Patent Application
20250229214
The present invention relates to a process and an apparatus for capture of CO2.
A carbon dioxide (CO2) capture unit using partial condensation and/or distillation is used to separate a gas from a hydrogen (H2) production unit comprising a pressure swing adsorption (PSA) unit producing a H2 rich stream is often combined with membrane separation. These membranes are used to separate the CO2 and H2 from the remaining molecules coming from the carbon dioxide capture unit. However, this membrane separation can be replaced by at least one pressure swing adsorption separation step.
It is known that the off-gas of a CO2 capture unit downstream a H2 production unit can be valorized as fuel in the burners of the H2 production unit.
The feed gas of the CO2 capture unit by partial condensation and/or distillation must be dried before being cooled in the low temperature section to avoid any risk of freezing. The drying process can be done by adsorption of the water on an adsorbent. This drying process by temperature swing adsorption is a cyclic process. The adsorbent switches from an adsorption step to remove water from the wet gas to a regeneration step to desorb water from the adsorbent. The regeneration step requires a hot and dry gas to regenerate the adsorbent.
The regeneration gas for the driers leaves the adsorbent wet. It must be recycled upstream the driers.
In certain embodiments, the invention proposes to use the CO2 capture off gas to regenerate the driers, since this gas is recycled to a fuel-consuming unit as a fuel, for example to the burners of the H2 production unit. The fuel-consuming unit, for example burners or a fired heater, can handle wet gas, and thus the water removed by the TSA leaves the process with the flue gas of the burners.
Recycling the wet regeneration gas at TSA inlet implies significantly increasing the size of the driers, except if a gas is already recycled upstream the TSA. The low pressure CO2 rich gas from the CO2 PSA is recycled at the inlet of the CO2 capture unit. This gas can be used as a regeneration gas but it implies increasing the tail gas pressure of the CO2 PSA, thus the CO2 PSA performances are degraded.
According to an object of the invention, there is provided A separation process for a gaseous mixture containing CO2, hydrogen, water and at least one component chosen in the list: methane, carbon monoxide with the following steps:
According to other optional features:
According to another object of the invention, there is provided an apparatus for separation of a gaseous mixture containing CO2, hydrogen, water and at least one component chosen in the list: methane, carbon monoxide including a compressor for compressing the gaseous mixture to a first pressure between 20 to 60 bara, a temperature swing adsorption unit for drying the compressed gas mixture comprising at least two adsorbent beds, a separation unit for separation of the dry and compressed gaseous mixture by at least one of the following techniques: partial condensation, distillation, washing and solidification to produce at least two streams, being a rich CO2 liquid enriched in CO2 and depleted in at least one of methane and hydrogen and carbon monoxide as compared with the gaseous mixture and a first residual gas depleted in CO2 and enriched in at least one of methane and hydrogen and carbon monoxide as compared with the gaseous mixture, a pressure swing adsorption unit for separation of the first residual gas depleted in CO2 from iii) by at least one pressure swing adsorption unit in order to produce at least one gas richer in CO2 than the first residual first residual gas and at least one gas depleted in CO2 and enriched in at least one of methane and hydrogen and carbon monoxide as compared to the first residual gas, a conduit for sending to one of said adsorbent beds a regeneration gas thereby producing a regeneration gas containing water wherein the regeneration gas is chosen from the list: at least a part of the at least one gas depleted in CO2 as compared to the first residual gas and a gas containing at least one of methane and carbon monoxide formed by separating the at least one gas depleted in CO2 and a conduit for sending the regeneration gas containing water as a fuel to a fuel-consuming unit.
In certain embodiments, the invention may include use of the off gas of the pressure swing adsorption unit or a gas derived therefrom as a regeneration gas for the driers upstream the cryogenic section. The invention may have at least some of the following steps:
Other features and advantages of the invention will become further apparent via, on the one hand, the following description and, on the other hand, several exemplary embodiments given by way of non-limiting indication and with reference to the attached schematic drawings, in which:
In
The gas S is separated by permeation and/or adsorption, in this case by a single pressure swing adsorption unit H2 PSA to produce a gas H2 1 richer in hydrogen than gas S, which may be a hydrogen product and a gaseous mixture GM depleted in hydrogen and enriched in carbon dioxide, still containing water and methane and/or carbon monoxide.
The gaseous mixture GM is compressed in a compressor C and then dried in a temperature swing adsorption unit TSA. The gaseous mixture GM may contain for example 50% CO2, 30% hydrogen and 10% methane all percentages being molar.
The dried gaseous mixture is preferably further compressed in compressors C1, C2 to a pressure between 20 and 60 bara, cooled by cooler R and separated in a separation unit CC at a temperature below −30° C. by partial condensation and/or distillation and/or washing and/or solidification. The separation unit produces as a product a fluid enriched in carbon dioxide and depleted in methane and/or carbon monoxide with respect to the gaseous mixture GM, which may also contain nitrogen. The separation unit also produces a first residual gas PGR at a pressure substantially equal to that of the gaseous mixture GM depleted in carbon dioxide and enriched in methane and/or hydrogen and/or carbon monoxide with respect to the gaseous mixture GM, which may also contain nitrogen. The first residual gas PGR may contain 19% CO2, 50% hydrogen and 20% methane. The first residual gas PGR depleted in carbon dioxide is expanded in a turbine T to a pressure between 6 and 30 bara, and sent to a CO2 PSA to be separated forming a gas E richer in carbon dioxide than the gas PGR and a gas RG depleted in carbon dioxide with respect to the gas PGR. Optionally the first residual gas PGR may provide refrigeration to the separation unit CC down stream of the turbine T and upstream of the CO2 PSA. The gas RG depleted in carbon dioxide contains methane and/or carbon monoxide and/or hydrogen in addition to remaining carbon dioxide and is used as a regeneration gas to regenerate the temperature swing adsorption (TSA) unit. Once the regeneration has been performed, the regeneration gas contains water adsorbed in one of the at least two adsorption beds of the TSA unit and can be sent as a fuel FG to a fuel consuming unit, for example a fuel system outside of the CO2 capture unit battery limit. In particular, the regeneration gas can be sent to burners B associated with the reformer R and/or a fired heater B associated with the reformer R. The regeneration gas may contain at least 15% mol methane.
The gas richer in carbon dioxide produced by the CO2 PSA is mixed with the gaseous mixture upstream of compressor C.
The regeneration gas RG contains water, 1% CO2, 70% hydrogen and 20% methane, all percentages being molar.
The process of
The regeneration gas of
While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims. The present invention may suitably comprise, consist or consist essentially of the elements disclosed and may be practiced in the absence of an element not disclosed. Furthermore, if there is language referring to order, such as first and second, it should be understood in an exemplary sense and not in a limiting sense. For example, it can be recognized by those skilled in the art that certain steps can be combined into a single step.
The singular forms “a”, “an” and “the” include plural referents, unless the context clearly dictates otherwise.
“Comprising” in a claim is an open transitional term which means the subsequently identified claim elements are a nonexclusive listing (i.e., anything else may be additionally included and remain within the scope of “comprising”). “Comprising” as used herein may be replaced by the more limited transitional terms “consisting essentially of” and “consisting of” unless otherwise indicated herein.
“Providing” in a claim is defined to mean furnishing, supplying, making available, or preparing something. The step may be performed by any actor in the absence of express language in the claim to the contrary.
Optional or optionally means that the subsequently described event or circumstances may or may not occur. The description includes instances where the event or circumstance occurs and instances where it does not occur.
Ranges may be expressed herein as from about one particular value, and/or to about another particular value. When such a range is expressed, it is to be understood that another embodiment is from the one particular value and/or to the other particular value, along with all combinations within said range.
