Coal gasification double-tower heat storage carbon capture and peak shaving method and device

Abstract

The present application provides a coal gas dual-tower heat storage carbon capture peak shaving method and device, the first adsorption tower and the second adsorption tower alternately carry out carbon dioxide adsorption and adsorbent regeneration, solve the problem of insufficient single tower capture, low adsorbent utilization rate and emission instability of load fluctuation; the boiler flue gas after purification treatment is first adsorbed by the first adsorption tower, which can reduce the risk of adsorbent poisoning and deactivation caused by heavy metals, hydrocarbons and moisture. When regenerating, the circulating carbon dioxide is heated by the second heat exchanger and then input into the second adsorption tower for desorption and heat storage, and part of the carbon dioxide is returned after compression and cooling to form a regeneration cycle, thereby improving energy utilization efficiency. Double source steam is obtained and input into the second heat exchanger, the double source steam and the heat storage and release state of the two towers are adjusted according to the process steam supply and demand state of the plant area, so as to avoid occupying process steam and peak shaving; the heat storage and release and the carbon dioxide regeneration cycle compression load are adjusted according to the power grid electricity consumption period, so as to realize the coordinated peak shaving of plant area steam and power grid, ensure continuous and stable, and avoid the corrosion of amine method and salt-containing wastewater.

Description

Technical Field

[0001] This invention relates to the field of carbon capture and thermal storage technology in coal chemical industry, and in particular to a method and apparatus for carbon capture and peak shaving in coal gasification using a dual-tower thermal storage system. Background Technology

[0002] Coal-to-natural-gas plants typically have their own boilers and steam turbine generator sets, generating large amounts of boiler flue gas containing carbon dioxide during production. Compared to flue gas from conventional thermal power plants, the flue gas from coal-to-gas boilers has a higher concentration of carbon dioxide and also carries impurities such as heavy metals and hydrocarbons. Furthermore, the flue gas volume and the supply and demand of process steam in the plant flue gas area fluctuate significantly due to changes in the load of gasification and subsequent production units. Therefore, higher requirements are placed on the capture efficiency, continuous operation capability, load adaptability, and energy utilization efficiency of the carbon capture system.

[0003] Existing commercial high-temperature adsorption carbon capture technologies are primarily designed for low-concentration carbon dioxide flue gas from thermal power plants, often employing a single-tower structure. When directly applied to coal gasification scenarios, they are prone to problems such as insufficient carbon dioxide capture, low adsorbent utilization, and unstable emissions during load fluctuations. Meanwhile, existing adsorbent regeneration processes typically rely on high-quality main steam for heating, resulting in high regeneration energy consumption and crowding out the process steam required for production. Furthermore, the peak-shaving function of existing thermal storage capture systems mainly targets grid peak and off-peak loads, making it difficult to simultaneously regulate the supply and demand of process steam within the plant. Excess steam can lead to energy waste, while insufficient supply may affect production load. In addition, conventional flue gas pretreatment is insufficient to fully remove heavy metals, hydrocarbons, and moisture, and long-term operation can easily lead to adsorbent poisoning and deactivation, increasing replacement and maintenance costs. Traditional amine chemical absorption methods also suffer from drawbacks such as highly corrosive adsorbents, significant equipment wear and tear, generation of saline wastewater, and high overall operating costs. Summary of the Invention

[0004] In view of this, embodiments of the present invention provide a method and apparatus for carbon capture and peak shaving in coal gasification with dual-tower thermal storage, in order to solve the problems of poor capture stability, high regeneration energy consumption and difficulty in balancing process steam in the plant area with peak shaving of the power grid in existing carbon capture technologies.

[0005] To achieve the above objectives, the embodiments of the present invention provide the following technical solutions:

[0006] The first aspect of this invention discloses a method for carbon capture and peak shaving in a coal-to-gas dual-tower thermal storage system, the method comprising:

[0007] The purified boiler flue gas is fed into the first adsorption tower to adsorb carbon dioxide in the boiler flue gas, and the purified boiler flue gas is discharged from the first adsorption tower.

[0008] The circulating carbon dioxide is heated by the second heat exchanger and then fed into the second adsorption tower, causing the carbon dioxide adsorbed by the adsorbent in the second adsorption tower to desorb, and storing the heat input during the regeneration process in the second adsorption tower; the carbon dioxide output from the second adsorption tower is compressed and cooled, and a portion of the compressed and cooled carbon dioxide is returned to the second heat exchanger to form a carbon dioxide regeneration cycle;

[0009] Dual-source steam is obtained and input into the second heat exchanger to heat the circulating carbon dioxide; the input of the dual-source steam and the heat storage and release status of the first adsorption tower and the second adsorption tower are adjusted according to the supply and demand status of process steam in the plant area.

[0010] Adjust the heat storage and release status of the first and second adsorption towers and the compression load of the carbon dioxide regeneration cycle according to the electricity consumption period of the power grid.

[0011] After the first adsorption tower completes carbon dioxide adsorption and the second adsorption tower completes adsorbent regeneration, the operating conditions of the first adsorption tower and the second adsorption tower are switched so that the first adsorption tower and the second adsorption tower alternately perform carbon dioxide adsorption and adsorbent regeneration.

[0012] Optionally, adjusting the input of the dual-source steam and the heat storage and release states of the first and second adsorption towers according to the supply and demand status of process steam in the plant area includes:

[0013] Obtain the pressure of the plant's process steam pipeline network;

[0014] When the pressure is less than or equal to the preset lower pressure threshold, the supply and demand status of the process steam in the plant area is determined to be a state of insufficient supply.

[0015] When the pressure is greater than or equal to the preset pressure upper limit threshold, the supply and demand status of the process steam in the plant area is determined to be a state of surplus supply.

[0016] When the pressure is greater than the preset lower pressure threshold and less than the preset upper pressure threshold, the supply and demand status of the process steam in the plant area is determined to be a supply and demand balance state.

[0017] The input of the dual-source steam is adjusted according to the determined supply and demand status of the process steam in the plant area;

[0018] Based on the determined supply and demand status of process steam in the plant area, adjust the heat storage and release status of the first adsorption tower and the second adsorption tower.

[0019] Optionally, adjusting the input of the dual-source steam according to the determined supply and demand status of the process steam in the plant area includes:

[0020] The main steam of the power plant and the process steam of the plant area are respectively transported to the manifold through the corresponding steam branch, and the manifold is connected to the second heat exchanger;

[0021] Based on the determined supply and demand status of the process steam in the plant area, the corresponding steam branch is controlled to be turned on or off, so as to select the main steam of the power plant or the process steam of the plant area to be input into the second heat exchanger;

[0022] If the supply parameters of a single steam line do not meet the heating requirements of the second heat exchanger, then the two steam branches are controlled to be connected, so that the main steam of the power plant and the process steam of the plant area are mixed through the manifold and then input into the second heat exchanger.

[0023] Optionally, adjusting the heat storage and release states of the first adsorption tower and the second adsorption tower according to the determined supply and demand status of the process steam in the plant area includes:

[0024] When the supply and demand of process steam in the plant area is insufficient, the input of the dual-source steam is adjusted, and the adsorption tower that performs carbon dioxide adsorption is controlled to release heat. The released heat is used to heat the boiler feedwater, thereby reducing the demand for extraction steam and indirectly supplementing the process steam in the plant area.

[0025] When the supply and demand of process steam in the plant area is in a state of surplus, the surplus process steam is fed into the adsorption tower for adsorbent regeneration, and the heat of the process steam is stored in the adsorption tower.

[0026] Optionally, adjusting the heat storage and release states of the first and second adsorption towers and the compression load of the carbon dioxide regeneration cycle according to the electricity consumption period of the power grid includes:

[0027] Acquire power grid dispatch instructions and electricity price signals;

[0028] The power grid peak shaving condition is determined according to the power grid dispatching instruction and the electricity price signal. When the peak shaving conditions corresponding to the power grid dispatching instruction and the electricity price signal are inconsistent, the power grid peak shaving condition is determined according to the power grid dispatching instruction.

[0029] Based on the determined power grid peak-shaving conditions, adjust the heat storage and release states of the first and second adsorption towers, as well as the compression load of the carbon dioxide regeneration cycle.

[0030] Optionally, adjusting the heat storage and release states of the first and second adsorption towers and the compression load of the carbon dioxide regeneration cycle according to the determined power grid peak-shaving conditions includes:

[0031] When the power grid is in peak electricity consumption period, the heat storage and release state of the first adsorption tower and the second adsorption tower is adjusted so that the adsorption tower performing carbon dioxide adsorption releases the stored heat and uses the released heat to heat the boiler feedwater, and controls the compression process of the carbon dioxide regeneration cycle to operate at a load lower than full load.

[0032] When the power grid is in a low-demand period, the heat storage and release states of the first and second adsorption towers are adjusted so that the adsorption towers performing adsorbent regeneration store the heat input during the regeneration process, and the adsorbent regeneration process and the compression process of the carbon dioxide regeneration cycle are controlled to operate at full load.

[0033] Optional, also includes:

[0034] When the heat storage and release state determined based on the supply and demand status of the process steam in the plant area is inconsistent with the heat storage and release state determined based on the peak shaving status of the power grid, the heat storage and release state of the first adsorption tower and the second adsorption tower shall be determined based on the supply and demand status of the process steam in the plant area.

[0035] The input of the dual-source steam and the compression load of the carbon dioxide regeneration cycle are adjusted according to the determined heat storage and release state.

[0036] Optionally, the step of recirculating a portion of the compressed and cooled carbon dioxide back to the second heat exchanger includes:

[0037] The heat of compression generated during the compression and cooling process of the carbon dioxide output from the second adsorption tower is recovered.

[0038] The recovered heat of compression is used to preheat the refluxed carbon dioxide;

[0039] The preheated carbon dioxide is fed into the second heat exchanger, and the preheated carbon dioxide is heated using the dual-source steam.

[0040] The heated carbon dioxide is fed into the second adsorption tower for adsorbent regeneration.

[0041] Optionally, storing the heat input during the regeneration process in the second adsorption tower includes:

[0042] The circulating carbon dioxide, heated by the second heat exchanger, is fed into the second adsorption tower, allowing the circulating carbon dioxide to flow through the molecular sieve adsorbent inside the second adsorption tower.

[0043] The circulating carbon dioxide exchanges heat with the molecular sieve adsorbent, causing the carbon dioxide adsorbed by the molecular sieve adsorbent to desorb, and the heat carried by the circulating carbon dioxide is stored in the molecular sieve adsorbent.

[0044] The second aspect of this invention discloses a coal-to-gas dual-tower thermal storage carbon capture and peak-shaving device, the device comprising:

[0045] An adsorption unit is used to input the purified boiler flue gas into the first adsorption tower, adsorb carbon dioxide in the boiler flue gas, and discharge the purified boiler flue gas from the first adsorption tower.

[0046] The desorption unit is used to heat the circulating carbon dioxide in the second heat exchanger and then input it into the second adsorption tower, so that the carbon dioxide adsorbed by the adsorbent in the second adsorption tower is desorbed, and the heat input during the regeneration process is stored in the second adsorption tower; the carbon dioxide output from the second adsorption tower is compressed and cooled, and a portion of the compressed and cooled carbon dioxide is returned to the second heat exchanger to form a carbon dioxide regeneration cycle.

[0047] A heating unit is used to obtain dual-source steam and input it into the second heat exchanger to heat the circulating carbon dioxide; the input of the dual-source steam and the heat storage and release status of the first adsorption tower and the second adsorption tower are adjusted according to the supply and demand status of process steam in the plant area.

[0048] The regulating unit is used to adjust the heat storage and release status of the first adsorption tower and the second adsorption tower, as well as the compression load of the carbon dioxide regeneration cycle, according to the power consumption period of the power grid.

[0049] The switching unit is used to switch the operating conditions of the first adsorption tower and the second adsorption tower after the first adsorption tower has completed carbon dioxide adsorption and the second adsorption tower has completed adsorbent regeneration, so that the first adsorption tower and the second adsorption tower alternately perform carbon dioxide adsorption and adsorbent regeneration.

[0050] Based on the above embodiments of the present invention, a method and apparatus for carbon capture and peak shaving in coal gasification using a dual-tower thermal storage system is provided. The first and second adsorption towers alternately perform carbon dioxide adsorption and adsorbent regeneration, solving the problems of insufficient capture in a single tower, low adsorbent utilization, and unstable emissions caused by load fluctuations. The purified boiler flue gas is first adsorbed by the first adsorption tower, reducing the risk of adsorbent poisoning and deactivation due to heavy metals, hydrocarbons, and moisture. During regeneration, circulating carbon dioxide is heated by the second heat exchanger and then input into the second adsorption tower for desorption and heat storage. After compression and cooling, some carbon dioxide is returned to form a regeneration cycle, improving energy utilization efficiency. Dual-source steam is obtained and input into the second heat exchanger. The dual-source steam and the heat storage and release states of the two towers are adjusted according to the plant's process steam supply and demand, avoiding the crowding out of process steam and achieving peak shaving. The heat storage and release and carbon dioxide regeneration cycle compression load are adjusted according to the power grid's electricity consumption periods, achieving coordinated peak shaving between plant steam and the power grid, ensuring continuous and stable operation, and eliminating amine corrosion and saline wastewater. Attached Figure Description

[0051] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0052] Figure 1 This is a first structural schematic diagram of a system for implementing a coal-to-gas dual-tower thermal storage carbon capture and peak-shaving method, provided in an embodiment of the present invention.

[0053] Figure 2 This is a second structural schematic diagram of a system for implementing a coal-to-gas dual-tower thermal storage carbon capture and peak-shaving method, provided in an embodiment of the present invention.

[0054] Figure 3 A flowchart of a coal-to-gas dual-tower thermal storage carbon capture and peak-shaving method provided in an embodiment of the present invention;

[0055] Figure 4 This is a structural block diagram of a coal-to-gas dual-tower thermal storage carbon capture and peak-shaving device provided in an embodiment of the present invention. Detailed Implementation

[0056] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0057] In this application, the terms "comprising," "including," or any other variations thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0058] As can be seen from the background technology, existing carbon capture technologies for coal gasification have drawbacks such as poor capture, low adsorbent utilization, unstable emissions, steam consumption during regeneration that encroaches on process steam, difficulty in peak shaving while also considering plant steam, easy poisoning of adsorbents, and high cost of wastewater corrosion from the amine method.

[0059] Therefore, this invention provides a method and apparatus for carbon capture and peak shaving in coal gasification using a dual-tower thermal storage system. The system uses a first adsorption tower and a second adsorption tower to alternately adsorb carbon dioxide and regenerate the adsorbent, solving the problems of insufficient capture in a single tower, low adsorbent utilization, and unstable emissions due to load fluctuations. The purified boiler flue gas is first adsorbed in the first adsorption tower, reducing the risk of adsorbent poisoning and deactivation caused by heavy metals, hydrocarbons, and moisture. During regeneration, circulating carbon dioxide is heated by a second heat exchanger and then input into the second adsorption tower, causing carbon dioxide desorption and storing heat in the second adsorption tower. After compression and cooling, some carbon dioxide is returned to form a carbon dioxide regeneration cycle, improving energy utilization efficiency. Dual-source steam is input into the second heat exchanger, and the dual-source steam input and the heat storage and release status of the two towers are adjusted according to the plant's process steam supply and demand, avoiding regeneration from crowding out process steam and achieving steam peak shaving. Furthermore, the heat storage and release status and the carbon dioxide regeneration cycle compression load are adjusted according to the power grid's electricity consumption period, achieving coordinated peak shaving of plant steam and the power grid, ensuring continuous and stable operation, and eliminating the corrosion and saline wastewater associated with traditional amine methods.

[0060] See Figure 1 This diagram illustrates a first structural schematic of a system for implementing a coal-to-gas dual-tower thermal storage carbon capture and peak-shaving method, according to an embodiment of the present invention. (See also...) Figure 2 The diagram shows a second structural schematic of a system for implementing a coal-to-gas dual-tower thermal storage carbon capture and peak-shaving method, according to an embodiment of the present invention.

[0061] like Figure 1 and Figure 2 As shown, the system includes a boiler steam-water system, a flue gas purification unit, a first adsorption tower, a second adsorption tower, a first heat exchanger, a second heat exchanger, a first compressor, a second compressor, a first intercooler, and a second intercooler. The first and second adsorption towers are used to alternately perform carbon dioxide adsorption and adsorbent regeneration. The first heat exchanger is used to recover the heat carried by the boiler flue gas after adsorption and purification. The second heat exchanger is used to heat the circulating carbon dioxide entering the adsorption tower for adsorbent regeneration. The first compressor, the first intercooler, the second compressor, and the second intercooler constitute a carbon dioxide compression and cooling circuit.

[0062] like Figure 1 As shown, the boiler steam-water system includes a boiler and a steam turbine connected to the boiler. Specifically, the boiler includes a furnace, air distributor, and steam drum; the steam output side of the boiler is connected to the steam turbine, which includes a high-pressure cylinder, an intermediate-pressure cylinder, and a low-pressure cylinder arranged sequentially in the steam work path, and is connected to a generator. The boiler steam-water system also includes a high-pressure heater, a deaerator, a low-pressure heater, and a condensate pump to transport and heat the condensate and boiler feedwater returning to the boiler. The steam generated by the boiler is input into the steam turbine to perform work; the steam after the turbine performs work is condensed, heated by the feedwater, and deaerated before returning to the boiler, forming a boiler steam-water cycle.

[0063] The boiler's flue gas outlet is connected to the inlet of the flue gas purification unit. This unit performs denitrification, dust removal, desulfurization, pre-washing to remove heavy metals and hydrocarbons, two-stage deep dehydration, and cooling on the boiler flue gas to obtain purified flue gas. The outlet of the flue gas purification unit is connected to the flue gas inlets of the first and second adsorption towers, allowing the purified boiler flue gas to be selectively input into the adsorption towers performing carbon dioxide adsorption, depending on the operating conditions of the first and second adsorption towers.

[0064] It should be noted that, see Figure 2 The first and second adsorption towers are connected in parallel, both containing molecular sieve adsorbent. The molecular sieve adsorbent adsorbs carbon dioxide from the boiler flue gas and serves as the heat storage medium during the adsorption tower's heat storage process, eliminating the need for a separate external heat storage tank. Valves are installed on the flue gas pipelines corresponding to the first and second adsorption towers to switch the flue gas flow direction, allowing the first and second adsorption towers to switch between carbon dioxide adsorption and adsorbent regeneration modes.

[0065] In one embodiment, the two adsorption towers are equipped with eight programmable switching valves, which are interlocked by a control system to isolate the media flow paths of the adsorption tower performing carbon dioxide adsorption and the adsorption tower performing adsorbent regeneration. Upon reaching the set switching conditions, the control system changes the on or off state of each switching valve, allowing the first and second adsorption towers to switch operating conditions.

[0066] Specifically, when the first adsorption tower is performing carbon dioxide adsorption and the second adsorption tower is performing adsorbent regeneration, the switching valves corresponding to the flue gas inlet and outlet of the first adsorption tower are controlled to be open, while the switching valves corresponding to the regeneration medium inlet and carbon dioxide outlet of the first adsorption tower are controlled to be closed; simultaneously, the switching valves corresponding to the flue gas inlet and outlet of the second adsorption tower are controlled to be closed, while the switching valves corresponding to the regeneration medium inlet and carbon dioxide outlet of the second adsorption tower are controlled to be open. When switching operating conditions, each switching valve operates in the opposite open or closed state, so that the flue gas path and carbon dioxide regeneration path of the two towers are synchronously interchanged. Through the above interlocking switching, cross-flow between the purified boiler flue gas and circulating carbon dioxide under non-corresponding operating conditions can be avoided.

[0067] Understandably, during adsorbent regeneration, high-temperature circulating carbon dioxide flows through the molecular sieve adsorbent bed and transfers heat to the molecular sieve adsorbent, storing the heat in the bed as solid sensible heat. During carbon dioxide adsorption, the lower-temperature purified boiler flue gas flows through the heat-storage molecular sieve adsorbent bed, releasing the stored sensible heat to the boiler flue gas. This, along with the adsorption heat generated by the physical adsorption of carbon dioxide, raises the temperature of the purified boiler flue gas.

[0068] The flue gas outlets of the first and second adsorption towers are connected to the first heat exchanger. When the first adsorption tower performs carbon dioxide adsorption, the purified boiler flue gas enters the first adsorption tower, adsorbs carbon dioxide through the molecular sieve adsorbent, and then exits from the first adsorption tower and enters the first heat exchanger. When the second adsorption tower switches to carbon dioxide adsorption mode, the purified boiler flue gas enters the second adsorption tower and, after completing carbon dioxide adsorption, enters the first heat exchanger. The first heat exchanger is the heat exchange node between the flue gas and the boiler feedwater. The hot-side medium is the adsorbed and purified boiler flue gas, and the hot-side inlet is connected to the flue gas outlet of the adsorption tower performing carbon dioxide adsorption, while the hot-side outlet is connected to the flue gas emission path. The cold-side medium is the boiler feedwater, and the cold-side inlet and outlet are connected to the boiler feedwater pipeline. The adsorbed and purified boiler flue gas releases heat to the boiler feedwater in the first heat exchanger. The boiler flue gas after heat exchange is discharged through the flue gas emission path, and the boiler feedwater, after absorbing the heat from the flue gas, enters the boiler steam-water system.

[0069] Thus, when the adsorption tower releases heat, a heat release path is formed: "molecular sieve adsorbent bed, adsorbed and purified boiler flue gas, first heat exchanger, and boiler feedwater". After absorbing heat, the boiler feedwater participates in the boiler steam-water cycle, which can reduce the steam extraction demand of the steam turbine generator set for feedwater heating; when the process steam supply in the plant area is insufficient, this heat can also be used to supplement the process steam in the plant area, thereby realizing the coupling of heat storage in the adsorption tower and peak steam regulation in the plant area.

[0070] Furthermore, the sensible heat released from the molecular sieve adsorbent bed and the adsorption heat generated during the physical adsorption of carbon dioxide are jointly transferred to the boiler flue gas flowing through the adsorption tower, raising the temperature of the purified boiler flue gas. The heated boiler flue gas then transfers heat to the boiler feedwater in the first heat exchanger. The boiler feedwater absorbs heat and enters the boiler steam-water system to form steam. The formed steam can participate in the steam cycle of the turbine generator set, or be used to supplement the plant's process steam supply when it is insufficient, thus forming a complete heat release path of "molecular sieve adsorbent bed, boiler flue gas, first heat exchanger, boiler feedwater, and steam".

[0071] like Figure 2As shown, the first and second adsorption towers are also connected to carbon dioxide regeneration pipelines. A second heat exchanger is installed on the carbon dioxide regeneration pipeline. The carbon dioxide outlet of the second heat exchanger is connected to the first and second adsorption towers through corresponding pipelines and valves, allowing the circulating carbon dioxide heated by the second heat exchanger to be input into the adsorption towers performing adsorbent regeneration according to the operating conditions of the two adsorption towers. When the second adsorption tower is performing adsorbent regeneration, the circulating carbon dioxide heated by the second heat exchanger is input into the second adsorption tower to exchange heat with the molecular sieve adsorbent in the second adsorption tower, causing the carbon dioxide adsorbed by the molecular sieve adsorbent to desorb, and at the same time, the heat carried by the circulating carbon dioxide is transferred and stored in the second adsorption tower. When the first adsorption tower switches to adsorbent regeneration mode, the circulating carbon dioxide is input into the first adsorption tower through the corresponding pipeline to perform the corresponding adsorbent regeneration and heat storage process.

[0072] The second heat exchanger is also connected to a dual-source steam pipeline, which includes main steam from the power plant side and process steam from the plant area side. The two steam sources are connected to the steam side of the second heat exchanger via corresponding steam pipelines, enabling the dual-source steam to exchange heat with the circulating carbon dioxide flowing through the second heat exchanger. The recycled carbon dioxide after heat exchange is transported from the carbon dioxide outlet of the second heat exchanger to the adsorption tower for adsorbent regeneration; the condensate formed after the steam completes the heat exchange is returned to the boiler steam-water system via a return water pipeline. Thus, the second heat exchanger constitutes the heat exchange node between the dual-source steam and the carbon dioxide regeneration cycle.

[0073] Specifically, the steam branch corresponding to the main steam of the power plant can be equipped with a main steam regulating valve and a main steam isolation valve, and the steam branch corresponding to the process steam of the plant area can be equipped with a process steam regulating valve and a process steam isolation valve. All of these valves are connected to the control system. The system primarily operates by selecting either the main steam of the power plant or the process steam of the plant area as the heat source for the second heat exchanger. When the supply parameters of a single steam branch cannot meet the heating requirements of the second heat exchanger, both steam branches are simultaneously activated, allowing the two steam branches to be mixed in a controlled manner within the main header before being input into the second heat exchanger. The condensate formed after heat exchange in the second heat exchanger is returned to the boiler steam-water system via the condensate return pipeline.

[0074] When the supply and demand of process steam in the plant area are balanced, the main steam of the power plant can be selected to be input into the second heat exchanger according to the regeneration heating demand. When the supply of process steam in the plant area is surplus, the process steam of the plant area can be selected to be input into the second heat exchanger to absorb the surplus process steam. When the supply parameters of a single steam line cannot meet the heating demand of the second heat exchanger, the two steam branches can be controlled to be connected so that the main steam of the power plant and the process steam of the plant area are mixed through the manifold and then input into the second heat exchanger.

[0075] The carbon dioxide outlets of the first and second adsorption towers are connected to a carbon dioxide compression and cooling circuit. Taking the second adsorption tower as an example of adsorbent regeneration, the carbon dioxide output from the second adsorption tower flows sequentially through the first compressor, the first intercooler, the second compressor, and the second intercooler along the carbon dioxide compression and cooling circuit. The first compressor performs primary compression on the carbon dioxide output from the second adsorption tower, and the first intercooler is located between the first and second compressors to cool the carbon dioxide after primary compression. The second compressor performs secondary compression on the carbon dioxide after primary cooling, and the second intercooler is located downstream of the second compressor to cool the carbon dioxide after secondary compression.

[0076] Combination Figure 2 As shown in the return pipeline, the compressed and cooled carbon dioxide is split into two streams. Part of the carbon dioxide is output along the carbon dioxide output pipeline, and the rest is returned to the second heat exchanger along the return pipeline. The carbon dioxide returning to the second heat exchanger is used as circulating carbon dioxide. After being reheated in the second heat exchanger, it is sent to the adsorption tower for adsorbent regeneration. This forms a carbon dioxide regeneration cycle consisting of the second heat exchanger, the adsorption tower for adsorbent regeneration, the carbon dioxide compression and cooling circuit, and the carbon dioxide return pipeline.

[0077] In one application, the carbon dioxide output along the carbon dioxide output pipeline can be further processed into liquid carbon dioxide, part of which is transported for underground storage, and the other part is transported to downstream processes in the plant for use as a chemical raw material.

[0078] The first and second intercoolers form a heat recovery node in the carbon dioxide compression process. The heat generated during carbon dioxide compression is recovered by the cooling medium and sent to the second heat exchanger for utilization, allowing the heat generated during compression to participate in the heating process of the circulating carbon dioxide. Thus, before entering the adsorption tower where adsorbent regeneration is performed, the circulating carbon dioxide can be heated using the recovered heat of compression and the steam heat input to the second heat exchanger, thereby forming a heat utilization path that couples heat recovery of compression with adsorbent regeneration.

[0079] Furthermore, the system can utilize heat in a tiered manner, utilizing compression heat, waste heat from adsorption-purified boiler flue gas, surplus process steam heat from the plant area, and supplementary heat from the power plant's main steam. By prioritizing the use of compression heat, waste heat from boiler flue gas, and surplus process steam heat from the plant area, the demand for main steam from the power plant can be reduced. In one application example, the consumption of high-quality main steam can be reduced by more than 35%, and the overall system energy efficiency can be improved by 20%.

[0080] The aforementioned heat utilization can form a four-stage tiered heat utilization relationship: the first stage recovers the heat of compression generated during carbon dioxide compression and cooling, used to preheat the reflux carbon dioxide; the second stage recovers the heat carried by the adsorbent-purified boiler flue gas, used to heat the boiler feedwater; the third stage, when there is a surplus of process steam in the plant area, utilizes the surplus process steam to regenerate the adsorbent and stores the heat in the adsorption tower; the fourth stage, when the aforementioned heat cannot meet the heating demand for adsorbent regeneration, utilizes the main steam of the power plant as a supplementary heat source. By utilizing heat in this tiered manner, the consumption of high-quality main steam can be reduced.

[0081] Switching valves are installed on the flue gas pipelines, carbon dioxide regeneration pipelines, and steam pipelines corresponding to the first and second adsorption towers, respectively, and the flow path of the corresponding media is changed by switching the valves.

[0082] While the first adsorption tower is performing carbon dioxide adsorption, the second adsorption tower is performing adsorbent regeneration. After both the first and second adsorption towers have completed their adsorbent regeneration, the corresponding pipelines are switched so that the second adsorption tower receives the purified boiler flue gas and performs carbon dioxide adsorption, while simultaneously, recirculated carbon dioxide heated by the second heat exchanger is input into the first adsorption tower to perform adsorbent regeneration. Thereafter, the two adsorption towers cycle and switch according to their respective operating conditions, thus forming a continuous carbon dioxide adsorption and adsorbent regeneration process, eliminating the need to stop carbon dioxide capture from the boiler flue gas during adsorbent regeneration.

[0083] Furthermore, the operating status of the dual-source steam pipeline, the heat storage and release processes of the first and second adsorption towers, and the carbon dioxide compression and cooling circuit can be coordinated and regulated. When the supply and demand of process steam in the plant area changes, peak shaving of process steam in the plant area is achieved by adjusting the dual-source steam input and the heat storage and release status of the first and second adsorption towers; when the power grid is in different power consumption periods, peak shaving of the power grid is achieved by adjusting the heat storage and release status of the first and second adsorption towers and the operating load of the carbon dioxide compression and cooling circuit. Specific process steam peak shaving control and power grid peak shaving control will be described separately in subsequent method embodiments.

[0084] See Figure 3 The diagram illustrates a flowchart of a coal-to-gas dual-tower thermal storage carbon capture and peak-shaving method provided by an embodiment of the present invention. The method includes:

[0085] Step S301: The purified boiler flue gas is fed into the first adsorption tower to adsorb carbon dioxide in the boiler flue gas, and the purified boiler flue gas is discharged from the first adsorption tower.

[0086] It should be noted that the purified boiler flue gas refers to the boiler flue gas obtained after undergoing denitrification, dust removal, desulfurization, pre-washing to remove heavy metals and hydrocarbons, two-stage deep dehydration, and cooling in a flue gas purification unit. Through the above purification process, the impact of heavy metals, hydrocarbons, and moisture on the molecular sieve adsorbent can be reduced.

[0087] During the carbon dioxide adsorption process, the purified boiler flue gas flows through the molecular sieve adsorbent in the first adsorption tower. The carbon dioxide is adsorbed by the molecular sieve adsorbent, and the purified boiler flue gas is discharged from the first adsorption tower and enters the first heat exchanger. The first heat exchanger uses the heat carried by the purified boiler flue gas to heat the boiler feedwater.

[0088] For example, when the first adsorption tower is in carbon dioxide adsorption mode, the flue gas path corresponding to the first adsorption tower is opened and the carbon dioxide regeneration path corresponding to the first adsorption tower is closed, so as to isolate the carbon dioxide adsorption path from the adsorbent regeneration path.

[0089] In the specific implementation step S301, the purified boiler flue gas is input into the first adsorption tower currently performing carbon dioxide adsorption. The molecular sieve adsorbent in the first adsorption tower adsorbs the carbon dioxide in the boiler flue gas, and the purified boiler flue gas is then transported to the first heat exchanger through the flue gas outlet.

[0090] It is understandable that removing heavy metals, hydrocarbons, and moisture before they enter the first or second adsorption tower can reduce the likelihood of impurities occupying adsorption sites on the molecular sieve adsorbent or causing performance degradation.

[0091] It should be noted that the two-stage deep dehydration includes primary and secondary deep dehydration. Primary deep dehydration utilizes a flue gas cooler and a steam-water separator. The pre-washed boiler flue gas enters the flue gas cooler, where cooling causes water vapor in the flue gas to condense and precipitate. The steam-water separator then separates and discharges the condensate, thus removing most of the condensable water. Secondary deep dehydration employs a molecular sieve adsorption dehydration tower. The boiler flue gas after primary deep dehydration enters the molecular sieve adsorption dehydration tower, where residual gaseous water vapor is removed by molecular sieve adsorption. After the molecular sieve adsorption dehydration tower becomes saturated, the tower is switched for heating and regeneration to maintain continuous deep drying.

[0092] Understandably, removing most of the moisture through condensation followed by deep dehydration via molecular sieve adsorption can reduce the processing load and regeneration energy consumption of the molecular sieve adsorption dehydration tower. In one optional embodiment, the volumetric water content of the boiler flue gas after two-stage deep dehydration treatment is no higher than 500 ppm, and the flue gas dew point is no higher than -40°C, to meet the operational requirements of the subsequent molecular sieve adsorbent.

[0093] Step S302: The circulating carbon dioxide is heated by the second heat exchanger and then fed into the second adsorption tower, so that the carbon dioxide adsorbed by the adsorbent in the second adsorption tower is desorbed, and the heat input during the regeneration process is stored in the second adsorption tower; the carbon dioxide output from the second adsorption tower is compressed and cooled, and part of the compressed and cooled carbon dioxide is returned to the second heat exchanger to form a carbon dioxide regeneration cycle.

[0094] It should be noted that recycled carbon dioxide refers to the portion of carbon dioxide output from the second adsorption tower that, after compression and cooling, returns to the second heat exchanger via the reflux pipeline and is used again for adsorbent regeneration.

[0095] During the adsorbent regeneration process, the circulating carbon dioxide, heated by the second heat exchanger, flows through the molecular sieve adsorbent in the second adsorption tower and exchanges heat, causing the carbon dioxide adsorbed by the molecular sieve adsorbent to desorb, while storing the heat carried by the circulating carbon dioxide in the molecular sieve adsorbent.

[0096] The carbon dioxide output from the second adsorption tower is compressed and cooled sequentially through the first compressor, the first intercooler, the second compressor, and the second intercooler. The heat of compression generated during the compression and cooling process is recovered to preheat the reflux carbon dioxide. The preheated carbon dioxide then enters the second heat exchanger for further heating using dual-source steam.

[0097] For example, when the second adsorption tower is in the adsorbent regeneration mode, the circulating carbon dioxide output from the second heat exchanger is input into the second adsorption tower; the carbon dioxide output from the second adsorption tower is partially output and partially returned to the second heat exchanger after compression and cooling, thus forming a carbon dioxide regeneration cycle.

[0098] It should be noted that the heat input during the regeneration process is stored in the second adsorption tower. Specifically, the circulating carbon dioxide, heated by the second heat exchanger, is input into the second adsorption tower, allowing the circulating carbon dioxide to flow through the molecular sieve adsorbent inside the second adsorption tower. Through heat exchange between the circulating carbon dioxide and the molecular sieve adsorbent, the carbon dioxide adsorbed by the molecular sieve adsorbent is desorbed, and the heat carried by the circulating carbon dioxide is stored in the molecular sieve adsorbent.

[0099] Understandably, some of the compressed and cooled carbon dioxide is returned to the second heat exchanger. Specifically, this recovers the heat of compression generated during the compression and cooling process of the carbon dioxide output from the second adsorption tower. The recovered heat of compression is used to preheat the returned carbon dioxide. The preheated carbon dioxide is then input into the second heat exchanger and heated using dual-source steam. Finally, the heated carbon dioxide is input into the second adsorption tower for adsorbent regeneration.

[0100] It should be noted that the carbon dioxide output from the second adsorption tower is compressed and cooled sequentially by the first compressor, the first intercooler, the second compressor, and the second intercooler. Part of the carbon dioxide is output, and part of the carbon dioxide is recycled to form circulating carbon dioxide.

[0101] Step S303: Obtain dual-source steam and input it into the second heat exchanger to heat the circulating carbon dioxide; adjust the input of dual-source steam and the heat storage and release status of the first and second adsorption towers according to the supply and demand status of process steam in the plant area.

[0102] It should be noted that the dual-source steam includes the main steam from the power plant and the process steam from the plant area. The main steam from the power plant and the process steam from the plant area are respectively delivered to the manifold through corresponding steam branches, and the manifold is connected to the second heat exchanger.

[0103] The supply and demand status of process steam in the plant area includes insufficient supply, surplus supply, and supply and demand balance. It can be determined by the relationship between the pressure of the process steam pipeline network in the plant area and the preset lower pressure threshold and the preset upper pressure threshold.

[0104] When the process steam supply in the plant area is insufficient, the input of dual-source steam is adjusted and the adsorption tower that performs carbon dioxide adsorption is controlled to release heat; when the process steam supply in the plant area is abundant, the abundant process steam in the plant area is used to regenerate the adsorbent and the heat is stored in the adsorption tower that performs adsorbent regeneration.

[0105] For example, when the supply parameters of a single steam line do not meet the heating requirements of the second heat exchanger, the two steam branches are controlled to be connected so that the main steam of the power plant and the process steam of the plant area are mixed through the manifold and then input into the second heat exchanger.

[0106] In the specific implementation step S303, the pressure of the plant's process steam pipeline network is obtained, and this pressure is compared with a preset lower pressure threshold and a preset upper pressure threshold to determine whether the supply is insufficient, excessive, or balanced. Based on the determined supply and demand status of the plant's process steam, the corresponding steam branches of the power plant's main steam and the plant's process steam are controlled to be opened or closed, and the heat storage and release status of the first and second adsorption towers is adjusted.

[0107] It should be noted that the specific implementation process of adjusting the input of dual-source steam and the heat storage and release status of the first and second adsorption towers according to the supply and demand status of process steam in the plant area is as follows (process A1 to process A):

[0108] Process A1: Obtain the pressure of the process steam pipeline network in the plant area.

[0109] In practical applications, the pressure of the plant's process steam pipeline network is compared with the preset upper pressure threshold and the preset lower pressure threshold, and the flow rate of the plant's process steam pipeline network is used as an auxiliary verification parameter.

[0110] It should be noted that the preset lower pressure threshold and the preset upper pressure threshold can be preset according to the design pressure and allowable fluctuation range of the process steam pipeline network in the coal gasification production unit. By setting two pressure thresholds, the supply and demand of process steam in the plant area can be prevented from frequently switching near the critical pressure, thereby improving the stability of dual-source steam regulation and adsorption tower heat storage and release regulation.

[0111] Process A2: When the pressure is less than or equal to the preset lower pressure threshold, the supply and demand status of process steam in the plant area is determined to be a state of insufficient supply.

[0112] Process A3: When the pressure is greater than or equal to the preset upper limit threshold, the supply and demand status of process steam in the plant area is determined to be a state of surplus supply.

[0113] Process A4: When the pressure is greater than the preset lower pressure threshold and less than the preset upper pressure threshold, the supply and demand status of process steam in the plant area is determined to be in a supply and demand balance state.

[0114] Process A5: Adjust the input of dual-source steam according to the determined supply and demand status of process steam in the plant area.

[0115] In the specific implementation process A5, the main steam of the power plant and the process steam of the plant area are respectively transported to the manifold through the corresponding steam branches, and the manifold is connected to the second heat exchanger. According to the determined supply and demand status of the process steam in the plant area, the corresponding steam branches are controlled to open or close, so as to select the main steam of the power plant or the process steam of the plant area to be input into the second heat exchanger. If the supply parameters of a single steam branch do not meet the heating requirements of the second heat exchanger, the two steam branches are controlled to open, so that the main steam of the power plant and the process steam of the plant area are mixed through the manifold and then input into the second heat exchanger.

[0116] Process A6: Adjust the heat storage and release status of the first and second adsorption towers according to the determined supply and demand status of process steam in the plant area.

[0117] In the specific implementation process A6, when the supply and demand of process steam in the plant area is insufficient, the input of dual-source steam is adjusted, and the adsorption tower performing carbon dioxide adsorption is controlled to release heat. The released heat is used to heat the boiler feedwater, thereby reducing the demand for extraction steam and indirectly supplementing the process steam in the plant area. When the supply and demand of process steam in the plant area is excessive, the excess process steam in the plant area is input into the adsorption tower performing adsorbent regeneration, and the heat of the process steam in the plant area is stored in the adsorption tower.

[0118] Step S304: Adjust the heat storage and release status of the first and second adsorption towers and the compression load of the carbon dioxide regeneration cycle according to the power consumption period of the power grid.

[0119] It should be noted that the power grid peak shaving condition is determined based on the power grid dispatch instructions and the electricity price signal; when the power grid peak shaving conditions corresponding to the two are inconsistent, the power grid peak shaving condition is determined based on the power grid dispatch instructions.

[0120] When the power grid is in peak electricity consumption period, the adsorption tower that performs carbon dioxide adsorption releases the stored heat and uses the released heat to heat the boiler feedwater, while the compression process of the carbon dioxide regeneration cycle operates at a load lower than full load.

[0121] When the power grid is in a low-demand period, the adsorption tower that performs adsorbent regeneration stores the heat input during the regeneration process, and the compression process of the adsorbent regeneration process and the carbon dioxide regeneration cycle operates at full load.

[0122] For example, when the supply and demand of process steam in the plant area is inconsistent with the heat storage and release status determined by the power grid peak shaving conditions, the heat storage and release status of the first adsorption tower and the second adsorption tower are determined according to the supply and demand of process steam in the plant area, and then the input of dual-source steam and the compression load of carbon dioxide regeneration cycle are adjusted.

[0123] In the specific implementation of step S304, the grid dispatching command and electricity price signal are obtained; the grid peak shaving condition is determined according to the grid dispatching command and electricity price signal, and when the peak shaving conditions corresponding to the grid dispatching command and electricity price signal are inconsistent, the grid peak shaving condition is determined according to the grid dispatching command; according to the determined grid peak shaving condition, the heat storage and release state of the first adsorption tower and the second adsorption tower and the compression load of the carbon dioxide regeneration cycle are adjusted.

[0124] It is understandable that when the peak-shaving conditions corresponding to the power grid dispatching instructions and the electricity price signals are consistent, the system will operate according to the corresponding peak or off-peak electricity conditions.

[0125] It should be noted that when the power grid is in peak electricity consumption period, the heat storage and release state of the first and second adsorption towers is adjusted so that the adsorption towers performing carbon dioxide adsorption release the stored heat and use the released heat to heat the boiler feedwater, thereby reducing the steam extraction demand of the steam turbine generator set; the compression process of the carbon dioxide regeneration cycle is controlled to operate at a load lower than full load, reducing the power load of the first and second compressors, thereby reducing the plant's power consumption.

[0126] When the power grid is in a low-demand period, the heat storage and release state of the first and second adsorption towers is adjusted so that the adsorption towers performing adsorbent regeneration store the heat input during the regeneration process, and the compression process of the adsorbent regeneration process and the carbon dioxide regeneration cycle are controlled to operate at full load, so as to complete adsorbent regeneration, carbon dioxide compression and adsorption tower heat storage during the low-demand period.

[0127] In some specific embodiments, the heat storage and release states of the first and second adsorption towers are determined based on the supply and demand of process steam in the plant area, and also based on the peak-shaving conditions of the power grid. When the heat storage and release states determined based on the supply and demand of process steam in the plant area differ from those determined based on the peak-shaving conditions of the power grid, the heat storage and release states of the first and second adsorption towers are determined based on the supply and demand of process steam in the plant area. The input of dual-source steam and the compression load of the carbon dioxide regeneration cycle are adjusted according to the determined heat storage and release states. Thus, when there is a conflict between the peak-shaving demand of process steam in the plant area and the peak-shaving demand of the power grid, priority is given to maintaining the stability of the process steam pipeline network in the plant area, and then participation in power grid peak-shaving is carried out under the condition of meeting the process steam demand in the plant area.

[0128] Step S305: After the first adsorption tower completes carbon dioxide adsorption and the second adsorption tower completes adsorbent regeneration, switch the operating conditions of the first adsorption tower and the second adsorption tower so that the first adsorption tower and the second adsorption tower alternately perform carbon dioxide adsorption and adsorbent regeneration.

[0129] It is understandable that the switching of operating conditions refers to changing the state of the switching valves on the flue gas pipeline and carbon dioxide regeneration pipeline corresponding to the first adsorption tower and the second adsorption tower, so that the adsorption tower that was originally performing carbon dioxide adsorption is switched to performing adsorbent regeneration, and the adsorption tower that was originally performing adsorbent regeneration is switched to performing carbon dioxide adsorption.

[0130] During the switching process, the flue gas paths and carbon dioxide regeneration paths of the two adsorption towers are synchronously interchanged, so that the purified boiler flue gas is input into the adsorption tower currently performing carbon dioxide adsorption, and the circulating carbon dioxide heated by the second heat exchanger is input into the adsorption tower currently performing adsorbent regeneration.

[0131] For example, after the first adsorption tower completes carbon dioxide adsorption and the second adsorption tower completes adsorbent regeneration, the flue gas path corresponding to the first adsorption tower is closed and the carbon dioxide regeneration path corresponding to the first adsorption tower is opened. At the same time, the flue gas path corresponding to the second adsorption tower is opened and the carbon dioxide regeneration path corresponding to the second adsorption tower is closed, so that the two towers switch operating conditions.

[0132] In the specific implementation of step S305, the control system changes the state of the switching valves on the corresponding pipelines of the first and second adsorption towers, so that the second adsorption tower receives the purified boiler flue gas and performs carbon dioxide adsorption, while the circulating carbon dioxide heated by the second heat exchanger is input into the first adsorption tower to perform adsorbent regeneration. The first and second adsorption towers alternate operating conditions in a cycle to maintain continuous carbon dioxide adsorption and adsorbent regeneration.

[0133] In some specific embodiments, safety interlocks are also provided. When the pressure of the process steam pipeline network in the plant area is abnormal, the bed temperature of the first adsorption tower or the second adsorption tower exceeds the allowable range, or the temperature or flow rate of the carbon dioxide regeneration cycle is abnormal, the control system can adjust or cut off the corresponding steam branch and medium pipeline to protect the adsorption tower, heat exchanger and carbon dioxide compression cooling circuit.

[0134] The triggering parameters for the safety interlock may include at least the pressure of the process steam pipeline network in the plant area and the bed temperature of the first adsorption tower and the second adsorption tower. When the corresponding parameters exceed the preset allowable range, the control system outputs a protection control command, causing the corresponding regulating valve or isolation valve to reduce its opening or shut down.

[0135] In this embodiment of the invention, carbon dioxide adsorption and adsorbent regeneration are performed alternately by the first and second adsorption towers, thereby improving the continuity of carbon dioxide capture and the utilization rate of the molecular sieve adsorbent. Flue gas purification reduces the risk of adsorbent deactivation caused by heavy metals, hydrocarbons, and moisture. The compression heat is recovered through carbon dioxide regeneration and the dual-source steam and the heat storage and release states of the two towers are adjusted according to the supply and demand of process steam in the plant area, thereby reducing the occupation of process steam during the regeneration process. The heat storage and release states of the two towers and the compression load are adjusted according to the power grid's electricity consumption period, thereby achieving coordinated peak shaving of process steam in the plant area and the power grid, thus improving the system's continuous operation capability and energy utilization efficiency.

[0136] In one application example, the method proposed in this invention is applied to a self-owned power plant in a coal-to-natural gas project. The original boiler steam-water system is retained, and a flue gas purification unit, a first adsorption tower, a second adsorption tower, a first heat exchanger, a second heat exchanger, and a carbon dioxide compression and cooling circuit are configured. Simultaneously, the main steam of the power plant and the process steam of the plant area are connected. After purification, the boiler flue gas enters the adsorption tower where carbon dioxide adsorption is performed. The purified boiler flue gas is discharged after heat recovery through the first heat exchanger. The adsorption tower where the adsorbent is regenerated receives the circulating carbon dioxide heated by the second heat exchanger. The desorbed carbon dioxide is compressed and cooled, with part output and part recycled.

[0137] For example, a self-owned power plant that can be applied to a coal-to-natural gas project with an annual output of 2 billion cubic meters can be configured with a flue gas purification treatment unit, a first adsorption tower and a second adsorption tower, a first heat exchanger and a second heat exchanger, and a carbon dioxide compression cooling circuit including a first compressor, a first intercooler, a second compressor and a second intercooler, while retaining the original boiler steam and water system.

[0138] In this application example, when changes in coal gasification production load lead to insufficient process steam supply in the plant area, the system reduces the use of dual-source steam by the adsorbent regeneration process and uses the heat released by the adsorption tower to supplement the process steam in the plant area; when the process steam supply in the plant area is abundant, the system uses the abundant process steam to heat the circulating carbon dioxide and stores the heat in the adsorption tower that performs adsorbent regeneration; when the power grid is in peak electricity demand, the system uses the adsorption tower to release heat and reduces the compression load; when the power grid is in off-peak electricity demand, the system increases the operating load of the adsorbent regeneration process and the carbon dioxide compression process and completes heat storage.

[0139] Under specific application conditions, when the flue gas load fluctuates within the range of 30% to 110%, the first and second adsorption towers maintain continuous carbon capture by alternating operation; the carbon dioxide capture rate of the system can be no less than 95%, the regeneration steam consumption can be reduced by 35%, and the operating cost can be reduced by about 45% compared with the traditional amine method. The above values ​​are used to illustrate the operating effect of one application example and do not constitute a limitation on the scope of protection of this invention.

[0140] In another application performance demonstration, the alternating operation of the dual towers can improve the utilization rate of the molecular sieve adsorbent and maintain continuous switching between carbon dioxide adsorption and adsorbent regeneration when the boiler flue gas load changes. The flue gas purification unit can reduce the poisoning and deactivation of molecular sieve adsorbents and extend the replacement cycle by removing heavy metals, hydrocarbons, and moisture; the use of molecular sieve adsorbents for physical adsorption eliminates the need for alkanolamine chemical absorbents, reducing operational problems caused by chemical absorbent corrosion and saline wastewater.

[0141] Corresponding to the coal-to-gas dual-tower thermal storage carbon capture and peak-shaving method provided in the above embodiments of the present invention, see also... Figure 4 The diagram shows a structural block diagram of a coal-to-gas dual-tower thermal storage carbon capture and peak-shaving device provided in an embodiment of the present invention.

[0142] The device includes: an adsorption unit 401, a desorption unit 402, a heating unit 403, an adjustment unit 404, and a switching unit 405.

[0143] The adsorption unit 401 is used to input the purified boiler flue gas into the first adsorption tower, adsorb carbon dioxide in the boiler flue gas, and discharge the adsorbed and purified boiler flue gas from the first adsorption tower.

[0144] The desorption unit 402 is used to heat the circulating carbon dioxide in the second heat exchanger and then input it into the second adsorption tower, so that the carbon dioxide adsorbed by the adsorbent in the second adsorption tower is desorbed, and the heat input during the regeneration process is stored in the second adsorption tower; the carbon dioxide output from the second adsorption tower is compressed and cooled, and part of the compressed and cooled carbon dioxide is returned to the second heat exchanger to form a carbon dioxide regeneration cycle.

[0145] Heating unit 403 is used to obtain dual-source steam and input it into the second heat exchanger to heat the circulating carbon dioxide; it adjusts the input of dual-source steam and the heat storage and release status of the first adsorption tower and the second adsorption tower according to the supply and demand status of process steam in the plant area.

[0146] The regulating unit 404 is used to adjust the heat storage and release status of the first adsorption tower and the second adsorption tower, as well as the compression load of the carbon dioxide regeneration cycle, according to the power consumption period of the power grid.

[0147] The switching unit 405 is used to switch the operating conditions of the first adsorption tower and the second adsorption tower after the first adsorption tower has completed carbon dioxide adsorption and the second adsorption tower has completed adsorbent regeneration, so that the first adsorption tower and the second adsorption tower alternately perform carbon dioxide adsorption and adsorbent regeneration.

[0148] In this embodiment of the invention, carbon dioxide adsorption and adsorbent regeneration are performed by an adsorption unit and a desorption unit, respectively. The operating conditions of the first adsorption tower and the second adsorption tower are switched by a switching unit to achieve alternating operation, thereby improving the continuity of carbon dioxide capture and the utilization rate of the adsorbent. A carbon dioxide regeneration cycle is formed by the desorption unit, and the input of dual-source steam and the heat storage and release state are adjusted by the heating unit according to the supply and demand of process steam in the plant area, thereby reducing the impact of adsorbent regeneration on process steam. The heat storage and release state and compression load are adjusted by the regulating unit 404 according to the power consumption period of the power grid, thereby achieving coordinated peak shaving of process steam in the plant area and the power grid, thereby improving the operational stability and energy utilization efficiency of the system.

[0149] exist Figure 4 Based on the device shown, the device provided in this embodiment of the invention can be further extended to include multiple units. The functions of each unit can be found in the descriptions of the various embodiments of the coal gasification dual-tower thermal storage carbon capture and peak shaving method provided above, and will not be further illustrated here.

[0150] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, for system or system embodiments, since they are basically similar to method embodiments, the description is relatively simple, and relevant parts can be referred to the descriptions in the method embodiments. The systems and system embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without creative effort.

[0151] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0152] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for carbon capture and peak shaving in a dual-tower thermal storage system for coal gasification, characterized in that, The method includes: The purified boiler flue gas is fed into the first adsorption tower to adsorb carbon dioxide in the boiler flue gas, and the purified boiler flue gas is discharged from the first adsorption tower. The circulating carbon dioxide is heated by the second heat exchanger and then fed into the second adsorption tower, causing the carbon dioxide adsorbed by the adsorbent in the second adsorption tower to desorb, and storing the heat input during the regeneration process in the second adsorption tower; the carbon dioxide output from the second adsorption tower is compressed and cooled, and a portion of the compressed and cooled carbon dioxide is returned to the second heat exchanger to form a carbon dioxide regeneration cycle; Dual-source steam is obtained and input into the second heat exchanger to heat the circulating carbon dioxide; the input of the dual-source steam and the heat storage and release status of the first adsorption tower and the second adsorption tower are adjusted according to the supply and demand status of process steam in the plant area. Adjust the heat storage and release status of the first and second adsorption towers and the compression load of the carbon dioxide regeneration cycle according to the power consumption period of the power grid. After the first adsorption tower completes carbon dioxide adsorption and the second adsorption tower completes adsorbent regeneration, the operating conditions of the first adsorption tower and the second adsorption tower are switched so that the first adsorption tower and the second adsorption tower alternately perform carbon dioxide adsorption and adsorbent regeneration.

2. The method according to claim 1, characterized in that, The adjustment of the dual-source steam input and the heat storage and release states of the first and second adsorption towers according to the supply and demand status of process steam in the plant area includes: Obtain the pressure of the plant's process steam pipeline network; When the pressure is less than or equal to the preset lower pressure threshold, the supply and demand status of the process steam in the plant area is determined to be a state of insufficient supply. When the pressure is greater than or equal to the preset pressure upper limit threshold, the supply and demand status of the process steam in the plant area is determined to be a state of surplus supply. When the pressure is greater than the preset lower pressure threshold and less than the preset upper pressure threshold, the supply and demand status of the process steam in the plant area is determined to be a supply and demand balance state. The input of the dual-source steam is adjusted according to the determined supply and demand status of the process steam in the plant area; Based on the determined supply and demand status of process steam in the plant area, adjust the heat storage and release status of the first adsorption tower and the second adsorption tower.

3. The method according to claim 2, characterized in that, The step of adjusting the input of the dual-source steam according to the determined supply and demand status of the process steam in the plant area includes: The main steam of the power plant and the process steam of the plant area are respectively transported to the manifold through the corresponding steam branch, and the manifold is connected to the second heat exchanger; Based on the determined supply and demand status of the process steam in the plant area, the corresponding steam branch is controlled to be turned on or off, so as to select the main steam of the power plant or the process steam of the plant area to be input into the second heat exchanger; If the supply parameters of a single steam line do not meet the heating requirements of the second heat exchanger, then the two steam branches are controlled to be connected, so that the main steam of the power plant and the process steam of the plant area are mixed through the manifold and then input into the second heat exchanger.

4. The method according to claim 2, characterized in that, The step of adjusting the heat storage and release states of the first adsorption tower and the second adsorption tower according to the determined supply and demand state of the process steam in the plant area includes: When the supply and demand of process steam in the plant area is insufficient, the input of the dual-source steam is adjusted, and the adsorption tower that performs carbon dioxide adsorption is controlled to release heat. The released heat is used to heat the boiler feedwater, thereby reducing the demand for extraction steam and indirectly supplementing the process steam in the plant area. When the supply and demand of process steam in the plant area is in a state of surplus, the surplus process steam is fed into the adsorption tower for adsorbent regeneration, and the heat of the process steam is stored in the adsorption tower.

5. The method according to claim 1, characterized in that, The adjustment of the heat storage and release states of the first and second adsorption towers and the compression load of the carbon dioxide regeneration cycle according to the electricity consumption period of the power grid includes: Acquire power grid dispatch instructions and electricity price signals; The power grid peak shaving condition is determined according to the power grid dispatching instruction and the electricity price signal. When the peak shaving conditions corresponding to the power grid dispatching instruction and the electricity price signal are inconsistent, the power grid peak shaving condition is determined according to the power grid dispatching instruction. Based on the determined power grid peak-shaving conditions, adjust the heat storage and release states of the first and second adsorption towers, as well as the compression load of the carbon dioxide regeneration cycle.

6. The method according to claim 5, characterized in that, The step of adjusting the heat storage and release states of the first and second adsorption towers and the compression load of the carbon dioxide regeneration cycle according to the determined power grid peak-shaving conditions includes: When the power grid is in peak electricity consumption period, the heat storage and release state of the first adsorption tower and the second adsorption tower is adjusted so that the adsorption tower performing carbon dioxide adsorption releases the stored heat and uses the released heat to heat the boiler feedwater, and controls the compression process of the carbon dioxide regeneration cycle to operate at a load lower than full load. When the power grid is in a low-demand period, the heat storage and release states of the first and second adsorption towers are adjusted so that the adsorption towers performing adsorbent regeneration store the heat input during the regeneration process, and the adsorbent regeneration process and the compression process of the carbon dioxide regeneration cycle are controlled to operate at full load.

7. The method according to claim 1, characterized in that, Also includes: When the heat storage and release state determined based on the supply and demand status of the process steam in the plant area is inconsistent with the heat storage and release state determined based on the peak shaving status of the power grid, the heat storage and release state of the first adsorption tower and the second adsorption tower shall be determined based on the supply and demand status of the process steam in the plant area. The input of the dual-source steam and the compression load of the carbon dioxide regeneration cycle are adjusted according to the determined heat storage and release state.

8. The method according to claim 1, characterized in that, The step of returning a portion of the compressed and cooled carbon dioxide to the second heat exchanger includes: The heat of compression generated during the compression and cooling process of the carbon dioxide output from the second adsorption tower is recovered. The recovered heat of compression is used to preheat the refluxed carbon dioxide; The preheated carbon dioxide is fed into the second heat exchanger, and the preheated carbon dioxide is heated using the dual-source steam. The heated carbon dioxide is fed into the second adsorption tower for adsorbent regeneration.

9. The method according to claim 1, characterized in that, The step of storing the heat input during the regeneration process in the second adsorption tower includes: The circulating carbon dioxide, heated by the second heat exchanger, is fed into the second adsorption tower, allowing it to flow through the molecular sieve adsorbent within the tower. The circulating carbon dioxide exchanges heat with the molecular sieve adsorbent, causing the carbon dioxide adsorbed by the molecular sieve adsorbent to desorb, and the heat carried by the circulating carbon dioxide is stored in the molecular sieve adsorbent.

10. A coal-to-gas dual-tower thermal storage carbon capture and peak-shaving device, characterized in that, The device includes: An adsorption unit is used to input the purified boiler flue gas into the first adsorption tower, adsorb carbon dioxide in the boiler flue gas, and discharge the purified boiler flue gas from the first adsorption tower. The desorption unit is used to heat the circulating carbon dioxide in the second heat exchanger and then input it into the second adsorption tower, so that the carbon dioxide adsorbed by the adsorbent in the second adsorption tower is desorbed, and the heat input during the regeneration process is stored in the second adsorption tower; the carbon dioxide output from the second adsorption tower is compressed and cooled, and a portion of the compressed and cooled carbon dioxide is returned to the second heat exchanger to form a carbon dioxide regeneration cycle. A heating unit is used to obtain dual-source steam and input it into the second heat exchanger to heat the circulating carbon dioxide; the input of the dual-source steam and the heat storage and release status of the first adsorption tower and the second adsorption tower are adjusted according to the supply and demand status of process steam in the plant area. The regulating unit is used to adjust the heat storage and release status of the first adsorption tower and the second adsorption tower, as well as the compression load of the carbon dioxide regeneration cycle, according to the power consumption period of the power grid. The switching unit is used to switch the operating conditions of the first adsorption tower and the second adsorption tower after the first adsorption tower has completed carbon dioxide adsorption and the second adsorption tower has completed adsorbent regeneration, so that the first adsorption tower and the second adsorption tower alternately perform carbon dioxide adsorption and adsorbent regeneration.

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