Sour gas and acid natural gas separation membrane process by pre removal of dissolved elemental sulfur for plugging prevention
Methods for removing sulfur from a gas stream prior to sending the gas stream to a gas separation membrane system are provided. Two schemes are available. When the sulfur content is high or flow is relatively high, a scheme including two columns where one tower is regenerated if the sulfur concentration exceeds a preset value can be used. When the sulfur content is low or flow is relatively low, a scheme including one column and an absorption bed.
1. A method of removing sulfur from a gas stream comprising the steps of:
a. contacting the gas stream with a solvent to selectively absorb at least a portion of elemental sulfur from the gas stream;
b. filtering entrained liquid droplets from the gas stream so that sulfur does not become deposited on a gas separation membrane;
c. passing the gas stream through the gas separation membrane;
d. analyzing a sulfur concentration of an overhead stream of the solvent scrubber and sending the gas stream to a second column if the sulfur concentration exceeds a sulfur solubility estimated in retentate and permeate flows by a membrane separation process simulation; and
e. regenerating the solvent by sending a gas capable of dissolving sulfur through the solvent scrubber.
2. The method of claim 1 , wherein the step of contacting the gas stream with a solvent occurs in a solvent scrubber.
3. The method of claim 1 , wherein the step of contacting the gas stream with a solvent occurs when the gas stream is flowing upstream and the solvent is flowing downstream counter currently to the gas stream.
4. The method of claim 1 , wherein the gas capable of dissolving sulfur comprises hydrogen sulfide recovered from the gas separation membrane.
5. The method of claim 1 , wherein the step of regenerating the solvent scrubber occurs at a pressure operative to compensate for pressure loss in the solvent scrubber and its piping.
6. The method of claim 1 , wherein the step of contacting the gas stream with the solvent occurs at a pressure substantially similar to a feed gas pressure of the gas stream.