METHOD FOR SEPARING METHANE AND CARBON DIOXIDE FROM BIOGAS AND PROCESSING PLANT

Abstract

The invention relates to a method for separating methane and carbon dioxide from biogas by means of scrubbing with an amine-containing scrubbing fluid in at least one scrubbing column (K1), and with a subsequent regeneration of the laden scrubbing fluid, comprising the following steps: dividing the laden scrubbing fluid exiting the scrubbing column (K1) into at least one first sub-flow and a second sub-flow; heating the sub-flows by means of at least one first heat exchanger (W1) and a second heat exchanger (W2) to a respective temperature of at least 60°C, wherein the at least two heat exchangers (W1, W2) are arranged parallel to one another; supplying at least the first heated sub-flow to a separator (F1), wherein a separation of dissolved methane from the laden, heated scrubbing fluid is carried out in the separator (F1), such that a pretreated scrubbing fluid is produced, supplying the pretreated scrubbing fluid and optionally the second sub-flow into the top of a stripping column (K2B), wherein, by supplying heat to a column sump of the stripping column (K2B), a separation of carbon dioxide occurs free of a releasing of the remaining methane. The invention also relates to a preparation system.

Claims

Patent claims: 1 . A process for the separation of methane ( 105 ) and carbon dioxide ( 107 ) from biogas ( 103 ) by means of washing with an amine-containing washing liquid in at least one washing column (Kl), in which the biogas is Countercurrent to the amine-containing scrubbing liquid through solid elements for separating gaseous methane and loading the amine-containing scrubbing liquid with carbon dioxide, and with a subsequent regeneration of the loaded scrubbing liquid, with the following steps: - dividing the loaded washing liquid emerging from the washing column (Kl ) into at least a first partial stream and a second partial stream, - heating the partial flows by means of at least one first heat exchanger (Wl) and a second heat exchanger (W2) to a temperature of at least 60 °C, wherein the at least two heat exchangers (Wl, W2) are arranged parallel to each other, - feeding at least the first heated partial flow into a separator (F1), wherein in the separator (F1) a separation of dissolved methane from the loaded, heated washing liquid is carried out, so that a pretreated washing liquid is present, - feeding the pretreated scrubbing liquid and optionally the second partial stream into a top of a stripping column (K2B), wherein by supplying heat at a column bottom of the stripping column (K2B) carbon dioxide is separated off without the release of residual methane, so that a regenerated scrubbing liquid is present. Process according to claim 1, characterized in that the heating of the partial streams of the loaded scrubbing liquid takes place by means of the at least two heat exchangers (Wl, W2) arranged parallel to one another to a temperature in a range from 70°C to 120°C, in particular from 80°C to 115°C, preferably from 90°C to 110°C. Process according to one of the preceding claims, characterized in that the division of the loaded scrubbing liquid into the first, larger partial stream and the second, smaller partial stream takes place, and the heating of the first, larger partial stream takes place by means of the first heat exchanger (Wl) using the regenerated scrubbing liquid from the stripping column (K2B) and the heating of the second, smaller partial stream takes place by means of the second heat exchanger (W2) using the water-containing and carbon dioxide-containing gas separated at the top of the stripping column (K2B).Process according to claim 3, characterized in that the separated, water-containing and carbon dioxide-containing gas is cooled downstream of the second heat exchanger (W2) by means of a further heat exchanger (W4) and phase separation takes place in a post-separator (F2), wherein a separated liquid phase is returned to the scrubbing column (K1) and the carbon dioxide-containing gas emerging from the post-separator (F2) is purified from residual amines in a post-scrubber (K4) so ​​that high-purity carbon dioxide (107) is present. Process according to claim 3 or 4, characterized in that the regenerated scrubbing liquid is returned to the scrubbing column (K1) downstream of the first heat exchanger (W1). Process according to one of the preceding claims, characterized in that emerging from the scrubbing column (K1). Methane is fed to a further scrubbing column (K3) and is purified in the further scrubbing column (K3) to remove any residual amines. Process according to claim 6, characterized in that the methane emerging from the further scrubbing column (K3) is cooled to a temperature of 5°C to -15°C. Process according to one of the preceding claims, characterized in that the first partial stream and / or the second partial stream is compressed to a pressure of up to 4.0 bar and / or heated to a temperature of below 115°C before entering the separator (Fl), gaseous methane is discharged under controlled pressure, and the pretreated scrubbing liquid is passed freely by a pump into the stripping column (K2B). Process according to one of the preceding claims, characterized in that regeneration of the pretreated scrubbing liquid in the stripping column (K2B) takes place at a lower pressure than a pressure in the separator (Fl).Method according to one of the preceding claims, characterized in that a gas (113) is introduced into the separator (Fl) to improve the separation of dissolved methane from the loaded, heated scrubbing liquid. . Method according to one of the preceding claims, characterized in that before the heating of the partial streams of the loaded scrubbing liquid by means of the at least two heat exchangers (Wl, W2) arranged parallel to one another, the loaded scrubbing liquid is heated in the bottom of the scrubbing column (Kl) or directly after exiting the scrubbing column (Kl) by means of a separate stripping vessel (F0) to a temperature below a temperature of. Release of CO2 from the loaded scrubbing liquid takes place. . Process according to claim 11, characterized in that methane escaping from the separate stripping vessel (FO) is directly returned to the scrubbing column (Kl). . Process according to claim 11 or 12, characterized in that a liquid phase from the separator (Fl) is fed into the top of the stripping column (K2B) and / or is returned to the scrubbing column (Kl) in a return line. . Treatment plant (101) for separating methane and carbon dioxide from biogas, wherein the treatment plant (101) has at least one washing column (Kl) with an amine-containing washing liquid, wherein in the at least one washing column (Kl) the biogas can be guided in a countercurrent to the amine-containing washing liquid through solid elements for separating gaseous methane from the washing column (Kl) and for loading the amine-containing washing liquid with carbon dioxide, and the treatment plant has, downstream of the washing column (Kl), a separator (Fl) for separating dissolved methane and a stripping column (K2B) for regenerating the loaded washing liquid, characterized in that the treatment plant has at least two heat exchangers (Wl, W2) arranged parallel to one another after the washing column (Kl),so that a loaded washing liquid emerging from the washing column (Kl) can be heated to a temperature of at least 60°C in a first partial stream by means of the first heat exchanger (Wl) and in a second partial stream by means of the second heat exchanger (W2) and then the first partial stream and the second partial stream are fed to the separator (Fl) for separating dissolved methane from the loaded, heated, washing liquid and / or the stripping column (K2B) for separating carbon dioxide from the loaded, heated washing liquid.