An online centralized monitoring and analysis system based on an electronic nose instrument for multi-point malodorous gases, comprising an odor electronic nose instrument (I), a plurality of gas sampling heads (II), an external vacuum pump (III), an ambient air purification device (IV), a clean air cylinder (V), gas pipelines, an electronic hygrometer (VI), a central control room (VII) and a plurality of stationary/mobile terminals (VIII), for long-term cyclical monitoring of 10 malodorous pollution sites, and online estimation and prediction of multiple concentration control index values of malodorous gases;
- wherein the odor electronic nose instrument (I) comprises a gas sensor array (I-1) and a thermostatic working room (I(a)) of the gas sensor array, a multi-point centralized auto-sampling system (I(b)), and a computer control and data analyzing system (1(c));
- the thermostatic working room (I(a)) of the gas sensor array is comprised of the gas sensor array and an annular working chamber of the gas sensor array, a thermal insulation layer (I-2), a resistance heating wire (I-3) and a fan (I-4);
- the gas sensor array (I-1) is comprised of 16 gas sensors, which are uniformly distributed in a sealed chamber having a middle diameter of 140 mm and a section size of 21 mm×17 mm and forms the annular working chamber of the gas sensor array;
- the thermostatic working room (I(a)) is with a constant temperature of 55±0.1° C. and located at a top right of the odor electronic nose instrument (I);
- wherein the multi-point centralized auto-sampling system (I(b)) comprises an internal miniature vacuum pump (I-14), a first two-position two-port electromagnetic valve (I-5), a second two-position two-port electromagnetic valve (I-6-1), a third two-position two-port electromagnetic valve (I-6-2), a fourth two-position two-port electromagnetic valve (I-6-3), a fifth two-position two-port electromagnetic valve (I-6-4), a sixth two-position two-port electromagnetic valve (I-6-5), a seventh two-position two-port electromagnetic valve (I-6-6), an eighth two-position two-port electromagnetic valve (I-6-7), a ninth two-position two-port electromagnetic valve (I-6-8), a tenth two-position two-port electromagnetic valve (I-6-9), an eleventh two-position two-port electromagnetic valve (I-6-10), a twelfth two-position two-port electromagnetic valve (I-8), a thirteenth two-position two-port electromagnetic valve (I-10), and a fourteenth two-position two-port electromagnetic valve (I-13), a throttle valve (I-11), a flowmeter (I-12), a vacuum pressure gauge (I-7), a gas buffer cavity (I-9), the multi-point centralized auto-sampling system (I(b)) is located at a lower right of the odor electronic nose instrument (I);
- wherein the computer control and data analyzing system (I(c)) comprises a computer mainboard (I-15), a data acquisition card (I-16), a monitor (I-17), a drive and control circuit module (I-18), a precision linear and switching power module (I-19), a hard disk, a network card, a video card, the computer control and data analyzing system (I(c)) is located on a left side of the odor electronic nose instrument (I);
- wherein the multi-point centralized auto-sampling system (I(b)) has a gas sampling period of T0=180-300 s for a malodorous gas of a single monitoring point, with a default value T0=240 s, so the gas sensor array (I-1) generates a 16-dimensional response vector for the single monitoring point;
- according to the 16-dimensional response vector, using, by the computer control and data analyzing system (I(c)) is configured to use a cascade machine learning model to perform real-time analysis and prediction of an olfactory concentration value of the malodorous gas of the single monitoring point, concentrations of eight compounds specified in a Chinese National Standard GB14554-1993:
- NH3, H2S, CS2, C3H9N, CH4S, C2H6S, C2H6S2, C8H8, and concentrations of SO2 and the total volatile organic compound (TVOC) specified in a Chinese National Standard GB/T18883-2002, totaling 10+1 items;
- and finally transmit through wireless Internet, monitoring data and prediction results to the central control room (VII) and designated ones of the plurality of stationary/mobile terminals (VIII);
- the odor electronic nose instrument (I) is configured to obtain the 16-dimensional response vector every single gas sampling period T0, which is stored in a data file of a computer hard disk, use 10 two-position two-port electromagnetic valves from the second two-position two-port electromagnetic valve (I-6-1) to the eleventh two-position two-port electromagnetic valve (I-6-10) to sequentially control on-and-off of the malodorous gases at 10 monitoring points within a 4 km2 area, online monitor the malodorous gases at the 10 monitoring points by using the cyclic sampling period of T=10×T0 to obtain 10 monitoring data results, and
- sequentially store the 10 monitoring data results in 10 data files, wherein the 10 monitoring data results are a numerical basis for the odor electronic nose instrument (I) to realize cyclically online quantitative prediction of 10+1 concentration control index values of the malodorous gases;
- wherein the gas sampling period T0 comprises following five stages:
- an initial recovery stage of the gas sensor array lasting 95-215 s, an accurate calibration stage of clean air lasting 30 s, a balance stage lasting 5 s, a stage of a headspace sampling of the malodorous gases lasting 30 s and a flushing stage of purified ambient air lasting 20 s;
- in the gas sampling period T0, under a control of a computer, a two-position two-port electromagnetic valve (I-6-k, k=1, 2, . . . , 10) corresponding to one of the 10 monitoring points is connected, and another nine two-position two-port electromagnetic valves corresponding to another nine of the 10 monitoring points are disconnected;
- the internal miniature vacuum pump (I-14) draws a malodorous gas into the gas buffer cavity (I-9) with a flow rate of 1,000 ml/min, thereby enabling the malodorous gas to flow through the annular working chamber of the gas sensor array and skim over surfaces of the sensitive films of the gas sensor array, so that the gas sensor array generates sensitive responses lasting 30 s;
- from a beginning of the balance stage, the computer control and data analyzing system (1(c)) continuously records sensitive response data, wherein the sensitive response data comprises response data of the gas sensor array in following three stages, which last 45 s:
- the balance stage lasting 5 s, the stage of the headspace sampling of the malodorous gases lasting 30 s, and the flushing stage of the purified ambient air lasting first 10 s, which are temporarily stored in a text file;
- response data of other time slots in the gas sampling period T0 are not recorded;
- in the response data of 45 s, a difference between a steady-state maximum value and a minimum value of a response curve of a single gas sensor is extracted as a response component, so that the gas sensor array generates the 16-dimensional response vector;
- in 10 s after the end of the data recording, that is, a later 10 s of the purified ambient air flushing stage, the computer control and data analyzing system (I(c)) predicts the 10+1 concentration control index values of the malodorous gases based on the 16-dimensional response vector;
- wherein the odor electronic nose instrument (I) is configured to perform long-term online monitoring of multiple monitoring points and online prediction of various concentration control index values of the malodorous gases in the pollution sites by executing the following operations:
- (1), a power-on operation:
- when the odor electronic nose instrument (I) is preheated for 30 minutes and an “Air purifier on” option on a screen menu is clicked, triggering the ambient air purification device (IV) to start purifying an ambient air where the odor electronic nose instrument (I) is located, and keeping the ambient air purification device (IV) working until an “Air purifier off” option is clicked;
- under a pumping action of the internal miniature vacuum pump (I-14) inside the ambient air purification device (IV), making the purified ambient air sequentially flow through the first two-position two-port electromagnetic valve (I-5), the annular working chamber of the gas sensor array (I-1) and the thirteenth two-position two-port electromagnetic valve (I-10) with a flow rate of 6,500 ml/min, and then be discharged to outdoor;
- wherein a temperature in the annular working chamber of the gas sensor array (I-1) reaches a constant 55±0.1° C. from a room temperature;
- when an “External vacuum pump on” option on the screen menu is clicked;
- drawing, by the external vacuum pump (III) with a suction flow rate of 250-280 l/min and a limit vacuum degree of 100-120 mbar, a malodorous gas from a certain monitoring point to the odor electronic nose instrument (I) with a linear distance of up to 2.5 km to the odor electronic nose instrument (I) within 1 minute through a stainless steel pipe with an inner diameter of ϕ10 mm, and then making the malodorous gas from the certain monitoring point flow through a corresponding two-position two-port electromagnetic valve (I-6-k) k=1, 2, . . . , 10, the vacuum pressure gauge (I-7) and the gas buffer cavity (I-9) and be directly discharged to outdoor;
- keeping, by the external vacuum pump (III) pump the malodorous gas from the certain monitoring point until an “external vacuum pump off” option on the screen menu is clicked;
- modifying a setting of the gas sampling period T0 on the screen menu as a default value T0=40 minutes and modifying a cycle sampling period of malodorous gases for 10 monitoring points as T=10×T0;
- (2), an operation for starting a cyclic sampling period of the malodorous gases:
- when a “start detection” button on the screen menu is clicked, sequentially monitoring, by the odor electronic nose instrument (I), the 10 monitoring points, and automatically generating, by the computer control and data analyzing system (I(c)), 10 text files in a designated folder to store the response data of the gas sensor array (I-1) to the malodorous gases at 10 monitoring points;
- (3), an operation for starting a single sampling period of the malodorous gas for a monitoring point k;
- taking T0=240 seconds as an example, wherein k=1, 2, . . . , 10:
- (3.1), a preliminary recovery operation of the gas sensor array (I-1):
- in the 0-155 s of the gas sampling period T0, under the pumping action of the internal miniature vacuum pump (I-14) inside the ambient air purification device (IV), making the purified ambient air sequentially flow through the first two-position two-port electromagnetic valve (I-5), the annular working chamber of the gas sensor array (I-1), the thirteenth two-position two-port electromagnetic valve (I-10) with a flow rate of 6,500 ml/min, and then be discharged to the outdoor;
- so that the accumulated heat in the annular working chamber of the gas sensor array (I-1) is taken away under an action of the 6,500 ml/min purified ambient air, the malodorous gas molecules adhered to the sensitive membrane surfaces of the gas sensor array (I-1) and the inner wall of pipelines are preliminarily washed away, and the gas sensor array (I-1) preliminarily returns to a reference state which lasts 155 s;
- wherein among 10 two-position two-port electromagnetic valves from the first second two-position two-port electromagnetic valve (I-6-1) to the eleventh two-position two-port electromagnetic valve (I-6-10), only one two-position two-port electromagnetic valve (I-6-k) is on, another nine two-position two-port electromagnetic values are off, and the external vacuum pump (III) pumps the malodorous gas in the monitoring point k into the odor electronic nose instrument (I), wherein k=1, 2, . . . , 10;
- (3.2), an accurate calibration operation of the gas sensor array by clean air:
- in 156-185 s range of the gas sampling period T0, when the fourteenth two-position two-port electromagnetic valve (I-13) is on, the first two-position two-port electromagnetic valve (I-5), the twelfth two-position two-port electromagnetic valve (I-8), and the thirteenth two-position two-port electromagnetic valve (I-10) are off, and among the 10 two-position two-port electromagnetic valves from the first second two-position two-port electromagnetic valve (I-6-1) to the eleventh two-position two-port electromagnetic valve (I-6-10), only the one two-position two-port electromagnetic valve (I-6-k) is on, the other nine two-position two-port electromagnetic values are off;
- under the pumping action of the internal miniature vacuum pump (I-14) inside the ambient air purification device (IV), making the clean air sequentially flow through the fourteenth two-position two-port electromagnetic valve (I-13), the gas pipelines, the annular working chamber of the gas sensor array (I-1), the throttle valve (I-11), the flowmeter (I-12) and the internal miniature vacuum pump (I-14) with the flow rate of 1,000 ml/min, and then be discharged to the outdoor;
- wherein the clean air makes the gas sensor array (I-1) accurately return to the reference state which lasts 30s;
- and the external vacuum pump (III) keeps pumping for 30 seconds;
- (3.3), an operation of a balance stage:
- in 186-190 s of the gas sampling period T0, when the first two-position two-port electromagnetic valve (I-5), the twelfth two-position two-port electromagnetic valve (I-8), the thirteenth two-position two-port electromagnetic valve (I-10) and the fourteenth two-position two-port electromagnetic valve (I-13) are disconnected, among the 10 two-position two-port electromagnetic valves from the first second two-position two-port electromagnetic valve (I-6-1) to the eleventh two-position two-port electromagnetic valve (I-6-10), only the one two-position two-port electromagnetic valve (I-6-k) is on, the other nine two-position two-port electromagnetic values are off;
- and there is no gas flow in the annular working chamber of the gas sensor array (I-1);
- from 186th second of the gas sampling period T0, recording and storing, by the computer control and data analyzing system (I(c)), real-time response data of the gas sensor array (I-1) in a designated temporary text file “temp.txt”;
- wherein the external vacuum pump (III) keeps drawing the malodorous gas for 5 seconds;
- (3.4), the headspace sampling operation of the malodorous gas at the monitoring point k:
- in 190-220 seconds of the gas sampling period T0, when the twelfth two-position two-port electromagnetic valve (I-8) is on, the first two-position two-port electromagnetic valve (I-5), the fourteenth two-position two-port electromagnetic valve (I-13) and the thirteenth two-position two-port electromagnetic valve (I-10) are off, and among the 10 two-position two-port electromagnetic valves from the first second two-position two-port electromagnetic valve (I-6-1) to the eleventh two-position two-port electromagnetic valve (I-6-10), only the one two-position two-port electromagnetic valve (I-6-k) is on, the other nine two-position two-port electromagnetic values are off;
- under the pumping action of the internal miniature vacuum pump (I-14) inside the ambient air purification device (IV), making the malodorous gas in the gas buffer cavity (I-9) sequentially flow through the annular working chamber of the gas sensor array (I-1), the throttle valve (I-11), the flowmeter (I-12), the internal miniature vacuum pump (I-14) with a flow rate of 1,000 ml/min, and be finally discharged to the outdoor;
- wherein sensitive responses of the gas sensor array (I-1) are recorded in the temporary file “temp.txt”, and the external vacuum pump (III) keeps pumping for 30 seconds;
- (3.5), a flushing operation of the gas sensor array:
- in the 221-230 seconds of the gas sampling period T0, when the first two-position two-port electromagnetic valve (I-5) and the thirteenth two-position two-port electromagnetic valve (I-10) are connected, and the twelfth two-position two-port electromagnetic valve (I-8) and the fourteenth two-position two-port electromagnetic valve (I-13) are disconnected;
- under the pumping action of the internal miniature vacuum pump (I-14) inside the ambient air purification device (IV), making the purified ambient air sequentially flows through the first two position two-port solenoid valve (I-5), the annular working chamber of the gas sensor array (I-1) and the thirteenth two-position two-port electromagnetic valve (I-10) with a flow rate of 6,500 ml/min, and then be discharged to the outdoor;
- at the same time, among the 10 two-position two-port electromagnetic valves from the first second two-position two-port electromagnetic valve (I-6-1) to the eleventh two-position two-port electromagnetic valve (I-6-10), only one two-position two-port electromagnetic valve (I-6-(k+1)) is on, another nine two-position two-port electromagnetic valves are off, and pumping, by the external vacuum pump (III), the malodorous gas at a monitoring point (k+1);
- due to the role of the purified ambient air, the accumulated heat in the annular working chamber of the gas sensor array (I-1) is taken away, the malodorous gas molecules adhered to the sensitive film surfaces of the gas sensor array (I-1) and the inner walls of the pipelines are preliminarily washed away, and the gas sensor array (I-1) gradually returns to the reference state, which takes 20 seconds, wherein:
- (a), in the 221-230 seconds of the gas sampling period T0, continuing to record the response data of the gas sensor array in the temporary file “temp.txt” which lasts 10 s;
- at the end of 230th second, stopping, by the computer control and data analyzing system (I(c)), recording the response data of the gas sensor array;
- (b), in the 231-240 seconds of the gas sampling period T0, performing, by the computer control and data analyzing system (I(c)), following three operations:
- (b1), a feature extraction:
- from the 231st second, extracting the maximum and the minimum steady-state response values of each gas sensor with a time duration of 45 seconds from the temporary file “temp.txt”, and taking and recording a difference between the maximum and the minimum response value as a characteristic response component xi(t) of each gas sensor to the malodorous gas at the monitoring point k at the current time t in a corresponding data file, wherein i=1, 2, . . . , 16;
- (b2), a response prediction of the gas sensor array:
- realizing, by the first level of the cascade machine learning model, an online self-learning according to the time-series response vectors of the gas sensor array within a period that have occurred before the current time t, and predicting responses of the gas sensor array (I-1) at a future time points of T0, 2T0 and 3T0;
- wherein the first level of the cascade machine learning model is 16*3 convolutional neural networks and the period comprises three time segments of [t−18, t], [t−19, t−1] and [t−20, t−2];
- (b3), a prediction of malodorous gas concentration control index values:
- continuing to predict, by the second level of the cascade machine learning model, the 10+1 concentration control index values of the malodorous gas at the monitoring point k according to the response values of the gas sensor array predicted by the 16*3 convolution neural networks in the first level of the cascade model, showing the 10+1 concentration control index values on the monitor, and transmitting monitoring and prediction results to a central control room (VII) and the plurality of stationary/mobile terminals (VIII) through the Internet network wherein the second level of the cascade machine learning model is 10+1 deep neural networks;
- (3.6), an ending operation of the gas sampling period T0 at the monitoring point k:
- k←k+1, returning to the step (3.1), and starting the gas sampling period T0 at the monitoring point (k+1);
- if k+1>10, then starting to detect a malodorous gas at a monitoring point k=1 of a next gas sampling period;
- repeating the steps (3.1)˜(3.6);
- so that the odor electronic nose instrument (I) realizes cyclically online measurement, identification and prediction of 10+1 concentration control index values of malodorous gases at 10 monitoring points.