method for producing silicate clinker using coal gangue as tail coal according to any one of claims 1 to 3, characterized in that: The grinding time in step 1) is 20 to 30 minutes and the temperature is 70 to 100° C.; The content of particles with a particle size of ≤0.08 mm in the modified coal gangue powder is 94-97%.

5. A method for producing silicate clinker using coal gangue as tail coal according to claim 4, characterized in that: The mass ratio of limestone, clay, slag and smelting waste residue in the raw material in step 2) is 75-80:10-15:2-5:2-5; The mass ratio of the raw material to the modified coal gangue powder is 10-16:0.5-1; The slag includes an aluminum correction material, wherein the aluminum correction material contains 20 to 30% aluminum oxide; The smelting waste slag includes iron correction material, and the content of ferric oxide in the iron correction material is 35-50%.

6. A method for producing silicate clinker using coal gangue as tail coal according to claim 5, characterized in that: The preheating temperature in step 2) is 300-550° C. and the preheating time is 30-60 seconds.

7. A method for producing silicate clinker using coal gangue as tail coal according to claim 6, characterized in that: The temperature of the combustion decomposition in the decomposition furnace in step 2) is 850-900° C. and the time is 10-20 minutes.

8. A method for producing silicate clinker using coal gangue as tail coal according to claim 7, characterized in that: Q of the bituminous coal in step 3) ar ≥21000KJ / Kg, A ar ≤25%, V ar ≥20%, moisture ≤1.5%, 0.08mm square hole sieve residue ≤10%; The content of particles with a particle size of ≤0.08 mm in the bituminous coal is 95-97%; The mass ratio of the intermediate material to bituminous coal is 30-32:

1.

9. A method for producing silicate clinker using coal gangue as tail coal according to claim 8, characterized in that: The process conditions for calcining in the rotary kiln in step 3) are: decomposition furnace outlet temperature: 750-850°C, calcining temperature in the rotary kiln: 1400-1500°C, calcining time: 30-35min; primary air temperature: room temperature; secondary air temperature: 950-1150°C; tertiary air temperature: 800-900°C.

10. A method for producing silicate clinker using coal gangue as tail coal according to claim 8 or 9, characterized in that: The basic chemical properties of the silicate clinker in step 3) are: C3S+C2S≥66%, CaO / SO2≥2%, SO3≤1.5%, LOSS≤1.5%, insoluble matter≤0.75%, MgO≤5%, f-CaO≤1.5%.

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