DEVICE AND USE OF THE DEVICE FOR PREHEATING AT LEAST ONE FLUID

Abstract

An apparatus (10) and the use thereof for preheating at least one fluid are proposed. The apparatus (10) has a solid heating body (12). Channels (16) for passage of the fluid are formed in the heating body (12). The heating body (12) is heatable. The heating body (12) is designed to heat the fluid to a target temperature within a target time, wherein the target temperature is at least a temperature at which a predetermined chemical reaction of the fluid takes place with a predetermined conversion within a predetermined time. The target time is shorter than the predetermined time. The heating body (12), for preheating of the fluid, is heated to the target temperature and the fluid is passed through the channels (16) within the target time.

Claims

1.-17. (canceled)

18. A process comprising preheating at least one fluid in an apparatus, wherein the apparatus has a solid heating body, wherein channels for passage of the fluid have been formed in the heating body, wherein the heating body is heatable, wherein the heating body is designed for heating of the fluid to a target temperature within a target time, wherein the target temperature is at least one temperature at which a predetermined chemical conversion of the fluid takes place with a predetermined conversion within a predetermined time, wherein the target time is less than the predetermined time, wherein the heating body, for preheating of the fluid, is heated to the target temperature and the fluid is guided through the channels within the target time, wherein the heating body is connected to a reaction section for performance of the predetermined conversion of the preheated fluid.

19. The process according to claim 18, wherein the difference between the target temperature and the temperature at which the predetermined reaction of the fluid takes place with the predetermined conversion rate within the predetermined time is from 200 K to +200 K.

20. The process according to claim 18, wherein the target time is 0.1 ms to 150 ms.

21. The process according to claim 18, wherein the fluid is guided through each of the channels (16) with a volume flow rate of 0.01 m.sup.3 (STP)/h to 500 m.sup.3 (STP)/h.

22. The process according to claim 18, wherein the fluid is a gas.

23. The process according to claim 18, wherein the predetermined reaction is a reaction selected from the group consisting of: thermal breakdown, dehydrogenation, and oxidation.

24. The process according to claim 18, wherein the heating body is heated to a temperature of 100 C. to 1600 C.

25. The process according to claim 18, wherein the heating body is heated directly or indirectly.

26. The process according to claim 18, wherein the channels extend in a straight line in a direction of longitudinal extent.

27. The process according to claim 18, wherein the channels are parallel to one another.

28. The process according to claim 18, wherein the heating body is cylindrical.

29. The process according to claim 28, wherein the channels are parallel to a cylinder axis.

30. The process according to claim 18, wherein the heating body has a longitudinal axis, wherein the channels are distributed homogeneously over a cross section of the heating body perpendicularly with respect to the longitudinal axis.

31. The process according to claim 18, wherein the sum total of the free cross sections of the flow channels based on the cross-sectional area of the heating body is from 0.1% to 50%.

32. The process according to claim 18, wherein the channels are cylindrical.

33. The process according to claim 18, wherein the channels have a diameter of 0.1 mm to 12.0 mm.

34. The process according to claim 18, wherein the heating body is connected to the reaction section for performance of the predetermined reaction of the preheated fluid, wherein the apparatus and the reaction section are integrated.

35. The process according to claim 18, wherein the target time is 0.5 ms to 75 ms.

36. The process according to claim 18, wherein the target time is 1 ms to 50 ms.

37. The process according to claim 18, wherein the target time is 2 ms to 25 ms.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0100] Further optional details and features of the present invention will be apparent from the description of preferred working examples which follows, these being shown in schematic form in the drawings.

[0101] The figures show:

[0102] FIG. 1 a schematic diagram of the proportions of the phases by area in an apparatus of the invention,

[0103] FIG. 2 a collection of possible cross sections of the apparatus of the invention sorted according to geometric features,

[0104] FIG. 3 a rear view of an apparatus in a first embodiment of the present invention, FIG. 4 a cross-sectional view along the line A-A in FIG. 3,

[0105] FIG. 5 a rear view of an apparatus in a second embodiment of the present invention,

[0106] FIG. 6 a cross-sectional view along the line A-A in FIG. 5,

[0107] FIG. 7 a reactor with a thermostated reaction zone, wherein the cross section of the heating blocks is roughly equal to the cross section of the reaction zone, and

[0108] FIG. 8 a reactor with an adiabatic reaction zone, wherein the cross section of the heating blocks is significantly smaller than the cross section of the reaction zone.

EMBODIMENTS OF THE INVENTION

[0109] FIG. 1 shows a schematic diagram of the proportions of the phases by area in an inventive apparatus 10 for preheating of at least one fluid in a first embodiment of the present invention. The apparatus 10 has a solid heating body 12. The heating body 12 is at least partly formed from at least one metal and/or at least one ceramic. For example, the heating body 12 is manufactured from -alumina (corundum). The heating body 12 is cylindrical, especially circular cylindrical. Correspondingly, the heating body 12 has a circular cross section. Alternatively, the heating body 12 may be prismatic or geometrically irregular, i.e. have a cross section of any shape, as described in more detail hereinafter. Correspondingly, the shape of the heating body 12 defines a longitudinal axis 14 along which the heating body 12 extends. In the example shown, the heating body 12 is fully surrounded by a heating chamber 15. Channels 16 are formed in the heating body 12. The channels 16 are designed for passage of a fluid to be heated. The channels 16 are designed, for example, as bores in the solid material of the heating body 12. The heating body 12 is heatable. The heating body 12 is especially directly or indirectly heatable. For example, the heating body itself may be designed as a heating element that electrically heats the fluid in the channels 16. In the example shown, the heating body 12 is fully surrounded by the heating chamber 15 and is separated therefrom by an impermeable joint 17. By means of conduction of heat, in operation, heat is transferred from the heating chamber 15 to the heating body 12 and thence to the channels 16 and the fluid present therein.

[0110] FIG. 2 shows a collection of possible cross sections of the inventive apparatus 10 sorted according to geometric features. FIG. 2 shows, on the left, possible cross sections with a regular shape and, on the right, possible cross sections with an irregular shape. The regular shapes shown are circular, rectangular with rounded edges, and star-shaped. In the case of the irregular shapes, all technically implementable shapes are possible, especially any desired shapes with roundings.

[0111] FIG. 3 shows a rear view of an apparatus in a first embodiment of the present invention. FIG. 4 shows a cross-sectional view along the line A-A in FIG. 3. The channels 16 extend in a straight line in a direction of longitudinal extent 18. The channels 16 here are parallel to one another. The channels 16 are parallel to the longitudinal axis 14. The channels 16, especially in the case of a cross section of the heating body 12 perpendicular to the longitudinal axis 14, are in irregular distribution. The channels 16 are cylindrical, especially circular cylindrical. Alternatively, the channels 16 may be prismatic. Alternatively, the heating body 12 may have a structured outer shell, in which case the channels 16 at least partly take the form of grooves in the outer shell.

[0112] Advantageously, the hydraulic diameter of the channels is from 0.1 mm to 12 mm, preferably from 0.2 mm to 8 mm, more preferably from 0.3 mm to 4 mm, especially from 0.4 mm to 2 mm. With these values for the hydraulic diameter, the dwell time in the heating body for the use of the invention can be adjusted in a particularly efficient manner. Moreover, this avoids deposits on the walls of the channels that could otherwise block these.

[0113] Advantageously, the ratio of the hydraulic diameter of the heating body to the hydraulic diameter of a channel is between 2 and 1000, preferably between 5 and 500, more preferably between 10 and 100. The hydraulic diameter is defined as the quotient of four times the cross section and the circumference of the body or the channel (chapter Ba in VDI-Wrmeatlas, 9th edition, 2002).

[0114] The number of channels based on the equivalent cross section of the heating body is from 2 to 1000, preferably from 5 to 500, more preferably from 10 to 100. The equivalent cross section of the heating body is defined here as the area of a circle having a diameter that corresponds to the hydraulic diameter of the heating body.

[0115] The total cross section of the flow channels (free cross section) is between 0.1% and 50%, preferably between 0.2% and 20%, more preferably between 0.5% and 10%, of the heating body cross section.

[0116] The length of the heating body is between 10 mm and 1000 mm, preferably from 30 mm to 300 mm. The fluid may be a gas and especially a gas mixture comprising one or more thermally unstable compounds and/or two or more components that chemically react with one another. The apparatus 10 may especially be used for continuous preheating of the fluid. The heating body 12 is especially designed to heat the fluid to a target temperature within a target time. The target temperature is at least a temperature at which a predetermined chemical conversion of the fluid takes place with a predetermined conversion within a predetermined time. The target time here is shorter than the predetermined time. The heating body 12, for preheating of the fluid, is then heated to the target temperature and the fluid is passed through the channels 16 within the target time. The predetermined time is determined on the basis of the nature of the fluid, as described in more detail hereinafter. For instance, the predetermined time can be determined theoretically or empirically on the basis of the nature of the fluid. For example, the predetermined time can be ascertained by simulation. Alternatively, there is standard software known to those skilled in the art, by means of which a conversion of the fluid can be determined (Kee, R. J., Miller, J. A., & Jefferson, T. H. (1980). CHEMKIN: A general-purpose, problem-independent, transportable, FORTRAN chemical kinetics code package. Sandia Labs).

[0117] The apparatus 10 may also have a closed-loop control system 20 for control of a temperature of the heating body 12. The target temperature here may be a target temperature in the closed-loop control system 20. A hydraulic diameter of the channels 16 of the heating body 12 is based here on the target time. The difference between the target temperature and the temperature at which the predetermined conversion of the fluid takes place within the predetermined time may be from 200 K to +200 K and preferably from 100 K to +100 K. The target time may be 0.1 ms to 150 ms, preferably 0.5 ms to 75 ms, more preferably 1 ms to 50 ms, most preferably 2 ms to 25 ms. The target time is based correspondingly on the dwell time of the fluid in the channels. The dwell time is defined as the quotient of the length of the channels and the mean velocity of the fluid through the channels under standard conditions. A pressure differential of the fluid between an inlet 22 and an outlet 24 of the apparatus 10 may be between 1 mbar and 900 mbar, preferably between 1 mbar and 500 mbar, more preferably between 1 mbar and 200 mbar and most preferably between 1 mbar and 100 mbar. A pressure differential of the fluid between the inlet 22 and the outlet 24 of the apparatus 10 may be between 0.1% and 50%, preferably between 0.1% and 20%, more preferably between 0.1% and 10%, of the absolute pressure of the fluid at the inlet 22. In general, the fluid can be guided through each of the channels 16 with a volume flow rate of 0.01 m.sup.3 (STP)/h to 500 m.sup.3 (STP)/h, preferably of 0.01 m.sup.3 (STP)/h to 200 m.sup.3 (STP)/h, more preferably of 0.01 m.sup.3 (STP)/h to 100 m.sup.3 (STP)/h and most preferably 0.01 m.sup.3 (STP)/h to 50 m.sup.3 (STP)/h. The predetermined conversion here may be a reaction selected from the group consisting of: thermal breakdown, dehydrogenation reaction, selectively heterogeneously catalyzed oxidation. The heating body 12 is heated to a temperature of 100 to 1600 C., preferably of 400 to 1400 C. and more preferably of 700 to 1300 C.

[0118] The heating body 12 may be connected to a reaction section 26 for performance of the predetermined conversion of the preheated fluid. The apparatus 10 and the reaction section 26 may be integrated, especially in a monolithic manner. The reaction section may have a channel section 28. The apparatus 10 and the reaction section 26 may be designed such that the channels 16 open into the channel section 28. The channel section 28 here may have a cross-sectional area essentially identical to a cross-sectional area of the heating body 12. The channel section 28 may be hollow. Alternatively, the channel section 28 may be filled with a solid packing. The predetermined conversion rate in the predetermined time is determined in the reaction section. Based on the diagram in FIG. 2, the fluid flows from right to left through the channels 16.

[0119] The design of the heating body 12 is based on the following relationship:

[00001]${}_{\mathrm{hex}}=\frac{\mathrm{NTU}}{4.Math.\mathrm{Nu}.Math.a}.Math.d_h^2$

[0120] The meanings of the symbols here are:

.sub.hex[s]: Dwell time of the fluid stream in the heating body 12. The dwell time is defined as the quotient of the volume of a channel 16 and the standard volume flow rate that flows through the channel 16.
NTU: Number of transfer units (NTU) which are to be implemented in the heating body 12. The determination of the NTU is known to those skilled in the art, for example from chapter Ca in VDI-Wrmeatlas, 9th edition, 2002.
Nu: The Nusselt number for heat transfer in a channel 16. Nu depends primarily on the flow regime. In the present case, in general, there is laminar flow in narrow capillary channels 16. In this case, Nu=3.66.

[00002]$a\left[\frac{m^2}{s}\right].Math.\text{:}$

specific thermal conductivity of the fluid stream:

[00003]$a=\frac{}{.Math.c_u}.$

a is a physical parameter.

[00004]$\left[\frac{\mathrm{kg}}{m^3}\right]:$

density of the fluid.

[00005]$c_p\left[\frac{J}{\mathrm{kg}.Math.K}\right]:$

specific heat capacity of the fluid at constant pressure.

[00006]$\left[\frac{W}{m.Math.s}\right]:$

coefficient of thermal conductivity of the fluid.
d.sub.h [m]: hydraulic diameter of a channel 16.

[0121] The length of the heating body 12 L.sub.hex can be determined with the aid of the following relationship:

[00007]$L_{\mathrm{hex}}=v_N.Math.{}_{\mathrm{hex}}=\frac{\mathrm{NTU}}{4.Math.\mathrm{Nu}}.Math.\frac{v_N}{a}.Math.d_h^2$

In this equation, v.sub.N means the mean superficial velocity in a channel 16. v.sub.N is defined as the quotient of the standard volume flow rate that flows through the channel 16 and the cross section of the channel 16. L.sub.hex and v.sub.N are free parameters for the purposes of the primary object of the heating body 12. In reality, they are defined by secondary conditions. Such secondary conditions may be: installation length, pressure drop, flow rate. The correlation between L.sub.hex and the available installation length is obvious. The pressure drop is an important process parameter which defines, for example, the strength-related design of the apparatuses or the power required for conveying of the process streams. In particular applications, the pressure drop permitted is determined by the vapor pressure of the process medium. It is advantageous, for example, to avoid any change of phase in the heating body 12. The permissible pressure drop can thus be fixed only in an application-specific manner. Therefore, two ranges are specified. One comprises absolute values; the second comprises relative values based on the pressure level of the process. For a given pressure drop, the flow rate is calculated from the following relationship:

[00008]$v_N=\sqrt{\frac{8}{{}_{\mathrm{eff}}}.Math.\frac{\mathrm{Nu}}{\mathrm{Pr}.Math.\mathrm{NTU}}.Math.\frac{.Math..Math.p}{{}_N}.Math.\frac{T_N}{T_{\mathrm{avg}}}.Math.\frac{p_N}{p_{\mathrm{avg}}}}$

where:
p: pressure drop across the preheater.
.sub.eff: pressure drop coefficient of the capillaries. .sub.eff is dependent on the flow regime. In the case of laminar flow: .sub.eff=64).
Pr: Prandtl number (substance value).
.sub.N: density under standard conditions (substance value at T=273 K, p=1.0135 bar).
T.sub.N: temperature under standard conditions according to DIN 1945 (273 K).
T.sub.avg: mean fluid temperature along the preheater.
p.sub.N: absolute pressure under standard conditions according to DIN 1945 (1.0135 bar).
p.sub.avg: mean pressure along the preheater.

[0122] For laminar flow in the capillaries:

[00009]$v_N=\sqrt{\frac{0.4575}{\mathrm{Pr}.Math.\mathrm{NTU}}.Math.\frac{.Math..Math.p}{{}_N}.Math.\frac{T_N}{T_{\mathrm{avg}}}.Math.\frac{p_N}{p_{\mathrm{avg}}}}$

[0123] There is an upper limit to the flow rate. For example, it should be lower than the speed of sound. Moreover, the backpressure of a jet on exit from a capillary should be restricted.

[0124] The power {dot over (Q)}.sub.cap that the fluid stream absorbs in a channel 16 can be determined with the aid of the following relationship:

[00010]${\stackrel{.}{Q}}_{\mathrm{cap}}=\frac{}{4}.Math.d_h^2.Math.\frac{v_N}{V_{m.Math..Math.\mathrm{ol}}}.Math.c_{p,N}.Math..Math..Math.T_{\mathrm{gas}}$

where:
V.sub.mol: molar volume under standard conditions

[00011]$\left(22.414.Math..Math.\frac{m^3}{k.Math..Math.\mathrm{mol}}\right).$

c.sub.p,N: mean molar heat capacity of the fluid.
T.sub.gas: the temperature differential by which the fluid stream is heated in the heating body 12

T.sub.gas=T.sub.targetT.sub.in(approximately: T.sub.wallT.sub.in).

[0125] The total power that the heating body 12 has to expend is calculated as:

[00012]${\stackrel{.}{Q}}_{\mathrm{tot}}=n.Math.{\stackrel{.}{Q}}_{\mathrm{cap}}=\mathrm{.Math.}.Math.{\left(\frac{D}{d_h}\right)}^2.Math.{\stackrel{.}{Q}}_{\mathrm{cap}}$

where:
: free cross section of the heating body 12 (total cross-sectional area of the channel 16 based on the cross section of the heating body 12).
D: diameter of a circle of equal area to the heating body 12.

[0126] The mean volume-based heat flow density in the heating body 12 is calculated as:

[00013]${\stackrel{.}{q}}_V=\frac{{\stackrel{.}{Q}}_{\mathrm{tot}}}{\frac{}{4}.Math.D^2.Math.L_{\mathrm{hex}}}$

and after substitution:

[00014]${\stackrel{.}{q}}_V=\frac{4.Math.\mathrm{.Math.}.Math.\mathrm{Nu}.Math.{}_g}{\mathrm{NTU}.Math.d_h^2}.Math..Math..Math.T_{\mathrm{gas}}$

If the heat is introduced entirely via the outer face of the heating body 12, the area-based heat flow density in the outer face is:

[00015]${\stackrel{.}{q}}_A=\frac{D}{4}.Math.{\stackrel{.}{q}}_V$

[0127] Using {dot over (q)}.sub.V and {dot over (q)}.sub.A, it is possible to obtain value ranges for the degrees of freedom and D. The volume flow rate is then calculated from the other parameters.

[0128] Possible value ranges for the aforementioned parameters are listed in table 1 below.

TABLE-US-00001 TABLE 1 ll llp llpp llvpp ulvpp ulpp ulp ul Adjustable parameters/degrees of freedom NTU [1] 0.1 0.2 0.5 2 5 20 50 100 [00016]${\stackrel{.}{V}}_N\left[\frac{m^3}{h}\right]$ 0.01 50 100 200 500 d.sub.h [mm] 0.1 0.2 0.3 0.4 2 4 8 12 [1] 0.001 0.002 0.005 0.1 0.2 0.5 L.sub.hex [m] 0.01 0.1 1 10 D [mm] 5 10 20 100 200 300 Target numbers for operating parameters [00017]$v_N\left[\frac{m}{s}\right]$ 1 2 5 10 100 150 200 300 .sub.hex [ms] 0.1 0.5 1 2 25 50 75 150 [00018]$\frac{.Math..Math.p}{p_{\mathrm{avg}}}\left[1\right]$ 0.1% 10% 20% 50% p [mbar] 1 100 200 500 900 [00019]${\stackrel{.}{q}}_V\left[\frac{\mathrm{MW}}{m^3}\right]$ 0.01 15 [00020]${\stackrel{.}{q}}_A\left[\frac{\mathrm{kW}}{m^2}\right]$ 0.1 500

[0129] Parameters in table 1 mean:

{u/l}l: upper/lower limit,
{u/l}lp: upper/lower limit preferred,
{u/l}lpp: upper/lower limit particularly preferred, and
{u/l}lvpp: upper/lower limit very particularly preferred.

[0130] FIG. 5 shows a rear view of an apparatus 10 for preheating of a fluid in a second embodiment of the present invention. FIG. 6 shows a cross-sectional view along the line A-A in FIG. 4. Only the differences from the previous embodiment are described hereinafter, and identical components are given the same reference numerals. In the apparatus 10 of the second embodiment, the heating body 12, by comparison with the heating body 12 from the first embodiment, has a shorter length in the direction 18 of longitudinal extent. In addition, the channels 16 are in denser distribution over the cross section of the heating body 12, meaning that they extend to close to an outer circumferential face of the heating body 12. Based on the diagram in FIG. 6, the fluid flows from the top downward through the channels 16.

[0131] It is emphasized explicitly that the apparatus described herein is not restricted to above-described embodiments or configurations. The above-described embodiments are merely a selection of possible constructions of the apparatus 10. The inventive apparatus 10 and the use thereof are to be illustrated by the examples which follow. It is emphasized explicitly that the apparatus 10 described herein is not restricted to the preheating of the working examples described below. The working examples elucidated hereinafter are merely a selection of possible fluids that can be preheated with the inventive apparatus 10.

[0132] FIG. 7 a reactor 30 with a thermostated reaction zone 32, wherein the cross section of the heating bodies 12 is roughly equal to the cross section of the reaction zone 32. What is shown is the arrangement of multiple heating bodies 12 in a preheating zone 34 of the reactor 30 and the adjoining reactor zone 32. The heating bodies 12 have been inserted into heat transferer tubes. The fluid to be heated passes via a feed 36 into the preheating zone 34, and thence into the heating bodies 12, in order to be preheated, then into the reaction zone 32, where the actual conversion of the fluid takes place in reaction tubes 38 with solid packing, and it leaves the reactor 30 via an outlet 40. For preheating of the fluid, the preheating zone 34 has a feed 42 for a heating medium and an outlet 44 for the heating medium. Analogously, the reaction zone 32 has a feed 46 for a heating medium and an outlet 48 for the heating medium.

[0133] FIG. 8 shows a reactor 30 with an adiabatic reaction zone 32, wherein the cross section of the heating bodies 12 is significantly smaller than the cross section of the reaction zone 32. The difference from the reactor of FIG. 7 can be seen in the reaction zone 32 which, rather than multiple reaction tubes 38, has a solid packing 50, such that the feed 46 and the outlet 48 are also dispensed with.

Example 1

[0134] Example 1 is described with reference to the first embodiment of the apparatus 10 in FIGS. 4 and 5. The fluid is methane. The predetermined time is ascertained depending on the nature of the fluid. This fluid is to be subjected to a conversion to hydrogen and pyrolysis carbon. The conversion takes place at a predetermined temperature of 1200 C. A predetermined relative conversion of 73.59% within a predetermined period of 1.2 s can be ascertained using measurements in the reaction section 26 in a thermostated flow reactor.

[0135] The relative conversion of methane is defined as follows:

[00021]$X_{\mathrm{CH}.Math..Math.4}=1-\frac{{\stackrel{.}{N}}_{\mathrm{CH}.Math..Math.4}^{\mathrm{prod}}}{{\stackrel{.}{N}}_{\mathrm{CH}.Math..Math.4}^{\mathrm{feed}}}$

where:
{dot over (N)}.sub.CH4.sup.prod: molar flow rate of methane at the outlet of the reaction zone.
{dot over (N)}.sub.CH4.sup.feed: molar flow rate of methane in the feed to the reaction zone.

[0136] In the specific case, the relative conversion can be determined purely from concentration measurements:

[00022]$X_{\mathrm{CH}.Math..Math.4}=1-.Math.\frac{y_{\mathrm{CH}.Math..Math.4}^{\mathrm{prod}}}{\left(1+y_{\mathrm{CH}.Math..Math.4}^{\mathrm{prod}}+y_{C.Math..Math.2.Math.H.Math..Math.4}^{\mathrm{prod}}+y_{C.Math..Math.6.Math..Math.H.Math..Math.6}^{\mathrm{prod}}\right).Math.y_{\mathrm{CH}.Math..Math.4}^{\mathrm{feed}}}$

where:
y.sub.j.sup.prod,j=CH4, C2H4, C6H6: the mole fractions of the methane, ethylene, benzene components at the exit from the reaction zone.
y.sub.CH4.sup.feed: the mole fraction of methane in the feed to the reaction zone.

[0137] The mole fractions of the components specified are measured with the aid of a Fourier transformation infrared spectrometer (FTIR).

[0138] The predetermined time for the performance of the reaction is defined as follows:

[00023]${}_{\mathrm{rx}}=\frac{{\mathrm{.Math.}}_{\mathrm{rx}}.Math./4.Math.D_{\mathrm{rx}}^2.Math.L_{\mathrm{rx}}}{{\stackrel{.}{V}}_N^{\mathrm{feed}}.Math.\frac{T_{\mathrm{rx}}}{T_N}.Math.\frac{p^{\mathrm{feed}}}{p_N}}$

where:
.sub.rx: void content of the solid packing in the reaction zone. A suitable measurement method is described in the following publication: Ridgway, K., and K. J. Tarbuck. Radial voidage variation in randomly-packed beds of spheres of different sizes. Journal of Pharmacy and Pharmacology 18.S1 (1966): 168S-175S.
D.sub.rx,L.sub.rx: diameter and length of the reaction zone.
{dot over (V)}.sub.N.sup.feed: standard volume flow rate in the feed to the flow reactor. A suitable measurement method is thermal mass flow meters.
T.sub.rx: the predetermined temperature in the reaction zone.
T.sub.N: the temperature under standard conditions according to DIN 1945 (273.15 K).
p.sup.feed: the absolute pressure in the feed to the reaction zone.
p.sub.N: the absolute pressure under standard conditions according to DIN 1945 (1.0135 bar).

[0139] At the predetermined methane conversion, the following product yields are achieved:

TABLE-US-00002 Carbon-containing product Yield pyrolysis carbon 61.2% C.sub.2H.sub.2 4.2% C.sub.2H.sub.4 4.0% C.sub.6H.sub.6 4.1% Sum total 73.5%

[0140] Pyrolysis carbon is the target product and the hydrocarbons C.sub.2H.sub.2, C.sub.2H.sub.4 and C.sub.6H.sub.6 are intermediates in the pyrolysis.

[0141] Therefore, for the preheating, a target temperature of 1200 C. based on the desired reaction temperature or predetermined temperature is ascertained. The permissible relative preliminary conversion allowed to take place in the heating body 12, measured at the exit 24 from the heating body 12, should be less than 5%. The value for the preliminary conversion is freely defined. The aim of the specification is that no significant conversion takes place at the end of the preheating zone, i.e. at the exit 24 from heating body 12. Based on experience, a sensible threshold value is fixed at a conversion of 5%. This value is guided by the accuracy of the carbon balance in the analysis of the gas phase composition. The fluid should be heated to this target temperature within a target time of less than 50 ms. The value for the target time is ascertained by the simulation of the homogeneous breakdown of methane in an ideal tubular reactor at 1200 C. with the aid of the GRI-3.0 mechanism (http://www.me.berkeley.edu/gri_mech/). The value specified corresponds to a dwell time at which the methane conversion is much less than 5%. Much less means here that the value reported corresponds to about of the time interval in which 5% conversion is theoretically achieved. The deviation from the target value should be less than 10 K. Within this target time, the fluid thus has to be guided through the channels 16 of the heating body 12. In this working example, the heating body 12 has a number of 16 channels 16. The number of channels 16 is determined by target parameters including those which follow.

[0142] The length of the heating body 12 is fixed at 200 mm by construction specifications of a first test zone. The maximum throughput is 1 m.sup.3 (STP)/h. The following design specifications are to be achieved: NTU not less than 5, pressure drop in the heating body 12 less than 10 mbar, corresponding to about 1% of the absolute pressure of the fluid of 1.15 bar at the exit 22 from the heating body 12, dwell time less than 10 ms.

[0143] The heating body 12 has a cross-sectional area of 18 cm.sup.2. Based on the target time, a hydraulic diameter of each channel 16 of 1.2 mm is ascertained. The fluid is guided through each channel 16 at a volume flow rate of 92.6 L (STP)/h. This gives rise to a mean velocity (theoretical value under standard conditions) of 22.75 m/s.

Example 2

[0144] Example 2 is described with reference to the second embodiment of the apparatus 10 in FIGS. 6 and 7. The fluid is methane. The predetermined time is determined depending on the nature of the fluid. This fluid is to be subjected to a conversion to hydrogen and pyrolysis carbon. Proceeding from example 1, there is a need in example 2 to achieve a higher reaction speed for the pyrolysis reaction, in order to increase the yield of pyrolysis carbon and to eliminate the intermediates. For this purpose, advantageously, the reaction temperature is raised and the dwell time in the reaction section 26 is extended. The conversion usually takes place at a predetermined temperature of 1400 C. A predetermined relative conversion higher than 99.5% within a predetermined period of 2.4 s can be ascertained using measurements in the reaction section 26.

[0145] At the predetermined methane conversion, the following product yields are achieved:

TABLE-US-00003 Carbon-containing product Yield pyrolysis carbon 99.5% C.sub.2H.sub.2 0% C.sub.2H.sub.4 0% C.sub.6H.sub.6 0% Sum total 99.5%

[0146] Therefore, a target temperature of 1400 C. based on the desired reaction temperature or predetermined temperature is ascertained. The fluid should be heated to this target temperature within a target time of less than 2 ms. The deviation from the target value should be less than 10 K. Within this target time, the fluid thus has to be guided through the channels 16 of the heating body 12. In this working example, the heating body 12 has a number of 44 channels 16. The number of channels 16 is determined by target parameters including those which follow. The length of the heating body 12 is fixed at 35 mm by construction specifications of a second test zone. The channels 16 are distributed homogeneously over the cross section of the heating body 12. The maximum throughput is 0.5 m.sup.3 (STP)/h. The following design specifications are to be achieved: NTU not less than 5, pressure drop in the heating body 12 less than 10 mbar, which corresponds to about 1% of the absolute pressure of the fluid of 1.15 bar at the exit 22 from the heating body 12, dwell time less than 1 ms.

[0147] The heating body 12 has a cross-sectional area of 18 cm.sup.2. Based on the target time, a hydraulic diameter of 0.5 mm is ascertained. For process-related reasons, the fluid is guided through each channel 16 at a volume flow rate of 11.5 L (STP)/h. This gives rise to a mean velocity (theoretical value under standard conditions) of 16 m/s. In order to heat the fluid to the target temperature within the target time with these parameters, the heating body 12 is heated under closed-loop control to a temperature of 1400 C.

[0148] In each of the examples 1 and 2 described above, the channels were examined for deposits or blockages after eight hours of operation of the apparatus 10. No significant deposits were found that would adversely affect the operation of the apparatus 10. This makes it clear that, with the inventive apparatus 10 and the use thereof, fluids, especially thermally sensitive organic compounds, can be preheated within a much shorter time compared to conventional apparatuses and, at the same time, the service life can be prolonged compared to conventional apparatuses.

LIST OF REFERENCE SIGNS

[0149] 10 apparatus [0150] 12 heating body [0151] 14 longitudinal axis [0152] 16 channels [0153] 18 direction of longitudinal extent [0154] 20 closed-loop control system [0155] 22 inlet [0156] 24 outlet [0157] 26 reaction section [0158] 28 channel section [0159] 30 flange