Method and device for degassing liquid sulphur

Abstract

Embodiments of the invention include a method for degassing liquid sulphur in a container, a first area of the container being flooded with liquid sulphur and a second area of the container being flooded with a gas, and a gas flow being injected into the first area, wherein liquid sulphur is sprayed into the second area. Embodiments of the invention include a device for degassing liquid sulphur having a container comprising two adjacent areas, the first area being flooded with liquid sulphur and the second area being flooded with gas, and having at least one device for injecting a gas flow into the first area, characterized by a device for spraying liquid sulphur opening into the second area. Other embodiments are also included herein.

Claims

1. A continuous method for degassing liquid sulphur in a container being divided into three chambers, a first area of the container being flooded with liquid sulphur and a second area of the container being flooded with a gas, and a gas flow being injected into the first area, wherein liquid sulphur is sprayed into the second area; wherein the degassing is carried out in the three chambers not fully separated from each other, wherein liquid sulphur is introduced continuously in the first chamber; wherein in at least a first and a second chamber of the three chambers H.sub.2S is removed and wherein in a third chamber downstream of the first and second chambers SO.sub.2 is removed; wherein in the second chamber an oxygen containing gas stream is used as an injected gas stream and in the third chamber downstream of the first and second chambers an inert gas is used as an injected gas stream; wherein at least some of the degassed liquid sulphur is drawn from the third chamber.

2. The method according to claim 1, wherein liquid sulphur is pumped from the first area into the second area, where it is sprayed.

3. The method according to claim 1, wherein a further gas flow flows through the second area.

4. The method according to claim 3, wherein the liquid sulphur is sprayed in counterflow to the gas flow flowing through the second area.

5. The method according to claim 1, wherein the liquid sulphur is kept at a temperature of 120 to 140 C.

6. The method according to claim 1, wherein the liquid sulphur is kept at a temperature of 130 to 135 C.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) In the drawings:

(2) FIG. 1 shows a basic degassing principle scheme,

(3) FIG. 2 is a schematic view of an embodiment according to the invention of a batch reactor,

(4) FIG. 3 is a schematic view of an embodiment according to the invention of a continuous method,

(5) FIG. 4 is a schematic view of an embodiment according to the invention of a continuous method with integrated SO.sub.2 degassing.

DETAILED DESCRIPTION

(6) FIG. 1 illustrates the reactions in liquid sulphur and material transfer mechanisms involved in the degassing process. It shows, inside a container, a gas phase GAS located above the liquid sulphur S(lq). H.sub.2S dissolved in the liquid sulphur can be transferred by diffusion into the gas phase via 3 interfaces constituted by: 1/stripping gas bubbling in mass sulphur, 2/atomised sulphur in flushing gas, 3/interface between mass sulphur phase (area 2) and flushing gas phase (area 3). At the same time, SO.sub.2 can be transferred in the same manner from the liquid phase into the gas phase. Dissolved H.sub.2S in the liquid sulphur is in equilibrium with the formation of hydrogen polysulphides. Water, sulphur, SO.sub.2 and SO.sub.3 can be produced from the hydrogen sulphide when GAS contains oxygen. Similar reactions also occur with hydrogen polysulphides and oxygen.

(7) FIG. 2 shows the design of the device according to the invention when it is implemented in discontinuous mode with a batch reactor. This reactor comprises a container 1 which is divided into the two areas 2 and 3. As the first area, the area 2 is flooded with liquid sulphur whilst the second area 3 is flooded with gas.

(8) A line 11 is guided into the first area 2, through which line a system for injecting stripping gas is fed with the stripping gas. This injection device 12 comprises a multiplicity of nozzles to create a fine dispersion of stripping gas in the bulk sulphur.

(9) Furthermore, gas is flushed through the second area 3, which gas flows in via a line 13 and escapes via a line 14. The gas flows basically parallel to the surface of the liquid sulphur. The gaseous sulphur compounds removed from the liquid sulphur are carried over in the gas drawn via the line 14.

(10) The container is filled with liquid sulphur via a line 20. This filling process does not take place continuously, but at the beginning of the method. Liquid sulphur can be removed from the first area via the pump system 21 via lines 22 and 24 and fed to an atomising device 25. This atomising device opens into the second area 3, where it atomises the liquid sulphur from the first area 2 into the second area 3 flooded with a gas mixture.

(11) Once the reactor 1 has been degassed, the liquid sulphur can be pumped out from the container 1 via the line 22 and the line 23 with the aid of the pump 21.

(12) FIG. 3 shows the design of a plant according to the invention for carrying out a continuous method. The method takes place in a container 1 which comprises a first area 2 flooded with liquid sulphur and a second area 3 flooded with gas. In addition, the container 1 is divided into two chambers a, b by a partition wall 4, wherein the partition wall 4 does not terminate flushly, and therefore the two chambers a, b are interconnected both through openings below and above the partition wall 4. The bottom opening allows the sulphur to flow continuously from chamber a to chamber b, and the above opening allows the flushing gas to flow at countercurrent from chamber b to chamber a. A stripping gas is fed to the spraying device 12 via the pump 10 and the line 11, through which injection device stripping gas is dispersed into the second chamber via a plurality of nozzles. The injection for the stripping gas can be provided at the base of the second chamber, however it is also possible to perform the injection in the first chamber or in both chambers. The embodiment shown has the advantage that the amounts of dissolved hydrogen sulphide and hydrogen polysulphides have already decreased in the first chamber and, in the second chamber, the additional bubbling through is only undertaken to reach the legally prescribed threshold of residual H2S in degassed sulphur. The number of bubbling through devices requires is thus reduced, minimal oxygen is introduced into the system with use of air, and at the same time a sufficiently good yield is obtained.

(13) A gas flow is also introduced, via the line 13, into the second area 3 flooded with gas, which gas flow flows out from the second chamber b in counterflow to the direction of flow of the liquid sulphur and into the first chamber a, from which it is removed via the line 14. The removal takes place via an appropriate educting device, such as a steam ejector, which is fed via the line 15. The contained mixture from the gas flows and gaseous H.sub.2S is then discharged via the line 17.

(14) Liquid sulphur is introduced continuously in the first chamber a via the line 20 into the first area 2 flooded with liquid sulphur. A pump 21 is located herein in the first chamber and draws liquid sulphur via the line 22 from the first area 2 and feeds it to the atomising device 25. This atomising device 25 is located in the second area 3, flooded with gas, of the first chamber. The liquid sulphur partially degassed in chamber a flows to chamber b through the opening at bottom of partition wall 4.

(15) A pump 21 which, via a line 22, takes liquid sulphur from the first area 2 of the second chamber is also located in the second chamber. This is fed, in part, via the line 24 to a second atomising device 25 which atomises liquid sulphur into the gas phase 3 of the second chamber. Liquid sulphur is also drawn from the system via the line 23, wherein the drawn amount corresponds to the fed amount. The removed amount can be controlled via a control device, for example a level control valve 26, to such an extent that the amount of liquid sulphur in areas 2 of the container is such that the total residence time of the sulphur is sufficient to reach the required legal specification of 10 ppm by weight H.sub.2S. In addition, the feed of sulphur can be regulated or controlled via the line 20 in a manner which is not illustrated.

(16) FIG. 4 shows a continuous method for simultaneous degassing of H.sub.2S and SO.sub.2. This method is also carried out in a container 1 which comprises a first area 2 flooded with sulphur and a second area 3 flooded with gas. The container is divided by two partition walls 4 and 5 into three chambers a, b and c, first two chambers a and b being dedicated to H2S removal and third chamber c being dedicated to SO2 removal. The partition walls 4 and 5 are installed in such a way that an opening is created above and below each wall and therefore gas and sulphur can freely circulate at countercurrent from one chamber to the next one.

(17) A first stripping gas, such as air, is fed via the pump 10 and line 11 to the bubbling device 12, such as a multiplicity of nozzles. This introduction of the stripping gas occurs in the second chamber b. In this chamber b, a gas flow is also injected into the second area 3, filled with gas, via the line 13. The total flow of gases introduced via lines 11 and 13 then sweeps the area 3 of chamber a and then escapes from the container via the line 14 in carrying away the H.sub.2S drawn from the liquid sulphur. This line 14 opens into an educting system 16, which can be designed as a steam rejector which is fed with the propellant via the line 15. The total gas volume of the method can then ultimately be discharged via the line 17.

(18) Liquid sulphur to be degassed is introduced via the line 20 into the first chamber a. This sulphur is recirculated into the first chamber a, via the pump 21, in the line 22, which opens into an atomising device 25. This atomising device 25 is located in the second area 3 of the first chamber a.

(19) The same device for recirculation and atomisation of the sulphur is also located in the second chamber b, where a pump 21 feeds liquid sulphur via the line 22 to an atomising device 25, which atomises the liquid sulphur in the second area 3, flooded with gas, of the second chamber b.

(20) Lastly, the third chamber c which is dedicated to the removal of SO2 is equipped in the same manner with an atomising and recirculation pump 21 which feeds the atomising device 25 via the line 22 and the line 24. The atomising device 25 is provided in the gas phase 3 of the third chamber c. At the same time, some of the liquid sulphur, which is now degassed, can be drawn from the container via the lines 22 and 23.

(21) The flow of degassed sulphur is drawn off at the rate of the crude sulphur fee ding the container via the line 20. It can be achieved by means of a control device such as a level control valve 26 on the withdrawal line 23; this control valve continuously maintaining the sulphur at a level in the container such as it provides the residence time needed to achieved the prescribed specifications of residual H2S and SO2 in the degassed sulphur.

(22) Lastly, in the third chamber c, a stripping gas is introduced into an injection device 31 via the line 30. This injection device 31 that is constituted of a plurality of nozzles installed at the bottom of the liquid phase ensures the proper dispersion of the stripping gas throughout the sulphur mass. This stripping gas can be inert gas, such as nitrogen, whilst air is injected via the fan 10 and line 11. The gas flow introduced via the line 13 can be air.

(23) The stripping gas flow introduced via the line 30, after it has contacted countercurrently the sulphur is directed to gas phase of the chamber b wherein it is mixed with the stripping gas and flushing gas respectively fed in through the lines 11 and 13. This mixture of gases is then routed to the gas phase of chamber a. The total flow of gases thus introduced in the container is withdrawn via an appropriate educting device 16, can be a steam ejector which is fed via the line 15. The total mixture of gas flows containing degassed H2S and SO2 is then discharged via line 17.

LIST OF REFERENCE NUMERALS

(24) 1 container 2 first area (liquid phase) 3 second area (gas phase) 4, 5 partition wall 10 fan-blower 11 line 12 bubbling device 13, 14, 15 line 16 educting device 17 line 20 line 21 pump 22, 23, 24 line 25 bubbling device 26 control device 30 line 31 injection device a first chamber b second chamber c third chamber