CA2135183A1 - Method and an apparatus for adding a malodorant to a consumer gas - Google Patents
Method and an apparatus for adding a malodorant to a consumer gasInfo
- Publication number
- CA2135183A1 CA2135183A1 CA002135183A CA2135183A CA2135183A1 CA 2135183 A1 CA2135183 A1 CA 2135183A1 CA 002135183 A CA002135183 A CA 002135183A CA 2135183 A CA2135183 A CA 2135183A CA 2135183 A1 CA2135183 A1 CA 2135183A1
- Authority
- CA
- Canada
- Prior art keywords
- gas
- master
- consumer
- odorant
- pressure vessel
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
- C10L3/00—Gaseous fuels; Natural gas; Synthetic natural gas obtained by processes not covered by subclass C10G, C10K; Liquefied petroleum gas
- C10L3/003—Additives for gaseous fuels
-
- A—HUMAN NECESSITIES
- A62—LIFE-SAVING; FIRE-FIGHTING
- A62C—FIRE-FIGHTING
- A62C99/00—Subject matter not provided for in other groups of this subclass
- A62C99/0009—Methods of extinguishing or preventing the spread of fire by cooling down or suffocating the flames
- A62C99/0018—Methods of extinguishing or preventing the spread of fire by cooling down or suffocating the flames using gases or vapours that do not support combustion, e.g. steam, carbon dioxide
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
- B01F23/00—Mixing according to the phases to be mixed, e.g. dispersing or emulsifying
- B01F23/10—Mixing gases with gases
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
- B01F23/00—Mixing according to the phases to be mixed, e.g. dispersing or emulsifying
- B01F23/10—Mixing gases with gases
- B01F23/12—Mixing gases with gases with vaporisation of a liquid
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10J—PRODUCTION OF PRODUCER GAS, WATER-GAS, SYNTHESIS GAS FROM SOLID CARBONACEOUS MATERIAL, OR MIXTURES CONTAINING THESE GASES; CARBURETTING AIR OR OTHER GASES
- C10J1/00—Production of fuel gases by carburetting air or other gases without pyrolysis
- C10J1/28—Odorising air gas
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
- C10L3/00—Gaseous fuels; Natural gas; Synthetic natural gas obtained by processes not covered by subclass C10G, C10K; Liquefied petroleum gas
- C10L3/06—Natural gas; Synthetic natural gas obtained by processes not covered by C10G, C10K3/02 or C10K3/04
- C10L3/10—Working-up natural gas or synthetic natural gas
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
- F17C2225/00—Handled fluid after transfer, i.e. state of fluid after transfer from the vessel
- F17C2225/01—Handled fluid after transfer, i.e. state of fluid after transfer from the vessel characterised by the phase
- F17C2225/0107—Single phase
- F17C2225/0123—Single phase gaseous, e.g. CNG, GNC
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
- F17C2265/00—Effects achieved by gas storage or gas handling
- F17C2265/02—Mixing fluids
- F17C2265/025—Mixing fluids different fluids
Landscapes
- Chemical & Material Sciences (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Engineering & Computer Science (AREA)
- Organic Chemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Health & Medical Sciences (AREA)
- Public Health (AREA)
- Business, Economics & Management (AREA)
- Emergency Management (AREA)
- Feeding, Discharge, Calcimining, Fusing, And Gas-Generation Devices (AREA)
Abstract
An arrangement for adding an odorant to a consumer gas which is distributed to a consumer site, in order to indicate to people in the vicinity of the risk of fire, explosion, poisoning, suffocation or some other danger, should consumer gas leak into the surrounding atmosphere. The odorant is dissolved in a condensed vehicle gas in a pressure vessel (3), to obtain a solution, master gas, which includes a liquid phase (6) and a gas phase (7). The consumer gas is diluted with an adapted quantity of the liquid phase of the master gas, which is vaporized prior to being mixed with the consumer gas. To this end, the arrangement includes means (18) for correcting the relationship between the two gas flows during the dilution process with respect to the increase in the concentration of odorant in the liquid phase (6) of the master gas that results from the decreasing relationship between the quantity of liquid gas and gas phase (7) in the pressure vessel. This provides for extremely accurate metering of the master gas. The invention also relates to a method of adding an odorant to a consumer gas.
Description
! . "~0 93/25638 213 ~ 1~ 3 PCT/SE92/00432 Method and an apparatus for addlng a melodorant to a consumer gas Field of Invention The present invention relates to a method of adding an odorant to a consumer gas which is distributed to a consumer site so as to draw to the at~ention of people in the vicinity of the risk of fire, explosion, poisoning, suffocation or some other danger should the consllmer gas escape to the surrounding atmosphere. In the event of a gas escape, the odorant, which is in a concentrated form, preferably an organic sulphur compound, is dissolved in a condensed vehicle gas contained in a pressure vessel, for instance carbon dioxide, propane or butane, so as to form a solution, a master gas, which includes a liquid phase and a gas phase.
The desired odorant concentration of the consumer gas is then achieved by diluting the odorant with an adapted quantity of the liquid phase of the master gas, which is vaporized prior to being mixed with the consumer gas. The amount of master - 20 gas added is determined by the flow rate of master g~s and the odorant concentration of said master gas and the flow-rate of the consumer gas. The invention also relates to an arrangement for use when carrying out the method.
Backqrourid of the Invention The concept of adding odorants to consumer gases in accordance with the aforegoing, so as to indicate the leak~ye of poisonous ~ar explosive gases for instance, has long been known to the art. One example of gases which may be odorized in this way is oxygen, which if leaking to the surroundings can result in extremely serious accidents caused by fire or explosion. Other examples include combustible gases, such as natural gas, propane, butane, town gas, etc., which can also cause serious accidents in the form of fire and explosions.
sincP the majority of odorous additives, such as tetrahydro thiophene, butyl mercaptan, dimethyl sulphide, etc., are readily ignitable substances which require the application of special techniques when added to oxygen for instance.
Finish Patent Application 870146 discloses a method of adding an odorant to oxygen, in which a concentrated gas, so-i 2 1 3 S 1 ~
W093/25638 . PCT/SE92/004~
,' called master gas, is produced in a separate chamber or spaseby adding to pure oxygen gas an odorant in a concentration of 1,OOo-10,000 ppm. This concentrated master gas is added to the consumer gas in a separate chamber, or space, in an amount such that the odorant will be present in the consumer gas in a concentration of 5-50 ppm.
When the master gas contains solely oxygen and odorant, for instance dimethyl sulphide, problems can occur, however, when filling the master gas containers. For instance, when filling the containers, it is impossible to avoid passing through a concentration range in which the mixture is combus-tible, at least in a part of the container. There is thus a ris~ of the mixture igniting and exploding.
One method of avoiding this risk is disclosed in the Finnish Patent Application No. 872278. This application describes a method of producing a concentrated master gas comprising oxygen and an odorant, such as dimethyl sulphide.
According to this method, the master gas container is first filled with a mixture of dimethyl sulphide and nitrogen or helium gas. The concentration of dimethyl sulphide lies within a range_of 0.5-2.5%. Pure oxygen gas is then added : until the~ desired working pressure in the container is reached, for instance a pressure of 200 barsO
One drawback with the master gas produced in accordance with the aforedescribed methods, however, is that the master gas must not be:subjected to temperatures which are so low as to cause the odorant to condense, for instance during trans-portation and storage. Once being condensed, it takes a very long time for the dimethyl sulphide to return to its gaseous state.
Prior publications DE-B-1185330 and WO 91/17817 des-cribes methods which reduce this problem in that the odorant is dissolved in a gas which exists in liquid phase at room temperature and under pressure. ~ropane, butanel carbon dioxide, sulphur hexafluoride and nitrous oxide have been given as examples of suitable gases in this respect. These gases also fulfil the requirement of not having a negative `W093/25638 21 3J~. 8 j PCT/SE92/00432 influence, in the majority of cases, on the process in which the odorized gas is used.
It is suggested in prior publication DE-B-1 185 3~ that the odorized master gas is taken from the pressure vessel and delivered to the consumer gas conduit via a fine setting valve which can normally be maintained at a predetermined setting during the consumption of all of the master gas.
However, in the case of large variations in the flow ra~e of the consumer gas, it is said that the flow rate of the master gas can be controlled in response to such variations.
In pra~tice, however, this and other known solutions do not provide the odorant metering accuracy that is desired.
This is because the odorant vehicle gas has a much higher vapor pressure than the liquid odorant. Thus, the gas ~olume present above the liquid phase of the master gas in the pressure vessel will consist essentially of vaporized vehicle gas and only a very small part of vaporized odorant liquid.
As the volume of the liquid phase in the pressure vessel diminishes when master gas is delivered to the consumer gas, the increasing volume of vaporized vehicle gas in the pres-sure vessel will result in an increase in the relative con-centration of the liquid odorant in the liquid phase in the pressure vessel.
Obiects of the Invention A main object of the present invention is therefore to propose a method which will solve the problem of a volume-dependent concentration of odorant in the master gas.
Another object is to provide an arrangement which can be used when applying the inventive method in order to eliminate the effect of the volume-dependent concentration of odorant in the master gas.
Disclosure of the Invention The aforesaid objects are achieved in accordance with the present invention by adjusting the amounts in which the master gas is metered to the consumer gas in accordance with the relationship between liquid phase and gas phase in the pressure vessel.
~ 1 3 ~
W093/25638 PCT/SE92/004~ -The significant characteristic feature of a method of the kind defined in the first paragraph of this document is therewith to correct the relationship between the flows of master gas and consumer gas during the dilution process while taking into account the increase in the concentration of odorant in the liquid phase of the master gas that results from the reducing relationship between the amount of liquid phase and the amount of gas phase in the pressure vessel.
This procedure eliminates the aforesaid problem encountered with earlier known solutions.
The amount of master gas remaining in the pressure vessel will preferably be determin d continuously by continu-ous integration of the master gas flow from the pressure vessel and by subtracting the value obtained from the amount of master gas that was initially present, and then correcting the relationship between the two gas flows continuously during the dilution process on the basis of this determina-tion. This will result in highly accurate metering of the amount ~f odorant mixed in the consumer gas.
According to one pref~rred embodiment, the accuracy at which the odorant is metered can be further improved by determining the temperature of the ~aster gas in the pressure vessel and also correcting the relationship between the two gas flows on the basis of detected temperature changes. Other characteristic features of the inventive method and of an inventive arrangement for use when practicing said method will be evident from the following Claims.
The invention will now be descri~ed in more detail with refe~ence to an exemplifying embodiment of the invention and also with reference to the accompanying drawings.
Brief Description of the ~rawinqs ~-Figure 1 is a schematic illustration of the principles according to which an inventive arrangement operates.
Figure 2 is a diagram which illustrates the relative concentration of odorant in the liquid phase of the master gas as a function of the amount of liquid phase taken from the pressure vessel at different temperatures.
'' YO93/25638 2 13 ~j 1 8 3 PCT/SE92/00432 Figure 3 illustrates schematically the principles ac-cording to which one embodiment of an inventive arrangement operates.
Description of a Preferred Embodiment of the Invention The arrangement illustrated in Figure 1 comprises a con-duit 1 for consumer gas, for instance oxyyen, ~hich flows in the direction of the arrow A and to which an odorant shall be added. The odorant is added through a conduit 2 which deliv-ers master gas from a pressure vessel 3, through a control valve 4. The master gas may consist of a mixture of an organ-ic sulphur compound, such as dimethyl sulphide, DMS, and carbon dioxide. The master gas is taken from the liquid phase 6 in the pressure vessel 3 by means of an im~ersion pipe 5, said master gas being driven from the vessel through a clos-ing valve 8, through the agency of the pressure exerted by the vaporized gas volume 7. The control valve 4 is controll-ed, among other things, in response to the flow of consumer gas through the conduit 1, this flow being determined with the aid of a flowmeter 9.
In the above example, the vapor pressure of carbon dioxide is 57 bars at 20C, whereas the vapor pressure of the odorant liquid is much lower, considerably lower than O.S bar at 20C in the case of DMS. The gaseous atmosphere 7 above the liquid phase 6 in the pressure vessel 3 will therefore mainly consist of vaporized carbon dioxide. Since the amount of liquid phase 6 decreases as it is supplied to the ~-onduit 1, the amount of vaporized gas above the liquid phase will increase accordingly. Since it is primarily carbon dioxide that is vaporized, as described above, the relative concen-tration of the odorant in the li~uid phase ~ will increase.
The successive change in the relative concentration of ~.
odorant in the liquid phase can be determined quantitatively.
When designating the initial odorant concentration in the liquid phase of a full pressure vessel C10 and when using the 3S designation C1 for the odorant concentration subsequent to a given relative consumption m /m10, where m is the amount of liquid phase consumed and m10 is the amount initially pres-213~1S~
W093/25638 PC~/SEg2/004 ent, the change in relative concentration in the liquid phase can be described with the aid of the following equation: I
,, , Clo ( 1 - k )mlo In this equation, k = P /P1, where Pl is the density of the liquid phase and p is the density of the gas phase. The calculated values:for C02 and DMS are given in a diagrammatic form in Figure 2. This diagram shows the relative concentra-tion of the odorant in the liquid phase as a function of ~he amount of liquid phase that has ~een consumed from an ini-tially full pressure vessel, i.e. m = 0, wherein m /m1 = 0 : until 90% of the liquid phase has been consumed, when m /m10 = 0.9. The concentration is shown at given temperatures within the range of 0C to 28C.
It will be seen from the diagram, for instance, that a~15 20C and when 70% of the liquid phase has been consumed, the odorant concentration of the liquid phase will be almost twice its original concentration. At a temperature of 26C, this state is reached when hardly 55% of the liquid phase has been consumed. If this is not corrected, there will automati-Gally occur a corresponding, unintentional increase in the level of odorant in the consumer gas. This is a serious drawback with earlier proposed methods and exS~^ludes the use of such methods in applications which require a constant odorant level within a very narrow range of concentration.
~ 25 With the intention of solving this problem, there is ¦ proposed in accordance with the invention an arrangement for adding an odorant to a consumer gas, this arrangement being ~3 illustrated schematically in Figure 3. As earlier mentioned, ~ this arrangement includes a conduit 1 for conducting consumer ~ ;
330 gas which flows in the direction of the arrow A, wherein the ~gas to which the odorant has been added is delivered from the Y~pressure vessel 3 through the conduit 2. The flow of consumer .gas is determined by means of the flowmeter 9. In the afore-i ~O 93/25638 ~ 1 ~ 5 1 8 :~ PC'r/SE92/00432 going, it has been assumed that the master gas is comprised of a mixture of C02 and DMS. The master gas is forced out from the pressure vessel 3 in a liquid state, through the agency of the pressure exerted by vaporized carbon dioxide, and through the closure valve 8 to a vaporizing and control-ling unit lQ, which includes three heating loops 11, 12, 13 through which hot or warm water flows, a pressure regulating valve 14 and a mass flowmeter 15 which is coupled with a control valve 16 of a so-called mass flow control device which measures and, at the same time, adjusts the flow of : master gas. A further closure valve 17 is coupled in the conduit 2, outwardly of the unit 10.
The arrangement also includes a central processor unit 18, CPU. This unit contains information concerning the de-sired odorant admixture, i.e. the concentration of odorant inthe consumer gas. The flowmeter 9 provides the central unit with information concerning the flow of consumer gas, while information concerning the temperature of ~he master gas in the pressure vessel 3 is delivered to the central unit from a t~mperature sensor 19.
The central unit 18 has also been provided with informa-tion concerning the initial amount o~ odorant in the master gas and the instant odorant concentration of the master gas in the pressure vessel 3 and receiYes, through a conductor 20, information concerning the momentary flow of master gas, which is integrated over the time taken to determine consump-tion. The central processing unit will thus always contain information concerning the quantity of master gas that re-mains in the pressure vessel at any given moment in time.
Thus, when applying the above equation, the central unit 18 is able to determine the relative change in concentration and therewith also to calculate the instant concentration of odorant in the liquid phase of the master gas. The central unit controls the delivery of master gas to the consumer gas an the basis of this determination and in accordance with the flow of consumer gas, with the aid of the control valve 16.
This enables odorant to be metered to the consumer gas very 2 ~ 3-~
W093/2~6~8 PCT/SE92/004' accurate]y.
The Figure 2 diagram illustrates changes in concentra-tion which occur as a result of vap~rization or condensation processes in a two-phase system which includes components of mutually different properties. Such effects are not limited to the pressure vessel in an odorizing arrangement of the aforedescribed kind, but can also occur at other places in the system where temperature or pressure change.
The presence of two phases in one stream results in different rates of flow, which may give rise to variations in the metering process. This problem can be eliminated in accordance with the present invention, by heating or cooling the system at given points therein, so as to obtain thermal - gradients which prevent undesirable condensation or vaporiza-tion. In the case of the Figure 3 arrangement, the liquid master gas is accordingly heated and vaporized in the heating Ioop 11 prior to entering the pressure regulator 14 and also l downstream of said regulator, since in the case of CO2 reduc-I tion to the working pressure required in the regulator, about 15 bars, requires expansion of the master gas, with the accompanying risk of condensation as a result of the decrease in temperature that occurs herewith. Consequently, the master gas is again heated by the hPating coil 12 prior to being delivered to the flowmeter 15.
A ~inal master gas expansion phase takes place down-stream of the control valve 16 and a fubak heating coil 13 ensures that no condensation will occur at this location, which could cause changes in the composition of the master gasland subsequent variations in the metering process. The three heating coils are mutually connected in series and hot water is conveniently passed through the coils. When the master gas includes CO2, this water may have a temperature of 50C, for instance. This enables the remainder of the ar-rangement to be maintained at a lower temperature level, so as to ensure that the master gas will definitely arri~e at the vaporizing unit 10 in a liquid state. In accordance with the invention, the coldest part of the inventive arrangement ~s~
~ VO ~3/25638 ~ 3 ;.~ 1 8 3 PCT/SE9~/00432 is the input to the vaporiz~r.
The gas conduit between the gas bottle 3 and the vapor-izer input is cooled by a cooling element 21 which is placed adjacent said conduit and through-passed by cold water. The requisite temperature gradient between the vaporizer input and the flask temperature is therewith achieved by passing the cooling water in counterflow to the direction of master gas flow, arrow B.
The temperature of the pressure vessel 3, about 18C in the case of CO2, is also related to the temperature of the ~ vaporizing unit lO, this temperature being sensed by a sensor ;~i22, in accordance with the invention. In order to maintain a constant temperature difference, the central unit 18 controls the temperature of the pressure vessel 3 through the combined effect of the heating coil 23 and the cooling coil 24, among other things ln dependence on ambient temperature.
Although the invention has been described with reference to an exemplifying embodiment thereof in which there is used i~a master gas which includes carbon dioxide and dimethyl sulphide, it will be understood that the same conditions also apply to other vehicle gases, such as propane, butane, sul-lphur hexafluoride and dinitrogen oxide, etc., wherein the ¦odorant used may alternatively be, for instance, tetrahydro ¦thiophene, methyl mercaptan, ethyl mercaptan, propyl mercap-¦25 tan or butyl mercaptan, and dimethyl sulphide, diethyl sul-phide and methylethyl sulphide. The odorant concentration of ~the master gas is conveniently 0.5-lO mol-%. The master gas jcan be delivered to the consumer gas in an amount to ob~ain a consumer gas odorant concentration within the range of 1-50 ppm, preferably 1-20 ppm.
The desired odorant concentration of the consumer gas is then achieved by diluting the odorant with an adapted quantity of the liquid phase of the master gas, which is vaporized prior to being mixed with the consumer gas. The amount of master - 20 gas added is determined by the flow rate of master g~s and the odorant concentration of said master gas and the flow-rate of the consumer gas. The invention also relates to an arrangement for use when carrying out the method.
Backqrourid of the Invention The concept of adding odorants to consumer gases in accordance with the aforegoing, so as to indicate the leak~ye of poisonous ~ar explosive gases for instance, has long been known to the art. One example of gases which may be odorized in this way is oxygen, which if leaking to the surroundings can result in extremely serious accidents caused by fire or explosion. Other examples include combustible gases, such as natural gas, propane, butane, town gas, etc., which can also cause serious accidents in the form of fire and explosions.
sincP the majority of odorous additives, such as tetrahydro thiophene, butyl mercaptan, dimethyl sulphide, etc., are readily ignitable substances which require the application of special techniques when added to oxygen for instance.
Finish Patent Application 870146 discloses a method of adding an odorant to oxygen, in which a concentrated gas, so-i 2 1 3 S 1 ~
W093/25638 . PCT/SE92/004~
,' called master gas, is produced in a separate chamber or spaseby adding to pure oxygen gas an odorant in a concentration of 1,OOo-10,000 ppm. This concentrated master gas is added to the consumer gas in a separate chamber, or space, in an amount such that the odorant will be present in the consumer gas in a concentration of 5-50 ppm.
When the master gas contains solely oxygen and odorant, for instance dimethyl sulphide, problems can occur, however, when filling the master gas containers. For instance, when filling the containers, it is impossible to avoid passing through a concentration range in which the mixture is combus-tible, at least in a part of the container. There is thus a ris~ of the mixture igniting and exploding.
One method of avoiding this risk is disclosed in the Finnish Patent Application No. 872278. This application describes a method of producing a concentrated master gas comprising oxygen and an odorant, such as dimethyl sulphide.
According to this method, the master gas container is first filled with a mixture of dimethyl sulphide and nitrogen or helium gas. The concentration of dimethyl sulphide lies within a range_of 0.5-2.5%. Pure oxygen gas is then added : until the~ desired working pressure in the container is reached, for instance a pressure of 200 barsO
One drawback with the master gas produced in accordance with the aforedescribed methods, however, is that the master gas must not be:subjected to temperatures which are so low as to cause the odorant to condense, for instance during trans-portation and storage. Once being condensed, it takes a very long time for the dimethyl sulphide to return to its gaseous state.
Prior publications DE-B-1185330 and WO 91/17817 des-cribes methods which reduce this problem in that the odorant is dissolved in a gas which exists in liquid phase at room temperature and under pressure. ~ropane, butanel carbon dioxide, sulphur hexafluoride and nitrous oxide have been given as examples of suitable gases in this respect. These gases also fulfil the requirement of not having a negative `W093/25638 21 3J~. 8 j PCT/SE92/00432 influence, in the majority of cases, on the process in which the odorized gas is used.
It is suggested in prior publication DE-B-1 185 3~ that the odorized master gas is taken from the pressure vessel and delivered to the consumer gas conduit via a fine setting valve which can normally be maintained at a predetermined setting during the consumption of all of the master gas.
However, in the case of large variations in the flow ra~e of the consumer gas, it is said that the flow rate of the master gas can be controlled in response to such variations.
In pra~tice, however, this and other known solutions do not provide the odorant metering accuracy that is desired.
This is because the odorant vehicle gas has a much higher vapor pressure than the liquid odorant. Thus, the gas ~olume present above the liquid phase of the master gas in the pressure vessel will consist essentially of vaporized vehicle gas and only a very small part of vaporized odorant liquid.
As the volume of the liquid phase in the pressure vessel diminishes when master gas is delivered to the consumer gas, the increasing volume of vaporized vehicle gas in the pres-sure vessel will result in an increase in the relative con-centration of the liquid odorant in the liquid phase in the pressure vessel.
Obiects of the Invention A main object of the present invention is therefore to propose a method which will solve the problem of a volume-dependent concentration of odorant in the master gas.
Another object is to provide an arrangement which can be used when applying the inventive method in order to eliminate the effect of the volume-dependent concentration of odorant in the master gas.
Disclosure of the Invention The aforesaid objects are achieved in accordance with the present invention by adjusting the amounts in which the master gas is metered to the consumer gas in accordance with the relationship between liquid phase and gas phase in the pressure vessel.
~ 1 3 ~
W093/25638 PCT/SE92/004~ -The significant characteristic feature of a method of the kind defined in the first paragraph of this document is therewith to correct the relationship between the flows of master gas and consumer gas during the dilution process while taking into account the increase in the concentration of odorant in the liquid phase of the master gas that results from the reducing relationship between the amount of liquid phase and the amount of gas phase in the pressure vessel.
This procedure eliminates the aforesaid problem encountered with earlier known solutions.
The amount of master gas remaining in the pressure vessel will preferably be determin d continuously by continu-ous integration of the master gas flow from the pressure vessel and by subtracting the value obtained from the amount of master gas that was initially present, and then correcting the relationship between the two gas flows continuously during the dilution process on the basis of this determina-tion. This will result in highly accurate metering of the amount ~f odorant mixed in the consumer gas.
According to one pref~rred embodiment, the accuracy at which the odorant is metered can be further improved by determining the temperature of the ~aster gas in the pressure vessel and also correcting the relationship between the two gas flows on the basis of detected temperature changes. Other characteristic features of the inventive method and of an inventive arrangement for use when practicing said method will be evident from the following Claims.
The invention will now be descri~ed in more detail with refe~ence to an exemplifying embodiment of the invention and also with reference to the accompanying drawings.
Brief Description of the ~rawinqs ~-Figure 1 is a schematic illustration of the principles according to which an inventive arrangement operates.
Figure 2 is a diagram which illustrates the relative concentration of odorant in the liquid phase of the master gas as a function of the amount of liquid phase taken from the pressure vessel at different temperatures.
'' YO93/25638 2 13 ~j 1 8 3 PCT/SE92/00432 Figure 3 illustrates schematically the principles ac-cording to which one embodiment of an inventive arrangement operates.
Description of a Preferred Embodiment of the Invention The arrangement illustrated in Figure 1 comprises a con-duit 1 for consumer gas, for instance oxyyen, ~hich flows in the direction of the arrow A and to which an odorant shall be added. The odorant is added through a conduit 2 which deliv-ers master gas from a pressure vessel 3, through a control valve 4. The master gas may consist of a mixture of an organ-ic sulphur compound, such as dimethyl sulphide, DMS, and carbon dioxide. The master gas is taken from the liquid phase 6 in the pressure vessel 3 by means of an im~ersion pipe 5, said master gas being driven from the vessel through a clos-ing valve 8, through the agency of the pressure exerted by the vaporized gas volume 7. The control valve 4 is controll-ed, among other things, in response to the flow of consumer gas through the conduit 1, this flow being determined with the aid of a flowmeter 9.
In the above example, the vapor pressure of carbon dioxide is 57 bars at 20C, whereas the vapor pressure of the odorant liquid is much lower, considerably lower than O.S bar at 20C in the case of DMS. The gaseous atmosphere 7 above the liquid phase 6 in the pressure vessel 3 will therefore mainly consist of vaporized carbon dioxide. Since the amount of liquid phase 6 decreases as it is supplied to the ~-onduit 1, the amount of vaporized gas above the liquid phase will increase accordingly. Since it is primarily carbon dioxide that is vaporized, as described above, the relative concen-tration of the odorant in the li~uid phase ~ will increase.
The successive change in the relative concentration of ~.
odorant in the liquid phase can be determined quantitatively.
When designating the initial odorant concentration in the liquid phase of a full pressure vessel C10 and when using the 3S designation C1 for the odorant concentration subsequent to a given relative consumption m /m10, where m is the amount of liquid phase consumed and m10 is the amount initially pres-213~1S~
W093/25638 PC~/SEg2/004 ent, the change in relative concentration in the liquid phase can be described with the aid of the following equation: I
,, , Clo ( 1 - k )mlo In this equation, k = P /P1, where Pl is the density of the liquid phase and p is the density of the gas phase. The calculated values:for C02 and DMS are given in a diagrammatic form in Figure 2. This diagram shows the relative concentra-tion of the odorant in the liquid phase as a function of ~he amount of liquid phase that has ~een consumed from an ini-tially full pressure vessel, i.e. m = 0, wherein m /m1 = 0 : until 90% of the liquid phase has been consumed, when m /m10 = 0.9. The concentration is shown at given temperatures within the range of 0C to 28C.
It will be seen from the diagram, for instance, that a~15 20C and when 70% of the liquid phase has been consumed, the odorant concentration of the liquid phase will be almost twice its original concentration. At a temperature of 26C, this state is reached when hardly 55% of the liquid phase has been consumed. If this is not corrected, there will automati-Gally occur a corresponding, unintentional increase in the level of odorant in the consumer gas. This is a serious drawback with earlier proposed methods and exS~^ludes the use of such methods in applications which require a constant odorant level within a very narrow range of concentration.
~ 25 With the intention of solving this problem, there is ¦ proposed in accordance with the invention an arrangement for adding an odorant to a consumer gas, this arrangement being ~3 illustrated schematically in Figure 3. As earlier mentioned, ~ this arrangement includes a conduit 1 for conducting consumer ~ ;
330 gas which flows in the direction of the arrow A, wherein the ~gas to which the odorant has been added is delivered from the Y~pressure vessel 3 through the conduit 2. The flow of consumer .gas is determined by means of the flowmeter 9. In the afore-i ~O 93/25638 ~ 1 ~ 5 1 8 :~ PC'r/SE92/00432 going, it has been assumed that the master gas is comprised of a mixture of C02 and DMS. The master gas is forced out from the pressure vessel 3 in a liquid state, through the agency of the pressure exerted by vaporized carbon dioxide, and through the closure valve 8 to a vaporizing and control-ling unit lQ, which includes three heating loops 11, 12, 13 through which hot or warm water flows, a pressure regulating valve 14 and a mass flowmeter 15 which is coupled with a control valve 16 of a so-called mass flow control device which measures and, at the same time, adjusts the flow of : master gas. A further closure valve 17 is coupled in the conduit 2, outwardly of the unit 10.
The arrangement also includes a central processor unit 18, CPU. This unit contains information concerning the de-sired odorant admixture, i.e. the concentration of odorant inthe consumer gas. The flowmeter 9 provides the central unit with information concerning the flow of consumer gas, while information concerning the temperature of ~he master gas in the pressure vessel 3 is delivered to the central unit from a t~mperature sensor 19.
The central unit 18 has also been provided with informa-tion concerning the initial amount o~ odorant in the master gas and the instant odorant concentration of the master gas in the pressure vessel 3 and receiYes, through a conductor 20, information concerning the momentary flow of master gas, which is integrated over the time taken to determine consump-tion. The central processing unit will thus always contain information concerning the quantity of master gas that re-mains in the pressure vessel at any given moment in time.
Thus, when applying the above equation, the central unit 18 is able to determine the relative change in concentration and therewith also to calculate the instant concentration of odorant in the liquid phase of the master gas. The central unit controls the delivery of master gas to the consumer gas an the basis of this determination and in accordance with the flow of consumer gas, with the aid of the control valve 16.
This enables odorant to be metered to the consumer gas very 2 ~ 3-~
W093/2~6~8 PCT/SE92/004' accurate]y.
The Figure 2 diagram illustrates changes in concentra-tion which occur as a result of vap~rization or condensation processes in a two-phase system which includes components of mutually different properties. Such effects are not limited to the pressure vessel in an odorizing arrangement of the aforedescribed kind, but can also occur at other places in the system where temperature or pressure change.
The presence of two phases in one stream results in different rates of flow, which may give rise to variations in the metering process. This problem can be eliminated in accordance with the present invention, by heating or cooling the system at given points therein, so as to obtain thermal - gradients which prevent undesirable condensation or vaporiza-tion. In the case of the Figure 3 arrangement, the liquid master gas is accordingly heated and vaporized in the heating Ioop 11 prior to entering the pressure regulator 14 and also l downstream of said regulator, since in the case of CO2 reduc-I tion to the working pressure required in the regulator, about 15 bars, requires expansion of the master gas, with the accompanying risk of condensation as a result of the decrease in temperature that occurs herewith. Consequently, the master gas is again heated by the hPating coil 12 prior to being delivered to the flowmeter 15.
A ~inal master gas expansion phase takes place down-stream of the control valve 16 and a fubak heating coil 13 ensures that no condensation will occur at this location, which could cause changes in the composition of the master gasland subsequent variations in the metering process. The three heating coils are mutually connected in series and hot water is conveniently passed through the coils. When the master gas includes CO2, this water may have a temperature of 50C, for instance. This enables the remainder of the ar-rangement to be maintained at a lower temperature level, so as to ensure that the master gas will definitely arri~e at the vaporizing unit 10 in a liquid state. In accordance with the invention, the coldest part of the inventive arrangement ~s~
~ VO ~3/25638 ~ 3 ;.~ 1 8 3 PCT/SE9~/00432 is the input to the vaporiz~r.
The gas conduit between the gas bottle 3 and the vapor-izer input is cooled by a cooling element 21 which is placed adjacent said conduit and through-passed by cold water. The requisite temperature gradient between the vaporizer input and the flask temperature is therewith achieved by passing the cooling water in counterflow to the direction of master gas flow, arrow B.
The temperature of the pressure vessel 3, about 18C in the case of CO2, is also related to the temperature of the ~ vaporizing unit lO, this temperature being sensed by a sensor ;~i22, in accordance with the invention. In order to maintain a constant temperature difference, the central unit 18 controls the temperature of the pressure vessel 3 through the combined effect of the heating coil 23 and the cooling coil 24, among other things ln dependence on ambient temperature.
Although the invention has been described with reference to an exemplifying embodiment thereof in which there is used i~a master gas which includes carbon dioxide and dimethyl sulphide, it will be understood that the same conditions also apply to other vehicle gases, such as propane, butane, sul-lphur hexafluoride and dinitrogen oxide, etc., wherein the ¦odorant used may alternatively be, for instance, tetrahydro ¦thiophene, methyl mercaptan, ethyl mercaptan, propyl mercap-¦25 tan or butyl mercaptan, and dimethyl sulphide, diethyl sul-phide and methylethyl sulphide. The odorant concentration of ~the master gas is conveniently 0.5-lO mol-%. The master gas jcan be delivered to the consumer gas in an amount to ob~ain a consumer gas odorant concentration within the range of 1-50 ppm, preferably 1-20 ppm.
Claims (10)
1. A method of adding an odorant to a consumer gas which is distributed to a consumer site, with the intention of indi-cating to people in the vicinity of the risk of fire, explo-sion, poisoning, suffocation or some other danger should consumer gas escape to atmosphere, wherein the odorant, in concentrated form, preferably an organic sulphur compound, is dissolved in a condensed vehicle gas in a pressure vessel, for instance carbon dioxide, propane or butane, to form a solution, master gas, which includes a liquid phase and a gas phase, and in which the desired concentration of odorant in the consumer gas is achieved by diluting the consumer gas with an adapted quantity of the master gas liquid phase, which is vaporized prior to being mixed with the consumer gas, said quantity being determined on the basis of the flow of master gas and the odorant concentration in said master gas and the flow of the consumer gas, characterized by cor-recting the relationship between the two gas flows during the dilution process with respect to the increase of concentra-tion of the odorant in the liquid phase of the master gas that results from the decreasing relationship between the amount of liquid phase and gas phase in the pressure vessel.
2. A method according to Claim 1, characterized by deter-mining the amount of master gas remaining in the pressure vessel by continuously integrating the flow of master gas from the vessel and subtracting the value obtained from the initial quantity of master gas; and by correcting the rela-tionship between the two gas flows continuously during the dilution process on the basis of this determination.
3. A method according to Claim 1 or 2, characterized by determining the temperature of the master gas in the pressure vessel, and by correcting the relationship between the two gas flows also in response to the temperature changes detect-ed.
4. A method according to any one of Claims 1-3, character-ized by maintaining such temperature gradients in the system by heating or cooling said system in a manner to prevent undesirable condensation or vaporization processes that are able to influence the accuracy of the dilution process.
5. An arrangement for adding an odorant to a consumer gas which is distributed to a consumer site, with the intention of indicating to people in the vicinity of the risk of fire, explosion, poisoning, suffocation or some other danger should consumer gas leak into the surrounding atmosphere, wherein the odorant, preferably an organic sulphur compound, is dissolved in a condensed vehicle gas in a pressure vessel (3), for instance carbon dioxide, propane or butane, to form a solution, master gas, which comprises a liquid phase (6) and a gas phase (7), wherein for the purpose of obtaining a desired concentration of odorant in the consumer gas, the arrangement includes means (2) for diluting the consumer gas with an adapted quantity of the master gas liquid, which is vaporized prior to being mixed with the consumer gas, and wherein means (16) are provided for determining this adapted quantity on the basis of the flow of master gas and the concentration of odorant in said master gas and also on the basis of the flow of consumer gas, characterized in that the arrangement further includes means (18) for correcting the relationship between the gas flows during the dilution pro-cess with respect to the increase in the concentration of odorant in the liquid phase (6) of the master gas that re-sults from the decreasing relationship between the amount of liquid phase and gas phase (7) in the pressure vessel.
6. An arrangement according to Claim 5, characterized in that the means (18) for continuously determining the amount of master gas remaining in the pressure vessel includes means for continuously integrating the flow of master gas from the vessel (3) and subtracting the value obtained from the ini-tial amount of master gas; and in that said means (18) for correcting the relationship between the two gas flows during the dilution process is intended to operate in accordance with this determination.
7. An arrangement according to Claim 5 or 6, characterized in that the arrangement includes means (19) for determining WO 93/25638 PCT/SE92/004?
the temperature of the master gas in the pressure vessel (3);
and in that said means (18) which functions to correct the relationship between the two gas flows during the dilution process is also intended to take into account variations in temperature.
the temperature of the master gas in the pressure vessel (3);
and in that said means (18) which functions to correct the relationship between the two gas flows during the dilution process is also intended to take into account variations in temperature.
8. An arrangement according to any one of Claims 5-7, char-acterized by means (23, 24) for maintaining the temperature of the pressure vessel (3) essentially constant and at a higher level than the temperature of a conduit which connects the pressure vessel with a vaporizer (10).
9. An arrangement according to any one of Claims 5-8, characterized by means (11, 12, 13) for heating and vaporiz-ing the liquid phase (6) of the master gas taken from the pressure vessel (3) at locations upstream and downstream of a pressure reducer (14) coupled in the delivery conduit, and downstream of a control valve (16) coupled in the connection conduit (2) which leads to the consumer gas conduit (1).
10. An arrangement according to any one of Claims 5-9, characterized by a central processor unit (18) which deter-mines metering of the master gas and which is intended to calculate the relative concentration of odorant in the liquid phase (6) of the master gas as a function of consumed master gas at the temperature prevailing at that time.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002135183A CA2135183A1 (en) | 1992-06-16 | 1992-06-16 | Method and an apparatus for adding a malodorant to a consumer gas |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002135183A CA2135183A1 (en) | 1992-06-16 | 1992-06-16 | Method and an apparatus for adding a malodorant to a consumer gas |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2135183A1 true CA2135183A1 (en) | 1993-12-23 |
Family
ID=4154614
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002135183A Abandoned CA2135183A1 (en) | 1992-06-16 | 1992-06-16 | Method and an apparatus for adding a malodorant to a consumer gas |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2135183A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP4197626A1 (en) * | 2021-12-16 | 2023-06-21 | Messer Cutting Systems GmbH | Odorising insert for expanding a gas supply system, gas supply system equipped with the odorising insert, and method for odorising a working gas |
-
1992
- 1992-06-16 CA CA002135183A patent/CA2135183A1/en not_active Abandoned
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP4197626A1 (en) * | 2021-12-16 | 2023-06-21 | Messer Cutting Systems GmbH | Odorising insert for expanding a gas supply system, gas supply system equipped with the odorising insert, and method for odorising a working gas |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US5632295A (en) | Method and an apparatus for adding a melodorant to a consumer gas | |
| US4025315A (en) | Method of odorizing liquid natural gas | |
| EP0770816A2 (en) | Apparatus for storing a multi-component cryogenic liquid | |
| US4219038A (en) | Gas mixing device for breath-protecting, diving, medical and laboratory techniques | |
| Pedersen et al. | Phase equilibrium calculations for unprocessed well streams containing hydrate inhibitors | |
| AU731273B2 (en) | Production of constant composition gas mixture streams | |
| US3527585A (en) | Method and apparatus for the control of the heating value of natural gas | |
| Crolet et al. | How to pressurize autoclaves for corrosion testing under carbon dioxide and hydrogen sulfide pressure | |
| CA2135183A1 (en) | Method and an apparatus for adding a malodorant to a consumer gas | |
| NO154262B (en) | RORBULP. | |
| JP2004099718A (en) | Method and apparatus for making lng having high calorific value have low calorie | |
| US5778678A (en) | Method and apparatus for producing liquid mixtures of oxygen and nitrogen | |
| CN1273762C (en) | Method and device for storing liquids and liquefied gases | |
| EP0873177B1 (en) | A method and an apparatus for odorization | |
| AU4012799A (en) | Method and apparatus for storing and dispensing a liquid composed of oxygen containing mixture | |
| CA2123501A1 (en) | Method and apparatus for determining the solid fraction of a stored cryogenic refrigeration system | |
| CZ312394A3 (en) | Method of addition malodourous substance in a consumer's gas and apparatus for making the same | |
| WO1993017941A1 (en) | Method and apparatus for purging a container | |
| US7267143B2 (en) | Dynamic filling with high-pressure gas mixtures, particularly an N2O/O2 mixture | |
| EP3839393A1 (en) | A method and apparatus for supplying a cryogenic stream with a controlled temperature from a back-up system | |
| Cross | The enrichment of gases of low calorific value with liquefied petroleum gases | |
| JPH0658173B2 (en) | Natural gas calorific value adjustment method | |
| EP3231854A1 (en) | Method and system for injecting an odourant into a gas stream | |
| Gracia et al. | File Number: LB3023 | |
| JPS60164098A (en) | Gasifying device for liquidized gas |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Discontinued |