Waste gas purification device for stainless steel smelting based on carbon dioxide

Abstract

The invention relates to the technical field of stainless steel smelting, and particularly discloses a waste gas purification device for stainless steel smelting based on carbon dioxide, which comprises a waste gas treatment system and a carbon dioxide recovery system, the waste gas treatment system comprises a concentration fan and a molecular sieve rotating wheel, and an inlet of the concentration fan is connected with a waste gas outlet of a converter; waste gas of the converter enters the waste gas treatment system through the waste gas inlet after being collected, an outlet of the concentration fan is connected with a concentration area of the molecular sieve rotating wheel, a desorption area of the molecular sieve rotating wheel is communicated with an inlet of the heat storage type oxidation furnace, and an outlet of the heat storage type oxidation furnace is connected with the carbon dioxide recovery system. Carbon dioxide gas generated by the regeneration tower returns to the blowing system at the upper part and / or the lower part of the converter; purified gas discharged from the upper part of the absorption tower is discharged by connecting a pipeline with an exhaust chimney; carbon dioxide is conveyed into the blowing system for converter smelting again, cyclic utilization of the carbon dioxide is achieved, the energy utilization rate is increased, and the production cost is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of stainless steel smelting, and in particular to an exhaust gas purification device for smelting stainless steel based on carbon dioxide. Background Art

[0002] During the high-temperature sintering process of stainless steel, gases containing iron oxide, chromium oxide, nickel oxide and other substances will be produced. These gases will form inhalable particulate matter and harmful gases in the atmosphere, seriously polluting the atmospheric environment. In addition, harmful substances in the exhaust gas, such as sulfur dioxide and nitrogen oxides, will react chemically with oxygen and water vapor in the atmosphere to form pollution phenomena such as acid rain and haze. Heavy metal elements in the exhaust gas will also settle to the ground and enter the soil, causing soil pollution.

[0003] The treatment of waste gas generated during stainless steel smelting mainly includes the following methods:

[0004] Waste gas collection: First of all, the waste gas generated during the stainless steel smelting process needs to be effectively collected. This is usually achieved by installing equipment such as suction hoods and gas collection hoods to ensure that the waste gas can be quickly collected after it is generated to avoid direct discharge into the atmosphere.

[0005] Washing method: Use washing liquid (such as water, alkali solution, etc.) to react chemically or physically absorb harmful substances in the waste gas to remove pollutants in the waste gas. This method is suitable for treating waste gas containing acidic gases (such as HCl, HF, etc.). The washing tower is a commonly used washing equipment. By spraying washing liquid, the waste gas is fully in contact with the washing liquid to achieve a purification effect.

[0006] Photocatalytic oxidation method: The strong oxidizing property of photocatalysts (such as TiO2) under ultraviolet light is used to decompose organic matter in the exhaust gas into harmless substances. This method is suitable for treating exhaust gas containing volatile organic compounds (VOCs), and has the advantages of good treatment effect and no secondary pollution.

[0007] Biological oxidation method: Use the metabolism of microorganisms to convert harmful substances in waste gas into harmless substances. This method is suitable for treating occasions containing low-concentration organic waste gas or malodorous gas, and has the advantages of low operating cost and stable treatment effect.

[0008] Low-temperature plasma method: high-energy electrons, free radicals and other active particles in low-temperature plasma react with harmful substances in waste gas to decompose them into harmless substances. This method is suitable for treating various types of waste gas, including organic waste gas, odorous gas, etc., and has the advantages of high treatment efficiency and wide application range.

[0009] Desulfurization and denitrification: Common methods for desulfurization include wet limestone gypsum method, alkaline oxidation method, activated carbon adsorption method, etc., which can effectively convert sulfur dioxide into sulfate or other harmless substances. Denitrification converts nitrogen oxides into nitrogen and water vapor through technologies such as selective catalytic reduction (SCR) and selective non-catalytic reduction (SNCR).

[0010] Dust removal: Commonly used dust removal equipment includes electrostatic precipitators, bag dust collectors, wet electrostatic precipitators, etc., which can effectively capture and remove particulate matter in exhaust gas.

[0011] Heat recovery: Recover heat energy from waste gas through waste heat boilers, hot air furnaces, heat exchangers and other technologies and use it in other production processes, which helps save energy, reduce emissions and improve the economic benefits of the enterprise.

[0012] Microbial treatment: For waste gas containing organic substances such as ammonia and hydrogen sulfide, microbial degradation can be carried out through bioreactors. This method has the advantages of simple equipment, low investment and low operating costs.

[0013] Steel production is a major emitter of carbon dioxide. How to reduce carbon dioxide emissions and utilize carbon dioxide as a resource has attracted more and more attention from metallurgical workers. At present, in the field of carbon steel smelting, there are certain technical barriers to the collection and reuse of carbon dioxide. The application of carbon dioxide in steelmaking for decarbonization and chromium preservation still relies on external supply of carbon dioxide, which requires the addition of a complete set of carbon dioxide preparation equipment and gas supply equipment, increasing production costs. In addition, waste gases such as carbon dioxide after removal cannot be directly and effectively collected, resulting in energy waste. Therefore, it is necessary to design a waste gas purification device based on carbon dioxide smelting stainless steel to solve the problem of low utilization rate of existing carbon dioxide and inability to recycle it, resulting in energy waste and high production costs. Summary of the invention

[0014] In view of the problems existing in the prior art, the object of the present invention is to provide an exhaust gas purification device based on carbon dioxide smelting stainless steel.

[0015] The technical solution adopted by the present invention to solve its technical problems is: a waste gas purification device based on carbon dioxide smelting of stainless steel, including a waste gas treatment system and a carbon dioxide recovery system, the waste gas treatment system including a concentrating fan and a molecular sieve rotor, the inlet of the concentrating fan is connected to the waste gas outlet of the converter, the waste gas of the converter enters the waste gas treatment system through the waste gas inlet after being collected, the outlet of the concentrating fan is connected to the concentrating zone of the molecular sieve rotor, the desorption zone of the molecular sieve rotor is connected to the inlet of the regenerative thermal oxidation furnace, the outlet of the regenerative thermal oxidation furnace is connected to the carbon dioxide recovery system, the carbon dioxide recovery system is provided with an absorption tower and a regeneration tower, the carbon dioxide gas generated by the regeneration tower is returned to the blowing system of the upper and / or lower part of the converter, and the purified gas discharged from the upper part of the absorption tower is discharged through a pipeline connected to the exhaust chimney.

[0016] Specifically, the exhaust gas inlet of the exhaust gas treatment system is connected to a filter, and the rear of the filter is connected to a concentrating fan.

[0017] Specifically, the molecular sieve rotor is powered by a reduction motor, activated carbon is placed in the molecular sieve rotor, and the cooling area of ​​the molecular sieve rotor is connected to a heating device through a pipeline, and the heating device adopts a water heating structure.

[0018] Specifically, the desorption zone of the molecular sieve rotor is connected to the desorption fan through a pipeline, and the desorption fan is connected to the inlet of the regenerative thermal oxidation furnace through a concentrated exhaust gas pipe.

[0019] Specifically, an ignition structure is arranged in the regenerative thermal oxidation furnace, the ignition structure is connected to a flame-retardant air pipe, the flame-retardant air pipe is connected to a fuel pipe, and exhaust gas is heated and burned in the regenerative thermal oxidation furnace to generate carbon dioxide.

[0020] Specifically, the outlet of the regenerative thermal oxidation furnace is connected to the bottom of an absorption tower, a sodium hydroxide solution is provided in the absorption tower, carbon dioxide enters the sodium hydroxide solution, the absorption tower is connected to a regeneration tower through a heat exchanger, the regeneration tower is connected to a heater, the carbon dioxide in the sodium hydroxide solution is heated and discharged from the regeneration tower, and purified gas is discharged from the absorption tower.

[0021] Specifically, the blowing system includes bottom blowing and top blowing, the oxygen content in the bottom blowing and the top blowing is 55%, the carbon dioxide content in the bottom blowing and the top blowing is 45%, which is used for decarburization and chromium preservation, and the blowing time is 19 minutes.

[0022] Specifically, the carbon dioxide is a weak oxidizing gas, and the carbon dioxide undergoes an oxidation reaction with the active elements in the molten steel. The active elements in the molten steel include but are not limited to C, Si, Mn, P, Al, Cr, and Fe.

[0023] Specifically, the oxygen oxidizes 1Kg of C, 1Kg of Si and 1Kg of Cr elements to raise the temperature of 1 ton of molten stainless steel by 14.1°C, 34.6°C and 12.7°C respectively; the carbon dioxide oxidizes 1Kg of C, 1Kg of Si and 1Kg of Cr elements to raise the temperature of 1 ton of molten stainless steel by -13.8°C, 10.9°C and 3.9°C respectively.

[0024] Specifically, the volume ratio of carbon dioxide in the bottom blowing gas should be higher than 30%, so that carbon dioxide can still participate in the decarburization reaction at the end of decarburization. The total flow rate of carbon dioxide gas should be lower than 6.56m / ton steel, so that the temperature of molten steel at the end of decarburization is above 1650°C.

[0025] The present invention has the following beneficial effects:

[0026] The waste gas purification device designed by the present invention for smelting stainless steel with carbon dioxide adopts a waste gas treatment system to effectively treat harmful waste gas, retains carbon dioxide through a regenerative oxidation furnace, and collects carbon dioxide in the waste gas again through a carbon dioxide recovery system, and transports the carbon dioxide again to the blowing system of the converter smelting, thereby realizing the recycling of carbon dioxide, improving energy utilization and reducing production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the structure of an exhaust gas purification device for smelting stainless steel based on carbon dioxide.

[0028] Figure 2 It is a structural schematic diagram of the carbon dioxide recovery system.

[0029] In the figure: 1-exhaust gas inlet; 2-carbon dioxide recovery system, 2.1-absorption tower, 2.2-regeneration tower, 2.3-heater, 2.4-heat exchanger;

[0030] 3-concentration fan; 4-concentration main pipe; 5-concentration branch pipe; 6-concentration zone; 7-cooling zone; 8-molecular sieve rotor; 9-desorption zone; 10-heating device; 11-reduction motor; 12-desorption fan; 13-concentration exhaust gas pipe; 14-regenerative oxidation furnace; 15-combustion air pipe; 16-fuel pipe; 17-filter; 18-exhaust chimney. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely further describe the technical solutions in the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0032] like Figure 1-Figure 2 As shown, a waste gas purification device for smelting stainless steel based on carbon dioxide includes a waste gas treatment system and a carbon dioxide recovery system. The waste gas treatment system includes a filter 17, a concentrator fan 3, a molecular sieve rotor 8, a desorption fan 12 and a heating device 10. The waste gas inlet 1 of the waste gas treatment system is connected to the filter 17, and the rear of the filter 17 is connected to the concentrator fan 3. The waste gas inlet 1 of the waste gas treatment system is connected to the waste gas outlet of the converter, and the waste gas of the converter is collected and enters the waste gas treatment system through the waste gas inlet 1.

[0033] The outlet of the concentration fan 3 is connected to the concentration zone 6 of the molecular sieve rotor 8, and the molecular sieve rotor 8 is powered by a reduction motor 11 to rotate. Activated carbon is placed in the molecular sieve rotor 8, and the activated carbon adsorbs substances in the exhaust gas. The cooling zone 7 of the molecular sieve rotor 8 is connected to the heating device 10 through a pipeline, and the heating device 10 adopts a water heating structure.

[0034] The desorption zone 9 of the molecular sieve rotor 8 is connected to the inlet of the regenerative thermal oxidizer 14, and the desorption zone 9 of the molecular sieve rotor 8 is connected to the desorption fan 12 through a pipeline, and the desorption fan 12 is connected to the inlet of the regenerative thermal oxidizer 14 through a concentrated exhaust gas pipe.

[0035] The outlet of the regenerative oxidation furnace 14 is connected to a carbon dioxide recovery system, which is provided with an absorption tower 2.1, a regeneration tower 2.2, a heater 2.3 and a heat exchanger 2.4. The carbon dioxide gas generated by the regeneration tower 2.2 is returned to the blowing system at the upper and / or lower part of the converter, and the purified gas discharged from the upper part of the absorption tower 2.1 is discharged through a pipeline connected to an exhaust chimney 18.

[0036] An ignition structure is arranged in the regenerative thermal oxidation furnace 14, the ignition structure is connected to a flame retardant air pipe, and the flame retardant air pipe is connected to a fuel pipe. The waste gas is heated and burned in the regenerative thermal oxidation furnace 14 to generate carbon dioxide.

[0037] The outlet of the regenerative thermal oxidizer 14 is connected to the bottom of the absorption tower 2.1. A sodium hydroxide solution is provided in the absorption tower 2.1. Carbon dioxide enters the sodium hydroxide solution. The absorption tower 2.1 is connected to the regeneration tower 2.2 through the heat exchanger 2.4. The regeneration tower 2.2 is connected to the heater 2.3. The carbon dioxide in the sodium hydroxide solution is heated and discharged from the regeneration tower 2.2. The purified gas discharged from the absorption tower 2.1 is discharged to the exhaust chimney 18.

[0038] Taking 430 series stainless steel as an example, the blowing system includes bottom blowing and top blowing. The oxygen content in bottom blowing and top blowing is 55%, and the carbon dioxide content in bottom blowing and top blowing is 45%, which is used for decarburization and chromium preservation. The blowing time is 19 minutes.

[0039] Carbon dioxide is a weak oxidizing gas. Carbon dioxide reacts with active elements in molten steel to produce an oxidation reaction. The active elements in molten steel include but are not limited to C, Si, Mn, P, Al, Cr, and Fe. The equation for the oxidation reaction between carbon dioxide and active elements in molten steel is as follows:

[0040] CO2(g)+[C]=2CO(g);

[0041] CO2(g)+[Fe]=(FeO)+CO(g);

[0042] CO2(g)+1 / 2[Si]=1 / 2(SiO2)+CO(g);

[0043] CO2(g)+[Mn]=(MnO)+CO(g);

[0044] CO2(g)+2 / 5[P]=1 / 5(P2O5)+CO(g);

[0045] CO2(g)+2 / 3[Cr]=1 / 3Cr2O3(s)+CO(g);

[0046] CO2(g)+[Ni]=NiO(S)+CO(g).

[0047] The stainless steel blowing process uses carbon-oxygen reaction to remove carbon while avoiding chromium oxidation, that is, decarbonization and chromium preservation. The chemical reaction is shown in the following formula:

[0048] 1 / 3Cr2O3(s)+[C]=2 / 3[Cr]+CO(g).

[0049] Lowering the partial pressure of carbon monoxide is beneficial to decarburization and chromium preservation. As the temperature of molten steel increases, the equilibrium partial pressure of carbon monoxide increases accordingly, which is beneficial to avoiding chromium oxidation. Assuming that the carbon monoxide pressure in molten steel is 1atm, if chromium oxidation is to be avoided, the molten steel temperature should be higher than 1650℃. Since the reaction of carbon dioxide and [C] is an endothermic reaction, carbon dioxide will reduce the temperature of molten steel when participating in carbon oxidation. Therefore, the proportion of carbon dioxide in the bottom blowing gas, that is, the total flow rate of carbon dioxide, should be strictly controlled to ensure that the molten steel temperature is higher than 1650℃ at the end of decarburization to inhibit chromium oxidation.

[0050] The chemical heat of oxidation of elements such as C, Si, Mn, and Cr is the most important heat source for molten steel. The oxidation of Si, Mn, and Cr by carbon dioxide is an exothermic reaction, while the oxidation of C by carbon dioxide is an endothermic reaction. The endothermic reaction of carbon dioxide and C will reduce the temperature of molten steel, which is very unfavorable for decarburization and chromium preservation, scrap steel addition, etc. Comparison of the effects of carbon dioxide and oxygen oxidation of 1kgC, 1kgSi, and 1kgCr on the temperature of 1 ton of 430 stainless steel molten steel. In addition, it is assumed that the hot melt of molten steel is the linear sum of the heat capacities of Fe and Cr, that is, C Fe ·W Fe +C Cr ·W Cr , where W Fe and W Cr is the mass percentage of Fe and Cr in molten steel (wt%), C Fe and C Cr are the heat capacities of Fe and Cr (J·k -1 ·mol -1 ), and their heat capacities are 46.02 J·k -1 ·mol -1 and 46.68 J·k -1 ·mol -1. Oxygen oxidizes 1Kg of C, 1Kg of Si and 1Kg of Cr elements, which raises the temperature of 1 ton of stainless steel liquid by 14.1℃, 34.6℃ and 12.7℃ respectively. Carbon dioxide oxidizes 1Kg of C, 1Kg of Si and 1Kg of Cr elements, which raises the temperature of 1 ton of stainless steel liquid by -13.8℃, 10.9℃ and 3.9℃ respectively. Carbon dioxide and oxidation reactions have a very significant effect on cooling molten steel.

[0051] In the converter process for smelting stainless steel, the molten iron entering the furnace usually contains about 5.0% C and about 0.1% Si, and the temperature of the molten iron entering the furnace is 1260C. The chromium-iron components added at the end of blowing are approximately: Fe, 69% Cr, 8% C, and 0.05% Si. After blowing, the C content of the molten steel at the end is 0.3%, and Si is basically completely oxidized. The thermal efficiency of the converter is 85%, and the effect of the volume proportion of carbon dioxide in the mixed injection gas of oxygen and carbon dioxide on the end temperature of 430 stainless steel molten steel is calculated. As the volume proportion of carbon dioxide increases, the temperature rise of the molten steel decreases linearly. In order to achieve decarburization and chromium preservation, the temperature of the molten steel at the end of blowing should be higher than 1650℃. Therefore, the molten steel should be heated by more than 390C during the converter process. The volume proportion of carbon dioxide in the mixed injection gas of oxygen and carbon dioxide should be higher than 30%. It should be noted that the oxygen in the mixed injection gas includes top blowing oxygen and bottom blowing oxygen. Further calculations show that for an 80t ladle, the total flow rate of carbon dioxide gas should be less than 6.56m / ton of steel to ensure that the final molten steel temperature is above 1650℃.

[0052] 55% oxygen + 45% carbon dioxide has a faster decarburization speed. In the same blowing time, a lower carbon content is obtained. Taking the blowing time of 19 minutes as an example, the carbon content of the original process is 2.64%, the carbon content of the process of the present invention is 2.05%, and the decarburization amount of the process of the present invention increases by 0.59%. Assume that the decarburization efficiency of bottom blowing oxygen and carbon dioxide gas is 100%. The difference in carbon content caused by the high oxygen flow rate of the process of the present invention is 0.09%, and the difference in carbon content caused by carbon dioxide in the process of the present invention is 0.25%. The decarburization amount increased by carbon dioxide and additional oxygen is 0.34%, which is much lower than the actual measured decarburization amount difference of 0.59%. The reason for this phenomenon is that bottom blowing carbon dioxide increases the decarburization amount of top blowing oxygen by 0.25%. 1 volume of carbon dioxide produces 2 volumes of CO. Therefore, CO can increase the stirring intensity of molten steel, thereby improving the decarburization efficiency of top blowing oxygen. The process of the present invention reduces the carbon content to 0.29% after blowing for 19 minutes, while the original process requires 22.5 minutes to reduce the carbon content to 0.32%. Therefore, bottom blowing carbon dioxide can significantly increase the decarburization speed.

[0053] The present invention is not limited to the above-mentioned implementation modes, and anyone should be aware of the structural changes made under the enlightenment of the present invention, and all those having the same or similar technical solutions as the present invention fall within the protection scope of the present invention.

[0054] The techniques, shapes, and structural parts not described in detail in the present invention are all well-known techniques.

Claims

1. A waste gas purification device based on carbon dioxide smelting stainless steel, characterized in that: It includes a waste gas treatment system and a carbon dioxide recovery system. The waste gas treatment system includes a concentrating fan and a molecular sieve rotor. The inlet of the concentrating fan is connected to the waste gas outlet of the converter. The waste gas of the converter enters the waste gas treatment system through the waste gas inlet after being collected. The outlet of the concentrating fan is connected to the concentrating area of ​​the molecular sieve rotor. The desorption area of ​​the molecular sieve rotor is connected to the inlet of the regenerative thermal oxidation furnace. The outlet of the regenerative thermal oxidation furnace is connected to the carbon dioxide recovery system. The carbon dioxide recovery system is provided with an absorption tower and a regeneration tower. The carbon dioxide gas generated by the regeneration tower is returned to the blowing system at the upper part and / or the lower part of the converter. The purified gas discharged from the upper part of the absorption tower is discharged through a pipeline connected to the exhaust chimney.

2. The exhaust gas purification device for smelting stainless steel based on carbon dioxide according to claim 1 is characterized in that: The exhaust gas inlet of the exhaust gas treatment system is connected to a filter, and the rear of the filter is connected to a concentration fan.

3. The exhaust gas purification device for smelting stainless steel based on carbon dioxide according to claim 1 is characterized in that: The molecular sieve rotor is powered by a reduction motor for rotation, activated carbon is placed in the molecular sieve rotor, and the cooling area of ​​the molecular sieve rotor is connected to a heating device through a pipeline, and the heating device adopts a water heating structure.

4. The exhaust gas purification device for smelting stainless steel based on carbon dioxide according to claim 3 is characterized in that: The desorption zone of the molecular sieve rotor is connected to the desorption fan through a pipeline, and the desorption fan is connected to the inlet of the regenerative thermal oxidation furnace through a concentrated exhaust gas pipe.

5. The exhaust gas purification device for smelting stainless steel based on carbon dioxide according to claim 4 is characterized in that: An ignition structure is arranged in the regenerative thermal oxidation furnace, the ignition structure is connected to a flame-retardant air pipe, the flame-retardant air pipe is connected to a fuel pipe, and waste gas is heated and burned in the regenerative thermal oxidation furnace to generate carbon dioxide.

6. The exhaust gas purification device for smelting stainless steel based on carbon dioxide according to claim 1 is characterized in that: The outlet of the regenerative thermal oxidation furnace is connected to the bottom of the absorption tower. A sodium hydroxide solution is arranged in the absorption tower. Carbon dioxide enters the sodium hydroxide solution. The absorption tower is connected to the regeneration tower through a heat exchanger. The regeneration tower is connected to a heater. The carbon dioxide in the sodium hydroxide solution is heated and discharged from the regeneration tower. Purified gas is discharged from the absorption tower.

7. The exhaust gas purification device for smelting stainless steel based on carbon dioxide according to claim 1 is characterized in that: The blowing system includes bottom blowing and top blowing, the oxygen content in the bottom blowing and the top blowing is 55%, the carbon dioxide content in the bottom blowing and the top blowing is 45%, which is used for decarburization and chromium preservation, and the blowing time is 19 minutes.

8. The exhaust gas purification device for smelting stainless steel based on carbon dioxide according to claim 7 is characterized in that: The carbon dioxide is a weak oxidizing gas, and the carbon dioxide undergoes an oxidation reaction with the active elements in the molten steel. The active elements in the molten steel include but are not limited to C, Si, Mn, P, Al, Cr, and Fe.

9. The exhaust gas purification device for smelting stainless steel based on carbon dioxide according to claim 8 is characterized in that: The oxygen oxidizes 1Kg of C, 1Kg of Si and 1Kg of Cr elements to raise the temperature of 1 ton of molten stainless steel by 14.1°C, 34.6°C and 12.7°C respectively; the carbon dioxide oxidizes 1Kg of C, 1Kg of Si and 1Kg of Cr elements to raise the temperature of 1 ton of molten stainless steel by -13.8°C, 10.9°C and 3.9°C respectively.

10. The exhaust gas purification device for smelting stainless steel based on carbon dioxide according to claim 8, characterized in that: The volume ratio of carbon dioxide in the bottom blowing gas should be higher than 30%, so that carbon dioxide can still participate in the decarburization reaction at the end of decarburization. The total flow rate of carbon dioxide gas should be lower than 6.56m / ton steel, so that the temperature of molten steel at the end of decarburization is above 1650°C.

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