CN1101545C - In-line continuous measuring method for concentration and density of liquid medium - Google Patents
In-line continuous measuring method for concentration and density of liquid medium Download PDFInfo
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- CN1101545C CN1101545C CN 01113259 CN01113259A CN1101545C CN 1101545 C CN1101545 C CN 1101545C CN 01113259 CN01113259 CN 01113259 CN 01113259 A CN01113259 A CN 01113259A CN 1101545 C CN1101545 C CN 1101545C
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Abstract
The present invention relates to an on-line continuous measuring method for the concentration and the density of a liquid medium. A section of vertical measuring pipe (4) is arranged on an original medium flowing pipeline (1); two pressure measuring points are set on the vertical measuring pipe (4); a pressure difference signal is measured by a differential pressure transmitter (11). In the middle of the two pressure measuring points, one liquid medium temperature measuring point is set in the center of a measuring pipeline; the temperature of a medium is measured by a medium temperature transmitter (9). One environmental temperature measuring point is set near the differential pressure transmitter (11), and one environment temperature transmitter (10) is installed near the differential pressure transmitter (11) to measure the environmental temperature. On the basis that the three signals are measured, the concentration of the medium is obtained by the formula Con=(dP+c1*T1-c2*T2)/c3+c4. The present invention realizes the continuous on-line measurement by creating simple linear corresponding relation among the concentration, the density and the measured signal and using conventional meters.
Description
Technical field:
The present invention relates to a kind of on-line continuous detection method of concentration and density of liquid medium, be used for the parameter detecting of process industrials such as chemical industry, oil refining.
Background technology:
Industrial process automation is the pacing items and the important assurance of realize to produce safe, steady, efficient, high-quality and low consumption, and for production run being implemented effectively control, an important prerequisite is exactly the information that will obtain controlled variable.Concerning concrete production run, wish really that controlled technological parameter mostly is that concentration, aggregate rate, yield, raw gasoline are done, the direct what is called " mass parameter " of reflection device situation and product quality such as light diesel fuel pour point, yield distribution.But the detection of these mass parameters is very difficult, even if some corresponding online analysing and measuring instruments are arranged, because the analysis to measure process has very big hysteresis characteristic usually, makes the very big difficulty of existence when Process Control System realizes.For this reason, general way is the purpose that reaches the control of quality index by so-called conventional variablees such as control temperature, pressure, liquid level and flows, but these parameters are indirect variable after all, can not reflect the mass parameter of process all-sidedly and accurately.
At present, occurred various online concentration analyzers both at home and abroad, having comprised: rays method, acoustic method, vibratory drilling method, conductance method, electromagnetic method, thermal conductivity method, refractometry, industrial chromatograph, mass spectrometer, viscosity meter method etc.But, nearly all these methods are when applying to the actual industrial scene, all there are various problems, as cost an arm and a leg, difficult in maintenance, measure to lag behind excessive, serviceable life short, a little less than the anti-on-the-spot interference performance, thereby many industrial processs all only depend on soft measurement and infer control the control of concentration.
As a crucial mass parameter, the detection of concentration has very important meaning to commercial production.Go up difficulty and the problem that exists mainly due to detecting, compare with parameters such as temperature, pressure, liquid level and flows, the control of mass parameter concentration still is a problem of failing to obtain fine solution.As: the concentration of polyvinyl acetate (PVAc) resin methanol solution is a key parameter that polyvinyl alcohol (PVA) (PVA) production is had material impact, at present, this resin concentration almost adopts viscosity meter to measure bar none, this surveying instrument mostly needs from external import, cost an arm and a leg, difficult in maintenance, range ability is difficult to adjust, relation between concentration and viscosity, temperature is seriously nonlinear, and (bright light is flat, and the polyvinyl acetate concentration control system is transformed and this relation will could obtain by a large amount of experiments, the polyvinyl communication, 2000,19 (4), 34-39.).And for example: sulphur hydracid sodium solution is as the solvent of polyacrylonitrile, and the variation of its concentration directly influences the quality of solubility property, so it will be controlled in the strict scope.For reducing unit consumption, need the sulphur hydracid sodium solution in the recovery system, it is carried out recycling after filtration treatment and the evaporation and concentration.In the process that it is concentrated with vaporising device, its outlet sulphur hydracid sodium solution concentration is to need to detect and the key parameter of control.Owing to there is not effective detection means, often adopt the method for " soft measurement ", promptly utilize the parameter that can record that exit concentration is estimated (" five imitate the foundation of vaporising device soft-sensing model ", Tian Ronghai etc., " chemical process automation and instrument ", 2000,27 (6) 8～10).The problem that this method exists is:
1) exit concentration and the relation between a plurality of measurable variable to be estimated usually are very complicated, are difficult to obtain the higher detection precision.Under many situations, even this relation also not necessarily exists.
Therefore 2) along with the variation of operating mode, it is inaccurate that the relation that originally obtained also can become usually, need carry out online correction to model, and this itself is exactly under study for action a problem still.
3) soft measurement is generally based on data analysis and processing, and its physical significance is indeterminate, and operating personnel often are difficult for accepting.
4) because model is comparatively complicated usually, the variable that relates to is also more, and soft measurement will take more computational resource.This computer-controlled enterprise that some still are unrealized, it realizes problem especially.
Can see that by above-mentioned analysis developing simple and practical, reliable and stable mass parameter detection system is highly significant, is with a wide range of applications.
Summary of the invention:
The present invention is directed to the problems referred to above of prior art, a kind of on-line continuous detection method of new concentration and density of liquid medium is provided, by setting up simple linear corresponding relation between concentration, density and measured signal, the signal that adopts conventional instrument to record obtains concentration and density information, realizes continuous on-line detection.Because under many circumstances, have the simple corresponding relation of determining between concentration and the density, therefore for sake of convenience, instructions of the present invention only is that example is described with concentration.
According to the fluid mechanics law, when medium flowed on vertical pipeline, the pressure differential of any two measuring points was made up of two parts, i.e. differential static pressure and frictional resistance, and wherein differential static pressure depends on the concentration (density) of medium under the fixing situation of two point positions.In order from the differential pressure output signal, to obtain the concentration information of medium exactly, need from the differential pressure signal that records, reject the frictional resistance signal.In addition, also to give and compensate the error that medium temperature and variation of ambient temperature cause.
Thus, in the technical scheme of the present invention, the on-line continuous that adopts conventional two flange differential pressure transmitters to carry out concentration and density detects, and liquid medium temperature measuring point and environment temperature measuring point rationally are set, and medium temperature and environment temperature are compensated.Measuring system disposes one section vertical survey pipe on former media flow pipeline, for implementing fast and effectively control automatically, this measuring tube should place the position to the control action sensitivity as far as possible, promptly near the concentration adjustment valve.The connection of vertical survey Guan Yuyuan trunk line can be adopted modes such as concentric reducer connection, welding.Respectively keep a bit of straight length before and after two pressure taps of vertical survey Guan Shangshe, two pressure taps, by the differential pressure signal between two pressure taps of differential pressure transmitter measurement.A valve respectively is installed on the pressure guiding pipe between vertical survey pipeline and the joint flange.The center is provided with a liquid medium temperature measuring point in the middle of two pressure taps, in the measuring channel, by medium temperature transmitter measuring media temperature.An environment temperature measuring point is set, by environment temperature transmitter measures ambient temperature near differential pressure transmitter.For attractive in appearance and easy for installation, the environment temperature transmitter can adopt micro temperature sensor.
The primary instrument that the present invention adopts has:
(a) two flange differential pressure transmitters: precision prescribed is 0.1, determines according to concentration change scope, medium temperature and environment temperature at range and zero point, makes the differential pressure of two measuring points in the measurement range of instrument.
(b) medium temperature transmitter: according to the variation range of medium temperature, select the temperature transmitter of suitable range for use, error is in 1 ℃.General thermal resistance, thermopair can reach requirement.
(c) environment temperature transmitter: according to the variation range of environment temperature, select the temperature transmitter of suitable range for use, error is in 1 ℃.General thermal resistance, thermopair can reach requirement.
The secondary instrument that the present invention adopts is less demanding, can carry out simple addition subtraction multiplication and division computing and get final product.
The present invention is on the basis that records above-mentioned three signals, and the calculating formula below utilizing can obtain concentration of medium Con:
Con＝(dP+c1*T1-c2*T2)/c3+c4
Wherein, dP is the differential pressure transmitter output signal; T1 is the resin temperature signal; T2 is an ambient temperature signal.C1, c2, c3, c4 are several important parameters, their meaning and act on as follows:
C1: the fluid media (medium) temperature variation was once the time, and the differential pressure that causes owing to volumetric expansion changes (can be calculated by the volume expansivity of medium), and it act as the medium temperature compensation.In general, to certain concrete measuring system, this parameter is fixed.
C2: variation of ambient temperature had been once the time, and owing to the differential pressure that causes that expands of filling liquid volume in the double flanges differential pressure transmitter kapillary changes (can be calculated by the volume expansivity of filling liquid), it act as ambient temperature compensation.In general, to certain concrete measuring system, this parameter is fixed.
C3: the caused differential pressure of a unit of concentration change (as 1%) changes, and its effect is that differential pressure signal is converted to concentration signal.In general, to certain concrete measuring system, this parameter is fixed.
C4: instrument is regulated, correction factor, and its effect is to make the adjustment of measuring system convenient and easy, and concerning certain concrete measuring system, it is unique adjusting parameter.
Compare with concentration detection system of the prior art, the present invention has following clear superiority:
1. system is based on the differential pressure method principle, has the simple linear relationship of determining between concentration and three signals being surveyed, is easy to realize.
2. the employing conventional instrument is stable and reliable for performance, the response time fast (retardation time is little), thereby closed-loop control is effective.
3. price is low, and the cost of a cover system is roughly 20,000 yuans; Easy to maintenance, long service life.
4. range (only need online adjustment zero shift and setup parameter c4) easy to adjust applicable to large-scale measurement of concetration, is promptly realized the measurement of any concentration is not needed any additional hardware input.
5. the precision owing to present differential pressure transmitter can reach more than 0.1%, and temperature detecting precision is also high, because of
And this measuring system has higher precision, and the typical error value is in 0.5%.
Densimeter formula of the present invention is a very common simple relation formula, and general secondary instrument all has this calculation function.
It is emphasized that a key property of the present invention is the concentration detection that it can be applied to flow media, the measurement of concetration of quiescent atmosphere is as a special case, and is then much easier.
Description of drawings:
Fig. 1 is system configuration of the present invention and scheme of installation.
As shown in the figure, measuring system disposes one section vertical survey pipe 4 on former media flow pipeline 1, long 1500mm, and caliber 400mm can be so that mobile stable, and frictional resistance is little, overcomes the influence of frictional resistance effectively.For implementing fast and effectively control automatically, this measuring tube 4 should place the position to the control action sensitivity as far as possible, promptly near the concentration adjustment valve.Vertical survey pipe 4 is connected by concentric reducer 2 with former media flow pipeline 1.One valve 5 respectively is installed on the pressure guiding pipe between vertical survey pipeline 4 and the joint flange 8, and valve-off 5 can pull down that differential pressure transmitter is debugged, maintenance etc. and do not influence production.Vertical survey pipe 4 is established two pressure taps, and the differential pressure signal between two pressure taps is drawn by pressure guiding pipe, is recorded by joint flange 8 by differential pressure transmitter 11.Distance between two pressure taps i.e. distance between two flanges, 8 central points is 1100mm, respectively keeps the 200mm straight length before and after two measuring points.The center is provided with a liquid medium temperature measuring point in the middle of two pressure taps, in the measuring channel, by medium temperature transmitter 9 measuring media temperature.An environment temperature measuring point is set near differential pressure transmitter 11, environment temperature transmitter 10 measures ambient temperature are installed.The signal output of differential pressure transmitter 11, medium temperature transmitter 9 and environment temperature transmitter 10 is connected to Distributed Control System (DCS) 12 (DCS) as the input of secondary instrument.
Specific implementation method:
Below describe how to realize the present invention in detail by a concrete application example.
Technological parameter and other parameter are: the medium maximum flow is 32m
3/ h, peak viscosity is 500cP, the proportion that concentration change 1% causes is changed to 0.0039, the concentration change scope is 20% to 30%, the proportion that medium temperature causes when changing 1 ℃ is changed to 0.000663, the medium temperature variation range is 55 ℃ to 70 ℃, and the proportion that causes during 1 ℃ of variation of ambient temperature is changed to 0.000891, and the variation of ambient temperature scope is-25 ℃ to 40 ℃.
The installation of measuring channel such as Fig. 1.Calculate as can be known according to fluid mechanics, fluid flowing in measuring channel is laminar flow, and the maximum friction pressure drop is 0.7917mmH
2O.
The selection of range: the differential pressure that concentration change causes is changed to: 1100*0.0039* (30-20)=42.9 (mmH
2O), medium temperature changes the differential pressure cause and is changed to: 1100*0.000663* (70-55)=10.4 (mmH
2O), the differential pressure that causes of variation of ambient temperature is changed to: 1100*0.000891* (40+25)=63.7 (mmH
2O).In view of the above, range is chosen as: (42.9+10.4+63.7)=117 (mmH
2O), be taken as 120mmH
2O.
Zero shift: zero shift is online to carry out, so that differential pressure signal drops in the range of differential pressure transmitter.
Parameter is definite in the densimeter formula: c1=1100*0.000663=0.7293; C2=1100*0.000891=0.9801; C3=1100*0.0039=4.29; C4 is obtained by on-line proving, and its value should make the resulting value of densimeter formula equate with actual calibration value.Because this effect of c4, make frictional pressure drop obtain finely overcoming, in addition the maximal value of frictional pressure drop is here compared or is smaller with the differential pressure that concentration change causes to the influence of precision.
Claims (2)
1, a kind of on-line continuous detection method of concentration and density of liquid medium, it is characterized in that going up configuration one section vertical survey pipe (4) at former media flow pipeline (1), measuring tube (4) places near the concentration adjustment valve, vertical survey pipe (4) is connected by concentric reducer (2) with former media flow pipeline (1), mounted valve (5) on the pressure guiding pipe between vertical survey pipeline (4) and the joint flange (8), vertical survey pipe (4) is established two pressure taps, differential pressure signal between two pressure taps is drawn by pressure guiding pipe, record by joint flange (8) by differential pressure transmitter (11), respectively keep a bit of straight length before and after two pressure taps, in the middle of two pressure taps, the center is provided with a liquid medium temperature measuring point in the measuring channel, by medium temperature transmitter (9) measuring media temperature, an environment temperature measuring point is set near differential pressure transmitter (11), an environment temperature transmitter (10) measures ambient temperature is installed, differential pressure transmitter (11), the signal output of medium temperature transmitter (9) and environment temperature transmitter (10) is connected to Distributed Control System (DCS) (12) as the input of secondary instrument.
2, as the on-line continuous detection method of the said a kind of concentration and density of liquid medium of claim 1, it is characterized in that recording on the basis of above-mentioned three signals in system, the calculating formula below utilizing obtains concentration of medium:
Con＝(dP+c1*T1-c2*T2)/c3+c4
Wherein, dP is that differential pressure transmitter output signal T1 is the resin temperature signal; T2 is an ambient temperature signal, c1 is that the fluid media (medium) temperature variation was once the time, the differential pressure that causes owing to volumetric expansion changes, c2 is that variation of ambient temperature was once the time, the differential pressure that causes owing to filling liquid volume expansion in the double flanges differential pressure transmitter kapillary changes, c3 is that the caused differential pressure of unit of concentration change changes, and c4 is that instrument is regulated, correction factor.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 01113259 CN1101545C (en) | 2001-07-05 | 2001-07-05 | In-line continuous measuring method for concentration and density of liquid medium |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 01113259 CN1101545C (en) | 2001-07-05 | 2001-07-05 | In-line continuous measuring method for concentration and density of liquid medium |
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| Publication Number | Publication Date |
|---|---|
| CN1338587A CN1338587A (en) | 2002-03-06 |
| CN1101545C true CN1101545C (en) | 2003-02-12 |
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| CN 01113259 Expired - Fee Related CN1101545C (en) | 2001-07-05 | 2001-07-05 | In-line continuous measuring method for concentration and density of liquid medium |
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Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7860669B2 (en) | 2008-06-17 | 2010-12-28 | Saudi Arabian Oil Company | System, program product, and related methods for estimating and managing crude gravity in flowlines in real-time |
| US7668688B2 (en) | 2008-06-17 | 2010-02-23 | Saudi Arabian Oil Company | System, program product, and related methods for estimating and managing crude gravity in real-time |
| CN102147625B (en) * | 2010-02-08 | 2013-03-13 | 鞍钢股份有限公司 | Regenerated acid density detection control device and method |
| CN102313138B (en) * | 2010-07-06 | 2013-05-01 | 中国石油天然气集团公司 | Online density measurement method of petroleum transmission pipeline |
| CN108195716A (en) * | 2017-12-25 | 2018-06-22 | 攀枝花钢企欣宇化工有限公司 | Brine strength on-line measuring device and detection method |
| CN110776341A (en) * | 2019-10-24 | 2020-02-11 | 中化重庆涪陵化工有限公司 | Automatic optimization online adjusting system and method for barren liquor regeneration |
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