CN116003197A - Method for preparing methane by utilizing offshore wind power to realize carbon dioxide - Google Patents

Abstract

The invention discloses a method for preparing methane from carbon dioxide by using offshore wind power. It includes the following steps: 1) Concentration and separation of carbon dioxide-rich natural gas mined on deep-sea offshore platforms, and is divided into methane-rich streams and carbon dioxide-rich streams; 2) carbon dioxide-rich streams are desulfurized and denitrified, Exchange heat with the process gas of the methanation unit, and then mix with the superheated steam produced by the methanation unit; 3) After mixing the carbon dioxide and the superheated steam produced by the methanation unit, exchange heat with the outlet gas of the high-temperature fuel cell, and use electric heating Finally, it enters the co-electrolysis unit of the high-temperature fuel cell for electrolysis to obtain a mixture of hydrogen and carbon monoxide; 4) The mixture enters the methanation unit after heat exchange with the inlet raw material gas of the high-temperature fuel cell and pressurized, and passes through 2 to 5 stages of series-parallel The methanation reaction produces methane gas. The method of the invention is simple and easy to operate, and can recycle and utilize the carbon dioxide developed in deep-sea oil and gas fields.

Description

A method for producing methane from carbon dioxide using offshore wind power

technical field

The invention belongs to the field of renewable energy hydrogen production and carbon emission reduction utilization technology, and relates to a method for preparing methane from carbon dioxide by using offshore wind power.

Background technique

In the context of low-carbon and environmental protection, the long-term development goals of clean energy are clear. Among them, wind power, a renewable energy source with huge resource potential and relatively mature technology, is getting more and more attention. Therefore, wind power will be a long-term development main line in the future and has relatively fast development opportunities. In addition, compared with onshore wind power, offshore wind power has the advantages of high power generation, abundant resources, and long unit life, so offshore wind power will become the focus of new energy development. With the gradual increase of my country's offshore wind power installed capacity, in the next few years, offshore wind power will usher in a leapfrog development.

Based on the orderly promotion of the construction of offshore wind power bases, the coordinated development of offshore wind power and deep-sea oil and gas resources will promote the rapid development of the deep-sea offshore wind power industry. Efficient utilization and reduction of carbon emissions are the problems that need to be overcome in the deep sea. Therefore, there is an urgent need to develop a method of using offshore wind power to realize carbon dioxide recovery and utilization at the same time. Contribute to carbon emission reduction, will have huge economic and social benefits.

Contents of the invention

The purpose of the present invention is to provide a method for producing methane from carbon dioxide by using offshore wind power.

The invention aims at the recovery and utilization of carbon dioxide in the exploitation process of oil and gas fields rich in carbon dioxide in the sea, and realizes the comprehensive utilization of multiple energy sources such as gas, electricity and heat through the power supply and hydrogen production of offshore wind renewable resources and the conditions of the technological process. Effectively solve offshore wind power consumption, carbon dioxide separation and chemical conversion utilization in offshore oil and gas fields. The invention utilizes offshore wind power and carbon dioxide conversion and utilization technology and energy mutually, has a simple method and is convenient to operate, and can well solve the problem of carbon dioxide recovery and utilization in the development of deep-sea oil and gas fields.

The invention provides a method for preparing methane from carbon dioxide by utilizing offshore wind power, comprising the following steps:

1) The carbon dioxide-rich natural gas exploited on deep-sea offshore platforms is separated by the hydrate method and enriched by the carbon dioxide enrichment unit, and after separating water and hydrate for decarbonation, it is divided into a methane-rich stream and a carbon dioxide-rich stream;

2) After the carbon dioxide-rich stream is desulfurized by iron-molybdenum catalyst and nickel-molybdenum catalyst, and denitrified by vanadium-titanium-tungsten catalyst, it exchanges heat with the process gas of the methanation unit, and then mixes with the superheated steam produced by the methanation unit ;

3) After the carbon dioxide is mixed with the superheated steam produced by the methanation unit, it exchanges heat with the outlet gas of the high-temperature fuel cell, and after being electrically heated, enters the co-electrolysis unit of the high-temperature fuel cell for electrolysis to obtain a mixture of hydrogen and carbon monoxide ;

The power source of the electric heating and the co-electrolysis unit is the electricity generated by the offshore wind power in the deep sea after passing through the electric energy storage unit;

4) The hydrogen and carbon monoxide mixture enters the methanation unit after exchanging heat with the inlet raw material gas of the high-temperature fuel cell and pressurized, and prepares and obtains methane gas through 2-5 stages of series-parallel methanation reactions.

In the present invention, the offshore wind power generation in the deep sea is a conventional setting in the field.

In the above method, after step 4), the obtained methane gas is cooled and dehydrated, and then mixed with the methane-rich stream in step 1), and then exported to an onshore natural gas processing plant through a submarine pipeline.

In the above method, in step 1), the temperature of the hydrate separation method can be 1-20°C, and the pressure can be 1-7MPaG;

The water produced by the hydrate separation and carbon dioxide enrichment unit is cooled and separated from the methanation unit to obtain demineralized water through the seawater purification unit, and the demineralized water is used as the cooling water of the methanation unit, and then enters the methanation unit. The waste heat boiler; wherein, the seawater purification unit uses 1-5 reverse osmosis membranes to purify seawater. In the above method, the volume concentration of carbon dioxide in the carbon dioxide-enriched natural gas is greater than 10%;

The volume concentration of methane in the methane-rich stream is greater than 80%;

The volume concentration of carbon dioxide in the carbon dioxide-enriched stream is greater than 70%.

In the above-mentioned method, in step 1), the deep sea offshore platform is an offshore platform established in a deep sea with a water depth greater than 100 meters or a distance from land greater than 20 kilometers;

In step 3), the deep sea is a sea area where the water depth is greater than 100 meters or the distance from the land is greater than 20 kilometers.

In the above method, in step 2), the volume ratio of the iron-molybdenum catalyst to the nickel-molybdenum catalyst may be 1:0.2-5;

The mass percent content of sulfur in the carbon dioxide-rich stream after desulfurization may be 1 ppm to 2%;

The mass percent content of nitrogen in the stream rich in carbon dioxide after denitrification may be 1 ppm to 3%.

In the present invention, the iron-molybdenum catalyst and the nickel-molybdenum catalyst are well-known reagents in the art;

Specifically, in the iron-molybdenum catalyst, the oxide content of iron may specifically be 5-15 wt%, and the oxide content of molybdenum may specifically be 5-25 wt%;

In the nickel-molybdenum catalyst, the oxide content of nickel may be 1-10 wt%, and the oxide content of molybdenum may be 1-20 wt%;

In the vanadium-titanium-tungsten catalyst, the oxide content of titanium may be 0.5-5 wt%, the oxide content of vanadium may be 0.5-10%, and the oxide content of tungsten may be 0.5-5 wt%.

In the above method, in step 3), the temperature of the electrolysis can be 600-900°C, specifically 700°C, 850°C or 700-850°C, and the absolute pressure can be 2kPa-2MPa, specifically 120kPa, 300kPa Or 120kPa ~ 300kPa.

In the present invention, the high-temperature fuel cell is a plate-type high-temperature fuel cell or a tube-type fuel cell.

In the above method, in step 3), the electric energy storage unit is a lithium battery as an energy storage medium.

In the above method, in step 4), the temperature of the hydrogen and carbon monoxide mixture after heat exchange may be 200-400°C, specifically 210°C, 350°C or 210-350°C, pressurized to 2-4MPa, specifically It can be 2.5MPa, 3MPa or 2.5~3MPa.

In the above-mentioned method, in step 4), the methanation reaction is catalyzed by a nickel-based catalyst;

The mass percentage content of nickel metal in the nickel-based catalyst can be 10-40wt%;

The temperature of the methanation reaction may be 200-800°C.

In the above method, step 4) further includes the step of recovering the superheated steam by-product of the methanation unit by using a waste heat boiler;

The temperature of the superheated steam by-produced by the methanation unit may be 200-600°C.

The present invention has the following beneficial effects:

1. This method effectively recycles and utilizes carbon dioxide in the process of oil and gas field exploitation, and realizes carbon emission reduction. Using a high-temperature fuel cell to electrolyze carbon dioxide and coupling a methanation process to convert carbon dioxide into methane.

2. Using offshore wind power as the power source of high-temperature fuel cells realizes the effective utilization of offshore wind power and solves the energy loss and economic cost of transportation caused by offshore wind power coming ashore in deep seas.

3. This method realizes the efficient utilization of energy cascades. The high-temperature fuel cell raw material gas and product gas are used for self-heat exchange, and the heat released by methanation is used to prepare superheated steam and mix it with carbon dioxide as a high-temperature fuel cell raw material, which improves the energy utilization efficiency of the entire process.

4. This method realizes the enrichment of natural gas in offshore exploitation through the hydrate separation unit, removes carbon dioxide, increases the cost of sea transportation of submarine natural gas pipelines, and reduces the risk of carbon dioxide corrosion.

Description of drawings

Fig. 1 is a schematic flow chart of the present invention for producing methane from carbon dioxide by using offshore wind power.

Detailed ways

The experimental methods used in the following examples are conventional methods unless otherwise specified.

The materials and reagents used in the following examples can be obtained from commercial sources unless otherwise specified.

In the following embodiments, the high temperature fuel cell is a plate type high temperature fuel cell.

In the following examples, in the iron-molybdenum catalyst, the iron oxide content is 5-15 wt% (specifically 10 wt%), and the molybdenum oxide content is 5-25 wt% (specifically 10 wt%);

In the nickel-molybdenum catalyst, the oxide content of nickel is 1-10wt% (specifically 5wt%), and the oxide content of molybdenum is 1-20wt% (specifically 10wt%);

In the vanadium-titanium-tungsten catalyst, the oxide content of titanium is 0.5-5wt% (specifically 2wt%), the oxide content of vanadium is 0.5-10% (specifically 5wt%), and the oxide content of tungsten is 0.5 ~5wt% (specifically, it can be 3wt%).

The carbon dioxide-rich natural gas mined on the deep-sea offshore platform is separated and enriched by the hydrate method on the seawater platform, and is divided into two streams rich in methane and rich in carbon dioxide; after separation, the stream rich in carbon dioxide is sent to the High-temperature fuel cell co-electrolysis unit; the carbon monoxide and hydrogen streams obtained by electrolysis enter the methanation unit to produce methane gas; the prepared methane is compressed and mixed, and then transported to the onshore natural gas processing plant through submarine pipelines, and then enters the natural gas pipeline network for supply Industrial and residential use.

Example 1

According to the process shown in Figure 1, the present invention utilizes offshore wind power to realize the process of preparing methane from carbon dioxide, and a specific example step is as follows:

The natural gas rich in carbon dioxide (volume concentration 20%) exploited on the deep-sea offshore platform is divided into a stream rich in methane (85% in volume concentration of methane) and a stream rich in carbon dioxide (volume Concentration 90%) stream.

After separation, the stream rich in carbon dioxide is desulfurized by iron-molybdenum catalyst and nickel-molybdenum catalyst (the mass content of sulfur is 50ppm) and vanadium-titanium-tungsten catalyst is denitrified (the mass content of nitrogen is 50ppm), and the process gas of the methanation unit is exchanged for heat. It is then mixed with the superheated steam produced by the methanation unit.

After the carbon dioxide and the superheated steam produced by the methanation unit are mixed, they exchange heat with the outlet gas of the high-temperature fuel cell, and enter the co-electrolysis unit of the high-temperature fuel cell through electric heating. After cell electrolysis, a mixture of hydrogen and carbon monoxide is obtained.

The offshore wind power generation in the deep sea (water depth 200 meters) is used as the power source in the common electrolysis unit after passing through the electric energy storage unit;

The mixed gas of hydrogen and carbon monoxide obtained from the high-temperature fuel cell is heat-exchanged with the inlet raw material gas to 210°C, then pressurized to 2.5 MPa and enters the methanation unit, and methane gas is produced through a three-stage series-parallel methanation reaction (reaction of carbon monoxide and hydrogen) , The methanation unit recovers heat by using a waste heat boiler to by-produce superheated steam at 560°C.

The prepared methane gas is dehydrated after being cooled to 40°C, and then mixed with the methane gas that has been decarbonized and enriched by offshore mining, and then transported to the onshore natural gas processing plant through submarine pipelines, and then enters the natural gas pipeline network for industrial and residential use .

Among them, the first-stage purified seawater decomposed in the separation and concentration unit of the hydrate method, and the demineralized water obtained by the second-stage seawater purification unit are used as cooling water for the methanation unit, and then enter the waste heat boiler.

Example 2

According to the process shown in Figure 1, the present invention utilizes offshore wind power to realize the process of preparing methane from carbon dioxide, and a specific example step is as follows:

1) The carbon dioxide-rich (40% by volume) natural gas exploited on the deep-sea offshore platform is separated by the hydrate method and the carbon dioxide enrichment unit on the seawater platform. concentration 95%) and a stream rich in carbon dioxide (volume concentration 96%).

2) The stream rich in carbon dioxide after separation is desulfurized by iron-molybdenum catalyst and nickel-molybdenum catalyst (mass content of sulfur is 50ppm) and denitrified by vanadium-titanium-tungsten catalyst (mass content of nitrogen is 50ppm), and is exchanged with the process gas of the methanation unit heat, which is then mixed with the superheated steam by-produced from the methanation unit.

3) After the carbon dioxide and the superheated steam produced by the methanation unit are mixed, they exchange heat with the outlet gas of the high-temperature fuel cell and enter the co-electrolysis unit of the high-temperature fuel cell through electric heating. Under the conditions of 850°C and 300kPa (absolute pressure), the After high-temperature fuel cell electrolysis, a mixture of hydrogen and carbon monoxide is obtained.

The offshore wind power generation in the deep sea (water depth 200 meters) is used as the power source for the electric heating and co-electrolysis unit after passing through the electric energy storage unit;

4) The mixed gas of hydrogen and carbon monoxide obtained from the high-temperature fuel cell is heat-exchanged with the inlet raw material gas to 350°C, then pressurized to 3MPa and enters the methanation unit, and produces methane through 5-stage series-parallel methanation reactions (reaction of carbon monoxide and hydrogen) For gas, the methanation unit recovers heat by using a waste heat boiler to by-produce superheated steam at 650°C.

5) The prepared methane gas is dehydrated after being cooled to 40°C, and mixed with the methane gas that has been extracted from carbon dioxide and concentrated in the sea, and then transported to the onshore natural gas processing plant through the submarine pipeline, and then enters the natural gas pipeline network for industrial and residents use.

Among them, the first-stage purified seawater produced by the hydrate separation and the decomposition of the carbon dioxide concentration unit, and the softened water obtained by the second-stage seawater purification unit are used as cooling water for the methanation unit, and then enter the waste heat boiler.

It can be seen from the above examples that the present invention can use offshore wind power to recover and utilize carbon dioxide in the process of exploiting offshore carbon dioxide-rich oil and gas fields, and explore the conditions of the process flow to realize the comprehensive utilization of multiple energy sources such as gas, electricity, and heat. It can effectively solve the problem of offshore wind power consumption, carbon dioxide separation and chemical conversion and utilization in offshore oil and gas fields.

Claims (10)

1. A method for preparing methane by utilizing offshore wind power to realize carbon dioxide comprises the following steps:

1) Separating natural gas rich in carbon dioxide extracted from a deep open sea offshore platform by a hydrate method, concentrating by a carbon dioxide concentrating unit, separating water and hydrate to remove carbon dioxide, and separating into a methane-rich stream and a carbon dioxide-rich stream;

2) The carbon dioxide-rich stream is subjected to desulfurization by an iron-molybdenum catalyst and a nickel-molybdenum catalyst, denitrification by a vanadium-titanium-tungsten catalyst, heat-exchanged with the process gas of the methanation unit, and then mixed with the superheated steam byproduct by the methanation unit;

3) The carbon dioxide and the superheated steam byproduct of the methanation unit are mixed and then exchange heat with the outlet gas of the high-temperature fuel cell, and enter a high-temperature fuel cell co-electrolysis unit for electrolysis after being electrically heated, so that a mixture of hydrogen and carbon monoxide is obtained;

the electric heating and power source of the co-electrolysis unit is the electricity generated by the offshore wind power generation of the deep open sea after passing through the electric energy storage unit;

4) And the mixture of the hydrogen and the carbon monoxide exchanges heat with the inlet feed gas of the high-temperature fuel cell and is pressurized, and then enters the methanation unit, and the methane gas is prepared through 2-5 stages of methanation reactions in series-parallel connection.

2. The method according to claim 1, further comprising, after step 4), cooling and dehydrating the methane gas obtained, and then mixing with the methane-enriched stream of step 1), and then carrying out export to an onshore natural gas processing plant via a subsea pipeline.

3. The method according to claim 1 or 2, wherein in step 1), the temperature of the hydrate process separation is 1-20 ℃ and the pressure is 1-7 MPaG;

the water generated by the hydrate method separation and carbon dioxide concentration unit and the water cooled and separated by the methanation unit are treated by a seawater purification unit to obtain softened water, and the softened water is used as cooling water of the methanation unit and then enters the waste heat boiler; wherein the seawater purifying unit adopts a 1-5-level reverse osmosis membrane to purify seawater.

4. The method of claim 1, wherein the carbon dioxide-enriched natural gas has a carbon dioxide volume concentration of greater than 10%;

the methane concentration by volume in the methane-enriched stream is greater than 80%;

the carbon dioxide in the carbon dioxide-rich stream has a volumetric concentration greater than 70%;

in the step 1), the deep open sea offshore platform is an offshore platform established by deep sea with the water depth of more than 100 meters or the distance from land of more than 20 km;

in the step 3), the deep and open sea is a sea area with a water depth of more than 100 meters or a distance of more than 20 kilometers from land.

5. The method according to claim 1, wherein in step 2), the volume ratio of the iron molybdenum catalyst to the nickel molybdenum catalyst is 1:0.2 to 5;

the mass percentage of sulfur in the stream rich in carbon dioxide after desulfurization is 1 ppm-2%;

the mass percentage of nitrogen after denitrification of the stream rich in carbon dioxide is 1 ppm-3%.

6. The method according to claim 1, wherein in step 3), the electrolysis is carried out at a temperature of 600 to 900 ℃ and an absolute pressure of 2kPa to 2MPa.

7. The method according to claim 1 or 6, wherein in step 3) the electrical energy storage unit is a lithium battery as energy storage medium.

8. The method according to claim 1, wherein in step 4), the mixture of hydrogen and carbon monoxide is subjected to heat exchange at a temperature of 200-400 ℃ and is pressurized to 2-4 MPa.

9. The method according to claim 1 or 8, characterized in that in step 4) the methanation reaction is catalyzed with a nickel-based catalyst;

the mass percentage of nickel metal in the nickel-based catalyst is 10-40 wt%;

the methanation reaction temperature is 200-800 ℃.

10. The method according to claim 1 or 8, characterized by further comprising, in step 4), a step in which the methanation unit recovers superheated steam by-produced by the methanation unit by using a waste heat boiler;

the temperature of the superheated steam by-produced by the methanation unit is 200-600 ℃.

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