Process and equipment for graded calcination of semi-dry cement clinker and CO2 capture

Abstract

The invention relates to the technical field of cement clinker production and CO2 capture, and particularly discloses a process and equipment for graded calcination and CO2 capture of semi-dry cement clinker, and the process combines the technology of preparing tricalcium silicate through semi-suspension preheating in a rotary kiln, light roasting of dicalcium silicate, synchronous and direct capture of high-concentration or high-purity CO2 and oxygen-enriched calcination. After being specifically treated, raw material powder enters a self-gravity dispersion type semi-suspended raw material preheating three-blade rotary kiln to be preheated, and then enters a closed electric heating three-blade rotary kiln capable of capturing CO2 and light burning dicalcium silicate. By controlling the electric heating condition, the uniform cross solid-phase reaction is realized, and CO2 is captured. The process solves the problem caused by material layering of a conventional novel dry-method preheater, reduces the loss of powdery materials, and effectively controls the ratio of raw materials to clinker. Meanwhile, high-concentration CO2 can be directly captured, and compared with other technologies, the investment is saved, the operation cost is reduced, the energy-saving and emission-reducing effects are remarkable, and the operation is simple.

Description

Technical Field

[0001] The present invention belongs to the field of cement clinker production and CO2 capture technology, and specifically relates to a process and equipment for semi-dry cement clinker graded calcination and CO2 capture. Background Art

[0002] Cement clinker production process problems and production control: In the cement clinker kiln technology, the decomposition furnace is a very important equipment in the pre-decomposition system. It undertakes the heavy combustion, heat exchange and carbonate decomposition tasks in the pre-decomposition system. Whether these tasks can be successfully completed in an efficient state mainly depends on whether the raw material and fuel can be well dispersed, mixed and distributed in the furnace; whether the fuel can be quickly and completely burned in the furnace and the combustion heat can be transferred to the material in time; whether the carbonate components in the raw material can quickly absorb heat and decompose the escaped carbon dioxide and whether it can be removed in time. Whether these requirements can be met depends to a large extent on the gas and solid flow mode in the furnace, that is, the reasonable organization of the flow field in the furnace. However, the cyclone preheater or pre-decomposition kiln outlet materials in the existing cement clinker process have different degrees of stratification, which proves that there are environmental conditions in the decomposition furnace and the suspension preheater or pre-decomposition kiln environment that are not conducive to the contact and solid phase reaction between various oxides such as dicalcium silicate, so that the solid phase reaction of the material is delayed until it is completed in the cement rotary kiln.

[0003] In response to the above problems, scientists have explored a variety of methods to improve the new dry cement process, such as increasing the height and number of preheaters in the precalciner kiln, and continuously improving the structure of the calciner. However, higher precalciner kilns and more preheaters significantly increase the energy consumption of lifting materials, which should not be the best direction for improving the process.

[0004] The impact of hot kiln dust on clinker production has increased. Recently, the quality of coal has changed greatly, with the most notable feature being the large amount of coal gangue mixed in, which has caused the calorific value of coal to decrease and the ash content to increase significantly, reaching more than 35%, which has brought great difficulties to the calcination process.

[0005] Generally, when using this inferior coal, the dry basis coal consumption can reach 150 kg, and the amount of coal ash sunk can reach 51-52 kg. The large increase in the amount of coal ash sunk in the kiln causes a significant change in the batching rate value. If the rate value is not adjusted in time, the calcination result will change significantly: First, the large amount of coal ash sunk brings in more Al2O3 and SiO2, and the silicon rate and aluminum rate increase, which reduces the saturation ratio and causes calcium deficiency in the calcined clinker. In the mineral composition of the clinker, C2S and C4AF increase, while the probability of C2S turning into C3S decreases, resulting in a decrease in the strength of the clinker; second, the significant difference between coal ash and fly ash is that the coal ash is in a hot state, and the temperature is much higher than that of the fly ash. Due to the low melting point of Al2O3, the amount of liquid phase in the coal ash is formed and increased in advance. The increase in the amount of liquid phase in the raw material makes the decomposition furnace prone to crusting and clogging; due to the increase of Al2O3 in the kiln, the aluminum rate increases, which makes it easy to form rings and increase the size of the clinker, which is not conducive to calcination, and large pieces of clinker are sandwiched in the middle, producing yellow material.

[0006] In order to achieve energy-saving kiln technology and meet the needs of large-scale production lines, the industry has developed a series of two-support and three-support rotary kiln products. The largest three-support rotary kiln can meet the needs of large-scale production lines of about 6,000 t / d. In order to improve the efficiency of heat recovery, air beam clinker grate cooler devices, double series and single series system pressure loss of 4,000 Pa preheater systems have also been developed, and by improving and optimizing the preheater inner tube, air lock valve and refractory materials, decomposition furnaces, etc., efforts are made to reduce the energy consumption of clinker calcination. However, from the perspective of the industry as a whole, the comprehensive standard coal consumption level of clinker is still generally higher than 95 kg standard coal / ton of clinker.

[0007] The industry is also exploring the method of calcining dicalcium silicate and tricalcium silicate separately to improve the preparation requirements of special cement clinker for different silicate mineral contents and achieve energy saving. The technology of calcining dicalcium silicate and tricalcium silicate separately will more likely change the mineral ratio in cement clinker, improve the hydration performance, durability and service life, fire resistance, deformation and creep of clinker, and provide basic cementitious materials for improving the structure and performance of high-performance modern concrete and high-performance cement-based materials.

[0008] The rapid cooling effect is not good, resulting in the decomposition of minerals such as tricalcium silicate generated at high temperature to form free oxides, and the α-type or partial α-type rate of clinker minerals is reduced, and a large amount of β-type silicate minerals and a small amount of γ-type silicate minerals appear. The content of tricalcium silicate and other minerals in the high-temperature melting furnace is more than 80%, and the content of tricalcium silicate at the outlet of the grate cooler and other coolers is reduced to 50-70%, and a large amount of free calcium oxide appears at the same time.

[0009] A large number of theoretical studies and production practices have proved that limestone particles with a diameter of 100μm can be 100% decomposed in 2s in a 900℃ decomposition furnace under the premise of good dispersion, and 90% can be decomposed in 1s. Therefore, the key to the development of carbonate decomposition equipment for cement production lies in the combustion organization of fuel and the dispersion of raw material powder. This is not only the development direction of decomposition furnaces, but also the development direction of new kilns used in cement production.

[0010] CO2 capture in the cement industry: According to statistics in 2018, CO2 emissions from cement production accounted for about 7% of the world's total CO2 emissions. The cement industry can reduce CO2 emissions by taking various technical measures, such as improving energy efficiency, using alternative fuels, using alternative raw materials, and reducing the amount of clinker in cement. However, these technologies have been adopted to a large extent, and the emission reduction effect is still limited.

[0011] CO2 capture and storage (CCS) can significantly reduce CO2 emissions from the cement industry, and is considered a major measure for further comprehensive carbon emission reduction in the cement industry. Currently, there are six CO2 capture technologies: MEA chemical absorption, pure oxygen combustion, cooling ammonia, membrane separation, split calcium cycle, and integrated calcium cycle.

[0012] These technical processes do not conform to the actual situation of the current building materials industry. Without exception, these technical processes have the disadvantages of excessive investment costs and high operating costs, and are difficult to promote in the cement industry.

[0013] The cement industry can reduce CO2 emissions by taking various technical measures mentioned above, but the emission reduction effect is limited, and some are just emission restriction measures (such as carbon trading). CO2 capture and storage (CCS) can significantly reduce CO2 emissions in the cement industry, and it is considered to be a major measure for further comprehensive CO2 emission reduction in the cement industry. However, the CO2 capture and storage (CCS) system in the existing technology is too complicated or the cost of the system is too high, which is not conducive to large-scale promotion and application. Summary of the invention

[0014] The purpose of the present invention is to provide a process and equipment for semi-dry cement clinker graded calcination and CO2 capture, so as to solve the difficulties of the separate calcination processes of dicalcium silicate and tricalcium silicate in the above-mentioned background technology, the problem of material stratification in the pre-decomposition system, the short residence time of raw materials in the pre-decomposition system making it difficult to induce solid-phase reaction in time, and the overly complicated CO2 capture and storage (CCS) system.

[0015] To achieve the above object, the present invention provides the following technical solutions:

[0016] A process and equipment for semi-dry cement clinker graded calcination and CO2 capture, characterized by comprising the following steps:

[0017] S1. The raw material powder is firstly pulverized by adding water and then filtered. After dehydration, dechlorination and removal of sodium ions, it is broken up into 1-5 mm materials and falls into the raw material preheating three-leaf rotary kiln (1). The broken material blocks are preheated in the raw material preheating three-leaf rotary kiln (1) in a state of self-gravity dispersion and semi-suspension. The heat used for preheating comes from the coal injection device at the kiln head. After preheating, the material is decomposed by the first CO2 gas and the material discharge controller (2) is used to achieve gas-solid separation, and then enters the slightly negative pressure, closed, electrically heated, closed electrically heated three-leaf rotary kiln (4) that can directly capture high-concentration or high-purity CO2 and lightly burn dicalcium silicate. The material is semi-suspended in a state of self-gravity dispersion and can undergo uniform cross-solid phase reaction. The flue gas discharged from the raw material preheating three-leaf rotary kiln (1) is sent to the boiler for heat exchange and then enters the waste heat recovery and utilization system. After dust removal, desulfurization and denitrification treatment, the emission meets the standard.

[0018] S2, the materials that have been preheated to different temperatures such as about 800°C, 800-900°C, 900-1100°C in the raw material preheating three-leaf rotary kiln (1) enter the closed electric heating three-leaf rotary kiln (4) from the unloading end of the raw material preheating three-leaf rotary kiln (1) through the first CO2 gas decomposition and unloading controller. In order to achieve the purpose of energy saving and meet the process requirements and energy saving goals of calcining dicalcium silicate and tricalcium silicate separately, it is best to control the unloading temperature of the materials to about 1000°C-1100°C before entering the closed electric heating three-leaf rotary kiln (4), so that the materials can undergo a uniform cross-solid phase reaction in a dispersed semi-suspended form by gravity, and the maximum calcination temperature can be controlled to about 1250°C by reaction heat and electric heating to generate high-belite cement clinker mainly composed of light-burned dicalcium silicate.

[0019] S3. To obtain high-belite cement clinker mainly composed of light-burned dicalcium silicate, the cement clinker enters a water cooling + liquefied nitrogen cooling and waste heat recovery system or a water cooling + liquefied CO2 cooling and waste heat recovery system or a molten salt power generation system at the tail end of the closed electric heating three-blade rotary kiln (4) to be rapidly cooled to below 500° C. The cement clinker can be produced into a finished product after rapid cooling and salt washing.

[0020] S4, during the reaction process of generating high-belite cement clinker mainly composed of light-burned dicalcium silicate, the closed electrically heated three-blade rotary kiln (4) is in a slightly negative pressure and closed state, and a uniform cross-solid phase reaction is induced by electrical heating, and the calcination temperature is mainly maintained by the exothermic reaction of dicalcium silicate. At this time, the CO2 generated by the decomposition of carbonate can be directly captured to form high-concentration or high-purity CO2. The high-temperature CO2 is recovered by waste heat, the gas temperature is reduced to 31°C, and then fine dust removal, compression and liquefaction are carried out for recycling.

[0021] S5. The materials that have completed the reaction in the closed electric heating three-blade rotary kiln (4) enter the oxygen-enriched calcination rapid melting rotary kiln (8), and are melted and calcined at a higher temperature (generally around 1450° C.) to produce high alite cement clinker. The fuel used is the injected coal powder, and the combustion-supporting gas comes from the oxygen produced by the oxygen production device.

[0022] S6. After the high-alite cement clinker is calcined in the oxygen-enriched calcination rapid melting rotary kiln (8), it enters the water cooling + liquefied nitrogen cooling and waste heat recovery system or the water cooling + liquefied CO2 cooling and waste heat recovery system or the molten salt power generation system to be rapidly cooled to below 500° C. The cement clinker can be produced into a finished product after rapid cooling and salt washing.

[0023] Preferably, the process Figure 1 and / or Figure 2 and or Figure 3 and or Figure 4 A first CO2 gas decomposition and material discharge controller is arranged between the raw material preheating three-leaf rotary kiln (1) and the sealed electric heating three-leaf rotary kiln (4), and at least two sealing methods such as a labyrinth type (tortuous path type), a contact type (friction type) and a gas seal type are adopted to achieve a high concentration of carbon dioxide in the sealed electric heating three-leaf rotary kiln (4), and to capture carbon dioxide and balance the gas and pressure of carbonate decomposition under a slightly negative pressure.

[0024] Preferably, from the process Figure 1 and / or Figure 2 and or Figure 3 and or Figure 4 A CO2 decomposition and material discharge controller (3) is provided between the sealed electric heating three-leaf rotary kiln (4) and the oxygen-enriched calcination rapid melting rotary kiln (8), and at least two sealing methods such as a labyrinth type (tortuous path type), a contact type (friction type) and a gas seal type are adopted to achieve a high concentration of carbon dioxide in the sealed electric heating three-leaf rotary kiln (4), and to capture carbon dioxide and balance the gas and pressure of carbonate decomposition under a slight negative pressure.

[0025] Preferably, the negative pressure inside the closed electrically heated three-leaf rotary kiln (4) is generally controlled at 5-10 Pa.

[0026] Preferably, the CO2 output pipeline should pass through the CO2 decomposition and feeding controller, the waste heat boiler heat exchanger and power generation system, the high-temperature dust collector, the fine dust collector in sequence, and then enter the CO2 gaseous output pipeline or be compressed and liquefied and placed in a storage tank.

[0027] Preferably, the oxygen concentration in the oxygen-enriched calcination rapid melting rotary kiln (8) is controlled to be above 30%.

[0028] Preferably, the second cooling and waste heat recovery system (7) is a water cooling + liquefied nitrogen cooling and waste heat recovery system or a water cooling + liquefied CO2 cooling and waste heat recovery system or a molten salt power generation system, which is a key link in the rapid cooling of clinker. In view of the fact that there is an oxygen production link required for oxygen enrichment in this process, the oxygen generator can also produce liquid nitrogen, which should be preferably used as a rapid cooling and heat exchange medium. Similarly, in view of the fact that the closed electric heating three-leaf rotary kiln (4) captures high-concentration / high-purity carbon dioxide, the compressed and liquefied carbon dioxide can also be preferably used as a rapid cooling and heat exchange medium.

[0029] Preferably, Figure 1 and / or Figure 2 and or Figure 3 and or Figure 4 The raw material powder ground into raw material powder is firstly slurried by adding water and then filtered, and then broken into 1-5 mm materials after dehydration, dechlorination and removal of sodium ions. The raw material powder enters the raw material preheating three-leaf rotary kiln (1) which is semi-suspended by gravity dispersion to complete preheating. Then, the gas-solid separation is achieved by the first CO2 gas decomposition and the material discharge controller. After that, the raw material powder enters the slightly negative pressure, closed, electrically heated, closed three-leaf rotary kiln (4) which can directly capture high-concentration or high-purity CO2 and lightly burn dicalcium silicate, and the materials are semi-suspended by gravity dispersion and can undergo uniform cross-solid phase reaction. The preheated material can be selected to enter the closed electric heating three-leaf rotary kiln (4) at different temperatures such as about 800°C, 800-900°C, 900-1100°C, etc. The material undergoes a uniform cross-solid phase reaction in a dispersed semi-suspended form by gravity, and the electric heating temperature, intensity, frequency, etc. are controlled to balance the heat absorption of carbonates and the exothermic reaction of dicalcium silicate, the capture of CO2, etc., and the sintering temperature of the closed electric heating three-leaf rotary kiln (4) is always controlled to be 1100-1200°C, so as to induce the formation of a large amount of silicate minerals mainly composed of C3A, C4AF, and C2S in the kiln. The operating structure of the closed electrically heated three-leaf rotary kiln (4) makes the materials in the kiln in a dispersed and semi-suspended form, and the solid phase reaction is a uniform reaction. It not only solves the problem that the materials discharged from the conventional new dry preheater are generally stratified, which makes it difficult to have a solid phase reaction or the reaction speed is slow, but also reduces the problem of excessive amount of powdered materials being carried away by dust removal and circulating flue gas, and can effectively control the ratio of raw materials to clinker to about 1.52.

[0030] Preferably, after reacting in the closed electric heating three-blade rotary kiln (4) for about 5 minutes, the material falls into the oxygen-enriched calcination rapid melting rotary kiln (8) at a temperature of about 1250°C. The oxygen-enriched calcination rapid melting rotary kiln (8) uses coal powder as fuel, and then introduces pure oxygen prepared by an oxygen generator. The high-belite cement clinker that completes the cross-solid phase reaction in the closed electric heating three-blade rotary kiln (4) continues to be oxygen-enriched calcined in the oxygen-enriched calcination rapid melting rotary kiln (8) for about 25 minutes. The high-belite cement clinker then directly enters the water cooling + liquefied nitrogen cooling and waste heat recovery system or the water cooling + liquefied CO2 cooling and waste heat recovery system or the molten salt power generation system at a temperature of about 1350-1450°C to complete sufficient rapid cooling. In order to promote the formation of minerals such as tricalcium silicate, a small amount of steel slag powder and other crystal seeds can be added to the feeding end of the oxygen-enriched calcination rapid melting rotary kiln (8) to achieve a rapid melting reaction of oxygen-enriched calcination.

[0031] Preferably, the solid phase reaction process for generating dicalcium silicate as the main mineral is carried out in an electrically heated, sealed, three-leaf rotary kiln (4). While the solid phase reaction is occurring, the high concentration or high purity CO2 decomposed from the carbonate can be directly captured in a slightly negative pressure manner.

[0032] Preferably, the kiln head and kiln tail of the closed electric heating three-leaf rotary kiln (4) are both in at least two forms, such as a labyrinth type (tortuous path type), a contact type (friction type) and a gas-sealed type, and a first CO2 gas decomposition and unloading controller and a second CO2 gas decomposition and unloading controller (3) are arranged at the feeding end and the discharging end to achieve gas-solid separation and complete sealing, which is conducive to directly capturing high-concentration or high-purity CO2 decomposed from carbonate in a micro-negative pressure manner, and controlling and adjusting the CO2 capture amount according to production needs. Compared with other process technologies such as CCUS, the present invention saves 50.0% to 70.0% of investment, reduces operating costs by 60% to 80%, has a large energy-saving and emission-reduction range, good effects, and is simple to operate.

[0033] Preferably, after reacting in the closed electric heating three-leaf rotary kiln (4) for about 5 minutes, the material is decomposed by ③CO2 gas at a temperature of about 1250°C and separated by gas and solid by the material discharge controller (3), and then the material can be directly dropped into the water cooling + liquefied nitrogen cooling and waste heat recovery system or the water cooling + liquefied CO2 cooling and waste heat recovery system or the molten salt power generation system to complete full rapid cooling to below 500°C, and then further use molten salt / CO2 / nitrogen for efficient waste heat recovery. At this time, the cooled material is high-belite cement clinker mainly composed of dicalcium silicate.

[0034] Preferably, after reacting in the closed electric heating three-leaf rotary kiln (4) for about 5 minutes, the material is decomposed by the second CO2 gas at a temperature of about 1250°C and separated by gas and solid by the unloading controller (3), and the material can also directly fall into the oxygen-enriched calcination rapid melting rotary kiln (8). Using coal powder as fuel, pure oxygen prepared by an oxygen generator is introduced, and the high-belite cement clinker that has basically completed the solid phase reaction in the closed electric heating three-leaf rotary kiln (4) continues to be oxygen-enriched calcined in the melting rotary kiln for about 25 minutes. The high-belite cement clinker then directly enters the water cooling + liquefied nitrogen cooling and waste heat recovery system or the water cooling + liquefied CO2 cooling and waste heat recovery system or the molten salt power generation system at a temperature of about 1350-1450°C to complete full rapid cooling to below 500°C, and then uses molten salt / CO2 / nitrogen for efficient waste heat recovery. In order to promote the formation of tricalcium silicate and other minerals, a small amount of steel slag powder and other seeds can be added to the feeding end of the oxygen-enriched calcination rapid melting rotary kiln (8) to achieve a rapid melting reaction of oxygen-enriched calcination. At this time, the cooled material is high alite cement clinker mainly composed of tricalcium silicate.

[0035] Preferably, Figure 1 and / or Figure 2 and or Figure 3 and or Figure 4 The heat energy of the raw material preheating three-blade rotary kiln (1) is injected into the kiln by the coal injection device to complete the preheating.

[0036] Preferably, the material is subjected to a solid phase reaction in the closed electric heating three-leaf rotary kiln (4) for about 5 minutes under the conditions of controlling the electric heating temperature, intensity, frequency, etc., the heat balance of the carbonate endothermic reaction and the exothermic reaction of dicalcium silicate, the capture of CO2, etc., and the pressure in the kiln, the particle size of the material, the reaction time, the reaction environment (uniformity, segregation), etc., and the material is mainly lightly burned dicalcium silicate when the material is discharged at a temperature of about 1250°C. The whole reaction process can make full use of the exothermicity of the dicalcium silicate generation reaction, thereby improving the thermal energy utilization rate of the physical and chemical reaction. The electric heating device should ensure that the temperature in the kiln is always not less than 880°C to maintain the occurrence of the solid phase reaction.

[0037] Preferably, after the solid phase reaction in the closed electrically heated three-blade rotary kiln (4) generates silicate minerals mainly composed of dicalcium silicate, the water cooling + liquefied nitrogen cooling and waste heat recovery system or the water cooling + liquefied CO2 cooling and waste heat recovery system or the molten salt power generation system can be entered at the tail end of the kiln to directly produce high-belite cement clinker.

[0038] Preferably, after the reaction of the silicate minerals mainly composed of C2S in the closed electric heating three-blade rotary kiln (4) is basically complete, the materials enter the oxygen-enriched calcination rapid melting rotary kiln (8) and are melt-calcined at a higher temperature (generally around 1450°C) to generate cement clinker minerals mainly composed of alite. The reaction speed in the kiln is faster, so there is no need to build an overly long kiln body, and the reaction time can be shortened to about 25 minutes. The total time in the kiln for solid-phase reaction and melting reaction is 30 to 35 minutes, which is much shorter than the production time in the new dry process cement clinker kiln, thereby being more energy-efficient.

[0039] Preferably, the high-belite cement clinker generated by the calcination is rapidly cooled by a second cooling and waste heat recovery system (7), including a water cooling + liquefied nitrogen cooling and waste heat recovery system or a water cooling + liquefied CO2 cooling and waste heat recovery system or a molten salt power generation system, which improves the rapid cooling effect, greatly reduces the generation of free oxides, and improves the heat exchange and recovery efficiency. It can also achieve α-type or partial α-type of clinker minerals, greatly reduce β-type silicate minerals, and eliminate γ-type silicate minerals, thereby optimizing the silicate mineral composition in cement clinker.

[0040] Preferably, the quenching of the high alite cement clinker generated by the calcination no longer uses the cooling machine commonly used in the traditional new dry process cement clinker production line, but uses a second cooling and waste heat recovery system (7) with a faster quenching rate and better effect, including a water cooling + liquefied nitrogen cooling and waste heat recovery system or a water cooling + liquefied CO2 cooling and waste heat recovery system or a molten salt power generation system, which improves the quenching effect, greatly reduces the generation of free oxides, and improves the heat exchange and recovery efficiency. It can also achieve α-type or partial α-type clinker minerals, greatly reduce β-type silicate minerals, and eliminate γ-type silicate minerals, thereby optimizing the silicate mineral composition in cement clinker.

[0041] Preferably, the present invention deconstructs the solid phase reaction of dicalcium silicate and the melting reaction of tricalcium silicate, so that they are graded and separately calcined in a closed electric heating three-blade rotary kiln (4) and an oxygen-enriched calcination rapid melting rotary kiln (8), which has higher production efficiency and realizes overall energy saving of clinker calcination. Moreover, the length of the above-mentioned kiln body can be greatly shortened to meet the needs of graded and separate calcination. Taking a cement clinker line with a daily output of 4,000 tons as an example, it is only necessary to build a Φ4.6m×22m raw material preheating three-blade rotary kiln, a Φ4.6m×22m closed electric heating three-blade rotary kiln and a Φ4.6m×8m oxygen-enriched calcination rapid melting rotary kiln to realize graded calcination of cement clinker. While graded calcination of cement clinker, the α-type or partial α-type of clinker minerals can also be achieved, β-type silicate minerals are greatly reduced, and γ-type silicate minerals are eliminated, thereby optimizing the silicate mineral composition in cement clinker.

[0042] Preferably, this process and equipment can be used to carry out appropriate technical transformation and equipment update for various types of existing new dry process cement clinker production lines. By transforming or updating the cement clinker rotary kiln according to the requirements of this process, low-cost recovery of CO2 from carbonate decomposition and continuous and graded calcination of the reaction process of cement clinker production of dicalcium silicate and tricalcium silicate can be achieved, which greatly improves the silicate mineral generation rate of cement clinker, saves more than 50% energy, saves 50.0% to 70.0% investment, and reduces operating costs by 60% to 80%. The comprehensive energy consumption of clinker can be about 75kg to 80kg standard coal per ton.

[0043] Preferably, the high-belite cement clinker and high-alite cement clinker calcined by the process can be matched with minerals as required to produce various high-quality special cements in an energy-saving manner.

[0044] Preferably, the raw material preheating three-blade rotary kiln (1) preheating, the production process of calcining dicalcium silicate and tricalcium silicate separately, the functional design of the kiln for separate calcination, the kiln firing parameters and system design, the improvement of the rapid cooling method, etc., are subjected to various changes, modifications, replacements and variants. The process equipment can carry out appropriate technical transformation and equipment renewal of various types of existing new dry process cement clinker production lines.

[0045] Preferably, the firing temperature control fluctuation range of each subsystem can be accurately controlled to ±10°C. This can effectively avoid excessive decomposition of calcium silicate caused by excessive temperature, affecting the quality of clinker, and the influence of excessive temperature fluctuation on the formation of α-type or α-type silicate minerals.

[0046] Preferably, the total burning time of the material in the closed electric heating three-blade rotary kiln (4) and the oxygen-enriched calcination rapid melting rotary kiln (8) is about 30 minutes, which is about 15 minutes less than the total burning time of new dry-process cement clinker and wet-process cement clinker, thus having a significant energy-saving effect.

[0047] Preferably, the kiln body internal structure of the raw material preheating three-leaf rotary kiln (1) and the closed electric heating three-leaf rotary kiln (4) are both three-leaf, the material can exist in the kiln in a self-gravity dispersed state or semi-suspended state, all materials are in a continuous tumbling state, the material filling rate reaches 30%, the solid-gas ratio is between 2.8≤Z≤3.5, there is no material accumulation in the kiln, and the gas-solid two-phase suspended state heat exchange and mass exchange rate are significantly improved. In addition, the preheating and carbonate decomposition solid phase reaction firing time is generally extended by 2 to 4 times compared with the pre-decomposition kilns and vertical kilns of new dry cement clinker, wet cement clinker, etc., and the CO2 generated by carbonate decomposition is balanced and recovered in the closed electric heating three-leaf rotary kiln (4) in the form of micro-negative pressure or micro-positive pressure, and the reaction atmosphere with a CO2 content of about 30% when the temperature in the kiln is controlled at the optimal state of 880°C to 900°C can accelerate the carbonate decomposition to complete 100% decomposition within 1 to 2 seconds. The sealed, electrically heated three-leaf rotary kiln (4) eliminates the interference of impurities and creates the possibility of directly capturing CO2 produced by carbonate decomposition in the kiln. The purity of the directly captured CO2 can reach 99.99%.

[0048] Preferably, in addition to producing high-belite cement clinker and high-alite cement clinker, the process and equipment can also adjust the ingredients and process parameters to produce white cement clinker, sulphoaluminate cement clinker, aluminate cement clinker, oil well cement clinker, etc.

[0049] Beneficial Effects

[0050] The present invention provides a process and equipment for semi-dry cement clinker graded calcination and CO2 capture, which has the following beneficial effects:

[0051] 1. Improved calcination conditions for carbonate decomposition and solid-phase reaction of silicate minerals. In a continuous production process, carbonate decomposition and solid-phase reaction are controlled to be calcined in the range of 750-1250°C. The internal structure of the kiln body is a three-leaf electric heating, which not only keeps the material in a semi-suspended and dispersed state in the kiln, but also overcomes the material stratification phenomenon of the pre-decomposition kiln, prolongs the residence time of the material in the kiln, realizes sufficient carbonate decomposition and solid-phase reaction, and eliminates the problem of gas combustion affecting the purity of carbon dioxide. At the same time, when gas-solid separation devices are set at the head and tail of the kiln, high-concentration or high-purity carbon dioxide can be directly captured in this kiln to achieve a balance between pressure and gas generation rate under a slightly negative pressure state.

[0052] 2. The present invention allows the material preheating and carbonate decomposition reaction stages to be carried out in a three-blade rotary kiln. All materials are in a self-gravity dispersed, semi-suspended, continuous tumbling state in the kiln, the material filling rate reaches 30%, the solid-gas ratio is between 2.8≤Z≤3.5, there is no material accumulation in the kiln, and the high solid-gas ratio effectively improves the apparent decomposition rate of carbonate entering the melting kiln, such as the dispersion degree of the material in the airflow, the size of the particles, the temperature of the decomposition furnace, the partial pressure of carbon dioxide, and the reaction time (residence time), so that the gas-solid two-phase suspended heat exchange and mass exchange rate are significantly improved.

[0053] 3. Improved the calcination conditions of silicate mineral melting reaction. In a continuous production process, the controllable calcination of tricalcium silicate and other minerals in the range of 1250-1450°C is achieved. In an oxygen-rich environment, the melting reaction of dicalcium silicate and calcium oxide is accelerated, making the length of the melting furnace shorter and more energy-efficient.

[0054] 4. Improved clinker cooling method. Water cooling + liquefied nitrogen cooling and waste heat recovery system or water cooling + liquefied CO2 cooling and waste heat recovery system or molten salt cooling and waste heat recovery system are introduced. In particular, CO2 captured by the production process system or liquefied nitrogen produced as a byproduct of oxygen production can be used as the preferred quenching and heat exchange medium, which not only improves the clinker quenching effect and power generation efficiency, but also saves more energy than grate coolers and other cooling machines, and also achieves the best energy saving and recycling effect.

[0055] 5. The continuous and graded calcination and separate calcination of the reaction process of producing dicalcium silicate and tricalcium silicate in cement clinker are realized, which greatly improves the silicate mineral generation rate of cement clinker and can save more than 50% of energy. The comprehensive coal consumption of clinker can be reduced to about 85kg standard coal / ton.

[0056] 6. Compared with other process technologies such as terminal flue gas CCUS, the method of directly capturing high-concentration or high-purity CO2 of the present invention saves 50.0% to 70.0% of investment, reduces operating costs by 60% to 80%, has a large energy-saving and emission-reduction range, good effects, and is simple to operate.

[0057] 7. This process and equipment also have high flexibility in raw material ratio, parameter adjustment and product variety. In addition to producing high-belite cement clinker and high-alite cement clinker, it can also adjust the ingredients and process parameters to produce white cement clinker, sulphoaluminate cement clinker, aluminate cement clinker, oil well cement clinker, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 This is a schematic diagram of the process and equipment flow of semi-dry cement clinker graded calcination and direct capture of high-purity CO2 in Embodiment 1 of the present invention;

[0059] Figure 2It is a schematic diagram of the process and equipment flow of the semi-dry process for graded calcination of cement clinker and direct capture of high-purity CO2 in the second embodiment of the present invention;

[0060] Figure 3 It is a schematic diagram of the process and equipment flow of the non-injection fuel process in the second embodiment of the present invention;

[0061] Figure 4 The figure is a schematic diagram of the process and equipment flow of raw material powder after being pelletized and dried in the present invention. DETAILED DESCRIPTION

[0062] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0063] Embodiment 1:

[0064] like Figure 1 As shown, a process and equipment for semi-dry cement clinker graded calcination and CO2 capture includes the following steps:

[0065] S1. The raw material powder is firstly pulverized by adding water and then filtered. After dehydration, dechlorination and removal of sodium ions, it is broken up into 1-5 mm materials and falls into the raw material preheating three-leaf rotary kiln (1). The broken material blocks are preheated in the raw material preheating three-leaf rotary kiln (1) in a state of self-gravity dispersion and semi-suspension. The heat used for preheating comes from the coal injection device at the kiln head. After preheating, the material is decomposed by the first CO2 gas and the material discharge controller is used to achieve gas-solid separation. Then, it enters the slightly negative pressure, closed, electrically heated, closed electrically heated three-leaf rotary kiln (4) that can directly capture high-concentration or high-purity CO2 and lightly burn dicalcium silicate. The material is semi-suspended in a state of self-gravity dispersion and can undergo uniform cross-solid phase reaction. The flue gas discharged from the raw material preheating three-leaf rotary kiln (1) is sent to the boiler for heat exchange and then enters the waste heat recovery and utilization system. After dust removal, desulfurization and denitrification treatment, the emission meets the standard.

[0066] S2. The material that has been preheated to about 880°C in the raw material preheating three-leaf rotary kiln (1) enters the closed electric heating three-leaf rotary kiln (4) from the unloading end of the raw material preheating three-leaf rotary kiln (1) through the first CO2 gas decomposition and unloading controller. In order to achieve the purpose of energy saving and meet the process requirements and energy saving goals of calcining dicalcium silicate and tricalcium silicate separately, the unloading temperature of the material is controlled to be about 1050°C before entering the closed electric heating three-leaf rotary kiln (4), so that the material undergoes a uniform cross-solid phase reaction in a dispersed semi-suspended form by gravity, and the maximum calcination temperature is controlled to be about 1250°C by reaction heat and electric heating to generate high-belite cement clinker mainly composed of light-burned dicalcium silicate.

[0067] S3. In order to obtain high-belite cement clinker mainly composed of light-burned dicalcium silicate, the molten salt power generation system in the first cooling and waste heat recovery system (6) enters the tail end of the closed electric heating three-blade rotary kiln (4) to rapidly cool it to below 500° C. The cement clinker can be produced into a finished product after rapid cooling and salt washing.

[0068] S4, during the reaction process of generating high-belite cement clinker mainly composed of light-burned dicalcium silicate, the closed electrically heated three-blade rotary kiln (4) is in a slightly negative pressure and closed state, and electrically heated to induce a uniform cross-solid phase reaction based on the Internet of Things management of smart city construction, mainly using the exothermic reaction of dicalcium silicate to maintain the calcination temperature. At this time, the CO2 generated by the decomposition of carbonate can be directly captured to form high-concentration or high-purity CO2. The high-temperature CO2 is recovered by waste heat, the gas temperature is reduced to 31°C, and then fine dust removal, compression and liquefaction are carried out for recycling.

[0069] S5. The materials that have completed the reaction in the closed electric heating three-blade rotary kiln (4) enter the oxygen-enriched calcination rapid melting rotary kiln (8) and are melted and calcined at about 1350° C. to produce high alite cement clinker. The fuel used is the injected coal powder, and the combustion-supporting gas comes from the oxygen produced by the oxygen production device.

[0070] S6. After the high-alite cement clinker is calcined in the oxygen-enriched calcination rapid melting rotary kiln (8), it enters the molten salt power generation system in the second cooling and waste heat recovery system (7) to be rapidly cooled to below 500° C. The cement clinker can be produced into a finished product after rapid cooling and salt washing.

[0071] Embodiment 2:

[0072] like Figure 1 As shown, a process and equipment for semi-dry cement clinker graded calcination and CO2 capture includes the following steps:

[0073] S1. The raw material powder is firstly pulverized by adding water and then filtered. After dehydration, dechlorination and removal of sodium ions, it is broken up into 1-5 mm materials and falls into the raw material preheating three-leaf rotary kiln (1). The broken material blocks are preheated in the raw material preheating three-leaf rotary kiln (1) in a state of self-gravity dispersion and semi-suspension. The heat used for preheating comes from the coal injection device at the kiln head. After preheating, the material is decomposed by the first CO2 gas and the material discharge controller is used to achieve gas-solid separation. Then, it enters the slightly negative pressure, closed, electrically heated, closed electrically heated three-leaf rotary kiln (4) that can directly capture high-concentration or high-purity CO2 and lightly burn dicalcium silicate. The material is semi-suspended in a state of self-gravity dispersion and can undergo uniform cross-solid phase reaction. The flue gas discharged from the raw material preheating three-leaf rotary kiln (1) is sent to the boiler for heat exchange and then enters the waste heat recovery and utilization system. After dust removal, desulfurization and denitrification treatment, the emission meets the standard.

[0074] S2. The material that has been preheated to about 880°C in the raw material preheating three-leaf rotary kiln (1) enters the closed electric heating three-leaf rotary kiln (4) from the discharge end of the raw material preheating three-leaf rotary kiln (1) through the first CO2 gas decomposition and discharge controller. In order to achieve the purpose of energy saving and meet the process requirements and energy saving goals of calcining dicalcium silicate and tricalcium silicate separately, the material discharge temperature is controlled at about 1100°C before entering the closed electric heating three-leaf rotary kiln (4), so that the material undergoes a uniform cross-solid phase reaction in a dispersed semi-suspended form by gravity, and the maximum calcination temperature is controlled at about 1250°C by reaction heat and electric heating to generate high-belite cement clinker mainly composed of light-burned dicalcium silicate.

[0075] S3. In order to obtain high-belite cement clinker mainly composed of light-burned dicalcium silicate, the water cooling + liquefied nitrogen cooling and waste heat recovery system in the first cooling and waste heat recovery system (6) is entered at the tail end of the closed electric heating three-blade rotary kiln (4). The water cooling system can rapidly cool the cement clinker from 1250° C. to below 900° C., and then rapidly cool it to below 500° C. by liquefied nitrogen. After rapid cooling, the cement clinker can be converted into a finished product.

[0076] S4, during the reaction process of generating high-belite cement clinker mainly composed of light-burned dicalcium silicate, the closed electrically heated three-blade rotary kiln (4) is in a slightly negative pressure and closed state, and a uniform cross-solid phase reaction is induced by electrical heating, and the calcination temperature is mainly maintained by the exothermic reaction of dicalcium silicate. At this time, the CO2 generated by the decomposition of carbonate can be directly captured to form high-concentration or high-purity CO2. The high-temperature CO2 is recovered by waste heat, the gas temperature is reduced to 31°C, and then fine dust removal, compression and liquefaction are carried out for recycling.

[0077] S5. The materials that have completed the reaction in the closed electric heating three-blade rotary kiln (4) enter the oxygen-enriched calcination rapid melting rotary kiln (8) and are melted and calcined at about 1350° C. to produce high alite cement clinker. The fuel used is the injected coal powder, and the combustion-supporting gas comes from the oxygen produced by the oxygen production device.

[0078] S6, after the high alite cement clinker is calcined in the oxygen-enriched calcination rapid melting rotary kiln (8), it enters the water cooling + liquefied nitrogen cooling and waste heat recovery system in the second cooling and waste heat recovery system (7). The water cooling system can rapidly cool the cement clinker from 1350°C to below 900°C, and then rapidly cool it to below 500°C by liquefied nitrogen. After rapid cooling, the cement clinker can be produced into a finished product.

[0079] The present invention deconstructs the solid phase reaction of dicalcium silicate and the melting reaction of tricalcium silicate, so that they can be calcined separately in a closed electric heating three-blade rotary kiln (4) and an oxygen-enriched calcination rapid melting rotary kiln (8), with higher production efficiency, and realizes overall energy saving of clinker calcination. Moreover, the length of the above-mentioned kiln body can be greatly shortened to meet the needs of calcination in different stages. Taking a cement clinker line with a daily output of 4,000 tons as an example, it is only necessary to build a Φ4.6m×22m raw material preheating three-blade rotary kiln, a Φ4.6m×22m closed electric heating three-blade rotary kiln and a Φ4.6m×8m oxygen-enriched calcination rapid melting rotary kiln to realize the graded calcination of cement clinker. While calcining cement clinker in different stages, the α-type or partial α-type of clinker minerals can also be realized, β-type silicate minerals are greatly reduced, and γ-type silicate minerals are eliminated, thereby optimizing the silicate mineral composition in cement clinker.

[0080] This process and equipment can be used to carry out appropriate technical transformation and equipment update for various types of existing new dry process cement clinker production lines. By transforming or updating the cement clinker rotary kiln according to the requirements of this process, low-cost recovery of CO2 from carbonate decomposition and continuous and graded calcination of the reaction process of cement clinker production of dicalcium silicate and tricalcium silicate can be achieved, which greatly improves the silicate mineral generation rate of cement clinker, saves more than 50% energy, saves 50.0% to 70.0% investment, and reduces operating costs by 60% to 80%. The comprehensive energy consumption of clinker can be about 75 to 80 kg standard coal per ton.

[0081] At the same time, the high-belite cement clinker and high-alite cement clinker calcined by this process can be matched with minerals as required to produce various high-quality special cements in an energy-saving manner.

[0082] The firing temperature control fluctuation range of each subsystem of the present invention can be accurately controlled to ±10°C. This can effectively avoid excessive decomposition of calcium silicate caused by excessive temperature, affecting the quality of clinker, and the influence of excessive temperature fluctuation on the formation of α-type or α-type silicate minerals.

[0083] The kiln body internal structure of the raw material preheating three-leaf rotary kiln (1) and the closed electric heating three-leaf rotary kiln (4) are both three-leaf, materials can exist in the kiln in a dispersed state or semi-suspended state by gravity, all materials are in a continuous tumbling state, the material filling rate reaches 30%, the solid-gas ratio is between 2.8≤Z≤3.5, there is no material accumulation in the kiln, and the gas-solid two-phase suspended state heat exchange and mass exchange rate are significantly improved. In addition, the preheating and carbonate decomposition solid phase reaction firing time is generally extended by 2 to 4 times compared with the pre-decomposition kilns and vertical kilns of new dry cement clinker, wet cement clinker, etc., and the CO2 generated by carbonate decomposition is balanced and recovered in the closed electric heating three-leaf rotary kiln (4) in the form of micro-negative pressure or micro-positive pressure, and the reaction atmosphere with a CO2 content of about 30% when the temperature in the kiln is controlled at the optimal state of 880°C to 900°C can accelerate the carbonate decomposition to complete 100% decomposition within 1 to 2 seconds. The sealed, electrically heated three-leaf rotary kiln (4) eliminates the interference of impurities and creates the possibility of directly capturing CO2 produced by carbonate decomposition in the kiln. The purity of the directly captured CO2 can reach 99.99%.

[0084] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A process and equipment for semi-dry cement clinker graded calcination and CO2 capture, characterized in that: The following steps are involved: S1, the ground raw meal powder is watered by a pulping machine to form a slurry, which is then filtered by a filter press, dehydrated, and freed of chloride ions and sodium salts, and then broken into a semi-dry material of 1 to 5 mm by a break-up machine. The material falls into a raw meal preheating three-leaf rotary kiln (1), where the material is preheated in a dispersed and semi-suspended state due to gravity. The heat used for preheating comes from a coal injection device at the kiln head. After preheating, the material is decomposed by a first CO2 gas and separated from the gas and solid by a feed controller (2), and then enters a closed electric heating three-leaf rotary kiln (4). The flue gas discharged from the raw meal preheating three-leaf rotary kiln (1) is sent to a boiler for heat exchange and then enters a waste heat recovery and utilization system. After dust removal, desulfurization and denitrification treatment, the material meets the emission standards; S2, the materials that have been preheated to different temperatures of about 800° C., 800-900° C., and 900-1100° C. in the raw material preheating three-leaf rotary kiln (1) are passed through the first CO2 gas decomposition and material discharge controller (2) from the discharge end of the raw material preheating three-leaf rotary kiln (1) into the closed electric heating three-leaf rotary kiln (4), and the material discharge temperature is controlled at 1000° C.-1100° C. before entering the closed electric heating three-leaf rotary kiln (4), so that the materials undergo a uniform cross-solid phase reaction in a dispersed semi-suspended form under their own gravity, and the maximum calcination temperature is controlled at 1250° C. by means of reaction heat and electric heating, so as to generate high-belite cement clinker mainly composed of light-burned dicalcium silicate; S3, in order to obtain high-belite cement clinker mainly composed of light-burned dicalcium silicate, the cement clinker enters the first cooling and waste heat recovery system (6) at the tail end of the closed electric heating three-blade rotary kiln (4), wherein the first cooling and waste heat recovery system (6) is a water cooling + liquefied nitrogen cooling and waste heat recovery system or a water cooling + liquefied CO2 cooling and waste heat recovery system or a molten salt power generation system, so that the cement clinker is rapidly cooled to below 500° C. After rapid cooling and salt washing, the cement clinker can be produced into a finished product; S4, during the reaction process of generating high-belite cement clinker mainly composed of light-burned dicalcium silicate, the closed electrically heated three-blade rotary kiln (4) is in a slightly negative pressure and closed state, and a uniform cross-solid phase reaction is induced by electrical heating, and the calcination temperature is mainly maintained by the exothermic reaction of dicalcium silicate. The CO2 generated by the decomposition of carbonates is directly captured to form high-concentration or high-purity CO2. The high-temperature CO2 is recovered by waste heat, and the gas temperature is reduced to 31° C., and then fine dust removal, compression and liquefaction are carried out for recycling; S5. The materials that have completed the reaction in the closed electrically heated three-blade rotary kiln (4) enter the oxygen-enriched calcination rapid melting rotary kiln (8), and are melt-calcined at 1450° C. to produce high-alite cement clinker, wherein the fuel used is the injected coal powder, and the combustion-supporting gas comes from the oxygen produced by the oxygen production device. S6, after being calcined in the oxygen-enriched calcination rapid melting rotary kiln (8) to generate high alite cement clinker, it enters the second cooling and waste heat recovery system (7), which is a water cooling + liquefied nitrogen cooling and waste heat recovery system or a water cooling + liquefied CO2 cooling and waste heat recovery system or a molten salt power generation system, so that it is rapidly cooled to below 500°C. After rapid cooling and salt washing, the cement clinker can be converted into a finished product.

2. The process and equipment for semi-dry cement clinker graded calcination and CO2 capture according to claim 1, characterized in that: The raw material powder is first pulped, filtered, and broken up, and then enters a raw material preheating three-leaf rotary kiln (1) in which the raw material is dispersed and semi-suspended by gravity to complete preheating. Then, the first CO2 gas is decomposed and the material discharge controller (2) is used to achieve gas-solid separation. After that, the raw material powder enters a slightly negative pressure, closed, electrically heated, material-dispersed semi-suspended by gravity, uniform cross-solid phase reaction closed electrically heated three-leaf rotary kiln (4) that can directly capture high-concentration or high-purity CO2 and lightly burn dicalcium silicate. The raw material is preheated at 800°C and 8 The materials enter the closed electric heating three-leaf rotary kiln (4) at different temperatures of 100-900°C and 900-1100°C, and the materials undergo a uniform cross-solid phase reaction in a dispersed semi-suspended form by gravity. The electric heating temperature, intensity, frequency, etc. are controlled to balance the heat absorption of carbonates and the exothermic reaction of dicalcium silicate, the capture of CO2, etc., and the sintering temperature of the closed electric heating three-leaf rotary kiln (4) is always controlled to be 1100-1200°C, so as to induce the formation of high silicate minerals mainly composed of C3A, C4AF, and C2S in the kiln. The operating structure of the closed electric heating three-leaf rotary kiln (4) makes the materials in the kiln in a dispersed semi-suspended form.

3. The process and equipment for semi-dry cement clinker graded calcination and CO2 capture according to claim 1, characterized in that: After reacting in the closed electric heating three-blade rotary kiln (4) for 5 minutes, the material falls into the oxygen-enriched calcination rapid melting rotary kiln (8) at a temperature of 1250° C. The oxygen-enriched calcination rapid melting rotary kiln (8) uses coal powder as fuel and then introduces pure oxygen prepared by an oxygen generator. The high-belite cement clinker that completes the cross-solid phase reaction in the closed electric heating three-blade rotary kiln (4) continues to be oxygen-enriched calcined in the oxygen-enriched calcination rapid melting rotary kiln (8) for about 25 minutes. The high-belite cement clinker then directly enters the water cooling + liquefied nitrogen cooling and waste heat recovery system or the water cooling + liquefied CO2 cooling and waste heat recovery system or the molten salt power generation system at a temperature of 1450° C. to complete sufficient rapid cooling. The formation of tricalcium silicate minerals is promoted, and steel slag powder seeds are added to the feeding end of the oxygen-enriched calcination rapid melting rotary kiln (8) to achieve a rapid melting reaction of oxygen-enriched calcination.

4. The process and equipment for semi-dry cement clinker graded calcination and CO2 capture according to claim 1, further characterized by: The solid phase reaction process for generating dicalcium silicate as the main mineral is carried out in an electrically heated, sealed three-leaf rotary kiln (4). While the solid phase reaction is taking place, the high concentration or high purity CO2 decomposed from the carbonate is directly captured by a slight negative pressure method.

5. The process and equipment for semi-dry cement clinker graded calcination and CO2 capture according to claim 1, further characterized by: The kiln head and kiln tail of the closed electrically heated three-blade rotary kiln (4) are both in at least two forms, namely, a labyrinth type (tortuous path type), a contact type (friction type) and a gas-sealed type. A first CO2 gas decomposition and unloading controller (2) and a second CO2 gas decomposition and unloading controller (3) are arranged at the feeding end and the discharging end to achieve gas-solid separation and complete sealing.

6. The process and equipment for semi-dry cement clinker graded calcination and CO2 capture according to claim 1, further characterized by: After reacting for 5 minutes in the closed electrically heated three-blade rotary kiln (4), the material is decomposed at 1250°C by the second CO2 gas and separated into gas and solid by the material discharge controller (3). The material can then directly fall into a water cooling + liquefied nitrogen cooling and waste heat recovery system or a water cooling + liquefied CO2 cooling and waste heat recovery system or a molten salt power generation system to be fully quenched to below 500°C, and then further utilize molten salt / CO2 / nitrogen for waste heat recovery.

7. The process and equipment for semi-dry cement clinker graded calcination and CO2 capture according to claim 1, further characterized by: After reacting in the closed electric heating three-blade rotary kiln (4) for 5 minutes, the material is decomposed by the second CO2 gas at a temperature of 1250°C and separated by gas and solid by the feed controller (3). The material then falls directly into the oxygen-enriched calcination rapid melting rotary kiln (8), which uses coal powder as fuel and then introduces pure oxygen prepared by an oxygen generator. The high-belite cement clinker that has basically completed the solid phase reaction in the closed electric heating three-blade rotary kiln (4) continues to be calcined in the oxygen-enriched calcination rapid melting rotary kiln (8) for 25 minutes. The high-belite cement clinker is then heated to 1350°C. The temperature of the raw material is directly cooled to below 500°C by water cooling + liquefied nitrogen cooling and waste heat recovery system or water cooling + liquefied CO2 cooling and waste heat recovery system or molten salt power generation system, and then the molten salt / CO2 / nitrogen is used for efficient waste heat recovery. In order to promote the formation of tricalcium silicate minerals, steel slag powder seeds are added to the feeding end of the oxygen-enriched calcination rapid melting rotary kiln (8) to achieve a rapid melting reaction of oxygen-enriched calcination. At this time, the cooled material is high alite cement clinker mainly composed of tricalcium silicate.

8. The process and equipment for semi-dry cement clinker graded calcination and CO2 capture according to claim 1, further characterized by: The flue gas discharged from the raw material preheating three-leaf rotary kiln (1) enters the waste heat recovery system after heat exchange through the boiler, and is finally discharged after reaching the standard. The heat energy of the raw material preheating three-leaf rotary kiln (1) is sprayed into the kiln by the coal injection device to complete the preheating. Under the control of the electric heating temperature, intensity, frequency and the heat balance of the carbonate endothermic reaction and the exothermic reaction of dicalcium silicate and the capture of CO2, and the pressure in the kiln, the particle size of the material, the reaction time, and the reaction environment (uniformity, segregation), the material is solid-phase reacted in the closed electric heating three-leaf rotary kiln (4) for 5 minutes, and when the material is discharged at a temperature of 1250°C, the material is mainly lightly burned dicalcium silicate. After the solid-phase reaction in the closed electric heating three-leaf rotary kiln (4) generates silicate minerals mainly composed of dicalcium silicate, At the rear end of the kiln, the material enters a water cooling + liquefied nitrogen cooling and waste heat recovery system or a water cooling + liquefied CO2 cooling and waste heat recovery system or a molten salt power generation system to directly produce high-belite cement clinker. After the reaction of the silicate minerals mainly composed of C2S in the closed electric heating three-blade rotary kiln (4) is basically complete, the material enters an oxygen-enriched calcination rapid melting rotary kiln (8) and is melt-calcined at 1450°C to generate cement clinker minerals mainly composed of alite. The high-belite cement clinker generated by the calcination is rapidly cooled using a water cooling + liquefied nitrogen cooling and waste heat recovery system or a water cooling + liquefied CO2 cooling and waste heat recovery system or a molten salt power generation system to achieve α-type or α-biased clinker minerals, reduce β-type silicate minerals, and optimize the silicate mineral composition in the cement clinker.

9. The process and equipment for semi-dry cement clinker graded calcination and CO2 capture according to claim 1, characterized in that: The production process of preheating the raw material preheating three-leaf rotary kiln (1), calcining dicalcium silicate and tricalcium silicate separately, the functional design of the kiln for calcining separately, the design of kiln firing parameters and system, and the improvement of the rapid cooling method are subjected to various changes, modifications, replacements and variants. The process equipment can carry out appropriate technical transformation and equipment renewal for various types of existing new dry process cement clinker production lines. The firing temperature control fluctuation range of each subsystem can be accurately within ±10°C. The total firing time of the material in the closed electric heating three-leaf rotary kiln (4) and the oxygen-enriched calcining rapid melting rotary kiln (8) is 30 minutes, which is about 15 minutes less than the total firing time of new dry process cement clinker and wet process cement clinker. The internal structure of the kiln body of the raw material preheating three-leaf rotary kiln (1) and the closed electric heating three-leaf rotary kiln (4) are both three-leaf, and the material can exist in the kiln in a dispersed state or a semi-suspended state by gravity.

10. The process and equipment for semi-dry cement clinker graded calcination and CO2 capture according to claim 1, further characterized by: In addition to producing high-belite cement clinker and high-alite cement clinker, the process and equipment also include producing white cement clinker, sulphoaluminate cement clinker, aluminate cement clinker and oil well cement clinker by adjusting ingredients and process parameters.

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