Method and apparatus for separating a gas containing carbon dioxide by partial condensation and / or distillation
The method integrates NO2 removal and low-temperature condensation/distillation to efficiently separate CO2 from combustion fumes, addressing mercury and NO2 challenges while optimizing energy use and reducing costs.
Patent Information
- Application Number
- FR2023004615
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- Filing Date
- 2023-05-10
- Publication Date
- 2025-10-31
- Estimated Expiration
- 2043-05-10
AI Technical Summary
Existing methods for capturing carbon dioxide from combustion fumes face challenges in efficiently removing mercury and nitrogen oxides, particularly NO2, which can damage aluminum equipment and require significant heating energy, leading to increased costs and equipment material changes.
A method and apparatus that integrates NO2 removal before mercury removal, compresses the gas, uses a mercury adsorption reactor, and employs partial condensation and/or distillation at low temperatures to separate CO2, with heat recovery and reuse, minimizing heating needs and utilizing a turbocharger for energy efficiency.
Effectively separates CO2 with high purity while reducing mercury and NO2 levels, minimizing heating requirements, and recovers residual heat for other process uses, thus enhancing energy efficiency and reducing equipment costs.
Smart Images
Figure 00000009_0000
Abstract
Description
Title of the invention: Method and apparatus for separating a gas containing carbon dioxide by partial condensation and / or distillation
[0001] The present invention relates to a method and apparatus for separating a gas containing carbon dioxide, at least one gas from the air, and mercury and possibly NO2 by partial condensation and / or distillation.
[0002] Air gases include nitrogen, oxygen or argon.
[0003] The invention relates to the integration of a demercurizer into a capture unit of CO2 coming from a gas containing CO2, which could be, for example, fumes from combustion processes.
[0004] According to one object of the invention, a process is provided for separating a gas containing CO2, at least one gas from air and mercury containing the following steps: i. Compression of gas in a turbocharger coupled to a turbine, forming a compressed gas, ii. Heating, if necessary, of the compressed gas at the compressor outlet, and demercurization of the compressed gas, possibly heated, in one or more non-regenerative mercury adsorption reactors producing a demercurized gas, iii. Cooling of the demercurized gas, iv. Separation of the cooled gas in a unit operating at temperatures below 10°C, or even below -50°C, by partial condensation in one or more stages and / or by distillation, producing at least a fluid containing at least 95 mol% or even at least 99 mol% of CO2 and a pressurized stream of CO2-depleted gas and v. At least part of the CO2-depleted gas is expanded in the turbine coupled to the turbocharger, possibly after being heated to a temperature above 10°C.
[0005] According to other optional objects: • The demercurized gas is cooled by indirect heat exchange with a refrigerant. • the refrigerant, preferably water, which was used to cool the demercurized gas is then used to heat a regeneration gas in a CO2-containing gas dryer, at least one gas from air and mercury. • a refrigerant used to cool the demercurized gas is then used to heat at least part of the CO2-depleted gas to be expanded in the turbine. • the refrigerant, preferably water, which was used to cool the demercurized gas is used to heat the compressed gas. • the refrigerant, preferably water, which has been used to cool the demercurized gas, is used for heating and / or cooling at least one building. • The refrigerant is water and, having been used to cool the demercurized gas, is heated to generate water vapor. • the refrigerant, preferably water, which was used to cool the demercurized gas, is used to vaporize a purge liquid from the separation operating at less than 10°C. • the refrigerant, preferably water, which was used to cool the demercurized gas, is used to superheat a humid gas. • The refrigerant, preferably water, used to cool the demercurized gas, is used to heat a flow intended to be expanded in a turbine • the CO2-depleted gas is enriched in at least one gas from the air, for example in nitrogen and / or oxygen and / or argon. • the gas containing CO2, at least one gas of air and mercury contains NO2 and is treated to remove the NO2 in a unit enabling the NO2 to be removed to a concentration of less than 5ppm, or even less than 1ppm in NO2 producing a gas lean in NO2 upstream of compression in the turbocharger. • The treatment to remove NO2 is a separation process by partial condensation and / or distillation. • the gas containing CO2, at least one gas from the air and mercury and possibly NO2 is composed of combustion fumes. • the gas containing CO2, at least one gas from the air and mercury and possibly NO2 is composed of combustion fumes separated by adsorption to reduce their content of at least one gas from the air.
[0006] According to another object of the invention, an apparatus for separating a gas containing CO2, at least one gas from air and mercury is provided, comprising a turbocharger, a turbine coupled to the turbocharger, a mercury removal unit, a cooler, a one- or multi-stage partial condensation separation unit and / or a distillation unit operating at temperatures below 10°C, or even below -50°C, means for sending the gas containing CO2, at least one gas from air and mercury to the turbocharger, means for sending the compressed gas in the turbocharger to the demercurizing unit to form a demercurized gas, means for sending the demercurized gas to the cooler and from the cooler to the separation unit to produce at least a fluid containing at least 95 mol% or even at least 99 mol% of CO2 and a pressurized stream of CO2-depleted gas and means for sending at least a part of the CO2-depleted gas to expand in the turbine coupled to the turbocharger.
[0007] Combustion process fumes contain large quantities of CO2. Capturing the CO2 contained in these fumes is one of the ways being considered to reduce the effects of climate change.
[0008] These fumes contain numerous pollutants, including mercury. Mercury can be particularly damaging to aluminum equipment, as it forms a liquid metallic complex with it, leading to progressive destruction.
[0009] As a result, processes using aluminum equipment (such as cryogenic processes) remove mercury, or move towards more expensive stainless steel equipment.
[0010] Mercury removal is a well-known process, typically carried out by adsorption onto sulfided metals or sulfided activated carbon. It may require heating to limit the amount of NO2 adsorbed (if present) and thus eliminate the risk of auto-ignition of the adsorbent bed. A heat exchanger can recover some of the heat from the treated gas and minimize heating requirements.
[0011] However, the use of conventional adsorbents may be hindered by the presence of nitrogen oxides (NOx), and in particular NO2. Consequently, when these combustion products are present in the flue gases, they must be removed before mercury removal.
[0012] One object of the invention is to minimize the heating energy required for demercurization, while preferably recovering some of this heat for other uses in the capture process.
[0013] The invention proposes an integrated scheme allowing to minimize the need for heat and to valorize the heat used for other consumers of the process.
[0014] The invention aims to treat a gas containing CO2, mercury, nitrogen or another component of air, as well as possibly NO2. For example, this gas could be composed of the fumes from a combustion unit, or of fumes pre-concentrated by a first treatment, such as a pressure-modulated adsorption (PSA) unit.
[0015] These fumes are initially treated to remove any NO2 they contain, typically up to 5 ppm or even 1 ppm of NO2. This treatment can by An example could be a low-temperature treatment such as partial condensation and / or distillation (with possible upstream gas drying).
[0016] The gas, once its NO2 has been removed (if present), is then compressed in a turbocompressor. The gas exiting the machine is hot and may be further heated to reach the conditions necessary for mercury removal. The gas then passes through a mercury remover operating by adsorption, and the mercury-free gas is cooled in a heat exchanger against a refrigerant (for example, water). The outlet temperature of this water is maximized, and the heat it contains can be reused elsewhere in the process (dryer regeneration, gas preheating, building heating, refrigeration, steam production, etc.).
[0017] The compressed and demercurized gas is then processed in a unit operating by partial condensation and / or distillation, in one or more stages. This unit produces CO2, while the non-condensable fraction of the flue gases exiting the unit is expanded in the turbine coupled to the aforementioned compressor.
[0018] These non-condensables can optionally be superheated before expansion, for example against all or part of the heat transfer fluid recovering the heat upstream of the demercurizer.
[0019] The process is characterized by the fact that: • NO2 (if present) is removed before demercurization • The gas is compressed before demercurization • The heat of compression is used to minimize the need for heating before demercurization • Residual heat is recovered and reused • The compressor is driven by the expansion of non-condensables from partial condensation.
[0020] The invention will be described in more detail with reference to the figure:
[0021] [Fig-1] represents a method according to the invention in a schematic way.
[0022] A gas 1 contains CO2, NO2, at least one gas from the air and mercury and may be fumes from a combustion.
[0023] The gas 1 is treated in a unit 3 allowing the NO2 to be removed down to a concentration of less than 5ppm, or even to Ippm of NO2, producing a gas low in NO2 5. The unit 3 can be a separation unit by partial condensation and / or distillation.
[0024] The NO2-lean gas 5 is compressed in a turbocharger C coupled to a turbine T and produces a compressed gas 7. The turbocharger C may not have an aftercooler or may be an adiabatic compressor to maximize the temperature of the gas 7. The compressed gas is optionally heated in a A heater R is placed at the compressor outlet to reach a temperature between 50 and 150°C. Then the gas 7 is demercurized in one or more mercury adsorption reactors D, producing a demercurized gas 9.
[0025] The demercurized gas 9 is cooled in a cooler G using a flow of refrigerant fluid W, for example water.
[0026] The cooled gas 11 in the cooler G is separated in a unit CC operating at temperatures below 10°C, or even below -50°C, by partial condensation in one or more stages and / or by distillation, producing at least one fluid 13 containing at least 95 mol% or even at least 99 mol% of CO2c and a pressurized stream of gas 15 depleted in CO2 and enriched in at least one gas from the air.
[0027] At least part of the CO2-depleted gas 15 is expanded in the turbine T coupled to the turbocharger C, possibly after being heated in a heater H to a temperature above 10°C.
[0028] The expanded gas 17 is evacuated from the process.
[0029] The fluid W used to cool the demercurized gas 9 can be used to heat the gas 15 in the heater H.
[0030] This fluid W can also be used to heat the gas 7 in the heater R, to heat a regeneration gas for a dryer, for example a gas dryer 1 upstream of the unit 3.
[0031] It will be understood that gas 1 does not necessarily contain NO2. In this case, unit 3 is not necessarily present.
Claims
Demands
1. A method for separating a gas containing CO2, at least one gas from air and mercury containing the following steps: i. Compression of the gas (1,5) in a turbocompressor (C) coupled to a turbine (T) forming a compressed gas (7), ii. Heating of the compressed gas at the outlet of the compressor, and demercurization (D) of the heated compressed gas in one or more non-regenerative mercury adsorption reactors producing a demercurized gas (9), iii. Cooling (G) of the demercurized gas, iv. Separation (CC) of the cooled gas (11) in a unit operating at temperatures below 10°C, or even below -50°C, by partial condensation in one or more stages and / or by distillation, producing at least a fluid containing at least 95 mol% or even at least 99 mol% of CO2 (13) and a pressurized stream of CO2-depleted gas (15) and v.At least part of the CO2-depleted gas is expanded in the turbine coupled to the turbocharger, possibly after being heated (H) to a temperature above 10°C. vi. The demercurized gas (9) is cooled by indirect heat exchange with a refrigerant (W) and the refrigerant (W), preferably water, which was used to cool the demercurized gas (9), is used to heat the compressed gas (7) upstream of the demercurization.
2. A method according to claim 1 wherein the refrigerant (W), preferably water, which has been used to cool the demercurized gas (9) is then used to heat a regeneration gas from a CO2-containing gas dryer, at least one gas from air and mercury.
3. Method according to claim 1 or 2 wherein a refrigerant (W) used to cool the demercurized gas is then used to heat at least a part (15) of the CO2-depleted gas to be expanded in the turbine (T).
4. A method according to any one of the preceding claims, wherein the refrigerant (W), preferably water, having been used to cool demercurized gas (9) is used for heating and / or cooling at least one building.
5. A method according to any one of the preceding claims wherein the refrigerant (W) is water and having been used to cool the demercurized gas (9), is heated to generate water vapor.
6. A method according to any one of the preceding claims wherein the CO2-depleted gas (15) is enriched in at least one gas from the air, for example in nitrogen and / or oxygen and / or argon.
7. A method according to any one of the preceding claims wherein the gas containing CO2, at least one gas of air and mercury (1) contains NO2 and is treated to remove the NO2 in a unit (3) enabling the NO2 to be removed to a concentration of less than 5 ppm, or even less than 1 ppm in NO2 producing a NO2-lean gas (5) upstream of compression in the turbocharger.
8. A process according to claim 7 wherein the treatment for removing NO2 is a separation process by partial condensation and / or distillation.
9. A method according to any one of the preceding claims wherein the gas containing CO2, at least one gas from air and mercury and optionally NO2 (1) is composed of combustion fumes.
10. Apparatus for separating a gas containing CO2, at least one gas from air and mercury (1,5) comprising a turbocharger (C), a turbine (T) coupled to the turbocharger, a demercury unit (D), a cooler (G), a heater (R), a separation unit (CC) by partial condensation in one or more stages and / or by distillation operating at temperatures below 10°C, or even below -50°C, means for sending the gas containing CO2, at least one gas from air and mercury (1,5) to the turbocharger, means for sending the compressed gas (7) in the turbocharger to the heater, means for sending the compressed gas from the heater to the demercury unit to form a demercury gas,means for sending the demercurized gas (9) to the cooler and from the cooler to the separation unit to produce at least a fluid containing at least 95 mol% or even at least 99 mol% of CO2 (13) and a pressurized stream of CO2-depleted gas (15) and means for sending at least part of the CO2-depleted gas to expand in the turbine, coupled to the turbocharger, means for sending a refrigerant (W) to the cooler and means for sending the refrigerant (W), preferably water, which has been used to cool the demercurized gas (9) in the cooler to the heater to heat the compressed gas (7) upstream of the demercurization.