Integrated reaction device, system and method for embedded scr denitration and heat exchange

Abstract

The application relates to the technical field of industrial flue gas denitration and waste heat recovery, and particularly discloses an embedded SCR denitration-heat exchange integrated reaction device, system and method. x The SCR denitration unit is located at the core position of the device and is used for removing NOx in flue gas discharged from a preheating II section of a chain grate-rotary kiln The heat exchange unit is arranged in a shell flue around the SCR denitration unit, heat exchange between flue gas discharged from the preheating II section and flue gas before entering a blast drying section is realized. The application has a small land occupation area, can effectively adjust the flue gas temperature before SCR denitration and before the blast drying section, helps to inhibit the generation of N2O by-products in high-temperature flue gas, and solves the problem that the existing embedded SCR denitration technology has too high temperature, leading to an increase in by-products.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of industrial flue gas denitrification and waste heat recovery, and particularly relates to an embedded SCR denitrification-heat exchange integrated reaction device, system and method. BACKGROUND

[0002] As the main process of pellet production in the metallurgical industry, the chain grate-rotary kiln system has a high proportion in the total production capacity of pellets due to its strong fuel adaptability and high thermal efficiency. The high-temperature section (preheating stage II of the chain grate to the rotary kiln) is a concentrated NOx generation zone, and the peak value of NOx concentration in the measured flue gas can reach 500-800 mg / m 3 mg / m 3 , and the preheating stage II front part has two to three times higher NOx generation intensity than other sections due to the synergistic effect of the oxidizing atmosphere and the high temperature of 900-1300 DEG C in the rear part of the rotary kiln, constituting the main pollution source. The traditional end denitrification technology uses multi-stage ammonia injection or post-SCR device, which has the disadvantages of high ammonia escape rate and large heat supplement energy consumption, and is difficult to meet the green production demand of low energy consumption and low by-products.

[0003] CN214680987U discloses a chain grate-rotary kiln embedded SCR+SNCR flue gas denitrification device. According to the main source of NOx in the flue gas discharged by the chain grate-rotary kiln, combined with the principle of the pellet air flow system, the SNCR denitrification system is arranged in the preheating stage II as the primary denitrification; the SCR denitrification device is arranged between the multi-tube dust collector and the regenerative air fan in the pellet process air flow system as the secondary denitrification, and the flue gas after NOx removal is returned to the chain grate suction drying section through the regenerative air fan. Although the device system can significantly reduce energy consumption and operating cost compared with the most commonly used main suction post full flue gas denitrification system, the flue gas temperature between the multi-tube dust collector and the regenerative air fan is too high (350-500 DEG C), and direct denitrification can easily lead to strong oxidation reaction of the reducing agent on the surface of the catalyst, generating a large amount of by-product N2O and reducing the denitrification efficiency.

[0004] The existing improvement scheme focuses on single temperature zone optimization (such as preheating stage II strengthening denitrification or ring cooler flue gas external heat supplement), but fails to solve the problem of differentiated processing of flue gas in multiple temperature zones from the perspective of heat energy cascade utilization-gas path closed loop regulation, resulting in difficulty in achieving both denitrification efficiency and system energy efficiency. Therefore, it is urgent to develop an integrated denitrification-waste heat recovery device to simultaneously achieve the dual goals of by-product inhibition in the high-temperature section and drying efficiency improvement of low-temperature flue gas by dynamically adjusting the heat source distribution and air flow path, and to provide technical support for low-carbon transformation of the metallurgical industry. SUMMARY

[0005] The purpose of the present application is to provide an embedded SCR denitrification-heat exchange integrated reaction device, system and method to solve the problems existing in the prior art.

[0006] To achieve the above object, the application provides an embedded SCR denitration-heat exchange integrated reaction device, which comprises:

[0007] An SCR denitration unit, a flue gas inlet of the SCR denitration unit is connected with a flue gas outlet of the chain grate preheating II section, and the SCR denitration unit is used for removing NOx in flue gas discharged by the chain grate preheating II section x ;

[0008] A heat exchange unit, the heat exchange unit is arranged in multiple independent shell flues outside the SCR denitration unit, and the heat exchange unit is used for realizing heat exchange between flue gas discharged by the chain grate preheating II section and flue gas discharged by a second cooling section of a circular cooler; a valve for gradient adjustment of a heat exchange area is arranged on the shell flue.

[0009] Preferably, the shell flue comprises a denitration flue gas layer and a drying flue gas layer, the SCR denitration unit is arranged inside the drying flue gas layer, the denitration flue gas layer is arranged outside the drying flue gas layer, the denitration flue gas layer is communicated with a top of the SCR denitration unit, a flue gas outlet of the chain grate preheating II section is communicated with the denitration flue gas layer, and a flue gas outlet of the second cooling section of the circular cooler is communicated with the drying flue gas layer.

[0010] Flue gas discharged from a bottom of the SCR denitration unit and flue gas discharged from the drying flue gas layer are both used for drying pellet ore raw materials of a drying section of the chain grate.

[0011] Preferably, the SCR denitration unit comprises an ammonia injection device, an SCR reactor and an SCR catalyst arranged in sequence from top to bottom.

[0012] Preferably, the SCR catalyst comprises a vanadium-tungsten-titanium catalyst and / or a vanadium-molybdenum-titanium catalyst.

[0013] An embedded SCR denitration-heat exchange integrated reaction system, which comprises a circular cooler, a rotary kiln, a chain grate, a dust collector, a desulfurization tower and a chimney, and further comprises the embedded SCR denitration-heat exchange integrated reaction device.

[0014] An embedded SCR denitration-heat exchange integrated reaction method, which is performed by using the embedded SCR denitration-heat exchange integrated reaction system.

[0015] Preferably, the method comprises the following steps:

[0016] High-temperature flue gas discharged by the chain grate preheating II section is used as a hot-end gas flow, and the hot-end gas flow is cooled after heat exchange with flue gas of the denitration flue gas layer and the drying flue gas layer.

[0017] After the temperature drops, the hot end gas flow is mixed with the ammonia source through the ammonia injection device, and then enters the SCR reactor to carry out the denitrification reaction under the action of the SCR catalyst to obtain denitrified flue gas.

[0018] The flue gas discharged from the second cooling section of the annular cooler serves as the cold-end airflow. The cold-end airflow enters the drying flue gas layer and exchanges heat with the denitrification flue gas layer and the hot-end airflow in the SCR denitrification unit. After the temperature rises, the cold-end airflow enters the drying section of the chain grate machine to dry the pellet raw materials.

[0019] Preferably, the high-temperature flue gas discharged from the preheating stage II of the chain grate machine has a temperature of 350-500°C and contains NO. x The concentration is 500-800 mg / m³ 3 The temperature of the hot-end airflow is 250-320°C after heat exchange with the flue gas in the denitrification flue gas layer and the drying flue gas layer.

[0020] Preferably, the NO in the denitrified flue gas is... x The concentration is 20-40 mg / m³ 3 .

[0021] Preferably, the flue gas temperature discharged from the second cooling section of the annular cooler is 80-150°C, and the temperature of the cold-end airflow after heat exchange is 180-230°C.

[0022] Compared with the prior art, the present invention has the following advantages and technical effects:

[0023] 1. The embedded SCR denitrification-heat exchange integrated reaction device provided by the present invention organically combines the SCR denitrification unit and the heat exchange unit, which greatly reduces the footprint of the equipment and can effectively regulate the flue gas temperature before SCR denitrification and before the blower drying section. It helps to suppress the generation of N2O byproducts in high-temperature flue gas and solves the problem of excessive temperature leading to increased byproducts in existing embedded SCR denitrification technology.

[0024] 2. This invention overcomes the problems of excessive N2O byproducts and low denitrification efficiency caused by excessively high flue gas temperature in the prior art. Combined with the pellet production process, it effectively adjusts the flue gas temperature before SCR denitrification and before the blower drying section, thereby improving the efficiency of flue gas waste heat utilization and showing good application prospects. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 A schematic diagram of the embedded SCR denitration-heat exchange integrated reaction system of the present application;

[0027] Figure 2 A front view of the embedded SCR denitration-heat exchange integrated reaction device of the present application;

[0028] Figure 3 A top view of the embedded SCR denitration-heat exchange integrated reaction device of the present application;

[0029] Figure 4 A schematic diagram of the embedded SCR denitration system provided in the comparative example;

[0030] In the figure: 1, SCR denitration unit; 2, heat exchange unit; 3, circular cooler; 4, rotary kiln; 5, chain grate machine; 6, dust collector; 7, desulfurization tower; 8, chimney; 11, ammonia injection device; 12, SCR reactor; 13, SCR catalyst; 21, denitration flue gas layer; 22, dry flue gas layer. DETAILED DESCRIPTION

[0031] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The described embodiments are only part of the embodiments of the present application, not all. All other embodiments obtained by a person of ordinary skill in the art without creative labor fall within the scope of protection of the present application. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0032] As shown in Figures 1 to 3 , the present application provides an embedded SCR denitration-heat exchange integrated reaction device, comprising:

[0033] The SCR denitration unit 1 is connected with the flue gas outlet of the second preheating section of the chain grate machine 5, and the SCR denitration unit 1 is used to remove NOx in the flue gas discharged by the second preheating section of the chain grate machine 5. x

[0034] The heat exchange unit 2 is arranged in multiple independent shell flues outside the SCR denitration unit 1, and the heat exchange unit 2 is used to realize heat exchange between the flue gas discharged by the second preheating section of the chain grate machine 5 and the flue gas discharged by the second cooling section of the circular cooler 3; a valve for gradient adjustment of the heat exchange area is arranged on the shell flue.

[0035] ​Further optimization scheme, the shell flue includes denitration flue gas layer 21 and dry flue gas layer 22, the SCR denitration unit 1 is arranged at the inner side of the dry flue gas layer 22, the denitration flue gas layer 21 is arranged at the outer side of the dry flue gas layer 22, the denitration flue gas layer 21 is communicated with the top of the SCR denitration unit 1, the flue gas outlet of the second preheating section of the chain grate 5 is communicated with the denitration flue gas layer 21, and the flue gas outlet of the second cooling section of the ring cooler 3 is communicated with the dry flue gas layer 22.

[0036] The flue gas discharged from the bottom of the SCR denitration unit 1 and the flue gas discharged from the dry flue gas layer 22 are used for drying the pellet ore raw materials in the drying section of the chain grate 5.

[0037] Further optimization scheme, the SCR denitration unit 1 includes the ammonia injection device 11, the SCR reactor 12 and the SCR catalyst 13 arranged in sequence from top to bottom.

[0038] Further optimization scheme, the SCR catalyst 13 includes vanadium-tungsten-titanium catalyst and / or vanadium-molybdenum-titanium catalyst.

[0039] An embedded SCR denitration-heat exchange integrated reaction system, comprising a ring cooler 3, a rotary kiln 4, a chain grate 5, a dust collector 6, a desulfurization tower 7 and a chimney 8, and further comprising the embedded SCR denitration-heat exchange integrated reaction device.

[0040] An embedded SCR denitration-heat exchange integrated reaction method, which is performed by using the embedded SCR denitration-heat exchange integrated reaction system.

[0041] Further optimization scheme, the method comprises the following steps:

[0042] The high-temperature flue gas discharged from the second preheating section of the chain grate 5 is used as a hot-end gas flow, and the hot-end gas flow is heat-exchanged with the flue gas in the denitration flue gas layer 21 and the dry flue gas layer 22, so that the temperature of the hot-end gas flow is lowered;

[0043] The hot-end gas flow with lowered temperature is mixed with an ammonia source by the ammonia injection device 11, and then enters the SCR reactor 12 to perform a denitration reaction under the action of the SCR catalyst 13, so that flue gas after denitration is obtained;

[0044] The flue gas discharged from the second cooling section of the ring cooler 3 is used as a cold-end gas flow, and the cold-end gas flow is heat-exchanged with the hot-end gas flow in the denitration flue gas layer 21 and the SCR denitration unit 1, so that the temperature of the cold-end gas flow is raised, and the cold-end gas flow with raised temperature is used to dry the pellet ore raw materials in the drying section of the chain grate 5.

[0045] Further optimization scheme, the high-temperature flue gas discharged from the second preheating section of the chain grate 5, the temperature of the high-temperature flue gas is 350-500 ℃, and the concentration of NOx in the high-temperature flue gas is 500-800 mg / m3. x 3 ​; the hot end gas stream is heated by the flue gas of the dry flue gas layer 22 after passing through the denitration flue gas layer 21, and the temperature of the hot end gas stream is 250-320℃.

[0046] Further optimization scheme, the concentration of NO x in the flue gas after denitration is 20-40mg / m 3 .

[0047] Further optimization scheme, the temperature of the flue gas discharged from the second cooling section of the ring cooler 3 is 80-150℃, and the temperature of the cold end gas stream after heat exchange is 180-230℃.

[0048] Embodiment 1

[0049] The embodiment provides an embedded SCR denitration-heat exchange integrated reaction device system, which comprises an SCR denitration unit 1 and a heat exchange unit 2; the SCR denitration unit 1 is located at the core position of the device, and is used for removing NO x in the flue gas after the preheating II section of the chain grate 5-rotary kiln 4; the heat exchange unit 2 is arranged in the shell flue around the SCR denitration unit 1, so as to realize heat exchange between the flue gas after the preheating II section and the flue gas before the blast drying section. The shell flues are independent of each other, are provided with valves, and can gradiently adjust the heat exchange area, so as to facilitate control of the heat exchange efficiency.

[0050] The flue gas inlet of the SCR denitration unit 1 is connected with the flue gas outlet of the preheating II section of the chain grate 5-rotary kiln 4, the flue gas outlet of the SCR denitration unit 1 is connected with the flue gas inlet of the blast drying section of the chain grate 5-rotary kiln 4, the SCR denitration unit 1 is composed of an ammonia injection device 11, an SCR reactor 12 and an SCR catalyst 13; the heat exchange unit 2 is arranged in the four shell flues around the SCR denitration unit 1, so as to realize heat exchange between the flue gas after the preheating II section and the flue gas before the blast drying section.

[0051] The four shell flues are divided into two layers, the outermost layer is a denitration flue gas layer 21, the second layer is a dry flue gas layer 22, and the middle of the device is an SCR denitration reaction area; the flue gas inlet of the dry flue gas layer 22 is connected with the flue gas outlet of the second cooling section of the ring cooler 3, and the flue gas outlet of the dry flue gas layer 22 is connected with the flue gas inlet of the blast drying section of the chain grate 5-rotary kiln 4; the denitration flue gas layer 21 and the dry flue gas layer 22 are not connected, the four faces of each layer are independent of each other, are provided with valves, and can gradiently adjust the heat exchange area, so as to facilitate control of the temperature of the flue gas after heat exchange.

[0052] The temperature of the flue gas before denitration is 500℃, the concentration of NO x is 800mg / m 3; the flue gas before denitration as a hot end gas flow, after heat exchange with the flue gas of the dry flue gas layer 22, the temperature of the flue gas is 320℃; then mixed with ammonia source by the ammonia injection device 11, enters the SCR reactor 12, and denitration reaction is carried out under the action of the SCR catalyst 13, and the flue gas after denitration is obtained, and the concentration of NO x 3 .

[0053] The flue gas of the dry flue gas layer 22 is the flue gas after the second cooling section, and the temperature of the flue gas is 80℃; the flue gas as a cold end gas flow enters the dry flue gas layer 22 and exchanges heat with the flue gas of the denitration flue gas layer 21 and the SCR denitration reaction zone, and the temperature after heat exchange is 230℃, and then enters the drying section of the grate 5 to dry the pellet ore raw material.

[0054] Comparative Example 1

[0055] The present comparative example provides a kind of existing embedded SCR denitration device system, as shown in Figure Figure 4 , device system only includes SCR denitration unit 1, the flue gas inlet of SCR denitration unit 1 is connected with the flue gas outlet of chain grate 5-rotary kiln 4 preheating II section, the flue gas outlet of SCR denitration unit 1 is connected with the flue gas inlet of chain grate 5-rotary kiln 4 blast drying section; The flue gas outlet of the second cooling section of the circular cooler 3 is directly connected with the flue gas inlet of the blast drying section of the chain grate 5-rotary kiln 4, and does not exchange heat with the flue gas before denitration.

[0056] The infrared flue gas analyzer is used to detect the concentration of NO x in the purified flue gas and the flue gas temperature, and the results are shown in Table 1.

[0057] Table 1

[0058] SCR reaction temperature N2O concentration after denitration De-NOx NO x Concentration De-NOx efficiency Example 1 320℃ 0 32 ppm 96％ Comparative Example 1 480℃ 40 ppm 120 ppm 85％

[0059] The existing embedded SCR denitration device system, the temperature of the flue gas after the preheating II section of the chain grate 5-rotary kiln 4 is 350-500℃, which leads to strong oxidation reaction of the reducing agent on the surface of the catalyst at high temperature, generates a large amount of by-product N2O, and the denitration efficiency is low.

[0060] ​The device system provided by the application organically combines the SCR denitration unit 1 and the heat exchange unit 2, places the SCR denitration unit 1 in the central region of the device, and sets the dry flue gas layer 22 and the denitration flue gas layer 21 around the SCR denitration unit 1, so that the flue gas discharged after the preheating II enters the denitration flue gas layer 21 and the dry flue gas layer 22 to exchange heat with the flue gas before entering the air blowing drying section, thereby effectively adjusting the flue gas temperature before the SCR denitration and before the air blowing drying section, and helping to inhibit the generation of N2O by-products in the high-temperature flue gas. Therefore, the device system provided by the application is beneficial to solve the problem of excessive by-products caused by excessively high temperature in the existing embedded SCR denitration technology, and has important significance for efficient denitration of pellet flue gas.

[0061] The above is only a preferred specific embodiment of the application, but the protection scope of the application is not limited thereto, and any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the application, which should be covered within the protection scope of the application.

Claims

1. An embedded SCR denitration-heat exchange integrated reaction device, characterized in that, The application relates to a built-in SCR denitration-heat exchange integrated reaction device. The SCR denitration unit (1) is connected with the flue gas outlet of the chain grate (5) preheating II section, and is used for removing NO in the flue gas discharged from the chain grate (5) preheating II section x ; The heat exchange unit (2) is arranged in multiple independent shell flues outside the SCR denitration unit (1), and is used for realizing heat exchange between flue gas discharged from a preheating II section of the chain grate machine (5) and flue gas discharged from a second cooling section of the ring cooler (3); and a valve for gradient adjustment of a heat exchange area is arranged on the shell flue.

2. The embedded SCR De-NOx heat exchange integrated reaction device according to claim 1, characterized in that, The shell flue comprises a denitration flue gas layer (21) and a drying flue gas layer (22), the SCR denitration unit (1) is arranged inside the drying flue gas layer (22), the denitration flue gas layer (21) is arranged outside the drying flue gas layer (22), the denitration flue gas layer (21) is communicated with the top of the SCR denitration unit (1), the flue gas outlet of the preheating II section of the chain grate machine (5) is communicated with the denitration flue gas layer (21), and the flue gas outlet of the second cooling section of the ring cooler (3) is communicated with the drying flue gas layer (22). The flue gas discharged from the bottom of the SCR denitration unit (1) and the flue gas discharged from the drying flue gas layer (22) are used for drying the pellet ore raw material in the drying section of the chain grate machine (5).

3. The embedded SCR de-NOx heat exchange integrated reaction device according to claim 1, characterized in that, The SCR denitration unit (1) comprises, from top to bottom, an ammonia injection device (11), an SCR reactor (12) and an SCR catalyst (13).

4. The embedded SCR De-NOx heat exchange integrated reaction device according to claim 3, characterized in that, The SCR catalyst (13) comprises a vanadium-tungsten-titanium catalyst and / or a vanadium-molybdenum-titanium catalyst.

5. An embedded SCR denitration-heat exchange integrated reaction system, comprising a circular cooler (3), a rotary kiln (4), a chain grate machine (5), a dust collector (6), a desulfurization tower (7) and a chimney (8), characterized in that, The application further relates to the built-in SCR denitration-heat exchange integrated reaction device.

6. A method for embedded SCR denitration and heat exchange integrated reaction, characterized in that, The application further relates to an SCR denitration-heat exchange integrated reaction system.

7. The method of claim 6, wherein, The application further relates to a method for realizing the built-in SCR denitration-heat exchange integrated reaction device. The high-temperature flue gas discharged from the preheating II section of the chain grate machine (5) is used as a hot-end gas flow, the hot-end gas flow is subjected to heat exchange with flue gas in the denitration flue gas layer (21) and the drying flue gas layer (22), and the temperature of the hot-end gas flow is lowered; The hot-end gas flow after the temperature is lowered is mixed with an ammonia source through the ammonia injection device (11), enters the SCR reactor (12) and is subjected to a denitration reaction under the action of the SCR catalyst (13), and denitration flue gas is obtained; The flue gas discharged from the second cooling section of the ring cooler (3) is used as a cold-end gas flow, the cold-end gas flow is subjected to heat exchange with the hot-end gas flow in the denitration flue gas layer (21) and the SCR denitration unit (1), the temperature of the cold-end gas flow is increased, and the cold-end gas flow is used for drying the pellet ore raw material in the drying section of the chain grate machine (5).

8. The method of claim 7, wherein, The chain grate (5) preheats high-temperature flue gas discharged from the second stage, the temperature of the high-temperature flue gas is 350-500 DEG C, the concentration of NOx in the high-temperature flue gas is 500-800 mg / m x 3 ; after the heat exchange of the hot-end gas flow with the flue gas of the dry flue gas layer (22) through the denitration flue gas layer (21), the temperature of the hot-end gas flow is 250-320 DEG C.​ 9. The method of claim 8, wherein, NO in the denitrification flue gas x The concentration is 20-40 mg / m³ 3 .

10. The method of claim 7, wherein, The temperature of the flue gas discharged from the second cooling section of the ring cooler (3) is 80-150 DEG C, and the temperature of the cold-end gas flow after heat exchange is 180-230 DEG C.

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