PROCESS FOR ELIMINATING Co2 AND/OR H2s FROM GASEOUS MIXTURES

Claim 2

In a process for removing gaseous impurities selected from the group consisting of CO2, H2S and mixtures thereof from hot gaseous mixtures containing said impurities, said process comprising: absorbing said gaseous impurities in an aqueous absorbent solution by contacting said hot gaseous mixtures with said solution at above atmospheric pressure, regenerating the solution having said impurities absorbed therein by heating said solution at about atmospheric pressure to expel a vapor containing said impurities, removing said vapor containing said impurities from the system, and recycling the regenerated solution to the absorption step with an optional cooling step prior to introducing the recycle into the absorption step, wherein at least part of the heat necessary for heating the solution in the regeneration step is derived from said hot gaseous mixtures by passing said hot gaseous mixtures, prior to feeding said hot gaseous mixtures to said absorption step, in indirect heat-exchange with the solution undergoing regeneration in a reboiler, the improvement comprising reducing or eliminating the reboiler requirement by extracting a greater amount of heat from said gaseous mixtures containing said impurities than that amount extracted in said reboiler by a process which comprises: a. feeding said gaseous mixtures at a temperature of from 165* to 225*C to the bottom of an absorption column divided into a lower heat transfer zone and an upper absorption zone wherein said gaseous mixtures ascend firstly through said heat transfer zone and secondly through said absorption zone; b. feeding said aqueous absorbent solution to the top of said absorption zone wherein said solution descends therethrough and absorbs said gaseous impurities from the gas mixtures ascending therethrough wherein absorption occurs until the partial pressure of the gaseous impurities in the ascending gaseous stream is at least 1.5 times the partial pressure of the impurities in tbe solution and wherein the solution becomes heated by the heat of reaction of the absorption, c. feeding an aqueous liquid compatible with the gaseous impurities contained in said hot gaseous mixtures to the top of said heat transfer zone, which liquid descends therethrough and becomes heated by direct heat exchange with the hot gaseous mixtures ascending therethrough, d. removing the aqueous absorbent solution containing said impurities absorbed therein from the bottom of said absorption zone and feeding the solution containing said impurities to the top of a regeneration column through which said solution descends, e. removing the heated aqueous liquid from the bottom of the heat transfer zone and feeding it to the bottom of said regeneration column wherein a vapor is expelled therefrom due to the lower pressure existing in the regeneration column, f. recycling the regenerated aqueous absorbent solution to the top of said absorption zone, and g. recycling said aqueous liquid from the bottom of said regeneration column to the top of said heat transfer zone, wherein the composition of said aqueous absorbent solution circulating between said absorption zone and said regeneration column is maintained constant by passing the hot gaseous mixtures through said reboiler only to the extent necessary to maintain the amount of water in said aqueous absorbent solution constant by providing Heat to evaporate excess water.

Claim 3

The process of claim 3 wherein said aqueous liquid comprises an aqueous absorbent solution.

Claim 4

The process of claim 4 wherein the heated aqueous absorbent solution removed from the bottom of said heat transfer zone is preliminarily expanded at a pressure intermediate the pressure of the absorption column and the regeneration column, the vapor resulting from said preliminary expansion being introduced into an intermediate level of said regeneration column wherein the aqueous absorbent solution resulting from said preliminary expansion is introduced into the bottom of said regeneration column wherein a vapor is expelled therefrom due to the lower pressure existing therein.

Claim 5

In a process for removing gaseous impurities selected from the group consisting of CO2, H2S and mixtures thereof from hot gaseous mixtures containing said impurities, said process comprising: absorbing said gaseous impurities in an aqueous absorbent solution by contacting said hot gaseous mixtures with said solution at above atmospheric pressure; regenerating the solution having said impurities absorbed therein by heating said solution at about atmospheric pressure to expel a vapor containing said impurities; removing said vapor containing said impurities from the system, and recycling the regenerated solution to the absorption step with an optional cooling step prior to introducing the recyle into the absorption step, wherein at least part of the heat necessary for heating the solution in the regeneration step is derived from said hot gaseous mixtures by passing said hot gaseous mixtures, prior to feeding said hot gaseous mixtures to said absorption step, in indirect heat-exchange with the solution undergoing regeneration in a reboiler, the improvement comprising eliminating the reboiler requirement and extracting a greater amount of heat from said hot gaseous mixtures containing said impurities than that amount extracted in said reboiler by a process which comprises: a. feeding said gaseous mixtures at a temperature of from 165* to 225*C to the bottom of an absorption column without feeding said hot gaseous mixtures through the reboiler of a regenerating column, wherein said hot gaseous mixtures ascend through said absorption column, b. feeding an aqueous absorbent solution to the top of said absorption column wherein said solution descends therethrough and becomes heated by the direct heat exchange contact between the descending solution and the ascending gaseous mixture and wherein the descending solution absorbs said gaseous impurities from the ascending gaseous mixture, the absorption occurring until the partial pressure of the impurities in the ascending gaseous mixture is at least 1.5 times the partial pressure of the impurities in the solution descending therethrough and wherein said solution is further heated by the heat of reaction of said absorption, c. removing the heated aqueous absorbent solution from the bottom of the absorption column and expanding it in an expansion zone thereby expelling a vapor therefrom containing said gaseous impurities.