Patent Application
20170226431
The subject matter relates to the use of Natural Gas to synthesize high-energy transportable liquids like gasoline.
Enormous quantities of Natural Gas, NG, have been found recently. NG is used for electricity generation, in heating (residential and industrial), in the production of chemicals and in transportation.
Despite its abundance and the variety of its uses, the NG has a backdrop: it has a very low energy concentration at ambient temperatures and pressures. The low energy concentration makes difficult to transport the NG from the production field to the processing sites or to the markets. The purposes of the system and method described in the present invention are to enable the production from NG of:
Gasoline is a mixture of alkanes, which has three prominent features:
In the description of the process, the mixture of alkanes linear or branched synthesized in the method of this patent, and having 10≦n≦5, will be called “Natural Gas Gasoline”, NGG.
The synthetic NGG is not an exact chemical replica of the components of the regular gasoline obtained from petroleum, PG. The NGG will imitate the PG in its behavior in internal combustion engines, in its transportability and its storage.
In Table 1 we find the physical properties of the substances involved in the invention (alkanes and Hydrogen). The Molecular Mass, MM, was calculated using:
MM=14n+2 [dalton] [Eq. 1]
The table includes the boiling point, b.p., only for the linear isomers. The branched isomers have lower b.p. than their correspondent linear isomer. Branched isomers appear also in the PC gasoline mixture. They can also be formed during the process described in this patent.
Methanoleum is also a mixture of alkanes: Pentane and Hexane. The higher energy concentration of liquid alkanes is shown Table 2, which contains the High Value Heat of Combustion, (ΔHc), of alkanes relevant to this invention. To convert the gravimetric value (ΔHc)G, given in [MJ/Kg], into the volumetric (ΔHc)v, measured in [MJ/L], we used:
(ΔHc)V [MJ/L]=(ΔHc)G [MJ/Kg]×ρg/L×10−3 [eq. 2]
where ρg/L is the density of the alkane given in [g/L].
Table 2 also includes the Volumetric Energy Concentration Ratio relative to Methane, ECR, given by:
where:
(ΔHc)V, Cn is the Heat of Combustion of the alkane with n carbons in the molecule, and
(ΔHc)V, CH4 is the Heat of Combustion of Methane
From Table 2 we see that liquid alkanes included in the Methanoleum, Pentane and Hexane, carry energy per unit volume higher than 800 times the energy carried by Methane.
Several studies on the UV photolysis of Methane and the consequent production of higher alkanes have been performed in the past. Some examples are given in table 3.
Table 3 shows that in the prior investigations, the UV sources used in Methane's photolysis were: Discharge Lamps, Gas Lasers, Doped Isolator Lasers and Non-linear media Four Wave Mixing. In contrast, in the system described in this patent, the UV source is a Semiconductor LED or Laser. Semiconductor sources have the following advantages over the sources in the past investigations:
Another innovation of the present patent is the Photon Energy, Eph, used to break the C—H bond of the Methane. In the earlier works, Eph>10 eV. This high energy enables the photolysis of the C—H bond by elevating an electron from the ground electronic state to the first excited electronic state. In the present patent the C—H bond is broken by increasing the distance, rC—H, between the H and the Methyl group by vibration. The energy needed by such process is the “Bond Dissociation Enthalpy”, BDE. At T=298 K, the BDE of the H3C—H bond is 104.99 (±0.07) Kcal/mol or 4.55 eV/molecule. A photon with this energy has a wavelength λdis=272.5 nm.
Another innovation of the present patent is the use of heated UV sources. This heating avoids the formation of thin polymer films that may cover the optics of the UV source and lower the UV transmittance.
Another innovation of the present patent is the use of a controlled temperature during photolytic reactions to produce desired alkanes. The gaseous reaction media is maintained at a temperature that enables the elongation reactions of short alkanes in order to convert the short alkanes into larger chains, while trapping-out the desired alkanes by condensation.
For simplicity of the explanation, we will consider the NG, used in the process as raw material, contains mainly Methane, CH4. We will assume that all the chemical reactions and physical separation effects take place in a closed volume that contains one or several UV sources. This volume will be called “Photoreactor”.
The first reaction of the process is the initiation reaction [1] that occurs when UV photons break the C—H bond of Methane. This reaction has been very well studied for the last 40 years. At least, five different dissociation channels have been established:
CH4+hv(4.47 eV)→CH3.+H. [1]
CH4+hv(5.01−6.04 eV)→CH2:+H2 [1a]
CH4+hv(9.04−9.53 eV)→CH2:+2H. [1b]
CH4+hv(9.06 eV)→CH+H2+H. [1c]
CH4+hv(9.27 eV)→C+2H2 [1d]
where hv represents ultra-violet photons. The energy values (in eV) given for the photons in each reaction are based on Romanzin et al. (2005). Since the photons used in the system described in the present patent have Eph=4.55 eV, only reaction [1] is a feasible path for the photolysis of Methane. This assumption will be used in the rest of the present patent.
Generally, in a Methane saturated atmosphere, the radicals react with Methane to form successively higher alkanes. The general overall reaction is:
nCH4→CnH2n+2+(n−1)H2 [2]
In Methane saturated atmospheres, the most probable reaction for the Hydrogen radical will be the formation of a Hydrogen molecule, while reacting with Methane:
H.+CH4→CH3.+H2 [3]
To avoid the reverse reaction:
CH3.+H2→H.+CH4 [3]R
the H2 is filtered out from the System through a Membrane Hydrogen Filter, by Buoyancy or Centrifugally. The filtered out Hydrogen molecules are transferred to an Electricity Generator, where the H2 is oxidized by ambient Oxygen.
2H2+O2→2H2O [4]
1.6.3—Reactions of the Methyl Radical with Methane
The concentration of Methyl radicals in the Photoreactor increases constantly since:
In Methane saturated atmosphere, as the one that exists in the Photoreactor, the Methyl radical reacting with Methane molecules, has 2 probable paths:
CH3.+C′H4→CH4+C′H3. [5]
CH3.+CH4→C2H6+H. [6]
At the first look reaction [5] may be considered as a meaningless “dummy” reaction. In the absence of isotopic marking it is impossible to follow its existence. But, reaction [5] enables, in rich Methane environments, a very long “life time” to the Methyl radical and the increase of Methyl radical concentration in the Photoreactor.
Reaction [6] has a low probability to occur because of steric hindrance reasons. But, since the population of Methane is big, it may occur. The resulting H. from reaction [6] will enter into the Hydrogen path described in paragraph 1.6.2. This statement also is valid for other H. formed in reactions that will be presented in the following paragraphs.
Let's assume a constant irradiation of UV photons into the gas mixture. After a radiation period, Δt1, the concentration of the Methyl radical will increase at such a point that the formation of Ethane by the termination reaction [7] will become significant.
2CH3.→C2H6 [7]
This probability is dictated by the thermodynamic “Equilibrium Constant of the reaction [7]”:
where [CH3.] is the concentration of the Methyl radical and [C2H6] is the concentration of the Ethane.
After a time period the gaseous mixture contains mainly molecular Methane, but also traces of the reactive Methyl radical and molecular Ethane. At a time Δt2 from the beginning of the process, where Δt2>>Δt1, the concentration of Ethane will reach a level where its presence affects the chemistry of the gas. The formation of the Ethyl radical may be predicted by the following reactions:
Photolytic Initiation: C2H6+hv→C2H5.+H. [8]
Propagation: C2H6+CH3.→C2H5.+CH4 [9]
The Ethyl radical has a very short “life time” in a Methane saturated atmosphere. The reverse reaction of [9] is responsible for this short “life time”:
C2H5.+CH4→C2H6+CH3. [9]R
Since the relative concentration of Methyl radicals is high, Propane may be formed by two different reactions:
Termination: C2H5.+CH3.→C3H8 [10]
Propagation: C2H6+CH3.→C3H8+H. [11]
Reaction [11] has a low probability to occur because of steric hindrance reasons. But, since the concentration of methyl radical is big, it may occur.
1.6.6—from Propane to Higher Alkanes
For reactions of alkanes (having a generic formula CnH2n+2) in a rich Methane atmosphere, the general photolytic initiation reaction will be:
CnH2n+2+hv→CnH2n+1.+H. [12]
The Hydrogen radical will react as given in reaction [3] and it will follow the Hydrogen path explained in paragraph 1.6.2.
The Alkyl radical, CnH2n+1., will probably react with the surrounding Methane molecule to produce a Methyl radical:
CnH2n+1.+CH4→CnH2n+2+CH3. [13]
But also the substitution reaction (with low probability for steric reasons) may occur:
CnH2n+1.+CH4→Cn+1H2n+4+H. [14]
The termination reaction with the methyl radical is the main route for the formation of longer alkane molecules:
CnH2n+1.+CH3.→Cn+1H2n+4 [15]
The experimental results show that the relative concentration of the produced alkenes will obey a Flory Distribution (Derk, 2008). This is in accordance with the chemical reactions sequence described in this last section.
As the concentration of different alkyl radicals increases, the possibility of other termination reactions becomes significant. The general formulation of this possibility is:
CnH2n+1.+Cn′H2n′+1.→Cn+n′H2(n+n′)+2 [16]
Steric hindrance gives preference to the formation of the linear isomer. But, with a lower probability, branched isomers are also formed by reaction [15] and [16]. Branching isomerization can be obtained also by the use of selective membranes or by radical internal reorganization.
In conjunction with the appropriate figures, four non-limited embodiments will be described. The exemplary embodiments concentrate on the production of “not-from-petroleum gasoline”, NGG, and Methanoleum, using NG as raw material and Ultra-Violet radiation to produce photolytic reactions. Both products, NGG and Methanoleum, will be named “Products” in the following descriptions. Similar embodiments may be used in the synthesis of other materials by irradiation of NG with UV radiation.
The figures are not shown to scale and any sizes are only meant to be exemplary and not necessarily limiting. Corresponding or like elements are designated by numerals and names. It will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the subject matter. In addition, many modifications may be made to adapt a particular situation or material to the teachings without departing from the essential scope thereof. For example, in the exemplary embodiments, only two methods are used for the physical separation of alkanes from the reaction mixture: (A) the Boiling Points, b.p. of the alkanes, and (B) the Buoyancy. But other separation methods, like Centrifugal Forces or Selective Membranes may be used.
In the drawings, solid arrows, → indicate the direction of the fluid. The components and sub-components are linked to their corresponding numbers by dashed arrows, .
In the First Exemplary Embodiment the Products are obtained at temperatures higher than Standard Temperature and Pressure, >STP, conditions.
In the Second Exemplary Embodiment the Products are obtained after compression of the NG.
In the Third Exemplary Embodiment the Products are obtained from Liquid Natural Gas, LNG that serves as raw material and as cooling fluid.
In the Fourth Exemplary Embodiment the Products are obtained from Natural Gas at temperatures higher than Standard Temperature and Pressure, >STP, conditions. But in this case the photoreactor is slanted.
In the First Exemplary Embodiment the Products are obtained at temperatures higher than Standard Temperature and Pressure, >STP, conditions.
The selected Product, NGG or Methanoleum, is formed in the system depicted in
Throw the “NG-Inlet” (2) NG is introduced into the Photoreactor (1). The UV-Sources (3) emit UV photons that break the C—H bonds of the Methane into two radicals: Methyl (CH3.) and Hydrogen (H.). This initiation reaction is the beginning of a series of radical reactions described in paragraph 1.6. The system is designed in a way that, at least, the two kinds of mixtures of alkenes, defined before as “Products”, can be formed:
The reactions produce, beside the Products, molecular Hydrogen, H2. At the top of the Photoreactor (1) a Tubular Hydrogen Membrane Filter (4) is installed. It is a tube, made of a selective membrane with high permeability for H2 while highly impermeable towards alkanes. Thus, it extracts out the H2 formed in the Photoreactor (1), and transfers the extracted H2 to the Electricity Generator, EG (5).
In the EG (5) the H2 is oxidized with air Oxygen, incoming from the surrounding air through the Ambient-Oxygen-Inlet (12) to produce electricity and water. The Water Exhaust (6) will expel out the water from the EG, while the electricity will be conducted by the Electrical Wires (7) to activate the UV-sources (3) or other electricity consuming parts of the system.
The lower part of the Photoreactor (1) is a Funnel Shaped Floor, FSF (8). This component has two tasks:
The mixture of condensed alkanes falls through the orifice of the FSF (8) to the Product-Conduit (9). This Conduit translates the condensed Product at the FSF (8) to the Product Reservoir (10) while thermally isolating the Product from the temperature in the Photoreactor (1). The Product is stored in the Product Reservoir (10) for delivery to the customers through the Product Outlet (11).
During the process, NG is injected to the Photoreactor (1) through the NG Inlet (2), because the pressure tends to decrease since:
If the decrease in pressure is not compensated:
Heat is induced to gaseous phase of the Photoreactor (1) to maintain TPhR, in four ways:
εUV=1−εIH−εEH [Eq. 5]
Cooling also occurs in the Photoreactor (1) by the following ways:
The simultaneous processes of cooling and heating bring the gaseous mixture in the Photoreactor (1) to an equilibrium temperature, TPhR. When producing NGG, the system is planned in such a way that TPhR will be high enough to maintain alkanes with a certain n, nc, like nc=5, 6 and 7, to stay in the gaseous phase. This will enable reactions of the alkanes with nc to form alkanes with n>nc. For example if Teq=40° C., all isomers of pentane will stay in the gaseous phase where they can be converted into heavier alkane molecules.
When the desired product is NGG, TPhR should not be too high, since this will maintain in the gaseous phase alkanes with n>nc that may be enlarged to form large chain alkanes that solidify at room temperature. These large chain alkanes are known as “waxes”, and are not part of the NGG mixture or the Methanoleum mixtures. Of course, if the goal is to manufacture such waxes, higher temperatures will be used in the process. Table 5 includes the boiling points, b.p., of the alkane isomers relevant to the discussion.
At the beginning of the process, we presume that the Photoreactor (1) is a column full with a single fluid: gas Methane. During the reactions other gases, different than Methane, are formed. The gases formed will be affected by Buoyancy that will induce a small separation with height of the different molecules in the gas mixture due to their different density. Table 6 includes the density of the different gases and liquids present in the Photoreactor (1).
In the gas mixture, the movement and relative position of the molecules is affected not only by the Buoyancy, but also by Gravity, Thermal Energy and the Viscosity. But Buoyancy will add a force vector that produces a slight separation between the components of the gas mixture.
Hydrogen molecules will tend to be in a higher concentration at the higher part of the Photoreactor (1) column, relative to the other parts of the column. Going down the column will be a volume richer in Methane, relative to the rest of the column. Below the relative Methane-rich volume, there is a volume where Ethane will have a higher concentration, relative to the rest of the Photoreactor (1). The lower part of the Photoreactor (1) will contain a gas mixture relatively richer in the higher alkanes, butane and pentane. In the volume of the Funnel Shaped Floor (8) will be occupied by the alkanes that condense at TPhR=40 C, for example.
Another way to explain Buoyancy in the Photoreactor (1) is to think of the fluid gas Methane as it would be water. Objects with specific mass lower than water will float on the water's surface. In the case of the Photoreactor (1), the Hydrogen will “float” over the Methane. Molecules with specific mass higher than Methane will “sink” down from the Methane.
Ideally, since the gas mixture in the Photoreactor (1) is maintained at TPhR, alkanes formed in the reactions having b.p.>TPhR will stay in the gaseous phase while those with b.p.<TPhR will condensate. For example if TPhR=40° C., based on data given in table 5, all the isomers of Pentane will stay in the gaseous phase. This will enable further chain elongation of the Pentane molecules via the reactions 14 and 15.
Also ideally, at TPhR=40° C. alkanes with n≧6 to n=10 will condense. But in real conditions, the condensable alkanes will first form droplets. These droplets will be affected by two processes:
The adhesion of the droplets and the dissolution of alkanes with n≦4, will increase in the size and mass of the droplets. The heavier droplets will sink into the funnel shaped floor containing the alkanes with n≦4 as impurities. The alkanes, with n≦4, do not belong to the NGG mixture and can be extracted by a mild distillation or by selective membranes.
Another concern that should be taken into account, in real conditions, is the high vapor pressure of the components of the NGG and the Metanoleum. For this reason the gaseous phase of the system will contain also vapor molecules of alkanes with n>6 that ideally condense at TPhR.
Alkane molecules with n>6 that remain in the gaseous phase can be converted into alkanes with n higher than 6. This possibility is in favor of the formation of NGG as long as n≦10. Alkanes with n>10 are solid waxes that do not belong to the NGG mixture.
All the Major components have an Inlet. The 3 Photoreactors have, beside the inlet, other corresponding components:
The letters M, E, and B indicate Methane, Ethane and Butane respectively.
As shown in
The compressed NG in the NGC (20) flows through the “JT-Inlet” (31) to the Joule Thompson Cooler (30), JT. At the JT Cooler (30) the NG expands to a pressure P1<PNGC while cooling to the temperature T1.
The cooled gas NG from the JT (30) is introduced to the Methane Photoreactor MPR, (40), by the “M-Inlet”. The MPR is maintained at the temperature T1.
4.2.2—Operation of the MPR (40)
In the MPR (40) the NG is irradiated with the corresponding Ultra-Violet source UV-M (42). The initiation photoreaction [1] and the subsequent radical reactions take place. As a consequence of these reactions, Ethane and Hydrogen are formed following the overall reaction:
2CH4+hv→C2H6+H2 [17]
The temperature T1 is selected in such a way that Methane stays in the gaseous phase while Ethane condenses into the liquid phase. This means that T1 is between the temperature interval from the b.p. of the Methane and the b.p of the Ethane. For example, if:
The molecular Hydrogen formed in MPR (40) is filtered out from Photoreactor (20) through the Selective Membrane of the MPR, SM-M (43). The filtered-out Hydrogen is brought to the “H2-Inlet-Manifold”, (71) that feeds the Electricity Generator (5), EG.
The Ethane produced, that is liquid at T1, condenses and sinks to the bottom of the MPR (40). At this point it is translated to the Ethane Photoreactor, EPR (50), via the “E-Inlet” (51).
The liquid Ethane transferred to the EPR (50) is heated to the temperature T2, where it becomes gaseous. In the EPR (50) the gaseous Ethane is irradiated with the Ultra-Violet source (52), UV-E. An initiation photoreaction where a C—H bond of the Ethane is broken into atomic Hydrogen and Ethyl radical occurs, as described before by the reaction [8].
C2H6+hv′→C2H5.+H. [8]
The use of v′ is done to note that the C—H bond in Ethane (and other alkanes higher than Methane) has an BDE of 101 Kcal/mol (4.38 eV/molecule, 283.1 nm). This value is smaller than the BDE of Methane, 105 Kcal/mol (4.55 eV/molecule, 272.5 nm).
In a Ethane saturated atmosphere, as the one that exists in the EPR (50), the most probable reaction for the Hydrogen radical will be the formation of a Hydrogen molecule, while reacting with Ethane:
H.+C2H6→C2H5.+H2 [18]
To avoid the reverse reaction:
C2H5.+H2→H.+C2H6 [18]R
the H2 molecules are filtered out from the EPR through the EPR's Selective Membrane Hydrogen Filter, SM-E (53). The overall effect of reactions [8] and [18] is the formation of two Ethyl radicals and one Hydrogen molecule, H2, each time that a photon breaks a C—H bond in an Ethane molecule.
In an Ethane saturated atmosphere, like the one that exists in the EPR, there is “dummy” reaction:
C2H6+C2H5.→C2H5.+C2H6 [19]
In the absence of isotopic marking it is impossible to follow existence of reaction [19]. But, reaction [19] enables, in rich Ethane environments, a very long “life time” to the Ethyl radical and the increase of Ethyl radical concentration in the EPR (50).
The concentration of Ethyl radicals in the EPR (50) will increase constantly since:
After an irradiation period, the concentration of the Ethyl radical will increase at such a point that the formation of Butane by the termination reaction [20] will become significant:
2C2H5→C4H10 [20]
The temperature T2 is selected in such a way that Ethane stays in the gaseous phase while Butane condenses into a liquid phase. This means that T2 is between the temperature interval from the b.p. of the Ethane and the b.p of the Butane. For example, if:
The Butane produced in the EPR (50) that is liquid at T2, condenses and sinks to the bottom of the EPR (50). At this point it is translated to the Butane Photoreactor, BPR (60), via the B-Inlet (61).
The liquid Butane transferred to the BPR (60) is heated to a temperature T3, where it becomes gaseous. In the BPR (60) the gaseous Butane is irradiated with the BPR's Ultra-Violet source, UV-B (62). An initiation photoreaction, where a C—H bond in the Butane is broken into atomic Hydrogen and Butyl radical, takes place:
C4H10+hv′→C4H9.+H. [21]
In a Butane saturated atmosphere, as the one that exists in the BPR (60), the most probable reaction for the Hydrogen radical will be the formation of a Hydrogen molecule, while reacting with Butane:
H.+C4H10→C4+H2 [22]
To avoid the reverse reaction:
C4H9.+H2→H.+C4H10 [22]R
the H2 molecules are filtered out by the BPR's Selective Membrane Hydrogen Filter SM-B (63). The overall effect of reactions pi and [22] is the formation of two Butyl radicals and one Hydrogen molecule, H2, each time that a photon breaks a C—H bond in a Butane molecule.
In a Butane saturated atmosphere, like the one that exists in the BPR, there is “dummy” reaction:
C4H9.+C4H10→C4H10+C4H9. [23]
In the absence of isotopic marking it is impossible to follow existence of reaction [23]. But, reaction [23] enables, in rich Butane environments, a very long “life time” to the Butyl radical and the increase of Butyl radical concentration in the BPR (60).
The concentration of Butyl radicals in the BPR will increase constantly since:
After an irradiation period, the concentration of the Butyl radical will increase at such a point that formation of Octane by the termination reaction [24] will become significant:
2C4H9.→C8H18 [24]
The temperature T3 is selected in such a way that Butane stays in the gaseous phase while Octane condenses into the liquid phase. This means that T3 is between the temperature interval from the b.p. of the Butane and the b.p of the Octane. For example, if:
The filtered-out Hydrogen is brought to the “H2-Inlet-Manifold”, (71) that feeds the Electricity Generator (5), EG.
The liquid Octane produced at T3 condenses and sinks to the bottom of the BPR (60). This liquid is considered as NGG. At this point it is translated by the NGG Outlet (64) for distribution or storage.
The above description of the principle of operation of the Second Exemplary Embodiment, may give the impression that the liquid alkanes transferred from one photoreactor to the next one, are liquids with high purity composition. This impression has been taken for explanation purposes. In reality, as explained in paragraph 3.2.4, the liquid alkanes at the bottom of the photoreactors contain dissolved molecules of the gaseous phase.
Liquid Ethane formed in the MPR (40) contains dissolved Methane. The solution is translated to the EPR (50) where it is heated and gasified. So, the atmosphere of the EPR (50) contains mostly Ethane and small amounts of Methane. The gaseous molecules of Methane can be converted into Methyl radicals by the photolytic reaction [1], or by the reverse reaction of [3]R. The Methyl radicals can form Propane by reactions [10] and [11]:
Termination: C2H5.+CH3.→C3H8 [10]
Propagation: C2H6+CH3.→C3H8+H. [11]
Liquid Butane introduced into the BPR (60) contains, beside Propane, dissolved Ethane and even Methane from the EPR's atmosphere. This solution is translated to the BPR (60) were it is heated and gasified. So, the atmosphere of the BPR contains mostly Butane and small amounts of Propane, Ethane and Methane. The gaseous molecules of Propane, Ethane and Methane can be converted into radicals by: 1) the photolytic general initiation reaction [12], or the propagation reactions with the Butyl radical (relatively abundant in the BPR gaseous phase):
CH4+C4H9.→CH3.+C4H10 [25]
C2H6+C4H9.→C2H5.+C4H10 [26]
C3H8+C4H9.→C3H8.+C4H10 [27]
The Methyl, Ethyl and Propyl radicals formed in reactions [25], [26] and [27] can react with the relatively abundant Butyl radical to form Pentane, Hexane and Heptane (alkanes are part of the NGG mixture):
C4H9.+CH3.→C5H12 [28]
C4H9.+C2H5.→C6H14 [29]
C4H9.+C3H8.→C7H16 [30]
Another exemplary embodiment is used to process Liquefied Natural Gas, LNG. In this case a modified version of the Second Exemplary Embodiment can be used. Since the NG is liquid when reaching the processing plant, there is no need to compress and cool down the NG. This means that in this embodiment there is no need for two first Major components that are part of the Second Exemplary Embodiment: the Natural Gas Compressor, NGC, and the Joule Thomson Cooler, JT. Instead of the two unnecessary Major components of the Second Exemplary Embodiment, the Photoreactors MPR (40) and EPR (50) include Heat Exchangers that use the low temperature LNG to obtain T1 at the MPR (40) and T2 at the EPR (50).
The cooling fluid from the EPR's Heat Exchanger (54) is NG at T2 that is transferred to the MPR (40) as raw material for the photolytic initiated process of reaction (1).
The principle of operation of the Third Exemplary Embodiment is similar to principle of operation of the Second Exemplary Embodiment. The operation of the MPR is given in paragraph 4.2.3. The operation of the EPR is given in paragraph 4.2.4. The operation of the BPR is given in paragraph 4.2.5.
In the Second Embodiment NG at RT is used as raw material. In the Third Embodiment NG enters the system as LNG and it also used as a cooling fluid to maintain T1 and T2 before it is introduced to the MPR (40).
The description of another exemplary embodiment is given schematically in
The Principle of Operation of the First and Fourth Exemplary Embodiments are similar. The main difference is the use of Buoyancy to separate Hydrogen from the reaction mixture in the Photoreactor in the Fourth Embodiment, compared to the use of a Hydrogen Selective Membrane used in the First Embodiment.
In paragraph 3.2.3 there is a discussion on gas separation by Buoyancy in a Photoreactor (1) perpendicular to the horizon (α=90°). In the Fourth Exemplary Embodiment, the Photoreactor (90) is inclined by an angle α, relative to the horizon. This is done in order to increase the separation velocity of the fluids in the photoreactor (90).
In similarity with the Photoreactor (1) of the First Embodiment, at the beginning of the process, the Photoreactor (90) is a column full with a single fluid, gas Methane. During the reactions, when the system reaches a dynamic equilibrium, other alkanes and Hydrogen are formed. Due to the Kinetic (Thermal) Energy, ideally, the gas mixture should be homogenous. But the gases formed in the Slanted Photoreactor (90), will be affected by Buoyancy that will induce a small separation with height of the different molecules in the gas mixture due to their different density. In the gas mixture, the movement and relative position of the molecules is affected not only by Buoyancy, but also by the Thermal Energy and the Viscosity. But Buoyancy will add a force vector that produces a slight separation between the components of the gas mixture.
The inclination of the Slanted Photoreactor (90) will enhance the separation of the fluids in the Photoreactor (90).
In volume (A) we see, schematically, that the radical products of reaction [1] (CH4+hv→CH3.+H.) are separated. The Methyl radical has a mass, mCH3=15 dalton, while the Hydrogen's mass, mH=1 dalton. Gravitation will push down the Methyl radical, increasing its concentration near the Lower Wall. Buoyancy will push up the Hydrogen radical, increasing its concentration near the Upper Wall.
In volume (B) we see, schematically, that the possibility of reaction [3] (H.+CH4→CH3.+H2) will occur mostly near the Upper Wall, since his region is rich in H. radicals. Again, the lower mass of the H2 molecule, mH2=2 dalton, will produce a lift towards the Upper Wall by Buoyancy, while Gravity will push down the Methyl radical towards the Lower Wall. Since the region near the Lower Wall is rich in Methyl radicals, there is an increase in the probability for the radical termination reaction [7] (2CH3.→C2H6) that produces Ethane.
In volume (C) we see schematically that the low mass H2 molecule will raise up to the top of the photoreactor, by Buoyancy, passing through a region rich in Hydrogen, near the Upper Wall, thus avoiding collisions with heavier molecules and allowing a faster rise of Hydrogen to the Hydrogen Conduit. Also, the heavier molecules, most probably formed near the Lower Wall, will slide down towards the lower part of the Photoreactor (90), by Gravity, in the region near the “Lower Wall”, where collisions with lighter molecules are avoided.
It is evident that photolytic reactions with higher alkanes will have a similar behavior than the Methane radicals formed by reaction [1] described in (A). Thus, the alkyl radical will preferentially move down, while the Hydrogen radical will move up. Also it is clear that the concentration of the alkyl radicals will be higher near the Lower Wall, so that there is an increase in the probability of radical termination reactions.
The overall contributions of Slanted Photoreactor (90) are:
At the top of the Photoreactor (90) a Hydrogen conduit (93) is installed. It is a tube that extracts out the H2 formed in the Photoreactor (90), and transfers the extracted H2 to the Electricity Generator, EG, (5). Oxygen is also introduced by the Ambient-O2-Inlet (12) to the EG (5)
In the EG (5), the H2 is oxidized with Oxygen to produce electricity and water. The Water Exhaust (6) will expel out the water from the EG, while the electricity will be used to activate the UV sources (92) and other consumers of electrical energy in the system.
The mixture of condensed alkanes falls through the orifice at the bottom of the Slanted Photoreactor (90) to the Product Conduit (94). This Conduit translates the condensed Product to the Product Reservoir (95). The product is delivered to the marked or stored trough the Product Outlet (96).
| Number | Date | Country | Kind |
|---|---|---|---|
| 234196 | Aug 2014 | IL | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IL2015/050796 | 8/3/2015 | WO | 00 |
