Method and apparatus for degassing sulphur

A process for removing hydrogen sulfide out of liquid sulfur is provided by passing liquid sulfur and saturated steam through at least one acceleration nozzle within a container maintained at less than atmospheric pressure. The saturated steam and liquid sulfur discharged from the acceleration nozzles converge at a common point outside the acceleration nozzle and collide against an impact target so that hydrogen sulfide is removed out of the liquid sulfur. Two acceleration nozzles may be used positioned on a common plane with the outlets of the nozzles facing each other. The discharged steam adiabatically expands within the container which causes the discharged streams to accelerate and which also causes the temperature of the liquid sulfur drop.

FIELD OF THE INVENTION 
The present invention relates to the removal of Hydrogen Sulfide gas from 
liquid sulphur. 
BACKGROUND OF THE INVENTION 
Hydrogen sulfide gas is nearly always present in sulphur produced during 
the processing of hydrocarbons. When the hydrogen sulfide gas exceeds 30 
parts per million, it presents a danger to personnel of hydrocarbon 
processing plants. It is, therefore, desirable to degas the sulphur to 
remove hydrogen sulfide gas to below these levels. 
The most common method for degassing sulphur involves steam sparging. In 
accordance with this method, steam is introduced into the liquid sulphur 
from below. The steam creates air bubbles which rise up through the liquid 
sulphur. As the air bubbles rise the volume of liquid sulphur above 
decreases and the surface pressure upon the air bubble decreases causing 
it to expand. The steam sparging method, as described, does not produce 
satisfactory results. The residence time in the liquid sulphur of the 
rapidly rising bubbles is too short and the surface area of the large 
bubbles is too limited to effectively release hydrogen sulfide gas from 
the liquid sulphur. 
SUMMARY OF THE INVENTION 
What is required is a method and apparatus for degassing sulphur that is 
more effective at releasing hydrogen sulfide gas. 
According to one aspect of the present invention there is provided a method 
for degassing sulphur. Firstly, focus at least one nozzle at an impaction 
target. Secondly, direct streams of liquid sulphur through the at least 
one nozzle at the impaction target. Thirdly, inject saturated steam into 
the stream of liquid sulphur to create a mixed stream of steam and liquid 
sulphur. A rapid expansion of the steam causes an acceleration of each of 
the mixed stream of steam and liquid sulphur resulting in a violent 
collision with the impaction target. 
With the method, as described, a stream of liquid sulphur is violently 
collided with an impaction target. Steam is used to dramatically increase 
the impact velocity. By following the teachings of this method impact 
velocities approaching 7000 feet per minute can be attained. It is 
preferred that a plurality of nozzles be positioned on a common horizontal 
plane with a stream from one of the nozzles serving as the impaction 
target for the other of the nozzles. A preferred configuration has two 
nozzles positioned in 180 degree opposed relation. 
Although beneficial results can be obtained through the use of the method, 
as described, even more beneficial results may be obtained when a catalyst 
is injected with the saturated steam into the stream of liquid sulphur. 
The catalyst is a bonding agent capable of forming a chemical bond with 
hydrogen sulfide gas. The use of such a catalyst bonding agent enhances 
the process of degassing the sulphur. There are a variety of suitable 
catalyst bonding agents that can be used, such as amine or potassium 
citrate, to name just a few. 
According to another aspect of the present invention there is provided an 
apparatus for degassing sulphur which is comprised of a containment vessel 
having a top, a bottom, and peripheral sidewalls. A plurality of inlet 
nozzles are secured on a common horizontal plane to the peripheral 
sidewalls. Each nozzle has a first inlet for receiving a first fluid, a 
second inlet for receiving a second fluid and a single outlet for 
discharging a mixed stream of the first fluid and the second fluid. The 
mixed discharge stream of one of the nozzles is focused at the mixed 
discharge stream of the other of the nozzles, such that the mixed 
discharge streams impact with each other. Means is provided for drawing 
vapours from the containment vessel positioned adjacent the top of the 
containment vessel. An outlet is positioned adjacent the bottom of the 
containment vessel for removing degassed sulphur. 
Although there are a variety of configurations that can be used in terms of 
the number of nozzles, it is preferred that two nozzles are provided 
oriented in 180 degree opposed rotation. 
Although there are a variety of nozzles that are capable of handling a 
mixed stream of steam and sulphur, it is preferred that the nozzle enhance 
the accelerating effect of the rapidly expanding steam. Even more 
beneficial results may be obtained when each nozzle includes a body having 
a passage leading to the outlet and the first inlet has an extension 
portion disposed in the passage. A steam chamber communicates with the 
first inlet and circumscribes the second inlet. The steam chamber has a 
plurality of injection ports focused to discharge at a single intersection 
point in the passage leading to the outlet. The "focused" injection ports, 
as described, tend to push the stream of liquid sulphur further enhancing 
the impact velocity.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
The preferred embodiment, an apparatus for degassing sulphur generally 
identified by reference numeral 10, will now be described with reference 
to FIGS. 1 through 5. 
Referring to FIG. 1, apparatus 10 includes a containment vessel 12 having a 
top 14, a bottom 16, and peripheral sidewalls 18. Two inlet nozzles 20 and 
22 are secured on a common horizontal plane to peripheral sidewalls 18. 
Referring to FIG. 3, each nozzle 20 and 22 has a first inlet 24 for 
receiving a first fluid, a second inlet 26 for receiving a second fluid 
and a single outlet 28 for discharging a mixed stream of the first fluid 
and the second fluid. Referring to FIG. 1, nozzles are oriented in 180 
degree opposed relation, such that the mixed discharge streams are 
directed to impact with each other. An eductor 30 is used as means for 
drawing vapours from containment vessel 12. Eductor 30 is positioned at 
top 14 of containment vessel 12. Vapours pass through a demister pad 31 to 
eductor 30. An outlet 32 is positioned adjacent bottom 16 of containment 
vessel 12 for removing degassed sulphur. A pump 34 is used to pump liquid 
sulphur through flow lines 36 to nozzles 20 and 22. Saturated steam passes 
through flow line 38, where it is diverted by a series of secondary flow 
lines. Secondary flow line 40 controlled by valve 42 brings saturated 
steam to eductor 30. Secondary flow lines 44 and 46 controlled by valves 
48 and 50, respectively, bring saturated steam to nozzles 20 and 22. 
Secondary flow line 52 controlled by valve 54 brings saturated steam to 
steam sparger 56 positioned within containment vessel 12 spaced from 
bottom 16. Associated with the various saturated steam lines is a catalyst 
injection system. A catalyst from reservoir 58 passes through injection 
unit 50 and meter 62 into injection lines 64 and 66. Injection line 64 
splits into two branches 64a and 64b leading to nozzles 20 and 22, 
respectively. Each of branches 64a and 64b is controlled by valves 68 and 
70, respectively. Branches 64a and 64b tap into secondary steam flow lines 
44 and 46, respectively, downstream of valves 48 and 50. Injection line 66 
is controlled by valve 72. Injection line 66 taps into secondary steam 
flow line 52 leading to steam sparger 56, downstream of valve 54. Outlet 
32 is connected to a drainage line 74, having two branches 74a and 74b. 
Connected to branch 74a of drainage line 74 is a drain valve 76; the use 
of which is limited to the cleaning of containment unit 12. Connected to 
branch 74b of drainage line 74 is a control valve 78 leading to a pump 80 
driven by motor 82 and through a series of valves 84 and 86. Referring to 
FIG. 3, the preferred form of nozzle 20 and 22 includes a body 88 having a 
passage 90 leading to outlet 28. First inlet 24 has an extension portion 
92 disposed in passage 80. A steam chamber 94 communicates with second 
inlet 26 and circumscribes extension portion 92 of first inlet 24. First 
inlet 24 communicates with sulphur flow lines 36. Second inlet 26 of 
nozzle 20 communicates with steam flow line 44 and second inlet 26 of 
nozzle 22 communicates with steam flow line 46. Steam chamber 94 has a 
plurality of injection ports 96 focused to discharge at a single 
intersection point 98 in passage 90 leading to outlet 28. Referring to 
FIG. 5, it can be seen that injection ports 96 are shaped to create a 
venturi effect. Referring to FIG. 3, the focusing of injection ports 96, 
as described, tend to push the stream of liquid sulphur further enhancing 
the impact velocity. The configuration of injection ports is further 
illustrated in FIG. 4. Referring to FIG. 2, it is preferred that 
containment unit 12 be made portable. For that purpose it is mounted on a 
platform 100 supported by ground engaging wheels 102. Containment unit 12 
is mounted to platform 100 by means of a hinged mounting assembly 104. 
This enables containment unit 12 to be moved from a substantially vertical 
position, into a substantially horizontal position where top 14 of 
containment unit 12 is supported by a saddle support 106. 
The use and operation of apparatus 10, as illustrated in FIGS. 1 through 5 
will now be described in relation to the preferred method for which such 
apparatus was developed. Firstly, focusing at least one nozzle at an 
impaction target. In this case two nozzles 20 and 22 positioned in 180 
degree relation on a common horizontal plane are used with a stream from 
one of the nozzles serving as the impaction target for the other of the 
nozzles, as previously described and illustrated with reference to FIG. 1. 
Additional nozzles can be added, if desired, Secondly, direct streams of 
liquid sulphur through nozzles 20 and 22. With reference to FIG. 1, liquid 
sulphur is pumped by pump 34 along flow lines 36 to first inlet 24 of both 
nozzles 20 and 22. Thirdly, inject saturated steam into the streams of 
liquid sulphur to create mixed streams of steam and liquid sulphur. With 
reference to FIG. 1, the saturated steam, as described, is provided to 
second inlet 26 of nozzles 20 and 22 through secondary steam flow lines 44 
and 46, respectively. Referring to FIG. 3, it can be seen how saturated 
steam flowing through secondary inlet 26 is mixed with liquid sulphur 
pumped through first inlet 24. Liquid sulphur passes from first inlet 24 
along extension portion 92 and into passage 90 leading to outlet 28. 
Saturated steam from secondary inlet 26, enters stem chamber 94 and then 
passes through injection ports 96 to intersect with the liquid sulphur at 
intersection point 98; prior to passing out of outlet 28 as a mixed 
stream. When a mixed stream of steam and liquid sulphur is created, as 
described, a rapid expansion of the steam causes an acceleration of each 
of the mixed streams of steam and liquid sulphur resulting in a violent 
collision of the mixed streams. In addition, it can be seen from a review 
of FIG. 3, having injection ports 96 focused upon intersection point 98 
tend to push the stream of liquid sulphur further enhancing the impact 
velocity. With the method, as described, impact velocities approaching 
7000 feet per minute can be attained. It is preferred that a catalyst be 
injected with the saturated steam into the stream of liquid sulphur. The 
catalyst is a bonding agent capable of forming a chemical bond with 
hydrogen sulfide gas. The use of such a catalyst bonding agent enhances 
the process of degassing the sulphur. There are a variety of suitable 
catalyst bonding agents that can be used, such as amine or potassium 
citrate. In FIG. 1, the containment unit 12 is set up for use with amine 
as the catalyst. Amine is placed in reservoir 58. It passes through 
injection unit 60 and meter 62 into injection lines 64 and 66. Injection 
line 64 splits into two branches 64a and 64b leading to nozzles 20 and 22, 
respectively. Each of branches 64a and 64b is controlled by valves 68 and 
70, respectively. Branches 64a and 64b tap into secondary steam flow lines 
44 and 46, respectively, downstream of valves 48 and 50. In this way amine 
is mixed with the saturated steam as it passes through secondary inlet 26 
into steam chamber 94. 
The degassing operation will now be summarized. High velocity sulphur 
steams are emitted from diametrically opposed nozzles 20 and 22. The 
streams are accelerated through steam injection. The mixed streams impact 
onto each other to produce an impact area that squeezes the dissolved 
Hydrogen sulfide gas out of the host sulphur molecule structure. The 
hydrogen sulfide gas is thus squeezed out of the liquid sulphur and 
removed from top 14 of containment unit 12 by a vacuum generated by 
eductor 30. The hydrogen sulfide gas will be evacuated, together with low 
pressure steam from inside containment unit 12. To achieve the above 
mentioned velocity, saturated steam at approximately 150 pounds per square 
inch is allowed to expand from steam chamber 94 through injection ports 
96. The steam velocities so attained can reach speeds of 7000 feet per 
minute, depending upon the back pressure inside containment unit 12. The 
focus on intersection point 98 impacts further velocity to the mixed steam 
of steam and liquid sulphur. When the mixed stream collide, kinetic energy 
will be converted to potential energy (or pressure energy). The pressure 
change will be rapid, thus squeezing out the hydrogen sulfide gas in a 
solution state from inside the sulphur. A very large spray of small 
droplets is generated surrounding the impact area. The remaining hydrogen 
sulfide gas inside the droplets is presented with a second opportunity to 
escape through the surface area of the droplets. The pressure of 
containment unit 12 (steam, hydrogen sulfide gas and sulphur) will be kept 
low by eductor 30, thus assisting in the escape of the hydrogen sulfide 
gas out of the droplets. A catalyst, preferably amine, that is evaporated 
inside the steam will offer the hydrogen sulfide gas an easy replacement 
host, instead of the liquid sulphur. There is one last area where hydrogen 
sulfide gas can be removed from liquid sulphur. Steam sparger 56 receives 
amine through injection line 66. The result is that steam sparger 56, not 
only keeps the liquid sulphur hot, but also assists in additional hydrogen 
sulfide gas trace removal. The adiabatic expansion of the steam will cause 
the temperature of the sulphur to drop. This is the main function of steam 
sparger 56, to keep the liquid sulphur hot. The degassed liquid sulphur is 
withdrawn through outlet 32 at a fixed rate and under level control via 
pump 80 to a storage unit (not shown). 
It will be apparent to one skilled in the art that modifications may be 
made to the illustrated embodiment without departing from the spirit and 
scope of the invention as hereinafter defined in the claims.