Separation system for natural gas cracking tail gas

Abstract

The utility model relates to a natural gas cracking tail gas separation system, which comprises two adsorption tower groups, a cracking tail gas pipeline, a desorption gas pipeline and a hydrogen pipeline, the adsorption tower groups are provided with a plurality of adsorption towers according to different methane concentrations in the cracking tail gas, and the plurality of adsorption towers are connected in series on the same pipeline; methane adsorbents are filled in the absorption towers; the cracking tail gas pipeline provides cracking tail gas for the two adsorption tower groups, and the desorption gas pipeline and the hydrogen pipeline are used for discharging desorption gas and hydrogen of the two adsorption tower groups; cracking tail gas under the rated pressure enters the adsorption tower group, and methane in the cracking tail gas is sequentially adsorbed by methane adsorbents in the adsorption towers and then becomes high-purity hydrogen under the rated pressure to be discharged. The device has the advantages of simple process system, compact structure, small equipment investment and low operation cost.

Description

Technical Field

[0001] This application belongs to the field of new energy technologies, and particularly relates to a separation system for natural gas cracking tail gas. Background Art

[0002] The production of hydrogen from natural gas cracking and carbon nanotubes is an important research direction in the current fields of energy and materials science. With the increasing global demand for clean energy, hydrogen energy, as a new type of energy with characteristics such as high efficiency and cleanness, has gradually received extensive attention. In the process of hydrogen production, natural gas cracking has become a promising method due to its high efficiency and potential economic benefits. In addition, the introduction of carbon nanotubes provides additional economic and environmental benefits for this technology.

[0003] In the production of hydrogen from natural gas cracking and carbon nanotubes, due to the influence of the cracking furnace structure, catalyst activity, and carbon deposition, the cracking efficiency is only 30 - 50%. The volume ratio of methane to hydrogen in the tail gas after the first cracking of methane is (54:46) - (33:67). In order to obtain higher purity hydrogen and improve the utilization rate of natural gas, an efficient and economic separation device for methane and hydrogen is required. The traditional separation method uses cryogenic separation to turn methane in the cracking tail gas into a liquid phase, thereby achieving the separation of methane and hydrogen. However, it has deficiencies such as a complex process system, large equipment investment, and high operating costs. Summary of the Utility Model

[0004] The technical problem to be solved by this utility model is: to solve the deficiencies in the prior art of a complex process system, large equipment investment, and high operating costs, and thus provide a separation system for natural gas cracking tail gas.

[0005] The technical solution adopted by this utility model to solve its technical problem is: a separation system for natural gas cracking tail gas, including two groups of adsorption tower groups, a cracking tail gas pipeline, a desorption gas pipeline, and a hydrogen pipeline. The adsorption tower groups are provided with multiple adsorption towers according to the different methane concentrations in the cracking tail gas, and the multiple adsorption towers are connected in series on the same pipeline; methane adsorbents are filled in all the adsorption towers; the cracking tail gas pipeline supplies cracking tail gas to the two groups of adsorption tower groups, and the desorption gas pipeline and the hydrogen pipeline are used to discharge the desorption gas and hydrogen of the two groups of adsorption tower groups; the cracking tail gas under the rated pressure enters the adsorption tower group. After the methane in the cracking tail gas is successively adsorbed by the methane adsorbents in the adsorption towers, high-purity hydrogen under the rated pressure is discharged.

[0006] Further, pneumatic control valves I for controlling the flow or non-flow of pipelines are provided on the cracking tail gas pipeline, the desorption gas pipeline, and the hydrogen gas pipeline, and pneumatic control valves II are also provided on the pipelines in series of the adsorption tower group; when the methane adsorbent inside the adsorption tower group is saturated, the cracking tail gas and hydrogen gas pipelines are cut off by the pneumatic control valves, the pneumatic control valve of the desorption gas pipeline is opened, the back pressure of the adsorption tower group is reduced to atmospheric pressure, and the methane adsorbent inside the adsorption tower group releases the adsorbed methane gas and a small amount of hydrogen gas mixture, and then enters the natural gas cracking furnace again for cracking.

[0007] Further, the methane adsorbent is a nano-level activated carbon with multi-micropores and a super high specific surface area, and its specific surface area is about 3000m 2 / g, the micropore diameter is 1-2 nanometers, the pore volume ratio is about 90%, and the methane molecule adsorption ratio is about 160L / L.

[0008] Further, both the pneumatic control valve I and the pneumatic control valve II adopt a two-position three-way valve structure, and the actuator is driven by pressurized air.

[0009] Further, it also includes a controller, and the controller controls the pneumatic control valve I and the pneumatic control valve II through a time logic control program to realize the switching of the adsorption and desorption processes of the methane adsorption tower.

[0010] Further, the adsorption tower adopts a vertical structure.

[0011] The adsorption forces mainly include two types: one is the force between methane molecules and adsorbent molecules; the other is the force between methane molecules. When the force between methane molecules and adsorbent molecules dominates, methane molecules are adsorbed on the surface of the micropores of the adsorbent; when the force between methane molecules dominates, methane molecules desorb from the surface of the micropores of the adsorbent. The adsorbent adsorbs methane molecules under certain pressure conditions, and methane molecules desorb from the surface of the micropores of the adsorbent by reducing the pressure.

[0012] The beneficial effects of the present utility model are:

[0013] Using nano-level activated carbon with multi-micropores and a super high specific surface area as the methane adsorbent, the methane molecules in the natural gas cracking tail gas are adsorbed step by step through multiple series-connected adsorption towers. After multi-stage adsorption, the cracking tail gas reaches the purity of hydrogen, and the methane gas in the adsorption tower is released to the cracking furnace for cracking by pressure reduction desorption. Therefore, the product of the present utility model has the advantages of simple process system, compact structure, small equipment investment, and low operation cost. Description of the Drawings

[0014] The technical solutions of the present application will be further described below in conjunction with the drawings and embodiments.

[0015] Figure 1 It is a schematic structural diagram of an embodiment of the present application;

[0016] The reference numerals in the figure are as follows:

[0017] 10. Adsorption tower group, 11. Adsorption tower, 12. Methane adsorbent, 13. Pneumatic control valve II, 20. Pyrolysis tail gas pipeline, 21. Pneumatic control valve I, 30. Desorption gas pipeline, 40. Hydrogen gas pipeline, 50. Controller. Detailed implementation manners

[0018] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments may be combined with each other.

[0019] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the protection scope of the present application. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, the meaning of "a plurality" is two or more.

[0020] In the description of the present application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected, or indirectly connected through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood through specific situations.

[0021] The technical solutions of the present application will be described in detail below with reference to the drawings and in combination with the embodiments. Embodiment

[0022] This embodiment provides a separation system for natural gas cracking tail gas, including two groups of adsorption tower groups 10, a cracking tail gas pipeline 20, a desorption gas pipeline 30, and a hydrogen gas pipeline 40. The adsorption tower groups 10 are provided with multiple adsorption towers 11 according to the different methane concentrations in the cracking tail gas. The adsorption towers 11 adopt a vertical structure, and multiple adsorption towers 11 are connected in series on the same pipeline; methane adsorbents 12 are filled in each adsorption tower 11. The methane adsorbent 12 is a nano-scale activated carbon with multi-micropores and a super high specific surface area, and its specific surface area is about 3000m 2 / g, the micropore diameter is 1-2 nanometers, the pore volume ratio is about 90%, and the methane molecule adsorption ratio is about 160L / L.

[0023] The cracking tail gas pipeline 20 supplies cracking tail gas to the two groups of adsorption tower groups 10. The desorption gas pipeline 30 and the hydrogen gas pipeline 40 are used to discharge the desorption gas and hydrogen gas of the two groups of adsorption tower groups 10. Specifically, the desorption gas discharged from each adsorption tower 11 is connected through the same pipeline, and the hydrogen gas discharged from each adsorption tower 11 is connected through the same pipeline; the cracking tail gas under the rated pressure enters the adsorption tower group 10. After the methane in the cracking tail gas is successively adsorbed by the methane adsorbent 12 in the adsorption tower 11, high-purity hydrogen gas under the rated pressure is discharged.

[0024] Furthermore, pneumatic control valves 21 for controlling the flow or non-flow of the pipeline are provided on the cracking tail gas pipeline 20, the desorption gas pipeline 30, and the hydrogen gas pipeline 40. The pneumatic control valve 21 on the cracking tail gas pipeline 20 controls whether the cracking tail gas enters each group of adsorption tower groups 10. A pneumatic control valve 13 is also provided on the pipeline in which the adsorption tower groups 10 are connected in series; when the methane adsorbent 12 inside the adsorption tower groups 10 is saturated, the cracking tail gas and the hydrogen gas pipeline 40 are cut off by the pneumatic control valve 21, and the pneumatic control valve 21 of the desorption gas pipeline 30 is opened. The back pressure inside the adsorption tower groups 10 is reduced to atmospheric pressure, and the methane adsorbent 12 inside the adsorption tower groups 10 releases the adsorbed methane gas and a small amount of hydrogen gas mixture, and enters the natural gas cracking furnace again for cracking.

[0025] Both the pneumatic control valve 21 and the pneumatic control valve 13 adopt a two-position three-way valve structure, and the actuator is driven by pressurized air.

[0026] It further includes a controller 50. The controller 50 controls the pneumatic control valve 21 and the pneumatic control valve 13 through a time logic control program to realize the switching of the adsorption and desorption processes of the methane adsorption tower 11.

[0027] When the product of the present utility model is in use:

[0028] The pyrolysis tail gas containing 54% methane enters one of the adsorption tower groups. After the methane in the pyrolysis tail gas is successively adsorbed by the methane adsorbents in multiple adsorption towers (preferably 5), hydrogen with a purity of over 99.9% is discharged. When the methane adsorbents in the 5 adsorption towers inside the adsorption tower group are saturated, the pneumatic control valve I on the pyrolysis tail gas pipeline and the analytical gas pipeline, and the pneumatic control valve II on the series pipeline of the adsorption tower group are closed, cutting off the pyrolysis tail gas pipeline and the hydrogen pipeline of the adsorption tower group. At the same time, the pneumatic control valve I on the pyrolysis tail gas pipeline and the hydrogen pipeline of the other adsorption tower group, and the pneumatic control valve II on the series pipeline of the adsorption tower group are opened, and the pyrolysis tail gas containing 54% methane enters the adsorption tower group for methane adsorption. The pneumatic control valve I on the pyrolysis tail gas pipeline and the pneumatic control valve II on the series pipeline of the adsorption tower group are opened, and the back pressure of the adsorption tower group is reduced to atmospheric pressure. The methane adsorbents in the 5 adsorption towers release the adsorbed methane gas and a small amount of hydrogen mixture, and then enter the natural gas pyrolysis furnace for pyrolysis again. When the methane adsorbents in the 5 adsorption towers inside the adsorption tower group release all the methane gas, the pneumatic control valve I on the pyrolysis tail gas pipeline and the pneumatic control valve II on the series pipeline of the adsorption tower group are closed, and the pneumatic control valve I on the pyrolysis tail gas pipeline and the hydrogen pipeline, and the pneumatic control valve II on the series pipeline of the adsorption tower group are opened. The pyrolysis tail gas containing 54% methane enters the adsorption tower group for methane adsorption, thus completing the adsorption-desorption cycle process of the pyrolysis tail gas and realizing the efficient separation of methane and hydrogen.

[0029] The product of the present utility model uses nano-activated carbon with multi-micropores and a large specific surface area as the methane adsorbent, and adsorbs methane molecules in the natural gas pyrolysis tail gas step by step through multiple series-connected adsorption towers. The pyrolysis tail gas after multi-stage adsorption reaches the purity of hydrogen, and the methane gas in the adsorption tower is released to the pyrolysis furnace for pyrolysis through pressure reduction and desorption;

[0030] This system has the advantages of a simple process system, a compact structure, a small equipment investment, and low operating costs. It can effectively solve the problems of the efficient separation of natural gas pyrolysis tail gas and the high utilization rate of natural gas, and has great significance in promoting the development of natural gas pyrolysis to produce hydrogen and carbon nanotube generation technology.

[0031] Inspired by the above ideal embodiments based on this application, through the above description, relevant staff can completely make various changes and modifications without departing from the technical idea of this application. The technical scope of this application is not limited to the content in the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A separation system for natural gas cracking tail gas, characterized in that, It includes two groups of adsorption tower groups, a pyrolysis tail gas pipeline, a desorption gas pipeline, and a hydrogen pipeline. The adsorption tower groups are provided with multiple adsorption towers according to the different methane concentrations in the pyrolysis tail gas, and the multiple adsorption towers are connected in series on the same pipeline; methane adsorbents are filled in all the adsorption towers; the pyrolysis tail gas pipeline supplies pyrolysis tail gas to the two groups of adsorption tower groups, and the desorption gas pipeline and the hydrogen pipeline are used to discharge the desorption gas and hydrogen of the two groups of adsorption tower groups.

2. The separation system for natural gas cracking tail gas according to claim 1, characterized in that, Pneumatic control valves I for controlling the flow or non-flow of the pipeline are provided on the pyrolysis tail gas pipeline, the desorption gas pipeline, and the hydrogen pipeline, and pneumatic control valves II are also provided on the pipeline where the adsorption tower groups are connected in series.

3. The separation system for the cracked tail gas of natural gas according to claim 2, characterized in that, The methane adsorbent is a nanoscale activated carbon with multiple micropores and a super specific surface area.

4. The separation system for the tail gas of natural gas cracking according to claim 3, characterized in that, The pneumatic control valves I and II adopt a two-position three-way valve structure, and the actuator is driven by pressurized air.

5. The separation system for natural gas cracking tail gas according to claim 2, wherein It further includes a controller, and the controller controls the pneumatic control valves I and II through a time logic control program to realize the switching of the adsorption and desorption processes of the methane adsorption tower.

6. A separation system for natural gas cracking tail gas according to any one of claims 1-5, characterized in that, The adsorption tower adopts a vertical structure.

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