Method and apparatus for releasing gas

Abstract

The present invention provides a method and apparatus for separating CO2 and releasing the gas. [Solution] The apparatus comprises a contact tower (T) having a lower section (I), an upper section (C), and a heat and mass transfer promoting means (P) within the lower section; a CO2 capture unit (PSA, CB); means for supplying gas to the capture unit; means for supplying high nitrogen gas (N) from the capture unit to the bottom of the lower section of the cooling tower; means for supplying water (H) above the lower section of the tower and below the upper section; and means connected at a height above the lower section for supplying released gas (G), which is a portion of the gas separated in the capture unit.

Description

Technical Field

[0001] The present invention relates to a method and an apparatus for discharging gas.

Background Art

[0002] In many cases, it is necessary to discharge gas by diffusing it so that the gas does not exist on the ground surface or inside or near a house. Such gas may contain at least 15 mol% of CO2, at least 30 mol% of CO2, at least 60 mol% of CO2, and according to some, at least 90% of CO2.

[0003] The gas to be discharged can originate from, for example, at least one cement factory, and / or at least one lime production unit, and / or at least one combustion furnace, and / or at least one oxy-fuel combustion unit, and / or at least one steam methane reformer (SMR), and / or at least one autothermal reformer (ATR), and / or a metal production unit.

[0004] Alternatively, the gas to be discharged can originate from a CO2 capture unit provided with gas generated from at least one cement factory, and / or at least one lime production unit, and / or at least one combustion furnace, and / or at least one oxy-fuel combustion unit, and / or at least one steam methane reformer (SMR), and / or at least one autothermal reformer (ATR).

[0005] The CO2 capture unit can include an adsorption separation unit and / or a unit for separation by partial condensation and / or distillation and / or freezing.

[0006] Separating the gas coming from one of the above sources in an adsorption separation unit, such as a PSA unit, that produces low CO2 gas and high CO2 gas is a known practice, and the high CO2 gas is then supplied for separation to a unit for separation by partial condensation and / or distillation and / or freezing.

[0007] Processes for capturing CO2 from flue gases from cement plants, lime production units, combustion furnaces, oxygen combustion units, SMRs, etc., typically include a first step of cooling and scrubbing the flue gas. Scrub scrubbing and cooling are often carried out in one or more scrubbing towers and optionally include the injection of a basic agent. The scrubbed and cooled gas is then supplied to a filter to remove dust before typically being drawn out in a first compressor. Finally, in some configurations, a fan is used to discharge or draw in the flue gas from the discharge point to the inlet of the CO2 capture unit (depending on whether the fan is located near the discharge point or near the CO2 capture unit).

[0008] A typical CO2 capture unit separates the aforementioned scrubbing, cooling, and compressed (and possibly dried) gas by fractional condensation and / or distillation and / or solidification.

[0009] The CO2 capture unit enriches the treated gas with CO2, particularly by exhausting the high nitrogen gas contained in the flue gas into the atmosphere via a pipe, in order to move the gas to a location safe for workers. The gas may come from, for example, an adsorption separation unit, which is a low CO2 gas, and / or from a unit for separation by partial condensation and / or distillation and / or solidification. When the flue gas contains a large amount of nitrogen (>15 mol%, preferably >25 mol%, preferably >50 mol%), the high nitrogen gas may be used to produce chilled water (<25°C, preferably <15°C) by a water / nitrogen tower, and this water is used in the CO2 capture process (e.g., to cool the gas at the inlet of the dryer) or elsewhere. The high nitrogen gas is colder than the water being cooled because it undergoes continuous changes such as compression, cooling, and expansion in the CO2 capture unit.

[0010] Such processes are described in EP1712858A1 and EP0503910A1.

[0011] A water / nitrogen tower may have an exhaust pipe for high-N2 gas located at the top of the tower, thereby, · Installation area, • Civil engineering work required to support exhaust pipes for high-nitrogen gases. • Pressure drop, • Costs are reduced (the exhaust pipe starts above the water / nitrogen tower).

[0012] If the CO2 capture unit unexpectedly stops (for example, if the scrub tower, filter, or flue gas compressor stops operating), it is necessary to be able to immediately release the flue gas to minimize the impact on upstream equipment, and in particular to avoid unexpected shutdowns of the flue gas discharge unit due to sudden pressure changes downstream of the discharge unit. Furthermore, it is necessary to be able to release the flue gas while various equipment components are starting up in sequence, and also when valves are opened (pressure safety measures).

[0013] Solutions for redirecting flue gas to a discharge point (such as a damper) generally have too long a reaction time (control system reaction time and equipment reaction time) for interruptions that the discharge unit can tolerate, considering that the buffer gas capacity provided by the connection between the discharge unit and the capture unit is small (particularly due to the low pressure of the flue gas).

[0014] If a chimney already exists (especially at the outlet of the exhaust unit), and it is not too far from the CO2 capture unit, then that chimney can be used in the event of an unexpected failure of the CO2 capture unit. If the exhaust unit is far from the CO2 capture unit, then in terms of technical feasibility and cost, • Construct a flue gas discharge chimney for the CO2 capture unit, or • Constructing a low-pressure pipe to transport flue gas from the capture unit to the existing chimney of the discharge unit. While this is necessary, the construction of low-pressure pipes presents technical challenges regarding the risk of pipe corrosion due to the risk of condensation of humid acidic gases.

[0015] The use of a water / nitrogen tower to produce ice-cooled water is well known in air / gas separation units. Typically, this tower consists of a metal or concrete chamber, where packing allows for good contact between water and gas. The tower sometimes has a chimney located at the top, depending on local constraints on the emission of the exhaust gas.

[0016] The materials used are typically carbon steel or concrete, as the droplets contained in the exhaust gas are not corrosive.

[0017] The use of water / nitrogen columns to produce ice-cold water is also known in units for capturing CO2 from flue gases by partial condensation and / or distillation and / or solidification to produce cold water for reuse in the process. High nitrogen gas can be produced from cryogenic separation by partial condensation and / or distillation and / or solidification, or from an adsorption separation step upstream of cryogenic separation. Typically, in these processes, high nitrogen gas with a high water content is discharged through a dedicated chimney or exhaust chimney, while high nitrogen gas is discharged through a pipe connected to a water / nitrogen column. [Overview of the project]

[0018] The present invention proposes using a nitrogen / water tower to release CO2-containing gases, except for the nitrogen supplied to the bottom of the tower. In one modification, the present invention proposes combining a water / nitrogen tower with a localized chimney, for example in a CO2 capture unit, for exhausting combustion flue gases or gases generated from combustion flue gases, in order to reduce the number of emission points and the total number of chimneys (reducing cost and visual impact, and improving miniaturization and technical feasibility).

[0019] The present invention minimizes the number of components by integrating a water / nitrogen tower with a local chimney for exhausting gas, such as flue gas or gases resulting from the treatment of flue gas (e.g., flue gas after steps of water scrubbing, alkaline chemical scrubbing, filtration, and / or compression). The present invention avoids the need to construct a dedicated local chimney for exhausting flue gas or gases resulting from the treatment of flue gas, and the need to associate it with a regulated exhaust control device. The present invention also avoids the need to construct a pipe to return flue gas to an existing chimney, even if it is far from the CO2 capture unit. The present invention also makes it possible to limit the risk of flue gas exhaust unit interruption due to CO2 capture unit interruption in the event of abrupt changes in process conditions and / or unexpected shutdown of a part of the unit (which could lead to warnings or triggers in upstream units, or operation of upstream units under conditions different from their intended operating conditions). Such interruptions can occur when valves open, or when the unit exceeds acceptable temperature, pressure, flow rate, or composition values ​​from an equipment design or safety standpoint.

[0020] The exhaust gas is a gas that is supplied to the atmosphere at least at specific locations and contains at least one pollutant, such as CO or CO2, at at least specific locations.

[0021] FR2976059A1 describes a method relating to the preamble of claim 1. According to one subject of the present invention, a method for releasing a gas is provided, in this method, i) During a first operating mode, a gas stream containing at least 50 mol% nitrogen, preferably at least 70 mol% nitrogen, is supplied to a contact tower, the contact tower comprising a lower section, an upper section, and heat and mass transfer facilitating means in the lower section at a first height at the bottom of the lower section, the tower is given a water stream arriving at a second height in the lower section above the first height, the gas stream being colder or at the same temperature as the water stream entering the tower, the cooling water being drawn out from the bottom of the tower, the water-enriched gas stream exiting to the atmosphere from the top of the tower, and no gas being supplied to the tower at heights above the first height. ii) During the second operating mode, a) A gas stream containing at least 50 mol% nitrogen is supplied to the contact tower at a first height, the tower is given a water stream arriving at a second height above the first height, the gas stream being colder or at the same temperature as the water stream entering the tower, cooling water being drawn out from the bottom of the tower, the released gas being supplied to the tower at a third height above the second height, the water-enriched gas stream being released upward and mixed with the gas exiting the tower, exiting from the top of the tower, and / or b) After or instead of step a), a gas stream containing at least 50 mol% nitrogen is not supplied to the contact column, the column is not given a water stream arriving at a second height above the first height, the gas to be released is supplied to the column at a third height above the second height, the water-enriched gas stream is released upward and mixed with the gas exiting the column, and exits from the top of the column.

[0022] According to several optional configurations, the following applies:

[0023] • The released gas contains at least 15 mol% CO2.

[0024] · The gas released is at least a part of the exhaust gas from a source that can be at least one combustion unit, and / or at least one oxy-fuel combustion unit, and / or at least one cement plant, and / or at least one lime production unit, and / or at least one metal production unit, and / or at least one steam reforming unit, and / or at least one autothermal reforming unit.

[0025] · The exhaust gas is supplied to at least one carbon dioxide capture unit for separation, at least during the first operating mode.

[0026] · The exhaust gas contains nitrogen, and the gas stream supplied to the column results from at least one CO2 adsorption or permeation unit that produces at least one or the at least one carbon dioxide capture unit, preferably the high CO2 gas that is then separated in the capture unit and the low CO2 gas that constitutes the gas stream supplied to the column.

[0027] · The exhaust gas containing CO2 and nitrogen generated from a source that can be at least one combustion unit, and / or at least one oxy-fuel combustion unit, and / or at least one cement plant, and / or at least one lime production unit, and / or at least one metal production unit, and / or at least one steam reforming unit, and / or at least one autothermal reforming unit is supplied to the carbon dioxide capture unit at least during the first operating mode and the second operating mode, or the exhaust gas containing CO2 and nitrogen generated from a source that can be at least one combustion unit, and / or at least one oxy-fuel combustion unit, and / or at least one cement plant, and / or at least one lime production unit, and / or at least one metal production unit, and / or at least one steam reforming unit, and / or at least one autothermal reforming unit is supplied to at least one carbon dioxide capture unit at least during the first operating mode and the second operating mode, and the gas released results from at least one capture unit.

[0028] The released gases are produced by scrubbing the exhaust gas containing CO2 and nitrogen, and / or by compression of the exhaust gas containing CO2 and nitrogen, and / or by adsorption or permeation separation of the exhaust gas containing CO2 and nitrogen, and / or by drying of the exhaust gas containing CO2 and nitrogen, and / or by partial condensation and / or distillation and / or solidification of the gas produced by the separation of the exhaust gas containing CO2 and nitrogen or the exhaust gas containing CO2 and nitrogen.

[0029] The second operating mode corresponds to the interruption and / or unintended stopping and / or starting of the unit, resulting in the release of gas from the unit.

[0030] In the third operating mode immediately following the second operating mode, the emitted gas is no longer supplied to the tower but is supplied to the exhaust chimney, and at least one other gas originating from the source is supplied to the exhaust chimney.

[0031] • The first operating mode corresponds to the normal operating mode of the capture unit.

[0032] • The second operating mode lasts for less than one hour, possibly less than 10 minutes.

[0033] In the second operating mode, the released gas is supplied to the tower over a specific time period, and preferably, at the end of the specific time period, the released gas is supplied to another location.

[0034] In the second operating mode, the first gas to be released is supplied to the tower, and in the third operating mode, the second gas to be released is supplied to the tower, and the first and second gases have at least one common composition that is at least 5 mol% different and / or have at least 40°C different temperatures, and each of the first and second gases is either a portion of the exhaust gas or a gas produced from a CO2 capture unit, and the first and second gases are not supplied to the tower during both the second and third operating modes.

[0035] • The gas flow is at a temperature below 20°C.

[0036] • The gas flow is dry.

[0037] The released gas is at a temperature higher than 20°C, possibly even higher than 70°C.

[0038] • The released gas is moist.

[0039] • The water droplet removal element is located below the top.

[0040] • Exhaust gas is separated by fractional condensation and / or distillation and / or coagulation, without being separated by adsorption to remove components other than water.

[0041] The exhaust gas is treated by adsorption to remove any contained water, and then separated by fractional condensation and / or distillation and / or solidification.

[0042] • Exhaust gas is separated by adsorption to remove components other than water, such as nitrogen and / or hydrogen, and then separated by fractional condensation and / or distillation and / or solidification.

[0043] Another object of the present invention is to provide a device for separating CO2 and releasing the gas, the device comprising: a contact tower having a lower section, an upper section, and means for promoting heat and mass transfer within the lower section; a CO2 capture unit; means for supplying a gas optionally containing at least 15% CO2 to the CO2 capture unit; means for supplying high nitrogen gas from the CO2 capture unit to the bottom of the lower section of the cooling tower; means for supplying water above the lower section of the tower and below the upper section at a temperature hotter than or equal to the temperature of the high nitrogen gas entering the tower; and means connected at a height above the lower section for supplying a portion of the gas separated in the CO2 capture unit and / or a released gas which is the gas processed in the CO2 capture unit.

[0044] The lower section preferably has a larger diameter than the upper section.

[0045] The present invention • Contacting water with a gas containing at least 50 mol% nitrogen and possibly other components lighter than CO2, and which is colder than water, to produce cooling water at a temperature lower than that of the cooling water network, for example. • Releasing a nitrogen-rich gas saturated with water (the gas is produced by the contact of liquid and vapor in the preceding step) containing at least 50 mol% nitrogen and possibly other components lighter than CO2, for example, in a safe place. • Functions added by the present invention: Releasing gas generated from the flue gas of the exhaust unit into the atmosphere, for example, in a safe location, i.e., i) For flue gases from the exhaust unit, connect the exhaust line to a safe location for releasing the flue gases into the atmosphere, or ii) Connecting the exhaust line for flue gas from the exhaust unit after pretreatment (e.g., scrubbing with water, scrubbing with a basic chemical, physical filtration, compression, and / or drying), This can consist of equipment for a water / nitrogen tower that combines these functions.

[0046] The water / nitrogen tower may be part of a CO2 capture unit and can enable the production of ice-cold water from low-CO2 gas containing at least 50 mol% nitrogen, generated by a CO2 PSA that is part of or constituting the capture unit. This impurity nitrogen contains a significant proportion of CO2 (e.g., 0.1% to 2%). To dissolve this CO2 in ice-cold water, a water / nitrogen tower made of material resistant to pH lower than 3.5 (or more broadly, acidic pH, i.e., pH < 7) is required. The ice-cold water tubing network is also made of material resistant to pH lower than 3.5.

[0047] Except during startup and unexpected shutdown phases, the water / nitrogen column operates normally, and high nitrogen gas (nitrogen content >50 mol%, preferably >70 mol%) is injected into the bottom of the column through a dedicated inlet, as in the conventional manner. The packing material in the column allows the water flowing above it to evaporate, adding water vapor to the gas. This evaporation is endothermic, allowing the remaining portion of the water flowing to the bottom of the column to cool before being pressurized into the ice-cooled water section.

[0048] The upper part of the tower is used in the event of at least one of the startup or unexpected shutdown of one of the elements of the flue gas treatment unit or CO2 capture unit shown in the diagram below (water scrubbing, basic chemical scrubbing, heater, blower, filtration, compression, drying, separation by PSA process).

[0049] If one of these elements unexpectedly fails, the gas at the outlet of the last remaining element is supplied to the water / nitrogen tower and released into the atmosphere from the top (chimney) of the water / nitrogen tower.

[0050] In particular, if the scrub scrub tower unexpectedly stops, it is necessary to release high-temperature polluting gases into the atmosphere. These gases generally contain high levels of acids (e.g., NOx and SOx) and dust. Releasing these polluting gases from the tower into the atmosphere for an excessively long period of time could risk concentrating these acids and dust in the ice-cooled water circuit. Therefore, flue gases can only be released from this chimney for short periods of time. Dispersive purging makes it possible to disperse the dust and acids accumulated in the ice-cooled water circuit. Exhaust into this chimney is typically limited to the period necessary to stop the flue gases from being introduced into the CO2 capture unit and redirect these flue gases towards the existing chimney of the discharge unit. The flue gases are redirected towards the discharge unit's chimney by a set of valves or dampers between the discharge unit and the CO2 capture unit. The temporary phase of exhausting the gas into the water / nitrogen tower lasts from a few seconds to several minutes, depending on the damper opening / closing reaction time, the reaction time of the control system (e.g., DCS), the amount of equipment, and the sensitivity of the upstream process (of the exhaust unit) to the interruption of the downstream process.

[0051] More generally, this refers to the temporary exhaust of flue gas or gases resulting from the treatment of flue gas in a water / nitrogen tower, due to material selection, environmental constraints, and the need to control solid particles and impurities within the water / nitrogen tower.

[0052] The flue gas is hot and humid, and when released through a cold chimney (cooled by nitrogen exiting the water / nitrogen tower during normal operation), it will cause acid and water to condense on the walls. These acidic droplets will flow to the bottom of the water / nitrogen tower. This does not present a particular problem as the flue gas is released at a limited frequency over a limited time period, and the ice-cooled water circuit is sized to withstand corrosion at a pH close to 3. Furthermore, pressure-increasing elements (blowers, compressors) are expected to be triggered more frequently than in the scrub cleaning tower, thereby limiting the frequency with which dust and strong acid (SO3, H2SO4, HCl, HF, HBr, etc.)-rich flue gas is supplied to the water / nitrogen tower chimney.

[0053] Nitrogen and high-temperature contaminated flue gas are never exhausted simultaneously, and high-temperature contaminated flue gas is only exhausted in the event of an unexpected shutdown of the scrub tower. However, this unexpected shutdown also includes stopping nitrogen discharge. Since the compressor is expected to shut down unexpectedly more frequently than the scrub tower, the exhaust gas from the flue is usually cooled and scrubbed (with water and one or more basic chemicals) before being supplied to the chimney of the water / nitrogen tower. In particular, the scrub tower is sized to avoid frequent unexpected shutdowns (e.g., redundancy of circulation pumps).

[0054] Finally, the present invention makes it possible to concentrate all exhaust at a single point, and these exhausts are continuous and / or require an emission permit. Thus, either during startup or continuous operation of the CO2 capture unit, all vents, especially those containing hazardous impurities (e.g., NOx and SOx), are directed towards this single chimney. This thus makes it possible to have a single emission point for the entire capture unit.

[0055] The present invention will be described in detail with reference to the figures. [Brief explanation of the drawing]

[0056] [Figure 1] A cooling tower for use in the method of the present invention is shown. [Figure 2] The method according to the present invention is outlined below. [Modes for carrying out the invention]

[0057] [Figure 1] shows a cooling tower comprising a lower section I containing packing material P to facilitate the exchange of matter and heat, and an upper section C having a smaller diameter than the lower section and containing no packing material. The bottom of the tower T has an inlet for gas N, which is preferably dry, at a temperature below 20°C, contains at least 50 mol% nitrogen, and does not contain solid particles. The tower has a water inlet H at the top of the lower section and below the upper section C. The tower has a cooling water outlet HR at the bottom. At the bottom of the tower, above the water inlet H, there is a water droplet removal element DM, which is located below the upper section C. A gas inlet G for the gas to be released is located below the upper section C, in a frustoconical section connecting the upper section C to the lower section I. Gas G is moist and can be at a temperature above 20°C, possibly above 70°C.

[0058] Therefore, contact between gas N and water H makes it possible to cool the water exiting from the bottom of the tower T. The moist nitrogen rises within the lower part I, some of the water is removed by element DM, and when gas G is present, it mixes with gas G and exits from the upper part C. Even when gas G is absent, a nitrogen-rich moist gas exits from the upper part C.

[0059] The upper part C, preferably only the upper part, may be made of ferrite-austenite type or austenitic steel type stainless steel.

[0060] Lower section I and upper section C may be made of stainless steel or any other material resistant to corrosion at a pH close to 3.

[0061] Gas G is supplied to the tower for a short period of time, preferably less than 1 hour, and possibly less than 10 minutes, depending on its composition, and the supply is regulated by a timer, a suitable control system and / or a set of valves or dampers.

[0062] Figure 2 schematically illustrates the method according to the present invention.

[0063] The emission unit UE may be at least one cement plant and / or at least one lime production unit and / or at least one combustion furnace and / or at least one oxygen combustion unit and / or at least one steam methane reformer (SMR) and / or at least one self-heating reformer (ATR).

[0064] In the first operating mode, the exhaust unit UE produces a gas F (often called flue gas) containing CO2 and nitrogen. Gas F may also contain at least one component selected from the list of oxygen, argon, carbon monoxide, hydrogen, dust, strong acids (SO3, H2SO4, HCl, HF, HBr, etc.), SOx, and NOx. Gas F is supplied to the CO2 capture unit CC, where it is treated first by scrubbing with water L, and optionally then by scrubbing with a basic agent LB. The scrubbed gas is heated by a heater R, compressed by a blower SF, filtered in a filtration unit to remove dust if present, compressed by a compressor V, dried by a dryer S, and separated by adsorption in unit PSA to form a high CO2, low nitrogen gas TG and a high nitrogen, low CO2 gas N containing at least 50 mol% nitrogen. The high-CO2 gas is compressed to form compressed gas CTG, which is cooled and then separated in the cryogenic separation unit CB by partial condensation and / or distillation and / or solidification to form low-CO2, high-oxygen and / or high-nitrogen and / or high-argon gas IN and CO2-rich fluid CO2. Gas N is supplied to the bottom of the cooling tower T in [Figure 1], and the tower has a lower section I and an upper section C. Water is supplied to the lower section of tower T to be cooled to a temperature above the temperature of gas N, and the cooled water exits from the bottom of tower T. Due to the evaporation of water, cold air is generated in addition to heat exchange. In the second operating mode, • At least a portion of the gas F emitted from unit UE, and / or · At least a portion of the gas F treated in the capture unit CC by a process using at least one of the following means: scrubbing with water L, scrubbing with a basic agent LB, heating R, compression with a blower SF, filtration in a filtration unit F to remove dust if present, compression with a compressor V, drying with a dryer S, and separation by adsorption in unit PSA. • and / or a portion of gas TG, • and / or a portion of the gas CTG, and / or • At least a portion of the gas in, It may be necessary to supply it to the air.

[0065] This second operating mode can be used when unit CB and / or unit PSA and / or unit UE are stopped, and when a unit is completely stopped, at least one gas is temporarily supplied to the air. If a unit is stopped and its pressure drops, nitrogen N is temporarily supplied to column T. If nitrogen N is no longer supplied to column T, gas G and / or TG and / or CTG and / or IN is supplied to column T.

[0066] However, in the second operating mode, it is possible that the compressor V1 downstream of the PSA stops, but the remaining equipment upstream of compressor V1 does not stop. In this case, nitrogen N and CO2-containing gases G and / or TG and / or CTG and / or IN are supplied to column T (for a longer period of time than in the above case).

[0067] In this case, gas G from the exhaust unit UE, which is part of or composed of gas F, may be supplied to the bottom of the upper C of the tower T without being treated by units L, LB, R, SF, etc. In this case, it will probably have a temperature above 20°C, possibly above 70°C, and / or a nitrogen concentration lower than that of gas N.

[0068] As an addition or alternative, gas G treated by at least one of the following means may be supplied to the bottom of the upper C of the column T: scrubbing with water L, scrubbing with a basic agent LB, heating R, compression with a blower SF, filtration in a filtration unit F to remove dust if present, compression with a compressor V, drying with a dryer S, adsorption separation in a unit PSA that generates gas TG (tail gas), compression V1 downstream of unit PSA that generates gas CTG (compressed tail gas), or separation by partial condensation and / or distillation and / or scrubbing and / or coagulation in a unit CB that forms low CO2 gas IN. Therefore, G can be removed as shown in the diagram downstream of the scrub wash with water L and upstream of the scrub wash with basic agent LB, and / or downstream of the scrub wash with basic agent LB and upstream of the heater R, and / or downstream of the heater R and upstream of the blower SF, and / or downstream of the filtration unit F and upstream of the compressor V, and / or downstream of the compressor V and upstream of the dryer D, and / or downstream of the dryer and upstream of separation by permeation or adsorption. It will be understood that at least one of the enumerated elements may not be present. Therefore, if scrub wash with basic agent is not used, the gas is removed between the scrub wash with water L and the heater R.

[0069] It should be understood that gas G may consist of a mixture of at least two gases taken out immediately downstream of different processing units. For example, one gas may be taken out immediately downstream of filtration unit G, and another gas may be taken out immediately downstream of the dryer, and the two gases may be mixed and fed to the tower above the bottom.

[0070] The gas may consist of gases produced from different CO2 capture units, and as a result, tower T functions as a common release tower for multiple capture units.

[0071] It is possible to provide different operating modes to supply various gases G to the tower at different times. For example, in a second operating mode, a first gas to be released is supplied to the tower. This gas may be, for example, a part of gas F. In a third operating mode, a second gas to be released is supplied to the tower, and the first and second gases have a composition of at least one common component that differs by at least 5 mol%, and / or have temperatures that differ by at least 40°C. Each of the first and second gases is either a part of the exhaust gas F or a gas produced from a CO2 capture unit.

[0072] For example, during the first step, a portion of gas F may be supplied to the column as, for example, the sole component of gas G, and during the second step, gas F is no longer supplied to the column, but gas extracted immediately downstream of the processing unit, which is part of the capture unit, may be supplied to the column. This gas may be, for example, dust-free gas at a temperature below 70°C originating from one of the sources, such as the safety valve of the capture unit or the mechanical vent of the capture unit, purge fluid within the capture unit, or products of the capture unit in a desired proportion.

[0073] The separation unit CB may be equipped with a temperature swing adsorption separation unit for drying the gas CTG upstream of the separation by fractional condensation and / or distillation and / or scrubbing and / or solidification. During normal operation, in the first operating mode, a purge (low flow rate) of regenerated gas may also be supplied from this temperature swing adsorption separation unit TSA to column T, optionally by pre-mixing it with nitrogen N.

[0074] During startup, in the second operating mode, nitrogen (N) can be supplied to the column T, and gas can be supplied to the column T along with it (a portion of the N2 flows to the lower part I of the column T, and a portion of the CO2-containing gas flows to the upper part C of the column T).

Claims

1. A method for releasing gas, i. During a first operating mode, a gas stream (N) containing at least 50 mol% nitrogen, preferably at least 70 mol% nitrogen, is supplied to a contact tower (T), the contact tower comprising a lower section (I), an upper section (C), and a heat / mass transfer facilitating means (P) within the lower section at a first height at the bottom of the lower section, the contact tower being given a water stream (H) arriving at a second height of the lower section above the first height, the gas stream being colder or at the same temperature as the water stream entering the contact tower, cooling water (HR) being drawn out from the bottom of the contact tower, the water-enriched gas stream exiting to the atmosphere from the top of the contact tower, and no gas being supplied to the contact tower at heights above the first height. In the method, ii. During the second operating mode, a) A gas stream (N) containing at least 50 mol% nitrogen is supplied to the contact tower at the first height, the contact tower is given a water stream (H) arriving at the second height above the first height, the gas stream is colder than or at the same temperature as the water stream entering the contact tower, cooling water (HR) is drawn out from the bottom of the contact tower, and discharged gases (G, F, TG, CTG, IN) are supplied to the contact tower at the third height above the second height, the water-enriched gas stream is discharged upward and mixed with the gases exiting the contact tower, exiting from the top of the contact tower, and / or b) After step a), or instead of step a), a gas stream containing at least 50 mol% nitrogen is not supplied to the contact tower, and the contact tower is not given a water stream arriving at the second height above the first height, and the discharged gases (G, F, TG, CTG, IN) are supplied to the contact tower at a third height above the second height, and the water-enriched gas stream is discharged upward and mixed with the gases exiting the contact tower, and exits from the top of the contact tower. A method characterized by the following features.

2. The method according to claim 1, wherein the released gas (G, F, TG, CTG, IN) contains at least 15 mol% CO2.

3. The method according to claim 1 or 2, wherein the released gas (G) is at least a portion of exhaust gas (F) from a source (UE) which may be at least one combustion unit and / or at least one oxygen combustion unit and / or at least one cement plant and / or at least one lime production unit and / or at least one metal production unit and / or at least one steam reforming unit and / or at least one self-thermal reforming unit.

4. The method according to claim 3, wherein the exhaust gas (F) is supplied to at least one carbon dioxide capture unit (PSA, CC) for separation, at least during the first operating mode.

5. The method according to any one of claims 1 to 4, wherein the exhaust gas (F) contains nitrogen, and the gas flow (N) supplied to the contact tower (T) originates from at least one or at least one carbon dioxide capture unit (PSA, CB, CC), preferably at least one CO2 adsorption or permeation unit that generates high CO2 gas to be separated in the carbon dioxide capture unit and low CO2 gas constituting the gas flow supplied to the contact tower.

6. The method according to claim 1, wherein exhaust gas (F) containing CO2 and nitrogen, generated from a source (UE) which may be at least one combustion unit and / or at least one oxygen combustion unit and / or at least one cement plant and / or at least one lime production unit and / or at least one metal production unit and / or at least one steam reforming unit and / or at least one self-thermal reforming unit, is supplied to a carbon dioxide capture unit (PSA, CB) at least during the first and second operating modes, or at least one combustion unit and / or at least one oxygen The method according to claim 2 or 5, wherein exhaust gas (F) containing CO2 and nitrogen generated from a source (UE) which may be a combustion unit and / or at least one cement plant and / or at least one lime production unit and / or at least one metal production unit and / or at least one steam reforming unit and / or at least one self-thermal reforming unit is supplied to the at least one carbon dioxide capture unit during at least the first and second operating modes, and the released gas (TG, CTG, IN) is generated from the at least one carbon dioxide capture unit (PSA, CB).

7. The method according to claim 6, wherein the released gases (G, TG, CTG, IN) are produced by scrubbing (L, LB) the exhaust gas containing CO2 and nitrogen, and / or by compression (V) the exhaust gas containing CO2 and nitrogen, and / or by adsorption or permeation separation of the exhaust gas containing CO2 and nitrogen, and / or by drying (S) the exhaust gas containing CO2 and nitrogen, and / or by partial condensation and / or distillation and / or solidification (CB) of the gas produced by the separation of the exhaust gas containing CO2 and nitrogen or the exhaust gas containing CO2 and nitrogen.

8. The method according to any one of claims 1 to 7, wherein the second operating mode corresponds to interruption and / or unintended stopping and / or starting of the unit (UE, PSA, L, LB, R, SF, V, S, PSA, CB, V1), and the gas (G, F, TG, CTG, IN) is released from the unit.

9. The method according to any one of claims 3 to 7, wherein in a third operating mode immediately following the second operating mode, the released gases (G, F, TG, CTG, IN) are no longer supplied to the contact tower (T) but are supplied to the exhaust chimney, and at least one other gas generated from the source (UE) is supplied to the exhaust chimney.

10. The method according to any one of claims 3 to 7, wherein the first operating mode corresponds to the normal operating mode of the carbon dioxide capture unit (PSA, CB, CC).

11. The method according to any one of claims 1 to 10, wherein the second operating mode lasts for less than one hour, possibly less than ten minutes.

12. The method according to any one of claims 1 to 11, wherein in the second operating mode, the released gas (G, TG, CTG, IN) is supplied to the contact tower (T) over a specific time period, and preferably, at the end of the specific time period, the released gas is supplied to another location.

13. The method according to claim 12, wherein in the second operating mode, a first gas (G, TG, CTG, IN) to be released is supplied to the contact tower, and in the third operating mode, a second gas (G, TG, CTG, IN) to be released is supplied to the contact tower, the first gas and the second gas have at least one common composition that differs by at least 5 mol%, and / or have at least 40°C different temperatures, each of the first gas and the second gas is either a portion of the exhaust gas (F) or a gas generated from the CO2 capture unit, and the first gas and the second gas are not supplied to the contact tower in both the second and third operating modes.

14. An apparatus for separating CO2 and releasing gas, comprising: a contact tower (T) having a lower section (I), an upper section (C), and heat and mass transfer promoting means within the lower section; a CO2 capture unit (PSA, CB, CC); means for supplying a gas optionally containing at least 15% CO2 to the CO2 capture unit; means for supplying high nitrogen gas (N) from the CO2 capture unit to the bottom of the lower section of the cooling tower; means for supplying water (H) at a temperature hotter or equal to the temperature of the high nitrogen gas entering the contact tower, above the lower section and below the upper section of the contact tower; and means connected at a height above the lower section for supplying a portion of the gas separated in the CO2 capture unit (PSA, CB, CC) and / or a released gas (G, TG, CTG, IN) which is the gas processed in the CO2 capture unit (PSA, CB, CC).

15. The apparatus according to claim 14, wherein the lower section (I) has a larger diameter than the upper section (C).

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