US 4,391,791 A · Low temperature sulfur recovery

Abstract

Vaporized elemental sulfur is recovered from a gaseous stream by cooling said stream in a first heat exchanger to condense elemental sulfur and then cooling said stream in a second heat exchanger to solidify the remaining elemental sulfur. The plugging of the heat exchanger is avoided by switching the operating conditions of the two exchangers and reversing the sequence of the flow through these two heat exchangers. The process and apparatus are especially useful in treating the tail gas and the intermediate streams in the Claus process or in the modified Claus process. Instead of reversing the flow, the plugging can be avoided by using two two-zone heat exchangers. One of the heat exchangers is operated to effect the condensation of elemental sulfur in the first zone and melting the solidified sulfur deposited in the second zone. The second heat exchanger is operated to effect condensation of sulfur in the first zone and solidification of sulfur in the second zone. The operating conditions in the second zones are continually reversed before the flow through the heat exchanger is restricted by solidified sulfur.

Claims15

Dependent claims

A process for removing and recovering vaporized elemental sulfur from a gas stream, said process comprising:

(a) passing said gas stream through a first cooling zone maintained at such conditions, including temperature, so as to effect condensation of elemental sulfur without solidification thereof;
(b) passing said gas stream from said first cooling zone through a second cooling zone maintained at such conditions, including temperature, so as to effect solidification of elemental sulfur therein;
(c) interchanging conditions of said first cooling zone and said second cooling zone and directing said gas stream to flow through said second cooling zone first and then through said first cooling zone;
(d) interchanging conditions of said first cooling zone and said second cooling zone and directing said gas stream to flow through said first cooling zone first then through said second cooling zone, said steps (c) and (d) being carried out after at least a significant part of the build-up of elemental sulfur is melted in the zone maintained at condensation conditions but before the build-up in the zone maintained at solidification conditions significantly restricts the flow of said stream.

1 more element

An apparatus for removing and recovering vaporized elemental sulfur from a gas stream, said apparatus comprising:

first heat exchange means;
second heat exchange means communicating with said first heat exchange means;
means for directing said gas stream through said first heat exchange means and said second heat exchange means in one of two modes, in the first mode said gas stream being directed to said first heat exchange means first and then to said second heat exchange means, in the second mode said gas stream being directed to said second heat exchange means first and then to said first heat exchange means;
means for cooling said gas stream passing through said first heat exchange means in the first mode, and said second heat exchange means in the second mode to a temperature that effects condensation of vaporized elemental sulfur and for cooling said gas stream passing through said second heat exchange means in the first mode and said first heat exchange means in the second mode to a temperature that effects solidification of vaporized elemental sulfur, said directing means being switched from the first to the second mode and vice versa before the build-up of solidified sulfur in the heat exchanger maintained to effect solidification significantly interferes with the flow of the gas stream therethrough;
and
means for recovering liquid sulfur from said first and said second heat exchange means.

3 more elements

In the modified Claus process for producing elemental sulfur of the type including the steps of reacting hydrogen sulfide and sulfur dioxide in a thermal reaction zone, passing the resulting gaseous stream through a first condensing zone to recover elemental sulfur therefrom and then passing through a plurality of high-temperature catalytic reactor zones arranged in series and operating at progressively lower temperatures, each of said high-temperature catalytic reactor zones being followed by a corresponding condensing zone for condensing and removing elemental sulfur from said gaseous stream, then passing said gaseous stream into a low-temperature catalytic reactor zone, the sulfur produced therein being condensed onto the catalyst present in said low-temperature catalytic reactor zone, the improvement comprising:

(a) passing a gas stream exiting from said final high-temperature catalytic reactor through a first cooling zone maintained at such conditions, including temperature, so as to effect condensation of elemental sulfur without solidification thereof;
(b) passing said gas stream from said first cooling zone through a second zone maintained at such conditions, including temperature, so as to effect solidification of elemental sulfur therein;
(c) interchanging conditions of said first cooling zone and said second cooling zone and directing said gas stream to flow through said second cooling zone first and then through said first cooling zone;
(d) interchanging conditions of said first cooling zone and said cooling second zone and directing said gas stream to flow through said first zone first then through said second zone, said steps (c) and (d) being carried out after at least a significant part of the build-up of elemental sulfur is melted in the zone maintained at condensation conditions but before the build-up in the zone maintained at solidification conditions significantly restricts the flow of said stream;
(e) recovering liquid sulfur from said first and said second zone;
and
(f) passing effluent from said second zone in step (b), from said first zone in step (c), and from said second zone in step (d) to said low-temperature catalytic reaction zone.

4 more elements

A process for production of sulfur from hydrogen sulfide and oxygen comprising:

(a) reacting some of said hydrogen sulfide with oxygen to produce sulfur dioxide in a first reaction zone;
(b) reacting sulfur dioxide produced in step (a) with the remaining hydrogen sulfide to produce a mixture of vaporized elemental sulfur, water, volatile sulfur compounds and unreacted hydrogen sulfide and sulfur dioxide;
(c) cooling said mixture to separate it into liquid sulfur and gaseous effluent;
(d) reacting said gaseous effluent in the presence of a catalyst to produce a mixture of vaporized elemental sulfur, water, volatile sulfur compounds, and unreacted hydrogen sulfide and sulfur dioxide;
(e) passing said mixture through a first cooling zone maintained at such conditions, including temperature and pressure, so as to effect condensation of elemental sulfur without solidification thereof;
(f) passing said mixture from said first cooling zone through a second cooling zone maintained at such conditions, including temperature and pressure, so as to effect solidification of elemental sulfur therein;
(g) interchanging conditions of said first cooling zone and said second cooling zone and directing said mixture to flow through said second cooling zone first and then through said first cooling zone;
(h) interchanging conditions of said first zone and said second zone and directing said mixture to flow through said first zone first then through said second zone, said steps (g) and (h) being carried out after at least a significant part of the build-up of elemental sulfur is melted in the zone maintained at condensation conditions but before the build-up in the zone maintained at solidification conditions significantly restricts the flow of said stream;
(i) recovering liquid sulfur from said first and said second zones.

6 more elements

A process for removing and recovering sulfur from hot and cold gas streams containing hydrogen sulfide, sulfur dioxide and vaporized elemental sulfur, said hot gas stream being at a temperature sufficient to regenerate catalyst in a low-temperature catalytic reactor, said process comprising:

(a) passing said cold gas stream through a first zone maintained at such conditions, including temperature, so as to effect condensation of elemental sulfur without solidification thereof;
(b) passing said gas stream from said first zone through a second zone maintained at such conditions, including temperature, so as to effect melting of elemental sulfur therein;
(c) combining said gas stream from said second zone with said hot gas stream and passing said mixture to a first reactor condenser to vaporize condensed sulfur and regenerate a catalyst therein;
(d) passing said gas stream from said first reactor condenser to a third zone maintained at such conditions, including temperature, so as to effect condensation of elemental sulfur without solidification thereof;
(e) passing said gas stream from said third zone to a fourth zone maintained at conditions, including temperature, that effect solidification of sulfur;
(f) passing said gas stream from said fourth zone into a second reactor condenser and therein reacting hydrogen sulfide with sulfur dioxide on the surface of a catalyst to produce condensed sulfur which is condensed thereon;
(g) subsequently directing the flow of the cold gas to the third zone and the flow of hot gas to the second reactor condenser;
(h) reversing the conditions in the second and the fourth zones such that sulfur is solidified in the second zone and melted in the fourth zone, the reaction proceeding on the catalyst of the first reactor and the second reactor being regenerated;
(i) recovering sulfur from said first, second, third, and fourth zones.

6 more elements

A process for removing and recovering elemental sulfur from hot and cold gaseous streams containing hydrogen sulfide, sulfur dioxide and vaporized elemental sulfur, said process comprising:

(a) passing said stream through a first zone maintained at such conditions, including temperature, so as to effect condensation of elemental sulfur without solidification thereof;
then
(b) passing said gas stream from said first zone through a second zone maintained at such conditions, including temperature, so as to effect melting of any elemental sulfur deposited therein;
(c) passing said stream through a heating zone to impart thereto a sufficiently high temperature to vaporize condensed sulfur and regenerate a catalyst;
then
(d) passing said stream to a first reactor condenser containing a catalyst to vaporize condensed sulfur and to regenerate the catalyst;
(e) passing said stream from said first reactor condenser to a third zone maintained at such conditions, including temperature, so as to effect condensation of elemental sulfur without solidification thereof;
(f) passing said stream from said third zone to a fourth zone maintained at conditions, including temperature, that effect solidification of sulfur;
(g) passing said stream from said fourth zone into a second reactor condenser and therein reacting hydrogen sulfide with sulfur dioxide on the surface of a catalyst to produce condensed sulfur thereon;
then
(h) before the accumulation of sulfur significantly restricts the flow of said stream through said fourth zone but after the catalyst is regenerated in said first reactor, reversing the conditions in the second and the fourth zones such that sulfur is solidified in the second zone and melted in the fourth zone, directing the flow of the stream of step (a) to the third zone rather than to said first zone and from there to said fourth zone, then passing said stream through said heating zone and therefrom to said second reactor condenser to vaporize condensed sulfur and to regenerate the catalyst, the reaction proceeding in the first reactor and the second reactor being regenerated;
(i) repeating steps (a) through (g) before the accumulation of sulfur significantly restricts the flow of said stream through said second zone but after the catalyst is regenerated in said second reactor;
(j) recovering sulfur from said first, second, third, and fourth zones.

10 more elements

Dependencies are inferred from the claim text.

Low temperature sulfur recovery

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Low temperature sulfur recovery

Life of this patent

Abstract

Claims15