Method for treating a hydrocarbon-rich gas mixture containing mercury and acid gases

Abstract

A method for treating a hydrocarbon-rich gas mixture containing mercury and acid gases, said gas mixture being natural gas in particular, wherein the gas mixture is subject to an adsorptive mercury removal and a downstream acid-gas scrubbing. Before the gas mixture to be treated is fed to the adsorptive mercury removal, the gas mixture to be treated is heated at least to such an extent that the gas mixture does not fall below the water dew point in the adsorptive mercury removal and does not fall below the hydrocarbon dew point in the acid-gas scrubbing.

Claims

1. A method for treating a mercury- and acid gases-containing hydrocarbon-rich gas mixture, wherein said mixture is subjected to an adsorptive mercury removal, having a separation process connected upstream of it, and a subsequent acid gas scrub, characterized in that between exiting the separation process and being supplied to the adsorptive mercury removal the gas mixture to be treated is warmed at least to an extent sufficient to avoid the temperature thereof falling below the water dew point in the adsorptive mercury removal and falling below the hydrocarbon dew point in the acid gas scrub.

2. The method according to claim 1, characterized in that the gas mixture to be treated is warmed (E) by at least 5 C. to 30 C., between exiting the separation process and entering the acid gas scrub.

3. The method according to claim 1, characterized in that the gas mixture to be treated is warmed against the acid gas-freed fraction withdrawn from the top of the acid gas scrub.

4. The method according to claim 1, characterized in that the proportion of mercury in the gas mixture to be treated is between 1 and 1000 g/Nm.sup.3.

5. The method according to claim 1, characterized in that the gas mixture is natural gas.

6. The method according to claim 2, characterized in that the gas mixture to be treated is warmed by at least 15 C. to 25 C.

Description

(1) The method according to the invention for treating a mercury- and acid gases-containing hydrocarbon-rich gas mixture and advantageous embodiments thereof are more particularly elucidated hereinbelow with reference to the working example shown in FIG. 1.

(2) The damp, mercury- and acid gases-containing hydrocarbon-rich gas mixture 1 is supplied to a separator D in which it is freed of liquid, for example water, said liquid being withdrawn from the separator D via line 7. In accordance with the invention the gas mixture 2 withdrawn at the top of the separator D is warmed in the heat exchanger E at least to an extent sufficient to avoid the temperature thereof falling below the water dew point in the subsequent adsorptive mercury removal A and falling below the hydrocarbon dew point in the acid gas scrub T. In the working example shown in FIG. 1, this warming is accomplished against the acid-gas freed fraction 6 withdrawn from the top of the acid gas scrub T and subsequently supplied, for example, to a complete drying.

(3) The gas mixture 2 warmed in heat exchanger E is freed of mercury in the adsorptive mercury removal to achieve residual mercury contents of from 0.01 to 0.001 g/Nm.sup.3. For clarity, the adsorptive mercury removal is shown in the form of an adsorber A. Said adsorber contains an adsorbent/adsorption material suitable for the adsorption of mercury. Said adsorbent/adsorption material requires replacement once exhausted; in-situ regeneration is generally not carried out. Typically, two adsorbers are connected in series. The second adsorber is brought on-line in place of the first as soon as the adsorbent in the first adsorber is exhausted.

(4) The gas mixture 3 withdrawn from the adsorptive mercury removal A and freed of mercury is supplied to the column T which removes the unwanted acid gas components. A suitable scrubbing medium 4 is supplied to the top region of column T. The gas mixture freed of unwanted acid gas components is withdrawn from the top of the column T and sent for further treatment for example a liquefaction, or use.