Acrylonitrile tail gas low emission incineration treatment system and process

Abstract

This application discloses a low-emission incineration treatment system for acrylonitrile tail gas, relating to the field of environmentally friendly chemical waste treatment. The system includes a two-stage incinerator, a waste heat boiler, an air preheater, a secondary tail gas preheater, an economizer, a primary tail gas preheater, and a chimney. It is energy-efficient and highly effective, achieving low NOx emissions from acrylonitrile tail gas produced through high-flow, multi-stage blending. x emission.

Description

Technical Field

[0001] This invention belongs to the field of environmental protection treatment of chemical waste, specifically relating to a low-emission incineration treatment system and process for acrylonitrile tail gas. Background Technology

[0002] Acrylonitrile tail gas is characterized by large volume, high toxicity, and low calorific value, typically fluctuating within 30% to 110% of its design load. High-temperature incineration (HTI) is a simple, stable, and efficient process that meets the high reliability requirements for acrylonitrile tail gas incineration, achieving complete decomposition of harmful components in the tail gas. Therefore, HTI is an excellent solution for the environmentally friendly treatment of acrylonitrile tail gas.

[0003] Patent application number 201410037578.4, entitled "A Process and System for Treating Acrylonitrile Tail Gas by High-Temperature Incineration," describes an incineration process for treating acrylonitrile tail gas. It employs a continuous regenerative heat exchanger to preheat the tail gas and combustion air separately. However, this regenerative heat exchanger has a complex structure and poor reliability. Furthermore, the patent uses a vertical incinerator, requiring a vertical frame, which makes maintenance and operation inconvenient. This patent only addresses localized oxygen deficiency in a small portion of the space at the burner outlet, failing to achieve low NO₂ levels in large-flow, multi-stage blended acrylonitrile tail gas. x emission. Summary of the Invention

[0004] The technical problem solved by this application is to overcome the shortcomings of the existing technology and provide a low-emission incineration treatment process for acrylonitrile tail gas. This process is compact, energy-efficient, and produces low nitrogen emissions, achieving low NOx emissions from large-flow, multi-stage blended acrylonitrile tail gas. x emission.

[0005] The technical solution provided in this application is as follows:

[0006] In the first aspect, a low-emission incineration treatment system for acrylonitrile tail gas is provided, including a two-stage incinerator, a waste heat boiler, an air preheater, a secondary tail gas preheater, an economizer, a primary tail gas preheater, and a chimney.

[0007] The waste heat boiler includes a boiler shell with a boiler heat exchange channel inside; the air preheater includes an air preheating shell with an air preheating channel inside, where secondary air passes through the air preheating channel to obtain reducing and oxidizing air; the secondary exhaust gas preheater includes a secondary preheating shell with a secondary preheating flow channel inside; the economizer includes an economizer shell with an economizer flow channel inside, where boiler feedwater first passes through the economizer flow channel and then enters the boiler heat exchange channel; the primary exhaust gas preheater includes a primary preheating shell with a primary preheating flow channel inside, where acrylonitrile exhaust gas flows out from the primary preheating flow channel to obtain preheated acrylonitrile exhaust gas, which then flows out through the secondary preheating flow channel to obtain high-temperature acrylonitrile exhaust gas;

[0008] High-temperature acrylonitrile tail gas, fuel gas, reducing air and oxidizing air enter the two-stage incinerator and are burned inside the two-stage incinerator;

[0009] The other end of the dual-stage incinerator, the boiler shell of the waste heat boiler, the air preheating shell of the air preheater, the secondary preheating shell of the secondary tail gas preheater, the economizer's economizer shell, and the primary preheating shell of the primary tail gas preheater are connected in sequence, and the outlet of the primary preheating shell is connected to the chimney.

[0010] The dual-stage incinerator includes a reduction section and an oxidation section. The outlet of the oxidation section is connected to the waste heat boiler. The volume of the reduction section accounts for 50% of the dual-stage incinerator. High-temperature acrylonitrile tail gas, fuel gas, and reducing air enter from the end of the reduction section away from the oxidation section; the oxidation air enters from the position of the oxidation section close to the reduction section.

[0011] The oxygen deficiency coefficient of the reduction section ranges from 0.8 to 0.95;

[0012] The reducing air has a substoichiometric ratio with the fuel gas and high-temperature acrylonitrile tail gas entering the reduction section, and the excess air coefficient in the reduction section ranges from 0.7 to 0.95.

[0013] A flue gas component analyzer is installed at the end of the reduction section to determine the degree of flue gas reduction in real time, and the oxygen deficiency coefficient of the reduction section is controlled by adjusting the reduction air volume.

[0014] The reduction section is equipped with a first reducing agent spray gun, through which ammonia water, ammonia gas, or urea are sprayed into the furnace. The molar flow rate of ammonia gas or urea is 5%-25% of the molar flow rate of fuel gas.

[0015] The oxidation section is equipped with a second reducing agent spray gun, through which ammonia water, ammonia gas, or urea are sprayed into the oxidation section to dissolve the generated NO through an SNCR reaction. X Convert to N2.

[0016] The oxygen content at the outlet of the oxidation section is 2% to 6%.

[0017] The reduction section of the dual-stage incinerator is equipped with a burner. The fuel gas pipeline includes two lines: primary fuel gas and secondary fuel gas. The primary fuel gas enters the burner together with the low stoichiometric ratio combustion air and enters the reduction section of the dual-stage incinerator after being ignited by the burner. The secondary fuel gas enters the reduction section of the dual-stage incinerator directly.

[0018] The primary fuel gas accounts for approximately 50% to 80% of the total fuel gas; the secondary fuel gas accounts for approximately 20% to 50% of the total fuel gas.

[0019] Secondly, a low-emission incineration treatment process for acrylonitrile tail gas is provided, based on the acrylonitrile tail gas low-emission incineration treatment system described in any one of the above claims, comprising:

[0020] Acrylonitrile tail gas enters the first-stage tail gas preheater and is preheated to 150℃~200℃ to obtain preheated acrylonitrile tail gas; the preheated acrylonitrile tail gas enters the second-stage tail gas preheater and is further heated to 400℃-500℃ to obtain high-temperature acrylonitrile tail gas.

[0021] High-temperature acrylonitrile tail gas, combustion air, reduction air, and oxidation air enter the two-stage incinerator to generate high-temperature flue gas of 800℃~950℃. The 800℃~950℃ high-temperature flue gas first enters the waste heat boiler, where it is cooled to 600℃~700℃ and then flows through the air preheater. The flue gas temperature exiting the air preheater is about 500℃~600℃. It then flows through the secondary tail gas preheater, where the flue gas temperature drops to 300℃~400℃. It then enters the economizer, where the flue gas temperature drops to 200℃~300℃. It then enters the primary tail gas preheater, where the flue gas temperature drops to 120℃~150℃ and is finally discharged through the chimney.

[0022] In summary, this application includes at least the following beneficial technical effects:

[0023] (1) The acrylonitrile tail gas incineration treatment process of the present invention adopts a two-stage tail gas preheater and a one-stage air preheater, which brings most of the energy of the flue gas back, reduces the fuel burned by the burner, and maximizes the reuse of flue gas energy at the system level, ensuring that the incineration system is highly efficient and energy-saving.

[0024] (2) The acrylonitrile tail gas incineration treatment process involved in this invention adopts a two-stage incinerator with self-denitrification combustion technology and is equipped with a two-stage reducing agent injection method. It combines advanced reburning combustion technology and SNCR denitrification technology to ensure low nitrogen emissions of flue gas.

[0025] (3) The acrylonitrile tail gas incineration treatment process involved in this invention has the main equipment connected in sequence. The secondary tail gas preheater and air preheater are arranged at the high temperature flue gas, with a large heat exchange temperature difference, high heat exchange efficiency, compact equipment, and economical and practical.

[0026] (4) The acrylonitrile tail gas incineration treatment process involved in this invention can achieve the complete decomposition of harmful substances in acrylonitrile tail gas. Attached Figure Description

[0027] Figure 1 This is a flow chart of the acrylonitrile tail gas low-emission incineration system of the present invention.

[0028] Explanation of the reference numerals: (10) burner; (20) two-stage incinerator; (30) waste heat boiler; (40) air preheater; (50) secondary tail gas preheater; (60) economizer; (70) primary tail gas preheater; (80) chimney; (110) steam preheater; (710) gas-liquid separator.

[0029] Acrylonitrile tail gas (72); preheated acrylonitrile tail gas (73); high-temperature acrylonitrile tail gas (74);

[0030] Reduction section (210); Oxidation section (250);

[0031] First reducing agent spray gun (220); Second reducing agent spray gun (240);

[0032] Fuel gas (121); primary fuel gas (122); combustion air (112); secondary fuel gas (123);

[0033] Secondary air (41); reducing air (43); oxidizing air (44);

[0034] Boiler feedwater (61); superheated steam (63). Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments disclosed in the present invention will be described in further detail below with reference to the accompanying drawings.

[0036] This application discloses an acrylonitrile tail gas incineration treatment process, suitable for the environmentally friendly incineration of large-volume acrylonitrile tail gas, and particularly applicable to the acrylonitrile industry. For industries that also produce large-volume, low-calorific-value nitrogen-containing tail gas, such as hydrogen cyanide, carbon fiber, adiponitrile, and NMP, the self-denitrification combustion technology, advanced re-combustion combustion technology, and process equipment layout structure adopted in this invention have universal applicability in terms of technical principles. It should be understood that the specific embodiments described in this invention are only some embodiments of this invention, and are only used to explain this invention, and do not constitute a limitation of this invention. Where there is no conflict, the embodiments and technical features involved in this invention can be combined.

[0037] For ease of explanation, a brief overview of the invention will be given first, such as... Figure 1 As shown, the acrylonitrile tail gas 71 discharged from the upstream unit enters the boundary area. First, the condensate is separated by the gas-liquid separator 710. The acrylonitrile tail gas 72 discharged from the gas-liquid separator then undergoes two stages of preheating. It first enters the first-stage tail gas preheater 70 and is preheated to 150℃~200℃. Then, it is transported through pipeline to the second-stage tail gas preheater 50 and further heated to 400℃~500℃. Finally, it enters the reduction section 210 of the two-stage incinerator 20.

[0038] A low-emission incineration treatment system for acrylonitrile tail gas, such as Figure 1 As shown, the system includes: a burner 10, a two-stage incinerator 20, a waste heat boiler 30, an air preheater 40, a secondary tail gas preheater 50, an economizer 60, a primary tail gas preheater 70, a gas-liquid separator 710, and a chimney 80. This process equipment adopts a cascaded arrangement structure, meaning the above equipment is connected sequentially in a horizontal structure, saving a significant amount of high-temperature flue gas piping, making it economical and practical. The secondary tail gas preheater 50 and the air preheater 40 are located at the high-temperature flue gas level, resulting in a large heat exchange temperature difference, high heat exchange efficiency, and a compact, economical design.

[0039] Burner 10 is installed on one side of the horizontal two-stage incinerator 20, and burner 10 assists in the combustion of acrylonitrile tail gas. Waste heat boiler 30 includes a boiler shell, and a boiler heat exchange channel is provided inside the boiler shell. Boiler feedwater 61 flows in the boiler heat exchange channel. Air preheater 40 includes an air preheating shell, and an air preheating channel is provided inside the air preheating shell. Secondary air 41 flows in the air preheating channel. Secondary tail gas preheater 50 includes a secondary preheating shell, and a secondary preheating channel is provided inside the secondary preheating shell. Preheated acrylonitrile tail gas 73 flows in the secondary preheating channel. After preheating, the acrylonitrile tail gas 73 flows out of the secondary preheating channel to obtain high-temperature acrylonitrile tail gas 74. Economizer 60 includes an economizer shell, and an economizer channel is provided inside the economizer shell. Boiler feedwater 61 first passes through the economizer channel and then enters the boiler heat exchange channel. The primary exhaust gas preheater 70 includes a primary preheating shell, within which a primary preheating channel is provided. Acrylonitrile exhaust gas 72 flows through the primary preheating channel and exits to obtain preheated acrylonitrile exhaust gas 73. Fuel gas 121 directly enters and / or passes through burner 10 into one end of the dual-stage incinerator 20. The other end of the dual-stage incinerator 20, the boiler shell of the waste heat boiler 30, the air preheating shell of the air preheater 40, the secondary preheating shell of the secondary exhaust gas preheater 50, the economizer shell of the economizer 60, and the primary preheating shell of the primary exhaust gas preheater 70 are connected in sequence. The outlet of the primary preheating shell is connected to the chimney 80. This allows the flue gas from the outlet of the dual-stage incinerator 20 to directly enter the boiler shell, air preheating shell, secondary preheating shell, economizer shell, and primary preheating shell in sequence, saving a significant amount of high-temperature flue gas piping.

[0040] High-temperature acrylonitrile tail gas 74 enters the two-stage incinerator 20, where it is combusted to produce high-temperature flue gas at 800℃~950℃. The high-temperature flue gas produced by the two-stage incinerator 20 first enters the waste heat boiler 30, where it is cooled to 600℃~700℃ before flowing through the air preheater 40. The flue gas temperature exiting the air preheater 40 is approximately 500℃~600℃. It then flows through the secondary tail gas preheater 50, where the flue gas temperature drops to 300℃~400℃ before entering the economizer 60. The flue gas temperature exiting the economizer 60 is cooled to 200℃~300℃ before entering the primary tail gas preheater 70. The flue gas temperature exiting the primary tail gas preheater 70 drops to 120℃~150℃ before finally being discharged through the chimney 80.

[0041] The acrylonitrile tail gas 72 separated by the gas-liquid separator 710 enters the first-stage tail gas preheater 70 through a pipeline and is preheated to 150℃~200℃. After preheating, the acrylonitrile tail gas 73 enters the second-stage tail gas preheater 50 through a pipeline and is further heated to 400℃-500℃. Finally, the high-temperature acrylonitrile tail gas 74 enters the two-stage incinerator 20 for self-denitrification incineration treatment.

[0042] The dual-stage incinerator 20 is divided into a reduction section 210 and an oxidation section 250 based on different combustion efficiencies. The volume of the reduction section 210 accounts for 50% of the dual-stage incinerator 20. High-temperature acrylonitrile tail gas 74 and fuel gas 121 enter from the end of the reduction section 210 away from the oxidation section 250, resulting in a longer residence time of the high-temperature acrylonitrile tail gas 74 in the reduction section 210. All of the high-temperature acrylonitrile tail gas 74 enters the reduction section 210. At the same time, fuel gas 123 and reducing air 43 with a lower stoichiometric ratio are introduced into the reduction section 210. The oxygen deficiency coefficient of the reduction section 210 ranges from 0.8 to 0.95, preferably 0.85. A flue gas component analyzer 230 is installed at the tail end of the reduction section 210 to judge the degree of flue gas reduction in real time. The oxygen deficiency coefficient of the reduction section 210 is controlled by adjusting the air volume of the reducing air 43, so as to achieve precise implementation of self-denitrification combustion technology under varying acrylonitrile tail gas conditions and ensure that most of the fuel nitrogen in the acrylonitrile tail gas is converted into N2. The oxidizing air 44 entering the oxidation section 250 of the dual-stage incinerator achieves complete combustion of all harmful substances and unburned organic matter discharged from the reduction section 210. The oxygen content at the outlet of the dual-stage incinerator 20 is controlled at 2% to 3%, and the outlet temperature of the dual-stage incinerator 20 is in the range of 800℃ to 950℃. The outlet temperature of the dual-stage incinerator 20 is automatically controlled by the flow rate of the fuel gas 121 through cascade regulation.

[0043] The dual-stage incinerator 20's reduction section 210 employs advanced re-combustion technology. This technology includes: the reduction section 210 is equipped with a first reducing agent spray gun 220, which injects ammonia water, ammonia gas, or urea into the furnace to enhance the reducing atmosphere in the combustion reaction zone, promoting the conversion of nitrogen in the acrylonitrile tail gas 74 into N2 as much as possible, thereby reducing NO at the source. X Emissions; the molar flow rate of ammonia or urea is 5%-25% of the molar flow rate of fuel gas 121. The oxidation section 250 is also equipped with a second reducing agent spray gun 240. A reducing agent spray gun is located at the end of the oxidation section 250. By spraying ammonia water, ammonia gas, or urea into the oxidation section, the already generated NO... X Converted into N2, thereby reducing NO in flue gas. X The content, that is, the NO content generated through the SNCR reaction. X Convert to N2.

[0044] High-temperature acrylonitrile tail gas 74 is assisted in combustion by fuel gas 121. Fuel gas 121 is divided into two lines: primary fuel gas 122 and secondary fuel gas 123. Primary fuel gas 122 enters burner 10 together with low stoichiometric combustion air 112. Combustion air 112 is heated to 250℃-320℃ by steam preheater 110 before entering burner 10. Primary fuel gas 122 accounts for approximately 50%–80% of the total fuel gas 121. Secondary fuel gas 123 enters the reduction section 210 of the two-stage incinerator 20 through multiple fuel gas nozzles, enhancing the oxygen-deficient combustion atmosphere in the reduction section 210. Secondary fuel gas 123 accounts for approximately 20%–50% of the total fuel gas 121.

[0045] High-temperature acrylonitrile tail gas 74 is thoroughly mixed and combusted with reducing air 43 and oxidizing air 44 in the two-stage incinerator 20. Secondary air 41, pressurized by a blower, first enters the air preheater 40 through pipelines and is heated to 500-650℃. It is then divided into two streams: reducing air 43 and oxidizing air 44. One stream of reducing air 43 enters the reduction section 210 of the two-stage incinerator 20, and the other stream of oxidizing air 44 enters the oxidation section 250. The reducing air 43 has a slightly stoichiometric ratio with the fuel gas 123 and acrylonitrile tail gas 74 entering the reduction section 210. The excess air coefficient in the reduction section is between 0.7 and 0.95, preferably 0.85. The oxidizing air 44 entering the oxidation section 250 achieves complete combustion of all harmful substances and unburned organic matter discharged from the upstream reduction section 210.

[0046] Burner 10 uses oxygen-deficient combustion technology to suppress NO. X The combustion air 112 entering the burner 10 is in a substoichiometric ratio with the primary fuel gas 122, and the excess air coefficient of the burner 10 is in the range of 0.5-0.8, preferably 0.7.

[0047] The boiler feedwater 61 is first pumped to the economizer 60, heated, and then transported through pipelines to the waste heat boiler 30. It then passes through the evaporation section and superheating section of the waste heat boiler 30 in sequence, and finally produces qualified superheated steam 63 which is sent out of the boundary area.

[0048] Air preheater 40 is a metal plate or metal tube heat exchanger. Primary exhaust gas preheater 70 and secondary exhaust gas preheater 50 are metal plate or metal tube heat exchangers.

[0049] When the nitrogen content in acrylonitrile tail gas is high, an SCR (Selective Catalytic Reduction) system is installed between the economizer 60 and the secondary tail gas preheater 50 to reduce NO. X Emissions.

[0050] Acrylonitrile tail gas auxiliary fuel gas 121 can be replaced with fuel oil, waste liquid or other high calorific value waste gas.

[0051] Example 1

[0052] The components and state parameters of the acrylonitrile tail gas to be treated are shown in Table 1:

[0053]

[0054] The acrylonitrile tail gas treatment steps using the incineration process described in this invention are as follows:

[0055] 1. Acrylonitrile tail gas 71 is separated into condensate by gas-liquid separator 710. The purified acrylonitrile tail gas 72 enters the first-stage metal plate tail gas preheater 70 through pipeline and is preheated to 150℃~200℃. After preheating, acrylonitrile tail gas 73 enters the second-stage metal plate tail gas preheater 50 through pipeline and is further heated to 400℃~500℃. Finally, the high-temperature acrylonitrile tail gas 74 enters the reduction section 210 of the two-stage incinerator 20 for self-denitrification incineration treatment.

[0056] 2. The dual-stage incinerator 20 uses fuel gas to assist combustion. The fuel gas 121 pipeline is divided into two lines. The primary fuel gas 122 and the low stoichiometric ratio combustion air 112 enter the burner 10. The primary fuel gas 122 accounts for about 67% of the total fuel gas 121. The secondary fuel gas 123 enters the reduction section 210 of the dual-stage incinerator 20. The primary fuel gas 123 accounts for about 33% of the total fuel gas 121.

[0057] 3. Acrylonitrile tail gas 74 and secondary air 41 are fully mixed and combusted in the two-stage incinerator 40. After being pressurized by a blower, the secondary air 41 first enters the air preheater 40 through pipeline and is heated to 550-650℃. Then it is divided into two paths: one is reduction air 43, which enters the reduction section 210 of the two-stage incinerator 20, and the other is oxidation air 44, which enters the oxidation section 250 of the two-stage incinerator 20. The reduction air 43 has a substoichiometric ratio with the fuel gas 123 and acrylonitrile tail gas 74 entering the reduction section 210. The excess air coefficient of the reduction section 210 is in the range of 0.8-0.95. The oxidation air 44 entering the oxidation section 250 achieves complete combustion of all harmful substances and unburned organic matter discharged from the upstream reduction section 210. The oxygen content at the outlet of the oxidation section 250 is 2% to 3%.

[0058] 4. Acrylonitrile tail gas 74, primary fuel gas 122, secondary fuel gas 123, combustion air 112, reduction air 43, and oxidation air 44 undergo complete combustion in the two-stage incinerator 20. The resulting high-temperature flue gas of 800℃~900℃ first enters the waste heat boiler 30. After being cooled to 600℃~700℃ by the waste heat boiler 30, the flue gas flows through the metal plate air preheater 40. The flue gas temperature exiting the metal plate air preheater 40 is approximately 500℃~60℃. The flue gas flows from 0℃ to 300℃~400℃ through a secondary metal plate exhaust gas preheater 50. It then enters an economizer 60, where the temperature drops to 200℃~300℃. After exiting the economizer 60, the flue gas temperature drops to 120℃~150℃. Finally, it is discharged through a chimney 80. The flue gas emission data are shown in Table 2.

[0059]

[0060] Example 2

[0061] The components and state parameters of the nitrogen-containing exhaust gas to be treated are shown in Table 3.

[0062]

[0063] The nitrogen-containing exhaust gas treatment steps using the incineration process described in this invention are as follows:

[0064] 1. Nitrogen-containing tail gas 71 is separated into condensate by gas-liquid separator 710. The purified nitrogen-containing tail gas 72 enters the first-stage metal tubular tail gas preheater 70 through pipeline and is preheated to 150℃~200℃. After preheating, nitrogen-containing tail gas 73 enters the second-stage metal tubular tail gas preheater 50 through pipeline and is further heated to 400℃~450℃. Finally, the high-temperature nitrogen-containing tail gas 74 enters the reduction section 210 of the two-stage incinerator 20 for self-denitrification incineration treatment.

[0065] 2. The dual-stage incinerator 20 uses fuel gas to assist combustion. The fuel gas 121 pipeline is divided into two lines. The primary fuel gas 122 and the low stoichiometric ratio combustion air 112 enter the burner 10. The primary fuel gas 122 accounts for about 80% of the total fuel gas 121. The secondary fuel gas 123 enters the reduction section 210 of the dual-stage incinerator 20. The primary fuel gas 123 accounts for about 20% of the total fuel gas 121.

[0066] 3. Nitrogen-containing exhaust gas 74 and secondary air 41 are fully mixed and combusted in the dual-stage incinerator 40. After being pressurized by a blower, the secondary air 41 first enters the metal tubular air preheater 40 through pipeline and is heated to 500-600℃. Then it is divided into two paths: one is reduction air 43, which enters the reduction section 210 of the dual-stage incinerator 20, and the other is oxidation air 44, which enters the oxidation section 250 of the dual-stage incinerator 20. The reduction air 43 has a slightly stoichiometric ratio with the fuel gas 123 and acrylonitrile exhaust gas 74 entering the reduction section 210. The excess air coefficient of the reduction section 210 is in the range of 0.75-0.85. The oxidation air 44 entering the oxidation section 250 achieves complete combustion of all harmful substances and unburned organic matter discharged from the upstream reduction section 210. The oxygen content at the outlet of the oxidation section 250 is 5% to 6%.

[0067] 4. Nitrogen-containing tail gas 74, primary fuel gas 122, secondary fuel gas 123, combustion air 112, reduction air 43, and oxidation air 44 undergo complete combustion in the two-stage incinerator 20. The resulting high-temperature flue gas of 900℃~950℃ first enters the waste heat boiler 30. After being cooled to 650℃~750℃ by the waste heat boiler 30, the flue gas flows through the metal tube air preheater 40. The flue gas temperature exiting the metal tube air preheater 40 is approximately 500℃~60℃. The flue gas flows from 0℃ to 300℃~400℃ through a secondary metal tube exhaust gas preheater 50. It then enters an economizer 60, where the temperature drops to 200℃~300℃. After exiting the economizer 60, the flue gas temperature drops to 120℃~150℃. Finally, it is discharged through a chimney 80. The flue gas emission data are shown in Table 2.

[0068]

[0069]

[0070] The contents not described in detail in this application specification are common knowledge to those skilled in the art.

[0071] The present application has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present application. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and implementation methods of the present application without departing from the spirit and scope of the present application, and all such modifications and improvements fall within the scope of the present application. The scope of protection of the present application is determined by the appended claims.

Claims

1. A low-emission incineration treatment system for acrylonitrile tail gas, characterized in that: It includes a two-stage incinerator (20), a waste heat boiler (30), an air preheater (40), a secondary tail gas preheater (50), an economizer (60), a primary tail gas preheater (70), and a chimney (80); The waste heat boiler (30) includes a boiler shell, and a boiler heat exchange channel is provided inside the boiler shell; the air preheater (40) includes an air preheating shell, and an air preheating channel is provided inside the air preheating shell, and secondary air (41) obtains reducing air (43) and oxidizing air (44) after passing through the air preheating channel; the secondary tail gas preheater (50) includes a secondary preheating shell, and a secondary preheating flow channel is provided inside the secondary preheating shell; the economizer (60) includes an economizing shell, and an economizing flow channel is provided inside the economizing shell, and boiler feedwater (61) first passes through the economizing flow channel and then enters the boiler heat exchange channel; the primary tail gas preheater (70) includes a primary preheating shell, and a primary preheating flow channel is provided inside the primary preheating shell, and acrylonitrile tail gas (72) flows out from the primary preheating flow channel to obtain preheated acrylonitrile tail gas (73), and the preheated acrylonitrile tail gas (73) flows out through the secondary preheating flow channel to obtain high-temperature acrylonitrile tail gas (74); High-temperature acrylonitrile tail gas (74), fuel gas (121), reducing air (43) and oxidizing air (44) enter the two-stage incinerator (20) and are burned in the two-stage incinerator (20); The other end of the dual-stage incinerator (20), the boiler shell of the waste heat boiler (30), the air preheating shell of the air preheater (40), the secondary preheating shell of the secondary tail gas preheater (50), the economizer shell of the economizer (60), and the primary preheating shell of the primary tail gas preheater (70) are connected in sequence, and the outlet of the primary preheating shell is connected to the chimney (80). The dual-stage incinerator (20) includes a reduction section (210) and an oxidation section (250). The outlet of the oxidation section (250) is connected to the waste heat boiler (30). The volume of the reduction section (210) accounts for 50% of the volume of the dual-stage incinerator (20). High-temperature acrylonitrile tail gas (74), fuel gas (121), and reducing air (43) enter from the end of the reduction section (210) away from the oxidation section (250). The oxidation air (44) enters from the position of the oxidation section (250) close to the reduction section (210). The reduction section (210) is equipped with a first reducing agent spray gun (220), through which ammonia water, ammonia gas, or urea are sprayed into the furnace. The molar flow rate of ammonia gas or urea is 5%-25% of the molar flow rate of fuel gas (121).

2. The acrylonitrile tail gas low-emission incineration treatment system according to claim 1, characterized in that: The oxygen deficiency coefficient of the reduction section (210) ranges from 0.8 to 0.95; The reducing air (43) has a substoichiometric ratio with the fuel gas and high-temperature acrylonitrile tail gas (74) entering the reducing section (210), and the excess air coefficient of the reducing section (210) ranges from 0.7 to 0.

95.

3. The acrylonitrile tail gas low-emission incineration treatment system according to claim 2, characterized in that: A flue gas component analyzer (230) is installed at the end of the reduction section (210) to determine the degree of flue gas reduction in real time, and to regulate the oxygen deficiency coefficient of the reduction section (210) by adjusting the air volume of the reduction air (43).

4. The acrylonitrile tail gas low-emission incineration treatment system according to claim 1, characterized in that: The oxidation section (250) is equipped with a second reducing agent spray gun (240). Ammonia water, ammonia gas, or urea are sprayed into the oxidation section through the second reducing agent spray gun (240) to dissolve the generated NO through an SNCR reaction. X Convert to N2.

5. The acrylonitrile tail gas low-emission incineration treatment system according to claim 1, characterized in that: The oxygen content at the outlet of the oxidation section (250) is 2% to 6%.

6. The acrylonitrile tail gas low-emission incineration treatment system according to claim 1, characterized in that: The reduction section (210) of the dual-stage incinerator (20) is equipped with a burner (10). The fuel gas (121) pipeline includes two lines: primary fuel gas (122) and secondary fuel gas (123). The primary fuel gas (122) enters the burner (10) together with the low stoichiometric ratio combustion air (112). After being ignited in the burner (10), it enters the reduction section (210) of the dual-stage incinerator (20). The secondary fuel gas (123) directly enters the reduction section (210) of the dual-stage incinerator (20).

7. The acrylonitrile tail gas low-emission incineration treatment system according to claim 6, characterized in that: The primary fuel gas (122) accounts for 50% to 80% of the total fuel gas; the secondary fuel gas (123) accounts for 20% to 50% of the total fuel gas (121).

8. A low-emission incineration treatment process for acrylonitrile tail gas, characterized in that: A low-emission incineration treatment system for acrylonitrile tail gas according to any one of claims 1-7 includes: Acrylonitrile tail gas (72) enters the first-stage tail gas preheater (70) and is preheated to 150℃~200℃ to obtain preheated acrylonitrile tail gas (73); the preheated acrylonitrile tail gas (73) enters the second-stage tail gas preheater (50) and is further heated to 400℃-500℃ to obtain high-temperature acrylonitrile tail gas (74). High-temperature acrylonitrile tail gas (74), combustion air (112), reduction air (43), and oxidation air (44) enter the two-stage incinerator (20) to generate high-temperature flue gas of 800℃~950℃. The high-temperature flue gas of 800℃~950℃ first enters the waste heat boiler (30), and the flue gas is cooled to 600℃~700℃ by the waste heat boiler (30) and then flows through the air preheater (40). The flue gas temperature exiting the air preheater (40) is... The flue gas temperature is 500℃~600℃, and then flows through the secondary tail gas preheater (50). The flue gas temperature drops to 300℃~400℃ after exiting the secondary tail gas preheater (50). Then it enters the economizer (60). The flue gas temperature drops to 200℃~300℃ after exiting the economizer (60). Then it enters the primary tail gas preheater (70). The flue gas temperature drops to 120℃~150℃ after exiting the primary tail gas preheater (70). Finally, it is discharged through the chimney (80).

Images