Exxon Mobil Upstream Research Company v Shell Internationale Research Maatschappij B.V
[2012] APO 92
•23 August 2012
IP AUSTRALIA
AUSTRALIAN PATENT OFFICE
ExxonMobil Upstream Research Company v Shell Internationale Research Maatschappij B.V. [2012] APO 92
Patent Application: 2004209623
Title:Removing contaminants from natural gas
Patent Applicant: Shell Internationale Research Maatschappij B.V.
Opponent: ExxonMobil Upstream Research Company
Delegate: Dr. F. Rabbani
Decision Date: 23 August 2012
Hearing Date: 22-23 May 2012, in Canberra
Catchwords: PATENTS - section 59 - opposition to the grant of a patent – grounds fair basis, novelty, inventive step - whether claimed process is fairly based - opposition successful on lack of fair basis in relation to some claims – claims were considered novel and inventive in view of the common general knowledge – addition of integer in novelty consideration was rejected – evidence provided in relation to common general knowledge was not directed to a single process for removing contaminants as claimed
Representation: Patent applicant: Ms Katrina Howard, SC of Counsel
and Mr. Andrew Lee of Pizzeys
Opponent:Mr. David Shavin, QC,
and Mr. Richard H Baddeley of Watermark Patent and Trade Mark Attorneys
IP AUSTRALIA
AUSTRALIAN PATENT OFFICE
Patent Application: 2004209623
Title:Removing contaminants from natural gas
Patent Applicant: Shell Internationale Research Maatschappij B.V.
Date of Decision: 23 August 2012
DECISION
The opposition was successful on the ground of lack of fair basis for claim 1 and claims 2-24 & 26-31 (when appended to claim 1). Applicant is allowed 60 days from the date of this decision to file amendments to address the deficiencies. Costs are awarded according to Schedule 8 against Shell Internationale Research Maatschappij B.V.
REASONS FOR DECISION
Background
Patent application 2004209623 in the name of Shell Internationale Research Maatschappij B.V. (hereinafter referred to as Shell or the applicant) was filed on 4 February 2004, bearing a priority date of 7 February 2003. The application was accepted on 28 June 2007 and a notice of acceptance was published in the Supplement to the Australian Official Journal of Patents on 12 July 2007.
ExxonMobile Upstream Research Company, (hereinafter referred to as Exxon or the opponent), filed an opposition under Section 59 of the Patents Act to the grant of the application on 25 September 2007.
Prior to the hearing the accepted specification was amended twice, on the 5 May 2009 and 13 May 2010.
Opponent requested to amend the statement of grounds and particulars on the day of the hearing to include a citation introduced earlier by one of the experts, US 5,819,555, in the name of Engdhal. At the hearing this citation was used in relation to novelty. Applicant was provided the opportunity to submit further evidence in relation to this citation and chose not to do so.
At the hearing opponent pursued the following grounds of opposition: fair basis, novelty, and inventive step based on common general knowledge alone.
Evidence
Evidence in support of the opposition was provided in the form of statutory declarations by Professor Jaime A Valencia (hereinafter referred to as Valencia) with Exhibits JAV-1 to JAV-30; and Mr Costa Tsesmelis (hereinafter referred to as Tsesmelis) with Exhibits RHB-1 to RHB-4.
Valencia’s declaration of 21 May 2008 qualified that his training is in the field of Chemical Engineering with expertise in the field of cryogenic processes and in particular with the Controlled Freeze Zone (CFZTm) process used to remove contaminants from natural gas. He is also an employee of Exxon.
Tsesmelis is likewise qualified in the field of chemical engineering with many years of consulting experience.
Evidence in answer was provided in the form of a statutory declaration by Professor Robert Amin (herein referred to as Amin) with Exhibits RA-1 to RA-4 on the 27 October 2009. Amin is co-inventor of the current application and a Professor of petroleum engineering at Curtin University of Technology in Perth, Australia.
Evidence in reply was served in the form of a second statutory declaration by Valencia with exhibits JAV-31 and JAV-32 on the 26 February 2010.
Further evidence was supplied by the opponent in a second statutory declaration by Tsesmelis with accompanying exhibits CMT-2 to CMT-9 on the 8th March 2011.
Applicant responded to the further evidence by way of a statutory declaration from Mr Craig Francis Dugan (hereinafter referred to as Dugan) with annexure CD-1. Dugan has extensive experience and knowledge in process design, particularly in the oil and gas industry. This declaration was corrected on 8 May 2012 to include his “final comments”.
Both parties made oral submissions at the hearing and had filed written submissions prior to the hearing. I shall refer to these as well as the evidence wherever relevant in my decision.
Standard of proof
The onus of proof in opposition proceedings lies with the opponent, who must establish that it is clear that a valid patent cannot be granted (F.Hoffman-La Roche AG v New England Biolabs Inc [2000] FCA 283 at [29], [67]; (2001) 50 IPR 305 at 311 [29], 319 [67]; Commissioner of Patents v Sherman [2008] FCAFC 182 at [18], [22]; (2009) 79 IPR 426 at 430 [18], 432 [22]).
THE SPECIFICATION
The specification under opposition has been amended twice during the opposition period, amendments having been filed on 5 March 2009 and then again on 13 May 2010. To enable an assessment with regards to fair basis a detailed analysis of the specification has been undertaken, as follows.
The title of the application is: “Removing contaminants from natural gas”.
The first three paragraphs have been relied upon by the applicant for the breath of claim 1 and for this reason will be scrutinized in detail, as follows:
“The present invention relates to a process and apparatus for removing a contaminant from a natural gas feed stream by forming a solid of the contaminant and suitably subsequently melting the solid contaminant.
When the contaminant is water, the present invention relates particularly, though not exclusively, to a process and apparatus for dehydrating a natural gas feed stream.
When the contaminant is a sour species, for example hydrogen sulphide or carbon dioxide, the present invention relates particularly, though not exclusively, to a process and apparatus for sweetening the natural feed stream.”
The first paragraph emphasises that the invention is about removing contaminants from a gas stream by forming solids of the contaminants regardless of the chemical composition of the contaminant, i.e., the contaminant can include either or both water and sour species.
The second and third paragraphs indicate that the process and apparatus as described in the application can be used to either remove water (dehydrate) or remove sour species (sweeten) the natural gas feed. I note that the processes and apparatus as described are directed toward formation of solid hydrates or solids of the sour species, and not toward other forms of contaminant removal such as adsorption or absorption. The ‘non-exclusive’ nature of the invention is understood to be in use of the process and apparatus for removing either type of contaminant should they be present (water or sour species such as CO2 or H2S).
The specification goes on to state at the fourth paragraph that the invention also relates particularly, though not exclusively, to a process and apparatus for sequentially dehydrating and sweetening the natural gas feed stream.
This paragraph allows for use of the process and apparatus of the specification to sequentially dehydrate and sweeten a natural gas feed stream. This means that wet sour gas enters the apparatus and dry sweetened gas exits at the end.
Next the specification sets out the problem that the application is concerned with, that being:
“Natural gas from either production reservoirs or storage reservoirs typically contains water, as well as other species, which form solids during the liquefaction to produce liquefied natural gas (LNG). It is common practice for the natural gas to be subjected to a dehydration process prior to the liquefaction. Water is removed to prevent hydrate formation occurring in pipelines and heat exchangers upstream of the liquefaction vessel.”
This paragraph clearly delineates the problem faced by the industry, that being, contaminants forming solids during liquefaction to produce LNG. It further explains that in so far as the contaminant is water, this problem is overcome by dehydration processes prior to liquefaction. The specification further explains that if water is not removed, solid hydrates may form in pipe works, heat exchangers and/or the liquefaction vessel. In this context hydrates are stable solids comprising water and natural gas having the outward appearance of ice, with the natural gas stored within the crystal lattice of the hydrate.
Importantly, the specification then sets in context the invention by explaining that historically, formation of natural gas hydrates has been viewed as undesirable. However, two prior art patent applications are cited (WO 2001/00755 & WO 2001/12758) where the invention lie in the on-purpose creation of natural gas hydrates. In these applications natural gas and water are combined on purpose to form hydrates which are either used to store natural gas or to facilitate transport of natural gas in solid form. These inventions differ from the current application in that they add water to the natural gas to facilitate formation of natural gas hydrates.
Known methods of dehydrating or removing water from natural gas feed streams are discussed in the next paragraph, none of which are based on hydrate formation:
“Methods of dehydrating natural gas feed streams known in the art include absorption of water in glycol or adsorption of the water using a solid such as hydrated aluminium oxide, silica gels, silica-alumina gels and molecular sieves.”
The specification explains what gases are considered to be sour, and in this context both hydrogen sulphide (H2S) and carbon dioxide (CO2) are considered to be sour. These species are undesirable as they are toxic and corrosive. Removal of these species renders the natural gas feed “sweet”.
The specification continues to explain: “Like dehydration, gas sweetening processes are known in the art, such processes typically include adsorption using solid adsorption processes or absorption using amine processes, molecular sieves etc… Existing dehydration and gas sweetening processes are extremely complex and expensive.”
Then the application states that the present invention is an improvement on the process and device discussed in WO 2003/062725 (hereinafter abbreviated to WO ‘725). Robert Amin, co-inventor of the opposed application, is also listed as an inventor of WO ‘725.
It is necessary to look at WO ‘725 to understand the starting point of the invention in the opposed application. This approach was used in the judgements of Bennett and Middleton JJ in Apotex Pty Ltd v Sanofi-Aventis, [2009] FCAFC 134, at para 161; 82 IPR 416, [2011] ALMD 1848.
The summary of this invention states (refer to page 3 of WO ‘725):
“According to a first aspect of the present invention, there is provided a method of removal of the freezable species from the natural gas feed stream, the method comprising the steps of: cooling the feed stream in a cooling vessel to produce pressurised LNG in a manner such that the freezable species solidify forming a slurry with the pressurised LNG; and, removing the slurry from the cooling vessel whilst maintaining the freezable species as a solid.”
The invention of WO ‘725 is generally directed to freezing of any contaminant in a vessel, highlighting the significance of the vessel. The freezable species may include but are not limited to CO2 and H2S.
The WO ‘725 application explains that the step of cooling is conducted in a manner such that the freezable species solidify away from a wall of the cooling vessel and defines the zone in which the freezable species solidify within the cooling vessel as the "solidification zone".
“One way of promoting the formation of the solidification of the freezable species away from the walls of the cooling vessels is to maintain a temperature gradient within the cooling vessel such that the temperature towards the centre of the cooling vessel is less than the temperature at the wall of the cooling vessel. In practice, one way of achieving this is to use a material of construction for at least the internal wall of the cooling vessel surrounding the solidification zone from a material having a low thermal conductivity.”
On page 9, the WO ‘725 application continues to explain that: “Whilst the natural gas feed stream would typically be dehydrated to remove water, this is not considered an essential step of the present invention and the natural gas feed stream 12 entering the cooling vessel 11 may contain water as one of the freezable species.” Therefore, the invention of the WO ‘725 application provides for contaminant removal (including water) in one vessel without having to dehydrate the natural gas first.
The improvement of the opposed application over the invention in WO ‘725 is in part that water is separated from the natural gas feed through freezing in a separate vessel prior to decontamination of sour species in a second vessel, refer to pg. 3, lines 8-11:
“… the process for removing contaminants from a natural gas feed stream including water according to the present invention comprises the steps of cooling the natural gas feed stream in a first vessel to a first operating temperature at which hydrates are formed; and removing from the first vessel a stream of dehydrated gas.”
The next sentence brings the invention into sharp focus by stating (pg 3, lines 12-14):
“An essential feature of the process of the present invention is that on purpose hydrates are formed in order to remove water. Normally formation of hydrates is prevented.” [Emphasis added]
And continues (pg 3, lines 15-19):
“When the natural gas feed stream further includes sour species, the process according to the present invention suitably further comprises the steps of cooling a dehydrated gas in a second vessel to a second operating temperature at which solids of the sour species are formed or at which the sour species dissolve in a liquid; and removing from the second vessel a stream of dehydrated sweetened gas.” [Emphasis added]
These two paragraphs emphasise that the invention is really in relation to dehydration of natural gas feeds through formation of hydrates and can include a further step of sweetening when sour species are present. It is interesting to note that the sour species can be removed using either freezing or dissolution in a liquid.
The next paragraph was relied upon by the applicant to justify a broader view of the invention. This paragraph was inserted by way of amendment after claim 1 had been amended on 5 May 2009. This paragraph is a consistory clause and states:
“In an alternative aspect of the present invention there is provided a process for removing contaminants from natural gas feed stream including water and sour species, which process comprises the steps of dehydrating the natural gas feed stream in a first vessel; removing from the first vessel a stream of dehydrated gas; cooling by means of expansion the dehydrated gas in a second vessel to a second operating temperature at which solids of the sour species are formed; and removing from the second vessel a stream of dehydrated sweetened gas.”
Applicant maintained at the hearing that the qualifier “in an alternative aspect” signifies that the invention was in removing sour species from a dehydrated gas through expansion cooling to form the solid species. They also argued that the step of dehydration carried out in the first vessel was not restricted to formation of hydrates through freezing, and encompassed all modes of dehydration known in the art.
Opponent disagreed in so far as they saw the qualifier “in an alternative aspect” to mean that a further step of removing sour species through formation of the solids of said contaminants was envisioned within the scope of the invention; but that the step of dehydrating in a first vessel was to be carried out as per the overall teachings of the application, that being through formation of solid hydrates.
In my view opponent’s position is consistent with the disclosure of the specification and this consistory clause does not provide for the added breath that the applicant has argued for.
The specification continues to define the terms “operating temperature” and a “warm” liquid. The former being a temperature below the solid/liquid transition temperature for the contaminant at a given pressure of operation of the first or second vessel; and the latter being a temperature above the solid/liquid transition temperature of the contaminant for a given pressure of operation of the first or second vessel.
From page 4 onwards the specification provides a detailed description of two embodiments of the invention with reference to the process flow diagrams of Fig. 1 and Fig. 2. Figure 1 illustrates an embodiment where wet (possibly sour) feed gas from a well head is dehydrated in a vessel using expansion cooling to form solid hydrates. Figure 2 shows a further embodiment where wet sour feed gas is sequentially dehydrated and then processed to remove sour species using cooling to form the solid contaminant. Therefore, Fig. 2 incorporates the process steps of Fig. 1 and provides a further processing step to remove the sour gas species in a second vessel using cooling to form the solid of the species.
It seems clear that the second embodiment is to a sequential process for dehydrating and sweetening a natural gas feed, where each sequence is based on the formation of solids of the contaminants. The continuous nature of the process can be viewed in the process flow diagram of Fig. 2 (Annexure A).
It is instructive to review what the applicant has to say about Fig. 1 (refer to pg 4 to 5):
“Figure 1 shows an apparatus 10 for carrying out the process of the present invention. The apparatus 10 comprises a first vessel 12. The contaminant removed in the first vessel 12 is water and thus the gas exiting the first vessel is dry…The water dew point of the gas exiting the first vessel 12, however, is lower than its equilibrium dew point due to the formation of hydrates. In the embodiment as illustrated in Figure 1, wet feed gas from a wellhead is fed through conduit 15 to a first flash tank 16 in which condensate is separated from the feed gas. The pressure and temperature conditions within the first flash tank 16 would typically be in the order of 75 to 130 bar and between 25 and 40 °C (about 5 to 10 °C above the hydrate formation temperature)…The gas stream separated from the sour wet feed gas in the first flash tank 16 enters the first vessel 12 via wet sour gas feed stream inlet 20. An intermediate heat exchanger 22 may be used to cool the wet sour gas between the first flash tank 16 and the first vessel 12. The intermediate heat exchange 22 drops the temperature of the wet sour gas to a temperature just above the hydrate formation temperature for the particular pressure of this feed stream. The hydrate formation temperature for the particular pressure of the feed stream is the maximum operating temperature in the first vessel 12….
The wet gas feed stream fed to the first vessel 12 is expanded using a Joule-Thompson valve 24 or other suitable expansion means such as a turbo expander to further cool the stream as it enters the first vessel 12…
Upon expansion of the wet sour gas feed stream into the first vessel 12, the gas pressure-temperature conditions within the vessel allow hydrates to form. The necessary degree of cooling is achieved by the degree of expansion of the wet sour gas feed stream through the Joule-Thompson valve 24.
The first operating temperature and the pressure in the first vessel 12 are maintained at a level whereby hydrates are formed. The natural gas feed stream entering downstream of the Joule-Thompson valve 24 into the first vessel 12 is at the first operating temperature.”
At page 7 last paragraph, the specification clearly states:
“As observed earlier, the present invention relates to dehydrating natural gas by forming hydrates.”
The rest of the description provides detail on process conditions such as temperature, pressure, hydrocarbon composition, and some alternatives on the mechanics of cooling (turbo expander, Joule-Thompson valve or sub-cooled liquid spray). The processes of these embodiments as captured by the process flow diagrams of Figs 1 and 2 are continuous and conserve on energy by recycling condensate and gas to effect heat exchange. However, there is no departure from the embodiments already discussed and no reference to prior art means of dehydrating the initial feed.
Therefore, it is my conclusion that the body of the specification when read as a whole describes an invention concerned with the dehydration of a natural gas feed through formation of solid hydrates using a vessel. In an alternative form, the invention is concerned with sequential removal of water and sour contaminants from a natural gas feed using separate vessels to form solid hydrates and solids of the sour species by cooling to the relevant temperatures where the contaminant gases form solids. Therefore, the process associated with dehydration necessarily involves formation of solid hydrates using some means of cooling.
THE CLAIMS
There are 31 claims in the presently opposed application, included in this decision as Annexure B. Claim 1 directed to a process for removing contaminants from a natural gas feed stream, can be divided into separate steps as follows:
“A process for removing contaminants from a natural gas feed stream including water and sour species, which process comprises the steps of:
(a) dehydrating the natural gas feed stream in a first vessel;
(b) removing from the first vessel a stream of dehydrated gas;
(c) cooling by means of expansion the dehydrated gas in a second vessel to a second operating temperature (a temperature below the solid/liquid transition temperature for the contaminant at a given pressure of operation of the second vessel) at which solids of the sour species are formed; and
(d) removing from the second vessel a stream of dehydrated sweetened gas.”To facilitate the construction of this claim, the definition provided in the description for the term “operating temperature” has been inserted into the claim in brackets (refer to specification pg. 3, lines 27-29). This definition introduces the temperature/pressure relationship for the solid/liquid transition. The pressure of operation will dictate the temperature at which the solid/liquid transition will occur.
It is also appropriate to note that evidence was submitted on both sides regarding the construction of the word “vessel”. At the hearing it was agreed by both parties that the dictionary definition of a “vessel” could be used in the construction of the claims. This dictionary definition as provided in JAV-31 defines “vessel”: as a container used as a structural envelope.
The Macquarie dictionary defined the word “dehydrate” as to lose water or moisture, with no limitation associated with how this is achieved. Therefore, dehydrating a natural gas feed simply means to remove water or moisture by any means not restricted to formation of hydrates.
Claim 1 is to “a process”, i.e. a single process, that sequentially achieves dehydration with CO2/H2S removal using two vessels, where the first vessel is used to dehydrate the natural gas and provide as feed to the second vessel a dehydrated gas; and the second vessel is used to solidify the sour species through freezing effected by gas expansion. The process also requires that dehydrated sweetened gas be removed from the second vessel.
It is important to note the composition of the feed gas and the end gas associated with this process. The process of claim 1 starts with a natural gas feed containing water and sour species, there is an intermediate dehydration step where the gas is dried (water is removed), and that gas is fed to the second vessel where the gas is sweetened. Implicit in the claim is the fact that the dehydrated gas leaving the first vessel must be at a pressure where cooling by way of expansion will reduce the temperature to a value below the solid/liquid transition temperature of the contaminant and allow for formation of solids of the sour species.
Claim 2 defines the process according to claim 1, wherein dehydrating the natural gas feed stream includes cooling the natural gas feed stream to a first operating temperature at which hydrates are formed.
This claim defines how dehydration of the natural feed gas takes place, that being through formation of hydrates. Furthermore, it is understood that in the context of claim 2, hydrates are stable solids comprising water and natural gas, with the natural gas stored within the crystal lattice of the hydrate.
Claim 3 defines the means of expansion to be a Joule-Thompson valve.
Claim 4 defines the process according to claim 2 or claim 3, wherein the step of cooling the natural gas feed stream in a first vessel to a first operating temperature comprises introducing the natural gas feed stream into the first vessel at a temperature that is below the first operating temperature. The notable feature of this claim is the reference to the implicit condition defined in claim 1, that being that the first vessel is operated at a first temperature. This claim requires that the wet sour natural gas feed stream be introduced into the first vessel at a temperature that is below the operating temperature of the vessel.
Claim 5 defines the process according to anyone of claims 1 to 3, wherein the step of cooling the dehydrated gas in a second vessel to a second operating temperature comprises introducing the dehydrated gas into the second vessel at a temperature that is below the second operating temperature. The important feature of this claim is in the definition of the “second operating temperature”, that being a temperature below the solid/liquid transition temperature for the contaminant at a given pressure of operation of the second vessel. Therefore, this claim requires that the temperature at which sour natural gas is introduced into the second vessel be cooler than that defined as the second operating temperature.
The remaining dependent claims define further processing conditions whose limitations were not disputed by the opponent. However, it is noted that claims 12-15 & 17-21 define an embodiment where condensate or liquid is introduced into the second vessel via a plurality of spray nozzles to provide for further cooling. These steps are considered to provide for better cooling efficiency and are not an alternate form of cooling to what has been defined in claim 1.
For the sake of brevity the limitations of the remaining claims have been included in Annexure B and will not be repeated here.
Fair basis
S40(3) provides that the claims must be fairly based on the matter described in the specification. The general principle underlying fair basis is discussed in Kimberly-Clark v Arico at [12]:
“... where the issue is one under S40(3) of "fair basing" of a claim, what the 1990 Act requires is a comparison between the matter described in the specification and the claim which defines the scope of the monopoly.”
In assessing so-called “internal” fair basis, the comparison to be made is between the disclosure of the body of the specification as a whole and the claims.
In Lockwood v Doric [2004] HCA 58 at [69], the High Court stated that there must be a “real and reasonably clear disclosure” of the claimed invention. This does not limit the claimed invention to the preferred embodiments.
In Lockwood (No. 1), the High Court stated:
“…the correct position is that a claim based on what has been cast in the form of a consistory clause is not fairly based if other parts of the matter in the specification show that the invention is narrower than that consistory clause. The inquiry is into what the body of the specification read as a whole discloses as the invention. An assertion by the inventor in a consistory clause of that of which the invention consists does not compel the conclusion by the court that the claims are fairly based. The consistory clause is to be considered with the rest of the specification.”
When the specification is considered as a whole, the invention defines a process concerned with the dehydration of a wet sour natural gas feed through formation of solid hydrates by cooling. In an alternative embodiment, the invention is concerned with sequential removal of water and sour contaminants from a natural gas feed using separate vessels to form solid hydrates and solids of the sour species by cooling to the relevant temperatures where the contaminant gases form solids. Therefore, the process associated with dehydration necessarily involves formation of solid hydrates using some means of cooling.
Applicant maintained at the hearing that the step of dehydration could include prior art means of dehydrating the gas and still remain fairly based. I note however, that aside from a brief mention of these prior art means and the qualification that these means are costly and complex, the specification does not include them in any of the embodiments described. In fact, the whole disclosure is about a process that circumvents use of adsorption, absorption and molecular sieves to remove contaminants. Therefore, there is no real and reasonably clear disclosure of other means of dehydrating the natural gas feed, except for the method of forming hydrates.
Lastly, it is difficult to ignore explicit statements made by the applicant in the description regarding the essentiality of hydrate formation to the process of the invention (refer to description pg 3, lines 12-14 and last para on pg 7; paragraph 35 and 46 of this decision).
Claim 1 is to a process that more closely resembles the second embodiment that being a sequential removal of water and sour contaminants from a natural gas feed. As the step of dehydration in a first vessel has been construed to include prior art means of dehydrating a natural gas feed, this claim lacks fair basis.
Conclusion on fair basis
It is my finding that the invention of claim 1 travels beyond the matter disclosed and is not fairly based.
Claim 2 which defines dehydrating the natural gas feed stream to include cooling the natural gas feed stream to a first operating temperature at which hydrates are formed is considered to be fairly based.
Claims 3-24 and 26-31 (when not appended to claim 2) are also not fairly based because they also travel beyond the matter disclosed as they fail to limit dehydration to formation of hydrates.
Novelty
The "reverse infringement" test as enunciated by Aickin J in Meyers Taylor Pty Ltd v Vicarr Industries Ltd (1977) 137 CLR 228; 13 ALR 605 at CLR 235; ALR 611 is relevant to determining whether a citation deprives a claim of novelty.
“The basic test for anticipation of want of novelty is the same as that for infringement and generally one can properly ask oneself whether the alleged anticipation would, if the patent were valid, constitute an infringement.”
Claim 1 of the opposed application is directed to:
“A process for removing contaminants from a natural gas feed stream including water and sour species, which process comprises the steps of:
(a) dehydrating the natural gas feed stream in a first vessel;
(b) removing from the first vessel a stream of dehydrated gas;
(c) cooling by means of expansion the dehydrated gas in a second vessel to a second operating temperature (a temperature below the solid/liquid transition temperature for the contaminant at a given pressure of operation of the second vessel) at which solids of the sour species are formed; and
(d) removing from the second vessel a stream of dehydrated sweetened gas.”As discussed under the heading “Construction of Claims”, claim 1 is to a process (i.e., single process) that sequentially achieves dehydration with CO2/H2S removal using two vessels, where the first vessel is used to dehydrate the natural gas and the second vessel is used to solidify the sour species through freezing effected by gas expansion. The process also requires that decontaminated gases be removed from each vessel.
A review of the expert testimony regarding the scope of claim 1 corroborates this construction:
Tsesmelis Report, first declaration, Section 6.1,
“The Shell application on the other hand includes dehydration and acid gas (sour species) removal in a single process description with feed to the process being saturated with water (i.e. “wet” gas). The Shell application is described as a single “process” consisting of two main vessels. Dehydration (water removal) is completed in the 1st vessel and CO2/H2S removal is completed in the 2nd vessel.”
Valencia, first declaration, Section 4.1 (based on the claims before amendment),
“The process comprises two stages. In the first stage, the natural gas feed stream is dehydrated in a first vessel. In the second stage, the natural gas feed stream is cooled in a second vessel to a second operating temperature at which solids of the sour species are formed or at which the sour species dissolve in a liquid.”
Dugan, declaration, as amended 8 May 2012, para 4.3:
“I understand that the invention defined in claim 1 of the Shell application utilises two vessels, where the first vessel dehydrated the natural gas feed stream and this is used in combination with a second vessel where cooling is achieved by means of expansion so as to form solids of the sour species and where the dehydrated sweetened gas is removed.”
Therefore for anticipation to occur the prior art needs to disclose a single process where a wet sour natural gas feed is dehydrated in a first vessel and then solids of the sour species generated through expansion cooling in a second vessel, allowing for removal of dehydrated sweetened gas.
Opponent relied on two prior art citations in relation to novelty:
- D1. US Patent No. 4,533,372 - Valencia et. al., issued August 6, 1985
Titled: ‘Method and Apparatus for Separating Carbon Dioxide and Other Acid Gases from Methane by the Use of Distillation and a Controlled Freezing Zone’
- D2. US Patent No. 5,819,555 - Engdahl issued October 13 1998
Titled: ‘Removal of Carbon Dioxide from a Feed Stream by Carbon Dioxide Solids Separation’
D1. US 4,533,372 Valencia et. al.
D1 had been addressed at length by the experts as it was relied upon in the original statement of grounds and particulars. D1 describes what is referred to as a controlled freeze zone, CFZTM, process in which the feedstream is treated in at least one distillation zone and a controlled freezing zone. The freezing zone produces a carbon dioxide slush which is melted and fed into a distillation section (Valencia, first declaration, para 2.2).
The abstract for D1 describes the invention in the following words:
“The invention relates to method and apparatus for separating carbon dioxide and other acid gases from methane by treating the feedstream in at least one distillation zone and a controlled freezing zone. The freezing zone produces a carbon dioxide slush which is melted and fed into a distillation section. The apparatus used to practice the process is preferably in a single vessel.”
The rest of the disclosure of D1 emphasises the removal of carbon dioxide and other acid gases and does not concern itself with dehydration of the gas feed. The patent does provide the caveat that the feedstream must be dried prior to introduction into the distillation tower (col. 3, lines 25-27), and again specifies that ‘dried’ gas is introduced into the unit 10 (col. 5, lines 6-12).
Therefore, D1 can not be said to be directed to a single process that sequentially dehydrates and removes sour species from a natural gas stream.
Furthermore, the process of D1 relies on solid formation through contact of vapour with liquid spray from nozzles (D1, col. 6, lines 18-20). This feature is different to opposed claim 1, where cooling of the gas is by means of expansion to a second operating temperature at which solids of the sour species are formed.
My understanding regarding this point is collaborated by the expert evidence provided by Amin in relation to the CFZTM process (pg 6, para 18 of his declaration):
“In the freezing zone solid CO2 is produced by introducing a cold liquid spray (LNG reflux) and collected at the bottom of the freezing zone and melted to a liquid CO2 stream that is introduced in the top of the lower distillation zone (col. 6, lines 17-24 and 50-53).”
And also by the testimony of Dugan, refer to declaration at pg 7, para 4.9:
“The CFZ process relies on the chilled liquid to form the solids and knock them down into the sump whereas the Shell process uses the Joule-Thompson valve to form the solids which are then in one aspect knocked down by a liquid.”
Certain dependent claims (e.g. claim 12 of the present application) further qualify that “the step of cooling the dehydrated gas ….further comprises introducing at least part of the liquid stream of the condensate removed from the flash tank into the second vessel at a temperature that is below the second operating temperature to form a slurry or mixture with the sour species”.
Although this further cooling step may appear reminiscent to the cooling in the CFZTM process, it is nonetheless not the way by which solid formation is achieved. Claim 1 of the opposed application limits solid formation to expansion to a second operating temperature which is a temperature below the solid/liquid transition temperature for the contaminant at a given pressure of operation; therefore any further cooling is to provide for efficiency gains of the overall process of the invention and to achieve reduced costs of operation.
The invention of claim 1 is distinguished over the disclosure of D1 in both the manner in which solids are formed, and in that the claim is directed to a sequential process for dehydrating and sweetening natural gas, which is not the object of D1.
D2 – US 5,819,555 Engdahl
D2 was formally introduced as a citation by amendment of particulars on the day of the hearing (said amendments were allowed on 18 June 2012). However, D2 had been discussed by the experts as it was first introduced by Valencia in his first declaration to establish common general knowledge in relation to the process of cooling a natural gas stream to form solid sour species (Valencia, first declaration pg 8):
“This cooling can take place by expansion of the natural gas from high pressure to a lower pressure resulting in cooling to a temperature below that at which solids of the sour species form. The solids of sour species are separated by gravity or cyclonic forces from the existing gas which is correspondingly leaner in the sour species. The solids are then melted by addition of heat… See US Patent 5,819,555 Engdahl issued October 13, 1998…(Exhibit JAV-30).”
The invention of D2 as described in the abstract is to:
“A process with few parts is provided to remove carbon dioxide from a feed stream. The solid forming property of carbon dioxide and the low vapour phase solubility of carbon dioxide at cold temperatures form the basis for the separation process. The cooled feed stream enters a separation vessel where process means are provided to produce and separate carbon dioxide solids. Carbon dioxide is removed from the vessel as a carbon dioxide rich liquid stream. Purified cold vapour is removed from the separation vessel as a product stream.”
The starting point for the process of D2 is introduction of a dried precooled feed stream into the system of the invention (col. 5, lines 9-11). In fact, it is instructive to review what D2 states in relation to its invention at col. 5, lines 9-17:
“A dried and precooled feed stream enters the system through line 10. The feed stream can be dried by an adsorption system or other systems including a methanol injection system. Cooling conditions need to be such that carbon dioxide plugging of upstream lines and equipment is avoided. The stream is expanded through valve 100 into the solids formation zone 101 where solids are formed in the presence of liquid. The formation zone provides contact surface area between liquid, vapor, and solids and provides cooling for the formation of these solids. The solids formation zone is utilized to provide cooling and area for the formation of solids while the stream is within the confines of the formation zone.” [Emphasis added]
Dugan addresses D2 in his declaration at pg 7, para 4.8 and 4.9, where he states:
“I note that the Engdahl patent does not disclose a two vessel system as defined in claim 1 of the Shell application….”
“The Shell application is different from the Engdahl process since the Engdahl patent has a single chamber as shown in the figures which contain an internal pipe and one or more smooth elbows (102) which is used for the separation of the solid sour species from the gas. The Shell application utilises two vessels as discussed previously.”
Therefore, D2 discloses a process to remove carbon dioxide from a natural gas feed by cooling the contaminant gas to form a solid. However, in this citation as with D1, the process starts at the point where dried feed gas is fed into the system (refer to the Example provided at col. 7, line 36-38). D2 does not disclose a single process for removing contaminants including water and sour species where sequential dehydration and sweetening is carried out in two separate vessels, the first step providing feed for the second step.
The single vessel operation of D2 is akin to WO ‘725, with the omission of how to operate the vessel to dehydrate the gas whilst removing sour species. D2 therefore, lacks enablement for a single process that both dehydrates and sweetens a wet sour gas feed using two vessels.
Opponent made reference to the decision in H Lundbeck A/S v Alphapharm Pty Ltd [2009] FCAFC 70; 81 IPR 228; 177 FCR 151, and in particular to the discussion regarding the nature and extent of a disclosure necessary to constitute anticipation of a product claim. At para 173, of Lundbeck (supra) some general propositions have been supplied to help answer this question and in particular the dot points in relation to the decision in Nicaro Holdings Pty Ltd v Martin Engineering Co [1990] FCA 40; 91 ALR 513, 16 IPR 545, [1990] AIPC 36, 266 (90-670) have been transcribed below:
• Something less than a full description of the invention allegedly anticipated may be sufficient to invalidate it for want of novelty (Nicaro at 529).
• Something less than a full description of an effective means by which the combination claimed in a patent may be produced may be sufficient to a reader having common general knowledge in the art (Nicaro at 531)….
• A disclosure that describes an effective means by which a claimed invention may be produced falls short of anticipation if it requires the exercise of inventive ingenuity or the taking of any inventive step (Nicaro at 531).”
These passages and the further clarifications provided at para [180]-[181] of Lundbeck (supra) are highly instructive as to what can be considered in Australia to be an enabling disclosure. However, it is important to note that claim 1 of the present application is to a process and not to a product, which was the subject of the cases cited above.
Opponent proposed that it may be permissible to assume that the person skilled in the art would see the teaching in D2 regarding use of a dried and precooled feed stream and introduce this step into the process described in D2 to arrive at the two vessel process of the opposed claim.
The step of “dehydrating the natural gas feed stream in a first vessel” as set out in claim 1 is an essential part of the overall process for removing contaminants from a natural gas feed stream including water and sour species. The fact that the claim is broadly drafted does not diminish this essentiality. Furthermore, the complexity associated with this step dictates that the person skilled in the art would not modify a single vessel process, but would rather carry out the instructions of D2, and dehydrate using a separate process.
Engdahl at col. 3, lines 21-43, explains one process for removing water and hydrocarbon liquids from well heads by providing a cool zone in a separator, but acknowledges that there are several operational concerns in providing for separation. Hydrates can form in the expansion device and cause plugging. Engdahl does not foresee modification of these separators to include a carbon dioxide removal step, stating that the apparatus does not include cooling and heat mass transfer provisions which are required for forming carbon dioxide solids.
100. Therefore it is evident that the process of dehydrating the gas feed would be conducted separately to the process of sour gas removal and would not qualify for consideration as a single process for removing both water and sour species. Hence, it is a moot point to introduce the concept of “mechanical equivalents” for the first vessel, into the disclosure of D2, as the prior art relied upon does not contain a suggestion that the dehydrating step and the sour gas removal step should be carried out in one process as presently claimed. The prior art simply starts the process with dehydrated or dry gas.
Conclusion on novelty
101. I find that neither D1 nor D2 anticipate the claims of the Shell application which are directed to a sequential process that combines a dehydration step carried out in a first vessel with a further freezing step carried out in a second vessel to solidify the contaminants of sour species by way of expansion.
Inventive Step
102. The opponent based its case on obviousness on section 7(2) only – common general knowledge alone. According to section 7(2) of the Patents Act:
(2)an invention is to be taken to involve an inventive step when compared with the prior art base unless the invention would have been obvious to a person skilled in the relevant art in the light of the common general knowledge as it existed in the patent area before the priority date of the relevant claim, whether that knowledge is considered separately or together with the information mentioned in subsection (3).
103. Opponent also submitted that unless Dugan or Amin have expressly denied publications in evidence as common general knowledge, it is taken that the publications are admitted as common general knowledge. On this point, Dugan at para 4.13 has excluded the Engdahl patent from what he considers to be common general knowledge. Therefore, D2 has not been considered under this analysis.
104. Moreover, Dugan’s statement makes it clear that Engdahl would not have been ascertained as he states:
“Specifically, it is my view that the patents set out in this section are not indicative of what I or I believe other person in my field would have commonly referred to or would have known in Australia prior to 7 February 2003. I refer in particular to…f) The Engdahl patent (Exhibit JAV-30).”
105. Therefore the Engdahl patent does not pass the 7(3) hurdle which requires that the information be ascertained.
106. D1 basically defines the CFZTM process which Dugan has acknowledged as common general knowledge.
107. As the legislation does not provide for a definition for obviousness, recourse needs to be had to the relevant case law. The test for obviousness as set out by Aickin J is whether it would have been a matter of routine to proceed to the claimed invention:
"The test is whether the hypothetical addressee faced with the same problem would have taken as a matter of routine whatever steps might have led from the prior art to the invention, whether they be the steps of the inventor or not."
[Wellcome Foundation Ltd v V.R. Laboratories (Aust.) Pty Ltd [1981] HCA 12; (1981) 148 CLR 262 at page 286]
108. More recently, the High Court in Aktiebolaget Hässle v Alphapharm Pty Ltd [2002] HCA 59 at [51] - [53]; 212 CLR 411 at [51] - [53] approved the restatement by Graham J in Olin Mathieson Chemical Corporation v Biorex Laboratories Ltd [1970] RPC 157 at 187-188 of the so-called “Cripps question”:
“Would the notional research group at the relevant date in all the circumstances directly be led as a matter of course to try [the claimed invention] in the expectation that it might well produce a useful [desired result]?”
109. The problem that the application addresses is the complexity and expense associated with prior art means of removing contaminants whether these contaminants are water, sour species or both. Furthermore, as outlined in the WO’ 725 application (the predecessor to the current application), there are special problems associated with high CO2 containing natural gas compositions (i.e. compositions containing carbon dioxide of 10%, 20% and above).
110. Starting from this point, one can apply the “Cripps question” to the processes that constitute common general knowledge and ask whether the skilled worker at the relevant date have taken as a matter of course the steps leading from this starting point to the invention claimed in the expectation that it might well produce a less complex and cost-effective result?
111. There is no dispute as to the following matters being common general knowledge before the priority date (from applicant’s submissions):
(a)CFZTM process for removing CO2 from natural gas (Dugan 3.6-3.9)
(b)LTX process used to achieve hydrocarbon dew point control (Dugan 3.6, 3.12-3.13)
(c)Ryan-Holmes process to remove acid gases such as CO2 using adsorption (Dugan 3.6, 3.10-3.11)
(d)dehydration of a natural gas feed stream by various processes (Dugan, 3.3-3.5)
112. Would the application of these processes provide for the desired result or alternatively was there enough reason to modify these processes to arrive at the current invention as claimed?
113. The CFZTM process uses one vessel referred to as a splitter tower that comprises at least one distillation zone and a controlled freezing zone to treat a natural gas feedstream containing carbon dioxide as the predominant sour species. The freeze zone is designed to control the formation and melting of solids and to prevent the introduction of solids from the freeze zone into the distillation zone. Starting from this process would the person skilled in the art be directly led as a matter of course to eliminate the distillation zone that produces the freezing zone vapour feed and convert the process to one where simple expansion would provide for freezing of the sour species? Would the person skilled in the art then add a first vessel into the process to dehydrate the gas?
114. As there is no evidence provided by the opponent to support that the person skilled in the art would modify the CFZTM process to arrive at the two vessel process of the current application, the CFZTM process does not render claim 1 obvious.
115. The LTX/LTS (low temperature extraction or separation) process is discussed at length in exhibit JAV-15, Engineering Data Book, FPS version, Volume II, Sections 16-26, 1998. This process is used to prevent formation of liquids in pipelines by controlling the hydrocarbon dew point below the pipeline operating conditions. If sufficient pressure is available, the removal can be accomplished by expansion refrigeration in an LTS (low temperature separation) unit. The expansion refrigeration system uses the Joule-Thompson effect to reduce the gas temperature upon expansion. This temperature reduction results in not only hydrocarbon liquid condensation but also water condensation. The water is generally removed as hydrates in this process, melted and removed. Thus the process can actually accomplish dew point control of both water and hydrocarbon in a single unit.
116. The hydrocarbon and water dew points achievable with this process are limited by the pressure differential available as well as the composition of the feed gas. The LTX/LTS system can only be used where sufficient pressure is available to perform the desired processing and separation. Therefore, the question of whether the system can be sequentially operated to remove hydrates and sour contaminants becomes critical.
117. Only Dugan provides some guidance on whether the LTX process would be used to remove sour species such as CO2. He states that (para 3.13):
“Given the process relies on gravity for the separation of the species to be removed, in my opinion it is unlikely that the LTX process would work for removal of sour species such as CO2 or H2S as the solid particles formed would be very small and have very low weight, making it difficult to achieve any significant degree of separation by gravity. Filters would not be suitable as the solid particles would quickly build up on the filter surface and they would block up.”
118. Therefore, the evidence on hand suggests that the person skilled in the art would not be led as a matter of course to apply the LTX/LTS process to the solidification of sour species nor to adopt it to a two vessel process for the sequential removal of water and sour species. Moreover, the various remaining means of dehydrating natural gas feed such as adsorption, absorption, and use of molecular sieves are not characterised by the experts as processes that use one vessel to achieve their end. The process flow diagrams for these processes are complex and include multiple vessels.
119. Furthermore, none of the experts opined that they considered operation of a LTX/LTS process adjacent to a CFZ process to allow a feed of dehydrated gas from the former process to the latter, to constitute a single process as defined in claim 1. Indeed this collocation would not achieve the reductions in cost and complexity that is the problem addressed by the current application.
120. The Ryan-Holmes process is a cryogenic process for removing CO2 from natural gas feeds containing high concentrations of this contaminant which avoids solid formation and is therefore fundamentally different to the current claimed invention.
121. It is not in dispute that the limitations set out in claim 1 and which define a process for removing contaminants from a natural gas feed stream including water and sour species, are based on known scientific principles. For example, it is known that expanding a gas can lead to cooling, and that a gas can be phase shifted into a solid. The mere fact that these integers are known scientific principles does not render their application in the process of claim 1 obvious; it is not necessary to discover new laws of nature to pass the obviousness hurdle.
122. Claim 1 which is directed to a process which uses two separate vessels to dehydrate and subsequently remove sour gas species using expansion to achieve solidification of the sour specie contaminant is non-obvious in view of the common general knowledge. Opponent was not successful in establishing obviousness in relation to claim 1.
Conclusion on inventive step
123. I find that the combination of integers as set out in claim 1 is non-obvious over what has been declared to be common general knowledge. The dependent claims define further additions that provide for the efficiency gains of a process engineering system and are therefore also considered to be non-obvious.
CONCLUSION
124. The opposition is successful on the ground that claim 1 and dependent claims 3-24 and 26-31 (when not appended to claim 2) lack fair basis. Of the remaining grounds, the opponent has not established that the claims are not novel or lack an inventive step.
125. The lack of fair basis is a matter that can be overcome by amendment. I believe it is appropriate to allow the applicant an opportunity to make such amendments. I therefore allow the applicant 60 days from the date of this decision to propose suitable amendments.
COSTS
126. In proceedings such as these it is usually the case that costs follow the event. The opposition was successful on the ground that independent claim 1, and dependent claims 3-24 and 26-31 (when not appended to claim 2) are not fairly based. While this is only one ground of many put forward, it does not change the fact that the opponent was successful and I see no reason to vary the usual approach on this occasion. I award costs in accordance with Schedule 8 against Shell.
Dr. F. Rabbani
Delegate of the Commissioner of PatentsANNEXURE A: Process flow diagram illustrating the embodiment where sequential dehydration and de-souring of a natural gas feed takes place (Fig. 2).
ANNEXURE B: Claims under opposition
The claims defining the invention are as follows:
1. A process for removing contaminants from a natural gas feed stream including water and sour species, which process comprises the steps of dehydrating the natural gas feed stream in a first vessel; removing from the first vessel a stream of dehydrated gas; cooling by means of expansion the dehydrated gas in a second vessel to a second operating temperature at which solids of the sour species are formed; and removing from the second vessel a stream of dehydrated sweetened gas.2. The process according to claim 1, wherein dehydrating the natural gas feed stream includes cooling the natural gas feed stream to a first operating temperature at which hydrates are formed.
3. The process according to claim 1 or claim 2, wherein the means of expansion is a Joule-Thompson valve.
4. The process according to claim 2 or claim 3, wherein the step of cooling the natural gas feed stream in a first vessel to a first operating temperature comprises introducing the natural gas feed stream into the first vessel at a temperature that is below the first operating temperature.
5. The process according to anyone of claims 1 to 3, wherein the step of cooling the dehydrated gas in a second vessel to a second operating temperature comprises introducing the dehydrated gas into the second vessel at a temperature that is below the second operating temperature.
6. The process according to claim 2 or claim 3, wherein the step of cooling the natural gas feed stream in a first vessel to a first operating temperature comprises introducing the natural gas feed stream into the first vessel at a temperature that is below the first operating temperature, and wherein the step of cooling the dehydrated gas in a second vessel to a second operating temperature comprises introducing the dehydrated gas into the second vessel at a temperature that is below the second operating temperature.
7. The process according to claim 1, comprising:
cooling the stream of dehydrated gas removed from the first vessel to form a two-phase mixture of dehydrated gas and condensate,
passing the two-phase mixture of dehydrated gas and condensate into a flash tank,
separating the condensate from the dehydrated gas in the flash tank,
removing the dehydrated gas from which the condensate has been separated from the flash tank, and introducing the dehydrated gas from which the condensate has been separated into the second vessel.8. The process according to claim 7, wherein the stream of dehydrated gas removed from the first vessel is cooled in a heat exchanger to form the two-phase mixture of dehydrated gas and condensate.
9. The process according to claim 7 or claim 8, wherein the stream of dehydrated gas removed from the first vessel is cooled to form the two-phase mixture of dehydrated gas and condensate at a temperature higher than -56°C.
10. The process according to anyone of claims 7 to 9, further comprising:
removing a liquid stream of condensate from the flash tank.
11. The process according to claim 10, further comprising:
introducing at least part of the liquid stream of the condensate into the second vessel.12. The process according to claim 1, comprising:
cooling the stream of dehydrated gas removed from the first vessel to form a
two-phase mixture of dehydrated gas and condensate, passing the two-phase mixture of dehydrated gas and condensate into a flash tank,
separating the condensate from the dehydrated gas in the flash tank,
removing a liquid stream of condensate from the flash tank,
removing the dehydrated gas from which the condensate has been separated from the flash tank, and introducing the dehydrated gas from which the condensate has been separated into the second vessel, wherein the step of cooling the dehydrated gas from which the condensate has been separated in the second vessel to the second operating temperature further comprises introducing at least part of the liquid stream of the condensate removed from the flash tank into the second vessel at a temperature that is below the second operating temperature to form a slurry or mixture with the sour species.
13. The process according to claim 11 or 12, wherein the concentration of C2-C4 hydrocarbon components in the at least part of the stream of condensate removed from the flash tank and introduced into the second vessel is from about 0.5 to 1.5 per mol of CO2 in the natural gas feed stream.
14. The process according to anyone of claims 11 to 13, wherein the at least part of the stream of condensate removed from the flash tank is introduced into the second vessel through an inlet located above an inlet introducing the dehydrated gas from which the condensate has been separated.
15. The process according to claim 14, wherein the inlet introducing the at least part of the stream of condensate removed from the flash tank into the second vessel is a plurality of spray nozzles.
16. The process according to anyone of claims 1-6, wherein the step of cooling the dehydrated gas in a second vessel to a second operating temperature further comprises introducing the dehydrated gas into the second vessel and introducing a stream of liquid into the second vessel at a temperature that is below the second operating temperature to form a slurry or mixture with the sour species.
17. The process according to anyone of claims 2 to 4, wherein the step of cooling the natural gas feed stream in a first vessel to a first operating temperature comprises introducing the natural gas feed stream into the first vessel and introducing a stream of liquid into the first vessel at a temperature that is below the first operating temperature to form a slurry with the hydrates, and wherein the step of cooling the dehydrated gas in a second vessel to a second operating temperature further comprises introducing the dehydrated gas into the second vessel and introducing a stream of liquid into the second vessel at a temperature that is below the second operating temperature to form a slurry or mixture with the sour species.
18. The process according to claim 16 or claim 17, wherein the stream of liquid is a natural gas liquid.
19. The process according to claim 16 or 17, wherein the concentration of C2-C4 hydrocarbon components in the stream of liquid introduced into the second vessel is from about 0.5 to 1.5 per mol of CO2 in the natural gas feed stream.
20. The process according to claim 17 or claim 19, wherein the stream of liquid is introduced into the second vessel through an inlet located above an inlet introducing the dehydrated gas.
21. The process according to claim 20, wherein the inlet introducing the stream of liquid into the second vessel is a plurality of spray nozzles.
22. The process according to anyone of claims 1 to 6 or 16 to 21, further comprising the step of heating the sour species in the second vessel to a temperature that is above the second operating temperature to obtain a sour species-containing liquid.
23. The process according to claim 22, wherein heating the sour species in the second vessel comprises adding to the sour species a warm liquid.
24. The process according to claim 23, wherein the warm liquid is a natural gas liquid.
25. A process for removing contaminants from a natural gas feed stream including water and sour species comprising the steps, substantially as hereinbefore described with reference to the examples and figures 1 and 2.
26. The process according to anyone of claims 2, 17 or 19 to 20, wherein the stream of dehydrated sweetened gas removed from the second vessel is at a temperature of not less than -85°C.
27. The process according to anyone of claims 2, 17, 19 to 20 or 26, wherein the stream of dehydrated sweetened gas removed from the second vessel is at a pressure of between 20 and 50 bar.
28. The process according to anyone of claims 1 to 6, 16 to 24, 26 or 27, wherein the stream of dehydrated sweetened gas removed from the second vessel is further cooled by means of expansion and passed to one or more heat exchangers to effect cooling of one or more other process streams, but the temperature to which the stream of dehydrated gas removed from the first vessel is cooled in any such heat exchanger is greater than the temperature at which solids of the sour species are formed.
29. The process according to claim 28, wherein the stream of dehydrated sweetened gas removed from the second vessel and further cooled by means of expansion is passed to a heat exchanger to effect cooling of the stream of dehydrated gas removed from the first vessel.
30. The process according to anyone of claims 16 to 23, 26 or 27, wherein the stream of dehydrated sweetened gas removed from the second vessel is further cooled by means of expansion and passed to a first heat exchanger to effect cooling of the stream of liquid to be introduced into the second vessel, the stream of dehydrated sweetened gas is then passed to a second heat exchanger to effect cooling of the stream of dehydrated gas removed from the first vessel, but the temperature to which the stream of dehydrated gas removed from the first vessel is cooled in the second heat exchanger is greater than the temperature at which solids of the sour species are formed.
31. The dehydrated sweetened gas of the process of anyone of claims 1 to 30.
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