Control device for controlling the temperature of a process gas and heat exchanger with a control device

Description

Technical field of the invention

[0001] The invention relates to a control device for controlling the temperature of a process gas, in particular for controlling the temperature of a process gas in a heat exchanger. The invention further relates to a heat exchanger comprising a control device according to the invention. State of the art

[0002] Heat exchangers for cooling hot process gases, for example from petrochemical plants such as steam reformers, are well known in the art. Such heat exchangers are often designed as shell-and-tube heat exchangers, comprising a bundle of indirectly cooled heat exchanger tubes carrying process gas and a bypass tube, often located centrally, which also carries process gas. In the heat exchanger tubes, the hot process gas is cooled by a cooling medium conducted in a shell space of the heat exchanger. The process gas conducted in the bypass tube is not cooled or is only cooled insignificantly because the bypass tube has a much larger diameter than the heat exchanger tubes. Alternatively, the bypass tube can also be routed outside the shell of the heat exchanger, so that the portion of the process gas flowing through the bypass tube is not cooled at all.

[0003] The cooling medium used, usually water, is converted into steam and can be used for other purposes, such as heating steam or process steam. Heat exchangers of this type are often referred to as waste heat boilers.

[0004] The temperature of the process gas at the heat exchanger outlet is controlled by the amount of process gas passing through the heat exchanger tubes or the bypass tube. Often, the sole control of the flow rate through the bypass tube is used, with corresponding control devices located within the bypass tube serving as temperature control devices.

[0005] Another prior art solution is known from EP 0 617 230 B1. Here, the heat exchanger comprises at least two tube bundles, each of which is provided with a dedicated gas flow control device. The flow distribution and flow rate between the different tube bundles are controlled to regulate the temperature of the process gas at the heat exchanger outlet.

[0006] The damper-based temperature control devices commonly used in industry often do not allow the maximum possible control range, i.e., from no flow through the bypass to full flow through the bypass. This may be due to the fact that damper control creates a pressure drop that shifts the flow from the main cooling surface of the heat exchanger to the bypass (and vice versa). The main cooling surface is defined by the heat exchanger tubes, which are indirectly cooled by the cooling medium.

[0007] Undesirable (leakage) flows also often occur within the heat exchanger itself if the corresponding temperature control device is not completely sealed. This is particularly the case with damper-based systems.

[0008] In known industrially applied solutions, a complete closure of the bypass pipe (no flow through the bypass pipe) is therefore not readily possible. This limitation of the control range means that the main cooling surface must be designed larger than necessary to compensate for this constant hot process gas flow through the bypass pipe.

[0009] Also, fully opening the bypass pipe while simultaneously interrupting the flow from the main cooling surface is not readily possible in known industrially applied solutions. This limitation can limit the overall capacity of the plant for operation at low loads, since the required minimum outlet temperature of the process gas from the heat exchanger can only be achieved above a certain (higher) plant load.

[0010] Considering the potential failure of the temperature control device and its actuator, which could lead to an undesirable complete opening of the bypass tube, the maximum opening rate of the bypass tube should be mechanically limited for the worst-case critical design case. This design case is typically defined as the plant operating at full load and, in particular, the internal fouling of the heat exchanger tubes being maximal. The heat transfer to the process gas is therefore significantly poorer than with unfouled heat exchanger tubes, and the temperature of the cooled process gas is correspondingly higher.

[0011] A temperature control device which, in the event of a fault, closes with spring support and thus reduces the flow through the bypass pipe to zero is not desirable, since an uncontrolled closing of the bypass can reduce the outlet temperature of the process gas (mixed from uncooled and cooled process gas) below a defined minimum temperature, which is required for the safe operation of downstream system components.

[0012] EP 1 498 678 discloses a heat exchanger with a bypass tube that is tightly connected to a guide tube, wherein a piston designed as a closure member is axially displaceably arranged in the guide tube. The piston is double-walled, and cooling channels through which a coolant flows are arranged in the double wall of the piston.

[0013] DE 10 2012 007 721 A1 discloses a process gas cooler with lever-controlled process gas cooler flaps. A flap shaft is provided, which is connected to a drive body by means of levers and connecting rods in such a way that the gas flow rate and flow rate of the process gas through the process gas cooler flaps can be controlled externally using the drive body.

[0014] EP 3 159 646 A1 discloses a heat exchanger with a control device comprising a throttle valve connected to a drive for adjusting a gas outlet temperature of the heat exchanger to a specific temperature range. An outlet velocity and outlet quantity of the uncooled exhaust gas flow from the bypass pipe can be controlled by a throttle valve arranged at the outlet end of a bypass pipe and adjustable by means of the drive of the control device. The throttle valve is made of a material resistant to high-temperature corrosion in a temperature range sensitive to high-temperature corrosion.

[0015] DE-A-2846455 discloses another heat exchanger with a control device for setting a gas outlet temperature of the heat exchanger to a specific temperature range. Description of the invention

[0016] An object of the present invention is to at least partially overcome the disadvantages of the prior art.

[0017] In particular, it is an object of the present invention to provide a control device for controlling the temperature of a process gas, which enables the largest possible control range with regard to the process gas temperature to be set.

[0018] In particular, it is an object of the present invention to provide a control device for controlling the temperature of a process gas, which comprises the control of the entire temperature range from maximally cooled process gas to uncooled process gas.

[0019] Another object of the present invention is to provide a control device for controlling the temperature of a process gas, which minimizes the occurrence of leakage flows with respect to the process gas flow.

[0020] A further object of the present invention is to provide a control device for controlling the temperature of a process gas, which, in the event of a technical failure of the control device, does not lead to a state in which a maximum permissible outlet temperature of the process gas can be exceeded.

[0021] A further object of the present invention is to provide a heat exchanger with a control device for controlling the temperature of a process gas, which at least partially solves at least one of the aforementioned objects.

[0022] A contribution to at least partially fulfilling at least one of the above objects is made by the independent claims. The dependent claims provide preferred embodiments that contribute to at least partially fulfilling at least one of the objects. Preferred embodiments of components of one category of the invention are, where applicable, also preferred for components of the same name or corresponding components of another category of the invention.

[0023] The expressions "comprising," "comprising," or "containing," etc., do not exclude the possibility of additional elements, ingredients, etc. The indefinite article "a" does not exclude the possibility of a plural.

[0024] According to one aspect of the present invention, a control device for controlling the temperature of a process gas is proposed, comprising an outer housing; an inflow chamber for cooled process gas arranged within the outer housing, wherein the inflow chamber is fluidically connected to at least one cold gas line for conducting the cooled process gas; an outflow chamber for temperature-controlled process gas arranged within the outer housing; an outlet nozzle extending through the outer housing in the region of the outflow chamber, wherein the outlet nozzle is configured to discharge the temperature-controlled process gas from the outer housing; a mechanical separating element spatially separating the inflow chamber and the outflow chamber; an inner housing with an interior space, wherein the interior space is fluidically connected to at least one hot gas line for conducting hot process gas, wherein the inner housing extends within the inflow chamber and through the mechanical separating element into the outflow chamber,wherein the inner housing comprises a first housing inlet opening which is arranged such that the hot process gas can flow into the interior of the inner housing, and wherein the inner housing comprises a second housing inlet opening which is arranged such that cooled process gas can flow into the interior of the inner housing, and wherein the inner housing comprises a housing outlet opening which is arranged such that temperature-controlled process gas can flow out of the interior of the inner housing into the outflow space; a piston which can be flowed through and is designed as a hollow body and has a piston interior, wherein the piston is displaceable in the axial direction within the inner housing via an actuator, wherein the piston comprises a first piston inlet opening which is arranged such that hot process gas can flow into the piston interior, and wherein the piston comprises a second piston inlet opening which is arranged such thatthat cooled process gas can flow into the piston interior, and wherein the piston comprises a piston outlet opening which is arranged such that temperature-controlled process gas can flow out of the piston interior into the interior of the inner housing, wherein the second housing inlet opening of the inner housing and the second piston inlet opening are arranged relative to one another such that a freely flowable cross-sectional area of ​​the second piston inlet opening can be changed by displacing the piston in the axial direction, whereby a quantity of cooled process gas can be regulated, which can flow into the piston interior via the second housing inlet opening of the inner housing and via the second piston inlet opening.

[0025] The control device according to the invention has an inner housing which extends from an inflow chamber of the control device through a mechanical separating element into an outflow chamber, and a piston designed as a hollow body which is arranged within the inner housing and is displaceable in the axial direction within the inner housing. The inner housing has openings through which hot process gas can flow into the inner housing via the first housing inlet opening and cooled process gas can flow into the inner housing via the second housing inlet opening. Furthermore, the inner housing has at least one further opening, here a housing outlet opening, through which temperature-controlled process gas can flow out of the interior of the inner housing into the outflow chamber.

[0026] The piston, which is designed as a hollow body and through which flow can pass, has corresponding openings. Hot process gas can flow into the piston interior via a first piston inlet opening, in particular after it has passed through the first housing inlet opening of the inner housing. Cooled process gas can flow into the piston interior via the second piston inlet opening, in particular after it has passed through the second housing inlet opening of the inner housing. The hot process gas and the cooled process gas are mixed in the piston interior. This mixing makes the temperature-controlled process gas available. This can then first pass through the piston outlet opening, can thereby flow into the interior of the inner housing, and can then pass through the housing outlet opening of the inner housing, in particular.The temperature-controlled process gas can then flow into the outlet chamber, as the inner housing extends through the mechanical separating element into the outlet chamber, and the housing outlet opening is arranged so that temperature-controlled process gas can flow from the interior of the inner housing into the outlet chamber. The temperature-controlled process gas can then flow out of the control device via the outlet nozzle.

[0027] The inner housing comprises a first housing inlet opening which is arranged such that hot process gas can flow into the interior of the inner housing, in particular from the at least one hot gas line into the interior of the inner housing.

[0028] The inner housing comprises a second housing inlet opening which is arranged such that cooled process gas can flow into the interior of the inner housing, in particular from the inflow space into the interior of the inner housing.

[0029] The interior of the inner housing is fluidically connected to at least one hot gas line for conducting hot process gas, in particular fluidically connected to the at least one hot gas line via the first housing inlet opening. Furthermore, the interior of the inner housing is fluidically connected to the inflow chamber, in particular fluidically connected to the inflow chamber via the second housing inlet opening. Furthermore, the interior of the inner housing is fluidically connected to the outflow chamber, in particular fluidically connected to the outflow chamber via the housing outlet opening.

[0030] The piston comprises a first piston inlet opening which is arranged such that hot process gas can flow into the piston interior, in particular from the interior of the inner housing into the piston interior.

[0031] The piston comprises a second piston inlet opening which is arranged such that cooled process gas can flow into the piston interior, in particular from the inflow space into the piston interior.

[0032] The piston comprises a piston outlet opening which is arranged so that temperature-controlled process gas can flow out of the piston interior, in particular from the piston interior into the interior of the inner housing.

[0033] According to one embodiment, the housing outlet opening of the inner housing is arranged adjacent to the outflow chamber. According to one embodiment, the first housing inlet opening of the inner housing is arranged adjacent to the hot gas line. According to one embodiment, the second housing inlet opening of the inner housing is arranged adjacent to the inflow chamber.

[0034] The piston is axially displaceable within the inner housing. This allows the freely flowable cross-sectional area defined by the second piston inlet opening to be varied. This is possible because the second housing inlet opening and the second piston inlet opening are arranged in such a way that the freely flowable cross-sectional area of ​​the second piston inlet opening can be increased or decreased by axially displacing the piston within the interior of the inner housing, or in extreme cases, can be closed.

[0035] The wall of the inner housing and the second housing inlet located within the wall of the inner housing allow the free-flow cross-sectional area of ​​the second piston inlet to be varied, i.e., changed, by moving the piston in the axial direction. Depending on the degree of opening of the second piston inlet and the resulting freely flowable cross-sectional area, a large amount, a small amount, or no cooled process gas flows into the piston interior. This allows for appropriate temperature control of the process gas.

[0036] According to one embodiment, the outer side of the piston's shell-side wall is in surface contact with the inner side of the shell-side wall of the inner housing. Appropriate seals can be provided to minimize leakage currents between the piston and the inner housing. In principle, the design of the control device with a piston and defined openings offers the advantage that leakage currents can be largely or completely avoided, which is not the case, for example, with devices based on flap systems.

[0037] The piston is displaceable in the axial direction via an actuator. In other words, the piston is displaceable along its physical or imaginary longitudinal axis.

[0038] According to one embodiment, the first housing inlet opening is arranged in the region of a front wall of the inner housing, in particular a first front wall of the inner housing.

[0039] According to one embodiment, the second housing inlet opening is arranged in the region of a shell-side wall of the inner housing.

[0040] According to one embodiment, the housing outlet opening is arranged in the region of a further end wall of the inner housing, in particular in the region of a second end wall of the inner housing.

[0041] According to one embodiment, the first end wall of the inner housing borders the hot gas line. According to one embodiment, the second end wall of the inner housing borders the outflow chamber. According to one embodiment, the shell-side wall of the inner housing borders the inflow chamber and the outflow chamber.

[0042] According to one embodiment, the first piston inlet opening is arranged in the region of an end wall of the piston, in particular a first end wall of the piston.

[0043] According to one embodiment, the second piston inlet opening is arranged in the region of a jacket-side wall of the piston.

[0044] According to one embodiment, the piston outlet opening is arranged in the region of an end wall of the piston, in particular in the region of a second end wall of the piston.

[0045] A "shell-side wall" is understood to mean, regardless of the geometric design of the piston or the inner housing, a wall which runs around the piston and / or the inner housing parallel or substantially parallel to a physical or imaginary longitudinal axis of the piston and / or the inner housing.

[0046] A "frontal wall" is understood to mean a wall which is arranged perpendicular or substantially perpendicular to a physical or imaginary longitudinal axis of the piston and / or the inner housing, regardless of the geometric design of the piston or the inner housing.

[0047] In particular, the inner housing and the piston each have two end walls (a first and a second end wall), and the respective shell-side wall extends between these two end walls.

[0048] By displacing the piston in the axial direction, not only the freely flowable cross-sectional area of ​​the second piston inlet opening, in particular its size, can be changed. Rather, by displacing the piston in the axial direction, the distance between, in particular, a first end wall of the piston and a first end wall of the inner housing, and thus the distance between the first housing inlet opening and the first piston inlet opening, can also be changed.

[0049] The change in the freely flowable cross-sectional area of ​​the second piston inlet opening and the resulting change in the volume flow of cooled process gas flowing into the piston interior results in a corresponding pressure drop, which in turn leads to different pressure levels in the inlet and outlet chambers. As the fluidically connected chambers and the prevailing flows therein attempt to compensate for this resulting different pressure level, the volume flow of the hot process gas flowing into the piston interior via the first housing inlet opening and the first piston inlet opening changes accordingly. This also regulates the volume flow of the hot process gas.

[0050] The hot process gas emerging from the at least one hot gas line and flowing into the piston interior via the first housing inlet opening and the first piston inlet opening can also be referred to as uncooled process gas or essentially uncooled process gas. The (at least one) hot gas line can also be referred to as a bypass line. This means that the hot gas line in question is not cooled or is only insignificantly cooled, i.e. its cooling is bypassed. This can be due to the fact that the hot process gas in the hot gas line is not cooled by indirect cooling with the aid of a cooling medium, or the hot gas line has such a large diameter that no cooling or only insignificant cooling occurs through indirect cooling via a cooling medium flowing around the hot gas line.

[0051] The interior of the inner housing is fluidically connected to the at least one hot gas line. The interior of the inner housing can be connected to the hot gas line directly or, for example, via one or more transition pieces. The control device can also comprise multiple hot gas lines, for which the same configuration applies. This means that the interior of the inner housing is then fluidically connected to this plurality of hot gas lines, so that the total amount of hot process gas from these hot gas lines can flow into the interior of the inner housing.

[0052] The inflow chamber is fluidically connected to at least one cold gas line, but usually to a plurality of cold gas lines. The cold gas line or the plurality of cold gas lines forms / form the main cooling surface of the device for providing the cooled process gas. In particular, a cooling medium flows around the cold gas line or the plurality of cold gas lines, which cools the process gas and thus provides cooled process gas. Accordingly, the cold gas line(s) carry the cooled process gas.

[0053] "Temperature-controlled process gas" is understood to mean, in particular, the process gas which can be generated by mixing the hot process gas and the cooled process gas in the piston interior and which, after flowing out of the piston interior into the interior of the inner housing and then flowing out into the outflow chamber, can be discharged from the device via the outlet nozzle, i.e. can be flowed out.

[0054] Since the device according to the invention advantageously allows the second piston inlet opening to be completely closed so that the freely flowable cross-sectional area of ​​the second piston inlet opening is zero, the "temperature-controlled process gas" for this extreme case can also be a process gas which has the same or substantially the same temperature as the hot process gas.

[0055] The device according to the invention further advantageously allows the first piston inlet opening to be completely closed, wherein the control device is configured such that the first piston inlet opening is simultaneously open, according to one embodiment, completely open. For this extreme case, the "temperature-controlled process gas" can be a process gas that has the same or substantially the same temperature as the cooled process gas.

[0056] An embodiment of the control device is characterized in that the first housing inlet opening of the inner housing is arranged within a first end wall of the inner housing, and the first piston inlet opening is arranged within a first end wall of the piston, wherein said openings are arranged relative to one another in such a way that the first housing inlet opening of the inner housing and the first piston inlet opening cannot be flowed through by the hot process gas when there is surface contact between said end walls.

[0057] This allows the control device to be operated in such a way that no hot process gas passes through the inner housing toward the discharge chamber. According to a preferred embodiment, the second piston inlet opening is simultaneously fully open.

[0058] The first housing inlet opening and the first piston inlet opening can be arranged offset from one another in such a way that the hot process gas cannot flow through these openings when the said end walls are in surface contact. In other words, these openings are arranged in such a way that they do not overlap when the said end walls are in surface contact, thus preventing flow through these openings.

[0059] By axially displacing the piston, the second piston inlet opening can be completely closed, allowing only hot process gas to pass through the device. The aforementioned design thus allows the other extreme case to be realized, namely, allowing only hot process gas to pass through the device.

[0060] The control device thus makes it possible to control the temperature of the process gas over the entire temperature range of the two process gas types, cooled and hot process gas.

[0061] According to one embodiment, the second housing inlet opening and the second piston inlet opening are arranged in such a way, in particular the second housing inlet opening is arranged in the region of the jacket-side wall of the inner housing and the second piston inlet opening is arranged in the region of the jacket-side wall of the piston in such a way that when the first end wall of the inner housing and the first end wall of the piston are in planar contact, the freely flowable cross-sectional area of ​​the second piston inlet opening corresponds to the maximum opening area of ​​the second piston inlet opening.

[0062] A preferred embodiment of the control device is characterized in that the first housing inlet opening of the inner housing and / or the first piston inlet opening are / is designed as an annular gap.

[0063] A preferred embodiment of the control device is characterized in that the first end wall of the piston has a sealing element mechanically connected to this end wall.

[0064] This allows leakage currents on the hot gas line side to be reduced to a minimum.

[0065] An embodiment of the control device is characterized in that the piston is mechanically connected to the actuator via a shaft.

[0066] A preferred embodiment of the control device is characterized in that the piston is mechanically connected to the actuator via a shaft, and the shaft has a mechanical stop element firmly connected to it, wherein the stop element is arranged in the interior of the inner housing and outside the piston, or is arranged within the outflow chamber and outside the inner housing, and is arranged in such a way that a complete closure of the opening, which is defined by the freely flowable cross-sectional area of ​​the second piston inlet opening, can be prevented.

[0067] The mechanical stop element is permanently connected to the shaft, i.e., connected to the shaft in such a way that the position of the stop element cannot be changed during operation of the control device. According to one example, the stop element is connected to the shaft in a force-locking manner, for example, via a screw connection or a clamp connection.

[0068] The stop element can be arranged in the interior of the inner housing and thus outside the piston. According to this embodiment, the stop element can, according to one example, strike against a wall of the inner housing during a corresponding stroke of the piston, in particular strike against the inner side of the second end wall of the inner housing.

[0069] The stop element can be arranged within the outflow chamber and thus outside the inner housing. According to this embodiment, the stop element can, according to one example, strike against a wall of the outer housing during a corresponding stroke of the piston, in particular strike against an inner side of a wall of the outer housing.

[0070] The stop element is arranged in such a way that a complete closure of the opening defining the freely flowable cross-sectional area of ​​the second piston inlet opening is prevented or prevented. In other words, the stop element is mechanically firmly connected to the shaft at a defined position, whereby the positioning of the stop element prevents the second piston inlet opening from being closed, which would prevent cooled process gas from the inflow chamber from flowing through it.

[0071] In the event of a control device failure, the stop element prevents the connection between the inlet chamber and the piston interior from closing completely, which would then result in the control device only being flowed through by hot process gas from the hot gas line. This prevents excessive temperatures in the area of ​​the control device outlet, particularly in the area of ​​the outlet nozzle. Excessive temperatures at the device outlet can damage devices located downstream of the control device.

[0072] A preferred embodiment of the control device is characterized in that the mechanical stop element can be changed in its position along the shaft in the axial direction, in particular its position can be changed depending on the prevailing operating conditions.

[0073] According to this embodiment, the mechanical stop element is not connected to the shaft by a material connection, such as a welded joint. Rather, the stop element is connected to the shaft by a detachable connection, such as a force-locking connection, so that the position of the stop element can be changed, for example, during maintenance work on a respective system.

[0074] For example, it may be useful to increase the freely flowable cross-sectional area defined by the second piston inlet opening in the event of the stop element hitting the piston (due to failure of the control device) as contamination or corrosion of the cold gas lines progresses. Such progressive contamination or corrosion results in less cooling of the process gas in question, making it advantageous to increase the volume flow of the cooled process gas accordingly. Increasing the volume flow through the cold gas lines improves the heat transfer from gas to water (coolant). This compensates for the insulating effect of a layer of dirt, which primarily forms on the outside of the cold gas lines, i.e. on the coolant side. Corresponding considerations must be made with regard to the hot gas line(s) that carry the uncooled process gas.

[0075] A preferred embodiment of the control device is therefore characterized in that the position of the mechanical stop element can be changed in the axial direction along the shaft depending on the temperature of the cooled process gas and / or the temperature of the uncooled process gas.

[0076] For the above reasons, a preferred embodiment of the control device is advantageously characterized in that the position of the mechanical stop element can be changed along the shaft in the axial direction depending on the degree of contamination of the at least one cold gas line and / or the degree of contamination of the at least one hot gas line.

[0077] A preferred embodiment of the control device is characterized in that the piston is rotatable in the radial direction via an actuator, so that the freely flowable cross-sectional area of ​​the second piston inlet opening can be changed by rotating the piston in the radial direction.

[0078] According to this embodiment, a further degree of freedom is introduced, which relates to the variability of the freely flowable cross-sectional area defined by the second piston inlet opening.

[0079] This allows the shaft to be rotated radially, for example, when the stop element has reached its end position, i.e., the position of the mechanical stop. This allows the second piston inlet opening to be closed even when the stop is reached, enabling the temperature of the temperature-controlled process gas to be increased to the maximum temperature (corresponding to the temperature of the hot process gas) even at the mechanical stop. This is independent of the operation of the actuator, which controls the axial displacement of the piston. This enables adjustment of the mechanical stop depending on the contamination rate of the cold gas lines and hot gas line(s).

[0080] A preferred embodiment of the control device is characterized in that the piston is displaceable in the axial direction via a first actuator and the piston is rotatable in the radial direction via a second actuator.

[0081] This allows axial and radial displacement to be operated independently of each other. For example, radial rotation of the piston by the second actuator is still possible even if the first actuator fails and the piston is in the position of the mechanical stop.

[0082] A preferred embodiment of the control device is characterized in that the piston has the shape of a straight hollow cylinder.

[0083] According to this embodiment, the piston has the shape of a straight hollow cylinder, or the shape of a substantially straight hollow cylinder, or substantially the shape of a straight hollow cylinder.

[0084] To simplify design and maintenance, the piston is preferably shaped as a straight hollow cylinder. This geometry allows for complete closure of the opening(s) to at least one hot gas line while simultaneously maintaining low leakage rates in the space between the piston and the inside of the inner housing.

[0085] Alternatively, the piston has the shape of a hollow truncated cone, with the diameter of the truncated cone decreasing along the flow direction of the gases flowing through the piston interior.

[0086] This allows the surface of the piston to be efficiently sealed against the inside of the inner housing, especially at large strokes (distance between the front walls of the inner housing and the piston), which allows lower leakage rates to be achieved than in the case of a straight hollow cylinder design.

[0087] At least one of the aforementioned objects is further at least partially achieved by a heat exchanger comprising a control device according to one of the aforementioned embodiments, wherein the heat exchanger has a plurality of cold gas lines arranged parallel to one another and configured as tube bundles, which are fluidically connected to the inflow space, and wherein the heat exchanger has a centrally arranged hot gas line which has a larger diameter than the cold gas lines.

[0088] The heat exchanger comprises the control device according to the invention, or the control device forms part of the heat exchanger. The heat exchanger is preferably a tube-bundle heat exchanger. The heat exchanger has a centrally arranged hot gas line, but according to one embodiment, it can also comprise several centrally arranged hot gas lines. The hot gas line or lines and the cold gas lines can be arranged coaxially. The hot gas line can also be referred to as a bypass line. This means that the cooling of the process gas in the hot gas line is either completely or essentially completely bypassed.

[0089] A preferred embodiment of the heat exchanger is characterized in that the cold gas lines each have an inlet end and an outlet end, and the hot gas line has an inlet end and an outlet end, wherein the outlet ends of the cold gas lines merge into the inflow space and the outlet end of the hot gas line merges into the inner housing, and wherein the inlet ends of the cold gas lines and the inlet end of the hot gas line merge into a process gas inflow space, wherein the process gas inflow space has a process gas inlet nozzle.

[0090] Hot process gas can flow into both the hot gas line and the cold gas lines via the process gas inlet chamber. Part of the hot process gas is subsequently cooled in the cold gas lines, while part flows through the hot gas line and is not cooled or essentially not cooled.

[0091] At least one of the aforementioned objects is further at least partially achieved by the use of the control device according to one of the aforementioned embodiments of the control device or according to one of the aforementioned embodiments of the heat exchanger for cooling synthesis gas from a steam reformer or an autothermal reformer. Example

[0092] The invention is explained in more detail below by means of exemplary embodiments. In the following detailed description, reference is made to the accompanying drawings, which illustrate specific embodiments of the invention. In this context, directional terminology such as "top", "bottom", "front", "back", etc. is used with reference to the orientation of the described figure. Since components of embodiments can be positioned in a variety of orientations, the directional terminology is for illustrative purposes and is in no way limiting. Those skilled in the art will appreciate that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the invention.The following detailed description is therefore not to be taken in a limiting sense, and the scope of the embodiments is defined by the appended claims. The drawings are not to scale unless otherwise indicated.

[0093] It shows Figure 1 shows a side cross-sectional view of a control device according to the invention with the first piston inlet opening closed and the second piston inlet opening fully open, Figure 2 shows a side cross-sectional view of a control device according to the invention with the first piston inlet opening open and the second piston inlet opening fully closed, and Figure 3 shows a side cross-sectional view of a control device according to the invention with a mechanical stop element, with the first piston inlet opening open and the second piston inlet opening partially open.

[0094] In the Figures 1 to 3The same elements are each provided with the same reference numbers.

[0095] Figure 1 shows a simplified representation of a lateral cross-sectional view of the control device according to the invention with the first piston inlet opening closed and the second piston inlet opening fully open.

[0096] The control device 1 has an outer housing 10, which comprises an inflow chamber 11 and an outflow chamber 14. The inflow chamber 11 and the outflow chamber 14 are spatially separated from one another by a mechanical separating element 17. An inner housing 18 is arranged within the outer housing 10 and extends within the inflow chamber 11, through the mechanical separating element 17, and within the outflow chamber 14. The inner housing is fluidically connected via several openings 22, 23, and 24 (opening 24 not shown) to a hot gas line 20, the inflow chamber 11, and the outflow chamber 14. The inner housing 18 has an interior space 19. The openings 22, 23 and 24 are located within the wall of the inner housing and thus establish fluidic connections between the interior 19 of the inner housing 18 and the hot gas line 20, the inflow chamber 11 and the outflow chamber 14.The control device 1 further comprises a plurality of cold gas lines 13 which are fluidically connected to the inflow chamber. While cooled process gas 12 flows through the cold gas lines 13, hot process gas 21 flows through the hot gas line 20. Due to the large diameter of the hot gas line 20 compared to the small diameter of the cold gas lines 13, the hot process gas 21 in the hot gas line 20 is only insignificantly cooled. The outlet ends of the cold gas lines 13 (not shown) and the outlet end of the hot gas line 20 (not shown) are fixed within the holes (not shown) of a perforated plate 37 which extends over the cross-sectional area of ​​the outer housing. A cooling medium flows around the cold gas lines 13 and the hot gas line 20, thereby cooling the process gas flowing in the cold gas lines 13.

[0097] The control device 1 can also be considered part of a shell-and-tube heat exchanger with a centrally arranged bypass pipe, here the hot gas line 20. Such a heat exchanger, as is known to those skilled in the art, has a corresponding inlet connection and an outlet connection for the cooling medium. The connections are not shown in the figures. The cooling medium is, in particular, cooling water, which is discharged from the heat exchanger as steam due to the cooling of the hot process gas and can subsequently be used as heating steam or process steam.

[0098] The hot gas line 20 extends through the perforated plate 37 into the inflow chamber 11 and is thereby mechanically firmly connected to the inner housing 18. The part of the hot gas line 20 which extends through the inflow chamber 14 can also be regarded not as part of the hot gas line 20, but as a connecting piece or transition piece between the hot gas line 20 and the inner housing 18. The inner housing 18 has a first end wall 31 in which a first housing inlet opening 22 designed as an annular gap is arranged. The hot process gas 21 can flow through the first housing inlet opening 22 into the interior space 19 of the inner housing 18 when the opening 22 is open and thus flowable. The inner housing 18 also has a housing outlet opening 24 (opening not shown), which is arranged within a second end wall 32 of the inner housing.A temperature-controlled process gas 15 can flow out of the interior space 19 of the inner housing 18 into the outflow chamber 14 via the housing outlet opening 24. The temperature-controlled process gas 15 can then be discharged from the control device 1 via an outlet nozzle 16 from the outflow chamber 14. The inner housing 18 further has a second housing inlet opening 23, which is arranged within the shell-side wall 38 of the inner housing. As shown in the figure, several such openings 23 can be present.

[0099] Arranged in the interior 19 of the inner housing 18 is a piston 25, which is designed as a cylindrical hollow body and is connected to an actuator 27a and another actuator 27b via a shaft 35. The piston 25 has a piston interior 26. The shaft is mechanically fixedly connected to the piston, i.e., the piston 25 and the shaft 35 form a mechanical unit that is movable via the actuators 27a and 27b.

[0100] Via the actuator 27a, the piston 25 can be displaced in the axial direction, i.e., along its longitudinal axis, which is partially formed by the shaft 35. This type of movement is indicated by the arrow on both sides of the actuator 27a.

[0101] The piston 25, designed as a hollow body, has a plurality of openings 28, 29, and 30 through which flow can pass. A first piston inlet opening 28 is arranged within a first end wall 33 of the piston 25. Hot process gas 21 can flow into the piston interior 26 through the first piston inlet opening 28 after passing through the first housing inlet opening 22, provided the piston 25 is positioned accordingly. A second piston inlet opening 29 is arranged within a jacket-side wall 39 of the piston. As shown in the figure, a plurality of such openings 29 can be present. Cooled process gas 12 can flow into the piston interior 25 through the second piston inlet opening 29 after passing through the second housing inlet opening 23, provided the piston 25 is positioned accordingly.

[0102] By displacing the piston 25 in the axial direction by the actuator 27a, the freely flowable cross-sectional area of ​​the second piston inlet opening can be varied. This means that the second housing inlet opening 23 and the second piston inlet opening 29 are arranged relative to one another in such a way that the size of the second piston inlet opening, and thus the amount of the freely flowable cross-sectional area of ​​this opening, can be varied.

[0103] In the example according to Figure 1 the piston 25 is in a position in which the second piston inlet opening 29 is opened to its maximum extent, i.e. the entire opening or the entire cross-sectional area of ​​this opening is available for the flow of cooled process gas 12. According to the example of the Figure 1The second housing inlet opening 23 and the second piston inlet opening 29 are congruently positioned one above the other. The flow-through areas defined by the second housing inlet opening 23 and the second piston inlet opening 29 do not have to be the same size, but can also be different. The only decisive factor is that both openings are arranged relative to each other in such a way that the freely flow-through cross-sectional area of ​​the second piston inlet opening 29 is variable.

[0104] In the example according to Figure 1the piston 25 is also in a position in which access to the hot gas line 20 is closed. This is achieved by arranging the first housing inlet opening 22 and the first piston inlet opening 28 relative to one another in such a way that the hot process gas 21 cannot flow through them when there is surface contact between the first end wall 31 of the inner housing 18 and the first end wall 33 of the piston 35. This is achieved by arranging the corresponding openings 22 and 28 offset from one another and, when there is corresponding surface contact, not overlapping.

[0105] Figure 2 shows a side cross-sectional view of a control device according to the invention with the first piston inlet opening open and the second piston inlet opening completely closed.

[0106] In the example according to the Figure 2The control device 1 is shown with a position of the piston 25 in which access to the second piston inlet opening 29 is completely closed. At the same time, access to the hot gas line 20 is completely open, thereby enabling a maximum flow of hot process gas 21. The flow of cooled process gas 12 is thus zero, or limited to negligible leakage flows. If the piston 25 is continuously moved to the left via the actuator 27a, the freely flowable cross-sectional area of ​​the second piston inlet opening 29 is continuously increased, and thus the flow of cooled process gas 12 is also continuously increased.The pressure drop between the inflow chamber 11 and the outflow chamber 14 also changes, whereby the amount of hot process gas 21 that can flow into the piston 25 also changes, i.e. the flow of hot process gas 21 is continuously reduced.

[0107] In the piston interior, the hot process gas 21 and the cooled process gas 12 mix, resulting in the temperature-controlled process gas 15. This gas flows into the outflow chamber via the piston outlet opening 30 and the housing outlet opening 24. As already mentioned above, the term "temperature-controlled process gas" 15 is also used when access to the hot gas line 20 or the inflow chamber 11 is closed, depending on the position of the piston 25.

[0108] The control device 1 further comprises a second actuator 27b, by means of which the piston can be moved in the radial direction, i.e., rotated about its longitudinal axis. This second actuator 27b thus provides a further degree of freedom with regard to the variability of the freely flow-through cross-sectional area of ​​the second piston inlet opening 29. If the second piston inlet opening is, for example, a circular opening, this opening 29 can be closed or at least further reduced by the radial movement, even if the openings 23 and 29 are located one above the other. The radial movement of the piston 25 via the shaft 35 by means of the second actuator 27b is indicated by the semicircular arrow.

[0109] Figure 3shows a side cross-sectional view of a control device according to the invention with a mechanical stop element, with the first piston inlet opening open and the second piston inlet opening partially open.

[0110] Figure 3shows an example of a control device 2 with an integrated mechanical stop element 36. The stop element 36 is arranged within the inner housing 18, i.e., in the interior space 19 of the inner housing 18, and is firmly connected to the shaft 35. This fixed connection can be realized, for example, by a force-locking connection such as a screw connection. It is crucial that the connection is a detachable connection. Therefore, the stop element 36 is preferably not connected to the shaft 35 via a material-locking connection such as a welded connection. A detachable connection enables the position of the stop element 36 to be changed depending on certain prevailing operating parameters, such as the degree of contamination of the hot gas line 20 and the cold gas lines 13.The stop element 36 ensures that the shaft 35 together with the piston 25 cannot be moved to the point where the second piston inlet opening 29 is closed, even in the event of a technical failure of the control device 2, in particular of the actuator 27a. This prevents only hot process gas 21 from leaving the control device 2 via the outlet nozzle 16. This may be desirable depending on the particular system, since excessively hot process gases can damage downstream system components. Should a complete closure of the second piston inlet opening 29 nevertheless be desirable in such a case, this is possible via the second actuator 27b. List of reference symbols

[0111] 1, 2 Control device 10 Outer housing 11 Inlet chamber 12 Cooled process gas 13 Cold gas line 14 Outlet chamber 15 Temperature-controlled process gas 16 Outlet nozzle 17 Mechanical separator 18 Inner housing 19 Interior of the inner housing 20 Hot gas line 21 Uncooled process gas 22 First housing inlet opening 23 Second housing inlet opening 24 Housing outlet opening 25 Piston 26 Piston interior 27a First actuator 27b Second actuator 28 First piston inlet opening 29 Second piston inlet opening 30 Piston outlet opening 31 First end wall of the inner housing 32 Second end wall of the inner housing 33 First end wall of the piston 34 Second end wall of the piston 35 Shaft 36 Stop element 37Perforated plate 38Shell-side wall of inner casing 39Shell-side wall of piston

Claims

1. Control device (1, 2) for controlling the temperature of a process gas, having - an outer housing (10); - an inflow chamber (11), arranged within the outer housing, for cooled process gas (12), wherein the inflow chamber is fluidically connected to at least one cold gas line (13) for carrying the cooled process gas; - an outflow chamber (14), arranged within the outer housing, for temperature-controlled process gas (15); - an outlet stub (16), which extends through the outer housing in the region of the outflow chamber, wherein the outlet stub is configured to discharge the temperature-controlled process gas from the outer housing; - a mechanical separating element (17), which spatially separates the inflow chamber and the outflow chamber from one another; - an inner housing (18) having an interior (19), wherein the interior is fluidically connected to at least one hot gas line (20) for carrying hot process gas (21), wherein the inner housing extends within the inflow chamber and through the mechanical separating element into the outflow chamber, wherein the inner housing comprises a first housing inlet opening (22), which is arranged in such a way that the hot process gas can flow into the interior of the inner housing, and wherein the inner housing comprises a second housing inlet opening (23), which is arranged in such a way that cooled process gas can flow into the interior of the inner housing, and wherein the inner housing comprises a housing outlet opening (24), which is arranged in such a way that temperature-controlled process gas can flow out of the interior of the inner housing into the outflow chamber; - a piston (25), through which flow can take place, which is designed as a hollow body and which has a piston interior (26), wherein the piston can be moved in the axial direction within the inner housing by means of an actuating drive (27a), wherein the piston comprises a first piston inlet opening (28), which is arranged in such a way that hot process gas can flow into the piston interior, and wherein the piston comprises a second piston inlet opening (29), which is arranged in such a way that cooled process gas can flow into the piston interior, and wherein the piston comprises a piston outlet opening (30), which is arranged in such a way that temperature-controlled process gas can flow out of the piston interior into the interior of the inner housing, wherein - the second housing inlet opening of the inner housing and the second piston inlet opening are arranged in such a way relative to one another that a free-flow cross-sectional area of the second piston inlet opening can be changed by the movement of the piston in the axial direction, thereby making it possible to control a quantity of cooled process gas which can flow into the piston interior via the second housing inlet opening of the inner housing and via the second piston inlet opening.

2. Control device according to Claim 1, characterized in that the first housing inlet opening of the inner housing is arranged within a first end wall (31) of the inner housing, and the first piston inlet opening is arranged within a first end wall (33) of the piston, wherein the said openings are arranged in such a way relative to one another that the hot process gas cannot flow through the first housing inlet opening of the inner housing and the first piston inlet opening when the said end walls are brought into surface contact.

3. Control device according to Claim 2, characterized in that the first housing inlet opening of the inner housing and / or the first piston inlet opening are / is designed as (an) annular gap(s).

4. Control device according to Claim 2 or 3, characterized in that the first end wall of the piston has a seal element mechanically connected to this end wall.

5. Control device according to any one of the preceding claims, characterized in that the piston is mechanically connected to the actuating drive via a shaft (35), and the shaft has a mechanical stop element (36) fixedly connected to it, wherein the stop element - is arranged in the interior of the inner housing and outside the piston, or - is arranged within the outflow chamber and outside the inner housing, and is arranged in such a way that complete closure of the opening, which is defined by the free-flow cross-sectional area of the second piston inlet opening, can be prevented.

6. Control device according to Claim 5, characterized in that the position of the mechanical stop element in the axial direction along the shaft can be changed, in particular can be changed in accordance with the prevailing operating conditions.

7. Control device according to Claim 6, characterized in that the position of the mechanical stop element in the axial direction along the shaft can be changed in accordance with the temperature of the cooled process gas and / or the temperature of the uncooled process gas.

8. Control device according to either of Claims 6 or 7, characterized in that the position of the mechanical stop element in the axial direction along the shaft can be changed in accordance with the degree of contamination of the at least one cold gas line and / or the degree of contamination of the at least one hot gas line.

9. Control device according to any one of the preceding claims, characterized in that the piston can be rotated in the radial direction by means of an actuating drive (27b), thus enabling the free-flow cross-sectional area of the second piston inlet opening to be changed by the rotation of the piston in the radial direction.

10. Control device according to Claim 9, characterized in that the piston can be moved in the axial direction by means of a first actuating drive (27a), and the piston can be rotated in the radial direction by means of a second actuating drive (27b).

11. Control device according to any one of the preceding claims, characterized in that the piston is in the form of a straight hollow cylinder.

12. Control device according to any one of Claims 1 to 10, characterized in that the piston is in the form of a hollow truncated cone, wherein the diameter of the truncated cone decreases along the direction of flow of the gases flowing through the piston interior.

13. Heat exchanger, having a control device (1, 2) according to any one of Claims 1 to 12, wherein the heat exchanger has a multiplicity of cold gas lines (13), which are arranged in parallel to one another and configured as a tube bundle and are fluidically connected to the inflow chamber, and wherein the heat exchanger has a centrally arranged hot gas line (20), which has a larger diameter than the cold gas lines.

14. Heat exchanger according to Claim 13, characterized in that the cold gas lines each have an inlet end and an outlet end, and the hot gas line has an inlet end and an outlet end, wherein the outlet ends of the cold gas lines merge into the inflow chamber and the outlet end of the hot gas line merges into the inner housing, and wherein the inlet ends of the cold gas lines and the inlet end of the hot gas line merge into a process gas inflow chamber, wherein the process gas inflow chamber has a process gas inlet stub.

15. Use of the control device according to any one of Claims 1 to 12 or of the heat exchanger according to either of Claims 13 or 14 to cool synthesis gas from a steam reformer or an autothermal reformer.