A waste gas recovery and auxiliary decomposition method and system for mass debinding of orthodontic brackets

Abstract

The present application relates to the field of control and regulation technology, in particular to a kind of waste gas recovery collaborative auxiliary decomposition method and system for large batch of orthodontic bracket degreasing, especially to the technology of concentration and pipeline pressure of degreasing waste gas are cooperatively controlled and regulated.The system is arranged between the waste gas outlet pipeline of degreasing furnace and tail gas treatment system, including concentration regulating system, pressure regulating bypass buffer system, concentration detection component and control system.The concentration regulating system collects low-concentration waste gas as diluent gas to mix into waste gas;Pressure regulating bypass buffer system shunts and temporarily stores gas;Concentration detection component is located upstream of the mixing position, obtains the concentration trend signal of original waste gas.Control system triggers mixing and synchronous shunting when concentration rises and has not reached preset threshold, offsets the flow increase and pressure disturbance caused by mixing;When concentration falls, synchronous mixing amount and shunt flow are reduced.The present application can reduce waste gas concentration peak and maintain stable pipeline pressure.

Description

Technical Field

[0001] This invention relates to the field of control and regulation technology, specifically to a method and system for the recovery and assisted decomposition of waste gas used in the large-scale degreasing of orthodontic brackets, and particularly to a technology for the coordinated control and regulation of the concentration of degreasing waste gas and pipeline pressure. Background Technology

[0002] Metal injection molding is a common process for manufacturing orthodontic brackets. The resulting green body needs to be degreased in a catalytic degreasing furnace to remove the binder inside. Taking an oxalic acid catalytic degreasing furnace as an example, during the degreasing process, the binder inside the green body decomposes under the catalytic action of high temperature and oxalic acid vapor, producing exhaust gases mainly containing formaldehyde vapor and oxalic acid vapor. The equipment typically integrates an environmentally friendly exhaust gas treatment system that can decompose and burn these exhaust gases generated during the degreasing process, emitting carbon dioxide, nitrogen, and water vapor under normal operating conditions.

[0003] The existing exhaust gas treatment system is designed based on conventional production load and has a fixed upper limit. In actual production, the degreasing furnace alternates between various operating conditions such as start-up replacement, small-batch degreasing, self-cleaning purging, and large-batch degreasing, resulting in a variable volume of exhaust gas. When the batch charge is occasionally higher than normal or the raw material characteristics fluctuate, the concentrations of formaldehyde and oxalic acid in the exhaust gas can rise rapidly within a short period, forming occasional instantaneous concentration peaks, while the total gas flow rate in the pipeline may not increase synchronously.

[0004] For these types of operating conditions, existing equipment with built-in exhaust gas treatment systems and conventional waste gas bypass buffering solutions have shortcomings. Firstly, they generally employ a fixed threshold triggering mode, intervening only when gas flow or pressure exceeds a set value. This response is delayed, and the concentration surge may have already partially entered the exhaust gas treatment unit, easily leading to incomplete decomposition. Secondly, there is a lack of measures to deal with sudden surges in harmful component concentrations where gas flow changes are minimal. Thirdly, if dilution is achieved by introducing purchased pure nitrogen into the exhaust gas outlet pipe, a large amount of high-purity nitrogen needs to be continuously consumed, increasing production costs.

[0005] Therefore, there is a need for a waste gas treatment solution that can intervene in advance during the rapid increase of concentration and does not rely on large amounts of externally purchased nitrogen for dilution. Summary of the Invention

[0006] To address the technical problems existing in the prior art, the present invention provides a waste gas recovery and synergistic decomposition system for large-scale degreasing of orthodontic brackets. This system utilizes the low-concentration waste gas generated during the degreasing process as a dilution gas source. Based on the trend of waste gas concentration changes, dilution gas is introduced in advance and simultaneously diverted and temporarily stored before the concentration reaches a preset threshold. This reduces the peak concentration of waste gas entering the exhaust gas treatment system while maintaining stable pipeline pressure, thus avoiding disturbance to the micro-positive pressure environment of the degreasing furnace.

[0007] This invention provides a waste gas recovery and synergistic decomposition system for large-scale degreasing of orthodontic brackets. The system is located between the waste gas outlet pipeline of the degreasing furnace and the tail gas treatment system, and includes:

[0008] The concentration adjustment system is connected to the exhaust gas outlet pipeline and is used to collect the low-concentration exhaust gas generated by the degreasing furnace during the low-concentration emission stage. The collected low-concentration exhaust gas is then added as a dilution gas to the exhaust gas flowing through the exhaust gas outlet pipeline to reduce the exhaust gas concentration.

[0009] A pressure regulating bypass buffer system is connected to the exhaust gas outlet pipeline to divert and temporarily store the gas in the exhaust gas outlet pipeline and to regulate the gas flow rate and pressure in the exhaust gas outlet pipeline.

[0010] A concentration detection component is installed on the exhaust gas outlet pipe and located upstream of the gas mixing position where the concentration adjustment system mixes the diluent gas into the exhaust gas outlet pipe. It is used to detect the concentration of the original exhaust gas flowing through the exhaust gas outlet pipe and to obtain a trend signal reflecting the trend of exhaust gas concentration change.

[0011] The control system is communicatively connected to the concentration detection component, the concentration adjustment system, and the voltage regulation bypass buffer system, respectively, and is used for:

[0012] When the trend signal indicates that the exhaust gas concentration is rising, before the exhaust gas concentration reaches the preset threshold, the concentration adjustment system is triggered to add dilution gas, and at the same time, the pressure regulation bypass buffer system is triggered to divert and temporarily store the gas. This allows the addition of dilution gas and the diversion and temporary storage of gas to be performed synchronously, so as to complete the dilution intervention before the exhaust gas concentration reaches the peak and to offset the increase in gas flow and pressure disturbance caused by the addition of dilution gas.

[0013] Furthermore, as the exhaust gas concentration decreases, the gas mixing volume of the concentration adjustment system and the flow rate of the pressure regulating bypass buffer system are reduced simultaneously according to the concentration decrease trend, so that the concentration regulation and pressure regulation maintain coordination throughout the intervention process.

[0014] It is understood that the system provided by the technical solution of this invention is installed as an auxiliary device between the exhaust gas outlet pipe of the degreasing furnace and the tail gas treatment system. The exhaust gas generated by the degreasing furnace first passes through the exhaust gas outlet pipe and then enters the tail gas treatment system for decomposition treatment. This system does not change the structure of the degreasing furnace body and its built-in tail gas treatment system, but adds a set of collaborative control devices to the connecting pipe between the two, so it can be directly adapted to existing degreasing equipment.

[0015] From a system composition perspective, this system comprises four parts: a concentration adjustment system, a pressure regulation bypass buffer system, a concentration detection component, and a control system. The function of each part and their coordination during operation are explained below.

[0016] The concentration adjustment system is responsible for addressing the issue of excessively high exhaust gas concentration. Connected to the exhaust gas outlet pipeline, it collects the low-concentration exhaust gas generated by the degreasing furnace during the low-concentration emission phase and then uses it as a diluent gas to mix with the exhaust gas flowing through the outlet pipeline, thereby reducing the exhaust gas concentration. The low-concentration emission phase refers to the period when the exhaust gas concentration is relatively low during the degreasing process, such as the equipment start-up and replacement phase or the cooling phase after degreasing. During these periods, the exhaust gas treatment system operates at a low load, its processing capacity is not fully utilized, and the emitted exhaust gas concentration is not high. This system collects and stores this low-concentration exhaust gas, reserving it for later use when the exhaust gas concentration increases. This is equivalent to using the exhaust gas generated during the degreasing process itself as a diluent gas, instead of purchasing pure nitrogen from an external source, which reduces the cost of obtaining diluent gas and reuses the exhaust gas generated during low-load periods.

[0017] The pressure regulating bypass buffer system is responsible for handling pipeline pressure stability. Connected to the exhaust outlet pipeline, it diverts and temporarily stores gas in the pipeline, regulating the gas flow and pressure. When the gas volume in the pipeline is excessive and the pressure tends to rise, the system diverts a portion of the gas for temporary storage to prevent further pressure increases. When the gas volume returns to normal, the stored gas is released back into the pipeline as needed. Its function is equivalent to adding a buffer layer to the exhaust outlet pipeline for storing and releasing gas.

[0018] The concentration detection unit is installed on the exhaust gas outlet pipe, upstream of the mixing point where the concentration system adds dilution gas to the exhaust gas outlet pipe. This placement is carefully considered. The concentration detection unit measures the concentration of the raw exhaust gas flowing through the exhaust gas outlet pipe, that is, the concentration before it has been mixed with dilution gas. If the detection point were downstream of the mixing point, it would measure the already diluted concentration, masking the true concentration risk. By placing it upstream, it always detects the raw concentration discharged from the degreasing furnace, ensuring the control system's judgment is based on accurate and reliable data. The concentration detection unit not only collects the absolute value of the concentration but also acquires trend signals reflecting changes in the exhaust gas concentration, i.e., whether the concentration is increasing or decreasing over time, and how quickly or slowly it is increasing.

[0019] The control system is communicatively connected to the concentration detection component, the concentration adjustment system, and the pressure regulation bypass buffer system, and is the core control component of the entire system. It receives the trend signal output by the concentration detection component and determines when to start gas mixing, when to start diversion, and to what extent each action should be performed.

[0020] The operation of the control system is divided into two stages.

[0021] The first stage is the concentration rise stage. When the trend signal indicates that the exhaust gas concentration is rising, the control system triggers the concentration adjustment system to add dilution gas before the exhaust gas concentration reaches the preset exceedance threshold. Simultaneously, it triggers the pressure regulating bypass buffer system to divert and temporarily store the gas. The preset exceedance threshold here refers to a pre-set concentration limit value used to determine whether the exhaust gas concentration is too high. The above intervention actions contain two key points. First, the intervention timing is advanced. The system does not wait until the concentration has exceeded the limit before taking action, but rather intervenes before the concentration reaches the preset exceedance threshold, judging that the concentration is rapidly rising. This ensures that the addition of dilution gas and the temporary storage of gas diversion are completed before the exhaust gas concentration reaches its peak. In this way, the concentration surge peak is partially reduced during its formation, and the peak exhaust gas concentration entering the tail gas treatment system is correspondingly reduced. Second, the addition of dilution gas itself increases the total amount of gas in the pipeline. If no treatment is performed, the pipeline pressure will increase, thereby disturbing the slightly positive pressure environment of the degreasing furnace. The slightly positive pressure environment here refers to a state where the pressure inside the furnace is slightly higher than the external atmospheric pressure. The degreasing furnace relies on this pressure state to prevent external air from seeping into the furnace. The control system triggers a diversion and temporary storage mechanism at the same time as triggering gas mixing, diverting the excess gas brought in by the mixing to offset the increase in gas flow and pressure disturbance caused by the addition of dilution gas, so that the concentration control action does not cause new airflow and pressure fluctuations.

[0022] The second stage is the concentration decline stage. As the exhaust gas concentration decreases, the control system, based on the concentration reduction trend, simultaneously reduces the gas mixing volume of the concentration enrichment system and the flow rate of the pressure regulating bypass buffer system. This is because if the mixing valve and the flow rate divider valve close rapidly, the gas flow rate in the pipeline will change abruptly, causing fluctuations in airflow and pressure. The control system follows the rhythm of the concentration decline, gradually and synchronously reducing the mixing volume and flow rate, ensuring that concentration control and pressure control remain coordinated throughout the intervention process.

[0023] In summary, this system comprises a concentration adjustment system responsible for reducing the concentration, and a pressure regulation bypass buffer system responsible for stabilizing the pressure. These two systems work in tandem based on concentration trend signals, and are linked through a control system: they activate synchronously when the concentration rises and terminate synchronously when the concentration falls. The location of the concentration detection components ensures that the control system always obtains the original concentration information. These components work together to achieve synchronous regulation of the exhaust gas concentration and pipeline pressure.

[0024] Meanwhile, the present invention also provides a method for waste gas recovery and synergistic decomposition for large-scale degreasing of orthodontic brackets, applied to the waste gas outlet pipeline between the waste gas outlet of the degreasing furnace and the tail gas treatment system, comprising the following steps:

[0025] Collect and store the low-concentration waste gas generated by the degreasing furnace during the low-concentration emission stage, as a source of dilution gas; detect the waste gas concentration in the waste gas outlet pipeline, and obtain trend signals reflecting the trend of waste gas concentration changes.

[0026] When the trend signal indicates that the exhaust gas concentration is rising, before the exhaust gas concentration reaches the preset threshold, the dilution gas is added to the exhaust gas in advance to reduce the exhaust gas concentration in the exhaust gas outlet pipeline. At the same time, the exhaust gas is diverted and temporarily stored simultaneously, so that the addition of dilution gas and the diversion and temporary storage of gas are performed synchronously, so as to complete the dilution intervention before the exhaust gas concentration reaches the peak and offset the increase in gas flow and pressure disturbance caused by the addition of dilution gas.

[0027] When the concentration of exhaust gas drops, the amount and flow rate of dilution gas introduced are reduced simultaneously according to the concentration decrease trend, so that concentration control and pressure control remain coordinated throughout the intervention process.

[0028] In summary, the waste gas recovery and assisted decomposition method of the present invention consists of four interconnected steps. The first step is to collect the low-concentration waste gas generated during the degreasing process for later use; the second step is to monitor changes in the waste gas concentration; the third step is to take action in advance when the concentration rises rapidly; and the fourth step is to smoothly conclude the process after the concentration has fallen back. The content of each step and the relationship between them will be explained below.

[0029] Step one involves collecting and storing low-concentration waste gas as a source of dilution gas. Specifically, the concentration of waste gas from the degreasing furnace is not consistently high during operation. During low-concentration emission stages, such as the equipment start-up and replacement phases and the cooling phase after degreasing, the formaldehyde and oxalic acid content in the emitted waste gas is low. At these times, the exhaust gas treatment system operates under low load, and its processing capacity is not fully utilized. This method collects and stores the low-concentration waste gas generated during these low-concentration emission stages, reserving it as a source of dilution gas for subsequent use. This approach has two considerations. First, the dilution gas originates from the degreasing process itself, eliminating the need to purchase pure nitrogen externally, thus reducing the cost of obtaining the dilution gas. Second, the waste gas from the low-concentration emission stages is what is intended to be treated under normal operating conditions; collecting it for later use effectively reserves waste gas resources from low-load periods for use during high-load periods.

[0030] Step one serves as the material preparation step in the entire process. The diluent gas added to the waste gas in the subsequent third step comes from the low-concentration waste gas collected and stored in step one. Without the gas source preparation in step one, the dilution action in step three would be impossible.

[0031] Step two involves detecting the concentration of exhaust gas in the exhaust outlet pipe and obtaining a trend signal reflecting the changing trend of the exhaust gas concentration. Specifically, the detection location is on the exhaust outlet pipe, upstream of the point where dilution gas is added to the exhaust gas. This location is chosen to ensure that the detected concentration is the original concentration actually discharged from the degreasing furnace. If the detection location were downstream of the gas addition point, the measured concentration would be the already diluted concentration, and the true concentration risk would be masked. This method not only records the concentration value itself but also obtains a trend signal, that is, to determine whether the concentration is rising or falling, and whether the rise is fast or slow. This step provides a basis for subsequent intervention actions. The timing of gas addition in step three and the timing of reducing the gas addition amount in step four are both based on the trend signal obtained in step two.

[0032] Step 3: When the concentration shows an upward trend, intervene before it reaches the preset threshold. Specifically: when the trend signal obtained in Step 2 indicates that the exhaust gas concentration is rising, this method introduces dilution gas into the exhaust gas before it reaches the preset threshold to reduce the concentration in the exhaust gas outlet pipeline, while simultaneously diverting and temporarily storing the exhaust gas. This involves two key points: First, the intervention timing is early. The method doesn't wait until the concentration has already exceeded the limit before acting; instead, it intervenes before the concentration reaches the preset threshold, based on the indication of a rapid increase. This ensures that the introduction of dilution gas and the temporary storage of the diverted gas are completed before the peak concentration is reached. In this way, the peak concentration is reduced during its formation, and the peak concentration of the exhaust gas entering the exhaust gas treatment system is correspondingly lower. Second, the dilution and diversion are performed simultaneously. Introducing dilution gas into the exhaust gas increases the total gas volume in the pipeline. If left untreated, this will increase the pipeline pressure, thereby disturbing the slightly positive pressure environment of the degreasing furnace. The slightly positive pressure environment here refers to a state where the pressure inside the furnace is slightly higher than the external atmospheric pressure. The degreasing furnace relies on this pressure state to prevent external air from seeping into the furnace. The method involves simultaneously diverting and temporarily storing the waste gas while adding dilution gas, diverting excess gas brought in by the gas addition, offsetting the increase in gas flow and pressure disturbance caused by the addition of dilution gas, and ensuring that the concentration control action does not cause new airflow and pressure fluctuations.

[0033] Step four: Simultaneously reduce the amount of diluent gas and the flow rate as the concentration decreases. Specifically, when the exhaust gas concentration decreases, this method reduces the amount of diluent gas and the flow rate simultaneously, based on the concentration decrease trend. The rationale for this is that if the diluent valve and the flow rate valve are closed rapidly, the gas flow rate in the pipeline will change abruptly, causing fluctuations in airflow and pressure. By gradually reducing the amount of diluent gas and the flow rate in sync with the decrease in concentration, the method ensures that concentration control and pressure control remain coordinated throughout the intervention process.

[0034] In summary, the coordination between the four steps described above can be understood as follows: Step one addresses the source of the dilution gas, providing the material basis for the entire method. Step two addresses the timing of the operation, providing a basis for judgment. Steps three and four address the method of operation: simultaneous activation when the concentration rises and simultaneous deactivation when the concentration falls, with the entire process revolving around the concentration trend signal. These four steps are interconnected and mutually supportive, working together to achieve peak reduction in waste gas concentration and stabilization of pipeline pressure.

[0035] Compared with the prior art, the technical solution of the present invention has at least the following beneficial technical effects:

[0036] 1. This invention utilizes the low-concentration waste gas generated during the degreasing process as a source of dilution gas to replace the purchase of high-purity nitrogen for dilution. As a result, this invention can reduce the cost of obtaining dilution gas and reduce dependence on external nitrogen supply.

[0037] 2. Based on the concentration change trend, the present invention introduces dilution gas in advance before the exhaust gas concentration reaches the preset threshold, and the introduction of dilution gas and the diversion and temporary storage of gas are carried out simultaneously. As a result, the present invention shortens the time interval between the occurrence of concentration abnormality and the intervention taking effect, so that the concentration impact peak is partially reduced during the formation process, thereby reducing the peak exhaust gas concentration entering the exhaust gas treatment system.

[0038] 3. The present invention simultaneously diverts the gas in the temporary storage pipeline while diluting the gas, thereby offsetting the increase in gas flow and pressure disturbance caused by diluting the gas, and reducing the impact on the micro-positive pressure environment of the degreasing furnace.

[0039] 4. When the exhaust gas concentration drops, the present invention simultaneously reduces the gas mixing volume and the flow rate according to the concentration decrease trend. Thus, the present invention can avoid airflow and pressure fluctuations caused by rapid shutdown of the intervention action, so that the concentration control and pressure control remain coordinated throughout the intervention process.

[0040] 5. As an auxiliary device, this invention is installed between the exhaust gas outlet pipeline and the tail gas treatment system. It does not require modification of the structure of the degreasing furnace body and its built-in tail gas treatment system. Therefore, this invention is easy to implement and promote on existing degreasing equipment. Attached Figure Description

[0041] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0042] Figure 1 This is a schematic diagram of the overall system structure and air circuit connection of the present invention;

[0043] Figure 2 This is a flowchart of the waste gas recovery and assisted decomposition method of the present invention;

[0044] Figure 3 This is the concentration change feedforward collaborative control logic diagram of the present invention;

[0045] Figure 4 This is a schematic diagram of the tiered gas extraction structure of the graded storage tank of the present invention;

[0046] Figure 5This is a partially enlarged view of the dilution gas being injected in the co-current direction according to the present invention;

[0047] Figure 6 This is a concentration spectrum curve of the exhaust gas during the degreasing process of this invention;

[0048] Figure 7 This is a diagram showing the correspondence between the categorized storage tanks and the corresponding gas extraction numbers in this invention.

[0049] Figure label:

[0050] none. Detailed Implementation

[0051] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The following specific embodiments are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0052] This embodiment provides a waste gas recovery and synergistic auxiliary decomposition system for large-scale degreasing of orthodontic brackets. For example... Figure 1 As shown, the system is installed between the exhaust gas outlet pipe of the degreasing furnace and the tail gas treatment system. It is used to regulate the concentration and pressure of the exhaust gas discharged from the degreasing furnace, so that the concentration and flow rate of the exhaust gas entering the tail gas treatment system are kept within the range that the tail gas treatment system can stably handle.

[0053] In terms of overall composition, the system consists of four parts: concentration adjustment system, pressure regulation bypass buffer system, concentration detection component and control system.

[0054] The concentration adjustment system is connected to the exhaust gas outlet pipeline and is used to collect the low-concentration exhaust gas generated by the degreasing furnace during the low-concentration emission stage. This collected low-concentration exhaust gas is then added back as a diluent to the exhaust gas flowing through the outlet pipeline to reduce its concentration. In simpler terms, the concentration adjustment system does two things: first, it collects the lower-concentration portion of the exhaust gas discharged from the degreasing furnace for later use; second, when the exhaust gas concentration in the pipeline is too high, it uses the collected low-concentration exhaust gas as a diluent to reduce the concentration.

[0055] The pressure regulating bypass buffer system is connected to the exhaust gas outlet pipeline to divert and temporarily store the gas in the pipeline, and to regulate the gas flow and pressure within the pipeline. After the diluent gas is added to the exhaust gas, the total gas volume in the pipeline will increase, and the pressure will rise accordingly; the function of the pressure regulating bypass buffer system is to temporarily divert and store this excess gas, keeping the flow and pressure in the pipeline stable.

[0056] The concentration detection component is installed on the exhaust gas outlet pipe, upstream of the mixing point where the concentration system adds dilution gas to the exhaust gas outlet pipe. This placement is strategic: placing the detection point upstream of the mixing point measures the concentration of the raw, undiluted exhaust gas, not the mixed concentration after mixing; if the detection point were downstream, the measured concentration would already contain the dilution gas, masking the true concentration risk. The concentration detection component is used to detect the concentration of the raw exhaust gas flowing through the exhaust gas outlet pipe and to acquire trend signals reflecting changes in exhaust gas concentration.

[0057] The control system is communicatively connected to the concentration detection component, the enrichment system, and the pressure regulating bypass buffer system. The control system receives the concentration signal and trend signal output by the concentration detection component, and determines whether the exhaust gas concentration is rising, stable, or falling, and uniformly controls the opening and closing of each valve in the enrichment system and the pressure regulating bypass buffer system.

[0058] The following is combined with Figure 1 Explain the connection relationships between the various parts of the system. For example... Figure 1 As shown, the exhaust gas discharged from the degreasing furnace flows to the tail gas treatment system through the exhaust gas outlet pipe, and the flow direction of the exhaust gas is as indicated by the arrow on the main line in the figure. Along the exhaust gas flow direction, the exhaust gas outlet pipe is arranged with the following seven points in sequence: pre-diversion point, concentration detection, collection opening, gas mixing position, pressure detection, reflux point, and bypass diversion point.

[0059] The system includes the following components: a pre-diversion point at the upstream end, with one end of the pre-diversion pipeline connected to this point and the other end connected to a buffer storage tank; a concentration detection point, corresponding to the concentration detection component, located downstream of the pre-diversion point; a collection opening, the connection point between the low-concentration waste gas collection pipeline and the waste gas outlet pipeline, from which the collection pipeline branches into three paths, each connecting to one of the three staged storage tanks; a gas mixing point, where the concentration system mixes diluent gas into the waste gas outlet pipeline, with the diluent gas being transported to this point via the mixing pipeline; a pressure detection point, corresponding to the pressure detection component, located downstream of the gas mixing point; a return point, the connection point between the return pipeline and the waste gas outlet pipeline, where the return pipeline enters and returns the gas temporarily stored in the buffer storage tank to the waste gas outlet pipeline; and a bypass diversion point at the downstream end, with one end of the bypass diversion pipeline connected to this point and the other end connected to the buffer storage tank. Three graded storage tanks are arranged side by side below the exhaust gas outlet pipeline. The buffer storage tank is placed separately from the graded storage tank. The pre-drainage pipeline and the bypass pipeline are connected to the buffer storage tank from two diversion points respectively. The return pipeline is led out from the buffer storage tank and then reconnected to the return point.

[0060] The control system is connected as follows: it communicates with the concentration detection component, the pressure detection component, and the valves on each pipeline, outputs control signals to each valve, and receives concentration and pressure signals.

[0061] In one specific embodiment, optionally: the effective volume of a single degreasing furnace is 800L, the degreasing temperature is 120~150℃, and a slight positive pressure of 50~300Pa is maintained in the exhaust gas outlet pipeline. The concentration detection component adopts an infrared absorption gas sensor with a range covering 0~20000ppm, capable of covering the high concentration range of 3000~12000ppm during the degreasing heating and holding stage, with a response time of no more than 3s; the sensor probe is equipped with a heating structure, and the heating temperature is no less than 120℃ to prevent oxalic acid vapor in the high-temperature exhaust gas from sublimating and crystallizing before entering the sensor and blocking the sampling passage, ensuring continuous measurability of the concentration signal. The control system adopts a PLC or DCS controller with a sampling period of no more than 1s, supporting analog signal and digital signal output.

[0062] The following combination Figure 3 This document explains the cooperative operation principle of the system in this implementation method.

[0063] like Figure 3 As shown, the concentration detection component monitors the concentration of the raw exhaust gas flowing through the exhaust outlet pipe in real time and outputs a concentration signal to the control system. The control system then uses this concentration signal to obtain a trend signal reflecting the changing trend of the exhaust gas concentration. The trend signal indicates whether the exhaust gas concentration is rising or falling, and it is the basis for the control system to decide when and to what extent to take action.

[0064] When the trend signal indicates that the exhaust gas concentration is rising, the control system triggers the concentration enrichment system to introduce dilution gas before the exhaust gas concentration reaches the preset threshold. Simultaneously, it triggers the pressure regulating bypass buffer system to divert and temporarily store the gas. This synchronization refers to the simultaneous activation of both actions: the concentration enrichment system opens the flow regulating valve on the introduction pipeline to introduce low-concentration exhaust gas; at the same time, the pressure regulating bypass buffer system opens the diversion regulating valve on the bypass diversion pipeline to divert the increased gas due to the introduction of dilution gas to the buffer storage tank. The simultaneous introduction of dilution gas and diversion storage has two direct effects: first, the early introduction of dilution gas suppresses the exhaust gas concentration before it reaches its peak, enabling dilution intervention before the peak concentration is reached; second, the introduction of dilution gas increases the gas flow and pressure in the pipeline, while the diversion action precisely removes the increased gas, thus offsetting the increase in gas flow and pressure disturbance caused by the dilution gas, preventing pressure fluctuations in the pipeline.

[0065] The control system can also fine-tune the flow rate based on the pressure signal output by the pressure detection component: if the pipeline pressure still deviates after the input and output are executed synchronously, the opening of the flow regulating valve will be finely adjusted accordingly to keep the pipeline pressure within the normal range.

[0066] When the exhaust gas concentration drops, the control system, based on the concentration decrease trend, simultaneously reduces the gas mixing volume of the enrichment system and the flow rate of the pressure regulating bypass buffer system. In other words, after the concentration decreases, the dilution gas no longer needs to be added in large quantities, and the flow rate also decreases accordingly, avoiding excessive dilution and pipeline flow fluctuations; the gas mixing volume and the flow rate are always proportionally and synchronously increased and decreased, ensuring that concentration control and pressure control remain coordinated throughout the intervention process.

[0067] Through the above-mentioned coordinated control, this embodiment can complete the dilution intervention before the exhaust gas concentration reaches its peak, so that the exhaust gas concentration entering the exhaust gas treatment system never exceeds the rated treatment concentration limit of the exhaust gas treatment system, while maintaining stable pipeline pressure and avoiding disturbance to the micro-positive pressure environment of the degreasing furnace.

[0068] In one specific embodiment, optionally, both the inlet flow regulating valve and the diversion regulating valve are continuously adjustable electric regulating valves with a full stroke action time of no more than 2 seconds, so as to meet the response requirements of synchronous action of gas inlet and diversion.

[0069] This embodiment also provides a method for waste gas recovery and synergistic decomposition for large-scale degreasing of orthodontic brackets. This method is applied to the waste gas outlet pipeline between the degreasing furnace's waste gas outlet and the tail gas treatment system. For example... Figure 2 As shown, the method includes the following steps.

[0070] The first step involves collecting and storing the low-concentration waste gas generated by the degreasing furnace during the low-concentration emission phase, which will serve as a source of dilution gas. The waste gas emitted by the degreasing furnace during the start-up replacement phase and the shutdown cooling phase has a low concentration. Directly discharging it into the tail gas treatment system at this time results in a treatment load far below the design capacity, and the treatment capacity is not being fully utilized. This method collects these low-concentration waste gases and stores them in a staged storage tank, preparing a gas source for subsequent dilution.

[0071] The second step is to detect the concentration of exhaust gas in the exhaust outlet pipeline and obtain a trend signal reflecting the changing trend of the exhaust gas concentration. This step provides a basis for subsequent intervention: the control system needs to know whether the current concentration is high or low, rising or falling, in order to decide whether to intervene and to what extent.

[0072] The third step involves introducing dilution gas into the exhaust gas before it reaches the preset threshold, when the trend signal indicates an upward trend in exhaust gas concentration. This dilution reduces the concentration in the exhaust gas outlet pipeline. Simultaneously, the exhaust gas is diverted and temporarily stored. This synchronized dilution intervention ensures the dilution intervention is completed before the exhaust gas concentration reaches its peak, offsetting the increase in gas flow and pressure disturbance caused by the dilution. This step is crucial: the timing of the action is before the threshold is reached, and the action involves simultaneous dilution and diversion, effectively reducing both concentration and stabilizing pressure.

[0073] Fourth, as the exhaust gas concentration decreases, the amount and flow rate of the dilution gas introduced are simultaneously reduced based on the concentration decline trend, ensuring that concentration control and pressure control remain coordinated throughout the intervention process. The decrease in concentration indicates that the peak has passed, and the simultaneous reduction of the dilution gas introduction and flow rate allows the system to smoothly transition back to standby monitoring mode.

[0074] The above four steps are executed sequentially, with the output of the previous step serving as the input for the next: the first step prepares the gas source, the second step provides the basis for judgment, the third step executes the main intervention, and the fourth step smoothly concludes the process. The entire process revolves around one goal: to ensure that the concentration of exhaust gas entering the exhaust gas treatment system remains within a treatable range, while preventing the gas mixing process from causing disturbances to the pipeline pressure.

[0075] To facilitate understanding of the judgment criteria such as upward trend, preset over-limit threshold, and decline in the above methods, the following will combine... Figure 6 Explain the characteristics of changes in exhaust gas concentration during the degreasing process.

[0076] like Figure 6 As shown, the horizontal axis represents time, and the vertical axis represents the exhaust gas concentration. In a typical process cycle of oxalic acid catalytic degreasing for orthodontic brackets, the exhaust gas concentration exhibits a natural concentration spectrum characteristic of rising from low to high and then falling back down, with the concentration curve roughly divided into three segments.

[0077] The first stage is the replacement and purging stage. After the degreasing furnace is started, nitrogen is first introduced to replace the air in the furnace chamber. The exhaust gas discharged in this stage is mainly a mixture of residual air and a small amount of oxalic acid vapor, with a low concentration, which can be set to 200~800ppm, and lasts for about 15~30 minutes.

[0078] The second stage is the heating and holding stage. The furnace temperature is raised to 120-150℃ and held. Oxalic acid catalyzes the decomposition of the binder. During this stage, the concentration of oxalic acid vapor in the exhaust gas increases, for example, reaching 3000-12000 ppm. This is the main reaction stage for degreasing, lasting about 2-4 hours. In the early stage of this stage, the concentration rises rapidly, and there is a high risk of a sudden and rapid increase in concentration. This is the key period for concentration control.

[0079] The third stage is the cooling stage. After degreasing is completed, the furnace cools down, and the concentration of exhaust gas gradually decreases, lasting for about 30 to 60 minutes. In the later stage of the cooling stage, nitrogen is actively introduced to replace and discharge the residual exhaust gas in the furnace. The discharged gas is mainly nitrogen with an extremely low concentration.

[0080] Comparison Figure 6 It can be seen that: the low flat section on the left side of the concentration curve corresponds to the displacement purging stage, the part in the middle that rises rapidly and maintains a high level corresponds to the heating and heat preservation stage, and the flat section on the right side that falls rapidly from the peak corresponds to the cooling stage. Figure 6 The diagram also shows the threshold line for graded collection and the upper limit line for exhaust gas treatment.

[0081] In this method, the trend signal is obtained by the concentration detection component performing differential processing on the real-time concentration, that is, calculating the change in exhaust gas concentration per unit time, and judging whether the exhaust gas concentration is in an upward trend, a downward trend or a stable state based on the sign and magnitude of the change.

[0082] It should be noted that this method triggers intervention before the threshold is exceeded, rather than waiting until the concentration has reached the upper limit of exhaust gas treatment. Instead, it judges in advance based on the rate of concentration change. Optionally, when the rate of change of exhaust gas concentration exceeds the preset feedforward intervention threshold of 500 ppm / min, the control system determines that the exhaust gas concentration is rising and immediately triggers the introduction of dilution gas and simultaneous diversion and temporary storage. At this time, the actual concentration is usually still lower than the upper limit of exhaust gas treatment, leaving time margin for the dilution reaction, thereby ensuring that the dilution intervention is completed before the exhaust gas concentration reaches its peak.

[0083] The concentration detection component needs to cover the high concentration range of 3000~12000ppm during the heating and heat preservation stage, while also being able to detect the low concentration range of 200~800ppm during the displacement and purging stage. An infrared absorption gas sensor with a range of 0~20000ppm can be optionally used.

[0084] Furthermore, such as Figure 1 As shown, the enrichment system also includes a staged gas storage assembly, which includes multiple staged storage tanks, collection pipelines, and mixing pipelines.

[0085] Three tiered storage tanks are used to store low-concentration waste gas at different concentration levels. In this embodiment, three tiered storage tanks may be optionally provided and uniformly named Tank 1, Tank 2, and Tank 3. Tank 1 stores the lowest concentration waste gas with the highest purity, Tank 2 stores waste gas with intermediate concentrations, and Tank 3 stores waste gas with the highest concentration. The classification of each tank level is determined based on the natural concentration spectrum of waste gas at each stage of the degreasing production cycle; the specific concentration ranges will be further described in the subsequent explanation of the gas extraction method.

[0086] Each tiered storage tank is equipped with an independent inlet valve and an outlet valve. The inlet valve is located at the inlet end of the collection pipeline, and the outlet valve is located at the outlet end of the mixing pipeline. The opening and closing of each inlet and outlet valve is independently controlled by the control system. Therefore, each storage tank can independently decide when to introduce gas, how much gas to introduce, when to introduce gas, and how much gas to introduce, without interfering with each other.

[0087] The collection pipeline connects each staged storage tank to the exhaust gas outlet pipeline, used to divert and collect low-concentration exhaust gas discharged from the degreasing furnace. Specifically, one end of the collection pipeline connects to the collection opening on the exhaust gas outlet pipeline, and the other end splits into three branches, each connecting to the inlet valve of one of the three staged storage tanks. When the degreasing furnace discharges low-concentration exhaust gas, the control system opens the inlet valve of the corresponding storage tank, directing that portion of low-concentration exhaust gas into the corresponding tank.

[0088] The mixing pipeline connects the mixing points of each staged storage tank to the exhaust gas outlet pipeline, and is equipped with a flow regulating valve. One end of the mixing pipeline is connected to the outlet valve of each of the three staged storage tanks, and the other end is connected to the mixing point of the exhaust gas outlet pipeline. When dilution gas needs to be added, the control system opens the outlet valve of the selected storage tank and adjusts the opening of the flow regulating valve, adding the low-concentration exhaust gas stored in the staged storage tank selected by the control system as dilution gas to the exhaust gas.

[0089] Through the above structure, the graded gas storage component enables the independent collection and utilization of waste gas at different concentration levels, divided according to the natural concentration spectrum of waste gas at each stage of the degreasing production cycle. In other words, the control system can arrange which level of waste gas is collected, at what time, when it is utilized, and how much is utilized, based on the current concentration situation, without mixing between different levels.

[0090] Furthermore, such as Figure 1 As shown, along the flow direction of the exhaust gas in the exhaust gas outlet pipe, the concentration detection component, the connection point between the collection pipe and the exhaust gas outlet pipe, and the gas exchange point are arranged sequentially. That is to say, on the exhaust gas flow path, it first passes the location of the concentration detection component, then passes the connection point between the collection pipe and the exhaust gas outlet pipe, and finally reaches the gas exchange point.

[0091] This arrangement order involves two positional constraints, each with its own technical considerations.

[0092] Firstly, the concentration detection component is located upstream of the connection between the collection pipeline and the exhaust gas outlet pipeline. The reason for this arrangement is that the opening and closing of the collection pipeline will cause airflow disturbance near the connection. If the concentration detection component is located downstream of the collection opening, the detected concentration will be interfered with by the collection action and will not reflect the true concentration level of the exhaust gas in the pipeline. By placing the concentration detection component upstream of the collection opening, the opening and closing of the collection pipeline will not interfere with the flow field and concentration field at the concentration detection point, ensuring the purity of the concentration detection signal.

[0093] Secondly, the connection between the collection pipeline and the exhaust gas outlet pipeline is located upstream of the gas mixing point. The reason for this arrangement is that if the collection opening is located downstream of the gas mixing point, the collected exhaust gas may be mixed with the diluted gas that has already been mixed in, and it will no longer be the original exhaust gas. By placing the collection opening upstream of the gas mixing point, the collected exhaust gas is the original low-concentration exhaust gas without the addition of diluted gas, ensuring that the concentration of the collected diluted gas source is accurate.

[0094] With the above arrangement, the three stages of collection, storage, and retrieval of the graded gas storage component are spatially independent of the concentration detection stage: the concentration detection signal is pure, the collected dilution gas source is the original low-concentration waste gas, and the gas mixing location is downstream, so the mixing process after mixing does not affect detection and collection. The three are arranged sequentially along the waste gas outlet pipeline, which corresponds exactly to the operating logic of detection first, then collection, and then mixing.

[0095] In one specific embodiment, optionally: the graded storage tank is made of oxalic acid-resistant stainless steel, and the design pressure is not less than 1.5 times the upper limit of the pipeline micro-positive pressure; the tank volume is 1.5 to 3 times the effective volume of a single degreasing furnace; the inlet valve and outlet valve are pneumatic or electric switching valves, and the flow regulating valve is an electric continuous regulating valve with a regulation ratio of not less than 30:1.

[0096] Furthermore, such as Figure 5 As shown, the concentration system also includes an injection pipe. The injection pipe is a connection structure where the end of the mixing pipe is inserted into the exhaust gas outlet pipe: after the mixing pipe delivers the diluent gas to the mixing position, the injection pipe sends the diluent gas into the exhaust gas outlet pipe. The injection pipe includes interconnected vertical and horizontal pipe sections.

[0097] The vertical pipe section is used to connect to the dilution gas and is vertically inserted into the wall of the exhaust gas outlet pipe. Specifically, a through hole is opened in the wall of the exhaust gas outlet pipe at the gas exchange position. The vertical pipe section extends into the pipe through the pipe wall through the through hole, and its upper end is connected to the exchange pipe. The dilution gas flows downward after entering the vertical pipe section from the exchange pipe.

[0098] The lower ends of the horizontal pipe section are connected to the vertical pipe section, and the horizontal pipe section extends a certain length along the direction of the exhaust gas flow within the inner cavity of the exhaust gas outlet pipe. After the diluent gas flows from the vertical pipe section into the horizontal pipe section, it is discharged from the outlet at the end of the horizontal pipe section and enters the interior of the exhaust gas outlet pipe.

[0099] The outlet of the transverse pipe section has two directional features, which together determine the injection effect of the dilution gas.

[0100] First, the outlet of the horizontal pipe section should face away from the direction of the main exhaust gas flow inside the exhaust gas outlet pipe. The main exhaust gas flow flows from upstream to downstream. If the outlet faces the direction of the flow, the high-concentration exhaust gas from upstream will flow into the injection pipe through the outlet, and may even backflow into the storage tank below. With the outlet facing away from the direction of the flow, the main exhaust gas flow passes outside the outlet and will not flow into the injection pipe, thus preventing the exhaust gas from backflowing into the injection pipe.

[0101] Second, the outlet of the horizontal pipe section faces downstream of the main exhaust gas flow inside the exhaust gas outlet pipe. The outlet facing downstream means that the direction of the diluent gas discharge is consistent with the flow direction of the main exhaust gas flow. When the main exhaust gas flow passes rapidly near the outlet, a low-pressure area is formed at the outlet, creating a suction effect that helps the diluent gas to be smoothly discharged and merge into the main flow.

[0102] With the above structure, the dilution gas is guided through the transverse pipe section and mixed into the main exhaust gas flow in the same direction inside the exhaust gas outlet pipe. The main exhaust gas flow is in a turbulent state when it flows inside the pipe. After the dilution gas enters in the same direction as the main exhaust gas flow, it can be uniformly mixed with the main exhaust gas flow under the entrainment effect of the turbulence.

[0103] In this embodiment, the injection pipe sends the diluent gas from the bottom of the pipeline and injects it into the main airflow in the same direction. On the one hand, the outlet faces away from the incoming flow direction, blocking the path of high-concentration waste gas flowing back into the injection pipe; on the other hand, the negative pressure formed by the main airflow at the outlet provides auxiliary suction to the diluent gas, allowing it to flow in smoothly. After the diluent gas enters the turbulent main airflow, it achieves uniform mixing through the entrainment effect of the turbulence itself. The entire process does not require an additional mechanical stirring device.

[0104] In one specific embodiment, optionally: the flow velocity of the main exhaust gas flow in the exhaust gas outlet pipe is 0.5~2.0m / s, at which sufficient turbulence is formed in the pipe; the inner diameter of the injection pipe is smaller than the inner diameter of the exhaust gas outlet pipe, and the depth of the vertical pipe section inserted into the inner cavity of the pipe is preferably such that the horizontal pipe section is in the middle of the main airflow.

[0105] Furthermore, such as Figure 1 As shown, the pressure regulating bypass buffer system includes a bypass diversion pipeline, a buffer storage tank, and a return pipeline.

[0106] The bypass branch line is connected in parallel to the exhaust gas outlet line downstream of the enrichment system, and is equipped with a flow control valve. Parallel connection means that the bypass branch line is a branch of the exhaust gas outlet line, with one end connected to the downstream location of the enrichment system (the bypass branch point) and the other end connected to the buffer storage tank. The bypass branch line is used to divert the excess gas in the exhaust gas outlet line caused by the addition of dilution gas; that is, it diverts this excess gas from the main line and sends it to the buffer storage tank.

[0107] The buffer storage tank is connected to the bypass shunt line and is used to temporarily store the shunt gas. The shunt gas is temporarily stored in the buffer storage tank, awaiting further processing.

[0108] The return line connects the buffer storage tank to the exhaust gas outlet line. The connection point between the return line and the exhaust gas outlet line is upstream of the connection point between the bypass branch line and the exhaust gas outlet line. A return regulating valve is installed on the line. The return line is used to return the gas temporarily stored in the buffer storage tank to the exhaust gas outlet line. Figure 1 It can be seen that the reflux point is located downstream of the pressure detection point and upstream of the bypass diversion point. After the temporarily stored gas re-enters the main pipeline from the reflux point, it continues to flow downstream with the main gas flow, passes through the bypass diversion point again, and finally enters the exhaust gas treatment system together with the exhaust gas in the main pipeline.

[0109] During the dilution gas introduction, the increase in gas flow rate in the main pipeline due to the introduction is approximately equal to the introduced flow rate. According to the flow conservation principle, optionally: the bypass flow rate Qbypass is approximately equal to the introduced flow rate Qintroduced, meaning the amount of gas introduced from the bypass pipeline is roughly equal to the amount of dilution gas introduced. The effect of this is that the total flow rate in the main pipeline remains essentially constant, thus maintaining stable pipeline pressure and preventing pressure increases due to the introduction of dilution gas. This conservation principle is used to illustrate the approximate basis for the flow rate and is not intended as a limitation.

[0110] Through the coordination of bypass diversion lines, buffer storage tanks, and return lines, the pressure regulating bypass buffer system temporarily diverts, stores, and slowly returns excess gas brought in by the dilution gas. The entire process does not interrupt the airflow in the main pipeline, nor does it allow changes in the pressure of the main pipeline. This structure forms the basis for the operation of subsequent pre-diversion lines and pressure feedback control.

[0111] In one specific embodiment, optionally: the volume of the buffer storage tank is 2 to 5 times the effective volume of a single degreasing furnace, and the material is stainless steel resistant to oxalic acid corrosion; the diversion regulating valve and the reflux regulating valve are electric continuous regulating valves.

[0112] Furthermore, such as Figure 1As shown, the pressure regulating bypass buffer system also includes a pre-diversion pipeline. One end of the pre-diversion pipeline is connected to the pre-diversion point on the exhaust gas outlet pipeline located upstream of the concentration detection component, and the other end is connected to the buffer storage tank. A pre-diversion valve is installed on the pipeline.

[0113] In other words, a branch line is opened in the pre-diversion pipeline slightly upstream of the exhaust gas outlet pipeline: with the location of the concentration detection component as a reference, the pre-diversion point is located upstream of it, connecting the section of the main pipeline before the concentration detection point to the buffer storage tank. The pre-diversion valve controls the on / off state and flow rate of this branch line.

[0114] The pre-diverter pipeline is used to simultaneously open the pre-diverter valve when the control system triggers dilution intervention based on a trend signal. This diverts the main gas flow upstream of the concentration detection component, which passes through the exhaust gas outlet pipeline, to the buffer storage tank in advance, preemptively reducing pressure and peak load before the pipeline pressure actually rises. Its working principle is as follows: an increase in exhaust gas concentration is usually accompanied by an increase in the main gas flow rate and pipeline pressure. When the control system determines that the concentration is trending upwards and triggers dilution intervention, it preemptively diverts a portion of the main gas flow upstream of the concentration detection point, allowing this portion of gas to bypass the main pipeline and directly enter the buffer storage tank. The gas volume in the main pipeline is reduced before the pressure rises, thus preventing a pressure increase. This control method is directly triggered by the trend signal, and the action precedes pressure feedback; it is a type of feedforward control.

[0115] Furthermore, the gas diverted by the pre-shunting pipeline and the gas diverted by the bypass pipeline converge into the same buffer storage tank for temporary storage. In other words, the gas drawn from the pre-shunting point and the gas drawn from the bypassing point ultimately enter the same buffer storage tank, sharing the same temporary storage and return device, thus simplifying the pipeline structure.

[0116] The purpose of the pre-diversion pipeline is to advance the start of intervention: before the pressure actually rises, it reduces the gas volume in the main pipeline at the source, coordinating with bypass diversion and gas exchange to form a complete pressure regulation process of first shaving off peak pressure, then diverting, and finally returning the gas. The pre-diversion valve uses a quick-opening electric valve, with a full-opening time of no more than 1 second, to meet the response requirements of anticipating pressure rise.

[0117] Furthermore, such as Figure 1 As shown, the pressure regulating bypass buffer system also includes a pressure detection component. The pressure detection component is located on the exhaust gas outlet pipe downstream of the gas exchange point and upstream of the connection between the bypass diversion pipe and the exhaust gas outlet pipe.

[0118] This location lies on the main pipeline section between the gas exchange point and the bypass diversion point, precisely in the transition zone between concentration control and diversion control actions. The pressure detection component is used to monitor pipeline pressure in real time and output a pressure signal to the control system, serving as feedback for adjusting the diversion flow rate of the pressure regulating bypass buffer system.

[0119] In other words, the pressure signal serves as a reference for closed-loop control of the flow divider valve: the control system determines whether to open or close the flow divider valve based on the deviation between the pressure value measured by the pressure detection component and the set value. When the concentration rises and triggers gas exchange, the pressure detection component detects a pressure change downstream of the gas exchange location, and the control system fine-tunes the flow rate accordingly to keep the pipeline pressure within the set range.

[0120] Optionally: The pressure detection component uses a pressure transmitter with a range covering micro-positive pressure 50~300Pa, an accuracy of not less than 0.5 grade, and a sampling response time of not more than 1s.

[0121] Furthermore, such as Figure 1 As shown, the enrichment system also includes a high-purity nitrogen backup pipeline. This backup pipeline connects to a purchased high-purity nitrogen source and the mixing pipeline, and is equipped with an independent control valve.

[0122] The high-purity nitrogen backup pipeline is another source of dilution gas besides the mixing pipeline: under normal circumstances, the dilution gas is provided by the low-concentration waste gas stored in the staged gas storage components; the high-purity nitrogen backup pipeline connects the purchased high-purity nitrogen source with the mixing pipeline as a backup dilution gas source.

[0123] The high-purity nitrogen backup pipeline is used to switch to purchased high-purity nitrogen as a dilution gas when the gas storage capacity of the staged gas storage component is insufficient, ensuring the continuity of dilution gas supply. Its operation is as follows: when the control system detects that the available low-concentration waste gas storage capacity in the staged gas storage component is insufficient to meet the demand for continued dilution, it opens the independent control valve on the high-purity nitrogen backup pipeline, sending purchased high-purity nitrogen into the dilution pipeline to replace the low-concentration waste gas and continue diluting it without interruption.

[0124] Optionally: the purity of the purchased high-purity nitrogen gas shall not be less than 99.99%, and the diameter of the spare pipeline shall be the same as that of the incoming pipeline; the independent control valve shall be an electric on / off valve.

[0125] Furthermore, such as Figure 4 As shown, each graded storage tank is equipped with a nitrogen inerting interface, an oxygen content detection module, and a pressure relief valve.

[0126] The nitrogen inerting interface is used to introduce nitrogen into the storage tank before it is put into operation to replace the air and reduce the oxygen content in the tank to below a preset safety threshold. Low-concentration waste gas contains combustible organic components. If there is residual air in the storage tank, there is a safety risk when oxygen mixes with combustible gas. Before the storage tank is put into operation, nitrogen is introduced into the tank through the nitrogen inerting interface to replace the original air in the tank and reduce the oxygen content to below the preset safety threshold, thus creating safe conditions for the subsequent storage of waste gas containing organic matter.

[0127] The oxygen content detection module is used to monitor the oxygen content in the tank in real time and automatically triggers nitrogen replenishment when the oxygen content exceeds a preset safety threshold. In other words, the oxygen content detection module works continuously during the operation of the storage tank; once it detects that the oxygen content has risen above the preset safety threshold, it automatically replenishes nitrogen from the nitrogen inerting interface to reduce the oxygen content back to within the safe range.

[0128] The pressure relief valve is used to automatically open and release pressure when the pressure inside the tank exceeds the upper limit. During the collection and settling process, the pressure inside the storage tank may rise due to temperature changes or gas accumulation. When it exceeds the upper limit, the pressure relief valve automatically opens to release excess gas and prevent the pressure inside the tank from becoming too high.

[0129] Each graded storage tank is also equipped with a drain valve at the bottom to periodically discharge oxalic acid crystals that condense and precipitate during the settling process and liquid water that condenses and settles. When low-concentration waste gas is left to settle in the storage tank, oxalic acid vapor will condense into solid crystals and settle to the bottom of the tank, while water vapor will condense into liquid water and accumulate at the bottom of the tank. If these impurities remain in the tank for a long time, they will occupy the gas storage space and affect the purity of the gas taken out. The drain valve is opened periodically to discharge the oxalic acid crystals and liquid water accumulated at the bottom of the tank.

[0130] With the above safety configuration, the graded storage tank has corresponding safety protection measures in the three stages of commissioning, operation and long-term storage: air replacement before commissioning, monitoring of oxygen content and automatic nitrogen replenishment during operation, automatic pressure relief when the pressure is too high, and regular discharge of impurities at the bottom of the tank to ensure the long-term safe and stable operation of the storage tank.

[0131] Optionally: the purity of inert nitrogen is not less than 99.9%; the oxygen content detection module adopts an electrochemical oxygen sensor with a range of 0~25% and a preset safety threshold of 2% as an example; the opening pressure of the pressure relief valve is higher than the upper limit of the pipeline micro-positive pressure.

[0132] Furthermore, such as Figure 4 As shown, the gas inlet of each staged storage tank is located at the top of the tank. The gas inlet is located at the top of the tank and is used to extract purified gas from the upper gas phase region inside the tank as dilution gas during gas extraction.

[0133] The working principle is explained by the static purification process: After low-concentration waste gas is left to stand in the storage tank for a period of time, the gas inside the tank will naturally form upper and lower strata. The upper gas phase region has a lower impurity content and is relatively purer, while the lower region is deposited with impurities such as oxalic acid crystals and condensate. The gas intake is located at the top of the tank, and purified gas is directly extracted from the upper gas phase region, resulting in better quality diluted gas.

[0134] Meanwhile, there is another consideration in placing the gas intake at the top of the tank: the gas intake process does not disturb the stratification of the upper and lower gas phases formed by the static process inside the tank. If the gas intake is located on the side or bottom of the tank, the airflow will cause disturbance inside the tank during gas intake, bringing up the already settled impurities again, disrupting the stratification of the upper and lower gas phases, and affecting the purity of the gas intake; with the gas intake located at the top, the gas intake airflow draws out the upper gas from top to bottom, minimizing disturbance to the stratification state inside the tank.

[0135] Optionally, the gas inlet is located at the center or near the top of the tank, and the length of the gas inlet pipe extending into the tank is preferably close to the upper gas phase region. The gas inlet linear velocity is 0.1~0.5m / s, which is lower than the critical rate that disrupts static stratification.

[0136] Optionally, this method also includes a dilution gas pre-storage step before starting the degreasing furnace or during batch production intervals. The purpose of pre-storage is to collect the low-concentration waste gas required for subsequent dilution into a graded storage tank before the start of the formal degreasing batch, so that there is a usable dilution gas source at the beginning of formal production without occupying formal production time.

[0137] Pre-reserves are achieved through at least one of the following methods.

[0138] Method 1: Collect the low-concentration waste gas discharged during the degreasing and cooling stage of the previous batch. After the previous batch of degreasing is completed, the waste gas discharged during the furnace cooling process has a low concentration. When it is directly discharged into the tail gas treatment system, the treatment load is far below the design capacity. At this time, it is collected and used as the dilution gas source for this batch.

[0139] Method 2: Collect the low-concentration exhaust gas discharged during the degreasing and purging stage of this batch. Before the start of degreasing for this batch, the concentration of exhaust gas discharged during the furnace purging stage is relatively low, and it can also be collected and stored.

[0140] Method 3 involves actively triggering a self-cleaning purge during downtime, introducing nitrogen into the furnace to displace and collect residual waste gas, forming the near-pure nitrogen level storage tank for the waste gas to be stored. When the equipment is shut down or the batch interval is long, nitrogen is actively introduced into the furnace to displace the residual organic-containing waste gas, collecting it into the near-pure nitrogen level storage tank—the lowest concentration and highest purity level, corresponding to the first storage tank mentioned above. This method not only cleans the residual waste gas in the furnace but also obtains a high-purity dilution gas source.

[0141] By using at least one of the above methods, dilution gas can be stored before the formal degreasing begins, and can be directly used when dilution gas is added later. The dilution gas supply does not depend on purchased gas and does not take up formal production time.

[0142] Optionally: During the pre-storage collection process, the inlet valve is closed when the storage tank is filled to 70% to 90% of its volume, leaving a buffer space for the upper gas phase; the nitrogen flow rate introduced into the furnace during self-cleaning purging is, for example, 2 to 3 times the furnace volume per hour.

[0143] Furthermore, in this method, when the exhaust gas concentration drops below the preset collection threshold, the collection of low-concentration exhaust gas is activated, and the low-concentration exhaust gas is collected and stored.

[0144] Combination Figure 6 Explain when this step should be performed. For example... Figure 6 As shown, the concentration curve is at a high level during the heating and heat preservation stage. After degreasing is completed, the cooling stage begins, and the exhaust gas concentration gradually drops from the high level. When the concentration curve crosses the staged collection threshold line downwards, that is, when the exhaust gas concentration drops below the preset collection threshold, the control system starts the low-concentration exhaust gas collection and introduces the low-concentration exhaust gas discharged in this stage into the staged storage tank through the collection pipeline.

[0145] There are two considerations in choosing this triggering time. First, the exhaust gas concentration is low during the cooling phase, which is within the range of the exhaust gas treatment system's processing capacity, so collecting it will not increase the burden on the exhaust gas treatment system. Second, after this batch of low-concentration exhaust gas is collected and stored, it becomes the gas source for subsequent dilution. The lower the concentration of the exhaust gas, the better the dilution effect when used as a dilution gas.

[0146] Optionally: The preset collection threshold is 1500 ppm, that is, collection is started when the exhaust gas concentration drops below 1500 ppm; the collection action continues until the low concentration exhaust gas emission of this batch ends or the selected storage tank is full.

[0147] Furthermore, in this method, the steps of collecting and storing waste gas include: according to the natural concentration spectrum of waste gas at each stage of the degreasing production cycle, classifying low-concentration waste gas into multiple corresponding graded storage tanks according to concentration levels.

[0148] Combination Figure 7This explains the process of categorizing and storing waste gas. The concentration of waste gas emitted during each stage of the degreasing production cycle naturally varies: the concentration is lower during the displacement purging stage, higher during the heating and holding stage, gradually decreasing during the cooling stage, and lowest during the self-cleaning purging stage. Based on this natural concentration spectrum, the control system categorizes the low-concentration waste gas collected at different stages into corresponding graded storage tanks: the lowest concentration and highest purity waste gas is placed in the first tank, the intermediate concentration waste gas in the second tank, and the highest concentration waste gas in the third tank. Each tank controls its corresponding inlet valve during collection to ensure that waste gas from different grades does not mix.

[0149] The steps for adding dilution gas include: drawing gas from the corresponding concentration level of the graded storage tanks based on the severity of the increase in exhaust gas concentration. The storage tanks are selected according to the following rules: when the exhaust gas concentration increases drastically and requires strong dilution, the exhaust gas stored in the tank with the lowest concentration and highest purity is taken, i.e., the exhaust gas in the first storage tank; when the exhaust gas concentration increases moderately, the exhaust gas stored in the tank with the intermediate concentration is taken, i.e., the exhaust gas in the second storage tank; when only mild or trace dilution is required, the exhaust gas stored in the tank with the highest concentration is taken, i.e., the exhaust gas in the third storage tank.

[0150] In other words, the more the dilution process requires lower concentration, the purer, lower-concentration waste gas should be used for mixing; when the dilution process is mild, using higher-concentration waste gas is sufficient. By classifying and storing the gas in tanks according to different levels and selecting gas according to the corresponding levels, the concentration gradient between the dilution gas and the main waste gas flow in the waste gas outlet pipeline is matched to avoid insufficient or excessive dilution.

[0151] Optionally, based on the natural concentration spectrum: the first storage tank stores the near-pure nitrogen exhaust gas discharged during the initial stage of self-cleaning purging and replacement purging, with the lowest concentration; the second storage tank stores exhaust gas of 200~800ppm during the replacement purging stage; and the third storage tank stores exhaust gas of 500~1500ppm during the cooling stage.

[0152] Furthermore, this method includes a settling and purification step after sorting and classifying the materials. The settling and purification step includes:

[0153] Allow the waste gas in the storage tank to stand for 30-120 minutes under natural or active cooling conditions, utilizing the differences in the physical properties of the components in the waste gas for natural separation. During the cooling process, oxalic acid vapor sublimates and crystallizes, water vapor condenses and settles, and other denser impurities also settle. After a period of standing, an upper purified gas zone and a lower residual gas zone are formed in the storage tank: the upper purified gas zone is mainly composed of nitrogen and low-boiling-point gases with low impurity content; the lower residual gas zone accumulates oxalic acid crystals, liquid water, and impurities.

[0154] During gas extraction, purified gas is drawn from the upper purified gas zone of the storage tank as dilution gas. Combined with the aforementioned structure where the gas extraction port is located at the top of the tank, the gas extraction operation is performed directly from the upper purified gas zone without disturbing the upper and lower layers, ensuring the purity of the extracted dilution gas.

[0155] Through a static purification process, the low-concentration waste gas collected in the storage tank undergoes self-purification and separation during storage, requiring no additional heating or mechanical stirring energy. The separated oxalic acid crystals and condensate are periodically discharged through the drain valve at the bottom of the storage tank, without occupying storage space. This step, combined with tiered storage, ensures that the gas stored in the tiered storage tanks maintains a high level of purity, and will not introduce additional impurities when added as diluent gas.

[0156] Optionally, the settling time is 30 to 120 minutes. Active cooling is used when the ambient temperature is high in summer, and natural cooling is used when the ambient temperature is low in winter. During the settling period, the storage tank is kept sealed and no gas extraction or intake operations are performed.

[0157] Furthermore, in this method, the amount of diluent gas added is determined according to the following two rules.

[0158] Rule 1: After adding dilution gas, the concentration of the mixed waste gas in the exhaust outlet pipeline shall not exceed the upper limit of the rated treatment concentration of the tail gas treatment system. In other words, the goal of dilution is to bring the mixed concentration down to a range that the tail gas treatment system can stably handle, rather than indiscriminately adding more or less. Insufficient dilution will result in a mixed concentration still exceeding the treatment limit, rendering dilution ineffective; excessive dilution, while achieving the required concentration, will lead to rapid consumption of the dilution gas and may cause fluctuations in pipeline flow.

[0159] Rule 2: The amount of diluent gas added is adjusted according to the severity of the increase in exhaust gas concentration. The more drastic the increase in exhaust gas concentration and the higher the current concentration, the larger the diluent flow rate should be; conversely, the smaller the diluent flow rate should be when the increase in exhaust gas concentration is more gradual. In other words, the intensity of the dilution action should match the magnitude of the concentration risk: more dilution for higher risks, and less dilution for lower risks.

[0160] Combination Figure 6 Explain the above rules. Figure 6 The diagram shows the upper limit line for exhaust gas treatment, which is the concentration line corresponding to the upper limit of the rated treatment concentration of the exhaust gas treatment system. The goal of adding dilution gas is to ensure that the concentration curve of the mixed exhaust gas never exceeds the upper limit line for exhaust gas treatment.

[0161] The specific value of the added amount can be determined with reference to the material balance relationship. In this embodiment, let the flow rate of the main gas in the main pipeline be Qmain and the concentration be Cmain, and the flow rate of the added diluent gas be Qdilute and the concentration be Cdilute. Then, the concentration Cmixed of the mixed waste gas after addition satisfies the following material balance equation:

[0162] C_mix = (Q_main) C main + Q exchange C(exchange) / (Q_main+Q_exchange);

[0163] The control system calculates the required injection flow rate to meet Rule 1 based on the real-time detected main airflow rate and concentration, and then adjusts the flow rate according to the severity of the concentration increase, as per Rule 2. This material balance formula is only used to illustrate the basis for the injection amount calculation and is not intended to be limiting.

[0164] By applying the above two rules, the amount of gas added is always matched with the upper limit of the exhaust gas treatment system's processing capacity and the degree of concentration increase, ensuring that the mixed concentration does not exceed the standard and avoiding excessive dilution that would cause unnecessary consumption of dilution gas and fluctuations in pipeline flow.

[0165] Optionally, the control system calculates the required feed-in flow rate in real time with a 1-second calculation cycle and converts the calculated value into an opening command for the feed-in flow rate regulating valve.

[0166] Furthermore, in this method, when the rate of change of exhaust gas concentration exceeds the preset feedforward intervention threshold, it is determined that the exhaust gas concentration is on an upward trend, and the following feedforward diversion steps are executed.

[0167] Combination Figure 3 The execution conditions for this step are explained. The concentration detection component monitors the exhaust gas concentration in real time, and the control system performs differential processing on the concentration to obtain the rate of change of the exhaust gas concentration. When the rate of change exceeds the preset feedforward intervention threshold, the control system determines that the exhaust gas concentration is trending upward and immediately executes the feedforward diversion step, without waiting for the concentration itself to reach a certain high level. Optionally, the preset feedforward intervention threshold is set to 500 ppm / min, that is, feedforward diversion is triggered when the exhaust gas concentration increases by more than 500 ppm per minute.

[0168] The feedforward diversion step includes: synchronously opening a pre-diversion valve located upstream of the concentration detection point to divert and temporarily store the main airflow flowing through the exhaust gas outlet pipeline upstream of the concentration detection point. In other words, a portion of the main airflow upstream of the concentration detection point is diverted and sent to a buffer storage tank for temporary storage as soon as the concentration shows signs of rapid increase, rather than waiting for the pressure to rise before diverting.

[0169] The pre-diversion valve is triggered by a trend signal feedforward, causing the pre-diversion to be executed before the pipeline pressure actually rises. This triggering method utilizes the process correlation that the rise in exhaust gas concentration is usually accompanied by a synchronous or sequential rise in the main gas flow rate and pipeline pressure: the concentration rises first, followed by the flow rate and pressure. Therefore, a portion of the main gas flow is diverted in the early stage of the concentration rise, completing the pre-pressure relief and peak reduction before the pipeline pressure actually rises.

[0170] Furthermore, by pre-diverting the flow, the high-concentration waste gas segment that first forms during the initial concentration rise is intercepted and temporarily stored at the source. This allows the high-concentration waste gas segment to be stored directly without dilution or mixing, forming a source isolation path outside of the dilution and mixing intervention step. In the initial stage of concentration rise, the waste gas segment that first flows upstream of the concentration detection point has the highest concentration and is the most risky segment of the entire batch of waste gas. The pre-diversion intercepts it at the source and sends it directly to the buffer storage tank. This segment of high-concentration waste gas is isolated from the main pipeline without dilution or mixing. After the concentration peak has passed, it is treated according to the low-load period, thus forming another source isolation path besides the dilution and mixing intervention path.

[0171] Through the above-mentioned feedforward diversion steps, this method adds a second layer of protection in addition to dilution and mixing: when the concentration rises rapidly, the high-concentration exhaust gas section is intercepted and temporarily stored at the source, the pipeline pressure is reduced before it climbs, the burden of dilution and mixing is reduced accordingly, and both the concentration and pressure control lines remain stable.

[0172] Optionally: The pre-diverter valve adopts a quick-opening electric valve with a full-opening action time of no more than 1 second; the feedforward diversion and gas exchange actions are started synchronously.

[0173] Furthermore, in this method, during the process of adding dilution gas, the gas storage volume of the currently supplied staged storage tank is monitored in real time.

[0174] When the gas storage capacity of the currently supplying tiered storage tank falls below the preset lower limit, the system automatically switches to the next tiered storage tank whose gas storage capacity is not below the preset lower limit, according to the tier sequence, to continue supplying gas. In other words, when the gas storage capacity of the tank currently drawing gas approaches the lower limit, the system automatically switches the gas supply source to the next tiered storage tank before it is completely depleted. The switching process does not require manual intervention, and dilution and mixing do not stop.

[0175] When the gas storage capacity of all staged storage tanks falls below the preset lower limit, the high-purity nitrogen backup pipeline is automatically opened, switching to purchased high-purity nitrogen as the dilution gas to continue the dilution process, ensuring uninterrupted dilution. In other words, when all the low-concentration waste gas stored in the staged gas storage components is used up, the system automatically opens the high-purity nitrogen backup pipeline to continue the gas supply with purchased high-purity nitrogen, ensuring uninterrupted dilution throughout the entire process.

[0176] Through the above two-level switching logic, when the gas supply is insufficient, the dilution gas supply will automatically switch in the order of using the reserve first and then the backup, and the concentration control action will not stop because the gas source is exhausted.

[0177] Optionally: The gas storage capacity is measured in real time by a differential pressure level gauge or weighing sensor at the bottom of the storage tank, and the preset lower limit is 15% of the rated gas storage capacity of the storage tank; the switching of gear and the switching of the backup pipeline are both completed automatically by the control system, and the gas supply is not interrupted during the switching process.

[0178] Furthermore, in this method, after the exhaust gas concentration drops and the tail gas treatment system enters a low-load period, the gas temporarily stored in the diversion is slowly returned to the exhaust gas outlet pipeline at a ratio of 10% to 30% of the normal exhaust flow rate of the degreasing furnace, so that the returned gas eventually enters the tail gas treatment system for treatment.

[0179] Combination Figure 2 This step is performed when the concentration fluctuates significantly. During peak periods, the pre-diversion pipeline and bypass diversion pipeline divert a portion of the waste gas and temporarily store it in a buffer storage tank. After the waste gas concentration decreases, the processing load of the tail gas treatment system also decreases, entering a low-load period. At this time, the reflux regulating valve is opened, and the gas temporarily stored in the buffer storage tank is slowly returned to the waste gas outlet pipeline at a ratio of 10% to 30% of the normal exhaust flow rate of the degreasing furnace. The returned gas flows downstream with the main gas flow and eventually enters the tail gas treatment system for processing.

[0180] The return ratio is controlled at 10% to 30% of the normal exhaust flow rate to ensure that the return flow rate is lower than the spare processing capacity of the exhaust gas treatment system during low-load periods, and that the return process will not cause fluctuations in the treatment load. The return operation is carried out slowly, with temporarily stored gas returned in batches of small amounts, allowing the exhaust gas treatment system to receive the load smoothly.

[0181] By diverting and temporarily storing waste gas during peak concentration fluctuations to treat it during low-load periods, the excess treatment capacity of the exhaust gas treatment system is utilized in a staggered manner, thus achieving peak shaving and valley filling of treatment capacity. In other words, the excess waste gas during peak hours is stored first and then sent back for treatment during low-load periods, so that the exhaust gas treatment system operates at near full capacity throughout the entire cycle, and its treatment capacity is fully utilized.

[0182] Optionally, the return flow rate is a fixed proportion within the range of 10% to 30% of the normal exhaust flow rate of the degreasing furnace, and the return time continues until the gas temporarily stored in the buffer storage tank is completely returned or the production of this batch ends.

[0183] Furthermore, this method also includes a pressure catch-up closed-loop control step, which includes:

[0184] The pressure in the pipeline downstream of the point where dilution gas is added to the exhaust gas is monitored in real time. This step is performed by the aforementioned pressure detection component, which is located downstream of the gas addition point and outputs the pipeline pressure signal in real time.

[0185] When the pipeline pressure exceeds the preset pressure limit, the diversion opening is increased to divert and temporarily store the excess gas volume corresponding to the preset pressure limit. In other words, even if the feedforward diversion has been activated in advance, if the input volume is too large or other disturbances cause the pipeline pressure to still exceed the limit, the control system will increase the opening of the diversion regulating valve to divert and temporarily store the excess gas volume, allowing the pressure to drop back below the limit.

[0186] When the pipeline pressure is lower than the preset lower pressure limit, reduce the flow divider opening. A pressure lower than the lower limit indicates that the flow divider is too large and the gas volume in the pipeline is insufficient. In this case, reduce the opening of the flow divider regulating valve to divert less gas and allow the pressure to rise back above the lower limit.

[0187] Through the aforementioned closed-loop regulation, the pipeline pressure is always constrained between the preset upper and lower pressure limits. This step complements the feedforward diversion step: the feedforward diversion activates in advance to prevent pressure from rising, while the pressure fallback closed loop automatically corrects deviations when the pressure deviates from the preset range. The two mechanisms work together to ensure that changes in gas volume caused by the addition of dilution gas do not lead to uncontrolled pipeline pressure.

[0188] Optionally: the upper limit of the preset pressure is set to 300Pa, and the lower limit of the preset pressure is set to a slight positive pressure of 50Pa, that is, the pipeline pressure is maintained in the range of 50~300Pa; the flow control valve continuously adjusts the opening according to the pressure deviation.

[0189] The technical solution of the present invention has been described above with reference to preferred embodiments. The present invention is not limited to the specific embodiments described above; these embodiments are merely illustrative and not restrictive. Those skilled in the art, under the guidance of the present invention, can make various modifications without departing from the spirit of the present invention, and all such modifications fall within the protection scope of the present invention.

Claims

1. A waste gas recovery and synergistic decomposition system for large-scale degreasing of orthodontic brackets, characterized in that, The system is installed between the exhaust gas outlet pipe of the degreasing furnace and the tail gas treatment system, and includes: The concentration adjustment system is connected to the exhaust gas outlet pipeline and is used to collect the low-concentration exhaust gas generated by the degreasing furnace during the low-concentration emission stage. The collected low-concentration exhaust gas is then added as a dilution gas to the exhaust gas flowing through the exhaust gas outlet pipeline to reduce the exhaust gas concentration. A pressure regulating bypass buffer system is connected to the exhaust gas outlet pipeline to divert and temporarily store the gas in the exhaust gas outlet pipeline and to regulate the gas flow rate and pressure in the exhaust gas outlet pipeline. A concentration detection component is installed on the exhaust gas outlet pipe and located upstream of the gas mixing position where the concentration adjustment system mixes the diluent gas into the exhaust gas outlet pipe. It is used to detect the concentration of the original exhaust gas flowing through the exhaust gas outlet pipe and to obtain a trend signal reflecting the trend of exhaust gas concentration change. The control system is communicatively connected to the concentration detection component, the concentration adjustment system, and the voltage regulation bypass buffer system, respectively, and is used for: When the trend signal indicates that the exhaust gas concentration is rising, before the exhaust gas concentration reaches the preset threshold, the concentration adjustment system is triggered to add dilution gas, and at the same time, the pressure regulation bypass buffer system is triggered to divert and temporarily store the gas. This allows the addition of dilution gas and the diversion and temporary storage of gas to be performed synchronously, so as to complete the dilution intervention before the exhaust gas concentration reaches the peak and to offset the increase in gas flow and pressure disturbance caused by the addition of dilution gas. Furthermore, as the exhaust gas concentration decreases, the gas mixing volume of the concentration adjustment system and the flow rate of the pressure regulating bypass buffer system are reduced simultaneously according to the concentration decrease trend, so that the concentration regulation and pressure regulation maintain coordination throughout the intervention process.

2. The waste gas recovery and assisted decomposition system according to claim 1, characterized in that, The enrichment system also includes a staged gas storage component, which includes multiple staged storage tanks, collection pipelines, and mixing pipelines. The collection pipeline connects each of the graded storage tanks to the exhaust gas outlet pipeline, which is used to divert and collect low-concentration exhaust gas when the degreasing furnace discharges low-concentration exhaust gas. Each of the aforementioned graded storage tanks is equipped with an independent inlet valve and an outlet valve, and the opening and closing of each valve is independently controlled by the control system to achieve independent collection and use of waste gas at different concentration levels according to the natural concentration spectrum of waste gas at each stage of the degreasing production cycle. The mixing pipeline connects each of the graded storage tanks to the gas mixing position of the exhaust gas outlet pipeline. The pipeline is equipped with a flow regulating valve, which is used to mix the low-concentration exhaust gas stored in the graded storage tank selected by the control system as the dilution gas into the exhaust gas.

3. The waste gas recovery and assisted decomposition system according to claim 2, characterized in that, Along the flow direction of the exhaust gas in the exhaust gas outlet pipe, the concentration detection component, the connection point between the collection pipe and the exhaust gas outlet pipe, and the gas mixing position are arranged sequentially, wherein: The concentration detection component is located upstream of the connection between the collection pipeline and the exhaust gas outlet pipeline, so that the opening and closing of the collection pipeline does not interfere with the flow field and concentration field at the concentration detection point, thus ensuring the purity of the concentration detection signal. The connection between the collection pipeline and the exhaust gas outlet pipeline is located upstream of the gas mixing location, so that the collected exhaust gas is the original low-concentration exhaust gas without the addition of dilution gas.

4. The waste gas recovery and assisted decomposition system according to claim 1, characterized in that, The concentration system includes an injection pipe, which comprises a vertical pipe section and a horizontal pipe section that are interconnected. The vertical pipe section is used to connect to the dilution gas and is vertically inserted into the pipe wall of the exhaust gas outlet pipe; The transverse pipe section extends a certain length along the direction of exhaust gas flow within the inner cavity of the exhaust gas outlet pipe. The outlet of the transverse pipe section is opposite to the direction of the main flow of exhaust gas inside the exhaust gas outlet pipe, so as to prevent exhaust gas from flowing back into the injection pipe. The outlet of the transverse pipe section is located inside the exhaust gas outlet pipe and faces downstream of the main exhaust gas flow, so that the main exhaust gas flow inside the exhaust gas outlet pipe creates a negative pressure on the outlet of the transverse pipe section and generates a suction effect on the outlet of the transverse pipe section. Furthermore, the diluent gas is guided into the main exhaust gas flow in the direction of the exhaust gas outlet pipe through the transverse pipe section, so that the diluent gas can be mixed into the main exhaust gas flow in the turbulent state, thereby allowing the diluent gas and the main exhaust gas flow to be mixed evenly.

5. The waste gas recovery and assisted decomposition system according to claim 1, characterized in that, The voltage regulating bypass buffer system includes: A bypass diversion pipeline is connected in parallel to the exhaust gas outlet pipeline at a position downstream of the enrichment system. The pipeline is equipped with a diversion regulating valve to divert the gas that increases in the exhaust gas outlet pipeline due to the addition of dilution gas. A buffer storage tank, connected to the bypass diversion pipeline, is used to temporarily store the diverted gas; A return pipeline connects the buffer storage tank to the exhaust gas outlet pipeline. The connection point between the return pipeline and the exhaust gas outlet pipeline is located upstream of the connection point between the bypass diversion pipeline and the exhaust gas outlet pipeline. A return regulating valve is provided on the pipeline to return the gas temporarily stored in the buffer storage tank to the exhaust gas outlet pipeline.

6. The waste gas recovery and assisted decomposition system according to claim 5, characterized in that, The voltage regulating bypass buffer system also includes a pre-shunt pipeline; One end of the pre-diversion pipeline is connected to the pre-diversion point on the exhaust gas outlet pipeline located upstream of the concentration detection component, and the other end is connected to the buffer storage tank. A pre-diversion valve is provided on the pipeline. The pre-diversion pipeline is used to simultaneously open the pre-diversion valve when the control system triggers dilution intervention according to the trend signal, so as to divert the main airflow located upstream of the concentration detection component and flowing through the exhaust gas outlet pipeline to the buffer storage tank in advance, and perform pressure relief and peak reduction in advance before the pipeline pressure actually rises. Furthermore, the gas diverted by the pre-diversion pipeline and the gas diverted by the bypass diversion pipeline are temporarily stored in the same buffer storage tank.

7. A method for waste gas recovery and synergistic decomposition for large-scale degreasing of orthodontic brackets, characterized in that, The exhaust gas outlet pipeline used between the exhaust gas outlet of the degreasing furnace and the tail gas treatment system includes the following steps: Collect and store the low-concentration waste gas generated by the degreasing furnace during the low-concentration emission stage, as a source of dilution gas; detect the waste gas concentration in the waste gas outlet pipeline, and obtain trend signals reflecting the trend of waste gas concentration changes. When the trend signal indicates that the exhaust gas concentration is rising, before the exhaust gas concentration reaches the preset threshold, the dilution gas is added to the exhaust gas in advance to reduce the exhaust gas concentration in the exhaust gas outlet pipeline. At the same time, the exhaust gas is diverted and temporarily stored simultaneously, so that the addition of dilution gas and the diversion and temporary storage of gas are performed synchronously, so as to complete the dilution intervention before the exhaust gas concentration reaches the peak and offset the increase in gas flow and pressure disturbance caused by the addition of dilution gas. When the concentration of exhaust gas drops, the amount and flow rate of dilution gas introduced are reduced simultaneously according to the concentration decrease trend, so that concentration control and pressure control remain coordinated throughout the intervention process.

8. The method according to claim 7, characterized in that: When the exhaust gas concentration drops below the preset collection threshold, the low-concentration exhaust gas collection is activated to collect and store the low-concentration exhaust gas. Furthermore, the steps for collecting and storing waste gas include: according to the natural concentration spectrum of waste gas at each stage of the degreasing production cycle, classifying low-concentration waste gas into multiple corresponding graded storage tanks according to concentration levels. The steps for adding diluent gas include: taking gas from the graded storage tanks corresponding to the concentration level according to the severity of the increase in exhaust gas concentration; when the exhaust gas concentration increases sharply and strong dilution is required, exhaust gas stored in the storage tank with the lowest concentration and highest purity is taken; when the exhaust gas concentration increases moderately, exhaust gas stored in the storage tank with the intermediate concentration level is taken; when only mild or trace dilution is required, exhaust gas stored in the storage tank with the highest concentration level is taken. By classifying and storing the gas in different tanks and taking gas according to the corresponding gear, the concentration gradient between the diluted gas and the main gas flow in the exhaust outlet pipeline is matched to avoid insufficient or excessive dilution.

9. The method according to claim 8, characterized in that, After the sorting and grading process, a settling and purification step is also included, which includes: Allow the waste gas in the storage tank to stand for 30 to 120 minutes under natural or active cooling conditions, and use the differences in physical properties of the components in the waste gas to separate them naturally. Oxalic acid vapor sublimates and crystallizes out, while water vapor condenses and settles, so that an upper purified gas zone and a lower residual gas zone are formed in the storage tank. Furthermore, purified gas is drawn from the purified gas zone at the top of the storage tank as dilution gas during gas extraction.

10. The method according to claim 7, characterized in that, The amount of diluent gas added should be according to: After dilution gas is added, the concentration of the mixed waste gas in the waste gas outlet pipeline does not exceed the upper limit of the rated treatment concentration of the tail gas treatment system. The amount of dilution gas added is adjusted according to the severity of the increase in waste gas concentration. When the waste gas concentration increases more drastically and the current concentration is higher, the added flow rate is correspondingly larger. When the waste gas concentration increases more slowly, the added flow rate is correspondingly smaller.

11. The method according to claim 7, characterized in that, When the rate of change of exhaust gas concentration exceeds the preset feedforward intervention threshold, it is determined that the exhaust gas concentration is trending upward, and the following feedforward diversion steps are executed: A pre-diversion valve located upstream of the concentration detection point is opened synchronously to divert and temporarily store the main airflow flowing through the exhaust gas outlet pipeline upstream of the concentration detection point. The pre-diversion valve is triggered by the trend signal feedforward, so that the pre-diversion is performed before the pipeline pressure actually rises. This utilizes the process correlation that the rise in exhaust gas concentration is usually accompanied by a synchronous or sequential rise in the main airflow flow rate and pipeline pressure, and pre-pressure relief and peak reduction are completed before the pipeline pressure actually rises. Furthermore, by pre-diverting the high-concentration exhaust gas segment that first forms during the initial stage of concentration increase, the high-concentration exhaust gas segment is intercepted and temporarily stored at the source, allowing it to be temporarily stored directly without dilution and mixing, thus forming a source isolation path outside of the dilution and mixing intervention steps.

12. The method according to claim 8, characterized in that, Before starting the degreasing furnace or during batch production intervals, a dilution gas pre-storage step is also included, wherein the pre-storage is achieved through at least one of the following methods: Collect low-concentration waste gas discharged during the previous degreasing and cooling stage; Collect low-concentration waste gas discharged during the degreasing, replacement, and purging stage of the current batch; During the standby interval, the self-cleaning purging is actively triggered to introduce nitrogen into the furnace, and the residual waste gas in the furnace is replaced, discharged and collected to form the waste gas to be stored in the near-pure nitrogen level storage tank.

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