Low-cost method for preventing and controlling excessive emission of sintering flue gas during ammonia desulfurization

Abstract

The invention belongs to the technical field of flue gas treatment, and discloses a method for low-cost prevention and control of sintering flue gas ammonia process desulfurization standard exceeding emission, which comprises the following steps: S1, calculating the residual coefficient of sulfur in sintering ore produced at an earlier stage according to the sulfur content of sintering production raw materials at the earlier stage and the sulfur content in the sintering ore at the same production time; s2, predicting the residual coefficient of sulfur in the sintered ore after the raw materials are changed according to the alkalinity change of the sintering production raw materials; s3, according to the change of the sulfur content of the sintering production raw materials, predicting the change amplitude of the concentration of SO2 in the sintering flue gas after the raw materials are changed; and S4, according to the predicted variation amplitude of the SO2 concentration in the sintering flue gas, predicting the liquid ammonia supply quantity required after the raw materials are changed by combining the early-stage production liquid ammonia supply quantity. According to the method, sulfur balance calculation is performed according to the sulfur content of the raw materials for sintering production, and the change of the concentration of SO2 in the sintering flue gas is estimated, so that the supply quantity of liquid ammonia is adjusted in time, the concentration of SO2 in the flue gas discharged after ammonia desulfurization is prevented from exceeding the standard, and the operation cost of a desulfurization system is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of flue gas treatment, and specifically relates to a low-cost method for preventing and controlling excessive emissions of sintering flue gas by ammonia desulfurization. Background Art

[0002] Steel production includes coking, sintering, ironmaking, steel rolling and other processes, among which SO2 emitted from sintering accounts for more than 60% of the annual emissions of the steel industry. Therefore, sintering flue gas desulfurization is the focus of pollution reduction in the steel industry. Based on the current national control requirements for SO2 emissions, both existing and newly built enterprises should build flue gas desulfurization equipment to achieve standard emissions.

[0003] Ammonia desulfurization is an efficient desulfurization technology suitable for sintering flue gas. Liquid ammonia reacts with SO2 to form ammonium sulfate, which can not only desulfurize efficiently but also partially remove nitrogen oxides in flue gas. The byproduct is ammonium sulfate. It is an effective and environmentally friendly wet flue gas desulfurization technology for controlling acid rain and sulfur dioxide pollution. In the process of ammonia desulfurization, the supply of desulfurizer liquid ammonia is the key to regulating the concentration of SO2 in the flue gas. When the supply of liquid ammonia increases, the amount of SO2 reacted by liquid ammonia increases, and the concentration of SO2 in the flue gas decreases. However, in order to reduce production costs, the supply of liquid ammonia cannot be increased blindly. Production enterprises hope to reduce the supply of liquid ammonia as much as possible while ensuring that the concentration of SO2 in the flue gas meets the emission standards. The difficulty of ammonia desulfurization of sintering flue gas at present is that the sulfur content of the raw materials used in sintering production fluctuates, which causes the fluctuation of SO2 concentration in the sintering flue gas. If the supply of liquid ammonia cannot be adjusted in time, it is easy to exceed the emission standard or operate uneconomically. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a low-cost method for preventing and controlling excessive emissions of sintering flue gas by ammonia desulfurization in response to the shortcomings of the prior art. The sulfur balance calculation is performed through the sulfur content of the raw materials used in the sintering production, and the change in the SO2 concentration in the sintering flue gas is estimated, so as to timely adjust the liquid ammonia supply amount, avoid excessive SO2 concentration in the flue gas discharged after ammonia desulfurization, and reduce the operating cost of the desulfurization system.

[0005] In order to solve the technical problem proposed by the present invention, the present invention provides a low-cost method for preventing and controlling excessive emissions of sintering flue gas by ammonia desulfurization, comprising the following steps:

[0006] S1, based on the sulfur content of raw material i in the previous sintering production and the sulfur content in the sintered ore at the same production time, calculate the residual sulfur coefficient S in the sintered ore when using raw material i i ;

[0007] S2, based on the change in basicity of the raw material from raw material i to raw material j, predict the residual coefficient S of sulfur in the sintered ore after the raw material is changedj ;

[0008] S3, based on the change in sulfur content when the sintering production raw material is changed from raw material i to raw material j, predict the change range δ of SO2 concentration in the sintering flue gas after the raw material is changed;

[0009] S4, based on the predicted change in SO2 concentration in the sintering flue gas and the liquid ammonia supply when using raw material i, predict the liquid ammonia supply required after the raw material is changed Q j ;

[0010] S5, adjusting the production of the ammonia desulfurization system according to the predicted liquid ammonia supply required after the raw material is changed.

[0011] In the above scheme, the residual coefficient S i Calculated using the following formula:

[0012]

[0013] In the formula, c s M is the sulfur content in the sintered ore when using raw material i; i is the consumption of raw material i per ton of sintered ore, kg; c i is the sulfur content of raw material i.

[0014] In the above scheme, the residual coefficient S j Predict according to the following formula:

[0015]

[0016] In the formula, R j R is the basicity of sintered ore after changing the raw materials; i is the basicity of sintered ore when using raw material i; S i is the residual coefficient of sulfur in the sintered ore when raw material i is used.

[0017] In the above scheme, the variation range δ is predicted according to the following formula:

[0018]

[0019] Where M j is the consumption of raw material j corresponding to one ton of sintered ore, kg; c j is the sulfur content of raw material j; S j M is the residual coefficient of sulfur in sintered ore after raw material change; i is the consumption of raw material i corresponding to one ton of sintered ore, kg; c i is the sulfur content of raw material i; S i is the residual coefficient of sulfur in the sintered ore when raw material i is used.

[0020] In the above scheme, the liquid ammonia supply amount Qj Predict according to the following formula:

[0021] Q j =Q i ×δ;

[0022] In the formula, Q i is the amount of liquid ammonia supplied when using raw material i; δ is the predicted change in SO2 concentration in the sintering flue gas after the raw material is changed.

[0023] In the above scheme, the sintering production raw materials include mixed ore, solid fuel, flux and return ore, but the consumption and sulfur content of the return ore are not included in the above formula.

[0024] Furthermore, the sulfur content of the mixed ore is ≤0.035wt%.

[0025] Furthermore, the sulfur content of the solid fuel is ≤0.6wt%.

[0026] Furthermore, the flux is one or more of quicklime, limestone and dolomite.

[0027] Furthermore, the mixed ore accounts for 55-65wt% of the sintering raw materials; the solid fuel accounts for 3.0-4.5wt% of the sintering raw materials; the flux accounts for 8-15wt% of the sintering raw materials; and the return ore accounts for 22-30wt% of the sintering raw materials.

[0028] Furthermore, the sintering production raw materials also include secondary resources, and the secondary resources are one or more of blast furnace ash, converter ash, and slag iron powder, and the secondary resources account for 2.0-5.0wt% of the sintering production raw materials.

[0029] In the above scheme, the basicity of the sintered ore adopts binary basicity.

[0030] Furthermore, the sintered ore basicity R when using raw material i i According to the actual measurement of sintered ore produced in the early stage, the basicity R of sintered ore after changing the raw materials j Calculated based on the composition of sintering production raw material j.

[0031] In the above scheme, the liquid ammonia supply amount Q required after the raw material is changed j 15 to 20 tons / day.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] The present invention can predict the change of SO2 concentration in sintering flue gas in advance, and prejudge and adjust the liquid ammonia supply of the ammonia desulfurization system. On the one hand, it can avoid the SO2 concentration in the flue gas discharged after ammonia desulfurization exceeding the emission standard, which is more environmentally friendly. On the other hand, there is no need to maintain a high liquid ammonia supply for a long time, so the liquid ammonia supply can be controlled, the liquid ammonia utilization rate can be improved, and the operating cost of the ammonia desulfurization system can be reduced. DETAILED DESCRIPTION

[0034] In order to better understand the present invention, the content of the present invention is further explained below in conjunction with the embodiments, but the content of the present invention is not limited to the following embodiments.

[0035] Example 1

[0036] A low-cost method for preventing and controlling excessive emissions of sintering flue gas from ammonia desulfurization comprises the following steps:

[0037] S1, based on the sulfur content of raw material i in the previous sintering production and the sulfur content in the sintered ore at the same production time, calculate the residual sulfur coefficient S in the sintered ore when using raw material i i ;

[0038] Among them, the basic information when using raw material i for production is as follows:

[0039]

[0040]

[0041] Calculate the residual sulfur coefficient S in sintered ore when using raw material i i as follows:

[0042] ∑M i ×C i =930×0.03%+61.33×0.017%+103.69×0.017%+58.72×0.114%+68.85×0.51%=0.73

[0043]

[0044] S2, based on the change in basicity of the raw material from raw material i to raw material j, predict the residual coefficient S of sulfur in the sintered ore after the raw material is changed j ;

[0045] Among them, the binary basicity R of the sintered ore when using raw material i i According to the actual measurement of sintered ore, it is 1.87; the binary basicity R of sintered ore when using raw material j j Calculated based on the CaO and SiO2 contents of raw material j, it is 1.85.

[0046] Predict the residual sulfur coefficient S in sintered ore after raw material changej as follows:

[0047]

[0048] S3, based on the change in sulfur content when the sintering production raw material is changed from raw material i to raw material j, predict the change range δ of SO2 concentration in the sintering flue gas after the raw material is changed;

[0049] Among them, the S content of the mixed ore in raw material j is increased to 0.035%, the S content of the fuel is increased to 0.592%, and the S content of the other raw materials remains unchanged;

[0050] The predicted change range δ of SO2 concentration in sintering flue gas after raw material change is as follows:

[0051] ∑M j ×C ji =930×0.035%+61.33×0.017%+103.69×0.017%+58.72×0.114%+68.85×0.592%=0.83

[0052]

[0053] S4, based on the predicted change in SO2 concentration in the sintering flue gas and the liquid ammonia supply when using raw material i, predict the liquid ammonia supply required after the raw material is changed Q j ;

[0054] Among them, the liquid ammonia supply amount Q when using raw material i i 16 tons / day;

[0055] Predict the required liquid ammonia supply Q after the raw material change j as follows;

[0056] Q j =Q i ×δ=16×1.15=18.2

[0057] S5, adjusting the production of the ammonia desulfurization system according to the predicted liquid ammonia supply required after the raw material is changed.

[0058] After testing, when raw material i is used for production, the average SO2 concentration of the sintering flue gas at the outlet of the ammonia-based desulfurization system is 18.5ppm according to the liquid ammonia supply of 16 tons / day; after changing to raw material j for production, when the liquid ammonia supply is still not adjusted at 16 tons / day, the SO2 concentration of the sintering flue gas at the outlet of the ammonia-based desulfurization system reaches the ultra-low emission critical value of 35ppm, and even exceeds the emission standard in some periods; after changing to raw material j for production, when the liquid ammonia supply is adjusted to 18.2 tons / day, the average SO2 concentration of the sintering flue gas at the outlet of the ammonia-based desulfurization system is 26.8ppm, and no excessive emissions occur.

[0059] Example 2

[0060] A low-cost method for preventing and controlling excessive emissions of sintering flue gas from ammonia desulfurization comprises the following steps:

[0061] S1, based on the sulfur content of raw material i in the previous sintering production and the sulfur content in the sintered ore at the same production time, calculate the residual sulfur coefficient S in the sintered ore when using raw material i i ;

[0062] Among them, the basic information when using raw material i for production is as follows:

[0063]

[0064] Calculate the residual sulfur coefficient S in sintered ore when using raw material i i as follows:

[0065] ∑M i ×C i =930×0.032%+61.33×0.017%+103.69×0.017%+58.72×0.114%+68.85×0.56%=0.778

[0066]

[0067] S2, based on the change in basicity of the raw material from raw material i to raw material j, predict the residual coefficient S of sulfur in the sintered ore after the raw material is changed j ;

[0068] Among them, the binary basicity R of the sintered ore when using raw material i i According to the actual measurement of sintered ore, it is 1.85; the binary basicity R of sintered ore when using raw material j j Calculated based on the CaO and SiO2 contents of raw material j, it is 1.85.

[0069] Predict the residual sulfur coefficient S in sintered ore after raw material change j as follows:

[0070]

[0071] S3, based on the change in sulfur content when the sintering production raw material is changed from raw material i to raw material j, predict the change range δ of SO2 concentration in the sintering flue gas after the raw material is changed;

[0072] Among them, the S content of the fuel in raw material j is reduced to 0.51%, and the S content of the other raw materials remains unchanged;

[0073] The predicted change range δ of SO2 concentration in sintering flue gas after raw material change is as follows:

[0074] ∑M j ×C ji =930×0.03%+61.33×0.017%+103.69×0.017%+58.72×0.114%+68.85×0.51%=0.725

[0075]

[0076] S4, based on the predicted change in SO2 concentration in the sintering flue gas and the liquid ammonia supply when using raw material i, predict the liquid ammonia supply required after the raw material is changed Q j ;

[0077] Among them, the liquid ammonia supply amount Q when using raw material i i 18 tons / day;

[0078] Predict the required liquid ammonia supply Q after the raw material change j as follows;

[0079] Q j =Q i ×δ=18×0.932=16.8

[0080] S5, adjusting the production of the ammonia desulfurization system according to the predicted liquid ammonia supply required after the raw material is changed.

[0081] After testing, when using raw material i for production, according to the liquid ammonia supply of 18 tons / day, the average SO2 concentration of the sintering flue gas at the outlet of the ammonia desulfurization system was 26.9ppm; after changing to raw material j for production, when the liquid ammonia supply was adjusted to 16.8 tons / day, the average SO2 concentration of the sintering flue gas at the outlet of the ammonia desulfurization system was 26.5ppm, no excessive emissions occurred, and the operating cost of the ammonia desulfurization system was reduced.

[0082] The above embodiments are merely examples for clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above descriptions. It is not necessary and impossible to list all the implementation methods here, and the obvious changes or modifications derived therefrom are still within the protection scope of the invention.

Claims

1. A low-cost method for preventing and controlling excessive emissions of sintering flue gas from ammonia desulfurization, characterized in that: The following steps are involved: S1, based on the sulfur content of raw material i in the previous sintering production and the sulfur content in the sintered ore at the same production time, calculate the residual sulfur coefficient S in the sintered ore when using raw material i i ; S2, based on the change in basicity of the raw material from raw material i to raw material j, predict the residual coefficient S of sulfur in the sintered ore after the raw material is changed j ; S3, according to the change in sulfur content of the sintering production raw material from raw material i to raw material j, the change range of SO2 concentration in the sintering flue gas after the raw material change is predicted by the following formula: Where M j is the consumption of raw material j corresponding to one ton of sintered ore, kg; c j is the sulfur content of raw material j; S j M is the residual coefficient of sulfur in sintered ore after raw material change; i is the consumption of raw material i corresponding to one ton of sintered ore, kg; c i is the sulfur content of raw material i; S i is the residual coefficient of sulfur in the sintered ore when using raw material i; S4, based on the predicted change in SO2 concentration in the sintering flue gas and the liquid ammonia supply when using raw material i, predict the liquid ammonia supply required after the raw material is changed Q j ; S5, adjusting the production of the ammonia desulfurization system according to the predicted liquid ammonia supply required after the raw material is changed.

2. The low-cost method for preventing and controlling excessive emissions of sintering flue gas from ammonia desulfurization according to claim 1 is characterized in that: The residual coefficient S i Calculated using the following formula: In the formula, c s M is the sulfur content in the sintered ore when using raw material i; i is the consumption of raw material i per ton of sintered ore, kg; c i is the sulfur content of raw material i.

3. The low-cost method for preventing and controlling excessive emissions of sintering flue gas from ammonia desulfurization according to claim 1 is characterized in that: The residual coefficient S j Predict according to the following formula: In the formula, R j R is the basicity of sintered ore after changing the raw materials; i is the basicity of sintered ore when using raw material i; S i is the residual coefficient of sulfur in the sintered ore when raw material i is used.

4. The low-cost method for preventing and controlling excessive emissions of sintering flue gas from ammonia desulfurization according to claim 3 is characterized in that: The sintered ore basicity adopts binary basicity, and the sintered ore basicity R when using raw material i i According to the actual measurement of sintered ore produced in the early stage, the basicity R of sintered ore after changing the raw materials j Calculated based on the composition of raw material j.

5. The low-cost method for preventing and controlling excessive emissions of sintering flue gas from ammonia desulfurization according to claim 1 is characterized in that: The liquid ammonia supply amount Q j Predict according to the following formula: Q j =Q i ×δ; In the formula, Q i is the amount of liquid ammonia supplied when using raw material i; δ is the predicted change in SO2 concentration in the sintering flue gas after the raw material is changed.

6. The low-cost method for preventing and controlling excessive emissions of sintering flue gas from ammonia desulfurization according to claim 1 is characterized in that: The sintering production raw materials include mixed ore, solid fuel, flux and return ore, but the consumption and sulfur content of the return ore are not included in the formula.

7. The low-cost method for preventing and controlling excessive emissions of sintering flue gas from ammonia desulfurization according to claim 6 is characterized in that: The mixed ore accounts for 55-65wt% of the sintering raw materials; the solid fuel accounts for 3.0-4.5wt% of the sintering raw materials; the flux accounts for 8-15wt% of the sintering raw materials; and the return ore accounts for 22-30wt% of the sintering raw materials.

8. The low-cost method for preventing and controlling excessive emissions of sintering flue gas from ammonia desulfurization according to claim 6 is characterized in that: The sulfur content of the mixed ore is ≤0.035wt%; the sulfur content of the solid fuel is ≤0.6wt%; the flux is one or more of quicklime, limestone and dolomite.

9. The low-cost method for preventing and controlling excessive emissions of sintering flue gas from ammonia desulfurization according to claim 6 is characterized in that: The sintering production raw materials also include secondary resources, which are one or more of blast furnace ash, converter ash, and slag iron powder. The secondary resources account for 2.0-5.0wt% of the sintering production raw materials.

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