CN111701412A - A sintering flue gas ultra-cleaning system and method - Google Patents

Abstract

The invention provides a comprehensive ultra-clean treatment system and method for sintering flue gas with high efficiency, low investment, no secondary waste, and stable and reliable operation. The sintering flue gas ultra-clean system of the present invention includes a desulfurization tower and a denitration reactor. Among them, the desulfurization tower is a wet desulfurization tower, which is used to remove SO ₂ and soot from the sintering flue gas; the denitration reactor is used to remove NO _x from the sintering flue gas, and is located downstream of the desulfurization tower. The invention adopts the technical scheme of first desulfurization and then denitrification, which can avoid the influence of other impurities in flue gas, such as SO ₂ , SO ₃ , NH ₄ HSO ₄ and soot, on the denitration catalyst, and improve the operation reliability and stability.

Description

A sintering flue gas ultra-cleaning system and method

technical field

The invention belongs to the technical field of steelmaking and environmental protection, and particularly relates to a sintering flue gas ultra-cleaning system and method.

Background technique

The main pollutants of exhaust gas pollution are SO ₂ , NO _x and dust. The most prominent industries with exhaust gas emissions are coal-fired power generation industry, followed by iron and steel industry. At present, the treatment technology of SO ₂ and dust has been relatively mature in various industries, which can reach ultra-low emission levels of 35mg/Nm ³ and 10mg/Nm ³ . Flue gas denitrification generally adopts the selective catalytic reduction (Selectively Catalytic Reduction, SCR) method that consumes ammonia or urea. However, due to the limitation of production process in some industries, SCR still has great difficulties and it is difficult to meet strict environmental protection standards.

The iron and steel production process also produces a large amount of waste gas, mainly from the sintering flue gas of the sintering machine. The _NOx content is generally between 150-450mg/ ^Nm3 , which is slightly lower than the emission level of coal-fired boilers. Different from the operation process of coal-fired boilers, the temperature of flue gas emitted by the sintering machine is relatively low, generally lower than 200 °C, and the current mature flue gas denitration technology cannot be used. Because the conventional flue gas denitrification process is affected by the condensation and corrosion of ammonium bisulfite caused by SO2 in the flue gas, the operating temperature is required to be greater _than 300-350 °C to avoid catalyst deactivation and equipment corrosion.

At present, there are two methods to solve the problem of low temperature denitrification of flue gas from sintering machines: (1) low temperature denitration method using activated coke, the reaction temperature is 80-150 °C, which is called activated coke method; (2) using flue gas to supplement heat + Medium temperature denitrification method of flue gas/flue gas heat exchanger (GGH), referred to as supplementary heat exchange method, the reaction temperature is 300-350 °C.

Using its own good adsorption and oxidation characteristics, the activated coke method can simultaneously treat SO ₂ , NO _x , dust and other pollutants, and the flue gas can be discharged at a temperature higher than the dew point temperature, and there is no white smoke effect of the wet method. It has good development prospects, but it has high investment, high energy consumption, high cost, and has certain flammable and explosive safety risks.

In terms of denitration, in order to utilize the SCR technology, the external heating method of the flue gas of coal gas or natural gas is mainly used to heat the flue gas at about 150°C to above 320°C and send it to the SCR reactor, and the high temperature flue gas then passes through The gas-to-air heat exchanger recovers heat, which undoubtedly requires large investment and high energy consumption. For example, "Yu Shubin, etc., "Discussion on Sintering Flue Gas Denitration Technology", Proceedings of the 8th China Iron and Steel Annual Conference, 2011", "Zhou Lirong, "Sintering Flue Gas SCR Denitration Technology Application in Iron and Steel Plants", China Environmental Protection Industry, 2014" reported method. Patent CN104195326A discloses a process and system for sintering energy-saving and removing various pollutants. The flue gas is first heated by a two-stage gas-gas heat exchanger (GGH), and then the gas burner is used to supplement heat to heat up. Desulfurization is the process of denitrification first and then desulfurization, and the denitration reaction temperature is greater than 300 ℃. Patents CN107983155A and CN108786455A disclose a sintering flue gas desulfurization and denitrification system, which is also a process of using GGH to heat up, then use gas to supplement heat to heat up and denitrify, and then desulfurize, and the denitration reactor temperature is 300-320 ℃.

However, the existing medium-temperature SCR method with heat exchange has a problem that affects the operation stability and denitration efficiency. Because it is denitrification first, SO ₂ in the flue gas will be oxidized to SO ₃ , although the oxidation rate is lower than 1%, but due to the problem of alternating heat and cold inside the flue gas heat exchanger, it will inevitably lead to the occurrence of condensed hydrogen sulfate Ammonium causes fouling, clogging and corrosion of heat exchange channels in heat exchangers. In particular, the GGH used in industry are all rotary heat exchangers, the hot side flue gas and the cold side flue gas will pass through the same flue, and the frequency of blockage is generally higher, especially in the case of high dust content in the flue gas. . In order to solve this problem, the industry can only be equipped with a high-pressure flushing water system, which is regularly and frequently flushed, which further aggravates the corrosion problem of the equipment. In addition, the process of first denitrification and then desulfurization is adopted, and limestone-gypsum and ammonia methods are used for desulfurization. The flue gas has high moisture content and low temperature, which is prone to flue gas tailing and white smoke pollution caused by flue gas emissions close to the dew point temperature. . Patent CN108837677A discloses a pre-desulfurization and post-denitrification process for semi-dry desulfurization. The semi-dry method uses lime slurry and baking soda as raw materials, which has high cost and secondary waste discharge.

In a word, the existing sintering flue gas denitration technology has some shortcomings, which restricts the development of this environmental protection work. It is of great value to develop a new comprehensive treatment technology suitable for sintering flue gas.

SUMMARY OF THE INVENTION

In view of the above-mentioned defects of the prior art, the purpose of the present invention is to provide a comprehensive ultra-clean treatment system and method for sintering flue gas with high efficiency, low investment, no secondary waste, and stable and reliable operation.

In order to achieve the above object, on the one hand, the present invention provides a sintering flue gas ultra-clean system, including a desulfurization tower and a denitration reactor. Among them, the desulfurization tower is used to remove SO ₂ and soot from the sintering flue gas, and the desulfurization tower is a wet desulfurization tower; the denitration reactor is used to remove NO _x from the sintering flue gas, and the denitration reactor is located downstream of the desulfurization tower. The invention adopts the technical scheme of first desulfurization and then denitrification, which can avoid the influence of other impurities in flue gas, such as SO ₂ , SO ₃ , NH ₄ HSO ₄ and soot, on the denitration catalyst, and improve the operation reliability and stability.

Further, the sintering flue gas ultra-cleaning system of the present invention further includes a first heat exchanger and a second heat exchanger, each including a cooling section and a heating section respectively. Among them, the cooling section of the first heat exchanger is located on the inlet flue of the desulfurization tower, which is used to cool down the original flue gas and obtain heat; the heating section of the first heat exchanger is located at the outlet of the desulfurization tower and the heating section of the second heat exchanger On the flue between the inlets, it is used to heat the flue gas after desulfurization. The heating section of the second heat exchanger is used to further heat the desulfurized flue gas, its inlet is connected to the outlet of the heating section of the first heat exchanger, and the outlet of the heating section of the second heat exchanger is connected to the denitration reactor The inlet flue of the second heat exchanger is connected; the cooling section of the second heat exchanger is used to cool down the denitrified flue gas and obtain heat, its inlet is connected with the outlet of the denitration reactor, and its outlet is connected with the downstream equipment.

Further, the first heat exchanger is preferably a water-borne flue gas heat exchanger, and the second heat exchanger is preferably a rotary flue gas heat exchanger, each including a cooling section and a heating section respectively.

Further, the cooling section of the water-borne flue gas heat exchanger is arranged on the inlet flue of the desulfurization tower, and the heating section is arranged on the flue between the outlet of the desulfurization tower and the inlet of the rotary flue gas heat exchanger, which can eliminate the rotary flue gas. The corrosion and blockage of the gas heat exchanger improves its operational stability. The water-mediated heat exchanger uses desalinated hot water as the working medium, and the hot water is transported through the circulating pump to flow between the cooling section and the heating section. The flue gas after desulfurization is heated, using the heat of the flue gas itself, and the heat transfer element is a finned heat transfer tube, which saves energy and has high efficiency.

Further, the rotary flue gas heat exchanger is located above the denitration reactor, so the structure is compact, the floor space is small, and the flue gas resistance is also small. The inlet of the heating section of the rotary flue gas heat exchanger is connected with the outlet of the heating section of the water-borne flue gas heat exchanger, and the outlet of the heating section of the rotary flue gas heat exchanger is connected with the inlet flue of the denitration reactor. ; The inlet of the cooling section of the rotary flue gas heat exchanger is connected with the outlet of the denitration reactor, and the outlet of the cooling section of the rotary flue gas heat exchanger is connected with the downstream equipment, so that the efficiency of the denitration reactor can be improved and the guarantee Good heat transfer performance.

Further, the desulfurization tower includes at least two circulating spray water washing sections, typically two, three, four or five water washing sections, and each water washing section includes a spray component, a flue gas dehydration component, a circulating pump and a circulating pool. Among them, according to the flow direction of the flue gas, the first washing section that the flue gas passes through is the front washing section, and the last washing section is the rear washing section. The front washing section is connected to the flue gas inlet of the desulfurization tower, and the rear washing section is connected to the flue gas outlet of the desulfurization tower. Among them, the front washing section can significantly reduce the content of salt and dust in the rear washing section, so that the latter washing section is basically clean water, so that the exhausted flue gas does not corrode and block the subsequent heat exchangers, which provides a good solution for the realization of ultra-low dust indicators. ensure.

Further, water enters the desulfurization tower from the rear washing section, first flows through the rear washing section, and then enters the front washing section; desulfurization raw materials and oxidizing air enter the desulfurization tower from the front washing section, and the desulfurization products are taken out from the front washing section, which can ensure the desulfurization tower. The SO ₂ and soot content in the outlet flue gas can reach the ultra-low emission index, and it will not block or corrode the subsequent equipment.

Further, the desulfurization raw material in the present invention can be any alkaline substance, such as limestone (CaCO ₃ ) or lime (CaO), magnesium carbonate (MgCO ₃ ) or magnesium oxide (MgO), soda ash (Na ₂ CO ₃ ) Or caustic soda (NaOH), ammonia (including ammonia gas, ammonia water or liquid ammonia), the corresponding desulfurization technologies are called calcium method, magnesium method, sodium method and ammonia method, respectively, and the desulfurization products are gypsum, magnesium sulfate, sodium sulfate (mirabilite) ) and ammonium sulfate. Preferably, calcium method and ammonia method are used for desulfurization, for example, limestone or ammonia water is used as the desulfurization raw material, and the obtained desulfurization product is gypsum or ammonium sulfate, which can be respectively sold as retarding additives and fertilizers for building materials cement, with good economic benefits.

Further, the denitration reactor is filled with a honeycomb type denitration catalyst, and a high temperature hot air generating member and an ammonia mixing member are arranged on the inlet flue of the denitration reactor.

Further, the denitration catalyst is a vanadium-titanium catalyst, the active component of the catalyst is V ₂ O ₅ , as well as auxiliary agents WO ₃ and MoO ₃ , and the carrier is titanium dioxide TiO ₂ , which can be a commercial honeycomb catalyst. It is square, and the equivalent aperture is 3-5mm. Since the present invention is a method of first desulfurization and then denitration, there is no need to worry about the side reaction of SO2 oxidation, the vanadium content in the catalyst can be higher, between _1-2 %; the SCR reaction temperature can be lower, for example, less than 300 ° C, preferably Between 200-300 °C, this can reduce the design requirements and manufacturing costs of the rotary flue gas heat exchanger.

Further, the high temperature hot air generating component is preferably a blast furnace gas or coke oven gas burning hot air furnace, which can be directly installed on the flue, or can form high temperature hot air of about 1000°C and be transported into the flue. The high temperature hot air generating component supplements heat to the flue gas, which can improve the efficiency of the denitration reactor, and ensure good heat transfer performance and high flue gas discharge temperature.

Further, the ammonia mixing component is preferably a multi-nozzle spray mixing element, and the nozzles are generally two-fluid atomizing nozzles of compressed air, which have high efficiency and good mixing effect. The ammonia mixing component can fully mix and atomize the denitration reagent ammonia, further improve the efficiency of the denitration reactor, and ensure better heat transfer performance.

On the other hand, the present invention also provides a method for processing sintering flue gas using the above-mentioned sintering flue gas ultra-cleaning system, comprising the following steps:

(1) Cooling and taking heat from flue gas: the high-temperature raw flue gas containing SO ₂ , NO _x and soot is introduced into the cooling section of the first heat exchanger, and the heat exchange with the heat medium of the first heat exchanger is countercurrent, and the temperature of the flue gas decreases , the heat medium temperature rises;

Preferably, the cooling range of the flue gas is 20-50°C;

(2) Flue gas desulfurization: the flue gas after cooling and heating is introduced into the desulfurization tower, the desulfurization tower has at least two circulating spray water washing sections, and the flue gas is washed and dedusted and absorbed and desulfurized in the circulating spray water washing section;

Preferably; the relative density of the circulating water in the last washing section is less than 1.01, the desulfurization product is sulfate, the SO ₂ content of the desulfurized flue gas is less than 35mg/Nm ³ , and the soot content is less than 10mg/Nm ³ , meeting the ultra-low emission index; And the flue gas temperature is 45-60 ℃, which is close to the water dew point of the flue gas;

(3) Heating and heating of flue gas: introduce the desulfurized flue gas into the heating section of the first heat exchanger, and exchange heat in countercurrent with the heat medium from the cooling section of the first heat exchanger, the temperature of the flue gas rises, and the heat medium temperature drop;

Preferably, the temperature rise range of the flue gas is 20-50°C, which is 20°C higher than the water dew point of the flue gas, so as to prevent corrosion of subsequent equipment;

(4) Reheating and heating of flue gas: the flue gas from step (3) is introduced into the heating section of the second heat exchanger, and the heat exchange element is exchanged with the heat exchange element of the second heat exchanger to heat up, so that the temperature of the flue gas reaches the following the reaction activity temperature required for the denitration step;

Preferably, the temperature rise range of the flue gas is 100-200°C;

(5) heat-up of the flue gas: after the flue gas from step (4) is mixed with the hot air generated by the high-temperature hot air generating member, the flue gas is further heated up to provide the necessary heat transfer temperature difference for the second heat exchanger;

Preferably, the temperature rise range of the flue gas is 20-30°C;

(6) Flue gas denitrification: the flue gas from step (5) is introduced into the denitration reactor, and the _NOx in the flue gas reacts with the denitration reagent ammonia introduced through the ammonia mixing component to become nitrogen and water, thereby realizing flue gas denitrification;

Preferably, the NO _x content in the flue gas after denitration is less than 50 mg/Nm ³ , which meets the ultra-low emission index;

(7) flue gas cooling heat recovery: the flue gas from step (6) is introduced into the cooling section of the second heat exchanger, the heat is absorbed by the heat exchange element of the second heat exchanger, and the flue gas temperature is reduced;

Preferably, the cooling range of the flue gas is 100-200°C to fully recover heat;

(8) Flue gas discharge: the flue gas from step (7) is introduced into the induced draft fan, and then sent into the chimney to be discharged into the atmosphere;

Preferably, the emission temperature of the flue gas is greater than 90° C. to satisfy the emission of the flue gas without white smoke.

The beneficial technical effects of the sintering flue gas ultra-cleaning system of the present invention are at least manifested in the following aspects:

(1) The influence of SO ₂ , SO ₃ , ammonium hydrogen sulfate and smoke on the denitration reactor and catalyst is eliminated, and the service life of the reactor and catalyst is improved;

(2) The influence of ammonium hydrogen sulfate and desulfurization entrained slurry on the clogging and corrosion of the rotary heat exchanger is eliminated, and the operation stability and efficiency of the heat exchanger are improved;

(3) The desulfurization process uses calcium carbonate or ammonia as raw materials, and the desulfurization product has a good use, and also eliminates the problem of secondary waste;

(4) The temperature of exhaust flue gas is greater than 100 ℃, which can eliminate white smoke pollution;

(5) The ultra-low emission index of sintering flue gas can be achieved, and the environmental protection benefit is good.

In a word, the comprehensive performance of the sintering flue gas ultra-cleaning system and method of the present invention is superior to that of the prior art, and the environmental protection, social and economic benefits are remarkable.

Description of drawings

FIG. 1 is a schematic diagram of the structure and flow of a sintering flue gas ultra-cleaning system according to a preferred embodiment of the present invention.

Detailed ways

The embodiments of the present invention are described in detail below. The following embodiments are implemented on the premise of the technical solutions of the present invention, and provide detailed embodiments and specific operation processes, but the protection scope of the present invention is not limited to the following example.

Example 1

A steel plant has a sintering machine with a scale of 265m ² , with an annual output of 2 million tons of sintered ore, a flue gas volume of 720,000 Nm ³ /hr, and a raw flue gas temperature of 160°C, where SO ₂ = 2000mg/Nm ³ , NO _x = 300mg /Nm ³ , soot=50mg/Nm ³ , the sintering flue gas ultra-cleaning system of this embodiment is applied to implement the environmental protection goal of ultra-low emission.

As shown in FIG. 1 , the sintering flue gas ultra-cleaning system in this embodiment includes a desulfurization tower 100 and a denitration reactor 300, and the denitration reactor 300 is located downstream of the desulfurization tower 100, so as to avoid other Impurities, including SO ₂ , SO ₃ , NH ₄ HSO ₄ and soot, etc., affect the denitration catalyst and improve the operational reliability and stability.

The sintering flue gas ultra-cleaning system further includes a rotary flue gas heat exchanger 200 and a water-borne flue gas heat exchanger 400 . Among them, the rotary flue gas heat exchanger 200 is located above the denitration reactor 300, and has a compact structure, small footprint and low flue gas resistance.

The water-borne flue gas heat exchanger 400 includes a cooling section 401 and a heating section 402 . The cooling section 401 is arranged on the inlet flue of the desulfurization tower 100 , and the heating section 402 is arranged on the flue between the outlet of the desulfurization tower 100 and the inlet of the rotary flue gas heat exchanger 200 . The water-based flue gas heat exchanger 400 uses desalinated hot water as the working medium, and the hot water is transported by the circulating pump 403 to flow between the cooling section 401 and the heating section 402, and the heat is taken out in the cooling section 401 from the hot raw flue gas. , and sent to the heating section 402 to heat the desulfurized flue gas from the desulfurization tower 100, fully utilizing the heat of the flue gas itself, and the heat transfer element is a finned heat transfer tube, which saves energy and has high efficiency.

The desulfurization tower 100 includes at least two circulating spray water washing sections, the front water washing section 101 is connected to the flue gas inlet of the desulfurization tower 100 , and the rear water washing section 102 is connected to the flue gas outlet of the desulfurization tower 100 . The front washing section 101 includes a spray member 1011, a flue gas dehydration member 1012, a circulation pump 1013 and a first circulation pool 1014, and the rear washing section 102 includes a first spray member 1021, a first flue gas dehydration member 1022, The first circulating pump 1023 and the first circulating pool 1024. The process water required for desulfurization enters from the rear washing section 102, first flows through the rear washing section 102, and then enters the front washing section 101. The desulfurization raw materials and oxidizing air enter the front washing section 101, and the desulfurization product is taken out from the front washing section 101.

The desulfurization in this embodiment adopts the calcium method, the desulfurization raw material is limestone (CaCO ₃ ), and the desulfurization product is gypsum, which can be used as a retarding additive for building material cement, which is a wet desulfurization process. After the combined action of the first spray member 1011 , the first flue gas dehydration member 1012 , the first circulating pump 1013 and the first circulating pool 1014 of the front water washing section 101 , the SO ₂ content of the flue gas is 30 mg/Nm ³ . The circulating water in the front washing section 101 is a slurry containing salts such as gypsum and sodium chloride, equivalent to 30% wt solid content, and the flue gas contains 40-60 mg/Nm ³ of desulfurized slurry. The flue gas passes through the post-washing section 102, and passes through the combined action of the second spray component 1021, the second flue gas dehydration component 1022, the second circulating pump 1023 and the second circulating pool 1024. The SO ₂ in the flue gas is 20 mg/Nm ³ . The circulating water in the post-washing section 102 is basically clean water, the solid content of which is less than 0.05%, and the water content in the flue gas is 50 mg/Nm ³ , and it is basically clean water. The temperature-raising section 402 has no influence, and the problem of scaling and clogging will not occur.

The rotary flue gas heat exchanger 200 includes a cooling section 201 and a heating section 202. The inlet of the heating section 202 is connected to the outlet of the heating section 402 of the water-borne flue gas heat exchanger 400, and the outlet of the heating section 202 is connected to the denitration reactor. The inlet flue of 300 is connected, the outlet of the denitration reactor 300 is connected with the inlet of the cooling section 201, and the outlet of the cooling section 201 is connected with the downstream equipment.

The flue gas denitration reactor 300 is filled with a honeycomb SCR denitration catalyst 301 , and a mixing member 302 for ammonia denitration reagent and a high temperature hot air generating member 303 are also provided on the inlet flue of the denitration reactor 300 .

The denitration catalyst is a vanadium-titanium catalyst, the active component of the catalyst is V ₂ O ₅ , as well as auxiliary agents WO ₃ and MoO ₃ , the carrier is titanium dioxide TiO ₂ , a commercial honeycomb catalyst is used, and the honeycomb pores of the catalyst are square, etc. The effective pore diameter is 4.0mm, because it is a method of first desulfurization and then denitrification, there is no need to worry about the side reaction of SO2 oxidation, the vanadium content in the catalyst is ₂ %, and the reaction temperature is 280 ° C.

The mixing component 302 of the ammonia denitration reagent is a multi-nozzle spray mixing element, and the nozzle is a two-fluid atomizing nozzle of compressed air, which has high efficiency and good mixing effect.

The high temperature hot blast generating member 303 adopts a blast furnace gas burning hot blast stove, and is directly installed on the inlet flue of the denitration reactor 300 .

The method for processing sintering flue gas using the sintering flue gas ultra-cleaning system of this embodiment includes the following steps:

(1) Cooling and taking heat from flue gas: the high-temperature raw flue gas containing SO ₂ , NO _x and dust is introduced into the cooling section 401 of the water-medium heat exchanger 400 to conduct countercurrent heat exchange with the hot water delivered by the circulating pump 403 , and the flue gas Air cooling, the cooling range is 20-50 °C, and the heat is stored in the heat medium water;

(2) Flue gas desulfurization: the flue gas after cooling down and taking heat is introduced into the desulfurization tower 100. The desulfurization tower 100 has two washing sections 101 and 102. The water washing section 102 is further washed for dust removal and absorption desulfurization, and the density of the post-washing section is less than 1.01, the desulfurization product is sulfate, the SO ₂ content of the desulfurized flue gas is less than 35mg/Nm ³ , and the soot content is less than 10mg/Nm ³ , Meet the ultra-low emission index; and the temperature is 45-60 ℃, close to the water dew point of the flue gas;

(3) Heating and heating of flue gas: the flue gas after desulfurization is introduced into the heating section 402 of the water-medium heat exchanger 400, and the heat-medium water from the cooling section 401 is countercurrently exchanged for heat, and the flue gas is heated up, and the temperature rise range is 20-50 ° C , 20°C higher than the water dew point of the flue gas to prevent the corrosion of subsequent equipment;

(4) Reheating and heating of flue gas: the flue gas from step (3) is introduced into the heating section 202 of the rotary heat exchanger 200, and the temperature is increased by exchanging heat with the continuously rotating heat exchange element. The flue gas temperature reaches the reaction activity temperature required by the subsequent denitration step;

(5) Supplementary heating of flue gas: after the flue gas from step (4) is mixed with the hot air generated by the high-temperature hot air generating member 303, the temperature of the flue gas is further increased by 20-30 °C, which is a rotary exchange The heater provides the necessary heat transfer temperature difference;

(6) Flue gas denitrification: the flue gas from step (5) is introduced into the denitration reactor 300, and the _NOx in the flue gas reacts with the denitrification reagent ammonia introduced through the ammonia mixing member 302 to become nitrogen and water, so as to realize the flue gas Denitrification, the NO _x content in the flue gas after denitration is less than 50mg/Nm ³ , which meets the ultra-low emission index;

(7) Flue gas cooling heat recovery: the flue gas from step (7) is introduced into the cooling section 201 of the rotary heat exchanger 200, the heat is absorbed by the rotating heat exchange element, and the flue gas temperature is reduced by 100-200 ℃, fully recover heat;

(8) Flue gas emission: the flue gas from step (7) is introduced into the induced draft fan 500, and then sent to the chimney 600 to be discharged into the atmosphere.

Using the ultra-clean system of this embodiment to process the sintering flue gas, the SO ₂ content in the flue gas discharged from the flue gas outlet of the desulfurization tower 100 is 20 mg/Nm ³ and the dust content is 4.1 mg/Nm ³ . The inlet flue gas temperature is 78°C, the flue gas outlet temperature of the rotary flue gas heat exchanger 200 is 105°C, the _NOx content is 36mg/Nm ³ , the comprehensive environmental protection indicators are excellent, and the flue gas emission is free of white smoke. In addition, the desulfurization tower 100 uses limestone as the desulfurization raw material, and the obtained desulfurization product is gypsum, which has good economy as a retarding additive for building materials cement.

Example 2

A steel plant has a sintering machine with a scale of 360m ² , with an annual output of 4 million tons of sintered ore, a flue gas volume of 1.2 million Nm ³ /hr, and a raw flue gas temperature of 170°C, where SO ₂ =1500mg/Nm ³ , NO _x =250mg /Nm ³ , soot=40mg/Nm ³ , the sintering flue gas ultra-cleaning system of this embodiment is applied to implement the environmental protection goal of ultra-low emission.

The sintering flue gas ultra-cleaning system in this embodiment is roughly the same as that in Embodiment 1, except that the flue gas desulfurization in this embodiment adopts the ammonia method, the desulfurization raw material is ammonia water, the concentration of ammonia water is 15%, and the desulfurization product is ammonium sulfate. Used as a fertilizer, it is also a wet desulfurization process. After the joint action of the first spray member 1011 , the first flue gas dehydration member 1012 , the first circulating pump 1013 and the first circulating pool 1014 of the front water washing section 101 , the SO ₂ content of the flue gas is 25 mg/Nm ³ . The circulating water of the front washing section is a slurry containing ammonium sulfate, equivalent to 20% wt of solid content, and the flue gas contains 40-60 mg/Nm ³ of desulfurized slurry. The flue gas passes through the post-washing section 102, and passes through the combined action of the second spray component 1021, the second flue gas dehydration component 1022, the second circulating pump 1023 and the second circulating pool 1024, and the SO ₂ in the flue gas is 12 mg/Nm ³ . The circulating water in the post-washing section 102 is basically clean water, the solid content of which is less than 0.05%, and the water content in the flue gas is 50 mg/Nm ³ , and it is basically clean water. The temperature-raising section 402 has no influence, and the problem of scaling and clogging will not occur.

In addition, the denitration catalyst is a vanadium-titanium catalyst, the active component of the catalyst is V ₂ O ₅ , as well as auxiliary agents WO ₃ and MoO ₃ , the carrier is titanium dioxide TiO ₂ , a commercial honeycomb catalyst is used, and the honeycomb pores of the catalyst are square , the equivalent pore diameter is 3.2mm, because it is a method of first desulfurization and then denitrification, there is no need to worry about the side reaction of SO2 oxidation, the vanadium content in the catalyst is 1.8%, and the reaction temperature is ₂₅₀ ℃.

Using the ultra-clean system of this embodiment to process the sintering flue gas, the SO ₂ content in the flue gas discharged from the flue gas outlet of the desulfurization tower 100 is 12 mg/Nm ³ and the dust content is 3.1 mg/Nm ³ . The inlet flue gas temperature is 75°C, the flue gas outlet temperature of the rotary flue gas heat exchanger 200 is 103°C, the _NOx content is 24mg/Nm ³ , the comprehensive environmental protection indicators are excellent, and the flue gas emission is free of white smoke. In addition, the desulfurization tower 100 uses ammonia water as the desulfurization raw material, and the obtained desulfurization product is ammonium sulfate, which can be used as a chemical fertilizer and has good economy.

The preferred embodiments of the present invention have been described in detail above. It should be understood that many modifications and changes can be made according to the concept of the present invention by those skilled in the art without creative efforts. Therefore, any technical solutions that can be obtained by those skilled in the art through logical analysis, reasoning or limited tests on the basis of the prior art according to the concept of the present invention shall fall within the protection scope determined by the claims.

Claims (10)

1. a sintering flue gas ultra-clean system, is characterized in that, described ultra-clean system comprises: Desulfurization towers to remove SO2 and soot from sintering flue gas _; and a denitration reactor for removing NO _x in the sintering flue gas; wherein, The desulfurization tower is a wet desulfurization tower, and the denitration reactor is located downstream of the desulfurization tower. 2. The sintering flue gas ultra-cleaning system according to claim 1, wherein the ultra-cleaning system further comprises a first heat exchanger and a second heat exchanger, the first heat exchanger and the first heat exchanger The second heat exchangers respectively include a cooling section and a heating section; wherein, The cooling section of the first heat exchanger is located on the inlet flue of the desulfurization tower, and is used for cooling the original flue gas to obtain heat; The heating section of the first heat exchanger is located on the flue between the outlet of the desulfurization tower and the inlet of the heating section of the second heat exchanger, and is used for heating the flue gas after desulfurization; The heating section of the second heat exchanger is used to further heat the desulfurized flue gas, and the inlet of the heating section of the second heat exchanger is connected to the outlet of the heating section of the first heat exchanger, The outlet of the heating section of the second heat exchanger is connected with the inlet flue of the denitration reactor; The cooling section of the second heat exchanger is used to cool the denitrified flue gas to obtain heat, and the inlet of the cooling section of the second heat exchanger is connected to the outlet of the denitration reactor. The outlet of the cooling section of the heat exchanger is connected to the downstream equipment. 3. The sintering flue gas ultra-cleaning system according to claim 2, wherein the first heat exchanger is a water-borne flue gas heat exchanger, and the second heat exchanger is a rotary flue gas exchange Heater. 4. The sintering flue gas ultra-cleaning system according to claim 3, characterized in that, the water-mediated heat exchanger uses desalinated hot water as a working medium, and the desalinated hot water is transported by a circulating pump in its cooling section and The heat transfer element of the water medium heat exchanger is a finned heat transfer tube. 5. The sintering flue gas ultra-cleaning system according to claim 4, wherein the rotary flue gas heat exchanger is located above the denitration reactor, The inlet of the heating section of the rotary flue gas heat exchanger is connected with the outlet of the heating section of the water-mediated flue gas heat exchanger, and the outlet of the heating section of the rotary flue gas heat exchanger is connected to the denitrification section. The inlet flue of the reactor is connected; The inlet of the cooling section of the rotary flue gas heat exchanger is connected with the outlet of the denitration reactor, and the outlet of the cooling section of the rotary flue gas heat exchanger is connected with downstream equipment. 6. The sintering flue gas ultra-cleaning system according to any one of claims 1-5, wherein the desulfurization tower comprises at least two circulating spray water washing sections, and the at least two circulating spray water washing sections Each of them respectively includes a spray component, a flue gas dehydration component, a circulating pump and a circulating pool. 7. The sintering flue gas ultra-cleaning system according to claim 6, wherein the desulfurization tower comprises two circulating spray water washing sections, namely a front water washing section and a rear water washing section, and the front water washing section is connected to the The flue gas inlet of the desulfurization tower, and the post-washing section is connected to the flue gas outlet of the desulfurization tower. 8. The sintering flue gas ultra-cleaning system according to claim 7, characterized in that, water enters the desulfurization tower from the rear washing section, first flows through the rear washing section, and then enters the front washing section; Desulfurization raw materials and oxidizing air enter the desulfurization tower from the pre-water washing section, and the desulfurized product is taken out from the pre-water washing section. 9. The sintering flue gas ultra-cleaning system according to claim 8, wherein the desulfurization raw material is selected from one of limestone, lime, magnesium carbonate, magnesium oxide, soda ash, caustic soda, ammonia gas, ammonia water, and liquid ammonia. kind. 10. A method for processing sintering flue gas using the sintering flue gas ultra-cleaning system according to claim 2, wherein the method comprises the following steps: (1) Cooling the flue gas to obtain heat: introducing the high-temperature raw flue gas containing SO ₂ , NO _x and soot into the cooling section of the first heat exchanger, and exchanging heat in countercurrent with the heat medium of the first heat exchanger, The temperature of the flue gas decreases and the temperature of the heat medium increases; (2) Flue gas desulfurization: the flue gas after cooling and taking heat is introduced into the desulfurization tower, the desulfurization tower has at least two circulating spray water washing sections, and the flue gas is washed in the at least two circulating spray water washing sections Dust removal and absorption desulfurization; (3) Heating and heating of flue gas: introducing the desulfurized flue gas into the heating section of the first heat exchanger, and exchanging heat in countercurrent with the heat medium from the cooling section of the first heat exchanger, the flue gas temperature rises high, the temperature of the heat medium decreases; (4) Reheating and heating of flue gas: the flue gas from step (3) is introduced into the heating section of the second heat exchanger, and exchanges heat with the heat exchange element of the second heat exchanger to increase the temperature, so that the smoke The gas temperature reaches the reaction activity temperature required by the subsequent denitration step; (5) Supplementary heating of flue gas: after the flue gas from step (4) is mixed with the hot air generated by the high-temperature hot air generating component, the flue gas is further heated up; (6) Flue gas denitrification: the flue gas from step (5) is introduced into the denitration reactor, and the _NOx in the flue gas reacts with the denitrification reagent ammonia introduced through the ammonia mixing member to become nitrogen and water, and the flue gas is realized denitrification; (7) Flue gas cooling heat recovery: the flue gas from step (6) is introduced into the cooling section of the second heat exchanger, the heat is absorbed by the heat exchange elements of the second heat exchanger, and the temperature of the flue gas decreases ; (8) Flue gas discharge: the flue gas from step (7) is introduced into the induced draft fan, and then sent to the chimney to be discharged into the atmosphere.

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