Residual heat utilization type reduction loop system suitable for direct reduction shaft furnace process

Abstract

The utility model provides a waste heat utilization type reduction loop system suitable for a direct reduction shaft furnace process, and belongs to the technical field of ferrous metallurgy energy conservation and emission reduction. Comprising a first-stage heat exchange unit and a second-stage heat exchange unit which are communicated in sequence, an outlet of the purification unit is further communicated with an inlet of the second-stage heat exchange unit, and an outlet of the first-stage heat exchange unit is further communicated with an outlet of the second-stage heat exchange unit. And the outlet of the second-stage heat exchange unit is also communicated with a burner at the bottom of the heating furnace. A traditional direct reduction shaft furnace method reduction loop system is changed, the high-temperature advantage of the furnace top gas is fully utilized, the furnace top gas is subjected to primary heat exchange and then passes through a low-temperature waste heat recovery system, waste heat of the furnace top gas is fully utilized, energy waste of enterprises is reduced, and the purposes of cleaning energy, saving energy and reducing emission are achieved.

Description

Technical Field

[0001] The utility model belongs to the technical field of energy conservation and emission reduction in iron and steel metallurgy, and in particular relates to a residual heat utilization type reduction circuit system suitable for a direct reduction shaft furnace process. Background Art

[0002] At present, the ironmaking processes in the field of iron and steel metallurgy in the world mainly include blast furnace ironmaking process and non-blast furnace ironmaking process. Non-blast furnace ironmaking process includes direct reduction ironmaking process and smelting reduction ironmaking process. Among the non-blast furnace ironmaking processes, the gas-based vertical furnace direct reduction ironmaking process is dominant.

[0003] As the name implies, the gas-based vertical furnace ironmaking process uses gas as a reducing medium to reduce iron-containing raw materials to produce solid sponge iron. The gas-based vertical furnace ironmaking process mainly includes a reduction circuit, a cooling circuit system, etc.

[0004] The reduction loop system is that the gaseous reducing medium entering the vertical furnace reacts with the iron-containing oxides and exchanges heat in the vertical furnace, and is discharged from the top of the vertical furnace. Then, it undergoes heat exchange, dust removal, dehydration, pressurization, decarbonization, and heating at the top of the furnace and then re-enters the vertical furnace to form a reduction loop circulation system.

[0005] According to the minimum temperature requirement of iron ore for direct reduction reaction, the reducing gas entering the vertical furnace is required to be no less than 950°C. When the H2 content in the reducing medium is high, the furnace temperature requirement is higher. After the reducing gas enters the vertical furnace, it is reduced and heat exchanged and discharged from the top of the furnace. Usually, the top gas discharge temperature is above 450°C, even reaching 600°C. In the conventional gas-based direct reduction loop system, this part of sensible heat will be used to generate steam for other purposes or to preheat the reducing gas. However, even after the top gas is heat exchanged, its gas temperature is still very high. The top gas temperature after heat exchange in the conventional gas-based direct reduction process is also above 230°C. This part of heat is often not used due to its low temperature, but enters the downstream dust removal and dehydration process with the top gas, and this part of heat is wasted.

[0006] The information disclosed in this background technology section is only intended to increase the understanding of the overall background of the present invention, and should not be regarded as acknowledging or suggesting in any form that the information constitutes the prior art already known to a person skilled in the art. Utility Model Content

[0007] The utility model aims to solve the technical problem of insufficient heat utilization in the prior art gas-based vertical furnace ironmaking process and to provide a residual heat utilization type reduction circuit system suitable for the direct reduction vertical furnace process.

[0008] A low-temperature residual heat utilization reduction circuit system suitable for a direct reduction vertical furnace process, comprising: a vertical furnace top gas outlet is connected to a heat exchange unit, a purification unit, a compressor, and a heating furnace in sequence through a pipeline, and circulates to a reduction gas inlet at the bottom of the vertical furnace, the heat exchange unit comprises a primary heat exchange unit and a secondary heat exchange unit connected in sequence, the purification unit outlet is also connected to the secondary heat exchange unit inlet, and the secondary heat exchange unit outlet is also connected to the bottom burner of the heating furnace.

[0009] In some embodiments, the purification unit includes a dust collector and a mist eliminator connected in sequence.

[0010] In some embodiments, a deoxidizer unit is provided between the compressor and the heating furnace.

[0011] In some embodiments, a humidifier is provided between the compressor and the heating furnace.

[0012] In some embodiments, a humidifier is provided between the compressor and the heating furnace, and the humidifier is disposed downstream of the deoxidizer unit.

[0013] In some embodiments, a thermoelectric conversion system is provided between the secondary heat exchange unit and the purification unit.

[0014] In some embodiments, the thermoelectric conversion system includes an evaporator, and the evaporator is connected in series between the secondary heat exchange unit and the purification unit.

[0015] In some embodiments, the heat-to-electricity conversion system further includes an expander, a condenser, and a working fluid pump. The evaporator, the expander, the condenser, the working fluid pump, and the evaporator are sequentially connected to form a closed circulation loop.

[0016] In some embodiments, the expander is further connected to a generator.

[0017] Compared with the prior art, the technical effects achieved by the utility model are as follows:

[0018] (1) The utility model can make full use of the high temperature advantage of the top gas type of the vertical furnace, and make dual use of the residual heat of the top gas. On the one hand, it is used to heat the fuel of the heating furnace, increase the theoretical combustion temperature of the fuel, reduce the fuel consumption of the heating furnace, and indirectly increase the amount of reducing gas entering the vertical furnace, thereby increasing the output of the vertical furnace; on the other hand, the low-temperature residual heat of the top gas type can be used to generate steam and then converted into electrical energy, achieving the effect of fully utilizing the high-temperature gas advantage of the reduction circuit and increasing the output of the vertical furnace. The utility model reduces the energy consumption and energy waste of the enterprise to the greatest extent, and achieves the effects of clean energy, energy conservation and emission reduction, and increased production and efficiency.

[0019] (2) The utility model has a simple system process, requires little investment, does not increase operating costs, and has little impact on the existing reduction loop system. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of the structure of the residual heat utilization type reduction circuit system in Example 1;

[0021] Figure 2 This is a schematic diagram of the structure of the residual heat utilization reduction circuit system in Example 2.

[0022] In the figure:

[0023] 1-vertical furnace; 2-primary heat exchange unit; 3-secondary heat exchange unit; 4-dust collector; 5-demister; 6-compressor; 7-deoxidizer unit; 8-humidifier; 9-heating furnace; 10-evaporator; 11-expander; 12-generator; 13-condenser; 14-working fluid pump. DETAILED DESCRIPTION

[0024] The technical solution of the present invention is described below by means of specific embodiments in conjunction with the accompanying drawings. It should be understood that one or more steps mentioned in the present invention do not exclude the existence of other methods and steps before and after the combination step, or other methods and steps can be inserted between these explicitly mentioned steps. It should also be understood that these examples are only used to illustrate the present invention and are not used to limit the scope of the present invention. Unless otherwise specified, the numbering of each method step is only for the purpose of identifying each method step, and does not limit the order of arrangement of each method or the scope of implementation of the present invention. Changes or adjustments in their relative relationships can also be regarded as the scope of implementation of the present invention without substantial changes in the technical content.

[0025] The sources of the raw materials and instruments used in the examples are not particularly limited and can be purchased from the market or prepared according to conventional methods known to those skilled in the art.

[0026] Example 1

[0027] like Figure 1 As shown, a low-temperature residual heat utilization type reduction circuit system for a direct reduction vertical furnace process includes: the top gas outlet of the vertical furnace 1 is connected to a heat exchange unit, a purification unit, a compressor 6, and a heating furnace 9 in sequence through a pipeline, and circulates to the reduction gas inlet at the bottom of the vertical furnace 1, the heat exchange unit includes a primary heat exchange unit 2 and a secondary heat exchange unit 3 connected in sequence, the purification unit outlet is also connected to the secondary heat exchange unit 3 inlet, and the secondary heat exchange unit 3 outlet is also connected to the bottom burner of the heating furnace 9.

[0028] The purification unit comprises a dust collector 4 and a demister 5 which are connected in sequence. The outlet of the demister 5 is divided into two branches, one branch is connected to the inlet of the compressor 6 , and the other branch is connected to the inlet of the secondary heat exchange unit 3 .

[0029] A deoxidizer unit 7 and a humidifier 8 are provided between the compressor 6 and the heating furnace. The humidifier is provided downstream of the deoxidizer unit.

[0030] The gas flow in the low-temperature residual heat utilization reduction circuit system used in the direct reduction shaft furnace process is as follows:

[0031] The high-temperature top gas generated by the vertical furnace 1 has a temperature of more than 450°C. The top gas first enters the primary heat exchange unit 2 through the top gas outlet for heat exchange to generate steam. After heat exchange in the primary heat exchange unit 2, the top gas temperature is reduced from 450°C to more than 230°C. Then the top gas enters the secondary heat exchange unit 3. Through the heat exchange of the secondary heat exchange unit 3, the top gas is reduced from the initial 230°C to less than 220°C. Since the top gas contains N2 and H2O in addition to high calorific value gases such as CO, H2, and CH4, the top gas that has been fully heat exchanged will precipitate some moisture under low temperature conditions; the top gas after two-stage heat exchange enters the downstream dust collector 4, which is a wet dust collector In the dust collector 4, in addition to removing dust from the furnace top gas, moisture in the furnace top gas is also removed at the same time; the reducing gas after wet dust removal enters the demister 5 to further remove moisture and fine particles in the gas to meet the gas quality requirements of the downstream compressor 6; the reducing gas discharged from the demister 5 has a temperature of about 30°C, and this part of the reducing gas enters the deoxidizer unit 7 after being pressurized by the compressor 7. The purpose of the deoxidizer unit 7 is to remove CO2 in the reducing gas to reduce the enrichment of useless gas and reduce the oxidation degree of the reducing gas; the reducing gas after decarburization enters the humidifier 8 to adjust the moisture content in the reducing gas. At this time, the reducing gas temperature is about 80°C, and then enters the heating furnace 9 for heating. Through the heat exchange of the heating furnace 9, the reducing gas is heated to above 950°C. After obtaining the reducing gas of qualified temperature, the gas enters the vertical furnace 1 through the reducing gas inlet at the bottom of the vertical furnace, and chemically reacts with the iron-containing raw material in the vertical furnace 1 while performing heat exchange. The reducing gas after a series of reactions is discharged again through the top of the vertical furnace 1 to complete a reduction loop cycle.

[0032] After the top gas is dusted and demisted, part of the gas goes to the compressor 6 to be pressurized, that is, used as the reducing gas of the reduction circuit (reducing gas heating), and the other part goes to the burner of the heating furnace 9 as the fuel of the heating furnace 9 (combustion gas circuit). Before the other part of the reducing gas enters the burner of the heating furnace 9 to be burned, it first passes through the secondary heat exchange unit 3 on the top of the vertical furnace to exchange heat with the top gas. After the secondary heat exchange, the temperature of the top gas of 3 is reduced from 230°C to less than 50°C, and the fuel gas after heat exchange is heated to about 200°C, and the thermal energy of the top reducing gas is fully utilized. The preheated fuel gas enters the burner of the heating furnace 9 to burn and release heat to provide heat for the reducing gas.

[0033] The reducing gas used as fuel accounts for 5% to 20% of the total reducing gas on the furnace top.

[0034] Since the heating furnace 9 consumes part of the reducing gas, in order to meet the gas balance of the reduction circuit, continuous gas replenishment treatment is required after the deoxidizer unit 7 and before the humidifier 8. The replenished gas components mainly include hydrogen, methane, reformed gas and highly reducing gas.

[0035] This implementation case proposes a waste heat utilization reduction circuit system suitable for a direct reduction shaft furnace process based on a direct reduction shaft furnace process. The system is not only suitable for conventional direct reduction shaft furnace processes, but also for other non-blast furnace and blast furnace ironmaking processes with relatively high furnace top operating temperatures.

[0036] For example, for a project with an annual output of 1 million tons of direct reduced iron, the energy consumption per ton of direct reduced iron is about 9GJ / t. If the above-mentioned low-temperature waste heat utilization reduction circuit system is adopted, the increased reducing gas volume of the reduction circuit system can increase the annual output of direct reduced iron by 15,000 tons. At the same time, the electric energy recovered and converted by using low-temperature waste heat also greatly reduces the production cost of the enterprise and increases the production profit of the enterprise.

[0037] Example 2

[0038] This embodiment is consistent with the inventive concept of embodiment 1, and is different from embodiment 1 in that: a thermoelectric conversion system is provided between the secondary heat exchange unit and the purification unit 3, and the thermoelectric conversion system includes an evaporator 10, and the evaporator 10 is connected in series between the secondary heat exchange unit 3 and the purification unit. Specifically, the evaporator 10 is connected in series between the secondary heat exchange unit 3 and the dust collector 4. The thermoelectric conversion system also includes an expander 11, a condenser 13, and a working fluid pump 14. The evaporator 10, the expander 11, the condenser 13, the working fluid pump 14, and the evaporator 10 are connected in sequence to form a closed circulation loop, wherein the expander 11 is also connected to the generator 12. The circulation loop formed by the thermoelectric conversion system is arranged in parallel with the reduction gas heating loop and the combustion gas loop.

[0039] The gas flow of the reduction loop system of the low-temperature residual heat utilization direct reduction vertical furnace is as follows: the high-temperature top gas generated by the vertical furnace has a temperature of more than 450°C, and first enters the first-level heat exchange unit 2 on the top of the furnace 1 for heat exchange to generate steam. The temperature of the top gas after heat exchange in the first-level heat exchange unit 2 is reduced from 450°C to more than 230°C, and then the top gas enters the second-level heat exchange unit 3. Through the heat exchange of the second-level heat exchange unit 3, the cold medium of the second-level heat exchange unit 3 is the heating furnace fuel. Since the amount of heating furnace fuel is very small, accounting for about 1 / 10 to 1 / 15 of the top gas, the temperature of the top gas after passing through the second-level heat exchange unit is slightly reduced, from about 230°C at the initial time to within 220°C. After the secondary heat exchange, the top gas enters the downstream evaporator 10 to generate steam again. At the same time, the temperature of the top gas is reduced from 220°C to room temperature, realizing the third-stage heat exchange. Since the top gas contains N2 and H2O in addition to high calorific value gases such as CO, H2, and CH4, the top gas after sufficient heat exchange will precipitate some moisture under low temperature conditions. After the third-stage heat exchange, the top gas enters the downstream dust removal system, which is a wet dust removal system. In this dust removal system, in addition to removing dust from the top gas, the moisture in the top gas is also removed at the same time.

[0040] The reducing gas after wet dust removal enters the demister 5 to further remove moisture and fine particles in the gas to meet the gas quality requirements of the downstream compressor. The temperature of the reducing gas discharged from the demister 5 is about 30°C. The reducing gas enters the deoxidizer unit 7 after being pressurized by the compressor 6. The purpose of the deoxidizer unit is to remove the oxidant in the reducing gas to reduce the enrichment of useless gas and reduce the oxidation degree of the reducing gas. The reducing gas after the deoxidizer enters the humidifier 8 to adjust the moisture content in the reducing gas. At this time, the reducing gas temperature is about 80°C, and then enters the heating furnace 9 for heating. Through the heat exchange of the heating furnace 9, the reducing gas is heated to above 950°C. After obtaining the reducing gas of qualified temperature, the gas enters the vertical furnace, and reacts chemically with the iron-containing raw material in the vertical furnace while performing heat exchange. The reducing gas after a series of reactions is discharged again through the top of the vertical furnace to complete a reduction loop cycle.

[0041] After the furnace top gas is dusted and demisted, part of the gas goes to the compressor to be pressurized, that is, used as reducing gas in the reduction circuit, and the other part goes to the heating furnace as fuel for the heating furnace. The reducing gas used as fuel accounts for 5% to 20% of the total reducing gas at the furnace top.

[0042] Before the other part of the reducing gas enters the heating furnace for combustion, it first passes through the secondary heat exchange unit on the top of the vertical furnace to exchange heat with the top gas. After the secondary heat exchange, the top gas temperature is reduced from 230℃ to about 220℃, and the fuel gas after heat exchange is heated from 30℃ to about 200℃, so that the thermal energy of the top reducing gas is fully utilized. The preheated fuel gas enters the heating furnace for combustion and releases heat to provide heat for the reducing gas.

[0043] The temperature of the furnace top gas after passing through the secondary heat exchange unit is about 220°C. This part belongs to low-temperature waste heat, which cannot be fully utilized by conventional heat exchange technology. This process uses a low-temperature waste heat medium, which can effectively use the low-temperature waste heat of the system to generate steam, that is, the furnace top gas enters the downstream evaporator 10 to generate high-temperature steam, and then the generated steam causes the expander 11 to work and generate electricity, so that the waste heat energy is converted into mechanical energy, and then converted into electrical energy, making full use of the low-temperature waste heat. The steam that passes through the expander enters the downstream condenser 13 to condense, and then uses the downstream working fluid pump to pump it into the evaporator again for the next cycle.

[0044] This process can make full use of the low-temperature waste heat energy in the reduction circuit, convert the low-temperature waste heat into electrical energy, and use the electrical energy for corporate users to achieve energy saving.

[0045] The foregoing description of specific exemplary embodiments of the utility model is for the purpose of illustration and illustration. These descriptions are not intended to limit the utility model to the precise form disclosed, and it is clear that many changes and variations can be made based on the above teachings. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the utility model and its practical application, so that those skilled in the art can realize and utilize various different exemplary embodiments of the utility model and various different options and changes. The scope of the utility model is intended to be defined by the claims and their equivalents.

Claims

1. A residual heat utilization type reduction circuit system suitable for a direct reduction shaft furnace process, comprising: The gas outlet at the top of the vertical furnace is connected to the heat exchange unit, the purification unit, the compressor, and the heating furnace in sequence through a pipeline, and circulates to the reducing gas inlet at the bottom of the vertical furnace. It is characterized in that the heat exchange unit includes a primary heat exchange unit and a secondary heat exchange unit connected in sequence, the purification unit outlet is also connected to the secondary heat exchange unit inlet, and the secondary heat exchange unit outlet is also connected to the burner at the bottom of the heating furnace.

2. The residual heat utilization type reduction circuit system suitable for the direct reduction shaft furnace process according to claim 1 is characterized in that: The purification unit includes a dust collector and a mist eliminator which are connected in sequence.

3. The residual heat utilization type reduction circuit system suitable for direct reduction shaft furnace process according to claim 1 is characterized in that: A deoxidant unit is provided between the compressor and the heating furnace.

4. The residual heat utilization type reduction circuit system suitable for direct reduction shaft furnace process according to claim 1 is characterized in that: A humidifier is provided between the compressor and the heating furnace.

5. The residual heat utilization type reduction circuit system suitable for direct reduction shaft furnace process according to claim 3 is characterized in that: A humidifier is provided between the compressor and the heating furnace, and the humidifier is arranged downstream of the deoxidizer unit.

6. The residual heat utilization type reduction circuit system suitable for direct reduction shaft furnace process according to claim 1 is characterized in that: A thermoelectric conversion system is provided between the secondary heat exchange unit and the purification unit.

7. The residual heat utilization type reduction circuit system suitable for direct reduction shaft furnace process according to claim 6, characterized in that: The thermoelectric conversion system includes an evaporator, which is connected in series between the secondary heat exchange unit and the purification unit.

8. The residual heat utilization type reduction circuit system suitable for the direct reduction shaft furnace process according to claim 7, characterized in that: The heat-to-electricity conversion system further comprises an expander, a condenser, and a working fluid pump. The evaporator, the expander, the condenser, the working fluid pump, and the evaporator are sequentially connected to form a closed circulation loop.

9. The residual heat utilization type reduction circuit system suitable for the direct reduction shaft furnace process according to claim 8, characterized in that: The expander is also connected to a generator.

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