A closed loop system for co-production of ethylene oxide and methanol
By using a dual-reactor linkage design and an automated control system, the hydrogenation of carbon dioxide in the ethylene epoxidation reaction to co-produce methanol was achieved, solving the problem of unused carbon dioxide and realizing closed-loop utilization of carbon resources and reduction of system energy consumption.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- NINGBO JINYUANDONG PETROCHEM ENG TECH
- Filing Date
- 2025-05-22
- Publication Date
- 2026-06-30
AI Technical Summary
The carbon dioxide byproducts generated by the existing ethylene epoxidation reaction have not been effectively recovered and utilized. Direct emissions result in high carbon emissions and the products are not converted into high-value-added chemicals, thus lacking closed-loop utilization of carbon resources.
The system employs a dual-reactor linkage design with a membrane separation unit, combined with an automated feedback control system, to achieve the co-production of methanol from carbon dioxide hydrogenation. Carbon dioxide is recovered and utilized through membrane separation and adsorption devices, and the system operation is optimized by combining PID and MPC controllers.
It significantly reduces carbon emissions per ton of ethylene oxide, improves carbon resource utilization, reduces system energy consumption, and enhances stability and intelligent control capabilities.
Smart Images
Figure CN224422804U_ABST
Abstract
Description
Technical Field
[0001] This utility model belongs to the field of ethylene oxide production, specifically relating to a closed-loop system for the co-production of ethylene oxide and methanol. Background Technology
[0002] Ethylene oxide is a high-value chemical, and its industrial production mainly relies on the ethylene epoxidation process. However, this process is also one of the most carbon-intensive chemical processes currently in operation. For every ton of ethylene oxide produced, approximately 1.3 tons of carbon dioxide are emitted (mainly as byproducts and separation energy consumption). Currently, most of the carbon dioxide produced as a byproduct of the industrial ethylene epoxidation reaction (accounting for approximately 15%–30% of total carbon input) is directly emitted, a method that is no longer acceptable. Another common treatment method reported is CO2 recovery through physical absorption, which is then used as a diluent in ethylene cracking furnaces.
[0003] Patent CN110937632A describes a method for separating CO2 from the tail gas of ethylene oxide reactions using amine absorption. The recovered CO2 is then reused as a diluent in ethylene cracking furnaces to reduce the risk of coking. While this technology recovers and reuses CO2, preventing direct emissions, the CO2 can only be reused as a diluent and cannot be converted into high-value-added chemicals (such as methanol), thus failing to achieve closed-loop utilization of carbon resources.
[0004] Patent US20180037473A1 uses pressure swing adsorption (PSA) technology to separate CO2 from the reaction gas of ethylene oxide, and uses the CO2-enriched gas to prepare carbonates or urea. The two reactions in this method are completely independent, which increases the process of transportation and management, and lacks real-time control with downstream reactions.
[0005] Therefore, it is necessary to continue to upgrade the research on ethylene epoxidation systems and provide a new system that can achieve closed-loop utilization of carbon resources.
[0006] This utility model is hereby proposed. Utility Model Content
[0007] To address the aforementioned technical problems, this invention provides a closed-loop system for the co-production of ethylene epoxidation and carbon dioxide hydrogenation. This system includes a dual-reactor linkage design and automated feedback control, and also involves the application of a membrane separation unit.
[0008] The technical solution adopted in this utility model is conceived as follows:
[0009] A closed-loop system for co-producing ethylene oxide and methanol includes a first reactor, a first heat exchanger, a product separation device, a membrane separation unit, a compressor, a second reactor, a second heat exchanger, a premixer, an adsorption device loaded with activated carbon or molecular sieves, and a control system.
[0010] The ethylene supply unit and the oxygen supply unit are connected to the inlet of the first reactor via the first heat exchanger. The outlet of the first reactor is connected to the product separation unit via the first heat exchanger. The top outlet of the product separation unit is connected to the membrane separation unit, and the bottom outlet outputs ethylene oxide. The first outlet of the membrane separation unit is connected to the inlet of the first reactor via an adsorption unit, a compressor, and the first heat exchanger in sequence. The second outlet is connected to the premixer via both the hydrogen supply unit and the carbon dioxide supply unit. The premixer is connected to the inlet of the second reactor via the second heat exchanger, and the outlet of the second reactor outputs methanol via the second heat exchanger.
[0011] A laser oxygen analyzer and a non-dispersive infrared sensor for monitoring CO2 concentration are installed around the outlet of the first reactor. The inlet pipeline of the first reactor is connected to an oxygen concentration analyzer. Multiple armored K-type thermocouples are installed in the catalyst packing layers inside the first and second reactors. A first valve is installed on the pipeline between the outlet of the first reactor and the first heat exchanger. The inlet of the second reactor is connected to a mass spectrometer for monitoring the H2 / CO2 molar ratio, and an H2 sensor is installed around it. The circulation pipeline of the second reactor is connected to a hydrogen concentration sensor.
[0012] In the control system, the DCS control unit is connected to the laser oxygen analyzer and the non-dispersive infrared sensor via a 4~20mA analog signal, and communicates with the armored K-type thermocouple via an RS485 bus; the DCS host computer is embedded with an MPC model, which periodically receives temperature, pressure, concentration and flow data collected by the DCS control unit and performs thermodynamic prediction calculations; the PID controller is linked with the compressor's frequency converter and the first valve via the Modbus RTU protocol, receives the set value output by the MPC in real time and feeds back the adjustment amount to the DCS control unit.
[0013] As one implementation method, the product separation device uses an absorption tower, or a multi-stage condensation device with a built-in wire mesh demister and a low-temperature condenser.
[0014] In one implementation, the first reactor is a multi-tube fixed-bed reactor with multiple built-in vertical reaction tubes. In each vertical reaction tube, multiple armored K-type thermocouples are respectively installed at the top, middle and bottom of the catalyst bed along the axial direction.
[0015] In one implementation, the armored K-type thermocouple probe of the first reactor is inserted through the flange sealing structure at the top of the reaction tube, isolated by an alumina ceramic sleeve, and a high-temperature graphite gasket is filled between the outer wall of the sleeve and the 316L stainless steel tube wall.
[0016] As one implementation method, the second reactor is a segmented adiabatic reactor with a horizontal layout and radial flow.
[0017] In one implementation, the membrane separation unit is equipped with a polyimide hollow fiber membrane, and the second outlet of the membrane separation unit is the outlet for outputting CO2.
[0018] As one implementation, the outlet of the second reactor is connected to an online Raman spectrometer for real-time monitoring of product components.
[0019] In one implementation, the premixer is equipped with three sets of 304 stainless steel static spiral blades, with a pitch-to-diameter ratio of 0.5 to 1 and a blade inclination angle of 45°.
[0020] In one embodiment, the adsorption device is a parallel dual-tower structure that can periodically switch between controlling one tower for adsorption and the other tower for regeneration by nitrogen purging.
[0021] Compared with the prior art, this utility model has the following advantages:
[0022] 1. This utility model uses membrane separation + CO2 hydrogenation technology to convert CO2, a byproduct of ethylene epoxidation, into methanol, thereby achieving closed-loop utilization of carbon. The carbon resource utilization rate is significantly improved compared with traditional processes, and the carbon emissions per ton of ethylene oxide are greatly reduced.
[0023] 2. The first heat exchanger recovers the waste heat from the reaction tail gas for preheating the feed, reducing the total energy consumption of the system; the second heat exchanger realizes the cascade utilization of the heat of methanol synthesis reaction, optimizing energy integration.
[0024] 3. The MPC model has a high accuracy rate in predicting thermal runaway. Combined with the dynamic adjustment of the PID controller, the system stability is improved, the unplanned downtime rate is reduced, and the intelligent control capability is stronger. Attached Figure Description
[0025] The accompanying drawings are provided to further illustrate the technical solution of this utility model and constitute a part of the specification. They are used together with the embodiments of this application to explain the technical solution of this utility model and do not constitute a limitation on the technical solution of this utility model.
[0026] Figure 1 This is a schematic diagram of the closed-loop system for the co-production of ethylene epoxidation and carbon dioxide hydrogenation provided by this utility model.
[0027] The diagram is labeled as follows: 1-First reactor; 2-First heat exchanger; 3-Product separation device; 4-Membrane separation unit; 5-Compressor; 6-Second reactor; 7-Second heat exchanger; 8-Premixer; 9-Adsorption device; 10-First valve; 11-Second valve; A-Ethylene; B-Oxygen; C-Cooling water; D-Ethylene oxide; E-Methanol; F-Hydrogen; G-Supplemental carbon dioxide; PI-Pressure sensor; TI-Sheathed K-type thermocouple. Detailed Implementation
[0028] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this utility model. All other embodiments obtained by those skilled in the art based on the described embodiments of this utility model without creative effort are within the scope of protection of this utility model.
[0029] In the closed-loop system for co-producing ethylene oxide and methanol of this invention, auxiliary components for detecting temperature, pressure, concentration, and flow rate are provided on the connection lines. These include temperature sensors, pressure sensors, and flow meters. These can be directly used by technicians according to their actual needs. In order to simplify the drawing and facilitate understanding of the main design concept of the system, some auxiliary components (such as flow meters for each device and valves on the pipeline) have been omitted. This does not affect the operation of the system.
[0030] The abbreviations and their explanations are as follows:
[0031] MPC: Model Predictive Control. An MPC model is embedded in the DCS host computer. It receives temperature, pressure and concentration data every 5 seconds and performs thermodynamic prediction calculations to predict the temperature rise rate of the first reactor bed and the risk of deviation of the H2 / CO2 molar ratio in the second reactor in real time.
[0032] PID: Proportional-Integral-Derivative Controller, which is linked with the inverter of compressor 5 and the first valve 10 via Modbus protocol, and dynamically adjusts the equipment parameters according to the set value output by MPC.
[0033] PI: Pressure Indicator. Figure 1 The PI marked in the middle refers to the pressure sensor installed at the inlet and outlet of the membrane separation unit, which is used to monitor the pressure difference ΔP (50~80kPa). The data is transmitted to the DCS via the HART protocol.
[0034] TI: Temperature Indicator. Figure 1 The TI marked in the middle refers to the armored K-type thermocouple in the second reactor, which monitors the bed temperature in real time (accuracy ±0.5℃), and the signal is transmitted to the DCS via the Profibus-DP bus.
[0035] QMS stands for mass spectrometer.
[0036] Example 1
[0037] A closed-loop system for the co-production of ethylene oxide and methanol, such as Figure 1 As shown, it includes a first reactor 1, a first heat exchanger 2, a product separation device 3, a membrane separation unit 4, a compressor 5, a second reactor 6, a second heat exchanger 7, a premixer 8, an adsorption device 9, and a control system.
[0038] The ethylene supply unit and the oxygen supply unit are connected to the inlet of the first reactor 1 via the first heat exchanger 2. The outlet of the first reactor 1 is connected to the product separation unit 3 via the first heat exchanger 2. The top outlet of the product separation unit 3 is connected to the membrane separation unit 4, and the bottom outlet outputs ethylene oxide. The first outlet of the membrane separation unit 4 is connected to the inlet of the first reactor 1 via the adsorption unit 9, the compressor 5, and the first heat exchanger 2 in sequence. The second outlet is connected to the premixer 8 via the hydrogen supply unit and the carbon dioxide supply unit. The premixer 8 is connected to the inlet of the second reactor 6 via the second heat exchanger 7. The outlet of the second reactor 6 is connected to the inlet of the second reactor 6 via one pipeline after passing through the second heat exchanger 7, and methanol is output via another pipeline.
[0039] A laser oxygen analyzer and a non-dispersive infrared sensor for monitoring CO2 concentration are installed around the outlet of the first reactor 1; armored K-type thermocouples are installed in the catalyst packing layer inside the first reactor 1 and the second reactor 6; a first valve 10 is installed on the pipeline between the outlet of the first reactor 1 and the first heat exchanger 2, specifically 1 to 2 meters downstream of the outlet flange of the first reactor 1.
[0040] In the control system, the DCS control unit is connected to the laser oxygen analyzer and the non-dispersive infrared sensor via a 4~20mA analog signal, and communicates with the armored K-type thermocouple via an RS485 bus; the DCS host computer is embedded with an MPC model, which receives temperature, pressure, concentration and flow data collected by the DCS control unit every 5 seconds and performs thermodynamic prediction calculations; the PID controller is linked with the frequency converter of compressor 5 and the first valve 10 via the Modbus RTU protocol, receives the set value output by MPC in real time and feeds back the adjustment amount to the DCS control unit.
[0041] An oxygen concentration analyzer is installed on the inlet pipeline of the first reactor 1. When the oxygen concentration exceeds 8%, the DCS triggers the emergency shut-off valve and injects nitrogen to dilute it. A hydrogen concentration sensor is installed on the circulation pipeline of the second reactor 6. When the hydrogen concentration is >4%, the DCS activates the emergency discharge valve and cuts off the hydrogen supply.
[0042] The PID controller is an extension module of the distributed control system (DCS). It is installed in the DCS cabinet in the central control room and shares a backplane with the DCS I / O cards (AI / AO modules).
[0043] Specifically, as an example rather than a specific limitation, the MPC model calculates the temperature rise rate of the first reactor 1 based on the Arrhenius equation and combines it with an LSTM neural network to predict the oxygen concentration deviation within the next 3 seconds, outputting an ethylene feed rate correction factor (±5%). The PID controller uses a proportional gain Kp=1.2, integral time Ti=8s, derivative time Td=0.5s, and an output frequency adjustment limit of ±5Hz. Those skilled in electrical engineering can adopt more appropriate specific methods as technology develops.
[0044] A second valve 11 is provided at the connection section between the hydrogen supply pipeline and the premixer 8. Specifically, it can be set 1 to 2 meters upstream of the mixing node of the premixer 8 and the second outlet (i.e. CO2 outlet) of the membrane separation unit 4.
[0045] As a specific example, product separation device 3 may use an absorption tower or a multi-stage condensation device with a built-in wire mesh demister and low-temperature condenser.
[0046] As a specific example, the first reactor 1 is a multi-tube fixed-bed reactor with multiple built-in vertical reaction tubes. In each vertical reaction tube, the catalyst bed is equipped with armored K-type thermocouples at the top, middle and bottom of the bed along the axial direction, and has a 316L stainless steel lining with a ceramic coating.
[0047] Specifically, three sets of armored K-type thermocouples are installed axially within the catalyst bed of each vertical reaction tube, located at the top, middle, and bottom of the bed (50 mm from the tube inlet), respectively, to monitor the axial temperature gradient. The armored K-type thermocouple probes are inserted through the flange sealing structure at the top of the reaction tube. An alumina ceramic sleeve (2 mm thick) is used to isolate the reactants, and a high-temperature graphite gasket (800℃ resistant) is filled between the outer wall of the sleeve and the 316L stainless steel tube wall to ensure airtightness. The thermocouple signal lines use MI mineral-insulated cables and are run through an explosion-proof junction box to avoid the risk of combustion and explosion in an ethylene / oxygen mixture environment.
[0048] The first reactor 1 is filled with Ag / α-Al2O3 catalyst with a loading of 10%-15 wt% and a particle size of 3~5 mm.
[0049] As a specific example, the second reactor 6 is a horizontally laid-out, radially flowing, segmented adiabatic reactor with multiple catalyst packing layers inside. The second reactor 6 uses a Cu-Zn-Al catalyst. Specifically, the second reactor 6 has a diameter of 2.5 m and a length of 6 m, and is packed with catalyst in three sections.
[0050] Specifically, three sets of thermocouple signals for each reaction tube are connected to a distributed I / O module and transmitted to the DCS control unit via a redundant Profibus-DP bus, with a sampling frequency of 1Hz. The DCS control unit calculates the axial temperature difference of each reaction tube in real time (ΔT = top - bottom temperature). When ΔT > 15℃, the MPC model is triggered to dynamically adjust the oxygen feed ratio (reducing it by 2%~5%) to suppress local overheating. The PID controller adjusts the opening of the electric regulating valve of the cooling water jacket outside the tube (adjustment accuracy ±0.5%) according to the central temperature setpoint (T_set = 220±5℃).
[0051] As a specific example, membrane separation unit 4 is equipped with a polyimide hollow fiber membrane, and the second outlet of membrane separation unit 4 is the CO2 output outlet. The operating temperature of membrane separation unit 4 is 25~50℃, the pressure difference is 0.5~2MPa, and the membrane area / flow rate (A / Q) is 0.1~1m². 2 / (m 3 Between / h).
[0052] As a specific example, the adsorption device 9 is loaded with activated carbon or molecular sieves.
[0053] As a specific example, a laser oxygen analyzer and a non-dispersive infrared sensor for analyzing CO2 concentration are installed around the outlet of the first reactor 1.
[0054] As a specific example, the inlet of the second reactor 6 is connected to a mass spectrometer for monitoring the H2 / CO2 molar ratio, and an H2 sensor is installed around it; the outlet of the second reactor 6 is connected to an online Raman spectrometer.
[0055] The following is combined Figure 1 The main working process of a closed-loop system for the co-production of ethylene oxide and methanol is described below:
[0056] Figure 1 In this reactor, the first reactor 1 is vertically arranged, while the second reactor 6 is horizontally arranged. Therefore, the first reactor 1 and the second reactor 6 have an overall L-shaped layout, with fewer devices and a compact setup with short pipelines. The first reactor 1 is an ethylene epoxidation reactor, and its outlet gas mainly includes unreacted ethylene, oxygen, the product ethylene oxide (EO), byproducts carbon dioxide and trace amounts of water vapor and chlorinated hydrocarbons (such as dichloroethane). The waste heat from the tail gas of the first reactor 1 exchanges heat with the inlet gas (ethylene A and oxygen B) in the first heat exchanger 2. After the tail gas is cooled by the heat exchange, it undergoes product separation through the product separation device 3 (specifically, an absorption tower).
[0057] As an example, the outlet gas from the first reactor 1 enters an absorption tower for treatment, using ethylene carbonate or water as the absorbent, and EO is absorbed in a countercurrent contact manner within the absorption tower. The absorption tower is vertically arranged, using ethylene carbonate or water as the absorbent for countercurrent contact absorption of ethylene oxide (EO). The gas exiting the absorption tower enters a membrane separation unit 4 equipped with a polyimide hollow fiber membrane. Unreacted ethylene, after passing through an adsorption device 9 and a compressor 5, is recycled back into the first reactor 1 along with the reaction inlet gas (ethylene A, oxygen B), improving the ethylene recycling rate. The adsorption device 9 removes trace amounts of chlorinated hydrocarbons (such as dichloroethane) and O2 (controlled concentration <8% of the explosion limit). The carbon dioxide selectively separated by the membrane separation unit 4, along with hydrogen F and supplementary carbon dioxide G, enters a premixer 8. After premixing, it enters the second reactor 6. The outlet gas and inlet gas of the second reactor 6 exchange heat through a second heat exchanger 7. The operating temperature of membrane separation unit 4 is 25~50℃, the pressure difference is 0.5~2MPa, and the membrane area / flow rate (A / Q) is 0.1~1m³. 2 / (m 3 Between / h).
[0058] In the control system of the closed-loop system for co-producing ethylene oxide and methanol, the distributed control system (DCS) integrates model predictive control (MPC) and proportional-integral-derivative (PID) control algorithms through real-time data acquisition and communication networks, forming a three-level control architecture:
[0059] Data layer: The DCS acquires reactor temperature (TI), pressure (PI), gas concentration (NDIR / QMS) and flow rate data in real time via 4~20mA analog signals, HART protocol and Profibus-DP bus;
[0060] Prediction layer: The MPC model is embedded in the DCS host computer, and predicts the risk of thermal runaway and the deviation of CO2 conversion rate based on thermodynamic equations and LSTM algorithm;
[0061] Execution layer: The PID controller receives the set value output by the MPC and dynamically adjusts the frequency of the compressor 5, the opening degree of the first valve 10, and the cooling water valve position through the Modbus RTU / TCP protocol to achieve closed-loop fine-tuning.
[0062] Its main control logic is as follows:
[0063] (1) At the outlet of the first reactor 1, the CO2 concentration increases → DCS calculates the required H2 increment (ΔH2= k×ΔCO2) → Adjust the compression ratio valve on the H2 supply line;
[0064] (2) Abnormal bed temperature in the second reactor 6 → MPC model predicts risk of thermal runaway → Reduce feed rate in the first reactor 1 + start emergency cooling water;
[0065] (3) The pressure difference of membrane separation unit 4 exceeds the limit → the PID controller adjusts the opening of the first valve 10 of the first reactor 1 → maintain ΔP in the range of 50~80 kPa.
[0066] The following is an example of the collaborative logic between the PID control algorithm and MPC and DCS:
[0067] I. Compressor Frequency Adjustment
[0068] Input: Based on the pressure difference (ΔP) of the membrane separation unit, the MPC outputs the compressor frequency setpoint (fset);
[0069] PID function: The PID controller communicates with the compressor inverter (ABB ACS880) via Modbus TCP protocol, takes the deviation between the actual frequency and fset as input, calculates the adjustment amount, and has an adjustment accuracy of ±0.5Hz;
[0070] Safety limit: When f_actual > 50Hz, the PID output is locked at 50Hz to avoid compressor overload.
[0071] II. Adjustment of the opening degree of the first valve 10
[0072] Input: DCS monitors the inlet and outlet pressure difference of the membrane separation unit in real time (ΔP), and MPC calculates the target pressure difference (ΔP_set=60kPa);
[0073] PID function: The PID controller (Fisher GX) takes the deviation between ΔP and ΔP_set as input, adopts an anti-integral saturation algorithm, and outputs the first valve opening degree (0~100%), with a regulation response time of <3s;
[0074] Interlock protection: When ΔP > 80kPa, the PID override control valve position is fully open (100%).
[0075] III. Dynamic Adjustment of Cooling Water Valves
[0076] Input: The deviation between the temperature (T_mid) at the middle of the vertical reaction tube of the first reactor 1 and the set value (T_set=220℃);
[0077] PID function: The PID controller drives the electric regulating valve through pulse width modulation (PWM) signal, with valve position adjustment accuracy of ±0.5% and ensures T_mid fluctuation ≤ ±3℃.
[0078] This closed-loop combined production of ethylene oxide and methanol improves material utilization, increases the added value of the production line, and yields good economic benefits.
[0079] Although the embodiments disclosed in this utility model are as described above, the content described is only for the purpose of facilitating understanding of this utility model and is not intended to limit this utility model. Any person skilled in the art to which this utility model pertains may make any modifications and changes in the form and details of the implementation without departing from the spirit and scope disclosed in this utility model, but the patent protection scope of this utility model shall still be determined by the scope defined in the appended claims.
Claims
1. A closed-loop system for the co-production of ethylene oxide and methanol, characterized in that, It includes a first reactor (1), a first heat exchanger (2), a product separation device (3), a membrane separation unit (4), a compressor (5), a second reactor (6), a second heat exchanger (7), a premixer (8), an adsorption device (9) loaded with activated carbon or molecular sieves, and a control system; The ethylene supply unit and the oxygen supply unit are connected to the inlet of the first reactor (1) via the first heat exchanger (2), and the outlet of the first reactor (1) is connected to the product separation unit (3) via the first heat exchanger (2); the top outlet of the product separation unit (3) is connected to the membrane separation unit (4), and the bottom outlet outputs ethylene oxide; the first outlet of the membrane separation unit (4) is connected to the inlet of the first reactor (1) via the adsorption unit (9), the compressor (5) and the first heat exchanger (2) in sequence, and the second outlet is connected to the premixer (8) along with the hydrogen supply unit and the carbon dioxide supply unit; the premixer (8) is connected to the inlet of the second reactor (6) via the second heat exchanger (7), and the outlet of the second reactor (6) outputs methanol via the second heat exchanger (7); A laser oxygen analyzer and a non-dispersive infrared sensor for monitoring CO2 concentration are installed around the outlet of the first reactor (1). The inlet pipeline of the first reactor (1) is connected to the oxygen concentration analyzer. Multiple armored K-type thermocouples are installed in the catalyst packing layer inside the first reactor (1) and the second reactor (6). A first valve (10) is installed on the pipeline between the outlet of the first reactor (1) and the first heat exchanger (2). The inlet of the second reactor (6) is connected to a mass spectrometer for monitoring the H2 / CO2 molar ratio, and an H2 sensor is installed around it. The circulation pipeline of the second reactor (6) is connected to a hydrogen concentration sensor. In the control system, the DCS control unit is connected to the laser oxygen analyzer and the non-dispersive infrared sensor via a 4~20mA analog signal, and communicates with the armored K-type thermocouple via an RS485 bus; the DCS host computer is embedded with an MPC model, which periodically receives temperature, pressure, concentration and flow data collected by the DCS control unit and performs thermodynamic prediction calculations; the PID controller is linked with the inverter of the compressor (5) and the first valve (10) via the Modbus RTU protocol, and receives the set value output by the MPC in real time and feeds back the adjustment amount to the DCS control unit.
2. The closed-loop system for co-producing ethylene oxide and methanol according to claim 1, characterized in that, The product separation device (3) adopts an absorption tower or a multi-stage condensation device with a built-in wire mesh demister and a low-temperature condenser.
3. The closed-loop system for co-producing ethylene oxide and methanol according to claim 1, characterized in that, The first reactor (1) is a multi-tube fixed-bed reactor with multiple vertical reaction tubes. In each vertical reaction tube, multiple armored K-type thermocouples are installed along the axial direction at the top, middle and bottom of the catalyst bed.
4. The closed-loop system for co-producing ethylene oxide and methanol according to claim 3, characterized in that, The armored K-type thermocouple probe of the first reactor (1) is inserted through the flange sealing structure at the top of the reaction tube and isolated by an alumina ceramic sleeve. The outer wall of the sleeve and the wall of the 316L stainless steel tube are filled with a high-temperature graphite gasket.
5. The closed-loop system for co-producing ethylene oxide and methanol according to claim 1, characterized in that, The second reactor (6) is a segmented adiabatic reactor with a horizontal layout and radial flow.
6. The closed-loop system for co-producing ethylene oxide and methanol according to claim 1, characterized in that, The membrane separation unit (4) is equipped with a polyimide hollow fiber membrane, and the second outlet of the membrane separation unit (4) is the outlet for outputting CO2.
7. The closed-loop system for co-producing ethylene oxide and methanol according to claim 1, characterized in that, The outlet of the second reactor (6) is connected to an online Raman spectrometer for real-time monitoring of product composition.
8. The closed-loop system for co-producing ethylene oxide and methanol according to claim 1, characterized in that, The premixer (8) is equipped with three sets of 304 stainless steel static spiral blades, with a pitch-to-diameter ratio of 0.5 to 1 and a blade inclination angle of 45°.
9. A closed-loop system for co-producing ethylene oxide and methanol according to claim 1, characterized in that, The adsorption device (9) is a parallel dual-tower structure that can periodically switch between controlling one tower for adsorption and the other tower for regeneration by nitrogen purging.