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. cooling the gas stream to produce a gas stream without liquids and a chilled solvent;
b. contacting the gas stream without liquid with the chilled solvent to selectively absorb at least a portion of elemental sulfur from the gas stream;
c. contacting the chilled solvent with an absorbent bed or a filter to remove sulfur in excess of solubility;
d. analyzing a sulfur concentration in the gas stream without liquids to determine if the sulfur concentration exceeds a sulfur solubility estimated in retentate and permeate flows by a membrane separation process simulation; and
e. passing the gas stream without liquids through gas separation membranes.
2. The method of claim 1 where the absorbent bed contains activated carbon, supported metallic oxides, supported organic oxides, or combinations thereof.
3. The method of claim 1 where the filter contains supported metallic filters, supported organic filters, polymeric filters, or combinations thereof.
4. The method of claim 1 where the solvent is polyethylene glycol, ethers of polyethylene glycol, polypropylene glycol, ethers of propylene glycol, n-methylpyrolidone, n-ethyl pyrolidone, n-cyclohexyl pyrolidone, n-phenyl morpholine, n-cyclohexyl morpholine, dimethyl disulfur, dimethyl-sulfur, carbon disulfide, xylene, toluene, BTX (a mixture of benzene, toluene, and xylenes), kerosene, naphthalene, alkyl-naphthalene, or combinations thereof.
5. The method of claim 1 further including the step of separating a heavy hydrocarbon stream from the gas stream without liquids prior to passing the gas stream without liquids through gas separation membranes.