A method for preventing and controlling excessive emission of sintering flue gas ammonia desulfurization

Abstract

The present application belongs to the field of flue gas treatment technology, and discloses a method for preventing and controlling excessive emission of sintering flue gas ammonia desulfurization with low cost, comprising the following steps: S1, calculating the residual coefficient of sulfur in the sinter ore produced in the early stage according to the sulfur content of the raw materials for sintering production in the early stage and the sulfur content in the sinter ore in the same production time; S2, predicting the residual coefficient of sulfur in the sinter ore after changing the raw materials according to the change of the alkalinity of the raw materials for sintering production; S3, predicting the change range of the SO2 concentration in the sintering flue gas after changing the raw materials according to the change of the sulfur content of the raw materials for sintering production; S4, predicting the required liquid ammonia supply amount after changing the raw materials according to the predicted change range of the SO2 concentration in the sintering flue gas and combining the liquid ammonia supply amount in the early stage. The present application calculates the sulfur balance according to the sulfur content of the raw materials for sintering production, estimates the change of the SO2 concentration in the sintering flue gas, thereby timely adjusts the liquid ammonia supply amount, avoids the SO2 concentration in the flue gas after ammonia desulfurization exceeding the standard, and reduces the operation cost of the desulfurization system.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of flue gas treatment, and particularly relates to a method for preventing and controlling over-standard emission of sintering flue gas ammonia desulfurization. BACKGROUND

[0002] Steel production includes processes such as coking, sintering, iron smelting, and rolling, among which the SO2 emitted by 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 enterprises and newly built enterprises should build flue gas desulfurization devices to achieve standard emission.

[0003] Ammonia desulfurization is a high-efficiency desulfurization technology suitable for sintering flue gas. Through chemical reaction between liquid ammonia and SO2, ammonium sulfate is formed, which can not only efficiently desulfurize but also partially remove nitrogen oxides in the flue gas. The byproduct is ammonium sulfate, which is an effective and environmentally friendly wet flue gas desulfurization technology for controlling acid rain and sulfur dioxide pollution. In the ammonia desulfurization process, the supply amount of the desulfurizer liquid ammonia is the key to regulating the SO2 concentration in the emitted flue gas. When the supply amount of liquid ammonia increases, the SO2 reacted with liquid ammonia also increases, thereby reducing the SO2 concentration in the emitted flue gas. However, in order to reduce production costs, the supply amount of liquid ammonia cannot be increased blindly. The production enterprises hope to reduce the supply amount of liquid ammonia as much as possible while ensuring that the SO2 concentration in the flue gas meets the emission standard. The difficulty of sintering flue gas ammonia desulfurization at present lies in the fluctuation of the sulfur content of the raw materials used in sintering production, which causes the fluctuation of the SO2 concentration in the sintering flue gas. If the supply amount of liquid ammonia cannot be timely regulated, over-standard emission or uneconomic operation may occur. SUMMARY

[0004] The technical problem to be solved by the present application is to provide a method for preventing and controlling over-standard emission of sintering flue gas ammonia desulfurization, which solves the problems existing in the prior art. Through sulfur balance calculation based on the sulfur content of the raw materials used in sintering production, the change of the SO2 concentration in the sintering flue gas is estimated, so that the supply amount of liquid ammonia can be adjusted in time to avoid over-standard emission of SO2 concentration in the flue gas after ammonia desulfurization, and the operating cost of the desulfurization system is reduced.

[0005] To solve the technical problems proposed in the present application, the present application provides a method for preventing and controlling over-standard emission of sintering flue gas ammonia desulfurization, which comprises the following steps:

[0006] S1, calculating the residual coefficient S of sulfur in the sinter according to the sulfur content of the raw material i used in the previous sintering production and the sulfur content in the sinter at the same production time; i ;

[0007] S2, predicting the residual coefficient S of sulfur in the sinter after the change of the raw material from the raw material i to the raw material j according to the change of the basicity of the sintering raw material.j ;

[0008] S3, according to the change of the sulfur content of the raw material from the raw material i to the raw material j, predicting the change range δ of the SO2 concentration in the sintering flue gas after the change of the raw material;

[0009] S4, according to the predicted change range of the SO2 concentration in the sintering flue gas, combining the liquid ammonia supply amount when the raw material i is used, predicting the required liquid ammonia supply amount Q after the change of the raw material j ;

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

[0011] In the above scheme, the residual coefficient S i is calculated according to the following formula:

[0012]

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

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

[0015]

[0016] In the formula, R j is the sinter basicity after the change of the raw material; R i is the sinter basicity when the raw material i is used; S i is the residual coefficient of sulfur in the sinter when the raw material i is used.

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

[0018]

[0019] In the formula, M j is the raw material j consumption per ton of sinter, kg; c j is the sulfur content of the raw material j; S j is the residual coefficient of sulfur in the sinter after the change of the raw material; M i is the raw material i consumption per ton of sinter, kg; c i is the sulfur content of the raw material i; S i is the residual coefficient of sulfur in the sinter when the raw material i is used.

[0020] In the above scheme, the liquid ammonia supply amount Qj The prediction is made according to the following formula:

[0021] Q j = Q i × δ.

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

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

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

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

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

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

[0028] Further, the sintering production raw materials further include secondary resources, the secondary resources are one or more of blast furnace slag, converter slag, 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 sinter basicity is a binary basicity.

[0030] Further, the sinter basicity R i is measured according to the sinter produced in the early stage. j is calculated according to the composition of the sintering production raw material j.

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

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

[0033] The present application can predict the change of SO2 concentration in sintering flue gas in advance, predict the adjustment of liquid ammonia supply amount of ammonia method desulfurization system, thereby on the one hand, the SO2 concentration in the flue gas discharged after ammonia method desulfurization can be avoided to exceed the emission standard, the environment is more friendly, on the other hand, the high liquid ammonia supply amount does not need to be maintained for a long time, the liquid ammonia supply amount is controlled, the liquid ammonia utilization rate is improved, and the operation cost of ammonia method desulfurization system is reduced. DETAILED DESCRIPTION

[0034] In order to better understand the present application, the content of the present application will be further illustrated below in combination with examples, but the content of the present application is not limited to the following examples only.

[0035] Example 1

[0036] A low-cost method for preventing and controlling excessive ammonia method desulfurization discharge of sintering flue gas, comprising the following steps:

[0037] S1, according to the sulfur content of the raw material i in the early sintering production and the sulfur content in the sinter at the same production time, the residual coefficient S of sulfur in the sinter when using the raw material i is calculated i ;

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

[0039]

[0040]

[0041] The residual coefficient S of sulfur in the sinter when using the raw material i is calculated 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, according to the change of the basicity of the sintering raw material changed from the raw material i to the raw material j, the residual coefficient S of sulfur in the sinter after the raw material is changed is predicted j ;

[0045] Among them, the binary basicity R of the sinter when using the raw material i i According to the measured value of the sinter, it is 1.87; the binary basicity R of the sinter when using the raw material j j According to the CaO and SiO2 content of the raw material j, it is calculated as 1.85.

[0046] The residual coefficient S of sulfur in the sinter after the raw material is changed is predictedj As follows:

[0047]

[0048] S3, according to the change of the sulfur content of the sintering raw material from raw material i to raw material j, predict the change range δ of the SO2 concentration in the sintering flue gas after the change of the raw material;

[0049] Wherein, the S content of the mixed ore in the 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 remaining raw materials remains unchanged;

[0050] The change range δ of the SO2 concentration in the sintering flue gas after the change of the raw material 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, according to the predicted change range of the SO2 concentration in the sintering flue gas, combined with the liquid ammonia supply amount when using raw material i, predict the required liquid ammonia supply amount Q after the change of the raw material j ;

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

[0055] The required liquid ammonia supply amount Q after the change of the raw material j is as follows:

[0056] Q j = Q i × δ = 16 × 1.15 = 18.2

[0057] S5, according to the predicted required liquid ammonia supply amount after the change of the raw material, adjust the ammonia desulfurization system production.

[0058] Through testing, when using raw material i to produce, according to the liquid ammonia supply amount of 16 tons / day, the average SO2 concentration of the sintering flue gas at the outlet of the ammonia desulfurization system is 18.5 ppm; after changing to raw material j to produce, when the liquid ammonia supply amount is still adjusted to 16 tons / day, the SO2 concentration of the sintering flue gas at the outlet of the ammonia desulfurization system reaches the critical value of 35 ppm of the ultra-low emission, and even exceeds the emission standard in some period; after changing to raw material j to produce, when the liquid ammonia supply amount is adjusted to 18.2 tons / day, the average SO2 concentration of the sintering flue gas at the outlet of the ammonia desulfurization system is 26.8 ppm, and no over-standard emission occurs.

[0059] Example 2

[0060] A low-cost method for preventing and controlling excessive emission of sintering flue gas ammonia desulfurization, comprising the following steps:

[0061] S1, according to the sulfur content of the raw material i for the previous sintering production and the sulfur content in the sinter at the same production time, calculate the residual coefficient S of sulfur in the sinter when using raw material i i ;

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

[0063]

[0064] Calculate the residual coefficient S of sulfur in the sinter when using raw material i i As follows:

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

[0066]

[0067] S2, according to the change of the basicity of the sintering raw material from raw material i to raw material j, predict the residual coefficient S of sulfur in the sinter after changing the raw material j ;

[0068] Wherein, the binary basicity R of the sinter when using raw material i i According to the measured value of the sinter is 1.85; the binary basicity R of the sinter when using raw material j j According to the CaO and SiO2 content of raw material j, it is calculated as 1.85.

[0069] Predict the residual coefficient S of sulfur in the sinter after changing the raw material j As follows:

[0070]

[0071] S3, according to the change of the sulfur content of the sintering raw material from raw material i to raw material j, predict the change range δ of SO2 concentration in the sintering flue gas after changing the raw material;

[0072] Wherein, the S content of fuel in raw material j is reduced to 0.51%, and the S content of the remaining raw material remains unchanged;

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

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

[0075]

[0076] S4, according to the predicted change range of SO2 concentration in sintering flue gas, combined with the liquid ammonia supply amount when using raw material i, predict the required liquid ammonia supply amount Q after changing raw material j ;

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

[0078] The required liquid ammonia supply amount Q after changing raw material is predicted as follows; j ;

[0079] Q j = Q i x δ = 18 x 0.932 = 16.8

[0080] S5, according to the predicted liquid ammonia supply amount required after changing raw material, adjust the ammonia desulfurization system production.

[0081] After testing, when using raw material i to produce, according to the liquid ammonia supply amount of 18 tons / day, the average concentration of SO2 in sintering flue gas at the outlet of ammonia desulfurization system is 26.9 ppm; After changing to raw material j to produce, when the liquid ammonia supply amount is adjusted to 16.8 tons / day, the average concentration of SO2 in sintering flue gas at the outlet of ammonia desulfurization system is 26.5 ppm, no over-standard emission occurs, and the operation cost of ammonia desulfurization system is reduced.

[0082] The above examples are only examples for clearly illustrating, but not limit the embodiments. For those skilled in the art, on the basis of the above description, other different forms of changes or variations can also be made, here it is not necessary and also cannot exhaust all the embodiments, and the obvious changes or variations derived from the above are still within the protection scope of the present application.

Claims

1. A low-cost method for preventing and controlling excessive emissions from sintering flue gas using ammonia-based 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 sulfur residual coefficient S in the sintered ore when using raw material i according to the following formula: i : ； Where c s M is the mass percentage of sulfur 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 mass percentage of sulfur in raw material i; S2, based on the change in basicity of the sintering raw material from raw material i to raw material j, predict the residual sulfur coefficient S in the sintered ore after the raw material change according to the following formula: j : ； Where R j is the basicity of sintered ore after changing the raw materials; R i is the basicity of sintered ore when using raw material i; R j and R i Both are binary basicity, R i According to the actual measurement of sintered ore produced in the early stage, R j Calculated based on the composition of raw material j; S i is the residual coefficient of sulfur in the sintered ore when raw material i is used; S3, based on the change in sulfur content when the sintering production raw material is changed from raw material i to raw material j, the change in SO2 concentration in the sintering flue gas after the raw material change is predicted according to 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 mass percentage of sulfur in 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 a ton of sintered ore, kg; c i is the mass percentage of sulfur in raw material i; S i is the residual coefficient of sulfur in the sintered ore when raw material i is used; S4, based on the predicted change in SO2 concentration in the sintering flue gas and the liquid ammonia supply when using raw material i, the liquid ammonia supply required after the raw material change is predicted according to the following formula Q j : ； Where 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; S5: Adjust 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-based desulfurization according to claim 1 is characterized in that: The raw materials for sintering production 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.

3. The low-cost method for preventing and controlling excessive emissions of sintering flue gas from ammonia desulfurization according to claim 2 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.

4. The low-cost method for preventing and controlling excessive emissions of sintering flue gas from ammonia-based desulfurization according to claim 2 is characterized in that: The sulfur content of the mixed ore is ≤0.035wt%; the sulfur content of the solid fuel is ≤0.6wt%; and the flux is one or more of quicklime, limestone, and dolomite.

5. The low-cost method for preventing and controlling excessive emissions of sintering flue gas from ammonia-based desulfurization according to claim 2 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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