Off-grid system for preparing electronic methanol through hydrogenation of carbon dioxide and control method of off-grid system

Abstract

The invention discloses an off-grid system for preparing electronic methanol through carbon dioxide hydrogenation and a control method thereof, and the off-grid system comprises a wind and light power generation system, a water electrolysis hydrogen production system, a hydrogen storage system, a biomass direct combustion power generation system, a carbon dioxide capturing system and a methanol production system, the control method specifically comprises the step of dynamically adjusting the methanol synthesis load of the next node and the running state of each system according to the methanol synthesis load ratio K of the methanol synthesis system corresponding to the hydrogen production amount of the water electrolysis hydrogen production system connected with the wind-solar power generation system of the previous node in cooperation with the current biomass electric hydrogen production on-off state and the hydrogen storage amount of the current hydrogen storage system. The system has the advantages that a stable power supply is provided through the biomass direct-fired power generation system to guarantee stable operation of the production system in an off-grid state, and meanwhile, excessive biomass electricity is utilized to produce hydrogen when wind-light hydrogen production is insufficient to guarantee that the production system steadily passes through a wind-light valley period.

Description

Technical Field

[0001] The invention relates to the technical field of green methanol synthesis, and in particular to an off-grid system for preparing electronic methanol by hydrogenating carbon dioxide and a control method thereof. Background Art

[0002] The methanol produced by electrolyzing water with green electricity from wind and solar power and then reacting it with carbon dioxide is called electronic methanol. It is recognized as the green methanol with the lowest carbon emissions.

[0003] Since wind and solar power generation is unstable and not suitable as a source of electricity for chemical production systems, methanol synthesis generally uses grid electricity as support. However, the proportion of domestic grid electricity generated by fossil fuels is still relatively high, resulting in relatively high overall carbon emissions from products.

[0004] Limited by the stability of equipment operation, the lower limit of methanol production load is generally not less than 50%. Even through methods such as bypass circulation and auxiliary heating, the lower limit of production load can only reach about 30%. When encountering a long period of low wind and solar power output, the stored hydrogen will be consumed in a short time, resulting in shutdown and causing huge losses.

[0005] Biomass direct combustion power generation technology is highly mature and has low carbon emissions, and can provide stable electricity and green carbon sources for electronic methanol synthesis. Summary of the invention

[0006] The purpose of the present invention is to provide an off-grid system for producing electronic methanol by hydrogenating carbon dioxide and a control method thereof, so as to solve the problems of green and stable power supply, green carbon dioxide raw material supply, and smooth transition from wind and solar trough in the production process of electronic methanol.

[0007] The above technical objectives of the present invention are achieved through the following technical solutions:

[0008] An off-grid system for producing electronic methanol by hydrogenating carbon dioxide, characterized in that it comprises a wind-solar power generation system, a water electrolysis hydrogen production system, a hydrogen storage system, a biomass direct-fired power generation system, a carbon dioxide capture system and a methanol production system, wherein the biomass direct-fired power generation system is provided with a biomass input port, the biomass electricity output port of the biomass direct-fired power generation system is respectively connected to the carbon dioxide capture system and the methanol production system, the steam output port of the biomass direct-fired power generation system is respectively connected to the carbon dioxide capture system and the methanol production system, the flue gas output port of the biomass direct-fired power generation system is connected to the carbon dioxide capture system, the wind-solar green electricity output port of the wind-solar power generation system is connected to the water electrolysis hydrogen production system, the hydrogen output port of the water electrolysis hydrogen production system is connected to the hydrogen storage system, the hydrogen output port of the hydrogen storage system is connected to the methanol production system, and the carbon dioxide output port of the carbon dioxide capture system is connected to the methanol production system.

[0009] Preferably, the biomass power output port of the biomass direct combustion power generation system is also connected to the electrolytic water hydrogen production system. When biomass power hydrogen production is turned on, biomass fuel is first used to meet the steam and power demands of the methanol production system, and the remainder is used for biomass power hydrogen production.

[0010] Preferably, the hydrogen storage system uses low-pressure hydrogen storage spherical tanks.

[0011] Preferably, the biomass direct combustion power generation system uses a condensing extraction generator set.

[0012] A control method for an off-grid system for hydrogenating carbon dioxide to electronic methanol, characterized in that: specifically, according to the ratio K of the hydrogen production amount of the electrolytic water hydrogen production system connected to the wind-solar power generation system at the previous node corresponding to the methanol synthesis load of the methanol synthesis system, in conjunction with the current on-off state of biomass power hydrogen production and the hydrogen storage amount of the current hydrogen storage system, the methanol synthesis load of the next node and the operating states of each system are dynamically adjusted.

[0013] Preferably, each of the indicated node times is 1 hour, and the ratio K is specifically the ratio of the hydrogen production amount of the electrolytic water hydrogen production system to the hydrogen demand under full methanol load.

[0014] Preferably, when the ratio K of the hydrogen production amount of the electrolytic water hydrogen production system connected to the wind-solar power generation system at the previous node corresponding to the methanol synthesis load of the methanol synthesis system is ≥ 110%, the biomass power hydrogen production is kept in the off state;

[0015] If the hydrogen storage amount of the hydrogen storage system exceeds or is equal to the first threshold, the first threshold is set to be lower than the total hydrogen storage amount of the hydrogen storage system, the methanol synthesis system is kept running at the highest load of 110%, and the excess hydrogen is stored in the hydrogen storage system;

[0016] If the hydrogen storage amount of the hydrogen storage system is lower than the first threshold, the methanol synthesis system is kept running at 100% load, and the excess hydrogen is stored in the hydrogen storage system.

[0017] Preferably, when the wind-solar power generation is relatively sufficient and the ratio K of the hydrogen production amount of the electrolytic water hydrogen production system connected to the wind-solar power generation system at the previous node corresponding to the methanol synthesis load of the methanol synthesis system ranges from 50% ≤ K < 110%, the biomass power hydrogen production is kept in the off state;

[0018] If the hydrogen storage amount exceeds or is equal to the first threshold, the load of the methanol synthesis system is adjusted to just consume the hydrogen production amount, that is, the methanol synthesis load of the methanol synthesis system is adjusted to run at the K value;

[0019] If the hydrogen storage amount is lower than the first threshold, part of the hydrogen is separated and stored in the hydrogen storage system, and the remaining hydrogen is all used for methanol synthesis, and the methanol synthesis load of the methanol synthesis system is adjusted to run at the K value minus 20%.

[0020] Preferably, when the wind and solar power generation is low, and the ratio K of the hydrogen production amount of the electrolytic water hydrogen production system connected to the wind and solar power generation system at the previous node to the methanol synthesis load of the methanol synthesis system ranges from 30% ≤ K < 50%;

[0021] If the biomass power-to-hydrogen is in the off state and the hydrogen storage amount exceeds or is equal to the first threshold, the methanol synthesis system load is adjusted to just consume the hydrogen production amount, that is, the methanol synthesis load of the methanol synthesis system is adjusted to operate at the K value;

[0022] If the biomass power-to-hydrogen is in the off state and the hydrogen storage amount is lower than the first threshold, the methanol synthesis system load is adjusted to the load lower limit of 30%, and the remaining hydrogen is stored in the hydrogen storage system;

[0023] If the biomass power-to-hydrogen is in the on state and the hydrogen storage amount exceeds or is equal to the first threshold, the methanol synthesis system load is adjusted to just consume the sum of the wind and solar power-to-hydrogen amount and the maximum biomass power-to-hydrogen amount, that is, the methanol synthesis load of the methanol synthesis system is adjusted to operate at the K value plus 20%;

[0024] If the biomass power-to-hydrogen is in the on state and the hydrogen storage amount is lower than the first threshold, the methanol synthesis system load is adjusted to just consume the wind and solar power-to-hydrogen amount, that is, the methanol synthesis load of the methanol synthesis system is adjusted to operate at the K value, and all the biomass power-to-hydrogen is stored in the hydrogen storage system.

[0025] Preferably, when the wind and solar hydrogen production amount is lower than the required amount of the methanol synthesis load lower limit, but the sum of the maximum biomass power-to-hydrogen amount is higher than the required amount of the lower limit, that is, the ratio K of the hydrogen production amount of the electrolytic water hydrogen production system connected to the wind and solar power generation system at the previous node to the methanol synthesis load of the methanol synthesis system ranges from 10% ≤ K < 30%;

[0026] If the biomass power-to-hydrogen is in the on state and the hydrogen storage amount exceeds or is equal to the first threshold, the methanol synthesis system load is adjusted to just consume the sum of the wind and solar power-to-hydrogen amount and the maximum biomass power-to-hydrogen amount, that is, the methanol synthesis load of the methanol synthesis system is adjusted to operate at the K value plus 20%;

[0027] If the biomass power-to-hydrogen is in the on state and the hydrogen storage amount is lower than the first threshold, the methanol synthesis system load is adjusted to the load lower limit of 30%, and the remaining hydrogen is stored in the hydrogen storage system;

[0028] If the biomass power-to-hydrogen is in the off state and the hydrogen storage amount exceeds or is equal to the first threshold, the methanol synthesis system load is adjusted to the load lower limit of 30%, and the insufficient hydrogen is supplemented by the hydrogen storage system;

[0029] If the biomass power-to-hydrogen is in the off state and the hydrogen storage amount is lower than the first threshold, the biomass power-to-hydrogen is turned on, the methanol synthesis system load is adjusted to the load lower limit of 30%, and the remaining hydrogen is stored in the hydrogen storage system.

[0030] Preferably, when the hydrogen production from wind and light is so low that even adding the maximum hydrogen production from biomass power still does not meet the lower limit requirement for methanol synthesis, that is, when the ratio K of the hydrogen production of the electrolytic water hydrogen production system connected to the wind and light power generation system at the previous node to the methanol synthesis load of the methanol synthesis system is less than 10%;

[0031] If the biomass power hydrogen production is in the on state and the hydrogen storage amount exceeds or is equal to the third threshold, the third threshold is set to the hydrogen amount required for the methanol synthesis system to operate at the lowest load of 30% within a node time minus the maximum hydrogen production from biomass power, that is, if the hydrogen storage amount plus the maximum hydrogen production from biomass power exceeds or is equal to 30% of the lower limit of the methanol synthesis load, then the load of the methanol synthesis system is adjusted to 30% of the lower limit, and the insufficient hydrogen is supplemented by the hydrogen storage system;

[0032] If the biomass power hydrogen production is in the on state and the hydrogen storage amount is lower than the third threshold, that is, the hydrogen storage amount plus the maximum hydrogen production from biomass power is lower than 30% of the lower limit of the methanol synthesis load, then the whole system shuts down or keeps warm, and the remaining hydrogen is stored in the hydrogen storage system;

[0033] If the biomass power hydrogen production is in the off state and the hydrogen storage amount exceeds or is equal to the second threshold, the second threshold is set to the hydrogen amount required for the methanol synthesis system to operate at the lowest load of 30% within a node time, that is, if the hydrogen storage amount exceeds or is equal to 30% of the lower limit of the methanol synthesis load, then the load of the methanol synthesis system is adjusted to 30% of the lower limit, and the insufficient hydrogen is supplemented by the hydrogen storage system;

[0034] If the biomass power hydrogen production is in the off state and the hydrogen storage amount is lower than the second threshold, that is, the hydrogen storage amount is lower than 30% of the lower limit of the methanol synthesis load, then the whole system shuts down or keeps warm, and the remaining hydrogen is stored in the hydrogen storage system.

[0035] In summary, the present invention has the following beneficial effects:

[0036] 1. The present invention uses biomass as fuel to provide the stable power and steam required by the electronic methanol production system, ensuring the safe and stable operation of the system while ensuring the green attribute of the methanol product.

[0037] 2. The present invention captures carbon dioxide from the flue gas by-produced by the biomass direct combustion power generation system as the carbon source for methanol synthesis, and has a significant carbon emission reduction effect.

[0038] 3. The present invention makes a decision on the operation state of the next node based on the hydrogen production of the previous node and the current system state, and the decision input quantities are all determined data, avoiding the uncertainty deviation caused by making decisions based on wind and light power generation predictions.

[0039] 4. The present invention can flexibly adjust the operation plan according to different working conditions and is suitable for automatic operation.

[0040] 5. The present invention can achieve a high utilization rate of the device without configuring expensive energy storage facilities, and greatly improves the ability of the system to operate continuously through the low valley of wind and light power generation. Without expanding the design scale of the biomass direct combustion power generation system, even if the hydrogen production from wind and light is as low as 10% of the hydrogen required for methanol full load, the system can operate continuously and stably without relying on hydrogen storage; in the case of completely no wind and light, the continuous operation time of the system at 30% methanol synthesis load can be increased to more than 3 times. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 is a schematic diagram of an off-grid system for hydrogenating carbon dioxide to electronic methanol according to the present invention;

[0042] Figure 2 is a schematic diagram of a control method for an off-grid system for hydrogenating carbon dioxide to electronic methanol according to the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0043] In order to elaborate in detail the technical solutions adopted by the present invention to achieve the predetermined technical objectives, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. And, without creative efforts, the technical means or technical features in the embodiments of the present invention can be replaced. The present invention will be described in detail below with reference to the drawings and in conjunction with the embodiments.

[0044] As Figure 1 shown, an off-grid system for hydrogenating carbon dioxide to electronic methanol includes a wind and solar power generation system, an electrolytic water hydrogen production system, a hydrogen storage system, a biomass direct combustion power generation system, a carbon dioxide capture system, and a methanol production system. The biomass direct combustion power generation system is provided with a biomass input port. The biomass power output port of the biomass direct combustion power generation system is respectively connected to the carbon dioxide capture system and the methanol production system. The steam output port of the biomass direct combustion power generation system is respectively connected to the carbon dioxide capture system and the methanol production system. The flue gas output port of the biomass direct combustion power generation system is connected to the carbon dioxide capture system. The wind and solar green power output port of the wind and solar power generation system is connected to the electrolytic water hydrogen production system. The hydrogen output port of the electrolytic water hydrogen production system is connected to the hydrogen storage system. The hydrogen output port of the hydrogen storage system is connected to the methanol production system. The carbon dioxide output port of the carbon dioxide capture system is connected to the methanol production system.

[0045] The biomass power output port of the biomass direct combustion power generation system is also connected to the electrolytic water hydrogen production system.

[0046] The hydrogen storage system adopts a low-pressure hydrogen storage spherical tank, and the biomass direct combustion power generation system adopts a condensing extraction generator set.

[0047] An off-grid system control method for hydrogenating carbon dioxide to produce e-methanol, specifically, according to the ratio K of the hydrogen production amount of the electrolytic water hydrogen production system connected to the previous node's wind-solar power generation system corresponding to the methanol synthesis load of the methanol synthesis system, in coordination with the on-off state of the current biomass power-to-hydrogen and the hydrogen storage amount of the current hydrogen storage system, dynamically adjust the methanol synthesis load of the next node and the operating states of each system.

[0048] The time of each indicated node is 1 hour. Specifically, the ratio K is the ratio of the hydrogen production amount of the electrolytic water hydrogen production system to the hydrogen demand under full load of methanol.

[0049] Such as Figure 2 The specific control strategy of an off-grid system control method for hydrogenating carbon dioxide to produce e-methanol as shown is as follows:

[0050] When the ratio K of the hydrogen production amount of the electrolytic water hydrogen production system connected to the previous node's wind-solar power generation system corresponding to the methanol synthesis load of the methanol synthesis system is ≥ 110%, keep the biomass power-to-hydrogen in the closed state;

[0051] If the hydrogen storage amount of the hydrogen storage system exceeds or is equal to the first threshold of 7.5 t, keep the methanol synthesis system running at the highest load of 110%, and store the excess hydrogen in the hydrogen storage system;

[0052] If the hydrogen storage amount of the hydrogen storage system is lower than the first threshold of 7.5 t, keep the methanol synthesis system running at 100% load, and store the excess hydrogen in the hydrogen storage system.

[0053] When the wind-solar power generation is relatively sufficient and the ratio K of the hydrogen production amount of the electrolytic water hydrogen production system connected to the previous node's wind-solar power generation system corresponding to the methanol synthesis load of the methanol synthesis system ranges from 50% ≤ K < 110%, keep the biomass power-to-hydrogen in the closed state;

[0054] If the hydrogen storage amount exceeds or is equal to the first threshold of 7.5 t, adjust the load of the methanol synthesis system to just consume the hydrogen production amount, that is, adjust the methanol synthesis load of the methanol synthesis system to run at the K value;

[0055] If the hydrogen storage amount is lower than the first threshold of 7.5 t, then separate part of the hydrogen and store it in the hydrogen storage system, and use all the remaining hydrogen for methanol synthesis. Adjust the methanol synthesis load of the methanol synthesis system to run at the K value minus 20%.

[0056] When the wind-solar power generation is low and the ratio K of the hydrogen production amount of the electrolytic water hydrogen production system connected to the previous node's wind-solar power generation system corresponding to the methanol synthesis load of the methanol synthesis system ranges from 30% ≤ K < 50%;

[0057] If the biomass power-to-hydrogen is in the closed state and the hydrogen storage amount exceeds or is equal to the first threshold of 7.5 t, then adjust the load of the methanol synthesis system to just consume the hydrogen production amount, that is, adjust the methanol synthesis load of the methanol synthesis system to run at the K value;

[0058] If the biomass power-to-hydrogen is in the off state and the hydrogen storage amount is lower than the first threshold of 7.5 t, the load of the methanol synthesis system is adjusted to the lower limit of 30%, and the excess hydrogen is stored in the hydrogen storage system;

[0059] If the biomass power-to-hydrogen is in the on state and the hydrogen storage amount is greater than or equal to the first threshold of 7.5 t, the load of the methanol synthesis system is adjusted to just consume the sum of the hydrogen produced by wind and solar power-to-hydrogen and the maximum hydrogen production of biomass power-to-hydrogen, that is, the methanol synthesis load of the methanol synthesis system is adjusted to operate at K value plus 20%;

[0060] If the biomass power-to-hydrogen is in the on state and the hydrogen storage amount is lower than the first threshold of 7.5 t, the load of the methanol synthesis system is adjusted to just consume the hydrogen produced by wind and solar power-to-hydrogen, that is, the methanol synthesis load of the methanol synthesis system is adjusted to operate at K value, and all the hydrogen produced by biomass power-to-hydrogen is stored in the hydrogen storage system.

[0061] When the hydrogen production from wind and solar power is lower than the required lower limit of the methanol synthesis load, but when adding the maximum hydrogen production of biomass power, it is higher than the required lower limit, that is, when the ratio K of the hydrogen production of the electrolytic water hydrogen production system connected to the wind and solar power generation system at the previous node to the methanol synthesis load of the methanol synthesis system ranges from 10% ≤ K < 30%;

[0062] If the biomass power-to-hydrogen is in the on state and the hydrogen storage amount is greater than or equal to the first threshold of 7.5 t, the load of the methanol synthesis system is adjusted to just consume the sum of the hydrogen produced by wind and solar power-to-hydrogen and the maximum hydrogen production of biomass power-to-hydrogen, that is, the methanol synthesis load of the methanol synthesis system is adjusted to operate at K value plus 20%;

[0063] If the biomass power-to-hydrogen is in the on state and the hydrogen storage amount is lower than the first threshold of 7.5 t, the load of the methanol synthesis system is adjusted to the lower limit of 30%, and the excess hydrogen is stored in the hydrogen storage system;

[0064] If the biomass power-to-hydrogen is in the off state and the hydrogen storage amount is greater than or equal to the first threshold of 7.5 t, the load of the methanol synthesis system is adjusted to the lower limit of 30%, and the insufficient hydrogen is supplemented by the hydrogen storage system;

[0065] If the biomass power-to-hydrogen is in the off state and the hydrogen storage amount is lower than the first threshold of 7.5 t, the biomass power-to-hydrogen is started, the load of the methanol synthesis system is adjusted to the lower limit of 30%, and the excess hydrogen is stored in the hydrogen storage system.

[0066] When the hydrogen production from wind and solar power is so low that even adding the maximum hydrogen production of biomass power still does not meet the required lower limit of methanol synthesis, that is, when the ratio K of the hydrogen production of the electrolytic water hydrogen production system connected to the wind and solar power generation system at the previous node to the methanol synthesis load of the methanol synthesis system is < 10%;

[0067] If the biomass power-to-hydrogen is in the on state and the hydrogen storage amount is greater than or equal to the third threshold of 0.48 t, the load of the methanol synthesis system is adjusted to the lower limit of 30%, and the insufficient hydrogen is supplemented by the hydrogen storage system;

[0068] If the biomass power - to - hydrogen is in the on state and the hydrogen storage amount is lower than the third threshold of 0.48 t, the whole system shuts down or keeps warm, and the remaining hydrogen is stored in the hydrogen storage system;

[0069] If the biomass power - to - hydrogen is in the off state and the hydrogen storage amount is greater than or equal to the second threshold of 1.5 t, the load of the methanol synthesis system is adjusted to the lower limit of the load, which is 30%, and the insufficient hydrogen is supplemented by the hydrogen storage system;

[0070] If the biomass power - to - hydrogen is in the off state and the hydrogen storage amount is lower than the second threshold of 1.5 t, the whole system shuts down or keeps warm, and the remaining hydrogen is stored in the hydrogen storage system.

[0071] Among the three hydrogen storage amount thresholds set for the above - mentioned hydrogen storage system, the first threshold is set to be lower than the total hydrogen storage amount but greater than the second threshold; the second threshold is set to be the amount of hydrogen required for the methanol synthesis system to operate at the lowest load of 30% within a node time; the third threshold is set to be the amount of hydrogen required for the methanol synthesis system to operate at the lowest load of 30% within a node time minus the maximum hydrogen production amount of biomass power.

[0072] The maximum hydrogen production amount of biomass power is the amount of hydrogen that can be obtained when the fuel feeding amount of the biomass direct - combustion power generation system reaches 100% within a node time. First, it satisfies the steam and electricity requirements for the methanol production system to operate at the lowest load, and the remaining amount is all used for power generation and further hydrogen production.

[0073] The maximum hydrogen production amount of biomass power is rounded after calculation and is calculated as 20% of the hydrogen consumption when the methanol synthesis is in full - load production.

[0074] In this embodiment, the characteristics of each subsystem of an off - grid system for carbon dioxide hydrogenation to electronic methanol are shown in Table 1 below:

[0075]

[0076] The system control method of this embodiment is carried out according to Figure 2 as shown. During the operation of the system, each node duration is 1 hour, and the operation strategies of the following 16 typical working conditions are introduced:

[0077] Working condition 1: The hydrogen supply amount from wind - solar power generation in the previous hour is 5.8 t, the K value is 116%, and the current hydrogen storage amount is 8 t. Then, keep the biomass power - to - hydrogen in the off state and adjust the methanol production load to 110%;

[0078] Working condition 2: The hydrogen production amount from wind - solar power generation in the previous hour is 5.8 t, the K value is 116%, and the current hydrogen storage amount is 6.5 t. Then, keep the biomass power - to - hydrogen in the off state and adjust the methanol production load to 100%;

[0079] Operating condition 3: The hydrogen production from wind and solar power generation in the previous hour was 3t, the K value was 60%, and the current hydrogen storage was 8t. Then, keep the hydrogen production from biomass power generation in the off state and adjust the methanol production load to 60%;

[0080] Operating condition 4: The hydrogen production from wind and solar power generation in the previous hour was 3t, the K value was 60%, and the current hydrogen storage was 6.5t. Then, keep the hydrogen production from biomass power generation in the off state and adjust the methanol production load to 40%;

[0081] Operating condition 5: The hydrogen production from wind and solar power generation in the previous hour was 1.75t, the K value was 35%, and the current hydrogen storage was 8t. The current hydrogen production from biomass power generation was in the off state. Then, adjust the methanol production load to 35%;

[0082] Operating condition 6: The hydrogen production from wind and solar power generation in the previous hour was 1.75t, the K value was 35%, and the current hydrogen storage was 6.5t. The current hydrogen production from biomass power generation was in the off state. Then, adjust the methanol production load to 30%;

[0083] Operating condition 7: The hydrogen production from wind and solar power generation in the previous hour was 1.75t, the K value was 35%, and the current hydrogen storage was 8t. The current hydrogen production from biomass power generation was in the on state. Then, adjust the methanol production load to 55%;

[0084] Operating condition 8: The hydrogen production from wind and solar power generation in the previous hour was 1.75t, the K value was 35%, and the current hydrogen storage was 6.5t. The current hydrogen production from biomass power generation was in the on state. Then, adjust the methanol production load to 35%;

[0085] Operating condition 9: The hydrogen production from wind and solar power generation in the previous hour was 1t, the K value was 20%, and the current hydrogen storage was 8t. The current hydrogen production from biomass power generation was in the off state. Then, adjust the methanol production load to 30%;

[0086] Operating condition 10: The hydrogen production from wind and solar power generation in the previous hour was 1t, the K value was 20%, and the current hydrogen storage was 6.5t. The current hydrogen production from biomass power generation was in the off state. Then, turn on the hydrogen production from biomass power generation and adjust the methanol production load to 30%;

[0087] Operating condition 11: The hydrogen production from wind and solar power generation in the previous hour was 1t, the K value was 20%, and the current hydrogen storage was 8t. The current hydrogen production from biomass power generation was in the on state. Then, adjust the methanol production load to 40%;

[0088] Operating condition 12: The hydrogen production from wind and solar power generation in the previous hour was 1t, the K value was 20%, and the current hydrogen storage was 6.5t. The current hydrogen production from biomass power generation was in the on state. Then, adjust the methanol production load to 30%;

[0089] Operating condition 13: The hydrogen production from wind and solar power generation in the previous hour was 0.25 t, the K value was 5%, the current hydrogen storage was 0.6 t, and the current biomass power-to-hydrogen production was in the on state. Then, adjust the methanol production load to 30%;

[0090] Operating condition 14: The hydrogen production from wind and solar power generation in the previous hour was 0.25 t, the K value was 5%, the current hydrogen storage was 0.2 t, and the current biomass power-to-hydrogen production was in the on state. Then, shut down the entire system or keep it warm.

[0091] Operating condition 15: The hydrogen production from wind and solar power generation in the previous hour was 0.25 t, the K value was 5%, the current hydrogen storage was 2 t, and the current biomass power-to-hydrogen production was in the off state. Then, adjust the methanol production load to 30%;

[0092] Operating condition 16: The hydrogen production from wind and solar power generation in the previous hour was 0.25 t, the K value was 5%, the current hydrogen storage was 1 t, and the current biomass power-to-hydrogen production was in the off state. Then, shut down the entire system or keep it warm.

[0093] The operation plans of each subsystem for operating conditions 1 to 8 are shown in Table 2 below.

[0094]

[0095]

[0096] The operation plans of each subsystem for operating conditions 9 to 16 are shown in Table 3 below.

[0097]

[0098] In this embodiment, the scale of the biomass direct combustion power generation system is designed according to the requirements for 100% load of electronic methanol production. During the low period of wind and solar power generation, when the electronic methanol production operates at the lower load limit, the demands for biomass power, steam, etc. are significantly reduced. By maintaining the full load operation of the biomass direct combustion power generation system, the excess hydrogen production from biomass power-to-hydrogen reaches 1.02 tons, which can maintain about 20.5% of the hydrogen demand under the full load production of electronic methanol. That is, as long as the hydrogen production from wind and solar reaches 9.5% of the hydrogen demand under the full load production of electronic methanol, the entire system can continuously and stably operate at 30% load of electronic methanol, significantly reducing the shutdown risk. After being equipped with a hydrogen storage system, in the case of completely no wind and solar power, the electronic methanol production system can be maintained to operate at the lowest load of 30% for more than 18 hours. Without biomass power-to-hydrogen production, with the same hydrogen storage capacity, it can only be maintained for 6 hours, significantly improving the ability of the system to smoothly pass through the low period of wind and solar without shutdown.

[0099] In summary, the present invention uses biomass as fuel to provide stable power and steam required for the electronic methanol production system, ensuring the safe and stable operation of the system while ensuring the green attributes of methanol products.

[0100] The present invention captures carbon dioxide from the flue gas by-produced in a biomass direct combustion power generation system as a carbon source for methanol synthesis, and has a remarkable carbon emission reduction effect.

[0101] The present invention makes a decision on the operating state of the next node based on the hydrogen production amount of the previous node and the current system state, and the decision input quantities are all determined data, avoiding the uncertainty deviation caused by making decisions based on wind and solar power generation predictions.

[0102] The present invention can flexibly adjust the operation plan according to different working conditions and is suitable for automatic operation.

[0103] The present invention can achieve a high utilization rate of the device without configuring expensive energy storage facilities, and greatly improves the ability of the system to pass through the low valley of wind and solar power output without shutdown; on the premise of not expanding the design scale of the biomass direct combustion power generation system, even if the hydrogen production from wind and solar is as low as 10% of the hydrogen required for methanol full load, the system can still operate continuously and stably without relying on hydrogen storage; in the case of completely no wind and solar, the continuous operation time of the system at 30% methanol synthesis load can be increased to more than 3 times.

[0104] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. Those skilled in the art can make various modifications or equivalent replacements to the present invention within the essence and protection scope of the present invention, and such modifications or equivalent replacements should also be regarded as falling within the protection scope of the technical solution of the present invention.

Claims

1. An off-grid system for producing electronic methanol by hydrogenation of carbon dioxide, characterized in that: The invention comprises a wind-solar power generation system, a water electrolysis hydrogen production system, a hydrogen storage system, a biomass direct-fired power generation system, a carbon dioxide capture system and a methanol production system. The biomass direct-fired power generation system is provided with a biomass input port. The biomass electricity output port of the biomass direct-fired power generation system is respectively connected to the carbon dioxide capture system and the methanol production system. The steam output port of the biomass direct-fired power generation system is respectively connected to the carbon dioxide capture system and the methanol production system. The flue gas output port of the biomass direct-fired power generation system is connected to the carbon dioxide capture system. The wind-solar green electricity output port of the wind-solar power generation system is connected to the water electrolysis hydrogen production system. The hydrogen output port of the water electrolysis hydrogen production system is connected to the hydrogen storage system. The hydrogen output port of the hydrogen storage system is connected to the methanol production system. The carbon dioxide output port of the carbon dioxide capture system is connected to the methanol production system.

2. The off-grid system for producing electronic methanol by hydrogenation of carbon dioxide according to claim 1, characterized in that: The biomass electricity output port of the biomass direct combustion power generation system is also connected to the water electrolysis hydrogen production system.

3. The off-grid system for producing electronic methanol by hydrogenation of carbon dioxide according to claim 1, characterized in that: The hydrogen storage system adopts a low-pressure hydrogen storage spherical tank, and the biomass direct combustion power generation system adopts an extraction condensing generator set.

4. A method for controlling an off-grid system for producing electronic methanol by hydrogenation of carbon dioxide, characterized in that: Specifically, the methanol synthesis load ratio K of the methanol synthesis system corresponding to the hydrogen production capacity of the water electrolysis hydrogen production system connected to the previous node wind and solar power generation system is coordinated with the current start and stop status of biomass hydrogen production and the hydrogen storage capacity of the current hydrogen storage system to dynamically adjust the methanol synthesis load of the next node and the operating status of each system.

5. The off-grid system control method for producing electronic methanol by hydrogenation of carbon dioxide according to claim 4, characterized in that: The time of each node shown is 1 hour, and the ratio K is specifically the ratio of the hydrogen production of the water electrolysis hydrogen production system to the hydrogen demand under full load of methanol.

6. The off-grid system control method for producing electronic methanol by hydrogenation of carbon dioxide according to claim 4, characterized in that: When the hydrogen production of the water electrolysis hydrogen production system connected to the previous node wind and solar power generation system corresponds to the methanol synthesis load ratio K of the methanol synthesis system ≥ 110%, the biomass electricity hydrogen production is kept closed; If the hydrogen storage capacity of the hydrogen storage system exceeds or is equal to the first threshold value, the first threshold value is set to be lower than the total hydrogen storage capacity of the hydrogen storage system, the methanol synthesis system is kept running at a maximum load of 110%, and the remaining hydrogen is stored in the hydrogen storage system; If the hydrogen storage capacity of the hydrogen storage system is lower than the first threshold value, the methanol synthesis system is kept running at 100% load and the remaining hydrogen is stored in the hydrogen storage system.

7. The off-grid system control method for producing electronic methanol by hydrogenation of carbon dioxide according to claim 4, characterized in that: When the wind and solar power generation is sufficient, and the hydrogen production of the water electrolysis hydrogen production system connected to the previous node wind and solar power generation system corresponds to the methanol synthesis load ratio K of the methanol synthesis system in the range of 50%≤K<110%, the biomass electricity hydrogen production is kept closed; If the hydrogen storage capacity exceeds or is equal to the first threshold, the methanol synthesis system load is adjusted to just absorb the hydrogen production capacity, that is, the methanol synthesis load of the methanol synthesis system is adjusted to operate at the K value; If the hydrogen storage amount is lower than the first threshold, part of the hydrogen is separated and stored in the hydrogen storage system, and the remaining hydrogen is all used for methanol synthesis. The methanol synthesis load of the methanol synthesis system is adjusted to the K value minus 20%.

8. The off-grid system control method for producing electronic methanol by hydrogenation of carbon dioxide according to claim 4, characterized in that: When the wind and solar power generation is low, the hydrogen production of the water electrolysis hydrogen production system connected to the previous node wind and solar power generation system corresponds to the methanol synthesis load ratio K of the methanol synthesis system in the range of 30%≤K<50%; If the biomass electric hydrogen production is in the closed state and the hydrogen storage capacity exceeds or is equal to the first threshold, the methanol synthesis system load is adjusted to just absorb the hydrogen production capacity, that is, the methanol synthesis load of the methanol synthesis system is adjusted to the K value; If the biomass hydrogen production is in the off state and the hydrogen storage capacity is lower than the first threshold, the methanol synthesis system load is adjusted to 30% of the load lower limit, and the remaining hydrogen is stored in the hydrogen storage system; If the biomass electricity hydrogen production is in the on state and the hydrogen storage capacity exceeds or equals the first threshold, the methanol synthesis system load is adjusted to just absorb the sum of the wind and solar power hydrogen production and the maximum biomass electricity hydrogen production, that is, the methanol synthesis load of the methanol synthesis system is adjusted to the K value plus 20%; If biomass hydrogen production is in the on state and the hydrogen storage capacity is lower than the first threshold, the methanol synthesis system load is adjusted to just absorb the hydrogen production from wind and solar power, that is, the methanol synthesis load of the methanol synthesis system is adjusted to the K value, and all the biomass hydrogen production is stored in the hydrogen storage system.

9. The off-grid system control method for producing electronic methanol by hydrogenation of carbon dioxide according to claim 4, characterized in that: When the amount of hydrogen produced by wind and solar power is lower than the lower limit of the methanol synthesis load, but the amount of hydrogen produced by biomass electricity is higher than the lower limit, that is, the hydrogen produced by the electrolytic water hydrogen production system connected to the wind and solar power generation system at the previous node corresponds to the methanol synthesis load ratio K of the methanol synthesis system in the range of 10%≤K<30%; If the biomass electricity hydrogen production is in the on state and the hydrogen storage capacity exceeds or equals the first threshold, the methanol synthesis system load is adjusted to just absorb the sum of the wind and solar power hydrogen production and the maximum biomass electricity hydrogen production, that is, the methanol synthesis load of the methanol synthesis system is adjusted to the K value plus 20%; If the biomass electric hydrogen production is in the on state and the hydrogen storage capacity is lower than the first threshold, the methanol synthesis system load is adjusted to 30% of the load lower limit, and the remaining hydrogen is stored in the hydrogen storage system; If the biomass electricity-generated hydrogen is in the off state and the hydrogen storage capacity exceeds or equals the first threshold, the methanol synthesis system load is adjusted to 30% of the load lower limit, and the insufficient hydrogen is supplemented by the hydrogen storage system; If biomass hydrogen production is in the off state and the hydrogen storage capacity is lower than the first threshold, biomass hydrogen production is turned on, the load of the methanol synthesis system is adjusted to 30% of the load lower limit, and the remaining hydrogen is stored in the hydrogen storage system.

10. The off-grid system control method for producing electronic methanol by hydrogenation of carbon dioxide according to claim 4, characterized in that: When the amount of hydrogen produced by wind and solar power is so low that the amount of hydrogen produced by biomass electricity still cannot meet the lower limit of methanol synthesis, that is, the hydrogen production of the electrolytic water hydrogen production system connected to the wind and solar power generation system at the previous node corresponds to the methanol synthesis load ratio K of the methanol synthesis system < 10%; If biomass electricity hydrogen production is in the on state and the hydrogen storage capacity exceeds or equals the third threshold, the third threshold is set as the amount of hydrogen required for the methanol synthesis system to operate at a minimum load of 30% within a node time minus the maximum hydrogen production of biomass electricity, that is, the hydrogen storage capacity plus the maximum hydrogen production of biomass electricity exceeds or equals 30% of the lower limit of the methanol synthesis load, then the methanol synthesis system load is adjusted to 30% of the lower limit of the load, and the insufficient hydrogen is supplemented by the hydrogen storage system; If the biomass electricity hydrogen production is in the on state and the hydrogen storage capacity is lower than the third threshold, that is, the hydrogen storage capacity plus the maximum hydrogen production capacity of biomass electricity is lower than the 30% lower limit of the methanol synthesis load, the whole system will be shut down or kept warm, and the remaining hydrogen will be stored in the hydrogen storage system; If the biomass electricity-generated hydrogen is in the off state and the hydrogen storage capacity exceeds or is equal to the second threshold, the second threshold is set to the amount of hydrogen required for the methanol synthesis system to operate at a minimum load of 30% within a node time, that is, the hydrogen storage capacity exceeds the lower limit of the methanol synthesis load by 30%, then the methanol synthesis system load is adjusted to 30% of the lower limit, and the insufficient hydrogen is supplemented by the hydrogen storage system; If the biomass hydrogen production is in the off state and the hydrogen storage capacity is lower than the second threshold, that is, the hydrogen storage capacity is lower than the 30% lower limit of the methanol synthesis load, the entire system will be shut down or insulated, and the remaining hydrogen will be stored in the hydrogen storage system.

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