CN115591497A - Control system suitable for reactor temperature of low-pressure oxo-synthesis acetic acid device - Google Patents
Control system suitable for reactor temperature of low-pressure oxo-synthesis acetic acid device Download PDFInfo
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- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 title claims abstract description 183
- 238000003786 synthesis reaction Methods 0.000 title abstract description 11
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims description 57
- 239000007788 liquid Substances 0.000 claims description 41
- 238000006243 chemical reaction Methods 0.000 claims description 33
- 239000000463 material Substances 0.000 claims description 27
- XBDQKXXYIPTUBI-UHFFFAOYSA-N dimethylselenoniopropionate Natural products CCC(O)=O XBDQKXXYIPTUBI-UHFFFAOYSA-N 0.000 claims description 26
- 238000000034 method Methods 0.000 claims description 26
- INQOMBQAUSQDDS-UHFFFAOYSA-N iodomethane Chemical compound IC INQOMBQAUSQDDS-UHFFFAOYSA-N 0.000 claims description 21
- HHLFWLYXYJOTON-UHFFFAOYSA-N glyoxylic acid Chemical group OC(=O)C=O HHLFWLYXYJOTON-UHFFFAOYSA-N 0.000 claims description 15
- 235000019260 propionic acid Nutrition 0.000 claims description 13
- IUVKMZGDUIUOCP-BTNSXGMBSA-N quinbolone Chemical compound O([C@H]1CC[C@H]2[C@H]3[C@@H]([C@]4(C=CC(=O)C=C4CC3)C)CC[C@@]21C)C1=CCCC1 IUVKMZGDUIUOCP-BTNSXGMBSA-N 0.000 claims description 13
- 230000018044 dehydration Effects 0.000 claims description 9
- 238000006297 dehydration reaction Methods 0.000 claims description 9
- 230000008569 process Effects 0.000 claims description 8
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 8
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 claims description 7
- 229910002091 carbon monoxide Inorganic materials 0.000 claims description 7
- 239000003054 catalyst Substances 0.000 claims description 5
- 229910052751 metal Inorganic materials 0.000 claims description 5
- 239000002184 metal Substances 0.000 claims description 5
- XBDQKXXYIPTUBI-UHFFFAOYSA-M Propionate Chemical compound CCC([O-])=O XBDQKXXYIPTUBI-UHFFFAOYSA-M 0.000 claims description 3
- 238000010521 absorption reaction Methods 0.000 claims description 3
- KXKVLQRXCPHEJC-UHFFFAOYSA-N acetic acid trimethyl ester Natural products COC(C)=O KXKVLQRXCPHEJC-UHFFFAOYSA-N 0.000 claims description 3
- 238000009960 carding Methods 0.000 claims description 3
- 239000012530 fluid Substances 0.000 claims description 3
- 239000008240 homogeneous mixture Substances 0.000 claims description 3
- XMBWDFGMSWQBCA-UHFFFAOYSA-N hydrogen iodide Chemical compound I XMBWDFGMSWQBCA-UHFFFAOYSA-N 0.000 claims description 3
- 239000012295 chemical reaction liquid Substances 0.000 claims description 2
- OKJPEAGHQZHRQV-UHFFFAOYSA-N Triiodomethane Natural products IC(I)I OKJPEAGHQZHRQV-UHFFFAOYSA-N 0.000 claims 1
- 238000004519 manufacturing process Methods 0.000 abstract description 8
- 230000015572 biosynthetic process Effects 0.000 abstract description 7
- YCIPHHOEXQJHNT-UHFFFAOYSA-N 3-oxoprop-2-enoic acid Chemical compound OC(=O)C=C=O YCIPHHOEXQJHNT-UHFFFAOYSA-N 0.000 abstract 1
- 239000000047 product Substances 0.000 description 17
- 238000001704 evaporation Methods 0.000 description 8
- 230000008020 evaporation Effects 0.000 description 8
- 238000005810 carbonylation reaction Methods 0.000 description 6
- 239000007789 gas Substances 0.000 description 6
- 230000006315 carbonylation Effects 0.000 description 5
- 238000010586 diagram Methods 0.000 description 5
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 4
- 230000001276 controlling effect Effects 0.000 description 4
- WFDIJRYMOXRFFG-UHFFFAOYSA-N Acetic anhydride Chemical compound CC(=O)OC(C)=O WFDIJRYMOXRFFG-UHFFFAOYSA-N 0.000 description 3
- XEKOWRVHYACXOJ-UHFFFAOYSA-N Ethyl acetate Chemical compound CCOC(C)=O XEKOWRVHYACXOJ-UHFFFAOYSA-N 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 3
- 230000001105 regulatory effect Effects 0.000 description 3
- 238000007086 side reaction Methods 0.000 description 3
- KKEYFWRCBNTPAC-UHFFFAOYSA-N Terephthalic acid Chemical compound OC(=O)C1=CC=C(C(O)=O)C=C1 KKEYFWRCBNTPAC-UHFFFAOYSA-N 0.000 description 2
- XTXRWKRVRITETP-UHFFFAOYSA-N Vinyl acetate Chemical group CC(=O)OC=C XTXRWKRVRITETP-UHFFFAOYSA-N 0.000 description 2
- 230000009471 action Effects 0.000 description 2
- 239000001569 carbon dioxide Substances 0.000 description 2
- 229910002092 carbon dioxide Inorganic materials 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 238000009833 condensation Methods 0.000 description 2
- 230000005494 condensation Effects 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- 239000001257 hydrogen Substances 0.000 description 2
- 238000012544 monitoring process Methods 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 230000036632 reaction speed Effects 0.000 description 2
- 238000005406 washing Methods 0.000 description 2
- QTBSBXVTEAMEQO-UHFFFAOYSA-M Acetate Chemical compound CC([O-])=O QTBSBXVTEAMEQO-UHFFFAOYSA-M 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 239000004372 Polyvinyl alcohol Substances 0.000 description 1
- 239000006096 absorbing agent Substances 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 229920002301 cellulose acetate Polymers 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000013064 chemical raw material Substances 0.000 description 1
- FOCAUTSVDIKZOP-UHFFFAOYSA-N chloroacetic acid Chemical compound OC(=O)CCl FOCAUTSVDIKZOP-UHFFFAOYSA-N 0.000 description 1
- 229940106681 chloroacetic acid Drugs 0.000 description 1
- 239000003245 coal Substances 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 239000012043 crude product Substances 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 239000003814 drug Substances 0.000 description 1
- 229940079593 drug Drugs 0.000 description 1
- 239000000975 dye Substances 0.000 description 1
- 235000019439 ethyl acetate Nutrition 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 150000002431 hydrogen Chemical class 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 239000012452 mother liquor Substances 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 239000000575 pesticide Substances 0.000 description 1
- 229920002451 polyvinyl alcohol Polymers 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 239000000376 reactant Substances 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 230000002194 synthesizing effect Effects 0.000 description 1
- 239000002918 waste heat Substances 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
- B01J19/0006—Controlling or regulating processes
- B01J19/0013—Controlling the temperature of the process
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
- B01D3/06—Flash distillation
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/002—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by condensation
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/26—Drying gases or vapours
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
- B01J19/0006—Controlling or regulating processes
Abstract
The invention discloses a control system suitable for the temperature of a reactor of a low-pressure carbonyl acetic acid synthesis device, which relates to the technical field of automatic control of acetic acid production, and adopts boiler pressure to control the temperature of the reactor.
Description
Technical Field
The invention belongs to the technical field of acetic acid synthesis, relates to an automatic control technology for acetic acid production, and particularly relates to a control system suitable for the temperature of a reactor of a low-pressure oxo-synthesis acetic acid device.
Background
Acetic acid is an important basic organic chemical raw material, can be used for preparing vinyl acetate monomer (VCM), cellulose acetate, acetic anhydride, terephthalic acid, chloroacetic acid, polyvinyl alcohol, acetic ester, metal acetate and the like, has wide application in the aspects of dyes, medicines, pesticides, adhesives, organic solvents and the like, and is one of important organic chemical products which are developed rapidly in recent years.
The method for preparing acetic acid by the methanol low-pressure oxo process can use coal as a raw material, has high yield and low cost, is an advanced technology for producing acetic acid, and is also a commonly used method for preparing acetic acid at present.
At present, the production route of the process for synthesizing acetic acid by adopting a methanol low-pressure carbonylation method is as follows: methanol and CO are used as raw materials to continuously react under the action of a VIII-group metal catalyst, acetic acid with the purity higher than 99.8 percent (mass fraction) can be obtained through rectification, a small amount of propionic acid, hydrogen and carbon dioxide can be produced as byproducts in a reaction working section, the propionic acid can be recycled or can be incinerated, and the hydrogen, the carbon dioxide and a small amount of unreacted carbon monoxide can be recycled. The rectification section aims at purifying acetic acid: the crude product extracted from the reaction section enters a lightness-removing tower through flash evaporation (flash evaporation), methyl iodide and unreacted methanol and reactive derivatives thereof are removed to obtain hydrous acetic acid, the hydrous acetic acid enters a dehydrating tower, after the dehydration in the dehydrating tower, anhydrous acetic acid containing a small amount of propionic acid is sent to a finished product tower, and the propionic acid and heavy components are removed in the finished product tower to obtain a qualified acetic acid product.
The synthesis section is the core of acetic acid production and has the function of leading CO and methanol to carry out carbonylation reaction to generate acetic acid under the action of a catalyst and a cocatalyst system, wherein the reaction is exothermic reaction, and reaction heat needs to be removed so as to maintain the temperature of a reactor; the flash evaporation of the reaction liquid can take away a part of heat, and the other part of heat can be removed through an external circulation heat exchanger. In a synthesis section, the temperature in the reactor is an important factor influencing the yield of acetic acid, the temperature in the reactor is too high, the reaction speed is high, the productivity per unit time and unit volume can be improved, but the too high reaction temperature can cause the increase of side reactions and the corrosion of equipment, influence the product yield and reduce the service life of the equipment; the low temperature in the reactor leads to low reaction speed, and the productivity per unit time and unit volume can be reduced, so that the temperature of the reactor needs to be controlled in a better temperature range, the production capacity can be ensured, the side reaction can be controlled, and the service life of equipment can be ensured.
For example, the invention patent of the national intellectual property office published on 11/19/2003 with the publication number of "CN1457335A" method and control device for controlling reaction "proposes a method for controlling the temperature of a reactor by monitoring the temperature and flow rate of the circulating mother liquor after flash evaporation, and the temperature feedback of the control method is not timely, and the fluctuation of the rectification process is easy to cause, which is not favorable for the stable operation of the whole acetic acid synthesis process. At present, the temperature of the reactor is also regulated by monitoring the flash ratio, and the control method does not utilize the temperature stability of a reaction system because the fluctuation range of the temperature of the reactor is large, and the flow of the material entering a rectification system fluctuates along with the temperature stability of the reaction system, and is also not beneficial to the stable operation of the whole system.
Disclosure of Invention
The invention aims to provide a control system suitable for the reactor temperature of a low-pressure oxo-synthesis acetic acid device, which can effectively control the temperature in the reactor within a preset temperature range, can provide an expected temperature environment for the reaction of methanol and reactive derivatives thereof with CO, is quick in reaction control system, can well maintain the temperature in the reactor within a certain level, and can ensure that the reaction rate of materials is maintained at a higher level on one hand and the content ratio of each component of a product is stable on the other hand, thereby ensuring the better quality of the obtained product.
The invention is realized by the following technical scheme:
a control system suitable for controlling the temperature of a reactor of a low-pressure oxo acetic acid device, which controls the temperature in a first-stage reactor by controlling the pressure of a boiler, comprises: one section reactor, boiler, vapour and liquid separator, flash vessel, lightness-removing tower, dehydration tower, finished product tower and DCS, one section reactor is connected with the extrinsic cycle heat exchanger, and partial material in one section reactor returns to one section reactor after the extrinsic cycle heat exchanger heat exchange treatment again, the medium in the heat exchanger is the hot water that comes from the boiler, and hot water takes away the heat in the reaction solution through the extrinsic cycle heat exchanger, produces low pressure steam, returns to the boiler again, through the temperature sensor on pressure sensor and the reation kettle who sets up on the boiler, gathers pressure signal and temperature signal respectively to reach DCS on with pressure signal and temperature signal, DCS compares the temperature signal that receives and the temperature that sets up in advance:
when the collected temperature signal is equal to the set temperature, the DCS sends a signal for maintaining the steam pressure to the pressure sensor;
when the collected temperature signal is less than the set temperature, the DCS sends a signal for reducing the steam pressure to the pressure sensor, controls and adjusts the opening of a valve which is in control connection with the pressure sensor, adjusts the controlled pressure signal, returns to the DCS, and compares the pressure signal with the set temperature again until the temperature signal is equal to the set temperature;
when the collected temperature signal is higher than the set temperature, the DCS sends a signal for increasing the steam pressure to the flow sensor, controls and adjusts the opening of the corresponding valve, adjusts and controls the controlled medium pressure signal, returns to the DCS, and compares the medium pressure signal and the medium pressure signal again until the temperature signal is equal to the set temperature.
Further, a second-stage reactor can be arranged between the first-stage reactor and the gas-liquid separator, and the reaction process carried out in the second-stage reactor is as follows: the liquid and gas at the top of the first-stage reactor enter the second-stage reactor in a mode close to plug flow after heat exchange and fluid carding by the heat exchanger I, and unreacted methanol and reactive derivatives thereof continue to react with carbon monoxide.
Further, the reaction process carried out in the first stage reactor is: methanol or a reactive derivative thereof and carbon monoxide enter a first-stage reactor, the first-stage reactor contains a homogeneous mixture of a group VIII metal catalyst, a methyl iodide promoter, water, acetic acid, methyl acetate and iodide, and the reactor is a full mixed flow reactor.
Further, the gas-liquid separator is used for separating materials conveyed out of the reactor, gas obtained after treatment of the gas-liquid separator enters the heat exchanger II from the top for condensation, condensed liquid returns to the front-end reactor, and uncondensed non-condensable gas is conveyed into the high-pressure absorption tower for further treatment; the liquid obtained by the separation of the gas-liquid separator enters a flash evaporator.
Further, the flash evaporator is used for processing the liquid output from the gas-liquid separator and is operated at a pressure lower than that of the reactor to obtain a stream rich in methyl iodide and a stream rich in acetic acid compared with the outlet of the gas-liquid separator, and the stream rich in acetic acid is recycled to the first-stage reactor through a pump; the stream rich in methyl iodide enters a lightness-removing column.
Further, the light component removal tower is used for further separating the stream entering the light component removal tower, so as to obtain an overhead stream which is richer in methyl iodide and a side stream which is richer in acetic acid compared with the stream entering the light component removal tower.
Further, the dehydration tower is used for treating a side stream containing acetic acid input from the light component removal tower, and a stream rich in acetic acid and propionic acid compared with the feed material is obtained at the tower bottom of the dehydration tower.
Further, the finished product tower is used for separating heavy components such as acetic acid and propionic acid, and finally, finished product acetic acid and a bottom material flow rich in propionic acid are obtained.
Further, an evaporator is arranged below the flash evaporator, the materials are treated by the flash evaporator and the evaporator to obtain a material flow rich in methyl iodide and a material flow rich in acetic acid compared with the outlet of the gas-liquid separator, and the material flow rich in acetic acid is circulated back to the front-end reactor through a pump; the stream rich in methyl iodide enters a lightness-removing column.
Further, when the medium inlet of the external circulation heat exchanger is connected with a steam feeding pipeline, the temperature range set by DCS is 180-205 ℃, and the pressure range is 0.52-1.2MPa.
Furthermore, the temperature sensors are arranged at the upper part, the middle part and the lower part of the reaction kettle, a plurality of temperature sensors are adopted to collect temperature signals of the reaction kettle at different positions of the reaction kettle and upload the temperature signals to the DCS, the DCS analyzes and processes all the received temperature signals to obtain a final temperature signal, and the final temperature signal is compared with the preset temperature.
Compared with the prior art, the invention has the following advantages and beneficial effects:
1. in the invention, the temperature of the reactor is controlled by adopting the boiler pressure, the pressure regulation lag is small, the sensitivity is high, the temperature change amplitude is small, the temperature fluctuation in the reactor can be ensured in a small range, the reactant is ensured to be in an ideal reaction environment, and simultaneously, each component in the product in the reactor is kept stable, thereby being beneficial to the stable operation of the subsequent working section.
2. According to the invention, the control system suitable for the temperature of the reactor of the low-pressure oxo acetic acid synthesis device is applied to the acetic acid synthesis process, and has the advantages of high safety, more accurate control, timely mastering and adjusting the reaction process, contribution to whole-line control, guarantee of long-term stable operation of a production line, accurate control of indexes and cost saving.
Drawings
FIG. 1 is a logic control diagram of the control system of the present invention.
FIG. 2 is a schematic diagram showing the system connection for low-pressure carbonylation of methanol to acetic acid in example 1.
FIG. 3 is a schematic diagram showing the system connection for low-pressure methanol carbonylation to produce acetic acid in example 2.
FIG. 4 is a schematic diagram showing the system connection for low-pressure methanol carbonylation to produce acetic acid in example 3.
FIG. 5 is a schematic diagram showing the system connection for low-pressure methanol carbonylation to produce acetic acid in example 4.
FIG. 6 is a schematic view of the structure of the reactor in example 5.
Wherein, 1, a first-stage reactor; 2. a gas-liquid separator; 3. a flash evaporator; 4. a light component removal tower; 5. a dehydration tower; 6. a finished product tower; 7. DCS; 8. a second stage reactor; 9. an evaporator; 10. an integrated flash evaporator; 11. a temperature sensor I; 12. a temperature sensor II; 13. a temperature sensor III; 14. a pressure sensor I; 15. a valve I; 16. a boiler; 17. an external circulation heat exchanger; 18. a hot water feed line; 19. a heat exchanger I; 20. a heat exchanger II; 21. a high pressure absorber; 22. a CO feed line; 23. a methanol feed line; 24. a finished product acetic acid pipeline; 25. a waste acid extraction line; 26. a heat exchanger III;10.1, a flash evaporation section; 10.2, an evaporation section; 10.3, a washing section.
Detailed Description
The present invention will be described in further detail with reference to examples, but the embodiments of the present invention are not limited thereto.
Example 1
This example further illustrates the present technical solution by taking four lines for methanol low pressure oxo acetic acid production, which produce 75 tons of acetic acid product per hour, as an example. What this production line of methyl alcohol low pressure oxo acetic acid adopted is that one kind in this scheme is applicable to the control system of low pressure oxo acetic acid device reactor temperature, includes: a first-stage reactor 1, a boiler 16, a gas-liquid separator 2, a flash evaporator 3, a light component removal tower 4, a dehydration tower 5, a finished product tower 6 and a centralized dispersion control system (hereinafter referred to as DCS 7), referring to FIG. 2.
In this example, the reaction process carried out in the first stage reactor 1 is: methanol or reactive derivatives thereof and carbon monoxide enter a first-stage reactor 1, the first-stage reactor 1 contains a homogeneous mixture of a group VIII metal catalyst, a methyl iodide promoter, water, acetic acid, methyl acetate and iodide, and the reactor is a fully mixed flow reactor.
In this embodiment, the gas-liquid separator 2 is used for separating the material conveyed out from the reactor, the gas obtained after the treatment by the gas-liquid separator 2 enters the heat exchanger from the top for condensation, the condensed liquid returns to the front-end reactor, and the uncondensed non-condensable gas is conveyed to the high-pressure absorption tower 21 for further treatment; the liquid separated by the gas-liquid separator 2 is introduced into a flash evaporator 3.
In this embodiment, the flash evaporator 3 is used for processing the liquid output from the gas-liquid separator 2 and is operated at a pressure lower than that of the reactor to obtain a stream rich in methyl iodide and a stream rich in acetic acid compared with the outlet of the gas-liquid separator 2, and the stream rich in acetic acid is recycled to the first-stage reactor 1 through a pump; the stream rich in methyl iodide enters the lightness-removing column 4.
In this embodiment, the light component removal column 4 is used to further separate the stream entering the light component removal column 4, resulting in an overhead stream that is richer in methyl iodide and a side stream that is richer in acetic acid than the stream entering the light component removal column 4.
In this embodiment, the dehydrating tower 5 is used for treating the side stream containing acetic acid input from the light component removal tower 4, and the bottom of the dehydrating tower 5 obtains a stream rich in acetic acid and propionic acid compared with the feed material.
In this embodiment, the finished product tower 6 is used for separating heavy components such as acetic acid and propionic acid, and finally obtaining a finished product acetic acid and a bottom stream rich in propionic acid.
Further, the first section of reactor 1 is connected with an external circulation heat exchanger 17, a medium of the external circulation heat exchanger 17 and a waste heat boiler 16 form a circulation passage, a pressure sensor arranged on the boiler 16 and a temperature sensor arranged on the first section of reactor 1 are used for respectively acquiring a pressure signal and a temperature signal and uploading the pressure signal and the temperature signal to a DCS7, the DCS7 compares the received temperature signal with a preset temperature and controls the temperature environment in the reactor by adjusting the opening degree of a valve on a low-pressure steam discharge pipe line interlocked with the pressure sensor, and the temperature stability of the reactor is ensured.
Specifically, a pressure sensor I14 and a valve I15 are arranged on a low-pressure steam discharge pipe line of the boiler 16, a temperature sensor I11 is arranged on the first-stage reactor 1, referring to FIG. 2, the DCS7 is respectively in control connection with the pressure sensor I14, the valve I15 and the temperature sensor I11, and the temperature sensor I11 is used for miningUploading the collected temperature signal to DCS7 to obtain a real-time temperature T 1 The pressure sensor I14 uploads the collected pressure signal to DCS7 to obtain an initial pressure P 1 The pressure after being controlled and adjusted by the controller is P 1 ＇。
When T is 1 ＝T 0 When the pressure sensor I14 is in operation, the DCS sends a signal for maintaining the low-pressure steam pressure to the pressure sensor I14;
when T is 1 ＜T 0 When the temperature is adjusted, the DCS sends a signal for reducing the pressure of the low-pressure steam to the pressure sensor I14, controls the opening degree of the valve I15, returns the pressure signal after adjustment and control to the DCS7, and compares the pressure signal again until the adjusted temperature T is reached 1 ' equal to the set temperature T 0 Until now, the pressure on the low-pressure steam discharge pipeline collected by the pressure sensor I14 is P 1 ＇；
When T is 1 ＞T 0 When the temperature is regulated, the DCS sends a signal for increasing the pressure of the low-pressure steam to the pressure sensor I14, controls and adjusts the opening degree of the corresponding valve I15, returns the temperature signal after the control to the DCS7, and compares the temperature signal until the regulated temperature T 1 ' equal to the set temperature T 0 Until now, the pressure on the medium discharge pipeline collected by the pressure sensor I14 is P 1 ＇。
The following table 1 shows the set temperature, the temperature feedback from the temperature sensor I11 received by the DCS7, the pressure feedback from the pressure sensor I14 to the pressure on the low-pressure steam discharge line (before and after the opening of the valve I15), and the fluctuation range between the adjusted temperature and the preset temperature (Δ T = T) at every 10min 1 ＇- T 0 ) The statistical table of (1).
TABLE 1
As can be seen from Table 1, the temperature in the reaction kettle can be maintained in a narrow range and can be adjusted rapidly by the control method, so that the temperature of the reactor can be maintained in a stable range, the reaction rate can be improved, the side reaction can be reduced, and the service life of equipment can be prolonged.
Example 2
This embodiment is different from embodiment 1 in that, referring to fig. 3, a second-stage reactor 8 may be further disposed between the first-stage reactor 1 and the gas-liquid separator 2, and the reaction process performed in the second-stage reactor 8 is as follows: the liquid and gas at the top of the first-stage reactor 1 enter the second-stage reactor 8 in a manner of approximate plug flow after heat exchange by a heat exchanger I19 and fluid carding, the unreacted methanol and reactive derivatives thereof continuously react with carbon monoxide, and the control method is the same as that in the embodiment 1.
In this embodiment, the preset temperature value T 0 The temperature was 200 ℃.
The following table 2 shows the set temperature, the temperature feedback from the temperature sensor I11 received by the DCS7, the pressure feedback from the pressure sensor I to the pressure on the low-pressure steam discharge pipe line (before and after the opening of the valve I), and the fluctuation range between the adjusted temperature and the preset temperature (Δ T = T) at every 10min 1 ＇- T 0 ) The statistical table of (1).
TABLE 2
As can be seen from Table 2, by adopting the above control method, the temperature in the reaction kettle can be maintained within a certain range, and the adjustment is rapid, so that the temperature of the reactor can be maintained within a stable range, and the temperature of the reactor can be ensured to be stable.
Example 3
This example is compared with example 1 with the difference that, referring to fig. 4, an evaporator 9 is arranged below the flasher 3, the liquid after passing through the flasher 3 and the evaporator 9 is operated at a pressure lower than the reactor pressure to obtain a stream rich in methyl iodide and a stream rich in acetic acid compared with the outlet of the gas-liquid separator 2, and the stream rich in acetic acid is recycled to the first stage reactor 1 by a pump; the stream rich in methyl iodide enters the lightness-removing column 4 by the same control method as in example 1.
In this embodiment, the preset temperature value T 0 The temperature was 185 ℃.
The following table 3 shows the set temperature, the temperature feedback from the temperature sensor I11 received by the DCS7 is manually recorded every 10min, the pressure on the low-pressure steam discharge pipe line fed back by the pressure sensor I14 (before and after the opening of the valve I15), and the fluctuation range between the adjusted temperature and the preset temperature (Δ T = T) 1 ＇- T 0 ) The statistical table of (1).
TABLE 3
As can be seen from Table 3, by adopting the above control method, the temperature in the reaction kettle can be maintained within a certain range, and the adjustment is rapid, so that the temperature of the reactor can be maintained within a stable range, and the temperature of the reactor can be ensured to be stable.
Example 4
In this embodiment, compared with embodiment 2, the difference is that, referring to fig. 5, an evaporator 9 is disposed below the flash evaporator 3, the flash evaporator 3 and the evaporator 9 are an integrated flash evaporator 10, the liquid passing through the integrated flash evaporator 10 is operated at a pressure lower than that of the reactor to obtain a stream rich in methyl iodide and a stream rich in acetic acid compared with the outlet of the gas-liquid separator 2, and the stream rich in acetic acid is recycled to the first stage reactor 1 by a pump; the stream rich in methyl iodide enters the lightness-removing column 4, and the control method is the same as that of example 2.
In this embodiment, the preset temperature value T 0 The temperature was 190 ℃.
The following table 4 shows the set temperature, the temperature feedback from the temperature sensor I11 received by the DCS7, the pressure feedback from the pressure sensor I14 to the low-pressure steam discharge line (before and after the opening of the valve I15), and the fluctuation range between the adjusted temperature and the preset temperature (Δ T = T) at every 10min 1 ＇- T 0 ) The statistical table of (1).
TABLE 4
As can be seen from Table 4, by adopting the above control method, the temperature in the reaction kettle can be maintained within a certain range, and the adjustment is rapid, so that the temperature of the reactor can be maintained within a stable range, and the temperature of the reactor can be ensured to be stable.
Example 5
Compared with the embodiments 1-4, the difference of this embodiment is that, referring to fig. 6, the upper, middle and lower positions of the first stage reactor 1 are respectively provided with the temperature sensor I11, the temperature sensor II12 and the temperature sensor III13, and the temperature sensor I11, the temperature sensor II12 and the temperature sensor III13 acquire the temperature signal T at the corresponding positions of the first stage reactor 1 1 、T 2 、T 3 And uploading all temperature signals to DCS7, and analyzing and processing all the received temperature signals by DCS7 to obtain new temperature signals T 1 Cutting off the new temperature signal T 1 With a predetermined temperature T 0 For comparison, the control method was the same as in example 2. In this embodiment, taking the integrated flash evaporator 10 connected to the rear end of the gas-liquid separator 2 as an example, the integrated flash evaporator 10 includes a washing section 10.3, a flash section 10.1 and an evaporation section 10.2, the evaporation section 10.2 is externally connected to a heat exchanger III26, and referring to fig. 6, the relationship between the reactor temperature and the steam pressure is further studied.
In this embodiment, the preset temperature value T 0 The temperature was 195 ℃.
The following table 5 is to set the temperature, select the temperature signals fed back by the temperature sensor I11, the temperature sensor II12 and the temperature sensor III13 received by the DCS7 to be manually recorded every 10min, the pressure on the low-pressure steam discharge pipeline fed back by the pressure sensor I14 (before and after the opening of the valve I15), and the fluctuation range of the adjusted temperature and the preset temperature (Δ T = T) 1 ＇- T 0 ) The statistical table of (1). "temperature T1" in Table 5 is a temperature value obtained by DCS7 analysis.
TABLE 5
As can be seen from Table 5, the temperature difference inside the reactor was about 5 ℃On the right, the temperature difference between the upper, middle and lower parts is relatively fixed, so the middle temperature value is selected as the final new temperature signal T 1 The value,. DELTA.T, fluctuated to a small extent. Therefore, the temperature in the reaction kettle can be maintained within a certain range and can be adjusted quickly by adopting the control method, so that the temperature of the reactor is maintained within a stable range, and the temperature in the reactor is stable.
Comparative example 1
The traditional process is to control and adjust the temperature in the reactor by adjusting the flash ratio, when the temperature of the reactor is high, the flash ratio is increased, and the temperature of the reactor is reduced by more extracted materials; when the reactor temperature was low, the flash ratio was decreased, and the reactor temperature was raised by decreasing the withdrawal of the material, and other operation methods and steps were the same as in examples 1 to 4, and Table 6 shows the results of the reactor temperature obtained by using this method.
TABLE 6
Table 6 shows that small variations in the flash ratio affect large fluctuations in the reactor temperature because the flash takes away a lot of heat, which is not good for fine adjustment of the temperature.
To sum up, as can be seen from the above embodiments and comparative examples, in the control system, the temperature sensor disposed on the reactor and the pressure sensor disposed on the boiler 16 respectively collect the temperature signal and the pressure signal, and upload the temperature signal and the pressure signal to the DCS7, the DCS7 compares the received temperature signal with the preset temperature, and adjusts the control system of the valve connected to the pressure sensor, so as to effectively control the temperature stability of the reactor.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any way, and any simple modifications and equivalent variations of the above embodiment according to the technical spirit of the present invention are within the scope of the present invention.
Claims (10)
1. A system for controlling the temperature of a reactor of a low pressure oxo acetic acid unit, wherein the temperature in a primary reactor (1) is controlled by controlling the pressure in a boiler (16), comprising: one section reactor (1), boiler (16), vapour and liquid separator (2), flash vessel (3), lightness-removing tower (4), dehydration tower (5), finished product tower (6) and DCS (7), one section reactor (1) is connected with extrinsic cycle heat exchanger (17), and partial material in one section reactor (1) returns to one section reactor (1) after extrinsic cycle heat exchanger (17) heat exchange treatment again, the medium in the heat exchanger is the hot water that comes from boiler (16), and extrinsic cycle heat exchanger (17) produce low-pressure steam after carrying out the heat exchange with the reaction liquid in one section reactor (1), and low-pressure steam sends back to boiler (16), through the pressure sensor who sets up on boiler (16) and the temperature sensor on the reation kettle, gathers pressure signal and temperature signal respectively to reach DCS (7) on with pressure signal and temperature signal, DCS (7) will receive temperature signal and preset temperature and compare:
when the collected temperature signal is equal to the set temperature, the DCS (7) sends a signal for maintaining the steam pressure to the pressure sensor;
when the acquired temperature signal is less than the set temperature, the DCS (7) sends a signal for reducing the steam pressure to the pressure sensor, controls and adjusts the opening of a valve in control connection with the pressure sensor, adjusts the controlled pressure signal, returns to the DCS (7), and compares the pressure signal with the set pressure again until the temperature signal is equal to the set temperature;
when the collected temperature signal is greater than the set temperature, the DCS (7) sends a signal for increasing steam pressure to the flow sensor, controls and adjusts the opening of the corresponding valve, adjusts the controlled medium pressure signal, returns to the DCS (7), and compares the medium pressure signal again until the temperature signal is equal to the set temperature.
2. The system for controlling the temperature of a reactor of a low pressure oxo acetic acid apparatus according to claim 1, wherein: a second-stage reactor (8) can be arranged between the first-stage reactor (1) and the gas-liquid separator (2), and the reaction process carried out in the second-stage reactor (8) is as follows: the liquid and gas at the top of the first-stage reactor (1) enter the second-stage reactor (8) in a mode of approximately plug flow after heat exchange and fluid carding by a heat exchanger I (19), and unreacted methanol and reactive derivatives thereof continue to react with carbon monoxide.
3. The system for controlling the temperature of a reactor of a low pressure oxo acetic acid apparatus according to claim 1, wherein: the reaction process carried out in the one-stage reactor (1) is as follows: methanol or reactive derivatives thereof and carbon monoxide are fed into a first stage reactor (1), the first stage reactor (1) contains a homogeneous mixture of a group VIII metal catalyst, a methyl iodide promoter, water, acetic acid, methyl acetate and iodide, and the reactor is a fully mixed flow reactor.
4. A system for controlling the temperature of a reactor suitable for use in a low pressure oxo acetic acid plant according to claim 1 or claim 2, wherein: the gas-liquid separator (2) is used for separating materials conveyed out of the reactor, gas obtained after treatment of the gas-liquid separator (2) enters the heat exchanger II (20) from the top to be condensed, condensed liquid returns to the front-end reactor, and uncondensed non-condensable gas is conveyed into the high-pressure absorption tower (21) to be further treated; the liquid separated by the gas-liquid separator (2) enters a flash evaporator (3).
5. The system for controlling the temperature of a reactor of a low pressure oxo acetic acid apparatus according to claim 1, wherein: the flash evaporator (3) is used for processing the liquid output from the gas-liquid separator (2) and operating at a pressure lower than the pressure of the reactor to obtain a stream rich in methyl iodide and a stream rich in acetic acid compared with the outlet of the gas-liquid separator (2), and the stream rich in acetic acid is recycled to the first-stage reactor (1) through a pump; the stream rich in methyl iodide enters a lightness-removing column (4).
6. The system for controlling the temperature of a reactor of a low pressure oxo acetic acid apparatus according to claim 1, wherein: the light component removal tower (4) is used for further separating the material flow entering the light component removal tower (4) to obtain an overhead material flow which is richer in methyl iodide and a side material flow which is richer in acetic acid compared with the material flow entering the light component removal tower (4).
7. The system for controlling the temperature of a reactor of a low pressure oxo acetic acid apparatus according to claim 1, wherein: the dehydration tower (5) is used for treating a side stream containing acetic acid input from the light component removal tower (4), and a material stream rich in acetic acid and propionic acid compared with the feeding material is obtained at the tower bottom of the dehydration tower (5); the finished product tower (6) is used for separating acetic acid and propionic acid to finally obtain finished product acetic acid and a tower bottom material flow rich in propionic acid.
8. A system for controlling the temperature of a reactor suitable for use in a low pressure oxo acetic acid unit according to claim 1 or claim 5, wherein: an evaporator (9) is arranged below the flash evaporator (3), a material treated by the flash evaporator (3) and the evaporator (9) obtains a material flow rich in iodomethane and a material flow rich in acetic acid compared with the outlet of the gas-liquid separator (2), and the material flow rich in acetic acid is circulated back to the front-end reactor through a pump; the stream rich in methyl iodide enters a lightness-removing column (4).
9. The system for controlling the temperature of a reactor of a low pressure oxo acetic acid apparatus according to claim 1, wherein: when a medium inlet of the external circulation heat exchanger (17) is connected with a hot water feeding pipeline (18), the temperature range set by the DCS (7) is 180-205 ℃, and the pressure range is 0.52-1.2MPa.
10. The system for controlling the temperature of a reactor of a low pressure oxo acetic acid apparatus according to claim 1, wherein: the temperature sensors are arranged on the upper portion, the middle portion and the lower portion of the reaction kettle, a plurality of temperature sensors are adopted to collect temperature signals of the reaction kettle at different positions of the reaction kettle and upload the temperature signals to the DCS (7), the DCS (7) analyzes and processes all the received temperature signals to obtain a final temperature signal, and the temperature signal is compared with a preset temperature.
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