Method and system for deeply removing trace NOX from high-concentration CO2

Abstract

The invention discloses a method for deeply removing trace NOX from high-concentration CO2, and belongs to the technical field of CO2 purification, and the method comprises the following steps: dehydrating CO2 raw material gas containing NO and NO2, using the dehydrated CO2 raw material gas as a heat source, respectively introducing the heat source into evaporators of a first rectifying tower and a second rectifying tower, collecting the raw material gas output by the two evaporators, and liquefying to obtain liquid CO2 containing NO and NO2; the liquid CO2 containing NO and NO2 passes through the first rectifying tower to remove NO, and passes through the second rectifying tower to remove NO2. The invention further discloses a system for deeply removing the trace NOX from the high-concentration CO2. The system comprises a dehydration subsystem, a refrigeration subsystem and a rectification subsystem. According to the invention, the flow of the raw material gas entering the two evaporators is adjusted by detecting whether the NOX gas at the gas outlet at the top of the second rectifying tower exceeds a set threshold value or not, so that closed-loop control is realized, deep removal of trace NOX in high-concentration CO2 can be realized, and the contents of trace NO and NO2 in the high-concentration CO2 are respectively reduced to 1.5 ppm or below.

Description

Technical Field

[0001] The present invention belongs to the technical field of CO2 purification, and specifically relates to a method for deeply removing trace NO from high-concentration CO2. X method and system. Background Art

[0002] The exhaust gas from ship engines generally contains 5% CO2, 70% N2, 24% O2 and a small amount of SO2 and NO. X The flue gas first passes through the desulfurization system, which generally uses the alkalinity of seawater to absorb and remove SO2 and NO2 in the flue gas. The flue gas after desulfurization mainly contains N2, O2, CO2 and NO. It enters the carbon capture system, where the CO2 in the flue gas is absorbed by organic amine liquid at room temperature. Most of the O2, N2 and NO are not absorbed by the amine liquid and are discharged into the air from the top of the absorption tower, but a small amount of N2, O2 and NO will be entrained by the amine liquid into the analysis tower, and will be analyzed from the amine liquid with CO2 at high temperature. After dehydration and purification, the content of NO in CO2 is about 30ppm. In the presence of oxygen, a very small amount of NO will be converted into NO2.

[0003] If the above CO2 is made into food grade, the NOx content in CO2 should be below 5ppm. In addition, some countries and regions store the captured CO2 underground and in rock formations. X It will cause erosion and damage to rock formations and geology. In this case, the NO in CO2 X The existing technologies, such as catalytic reduction, low nitrogen combustion and activated carbon adsorption, are very rough for the removal of trace NOx. Therefore, the existing technologies are not suitable for the removal of trace NOx in high concentration CO2. X The deep removal cannot meet the requirements of extremely low NOx content in CO2 (such as <1.5ppm) in some applications. Summary of the invention

[0004] In view of one or more of the above defects or improvement needs of the prior art, the present invention provides a method for deeply removing trace NO from high concentration CO2. X Method and system capable of achieving trace NO in high concentration CO2 x It is removed to obtain high-purity CO2 products.

[0005] To achieve the above object, according to one aspect of the present invention, a method for deeply removing trace NO from high concentration CO2 is provided. X The method comprises the following steps: S1: Dehydrating the CO2 raw gas containing NO and NO2; S2: a first distillation tower with a first evaporator at the bottom and a second distillation tower with a second evaporator at the bottom are provided; the raw gas dehydrated in S1 is used as a heat source to be respectively introduced into the two evaporators, and the raw gas output from the two evaporators is collected and liquefied to obtain liquid CO2 containing NO and NO2; S3: passing the liquid CO2 in S2 into the first distillation tower, controlling the flow rate of the feed gas passing into the first evaporator, reaching the boiling point of CO2 under the heat provided by the feed gas so that part of the CO2 evaporates, and removing NO while discharging from the gas outlet at the top of the first distillation tower, and discharging the liquid CO2 containing NO2 from the liquid outlet at the bottom of the first distillation tower; S4: The liquid CO2 in S3 is passed into the second distillation tower, and the flow rate of the raw gas passed into the second evaporator is controlled. The CO2 is evaporated under the heat provided by the second evaporator and discharged from the top outlet of the second distillation tower and collected. At the same time, NO2 is discharged from the bottom outlet of the second distillation tower in liquid form to remove NO2.

[0006] As a further improvement of the present invention, by detecting the NO at the outlet of the second distillation tower, X Whether the gas exceeds the set threshold, adjust the amount of dehydrated raw gas entering the first evaporator and the second evaporator; If it is detected that NO exceeds the set threshold, the amount of raw gas introduced into the first evaporator is increased; if it is detected that NO2 exceeds the set threshold, the amount of raw gas introduced into the second evaporator is reduced.

[0007] As a further improvement of the present invention, in step S2, the dehydrated raw gas is divided into three routes, including a first pipeline leading to the first evaporator, a second pipeline leading to the second evaporator, and a third pipeline for direct liquefaction.

[0008] As a further improvement of the present invention, when the total flow rate of the raw gas is constant, the control process of the raw gas flow rate in the three pipelines is as follows: Detect NO at the outlet of the second distillation tower X Whether the gas exceeds the set threshold; If it is detected that NO exceeds the set threshold, the amount of raw gas introduced into the first pipeline is increased, and the amount of raw gas introduced into the second pipeline is reduced or the amount of raw gas directly liquefied is reduced; if it is detected that NO2 exceeds the set threshold, the amount of raw gas introduced into the second pipeline is reduced, and the amount of raw gas introduced into the first pipeline is increased or the amount of raw gas directly liquefied is increased.

[0009] As a further improvement of the present invention, when the total flow rate of the raw gas is constant, the control process of the raw gas flow rate in the three pipelines is as follows: 1) introducing the raw gas into the first pipeline, and gradually increasing the amount of the raw gas introduced into the first pipeline, detecting the amount of NO output from the gas outlet of the first distillation tower, and comparing the amount of NO with the amount of NO in the raw gas, until the amount of NO output is not greater than a set threshold value, that is, obtaining the minimum flow rate of the raw gas introduced into the first pipeline; 2) All the remaining raw gas is introduced into the second pipeline, and the amount of NO2 in the gas outlet of the second distillation tower is detected. If it is less than the set threshold, the maximum flow rate is obtained; if it is greater than the set threshold, the flow rate introduced into the second pipeline is gradually reduced until the output amount of NO2 is no greater than the set threshold, that is, the maximum flow rate of the raw gas introduced into the second pipeline is obtained; 3) The remaining raw gas is introduced into the third pipeline and directly liquefied.

[0010] According to another aspect of the present invention, a method for deeply removing trace NO from high concentration CO2 is provided. X The system includes a dehydration subsystem, a refrigeration subsystem and a distillation subsystem; The rectification subsystem comprises a first rectification tower with a first evaporator at the bottom and a second rectification tower with a second evaporator at the bottom, and both the first rectification tower and the second rectification tower have a liquid inlet and a gas outlet at the top, and a liquid outlet at the bottom; The dehydration subsystem is connected to the inlet of the first evaporator and the second evaporator through pipelines, so as to dehydrate the CO2 raw gas containing NO and NO2 and pass it into the two evaporators as a heat source; the outlets of the first evaporator and the second evaporator are connected to the inlet of the refrigeration subsystem, so as to liquefy the CO2 raw gas to obtain liquid CO2 containing NO and NO2; The outlet of the refrigeration subsystem is connected to the liquid inlet of the first distillation tower, so that the liquid CO2 is passed into the first distillation tower, and the boiling point of CO2 is reached under the heat provided by the first evaporator to make part of the CO2 evaporate, and NO is removed while being discharged from the gas outlet of the first distillation tower; the liquid outlet of the first distillation tower is connected to the liquid inlet of the second distillation tower, so that the liquid CO2 containing NO2 discharged from the liquid outlet of the first distillation tower is passed into the second distillation tower, and the CO2 is evaporated under the heat provided by the second evaporator and discharged and collected from the gas outlet of the second distillation tower, and NO2 is discharged from the liquid outlet of the second distillation tower in liquid form to remove NO2.

[0011] As a further improvement of the present invention, a NO X The analyzer detects NO XWhether the gas exceeds the set threshold, adjust the amount of dehydrated raw gas entering the first evaporator and the second evaporator; If it is detected that NO exceeds the set threshold, the amount of raw gas introduced into the first evaporator is increased; if it is detected that NO2 exceeds the set threshold, the amount of raw gas introduced into the second evaporator is reduced.

[0012] As a further improvement of the present invention, the dehydrated raw gas is divided into three paths, the dehydration subsystem is connected to the first evaporator through a first pipeline, connected to the second evaporator through a second pipeline, and directly connected to the refrigeration subsystem through a third pipeline.

[0013] As a further improvement of the present invention, a NO X Analyzer, when the total flow rate of raw gas is constant, the control process of the raw gas flow in the three pipelines is as follows: If it is detected that NO exceeds the set threshold, the amount of raw gas entering the first evaporator is increased, and the amount of raw gas entering the second evaporator is reduced, or the amount of raw gas directly entering the refrigeration subsystem is reduced; if it is detected that NO2 exceeds the set threshold, the amount of raw gas entering the second evaporator is reduced, and the amount of raw gas entering the first evaporator is increased, or the amount of raw gas directly entering the refrigeration subsystem is increased.

[0014] As a further improvement of the present invention, a waste gas flow meter is provided at the gas outlet of the first distillation tower, and a NO X Analyzer; When the total flow rate of raw gas is constant, the control process of the raw gas flow rate in the three pipelines is as follows: 1) introducing the raw gas into the first pipeline, and gradually increasing the amount of the raw gas introduced into the first pipeline, detecting the amount of NO output from the gas outlet of the first distillation tower, and comparing the amount of NO with the amount of NO in the raw gas, until the amount of NO output is not greater than a set threshold value, that is, obtaining the minimum flow rate of the raw gas introduced into the first pipeline; 2) All the remaining raw gas is introduced into the second pipeline, and the amount of NO2 in the gas outlet of the second distillation tower is detected. If it is less than the set threshold, the maximum flow rate is obtained; if it is greater than the set threshold, the flow rate introduced into the second pipeline is gradually reduced until the output amount of NO2 is no greater than the set threshold, that is, the maximum flow rate of the raw gas introduced into the second pipeline is obtained; 3) The remaining raw gas is introduced into the third pipeline and directly liquefied.

[0015] As a further improvement of the present invention, the dehydration subsystem comprises a first molecular sieve adsorber and a second molecular sieve adsorber arranged in parallel, and the inlet end and the outlet end of the first molecular sieve adsorber and the second molecular sieve adsorber are respectively connected to the raw gas main pipe through valves; The outlet ends of the first molecular sieve adsorber and the second molecular sieve adsorber are respectively connected to the outlet end of the heater through valves, and the inlet end of the heater is connected to the raw gas main pipe through a valve; at the same time, the inlet ends of the first molecular sieve adsorber and the second molecular sieve adsorber are respectively connected to the inlet end of the cooler, and the outlet end of the cooler is connected to the raw gas main pipe through a valve; the valves are alternately controlled so that when one of the molecular sieve adsorbers is adsorbing, the other molecular sieve adsorber is regenerated.

[0016] As a further improvement of the present invention, a water analyzer is provided on the raw gas main pipe at the outlet of the first molecular sieve adsorber and the second molecular sieve adsorber, which is used to determine whether the first molecular sieve adsorber or the second molecular sieve adsorber is adsorbed saturated, thereby controlling the valve connecting one of the molecular sieve adsorbers to the raw gas main pipe to open, and the other molecular sieve adsorber to be connected to the heater and the cooler to achieve regeneration.

[0017] As a further improvement of the present invention, the gas outlet at the top of the second distillation tower is connected to the refrigeration subsystem through a valve to X When the analyzer detects that the content of NO or NO2 exceeds the set threshold, the top gas of the second distillation tower is reliquefied and then passed into the first distillation tower for re-separation; The top gas outlet of the second distillation tower is also connected to a refrigerator through a valve to liquefy the CO2 gas with the required purity at the top of the tower and store it.

[0018] In general, the above technical solution conceived by the present invention has the following beneficial effects compared with the prior art: (1) The present invention removes NO and NO2 respectively through a first distillation tower and a second distillation tower. An evaporator is provided at the bottom of the distillation tower. The dehydrated raw gas is introduced into the evaporator as a heat source, which can not only realize the utilization of the heat source and reduce the power of cooling and liquefaction, but also can reduce the trace NO and NO2 contents in high-concentration CO2 to below 1.5 ppm by controlling the flow rate of the raw gas introduced into the first evaporator and the evaporator, thereby obtaining a high-purity CO2 product.

[0019] (2) The present invention detects NO at the top outlet of the second distillation tower. X The gas exceeds the set threshold to adjust the flow of raw gas into the two evaporators to achieve closed-loop control, thereby ensuring that trace NO in high-concentration CO2 X Perform deep removal.

[0020] (3) The present invention further divides the dehydrated raw gas into three paths. When the raw gas flow rate is constant, the dehydrated raw gas is divided into one path for direct liquefaction, which can further balance the flow rate of the raw gas entering the first evaporator and the second evaporator. By controlling the flow distribution of the raw gas entering the first evaporator, the second evaporator and the direct liquefaction, NO can be removed as much as possible while the loss of CO2 in the first distillation tower is minimized, and CO2 can be evaporated as much as possible while avoiding the evaporation of NO2 in the second distillation tower, thereby achieving optimal thermal energy utilization and reducing the loss of CO2.

[0021] (4) The present invention uses two sets of molecular sieve adsorbers connected in parallel to perform dehydration, and uses a water analyzer set on the corresponding molecular sieve adsorbers to determine whether the adsorption is saturated. By switching the valve, when one set of molecular sieve adsorbers is adsorbing, the other set of molecular sieve adsorbers can be controlled to be connected to the heater and the cooler, so that the water in the molecular sieve adsorbers can be analyzed, thereby being regenerated and reused. In addition, the present invention can use the system's own raw gas to achieve regeneration. A small amount of raw gas from the raw gas main is heated by the heater and then passed into the molecular sieve adsorber for regeneration, and then re-enters the raw gas main after cooling. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The present invention is to deeply remove trace NO from high concentration CO2 X System diagram of the system.

[0023] In all the drawings, the same reference numerals represent the same technical features, specifically: 1. first distillation tower; 2. second distillation tower; 3. first evaporator; 4. second evaporator; 5. first refrigerator; 6. exhaust gas flow meter; 7. NO X Analyzer; 8. First molecular sieve adsorber; 9. Second molecular sieve adsorber; 10. Heater; 11. First cooler; 12. Second cooler; 13. Water analyzer; 14. Second refrigerator. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0025] In the description of the present invention, it is to be understood that the terms “center”, “longitudinal”, “lateral”, “length”, “width”, “thickness”, “up”, “down”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside”, “outside”, “clockwise”, “counterclockwise”, “axial”, “radial”, “circumferential”, etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0026] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0027] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0028] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0029] As a preferred embodiment of the present invention, the present invention provides a method for deeply removing trace NO from high concentration CO2. X The method comprises the following steps: S1: Dehydrating the CO2 raw gas containing NO and NO2; S2: a first distillation tower with a first evaporator at the bottom and a second distillation tower with a second evaporator at the bottom are provided; the raw gas dehydrated in S1 is used as a heat source to be respectively introduced into the two evaporators, and the raw gas output from the two evaporators is collected and liquefied to obtain liquid CO2 containing NO and NO2; S3: passing the liquid CO2 in S2 into the first distillation tower, controlling the flow rate of the feed gas passing into the first evaporator, reaching the boiling point of CO2 under the heat provided by the feed gas so that part of the CO2 evaporates, and removing NO while discharging from the gas outlet at the top of the first distillation tower, and discharging the liquid CO2 containing NO2 from the liquid outlet at the bottom of the first distillation tower; S4: The liquid CO2 in S3 is passed into the second distillation tower, and the flow rate of the raw gas passed into the second evaporator is controlled. The CO2 is evaporated under the heat provided by the second evaporator and discharged from the top outlet of the second distillation tower and collected. At the same time, NO2 is discharged from the bottom outlet of the second distillation tower in liquid form to remove NO2.

[0030] In step S3, since the application scenario of the embodiment of the present invention is to remove trace NO from high concentration CO2 X The content of NO in CO2 is trace (about 30ppm), and the content of NO2 is even less, so it is necessary to evaporate part of the gas CO2 and carry NO to be discharged from the outlet of the distillation tower.

[0031] Therefore, the heat provided by the first evaporator needs to reach the boiling point of CO2, for example, at the critical temperature of CO2 evaporation or slightly above the critical temperature, but below the evaporation temperature of NO2, so that CO2 partially evaporates into gas during the heat exchange process, and partially condenses and is located at the bottom of the first distillation tower in liquid form. In the rising steam, high-boiling-point CO2 and NO2 (a small amount of NO2 will evaporate from the mixed liquid containing NO, NO2, and CO2) at the same pressure continuously condense into liquid, and low-boiling-point NO in the downstream liquid continuously evaporates into gas, and at the same time, part of the CO2 evaporates and is discharged from the top outlet of the first distillation tower to remove NO.

[0032] In step S4, since the boiling point of CO2 is much lower than that of NO2 under the same pressure, in order to separate CO2 and NO2, the heat provided by the second evaporator in the second distillation tower needs to reach the boiling point of CO2 and be lower than the boiling point of NO2. During the distillation process, CO2 in the liquid continuously evaporates and enters the top of the tower, and low-boiling-point pure CO2 gas is obtained at the top of the tower. At the same time, NO2 is discharged from the bottom liquid outlet of the second distillation tower in liquid form to remove NO2. Usually, liquid CO2 rich in NO2 is obtained at the bottom of the tower, and it is only necessary to ensure the purity of the evaporated CO2 gas.

[0033] In the actual evaporation process, due to the mutual influence between different gases in the mixed gas, a small amount of NO2 will evaporate during the CO2 evaporation process in step S4, but in the process of the evaporated gas moving upward, the CO2 gas containing NO2 is constantly in contact with the liquid CO2 containing NO2 passed into the second distillation tower for heat exchange, so that the high-boiling-point NO2 gas is continuously condensed into liquid, ensuring that the NO2 content in the output CO2 gas is lower than the set threshold, thereby ensuring the purity of the separated CO2 gas.

[0034] In a preferred embodiment, the amount of dehydrated raw gas entering the first evaporator 3 is about 8-10% of the amount entering the second evaporator 4. Under this distribution ratio, the evaporation requirements of the first distillation tower and the second distillation tower can be met.

[0035] In a preferred embodiment, by detecting NO at the outlet of the second distillation tower X Whether the gas exceeds the set threshold, the amount of dehydrated raw gas entering the first evaporator and the second evaporator is adjusted, so as to perform closed-loop control on the heat provided by the two evaporators at the bottom of the corresponding distillation tower, realize the distribution of raw gas, and thus ensure that trace NO in high-concentration CO2 X Perform deep removal.

[0036] If NO is detected to exceed the set threshold, the amount of raw gas entering the first evaporator is increased; if NO2 is detected to exceed the set threshold, the amount of raw gas entering the second evaporator is reduced. When the raw gas flow rate is constant, if the flow rate of raw gas entering one of the evaporators is increased, if reducing the flow rate of raw gas entering the other evaporator has little effect on the distillation effect of the distillation tower, the flow rate is balanced by reducing the flow rate of raw gas entering the other evaporator; vice versa. Otherwise, it is necessary to balance the flow of the pipeline by adjusting the flow rate of raw gas.

[0037] It should be noted that NO X The threshold value is ≥0, which is determined by the NO X In this embodiment, NO X The set threshold is ≥1.5ppm.

[0038] In a preferred embodiment, in step S2, the dehydrated raw gas is divided into three routes, including a first pipeline leading to the first evaporator, a second pipeline leading to the second evaporator, and a third pipeline for direct liquefaction. In the first pipeline and the second pipeline, the raw gas output from the two evaporators is collected and liquefied to obtain liquid CO2 containing NO and NO2; the raw gas in the third pipeline is directly liquefied to obtain liquid CO2 containing NO and NO2.

[0039] In one embodiment, when the raw gas flow rate is constant, the control process of the raw gas flow rate in the three pipelines is as follows: If it is detected that NO exceeds the set threshold, the amount of raw gas entering the first evaporator is increased. If at this time the amount of raw gas in the second evaporator is reduced, which affects the distillation effect of the second distillation tower, the amount of raw gas for direct liquefaction is reduced. Similarly, if it is detected that NO2 exceeds the set threshold, the amount of raw gas entering the second evaporator is reduced. If at this time the amount of raw gas in the first evaporator is increased, which affects the distillation effect of the first distillation tower, the amount of raw gas for direct liquefaction is increased.

[0040] In this embodiment, the flow of the raw gas entering the first evaporator and the second evaporator can be further balanced by dividing the dehydrated raw gas into one path for direct liquefaction. By controlling the flow distribution of the raw gas entering the first evaporator, the second evaporator and the direct liquefaction, it is ensured that NO is removed as much as possible while the loss of CO2 in the first distillation tower is as small as possible, and at the same time, CO2 is evaporated as much as possible while avoiding the evaporation of NO2 in the second distillation tower.

[0041] In another embodiment, when the raw gas flow rate is constant, the control process of the raw gas flow rate in the three pipelines is as follows: 1) introducing the raw gas into the first pipeline, and gradually increasing the amount of the raw gas introduced into the first pipeline, detecting the amount of NO output from the gas outlet of the first distillation tower, and comparing the amount of NO with the amount of NO in the raw gas, until the amount of NO output is not greater than a set threshold value, that is, obtaining the minimum flow rate of the raw gas introduced into the first pipeline; 2) All the remaining raw gas is introduced into the second pipeline, and the amount of NO2 in the gas outlet of the second distillation tower is detected. If it is less than the set threshold, the maximum flow rate is obtained; if it is greater than the set threshold, the flow rate introduced into the second pipeline is gradually reduced until the output amount of NO2 is no greater than the set threshold, that is, the maximum flow rate of the raw gas introduced into the second pipeline is obtained; 3) The remaining raw gas is introduced into the third pipeline and directly liquefied.

[0042] In this embodiment, by determining the minimum flow rate of the raw gas introduced into the first evaporator and the maximum flow rate of the raw gas introduced into the second evaporator, it is possible to further ensure in the first distillation tower that NO is removed as much as possible while minimizing the loss of CO2 in the first distillation tower, and at the same time, to evaporate CO2 as much as possible while avoiding the evaporation of NO2 in the second distillation tower, and on the premise of satisfying the input amounts of the first evaporator and the second evaporator, to minimize the amount of raw gas directly liquefied, thereby achieving a more ideal flow distribution method.

[0043] like Figure 1As shown, the embodiment of the present invention also provides a method for deeply removing trace NO from high concentration CO2 X The system includes a dehydration subsystem, a refrigeration subsystem and a distillation subsystem.

[0044] The dehydration subsystem is used to dehydrate the CO2 raw gas containing NO and NO2; the distillation subsystem includes a first distillation tower 1 and a second distillation tower 2, and the first distillation tower 1 and the second distillation tower 2 are provided with a first evaporator 3 and a second evaporator 4 at the bottom, and the first distillation tower 1 and the second distillation tower 2 both have a liquid inlet and a gas outlet at the top, and a liquid outlet at the bottom. The dehydration subsystem is connected to the inlets of the first evaporator 3 and the second evaporator 4 through pipelines, and the outlets of the first evaporator 3 and the second evaporator 4 are connected to the inlet of the refrigeration subsystem; the outlet of the refrigeration subsystem is connected to the liquid inlet of the first distillation tower 1, and the liquid outlet of the first distillation tower 1 is connected to the liquid inlet of the second distillation tower 2.

[0045] The CO2 raw gas containing NO and NO2 entering the system is dehydrated by the dehydration subsystem, and is respectively passed into the first evaporator 3 and the second evaporator 4 as a heat source. The raw gas output from the first evaporator 3 and the second evaporator 4 is passed into the refrigeration subsystem for liquefaction to obtain liquid CO2 containing NO and NO2, and the liquid CO2 is pumped into the first distillation tower 1 from the liquid inlet at the top of the first distillation tower 1, flows from top to bottom into the bottom of the tower, and is heated by the raw gas in the first evaporator 3 to generate rising steam. During the rising process, the high-boiling-point CO2 and NO2 are continuously condensed into liquid, and the low-boiling-point NO in the downstream liquid is continuously evaporated into gas, so that the exhaust gas rich in NO is obtained at the top of the tower, and the liquid CO2 containing NO2 is obtained at the bottom of the tower, thereby removing the NO impurity component in CO2.

[0046] Furthermore, liquid CO2 containing NO2 is pumped into the first distillation tower 1 from the liquid inlet at the top of the second distillation tower 2, flows into the bottom of the tower from top to bottom, and is heated by the raw gas in the first evaporator 3 to generate rising steam. Since the boiling point of NO2 is much higher than that of CO2 under the same pressure, the rising high-boiling-point NO2 gas is continuously condensed into liquid during the distillation process, and the low-boiling-point CO2 in the downstream liquid is continuously evaporated into gas, so that pure CO2 gas is obtained at the top of the tower, and liquid CO2 rich in NO2 is obtained at the bottom of the tower.

[0047] In a preferred embodiment, valves V11 and V12 are respectively provided on the pipelines connecting the dehydration subsystem and the inlet of the first evaporator 3 and the second evaporator 4, and a NO X Analyzer 7.

[0048] According to the above, through NO X Analyzer 7 detects NO at the outlet of the second distillation tower 2X Whether it exceeds the set threshold, the amount of dehydrated raw gas entering the first evaporator 3 and the second evaporator 4 is adjusted, so as to control the heat provided by the two evaporators at the bottom of the corresponding distillation tower. The heat of the first evaporator 3 is required to evaporate part of the CO2 and discharge it from the gas outlet at the top of the first distillation tower while removing NO, and at the same time discharge the CO2 liquid containing NO2 from the liquid outlet at the bottom of the first distillation tower. The heat of the second evaporator 4 is required to evaporate CO2 and discharge and collect it from the gas outlet at the top of the second distillation tower, and at the same time discharge NO2 in liquid form from the liquid outlet at the bottom of the second distillation tower to remove NO2.

[0049] More preferably, the dehydration subsystem is also directly connected to the inlet of the refrigeration subsystem through valve V19. When the raw gas flow rate is constant, the raw gas after dehydration is divided into one path for direct liquefaction, so that the flow rate of the raw gas entering the first evaporator and the second evaporator can be further balanced, so that the first distillation tower can remove NO as much as possible with as little loss of CO2 as possible, and avoid evaporating CO2 as much as possible while avoiding the evaporation of NO2 in the second distillation tower. The control process of the raw gas flow in the three pipelines is as described above and will not be repeated here.

[0050] In a preferred embodiment, the middle of the first distillation tower 1 and the second distillation tower 2 are filled with fillers (such as stainless steel structured packing), and the falling liquid and the rising steam are in contact with the fillers, which is beneficial to increase the heat exchange area between the rising high-temperature steam and the falling low-temperature liquid, so as to achieve a better heat exchange effect.

[0051] In a preferred embodiment, a waste gas flow meter 6 is further provided at the gas outlet at the top of the first distillation tower 1. The amount of NO detected by the waste gas flow meter 6 is compared with the known amount of NO in the raw gas. On the one hand, it can provide a reference for whether the NO content in the raw gas is removed below the set threshold, and then the NO set at the gas outlet at the top of the second distillation tower 2 is used to determine whether the NO content in the raw gas is removed below the set threshold. X Analyzer 7 detects NO X If the gas exceeds the set threshold, the amount of dehydrated raw gas entering the first evaporator and the second evaporator is adjusted to remove NO and NO2 impurities below the set threshold. On the other hand, when three pipelines are set, it is possible to X The analyzer 7 cooperates to determine the minimum flow rate of the raw gas entering the first evaporator and the maximum flow rate of the raw gas entering the second evaporator, and further optimizes the flow distribution in the three pipelines.

[0052] In a preferred embodiment, the top gas outlet of the second distillation tower 2 is also connected to the refrigeration subsystem (the first refrigerator 5) through a valve (not shown in the figure). XWhen the analyzer 7 detects that the content of NO or NO2 exceeds the threshold value, the gas at the top of the second distillation tower 2 is controlled by a valve to be re-introduced into the first refrigerator 5 for liquefaction and then enters the first distillation tower 1 for separation again.

[0053] In a preferred embodiment, the top gas outlet of the second distillation tower 2 is also connected to the second refrigerator 14 through a valve V16. The high-purity CO2 gas at the bottom of the tower is controlled by the valve to be cooled into liquid CO2 by the second refrigerator 14 and then stored. The liquid CO2 containing NO2 at the bottom is passed into the treatment system for waste liquid treatment.

[0054] Since the CO2 raw gas from carbon capture and compressed by the compressor contains a certain amount of saturated water, it needs to be dehydrated before entering the refrigerator for liquefaction to prevent water from freezing and causing blockage under low temperature conditions. Therefore, the present invention dehydrates the raw gas through a dehydration subsystem before distillation, and the dehydration subsystem includes at least one group of molecular sieve adsorbers.

[0055] In a preferred embodiment, the dehydration subsystem includes a first molecular sieve adsorber 8 and a second molecular sieve adsorber 9 arranged in parallel, and the inlet end and the outlet end of the first molecular sieve adsorber 8 and the second molecular sieve adsorber 9 are connected to the raw gas main pipe through valves, respectively. Specifically, the inlet end and the outlet end of the first molecular sieve adsorber 8 are connected to the raw gas main pipe through valves V2 and V4, respectively, and the inlet end and the outlet end of the second molecular sieve adsorber 9 are connected to the raw gas main pipe through valves V3 and V5, respectively.

[0056] The outlet ends of the first molecular sieve adsorber 8 and the second molecular sieve adsorber 9 are connected to the outlet end of the heater 10 through valves V7 and V8, respectively, and the inlet end of the heater 10 is connected to the raw gas main through valve V6; at the same time, the inlet ends of the first molecular sieve adsorber 8 and the second molecular sieve adsorber 9 are connected to the inlet ends of the first cooler 11 and the second cooler 12, respectively, the outlet end of the first cooler 11 is connected to the raw gas main through valve V9, and the outlet end of the second cooler 12 is connected to the raw gas main through valve V10.

[0057] The valve switching control makes it possible for one of the molecular sieve adsorbers to adsorb while the other molecular sieve adsorber is regenerated. Preferably, a water analyzer 13 is provided on the raw gas main pipe at the outlet of the first molecular sieve adsorber 8 and the second molecular sieve adsorber 9, which is used to determine whether the first molecular sieve adsorber 8 or the second molecular sieve adsorber 9 is saturated with adsorption, thereby controlling the valve connecting one of the molecular sieve adsorbers to the raw gas main pipe to open and the valve connecting the other molecular sieve adsorber to the raw gas main pipe to close through the automatic valve switching program, and connecting the molecular sieve adsorber to the heater and the cooler, so that the water in the molecular sieve adsorber is analyzed, thereby being regenerated and reused.

[0058] The specific control process is as follows: When the first molecular sieve adsorber 8 performs adsorption, the CO2 raw gas containing NO and NO2 (i.e. Figure 1 The GCO2 in the system enters the system through valve V1, and valves V2 and V4 are opened for adsorption (V3, V5, V6, V7, and V9 are closed). The dehydrated raw gas is sent out through valves V11, V12, and V19. The first molecular sieve adsorber 8 is monitored by a water analyzer 13 to see if the adsorption is saturated. If the adsorption is saturated, valves V2 and V4 are closed, valves V3 and V5 are opened, and the second molecular sieve adsorber 9 starts adsorption. At the same time, valve V6 is opened, and a set amount (about 15% of the total gas volume) of the dehydrated raw gas is heated by a heater 10, and valves V7 and V9 are opened. The first molecular sieve adsorber 8 is regenerated by the heated CO2 gas, and the regenerated CO2 gas is cooled by the first cooler 11 and then merged into the raw gas main pipe for dehydration adsorption, thus completing an adsorption and regeneration cycle. Similarly, if the water analyzer 13 detects that the second molecular sieve adsorber 9 reaches the adsorption saturation state, the second molecular sieve adsorber 9 is controlled to regenerate according to the above principle, and the first molecular sieve adsorber 8 is adsorbed. The adsorption and regeneration of the two molecular sieves are carried out simultaneously, which will not be repeated here.

[0059] It should be noted that in a specific embodiment shown in the accompanying drawings of the present invention, the first molecular sieve adsorber 8 and the second molecular sieve adsorber 9 are connected to the same heater 10 through valves V7 and V8, that is, the raw gas is heated by the same heater and used as a heat source for regeneration; of course, corresponding heaters can be respectively set for the first molecular sieve adsorber 8 and the second molecular sieve adsorber 9 according to actual conditions, that is, the raw gas is heated by the corresponding heaters controlled by valves respectively, as a heat source for the regeneration of the two molecular sieve adsorbers. In addition, the first molecular sieve adsorber 8 and the second molecular sieve adsorber 9 are respectively provided with a first cooler 11 and a second cooler 12, and the two coolers are respectively connected to the raw gas main pipe through valves V9 and V10; similarly, the first molecular sieve adsorber 8 and the second molecular sieve adsorber 9 can also be connected to the same cooler according to actual conditions, and the regenerated CO2 gas output from the two molecular sieve adsorbers is cooled by a common cooler.

[0060] It should also be noted that in the system shown in the drawings, other valves, such as valves V13, V14, V15, V17, V18, etc., can be provided in the corresponding connecting pipelines as required. These valves only serve as switches, and existing valves can be used.

[0061] In addition, under the same pressure, the boiling points of NO, CO2 and NO2 increase in sequence, but under different pressures, the boiling points of NO, NO2 and CO2 are different, so the boiling points of NO, NO2 and CO2 can be controlled by controlling the tower pressures of the first distillation tower 1 and the second distillation tower 2. In the present invention, it is preferred that the tower pressures of the first distillation tower 1 and the second distillation tower 2 are first reached by introducing pure CO2 gas before the raw gas is introduced into the system, and the specific tower pressures can be adjusted according to actual conditions.

[0062] In a specific application, during the distillation process, the tower pressure of the first distillation tower is 17.0~17.8barA, and the temperature inside the tower is -32~-23℃; the tower pressure of the second distillation tower is 17.0~17.8barA, and the temperature inside the tower is -23~-20℃. The above tower pressure and temperature can meet the evaporation temperature requirements of the two distillation towers, and can effectively reduce the trace NO in high-concentration CO2. X Deep removal. In addition, the raw gas after molecular sieve dehydration in the embodiment of the present invention has a temperature of about 40°C and a pressure of 18 barA; the temperature of the raw gas leaving the first evaporator is reduced to about -18~-20°C, and the low-temperature raw gas is cooled to a liquefied to supercooled state by the first refrigerator 5, and the temperature of the liquid CO2 output from the first refrigerator 5 is about -35°C.

[0063] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for deep removal of trace NO from high concentration CO2 X The method is characterized in that The steps include: S1: Dehydrating the CO2 raw gas containing NO and NO2; S2: a first distillation tower with a first evaporator at the bottom and a second distillation tower with a second evaporator at the bottom are provided; the raw gas dehydrated in S1 is used as a heat source to be respectively introduced into the two evaporators, and the raw gas output from the two evaporators is collected and liquefied to obtain liquid CO2 containing NO and NO2; S3: passing the liquid CO2 in S2 into the first distillation tower, controlling the flow rate of the feed gas passing into the first evaporator, reaching the boiling point of CO2 under the heat provided by the feed gas so that part of the CO2 evaporates, and removing NO while discharging from the gas outlet at the top of the first distillation tower, and discharging the liquid CO2 containing NO2 from the liquid outlet at the bottom of the first distillation tower; S4: The liquid CO2 in S3 is passed into the second distillation tower, and the flow rate of the raw gas passed into the second evaporator is controlled. The CO2 is evaporated under the heat provided by the second evaporator and discharged from the top outlet of the second distillation tower and collected. At the same time, NO2 is discharged from the bottom outlet of the second distillation tower in liquid form to remove NO2.

2. The method for deeply removing trace NO from high concentration CO2 according to claim 1 X The method is characterized in that By detecting the NO X Whether the gas exceeds the set threshold, adjust the amount of dehydrated raw gas entering the first evaporator and the second evaporator; If it is detected that NO exceeds the set threshold, the amount of raw gas introduced into the first evaporator is increased; if it is detected that NO2 exceeds the set threshold, the amount of raw gas introduced into the second evaporator is reduced.

3. The method for deeply removing trace NO from high concentration CO2 according to claim 1 X The method is characterized in that In step S2, the dehydrated raw gas is divided into three routes, including a first pipeline leading to the first evaporator, a second pipeline leading to the second evaporator, and a third pipeline for direct liquefaction.

4. The method for deeply removing trace NO from high concentration CO2 according to claim 3 X The method is characterized in that When the total flow rate of raw gas is constant, the control process of the raw gas flow rate in the three pipelines is as follows: Detect NO at the outlet of the second distillation tower X Whether the gas exceeds the set threshold; If it is detected that NO exceeds the set threshold, the amount of raw gas introduced into the first pipeline is increased, and the amount of raw gas introduced into the second pipeline is reduced or the amount of raw gas directly liquefied is reduced; if it is detected that NO2 exceeds the set threshold, the amount of raw gas introduced into the second pipeline is reduced, and the amount of raw gas introduced into the first pipeline is increased or the amount of raw gas directly liquefied is increased.

5. The method for deeply removing trace NO from high concentration CO2 according to claim 3 X The method is characterized in that When the total flow rate of raw gas is constant, the control process of the raw gas flow rate in the three pipelines is as follows: 1) introducing the raw gas into the first pipeline, and gradually increasing the amount of the raw gas introduced into the first pipeline, detecting the amount of NO output from the gas outlet of the first distillation tower, and comparing the amount of NO with the amount of NO in the raw gas, until the amount of NO output is not greater than a set threshold value, that is, obtaining the minimum flow rate of the raw gas introduced into the first pipeline; 2) All the remaining raw gas is introduced into the second pipeline, and the amount of NO2 in the gas outlet of the second distillation tower is detected. If it is less than the set threshold, the maximum flow rate is obtained; if it is greater than the set threshold, the flow rate introduced into the second pipeline is gradually reduced until the output amount of NO2 is no greater than the set threshold, that is, the maximum flow rate of the raw gas introduced into the second pipeline is obtained; 3) The remaining raw gas is introduced into the third pipeline and directly liquefied.

6. A method for deep removal of trace NO from high concentration CO2 X A system, characterized in that It includes dehydration subsystem, refrigeration subsystem and distillation subsystem; The rectification subsystem comprises a first rectification tower with a first evaporator at the bottom and a second rectification tower with a second evaporator at the bottom, and both the first rectification tower and the second rectification tower have a liquid inlet and a gas outlet at the top, and a liquid outlet at the bottom; The dehydration subsystem is connected to the inlet of the first evaporator and the second evaporator through pipelines, so as to dehydrate the CO2 raw gas containing NO and NO2 and pass it into the two evaporators as a heat source; the outlets of the first evaporator and the second evaporator are connected to the inlet of the refrigeration subsystem, so as to liquefy the CO2 raw gas to obtain liquid CO2 containing NO and NO2; The outlet of the refrigeration subsystem is connected to the liquid inlet of the first distillation tower, so that the liquid CO2 is passed into the first distillation tower, and the boiling point of CO2 is reached under the heat provided by the first evaporator to make part of the CO2 evaporate, and NO is removed while being discharged from the gas outlet of the first distillation tower; the liquid outlet of the first distillation tower is connected to the liquid inlet of the second distillation tower, so that the liquid CO2 containing NO2 discharged from the liquid outlet of the first distillation tower is passed into the second distillation tower, and the CO2 is evaporated under the heat provided by the second evaporator and discharged and collected from the gas outlet of the second distillation tower, and NO2 is discharged from the liquid outlet of the second distillation tower in liquid form to remove NO2.

7. The method for deeply removing trace NO from high concentration CO2 according to claim 6. X A system, characterized in that The outlet of the second distillation tower is provided with NO X The analyzer detects NO X Whether the gas exceeds the set threshold, adjust the amount of dehydrated raw gas entering the first evaporator and the second evaporator; If it is detected that NO exceeds the set threshold, the amount of raw gas introduced into the first evaporator is increased; if it is detected that NO2 exceeds the set threshold, the amount of raw gas introduced into the second evaporator is reduced.

8. The method for deeply removing trace NO from high concentration CO2 according to claim 6 X A system, characterized in that The dehydrated raw gas is divided into three paths. The dehydration subsystem is connected to the first evaporator through a first pipeline, connected to the second evaporator through a second pipeline, and directly connected to the refrigeration subsystem through a third pipeline.

9. The method for deeply removing trace NO from high concentration CO2 according to claim 8. X A system, characterized in that The outlet of the second distillation tower is provided with NO X Analyzer, when the total flow rate of raw gas is constant, the control process of the raw gas flow in the three pipelines is as follows: If it is detected that NO exceeds the set threshold, the amount of raw gas entering the first evaporator is increased, and the amount of raw gas entering the second evaporator is reduced, or the amount of raw gas directly entering the refrigeration subsystem is reduced; if it is detected that NO2 exceeds the set threshold, the amount of raw gas entering the second evaporator is reduced, and the amount of raw gas entering the first evaporator is increased, or the amount of raw gas directly entering the refrigeration subsystem is increased.

10. The method for deeply removing trace NO from high concentration CO2 according to claim 8 X A system, characterized in that The outlet of the first distillation tower is provided with an exhaust gas flow meter, and the outlet of the second distillation tower is provided with a NO X Analyzer; When the total flow rate of raw gas is constant, the control process of the raw gas flow rate in the three pipelines is as follows: 1) introducing the raw gas into the first pipeline, and gradually increasing the amount of the raw gas introduced into the first pipeline, detecting the amount of NO output from the gas outlet of the first distillation tower, and comparing the amount of NO with the amount of NO in the raw gas, until the amount of NO output is not greater than a set threshold value, that is, obtaining the minimum flow rate of the raw gas introduced into the first pipeline; 2) All the remaining raw gas is introduced into the second pipeline, and the amount of NO2 in the gas outlet of the second distillation tower is detected. If it is less than the set threshold, the maximum flow rate is obtained; if it is greater than the set threshold, the flow rate introduced into the second pipeline is gradually reduced until the output amount of NO2 is no greater than the set threshold, that is, the maximum flow rate of the raw gas introduced into the second pipeline is obtained; 3) The remaining raw gas is introduced into the third pipeline and directly liquefied.

11. The method for deeply removing trace NO from high concentration CO2 according to any one of claims 6 to 10. X A system, characterized in that The dehydration subsystem comprises a first molecular sieve adsorber and a second molecular sieve adsorber arranged in parallel, wherein the inlet end and the outlet end of the first molecular sieve adsorber and the second molecular sieve adsorber are respectively connected to the raw gas main pipe through valves; The outlet ends of the first molecular sieve adsorber and the second molecular sieve adsorber are respectively connected to the outlet end of the heater through valves, and the inlet end of the heater is connected to the raw gas main pipe through a valve; at the same time, the inlet ends of the first molecular sieve adsorber and the second molecular sieve adsorber are respectively connected to the inlet end of the cooler, and the outlet end of the cooler is connected to the raw gas main pipe through a valve; the valves are alternately controlled so that when one of the molecular sieve adsorbers is adsorbing, the other molecular sieve adsorber is regenerated.

12. The method for deeply removing trace NO from high concentration CO2 according to claim 11. X A system, characterized in that A water analyzer is provided on the raw gas main pipe at the outlet of the first molecular sieve adsorber and the second molecular sieve adsorber, which is used to determine whether the first molecular sieve adsorber or the second molecular sieve adsorber is saturated with adsorption, thereby controlling the valve connecting one of the molecular sieve adsorbers to the raw gas main pipe to open, and the other molecular sieve adsorber to be connected to the heater and the cooler to achieve regeneration.

13. The method for deeply removing trace NO from high concentration CO2 according to any one of claims 6 to 10 or 12. X A system, characterized in that The gas outlet at the top of the second distillation tower is connected to the refrigeration subsystem through a valve to X When the analyzer detects that the content of NO or NO2 exceeds the threshold, the top gas of the second distillation tower is reliquefied and then passed into the first distillation tower for separation again; The top gas outlet of the second distillation tower is also connected to a refrigerator through a valve to liquefy the CO2 gas with the required purity at the top of the tower and store it.

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