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1. WO1992017401 - PROCEDE ET APPAREIL POUR ELIMINER LE H¿2?S CONTENU DANS DES COURANTS GAZEUX GRACE A LA PURIFICATION PAR FILTRE POREUX DE LA SOLUTION DE RECYCLAGE

Note: Texte fondé sur des processus automatiques de reconnaissance optique de caractères. Seule la version PDF a une valeur juridique

[ EN ]

WHAT IS CLAIMED IS:

1. A process for the removal of hydrogen sulfide from a gaseous stream comprising:

a) contacting the gaseous stream with a
reaction solution comprising an oxidizing
polyvalent metal ion bound to a
substantially monomeric chelant so as to
convert hydrogen sulfide to elemental
sulfur;
0 b) separating the reaction solution containing
elemental sulfur suspended therein from the
gaseous stream;

c) treating at least a portion of the
5 separated reaction solution by a filtration
step to produce a fully clarified reaction
solution filtrate essentially free of
suspended sulfur;
0 d) contacting the fully clarified reaction
solution with a nanofiltration membrane to
produce a permeate portion comprising water
and solutes of up to 225 molecular weight r- dissolved therein, and a nonpermeate concentrate portion comprising water and
the polyvalent metal ion bound to the
substantially monomeric chelant;

e) combining the nonpermeate concentrate
portion with any of the separated reaction solution not converted to fully clarified
reaction solution to form a combined
stream;

f) oxidizing the polyvalent metal ion in the
combined stream to produce a regenerated
reaction solution; and

h) recycling the regenerated reaction solution to (a).

2. A process for the removal of hydrogen sulfide from a gaseous stream comprising:

a) contacting the gaseous stream with a
reaction solution comprising an oxidizing
polyvalent metal ion bound to a
substantially monomeric chelant so as to
convert hydrogen sulfide to elemental
sulfur;

b) separating the reaction solution containing elemental sulfur suspended therein from the gaseous stream;

c) removing at least a portion of the
elemental sulfur from the reaction solution in a first filtration step to produce a
partially clarified reaction solution;

d) passing at least a portion of the partially clarified reaction solution through a
membrane process comprising in sequence the steps of:

i) filtering the partially clarified
reaction solution in a second filtration
step to produce a fully clarified
reaction solution filtrate essentially
free of suspended sulfur,

ii) contacting the filtrate with a
nanofiltration membrane to produce a
permeate portion comprising water and
solutes of up to 225 molecular weight
dissolved therein, and a nonpermeate
concentrate portion comprising water and
the polyvalent metal ion bound to the
substantially monomeric chelant;

e) combining the nonpermeate concentrate
portion with any portion of the separated
reaction solution not converted to fully
clarified reaction solution to form a
combined stream;

f) oxidizing the polyvalent metal ion in the
combined stream to provide a regenerated
reaction solution; and

g) recycling the regenerated reaction solution to step (a) .

3. The process according to Claim 1 or 2 wherein the reaction solution separated from contact with the gaseous stream is treated with a degasifier prior to filtration.

4. The process according to Claim 2 wherein the second filtration step is effected by means of a cross-flow filtration device.

5. The process according to Claim 1 wherein the filtration step is effected by means of a cross-flow filtration device.

6. The process according to Claim 4 or 5 wherein the cross-flow filtration device contains a membrane selected from the group consisting of
microfiltration and ultrafiltration membranes.

7. The process according to Claim 6 wherein the cross-flow filtration device consists of a hollow fiber, tubular, spiral-wound, or plate-and-frame device.

8. The process according to Claim 1 or 2 wherein at least 90 percent of the polyvalent metal ion bound to the substantially monomeric chelant in the fully clarified reaction solution is recovered in the nonpermeate concentrate portion.

9. The process according to Claim 1 or 2 wherein the nanofiltration membrane is characterized by an oxalate ion permeation rate at least about five-fold greater than that of the polyvalent metal ion bound to the substantially monomeric chelant at operating
conditions effective for the removal of water as
permeate.

10. The process according to Claim 1 or 2 wherein the oxidizing polyvalent metal ion is ferric ion.

11. The process according to Claim 10 wherein the substantially monomeric chelant is selected from the group consisting of nitrilotriacetic acid,
ethylenediamine-N,N,N' ,N'-tetraacetic acid, N-hydroxyethyl ethylene-diamine-N,N' ,N'-triacetic acid, citric acid, and salts derived therefrom.

12. A process for the removal of hydrogen sulfide from a gaseous stream by contact with a reaction solution comprising an oxidizing polyvalent metal ion bound to a substantially monomeric chelant wherein water introduced into the reaction solution from the gaseous stream contacting step is removed through a
nanofiltration membrane device as a permeate stream.

13. An apparatus for purifying an aqueous reaction solution comprising an oxidizing polyvalent metal ion bound to a substantially monomeric chelant used in the removal of hydrogen sulfide from a gaseous stream, the reaction solution containing suspended sulfur therein, comprising:

a) filtration means having an inlet, a first
outlet for removal of filtered fluid, and a second outlet for removal of a concentrate
stream of elemental sulfur;

b) a pressurizing pump having an inlet and an
outlet;

c) means for conveying at least a portion of
filtered fluid from the first outlet of the filtration means to the inlet of the
pressurizing pump;

d) a membrane device having first and second
compartments, said first and second
compartments being separated from each 5
other by a nanofiltration membrane means
interposed between them, the first
compartment having a high pressure inlet
and an outlet, the second compartment 0 having at least one outlet for permeate
passing from the first compartment into the
second compartment through the
nanofiltration membrane means;

5 e) means for conveying pressurized filtered
fluid from the outlet of the pressurizing
pump to the high pressure inlet of the
first compartment of the membrane device;

0 f) means for recovering of nonpermeate
concentrate from the outlet of the first
compartment of the membrane device.

14. The apparatus according to Claim 13,
(- wherein the filtration means comprises a first
filtration device and a second filtration device, the first filtration device having an inlet, a first outlet for removal of filtered fluid and a second outlet for removal of a stream concentrated in elemental sulfur, 0 the second filtration device having an inlet means in fluid communication with the first outlet means of the first filtration device, the second filtration device also having at least one outlet means in fluid communication with a means for conveying twice-filtered fluid to the pressurizing pump.

15. The apparatus according to Claim 14, wherein the second filtration device has a first compartment and a second compartment, the first and ' second compartments of the second filtration device being separated from each other by a filtration
material, the first compartment of the second filtration device having an inlet and an outlet for conveyance of 0 fluid through said compartment, the second compartment of the second filtration device having at least one fluid outlet in fluid communication with the means for conveying the twice-filtered fluid to the pressurizing pump.
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16. The apparatus according to Claim 16 wherein the nanofiltration membrane is contained in the form of a sheet-like, hollow fiber, or tubular configuration.

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