Process and system for conversion of carbon dioxide to carbon monixide

Abstract

A process and an apparatus for converting carbon dioxide CO.sub.2 into carbon monoxide CO using hydrocarbons are described. In further embodiments, processes and apparatuses for generating synthesis gas and processes and apparatuses for converting synthesis gas into synthetic functionalised and/or non-functionalised hydrocarbons using CO.sub.2 and hydrocarbons are described. The processes and apparatuses are adapted to convert CO.sub.2 emitted by industrial processes, and thus the amount of carbon dioxide emitted into the atmosphere may be reduced.

Claims

1. An apparatus for converting carbon dioxide CO.sub.2 into carbon monoxide CO comprising: a hydrocarbon converter for decomposing a hydrocarbon containing fluid into carbon and hydrogen, wherein the hydrocarbon converter comprises at least one process chamber having at least one inlet for a hydrocarbon containing fluid and at least one outlet for carbon and hydrogen, and wherein the hydrocarbon converter comprises at least one unit for introducing energy into the process chamber, the energy consisting at least partially of heat, wherein the at least one unit for introducing energy into the process chamber is designed in such a way that it can generate, at least locally, temperatures above 1000 C.; a CO.sub.2 converter for converting CO.sub.2 into CO, the CO.sub.2 converter comprising at least one further process chamber having at least one inlet for CO.sub.2 adapted to introduce CO.sub.2 from an external CO.sub.2 source into the CO.sub.2 converter, at least one inlet for carbon and hydrogen, and at least one outlet, wherein the inlet for carbon and hydrogen is directly connected to the at least one outlet of the hydrocarbon converter.

2. The apparatus for converting carbon dioxide CO.sub.2 into carbon monoxide CO according to claim 1, wherein the at least one unit for introducing energy into the process chamber comprises a plasma unit or a microwave plasma unit.

3. The apparatus for converting carbon dioxide CO.sub.2 into carbon monoxide CO according to claim 1, wherein the process chamber of the CO.sub.2 converter is formed by an outlet pipe of the hydrocarbon converter, wherein the outlet pipe is connected to an inlet for CO.sub.2 gas.

4. The apparatus for converting carbon dioxide CO.sub.2 into carbon monoxide CO according to claim 1, wherein the hydrocarbon converter comprises a Kvaerner reactor.

5. The apparatus according to claim 1 having at least one additional hydrocarbon converter for decomposing a hydrocarbon containing fluid into carbon and hydrogen, the additional hydrocarbon converter comprising: at least one process chamber having at least one inlet for the hydrocarbon containing fluid; at least one unit for introducing energy into the process chamber, the energy at least partially consisting of heat; a separation unit for separating the carbon obtained by decomposing and the hydrogen obtained by decomposing, the separation unit having separate outlets for carbon and hydrogen, wherein the outlet for hydrogen of the separation unit is connected to a separate inlet pipe for hydrogen leading into the CO.sub.2 converter or into a mixing chamber located downstream.

6. The apparatus according to claim 5, wherein the at least one additional hydrocarbon converter is of a type carrying out decomposing at temperatures below 1000 C. by means of a microwave plasma.

7. An apparatus for converting a synthesis gas into synthetic functionalised and/or non-functionalised hydrocarbons comprising: an apparatus according to claim 5; and a CO converter having a process chamber, in which a catalyst is located, and means for bringing the synthesis gas into contact with the catalyst, and a control unit open-loop controlling or close-loop regulating the temperature of at least one of the catalyst and the synthesis gas to a predetermined temperature.

8. The apparatus according to claim 7, wherein the CO converter comprises one of the following: a Fischer-Tropsch converter, a SMDS converter, a Bergius_pier converter, a Pier converter or a combination of a Pier converter with a MtL converter.

9. The apparatus according to claim 7 further comprising a control unit for open-loop controlling or close-loop regulating the pressure of the synthesis gas in the CO converter.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Below, the invention is explained in more detail with reference to certain embodiments and drawings, wherein

(2) FIG. 1 is a schematic representation of a plant for generating carbon monoxide;

(3) FIG. 2 is a schematic representation of a plant for generating synthesis gas,

(4) FIG. 3 is a schematic representation of a plant for generating functionalised and/or non-functionalised hydrocarbon;

(5) FIG. 4 is a schematic representation of another plant for generating functionalised and/or non-functionalised hydrocarbons according to another embodiment;

(6) FIG. 5 is a schematic representation of a plant for generating functionalised and/or non-functionalised hydrocarbons according to another embodiment;

(7) FIG. 6 is a schematic representation of a plant for generating functionalised and/or non-functionalised hydrocarbons according to another embodiment;

(8) FIG. 7 is a schematic representation of a plant for generating synthesis gas according to another embodiment; and

(9) FIG. 8 is a schematic representation of a plant for generating functionalised and/or non-functionalised hydrocarbons according to another embodiment

DESCRIPTION OF EMBODIMENTS

(10) It shall be noted the terms top, bottom, right and left as well as similar terms in the following description relate to the orientations and arrangements, respectively, shown in the figures and are only meant for the description of the embodiments. These terms are not limiting. Further, in the different figures, the same reference numerals are used for describing the same or similar parts.

(11) In the following description, processes and apparatuses are described that handle hot materials or carry out hot processes. In the context of this description, the expression hot shall describe a temperature above 200 C. and preferably above 300 C.

(12) FIG. 1 schematically shows a plant 1 for converting carbon dioxide to carbon monoxide. FIG. 1 also clarifies the basic process steps for converting carbon dioxide to carbon monoxide according to this description.

(13) Plant 1 comprises a hydrocarbon converter 3 that comprises a hydrocarbon inlet 4 and a first carbon outlet 5, an optional hydrogen outlet 6 as wall as an optional second carbon outlet 7. Plant 1 for generating carbon monoxide further comprises a CO.sub.2 converter 9 having a CO.sub.2 inlet 10, a carbon outlet 11 (also referred to as C inlet) and an outlet 12. The hydrocarbon converter 3 and the CO.sub.2 converter 9 are arranged such that the carbon outlet 5 of the hydrocarbon converter 3 is connected to the carbon inlet 11 of the CO.sub.2 converter 9 via a direct connection 8, wherein the outlet 5 may directly define the carbon inlet 11 of the CO.sub.2 converter 9. In this way carbon may be directly transported from the hydrocarbon converter 3 into the CO.sub.2 converter 9.

(14) The hydrocarbon converter 3 is any hydrocarbon converter that can convert or decompose introduced hydrocarbons into carbon and hydrogen. The hydrocarbon converter 3 comprises a process chamber having an inlet for a hydrocarbon containing fluid, at least one unit for introducing decomposing energy into the fluid and at least one outlet. The decomposing energy is provided at least partially by heat, which is for instance provided by a plasma. Nevertheless, the decomposing energy may also be provided by other means and, if decomposing is primarily effected by heat, the fluid should be heated to above 1000 C. and particularly to a temperature above 1500 C.

(15) In the described embodiment, a Kvaerner reactor is used, which provides the required heat by means of a plasma arc and a plasma torch. However, other reactors are known, which operate at lower temperatures, particularly below 1000 C., and introduce additional energy besides heat into the hydrocarbon, e.g. by means of a microwave plasma. As is further explained below, the invention considers both types of reactors (and also those which operate without plasma), in particular also both types of reactors in combination with each other. Hydrocarbon converters operating at a temperature above 1000 C. are referred to as high temperature reactors, whereas those converters operating at temperatures below 1000 C., particularly at temperatures between 200 C. and 1000 C., are referred to as low temperature reactors.

(16) Within the hydrocarbon converter, hydrocarbons (C.sub.nH.sub.m) are decomposed into hydrogen and carbon by means of heat and/or a plasma. These hydrocarbons are preferably introduced into the reactor as gases. Hydrocarbons that are liquids under standard conditions may be vaporised prior to introduction into the reactor or they may be introduced as micro-droplets. Both forms are referred to as fluids in the following.

(17) Decomposing of the hydrocarbons should be done, if possible, in the absence of oxygen in order to suppress the formation of carbon oxides or water. Nevertheless, small amounts of oxygen, which might be introduced together with the hydrocarbons, are not detrimental for the process.

(18) The Kvaerner reactor described above decomposes hydrocarbon containing fluids in a plasma burner at high temperatures into pure carbon (for instance as activated coal, carbon black, graphite or industrial soot) and hydrogen and, possibly impurities. The hydrocarbon containing fluids used as starting material for the hydrocarbon converter 3 are for instance methane, natural gas, biogases, wet gases or heavy oil. However, synthetic functionalised and/or non-functionalised hydrocarbons may also be used as starting material for the hydrocarbon converter 3. After the initial decomposing step, the elements are usually present as a mixture, particularly in form of an aerosol. This mixture may, as described below, be introduced into another process in this form, or the mixture may be separated into its individual elements in a separation unit, which is not shown. In the context of this application, such a separation unit is considered as part of the hydrocarbon converter 3, although the separation unit may be constructed as a separate unit, if no separation unit is provided, the carbon outlet 5 is the only outlet of the hydrocarbon converter 3 and directs a mixture (an aerosol) of carbon and hydrogen directly into the CO.sub.2 converter 9. If the separation unit is provided, carbon, which is at least partially separated from hydrogen, may be directed into the CO.sub.2 converter 9 using the carbon outlet 5. Separated hydrogen and, possibly, additional carbon may be discharged by means of the optional outlets 6 and 7.

(19) The CO.sub.2 converter 9 may be any suitable CO.sub.2 converter that can generate carbon monoxide (CO) from carbon (C) and carbon dioxide (CO.sub.2). In the embodiment of FIG. 1 , the CO.sub.2 converter 9 operates according to a part of a known reaction in a blast furnace, wherein said part reaction takes place at temperatures between about 750 C. and 1200 C. without the necessity of a catalyst. Preferably, the CO.sub.2 converter operates at a temperature between 800 C. and 1000 C., wherein the heat required to reach that temperature primarily is provided by the exit material of the hydrocarbon converter 3, as will be described below in more detail. In the CO.sub.2 converter 9, CO.sub.2 is directed over hot carbon or is mixed with hot carbon (and possibly hydrogen) so as to be converted according to the chemical reaction CO.sub.2+C.fwdarw.2 CO. The CO.sub.2 converter 9 operates best at the Boudouard equilibrium and at a temperature of 1000 C. At temperatures of around 800 C., about 94% carbon monoxide will be provided, and at temperatures of around 1000 C., around 99% carbon monoxide will be provided. A further increase in temperature does not result in significant changes.

(20) The operation of plant 1 for converting carbon dioxide into carbon monoxide is described in more detail below, with reference to FIG. 1. In the following, it is assumed that the hydrocarbon converter 3 is a high temperature (HT) reactor of the Kvaerner type. Hydrocarbon containing fluids (specifically in gaseous form) are introduced into the hydrocarbon converter 3 via the hydrocarbon inlet 4. If the hydrocarbon is for instance methane (CH.sub.2), then 1 mol carbon and 2 mol hydrogen will be produced from 1 mol methane. The hydrocarbons are decomposed at about 1600 C. in the hydrocarbon converter 3 according to the following reaction equation, wherein the introduced energy is heat that is generated in the plasma by means of electric energy:
C.sub.nH.sub.m+Energy.fwdarw.n C+m/2 H.sub.2
With appropriate process control, the Kvaerner reactor is capable to convert almost 100% of the hydrocarbons into their components in a continuous operation.

(21) In the following, it is assumed that the carbon and the hydrogen are separated in the hydrocarbon converter 3 and that carbon and hydrogen will be discharged largely separated. However, it is also possible that separation does not occur but carbon and hydrogen will be discharged and introduced into the CO.sub.2 converter 9 as a mixture. The hydrogen does not compromise the conversion process in the CO.sub.2 converter 9, but may serve as an additional heat transfer substance. The carbon is at least partially directed directly via the carbon outlet 5 into the carbon inlet 11 of the CO.sub.2 converter 9. The term directly directing from outlet 5 of the hydrocarbon converter 3 to the carbon inlet 11 of the CO.sub.2 converter 9 shall include all embodiments wherein the directed materials do not experience a cooling down of more than 50% of the temperature (preferably not more than 20%, i.e. 80% residual energy/temperature). Since the carbon that exits from the hydrocarbon converter 3 has a high temperature, preferably over 1000 C., the heat energy contained therein may be used to maintain the temperature necessary for the conversion process in the CO.sub.2 converter 9, which preferably operates at a temperature of about 1000 C.

(22) The connection 8 between the hydrocarbon converter 3 and the CO.sub.2 converter 9 is designed such that the carbon does not cool down much (less than 50%, preferably less than 20% with respect to the temperature) on its way from the hydrocarbon converter 3 to the CO.sub.2 converter 9. For instance, the connection 3 may be specially insulated and/or actively heated, wherein the system is preferably not provided with additional heati.e. not in addition to the heat introduced in the hydrocarbon converter 3. The hydrogen generated in the hydrocarbon converter 3 also contains heat energy because of the operating temperature in the hydrocarbon converter 3. Therefore, one possibility for heating the connection 8 is to use the heat energy of the hydrogen that exits through the hydrogen outlet 6 to heat the connection 8 between the hydrocarbon converter 3 and the CO.sub.2 converter 9 either directly or indirectly via a heat exchanger unit.

(23) In the CO.sub.2 converter, CO.sub.2, which is introduced through the CO.sub.2 inlet 10 of the CO.sub.2 converter 9, is directed over hot carbon and/or is mixed with hot carbon. The CO.sub.2 converter operates best at the Boudouard equilibrium, which occurs during the reaction of carbon dioxide with hot carbon. The reaction, which is known to the person skilled in the art, depends on pressure and temperature and will not be described in detail. Either the amount of the CO.sub.2 or the amount of carbon introduced into the CO.sub.2 converter 9 may be (open loop) controlled and/or (close loop) regulated by appropriate means.
CO.sub.2+C.fwdarw.2COH=+172.45 kJ/mol

(24) The CO.sub.2 may originate e.g. from a power plant (coal, gas and/or oil operated) or from another industrial process (e.g. steel or cement production) generating appropriate amounts of CO.sub.2. Depending on the temperature of the CO.sub.2 from the CO.sub.2 source, it is advantageous to preheat the CO.sub.2 introduced into the CO.sub.2 inlet 10 of the CO.sub.2 converter 9, as the CO.sub.2 converter 9 operates at a temperature between 800 and 1200 C. Preheating of the CO.sub.2 may be achieved e.g. by using the heat energy contained in the hot hydrogen either directly or indirectly via a heat exchange unit to preheat the CO.sub.2. Preferably, the heat contained in the carbon is sufficient to heat the CO.sub.2 to the desired temperature. Only in the case where the heat generated in the hydrocarbon converter 3 is not sufficient to reach the desired conversion temperature of about 1000 C., an optional additional heating unit for heating the CO.sub.2 converter 9 or elements contained therein may be provided. Such a unit may also be provided as a preheating unit in the vicinity of a supply line for CO.sub.2 or carbon. Such a unit may also be provided only for the start-up phase of the plant in order to bring the CO.sub.2 converter 9 or media containing parts of the plant to a starting temperature so that the system can faster reach a desired temperature state. Heating of all media containing parts exclusively via the heat generated in the hydrocarbon converter 3 might take too long in the beginning.

(25) Hot carbon monoxide (CO) having a temperature of about 800 to 1000 C. (depending on the operating temperature of the CO.sub.2 converter 9) exits from the CO.sub.2 converter 9. The carbon monoxide that exits from the CO.sub.2 converter 9 also contains heat energy which may be used e.g. to preheat the CO.sub.2 introduced into the CO.sub.2 inlet 10, either directly or indirectly via a heat exchange unit (not shown in FIG. 1).

(26) As mentioned above, the hydrocarbon converter 3 may comprise a second carbon outlet 7 to discharge carbon. The carbon generated in the hydrocarbon converter 3 may be dischargedafter a respective separation step (or as a CH.sub.2 mixture)in different proportions through the first carbon outlet 5 and the second carbon outlet 7. The second carbon outlet 7 is used to discharge a portion of the generated carbon that is not used in the CO.sub.2 converter 9 to generate carbon monoxide. The carbon discharged through the second carbon outlet 7 may be discharged as activated carbon, graphite, carbon black or another modification such as carbon cones or carbon discs. Depending on the form and the quality of the discharged carbon, the discharged carbon may be used as raw material for the chemical industry or the electronics industry. Possible applications are for instance the manufacture of semiconductors, the production of tires, inks, toner or similar products. The carbon generated by the hydrocarbon converter 3 is a highly pure raw material that can be processed very well.

(27) By means of the method described above for converting carbon dioxide into CO, it is possible to convert the hot carbon from the hydrocarbon converter 9 in the CO.sub.2 converter 3 with warm or hot carbon dioxide from the exhaust gas from industrial processes to CO without or at least without significant external energy supply. Preferably, at least 80%, specifically at least 90%, of the heat necessary to reach the conversion temperature should originate from the hydrocarbon converter 3.

(28) FIG. 2 shows a plant 20 for generating synthesis gas that comprises the above described elements of plant 1 for generating carbon monoxide as well as a mixing chamber 21, the mixing chamber 21 comprising a CO inlet 22 for introducing carbon monoxide and a H.sub.2 inlet 23 for introducing hydrogen as well as a synthesis gas outlet 24 for discharging synthesis gas. The CO inlet 22 is connected to the CO outlet 12 of the CO.sub.2 converter 9. The H.sub.2 inlet 23 of the mixing chamber 21 is connected to the H.sub.2 outlet 6 of the hydrocarbon converter 3. As is obvious to the skilled person, the embodiment, which introduces a CH.sub.2 mixture into the CO.sub.2 converter 9 through the carbon outlet 5 automatically generates a synthesis gas having a mixing ratio of COH.sub.2 of about 1:1. In such a case, the mixing chamber 21 may not be present, or the mixing chamber 21 may be used to produce a different mixing ratio.

(29) The mixing chamber 21 may be any suitable apparatus for mixing gases and, in a simple case, the mixing chamber 21 may be in the form of a pipe having suitable inlets and an outlet. By means of the mixing chamber 21 and specifically by means of controlling/regulating (open/closed loop) the amount of (additional) hydrogen introduced through the H.sub.2 inlet 23 of the mixing unit 21, the mixture of the synthesis gas at the synthesis gas outlet 24 may be influenced such that a composition can be achieved, which is suitable for subsequent processes.

(30) For many processes, for instance the Fischer-Tropsch synthesis, the ratio of hydrogen to CO should be high. By means of the mixing chamber 21, any desired ratio of hydrogen to CO may be achieved at the synthesis gas outlet 24. It is considered that only a portion of the CO and/or part of the hydrogen is introduced into the mixing chamber 21, whereas those portions of CO and hydrogen that are not introduced into the mixing chamber are each discharged from the process as pure gases. Therefore, it is for instance possible, a) to discharge only CO, b) to discharge only hydrogen, c) to discharge a synthesis gas mixture of CO and hydrogen or d) to discharge a stream of CO, a stream of hydrogen and a stream of a synthesis gas mixture (CO+hydrogen),

(31) Furthermore, the plant 20 for generating synthesis gas shown in FIG. 2 comprises a first heat exchange unit 25, a second heat exchange unit 26 and a third heat exchange unit 27. The first heat exchanger unit 25 is in thermally conductive contact with the connection 8 between the hydrocarbon converter 3 and the CO.sub.2 converter 9 and is adapted to, if necessary, extract surplus heat not required to reach the conversion temperature in the CO.sub.2 converter 9 from the connection or to introduce heat from other areas of the plant, if necessary.

(32) The second heat exchanger unit 26 is in thermally conductive contact with the connection between the CO.sub.2 converter 9 and the mixing chamber 21 and is adapted to extract surplus heat from the connection and thus to extract surplus heat contained in the hot CO. This surplus heat may be used e.g. to preheat the CO.sub.2 that is introduced into the CO.sub.2 converter 9. For this heat transfer a so-called counter flow heat exchanger unit as known in the art would be particularly suitable.

(33) The third heat exchanger unit 27 is in thermally conductive contact with the connection between the hydrocarbon converter 3 and the mixing chamber 21 and is adapted to extract surplus heat from the connection and thus from the hot hydrogen contained therein. The heat extracted at one of the first, second or third heat exchanger units may be used to heat other areas of the plant, specifically to keep the CO.sub.2 converter warm or to preheat the CO.sub.2 that is introduced into the CO.sub.2 converter. A portion of the heat may be converted into electricity, for instance by a steam generator and a steam turbine or by another suitable apparatus.

(34) The operation of plant 20 for generating synthesis gas is, with respect to the operation of the hydrocarbon converter 3 and the CO2 converter 9, similar to the above described operation of plant 1 according to FIG. 1. In plant 20 for generating synthesis gas, a desired mixing ratio of hydrogen to CO is set in the mixing chamber and is discharged through the synthesis gas outlet 24 of the mixing chamber, depending on the desired composition of the synthesis gas. Preferably, but not necessarily, the hydrogen is provided by the hydrocarbon converter 3, as was described. Other hydrogen sources may be considered, particularly a second hydrocarbon converter 3, particularly a low temperature hydrocarbon converter, if not the entire available amount of CO and/or the entire available amount of H.sub.2 are used, those parts of the gases CO and H.sub.2 that are not mixed in the mixing chamber may be processed separately.

(35) FIG. 3 shows a plant 30 for generating synthetic functionalised and/or non-functionalised hydrocarbons that comprises a plant 1 for converting carbon dioxide into carbon monoxide (as shown in FIG. 1) and a CO converter 31. Those parts of the plant corresponding to plant 1 are not explained in detail in order to avoid repetitions. The CO converter 31 is located downstream from the CO.sub.2 converter 9 and comprises a CO inlet 32 for introducing CO, a H.sub.2 inlet 33 for introducing hydrogen and a hydrocarbon outlet 34 for discharging synthetic functionalised and/or non-functionalised hydrocarbons. The CO inlet 32 of the CO converter 31 is connected to the CO outlet 12 of the CO.sub.2 converter 9 by means of the CO connection 35. The H.sub.2 inlet 33 of the CO converter 31 is connected to the H.sub.2 outlet 6 of the hydrocarbon converter 3 by means of the H.sub.2 connection 38.

(36) The plant 30 for generating hydrocarbons optionally also comprises the heat exchanger units 25, 26, 27 described in conjunction with plant 20 (FIG. 2), wherein all of these operate in the above described way (see description to FIG. 2).

(37) The CO converter 31 may be any CO converter for generating synthetic functionalised and/or non-functionalised hydrocarbons. In the embodiment shown in FIG. 3, the CO converter is preferably a Fischer-Tropsch converter, a Bergius-Pier converter or a Pier converter with a suitable catalyst and a control unit for temperature and/or pressure.

(38) In one embodiment, the CO converter 31 comprises a Fischer-Tropsch converter. A Fischer-Tropsch converter catalytically converts a synthesis gas into hydrocarbons and water. Several embodiments of Fischer-Tropsch reactors and Fischer-Tropsch processes are known to the person skilled in the art and are not explained in detail. The main reaction equations are as follows:
n CO+(2n+1)H.sub.2.fwdarw.C.sub.nH.sub.2n+2+n H.sub.2O for alkanes
n CO+2n H.sub.2.fwdarw.C.sub.nH.sub.2n+n H.sub.2O for alkenes
n CO+2n H.sub.2.fwdarw.C.sub.nH.sub.2n+10H+(n1)H.sub.2O for alcohols

(39) The Fischer-Tropsch processes may be carried out as high temperature processes or as low temperature processes, wherein the process temperatures are usually in the range of 200 to 400 C. Known variants of the Fischer-Tropsch process are, among others, the Hochlast synthesis, the Synthol synthesis and the SMDS process of Shell (SMDS=Shell Middle Distillate Synthesis). A Fischer-Tropsch converter typically produces a hydrocarbon compound of wet gases (propane, butane), petrol, kerosene, soft paraffin, bard paraffin, methanol, methane, Diesel fuel or a mixture of several of these. It is known to the person skilled in the art that the Fischer-Tropsch synthesis is exothermic. The heat of reaction from the Fischer-Tropsch process may be used e.g. by means of a heat exchanger unit (not shown in the figures) to preheat the CO.sub.2. As an example, a two-step preheating process for the CO.sub.2 to be introduced into the CO.sub.2 converter 9 is considered, wherein a first preheating step is realised with the surplus heat of the CO converter 31 (in the embodiment of a Fischer-Tropsch converter) and subsequently a step of further heating of the CO.sub.2 by means of the heat from one or more of the heat exchanger units 25, 26, 27.

(40) In an alternative embodiment, the CO converter 31 comprises a Bergius-Pier converter or a combination of a Pier converter with a MtL converter (MtL=Methanol-to-Liquid).

(41) In a Bergius-Pier reactor, the Bergius-Pier process, which is well known to a person skilled in the art, is carried out, wherein hydrocarbons are generated by hydrogenation of carbon with hydrogen in an exothermic chemical reaction. The range of products from the Bergius-Pier process depends on the reaction conditions and control of the reaction process. Mainly liquid products are obtained, which may be used as transportation fuels, for instance heavy and medium oils. Known variants of the Bergius-Pier process are for instance the Konsoi process and the H-Coal process.

(42) In the above mentioned combination of a Pier converter with a MtL converter, at first synthesis gas is converted into methanol according to the Pier process. The MtL converter is a converter that converts methanol into petrol. A widespread process is the MtL process of ExxonMobil respectively Esso. Starting material of the MtL converter is typically methanol, for instance from the Pier converter. The exit product generated by the MtL converter typically is petrol, which is suitable for the operation of an Otto engine.

(43) It may be summarized that the CO converter 31, regardless of the operating principles explained above, generates synthetic functionalised and/or non-functionalised hydrocarbons from CO and H.sub.2 as its output or end products. By means of a heat exchanger unit, the process heat produced during the exothermic conversion in the CO converter 31, may be used to heat different sections of the plant or to generate electricity in order to increase the efficiency of the described plant.

(44) As far as a mixture of hydrocarbons, which cannot be further processed directly or sold profitably as a final product after separation and specification, is obtained as exit products of the CO converter 31, these hydrocarbons, for instance methane or short-chain paraffins, may be recycled into the process described above. For this purpose, the plant 30 comprises a recycle connection 39, which can direct a portion of the synthetically generated hydrocarbons back to the hydrocarbon inlet 4 of the hydrocarbon converter 3. Depending on the composition of the recycled, synthetically generated hydrocarbons, a treatment or separation step of unsuitable hydrocarbons is carried out prior to introducing the unsuitable hydrocarbons into the hydrocarbon inlet 4.

(45) FIG. 4 shows a further embodiment of a plant 40 for generating synthetic functionalised and/or non-functionalised hydrocarbons. The plant 40 comprises the above described plant 20 for generating a synthesis gas as well as a CO converter 31 as described above with reference to the embodiment in FIG. 3. The synthesis gas outlet 24 of the mixing chamber 21 is connected to the CO converter 31. The mixing chamber 21 is set in such a way that it provides a synthesis gas specifically adapted to the needs of the CO converter 31 in use at the synthesis gas outlet 24. The other elements of plant 40 are the same as described above and the operation of the individual elements essentially takes place in the way described above.

(46) It is considered that depending on the size of the plant, a plurality of hydrocarbon converters are operated in parallel in order to provide the desired conversion capacity. As mentioned above, the hydrocarbon converters may be constructed as high temperature hydrocarbon converters and/or as low temperature hydrocarbon converters. A high temperature hydrocarbon converter operates at temperatures above 1000 C. and a low temperature hydrocarbon converter operates at temperatures between 200 and 1000 C., wherein an additional source of energy for instance a microwave unit, may be provided in order to achieve decomposition of the hydrocarbon into carbon and hydrogen.

(47) As an example for a plant with a plurality of parallel operated hydrocarbon converters, FIG. 5 shows a further embodiment of plant 30 for generating synthetic functionalised and/or non-functionalised hydrocarbons. FIG. 5 uses the same reference numerals as in earlier embodiments, as far as the same or similar elements are described. In the embodiment shown in FIG. 5, a combination of a high temperature hydrocarbon converter 3a and a low temperature hydrocarbon converter 3b is shown instead of a single hydrocarbon converter 3.

(48) The high temperature hydrocarbon converter 3a comprises a hydrocarbon inlet 4a, a first outlet 5a to discharge carbon and a second outlet 6a to discharge hydrogen. Again, a single outlet 5a may be provided for a mixture (particularly an aerosol) of carbon and hydrogen. The outlet 5a is connected to the inlet 11 of the CO.sub.2 converter 9 by a connection 8. The optional outlet 6a of the high temperature hydrocarbon converter 3a is connected to the H.sub.2 inlet 33 of the CO converter 31. The high temperature hydrocarbon converter 3a may optionally comprise a further outlet for carbon (not shown in FIG. 5).

(49) The low temperature hydrocarbon converter 3b comprises a process chamber having a hydrocarbon inlet 4b, a first outlet 5b to divert carbon, a second outlet 6b for discharging hydrogen and an optional third outlet 7b for discharging carbon. Preferably, the low temperature hydrocarbon converter 3b comprises a separation unit for separating hydrogen and carbon after decomposition and for directing the hydrogen and carbon to their respective outlets. The first outlet 5b is optionally connected to inlet 11 of the CO.sub.2 converter 9 via connection 8, but may also be connected to a carbon collection unit. The outlet 6b of the low temperature hydrocarbon converter 3b is connected to the H.sub.2 inlet 33 of the CO converter 31. The optional third outlet 7b is connected to a carbon collection unit from which collected carbon may be withdrawn, for instance as carbon black, activated coal or in another form.

(50) The hydrocarbon introduced into the hydrocarbon inlet 4a and the hydrocarbon introduced into the hydrocarbon inlet 4b may be the same hydrocarbon or may be different hydrocarbons. A hydrocarbon from a first hydrocarbon source may be introduced into the hydrocarbon inlet 4a, for instance natural gas from a natural gas source. However. e.g. functionalised and/or non-functionalised, synthetically generated hydrocarbon may be introduced into the hydrocarbon inlet 4b of the low temperature hydrocarbon converter 3b, for instance via the earlier mentioned optional recycle connection 39. Because of the utilisation of several parallel operated hydrocarbon converters 3a, 3b, the plant 30 may be scaled easier, may be controlled easier, and different kinds of carbon may be produced.

(51) Furthermore, the high temperature hydrocarbon converter 3a may for instance be used advantageously to generate hot carbon, preferably at a temperature over 1000 C., for the CO.sub.2 conversion process in the CO.sub.2 converter 9. In particular, the high temperature hydrocarbon converter 3a may operate in this case without a separation unit, since the CH.sub.2 mixture, obtained by decomposing, may be introduced directly into the CO.sub.2 converter. In this case, the CO.sub.2 converter 9 produces a synthesis gas having a CH.sub.2 mixing ratio of e.g. about 1:1 at the outlet.

(52) The low temperature hydrocarbon converter 3b, however, is primarily used in order to provide additional hydrogen for the generation of a synthesis gas or a CH.sub.2 mixture having a CH.sub.2 mixing ratio of greater than 1:1, in particular greater than 1:2 in the CO converter 31. As no heat transfer from the low temperature hydrocarbon converter 3b to a subsequent process is necessary, the low temperature hydrocarbon converter 3b may advantageously be operated at temperatures below 1000 C. and preferably at the lowest possible temperature.

(53) Thus, a portion of the carbon produced in the hydrocarbon converters 3a, 3b (preferably the portion from the high temperature hydrocarbon converter 3a) may be introduced into the CO.sub.2 converter 9 during the operation of plant 30, whereas another portion (preferably the portion from the low temperature hydrocarbon converter 3b) may be discharged from the process as raw material for producing further products. Such products are for instance carbon black or industrial soot, activated coal, special kinds of carbon such as carbon discs and carbon cones etc., which is obtained as black powdery solid matter. This carbon is an important technical product which may be used e.g. as filler in the rubber industry as pigment soot for printing colours, inks, paints or as starting material for the generation of electrical components, for instance zinc-carbon-batteries and for the production of cathodes or anodes. Any surplus hydrogen may be discharged for the chemical industry or may be used for generating electricity (by burning), whereby the low temperature hydrocarbon converter 3b is preferably operated in such a way that it only provides the necessary additional hydrogen.

(54) FIG. 6 shows an alternative embodiment of the above described plant 40 for generating synthetic functionalised and/or non-functionalised hydrocarbons, for which a plurality of parallel operated high temperature and/or low temperature hydrocarbon converters are provided as well.

(55) The plant 40 for generating hydrocarbons shown in FIG. 6 differs from the plant 30 shown in FIG. 5 in such a way that a mixing chamber 21 is located upstream of the CO converter 31. The mixing chamber 21 mixes a synthesis gas specifically adapted to the CO converter 31 and provides the synthesis gas to the CO converter 31. The elements depicted in FIG. 6 have already been described above and work according to the principles described above. Therefore, no detailed description is given on order to avoid repetitions.

(56) FIGS. 7 and 8 show embodiments of the plants 20 and 30 comprising a first heat exchanger unit 25, a second heat exchanger unit 26 and a third heat exchanger unit 27, wherein each is connected to an engine/generator device 45. The engine/generator device 45 is adapted to at least partially generate electricity from surplus heat from different sections of the plant, wherein said electricity may either be fed into the main grid or may be used to operate the plant 20, especially the hydrocarbon converter(s). Further, the engine/generator device 45 may be connected to a heat exchanger unit (not shown in FIG. 8), which dissipates the heat generated by the exothermic conversion process taking place inside the CO converter 31. Thus, on the one hand the CO converter may be cooled in a controlled and regulated way, which is advantageous for the operation of the process, and on the other hand electricity may be generated. The engine/generator device 45 may be any device that is adapted to transform heat energy into electricity for instance a combination of a steam turbine and a generator or a piston engine and a generator.

(57) During operation, the engine/generator device 45 transforms the surplus heat of the plant into electricity i.e. the heat that is not necessary for CO.sub.2 conversion.

(58) The engine/generator device 45 and the heat exchanger units 25, 26 and 27 are optional elements that may be used at all plants described above. Due to the operation temperature in the respective hydrocarbon converter 3, 3a, 3b, the carbon discharged from the respective second outlets 7, 7a, 7b also contains significant amounts of heat energy. Depending on the desired temperature of the discharged carbon, a large amount of this heat energy may be dissipated by means of heat exchanger units (not shown in the figures) and the heat may be reused in the processes described herein and/or may be transformed into electricity using the engine/generator device 45.

(59) In the plants 30 and 40 for generating synthetic functionalised and/or non-functionalised hydrocarbons, cooling of the hydrogen from the hydrocarbon converters 3, 3a, 3b and/or cooling of the CO from the CO.sub.2 converter 9 is performed only as far as the temperature of the hydrocarbons and of the hydrogen does not fall below the operating temperature of the CO converter 31. The operating temperature of the CO converter 31 is usually between 200 and 400 C. depending on the chosen process.

(60) In all plants described above, the hydrocarbon converter 3 may be a high temperature reactor operating at a temperature of more than 1000 C. (e.g. a high temperature Kvaerner reactor) or a low temperature reactor operating at a temperature between 200 C. and 1000 C. (e.g. a low temperature Kvaerner reactor). A presently tested low temperature reactor operates at temperatures between 300 and 800 C. In the case of a low temperature reactor operating at temperatures between 200 and 800 C. It is considered that the introduced carbon is preheated in the connection 8 between the hydrocarbon converter 3 and the CO.sub.2 converter 9, as the CO.sub.2 converter 9 operates at temperatures between 800 and 1000 C. Further, it becomes clear from FIGS. 7 and 8 that a combination between high temperature and/or low temperature converters may be used in all plants 1, 20, 30 and 40 described above.

(61) In all plants 1, 20, 30 and 40 described above, a portion of the carbon generated in the hydrocarbon converters 3, 3a, 3b may be discharged as carbon black, as activated coal or as another raw material as long as said carbon is not converted in the CO.sub.2 converter 9 of plant 1, 20, 30, 40. It shall further be noted that also a portion of the hydrogen produced in the hydrocarbon converter 3 may be directly discharged out of the process and may be sold as commodity. Further, undesired synthetic functionalised and/or non-functionalised hydrocarbons generated in the CO converter 31 may be returned and fed into the hydrocarbon inlets 4, 4a, 4b of the hydrocarbon converter 3 in all plants 30 and 40 described above.

(62) It is considered that the CO.sub.2 introduced into the CO.sub.2 converter 9 is a exhaust gas from a combustion power plant or that the CO.sub.2 is generated in another industrial process. Recently, emphasis is put on releasing smaller amounts of CO.sub.2 into the environment, as CO.sub.2 is seen as a climate pollutant. In the above mentioned exhaust gases, the CO.sub.2 is mixed with other gases including, amongst others, a large amount of nitrogen from the air. With none of the above described plants 1, 20, 30, 40 is it necessary to separate the nitrogen prior to introducing the mixture of CO.sub.2 and other gases into the CO.sub.2 converter 9. As far as these other gases are only present in small amounts or are chemically inert (e.g. nitrogen), the operation of the CO.sub.2 converter 9 is not compromised by the additional gases. A residual component of oxygen is burned in the CO.sub.2 converter at the high operating temperature in presence of carbon.

(63) Some examples follow for further clarification:

EXAMPLE 1

CO2 Neutral Gas Power Plant

(64) By means of a Kvaerner reactor as the hydrocarbon converter 3, methane is decomposed into carbon and hydrogen. For each atom of carbon, two molecules of hydrogen will be obtained (CH.sub.4.fwdarw.C+2 H.sub.2). Starting from a conventional natural gas power station, for instance of the type Irsching IV, manufactured by Siemens AG, having a nominal capacity of 581 MW, the CO.sub.2 contained in the exhaust gas is introduced into the CO.sub.2 converter 9about 1.5 million tons a year. The CO.sub.2 from the exhaust gas of the natural gas power plant is reduced with half of the carbon discharged from the hydrocarbon converter 3. The hydrogen from the hydrocarbon converter 3 is cooled down and the dissipated heat is transformed into electricity by means of the engine/generator device 45. The CO.sub.2 from the natural gas power plant is directed over hot carbon inside the CO.sub.2 converter 9 and is converted into twice the amount of carbon monoxide according to the Boudouard equilibrium (CO.sub.2+C.fwdarw.2 CO). The hot carbon monoxide exiting from the CO.sub.2 converter 9 is cooled down, and the dissipated heat is transformed into electricity. The carbon monoxide from the CO.sub.2 converter 9 (Boudouard equilibrium) and the hydrogen from the hydrocarbon converter 3 (Kvaerner process) are converted in a CO converter 31 (Fischer-Tropsch plant) to form hydrocarbons. A Heavy Paraffin Synthesis module connected to a subsequent Heavy Paraffin Conversion module from the SMDS-process (=Shell Middle Distillate Synthesis process) manufactured by Shell is preferred. The heat from the process is transformed into electricity. The nature of the resulting hydrocarbons depends on the chosen Fischer-Tropsch process and may be varied in the Shell SMDS process.

(65) In the specific natural gas power plant (561 MW) having an efficiency of 60.4%, assuming an efficiency of 60% when transforming the process heat into electricity and assuming an efficiency of 50% when transforming dissipated heat into electricity, the process has the following parameters:

(66) TABLE-US-00001 Consumption of methane: 2515 million S m.sup.3 CH.sub.4 per year Generation of electricity: 313 MW Carbon black production: 447 000 tons per year Paraffin production: 1.0 million tons per year CO.sub.2 emission: almost 0 Efficiency: Natural gas power plant 33.7% Total 66.8%

EXAMPLE 2

Gas-to-Liquid Plant

(67) If the plant from example 1 is operated without transforming the process heat and the dissipated heat into electricity, then no significant amount of electricity is generated. In this case, the example is a process for converting gaseous materials (carbon dioxide and methane) into liquid fuels (Otto and Diesel fuels, kerosine), i.e. a Gas-to-Liquid or GtL plant in the present example, an additional amount of carbon is produced.

(68) The parameters are as follows:

(69) TABLE-US-00002 Consumption of methane 2515 million S m.sup.3 CH.sub.4 per year Generation of electricity 0 MW Carbon black production 447 000 tons per year Paraffin production 1.0 million tons per year CO.sub.2 emission almost 0

(70) The invention has been explained in some detail with respect to specific embodiments and examples without being limited to these examples. In particular, the elements of the individual embodiments may be combined and/or exchanged with each other, if compatible. The skilled person will become aware of manifold modifications and deviations within the scope of the following claims. In a particularly simple embodiment of the plant for generating synthetic functionalised and/or non-functionalised hydrocarbons, the CO.sub.2 converter may be designed e.g. as a simple pipe (for instance as an outlet pipe of a high temperature hydrocarbon converter not having a separation unit), wherein a CO.sub.2 pipe leads to said pipe. The CO.sub.2 pipe should join said pipe such that the two gas streams get well mixed. The pipe should be insulated and could be connected to a heating unit e.g. at an inlet section in order to heat up the pipe (especially at the beginning of the operation) to an operating temperature. Further downstream, the pipe could be connected to a heat exchanger unit adapted to extract surplus heat and to use this heat for heating other sectors of the plant and/or for generating electricity. Additionally, the pipe may comprise an inlet pipe for hydrogen (for instance downstream of the heat exchanger unit) so that the same pipe not only functions as a CO.sub.2 converter, but also functions as a mixing chamber for generating a synthesis gas. The inlet pipe for hydrogen may originate e.g. from an outlet for hydrogen of a low temperature hydrocarbon converter (having a separation unit). In this case, an output end of the pipe, where a synthesis gas having a predetermined mixing ratio may be discharged, could end in a CO converter.