INTEGRATED PROCESS FOR THE PARALLEL PRODUCTION OF ALKALI METAL METHOXIDES

Abstract

The present invention relates to an integrated process for simultaneously preparing at least two mixtures comprising alkali metal methoxide and methanol in at least two parallel reactive distillation columns, wherein one rectification column is used for providing a methanol stream which is then used as methanol source for the reactive distillation columns, and wherein the top streams of said reactive distillation columns are used as methanol source for said rectification column.

Claims

1.-15. (canceled)

16. An integrated process for simultaneously preparing n mixtures P(i) comprising alkali metal methoxide and methanol, comprising providing n reactive distillation columns K(i); providing n aqueous liquid streams H(i), a given stream H(i) comprising a dissolved alkali metal hydroxide A(i)OH, wherein n is an integer with n2 and i=1 . . . n; and providing a rectification column D; the process further comprising (a) providing a stream G comprising methanol; (b) dividing the stream G into n streams G(i), each stream G(i) having the same composition as G; (c) preparing the one or more alkali metal methoxides comprising feeding each stream G(i) into the lower part of a respective reactive distillation column K(i), and feeding the aqueous liquid stream H(i) comprising the dissolved alkali metal hydroxide A(i)OH into the upper part of said reactive distillation column K(i); and subjecting G(i) and H(i) in each K(i) to reactive distillation conditions, obtaining n top streams W(i) comprising methanol and water; and obtaining n bottoms streams P(i) comprising alkali metal methoxide A(i)OMe and methanol; (d) feeding each stream W(i) into the lower part of the rectification column D, and feeding a stream M comprising methanol into the rectification column D; and subjecting the n streams W(i) and M in D to distillation conditions, obtaining the stream G according to (a) as a top stream.

17. The process of claim 16, wherein n is in the range of from 2 to 10.

18. The process of claim 16, wherein each alkali metal hydroxide A(i)OH is selected from the group consisting of lithium hydroxide, sodium hydroxide and potassium hydroxide, and wherein a given aqueous liquid stream H(i) comprises an alkali metal hydroxide A(i)OH dissolved in water, in methanol, or in a mixture comprising water and methanol.

19. The process of claim 16, being an integrated process for simultaneously preparing at least 2 mixtures P(i), wherein the mixture P(1) comprises A(1)OMe, and methanol and the mixture P(2) comprises A(2)OMe, and methanol, the process comprising (a) providing a stream G comprising methanol; (b) dividing the stream G into at least two streams G(1) and G(2), G(1) and G(2) having the same composition as G; (c.1) preparing A(1)OMe, comprising (c.1.1) feeding the stream G(1) into the lower part of a reactive distillation column K(1), and feeding an aqueous liquid stream H(1) comprising dissolved A(1)OH, into the upper part of the reactive distillation column K(1); (c.1.2) subjecting G(1) and H(1) in K(1) to reactive distillation conditions, obtaining a top stream W(1) comprising methanol and water; and obtaining a bottoms stream P(1) comprising A(1)OMe, and methanol; (c.2) preparing A(2)OMe, comprising (c.2.1) feeding the stream G(2) into the lower part of a reactive distillation column K(2), K(2) being arranged in parallel with K(1), and feeding an aqueous liquid stream H(2) comprising dissolved A(2)OH, into the upper part of the reactive distillation column K(2); (c.2.2) subjecting G(2) and H(2) in K(2) to reactive distillation conditions, obtaining a top stream W(2) comprising methanol and water; and obtaining a bottoms stream P(2) comprising A(2)OMe, and methanol; (d.1) feeding W(1) and W(2) into the lower part of a rectification column D, and feeding a stream M comprising methanol into the rectification column D; (d.2) subjecting W(1), W(2) and M in D to distillation conditions, obtaining the stream G according to (a) as a top stream.

20. The process of claim 19, wherein W(1) and W(2) are fed as gas streams into the rectification column D.

21. The process of claim 16, wherein from 99 to 100 weight-% of the stream M consist of methanol and optionally water, wherein the amount of water comprised in the stream M is at most 2000 weight-ppm, wherein the stream M is fed to the upper part of D, at a temperature of M in the range of from ambient temperature to the boiling point of methanol at the column pressure of D.

22. The process of claim 16, wherein the rectification column D is operated at a reflux ratio of at least 0.5:1, wherein for realizing the reflux ratio, the process comprises (i) removing, in addition to G, a top stream T(2) from the rectification column D, passing said stream T(2) through a condenser V(4), obtaining a liquid stream and a waste gas stream T(2w); (ii) removing, in addition to G and T(2), a further top stream T(1) from the rectification column D, passing said stream T(2) through a compressor C(3), passing the thus compressed stream through a reboiler V(6), obtaining a liquid stream, wherein the reboiler V(6) is a reboiler of the rectification column D; (iii) feeding the liquid streams obtained according to (i) and (ii) into the top of the rectification column D; or (i) removing, in addition to G, a top stream T(2) from the rectification column D, passing said stream T(2) through a condenser V(4), obtaining a liquid stream T(2l) and a gas stream T(2g); passing the gas stream T(2g) through a condenser V(5), obtaining a liquid stream T(2gl) and a waste gas stream T(2w); and combining the liquid streams T(2l) and (T2gl), obtaining a combined liquid stream T(2cl); (ii) removing, in addition to G and T(2), a further top stream T(1) from the rectification column D, passing said stream T(2) through a compressor C(3), passing the thus compressed stream through a reboiler V(6), obtaining a liquid stream, wherein the reboiler V(6) is a reboiler of the rectification column D; (iii) feeding the combined liquid stream obtained according to (i) and the liquid stream obtained according to (ii) into the top of the rectification column D.

23. The process of claim 16, wherein the stream G provided according to (a) by obtaining from distillation according to (d.2) comprises methanol and water, and wherein the water content of G is at most 200 weight-ppm.

24. The process of claim 16, wherein according to (b), the stream G is divided into the two streams G(1) and G(2).

25. The process of claim 16, wherein prior to be fed into the reactive distillation column K(1), the stream G(1) is passed through a compressor C(1), thereby realizing a pressure increase of G(1) in the range of from 0.1 to 0.8 bar(abs); and/or, prior to be fed into the reactive distillation column K(2), the stream G(2) is passed through a compressor C(2), thereby realizing a pressure increase of G(2) in the range of from 0.1 to 0.8 bar(abs).

26. The process of claim 16, wherein prior to being fed into the rectification column D, the stream W(1) is passed through a compressor C(1), thereby realizing a pressure increase of W(1) in the range of from 0.1 to 0.8 bar(abs); and/or, prior to being fed into the rectification column D, the stream W(2) is passed through a compressor C(2), thereby realizing a pressure increase of W(2) in the range of from 0.1 to 0.8 bar(abs).

27. A chemical production unit for carrying out the process according to claim 16, comprising a rectification column D comprising inlet means for feeding the stream M into D; in a lower part, inlet means for feeding the streams W(i) or one or more combined stream thereof into D; outlet means for removing the streams T(2) and G or a combined stream thereof from the top of D; at least one condenser V(4) and optionally a further condenser V(5) arranged downstream of V(4), having inlet means for receiving the stream T(2) and having outlet means for removing the condensed stream T(3) and for removing a waste gas stream; inlet means for feeding the stream T(3) to the top of D; a bottom reboiler; a stream dividing device S for dividing the stream G into n streams G(i); means for passing the stream G to said stream dividing device S; n reactive distillation columns K(i), n2 and i=1 . . . n; said reactive distillation columns K(i) being arranged in parallel, each reactive distillation column K(i) comprising in an upper part, an inlet means for feeding a stream H(i) into K(i); in a lower part, inlet means for feeding a stream G(i) into K(i); outlet means for removing a stream W(i) from the top of K(i); a bottom reboiler; outlet means for removing a bottoms stream from K(i); a stream dividing means for separating a stream P(i) from the bottoms stream removed from K(i); means for passing the streams G(i) to the reactive distillation columns K(i); means for passing the streams W(i) to the rectification column D; one or more compressors C(i) for compressing either the stream G and/or the streams G(i) and/or the streams W(i).

28. The unit of claim 27, comprising n compressors C(i) arranged upstream of K(i) for compressing the streams G(i) or comprising n compressors C(i) arranged downstream of K(i) and upstream of D for compressing the streams W(i).

29. The unit of claim 27, wherein the inlet means for feeding the streams W(i) or one or more combined stream thereof into D is/are located at a position between the bottoms and the 15.sup.th theoretical stage; and/or wherein the inlet means for feeding the stream M into D are located in the upper part of D.

30. A method comprising providing the chemical production unit according to claim 27 or and simultaneously producing n mixtures P(i) comprising alkali metal methoxide A(i)OMe and methanol, n being an integer with n2 and i=1 . . . n, wherein either at least 2 of the mixtures P(i) comprise different alkali metal methoxides A(i)OMe, and/or at least 2 of the mixtures P(i) comprise the same alkali metal alkoxide A(i)OMe at different concentrations.

Description

EXAMPLES

Example 1: Simultaneous Production of Sodium Methoxide and Potassium Methoxide without Top Vapor Recompression in Rectification Column D

[0253] FIG. 2 shows a process scheme for preparing a mixture P(1) comprising NaOMe and MeOH and a mixture P(2) comprising KOMe and MeOH. Regarding the operating conditions of the rectification column D and of the reactive distillation columns K(1) and K(2), reference is made to Table 1a below. Regarding the relative mass flow rates, reference is made to Table 1 b below.

TABLE-US-00001 TABLE 1a Operating conditions of the columns D, K(1) and K(2) Column D Pressure at the top/bar(abs) 2.1 Temperature at the top/ C. 84 Pressure at the bottom/bar(abs) 2.23 Temperature at the bottom/ C. 124 Theoretical stages 50 W(1), W(2) to theoretical stage from bottom 8th M fed to theoretical stage from bottom 42th Column K(1) Pressure at the top/bar(abs) 2.15 Temperature at the top/ C. 89 Pressure at the bottom/bar(abs) 2.3 Temperature at the bottom/ C. 117 Number of trays 40 Column K(2) Pressure at the top/bar(abs) 2.15 Temperature at the top/ C. 89 Pressure at the bottom/bar(abs) 2.3 Temperature at the bottom/ C. 116 Number of trays 40

TABLE-US-00002 TABLE 1b Relationships between the mass flow rates f of the different streams Definition of Specified: H(1), H(2) streams M(1), M(2): part of condensate from V(4) H(1): NaOH 50 weight-% in water H(2): KOH 48 weight-% in water Ratios of f(G(1))/f(H(1)) 13.3 mass flow rates f(G(2))/f(H(2)) 9.03 of streams f(M(1))/f(H(1)) 0.55 f(M(2))/f(H(2)) 0.40 f(T(3))/f(G) *) 0.92 f(P(1))/f(H(1)) 2.25 f(P(2))/f(H(2)) 1.86 f(waste gas)/f(G) *) <0.0015 *) f(G) = f(G(1)) + f(G(2)) [0254] P(1): 30 weight-% of sodium methoxide in methanol, <1000 ppm of water. [0255] P(2): 32 weight-% of potassium methoxide in methanol, <1000 ppm of water.

[0256] In the following, it is indicated how the mass flow rate of the methanol contained in the stream M (methanol balance, fresh methanol stream), f.sub.MeOH(M), is calculated. In this calculation, the water contents of P(1) and P(2), both being less than 1000 weight-ppm, are neglected. According to this calculation, f.sub.MeOH(P(1)) is the mass flow rate of MeOH contained in the stream P(1), f.sub.MeOH(P(2)) is the mass flow rate of MeOH contained in the stream P(2), f.sub.MeOH(water) is the mass flow rate of MeOH contained in the water stream, and f.sub.MeOH(waste gas) is the mass flow rate of MeOH contained in the waste gas stream:

f.sub.MeOH(M)=f.sub.MeOH(P(1))+f.sub.MeOH(P(2))+f.sub.MeOH(water)+f.sub.MeOH(waste gas)

N.sub.MeOH(P(1))=[(1c.sub.NaoME)*f(P(1))]+[(M.sub.MeOH/M.sub.NaOH*c.sub.NaOH)*f(H(1))]1.1

TABLE-US-00003 Molecular mass M/concentration c values units M.sub.MeOH 32 kg/kmol M.sub.NaOH 40 kg/kmol c.sub.NaOH in H(1) 0.5 kg/kg c.sub.NaOMe in P(1) 0.3 kg/kg

f.sub.MeOH(P(2))=[(1c.sub.KOMe)*f(P(2))]+[(M.sub.MeOH/M.sub.KOH*c.sub.KOH)*f(H(2))]1.2

TABLE-US-00004 Molecular mass M/concentration c values units M.sub.MeOH 32 kg/kmol M.sub.KOH 56 kg/kmol c.sub.KOH in H(2) 0.48 kg/kg c.sub.KOMe in P(2) 0.32 kg/kg

f.sub.MeOH(water)=0.001*f(water)(maximum value)1.3

f.sub.MeOH(waste gas)=0(neglected)1.4

[0257] In the following, it is indicated how the mass flow rate of the water contained in the stream water (bottom stream of D, waste water stream), f(water), is calculated. In this calculation, the water contents of P(1) and P(2), both being less than 1000 weight-ppm, are neglected.

f(water)=f.sub.H2O(H(1))+f.sub.H2O(H(2))+f.sub.H2O(M)f.sub.H2O(waste gas)1.5 [0258] f.sub.H2O(H(1)) is the mass flow rate of water contained in the stream H(1) and f.sub.H2O(H(2)) is the mass flow rate of water contained in the stream H(2) and f.sub.H2O(M) is the mass flow rate of water contained in the stream M:

TABLE-US-00005 Molecular mass M/concentration c values units M.sub.H2O 18 kg/kmol M.sub.NaOH 40 kg/kmol c.sub.NaOH in H(1) 0.5 kg/kg

f.sub.H2O(H(1))=[(1c.sub.NaOH)*f(H(1))]+[(M.sub.H2O/M.sub.NaOH*c.sub.NaOH)*f(H(1))]1.5.1

TABLE-US-00006 Molecular mass M/concentration c values units M.sub.H2O 18 kg/kmol M.sub.KOH 56 kg/kmol c.sub.KOH in H(2) 0.48 kg/kg

f.sub.H2O(H(2))=[(1c.sub.KOH)*f(H(2))]+[(M.sub.H2O/M.sub.KOH*c.sub.KOH)*f(H(2))]1.5.2

f.sub.H2O(M)=0.001*f(M)1.5.3

f.sub.H2O(waste gas)=0(neglected)1.5.4

Example 2: Simultaneous Production of Sodium Methoxide and Potassium Methoxide with Top Vapor Recompression in Rectification Column D

[0259] The use of vapor recompression reduces the energy demand of the distillation in D considerably. It is possible to have a ratio of the heat streams to V(3) and V(6) of about 1:4. That means the energy demand decreases to 20%. But about 10% (depending on the pressure) of the energy which is transferred in V(6) is needed as power for the compressor C(3). All in all, there is a large energy saving by using vapor recompression.

[0260] FIG. 5 shows a process scheme for preparing a mixture P(1) comprising NaOMe and MeOH and a mixture P(2) comprising KOMe and MeOH. Regarding the operating conditions of the rectification column D and of the reactive distillation columns K(1) and K(2), reference is made to Table 2a below. Regarding the relative mass flow rates, reference is made to Table 2b below.

TABLE-US-00007 TABLE 2a Operating conditions of the columns D, K(1) and K(2) Column D Pressure at the top/bar(abs) 2.1 Temperature at the top/ C. 84 Pressure at the bottom/bar(abs) 2.23 Temperature at the bottom/ C. 124 Theoretical stages 50 W(1), W(2) to theoretical stage from bottom 8th M fed to theoretical stage from bottom 42th Pressure at outlet of C(3)/bar(abs) 5 Column K(1) Pressure at the top/bar(abs) 2.15 Temperature at the top/ C. 89 Pressure at the bottom/bar(abs) 2.3 Temperature at the bottom/ C. 117 Number of trays 40 Column K(2) Pressure at the top/bar(abs) 2.15 Temperature at the top/ C. 89 Pressure at the bottom/bar(abs) 2.3 Temperature at the bottom/ C. 116 Number of trays 40

TABLE-US-00008 TABLE 2b Relationships between the mass flow rates f of the different streams Definition of Specified: H(1), H(2) streams M(1), M(2): part of condensate from V(4) H(1): NaOH 50 weight-% in water H(2): KOH 48 weight-% in water Ratios of f(G(1))/f(H(1)) 13.3 mass flow rates f(G(2))/f(H(2)) 9.03 of streams f(M(1))/f(H(1)) 0.55 f(M(2))/f(H(2)) 0.40 f(T(3))/f(G) *) 1.0 f(P(1))/f(H(1)) 2.25 f(P(2))/f(H(2)) 1.86 f(waste gas)/f(G) *) <0.0015 f(T(1))/f(T(2)) 3.97 *) f(G) = f(G(1)) + f(G(2)) [0261] P(1): 30 weight-% of sodium methoxide in methanol, <1000 ppm of water. [0262] P(2): 32 weight-% of potassium methoxide in methanol, <1000 ppm of water.

[0263] In the following, it is indicated how the mass flow rate of the methanol contained in the stream M (methanol balance, fresh methanol stream), f.sub.MeOH(M), is calculated. In this calculation, the water contents of P(1) and P(2), both being less than 1000 weight-ppm, are neglected. According to this calculation, f.sub.MeOH(P(1)) is the mass flow rate of MeOH contained in the stream P(1), f.sub.MeOH(P(2)) is the mass flow rate of MeOH contained in the stream P(2), f.sub.MeOH(water) is the mass flow rate of MeOH contained in the water stream, and f.sub.MeOH(waste gas) is the mass flow rate of MeOH contained in the waste gas stream:

f.sub.MeOH(M)=f.sub.MeOH(P(1))+f.sub.MeOH(P(2))+f.sub.MeOH(water)+f.sub.MeOH(waste gas)

N.sub.MeOH(P(1))=[(1c.sub.NaOME)*f(P(1))]+[(M.sub.MeOH/M.sub.NaOH*c.sub.NaOH)*f(H(1))]2.1

TABLE-US-00009 Molecular mass M/concentration c values units M.sub.MeOH 32 kg/kmol M.sub.NaOH 40 kg/kmol c.sub.NaOH in H(1) 0.5 kg/kg c.sub.NaOMe in P(1) 0.3 kg/kg

N.sub.MeOH(P(2))=[(1c.sub.KOMe)*f(P(2))]+[(M.sub.MeOH/M.sub.KOH*c.sub.KOH)*f(H(2))]2.2

TABLE-US-00010 Molecular mass M/concentration c values units M.sub.MeOH 32 kg/kmol M.sub.KOH 56 kg/kmol c.sub.KOH in H(2) 0.48 kg/kg c.sub.KOMe in P(2) 0.32 kg/kg

f.sub.MeOH(Water)=0.001*f(water)(maximum value)2.3

f.sub.MeOH(waste gas)=0(neglected)2.4

[0264] In the following, it is indicated how the mass flow rate of the water contained in the stream water (bottom stream of D, waste water stream), f(water), is calculated. In this calculation, the water contents of P(1) and P(2), both being less than 1000 weight-ppm, are neglected.

f(water)=f.sub.H2O(H(1))+f.sub.H2O(H(2))+f.sub.H2O(M)f.sub.H2O(waste gas)2.5 [0265] f.sub.H2O(H(1)) is the mass flow rate of water contained in the stream H(1) and f.sub.H2O(H(2)) is the mass flow rate of water contained in the stream H(2) and f.sub.H2O(M) is the mass flow rate of water contained in the stream M:

f.sub.H2O(H(1))=[(1c.sub.NaOH)*f(H(1))]+[(M.sub.H2O/M.sub.NaOH*c.sub.NaOH)*f(H(1))]2.5.1

TABLE-US-00011 Molecular mass M/concentration c values units M.sub.H2O 18 kg/kmol M.sub.NaOH 40 kg/kmol c.sub.NaOH in H(1) 0.5 kg/kg

f.sub.H2O(H(2))=[(1c.sub.KOH)*f(H(2))]+[(M.sub.H2O/M.sub.KOH*c.sub.KOH)*f(H(2))]2.5.2

TABLE-US-00012 Molecular mass M/concentration c values units M.sub.H2O 18 kg/kmol M.sub.KOH 56 kg/kmol c.sub.KOH in H(2) 0.48 kg/kg

f.sub.H2O(M)=0.001*f(M)2.5.3

f.sub.H2O(waste gas)=0(neglected)2.5.4

DESCRIPTION OF THE FIGURES

[0266] FIG. 1 shows a schematic overview of a process according to the present invention wherein the rectification column D is operated without top vapor recompression. In particular, a fresh methanol stream M is fed into the upper part of a rectification column D. From the top of the rectification column D, a gas stream T(2), a dry methanol stream, is removed which as passed through the condenser V(4), from which condenser V(4) a waste gas stream T(2w), essentially consisting of inerts and methanol, and a liquid stream T(3) are obtained. The liquid stream T(3) is fed back to the top of the column D. A part of the bottoms stream removed from the column D is fed into the bottom reboiler V(3) of D, the other part of the bottoms stream, essentially consisting of water, is disposed. Further, from the top of the column D, a dry methanol gas stream G is removed, in addition to T(2). This gas stream G, exhibiting a flow rate f(G), is divided into two streams G(1) and G(2), both having the same composition as G. The stream G(1) exhibits a flow rate f(G(1)), the stream G(2) exhibits a flow rate f(G(2)), wherein f(G(1))+f((G2))=f(G). The stream G(1) is then passed through a compressor C(1), and the thus compressed stream G(1) is then fed into the lower part of reactive distillation column K(1), wherein into the upper part of K(1), a liquid aqueous stream H(1) comprising a dissolved alkali metal hydroxide A(1)OH is fed. A part of the bottoms stream removed from the column K(1) is fed into the reboiler V(1) of K(1), the other part of the bottoms stream is the mixture P(1) comprising alkali metal methoxide A(1)OMe and methanol. From the top of the column K(1), which is operated without reflux, a gas stream W(1) essentially consisting of methanol and water is removed, wherein W(1) is fed into a lower part of the rectification column D. The stream G(2) is then passed through a compressor C(2), and the thus compressed stream G(2) is then fed into the lower part of reactive distillation column K(2), wherein into the upper part of K(2), a liquid aqueous stream H(2) comprising a dissolved alkali metal hydroxide A(2)OH is fed. A part of the bottoms stream removed from the column K(2) is fed into the reboiler V(2) of K(2), the other part of the bottoms stream is the mixture P(2) comprising alkali metal methoxide A(2)OMe and methanol. From the top of the column K(2), which is operated without reflux, a gas stream W(2) essentially consisting of methanol and water is removed, wherein W(2) is fed, together with W(1), into a lower part of the rectification column D.

[0267] FIG. 2 shows the schematic overview according to FIG. 1, wherein in the top of the reactive distillation columns K(1) and K(2), droplet separating devices D(1) and D(2), preferably demisters, are located, with the streams M(1) and M(2) used for an at least temporary spraying.

[0268] FIG. 3 shows the schematic overview according to FIG. 2, wherein the compressors C(1) and C(2) are not located upstream of K(1) and K(2) for compressing G(1) and G(2), but located downstream of K(1) and K(2) for compressing W(1) and W(2) prior to feeding W(1) and W(2) into D.

[0269] FIG. 4 shows a schematic overview of a process according to the present invention wherein, compared to the process shown in FIG. 1, the rectification column D is operated with top vapor recompression. Regarding said top vapor recompression, a dry methanol top stream is removed from the rectification column D, in addition to G and T(2). This gas stream T(1) is passed through compressor C(3), and this compressed stream T(1) is then passed through the intermediate reboiler V(6) of the column D. The thus obtained compressed and condensed stream T(1) obtained from V(6) is then passed to a first condensate drum. Inerts which are comprised in T(1) are removed as gas stream T(1g) from the first condensate drum via a control valve (not shown) and fed into the condenser V(4) into which also the top stream T(2) is fed. The other part of T(1), T(11), is depressurized into a second condensate drum. Into said second condensate drum, a further stream T(2gl) is fed which is obtained from the condenser V(5) into which the stream T(2g) obtained from V(4), T(2l) is fed. Further, the stream T(2l) obtained from V(4) is fed in to the second condensate drum. From the second condensate drum, a liquid stream T(3) is removed and fed to the top of the column D.

[0270] FIG. 5 shows the schematic overview according to FIG. 4, wherein in the top of the reactive distillation columns K(1) and K(2), droplet separating devices D(1) and D(2), preferably demisters, are located, with the streams M(1) and M(2) used for an at least temporary spraying.

[0271] FIG. 6 shows the schematic overview according to FIG. 5, wherein the compressors C(1) and C(2) are not located upstream of K(1) and K(2) for compressing G(1) and G(2), but located downstream of K(1) and K(2) for compressing W(1) and W(2) prior to feeding W(1) and W(2) into D.

CITED LITERATURE

[0272] US 2002/0183566 A1 [0273] US 2008/0296786 A1 [0274] WO 2013/168113 A1