Dry cement clinker and production process thereof

Abstract

The invention relates to the field of environment-friendly production of cement clinker, in particular to dry-process cement clinker and a production process thereof, and the dry-process cement clinker comprises the following components in percentage by mass: 78-82% of limestone, 14-15% of sandstone, 2-2.5% of sulfuric-acid residue, 0-1.4% of aluminum mud and 0-3.90% of pretreated fly ash. The invention also discloses a dry-process cement clinker production process, which comprises the steps of fly ash pretreatment, raw material compatibility, raw material grinding, clinker firing, fuel desulfurization, denitration and purification, waste heat utilization and the like. According to the dry-process cement clinker and the production process thereof, the pretreated waste incineration fly ash and industrial byproducts such as sulfuric-acid residues and aluminum mud are introduced, so that the problems of high resource consumption, serious environmental pollution and the like in traditional cement production are effectively solved. The pretreated fly ash is subjected to processes such as washing desalination and drying, so that effective control of chloride ions and reutilization of calcium resources are realized, part of limestone is replaced, mining pressure of natural mineral resources is reduced, resource utilization of hazardous wastes is realized, and land occupation and secondary pollution risks caused by landfill are reduced.

Description

Technical Field

[0001] This invention belongs to the field of environmentally friendly cement clinker production, specifically relating to a dry-process cement clinker and its production process. Background Technology

[0002] In traditional dry process cement production, raw materials such as limestone, clay, and iron powder are commonly used to prepare raw meal, which is then processed into cement clinker through grinding, preheating, decomposition, and calcination.

[0003] In existing technologies, traditional dry-process cement clinker production mainly relies on natural mineral resources such as limestone and clay. The large-scale use of these non-renewable resources not only exacerbates the pressure of resource extraction but also has a serious impact on the environment. Simultaneously, the industrial solid waste generated during production, such as fly ash from waste incineration, contains high concentrations of chloride ions (Cl⁻) and heavy metals, making it difficult to treat and typically requiring landfill disposal. This not only occupies valuable land resources but also may cause secondary pollution. Therefore, overcoming these technical problems and shortcomings has become a key issue that needs to be addressed. Summary of the Invention

[0004] The purpose of this invention is to overcome the defects described in the background art, thereby realizing a dry process for cement clinker production, which solves the problems of large consumption of natural mineral resources, land occupation of land resources by fly ash from waste incineration, and potential secondary pollution in the traditional dry process for cement clinker production.

[0005] To achieve the above-mentioned objectives, the technical solution of the present invention is: a dry-process cement clinker, wherein the clinker mineral components, by mass percentage, include 78%-82% limestone, 14%-15% sandstone, 2%-2.5% sulfuric acid slag, 0%-1.4% alumina mud, and 0%-3.90% pretreated fly ash.

[0006] Preferably, the clinker mineral composition, by mass percentage, includes 79.51% limestone, 14.27% sandstone, 2.32% sulfuric acid slag, and 3.90% pretreated fly ash.

[0007] Preferably, the clinker mineral composition, by mass percentage, includes 81.80% limestone, 14.67% sandstone, 1.40% alumina mud, and 2.13% sulfuric acid slag.

[0008] In addition, this invention also protects a dry process for producing cement clinker, comprising the following steps: Step 1, fly ash pretreatment: The fly ash from waste incineration is mixed with water in a certain mass ratio and stirred. After stirring, it is desalinated by centrifugation or pressure filtration and then dried.

[0009] Step 2, Raw material formulation: Mix limestone, sandstone, sulfuric acid slag, aluminum mud and pretreated fly ash according to the mass percentage.

[0010] Step 3, raw material grinding: The mixed raw materials are processed using a roller press final grinding system.

[0011] Step 4, clinker calcination: The raw meal is preheated by a dual-series six-stage low-pressure-loss cyclone preheater and then enters the TDF decomposition furnace and rotary kiln.

[0012] Step 5, Fuel and Desulfurization: Pulverized coal is injected into the decomposition furnace and rotary kiln respectively, and calcium-based desulfurization powder is fed into the kiln elevator at the same time.

[0013] Step 6, Denitrification and Purification: The kiln tail flue gas is denitrified sequentially by SNCR and SCR.

[0014] Step 7, Waste Heat Utilization: Waste heat from the kiln head grate cooler and the kiln tail exhaust gas is recovered via SP boiler and AQC boiler.

[0015] In the above-mentioned dry process cement clinker production process, in step one, fly ash and water are mixed and stirred at a mass ratio of 1:3-1:5 for 30-60 minutes.

[0016] The fly ash drying process uses waste heat from the kiln tail exhaust gas as a heat source, drying the fly ash to a moisture content of ≤5.0%, a desalinated fly ash particle size of ≤5mm, and a chloride ion removal rate of ≥80%.

[0017] The fly ash obtained contains Cl⁻≤0.5%, CaO≥35.00%, K₂O+Na₂O≤7.00%, and SO₃≤8.00%.

[0018] In the above-mentioned dry process cement clinker production process, after the raw meal exits the mill in step three, the specific surface area is ≥3400cm² / g, the residue on the 80μm sieve is ≤16%, and the residue on the 200μm sieve is ≤2%.

[0019] In the above-mentioned dry process cement clinker production process, the exhaust gas temperature at the outlet of the cyclone preheater in step four is ≤250℃, the temperature of the decomposition furnace is 850-1100℃, and the temperature of the rotary kiln is 1400-1450℃.

[0020] In the above-mentioned dry process cement clinker production process, 60%-62% pulverized coal is injected into the decomposition furnace in step five, and 38-40% pulverized coal is injected into the rotary kiln. The pulverized coal is a mixture of Shenmu bituminous coal and Shanxi anthracite in a 9:1 ratio. The pulverized coal contains Aad≤15.00%, St,ad≤0.60%, and Qnet,ad≥26334kJ / kg.

[0021] Furthermore, when the coal quota is insufficient, natural gas is used to replace part of the pulverized coal, with a calorific value ≥35000kJ / Nm³. Coal-gas co-firing is implemented at the kiln head, with a natural gas replacement ratio ≤30%, and the CO concentration in the flue gas after combustion ≤500ppm. The calcium-based desulfurization powder contains 90%-95% CaO and 5%-10% iron oxide red / magnesium oxide additives.

[0022] In the above-mentioned dry process for cement clinker production, in step six, 20% ammonia water is injected into the kiln tail flue gas during SNCR denitrification, with an NH3 / NO molar ratio of 1.2-1.5.

[0023] The catalyst used in SCR denitrification is V₂O₅-WO₃ / TiO₂, the temperature is 200-230℃, and the space velocity is ≤10000h⁻¹. The SCR reactor is arranged between the waste heat boiler and the high-temperature fan, and the inlet dust concentration is ≤60g / Nm³. The SCR nozzle is located in the high-temperature zone of 850-1100℃ from the decomposition furnace outlet to the kiln hood, and the SCR denitrification efficiency is ≥90%.

[0024] In the above-mentioned dry process cement clinker production process, in step seven, the discharge temperature of the kiln head grate cooler is ≤ ambient temperature + 65℃, and the boiler outlet exhaust gas temperature is ≤ 215℃.

[0025] The dry process for producing cement clinker of the present invention has the following beneficial effects: 1. The dry-process cement clinker and its production process of this invention effectively solve the problems of high resource consumption and serious environmental pollution in traditional cement production by introducing pre-treated waste incineration fly ash and industrial byproducts such as sulfuric acid slag and alumina sludge. The pre-treated fly ash, through processes such as water washing and desalination and drying, achieves effective control of chloride ions and reuse of calcium resources. This not only replaces part of the limestone, reducing the pressure on the extraction of natural mineral resources, but also realizes the resource utilization of hazardous waste, reducing the land occupation and secondary pollution risks associated with landfilling.

[0026] 2. The dry-process cement clinker and its production process of this invention, in terms of raw material compatibility and process optimization, ensures the stability of the clinker mineral composition by precisely controlling the proportion of each component, thereby guaranteeing the strength and stability of the cement. Simultaneously, the use of a roller press final grinding system and a multi-stage cyclone preheater improves the fineness of the raw meal and preheating efficiency, reduces the amount of undecomposed calcium carbonate entering the kiln, avoids excessive free calcium oxide, and significantly improves firing efficiency and clinker quality.

[0027] 3. This invention employs a combined SNCR and SCR denitrification technology, achieving a denitrification efficiency of over 90% and controlling ammonia slip to within 7.5 ppm, meeting national emission standards. Simultaneously, by injecting calcium-based desulfurizer into the kiln and adjusting the sulfur content in fly ash, SO2 emissions are effectively controlled, reducing the risk of preheater scaling. Furthermore, when coal quality fluctuates, natural gas can be introduced for co-firing, which not only improves combustion efficiency but also further reduces NOx and CO2 emissions, achieving clean production and efficient resource utilization in a synergistic manner.

[0028] 4. In terms of energy saving, the present invention uses the kiln head grate cooler and the kiln tail exhaust gas waste heat recovery system to use the waste heat of the exhaust gas for fly ash drying and power generation, which significantly reduces coal consumption and electricity consumption, improves waste heat utilization efficiency, and realizes efficient recycling of energy. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the dry process cement clinker production process of the present invention. Detailed Implementation

[0030] The dry process for producing cement clinker of the present invention will be described in more detail below with reference to the accompanying drawings and specific embodiments.

[0031] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention. Example

[0032] This embodiment discloses a dry-process cement clinker and its production process. Cement clinker is produced by adding treated waste incineration fly ash to the cement clinker, thereby solving the problems of large consumption of natural mineral resources, land occupation of waste incineration fly ash through landfill, and potential secondary pollution in the production of traditional dry-process cement clinker. See the following for details.

[0033] In this embodiment, the dry process cement clinker comprises, by mass percentage, 78%-82% limestone, 14%-15% sandstone, 2%-2.5% sulfuric acid slag, 0%-1.4% alumina mud, and 0%-3.90% pretreated fly ash.

[0034] In this embodiment, limestone serves as the main calcareous raw material, providing the CaO required for clinker minerals. A lower limit of 78% limestone ensures sufficient liquid phase to promote sintering, while an upper limit of 82% avoids excessive free calcium oxide from affecting cement stability.

[0035] Sandstone serves as a silica correction material, precisely supplementing SiO2 to balance the high-calcium properties of limestone. Strict control of the ratio is maintained to avoid silica imbalance (target SM = 2.5 ± 0.1), ensuring the formation of C3S-dominant minerals.

[0036] Sulfuric acid slag serves as an iron-based corrective material, providing Fe2O3 to adjust the aluminum ratio (target IM = 1.6 ± 0.1). Its trace SO3 content (<1%) can lower the firing temperature.

[0037] Alumina mud is a supplementary aluminum raw material used in low-grade sandstone environments. It is activated when the sandstone Al2O3 content is less than 3% to increase the C3A content of the early-strength mineral in the clinker; if the raw material has sufficient aluminum content, no addition is necessary.

[0038] Using pretreated fly ash as part of the raw material is key to the resource utilization of hazardous waste. When pretreated fly ash is not added, it is suitable for traditional production lines that do not have the need for co-processing of solid waste. The upper limit is ≤3.90%. After washing and desalination, its high calcium properties can replace part of the limestone, while controlling the total alkali content to prevent crusting.

[0039] The synergistic effect of the formulation is shown in Table 1: Table 1 (Synergistic Effect of Proportioning) This embodiment also discloses a dry process for producing cement clinker with the above-mentioned weight percentage components, including the following steps: Step 1: Fly ash pretreatment. The fly ash from waste incineration is mixed with water in a certain mass ratio and stirred. After stirring, it is desalinated by centrifugation or pressure filtration and then dried.

[0040] In this step, fly ash and water are mixed and stirred at a mass ratio of 1:3-1:5 for 30-60 minutes. Fly ash drying utilizes waste heat from the kiln tail exhaust gas as a heat source, drying until the moisture content is ≤5.0%, the desalinated fly ash particle size is ≤5mm, and the chloride ion removal rate is ≥80%. The resulting fly ash contains Cl⁻≤0.5%, CaO≥35.00%, K₂O+Na₂O≤7.00%, and SO₃≤8.00%.

[0041] Waste heat utilization (250℃→120℃) reduces coal consumption for drying by 1.8 kg of coal / ton of fly ash. Based on a fly ash content of 3.90%, this translates to a coal saving of 7.02 tons per 10,000 tons of clinker.

[0042] Salty wastewater needs to be evaporated and crystallized to recover NaCl / KCl (purity > 95%) to avoid secondary pollution.

[0043] Step 2: Raw material formulation. Limestone, sandstone, sulfuric acid slag, aluminum mud and pretreated fly ash are mixed according to the mass percentage.

[0044] Step 3: Raw material grinding. The mixed raw materials are processed using a roller press final grinding system.

[0045] In this step, after the raw material exits the mill, the specific surface area is ≥3400cm² / g, the residue on the 80μm sieve is ≤16%, and the residue on the 200μm sieve is ≤2%.

[0046] Fine particles increase the contact area between C2S and CaO, accelerating the solid-phase reaction: the reaction rate of C2S + CaO → C3S increases by 20%.

[0047] It takes 18 seconds for 80μm particles to be completely decomposed in the preheater (>15 seconds residence time in the cyclone). Control the sieve residue to ≤16% and ensure that the amount of undecomposed limestone entering the kiln is <3% to avoid the formation of "encapsulated f-CaO" in the rotary kiln (which leads to poor clinker stability).

[0048] See Table 2 for experimental results: 80μm sieve residue clinker f-CaO content 28d strength loss 16% 1.05% 0% benchmark 20% 1.82% ↓4.5MPa Table 2 (Experimental Verification) To prevent system blockage, the residue on the 200μm sieve should be ≤2%. 200μm particles tend to settle in the cyclone cone, forming a crust nucleus (the crusting rate increases by 300% after combining with the alkali and chlorine components in the fly ash). Simultaneously, coarse particles lead to incomplete combustion of pulverized coal, resulting in excessive CO concentration in the flue gas (>500ppm).

[0049] Step four, clinker calcination: raw materials are preheated by a dual-series six-stage low-pressure-loss cyclone preheater and then enter the TDF decomposition furnace and rotary kiln.

[0050] In this step, the exhaust gas temperature at the cyclone preheater outlet is ≤250℃, the decomposition furnace temperature is 850-1100℃, and the rotary kiln temperature is 1400-1450℃.

[0051] The TDF decomposition furnace operates at temperatures between 850 and 1100℃, with a lower limit of 850℃. This is the critical temperature for calcium carbonate decomposition, where an endothermic reaction occurs, resulting in calcium carbonate decomposing into calcium oxide and carbon dioxide. If the temperature falls below this critical value, the decomposition rate will be less than 85%, leading to a significant increase in the load on the rotary kiln and affecting its normal operation.

[0052] Controlling the temperature upper limit at 1100℃ can prevent premature ash formation of pulverized coal (ash melting point > 1100℃), which would affect its combustion efficiency. Controlling the temperature below 1100℃ ensures that the pulverized coal has sufficient time and space to complete the combustion process in the furnace, thereby guaranteeing a pulverized coal burnout rate of ≥98%.

[0053] The gradient control strategy for the TDF precalciner is shown in Table 3. area Temperature range Core Response Bottom of the volcanic layer 850~900℃ <![CDATA[Quick decomposition of CaCO3 in raw materials (decomposition rate ≥ 92%)]]> Central reduction zone 950~1000℃ <![CDATA[Fuel gasification (C + CO2 → 2CO), inhibiting NOx formation]]> Export oxidation zone 1050~1100℃ Residual CO is completely combusted, and raw materials are pre-sintered. Table 3 (Gradient Control Strategy) The rotary kiln temperature is 1400-1450℃, at which point tricalcium silicate (C3S) is generated in large quantities (at which point the liquid phase content of allite minerals is greater than or equal to 24%). If the temperature is below this range, the content of free calcium oxide (f-CaO) in the clinker will exceed 2.5%.

[0054] The rotary kiln temperature should not exceed 1450℃. Overheating of refractory bricks will result in a 50% increase in brick consumption (the softening point of magnesium aluminate spinel bricks is 1480℃).

[0055] Step 5: Fuel and desulfurization. Pulverized coal is injected into the decomposition furnace and rotary kiln respectively, and calcium-based desulfurization powder is fed into the kiln elevator simultaneously.

[0056] In this step, 60%-62% pulverized coal is injected into the decomposition furnace and 38-40% pulverized coal is injected into the rotary kiln. The pulverized coal is a blend of Shenmu bituminous coal and Shanxi anthracite in a 9:1 ratio. The pulverized coal contains Aad≤15.00%, St,ad≤0.60%, and Qnet,ad≥26334kJ / kg.

[0057] The gain effect of pulverized coal blending is shown in Table 4: Table 4 (Composite Gain Effect) When Aad exceeds 15.00%, the excessive ash content will coat the raw meal particles, thus reducing the C3S formation efficiency (for every 1% increase in ash content, f-CaO will increase by 0.15%). When St,ad exceeds 0.60%, the sulfur content exceeds the limit, disrupting the sulfur-alkali balance and causing the preheater to scale up at a rate exceeding 5 mm / day. Qnet,ad needs to be greater than or equal to 26334 kJ / kg to ensure that the theoretical heat consumption is below 3050 kJ / kg clinker (the actual heat consumption is usually between 3180 and 3250 kJ / kg).

[0058] In the decomposition furnace, the amount of fuel injected should be controlled between 60% and 62%, and the residence time of the fuel in the furnace can reach 12 to 15 seconds. During this process, high-volatile bituminous coal should be the main component to guide the gasification reaction smoothly. The specific reaction formula is: C + H₂O → CO + H₂, which helps to reduce the local temperature and thus inhibit the formation of NOx.

[0059] If the pulverized coal injection rate exceeds 62%, the furnace temperature will exceed 1100℃, which may cause the coal ash to melt and trigger coking problems.

[0060] In a rotary kiln, the fuel injection rate should be 38% to 40% of the total. This is to match the high fixed carbon characteristics of anthracite and ensure its complete combustion during the 25-minute residence time in the kiln. If the fuel injection rate is lower than 38%, the kiln tail temperature will be lower than 1000°C, resulting in insufficient pre-sintering of the raw materials, which in turn leads to an 8% increase in the porosity of the clinker.

[0061] The calcium-based desulfurization powder contains 90%-95% CaO and 5%-10% iron oxide red / magnesium oxide additives.

[0062] The composition and function of calcium-based desulfurization powder are shown in Table 5: Step six, denitrification and purification: the kiln tail flue gas is denitrified sequentially by SNCR and SCR.

[0063] In this step, 20% ammonia water is injected into the kiln tail flue gas during SNCR denitrification, with an NH3 / NO molar ratio of 1.2-1.5. The catalyst for SCR denitrification is V2O5-WO3 / TiO2, at a temperature of 200-230℃ and a space velocity ≤10000h⁻¹. The SCR reactor is located between the waste heat boiler and the high-temperature fan, with an inlet dust concentration ≤60g / Nm³. The SNCR spray gun is located in the 850-1100℃ high-temperature zone from the decomposition furnace outlet to the kiln hood, achieving an SCR denitrification efficiency ≥90%.

[0064] In the synergistic mechanism of the two-stage denitrification system, the working principle of SNCR high-temperature denitrification is shown in Table 6: Table 6 (Principle of SNCR High-Temperature Denitrification) The SNCR spray gun is positioned in the area from the decomposition furnace outlet to the kiln hood. The flue gas velocity in this section is extremely high, with turbulence exceeding 30 meters per second, resulting in a mixing time of less than 0.3 seconds between ammonia and the flue gas. Within this area, it is crucial to ensure thorough mixing of ammonia (NH3) with the flue gas to prevent excessively high local NH3 concentrations (exceeding 8 ppm), which could lead to the formation of ammonium bisulfate.

[0065] The working principle of SCR low-temperature denitrification is shown in Table 7: Table 7 (Principle of SCR Low-Temperature Denitrification) When optimizing the location of the SCR reactor, it is placed between the waste heat boiler and the high-temperature fan to achieve precise temperature control. The waste heat boiler reduces the flue gas temperature from 350℃ to 220±10℃, which falls precisely within the optimal activity range of the SCR catalyst, namely 200~230℃. This not only ensures the efficient conduction of the reaction but also effectively extends the catalyst's lifespan.

[0066] To ensure the stable operation of the system, the dust concentration in the flue gas is reduced from 120g / Nm³ to ≤60g / Nm³ through the settling chamber of the waste heat boiler, effectively preventing catalyst wear.

[0067] See Table 8 for the verification of the two-stage denitrification efficiency: stage NOx inhalation (mg / Nm³) NOx emissions (mg / Nm³) Denitrification rate Ammonia slip (ppm) SNCR 650~800 400~480 38%~40% 3~5 SCR 400~480 ≤50 88%~92% ≤2.5 total - - ≥90% ≤7.5 Table 8 (Verification of Two-Stage Denitrification Efficiency) It meets the special emission limits of GB 4915-2013 "Emission Standard of Air Pollutants for Cement Industry", namely, NOx emission concentration not exceeding 100mg / Nm³ and ammonia slip rate not exceeding 8ppm.

[0068] Step 7: Waste heat recovery. The waste heat from the kiln head grate cooler and the kiln tail exhaust gas is recovered through SP boiler and AQC boiler.

[0069] In this step, the discharge temperature of the kiln head grate cooler is ≤ ambient temperature + 65℃, and the exhaust gas temperature at the boiler outlet is ≤ 215℃.

[0070] When the discharge temperature exceeds 100℃, β-C2S will transform into γ-C2S. This process is accompanied by a 10% volume expansion, which leads to an increase in clinker pulverization rate of about 5%. In order to completely suppress this crystal transformation, the discharge temperature can be controlled below 95℃. XRD verification confirmed that no γ phase is generated at this temperature.

[0071] The energy-saving benefits are quantified in Table 9: discharge temperature clinker cooling power consumption Waste heat power generation gain 120℃ 9.5kWh / t benchmark 95℃ 7.8kWh / t +3.2kWh / t Table 9 (Quantification of Energy Saving Benefits) During boiler operation, the outlet exhaust gas temperature is strictly controlled below 215℃. The exhaust gas is preferentially introduced into the fly ash drying system, which requires a heat source of 200-250℃ to ensure efficient operation. Through this process, the goal of saving 1.8 kg of coal per ton of fly ash dried is achieved. After passing through the drying system, the final emission temperature of the exhaust gas drops to 105℃, which not only improves the utilization efficiency of potential energy sources but also meets environmental emission requirements.

[0072] At 215℃, the resistivity of dust is approximately 3×10¹. 0 The Ω·cm value falls within the optimal operating range of the electrostatic precipitator, resulting in a significant improvement in dust removal efficiency. After treatment, the emission concentration can be reduced to <10mg / Nm³, an improvement of approximately 25% compared to the efficiency at 300℃. Example

[0073] The similarities to the above embodiments will not be repeated, the differences are as follows: When the coal quota is insufficient, natural gas is used to replace part of the pulverized coal. The calorific value is ≥35000kJ / Nm³. Coal-gas co-firing is implemented at the kiln head. The natural gas replacement ratio is ≤30%, and the CO concentration in the flue gas after combustion is ≤500ppm.

[0074] In this embodiment, when the coal quota is insufficient, natural gas is used to replace part of the pulverized coal, as shown in Table 10: Table 10 (Fuel Adaptability Switching) Additionally, when the CO concentration in the flue gas after combustion is ≤500ppm, please refer to Table 11: CO concentration range Regulation measures Mechanism of action 400~500ppm Increase axial flow pressure (+5%) Enhanced flue gas turbulent mixing 500~600ppm Reduce natural gas volume (-3%) + increase oxygen (+0.3%) Suppressing incomplete combustion >600ppm Switch back to pure coal combustion mode Preventing the risk of explosion Table 11 (Adaptive Scheme for Exceeding Flue Gas CO Concentration Standards) The quantitative table of clinker quality improvement after replacing part of the pulverized coal with natural gas is shown in Table 12: index pure coal combustion 30% natural gas substitution Improvement mechanism f-CaO 1.05% 0.82% Increased flame temperature uniformity and more complete sintering <![CDATA[C3S content]]> 58% 61% Extend the dwell time in the high-temperature zone by 5 seconds 28d strength 58MPa 62MPa More complete mineral crystals Table 12 (Quantification of Clinker Quality Improvement) By employing a coal-natural gas co-firing process with a natural gas substitution rate of no more than 30% and precise control of oxygen content, carbon monoxide emissions are kept below 500 ppm. Even under conditions of fluctuating coal quality, clinker quality is ensured, with free calcium content reduced by 21% and strength increased by 6.9%. Furthermore, this process also achieves an 18% reduction in nitrogen oxide emissions at the source and a 6.2% reduction in carbon dioxide emissions per ton of clinker, effectively promoting both environmental protection and efficiency improvements. Example

[0075] The similarities with the above embodiments and their combinations will not be repeated, the differences being: The clinker mineral composition by mass percentage is limestone 79.51%, sandstone 14.27%, sulfuric acid slag 2.32%, and pretreated fly ash 3.90%.

[0076] The chemical composition of the raw and cooked materials in this embodiment is shown in Table 13: Table 13 (chemical composition of raw and clinker materials) In this embodiment, the introduction of fly ash significantly improves the performance of the final product due to its higher alkali content (K₂O + Na₂O = 1.25%), sulfur (SO₃ = 1.08%), and chlorine (Cl⁻ = 0.051%), particularly in terms of stability and corrosion resistance under high-temperature environments. Furthermore, the addition of fly ash not only reduces production costs but also minimizes negative environmental impacts, achieving resource utilization of fly ash.

[0077] The clinker performance indicators of this embodiment are shown in Table 14: rate value Mineral composition (%) Other parameters KH=0.910 <![CDATA[C3S=60.01]]> Sodium equivalent = 0.96 SM=2.60 <![CDATA[C2S=16.74]]> Sulfur-alkali ratio = 1.09 AM=1.46 <![CDATA[C3A=7.35,C4AF=10.28]]> Liquid phase volume = 26.48% Table 14 (Clinker Performance Indicators) This embodiment's formulation utilizes deep dechlorination pretreatment and enhanced desulfurization and denitrification processes to achieve fly ash resource utilization while controlling harmful components (Cl⁻, alkali). The clinker yield is stable (KH / SM / AM ratio is reasonable), and its mineral composition fully meets the production requirements of high-quality silicate cement. This formulation not only effectively enhances the utilization value of fly ash but also provides a new technological path for environmental protection and resource recycling, helping to reduce environmental pollution and promoting sustainable resource utilization, aligning with the concept of green development in modern industry. Example

[0078] The similarities with the above embodiments and their combinations will not be repeated, the differences being: The clinker mineral composition by mass percentage is limestone 81.80%, sandstone 14.67%, alumina mud 1.40%, and sulfuric acid slag 2.13%.

[0079] The chemical composition of the raw and cooked materials in this embodiment is shown in Table 15: materials LOI <![CDATA[SiO2]]> <![CDATA[Al2O3]]> <![CDATA[Fe2O3]]> CaO MgO <![CDATA[K2O]]> <![CDATA[Na2O]]> <![CDATA[SO3]]> Cl⁻ raw materials 35.86 13.68 3.06 2.12 42.26 1.77 0.45 0.17 0.16 0.014 Cooked — 21.81 5.03 3.36 65.06 2.74 0.71 0.27 0.64 0.023 Table 15 (chemical composition of raw and clinker materials) The clinker performance indicators of this embodiment are shown in Table 16: Table 16 (Clinker Performance Indicators) In this embodiment, no fly ash is introduced, so the alkali content (K2O+Na2O=0.98%), sulfur (SO3=0.64%) and chlorine (Cl⁻=0.023%) are lower than in Example 3. In this embodiment, aluminum mud is added to provide additional Al2O3 (5.03% in clinker), which helps in the formation of C3A minerals.

[0080] Meanwhile, the reduced alkali content (K₂O + Na₂O = 0.98%), sulfur (SO₃ = 0.64%), and chlorine (Cl⁻ = 0.023%) makes the kiln system more stable and reliable during operation. Furthermore, the chloride ion (Cl⁻) content is only 0.023%, an extremely low level, thus eliminating the need for additional bypass ventilation measures to reduce its impact. Supplementing with alumina (Al₂O₃) through alumina sludge increases the C₃A content to 7.65%, which helps improve the early strength of the cement, thereby enhancing its overall performance.

[0081] It should be noted that, in actual implementation, the structure depicted in the accompanying drawings is not a fixed or unchanging embodiment. The components of the embodiments of the invention described and shown in these drawings can typically be arranged and designed in various different configurations. Furthermore, the accompanying drawings and abstract drawings are merely illustrative and do not represent the specific structure or actual quantity in a concrete implementation.

[0082] Unless otherwise defined, the technical or scientific terms used herein should be understood in their ordinary sense as would be understood by one of ordinary skill in the art to which this invention pertains. The use of terms such as "a" or "an" in this specification and claims does not necessarily indicate a limitation of quantity. Terms such as "comprising" or "including" mean that the element or component preceding the word encompasses the element or component listed following the word and its equivalents, without excluding other elements or components. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect.

[0083] The exemplary embodiments of the present invention have been described in detail above with reference to preferred embodiments. However, those skilled in the art will understand that various modifications and alterations can be made to the above specific embodiments without departing from the concept of the present invention, and various combinations can be made to the various technical features and structures proposed in the present invention without exceeding the protection scope of the present invention.

Claims

1. A dry process cement clinker, characterized in that, The clinker mineral components include limestone 78%-82%, sandstone 14%-15%, sulfuric acid slag 2%-2.5%, aluminum mud 0%-1.4% and pretreated fly ash 0%-3.90% in percentage by mass.

2. The dry-process cement clinker according to claim 1, characterized in that, The clinker mineral components include limestone 79.51%, sandstone 14.27%, sulfuric acid slag 2.32% and pretreated fly ash 3.90% in percentage by mass.

3. The dry process cement clinker according to claim 1, characterized in that, The clinker mineral components include limestone 81.80%, sandstone 14.67%, aluminum mud 1.40% and sulfuric acid slag 2.13% in percentage by mass.

4. A dry process cement clinker production process, characterized by, The method comprises the following steps: Step one, fly ash pretreatment, waste incineration fly ash is mixed with water in a mass ratio, and after stirring, the salt is removed by centrifugation or pressure filtration, and then dried; Step two, raw material preparation, limestone, sandstone, sulfuric acid slag, aluminum mud and pretreated fly ash are mixed in percentage by mass; Step three, raw material grinding, the mixed raw material is processed by a roller press final grinding system; Step four, clinker sintering, the raw material is preheated by a double series six-stage low pressure loss cyclone preheater, and then enters a TDF decomposition furnace and a rotary kiln; Step five, fuel and desulfurization, coal powder is sprayed into the decomposition furnace and the rotary kiln respectively, and calcium-based desulfurization powder is fed into the kiln elevator synchronously; Step six, denitration and purification, the kiln tail flue gas is sequentially subjected to SNCR and SCR denitration; Step seven, waste heat utilization, the kiln head grate cooler and the kiln tail exhaust gas are subjected to waste heat recovery by an SP boiler and an AQC boiler.

5. Dry process cement clinker production process according to claim 4, characterized in that: In step one, the fly ash is mixed with water in a mass ratio of 1:3-1:5 for 30-60 minutes; The fly ash is dried by using the waste heat of the kiln tail exhaust gas as a heat source, and the moisture content is ≤5.0%, the particle size of the desalted fly ash is ≤5mm, and the removal rate of chloride ions is ≥80%; In the prepared fly ash, Cl⁻≤0.5%, CaO≥35.00%, K2O+Na2O≤7.00% and SO3≤8.00%.

6. Dry process cement clinker production process according to claim 4, characterized in that: In step three, the specific surface area of the raw material after grinding is ≥3400cm² / g, the 80μm screen residue is ≤16%, and the 200μm screen residue is ≤2%; In step four, the exhaust gas temperature at the outlet of the cyclone preheater is ≤250℃, the decomposition furnace temperature is 850-1100℃, and the rotary kiln temperature is 1400-1450℃.

7. Dry process cement clinker production process according to claim 4, characterized in that: In step five, 60%-62% of the coal powder is sprayed into the decomposition furnace, and 38-40% of the coal powder is sprayed into the rotary kiln, wherein the Aad of the coal powder is ≤15.00%, the St,ad is ≤0.60%, and the Qnet,ad is ≥26334kJ / kg; The calcium-based desulfurization powder contains 90%-95% CaO and 5%-10% iron oxide red / magnesium oxide additives.

8. Dry process cement clinker production process according to claim 7, characterized in that: When the coal index is insufficient, natural gas is used to replace part of the coal powder, the calorific value is ≥35000kJ / Nm³, coal-gas mixed combustion is implemented at the kiln head, the replacement ratio of natural gas is ≤30%, and the CO concentration in the flue gas after combustion is ≤500ppm.

9. Dry process cement clinker production process according to claim 4, characterized in that: In step six, when the kiln tail flue gas is subjected to SNCR denitration, 20% concentration ammonia water is sprayed, and the NH3 / NO molar ratio is 1.2-1.5; When the kiln tail flue gas is subjected to SCR denitration, the catalyst is V2O5-WO3 / TiO2, the temperature is 200-230℃, and the space velocity is ≤10000h⁻¹. The SCR reactor is arranged between the waste heat boiler and the high-temperature fan, the inlet dust concentration is less than or equal to 60 g / Nm3; the SNCR spray gun is located in the high-temperature zone of 850-1100 DEG C from the outlet of the decomposing furnace to the kiln head cover, and the SCR denitration efficiency is greater than or equal to 90%.

10. Dry process cement clinker production process according to claim 4, characterized in that: In the step seven, the discharge temperature of the kiln head grate cooler is less than or equal to ambient temperature + 65 DEG C, and the outlet exhaust gas temperature of the boiler is less than or equal to 215 DEG C.

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