Efficient acrylonitrile waste gas incineration system

Abstract

The invention provides an efficient acrylonitrile waste gas incineration system, which relates to the technical field of acrylonitrile waste gas incineration and comprises a waste gas pretreatment unit, a graded incineration unit, a combustion-supporting system, a waste heat recovery unit, a deep denitration unit, a flue system and a control system. After gas-liquid separation, the waste gas is heated step by step through a low-temperature AOG preheater and a high-temperature AOG preheater; cracking in a reduction section of an incinerator, fully combusting in an oxidation section, and preliminarily denitrifying in an SNCR section; and flue gas is subjected to heat recovery through a waste heat boiler, and is discharged after reaching the standard after being deeply denitrified by an SCR reactor. Harmless treatment of highly toxic waste gas is achieved, the gradient utilization rate of energy is increased by 40%, NOX emission is smaller than 50 mg / m, and the problems of high pollution and high energy consumption in the prior art are solved.

Description

TECHNICAL FIELD

[0001] The present application mainly relates to the technical field of acrylonitrile waste gas incineration, and particularly relates to a high-efficiency acrylonitrile waste gas incineration system. BACKGROUND

[0002] The acrylonitrile (AN) waste gas incineration system is used for treating waste gas from an acrylonitrile absorption tower, and the incineration product is finally discharged into the atmosphere through a chimney. In order to meet the environmental protection requirements, the toxic waste gas containing water, nitrogen, acrylonitrile, acetonitrile, hydrocyanic acid, carbon monoxide, carbon dioxide and other components must be treated.

[0003] The waste gas (AOG) generated in the acrylonitrile production process contains toxic components (such as acrylonitrile and hydrocyanic acid), combustible organic matter (propylene and carbon monoxide) and a large amount of inert gas (nitrogen accounts for 80-95%). At present, the organic matter is mainly decomposed through incineration technology, but there are significant defects: Firstly, the traditional incineration system relies on manual adjustment of combustion parameters (such as air volume and temperature), especially when dealing with waste gas component fluctuations, frequent intervention is required, which increases the operation complexity and safety risk; secondly, the single furnace design leads to insufficient combustion, NO x emission is often >200mg / m 3 ( far more than the national standard limit of 100mg / m 3 ); and the flue gas waste heat recovery rate is low (flue gas temperature >200 degrees Celsius), the fuel consumption is high (natural gas >2000Nm 3 / h); finally, the traditional incinerator has insufficient combustion stability for low-calorific-value waste gas, which is easy to extinguish or produce toxic residues.

[0004] It should be noted that the above content belongs to the technical cognition of the skilled person. Since the technical content in this field is vast and complex, the above content of the present application does not necessarily constitute the prior art. SUMMARY

[0005] 1. Technical problems to be solved by the present application: The present application provides a high-efficiency acrylonitrile waste gas incineration system to solve the technical problems in the background art.

[0006] 2. Technical solutions: In order to achieve the above purpose, the technical solutions provided by the present application are as follows: a high-efficiency acrylonitrile waste gas incineration system, comprising a waste gas pretreatment unit: containing a gas-liquid separation tank, a low-temperature AOG preheater and a high-temperature AOG preheater connected in series, for gradually preheating the waste gas from the acrylonitrile absorption tower; Staged incineration unit: including horizontal cylindrical incinerator, which is divided into reduction section, oxidation section and SNCR section along the flue gas flow direction; the reduction section is connected with the exhaust gas inlet and the side wall is provided with a low-nitrogen burner and an ignition device; the oxidation section is provided with a secondary air inlet; the AOG gas passes through the reduction section and the oxidation section and then enters the SNCR section; Combustion support system: including primary combustion fan and secondary combustion fan, the outlet of the primary combustion fan is connected with the primary combustion air preheater, and the outlet of the secondary combustion fan is connected with the secondary combustion air preheater; Waste heat recovery unit: including waste heat boiler, the flue gas inlet of which is connected with the outlet of the incinerator, and the inside is provided with a superheater, an evaporator and an economizer for producing by-product superheated steam; Deep denitration unit: including SCR reactor, the inlet of which is connected with the flue gas outlet of the waste heat boiler, and the inside is filled with vanadium-titanium-based catalyst; Flue system: including induced draft fan and chimney connected with the outlet of the SCR reactor; Control system: including DCS system and BMS safety interlocking system for realizing automatic adjustment of incineration parameters and fault protection.

[0007] The device first introduces AOG tail gas discharged from the acrylonitrile absorption tower at a temperature of 36 degrees Celsius and a pressure of 0.015 MPa (G) into a gas-liquid separation tank to separate liquid impurities, and the gas successively passes through a low-temperature AOG preheater, exchanges heat with 280-degree-Celsius flue gas at the outlet of the economizer to be heated to 240 degrees Celsius, and passes through a high-temperature AOG preheater to exchange heat with 550-degree-Celsius flue gas at the outlet of the waste heat boiler to be heated to 450 degrees Celsius; Then the 450-degree-Celsius exhaust gas enters the reduction section of the incinerator, is heated to 900-1100 degrees Celsius by the low-nitrogen burner in the lean oxygen reduction atmosphere, and is cracked into CO, H2 and N2 from acrylonitrile (AN) and hydrogen cyanide (HCN); the outlet temperature of the cracking gas is 900 degrees Celsius, enters the oxidation section, and is mixed with 500-degree-Celsius secondary air for combustion to completely oxidize CO and H2; The flue gas flows into the SNCR section, and then ammonia water / urea is sprayed in the interval of 850-1050 degrees Celsius to preliminarily remove NO X .

[0008] The 900-degree-Celsius flue gas after removal enters the waste heat boiler: Flue gas side: successively passing through the convection tube bundle, the high-temperature superheater and the low-temperature superheater to be cooled to 550 degrees Celsius; Steam-water side: the feed water is heated by the economizer, evaporated in the drum, and the saturated steam passes through the low-temperature / high-temperature superheater and the desuperheater to output 4.2 MPa (G) / 390 degrees Celsius superheated steam, part of which is used for primary air preheating; 550℃ flue gas enters high-temperature AOG preheater in parallel, part of which heats acrylonitrile absorption tower exhaust gas heated by coal gas, and part of which enters secondary combustion air preheater to heat combustion air, and the temperature is reduced to 320℃; 320℃ flue gas enters SCR reactor, generally uses vanadium-titanium-based catalyst, and after deep denitration, the temperature is reduced to 130℃ by coal economizer and low-temperature AOG preheater, and finally discharged through chimney.

[0009] In the above process, the BMS system realizes automatic ignition, flame monitoring and flameout interlocking; The DCS system automatically adjusts the amount of natural gas according to the furnace temperature of 900-1100℃, automatically adjusts the liquid level of the steam drum, and realizes low-low interlocking and high-high interlocking of the liquid level of the steam drum; By using the application for treating acrylonitrile waste gas, AN and HCN are fully decomposed at 900-1100℃ in the reducing section under a lean oxygen environment, avoiding the formation of dioxin; and in actual measurement, the energy cascade utilization rate is improved by 40%, mainly including the waste gas two-stage preheating stage, which can reduce the fuel consumption of the reducing section by 35% from 36℃ to 450℃; the secondary air preheating gas is heated from room temperature to 500℃, reducing the combustion energy consumption of the oxidation section by 30%; the system thermal efficiency reaches 92% from 320℃ to 130℃ in the exhaust gas heat recovery stage, greatly saving energy consumption. At the same time, the device of the application adopts double-stage denitration: SNCR in the furnace + SCR outside the furnace, so that NO X emission < 50 mg / m 3 The embodiment realizes harmlessness of toxic waste gas, reduces energy consumption by 40%, and achieves a technical breakthrough of emission better than national standard and steam self-sufficiency rate of 100% through the design of staged incineration + four-stage waste heat recovery + intelligent control, solving the industry pain points of high pollution and high energy consumption of traditional technology.

[0010] Further, the reducing section of the incinerator controls the excess air coefficient to be less than 1, forming a lean oxygen reducing atmosphere; and the oxidation section is supplied with combustion air preheated to 500℃ by the secondary combustion air preheater.

[0011] Further, the SNCR section is located behind the reducing section and the oxidation section, and urea or ammonia water is sprayed at 850-1050℃. The SCR reactor operates at 320℃, and the catalyst is arranged in a 2+1 redundancy mode.

[0012] Further, the waste heat recovery unit realizes energy cascade utilization through a cascade heat exchange network. 550℃ flue gas from the outlet of the waste heat boiler is input into the high-temperature AOG preheater and the secondary combustion air preheater in parallel, and acrylonitrile waste gas and secondary air are heated to 450℃ and 500℃, respectively. The 320-degree-Celsius flue gas from the secondary combustion air preheater outlet enters the SCR reactor; The flue gas from the SCR reactor outlet successively flows through the economizer and the low-temperature AOG preheater, and the final flue gas temperature is reduced to 130 degrees Celsius.

[0013] Further, the low-nitrogen burner adopts air staging and fuel staging technologies, and integrates a flame detector, an extinguishing protection and an automatic ignition function; the incinerator is lined with mullite refractory material with a thickness of not less than 350 mm, and the flue gas residence time is not less than 2 seconds.

[0014] Further, the low-temperature AOG preheater, the high-temperature AOG preheater and the secondary combustion air preheater all adopt 304H stainless steel plate heat exchangers.

[0015] Further, the primary combustion air preheater uses the superheated steam by-produced by the waste heat boiler as a heat source to heat the primary air from 20 degrees Celsius to 250 degrees Celsius.

[0016] Further, the waste heat boiler of the waste heat recovery unit realizes the recycling of heat energy, and the boiler feed water is heated by the economizer and then enters the boiler drum; A steam-water separation device is arranged in the boiler drum, and the saturated steam is successively output through a low-temperature superheater, a high-temperature superheater and an attemperator to output 390-degree-Celsius superheated steam; Part of the superheated steam is branched to the primary combustion air preheater.

[0017] Further, the BMS functions include: through the operation of the on-site operation panel arranged with display lights and switch buttons, the on-site automatic or manual ignition, fuel gas input, parking and purging of the incinerator burner are completed; the BMS can be placed in a cabinet with a man-machine interface, has a manual / automatic switching function, and can realize ignition operation; the DCS control system functions include: automatic control and fault protection of the incineration system, and the like, the information of each control point on site is connected to the terminal box through hard wiring, the state of the on-site equipment is fed back to the DCS system, the working conditions are monitored in real time through the computer display in the central control room, and timely adjustment is made in cooperation with the on-site operators, and emergency treatment is performed on abnormal conditions and sudden accidents.

[0018] Further, the system is operated by the induced draft fan under negative pressure.

[0019] 3. Beneficial effects: Compared with the prior art, the technical scheme provided by the present application has the following beneficial effects: The present application is reasonable in design, and the synergistic effect of the oxygen-poor environment and the high temperature of 1100 DEG C in the reduction section makes the burning rate of acrylonitrile (AN) and hydrocyanic acid (HCN) ≥ 99.99%, and the generation of dioxin is eliminated from the source; the SNCR+SCR combined process realizes the NOx emission < 50mg / m 3 Much lower than the national standard; Adopting four-stage waste heat gradient recovery and two-stage preheating of waste gas: making the initial temperature 36 DEG C to 450 DEG C, reducing the fuel consumption of the reduction section by 35%; combustion air heating: secondary air normal temperature to 500 DEG C, reducing the energy consumption of the oxidation section by 30%; steam self-circulation: 1.2t / h of 21t / h steam is used for primary air preheating, realizing energy self-sufficiency; exhaust gas temperature limit compression: 130 DEG C, and the system thermal efficiency reaches 92%; Designing refractory lining: ≥ 350mm mullite material, temperature resistance > 1600 DEG C, service life > 15 years; redundant denitration: SCR catalyst "2+1" mode, online supplementing without stopping the furnace, reducing the maintenance cost by 70%; corrosion-resistant heat exchanger: 304H stainless steel plate structure, resistant to 550 DEG C acid flue gas, service life doubled.

[0020] It should be noted that the structures not introduced in the present application do not involve the design points and improvement directions of the present application, and are the same as or can be realized by using the prior art. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 It is a process flow structure diagram of the present application; Figure 2 It is a process flow pre-set waste gas parameter diagram of the present application; Figure 3 It is a process flow thermal calculation 100% design working condition parameter diagram of the present application. DETAILED DESCRIPTION

[0022] In order to facilitate the understanding of the present application, the present application will be described more fully below with reference to the related drawings, which show several embodiments of the present application. However, the present application can be realized in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0023] It should be noted that the structures not introduced in the present application do not involve the design points and improvement directions of the present application, and can adopt the prior art known by those skilled in the art.

[0024] The specific implementation of the present application will be described in detail below in combination with specific embodiments.

[0025] Referring to the drawings Figure 1 An efficient acrylonitrile waste gas incineration system, comprising Waste gas pretreatment unit: comprising a gas-liquid separation tank, a low-temperature AOG preheater and a high-temperature AOG preheater connected in series, for gradually preheating the waste gas from the acrylonitrile absorption tower; Staged incineration unit: comprising a horizontal cylindrical incinerator, which is divided into a reduction section, an oxidation section and an SNCR section along the flue gas flow direction; the reduction section is connected with the waste gas inlet and is provided with a low-nitrogen burner and an ignition device on the side wall; the oxidation section is provided with a secondary air inlet; the AOG gas passes through the reduction section and the oxidation section and then enters the SNCR section; Combustion support system: comprising a primary combustion fan and a secondary combustion fan, the outlet of the primary combustion fan is connected with a primary combustion air preheater, and the outlet of the secondary combustion fan is connected with a secondary combustion air preheater; Waste heat recovery unit: comprising a waste heat boiler, the flue gas inlet of which is connected with the outlet of the incinerator, and the inside of which is provided with a superheater, an evaporator and an economizer, for producing superheated steam as a byproduct; Deep denitration unit: comprising an SCR reactor, the inlet of which is connected with the flue gas outlet of the waste heat boiler, and the inside of which is filled with a vanadium-titanium-based catalyst; Flue system: comprising an induced draft fan and a chimney connected with the outlet of the SCR reactor; Control system: comprising a DCS system and a BMS safety interlocking system, for realizing automatic adjustment of incineration parameters and fault protection.

[0026] In this embodiment, please refer to Figure 2 , the content of each component in the waste gas parameters is shown in the figure, first, the AOG tail gas discharged from the acrylonitrile absorption tower has a temperature of 36 degrees Celsius and a pressure of 0.015 MPa (G), enters the gas-liquid separation tank, separates the liquid impurities, and the gas successively passes through the low-temperature AOG preheater, is heated to 240 degrees Celsius by heat exchange with the 280 degrees Celsius flue gas at the outlet of the economizer, and passes through the high-temperature AOG preheater, is heated to 450 degrees Celsius by heat exchange with the 550 degrees Celsius flue gas at the outlet of the waste heat boiler; Then, the 450 degrees Celsius waste gas enters the reduction section of the incinerator, is heated to 900-1100 degrees Celsius by the low-nitrogen burner in the oxygen-poor reduction atmosphere, and makes acrylonitrile (AN) and hydrogen cyanide (HCN) crack into CO, H2 and N2; the cracked gas outlet temperature is 900 degrees Celsius, enters the oxidation section, and is mixed with 500 degrees Celsius secondary air for combustion, so that CO and H2 are completely oxidized; The flue gas flows into the SNCR section, and then ammonia water / urea is sprayed in the 850-1050 degrees Celsius interval, so that NO X is preliminarily removed.

[0027] The 900 degrees Celsius flue gas after removal enters the waste heat boiler: Flue gas side: successively through the convection tube bundle→high-temperature superheater→low-temperature superheater, and is cooled to 550 degrees Celsius; Steam and water side: Feedwater is heated by the economizer → evaporated in the boiler drum → saturated steam passes through the low-temperature / high-temperature superheater and desuperheater, outputting 4.2MPa(G) / 390 degrees Celsius superheated steam, part of which is used for primary air preheating). The 550°C flue gas enters the high-temperature AOG preheater in parallel, part of which reheats the acrylonitrile absorption tower exhaust gas that has been heated by the economizer gas, and part of which enters the secondary combustion air preheater to heat the combustion air and cool it down to 320°C. Flue gas at 320 degrees Celsius enters the SCR reactor, which typically uses a vanadium-titanium-based catalyst for deep denitrification. After denitrification, the gas is cooled to 130 degrees Celsius by an economizer and a low-temperature AOG preheater before being discharged through the chimney in compliance with emission standards.

[0028] During the above process, the BMS system realizes automatic ignition, flame monitoring, and flameout interlock; The DCS system automatically adjusts the natural gas volume based on the furnace temperature of 900~1100 degrees Celsius, automatically adjusts the steam drum liquid level, and realizes low-low interlock and high-high interlock of the steam drum liquid level. Finally, please refer to Figure 3 The diagram shows test parameters based on 100% design operating conditions according to thermal calculations. This system, employing the methods described in this application, treats acrylonitrile waste gas. In the oxygen-deficient environment of the reduction section, AN and HCN are fully decomposed at 900-1100 degrees Celsius, preventing dioxin formation. Furthermore, actual calculations show a 40% improvement in energy utilization efficiency, primarily due to the two-stage preheating stage of waste gas (36°C → 450°C), which reduces fuel consumption in the reduction section by 35%; the secondary air preheating stage (from ambient temperature to 500°C) reduces combustion energy consumption in the oxidation section by 30%; and the waste heat recovery stage (320°C → 130°C) achieves a system thermal efficiency of 92%, significantly saving energy. Simultaneously, this application's device employs a two-stage denitrification process: SNCR in-furnace + SCR outside-furnace to reduce NO... X Emissions <50mg / m³ 3 This embodiment achieves a technological breakthrough by using a design of staged incineration, four-stage waste heat recovery, and intelligent control to render highly toxic waste gas harmless, while reducing energy consumption by 40%, achieving emissions better than national standards, and achieving 100% steam self-sufficiency. This solves the industry pain points of high pollution and high energy consumption associated with traditional technologies.

[0029] The reduction section of the incinerator controls the excess air coefficient to be less than 1, forming an oxygen-deficient reducing atmosphere. The oxidation section introduces combustion air preheated to 500 degrees Celsius by a secondary combustion air preheater, and controls the excess air coefficient to ensure that the CO and H2 generated in the reduction section are fully oxidized. The pyrolysis gas, with an outlet temperature of 900 degrees Celsius, enters the oxidation section and mixes with the 500-degree Celsius secondary air for combustion, thoroughly oxidizing CO and H2, thereby improving the processing efficiency.

[0030] The SNCR section is located after the reduction and oxidation sections, and urea or ammonia is sprayed in the range of 850 to 1050 degrees Celsius. The SCR reactor operates at 320 degrees Celsius, and the catalyst is arranged in a 2+1 redundancy mode. In this embodiment, the combined process utilizes a staged denitrification mechanism of high-temperature free radical reaction + medium-temperature catalytic reduction to achieve ultra-low emissions. Simultaneously, through temperature coordination and redundant design, it reduces operating costs to 60% of traditional technologies, thereby achieving low NOx emissions. x Combustion + Deep Emission Reduction; When the high-temperature non-nitrification (SNCR) section of the incinerator is operating, the temperature of the SNCR section is maintained at 850–1050 degrees Celsius. Urea solution or 20% ammonia water is injected into the flue gas at the outlet of the reduction section through a spray gun. Amino free radicals react with NO in the flue gas. x A reduction reaction occurs: 4NO + 4NH3 + O2 → 4N2 + 6H2O, denitrification efficiency 60~70%; During operation of the SCR section for low-temperature deep denitrification outside the furnace, the flue gas from the waste heat boiler outlet, initially at 550°C, is cooled to 320°C via heat exchange before entering the vertical SCR reactor. The flue gas passes vertically through the vanadium-titanium-based catalyst layer, where a catalytic reduction reaction occurs at the active sites of the catalyst. NO + NO2 + 2NH3 → 2N2 + 3H2O, denitrification efficiency > 90%; The system designed in this application utilizes the high temperature of the incinerator itself, eliminating the need for an external heat source and saving 35% of catalyst heating energy compared to the pure SCR process. The SCR operates at a medium temperature of 320 degrees Celsius, which reduces steam consumption for insulation by 15% compared to conventional high-temperature SCRs, such as those operating at 380-400 degrees Celsius. Simultaneously, the reactor actually operates with two catalyst layers, meeting the denitrification efficiency requirements under the design conditions.

[0031] One spare layer is reserved between the two operating catalyst layers as an empty installation space. Initially, no catalyst is filled in, which serves as a spare space for future expansion or replacement.

[0032] The waste heat recovery unit achieves graded energy utilization through a cascaded heat exchange network. The 550°C flue gas from the waste heat boiler outlet is fed in parallel into the high-temperature AOG preheater and the secondary combustion air preheater, which heat the acrylonitrile waste gas to 450°C and the secondary air to 500°C, respectively. The 320°C flue gas from the outlet of the secondary combustion air preheater enters the SCR reactor. The flue gas from the SCR reactor outlet flows sequentially through the economizer and the low-temperature AOG preheater, and the final exhaust gas temperature drops to 130 degrees Celsius. The specific process is as follows: High-temperature energy recovery stage: The 550°C high-temperature flue gas discharged from the waste heat boiler is diverted into the parallel high-temperature AOG preheater and secondary combustion air preheater: High-temperature AOG preheater: The flue gas exchanges heat with the acrylonitrile waste gas from 550 degrees Celsius to 240 degrees Celsius, the waste gas temperature rises to 450 degrees Celsius, and the flue gas temperature drops to 320 degrees Celsius. Secondary combustion air preheater: The flue gas exchanges heat with the ambient temperature combustion air, and the secondary air is heated to 500 degrees Celsius to reduce the energy consumption of the oxidation section. The flue gas is simultaneously cooled to 320 degrees Celsius.

[0033] This stage utilizes a parallel heat exchange design for high-temperature flue gas to achieve synchronous preheating of the exhaust gas and combustion air, thus avoiding pressure drop losses caused by series heat exchange.

[0034] In addition to deep recovery in the medium and low temperature range, after the 320°C flue gas enters the SCR denitrification process, it flows sequentially through: Economizer: It exchanges heat with the 104°C boiler feedwater, preheats the feedwater to near saturation, and cools the flue gas to 280°C; Low-temperature AOG preheater: It exchanges heat with the original exhaust gas at 36 degrees Celsius, raising the exhaust gas temperature to 240 degrees Celsius, laying the foundation for the secondary high-temperature preheating stage, and finally cooling the flue gas to 130 degrees Celsius before emission.

[0035] This process forms an energy closed loop: the waste heat of low-temperature flue gas is used for boiler feedwater preheating and initial preheating of exhaust gas, thoroughly tapping the residual calorific value. This cascade network, through a four-stage heat exchange architecture of high-temperature parallel diversion and medium-low temperature series recovery, compresses the exhaust gas temperature to near the theoretical limit while ensuring safe operation, achieving a dual breakthrough in energy consumption and environmental performance.

[0036] The low-NOx burner employs air staging and fuel staging technologies to precisely adjust combustion efficiency, ensuring complete fuel combustion while significantly reducing NOx emissions. x To reduce emissions and improve environmental performance, the system integrates flame detectors, flameout protection, and automatic ignition functions; the incinerator is lined with mullite refractory material with a thickness of not less than 350 mm, and the flue gas residence time is not less than 2 seconds; in this embodiment, primary air is introduced from the center of the burner during operation to maintain oxygen-deficient combustion and suppress thermal NOx. x Secondary air is generated; it is introduced into the periphery of the flame through a swirl device to achieve air staging, ensuring complete combustion of fuel; natural gas and exhaust gas are premixed in a multi-tube burner, and the flame temperature is controlled at 900~1100 degrees Celsius by adjusting the fuel / exhaust gas ratio to achieve fuel staging and avoid local high temperature generation of NO. x A mullite lining ≥350mm forms an insulation barrier, reducing heat loss from the furnace and stabilizing the reduction section temperature at 1100 degrees Celsius; through staged combustion control and a highly reliable refractory structure, NO0.05 is achieved. xWhile reducing emissions at the source, the incinerator achieves low emissions and low maintenance through fully automated operation and long lifespan design.

[0037] The low-temperature AOG preheater, high-temperature AOG preheater, and secondary combustion air preheater all adopt 304H stainless steel plate heat exchangers. In this embodiment, the 304 / 304H plate heat exchangers achieve ultra-high temperature preheating of 450 degrees Celsius and extreme flue gas temperature of 130 degrees Celsius with a compact structure by selecting high-temperature corrosion-resistant materials and parallel turbulent heat transfer enhancement, providing industry-leading energy efficiency and reliability support for the incineration system.

[0038] The primary combustion air preheater uses superheated steam produced by the waste heat boiler as a heat source to heat the primary air from 20 degrees Celsius to 250 degrees Celsius. In this embodiment, the 4.2 MPa(G) / 390 degrees Celsius superheated steam produced by the waste heat boiler enters the shell-and-tube primary air preheater and exchanges heat with the ambient temperature primary air. Latent heat released on the steam side: 390 degrees Celsius → 255 degrees Celsius; Sensible heat absorbed on the air side: 20 degrees Celsius → 250 degrees Celsius; The preheated primary air is sent into the reduction section of the incinerator to support oxygen-deficient combustion.

[0039] The waste heat recovery unit's waste heat boiler realizes the recovery and utilization of heat energy, and the boiler feedwater enters the boiler drum after being heated by the economizer. A steam-water separator is installed inside the boiler drum. Saturated steam passes through a low-temperature superheater, a high-temperature superheater, and a desuperheater in sequence before outputting 390-degree Celsius superheated steam. Some of the superheated steam is diverted to the primary combustion air preheater.

[0040] In this embodiment, the 104°C boiler feedwater is preheated by the economizer and heat exchanged with the 280°C flue gas to reach a saturated temperature of nearly 200°C before entering the boiler drum.

[0041] Water in the boiler drum flows through the downcomer to the convection tube bundle, where it absorbs heat to generate a steam-water mixture. After separation by the corrugated plate separator and baffles, saturated steam is output.

[0042] The saturated steam then passes sequentially through a low-temperature superheater and a high-temperature superheater for heat exchange, raising the temperature to 410 degrees Celsius. Water spray desuperheater: If the temperature of the saturated steam after heating is too high, and the temperature sensor detects that the temperature is higher than the safe value (390 degrees Celsius), the water spray desuperheater injects 104 degrees Celsius feedwater for fine adjustment, and finally outputs 4.2MPa(G) / 390 degrees Celsius stable superheated steam.

[0043] Steam diversion: Of the 21t / h superheated steam, 1.2t / h is diverted to the primary air preheater, and the remainder is supplied externally. This structure completes the primary air preheating with zero external energy consumption, realizing a closed-loop energy chain of "waste gas treatment → steam production → self-heating", and the overall energy efficiency is improved by more than 40% compared with the traditional system.

[0044] The BMS functions include: enabling automatic or manual ignition, fuel gas injection, shutdown, and purging of the incinerator burner via a local control panel equipped with indicator lights and switches; the BMS can be placed in a cabinet, has a human-machine interface, and features manual / automatic switching capabilities, allowing for ignition operation; the DCS control system functions include automatic control and fault protection of the incineration system, with information from local control points connected to a junction box via hardwiring, feeding back the status of field equipment to the DCS system, real-time monitoring of operating conditions via computer monitors in the central control room, timely adjustments in collaboration with field operators, and emergency handling of abnormal situations and accidents, improving the overall system's intelligence level, achieving automated operation, and ultimately achieving a dual breakthrough in low human error rate and low energy consumption per ton of incineration system processing.

[0045] This system operates under negative pressure via an induced draft fan. In this embodiment, to prevent the leakage of high-temperature flue gas, the incineration system maintains a slight negative pressure, and the induced draft fan controls the negative pressure in the furnace to prevent toxic and harmful gases from escaping.

[0046] It should be understood that the temperature values ​​described in the specific embodiments of this application refer to the expected target values ​​for process control. Those skilled in the art fully understand and acknowledge that any actual process operation has inherent errors; therefore, achieving the stated temperature values ​​will inevitably involve a reasonable fluctuation range. The specific temperature values ​​should be considered to implicitly include this reasonable fluctuation range, which is a meaning that can be clearly interpreted by those skilled in the art based on common sense; therefore, its error tolerance will not be detailed further.

[0047] The above-described embodiments are merely illustrative of certain implementations of the present invention, and are described in a relatively specific and detailed manner. However, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements are all within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. A high-efficiency acrylonitrile waste gas incineration system, characterized in that: include Waste gas pretreatment unit: includes a gas-liquid separator, a low-temperature AOG preheater and a high-temperature AOG preheater connected in series, used to preheat the waste gas from the acrylonitrile absorption tower in stages. Staged incineration unit: includes a horizontal cylindrical incinerator, which is divided into a reduction section, an oxidation section and an SNCR section along the flue gas flow direction; the reduction section is connected to the exhaust gas inlet and a low-NOx burner and ignition device are installed on the side wall; the oxidation section is equipped with a secondary air inlet; AOG gas enters the SNCR section after passing through the reduction section and the oxidation section. Combustion support system: includes a primary combustion air fan and a secondary combustion air fan. The outlet of the primary combustion air fan is connected to the primary combustion air preheater, and the outlet of the secondary combustion air fan is connected to the secondary combustion air preheater. Waste heat recovery unit: includes a waste heat boiler, whose flue gas inlet is connected to the incinerator outlet, and is equipped with a superheater, evaporator and economizer to produce superheated steam as a by-product; Deep denitrification unit: includes an SCR reactor, whose inlet is connected to the flue gas outlet of the waste heat boiler, and is filled with vanadium-titanium-based catalyst; Flue system: includes the induced draft fan and chimney connected to the SCR reactor outlet; Control system: Includes DCS system and BMS safety interlock system, used to realize automatic adjustment of incineration parameters and fault protection.

2. The high-efficiency acrylonitrile waste gas incineration system according to claim 1, characterized in that: The reduction section of the incinerator controls the excess air coefficient to be less than 1, forming an oxygen-deficient reducing atmosphere; the oxidation section introduces combustion air preheated to 500 degrees Celsius by a secondary combustion air preheater.

3. The high-efficiency acrylonitrile waste gas incineration system according to claim 1, characterized in that: The SNCR section is located after the reduction and oxidation sections, and urea or ammonia is sprayed in the range of 850 to 1050 degrees Celsius. The SCR reactor operates at 320 degrees Celsius, and the catalyst is arranged in a 2+1 redundancy mode.

4. The high-efficiency acrylonitrile waste gas incineration system according to claim 1, characterized in that: The waste heat recovery unit achieves graded energy utilization through a cascaded heat exchange network. The 550°C flue gas from the waste heat boiler outlet is fed in parallel into the high-temperature AOG preheater and the secondary combustion air preheater, which heat the acrylonitrile waste gas to 450°C and the secondary air to 500°C, respectively. The 320°C flue gas from the outlet of the secondary combustion air preheater enters the SCR reactor. The flue gas from the SCR reactor outlet flows sequentially through the economizer and the low-temperature AOG preheater, and the final exhaust gas temperature drops to 130 degrees Celsius.

5. The high-efficiency acrylonitrile waste gas incineration system according to claim 1, characterized in that: The low-NOx burner adopts air grading and fuel grading technology and integrates flame detector, flameout protection and automatic ignition functions; the incinerator is lined with mullite refractory material with a thickness of not less than 350 mm and the flue gas residence time is not less than 2 seconds.

6. The high-efficiency acrylonitrile waste gas incineration system according to claim 1, characterized in that: The low-temperature AOG preheater, high-temperature AOG preheater, and secondary combustion air preheater all use 304H stainless steel plate heat exchangers.

7. The high-efficiency acrylonitrile waste gas incineration system according to claim 1, characterized in that: The primary combustion air preheater uses superheated steam produced by the waste heat boiler as a heat source to heat the primary air from 20 degrees Celsius to 250 degrees Celsius.

8. The high-efficiency acrylonitrile waste gas incineration system according to claim 1, characterized in that: The waste heat recovery unit's waste heat boiler realizes the recovery and utilization of heat energy, and the boiler feedwater enters the boiler drum after being heated by the economizer. A steam-water separator is installed inside the boiler drum. Saturated steam passes through a low-temperature superheater, a high-temperature superheater, and a desuperheater in sequence before outputting 390-degree Celsius superheated steam. Some of the superheated steam is diverted to the primary combustion air preheater.

9. The high-efficiency acrylonitrile waste gas incineration system according to claim 1, characterized in that: The BMS safety interlock system functions include: enabling automatic or manual ignition, fuel gas injection, shutdown, and purging of the incinerator burner via a local control panel equipped with indicator lights and switches; the BMS can be placed in a cabinet, has a human-machine interface, and features manual / automatic switching capabilities, allowing for ignition operation; the DCS system functions include automatic control and fault protection of the incineration system, with information from local control points connected to a junction box via hardwiring, feeding back the status of field equipment to the DCS system, allowing real-time monitoring of operating conditions via computer monitors in the central control room, enabling timely adjustments in collaboration with field operators, and providing emergency handling for abnormal situations and accidents.

10. The high-efficiency acrylonitrile waste gas incineration system according to claim 1, characterized in that: This system operates under negative pressure via an induced draft fan.

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