Natural gas-to-ethylene glycol fuel gas-steam combined cycle thermoelectric supply system

Abstract

The utility model belongs to the technical field of steam utilization equipment, and particularly relates to a natural gas-to-ethylene glycol fuel gas-steam combined cycle thermoelectric supply system. Comprising a steam pipe network, a back pressure steam turbine, a steam compressor, a natural gas conversion device, a natural gas conversion steam pocket, an esterification carbonylation device, an esterification carbonylation steam pocket, an oxalate hydrogenation device, an oxalate hydrogenation steam pocket, an EG refining separation device, an EG refining waste heat boiler, a gas turbine waste heat boiler and a start-up boiler. The steam pipe network comprises a 4.4 MPa steam pipe network, a 1.7 MPa steam pipe network, a 1.4 MPa steam pipe network, a 0.5 MPa steam pipe network and a 0.1 MPa steam pipe network. According to the utility model, the process waste heat is recovered and utilized in a grading manner, the steam unit consumption is effectively reduced, and the steam is prevented from being produced and supplied by a natural gas-fired boiler; moreover, the combined heat and power generation is adopted, notch steam and part of electric power supply are provided, the overall energy utilization efficiency is improved, and the electric power cost and the steam cost are reduced.

Description

Technical Field

[0001] The utility model belongs to the technical field of steam utilization equipment, and particularly relates to a gas-steam combined cycle thermoelectric supply system for producing ethylene glycol from natural gas. Background Technique

[0002] The process of producing ethylene glycol from natural gas consists of a natural gas conversion unit, a syngas separation and purification unit, an esterification unit, a carbonylation unit, a hydrogenation unit, and an EG separation unit. In the natural gas conversion unit, the normal-temperature natural gas from the natural gas pipeline network enters the boundary area natural gas compression section, and after compression and preheating, it is mixed with 4.2 MPa and 400 °C superheated steam in a certain proportion. The mixed gas is further preheated to 550 °C and enters the conversion tubes of the reformer, where the steam reforming reaction of hydrocarbons occurs. After the high-temperature reformed gas is cooled, it enters the separator to separate the reformed gas and the process condensate, and the reformed gas enters the syngas separation and purification unit.

[0003] After the syngas from the natural gas conversion unit is purified, the PSA pressure swing adsorption combined process is used to extract H2 from the syngas. The main component of the off-gas after extracting H2 is CO, and this off-gas goes to the carbonylation unit, while H2 goes to the hydrogenation unit.

[0004] In the esterification unit, a certain amount of liquid ammonia is vaporized by heat exchange and then mixed with compressed air and enters the ammonia oxidation furnace, where it reacts at about 800 °C under the action of a catalyst to obtain nitrogen oxides. The nitrogen oxides react with oxygen and methanol to obtain methyl nitrite.

[0005] In the carbonylation unit, methyl nitrite from the esterification unit and CO from the syngas separation and purification unit enter the DMO synthesis reactor after further pressurization, and a synthesis reaction occurs at 120 - 140 °C. The reaction liquid-phase product is separated and purified to obtain dimethyl oxalate, and the reaction gas-phase product (NO) goes to the esterification unit for recycling.

[0006] In the hydrogenation unit, dimethyl oxalate from the carbonylation unit, H2 from the syngas separation and purification unit, and recycled hydrogen are mixed, and after heat exchange, they enter the hydrogenation reactor. The reaction liquid-phase product enters the EG separation unit, most of the gas phase is recycled, and a small amount of by-product non-condensable gas is discharged into the fuel gas system.

[0007] In the EG separation unit, the reaction liquid-phase product from the hydrogenation unit enters the EG separation column system to obtain qualified EG products and by-product mixed alcohol esters.

[0008] It can be seen that in the process of producing ethylene glycol from natural gas, a large amount of steam is used in the natural gas conversion unit, esterification unit, carbonylation unit, hydrogenation unit, and EG separation unit. If only a natural gas-fired boiler is used to produce and supply steam, the natural gas consumption is huge and the production cost is too high. Content of the Utility Model

[0009] The utility model aims to provide a gas-steam combined cycle thermoelectric supply system for producing ethylene glycol from natural gas, so as to solve the problem of excessively high production cost caused by solely using a natural gas-fired boiler to produce and supply steam.

[0010] To achieve the above object, the solution of the utility model is: a gas-steam combined cycle thermoelectric supply system for producing ethylene glycol from natural gas, comprising a steam pipe network, a back-pressure steam turbine, a steam compressor, a natural gas conversion device, a natural gas conversion steam drum, an esterification and carbonylation device, an esterification and carbonylation steam drum, an oxalate hydrogenation device, an EG refining and separation device, a gas turbine waste heat boiler and a start-up boiler, characterized in that: the steam pipe network includes a 4.4 MPa steam pipe network, a 1.7 MPa steam pipe network, a 1.4 MPa steam pipe network, a 0.5 MPa steam pipe network and a 0.1 MPa steam pipe network; the natural gas conversion steam drum and the start-up boiler generate 4.4 MPa steam and supply it to the 4.4 MPa steam pipe network, the natural gas conversion steam drum utilizes the waste heat of the natural gas conversion device to generate steam, the back-pressure steam turbine is connected to the 4.4 MPa steam pipe network, and the back-pressure steam turbine extracts 1.4 MPa steam and sends it to the 1.4 MPa steam pipe network; the 4.4 MPa steam pipe network supplies steam to the 1.7 MPa steam pipe network through a desuperheating and pressure-reducing valve I, and the steam of the 1.7 MPa steam pipe network is used by the oxalate hydrogenation device; the gas turbine waste heat boiler generates 1.4 MPa steam and supplies it to the 1.4 MPa steam pipe network, the steam of the 1.4 MPa steam pipe network is used by the EG refining and separation device, the 1.4 MPa steam pipe network is sent into the 0.5 MPa steam pipe network through a desuperheating and pressure-reducing valve II, and the steam of the 0.5 MPa steam pipe network is used by the esterification and carbonylation device and the EG refining and separation device; the esterification and carbonylation steam drum generates 0.1 MPa steam and supplies it to the 0.1 MPa steam pipe network, and the steam of the 0.1 MPa steam pipe network is compressed by the steam compressor and then sent into the 0.5 MPa steam pipe network, and the esterification and carbonylation steam drum utilizes the waste heat of the esterification and carbonylation device to generate steam.

[0011] The working principle and beneficial effects of this solution are as follows: In this solution, the process waste heat is recovered by the natural gas conversion steam drum and the esterification carbonylation steam drum, and the generated steam at all levels enters the steam pipe network for use by each device. The remaining steam gap is filled by the gas turbine waste heat boiler, avoiding the production and supply of steam solely by the natural gas-fired boiler. At the same time, the steam is used to generate electricity through a back-pressure steam turbine. On the one hand, the extracted steam from the back-pressure steam turbine can provide low-grade steam for the production device to meet the production requirements of the device. On the other hand, using the back-pressure steam turbine to generate electricity reduces the electricity consumption of the enterprise, saves the electricity cost, and avoids the energy loss caused by directly reducing high-grade steam to low-grade steam. In summary, this solution recovers and utilizes the process waste heat in a hierarchical manner, effectively reducing the steam unit consumption and avoiding the production and supply of steam solely by the natural gas-fired boiler. Moreover, this solution adopts combined heat and power generation to provide the gap steam and part of the power supply, improving the overall energy utilization efficiency and reducing the power cost and steam cost.

[0012] Optionally, the system further includes an oxalate hydrogenation steam drum, and the oxalate hydrogenation steam drum generates 0.5 MPa steam and supplies it to the 0.5 MPa steam pipe network. The oxalate hydrogenation steam drum utilizes the waste heat of the oxalate hydrogenation device to generate steam.

[0013] In this solution, the waste heat of the oxalate hydrogenation device is recovered and utilized through the oxalate hydrogenation steam drum to provide 0.5 MPa steam for the production process, further reducing heat waste.

[0014] Optionally, the system further includes an EG refining waste heat boiler, and the EG refining waste heat boiler generates 0.1 MPa steam and supplies it to the 0.1 MPa steam pipe network.

[0015] In this solution, the waste heat of the EG refining and separation device is recovered and utilized through the EG refining waste heat boiler to provide 0.1 MPa steam for the production process, further reducing heat waste.

[0016] Optionally, the system further includes an exhaust gas incineration boiler, and the exhaust gas incineration boiler generates 1.7 MPa and supplies it to the 1.7 MPa steam pipe network.

[0017] In this solution, the heat generated by the combustion of the exhaust gas is recovered and utilized through the exhaust gas incineration boiler to provide 1.7 MPa steam for the production process, further reducing heat waste. Description of the Drawings

[0018] Figure 1 It is a schematic structural diagram of a natural gas to ethylene glycol gas-steam combined cycle cogeneration system in Embodiment 1 of the present utility model. Detailed Embodiments

[0019] The following is a further detailed description through specific embodiments:

[0020] The markings in the attached drawings of the specification include: back-pressure steam turbine 1, steam compressor 2, natural gas reforming unit 3, natural gas reforming steam drum 4, esterification and carbonylation unit 5, esterification and carbonylation steam drum 6, oxalate hydrogenation unit 7, oxalate hydrogenation steam drum 8, EG refining and separation unit 9, EG refining waste heat boiler 10, gas turbine waste heat boiler 11, start-up boiler 12, waste gas incineration boiler 13, desuperheating and pressure reducing valve I 14, desuperheating and pressure reducing valve II 15, syngas separation and purification unit 16, gas turbine 17.

[0021] Example 1

[0022] This example is basically as Figure 1 shown: A gas-steam combined cycle thermoelectric supply system for producing ethylene glycol from natural gas, comprising a steam pipe network, a back-pressure steam turbine 1, a steam compressor 2, a natural gas reforming unit 3, a natural gas reforming steam drum 4, an esterification and carbonylation unit 5, an esterification and carbonylation steam drum 6, an oxalate hydrogenation unit 7, an oxalate hydrogenation steam drum 8, an EG refining and separation unit 9, an EG refining waste heat boiler 10, a gas turbine waste heat boiler 11, a start-up boiler 12, and a waste gas incineration boiler 13. The steam pipe network includes a 4.4 MPa steam pipe network, a 1.7 MPa steam pipe network, a 1.4 MPa steam pipe network, a 0.5 MPa steam pipe network, and a 0.1 MPa steam pipe network.

[0023] The natural gas reforming steam drum 4 and the start-up boiler 12 generate 4.4 MPa steam and supply it to the 4.4 MPa steam pipe network. The natural gas reforming steam drum 4 utilizes the waste heat of the natural gas reforming unit 3 to generate steam. The back-pressure steam turbine 1 is connected to the 4.4 MPa steam pipe network, and the back-pressure steam turbine 1 then extracts 1.4 MPa steam and sends it to the 1.4 MPa steam pipe network. The 4.4 MPa steam pipe network supplies steam to the 1.7 MPa steam pipe network through the desuperheating and pressure reducing valve I 14. The waste gas incineration boiler 13 generates 1.7 MPa steam and supplies it to the 1.7 MPa steam pipe network. The steam in the 1.7 MPa steam pipe network is used by the oxalate hydrogenation unit 7.

[0024] The gas turbine waste heat boiler 11 generates 1.4 MPa steam and supplies it to the 1.4 MPa steam pipe network. The steam in the 1.4 MPa steam pipe network is used by the EG refining and separation unit 9. The 1.4 MPa steam pipe network is sent into the 0.5 MPa steam pipe network through the desuperheating and pressure reducing valve II 15. The oxalate hydrogenation steam drum 8 generates 0.5 MPa steam and supplies it to the 0.5 MPa steam pipe network. The oxalate hydrogenation steam drum 8 utilizes the waste heat of the oxalate hydrogenation unit 7 to generate steam. The steam in the 0.5 MPa steam pipe network is used by the esterification and carbonylation unit 5 and the EG refining and separation unit 9.

[0025] The esterification carbonylation steam drum 6 and the EG refining waste heat boiler 10 generate 0.1 MPa steam and supply it to the 0.1 MPa steam pipe network. The steam in the 0.1 MPa steam pipe network is compressed by the steam compressor 2 and then sent into the 0.5 MPa steam pipe network. The esterification carbonylation steam drum 6 generates steam by using the waste heat of the esterification carbonylation unit 5.

[0026] In actual use, the normal-temperature natural gas from the natural gas pipe network enters the natural gas reforming unit 3 for reaction to obtain syngas. The syngas enters the syngas separation and purification unit 16. The separated carbon monoxide enters the esterification carbonylation unit 5, and the separated hydrogen enters the oxalate hydrogenation unit 7. During the operation of the natural gas reforming unit 3, the waste heat of the natural gas reforming unit 3 is utilized by the natural gas reforming steam drum 4 to generate 4.4 MPa steam and supply it to the 4.4 MPa steam pipe network. At the same time, when the entire natural gas-to-ethylene glycol plant is started up, the start-up boiler 12 generates 4.4 MPa steam and supplies it to the 4.4 MPa steam pipe network to ensure that the amount of 4.4 MPa steam is sufficient. In the 4.4 MPa steam pipe network, a part of the 4.4 MPa steam is sent to the 1.7 MPa steam pipe network through the desuperheating and pressure-reducing valve I 14. At the same time, the waste gas incineration boiler 13 generates 1.7 MPa and supplies it to the 1.7 MPa steam pipe network. Another part of the 4.4 MPa steam enters the back-pressure steam turbine 1 for power generation, and during the process, the back-pressure steam turbine 1 extracts part of the 1.4 MPa steam and sends it to the 1.4 MPa steam pipe network.

[0027] In addition, the normal-temperature natural gas from the natural gas pipe network enters the gas turbine 17 for combustion to drive the first-stage generator for power generation. The exhaust gas (500 - 600 °C) of the gas turbine 17 enters the gas turbine waste heat boiler 11, and the gas turbine waste heat boiler 11 generates 1.4 MPa steam and enters the 1.4 MPa steam pipe network.

[0028] The steam in the 1.7 MPa steam pipe network is supplied for use in the oxalate hydrogenation unit 7. During the operation of the oxalate hydrogenation unit 7, the oxalate hydrogenation steam drum 8 generates 0.5 MPa steam by using the waste heat of the oxalate hydrogenation unit 7 and supplies it to the 0.5 MPa steam pipe network. The steam in the 1.4 MPa steam pipe network is supplied for use in the EG refining and separation unit 9. The steam in the 0.5 MPa steam pipe network is supplied for use in the esterification carbonylation unit 5 and the EG refining and separation unit 9. During the operation of the esterification carbonylation unit 5, the esterification carbonylation steam drum 6 generates 0.1 MPa steam by using the waste heat of the esterification carbonylation unit 5 and supplies it to the 0.1 MPa steam pipe network. During the operation of the EG refining and separation unit 9, the EG refining waste heat boiler 10 generates 0.1 MPa steam and supplies it to the 0.1 MPa steam pipe network, and the steam in the 0.1 MPa steam pipe network is compressed by the steam compressor 2 and then sent into the 0.5 MPa steam pipe network for use.

[0029] Thus, in this embodiment, the process waste heat is recovered to produce steam of various grades for hierarchical utilization, effectively reducing the steam unit consumption. And cogeneration is adopted to provide the missing steam and part of the power supply, avoiding solely using natural gas-fired boilers to produce and supply steam, improving the overall energy utilization efficiency, and reducing the power cost and steam cost.

[0030] The above are only the embodiments of the present utility model, and common knowledge such as the specific structures and characteristics known in the solutions is not described in detail herein. It should be noted that for those skilled in the art, without departing from the structure of the present utility model, several deformations and improvements can be made, which should also be regarded as the protection scope of the present utility model, and these will not affect the implementation effect of the present utility model and the practicality of the present utility model. The specific implementation manners and other records in the specification can be used to explain the content of the claims.

Claims

1. A natural gas-to-ethylene glycol gas-steam combined cycle thermal power supply system, comprising a steam network, a back-pressure steam turbine, a steam compressor, a natural gas reforming unit, a natural gas reforming drum, an esterification carbonylation unit, an esterification carbonylation drum, an oxalate hydrogenation unit, an EG refining and separation unit, a gas turbine waste heat boiler and a start-up boiler, characterized in that: The steam pipeline network includes a 4.4MPa steam pipeline network, a 1.7MPa steam pipeline network, a 1.4MPa steam pipeline network, a 0.5MPa steam pipeline network and a 0.1MPa steam pipeline network; the natural gas conversion drum and the start-up boiler generate 4.4MPa steam and provide it to the 4.4MPa steam pipeline network, the natural gas conversion drum uses the waste heat of the natural gas conversion device to generate steam, the back-pressure steam turbine is connected to the 4.4MPa steam pipeline network, and the back-pressure steam turbine then extracts 1.4MPa steam and sends it to the 1.4MPa steam pipeline network; the 4.4MPa steam pipeline network provides steam to the 1.7MPa steam pipeline network through the temperature and pressure reducer I, and the steam of the 1.7MPa steam pipeline network The steam is supplied to the oxalate hydrogenation unit; the gas turbine waste heat boiler generates 1.4MPa steam and supplies it to the 1.4MPa steam network. The steam in the 1.4MPa steam network is supplied to the EG refining and separation unit. The 1.4MPa steam network is sent to the 0.5MPa steam network through the temperature reducing device II. The steam in the 0.5MPa steam network is supplied to the esterification carbonylation unit and the EG refining and separation unit; the esterification carbonylation steam drum generates 0.1MPa steam and supplies it to the 0.1MPa steam network. The steam in the 0.1MPa steam network is compressed by the steam compressor and then sent to the 0.5MPa steam network. The esterification carbonylation steam drum generates steam using the waste heat of the esterification carbonylation unit.

2. The natural gas-to-ethylene glycol gas-steam combined cycle thermal power supply system according to claim 1, characterized in that: The system also includes an oxalate hydrogenation drum, which generates 0.5MPa steam and provides it to a 0.5MPa steam network. The oxalate hydrogenation drum generates steam using waste heat from the oxalate hydrogenation device.

3. The natural gas-to-ethylene glycol gas-steam combined cycle thermal power supply system according to claim 1, characterized in that: The system further comprises an EG refining waste heat boiler, which generates 0.1 MPa steam and provides it to a 0.1 MPa steam pipeline network.

4. The natural gas-to-ethylene glycol gas-steam combined cycle thermal power supply system according to claim 1, characterized in that: The system also includes a waste gas incineration boiler, which generates 1.7 MPa and provides it to a 1.7 MPa steam network.

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