Hot gas collection device, in particular for a reformer for hydrogen production

Abstract

The present invention relates to a hot gas collecting device 10, wherein the hot gas collecting device 10 has a pressure jacket 20 and an inner tube 30, wherein a thermal insulation layer 40 is arranged between the pressure jacket 20 and the inner tube 30, wherein the hot gas collecting device 10 has at least two hot gas supply tubes 50, wherein the pressure jacket 20 has pressure jacket openings 22 for the passage of the hot gas supply tubes 50, wherein the hot gas supply tubes 50 lead through the pressure jacket openings 22 of the pressure jacket 20 and the thermal insulation layer 40, characterized in that the inner tube 30 has at least two segments 32 in the longitudinal direction, wherein the segments 32 are arranged in series in the longitudinal direction of the inner tube 30, wherein an expansion joint 60 is arranged between two adjacent segments 32.wherein each hot gas supply tube 50 is rigidly connected to exactly one segment 32 and each segment 32 is connected to only exactly one hot gas supply tube 50.

Description

[0001] The invention relates to a hot gas collecting device in which, in particular, hot hydrogen mixture coming from a reformer is collected and discharged.

[0002] In a steam reformer, a hydrocarbon, for example methane, is converted into hydrogen, carbon monoxide, and ultimately carbon dioxide using energy input. This process typically involves vertically guiding catalyst-filled tubes through a heated chamber. The reactants are fed in from above, and the product gas mixture is drawn off downwards, collected in a hot gas collector, and then removed. The gas mixture has a temperature of roughly 800 to 900 °C. The catalyst-filled tubes are usually arranged in a row. Because steam reforming splits the hydrocarbon molecules, the catalyst tubes are also called cracking tubes, and the entire steam reformer is accordingly referred to as a tube cracking furnace. The catalyst-filled tubes are typically arranged in rows within a combustion chamber.Accordingly, a hot gas collecting device is arranged horizontally under each row, located below the heated space, with the pipes of a row opening into the hot gas collecting device via individual nozzles.

[0003] Therefore, it has proven advantageous to construct the hot gas collection device with an outer pressure jacket and an inner tube, commonly referred to as a jacket, inside. The inner tube or jacket is not pressure-tight or gas-tight. An insulation layer, usually concrete, is placed between the pressure jacket and the inner tube, protecting it from erosion by the gas flow within the inner tube. Because the inner tube is not airtight, it does not have to withstand the pressure of the gas mixture. Due to the insulation, the pressure jacket is typically only exposed to temperatures up to 200 °C. This makes it possible to use a low-alloy steel despite the hydrogen-containing atmosphere inside, which is advantageous compared to direct contact between the pressure jacket and the hot gas mixture, as this would require extremely high-grade alloys.

[0004] A manifold for tube-slitting furnaces is known from DE 10 2006 022 898 B3.

[0005] From DE 10 2013 109 209 A1 a collection line for the joint removal of process gases fed from several reformer tubes of a reformer is known.

[0006] A manifold for tube-slitting furnaces is known from DE 10 2006 052 937 A1.

[0007] Since the pressure jacket, the inner tube, and the laterally inlet gas supply pipes are made of different materials and are exposed to different temperatures during operation, different thermal expansion rates occur, leading to an offset between the inner tubes and the gas supply pipes. As indicated in DE 10 2006 052 937 A1, these expansion differences and offsets are accommodated by providing the inner tube with individual elongated holes for the inlets of the hot gas supply pipes. Simultaneously, each hot gas supply pipe has a collar plate to roughly seal the elongated hole. This seal is not intended to be gas-tight, so as not to impede the lateral movement between the inner tube and the gas supply pipe resulting from thermal expansion.

[0008] In known designs, the length of the elongated holes must increase proportionally with the length of the inner pipe sections to compensate for the offset between the inner pipe and the gas supply pipes, which increases steadily with the length of the inner pipe. Since the elongated holes cannot be extended arbitrarily for various reasons, the length of the inner pipe sections is practically limited so that the total thermal expansion of a manifold is divided into several sections. A common guideline is to limit the section length so that only five gas supply pipes enter, and therefore five elongated holes are required.

[0009] However, it has been found that the concrete used as insulation between the pressure jacket and the inner pipe exhibits cracks originating from the hot gas supply pipes in the event of failure. These cracks occur either in the plane between two hot gas supply pipes or perpendicular to the longitudinal direction of the inner pipe, i.e., within the pipe cross-section. Consequently, the potential cracks in the concrete coincide with the planned leaks in the inner pipe, the liner. Therefore, in the event of such a crack, there is a risk that significantly more hot gas will reach the pressure jacket and heat it up considerably. This poses an enormous safety risk.

[0010] The object of the invention is to modify the hot gas collecting device in such a way as to reduce the risk of a hot gas flow to the pressure jacket.

[0011] This problem is solved by the hot gas collecting device with the features specified in claim 1. Advantageous further developments are described in the dependent claims, the following description, and the drawing.

[0012] The hot gas collecting device according to the invention serves, for example, to collect and discharge hydrogen-containing gas from a reformer. As is known from the prior art, the hot gas collecting device has a pressure jacket and an inner tube. This means that the pressure jacket is exposed to lower temperatures, so the requirements for the alloy are significantly reduced. For this purpose, a thermal insulation layer, usually made of concrete, is arranged between the pressure jacket and the inner tube. The hot gas collecting device has at least two hot gas supply pipes. More commonly, there are 30 to 50 hot gas supply pipes arranged in a row, which are fed from above from a reformer with a hydrogen-containing gas mixture. The pressure jacket has openings for the passage of the hot gas supply pipes. The hot gas supply pipes pass through the openings of the pressure jacket and the thermal insulation layer.This corresponds to the classic construction method as described, for example, in DE 10 2006 052 937 A1.

[0013] According to the invention, the inner pipe has at least two segments in the longitudinal direction. The segments are arranged in series along the length of the inner pipe. An expansion joint is arranged between two adjacent segments. Each hot gas supply pipe is rigidly connected to exactly one segment, and each segment is connected to only exactly one hot gas supply pipe. This means that the expansion joints represent the only leaks in the inner pipe and, in principle, the only possible flow paths for the hot gas. Consequently, these flow paths are no longer located in close proximity to the hot gas supply pipe via the slotted opening, as was previously the case. This also creates a spatial separation between a potential crack in the concrete and the intended leak in the inner pipe. This significantly reduces the risk of the pressure jacket being overheated by a gas flow through a potential crack.

[0014] Preferably, the hot gas supply pipe is connected to the segment along its longitudinal axis at its center. This maximizes the distances to the expansion joints.

[0015] In a further embodiment of the invention, the hot gas supply pipe is arranged perpendicular to the longitudinal direction in the area of ​​the pressure jacket. The hot gas supply pipe has a bend at the end leading into the inner pipe. This is known from the prior art, for example from DE 10 2006 052 937 A1, and serves to reduce the flow resistance in the inner pipe by deflecting the gas flow. The reduction of the flow resistance decreases the probability that hot gas will find its way through the insulation to the pressure jacket. However, since the inner pipe has an elongated hole due to thermal expansion, a collar plate is attached to the hot gas supply pipe according to the prior art, which closes the slotted hole. Therefore, during manufacturing, i.e., filling with concrete, the collar plate must be pressed against the hot gas supply pipe, which is why the collar plate is only possible in the vertical part of the hot gas supply pipe.This means that the curvature is located entirely within the inner tube and thus itself represents a flow resistance. Since, according to the invention, the hot gas supply tube is now connected to the segment, no pressure is required. Therefore, it is possible for the hot gas supply tube to be firmly connected to the inner tube in the area that is not perpendicular to the longitudinal direction. This reduces the flow resistance and thus further minimizes the risk of hot gas being drawn towards the pressure jacket.

[0016] In a further embodiment of the invention, the hot gas collecting device includes a gas barrier. A gas barrier is a gas-tight connection between the pressure jacket and the inner tube. This prevents gas from flowing parallel to the inner tube outside of it. The gas barrier thus constitutes a fixed connection between the pressure jacket and the inner tube. The gas barrier is rigidly connected to both the pressure jacket and the inner tube. The gas barrier is rigidly connected to exactly one segment of the inner tube. This segment is connected only to the gas barrier and not to a hot gas supply pipe. This ensures that the different thermal expansion rates of the pressure jacket and the inner tube can be compensated for by the expansion joint between the segments.Preferably, the gas barrier is not designed in the simplest form of a circular disk, but has an inclined stepped shape so that thermal expansion effects can be compensated.

[0017] In a further embodiment of the invention, the hot gas supply pipes project beyond the pressure jacket by a first distance. This first distance is smaller than the distance between the pressure jacket and the inner pipe. This allows the segments to be assembled into a complete inner pipe outside the pressure jacket and then inserted into the pressure jacket. Subsequently, the inner pipe is lifted within the pressure jacket until it is centrally located and the hot gas supply pipes protrude through the pressure jacket openings.

[0018] In a further embodiment of the invention, the inner tube between two segments has an overlap ring. The overlap ring is firmly connected to exactly one segment. The overlap ring serves to roughly seal the expansion joint, but gas permeability for pressure equalization must still be maintained. The aim is therefore to minimize gas flow while still allowing pressure equalization. For this reason, the overlap ring can be connected to one segment only at certain points to create a simple, firm mechanical connection. Alternatively, the overlap ring can also be fully connected to one segment, since gas passage is possible between the overlap ring and the other segment to which the overlap ring is not connected.A further advantage has emerged: the expansion joint can be closed more completely than was previously possible with the elongated hole, especially when the overlap ring is firmly and gas-tightly connected to one segment. The gap between the overlap ring and the second segment can also be selected to be smaller and adjusted more precisely than was previously possible with the elongated hole and the collar plate. This also minimizes gas flow towards the pressure jacket.

[0019] In a further embodiment of the invention, the hot gas collecting device comprises at least two parts. The hot gas collecting device is assembled on-site from these at least two parts. Each part has 6 to 15 hot gas supply tubes. According to the prior art, as described in DE 10 2006 052 937 A1, only 4 to 5 hot gas supply tubes per part were previously possible, as otherwise the slotted holes would become too long and the retention function of the inner tube would be too severely impaired. Although two or three of these previous parts could already be largely pre-assembled, manufacturing is nevertheless more complex, and the finished pressure jacket has more welds, which always represent additional effort and a potential source of defects.Thus, by manufacturing larger parts, production can be simplified and the testing effort required for the safety of the entire hot gas collection device for weld seams can ultimately be reduced.

[0020] In a further embodiment, the invention relates to a reformer with a hot gas collection device according to the invention. The hot gas collection device is located in the lower region of the reformer. The hot gas collection device has contact with the ambient air on its outer surface. Thus, the hot gas collection device differs fundamentally from a hot gas collection device arranged in the heated chamber of the reformer.

[0021] The hot gas collecting device according to the invention is explained in more detail below with reference to an embodiment shown in the drawing. Fig. 1 cross-section

[0022] In Fig.Figure 1 shows an exemplary, purely schematic cross-section of an exemplary hot gas collecting device 10 to illustrate the invention. The hot gas collecting device 10 shown has, purely by way of example, four hot gas supply pipes 50 to maintain clarity; preferably, there would be 8 to 12 hot gas supply pipes 50.

[0023] The hot gas collecting device 10 has an outer pressure jacket 20 and an inner tube 30. An insulating layer 40 is arranged between them. As a result, the temperature of the gas inside the inner tube 30 is, for example, 800 to 900 °C, while that of the pressure jacket 20 is only 200 °C, which means that the pressure jacket 20 can be made of a low-alloy steel.

[0024] The structure of the inner tube 30 is essential. In the example shown, it is composed of five segments 32 arranged in a row along the length of the tube. Since the segments 32 are separate, they can move independently of one another, particularly changing their length during heating and cooling. Expansion joints 60 are provided between the segments 32 for this purpose. The four segments shown on the left are each connected to a hot gas supply pipe 50. Because the hot gas supply pipe 50 passes through the insulation layer 40, which is usually made of concrete, it remains stationary even during heating or cooling. The hot gas supply pipes 50 are firmly connected to their respective segments 32, preferably by welding, and ideally in the area of ​​the bend 52, which serves to direct the incoming gas flow in the direction of flow and thereby reduce flow resistance.Since, unlike before, the hot gas supply pipes 50 protrude significantly less into the inner pipe 30 due to the connection in the bend, the flow resistance is further reduced. With suitable design of the hot gas supply pipes 50, the portion protruding into the inner pipe can be completely omitted.

[0025] To minimize the gas flow between the segments 32, overlapping rings are arranged. These are preferably rigidly connected to one of the segments 32. This allows movement of the segments 32 relative to each other, with one segment 32 sliding under the overlapping ring 90, which is rigidly connected to the adjacent segment 32.

[0026] The segment 32 located on the right is also firmly connected to the pressure jacket 20 via a gas barrier 70. The gas barrier 70 ensures that all gas at this point can flow exclusively through the inner tube 30.

[0027] In order to be able to insert the inner tube 30 well into the pressure jacket 20 during manufacturing, the hot gas supply tubes 50 only protrude beyond the pressure jacket 20 by the first distance 81, wherein the first distance 81 is smaller than the second distance 82, which is the distance between the inner tube 30 and the pressure jacket 20.

[0028] The advantage of the invention is clearly visible in this illustration. If cracks form in the insulation layer 40, they are mainly located in the immediate vicinity of the hot gas supply pipes 50. However, the gas from the inner pipe can only flow into the insulation layer 40 via the expansion joint 60, i.e., as far away as possible from the potential cracks. This significantly reduces the flow resistance for potential gas flows outside the inner pipe and thus the risk of hot gas from the inner pipe 30 reaching the pressure jacket 20 and overheating it. Reference sign 10 Hot gas collecting device 20 pressure jacket 22 Pressure jacket opening 30 inner tube 32 segments 40 Insulation layer 50 Hot gas supply pipe 52 Curvature 60 Expansion joint 70 Gas lock 81 first distance 82 second distance 90 overlap ring QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2006 022 898 B3

[0004] DE 10 2013 109 209 A1

[0005] DE 10 2006 052 937 A1 [0006, 0007, 0012, 0015, 0019]

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