Gas system and process of LNG device matched with independent coking plant
1. A gas system of an LNG device matched with an independent coking plant is characterized by comprising a coke oven, a gas purification device, an LNG device and a mixing station; an inlet of the gas purification device is connected with a gas outlet of the coke oven through a pipeline, and an outlet of the gas purification device is respectively connected with a gas inlet of the LNG device and a gas inlet of the blending station through pipelines; a hydrogen-rich outlet of the LNG device is connected with an inlet of the blending station through a pipeline; and the outlet of the mixing station is connected with a return gas inlet of the coke oven through a pipeline.
2. The gas system of an independent coke plant matched LNG facility as claimed in claim 1, further comprising a gas diffusing device; and a gas inlet of the gas diffusing device is connected with a gas inlet pipeline of the LNG device through a gas pipeline.
3. The gas system of the LNG facility of the independent coke-oven plant as claimed in claim 2, wherein a first valve is disposed on a gas inlet pipe of the LNG facility, and a second valve is disposed on a gas inlet pipe of the gas diffusing device.
4. A process of a gas system based on an LNG plant associated with an independent coke plant as claimed in claim 1, 2 or 3, characterized in that it comprises the following steps:
1) raw coke gas generated by coke ovens of independent coking plants is conveyed to a gas purification device through a pipeline, and is sent to an LNG device through tar removal, desulfurization, deamination, naphthalene removal and benzene removal purification processes in the gas purification device;
2) the LNG device adopts the processes of pretreatment, deep purification, methanation and liquefaction, and generates a byproduct hydrogen-rich gas besides producing an LNG product;
3) hydrogen-rich gas produced by the LNG plant is used as a regeneration gas for a naphthalene removal column of a pretreatment unit in the LNG plant before being sent to a blending plant;
4) the hydrogen-rich gas is sent to a blending station to be blended with the coke oven gas from the gas purification device to form mixed gas which is sent to the coke oven to be used as fuel gas for heating the coke oven;
5) the coke oven continuously operates for a long time without stopping production, and the LNG device needs to be shut down and overhauled periodically every year; when the LNG device stops working, the first valve is closed, the second valve is opened at the same time, and at the moment, the coke oven gas produced by the coke oven is used for self heating, and the redundant gas is conveyed to the diffusing device to be combusted at high altitude and then is exhausted to the atmosphere.
5. The process of claim 4, wherein the LNG plant is produced in a scale determined by the following calculation according to the gas production and heat consumption of the coke oven and the yield and heat value of the hydrogen-rich gas generated by the LNG plant;
it is known that:
the raw gas amount generated by coke oven of certain coke-oven plant is as follows: v, Nm3/h；
Low heat value of coke oven gas: LHVCOG，kJ/Nm3；
Heat consumption required for coke oven production: qConsumption unit，kJ/h；
Gas amount consumed by users such as gas purification devices: v', Nm3/h
LNG plant tail gas, i.e. hydrogen rich gas yield, relative to raw gas throughput of the LNG plant: a,%;
LNG plant tail gas, i.e. low heating value of hydrogen rich gas: LHVHRG，kJ/Nm3；
Solving the following steps: raw gas throughput of LNG plant
Solution:
the coal gas quantity at the outlet of the coal gas purification device is as follows: v1＝V－V′
If the raw material gas treatment capacity of the LNG device is x, the LNG device
Hydrogen-rich production: v2＝a·x
Heat consumption required for coke oven production:
Qconsumption unit＝(V1－x)×LHVCOG+a·x·LHVHRG
Solving the equation to obtain x, namely obtaining the raw material gas treatment capacity of the LNG device.
Background
China is a big country for coke production, and a coking enterprise can produce a large amount of coke oven gas while producing coke by using a coke oven. For the coke oven gas generated by a coking plant in an iron and steel combination enterprise, in addition to the self heating of the coke oven, the surplus coke oven gas can be used as fuel gas or industrial gas in a smelting device in the enterprise, and all the coke oven gas can be well utilized.
However, for an independent coke-oven plant, about 40-50% of coke-oven gas generated by the coke-oven can be used even if the coke-oven gas is completely used for heating the coke-oven, and a good outlet must be found for the residual coke-oven gas of more than half of the coke-oven gas. In recent years, many independent coking enterprises are continuously developing the technical field of comprehensive utilization of coke oven gas, such as city gas, power generation and hydrogen extraction, and also can use coke oven gas to prepare methanol, coke oven gas to prepare LNG and the like.
The coke oven gas is used as a byproduct of coke oven coking and comprises the main component of H2、CH4、CO、CO2And the like. The process technology for preparing LNG from coke oven gas utilizes carbon (CO and CO) in the coke oven gas2Etc.) and hydrogen under the action of a catalyst to synthesize methane, and then the methane is liquefied at low temperature to obtain Liquid Natural Gas (LNG). Since coke oven gas contains a large amount of hydrogen and a small amount of carbon, LNG tail gas, that is, hydrogen-rich gas containing components such as hydrogen, nitrogen, and a small amount of methane, is generated in an LNG plant in addition to LNG products. Therefore, for a production enterprise which is matched with an independent coking plant to produce LNG, the following factors must be comprehensively considered:
1) the heat requirement required by the heating of the coke oven is met, and the production stability of the coke oven is ensured;
2) economically and reasonably determining the production scale of the LNG device;
3) LNG tail gas (rich in hydrogen) is well utilized;
4) gas balance between coke ovens which are continuously produced throughout the year and LNG plants which must be shut down and overhauled each year.
When an existing independent coking enterprise is matched with an LNG device, the problems that the design scale of the LNG device is unreasonable, the normal production of a coke oven is influenced by the LNG device, LNG tail gas is not reasonably utilized, and the enterprise benefit cannot be maximized exist.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides a gas system and a process of an LNG device matched with an independent coking plant. The LNG is produced by utilizing redundant coke oven gas of an independent coke-oven plant, and the production scale of the LNG device is reasonably determined by combining the respective production characteristics of the coke oven and the LNG device, so that the normal production of the coke oven is ensured, LNG products with high added values are produced as much as possible, and the economic benefit of enterprises is improved.
In order to achieve the purpose, the invention adopts the following technical scheme:
a gas system of an LNG device matched with an independent coking plant comprises a coke oven, a gas purification device, an LNG device and a mixing station; an inlet of the gas purification device is connected with a gas outlet of the coke oven through a pipeline, and an outlet of the gas purification device is respectively connected with a gas inlet of the LNG device and a gas inlet of the blending station through pipelines; a hydrogen-rich outlet of the LNG device is connected with an inlet of the blending station through a pipeline; and the outlet of the mixing station is connected with a return gas inlet of the coke oven through a pipeline.
The coal gas diffusion device is also included; and a gas inlet of the gas diffusing device is connected with a gas inlet pipeline of the LNG device through a gas pipeline.
The LNG device is characterized in that a first valve is arranged on a gas inlet pipeline of the LNG device, and a second valve is arranged on a gas inlet pipeline of the gas diffusing device.
A coal gas treatment process of an LNG device matched with an independent coking plant specifically comprises the following steps:
1) raw coke gas generated by coke ovens of independent coking plants is conveyed to a gas purification device through a pipeline, and is sent to an LNG device through purification processes such as tar removal, desulfurization, deamination, naphthalene removal, benzene removal and the like in the gas purification device;
2) the LNG device adopts the processes of pretreatment, deep purification, methanation and liquefaction, and generates a byproduct hydrogen-rich gas besides producing an LNG product;
3) hydrogen-rich gas produced by the LNG plant is used as a regeneration gas for a naphthalene removal column of a pretreatment unit in the LNG plant before being sent to a blending plant;
4) the hydrogen-rich gas is sent to a blending station to be blended with the coke oven gas from the gas purification device to form mixed gas which is sent to the coke oven to be used as fuel gas for heating the coke oven;
5) the coke oven continuously operates for a long time without stopping production, and the LNG device needs to be shut down and overhauled periodically every year; when the LNG device stops working, the first valve is closed, the second valve is opened at the same time, and at the moment, the coke oven gas produced by the coke oven is used for self heating, and the redundant gas is conveyed to the diffusing device to be combusted at high altitude and then is exhausted to the atmosphere.
The production scale of the LNG device is determined by the following formula according to the gas production rate and the heat consumption of the coke oven and the yield and the heat value of the hydrogen-rich gas generated by the LNG device;
it is known that:
the raw gas amount generated by coke oven of certain coke-oven plant is as follows: v, Nm3/h；
Low heat value of coke oven gas: LHVCOG，kJ/Nm3；
Heat consumption required for coke oven production: qConsumption unit，kJ/h；
Gas amount consumed by users such as gas purification devices: v', Nm3/h
LNG plant tail gas, i.e. hydrogen rich gas yield, relative to raw gas throughput of the LNG plant: a,%;
LNG plant tail gas, i.e. low heating value of hydrogen rich gas: LHVHRG，kJ/Nm3；
Solving the following steps: raw gas throughput of LNG plant
Solution:
the coal gas quantity at the outlet of the coal gas purification device is as follows: v1＝V－V′
If the raw material gas treatment capacity of the LNG device is x, the LNG device
Hydrogen-rich production: v2＝a·x
Heat consumption required for coke oven production:
Qconsumption unit＝(V1－x)×LHVCOG+a·x·LHVHRG
Solving the equation to obtain x, namely obtaining the raw material gas treatment capacity of the LNG device.
Compared with the prior art, the invention has the beneficial effects that:
1) on the premise of meeting the heat requirement required by the heating of the coke oven, the production safety and stability of the coke oven are ensured;
2) according to the gas production amount and the heat consumption of the coke oven and the yield and the heat value of the hydrogen-rich gas generated by the LNG device, the production scale of the LNG device is calculated and reasonably determined, the LNG product with high added value is produced as much as possible, and the economic benefit of an enterprise is improved;
3) the production characteristics of the coke oven and the LNG device are considered, the gas diffusing device is arranged, and the enterprise is flexible, stable and reliable in production;
4) redundant coke oven gas of an independent coking plant and byproducts of an LNG device are effectively utilized, and the production process is complete, safe, environment-friendly and good in economic benefit.
Drawings
FIG. 1 is a schematic diagram of the structure and process of the present invention.
In the figure: the method comprises the following steps of 1-a coke oven, 2-a gas purification device, 3-an LNG device, 4-a mixing station, 5-a gas diffusing device, 6-a first valve and 7-a second valve.
Detailed Description
The following further describes embodiments of the present invention with reference to the accompanying drawings:
as shown in fig. 1, a gas system of an LNG device associated with an independent coke plant includes a coke oven 1, a gas purification device 2, an LNG device 3, a blending station 4, and a gas diffusion device 5.
An inlet of the gas purification device 2 is connected with a gas outlet of the coke oven 1 through a pipeline, and an outlet of the gas purification device 2 is respectively connected with gas inlets of the LNG device 3 and the blending station 4 through pipelines; the hydrogen-rich outlet of the LNG device 3 is connected with the inlet of the blending station 4 through a pipeline; the outlet of the blending station 4 is connected with the return gas inlet of the coke oven 1 through a pipeline.
The gas inlet of the gas diffusing device 5 is connected with the gas inlet pipeline of the LNG device 3 through a gas pipeline. A first valve 6 is arranged on a gas inlet pipeline of the LNG device 3, and a second valve 7 is arranged on a gas inlet pipeline of the gas diffusing device 5.
A coal gas treatment process of an LNG device matched with an independent coking plant specifically comprises the following steps:
1) raw coke gas generated by a coke oven 1 of an independent coke plant is conveyed to a gas purification device 2 through a pipeline, and is sent to an LNG device 3 through purification processes of tar removal, desulfurization, deamination, naphthalene removal, benzene removal and the like in the gas purification device 2.
2) The LNG device 3 adopts the processes of pretreatment, deep purification, methanation and liquefaction, and the LNG device 3 produces a byproduct rich hydrogen besides producing an LNG product. Wherein the pretreatment unit comprises the working procedures of tar removal, desulfurization, naphthalene removal and the like, and the desulfurization adopts a dry process; the naphthalene removal adopts a Temperature Swing Adsorption (TSA) process, two naphthalene removal towers are arranged, one of the towers is used for adsorption, the other tower is used for desorption, and the two towers are used for cyclic and alternate operation.
3) The hydrogen-rich gas produced by the LNG plant 3 is used as a regeneration gas for the naphthalene removal column of the pre-treatment unit in the LNG plant 3 before being sent to the blending plant 4.
4) Since the coke oven gas contains more hydrogen and less carbon, after the synthetic natural gas is methanated, excessive hydrogen exists in the tail gas of the LNG device to become rich hydrogen and is discharged as a byproduct of the LNG device. The rich hydrogen is heated by steam to raise the temperature before being sent to the blending station 4, and then enters a naphthalene removal tower needing desorption in a pretreatment unit to desorb naphthalene in an adsorbent in the naphthalene removal tower. The desorbed hydrogen-rich gas containing naphthalene is sent to a blending station 4 to be blended with the coke oven gas from the gas purification device 2 to form mixed gas which is sent to the coke oven 1 to be used as fuel gas for heating the coke oven.
5) The coke oven 1 is continuously operated for a long time without stopping production, and the LNG device 3 needs to be periodically stopped and overhauled every year. When the LNG device 3 stops working, the first valve 6 is closed, the second valve 7 is opened at the same time, and at the moment, the coke oven gas produced by the coke oven 1 is used for self heating, and the redundant gas is sent to the diffusing device 5 for high altitude combustion and then is discharged to the atmosphere.
The production scale of the LNG plant 3 should be determined by calculation according to the gas production and heat consumption of the coke oven 1, and the yield and heat value of the hydrogen-rich gas generated by the LNG plant 3. With reference to fig. 1, the following is illustrated:
it is known that:
1) the raw gas amount generated by coke oven of certain coke-oven plant is as follows: v52933 Nm3/h
2) Low heat value of coke oven gas: LHVCOG＝17900kJ/Nm3
3) Heat consumption required for coke oven production: qConsumption unit＝375835560kJ/h
4) Gas amount consumed by users such as gas purification devices: v1600 Nm3/h
5) Yield of LNG plant tail gas (hydrogen rich) (relative to raw gas throughput of LNG plant): a is 16%
6) Low heating value of LNG plant tail gas (hydrogen rich): LHVHRG＝8318kJ/Nm3
Solving the following steps: raw gas throughput of LNG plant
Solution:
the coal gas quantity at the outlet of the coal gas purification device is as follows: v1＝V－V’＝52933－1600＝51333Nm3/h
If the raw material gas treatment capacity of the LNG device is x, the LNG device
Hydrogen-rich production: v2＝a·x
Heat consumption required for coke oven production:
Qconsumption unit＝(V1－x)×LHVCOG+a·x·LHVHRG
Namely: 375835560 (51333-x) x 17900+ 16%. x · 8318
Solving the equation to obtain: x 32773Nm3/h
Therefore, the production scale of the LNG plant is 32773Nm according to the amount of the coke oven gas used for processing the raw material3/h。
The LNG production system utilizes redundant coke oven gas of an independent coke-oven plant to produce LNG, combines the production characteristics of the coke oven and the LNG device, reasonably determines the production scale of the LNG device, ensures the normal production of the coke oven, produces LNG products with high added value as much as possible, and effectively utilizes the redundant coke oven gas of the independent coke-oven plant and byproducts of the LNG device; the invention has the advantages of complete production process, safety, environmental protection and good economic benefit.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the scope of the present invention.
