Flue gas purification system of iron ore suspension magnetization roasting furnace

Abstract

The utility model discloses a flue gas purification system for an iron ore suspension magnetization roasting furnace, which comprises a roasting main furnace, roasting flue gas discharged from the roasting main furnace sequentially enters a main furnace cyclone and a secondary preheating cyclone and then enters an SCR (Selective Catalytic Reduction) denitration tower, flue gas discharged from the SCR denitration tower enters a Venturi preheater, and the Venturi preheater is communicated with the main furnace cyclone and the secondary preheating cyclone. The flue gas enters a Venturi preheater and exchanges heat with iron ore powder added into the Venturi preheater, then the flue gas subjected to heat exchange and cooling enters a first-stage preheating cyclone cylinder, the flue gas subjected to gas-solid separation enters a bag-type dust collector and a wet desulfurization tower for dust removal and desulfurization purification treatment, and then the flue gas is discharged into the atmosphere through a top chimney; compared with the prior art, investment cost and operation cost can be reduced, system operation is safer, arrangement is more compact, ultra-low emission can be achieved even under the condition that a wet-type electric precipitator is not arranged, and the investment cost, the occupied area and the operation cost of the whole device are obviously reduced.

Description

TECHNICAL FIELD

[0001] The utility model relates to the technical field of flue gas desulfurization, denitration, dust removal, and particularly relates to a flue gas desulfurization, denitration, dust removal and purification system for a suspended magnetization roasting furnace for iron ore. BACKGROUND

[0002] The proportion of China's crude steel output in the global total has been kept above 50% for a long time, and the crude steel output of China exceeded 1 billion tons in 2024, accounting for about 53% of the global proportion, and iron ore needs to be imported in large quantities; China has abundant refractory iron oxide resources, which mainly have the characteristics of fine crystalline grain size, complex composition, weak magnetism and the like, and it is difficult to obtain ideal technical and economic indicators by using conventional beneficiation technical means, so a large amount of resources has been abandoned for a long time and cannot be effectively applied.

[0003] In recent years, the suspended magnetization roasting technology has begun to be applied and developed in the ironmaking industry, which mainly changes the magnetic properties of the ore to optimize the subsequent magnetic separation efficiency, so that the iron recovery rate is increased from 50-60% in the traditional process to 80-90%, which can produce good economic efficiency, and practice has proved that it is a practical and effective utilization method that suits China's actual conditions.

[0004] Because the roasting of iron ore in the suspended magnetization roasting furnace produces a large amount of waste gas, the negative pressure is relatively large, about-15000Pa, the composition of the waste gas varies according to the composition of the iron ore, the SO2 concentration can reach above 3000mg / Nm³, the NOx is generally about 200-300mg / Nm³, the dust concentration in the flue gas at the denitration inlet is very high, about 100g / Nm³, and the total iron content in the ash is above 40%, which has a large grinding turbidity; in addition, the oxygen content at the desulfurization inlet is relatively high, about 16-18%.

[0005] At present, there are few suspension magnetization roasting furnace production lines for iron ore, and there is no mature waste gas purification treatment technology for this working condition on the market. Basically, the waste gas treatment process of other roasting furnaces is used, which mainly has the following two technologies: One is an alumina roasting furnace flue gas zero emission system with authorization announcement number CN210410140U, which adopts SNCR+SCR in denitration, and SNCR spray guns are arranged at the inlet / outlet of the secondary preheating separator at the outlet of the roasting furnace. The core of the suspension magnetization roasting furnace for iron ore lies in mineral reduction modification and magnetic enhancement. Generally, the highest combustion temperature is controlled at about 900℃, and the outlet temperature at the top of the furnace is controlled at 500-600℃. Therefore, neither at the outlet of the main furnace nor at the inlet / outlet of the secondary preheating cyclone does it have the condition to arrange SNCR spray guns, which will only waste a large amount of reducing agent and has very low denitration efficiency. Of course, spray guns can also be arranged at the throat of the main roasting furnace, but the consumption of reducing agent is large, and the economy is not high. In dust removal, the patent recommends using an electrostatic precipitator. Mainly considering that the flue gas temperature after the roasting furnace is high, the filter material will be burned out if a bag filter is used, and the cost is too high if a metal filter bag is used. However, the dust concentration at the outlet is high if an electric precipitator is used, which is generally 30-50 mg / Nm³. In order to achieve ultra-clean emission, the dust removal efficiency of desulfurization is needed, and a wet electrostatic precipitator needs to be added subsequently to achieve 5-10 mg / Nm³. At the same time, the high dust concentration at the inlet of the induced draft fan will also wear the blades.

[0006] The other is a patent "industrial mineral heat furnace flue gas desulfurization and denitration device" with authorization announcement number CN218307178U. Its SNCR technology is also not suitable for the denitration purification of the flue gas of the suspension magnetization roasting furnace. Considering the high dust concentration and high turbidity at the inlet of the denitration, the catalyst will be washed away. It adopts the process of dust removal and desulfurization first and then denitration. Because of the temperature requirement of the denitration catalyst, it adopts dry / half-dry desulfurization to minimize the temperature drop during desulfurization and dust removal. However, the low-temperature catalyst needs to ensure that the inlet flue gas temperature is above 180 degrees. When the temperature is not enough, the flue gas needs to be heated, which wastes energy. Since the low-temperature catalyst has a high price and a short service life compared with the high-temperature catalyst, the equipment investment and operating cost are increased. Moreover, since a bag filter is arranged after the dry method, the denitration is arranged at the rear end, and the risk of excessive dust is also relatively large. SUMMARY

[0007] The purpose of the utility model is to solve the problems in the prior art, and a flue gas purification system for a suspension magnetization roasting furnace for iron ore is proposed, which can reduce investment cost and operating cost, and the system runs more safely and compactly. Even without a wet electrostatic precipitator, it can also achieve ultra-low emission, so that the investment cost, land area and operating cost of the whole device are significantly reduced.

[0008] In order to realize the above-mentioned purpose, the utility model provides a kind of iron ore suspension magnetization roasting furnace flue gas purification system, including roasting main furnace, the flue gas outlet of roasting main furnace is communicated with the flue gas import of main furnace cyclone, the flue gas outlet of main furnace cyclone is communicated with the flue gas import of secondary preheating cyclone, the flue gas outlet of secondary preheating cyclone is communicated with the flue gas import of SCR denitration tower, the flue gas outlet of SCR denitration tower is communicated with the flue gas import of Venturi preheater, the flue gas outlet of Venturi preheater is communicated with the flue gas import of primary preheating cyclone, the flue gas outlet of primary preheating cyclone is communicated with the flue gas import of bag filter, the flue gas outlet of bag filter is communicated with wet desulphurization tower by induced draft fan, the downcomer of secondary preheating cyclone is communicated with roasting main furnace, the downcomer of primary preheating cyclone is communicated with the flue duct between the flue gas outlet of main furnace cyclone and the flue gas import of secondary preheating cyclone.

[0009] As preferred, the SCR denitration tower inlet flue and Venturi preheater inlet flue are respectively provided with cold air valve.

[0010] As preferred, the filter material of the bag filter is selected from PTFE or the blended structure of PTFE and high-performance fiber.

[0011] As preferred, a wet-type electric dust collector is arranged above the wet desulphurization tower, and the wet desulphurization tower, the wet-type electric dust collector and the top chimney are sequentially arranged to form a three-tower-in-one arrangement.

[0012] As preferred, when the outlet dust emission requirement is 5mg / Nm³, the wet-type electric dust collector can be omitted.

[0013] As preferred, the wet desulphurization tower inlet flue is provided with an emergency cooling device.

[0014] As preferred, the inlet flue gas temperature of the SCR denitration tower is 320-400℃, and the SCR denitration adopts a medium-high temperature catalyst.

[0015] The utility model has the advantages that considering the flue gas temperature distribution of the suspension magnetization roasting furnace top and the primary and secondary preheating cyclones, the conventional SNCR+SCR combined denitration technology of the roasting furnace is not suitable for denitration, and the medium-high temperature SCR denitration technology is adopted, which ensures the denitration efficiency and greatly saves the reducing agent consumption.

[0016] According to the flue gas characteristics of the suspension magnetization roasting furnace, the bag filter is adopted, the mineral material recovery efficiency is improved, the investment is saved, the subsequent desulphurization condition is ensured, and the dust can be easily discharged to achieve ultra-low emission or nearly zero emission.

[0017] The three-tower (two-tower) integration technology is adopted, so that the equipment layout site is greatly reduced, and investment cost, operation power consumption, etc.

[0018] The conventional wet desulfurization is adopted, only the emergency spray cooling device in fault state is arranged, the safety of the equipment in the desulfurization tower is ensured, and the desulfurization efficiency meets the ultra-low emission requirement.

[0019] Due to the bag-type dust collector arranged before desulfurization, the dust at the inlet of the desulfurization tower can be ensured to be below 5 mg / Nm³, if a wet-type electric dust collector is further arranged, the dust concentration discharged from the chimney can be less than 2 mg / Nm³, and the near-zero emission is truly realized.

[0020] Compared with the prior art, the investment cost and operation cost can be reduced, the system operation is safer, the layout is more compact, the ultra-low emission can be realized even without the wet-type electric dust collector, and the investment cost, land area and operation cost of the whole device are obviously reduced.

[0021] The features and advantages of the utility model will be described in detail by combining with the drawings. DRAWINGS

[0022] Figure 1 is a structural schematic view of the iron ore suspension magnetization roasting furnace flue gas purification system of the utility model of example 1;

[0023] Figure 2 is a structural schematic view of the iron ore suspension magnetization roasting furnace flue gas purification system of the utility model of example 2.

[0024] In the drawing: 1 is a roasting main furnace, 2 is a main furnace cyclone, 3 is a first-stage preheating cyclone, 4 is a second-stage preheating cyclone, 5 is an SCR denitration tower, 6 is a Venturi preheater, 7 is a cold air valve, 8 is a bag-type dust collector, 9 is an induced draft fan, 10 is a wet desulfurization tower, 11 is a wet-type electric dust collector, and 12 is a top chimney. DETAILED DESCRIPTION

[0025] Example 1

[0026] Reference Figure 1The utility model relates to an iron ore suspension magnetization roasting furnace flue gas purification system, including roasting main furnace 1, the flue gas outlet of roasting main furnace 1 is sequentially linked with main furnace cyclone 2, two stage preheating cyclone 4, SCR denitration tower 5, venturi preheater 6, first stage preheating cyclone 3, cloth bag dust collector 8, induced draft fan 9 and wet desulphurization tower 10, and the roasting flue gas of roasting main furnace 1 is sequentially entered main furnace cyclone 2, two stage preheating cyclone 4, then enters to SCR denitration tower 5, the flue gas of the exit of SCR denitration tower 5 enters venturi preheater 6, and the iron ore powder in the inside of venturi preheater 6 is added to carry out heat exchange, then the flue gas after heat exchange cooling enters first stage preheating cyclone 3 again, and the flue gas after the gas-solid separation of first stage preheating cyclone 3 enters cloth bag dust collector 8, and the flue gas after the purification of cloth bag dust collector 8 enters wet desulphurization tower 10 after the pressurization of induced draft fan 9, then again through top chimney 12 and is discharged into the atmosphere.

[0027] The SCR denitration tower 5 inlet flue and venturi preheater 6 inlet flue are respectively provided with cold air valve 7.

[0028] The filter material of the cloth bag dust collector 8 is selected from PTFE or a blended structure of PTFE and other high-performance fibers.

[0029] The wet desulphurization tower 10 and the top chimney 12 are double-tower integrated and vertically arranged.

[0030] The wet desulphurization tower 10 inlet flue is provided with an emergency cooling device.

[0031] The inlet flue gas temperature of the SCR denitration tower 5 is 320-400 DEG C, and the SCR denitration tower 5 adopts a medium-high temperature conventional catalyst.

[0032] The reducing agent supply of the SCR denitration tower 5 adopts an ammonia water gasification, urea hydrolysis or pyrolysis process.

[0033] Example 2

[0034] Reference Figure 2 The difference from example 1 is that a wet-type electric dust collector 11 is arranged above the wet desulphurization tower 10, so that the chimney emission dust concentration can be less than 2 mg / Nm3, and near-zero emission is truly achieved.

[0035] The utility model working process:

[0036] The utility model discloses a kind of iron ore suspension magnetization roasting furnace flue gas purification systems, in working process, iron ore suspension magnetization roasting furnace flue gas is controlled at 500~600 ℃ in roasting main furnace 1 flue gas outlet, generally control is at the outlet temperature of two-stage preheating cyclone 4 320~400 ℃, just meet the requirement of SCR denitration;Enter SCR denitration tower 5, by 2~3 layers of catalyst effect, NOxIt can be reduced to 50mg / Nm³, after denitration flue gas passes through venturi preheater 6 and first-stage preheating cyclone 3, temperature fluctuates in the range of 130~230 ℃, so PTFE type filter material can meet the requirement, and bag outlet can guarantee that dust concentration is at 10mg / Nm³, after roasting furnace system runs normally, desulfurization inlet flue gas temperature can be guaranteed to be stably below 150 ℃, meet the temperature condition of long-term operation of desulfurization;Again through wet desulfurization tower 10, after 3~5 layers of spraying and multilayer demister effect, SO2It can be reduced to below 35mg / Nm³, dust can be reduced to 5mg / Nm 3 If wet-type electric dust collector 11 is configured behind, outlet dust can be reduced to 2mg / Nm 3 Below.

[0037] In addition, desulfurization tower inlet flue should be provided with flue gas emergency cooling device, guarantee that desulfurization tower runs safely under fault condition.

[0038] When entire roasting furnace system fails, smoke temperature suddenly rises and exceeds catalyst temperature resistance value or bag filter material temperature limit, corresponding cold air valve 7 will be automatically opened, guarantee that SCR denitration tower 5 and bag dust collector 8 inlet flue gas temperature does not exceed set value.

[0039] To reduce the investment cost of complete set of purification system, land area and operating power consumption, adopt wet desulfurization tower 10, wet-type electric dust collector 11 and top chimney 12 three towers in one, vertical arrangement.

[0040] The above embodiment is to the utility model, is not the limitation of the utility model, any simple transformation of the utility model is the protection range of the utility model.

Claims

1. A system for flue gas cleaning of an iron ore suspension magnetization roaster, characterized by: The application relates to a calcination main furnace (1), a flue gas outlet of the calcination main furnace (1) is communicated with a flue gas inlet of a main furnace cyclone (2), a flue gas outlet of the main furnace cyclone (2) is communicated with a flue gas inlet of a secondary preheating cyclone (4), a flue gas outlet of the secondary preheating cyclone (4) is communicated with a flue gas inlet of an SCR denitration tower (5), a flue gas outlet of the SCR denitration tower (5) is communicated with a flue gas inlet of a Venturi preheater (6), a flue gas outlet of the Venturi preheater (6) is communicated with a flue gas inlet of a primary preheating cyclone (3), a flue gas outlet of the primary preheating cyclone (3) is communicated with a flue gas inlet of a bag-type dust collector (8), a flue gas outlet of the bag-type dust collector (8) is communicated with a wet desulfurization tower (10) through an induced draft fan (9), a discharging pipe of the secondary preheating cyclone (4) is communicated with the calcination main furnace (1), and a discharging pipe of the primary preheating cyclone (3) is communicated with a flue channel between the flue gas outlet of the main furnace cyclone (2) and the flue gas inlet of the secondary preheating cyclone (4).

2. A system for cleaning the flue gases of an iron ore suspension magnetization roaster according to claim 1, characterized in that: Cold air valves (7) are arranged in the inlet flue channel of the SCR denitration tower (5) and the inlet flue channel of the Venturi preheater (6).

3. A system for cleaning the flue gas of an iron ore suspension magnetization roaster as claimed in claim 1, characterized in that: The filter material of the bag-type dust collector (8) is selected from PTFE or a mixed structure of PTFE and high-performance fibers.

4. A system for cleaning the flue gas of an iron ore suspension magnetization roaster as claimed in claim 1, characterized in that: A wet-type electric dust collector (11) is arranged above the wet desulfurization tower (10), and the wet desulfurization tower (10), the wet-type electric dust collector (11) and a top chimney (12) are sequentially arranged to form a three-tower integrated arrangement.

5. A system for cleaning the flue gases of an iron ore suspension magnetization roaster according to claim 4, characterized in that: When the outlet dust emission requirement is 5 mg / Nm3, the wet-type electric dust collector (11) can be omitted.

6. A system for cleaning the flue gases of an iron ore suspension magnetization roaster according to claim 1, characterized in that: An emergency cooling device is arranged in the inlet flue channel of the wet desulfurization tower (10).

7. A system for cleaning the flue gas of an iron ore suspension magnetization roaster according to claim 1, characterized in that: The denitration adopts an SCR technology, the inlet flue gas temperature of the SCR denitration tower (5) is 320-400 DEG C, and a medium-high temperature catalyst is adopted.

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