Method and device for efficiently degrading and recycling waste polyurethane foam

Abstract

The invention relates to the technical field of degradation and recovery of polyurethane foam, in particular to a method and a device for efficiently degrading and recovering waste polyurethane foam. The method comprises the following steps: acquiring a liquid level value and a vibration signal of each stirring period in a waste polyurethane foam degradation process; obtaining the reaction progress amount of each stirring period based on the change characteristics of the liquid level values of the adjacent stirring periods; obtaining an amplitude spectrum and a phase spectrum in each short-time window, and screening a target vibration signal section of each stirring period according to the frequency of the vibration signal; according to the distribution characteristics of the amplitude spectrum in the short-time window of the target vibration signal section of each stirring period and the richness of the phase spectrum, obtaining a stage reaction amount; determining the actual degradation amount of each stirring period by combining the reaction progress amount and the stage reaction amount; and generating a real-time control strategy based on the actual degradation amount to carry out degradation regulation and control, and carrying out recovery based on a degradation result. According to the invention, the regulation and control precision and real-time performance of the polyurethane foam reaction process can be improved.

Description

Technical Field

[0001] The invention relates to the technical field of polyurethane foam degradation and recovery, and in particular to a method and a device for efficiently degrading and recovering waste polyurethane foam. Background Art

[0002] In modern industry and daily life, polyurethane foam is an important material widely used in many fields such as thermal insulation, sound absorption, and cushioning. However, due to the difficult-to-degrade nature of polyurethane foam, the waste disposal of polyurethane foam has become a thorny environmental issue. Therefore, polyurethane foam degradation devices have been widely used. The device is composed of key parts such as a feeding system, a reaction system, a control system, and a product recovery system, which can meet the degradation needs of polyurethane foam of different scales and types.

[0003] In the process of degradation using existing polyurethane foam degradation equipment, since the products in the degradation reaction are mostly high-viscosity liquid substances converted from polyurethane foam, the progress of conventional degradation reactions is difficult to monitor directly by the naked eye or sensors. Therefore, it is impossible to intervene in and control the degradation reaction process, which may cause uneven degradation or excessive degradation in the reaction process, both of which will affect the subsequent processing cost and efficiency of regenerated polyols. Therefore, there is an urgent need to solve the problem of tracking and monitoring the degradation process of polyurethane foam. Summary of the invention

[0004] In order to solve the problem that the existing method cannot monitor and control the polyurethane foam degradation reaction process in real time, the purpose of the present invention is to provide a method and device for efficient degradation and recovery of waste polyurethane foam. The technical scheme adopted is as follows:

[0005] In a first aspect, the present invention provides a method for efficiently degrading and recycling waste polyurethane foam, the method comprising the following steps:

[0006] Obtain the liquid level value and vibration signal of each stirring cycle during the degradation process of waste polyurethane foam;

[0007] The reaction process amount of each stirring cycle is obtained based on the change characteristics of the liquid level values ​​of adjacent stirring cycles; the vibration signal is subjected to short-time Fourier transform to obtain the amplitude spectrum and phase spectrum in each short-time window, and the target vibration signal segment of each stirring cycle is screened according to the frequency of the vibration signal; the stage reaction amount corresponding to the vibration signal of each stirring cycle is obtained according to the distribution characteristics of the amplitude spectrum in the short-time window of the target vibration signal segment of each stirring cycle and the richness of the phase spectrum;

[0008] The actual degradation amount of each stirring cycle is determined in combination with the reaction process amount and the stage reaction amount; a real-time control strategy is generated based on the actual degradation amount to perform degradation regulation, and recycling is performed based on the degradation result.

[0009] Preferably, obtaining the reaction progress amount of each stirring cycle based on the change characteristics of the liquid level values ​​of adjacent stirring cycles includes:

[0010] Taking the stirring period before the candidate period and adjacent to the candidate period as the first reference period of the candidate period, and taking the stirring period before the first reference period and adjacent to the first reference period as the second reference period of the candidate period;

[0011] Calculating a first difference between the liquid level value of the candidate cycle and the liquid level value of the first reference cycle, and a second difference between the liquid level value of the first reference cycle and the liquid level value of the second reference cycle;

[0012] Obtaining a reaction progress amount of the candidate cycle according to a difference between the first difference and the second difference, wherein the difference between the first difference and the second difference is positively correlated with the reaction progress amount;

[0013] The candidate cycle is any stirring cycle in the degradation process of waste polyurethane foam.

[0014] Preferably, the step of screening the target vibration signal segment of each stirring cycle according to the frequency of the vibration signal comprises:

[0015] For a vibration signal of any stirring cycle: a signal segment in the vibration signal whose frequency is greater than a frequency threshold is taken as a target vibration signal segment.

[0016] Preferably, the acquisition of the frequency threshold includes:

[0017] Obtain reference vibration signals of each stirring cycle during several historical degradation processes of waste polyurethane foam;

[0018] Obtaining a mapping value of each frequency type of each reference vibration signal according to a cross-correlation function between vibration sub-signal segments of each frequency type of each reference vibration signal, wherein the vibration sub-signal segments of each frequency type are extracted using a bandpass filter;

[0019] Calculate the average mapping value of each frequency type in the reference vibration signals of all stirring cycles during the historical degradation processes of several waste polyurethane foams;

[0020] The frequency type corresponding to the maximum average mapping value is used as the frequency threshold.

[0021] Preferably, obtaining the stage reaction amount corresponding to the vibration signal of each stirring cycle according to the distribution characteristics of the amplitude spectrum and the richness of the phase spectrum in the short-time window of the target vibration signal segment of each stirring cycle includes:

[0022] Calculate the correlation between the frequency and amplitude in each short-time window of the target vibration signal segment of the candidate period as the correlation index of the corresponding short-time window;

[0023] According to the standard deviation of the correlation index of all short-time windows of the target vibration signal segment of the candidate period and the standard deviation of the richness of the phase in all short-time windows of the target vibration signal segment of the candidate period, the phase reaction amount corresponding to the vibration signal of the candidate period is obtained.

[0024] Preferably, obtaining the correlation between the frequency and amplitude in each short-time window of the target vibration signal segment of the candidate period includes: determining the Pearson correlation coefficient between the frequency and amplitude in each short-time window of the target vibration signal segment of the candidate period as the correlation between the frequency and amplitude in each short-time window of the target vibration signal segment of the candidate period.

[0025] Preferably, the step reaction amount corresponding to the vibration signal of the candidate period is obtained based on the standard deviation of the correlation index of all short-time windows of the target vibration signal segment of the candidate period and the standard deviation of the richness of the phase within all short-time windows of the target vibration signal segment of the candidate period, including: taking the normalized result of the Euclidean norm between the standard deviation of the correlation index of all short-time windows of the target vibration signal segment of the candidate period and the standard deviation of the richness of the phase within all short-time windows of the target vibration signal segment of the candidate period as the step reaction amount corresponding to the vibration signal of the candidate period.

[0026] Preferably, the acquisition of the richness of the phase in each short-time window of the target vibration signal segment of the candidate period includes:

[0027] The entropy values ​​of all phases in each short-time window of the target vibration signal segment of the candidate period are used as the richness of the phases in each short-time window of the target vibration signal segment of the candidate period.

[0028] Preferably, the actual degradation amount of each stirring cycle is determined by combining the reaction progress amount and the stage reaction amount, comprising:

[0029] The absolute value of the difference between the reaction progress amount of the candidate cycle and the stage reaction amount of the candidate cycle is taken as the actual degradation amount of the candidate cycle.

[0030] In a second aspect, the present invention provides a waste polyurethane foam efficient degradation and recovery device, which includes a feeding mechanism and a degradation mechanism, wherein the feeding mechanism includes a main feed port and a secondary feed port, wherein the main feed port is connected to a crusher, and the degradation mechanism includes a reaction chamber and a shuttle-shaped agitator, wherein the polyurethane foam and the degradation agent undergo a chemical reaction in the reaction chamber.

[0031] The present invention has at least the following beneficial effects:

[0032] Aiming at the problem that most of the degradation products of polyurethane foam are high-viscosity liquid substances, it is difficult to observe and monitor the reaction process, resulting in poor degradation effect of polyurethane foam, the present invention calculates the reaction process amount according to the change characteristics of the liquid level values ​​of adjacent stirring cycles, then separates the effective frequency according to the vibration signal to obtain the target vibration signal segment, and then calculates the stage reaction amount according to the distribution characteristics of the amplitude spectrum in the short-time window of the target vibration signal segment and the richness of the phase spectrum, the purpose of which is to extract the bubbles generated by the degradation reaction in each stirring cycle, which is used to evaluate whether the stage reaction is violent in a short period of time, and finally estimates the solid reaction products that may be generated in each stirring cycle according to the reaction process amount and the stage reaction amount, so as to achieve tracking of the reaction process, provide accurate feedback input for the control system, and be beneficial to improving the monitoring and regulation accuracy and real-time performance of the polyurethane foam reaction process, and ensure the degradation effect of the polyurethane foam. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions and advantages in the embodiments of the present invention or the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0034] Figure 1 A schematic diagram of the overall mechanical structure of a waste polyurethane foam efficient degradation and recovery device provided by an embodiment of the present invention;

[0035] Figure 2 A schematic diagram of the internal mechanical structure of a waste polyurethane foam efficient degradation and recovery device provided by an embodiment of the present invention;

[0036] Figure 3 A schematic diagram of the structure of a pre-tightening device of a waste polyurethane foam efficient degradation and recovery device provided by an embodiment of the present invention;

[0037] Figure 4 A flow chart of a method for efficient degradation and recovery of waste polyurethane foam provided by an embodiment of the present invention;

[0038] In the figure: 1 is the main feed port; 2 is the display; 3 is the temperature control system; 4 is the reaction chamber; 5 is the motor; 6 is the gas discharge port; 7 is the shuttle stirrer; 8 is the pre-tightening device; 9 is the auxiliary feed port; 10 is the slide bar; 11 is the resistance wire tube; 12 is the resistance wire tube; 13 is the filter screen; 14 is the valve; 15 is the recovery chamber; 16 is the bracket. DETAILED DESCRIPTION

[0039] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, the method and device for efficiently degrading and recycling waste polyurethane foam proposed by the present invention are described in detail below in combination with the accompanying drawings and preferred embodiments.

[0040] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0041] The specific scheme of the method and device for efficiently degrading and recycling waste polyurethane foam provided by the present invention is described in detail below with reference to the accompanying drawings.

[0042] Example of a waste polyurethane foam efficient degradation and recovery device:

[0043] This embodiment proposes a waste polyurethane foam efficient degradation and recovery device, such as Figure 1 As shown, this figure is a schematic diagram of the overall mechanical structure of the waste polyurethane foam efficient degradation and recovery device.

[0044] The waste polyurethane foam efficient degradation and recovery device proposed in this embodiment includes a main feed port 1, a display 2, a temperature adjustment system 3, a reaction chamber 4, a motor 5, a gas discharge port 6, a shuttle stirrer 7, a pre-tightening device 8, a secondary feed port 9, a slide bar 10, a resistance wire tube 11, a resistance wire tube 12, a filter 13, a valve (with a detection system) 14, a recovery chamber 15, and a bracket 16. Figure 2 and Figure 3 As shown, Figure 2 The internal mechanical structure diagram of the device is shown in Figure 1. Figure 3 It is a schematic structural diagram of the pre-tightening device 8 of the device.

[0045] The waste polyurethane foam efficient degradation and recovery device proposed in this embodiment includes a feeding mechanism, a degradation mechanism and a control system. The feeding mechanism is used to feed the polyurethane foam waste into the degradation and recovery device. The main feed port 1 is connected to the crusher. After the external crusher breaks the large pieces of polyurethane foam into small pieces, the contact area with the degradation agent can be increased. The broken polyurethane foam enters the degradation and recovery device from the main feed port 1. The auxiliary feed port 9 is used to add degradation substances such as degradation liquid, catalyst, stabilizer, water, etc. The degradation mechanism includes a container for the degradation process, stirring, heating and other auxiliary functions of the reaction process. The polyurethane foam and the degradation agent react chemically in the reaction chamber 4, and the shuttle-shaped agitator 7 is driven by the motor 5 to flip and stir up and down to ensure that the polyurethane foam and the degradation agent are fully mixed. The control system is used to monitor and adjust the entire degradation process.

[0046] The stirring system of this embodiment adopts a downward pressure-lifting method for stirring. This is because the polyurethane foam is relatively light and may float on the top in the degradation liquid. Therefore, the upper layer of polyurethane foam is pressed into the degradation liquid through a cyclic downward pressure-lifting method. When the degradation liquid is squeezed, it will flip up from the edge of the shuttle-shaped agitator 7. When the shuttle-shaped agitator 7 is lifted, the degradation liquid slides down from the edge of the shuttle-shaped agitator 7, forming an exchange of the upper and lower layers of liquid. In order to avoid the degradation liquid being hooked during the downward pressure-lifting process of the shuttle-shaped agitator 7, the stirring component is designed to be shuttle-shaped to promote smoother exchange of the liquid. In addition, a pre-tightening device 8 is installed inside the slide rod 10 to control the stability of the downward pressure-lifting process of the shuttle-shaped agitator 7 to avoid excessive shocks.

[0047] The degradation reaction is usually an exothermic reaction, and this exothermic reaction generally occurs locally, because the polyurethane foam contacts the degradation liquid and the reaction occurs locally. The large-scale stirring process in this embodiment can achieve a uniform heat distribution, and also has the effect of accelerating heat dissipation and evaporation, so that the ambient temperature in the reaction chamber 4 can be better balanced.

[0048] The degradation mechanism also includes a temperature regulating device 3, which accurately controls the temperature of the resistance wire in the resistance wire tube 12 by adjusting the current, and uses the temperature regulating device 3 to provide necessary heat to accelerate the degradation process.

[0049] The whole process of degradation of polyurethane foam by the degradation mechanism is as follows:

[0050] 1. Device inspection and cleaning: Confirm that the polyurethane foam degradation and recovery device is not damaged and all connecting parts are well sealed. Then use an appropriate solvent to clean the reaction chamber 4 to ensure that there is no residue;

[0051] 2. Material preparation: Take 200 kg of polyurethane foam sample and put it into the reaction chamber 4 of the polyurethane foam efficient degradation and recovery device, then select a suitable degradation agent according to production requirements, such as diethylene glycol, weigh 40 kg of diethylene glycol, and prepare 50 kg of water, 15 kg of catalyst (sodium hydroxide) and other solvents accordingly;

[0052] 3. Parameter setting: Set the temperature of the temperature regulating device 3 to 180°C to provide a suitable degradation temperature; set the stirring cycle to 5s, that is, slowly and evenly complete the pressing-lifting process every 5s to ensure that the reactants are evenly mixed;

[0053] 4. Start the degradation reaction: Turn on the temperature adjustment system 3 and preheat the temperature of the reaction chamber 4 to 80°C. This process takes about 30 minutes. When the reaction chamber 4 reaches the preset temperature, diethylene glycol is slowly added to the reaction chamber 4. Start timing and set the reaction time to 2 hours.

[0054] 5. Reaction monitoring: Use an integrated sensor system to monitor the reaction conditions in the reaction chamber 4, including temperature, pressure, flow, vibration, etc., and manually record the amount of polyurethane foam, degradation liquid, catalyst, etc. added (in kg); if the temperature sensor is installed below the liquid level of the degradation liquid, it is used to monitor the temperature in the reaction chamber 4 in real time to ensure that the temperature fluctuation does not exceed ±2°C. Regularly observe the progress of the reaction through a camera or observation window and record the degradation of the foam.

[0055] 6. End of reaction: After the reaction time is over, turn off the temperature regulating system 3 and the shuttle agitator 7, allow the reaction chamber 4 to cool naturally to room temperature, then open the valve 14 to allow the solution after the reaction to pass through the filter 13 into the recovery chamber 15. The filter 13 will isolate the unreacted solids. The solution after the reaction is completed is separated in the recovery chamber 15 to obtain a degraded product.

[0056] The control system is connected to all integrated sensors in the degradation device, collects all monitoring data in the degradation process in real time, and sends it to the high-speed processor for processing. The processing result is a signal data, which is fed back to the central controller and converted into a control signal. The central controller controls different units and mechanisms to implement control instructions. Due to factors such as the contact area of ​​the reactants, material consumption, and changes in the reaction environment, the degradation reaction process is a continuous and dynamic process. The control system mainly coordinates the operation of various mechanisms based on the real-time reaction process.

[0057] Example of efficient degradation and recovery method of waste polyurethane foam:

[0058] This embodiment proposes a method for efficiently degrading and recycling waste polyurethane foam. Figure 4 As shown, the waste polyurethane foam efficient degradation and recovery method of this embodiment comprises the following steps:

[0059] Step S1, obtaining the liquid level value and vibration signal of each stirring cycle during the degradation process of the waste polyurethane foam.

[0060] First, the liquid level value and vibration signal in the current waste polyurethane foam degradation process are collected. Since there is consumption in the degradation reaction process, the fluctuation of the liquid level can be directly observed. The evaporation of the previous solution and the reaction consumption may cause the liquid level to drop. As the reaction proceeds, the polyurethane foam gradually transforms into small molecules, the solution volume increases, and the liquid level may rise again. The stirring cycle of the shuttle stirrer 7 is obtained, that is, the total time used by the shuttle stirrer 7 to press down and lift once is recorded as one stirring cycle, that is, the liquid level values ​​and vibration signals of multiple stirring cycles in the current waste polyurethane foam degradation process are collected.

[0061] So far, this embodiment has obtained the liquid level value of each stirring cycle and the vibration signal of each stirring cycle during the degradation process of the waste polyurethane foam.

[0062] Step S2, obtaining the reaction process amount of each stirring cycle based on the change characteristics of the liquid level values ​​of adjacent stirring cycles; performing short-time Fourier transform on the vibration signal to obtain the amplitude spectrum and phase spectrum in each short-time window, and screening the target vibration signal segment of each stirring cycle according to the frequency of the vibration signal; obtaining the stage reaction amount corresponding to the vibration signal of each stirring cycle according to the distribution characteristics of the amplitude spectrum in the short-time window of the target vibration signal segment of each stirring cycle and the richness of the phase spectrum.

[0063] If the liquid level of a stirring cycle is the same as the liquid level of the previous stirring cycle, it means that the current stirring cycle is in the early stage of the reaction; if the liquid level of a stirring cycle is lower than the liquid level of the previous stirring cycle, and the larger the difference, it means that the current stirring cycle may be in the reaction acceleration stage; if the liquid level of a stirring cycle is higher than the liquid level of the previous stirring cycle, it means that the current stirring cycle may be in the final stage of the reaction.

[0064] Next, this embodiment is described by taking a stirring cycle in the current waste polyurethane foam degradation process as an example. The method provided in this embodiment can be used to process other stirring cycles in the current waste polyurethane foam degradation process.

[0065] Specifically, any stirring cycle in the degradation process of waste polyurethane foam is recorded as a candidate cycle, the stirring cycle before and adjacent to the candidate cycle is used as the first reference cycle of the candidate cycle, and the stirring cycle before and adjacent to the first reference cycle is used as the second reference cycle of the candidate cycle; the first difference between the liquid level value of the candidate cycle and the liquid level value of the first reference cycle, and the second difference between the liquid level value of the first reference cycle and the liquid level value of the second reference cycle are calculated; according to the difference between the first difference and the second difference, the reaction progress amount of the candidate cycle is obtained, and the difference between the first difference and the second difference is positively correlated with the reaction progress amount.

[0066] Among them, the positive correlation means that the dependent variable will increase as the independent variable increases, and the dependent variable will decrease as the independent variable decreases. It can be an additive relationship, a multiplicative relationship, etc., which is determined by practical applications.

[0067] In this embodiment, a specific calculation formula for the reaction progress amount is given. The reaction progress amount of the rth stirring cycle in the degradation process of the waste polyurethane foam can be expressed as:

[0068]

[0069] Among them, Er represents the reaction progress of the rth stirring cycle in the degradation process of waste polyurethane foam, W r-1 represents the liquid level value of the r-1th stirring cycle, W r represents the liquid level value of the rth stirring cycle, W r-2 It represents the liquid level value of the r-2th stirring cycle, e represents the natural constant, and norm() represents the normalization function.

[0070] W r -W r-1 represents the first difference, W r-1 -W r-2 represents the second difference, It is used to reflect the difference between the first difference and the second difference. The value is a positive number. When the value is larger, the liquid level difference from the r-1th stirring cycle to the rth stirring cycle is larger than the liquid level difference from the r-2th stirring cycle to the r-1th stirring cycle, indicating that the rth stirring cycle is in the stage of continuous decrease in liquid level. The faster the reaction growth rate, the greater the reaction process of the rth stirring cycle.

[0071] By adopting the above method, the reaction progress amount of each stirring cycle can be obtained. It should be noted that: since there is no stirring cycle before the first stirring cycle in the degradation process of waste polyurethane foam, and there is only one stirring cycle before the second stirring cycle, this embodiment does not calculate the reaction progress amount of the first stirring cycle in the current degradation process of waste polyurethane foam and the reaction progress amount of the second stirring cycle in the current degradation process of waste polyurethane foam, and directly uses the reaction progress amount of the third stirring cycle as the reaction progress amount of the first stirring cycle and the reaction progress amount of the second stirring cycle.

[0072] Considering that the reaction is only detected based on the change in liquid level, and the degradation reaction involves both solids and gases, if more accurate feedback is to be obtained, it is necessary to analyze the short-term reaction of each specific stirring cycle.

[0073] The vibration data in the reaction chamber 4 collected by the vibration sensor is in the form of a signal. When a large number of bubbles are generated inside the solution, there will be a weak vibration signal as they float to the surface of the solution and break. During the stirring process of the shuttle stirrer 7, the polyurethane foam contacts the degradation liquid over a large area, and a large amount of gas is generated inside the solution. When the reaction is intense, the dispersion of the gas in the solution may increase, forming more bubbles. However, the generation of bubbles cannot be directly monitored during the reaction process, so the stage reaction amount of the degradation reaction process can be extracted based on the vibration signal.

[0074] Specifically, the vibration signal of each stirring cycle in the current waste polyurethane foam degradation process is subjected to short-time Fourier transform, and the short-time window is set to 0.5s to obtain the amplitude spectrum and phase spectrum in each short-time window. Short-time Fourier transform is a prior art and will not be described in detail here.

[0075] When monitoring the progress of the reaction according to the bubbles generated during the degradation reaction, there will be a large stirring amplitude during the downward pressure-lifting process, that is, the stirring of the stirrer may also generate bubbles, which is different from the bubbles generated by the degradation reaction. The two need to be distinguished to estimate the true degree of degradation at each reaction stage, and the frequency threshold range of stirring to generate bubbles is obtained by the following method. Specifically, the vibration signal of each stirring cycle in the degradation process of multiple waste polyurethane foams in history is obtained, and these vibration signals are recorded as reference vibration signals. In this embodiment, the reference vibration signal of each stirring cycle in the degradation process of 30 waste polyurethane foams in history is obtained. In specific applications, the implementer selects the number of historical waste polyurethane foam degradation processes according to specific circumstances. Next, all frequency types in each vibration signal are obtained, and the signal components of each frequency type are extracted using a bandpass filter, and only signals within a specific frequency range are allowed to pass, so that a vibration signal with only one frequency type in the time sequence can be obtained, and the signal amplitudes of other positions are set to 0. The extraction process is a prior art and will not be described in detail here. The extracted signal is recorded as a sub-signal segment, that is, the vibration sub-signal segment of each frequency type of each reference vibration signal is extracted. A mapping value of each frequency type of each reference vibration signal is calculated according to a cross-correlation function between vibration sub-signal segments of each frequency type of each reference vibration signal.

[0076] The specific calculation formula of the mapping value is:

[0077]

[0078] Among them, P s,z represents the mapping value of the zth frequency type of the sth reference vibration signal, t represents the tth moment in any vibration sub-signal segment, M represents the number of vibration sub-signal segments of the zth frequency type of the sth reference vibration signal, represents the vibration value at the tth moment in the mth vibration sub-signal segment of the zth frequency type of the sth reference vibration signal, Represents the vibration value at the tth moment in the m-1th vibration sub-signal segment of the zth frequency type of the sth reference vibration signal.

[0079] The cross-correlation function between the mth vibration sub-signal segment of the zth frequency type and its previous adjacent vibration sub-signal segment, that is, the integral value thereof, is used as the cross-correlation function value. The average value of the cross-correlation function values ​​of all adjacent vibration sub-signal segments of the zth frequency type of the sth reference vibration signal, the larger the value is, the more autocorrelation the zth frequency type of the sth reference vibration signal has in the reference vibration signal, that is, the more relevant the occurrence of such frequency is to the stirring cycle of the shuttle stirrer 7, that is, the more likely the signal component of such frequency is the vibration generated by stirring or the bubble, that is, the larger its mapping value is.

[0080] By adopting the above method, the mapping value of each frequency type of each reference vibration signal in each historical waste polyurethane foam degradation process can be obtained, and the average mapping value of each frequency type in the reference vibration signal of all stirring cycles in the historical waste polyurethane foam degradation processes can be calculated respectively, and the frequency type corresponding to the largest average mapping value is used as the frequency threshold. Since the vibration signal emitted by the bubbles in the degradation process tends to be high frequency, the vibration generated by stirring and the vibration signal emitted by the bubbles generated by stirring tend to be low frequency, so for the vibration signal of any stirring cycle in the current waste polyurethane foam degradation process: the signal segment with a frequency greater than the frequency threshold in the vibration signal is used as the target vibration signal segment, that is, the signal with a frequency less than or equal to the frequency threshold is deleted from the vibration signal, and only the bubble vibration frequency that may be a degradation product in the degradation reaction process is retained. By adopting this method, the target vibration signal segment of each stirring cycle in the current waste polyurethane foam degradation process can be screened out.

[0081] The amplitude spectrum and phase spectrum of each target vibration signal segment are obtained respectively. The horizontal axis of the amplitude spectrum is frequency, and the vertical axis is the amplitude corresponding to different frequencies. The horizontal axis of the phase spectrum is also frequency, and the vertical axis is the phase corresponding to different frequencies. The correlation between the amplitude and frequency of the amplitude spectrum in each short-time window in each target vibration signal segment is obtained. Assuming that the vibration signal is caused by the bursting of bubbles, the frequency and amplitude of the bursting of large and small bubbles should be linearly related, that is, large bubbles have low frequency and large amplitude, and small bubbles have high frequency and small amplitude; if the linear relationship is met, the vibration source representing the vibration signal mostly comes from dense bubbles; specifically, the Pearson correlation coefficient between all amplitudes and frequencies in the amplitude spectrum in each short-time window is calculated respectively as the correlation index of each short-time window. The larger the value, the stronger the linear relationship between the two, and vice versa. The calculation method of the Pearson correlation coefficient is a prior art and will not be elaborated here.

[0082] Calculate the entropy value of the phase spectrum in each short-time window in each target vibration signal segment. The entropy value can represent the richness of information. If the phase at each frequency is greatly different, the larger the entropy value, the more irregular the multiple vibration sources appear during the stirring cycle. This vibration source is most likely derived from bubbles generated by violent degradation reactions in a short period of time. On the contrary, if the phase at each frequency is almost equal, the lower the entropy value, the more regular the phase spectrum, which means that during the stirring cycle, there is almost only periodic vibration generated by the agitator. It should be noted that each short-time window corresponds to an entropy value, which is used to reflect the richness of the phase in the short-time window. The larger the entropy value, the more chaotic the distribution of the phase in the short-time window. The entropy calculation method is a prior art and will not be described in detail here.

[0083] For the candidate period, the normalized result of the Euclidean norm between the standard deviation of the correlation index of all short-time windows of the target vibration signal segment of the candidate period and the standard deviation of the richness of the phase within all short-time windows of the target vibration signal segment of the candidate period is taken as the phase reaction amount corresponding to the vibration signal of the candidate period.

[0084] In this embodiment, a specific calculation formula for the stage reaction amount is given. The stage reaction amount corresponding to the vibration signal of the rth stirring cycle in the current waste polyurethane foam degradation process can be expressed as:

[0085]

[0086] Among them, F r represents the stage reaction amount corresponding to the vibration signal of the rth stirring cycle in the current waste polyurethane foam degradation process, σ(U r ) represents the standard deviation of the relevant indicators of all short-time windows of the target vibration signal segment of the rth stirring cycle, σ(H r ) represents the standard deviation of the entropy values ​​of all phases in all short-time windows of the target vibration signal segment of the rth stirring cycle, and norm() represents the normalization function.

[0087] The Euclidean norm between the standard deviation of the correlation index of all short-time windows of the target vibration signal segment of the r-th stirring cycle and the standard deviation of the richness of the phase in all short-time windows of the target vibration signal segment of the r-th stirring cycle is used to eliminate the dimension, and then the Euclidean norm is normalized to obtain the stage reaction amount. The larger the stage reaction amount, the more intense the short-term reaction of the r-th stirring cycle.

[0088] Using the above method, the reaction progress amount and stage reaction amount of the candidate cycle were obtained.

[0089] Step S3, determining the actual degradation amount of each stirring cycle in combination with the reaction process amount and the stage reaction amount; generating a real-time control strategy based on the actual degradation amount to perform degradation regulation, and performing recycling based on the degradation result.

[0090] Next, the actual degradation amount is determined by combining the reaction progress amount and the stage reaction amount.

[0091] Specifically, the absolute value of the difference between the reaction process amount of the candidate cycle and the stage reaction amount of the candidate cycle is taken as the actual degradation amount of the candidate cycle. The larger the value, the more it represents that the stirring cycle is in the reaction acceleration stage, but the short-term stage reaction amount does not conform to the current reaction acceleration stage, that is, the greater the difference between the two, it means that most of the degradation reaction products in this stage are not gases, fewer bubbles are generated, and they may be converted into solid products.

[0092] By adopting the above method, the actual degradation amount of each cycle in the current waste polyurethane foam degradation process can be obtained.

[0093] After obtaining the actual degradation amount of each stirring cycle in the current waste polyurethane foam degradation process, the control system then generates a real-time control strategy based on the actual degradation amount of each stirring cycle, and can effectively monitor and regulate each mechanism; for example: when the actual degradation amount is large, the control system replenishes the polyurethane foam raw materials in time; when the actual degradation amount is small, the catalyst is replenished, or the temperature in the reaction chamber is increased through the temperature control system to accelerate the reaction. Since the products in the degradation reaction are mostly high-viscosity liquid substances converted from polyurethane foam, the conventional degradation reaction process is difficult to directly monitor by the naked eye or sensors, and the control system of the present invention estimates the actual degradation amount of solid products in each stage based on the integrated sensor, and uses it as the core feedback input of the control system, and then regulates each mechanism according to the reaction degradation situation. The specific regulation process can be programmed using PLC, which will not be elaborated here.

[0094] The degradation products are separated from the unreacted raw materials to separate the useful monomer or polymer fragments. The reaction process of polyurethane foam is usually not carried out in a completely closed environment, but requires appropriate ventilation conditions to ensure that the heat and volatile organic compounds, carbon dioxide, ammonia, etc. generated during the reaction can be effectively discharged from the gas discharge port 6 to avoid environmental pollution.

[0095] The filter 13 is used to separate the solution from the larger solids, and the extracted solution contains low molecular weight polymers or oligomers generated by the degradation reaction. After this part of the solution reaches the separation mechanism, the degradation products are separated from the solution after the reaction is completed by fine filtration, centrifugal separation, solvent extraction, adsorption, etc. according to the characteristics of the degradation products. The recovery and discharge system recycles the separated useful substances and converts them into reusable materials, and treats the waste gas and wastewater generated during the degradation process to ensure compliance with environmental protection standards.

[0096] Thus, the method provided in this embodiment has been used to achieve efficient degradation and recycling of waste polyurethane foam.

[0097] The shuttle-shaped stirrer 7 in this embodiment optimizes the problem of uneven stirring during the degradation of polyurethane foam by a downward pressure-lifting method. Polyurethane foam is relatively light. In this embodiment, the polyurethane foam can be pressed into the degradation liquid, and the heat release and heat accumulation problems during the reaction process are well alleviated, and the ambient temperature in the reaction chamber 4 is kept stable. In view of the fact that most of the polyurethane foam degradation products are high-viscosity liquid substances, it is not easy to observe and monitor the reaction process, resulting in a poor degradation effect of polyurethane foam. The reaction process amount is calculated by the change characteristics of the liquid level values ​​of adjacent stirring cycles, and then the effective frequency is separated according to the vibration signal to obtain the target vibration signal segment, and then the stage reaction amount is calculated according to the distribution characteristics of the amplitude spectrum in the short-term window of the target vibration signal segment and the richness of the phase spectrum. The purpose is to extract the bubbles generated by the degradation reaction in each stirring cycle, which is used to evaluate whether the stage reaction is violent in a short period of time. Finally, the solid reaction products that may be generated in each stirring cycle are estimated according to the reaction process amount and the stage reaction amount, so as to achieve tracking of the reaction process, provide accurate feedback input for the control system, and help improve the monitoring and control accuracy and real-time performance of the polyurethane foam reaction process, and ensure the degradation effect of polyurethane foam.

[0098] It should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for efficiently degrading and recycling waste polyurethane foam, characterized in that: The method comprises the following steps: Obtain the liquid level value and vibration signal of each stirring cycle during the degradation process of waste polyurethane foam; The reaction process amount of each stirring cycle is obtained based on the change characteristics of the liquid level values ​​of adjacent stirring cycles; the vibration signal is subjected to short-time Fourier transform to obtain the amplitude spectrum and phase spectrum in each short-time window, and the target vibration signal segment of each stirring cycle is screened according to the frequency of the vibration signal; the stage reaction amount corresponding to the vibration signal of each stirring cycle is obtained according to the distribution characteristics of the amplitude spectrum in the short-time window of the target vibration signal segment of each stirring cycle and the richness of the phase spectrum; The actual degradation amount of each stirring cycle is determined in combination with the reaction process amount and the stage reaction amount; a real-time control strategy is generated based on the actual degradation amount to perform degradation regulation, and recycling is performed based on the degradation result.

2. The method for efficiently degrading and recycling waste polyurethane foam according to claim 1, characterized in that: The step of obtaining the reaction progress amount of each stirring cycle based on the change characteristics of the liquid level values ​​of adjacent stirring cycles includes: Taking the stirring period before the candidate period and adjacent to the candidate period as the first reference period of the candidate period, and taking the stirring period before the first reference period and adjacent to the first reference period as the second reference period of the candidate period; Calculating a first difference between the liquid level value of the candidate cycle and the liquid level value of the first reference cycle, and a second difference between the liquid level value of the first reference cycle and the liquid level value of the second reference cycle; Obtaining a reaction progress amount of the candidate cycle according to a difference between the first difference and the second difference, wherein the difference between the first difference and the second difference is positively correlated with the reaction progress amount; The candidate cycle is any stirring cycle in the degradation process of waste polyurethane foam.

3. The method for efficiently degrading and recycling waste polyurethane foam according to claim 1, characterized in that: The step of screening the target vibration signal segment of each stirring cycle according to the frequency of the vibration signal comprises: For a vibration signal of any stirring cycle: a signal segment in the vibration signal whose frequency is greater than a frequency threshold is taken as a target vibration signal segment.

4. The method for efficiently degrading and recycling waste polyurethane foam according to claim 3, characterized in that: The acquisition of the frequency threshold comprises: Obtain reference vibration signals of each stirring cycle during several historical degradation processes of waste polyurethane foam; Obtaining a mapping value of each frequency type of each reference vibration signal according to a cross-correlation function between vibration sub-signal segments of each frequency type of each reference vibration signal, wherein the vibration sub-signal segments of each frequency type are extracted using a bandpass filter; Calculate the average mapping value of each frequency type in the reference vibration signals of all stirring cycles during the historical degradation processes of several waste polyurethane foams; The frequency type corresponding to the maximum average mapping value is used as the frequency threshold.

5. The method for efficiently degrading and recycling waste polyurethane foam according to claim 2, characterized in that: The step reaction amount corresponding to the vibration signal of each stirring cycle is obtained according to the distribution characteristics of the amplitude spectrum and the richness of the phase spectrum in the short-time window of the target vibration signal segment of each stirring cycle, including: Calculate the correlation between the frequency and amplitude in each short-time window of the target vibration signal segment of the candidate period as the correlation index of the corresponding short-time window; According to the standard deviation of the correlation index of all short-time windows of the target vibration signal segment of the candidate period and the standard deviation of the richness of the phase in all short-time windows of the target vibration signal segment of the candidate period, the phase reaction amount corresponding to the vibration signal of the candidate period is obtained.

6. The method for efficient degradation and recovery of waste polyurethane foam according to claim 5, characterized in that: The acquisition of the correlation between the frequency and the amplitude in each short-time window of the target vibration signal segment of the candidate period includes: determining the Pearson correlation coefficient between the frequency and the amplitude in each short-time window of the target vibration signal segment of the candidate period as the correlation between the frequency and the amplitude in each short-time window of the target vibration signal segment of the candidate period.

7. The method for efficiently degrading and recycling waste polyurethane foam according to claim 5, characterized in that: The method of obtaining the stage reaction amount corresponding to the vibration signal of the candidate period based on the standard deviation of the correlation index of all short-time windows of the target vibration signal segment of the candidate period and the standard deviation of the richness of the phase within all short-time windows of the target vibration signal segment of the candidate period comprises: taking the normalized result of the Euclidean norm between the standard deviation of the correlation index of all short-time windows of the target vibration signal segment of the candidate period and the standard deviation of the richness of the phase within all short-time windows of the target vibration signal segment of the candidate period as the stage reaction amount corresponding to the vibration signal of the candidate period.

8. The method for efficient degradation and recovery of waste polyurethane foam according to claim 5, characterized in that: The acquisition of the richness of the phase in each short-time window of the target vibration signal segment of the candidate period includes: The entropy values ​​of all phases in each short-time window of the target vibration signal segment of the candidate period are used as the richness of the phases in each short-time window of the target vibration signal segment of the candidate period.

9. The method for efficiently degrading and recycling waste polyurethane foam according to claim 2, characterized in that: The step of combining the reaction progress amount and the stage reaction amount to determine the actual degradation amount of each stirring cycle comprises: The absolute value of the difference between the reaction progress amount of the candidate cycle and the stage reaction amount of the candidate cycle is taken as the actual degradation amount of the candidate cycle.

10. A waste polyurethane foam efficient degradation and recovery device, characterized in that: The device comprises a feeding mechanism and a degradation mechanism, wherein the feeding mechanism comprises a main feeding port (1) and a secondary feeding port (9), wherein the main feeding port (1) is connected to a crusher, and the degradation mechanism comprises a reaction chamber (4) and a shuttle-shaped agitator (7), wherein the polyurethane foam and the degradation agent undergo a chemical reaction in the reaction chamber (4).

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