CN111060478A - Method and device for automatically monitoring content of acetic anhydride - Google Patents
Method and device for automatically monitoring content of acetic anhydride Download PDFInfo
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- CN111060478A CN111060478A CN202010136425.0A CN202010136425A CN111060478A CN 111060478 A CN111060478 A CN 111060478A CN 202010136425 A CN202010136425 A CN 202010136425A CN 111060478 A CN111060478 A CN 111060478A
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Abstract
The invention belongs to the field of crude acetic anhydride production, and particularly relates to a method and a device for automatically monitoring the content of acetic anhydride. The method is characterized by comprising the steps of S1, measuring the refractive index n of the mixture in the circulating pipeline by using an online refractometer; s2, the controller judges whether the mixture refractive index n is between a first threshold value n1 and a second threshold value n2, adjusts the size of the feeding adjusting valve, and controls the discharge valve to output the mixture at proper time. The device comprises a material supplementing adjusting valve, a discharge valve, an online refractometer and a controller, wherein the online refractometer is arranged on a bypass branched by a mixture circulating pipeline, and the controller is electrically connected with the material supplementing adjusting valve, the discharge valve and the online refractometer respectively. The method can measure the concentration of acetic anhydride in the circulating pipeline in real time, and the controller can automatically adjust the supply amount of glacial acetic acid according to the concentration, so that the working efficiency is high. The device can be realized without great transformation, and the economic benefit is obvious.
Description
Technical Field
The invention belongs to the field of crude acetic anhydride production, and particularly relates to a method and a device for automatically monitoring the content of acetic anhydride.
Background
In the existing acetic anhydride production process, referring to fig. 2, ketene gas enters from the bottom of an absorption tower 1, glacial acetic acid enters from the top of the tower through a regulating valve 5 and reacts with the ketene to obtain acetic anhydride, a circulating pump 2 pumps a mixture of the acetic anhydride and the acetic acid obtained by reaction in the absorption tower 1 into a circulating pipeline, the circulating pipeline is provided with a sampling port and a discharge port which are respectively controlled by valves, the acetic anhydride content can be discharged outwards when the acetic anhydride content is about 85%, otherwise, the discharged mixture stops flowing back into the absorption tower, the existing method is to measure the acetic anhydride content of the mixture obtained by the sampling port by using a chromatograph, the obtained result is fed back to production operators, the operators adjust the glacial acetic acid supply according to the result, and when the acetic anhydride content is too high, the glacial acetic acid supply is increased, otherwise, the glacial acetic acid supply is reduced, so as. The method has the advantages that the content of the mixture of acetic anhydride and acetic acid needs to be continuously monitored in the production process of the acetic anhydride, the process is continuously operated, although the accuracy of measuring the content of the acetic anhydride by adopting a chromatographic method is high, the measuring speed is low, the content change of the mixture of the acetic anhydride in a circulating pipeline cannot be immediately tracked, the manufacturing cost of the chromatographic measuring instrument is high, the glacial acetic acid supply is manually adjusted, and the working efficiency is low.
Disclosure of Invention
The invention aims to provide a method and a device for automatically monitoring a valve for the content of acetic anhydride in a crude product, which aim to solve the technical problem that the existing production process has overhigh manufacturing cost and low working efficiency.
The technical scheme of the invention is realized as follows,
a method for automatically monitoring the content of acetic anhydride comprises the following steps of S1, measuring the refractive index n of a mixture in a circulating pipeline by using an online refractometer;
s2, the controller judges whether the mixture refractive index n is between a first threshold value n1 and a second threshold value n2, if not, the controller sends an instruction to close the discharge valve and adjust the size of the material supplementing regulating valve, and if yes, the controller sends an instruction to open the discharge valve to output the mixture.
Further, the first threshold n1 is 1.3835.
Further, the second threshold n2 is 1.3859.
Further, in the step S2, the controller determines whether the refractive index n of the mixture is between a first threshold n1 and a second threshold n2, if not, the controller instructs the discharge valve to be closed and the size of the feed supplement regulating valve to be adjusted, if yes, the controller instructs the discharge valve to be opened to output the mixture, and if n is not equal to the optimal value n3, the controller instructs the feed supplement regulating valve to be adjusted.
Further, the optimal value n3 is 1.3847.
The method for automatically monitoring the content of the acetic anhydride is different from the prior art in that an online refractometer is adopted to measure the refractive index of a mixture in a circulating pipeline, and the content of the acetic anhydride in the mixture is obtained according to the principle that a certain refractive index corresponds to a certain content (concentration) of the acetic anhydride.
Based on the method for automatically monitoring the content of the acetic anhydride, the invention provides a device for automatically monitoring the content of the acetic anhydride, which comprises a material supplementing adjusting valve, a discharge valve, an online refractometer and a controller, wherein the online refractometer is arranged on a bypass branched by a mixture circulating pipeline, the controller is respectively and electrically connected with the material supplementing adjusting valve, the discharge valve and the online refractometer, and the controller respectively controls the material supplementing adjusting valve and the discharge valve according to the output information of the online refractometer.
Further, the controller is a PLC controller.
Above-mentioned device can realize acetic anhydride content real-time detection and automatic control glacial acetic acid supply volume, and work efficiency is high, and current equipment need not big transformation can realize, and economic benefits is obvious.
It should be noted that the optimal value n3 refers to the refractive index of the mixture corresponding to the standard acetic anhydride content, the first threshold n1 and the second threshold n2 refer to the refractive index of the mixture corresponding to two content values which meet the discharge standard and are near the standard acetic anhydride content, respectively, and the standard acetic anhydride content and the two content values near the standard acetic anhydride content are determined by the production practice.
Drawings
FIG. 1 is a schematic structural diagram of an acetic anhydride production apparatus according to an embodiment of the present invention;
FIG. 2 is a schematic view of the structure of an acetic anhydride manufacturing apparatus in the prior art
FIG. 3 is a diagram showing the relationship between the content of acetic anhydride and the refractive index of the mixture.
In the figure, 1. an absorption tower; 2. a circulation pump; 3. an online refractometer; 4. a discharge valve; 5. a material supplementing regulating valve; 6, a PLC controller; 7. and a sampling valve.
Detailed Description
The present invention will be described in detail with reference to examples.
The results of the mixture refractive index test and the chromatographic test results are compared in a laboratory, and a relationship diagram of the acetic anhydride content and the mixture refractive index is obtained after linear regression statistics, and is shown in fig. 3. The precision of the refractometer used in the test data experiment of FIG. 3 is 0.0001, and the precision of the actually installed online refractometer can reach 0.00001 even 0.0000001.
Fig. 3 shows that when the content of acetic anhydride is increased, the refractive index is also increased, in this embodiment, the refractive index of the mixture corresponding to the standard content of acetic anhydride is 85%, the refractive index of the mixture is 1.3847, when the content of acetic anhydride is 80% -90%, the refractive index of the mixture corresponding to the 80% content of acetic anhydride is 1.3835, and the refractive index of the mixture corresponding to the 90% content of acetic anhydride is 1.3859.
A method for automatically monitoring the content of acetic anhydride comprises the following steps,
s1, measuring the refractive index n of the mixture in the circulating pipeline by using an online refractometer;
s2, the controller judges whether the refractive index n of the mixture is between 1.3835 and 1.3859, if not, the content of acetic anhydride in the mixture in the circulating pipeline does not meet the discharge standard, the controller sends an instruction to close the discharge valve and instructs to adjust the size of the feed supplement adjusting valve, the change of the amount of glacial acetic acid correspondingly changes the content of acetic anhydride until the content of acetic anhydride meets the discharge standard, if so, the content of acetic anhydride in the mixture in the circulating pipeline meets the discharge standard, the controller sends an instruction to open the discharge valve to output the mixture, when the refractive index n is less than 1.3847, the controller sends an instruction to reduce the size of the feed supplement adjusting valve and reduce the amount of glacial acetic acid to further improve the content (concentration) of acetic anhydride, when n is more than 1.3847, the controller sends an instruction to increase the size of the feed supplement adjusting valve and increase the amount of glacial acetic acid to further reduce the content of acetic anhydride until the content of, the mixture with the content meeting the standard acetic anhydride is obtained at the discharge port, and the automatic control effect is achieved.
Referring to fig. 1, a schematic structural diagram of the device for automatically monitoring the content of acetic anhydride in actual production is shown, and the device comprises a feeding adjusting valve 5 and a discharging valve 4, and further comprises an online refractometer 3 and a PLC controller 6, wherein the online refractometer 3 is arranged on a bypass branched by a mixture circulating pipeline, the PLC controller 6 is respectively electrically connected with the feeding adjusting valve 5, the discharging valve 4 and the online refractometer 3, and the PLC controller respectively controls the feeding adjusting valve and the discharging valve according to output information of the online refractometer 3. The device can automatically monitor the content of acetic anhydride by improving the circulating pipeline of the existing equipment to a certain extent, and has low modification cost and obvious obtained effect.
Claims (7)
1. A method for automatically monitoring the content of acetic anhydride is characterized by comprising the following steps of S1, measuring the refractive index n of a mixture in a circulating pipeline by using an online refractometer;
s2, the controller judges whether the mixture refractive index n is between a first threshold value n1 and a second threshold value n2, if not, the controller sends an instruction to close the discharge valve and adjust the size of the material supplementing regulating valve, and if yes, the controller sends an instruction to open the discharge valve to output the mixture.
2. The method for automatically monitoring the content of acetic anhydride as claimed in claim 1, wherein the first threshold n1 is 1.3835.
3. The method for automatically monitoring the content of acetic anhydride as claimed in claim 1, wherein the second threshold n2 is 1.3859.
4. The method of claim 1, wherein in step S2, the controller determines whether the refractive index n of the mixture is between a first threshold n1 and a second threshold n2, if not, the controller instructs the discharge valve to close and the feed adjusting valve to adjust, if yes, the controller instructs the discharge valve to open to output the mixture, and if n is not equal to the optimal value n3, the controller instructs the feed adjusting valve to adjust.
5. The method of claim 4, wherein the optimal value n3 is 1.3847.
6. The utility model provides an automatic device of control acetic anhydride content, includes feed supplement governing valve and bleeder valve, characterized in that, still includes online refractometer and controller, online refractometer sets up on the bypass by mixture circulating line branch, the controller is connected with feed supplement governing valve, bleeder valve, online refractometer electricity respectively, and the controller is controlled feed supplement governing valve and bleeder valve respectively according to the output information of online refractometer.
7. The apparatus according to claim 6, wherein the controller is a PLC controller.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
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| CN202010136425.0A CN111060478A (en) | 2020-03-02 | 2020-03-02 | Method and device for automatically monitoring content of acetic anhydride |
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| CN202010136425.0A CN111060478A (en) | 2020-03-02 | 2020-03-02 | Method and device for automatically monitoring content of acetic anhydride |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117969454A (en) * | 2024-04-01 | 2024-05-03 | 安徽天成新材料有限公司 | Method and device for automatically monitoring acetic anhydride content |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117969454A (en) * | 2024-04-01 | 2024-05-03 | 安徽天成新材料有限公司 | Method and device for automatically monitoring acetic anhydride content |
| CN117969454B (en) * | 2024-04-01 | 2024-06-18 | 安徽天成新材料有限公司 | Method and device for automatically monitoring acetic anhydride content |
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