Patent Application
20230381712
The present disclosure belongs to the technical field of recovery and utilization of the boiler flue gas, and particularly relates to a system and method for synchronously recovering nitrogen and carbon dioxide from boiler flue gas.
The capture and reuse of the carbon dioxide in the coal-fired boiler flue gas is an important measure to achieve the dual carbon goal. And, in the vent gas after recovering the carbon dioxide, the nitrogen content in that is about 90%, the recycling of nitrogen can not only improve the efficiency of nitrogen production, but also reduce the energy consumption and further reduce the carbon emission.
Chinese patent application CN107899376A discloses a “combined capture and recovery device and method for carbon dioxide and nitrogen from flue gas”, this device comprises a flue gas treatment system, a first CO2 membrane separation unit, a second CO2 membrane separation unit and a N2 membrane separation unit. This device belongs to the membrane recovery mode, although it can capture the carbon dioxide and the nitrogen at the same time, the product purity is low, the membrane barrel has a high requirement for gas source cleanliness, the equipment is easily blocked during use, the service life is short, and the membrane barrel has a high price, which is not suitable for industrial large-scale production.
Chinese patent application CN110498416A discloses a “system for synchronous recovery of carbon dioxide and nitrogen from boiler flue gas in coal-fired power plant”, which comprises a flue gas pretreatment system, a PSA1 system, a PSA2 system, a carbon dioxide compression and purification system, a carbon dioxide rectification and storage system and a PSA high-purity nitrogen preparation system. This system can capture the carbon dioxide and the nitrogen to the maximum extent, and the product purity is high, but there are some problems such as inflexible equipment operation, high energy consumption. When the nitrogen production of the later stage is reduced or the capture is not performed, the pressure compression value of the earlier stage is too high and the power consumption is large.
Accordingly, there is a need to provide an improved solution to the above-mentioned deficiencies of the prior art.
It is an object of the present disclosure to provide a system and method for synchronously recovering nitrogen and carbon dioxide from boiler flue gas, in order to solve or alleviate the problems existing in the prior art.
In order to achieve the above-mentioned object, the present disclosure provides the following technical solutions.
A system for synchronously recovering nitrogen and carbon dioxide from boiler flue gas includes:
In the system for synchronously recovering nitrogen and carbon dioxide from boiler flue gas as described above, alternatively, the flue gas pretreatment system includes a first cooler, a first gas-liquid separator and a flue gas induced draught fan, and an inlet of the first cooler is communicated with a boiler flue, an outlet of the first cooler is communicated with an inlet of the first gas-liquid separator, an outlet of the first gas-liquid separator is communicated with an inlet of the flue gas induced draught fan, and an outlet of the flue gas induced draught fan is communicated with the carbon and nitrogen separation system.
In the system for synchronously recovering nitrogen and carbon dioxide from boiler flue gas as described above, alternatively, the carbon and nitrogen separation system includes a flue gas compressor, a second gas-liquid separator, a first dryer, a first adsorption column set, a first vacuum pump, and a first buffer tank, and the first adsorption column set includes a plurality of first adsorption columns arranged in parallel, each first adsorption column is filled with a first adsorbent; wherein, an inlet of the flue gas compressor is communicated with the flue gas pretreatment system, an outlet of the flue gas compressor is communicated with an inlet of the second gas-liquid separator, an outlet of the second gas-liquid separator is communicated with an inlet of the first dryer, an outlet of the first dryer is communicated with a gas inlet of the first adsorption column set, a top vent gas of the first adsorption column set is a nitrogen-containing vent gas, a bottom vent gas is a crude carbon dioxide gas, a column-top gas outlet of the first adsorption column set is communicated with the nitrogen concentration and purification system, a column-bottom gas outlet of the first adsorption column set is communicated with an inlet of the first vacuum pump, an outlet of the first vacuum pump is communicated with an inlet of the first buffer tank, and an outlet of the first buffer tank is communicated with the carbon dioxide secondary purification system.
In the system for synchronously recovering nitrogen and carbon dioxide from boiler flue gas as described above, alternatively, a volume concentration of nitrogen in the nitrogen-containing vent gas is 88%-90%, and a volume concentration of carbon dioxide in the crude carbon dioxide gas is 45%-80%.
In the system for synchronously recovering nitrogen and carbon dioxide from boiler flue gas as described above, alternatively, the carbon dioxide secondary purification system includes a first carbon dioxide compressor, a third gas-liquid separator, a second adsorption column set, a second vacuum pump and a second buffer tank, and the second adsorption column set includes a plurality of second adsorption columns arranged in parallel, and each second adsorption column is filled with a second adsorbent; wherein, an inlet of the first carbon dioxide compressor is communicated with the carbon and nitrogen separation system, an outlet of the first carbon dioxide compressor is communicated with an inlet of the third gas-liquid separator, an outlet of the third gas-liquid separator is communicated with a gas inlet of the second adsorption column set, a column-top gas outlet of the second adsorption column set is communicated with the nitrogen concentration and purification system, a column-bottom gas outlet of the second adsorption column set is communicated with an inlet of the second vacuum pump, and an outlet of second vacuum pump is communicated with an inlet of the second buffer tank.
In the system for synchronously recovering nitrogen and carbon dioxide from boiler flue gas as described above, alternatively, the nitrogen concentration and purification system includes a third buffer tank, a nitrogen compressor, a second dryer, a filter and a third adsorption column set, and the third adsorption column set includes a plurality of third adsorption columns arranged in parallel, and the third adsorption columns are filled with a third adsorbent; wherein, an inlet of the third buffer tank is communicated with the carbon and nitrogen separation system and the carbon dioxide secondary purification system, an outlet of the third buffer tank is communicated with an inlet of the nitrogen compressor, an outlet of the nitrogen compressor is communicated with an inlet of the second dryer, an outlet of the second dryer is communicated with an inlet of the filter, an outlet of the filter is communicated with a gas inlet of the third adsorption column set, and a product nitrogen is obtained at a top gas outlet of the third adsorption column set.
In the system for synchronously recovering nitrogen and carbon dioxide from boiler flue gas as described above, alternatively, an adsorption pressure of the third adsorption column is 0.7-1.0 MPa, and a volume concentration of the product nitrogen is 99%-99.999%.
In the system for synchronously recovering nitrogen and carbon dioxide from boiler flue gas as described above, alternatively, the system also includes a carbon dioxide refining and liquefaction system, and the carbon dioxide refining and liquefaction system is communicated with the carbon dioxide secondary purification system for refining the carbon dioxide.
In the system for synchronously recovering nitrogen and carbon dioxide from boiler flue gas as described above, alternatively, the carbon dioxide refining and liquefaction system includes a second cooler, a fourth gas-liquid separator, a second carbon dioxide compressor, a fourth buffer tank, a desulfurization column set, a drying column set, a third cooler, a liquefaction module, a distillation module and a carbon dioxide storage tank; wherein, an inlet of the second cooler is communicated with the carbon dioxide secondary purification system, an outlet of the second cooler is communicated with an inlet of the fourth gas-liquid separator, an outlet of the fourth gas-liquid separator is communicated with an inlet of the second carbon dioxide compressor, an outlet of the second carbon dioxide compressor is communicated with an inlet of the fourth buffer tank, an outlet of the fourth buffer tank is communicated with an inlet of the desulfurization column set, an outlet of the desulfurization column set is communicated with an inlet of the drying column set, an outlet of the drying column set is communicated with an inlet of the third cooler, an outlet of the third cooler is communicated with an inlet of the liquefaction module, an outlet of the liquefaction module is communicated with an inlet of the distillation module, and a bottom outlet of the distillation module is communicated with the carbon dioxide storage tank.
The present disclosure also provides a method for synchronously recovering nitrogen and carbon dioxide from boiler flue gas, which uses the system for synchronously recovering nitrogen and carbon dioxide from boiler flue gas as described above, the method includes the following steps:
The present disclosure has achieved the following technical effects compared to the prior art.
(1) The system for synchronously recovering nitrogen and carbon dioxide from boiler flue gas of the present disclosure can recover carbon dioxide and nitrogen to the greatest extent, and generates no three wastes. And, the carbon and nitrogen separation system of the present disclosure uses a low-pressure adsorption mode of 0.20-0.40 MPa to separate carbon dioxide and nitrogen, which changes the prior art of adsorption at 1.0 MPa and effectively reduces energy consumption.
(2) The desorption gas in the carbon and nitrogen separation system of the present disclosure adopts vacuum pump desorption for desorbing, which not only reduces energy consumption but also improves the recovery rate of carbon dioxide.
(3) The nitrogen concentration and purification system of the present disclosure adopts a secondary compression mode, which involves a secondary pressure increase process, and the model and compression pressure of the compressor can be selected based on the actual nitrogen content demanded by the users, thereby further achieving the goal of energy conservation.
The drawings, which form a part of the present disclosure, are used to provide a further understanding of the present disclosure. The schematic examples and explanations of the present disclosure are used to explain the present disclosure and do not constitute an improper limitation of the present disclosure. Wherein:
In the drawings:
The technical solutions in the examples of the present disclosure will be described clearly and completely in the following, and it is obvious that the described examples are only a part of the examples of the present disclosure, but not all of the examples. Based on the examples of the present disclosure, all other examples obtained by a person skilled in the art are within the scope of the present disclosure.
The following will provide a detailed explanation of the present disclosure in conjunction with examples. It should be noted that, without conflict, the examples of the present disclosure and the features in the examples can be combined with each other.
With regard to the problems existing in the prior art, the present disclosure provides an energy-saving system for synchronously recovering nitrogen and carbon dioxide from boiler flue gas, as shown in
Wherein, the flue gas pretreatment system 1 is used for dehydrating and cooling the boiler flue gas; the carbon and nitrogen separation system 2 is communicated with the flue gas pretreatment system 1, and is used for performing pressure swing adsorption on the pretreated flue gas and separating the nitrogen-containing vent gas and the crude carbon dioxide gas, the adsorption pressure of the carbon and nitrogen separation system 2 is 0.20-0.40 MPa; the carbon dioxide secondary purification system 3 is communicated with the carbon and nitrogen separation system 2, and is used for performing secondary purification on the crude carbon dioxide gas separated from the carbon and nitrogen separation system 2; the nitrogen concentration and purification system 5 is communicated with the carbon and nitrogen separation system 2 and the carbon dioxide secondary purification system 3, and is used for purifying the nitrogen-containing vent gas separated from the carbon and nitrogen separation system 2 and the vent gas generated by the carbon dioxide secondary purification system 3; the carbon dioxide refining and liquefaction system 4 is communicated with the carbon dioxide secondary purification system 3 for refining the carbon dioxide.
The carbon and nitrogen separation system uses a low-pressure adsorption mode of 0.20-0.40 MPa (such as 0.20 MPa, 0.22 MPa, 0.25 MPa, 0.25 MPa, 0.27 MPa, 0.30 MPa, 0.32 MPa, 0.35 MPa, 0.37 MPa or 0.40 MPa) to separate carbon dioxide and nitrogen, which changes the prior art of adsorption at 1.0 MPa and effectively reduces energy consumption.
As shown in
As shown in
The volume concentration of nitrogen in the nitrogen-containing vent gas of the present disclosure is 88%-90% (such as 88%, 89% or 90%), and the volume concentration of carbon dioxide in the crude carbon dioxide gas is 45%-80% (such as 45%, 46%, 47%, 48%, 49%, 50%, 60%, 70% or 80%).
Furthermore, the first pneumatic valve is disposed on the pipeline which is connected to the outlet of the flue gas compressor 21, the first solenoid valve is disposed on the first pneumatic valve, and the first solenoid valve is electrically connected to the PLC, so that the first pneumatic valve is controlled by the PLC through the first solenoid valve.
In this example, the flue gas treated by the flue gas pretreatment system 1 is lifted to a compressed flue gas of about 0.25 MPa by the flue gas compressor 21, and is entered into the first adsorption column set 24. The first pneumatic valve is controlled by the PLC through the first solenoid valve to ensure the different working states of different first adsorption columns. The column-top gas is nitrogen-enriched gas, which is entered into the nitrogen concentration and purification system as the feed gas, and the column-bottom gas is about 50% crude carbon dioxide gas as the lower level feed gas.
As shown in
Preferably, the second pneumatic valve is disposed on the pipeline which is connected to the outlet of the first carbon dioxide compressor 31, the second solenoid valve is disposed on the second pneumatic valve, and the second solenoid valve is electrically connected to the PLC, so that the second pneumatic valve is controlled by the PLC through the second solenoid valve.
In this example, a plurality of second adsorption columns are disposed, and the second pneumatic valve is controlled by the PLC through the second solenoid valve to ensure the different working states of different second adsorption columns. The column-top gas is nitrogen-enriched gas, which is entered into the nitrogen concentration and purification system as the feed gas or vent, and the column-bottom gas is about 95% crude carbon dioxide gas, which is used as the feed gas for refining carbon dioxide.
As shown in
It should be noted that the desulfurization column set 44 includes a plurality of desulfurization columns arranged in parallel, the drying column set 45 includes a plurality of the drying columns arranged in parallel, and the distillation module 48 includes the distillation column.
As shown in
Optionally, the adsorption pressure of the third adsorption column is 0.7-1.0 MPa (such as 0.7 MPa, 0.75 MPa, 0.8 MPa, 0.9 MPa or 1.0 MPa), and the volume concentration of the product nitrogen is 99%-99.999%.
It can be understood that the two stages of the vent gas generated by the carbon and nitrogen separation system 2 and the carbon dioxide secondary purification system 3 is recovered by the nitrogen concentration and purification system 5 of the present disclosure, and after compression and filtration, the gas at a pressure of 0.7-1.0 MPa is entered into the third adsorption column, which is filled with the third adsorbent. For the vent gas with complex components, it has a high recovery rate, and after multi-column pressure swing adsorption separation, the product nitrogen with a volume concentration of 99%-99.999% is obtained on the column-top.
It should be noted that the first adsorbent, the second adsorbent and the third adsorbent used in the present disclosure are all existing adsorbents.
The present disclosure also provides a method for synchronously recovering nitrogen and carbon dioxide from boiler flue gas, which uses the system for synchronously recovering nitrogen and carbon dioxide from boiler flue gas as described above, the method includes the following steps:
The following is a detailed explanation of system and method for synchronously recovering nitrogen and carbon dioxide from boiler flue gas of the present disclosure through a specific example.
The example of the present disclosure is used for recovery of carbon dioxide and nitrogen from flue gas of a coal power plant, and the carbon dioxide gas is used to increase the income of smart agriculture, and the nitrogen is used to replace and purge the chemical plant of the factory. Wherein, the compositions of the flue gas is shown in TABLE 1 as below.
13%
A s shown in
The flue gas is entered from the outlet of the flue gas induced draught fan 13 into the flue gas compressor 21, when it is pressurized to 0.23 MPa, it is entered into the second gas-liquid separator 22, and then is entered into the first dryer 23 for deep dehydration, after that, it is entered into the first adsorption column set 24 for adsorption and separation. The vent gas with a nitrogen content of 88-90% is obtained on the column-top, which is used as the feed gas for nitrogen concentration and purification system. The desorption gas obtained on the column-bottom through the first vacuum pump 25 is a crude carbon dioxide gas with a carbon dioxide volume content of 45% and a pressure of 15 KPa.
The crude carbon dioxide gas with a content of 45% is compressed to 0.25 MPa through first carbon dioxide compressor 31, and it is entered into the third gas-liquid separator 32 for gas-liquid separation, and then is entered into the second adsorption column set 33 for further purification of carbon dioxide, the carbon dioxide secondary purification vent gas is obtained on the column-top, which is introduced into the raw gas pipeline of nitrogen concentration and purification system 5, the carbon dioxide gas with a purity of 95% and a pressure of about 15 kPa is desorbed and obtained through the second vacuum pump 34 on the column-bottom, which is stored in second buffer tank 35.
After 95% carbon dioxide gas is cooled and dehydrated again through the second cooler 41 and the fourth gas-liquid separator 42, the pressure thereof is increased to 2.5 MPa through the second carbon dioxide compressor 43, and then it is entered into the inlet of the fourth buffer tank 43a, the outlet of the fourth buffer tank 43a is communicated with the inlet of the desulfurization column set 44, and then it is orderly entered into the desulfurization column set 44 and the drying column set 45 for desulfurization and impurity removal, after it is entered into the third cooler 46 for cooling, is entered into the liquefaction module 47, which is cooled to −18° C. for returning to liquid state, and after liquid carbon dioxide is entered into the distillation module 48 for refining and purification, the column-bottom is 99.9% food grade carbon dioxide, which is stored in the carbon dioxide storage tank 49. The column-top vent gas is used as a regeneration gas source for desulfurization column set and drying column set, which saves the product gas and reduces energy consumption.
The vent gas produced by the column-top of the adsorption column in the carbon and nitrogen separation system 2 and the carbon dioxide secondary purification system 3 is entered into the third buffer tank 51, after that, it is entered into the nitrogen compressor 52, and is pressurized to 0.8-1.0 MPa, and then is entered into the second dryer 53 and the filter 54 for dehydration, drying, filtration, and purification, after that, it is entered into the third adsorption column set 55 for pressure swing adsorption to obtain the product nitrogen, with the purity ranging is from 99.5%-99.9%.
In this example, the carbon and nitrogen separation system adopts a low-pressure adsorption mode with an adsorption pressure of 0.25 MPa, which changes the prior art of adsorption at 1.0 MPa. Moreover, vacuum pump desorption is used for desorption, which not only reduces energy consumption but also improves the recovery rate of carbon dioxide. The nitrogen concentration and purification system adopts a secondary compression mode to increase the pressure from 0.23 MPa to 0.8-1.0 MPa, and only selects the compressor model based on the actual nitrogen content demanded by the users. Compared to compressors that compress a large amount of flue gas, the compressed gas volume here is only 68% of that of flue gas compression. In this example, the flue gas compression is increased from 0.01 MPa to 0.8-1.0 MPa, and the vent gas compression is increased from 0.23 MPa to 0.8-1.0 MPa. The compressed gas volume is also reduced to 68%, indicating that the energy-saving effect of the system of the present disclosure is obvious.
The foregoing descriptions are preferred examples of the present disclosure and are not intended to limit the present disclosure. For those skilled in the art, the present disclosure may have various changes and modifications. All modifications, identical replacements and improvements made without departing from the spirit and principle of the present disclosure shall be within the protection scope of the present disclosure.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202111216165.9 | Oct 2021 | CN | national |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/CN2022/124845 | Oct 2022 | US |
| Child | 18447072 | US |
