Method and device for efficient degradation and recycling of waste polyurethane foam

Abstract

The present application relates to the technical field of polyurethane foam degradation and recycling, and particularly relates to a method and device for efficient degradation and recycling of waste polyurethane foam. The method comprises: obtaining liquid level values and vibration signals of each stirring period in the degradation process of waste polyurethane foam; obtaining reaction progress amount of each stirring period based on the change characteristics of the liquid level values of adjacent stirring periods; obtaining amplitude spectrum and phase spectrum in each short-time window, and screening target vibration signal segments of each stirring period according to the frequency size of the vibration signals; obtaining stage reaction amount 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 segments of each stirring period; determining actual degradation amount of each stirring period in combination with the reaction progress amount and the stage reaction amount; generating real-time control strategy based on the actual degradation amount to perform degradation regulation, and recycling based on the degradation result. The present application can improve the regulation accuracy and real-time performance of the polyurethane foam reaction process.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of polyurethane foam degradation and recycling, in particular to a method and device for efficient degradation and recycling of waste polyurethane foam. BACKGROUND

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

[0003] In the process of degradation using existing polyurethane foam degradation devices, the products in the degradation reaction are mostly high-viscosity liquid substances converted from polyurethane foam. The conventional degradation reaction process is difficult to monitor directly by the naked eye or sensors, so it is impossible to intervene and control the degradation reaction process, which may cause uneven degradation or over-degradation, affecting the processing cost and efficiency of regenerated polyols in the subsequent process. Therefore, it is urgent to solve the problem of tracking and monitoring the degradation process of polyurethane foam. SUMMARY

[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 application is to provide a method and device for efficient degradation and recycling of waste polyurethane foam. The technical solution adopted is as follows:

[0005] In the first aspect, the present application provides a method for efficient degradation and recycling of waste polyurethane foam, which comprises the following steps:

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

[0007] Obtain the reaction progress amount of each stirring period based on the change characteristics of the liquid level value of the adjacent stirring period; obtain the amplitude spectrum and phase spectrum in each short-time window by performing short-time Fourier transform on the vibration signal, and select the target vibration signal segment of each stirring period according to the frequency size of the vibration signal; obtain the stage reaction amount corresponding to the vibration signal of each stirring period 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 period;

[0008] Determine the actual degradation amount of each stirring period by combining the reaction progress amount and the stage reaction amount; generate a real-time control strategy based on the actual degradation amount to control the degradation, and recycle based on the degradation result.

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

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

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

[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 includes:

[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 used as a target vibration signal segment.

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

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

[0018] Obtaining a mapping value for 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 degradation processes of the waste polyurethane foam in the history;

[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 within the short-time window of the target vibration signal segment of each stirring cycle includes:

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

[0023] The stage reaction quantity corresponding to the vibration signal of the candidate period is obtained 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.

[0024] Preferably, the correlation between the frequency and the amplitude in each short-time window of the target vibration signal segment of the candidate period is obtained by 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.

[0025] Preferably, the stage reaction quantity corresponding to the vibration signal of the candidate period is obtained 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 by determining 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 in all short-time windows of the target vibration signal segment of the candidate period as the stage reaction quantity corresponding to the vibration signal of the candidate period.

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

[0027] The entropy value of all phases in each short-time window of the target vibration signal segment of the candidate period is determined as the richness of the phase in each short-time window of the target vibration signal segment of the candidate period.

[0028] Preferably, the actual degradation quantity of each stirring period is determined by combining the reaction progress quantity and the stage reaction quantity, including:

[0029] The absolute value of the difference between the reaction progress quantity of the candidate period and the stage reaction quantity of the candidate period is determined as the actual degradation quantity of the candidate period.

[0030] In a second aspect, the present application provides a device for efficiently degrading and recycling waste polyurethane foam, which comprises a feeding mechanism and a degradation mechanism, the feeding mechanism comprises a main feeding port and a secondary feeding port, the main feeding port is connected with a crusher, the degradation mechanism comprises a reaction cavity and a shuttle-shaped stirrer, and the polyurethane foam and a degrading agent react chemically in the reaction cavity.

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

[0032] In order to solve the problem that the degradation product of polyurethane foam is mostly high-viscosity liquid substance, the reaction process is not easy to observe and monitor, and the degradation effect of polyurethane foam is poor, the reaction process amount is calculated according to the change characteristics of the liquid level value of adjacent stirring periods, then the effective frequency is separated from 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 and the richness of the phase spectrum in the short window of the target vibration signal segment, the purpose is to extract the bubbles generated in each stirring period due to the degradation reaction, and whether the stage reaction is violent in a short period is evaluated, and finally the solid reaction product possibly generated in each stirring period is estimated according to the reaction process amount and the stage reaction amount, so that the reaction process is tracked, accurate feedback input is provided for the control system, and the monitoring and control precision and real-time performance of the polyurethane foam reaction process are improved, and the degradation effect of the polyurethane foam is ensured. BRIEF DESCRIPTION OF DRAWINGS

[0033] In order to more clearly illustrate the technical solutions and advantages in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced below, and obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creating labor.

[0034] Figure 1 The overall mechanical structure schematic diagram of the waste polyurethane foam efficient degradation and recovery device provided by the embodiments of the present application is shown in the figure.

[0035] Figure 2 The internal mechanical structure schematic diagram of the waste polyurethane foam efficient degradation and recovery device provided by the embodiments of the present application is shown in the figure.

[0036] Figure 3 The pre-tightening device structure schematic diagram of the waste polyurethane foam efficient degradation and recovery device provided by the embodiments of the present application is shown in the figure.

[0037] Figure 4 The flow chart of the waste polyurethane foam efficient degradation and recovery method provided by the embodiments of the present application is shown in the figure.

[0038] In the figure, 1 is a main feed inlet, 2 is a display, 3 is a temperature adjusting system, 4 is a reaction cavity, 5 is a motor, 6 is a gas discharge port, 7 is a shuttle-shaped stirrer, 8 is a pre-tightening device, 9 is a secondary feed inlet, 10 is a sliding rod, 11 is a resistance wire tube, 12 is a resistance wire tube, 13 is a filter screen, 14 is a valve, 15 is a recovery cavity, and 16 is a support. DETAILED DESCRIPTION

[0039] In order to further clarify the technical means and effects taken by the present application to achieve the predetermined inventive objectives, the following will be described in detail according to the preferred embodiments of the present application and with reference to the accompanying drawings.

[0040] Unless otherwise defined, 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 application belongs.

[0041] The specific scheme of the waste polyurethane foam efficient degradation and recovery method and device provided by the present application will be described in detail below with reference to the accompanying drawings.

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

[0043] The present embodiment proposes a waste polyurethane foam efficient degradation and recovery device, as shown in Figure 1 , which 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 the present embodiment includes a main feed inlet 1, a display 2, a temperature adjustment system 3, a reaction cavity 4, a motor 5, a gas discharge port 6, a shuttle-shaped stirrer 7, a pre-tightening device 8, a secondary feed inlet 9, a slide bar 10, a resistance wire tube 11, a resistance wire tube 12, a filter screen 13, a valve (with detection system) 14, a recovery cavity 15, and a bracket 16. As shown in Figure 2 and Figure 3 , which are schematic diagrams of the internal mechanical structure of the device, Figure 2 , which is a schematic diagram of the pre-tightening device 8 of the device. Figure 3

[0045] The waste polyurethane foam efficient degradation and recovery device proposed in the present embodiment includes a feeding mechanism, a degradation mechanism, and a control system. The feeding mechanism is used to send polyurethane foam waste into the degradation and recovery device. The main feed inlet 1 is connected with a crusher. The external crusher breaks the large pieces of polyurethane foam into small pieces, which can increase the contact area with the degradation agent. The broken polyurethane foam enters the degradation and recovery device from the main feed inlet 1. The secondary feed inlet 9 is used to add degradation substances such as degradation liquid, catalyst, stabilizer, and water. The degradation mechanism includes a container for the degradation process, stirring for the reaction process, heating, and other auxiliary functions. The polyurethane foam and the degradation agent undergo a chemical reaction in the reaction cavity 4. The shuttle-shaped stirrer 7 is driven by the motor 5 to stir up and down, ensuring 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 the embodiment adopts the way of pressing down and lifting for stirring, because the polyurethane foam is lighter and can float on the top of the degradation liquid, so the polyurethane foam on the top is pressed into the degradation liquid by the way of pressing down and lifting, and when the degradation liquid is pressed, it will be turned over from the edge of the shuttle-shaped stirrer 7, and when the shuttle-shaped stirrer 7 is lifted, the degradation liquid will slide down from the edge of the shuttle-shaped stirrer 7, so as to exchange the upper and lower liquids. In order to avoid the hooking of the degradation liquid during the pressing down and lifting of the shuttle-shaped stirrer 7, the stirring assembly is designed as a shuttle shape, so as to facilitate the smooth exchange of the liquids. In addition, a pre-tightening device 8 is installed in the sliding rod 10, which controls the stability of the pressing down and lifting process of the shuttle-shaped stirrer 7, so as to avoid the generation of large amplitude oscillation.

[0047] The degradation reaction is generally an exothermic reaction, and such exothermic reaction generally occurs locally, because the contact and reaction between the polyurethane foam and the degradation liquid occur locally. The large amplitude stirring of the stirring process of the embodiment can play a role in uniform heat distribution, and also has the effects of accelerating heat dissipation and evaporation, so as to better balance the environmental temperature in the reaction cavity 4.

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

[0049] The whole process of the degradation mechanism for degrading the polyurethane foam 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 sealed well. Then clean the reaction cavity 4 with appropriate solvent to ensure that there is no residual material;

[0051] 2. Material preparation: take 200 kg of polyurethane foam sample and put it into the reaction cavity 4 of the polyurethane foam efficient degradation and recovery device, then select appropriate degradation agent according to the production demand, for example, diethylene glycol, weigh 40 kg of diethylene glycol, and prepare 50 kg of water, 15 kg of catalyst (sodium hydroxide) and other solvents;

[0052] 3. Parameter setting: set the temperature of the temperature adjusting device 3 to 180℃ to provide appropriate degradation temperature; set the stirring period to 5s, that is, complete the pressing down and lifting process slowly and uniformly every 5s to ensure uniform mixing of the reactants;

[0053] 4. Start of degradation reaction: start the temperature adjusting system 3, preheat the temperature of the reaction cavity 4 to 80℃, which takes about 30 minutes, and then slowly add diethylene glycol into the reaction cavity 4. Start timing, and set the reaction time to 2 hours.

[0054] 5、Reaction monitoring: Use the integrated sensor system to monitor the reaction in the reaction chamber 4, including temperature, pressure, flow, vibration, etc., manually record the amount of polyurethane foam, degradation solution, catalyst, etc. (unit: kg); if the temperature sensor is installed below the liquid level of the degradation solution, 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℃. Regularly observe the reaction progress through the camera or observation window, and record the degradation of the foam.

[0055] 6、Reaction end: After the reaction time is over, turn off the temperature regulation system 3 and the shuttle-shaped stirrer 7, and let the reaction chamber 4 cool down to room temperature naturally, then open the valve 14 to make the reaction completed solution pass through the filter screen 13 into the recovery chamber 15, and the filter screen 13 will isolate the incompletely reacted solids, and the reaction completed solution is separated in the recovery chamber 15 to obtain the degraded product.

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

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

[0058] The method for efficient degradation and recovery of waste polyurethane foam provided in this embodiment includes the following steps: Figure 4 As shown in the figure, the method for efficient degradation and recovery of waste polyurethane foam in this embodiment includes the following steps:

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

[0060] First, collect the liquid level value and vibration signal in the current degradation process of waste polyurethane foam. Since there is consumption in the degradation reaction process, the fluctuation change of the liquid level can be directly observed. The evaporation of the solution and the consumption of the reaction in the early stage may cause the liquid level to drop, while the polyurethane foam gradually converts into small molecular substances as the reaction proceeds, the solution volume increases, and the liquid level may rise again. The stirring period of the shuttle-shaped stirrer 7 is obtained, that is, the total time for one down-up of the shuttle-shaped stirrer 7 is recorded as a stirring period, that is, the liquid level value and vibration signal of multiple stirring periods in the current degradation process of waste polyurethane foam are collected.

[0061] Up to now, the liquid level value of each stirring period in the waste polyurethane foam degradation process and the vibration signal of each stirring period are obtained.

[0062] In step S2, the reaction progress amount of each stirring period is obtained based on the change characteristics of the liquid level value of the adjacent stirring period; the short-time Fourier transform is performed on the vibration signal to obtain the amplitude spectrum and the phase spectrum in each short-time window, and the target vibration signal segment of each stirring period is selected according to the frequency size of the vibration signal; and the stage reaction amount corresponding to the vibration signal of each stirring period 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 period.

[0063] The liquid level of one stirring period is flat with the liquid level of the previous stirring period, which represents that the current stirring period is in the early reaction stage; the liquid level of one stirring period is lower than the liquid level of the previous stirring period, and the greater the difference, the more likely the current stirring period is in the reaction acceleration stage; and if the liquid level of one stirring period is higher than the liquid level of the previous stirring period, the current stirring period is likely to be in the late reaction stage.

[0064] Next, the current stirring period in the waste polyurethane foam degradation process is taken as an example for description, and the method provided in the embodiment can be used to process other stirring periods in the waste polyurethane foam degradation process.

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

[0066] The positive correlation means that the dependent variable will increase with the increase of the independent variable, and the dependent variable will decrease with the decrease of the independent variable, which can be an additive relationship, a multiplication relationship, etc., and is determined by actual application.

[0067] In the embodiment, a specific calculation formula of the reaction progress amount is given, and the reaction progress amount of the rth stirring period in the waste polyurethane foam degradation process can be represented as:

[0068]

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

[0070] W r W r-1 W represents the first difference r-1 W r-2 W represents the second difference The value is a positive number, and the greater the value, the greater the liquid level difference between the r-1th stirring period and the rth stirring period than the liquid level difference between the r-2th stirring period and the r-1th stirring period, indicating that the rth stirring period is in a stage of continuously decreasing liquid level, and the reaction speed is faster, i.e. the reaction progress amount of the rth stirring period is greater.

[0071] By using the above method, the reaction progress amount of each stirring period can be obtained. It should be noted that since there is no stirring period before the first stirring period in the degradation process of the waste polyurethane foam, and there is only one stirring period before the second stirring period, the reaction progress amount of the first stirring period in the current degradation process of the waste polyurethane foam and the reaction progress amount of the second stirring period in the current degradation process of the waste polyurethane foam are not calculated, and the reaction progress amount of the third stirring period is directly taken as the reaction progress amount of the first stirring period and the reaction progress amount of the second stirring period.

[0072] It is considered that only according to the change of the liquid level, the reaction can be monitored, but the degradation reaction has both solid and gas, and if more accurate feedback is to be obtained, the short-term reaction of each stirring period needs to be analyzed.

[0073] The vibration data collected by the vibration sensor in the reaction cavity 4 is in the form of a signal. When a large number of bubbles are generated inside the solution, they will break as they float to the surface of the solution, causing weak vibration signals. During the stirring process of the shuttle-shaped stirrer 7, the polyurethane foam is in large-area contact with the degradation liquid, and a large amount of gas is generated inside the solution. When the reaction is intense, it may increase the dispersion of gas in the solution and form 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 according to the vibration signal.

[0074] Specifically, the vibration signal of each stirring period 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. The short-time Fourier transform is prior art, and will not be described in detail here.

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

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

[0077]

[0078] wherein, P s,z represents the mapping value of the zth frequency type of the st reference vibration signal, t represents the tth time in any vibration sub-signal segment, M represents the number of vibration sub-signal segments of the zth frequency type of the st reference vibration signal, represents the vibration value of the tth time in the mth vibration sub-signal segment of the zth frequency type of the st reference vibration signal, represents the vibration value of the tth time in the m-1th vibration sub-signal segment of the zth frequency type of the st reference vibration signal.

[0079] represents the cross-correlation function between the mth vibration sub-signal segment of the zth frequency type and its adjacent vibration sub-signal segment, that is, the integral value thereof is taken 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 s th reference vibration signal is obtained, and the larger the value is, the more self-correlation the zth frequency type of the s th reference vibration signal has in the reference vibration signal, that is, the more relevant the occurrence of such frequency is to the stirring period of the shuttle-shaped 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 the mapping value thereof is.

[0080] By using the above method, the mapping value of each frequency type of each reference vibration signal in each waste polyurethane foam degradation process in history can be obtained, the average mapping value of each frequency type in the reference vibration signal of all stirring periods in the historical multiple waste polyurethane foam degradation processes is calculated respectively, and the frequency type corresponding to the maximum average mapping value is taken as the frequency threshold. Since the vibration signal emitted by the bubble in the degradation process is biased to high frequency, and the vibration generated by stirring and the vibration signal emitted by the bubble generated by stirring is biased to low frequency, for the vibration signal of any stirring period in the current waste polyurethane foam degradation process: the signal segment with a frequency greater than the frequency threshold in the vibration signal is taken 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 of the degradation product in the degradation reaction process is obtained. By using this method, the target vibration signal segment of each stirring period in the current waste polyurethane foam degradation process can be screened out.

[0081] The amplitude spectrum and the phase spectrum of each target vibration signal segment are obtained respectively, the horizontal axis of the amplitude spectrum is the frequency, the vertical axis is the amplitude corresponding to different frequencies, and the horizontal axis of the phase spectrum is also the frequency, and the vertical axis is the phase corresponding to different frequencies. The correlation between the amplitude and the frequency of the amplitude spectrum in each short-time window in each target vibration signal segment is obtained. If the vibration signal is generated by the bubble breaking, the frequency and the amplitude of the large bubble and the small bubble breaking should be linearly related, that is, the frequency of the large bubble is low and the amplitude is large, and the frequency of the small bubble is high and the amplitude is small. If the linear relationship is met, it means that the vibration source of the vibration signal is mostly derived from the dense bubble. 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 is, the stronger the linear relationship between the two is, and vice versa. The calculation method of the Pearson correlation coefficient is a prior art, which will not be described in detail here.

[0082] The entropy value of the phase spectrum in each short-time window in each target vibration signal segment is calculated, the entropy value can represent the information richness, if the phase of each frequency has a large difference, the entropy value is larger, which represents that in the stirring period, there are many irregular vibration sources, and the vibration sources are probably bubbles generated by the degradation reaction in a short period; on the contrary, if the phase of each frequency is almost equal, the entropy value is lower, and the phase spectrum is more regular, which represents that in the stirring period, there is only periodic vibration generated by the stirrer. 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, and the larger the entropy value, the more chaotic the distribution of the phase in the short-time window. The calculation method of entropy is 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 in all short-time windows of the target vibration signal segment of the candidate period is taken as the stage reaction amount corresponding to the vibration signal of the candidate period.

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

[0085]

[0086] Wherein, F r represents the stage reaction amount corresponding to the vibration signal of the rth stirring period in the current waste polyurethane foam degradation process, σ(U r ) represents the standard deviation of the correlation index of all short-time windows of the target vibration signal segment of the rth stirring period, σ(H r ) represents the standard deviation of the entropy value of all phases in all short-time windows of the target vibration signal segment of the rth stirring period, and norm() represents a normalization function.

[0087] represents the standard deviation of the correlation index of all short-time windows of the target vibration signal segment of the rth stirring period and the standard deviation of the richness of the phase in all short-time windows of the target vibration signal segment of the rth stirring period, the purpose is to eliminate the dimension, and then to perform deviation normalization on the Euclidean norm to obtain the stage reaction amount. The larger the stage reaction amount, the more intense the short-term reaction of the rth stirring period.

[0088] By using the above method, the reaction progress amount and the stage reaction amount of the candidate period are obtained.

[0089] Step S3, determine the actual degradation amount of each stirring period in combination with the reaction progress amount and the stage reaction amount; generate a real-time control strategy based on the actual degradation amount to control degradation, and recycle 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 progress amount of the candidate period and the stage reaction amount of the candidate period is taken as the actual degradation amount of the candidate period. The larger the value, the more likely it is that the stirring period 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, the more likely it is that the degradation reaction product of the stage is not mostly gas, but is likely to be converted into solid product.

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

[0093] After obtaining the actual degradation amount of each stirring period in the current waste polyurethane foam degradation process, the control system generates a real-time control strategy based on the actual degradation amount of each stirring period, which can effectively monitor and control each mechanism; for example, when the actual degradation amount is large, the control system supplements the polyurethane foam raw material in time; when the actual degradation amount is small, the catalyst is supplemented, or the temperature in the reaction chamber is increased by the temperature control system to accelerate the reaction. Since the product in the degradation reaction is mostly high-viscosity liquid material converted from polyurethane foam, the conventional degradation reaction progress is difficult to monitor directly by the naked eye or sensor, but the control system of the present application estimates the actual degradation amount of solid product in each stage based on the integrated sensor, and takes it as the core feedback input of the control system. According to the reaction degradation condition, each mechanism is adjusted and controlled. The specific control process can be programmed by using PLC, which will not be described in detail here.

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

[0095] The solution and larger solids are separated by the filter screen 13, and the solution drawn away contains low molecular weight polymers or oligomers generated by the degradation reaction, and this part of the solution reaches the separation mechanism, and according to the characteristics of the degradation product, the degradation product is separated from the solution after the reaction is completed by means of fine filtration, centrifugal separation, solvent extraction, adsorption and the like. The recovery and discharge system recovers the separated useful substances, converts them into reusable materials, and treats the waste gas and waste water generated in the degradation process to ensure compliance with environmental protection standards.

[0096] Thus, by using the method provided in the embodiment, efficient degradation and recovery of waste polyurethane foam is achieved.

[0097] The shuttle-shaped stirrer 7 in the embodiment optimizes the problem of uneven stirring during the degradation of polyurethane foam by the down-pressing-lifting method. Polyurethane foam is relatively light, and the embodiment can press the polyurethane foam into the degradation liquid and better alleviate the heat release and heat accumulation problems during the reaction, maintaining the stability of the environment temperature in the reaction cavity 4. The embodiment is aimed at the problem that the degradation products of polyurethane foam are mostly high-viscosity liquid substances, which are not easy to observe and monitor the reaction progress, resulting in poor degradation effect of polyurethane foam. The reaction progress is calculated by the change characteristics of the liquid level value in adjacent stirring periods, then the effective frequency is separated from 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 and the richness of the phase spectrum in the short-time window of the target vibration signal segment. The purpose is to extract the bubbles generated in each stirring period due to the degradation reaction, to evaluate whether the stage reaction is intense in the short term, and finally to estimate the solid reaction product that may be generated in each stirring period according to the reaction progress and the stage reaction amount, so as to realize the tracking of the reaction progress and provide accurate feedback input for the control system, which is conducive to improving the monitoring and control accuracy and real-time performance of the polyurethane foam reaction process, and ensuring the degradation effect of the polyurethane foam.

[0098] It should be noted that the above description is only a preferred embodiment of the present application, and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the principles of the present application shall be included in the protection scope of the present application.

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 progress amount of each stirring cycle is obtained based on the change characteristics of the liquid level values ​​in adjacent stirring cycles; the vibration signal is subjected to a 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 selected according to the frequency of the vibration signal; the stage reaction amount corresponding to the vibration signal of each stirring cycle is obtained based on 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; Determine the actual degradation amount of each stirring cycle by combining the reaction progress amount and the stage reaction amount; generate a real-time control strategy based on the actual degradation amount to perform degradation regulation, and perform recycling based on the degradation result; The step of obtaining the reaction progress 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 a first reference period for the candidate period, and taking the stirring period before the first reference period and adjacent to the first reference period as a second reference period for the candidate period; calculating a first difference between the liquid level value of the candidate period and the liquid level value of the first reference period, and a second difference between the liquid level value of the first reference period and the liquid level value of the second reference period; 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; The step of obtaining the stage reaction amount corresponding to the vibration signal of each stirring cycle includes: 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; 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 phase richness within all short-time windows of the target vibration signal segment of the candidate period is used as the phase response amount corresponding to the vibration signal of the candidate period; The determining of the actual degradation amount of each stirring cycle by combining the reaction progress amount and the stage reaction amount includes: 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.

2. 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 used as a target vibration signal segment.

3. The method for efficiently degrading and recycling waste polyurethane foam according to claim 2, characterized in that: The acquisition of the frequency threshold includes: Obtain reference vibration signals for each stirring cycle during several historical degradation processes of waste polyurethane foam; Obtaining a mapping value for 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 degradation processes of the waste polyurethane foam in the history; The frequency type corresponding to the maximum average mapping value is used as the frequency threshold.

4. The method for efficiently degrading and recycling waste polyurethane foam according to claim 1, characterized in that: 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.

5. The method for efficiently degrading and recycling waste polyurethane foam according to claim 1, characterized in that: Acquisition of the phase richness within 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.

6. A waste polyurethane foam efficient degradation and recovery device, the system is used to implement the method of claim 1, characterized in that: The device comprises a feeding mechanism, a degradation mechanism and a control system, 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 stirrer (7), wherein the polyurethane foam and the degradation agent undergo a chemical reaction in the reaction chamber (4); The motor (5) drives the shuttle-shaped stirrer (7) to stir and flip up and down. When the degradation liquid is squeezed, it flips up from the edge of the shuttle-shaped stirrer (7). When the shuttle-shaped stirrer (7) is lifted, the degradation liquid slides down from the edge of the shuttle-shaped stirrer (7), forming an exchange of upper and lower liquids. The control system is connected to all integrated sensors in the degradation device, and the integrated sensors collect all monitoring data during the degradation process in real time; the core feedback input of the control system is the actual degradation amount calculated by the integrated sensors; The total time taken for the shuttle stirrer (7) to be pressed down and lifted up once is recorded as one stirring cycle.

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