This application corresponds to PCT/EP2016/075815, filed Oct. 26, 2016, which claims the benefit of German Application No. 10 2015 014 007.8, filed Oct. 30, 2015, the subject matter of which are incorporated herein by reference in their entirety.
The present invention relates to an apparatus and a method for producing synthesis gas.
From WO/2013/91878 a method for producing synthetic functionalized and/or non-functionalized hydrocarbons is known, the method comprising: decomposing a hydrocarbon-containing fluid into a H2/C aerosol consisting of carbon C and hydrogen H2 in a hydrocarbon converter, further directing at least a portion of the aerosol from the hydrocarbon converter into a C converter, and then introducing CO2, e.g. from an industry process, into the C converter. In the C-converter, the CO2 gas is mixed with the H2/C-aerosol wherein the CO2 gas and the carbon are converted into carbon monoxide CO at a high temperature. The temperature at the exit of the C-converter is about 800 to 1000° C. In a CO converter, the carbon monoxide and the hydrogen are converted into synthetic hydrocarbons by means of a catalyst.
In
The following problems have been observed in the known plasma reactor. In the reactor chamber 2′ and at the inlets 5′ for hydrocarbon fluid, carbon deposits have been formed (fouling). The portion of the hydrogen which gathers in upper portion of the reactor chamber 2′ causes a substantial increase of temperature. The produced synthesis gas had a temperature between 1000 and 1300° C. at the outlet which caused a great loss of energy and made the known method uneconomical.
The object of the present invention is to provide a high capacity apparatus for producing synthesis gas, which particularly provides fast conversion and long uninterrupted operation.
This object is achieved by an apparatus for producing synthesis gas according to claim 1 and by a method according to claim 9.
Particularly, this object is achieved by an apparatus for producing synthesis gas which comprises a reactor having a reactor chamber which comprises at least one first inlet connected to a source of hydrocarbon fluid and at least one outlet. The apparatus also comprises a plasma burner having a burner part adapted to produce plasma. Further, at least a second inlet connected to a source of CO2 or H2O leads into the reactor chamber. The reactor chamber defines a flow path from the first inlet to the outlet, wherein, with respect to the flow path, the burner part is located between the first inlet for hydrocarbon fluid and the second inlet for CO2 or H2O, and wherein the second inlet for CO2 or H2O is located with respect to the flow path such that the second inlet is at a location where between 90% and 96% of the hydrocarbon fluid is thermally decomposed. By means of this apparatus, a fast conversion into synthesis gas and reduced reaction times may be obtained since a stabile aerosol is present which comprises very small and easily floating C particles.
Particularly, the second inlet opens into the reactor chamber closer to the burner part than to the outlet. Thus, the conversion reaction of C and CO2 into CO has sufficient time.
In one embodiment, the second inlet is oriented against the direction of the flow path and is directed towards the first inlet. Thus, a better blending of the gas introduced via the second inlet and the C particles is obtained, and carbon deposits are reduced.
Preferably, the apparatus comprises a third inlet which is, with respect to the flow path, further away from the burner part than from the second inlet. Therefore, different gases can be introduced during operation nearer to the burner part and further away from the burner part, and the production of synthesis gas can be better controlled. In this regard it is particularly advantageous if the second inlet is connected to a source of CO2 and the third inlet is connected to a source of H2O. When compared to the prior art, it is thus possible to obtain a lower temperature of the produced synthesis gas at the outlet of the apparatus. In order to further simplify control of the apparatus, a heating element may be provided between the at least one second inlet and the at least one third inlet. Thereby, the apparatus can be controlled kinetically and thermodynamically.
In one embodiment of the apparatus, the burner part comprises a plasma gas inlet connected to a source of plasma gas and a plasma gas outlet, wherein the plasma gas outlet opens into the reactor chamber. In this case, the inlet for hydrocarbon fluid is arranged with respect to the inlet for plasma gas such that the hydrocarbon fluid and the plasma gas are closely mixed with each other when entering into the reaction chamber.
In one embodiment of the apparatus, the plasma burner comprises at least two elongated electrodes, wherein each electrode comprises a base portion at one end, which is mounted to the reactor wall. The burner part is arranged at the end opposite to the base portion and extends into the reactor chamber. In this embodiment, the hydrocarbon fluid flowing along the reactor wall protects it against the heat of the plasma. In an alternative embodiment of the apparatus, the plasma burner is located outside of the reactor chamber and is connected to the reactor chamber via an opening in the reactor wall. In this case, the burner part is oriented towards the opening such that the plasma gas is guided into the reactor chamber. This embodiment provides more freedom for the construction of the plasma burner.
Further, the object is obtained by a method for producing synthesis gas comprising the following steps: introducing a hydrocarbon fluid into a reactor chamber which comprises at least one first inlet for hydrocarbon fluid and at least one outlet; producing a fluid flow from the inlet to the outlet; decomposing the hydrocarbon fluid into carbon particles and hydrogen with the aid of a plasma burner which is located between the inlet and the outlet; and mixing the carbon particles and the hydrogen with CO2 or H2O in a region in the reactor chamber where between 90% and 95% of the hydrocarbon fluid is thermally decomposed. With this method, a fast conversion into synthesis gas and reduced reaction times may be obtained since a stabile aerosol is present which has very small and easily floating C particles.
Particularly, the step of mixing with CO2 or H2O is carried out, with respect to the fluid flow, after the plasma burner in a region of the reaction chamber where the carbon particles have a size of equal to or smaller than 250 nm and preferably of equal to or smaller than 100 nm, Thereby the aerosol remains stable also at a substantial temperature decrease which is caused by the conversion reactions of the C particles with CO2 or H2O.
Alternatively or additionally, the method provides the step of mixing with CO2 or H2O in a region of the reactor chamber which is, with respect to the fluid flow, after the plasma burner where a temperature of 1550 to 1800° C. prevails. If this step is alternatively provided, the method can be controlled more easily. If this step is additionally provided, the method may be controlled more precisely.
In the method, the steps of mixing with CO2 and mixing with H2O are preferably carried out separately and one after the other in the direction of the fluid flow. When compared to the prior art, a lower temperature of the produced synthesis gas at the outlet of the apparatus becomes thus possible which provides for energy savings. Particularly, the carbon particles and the hydrogen are mixed with CO2, with respect to the fluid flow, closer to the plasma burner and they are mixed with H2O, with respect to the fluid flow, further away therefrom.
For accelerated reaction and increased throughput, the pressure in the reaction chamber is set to 10 to 25 bar.
The method is preferably carried out such that the synthesis gas comprises an amount of residual or not decomposed hydrocarbon fluid in a range from 1.25 to 2.6 mol-% in the region of the outlet. Thus, the measurement is facilitated. A measurement near the point of thermal decomposition of the hydrocarbon fluid is very difficult because of the high temperatures of more than 1000° C.
The invention as well as further details and advantages thereof are described in the following with the aid of preferred embodiments taken with reference to the figures.
In the following description the terms top, bottom, right and left as well as similar terms relate to the orientations and arrangements shown in the figures and are meant for describing the embodiments. These terms may refer to preferred arrangements but are not meant to be limiting, In the context of this description the term hydrocarbon fluid means a fluid (gas, aerosol, liquid) which contains hydrocarbons.
The plasma reactor 1 comprises a reactor chamber 2 which is enclosed by a reactor wall 3 which comprises a lower part 3a and a cover 3b. The reactor chamber 2 can be divided also at a location different from that shown in the figures. The reactor chamber 2 is generally cylindrically and has a central axis 4. At the cover 3b of the reactor wall 3, a plasma burner 7 is mounted which comprises elongated electrodes (not shown in detail). The plasma burner 7 has a base part 9 which is fixed to the reactor wall 3 (here particularly at the cover 3b). At the other end thereof, opposite the base part 9, the plasma burner 7 has a burner part 11 which projects into the reactor chamber 2 and is located at the free end 12 of the electrodes. A plasma 13 is formed between the electrodes. At the other end of the reactor chamber 2, opposite the plasma burner 7, the plasma reactor 1 has an outlet 15 through which the substances which are produced inside the reactor chamber 2 can escape. The outlet 15 is located, seen in the direction of the flow, at the opposite end of the reactor chamber 2.
The plasma reactor 1 comprises one or more first inlets 5 for hydrocarbon fluid which are located near the base part 9 of the plasma burner 7. The first inlets 6 open into the reactor chamber 2 such that, during operation, a hydrocarbon fluid flowing therefrom flows into a space 17 between the reactor wall 3 and the electrodes of the plasma burner 7 in a direction towards the burner part 11. In the figures, the central axis 4 has an arrow head and indicates this direction of the flow. The reactor chamber 2 defines a flow path from the first inlets 6 to the outlet 15.
In the embodiment of
In operation, the second inlets 6 direct CO2 or H2O to a location in the reactor chamber where between 90% and 96% of the hydrocarbon fluid has been decomposed into hydrogen and C particles. The one or more second inlets 6 can be oriented in a right angle (as shown in
In the embodiment of
The apparatus shown in
The electrodes, which are not shown in detail in the figures, are e.g. nested tubular electrodes or tube electrode as known, e.g. from U.S. Pat. No. 5,481,080 A (see above). In the case of tubular electrodes, the introduced hydrocarbon fluid flows along one electrode, i.e. along the outer electrode. For tubular electrodes, the first inlets 5 are located radially outward of the outer tubular electrode. However, it is also envisaged that rod electrodes are used, such as two or more rod electrodes located next to each other. In the case of rod electrodes, the hydrocarbon fluid flows along two or more electrodes towards their free end. Thus, in each type of plasma reactor, the hydrocarbon fluid flows in the space 17 along at least one electrode between the reactor chamber 2 and the plasma burner 7. The plasma burner 7 has an inlet for plasma gas and an outlet for plasma gas which opens into the reactor chamber 2 near the burner part 11. Optionally, at least one of the first inlets 5 is located with respect to the inlet for plasma gas such that the hydrocarbon fluid and the plasma gas mix closely upon entering into the reaction chamber 2.
The plasma arc 13 is formed between the electrodes, preferably with CO, H2O or synthesis gas as a plasma gas, since these gases are produced anyway in the apparatus and the method described herein. However, every other suitable gas may be chosen as a plasma gas, such as inert gases as argon or nitrogen, which do not have an influence on or participate in the reaction or decomposition, respectively, in the plasma arc. The inlet for plasma gas is connected with a source of plasma gas, e.g. a storage container. The source of plasma gas may be also the outlet 15 if synthesis gas is used as the plasma gas. If CO2 or H2 are used as a plasma gas, these gases may be extracted from the reactor chamber 2 at a suitable location or may be separated from the synthesis gas from the outlet 15.
One or more sensors may be provided at the plasma reactor so as to sense operation parameters (not shown in the figures). With the aid of pressure sensors, the pressure may be measured inside the reactor chamber 2, at the inlets 5, 6, 8, at the outlet 15 and in the sources for plasma gas, hydrocarbon fluid, CO2 and H2O. With the aid of temperature sensors, the temperature of the introduced substances, of the extracted substances and at different locations inside the reactor chamber 2 may be measured. With the aid of gas sensors, the composition of the introduced substances and of the produced synthesis gas may be measured.
The supply of CO2 and H2O can be controlled in a simple way by measuring the composition of the produced synthesis gas. The amount, size, position and orientation of the inlets 6 with respect to the burner part 11 and the operation parameters for introducing CO2 or H2O, such as pressure and amount introduced per time, are chosen in one embodiment depending on the amount of residual or not decomposed hydrocarbon fluid in the synthesis gas in the region of the outlet 15. Particularly, the location of the inlets 6 and the operation parameters are chosen such that the synthesis gas comprises an amount of residual or not decomposed hydrocarbon fluid in a range of 1.25 to 2.5 mol-%. This operation is contrary to the prior art, where no residual or not decomposed hydrocarbon fluid in the synthesis gas is desired. Alternatively, the location of the inlets 6 and the operation parameters are chosen such that CO2 or H2O is introduced into the reaction chamber 2 where a temperature of 1550 to 1800° C. prevails. With respect to the fluid flow, the inlets 6 are located after the burner part 11 of the plasma burner 7.
During operation of the apparatus for producing synthesis gas, a plasma 13 is formed in the plasma reactor 1 between the electrodes near the burner part 11. The plasma 13 usually has temperatures between 5.000° C. and 10.000° C. The heat is transferred mainly by radiation to the media (gases) inside the reactor. A hydrocarbon fluid (preferably methane or natural gas) is fed into the reactor chamber 2 via the first inlets 5 for hydrocarbon fluid in a direction towards the plasma 13, wherein oxygen is excluded. In the apparatuses according to
As soon as the hydrocarbon fluid comes to a region near the plasma 13 where a decomposition temperature prevails, the hydrocarbons contained in the hydrocarbon fluid will be decomposed into C particles and gaseous hydrogen H2. For instance the hydrocarbon fluid CH4 is decomposed into C and 2 H2. The decomposition temperature depends on the supplied hydrocarbons and is e.g. more than 600° C. for natural gas or CH4. With respect to the direction of the fluid flow after the burner part 11 of the plasma burner 7, the hydrogen H2 and the C particles are present as a H2/C aerosol. The H2/C aerosol is mixed with CO2 or H2O coming from the second inlets 6 in a region in the reactor chamber 2 where between 90% and 95% of the hydrocarbon fluid is thermally decomposed. This region is near the burner part 11, so that the ripening zone, which is provided in the prior art, is not present in this case. Near the burner part 11, a high temperature of 800 to 3000° C. prevails in the reactor chamber 2. As soon as CO2 is supplied via the second inlets 6, the C particles are converted in this temperature range according to the equation C+CO2═2 CO. If H2O is supplied via the second inlets 6, the C particles are converted in this temperature range according to the equation C+H2O→CO+H2. The above mentioned reactions are executed without catalysts.
The above mentioned conversion reactions proceed fast and completely if small C particles are mixed with CO2 or H2O. With the prior art plasma reactor 1′ shown in
According to one embodiment of the invention, the skilled person can set the supply of CO2 or H2O depending on an amount of residual or not decomposed hydrocarbon fluid in the synthesis gas in the region of the outlet 15. The supply of CO2 or H2O depends on the number, size, position, and orientation of the second inlets 6 relative to the burner part 11 and from operation parameters such as pressure and supplied mass per time of the supply. Particularly, the location of the inlets 6 and the operation parameters are chosen such that the synthesis gas has an amount of residual or not decomposed hydrocarbon fluid in a range of 1.26 to 2.5 mol-%. This approach is contrary to the prior art, where no residual or not decomposed hydrocarbon fluid is present in the synthesis gas. Alternatively, the skilled person selects the location of the inlets 6 and the operation parameters such that the introduction of CO2 or H2O takes place in a region of the reactor chamber 2 where a temperature of 1550 to 1800° C. prevails, which is measured by a temperature sensor or another high temperature measuring method. In the region where CO2 or H2O are supplied, the C particles have a size of equal to or less than 250 nm, preferably equal to or less than 200 nm and particularly preferable of equal to or less than 100 nm, which leads to a fast conversion reaction and to a stabile aerosol. Malfunctions and deposits (fouling) can be avoided.
During operation of the apparatus of
During operation of the apparatus of
The operation of the apparatus of
The following features can independently be applied for all apparatuses of
It may be summarized that the following benefits can be obtained by the above described apparatus and method: deposits of C particles can be avoided; a stabile aerosol can be obtained also at substantial temperature decreases; fast conversion and reduced reaction time; compared to the prior art, lower temperature of the produces synthesis gas.
The invention has been described based on preferred embodiments, wherein individual features of the described embodiments may be combined freely and/or may be substituted as far as these features are compatible. Furthermore, individual features of the described embodiments may be omitted as long as these features are not essential. Thus, those skilled in the art will appreciate that various modifications and practical implementations are possible and obvious without departing from the full and fair scope of the present invention.
Number | Date | Country | Kind |
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10 2015 014 007.8 | Oct 2015 | DE | national |
Filing Document | Filing Date | Country | Kind |
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PCT/EP2016/075815 | 10/26/2016 | WO | 00 |