Patent Description:
Many catalytic processes are carried out in reactors which comprise catalytic beds and one or more fluid mixers each being disposed between successive catalytic beds. A fluid mixer is configured to mix first fluid coming out from a catalytic bed with second fluid fed to the fluid mixer, and to conduct the mixture of the first and second fluids to a next catalytic bed. A catalytic process can be for example hydrodeoxygenation "HDO" that removes oxygen from organic oxygen compounds as water, hydrodesulphurization "HDS" that removes sulfur from organic sulfur compounds as dihydrogensulfide H<NUM>S, hydrodenitrogenation "HDN" that removes nitrogen from organic nitrogen compounds as ammonia NH<NUM>, or hydrodechlorination "HDCI" that removes halogens e.g. chlorine from organic chloride compounds as hydrochloric acid HCl. For example, the hydrodeoxygenation "HDO" is suitable for upgrading plant oils and fats, as well as animal oils and fats, that normally contain too much oxygen to be considered diesel range hydrocarbons.

Plant oils and fats as well as animal oils and fats typically contain free fatty acids "FFA" that are very corrosive because of their acidity. Thus, free fatty acids may cause corrosion on equipment used in processes involving them, such as piping and reactors. Furthermore, free fatty acids may cause undesirable side reactions such as for example formation of harmful heavy molecular weight compounds, oligomerization, polymerization, cyclisation, aromatization, and/or cracking reactions. Therefore, when feedstock with high levels of free fatty acids and/or other organic acids is used, the equipment must be protected from corrosion. For example, in conjunction with the hydrodeoxygenation "HDO", first fluid that trickles down through a catalytic bed to a fluid mixer has a level of free fatty acids significantly lower than that of second fluid that is fed to the reactor via the fluid mixer. Thus, material surfaces which are in contact with the second fluid or with a mixture of the first and second fluids so that the local concentration of the second fluid is too high are exposed to corrosion. Corrosion prevention can be achieved by coating the exposed surfaces, adding corrosion inhibitors and/or anti-corrosion agents, and/or using corrosion resistant materials in the exposed surfaces. These corrosion prevention techniques are however not free from challenges relating to costs and/or complexity of usage. For example, <CIT> describes a method for making diesel fuel from renewable feedstock. Ammonia or amine compound is used to neutralize organic acids in the renewable feedstock. The ammonia or amine compound needs to be however removed from a product mixture before an isomerization zone to prevent the ammonia or amine compound from affecting an isomerization catalyst in an undesired way. <CIT> describes an apparatus similar to that of the invention, with static mixer, spiral flows and the relative flow guides.

The following presents a simplified summary in order to provide a basic understanding of some embodiments of the invention. In this document, the word "geometric" when used as a prefix means a geometric concept that is not necessarily a part of any physical object. The geometric concept can be for example a geometric point, a straight or curved geometric line, a geometric plane, a non-planar geometric surface, a geometric space, or any other geometric entity that is zero, one, two, or three dimensional.

In accordance with the invention, there is provided a new fluid mixer for a reactor of a hydrocarbon processing plant, e.g. a petroleum refinery. The reactor can be for example a hydrotreatment reactor such as e.g. a hydrodeoxygenation "HDO" reactor, a hydrodesulphurization "HDS" reactor, a hydrodenitrogenation "HDN" reactor, or a hydrodechlorination "HDCI" reactor. The fluid mixer is suitable for e.g. downflow -type reactors, especially trickle-bed reactors.

A fluid mixer according to the invention comprises:.

The outlet channel comprises a mixing structure that is located below an upper edge of the outlet channel and is suitable for producing turbulence in a stream of the first and second fluids flowing in the outlet channel. The mixing structure is configured to implement one or more stepwise reductions of a cross-sectional flow area of the outlet channel, wherein a wall of the outlet channel is shaped to implement at least one of the one or more stepwise reductions of the cross-sectional flow area of the outlet channel.

The mixing structure enhances mixing of the first and second fluids and thereby reduces local concentration maxima of the second fluid in the mixture of the first and second fluids. This reduces a corrosion risk of material surfaces that are in contact with the mixture of the first and second fluids coming out from the fluid mixer.

In accordance with the invention, there is provided also a new reactor for a hydrocarbon processing plant. The reactor comprises:.

In accordance with the invention, there is provided also a new method for mixing fluids in a reactor of a hydrocarbon processing plant. The method comprises:.

wherein the outlet channel comprises a mixing structure located below an upper edge of the outlet channel and producing turbulence in a stream of the first and second fluids flowing in the outlet channel. The mixing structure is configured to implement one or more stepwise reductions of a cross-sectional flow area of the outlet channel, wherein that a wall of the outlet channel is shaped to implement at least one of the one or more stepwise reductions of the cross-sectional flow area of the outlet channel.

Exemplifying and non-limiting embodiments of the invention are described in accompanied dependent claims.

Various exemplifying and non-limiting embodiments of the invention both as to constructions and to methods of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific exemplifying embodiments when read in connection with the accompanying drawings.

The features recited in the accompanied dependent claims are mutually freely combinable unless otherwise explicitly stated. Furthermore, it is to be understood that the use of "a" or "an", i.e. a singular form, throughout this document does as such not exclude a plurality.

Exemplifying and non-limiting embodiments of the invention and their advantages are explained in greater details below in the sense of examples and with reference to the accompanying drawings, in which:.

The specific examples provided in the description below should not be construed as limiting the scope and/or the applicability of the accompanied claims. Lists and groups of examples provided in the description are not exhaustive unless otherwise explicitly stated.

<FIG> shows a schematic section view of a reactor that comprises a fluid mixer <NUM> according to an exemplifying and non-limiting embodiment. The section plane is parallel with the xz-plane of a coordinate system <NUM>. The reactor can be for example a hydrotreatment reactor such as e.g. a hydrodeoxygenation "HDO" reactor, a hydrodesulphurization "HDS" reactor, a hydrodenitrogenation "HDN" reactor, or a hydrodechlorination "HDCI" reactor. The reactor comprises a reactor vessel <NUM> that contains a first catalyst bed <NUM> and a second catalyst bed <NUM>. The reactor comprises an inlet pipe <NUM> for receiving first fluid that enters a distribution tray <NUM> that distributes the first fluid evenly over the cross section of the first catalyst bed <NUM>. The fluid mixer <NUM> is located below the first catalyst bed <NUM> and thus the fluid mixer <NUM> receives the first fluid that is processed within the first catalyst bed <NUM> and trickles through the first catalyst bed <NUM>. The reactor comprises an inlet pipe <NUM> through which second fluid is fed to the fluid mixer <NUM>. The first and second fluids are mixed in the fluid mixer <NUM> and the mixture of the first and second fluids enters a distribution tray <NUM> that distributes the mixture of the first and second fluids evenly over the cross section of the second catalyst bed <NUM>. The reactor comprises an outlet pipe <NUM> through which product of the treatment process exits the reactor. In an exemplifying case where the reactor is a hydrodeoxygenation "HDO" reactor, the first fluid fed to the inlet pipe <NUM> may comprise a mixture of fresh feed substances and the product of the hydrodeoxygenation process so that a part of a material flow coming out from the outlet pipe <NUM> is fed back to the inlet pipe <NUM>. The fresh feed substances may comprise e.g. plant oils, plant fats, animal oils, and/or animal fats. The second fluid that is fed to the inlet pipe <NUM> may comprise the fresh feed substances. The second fluid may also act as temperature control medium with the aid of which the temperature of the treatment process can be controlled at least partly. More than two catalyst beds may also be used so that there is a fluid mixer between successive ones of the catalyst beds. The number of fluid mixers is typically N - <NUM> where N is the number of catalyst beds.

The fluid mixer <NUM> is illustrated in more details in <FIG>. In this exemplifying case, the fluid mixer <NUM> comprises a frame structure that has an upper section <NUM> and a lower section <NUM>. <FIG> shows the fluid mixer without the upper section <NUM>. The frame structure defines a mixing chamber <NUM> and first inlets <NUM> and <NUM> for conducting the first fluid to the mixing chamber <NUM> from above the mixing chamber <NUM>. As shown in <FIG>, the mixing chamber <NUM> is substantially cylindrical and the first inlets <NUM> and <NUM> are shaped to conduct the first fluid along a side wall of the mixing chamber <NUM> to produce a spiral stream in the mixing chamber <NUM>. In this exemplifying case, the first inlets <NUM> and <NUM> are placed equidistantly on the periphery of the mixing chamber <NUM> so that the first inlets <NUM> and <NUM> are on opposite sides of the mixing chamber <NUM>. The fluid mixer comprises second inlets <NUM> and <NUM> for conducting the second fluid tangentially into the spiral stream. The second inlets <NUM> and <NUM> are connected to inlet pipes shown in <FIG> so that e.g. the second inlet <NUM> is connected to the inlet pipe <NUM>. As illustrated in <FIG>, each opening of the second inlets is a distance away from the side wall of the mixing chamber <NUM> to reduce concentration of the second fluid at the side wall of the mixing chamber. In <FIG>, one of the openings of the second inlets is denoted with a reference <NUM>. In this exemplifying fluid mixer, the second inlets <NUM> and <NUM> are placed equidistantly on the periphery of the mixing chamber <NUM> so that the second inlets <NUM> and <NUM> are on opposite sides of the mixing chamber <NUM>. In this exemplifying case, each of the second inlets <NUM> and <NUM> comprises a tube protruding radially from the side wall of the mixing chamber <NUM> towards the center of the mixing chamber <NUM>, wherein the tube has a closed end and a side wall of the tube has the openings for passing the second fluid tangentially into the spiral stream occurring in the mixing chamber <NUM>.

The fluid mixer <NUM> comprises an outlet channel <NUM> that is substantially concentric to the mixing chamber <NUM> and conducts the first and second fluids downwards out from the mixing chamber <NUM>. The outlet channel <NUM> comprises a mixing structure <NUM> that is located below the upper edge of the outlet channel <NUM> and that produces turbulence in a stream of the first and second fluids flowing in the outlet channel <NUM>. In this exemplifying case, the mixing structure <NUM> is a stepwise reduction of the cross-sectional flow area of the outlet channel so that the stepwise reduction is located below the bottom of the mixing chamber <NUM>. According to computer simulations, the stepwise reduction of the cross-sectional flow area improves the mixing effect so that the maximum local concentration of the second fluid is about <NUM> % less than when using a corresponding fluid mixer without the stepwise reduction of the cross-sectional flow area in an exemplifying test case where the amount of the second fluid is about <NUM> weight-% of the mixture of the first and second fluids i.e. in ideal mixing the concentration of the second fluid would be about <NUM> weight-% all over the mixture.

<FIG> illustrates a part of a fluid mixer according to an exemplifying and non-limiting embodiment. The fluid mixer comprises a mixing chamber <NUM> and a first inlet <NUM> for conducting first fluid to the mixing chamber <NUM> from above the mixing chamber. The mixing chamber <NUM> is substantially cylindrical and the first inlet <NUM> is shaped to conduct the first fluid along a side wall of the mixing chamber <NUM> to produce a spiral stream in the mixing chamber <NUM>. The fluid mixer comprises a second inlet <NUM> for conducting second fluid tangentially into the spiral stream. As shown in <FIG>, an opening <NUM> of the second inlet <NUM> is a distance away from the side wall of the mixing chamber <NUM> to reduce concentration of the second fluid at the side wall of the mixing chamber <NUM>. In this exemplifying case, the second inlet <NUM> comprises a tube protruding radially from the side wall of the mixing chamber <NUM> towards the center of the mixing chamber <NUM>, wherein the tube is curved so that an end of the tube is tangential for passing the second fluid tangentially into the spiral stream occurring in the mixing chamber <NUM>.

The fluid mixer comprises an outlet channel <NUM> that is substantially concentric to the mixing chamber <NUM> and conducts the first and second fluids downwards out from the mixing chamber <NUM>. The outlet channel <NUM> comprises a mixing structure <NUM> that is located below the upper edge of the outlet channel <NUM> and that produces turbulence in a stream of the first and second fluids flowing in the outlet channel <NUM>. In this exemplifying case, the mixing structure <NUM> is a stepwise reduction of the cross-sectional flow area of the outlet channel so that the stepwise reduction is located substantially in flush with the bottom of the mixing chamber <NUM>. In this exemplifying case, the outlet channel <NUM> comprises a loop-shaped ridge <NUM> on the bottom of the mixing chamber <NUM>. The loop-shaped ridge <NUM> constitutes an upper portion of the outlet channel <NUM> and thus the upper rim of the loop-shaped ridge <NUM> constitutes the upper edge of the outlet channel <NUM>.

<FIG> illustrates a part of a fluid mixer according to an exemplifying and non-limiting embodiment. The fluid mixer comprises a mixing chamber <NUM> and a first inlet <NUM> for conducting first fluid to the mixing chamber <NUM> from above the mixing chamber <NUM>. The mixing chamber <NUM> is substantially cylindrical and the first inlet <NUM> is shaped to conduct the first fluid along a side wall of the mixing chamber <NUM> to produce a spiral stream in the mixing chamber <NUM>. The fluid mixer comprises a second inlet <NUM> for conducting second fluid tangentially into the spiral stream. In this exemplifying fluid mixer, the second inlet <NUM> comprises protrusions on the bottom of the mixing chamber <NUM>. Each of the protrusions is provided with an opening for passing the second fluid tangentially into the spiral stream. In this exemplifying case, the protrusions are located at a place of the bottom of the mixing chamber <NUM> where the first inlet <NUM> joins the mixing chamber <NUM>. <FIG> shows a magnified section view of one of the protrusions. The section plane is parallel with the xz-plane of a coordinate system <NUM>.

The fluid mixer comprises an outlet channel <NUM> that is substantially concentric to the mixing chamber <NUM> and conducts the first and second fluids downwards out from the mixing chamber <NUM>. The outlet channel <NUM> comprises a mixing structure <NUM> that is located below the upper edge of the outlet channel and that produces turbulence in a stream of the first and second fluids flowing in the outlet channel <NUM>. In this exemplifying case, the outlet channel <NUM> is like the outlet channel <NUM> of the fluid mixer <NUM> shown in <FIG>.

In the exemplifying fluid mixers illustrated in <FIG>, <FIG>, and <FIG>, the outlet channels are substantially circularly symmetric with respect to a vertical geometric line. It is however also possible that an outlet channel of a fluid mixer according to an exemplifying and non-limiting embodiment has a non-circular cross-sectional shape, e.g. oval, polygon, etc. In the exemplifying fluid mixers illustrated in <FIG>, <FIG>, and <FIG>, each first inlet is shaped to descend to the mixing chamber in a form of a curved ramp. It is however also possible that each first inlet of a fluid mixer according to an exemplifying and non-limiting embodiment is implemented with a curved tube for producing a spiral stream in a mixing chamber. The exemplifying fluid mixer illustrated in <FIG> comprises two first inlets and two second inlets, whereas the exemplifying fluid mixer illustrated in <FIG> comprises one first inlet and one second inlet. It is also possible that a fluid mixer according to an exemplifying and non-limiting embodiment comprises three or more first inlets and/or three of more second inlets.

<FIG> show section views of outlet channels of fluid mixers according to exemplifying and non-limiting embodiments. The section plane is parallel with the yz-plane of a coordinate system <NUM>. <FIG> shows an outlet channel 508a that comprises a mixing structure 509a that is located below the upper edge of the outlet channel 508a and produces turbulence in a stream of fluids flowing in the outlet channel 508a. The mixing structure 509a comprises a loop-shaped mixing ridge <NUM> on an upwards facing surface <NUM> of the outlet channel 508a, where the upwards facing surface <NUM> implements a stepwise reduction of the cross-sectional flow area of the outlet channel 508a. <FIG> shows an outlet channel 508b that comprises a mixing structure 509b that is located below the upper edge of the outlet channel 508b and produces turbulence in a stream of fluids flowing in the outlet channel 508b. The mixing structure 509b comprises loop-shaped mixing ridges <NUM> on a vertical surface of the outlet channel 508b. The loop-shaped mixing ridges <NUM> implement two stepwise reductions and two stepwise expansions of the cross-sectional flow area of the outlet channel 508b. <FIG> shows an outlet channel 508c that comprises a mixing structure 509c that produces turbulence in a stream of fluids flowing in the outlet channel 508c. The mixing structure 509c comprises a mixing element <NUM> mechanically supported inside the outlet channel 508c and implementing at least one stepwise reduction of the cross-sectional flow area of the outlet channel 508c. In this exemplifying case, the mixing element <NUM> is located below the upper edge of the outlet channel 508c. It is however also possible that only a part of the mixing element is below the upper edge of the outlet channel 508c. As shown in <FIG>, there are bar-shaped support elements in the outlet channel 508c so that the support elements mechanically support the mixing element <NUM>. One of the support elements is denoted with a reference <NUM>. The support elements may also improve the mixing.

It is to be noted that the above-presented mixing structures are non-limiting examples only, and many different mechanical shapes and arrangements can be used for producing turbulence in a stream of fluids flowing in an outlet channel of a fluid mixer. For example, it is possible to implement a combination of one or more of the above-presented mixing structures.

<FIG> shows a flowchart of a method according to an exemplifying and non-limiting embodiment for mixing fluids in a reactor of a hydrocarbon processing plant. The method comprises:.

In a method according to an exemplifying and non-limiting embodiment, the first fluid flows to the mixing chamber from a bottom of a first catalytic bed of the reactor and a mixture of the first and second fluids is conducted to a top of a second catalytic bed of the reactor. In an exemplifying case where the reactor comprises three or more catalytic beds, the above-mentioned first and second catalytic beds can be any two successive catalytic beds of the reactor. Furthermore, the method can be carried out between each successive two of the catalytic beds.

In a method according to an exemplifying and non-limiting embodiment, the mixing structure is located below the bottom of the mixing chamber.

In a method according to an exemplifying and non-limiting embodiment, the mixing structure implements one or more stepwise reductions of the cross-sectional flow area of the outlet channel.

In a method according to an exemplifying and non-limiting embodiment, a wall of the outlet channel is shaped to implement at least one stepwise reduction of the cross-sectional flow area of the outlet channel.

In a method according to an exemplifying and non-limiting embodiment, the mixing structure comprises a loop-shaped mixing ridge on an upwards facing surface of the outlet channel, where the upwards facing surface implements a stepwise reduction of the cross-sectional flow area of the outlet channel.

In a method according to an exemplifying and non-limiting embodiment, the mixing structure comprises a mixing element mechanically supported inside the outlet channel and implementing at least one stepwise reduction of the cross-sectional flow area of the outlet channel.

In a method according to an exemplifying and non-limiting embodiment, the outlet channel comprises a loop-shaped ridge on the bottom of the mixing chamber, where the loop-shaped ridge constitutes an upper portion of the outlet channel and the upper rim of the loop-shaped ridge constitutes the upper edge of the outlet channel.

In a method according to an exemplifying and non-limiting embodiment, the outlet channel is substantially circularly symmetric with respect to a vertical geometric line.

In a method according to an exemplifying and non-limiting embodiment, the first inlet is shaped to descend to the mixing chamber in a form of a curved ramp.

In a method according to an exemplifying and non-limiting embodiment, the second inlet comprises a tube protruding radially from the side wall of the mixing chamber towards the center of the mixing chamber and having one or more openings for passing the second fluid tangentially into the spiral stream. The tube can be for example curved so that an end of the tube is tangential for passing the second fluid tangentially into the spiral stream. For another example, the tube can have a closed end and a side wall of the tube can have one or more openings for passing the second fluid tangentially into the spiral stream.

In a method according to an exemplifying and non-limiting embodiment, the second inlet comprises one or more protrusions located on the bottom of the mixing chamber and each being provided with an opening for passing the second fluid tangentially into the spiral stream. The one or more protrusions can be located for example at a place of the bottom of the mixing chamber where the first inlet joins the mixing chamber.

In a method according to an exemplifying and non-limiting embodiment, the first inlet is one of at least two first inlets placed substantially equidistantly on the periphery of the mixing chamber.

In a method according to an exemplifying and non-limiting embodiment, the second inlet is one of at least two second inlets placed substantially equidistantly on the periphery of the mixing chamber.

Claim 1:
A fluid mixer (<NUM>) comprising:
- a frame structure (<NUM>, <NUM>) defining a mixing chamber (<NUM>, <NUM>, <NUM>) and at least one first inlet (<NUM>, <NUM>, <NUM>, <NUM>) for conducting first fluid to the mixing chamber from above the mixing chamber, the mixing chamber being substantially cylindrical and the first inlet being shaped to conduct the first fluid along a side wall of the mixing chamber to produce a spiral stream in the mixing chamber,
- at least one second inlet (<NUM>, <NUM>, <NUM>, <NUM>) for conducting second fluid tangentially into the spiral stream, each opening (<NUM>, <NUM>) of the second inlet being inside the mixing chamber and a distance away from the side wall of the mixing chamber to reduce concentration of the second fluid at the side wall of the mixing chamber, and
- an outlet channel (<NUM>, <NUM>, <NUM>, 508a-508c) for conducting the first and second fluids downwards out from the mixing chamber, the outlet channel being concentric to the mixing chamber,
wherein the outlet channel comprises a mixing structure (<NUM>, <NUM>, <NUM>, 509a, 509b) for producing turbulence in a stream of the first and second fluids flowing in the outlet channel, the mixing structure being located below an upper edge of the outlet channel, wherein the mixing structure (<NUM>, <NUM>, <NUM>, 509a, 509b) is configured to implement one or more stepwise reductions of a cross-sectional flow area of the outlet channel, characterized in that a wall of the outlet channel (<NUM>, <NUM>, <NUM>, 508a, 508b) is shaped to implement at least one of the one or more stepwise reductions of the cross-sectional flow area of the outlet channel.