A low-pressure steam power generation system for by-product oxalic dimethyl ester in natural gas-to-ethylene glycol synthesis

Abstract

The utility model discloses a natural gas is made into glycol and the oxalic acid dimethyl ester synthesis byproduct low pressure steam power generation system, including the inlet separation tank, bypass condenser and condensate pump that pass through pipeline are connected in proper order, still be equipped with with bypass condenser parallelly connected turbine, generator and main condenser between inlet separation tank and condensate pump, still include the equalizing chamber, and the equalizing chamber is used for guaranteeing turbine's shaft seal steam stability, and the low pressure steam of oxalic acid dimethyl ester synthesis section is transported to the inlet separation tank in the gas -liquid separation through the conveying pipeline, and the separated steam enters turbine and drives the impeller rotation, and the kinetic energy is converted to the generator and generates electricity, and then, enters the main condenser and cools down, and finally is pumped to the interface area outside through the condensate pump. Can effectively to natural gas is made into glycol and the oxalic acid dimethyl ester synthesis byproduct low pressure steam is used again and generates electric energy, and the simple use equipment, energy consumption is low, and the investment is little, and green environmental protection, and the production cost is low.

Description

Technical Field

[0001] This utility model relates to the field of dimethyl oxalate synthesis equipment, specifically to a low-pressure steam power generation system for the byproduct of dimethyl oxalate synthesis in natural gas-to-ethylene glycol production. Background Technology

[0002] Currently, ethylene glycol (EG) includes monoethylene glycol, diethylene glycol, and triethylene glycol, with monoethylene glycol (MEG) being the most commonly referred to type. Ethylene glycol, also known as glycol or ethylene glycol, is a colorless, clear, viscous liquid. It is soluble in water, lower alcohols, glycerol, acetone, acetic acid, pyridine, and aldehydes; slightly soluble in ethers; and almost insoluble in benzene, carbon disulfide, chloroform, and carbon tetrachloride. Ethylene glycol is an important basic organic raw material in the petrochemical industry, primarily used in the production of polyester fibers, antifreeze, unsaturated polyester resins, lubricants, plasticizers, nonionic surfactants, and explosives. It is also used in the coatings, photographic developing, brake fluid, and ink industries, as a solvent and medium for ammonium borate, and in the production of specialty solvents such as ethylene glycol ethers. Its applications are extremely wide-ranging.

[0003] In recent years, with the rapid growth of global polyester product consumption, the production of ethylene glycol worldwide has developed rapidly. Domestic ethylene glycol production facilities are still mainly imported ethylene oxide / ethylene glycol combined production units and ethylene direct air oxidation methods. In recent years, most ethylene glycol production has been coal-based, while natural gas-based ethylene glycol demonstration projects and several pilot projects have also made phased progress. In addition, several projects using biomass as feedstock to produce ethylene glycol are planned to be put into operation in China, but based on the current operation of existing facilities, the products are mainly polyols.

[0004] Currently, there are two main technical routes for ethylene glycol production: one is the petroleum route, which involves the gas-phase oxidation of ethylene over a silver catalyst to produce ethylene oxide, followed by liquid-phase non-catalytic hydration to obtain ethylene glycol. This route has the advantages of being technologically mature and widely applicable. The other method is the natural gas-to-ethylene glycol route, which uses natural gas to produce syngas to prepare dimethyl oxalate, which is then hydrogenated to produce ethylene glycol. With the increasing scarcity of global oil resources and the tight supply of petroleum, the natural gas-based ethylene glycol synthesis route has attracted widespread attention. Considering the economic rationality of raw material selection and my country's energy structure, the natural gas-to-ethylene glycol route is the most suitable for my country's current situation.

[0005] However, the low-pressure steam produced as a byproduct of dimethyl oxalate synthesis during the natural gas-to-ethylene glycol production process is not effectively utilized, resulting in energy waste. The cooled water is directly incorporated into the circulating water network, leading to low utilization efficiency and increasing production costs in industrial ethylene glycol production. Therefore, the problem of low-pressure steam generated as a byproduct of dimethyl oxalate synthesis during natural gas-to-ethylene glycol production has not been effectively addressed. Summary of the Invention

[0006] In order to solve one or more technical problems existing in the prior art, the purpose of this application is to provide a low-pressure steam power generation system for the synthesis of dimethyl oxalate as a by-product in the production of ethylene glycol from natural gas. This system can effectively reuse the low-pressure steam produced by the synthesis of dimethyl oxalate as a by-product in the production of ethylene glycol from natural gas to generate electricity. The system is simple to use, has low energy consumption, requires little investment, is environmentally friendly, and has low production costs.

[0007] To solve the aforementioned technical problems, this application adopts the following technical solution: A low-pressure steam power generation system for dimethyl oxalate synthesis byproducts in natural gas-to-ethylene glycol production includes an inlet separator, a bypass condenser, and a condensate pump connected in series via pipelines. A turbine, a generator, and a main condenser are also connected in parallel with the bypass condenser between the inlet separator and the condensate pump. The inlet separator, turbine, main condenser, and condensate pump are connected in series via pipelines. The system also includes a pressure equalization tank connected to the turbine to ensure the stability of the turbine's shaft seal steam. The low-pressure steam generated in the dimethyl oxalate synthesis section is transported to the inlet separator via pipelines for gas-liquid separation. When not generating electricity, the steam is cooled by the bypass condenser and then pumped out of the boundary via the condensate pump. When generating electricity, the steam enters the turbine, drives the impeller to rotate, converts kinetic energy into power generation, then enters the main condenser for cooling, and finally pumped out of the boundary via the condensate pump.

[0008] When processing the low-pressure steam produced as a byproduct of dimethyl oxalate synthesis in the upstream ethylene glycol production process, a bypass condenser allows the generator to effectively cool the steam during shutdown. This steam is then directly pumped out via a condensate pump, preventing unnecessary shutdowns due to generator unit issues. When the low-pressure steam is needed for power generation, it is piped to a generator set consisting of a turbine and a generator. The condensate from the generated steam is then cooled in the main condenser and returned to the condensate pump for external distribution. This allows the low-pressure steam to not only generate electricity but also achieve a water-steam cycle, reducing production costs. To ensure the low-pressure steam can be used for turbine power generation, a pressure equalization tank connected to the turbine is installed. The turbine's shaft seals are stabilized through the pressure equalization tank, ensuring sufficient power for the turbine. In the process of converting low-pressure steam into electricity, it is possible to effectively recover and utilize the low-pressure steam in the synthesis reaction of natural gas to ethylene glycol dimethyl oxalate. The steam is condensed and recycled. The equipment is simple, energy consumption is low, investment is low, and production cost is low.

[0009] Preferably, a steam seal heater and a shaft seal fan are provided between the steam turbine and the main condenser. The steam coming out of the shaft seal of the steam turbine is cooled by the steam seal heater and then returned to the main condenser in liquid phase. The non-condensable gas is drawn to the local vent by the shaft seal fan.

[0010] By combining the steam seal heater and the shaft seal fan, non-condensable gases inside the turbine shaft seal can be effectively discharged, preventing excessive internal pressure.

[0011] Preferably, the outlet pressure of the inlet separator is 110-120 kPa, and the steam pressure entering the turbine is 9-12 kPa.

[0012] Preferably, the steam turbine adopts a 3-impeller low-pressure blade structure.

[0013] Preferably, it also includes a vacuum system, through which the steam turbine is evacuated to a negative pressure of -8 to -13 kPa, and the vacuum degree of the generator is sealed by the steam in the equalizing tank.

[0014] To prevent insufficient power generation, the turbine operates under a negative back pressure of -8 to -13 kPa. By using a water ring vacuum pump to control the negative pressure of the main condenser, this problem can be effectively avoided.

[0015] Preferably, the vacuum system consists of a water ring vacuum pump and a liquid tank, and the steam turbine is evacuated by the water ring vacuum pump.

[0016] Preferably, it also includes a demineralized water supply pipeline, which is connected to the liquid tank and the steam turbine. The steam turbine is cooled by the demineralized water in the demineralized water supply pipeline, and the liquid level in the liquid tank is replenished by the demineralized water in the demineralized water supply pipeline.

[0017] It can effectively prevent steam turbines from being forced to shut down due to excessive temperature, and also solves the problem of needing to replenish the liquid level in the liquid tank regularly.

[0018] Preferably, the steam from the turbine, after being cooled by the main condenser, has a negative pressure, which facilitates the entry of low-pressure steam for power generation.

[0019] Preferably, two condensate pumps are used and connected in parallel. This allows for maintenance without shutting down the system when one of the pumps needs to be repaired.

[0020] Compared with the prior art, the beneficial effects of this utility model are as follows: Low-pressure steam from the synthesis of dimethyl oxalate can be piped to a low-pressure steam power generation system to convert the low-pressure steam into electricity. This effectively recovers and utilizes the low-pressure steam from the natural gas-to-ethylene glycol dimethyl oxalate synthesis reaction. Furthermore, the steam can be recycled after condensation. The equipment is simple to use, resulting in low energy consumption, low investment, energy saving, high efficiency, and environmental friendliness. This greatly reduces the production costs of chemical enterprises and enhances the price advantage of their products. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the process structure of this utility model; In the diagram: 1. Inlet separator; 2. Steam turbine; 3. Bypass condenser; 4. Main condenser; 5. Equalizing tank; 6. Condensate pump; 7. Vacuum system; 8. Steam seal heater; 9. Shaft seal fan; 10. Generator; 11. Demineralized water supply pipeline; 12. Water ring vacuum pump; 13. Liquid tank. Detailed Implementation

[0022] The present application will now be further described in conjunction with the accompanying drawings and specific embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0023] In the description of this application, it should be understood that the terms "upper", "lower", "left", "right", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0024] The terms "first," "second," etc., used in this application are used to distinguish similar objects and not to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class, without limiting the number of objects; for example, a first object can be one or more. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0025] like Figure 1 As shown, in the actual production process, the low-pressure steam generated in the dimethyl oxalate synthesis section is transported through pipelines to the inlet separator 1 for gas-liquid separation. When not generating electricity, it is cooled by the bypass condenser 3 and then sent to the outside of the boundary for recycling via one of the condensate pumps 6. When used for normal power generation, the gas phase after gas-liquid separation from the inlet separator 1 enters the turbine 2 through pipelines. At the same time, the equalization tank 5 acts as a buffer tank for the shaft seal steam of the turbine 2. The equalization tank 5 with 0.5MPa steam ensures the stable sealing of the shaft seal of the turbine 2, thereby driving the impeller to rotate and converting kinetic energy into generator 10 for power generation. The liquid after power generation then enters the main condenser 4 for cooling and is finally sent to the outside of the boundary via the condensate pump 6. The steam from the shaft seal of the turbine 2 is cooled by the steam seal heater 8 and the liquid phase is recovered to the main condenser 4. The non-condensable gas is drawn to the local vent by the shaft seal fan 9. The steam turbine employs a three-bladed low-pressure design. The outlet steam pressure of the inlet separator 1 is typically 110–120 kPa. After valve adjustment, the steam pressure entering the turbine is reduced to 9–12 kPa. The steam passing through the turbine 2, cooled by the main condenser 4, has a negative pressure. To ensure proper operation of the turbine 2, the entire system includes a vacuum system 7. After being evacuated by the vacuum system 7, the turbine 2 operates at a negative pressure of -8 to -13 kPa. Simultaneously, the vacuum level of the generator 10 is sealed by steam from the equalizing tank 5. The vacuum system 7 consists of a water ring vacuum pump 12 and a liquid tank 13, allowing the gas extracted from the turbine 2 to be directly discharged on-site. During the power generation process, in order to prevent the generator 10 from overheating and the liquid level in the liquid tank of the vacuum system 7 from being insufficient, the demineralized water supply pipeline 11 is connected to the 0.6 MPa demineralized water network. When the turbine 2 temperature is too high, the turbine 2 can be cooled by the demineralized water in the demineralized water supply pipeline 11. When the liquid level in the liquid tank 13 is too low, it can be automatically replenished by the demineralized water in the demineralized water supply pipeline 11.

[0026] Currently, a low-pressure steam generated as a byproduct of dimethyl oxalate synthesis in natural gas-to-ethylene glycol production has been designed to recover and utilize the low-pressure steam, in accordance with the Level 1 energy efficiency requirements of GB 18613-2020 "Minimum Allowable Values ​​of Energy Efficiency and Energy Efficiency Grades for Small Power Electric Motors". This design aims to utilize the low-pressure steam generated during the natural gas-to-ethylene glycol production process by modifying the original low-pressure steam treatment process and directly supplying it to the generator set for power generation. This allows for resource recovery and utilization while simultaneously generating electricity from the low-pressure steam, thus avoiding the waste of heat generated from the dimethyl oxalate synthesis byproduct.

[0027] Practical applications are as follows: Example 1: The intake air flow rate is controlled at 25 tons, the intake pressure is controlled at a slightly positive pressure of 9 kPa.A, the effective power output of the generator is 0.8 MW / h, and the generated electricity is: Taking a natural gas-to-ethylene glycol production capacity of 1.2 million tons / year as an example, this method can effectively convert the by-product low-pressure steam into electricity.

[0028] Example 2: The intake air flow rate is controlled at 35 tons, the intake pressure is controlled at a slightly positive pressure of 12 kPa.A, the effective power output of the generator is 0.8 MW / h, and the generated electricity is: Example 3: The intake air flow rate is controlled at 54 tons, the intake pressure is controlled at a slightly positive pressure of 12 kPa.A, the effective power output of the generator is 0.8 MW / h, and the generated electricity is: As shown by the results of the specific examples 1 to 3 above, Example 3 produces more steam and has a better treatment effect than the other examples.

[0029] The above embodiments are merely preferred embodiments of this application and should not be construed as limiting the scope of protection of this application. Any non-substantial changes and substitutions made by those skilled in the art based on this application shall fall within the scope of protection claimed by this application.

Claims

1. A low-pressure steam power generation system for the synthesis of dimethyl oxalate as a byproduct in the production of ethylene glycol from natural gas, characterized in that: The system includes an inlet separator (1), a bypass condenser (3), and a condensate pump (6) connected in series via pipelines. A steam turbine (2), a generator (10), and a main condenser (4) are also connected in parallel with the bypass condenser (3) between the inlet separator (1) and the condensate pump (6). The inlet separator (1), the steam turbine (2), the main condenser (4), and the condensate pump (6) are connected in series via pipelines. The system also includes a pressure equalization tank (5) connected to the steam turbine (2). The pressure equalization tank (5) is used to ensure the stability of the shaft seal steam of the steam turbine (2).

2. A low-pressure steam power generation system for the synthesis of dimethyl oxalate as a byproduct in the production of ethylene glycol from natural gas, as described in claim 1, is characterized in that: A steam seal heater (8) and a shaft seal fan (9) are provided between the steam turbine (2) and the main condenser (4). The steam coming out of the shaft seal of the steam turbine (2) is cooled by the steam seal heater (8) and then the liquid phase is recovered to the main condenser (4). The non-condensable gas is drawn to the local vent through the shaft seal fan (9).

3. A low-pressure steam power generation system for the synthesis of dimethyl oxalate as a byproduct in the production of ethylene glycol from natural gas, as described in claim 1, is characterized in that: The outlet pressure of the inlet separator (1) is 110-120 kPa, and the steam pressure entering the turbine (2) is 9-12 kPa.

4. A low-pressure steam power generation system for the synthesis of dimethyl oxalate as a byproduct in the production of ethylene glycol from natural gas, as described in claim 1, is characterized in that: The steam turbine (2) adopts a 3-impeller low-pressure blade structure.

5. A low-pressure steam power generation system for the synthesis of dimethyl oxalate as a byproduct in the production of ethylene glycol from natural gas, as described in claim 1, is characterized in that: It also includes a vacuum system (7), through which the steam turbine (2) is evacuated and operates at a negative pressure of -8 to -13 kPa, and the vacuum of the generator (10) is sealed by the steam in the equalization box (5).

6. A low-pressure steam power generation system for the synthesis of dimethyl oxalate as a byproduct in the production of ethylene glycol from natural gas, as described in claim 5, is characterized in that: The vacuum system (7) consists of a water ring vacuum pump (12) and a liquid tank (13), and the steam turbine (2) is evacuated by the water ring vacuum pump (12).

7. A low-pressure steam power generation system for the synthesis of dimethyl oxalate as a byproduct in the production of ethylene glycol from natural gas, as described in claim 6, is characterized in that: It also includes a demineralized water supply pipeline (11), which is connected to the liquid tank (13) and the steam turbine (2). The steam turbine (2) is cooled by the demineralized water in the demineralized water supply pipeline (11), and the liquid level in the liquid tank (13) is replenished by the demineralized water in the demineralized water supply pipeline (11).

8. A low-pressure steam power generation system for the synthesis of dimethyl oxalate as a byproduct in the production of ethylene glycol from natural gas, as described in claim 1, is characterized in that: The steam from the turbine (2) is cooled by the main condenser (4) and has a negative pressure.

9. A low-pressure steam power generation system for the synthesis of dimethyl oxalate as a byproduct in the production of ethylene glycol from natural gas, as described in claim 1, is characterized in that: The condensate pump (6) consists of two units connected in parallel.

Images