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 such that the gas stream has a sulfur concentration that is substantially less than prior to the gas stream being contacted with the solvent;
b. filtering entrained liquid droplets from the gas stream so that sulfur does not become deposited on a gas separation membrane; and
c. passing the gas stream through the gas separation membrane.
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 step of filtering entrained liquid droplets occurs in a coalescing filter.
5. The method of claim 2 , further comprising the step of regenerating the solvent by sending a gas capable of dissolving sulfur through the solvent scrubber.
6. The method of claim 5 , wherein the gas capable of dissolving sulfur comprises hydrogen sulfide recovered from the gas separation membrane or recovered from an amine unit regenerator outlet.
7. The method of claim 5 , 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.
8. 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.
9. The method of claim 1 , further comprising the step of 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 membrane separation process simulation.