A tail gas treatment system and process

Abstract

The application discloses a tail gas treatment system and process, wherein the treatment system comprises a pretreatment unit, a staged incineration unit, a synergistic purification unit, a gradient waste heat recovery unit and an intelligent control unit; the pretreatment unit, the staged incineration unit, the synergistic purification unit and the gradient waste heat recovery unit are sequentially connected, the input end of the pretreatment unit is connected with the tail gas pipeline inlet, the output end of the gradient waste heat recovery unit is connected with the chimney inlet; the pretreatment unit, the staged incineration unit, the synergistic purification unit and the gradient waste heat recovery unit are connected with the intelligent control unit. The technical effects are as follows: through the linkage of the intelligent control unit and each treatment unit, the real-time changes of tail gas components and emission indexes can be automatically adjusted, the operation parameters can be automatically adjusted, the treatment system has the advantages of high purification efficiency, high heat recovery efficiency, low equipment corrosion rate and strong self-adaptive capacity, and can be widely applied to the treatment of coal gas ethanol and other industrial tail gas containing sulfur and hydrocarbon.

Description

Technical Field

[0001] This invention relates to the field of industrial waste gas treatment and energy recovery technology, specifically to a tail gas treatment system and a tail gas treatment process. Background Technology

[0002] The coal gas-to-ethanol process is one of the important methods for producing ethanol through syngas fermentation or catalytic conversion. This process generates a large amount of complex tail gas. Typical tail gas components include: 15%-25% hydrogen, 8%-12% carbon monoxide, methane, and C2O. 2+ The exhaust gas contains 3%-8% hydrocarbons and 50%-65% nitrogen, along with 100-500 mg / Nm³ of sulfides (mainly H2S and COS) and trace amounts of tar, dust, and other impurities. This type of exhaust gas is characterized by large fluctuations in calorific value, high content of corrosive components, and dispersed combustible components; direct emission would cause serious environmental pollution.

[0003] Currently, the main method for treating the aforementioned exhaust gases is incineration technology, but it has the following significant shortcomings in practical applications:

[0004] 1. Secondary pollution and coking issues: Existing direct incineration technologies do not effectively pre-treat impurities such as sulfides and tar in the exhaust gas, leading to the generation of SO2 during combustion. x Secondary pollutants such as dioxins. At the same time, tar easily cokes inside the burner, affecting the stability and reliability of the system operation.

[0005] 2. Incomplete combustion and low energy utilization efficiency: Most existing incinerators adopt a single combustion mode and fail to match the combustion characteristics of multi-component combustible media (such as hydrogen, carbon monoxide, hydrocarbons, etc.) in the exhaust gas, resulting in incomplete combustion, which leads to excessive emissions of pollutants such as VOCs and CO, and the energy recovery efficiency is usually less than 60%, resulting in serious energy waste.

[0006] 3. Significant equipment corrosion issues: Corrosive components such as sulfides and chlorides in the exhaust gas form corrosive flue gas after high-temperature combustion, causing severe sulfur and chloride corrosion to the incinerator's heating surfaces and pipes. Especially in high-temperature areas such as superheaters, the corrosion rate can reach 0.5-1.2 mm / year, significantly shortening equipment lifespan and increasing maintenance costs.

[0007] 4. Poor adaptability of waste heat recovery systems: Existing waste heat recovery systems are poorly adapted to incineration conditions, and most adopt a single heat recovery mode, failing to achieve cascade utilization of energy, resulting in insufficient recovery of waste heat resources and further reducing overall energy efficiency. Summary of the Invention

[0008] Therefore, the present invention provides an exhaust gas treatment system and process to solve the above-mentioned problems in the prior art.

[0009] To achieve the above objectives, the present invention provides the following technical solution:

[0010] According to a first aspect of the present invention, an exhaust gas treatment system includes a pretreatment unit, a staged incineration unit, a synergistic purification unit, a cascade waste heat recovery unit, and an intelligent control unit. The pretreatment unit, the staged incineration unit, the synergistic purification unit, and the cascade waste heat recovery unit are connected in sequence, and the input end of the pretreatment unit is connected to the exhaust gas pipeline inlet, and the output end of the cascade waste heat recovery unit is connected to the chimney inlet.

[0011] The pretreatment unit, the staged incineration unit, the synergistic purification unit, and the cascade waste heat recovery unit are all connected to the intelligent control unit. The intelligent control unit is used to adjust the adsorbent regeneration frequency of the pretreatment unit, the air ratio of the staged incineration unit, the reagent dosage of the synergistic purification unit, and the heat exchange efficiency of the cascade waste heat recovery unit in real time.

[0012] The staged incineration unit includes multiple combustion chambers connected in series for fully combusting the exhaust gas; the cascaded waste heat recovery unit includes multiple heat exchangers connected in series for fully recovering the heat from the exhaust gas.

[0013] Furthermore, the pretreatment unit includes a tar collector, a desulfurization device, and a dust filter connected in sequence, and the tar collector, the desulfurization device, and the dust filter are all connected to the intelligent control unit.

[0014] Furthermore, the staged incineration unit includes a primary combustion chamber and a secondary combustion chamber connected in sequence, both of which are connected to the intelligent control unit.

[0015] Furthermore, the staged combustion unit also includes an auxiliary natural gas pipeline. Both the primary combustion chamber and the secondary combustion chamber employ dual-fuel nozzles. The main nozzle of the dual-fuel nozzle introduces pre-treated exhaust gas, while the auxiliary nozzle introduces natural gas as auxiliary fuel.

[0016] Furthermore, the collaborative purification unit adopts an integrated desulfurization and denitrification module.

[0017] Furthermore, the cascade waste heat recovery unit includes a high-temperature superheater, a medium-temperature economizer, an air preheater, and a low-temperature preheater arranged in sequence, and the high-temperature superheater, the medium-temperature economizer, the air preheater, and the low-temperature preheater are all connected to the intelligent control unit;

[0018] The high-temperature superheater is equipped with a steam output pipe for outputting high-temperature steam; the medium-temperature economizer is used to preheat boiler feedwater; the air preheater is used to input preheated air into the boiler; and the low-temperature preheater is used to heat the regeneration medium of the desulfurization unit to output desulfurization medium regeneration resources.

[0019] Furthermore, the intelligent control unit includes an intelligent control cabinet and an online flue gas composition monitor, the online flue gas composition monitor being installed inside the chimney and connected to the intelligent control cabinet.

[0020] The present invention has the following advantages:

[0021] 1. Significantly improved purification efficiency: Through a three-stage treatment process of pretreatment + staged incineration + synergistic purification, VOCs removal rate ≥99.5% and SO2 removal rate ≥99.5% are achieved. X Removal rate ≥95%, NO X The removal rate is ≥85%, the dust removal rate is ≥99.5%, and all emission indicators are better than GB16297-1996 "Integrated Emission Standard for Air Pollutants" and local ultra-low emission requirements;

[0022] 2. High energy recovery efficiency: The cascade waste heat recovery design achieves a total heat recovery efficiency of over 88%. The generated steam can be directly used in the distillation and fermentation stages of the coal gas to ethanol process, saving more than 300 tons of standard coal per year, with an investment payback period of ≤2.5 years.

[0023] 3. Excellent corrosion resistance: Through multiple measures such as reducing the concentration of corrosive media through desulfurization pretreatment, using corrosion-resistant materials and anti-corrosion coatings for key components, and optimizing the combustion atmosphere to avoid localized reducing corrosion, the corrosion rate of the equipment is reduced to less than 0.1 mm / year, and the service life is extended to 8-10 years.

[0024] 4. High adaptability: It can cope with fluctuations in the calorific value of coal gas-to-ethanol tail gas (500-1500 kcal / Nm³). 3 The system can adapt to changes in components and other parameters through intelligent control, eliminating the need for frequent manual intervention and ensuring high operational stability.

[0025] According to a second aspect of the present invention, an exhaust gas treatment process, employing the exhaust gas treatment system described in the first aspect, includes the following steps:

[0026] S1. Exhaust gas pretreatment: The exhaust gas is sequentially passed through a tar collector, a desulfurization device and a dust filter for pretreatment.

[0027] S2, Staged Combustion: The pretreated exhaust gas is introduced into the first-stage combustion chamber for preliminary combustion, and then into the second-stage combustion chamber for complete combustion;

[0028] S3, Collaborative Purification: The exhaust gas after staged combustion is fed into an integrated desulfurization and denitrification module for desulfurization and denitrification;

[0029] S4. Cascaded waste heat recovery: The exhaust gas after co-purification is sequentially passed into a high-temperature superheater, a medium-temperature economizer, an air preheater, and a low-temperature preheater for multi-stage waste heat recovery.

[0030] S5. Exhaust gas emission: The exhaust gas after waste heat recovery is introduced into the chimney and tested using an online flue gas composition monitor. If the test is qualified, the exhaust gas is emitted. If the test is unqualified, the exhaust gas is sent to the pretreatment unit and steps S1 to S5 are repeated for further treatment.

[0031] Furthermore, it also includes step S6, system adaptive operation: during the process, the intelligent control cabinet is used to adjust the regeneration frequency of the pretreatment unit adsorbent, the air ratio of the staged incineration unit, the dosage of the synergistic purification unit and the heat exchange efficiency of the cascade waste heat recovery unit in real time.

[0032] Furthermore, the tar collector in step S1 employs a low-temperature condensation + activated carbon adsorption composite process to control the tail gas temperature to 30℃-40℃; the desulfurization device uses a modified zeolite-based supported metal catalyst to reduce the total sulfur content of the tail gas to ≤10mg / Nm³. 3 The dust filter uses a ceramic filter element.

[0033] In step S2, the primary combustion chamber adopts a partial oxidation combustion mode, with 60%-70% of the theoretical air volume introduced and the combustion temperature controlled at 850℃-950℃ to allow the flammable components to undergo initial combustion; the secondary combustion chamber adopts swirl combustion technology, with the remaining air introduced and the combustion temperature controlled at 1100℃-1200℃, with a residence time ≥2s, to allow the incompletely combusted products to be completely oxidized and decomposed.

[0034] The integrated desulfurization and denitrification module mentioned in step S3 uses an integrated desulfurization and denitrification agent, which is made from modified fly ash from waste incineration. The dosage of the agent is 5-7 kg / 1000 Nm³. 3 exhaust;

[0035] The high-temperature superheater in step S4 is made of stainless steel and has an anti-corrosion coating on its tube wall. It is used to recover the heat of flue gas at 800℃-1000℃ to generate saturated steam at 0.8MPa-1.0MPa. The medium-temperature economizer is used to preheat the boiler feedwater to 150℃-180℃. The air preheater is used to preheat the air required for combustion to 300℃-350℃. The low-temperature preheater recovers the waste heat of flue gas at 150-100℃ to heat the regeneration medium of the desulfurization unit.

[0036] The present invention has the following advantages: by setting up multi-level processing steps and adaptive control, it can automatically adjust the operating parameters according to different working conditions, ensuring that the system is always in the best operating state, which significantly improves processing efficiency and operational reliability. Attached Figure Description

[0037] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0038] The structures, proportions, sizes, etc. illustrated in this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed herein, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should fall within the scope of the technical content disclosed in the present invention.

[0039] Figure 1 This is a process flow diagram of an exhaust gas treatment system provided for some embodiments of the present invention.

[0040] In the diagram: 1. Intelligent control cabinet; 2. Exhaust gas inlet; 3. Tar collector; 4. Desulfurization device; 5. Dust filter; 6. Primary combustion chamber; 7. Secondary combustion chamber; 8. Co-purification unit; 9. Auxiliary natural gas pipeline; 10. High-temperature superheater; 11. Medium-temperature economizer; 12. Air preheater; 13. Low-temperature preheater; 14. Chimney; 15. Desulfurization medium regeneration resource; 16. Preheated air; 17. Steam output pipeline. Detailed Implementation

[0041] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] Example 1

[0043] like Figure 1As shown, a tail gas treatment system in the first aspect embodiment of the present invention includes a pretreatment unit, a staged combustion unit, a synergistic purification unit 8, a cascade waste heat recovery unit and an intelligent control unit. The pretreatment unit, the staged combustion unit, the synergistic purification unit 8 and the cascade waste heat recovery unit are connected in sequence, and the input end of the pretreatment unit is connected to the tail gas pipeline inlet 2, and the output end of the cascade waste heat recovery unit is connected to the inlet of the chimney 14.

[0044] The pretreatment unit, the staged incineration unit, the synergistic purification unit 8, and the cascade waste heat recovery unit are all connected to the intelligent control unit. The intelligent control unit is used to adjust the adsorbent regeneration frequency of the pretreatment unit, the air ratio of the staged incineration unit, the reagent dosage of the synergistic purification unit, and the heat exchange efficiency of the cascade waste heat recovery unit in real time.

[0045] The staged incineration unit includes multiple combustion chambers connected in series to fully combust the exhaust gas; the cascaded waste heat recovery unit includes multiple heat exchangers connected in series to fully recover the heat from the exhaust gas.

[0046] In this embodiment, it should be noted that the intelligent control unit consists of an intelligent control cabinet 1, an online flue gas composition monitor (installed on the chimney 14), online sensor groups at the inlet and outlet of each unit, actuators (electric regulating valves, variable frequency fans, metering pumps, etc.), and embedded control algorithm software. The intelligent control cabinet 1 has a built-in industrial-grade PLC or DCS controller, which has data acquisition, logic operation, PID regulation, trend analysis, and alarm interlocking functions. The control principle is based on a feedforward-feedback composite control strategy, which is designed to address the characteristics of large fluctuations in the calorific value and rapid changes in the composition of the exhaust gas. It enables adaptive adjustment of the regeneration frequency of the adsorbent in the pretreatment unit, the air ratio in the staged incineration unit, the dosage of the reagent in the synergistic purification unit, and the heat exchange efficiency of the cascade waste heat recovery unit.

[0047] The technical effect achieved by this embodiment is that by setting up an intelligent control unit that is linked with each processing unit, the operating parameters can be automatically adjusted according to the real-time changes in exhaust gas composition and emission indicators, thereby ensuring long-term stable operation of the system and meeting emission standards.

[0048] Example 2

[0049] like Figure 1 As shown, this embodiment provides another exhaust gas treatment system, the structure of which includes all the contents of Embodiment 1. Only the different parts are described below.

[0050] In this embodiment, the pretreatment unit includes a tar collector 3, a desulfurization device 4, and a dust filter 5 connected in sequence, and the tar collector 3, the desulfurization device 4, and the dust filter 5 are all connected to the intelligent control unit.

[0051] Specifically, the tar collector 3 adopts a composite structure of a vertical finned tube condenser and an activated carbon fiber adsorption bed. Circulating cooling water is introduced through the finned tube side to rapidly reduce the exhaust gas temperature from 120℃-180℃ at the inlet to 30℃-40℃, causing the gaseous tar to condense into a liquid state and collect and discharge along the tube wall. The remaining trace amounts of tar vapor enter the activated carbon fiber adsorption bed, which has a packed specific surface area ≥1200 m². 2 / g of modified activated carbon fiber has a tar adsorption capacity of 0.35g / g and a collection efficiency of ≥95%; the adsorption bed is equipped with a steam regeneration interface, and 0.3MPa low-pressure steam is introduced for regeneration once every 8-12 hours of operation. The regenerated waste gas is led to the first-stage combustion chamber 6 for incineration.

[0052] Desulfurization unit 4 employs a two-stage moving bed adsorption tower structure, internally filled with a modified zeolite-based supported metal catalyst. The zeolite support is type ZSM-5, with a silica-alumina ratio of 25-30, and is modified by impregnation with a citric acid derivative (triethyl citrate) at 80℃ for 4 hours, resulting in a more uniform pore size distribution and reduced surface acidity, thus minimizing hydrocarbon polymerization side reactions. The active metal components are Pt and Cu, loaded via an equal-volume impregnation method, with a total loading of 3.5wt% and a Pt to Cu molar ratio of 1:2. Desulfurization unit 4 operates at 60℃-80℃, achieving a sulfur capacity of 8.5g sulfur / 100g adsorbent, a desulfurization efficiency ≥99%, and an outlet total sulfur content ≤10mg / Nm³. 3 After the adsorbent is saturated, it is regenerated by hot nitrogen through the command of the intelligent control unit. The regeneration temperature is 280℃-320℃ and the regeneration cycle is 8-12 hours.

[0053] The dust filter 5 uses a high-throughput ceramic filter element assembly. The filter element material is silicon carbide, with a filtration accuracy of 1μm, a porosity of 45%, and a temperature resistance of 400℃. The filter element surface is coated with an alumina-based dustproof film, resulting in a high dust removal rate. It is equipped with a pulse back-flushing cleaning system, with the back-flushing air source being purified compressed air. The cleaning pressure difference is set to 1.2kPa, and the particulate matter removal rate is ≥99.5%.

[0054] In this embodiment, it should be noted that the staged combustion unit includes a primary combustion chamber 6 and a secondary combustion chamber 7 connected in sequence, and both the primary combustion chamber 6 and the secondary combustion chamber 7 are connected to the intelligent control unit;

[0055] The primary combustion chamber 6 is a horizontal cylindrical structure lined with 250mm thick high-alumina refractory castable, with an operating temperature of 850℃-950℃; the burner uses low NO₂... XA dual-fuel swirl nozzle is positioned at the center of the combustion chamber end. Pre-treated exhaust gas is introduced through the main fuel passage, while natural gas is introduced through the auxiliary fuel passage. The flow rates of both passages are controlled by electrically operated regulating valves. The primary combustion chamber's air distribution system is equipped with an independent fan, introducing 60%-70% of the theoretical air volume to create a reducing atmosphere (excess air coefficient 0.6-0.7). Under these conditions, flammable components in the exhaust gas, such as hydrogen and carbon monoxide, preferentially combust, releasing heat to raise the temperature above 850℃, while simultaneously suppressing thermal NOx. X Generate; The combustion chamber outlet is equipped with a thermocouple and an oxygen analyzer to monitor temperature and residual oxygen concentration in real time;

[0056] The secondary combustion chamber 7 is a vertical swirl structure, located after the primary combustion chamber 6, and the two are connected in series via a high-temperature flue. The secondary combustion chamber 7 is lined with the same refractory material, operates at 1100℃-1200℃, and has a flue gas residence time ≥2 seconds. A high-intensity swirl burner is installed at the top, with a swirl intensity (swirl number) of 0.8-1.2, causing the flue gas to mix violently with the remaining air (30%-40% of the theoretical air volume) and creating a recirculation zone, ensuring the complete combustion of unburned CO, CH4, and C. 2+ Hydrocarbons are completely oxidized and decomposed; the outlet of the second-stage combustion chamber 7 is equipped with a temperature sensor, a CO analyzer, and an O2 analyzer to determine the degree of combustion completeness.

[0057] Furthermore, the staged combustion unit also includes an auxiliary natural gas pipeline 9. Both the primary combustion chamber 6 and the secondary combustion chamber 7 use dual-fuel nozzles. The main nozzle of the dual-fuel nozzle introduces pre-treated exhaust gas, while the auxiliary nozzle of the dual-fuel nozzle introduces natural gas as auxiliary fuel.

[0058] The auxiliary natural gas pipeline 9 is equipped with an electric regulating valve, flow meter, and pressure switch, and is connected in parallel to the auxiliary fuel nozzles of the two combustion chambers. The intelligent control unit determines whether auxiliary combustion needs to be activated based on the calorific value of the exhaust gas at the inlet of the first-stage combustion chamber 6 (measured by an online calorific value meter) and the CO concentration at the outlet of the second-stage combustion chamber 7. When the calorific value of the exhaust gas is lower than 800 kcal / Nm³, the auxiliary combustion system will activate the auxiliary combustion system. 3 Or the CO concentration at the outlet of the secondary combustion chamber is >50 mg / Nm³ 3 When the natural gas is introduced, the regulating valve is automatically opened, and the natural gas flow rate is 3%-8% of the exhaust gas flow rate, so that the combustion chamber temperature is maintained within the design range.

[0059] The technical effects achieved in this embodiment are as follows: by setting up a tar collector 3, a desulfurization device 4, and a dust filter 5, tar, sulfides, and particulate matter in the exhaust gas can be effectively removed, reducing the risk of corrosion and secondary pollution during subsequent incineration. Simultaneously, the use of a two-stage combustion chamber in conjunction with an auxiliary natural gas pipeline ensures combustion stability even when the calorific value of the exhaust gas fluctuates, preventing excessive pollutant levels due to incomplete combustion.

[0060] Example 3

[0061] like Figure 1 As shown, this embodiment provides another exhaust gas treatment system, the structure of which includes all the contents of Embodiment 1. Only the different parts are described below.

[0062] In this embodiment, the collaborative purification unit 8 adopts an integrated desulfurization and denitrification module, which can simultaneously remove sulfur oxides and nitrogen oxides from flue gas, simplifying the system structure and reducing equipment footprint and investment costs.

[0063] In this embodiment, it should be noted that the integrated desulfurization and denitrification module is a composite structure of a vertical spray absorption tower and a fixed-bed catalytic reactor, with the following specific features:

[0064] The spray absorption section is located at the bottom of the tower, with flue gas passing through from bottom to top. It is equipped with three layers of staggered silicon carbide hollow cone nozzles, with a spray density of 15-20 m³ / h. 3 / (m 2 The spray angle is 120°; the spray liquid is an aqueous solution of the integrated desulfurization and denitrification agent, with a mass concentration of 8%-12% and a pH value controlled at 7.5-8.5; the agent is circulated by a circulating pump, and the circulating liquid is periodically discharged with gypsum and fly ash residue through a plate and frame filter press; the integrated desulfurization and denitrification agent is prepared by modifying waste incineration fly ash. The fly ash is washed and dechlorinated, precipitated with sodium carbonate, dried and pulverized, and then mixed with a modified zeolite-based supported metal catalyst (desulfurization component) and a commercial denitrification agent (mainly Mn-Ce / TiO2) at a mass ratio of 2:1:1.2. This agent can achieve SO2 removal in the spray absorption section. X Removal rate ≥95%, NO X Partial removal (approximately 40%)

[0065] The fixed-bed catalytic section is located above the spray section and contains a honeycomb-shaped Mn-Ce / TiO2 catalyst with a honeycomb pore density of 300 mesh. The module size is 150mm×150mm×150mm, and two layers are arranged. After the flue gas is desulfurized by spraying, the temperature drops to about 80℃. When it enters the catalytic section, it is reheated to 120℃-150℃ by an electric heater. At this temperature, the catalyst will desulfurize the remaining NO. X (Mainly NO) undergoes a selective catalytic reduction reaction with NH3 (from the decomposition of denitrifying agents in the reagents) escaping from the spray solution, NO X The removal rate will be increased by more than 45%, and the overall NO... X Removal rate ≥85%. The catalytic section outlet is equipped with a NO removal device. X And an online SO2 analyzer, used for feedback control of reagent dosage;

[0066] The pesticide dosage is controlled by a metering pump, with a dosage of 5-7 kg / 1000 Nm³. 3 Exhaust gas, the specific value is determined by the intelligent control unit based on the inlet SO₂.X Concentration and export emission indicators will be dynamically adjusted.

[0067] The technical effect achieved in this embodiment is that by adopting an integrated desulfurization and denitrification module, the exhaust gas purification process is efficiently integrated, reducing the difficulty of operation and maintenance, while improving the purification efficiency.

[0068] Example 4

[0069] like Figure 1 As shown, this embodiment provides another exhaust gas treatment system, the structure of which includes all the contents of Embodiment 1. Only the different parts are described below.

[0070] In this embodiment, the cascade waste heat recovery unit includes a high-temperature superheater 10, a medium-temperature economizer 11, an air preheater 12, and a low-temperature preheater 13 arranged in sequence. The high-temperature superheater 10, the medium-temperature economizer 11, the air preheater 12, and the low-temperature preheater 13 are all connected to the intelligent control unit.

[0071] The high-temperature superheater 10 is equipped with a steam output pipe 17 for outputting high-temperature steam; the medium-temperature economizer 11 is used to preheat the boiler feedwater; the air preheater 12 is used to input preheated air 16 into the boiler; and the low-temperature preheater 13 is used to heat the regeneration medium of the desulfurization device 4 to output the desulfurization medium regeneration resource 15.

[0072] Specifically, the high-temperature superheater 10 is located in the outlet flue of the secondary combustion chamber 7, with a flue gas temperature range of 800℃-1000℃; the heat exchange tubes are made of Φ38×3mm 2205 duplex stainless steel, and the tube bundles are arranged in a staggered manner with a transverse pitch of 110mm and a longitudinal pitch of 80mm; the outer wall of the tubes is sprayed with an 80-120μm thick nickel-chromium alloy anti-corrosion coating (NiCr-80 / 20), and the coating porosity is ≤1%; saturated steam (0.8MPa-1.0MPa) flows inside the tubes, and the steam flow rate is controlled by the feedwater regulating valve, with the outlet superheated steam temperature reaching 350℃-400℃;

[0073] The medium-temperature economizer 11 is located downstream of the high-temperature superheater 10, with a flue gas temperature of 400℃-600℃. The heat exchange tubes are made of 20G boiler steel with a finned tube structure (fin height 15mm, thickness 1.5mm, pitch 8mm) to enhance heat transfer. Boiler feedwater (20℃-30℃) is introduced into the tubes, and the outlet water temperature is raised to 150℃-180℃ before being sent to the boiler drum.

[0074] The air preheater 12 is located downstream of the medium-temperature economizer 11, with a flue gas temperature of 250℃-400℃. It adopts a plate heat exchange structure, which has good resistance to dew point corrosion. Ambient air is introduced on the cold side and delivered by a blower. The air flow rate is matched with the air volume required for combustion. The outlet hot air temperature is 300℃-350℃ and is delivered to the air distribution system of the primary combustion chamber 6 and the secondary combustion chamber 7 through the pipeline 16, which can significantly improve combustion efficiency and save fuel.

[0075] The low-temperature preheater 13 is located downstream of the air preheater 12, with a flue gas temperature of 150℃-250℃. The heat exchange tubes are made of polytetrafluoroethylene (PTFE) plastic, which is corrosion-resistant and has a smooth surface that does not easily accumulate dust. The regeneration medium of the desulfurization device 4 is introduced into the tubes. After the medium is heated to 120℃-150℃, it is used for adsorbent regeneration and is output through the desulfurization medium regeneration resource 15 pipeline. The flue gas in this section is finally cooled to ≤100℃ before entering the chimney 14 for emission.

[0076] Each heat exchanger is equipped with an electric regulating bypass and a temperature sensor. The intelligent control unit adjusts the bypass opening and working fluid flow in real time according to the flue gas temperature and working fluid requirements of each section, so as to achieve dynamic heat balance and maximize heat recovery. The total heat recovery efficiency of the system is ≥88%.

[0077] The technical effects achieved in this embodiment are as follows: 1. Significantly improved purification efficiency: Through a three-stage treatment process of pretreatment + staged incineration + synergistic purification, a VOCs removal rate of ≥99.5% and SO2 removal rate of ≥99.5% are achieved. X Removal rate ≥95%, NO X The removal rate is ≥85%, the dust removal rate is ≥99.5%, and all emission indicators are better than GB 16297-1996 "Integrated Emission Standard for Air Pollutants" and local ultra-low emission requirements;

[0078] 2. High energy recovery efficiency: The cascade waste heat recovery design achieves a total heat recovery efficiency of over 88%. The generated steam can be directly used in the distillation and fermentation stages of the coal gas to ethanol process, saving more than 300 tons of standard coal per year, with an investment payback period of ≤2.5 years.

[0079] 3. Excellent corrosion resistance: Through multiple measures such as reducing the concentration of corrosive media through desulfurization pretreatment, using corrosion-resistant materials and anti-corrosion coatings for key components, and optimizing the combustion atmosphere to avoid localized reducing corrosion, the corrosion rate of the equipment is reduced to less than 0.1 mm / year, and the service life is extended to 8-10 years.

[0080] 4. High adaptability: It can cope with fluctuations in the calorific value of coal gas-to-ethanol tail gas (500-1500 kcal / Nm³). 3 The system can adapt to changes in components and other parameters through intelligent control, eliminating the need for frequent manual intervention and ensuring high operational stability.

[0081] Example 5

[0082] like Figure 1 As shown, a tail gas treatment process in a second aspect embodiment of the present invention, employing the tail gas treatment system of the first aspect, includes the following steps:

[0083] S1. Exhaust gas pretreatment: The exhaust gas is sequentially passed through the tar collector 3, the desulfurization device 4 and the dust filter 5 for pretreatment.

[0084] S2, Staged Combustion: The pretreated exhaust gas is introduced into the first-stage combustion chamber 6 for preliminary combustion, and then into the second-stage combustion chamber 7 for complete combustion;

[0085] S3, Collaborative Purification: The exhaust gas after staged combustion is fed into an integrated desulfurization and denitrification module for desulfurization and denitrification;

[0086] S4, cascade waste heat recovery: The exhaust gas after co-purification is sequentially passed into the high-temperature superheater 10, the medium-temperature economizer 11, the air preheater 12 and the low-temperature preheater 13 for multi-stage waste heat recovery.

[0087] S5. Exhaust gas emission: The exhaust gas after waste heat recovery is introduced into the chimney 14 and tested using an online flue gas composition monitor; if the test is qualified, it is emitted; if the test is unqualified, the exhaust gas is sent to the pretreatment unit and steps S1 to S5 are repeated for further treatment.

[0088] In this embodiment, it should be noted that step S6, system adaptive operation, is also included: during the processing, an online flue gas composition monitor (monitoring SO) is installed inside the chimney 14. X NO X The system includes a CO and O2 concentration sensor, a corrosion probe, and a temperature and pressure sensor, which are connected to the intelligent control cabinet 1. The intelligent control cabinet 1 is used to adjust the regeneration frequency of the pretreatment unit adsorbent, the air ratio of the staged incineration unit, the dosage of the synergistic purification unit, and the heat exchange efficiency of the cascade waste heat recovery unit in real time, so that the system can achieve adaptive operation.

[0089] The technical effect achieved by this embodiment is that by setting up multi-level processing steps and adaptive control, the operating parameters can be automatically adjusted according to different working conditions, ensuring that the system is always in the best operating state, which significantly improves processing efficiency and operational reliability.

[0090] Example 6

[0091] like Figure 1 As shown, another exhaust gas treatment process provided in this embodiment has the same structure as in Embodiment 5. Only the different parts are described below.

[0092] In this embodiment, in step S1, the tar collector 3 adopts a low-temperature condensation + activated carbon adsorption composite process to control the tail gas temperature to 30℃-40℃, with a tar collection efficiency ≥95%; the desulfurization device 4 uses a modified zeolite-based supported metal catalyst (the metal component is a Pt, Cu composite system), and the modified zeolite is a citric acid derivative modified product, with a desulfurization efficiency ≥99%, reducing the total sulfur content of the tail gas to ≤10mg / Nm³. 3 Dust filter 5 uses a ceramic filter element with a filtration accuracy of 1μm and a particulate matter removal rate of ≥99.5%.

[0093] In step S2, the primary combustion chamber 6 adopts a partial oxidation combustion mode, introducing 60%-70% of the theoretical air volume and controlling the combustion temperature at 850℃-950℃ to allow the flammable components to undergo initial combustion; the secondary combustion chamber 7 adopts swirl combustion technology, introducing the remaining air and controlling the combustion temperature at 1100℃-1200℃ with a residence time ≥2s to ensure the complete oxidation and decomposition of incompletely combusted products.

[0094] Both the primary combustion chamber 6 and the secondary combustion chamber 7 employ a dual-fuel nozzle design. The main nozzle supplies pre-treated exhaust gas, while the auxiliary nozzle supplies natural gas. This design is suitable for combustion chambers where the exhaust gas calorific value is below 800 kcal / Nm³. 3 At this time, the intelligent control cabinet automatically opens the valve of the auxiliary natural gas pipeline 9 to introduce natural gas and start auxiliary combustion, thereby ensuring combustion stability;

[0095] In step S3, the integrated desulfurization and denitrification module uses an integrated desulfurization and denitrification agent, which is made from modified fly ash from waste incineration. The dosage of the agent is 5-7 kg / 1000 Nm³. 3 Exhaust gas, achieving SO X Removal rate ≥95%, NO X Removal rate ≥85%;

[0096] In step S4, the high-temperature superheater 10 is made of 2205 duplex stainless steel and its tube wall is coated with a nickel-chromium alloy anti-corrosion coating. It is used to recover the heat of flue gas at 800℃-1000℃ to generate saturated steam at 0.8MPa-1.0MPa. The medium-temperature economizer 11 is used to preheat the boiler feedwater to 150℃-180℃. The air preheater 12 is used to preheat the air required for combustion to 300℃-350℃. The low-temperature preheater 13 recovers the waste heat of flue gas at 150-100℃ to heat the regeneration medium of the desulfurization device 4. The total heat recovery efficiency of the system is ≥88%.

[0097] In this embodiment, it should be noted that the preparation method of the agent in step S3 is as follows: fly ash and water are mixed and stirred for 10-20 minutes at a solid-liquid ratio of 1g:2mL to 1g:5mL, then sodium carbonate solution is added to precipitate soluble calcium. After solid-liquid separation, the mixture is dried and pulverized to 50-200 mesh. Subsequently, a modified zeolite-based supported metal catalyst of 100-300 mesh is added to form a desulfurizing agent. Finally, it is mixed with a denitrification agent at a mass ratio of 1.5:1 to 4:1.

[0098] Preferably, the preparation method of the agent in step S3 is as follows: fly ash and water are mixed and stirred for 15 minutes at a solid-liquid ratio of 1g:3mL, then sodium carbonate solution is added to precipitate soluble calcium, and after solid-liquid separation, the mixture is dried and pulverized to 100 mesh; subsequently, a modified zeolite-based supported metal catalyst of 200 mesh is added to form a desulfurizing agent; finally, it is mixed with a denitrification agent at a mass ratio of 2:1.

[0099] The technical effects achieved in this embodiment are as follows: by optimizing the specific process parameters and material selection of each unit, the purification efficiency, energy recovery efficiency and equipment corrosion resistance of the exhaust gas treatment system are further improved. In particular, by using waste incineration fly ash to prepare integrated desulfurization and denitrification agents, the resource utilization of waste is realized and the operating cost is reduced.

[0100] Application Example 1

[0101] A tail gas treatment project for a coal gas-to-ethanol plant has a tail gas treatment capacity of 50,000 Nm³. 3 / h, exhaust gas composition: hydrogen 20%, carbon monoxide 10%, methane 5%, nitrogen 63%, sulfides 300mg / Nm³ 3 Dust 50mg / Nm 3 Calorific value 850 kcal / Nm 3 .

[0102] The exhaust gas treatment system and process are used for treatment, and the parameters and effects of each unit are as follows:

[0103] Pretreatment unit: The tar collector is controlled at 35℃, with a tar collection efficiency of 96%; the desulfurization unit uses a Pt-Cu modified zeolite catalyst, with a desulfurization efficiency of 99.2% and an outlet sulfur content ≤2.4mg / Nm³. 3 The ceramic filter element of the dust filter has a filtration accuracy of 1μm and a dust removal rate of 99.6%.

[0104] Staged combustion unit: The first-stage combustion chamber is supplied with 65% of the theoretical air volume, and the combustion temperature is controlled at 900℃; the second-stage combustion chamber is supplied with 35% of the theoretical air volume, and the swirling combustion temperature is controlled at 1150℃ with a residence time of 2.5s.

[0105] Synergistic purification unit: The dosage of integrated desulfurization and denitrification chemicals is 6 kg / 1000 Nm³. 3 Exhaust gas, SO X Removal rate 95.3%, NO X Removal rate: 86.2%;

[0106] The cascade waste heat recovery unit consists of a high-temperature superheater that generates 1.2 tons / hour of 0.9MPa saturated steam, a medium-temperature economizer that preheats the feedwater to 160℃, an air preheater that preheats the combustion air to 320℃, and a low-temperature heat exchanger that recovers waste heat for the regeneration of the desulfurization unit, with a total heat recovery efficiency of 89%.

[0107] Operational results: Outlet VOCs concentration ≤ 5 mg / Nm³ 3 SO2 concentration ≤15mg / Nm 3 NO X Concentration ≤30mg / Nm 3 Dust concentration ≤ 0.5 mg / Nm 3 After 6 months of operation, the corrosion rate was found to be 0.08 mm / year. The steam generated meets 30% of the company's process steam demand, saving more than 2 million yuan in energy costs annually.

[0108] During operation, when the calorific value of the exhaust gas drops to 600 kcal / Nm³ 3 When the intelligent control cabinet detects a drop in calorific value, it automatically activates the flow regulating valve of the auxiliary natural gas pipeline, introducing 5% natural gas to assist combustion. The temperature of the primary combustion chamber is maintained at 880℃, and the temperature of the secondary combustion chamber is maintained at 1120℃. No other parameters need to be adjusted, the system operates stably, and the emission indicators still meet the ultra-low emission requirements.

[0109] During operation, when the concentration of sulfides in the exhaust gas rises to 450 mg / Nm³ 3 When the online monitoring instrument of the desulfurization unit detected that the outlet sulfur content exceeded the standard, the intelligent control cabinet automatically increased the regeneration frequency of the adsorbent in the desulfurization unit (from 8 hours / time to 6 hours / time), and at the same time increased the dosage of the co-purification unit to 6.5 kg / 1000 Nm³. 3 Exhaust gas, ensure SO at the outlet X Concentration ≤15mg / Nm 3 .

[0110] This application example fully demonstrates that the exhaust gas treatment system and process provided by the present invention have excellent purification efficiency, energy recovery performance and operational stability in actual engineering. It can adapt to significant fluctuations in exhaust gas composition and calorific value, meet ultra-low emission requirements, and has good economic benefits and promotional value.

[0111] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

[0112] The terms such as "upper," "lower," "left," "right," and "middle" used in this specification are merely for clarity of description and are not intended to limit the scope of the invention. Any changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

Claims

1. An exhaust gas treatment system, characterized in that, It includes a pretreatment unit, a staged incineration unit, a synergistic purification unit (8), a cascade waste heat recovery unit and an intelligent control unit. The pretreatment unit, the staged incineration unit, the synergistic purification unit (8) and the cascade waste heat recovery unit are connected in sequence. The input end of the pretreatment unit is connected to the exhaust gas pipeline inlet (2), and the output end of the cascade waste heat recovery unit is connected to the inlet of the chimney (14). The pretreatment unit, the staged incineration unit, the synergistic purification unit (8) and the cascade waste heat recovery unit are all connected to the intelligent control unit. The intelligent control unit is used to adjust the adsorbent regeneration frequency of the pretreatment unit, the air ratio of the staged incineration unit, the reagent dosage of the synergistic purification unit and the heat exchange efficiency of the cascade waste heat recovery unit in real time. The staged incineration unit includes multiple combustion chambers connected in series for fully combusting the exhaust gas; the cascaded waste heat recovery unit includes multiple heat exchangers connected in series for fully recovering the heat from the exhaust gas.

2. The exhaust gas treatment system according to claim 1, characterized in that, The pretreatment unit includes a tar collector (3), a desulfurization device (4), and a dust filter (5) connected in sequence, and the tar collector (3), the desulfurization device (4), and the dust filter (5) are all connected to the intelligent control unit.

3. The exhaust gas treatment system according to claim 1, characterized in that, The staged combustion unit includes a primary combustion chamber (6) and a secondary combustion chamber (7) connected in sequence, and both the primary combustion chamber (6) and the secondary combustion chamber (7) are connected to the intelligent control unit.

4. The exhaust gas treatment system according to claim 3, characterized in that, The staged combustion unit also includes an auxiliary natural gas pipeline (9). The primary combustion chamber (6) and the secondary combustion chamber (7) both use dual-fuel nozzles. The main nozzle of the dual-fuel nozzle is supplied with pretreated exhaust gas, and the auxiliary nozzle of the dual-fuel nozzle is supplied with natural gas as auxiliary fuel.

5. The exhaust gas treatment system according to claim 3, characterized in that, The collaborative purification unit (8) adopts an integrated desulfurization and denitrification module.

6. The exhaust gas treatment system according to claim 2, characterized in that, The cascade waste heat recovery unit includes a high-temperature superheater (10), a medium-temperature economizer (11), an air preheater (12), and a low-temperature preheater (13) arranged in sequence. The high-temperature superheater (10), the medium-temperature economizer (11), the air preheater (12), and the low-temperature preheater (13) are all connected to the intelligent control unit. The high-temperature superheater (10) is equipped with a steam output pipe (17) for outputting high-temperature steam; the medium-temperature economizer (11) is used to preheat the boiler feedwater; the air preheater (12) is used to input preheated air (16) into the boiler; and the low-temperature preheater (13) is used to heat the regeneration medium of the desulfurization device (4) to output desulfurization medium regeneration resources (15).

7. The exhaust gas treatment system according to claim 1, characterized in that, The intelligent control unit includes an intelligent control cabinet (1) and an online flue gas composition monitor. The online flue gas composition monitor is installed inside the chimney (14) and is connected to the intelligent control cabinet (1).

8. A tail gas treatment process, employing the tail gas treatment system according to any one of claims 1 to 7, characterized in that, Includes the following steps: S1. Exhaust gas pretreatment: The exhaust gas is sequentially passed through the tar collector (3), the desulfurization device (4) and the dust filter (5) for pretreatment; S2, Staged combustion: The pretreated exhaust gas is introduced into the first-stage combustion chamber (6) for preliminary combustion, and then introduced into the second-stage combustion chamber (7) for complete combustion; S3, Collaborative Purification: The exhaust gas after staged combustion is fed into an integrated desulfurization and denitrification module for desulfurization and denitrification; S4, cascade waste heat recovery: The exhaust gas after co-purification is sequentially passed into the high-temperature superheater (10), the medium-temperature economizer (11), the air preheater (12) and the low-temperature preheater (13) for multi-stage waste heat recovery. S5. Exhaust gas emission: The exhaust gas after waste heat recovery is introduced into the chimney (14) and tested using an online flue gas composition monitor; if the test is qualified, it is emitted; if the test is unqualified, the exhaust gas is sent to the pretreatment unit and steps S1 to S5 are repeated for further treatment.

9. The exhaust gas treatment process according to claim 8, characterized in that, It also includes step S6, system adaptive operation: During the process, the intelligent control cabinet (1) is used to adjust the regeneration frequency of the pretreatment unit adsorbent, the air ratio of the staged incineration unit, the dosage of the synergistic purification unit and the heat exchange efficiency of the staged waste heat recovery unit in real time.

10. The exhaust gas treatment process according to claim 9, characterized in that, The tar collector (3) in step S1 adopts a low-temperature condensation + activated carbon adsorption composite process to control the tail gas temperature to 30℃-40℃; the desulfurization device (4) adopts a modified zeolite-based supported metal catalyst to reduce the total sulfur content of the tail gas to ≤10mg / Nm³. 3 The dust filter (5) uses a ceramic filter element. In step S2, the primary combustion chamber (6) adopts a partial oxidation combustion mode, introduces 60%-70% of the theoretical air volume, and controls the combustion temperature at 850℃-950℃ to allow the flammable components to initially burn; the secondary combustion chamber (7) adopts swirl combustion technology, introduces the remaining air, controls the combustion temperature at 1100℃-1200℃, and has a residence time of ≥2s to allow the incompletely burned products to be completely oxidized and decomposed. The integrated desulfurization and denitrification module mentioned in step S3 uses an integrated desulfurization and denitrification agent, which is made from modified fly ash from waste incineration. The dosage of the agent is 5-7 kg / 1000 Nm³. 3 exhaust; The high-temperature superheater (10) in step S4 is made of stainless steel and has an anti-corrosion coating on the tube wall. It is used to recover the heat of flue gas at 800℃-1000℃ to generate 0.8MPa-1.0MPa saturated steam. The medium-temperature economizer (11) is used to preheat the boiler feedwater to 150℃-180℃. The air preheater (12) is used to preheat the air required for combustion to 300℃-350℃. The low-temperature preheater (13) recovers the waste heat of flue gas at 150-100℃ and is used to heat the regeneration medium of the desulfurization device (4).

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