Low-carbon blast furnace ironmaking system and method based on adsorption enhanced CO conversion

Abstract

The invention relates to a low-carbon blast furnace ironmaking system and method based on adsorption enhanced CO conversion. The system comprises a blast furnace, a dust removal device, a fine desulfurization device, a pressurization device, an adsorption enhanced conversion device, heat exchange devices I and II, a gas separation device and a heating device. After being subjected to dust removal and fine desulfurization treatment, blast furnace gas is pressurized through the pressurizing device, and enters the adsorption enhancement conversion device after being subjected to partial CO conversion through the pre-conversion device and the heat exchange device I; the adsorption enhancement conversion device adopts a low-temperature CO conversion catalyst and a CO2 adsorbent, efficient utilization of coal gas chemical energy is achieved by improving the CO conversion rate and the CO2 capture rate, and hydrogen-rich gas is produced. The hydrogen-rich gas is cooled and dehydrated by the heat exchange device II and then enters the gas separation device, and high-purity H2 obtained by separation is heated to 900 DEG C or above by the heating device and is injected into the blast furnace to replace part of solid carbon as a reducing agent, so that the carbon emission of blast furnace ironmaking is reduced. The method provided by the invention solves the problem of separation of CO and N2, simplifies the process flow, significantly improves the utilization efficiency of blast furnace gas, has high economical efficiency and carbon reduction effect, and is suitable for low-carbon development of the steel industry.

Description

Technical Field

[0001] The present invention belongs to the technical field of low-carbon ironmaking, and relates to a low-carbon blast furnace ironmaking system and method based on adsorption-enhanced CO conversion. Background Art

[0002] Blast furnace ironmaking will continue to dominate the ironmaking process for a considerable period of time. Currently, the idea of ​​reducing carbon emissions in blast furnaces by replacing carbon with hydrogen and coal with gas has gained widespread industry consensus. Blast furnace gas, the largest source of gas for steel companies, is currently used primarily as fuel, underutilizing the chemical energy of its reducing components. The most direct technical approach to utilizing the chemical energy of blast furnace gas in the ironmaking process is to separate the reducing component, CO, from the gas and inject it into the blast furnace, reducing coal and coke consumption and, therefore, carbon emissions from the blast furnace ironmaking process. However, because blast furnace gas contains a large amount of N2, whose molecular properties are very similar to those of CO, separating CO and N2 is extremely difficult.

[0003] Currently, the main methods for separating CO and N₂ are cryogenic separation and cuprous ion capture. Because the boiling points of N₂ and CO are very similar, cryogenic separation requires multiple distillations near their boiling points, which consumes a lot of energy. In contrast, cuprous ion capture requires removing sulfides from blast furnace gas to below 0.1 ppm, as cuprous ions are easily poisoned by sulfides. This significantly increases the cost of gas pretreatment and makes this technology difficult to promote and apply. Therefore, a technology that can effectively utilize the chemical energy of blast furnace gas for low-carbon smelting in blast furnaces is urgently needed. Summary of the Invention

[0004] In view of this, the object of the present invention is to solve the above problems and provide a low-carbon blast furnace ironmaking system and method based on adsorption enhanced CO conversion.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] A low-carbon blast furnace ironmaking system based on adsorption-enhanced CO2 conversion, comprising a blast furnace, a dust removal device, a fine desulfurization device, a pressurizing device, an adsorption-enhanced conversion device, a heat exchange device II, and a gas separation device arranged in sequence along the blast furnace gas flow direction;

[0007] The adsorption-enhanced conversion device is filled with a low-temperature CO conversion catalyst and a CO2 adsorbent, which converts CO into H2 and improves the conversion rate of the reactant CO by adsorbing the product CO2. Combined with the temperature and pressure change process, the desorption and enrichment of CO2 is achieved;

[0008] The heat exchange device II cools the hydrogen-rich gas to below 100°C, dehydrates it and makes the gas temperature meet the requirements of the gas separation device; the gas separation device is used to separate H2 and N2, and the separation method is one or a combination of pressure swing adsorption and membrane separation methods. The high-purity N2 obtained by separation is further used in other links of steel production.

[0009] Furthermore, the CO shift catalyst loaded in the adsorption enhanced shift device is a copper-zinc low-temperature shift catalyst or a cobalt-molybdenum wide-temperature shift catalyst, the type of CO2 adsorbent loaded is one or more of MgO, CaO, molecular sieve, solid amine, and dolomite, the mass ratio of CO shift catalyst to CO2 adsorbent is 1:(1-5), and the loading method is mixed loading or multi-layer interval loading;

[0010] The operating temperature in the adsorption enhanced conversion device is controlled to be 180-250°C, achieving a CO conversion rate ≥ 90% and a CO2 capture rate ≥ 95%. The obtained CO2 is used in the steelmaking process or for conversion and utilization and geological storage.

[0011] Furthermore, the dust removal device reduces the dust content in blast furnace gas to 10 mg / Nm 3 In the following, the dust removal method used is one or a combination of gravity dust removal, bag dust removal, and wet dust removal.

[0012] Furthermore, the fine desulfurization device removes COS and H2S in the coal gas to a sulfur content of ≤20mg / m 3 The desulfurization method used is one or a combination of wet alkaline washing, dry desulfurization, and solid adsorption.

[0013] Furthermore, the pressurizing device pressurizes the purified blast furnace gas to above 0.6 MPa, and the gas outlet pressure is ≥150°C.

[0014] Furthermore, a pre-conversion device and a heat exchange device I are provided between the pressurizing device and the adsorption enhancement conversion device;

[0015] The pre-conversion device is connected to low-pressure steam, which, together with the blast furnace gas pressurized by the pressurizing device, achieves partial conversion of CO through the water-gas shift reaction. The CO conversion catalyst loaded in the pre-conversion device is an iron-chromium high-temperature shift catalyst or a cobalt-molybdenum wide-temperature shift catalyst, and the operating temperature is controlled at 350-500°C to achieve a CO conversion rate of ≥50%;

[0016] The heat exchange device I cools the CO pre-shifted gas to below 150° C., so that the gas temperature meets the operating temperature requirements of the adsorption enhanced shift device.

[0017] Furthermore, a heating device is provided between the gas separation device and the blast furnace. The heating device heats the H2 separated by the gas separation device to above 900°C and then injects the H2 into the blast furnace as a reducing agent to replace part of the solid carbon and achieve carbon reduction.

[0018] A low-carbon blast furnace ironmaking method based on adsorption-enhanced CO2 conversion adopts the low-carbon blast furnace ironmaking system based on adsorption-enhanced CO2 conversion as described above; blast furnace ironmaking produces blast furnace gas, and the blast furnace gas is reduced to a dust content of 10 mg / Nm3 by a dust removal device. 3 Below, the sulfur content is reduced to 20mg / m3 by fine desulfurization device 3 Next, after entering the pressurizing device and being pressurized to above 0.6MPa, it enters the adsorption enhanced conversion device together with the low-pressure steam to achieve the final conversion of CO and capture of CO2. The obtained hydrogen-rich gas is cooled by the heat exchange device II and then enters the gas separation device to achieve the separation of H2 and N2. The obtained H2 is blown into the blast furnace as a reducing agent to replace part of the solid carbon and achieve carbon reduction.

[0019] Furthermore, a pre-conversion device and a heat exchange device I are provided between the pressurizing device and the adsorption enhanced conversion device; the blast furnace gas pressurized by the pressurizing device enters the pre-conversion device together with the low-pressure steam, and partial conversion of CO is achieved in the pre-conversion device through the water-gas shift reaction, with a CO conversion rate of more than 50%; the product gas of the pre-conversion device is cooled in the heat exchange device I and then passed into the adsorption enhanced conversion device to achieve final conversion of CO and capture of CO2.

[0020] Furthermore, the H2 separated by the gas separation device is heated and then enters the blast furnace as a reducing agent.

[0021] The beneficial effects of the present invention are:

[0022] 1. The present invention solves the problem of separation of CO and N2 in blast furnace gas from the source by converting CO into H2, realizes the use of chemical energy of blast furnace gas for blast furnace smelting, and reduces carbon emissions from blast furnace ironmaking.

[0023] 2. The present invention combines the low-temperature conversion, cooling and CO2 capture steps in the conventional process through adsorption enhanced conversion technology, greatly simplifying the process flow and improving the conversion rate of the reactant CO by adsorbing the reaction product CO2 in the gas.

[0024] 3. The present invention converts the carbon reducing agent CO in blast furnace gas into H2 and recycles it back to the blast furnace, further reducing carbon emissions from blast furnace ironmaking.

[0025] Other advantages, objects, and features of the present invention will be described in part in the following description and, in part, will be apparent to those skilled in the art upon examination of the following description or may be learned from practice of the present invention. The objects and other advantages of the present invention may be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below with reference to the accompanying drawings, in which:

[0027] Figure 1 This is a schematic diagram of the low-carbon blast furnace ironmaking system in Example 1 of the present invention.

[0028] Figure 2 This is a schematic diagram of the low-carbon blast furnace ironmaking system in Example 2 of the present invention.

[0029] Figure numerals: 1-blast furnace; 2-dust removal device; 3-fine desulfurization device; 4-pressurization device; 5-pre-conversion device; 6-heat exchange device I; 7-adsorption enhanced conversion device; 8-heat exchange device II; 9-gas separation device; 10-heating device. DETAILED DESCRIPTION

[0030] The following describes the embodiments of the present invention by means of specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present invention, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0031] Among them, the accompanying drawings are only for illustrative purposes and represent only schematic diagrams rather than actual pictures, and should not be understood as limiting the present invention. In order to better illustrate the embodiments of the present invention, some parts of the accompanying drawings may be omitted, enlarged or reduced, and do not represent the dimensions of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions may be omitted in the accompanying drawings.

[0032] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "left", "right", "front", "back", etc. indicating directions or positional relationships, they are based on the directions or positional relationships shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operate in a specific direction. Therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0033] Example 1

[0034] See also Figure 1 It is a low-carbon blast furnace ironmaking system based on adsorption-enhanced CO conversion, including: blast furnace 1, dust removal device 2, fine desulfurization device 3, pressurizing device 4, adsorption-enhanced conversion device 7, heat exchange device II8, gas separation device 9. Due to the low CO content in conventional blast furnace gas, pre-conversion device 5 and heat exchange device I6 are not set in this system.

[0035] A 500m 3 The main technical indicators of conventional blast furnaces are as follows:

[0036] Table 1 Main technical indicators of conventional blast furnace

[0037] Focal ratio Coal ratio Fuel ratio Blast oxygen enrichment rate 345kg / thm 170kg / thm 515kg / thm 5％

[0038] The H2S content in blast furnace gas is 38 mg / Nm 3 , COS content is 158mg / Nm 3 The dust content in blast furnace gas is reduced to 10mg / Nm3 by using bag dust removal, organic sulfur hydrolysis and dry H2S removal. 3 , sulfide removal to 15mg / Nm 3 The gas temperature after desulfurization is 80℃, the gas pressure is 0.2MPa, and the composition of the blast furnace gas after purification is shown in Table 2.

[0039] Table 2 Composition of blast furnace gas after purification

[0040] CO <![CDATA[CO2]]> <![CDATA[H2]]> <![CDATA[N2]]> 24.5％ 25.1％ 3.2％ 47.2％

[0041] The purified blast furnace gas is pressurized to 0.6 MPa via the pressure device 4, and the gas temperature is 150°C and directly passed into the adsorption enhanced conversion device 7. At the same time, low-pressure steam is passed into the adsorption enhanced conversion device 7, and the steam temperature is 200°C. The adsorption enhanced conversion device is filled with CaO as a CO2 adsorbent and Al2O3-loaded cobalt molybdenum oxide as a conversion reaction catalyst. The adsorbent and catalyst are physically mixed and loaded with a loading mass ratio of 1:1. The adsorption enhanced conversion device maintains a temperature of 350-380°C and a controlled air velocity of 1000h -1 The reaction proceeds with a CO conversion efficiency of 90%. The adsorbed CO2 is desorbed by reducing the pressure and purged with N2, producing hydrogen-rich gas primarily composed of H2 and N2, and CO2-rich gas primarily composed of CO2. The CO2-rich gas is recycled in processes such as steelmaking. The hydrogen-rich gas is cooled to 40°C by heat exchanger II8, where liquid water is removed. The H2 and N2 are then separated by gas separator 9, resulting in high-purity N2, which is used as a shielding gas in steel mills. The N2 impurity in the resulting H2 accounts for 5.5%.

[0042] The H2 obtained by the gas separation device 9 is directly injected into the blast furnace in a cold state through the tuyere sleeve. 3 Blast furnace, processing gas 20000Nm 3 / h, the amount of H2 obtained is 5083Nm 3 / h, hydrogen injection volume per ton of iron is 69.7m 3 After hydrogen injection, the coke ratio of the blast furnace is 337kg / t and the coal ratio is 157kg / t.

[0043] Using the conventional blast furnace ironmaking method and system based on adsorption-enhanced CO2 shifting in this embodiment, the chemical energy of blast furnace gas is converted and then used for smelting in blast furnace 1, reducing the fuel ratio by 21 kg / t of iron and CO2 emissions by 58 kg per ton of iron. Furthermore, the adsorption-enhanced CO2 shifting device avoids the complex process of CO2 shifting, cooling, and CO2 capture, significantly simplifying the production process.

[0044] Example 2

[0045] like Figure 2 As shown, an oxygen-enriched blast furnace ironmaking system based on adsorption-enhanced CO conversion includes: a blast furnace 1, a dust removal device 2, a fine desulfurization device 3, a pressurizing device 4, a pre-conversion device 5, a heat exchange device I6, an adsorption-enhanced conversion device 7, a heat exchange device II8, a gas separation device 9, and a heating device 10. Since the CO content in the oxygen-enriched blast furnace gas is relatively high, the CO conversion reaction process releases a large amount of heat. In this embodiment, a medium-temperature conversion series low-temperature conversion method is adopted, and a pre-conversion device 5 and a heat exchange device I6 are set.

[0046] A 1000m 3The main technical indicators of the oxygen-enriched blast furnace are as follows:

[0047] Table 3 Main technical indicators of oxygen-enriched blast furnace

[0048] Focal ratio Coal ratio Fuel ratio Blast oxygen enrichment rate 305kg / thm 140kg / thm 445kg / thm 80％

[0049] The dust content is reduced to 10mg / Nm by combining gravity dust removal with bag dust removal. 3 Below. The H2S content in blast furnace gas is 22mg / Nm 3 , COS content is 130mg / Nm 3 The sulfide in blast furnace gas is removed to 20mg / Nm by combining water cooling and dechlorination with direct dry adsorption. 3 The gas temperature after desulfurization is 40℃, the gas pressure is 0.2MPa, and the composition of the blast furnace gas after purification is shown in Table 4.

[0050] Table 4 Composition of oxygen-enriched blast furnace gas after purification

[0051] CO <![CDATA[CO2]]> <![CDATA[H2]]> <![CDATA[N2]]> 38.1％ 30.3％ 8.5％ 23.1％

[0052] The purified blast furnace gas is pressurized to 0.6 MPa and 160°C by the pressure device 4, and then passed into the pre-conversion device 5 together with 200°C low-pressure steam. The pre-conversion device 5 operates at a temperature of 360-390°C and is loaded with an iron-chromium high-temperature CO shift catalyst with Fe2O3 and Cr2O3 as the main components. The space velocity is controlled at 700h -1 The reaction is carried out to achieve a CO conversion rate of 65%. The product gas after pre-conversion is cooled to 160°C by the heat exchange device I6 and then passed into the adsorption enhanced conversion device 7 together with the supplementary steam. The adsorption enhanced conversion device 7 is filled with MgO as a CO2 adsorbent and a copper-based low-temperature conversion catalyst. The temperature is controlled at 220-240°C and the space velocity is 1000h -1 The reaction proceeds, achieving a CO conversion rate of 90%. The CO₂ adsorbed in the adsorption-enhanced conversion device 7 is desorbed by reducing the pressure and purged with N₂, producing a hydrogen-rich gas primarily composed of H₂ and N₂, and a CO₂-rich gas primarily composed of CO₂. The CO₂-rich gas is used for oil recovery and storage. The hydrogen-rich gas is cooled to 40°C by heat exchanger II8, where liquid water is removed. The H₂ and N₂ are then separated by gas separation device 9, which utilizes membrane separation technology. The resulting high-purity N₂ is used as a shielding gas in steel mills. The N₂ impurity content in the resulting H₂ is 1.6%.

[0053] The H2 obtained by the gas separation device 9 is heated to 1200℃ by the heating device 10 and then injected into the blast furnace 1. 3 Blast furnace, processing gas 15000Nm 3 / h, the amount of H2 obtained is 6557Nm3 / h, hydrogen injection capacity per ton of iron is 89.9m 3 After hydrogen injection, the coke ratio of the blast furnace is 287kg / t and the coal ratio is 113kg / t.

[0054] Therefore, an oxygen-enriched blast furnace ironmaking method and system based on adsorption-enhanced CO2 shift conversion was adopted. The chemical energy of blast furnace gas was converted and then used for blast furnace smelting, reducing the fuel ratio by 45kg / ton of iron and CO2 emissions by 125kg per ton of iron. Furthermore, the adsorption-enhanced CO2 shift device avoids the complex process of CO2 shift, followed by cooling, and then CO2 capture, significantly simplifying the production process.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions, which should all be included in the scope of the claims of the present invention.

Claims

1. A low-carbon blast furnace ironmaking system based on adsorption-enhanced CO2 shift, characterized by: It includes a blast furnace, a dust removal device, a fine desulfurization device, a pressurizing device, an adsorption enhancement conversion device, a heat exchange device II, and a gas separation device which are sequentially arranged along the blast furnace gas flow direction; The adsorption-enhanced conversion device is filled with a low-temperature CO conversion catalyst and a CO2 adsorbent, which converts CO into H2 and improves the conversion rate of the reactant CO by adsorbing the product CO2. Combined with the temperature and pressure change process, the desorption and enrichment of CO2 is achieved; The heat exchange device II cools the hydrogen-rich gas to below 100°C, dehydrates it and makes the gas temperature meet the requirements of the gas separation device; the gas separation device is used to separate H2 and N2, and the separation method is one or a combination of pressure swing adsorption and membrane separation methods. The high-purity N2 obtained by separation is further used in other links of steel production.

2. The low-carbon blast furnace ironmaking system based on adsorption-enhanced CO2 shift according to claim 1 is characterized in that: The CO conversion catalyst loaded in the adsorption enhanced conversion device is a copper-zinc low-temperature conversion catalyst or a cobalt-molybdenum wide-temperature conversion catalyst, and the type of the CO2 adsorbent loaded is one or more of MgO, CaO, molecular sieve, solid amine, and dolomite. The mass ratio of the CO conversion catalyst to the CO2 adsorbent is 1:(1-5), and the loading method is mixed loading or multi-layer interval loading; The operating temperature in the adsorption enhanced conversion device is controlled to be 180-250°C, achieving a CO conversion rate ≥ 90% and a CO2 capture rate ≥ 95%. The obtained CO2 is used in the steelmaking process or for conversion and utilization and geological storage.

3. The low-carbon blast furnace ironmaking system based on adsorption-enhanced CO2 shift according to claim 1 is characterized in that: The dust removal device reduces the dust content in blast furnace gas to 10mg / Nm 3 In the following, the dust removal method used is one or a combination of gravity dust removal, bag dust removal, and wet dust removal.

4. The low-carbon blast furnace ironmaking system based on adsorption-enhanced CO2 shift according to claim 1 is characterized in that: The fine desulfurization device removes COS and H2S in the coal gas to a sulfur content of ≤20mg / m 3 The desulfurization method used is one or a combination of wet alkaline washing, dry desulfurization, and solid adsorption.

5. The low-carbon blast furnace ironmaking system based on adsorption-enhanced CO2 shift according to claim 1 is characterized in that: The pressurizing device pressurizes the purified blast furnace gas to above 0.6 MPa, and the gas outlet pressure is ≥150°C.

6. The low-carbon blast furnace ironmaking system based on adsorption-enhanced CO2 shift according to claim 1 is characterized in that: A pre-conversion device and a heat exchange device I are also provided between the pressurizing device and the adsorption enhancement conversion device; The pre-conversion device is connected to low-pressure steam, which, together with the blast furnace gas pressurized by the pressurizing device, achieves partial conversion of CO through the water-gas shift reaction. The CO conversion catalyst loaded in the pre-conversion device is an iron-chromium high-temperature shift catalyst or a cobalt-molybdenum wide-temperature shift catalyst, and the operating temperature is controlled at 350-500°C to achieve a CO conversion rate of ≥50%; The heat exchange device I cools the CO pre-shifted gas to below 150° C., so that the gas temperature meets the operating temperature requirements of the adsorption enhanced shift device.

7. The low-carbon blast furnace ironmaking system based on adsorption-enhanced CO2 shift according to claim 1 is characterized in that: A heating device is provided between the gas separation device and the blast furnace. The heating device heats the H2 separated by the gas separation device to above 900°C and then injects it into the blast furnace as a reducing agent, replacing part of the solid carbon to achieve carbon reduction.

8. A low-carbon blast furnace ironmaking method based on adsorption-enhanced CO2 shift, characterized by: A low-carbon blast furnace ironmaking system based on adsorption-enhanced CO conversion as described in any one of claims 1 to 7 is used; blast furnace ironmaking produces blast furnace gas, and the blast furnace gas is reduced to 10 mg / Nm3 by a dust removal device. 3 Below, the sulfur content is reduced to 20mg / m3 by fine desulfurization device 3 Next, after entering the pressurizing device and being pressurized to above 0.6MPa, it enters the adsorption enhanced conversion device together with the low-pressure steam to achieve the final conversion of CO and capture of CO2. The obtained hydrogen-rich gas is cooled by the heat exchange device II and then enters the gas separation device to achieve the separation of H2 and N2. The obtained H2 is blown into the blast furnace as a reducing agent to replace part of the solid carbon and achieve carbon reduction.

9. The low-carbon blast furnace ironmaking method based on adsorption-enhanced CO shift according to claim 8, characterized in that: A pre-conversion device and a heat exchange device I are also provided between the pressurizing device and the adsorption-enhanced conversion device; the blast furnace gas pressurized by the pressurizing device enters the pre-conversion device together with low-pressure steam, and partial conversion of CO is achieved in the pre-conversion device through the water-gas shift reaction, with a CO conversion rate of more than 50%; the product gas of the pre-conversion device is cooled in the heat exchange device I and then passed into the adsorption-enhanced conversion device to achieve final conversion of CO and CO2 capture.

10. The low-carbon blast furnace ironmaking method based on adsorption-enhanced CO shift according to claim 8, characterized in that: The H2 separated by the gas separation device is heated and then enters the blast furnace as a reducing agent.

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