Thermal compensation system and method for producing direct reduction iron by pure hydrogen shaft furnace

Abstract

The invention discloses a thermal compensation system and method for producing direct reduced iron (DRI) by using a pure hydrogen shaft furnace. The thermal compensation system comprises the shaft furnace, a DRI cooling tower, a 1 # heat exchanger, a 2 # heat exchanger and a feeding device, a DRI outlet of the shaft furnace is communicated with a DRI cooling tower; a hydrogen pipeline is communicated with a hydrogen inlet of the DRI cooling tower, and a hydrogen outlet of the DRI cooling tower is communicated with a process gas inlet of the shaft furnace through a heat exchange passage of the 1 # heat exchanger; a furnace top gas outlet of the shaft furnace is communicated with a process gas inlet of the shaft furnace after passing through a heat exchange passage of the 2 # heat exchanger; and a nitrogen pipeline is sequentially communicated with the other heat exchange passage of the 1 # heat exchanger and the other heat exchange passage of the 2 # heat exchanger and then is communicated with the feeding device. According to the system and the method, heat of the hot-state DRI and the furnace top gas can be effectively utilized to preheat the raw materials entering the furnace, the utilization efficiency of heat energy and hydrogen is fully improved, and low-carbon and even zero-carbon ironmaking is practically achieved.

Description

Technical Field

[0001] The invention relates to the technical field of direct reduction, in particular to a heat compensation system and method for producing direct reduced iron in a pure hydrogen vertical furnace. Background Art

[0002] In the field of iron and steel metallurgy, we have long been committed to seeking more advanced, more environmentally friendly and more efficient technologies. As a clean energy, hydrogen is an ideal carbon substitute because its only reduction product is water.

[0003] As society's standards for ecological environmental protection and effective use of resources continue to rise, the defects of high energy consumption and high pollution in the traditional ironmaking model have become increasingly prominent. Pure hydrogen vertical furnace ironmaking technology uses pure hydrogen as a reducing agent, which shows significant superiority over traditional reducing agents. It can accelerate the reduction reaction and significantly reduce carbon dioxide emissions. However, this technology still has several constraints and links that need to be improved in the actual implementation process. At present, a major problem in pure hydrogen vertical furnace smelting is heat supply. Hydrogen reduction of iron oxides is a strong endothermic reaction. As the reaction proceeds, the temperature of the reduction area in the upper part of the vertical furnace decreases due to heat consumption, thereby affecting the reduction efficiency and the metallization rate of DRI. Therefore, the pure hydrogen vertical furnace requires external continuous heat supply in the reduction project, and the energy consumption is high. The vertical furnace has a lot of waste heat in the entire production process. If the waste heat can be applied to vertical furnace smelting and heat energy can be recovered, the production cost will be further reduced and the efficiency will be greatly improved.

[0004] Direct reduction ironmaking in a pure hydrogen vertical furnace can achieve a higher level of cleanliness, greenness and efficiency in steel production, making an important contribution to promoting progress in the entire industrial field.

[0005] The patent with publication number CN115612774A discloses a new method for direct reduction ironmaking in a hydrogen-based vertical furnace, which mainly divides the vertical furnace body into a reduction section and a cooling section below it; a water cooling jacket and an electromagnetic heating device are sequentially arranged outside the inner furnace lining of the reduction section, but the invention heats the vertical furnace from the outside, and the external heating consumes a lot of energy. The patent with publication number CN219603618U discloses a hydrogen electric heater and a pure hydrogen vertical furnace reduction system, which solves the technical problem that the metal heat exchanger in the prior art cannot directly heat hydrogen to 1050°C. The hydrogen electric heater comprises a plurality of silicon-molybdenum rods, which are connected in series or in series-parallel, and porous heat storage bodies are arranged between adjacent silicon-molybdenum rods, and hydrogen flows between the porous heat storage bodies and the heated silicon-molybdenum rods for heating; but the system also uses external energy to heat the vertical furnace, which consumes a lot of energy and does not fully utilize the heat released by the vertical furnace itself.

[0006] Currently, the related technologies all use external energy to heat the shaft furnace to maintain the reduction reaction, and do not make full use of the waste heat generated during the reduction process of the shaft furnace, resulting in high energy consumption in the whole production process. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a direct reduction iron thermal compensation system for a pure hydrogen shaft furnace that can effectively utilize waste heat; the present invention also provides a method for direct reduction iron thermal compensation in a pure hydrogen shaft furnace.

[0008] To solve the above technical problem, the technical solution adopted by the system of the present invention is: it includes a shaft furnace, a DRI cooling tower, a 1# heat exchanger, a 2# heat exchanger and a feeding device; the DRI outlet of the shaft furnace is connected to the DRI cooling tower; the hydrogen pipeline is connected to the hydrogen inlet of the DRI cooling tower, and the hydrogen outlet of the DRI cooling tower is connected to the process gas inlet of the shaft furnace through a heat exchange path of the 1# heat exchanger; the furnace top gas outlet of the shaft furnace is connected to the process gas inlet of the shaft furnace after passing through a heat exchange path of the 2# heat exchanger; the nitrogen pipeline is connected to the feeding device after sequentially connecting another heat exchange path of the 1# heat exchanger and another heat exchange path of the 2# heat exchanger.

[0009] Furthermore, a dust removal and dehydration device is also provided; the dust removal and dehydration device is connected between the 2# heat exchanger and the process gas inlet of the shaft furnace.

[0010] Furthermore, a gas heating device is also provided; the gas heating device is connected between the 1# heat exchanger, the 2# heat exchanger and the process gas inlet of the shaft furnace.

[0011] To solve the above technical problem, the method of the present invention adopts the above system, and the technical solution adopted includes the following steps: 1) The shaft furnace discharges the generated hot DRI into the DRI cooling tower, and externally supplied hydrogen enters the DRI cooling tower, and the hot DRI exchanges heat with hydrogen; the hydrogen after heat exchange enters the 1# heat exchanger to exchange heat with nitrogen, and then is sent into the shaft furnace; 2) The furnace top gas discharged from the furnace top gas outlet of the shaft furnace exchanges heat with nitrogen in the 2# heat exchanger and is sent back into the shaft furnace for recycling; 3) The nitrogen sequentially exchanges heat with hydrogen in the 1# heat exchanger and exchanges heat with the furnace top gas in the 2# heat exchanger, and then enters the feeding device to preheat the raw materials entering the furnace.

[0012] Furthermore, in step 1), the temperature of the externally supplied hydrogen after heat exchange with the hot DRI is 450 - 600 °C, and the temperature after heat exchange with nitrogen is 135 - 180 °C.

[0013] Furthermore, in step 2), the temperature of the furnace top gas is 350 - 500 °C, and the temperature after heat exchange with nitrogen is 125 - 275 °C.

[0014] Further, in step 3), the temperature of nitrogen gas after heat exchange with hydrogen gas and top gas of the furnace is 450 - 600 °C.

[0015] Further, in step 3), the raw materials charged into the furnace are preheated by nitrogen gas to 380 - 500 °C.

[0016] The beneficial effects of adopting the above technical solution are as follows: In the system and method of the present invention, hot DRI is cooled by pure hydrogen gas, and the hydrogen gas with increased temperature heats nitrogen gas through a heat exchanger; after being heated by hydrogen gas first and then by the top gas of the furnace, nitrogen gas preheats the raw materials charged into the furnace to make the raw materials charged into the furnace reach a specific temperature, which is used to compensate for the heat absorbed by hydrogen reduction, ensuring that the reaction can operate continuously and efficiently to cope with the situation that the temperature of the reactor drops due to the endothermic reduction of iron oxide by hydrogen gas during the smelting process of the pure hydrogen shaft furnace, thereby affecting the reduction efficiency; the top gas discharged from the top of the shaft furnace is recycled after recovering part of the heat through a heat exchanger. The system and method of the present invention can effectively utilize the heat of hot DRI and top gas to preheat the raw materials charged into the furnace, fully improving the utilization efficiency of thermal energy and hydrogen gas, and truly achieving low-carbon or even zero-carbon ironmaking. Description of the Drawings

[0017] The present invention will be further described in detail below with reference to the drawings and specific embodiments.

[0018] Figure 1 It is a structural schematic diagram of the present invention.

[0019] In the figure: shaft furnace 1; DRI cooling tower 2; 1# heat exchanger 3; 2# heat exchanger 4; feeding device 5; dust removal and dehydration device 6; gas heating device 7. Specific Embodiments

[0020] Figure 1As shown in the figure, the hot compensation system for the production of direct reduced iron (DRI) in a pure hydrogen shaft furnace includes a shaft furnace 1, a DRI cooling tower 2, a 1# heat exchanger 3, a 2# heat exchanger 4, a feeding device 5, and a gas heating device 7. The DRI outlet of the shaft furnace 1 is connected to the DRI cooling tower 2; the hydrogen pipeline is connected to the hydrogen inlet of the DRI cooling tower 2, and the hydrogen outlet of the DRI cooling tower 2 is connected to the inlet of one heat exchange path of the 1# heat exchanger 3. The outlet of this heat exchange path is connected to the inlet of the gas heating device 7, and the outlet of the gas heating device 7 is connected to the process gas inlet of the shaft furnace 1. After adopting such a structure, hydrogen first enters the DRI cooling tower 2 and directly contacts and exchanges heat with the hot DRI, realizing the cooling of the hot DRI, and at the same time the hydrogen temperature rises. By using the direct contact heat exchange method, first, the heat exchange efficiency is relatively high, and second, hydrogen can prevent DRI oxidation at high temperatures and can further reduce it; the heated hydrogen then enters the 1# heat exchanger 3 to conduct the first heating of the nitrogen flowing through another heat exchange path, and at the same time the hydrogen temperature drops; the cooled hydrogen is sent into the shaft furnace as process gas after passing through the gas heating device 7.

[0021] Figure 1 As shown in the figure, the hot compensation system for the production of direct reduced iron (DRI) in a pure hydrogen shaft furnace further includes a dust removal and dehydration device 6; the furnace top gas outlet of the shaft furnace 1 is connected to the inlet of one heat exchange path of the 2# heat exchanger 4. The outlet of this heat exchange path is connected to the inlet of the dust removal and dehydration device 6, and the outlet of the dust removal and dehydration device 6 is connected to the inlet of the gas heating device 7. After adopting such a structure, the high-temperature furnace top gas enters the 2# heat exchanger 4 to conduct the second heating of the nitrogen flowing through another heat exchange path, and at the same time the furnace top gas temperature drops; the cooled furnace top gas is dust-removed and dehydrated by the dust removal and dehydration device 6 and then sent into the shaft furnace as process gas for recycling after passing through the gas heating device 7.

[0022] Figure 1 As shown in the figure, for the hot compensation system for the production of direct reduced iron (DRI) in a pure hydrogen shaft furnace, the nitrogen pipeline is connected to the inlet of another heat exchange path of the 1# heat exchanger 3. The outlet of this heat exchange path of the 1# heat exchanger 3 is connected to the inlet of another heat exchange path of the 2# heat exchanger 4, and the outlet of this heat exchange path of the 2# heat exchanger 4 is connected to the feeding device 5. After adopting such a structure, nitrogen exchanges heat with hydrogen in the 1# heat exchanger 3 for the first heating; then exchanges heat with the furnace top gas in the 2# heat exchanger 4 for the second heating; the nitrogen after two heatings enters the feeding device 5 to preheat the raw materials entering the furnace.

[0023] Figure 1 As shown in the figure, for the hot compensation method for the production of direct reduced iron (DRI) in a pure hydrogen shaft furnace, using the above system, it includes the following steps: 1) The shaft furnace 1 discharges the generated hot DRI into the DRI cooling tower 2, and the externally supplied hydrogen enters the DRI cooling tower 2, and the flow rate of the externally supplied hydrogen is 30000 - 40000 m 3 / h; The hot DRI exchanges heat with hydrogen in the DRI cooling tower 2, the hot DRI is cooled down, and the hydrogen is heated up to 450 - 600 °C; The heated hydrogen enters the 1# heat exchanger 3 to exchange heat with nitrogen, the hydrogen is cooled down to 135 - 180 °C, and the nitrogen is heated up for the first time; The cooled hydrogen is sent into the shaft furnace as process gas after passing through the gas heating device 7.

[0024] 2) The top gas discharged from the top gas outlet of the shaft furnace 1 mainly consists of hydrogen and water vapor, and the temperature is 350 - 500 °C. The high-temperature top gas enters the 2# heat exchanger 4 and exchanges heat with nitrogen in the 2# heat exchanger 4. The top gas is cooled down to 125 - 275 °C, and the nitrogen is heated up for the second time; After the cooled top gas is dust-removed and dehydrated by the dust-removing and dehydrating device 6, it mainly consists of hydrogen and is sent into the shaft furnace as process gas for recycling after passing through the gas heating device 7.

[0025] 3) The flow rate of the nitrogen is 50000 - 70000 m 3 / h. The nitrogen first exchanges heat with hydrogen in the 1# heat exchanger 3 to realize the first heating-up. The temperature of the nitrogen after the first heating-up is 250 - 300 °C; Then it enters the 2# heat exchanger 4 to exchange heat with the top gas to realize the second heating-up. The temperature of the nitrogen after the second heating-up is 450 - 600 °C; The nitrogen with a temperature of 450 - 600 °C after two heating-ups enters the feeding device 5 to preheat the raw materials entering the furnace, and preheats the raw materials entering the furnace to 380 - 500 °C. Example 1

[0026] (1) The temperature of the top gas discharged from the top of the shaft furnace 1 is 500 °C, mainly consisting of hydrogen and water vapor. After passing through the 2# heat exchanger 4, the temperature drops to 275 °C, and then it is purified by the dust-removing and dehydrating device 6 and conveyed to the middle and upper part of the shaft furnace 1 for recycling.

[0027] (2) Pure hydrogen with an external supply flow rate of 40000 m3 / h contacts with the hot DRI through the DRI cooling tower 2 and the temperature rises to 450 °C, and then the temperature drops to 135 °C after passing through the 1# heat exchanger 3.

[0028] (3) The nitrogen flow rate is 70000 m 3 / h. After passing through the 1# heat exchanger 3 and the 2# heat exchanger 4, the temperature reaches 450 °C, and the raw materials entering the furnace are preheated to 380 °C in the feeding device 5 and then enter the shaft furnace 1 for reduction. Example 2

[0029] (1) The temperature of the top gas discharged from the top of the shaft furnace 2 is 425 °C, mainly consisting of hydrogen and water vapor. After passing through the 2# heat exchanger 4, the temperature drops to 200 °C, and after being purified by the dust-removing and dehydrating device 6, it is conveyed to the middle and upper part of the shaft furnace 1 for recycling.

[0030] (2)The external supply flow rate of pure hydrogen is 35000 m 3 / h. After contacting with hot DRI in the DRI cooling tower 2, the temperature rises to 525 °C, and then drops to 155 °C after passing through the 1# heat exchanger 3.

[0031] (3)The nitrogen flow rate is 60000 m 3 / h. After passing through the 1# heat exchanger 3 and the 2# heat exchanger 4, the temperature reaches 530 °C. The raw materials fed into the furnace are preheated to 450 °C and then enter the shaft furnace 1 for reduction. Example 3

[0032] (1)The top gas discharged from the top of the shaft furnace 2 has a temperature of 350 °C, and its main components are hydrogen and water vapor. After passing through the 2# heat exchanger 4, the temperature drops to 125 °C, and after being purified by the dust removal and dehydration device 6, it is sent to the middle and upper part of the shaft furnace 1 for circulation.

[0033] (2)The external supply flow rate of pure hydrogen is 30000 m 3 / h. After contacting with hot DRI in the DRI cooling tower 2, the temperature rises to 600 °C, and then drops to 180 °C after passing through the 1# heat exchanger 3.

[0034] (3)The nitrogen flow rate is 50000 m 3 / h. After passing through the 1# heat exchanger 3 and the 2# heat exchanger 4, the temperature reaches 600 °C. The raw materials fed into the furnace are preheated to 500 °C and then enter the shaft furnace 1 for reduction.

Claims

1. A pure hydrogen vertical furnace heat compensation system for producing direct reduced iron, characterized by: The invention comprises a vertical furnace (1), a DRI cooling tower (2), a No. 1 heat exchanger (3), a No. 2 heat exchanger (4) and a feeding device (5); the DRI outlet of the vertical furnace (1) is connected to the DRI cooling tower (2); a hydrogen pipeline is connected to the hydrogen inlet of the DRI cooling tower (2), and the hydrogen outlet of the DRI cooling tower (2) is connected to the process gas inlet of the vertical furnace (1) through a heat exchange passage of the No. 1 heat exchanger (3); the top gas outlet of the vertical furnace (1) is connected to the process gas inlet of the vertical furnace (1) after passing through a heat exchange passage of the No. 2 heat exchanger (4); and a nitrogen pipeline is connected to another heat exchange passage of the No. 1 heat exchanger (3) and another heat exchange passage of the No. 2 heat exchanger (4) in sequence and then connected to the feeding device (5).

2. A pure hydrogen vertical furnace heat compensation system for producing direct reduced iron according to claim 1, characterized in that: A dust removal and dehydration device (6) is also provided; the dust removal and dehydration device (6) is connected between the No. 2 heat exchanger (4) and the process gas inlet of the vertical furnace (1).

3. A pure hydrogen vertical furnace heat compensation system for producing direct reduced iron according to claim 1 or 2, characterized in that: A gas heating device (7) is also provided; the gas heating device (7) is connected between the No. 1 heat exchanger (3), the No. 2 heat exchanger (4) and the process gas inlet of the vertical furnace (1).

4. A method for heat compensation in producing direct reduced iron in a pure hydrogen vertical furnace, using the system of claim 1, 2 or 3, characterized in that: The method comprises the following steps: 1) the vertical furnace (1) discharges the generated hot DRI into a DRI cooling tower (2), external hydrogen is supplied into the DRI cooling tower (2), and the hot DRI and the hydrogen are heat exchanged; the hydrogen after heat exchange enters a No. 1 heat exchanger (3) to exchange heat with nitrogen, and then is sent into the vertical furnace (1); 2) the top gas discharged from the top gas outlet of the vertical furnace (1) exchanges heat with nitrogen in the No. 2 heat exchanger (4) and is then fed back into the vertical furnace (1) for recycling; 3) The nitrogen is sequentially heat exchanged with hydrogen through the No. 1 heat exchanger (3) and with furnace top gas through the No. 2 heat exchanger (4), and then enters the feeding device (5) to preheat the raw materials entering the furnace.

5. The heat compensation method for producing direct reduced iron in a pure hydrogen vertical furnace according to claim 4, characterized in that: In the step 1), the temperature of the externally supplied hydrogen after heat exchange with hot DRI is 450-600°C, and the temperature of the externally supplied hydrogen after heat exchange with nitrogen is 135-180°C.

6. The method for heat compensation of direct reduced iron produced by a pure hydrogen vertical furnace according to claim 4, characterized in that: In the step 2), the temperature of the furnace top gas is 350-500°C, and the temperature after heat exchange with nitrogen is 125-275°C.

7. The heat compensation method for producing direct reduced iron in a pure hydrogen vertical furnace according to claim 4, characterized in that: In the step 3), the temperature of the nitrogen after heat exchange with the hydrogen and the top gas is 450-600°C.

8. A heat compensation method for producing direct reduced iron in a pure hydrogen vertical furnace according to any one of claims 4 to 7, characterized in that: In the step 3), the raw materials entering the furnace are preheated to 380-500° C. by nitrogen.

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