CN105404251A - Polyvinyl chloride synthesis process low-boiling column exhaust condensation on-line monitoring and alarm method - Google Patents
Polyvinyl chloride synthesis process low-boiling column exhaust condensation on-line monitoring and alarm method Download PDFInfo
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- CN105404251A CN105404251A CN201510602436.2A CN201510602436A CN105404251A CN 105404251 A CN105404251 A CN 105404251A CN 201510602436 A CN201510602436 A CN 201510602436A CN 105404251 A CN105404251 A CN 105404251A
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- tail gas
- alm
- time
- gas condenser
- outlet temperature
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
- G05B19/00—Programme-control systems
- G05B19/02—Programme-control systems electric
- G05B19/418—Total factory control, i.e. centrally controlling a plurality of machines, e.g. direct or distributed numerical control [DNC], flexible manufacturing systems [FMS], integrated manufacturing systems [IMS], computer integrated manufacturing [CIM]
- G05B19/41875—Total factory control, i.e. centrally controlling a plurality of machines, e.g. direct or distributed numerical control [DNC], flexible manufacturing systems [FMS], integrated manufacturing systems [IMS], computer integrated manufacturing [CIM] characterised by quality surveillance of production
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- G—PHYSICS
- G08—SIGNALLING
- G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
- G08B21/00—Alarms responsive to a single specified undesired or abnormal condition and not otherwise provided for
- G08B21/18—Status alarms
Abstract
The invention provides a polyvinyl chloride synthesis process low-boiling column exhaust condensation on-line monitoring and alarm method. The method is characterized in that the changing trend of the temperature is estimated by employing the temperature of an outlet of an exhaust condenser, and the decrease of the condensation efficiency is detected as soon as possible by employing derivative information. If the efficiency of the exhaust condenser is reduced and the phenomenon of freezing occurs, the temperature of the exhaust outlet will be obviously reduced.
Description
Technical field
The invention belongs to production of chlor-alkali chemical industry process automation field, particularly relate to the low on-line monitoring of tower tail gas condensing and the alarm method of boiling of Polyvinylchloride building-up process.
Background technology
Polyvinylchloride (PVC) is a kind of important organic synthesis material in chlorine industry, is widely used in industry, agricultural and daily life.Vinyl Chloride Synthesis is one of key link in chlorine industry, provides base stock for producing PVC.VCM synthesis technique is mainly divided into acetylene method and ethylene process.Due to the energy structure that China is special, acetylene method becomes the main technique of producing vinyl chloride monomer.By the end of the year 2008, China will have accounted for more than 25% of global Production of PVC ability based on the Production of PVC ability of acetylene method.This technology utilization calcium carbide prepares acetylene gas, is mixed by hydrogen chloride gas, and be converted into vinyl chloride monomer by addition reaction with acetylene gas, as the raw material of subsequent polymerisation reaction.
Consider the productivity factors in actual production run, and in order to production safety be excessive as the hydrogen of one of reactant, be still mixed with the hydrogen of non-complete reaction, hydrogen chloride and acetylene gas in vinyl chloride monomer.Therefore, before carrying out final polyreaction, first should carry out rectifying to the raw material vinyl chloride monomer of polyreaction, reclaim foreign gas to improve the purity of vinyl chloride monomer.Vinyl chloride monomer is first through the too low tower that boils, and after rectifying, the vinyl chloride monomer concentration of bottom product obtains raising to a certain extent, and bottom product is sent to the height tower that boils and further purifies subsequently.It should be noted that the overhead product of the low tower that boils is still containing part vinyl chloride monomer.Therefore, in order to ensure the efficiency of rectifying, needing to carry out condensation operation to overhead product, then being sent into the charging of the low tower that boils by backflow.First overhead product carries out condensation by 7 degree of water, and then tail gas continues through tail gas condenser, utilizes negative 35 degree of salt solution to make vinyl chloride monomer condense into liquid state further.But, if containing more water vapor in tail gas, tail gas condenser can be caused to occur icing phenomenon, finally affect the condensation efficiency of tail gas.
In the production run of reality, once find that freezing appears in tail gas condenser, negative 35 degree of salt solution can be closed, utilize the heat of tail gas itself to carrying out of tail gas condenser ice.At present, industry spot judges that the method for tail gas condensing efficiency mainly relies on and arranges the exhaust temperature upper limit: if exhaust temperature exceedes this threshold value, then can conclude that more serious icing phenomenon appears in tail gas condenser.But this way does not have gratifying ageing, and consider the drift that actual temperature measured value exists, be also difficult to rational definite threshold.Therefore, in the application of reality, be difficult to the reduction detecting tail gas condenser efficiency in time: when final generation is reported to the police, very serious icing phenomenon may appear in tail gas condenser.
For above problem, the object of the invention is based on daily real-time service data, for real process variable measurement noises and skew, set up a kind of on-line monitoring and alarm method of effective tail gas condensing efficiency in real time, thus the decline of tail gas condensing efficiency can be found early, avoid tail gas condenser to occur too serious icing phenomenon.
Summary of the invention
Object of the present invention: provide the low on-line monitoring of tower tail gas condensing and the alarm method of boiling of Polyvinylchloride building-up process.The invention is characterized in: by utilizing the outlet temperature of tail gas condenser, estimating its trend changed, and utilize derivative information to detect the decline of condensation efficiency as early as possible.This is because if the efficiency of tail gas condenser reduces and starts to occur icing phenomenon, the outlet temperature of tail gas there will be obvious downtrending.
The invention is characterized in, described method realizes according to the following steps successively in host computer:
Step 1. initialization alarm configuration data.Be configured in initial time accumulative warning quantity: RL
alm(0)=0.
Step 2. utilizes OPC real-time data base, obtain tail gas condenser outlet temperature T (i) of current sample time and a N continuous sampling instant before tail gas condenser outlet temperature historical measurement data, structure monitor window { T (k), k=i-N, i-N+1 ... i}.
Step 3. estimates rate of change D (i) of current time outlet temperature in the following manner in real time:
D＝[D(i-N+1)D(i-N+2)…D(i)]
T
Step 4. upgrades the variation tendency T of exhaust temperature in the following manner
r(i):
Step 5., according to following logic, produces caution signal Alm (i)=0 of current time:
Step 6., according to following logic, upgrades current time accumulative warning amount R L
alm(i):
Step 7. on-line early warning.If accumulative warning amount R L
almi () is greater than n, be then alerting signal that associated field operating personnel point out tail gas condenser efficiency to decline.
Accompanying drawing explanation
Fig. 1 is on-line monitoring and the alarm method process flow diagram of the embodiment of the present invention.
Fig. 2 is a kind of mode that the on-line monitoring of the embodiment of the present invention and alarm method realize in host computer.
Embodiment
Below in conjunction with drawings and Examples, the specific embodiment of the present invention is described in further detail.Following examples for illustration of the present invention, but are not used for limiting the scope of the invention.
The technical scheme of the embodiment of the present invention provides a kind of Polyvinylchloride building-up process the low on-line monitoring of tower tail gas condensing and the alarm method of boiling, and said method comprising the steps of: from DCS (DistributedControlSystem) control system off-line data collecting and process; Off-line determination associated monitoring parameter; Utilize OPC (OLEforProcessControl), online acquisition tail gas condenser outlet temperature, and the rate of change of real-time estimated exhaust gas condensator outlet temperature; To the on-line monitoring of tail gas condenser outlet temperature, detect the reduction of tail gas condenser efficiency in advance.
In the production run of reality, the measured value of tail gas condenser outlet temperature has measurement noises.Further, due to the accuracy limitations of actual number mode convertion, the precision of the measured value of temperature can only be retained in one decimal place.Thus, the variation tendency of exhaust temperature is submerged in measurement noises, and its rate of change is also difficult to utilize the difference of offgas outlet temperature (differences of adjacent two sampling instants of measured temperature) to estimate exactly.
For the offgas outlet condensing temperature (T (i) of a current time i and upper moment i-1, T (i-1)), in ideal conditions, when also namely there is not the skew of measurement noises or measurement, offgas outlet rate temperature change D (i) of current time can utilize the difference of adjacent moment to calculate:
D(i)＝T(i)-T(i-1)，
But practical problems is, when there is measurement noises, utilize the rate of change of above formula estimated exhaust gas temperature to there is very large error, and the calculated value of D (i) is also difficult to the reasonable early warning reference as low tower tail gas condensing efficiency of boiling.
For the time series with certain Long-term change trend, the measured value in its neighbouring sample moment can't have obvious difference.In other words, the numerical value of T (i)-T (i-1) should be unable to be excessive.Based on above consideration, offgas outlet rate temperature change D (i) can utilize following optimization problem to estimate:
Wherein, N is the size of monitor window, and λ is the penalty factor of exhaust temperature rate of change.The final goal of above-mentioned optimization problem is from being extracted the essential change trend of data the observation data T (i) of noise pollution
Above-mentioned optimization problem can utilize the method for least square to solve:
D＝[D(1)D(2)…D(N)]
T
It should be noted that in above-mentioned optimization problem, give tacit consent to gas rate temperature change penalty factor λ is known quantity.For the value of optimum λ, can Bayes principle be utilized, estimate from historical operating data.The measured value of temperature can represent in such a way:
Wherein, e (i) is measurement noises.Above formula is extended to vectorial situation, obviously has:
E＝[e(1)e(2)…e(N)]
T
D＝[D(1)D(2)…D(N)]
T
In fact, the optimization problem involved by the estimation of exhaust temperature rate of change is considered
its essence is: if { D (i) } and { e (i) } is the independent identically distributed time series of Normal Distribution, and { D (i) } and { e (i) } is independent mutually, so in fact this optimization problem is equivalent to the maximum likelihood function of maximization observation data on probability meaning.If
then observation data { T (i)-T (0) } also obeys following normal distribution:
Further, under Bayesian frame, the correlation parameter of normal distribution
by the probability of maximization observation data, also namely can be determined by following optimization problem:
After the correlation parameter determining normal distribution, exhaust temperature rate of change penalty factor λ determines according to the following formula:
For the on-line implement of low boil tower tail gas condensing efficiency monitoring and early warning, this method is by the method for sliding window, rate of change D (i) of real-time monitoring tail gas condenser outlet temperature: if rate of change D (i) exceedes certain threshold value h, then can detect the decline of tail gas condenser efficiency in advance.Because it is the normal distribution of 0 that this method supposes that exhaust temperature rate of change obeys average in normal conditions, then monitoring threshold value can determine according to 3-sigma principle:
h＝3σ
2
In order to reduce rate of false alarm further, this method have employed RL (runlength) method process alerting signal, its concrete operations mode is as follows: only have the exhaust temperature rate of change in a continuous n moment to be greater than threshold value h, just can send early warning signal to associated field operating personnel.
Overall implementation calculation flow chart of the present invention is shown in accompanying drawing 1, mainly comprises following steps:
Steps A: off-line determination associated monitoring parameter, idiographic flow is as follows.
Steps A 1: utilize DCS system, from the historical measurement data of historical data base collection from tail gas condenser outlet temperature.
Steps A 2: from historical measurement data, extracts the outlet temperature measured value run in normal conditions with tail gas condenser: { T
b(i), i=i
0, i
0+ 1 ... i
0+ N
b.
Steps A 3: estimated exhaust gas outlet temperature measurement noises and tail gas condenser rate of change normal distribution probability model parameter
above parameter can be determined by following optimization problem:
Steps A 4: determine exhaust temperature rate of change penalty factor λ:
Steps A 5: determine exhaust temperature rate of change alarm threshold value h:
h＝3σ
2
Step B on-line monitoring and early warning, idiographic flow is as follows:
Step B1: initialization alarm configuration data.Be configured in initial time accumulative warning quantity: RL
alm(0)=0.
Step B2: utilize OPC real-time data base, obtain tail gas condenser outlet temperature T (i) of current sample time and a N continuous sampling instant before tail gas condenser outlet temperature historical measurement data, structure monitor window { T (k), k=i-N, i-N+1 ... i}.
Step B3: rate of change D (i) estimating current time outlet temperature in the following manner in real time:
D＝[D(i-N+1)D(i-N+2)…D(i)]
T
Step B4: the variation tendency T upgrading exhaust temperature in the following manner
r(i):
Step B5: according to following logic, produces caution signal Alm (i)=0 of current time:
Step B6: according to following logic, upgrades current time accumulative warning amount R L
alm(i):
Step B7: on-line early warning.If accumulative warning amount R L
almi () is greater than n, be then alerting signal that associated field operating personnel point out tail gas condenser efficiency to decline.
Above embodiment is only for illustration of the present invention; and be not limitation of the present invention; the those of ordinary skill of relevant technical field; without departing from the spirit and scope of the present invention; can also make a variety of changes and modification; therefore all equivalent technical schemes also belong to category of the present invention, and scope of patent protection of the present invention should be defined by the claims.The present invention has good adaptability to the random noise of actual industrial field process variable measurements and static deviation.Further, for different tail gas condensing apparatuses, the present invention can configure alarm threshold value according to unified mode, thus can reduce on-the-spot implementation cost in ground.Data acquisition and processing (DAP) in the present invention and calculating in the upper realization of Distributed Control System (DCS) (DCS), also can be realized by host computer.The calculation procedure of alerting signal can pass through real-time data base, or is obtained the real-time sampling of correlated process data by the mode of OPC, the variation tendency of offgas outlet temperature can be shown after host computer display or feeding DCS after having calculated.
Claims (1)
1. the low on-line monitoring of tower tail gas condensing and the alarm method of boiling of Polyvinylchloride building-up process, it is characterized in that, described method realizes successively according to the following steps:
Step 1. initialization alarm configuration data; Be configured in initial time accumulative warning quantity: RL
alm(0)=0;
Step 2. utilizes OPC real-time data base, obtain tail gas condenser outlet temperature T (i) of current sample time and a N continuous sampling instant before tail gas condenser outlet temperature historical measurement data, structure monitor window { T (k), k=i-N, i-N+1 ... i};
Step 3. estimates rate of change D (i) of current time outlet temperature in the following manner in real time:
D＝[D(i-N+1)D(i-N+2)…D(i)]
T
Step 4. upgrades the variation tendency T of exhaust temperature in the following manner
r(i):
Step 5., according to following logic, produces caution signal Alm (i)=0 of current time:
Step 6., according to following logic, upgrades current time accumulative warning amount R L
alm(i):
Step 7. on-line early warning; If accumulative warning amount R L
almi () is greater than n, be then alerting signal that associated field operating personnel point out tail gas condenser efficiency to decline.
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|---|---|---|---|
| CN201510602436.2A CN105404251B (en) | 2015-09-21 | 2015-09-21 | The low boiling tower tail gas condensing on-line monitoring of polyvinyl chloride building-up process and alarm method |
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|---|---|---|---|
| CN201510602436.2A CN105404251B (en) | 2015-09-21 | 2015-09-21 | The low boiling tower tail gas condensing on-line monitoring of polyvinyl chloride building-up process and alarm method |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113470331A (en) * | 2021-07-08 | 2021-10-01 | 哲弗智能系统（上海）有限公司 | Temperature difference detection method and device for temperature-sensitive detector, temperature-sensitive detector and medium |
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| US5854518A (en) * | 1998-02-23 | 1998-12-29 | Revis; Billy Wayne | Inline condensation alarm system for a central air conditioning unit |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113470331A (en) * | 2021-07-08 | 2021-10-01 | 哲弗智能系统（上海）有限公司 | Temperature difference detection method and device for temperature-sensitive detector, temperature-sensitive detector and medium |
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