AU645149B2

AU645149B2 - A method and apparatus for treating and storing sulfur containing gas so as to prohibit the degradation of same

Info

Publication number: AU645149B2
Application number: AU88151/91A
Authority: AU
Inventors: Rui Rodrigues; Irene Romero
Original assignee: Intevep SA
Current assignee: Intevep SA
Priority date: 1991-03-14
Filing date: 1991-11-25
Publication date: 1994-01-06
Anticipated expiration: 2011-11-25
Also published as: GB2254018A; CN1064940A; GB2254018B; RU2075750C1; AU8815191A; GB9124894D0; NO914612L; NL9102110A; CA2056659C; NO914612D0

Description

S F Ref: 198202

AUSTRALIA

PATENTS ACT 1990 IN COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

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4 u Name and Address of Applicant: Actual Inventor(s): Address for Service: Invention Title: Intevep, S.A.

Apartado 76343 Caracas 1070A

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Irene Romero, Rui Rodrigues Spruson Ferguson, Patent Attorneys Level 33 St Martins Tower, 31 Market Street Sydney, New South Wales, 2000, Australia A Method and Apparatus for Treating and Storing Sulfur Containing Gas so as to Prohibit the Degradation of Same The following statement is a full description of this invention, including the best method of performing it known to me/us:- 90-311 BACKGROUND OF THE INVENTION The present invention is drawn to a method and apparatus for treating a gas sample containing sulfur and, more particularly, a method and apparatus for treating a gas sample containing sulfur so as to prohibit the degradation of the sulfur content of the gas sample over time when stored.

One of the major concerns facing industry today is the control of environmental pollution. One of the most *0 10 harmful pollutants present in process gases used and/or produced by industry are sulfur compounds. The *0 e undesirability of sulfur compounds are exhibited not Sonly in environmental pollution caused by burning of gas S0* containing sulfur but also corrosion of plant and laboratory equipment which results from contact with sulfur compounds.

0 In light of the foregoing, it is highly desirable to be able to accurately analyze process gases and the 0 S like and their sulfur content in order to insure proper 2otreatm3nt of said gases so as to avoid the deleterious

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effects attributed to the sulfur .n such process gases.

0* To date, the sampling and storing of sulfur gases has -2- 90-311 remained an unsolved problem. The main reason for this is that the sulfur content of a gas sample which is being analyzed tends to degradate over time and, therefore, the value measured tends to be lower than the true value of the sulfur content of the gas actually being employed in various commercial situations. This decomposition of sulfur has been observed even at sulfur concentrations below 5% and occur in all types of gases whether they be natural gases, process gases or air.

10 The prior art has attempted to address the foregoing problem. "Methods of Sampling and Storage of OuOI Air containing Vapors and Gases", Int. J. Air. Poll., Vol. 2, pp. 142-158, 1959, quantifies several of the difficulties encountered in the storage of sulfur compounds including the difficulty of measuring concentrations of sulfur compounds as compared to various other compounds, and the fast decomposition time 0* S of the sulfur compounds over time. While it was found that the decomposition time of sulfur dioxide could be °*,ee2 2Dextended by proper choice of storage container, decomposition nevertheless occur. over a rather short 4 period of time. Thus even with a proper choice of materials, effective long-term storage is not possible.

In addition to the difficulties of storing sulfur aS compounds, it is likewise difficult to accurately measure the concentration of sulfur compounds in gases.

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90-311 One of the most reliable alternatives available to date for the quantitative determination of sulfur content is the Drager method. Although the Drager method allows measurements to be made in the field, the method has limitations: reduced accuracy, the method is sensitive to only some sulfur species, it requires a great deal of expertise by the operator, and optical interference appears whenever more than one sulfur compound is present. Further, the Drager method 0 Ioprovides no means for storage of the gas samples.

I0 *0 Other techniques have also been developed for the analysis of sulfur compounds.

0 0 o Kimbell, U.S. Patent No. 3,756,781 teaches a method of analyzing sulfur content in hydrocarbons by first breaking the hydrocarbons down into simpler molecular S structures.

0 Sisti, U.S. Patent No. 4,293,308 discloses a method e 0 and apparatus for determining very small percentages of 0 a 0BO 0 sulfur in gas samples.

0:090: 0 3 o Overall, sulfur compounds in gases are very difficult to measure with time due to the breakdown of 0 o* the compounds while in storage. Yet, as the harmful effects of these compounds appear from even very low concentrations, it is desirable to detect concentrations 2fof sulfur in the parts per billion range. There exists a need for a simple method and apparatus to sample and -4- A 1 L J7~: (Y~ITl'T n 7C- 90-311 store gases containing sulfur compounds with little or no breakdown of the ccmpounds while in storac-, so that sulfur concentrations can be accurately measured at later times. In addition, to be used more effectively, such an apparatus should be portable so that it may be moved to the supply of gas. There are many applications which require an accurate sulfur reading at later times, and none of the prior art suggests such a solution for this problem.

0°10 Accordingly, as aforementioned, it would be highly desirable to provide an efficient method and apparatus for treating sulfur containing gases so as to prohibit the degradation of the sulfur contained in the gases over time thereby allowing for an accurate measurement is of the actual sulfur content of the gases.

1 0Accordingly, it is a principal object of the present invention to provide a method and apparatus for S0 storing sulfur containing gases so as to prohibit the &seeom )egradation of the sulfur content of the gas over time.

It is a particular object of the present invention o. i t:o provide a method as aforesaid wherein the sulfur containing gas is pretreated prior to storage so as to prohibit degradation of the sulfur content of same over time.

3c It is a still further object of the present invention to provide a storage container which is yl- r I T1--l I 6 non-reactive to sulfur contained in a gas sample.

It is a further object of the present invention to treat a sulfur containing gas so as to prohibit the degradation of same over time by dehydrating the gas and storing the gas in non-reactive containers.

Further objects and advantages of the present invention will appear hereinbelow.

SUMMARY OF THE INVENTION In accordance with a first embodiment rof this invention there is provided a process for treating sulfur containing gases so as to prohibit the degradation of the sulfur content of the gas over time comprising the steps of: providing a sulfur containing gas sample; dehydrating said gas sample so as to obtain a water content in said gas sample of less than 100 ppm to produce a dried gas sample; and storing said dried gas sample in a container which is non reactive with the sulfur in the gas.

In accordance with a second embodiment of this invention there is provided a process for treating sulfur containing gases so as to prohibit the degradation of the sulfur content in those gases over time comprising 20 the steps of: providing a sulfur containing gas sample having a known water content; contacting said gas sample with a dehydrating agent in an amount of greater than or equal to 1.50kg of said dehydrating agent per 25 liter of water to be removed from said gas sample so as to obtain a dried gas sample; and 66 6 storing said dried gas sample in a container which is non 0 reactive to sulfur.

In accordance with a third embodiment of this invention there is provided an apparatus for treating sulfur containing gas samples by the process of the first embodiment so as to prevent a change in sulfur content over time when stored, which apparatus comprises: means for dehydrating said gas sample thereby producing a dried gas sample with a water content up to 00 ppm; and /means for storing said dried gas sample.

The present invention is drawn to a method and apparatus for treating and storing gas samples containing sulfur and, more FLY particularly, a method and apparatus for treating a gas sample containing I sulfur wherein the degradation of the sulfur content of the gas sample 1703alii 6A over time is prohibited.

In accordance with the method of the present invention, a gas sample containing sulfur is subjected to dehydration so as to obtain a dried gas sample having a water content of less than 100 ppm. In accordance with the present invention, it has been found that the gas sample must be treated with a dehydrating agent in an amount of greater than or equal to 1.5kg of dihydrating agent per liter of water to be removed from the gas sample. The dehydrated dried gas sample is GOa a 6 0s bQ

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o a S O 0 9 O *eO 550 1703a/ii 90-311 thereafter stored in a container which is non-reactive to the sulfur remaining in the gas and which is also water impermeable thereby prohibiting the reintroduction of water into the stored gas sample. In accordance with the process of the present invention, the dehydrated agent employed in the process is selected from the group consisting of carbon, magnesium perchlorate, glycol, silica gel, alum.'na and mixtures thereof with magnesium perchlorate being preferred. In accordance with a 0o further feature of the process of the present invention, o the temperature, pressure and flow rate of the gas B sample to the dehydration zone is maintained under 0 controlled conditions so as to maximize the dehydrating effect of the dehydration agent on the gas sample.

It The apparatus in accordance with the present invention comprises a dehydrating zone consisting of at least one trap containing a dehydrating agent through which the gas sample passes. In accordance with the 9 preferred embodiment of the present invention, the 2 odehydration zone comprises a plurality of traps which are selectively fed with the gas sample upon sensing of saturation of the dehydrant in any one of the traps.

The apparatus of the present invention further includes the employment of storage containers which are to sulfur contained in the gas sample and impermeable to water. The most preferred storage -7- 90-311 containers could be selected between aluminized plastic bags of the type sold under the Trademark Calibrated Systems, and Aluminium Cylinders with Spectra-Seal treatment sold under the Trademark Airco.

The method and apparatus of the present invention makes it possible to obtain accurate readings of the sulfur content of gas samoles many days after the gas samples are withdrawn from their source. Th~e improved accuracy allowed by the apparatus of the present io invention has numerous benefits including quality control in the production of natural gas, accurate guarantees of qualities and composition of the natural gas to suppliers and purchasers, reduced corrosion in transportation pipes and facilities employing the 1_gases, and reduction in harmful environmental consequences resulting from the use of said sulfur containing gases.

a BRIEF DESCRIPTION OF THE DRAWINGS 0 Figure 1 is a schematic illustration of the and process of the present invention.

ca Figure 2 is a graph illustrating the degradation of sulfur over time in wet and dehydrated gas samples.

Figure 3 is a graph showing the effect of various storage containers on the degradation of sulfur in dehydrated gas samples.

90-311 Figure 4 is a graph further illustrating the effect of storage containers on the degradation of dehydrated gas samples over time.

DETAILED DESCRIPTION SFigure 1 is a schematic illustration of the system of the present invention for carrying out the method for dehydrating and storing sulfur containing gas samples without sulfur degradation over time.

B The system 10 is provided with a connection 12 for 9.

o* to tapping into a gas line and removing a gas sample 904 therefrom. The gas sample might be generated from any source such as oil wells, environment, etc. Usually, depending on the source, the moisture content of the sample may be as high as 20,000 ppm water and the sulfur content could be as low as 10 ppm. The gas is permitted to flow through the pipe 14, a steel Teflon type pipe preferably, to which are connected successively a arua nanometer 16 for regulating the pressure, a thermometer S18 for measuring the temperature and a rotameter 20 to w control the flow rate of the gas to a dehydrating zone 22. The gas samples are preferably at a pressure between 10 and 100 psi, temperatures no higher than and a flow rate from 0.2 to 2.0 1/min. The reason why these parameters have to be maintained at the aforesaid a. values are the following: at pressures higher than -9- 90-311 psi the dehydrating apparatus would need to be reinforced; at temperatures higher than 60'C, the grain shape of the dehydration agent used in the method would deteriorate and consequently would not be effective for dehydration purposes; and at higher flow rates, the gas sample would not have enough residence time with the dehydration agent to effect the required dehydration. The dehydration agent may be selected from a group of well known substances such as *ges t silica gel, alumina, magnesium perchlorate, carbon, a S.

**glycol, and mixtures thereof with magnesium perchlorate S being most preferred.

Pipe 14 is also provided upstream of elements 16, 18 and 20 with a drainage "A,-Lve 24 which is used for removing from the system all liquids which may be gos$ present in the gas sample. Most natural gases contain a liquid phase which consists basically of C 6

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4 6 14 fractions which are carried with the gas. The liquid ae phase arises due to condensation which occurs by 0006 oaoexpansion effects due to the pressure difference between the main gas line and the system.

The valve 24 has two positions for connecting the flow line 14 with the dehydration zone 22 or for (b) connecting the flow line 14 with atmosphere so that the three parameters (temperature, pressure and flow rate) can be controlled and excess gas pr-issure can be 90-311 released out of the system. It must be appreciated that the system of the invention is a dynamic system which means the gas flows constantly through the whole system. With the valve 24 in position it is :)possible to measure the sulfur content of the gas sample to obtain a reference valve of the sulfur content so that the sulfur content measured after the dehydration and every several days storage can be compared and the performance of the system can be evaluated. The sulfur locontent is measured in known manner by conne,:ting to 0 valve 24 a DRAGER tube. With the valve 24 in position the gas sample is allowed to reach the distribution valve 28. Valve 28 is a single-inlet, multiple-nutlet m0 type valve and preferably a five way type valve. The 16 distribution valve 23 allows the gas samples to be selectively directed to any of a plurality of plexiglass traps 30 which are filled with the del:vdration agent to be used in the invention for removing or reducing the a. a moisture content of the gas sample. Each outlet of said 2odistribution valve 28 is connected to one plexiglass trap 30 by lines 26 so that only one trap 30 is in use eq at any one time. Thus, the number of plexiglass traps 0 so 30 correspond to the number of outlets on distribution valve 28. In a preferred embodiment of this invention, 2sjust one of the traps 30 is used for dehydiating a gas sample flowing through it; however, if necessary, it is -11- 90-311 possible to use a plurality of plexiglass traps 30. The feature which is critical is that the gas samples leaving the traps 30 must have a moisture content below 1UO ppm as it will be demonstrated hereinafter.

Distribution valve 32 which is a multiple inlet--ingle outlet type valve connects each trap with a moisture meter 34 where tc~ moisture content of the gas sample is removed.

The saturation point of the dehydrating agent in to any one of the traps 30 can be observed at said moisture goes** i meter 34 by measuring the moisture content of the gas e e o leaving the trap. When the saturation point of the e d agent in a trap is approached, one turns the distribution valve 28 in order to direct tie gas flow a 6 from trap 30 filled with the saturated dehydrating agent to another trap 30 filled with unused dehydrating agent. The ratio of dehydration agent to water content o* in the gas sample must be maintained higher than 1.50 kg/lt in order to obtain effective dehydration within e* So0the designed system. The valve 36 is provided o downstream of .he moisture meter 34 for connecting *a the flow line 38 coming from the moisture meter 34 with storage tank 40 or for connecting the system with atmosphere in order to reduce pressure in the system.

2SValve 36'in position controls the volume of gas flowing into the container 40. The container 40 to be -12-

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90-311 used in the invention is connected to the rest of the system by means of the air-tight connecting device 42.

The containers used in the apparatus and method of the present invention are selected based on materials which have no capacity for reacting with sulfur and which are not water permeable so as to raise the water content of the sulfur during storage. The containers preferably used in this invention are plastic bags with aluminized outside and aluminum cylinders coated with plastic such as epoxy or the like.

EXAMPLE I In order to demonstrate the effect of water content on the degradation of sulfur in a gas sample when stored, a natural gas sample h.iving a water content cf 16100 p)pm was treated in accordance with the me _hod of the present invention. The natural gas having a water content of 100 ppm is considered to be a very dry gas sample compared to typical natural gazi samples. The gas sample was fed at a pressure of 30 psi, a temperature of 16.55oC and a flow rate of 1.5 liters per minute to a dehydration zone containing magnesium perchlorate. The .magnesium perchlorate in the reaction zone was present in an amount sufficient to reduce the water content of the gas sample by approximately 90%, that is, in an of 1.50 kg per liter of water be removed. The -13- 90-311 sulfur content of the dehydrated dry gas sample was measured and found to be 12 ppm.

The dry gas sample was thereafter fed to an aluminized storage container having the interior surface thereof electrolytically coated. The cylinder is a commercially available cylinder sold by Airco. An untreated gas sample having the water content of 100 ppm.

was likewise stored in an identical storage container.

After three days of storage, the sulfur content of the gas samples was again measured and the sulfur 6*content of the treatel dehydrated gas sample was measured to be 11.9 ppm which is virtually identical to that of the original dehydrated gas sample whereas the sulfur content of the non-treated wet gas sample having an original water concentration of 100 ppm was found to be 1..9 ppm. This example clearly illustratus the "see.: benefit of treating by dehydration prior to storing on the degradation of sulfur in gas samples. The results *goo*: are graphically illustrated in Figure 2.

EXAMPLE II Example II was carried out to demonstrate the effect'of stcrage containers on the degradation of sulfi,: over time when stored. In this example, the gas sample of Example I which was dehydrated was stored in 26 three different containers. The first container is -14- 90-311 an aluminized plastic bag sold by Calibrated Systems.

The second sample was stored in a Teflon coated steel cylinder. The third sample was stored in a plexiglass syringe sold by Hamilton. As can be seen in Figure 3, the sample stored in the Calibrated System's aluminized bag showed less deterioration than the sample stored in the aluminized cylinder of Example I. The sample stored in the Teflon coated steel cylinder was slightly inferior to both the aluminized bag and the aluminium io cylinder. The sample stored in the plexiglass syringe sold by Hamilton showed nearly total sulfur degradation

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after a time of three days. This example t illustrates that the preferred storage container for prohibiting the degradation of sulfur in a gas sample is

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the aluminized bag container sold by Calibrated Systems.

EXAMPLE III 0 Again, in order to demonstrate the advantages of the process of the present invention, and particularly o the effect of dehydration on the degradation of sulfur o 2 gover time, a further test was conducted wherein a gas 00 sample having a sulfur content of 25 ppm was stored in a a the preferred aluminized bag discussed above with reference to Example II. A wet gas sample having a water content of 15,000 ppm was likewise stored in another aluminized bag. The sulfur content of both i 5 :IL

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90-311 samples were measured after eight days and again after sixteen (16) days. As can be seen in Figure 4, the sample content of the Wet gas sample totally degraded in terms of sulfur content after sixteen (16) days as compared to the gas sample treated in accordance with the process of the present invention which had a reduced sulfur concentration of less than The foregoing examples clearly demonstrate the positive effect of the process of the present invention 1 on prohibiting the degradation of sulfur in a gas sample 0** over time when stored in optimum storage containers.

This invention may be embodied in other forms or carried out in other ways without departing from the S* spirit or essential characteristics thereof. The embodiment is therefore to be considered as in all respects illustrative and not restrictive, the scope of the invention being indicated by the appended claims, and all changes which come within the meaning and range

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of equivalency are intended to be embraced therein.

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Claims

1. A process for treating sulfur containing gases so as to prohibit the degradation of the sulfur content of the gas over time comprising the steps of: providing a sulfur containing gas sample; dehydrating said gas sample so as to obtain a water content in said gas sample of less than 100 ppm to produce a dried gas sample; and storing said dried gas sample in a container which is non reactive with the sulfur in the gas.

2. A process according to claim 1 wherein said gas sample has a water content of up to 20,000 ppm.

3. A process according to claim 1 or claim 2 wherein dehydrating said gas sample :omprises the steps of: ,providing a dehydration zone, allowing said gas sample to flow 15 through said dehydration zone. S*,0

4. A process according to claim 3 wherein said dehydration zone comprises at least one plexiglass trap filled with a dehydration agent.

A process according to claim 4 wherein said dehydration agent is one or more of carbon, magnesium perchlorate, glycol, silica gel, 20 alumina or mixtures thereof. o

6. A process according to claim 4 including measuring the water S o content of said gas sample aownstream of said at least one plexiglass trap.

7. A process according to any one of claims 1 to 6 further comprising the steps of: regulating the temperature, pressure and flow rate of said gas sample prior to the dehydrating step.

8. A process according to claim 7 wherein said temperature is less than or equal to 60°C, said pressure is from 10 to 100 psi and said flow rate is from 0.2 to 2.0 1/min.

9. A process according to any one of claims 1 to 8 including the step of removing any liquid phase from said gas sample prior to the step of dehydrating.

A process according to any one of claims 1 to 8 including the step of measuring the moisture content of said gas sample prior to the step of dehydrating.

11. A process according to any one of claims 1 to 10 including the t i step of measuring the sulfur content in said gas sample prior to the step lof dehydrating. 1703a/ii 18

12. An apparatus for treating sulfur containing gas samples by the process claimed in claim 1 so as to prevent a change in sulfur content over time when stored, which apparatus comprises: means for dehydrating said gas sample thereby producing a dried gas sample with a water content up to 100 ppm; and COuirin~fz-ee octlon CjtOczfE4 jmeans for storing said dried gas sample.

13. An apparatus according to claim 12 wherein said means for dehydrating comprises a dehydration zone having at least one plexiglass trap containing a dehydration agent.

14. An apparatus according to claim 13 wherein said dehydration agent is one or more of carbon, glycol, magnesium perchlorate, silica gel O or alumina. Ge

15. An apparatus according to claim 13 or claim 14 wherein said dehydration agent means further comprises: 15 means for distributing said gas samples to only one of said plexiglass trap, and means for collecting said dried gas sample from only one of said plexiglass trap.

16. An apparatus according to claim 15 wherein said distributing means comprises a single-inlet, multiple outlet valve, and said 5 collecting means comprises a multiple-inlet, single outlet valve.

17. An apparatus according to any one of claims 12 to 16 including means for regulating the pressure of said gas sample; %S eans for regulating the temperature of said gas sample; and means for regulating the flow rate of said gas sample.

18. An apparatus according to any one of claims 12 to 17 including means for removing a liquid portion from said gas sample.

19. An apparatus according to any one of claims 15 to 18 further including a moisture meter to measure the moisture content of said dried gas sample.

An apparatus according to any one of claims 12 to 19 wherein said storing means comprises aluminized plastic bags.

21. An apparatus according to any one of claims 12 to 19 wherein said storing means comprise pretreated aluminum cylinders.

22. A process for treating sulfur containing gases so as to prohibit the degradation of the sulfur content in those gases over time comprising the steps of: a providing a sulfur containing gas sample having a known water Scontent; 1703a/ii 19 contacting said gas sample with a dehydrating agent in an amount of greater than or equal to 1.50kg of said dehydrating agent per liter of water to be removed from said gas sample so as to obtain a dried gas sample; and storing said dried gas sample in a container which is non reactive to sulfur.

23. A process according to claim 22 wherein the water co ;tnt of said gas sample is up to 20,000 ppm.

24. A process according to claim 22 or claim 23 wherein said 10 dehydration agent is one or more of carbon, magnesium perchlorate, glycol, silica-gel or alumina.

25. A process according to any one of claims 22 to 24 wherein the water content remaining in said dried gas sample is measured in order to determine when said dehydration agent is saturated. 15

26. A process according to any one of claims 22 to 25 wherein the pressure, the temperature and the flow rate of said gas samples are Smeasured prior to contacting said gas sample with said dehydration agent.

27. A process according to claim 26 wherein said pressure is from to 100 psi, said temperature is lower than or equal to 60*C and said 20 flow rate is from 0.2 to 2.0 I/min.

28. A process according to any one of claims 22 to 27 further a comprising the step of removing any liquid phase from said gas sample 0 prior to the step of dehydrating. 0

29. A process for treating sulfur containing gases so as to prohibit the degradation of the sulfur content of the gas over time 0. substantially as hereinbefore described with reference to any one of the °Examples. An apparatus for treating sulfur containing gas samples so as to prevent a change in sulfur content over time when sto'ed substantially as hereinbefore described with reference to any one of the Examples or to Figure 1. DATED this TNENTY-EIGHTH day of APFIL 1993 Intevep, S.A. t 4 Patent Attorneys for t'e Applicant SPRUSON FErGUSON 1703a/ii A Method and .A)paratus for Treating and Storing Sulfur Containing Gas so as to Prohibit the Degradation of Same Abstract A method and apparatus for treating gas samples containing sulfur comprises dehydrating (22) the gas sample so as to obtain a dried gas sample having a water content of less than 100 ppm and thereafter storing the dried gas sample in a container (40) which is non-reactive to sulfur in the gas. Figure 1 4 o ae o KRS/4861D