Exhaust method based on carbon dioxide concentration in flue gas and application thereof

Abstract

The present application relates to the technical field of concrete building materials, in particular to an exhaust method based on carbon dioxide concentration in flue gas, specifically: when the temperature reaches K0+(K1-K0) / (n+1) for the first time, exhaust; when the temperature reaches K0+(K1-K0)×2 / (n+1) for the second time, exhaust; when the temperature reaches K0+(K1-K0)×3 / (n+1) for the third time, exhaust; when the temperature reaches K0+(K1-K0)×4 / (n+1) for the fourth time, exhaust; when the temperature reaches K0+(K1-K0)×n / (n+1) for the nth time, exhaust; after each exhaust to normal pressure, the flue gas is replenished to the pressure P of the reaction kettle, and pressure maintaining is carried out to the corresponding temperature; wherein the exhaust times in the reaction process are n, the initial temperature of mineralization reaction is K0, and the final temperature of the system is K1.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of concrete building materials, in particular to an application method of flue gas concentration and exhaust method. BACKGROUND

[0002] Due to the limited proportion of carbon dioxide in flue gas, when participating in mineralization reaction, there is a large amount of unreacted gas. When this gas accumulates, it will make the reaction slow down, and the accumulation of too much waste gas will quickly increase the pressure in the reaction kettle, causing the carbon dioxide gas pressure in the mineralization reaction to drop, affecting the mineralization rate. Therefore, whether it is high-concentration carbon dioxide flue gas generated by the coal chemical industry or low-concentration carbon dioxide from coal-fired power plants, the accumulation of unreacted gas will affect the mineralization gas pressure, and the pressure limitation of the reactor and transportation equipment.

[0003] At present, most studies use high-concentration carbon dioxide for mineralization to solve the above problems. Chinese patent application document CN113955992A discloses a kind of high-efficiency carbon absorption mineralization aerated concrete and its preparation method, which uses 99.9% carbon dioxide gas, and adjusts the gas partial pressure to 1.0-1.2MPa to further ensure the progress of mineralization reaction. Chinese patent application document CN113998982A discloses a kind of full-solid waste-based carbonation non-fired lightweight aggregate and its preparation method, which also uses 99.9% carbon dioxide gas for mineralization. Although the above patent application documents achieve mineralization reaction by using high-concentration carbon dioxide, they cannot utilize low-concentration carbon dioxide, cannot mineralize and capture low-concentration carbon dioxide, and the mineralization reaction is limited. Moreover, the industrial production cost of high-concentration carbon dioxide is high, which cannot be applied on a large scale. SUMMARY

[0004] Therefore, in view of the above problems of low-concentration carbon dioxide utilization and equipment process parameters, the present application provides an exhaust method based on the concentration of carbon dioxide in flue gas and its application, which reduces the pressure in the pipeline and reaction kettle by exhaust, ensures the carbon dioxide partial pressure, greatly reduces the equipment demand, and realizes the industrial utilization of low-concentration carbon dioxide from the process point of view, improves the mineralization effect, and further promotes the utilization of carbon dioxide mineralization.

[0005] The first aspect of the present application provides a method for exhausting based on the concentration of carbon dioxide in flue gas, which is specifically: when the temperature reaches K0+(K1-K0) / (n+1) for the first time, exhaust; when the temperature reaches K0+(K1-K0)×2 / (n+1) for the second time, exhaust; when the temperature reaches K0+(K1-K0)×3 / (n+1) for the third time, exhaust; when the temperature reaches K0+(K1-K0)×4 / (n+1) for the fourth time, exhaust; and so on, when the temperature reaches K0+(K1-K0)×n / (n+1) for the nth time, exhaust; after each exhaust to normal pressure, the flue gas is replenished to the pressure P of the reaction kettle, and pressure maintaining is performed to the corresponding temperature; wherein the number of exhausts during the reaction is n, the initial temperature of the mineralization reaction is K0, and the final temperature of the system is K1.

[0006] As a preferred technical solution, the method for exhausting based on the concentration of carbon dioxide in flue gas satisfies the following relationship:

[0007] n>

[0008] 0.18774*K1*a*m*(1-w) / [w*v*(1-s)*(1-0.133322*10 -3 *10 [7.96681 -1668.21 / (K1-45.15)] -0.1*K1 / K0)]-1;

[0009] wherein the volume concentration of carbon dioxide in flue gas is w, unit %; the volume of the reaction kettle is v, unit m 3 ; the green body mass is m, unit t; the filling rate of the reaction kettle is s, unit %; the initial temperature of the mineralization reaction is K0, unit K; the final temperature of the system is K1, unit K; the empirical constant of the product reaction is a, and the value of n is the minimum integer corresponding to the formula calculation value. During the calculation process, the numerical values of various parameters are brought into the formula according to the unit, and the calculation process only involves numerical operation and does not involve unit.

[0010] As a preferred technical solution, the volume concentration of carbon dioxide in flue gas is 70%-99.9%, and the number of exhausts n is 0-4 times.

[0011] As a preferred technical solution, the pressure P of the reaction kettle satisfies the following relationship: P≥0.18774*K1*a*m*(1-w) / [(n+1)*w*v*(1-s)]+0.101322+0.1*K1 / K0; wherein the volume concentration of carbon dioxide in flue gas is w, unit %; the volume of the reaction kettle is v, unit m 3; the green body quality is m, in units of t; the filling rate of the reaction kettle is s, in units of %; the initial temperature of the mineralization reaction is K0, in units of K; the final temperature of the system is K1, in units of K; and the empirical constant of the product reaction is a. During the calculation process, the numerical values of the parameters are brought into the formula according to the units, and the calculation process only involves numerical operation and does not involve units. The pressure P of the reaction kettle is in units of MPa.

[0012] The filling rate of the reaction kettle is the proportion of the green body filled in the reaction kettle to the volume of the reaction kettle.

[0013] As a preferred technical solution, the pressure P of the reaction kettle is 0.05-1 MPa.

[0014] As a preferred technical solution, the filling rate s of the reaction kettle is 5-50%; the empirical constant a of the product reaction is 0.01-0.2; and the initial temperature K0 of the mineralization is 273.15 K-323.15 K, and the final temperature K1 of the mineralization reaction is 353.15 K-453.15 K.

[0015] The second aspect of the present application provides an application of an exhaust method based on the concentration of carbon dioxide in flue gas in the preparation of building products.

[0016] As a preferred technical solution, the preparation method of the building product is:

[0017] (1) placing the calcium-based solid waste mixture into a mold to form a green body;

[0018] (2) sending the green body into a mineralization reaction kettle, closing the reaction kettle, and introducing flue gas containing carbon dioxide into the mineralization reaction kettle to a pressure P;

[0019] (3) during the mineralization reaction, the exhaust is performed according to the exhaust method, and the building product can be obtained after the mineralization reaction is completed.

[0020] As a preferred technical solution, the calcium-based solid waste mixture in step (1) includes mixed solid waste and water, and the mass ratio of the water to the mixed solid waste is (0.05-0.30):1;

[0021] Preferably, the content of the mineralizable solid waste in the mixed solid waste accounts for 10-80% of the total weight of the mixed solid waste, and the mixed solid waste at least includes high-calcium solid waste and silico-aluminicalcic solid waste; preferably, the mass ratio of the high-calcium solid waste to the silico-aluminicalcic solid waste is (10-80):(20-90).

[0022] Preferably, the high-calcium solid waste is one or more of carbide slag, cement kiln dust, waste lime, waste cement, steel slag, coal cinder, and furnace slag; and the silico-alumina solid waste is one or more of recycled aggregate, phosphogypsum, construction debris, yellow phosphorus slag, fly ash, smelting slag, red mud, and power plant slag.

[0023] As a preferred technical solution, the forming method of the calcium-based solid waste mixture into a green body is press forming, and the forming pressure is 5-100 MPa.

[0024] As a preferred technical solution, the carbon dioxide-containing flue gas is one of coal-fired power plant flue gas, lime kiln flue gas, steel plant flue gas, chemical plant flue gas, cement plant flue gas, ammonia plant flue gas, and gas after carbon capture resolution; preferably, the volume concentration of carbon dioxide in the flue gas is 70%-99.9%.

[0025] As a preferred technical solution, in steps (2) and (3), the aeration rate of the flue gas in the pressure increasing and air supplementing stage of the reaction kettle is q, and the aeration rate q is 20-100 m 3 / min.

[0026] As a preferred technical solution, the total pressure maintaining time t of the mineralization reaction is 1-12 hours.

[0027] Beneficial effects:

[0028] 1. The exhaust method based on the concentration of carbon dioxide in flue gas is proposed in the application, the system pressure can be optimized by adjusting the exhaust times, which can be applied to flue gas containing different concentrations of carbon dioxide. For flue gas with low concentration of carbon dioxide, the carbon dioxide partial pressure in the system can also be maintained within a certain range, the mineralization efficiency is improved, and the existing equipment can be used without the need for pressure improvement of the existing equipment, which greatly reduces the cost of solid waste disposal and carbon capture, and is conducive to the popularization and application of low-concentration carbon dioxide mineralization.

[0029] 2. The exhaust method provided by the application can be applied to the preparation of building products, which can ensure that the carbon dioxide pressure in the system is maintained under the process parameter conditions by regulating the reaction through the exhaust method, ensure the degree of mineralization reaction of the system, improve the product performance, realize the comprehensive utilization of flue gas with low concentration of carbon dioxide, promote the disposal of industrial waste gas of coal chemical industry, power plant, cement plant, steel plant, ammonia plant, etc., realize the efficient utilization of waste CO2, and further reduce the production cost to promote the large-scale production and application of carbon dioxide mineralization products.

[0030] 3. This invention utilizes carbon dioxide waste gas emitted from industries such as coal chemical plants, coal-fired power plants, and steel plants. It uses active calcium components in solid waste to fix carbon dioxide and regulates the mineralization pressure through exhaust gas to ensure mineralization efficiency and improve the strength of the product. This invention realizes the utilization of low-concentration carbon dioxide flue gas in industrial production, further reduces process costs and equipment requirements, makes full use of solid waste, and produces high-performance building materials.

[0031] 4. This application proposes using low-concentration carbon dioxide flue gas as the curing gas, and directly using the carbon dioxide-containing flue gas for mineralization curing. Under certain processes, high-quality building products are produced, effectively realizing the efficient resource utilization of low-concentration carbon dioxide from coal chemical plants, coal-fired power plants, steel plants, etc. The building materials products prepared by the synergistic mineralization treatment have a total carbon emission that is more than 50% lower than that of traditional silicate cement products. This not only solves the solid waste disposal and carbon emission problems of enterprises such as coal chemical plants, coal-fired power plants, and steel plants, but also plays an important role in promoting the low-carbon development of my country's building materials industry. Detailed Implementation

[0032] In this embodiment of the application: a certain coal chemical plant carbide slag was selected as a high-calcium solid waste with a moisture content of 29.67%. Its chemical composition and weight percentage are shown in Table 1 by XRF analysis.

[0033] Table 1. Main elemental composition of calcium carbide slag

[0034] Elemental composition CaO P2O5 SiO2 Al2O3 Fe2O3 K2O SO3 Na2O Loss Content 82.7 4.75 4.28 2.32 0.31 0.18 0.15 0.1 5.21

[0035] Fly ash from a coal chemical plant was selected as a silica-alumina solid waste with a moisture content of 1.3%. Its chemical composition and weight percentage were obtained by XRF analysis and are shown in Table 2.

[0036] Table 2. Main elemental composition of fly ash

[0037] Elemental composition SiO ２ ]]> Al2O3 CO ２ ]] CaO Fe ２ O3]]> Na2O SO3 MgO Loss Content 47.36 31.57 8.54 3.35 2.41 0.8 0.6 0.2 5.17

[0038] Steel slag from a steel company was selected as a high-calcium solid waste with a moisture content of 3.5%. Its chemical composition and weight percentage were obtained by XRF analysis and are shown in Table 3.

[0039] Table 3. Main elemental composition of steel slag

[0040] Elemental composition CaO SiO2 Fe2O3 Al2O3 MgO MnO TiO P2O5 Loss Content 39.69 14.85 23.65 3.31 7.58 2.56 2.15 1.34 4.87

[0041] A recycled material from a building materials factory was selected as a silica-alumina solid waste with a moisture content of 1.4%. Its chemical composition and weight percentage were obtained by XRF analysis and are shown in Table 4.

[0042] Table 4. Main elemental composition of recycled aggregates

[0043] Elemental composition SiO2 Al2O3 CO2 CaO Fe2O3 [K2O] MgO Na2O Loss Content 46.2 17.5 18.2 8.31 3.85 1.23 1.07 0.71 2.93

[0044] Kiln ash from a cement plant was selected as a high-calcium solid waste with a moisture content of 1.3%. Its chemical composition and weight percentage were obtained by XRF analysis and are shown in Table 5.

[0045] Table 5. Main elemental composition of kiln ash

[0046] Elemental composition CaO SO3 SiO2 K2O Al2O3 Fe2O3 MgO Na2O Loss Content 55.27 13.1 12.85 5.74 5.41 1.95 1.58 0.98 3.12

[0047] A power plant slag was selected as a silica-alumina solid waste with a moisture content of 1.7%. Its chemical composition and weight percentage were obtained by XRF analysis and are shown in Table 6.

[0048] Table 6. Main elemental composition of power plant slag

[0049] Elemental composition SiO2 Al2O3 Fe2O3 CaO MgO TiO2 K2O Na2O Loss Content 44.41 37.75 8.35 3.65 1.25 1.11 0.62 0.33 2.53

[0050] Flue gas from a certain salt and coal chemical plant was selected, and its gas composition and weight percentage are shown in Table 7.

[0051] Table 7. Composition (volume fraction) of exhaust gas produced by a coal chemical plant.

[0052] Gas composition CO2 [N2] Loss Coal chemical tail gas 78.5％ 20.4％ 1.1％

[0053] The flue gas from a steel plant after carbon capture was selected, and its gas composition and weight percentage are shown in Table 8.

[0054] Table 8. Gas composition (volume fraction) after carbon capture at a steel plant.

[0055] Gas composition CO2 [N2] Loss Coal chemical tail gas 75.3％ 23.5％ 1.2％

[0056] Flue gas from a cement plant's carbon capture system was selected, and its gas composition and weight percentage are shown in Table 9.

[0057] Table 9. Composition (volume fraction) of exhaust gas produced by a cement plant.

[0058] Gas composition CO2 [N2] Loss Coal chemical tail gas 65.7％ 33.1％ 1.2％

[0059] The gas composition and volume percentage of flue gas collected from a coal-fired power plant are shown in Table 10.

[0060] Table 10. Gas composition (volume fraction) after carbon capture at a power plant.

[0061] Gas composition CO2 [N2] Loss Coal chemical tail gas 63.8％ 34.6％ 1.6％

[0062] Example 1

[0063] Example 1 of the present invention applies the exhaust method based on the carbon dioxide concentration in flue gas to prepare building products. The preparation method of the building products is as follows:

[0064] (1) Take 20wt% of the above-mentioned carbide slag and 70.93wt% of fly ash, add 9.07wt% of water and mix evenly. Put the mixture into a mold and press it into a blank under a molding pressure of 10MPa. The brick shape is 200mm*95mm*53mm; the filling rate of each batch is 30.00%, and a total of 91.16t of blanks are produced.

[0065] (2) The billet is fed into the reactor. After the reactor is sealed, flue gas containing carbon dioxide is introduced into the reactor until the pressure reaches 0.93 MPa and the CO2 concentration (v / v) is 78.5%. The flue gas composition is shown in Table 7. The gas flow rate during the pressurization stage of the reactor is 80 m³ / s. 3 / min, the initial reaction temperature is room temperature (25℃);

[0066] (3) During the mineralization reaction, exhaust is carried out according to the established exhaust method. The gas flow rate of the flue gas during the replenishment stage after exhausting the reactor is 80m. 3 / min, after the mineralization reaction is completed, building products can be obtained.

[0067] The parameters of the reactor are as follows:

[0068] The inner diameter is 2.55m, the length is 35m, and the volume of the reactor is 178m³. 3 The mass m of the bricks is 91.16t, the filling rate s of the reactor is 30%, and the density of the bricks is 1700kg / m³. 3 The volume concentration of carbon dioxide in the flue gas, w, is 78.5%. The initial reaction temperature, K0, is 298.15 K, and the final reaction temperature, K1, is 373.15 K. The empirical constant for the product, a, is 0.1. Substitute the values ​​of each parameter into the formula (only the numerical values, not the units), and use the formula n >

[0069] 0.18774*K1*a*m*(1-w) / [w*v*(1-s)*(1-0.133322*10 -3 *10 [7.96681 -1668.21 / (K1-45.15)] -0.1*K1 / K0)]-1, we calculate n>0.8, and take its smallest integer as 1, that is, the number of exhaust times is 1; according to the formula P≥0.18774*K1*a*m*(1-w) / [(n+1)*w*v*(1-s)]+0.101322+0.1*K1 / K0, we calculate P≥0.93MPa.

[0070] The exhaust process is as follows:

[0071] S1. When the reaction temperature reaches 62.5℃, open the vent to release pressure and discharge the gas in the reactor. After reaching atmospheric pressure, close the vent. Before venting, maintain the reactor pressure at 0.93MPa.

[0072] S2. Open the air inlet valve to reintroduce carbon dioxide flue gas and maintain the pressure of the mineralization reactor at 0.93 MPa. After the total pressure holding time reaches 4 hours, discharge the gas in the reactor to obtain the finished brick, which is the building product.

[0073] The resulting product was tested and found to have a weight gain of 10.22% and a compressive strength of 14.37 MPa.

[0074] Example 2

[0075] Example 2 of the present invention applies the exhaust gas method based on the carbon dioxide concentration in flue gas to prepare building products. The preparation method of the building products is as follows:

[0076] (1) Take 40wt% and 49.4wt% of the above-mentioned steel slag and mix them together. Add 10.6wt% of water and mix evenly. Put the mixture into a mold and press it into a blank brick shape of 200mm*95mm*53mm under a molding pressure of 10MPa. The filling rate of each batch is 30.00%, and a total of 91.16t of blanks are produced.

[0077] (2) The billet is fed into the mineralization reactor. After sealing the reactor, flue gas containing carbon dioxide is introduced into the mineralization reactor until the pressure reaches 0.80 MPa and the CO2 concentration (v / v) is 75.3%. The flue gas composition is shown in Table 8. The gas flow rate during the pressurization stage of the reactor is 80 m³ / s. 3 / min, the initial reaction temperature is room temperature (25℃);

[0078] (3) During the mineralization reaction, exhaust is carried out according to the established exhaust method. The gas flow rate of the flue gas during the replenishment stage after exhausting the reactor is 80m. 3 / min, after the mineralization reaction is completed, building products can be obtained.

[0079] The parameters of the reactor are as follows:

[0080] The inner diameter is 2.55m, the length is 35m, and the volume of the reactor is 178m³. 3 The mass m of the bricks is 91.16t, the filling rate s of the reactor is 30%, and the density of the bricks is 1700kg / m³. 3The volume concentration of carbon dioxide in the flue gas, w, is 75.3%. The initial reaction temperature, K0, is 298.15 K, and the final reaction temperature, K1, is 378.15 K. The empirical constant for the product, a, is 0.1. Substituting the values ​​of each parameter into the formula (only the values, not the units), the formula is: n > 0.18774 * K1 * a * m * (1 - w) / [w * v * (1 - s) * (1 - 0.133322 * 10^6]^2. -3 *10 [7.96681-1668.21 / (K1-45.15)] -0.1*K1 / K0)]-1, we calculate n>1.3, and take its smallest integer as 2, that is, the number of exhaust times is 2; according to the formula P≥0.18774*K1*a*m*(1-w) / [(n+1)*w*v*(1-s)]+0.101322+0.1*K1 / K0, we calculate P≥0.80MPa.

[0081] The exhaust process is as follows:

[0082] S1. When the reaction temperature reaches 51.7℃, open the vent to release pressure and discharge the gas in the reactor. After reaching atmospheric pressure, close the vent. Before venting, maintain the reactor pressure at 0.80MPa.

[0083] S2. Replenish flue gas. When the reaction temperature reaches 78.3℃, open the vent to release pressure and discharge the gas in the reactor. After reaching atmospheric pressure, close the vent. Before exhausting the gas, maintain the reactor pressure at 0.80MPa.

[0084] S3. Open the air inlet valve to reintroduce carbon dioxide flue gas and maintain the pressure of the mineralization reactor at 0.80 MPa. After the total pressure holding time reaches 4 hours, discharge the gas in the reactor to obtain the finished brick, which is the building product.

[0085] The resulting product was tested and found to have a weight gain of 9.75% and a compressive strength of 20.79 MPa.

[0086] Example 3

[0087] Example 3 of the present invention applies the exhaust method based on the carbon dioxide concentration in flue gas to prepare building products. The preparation method of the building products is as follows:

[0088] (1) Take 20.00wt% and 65.26wt% of the above-mentioned cement kiln ash and mix them together. Add 14.74wt% of water and mix evenly. Place the mixture into a mold and press it into a blank under a molding pressure of 10MPa. The brick shape is 200mm*95mm*53mm. The filling rate of each batch is 30.00%, and a total of 91.16t of blanks are produced.

[0089] (2) The billet is fed into the mineralization reactor. After sealing the reactor, flue gas containing carbon dioxide is introduced into the mineralization reactor until the pressure reaches 0.92 MPa and the CO2 concentration (v / v) is 65.7%. The flue gas composition is shown in Table 9. The gas flow rate during the pressurization stage of the reactor is 80 m³ / s. 3 / min, the initial reaction temperature is room temperature (25℃);

[0090] (3) During the mineralization reaction, exhaust is carried out according to the established exhaust method. The gas flow rate of the flue gas during the replenishment stage after exhausting the reactor is 80m. 3 / min, after the mineralization reaction is completed, building products can be obtained.

[0091] The parameters of the reactor are as follows:

[0092] The inner diameter is 2.55m, the length is 35m, and the volume of the reactor is 178m³. 3 The mass m of the bricks is 91.16t, the filling rate s of the reactor is 30%, and the density of the bricks is 1700kg / m³. 3 The volume concentration of carbon dioxide in the flue gas, w, is 65.7%. The initial reaction temperature, K0, is 298.15 K, and the final reaction temperature, K1, is 383.15 K. The empirical constant of the product, a, is 0.1. Substituting the values ​​of each parameter into the formula (only the values, not the units), the formula is: n > 0.18774 * K1 * a * m * (1 - w) / [w * v * (1 - s) * (1 - 0.133322 * 10^6]^2. -3 *10 [7.96681-1668.21 / (K1-45.15)] -0.1*K1 / K0)]-1, we calculate n>2.8, and take its smallest integer as 3, that is, the number of exhaust times is 3; according to the formula P≥0.18774*K1*a*m*(1-w) / [(n+1)*w*v*(1-s)]+0.101322+0.1*K1 / K0, we calculate P≥0.92MPa.

[0093] The exhaust process is as follows:

[0094] S1. When the reaction temperature reaches 46.25℃, open the vent to release pressure and discharge the gas in the reactor. After reaching atmospheric pressure, close the vent. Before venting, maintain the reactor pressure at 0.92MPa.

[0095] S2. Replenish flue gas. When the reaction temperature reaches 67.5℃, open the vent to release pressure and discharge the gas in the reactor. After reaching atmospheric pressure, close the vent. Before exhausting the gas, maintain the reactor pressure at 0.92MPa.

[0096] S3. Replenish flue gas. When the reaction temperature reaches 88.75℃, open the vent to release pressure and discharge the gas in the reactor. After reaching atmospheric pressure, close the vent. Before exhausting the gas, maintain the reactor pressure at 0.92MPa.

[0097] S4. Open the air inlet valve to reintroduce carbon dioxide flue gas, and maintain the pressure of the mineralization reactor at 0.92MPa. After the total pressure holding time reaches 4 hours, discharge the carbon dioxide gas to obtain the finished brick, which is a building product.

[0098] The resulting product was tested and found to have a weight gain of 10.37% and a compressive strength of 13.64 MPa.

[0099] Example 4

[0100] Example 4 of the present invention applies the exhaust method based on the carbon dioxide concentration in flue gas to prepare building products. The preparation method of the building products is as follows:

[0101] (1) Take 25.00wt% of the above-mentioned carbide slag and 67.42wt% of power plant slag, add 7.58% water and mix evenly. Put the mixture into a mold and press it into a green body under a molding pressure of 10MPa. The brick shape is 200mm*95mm*53mm. The filling rate of each batch is 30.00%, and a total of 91.16t of green bodies are produced.

[0102] (2) The billet is fed into the mineralization reactor. After sealing the reactor, flue gas containing carbon dioxide is introduced into the mineralization reactor until the pressure reaches 0.84 MPa and the CO2 concentration (v / v) is 63.8%. The flue gas composition is shown in Table 10. The gas flow rate during the pressurization stage of the reactor is 80 m³ / s. 3 / min, the initial reaction temperature is room temperature (25℃);

[0103] (3) During the mineralization reaction, exhaust is carried out according to the established exhaust method. The gas flow rate of the flue gas during the replenishment stage after exhausting the reactor is 80m. 3 / min, after the mineralization reaction is completed, building products can be obtained.

[0104] The parameters of the reactor are as follows:

[0105] The inner diameter is 2.55m, the length is 35m, and the volume of the reactor is 178m³. 3 The mass m of the brick body is 91.16t, the filling rate s of the reactor is 30%, and the density of the brick body is 1700kg / m³. 3 The volume concentration of carbon dioxide in the flue gas, w, is 63.8%. The initial reaction temperature, K0, is 298.15 K, and the final reaction temperature, K1, is 388.15 K. The empirical constant of the product, a, is 0.1. Substituting the values ​​of each parameter into the formula (only the values, not the units), the formula is: n > 0.18774 * K1 * a * m * (1 - w) / [w * v * (1 - s) * (1 - 0.133322 * 10^6]^2. -3 *10 [7.96681-1668.21 / (K1-45.15)]-0.1*K1 / K0)]-1, we calculate n>3.3, and take its smallest integer as 4, that is, the number of exhaust times is 4; according to the formula P≥0.18774*K1*a*m*(1-w) / [(n+1)*w*v*(1-s)]+0.101322+0.1*K1 / K0, we calculate P≥0.84MPa.

[0106] The exhaust process is as follows:

[0107] S1. When the reaction temperature reaches 43℃, open the vent to release pressure and discharge the gas in the reactor. After reaching atmospheric pressure, close the vent. Before venting, maintain the reactor pressure at 0.84MPa.

[0108] S2. Replenish flue gas. When the reaction temperature reaches 61℃, open the vent to release pressure and discharge the gas in the reactor. After reaching atmospheric pressure, close the vent. Before exhausting, maintain the reactor pressure at 0.84MPa.

[0109] S3. Replenish flue gas. When the reaction temperature reaches 79℃, open the vent to release pressure and discharge the gas in the reactor. After reaching atmospheric pressure, close the vent. Before venting, maintain the reactor pressure at 0.84MPa.

[0110] S4. Replenish flue gas. When the reaction temperature reaches 97℃, open the vent to release pressure and discharge the gas in the reactor. After reaching atmospheric pressure, close the vent. Before venting, maintain the reactor pressure at 0.84MPa.

[0111] S5. Open the air inlet valve to reintroduce carbon dioxide flue gas, and maintain the pressure of the mineralization reactor at 0.84 MPa. After the total pressure holding time reaches 4 hours, discharge the carbon dioxide gas to obtain the finished brick, which is the building product.

[0112] The resulting product was tested and found to have a weight gain of 10.74% and a compressive strength of 14.52 MPa.

[0113] Comparative Example 1

[0114] The specific implementation method of Comparative Example 1 is the same as that of Example 1, except that no venting was performed during the mineralization reaction in Comparative Example 1. The resulting product was tested and found to have a weight gain of 5.17% and a compressive strength of 7.26 MPa.

[0115] Comparative Example 2

[0116] Comparative Example 2 was carried out in the same manner as Example 2, except that venting was performed only once at 65°C. The resulting product was tested and showed a weight gain of 6.53% and a product strength of 12.72 MPa.

[0117] Comparative Example 3

[0118] Comparative Example 3 was carried out in the same manner as Example 3, except that the exhaust was performed twice at 53.3°C and 81.7°C. The resulting product was tested and found to have a weight gain of 5.27% and a product strength of 7.73 MPa.

[0119] Comparative Example 4

[0120] Comparative Example 4 was implemented in the same manner as Example 4, except that it underwent three venting processes at 47.5°C, 70°C, and 92.5°C. The resulting product, after testing, showed a weight gain of 8.57% and a product strength of 9.77 MPa.

[0121] Comparative Example 5

[0122] The specific implementation method of Comparative Example 5 is the same as that of Example 1, except that the pressure inside the reactor during the mineralization reaction in Comparative Example 5 is 0.73 MPa. The resulting product was tested and found to have a weight gain of 7.47% and a compressive strength of 8.27 MPa.

[0123] Comparative Example 6

[0124] The specific implementation method of Comparative Example 6 is the same as that of Example 2, except that the pressure inside the reactor during the mineralization reaction in Comparative Example 6 is 0.60 MPa. The resulting product was tested and found to have a weight gain of 6.92% and a product strength of 13.13 MPa.

[0125] Comparative Example 7

[0126] The specific implementation method of Comparative Example 7 is the same as that of Example 3, except that the pressure inside the reactor during the mineralization reaction in Comparative Example 7 is 0.72 MPa. The resulting product was tested and found to have a weight gain of 7.62% and a product strength of 10.87 MPa.

[0127] Comparative Example 8

[0128] The specific implementation method of Comparative Example 8 is the same as that of Example 4, except that the pressure inside the reactor during the mineralization reaction in Comparative Example 8 is 0.64 MPa. The resulting product was tested and found to have a weight gain of 6.13% and a product strength of 9.53 MPa.

[0129] Performance testing methods

[0130] 1. Weight gain rate: The weight gain rate of the finished bricks (test blocks) prepared in the examples and comparative examples was tested. In this invention, the weight gain rate is expressed as the weight gain rate of the test blocks. The change in mass before and after CO2 curing was determined by the mass weighing method. The calculation method of the weight gain rate is as follows:

[0131]

[0132] Where ω is the apparent weight gain rate.

[0133] m0 is the dry weight after CO2 compression.

[0134] m1 represents the mass of the specimen after CO2 curing (mass after drying).

[0135] The specific steps are as follows:

[0136] (1) The moisture content w1 of the digested raw material was measured, and the mass of the brick was weighed after pressing. The corresponding dry basis mass m0 in the test block was calculated based on the moisture content after digestion.

[0137] (2) After the mineralization of the test block is completed, the test block is dried to constant weight and its dry basis mass is measured as m1.

[0138] (3) The weight gain rate of the corresponding test block can be obtained by using the above formula.

[0139] The mass was measured using a PTY-B5000 electronic balance with a range of 5 kg and a linear error of ±0.04 g.

[0140] 2. Compressive strength test: Referring to GBT4111-2013 "Test methods for concrete blocks and bricks", the finished bricks prepared in the examples and comparative examples were naturally air-dried for 24 hours to obtain specimens, and the compressive strength of the specimens was tested.

[0141] (1) Experimental Procedure

[0142] 1) Measure the length and width of the connection surface or pressure surface of each specimen twice, and take the average value of each, accurate to 1 mm.

[0143] 2) Place 10 specimens flat in the center of the pressure plate and apply the load perpendicular to the pressure surface. The loading should be uniform and stable, without any impact or vibration. The loading rate is (5 ± 0.5) kN / s until the specimen fails. Record the maximum failure load F (in N) for each specimen.

[0144] (2) Calculation of test results: Calculate the compressive strength of 10 specimens according to the following formula, accurate to 0.1MPa.

[0145]

[0146] In the formula f mc —Compressive strength (MPa);

[0147] F—Maximum destructive load (N);

[0148] L—Length (mm) of the pressure-bearing surface (connection surface);

[0149] B—Width of the pressure-bearing surface (connection surface) (mm).

[0150] Calculate the average compressive strength of three to five specimens. If the difference between the measured values ​​and their average is no greater than 15%, then use the average as the compressive strength. If any value differs from the average by more than 15%, this value should be discarded, and the average should be calculated using the remaining values.

[0151] The building products prepared in Examples 1-4 had a weight gain of 9.75-10.74% and a compressive strength of 13.64-20.79 MPa. It can be seen that the building products prepared by the exhaust method of this application have good carbon fixation effect and compressive strength.

[0152] Compared with Example 1, Comparative Example 2, Comparative Example 3, and Comparative Example 4, the number of exhaust times in each comparative example was reduced. The weight gain and compressive strength of the prepared building products decreased significantly. This indicates that reducing the number of exhaust times will affect the mineralization effect, which will not only reduce the capture of carbon dioxide by the building products, but also lead to a decrease in the compressive strength of the products.

[0153] Compared with Example 1, Comparative Example 6 with Example 2, Comparative Example 7 with Example 3, and Comparative Example 8 with Example 4, the pressure inside the reactor in each comparative example was relatively low during the mineralization reaction. The weight gain and compressive strength of the prepared building products were significantly reduced, indicating that reducing the pressure inside the reactor also affects the mineralization effect.

[0154] Therefore, it can be seen that determining the degassing method in the mineralization reaction process according to the content defined in this application is beneficial to obtaining building products with good carbon fixation effect and high compressive strength.

Claims

1. A method for exhausting flue gas based on the concentration of carbon dioxide in the flue gas, characterized in that, The exhaust method is as follows: the first exhaust occurs when the temperature reaches K0 + (K1 - K0) / (n+1); the second exhaust occurs when the temperature reaches K0 + (K1 - K0) × 2 / (n+1); the third exhaust occurs when the temperature reaches K0 + (K1 - K0) × 3 / (n+1); the fourth exhaust occurs when the temperature reaches K0 + (K1 - K0) × 4 / (n+1); and so on, until the temperature reaches K0 + (K1 - K0) × n / (n+1). After each exhaust to atmospheric pressure, flue gas is replenished to the reactor pressure P and maintained at the corresponding temperature. The number of exhausts during the reaction process is n, the initial temperature of the mineralization reaction is K0, and the final temperature of the system is K1. n>0.18774*K1*a*m*(1-w) / [w*v*(1-s)*(1-0.133322*10 -3 *10 [7.96681-1668.21 / (k 1 -45.15)] -0.1*K1 / K0)] -1; where the volume concentration of carbon dioxide in the flue gas is w, in units of %; and the volume of the reactor is v, in units of m³. 3 The mass of the billet is m, in tons; the filling rate of the reactor is s, in percent; the initial temperature of the mineralization reaction is K0, in K; the final temperature of the system is K1, in K; the empirical constant of the product reaction is a, and the value of n is the smallest integer corresponding to the calculated value. The volume concentration of carbon dioxide in the flue gas is 63.8%-78.5%, and the number of exhaust times n is 1-4. The pressure P in the reactor satisfies the following relationship: P≥0.18774*K1*a*m*(1-w) / [(n+1)*w*v*(1-s)]+0.101322+0.1*K1 / K0; where w is the volume concentration of carbon dioxide in the flue gas (%) and v is the volume of the reactor (m³). 3 The mass of the billet is m, in tons; the filling rate of the reactor is s, in percent; the initial temperature of the mineralization reaction is K0, in K; the final temperature of the system is K1, in K; and the empirical constant for the product reaction is a. The filling rate s of the reactor is 5-50%; the empirical constant a of the product reaction is 0.01-0.2; the initial temperature K0 of the mineralization is 273.15K-323.15K, and the final temperature K1 of the mineralization reaction is 353.15K-453.15K.

2. The application of the exhaust method based on the carbon dioxide concentration in flue gas according to claim 1 in the preparation of building products.

3. The application according to claim 2, characterized in that, The method for preparing the building product is as follows: (1) Place the calcium-based solid waste mixture into a mold to form a blank; (2) The billet is fed into the mineralization reactor, the reactor is sealed, and flue gas containing carbon dioxide is introduced into the reactor to pressure P; (3) During the mineralization reaction, exhaust is carried out according to the exhaust method described above. After the mineralization reaction is completed, building products can be obtained.

4. The application according to claim 3, characterized in that, In step (1), the calcium-based solid waste mixture includes mixed solid waste and water, and the mass ratio of water to mixed solid waste is (0.05-0.30):1; the content of mineralizable solid waste in the mixed solid waste accounts for 10-80% of the total weight of the mixed solid waste.

5. The application according to claim 4, characterized in that, The mixed solid waste includes at least high-calcium solid waste and siliceous-aluminate solid waste; the high-calcium solid waste is one or more of the following: carbide slag, cement kiln ash, waste lime, waste cement, steel slag, coal slag, and furnace slag; the siliceous-aluminate solid waste is one or more of the following: recycled aggregate, construction waste, yellow phosphorus slag, fly ash, smelting slag, red mud, and power plant furnace slag; the carbon dioxide-containing flue gas is one of the following: flue gas from a coal-fired power plant, lime kiln, steel plant, cement plant, and ammonia plant.

6. The application according to claim 3, characterized in that, In steps (2) and (3), the gas flow rate of the flue gas during the pressurization and gas replenishment stages of the reactor is q, and the gas flow rate q is 20-100 m. 3 / min.

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