CN102297896A - Method and apparatus for detecting entrainment in multiphase flow equipment - Google Patents
Method and apparatus for detecting entrainment in multiphase flow equipment Download PDFInfo
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Abstract
The invention discloses a method and an apparatus for detecting entrainment in multiphase flow equipment. The method comprises steps that: (1) vibration signals or sound wave signals in the multiphase flow equipment are received; (2) a total energy of the vibration signals or the sound wave signals, and an energy of a characteristic frequency band or an energy resolution of the characteristic frequency band are selected as characteristic parameters; (3) the characteristic parameters are introduced into a pre-established forecasting model between the characteristic parameters and the entrainment, and the entrainment in the multiphase flow equipment is obtained by calculation. According to the invention, the signals are processed by using a non-linear method, such that the characteristic parameters of the signals can be obtained more accurately and effectively, and real-time entrainment can be obtained. The method provided by the invention has advantages of sensitive response, low detection error, and wide application range. The invention also discloses a detection apparatus, comprising a signal receiving device, a signal amplifying device, a signal collecting device, a signal processing device, an outputting and displaying device, and a controlling device. The apparatus is a non-plug-in type apparatus, and is convenient and easy to use. With the apparatus, motions and chemical reactions of fluids are not influenced, and emission source is not required.
Description
Technical field
The present invention relates to chemical industry dynamic monitoring and controlling method and device field, relate in particular to the dynamic testing method and the device of mist entrainment in a kind of polyphasic flow equipment.
Background technology
Many polyphasic flow equipment is arranged, as plate column, gas-liquid two-phase or gas-liquid-solid three-phase stirred tank, bubbling bed etc., when gas-liquid mixed, in the chemical process often with the entrainment phenomenon.Entrainment is meant that gas is bottom-up when the liquid layer, and liquid level enters the phenomenon of top device or pipeline because the droplet that turbulence produces is taken away by air-flow.For three-phase system, also have a spot of solid with droplet by gas entrainment.
Entrainment has adverse influence to chemical process.In the polymerizing reactor, a large amount of entrainments can be brought liquid into heat interchanger, and the interior fouling of heat interchanger is increased, and exchange capability of heat descends; In the distillation process, a large amount of entrainments can make the concentration gradient of volatile components reduce to some extent along tower height, thereby process driving force is reduced; A large amount of entrainments also can make nonvolatile impurity take in the overhead product, has influence on the purity of product.Therefore the detection of entrainment and elimination just seem extremely important in chemical process.
In general, the formation branch of entrainment does on the liquid level that mist generates and air-flow in drop carry two processes.At first, when gas passed through liquid layer bubbling mass transfer, liquid film was become countless drops by bubble breaking, and its size is relevant with uprising gas kinetic energy and surface energy of liquid, and gas kinetic energy is big more, and the surface energy of liquid is just more little, and the drop of generation is just thin more.Be subjected to the gas effect, a large amount of drops will be with different initial velocity impellings to the corresponding height of liquid layer superjacent air space.Secondly, drop moves in air-flow and is subjected to air-flow drag force, self gravitation and buoyancy, and wherein big drop is with certain settling velocity column plate that falls back, the part droplet then since the speed that air-flow makes progress greater than droplet settling speed, carried secretly to the upper strata column plate by updraft, formed entrainment.
The factor that influences the mist entrainment size is a lot, and in short, entrainment mainly is subjected to the influence of device structure, gas-liquid rerum natura, operating conditions three aspects.The structure of equipment mainly is the height of liquid level superjacent air space in the equipment, as the distance on material level in the polymer reactor and still top, the tray spacing in the plate column etc.In general, along with the increase of liquid level superjacent air space height, mist entrainment reduces to some extent.Have under the situation of demister existence, the structure of demister also has certain influence to mist entrainment.In the rectification column, structural factors such as the percentage of open area of column plate, open-cellular form are also influential to mist entrainment.The gas-liquid rerum natura is also influential to mist entrainment.The rerum natura of gas is little to the mist entrainment influence, but the rerum natura of liquid phase (viscosity, surface tension etc.) has bigger influence to mist entrainment.In general along with the viscosity and the capillary increase of liquid, mist entrainment decreases.For certain specific technology, device structure and gas-liquid rerum natura all are unmodifiable, and at this moment operating conditions seems even more important to the influence of mist entrainment.In the operating conditions, what mist entrainment was had the greatest impact is the size of gas speed.In general, mist entrainment increases along with the increase of gas speed, and under low gas velocity, the mist entrainment increase is very slow, and under high gas speed, entrainment enlarges markedly with the increase of gas speed.In addition, in the air agitation groove, speed of agitator has certain influence to entrainment; In the rectification column, flow stream velocity has certain influence to entrainment.
Some scholars have done certain research to the entrainment situation in the plate distillation column, find that mist entrainment is relevant with physical quantitys such as gas speed, liquid flowing strength, tray spacing, column plate forms, have obtained the compute associations formula of some mist entrainments.The formula that Hunt etc. is arranged relatively commonly used:
In the formula: e
v-mist entrainment, kg/kg gas; σ-liquid phase surface tension, mN/m; h
f-bubble level height, m; u
n-based on (A
s-A
d) gas speed, m/s; A
s-tower section is long-pending, m
2A
dThe area of-one downspout, m
2H
T-tray spacing, m.
The correlation that other scholars obtain is similar mostly with it, can be summarized as following form:
e
v＝AV
B
Be mist entrainment e
vGentle fast V exponent function relation, pre-exponential factor A is all relevant with rerum natura and device structure with index B, and is different along with the difference of technology.According to the correlation that some scholar's research obtain, B is substantially between 2～4.
About the research of entrainment, summary is got up, and mainly contains following deficiency:
1) research object mainly is a plate distillation column, and is for other equipment, less as researchs such as air agitation groove, bubble towers.
2) research emphasis mainly be reason that entrainment forms and major influence factors analysis with related, seldom to the research of entrainment detection method.
3) research system mainly is the gas-liquid mass transfer system, and is less to the phenomenon research that solid in the gas-liquid-solid three-phase system is together carried secretly.
4) mensuration to mist entrainment often adopts collecting method, and the big and inconvenient operation of error also can't be applied to commercial plant.The novel method that detects entrainment easily remains to be developed.
5) report about demister has a lot, mainly all is to carry out in the laboratory for the analysis of demister foam removal performance, the industrial because restriction of detection means, and the foam removal effect is difficult to obtain direct result.
The occasion that heterogeneous detection of many needs and metering are arranged on the chemical industry is as the detection by quantitative of gas extraction under oil-field development, the ocean water, gas-liquid mixture, the entrainment of polymerization reaction kettle circulation line etc.Traditional detection method is with separation vessel multiphase mixture to be separated, and detects respectively then.Separation vessel costliness, huge, whole device are comparatively complicated.In recent years, Chinese scholars has been invented some the new heterogeneous detections and the method for metering.Disclose a kind of method and apparatus among the Chinese patent ZL99808818.8, disclose a kind of device among the Chinese patent CN2646670Y by the ultrasound examination multiphase flow rates by X ray detection multiphase mixture flow.These methods all exist needs signal emitting-source, complicated, the not high shortcoming of measuring accuracy of device, has limited it in industrial application.
Acoustic emission testing technology is by receiving and analyze the acoustic emission signal of sending in the production run, and is associated with operating parameter in the process, thereby realizes detection and monitoring to production run.This technology has the advantages that to detect sensitivity, Environmental Safety, do not invade flow field and real-time online.Thereby the real-time online that acoustic emission is well suited for being used for the certain operations parameter of commercial plant detects.For example, sun honor forever etc. discloses the detection that acoustic emission is used for the fluidized-bed reactor operating parameter in Chinese patent ZL200610049599.3, can determine the judgement of luming in controlling level, minimum fluidizing velocity, initial turbulence fluidizing velocity and the fluidized bed in the fluidized bed; Wang Jingdai etc. disclose the detection that acoustic emission is used for the operating parameter of stirred tank reactor in Chinese patent application CN200710156124.9, CN200910095892.7, CN200910097678.5 and CN200910097679.X, can determine the interior spotting out rotating speed of stirred tank, liquid level, content of dispersed phase etc.
Traditional acoustical signal disposal route generally all is based on Fast Fourier Transform (FFT) (FFT).FFT is to be linear, processing signals on the basis stably at the signal that hypothesis receives.And in fact, the signal that obtains generally all right and wrong stably, the system that is showed is non-linear, under these conditions, traditional spectrum analysis can only obtain limited application.Yet owing to lack better method, spectrum analysis often also is used to handle this type of signal, and the stationarity of this unconfined use and putative signal and system linearityization just can be brought the result of some misleadings.
Spectrum analysis can be from frequency and times two aspect observation analysis signal, but retention time and frequency information simultaneously.And for non-linear, non-stationary signal, time frequency analysis has very big meaning.Just because of the needs to time frequency analysis, people's proposition has also developed a series of new signal analysis theories: Fourier conversion in short-term, Wigner-Ville distribution, wavelet transformation or the like.
In these theories, being most widely used of wavelet transformation theory.But wavelet analysis is based on that Fourier analyzes, and therefore has the shortcoming that Fourier analyzes, and can only provide the physical interpretation of linear case.Another problem of wavelet analysis is that it does not have adaptivity, in case basic small echo is chosen, must analyze all data to be analyzed with it.
1998, people such as N.E.Huang proposed a kind of new signal processing method: Hilbert-Huang conversion (HHT).This method is a signal to be carried out tranquilization handle in essence, decomposes (EMD) method with empirical modal, and the different scale fluctuation or the trend of necessary being in the signal are decomposed out step by step, produces a series of data sequences with different characteristic yardstick.Huang claims that this process of decomposing step by step is " screening " process.Each sequence is called an intrinsic mode function (IMF).The IMF component that obtains has good Hilbert conversion characteristics, calculates the frequency content that instantaneous frequency characterizes original signal after the Hilbert conversion, and having avoided needs to use many harmonic components to express deficiency non-linear, non-stationary signal in the Fourier transform.
Use as Hilbert-Huang conversion Modern Nonlinear treatment technologies such as (HHT), can extract the characteristic parameter of signal better, make its can be more accurate, more effectively join with the chemical process parameter correlation.
In the Chemical Manufacture, when entrainment takes place, on pipeline or appts wall, will produce the acoustical signal of mist drop bump.Mist entrainment is big more, and corresponding variation can take place the characteristic parameter of acoustical signal.By analysis to acoustical signal, divide rate etc. as the energy of analyzing acoustical signal, the energy of characteristic spectra, can obtain itself and the relation of mist entrainment, thereby realize the real-time online detection of acoustic emission entrainment.
Summary of the invention
The invention provides the detection method of mist entrainment in a kind of accuracy height, safety and environmental protection, the simple and easy equipment of polyphasic flow efficiently, by extracting the characteristic parameter in vibration signal or the acoustic signals, and, realize the online dynamic monitoring of mist entrainment in the polyphasic flow equipment in conjunction with the model of characteristic parameter and mist entrainment.
The present invention also provides the pick-up unit of mist entrainment in a kind of polyphasic flow equipment, the simple and easy operating of this apparatus structure.
The detection method of mist entrainment in a kind of polyphasic flow equipment may further comprise the steps:
1) vibration signal or the acoustic signals in the reception polyphasic flow equipment;
2) choose the energy branch rate of the energy of gross energy, characteristic spectra of described vibration signal or acoustic signals or characteristic spectra as characteristic parameter;
3) characteristic parameter that described characteristic parameter substitution is set up in advance and the forecast model between mist entrainment calculate the mist entrainment in the polyphasic flow equipment;
The energy of described characteristic spectra is after adopting in fast fourier transform spectrum analysis (FFT), wavelet analysis, wavelet packet analysis or Hilbert-Huang (Hilbert-Huang) conversion one or more that described vibration signal or acoustic signals are carried out multiscale analysis, integration after the squared magnitude to be obtained;
The energy branch rate of described characteristic spectra refers to that the energy of characteristic spectra accounts for the number percent of the gross energy of vibration signal or acoustic signals.
Described characteristic spectra is preferably 7kHz～16kHz.
The method for building up of the forecast model between described characteristic parameter and mist entrainment is: vibration signal or acoustic signals when collecting different known mist entrainment in the polyphasic flow equipment; Vibration signal or the acoustic signals of collecting carried out multiscale analysis, the calculated characteristics parameter; With the mist entrainment is independent variable, is dependent variable with the characteristic parameter, adopts curve fitting, partial least square method or neuroid method to set up forecast model.The relational expression of mist entrainment and characteristic parameter is:
Ent＝f(E)
Wherein, Ent represents mist entrainment (kg liquid/kg gas), E representation feature parameter;
Further gram is expressed as:
Ent＝A·exp(E/t)+y
Wherein, Ent represents mist entrainment (kg liquid/kg gas), E representation feature parameter, and A, t, y are coefficient.
Described polyphasic flow equipment is gas-liquid two-phase mass transfer apparatus or gas-liquid-solid phase reaction equipment, as gas-liquid two-phase stirred tank, gas-liquid-solid three-phase stirred tank, gas-liquid two-phase plate column, gas-liquid-solid three-phase plate column, gas-liquid two-phase bubble tower, gas-liquid-solid three-phase bubble tower, gas-liquid two-phase spray column or gas-liquid-solid three-phase spray column etc.
Described employing wavelet analysis comprises the step that described vibration signal or acoustic signals carry out multiscale analysis: select for use orthogonal wavelet as wavelet mother function vibration signal or acoustic signals to be carried out wavelet decomposition; Characterize the energy of vibration signal or acoustic signals with coefficient of wavelet decomposition.
The step that described employing described vibration signal of Hilbert-Huang transfer pair or acoustic signals carry out multiscale analysis comprises: vibration signal or acoustic signals are done empirical modal decomposition (EMD), try to achieve each rank intrinsic mode function (IMF); Use Hilbert and change, obtain the three-dimensional spectrum of energy-frequency-time distribution of vibration signal or acoustic signals, i.e. the Hilbert-Huang spectrum.
The receive frequency of described vibration signal or acoustic signals is generally 0Hz～100MHz, preferred 0Hz～1MHz.
The pick-up unit of mist entrainment in the described polyphasic flow equipment, comprise the signal receiving device that is used for receiving polyphasic flow equipment vibration signal or acoustic signals, signal amplifying apparatus, signal pickup assembly, signal processing apparatus, output display device and control device, signal receiving device is converted into electric signal with vibration signal in the polyphasic flow equipment or acoustic signals, amplify through signal amplifying apparatus, harvester A/D conversion back input signal treating apparatus, result is presented on the output display device, and control device is controlled polyphasic flow equipment according to result.General control device is according to testing result and needs, can control parameters such as pressure in the gas flow that enters polyphasic flow equipment, fluid flow, the polyphasic flow equipment, temperature, realizes the control to mist entrainment in the polyphasic flow equipment.
Described signal receiving device is arranged on the above optional position that entrainment takes place of polyphasic flow equipment liquid level, as placing on polyphasic flow device interior or the polyphasic flow equipment wall surface or the polyphasic flow device external; Preferably be arranged on gas outlet.
Described signal receiving device is selected this area commonly used vibration signal or acoustic signals receiving trap for use, can be selected from one or more the combination in nautical receiving set, microphone, acceleration transducer, the calibrate AE sensor.
Described signal receiving device and signal amplifying apparatus all can be set to one or more.
Described signal processing apparatus is selected the processor of band signal process software for use.
The present invention compared with prior art has following advantage:
(1) vibration signal or acoustic signals adopt nonlinear method such as HHT to handle, can be more accurate, the characteristic parameter of picked up signal more effectively, and obtain real-time mist entrainment.
(2) be quick on the draw, measuring error is little, and is widely applicable.
(3) the signal receiving device right and wrong are plug-type, use simple and convenient, do not influence the motion or the chemical reaction of fluid.
(4) do not need emissive source.Vibration signal or acoustic signals are that fluid self produces safety and environmental protection in motion process.
(5) low to the measuring condition requirement, can be comparing all weather operations under the rugged environment, even still can operate as normal under severe rugged environments such as High Temperature High Pressure.
(6) have control system, can in time regulate as required entrainment situation in the polyphasic flow equipment.
Description of drawings
Fig. 1 is the structural representation of the pick-up unit of mist entrainment in the polyphasic flow equipment of the present invention.
Fig. 2 is the position view of polymeric kettle still top signal receiving device among embodiment 1 and the embodiment 2.
Fig. 3 is acoustic signals 15 rank intrinsic mode function exploded views after EMD handles among the embodiment 1, and horizontal ordinate is time (unit is s), and ordinate is amplitude (unit is V).
Fig. 4 is the response-time diagram of original acoustic signals among the embodiment 1.
Fig. 5 be among the embodiment 1 original acoustic signals after EMD handles by the response-time diagram of IMF1～acoustic signals that IMF8 reconstruct obtains.
Fig. 6 is (the mist entrainment curve comparison diagram over time in energy of IMF4～IMF5) and the circulating air of the reconstruction signal characteristic spectra of load in the uphill process among the embodiment 1, among the figure, curve 1-acoustic feature signal band energy is curve over time, and curve 2-mist entrainment is curve over time.
Fig. 7 is (the mist entrainment curve comparison diagram over time in energy branch rate of IMF4～IMF5) and the circulating air of the reconstruction signal characteristic spectra of load in the uphill process among the embodiment 1, among the figure, curve 1-acoustic feature signal band energy divides rate curve over time, and curve 2-mist entrainment is curve over time.
Fig. 8 is a mist entrainment curve comparison diagram over time in the acoustic signals gross energy in the load decline process and the circulating air among the embodiment 2, among the figure, curve 1-acoustic signals gross energy is curve over time, and curve 2-mist entrainment is curve over time.
Fig. 9 be among the embodiment 2 acoustic signals at the spectrogram of 16:04 after the FFT conversion.
Figure 10 be among the embodiment 2 acoustic signals at the spectrogram of 16:09 after the FFT conversion.
Figure 11 be among the embodiment 2 acoustic signals at the spectrogram of 16:11 after the FFT conversion.
Figure 12 be among the embodiment 2 acoustic signals at the spectrogram of 16:18 after the FFT conversion.
Figure 13 is the acoustic signals d in the load decline process among the embodiment 2
6Band energy divides in rate and the circulating air mist entrainment curve comparison diagram over time, among the figure, and curve 1-acoustic signals d
6Band energy divides rate curve over time, and curve 2-mist entrainment is curve over time.
Figure 14 is the structural representation of the pick-up unit of mist entrainment in the stirred tank cold model rig among the embodiment 3.
Figure 15 is the structural representation of the pick-up unit of a plurality of position signalling receiving traps in the plate distillation column among the embodiment 4.
Among the figure, 1 is polyphasic flow equipment, and 2 is signal receiving device, and 3 is signal amplifying apparatus, 4 is signal pickup assembly, and 5 is signal processing apparatus, and 6 is output display device, 7 is control device, and 8 is the circulating air pipeline, and 9 is draft tube, 10 is manhole, and 11 is stirred tank, and 12 is stirring motor, 13 is the entrainment gathering-device, and 14 is spinner-type flowmeter, and 15 is paddle, 16 is condenser, and 17 is rectification column, and 18 is reboiler.
Embodiment
Respectively to producing 120000 tons of slurry process vinyl polymerization stills per year, producing the pick-up unit that 70,000 tons of slurry process vinyl polymerization still, laboratory gas-liquid two-phase or gas-liquid-solid three-phase stirred tank, four kinds of equipment of plate distillation column are used described entrainment per year.The signal (vibration signal or acoustic signals) that monitoring obtains adopts Hilbert-Huang conversion (HHT), fast fourier transform spectrum analysis (FFT), wavelet analysis to handle respectively, obtain the characteristic parameter of needs, thereby set up the detection model of mist entrainment.
The main processing procedure of HHT is as follows:
1. the empirical modal of signal decomposes
The EMD decomposition extracts each rank IMF from original signal, the IMF that is decomposited has given prominence to the local feature information of original signal.
IMF has following characteristics:
(1) on whole data length, the number of extreme point and zero crossing must equate or differ one at the most.
(2) in any data point, the average of the envelope of local maximum and the envelope of local minimum is necessary for 0 at any point place.
The concrete disposal route of extracting the IMF component of signal X (t) is: find out all maximum points of X (t) and it is become the coenvelope line of former data sequence with Cubic Spline Functions Fitting, find out all minimum points and it is become the lower envelope line of former data sequence with Cubic Spline Functions Fitting, the average of envelope is the average packet winding thread m of former data sequence up and down
1(t), after being deducted this average envelope, former data sequence X (t) can obtain a new data sequence h who removes low frequency
1(t):
X(t)-m
1(t)＝h
1(t)
H in general
1(t) still not the IMF component, need repeat above-mentioned processing procedure it.Repeat above-mentioned processing procedure k time, up to resulting average packet winding thread m
1k(t) go to zero till, so just obtained the 1st IMF component C
1(t):
h
1(k-1)(t)-m
1k(t)＝h
1k(t)
C
1(t)＝h
1k(t)
The 1st IMF component represented the component of high frequency in the original data sequence.Original data sequence X (t) is deducted the 1st IMF component C
1(t), can obtain a difference data sequence r who removes high-frequency components
1(t).To r
1(t) carry out above-mentioned EMD decomposable process, can obtain the 2nd IMF component C
2(t), so repeat down difference data sequence r to the last
n(t) can not be decomposed again till, this moment r
n(t) represent the residual term of original data sequence.
r
n-1(t)-C
n(t)＝r
n(t)
N.E.Huang likens such processing procedure to " screening " process visually.At last, original data sequence can be represented by these IMF components and a residual term:
2.Hilbert conversion
Can obtain its Hilbert conversion Y (t) to a time series X (t):
Wherein P is a Cauchy's principal value, generally gets P=1 during use.According to this definition, X (t) and Y (t) can form an analytic signal Z (t):
Z(t)＝X(t)+iY(t)＝a(t)e
iθ(t)
Wherein
Use the Hilbert conversion that instantaneous frequency is defined as following formula:
The instantaneous frequency that defines in the following formula is the single-valued function of time t, at any time, has only unique instantaneous frequency.Therefore in order to make instantaneous frequency meaningful, the time series of doing conversion must be a single component, and the intrinsic mode function sequence after the empirical modal decomposition can meet this requirement just.
Each IMF is used the Hilbert conversion, tries to achieve instantaneous frequency and the amplitude of each IMF, thereby can be signal indication:
ω wherein
j(t) be the instantaneous frequency of each IMF, a
j(t) be the instantaneous amplitude of each IMF.
Then just again the time-instantaneous frequency of each IMF of drawing on the frequency face with its amplitude weighting.This T/F-amplitude distributed in three dimensions just is called the Hilbert-Huang spectrum.
As shown in Figure 1, the pick-up unit of mist entrainment in the polyphasic flow equipment, comprise polyphasic flow equipment 1, signal receiving device 2, signal amplifying apparatus 3, signal pickup assembly 4, signal processing apparatus 5, output display device 6 and control device 7, signal receiving device 2 is converted into electric signal with vibration signal in the polyphasic flow equipment 1 or acoustic signals, input signal treating apparatus 5 after signal amplifying apparatus 3 amplifications, harvester 4A/D conversion, result is presented on the output display device 6, and control device 7 is controlled polyphasic flow equipment 1 according to result.Signal receiving device 2 is arranged on the above optional position that entrainment takes place of polyphasic flow equipment 1 liquid level.
In certain produces 120000 tons slurry process polyethylene production workshop per year, carry out commerical test, detect the entrainment situation in the load uphill process of polymeric kettle with acoustic emission.Vibration signal or acoustic signals when collecting different known mist entrainment in the polymeric kettle; Vibration signal or the acoustic signals of collecting adopted HHT processing carrying out multiscale analysis, calculated characteristics parameter; With the mist entrainment is independent variable, is dependent variable with the characteristic parameter, and adopting curve-fitting method to set up forecast model is regression model, is used for monitoring in real time entrainment situation in the polymeric kettle.
Polymeric kettle is interior to be solvent with the hexane, feeds ethene and carries out slurry polymerization production high density polyethylene (HDPE).The hexane of still top evaporation and unreacted ethene, hydrogen, comonomer (as propylene, 1-butylene etc.) constitute circulating air, can carry a part of mist (mainly being hexane, a spot of polymer beads) secretly and enter still top heat interchanger by the circulating air pipeline.
Afternoon 14:48, the load of polymeric kettle begins to rise, and rises to 10t/h by 9t/h (ton/hour), the circulating air flow also rises thereupon, thereby mist entrainment raises to some extent.
The acoustic emission signal receiving trap: calibrate AE sensor places the circulating air exit (as shown in Figure 2) on polymeric kettle still top, detects acoustic signals in the pipeline in real time.In the test, gathered an acoustic signals every 15 seconds, sample frequency is 500kHz, and acquisition time is 1 second.Mist entrainment is directly collected metering by circulating air after gas separates.
The acoustic signals of resulting 16:30～17:00 time period is carried out the HHT processing.The acoustical signal that collects during with 14:50 is an example, carries out EMD and decomposes, and obtains 15 rank intrinsic mode functions (IMF) as shown in Figure 3.As can be known, what IMF1～IMF8 described is needed acoustic feature signal from accompanying drawing 3, is effective IMF component.With IMF1～IMF8 reconstruct (directly add and obtain reconstruction signal), obtain acoustic signals such as Fig. 5 after the reconstruct, itself and original acoustic signals such as Fig. 4 compare, and the acoustic signals after reconstruct has been removed some undesired signals, can reflect the feature of measurand more accurately and effectively.To load in the uphill process, (acoustic signals of 14:30～15:00) is all done processing like this.
Be convenient to analyze the Changing Pattern of acoustical signal energy, signal after the reconstruct is divided into three frequency ranges: high band (IMF1～IMF3), Mid Frequency (IMF4～IMF5), low-frequency range (IMF6～IMF8), the frequency of mist bump is mainly at Mid Frequency, with Mid Frequency as characteristic spectra.Calculate the energy of acoustic feature signal frequency range, as characteristic parameter, the energy that obtains the acoustic feature signal frequency range is curve over time, shown in curve 1 in the accompanying drawing 6 with it.As can be seen, roughly the energy of Mid Frequency progressively rises between 16:48 to 16:53 from accompanying drawing 6, its variation tendency and load during elevation process in the circulating air variation (curve 2 in the accompanying drawing 6) of mist entrainment more consistent.Thereby obtain the energy of acoustic feature signal frequency range and the regression model between mist entrainment, the energy of the acoustic feature signal frequency range that the energy substitution of the acoustic feature signal frequency range that receives is in real time set up in advance and the regression model between mist entrainment, can calculate the mist entrainment in the polyphasic flow equipment, realize dynamic monitoring.Therefore, the energy of acoustic feature signal frequency range has the better prediction effect to mist entrainment, can be used for realizing that the real-time online of entrainment in the polymeric kettle detects.
The energy that calculates the acoustic feature signal frequency range accounts for the number percent of acoustic signals gross energy, it is the energy branch rate of acoustic feature signal frequency range, as characteristic parameter, the energy branch rate that obtains the acoustic feature signal frequency range is curve over time, shown in curve 1 in the accompanying drawing 7 with it.As can be seen, roughly the energy branch rate of characteristic spectra progressively rises between 16:48 to 16:53 from accompanying drawing 7, its variation tendency and load during elevation process in the circulating air variation (curve 2 in the accompanying drawing 7) of mist entrainment more consistent.Thereby obtain the energy branch rate of acoustic feature signal frequency range and the regression model between mist entrainment, the energy branch rate of the acoustic feature signal frequency range that the energy branch rate substitution of the acoustic feature signal frequency range that receives is in real time set up in advance and the regression model between mist entrainment, can calculate the mist entrainment in the polyphasic flow equipment, realize dynamic monitoring.Therefore, the energy branch rate of acoustic feature signal frequency range has the better prediction effect to mist entrainment, can be used for also realizing that the real-time online of entrainment in the polymeric kettle detects.
In certain produces 70000 tons slurry process polyethylene production workshop per year, carry out commerical test, detect the entrainment situation in the load decline process of polymeric kettle with acoustic emission.Vibration signal or acoustic signals when collecting different known mist entrainment in the polymeric kettle; Adopt the FFT processing to carry out multiscale analysis, the calculated characteristics parameter to vibration signal or the acoustic signals of collecting with wavelet decomposition; With the mist entrainment is independent variable, is dependent variable with the characteristic parameter, and adopting partial least square method to set up forecast model is regression model, is used for monitoring in real time entrainment situation in the polymeric kettle.
Polymeric kettle is interior to be solvent with the hexane, feeds ethene and carries out slurry polymerization production high density polyethylene (HDPE).The hexane of still top evaporation and unreacted ethene, hydrogen, comonomer (as propylene, 1-butylene etc.) constitute circulating air, can carry a part of mist (mainly being hexane, a spot of polymer beads) secretly and enter still top heat interchanger by the circulating air pipeline.
Afternoon 16:07, the load of polymeric kettle begins to descend, and reduces to 6.5t/h by 7.5t/h, the circulating air flow also descends thereupon, thereby mist entrainment decreases.
The acoustic emission signal receiving trap place polymeric kettle still top the circulating air exit (similar with embodiment 1, as shown in Figure 2), detect acoustic signals in the pipeline in real time.In the test, gathered an infrasound signals every 15 seconds, sample frequency is 500kHz, and acquisition time is 1 second.Mist entrainment is directly collected metering by circulating air after gas separates.
The acoustic signals of resulting 16:00～16:30 time period is carried out the FFT processing, integral and calculating after the squared magnitude is obtained the gross energy of acoustic signals.The gross energy of acoustic signals as characteristic parameter, is obtained its curve over time, shown in curve 1 in the accompanying drawing 8.As can be seen, approximately the gross energy of 16:07～16:13 acoustic signals begins synchronous decline from accompanying drawing 8, decline variation tendency (curve 2 in the accompanying drawing 8) basically identical of mist entrainment in circulating air when it descends with load.Thereby obtain the gross energy of acoustic signals and the regression model between mist entrainment, the gross energy of the acoustic signals that the gross energy substitution of the acoustic signals that receives is in real time set up in advance and the regression model between mist entrainment, can calculate the mist entrainment in the polyphasic flow equipment, realize dynamic monitoring.Therefore, the gross energy of acoustic signals has the better prediction effect to mist entrainment, can be used for realizing that the real-time online of entrainment in the polymeric kettle detects.
Further acoustic signals is carried out spectrum analysis.To 16:04,16:09,16:11, the acoustic signals of four times of 16:18 carries out the FFT spectrum analysis, obtains 4 acoustic signals spectrograms shown in accompanying drawing 9-12 respectively.Contrasting four spectrograms can clearly find, the energy of 7kHz-14kHz frequency range is along with the corresponding minimizing of the variation of mist entrainment, illustrate that this frequency range is comparatively sensitive to the change reflection of circulating air flow and mist entrainment, therefore, it can be measured the characteristic spectra of mist entrainment as acoustic signals.
Acoustic signals is carried out the wavelet decomposition of 8 yardsticks, and the frequency range of each frequency range is as shown in table 1.As shown in Table 1, the d of gained
6(7812.5Hz-15625Hz) frequency range is the characteristic spectra of above-mentioned discussion substantially.Therefore, in the calculated load decline process (16:00-16:30), each acoustic signals d
6The energy of frequency range divides rate, obtains its curve over time, shown in curve 1 in the accompanying drawing 13.From accompanying drawing 13 as can be seen, d between 16:07 to 16:13 roughly
6The energy branch rate of frequency range progressively descends, and it is more consistent that the decline of circulating air mist entrainment changes (curve 2 in the accompanying drawing 13) in its variation tendency and the load alternation process.Than the gross energy (accompanying drawing 8) of acoustic signals, d
6The energy branch rate of frequency range can reflect the variation of mist entrainment more reposefully.Thereby obtain acoustic signals d
6Band energy divides the regression model between rate and mist entrainment, with the acoustic signals d that receives in real time
6The acoustic signals d that the substitution of band energy branch rate is set up in advance
6Band energy divides the regression model between rate and mist entrainment, can calculate the mist entrainment in the polyphasic flow equipment, realizes dynamic monitoring.Therefore, acoustic signals d
6Band energy branch rate has the better prediction effect to mist entrainment, can use acoustic signals d
6Online mist entrainment is detected during the energy branch rate of frequency range.
The frequency range of each wave band of table 1 wavelet decomposition
| Frequency range | f/Hz |
| d 1 | 250000-500000 |
| d 2 | 125000-250000 |
| d 3 | 62500-125000 |
| d 4 | 31250-62500 |
| d 5 | 15625-31250 |
| d 6 | 7812.5-15625 |
| d 7 | 3906.25-7812.5 |
| d 8 | 1953.125-3906.25 |
Set up cold model unit in the laboratory, utilize detection and the control of acoustic emission realization stirred tank top mist entrainment.
The detection of entrainment and control system are that gas-liquid two-phase or gas-liquid-solid three-phase stir system in the stirred tank 11 as shown in Figure 14 in the stirred tank, and gas feeds in the still by draft tube, during from the outflow of still top, can carry a spot of liquid or liquid-solid mixture secretly.Entrainment gathering-device 13 is established on the still top, collects the metering mist entrainment, is used to set up the acoustic emission forecast model of mist entrainment.Acoustical signal receiving trap 2 places still top gas outlet, the acoustical signal that receives is handled through signal amplifying apparatus 3 amplifications, signal pickup assembly 4 collections, signal processing apparatus 5, go up at output display device 6 (as computing machine) then and show, information feedback on the output display device 6 is given control device, control device is by liquid level in the operation circuit 1 control still, by the operation circuit 2 control charge flow rates of band spinner-type flowmeter 14, by the operation circuit 3 control stirring rates that are connected with paddle 15 in stirring motor 12 and the still.
Signal Processing was divided into for two steps, the one, utilize HHT, concrete operations are with embodiment 1, obtain the characteristic parameter of reflection mist entrainment in the acoustic signals: the energy branch rate of the energy of acoustic feature signal frequency range, acoustic feature signal frequency range, the 2nd, respectively according to the energy of setting up good acoustic feature signal frequency range and the forecast model between mist entrainment, the energy of acoustic feature signal frequency range divides the forecast model between rate and mist entrainment, calculates real-time mist entrainment.
Perhaps, the one, utilize FFT and wavelet decomposition, concrete operations obtain the characteristic parameter of reflection mist entrainment in the acoustic signals: the gross energy of acoustic signals, acoustic signals d with embodiment 2
6The energy of frequency range divides rate, and the 2nd, respectively according to the gross energy of setting up good acoustic signals and the forecast model between mist entrainment, acoustic signals d
6The energy of frequency range divides the forecast model between rate and mist entrainment, calculates real-time mist entrainment.
This device is provided with three operation circuits, can regulate mist entrainment, is respectively liquid level control (operation circuit 1) in the still, charge flow rate control (operation circuit 2) and speed of agitator control (operation circuit 3).When mist entrainment exceeds standard, can be by reducing liquid level in the still, regulating three kinds of modes of speed of agitator that the spinner-type flowmeter 14 on the operation circuit 2 reduces charge flow rate or regulates the stirring motor 12 of control paddle 15, it is below the mark that mist entrainment is reduced to.
Therefore, can carry out the detection and the control of mist entrainment accurately, in real time, online based on acoustic emission.
Supervisory system is set up with the entrainment in plate distillation column 17 equipment of band condenser 16 and reboiler 18 in the laboratory, and its system's pie graph as shown in Figure 15.A plurality of signal receiving devices 2 are set as three parts respectively are provided with 1 signal receiving device 2 in the rectification column upper, middle and lower at rectification column 17 differing heights, receive vibration signal or acoustic signals on rectification column 17 walls.The acoustical signal that receives is handled through signal amplifying apparatus 3 amplifications, signal pickup assembly 4 collections, signal processing apparatus 5, goes up at output display device 6 (as computing machine) then to show.
Signal Processing was divided into for two steps, the one, utilize HHT, concrete operations are with embodiment 1, obtain the characteristic parameter of reflection mist entrainment in the acoustic signals: the energy branch rate of the energy of acoustic feature signal frequency range, acoustic feature signal frequency range, the 2nd, respectively according to the energy of setting up good acoustic feature signal frequency range and the forecast model between mist entrainment, the energy of acoustic feature signal frequency range divides the forecast model between rate and mist entrainment, calculates each highly real-time mist entrainment of rectification column.
Perhaps, the one, utilize FFT and wavelet decomposition, concrete operations obtain the characteristic parameter of reflection mist entrainment in the acoustic signals: the gross energy of acoustic signals, acoustic signals d with embodiment 2
6The energy of frequency range divides rate, and the 2nd, respectively according to the gross energy of setting up good acoustic signals and the forecast model between mist entrainment, acoustic signals d
6The energy of frequency range divides the forecast model between rate and mist entrainment, calculates each highly real-time mist entrainment of rectification column.The result is exported in the computing machine, to realize the real time on-line monitoring of entrainment.
Therefore, based on vibration signal or acoustic signals detection technique, can carry out the real-time online detection of entrainment situation simultaneously to a plurality of positions of equipment.
Claims (10)
1. the detection method of mist entrainment in the polyphasic flow equipment is characterized in that, may further comprise the steps:
1) vibration signal or the acoustic signals in the reception polyphasic flow equipment;
2) choose the energy branch rate of the energy of gross energy, characteristic spectra of described vibration signal or acoustic signals or characteristic spectra as characteristic parameter;
3) characteristic parameter that described characteristic parameter substitution is set up in advance and the forecast model between mist entrainment calculate the mist entrainment in the polyphasic flow equipment;
The energy of described characteristic spectra is after adopting in fast fourier transform spectrum analysis, wavelet analysis, wavelet packet analysis or the Hilbert-Huang transform one or more that described vibration signal or acoustic signals are carried out multiscale analysis, integration after the squared magnitude to be obtained;
The energy branch rate of described characteristic spectra refers to that the energy of characteristic spectra accounts for the number percent of the gross energy of vibration signal or acoustic signals.
2. the detection method of mist entrainment is characterized in that in the polyphasic flow equipment according to claim 1, and described characteristic spectra is 7kHz～16kHz.
3. the detection method of mist entrainment in the polyphasic flow equipment according to claim 1, it is characterized in that the method for building up of the forecast model between described characteristic parameter and mist entrainment is: vibration signal or acoustic signals when collecting different known mist entrainment in the polyphasic flow equipment; Vibration signal or the acoustic signals of collecting carried out multiscale analysis, the calculated characteristics parameter; With the mist entrainment is independent variable, is dependent variable with the characteristic parameter, adopts curve fitting, partial least square method or neuroid method to set up forecast model.
4. the detection method of mist entrainment is characterized in that in the polyphasic flow equipment according to claim 1, and described polyphasic flow equipment is gas-liquid two-phase mass transfer apparatus or gas-liquid-solid phase reaction equipment.
5. the detection method of mist entrainment in the polyphasic flow equipment according to claim 4, it is characterized in that described polyphasic flow equipment is gas-liquid two-phase stirred tank, gas-liquid-solid three-phase stirred tank, gas-liquid two-phase plate column, gas-liquid-solid three-phase plate column, gas-liquid two-phase bubble tower, gas-liquid-solid three-phase bubble tower, gas-liquid two-phase spray column or gas-liquid-solid three-phase spray column.
6. the detection method of mist entrainment in the polyphasic flow equipment according to claim 1, it is characterized in that described employing wavelet analysis comprises the step that described vibration signal or acoustic signals carry out multiscale analysis: select for use orthogonal wavelet as wavelet mother function vibration signal or acoustic signals to be carried out wavelet decomposition; Characterize the energy of vibration signal or acoustic signals with coefficient of wavelet decomposition.
7. the detection method of mist entrainment in the polyphasic flow equipment according to claim 1, it is characterized in that, described employing Hilbert-Huang transform comprises the step that described vibration signal or acoustic signals carry out multiscale analysis: vibration signal or acoustic signals are made empirical modal decompose, try to achieve each rank intrinsic mode function; The application Hilbert changes, and obtains the three-dimensional spectrum of energy-frequency-time distribution of vibration signal or acoustic signals, i.e. Hilbert-Huang spectrum.
8. the detection method of mist entrainment is characterized in that in the polyphasic flow equipment according to claim 1, and the receive frequency of described vibration signal or acoustic signals is 0Hz～100MHz.
9. according to the pick-up unit of mist entrainment in each described polyphasic flow equipment of claim 1～8, it is characterized in that, comprise the signal receiving device (2) that is used for receiving polyphasic flow equipment (1) vibration signal or acoustic signals, signal amplifying apparatus (3), signal pickup assembly (4), signal processing apparatus (5), output display device (6) and control device (7), signal receiving device (2) is converted into electric signal with vibration signal or the acoustic signals in the polyphasic flow equipment (1), amplify through signal amplifying apparatus (3), harvester (4) A/D conversion back input signal treating apparatus (5), result is presented on the output display device (6), and control device (7) is controlled polyphasic flow equipment (1) according to result.
10. the pick-up unit of mist entrainment is characterized in that in the polyphasic flow equipment according to claim 9, and described signal receiving device (2) is arranged on the above optional position that entrainment takes place of polyphasic flow equipment (1) liquid level.
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