CN109813400B - Boiler main steam flowmeter online checking and testing system based on internet of things technology - Google Patents
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Abstract
The invention provides an online checking and testing system for a main steam flowmeter of a boiler based on the internet of things technology, which comprises a data acquisition unit, a wireless transmission unit and a data processing unit, wherein the data acquisition unit acquires basic data comprising the combustion temperature of a boiler hearth, the water level of the boiler, the gas flow of the boiler, the water supply temperature and pressure and flow of the boiler, the temperature and flow of sewage discharged by the boiler and the steam temperature and pressure and flow of the main steam flowmeter, the wireless transmission unit transmits the basic data to the data processing unit, the data processing unit calculates the calculated value of the main steam flow according to a mass balance method after carrying out digital correction on the transmitted basic data, compares the calculated value with the indicating value of the flowmeter, carries out alarm prompt when the error exceeds the set limit range, and obtains a comprehensive flow proportion coefficient to carry out checking and correction on the indicating value of the main steam flowmeter in real time. The method and the device can meet the requirements of industrial site rapid judgment and online check on the accuracy of the main steam flow meter, and realize accurate measurement of the steam flow.
Description
Technical Field
The invention relates to the technical field of metering, in particular to an online checking and testing system for a main steam flowmeter of a boiler based on the technology of the Internet of things.
Background
Steam is an important secondary energy source, is an important carrier of heat energy, and can directly participate in chemical reaction in the production process, and can also utilize the heat energy to generate energy or do work. Because the steam has the characteristics of cleanness, environmental protection, high energy efficiency, transmissibility and the like, the steam is widely used in industrial production and daily life of people. The working pressure of industrial steam is 0.26-9.80 MPa and the temperature is 150-500 ℃. Steam can be classified into superheated steam, saturated steam and wet steam according to the state. Steam flow metering work presents certain difficulties due to the complex steam conditions and their unique physical characteristics. Therefore, the accuracy of steam metering is improved, accurate and reliable flow data are obtained, steam metering management is enhanced, and the method has very important significance for reasonably utilizing steam resources in China and promoting energy conservation and consumption reduction.
The steam flowmeter mainly measures the steam flow determined by the physical state, and when the working condition (temperature and pressure) changes, the steam flowmeter can possibly cause measurement errors due to phase change, and particularly for wet steam, the problem of inaccurate measurement often exists. The steam metering is accurate and reliable, so that the energy consumption of a user can be accurately reflected, the running condition of a heat energy system can be monitored, the reasonable distribution of heat energy, the optimal running of a thermodynamic system and energy consumption equipment can be used for energy consumption assessment and energy saving and consumption reduction transformation of steam energy are provided, and the steam metering device is a basis for guaranteeing fairness and fairness of steam trade settlement.
The verification method of the steam flowmeter can be generally divided into a direct measurement method and an indirect measurement method, wherein the direct measurement method is also called a real-flow calibration method and is realized by a flow standard device, namely, the flow of the detected flowmeter is measured by a standard flowmeter, and the two indication values are compared to obtain a measurement method of the accuracy of the detected flowmeter; an indirect measurement method is a method of indirectly calibrating a flow quantity value to obtain a corresponding accuracy by measuring a physical quantity related to the flow.
Currently, differential pressure type flow meters are commonly used for steam metering, and are verified according to a verification method specified by a verification procedure of JJG640-1994 differential pressure type flow meters: namely, the differential pressure transmitter and the pressure transmitter are detached respectively, the analog quantity is used for static verification by a metering department, and the differential pressure transmitter or the pressure transmitter is verified in isolation, and the orifice plate, the integrating instrument and the display are basically not checked (particularly, the orifice plate which is a primary element, the change of the geometric dimension directly influences the accuracy of steam flow metering, but is difficult to check and maintain for a plurality of years generally due to difficult detachment). In addition, the differential pressure transmitter and the pressure transmitter are static verification, and the replacement media (water and air) used for verification are inconsistent with the actual media, or the input current verification point parameters are used for completing verification by using analog quantities. Therefore, the traditional verification method of the differential pressure type flowmeter does not verify the metering performance of the differential pressure type flowmeter, but only verifies analog quantity instead of verification, and the differential pressure type flowmeter is in an unknown state for the actual condition of steam metering. Thus, steam flow inaccuracy is a ubiquitous and urgent issue to be addressed.
The traditional differential pressure flowmeter needs to form a complete flow measurement system by a throttling device, a pressure guiding pipeline, a differential pressure transmitter and a flow integrating instrument. For the measurement of the gas flow, a pressure transmitter and a temperature transmitter are also required to be configured for temperature and pressure compensation. As a classical flow metering device, an orifice plate flowmeter is composed of a plurality of independent units, and the orifice plate flowmeter is reasonable in configuration and standard in installation, so that the measurement accuracy of the orifice plate can be directly affected. The orifice plate flowmeter is worn for a long time to blunt the acute angle of the orifice plate, and researches show that the annual wear radius of the orifice plate increases by 0.04mm in the first two and three years of operation, and the orifice plate flowmeter tends to be stable after five and six years, so that the measurement accuracy cannot be ensured. For example, during start-up and shut-down of the boiler, water hammer may be generated due to condensate remaining in the steam pipe, and the orifice plate may be deformed. The orifice plate has the unavoidable problems of 'acute angle abrasion' and 'dirt accumulation', and the change is more remarkable in the occasions that the flow coefficient is larger and larger, the meter indication value is smaller and the flow rate is higher along with the increase of the service time. Furthermore, the zero point of the transmitter may drift over a longer period of time, and if it is negatively drifting, the differential pressure displayed will decrease and the flow displayed will decrease. Therefore, the orifice plate in the orifice plate flowmeter needs to be periodically checked, cleaned and detected in geometric dimensions, steam metering conditions are harsh, and the steam metering conditions are not managed enough, so that the orifice plate flowmeter on a plurality of metering points is difficult to periodically overhaul, and the orifice plate flowmeter on a plurality of metering points is not managed for a long time after being installed, and as a result, great waste is caused, and the actual problem is not really solved.
At present, the orifice plate flowmeter mainly adopts a dry detection method to carry out uncertainty control on the secondary measuring instrument and the metering orifice plate. The geometrical measurement method of dry detection is mainly to carry out annual weekly detection on the orifice plate, the secondary instrument and the flow computer to evaluate the uncertainty of the system of the whole set of orifice plate flowmeter, but the errors generated by the factors cannot be qualitatively and quantitatively analyzed, so the total uncertainty of the whole set of metering device cannot be completely and quantitatively determined, and reasonable and determined correction coefficients cannot be given to the generated deviations.
The on-line checking of the steam flowmeter is a key for developing energy conservation and consumption reduction and solving the problem of accuracy reduction of the flowmeter, plays a very good role in checking the metering of industrial life steam, and can eliminate disputes and the like caused by metering errors. Therefore, how to research a reliable, simple and online detection method under the situation of great development of national energy audit has become an urgent need for enterprises producing and consuming steam.
Disclosure of Invention
Aiming at the technical problems that the verification and the calibration of the existing main steam flow meter of the boiler by a third party metering mechanism are difficult, the online verification requirement of the existing main steam flow meter is difficult to meet, and the quick and convenient verification and the calibration cannot be realized in the prior art, the invention provides an online verification test system for the main steam flow meter of the boiler based on the technology of the Internet of things.
In order to solve the technical problems, the invention adopts the following technical scheme:
the online checking and testing system for the main steam flowmeter of the boiler based on the internet of things technology is characterized in that the main steam flowmeter of the boiler refers to a steam flowmeter on a main steam pipeline of an industrial site gas boiler, and the system comprises a data acquisition unit, a wireless transmission unit and a data processing unit; wherein,
the data acquisition unit is used for acquiring basic data including the combustion temperature of a boiler hearth, the water level of the boiler, the gas flow of the boiler, the temperature, the pressure and the flow of boiler feed water, the temperature, the flow of boiler sewage and the steam temperature, the pressure and the flow of a main steam flowmeter;
the wireless transmission unit comprises a wireless transmission module and a wireless receiving module, wherein the wireless transmission module is used for transmitting various basic data acquired by the data acquisition unit, and the wireless receiving module is used for receiving various basic data and transmitting the basic data to the data processing unit;
the data processing unit comprises a data server and a display, wherein the data server is used for carrying out digital correction on various basic data transmitted by the wireless receiving module, calculating a calculated value of the steam flow of the main steam pipeline according to a mass balance method, comparing and analyzing the calculated value with an indication value of the self flow of the main steam flowmeter, highlighting corresponding parameters and carrying out alarm prompt when the relative error between the calculated value and the indication value of the main steam flow exceeds a set limit range, and giving out the probability of performance decline or inaccuracy of the main steam flowmeter by combining with the historical data evaluation analysis of the main steam flowmeter, and obtaining the comprehensive flow proportional coefficient f under the stable operation condition of the boiler steam production system in the range or the common metering range of the main steam flowmeter for carrying out on-line correction on the indication value in real time, and the display is used for carrying out centralized display on various basic data and result data received by the data server.
Further, the data acquisition unit comprises a temperature sensor for acquiring the combustion temperature of a boiler furnace, the medium temperature in a boiler water supply pipeline, the medium temperature in a boiler sewage pipeline and the steam medium temperature in a main steam pipeline, a water level sensor for acquiring the water level of a boiler drum, a flowmeter for acquiring the fuel gas consumption of the boiler, the water supply flow of the boiler, the sewage discharge flow of the boiler and the steam flow in the main steam pipeline, and a pressure sensor for acquiring the medium pressure in the boiler water supply pipeline and the steam medium pressure in the main steam pipeline.
Further, the temperature sensor is a thermal resistor or thermocouple.
Further, the flowmeter is an orifice flowmeter, an electromagnetic flowmeter or a vortex shedding flowmeter.
Further, the wireless transmitting module and the wireless receiving module are WIFI modules, zigBee modules or GPRS modules.
Further, when the relative error between the calculated value and the indication value of the main steam flow exceeds the set limit value range, highlighting corresponding parameters, carrying out alarm prompt, and giving out performance degradation or inaccuracy probability of the main steam flow meter by combining with historical data evaluation analysis of the main steam flow meter, and obtaining the comprehensive flow proportionality coefficient f for correcting the indication value in real time under the stable operation condition of the boiler steam production system in the range or the common metering range of the main steam flow meter, wherein the data server further comprises judging the reason for causing the abnormal indication value monitoring data of the main steam flow meter through an expert database in a fuzzy algorithm, and giving an adjustment feedback strategy for continuous and stable operation of the boiler according to the real-time monitoring of the demand of steam and the calculated value of the main steam flow.
Further, the obtaining of the integrated flow scaling factor f specifically includes: according to the measuring range or the common measuring range of the main steam flowmeter, n flow check points i are selected, each flow point reads data for at least three times, and the average value is taken to obtain the water supply flow G of each flow check point 0i And the sewage flow rate G 1i Difference G of 0i -G 1i Main steam flow V i The method comprises the steps of carrying out a first treatment on the surface of the Calculating the proportionality coefficient f of each flow point i i ＝(G 0i -G 1i )/V i The method comprises the steps of carrying out a first treatment on the surface of the If the proportionality coefficient f of each flow point i i Near linearity, weighting lambda according to each point i A composite flow scaling factor f is calculated to fit the corrected primary steam flow meter indication,
compared with the prior art, the online checking and testing system for the main steam flowmeter of the boiler based on the Internet of things provided by the invention has the key points that the online checking and testing system for the main steam flowmeter of the boiler based on the Internet of things realizes the data acquisition of boiler operation parameters and sensor perception between the main steam flowmeter and the main steam pipeline steam flowmeter of the boiler by means of the Internet of things, calculates the steam flow of the main steam pipeline according to the water supply flow and the sewage flowmeter by a mass balance method under the condition of stable working condition operation, and compares and analyzes the calculated steam flow with the indication value of the main steam flowmeter to judge the metering performance of the main steam flowmeter so as to realize the online checking and evaluating of the metering characteristics of the main steam flowmeter. Specifically, in order to realize online checking of the indication value of the main steam flowmeter of the main steam pipeline of the boiler, basic data such as temperature, pipeline pressure and flow, boiler water level, fuel gas consumption and the like are mainly acquired through a sensor, then the basic data are transmitted to a data server analysis platform at the rear end in a wireless transmission mode, medium mass balance calculation and monitoring in the system are carried out, the main steam flow value is calculated and compared with the indication value to judge the performance of the main steam flowmeter, an optimization control reference strategy is given to realize the online checking function of the main steam pipeline steam, and an alarm signal is given when the metering characteristic of the main steam flowmeter deviates from a relative error threshold; on the other hand, through each operation parameter real-time supervision of system, know boiler combustion operation and steam production steady degree to give corresponding control strategy, provide data support for the control of boiler steam production system steady operation and steam quality. Therefore, the online checking of the indication value of the main steam flowmeter of the boiler can meet the requirement of rapidly judging the accuracy of the main steam flowmeter on the industrial site, the trouble of disassembly and inspection is avoided, and the important function is played in the aspects of ensuring the performance of the instrument and improving the economic benefit.
Drawings
Fig. 1 is a schematic structural diagram of an online checking and testing system for a main steam flowmeter of a boiler based on the internet of things technology.
FIG. 2 is a schematic view of the evaporation of a cross-flow boiler provided by the present invention.
FIG. 3 is a schematic diagram of the transfer of the check values provided by the present invention.
Detailed Description
The invention is further described with reference to the following detailed drawings in order to make the technical means, the creation characteristics, the achievement of the purpose and the effect of the implementation of the invention easy to understand.
In the description of the present invention, it should be understood that the terms "longitudinal," "radial," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like indicate orientations or positional relationships that are based on the orientation or positional relationships shown in the drawings, merely to facilitate describing the present invention and simplify the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present invention. In the description of the present invention, unless otherwise indicated, the meaning of "a plurality" is two or more.
In the description of the present invention, it should be noted that, unless explicitly specified and limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be either fixedly connected, detachably connected, or integrally connected, for example; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present invention will be understood in specific cases by those of ordinary skill in the art.
Referring to fig. 1, the invention provides an online checking and testing system for a main steam flowmeter of a boiler based on the internet of things technology, wherein the main steam flowmeter of the boiler refers to a steam flowmeter on a main steam pipeline of an industrial site gas boiler, is generally positioned at the rear end of the boiler and in front of a split cylinder, and main equipment or devices related to the online checking and testing system comprise a boiler water supply pipeline, a boiler body, a boiler sewage pipeline and a boiler steam pipeline, and the system comprises a data acquisition unit, a wireless transmission unit and a data processing unit; wherein,
the data acquisition unit is used for acquiring basic data including the combustion temperature of a boiler hearth, the water level of the boiler, the gas flow of the boiler, the temperature, the pressure and the flow of boiler feed water, the temperature, the flow of boiler sewage and the steam temperature, the pressure and the flow of a main steam flowmeter;
the wireless transmission unit comprises a wireless transmission module and a wireless receiving module, wherein the wireless transmission module is used for transmitting various basic data acquired by the data acquisition unit, and the wireless receiving module is used for receiving various basic data and transmitting the basic data to the data processing unit;
the data processing unit comprises a data server and a display, wherein an SQL database and a data analysis platform built by a computer technology tower are installed in the data server, the analysis platform has the functions of data storage, data display, control and adjustment and the like, the data server is used for carrying out digital correction on various basic data transmitted by the wireless receiving module, calculating a calculated value of the steam flow of the main steam pipeline according to a mass balance method and comparing and analyzing the calculated value with an indication value of the self flow of the main steam flowmeter, when the relative error of the calculated value and the indication value of the main steam flow exceeds a set limit range, highlighting corresponding parameters and carrying out alarm prompt, and giving out performance degradation or inaccuracy probability of the main steam flowmeter by combining with historical data evaluation analysis of the main steam flowmeter, and obtaining a comprehensive flow proportion coefficient f under the stable operation condition of a boiler steam generating system in the range or a common metering range of the main steam flowmeter, and the display is used for carrying out centralized display on various basic data and result data received by the data server.
Specifically, the data server digitally correcting various basic data includes: the elimination of significant errors and the coordination of data to process random errors in the measured data, etc., while the specific digital correction process belongs to conventional techniques well known to those skilled in the art, and thus will not be described in detail herein; then, calculating the mass flow of the generated main steam in real time according to the mass balance relation among the boiler water supply, the boiler water discharge and the boiler steam in the boiler steam generating system by adopting the data after digital correction processing; then calculated value V for main steam mass flow js And the main steam flowmeter indication value V are monitored in real time, and meanwhile, the relative error between the main steam flowmeter indication value V and the main steam flowmeter indication value V is calculated, wherein the relative error is the error rate delta= (V-V) of the main steam flowmeter js )/V js X 100%; when the relative error exceeds the set limit value range, the inaccuracy of the performance of the main steam flowmeter can be primarily judged, the corresponding parameters are highlighted and the alarm prompt is carried out, the probability of the degradation or inaccuracy of the performance of the main steam flowmeter is given by combining with the historical data evaluation analysis of the main steam flowmeter, and the measurement range or the common measurement range of the main steam flowmeter is shownIn the surrounding, the comprehensive flow proportionality coefficient f is obtained under the stable operation condition of the boiler steam generating system and is used for correcting the indication value in real time, so that the on-line check of the main steam flowmeter is realized.
As a specific embodiment, the data acquisition unit includes: the temperature sensor is used for acquiring the combustion temperature of a boiler hearth, the medium temperature in a boiler water supply pipeline, the medium temperature in a boiler sewage pipeline and the steam medium temperature in a main steam pipeline, wherein the medium temperature in the boiler water supply pipeline refers to the temperature of the medium in the pipeline before entering a boiler drum, the medium temperature in the boiler sewage pipeline refers to the temperature of the medium in the pipeline after a boiler sewage pipeline or a drain valve, the steam medium temperature in the main steam pipeline refers to the temperature when the water supply is converted into steam through heating of the boiler and then conveyed in the main steam pipeline, the temperature sensor can specifically adopt the existing thermal resistor or thermocouple temperature sensor to acquire data, the precision is not lower than 0.5 level, and the data are transmitted to the wireless transmission module through a connecting wire; the water level sensor is used for acquiring the water level of the boiler drum, and the value of the water level sensor can be displayed and acquired and transmitted from time to time according to the water level of the boiler drum; the flow meter for acquiring the fuel gas consumption of the boiler, the water supply flow of the boiler, the sewage flow of the boiler and the steam flow in the main steam pipeline is arranged on the boiler fuel pipeline, if other flow meters exist on the pipelines of the water supply of the boiler and the sewage of the boiler, the flow data signals of the flow meters can be acquired by directly adopting the other flow meters after the flow meters are calibrated, the flow meters for acquiring the steam flow in the main steam pipeline are arranged on the main steam pipeline, the flow meters can be acquired by adopting an orifice plate flow meter, an electromagnetic flow meter or a vortex street flow meter, the flow meter test precision for measuring the steam in a calibration state is not lower than 1 percent, and the flow meter test precision for testing the water flow is not lower than 0.5 percent; the pressure sensor is used for acquiring the pressure of the medium in the water supply pipeline of the boiler and the pressure of the steam medium in the main steam pipeline, pressure data of medium flowing in the pipeline can be acquired through the pressure sensor, and the acquired steam temperature and pressure are used for carrying out density compensation on the main steam flowmeter so as to accurately obtain the mass flow of the main steam.
As a preferred embodiment, according to the calibration principle, the accuracy grade of the boiler water supply flowmeter and the sewer water flowmeter needs to be selected into a higher grade flowmeter, and the electromagnetic flowmeter is preferably used as an online check standard meter by adopting a 0.5 grade electromagnetic flowmeter in combination with a boiler site, so that the check requirement can be met.
As a specific embodiment, the wireless transmission unit is a key place of the internet of things technology for data acquisition of the online checking and testing system, and is composed of a wireless transmission module and a wireless receiving module, wherein the wireless transmission module and the wireless receiving module can adopt a WIFI module, a ZigBee module, a GPRS module or the like, that is, wireless signals can be transmitted and received between the wireless transmission module and the wireless receiving module through the WIFI module, the ZigBee module or the GPRS module.
As a specific embodiment, when the relative error between the calculated value and the indication value of the main steam flow exceeds the set limit value range, highlighting the corresponding parameter and carrying out alarm prompt, and giving out the probability of performance degradation or inaccuracy of the main steam flow meter by combining with the historical data evaluation analysis of the main steam flow meter, and obtaining the comprehensive flow proportionality coefficient f for correcting the indication value in real time under the stable operation condition of the boiler steam production system in the range or the common metering range of the main steam flow meter, wherein the data server also comprises judging the reason for causing the abnormal indication value monitoring data of the main steam flow meter according to the historical monitoring data and the internally constructed mathematical control model by an expert database in a fuzzy algorithm, and giving out an adjustment feedback strategy for continuous and stable operation of the boiler according to the real-time monitoring of the demand of steam and the calculated value of the main steam flow, and the specific strategy comprises adjustment of the water supply flow rate of the boiler, adjustment of the gas supply quantity of the gas supply and the like, so as to ensure that the online check test system meets the precondition; the reasons for the abnormality of the main steam flowmeter indication monitoring data include: (1) Inaccurate measurement of the steam volume flow caused by the reduction of the metering performance of a flow sensor of the main steam flowmeter; (2) Steam density compensation inaccuracy caused by inaccurate metering of a steam temperature or pressure measurement sensor; (3) Unstable guide of boiler steam production systemThe indication value of the main steam flow meter is excessively fluctuated; (4) other interference terms. Specifically, the SQL database installed in the data server and the data analysis platform built by the computer technology can collect the boiler water supply flow G on line in real time according to the data collection unit 0 Flow rate G of boiler sewage 1 And main steam line flow meter indication V and other parameters for flow correction, such as feedwater temperature T 0 Water supply pressure P 0 The method comprises the steps of calculating a calculated value of steam flow of a main steam pipeline according to a mass balance relation by a computer, comparing and analyzing the calculated value with a flow indication value displayed by a steam flowmeter, alarming when an error exceeds a set limit value range or a threshold value, evaluating and analyzing probability of performance decline or inaccuracy of the main steam flowmeter when the calculated value and the indication value are larger in error by combining historical data, and simultaneously adopting a comprehensive flow proportionality coefficient to realize the purpose of online checking and testing of the main steam flowmeter.
As is known to those skilled in the art, liquid water enters a boiler and is heated to evaporate into steam, and only two different forms of water and different state parameters are converted, which provides a material condition for measuring the mass measurement of a main steam flowmeter of the boiler by using a water vapor mass balance equation. Therefore, it is theoretically possible to discuss a method of calibrating the main steam flow meter indication on-line at the industrial site using the water supply flow rate and the drain flow rate of the higher accuracy level. In particular, the theoretical water vapor mass balance is derived by the following mathematical physical process:
referring to FIG. 2, consider a medium area surrounded by a water line and a pipe wall in a water-cooled wall riser as a control body τ, and an inlet medium of the control body τ is riser feedwater M j The outlet medium being the generated steam M q And make the following steady-state assumptions: in the operation of the boiler in the time t, fluid medium in each pipeline of the steam-water system continuously flows, the water level line of the boiler is kept stable and unchanged, and the boilerThe pressure in the upper header is constant, and the water supply pressure and the water supply temperature in the lower header are constant. The following correlation can be obtained according to the control body steam-water quality change:
wherein M is j The unit kg/s is the water supply mass flow; m is M q The unit kg/s is the saturated steam mass flow with humidity which enters the upper part of the water line and is led out by a steam outlet pipe;in order to control the variation of the medium mass in the body tau in t time, the unit kg/s is adopted; ρ is the medium density; v is the volume of the control body tau; dV is a differential expression of volume.
The analysis of the steam production process shows that in the running of the boiler, the steam-water system fluid medium continuously flows, and the steam production process belongs to a constant-pressure saturated steam process, and the saturated steam temperature and the saturated water temperature are unchanged. And in the time t, the volume and the bubble density of the steam bubbles produced in the control body tau are unchanged, namely the bubble mass is unchanged, and when the water level line is unchanged, the total volume under the control body tau is constant, and then the volume of liquid water in the control body tau is unchanged. When the water supply pressure, the water supply temperature and the vapor pressure are constant, the density of the liquid water in the control body tau is unchanged, so that the quality of the liquid water under the control body tau is constant. I.e. the liquid water quality and bubble quality in the control body tau are unchanged in the t timeThen equation (1) can be transformed into:
equation (2) reflects that the boiler is in a boiler operation condition control body tau with constant water supply pressure and water supply temperature, water line position and steam pressure, and the water supply mass flow is equal to the generated steam mass flow. Similarly, it can be inferred that if the control body is extended to a control body including a lower header, a rising pipe, and an upper header, it can be obtained by the formula (2):
V＝G 0 -G 1 (3)
Wherein G is 0 The unit kg is the accumulated mass flow through the feedwater flowmeter within a given time t; g 1 The unit kg is the accumulated mass flow passing through the boiler blow-down water flowmeter; v is the accumulated mass flow of the main steam flowmeter of the boiler, and the unit is kg.
The formula (3) shows a closed continuous flow through-flow boiler steam-water system with water supply mass flow of a lower header as an inlet and steam mass flow of the upper header and sewage discharge amount as outlets in the same time under the control condition of stable working condition, wherein the steam mass flow delivered by the system is equal to the water supply mass flow entering the system and the sewage discharge mass flow flowing out of the system is subtracted, and the water vapor mass balance equation of the boiler under the control condition of stable working condition is obtained. Therefore, the water flow measurement technology is mature, the operation is convenient, the measurement accuracy is guaranteed, and the method can be used as a standard reference for checking steam.
In industrial field checking, in order to ensure the checking accuracy, the boiler operation needs to meet the following conditions:
(1) The steam-water system of the boiler is ensured to be an independent system, the operations of chemical sampling water, adding liquid medicine and the like are stopped, and each valve of the boiler is tight and has no leakage;
(2) The working condition parameters of the boiler are basically stable, and larger fluctuation, such as stable gas supply, is avoided so as to reduce the influence of combustion adjustment; any operation which disturbs the working condition of the boiler is not allowed to occur, such as the operation of starting and tripping a safety valve, adjusting the load of the boiler and the like; through control system linkage, when there is blowdown water outflow to change, the corresponding feedwater flow that improves ensures that the vapour-liquid interface in the tedge remains stable. The fluctuation value of the main thermal parameters of the boiler does not exceed the allowable value recommended in the following table 1:
table 1 allowable value of boiler condition fluctuation during on-line checking
After the boiler stably operates for a period of time, simultaneously measuring the water supply flow, the sewage discharge flow and the main steam flow to obtain the difference G between the water supply flow and the sewage discharge flow under certain parameters 0 -G 1 And the integrated flow ratio coefficient f between the main steam flow meter indication value V and the main steam flow meter indication value V to obtain a corrected value V' of the main steam flow meter indication value V. In this way, the water supply flow with higher accuracy grade is transmitted to the main steam flowmeter indication value, so that the purpose of on-line checking is achieved, and a checking value transmission schematic diagram is shown in figure 3.
As a specific embodiment, the online checking of the main steam flowmeter of the boiler can be completed according to the following steps, namely, the obtaining of the comprehensive flow proportionality coefficient f specifically comprises: according to the measuring range or the common measuring range of the main steam flowmeter, n flow check points i are selected, each flow point reads data for at least three times, and the average value is taken to obtain the water supply flow G of each flow check point 0i And the sewage flow rate G 1i Difference G of 0i -G 1i Indication value V of main steam flowmeter i The method comprises the steps of carrying out a first treatment on the surface of the Calculating the proportionality coefficient f of each flow point i i ＝(G 0i -G 1i )/V i The method comprises the steps of carrying out a first treatment on the surface of the If the proportionality coefficient f of each flow point i i Near linearity, weighting lambda according to each point i A composite flow scaling factor f is calculated to fit the corrected primary steam flow meter indication,
in summary, the flowmeter of the main steam pipeline of the boiler can be corrected by the data processing unit through the water vapor mass balance equation, and the corrected accurate calculated value is given to be compared with the main flowmeter indication value, so that the accuracy and repeatability of the metering performance of the main flowmeter can be analyzed and judged, and the purpose of online checking and testing of the main steam flowmeter is achieved.
Compared with the prior art, the online checking and testing system for the main steam flowmeter of the boiler based on the Internet of things provided by the invention has the key points that the online checking and testing system for the main steam flowmeter of the boiler based on the Internet of things realizes the data acquisition of boiler operation parameters and sensor perception between the main steam flowmeter and the main steam pipeline steam flowmeter of the boiler by means of the Internet of things, calculates the steam flow of the main steam pipeline according to the water supply flow and the sewage flowmeter by a mass balance method under the condition of stable working condition operation, and compares and analyzes the calculated steam flow with the indication value of the main steam flowmeter to judge the metering performance of the main steam flowmeter so as to realize the online checking and evaluating of the metering characteristics of the main steam flowmeter. Specifically, in order to realize online checking of the indication value of the main steam flowmeter of the main steam pipeline of the boiler, basic data such as temperature, pipeline pressure and flow, boiler water level, fuel gas consumption and the like are mainly acquired through a sensor, then the basic data are transmitted to a data server analysis platform at the rear end in a wireless transmission mode, medium mass balance calculation and monitoring in the system are carried out, the main steam flow value is calculated and compared with the indication value to judge the performance of the main steam flowmeter, an optimization control reference strategy is given to realize the online checking function of the main steam pipeline steam, and an alarm signal is given when the metering characteristic of the main steam flowmeter deviates from a relative error threshold; on the other hand, through each operation parameter real-time supervision of system, know boiler combustion operation and steam production steady degree to give corresponding control strategy, provide data support for the control of boiler steam production system steady operation and steam quality. Therefore, the online checking of the indication value of the main steam flowmeter of the boiler can meet the requirement of rapidly judging the accuracy of the main steam flowmeter on the industrial site, the trouble of disassembly and inspection is avoided, and the important function is played in the aspects of ensuring the performance of the instrument and improving the economic benefit.
Finally, it is noted that the above embodiments are only for illustrating the technical solution of the present invention and not for limiting the same, and although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications and equivalents may be made thereto without departing from the spirit and scope of the technical solution of the present invention, which is intended to be covered by the scope of the claims of the present invention.
Claims (6)
1. The online checking and testing system for the main steam flowmeter of the boiler based on the internet of things is characterized by comprising a data acquisition unit, a wireless transmission unit and a data processing unit, wherein the main steam flowmeter of the boiler refers to a steam flowmeter on a main steam pipeline of an industrial site gas boiler; wherein,
the data acquisition unit is used for acquiring basic data including the combustion temperature of a boiler hearth, the water level of the boiler, the gas flow of the boiler, the temperature, the pressure and the flow of boiler feed water, the temperature, the flow of boiler sewage and the steam temperature, the pressure and the flow of a main steam flowmeter;
the wireless transmission unit comprises a wireless transmission module and a wireless receiving module, wherein the wireless transmission module is used for transmitting various basic data acquired by the data acquisition unit, and the wireless receiving module is used for receiving various basic data and transmitting the basic data to the data processing unit;
the data processing unit comprises a data server and a display, wherein the data server is used for carrying out digital correction on various basic data transmitted by the wireless receiving module, calculating a calculated value of the steam flow of the main steam pipeline according to a mass balance method, comparing and analyzing the calculated value with an indication value of the self flow of the main steam flowmeter, highlighting corresponding parameters and carrying out alarm prompt when the relative error between the calculated value and the indication value of the main steam flow exceeds a set limit range, and carrying out evaluation analysis on the historical data of the main steam flowmeter to give out the probability of performance decline or inaccuracy of the main steam flowmeter; wherein,
the obtaining of the comprehensive flow proportionality coefficient f specifically comprises the following steps: according to the measuring range or the common measuring range of the main steam flowmeter, n flow check points i are selected, each flow point reads data for at least three times, and the average value is taken to obtain the water supply flow G of each flow check point 0i And the sewage flow rate G 1i Difference G of 0i -G 1i Indication value V of main steam flowmeter i Calculating the proportionality coefficient f of each flow point i i ＝(G 0i -G 1i )/V i The method comprises the steps of carrying out a first treatment on the surface of the If the proportionality coefficient f of each flow point i i Near linearity, weighting lambda according to each point i A composite flow scaling factor f is calculated to fit the corrected primary steam flow meter indication,
2. the online checking and testing system for the main steam flowmeter of the boiler based on the internet of things technology according to claim 1, wherein the data acquisition unit comprises temperature sensors for acquiring combustion temperature of a boiler furnace, medium temperature in a boiler water supply pipeline, medium temperature in a boiler sewage pipeline and steam medium temperature in a main steam pipeline, a water level sensor for acquiring water level of the boiler drum, flowmeters for acquiring fuel gas consumption of the boiler, water supply flow of the boiler, blowdown water flow of the boiler and steam flow in the main steam pipeline, and pressure sensors for acquiring medium pressure in the boiler water supply pipeline and steam medium pressure in the main steam pipeline.
3. The online checking and testing system for the main steam flowmeter of the boiler based on the internet of things technology according to claim 2, wherein the temperature sensor is a thermal resistor or a thermocouple.
4. The online checking and testing system for the main steam flowmeter of the boiler based on the internet of things technology according to claim 1, wherein the flowmeter is an orifice flowmeter, an electromagnetic flowmeter or a vortex shedding flowmeter.
5. The online checking and testing system of the boiler main steam flowmeter based on the internet of things technology according to claim 1, wherein the wireless transmitting module and the wireless receiving module are a WIFI module, a ZigBee module or a GPRS module.
6. The online checking and testing system for the main steam flowmeter of the boiler based on the internet of things technology according to claim 1, wherein when the relative error between the calculated value and the indication value of the main steam flow exceeds the set limit value range, the corresponding parameters are highlighted and the alarm prompt is carried out, the probability of the performance degradation or inaccuracy of the main steam flowmeter is given by combining with the historical data evaluation analysis of the main steam flowmeter, the comprehensive flow proportionality coefficient f is used for correcting the indication value in real time under the condition of stable operation of the main steam flowmeter in the range or the common metering range of the main steam flowmeter, and the data server also comprises a step of judging the reason for causing the abnormity of the indication value monitoring data of the main steam flowmeter through an expert database in a fuzzy algorithm according to the historical monitoring data and the mathematical control model built in the interior, and giving an adjustment feedback strategy for continuous and stable operation of the boiler according to the real-time monitoring of the demand of the steam and the calculated value of the main steam flow.
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