Efficient calcium-based carbon trapping and recycling system and method based on steel slag

Abstract

The invention discloses an efficient calcium-based carbon trapping and recycling system and method based on steel slag, in the system, firstly, a Solvay process is applied to steel slag treatment, efficient leaching of free Ca < 2 + > and effective fixation of CO2 in the steel slag are achieved through ammoniation treatment, high-purity CaCO3 is generated, then a novel plasma hydrogen activation CaCO3 decomposition technology is introduced, and the calcium-based carbon trapping and recycling system based on the steel slag is obtained. CaCO3 can be efficiently decomposed into synthesis gas and CaO at a low temperature through plasma hydrogen generated by the plasma generator, the synthesis gas returns to a blast furnace to replace metallurgical coke to reduce iron ore, CO2 resource recycling is achieved, CaO serves as a value-added product, and economic benefits are improved. According to the method, recycling of calcium ions in the steel slag and low-energy-consumption and low-cost trapping of the CO2 in the flue gas are achieved through cooperation of the steel slag and CO2 mineralization fixation and in-situ conversion. And meanwhile, CaO and synthesis gas value-added products are co-produced, so that the method has great economic value and social effect.

Description

Technical Field

[0001] The present invention belongs to the field of CO2 emission reduction and solid waste resource utilization, and specifically relates to a high-efficiency calcium-based carbon capture and recycling system and method based on steel slag. Background Art

[0002] The steel industry is a pillar industry of my country's national economy. my country is a major steel producer and consumer, and its crude steel output has ranked first in the world for many years. The steel industry is also one of the important areas of global energy consumption and carbon emissions. At present, the mainstream method for capturing CO2 from blast furnace and converter flue gas is the commercial wet carbon capture technology based on MEA. Although wet carbon capture technology has the advantages of high capture efficiency and high purity of recovered CO2, it faces key problems such as high regeneration energy consumption, solvent degradation loss and equipment corrosion. In addition, the separated and purified CO2 needs to be compressed and transported by pipeline to a suitable place for storage or utilization, which has defects such as high compression energy consumption, high pipeline investment cost, high risk of transportation leakage and low efficiency of CO2 resource utilization.

[0003] On the other hand, the rapid development of China's steel industry has led to a substantial increase in the output of steel slag. At present, the treatment processes of steel slag include: hot-suffocating self-lysis method, mechanical crushing method, steam aging method, pressure aging method and roller crushing-waste heat pressure hot-suffocating technology. These technologies aim to reduce the activity of steel slag and improve its stability through different physical or chemical methods, thereby reducing the impact on the environment. Although the above-mentioned treatment processes can effectively reduce the free CaO content in steel slag and achieve effective treatment of steel slag, they have defects such as large equipment loss, high process energy consumption, large land area, poor stability of steel slag and secondary pollution. In addition to treatment technology, the resource utilization of steel slag is also the key to its sustainable development. At present, the resource utilization channels of steel slag include: as roadbed material or road aggregate (road construction), as active mineral admixture (cement and concrete production), microcrystalline glass production, sintering additive, soil remediation, flue gas desulfurization and sewage heavy metal adsorption. Although certain progress has been made in the utilization of steel slag, there are still problems such as generally low utilization rate, single utilization channel and secondary pollution.

[0004] Free Ca in steel slag 2+ The content is as high as 40%-50%, which can cooperate with CO2 to achieve mineralization fixation and further realize the in-situ conversion of CO2. Therefore, the efficient disposal of steel slag to cooperate with CO2 mineralization fixation and in-situ conversion has great application prospects. However, the efficient calcium-based carbon capture and recycling system and method based on steel slag are rarely reported in the prior art. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention provides a high-efficiency calcium-based carbon capture and recycling system and method based on steel slag. The method realizes the recycling of calcium ions in steel slag and the low-energy and low-cost capture of flue gas CO2 through the coordinated CO2 mineralization fixation and in-situ conversion of steel slag. First, the Solvay process is applied to steel slag treatment, and the free Ca in steel slag is recovered by ammoniation treatment. 2+ High-purity CaCO3 is generated through efficient leaching and effective fixation of CO2. Then, a new plasma hydrogen-activated CaCO3 decomposition technology is introduced, which can efficiently convert CaCO3 into synthesis gas at a lower temperature and return it to the blast furnace, replacing metallurgical coke to reduce iron ore, realizing the recycling of CO2 resources, and at the same time co-producing CaO value-added products to improve economic benefits.

[0006] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is as follows: an efficient calcium-based carbon capture and recycling system based on steel slag, including two subsystems of calcium-based carbon capture and CO2 in-situ conversion. In the calcium-based carbon capture subsystem, it includes an ammonia reactor, a first solid-liquid separator, a leaching reactor, a conversion reactor, a second solid-liquid separator, and a recovery reactor connected in sequence. In the CO2 in-situ conversion subsystem, it includes an electrolysis device, a plasma generator, a bubbling bed catalytic reactor, a plasma torch, and a blast furnace. In the entire steel slag-based calcium-based carbon capture and recycling system and method, energy comes from the recovery of waste heat from high-temperature flue gas and steel slag. In the calcium-based carbon capture subsystem, the specific steps to achieve calcium-based carbon capture are as follows:

[0007] Step 1) The flue gas is introduced into an ammoniation reactor, and under the action of NH3 and NaCl, the flue gas CO2 is fixed to form NaHCO3 and NH4Cl, wherein NaHCO3 forms a precipitate due to excess.

[0008] Step 2) The cooled steel slag after waste heat utilization is sent to a leaching reactor, where the steel slag is leached in an alkali solution to remove Ca 2+ And react with ammonia to form CaCl2.

[0009] Step 3) The formed leachate is sent to a conversion reactor to react with NaHCO3 to form CaCO3 precipitation.

[0010] Step 4) NaHCO3 and NH4Cl mother liquors are further reacted in a recovery reactor to form NaCl and NH3.

[0011] Furthermore, the reaction temperature of the amination reactor is 10-60°C, preferably 20-40°C.

[0012] Furthermore, the reaction temperature of the leaching reactor is 60-120°C, preferably 70-90°C.

[0013] Furthermore, the reaction temperature of the conversion reactor is 10-60°C, preferably 20-40°C.

[0014] Furthermore, the reaction temperature of the recovery reactor is 60-120°C, preferably 70-90°C.

[0015] Furthermore, the energy of the ammonia reactor, the leaching reactor, the conversion reactor and the recovery reactor comes from the waste heat recovery of high-temperature flue gas and steel slag.

[0016] In the CO2 in-situ conversion subsystem, the solid phase product CaCO3, which is the product of CO2 fixation through slag co-mineralization, is fed into the bubbling bed catalytic reactor. The green hydrogen produced by the electrolysis of water by renewable energy is passed through a plasma generator to generate activated plasma hydrogen, which is then passed into the bubbling bed catalytic reactor. Under the action of plasma hydrogen, CaCO3 can be decomposed by hydrogenation (without a catalyst) to form CO and H2 (synthesis gas). The generated synthesis gas can be used as a reducing medium. After rapid heating by a plasma torch, it is circulated to the blast furnace to replace coke to reduce iron ore. The CaO produced by regeneration and decomposition can be used as a value-added product in the cement and building materials industries.

[0017] Furthermore, the reaction temperature of the bubbling bed catalytic reactor is 650-700°C.

[0018] Furthermore, the energy required by the bubbling bed catalytic reactor comes from the waste heat recovery of high-temperature flue gas and steel slag. The conversion reactor is connected to the bubbling bed catalytic reactor through a connecting pipe to realize the transportation of CaCO3, thereby realizing the connection between the two subsystems of calcium-based carbon capture and CO2 in-situ conversion.

[0019] This proposal proposes an innovative solution that combines the efficient disposal of steel slag with CO2 mineralization, fixation and conversion utilization, achieving low-cost CO2 emission reduction and waste resource utilization.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] 1. An innovative system design idea is proposed, which combines the efficient disposal of steel slag with the mineralization, fixation and conversion of CO2. This synergistic treatment method can improve the recycling rate of resources while reducing environmental pollution. For every 1000kg of steel slag processed, 380kg of CO2 can be fixed in the mineralization stage, and 860kg of high-purity CaCO3 can be produced; in the CaCO3 decomposition stage, 206.4kg of CO is produced, replacing 88.5kg of coke, and 474kg of CaO value-added products are co-produced. The energy consumption of carbon fixation using the Solvay process is less than 1.8GJ / t CO2, which is significantly reduced compared to the traditional wet carbon capture process (2.0~2.4GJ / t CO2). This system design not only helps to solve the environmental problems of the steel industry, but also can improve economic benefits through the resource utilization of steel slag and the reduction of CO2 emissions, promote the green transformation and sustainable development of the steel industry, and provide new ideas and methods for achieving green development and circular economy in the steel industry;

[0022] 2. Innovatively apply the Solvay process to steel slag treatment, and achieve the free Ca in steel slag through chemical reactions in the ammoniation treatment unit. 2+ The efficient leaching and effective mineralization and fixation of CO2 can be achieved by recovering high-purity CaCO3 precipitate with a purity of 98%, which improves the resource utilization rate of steel slag and the fixation efficiency of CO2. 2+ The leaching efficiency and precipitation efficiency are 80% and 95% respectively, far exceeding the traditional water leaching method in treating steel slag. 2+ Leaching efficiency (<50%). In the traditional process, the leaching of Ca 2+ The precipitation efficiency depends on the pH value of the liquid phase. When the pH of the CaCO3 precipitation end point drops from 8.0 to 7.3, Ca 2+ The precipitation rate of Ca2+ increased from 89.2% to 92.3%. 2+ The precipitation efficiency is high and there is no need to adjust the pH value of the reaction system.

[0023] 3. A new type of CaCO3 hydrogenation decomposition technology based on plasma hydrogen activation was introduced, which can efficiently convert CaCO3 into synthesis gas at a lower temperature, replacing the traditional coke reduction process of iron ore, and co-producing high-purity CaO for application in the cement and building materials industries, improving the utilization efficiency of resources. The temperature at which CaCO3 is completely decomposed in a N2 atmosphere exceeds 800°C, and the efficiency of CaCO3 activation and decomposition is significantly improved in an atmosphere of plasma hydrogen. When the reaction temperature is 650°C, the decomposition efficiency of CaCO3 under the action of plasma hydrogen is close to 100%. At 650°C, the CO yield is 0.24g CO / g CaCO3, and the CaCO3 decomposition efficiency and CO selectivity are 95% and 92%, respectively. Therefore, plasma hydrogen assistance can effectively promote the efficiency of CaCO3 hydrogenation decomposition, help produce efficient synthesis gas, and replace coke reduction of iron ore. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic diagram of the structure of the calcium-based carbon capture and recycling system based on steel slag provided in Example 1.

[0025] Among them: 1 is an ammoniation reactor, 2 is a first solid-liquid separator, 3 is a leaching reactor, 4 is a conversion reactor, 5 is a second solid-liquid separator, 6 is a recovery reactor, 7 is an electrolysis device, 8 is a plasma generator, 9 is a bubbling bed catalytic reactor, 10 is a plasma torch, and 11 is a blast furnace.

[0026] The material cycle includes: A. a solid-liquid mixture whose main components are NH4Cl and NaHCO3; B. a leachate mainly composed of NH4Cl; C. NaHCO3 precipitation; D. ammonia water and CaCl2 solution; E. a solid-liquid mixture of NaCl, NH4Cl and CaCO3; F. CaCO3 precipitation; G. NaCl and NH4Cl solution; H. NaCl and NH3 solution (ammoniated brine) and CO2 gas; I. H2 gas; J. plasma hydrogen; K. solid CaO; L. synthesis gas whose main components are CO and H2; M. high-temperature synthesis gas whose main components are CO and H2. DETAILED DESCRIPTION

[0027] The present invention is described in detail below in conjunction with specific embodiments. It is worth mentioning that the following is only a preferred specific implementation of the present invention, but the protection scope of the present invention is not limited thereto, and any technician familiar with the art within the technical scope disclosed by the present invention, according to the technical solution of the present invention, and the inventive concept, making equivalent replacements or changes, should be covered within the protection scope of the present invention.

[0028] Example 1

[0029] like Figure 1As shown, a high-efficiency calcium-based carbon capture and recycling system based on steel slag includes an amination reactor 1, a first solid-liquid separator 2, a leaching reactor 3, a conversion reactor 4, a second solid-liquid separator 5, a recovery reactor 6, an electrolysis device 7, a plasma generator 8, a bubbling bed catalytic reactor 9, a plasma torch 10, and a blast furnace 11.

[0030] The ammoniation reactor 1 is connected to the first solid-liquid separator 2, with high-temperature flue gas as the input end and mixed component A as the output end, including a solid-liquid mixture whose main components are NH4Cl and NaHCO3. The liquid output end of the first solid-liquid separator is connected to the leaching reactor 3, and the leachate B (main component NH4Cl) is output; the solid output end is connected to the conversion reactor 4, and the precipitate C (main component NaHCO3) is output.

[0031] The output end of the leaching reactor 3 is connected to the conversion reactor 4, and outputs a mixed component D including ammonia water and CaCl2 solution.

[0032] The output end of the conversion reactor 4 is connected to the second separator 5, which outputs a mixed component E, including a solid-liquid mixture of NaCl, NH4Cl and CaCO3. The solid output end of the second solid-liquid separator 5 is connected to the bubbling bed catalytic reactor 9, which outputs a solid component F (main component CaCO3); the liquid input end is connected to the recovery reactor 6, which outputs a liquid mixed component G (main components NaCl and NH4Cl solution).

[0033] The output end of the recovery reactor 6 is connected to the ammonia reactor 1, and outputs a mixed component H, including NaCl and NH3 solution (ammoniation brine) and CO2 gas.

[0034] The input end of the plasma generator 8 is connected to the electrolysis device 7, and the gas component I (main component H2) is input; the output end is connected to the bubbling bed catalytic reactor 9, and the plasma hydrogen J is output. The gas output end of the bubbling bed catalytic reactor 9 is connected to the plasma torch 10, and the mixed component L is output, including the synthesis gas whose main components are CO and H2. The solid output end outputs the value-added product K (main component CaO).

[0035] The plasma torch 10 is connected to the blast furnace 11, and outputs gas component H (high-temperature synthesis gas with main components of CO and H2)

[0036] like Figure 1 As shown, a method for efficient calcium-based carbon capture and recycling based on steel slag comprises:

[0037] The high-temperature flue gas enters the ammoniation reactor 1, and the CO2 in the high-temperature flue gas is captured after an ammoniation reaction occurs in the said ammoniation reactor. The generated mixed component A (a solid-liquid mixture of NH4ClB and NaHCO3 as the main components) is sent to the first solid-liquid separator 2. The ammoniation reaction of CO2 in the ammoniation reactor 1 is: 2NaCl+2H2O+2NH3+2CO2→2NaHCO3+2NH4Cl, the temperature in the ammoniation reactor 1 is 10-60°C, and the energy comes from the flue gas itself.

[0038] The first solid-liquid separator 2 separates the leachate B (main component NH4Cl) and sends it to the leaching reactor 3; the first solid-liquid separator 2 separates the precipitate C (main component NaHCO3) and sends it to the conversion reactor 4.

[0039] The pretreated steel slag is added to the leaching reactor 3 to achieve the leaching of calcium ions in the steel slag. The resulting mixed solution D (ammonia and CaCl2 solution) is sent to the conversion reactor 4. The leaching reaction in the leaching reactor 3 is: 2NH4Cl+Ca(OH)2→2NH3+CaCl2+2H2O. The temperature in the leaching reactor 3 is 60-120°C, and the energy comes from the waste heat recovery of high-temperature flue gas and steel slag.

[0040] The conversion reaction takes place in the conversion reactor 4 to achieve Ca 2+ The generated mixed component E (solid-liquid mixture of NaCl, NH4Cl and CaCO3) is sent to the second solid-liquid separator 5. The reaction occurring in the conversion reactor is: NaHCO3+NH3+CaCl2→NaCl+CaCO3+NH4Cl. The temperature of the conversion reactor 4 is 10-60°C, and the energy comes from the solution itself.

[0041] The second solid-liquid separator 5 separates the leachate G (NaCl and NH4Cl solution) and sends it to the recovery reactor 6; the separated precipitate F (main component CaCO3) is sent to the bubbling bed catalytic reactor 9.

[0042] A chemical reaction further occurs in the recovery reactor 6 to achieve recovery of the starting materials. The resulting mixed solution H (NaCl and NH3 solution (ammoniation brine)) is fed into the amination reactor 1. The reaction occurring in the recovery reactor 6 is: NaHCO3+NH4Cl→NaCl+CO2+NH3+H2O. The temperature in the recovery reactor 6 is 60-120°C, and the energy comes from the waste heat recovery of high-temperature flue gas and steel slag.

[0043] The electrolysis device 7 realizes the electrolysis of H2O, and the generated component I (mainly composed of H2 gas) is fed into the plasma generator 8. The plasma generator 8 generates plasma hydrogen and feeds it into the bubbling bed catalytic reactor 9. CaCO3 is catalytically decomposed in the bubbling bed catalytic reactor 9. The generated mixed gas L (synthesis gas with main components of CO and H2) is fed into the plasma torch for heating 10, and after high temperature addition, the mixed gas M (high-temperature synthesis gas with main components of CO and H2) is formed and returned to the blast furnace 11 to replace coke to reduce iron ore; the generated solid component K (mainly composed of CaO) is used as a value-added product to improve the economic benefits of the system. The catalytic reaction occurring in the bubbling bed catalytic reactor 9 is: CaCO3+H2→CaO+CO+H2O. The temperature in the bubbling bed catalytic reactor 9 is 550-700°C, and the energy comes from the waste heat recovery of high-temperature flue gas and steel slag.

[0044] Taking a steel plant with a daily output of 1,000 tons as an example, it is known by general economic calculation that based on the technical solution proposed in this work, it is possible to achieve low energy consumption (~1.8GJ / t CO2) to recover 570,000 tCO2 / yr, co-produce about 711,000 t / yr of CaO, co-produce about 309,000 t / yr of CO, and replace 133,000 tons of coke. Taking into account the carbon quota income, value-added product income, raw material substitution cost savings and slag treatment process costs, the net income of this technical solution is about 31 million yuan / yr. Compared with existing slag treatment technology and CO2 capture technology, it has obvious economic advantages.

[0045] In practical applications, Solvay soda ash production can be integrated with the steel production industry to achieve efficient integration of the two industries in terms of resource and energy allocation. For example, Solvay Hengchang (Zhangjiagang) Co., Ltd. is located within 10km of Jiangsu Zhangjiagang Lianfeng Steel Group. The two industries are geographically adjacent, and they have great integration potential in resource recycling, energy sharing, by-product exchange, waste disposal and reduction, and supply chain optimization.

[0046] The system and method proposed in this work are expected to realize a technology cluster of industrial CO2 emission reduction, waste resource utilization and efficient energy utilization, promote the industrial integration of soda ash production and steel production in the region, and promote the green transformation and sustainable development of the steel industry. It has good promotion value and market application prospects.

Claims

1. An efficient calcium-based carbon capture and recycling system based on steel slag, characterized in that: It includes a calcium-based carbon capture subsystem and a CO2 in-situ conversion subsystem. In the calcium-based carbon capture subsystem, it includes an ammonia reaction furnace, a first solid-liquid separator, a leaching reaction furnace, a conversion reaction furnace, a second solid-liquid separator, and a recovery reaction furnace which are connected in sequence; in the CO2 in-situ conversion subsystem, it includes an electrolysis device, a plasma generator, a bubbling bed catalytic reaction furnace, a plasma torch, and a blast furnace which are connected in sequence.

2. The high-efficiency calcium-based carbon capture and recycling system based on steel slag according to claim 1 is characterized in that: The ammoniation reactor is connected to the first solid-liquid separator, with high-temperature flue gas as the input end and mixed components as the output end, including a solid-liquid mixture whose main components are NH4Cl and NaHCO3. The liquid output end of the first solid-liquid separator is connected to the leaching reactor, and the leachate is output, the main component of which is NH4Cl; the solid output end is connected to the conversion reactor, and the precipitate is output, the main component of which is NaHCO3. The output end of the leaching reactor is connected to the conversion reactor, and outputs a mixed component, including ammonia water and CaCl2 solution. The output end of the conversion reactor is connected to the second separator, and outputs a mixed component, including a solid-liquid mixture of NaCl, NH4Cl and CaCO3. The solid output end of the second solid-liquid separator is connected to the bubbling bed catalytic reactor, and outputs a solid component, the main component of which is CaCO3; the liquid input end is connected to the recovery reactor, and outputs a liquid mixed component, the main components of which are NaCl and NH4Cl solution. The output end of the recovery reactor is connected to the ammonia reactor to output mixed components including NaCl and NH3 solutions and CO2 gas.

3. The high-efficiency calcium-based carbon capture and recycling system based on steel slag according to claim 1 is characterized in that: The input end of the plasma generator is connected to the electrolysis device to input gas components, mainly H2; the output end is connected to the bubbling bed catalytic reactor to output plasma hydrogen, the gas output end of the bubbling bed catalytic reactor is connected to the plasma torch to output mixed components, including synthesis gas mainly composed of CO and H2, the solid output end outputs value-added products, mainly composed of CaO, the plasma torch is connected to the blast furnace to output gas components, mainly composed of high-temperature synthesis gas mainly composed of CO and H2.

4. The high-efficiency calcium-based carbon capture and recycling system based on steel slag according to claim 1 is characterized in that: The H2 gas produced by the electrolysis device will be fed into the plasma generator to produce plasma hydrogen, and then fed into the bubbling bed catalytic reactor to realize the decomposition of CaCO3. The generated synthesis gas, whose main components are CO and H2 gas, will return to the blast furnace after being heated by the plasma torch.

5. The high-efficiency calcium-based carbon capture and recycling system based on steel slag according to claim 1 is characterized in that: Features: The reaction temperature of the bubbling bed catalytic reactor is 550-700°C.

6. A method for calcium-based carbon capture using steel slag, characterized in that: Using the recycling system according to any one of claims 1 to 5, the method comprises the following steps: Step 1, high-temperature flue gas enters the ammoniation reactor, CO2 in the high-temperature flue gas is captured after an ammoniation reaction occurs in the ammoniation reactor, and the resulting mixed component, the main component of which is a solid-liquid mixture of NH4Cl and NaHCO3, is sent to the first solid-liquid separator, the first solid-liquid separator separates the leachate, the main component of which is NH4Cl, and is sent to the leaching reactor; the precipitation component, the main component of which is NaHCO3, is separated and sent to the conversion reactor, Step 2, adding the pretreated steel slag into the leaching reactor to achieve the leaching of calcium ions in the steel slag, and the resulting mixed solution, i.e., ammonia water and CaCl2 solution, is sent to the conversion reactor, Step 3: a conversion reaction takes place in the conversion reactor to achieve Ca 2+ The solid phase precipitation, the mixed components, namely the solid-liquid mixture of NaCl, NH4Cl and CaCO3, are sent to the second solid-liquid separator, the second solid-liquid separator separates the leachate, namely the NaCl and NH4Cl solution, and sends it to the recovery reactor; the precipitation, the main component of which is CaCO3, is separated and sent to the bubbling bed catalytic reactor. Step 4, further chemical reaction occurs in the recovery reactor to achieve recovery of the starting materials, and the resulting mixed solution, i.e., NaCl and NH3 solution (ammoniation brine), is fed into the amination reactor.

7. The method of claim 6 using calcium-based carbon capture based on steel slag, characterized in that: The reaction temperature of the amination reactor is 10-60°C.

8. The method of claim 6 using calcium-based carbon capture based on steel slag, characterized in that: The reaction temperature of the leaching reactor is 60-120°C.

9. The method of claim 6, wherein: The reaction temperature of the conversion reactor is 10-60°C.

10. The method of claim 6, wherein: The reaction temperature of the recovery reactor is 60-120°C.

Images