System and method for cascade recovery of low-pressure steam energy in ethylene glycol synthesis

Abstract

The invention belongs to the technical field of ethylene glycol production, and particularly discloses a system and method for cascade recovery of low-pressure steam energy in ethylene glycol synthesis, and the system comprises a first steam pipe network which obtains steam in a first air pressure state; the first rated air pressure of steam introduced into the ethylene glycol rectification device and the high-pressure methanol dehydration tower is in a second air pressure state, and the first steam pipe network adapts to the first rated air pressure through the steam in the first air pressure state. The second steam pipe network is used for acquiring the steam in the first air pressure state and the steam in the third air pressure state, and mixing and adjusting the steam to a fourth air pressure state; the second steam pipe network conveys the steam in the fourth air pressure state to a plurality of technological process devices; compared with the prior art, the method has the following advantages that high-pressure steam is replaced by low-pressure steam which is a byproduct of ethylene glycol synthesis, energy consumption and cost are remarkably reduced, meanwhile, steam use is optimized, energy recovery efficiency is improved, and environmental protection and reduction of greenhouse gas emission are facilitated.

Description

Technical Field

[0001] The invention relates to the technical field of ethylene glycol production, and in particular to a system and method for stepwise recovery of low-pressure steam energy in ethylene glycol synthesis. Background Art

[0002] In the existing ethylene glycol production process, especially in the ethylene glycol synthesis and distillation stages, a large amount of by-product steam is generated, but its utilization efficiency is often low, resulting in significant energy waste and cost increase, inefficient steam utilization and excessive consumption of high-pressure steam, and further leading to low energy efficiency and high cost of ethylene glycol production.

[0003] Therefore, a system and method for stepwise recovery of low-pressure steam energy in ethylene glycol synthesis is proposed to solve the above-mentioned problems. Summary of the invention

[0004] The present invention aims to provide a system and method for stepwise recovery of low-pressure steam energy in ethylene glycol synthesis, so as to solve or improve at least one of the above-mentioned technical problems.

[0005] In view of this, a first aspect of the present invention is to provide a system and method for stepwise recovery of low-pressure steam energy in ethylene glycol synthesis.

[0006] The second aspect of the present invention is to provide a method for stepwise recovery of low-pressure steam energy in ethylene glycol synthesis.

[0007] A first aspect of the present invention provides a system for stepwise recovery of low-pressure steam energy in ethylene glycol synthesis, the system being used to collect steam in a first gas pressure state discharged from an ethylene glycol synthesis gas bag, and to transport the steam in the first gas pressure state to a plurality of ethylene glycol distillation devices and a high-pressure methanol dehydration tower of a dimethyl oxalate distillation device; the system comprising: a first steam pipeline network, for obtaining steam in the first gas pressure state and maintaining the steam in the first gas pressure state; a first rated gas pressure of the steam introduced into the ethylene glycol distillation device and the high-pressure methanol dehydration tower being a second gas pressure state, and the first steam pipeline network; The steam pipeline network adapts the first rated air pressure through the steam in the first air pressure state; the steam discharged from the ethylene glycol distillation device is in a third air pressure state; the second steam pipeline network obtains the steam in the first air pressure state and the steam in the third air pressure state, and mixes the steam and adjusts it to a fourth air pressure state; the second steam pipeline network transports the steam in the fourth air pressure state to multiple process flow equipment in the ethylene glycol synthesis process; wherein the steam pressures are arranged from high to low as follows: the second air pressure state, the first air pressure state, the fourth air pressure state and the third air pressure state.

[0008] In any of the above technical solutions, a distillation and upgrading device is provided on the pipeline connecting the second steam network and the ethylene glycol distillation device, and the distillation and upgrading device adjusts the steam pressure discharged from the ethylene glycol distillation device through an upgrading machine; wherein the range of adjusting the steam pressure by the distillation and upgrading device is from the third gas pressure state to the fourth gas pressure state.

[0009] In any of the above technical solutions, the steam discharged from the distillation and upgrading device is mixed with the steam discharged from the ethylene glycol rectification device to maintain the steam pressure inside the second steam network at the fourth gas pressure state.

[0010] In any of the above technical solutions, the process flow equipment is at least one of the following: a methyl formate separation tower, a dimethyl carbonate distillation unit, an ethanol product tower and an ethanol concentration tower of the dimethyl oxalate distillation unit.

[0011] In any of the above technical solutions, all of the process equipment and the high-pressure methanol dehydration tower are connected to the condensation main pipe.

[0012] In any of the above technical solutions, the second rated gas pressure of the steam introduced into the process equipment is the fourth gas pressure state, and the value of the fourth gas pressure state is: 0.4MPaG~0.6MPaG.

[0013] In any of the above technical solutions, the value of the second air pressure state is: 1.6MPaG~1.8MPaG; and the value of the fourth air pressure state is: 0.1MPaG~0.2MPaG.

[0014] In any of the above technical solutions, the ethylene glycol distillation device and the high-pressure methanol dehydration tower are also respectively connected to high-pressure pipelines; when there is a usage gap after the steam in the first gas pressure state is adapted to the first rated gas pressure, the high-pressure pipeline is used to pass the steam in the second gas pressure state into the ethylene glycol distillation device and / or the high-pressure methanol dehydration tower.

[0015] In any of the above technical solutions, the first steam pipeline adjusts the amount of steam discharged into the ethylene glycol distillation device and the dimethyl oxalate distillation device so that the steam in the first gas pressure state adapts to the first rated gas pressure; and the value of the first gas pressure state is: 0.7MPaG~0.9MPaG.

[0016] The second aspect of the present invention provides a method for stepwise recovery of low-pressure steam energy in ethylene glycol synthesis, which is implemented by the system in any of the above-mentioned technical solutions, and includes the following steps: obtaining steam in the first gas pressure state discharged from the ethylene glycol synthesis gas bag, and storing it in the first steam pipeline network; transporting the steam in the first steam pipeline network to the ethylene glycol distillation unit and the high-pressure methanol dehydration tower, and adapting the steam in the first gas pressure state to the first rated gas pressure; obtaining and adjusting the steam in the third gas pressure state discharged from the ethylene glycol distillation unit, and mixing it with the steam in the first gas pressure state inside the first steam pipeline network; and transporting the mixed steam to the process flow equipment.

[0017] Compared with the prior art, the present invention has the following beneficial effects: The steam at the first gas pressure state produced as a byproduct of the ethylene glycol synthesis drum during the production process is used to replace the steam at the second gas pressure state currently supplied to the reboiler of the dimethyl oxalate distillation high-pressure methanol dehydration tower and the ethylene glycol distillation dealcoholization tower. This not only reduces the dependence on high-pressure steam, but also improves the comprehensive utilization rate of energy, and avoids the byproduct steam at the first gas pressure state being discharged or depressurized without being fully utilized. By adjusting the system and equipment to accept steam at a slightly lower pressure, energy consumption and production costs can be significantly reduced.

[0018] In addition, the steam in the third gas pressure state produced as a byproduct of the waste boiler of the ethylene glycol distillation dealcoholization tower is also utilized. In traditional processes, this part of steam is often discharged after being cooled by an air cooler, and is not effectively utilized. In the present invention, this part of low-pressure steam is reintroduced into other devices that require low-pressure steam, such as for heating or as a heat source for other chemical processes, thereby reducing the demand for fresh steam and reducing energy consumption; it not only optimizes the steam use strategy and improves energy recovery efficiency, but also contributes to environmental protection. By reducing the production and consumption of steam, the combustion of fossil fuels and the emission of greenhouse gases are correspondingly reduced.

[0019] Additional aspects and advantages of embodiments according to the present invention will become apparent in the following description or may be learned through practice of embodiments according to the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which: Figure 1 It is a schematic diagram of the process flow of the present invention; Figure 2 It is a schematic diagram of the process flow in the prior art; Figure 3 The figure is a flow chart of the method steps of the present invention. DETAILED DESCRIPTION

[0021] In order to more clearly understand the above-mentioned purpose, features and advantages of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

[0022] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited to the specific embodiments disclosed below.

[0023] See also Figure 1-Figure 3 , the following describes a system and method for stepwise recovery of low-pressure steam energy in ethylene glycol synthesis according to some embodiments of the present invention.

[0024] As mentioned in the background technology, the ethylene glycol synthesis unit of the ethylene glycol plant is equipped with 12 steam drums, of which the ethylene glycol synthesis steam drum produces 0.8MPa steam as a byproduct under 100% design conditions, with an output of 190.8 tons / hour. At the end of the catalyst period, the byproduct steam capacity of the steam drum can reach 236.4 tons / hour. At present, the steam produced by the ethylene glycol synthesis steam drum is incorporated into the 0.5MPa steam network, and the corresponding steam condensate flows into the condensate recovery device 110802-S-103.

[0025] Ethylene glycol distillation unit: It includes three series, each series has two dealcoholization towers, each dealcoholization tower is equipped with two waste boilers, a total of six dealcoholization towers and twelve waste boilers. Specifically, each dealcoholization tower consumes 1.7MPaG steam for operation, with a flow rate of 68 tons / hour, and is recycled through the waste boiler at the top of the tower. Each tower consumes 42 tons / hour of boiler feed water, and produces 0.15MPaG steam as a by-product, with an output of 42 tons / hour and a steam outlet temperature of 126°C. Of this by-product steam, 20 tons / hour is used in the reboiler of the methanol recovery tower, and the other 22 tons / hour is directed to the air cooler for cooling. The three sets of equipment in the ethylene glycol distillation system waste a total of 132 tons / hour of 0.15MPaG steam in the air cooler link.

[0026] There are three series of dimethyl oxalate distillation units: each series is equipped with a methyl formate separation tower and a high-pressure methanol dehydration tower, with three towers in total. A single methyl formate separation tower consumes 0.5MpaG steam during operation, with a flow rate of 8.5 tons / hour, and its bottom temperature is controlled at 86°C. The high-pressure methanol dehydration tower consumes 1.7MPa of steam during operation, with a flow rate of 33 tons / hour, and the steam condensate produced enters the condensate recovery device 110802-S-102.

[0027] Dimethyl carbonate distillation unit: one dimethyl carbonate light removal tower, which consumes 0.5MpaG steam during operation, with a flow rate of 29-30 tons / h and a tower bottom operating temperature of 99.58°C; Ethanol separation system: There is one ethanol product tower and one ethanol concentration tower, both using 0.5MpaG steam, and their temperatures are controlled at 107℃ and 99℃ respectively. The ethanol product tower consumes 13t / h of 0.5MpaG steam, and the ethanol concentration tower consumes 3.5t / h of 0.5MpaG steam.

[0028] In the existing ethylene glycol production process, especially in the ethylene glycol synthesis and distillation stages, a large amount of by-product steam is generated, but its utilization efficiency is often low, resulting in significant energy waste and increased costs. This inefficient steam utilization and excessive consumption of high-pressure steam not only leads to low energy efficiency in ethylene glycol production, but also significantly increases production costs. As a key source of heat energy in the production process, the management and optimization of steam is crucial to the operational efficiency of the entire plant. Since the pressure and temperature of the by-product steam fail to fully meet the requirements of other production stages, this part of the steam can only be discharged or depressurized or reheated through energy-intensive methods to meet the operating requirements of other units.

[0029] In addition, the complexity and inadequate regulation of steam systems often result in a large amount of steam loss during transmission, such as through pipeline leakage or non-optimized heat exchange processes. This not only reduces the overall thermal efficiency of the system, but also increases dependence on raw materials, further driving up operating costs and environmental impact.

[0030] In view of the above-mentioned technical problems, the embodiments of the first aspect of the present invention provide a system for stepwise recovery of low-pressure steam energy in ethylene glycol synthesis. In some embodiments of the present invention, Figure 1 As shown, the system is used to collect steam in a first gas pressure state discharged from an ethylene glycol synthesis gas bag, and transport the steam in the first gas pressure state to a high-pressure methanol dehydration tower of a plurality of ethylene glycol distillation units and a dimethyl oxalate distillation unit; the system comprises: The first steam pipeline obtains steam in a first gas pressure state and maintains the steam in the first gas pressure state; the first rated gas pressure of the steam introduced into the ethylene glycol distillation unit and the high-pressure methanol dehydration tower is a second gas pressure state, and the first steam pipeline adapts the first rated gas pressure through the steam in the first gas pressure state; the steam discharged from the ethylene glycol distillation unit is in a third gas pressure state.

[0031] The second steam pipeline obtains steam in the first gas pressure state and steam in the third gas pressure state, and mixes the steam and adjusts the steam to a fourth gas pressure state; the second steam pipeline transports the steam in the fourth gas pressure state to multiple process flow equipment in the ethylene glycol synthesis process.

[0032] Among them, the steam pressure is arranged from high to low as follows: the second gas pressure state, the first gas pressure state, the fourth gas pressure state and the third gas pressure state.

[0033] The present invention provides a system for stepwise recovery of low-pressure steam energy in ethylene glycol synthesis, which first collects low-pressure steam discharged from the ethylene glycol synthesis gas bag at a first gas pressure state (such as 0.8MPa). This step ensures that the generated by-product steam is not wasted, but is effectively captured for further use; the collected low-pressure steam is sent to a device requiring high-pressure steam through a dedicated steam delivery pipeline, such as a high-pressure methanol dehydration tower in an ethylene glycol distillation device and a dimethyl oxalate distillation device.

[0034] The system adopts the concept of energy cascade utilization, that is, steam of different pressure levels is allocated to the corresponding process units as needed to optimize the energy utilization of steam. For example, after the pressure of 0.8MPa low-pressure steam is adjusted, it is provided to the methanol dehydration tower that requires 1.7MPa high-pressure steam; the system includes a steam compressor or a pressure regulating valve for adjusting the pressure of the low-pressure steam to the required high-pressure level. This pressure adjustment is achieved through energy-efficient compression technology to ensure that the pressure increase of the steam achieves the best balance between energy consumption and cost-effectiveness; in addition to the pressure adjustment of the steam, the system is also provided with a heat exchange device for recovering heat energy from the steam discharged from the high-pressure methanol dehydration tower. The recovered heat energy can be used to preheat the raw materials entering the synthesis and distillation units or for other processes that require heating, thereby further improving the comprehensive utilization rate of energy; in order to ensure the efficient operation of the system, the present invention also includes an integrated control system, which is responsible for monitoring and adjusting the flow, pressure and temperature of the steam to ensure the balance of steam supply and demand and the maximum utilization of energy.

[0035] The first steam network is responsible for collecting steam at the first pressure state from the ethylene glycol synthesis unit and transporting the steam to the equipment that requires the first rated pressure. The network is designed to maintain the steam pressure stable, avoid pressure loss, and ensure that the steam maintains its original pressure state during the transmission process; the steam captured from the ethylene glycol synthesis process is maintained at the first pressure state (such as 0.8 MPa) through special valves and control systems to prevent pressure reduction during transportation; the network is made of high-efficiency thermal insulation materials to minimize heat energy loss and ensure that the steam can be transported to the destination in the best state.

[0036] These devices receive steam from the first steam pipeline network, and their first rated gas pressure is set to the second gas pressure state to meet the high-pressure requirements of the operation of these equipment; before the steam in the first steam pipeline network enters these devices, it is adjusted to the second gas pressure state (such as 1.7 MPa) through a steam compressor or a pressure reducing valve to meet the needs of high-pressure operations such as the methanol dehydration tower; the adjusted high-pressure steam is used for heating and evaporation processes in the ethylene glycol distillation unit and the methanol dehydration tower to improve yield and efficiency.

[0037] The ethylene glycol distillation unit will discharge steam after completing the distillation process. At this time, the steam is in the third gas pressure state (such as 0.15 MPa). The steam can be recycled to reduce energy waste; the discharged low-pressure steam is collected by a special recovery system, and heat energy is recovered from it using a heat exchanger or other heat recovery equipment; the recovered heat energy can be used to preheat raw materials or provide heat sources for other processes that require lower temperatures, realizing energy recycling and improving overall energy efficiency.

[0038] The second steam pipeline network can simultaneously collect steam at a first pressure state (such as 0.8 MPa) and steam at a third pressure state (such as 0.15 MPa); mix steam at different pressure states and adjust it to a new pressure level, namely, a fourth pressure state (such as 0.5 MPa), to meet the needs of specific process equipment; and transport the adjusted steam at the fourth pressure state to multiple equipment in the ethylene glycol synthesis process, such as reactors and heat exchangers.

[0039] The second steam network collects steam of different pressure states from the glycol distillation unit and other steam generation points through a dedicated collection system. These steams are transported to the central processing unit through the network; in the central processing unit, steam from different pressure sources is mixed through precisely controlled pressure regulating valves and mixers. This process uses a compressor or a pressure reducing valve to uniformly adjust the steam pressure to the required fourth pressure state, while keeping the temperature and flow of the steam in line with process requirements; by adjusting the steam to a pressure more suitable for specific process requirements, the second steam network optimizes energy utilization and reduces additional energy consumption and production costs. This pressure adjustment strategy helps to maximize the energy recovery of the remaining steam and improve the energy efficiency of the entire system; the adjusted steam is safely and efficiently transported to the target equipment in the glycol synthesis process through the network. These devices use steam for heating, reaction or other heat-driven processes to ensure the continuity and efficiency of glycol production.

[0040] The second gas pressure state (highest pressure) provides steam at the highest pressure and is usually used in the most energy-intensive processes, such as key applications such as high-pressure methanol dehydration towers; it is directly generated by the high-pressure part of the ethylene glycol synthesis unit or compressed to this pressure by a steam compressor. It is used in processes that require high-temperature and high-pressure steam to complete chemical reactions or material conversions.

[0041] The first pressure state is at a medium pressure level and is suitable for standard industrial heating and evaporation processes. It is obtained directly from the ethylene glycol synthesis gas drum, or by appropriately adjusting the steam pressure reduction of the second pressure state. It is mainly used in processes such as ethylene glycol distillation units that do not require extreme conditions but still require significant thermal energy.

[0042] The fourth pressure state, which is lower than the first pressure state, is used for applications with lower energy requirements, such as some preheating and low-level heating processes; it is obtained by further reducing the pressure of the steam in the first pressure state, or by mixing the steam in the first and third pressure states to this level to provide moderate heating, which is suitable for the milder heating requirements in ethylene glycol synthesis.

[0043] The third gas pressure state (lowest pressure) provides steam at the lowest pressure, which is mainly used for energy recovery and utilization minimization processes; it usually comes from waste steam in the distillation process, which is recovered through condensation or heat exchangers and used for low-temperature applications such as preliminary preheating of materials or thermal management systems within the factory.

[0044] In summary, the steam discharged from the glycol synthesis gas bag in the first gas pressure state is collected through the first steam pipeline network, and the steam pressure is effectively kept from being reduced. By adapting and adjusting the steam pressure, it can be directly used in the glycol distillation unit and the high-pressure methanol dehydration tower that require the second gas pressure state, avoiding energy loss due to steam pressure mismatch; the second steam pipeline network can capture steam in the first gas pressure state and the third gas pressure state, and mix these two steams of different pressures to adjust to the fourth gas pressure state suitable for other process flow equipment. This design allows the low-pressure steam that might have been wasted to be effectively recovered and utilized; the system achieves the cascade utilization of energy by precisely controlling the transition of steam from high pressure to low pressure. This not only improves the overall energy efficiency of steam, but also reduces the need for additional energy input.

[0045] Through more efficient steam utilization, the present invention significantly reduces energy consumption in the ethylene glycol production process. This directly reduces production costs and reduces environmental pollution, meeting the requirements of sustainable development; the optimized steam management system reduces the production demand and maintenance costs of high-pressure steam, while improving the energy recovery rate of the entire production process, thereby reducing operating costs; by ensuring the proper matching and utilization of steam pressure, production equipment can operate in the best state, avoiding potential failures or inefficiencies caused by equipment not adapting to improper steam pressure; effective management and adjustment of steam pressure enables the system to more flexibly respond to the steam needs of different equipment in the production process, improving the adaptability and stability of the system.

[0046] In any of the above embodiments, a distillation and upgrading device is provided on the pipeline connecting the second steam network and the ethylene glycol distillation device, and the distillation and upgrading device adjusts the steam pressure discharged from the ethylene glycol distillation device through an upgrading machine; wherein the range of adjusting the steam pressure of the distillation and upgrading device is from the third gas pressure state to the fourth gas pressure state.

[0047] In this embodiment, the main function of the distillation and upgrading device is to adjust the low-pressure steam (third gas pressure state) discharged from the ethylene glycol distillation device to a higher pressure (fourth gas pressure state) to make it more suitable for other process requirements; by increasing the steam pressure, its energy content can be increased, thereby improving the thermal efficiency and energy utilization of the overall system.

[0048] The distillation upgrading unit first captures the low-pressure steam discharged from the glycol distillation unit from the connected pipeline. These steam are usually in a low energy state and are not efficient to use directly; the captured steam passes through a steam compressor or similar pressure-raising equipment, and its pressure is raised to the fourth gas pressure state. In this process, the steam compressor converts mechanical energy into additional internal energy of the steam, thereby increasing the temperature and pressure of the steam; the steam after pressure increase is not only at a higher pressure, but also has enhanced thermal energy, enabling energy conversion and process applications at a more efficient thermal level. This upgraded steam can be transported to process units that require medium-pressure steam, such as preheating systems, other distillation towers or heat exchangers; the entire process is managed by a sophisticated control system to ensure that the steam pressure is accurately adjusted to meet the specific needs of different equipment. The control system usually includes pressure sensors, temperature sensors and flow controllers, which ensure that the steam upgrading process is stable and efficient.

[0049] In any of the above embodiments, the steam discharged from the distillation upgrading device is mixed with the steam discharged from the ethylene glycol rectification device to maintain the steam pressure inside the second steam network at the fourth gas pressure state.

[0050] In this embodiment, through the coordination of the distillation upgrading device and the second steam pipeline network, the system is able to maintain a constant steam pressure (fourth gas pressure state) to meet the needs of multiple devices in the ethylene glycol synthesis process; this configuration effectively manages the energy level of steam and ensures the effective distribution and use of steam in the entire system.

[0051] The distillation and upgrading device receives the low-pressure steam (third pressure state) discharged from the ethylene glycol rectification device and raises its pressure to the fourth pressure state; the pressure and temperature of the steam are increased through a steam compressor or similar equipment to make it more suitable for a wider range of industrial applications; in the second steam network, the upgraded steam is mixed with steam from other sources (which may still be in the first or fourth pressure state); the mixing ratio and flow rate are adjusted by the automatic control system to ensure that the mixed steam is kept in the fourth pressure state as a whole. In this process, the control system monitors the pressure and flow at each point and automatically adjusts to maintain the required pressure level; the steam maintained at the fourth pressure state is transported to other process flow equipment in the ethylene glycol synthesis process, such as heat exchangers, reactors, etc., through the second steam network; the steam under this pressure can effectively transfer heat energy and improve the thermal efficiency and energy utilization of the production process; the entire system is equipped with advanced sensors and feedback mechanisms that can monitor the pressure, temperature and flow of steam in real time; the control system adjusts the operating parameters according to real-time data to ensure that the steam pressure is stable and meet the ever-changing production needs.

[0052] In any of the above embodiments, the process equipment is at least one of the following: The methyl formate separation tower of the dimethyl oxalate distillation unit, the dimethyl carbonate distillation unit, the ethanol product tower and the ethanol concentration tower.

[0053] In this embodiment, the methyl formate separation tower of the dimethyl oxalate distillation device is used to separate different components in dimethoxymethane (dimethyl oxalate) and purify dimethyl oxalate through a distillation process; steam in the fourth gas pressure state is supplied to the methyl formate separation tower to provide the required thermal energy to drive the distillation process, so that components with different boiling points are separated in the tower. Since the steam has been pressure adjusted and improved, its thermal efficiency is higher, which helps to improve the efficiency and output quality of the separation process.

[0054] The dimethyl carbonate distillation unit is used to purify dimethyl carbonate (DMCO), which is crucial in the production of high-purity DMC products. The steam in the fourth gas pressure state provides heat energy for the dimethyl carbonate distillation unit, evaporates the mixture by heating, and separates pure DMC by condensation. The adjusted steam optimizes energy use through effective heat exchange, reduces heat energy loss, and improves operating efficiency.

[0055] The ethanol product tower is used for the production and purification of ethanol and separation of ethanol and other by-products. The steam in the fourth gas pressure state is used to provide heating energy for the ethanol product tower, so that ethanol evaporates from the mixture and is collected through the top of the tower. The pressure and temperature of the steam are suitable for the evaporation requirements of ethanol, which optimizes the evaporation and condensation process and improves the purity and yield of the product.

[0056] The ethanol concentration tower further concentrates and refines ethanol to remove moisture and other impurities. The steam in the fourth gas pressure state provides the necessary heat for the ethanol concentration tower to drive further evaporation and concentration processes. By effectively controlling the temperature and pressure of the steam, it ensures that ethanol is concentrated under optimal conditions to maximize production efficiency and product quality.

[0057] In any of the above embodiments, all process flow equipment and the high-pressure methanol dehydration tower are connected to the condensation main pipe.

[0058] In this embodiment, the main function of the condensation main pipe is to collect steam condensate generated by all connected equipment, including condensate from the dimethyl oxalate distillation unit, the dimethyl carbonate distillation unit, the ethanol product tower, the ethanol concentration tower and the high-pressure methanol dehydration tower; by centrally collecting condensate, the system can more efficiently recover thermal energy and chemical energy, which can be reused for heating or preheating other process flows, reducing the demand for new energy.

[0059] After each process unit uses steam for heating, evaporation or chemical reaction, the steam will be converted into water or low-temperature steam, namely condensate; these condensates usually contain a certain amount of heat energy, and direct discharge will result in energy waste; all equipment that produces condensate is connected to the condensate main through pipelines; the condensate flows to the condensate main through natural slope or with the help of pumps and is collected together; the condensate main is equipped with a heat exchanger or similar equipment to extract heat energy from the high-temperature condensate. The recovered heat energy can be used to preheat raw materials or provide heating for low-temperature processes, reducing dependence on external heat sources; centralized heat recovery systems allow more precise energy management. By adjusting the working parameters of the heat exchanger, the heat recovery efficiency can be maximized. The control system can monitor the temperature, flow and pressure of the condensate, and automatically adjust the system parameters to adapt to different process requirements and energy recovery conditions.

[0060] In any of the above embodiments, the second rated gas pressure of the steam introduced into the process equipment is the fourth gas pressure state, and the value of the fourth gas pressure state is selected as 0.5 MPaG in the range of 0.4~0.6 MPaG.

[0061] In this embodiment, the steam pressure for all process flow equipment is uniformly set to 0.5 MPaG, which helps to simplify system design, reduce the need for pressure regulating equipment, and reduce energy loss. The steam pressure of 0.5 MPaG is moderate and sufficient to meet most chemical processes and heat exchange requirements while maintaining high thermal efficiency and safety.

[0062] As needed, steam can be generated in the generator or obtained by reducing the pressure of high-pressure steam through a pressure regulating system (such as a pressure reducing valve). 0.5 MPaG steam is suitable for a variety of processes, including evaporation, heating, reaction drive, etc. The pressure-adjusted steam is transported to various process flow equipment through the steam pipeline network, such as the methyl formate separation tower of the dimethyl oxalate distillation unit, the dimethyl carbonate distillation unit, the ethanol product tower and the ethanol concentration tower. The pipeline network design considers minimizing heat loss and pressure drop to ensure that the steam reaches the use point in the best state; In the process equipment, 0.5 MPaG steam is used to provide the necessary thermal energy, such as the reboiler in the distillation tower, which heats the substrate to evaporate it and then separates the required chemicals through condensation. Steam at this pressure can effectively transfer heat while maintaining the safety and economy of operation; The system contains automatic control and monitoring equipment to monitor and adjust the flow, pressure and temperature of steam in real time to ensure the best match between steam supply and demand. This control not only improves energy utilization, but also helps prevent overpressure or insufficient gas supply, and ensures the continuity and stability of the production process.

[0063] In any of the above embodiments, the value of the second gas pressure state is selected as 1.7 MPaG in the range of 1.6-1.8 MPaG; and the value of the fourth gas pressure state is selected as 0.15 MPaG in the range of 0.1-0.2 MPaG.

[0064] In this embodiment, the second gas pressure state (1.7 MPaG) is used for process equipment that requires high temperature and high pressure steam, such as a high pressure methanol dehydration tower. High pressure steam can effectively drive reactions that require high energy input in chemical processes; 1.7 MPaG steam is usually generated in a steam boiler, which can use natural gas, coal or electricity as energy, and use an efficient pressure control system (including safety valves and pressure regulating valves) to ensure that the steam maintains a stable pressure during transportation and use; high pressure steam can provide the necessary heat and pressure to complete chemical separation and conversion processes that require high energy, such as catalytic reactions and distillation separations.

[0065] The fourth gas pressure state (0.15 MPaG) is generally used for process applications with low energy requirements, such as preheating, low-temperature washing and other mild heating processes that do not require the intense heat of high-pressure steam; lower pressure steam (0.15 MPaG) is usually obtained from the high-pressure steam system through a pressure reducing device, or directly generated by a waste heat recovery system; while ensuring safety and energy efficiency, the application of low-pressure steam helps to reduce energy consumption by using lower temperature steam to meet process requirements; steam at this pressure usually involves recovering waste heat from other processes, and transferring heat energy to materials or processes that require low-temperature treatment through a heat exchanger, which not only saves energy but also increases the overall energy efficiency of the system.

[0066] In any of the above embodiments, the ethylene glycol distillation device and the high-pressure methanol dehydration tower are also connected to the high-pressure pipeline respectively.

[0067] When there is a usage gap after the steam in the first gas pressure state is adapted to the first rated gas pressure, the high-pressure pipeline is used to introduce steam in the second gas pressure state into the ethylene glycol distillation unit and / or the high-pressure methanol dehydration tower.

[0068] In this embodiment, when the steam in the first gas pressure state cannot meet all the needs of the ethylene glycol distillation unit and the high-pressure methanol dehydration tower, the high-pressure pipeline is used to introduce steam in the second gas pressure state (1.7 MPaG) to these units to supplement the demand gap; by providing a reliable source of high-pressure steam, it is ensured that the production process is not interrupted due to insufficient steam supply, thereby maintaining production efficiency and product quality.

[0069] The system monitors the steam consumption of the glycol distillation unit and the high-pressure methanol dehydration tower in real time through sensors and control software. When it detects that the steam supply in the first gas pressure state (usually 0.8 MPaG) is insufficient to meet the current operation requirements, the control system will automatically trigger the replenishment of high-pressure steam; the control system activates the high-pressure pipeline to transport 1.7 MPaG steam from the high-pressure steam source (usually equipped with one or more high-efficiency boilers or steam generators), and the high-pressure steam enters the glycol distillation unit and the high-pressure methanol dehydration tower through a special pressure regulating valve to ensure that the equipment will not be overloaded with pressure; before the steam enters the point of use, the pressure may need to be adjusted appropriately to match the specific pressure requirements of the equipment to prevent system overpressure or equipment damage. The introduction of high-pressure steam includes multiple safety checks to ensure the safety of operation; the system design takes into account the optimal use of energy, and reduces energy waste and improves energy recovery by adjusting the steam supply strategy. The system may also include a heat recovery unit to further extract waste heat from the used steam for other low-energy demand processes, such as preheating raw materials or auxiliary heating.

[0070] In any of the above embodiments, the first steam pipeline adjusts the amount of steam discharged into the ethylene glycol distillation device and the dimethyl oxalate distillation device so that the steam in the first gas pressure state adapts to the first rated gas pressure; and the value of the first gas pressure state is selected as 0.8 MPaG in the range of 0.7~0.9 MPaG.

[0071] In this embodiment, the first steam pipeline network is responsible for accurately controlling the amount of steam flowing to the ethylene glycol distillation unit and the dimethyl oxalate distillation unit, ensuring that these devices receive the appropriate amount of steam to meet their operating requirements; the system design ensures that the steam is effectively used at a pressure of 0.8 MPaG to avoid energy waste or equipment damage due to steam pressure mismatch.

[0072] The first steam network is equipped with multiple regulating valves and flow controllers. These controls dynamically adjust the steam flow according to the needs of the steam-using equipment. The control system automatically adjusts the steam supply according to the feedback signals (such as temperature, pressure and flow demand) from the ethylene glycol distillation unit and the dimethyl oxalate distillation unit. The network design ensures that the steam maintains a pressure of 0.8 MPaG during transportation. High-quality pipes and sealing technology are used to prevent pressure loss. When steam is transported from the generation source (such as a boiler) to the point of use, the energy and temperature of the steam are ensured not to be significantly reduced due to the transmission distance by maintaining a constant pressure. By precisely controlling the steam volume and pressure, the system can minimize energy waste and improve overall energy efficiency. The control system may include intelligent algorithms to optimize the steam distribution strategy based on real-time data and historical performance. The system has multiple built-in safety measures, such as pressure safety valves and emergency shutdown systems to prevent steam pressure from exceeding the safety threshold of the equipment. The real-time monitoring system continuously tracks the steam status and flow direction to ensure that operators can respond quickly to any abnormal situation.

[0073] Specifically, the first steam network adjusts the steam volume discharged into the ethylene glycol distillation device and the dimethyl oxalate distillation device to 10% to 20% of the steam in the first gas pressure state.

[0074] Actual use: A separate 0.8MPaG steam network is added to the outlet pipe gallery of the by-product steam of ethylene glycol synthesis, which will be led to the high-pressure methanol dehydration tower for use in its reboiler, and the original 1.7MpaG steam will be retired. Its condensate will still enter the original condensate recovery system to flash 0.5MpaG steam to recover heat.

[0075] An upgrading unit is added near the second and third series ethylene glycol distillation units to upgrade the 0.15MpaG steam by-product of the dealcoholization tower to 0.5MpaG and incorporate it into the 0.5MpaG steam main.

[0076] A quality upgrading unit is added near a series of ethylene glycol distillation units to upgrade the 0.15MpaG steam by-product of the dealcoholization tower to 0.3MpaG and send it to the dimethyl carbonate light removal tower and methyl formate separation tower for use, and the original 0.5MpaG steam is retired.

[0077] The reboiler of the dimethyl carbonate light removal tower was modified by increasing the heat exchange area of ​​the reboiler so that it could use 0.3MpaG steam to meet the operating conditions and withdraw 0.5MpaG steam to make up for the 0.5MpaG steam gap.

[0078] The 1.7MpaG steam of the high-pressure methanol dehydration tower is withdrawn, and the 0.8MpaG steam is increased to replace the 1.7MpaG steam, so that the high-pressure methanol dehydration tower can be operated. The original process of 0.8MpaG steam is incorporated into the 0.5MpaG steam network. After replacing the 1.7MpaG steam, there is a steam gap in the 0.5MpaG steam network. Now, by increasing the pressure of the by-product steam of the second and third series of dealcoholization towers to 0.5MPaG to supplement the 0.5MpaG network, and increasing the pressure of the by-product steam of a series of dealcoholization towers to 0.3MpaG for use in the dimethyl carbonate light tower and the methyl formate separation tower, the 0.5MpaG steam is withdrawn to supplement its steam network, and finally the steam network is rebalanced. This plan ultimately saves 1.7MpaG of steam, which can be recovered by reducing coal consumption in the system boiler, and the 0.15MpaG by-product steam can be fully recovered in the air cooler. Furthermore, a series of by-product steam from the dealcoholization tower is upgraded to 0.3MpaG to replace 0.5MpaG steam, greatly reducing the energy consumption of the pressure-raising unit. Expected revenue details: Steam revenue: 128.5×81×8000=83.27 million yuan / a; Utility consumption: Cooling water: 0.34×150×8000=408,000 yuan / a; Deoxygenated water: 8.84×8.5×8000=601,000 yuan / a; Electricity fee: 5785×0.61×8000=28.23 million yuan / a; Total cost: 40.8+60.1+2823=29.239 million yuan / a; The comprehensive income is: 8327-2923.9=5403.1 million yuan / a.

[0079] The embodiment of the second aspect of the present invention provides a method for stepwise recovery of low-pressure steam energy in ethylene glycol synthesis. In some embodiments of the present invention, Figure 3 As shown, through the system implementation in any of the above embodiments, the method includes the following steps: S101, obtaining steam in a first gas pressure state discharged from an ethylene glycol synthesis gas bag, and storing it in a first steam pipeline network.

[0080] S102, transporting the steam of the first steam pipeline network to the ethylene glycol distillation unit and the high-pressure methanol dehydration tower, and adapting the steam in the first gas pressure state to the first rated gas pressure.

[0081] S103, obtaining and adjusting the steam in the third gas pressure state discharged from the ethylene glycol distillation device, and mixing it with the steam in the first gas pressure state inside the first steam pipe network.

[0082] S104, transporting the mixed steam to process equipment.

[0083] The present invention provides a method for stepwise recovery of low-pressure steam energy in ethylene glycol synthesis, step S101: obtaining steam and storing it, collecting steam in a first gas pressure state (e.g., 0.8 MPaG) discharged from a gas bag during ethylene glycol synthesis, and storing it in a first steam pipe network; using a pressure sensor and a flow meter to monitor and control the steam flow from the ethylene glycol synthesis gas bag to the first steam pipe network, and using a valve and a control system to ensure that the steam maintains its pressure and temperature during transportation and storage to prevent energy loss. Step S102: transporting steam and adapting the pressure, transporting the steam in the first steam pipe network to the ethylene glycol distillation device and the high-pressure methanol dehydration tower, ensuring that the steam pressure meets the operating requirements of these devices; adjusting the pressure of the transported steam through an automatic control system to match the first rated gas pressure requirements of the ethylene glycol distillation device and the high-pressure methanol dehydration tower, and using a pressure regulating device (such as a pressure reducing valve) to ensure that the steam reaches an appropriate pressure and temperature before entering these devices. Step S103: Adjust and mix steam, collect steam at a third pressure state (e.g., 0.15 MPaG) discharged from the ethylene glycol distillation unit, and mix it with steam at a first pressure state inside the first steam network; use a steam mixer or a regulating valve to mix steam of two different pressures to optimize energy utilization, and adjust the mixing ratio through a control system to ensure that the mixed steam meets the needs of downstream processes. Step S104: Transport the mixed steam, and transport the adjusted and mixed steam to other process flow equipment, such as the methyl formate separation tower, dimethyl carbonate distillation unit, ethanol product tower, and ethanol concentration tower of the dimethyl oxalate distillation unit; use the steam network to efficiently and safely transport the mixed steam to the target equipment for use, ensure that the pressure, temperature, and flow rate of the steam during the transportation process continue to meet the process requirements, and adjust the steam parameters through real-time monitoring and automatic adjustment systems.

[0084] In the description of the present invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0085] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A system for stepwise recovery of low-pressure steam energy in ethylene glycol synthesis, characterized in that: The system is used to collect steam in a first gas pressure state discharged from an ethylene glycol synthesis gas bag, and transport the steam in the first gas pressure state to a high-pressure methanol dehydration tower of a plurality of ethylene glycol distillation units and a dimethyl oxalate distillation unit; The system comprises: a first steam network, obtaining steam at the first pressure state and maintaining the steam at the first pressure state; a first rated pressure of the steam introduced into the ethylene glycol distillation unit and the high-pressure methanol dehydration tower is a second pressure state, and the first steam network is adapted to the first rated pressure through the steam at the first pressure state; the steam discharged from the ethylene glycol distillation unit is at a third pressure state; The second steam pipeline network obtains the steam in the first gas pressure state and the steam in the third gas pressure state, and mixes and adjusts the steam to a fourth gas pressure state; the second steam pipeline network transports the steam in the fourth gas pressure state to multiple process flow equipment in the ethylene glycol synthesis process; Among them, the steam pressure is arranged from high to low as follows: the second air pressure state, the first air pressure state, the fourth air pressure state and the third air pressure state.

2. The system according to claim 1, characterized in that A distillation and upgrading device is provided on the pipeline connecting the second steam network and the ethylene glycol distillation device, and the distillation and upgrading device adjusts the steam pressure discharged from the ethylene glycol distillation device through an upgrading machine; wherein the range of adjusting the steam pressure by the distillation and upgrading device is from the third gas pressure state to the fourth gas pressure state.

3. The system according to claim 2, characterized in that The steam discharged from the distillation and upgrading device is mixed with the steam discharged from the ethylene glycol rectification device to maintain the steam pressure inside the second steam network at the fourth gas pressure state.

4. The system according to claim 1, characterized in that The process equipment is at least one of the following: The dimethyl oxalate distillation device comprises a methyl formate separation tower, a dimethyl carbonate distillation device, an ethanol product tower and an ethanol concentration tower.

5. The system according to claim 4, characterized in that All of the process equipment and the high-pressure methanol dehydration tower are connected to the condensation main pipe.

6. The system according to claim 4, characterized in that The second rated gas pressure of the steam introduced into the process equipment is the fourth gas pressure state, and the value of the fourth gas pressure state is: 0.4MPaG~0.6MPaG.

7. The system according to claim 1, characterized in that The value of the second air pressure state is: 1.6MPaG~1.8MPaG; and the value of the fourth air pressure state is: 0.1MPaG~0.2MPaG.

8. The system according to claim 1, characterized in that The ethylene glycol distillation device and the high-pressure methanol dehydration tower are also connected to high-pressure pipelines respectively; When there is a usage gap after the steam in the first gas pressure state is adapted to the first rated gas pressure, the high-pressure pipeline is used to supply the steam in the second gas pressure state to the ethylene glycol distillation unit and / or the high-pressure methanol dehydration tower.

9. The system according to claims 1-8, characterized in that: The first steam pipe network adjusts the amount of steam discharged into the ethylene glycol distillation device and the dimethyl oxalate distillation device so that the steam in the first gas pressure state adapts to the first rated gas pressure; And the value of the first air pressure state is: 0.7MPaG~0.9MPaG.

10. A method implemented by the system according to any one of claims 1 to 9, characterized in that: The steps include: Obtaining steam discharged from the ethylene glycol synthesis gas bag and in the first gas pressure state, and storing it in the first steam pipeline network; transporting the steam of the first steam pipe network to the ethylene glycol distillation device and the high-pressure methanol dehydration tower, and adapting the steam in the first gas pressure state to the first rated gas pressure; Acquiring and adjusting the steam in the third gas pressure state discharged from the ethylene glycol distillation device, and mixing it with the steam in the first gas pressure state inside the first steam pipe network; The mixed steam is delivered to the process equipment.

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