Low emission device for sulfur dioxide in flue gas of gas heating furnace and control method

Abstract

The invention belongs to the technical field of blast furnace ironmaking, and particularly discloses a low-emission device for sulfur dioxide in flue gas of a gas heating furnace and a control method, the control method comprises the steps of controlling a blast furnace batching system and optimizing furnace burning parameters of the heating furnace, and the control of the blast furnace batching system comprises the steps of proportion of ore entering the furnace, optimization of blast parameters and control of tuyere return batching amount. Optimization of furnace burning parameters of the heating furnace comprises heat value reduction and control of furnace top gas. The problems that a special desulfurization device needs to be built in a matched mode in the existing tail-end flue gas desulfurization technology, the capital investment of enterprises is increased, and then the production cost is increased are solved. Through source control strategies in two aspects, the proportion of sintered ore to pellet ore is reasonably adjusted, the ore batch weight is dynamically adjusted according to the furnace condition, the blast parameters and the fuel ratio are optimized, meanwhile, the heat value of furnace burning gas is effectively controlled in a nitrogen mixing or flue gas blending mode, the ultra-low emission standard that sulfur dioxide at a gas heating furnace exhaust port is stably lower than 50 mg / Nm < 3 > is achieved, and the method is suitable for industrial production. And the pollution to the environment is greatly reduced.

Description

Technical Field

[0001] The invention relates to the technical field of blast furnace ironmaking, and in particular to a low-emission device for sulfur dioxide in flue gas of a gas heating furnace and a control method thereof. Background Art

[0002] In the smelting process of traditional blast furnaces, the utilization rate of carbon's chemical energy is only 65%, and the remaining 35% of the chemical energy is retained in the by-product gas in the form of carbon monoxide and then lost. These by-product gases have complex compositions. In addition to carbon monoxide, they also contain a large amount of nitrogen, carbon dioxide and a certain amount of sulfur dioxide. Due to the limitations of thermodynamic and kinetic conditions, it is difficult for the top gas to be effectively reused in the blast furnace. The HyCROF process, as a key technical path for the transformation of traditional blast furnace smelting to green and low-carbon, innovatively removes carbon dioxide from the top gas. The gas with C oxygen removed is heated by a gas heating furnace and sprayed into the furnace from the tuyere or the furnace body to replace part of the coke added to the top of the furnace and the coal powder sprayed into the tuyere, further reducing the input of solid carbon sources in the blast furnace smelting process, achieving low coke ratio smelting, and thus reducing carbon emissions and solid fuel consumption.

[0003] Most of the by-product gas from traditional blast furnaces is transported to hot blast furnaces for combustion operations to heat blast, and its heat supply mainly relies on the heat storage cycle of self-produced gas. However, when faced with the problem of sulfur dioxide treatment in flue gas, the current mainstream approach is to use end-of-pipe flue gas desulfurization technology, including dry, wet and blast furnace gas fine desulfurization process methods, to ensure that the sulfur dioxide concentration in the exhaust gas can meet the emission standards and avoid pollution to the environment.

[0004] However, the above-mentioned end-of-pipe flue gas desulfurization technology requires the construction of special desulfurization equipment, which will increase the company's capital investment in equipment purchase, installation and commissioning, and subsequent operation and maintenance, thereby leading to a significant increase in production costs. Summary of the invention

[0005] The purpose of the present invention is to provide a low sulfur dioxide emission device and control method in the flue gas of a gas heating furnace, so as to solve the problem that the current end-of-pipe flue gas desulfurization technology requires the construction of a special desulfurization device, which increases the capital investment of the enterprise and leads to an increase in production costs.

[0006] To achieve the above-mentioned purpose, the basic scheme provided by the present invention is: a low emission device for sulfur dioxide in flue gas of a gas heating furnace, comprising a blast furnace, a decarbonization unit and a gas heating furnace body, the blast furnace top is connected with a furnace top gas main pipe, the furnace top gas main pipe is connected with the air inlet end of the gas heating furnace body, the furnace top gas main pipe is connected with a furnace top gas branch pipe for connecting to the decarbonization unit, the gas outlet end of the decarbonization unit is connected with a decarbonization gas pipe for connecting to the blast furnace tuyere, the gas outlet end of the gas heating furnace body is connected with a high-temperature gas pipe for connecting to the blast furnace tuyere, the exhaust end of the gas heating furnace body is connected with a flue gas discharge pipe, the flue gas discharge pipe is connected with a flue gas return pipe, one end of the flue gas return pipe is connected with one end of the furnace top gas main pipe close to the gas heating furnace body, a fan is arranged on the flue gas return pipe, a CO detection transmitter is arranged on the furnace top gas main pipe, and the CO detection transmitter is electrically connected to the fan inlet regulating valve.

[0007] The working principle of the present invention is as follows: during the smelting process of the blast furnace, top gas is generated, the top gas is transported through the top gas main pipe, part of the top gas enters the decarbonization unit through the top gas branch pipe for carbon dioxide removal treatment, and the decarbonized gas returns to the tuyere of the blast furnace 1 through the decarbonization gas pipe; at the same time, the gas in the top gas main pipe enters the gas heating furnace body for heating, and the heated high-temperature gas returns to the tuyere of the blast furnace through the high-temperature gas pipe, and at the same time, part of the flue gas discharged from the gas heating furnace body returns to the top gas main pipe and the top gas return in the top gas main pipe through the flue gas return pipe under the action of the fan for depreciation. After the top gas depreciation is completed, the flue gas generated by the gas heating furnace body is discharged through the flue gas discharge pipe, and part of the flue gas returns to the top gas main pipe and the top gas return in the top gas main pipe through the flue gas return pipe under the action of the fan for depreciation, and the cycle is repeated in sequence.

[0008] The beneficial effects of the present invention are as follows: through two-aspect source control strategies, the high equipment investment and operation and maintenance costs required by the traditional end-stage flue gas desulfurization technology are effectively avoided, and the cost pressure of enterprises caused by desulfurization is fundamentally alleviated. The first aspect is to accurately control the blast furnace batching system, reasonably adjust the ratio of sintered ore and pelletized ore, dynamically adjust the ore batch weight according to the furnace condition, optimize the blast parameters and fuel ratio, etc., which significantly improves the reaction process in the blast furnace, keeps the furnace condition stable and smooth, improves the chemical energy utilization rate of carbon, reduces the solid carbon source input and fuel consumption, and reduces carbon emissions. At the same time, it stabilizes the distribution of sulfur in molten iron, slag and coal gas, reduces the sulfur content in the furnace top gas, and lays the foundation for the subsequent control of sulfur dioxide in the flue gas of the gas heating furnace; the second aspect is to stabilize the combustion and emission of the heating furnace, and adopt the flue gas return method to effectively control the calorific value of the furnace gas, ensure the stable combustion of the furnace gas, and achieve the stable sulfur dioxide at the gas heating furnace outlet below 50mg / Nm 3The ultra-low emission standards have greatly reduced pollution to the environment and promoted the green and sustainable development of the steel industry.

[0009] Option 2, which is the preferred option of the basic option, is provided with an oxygen detection alarm on the flue gas return pipe, which is connected to a nitrogen pipe, and a gate valve is provided on the nitrogen pipe, which is electrically connected to the oxygen detection alarm; when the oxygen content in the added flue gas is greater than 1%, the gate valve on the nitrogen pipe is opened through interlocking control, and nitrogen is added to reduce the oxygen content in the flue gas return pipe, thereby reducing the risk.

[0010] Scheme 3, which is the preferred one of schemes 1 and 2, controls the emission of sulfur dioxide by optimizing the ratio of ore fed into the blast furnace, optimizing the blast parameters of the blast furnace, controlling the tuyere fuel ratio of the blast furnace, and reducing the calorific value of the coal gas used in the gas heating furnace body. Among them, the method of reducing the calorific value of the coal gas used in the gas heating furnace body adopts flue gas re-matching;

[0011] Option 4 is the preferred option of Option 3. In each batch of ore entering the blast furnace, the proportion of sintered ore is 49%, and the proportion of pelletized ore is 51%. Controlling the ratio of sintered ore to pelletized ore can make the top gas flow distribution reasonable.

[0012] Option 5 is the preferred option of Option 4. The quantity of each batch of ore entering the furnace is adjusted according to the airflow status of the furnace top gas center and the furnace top gas edge. When the airflow at the furnace top gas edge develops, the quantity of each batch of ore entering the furnace is adjusted to 63-65t. When the airflow at the furnace top gas center develops, the quantity of each batch of ore entering the furnace is adjusted to 60-62t. The above dynamic adjustment facilitates balancing the reaction in the furnace, making the gas production and flow more stable and reducing abnormal fluctuations in sulfur due to unstable furnace conditions.

[0013] Scheme 6, which is the preferred embodiment of Scheme 5, the optimized blast furnace blast parameters are: the oxygen volume at the tuyere of the blast furnace is controlled at 54000~56000Nm 3 / h, the tuyere gas injection rate of the blast furnace is controlled at 144000~146000Nm 3 / h, the wind speed of the tuyere of the blast furnace is controlled at 200-240m / s; blast parameter control is the fundamental reason for the sulfur content in the furnace top gas. Optimizing the blast parameters can improve the combustion and reduction process in the blast furnace, make fuels such as coke and coal powder burn and react more fully, reduce the incompletely reacted sulfur-containing substances entering the gas, and thus reduce the sulfur content in the furnace top gas.

[0014] Scheme 7, which is the preferred option of Scheme 3, controls the return volume of decarbonized coal gas at the tuyere of the blast furnace to 690m 3 ~720m 3, so that the fuel ratio is controlled at 385-395kg / t; controlling the fuel ratio below 390kg / t is convenient for energy utilization and chemical reaction in the blast furnace, reduces solid carbon source input, reduces carbon emissions, and also helps to stabilize the sulfur distribution in the furnace and reduce the sulfur content in the coal gas.

[0015] Option 8 is a preferred option of Option 7. The fuel ratio includes a coke ratio and a coal powder ratio. The coke ratio is 305-310 kg / t, and the coal powder ratio is 80-85 kg / t. Accurately controlling the ratio of coke and coal powder can further optimize the smelting process of the blast furnace. Because the sulfur content of coke and coal powder is different, the total sulfur amount entering the furnace can be controlled by adjusting their ratio, thereby reducing the sulfur entering the top gas.

[0016] Option nine, which is the preferred option of option three, is a method for reducing the calorific value of the gas heating furnace by flue gas recirculation: set the CO content to 30% on the CO detection transmitter; when the CO detection value of the CO detection transmitter is less than 30%, reduce the opening of the fan inlet regulating valve; when the CO detection value of the CO detection transmitter is greater than 30%, increase the opening of the fan inlet regulating valve; this can prevent the combustion of high calorific value gas from damaging the gas heating furnace equipment, and at the same time, by reasonably controlling the calorific value adjustment process, stabilize the combustion process of the furnace gas, and ensure that the sulfur dioxide emissions in the flue gas meet the low emission requirements.

[0017] Option 10 is the preferred option of Option 9. When the CO detection value of the CO detection transmitter decreases or increases by 1%, the opening of the fan inlet regulating valve is adjusted down or up by 1 to 1.5%. Through fine adjustment, the calorific value and composition of the furnace gas can be controlled more accurately, the combustion process of the furnace gas can be further stabilized, and the control accuracy of sulfur dioxide emissions can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The present invention discloses a flow chart of a device for low emission of sulfur dioxide in flue gas of a gas heating furnace. DETAILED DESCRIPTION

[0019] The present invention is further described in detail below through specific embodiments:

[0020] The figure marks in the drawings of the specification include: 1 blast furnace; 101 top gas main pipe, 102 top gas branch pipe, 103 CO detection transmitter, 2 decarbonization unit, 201 decarbonization gas pipe, 3 gas heating furnace body, 301 high-temperature gas pipe, 302 flue gas exhaust pipe, 303 flue gas return pipe, 304 fan, 305 oxygen detection alarm, 306 nitrogen pipe, 307 gate valve.

[0021] Example 1

[0022] like Figure 1As shown: a low emission device for sulfur dioxide in flue gas of a gas heating furnace, comprising a blast furnace 1, a decarbonization unit 2 and a gas heating furnace body 3, the decarbonization unit 2 is a prior art, the top of the blast furnace 1 is connected with a top gas main pipe 101, the top gas main pipe 101 is connected with the air inlet end of the gas heating furnace body 3, the top gas main pipe 101 is connected with a top gas branch pipe 102 for connecting with the decarbonization unit 2, the gas outlet end of the decarbonization unit 2 is connected with a decarbonization gas pipe 201 for connecting with the blast furnace 1 tuyere, the gas outlet end of the gas heating furnace body 3 is connected with a high-temperature gas pipe 301 for connecting with the blast furnace 1 tuyere, the exhaust end of the gas heating furnace body 3 is connected with a flue gas discharge pipe 302, the flue gas discharge pipe 302 is connected with a flue gas return pipe 106, the flue gas return pipe 107 is connected with a flue gas return pipe 108, and the flue gas return pipe 109 is connected with a flue gas return pipe 210. Pipe 303, one end of the flue gas return pipe 303 is connected with one end of the furnace top gas main pipe 101 close to the gas heating furnace body 3, the flue gas return pipe 303 is provided with a fan 304, the furnace top gas main pipe 101 is provided with a CO detection transmitter 103, the model of the CO detection transmitter 103 is: ERUN-PG51C1, the CO detection transmitter 103 is electrically connected to the inlet regulating valve of the fan 304, the flue gas return pipe 303 is provided with an oxygen detection alarm 305, the flue gas return pipe 303 is connected with a nitrogen pipe 306, the nitrogen pipe 306 is provided with a gate valve 307, the gate valve 307 is electrically connected to the oxygen detection alarm 305, the oxygen detection alarm 305 model is: ERUN-PG51O2.

[0023] The implementation method of this embodiment is as follows: during the smelting process of the blast furnace 1, top gas is generated, and the top gas is transported through the top gas main pipe 101. Part of the top gas enters the decarbonization unit 2 through the top gas branch pipe 102 for carbon dioxide removal treatment, and the decarbonized gas returns to the tuyere of the blast furnace 1 through the decarbonization gas pipe 201; another part of the top gas enters the gas heating furnace body 3 through the top gas main pipe 101 for heating, and the heated high-temperature gas returns to the tuyere of the blast furnace through the high-temperature gas pipe 301. Part of the flue gas discharged from the heating furnace body 3 returns to the furnace top gas main 101 and the furnace top gas return inside the furnace top gas main 101 through the flue gas return pipe 303 under the action of the fan 304 for reduction. After the reduction of the top gas is completed, the flue gas generated by the gas heating furnace body 3 is discharged through the flue gas discharge pipe 302, and then part of the flue gas returns to the furnace top gas main 101 and the furnace top gas return inside the furnace top gas main 101 through the flue gas return pipe 303 under the action of the fan 304 for reduction, and the cycle works in sequence.

[0024] On the flue gas return pipe 303, the oxygen detection alarm 305 will detect the oxygen content. When the oxygen content is greater than 1%, the gate valve 307 on the nitrogen pipe 306 will be opened through interlock control to add nitrogen to reduce the oxygen content in the flue gas return pipe.

[0025] Example 2

[0026] A low sulfur dioxide emission device and control method in the flue gas of a gas heating furnace, which controls the emission of sulfur dioxide by optimizing the ratio of the ore fed into the blast furnace 1, optimizing the blast parameters of the blast furnace 1, controlling the fuel ratio of the tuyere of the blast furnace 1, and reducing the calorific value of the burning gas of the gas heating furnace body 3. The proportion of sintered ore in each batch of ore fed into the blast furnace 1 is 49%, and the proportion of pelletized ore is 51%; the quantity of each batch of ore fed into the blast furnace is adjusted according to the airflow state of the furnace top gas center and the furnace top gas edge. When the airflow at the furnace top gas edge develops, the quantity of each batch of ore fed into the furnace is adjusted to 65t, and when the airflow at the furnace top gas center develops, the quantity of each batch of ore fed into the furnace is adjusted to 60t; the blast parameters of the blast furnace 1 are optimized as follows: the oxygen volume of the tuyere of the blast furnace 1 is controlled at 55000Nm 3 / h, the gas injection rate of blast furnace 1 is controlled at 145000Nm 3 / h, the wind speed of the tuyere of blast furnace 1 is controlled at 220m / s; the return amount of decarbonized coal gas at the tuyere of blast furnace 1 is controlled at 700m 3 , so that the fuel ratio is controlled at 385kg / t. The fuel ratio includes the coke ratio and the coal powder ratio. The coke ratio is 305kg / t and the coal powder ratio is 80kg / t.

[0027] Table 1: Sulfur content and sulfur load in the ore entering the furnace

[0028] Raw materials Unit consumption S content S Load Sintered ore 823.2kg 0.070％ 0.576 Pelletized Ore 856.8kg 0.010％ 0.086 Coke 315kg 0.570％ 1.796 Pulverized coal 80kg 0.520％ 0.416 Total 2.873

[0029] Table 2: Sulfur content and sulfur load in products and by-products

[0030] Raw materials Unit consumption S content S Load Slag 278kg 0.9000％ 2.502 molten iron 1000kg 0.030％ 0.300 Stove Top Gas <![CDATA[1450Nm 3 / t]]> 0.4897％ 0.071 Total 2.873

[0031] By controlling the blast furnace burden system at the source, the sulfur load entering the furnace is 2.873kg / t, of which the sulfur content in the slag is 2.502kg / t, the sulfur content in the molten iron is 0.3kg / t, and the sulfur content in the top gas is 0.071kg / t.

[0032] The unit consumption of top gas is 1450Nm 3 / t, the S content in the top gas is 48.97 mg / Nm 3 , then the S oxygen in the top gas is 97.93 mg / Nm 3 , as a first step to reduce the sulfur content.

[0033] The method for reducing the calorific value of the furnace gas of the gas heating furnace body 3 adopts flue gas re-matching, setting the CO content on the CO detection transmitter 103 to 30%, when the CO detection value of the CO detection transmitter 103 is less than 30%, reducing the opening of the inlet regulating valve of the fan 304; when the CO detection value of the CO detection transmitter 103 is greater than 30%, increasing the opening of the inlet regulating valve of the fan 304, when the CO detection value of the CO detection transmitter 103 decreases or increases by 1%, the opening of the inlet regulating valve of the fan 304 is reduced or increased by 1.5%, so as to obtain a reasonable distribution of the furnace top gas flow, the CO content in the furnace top gas is 50%, and the volume ratio of the furnace gas to the flue gas is 0.45:0.55.

[0034] Table 3: S oxygen content in heating furnace flue gas

[0035]

[0036] Gas heating furnace combustion 1Nm 3 of self-produced gas, generating 3.360Nm 3 The ratio of the S oxygen content in the self-produced gas to the gas heating furnace flue gas is 3.36:1, the S oxygen in the top gas is 29.15 mg / Nm 3 .

[0037] Through the operation in the above embodiment, the furnace condition can be kept running smoothly, and the CO in the furnace top gas can be stabilized at 50%. After the furnace condition is running smoothly, the fuel ratio per ton of iron is reduced by 140kg, and the sulfur content of the furnace top gas is 97.93mg / Nm 3 The oxygen concentration at the chimney outlet of the heating furnace is 29.15 mg / Nm 3 By controlling the sulfur content and sulfur load at the two sources of blast furnace and heating furnace, the sulfur dioxide concentration in the flue gas can be reduced to less than 50mg / Nm 3 purpose.

[0038] The above is only an embodiment of the present invention, and the common knowledge such as the known specific structure and characteristics in the scheme is not described in detail here. It should be pointed out that for those skilled in the art, several deformations and improvements can be made without departing from the structure of the present invention, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A device for reducing sulfur dioxide emissions from flue gas in a gas heating furnace, characterized in that: The invention comprises a blast furnace (1), a decarbonization unit (2) and a gas heating furnace body (3), wherein the top of the blast furnace (1) is connected to a top gas main pipe (101), the top gas main pipe (101) is connected to the gas inlet end of the gas heating furnace body (3), the top gas main pipe (101) is connected to a top gas branch pipe (102) for connecting to the decarbonization unit (2), the gas outlet end of the decarbonization unit (2) is connected to a decarbonization gas pipe (201) for connecting to the blast furnace (1) air outlet, and the gas outlet end of the gas heating furnace body (3) is connected to a blast furnace (1) air outlet. A warm coal gas pipe (301) is provided, the exhaust end of the coal gas heating furnace body (3) is connected to a smoke exhaust pipe (302), the smoke exhaust pipe (302) is connected to a smoke return pipe (303), one end of the smoke return pipe (303) is connected to one end of the furnace top coal gas main pipe (101) close to the coal gas heating furnace body (3), a fan (304) is provided on the smoke return pipe (303), a CO detection transmitter (103) is provided on the furnace top coal gas main pipe (101), and the CO detection transmitter (103) is electrically connected to an inlet regulating valve of the fan (304).

2. The device for reducing sulfur dioxide emissions from flue gas in a gas heating furnace according to claim 1, characterized in that: The flue gas return pipe (303) is provided with an oxygen detection alarm (305), the flue gas return pipe (303) is connected with a nitrogen pipe (306), the nitrogen pipe (306) is provided with a gate valve (307), and the gate valve (307) is electrically connected to the oxygen detection alarm (305).

3. The control method of a low sulfur dioxide emission device in flue gas of a gas heating furnace according to claims 1 and 2, characterized in that: The emission of sulfur dioxide is controlled by optimizing the proportion of the ore fed into the blast furnace (1), optimizing the blast parameters of the blast furnace (1), controlling the tuyere fuel ratio of the blast furnace (1), and reducing the calorific value of the coal gas used to burn the gas heating furnace body (3), wherein the method for reducing the calorific value of the coal gas used to burn the gas heating furnace body (3) adopts flue gas re-matching.

4. The control method of a low sulfur dioxide emission device in flue gas of a gas heating furnace according to claim 3 is characterized in that: In each batch of ore fed into the blast furnace (1), the proportion of sintered ore is 49%, and the proportion of pelletized ore is 51%.

5. The control method of a low sulfur dioxide emission device in flue gas of a gas heating furnace according to claim 4, characterized in that: The quantity of ore entering the furnace in each batch is adjusted according to the airflow status of the furnace top gas center and the furnace top gas edge. When the airflow at the furnace top gas edge develops, the quantity of ore entering the furnace in each batch is adjusted to 63-65t. When the airflow at the furnace top gas center develops, the quantity of ore entering the furnace in each batch is adjusted to 60-62t.

6. The control method of a low sulfur dioxide emission device in flue gas of a gas heating furnace according to claim 3, characterized in that: The optimized blast parameters of the blast furnace (1) are as follows: the oxygen volume at the tuyere of the blast furnace (1) is controlled at 54000-56000 Nm 3 / h, the tuyere gas injection rate of the blast furnace (1) is controlled at 144000~146000Nm 3 / h, and the wind speed at the tuyere of the blast furnace (1) is controlled at 200-240m / s.

7. The control method of a low sulfur dioxide emission device in flue gas of a gas heating furnace according to claim 3, characterized in that: The return amount of decarbonized coal gas from the tuyere of the blast furnace (1) is controlled at 690m 3 ~720m 3 , so that the fuel ratio is controlled at 385-395kg / t.

8. The control method of a low sulfur dioxide emission device in flue gas of a gas heating furnace according to claim 7, characterized in that: The fuel ratio includes a coke ratio and a pulverized coal ratio, the coke ratio is 305-310 kg / t, and the pulverized coal ratio is 80-85 kg / t.

9. The control method of a low sulfur dioxide emission device in flue gas of a gas heating furnace according to claim 3, characterized in that: The method for reducing the calorific value of the coal gas used to burn the coal heating furnace body (3) by flue gas recycling is as follows: setting the CO content on the CO detection transmitter (103) to 30%; when the CO detection value of the CO detection transmitter (103) is less than 30%, reducing the opening of the inlet regulating valve of the fan (304); and when the CO detection value of the CO detection transmitter (103) is greater than 30%, increasing the opening of the inlet regulating valve of the fan (304).

10. The control method of a low sulfur dioxide emission device in flue gas of a gas heating furnace according to claim 9, characterized in that: When the CO detection value of the CO detection transmitter (103) decreases or increases by 1%, the opening of the inlet regulating valve of the fan (304) is reduced or increased by 1 to 1.5%.

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