Efficient flue gas circulation purification system and method

Abstract

The invention relates to an efficient flue gas circulation purification system and method, and belongs to the technical field of flue gas purification. The system comprises a sintering device used for generating flue gas to be purified and recycling the flue gas subjected to dust removal treatment; the dust removal module performs dust removal treatment on the to-be-purified flue gas; the temperature control desulfurization module is used for adjusting the temperature of the flue gas subjected to dust removal treatment to meet a preset temperature condition and executing desulfurization treatment; and the denitration and CO removal module is used for carrying out denitration and CO removal treatment on the desulfurized flue gas to finally obtain purified flue gas. The efficient flue gas purification method integrating flue gas recycling and flue gas purification is adopted, the total amount of flue gas entering the purification module is reduced, and the advantages of a desulfurization device and a denitration and CO removal device can be fully exerted. The heat exchanger is additionally arranged on the desulfurization device, so that stable and reasonable control of the desulfurization module is realized, hot spots of the desulfurization device caused by over-high flue gas temperature are avoided, and the problem that corrosion of module equipment is accelerated due to over-low flue gas temperature is also solved.

Description

Technical Field

[0001] The present application relates to the field of flue gas purification, and in particular, to an efficient flue gas circulation purification system and method. Background Art

[0002] Sintering flue gas contains a large amount of SO2, NOx, dust and CO, so it needs to be purified before being discharged. At present, the main processes for sintering flue gas treatment include activated coke desulfurization and denitrification process, semi-dry desulfurization + SCR denitrification process, wet desulfurization + SCR denitrification process, etc. Among them, the advantage of the activated coke desulfurization and denitrification process is that it can simultaneously remove SO2 and NOx with strong removal ability; however, when carrying out the denitrification process, atomized ammonia water needs to be sprayed, resulting in agglomeration inside the module, and hot spots often appear when the activated coke circulation in the module is not smooth; when the activated coke circulation volume is insufficient, it will lead to excessive dust emission; when the NOx emission at the flue gas outlet exceeds the standard, after adjusting the ammonia injection volume, it generally takes 3 hours for the NOx concentration at the outlet to decrease significantly, and the lag time is too long. To ensure the compliance of the external discharge data, the main extraction damper needs to be reduced, affecting the output and quality of sintered ore. In addition, the advantage of using the semi-dry + SCR desulfurization and denitrification process is that the NOx removal ability is strong, and the reaction of adjusting the ammonia injection volume to the change of NOx emission concentration is relatively fast; however, the desulfurization ability of the semi-dry desulfurization is relatively low, and it often occurs that the fluctuation of SO2 at the flue gas inlet causes great difficulty in controlling the compliance of SO2 emission at the outlet. Summary of the Invention

[0003] The present application provides an efficient flue gas circulation purification system and method to solve the following technical problem: how to efficiently purify sintering flue gas.

[0004] In a first aspect, an embodiment of the present application provides an efficient flue gas circulation purification system, including:

[0005] A sintering device for generating flue gas to be purified and recycling the flue gas after dust removal treatment;

[0006] A first dust removal module for performing dust removal treatment on the flue gas to be purified and transmitting the flue gas after dust removal treatment to the sintering device and the purification module;

[0007] A purification module for receiving the flue gas after dust removal treatment and performing purification treatment on it to obtain purified flue gas.

[0008] Wherein, the purification module includes:

[0009] A temperature control desulfurization module including a heat exchanger and a desulfurization device for adjusting the temperature of the flue gas after dust removal treatment to meet the preset temperature condition of the desulfurization device and performing desulfurization treatment on the flue gas after temperature adjustment to obtain desulfurized flue gas;

[0010] The denitrification and CO removal module is used to perform denitrification and CO removal on the flue gas after desulfurization to obtain purified flue gas.

[0011] Optionally, the preset temperature condition of the desulfurization device satisfies: |T - A| ≤ B, where T is the temperature of the flue gas entering the desulfurization device, A is the target temperature of the desulfurization device, and B is the set deviation temperature.

[0012] Optionally, the denitrification and CO removal module is an SCR denitrification and CO removal device, including a flue gas inlet, a flue gas heating device, a denitrification catalyst module, a CO removal catalyst module, and a flue gas outlet arranged in sequence; the flue gas after desulfurization treatment enters through the flue gas inlet, and after being heated by the flue gas heating device, the heated flue gas is obtained; the heated flue gas enters the denitrification catalyst module for denitrification treatment; the flue gas after denitrification treatment passes through the CO removal catalyst module for CO removal treatment to obtain purified flue gas; the purified flue gas is discharged through the flue gas outlet.

[0013] Optionally, the denitrification and CO removal module is an SCR denitrification and CO removal device, including a flue gas inlet, a GGH flue gas heat exchanger, a denitrification catalyst module, a CO removal catalyst module, and a flue gas outlet. The flue gas inlet is connected to the high-temperature side of the GGH flue gas heat exchanger, and the flue gas outlet is connected to the low-temperature side of the GGH flue gas heat exchanger; the flue gas after desulfurization treatment enters through the flue gas inlet and exchanges heat through the high-temperature side of the GGH flue gas heat exchanger to obtain heated flue gas; the heated flue gas enters the denitrification catalyst module for denitrification treatment; the flue gas after denitrification treatment passes through the CO removal catalyst module for CO removal treatment to obtain purified flue gas; the purified flue gas exchanges heat through the low-temperature side of the GGH flue gas heat exchanger and is discharged through the flue gas outlet.

[0014] Optionally, between the desulfurization device and the denitrification and CO removal module, there is also a second dust removal module. The second dust removal module performs secondary dust removal on the flue gas after desulfurization and then inputs it to the denitrification and CO removal module.

[0015] In a second aspect, an embodiment of the present application provides an efficient flue gas circulation purification method, which is implemented based on the flue gas circulation purification system described in the first aspect, and includes the following steps:

[0016] Obtain the sintering flue gas to be purified;

[0017] Perform first dust removal treatment on the sintering flue gas to obtain the flue gas after dust removal;

[0018] Divide the flue gas after dust removal into external circulation flue gas and flue gas to be desulfurized according to a set volume ratio;

[0019] Recycle the external circulation flue gas into the sintering device for high-temperature combustion treatment to obtain purified external circulation flue gas;

[0020] Adjust the temperature of the flue gas to be desulfurized to meet the preset temperature conditions of the desulfurization device, and perform desulfurization treatment on the flue gas after temperature adjustment to obtain desulfurized flue gas;

[0021] Perform denitrification and CO removal treatment on the flue gas after desulfurization treatment to obtain purified flue gas.

[0022] Optionally, the set volume ratio of the external circulation flue gas to the flue gas to be temperature-controlled is 1:4 to 2:3.

[0023] Optionally, when the external circulation flue gas is subjected to high-temperature combustion treatment, the combustion temperature is 1000 - 1500 °C.

[0024] Optionally, adjusting the temperature of the flue gas to be desulfurized to meet the preset temperature conditions of the desulfurization device, and performing desulfurization treatment on the flue gas to be desulfurized after temperature adjustment to obtain desulfurized flue gas specifically includes:

[0025] Adjust the temperature of the flue gas to be desulfurized to the flue gas temperature T entering the desulfurization device;

[0026] Compare the difference |T - A| between the flue gas temperature T entering the desulfurization device and the target temperature A of the desulfurization device with the set deviation temperature B;

[0027] If |T - A| ≤ B, then perform desulfurization treatment on the flue gas to be desulfurized after temperature adjustment to obtain desulfurized flue gas;

[0028] If |T - A| > B, then continue to adjust the temperature of the flue gas to be desulfurized until |T - A| ≤ B is satisfied.

[0029] Optionally, before performing denitrification and CO removal treatment on the flue gas after desulfurization treatment to obtain purified flue gas, it further includes:

[0030] Perform secondary dust removal treatment on the flue gas after desulfurization treatment.

[0031] Optionally, performing denitrification and CO removal treatment on the flue gas after desulfurization treatment to obtain purified flue gas specifically includes:

[0032] Heat the flue gas after desulfurization treatment to the set temperature, enter the denitrification catalyst module for denitrification reaction to obtain denitrified flue gas;

[0033] Enter the denitrified flue gas into the CO removal catalyst module for CO removal reaction to obtain purified flue gas.

[0034] Optionally, the denitrification and CO removal treatment of the flue gas after desulfurization treatment to obtain purified flue gas specifically includes: passing the flue gas after desulfurization treatment through the high-temperature end of the GGH heat exchanger and entering the denitrification catalyst module for denitrification reaction to obtain denitrified flue gas;

[0035] Passing the denitrified flue gas into the CO removal catalyst module for CO removal reaction to obtain purified flue gas;

[0036] The purified flue gas passes through the low-temperature end of the GGH heat exchanger to recover heat and preheat the GGH heat exchanger.

[0037] The above technical solutions provided by the embodiments of the present application have the following advantages compared with the prior art:

[0038] The embodiments of the present application provide an efficient flue gas circulation purification system and method. The system includes: a sintering device for generating flue gas to be purified, recycling the flue gas after dust removal treatment, recycling part of the flue gas after dust removal treatment to the sintering device for high-temperature combustion, and removing harmful components such as NO X , CO, dioxins, etc.; a first dust removal module for performing dust removal treatment on the flue gas to be purified, removing more than 90% of the dust in the flue gas, preventing dust from affecting subsequent treatment processes, and transmitting the treated flue gas to the sintering device and the purification module; a purification module for receiving the flue gas after dust removal treatment and performing purification treatment on it to obtain purified flue gas. The purification module includes: a temperature control desulfurization module including a heat exchanger and a desulfurization device for adjusting the temperature of the flue gas after dust removal treatment to meet the preset temperature conditions of the desulfurization device, and performing desulfurization treatment on the temperature-adjusted flue gas to obtain desulfurized flue gas; a denitrification and CO removal module for performing denitrification and CO removal treatment on the desulfurized flue gas to finally obtain purified flue gas.

[0039] The present application adopts an efficient flue gas purification method that integrates flue gas circulation utilization and flue gas purification, that is, dividing the flue gas to be purified into two parts, one part is recycled to the sintering device to remove harmful gases in the flue gas by using the high temperature of the sintering material layer, and the other part enters the purification module for desulfurization, denitrification and CO removal treatment. This method reduces the total amount of flue gas and the total amount of pollutant treatment entering the purification module, and can give full play to the advantages of the desulfurization device and the denitrification and CO removal device. By adding a heat exchanger to the desulfurization device and realizing stable and reasonable control of the desulfurization module through PID fuzzy control, it not only avoids the generation of hot spots in the desulfurization device caused by too high flue gas temperature, but also solves the problem of accelerating the corrosion of module equipment caused by too low flue gas temperature. Description of the Drawings

[0040] The accompanying drawings here are incorporated into the specification and constitute a part of this specification, showing embodiments consistent with the present application, and are used together with the specification to explain the principles of the present application.

[0041] To more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the accompanying drawings required in the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0042] Figure 1 It is a schematic diagram of the principle of an efficient flue gas circulation purification system according to some embodiments of the present application;

[0043] Figure 2 It is a schematic diagram of the principle structure of a desulfurization device according to some embodiments of the present application;

[0044] Figure 3 It is a schematic diagram of the principle structure of a desulfurization and denitrification module according to some embodiments of the present application;

[0045] 1 - Burner, 2 - NOx removal catalyst, 3 - CO removal catalyst, 4 - GGH, 5 - Booster fan, 6 - Chimney;

[0046] Figure 4 It is a schematic diagram of the process of an efficient flue gas circulation purification method according to some embodiments of the present application. Detailed implementation manners

[0047] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are some, but not all, of the embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts fall within the scope of protection of the present application.

[0048] The various embodiments of the present application may exist in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be construed as a rigid limitation on the scope of the present application; therefore, it should be considered that the described range description has specifically disclosed all possible sub-ranges and individual values within that range; for example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and individual numbers within that range, such as 1, 2, 3, 4, 5, and 6, regardless of the range; additionally, whenever a numerical range is indicated herein, it means including any cited number (fraction or integer) within the indicated range.

[0049] In this text, terms including "comprising" and the like mean "including but not limited to". Relative terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. "And / or" describes the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone; where A and B can be singular or plural. "At least one" means one or more, "multiple" means two or more; "at least one kind", "at least one of the following items (pieces)" or similar expressions refer to any combination of these items, including any combination of single item (piece) or plural items (pieces); for example, "at least one of a, b, or c", or "at least one of a, b, and c" can both represent: a, b, c, a - b (that is, a and b), a - c, b - c, or a - b - c, where a, b, and c can be single or multiple respectively. "Part representation methods" such as parts by weight and parts by mass represent the proportional relationship between each component. In the proportional relationships involved in this text, the parameters that need to be described by proportion should be understood as the antecedents of the proportion formula in the order of description, and the proportional numbers should be understood as the consequents of the proportion formula. For example, if the mass ratio of substance A, substance B, and substance C is 1:2:3, then substance A, substance B, and substance C should correspond one by one with the proportional numbers in the proportion formula in the order of description, that is, the mass of substance A: the mass of substance B: the mass of substance C = 1:2:3.

[0050] Unless otherwise specifically stated, various raw materials, reagents, instruments, and equipment used in this text can be obtained through market purchase or can be prepared by existing methods.

[0051] In a first aspect, an embodiment of the present application provides an efficient flue gas circulation purification system, as Figure 1 shown, including:

[0052] A sintering device for generating flue gas to be purified and recycling the flue gas after dust removal treatment;

[0053] A first dust removal module for performing dust removal treatment on the flue gas to be purified and transmitting the treated flue gas to the sintering device and the purification module;

[0054] As a flue gas generation source, the sintering device generates flue gas to be purified containing harmful components such as dust, SO2, NOx, CO, and dioxins. The flue gas to be purified is transported to the first dust removal module for dust removal treatment under the action of a suction fan; after receiving the flue gas to be purified, the first dust removal device can remove most of the dust in the flue gas to be purified by means of electrostatic precipitation or bag dust removal, and then divide the flue gas after dust removal treatment into two parts and transport them to the sintering device and the heat exchange module respectively. One part returns to the sintering device through an external cycle and can be recycled through the sintering machine surface in the sintering device. The harmful components such as NOx, CO, and dioxins in it are removed by high-temperature combustion. This step can reduce the amount of flue gas entering the purification module and reduce the workload of the purification module.

[0055] The purification module is used to receive the flue gas after dust removal treatment and purify it to obtain purified flue gas, including:

[0056] The temperature control and desulfurization module, including a heat exchanger and a desulfurization device, is used to adjust the temperature of the flue gas after dust removal treatment to meet the preset temperature conditions of the desulfurization device, and perform desulfurization treatment on the flue gas after temperature adjustment to obtain desulfurized flue gas;

[0057] The denitrification and CO removal module is used to perform denitrification and CO removal treatment on the desulfurized flue gas to finally obtain purified flue gas.

[0058] In the above embodiment, the temperature control and desulfurization module adjusts the temperature of the flue gas after dust removal treatment to meet the preset temperature conditions of the desulfurization device by setting a heat exchanger in front of the desulfurization device, avoiding the formation of hot spots in the desulfurization device caused by too high flue gas temperature and affecting the desulfurization effect, and also solving the problem of accelerating the corrosion of module equipment due to too low flue gas temperature; the flue gas after temperature adjustment enters the desulfurization device and performs desulfurization treatment to remove sulfur dioxide in it to obtain desulfurized flue gas.

[0059] Since the desulfurized flue gas still contains nitrogen oxides and CO, it is necessary to use the denitrification and CO removal module to remove them to obtain purified flue gas.

[0060] In the above-described embodiment, a high-efficiency flue gas purification system integrating flue gas recycling and purification is adopted. That is, the flue gas to be purified is divided into two parts. One part is recycled to the sintering device to remove harmful gases in the flue gas by the high temperature of the sintering material layer, and the other part enters the purification module for desulfurization, denitrification, and CO removal. This method reduces the total amount of flue gas entering the purification module, reduces the total amount of pollutants to be treated, can give full play to the advantages of the desulfurization device and the denitrification and CO removal device, and realizes the efficient purification of flue gas. By adding a heat exchanger to the desulfurization device, stable and reasonable control of the desulfurization module is achieved through PID fuzzy control, that is, it avoids the generation of hot spots in the desulfurization device due to too high flue gas temperature, and also solves the problem of accelerating the corrosion of module equipment due to too low flue gas temperature.

[0061] As an alternative embodiment, the first dust removal module is an electrostatic precipitator.

[0062] As an alternative embodiment, the sintering device is a belt sintering machine.

[0063] In the above-described embodiment, the belt sintering machine generates sintering flue gas as the flue gas to be purified during the sintering of ore. After passing through the external circulation fan, the dust-removed flue gas is recycled to the sintering pallet material layer. The sintering pallet material layer is divided into a sintered ore zone, a combustion zone, a preheating zone, a drying zone, a over-wet zone, etc. Among them, the highest temperature of the sintered ore zone is about 1000°C, the temperature of the combustion zone is 1300°C - 1400°C, and the highest temperature of the preheating zone is about 700°C. The flue gas returning to the sintering machine passes through the sintered ore zone, the combustion zone, and the preheating zone in sequence, and harmful components such as NOx, CO, and dioxins are removed by high temperature.

[0064] As an alternative embodiment, the preset temperature condition of the desulfurization device satisfies: |T - A| ≤ B, where T is the flue gas temperature entering the desulfurization device, A is the target temperature of the desulfurization device, and B is the set deviation temperature.

[0065] In the above-described embodiment, the target temperature A of the desulfurization device is the optimal reaction temperature of the flue gas during the desulfurization reaction in the desulfurization device, and its value can be adjusted according to the characteristics of different desulfurizing agents; the set deviation temperature B is the actual temperature fluctuation range allowed for the operation of the desulfurization device, and it can also be adjusted according to actual needs. Controlling the difference between the flue gas temperature T entering the desulfurization device and the target temperature A within the set deviation temperature range can ensure that the flue gas entering the desulfurization device can normally carry out the desulfurization reaction.

[0066] As an alternative embodiment, the desulfurization device adopts an activated coke desulfurization device, and its principle structure is as Figure 2As shown in the figure, it includes an activated coke module, a desorption tower, and an acid-making system. A flue gas inlet, an activated coke outlet, an activated coke inlet, and a flue gas outlet are provided on the activated coke module. After the flue gas to be desulfurized enters the activated coke module through the flue gas inlet, it is captured in the moving layer of the activated coke module by physical adsorption and chemical adsorption. The principle is as follows:

[0067] Physical adsorption: SO2 → SO2*;

[0068] Chemical adsorption: SO2* + 1 / 2O2* → SO3* + nH2O* → H2SO4*(n - 1)H2O, H2SO4* + NH3 → NH4HSO4* + NH3 → (NH4)2SO4*;

[0069] Therefore, the flue gas discharged from the activated coke module has a low SO2 concentration and meets the emission index requirements.

[0070] The activated coke that has captured SO2 in the activated coke module enters the desorption tower through the activated coke outlet for high-temperature desorption and regeneration, releasing SO2 gas. The principle of the regeneration reaction is: H2SO4 + C = 2SO2 + CO2 + 2H2O, NH4HSO4 = SO2 + 2H2O + 1 / 3N2 + 1 / 3NH3. The SO2 gas released by the activated coke in the desorption tower can enter the acid-making system to produce industrial by-product sulfuric acid. The regenerated activated coke can also be supplied to the activated coke module again through the activated coke inlet via the conveying system for recycling. When the activated coke in the activated coke module is insufficient, external activated coke can be added to the activated coke module.

[0071] In the above embodiment, the flue gas treated by the desulfurization device is discharged through the flue gas outlet. In addition, in order to capture some spilled activated coke powder, a second dust removal device can be set to remove dust from the desulfurized flue gas to prevent the spilled activated coke powder from affecting subsequent denitrification and CO removal reactions.

[0072] As an optional embodiment, the temperature of the activated coke module is continuously and stably maintained below 140°C.

[0073] As an optional embodiment, the second dust removal device uses a bag filter for dust removal. After testing, the dust concentration of the flue gas after the second dust removal treatment is less than 5mg / NM 3 .

[0074] As an alternative embodiment, the denitrification and CO removal module is an SCR denitrification and CO removal device, which includes a flue gas inlet, a flue gas heating device, a denitrification catalyst module, a CO removal catalyst module, and a flue gas outlet arranged in sequence; the flue gas after desulfurization treatment enters through the flue gas inlet, and after being heated by the flue gas heating device, the heated flue gas is obtained; the heated flue gas enters the denitrification catalyst module for denitrification treatment; the flue gas after denitrification treatment passes through the CO removal catalyst module for CO removal treatment to obtain purified flue gas; the purified flue gas is discharged through the flue gas outlet.

[0075] As an alternative embodiment, the schematic structural diagram of the denitrification and CO removal module is as Figure 3 shown, and it includes a flue gas inlet, a GGH flue gas heat exchanger, a burner, a denitrification catalyst module, a CO removal catalyst module, and a flue gas outlet. The flue gas inlet is connected to the high-temperature side of the GGH flue gas heat exchanger, and the flue gas outlet is connected to the low-temperature side of the GGH flue gas heat exchanger; the flue gas after desulfurization treatment enters through the flue gas inlet and exchanges heat through the high-temperature side of the GGH flue gas heat exchanger to obtain heated flue gas; the heated flue gas enters the denitrification catalyst module for denitrification treatment; the flue gas after denitrification treatment passes through the CO removal catalyst module for CO removal treatment to obtain purified flue gas; the purified flue gas exchanges heat through the low-temperature side of the GGH flue gas heat exchanger and is discharged through the flue gas outlet.

[0076] In the above embodiment, the flue gas after desulfurization first exchanges heat at the hot end of the GGH (regenerative flue gas heat exchanger) to increase the flue gas temperature. Subsequently, in order to obtain flue gas at a higher temperature, a burner is needed to continue heating the flue gas to further increase its temperature to 280°C to 320°C and then enter the denitrification catalyst module; nitrogen oxides (NO x ) in the flue gas are mixed with atomized ammonia water, and when passing through the NOx catalyst, NOx reacts with the atomized ammonia water to remove NOx. The main chemical reaction equations are: 4NO + 4NH3 + O2 → 4N2 + 6H2O; 6NO2 + 8NH3 → 7N2 + 12H2O.

[0077] After the NO x is removed, when the flue gas passes through the CO removal catalyst module, the CO in it is catalytically combusted and undergoes an oxidation reaction with O2 to generate CO2. This process can be efficiently carried out at a relatively low temperature under the action of the catalyst. Since the catalytic combustion of CO is an exothermic reaction, the flue gas temperature further increases. At this time, the high-temperature flue gas enters the low-temperature side of the GGH to preheat the GGH, realizing the recovery and reuse of heat.

[0078] In the above embodiment, the GGH belongs to a regenerative heat exchanger, and transfers the heat of the flue gas to the SCR inlet flue gas through smooth or corrugated metal sheets or heat carriers. During operation, the rotor rotates slowly, and the heat transfer elements pass through the hot untreated denitrified flue gas and the cooler cleaned flue gas after denitrification and decarbonization in turn. When the cleaned flue gas after denitrification and decarbonization passes through the heat transfer element, part of the heat in the cleaned flue gas is transferred to the heat transfer element; when the heat transfer element rotates to the side of the untreated denitrified and decarbonized flue gas, the heat it carries is transferred to the untreated denitrified and decarbonized flue gas, raising its temperature, while the heat transfer element itself is cooled.

[0079] As an alternative embodiment, the flue gas after SCR denitrification and decarbonization is sent into the chimney and discharged into the atmosphere under the suction of the booster fan.

[0080] In a second aspect, the embodiments of the present application provide an efficient flue gas circulation purification method, which is implemented based on the flue gas circulation purification system described in the first aspect, and includes the following steps:

[0081] S1. Obtain the sintering flue gas to be purified;

[0082] The purpose of step S1 is to obtain the sintering flue gas to be purified from the flue gas production source, and provide raw materials for the subsequent steps. The flue gas production source can be a belt sintering machine, and the generated sintering flue gas has the following characteristics: low oxygen concentration, high humidity, high dust, O2 content of 10% - 18%, H2O content of 10% - 15%, dust particulate matter content of 5g / Nm 3 ~30g / Nm 3 ; the flue gas temperature is relatively low, generally 120°C - 180°C; the content of harmful gases is relatively high, among which the SO2 concentration is 500mg / m 3 -1500mg / m 3 , NO X concentration is 100mg / m 3 ~300mg / m 3 , CO concentration is 6000mg / m 3 ~10000mg / m 3 , and also contains harmful substances such as HCl, HF, dioxin, and heavy metals.

[0083] S2. Perform a first dust removal treatment on the sintering flue gas to obtain the flue gas after dust removal;

[0084] Step S2 first performs a dust removal treatment on the generated sintering flue gas. The main purpose is to remove the dust in the sintering flue gas, not only to prevent dust from overflowing and polluting the environment, but also to avoid the influence of dust particles on the subsequent purification equipment, such as blocking the pores of the desulfurizer in the activated coke desulfurization device.

[0085] S3. Divide the flue gas after dust removal into external circulation flue gas and flue gas to be desulfurized according to a set volume ratio;

[0086] In step S3, the flue gas after dust removal is divided into flue gas of two paths. Among them, the external circulation flue gas is purified through the action of step S4, and the flue gas to be desulfurized is purified through the steps in step S5. The purpose is to split the flue gas, reduce the total amount of flue gas entering the desulfurization module, and improve the purification efficiency.

[0087] S4. Recover the external circulation flue gas to the sintering device for high-temperature combustion treatment to obtain purified external circulation flue gas;

[0088] In step S4, the external circulation flue gas is recovered to the sintering device, and the flue gas is recycled through the sintered ore belt and combustion zone of the sintering machine surface. When the external circulation flue gas passes through the sintered ore belt and combustion zone of the sintering machine surface in sequence, chemical reactions such as secondary combustion of CO, reaction of CO with NO X to generate CO2 and N2, and intense combustion of dioxins occur, so that NO in the external circulation flue gas X , CO, dioxins, etc. are removed to obtain purified external circulation flue gas.

[0089] S5. Adjust the temperature of the flue gas to be desulfurized to meet the preset temperature conditions of the desulfurization device, and perform desulfurization treatment on the flue gas after temperature adjustment to obtain desulfurized flue gas;

[0090] In step S5, the temperature of the flue gas after dust removal treatment is controlled and adjusted to meet the preset temperature conditions of the desulfurization device, avoiding the generation of hot spots in the desulfurization device caused by too high flue gas temperature, which affects the desulfurization effect, and also solves the problem of accelerating the corrosion of module equipment due to too low flue gas temperature; the flue gas after temperature adjustment enters the desulfurization device and performs desulfurization treatment to remove sulfur dioxide therein to obtain desulfurized flue gas.

[0091] S6. Perform denitrification and CO removal treatment on the desulfurized flue gas to obtain purified flue gas.

[0092] The purpose of step S6 is that the desulfurized flue gas still contains nitrogen oxides and CO, so it is necessary to use a denitrification and CO removal module to remove them to obtain purified flue gas.

[0093] In the above embodiment, a high-efficiency flue gas purification system integrating flue gas circulation utilization and flue gas purification is adopted. That is, the flue gas to be purified is divided into two parts. One part is recycled to the sintering device to remove harmful gases in the flue gas by the high temperature of the sintering material layer, and the other part enters for desulfurization, denitrification, and CO removal treatment. This method reduces the total amount of flue gas for desulfurization reaction, reduces the total amount of pollutant treatment, can give full play to the advantages of the desulfurization device and the denitrification and CO removal device, and realizes efficient purification of flue gas. By controlling the temperature of the flue gas entering the desulfurization module, stable and reasonable control of the desulfurization module is achieved, which not only avoids damage to the desulfurization device caused by too high flue gas temperature, but also solves the problem of accelerating the corrosion of module equipment due to too low flue gas temperature.

[0094] As an alternative embodiment, the set volume ratio of the external circulation flue gas to the flue gas to be desulfurized is 1:4 to 2:3.

[0095] In the above embodiment, the reason for controlling the set volume ratio of the external circulation flue gas to the flue gas to be desulfurized to be 1:4 to 2:3 is that the oxygen content in this flue gas is relatively low, and it is generally used at the tail of the sintering machine trolley. Therefore, the sintering device has limited ability to recycle it. If the total amount of the external circulation flue gas is too large, additional oxygen input is required for utilization during treatment, resulting in increased costs. If the total external circulation is too low, the total amount of the flue gas to be desulfurized is too high, and the flue gas treatment capacity of the desulfurization module and the denitrification and CO removal modules is too large, which may lead to a decrease in treatment efficiency. Exemplarily, the set volume ratio of the external circulation flue gas to the flue gas to be desulfurized can be 1:4, 1:3, 3:7, or 2:3.

[0096] As an alternative embodiment, when the external circulation flue gas is subjected to high-temperature combustion treatment, the combustion temperature is 1000°C to 1500°C.

[0097] In the above embodiment, the combustion temperature of the external circulation flue gas is mainly determined by the combustion zone temperature on the surface of the sintering machine. Exemplarily, the high-temperature combustion temperature can be 1000°C, 1050°C, 1100°C, 1150°C, 1200°C, 1250°C, 1300°C, 1350°C, 1400°C, 1450°C, or 1500°C.

[0098] As an alternative embodiment, adjusting the temperature of the flue gas to be desulfurized to meet the preset temperature conditions of the desulfurization device, and performing desulfurization treatment on the temperature-adjusted flue gas to be desulfurized to obtain desulfurized flue gas, specifically includes:

[0099] Adjust the temperature of the flue gas to be desulfurized to the flue gas temperature T entering the desulfurization device;

[0100] Compare the difference |T - A| between the flue gas temperature T entering the desulfurization device and the target temperature A of the desulfurization device with the set deviation temperature B;

[0101] If |T - A| ≤ B, the flue gas to be desulfurized after temperature adjustment is subjected to desulfurization treatment to obtain the desulfurized flue gas;

[0102] If |T - A| > B, continue to adjust the temperature of the flue gas to be desulfurized until |T - A| ≤ B is satisfied.

[0103] In the above embodiment, by arranging a heat exchanger in front of the desulfurization module and controlling the temperature T of the flue gas entering the desulfurization device through PID, so that |T - A| ≤ B, to ensure that the temperature of the flue gas entering the desulfurization device is within the optimal temperature range for the operation of the desulfurization module, enhance the working efficiency of the desulfurization module, and at the same time, too high or too low flue gas temperature affects the activity of the desulfurization module.

[0104] As an alternative embodiment, before subjecting the desulfurized flue gas to denitrification and CO removal treatment to obtain the purified flue gas, it further includes:

[0105] Subject the desulfurized flue gas to a second dust removal treatment.

[0106] As an alternative embodiment, subjecting the desulfurized flue gas to denitrification and CO removal treatment to obtain the purified flue gas specifically includes:

[0107] Heat the desulfurized flue gas to a set temperature and enter the denitrification catalyst module for denitrification reaction to obtain the denitrified flue gas;

[0108] Enter the denitrified flue gas into the CO removal catalyst module for CO removal reaction to obtain the purified flue gas.

[0109] As an alternative embodiment, the set temperature is 280°C to 320°C.

[0110] As an alternative embodiment, subjecting the desulfurized flue gas to denitrification and CO removal treatment to obtain the purified flue gas specifically includes:

[0111] Pass the desulfurized flue gas through the high-temperature end of the GGH heat exchanger and enter the denitrification catalyst module for denitrification reaction to obtain the denitrified flue gas;

[0112] Enter the denitrified flue gas into the CO removal catalyst module for CO removal reaction to obtain the purified flue gas;

[0113] The purified flue gas can pass through the low-temperature end of the GGH heat exchanger to recover heat for preheating the GGH heat exchanger.

[0114] The present application will be further described below in conjunction with specific embodiments. For the experimental methods without specific conditions indicated in the following embodiments, they are usually determined in accordance with national standards / industry standards; if there are no corresponding national standards / industry standards, they are carried out in accordance with general international standards, conventional conditions or the conditions recommended by the manufacturer.

[0115] Example 1

[0116] This example provides an efficient flue gas circulation purification system, including:

[0117] A belt sintering machine, which is used to generate flue gas to be purified and recycle the flue gas after dust removal treatment;

[0118] An electrostatic precipitator, which is used to perform dust removal treatment on the flue gas to be purified and transmit the flue gas after dust removal treatment to the belt sintering machine and the purification module;

[0119] A purification module, which is used to receive the flue gas after dust removal treatment and perform purification treatment on it to obtain purified flue gas.

[0120] Among them, the purification module includes:

[0121] A temperature control desulfurization module, including a heat exchanger and an activated coke desulfurization device. The heat exchanger is used to adjust the temperature of the flue gas after dust removal treatment to meet the preset temperature conditions of the desulfurization device, and transmit the temperature-controlled flue gas to the activated coke desulfurization module. The activated coke module performs desulfurization treatment on the temperature-adjusted flue gas to obtain desulfurized flue gas;

[0122] A bag filter, which is used to perform secondary dust removal treatment on the desulfurized flue gas to remove the activated coke particles that may be contained in the flue gas;

[0123] A denitrification and CO removal module, which is used to perform denitrification and CO removal treatment on the desulfurized flue gas, remove NOx and CO in the flue gas, and obtain purified flue gas.

[0124] Among them, the structure of the activated coke desulfurization device is as Figure 2As shown in the figure, it includes an activated coke module, a desorption tower, and an acid-making system. The activated coke module is provided with a flue gas inlet, an activated coke outlet, an activated coke inlet, and a flue gas outlet. After the flue gas to be desulfurized enters the activated coke module through the flue gas inlet, it is captured in the moving layer of the activated coke module by physical adsorption and chemical adsorption methods. The activated coke that has captured SO2 in the activated coke module enters the desorption tower through the activated coke outlet for high-temperature desorption and regeneration, releasing SO2 gas. The SO2 gas released by the activated coke in the desorption tower can enter the acid-making system to produce industrial by-product sulfuric acid. The regenerated activated coke can also be supplied to the activated coke module again through the activated coke inlet via the conveying system for cyclic reuse. When the activated coke in the activated coke module is insufficient, external activated coke can be added to the activated coke module.

[0125] The structural schematic diagram of the denitrification and CO removal module is as shown in Figure 3 As shown in the figure, it includes a flue gas inlet, a GGH flue gas heat exchanger, a burner, a denitrification catalyst module, a CO removal catalyst module, and a flue gas outlet. The flue gas inlet is connected to the high-temperature side of the GGH flue gas heat exchanger, and the flue gas outlet is connected to the low-temperature side of the GGH flue gas heat exchanger. The flue gas after desulfurization treatment enters through the flue gas inlet and exchanges heat through the high-temperature side of the GGH flue gas heat exchanger to obtain the heated flue gas. If the temperature of the heated flue gas does not reach the set temperature for denitrification treatment, the burner is still needed to heat it up again to reach the set temperature, and then it enters the denitrification catalyst module for denitrification treatment. The flue gas after denitrification treatment undergoes CO removal treatment through the CO removal catalyst module to obtain the purified flue gas. The purified flue gas exchanges heat through the low-temperature side of the GGH flue gas heat exchanger and is discharged through the flue gas outlet.

[0126] Example 2

[0127] This example provides an efficient flue gas circulation purification method, including the following steps:

[0128] S1. Obtain the sintering flue gas to be purified;

[0129] The sintering flue gas in this example uses the sintering flue gas discharged from the 360m 2 sintering machine of Shougang Co., Ltd. The composition of the sintering flue gas is as follows: the O2 content is 10% - 12%, the H2O content is about 12%, the content of dust particulate matter after being treated by an electrostatic precipitator is 30mg / Nm 3 , the SO2 concentration is 1300mg / m 3 , NO X The concentration is 200mg / m 3 -280mg / m 3 , the CO concentration is 6000 - 8000mg / m 3Meanwhile, the sintering flue gas also contains harmful substances such as HCl, HF, dioxins, and heavy metals.

[0130] S2. Perform primary dust removal on the sintering flue gas to obtain the flue gas after dust removal;

[0131] S3. Divide the flue gas after dust removal into external circulation flue gas and flue gas to be desulfurized according to a volume ratio of 3:7;

[0132] S4. Recycle the external circulation flue gas to the sintering machine for high-temperature combustion treatment to obtain purified external circulation flue gas

[0133] In this embodiment, the external circulation flue gas is recycled to the surface of the sintering machine trolley with a wind volume of about 300,000 m 3 / h, accounting for 30% of the total sintering flue gas. The external circulation flue gas realizes the removal of pollutants such as CO, NO X , dioxins, etc. through high-temperature points such as the sintered ore zone and combustion zone of the sintering material layer, reducing the flue gas treatment volume of the desulfurization and denitrification system.

[0134] S5. Adjust the temperature of the flue gas to be desulfurized to meet the preset temperature conditions of the desulfurization device, and perform desulfurization treatment on the flue gas after temperature adjustment to obtain desulfurized flue gas;

[0135] 70% of the sintering flue gas is heated through a heat exchanger. The temperature of the sintering flue gas before heat exchange is about 150°C - 160°C. After PID fuzzy control of the heat exchanger, the temperature of the sintering flue gas is reduced to 135°C - 140°C, meeting |T - A| ≤ B, where T is the temperature of the flue gas entering the desulfurization device, A is the target temperature of the desulfurization device, and B is the set deviation temperature;

[0136] The temperature-controlled flue gas to be desulfurized is sent to the activated coke module for desulfurization treatment. In the desulfurized flue gas, the SO2 concentration is reduced from 1300 mg / m 3 to 5 mg / m 3 or less. After dust removal by a bag filter, the content of dust particles in the flue gas is reduced from 30 mg / Nm 3 to 5 mg / Nm 3 or less.

[0137] S6. Perform denitrification and CO removal on the flue gas after desulfurization treatment to obtain purified flue gas;

[0138] After SCR denitrification and CO removal of the flue gas after desulfurization treatment, the NO X concentration in the flue gas is reduced from 200 mg / m 3 -280 mg / m 3 to 30 mg / m 3 or less, and the CO concentration is also reduced from 6000 mg / m 3 -8000 mg / m3 Reduce to 3500 mg / m 3 or less.

[0139] After adopting the purification system and method provided in the application, compared with the integrated technology of activated coke desulfurization and denitrification in the prior art, the problems such as caking of the ammonia injection layer of the activated coke module and hot spots of the module are fundamentally solved. The cleaning cycle of the activated coke module is greatly reduced from the original 10 modules / month to 2 modules / month. The amount of ammonia compounds in the activated coke module is greatly reduced, and the problems of caking of activated coke powder and hot spots in the activated coke module are effectively solved.

[0140] In addition, although activated coke has a certain effect on removing dust particles, when the circulation amount of activated coke is insufficient, the concentration of dust particles often exceeds the standard. The problem of excessive emission of dust particles discharged due to insufficient circulation amount of activated coke is fundamentally solved by the bag filter. At the same time, the lag of NO X emission adjustment is solved, and it is also reduced from the original 3 hours to about 2 minutes, avoiding the situation of sintering machine load reduction for controlling NO X emission standard while also solving the problem of excessive NO X emission. This is beneficial to the stability of sintering production and the quality of sinter. After installing the CO catalyst in the SCR denitrification module, the CO concentration is reduced from 6000 - 8000 mg / m 3 to 3000 mg / m 3 or so. At the same time, the heat released by the catalytic combustion of CO is fully utilized to preheat the flue gas to be denitrified through the HCG heat exchanger, effectively reducing the amount of gas required to heat the flue gas to be denitrified. According to statistics, the gas consumption is reduced by about 16000 m 3 / h, with a reduction rate as high as 65%.

[0141] In summary, the present invention provides an efficient flue gas circulation purification system and method, which at least has the following advantages:

[0142] 1) Adopt the integrated high-efficiency flue gas purification method of external circulation flue gas recycling, activated coke desulfurization + bag filter dust removal + SCR denitrification and CO removal, which not only uses the high temperature of the sintering material layer to remove harmful gases in the flue gas to reduce the total amount of end-of-pipe pollutant treatment, but also can give full play to the strong desulfurization ability of activated coke and the advantages of SCR denitrification and CO removal;

[0143] 2) Solve the problems in the prior art such as caking inside the activated coke module caused by spraying atomized ammonia water, poor circulation of activated coke inside the module often resulting in hot spots, excessive dust discharge outside the pipe caused by insufficient circulation amount of activated coke, long lag time for adjusting the ammonia injection amount when the NOx emission at the flue gas outlet exceeds the standard, and ammonium salt tailing at the chimney outlet caused by denitrification of the activated coke module.

[0144] 3) By adding a heat exchanger between the sintering device and the activated coke desulfurization module, the present invention realizes stable and reasonable control of the activated coke module through PID fuzzy control, which not only avoids the problem of hot spots generated in the module due to too high flue gas temperature, but also solves the problem of accelerating the corrosion of the module equipment due to too low flue gas temperature.

[0145] The above are only specific embodiments of the present application, enabling those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined in the present application can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown in the present application, but rather to the widest scope consistent with the principles and novel features claimed in the present application.

Claims

1. An efficient flue gas circulation purification system, comprising: A sintering device for generating flue gas to be purified and recycling the flue gas after dust removal treatment; A first dust removal module for performing dust removal treatment on the flue gas to be purified and transmitting the flue gas after dust removal treatment to the sintering device and the purification module; A purification module for receiving the flue gas after dust removal treatment and performing purification treatment thereon to obtain purified flue gas; The purification module includes a temperature control desulfurization module and a denitrification and CO removal module, wherein: The temperature control desulfurization module includes a heat exchanger and a desulfurization device for adjusting the temperature of the flue gas after dust removal treatment to meet the preset temperature conditions of the desulfurization device and performing desulfurization treatment on the flue gas after temperature adjustment to obtain desulfurized flue gas; The denitrification and CO removal module is used for performing denitrification and CO removal treatment on the desulfurized flue gas to obtain purified flue gas.

2. According to the efficient flue gas circulation purification system described in claim 1, the preset temperature conditions of the desulfurization device satisfy: |T - A| ≤ B, where T is the temperature of the flue gas entering the desulfurization device, A is the target temperature of the desulfurization device, and B is the set deviation temperature.

3. The efficient flue gas circulation purification system according to claim 1, wherein the denitrification and CO removal module is an SCR denitrification and CO removal device, which includes a flue gas inlet, a flue gas heating device, a denitrification catalyst module, a CO removal catalyst module, and a flue gas outlet arranged in sequence; the flue gas after desulfurization treatment enters through the flue gas inlet, and after being heated by the flue gas heating device, the heated flue gas is obtained; The heated flue gas enters the denitrification catalyst module for denitrification treatment; The flue gas after denitrification treatment undergoes CO removal treatment through a CO removal catalyst module to obtain purified flue gas; the purified flue gas is discharged through the flue gas outlet.

4. The system according to claim 1, further comprising between the desulfurization device and the denitration and CO removal module: A second dust removal module, which performs secondary dust removal on the desulfurized flue gas and then inputs it to the denitrification and CO removal module.

5. An efficient flue gas circulation purification method, comprising the following steps: Obtaining sintering flue gas to be purified; Performing first dust removal treatment on the sintering flue gas to obtain dust-removed flue gas; Dividing the dust-removed flue gas into external circulation flue gas and flue gas to be desulfurized according to a set volume ratio; Recycling the external circulation flue gas to the sintering device for high-temperature combustion treatment to obtain purified external circulation flue gas; Adjusting the temperature of the flue gas to be desulfurized to meet the preset temperature conditions of the desulfurization device and performing desulfurization treatment on the flue gas after temperature adjustment to obtain desulfurized flue gas; Performing denitrification and CO removal treatment on the desulfurized flue gas to obtain purified flue gas.

6. According to the method described in claim 5, the set volume ratio of the external circulation flue gas to the flue gas to be temperature-controlled is 1:4 to 2:

3.

7. According to the method described in claim 5, when the external circulation flue gas undergoes high-temperature combustion treatment, the combustion temperature is 1000°C to 1500°C.

8. According to the method described in claim 5, the step of adjusting the temperature of the flue gas to be desulfurized to conform to the preset temperature conditions of the desulfurization device and performing desulfurization treatment on the flue gas to be desulfurized after temperature adjustment to obtain desulfurized flue gas specifically includes: Adjusting the temperature of the flue gas to be desulfurized to the temperature T of the flue gas entering the desulfurization device; Comparing the difference |T - A| between the temperature T of the flue gas entering the desulfurization device and the target temperature A of the desulfurization device with the set deviation temperature B; If |T - A| ≤ B, then performing desulfurization treatment on the flue gas to be desulfurized after temperature adjustment to obtain desulfurized flue gas; If |T - A| > B, continue to adjust the temperature of the flue gas to be desulfurized until |T - A| ≤ B is satisfied.

9. The method according to claim 5, before subjecting the flue gas after the desulfurization treatment to denitrification and CO removal treatment to obtain the purified flue gas, further comprising: Performing a second dust removal treatment on the flue gas after the desulfurization treatment.

10. The method according to claim 5, specifically comprising subjecting the flue gas after the desulfurization treatment to denitrification and CO removal treatment to obtain the purified flue gas: Raising the temperature of the flue gas after the desulfurization treatment to a set temperature, introducing it into a denitrification catalyst module for denitrification reaction to obtain the denitrified flue gas; Introducing the denitrified flue gas into a CO removal catalyst module for CO removal reaction to obtain the purified flue gas.

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