Kiln system for calcining cement without fossil energy

Abstract

The invention belongs to the technical field of cement processes, and particularly relates to a kiln system for calcining cement with zero fossil energy, the kiln system for calcining cement with zero fossil energy comprises a rotary kiln, the rotary kiln is provided with an ammonia hydrogen burner, and the ammonia hydrogen burner comprises a rotary kiln burner ammonia supply channel and a rotary kiln burner hydrogen supply channel. The invention provides a kiln system for calcining cement without fossil energy.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of cement process, and particularly relates to a kiln system for calcining cement with zero fossil energy. BACKGROUND

[0002] The cement industry is a typical high-temperature process industry, and the main sources of carbon dioxide emissions thereof include process emissions of limestone decomposition and fuel combustion emissions of calcination heat supply. For a long time, fossil fuels such as coal, heavy oil and petroleum coke have been the main force to provide high-temperature heat sources, resulting in high carbon emission intensity and great difficulty in emission reduction of the industry. In order to achieve the targets of carbon peak and carbon neutrality, the industry is exploring multiple low-carbon paths, including reducing the clinker factor, improving energy efficiency, electrifying heat supply, using zero-carbon fuels, and deploying carbon capture, utilization and storage (CCUS) technology. Among them, with the development of the green and clean energy industry, the cement industry is also constantly trying to use clean energy to realize the calcination process to eliminate CO2 emissions at the fuel end of the cement burning system. In recent years, with the rapid growth of renewable energy installations, the use of green electricity, green hydrogen and green ammonia and other clean energy to provide high-temperature heat sources for the heat demand of cement calcination has become an important research direction.

[0003] However, the existing technology still has outstanding challenges in high-temperature stable heat supply, long-distance transportation of hydrogen and comprehensive energy efficiency utilization of the system. Direct electric heating technologies represented by induction heating and plasma heating have high heating efficiency, and the liquid phase reaction in the cement burning process requires a calcination temperature of 1380-1450℃ to form C3S mineral-related bond components, but most current electric heating technologies are more suitable for calcination conditions with a temperature less than 1000℃. In addition, in the scene of "long distance, large scale" cross-regional allocation of clean energy, ammonia has obvious comprehensive advantages over hydrogen, it is easier to liquefy, has higher volumetric energy density, a more mature and low-cost storage and transportation system, extremely low transportation and distribution loss, and can be used as an efficient "hydrogen carrier" to obtain hydrogen by cracking at the end. When flame conditions are needed or compatibility with existing combustion equipment is required, ammonia is also more conducive to rapid landing. However, ammonia is a "difficult to ignite, slow to burn, low radiation, high NO x x" non-carbon fuel, and incomplete combustion will cause ammonia escape problems. Ammonia and hydrogen co-combustion or under oxygen-rich combustion conditions can significantly improve ignition and stability, but the high-temperature conditions required for ammonia cracking to produce hydrogen lead to an increase in product cost, which is one of the main factors restricting the industrial application of ammonia clean utilization technology.

[0004] The existing technologies for carbon emission reduction in the production of cement clinker by using green ammonia, green hydrogen and electric heating include the following: CN 116670457 A discloses a vertical reactor tube, in which the falling powder is heated by radiation from the outer heating wall of the reactor tube in the heating zone and its vicinity, but the invention mainly relies on the heat transfer mode of the tube wall, and its capacity for expanding production scale is limited, and it can only improve the production capacity by integrating parallel operation. In addition, since the materials in the furnace move from top to bottom, and the cement raw material has the characteristics of wide particle size range window and calcium raw material concentrated in the small particle size range, the particles with small particle size are prone to flow in the opposite direction under the action of negative pressure in the furnace, causing short circuit of calcium raw material and imbalance of the proportion of each group of raw material, affecting the quality of clinker.

[0005] CN 116817593 A discloses a system and method for green hydrogen-green ammonia fuel calcination of cement clinker, which proposes to use photovoltaic power generation to electrolyze water, and the generated oxygen is used as a combustion aid for oxygen-enriched combustion of a rotary kiln or cooling air for a grate cooler. Green hydrogen is used to synthesize ammonia, and green hydrogen and / or green ammonia are introduced into a decomposition furnace to replace coal, but the invention still has problems, including: (1) Ammonia hydrogen only replaces part of the coal powder in the decomposition furnace, and the rotary kiln still uses coal powder as fuel. In the cement production process, CO2 generated by fuel in the rotary kiln accounts for about 40% of the total CO2 generated by fuel, so this process does not completely solve the problem of carbon emission. (2) There is no excess heat in the cement process system based on the combustion process, and the high temperature and high pressure conditions required for ammonia synthesis require additional heat input, which will significantly increase the cost of cement clinker production. SUMMARY

[0006] The present application aims to solve the technical problems in the prior art and provides a kiln system for zero fossil energy calcination of cement.

[0007] The technical solutions adopted by the embodiments of the present application to solve the technical problems in the prior art are as follows: A kiln system for zero fossil energy calcination of cement, comprising a rotary kiln, wherein an ammonia hydrogen burner is arranged on the rotary kiln, and the ammonia hydrogen burner comprises a rotary kiln burner ammonia supply channel and a rotary kiln burner hydrogen supply channel.

[0008] The embodiments of the present application can also adopt the following technical solutions: In the above-mentioned kiln system for zero fossil energy calcination of cement, further, the rotary kiln burner ammonia supply channel gasification device is connected with a liquid ammonia storage tank; The rotary kiln burner hydrogen supply channel is connected with a nitrogen hydrogen separation device, and the liquid ammonia storage tank, the gasification device, the first heat exchange equipment, the ammonia in-situ cracking device, the second heat exchange equipment and the nitrogen hydrogen separation device are connected in sequence.

[0009] In the above-mentioned fossil-free energy calcining cement kiln system, further, the fossil-free energy calcining cement kiln system further comprises a cooler, an outlet pipeline of the cooler is divided into two routes, one route is communicated with the first heat exchange device, and the other route is connected with the waste heat boiler, the outlet of the first heat exchange device and the outlet of the waste heat boiler are connected with the dust collector; the first heat exchange device hot stream import pipeline is connected with the outlet pipeline of the cooler and the second heat exchange device cold stream outlet pipeline.

[0010] In the above-mentioned fossil-free energy calcining cement kiln system, further, the fossil-free energy calcining cement kiln system further comprises an electric direct heating decomposition furnace.

[0011] In the above-mentioned fossil-free energy calcining cement kiln system, further, the electric direct heating decomposition furnace adopts one of the following three electric direct heating decomposition furnaces: An internal heating induction heating electric direct heating decomposition furnace: the internal heating induction heating electric direct heating decomposition furnace comprises an internal heating induction heating device, and an alternating current magnetic flux can be generated in a coil of the internal heating induction heating device; An external heating induction heating electric direct heating decomposition furnace: the external heating induction heating electric direct heating decomposition furnace comprises an external heating induction heating device, and an alternating magnetic field formed by the external heating induction heating device forms an induced eddy current on the surface of a magnetic conductor, and the induced eddy current generates heat; A plasma torch electric direct heating decomposition furnace: the plasma torch electric direct heating decomposition furnace comprises a plasma torch, an electric arc formed between two electrodes, a gas penetrating the electric arc is ionized into a plasma state with electric conductivity, and a temperature of the electric arc is reached through Joule heating.

[0012] In the above-mentioned fossil-free energy calcining cement kiln system, further, the electric direct heating decomposition furnace, the flue gas chamber, the rotary kiln and the cooler are sequentially connected, a discharge pipe of a penultimate stage preheating separator in the multi-stage preheating separator is connected with the electric direct heating decomposition furnace, an outlet of the electric direct heating decomposition furnace is connected with an air inlet pipe of a last stage preheating separator in the multi-stage preheating separator, a discharge pipe of the last stage preheating separator in the multi-stage preheating separator is connected with the flue gas chamber, and an air outlet pipe of a first stage preheating separator in the multi-stage preheating separator is connected with the flue gas treatment system.

[0013] In the above-mentioned fossil-free energy calcining cement kiln system, further, the cooler is a grate cooler, the grate cooler comprises a first stage cooling subzone of the grate cooler, a second stage cooling subzone of the grate cooler and a third stage cooling subzone of the grate cooler, a cooling medium of the second stage cooling subzone of the grate cooler and the third stage cooling subzone of the grate cooler is air, and a cooling medium of the first stage cooling subzone of the grate cooler is air or a mixed gas composed of high-concentration industrial oxygen and circulating flue gas containing O2 / CO2 / N2.

[0014] In the kiln system for the zero-fossil-energy calcined cement, further, when the cooling medium of the first-stage cooling section of the grate cooler is a mixed gas composed of high-concentration industrial oxygen and circulating flue gas containing O2 / CO2 / N2, the flue gas treatment system is connected with the flue gas carbon capture device and the first-stage cooling section of the grate cooler, and the first-stage cooling section of the grate cooler is connected with the air separation device.

[0015] A process for zero-fossil-energy calcined cement, which adopts the kiln system for the zero-fossil-energy calcined cement according to any one of the above.

[0016] In the process for zero-fossil-energy calcined cement, further, the H2 / NH3 volume ratio of the ammonia-hydrogen burner is 0.01-0.25.

[0017] The one or more technical solutions provided in the embodiments of the present application have at least the following beneficial effects: 1. The energy hierarchical utilization process of electric direct heating coupled with ammonia-hydrogen combustion completely eliminates the CO2 emission at the fuel end in the cement clinker sintering process, and can reduce the carbon emission of the cement industry by more than 40%. At the same time, the CO2 at the raw material end can be effectively enriched, and the operation cost of carbon capture of the cement industry is significantly reduced.

[0018] 2. The present application utilizes the cement kiln waste heat to provide energy source for the high-temperature ammonia cracking process, proposes a coupling process of flue gas waste heat recovery path and ammonia decomposition hydrogen production, and provides an economically feasible process scheme for the cement industry to produce clinker by using clean energy.

[0019] 3. The present application fully considers the adverse effects of CO2 equilibrium partial pressure inhibiting the decomposition rate in the carbonate decomposition process and the decline of raw material decomposition rate caused by the change of main heat transfer mode, and through the regulation of flue gas components, the CO2 partial pressure is reduced and the residence time of raw material in the kiln is prolonged, so that the raw material can meet the requirement of decomposition rate at the conventional decomposition temperature.

[0020] 4. The present application adjusts the ammonia-hydrogen supply ratio through the ammonia online upgrading feed process route to adapt to the flame thermal intensity, length and temperature of the rotary kiln sintering zone, and ensures the stability of the thermal system of the cement sintering system and the quality of the clinker.

[0021] 5. The application utilizes green electricity, green hydrogen and green ammonia by means of electric direct heating and ammonia-hydrogen mixed combustion energy grading, uses electricity for direct heating of fuel for the decomposition furnace, and uses ammonia-hydrogen mixed combustion for the rotary kiln clinker burning, realizes stable and efficient heating in the full temperature range of 900-1450℃, and improves the source separation and efficient capture of CO2 in the process. At the same time, the waste heat of the cooler can be fully utilized to provide heat source for ammonia online cracking, ensuring the optimal energy efficiency of the system. The process system and method provided by the patent can significantly reduce carbon emissions per unit product while ensuring clinker quality and meeting environmental protection standards, and form a system solution with optimal energy efficiency throughout the chain. BRIEF DESCRIPTION OF DRAWINGS

[0022] The technical solutions of the embodiments of the application will be further described in detail below with reference to the drawings, but it should be understood that these drawings are designed for explanatory purposes only, and therefore do not limit the scope of the application. In addition, unless specifically indicated, these drawings are only intended to conceptually illustrate the structural configurations described herein, and are not necessarily drawn to scale.

[0023] Figure 1 is a kiln system for calcining cement with zero fossil energy provided by an embodiment of the application, using air as a combustion medium; Figure 2 is a kiln system for calcining cement with zero fossil energy provided by an embodiment of the application, using industrial oxygen as a combustion medium; Figure 3 is a schematic diagram of an internal heating induction heating electric direct heating decomposition furnace provided by an embodiment of the application; Figure 4 is a schematic diagram of an external heating induction heating electric direct heating decomposition furnace provided by an embodiment of the application; Figure 5 is a schematic diagram of a plasma torch electric direct heating decomposition furnace provided by an embodiment of the application.

[0024] In the drawings: 1, grate cooler; 2, burner; 3, rotary kiln; 4, electric direct heating decomposition furnace; 5, multi-stage preheating separator; 6, smoke chamber; 7, flue gas treatment system; 401, internal heating induction heating device; 402, external heating induction heating device; 403, plasma torch; 404, temperature measuring thermocouple 8, liquid ammonia storage tank; 9, gasification device; 10, first heat exchange equipment; 101, retaining wall; 11, ammonia in-situ cracking device; 12, second heat exchange equipment; 13, nitrogen-hydrogen separation device; 14, waste heat boiler; 15, dust collector; 16, chimney; 17, air separation device; 18, flue gas carbon capture device. DETAILED DESCRIPTION

[0025] For better understanding of the above technical solutions, the above technical solutions will be described in detail below in combination with the description of the accompanying drawings and specific embodiments.

[0026] Embodiment one As shown in the description of the accompanying drawings Figure 1 The last stage preheating separator in the multi-stage preheating separator 5 of the embodiment is directly connected with the outlet of the electric direct-heating decomposing furnace 4, the bottom of the electric direct-heating decomposing furnace 4 is the flue gas inlet, the electric direct-heating decomposing furnace 4 is directly communicated with the rotary kiln 3 through the smoke chamber 6, and the outlet of the rotary kiln 3 is directly connected with the grate cooler 1. The electric direct-heating decomposing furnace 4 is internally or externally provided with an electric heating conversion device, and the rotary kiln 3 is internally provided with an ammonia-hydrogen burner.

[0027] The cooling medium in the grate cooler for cooling the clinker is divided into three paths to enter the grate cooler and exchange heat with the clinker. The first-stage cooling partition, the second-stage cooling partition and the third-stage cooling partition of the grate cooler are all communicated with air to rapidly cool the clinker to 60-100℃ to obtain the cement clinker product.

[0028] The outlet of the second-stage cooling partition of the grate cooler is divided into two paths, one of which is communicated with the first heat exchange equipment 10, and the other of which is connected with the waste heat boiler 14. The outlet of the first heat exchange equipment 10 and the outlet of the waste heat boiler 14 are both connected with the dust collector 15, and the air after waste heat utilization of the grate cooler is discharged after being collected by the kiln head chimney 16.

[0029] Compared with the decomposing furnace system with a combustion process, the cooling air with heat enthalpy is usually introduced into the decomposing furnace as the third air for combustion. However, for the electric direct-heating decomposing furnace system proposed in the embodiment, the cooling air with heat enthalpy needs to be utilized as much as possible to ensure the thermal efficiency of the grate cooler 1. Therefore, the second-stage cooling medium of the grate cooler 1 is introduced into the first heat exchange equipment 10 in the embodiment, thereby improving the overall waste heat utilization efficiency of the system.

[0030] The liquid ammonia storage tank 8 is communicated with the ammonia in-situ cracking device 11. The gasification device 9 and the first heat exchange equipment 10 are arranged between the liquid ammonia storage tank and the ammonia in-situ cracking device. The outlet of the gasification device 9 is respectively connected with the ammonia supply channel of the rotary kiln burner and the inlet of the first heat exchange equipment 10. The cold stream at the inlet of the first heat exchange equipment 10 is ammonia gas, and the hot stream is air exchanged with the clinker after the second-stage cooling partition of the grate cooler. The flow of the hot stream entering the first heat exchange equipment 10 is adjusted by a valve.

[0031] The outlet of the hot stream of the first heat exchange equipment 10 is connected with the inlet of the ammonia in-situ cracking device 11. The ammonia in-situ cracking device 11 is a fixed bed reactor filled with Pt, Pd, Ru, Ni, Fe and Co-based active reaction catalysts. The device reaction temperature is kept constant at a certain temperature in the range of 550-850℃ by means of indirect heat exchange coil or auxiliary electric heating, and H2 / N2 mixed gas with an ammonia decomposition rate ≥95% is obtained.

[0032] The outlet of the ammonia in-situ cracking device 11 is connected to the inlet of the second heat exchange device 12, the inlet hot stream is ammonia cracking gas, and the cold stream is air.

[0033] The outlet of the second heat exchange device 12 is connected to the inlet of the nitrogen-hydrogen separation device 13, the outlet of the nitrogen-hydrogen separation device 13 is directly connected to the hydrogen supply channel of the rotary kiln burner, and high-concentration H2 is supplied into the separation. The nitrogen-hydrogen separation device 13 is preferably temperature swing adsorption, and high-concentration H2 generated in-situ cracking is obtained through selective adsorbents in the bed.

[0034] The raw material is preheated to 700-800°C in the multi-stage preheating separator 5 and then enters the electric direct-heating decomposition furnace 4. The electric direct-heating decomposition furnace 4 is internally / surfacely arranged with an electric heating conversion device, and an internal heating / external heating induction heating / plasma torch heating mode is selected to provide a stable heat source for the decomposition of the raw material.

[0035] In order to improve the heat transfer efficiency of the raw material within a certain time, the combustion flue gas from the rotary kiln 3 enters the electric direct-heating decomposition furnace 4 through the smoke chamber 6 under the action of the fan, and the heat energy generated by the electric heating conversion process is transferred to the raw material particles within a certain particle size range through convection and radiation by using the suspension and dispersion process of the combustion flue gas entraining the raw material, so that the raw material is uniformly heated, and the particle size range of the raw material is 5-100 μm; the suspension calcination time of the raw material in the furnace is 5-15 s, and the outlet temperature of the electric direct-heating decomposition furnace 4 is controlled to be in the range of 800-950°C, so that the decomposition rate of the raw material is ≥85%. The raw material reaching a certain decomposition rate enters the rotary kiln 3 through the last-stage preheating separator.

[0036] The outlet of the first-stage preheater in the multi-stage preheating separator 8 is connected to the flue gas treatment system 7, and gas pollutants such as NO, NO2, N2O, SO2 and part of the condensed water are removed. Further, in this embodiment, a flue gas carbon capture device can be arranged after the flue gas treatment system 7, and at this time, the dry basis CO2 concentration entering the flue gas carbon capture device is 25%-35%.

[0037] This embodiment can fully utilize green electricity and green ammonia clean energy to provide a stable and efficient heat source for the cement plant, realize efficient decomposition of the cement raw material through the direct heating effect of green electricity, and make the raw material decompose under the action of the generated high-temperature flue gas or radiation heat by using built-in or external induction heating or plasma torch. The combustion characteristics of NH3 and the cracking products mainly containing H2 and combustion aids in the rotary kiln make the flame have the basic characteristics of high temperature and long flame, and greatly reduce the carbon emission of the cement firing system.

[0038] Embodiment Two This embodiment includes the following steps: Material flow direction: Step one, raw meal is preheated in multi-stage preheating separator 5 and enters the electric direct-heating decomposing furnace 4. At this time, the flue gas produced by combustion and the CO2 mixed gas produced by decomposition enter the multi-stage preheating separator 5, and the high-temperature flue gas exchanges heat with the raw meal fed into the multi-stage preheating separator, recovering the heat enthalpy of the flue gas.

[0039] Step two, the electric direct-heating decomposing furnace 4 provides a stable heat source for the decomposition of raw meal by the electric heating conversion device arranged inside / surface of the furnace. The combustion flue gas out of the rotary kiln 3 enters the electric direct-heating decomposing furnace 4 synchronously under the action of the fan. Since the decomposition reaction of calcium carbonate / magnesium carbonate in the raw meal in the furnace is controlled by kinetics, the heat energy is transferred to the raw meal particles within a certain particle size range by convection and radiation heat transfer through the process of suspension and dispersion of the raw meal entrained by the combustion flue gas, so that the raw meal is uniformly heated, and the raw meal with a certain decomposition rate enters the rotary kiln 3 through the last-stage preheating separator of the multi-stage preheating separator 5.

[0040] Step three, the material out of the rotary kiln enters the grate cooler 1, at this time, the cooling medium for cooling clinker in the grate cooler 1 is divided into three paths and enters the grate cooler to exchange heat with the clinker.

[0041] Gas flow direction: Step one, liquid ammonia is controlled by a valve group to enter the liquid ammonia storage tank 8 under working pressure, and the ammonia gas is generated by heat exchange between the circulating water / heat conducting oil and the ammonia liquid fuel stored in the liquid ammonia storage tank 8 in the gasification device 9. The temperature of the generated ammonia gas is between ambient temperature and 60℃.

[0042] Step two, the ammonia gas is divided into two parts for feeding, the first ammonia gas stream is directly introduced into the rotary kiln 3 through the Roots blower via the gasification device 9 outlet for ammonia supply channel of the kiln head burner, and the second ammonia gas stream is indirectly heat-exchanged to 380~550℃ in the first heat exchange equipment 10. The first heat exchange equipment 10 hot stream inlet selects the heat exchange air out of the second cooling partition of the grate cooler and the mixed air out of the second heat exchange equipment 12. According to the required preheating temperature of ammonia gas, the second ammonia gas stream can be preheated by one or more stages, and the heat-exchanged and heated ammonia gas enters the ammonia in-situ cracking device 11.

[0043] Step three, the ammonia in-situ cracking device 11 keeps the device reaction temperature constant by indirect heat exchange or auxiliary electric heating, and obtains a mixed gas of H2, N2 and a small amount of unconverted ammonia by catalytic decomposition or plasma-assisted catalytic decomposition. The H2 / N2 mixed gas is heat-exchanged with conventional air in the second heat exchange equipment 12, which can be preheated by one or more stages, so that the mixed gas is cooled to ambient temperature~50℃.

[0044] Step four, the mixed gas enters the nitrogen-hydrogen separation device 13, and the excess N2 is discharged by using pressure swing adsorption / temperature swing adsorption / membrane separation to obtain high-concentration H2, which is introduced into the rotary kiln head burner for hydrogen supply channel by the Roots blower. In order to effectively inhibit the formation of thermal NO xThe H2 / N2 volume ratio in the hydrogen supply channel is 0.25-0.6.

[0045] Preferably, the temperature of the flue gas is kept above the acid dew point before entering the flue gas treatment system 7, and the NO, NO2, N2O and SO2 in the flue gas are removed in sequence by the SCR and wet / half-dry desulfurization process after entering the flue gas treatment system 7, so that the NO x to meet the emission requirements, SO2 in the flue gas ≤5 mg / Nm 3 , and the temperature is reduced to ambient temperature-60℃, and the flue gas is washed and cooled by water and the condensed water is removed by a gas-water separator.

[0046] Preferably, based on the combustion characteristics of ammonia and hydrogen, the H2 / NH3 volume ratio and the air supply channel of the burner are coordinated to make the combustion process uniform and stable, the H2 / NH3 volume ratio entering the burner of the rotary kiln is controlled to be 0.01-0.25, the average flame temperature of ammonia-hydrogen combustion is 1600-1800℃, and the flame length is in the range of 4.5-5.5 times the diameter of the rotary kiln.

[0047] The main components of the ammonia-hydrogen combustion products are H2O and N2, and the atmosphere characteristics formed by them have a significant promoting effect on the decomposition kinetics of carbonates in the electric direct-heating decomposition furnace 4. According to the experimental research and theoretical calculation results, increasing the H2O partial pressure is beneficial to the forward reaction, and its promoting effect on decomposition is more significant than N2. Compared with the conventional coal-fired cement production system (H2O in the flue gas chamber ≤5% vol.), the ammonia-hydrogen combustion process in the rotary kiln 3 makes the H2O content in the flue gas chamber 6 ≥30%. Therefore, from the perspective of kinetics, the outlet temperature of the electric direct-heating decomposition furnace 4 can be maintained in a similar temperature range as the conventional production system, which can ensure the decomposition rate of raw meal.

[0048] In order to improve the heat transfer efficiency of raw meal within a certain time, the particle size of raw meal is controlled in the range of 5-100 μm, the suspension calcination time of raw meal in the electric direct-heating decomposition furnace 4 is ≥15 s, and the outlet temperature of the electric direct-heating decomposition furnace 4 is controlled in the range of 800-950℃, so that the decomposition rate of raw meal is ≥85%.

[0049] In order to avoid the liquid phase formed by Al, Fe, Na, K and other solvent components in raw meal at high temperature from accumulating on the surface of the heating element in the electric direct-heating decomposition furnace 4 to hinder the heat transfer process, the maximum temperature of the heating element in the internal heating induction heating device 401 or the external heating induction heating device 402 is controlled to be ≤1200℃.

[0050] Since the ammonia-hydrogen combustion process still produces thermal NO x Therefore, a first-stage NO xThe non-reduction reaction (SNCR) pathway has a reaction temperature window range of 950~1050℃. The cone and inner cylinder outlet of the final stage preheating separator in the multi-stage preheating separator 5 are equipped with a second-stage NO₂. x The non-reduction reaction (SNCR) pathway operates within a temperature window of 750–950°C. The reduction medium is ammonia gas drawn from the gasification unit 9, which reduces NO in the flue gas discharged from the multi-stage preheating separator 5. x In 100~250 mg / Nm 3 .

[0051] Example 3 As per the instruction manual Figure 2 As shown, this embodiment adds an air separation device 17 and a flue gas circulation pipeline to the first embodiment. Additionally, the grate cooler 1 in this embodiment features a centrally located roller crusher, and the cooling zone is divided into three sections. The cooling medium in the first cooling zone of the grate cooler is a mixture of high-concentration industrial oxygen and circulating flue gas containing O2 / CO2 / N2. The cooling medium in the second and third cooling zones of the grate cooler is air. The outlet of the second cooling zone of the grate cooler is divided into two paths: one connected to the first heat exchanger 10, and the other connected to the waste heat boiler 14.

[0052] After impurities are removed by the flue gas treatment system 7, the flue gas undergoes water washing and cooling, and condensate is removed by a gas-liquid separator. Depending on the CO2 concentration in the flue gas, one stream of flue gas can enter the flue gas carbon capture device 18 to obtain CO2 product. The dry basis CO2 concentration entering the flue gas carbon capture device 18 is 70%~95%. Another stream can be connected to the cooling medium supply duct of the first cooling section of the grate cooler, serving as circulating flue gas entering the grate cooler 1. Simultaneously, the air separator 17 is connected to the cooling medium supply duct of the first cooling section of the grate cooler. Valves are installed on the duct, and the oxygen concentration in the supplied mixed gas is adjusted by regulating the circulating airflow. The air separator 17 can utilize pressure swing adsorption or cryogenic distillation techniques to produce high-concentration oxygen with an oxygen volume fraction ≥85%.

[0053] The high-concentration O2 generated by the air separator 17 and the circulating flue gas treated by the flue gas form a certain O2 concentration of regulated combustion gas. This gas enters the grate cooler 1 and exchanges heat fully with the hot clinker. It then enters the rotary kiln 3 as secondary air to stabilize the flame combustion, giving the ammonia-hydrogen combustion flame the characteristics of high temperature and long flame, thus meeting the radiant heat intensity and residence time required for clinker formation in the rotary kiln.

[0054] Furthermore, the grate cooler is equipped with baffles 101 in the first and second cooling zones, and a centrally located roller crusher cooling system is adopted to reduce cross-flow between cooling zones. The cooling medium in the first cooling zone is a mixture of high-concentration industrial oxygen and circulating flue gas. The air separator 17 is connected to the cooling medium supply pipeline of the first cooling zone, and valves are installed on the pipeline. The oxygen concentration in the supplied mixture is adjusted by regulating the circulating air volume, thereby controlling the volume fraction of N2 in the flue gas to 20%~30%, so that the dry basis CO2 concentration entering the flue gas carbon capture device 18 is 70%~95%. Compared with the dry basis CO2 concentration of 25%~35% entering the flue gas carbon capture device in Example 1, this embodiment can significantly increase the carbon dioxide enrichment concentration of the cement kiln by changing the composition of the combustion aid, thereby reducing the capture cost.

[0055] Example 4 Based on Example 3, this embodiment calculates the oxygen volume fraction in the cooling medium of the first cooling zone of the grate cooler to be 21%~45% per kg of clinker, the temperature range of the material entering the rotary kiln 3 is 1100~1250℃, and the cooling air volume is 0.18~0.25 Nm³. 3 The cooling medium in the second-stage cooling zone of the grate cooler is conventional air, and the temperature range of the cooled clinker is 580~690℃; the cooling air volume is 1.2~1.4 Nm³. 3 The cooling medium for the three-stage cooling zone of the grate cooler is conventional air. The temperature range of the hot air exiting the three-stage cooling zone is 150~350℃, and the air volume required for cooling is 0.15~0.4 Nm³. 3 The temperature of the clinker after cooling by the grate cooler 1 is 60-100℃.

[0056] The clinker cooling air entering the first heat exchanger 10 from the second-stage cooling zone of the grate cooler has an intake air volume of 0.36~0.62 Nm³. 3 The ammonia gas temperature in the first heat exchanger 10 reaches 380~550℃; the remaining air enters the waste heat boiler 14 at the kiln head, and the generated electricity is used for the ammonia in-situ cracking unit 11.

[0057] The reaction bed temperature of the ammonia in-situ cracking unit 11 is kept constant within the range of 550~850℃, so that the conversion rate of ammonia gas under the assistance of active catalyst and plasma torch is ≥95%. The heating method of the ammonia in-situ cracking unit 11 can utilize one or more combined methods such as gas indirect heat exchange, resistance heating, and induction heating.

[0058] The flue gas and CO2 mixture generated during decomposition in the kiln enter the multi-stage preheating separator 5. The high-temperature flue gas exchanges heat fully with the raw material fed into the multi-stage preheating separator 5, recovering the enthalpy of the flue gas. The flue between the outlet of the first-stage cyclone of the multi-stage preheating separator 5 and the flue gas treatment system 7 is controlled to maintain the temperature between 200 and 250°C through insulation measures to prevent the flue gas temperature from reaching the acid dew point, which would cause the volatile sulfur in the raw material to condense and corrode the pipes and equipment.

[0059] Flue gas treatment system 7 uses SCR to reduce NO x To meet emission requirements, further wet / semi-dry desulfurization is performed to ensure SO2 in the flue gas is ≤5 mg / Nm³. 3 The temperature drops to ambient temperature ~60℃.

[0060] Example 5 As per the instruction manual Figure 3 As shown, the electrothermal conversion device in the internal heating induction heating direct-heating decomposition furnace includes a power supply unit for providing alternating current, an insulation unit for generating an induced current in response to the alternating current, an internal heating induction heating device 401 for resistance heating through the induced current, and a temperature measuring thermocouple 404. The insulation unit can be composed of a transformer, which generates an induced current in response to the alternating current. The internal heating induction heating device 401 can be composed of a coil, which performs resistance heating through a first induced current generated by the transformer. The first induced current generated by the transformer is an alternating current signal, corresponding to the alternating current signal input to the transformer. When the first induced current of the alternating current signal is input to the coil of the internal heating induction heating device 401, an alternating magnetic flux that changes according to the first induced current is generated in the coil of the internal heating induction heating device 401. The alternating magnetic flux passes through the built-in heating element, generating eddy currents in the built-in element, which counteract the change in alternating magnetic flux. The eddy currents generated in the heating element are called the second induced current. The heating element is required to have a Curie temperature point ≥1200℃ and resistance, and performs resistance heating through the second induced current.

[0061] In Example 1, under the condition of using air as the combustion medium, the H2 / NH3 ratio is 0.25, and the wet CO2 concentration at the outlet of the final preheating separator is approximately 20%. After impurity removal and dehydration, the dry CO2 concentration can reach 28.6%.

[0062] In Example 3, under the condition of using industrial oxygen as the combustion medium, the wet CO2 concentration at the outlet of the final preheating separator is about 35.4%, the H2O content is 53%, and the dry CO2 concentration can reach 75.3% after impurity removal and dehydration.

[0063] Example 6 As per the instruction manual Figure 4As shown, an electromagnetic induction coil is placed on the outer side of the wall of the electric direct-heating decomposition furnace, forming an external heating induction heating device 402. The alternating magnetic field generated by the external heating induction heating device 402 forms induced eddy currents on the surface of the magnetic conductor. The heat generated by the induced eddy currents is transferred to the interior of the suspension calcining furnace by heating the wall.

[0064] The suspension calcining furnace wall has at least two layers. The inner wall surface near the furnace chamber is made of a magnetically conductive, thermally shock-resistant, and high-temperature resistant alloy material, while the outer wall surface near the environment is wrapped with insulating material to reduce heat loss to the outside. The gas composition will not change significantly.

[0065] This embodiment may also include a temperature-measuring thermocouple 404.

[0066] Example 7 As per the instruction manual Figure 5 As shown, the plasma torch 403 includes internal electrodes, output electrodes, and an insulator between the electrodes. High-purity gaseous CO2 is introduced into the plasma torch through the insulator, and an electric arc is formed between the two electrodes. The gaseous CO2 that penetrates the arc is ionized into a conductive plasma state and reaches the arc temperature through Joule heating. The CO2 that does not penetrate the arc remains gaseous, and the mixture of the two can still generate a high temperature of 3000℃-3500℃. The energy density of the plasma CO2 within this temperature range is 7.5~8.0 MJ / kg. Based on the clinker production scale, the amount of high-purity CO2 used is adjusted, and theoretical calculations are performed. Considering a plasma efficiency of 85%, a 2500-ton / day online clinker production line requires approximately 60MW of energy for the raw material decomposition process, corresponding to a CO2 supply of 0.42 Nm³ per unit of clinker. 3 The temperature after mixing with the flue gas from the kiln can reach 1800℃, which is close to the average flame temperature in a coal-fired decomposition furnace.

[0067] This embodiment may also include a temperature-measuring thermocouple 404.

[0068] In Example 1, under the condition of using air as the combustion medium, the H2 / NH3 ratio was 0.25, and the wet CO2 concentration at the outlet of the final preheating separator was 39%. The inhibitory effect on the raw material decomposition rate under this CO2 equilibrium partial pressure was not significant. The suspension and calcination time of the raw material in the furnace was ≥15 s. By controlling the outlet temperature of the electric direct-heating decomposition furnace within the range of 800~950℃, the raw material decomposition rate could be ≥85%. After impurity removal and dehydration, the dry CO2 concentration could reach 51%.

[0069] In Example 3, under the condition of using industrial oxygen as the combustion medium, the wet CO2 concentration in the furnace is about 59%, and the dry CO2 concentration can reach 88.7% after impurity removal and dehydration.

[0070] In summary, this invention provides a kiln system for calcining cement using zero fossil energy.

[0071] The above embodiments have provided a detailed description of the present invention, but the content described is only a preferred embodiment of the present invention and should not be considered as limiting the scope of the present invention. All equivalent variations and improvements made within the scope of the present invention should still fall within the patent coverage of the present invention.

Claims

1. A kiln system for calcining cement using zero fossil energy, characterized in that: The zero-fossil energy calcination cement kiln system includes a rotary kiln, which is equipped with an ammonia-hydrogen burner. The ammonia-hydrogen burner includes an ammonia supply channel and a hydrogen supply channel for the rotary kiln burner.

2. The kiln system for zero-fossil energy calcination of cement according to claim 1, characterized in that: The ammonia supply channel gasification device of the rotary kiln burner is connected to the liquid ammonia storage tank. The hydrogen supply channel of the rotary kiln burner is connected to the nitrogen-hydrogen separation device, and the liquid ammonia storage tank, gasification device, first heat exchange equipment, ammonia in-situ cracking device, second heat exchange equipment and nitrogen-hydrogen separation device are connected in sequence.

3. The kiln system for zero-fossil energy calcination of cement according to claim 2, characterized in that: The kiln system for zero-fossil energy calcination of cement also includes a cooler. The cooler's outlet pipe is divided into two paths: one path is connected to the first heat exchanger, and the other path is connected to the waste heat boiler. The outlet of the first heat exchanger and the outlet of the waste heat boiler are both connected to a dust collector. The inlet pipe of the hot flow stream of the first heat exchanger is connected to the outlet pipe of the cooler and the outlet pipe of the cold flow stream of the second heat exchanger.

4. The kiln system for zero-fossil energy calcination of cement according to claim 1, characterized in that: The kiln system for zero-fossil energy calcination of cement also includes an electric direct-heat decomposition furnace.

5. The kiln system for zero-fossil energy calcination of cement according to claim 4, characterized in that: The electric direct-heating decomposition furnace is one of the following three types of electric direct-heating decomposition furnaces: Internal heating induction heating electric direct heating decomposition furnace: The internal heating induction heating electric direct heating decomposition furnace includes an internal heating induction heating device, and the coil of the internal heating induction heating device can generate alternating magnetic flux. External heating induction heating electric direct heating decomposition furnace: The external heating induction heating electric direct heating decomposition furnace includes an external heating induction heating device. The alternating magnetic field generated by the external heating induction heating device forms induced eddy currents on the surface of the magnetic conductor, and the induced eddy currents generate heat. Plasma torch direct-heating decomposition furnace: The plasma torch direct-heating decomposition furnace includes a plasma torch, an electric arc generated by the plasma torch is formed between two electrodes, and the gas penetrating the electric arc is ionized into a plasma state with electrical conductivity, and the arc temperature is reached by Joule heating.

6. The kiln system for zero-fossil energy calcination of cement according to claim 4, characterized in that: The electric direct-heat decomposition furnace, flue, rotary kiln, and cooler are connected in sequence. The feed pipe of the penultimate preheating separator in the multi-stage preheating separator is connected to the electric direct-heat decomposition furnace. The outlet of the electric direct-heat decomposition furnace is connected to the air inlet pipe of the penultimate preheating separator in the multi-stage preheating separator. The feed pipe of the penultimate preheating separator in the multi-stage preheating separator is connected to the flue gas chamber. The air outlet pipe of the first preheating separator in the multi-stage preheating separator is connected to the flue gas treatment system.

7. The kiln system for zero-fossil energy calcination of cement according to claim 6, characterized in that: The cooler is a grate cooler, which includes a first-stage cooling zone, a second-stage cooling zone, and a third-stage cooling zone. The cooling medium for the second-stage and third-stage cooling zones is air, while the cooling medium for the first-stage cooling zone is air or a mixture of high-concentration industrial oxygen and circulating flue gas containing O2 / CO2 / N2.

8. The kiln system for zero-fossil energy calcination of cement according to claim 7, characterized in that: When the cooling medium of the first cooling zone of the grate cooler is a mixture of high-concentration industrial oxygen and circulating flue gas containing O2 / CO2 / N2, the flue gas treatment system is connected to the flue gas carbon capture device and the first cooling zone of the grate cooler, and the first cooling zone of the grate cooler is connected to the air separation device.

9. A process for calcining cement using zero fossil energy, characterized in that: The process for zero-fossil energy calcining cement adopts the kiln system for zero-fossil energy calcining cement as described in any one of claims 1-8.

10. The process for zero-fossil energy calcination of cement according to claim 9, characterized in that: The H2 / NH3 volume ratio of the ammonia-hydrogen burner is 0.01-0.25.

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