Patent Description:
Hydrocarbons may be indirectly obtained by specific chemical reactions e.g. Fischer-Tropsch (FTS) reaction or Sabatier reaction. FTS is a reaction that transforms hydrogen and carbon monoxide gases into hydrocarbons. Besides, methane is obtained from hydrogen and carbon monoxide and/or carbon dioxide gases by a Sabatier Reaction also known as hydrogenation of carbon dioxide or methanation. Both reactions usually take place between <NUM> - <NUM>. Regarding pressure, FTS normally occurs between <NUM> - <NUM> bar, and Sabatier reaction may happen between <NUM> - <NUM> bar.

The use of solid catalysts to accelerate these reactions is a common practice.

FTS and Sabatier reactions are highly exothermic i.e. a large amount of heat is released as a consequence of the process. Exothermic reactions take place in adapted reactors that are continuously cooled in order to dissipate the heat released by the reaction. Heat transfer is a key point to get the reaction under controlled conditions and achieve high efficiencies in the reaction.

Current industrial cooling processes show a limited efficiency, and so an isothermal regime is not always reached. In both reactions, the isothermal conditions corresponding to the optimal temperature for the desired products should be assured.

Depending on the operating conditions, the FTS can produce a wide range of olefins, paraffin and oxygenated products (alcohols, aldehydes, acids and ketones). This range of different products is influenced by combinations of variables e.g. temperature, feeding gas composition, pressure, catalyst type and promoters. In this sense, depending on the catalyst and type of process employed, hydrocarbons ranging from methane to higher molecular paraffins and olefins can be obtained. Although differences in the product distribution for different catalysts at similar temperatures and pressures can be observed, in general, the product distribution is primarily driven by the operating temperature: higher temperatures than <NUM> shift selectivity towards lower carbon number products and more hydrogenated products.

Concerning to the Sabatier reaction, this is thermodynamically favored at relatively low temperatures and high pressures. The reaction is highly exothermal and the adiabatic temperature rises highly as the reaction progresses. As the temperature increases, the chemical equilibrium of the methane formation process shifts towards the reactants. The reaction reaches an equilibrium state at high temperatures depending on the prevailing pressure and that limits the CO2 conversion. Thus, the greatest challenge involved in exothermic reactions such us methanation is the temperature control. Indeed, the reactor design is closely linked to an efficient heat removal.

Some kinetic problems could happen when the released heat is not properly dissipated due to the high temperatures in the reactor resulting in e.g. catalyst deactivation because of the creation of hot spots in the catalytic bed.

Additionally, when reactors for catalytic reactions are designed, a wide contact surface is sought in order to increase both gas-solid contact and heat transfer. Several reactors configurations are designed in order to improve the multiphasic reactants i.e. more than one state of matter, and some of the most promising are the microreactors. The microreactors or microchannel reactors allow a high contact surface between gas and solid material and dissipate the heat properly.

The conventional manufacturing technique used to make microchannel reactors i.e. stacking different featured layers and then joining them together, implies several phases to construct and to assemble one reactor. Numerous pieces have to be stacked together and could lead assembling problems. The bigger stacks reactors, the more serious problems and more materials required and more overall costs and required time to assemble it appear. at the same time the gas-solid contact, having reduced the required assembling steps and minimizing the overall costs.

<NPL> describes use of selective laser melting to fabricate micro cross-flow heat exchangers from <NUM> Stainless Steel powder.

There is provided a reaction unit according to the independent claim. Other aspects of the invention are set forth in the dependent claims.

The use of a plurality of parallel tubes having a narrow internal diameter improves the reaction output. The gas-solid contact between reactants and catalyst is increased and as energy transfer is improved, isothermal conditions are achieved. As a result, an improved output is achieved.

Besides, the use of a body manufactured in a single part provides a compact, secure, flexible and homogeneous reactor. In the present application, the term body manufactured in a single part must be understood as a body comprising only one, individual, integral piece. In other words, a body which has not been formed by parts, e.g. tubes, manufactured separately and then joined together e.g. by welding.

According to an example, the reactor could integrate fins attached on the outer surface of the tubes. These fins may connect each tube to other adjacent tubes. The use of fins enhances the energy transfer from or to the reaction.

According to an example, the body of the reactor is built by an additive manufacturing technique. The use of this manufacturing process allows a more flexible design of the reactor than when using other techniques, which leads to save materials and time.

In a preferred example, the additive manufacturing technique is Selective Laser Melting. By using this technique, a reliable reactor having the required accurate dimensions and characteristics is obtained.

In a second aspect, a reaction unit for exothermic or endothermic reactions which comprises a reactor according to any of the disclosed examples and a housing for receiving the reactor and inlets/outlets, is provided. The reaction unit may comprise an inlet for feeding the reactants into the tubes and an outlet for collecting the reaction products. The reaction unit may additionally comprise an inlet and an outlet to enable a thermal fluid to flow inside the housing and around the tubes of the reactor and may also comprise a preheater to regulate the temperature of the reactants before feeding them into the tubes.

In a third aspect, a method for manufacturing a reactor according to any of the disclosed examples is disclosed. Firstly, a metal powder layer is spread onto a substrate. Secondly, the metal powder layer is selectively melted. Previous steps are repeated until the reactor is finished.

also fixed by an adhesive or they may be welded to the external element. Any other suitable manner may be used to fix the reactor <NUM> to an external element.

For example, connector <NUM> may be used as inlet connector to feed the tubes <NUM> with reactants, e.g. carbon dioxide and hydrogen in Sabatier reaction, while connector <NUM> may be used as outlet connector to collect reaction products e.g. methane and water in a Sabatier reaction. Such reactants may be previously heated in a preheater e.g. a coil.

<FIG> shows in cross-section an array of parallel tubes <NUM> according to an example. In <FIG>, fins attached on the outer surfaces of the tubes <NUM> and tubes internal diameters Φ are depicted. According to an example fins length, and so, the distance between adjacent tubes, may be of about <NUM>. According to another example, the internal diameter Φ of the tubes <NUM> may be less than <NUM>, preferably between <NUM> - <NUM> and more preferably between <NUM> - <NUM>.

This range has been found suitable for containing e.g. catalyst particles, but also for achieving a high gas-solid contact between the reactants and catalyst increasing the efficiency of the reactor <NUM>.

The parallel tubes <NUM> may contain a catalyst e.g. catalyst particles, to increase the reaction rate. Depending on the reaction, different catalysts may be used, e.g. in case of a Fischer-Tropsch reaction such catalyst particles may be based on Fe or Co, and in case of a Sabatier reaction those particles may be based on Ni or Ru.

Catalyst particles may have a particle size between <NUM> - <NUM> and/or a density about <NUM> - <NUM>/cm<NUM>.

When carrying out catalytic reactions, the reactor <NUM> may comprise a metallic filter (not shown) at the outlet of the tubes <NUM> to avoid catalyst loss.

<FIG> shows a top view of a reactor <NUM> comprising a connector <NUM> with holes <NUM> which may receive screws to fix the reactor <NUM> to an external element. The reactor <NUM> shown in <FIG> may also comprise holes <NUM>, in be used, e.g. in case of a Fischer-Tropsch reaction such catalyst particles may be based on Fe or Co, and in case of a Sabatier reaction those particles may be based on Ni or Ru.

<FIG> shows a top view of a reactor <NUM> comprising a connector <NUM> with holes <NUM> which may receive screws to fix the reactor <NUM> to an external element. The reactor <NUM> shown in <FIG> may also comprise holes <NUM>, in correspondence with the parallel tubes, which may be used as inlet for reactants in inlet connector <NUM>. Finally, connector <NUM> (not shown) placed at the opposite end of the parallel tubes may be used as outlet for reaction products.

The reactor module <NUM> may further be part of an exemplary reaction unit <NUM> shown in <FIG>. The reactor unit <NUM> may comprise a housing <NUM> for receiving at least a reactor module <NUM> and a plurality of anchoring elements (not shown) to receive e.g. screws, for securing the reaction unit <NUM>. The number of modules <NUM> may be modified depending on the targeted capacity production rate. The housing <NUM> should be provided an inlet <NUM> (indicated by an arrow) for feeding reaction products into the tubes <NUM> and an outlet <NUM> (also indicated by an arrow) for collecting reaction products. When more than one single reaction module <NUM> is implemented, the reaction products may be firstly collected in individual reaction product collectors that may converge in a collective reaction product collector which may be connected to the reaction product outlet <NUM>.

The housing <NUM> may further comprise a thermal fluid inside the housing (not shown) in which the reactor modules <NUM>, or at least the reactor tubes <NUM>, may be immersed. A thermal fluid may be any fluid e.g. thermal oil, which enables heat transfer and capable of being warmed or cooled depending on the requirements of each case. Therefore, a thermal fluid may be cooled to may be located inside or outside the housing <NUM>. To do so, the reactor unit <NUM> may comprise an inlet <NUM> and an outlet <NUM> (both indicated by an arrow) for the thermal fluid flow. The fluid may flow continuously and, consequently, an isothermal medium e.g. at reaction temperature, which contributes to improve the reaction may be created. A pump (not shown) may be used to maintain the fluid flow at a desired rate e.g. a rate that minimizes the gradient between the thermic fluid and the reactor output gases.

Reaction unit <NUM> (see <FIG>) may additionally comprise a distribution chamber (not shown) for feeding the tubes <NUM> with e.g. gaseous reactants, in a homogeneous manner.

In a further example, reaction unit <NUM> may further comprise thermocouple nozzles (not shown) to connect thermocouples and measure temperature inside the housing <NUM>. Additionally, the reaction unit <NUM> may further comprise a coil immersed in the thermic fluid so as to put the reactants into the reaction temperature by e.g. warming it.

In an example, the reaction unit <NUM> shown in <FIG> may comprise <NUM> reaction modules, each of them having <NUM> parallel tubes. However, both the number of reactors and/or the number of parallel tubes may be determined e.g. for a target production. In another example, the reaction unit may comprise <NUM> reactors, each them comprising <NUM> parallel tubes.

The number of parallel tubes <NUM> may depend not only on the reaction and/or its variables but on the gas flow and the catalyst performance. For example, in a reactor where the tubes have an internal diameter of <NUM> and a length of <NUM>, and the catalyst density is <NUM>/cm<NUM>, the number of tubes for different reactions and parameters is summarized below:.

e.g. for a target production. In another example, the reaction unit may comprise <NUM> reactors, each them comprising <NUM> parallel tubes.

In the table, T is the reaction temperature range measured in degrees Celsius, P is the gas line pressure measured in bars, Q is the gas flow measured in liters per hour, M is the total catalyst mass used in the reactor measured in grams and N is the number of tubes in the reactor of each example.

Furthermore, the reactor may be designed to have an elevated length to diameter ratio and thus a higher amount of tube surface in contact with a thermal fluid. According to an example, the length of each tube may be <NUM> - <NUM> and the internal diameter may be <NUM> - <NUM>. The wall thickness of the parallel tubes <NUM> may be e.g. about <NUM> - <NUM>, to further improve heat dissipation while maintaining mechanical strength to support the pressures.

The reactor design parameters such as material selections, parallel tubes internal diameter, wall thickness, geometry; the number and distribution of tubes and fins, etc., may be selected according to requirements of each case taking into consideration the reactant media, catalyst particle size, the pressure, temperature, etc.
powder may be e.g. stainless steel or FeCr alloy, and the thickness of each layer may be between <NUM> - <NUM>. Finally, the additive manufacturing machine, and according to the loaded 2D file, may selectively melt <NUM> the layer of metal powder. After selectively melting the metal powder layer, the substrate plate may be lowered <NUM>. These steps may be repeated until the reactor is finished and then, the remaining powder may be removed. The finished reactor may further be subjected to finishing operations.

Such manufacturing method allows obtaining a reactor with the required dimensions, suitable for enhancing both gas-solid contact and energy transfer while at the same time improves the output of the reactor and the required thermal stability to provide an effective reaction i.e. as an isothermal environment is achieved. At the same time, the manufactured reactor is compact, stable and homogeneous and it has reliable mechanical properties. Moreover, as the reactor is free from joints, the risk of leaks is avoided.

Although only a number of examples have been disclosed herein, other alternatives, modifications, uses and/or equivalents thereof are possible.

Claim 1:
A reaction unit (<NUM>) comprising:
- a reactor (<NUM>) for multiphasic reactions comprising:
a body (<NUM>) manufactured in a single part by Selective Laser Melting, SLM, forming a plurality of parallel tubes (<NUM>) containing catalyst particles to increase a reaction rate and intended to contact a reactant that circulates within the tubes (<NUM>) during operation of the reactor (<NUM>),
an inlet (<NUM>) for feeding the reactant into the tubes (<NUM>) and an outlet (<NUM>) for collecting reaction products,
- a housing (<NUM>) for receiving the reactor (<NUM>) with an inlet (<NUM>) and an outlet (<NUM>) for the flow of a thermal fluid inside the housing (<NUM>) and around the tubes (<NUM>) of the reactor (<NUM>), and
- a preheater to regulate a reactant temperature before feeding the reactant into the tubes (<NUM>),
wherein an internal diameter of the tubes (<NUM>) is <NUM> - <NUM>.