Reactor and process for preparing hydrogen sulphide

Abstract

The present invention relates to a reactor and to a process for synthesis of hydrogen sulphide from elemental sulphur and hydrogen at elevated pressure and elevated temperature. The invention further relates to the use of the reactor for preparation of hydrogen sulphide in high yield and with a low H.sub.2S.sub.x content.

Claims

1. A reactor for continuous preparation of hydrogen sulphide by exothermic reaction of sulphur and hydrogen to form a final product gas mixture P.sub.final comprising hydrogen sulphide and sulphur at an elevated temperature and an elevated pressure relative to standard conditions, said reactor comprising: a lower reactor region including a sulphur melt, a non-pressure-bearing first cavern and a supply device providing a controlled supply of pressurized gaseous hydrogen per first cavern, said cavern being configured for at least temporary accommodation of a product gas mixture P.sub.1 which forms in exothermic reaction and comprises hydrogen sulphide, sulphur and hydrogen, a non-pressure bearing second cavern which is arranged above the first cavern and is configured for at least temporary accommodation of the product gas mixture P.sub.1 formed in the first cavern and for formation of further hydrogen sulphide by exothermic reaction of sulphur and hydrogen to form a product gas mixture P.sub.2, and a gas collecting region configured for accommodating the product gas mixture P.sub.final at an elevated temperature and an elevated pressure relative to standard conditions, wherein the second cavern comprises a supply device providing a controlled supply of pressurized gaseous hydrogen.

2. The reactor according to claim 1, wherein the reactor comprises at least two non-pressure-bearing first caverns and a supply device providing a controlled supply of pressurized gaseous hydrogen per first cavern, said first caverns being configured for at least temporary accommodation of the product gas mixture P.sub.1 which forms.

3. The reactor according to claim 1, wherein the reactor further comprises a non-pressure-bearing third cavern, and optionally correspondingly configured caverns arranged above the second cavern.

4. The reactor according to claim 3, wherein at least one of the second or third caverns has a greater volume than each of the first caverns, and/or wherein at least one of the second or third caverns has lower heat removal for construction reasons than each of the first caverns.

5. The reactor according to claim 1, wherein the reactor further comprises a non-pressure-bearing installed device configured for continuous transfer of the total amount of product gas mixture P.sub.u formed in the lower reactor region to the gas collecting region and, wherein a catalyst is present in the installed device, the catalyst being suitable for reaction of sulphur and hydrogen still present in the product gas mixture P.sub.u to hydrogen sulphide.

6. The reactor according to claim 5, wherein at least one of the installed devices for transfer of the product gas mixture P.sub.u from the lower reactor region to the gas collecting region are arranged in terms of construction such that, after sufficient filling of the lower reactor region with the sulphur melt the installed device is in thermal contact with the sulphur melt such that, when the installed device comprises a catalyst, the catalyst is cooled by transfer of heat to the sulphur melt.

7. The reactor according to claim 1, wherein the reactor comprises an inner wall which, in the course of operation of the reactor with involvement of the space between outer reactor wall and the inner wall, allows continuous circulation of the sulphur melt according to the airlift pump principle.

8. The reactor according to claim 1, wherein the reactor further comprises: a reflux condenser suitable for condensation of the sulphur present in the product gas mixture P.sub.final, an input line suitable for transport of the product gas mixture P.sub.final from the gas collecting region to the reflux condenser and a return line suitable for return of the condensed sulphur to the reactor.

9. The reactor according to claim 1, wherein the hydrogen sulphide produced by the reactor comprises a sulphane content not exceeding 600 ppm.

10. A process for preparing hydrogen sulphide by exothermic reaction of sulphur with hydrogen at an elevated temperature and an elevated pressure relative to standard conditions to form a product gas mixture P.sub.final comprising hydrogen sulphide and sulphur, said process comprising: providing a sulphur melt in a lower reactor region of a pressurized reactor, supplying pressurized hydrogen into the sulphur melt, the hydrogen supplied being accommodated at least partly, together with sulphur converted from the sulphur melt to the gaseous state, by at least one non-pressure-bearing first and at least one non-pressure-bearing second cavern, at least temporarily leaving the hydrogen and the sulphur in the first cavern, so as to form, in exothermic reaction, a product gas mixture P.sub.1 comprising hydrogen sulphide, sulphur and hydrogen, accommodating the product gas mixture P.sub.1 in the second cavern and at least temporarily leaving the product gas mixture P.sub.1 therein, such that the sulphur and hydrogen present in the product gas mixture P.sub.1 is reacted with formation of further hydrogen sulphide to a product gas mixture P.sub.2, supplying pressurized hydrogen into the sulphur melt, wherein the hydrogen is at least partly directly supplied by a supply device to the at least one non-pressure-bearing second cavern, together with sulphur converted to the gaseous state from the sulphur melt, and collecting the product gas mixture P.sub.final in a gas collecting region.

11. The process according to claim 10, wherein the product gas mixture is accommodated and left at least temporarily in one or more third or higher caverns, so as to react the sulphur and hydrogen present in the product gas mixture P.sub.2 with formation of further hydrogen sulphide.

12. The process according to claim 10, wherein the total amount of the product gas mixture P.sub.u, formed in the lower reactor region is continuously transferred to the gas collecting region by one or more non-pressure-bearing installed device(s), wherein in the presence a catalyst in the installed device(s) the sulphur and hydrogen present in the product gas mixture P.sub.u are reacted to form further hydrogen sulphide.

13. The process according to claim 12, wherein the catalyst is cooled by heat transfer of the heat of reaction, released by the reaction of sulphur and hydrogen in the catalyst, to the sulphur melt.

14. The process according to claim 12, wherein the proportion of hydrogen sulphide in the product gas mixture P.sub.u prior to introduction into the one or more installed devices comprising the catalyst is at least 60% of the gas volume.

15. The process according to claim 10, further comprising condensing the sulphur present in the product gas mixture P.sub.final and recycling the condensed sulphur directly into the reactor.

16. The process according to claim 10, wherein the hydrogen sulphide is prepared at a pressure of 5 to 15 bar.

17. The process according to claim 10, wherein the sulphur melt has a temperature of 400 to 450 C.

18. The process according to claim 10, wherein the sulphur melt is circulated continuously according to the airlift pump principle.

Description

(1) FIG. 1 shows, by way of example and schematically, a reactor which can be used in accordance with the invention for preparation of hydrogen sulphide from hydrogen and sulphur.

(2) The reactor 1, shown in FIG. 1, comprises an outer, pressure-bearing vessel containing a sulphur melt 3 in the lower region 2 thereof. By means of supply devices 5, hydrogen can be introduced into the sulphur melt, and is accommodated directly by the first caverns 4. Supply devices 5a can also be used to introduce hydrogen directly into the gas space 12 of the first caverns 4. In the gas space 12 of the first caverns 4, the product gas mixture P.sub.1 comprising hydrogen, sulphur and hydrogen sulphide is formed. The reactor shown also has additional supply devices 9, by means of which hydrogen can be supplied directly to the second caverns 8, wherein the product gas mixture P.sub.2 forms in the gas space 13. By means of supply devices 9a, hydrogen can also be introduced directly into the gas space 13 of the second caverns 8. The gas mixture flowing upward is temporarily accommodated by the third caverns 10, wherein the product gas mixture P.sub.3 forms in the gas space 14. In the gas space 15, the entire product gas mixture P.sub.u formed in the lower reactor region collects. The gas space 15 is separated from the gas collecting region 6 by an intermediate tray 16. The product gas mixture P.sub.u is transferred from the gas space 15 to the gas collecting region 6 using the installed device 7. The installed device 7 is designed as a U-shaped tube which dips into the sulphur melt 3. Via orifices 17 and 18, gas can flow into and out of the installed device 7. The installed device 7 can accommodate a catalyst which enables the further conversion of sulphur and hydrogen in the product gas mixture P.sub.u to form the product gas mixture P.sub.final. The product gas mixture P.sub.final comprising sulphur and hydrogen sulphide is accommodated in the gas collecting region 6 and can be withdrawn from the reactor via the orifice 19, or optionally supplied to a reflux condenser. In the region of the sulphur melt, the reactor also comprises an inner wall 11 which serves for continuous circulation of the sulphur melt by the airlift pump principle.

(3) FIG. 2 shows a schematic of four different illustrative cavern arrangements in the case of a reactor with first, second and third caverns. The caverns consist of intermediate trays each having one orifice. The orifices are each arranged such that the gas mixture must flow from the first to the second and from the second to the third cavern. Top left is a reactor according to the invention with a first, second and third cavern in each case. The three caverns each have the same geometry. Top right is a reactor according to the invention with a first, second and third cavern in each case, with continuously increasing weir height and hence increasing residence time of the gas mixture from the first to the third cavern. Bottom left is a reactor according to the invention with a first, second and third cavern in each case, all caverns having the same weir height. The second cavern has a circular orifice in the middle of the intermediate tray. Bottom right is a reactor according to the invention with a first, second and third cavern in each case, with continuously increasing weir height and hence increasing residence time of the gas mixture from the first to the third cavern.

(4) FIG. 3 shows a schematic of illustrative embodiments of caverns. The caverns shown have an intermediate tray with a weir running along the edge thereof. Various embodiments are shown for the lower edge of the weir A and the profile of the weir B.

EXAMPLES

Example 1 (Comparative Example)

(5) 1000 l (STP)/h of hydrogen were introduced continuously via a frit at the base into a tube having an internal diameter of 5 cm which had been filled with liquid sulphur up to a height of 1 m. The consumption of sulphur was compensated for by further metered addition of liquid sulphur, while keeping the fill level constant. Sulphur removed from the product gas stream by condensation was recycled into the upper region of the tube in liquid form. Above the liquid sulphur, jacketed thermocouples for temperature measurement were provided at intervals of 10 cm. While the reactor was heated to 400 C. electrically via the outer wall, a homogeneous temperature of about 397 C. was present within the sulphur. However, the thermocouples above the sulphur showed a maximum temperature of 520 C. In addition, above the liquid sulphur, new material samples made from standard stainless steel (1.4571) were provided at the location of maximum temperature. After an operating time of about 400 h, the material samples were removed and showed severe corrosion phenomena in the form of flaking and weight loss.

Example 2 (Comparative Example)

(6) Example 1 was repeated, except that the height of the liquid sulphur was raised to 4 m. The value of the maximum temperature above the liquid sulphur was maintained. Severe corrosion phenomena likewise occurred on the material samples.

Example 3 (Comparative Example)

(7) Example 2 was repeated, except that 15% by weight of a pulverulent Co.sub.3O.sub.4MoO.sub.3/Al.sub.2O.sub.3 catalyst were suspended in liquid sulphur. The value of the maximum temperature above the liquid sulphur was maintained. Severe corrosion phenomena likewise occurred on the material samples.

Example 4

(8) The process according to the invention was examined in a pilot plant. The pilot reactor had a height of approx. 5.5 m, a diameter of approx. 0.5 m and a volume of approx. 0.8 m.sup.3. The pilot plant was equipped with four caverns of equal dimensions in series. 70 m.sup.3 (STP)/h of hydrogen were metered in continuously via the hydrogen feeds, which corresponded to a hydrogen load of 3700 m.sup.3 (STP)(H.sub.2)/(m.sup.3 (cavern volume).Math.h) based on the single cavern. Spent sulphur was replenished under fill level control. Sulphur removed from the product gas stream by condensation was recycled into the reactor in liquid form. The pressure in the reactor was 12 bar. The temperature in the liquid sulphur was 430 C. The residence time in the caverns was 5 s in each case. The H.sub.2 conversion through homogeneous reaction in the caverns was about 90%. By means of thermocouples installed in a fixed manner in the reactor, the temperature within the caverns and above the sulphur melt was measured. The highest temperature measured in the caverns under these circumstances was 479 C. Above the liquid sulphur phase, no commencement of a homogeneous reaction was discernible. The gas temperature above the liquid sulphur corresponded virtually to the temperature of the liquid sulphur, such that there were no increased demands on the material of the pressure-bearing jacket in the region of the gas phase above the liquid sulphur.

(9) The gas phase then flowed to and through the catalyst in the installed device, as shown schematically in FIG. 1 (7). The hydrogen remaining was then converted virtually completely over the catalyst (overall conversion of H.sub.2: 99.86 mol %). The gas hourly space velocity on the catalyst was 3700 m.sup.3 (STP)(H.sub.2)/(m.sup.3 (bed volume of catalyst).Math.h). There was virtually no occurrence of corrosion in the form of flaking or weight loss on the material used. Material samples made from standard stainless steel (1.4571) which were installed for comparative purposes had only moderate corrosion attack.

LIST OF REFERENCE NUMERALS

(10) (1) Reactor (2) Lower reactor region (3) Sulphur melt (4) First caverns (5, 5a) Hydrogen supply device to the first caverns (6) Gas collecting region (7) Installed device for transfer of gas from the lower reactor region to the gas collecting region, optionally containing a catalyst (8) Second caverns (9, 9a) Hydrogen supply device to the second caverns (10) Third caverns (11) Inner wall (12) Gas space of the first caverns (13) Gas space of the second caverns (14) Gas space of the third caverns (15) Gas space of the lower reactor region (16) Intermediate tray (17) Orifice (18) Orifice (19) Orifice