Zero-carbon-emission cement production process for decomposing CO2 and co-producing synthesis gas by using carbonate in situ

Abstract

The invention discloses a zero-carbon-emission cement production process for decomposing CO2 and co-producing synthesis gas by using carbonate in situ, which is characterized in that nitrogen is adopted as a medium to enter a system only at the beginning of starting, and is switched to a spiral coil in a grate cooler without entering the system after the system runs normally; methane is adopted as a fuel for cement firing, and meanwhile, steam generated by methane combustion and methane are subjected to a reforming reaction, so that synthesis gas is prepared; o2 is introduced into the thermal decomposition coupling reforming reactor in a segmented manner, and catalyst beds are arranged in a layered manner; the catalyst suspends in the catalyst bed layer, and the raw material passes through the reactor along with airflow. According to the method, gas and heat generated in each step are fully utilized, energy is saved to the greatest extent, obtained products only comprise chemical raw material synthesis gas and pure nitrogen, CO2 is not discharged in the whole cement production process, CO2 generated by carbonate decomposition is converted and utilized in situ, CO2 generated in the sintering process is converted and utilized, and the production cost is reduced. And a high-added-value synthesis gas product is produced.

Description

Technical Field

[0001] The present invention belongs to the technical field of environmental engineering, and particularly relates to a zero-carbon cement production process for in-situ utilization of carbonate to decompose CO2 and co-produce syngas. Background Art

[0002] In the process of cement production, in addition to CO2 generated by fuel combustion, a large amount of CO2 is also generated during the decomposition of raw meal, accounting for about half of the total CO2 emissions in cement production. Therefore, the cement industry generates more carbon emissions than the steel and thermal power industries. The CO2 emissions of the cement industry in China in 2022 were approximately 1.26 billion tons, making it a major emitter of CO2. At the same time, the large flue gas volume and low CO2 concentration in the cement industry pose greater difficulties for carbon capture and utilization. Currently, the main paths for carbon emission reduction in the cement industry include: 1. Extreme energy efficiency improvement of existing process equipment; 2. Low-carbon cement technology based on raw material substitution; 3. Fuel substitution for coal combustion emissions in the calcination process; 4. Carbon capture, utilization, and storage (CCUS) for end-of-pipe treatment. However, due to the particularity of cement production, a large amount of CO2 will still be inevitably generated during the production process. Therefore, exploring economic and efficient CO2 emission reduction technologies is of great significance in the cement industry. If a cement production process for in-situ conversion and utilization of CO2 can be developed, it can minimize carbon emission reduction during cement production and provide technical support for the cement industry to achieve carbon neutrality at an early date.

[0003] There are existing technologies for reducing carbon emissions by converting CO2 to prepare synthesis gas during cement clinker production. For example, Chinese Patent Publication No. CN114735956A discloses a low-carbon production method and system for cement clinker, which proposes that the carbonate in the raw material is subjected to CH4 dry reforming to obtain metal oxides, which are then calcined to form cement clinker and synthesis gas is obtained at the same time. However, the invention still has the following problems: ① The rotary kiln still uses coal powder as fuel. During the cement production process, the CO2 produced by the fuel in the rotary kiln accounts for about 40% of the total CO2 produced by the fuel. Therefore, the process does not completely solve the problem of carbon emissions, and the destination of the gas in the kiln is not clear; ② The catalyst is added together with the raw material, and the catalyst uses components in steel slag, and the content of active components is very low, and It is difficult to achieve catalytic effect without reducing and reconstructing the steel slag to activate it; ③ CH4 partial oxidation is used to provide heat for raw material pre-decomposition and catalytic reforming, but a large amount of water vapor will be generated during the CH4 partial oxidation process, and the Gibbs free energy of CH4 water vapor reforming is about 79 kJ / mol, the Gibbs free energy of CH4 carbon dioxide reforming is about 97 kJ / mol, and the Gibbs free energy of carbonate decomposition coupled with CH4 dry reforming is about 184 kJ / mol. Given that the Gibbs free energy of CH4 water vapor reforming is the lowest, in a mixed atmosphere with excess CH4, CH4 is very likely to undergo reforming reaction with water vapor first, and CO2 will still remain in the atmosphere. Therefore, there is a high probability that the reaction will not occur as stated using this process, and there will still be a large amount of CO2 in the tail gas. Chinese Patent Publication No. CN109437604A discloses a method for recovering sensible heat from burning lime and utilizing tail gas by methane reforming. This method does not realize in-situ catalytic reduction of CO2. It is necessary to mix the CO2 tail gas with CH4 and then reintroduce it into the system through a pipeline. The sensible heat of lime is used to provide heat for the catalytic reaction. It is only a series connection of the two processes of lime production and chemical catalysis, and additional pipelines and equipment are required during the process. Chinese Patent Publication No. CN216799768U discloses a novel carbonate decomposition CO2 high-value utilization reaction system, which also produces CO2 first and then enters the catalytic reaction bed, and does not realize in-situ utilization.

[0004] In summary, the existing cement industry still has the following problems in the catalytic conversion and utilization of CO2:

[0005] (1) Coal combustion and carbonate decomposition in the cement industry both produce a large amount of CO2, and existing technologies have not completely solved the problem of CO2 conversion and utilization;

[0006] (2) Considering that a considerable proportion of water vapor exists in the flue gas during cement production, partial oxidation of CH4 will also produce a large amount of water vapor. The existing technology does not solve the problem of water vapor and CH4 competing for CO2 in cement kilns;

[0007] (3) The ratio of H2 to CO in the produced syngas is on the low side, and there is still a certain distance from direct utilization.

[0008] (4) Using solid waste as a catalyst requires reduction and reconstruction, which is difficult to achieve catalytic effects, and adding the prepared catalyst will increase costs.

[0009] Therefore, with the gradual implementation of carbon peaking and carbon neutrality, it is urgent to find a technical route for the catalytic conversion and utilization of CO2 in the cement industry to reduce emissions. Summary of the Invention

[0010] Aiming at the problems existing in the prior art, the present invention provides a zero-carbon emission cement production process for in-situ utilization of carbonate decomposition of CO2 and co-production of syngas. Using this process for the production of cement clinker, the existing cement production equipment can be transformed, and no CO2 emissions will be generated during the production process. A large amount of syngas products can be co-produced for chemical synthesis, and the heat and material utilization in the cement production system can be maximized.

[0011] The present invention is realized as follows. A zero-carbon emission cement production process for in-situ utilization of carbonate decomposition of CO2 and co-production of syngas includes the following steps:

[0012] First, N2 and O2 are generated by an air separation unit. N2 is introduced into the cement production system through the tail cavity of the grate cooler to start the system. After being introduced for a period of time, the air in the system is replaced with N2.

[0013] While maintaining the introduction of N2, a catalyst is gradually added to the thermal decomposition coupling reforming reactor to keep the catalyst in a suspended state in different catalyst beds of the reactor. The two catalyst beds are respectively heated to a certain temperature, and then the introduction amount of N2 is gradually reduced. At the same time, a reducing gas is introduced at the bottom of the reactor and the introduction amount of the reducing gas is gradually increased to activate the catalyst activity. After the reducing gas is continuously introduced for a period of time, it is closed.

[0014] N2 is switched to be introduced into the spiral coil in the grate cooler to cool the clinker, and at the same time it becomes high-temperature N2. The high-temperature N2 after leaving the grate cooler enters Heat Exchanger 1, and at the same time O2 enters Heat Exchanger 1. The two exchange heat, the high-temperature N2 becomes low-temperature N2, and the O2 is preheated and then divided into two parts through Flow Controller Group 1, namely Oxygen 1 and Oxygen 2. Among them, Oxygen 1 is introduced into the rotary kiln burner, and Oxygen 2 is divided into three parts through Flow Controller Group 4, namely Oxygen 21, Oxygen 22 and Oxygen 23.

[0015] The main natural gas pipeline leads out two paths of natural gas through Flow Controller Group 2, namely Natural Gas 1 and Natural Gas 2. Among them, Natural Gas 1 enters Heat Exchange Device 2. At the same time, the flue gas after combustion in the rotary kiln enters Heat Exchange Device 2, and the two exchange heat. After being preheated, Natural Gas 1 is divided into two parts through Flow Controller Group 3, namely Natural Gas 11 and Natural Gas 12. Among them, Natural Gas 11 enters the rotary kiln burner, mixes with Oxygen 1 and burns to generate CO2 and H2O, which is used to provide heat for raw meal calcination. Natural Gas 12 enters Feed Buffer Device 1; the flue gas after calcination cools down and then enters the Gas Mixer. Oxygen 21 enters the Gas Mixer at the same time. After the two gases are evenly mixed, the mixed gas enters the lower burner of the Thermal Decomposition Coupled Reforming Reactor;

[0016] The raw meal after grinding and drying is divided into two paths, namely Raw Meal 1 and Raw Meal 2. Raw Meal 1 enters Feed Buffer Device 1. Natural Gas 12 and Raw Meal 1 are mixed to obtain Gas-Solid Mixture 1, and then enter the lower burner of the Thermal Decomposition Coupled Reforming Reactor. After contacting the mixed gas, a partial combustion reaction occurs, and the formed flue gas continues to move upward in the Thermal Decomposition Coupled Reforming Reactor; Raw Meal 2 enters Feed Buffer Device 2;

[0017] Natural Gas 2 enters Heat Exchange Device 3. After being preheated, Natural Gas 2 enters Feed Buffer Device 2. Raw Meal 2 and Natural Gas 2 are mixed to obtain Gas-Solid Mixture 2, and then enter Flow Controller Group 5 and are divided into two parts, namely Gas-Solid Mixture 21 and Gas-Solid Mixture 22. Among them, Gas-Solid Mixture 21 enters the lower part of the middle section of the Thermal Decomposition Coupled Reforming Reactor. Oxygen 22 enters the lower part of the middle section of the Thermal Decomposition Coupled Reforming Reactor at the same time. After the two are evenly mixed with the flue gas formed by the combustion reaction in the lower burner of the Thermal Decomposition Coupled Reforming Reactor, they enter Catalyst Bed 1, and the flue gas formed after the catalytic reaction continues to move upward;

[0018] Gas-Solid Mixture 22 enters the lower part of the upper section of the Thermal Decomposition Coupled Reforming Reactor. Oxygen 23 enters the lower part of the upper section of the Thermal Decomposition Coupled Reforming Reactor at the same time. After being evenly mixed with the flue gas formed by the catalytic reaction in Catalyst Bed 1, they enter Catalyst Bed 2, and the formed gas-solid mixture continues to move upward until it exits the reactor; then it enters the Cyclone Separation Device for cyclone separation. The pre-calcined raw meal obtained by separation enters the rotary kiln; the separated gas enters Heat Exchange Device 3 to cool down and then enters the Dust Removal Device. The solid powder obtained after dust removal is mixed with the pre-calcined raw meal and enters the rotary kiln, is calcined to produce clinker, and then enters the Grate Cooler, where it is cooled down, ground and packaged to obtain the clinker product; the gas obtained after dust removal is the syngas product.

[0019] Preferably, the air in the system is replaced with N2. The introduction time of N2 is 1 - 5 h, and the flow rate of N2 is 500 m 3 / h - 6000 m 3 / h.

[0020] Preferably, the O2 concentration in the system after replacement is lower than 0.2%.

[0021] Preferably, in the thermal decomposition coupling reforming reactor, the sum of the inlet flow rates of N2 and the reducing gas is maintained within a certain range.

[0022] Preferably, the reducing gas is H2, CO or a mixture thereof, the inlet time is 1 - 7 h, and the heating temperatures of catalyst bed 1 and catalyst bed 2 are 500 - 650 °C and 600 - 750 °C respectively.

[0023] Preferably, the heat for heating the catalyst bed comes from green hydrogen oxidation, electric heating or solar heating.

[0024] Preferably, the temperature of the high-temperature N2 is 800 - 1100 °C, and the temperature of the preheated O2 is 500 - 800 °C.

[0025] Preferably, the volume ratio of oxygen 1 to oxygen 2 is between 0.5 and 1.

[0026] Preferably, the volume ratio of oxygen 21 to oxygen 22 is between 0.5 and 1, and the volume ratio of oxygen 22 to oxygen 23 is between 1.5 and 2.5.

[0027] Preferably, the waste heat in the low-temperature N2 is used for raw material drying.

[0028] Preferably, the temperature of the preheated natural gas 1 is 400 - 900 °C.

[0029] Preferably, the volume ratio of natural gas 11 to natural gas 12 is between 0.5 and 1; the volume ratio of natural gas 1 to natural gas 2 is between 0.05 and 0.2.

[0030] Preferably, the mass ratio of raw material 1 to raw material 2 is between 0.08 and 0.15.

[0031] Preferably, raw material 1 enters the feed buffer device 1 at a certain angle, and natural gas 12 enters tangentially, and natural gas 12 carries raw material 1 to move.

[0032] Preferably, the temperature of the flue gas formed by the combustion reaction in the lower burner of the thermal decomposition coupling reforming reactor is between 550 °C and 650 °C.

[0033] Preferably, in catalyst bed 1, partial oxidation reaction of methane, calcium carbonate decomposition reaction, and CH4 steam reforming reaction mainly occur.

[0034] Preferably, granular CH4 steam reforming catalyst is suspended in catalyst bed 1, and the temperature range maintained by the catalytic reaction in catalyst bed 1 is 650 °C - 700 °C.

[0035] Preferably, when it is necessary to supplement an additional amount of heat to the catalyst bed layer 1 to maintain the catalytic reaction, the supplementary heat comes from green hydrogen combustion, electric heating, or solar heating.

[0036] Preferably, the mass ratio of the gas-solid mixture 21 to the gas-solid mixture 22 is between 0.3 and 1.5.

[0037] Preferably, the steam reforming reaction, calcium carbonate decomposition reaction, and CH4 dry reforming reaction mainly occur in the catalyst bed layer 2.

[0038] Preferably, a mixture of particulate CH4 dry reforming catalyst and a small amount of CH4 steam reforming catalyst is suspended in the catalyst bed layer 2, and the temperature range maintained by the catalytic reaction in the catalyst bed layer 2 is 650°C to 750°C.

[0039] Preferably, when it is necessary to supplement an additional amount of heat to the catalyst bed layer 2 to maintain the catalytic reaction, the supplementary heat comes from green hydrogen combustion, electric heating, or solar heating.

[0040] Preferably, the cyclone separation efficiency of the cyclone separation device is 95% to 99%.

[0041] Preferably, the volume ratio of H2 to CO in the syngas product is between 1 and 2, and after proportioning, it can be used for organic synthesis.

[0042] The advantages and positive effects of the present invention are:

[0043] (1) During the cement production process of the present invention, CO2 is not emitted throughout the process. Not only is the CO2 generated by carbonate decomposition in-situ converted and utilized, but also the CO2 generated during the firing process is converted and utilized to produce high-value-added syngas products.

[0044] (2) The present invention uses methane as the fuel for cement firing, solving the problem of catalyst poisoning caused by SO2 generated from coal combustion. At the same time, the water vapor generated by methane combustion reacts with methane reforming to produce syngas, which can increase the proportion of H2 in the syngas product and solve the problem of the low ratio of H2 to CO in the syngas synthesized by using only methane dry reforming reaction; it is beneficial for subsequent Fischer-Tropsch synthesis.

[0045] (3) In the present invention, O2 is introduced in stages into the thermal decomposition coupling reforming reactor, which can intermittently heat the carbonate to control the gradual release of CO2 and increase the catalytic reaction time; at the same time, the layered arrangement of the catalyst bed solves the problem of water vapor and CH4 competing for CO2 in the cement kiln.

[0046] (4) The present invention solves the problem of the need for reduction and reconstruction when using solid waste as a catalyst. The catalyst is suspended in the catalyst bed layer, and the raw meal passes through the reactor with the gas flow, increasing the service life of the catalyst and significantly reducing the cost of the catalytic reaction.

[0047] (5) The present invention makes full use of the gases and heat generated in each step, saves energy to the greatest extent, and the obtained products are only syngas for chemical raw materials and pure nitrogen gas;

[0048] (6) When using the present invention to produce cement, nitrogen only enters the system as a medium at the very beginning of startup, and after the system operates normally, it is switched to the spiral coil in the grate cooler and does not enter the system. Since N2 does not enter the system throughout the normal operation of the system and methane is used as fuel to replace pulverized coal, almost no nitrogen oxides and sulfur dioxide are generated, solving the problem of ultra-low emissions of nitrogen oxides and sulfides. Description of the Drawings

[0049] Figure 1 is a flowchart of a zero-carbon emission cement production process for in-situ utilization of carbonate decomposition of CO2 and co-production of syngas provided by an embodiment of the present invention. Detailed Embodiment

[0050] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0051] In the description of the present invention, it should be noted that unless otherwise clearly specified and limited, the terms "connected" and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0052] Embodiment

[0053] The following elaborates in detail the specific working process of the present invention:

[0054] A zero-carbon emission cement production process for in-situ utilization of carbonate decomposition of CO2 and co-production of syngas, which is realized by the following equipment. According to the movement direction of the raw meal, it includes a feeding buffer device, a thermal decomposition coupling reforming reactor, a cyclone separation device, a rotary kiln, and a grate cooler. The other equipment also includes an air separation device, an O2 storage tank, an N2 storage tank, a heat exchange device, a flow controller group, a dust removal device, and also includes some pipelines, valves, etc.

[0055] The process includes the following steps:

[0056] First, N2 and O2 are generated by an air separation unit. Among them, N2 enters the N2 storage tank and O2 enters the O2 storage tank; N2 is introduced into the cement production system from the tail cavity of the grate cooler to start the system. After introducing it for a period of time, the air in the system is replaced with N2.

[0057] Keep introducing N2. Gradually add the catalyst in the thermal decomposition coupling reforming reactor to keep the catalyst in a suspended state in different catalyst beds of the reactor. Heat the two catalyst beds to a certain temperature respectively. Then gradually reduce the amount of N2 introduced. At the same time, introduce a reducing gas at the bottom of the reactor and gradually increase the amount of the reducing gas introduced to activate the catalyst activity. After the reducing gas is continuously introduced for a period of time, it is closed.

[0058] Switch N2 to be introduced into the spiral coil in the grate cooler to cool the clinker, and at the same time it becomes high-temperature N2; the high-temperature N2 after leaving the grate cooler enters Heat Exchanger 1. At the same time, O2 in the O2 storage tank enters Heat Exchanger 1. The two exchange heat. The high-temperature N2 becomes low-temperature N2 to achieve its own cooling. After O2 is preheated, it is divided into two parts by Flow Controller Group 1, namely Oxygen 1 and Oxygen 2. Among them, Oxygen 1 is introduced into the rotary kiln burner, and Oxygen 2 is divided into three parts by Flow Controller Group 4, namely Oxygen 21, Oxygen 22 and Oxygen 23.

[0059] The main natural gas pipeline leads out two paths of natural gas through Flow Controller Group 2, namely Natural Gas 1 and Natural Gas 2. Among them, Natural Gas 1 enters Heat Exchanger 2. At the same time, the flue gas after the rotary kiln is burned enters Heat Exchanger 2. The two exchange heat. After Natural Gas 1 is preheated, it is divided into two parts by Flow Controller Group 3, namely Natural Gas 11 and Natural Gas 12. Among them, Natural Gas 11 enters the rotary kiln burner and mixes with Oxygen 1 to burn to generate CO2 and H2O, which is used to provide heat for the raw material burning. Natural Gas 12 enters Feed Buffer 1; the flue gas after burning cools down and then enters the Gas Mixer. Oxygen 21 also enters the Gas Mixer. The two gases are evenly mixed and then the mixture enters the lower burner of the thermal decomposition coupling reforming reactor.

[0060] It should be noted here that the purpose of designing Heat Exchanger 1 and Heat Exchanger 2 is to make the temperature of the gas entering the burner and the rotary kiln as high as possible to achieve the energy-saving effect. When the temperature in the rotary kiln is low in the early stage, the nitrogen pipe valve is closed and nitrogen does not enter the grate cooler to exchange heat with Heat Exchanger 1. When the pre-decomposed raw material is put into the rotary kiln, slowly increase the nitrogen flow rate, and the nitrogen flow rate is adjusted according to the temperature of the clinker leaving the grate cooler. In the early stage, the flue gas volume after burning is small and the temperature is low, and the heating effect of Heat Exchanger 2 on natural gas is weak. Low-temperature natural gas can be mixed with low-temperature Oxygen 2 and enter the burner to burn, gradually increasing the temperature in the whole system and slowly reaching the predetermined temperature. This process is similar to the early stage of ignition of an ordinary rotary kiln.

[0061] After grinding and drying, the raw meal is divided into two paths, namely raw meal one and raw meal two. Raw meal one enters the first feed buffer device. Natural gas one and two are mixed with raw meal one to obtain a gas-solid mixture one, which then enters the lower burner of the pyrolysis coupling reforming reactor. After contacting with the mixed gas, a partial combustion reaction occurs to release heat, and the formed flue gas continues to move upward in the pyrolysis coupling reforming reactor; raw meal two enters the second feed buffer device.

[0062] Natural gas two enters the third heat exchange device. After being preheated, natural gas two enters the second feed buffer device. Raw meal two is mixed with natural gas two to obtain a gas-solid mixture two, which then enters the fifth flow controller group and is divided into two parts, namely gas-solid mixture two one and gas-solid mixture two two; it should be noted here that in the initial stage of igniting the rotary kiln, only a small amount of low-temperature gas enters the cyclone separator, and the heating effect of the third heat exchange device on natural gas two is weak and cannot reach the temperature during normal production. Therefore, the system needs to be slowly heated in the initial stage of ignition until the preset temperature is reached after the rotary kiln is normally fed.

[0063] Among them, gas-solid mixture two one enters the lower part of the middle section of the pyrolysis coupling reforming reactor, and oxygen two two also enters the lower part of the middle section of the pyrolysis coupling reforming reactor. After the two are evenly mixed with the flue gas formed by the combustion reaction in the lower burner of the pyrolysis coupling reforming reactor, they enter the first catalyst bed, and the flue gas formed after the catalytic reaction continues to move upward.

[0064] Gas-solid mixture two two enters the lower part of the upper section of the pyrolysis coupling reforming reactor, and oxygen two three also enters the lower part of the upper section of the pyrolysis coupling reforming reactor. After being evenly mixed with the flue gas formed by the catalytic reaction in the first catalyst bed, it enters the second catalyst bed, and the gas-solid mixture generated after the catalytic reaction continues to move upward until it exits the reactor; then it enters the cyclone separator for cyclone separation. The pre-calcined raw meal obtained by separation enters the rotary kiln; the separated gas enters the third heat exchange device to be cooled and then enters the dust removal device. The solid powder obtained after dust removal is mixed with the pre-calcined raw meal and enters the rotary kiln, is calcined to form clinker, and then enters the grate cooler, where it is cooled, and after being ground and packaged, the clinker product is obtained; the gas obtained after dust removal is the syngas product for subsequent chemical synthesis.

[0065] As a preferred embodiment, the air in the system is replaced with N2. The introduction time of N2 is 1 - 5 h, and the flow rate of N2 is 500 m 3 / h - 6000 m 3 / h. The purpose of cleaning the system is achieved.

[0066] As a preferred embodiment, the O2 concentration in the system after replacement is lower than 0.2%. The oxygen concentration is reduced to ensure the reforming effect.

[0067] As a preferred embodiment, in the thermal decomposition coupled reforming reactor, the sum of the flow rates of N2 and the reducing gas introduced is maintained within a certain range. Ensuring a certain gas volume can suspend the catalyst.

[0068] As a preferred embodiment, the reducing gas is H2, CO or a mixture thereof, and the introduction time is 1 - 7 h. The heating temperatures of catalyst bed 1 and catalyst bed 2 are 500 - 650 °C and 600 - 750 °C respectively. This ensures that the catalyst is completely reduced.

[0069] As a preferred embodiment, the heat for heating the catalyst bed comes from green hydrogen oxidation, electric heating or solar heating.

[0070] As a preferred embodiment, the temperature of the high - temperature N2 is 800 - 1100 °C, and the temperature of the pre - heated O2 is 500 - 800 °C. This ensures the subsequent reaction temperature.

[0071] As a preferred embodiment, the volume ratio of oxygen 1 to oxygen 2 is between 0.5 and 1. This ensures the reaction ratio.

[0072] As a preferred embodiment, the volume ratio of oxygen 21 to oxygen 22 is between 0.5 and 1, and the volume ratio of oxygen 22 to oxygen 23 is between 1.5 and 2.5. This ensures the reaction ratio.

[0073] As a preferred embodiment, the waste heat in the low - temperature N2 is used for raw material drying. This makes full use of energy.

[0074] As a preferred embodiment, the temperature of the pre - heated natural gas 1 is 400 - 900 °C. This makes full use of energy.

[0075] As a preferred embodiment, the volume ratio of natural gas 11 to natural gas 12 is between 0.5 and 1; the volume ratio of natural gas 1 to natural gas 2 is between 0.05 and 0.2. This ensures the reaction ratio.

[0076] As a preferred embodiment, the mass ratio of raw material 1 to raw material 2 is between 0.08 and 0.15. The raw materials are added step by step to ensure step - by - step reactions.

[0077] As a preferred embodiment, raw material 1 enters the feed buffer device 1 at a certain angle, and natural gas 12 enters in a direction tangent to the inner wall of the feed buffer device. Natural gas 12 carries raw material 1 to move. This ensures uniform mixing.

[0078] As a preferred embodiment, the temperature of the flue gas formed by the combustion reaction in the burner at the lower end of the thermal decomposition coupled reforming reactor is between 550 °C and 650 °C. This ensures the reaction temperature.

[0079] As a preferred embodiment, partial oxidation reaction of methane, decomposition reaction of calcium carbonate, and steam reforming reaction of CH4 mainly occur in the first catalyst bed.

[0080] As a preferred embodiment, particulate CH4 steam reforming catalyst is suspended in the first catalyst bed, and the temperature range maintained for the catalytic reaction in the first catalyst bed is 650°C to 700°C. Ensure the catalytic reaction temperature.

[0081] As a preferred embodiment, when it is necessary to supplement a part of heat to the first catalyst bed to maintain the catalytic reaction, the supplemented heat comes from green hydrogen combustion, electric heating or solar heating.

[0082] As a preferred embodiment, the mass ratio of the gas-solid mixture 2-1 to the gas-solid mixture 2-2 is between 0.3 and 1.5. Ensure the reaction ratio.

[0083] As a preferred embodiment, steam reforming reaction, calcium carbonate decomposition reaction, and CH4 dry reforming reaction mainly occur in the second catalyst bed.

[0084] As a preferred embodiment, a mixture of particulate CH4 dry reforming catalyst and a small amount of CH4 steam reforming catalyst is suspended in the second catalyst bed, and the temperature range maintained for the catalytic reaction in the second catalyst bed is 650°C to 750°C. Ensure the reaction temperature.

[0085] As a preferred embodiment, when it is necessary to supplement a part of heat to the second catalyst bed to maintain the catalytic reaction, the supplemented heat comes from green hydrogen combustion, electric heating or solar heating.

[0086] As a preferred embodiment, the efficiency of cyclone separation is 95% to 99%, ensuring the separation effect.

[0087] As a preferred embodiment, the volume ratio of H2 to CO in the syngas product is between 1 and 2, and after proportioning, it can be used for organic synthesis. Ensure the subsequent synthesis reaction.

[0088] In summary, the present invention makes full use of the gases and heat generated in each step, saves energy to the greatest extent, and the obtained products are only chemical raw material syngas and pure nitrogen; no CO2 is emitted during the entire cement production process. Not only is the CO2 generated by carbonate decomposition in-situ converted and utilized, but also the CO2 generated during the firing process is converted and utilized to produce high-value-added syngas products.

[0089] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features, and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A zero-carbon-emission cement production process that in-situ utilizes carbonate to decompose CO2 and co-produces syngas, characterized by: It includes the following steps: First, N2 and O2 are generated by an air separation unit. N2 is introduced into the cement production system from the tail cavity of the grate cooler to start the system. After being introduced for a period of time, the air in the system is replaced with N2; Keep introducing N2. Gradually add a catalyst into the thermal decomposition coupling reforming reactor to keep the catalyst in a suspended state in different catalyst beds of the reactor. Heat the two catalyst beds to a certain temperature respectively. Then gradually reduce the amount of N2 introduced. At the same time, introduce a reducing gas at the bottom of the reactor and gradually increase the amount of the reducing gas introduced to activate the catalyst activity. After the reducing gas is continuously introduced for a period of time, it is closed; Switch N2 to be introduced into the spiral coil in the grate cooler to cool the clinker, and at the same time it becomes high-temperature N2. The high-temperature N2 after leaving the grate cooler enters Heat Exchange Device 1. At the same time, O2 enters Heat Exchange Device 1. The two exchange heat. The high-temperature N2 becomes low-temperature N2. After O2 is preheated, it is divided into two parts by Flow Controller Group 1, namely Oxygen 1 and Oxygen 2. Among them, Oxygen 1 is introduced into the rotary kiln burner, and Oxygen 2 is divided into three parts by Flow Controller Group 4, namely Oxygen 21, Oxygen 22 and Oxygen 23; Two paths of natural gas are led out from the natural gas main pipe through Flow Controller Group 2, namely Natural Gas 1 and Natural Gas 2. Among them, Natural Gas 1 enters Heat Exchange Device 2. At the same time, the flue gas after the rotary kiln is burned enters Heat Exchange Device 2. The two exchange heat. After Natural Gas 1 is preheated, it is divided into two parts by Flow Controller Group 3, namely Natural Gas 11 and Natural Gas 12. Among them, Natural Gas 11 enters the rotary kiln burner and mixes with Oxygen 1 to burn to generate CO2 and H2O, which is used to provide heat for the raw material calcination. Natural Gas 12 enters Feed Buffer Device 1. The flue gas after being burned is cooled, and then enters the gas mixer. Oxygen 21 also enters the gas mixer. After the two gases are mixed evenly, the mixture enters the lower burner of the thermal decomposition coupling reforming reactor; The raw material after being ground and dried is divided into two paths, namely Raw Material 1 and Raw Material 2. Raw Material 1 enters Feed Buffer Device 1. Natural Gas 12 and Raw Material 1 are mixed to obtain Gas-Solid Mixture 1, and then enter the lower burner of the thermal decomposition coupling reforming reactor. After contacting the mixture gas, a partial combustion reaction occurs, and the formed flue gas continues to move upward in the thermal decomposition coupling reforming reactor. Raw Material 2 enters Feed Buffer Device 2; Natural Gas 2 enters Heat Exchange Device 3. After Natural Gas 2 is preheated, it enters Feed Buffer Device 2. Raw Material 2 and Natural Gas 2 are mixed to obtain Gas-Solid Mixture 2, and then enter Flow Controller Group 5 and are divided into two parts, namely Gas-Solid Mixture 21 and Gas-Solid Mixture 22. Among them, Gas-Solid Mixture 21 enters the lower part of the middle section of the thermal decomposition coupling reforming reactor. Oxygen 22 also enters the lower part of the middle section of the thermal decomposition coupling reforming reactor. The two are mixed evenly with the flue gas formed by the combustion reaction in the lower burner of the thermal decomposition coupling reforming reactor and then enter Catalyst Bed 1. After the catalytic reaction occurs, the formed flue gas continues to move upward; The gas-solid mixture 22 enters the lower part of the upper section of the pyrolysis coupling reforming reactor, and the oxygen 23 also enters the lower part of the upper section of the pyrolysis coupling reforming reactor. After being evenly mixed with the flue gas formed by the catalytic reaction with the catalyst bed 1, it enters the catalyst bed 2, and after the catalytic reaction, the generated gas-solid mixture continues to move upward to exit the reactor; then it enters the cyclone separation device for cyclone separation. The pre-decomposed raw meal obtained by separation enters the rotary kiln; the gas obtained by separation enters the heat exchange device 3 to be cooled and then enters the dust removal device. The solid powder obtained after dust removal is mixed with the pre-decomposed raw meal and enters the rotary kiln, where it is calcined to produce clinker, and then enters the grate cooler, where it is cooled, and after grinding and packaging, the clinker product is obtained; the gas obtained after dust removal is the syngas product.

2. The zero-carbon emission cement production process for in-situ utilization of carbonate to decompose CO2 and co-produce syngas according to claim 1, characterized in that, Replace the air in the system with N2. The introduction time of N2 is 1 - 5 h, and the flow rate of N2 is 500 m 3 / h - 6000 m 3 / h; after replacement, the O2 concentration in the system is lower than 0.2%.

3. The zero-carbon emission cement production process for in-situ utilization of carbonate to decompose CO2 and co-produce syngas according to claim 1, characterized in that, In the pyrolysis coupling reforming reactor, the sum of the flow rates of N2 and the reducing gas introduced is maintained within a certain range; The reducing gas is H2, CO or a mixture thereof, and the introduction time is 1 - 7 h. The heating temperatures of the catalyst bed 1 and the catalyst bed 2 are 500 - 650 °C and 600 - 750 °C respectively; The heat for heating the catalyst bed comes from green hydrogen oxidation, electric heating or solar heating.

4. The zero-carbon emission cement production process for in-situ utilization of carbonate to decompose CO2 and co-produce syngas according to claim 1, characterized in that The temperature of the high-temperature N2 is 800 - 1100 °C, and the waste heat in the low-temperature N2 is used for raw meal drying. The temperature of the O2 after preheating is 500 - 800 °C; The volume ratio of oxygen 1 to oxygen 2 is between 0.5 and 1; The volume ratio of oxygen 21 to oxygen 22 is between 0.5 and 1, and the volume ratio of oxygen 22 to oxygen 23 is between 1.5 and 2.

5.

5. The zero-carbon emission cement production process for in-situ utilization of carbonate to decompose CO2 and co-produce syngas according to claim 1, characterized in that, The temperature of the natural gas 1 after preheating is 400 - 900 °C; The volume ratio of natural gas 11 to natural gas 12 is between 0.5 and 1; the volume ratio of natural gas 1 to natural gas 2 is between 0.05 and 0.

2.

6. The zero-carbon emission cement production process for in-situ utilization of carbonate to decompose CO2 and co-produce syngas according to claim 1, characterized in that, The mass ratio of raw meal 1 to raw meal 2 is between 0.08 and 0.15; Raw meal 1 enters the feeding buffer device 1 at a certain angle, and natural gas 12 enters tangentially, and natural gas 12 carries raw meal 1 to move; The temperature of the flue gas formed by the combustion reaction in the burner at the lower end of the pyrolysis coupling reforming reactor is between 550 °C and 650 °C; 7. The zero-carbon-emission cement production process for in-situ utilization of carbonate to decompose CO2 and co-produce syngas according to claim 1, characterized in that, The mass ratio of the gas-solid mixture 21 to the gas-solid mixture 22 is between 0.3 and 1.5; In the catalyst bed 1, the partial oxidation reaction of methane, the decomposition reaction of calcium carbonate, and the steam reforming reaction of CH4 mainly occur; There is particulate CH4 steam reforming catalyst suspended in the catalyst bed 1, and the temperature range maintained by the catalytic reaction in the catalyst bed 1 is 650 °C - 700 °C; When additional heat needs to be supplemented to the catalyst bed 1 to maintain the catalytic reaction, the supplementary heat comes from green hydrogen combustion, electric heating or solar heating.

8. The zero-carbon emission cement production process for in-situ utilization of carbonate to decompose CO2 and co-produce syngas according to claim 1, characterized in that, In the catalyst bed 2, the steam reforming reaction, the calcium carbonate decomposition reaction, and the dry reforming reaction of CH4 mainly occur; There is a mixture of particulate CH4 dry reforming catalyst and a small amount of CH4 steam reforming catalyst suspended in the catalytic bed 2, and the temperature range maintained by the catalytic reaction in the catalyst bed 2 is 650 °C - 750 °C; When additional heat needs to be supplemented to the catalytic bed to maintain the catalytic reaction, the supplemented heat comes from green hydrogen combustion, electric heating or solar heating.

9. The zero-carbon emission cement production process for in-situ utilization of carbonate to decompose CO2 and co-produce syngas according to claim 1, characterized in that, The cyclone separation efficiency of the cyclone separation device is 95% - 99%.

10. The zero-carbon emission cement production process for in-situ utilization of carbonate to decompose CO2 and co-produce syngas according to claim 1, characterized in that, The volume ratio of H2 to CO in the syngas product is between 1 and 2, and after proportioning, it can be used for organic synthesis.

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