CN112403218A

CN112403218A - Flue gas decarburization and denitration treatment system and method

Info

Publication number: CN112403218A
Application number: CN201911069860.XA
Authority: CN
Inventors: 叶恒棣; 康建刚; 魏进超; 李俊杰
Original assignee: Zhongye Changtian International Engineering Co Ltd
Current assignee: Zhongye Changtian International Engineering Co Ltd
Priority date: 2019-11-05
Filing date: 2019-11-05
Publication date: 2021-02-26
Anticipated expiration: 2039-11-05
Also published as: CN112403218B

Abstract

The invention discloses a system and a method for decarbonizing and denitrating flue gas. And the flue gas inlet pipe is connected with the air inlet of the CO reactor according to the trend of the flue gas. And the exhaust port of the CO reactor is connected with the air inlet of the SCR reactor through a first pipeline. And an exhaust port of the SCR reactor is connected with a flue gas exhaust pipe. A first heating device is arranged on the smoke inlet pipe, and a second heating device is arranged on the first pipeline. According to the scheme, organic combination is realized when CO catalytic oxidation removal is cooperated with SCR denitration, so that the CO catalyst and the SCR catalyst can be in a high-efficiency catalytic working state for a long time, and meanwhile, system heat is fully utilized, and unnecessary energy consumption is avoided. The reaction temperature of the system can be accurately regulated, the catalyst is protected, and the stable and efficient operation of the system is guaranteed.

Description

Flue gas decarburization and denitration treatment system and method

Technical Field

The invention relates to a flue gas treatment device technology, in particular to a flue gas decarburization and denitration treatment system and a flue gas decarburization and denitration treatment method, and belongs to the technical field of flue gas purification.

Background

The ultra-low emission modification of the thermal power industry is basically completed, and the non-electric field is mainly characterized by the ultra-low emission modification of steel sintering flue gas. The sintering flue gas dedusting and desulfurization process is mature, and the key and difficult point of ultralow emission is denitration, because the sintering flue gas is low in temperature, the medium-high temperature (200-350 ℃) SCR technology widely applied to the thermal power industry needs to heat the flue gas when being applied to denitration of the sintering flue gas, and a large amount of flue gas is heated to bring huge energy consumption.

The sintering flue gas contains CO (6000 mg/Nm) with higher concentration³Left and right), CO is converted to CO by catalytic oxidation₂And meanwhile, a large amount of heat can be released, if the CO catalytic oxidation technology is coupled with the SCR denitration technology, the heat emitted in the CO catalytic oxidation process is fully utilized, and the heat supplement of an external heat source to the flue gas is reduced or even avoided, the mature medium-high temperature SCR technology is expected to be directly transplanted and applied to the denitration of the sintering flue gas, and the medium-high temperature SCR denitration catalyst is low in price and easy to obtain, high in denitration efficiency, strong in sulfur poisoning resistance and long in service life, so that the sintering flue gas is efficiently, economically and environmentally-friendly to denitrate.

When the CO catalyst components are different, the reaction characteristics are different. For example, the commercial Pt/Al catalyst reaction is characterized by a typical catalytic combustion reaction, namely, when the reaction temperature reaches a certain value, the CO catalytic oxidation process is vigorously carried out, the temperature is called as the light-off temperature of the catalyst, and the light-off temperature is just like a catalytic combustion 'fuse', and the reaction is vigorously carried out after the critical point; and non-noble metal catalysts such as metal oxide catalyst systems of Cu, Co or Mn, the reaction characteristics are as follows: the reaction efficiency gradually increases to a plateau with a gradual increase in temperature, and the rate of increase in catalytic activity gradually slows down during the temperature increase.

The CO catalytic oxidation removal and SCR denitration of the sintering flue gas are respectively carried out under the action of corresponding catalysts, and the catalysts with different components have specific catalytic activity temperature windows. When the two are used for the synergistic decarbonization and denitration, the principle of selecting the CO catalytic oxidation catalyst and the SCR denitration catalyst is as follows: the optimal catalytic activity temperature windows of the two are close to each other as much as possible so as to ensure that the CO and the NOx simultaneously realize the optimal removal effect. However, the decarburization and the denitration are difficult to perfectly match in the engineering operation due to the fluctuation of the actual working conditions, the self properties of the catalyst and the like.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a system and a method for decarbonizing and denitrating flue gas, and the scheme aims to solve the problem that when CO catalytic oxidation removal is cooperated with SCR denitration, the system and the control method are organically combined. The CO catalyst and the SCR catalyst are ensured to be in a high-efficiency catalytic working state for a long time, and meanwhile, the system heat is fully utilized, so that unnecessary energy consumption is avoided. The scheme can accurately regulate and control the reaction temperature of the system, protects the catalyst, and ensures stable and efficient operation of the system.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

according to a first embodiment of the invention, a flue gas decarbonization and denitration treatment system is provided, and the system comprises a CO reactor and an SCR reactor. And the flue gas inlet pipe is connected with the air inlet of the CO reactor according to the trend of the flue gas. And the exhaust port of the CO reactor is connected with the air inlet of the SCR reactor through a first pipeline. And an exhaust port of the SCR reactor is connected with a flue gas exhaust pipe. A first heating device is arranged on the smoke inlet pipe, and a second heating device is arranged on the first pipeline.

Preferably, the system further comprises a GGH heat exchanger. The GGH heat exchanger is respectively connected with the flue gas inlet pipe and the flue gas exhaust pipe. The flue gas conveyed by the flue gas inlet pipe is subjected to heat exchange by the GGH heat exchanger and then conveyed to the gas inlet of the CO reactor. And the clean flue gas discharged by the SCR reactor is subjected to heat exchange by the GGH heat exchanger and then discharged by the flue gas exhaust pipe, and the first heating device is positioned at the downstream of the connecting position of the GGH heat exchanger and the flue gas inlet pipe.

Preferably, m layers of CO catalytic oxidation layers are arranged in the CO reactor. And n layers of SCR denitration layers are arranged in the SCR reactor.

Preferably, m and n are each independently 1 to 5, preferably 2 to 4.

Preferably, a first temperature detector, a first flow rate detector and a first CO concentration detector are arranged on a flue gas inlet pipe between the first heating device and the GGH heat exchanger.

Preferably, a second temperature detector is arranged at the air inlet of the CO reactor or at one end of the flue gas inlet pipe close to the CO reactor.

Preferably, a third temperature detector, a second flow detector and a second CO concentration detector are arranged at the exhaust port of the CO reactor or at one end of the first pipeline close to the CO reactor.

Preferably, a fourth temperature detector is disposed on the first pipeline downstream of the second heating device.

Preferably, a first cooling medium delivery pipe is externally connected to the flue gas inlet pipe between the first heating device and the second temperature detector. And a first flow control valve is arranged on the first cooling medium conveying pipe.

Preferably, a second cooling medium delivery pipe is externally connected to the first pipeline between the second heating device and the fourth temperature detector. And a second flow control valve is arranged on the second cooling medium conveying pipe. And/or

Preferably, the air inlet of the SCR reactor is further provided with a rectifier. And/or

Preferably, an ammonia spraying device is further arranged in the first pipeline between the second heating device and the rectifier.

According to a second aspect of the present invention, there is provided a flue gas decarburization and denitration treatment method using the flue gas decarburization and denitration treatment system according to the first aspect, characterized in that: the method comprises the following steps:

1) when the system is started:

1a) the original flue gas is heated by a first heating device from a flue gas inlet pipe to reach the temperature required by decarburization and then is conveyed to a CO reactor. And carrying out decarburization treatment on the raw flue gas by a CO catalytic oxidation layer in the CO reactor, and discharging the decarburized flue gas after the decarburization treatment from an exhaust port of the CO reactor.

1b) The decarbonized flue gas discharged from the exhaust port of the CO reactor is heated by a second heating device or not and then is conveyed to the SCR reactor through a first pipeline. Denitration treatment is carried out layer by SCR denitration in the SCR reactor, and the clean flue gas after denitration is discharged through a flue gas exhaust pipe after heat exchange and temperature reduction of the GGH heat exchanger.

2) In the operation process:

2a) the original flue gas is heated by heat exchange of a flue gas inlet pipe through a GGH heat exchanger, optionally heated to the temperature required by decarburization through or without a first heating device, and then conveyed to a CO reactor. In the CO reactor, the raw flue gas is decarbonized by a CO catalytic oxidation layer, and the decarbonized flue gas after the decarbonization is discharged from an exhaust port of the CO reactor 1.

2b) The decarbonized flue gas discharged from the exhaust port of the CO reactor is heated by a second heating device or not and then is conveyed to the SCR reactor through a first pipeline. Denitration treatment is carried out layer by SCR denitration in the SCR reactor, and the clean flue gas after denitration is discharged through a flue gas exhaust pipe after heat exchange and temperature reduction of the GGH heat exchanger.

Preferably, step 1a) further comprises: a first CO concentration detector is arranged on a flue gas inlet pipe between the first heating device and the GGH heat exchanger, and the initial concentration of CO in the original flue gas is detected to be a1, mg/Nm³. And a second temperature detector is arranged at the air inlet of the CO reactor or at one end of the flue gas inlet pipe close to the CO reactor, and the original flue gas temperature before decarburization is detected to be t2 and DEG C in real time. A second CO concentration detector is arranged at the exhaust outlet of the CO reactor or at one end of the first pipeline close to the CO reactor, and the concentration of CO in the decarbonized flue gas is detected to be a2, mg/Nm³。

Preferably, the optimum temperature for detecting the flue gas decarburization is t0, DEG C, and specifically comprises the following steps:

1a1) when the catalytic reaction of the catalyst adopted by the CO catalytic oxidation layer is characterized by catalytic combustion (namely when the reaction temperature reaches a certain value, the CO catalytic oxidation process is vigorously carried out): the first heating device is turned on to continuously heat the raw flue gas entering the CO reactor until the following formula is satisfied:

(a1-a2)/a1 ═ k1..

Wherein, k1 is more than or equal to 5% and less than or equal to 20% (preferably, k1 is more than or equal to 8% and less than or equal to 15%). When the formula I is established, the synchronously detected temperature value t2 is the optimal temperature t0 for the smoke decarburization.

1a2) When the catalytic reaction of the catalyst adopted by the CO catalytic oxidation layer is characterized in that the CO removal efficiency is in a slow increasing trend along with the temperature: the first heating device is turned on to continuously heat the raw flue gas entering the CO reactor until the following formula is satisfied:

(a1-a2)/a1 ═ k2..

Wherein k2 is more than or equal to 90 percent (preferably k2 is more than or equal to 95 percent), and the temperature value of t2 synchronously detected when the formula II is established is the optimal temperature t0 for the flue gas decarburization.

Preferably, step 2a) further comprises: a first temperature detector is arranged on a flue gas inlet pipe between the first heating device and the GGH heat exchanger to detect that the original flue gas temperature is t1 and DEG C. Meanwhile, a first flow detector is arranged to detect the flow of the original flue gas as q1, L/s. And a first cooling medium conveying pipe is externally connected to the flue gas inlet pipe between the first heating device and the second temperature detector, and a first flow control valve is arranged on the first cooling medium conveying pipe. Setting the safety temperature t for the decarbonization of the flue gas_{Carbon (C)}，℃。

Preferably, 2a1) when t1 < t0, the first heating device is started to heat the raw smoke so that the temperature of the raw smoke is t 2-t 0.

Preferably, 2a2) when t 0. ltoreq.t 1 < t_{Carbon (C)}And when the first heating device is not started, the system maintains the state and continues to operate.

Preferably, 2a3) at t1 ≧ t_{Carbon (C)}When the first heating device is not started, the first cooling medium conveying pipe is started to input cooling medium to cool the raw flue gas, so that the temperature of the raw flue gas is lower than t_{Carbon (C)}。

Preferably, in step 2a3), the heat dissipated when the high-temperature raw flue gas in the system is cooled to t0 is equal to the heat absorbed when the cooling medium is heated to t0, according to the heat balance principle:

C1*q1(t1-t0)＝C_cold*q3(t0-t_Cold)...III。

Wherein C1 is the specific heat capacity of the smoke, and J/(kg ℃). C_ColdThe specific heat capacity of the cooling medium is J/(kg ℃). t is t_ColdThe temperature of the cooling medium is measured in degrees centigrade. q3 is the input amount of the cooling medium, L/s.

Preferably, formula III converts to:

q3＝[C1*q1(t1-t0)]/[C_cold(t0-t_Cold)]...IV。

By controlling the first flow rate adjustment valve on the first cooling medium delivery pipe, the total flow rate of the cooling medium delivered through the first cooling medium delivery pipe is q 3.

Preferably, step 1b) and step 2b) further comprise: and a third temperature detector is arranged at the exhaust outlet of the CO reactor or at one end of the first pipeline close to the CO reactor to detect the temperature of the decarbonized flue gas to be t3 and DEG C. Meanwhile, a second flow detector is arranged to detect the flow of the decarbonized flue gas as q2, L/s. The first pipeline is internally provided with a fourth temperature detector for detecting the temperature t4 and DEG C of the flue gas before denitration. And a second cooling medium conveying pipe is externally connected to the first pipeline between the second heating device and the fourth temperature detector, and a second flow control valve is arranged on the second cooling medium conveying pipe. The optimal temperature for flue gas denitration is set to t5 and DEG C. Setting the safe temperature of flue gas denitration as t_Mirabilite，℃。

Preferably, 301) when t3 < t5, the second heating device is started to heat the decarbonized flue gas so that the temperature of the decarbonized flue gas is t 4-t 5.

Preferably, 302) when t5 ≦ t3 < t_MirabiliteAnd when the second heating device is not started, the system maintains the state and continues to operate.

Preferably, 303) when t3 ≧ t_MirabiliteWhen the second heating device is not started, the second cooling medium conveying pipe is started to input the cooling medium to cool the decarburized flue gas so that the temperature of the decarburized flue gas is lower than t_Mirabilite。

Preferably, in step 303), the heat quantity dissipated when the high-temperature decarbonized flue gas in the system is cooled to t5 is equal to the heat quantity absorbed when the cooling medium is heated to t5, according to the heat balance principle:

C2*q2(t3-t5)＝C_cold*q4(t5-t_Cold)...V。

Wherein C2 is the specific heat capacity of the decarbonized flue gas, and J/(kg ℃). C_ColdThe specific heat capacity of the cooling medium is J/(kg ℃). t is t_ColdThe temperature of the cooling medium is measured in degrees centigrade. q4 is the input amount of the cooling medium, L/s.

Preferably, formula V is converted to:

q4＝[C2*q2(t3-t5)]/[C_cold(t5-t_Cold)]...VI。

By controlling the second flow rate adjustment valve on the second cooling medium delivery pipe, the total flow rate of the cooling medium delivered through the second cooling medium delivery pipe is q 4.

Preferably, the decarbonized flue gas is subjected to ammonia injection treatment in the first duct. And/or

Preferably, the safety temperature t for the decarbonization of the flue gas_{Carbon (C)}380 ℃ and 420 ℃.

Preferably, the flue gas denitration safe temperature t_Mirabilite380 ℃ and 420 ℃.

Generally, the temperature of the flue gas after desulfurization is about 120 ℃, and the temperature of the flue gas required for CO catalytic oxidation decarburization and SCR catalytic denitration is often higher than that of the raw flue gas itself, so that in order to improve the treatment effect of the raw flue gas for decarburization and denitration, the raw flue gas is heated by an external heat source before the raw flue gas is subjected to CO catalytic oxidation decarburization or before the raw flue gas is subjected to SCR catalytic denitration so that the raw flue gas reaches the optimal temperature range for CO catalytic oxidation decarburization or the optimal temperature range for SCR catalytic denitration.

In the invention, the heating devices are respectively arranged on the flue gas conveying pipeline in front of the CO reactor and the flue gas conveying pipeline in front of the SCR reactor, so that the flue gas can be heated to the optimum temperature window for CO catalytic oxidation before decarburization, and simultaneously the flue gas is heated to the optimum temperature window for SCR catalytic oxidation before denitration, thereby ensuring that the CO and NOx of the original flue gas can be simultaneously removed optimally.

In the invention, the GGH heat exchanger is respectively connected with the flue gas inlet pipe and the flue gas outlet pipe. The flue gas conveyed by the flue gas inlet pipe is subjected to heat exchange by the GGH heat exchanger and then conveyed to the gas inlet of the CO reactor. And the clean flue gas discharged by the SCR reactor is subjected to heat exchange by the GGH heat exchanger and then discharged through a flue gas exhaust pipe. Generally, the clean flue gas subjected to denitration by the SCR reactor has the temperature of about 180-300 ℃, partial heat of the clean flue gas can be exchanged to the low-temperature desulfurized flue gas by arranging the GGH heat exchanger so as to improve the temperature of the desulfurized flue gas, so that firstly, the emission temperature of the clean flue gas can be further reduced, the environmental pollution is reduced, and simultaneously, the consumption and the heating time of energy sources required by the following steps of heating the desulfurized flue gas to the optimal temperature window required by CO catalytic oxidation or the optimal temperature window for SCR denitration treatment are reduced after the temperature of the desulfurized flue gas is increased.

In the invention, in order to further improve the decarbonization effect of the CO reactor and the denitration effect of the SCR reactor, a plurality of CO catalytic oxidation layers are arranged in the CO reactor and a plurality of SCR denitration layers are arranged in the SCR reactor, so that the problem that the flue gas is not completely decarbonized and denitrated when only a single catalytic layer is arranged is solved, the aim that another catalytic layer can continuously play a catalytic role after a certain catalytic layer is saturated and inactivated is fulfilled, meanwhile, the use periods of the CO reactor and the SCR reactor can be prolonged by arranging a plurality of catalytic layers, the times of replacing the catalytic layers can be reduced, and the continuous production capacity is enhanced.

In the invention, as CO catalytic oxidation is a continuous heat release process, and the heat of the system can be continuously transmitted to the original flue gas through the GGH reactor, the temperature of the original flue gas is a continuous change process, in order to more conveniently and accurately monitor the temperature change of the flue gas before and after decarburization and denitration, and further judge whether the temperature of the flue gas is in the optimal temperature range of decarburization and denitration, and further judge whether a hotter device is started or not started to heat the flue gas before decarburization or denitration, a first temperature detector is arranged in a flue gas inlet pipe between the first heating device and the GGH heat exchanger. And a second temperature detector is arranged at the air inlet of the CO reactor or at one end of the flue gas inlet pipe close to the CO reactor. And a third temperature detector is arranged at the exhaust port of the CO reactor or at one end of the first pipeline close to the CO reactor. And a fourth temperature detector is arranged at the downstream of the first pipeline on the second heating device. The result through above-mentioned temperature detection feedback and then can be swiftly effectual messenger's flue gas no matter be before the decarbonization or before the denitration all be in optimum temperature range, can also the energy saving simultaneously, avoid causing unnecessary extravagant (general CO catalyst is after reaching the uniform temperature, catalytic activity has become stable, continues to heat up, and its catalytic activity changes and also is little, but does so undoubtedly can consume the energy, causes the waste).

Furthermore, in order to prevent potential safety hazards caused by continuous temperature rise of flue gas (the temperature of the system is continuously accumulated or the CO concentration in the flue gas is increased to cause the heat release of CO catalytic oxidation to be increased, so that the temperature of the system is further increased), and ensure the safe and stable operation of the system, a first flow detection meter is arranged in a flue gas inlet pipe between the first heating device and the GGH heat exchanger, a second flow detection meter is arranged at an exhaust port of the CO reactor or at one end of the first pipeline close to the CO reactor, and a first cooling medium conveying pipe is externally connected to the flue gas inlet pipe between the first heating device and the second temperature detection meter. And a first flow control valve is arranged on the first cooling medium conveying pipe. And a second cooling medium conveying pipe is externally connected to the first pipeline between the second heating device and the fourth temperature detector. And a second flow control valve is arranged on the second cooling medium conveying pipe. When the temperature of the flue gas before decarburization is detected to be higher than the safe temperature of the CO catalyst, the first cooling medium conveying device conveys the cooling medium to reduce the temperature of the flue gas to the temperature required by the optimal CO catalytic oxidation, and the input amount of the cooling medium is determined by the detected flow of the flue gas and is accurately controlled by the first flow control valve. When the detected flue gas temperature before denitration is higher than the safe temperature of the SCR catalyst, the cooling medium is conveyed by the second cooling medium conveying device to reduce the flue gas temperature to the optimal temperature required by SCR catalytic oxidation, and the input amount of the cooling medium is determined by the detected flow of the flue gas and is accurately controlled by the second flow control valve.

In the present invention, since there are two types of reaction characteristics in catalytic oxidation of CO, for example, when a noble metal catalyst such as Pt/Al type is used, the reaction is characterized by catalytic combustion, and the important point of such a reaction is determination of the light-off temperature, and generally, the temperature at which the conversion of the reactant reaches 5 to 20% is defined as the light-off temperature, and as represented by t0, the catalytic oxidation of CO proceeds rapidly until the conversion of CO is completed. At this point, even if the flue gas temperature continues to be increased above the catalyst light-off temperature, there is no significant contribution to CO conversion, while the flue gas inlet temperature is below the light-off temperature, and little CO conversion occurs. When the non-noble metal catalyst is adopted, the temperature of the flue gas entering the CO reactor needs to be ensured to reach the temperature required by the maximum CO conversion value. No matter which catalyst is adopted, the temperature of the flue gas at the inlet of the CO reactor has an optimal value, when the temperature is lower, the requirement of the removal rate is difficult to meet, when the temperature is higher, unnecessary energy consumption is brought, and if the temperature of the flue gas at the inlet is higher than 400 ℃, the CO catalyst is easy to be damaged by thermal sintering and the like when being operated at a higher temperature for a long time.

Further, when the CO reaction is characterized by catalytic combustion reaction, when the system is started, the heating device in front of the CO reactor is started, the concentrations a1 and a2 of CO in front of and behind the CO reactor are monitored, when (a1-a2)/a1 is equal to k1 (k 1 is equal to or greater than 5% and equal to or less than 20%, preferably k1 is equal to or greater than 8% and equal to or less than 15%), the corresponding temperature is the ignition temperature t0, at the moment, the temperature of the flue gas at the CO inlet is t0, the flue gas is subjected to CO catalytic oxidation reaction in the CO reactor, and simultaneously emits heat to raise the temperature of the flue gas, at the moment, whether the heating device in back of the CO reactor is started and started according to the requirement of the SCR catalyst for the reaction temperature, so that the flue gas before denitration meets the requirement of. And after passing through the SCR reactor, the flue gas enters the GGH heat exchanger to transfer heat to cold flue gas at the inlet end, so that the temperature of the cold flue gas is raised, the relation between the temperature of the flue gas before decarburization and t0 is judged, and a front heating device of the CO reactor is adjusted in time. When T1 is less than T0, adjusting the heating device to ensure that T2 is T0; when t1 is more than or equal to t0, the heating device is closed.

Further, when the CO reaction is characterized in that the removal efficiency is in a slowly increasing trend along with the temperature, when the system is started, the front heating device of the CO reactor is started, the front and rear CO concentrations a1 and a2 of the CO reactor are monitored, when the (a1-a2)/a1 is equal to or more than 90% and preferably k2 is equal to or more than 95%, the CO catalyst reaches the efficient removal effect at the temperature of t2, the flue gas generates CO catalytic oxidation reaction in the CO reactor, and heat is released to increase the temperature of the flue gas at the same time, at the moment, whether the rear heating device of the CO reactor is started or not and the size of the rear heating device of the CO reactor is adjusted according to the requirement of the SCR catalyst on the reaction temperature, so that t4 meets the requirement of the SCR reaction. After passing through the SCR reactor, the flue gas enters the GGH heat exchanger to transfer heat to inlet-end cold flue gas, so that the cold flue gas is heated before decarburization, the relation between the flue gas before decarburization and t0 is judged at the moment, and the heating device is adjusted in time. When T1 is less than T0, adjusting the heating device to ensure that T2 is equal to T0; when t1 is more than or equal to t0, the heating device is closed.

In the present invention, since the catalyst used for the CO catalytic oxidation is different, the optimum catalytic temperature t0 is different.

When the catalytic reaction of the catalyst adopted by the CO catalytic oxidation layer is characterized by catalytic combustion (namely when the reaction temperature reaches a certain value, the CO catalytic oxidation process is vigorously carried out): the first heating device is turned on to continuously heat the raw flue gas entering the CO reactor until the following formula is satisfied:

(a1-a2)/a1 ═ k1..

When the catalytic reaction of the catalyst adopted by the CO catalytic oxidation layer is characterized in that the CO removal efficiency is in a slow increasing trend along with the temperature: the first heating device is turned on to continuously heat the raw flue gas entering the CO reactor until the following formula is satisfied:

(a1-a2)/a1 ═ k2..

Further, in the firstA first temperature detector is arranged on a flue gas inlet pipe between the heating device and the GGH heat exchanger to detect that the original flue gas temperature is t1 and DEG C. Meanwhile, a first flow detector is arranged to detect the flow of the original flue gas as q1, L/s. And a first cooling medium conveying pipe is externally connected to the flue gas inlet pipe between the first heating device and the second temperature detector, and a first flow control valve is arranged on the first cooling medium conveying pipe. Setting the safety temperature t for the decarbonization of the flue gas_{Carbon (C)}，℃。

When t1 < t0, the first heating device 5 is started to heat the raw smoke so that the temperature of the raw smoke is t 2-t 0.

When t0 is not less than t1 < t_{Carbon (C)}In this case, the system is maintained in this state without starting the first heating device 5.

When t1 is more than or equal to t_{Carbon (C)}In the process, the first heating device 5 is not required to be started, the first cooling medium conveying pipe is started to input cooling medium to cool the raw flue gas, so that the temperature of the raw flue gas is lower than t_{Carbon (C)}。

In the invention, the heat dissipated when the high-temperature raw flue gas in the system is cooled to t0 is equal to the heat absorbed when the cooling medium is heated to t0, according to the heat balance principle:

C1*q1(t1-t0)＝C_cold*q3(t0-t_Cold)...III。

Formula III converts to:

q3＝[C1*q1(t1-t0)]/[C_cold(t0-t_Cold)]...IV。

In the invention, a third temperature detector is arranged at the exhaust outlet of the CO reactor or at one end of the first pipeline close to the CO reactor to detect the temperature of the decarbonized flue gas to be t3℃. Meanwhile, a second flow detector is arranged to detect the flow of the decarbonized flue gasIs q2, L/s. The first pipeline is internally provided with a fourth temperature detector for detecting the temperature t4 and DEG C of the flue gas before denitration. And a second cooling medium conveying pipe is externally connected to the first pipeline between the second heating device and the fourth temperature detector, and a second flow control valve is arranged on the second cooling medium conveying pipe. The optimal temperature for flue gas denitration is set to t5 and DEG C. Setting the safe temperature of flue gas denitration as t_Mirabilite，℃。

When t3 is less than t5, the second heating device 6 is started to heat the decarbonized flue gas so that the temperature of the decarbonized flue gas is t4 to t 5.

When t5 is not less than t3 < t_MirabiliteIn this case, the second heating device 6 is not required to be started, and the system is maintained in this state and continues to operate.

When t3 is more than or equal to t_MirabiliteIn the process, the second heating device 6 does not need to be started, the second cooling medium conveying pipe 8 is started to input the cooling medium to cool the decarburized flue gas, so that the temperature of the decarburized flue gas is lower than t_Mirabilite。

In the invention, the heat dissipated when the high-temperature decarburization flue gas in the system is cooled to t5 is equal to the heat absorbed when the cooling medium is heated to t5, according to the heat balance principle:

C2*q2(t3-t5)＝C_cold*q4(t5-t_Cold)...V。

Formula V is converted to:

q4＝[C2*q2(t3-t5)]/[C_cold(t5-t_Cold)]...VI。

According to the technical scheme, the temperature of the flue gas before entering the CO reactor can be accurately controlled through the first heating device, the starting and stopping and heating power of the first heating device can be timely adjusted along with the operation of the system, and the temperature of the flue gas before entering the CO reactor can reach the optimal temperature for CO conversion through the first heating device, so that the occurrence of catalytic poisoning in the CO reactor is avoided, and the decarbonization effect of the CO reactor on the flue gas is further ensured. In addition, through the setting of first cooling medium conveyer pipe, can avoid getting into the high temperature of flue gas before the CO reactor to the safety of catalyst in the guarantee CO reactor. In short, the temperature of the flue gas before entering the CO reactor is ensured to be in a proper range through the arrangement of the first heating device and the first cooling medium conveying pipe.

According to the technical scheme, the temperature of the flue gas before entering the SCR reactor can be accurately controlled through the second heating device, the starting and stopping and heating power of the second heating device can be timely adjusted along with the operation of the system, and the temperature of the flue gas before entering the SCR reactor can reach the optimal temperature for SCR conversion through the second heating device, so that the occurrence of catalytic poisoning in the SCR reactor is avoided, and the denitration effect of the SCR reactor on the flue gas is further ensured. In addition, through the setting of second cooling medium conveyer pipe, can avoid getting into the temperature of flue gas too high before the SCR reactor to the safety of catalyst in the guarantee SCR reactor. In short, the temperature of the flue gas before entering the SCR reactor is ensured to be in a proper range through the arrangement of the second heating device and the second cooling medium conveying pipe.

In the present invention, the height of the CO reactor is from 1 to 50m, preferably from 2 to 30m, more preferably from 3 to 20 m.

In the present invention, the height of the SCR reactor is 1 to 50m, preferably 2 to 30m, more preferably 3 to 20 m.

In the present invention, the first heating device is an electric heating device or a gas heating device.

In the present invention, the second heating device is an electric heating device or a gas heating device.

Compared with the prior art, the invention has the following beneficial technical effects:

1. when the CO catalyst reaction is characterized by catalytic combustion reaction, the ignition temperature is related to physical properties such as reactant concentration, flue gas working condition of the catalyst, whether dust is deposited on the surface of the catalyst, and ammonium sulfate product adhesion besides the catalyst active components. The invention can timely judge the light-off temperature of the catalyst under a specific working condition and feed the light-off temperature back to the system heating module, so that the temperature of the flue gas inlet of the system is kept at the light-off temperature of the catalyst, and the system is ensured to operate stably and efficiently.

2. The invention can ensure that the CO catalyst and the SCR catalyst are in a high-efficiency catalytic working state for a long time, simultaneously avoids unnecessary energy consumption, fully utilizes the system heat, reduces the energy consumption and improves the economic benefit.

3. The invention can effectively avoid the unfavorable phenomena of thermal sintering and the like of the system caused by violent heat release in the CO catalytic oxidation process, and simultaneously accurately regulate and control the reaction temperature of the system, protect the catalyst and ensure the safety and the stability of the system.

Drawings

FIG. 1 is a structural diagram of a flue gas decarburization and denitration treatment system;

FIG. 2 is a structural diagram of a flue gas decarburization and denitration treatment system provided with a CO concentration detection device;

FIG. 3 is a structural diagram of a flue gas decarburization and denitration treatment system provided with a cooling mechanism.

Reference numerals: 1: a CO reactor; 101: a CO catalytic oxidation layer; 2: an SCR reactor; 201: an SCR denitration layer; 202: a rectifier; 3: an ammonia injection device; 4: a GGH heat exchanger; 5: a first heating device; 6: a second heating device; 7: a first cooling medium delivery pipe; 8: a second cooling medium delivery pipe; 9: a flue gas inlet pipe; 10: a flue gas exhaust pipe; l1: a first conduit; a1: a first CO concentration detector; a2: a second CO concentration detector; q1: a first flow detector; q2: a second flow rate detector; t1: a first temperature detector; t2: a second temperature detector; t3: a third temperature detector; t4: a fourth temperature detector; m1: a first flow control valve; m2: a first flow control valve.

Detailed Description

The technical solution of the present invention is illustrated below, and the claimed scope of the present invention includes, but is not limited to, the following examples.

A flue gas decarbonization and denitration treatment system comprises a CO reactor 1 and an SCR reactor 2. According to the trend of the flue gas, a flue gas inlet pipe 9 is connected with the air inlet of the CO reactor 1. The exhaust of the CO reactor 1 is connected to the inlet of the SCR reactor 2 via a first conduit L1. And an exhaust port of the SCR reactor 2 is connected with a flue gas exhaust pipe 10. The flue gas inlet pipe 9 is provided with a first heating device 5, and the first pipeline L1 is provided with a second heating device 6.

Preferably, the system further comprises a GGH heat exchanger 4. The GGH heat exchanger 4 is respectively connected with a flue gas inlet pipe 9 and a flue gas outlet pipe 10. The flue gas conveyed by the flue gas inlet pipe 9 is subjected to heat exchange by the GGH heat exchanger 4 and then conveyed to the gas inlet of the CO reactor 1. And the clean flue gas discharged from the SCR reactor 2 is subjected to heat exchange by the GGH heat exchanger 4 and then discharged through the flue gas exhaust pipe 10, and the first heating device 5 is positioned at the downstream of the connecting position of the GGH heat exchanger 4 and the flue gas inlet pipe 9.

Preferably, m layers of the CO catalytic oxidation layer 101 are arranged in the CO reactor 1. And n layers of SCR denitration layers 201 are arranged in the SCR reactor 2.

Preferably, m and n are each independently 1 to 5, preferably 2 to 4.

Preferably, a first temperature detector T1, a first flow rate detector Q1, and a first CO concentration detector a1 are provided in the flue gas intake pipe 9 between the first heating device 5 and the GGH heat exchanger 4.

Preferably, a second temperature detector T2 is arranged at the air inlet of the CO reactor 1 or at one end of the flue gas inlet pipe 9 close to the CO reactor 1.

Preferably, a third temperature detector T3, a second flow rate detector Q2 and a second CO concentration detector a2 are provided at the gas outlet of the CO reactor 1 or at one end of the first pipe L1 near the CO reactor 1.

Preferably, a fourth temperature detector T4 is provided on the first conduit L1 downstream of the second heating device 6.

Preferably, the flue gas inlet pipe 9 between the first heating device 5 and the second temperature detector T2 is externally connected with a first cooling medium conveying pipe 7. The first cooling medium feed pipe 7 is provided with a first flow rate control valve M1.

Preferably, the second cooling medium delivery pipe 8 is externally connected to the first pipe L1 between the second heating device 6 and the fourth temperature detector T4. The second cooling medium delivery pipe 8 is provided with a second flow rate control valve M2. And/or

Preferably, the air inlet of the SCR reactor 2 is further provided with a rectifier 202. And/or

Preferably, an ammonia injection device 3 is further arranged in the first pipeline L1 between the second heating device 6 and the rectifier 202.

Example 1

As shown in fig. 1-3, a system for decarbonizing and denitrating flue gas comprises a CO reactor 1 and an SCR reactor 2. According to the trend of the flue gas, a flue gas inlet pipe 9 is connected with the air inlet of the CO reactor 1. The exhaust of the CO reactor 1 is connected to the inlet of the SCR reactor 2 via a first conduit L1. And an exhaust port of the SCR reactor 2 is connected with a flue gas exhaust pipe 10. The flue gas inlet pipe 9 is provided with a first heating device 5, and the first pipeline L1 is provided with a second heating device 6.

Example 2

Example 1 is repeated except that the system further comprises a GGH heat exchanger 4. The GGH heat exchanger 4 is respectively connected with a flue gas inlet pipe 9 and a flue gas outlet pipe 10. The flue gas conveyed by the flue gas inlet pipe 9 is subjected to heat exchange by the GGH heat exchanger 4 and then conveyed to the gas inlet of the CO reactor 1. And the clean flue gas discharged from the SCR reactor 2 is subjected to heat exchange by the GGH heat exchanger 4 and then discharged through the flue gas exhaust pipe 10, and the first heating device 5 is positioned at the downstream of the connecting position of the GGH heat exchanger 4 and the flue gas inlet pipe 9.

Example 3

Example 2 was repeated except that the CO reactor 1 was provided with 2 CO catalytic oxidation layers 101. And 2 layers of SCR denitration layers 201 are arranged in the SCR reactor 2.

Example 4

Example 3 was repeated except that a first temperature detector T1, a first flow rate detector Q1, and a first CO concentration detector a1 were provided in the flue gas intake pipe 9 between the first heating device 5 and the GGH heat exchanger 4.

Example 5

Example 4 is repeated, except that a second temperature detector T2 is arranged at the inlet of the CO reactor 1 or at the end of the flue gas inlet 9 close to the CO reactor 1.

Example 6

Example 5 was repeated except that a third temperature detector T3, a second flow rate detector Q2 and a second CO concentration detector a2 were provided at the gas outlet of the CO reactor 1 or at the end of the first pipe L1 near the CO reactor 1.

Example 7

Example 6 was repeated except that a fourth temperature detecting gauge T4 was provided on the second heating means 6 downstream of the first conduit L1.

Example 8

Embodiment 7 is repeated, and the flue gas inlet pipe 9 between the first heating device 5 and the second temperature detector T2 is externally connected with a first cooling medium conveying pipe 7. The first cooling medium feed pipe 7 is provided with a first flow rate control valve M1.

Example 9

Example 8 was repeated except that the second cooling medium feed pipe 8 was circumscribed to the first pipe L1 between the second heating means 6 and the fourth temperature detector T4. The second cooling medium delivery pipe 8 is provided with a second flow rate control valve M2.

Working example 10

Example 9 is repeated, except that the inlet of the SCR reactor 2 is also provided with a rectifier 202.

Example 11

Example 10 is repeated except that an ammonia injection device 3 is further provided in the first conduit L1 between the second heating device 6 and the rectifier 202.

Claims

1. The utility model provides a flue gas decarbonization denitration treatment system which characterized in that: the system comprises a CO reactor (1) and an SCR reactor (2); according to the trend of the flue gas, a flue gas inlet pipe (9) is connected with an air inlet of the CO reactor (1); the exhaust port of the CO reactor (1) is connected with the air inlet of the SCR reactor (2) through a first pipeline (L1); the exhaust port of the SCR reactor (2) is connected with a flue gas exhaust pipe (10); a first heating device (5) is arranged on the flue gas inlet pipe (9), and a second heating device (6) is arranged on the first pipeline (L1).

2. The system of claim 1, wherein: the system further comprises a GGH heat exchanger (4); the GGH heat exchanger (4) is respectively connected with a flue gas inlet pipe (9) and a flue gas outlet pipe (10); the flue gas conveyed by the flue gas inlet pipe (9) is subjected to heat exchange by the GGH heat exchanger (4) and then conveyed to the gas inlet of the CO reactor (1); and the clean flue gas discharged from the SCR reactor (2) is discharged from a flue gas exhaust pipe (10) after being subjected to heat exchange by a GGH heat exchanger (4), and the first heating device (5) is positioned at the downstream of the connecting position of the GGH heat exchanger (4) and a flue gas inlet pipe (9).

3. The system according to claim 1 or 2, characterized in that: m layers of CO catalytic oxidation layers (101) are arranged in the CO reactor (1); n layers of SCR denitration layers (201) are arranged in the SCR reactor (2); wherein: m and n are each independently 1 to 5, preferably 2 to 4.

4. The system according to any one of claims 1-3, wherein: a first temperature detector (T1), a first flow rate detector (Q1) and a first CO concentration detector (A1) are arranged on a flue gas inlet pipe (9) between the first heating device (5) and the GGH heat exchanger (4); a second temperature detector (T2) is arranged at the air inlet of the CO reactor (1) or at one end of the flue gas inlet pipe (9) close to the CO reactor (1); a third temperature detector (T3), a second flow detector (Q2) and a second CO concentration detector (A2) are arranged at the air outlet of the CO reactor (1) or at one end of the first pipeline (L1) close to the CO reactor (1); a fourth temperature detector (T4) is arranged on the first pipeline (L1) downstream of the second heating device (6).

5. The system of claim 4, wherein: a first cooling medium conveying pipe (7) is externally connected to the flue gas inlet pipe (9) between the first heating device (5) and the second temperature detector (T2), and a first flow control valve (M1) is arranged on the first cooling medium conveying pipe (7); a second cooling medium conveying pipe (8) is externally connected to the first pipeline (L1) between the second heating device (6) and the fourth temperature detector (T4), and a second flow control valve (M2) is arranged on the second cooling medium conveying pipe (8); and/or

The air inlet of the SCR reactor (2) is also provided with a rectifier (202); and/or

An ammonia spraying device (3) is also arranged in the first pipeline (L1) between the second heating device (6) and the rectifier (202).

6. The flue gas decarburization and denitration treatment method using the flue gas decarburization and denitration treatment system according to any one of claims 1 to 5, characterized in that: the method comprises the following steps:

1) when the system is started:

1a) heating the raw flue gas from a flue gas inlet pipe (9) through a first heating device (5) to a temperature required by decarburization, conveying the raw flue gas to a CO reactor (1), performing decarburization treatment on the raw flue gas in the CO reactor (1) through a CO catalytic oxidation layer (101), and discharging the decarburized flue gas after decarburization from an exhaust port of the CO reactor (1);

1b) the decarbonized flue gas discharged from the exhaust port of the CO reactor (1) is heated by a second heating device (6) or not and then is conveyed to the SCR reactor (2) through a first pipeline (L1), denitration treatment is carried out on the SCR denitration layer (201) in the SCR reactor (2), and the clean flue gas after denitration is subjected to heat exchange and temperature reduction through a GGH heat exchanger (4) and then is discharged through a flue gas exhaust pipe (10);

2) in the operation process:

2a) the method comprises the following steps that raw flue gas is heated through heat exchange of a flue gas inlet pipe (9) through a GGH heat exchanger (4), optionally heated through or without a first heating device (5) to a temperature required by decarburization, and then conveyed to a CO reactor (1), decarburization treatment is carried out on the raw flue gas in the CO reactor (1) through a CO catalytic oxidation layer (101), and the decarburized flue gas after decarburization is discharged from an exhaust port of the CO reactor (1);

2b) the decarbonized flue gas discharged from the exhaust port of the CO reactor (1) is heated by a second heating device (6) or not and then is conveyed to the SCR reactor (2) through a first pipeline (L1), denitration treatment is carried out on the SCR denitration layer by layer (201) in the SCR reactor (2), and the purified flue gas after denitration is discharged through a flue gas exhaust pipe (10) after being subjected to heat exchange and temperature reduction through a GGH heat exchanger (4).

7. The method of claim 6, wherein: step 1a) further comprises: a first CO concentration detector (A1) is arranged on a flue gas inlet pipe (9) between the first heating device (5) and the GGH heat exchanger (4), and the initial concentration of CO in the original flue gas is detected to be a1 in real time, mg/Nm³(ii) a A second temperature detector (T2) is arranged at the air inlet of the CO reactor (1) or at one end of the flue gas inlet pipe (9) close to the CO reactor (1), and the original flue gas temperature before decarburization is detected to be T2 and DEG C in real time; a second CO concentration detector (A2) is arranged at the exhaust outlet of the CO reactor (1) or at one end of the first pipeline (L1) close to the CO reactor (1), and the concentration of CO in the decarbonized flue gas is detected to be a2 mg/Nm in real time³(ii) a The optimal temperature for detecting the smoke decarburization is t0 and DEG C, and specifically comprises the following steps:

1a1) when the catalytic reaction of the catalyst adopted by the CO catalytic oxidation layer (101) is characterized by catalytic combustion (namely when the reaction temperature reaches a certain value, the CO catalytic oxidation process is vigorously carried out): the first heating device (5) is switched on to continuously heat the raw flue gas entering the CO reactor (1) until the following formula is established:

(a1-a2)/a1 ═ k1... formula I;

wherein k1 is more than or equal to 5% and less than or equal to 20%; when the formula I is established, the synchronously detected temperature value t2 is the optimal temperature t0 for the smoke decarburization;

1a2) when the catalytic reaction of the catalyst adopted by the CO catalytic oxidation layer (101) is characterized in that the CO removal efficiency is in a slow increasing trend along with the temperature: the first heating device (5) is switched on to continuously heat the raw flue gas entering the CO reactor (1) until the following formula is established:

(a1-a2)/a1 ═ k2... formula II;

wherein k2 is more than or equal to 90 percent, and the synchronously detected temperature value t2 when the formula II is established is the optimal temperature t0 for the flue gas decarburization.

8. The method of claim 7, wherein: step 2a) further comprises: in the above-mentionedA first temperature detector (T1) is arranged on a flue gas inlet pipe (9) between the first heating device (5) and the GGH heat exchanger (4) to detect that the original flue gas temperature is T1℃; meanwhile, a first flow detector (Q1) is arranged to detect the flow of the original smoke as Q1, L/s; a first cooling medium conveying pipe (7) is externally connected to the flue gas inlet pipe (9) between the first heating device (5) and the second temperature detector (T2), and a first flow control valve (M1) is arranged on the first cooling medium conveying pipe (7); setting the safety temperature t for the decarbonization of the flue gas_{Carbon (C)}，℃；

2a1) When t1 is less than t0, the first heating device (5) is started to heat the raw smoke so that the temperature of the raw smoke is t 2-t 0;

2a2) when t0 is not less than t1 < t_{Carbon (C)}When the system is in the normal state, the first heating device (5) is not started, and the system keeps the state to continue to operate;

2a3) when t1 is more than or equal to t_{Carbon (C)}When the first heating device (5) is not started, the first cooling medium conveying pipe (7) is started to input cooling medium to cool the raw flue gas so that the temperature of the raw flue gas is lower than t_{Carbon (C)}。

9. The method of claim 8, wherein: in step 2a3), the heat dissipated when the high-temperature raw flue gas in the system is cooled to t0 is equal to the heat absorbed when the cooling medium is heated to t0, according to the heat balance principle:

C1*q1(t1-t0)＝C_cold*q3(t0-t_Cold)...III；

Wherein C1 is the specific heat capacity of the flue gas, J/(kg ℃); c_ColdIs the specific heat capacity of the cooling medium, J/(kg ℃); t is t_ColdThe temperature of the cooling medium, DEG C; q3 is the input quantity of the cooling medium, L/s;

formula III converts to:

q3＝[C1*q1(t1-t0)]/[C_cold(t0-t_Cold)]...IV；

By controlling the first flow rate adjustment valve (M1) on the first cooling medium delivery pipe (7), the total flow rate of the cooling medium delivered through the first cooling medium delivery pipe (7) is made q 3.

10. According to any of claims 6-9A method as described, characterized by: step 1b) and step 2b) further comprise: a third temperature detector (T3) is arranged at the exhaust outlet of the CO reactor (1) or at one end of the first pipeline (L1) close to the CO reactor (1) to detect the temperature of the decarbonized flue gas as T3 and DEG C; meanwhile, a second flow detector (Q2) is arranged to detect the flow of the decarbonized flue gas as Q2, L/s; a fourth temperature detector (T4) is arranged in the first pipeline (L1) and used for detecting the temperature of the flue gas before denitration to be T4 and DEG C; a second cooling medium conveying pipe (8) is externally connected to the first pipeline (L1) between the second heating device (6) and the fourth temperature detector (T4), and a second flow control valve (M2) is arranged on the second cooling medium conveying pipe (8); setting the optimal temperature of flue gas denitration as t5 and DEG C; setting the safe temperature of flue gas denitration as t_Mirabilite，℃；

301) When t3 is less than t5, the second heating device (6) is started to heat the decarburization flue gas so that the temperature of the decarburization flue gas is t 4-t 5;

302) when t5 is not less than t3 < t_MirabiliteWhen the system is in the normal state, the second heating device (6) is not started, and the system keeps the state to continue to operate;

303) when t3 is more than or equal to t_MirabiliteWhen the second heating device (6) is not started, the second cooling medium conveying pipe (8) is started to input cooling medium to cool the decarbonized flue gas so that the temperature of the decarbonized flue gas is lower than t_Mirabilite。

11. The method of claim 10, wherein: in the step 303), the heat dissipated when the high-temperature decarbonized flue gas in the system is cooled to t5 is equal to the heat absorbed when the cooling medium is heated to t5, according to the heat balance principle:

C2*q2(t3-t5)＝C_cold*q4(t5-t_Cold)...V；

Wherein C2 is the specific heat capacity of the decarbonized flue gas, and J/(kg ℃); c_ColdIs the specific heat capacity of the cooling medium, J/(kg ℃); t is t_ColdThe temperature of the cooling medium, DEG C; q4 is the input quantity of the cooling medium, L/s;

formula V is converted to:

q4＝[C2*q2(t3-t5)]/[C_cold(t5-t_Cold)]...VI；

By controlling the second flow rate adjustment valve (M2) on the second cooling medium delivery pipe 8), the total flow rate of the cooling medium delivered through the second cooling medium delivery pipe 8 is made q 4.

12. The method according to any one of claims 7-11, wherein: performing ammonia spraying treatment on the decarbonized flue gas in a first pipeline (L1); and/or

The safety temperature t of the decarbonization of the flue gas_{Carbon (C)}380 ℃ and 420 ℃; flue gas denitration safe temperature t_Mirabilite380 ℃ and 420 ℃.