A rectification system and rectification method in a methanol low-pressure carbonyl synthesis acetic acid process

Abstract

The application discloses a kind of rectification system and rectification method in methanol low-pressure carbonyl synthesis acetic acid process, it is related to chemical engineering and rectification separation field, the method is by collecting acetic acid reaction liquid in reaction kettle and the temperature, flow and component parameters of flash gas phase, calculates flash energy utilization coefficient, realizes the evaluation and strategy control of whether gas phase heat is sufficient;Flash gas phase is sent into light component tower, and the comprehensive separation efficiency coefficient is calculated, realizes the evaluation and optimization of double separation performance of tower device;After being treated by light component tower, crude acetic acid is sent into finished product tower, and the parameters of top acetic acid and bottom propionic acid are collected, and propionic acid separation purity index is calculated and control strategy is generated;Energy optimization mechanism between towers is introduced, and energy coupling coefficient is calculated, to realize heat energy recovery and process optimization;By this method and system, equipment investment and energy consumption can be effectively reduced, the purity of rectification separation efficiency and finished product acetic acid is improved, energy utilization is optimized, and the intelligentization and sustainability of acetic acid production process are realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of chemical engineering and rectification separation technology, in particular to a rectification system and a rectification method in a low-pressure carbonyl synthesis process of acetic acid from methanol. BACKGROUND

[0002] The low-pressure carbonyl synthesis process of acetic acid from methanol is one of the main routes for preparing acetic acid in industry. The basic process includes: the raw materials of methanol and carbon monoxide continuously enter the reaction kettle, and under the action of catalyst and co-catalyst, the low-pressure carbonyl reaction is carried out at 2.8-3.0 MPa A and 180-190℃ to generate acetic acid reaction liquid. The reaction liquid is reduced in pressure by a flash valve and enters a flash evaporator to realize vapor-liquid separation under the action of instantaneous pressure difference, and the gas phase flows out from the top, and the liquid phase enters the downstream tower.

[0003] In the existing process, the acetic acid vapor in the flash vapor first enters a light component tower (light component removal tower), the light components therein are recovered, and the recovered light components are returned to the reaction system; the crude acetic acid flowing out from the bottom of the light component removal tower enters a dehydration tower to remove the water therein; the crude acetic acid flowing out from the bottom of the dehydration tower is sent into a product tower to separate acetic acid and propionic acid, the acetic acid meeting the requirements is collected from the top of the product tower, and a large amount of propionic acid is discharged into a waste acid tank.

[0004] However, the existing process has the following technical problems:

[0005] The tower functions are independent and the operation is complex, the removal of light components and the removal of water are completed in the light component removal tower and the dehydration tower respectively, the top reflux ratio, the reboiler power and the temperature distribution need to be independently adjusted, the gas-liquid balance is difficult to be simultaneously optimized, the comprehensive separation efficiency of the tower is not high, and the product purity and yield fluctuate greatly.

[0006] The equipment investment and land occupation increase, since the light component removal tower and the dehydration tower are independent function towers, the process needs additional equipment, pipelines and conveying pumps. Most of the above-mentioned equipment is made of zirconium material, which is expensive and occupies a large area, increasing the construction and operation cost of the factory.

[0007] The energy utilization efficiency is low, the heat generated by the flash vapor is not fully recovered, part of the heat is lost in the operation process of the independent tower, the circulation amount of the rectification system increases, the steam consumption rises, and at the same time, the amount of circulating water also increases, increasing the energy consumption and operation cost.

[0008] The system heat energy coupling is insufficient, there is a lack of heat cascade and energy optimization mechanism between the towers, the waste heat of the flash vapor cannot be efficiently used for evaporation and separation of the downstream tower, the heat energy utilization rate is low, and the stability of the separation process is insufficient.

[0009] In summary, the existing methanol low-pressure carbonylation synthesis acetic acid rectification process has problems such as many towers, high investment cost, high energy consumption, complex operation and insufficient heat utilization, and an optimized rectification method that can comprehensively utilize flash gas phase heat, couple tower functions, improve separation efficiency and heat utilization rate is urgently needed. SUMMARY

[0010] In view of the deficiencies of the prior art, the present application provides a rectification system and method in a methanol low-pressure carbonylation synthesis acetic acid process to solve the problems mentioned in the background art.

[0011] To achieve the above object, the present application is implemented by the following technical scheme: a rectification method in a methanol low-pressure carbonylation synthesis acetic acid process, comprising the following steps:

[0012] Step one, in the reaction kettle, methanol and carbon monoxide are reacted under the action of a catalyst and a co-catalyst to generate an acetic acid reaction liquid; the initial state parameters of the acetic acid reaction liquid are collected, the flash energy utilization coefficient SNX is calculated and obtained, and compared with the flash energy utilization threshold Sth to determine whether the heat carried by the gas phase is sufficient, and if not, a strategy is given;

[0013] Step two, the acetic acid vapor at the gas phase outlet of the top of the flash evaporator is directly sent to the top feed inlet of the light component tower; the coupling of light component recovery and dehydration function is realized through the double separation structure of the tower; the gas-liquid state parameters at the top and bottom of the light component tower are collected, the light component recovery rate index QHZ and the dehydration efficiency coefficient TSX are calculated and obtained, and the comprehensive separation efficiency coefficient FLX is further calculated and obtained, and compared with the comprehensive separation efficiency threshold Fth to determine whether the tower separation performance meets the standard, and if not, a strategy is given;

[0014] Step three, the crude acetic acid treated by the light component tower is sent to the product tower, and the separation of acetic acid and propionic acid is completed in the product tower; the molar fraction and flow parameters of acetic acid at the top of the product tower and propionic acid at the bottom are collected, the propionic acid separation purity index BSZ is calculated, and compared with the propionic acid separation purity threshold Bth to determine whether the acetic acid product purity is qualified, and if not, a strategy is given;

[0015] Step four, after the acetic acid purity at the outlet of the product tower meets the standard, an energy optimization mechanism between the light component tower and the product tower is introduced, the flash residual heat, inter-tower heat exchange and total heat required for separation maintenance parameters are collected, the energy coupling coefficient EOI is calculated, and compared with the energy coupling threshold Oth to determine whether the heat energy utilization meets the set standard, and if not, a strategy is given.

[0016] Preferably, step one comprises:

[0017] S11, in the acetic acid synthesis process, methanol and carbon monoxide continuously enter the reaction kettle, under the action of catalyst and co-catalyst, low pressure carbonyl synthesis reaction occurs under the pressure of 2.8~3.0MPaA and the temperature of 180~190℃, acetic acid reaction liquid is generated;

[0018] S12, by monitoring the temperature, pressure, flow and components of acetic acid reaction liquid at the outlet of the reaction kettle in real time, the initial state parameters of acetic acid reaction liquid are obtained; by arranging thermocouple on the outlet pipeline, the outlet temperature Tout of acetic acid reaction liquid is collected in real time; coriolis mass flowmeter is installed in the outlet flow path to collect the flow of acetic acid reaction liquid in real time ; online gas chromatograph GC is arranged on the outlet pipeline to collect the concentration ratio of main components of acetic acid reaction liquid , including methanol, carbon monoxide, target product acetic acid and by-product;

[0019] S13, acetic acid reaction liquid enters the flash evaporator after pressure reduction through the flash valve, and realizes vapor-liquid separation under the action of instantaneous pressure difference, forming two streams of gas phase and liquid phase; the working conditions of the top and bottom outlets of the flash evaporator are monitored in real time;

[0020] S14, the temperature and flow of the gas phase stream at the top outlet of the flash evaporator are continuously monitored to obtain the gas phase temperature value and the gas phase flow value , infrared gas analyzer is arranged on the gas phase branch to collect the gas phase component molar fraction .

[0021] Preferably, step one also includes:

[0022] S15, by collecting the outlet temperature of acetic acid reaction liquid, the flow Fout of acetic acid reaction liquid, the main component molar fraction of acetic acid reaction liquid, the gas phase component molar fraction , the gas phase temperature value and the gas phase flow value , after dimensionless treatment, the flash energy utilization coefficient SNX is calculated and obtained;

[0023] S16, by presetting the flash energy utilization threshold Sth, and comparing the flash energy utilization coefficient SNX with the flash energy utilization threshold Sth, the first evaluation result is obtained, including:

[0024] When the flash energy utilization coefficient SNX is greater than or equal to the flash energy utilization threshold Sth, it means that the heat carried by the gas phase is sufficient, and continuous monitoring is needed;

[0025] When the flash energy utilization coefficient SNX < the flash energy utilization threshold Sth, it indicates that the heat carried by the gas phase is insufficient, and there is a risk of downstream separation efficiency decline, triggering the first early warning instruction, and generating the first strategy: starting the external heating device, increasing the temperature of the gas phase, supplementing the heat required for evaporation; adjusting the operation conditions of the reaction kettle, increasing the reaction temperature and flow rate, optimizing the flash gas phase heat energy distribution; recalculating until the flash energy utilization coefficient SNX ≥ the flash energy utilization threshold Sth.

[0026] Preferably, step two comprises:

[0027] S21, the acetic acid vapor at the top gas phase outlet of the flash evaporator is directly sent to the top inlet of the light component column; by installing a mass flow meter at the top outlet, the gas phase flow rate is collected in real time ; an online GC is arranged on the gas phase branch to collect the light component molar fraction in the gas phase ; a mass flow meter is installed on the flash evaporator top outlet pipeline to collect the top inlet gas phase flow rate in real time ; an online GC is arranged on the flash evaporator top outlet pipeline to collect the light component molar fraction in the top inlet of the column in real time ;

[0028] S22, by collecting the obtained gas phase flow rate , the light component molar fraction in the gas phase , the top inlet gas phase flow rate and the light component molar fraction in the top inlet of the column , after dimensionless processing, the light component recovery rate index QHZ is calculated and obtained;

[0029] S23, by installing a moisture analyzer at the bottom outlet of the light component column, the moisture content of the crude acetic acid at the bottom of the light component column is collected ; a moisture analyzer is arranged at the outlet pipeline of the flash evaporator liquid phase to collect the moisture content Whi of the crude acetic acid entering the column;

[0030] S24, by collecting the obtained moisture content of the crude acetic acid at the bottom of the light component column and the moisture content Whi of the crude acetic acid entering the column, after dimensionless processing, the dehydration efficiency coefficient TSX is calculated and obtained.

[0031] Preferably, step two further comprises:

[0032] S25, by calculating the light component recovery rate index QHZ and the dehydration efficiency coefficient TSX obtained, after dimensionless processing, the comprehensive separation efficiency coefficient FLX is calculated and obtained;

[0033] S26, by presetting the comprehensive separation efficiency threshold Fth, and comparing and analyzing the comprehensive separation efficiency coefficient FLX with the comprehensive separation efficiency threshold Fth, a second evaluation result is obtained, including:

[0034] When the comprehensive separation efficiency coefficient FLX≥ the comprehensive separation efficiency threshold Fth, it indicates that the tower separation performance meets the standard, and continuous monitoring is performed;

[0035] When the comprehensive separation efficiency coefficient FLX< the comprehensive separation efficiency threshold Fth, it indicates that the tower separation performance does not meet the standard, a second early warning instruction is triggered, and a second strategy is generated: adjusting the tower top reflux ratio to improve the light component recovery efficiency; adjusting the tower bottom reboiler heating power to improve the dehydration capacity; adjusting the temperature or pressure distribution in the tower to optimize the gas-liquid balance; recalculating until the comprehensive separation efficiency coefficient FLX≥ the comprehensive separation efficiency threshold Fth.

[0036] Preferably, step three comprises:

[0037] S31, sending the crude acetic acid treated by the light component tower to the middle feeding port of the product tower; arranging an online GC or infrared gas analyzer at the top outlet of the product tower to collect the top acetic acid molar fraction in real time ; installing a flow meter at the top outlet of the product tower to collect the top acetic acid flow ; arranging an online GC or infrared gas analyzer at the bottom outlet of the product tower to collect the bottom propionic acid molar fraction ; installing a flow meter at the bottom outlet of the product tower to collect the bottom propionic acid flow .

[0038] Preferably, step three further comprises:

[0039] S32, calculating the propionic acid separation purity index BSZ after non-dimensional processing of the collected top acetic acid molar fraction , the top acetic acid flow , the bottom propionic acid molar fraction and the bottom propionic acid flow .

[0040] S33, obtaining a third evaluation result by presetting a propionic acid separation purity threshold Bth and comparing the propionic acid separation purity index BSZ with the propionic acid separation purity threshold Bth, which comprises:

[0041] When the propionic acid separation purity index BSZ≥ the propionic acid separation purity threshold Bth, it indicates that the separation purity is qualified, the top-produced acetic acid enters the product tank, and the bottom propionic acid is discharged into the waste acid tank;

[0042] When the propionic acid separation purity index BSZ< the propionic acid separation purity threshold Bth, it indicates that the separation purity is unqualified, a third early warning instruction is triggered, and a third strategy is generated: adjusting the tower top reflux ratio to improve the acetic acid purity; adjusting the tower bottom reboiler heating power to strengthen the propionic acid separation; adjusting the temperature or pressure distribution in the tower to optimize the gas-liquid separation; recalculating until the propionic acid separation purity index BSZ≥ the propionic acid separation purity threshold Bth.

[0043] Preferably, step four comprises:

[0044] S41, after the acetic acid purity at the outlet of the product tower meets the standard, an energy optimization mechanism between the light component tower and the product tower is introduced; a heat flow meter and a temperature sensor are arranged at the outlet of the flash evaporator to collect the residual heat quantity Qfla of the flash vapor phase; temperature and flow sensors are arranged at the inlet and outlet of the reboiler at the bottom of the light component tower to obtain the heat coupling exchange quantity Qcou between the towers; a heat meter is arranged at the reboiler of the product tower to collect the total heat quantity Qdem required for separation maintenance.

[0045] Preferably, step four further comprises:

[0046] S42, by collecting the residual heat quantity Qfla of the flash vapor phase, the heat coupling exchange quantity Qcou between the towers and the total heat quantity Qdem required for separation maintenance, and after non-dimensional processing, the energy coupling coefficient EOI is calculated and obtained;

[0047] S43, by presetting the energy coupling threshold Oth and comparing and analyzing the energy coupling coefficient EOI with the energy coupling threshold Oth, the fourth evaluation result is obtained, including:

[0048] When the energy coupling coefficient EOI is greater than or equal to the energy coupling threshold Oth, it indicates that the heat energy utilization reaches the set standard, the system can maintain stable separation without additional heating, the process flow ends, a process optimization completion instruction is generated and an energy utilization log is recorded;

[0049] When the energy coupling coefficient EOI is less than the energy coupling threshold Oth, it indicates that the heat energy utilization does not reach the set standard, a fourth early warning instruction is triggered, and a fourth strategy is generated: adjusting the operating condition of the heat exchanger, preferentially improving the flash residual heat recovery efficiency; moderately increasing the circulating heat exchange ratio between the light component tower and the product tower to strengthen the heat coupling between the towers; starting the external auxiliary heating device to ensure the separation stability of the product tower; recording the coupling parameters and energy consumption data that do not meet the standard and storing them in the database as input data for subsequent optimization and operation and maintenance.

[0050] Preferably, a distillation system in a methanol low-pressure carbonylation synthesis acetic acid process comprises:

[0051] A flash energy evaluation module is used to generate an acetic acid reaction liquid by reacting methanol and carbon monoxide in a reaction kettle under the action of a catalyst and a co-catalyst; the initial state parameters of the acetic acid reaction liquid are collected, the flash energy utilization coefficient SNX is calculated and obtained, and a comparison and analysis is performed with the flash energy utilization threshold Sth to determine whether the heat carried by the gas phase is sufficient, and a strategy is given if it is insufficient;

[0052] The light component separation monitoring module is used for sending acetic acid vapor directly from the top gas phase outlet of the flash evaporator into the light component tower top inlet; the coupling of light component recovery and dehydration function is realized through the double separation structure of the tower; the gas-liquid state parameters at the top and bottom of the light component tower are collected, the light component recovery rate index QHZ and the dehydration efficiency coefficient TSX are respectively calculated and obtained, the comprehensive separation efficiency coefficient FLX is further calculated and obtained, and comparison and analysis are carried out with the comprehensive separation efficiency threshold Fth, so as to judge whether the separation performance of the tower meets the standard, and if not, a strategy is given;

[0053] The acetic acid product separation monitoring module is used for sending the crude acetic acid treated by the light component tower into the product tower, and completing the separation of acetic acid and propionic acid in the product tower; the molar fraction and flow parameters of acetic acid at the top of the product tower and propionic acid at the bottom are collected, the propionic acid separation purity index BSZ is calculated, and comparison and analysis are carried out with the propionic acid separation purity threshold Bth, so as to judge whether the purity of the acetic acid product is qualified, and if not, a strategy is given;

[0054] The heat coupling optimization module is used for introducing the energy optimization mechanism between the light component tower and the product tower after the acetic acid purity at the outlet of the product tower meets the standard, collecting the flash residual heat, heat exchange amount between the towers and total heat parameters required for separation maintenance, calculating the energy coupling coefficient EOI, and carrying out comparison and analysis with the energy coupling threshold Oth, so as to judge whether the heat energy utilization reaches the set standard, and if not, a strategy is given.

[0055] The present application provides a kind of rectification system and rectification method in methanol low pressure carbonyl synthesis acetic acid process.There are following beneficial effects:

[0056] (1) the rectification system and rectification method in methanol low pressure carbonyl synthesis acetic acid process, through the flash energy evaluation module, the heat energy of acetic acid reaction liquid and flash gas phase generated in the reaction kettle is calculated and analyzed in real time, whether the heat carried by gas phase is sufficient can be judged, and according to the evaluation result, strategy is taken in time to supplement or optimize, so as to effectively improve the heat energy utilization efficiency of flash gas phase, reduce energy waste.

[0057] (2) the rectification system and rectification method in methanol low pressure carbonyl synthesis acetic acid process, through the light component separation monitoring module, the light component of flash gas phase is recovered, and the crude acetic acid is dehydrated in the double separation structure, the coupling of light component recovery and dehydration function is realized, the number of towers and the floor area are reduced, and the investment cost of equipment, pipeline and delivery pump is reduced.

[0058] (3) The rectification system and rectification method in the methanol low-pressure carbonyl synthesis acetic acid process can accurately determine the separation purity of the acetic acid product by monitoring and calculating the molar fraction and flow of the acetic acid at the top of the product tower and the propionic acid at the bottom in real time through the acetic acid product separation monitoring module, and can improve the stability and reliability of the quality of the product acetic acid by adjusting the tower operation parameters in real time according to the purity deviation.

[0059] (4) The rectification system and rectification method in the methanol low-pressure carbonyl synthesis acetic acid process can realize the heat energy optimization mechanism between the light component tower and the product tower through the heat coupling optimization module, and can monitor and analyze the flash heat, heat exchange between towers and the total heat required for separation in real time, and can dynamically adjust the heat energy distribution or start the auxiliary heating device, so as to effectively improve the heat energy utilization rate, reduce the steam consumption and the amount of circulating water, and realize the effect of energy saving and consumption reduction. BRIEF DESCRIPTION OF DRAWINGS

[0060] Figure 1 It is a rectification method step schematic diagram in the methanol low-pressure carbonyl synthesis acetic acid process of the present application.

[0061] Figure 2 It is a rectification system block diagram flow chart in the methanol low-pressure carbonyl synthesis acetic acid process of the present application. DETAILED DESCRIPTION

[0062] The technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0063] Example 1

[0064] Please refer to Figure 1 The present application provides a rectification method in the methanol low-pressure carbonyl synthesis acetic acid process, which comprises the following steps:

[0065] Step one, in the reaction kettle, methanol and carbon monoxide are reacted under the action of catalyst and cocatalyst to generate acetic acid reaction liquid; the initial state parameters of the acetic acid reaction liquid are collected, the flash energy utilization coefficient SNX is calculated and obtained, and compared with the flash energy utilization threshold Sth to determine whether the heat carried by the gas phase is sufficient, and if not, a strategy is given;

[0066] Step two, the acetic acid vapor at the top of the flash evaporator is directly sent to the top of the light component column; the coupling of light component recovery and dehydration function is realized through the double separation structure of the column; the gas-liquid state parameters at the top and bottom of the light component column are collected, and the light component recovery index QHZ and the dehydration efficiency coefficient TSX are calculated and obtained, and the comprehensive separation efficiency coefficient FLX is further calculated and obtained, and compared with the comprehensive separation efficiency threshold Fth to judge whether the column separation performance meets the standard, and if not, a strategy is given;

[0067] Step three, the crude acetic acid treated by the light component column is sent to the finished product column, and the separation of acetic acid and propionic acid is completed in the finished product column; the molar fraction and flow parameters of acetic acid at the top of the finished product column and propionic acid at the bottom are collected, the propionic acid separation purity index BSZ is calculated, and compared with the propionic acid separation purity threshold Bth to judge whether the acetic acid product purity is qualified, and if not, a strategy is given;

[0068] Step four, after the acetic acid purity at the outlet of the finished product column meets the standard, an energy optimization mechanism between the light component column and the finished product column is introduced, the flash residual heat, heat exchange between columns and total heat required for separation maintenance parameters are collected, the energy coupling coefficient EOI is calculated, and compared with the energy coupling threshold Oth to judge whether the heat energy utilization reaches the set standard, and if not, a strategy is given.

[0069] In this embodiment, through the establishment of the four-step rectification control process, the whole process dynamic monitoring and adjustment from flash energy evaluation, light component recovery and dehydration coupling, acetic acid product purity monitoring to inter-column heat energy optimization is realized, which can effectively improve the flash energy utilization rate, improve the column separation efficiency, ensure the quality stability of acetic acid product, optimize the inter-column heat energy utilization, reduce energy consumption and operation cost, and thus significantly improve the economic efficiency and process reliability of the methanol low-pressure carbonyl synthesis acetic acid process.

[0070] Example 2

[0071] This embodiment is an explanation and description in Example 1, please refer to Figure 1 , specifically, step one includes:

[0072] S11, in the acetic acid synthesis process, methanol and carbon monoxide continuously enter the reaction kettle, and under the action of catalyst and co-catalyst, low-pressure carbonyl synthesis reaction occurs at a pressure of 2.8~3.0MPaA and a temperature of 180~190℃, generating acetic acid reaction liquid;

[0073] S12, the initial state parameters of the acetic acid reaction liquid are obtained by monitoring the temperature, pressure, flow and components of the acetic acid reaction liquid at the outlet of the reaction kettle in real time; the outlet temperature Tout of the acetic acid reaction liquid is collected in real time by arranging a thermocouple on the outlet pipeline; a Coriolis mass flowmeter is installed in the outlet flow path to collect the flow of the acetic acid reaction liquid in real time ; an online gas chromatograph GC is arranged on the outlet pipeline to collect the concentration ratio of the main component molar fraction of the acetic acid reaction liquid , including methanol, carbon monoxide, target product acetic acid and by-product;

[0074] S13, the acetic acid reaction liquid enters the flash evaporator after being depressurized by the flash valve, and the vapor-liquid separation is realized under the action of the instantaneous pressure difference to form two streams of gas phase and liquid phase; the working conditions of the top and bottom outlets of the flash evaporator are monitored in real time;

[0075] S14, the temperature and flow of the gas phase stream at the top outlet of the flash evaporator are continuously monitored to obtain the gas phase temperature value and the gas phase flow value , and an infrared gas analyzer is arranged on the gas phase branch to collect the gas phase component molar fraction .

[0076] In this embodiment, by arranging real-time monitoring devices of temperature, pressure, flow and components at the outlets of the reaction kettle and the flash evaporator, the initial state parameters of the acetic acid reaction liquid and the component information of the flash gas phase can be accurately obtained, the online dynamic evaluation of the vapor-liquid separation process is realized, reliable data for calculating the flash energy utilization coefficient is provided, the heat energy sufficiency of the downstream rectification separation is ensured, and the process control precision and reaction stability are effectively improved.

[0077] Example 3

[0078] This embodiment is an explanation and description in example 2, please refer to Figure 1 , specifically, step one further comprises:

[0079] S15, the flash energy utilization coefficient SNX is calculated and obtained after the dimensionless treatment of the collected outlet temperature of the acetic acid reaction liquid, the acetic acid reaction liquid flow Fout, the main component molar fraction of the acetic acid reaction liquid, the gas phase component molar fraction , the gas phase temperature value and the gas phase flow value , the formula is as follows:

[0080]

[0081] In the formula, Hvo represents the available enthalpy value carried by the flash vapor phase, represents the theoretical enthalpy value of the vaporizable portion in the liquid entering the flash evaporator, represents the sensible heat value of the liquid phase entering the flash evaporator;

[0082] ;

[0083] wherein, represents the molar fraction of the i-th component in the gas phase, represents the gas phase flow value, represents the gas phase outlet temperature value, represents the specific enthalpy value of the i-th gas phase component at temperature , which is obtained by querying the property table, represents the vaporization latent heat value of the i-th gas phase component, which is obtained by querying the property table;

[0084] ;

[0085] wherein, represents the molar fraction of the j-th component in the liquid phase, represents the total flow of the acetic acid reaction liquid outlet, represents the acetic acid reaction liquid outlet temperature, represents the specific enthalpy value of the liquid phase component at temperature , which is obtained by querying the property table;

[0086] ;

[0087] wherein, represents the vaporization latent heat value of the j-th liquid phase component, which is obtained by querying the property table;

[0088] S16, by presetting a flash energy utilization threshold Sth, and comparing and analyzing the flash energy utilization coefficient SNX with the flash energy utilization threshold Sth, to obtain a first evaluation result, comprising:

[0089] When the flash energy utilization coefficient SNX is greater than or equal to the flash energy utilization threshold Sth, it indicates that the heat carried by the gas phase is sufficient, and continuous monitoring is performed.

[0090] When the flash energy utilization coefficient SNX is less than the flash energy utilization threshold Sth, it indicates that the heat carried by the gas phase is insufficient, and there is a risk of a decrease in downstream separation efficiency, a first warning instruction is triggered, and a first strategy is generated: starting an external heating device, increasing the gas phase temperature, and supplementing the heat required for evaporation; adjusting the operation conditions of the reaction kettle, increasing the reaction temperature and flow, and optimizing the flash gas phase heat energy distribution; recalculate until the flash energy utilization coefficient SNX is greater than or equal to the flash energy utilization threshold Sth.

[0091] The acquisition method of the flash energy utilization threshold Sth is as follows: through statistical analysis on a large amount of acetic acid synthesis and flash process operation data, the energy utilization coefficient range when the gas phase heat of the flash evaporator is sufficient and the separation effect is stable is extracted, the reasonable flash energy critical value is determined in combination with the experience of process engineers and the heat balance specification of the rectification system, and the threshold is formulated by referring to the industry process manual, equipment design parameters and energy utilization best practices, so as to effectively identify whether the heat carried by the gas phase is sufficient, and provide reliable early warning and control basis for the downstream separation process.

[0092] In the embodiment, by calculating the flash energy utilization coefficient SNX and comparing it with the preset threshold Sth, the present application can quantitatively evaluate whether the heat carried by the flash gas phase is sufficient, and realize the prospective control of the downstream rectification separation efficiency. When the heat is insufficient, the operation conditions of the reaction kettle can be adjusted or the external heating device can be started in time, so as to ensure the reasonable utilization of heat energy in the flash process, reduce the steam consumption, and improve the overall process energy efficiency and system stability.

[0093] Embodiment 4

[0094] This embodiment is an explanation and description in embodiment 3, please refer to Figure 1 , specifically, step two includes:

[0095] S21, the acetic acid vapor at the top gas phase outlet of the flash evaporator is directly sent to the top feed inlet of the light component column; by installing a mass flow meter at the top outlet, the gas phase flow rate is collected in real time ; an online GC is arranged on the gas phase branch to collect the molar fraction of light components in the gas phase ; a mass flow meter is installed on the top outlet pipeline of the flash evaporator to collect the top inlet gas phase flow rate in real time ; an online GC is arranged on the top outlet pipeline of the flash evaporator to collect the molar fraction of light components in the top inlet in real time ;

[0096] S22, by collecting the gas phase flow rate , the molar fraction of light components in the gas phase , the top inlet gas phase flow rate and the molar fraction of light components in the top inlet , after non-dimensional processing, the light component recovery rate index QHZ is calculated and obtained, and the formula is as follows:

[0097]

[0098] S23, by installing a water content analyzer at the bottom outlet of the light component column, the water content of the crude acetic acid at the bottom of the light component column is collected ; a water content analyzer is arranged on the liquid phase outlet pipeline of the flash evaporator to collect the water content Whi of the crude acetic acid entering the column;

[0099] S24, obtaining the crude acetic acid water content at the bottom of the light component column by collecting and the crude acetic acid water content Whi, dimensionless, to calculate the dehydration efficiency coefficient TSX, as follows:

[0100]

[0101] In this embodiment, by collecting the gas-liquid state parameters at the top and bottom of the light component column in real time, and calculating the light component recovery rate index QHZ and the dehydration efficiency coefficient TSX, the separation performance of the column can be accurately evaluated, online monitoring and quantitative management of light component recovery and crude acetic acid dehydration can be realized, thereby improving the separation efficiency, reducing raw material loss, and optimizing the operation stability and energy utilization rate of the rectification system.

[0102] Example 5

[0103] This embodiment is an explanation and illustration in Example 4, please refer to Figure 1 , specifically, step two further comprises:

[0104] S25, obtaining the light component recovery rate index QHZ and the dehydration efficiency coefficient TSX by calculation, and after dimensionless processing, calculating the comprehensive separation efficiency coefficient FLX, as follows:

[0105]

[0106] In the formula, w1 and w2 represent weight coefficients;

[0107] The method for obtaining w1 and w2: by statistically analyzing a large amount of light component column operation data and dehydration performance test data, evaluating the influence degree of light component recovery rate QHZ and dehydration efficiency TSX on the final quality of crude acetic acid and the separation stability of downstream products, combining the gas-liquid equilibrium model and heat distribution simulation results in the column, and comprehensively determining the reasonable weight proportion; referring to the operation specifications of the acetic acid rectification industry, equipment design parameters and historical operation experience, and combining the process and separation efficiency control expert experience, the following empirical weight coefficients are set to ensure the calculation accuracy and operability of the comprehensive separation efficiency coefficient , to support subsequent column control strategies and process optimization decisions:

[0108] : representing the influence of light component recovery rate on comprehensive separation efficiency, accounting for a medium weight, reflecting the contribution of top gas phase recovery performance to downstream product quality and circulating load;

[0109] : representing the influence of dehydration efficiency on comprehensive separation efficiency, accounting for a higher weight, being a key indicator, directly affecting the crude acetic acid water content and the separation stability of the product column;

[0110] By constructing the comprehensive separation efficiency coefficient FLX which is weighted fusion of light component recovery rate QZH and dehydration efficiency TSX, the overall performance of the dual separation function of the tower can be quantified, a scientific basis is provided for light component tower operation optimization, heating power adjustment and reflux ratio adjustment, and closed-loop quality control of the crude acetic acid rectification process is realized.

[0111] S26, by presetting a comprehensive separation efficiency threshold Fth, and comparing and analyzing the comprehensive separation efficiency coefficient FLX with the comprehensive separation efficiency threshold Fth, a second evaluation result is obtained.

[0112] When the comprehensive separation efficiency coefficient FLX is greater than or equal to the comprehensive separation efficiency threshold Fth, it indicates that the separation performance of the tower meets the standard, and continuous monitoring is performed.

[0113] When the comprehensive separation efficiency coefficient FLX is less than the comprehensive separation efficiency threshold Fth, it indicates that the separation performance of the tower does not meet the standard, a second early warning instruction is triggered, and a second strategy is generated: adjusting the reflux ratio at the top of the tower to improve the recovery efficiency of the light component; adjusting the heating power of the reboiler at the bottom of the tower to improve the dehydration capacity; adjusting the temperature or pressure distribution in the tower to optimize the gas-liquid balance; recalculating until the comprehensive separation efficiency coefficient FLX is greater than or equal to the comprehensive separation efficiency threshold Fth.

[0114] The acquisition method of the comprehensive separation efficiency threshold Fth: through a large amount of statistical analysis on the light component tower operation data and the dehydration efficiency of crude acetic acid, the separation efficiency range under the condition that the recovery rate and dehydration effect meet the standard is extracted, combined with the process expert experience and the rectification tower operation specification, a reasonable separation efficiency critical value is determined; referring to the industry standard, design manual and historical production data, the threshold is formulated to effectively monitor the separation performance of the tower, and to ensure the collaborative optimization of the light component recovery and dehydration function.

[0115] In this embodiment, by introducing the comprehensive separation efficiency coefficient FLX, the present application can unify the light component recovery rate and the dehydration efficiency, realize the accurate evaluation and dynamic adjustment of the overall separation performance of the tower, and when the separation efficiency does not meet the standard, an optimization strategy can be automatically generated to guide the adjustment of the reflux ratio, heating power and tower operating conditions, so as to ensure stable and efficient separation process, reduce energy consumption and improve product quality.

[0116] Embodiment 6

[0117] This embodiment is an explanation and description in embodiment 5, please refer to Figure 1 , specifically, step three includes:

[0118] S31, the crude acetic acid treated by the light component tower is sent to the middle feeding port of the product tower; an online GC or infrared gas analyzer is arranged at the top outlet of the product tower to collect the molar fraction of acetic acid at the top in real time ; install a flow meter at the top outlet of the product tower to collect the top acetic acid flow ; arrange an online GC or infrared gas analyzer at the bottom outlet of the product tower to collect the bottom propionic acid molar fraction ; install a flow meter at the bottom outlet of the product tower to collect the bottom propionic acid flow .

[0119] In this embodiment, by setting online component analysis and flow monitoring at the top and bottom of the product tower, the present application can real-time master the separation state of acetic acid and propionic acid, realize online monitoring of the working condition of the product tower, thereby timely discovering separation abnormalities, ensuring the stability of acetic acid product purity and propionic acid discharge, and improving product quality and production safety.

[0120] Embodiment 7

[0121] This embodiment is an explanation and description in embodiment 6, please refer to Figure 1 , specifically, step three further comprises:

[0122] S32, by collecting the acquired top acetic acid molar fraction , top acetic acid flow , bottom propionic acid molar fraction and bottom propionic acid flow , after dimensionless processing, the propionic acid separation purity index BSZ is calculated and acquired, and the formula is as follows:

[0123]

[0124] S33, by presetting the propionic acid separation purity threshold Bth, and comparing and analyzing the propionic acid separation purity index BSZ with the propionic acid separation purity threshold Bth, a third evaluation result is acquired, including:

[0125] When the propionic acid separation purity index BSZ is greater than or equal to the propionic acid separation purity threshold Bth, it indicates that the separation purity is qualified, the top-produced acetic acid enters the product tank, and the bottom propionic acid is discharged into the waste acid tank;

[0126] When the propionic acid separation purity index BSZ is less than the propionic acid separation purity threshold Bth, it indicates that the separation purity is unqualified, a third early warning instruction is triggered, and a third strategy is generated: adjusting the tower top reflux ratio, improving the acetic acid purity; adjusting the heating power of the tower bottom reboiler, strengthening the propionic acid separation; adjusting the temperature or pressure distribution in the tower, optimizing the gas-liquid separation; recalculating until the propionic acid separation purity index BSZ is greater than or equal to the propionic acid separation purity threshold Bth.

[0127] The acquisition method of the propionic acid separation purity threshold Bth: by analyzing the product column acetic acid and propionic acid separation experimental data and production conditions, the separation index range under the condition that the acetic acid purity meets the specification and the propionic acid bottom stream purity is stable is extracted, the reasonable propionic acid separation purity threshold is determined by combining with the process engineering experience and product quality control requirements; the threshold is formulated by referring to the relevant industry product standards, equipment design parameters and historical quality data to effectively identify the abnormal risk of product acetic acid purity, and realize the stable and controllable product quality.

[0128] In the embodiment, by calculating the propionic acid separation purity index and comparing with the preset threshold, the application can evaluate the separation effect of product acetic acid and propionic acid in real time, and automatically trigger the optimization strategy when the separation purity is not up to standard, so as to accurately control the reflux ratio in the column, the reboiler power and the temperature and pressure distribution, thereby significantly improving the acetic acid product purity and the propionic acid separation efficiency, and ensuring the product quality stability and the reliability of the production process.

[0129] Embodiment 8

[0130] This embodiment is an explanation and description in embodiment 7, please refer to Figure 1 , specifically, step four includes:

[0131] S41, after the product column outlet acetic acid purity meets the standard, an energy optimization mechanism between the light component column and the product column is introduced; a heat flow meter and a temperature sensor are arranged at the outlet of the flash evaporator to collect the flash gas phase residual heat Qfla; temperature and flow sensors are arranged at the inlet and outlet of the reboiler at the bottom of the light component column to obtain the inter-column heat coupling heat exchange amount Qcou; a heat meter is arranged at the reboiler of the product column to collect the total heat required for separation maintenance Qdem.

[0132] In the embodiment, by collecting the flash residual heat, the inter-column heat exchange amount and the total heat required for separation maintenance, the application can monitor the energy flow between the product column and the light component column in real time, provide accurate data support for subsequent heat energy optimization, and help to realize the inter-column heat coupling, reduce the external energy consumption, and improve the energy utilization efficiency of the whole rectification system.

[0133] Embodiment 9

[0134] This embodiment is an explanation and description in embodiment 8, please refer to Figure 1 , specifically, step four further includes:

[0135] S42, by collecting the flash gas phase residual heat Qfla, the inter-column heat coupling heat exchange amount Qcou and the total heat required for separation maintenance Qdem, the energy coupling coefficient EOI is calculated after non-dimensional treatment, and the formula is as follows:

[0136]

[0137] S43, by presetting an energy coupling threshold Oth, and comparing the energy coupling coefficient EOI with the energy coupling threshold Oth, a fourth evaluation result is obtained, including:

[0138] When the energy coupling coefficient EOI is greater than or equal to the energy coupling threshold Oth, it indicates that the heat energy utilization reaches the set standard, and the system can maintain stable separation without additional heating, and the process flow is ended, and a process optimization completion instruction is generated and an energy utilization log is recorded;

[0139] When the energy coupling coefficient EOI is less than the energy coupling threshold Oth, it indicates that the heat energy utilization does not reach the set standard, a fourth warning instruction is triggered, and a fourth strategy is generated: adjusting the operating condition of the heat exchanger, preferentially improving the flash heat recovery efficiency, moderately increasing the circulating heat exchange ratio between the light component column and the product column, and strengthening the heat coupling between the columns; starting the external auxiliary heating device to ensure the separation stability of the product column; recording the coupling parameters and energy consumption data that do not meet the standard and storing them into a database as input data for subsequent optimization and operation.

[0140] The energy coupling threshold Oth is obtained by: statistically analyzing the operating data of the heat exchange system between the light component column and the product column and the flash heat recovery situation, extracting the coupling efficiency range under the condition of energy efficient recovery and stable separation between the columns, combining process optimization experience and thermodynamic energy balance specification, determining a reasonable energy coupling critical value; referring to the equipment design parameters, industry thermal efficiency standard and historical operation experience, formulating the threshold to effectively evaluate the heat energy utilization level, guiding the heat regulation strategy, and improving the overall energy efficiency of the system.

[0141] In the embodiment, by calculating the energy coupling coefficient EOI and comparing it with the threshold Oth, the present application can dynamically judge whether the heat energy utilization between the columns meets the standard, and when the heat energy is insufficient, the optimization strategy can be automatically triggered to realize intelligent regulation and control of flash heat recovery and inter-column circulating heat exchange, ensure the separation stability of the product column, effectively reduce the external energy consumption, and improve the overall energy efficiency and operation reliability of the rectification system.

[0142] Embodiment 10

[0143] Please refer to Figure 2 A rectification system in a methanol low-pressure carbonylation synthesis of acetic acid process, comprising:

[0144] A flash energy evaluation module is used to generate an acetic acid reaction liquid by reacting methanol and carbon monoxide in a reaction kettle under the action of a catalyst and a co-catalyst; the initial state parameters of the acetic acid reaction liquid are collected, the flash energy utilization coefficient SNX is calculated and obtained, and compared with the flash energy utilization threshold Sth to determine whether the heat carried by the gas phase is sufficient, and if not, a strategy is given;

[0145] The light component separation monitoring module is used for sending acetic acid vapor directly from the top gas phase outlet of the flash evaporator into the top inlet of the light component column; the coupling of light component recovery and dehydration function is realized through the double separation structure of the column; the gas-liquid state parameters at the top and bottom of the light component column are collected, the light component recovery index QHZ and the dehydration efficiency coefficient TSX are respectively calculated and obtained, the comprehensive separation efficiency coefficient FLX is further calculated and obtained, and comparison and analysis are performed with the comprehensive separation efficiency threshold Fth to determine whether the separation performance of the column meets the standard, and a strategy is given if the standard is not met;

[0146] The acetic acid product separation monitoring module is used for sending the crude acetic acid after being treated by the light component column into the product column, and separating acetic acid and propionic acid in the product column; the molar fraction and flow parameters of acetic acid at the top of the product column and propionic acid at the bottom of the product column are collected, the propionic acid separation purity index BSZ is calculated, and comparison and analysis are performed with the propionic acid separation purity threshold Bth to determine whether the purity of the acetic acid product is qualified, and a strategy is given if the product is not qualified;

[0147] The heat coupling optimization module is used for introducing an energy optimization mechanism between the light component column and the product column after the purity of acetic acid at the outlet of the product column meets the standard, collecting the parameters of flash residual heat, heat exchange between columns and total heat required for separation maintenance, calculating the energy coupling coefficient EOI, and performing comparison and analysis with the energy coupling threshold Oth to determine whether the heat energy utilization meets the set standard, and a strategy is given if the set standard is not met.

[0148] In the embodiment, through the cooperative monitoring and control of the four modules, the dynamic regulation and control of the whole process from the flash energy evaluation of the reaction liquid, the light component recovery and dehydration, the acetic acid product separation to the heat coupling optimization between columns is realized, so that the rectification system can sense the working conditions of each link in real time, automatically adjust the operation parameters, ensure that the separation efficiency and product purity meet the standard, maximize the use of flash residual heat, reduce energy consumption, and improve the process stability and overall economy.

[0149] The size of the threshold is set for the purpose of comparison, and the size of the threshold depends on the amount of sample data and the base number set by the person skilled in the art for each group of sample data; as long as the proportional relationship of the parameters and the quantized values is not affected.

[0150] The above formulas are obtained by collecting a large amount of data for software simulation and selecting a formula close to the true value, and the coefficients in the formulas are set by the person skilled in the art according to the actual situation. The above is only a preferred specific embodiment of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art can make equivalent substitutions or changes to the technical solutions and inventive concepts of the present application within the technical scope disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. A rectification method in a low-pressure oxo synthesis of acetic acid process from methanol, characterized in that, The method comprises the following steps: Step one, in the reaction kettle, methanol and carbon monoxide are reacted under the action of catalyst and promoter to generate acetic acid reaction liquid; the initial state parameters of the acetic acid reaction liquid are collected, the flash energy utilization coefficient SNX is calculated and obtained, and is compared and analyzed with the flash energy utilization threshold Sth to judge whether the heat carried by the gas phase is sufficient, if not, a strategy is given; Step two, the acetic acid vapor at the top gas phase outlet of the flash evaporator is directly sent to the top inlet of the light component column; the coupling of light component recovery and dehydration function is realized through the double separation structure of the column; the gas-liquid state parameters at the top and bottom of the light component column are collected, the light component recovery rate index QHZ and the dehydration efficiency coefficient TSX are calculated and obtained, respectively, and the comprehensive separation efficiency coefficient FLX is further calculated and obtained, and is compared and analyzed with the comprehensive separation efficiency threshold Fth to judge whether the column separation performance meets the standard, if not, a strategy is given; Step three, the crude acetic acid treated by the light component column is sent to the product column, and the separation of acetic acid and propionic acid is completed in the product column; the molar fraction and flow parameters of acetic acid at the top of the product column and propionic acid at the bottom are collected, the propionic acid separation purity index BSZ is calculated, and is compared and analyzed with the propionic acid separation purity threshold Bth to judge whether the purity of acetic acid product meets the standard, if not, a strategy is given; Step four, after the acetic acid purity at the outlet of the product column meets the standard, an energy optimization mechanism between the light component column and the product column is introduced, the flash residual heat, the heat exchange amount between the columns and the total heat required for separation maintenance are collected, the energy coupling coefficient EOI is calculated, and is compared and analyzed with the energy coupling threshold Oth to judge whether the heat energy utilization meets the set standard, if not, a strategy is given.

2. The rectification method in a low-pressure carbonyl synthesis acetic acid process of methanol according to claim 1, characterized in that, Step one includes: S11, in the acetic acid synthesis process, methanol and carbon monoxide continuously enter the reaction kettle, and under the action of catalyst and promoter, low-pressure carbonyl synthesis reaction occurs at a pressure range of 2.8~3.0MPaA and a temperature condition of 180~190℃, to generate acetic acid reaction liquid; S12, the initial state parameters of the acetic acid reaction liquid are obtained by monitoring the temperature, pressure, flow and components of the acetic acid reaction liquid at the outlet of the reaction kettle in real time; the outlet temperature Tout of the acetic acid reaction liquid is collected in real time by arranging a thermocouple on the outlet pipeline; a Coriolis mass flowmeter is installed in the outlet flow path to collect the flow of the acetic acid reaction liquid in real time ; an online gas chromatograph GC is arranged on the outlet pipeline to collect the molar fraction of the main components of the acetic acid reaction liquid , including the concentration ratio of methanol, carbon monoxide, target product acetic acid and by-products. S13, after the acetic acid reaction liquid is depressurized through the flash valve and enters the flash evaporator, it realizes vapor-liquid separation under the action of instantaneous pressure difference to form two streams of gas phase and liquid phase; the working conditions of the top and bottom outlets of the flash evaporator are monitored in real time; S14, continuously monitor the temperature and flow rate of the gas phase stream at the top outlet of the flasher, obtaining the gas phase temperature value and the gas phase flow rate value An infrared gas analyzer is arranged on the gas phase branch to collect the gas phase component molar fraction .

3. The rectification method in a low-pressure carbonyl synthesis of acetic acid process according to claim 2, characterized in that, Step one further includes: S15, acquiring the outlet temperature of the acetic acid reaction solution by collection , the acetic acid reaction solution flow rate Fout, the molar fraction of the main component of the acetic acid reaction solution , the molar fraction of the gas phase component , the gas phase temperature value , and the gas phase flow rate value After non-dimensional processing, the flash energy utilization coefficient SNX is calculated and acquired; S16, by presetting the flash energy utilization threshold Sth, comparing and analyzing the flash energy utilization coefficient SNX with the flash energy utilization threshold Sth, the first evaluation result is obtained, including: When the flash energy utilization coefficient SNX is greater than or equal to the flash energy utilization threshold Sth, it indicates that the heat carried by the gas phase is sufficient, and continuous monitoring is carried out; When the flash energy utilization coefficient SNX is less than the flash energy utilization threshold Sth, it indicates that the heat carried by the gas phase is insufficient, there is a risk of decreased downstream separation efficiency, a first early warning instruction is triggered, and a first strategy is generated: start the external heating device, increase the temperature of the gas phase, supplement the heat required for evaporation; adjust the operation conditions of the reaction kettle, improve the reaction temperature and flow, and optimize the heat energy distribution of the flash gas phase; recalculate until the flash energy utilization coefficient SNX is greater than or equal to the flash energy utilization threshold Sth.

4. The rectification method in a low-pressure carbonyl synthesis acetic acid process of methanol according to claim 3, characterized in that, Step two includes: S21, the acetic acid vapor from the top gas phase outlet of the flash evaporator is directly sent into the top feed port of the light component column; by installing a mass flow meter at the top outlet, the gas phase flow is collected in real time ; an online GC is arranged at the gas phase branch to collect the light component molar fraction in the gas phase ; a mass flow meter is installed on the pipeline of the top outlet of the flash evaporator to collect the gas phase flow into the column in real time ; an online GC is arranged on the pipeline of the top outlet of the flash evaporator to collect the light component molar fraction into the column in real time ; S22, the gas phase flow rate is obtained by acquisition , the molar fraction of light components in the gas phase , the gas phase flow rate into the column at the top and the molar fraction of light components into the column at the top , after dimensionless processing, the light component recovery index QHZ is calculated S24, by collecting the light component column bottom crude acetic acid water content and the tower crude acetic acid moisture content Whi, dimensionless after processing, the dehydration efficiency coefficient TSX is calculated.

5. The rectification method in a low-pressure carbonyl synthesis acetic acid process of methanol according to claim 4, characterized in that, Step two further includes: S25, obtaining the comprehensive separation efficiency coefficient FLX by dimensionless processing of the obtained light component recovery index QHZ and dehydration efficiency coefficient TSX by calculation; S26, obtaining the second evaluation result by comparing the comprehensive separation efficiency coefficient FLX with the preset comprehensive separation efficiency threshold Fth, including: When the comprehensive separation efficiency coefficient FLX is greater than or equal to the comprehensive separation efficiency threshold Fth, it indicates that the separation performance of the tower meets the standard, and the monitoring is continued; When the comprehensive separation efficiency coefficient FLX is less than the comprehensive separation efficiency threshold Fth, it indicates that the separation performance of the tower does not meet the standard, a second early warning instruction is triggered, and a second strategy is generated: adjusting the reflux ratio at the top of the tower to improve the light component recovery efficiency; adjusting the heating power of the reboiler at the bottom of the tower to improve the dehydration capacity; adjusting the temperature or pressure distribution in the tower to optimize the gas-liquid equilibrium; recalculating until the comprehensive separation efficiency coefficient FLX is greater than or equal to the comprehensive separation efficiency threshold Fth.

6. The rectification method in a low-pressure carbonyl synthesis of acetic acid process according to claim 5, characterized in that, Step three includes: S31, the crude acetic acid treated by light component column is sent to the middle feeding port of the product column; the online GC or infrared gas analyzer is arranged at the top outlet of the product column to collect the molar fraction of acetic acid at the top in real time ; the flow meter is installed at the top outlet of the product column to collect the flow of acetic acid at the top ; the online GC or infrared gas analyzer is arranged at the bottom outlet of the product column to collect the molar fraction of propionic acid at the bottom ; the flow meter is installed at the bottom outlet of the product column to collect the flow of propionic acid at the bottom .

7. The rectification method in a low-pressure carbonyl synthesis of acetic acid process according to claim 6, characterized in that, Step three also includes: S32, the top acetic acid molar fraction is obtained by acquisition , the top acetic acid flow rate , the bottom propionic acid molar fraction , and the bottom propionic acid flow rate After dimensionless processing, the propionic acid separation purity index BSZ is calculated S33, obtaining the third evaluation result by comparing the propionic acid separation purity index BSZ with the preset propionic acid separation purity threshold Bth, including: When the propionic acid separation purity index BSZ is greater than or equal to the propionic acid separation purity threshold Bth, it indicates that the separation purity is qualified, the acetic acid produced at the top is discharged into the product tank, and the propionic acid at the bottom is discharged into the waste acid tank; When the propionic acid separation purity index BSZ is less than the propionic acid separation purity threshold Bth, it indicates that the separation purity is unqualified, a third early warning instruction is triggered, and a third strategy is generated: adjusting the reflux ratio at the top of the tower to improve the acetic acid purity; adjusting the heating power of the reboiler at the bottom of the tower to strengthen the separation of propionic acid; adjusting the temperature or pressure distribution in the tower to optimize the gas-liquid separation; recalculating until the propionic acid separation purity index BSZ is greater than or equal to the propionic acid separation purity threshold Bth.

8. The rectification method in a low-pressure carbonyl synthesis of acetic acid process according to claim 7, characterized in that, Step four includes: S41, after the purity of acetic acid at the outlet of the product tower meets the standard, an energy optimization mechanism between the light component tower and the product tower is introduced; a heat flow meter and a temperature sensor are arranged at the outlet of the flash evaporator to collect the residual heat Qfla of the flash evaporator gas phase; temperature and flow sensors are arranged at the inlet and outlet of the reboiler at the bottom of the light component tower to obtain the heat exchange amount Qcou of the heat coupling between the towers; a heat meter is arranged at the reboiler of the product tower to collect the total heat Qdem required for separation maintenance.

9. The rectification method in a low-pressure carbonyl synthesis of acetic acid process according to claim 8, characterized in that, Step four also includes: S42, obtaining the energy coupling coefficient EOI by dimensionless processing of the collected residual heat Qfla of the flash evaporator gas phase, the heat exchange amount Qcou of the heat coupling between the towers, and the total heat Qdem required for separation maintenance; S43, obtaining the fourth evaluation result by comparing the energy coupling coefficient EOI with the preset energy coupling threshold Oth, including: When the energy coupling coefficient EOI is greater than or equal to the energy coupling threshold Oth, it indicates that the heat energy utilization reaches the set standard, the system can maintain stable separation without additional heating, the process flow is completed, a process optimization completion instruction is generated, and an energy utilization log is recorded; When the energy coupling coefficient EOI is less than the energy coupling threshold Oth, it indicates that the heat energy utilization does not reach the set standard, a fourth early warning instruction is triggered, and a fourth strategy is generated: adjusting the operating condition of the heat exchanger, preferentially improving the flash heat recovery efficiency, moderately increasing the circulating heat exchange ratio between the light component column and the product column, strengthening the heat coupling between the columns, starting the external auxiliary heating device to ensure the stability of the product column separation, and recording the substandard coupling parameters and energy consumption data into the database as input data for subsequent optimization and operation and maintenance.

10. A rectification system in a methanol low-pressure carbonyl synthesis acetic acid process, applied to a rectification method in a methanol low-pressure carbonyl synthesis acetic acid process according to any one of claims 1-9, characterized in that, Comprise: The flash energy evaluation module is used for generating an acetic acid reaction liquid by reacting methanol and carbon monoxide in a reaction kettle under the action of a catalyst and a co-catalyst; the initial state parameters of the acetic acid reaction liquid are collected, the flash energy utilization coefficient SNX is calculated and obtained, and compared and analyzed with the flash energy utilization threshold Sth to determine whether the heat carried by the gas phase is sufficient, and if not, a strategy is given; The light component separation monitoring module is used for directly feeding the acetic acid vapor at the gas phase outlet of the flash evaporator into the light component column top inlet; the coupling of light component recovery and dehydration function is realized through the double separation structure of the column; the gas-liquid state parameters at the top and bottom of the light component column are collected, the light component recovery rate index QHZ and the dehydration efficiency coefficient TSX are calculated and obtained, and the comprehensive separation efficiency coefficient FLX is further calculated and obtained, and compared and analyzed with the comprehensive separation efficiency threshold Fth to determine whether the column separation performance meets the standard, and if not, a strategy is given; The acetic acid product separation monitoring module is used for feeding the crude acetic acid treated by the light component column into the product column to complete the separation of acetic acid and propionic acid in the product column; the molar fraction and flow parameters of acetic acid at the top of the product column and propionic acid at the bottom of the product column are collected, the propionic acid separation purity index BSZ is calculated, and compared and analyzed with the propionic acid separation purity threshold Bth to determine whether the acetic acid product purity is qualified, and if not, a strategy is given; The heat coupling optimization module is used for introducing the energy optimization mechanism between the light component column and the product column after the acetic acid purity at the outlet of the product column meets the standard, collecting the flash heat, inter-column heat exchange and total heat required for separation maintenance parameters, calculating the energy coupling coefficient EOI, and comparing and analyzing with the energy coupling threshold Oth to determine whether the heat energy utilization meets the set standard, and if not, a strategy is given.

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