A reduction shaft furnace ironmaking system and process

Abstract

The present application belongs to the technical field of metallurgy-iron making, and discloses a reducing shaft furnace iron making system and process, wherein a new gas phase outlet is arranged in the middle of the reduction section, and an oxygen injection device is arranged above the new gas phase outlet; the process is that the iron-containing furnace charge is fed into the shaft furnace, and hot reduction gas is continuously introduced into the bottom of the reduction section to reduce the iron-containing furnace charge; in the reduction process, part of the gas is discharged through the new gas phase outlet, and oxygen is injected through the oxygen injection device, the oxygen and the remaining reduction gas are combusted to release heat, all the reduction gas is oxidized, so that the temperature of the reduction section is maintained; the gas discharged through the new gas phase outlet is mixed with the hot reduction gas after H2O and CO2 are removed, and is introduced into the reduction section again; the top gas is separated from H2O through condensation, and CO2 is captured. The present application realizes full application of the chemical energy of the top gas and in-situ capture of CO2 in the tail gas, and solves the problem of high energy consumption of CO2 separation in the direct reduction of the shaft furnace.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical-ironmaking technology, specifically, it relates to a reduction shaft furnace ironmaking system and process. Background Technology

[0002] Greenhouse gas emissions are causing increasingly severe climate change, and energy conservation and emission reduction have become a global consensus. The steel industry, in particular, is extremely reliant on fossil fuels and generates enormous carbon emissions. To reduce carbon dioxide emissions, technological innovation in the high-emission steel industry is imperative. Currently, replacing the traditional blast furnace long-process process with a vertical shaft furnace direct reduction short-process technology has become the future trend in industrial ironmaking.

[0003] 75% of the world's direct reduced iron (DRI) is produced by gas-based shaft furnaces. Currently, the most widely used gas-based shaft furnace technologies are the Midrex and HYL processes. The Midrex process uses natural gas reforming to produce reducing gas, which is introduced from the central air inlet of the shaft furnace. This reducing gas reduces iron ore pellets and lump iron ore added from the top into sponge iron through convection. The top gas contains approximately 60-70% CO and H2. A portion of the top gas is pressurized and sent to a mixing chamber to be mixed uniformly with an equivalent amount of natural gas. This mixture is then converted into reducing gas through catalytic cracking at a temperature of 850-900℃, with a CO and H2 content of approximately 95%. The remaining top gas, after adding a small amount of natural gas, is used as fuel outside the reformer reactor tubes to provide heat for the natural gas catalytic cracking reaction. Simultaneously, the reformer flue gas enters a heat exchanger to preheat the mixed feed gas and combustion air, further recovering and utilizing the heat. This process uses an external conversion furnace, increasing investment and requiring a large amount of Ni-based and other precious metal catalysts, resulting in high operating costs. Furthermore, the flue gas contains a large amount of CO2, requiring further treatment before emission. The HYL process can directly use coke oven gas, coal gas, or other syngas as reducing gas. Its iron ore reduction process is similar to the Midrex process. The gas from the furnace top is dehydrated and de-CO2ed, then mixed with dehydrated fresh syngas, heated by a heater, and burned with a suitable amount of oxygen before being sent to the iron reduction shaft furnace. This process consumes a large amount of gas, and the gas from the furnace top also has high CO and H2 content. Subsequent separation processes consume significant power and emit large amounts of CO2, which is inconsistent with the current clean and green development path.

[0004] In the Midrex and HYL processes, the top gas contains high levels of CO and H2, resulting in inefficient utilization of the reducing potential chemical energy. Direct emission of this energy leads to waste. This necessitates the re-entry of some top gas into the shaft furnace after CO2 removal, as excessively high CO2 content directly impacts the quality of reduced iron. Consequently, significant energy is required for CO2 separation, resulting in high operating costs. Simultaneously, the endothermic hydrogen reduction in the reducing gas causes a substantial increase in heat demand at the top of the shaft furnace, necessitating external heating of the reducing gas at the bottom of the furnace to maintain thermal balance, leading to substantial energy consumption.

[0005] Therefore, there is an urgent need for a green, clean, and low-carbon reduced iron process that can reduce process energy consumption and production costs. This process can simultaneously meet the heat requirements of hydrogen reduction in the upper part of the gas-based vertical shaft furnace and CO2 capture of the furnace top gas, thereby reducing subsequent separation energy consumption and equipment investment. Summary of the Invention

[0006] In order to fully utilize the chemical energy of the furnace top gas and capture CO2 in the tail gas in situ, while reducing the energy consumption of CO2 separation in the circulating gas, this invention proposes a reducing shaft furnace ironmaking system and process.

[0007] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution:

[0008] According to one aspect of the present invention, a reduction shaft furnace ironmaking system is provided, comprising a shaft furnace, wherein at least one additional gas phase outlet is provided in the middle of the reduction section of the shaft furnace, and at least one oxygen injection device is provided above the additional gas phase outlet in the reduction section of the shaft furnace.

[0009] Preferably, the newly added gas phase outlets are evenly arranged circumferentially along the furnace body in the reduction section.

[0010] Preferably, the newly added gas phase outlet is evenly arranged along the longitudinal direction of the furnace body in the reduction section.

[0011] Preferably, the oxygen injection device is evenly arranged circumferentially along the furnace body in the reduction section.

[0012] Preferably, the oxygen injection device is evenly arranged along the longitudinal direction of the furnace body in the reduction section.

[0013] Furthermore, the newly added gas phase outlet is connected to the inlet of the gas purification device, and the outlet of the gas purification device is connected to the fresh reducing gas pipeline at the bottom of the vertical furnace; the gas outlet at the top of the vertical furnace is connected to the inlet of the waste gas condensation device, and the outlet of the waste gas condensation device is used for CO2 capture.

[0014] According to another aspect of the present invention, a reduction shaft furnace ironmaking process based on the above-described system is provided, comprising the following steps:

[0015] Iron-containing furnace charge is fed into the vertical furnace, and hot reducing gas is continuously introduced into the bottom of the reduction section of the vertical furnace to reduce the iron-containing furnace charge. During the reduction process, according to the temperature of the iron-containing furnace charge in the reduction section of the vertical furnace, some gas is discharged through the newly added gas phase outlet, and oxygen is injected into the reduction section of the vertical furnace through the oxygen injection device. The oxygen and the remaining reducing gas are burned and released heat, oxidizing all the reducing gas, thereby maintaining the temperature of the reduction section at 500-1200℃.

[0016] The gas discharged from the newly added gas phase outlet enters the gas purification device, where H2O and CO2 are removed, and then it is mixed with the hot reducing gas and reintroduced into the reduction section of the vertical furnace.

[0017] The gas from the top of the vertical furnace enters the waste gas condensation device, where H2O is separated by condensation and CO2 is captured.

[0018] Furthermore, the thermal reducing gas is CO, H2, CH4, syngas, natural gas, shale gas, water gas, or biogas, etc.

[0019] Furthermore, the proportion of the gas discharged from the newly added gas phase outlet accounts for 50%-90% of the reducing gas introduced into the vertical furnace.

[0020] Furthermore, the oxygen injected into the vertical furnace by the oxygen injection device can oxidize all the remaining reducing gas in the vertical furnace, so that the composition of the furnace top gas consists only of H2O and CO2.

[0021] The beneficial effects of this invention are:

[0022] (i) In this invention, a portion of the reducing gas is discharged in the middle of the reduction section of the vertical furnace and then reintroduced into the vertical furnace from the bottom after purification. Compared with the original process where all the gas is discharged from the top of the furnace, which requires a lot of energy to separate CO2, this invention only needs to separate a portion of the gas discharged from the middle of the vertical furnace, which can effectively reduce the energy consumption of CO2 separation.

[0023] (II) In this invention, a portion of oxygen is uniformly introduced from the upper part of the reduction section of the vertical furnace. The combustion of oxygen and reducing gas in the furnace releases a large amount of heat, which can raise and maintain the temperature inside the vertical furnace at 500-1200°C. This improves the reaction rate, reducing gas utilization rate and direct reduced iron conversion rate in the vertical furnace, making up for the problem of insufficient heat supply in the metallurgical process. It eliminates the need for cumbersome external heating equipment or additional natural gas combustion for heating, greatly reducing process investment.

[0024] (III) This invention can achieve in-situ capture of CO2 during the metallurgical process. By introducing sufficient oxygen into the upper part of the reduction section of the vertical furnace, the excess CO and H2 in the vertical furnace can be consumed, and the reduced gas that is basically completely converted can be obtained at the top of the vertical furnace. That is, the composition of the top gas is basically only carbon dioxide and water vapor. Since the composition of the flue gas at the top of the furnace is very simple, it is only necessary to recover the heat in the flue gas and condense the water vapor in it to capture CO2. No additional CO2 capture device is required, nor is it necessary to recover and reuse the unconverted reduced gas, thus reducing the energy consumption of the process. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the reduction shaft furnace ironmaking system and a process flow diagram of the present invention.

[0026] In the diagram: 1: Oxygen injection device; 2: New gas phase outlet; 3: Coal gas purification device; 4: Heat reduction gas injection device; 5: Furnace top gas output device; 6: Waste gas condensation device. Detailed Implementation

[0027] like Figure 1 As shown, this embodiment provides a direct reduction iron (DRI) blast furnace ironmaking system that can extract gas in the middle of the reduction section of the blast furnace and uniformly introduce oxygen into the upper middle part of the reduction section. The system includes an oxygen injection device 1, a new gas phase outlet 2, a gas purification device 3, a hot reducing gas injection device 4, a furnace top gas output device 5, and a waste gas condensation device 6.

[0028] The newly added gas phase outlet 2 includes one or more outlets, all located in the middle of the reduction section of the vertical shaft furnace, for discharging part of the reducing gas within the reduction section. In a preferred embodiment, the newly added gas phase outlets 2 can be uniformly arranged circumferentially along the furnace body in the reduction section, or uniformly arranged longitudinally along the furnace body in the reduction section.

[0029] The oxygen injection device 1 includes one or more units, all disposed in the upper part of the reduction section of the vertical shaft furnace, and all located above the newly added gas phase outlet 2. In a preferred embodiment, the oxygen injection device 1 is used to uniformly introduce oxygen into the upper part of the reduction section of the vertical shaft furnace.

[0030] The specific structures of the gas purification device 3, the hot reducing gas injection device 4, the furnace top gas output device 5, and the waste gas condensation device 6 are all existing technologies. In this invention, the gas purification device 3 is used to separate CO2 and H2O from the gas discharged from the newly added gas phase outlet 2; the hot reducing gas injection device 4 is used to introduce hot reducing gas into the bottom of the reduction section of the vertical furnace; the furnace top gas output device 5 is used to discharge the furnace top gas; and the waste gas condensation device 6 is used for tail gas waste heat recovery and CO2 capture.

[0031] Specifically, the newly added gas phase outlet 2 is connected to the inlet of the gas purification device 3, and the outlet of the gas purification device 3 is connected to the fresh reducing gas pipeline at the bottom of the vertical shaft furnace. This allows the hot reducing gas, after removing H2O and CO2, to mix with the fresh reducing gas before being introduced into the vertical shaft furnace through the hot reducing gas injection device 4. The furnace top gas outlet 5 is connected to the inlet of the waste gas condensation device 6, and the outlet of the waste gas condensation device 6 is used for CO2 capture.

[0032] This embodiment is based on the reduction shaft furnace ironmaking process proposed in the above system, and includes the following process steps:

[0033] S1. The iron-containing furnace charge is fed from the top of the vertical shaft furnace into the reduction section, while the hot reducing gas injection device 4 continuously introduces hot reducing gas into the bottom of the reduction section to reduce the iron-containing furnace charge. The fully reduced iron component enters the cooling section of the vertical shaft furnace and is discharged from the bottom of the cooling section after cooling.

[0034] Among them, thermal reducing gas refers to gas that has a reducing effect after heating, and can be CO, H2, CH4, syngas, natural gas, shale gas, water gas, biogas, etc.

[0035] It is important to note that the reducing gas needs to be preheated before being introduced into the vertical furnace. The specific preheating temperature depends on the actual reaction conditions.

[0036] The reduction temperature inside the vertical furnace needs to be controlled between 500 and 1200℃.

[0037] S2. During the reduction process, based on the temperature of the iron-containing charge in the reduction section of the vertical furnace, a certain amount of gas in the furnace is discharged through the newly added gas phase outlet 2 of the reduction section of the vertical furnace.

[0038] The gas discharged from the newly added gas phase outlet 2 is a mixture of gases such as H2, CO, H2O, and CO2.

[0039] The amount of gas discharged from the newly added gas phase outlet 2 is determined by the temperature inside the reduction section of the vertical shaft furnace. If the temperature inside the vertical shaft furnace is higher than the set temperature, the gas discharge rate is increased; if the temperature inside the vertical shaft furnace is lower than the set temperature, the gas discharge rate is decreased.

[0040] Meanwhile, based on the composition of the reducing gas in the upper part of the vertical furnace, the oxygen injection device 1 injects a certain amount of oxygen into the upper part of the reduction section of the vertical furnace until all the reducing gas is oxidized, leaving only CO2 and H2O in the top gas; the oxygen injected into the vertical furnace by the oxygen injection device 1 burns with the unreacted reducing gas, releasing heat, thereby maintaining the temperature of the reduction section of the vertical furnace at 500-1200℃.

[0041] The amount of oxygen injected by the oxygen injection device 1 depends on the composition of the reducing gas in the upper part of the reduction section of the vertical shaft furnace. The amount of oxygen introduced into the vertical shaft furnace must be just enough to completely oxidize all the reducing gas. At this time, the composition of the gas at the furnace top is only H2O and CO2, and does not contain reducing gas or oxygen.

[0042] S3. The gas discharged from the newly added gas phase outlet 2 enters the gas purification device 3 to remove H2O and CO2 from the hot reducing gas, and then mixes with fresh reducing gas and is reintroduced into the vertical furnace from the hot reducing gas injection device 4.

[0043] Among them, the gas purification device 3 does not need to separate all H2O and CO2; it only needs to ensure that the purified gas meets the requirements for heat reduction gas feed.

[0044] S4. The top gas is discharged through the top gas output device 5 and enters the waste gas condensation device 6, where CO2 and H2O are separated by condensation and CO2 is captured.

[0045] The waste heat in the exhaust gas is recovered and reused.

[0046] To further understand the content, features, and effects of this invention, the following embodiments are provided, and detailed descriptions are given below in conjunction with the accompanying drawings:

[0047] Example 1

[0048] In this embodiment, hematite lump ore with an iron content of 70% is selected as the iron-bearing furnace charge. During the reduction process of the iron-bearing furnace charge, some gas is extracted from the middle of the reduction section of the vertical shaft furnace, and oxygen is uniformly introduced into the upper part of the reduction section. Direct reduced iron is prepared using hot reducing gas preheated to 900°C. To facilitate the explanation of this process, the reduction section of the vertical shaft furnace is divided into 8 sections from top to bottom, namely L1-L8. The iron-bearing furnace charge is fed from L1, and the hot reducing gas is introduced from L8. The specific steps are as follows:

[0049] (1) The iron-containing furnace charge is fed from the top (L1) of the vertical shaft furnace into the reduction section of the hydrogen vertical shaft furnace. The iron ore mass flow rate is 821,274 kg / hr, the temperature is 25°C, and the pressure is 2 atm. Simultaneously, hot reducing gas (a mixture of hydrogen and carbon monoxide in this embodiment) at a temperature of 900°C is continuously introduced into the bottom (L8) of the reduction section of the vertical shaft furnace. The volume ratio of hydrogen to carbon monoxide is 1:1, the molar flow rate is 22,280 kmol / h, and the pressure is 2 atm. The iron-containing furnace charge reacts with the hot reducing gas in the reduction section.

[0050] (2) Part of the reducing gas is extracted from the middle of the reduction section (L4) of the vertical shaft furnace through an additional gas phase outlet. The molar flow rate of the extracted gas is 14705 kmol / h, accounting for 66% of the total reducing gas flow in the vertical shaft furnace. The temperature is 911℃, the pressure is 2 atm, and the composition is CO 34.6%, CO2 15.4%, H2 31.3%, and H2O 18.7%. After the extracted gas passes through the gas purification device 3 to separate CO2 and H2O, it is reintroduced from the bottom of the vertical shaft furnace (L1).

[0051] (3) Oxygen is uniformly introduced into the upper part of the reduction section of the vertical shaft furnace at points L1, L2, and L3, at a temperature of 25°C and a pressure of 2 atm. Specifically, the molar flow rate of oxygen introduced at L1 is 580 kmol / hr, at L2 it is 217 kmol / hr, and at L3 it is 100 kmol / hr. The oxygen reacts with the remaining reducing gas in the vertical shaft furnace, releasing heat to maintain the temperature of the iron-containing charge in the reduction section at 900-1050°C.

[0052] (4) The reduced high-temperature iron enters the cooling section of the vertical furnace for cooling and is discharged from the bottom outlet of the cooling section to obtain reduced iron. The furnace top gas is discharged from the top of the vertical furnace. At this time, the furnace top gas temperature is 759℃, the pressure is 2atm, the flow rate is 7576kmol / hr, and the composition is 50% CO2 and 50% H2O.

[0053] (5) The top gas enters the waste gas condensation device 6 to separate CO2 and H2O, and the captured pure CO2 is stored. The flow rate is 3788 kmol / hr and the temperature is 25℃.

[0054] The specific details of each section within the vertical shaft furnace reduction section are shown in Table 1.

[0055] Table 1. Specific conditions and composition of each section in the reduction section of the vertical shaft furnace (L1-L8) with 900℃ reducing gas feed.

[0056]

[0057] As shown in Table 1, in this embodiment, the proportion of gas extracted from the newly added gas phase outlet 2 in the reduction section of the vertical furnace accounts for 66% of the reducing gas introduced into the vertical furnace, which increases the temperature in the reduction section of the vertical furnace and realizes in-situ capture of CO2.

[0058] Example 2

[0059] In this embodiment, hematite lump ore with an iron content of 70% is selected as the iron-bearing furnace charge. During the reduction process of the iron-bearing furnace charge, some gas is extracted from the middle of the reduction section of the vertical shaft furnace, and oxygen is uniformly introduced into the upper part of the reduction section. Direct reduced iron is prepared using hot reducing gas preheated to 500°C. To facilitate the explanation of this process, the reduction section of the vertical shaft furnace is divided into 8 sections from top to bottom, namely L1-L8. The iron-bearing furnace charge is fed from L1, and the hot reducing gas is introduced from L8. The specific steps are as follows:

[0060] Iron-containing furnace charge is fed from the top (L1) of the vertical shaft furnace into the hydrogen reduction section. The iron ore mass flow rate is 821,274 kg / hr, the temperature is 25°C, and the pressure is 2 atm. Simultaneously, hot reducing gas (a mixture of hydrogen and carbon monoxide in this embodiment) at a temperature of 500°C is continuously introduced into the bottom (L8) of the reduction section. The volume ratio of hydrogen to carbon monoxide is 6:4, the molar flow rate is 22,500 kmol / h, and the pressure is 2 atm. The iron-containing furnace charge reacts with the hot reducing gas in the reduction section.

[0061] Partial reducing gas is extracted from the middle (L4) of the reduction section of the vertical shaft furnace through the newly added gas phase outlet 2. The molar flow rate of the extracted gas is 13500 kmol / h, accounting for 66% of the total reducing gas flow in the vertical shaft furnace. The temperature is 911℃, the pressure is 2 atm, and the composition is CO 25.7%, CO2 14.3%, H2 40.5%, and H2O 19.5%. After the extracted gas passes through the gas purification device 3 to separate CO2 and H2O, it is reintroduced from the bottom (L1) of the vertical shaft furnace.

[0062] Oxygen is uniformly introduced into the upper part of the reduction section of the vertical shaft furnace at points L1, L2, and L3, at a temperature of 25°C and a pressure of 2 atm. The molar flow rate of oxygen introduced at L1 is 1000 kmol / hr, at L2 it is 200 kmol / hr, and at L3 it is 180 kmol / hr.

[0063] The reduced high-temperature iron enters the cooling section of the vertical shaft furnace for cooling and is discharged from the bottom outlet of the cooling section, thus obtaining reduced iron. The furnace top gas is discharged from the top of the vertical shaft furnace. At this time, the furnace top gas temperature is 1055℃, the pressure is 2 atm, the flow rate is 9000 kmol / hr, and the composition is 40% CO2 and 60% H2O.

[0064] The gas from the furnace top enters the waste gas condenser, where CO2 and H2O are separated, and the captured pure CO2 is stored. The flow rate is 3599 kmol / hr, and the temperature is 25℃.

[0065] The specific details of each section within the vertical shaft furnace reduction section are shown in Table 2.

[0066] Table 2. Specific conditions and composition of each section in the reduction section of the vertical shaft furnace with 500℃ reducing gas feed (L1-L8)

[0067]

[0068] As shown in Table 2, in this embodiment, the proportion of gas extracted from the newly added gas phase outlet 2 in the reduction section of the vertical furnace accounts for 66% of the reducing gas introduced into the vertical furnace, which increases the temperature in the reduction section of the vertical furnace and realizes in-situ capture of CO2.

[0069] Although the preferred embodiments of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many specific modifications under the guidance of the present invention without departing from the spirit of the invention and the scope of protection of the claims, and these modifications all fall within the scope of protection of the present invention.

Claims

1. A reduced shaft furnace ironmaking process, characterized in that, The present application is realized by using a reduction shaft furnace ironmaking system, which comprises a shaft furnace, at least one new gas phase outlet is arranged in the middle of the reduction section of the shaft furnace, and at least one oxygen injection device is arranged above the new gas phase outlet in the reduction section of the shaft furnace; the new gas phase outlet is connected with the inlet of a coal gas purification device, the outlet of the coal gas purification device is connected to a fresh reduction gas pipeline at the bottom of the shaft furnace; the top gas of the shaft furnace enters a waste gas condensing device, H2O is separated by condensation, and CO2 is captured; the top gas outlet of the shaft furnace is connected with the inlet of the waste gas condensing device, and the outlet of the waste gas condensing device is used for capturing CO2. The reduction shaft furnace ironmaking process comprises the following processes: Iron-containing furnace charges are fed into the shaft furnace, and hot reduction gas is continuously introduced into the bottom of the reduction section of the shaft furnace to reduce the iron-containing furnace charges; during the reduction process, part of the gas is discharged through the new gas phase outlet according to the temperature of the iron-containing furnace charges in the reduction section of the shaft furnace, and oxygen is injected into the reduction section of the shaft furnace through the oxygen injection device, the oxygen and the remaining reduction gas are combusted to release heat, all of the reduction gas is oxidized, and thus the temperature of the reduction section is maintained at 500-1200℃; The gas discharged from the new gas phase outlet enters a coal gas purification device, is mixed with hot reduction gas after removal of H2O and CO2, and is introduced into the reduction section of the shaft furnace again; The oxygen introduced into the shaft furnace by the oxygen injection device can oxidize all of the remaining reduction gas in the shaft furnace, so that only H2O and CO2 are present in the composition of the top gas.

2. A reduced shaft furnace ironmaking process according to claim 1, characterized in that, The new gas phase outlets are evenly arranged along the circumference of the shaft body in the reduction section.

3. A reduced shaft furnace ironmaking process according to claim 1, characterized in that, The new gas phase outlets are evenly arranged along the length of the shaft body in the reduction section.

4. A reduced shaft furnace ironmaking process according to claim 1, characterized in that, The oxygen injection devices are evenly arranged along the circumference of the shaft body in the reduction section.

5. A reduced shaft furnace ironmaking process according to claim 1, characterized in that, The oxygen injection devices are evenly arranged along the length of the shaft body in the reduction section.

6. A reduced shaft furnace ironmaking process according to claim 1, characterized in that, The hot reduction gas is CO, H2, CH4, synthetic gas, natural gas, shale gas, water gas or marsh gas.

7. A reduced shaft furnace ironmaking process according to claim 1, characterized in that, The proportion of the gas discharged from the new gas phase outlet accounts for 50%-90% of the reduction gas introduced into the shaft furnace.

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