A natural gas to syngas plant waste heat efficient utilization system

Abstract

The utility model belongs to the waste heat recycling technical field, concretely relates to a natural gas makes synthetic gas device waste heat efficient utilization system, including converter, waste heat recovery ware, conversion steam pocket, boiler feed water preheater and gas boiler steam pocket, the export of converter, the pipe of waste heat recovery ware, the pipe of boiler feed water preheater import connect in proper order, the shell of boiler feed water preheater export is connected with make -up water pipe I, make -up water pipe I links to each other with the make -up water of conversion steam pocket, and the gas inlet and backwater of conversion steam pocket link to each other with the shell of waste heat recovery ware, make -up water pipe I is linked with make -up water pipe II, and make -up water pipe II links to each other with the make -up water of gas boiler steam pocket, and make -up water pipe I and make -up water pipe II all are equipped with regulating valve. In the utility model, the water quantity of boiler feed water preheater under the driving condition can keep consistent with normal condition, to ensure the cooling effect of synthetic gas, avoid the temperature of synthetic gas when entering decarburization unit too high, eliminate the risk of decarburization MDEA solution thermal decomposition.

Description

Technical Field

[0001] This utility model belongs to the field of waste heat recovery and utilization technology, specifically relating to a high-efficiency waste heat utilization system for a natural gas to syngas production plant. Background Technology

[0002] Natural gas is a high-quality clean energy source with low sulfur content and minimal pollution. It is widely used globally to produce hydrogen, methanol, ethylene glycol, synthetic ammonia, and synthetic oils. The natural gas-to-ethylene glycol (PGG) production process involves converting natural gas into syngas, which is then converted into ethylene glycol through a catalyst. In this process, natural gas, as the feedstock, is compressed, desulfurized, purified, and heated before being sent to a reformer to produce syngas. The syngas then undergoes a decarbonization unit to remove CO2, followed by a cryogenic H2 / CO separation unit and a pressure swing adsorption (PSA) unit to separate H2 and CO for ethylene glycol synthesis. The syngas exiting the reformer is at a high temperature and needs to be cooled before being sent to the decarbonization unit. If this heat is not recovered and utilized, a significant amount of heat is wasted. To address this, existing processes typically install a waste heat recovery unit at the converter outlet to recover most of the heat from the syngas and produce medium-pressure steam. Furthermore, a boiler feedwater preheater is installed downstream of the waste heat recovery unit to further recover waste heat from the syngas, and the preheated boiler water is then sent to the converter steam drum. While this recovers and utilizes the waste heat from the syngas, during plant start-up, the low evaporation rate of the converter steam drum results in a reduced water supply to the boiler feedwater preheater, decreasing the cooling effect on the syngas. This leads to higher temperatures of the syngas entering the decarbonization unit, posing a risk of thermal decomposition of the MDEA decarbonization solution. Summary of the Invention

[0003] The present invention aims to provide a system for efficient utilization of waste heat from a natural gas-to-syngas production plant, in order to solve the problem of poor syngas cooling effect during start-up.

[0004] To achieve the above objectives, the present invention provides a waste heat utilization system for a natural gas-to-syngas production plant, comprising a converter, a waste heat recovery unit, a converter steam drum, and a boiler feedwater preheater. The outlet of the converter is connected to the tube-side inlet of the waste heat recovery unit, and the tube-side outlet of the waste heat recovery unit is connected to the tube-side inlet of the boiler feedwater preheater. The shell-side outlet of the boiler feedwater preheater is connected to a water supply pipe I, and the end of the water supply pipe I away from the boiler feedwater preheater is connected to the water supply port of the converter steam drum. The air inlet and water outlet of the converter steam drum are respectively connected to the shell side of the waste heat recovery unit. The system also includes a gas-fired boiler steam drum, wherein the water supply pipe I is connected to a water supply pipe II, and the end of the water supply pipe II away from the water supply pipe I is connected to the water supply port of the gas-fired boiler steam drum. Both the water supply pipe I and the water supply pipe II are equipped with regulating valves.

[0005] The working principle and beneficial effects of this scheme are as follows: Under normal operating conditions, the regulating valve on water supply pipe II is closed, and the boiler feedwater preheater only supplies water to the conversion boiler drum. Under start-up conditions, the regulating valve on water supply pipe II is opened, and the opening of the regulating valve on water supply pipe I is reduced. In this way, part of the preheated boiler water enters the conversion boiler drum, and the other part enters the gas-fired boiler drum. The water supply to the boiler feedwater preheater can be maintained, thereby ensuring the cooling effect on the syngas and preventing the syngas from entering the decarbonization unit at excessively high temperatures, thus eliminating the risk of thermal decomposition of the decarbonization MDEA solution. Furthermore, this scheme, by sending part of the preheated boiler water to the gas-fired boiler drum under start-up conditions, can reduce gas consumption and lower production costs.

[0006] Optionally, it also includes a decarbonized CO2 regeneration tower reboiler, the tube-side inlet of which is connected to the tube-side outlet of the boiler feedwater preheater.

[0007] In this scheme, the syngas from the boiler feedwater preheater enters the decarbonization CO2 regeneration tower reboiler to exchange heat with the MDEA solution, heating the MDEA solution and further reducing the temperature of the syngas, thereby further recovering and utilizing the heat of the syngas.

[0008] Optionally, it also includes a demineralized water preheater and a deaerator, wherein the tube-side inlet of the demineralized water preheater is connected to the tube-side outlet of the reboiler of the decarbonized CO2 regeneration tower, the shell-side outlet of the demineralized water preheater is connected to the inlet of the deaerator, and the outlet of the deaerator is connected to the shell-side inlet of the boiler feedwater preheater.

[0009] In this scheme, the syngas exiting the reboiler of the decarbonized CO2 regeneration tower enters the demineralized water preheater, where it exchanges heat with the demineralized water. The temperature of the demineralized water increases, while the temperature of the syngas decreases further, thereby further recovering and utilizing the heat of the syngas and realizing the cascade utilization of syngas heat. Attached Figure Description

[0010] Figure 1 This is a schematic diagram of the structure of a waste heat utilization system for a natural gas to syngas production device in Embodiment 1 of this utility model. Detailed Implementation

[0011] The following detailed description illustrates the specific implementation method: The markings in the accompanying drawings include: 1. Converter; 2. Waste heat recovery unit; 3. Converter steam drum; 4. Boiler feedwater preheater; 5. Gas boiler steam drum; 6. Decarbonized CO2 regeneration tower reboiler; 7. Deaerator; 8. Makeup water pipe I; 9. Makeup water pipe II; 10. Regulating valve; 11. Boiler water pump; 12.

[0012] Example 1 This embodiment is basically as follows: Figure 1As shown, a high-efficiency waste heat utilization system for a natural gas-to-syngas plant includes a reformer 1, a waste heat recovery unit 2, a reforming steam drum 3, a boiler feedwater preheater 4, a gas-fired boiler steam drum 5, a decarbonized CO2 regeneration tower reboiler 6, a demineralized water preheater 7, and a deaerator 8. The outlet of the reformer 1 is connected to the tube-side inlet of the waste heat recovery unit 2, the tube-side outlet of the waste heat recovery unit 2 is connected to the tube-side inlet of the boiler feedwater preheater 4, the tube-side outlet of the boiler feedwater preheater 4 is connected to the tube-side inlet of the decarbonized CO2 regeneration tower reboiler 6, and the tube-side outlet of the decarbonized CO2 regeneration tower reboiler 6 is connected to the tube-side inlet of the demineralized water preheater 7. Thus, the syngas from the reformer 1 passes through the tube-side of the waste heat recovery unit 2, the boiler feedwater preheater 4, the decarbonized CO2 regeneration tower reboiler 6, and the demineralized water preheater 7 before proceeding to the next stage.

[0013] The shell-side outlet of the boiler feedwater preheater 4 is connected to a water supply pipe I9. The end of the water supply pipe I9 furthest from the boiler feedwater preheater 4 is connected to the water supply port of the steam drum 3. The air inlet and water outlet of the steam drum 3 are respectively connected to the shell side of the waste heat recovery unit 2. The water supply pipe I9 is ​​connected to a water supply pipe II10. The end of the water supply pipe II10 furthest from the water supply pipe I9 is ​​connected to the water supply port of the gas boiler drum 5. Both the water supply pipe I9 and the water supply pipe II10 are equipped with regulating valves 11, and the regulating valve 11 on the water supply pipe I9 is ​​located between the connection point of the water supply pipe II10 and the water supply pipe I9 and the steam drum 3.

[0014] The shell-side inlet of the boiler feedwater preheater 4 is connected to the outlet of the deaerator 8, and the inlet of the deaerator 8 is connected to the shell-side outlet of the demineralized water preheater 7. A boiler water pump 12 is installed on the pipeline between the deaerator 8 and the boiler feedwater preheater 4, thereby pumping the demineralized water in the deaerator 8 to the boiler feedwater preheater 4.

[0015] In actual use, the demineralized water enters from the shell-side inlet of the demineralized water preheater 7, and after heating, enters the deaerator 8, then the boiler feedwater preheater 4, and after further heating, enters the reformer drum 3 or the reformer drum 3 and the gas-fired boiler drum 5. Specifically, under normal operating conditions, the regulating valve 11 on the makeup water pipe II 10 is closed, and all the boiler water in the boiler feedwater preheater 4 is supplied to the reformer drum 3. Thus, the syngas from the converter 1 exchanges heat with the boiler water in the waste heat recovery unit 2, lowering the syngas temperature and raising the boiler water temperature to generate steam. The steam enters the converter steam drum 3 and is then sent to the steam network for use in the process units. The syngas, now at a lower temperature, enters the boiler feedwater preheater 4, where it exchanges heat with the boiler water, raising the boiler water temperature and further lowering the syngas temperature, thereby further recovering and utilizing the heat from the syngas. The syngas from the boiler feedwater preheater 4 enters the decarbonization CO2 regeneration tower reboiler 6, where it exchanges heat with the MDEA solution, raising the MDEA solution temperature and further lowering the syngas temperature. The syngas from the decarbonization CO2 regeneration tower reboiler 6 enters the demineralized water preheater 7, where it exchanges heat with the demineralized water, raising the demineralized water temperature and further lowering the syngas temperature. At this point, the syngas temperature meets the requirements of the decarbonization unit and is sent to the next stage for use, achieving a cascade recovery and utilization of the syngas heat.

[0016] When the device is in start-up operation, the regulating valve 11 on the water supply pipe II 10 is opened. By adjusting the opening of the two regulating valves 11, the flow rates of the water supply pipes I 9 and II 10 are made to meet actual needs (the amount of boiler water entering the conversion drum 3 is reduced compared to normal operation). Thus, after the boiler water in the boiler feedwater preheater 4 is heated, a portion enters the conversion drum 3 via the water supply pipe I 9, and the other portion enters the gas-fired boiler drum 5 via the water supply pipes I 9 and II 10. This ensures that the water supply to the boiler feedwater preheater 4 remains consistent with the water supply under normal operation, guaranteeing the cooling effect of the boiler feedwater preheater 4 on the syngas and preventing excessively high temperatures when the syngas enters the decarbonization unit, thus eliminating the risk of thermal decomposition of the decarbonization MDEA solution. Furthermore, in this embodiment, sending a portion of the preheated boiler water to the gas-fired boiler drum 5 during start-up reduces gas consumption and lowers production costs.

[0017] The above descriptions are merely embodiments of this utility model, and common knowledge regarding specific structures and characteristics is not elaborated upon here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the structure of this utility model, and these should also be considered within the scope of protection of this utility model. These modifications will not affect the effectiveness or practicality of this utility model. The specific embodiments described in the specification can be used to interpret the claims.

Claims

1. A high-efficiency waste heat utilization system for a natural gas-to-syngas production unit, comprising a reformer, a waste heat recovery unit, a reforming steam drum, and a boiler feedwater preheater; the outlet of the reformer is connected to the tube-side inlet of the waste heat recovery unit, the tube-side outlet of the waste heat recovery unit is connected to the tube-side inlet of the boiler feedwater preheater, the shell-side outlet of the boiler feedwater preheater is connected to a water supply pipe I, the end of the water supply pipe I furthest from the boiler feedwater preheater is connected to the water supply port of the reforming steam drum, and the steam inlet and outlet of the reforming steam drum are respectively connected to the shell side of the waste heat recovery unit; characterized in that: It also includes a gas boiler steam drum, wherein the water supply pipe I is connected to a water supply pipe II, and the end of the water supply pipe II away from the water supply pipe I is connected to the water supply port of the gas boiler steam drum. Both the water supply pipe I and the water supply pipe II are equipped with regulating valves.

2. The waste heat utilization system for a natural gas-to-syngas production unit according to claim 1, characterized in that: It also includes a decarbonized CO2 regeneration tower reboiler, whose tube-side inlet is connected to the tube-side outlet of the boiler feedwater preheater.

3. The waste heat utilization system for a natural gas to syngas production unit according to claim 2, characterized in that: It also includes a demineralized water preheater and a deaerator. The tube-side inlet of the demineralized water preheater is connected to the tube-side outlet of the reboiler of the decarbonized CO2 regeneration tower. The shell-side outlet of the demineralized water preheater is connected to the inlet of the deaerator. The outlet of the deaerator is connected to the shell-side inlet of the boiler feedwater preheater.

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