Classifications

• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
  • C10G2/00—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon
  • C10G2/30—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen
  • C10G2/32—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen with the use of catalysts
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C1/00—Preparation of hydrocarbons from one or more compounds, none of them being a hydrocarbon
  • C07C1/02—Preparation of hydrocarbons from one or more compounds, none of them being a hydrocarbon from oxides of a carbon
  • C07C1/04—Preparation of hydrocarbons from one or more compounds, none of them being a hydrocarbon from oxides of a carbon from carbon monoxide with hydrogen
  • C07C1/0485—Set-up of reactors or accessories; Multi-step processes
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
  • C07C29/15—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively
  • C07C29/151—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively with hydrogen or hydrogen-containing gases
  • C07C29/1516—Multisteps
  • C07C29/1518—Multisteps one step being the formation of initial mixture of carbon oxides and hydrogen for synthesis

Definitions

• the present invention relates to an improved process and system for the production of heavier hydrocarbons from lighter hydrocarbons, and more particularly to turbine-powered, synthesis-gas system and method.
• the synthetic production of hydrocarbons by the catalytic reaction of carbon monoxide and hydrogen is well known and is generally referred to as the Fischer-Tropsch reaction.
• Numerous catalysts have been used in carrying out the reaction, and at relatively low to medium pressure (near atmospheric to 600 psig) and temperatures m the range of from about 300° F. to 600° F., both saturated and unsaturated hydrocarbons can be produced.
• the synthesis reaction is very exothermic and temperature sensitive whereby temperature control is required to maintain a desired hydrocarbon product selectivity.
• the Fischer-Tropsch reaction can be characterized by the following general reaction: 2H 2 + CO C ⁇ atalyst- CH, ⁇ " + H,0
• the steam reforming reaction is endothermic and a catalyst containing nickel is often utilized.
• Partial oxidation is the non-catalytic, sub-stoichiometric combustion of light hydrocarbons such as methane to produce the synthesis gas.
• the basic reaction is represented as follows: CHReg + ⁇ _ 0 2 ⁇ CO + 2H 2
• the partial oxidation reaction is typically carried out using high purity oxygen.
• High purity oxygen can be quite expensive.
• a combination of partial oxidation and steam reforming known as autothermal reforming, wherein air is used as a source of oxygen for the partial oxidation reaction has also been used for producing synthesis gas heretofore.
• autothermal reforming is a simple combination of partial oxidation and steam reforming where the exothermic heat of the partial oxidation supplies the necessary heat for the endothermic steam reforming reaction.
• the autothermal reforming process can be carried out m a relatively inexpensive refractory lined carbon steel vessel whereby low cost is typically involved.
• the autothermal process results m a lower hydrogen to carbon monoxide ratio m the synthesis gas than does steam reforming alone. That s, the steam reforming reaction with methane results m a ratio of about 3:1 while the partial oxidation of methane results in a ratio of about 2:1.
• a good ratio for the hydrocarbon synthesis reaction carried out at low or medium pressure over a cobalt catalyst is 2:1.
• the feed to the autothermal reforming process is a mixture of light hydrocarbons such as a natural gas stream
• some form of additional control is required to maintain the ratio of hydrogen to carbon monoxide m the synthesis gas at the optimum ratio of about 2:1.
• For the Fischer-Tropsch process to become widely used will require efficient conversion techniques. Efforts have been made toward that end. See U.S. Patents 4,883,170 and 4,973,453, which are assigned to the owner of this application and which are incorporated by reference herein for all purposes.
• a synthesis gas production unit and synthesizing unit are disposed between the compression section and turbine expansion section of a gas turbine.
• a synthesis gas production unit and synthesizing unit are disposed between the compression section and turbine expansion section of a gas turbine with an additional compressor disposed after the synthesis gas production unit and before a synthesizing reactor.
• a technical advantage of the present invention is that it allows for a self-powered, low-pressure synthesis gas production unit to be produced m a cost-effective manner.
• Another technical advantage of the present invention is that a system and method are provided that provide a self-powered, low-pressure synthesis gas production unit with a relatively-high-pressure synthesizing unit.
• FIGURE 1 is a schematic representation of a process flow m which the present invention is particularly well suited
• FIGURE 2 is a schematic representation of a process flow showing an aspect of the present invention
• FIGURE 3 is a schematic representation of a process flow showing an aspect of the present invention
• FIGURE 4 is a schematic representation of a process flow showing an aspect of the present invention.
• FIGURES 1-4 of the drawings like numerals being used for like and corresponding parts of the various drawings.
• A. INTRODUCTION The present invention is applicable in process flows involving the production of a synthesis gas and synthesizing to produce methanol, DME, gasoline, or numerous other substances.
• the invention is believed to be particularly well suited for inclusion in a Fischer- Tropsch process, and for illustration purposes, the invention is presented in that context although it is to be understood its application is broader.
• a process flow in which the invention may be incorporated is first presented, and then a few specific embodiments are described.
• a continuous stream of normally gaseous light hydrocarbons (e.g., gaseous at at osphereic pressure and 70 degrees Fahrenheit) conducted to a heat exchanger 10 of a conduit 12.
• the gasesous light hydrocarbons may be, for example, a natural gas stream.
• the stream of light hydrocarbons While flowing through the heat exchanger 10, the stream of light hydrocarbons is heated by exchange of heat with a process stream of generated synthesis gas that, as will be described below, comes from reactor 28.
• the feed stream of light hydrocarbons is at a pressure in the range of from near atmospheric pressure to 600 psig and is heated in the heat exchanger 10 to a temperature in the range of from about 500° F. to about 1000° F.
• the preheated feed stream is conducted by a conduit 14 to a synthesis gas generator 16.
• Air is drawn into an air compressor 18 by way of an inlet conduit 20, and from the compressor 18, a stream of air is conducted to a heat exchanger 22 by a conduit 21.
• the stream of air is preheated in the heat exchanger 22 to a temperature in the range of from about 500° F. to about 1000° F. by exchange of heat with the synthesis gas stream exiting the heat exchanger 10.
• the preheated air is conducted to the synthesis gas generator 16 by a conduit 24.
• the synthesis gas generator 16 can take various forms, it generally includes a burner 26 connected to one end of a reactor vessel 28.
• a bed of steam reforming catalyst 30, which typically contains nickel, is disposed within the reactor 28 at the end opposite the burner 26.
• the reactor 28 is a refractory lined carbon steel vessel. Steam or water, which instantly converts to steam, is introduced into the reactor 28 by way of a conduit 32 connected thereto, and optionally carbon dioxide may be introduced into the reactor 28 by way of a conduit 34 connected thereto.
• the preheated feed stream of gaseous light hydrocarbons from conduit 14 is thoroughly mixed with a preheated stream of air from conduit 24 m the burner 26 and ignited whereby the combustion reaction takes place within the reactor 28.
• the combustion reaction is carried out at a temperature in the range of from about 2000° F. to about 3000° F. under sub-stoichiometric conditions whereby the light hydrocarbons are partially oxidized.
• a gas stream including nitrogen, unreacted light hydrocarbons, hydrogen and carbon monoxide is produced.
• the unreacted light hydrocarbons m the combustion gas stream react with steam introduced into the reactor 28 m the presence of the reforming catalyst whereby additional hydrogen and carbon monoxide are produced therefrom.
• carbon dioxide may be introduced into the reactor 28 to react with unreacted light hydrocarbons to produce additional carbon monoxide and hydrogen.
• the resulting synthesis gas stream generated within the generator 16 includes hydrogen, carbon monoxide, carbon dioxide, nitrogen and unreacted light hydrocarbons.
• the synthesis gas exits the reactor 28 by way of a conduit 36.
• the rates of water introduced into the reactor 28 by way of the conduit 32 and carbon dioxide introduced by way of the conduit 34 are varied. That is, the ratio of hydrogen to carbon monoxide in the produced synthesis gas stream, or the composition of the feed light hydrocarbon stream, or both, are monitored and used as the basis for changing the flow rates of steam and carbon dioxide to the reactor 28 whereby a constant ratio of hydrogen to carbon monoxide preferably at about 2:1 is maintained in the existing synthesis gas.
• the synthesis gas product stream produced in the generator 16 is conducted by the conduit 36 through the heat exchanger 10, then through the heat exchanger 22 and then to the inlet connection of a first hydrocarbon synthesis reactor 38.
• the synthesis gas is at a temperature in the range of from about 1000° F. to about 2000° F.
• the synthesis gas stream flows through the heat exchanger 22 on conduit 36, it gives up heat to the air flowing to the generator 16 through conduit 24 whereby the air is also preheated to a temperature in the range of from about 500° F. to about 1000° F.
• Additional cooling of the synthesis gas stream is provided by a cooler or heat exchanger 23 disposed in the conduit 36 whereby the temperature of the synthesis gas entering the reactor 38 is then m the range of from about 350° F. to about 550- * F.
• reactor 38 can take various forms, but m the embodiment shown, it is a tubular reactor containing a fixed bed 37 of hydrocarbon synthesis catalyst.
• the catalyst of bed 37 may be of cobalt that is supported on silica, alumina or silica-alumina material in an amount in the range of from about five to about fifty parts by weight of cobalt per 100 parts by weight of the support material.
• the catalyst may also contain in the range of from about 0.05 to about 1 parts by weight of ruthenium per 100 parts by weight of support material as a promoter.
• the synthesis gas stream flows into and through the reactor 38.
• the gas is delivered to reactor 38 by conduit 36 and carried on its way by conduit 40.
• the temperature within the reactor 38 is in the range of from about 350 c F. to about 550° F., and upon contact with the catalyst, hydrogen and carbon monoxide in the synthesis gas stream react to form heavier hydrocarbons and water.
• Conduit 40 leads the stream to a condenser 42. While flowing through the condenser 42, the heavier hydrocarbons and water contained m the stream are condensed. From the condenser 42, a conduit 44 conducts the stream containing condensed components to a separator 46 wherein the condensed heavier hydrocarbons and water are separated and separately withdrawn. That is, the condensed water is withdrawn from the separator 46 by way of a conduit 48 connected thereto, and the condensed heavier hydrocarbons are withdrawn from the separator 46 by way of a conduit 50 connected thereto.
• a residue gas stream from the separator 46 includes nitrogen and unreacted hydrogen, carbon monoxide, light hydrocarbons and carbon dioxide.
• a conduit 52 connected to the separator 46 leads the residue gas stream from the separator 46 to a second hydrocarbon synthesis reactor 54 containing a fixed bed 56 of a nydrocarbon synthesis catalyst, such as the one described above.
• the pressure and temperature of the gas stream flowing through the reactor 54 are maintained at approximately the same levels as the pressure and temperature within the reactor 38 by means of a heater or heat exchanger 58 disposed m the conduit 52 between the separator 46 and reactor 54. While flowing through the reactor 54, additional heavier hydrocarbons are formed from hydrogen and carbon monoxide in the residue gas stream and the resulting product stream exits the reactor 54 by way of a conduit 60 connected thereto.
• the conduit 60 leads the stream to a condenser 62 wherein heavier hydrocarbons and water contained therein are condensed.
• a condenser 62 From the condenser 62, the stream containing condensed components is conducted to a chiller 66 of a refrigeration unit by a conduit 64 wherein additional hydrocarbons and water are condensed.
• the resulting stream is conducted from the chiller 66 to a separator 70 by a conduit 68 connected therebetween. Separator 70 will have water, heavier hydrocarbons, and residue gas exit through three conduits 72, 74, 86, respectively.
• Water is withdrawn from the separator 70 by a conduit 72 connected thereto.
• the conduit 72 is m turn connected by way of conventional valves and controls (not shown) to the conduit 48, to a drain conduit 31 and to the conduit 32 previously described whereby all or part of the condensed water separated in the separators 46 and 70 is selectively conducted to the synthesis gas generator 16.
• the condensed heavier hydrocarbons separated within the separator 70 are withdrawn therefrom by a conduit 74 which connects to the conduit 50 from the separator 46.
• the conduit 50 leads the heavier hydrocarbons from both the separators 46 and 70 to a conventional fractionation unit 76.
• a hydrocarbon product stream containing selected components is withdrawn from the fractionation unit 76 by way of a conduit 78 which conducts the product stream to storage or other location.
• the product stream includes heavier hydrocarbons, which are liquid or solid at standard tempterature and pressure (e.g., 14.7 psia and 70 degrees Fahrenheit) .
• Undesirable light and heavy hydrocarbon fractions produced in the fractionation unit 76 are withdrawn therefrom by conduits 80 and 82, respectively.
• the conduits 80 and 82 connect to a conduit 84 which conducts the undesirable hydrocarbons to the inlet conduit 12 where they mix with the feed stream of gaseous light hydrocarbons and are recycled.
• the residue gas stream produced in the separator 70 which may include nitrogen and unreacted hydrogen, carbon monoxide, light hydrocarbons and carbon dioxide, is withdrawn therefrom by a conduit 86 which leads the residue gas stream to a catalytic combustor 88.
• the catalytic combustor 88 may include a burner 90 into which the residue gas stream is conducted.
• a stream of air is conducted to the burner 90 by a conduit 92 connected to the discharge of an air blower 94.
• the residue gas stream from the separator 70 and the air conducted to the burner 90 are thoroughly mixed therein, ignited and discharged into a reactor 96 connected to the burner 90.
• the reactor 96 contains a fixed bed of suitable novel metal containing catalyst 98, e.g., platinum or palladium, for promoting and catalyzing the oxidation of the oxidizable components in the residue gas stream.
• a conduit 100 connected thereto.
• Conduit 100 optionally leads the product stream to a conventional carbon dioxide removal unit 102.
• Carbon dioxide and water are removed from the stream by the carbon dioxide removal unit 102 thereby producing a relatively pure nitrogen product stream which is conducted from the unit 102 by a conduit 104 to a location of sale, storage or further processing.
• the carbon dioxide removed by the unit 102 is withdrawn therefrom by a conduit 106 which leads the carbon dioxide to a compressor 108.
• the discharge of the compressor 108 is connected by way of conventional valves and controls (not shown) to a vent 35 and to the conduit 34 previously described whereby all or part of the carbon dioxide is selectively introduced into the synthesis gas generator 16.
• the flow rates of the water conducted to the synthesis gas generator 16 by way of the conduit 32 and carbon dioxide conducted thereto by way of the conduit 34 are varied as is necessary to control the ratio of hydrogen to carbon monoxide in the synthesis gas stream produced to preferably a 2:1 ratio. This in turn improves the efficiency of the hydrocarbon synthesis reactions carried out m the reactors 38 and 54.
• the use of air, delivered by conduit 24, in the synthesis gas generator 16 as the source of oxygen for the partial oxidation reaction carried out therein produces nitrogen m the synthesis gas stream. Such nitrogen acts as a diluent in the hydrocarbon synthesis reactors 38 and 54 and prevents hot spots on the catalyst and further increases the efficiency of the hydrocarbon synthesis reactions.
• the recycling of all or part of the optional carbon dioxide, which is transported in conduit 106 provides additional carbon for producing heavier hydrocarbons and increases overall process efficiency.
• the system of FIGURE 1 could be redesigned to include a gas turbine as will be further described below.
• a gas turbine As an example of one way the system of FIGURE 1 could be redesigned, catalytic combustor 88, the burner 90, the blower 94, and air compressor 18 may be removed and replaced with a gas turbine.
• the gas turbine could include a combustor to burn the gas and the compressor section of the gas turbine could provide combustion air as blower 94 previously did and compressed air as compressor 18 previously did.
• GAS TURBINE ENHANCEMENTS Referring now to FIGURE 2, advantages may be obtained for a system 200 by combining a synthesis gas unit 202 w th a synthesis unit 204 and a gas turbine 206.
• System 200 uses gas turbine 206 to provide power for the process at a minimum, but may be designed to provide at least some additional power.
• Gas turbine 206 has a compressor section 208 and an expansion turbine section 210.
• the power generated by the expansion turbine section 210 drives the compressor section 208 by means of linkage 212, which may be a shaft, and any excess power beyond the requirements of compressor section 208 may be used to generate electricity or drive other equipment as figuratively shown by output 214.
• Compressor section 208 has inlet or conduit 216, where in the embodiment shown compressor 208 receives air.
• Compressor section 208 also has an outlet or conduit 218 for releasing compressed air. Outlet 218 of compressor section 208 provides compressed air to synthesis gas unit 202 through conduit 260.
• Expansion turbine 210 has inlet or conduit 220 and outlet or conduit 222.
• Synthesis gas unit 202 may take a number of configurations, but in the specific embodiment shown, includes syngas reactor 224, which as shown here may be an autothermal reforming reactor.
• a stream of gaseous light hydrocarbons e.g., a natural gas stream, is delivered to syngas reactor 224 by inlet or conduit 225.
• natural gas containing elevated levels of components i.e., N 2 , CO, He, etc. that reduce the BTU value of the gas m conduit 225.
• the synthesis gas unit 202 may also include one or more heat exchangers 226, which in the embodiment shown is a cooler for reducing the temperature of the synthesis gas exiting outlet 228 of syngas reactor 224.
• Heat exchanger 226 delivers its output to inlet 230 of separator 232. Separator 232 removes moisture which is delivered to outlet 234. It may be desirable in some instances to introduce the water in conduit 234 as steam to expansion turbine 210. Synthesis gas exits separator 232 through outlet or conduit 236. The synthesis gas exiting through outlet 236 is delivered to synthesis unit 204.
• Synthesis unit 204 may be used to synthesize a number of materials as previously mentioned, but m the specific example here is used to synthesize heavier hydrocarbons as referenced m connection with FIGURE 1.
• Synthesis unit 204 includes Fischer-Tropsch reactor 238, which contains an appropriate catalyst. The output of Fischer-Tropsch reactor 238 is delivered to outlet 240 from which it travels to heat exchanger 242 and on to separator 24 .
• the product entering separator 244 is first delivered to inlet 246.
• Separator 244 distributes the heavier hydrocarbons separated therein to storage tank or container 248 through outlet or conduit 250.
• Conduit 250 may include additional components such as a conventional fractionation unit as shown in FIGURE 1.
• Water withdrawn from separator 244 is delivered to outlet or conduit 252. It may be desirable in some instances to deliver the water in conduit 252 as steam into expansion turbine 210.
• the residue gas from separator 244 exits through outlet or conduit 254.
• System 200 includes a combustor 256.
• Combustor 256 receives air from compression section 208 delivered through conduit 258, which is fluidly connected to conduit 260 connecting outlet 218 with syngas reactor 224. Also, residue gas delivered by separator 244 into conduit 254, which is connected to combustor 256. Residue gas within conduit 254 is delivered to conduit
• Combustor 256 may include a catalyst that is useful for promoting combustion reactions; the combustion-promoting catalyst may facilitate combustion of low BTU gas in combustor 256. In some embodiments, combustor 256 may be incorporated as part of gas turbine 206 itself.
• FIGURES 3 and 4 systems 300 and 400 are shown.
• Systems 300 and 400 are analogous m most respects to system 200. Analogous or corresponding parts are shown with reference numerals having the same last two digits to show their correspondence with that of FIGURE 2. The modifications m FIGURES 3 AND 4 will be described later.
• the preferred operating pressure of the process described m connection with FIGURES 2-4 is in the range of 50 psig to 500 psig, and more specifically, m the range of 100 psig to 400 psig.
• This relatively low operating pressure has the benefit of being in the range of most gas turbines so additional compression is minimized.
• the operating of the syngas production unit 202 at relatively low pressure has the benefit of improved efficiency of the reforming reactions resulting m higher conversion of carbonaceous feeds like natural gas into carbon monoxide instead of carbon dioxide. Additionally, undesirable reactions that lead to the formation of carbon are less likely to occur at lower pressures .
• the process pressure of system 200 it may be desirable to increase the process pressure of system 200 if the pressure drop is too great to recover sufficient energy to drive the compressor section 208 or if the catalyst used in the Fischer-Tropsch reactor 238 requires higher operating pressure.
• the synthesis gas produced m syngas unit 202 may be further compressed by an additional compressor.
• This alternative embodiment is shown as System 300 in FIGURE 3.
• the additional compressor, or syngas compressor, is shown by reference numeral 364.
• the syngas unit 302 is operated at a relatively low pressure for the reasons provided above (greater efficiency of reactor 224 and less probability of forming solid carbons) while the Fischer-Tropsch reactor 338 is operated at an elevated pressure.
• System 300 has the advantage of recovering more power from turbine 306, but most of this power will probably be required to drive the syngas booster compressor 364. This configuration also has the advantage of operating the Fischer-Tropsch reactor 338 at an elevated pressure, which depending on the catalyst employed, improves the efficiency of that reaction.
• FIGURE 4 another version of the process is shown having a compressor 464 used to compress the residue gas from the reactor 438 to make up for all or a part of the system pressure losses and to improve turbine efficiencies.
• excess energy from heat exchanger 426 and reactor 438 may be used to power a steam turbine 480.
• Steam from heat exchanger 426 is delivered by conduit 482 to an expansion portion 484 of turbine 480.
• steam from a coil running m reactor 438 may be delivered by conduit 486 to conduit 482 and then to expansion section 484.
• Expansion section 484 drives compressor section 488 of turbine 480 and exhausts 494.
• Compressor section 488 receives air through conduit 490, compresses the air, and delivers the air to conduit 492.
• Conduit 492 delivers the additional compressed air to conduit 460 for delivery to reactor 424.
• the excess energy of system 400 (e.g., from exchanger 426 and reactor 438) may also be used to provide driving energy 17
• compressor 464 (FIG. 4) or syngas booster 364 (FIG. 3).

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• General Chemical & Material Sciences (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
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• 1997
  • 1997-03-10 WO PCT/US1997/003729 patent/WO1997033847A1/en not_active Application Discontinuation
  • 1997-03-10 JP JP09532742A patent/JP2000515899A/ja active Pending
  • 1997-03-10 BR BR9708158-2A patent/BR9708158A/pt unknown
  • 1997-03-10 EA EA199800803A patent/EA000674B1/ru not_active IP Right Cessation
  • 1997-03-10 AU AU22021/97A patent/AU714133B2/en not_active Expired
  • 1997-03-10 CA CA 2247414 patent/CA2247414A1/en not_active Abandoned
  • 1997-03-10 EP EP97914950A patent/EP0888263A1/de not_active Withdrawn
• 1998
  • 1998-09-10 NO NO984167A patent/NO984167D0/no unknown

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