CN116904685A - A reduction shaft furnace ironmaking system and process - Google Patents

Abstract

The invention belongs to the technical field of metallurgy-iron making, and discloses a reduction shaft furnace iron making system and a process, wherein a newly added gas phase outlet is arranged in the middle of a reduction section of the system, and an oxygen injection device is arranged above the newly added gas phase outlet; the process is that the iron-containing furnace material is sent into a shaft furnace, and hot reducing gas is continuously introduced into the bottom of a reduction section to reduce the iron-containing furnace material; in the reduction process, partial gas is discharged through a newly added gas phase outlet, oxygen is blown into the gas phase outlet through an oxygen blowing device, the oxygen and the rest reducing gas are combusted to release heat, and all the reducing gas is oxidized, so that the temperature of a reduction section is maintained; the gas discharged from the newly added gas phase outlet removes H ₂ O and CO ₂ Then mixing the mixture with hot reducing gas and re-introducing the mixture into a reducing section; separation of H from top gas by condensation ₂ O, CO ₂ And (5) collecting. The invention realizes the full application of the chemical energy of the top gas and CO in the tail gas ₂ In-situ capture of CO in the presence of direct reduction of shaft furnace ₂ High separation energy consumption.

Description

A reduction shaft furnace ironmaking system and process

Technical field

The invention belongs to the technical field of metallurgy and ironmaking, and specifically relates to a reduction shaft furnace ironmaking system and process.

Background technique

Greenhouse gas emissions have led to increasingly severe climate change, and energy conservation and emission reduction have become the consensus of all mankind. Among them, the steel industry is extremely dependent on fossil energy and has huge carbon emissions. In order to reduce carbon dioxide emissions, technological innovation in the high-emission steel industry is urgent. At present, it has become the future development trend of industrial ironmaking to use the shaft furnace direct reduction short process process to replace the previous blast furnace long process process.

75% of the world's direct reduced iron 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 method uses the natural gas reforming method to produce reducing gas. The reducing gas is fed from the air inlet in the middle of the shaft furnace and reduces the oxidized iron ore pellets and lump iron ore added from the top into sponge iron during convective motion. The top gas contains about 60-70% CO and _H2 . A part of the top gas is pressurized and sent to the mixing chamber to mix evenly with the equivalent amount of natural gas. The mixed gas is converted into reducing gas after catalytic cracking reaction. The temperature of the reducing gas is 850-900°C, and the CO and H ₂ content is about 95%. After adding a small amount of natural gas, the remaining top gas is sent as fuel to the outside of the reformer reaction tube to provide heat for the catalytic cracking reaction of natural gas. At the same time, the reformer flue gas enters the heat exchanger to preheat the mixed raw gas and combustion air, and further recovers and utilizes the heat. This process uses an external reforming furnace, which increases investment and consumes a large amount of Ni-based and other precious metal catalysts, resulting in high operating costs. And the flue gas contains a large amount of CO ₂ and needs further treatment before it can be discharged. The HYL process can directly use coke oven gas, coal gas and 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 CO ₂ removed and synthesized with the dehydrated fresh The gas is mixed, then heated by a heater and burned with an appropriate amount of oxygen, and then sent to the iron reduction shaft furnace. This process consumes a lot of gas, and the CO and H ₂ content in the furnace top gas is also high. The power consumption of the subsequent separation process is large, and a large amount of CO ₂ will be emitted during the process, which is incompatible with the current clean and green development route.

In the Midrex and HYL processes, the CO and H ₂ contents in the top gas are relatively high, and the reduction potential chemical energy in the gas cannot be efficiently utilized. Direct emission will cause a waste of chemical energy in the gas. This requires that part of the top gas needs to re-enter the shaft furnace after removing _CO2 . Excessive _CO2 content directly affects the quality of reduced iron. Therefore, a large amount of energy is required to separate CO ₂ and the operating cost is high. At the same time, the hydrogen reduction heat absorption in the reducing gas leads to a significant increase in heat demand in the upper part of the shaft furnace, making it necessary to externally heat the reducing gas at the bottom of the shaft furnace in order to meet the thermal balance, which will generate a lot of energy consumption.

Therefore, there is an urgent need for a green, clean, low-carbon reduced iron process that reduces process energy consumption and production costs. This process can simultaneously meet the heat demand of hydrogen reduction in the upper part of the gas-based shaft furnace and the CO ₂ capture of the top gas, reducing Subsequent separation of energy consumption and equipment investment.

Contents of the invention

In order to realize the full application of the chemical energy of the furnace top gas and the in-situ capture of CO ₂ in the tail gas, while reducing the energy consumption of CO ₂ separation in the circulating gas, the present invention proposes a reduction shaft furnace ironmaking system and process.

In order to solve the above technical problems, the present invention is implemented through the following technical solutions:

According to one aspect of the present invention, a reduction shaft furnace ironmaking system is provided, including a shaft furnace, at least one new gas phase outlet is provided in the middle of the reduction section of the shaft furnace, and the reduction section of the shaft furnace is in the new At least one oxygen injection device is provided above the gas-increasing phase outlet.

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

Preferably, the newly added gas phase outlets are evenly arranged along the longitudinal direction of the furnace body in the reduction section.

Preferably, the oxygen injection device is evenly arranged along the circumferential direction of the furnace body in the reduction section.

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

Further, 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 shaft furnace; the top gas outlet of the shaft furnace is connected to the exhaust gas The inlet of the condensation device is connected, and the outlet of the exhaust gas condensation device is used to capture CO ₂ .

According to another aspect of the present invention, a reduction shaft furnace ironmaking process based on the above system is provided, including the following processes:

The iron-containing charge is fed into the shaft furnace, and at the same time, hot reducing gas is continuously introduced to the bottom of the reduction section of the shaft furnace to reduce the iron-containing charge; during the reduction process, the iron-containing charge in the reduction section of the shaft furnace is temperature, part of the gas is discharged through the newly added gas phase outlet, and oxygen is injected into the reduction section of the shaft furnace through the oxygen injection device. The oxygen and the remaining reducing gas burn and release heat, and all the reducing gas is completely oxidized. Thereby maintaining the temperature of the reduction section at 500-1200°C;

The gas discharged from the newly added gas phase outlet enters the gas purification device. After removing H ₂ O and CO ₂ , it is mixed with the hot reduction gas and re-entered into the shaft furnace reduction section;

The top gas of the shaft furnace enters the exhaust gas condensation device, H ₂ O is separated through condensation, and CO ₂ is captured.

Further, the thermal reduction gas is CO, H ₂ , CH ₄ , synthesis gas, natural gas, shale gas, water gas or biogas, etc.

Further, the proportion of the exhaust gas from the newly added gas phase outlet accounts for 50%-90% of the reducing gas flowing into the shaft furnace.

Furthermore, the oxygen introduced into the shaft furnace by the oxygen injection device can completely oxidize all remaining reducing gases in the shaft furnace, so that the composition of the top gas only consists of H ₂ O and CO ₂ .

The beneficial effects of the present invention are:

(1) This invention discharges a part of the reducing gas in the middle of the reduction section of the shaft furnace, and passes it back into the shaft furnace from the bottom after purification. Compared with the original process, which discharges all the gas from the top of the furnace, a large amount of energy is consumed. To separate CO ₂ , the present invention only needs to separate part of the gas discharged from the middle part of the shaft furnace, which can effectively reduce CO ₂ separation energy consumption.

(2) The present invention evenly introduces part of the oxygen from the upper part of the reduction section of the shaft furnace. The combustion of oxygen and the reducing gas in the furnace releases a large amount of heat, which can increase and maintain the temperature in the shaft furnace at 500-1200°C, thus improving the temperature inside the shaft furnace. The reaction rate, reducing gas utilization rate and direct reduced iron conversion rate make up for the problem of insufficient heat supply in the metallurgical process. There is no need for cumbersome external heating equipment or the addition of natural gas combustion for heating, which greatly reduces process investment.

(3) The present invention can capture CO ₂ in situ during the metallurgical process. By introducing sufficient oxygen into the upper part of the reduction section of the shaft furnace, the excess CO and H ₂ in the shaft furnace can be consumed, and basic CO 2 can be obtained at the top of the shaft furnace. Completely converted reducing gas, that is, the furnace top gas basically only contains carbon dioxide and water vapor; since the composition of the furnace top flue gas is very simple, CO can be captured only by recovering the heat in the flue gas and condensing the water vapor in it. _2. No additional CO ₂ capture device is required, and there is no need to recycle unconverted reducing gas, reducing process energy consumption.

Description of the drawings

Figure 1 is a schematic structural diagram and process flow chart of the reduction shaft furnace ironmaking system of the present invention.

In the picture: 1: Oxygen injection device; 2: New gas phase outlet; 3: Gas purification device; 4: Hot reducing gas injection device; 5: Furnace top gas output device; 6: Waste gas condensation device.

Detailed ways

As shown in Figure 1, this embodiment provides a reduction shaft furnace ironmaking method that can extract gas in the middle of the reduction section of the shaft furnace, and evenly introduce the reducing gas with oxygen into the middle and upper parts of the reduction section to directly reduce iron (DRI). 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 top gas output device 5, and an exhaust gas condensation device 6.

The newly added gas phase outlet 2 includes one or more, which are all arranged in the middle of the reduction section of the shaft furnace, and are used to discharge part of the reducing gas in the reduction section of the shaft furnace. As a preferred embodiment, the newly added gas phase outlets 2 can be evenly arranged along the circumferential direction of the furnace body in the reduction section, or can also be evenly arranged along the longitudinal direction of the furnace body in the reduction section.

The oxygen injection device 1 includes one or more oxygen injection devices, all of which are arranged in the middle and upper part of the reduction section of the shaft furnace, and are located above the newly added gas phase outlet 2. As a preferred embodiment, the oxygen injection device 1 is used to uniformly inject oxygen into the upper and middle parts of the reduction section of the shaft furnace.

The specific structures of the gas purification device 3, the hot reducing gas injection device 4, the top gas output device 5, and the exhaust gas condensation device 6 are all existing technical contents. In the present invention, the gas purification device 3 is used to separate CO ₂ and H ₂ O in the exhaust gas from the newly added gas phase outlet 2; the hot reducing gas injection device 4 is used to pass hot reducing gas to the bottom of the reduction section of the shaft furnace; The top gas output device 5 is used to discharge the top gas; the exhaust gas condensation device 6 is used for tail gas waste heat recovery and CO ₂ capture.

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 reduction gas pipeline at the bottom of the shaft furnace, so that the hot reduction gas after removing H ₂ O and CO ₂ is combined with the fresh reduction gas. After the gas is mixed, it is passed into the shaft furnace from the hot reducing gas injection device 4. The top gas outlet 5 of the shaft furnace is connected to the inlet of the exhaust gas condensation device 6, and the outlet of the exhaust gas condensation device 6 is used to capture _CO2 .

This embodiment is based on the reduction shaft furnace ironmaking process proposed by the above system, including the following process:

S1. Send the iron-containing charge from the top of the shaft furnace into the reduction section of the shaft furnace. At the same time, the hot reducing gas injection device 4 continues to pass the hot reducing gas to the bottom of the reduction section to reduce the iron-containing charge. The fully reduced iron component enters the cooling section of the shaft furnace and is discharged from the bottom of the cooling section of the shaft furnace after cooling.

Among them, thermal reducing gas refers to gas that has reducing effect after heating, which can be CO, H ₂ , CH ₄ , synthesis gas, natural gas, shale gas, water gas, biogas, etc.

It should be noted that the reducing gas needs to be preheated before it is passed into the shaft furnace. The specific preheating temperature is determined according to the actual reaction conditions.

Among them, the reduction temperature in the shaft furnace needs to be controlled at an overall range of 500 to 1200°C.

S2. During the reduction process, according to the temperature of the iron-containing charge in the reduction section of the shaft furnace, a certain amount of gas in the furnace is discharged through the new gas phase outlet 2 of the reduction section of the shaft furnace.

Among them, the gas discharged from the newly added gas phase outlet 2 is a mixture of H ₂ , CO, H ₂ O, CO ₂ and other gases.

Among them, the amount of gas discharged from the newly added gas phase outlet 2 is determined by the temperature in the reduction section of the shaft furnace. If the temperature in the shaft furnace is higher than the set temperature, the gas discharge volume will be increased; if the temperature in the shaft furnace is lower than the set temperature, the gas discharge volume will be reduced.

At the same time, according to the composition of the reducing gas in the upper part of the shaft furnace, the oxygen injection device 1 injects a certain amount of oxygen to the upper part of the reduction section of the shaft furnace until all the reducing gas is oxidized and only CO ₂ and H ₂ remain in the top gas. O; The oxygen injected into the shaft furnace by the oxygen injection device 1 burns with the unreacted reducing gas and releases heat, thereby maintaining the temperature of the reduction section of the shaft furnace at 500-1200°C.

Among them, 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 shaft furnace. The amount of oxygen introduced into the shaft furnace must be just enough to completely oxidize all the reducing gas. At this time, the top gas only contains H ₂ O and CO ₂ and does not contain reducing gas and oxygen.

S3. The gas discharged from the newly added gas phase outlet 2 enters the gas purification device 3 to remove H ₂ O and CO ₂ from the hot reducing gas, and then mixes it with fresh reducing gas and passes it through the hot reducing gas injection device 4 to the shaft furnace again.

Among them, the gas purification device 3 does not need to separate all H ₂ O and CO ₂ , and only needs to make the purified gas meet the thermal reduction gas feed requirements.

S4. The top gas is discharged through the top gas output device 5 and enters the exhaust gas condensation device 6. CO ₂ and H ₂ O are separated through condensation, and CO ₂ is captured.

Among them, the waste heat in the exhaust gas is recovered and reused.

In order to further understand the content, characteristics and effects of the present invention, the following examples are given and described in detail with reference to the accompanying drawings:

Example 1

In this embodiment, hematite lump ore with an iron grade of 70% is selected as the iron-containing charge. During the reduction process of the iron-containing charge, part of the gas is extracted from the middle of the reduction section of the shaft furnace and evenly introduced into the middle and upper part of the reduction section. Oxygen, direct reduced iron is prepared using hot reducing gas preheated to 900°C. In order to facilitate the explanation of the process, the shaft furnace reduction section is divided into 8 sections from top to bottom, namely L1-L8. The iron-containing charge is fed from L1, and the hot reduction gas is introduced from L8. The specific steps are as follows:

(1) Send the iron-containing charge from the top of the shaft furnace (L1) into the reduction section of the hydrogen shaft furnace. The iron ore mass flow rate is 821274kg/hr, the temperature is 25°C, and the pressure is 2atm. At the same time, hot reducing gas with a temperature of 900°C (a mixture of hydrogen and carbon monoxide in this embodiment) is continuously introduced into the bottom (L8) of the reduction section of the shaft furnace. The volume ratio of hydrogen and carbon monoxide is 1:1, and the molar flow rate is 22280kmol/h, pressure is 2atm. The iron-containing charge reacts with hot reducing gas in the reduction section.

(2) Part of the reducing gas is extracted from the middle part of the shaft furnace reduction section (L4) through the 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 rate in the shaft furnace, and the temperature is 911°C. The pressure is 2atm, and the composition is 34.6% CO, 15.4% _CO2 , 31.3% _H2 , and 18.7% _H2O . The produced gas passes through the gas purification device 3 to separate CO ₂ and H ₂ O, and then is introduced again from the bottom of the shaft furnace (L1).

(3) Inject oxygen evenly at L1, L2, and L3 in the upper part of the reduction section of the shaft furnace, with a temperature of 25°C and a pressure of 2 atm. Among them, the molar flow rate of oxygen introduced at L1 is 580kmol/hr, the molar flow rate of oxygen introduced at L2 is 217kmol/hr, and the molar flow rate of oxygen introduced at L3 is 100kmol/hr. Oxygen and the remaining reducing gas in the shaft furnace are burned to release heat to maintain the temperature of the iron-containing charge in the reduction section at 900-1050°C.

(4) The reduced high-temperature iron enters the cooling section of the shaft furnace for cooling, and is discharged from the bottom outlet of the cooling section to obtain reduced iron. The top gas is discharged from the top of the shaft furnace. At this time, the top gas temperature is 759°C, the pressure is 2 atm, the flow rate is 7576 kmol/hr, and the composition is 50% CO ₂ and 50% H ₂ O.

(5) The furnace top gas enters the exhaust gas condensation device 6 to separate CO ₂ and H ₂ O, and store the captured pure CO ₂ with a flow rate of 3788 kmol/hr and a temperature of 25°C.

The details of each section in the shaft furnace reduction section are shown in Table 1.

Table 1 Reducing gas fed at 900°C - specific conditions and composition of each section in the shaft furnace reduction section (L1-L8)

As can be seen from Table 1, in this embodiment, the proportion of gas extracted from the new gas phase outlet 2 in the reduction section of the shaft furnace accounts for 66% of the reduction gas flowing into the shaft furnace, which increases the temperature in the reduction section of the shaft furnace and achieves CO ₂ In situ capture.

Example 2

In this embodiment, hematite lump ore with an iron grade of 70% is selected as the iron-containing charge. During the reduction process of the iron-containing charge, part of the gas is extracted from the middle of the reduction section of the shaft furnace and evenly introduced into the middle and upper part of the reduction section. Oxygen, direct reduced iron is prepared using hot reducing gas preheated to 500°C. In order to facilitate the explanation of the process, the shaft furnace reduction section is divided into 8 sections from top to bottom, namely L1-L8. The iron-containing charge is fed from L1, and the hot reduction gas is introduced from L8. The specific steps are as follows:

The iron-containing charge is sent from the top of the shaft furnace (L1) to the hydrogen shaft furnace reduction section. The iron ore mass flow rate is 821274kg/hr, the temperature is 25°C, and the pressure is 2atm. At the same time, hot reducing gas with a temperature of 500°C (a mixture of hydrogen and carbon monoxide in this embodiment) is continuously introduced into the bottom (L8) of the reduction section of the shaft furnace. The volume ratio of hydrogen and carbon monoxide is 6:4, and the molar flow rate is 22500kmol/h, pressure is 2atm. The iron-containing charge reacts with hot reducing gas in the reduction section.

Part of the reducing gas is extracted from the middle part of the reduction section (L4) of the 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 rate in the shaft furnace. The temperature is 911°C. The pressure is 2atm, and the composition is 25.7% CO, 14.3% _CO2 , 40.5% _H2 , and 19.5% _H2O . The produced gas passes through the gas purification device 3 to separate CO ₂ and H ₂ O, and then is introduced again from the bottom of the shaft furnace (L1).

Oxygen is evenly introduced into L1, L2, and L3 in the upper part of the reduction section of the shaft furnace, the temperature is 25°C, and the pressure is 2 atm. Among them, the molar flow rate of oxygen introduced at L1 is 1000kmol/hr, the molar flow rate of oxygen introduced at L2 is 200kmol/hr, and the molar flow rate of oxygen introduced at L3 is 180kmol/hr.

The reduced high-temperature iron enters the cooling section of the shaft furnace for cooling, and is discharged from the bottom outlet of the cooling section to obtain reduced iron. The top gas is discharged from the top of the shaft furnace. At this time, the top gas temperature is 1055°C, the pressure is 2 atm, the flow rate is 9000 kmol/hr, and the composition is CO ₂ accounting for 40% and H ₂ O accounting for 60%.

The furnace top gas enters the exhaust gas condensation device to separate CO ₂ and H ₂ O, and store the captured pure CO ₂ with a flow rate of 3599 kmol/hr and a temperature of 25°C.

The details of each section in the shaft furnace reduction section are shown in Table 2.

Table 2 Reducing gas 500℃ feed - specific conditions and composition of each section in the shaft furnace reduction section (L1-L8)

It can be seen from Table 2 that in this embodiment, the proportion of gas extracted from the new gas phase outlet 2 in the reduction section of the shaft furnace accounts for 66% of the reduction gas flowing into the shaft furnace, which increases the temperature in the reduction section of the shaft furnace and achieves CO ₂ In situ capture.

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 above-mentioned specific implementations. The above-mentioned specific implementations are only illustrative and not restrictive. Those of ordinary skill in the art Under the inspiration of the present invention, without departing from the spirit of the invention and the scope protected by the claims, people can also make many specific changes, which all fall within the protection scope of the present invention.

Claims (10)

1. A reduction shaft furnace ironmaking system, including a shaft furnace, characterized in that at least one new gas phase outlet is provided in the middle of the reduction section of the shaft furnace, and the reduction section of the shaft furnace is at the newly added gas phase outlet. At least one oxygen injection device is provided above. 2. A reduction shaft furnace ironmaking system according to claim 1, characterized in that the newly added gas phase outlets are evenly arranged in the reduction section along the circumferential direction of the furnace body. 3. A reduction shaft furnace ironmaking system according to claim 1, characterized in that the newly added gas phase outlets are evenly arranged along the longitudinal direction of the furnace body in the reduction section. 4. A reduction shaft furnace ironmaking system according to claim 1, characterized in that the oxygen injection device is evenly arranged in the reduction section along the circumferential direction of the furnace body. 5. A reduction shaft furnace ironmaking system according to claim 1, characterized in that the oxygen injection device is evenly arranged along the longitudinal direction of the furnace body in the reduction section. 6. A reduction shaft furnace ironmaking system according to claim 1, characterized in that 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 bottom of the shaft furnace. fresh reducing gas pipeline; the top gas outlet of the shaft furnace is connected to the inlet of the exhaust gas condensation device, and the outlet of the exhaust gas condensation device is used to capture CO ₂ . 7. A reduction shaft furnace ironmaking process based on the system according to any one of claims 1 to 6, characterized in that it includes the following process: The iron-containing charge is fed into the shaft furnace, and at the same time, hot reducing gas is continuously introduced to the bottom of the reduction section of the shaft furnace to reduce the iron-containing charge; during the reduction process, the iron-containing charge in the reduction section of the shaft furnace is temperature, part of the gas is discharged through the newly added gas phase outlet, and oxygen is injected into the reduction section of the shaft furnace through the oxygen injection device. The oxygen and the remaining reducing gas burn and release heat, and all the reducing gas is completely oxidized. Thereby maintaining the temperature of the reduction section at 500~1200℃; The gas discharged from the newly added gas phase outlet enters the gas purification device. After removing H ₂ O and CO ₂ , it is mixed with the hot reduction gas and re-entered into the shaft furnace reduction section; The top gas of the shaft furnace enters the exhaust gas condensation device, H ₂ O is separated through condensation, and CO ₂ is captured. 8. A reduction shaft furnace ironmaking process according to claim 7, characterized in that the thermal reduction gas is CO, _H2 , _CH4 , synthesis gas, natural gas, shale gas, water gas or biogas. 9. A reduction shaft furnace ironmaking process according to claim 7, characterized in that the proportion of gas discharged from the newly added gas phase outlet accounts for 50%-90% of the reducing gas flowing into the shaft furnace. 10. A reduction shaft furnace ironmaking process according to claim 7, characterized in that the oxygen injected into the shaft furnace by the oxygen injection device can completely oxidize all remaining reducing gases in the shaft furnace. , so that the top gas only contains H ₂ O and CO ₂ .