ADVANCED SMR REACTOR DESIGN FEATURING HIGH THERMAL EFFICIENCY

Abstract

An improved reactor process is provided. This process includes providing at least one reactor tube, the reactor tube comprising an exterior and an interior, the interior comprising an inside surface, providing a heat source to the exterior of the at least one reactor tube, providing a reactant gas stream to the interior of the at least one reactor tube, placing at least one heat transfer structure in thermal contact with the inside surface of the at least one reactor tube, and transferring heat from the heat source to at least a portion of the reactant gas stream at least partially through the at least one heat transfer structure, thereby producing a product gas stream. There may be a catalyst on the interior of the at least one reactor tube. The reactant gas stream may comprise methane and steam.

Description

BACKGROUND

The production of gas products rich in hydrogen by reforming of hydrocarbons is well established in industry. Typically, long tubes are filled with catalyst, into which the hydrocarbon and steam are introduced. The obtained reformate, known as “synthesis gas”, contains primarily hydrogen and carbon monoxide. The overall reaction is endothermic, and consequently a source of heat is required to externally heat the reaction tubes in which the input mixture of methane and steam is passed. It has been found that by directing heat from the tube wall to the interior of the catalyst, throughput may be improved.

SUMMARY

An improved reactor process is provided. This process includes providing at least one reactor tube, the reactor tube comprising an exterior and an interior, the interior comprising an inside surface, providing a heat source to the exterior of the at least one reactor tube, providing a reactant gas stream to the interior of the at least one reactor tube, placing at least one heat transfer structure in thermal contact with the inside surface of the at least one reactor tube, and transferring heat from the heat source to at least a portion of the reactant gas stream at least partially through the at least one heat transfer structure, thereby producing a product gas stream. There may be a catalyst on the interior of the at least one reactor tube. The reactant gas stream may comprise methane and steam.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 illustrates a heat transfer structure in thermal contact with the inside of a reactor tube, in accordance with one embodiment of the present invention.

FIGS. 2a-2h illustrate various configurations for a heat transfer structure, in accordance with one embodiment of the present invention.

FIGS. 3a-3c illustrate possible placements of the heat transfer structures within the length of the reactor tube, in accordance with one embodiment of the present invention.

FIG. 4 illustrates the temperature profiles along the reactor centerline for with and without heat transfer structures, in accordance with one embodiment of the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

Illustrative embodiments of the invention are described below. While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.

It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developer's specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.

Turning to FIG. 1, in one aspect of the current invention, at least one metal structure 105 is installed inside a reactor tube 101. This reactor tube may be a steam methane reformer (SMR) tube. Catalyst bed 106 and gases 107 inside reactor tube 101 are simultaneously heated by tube walls 108 and metal structures 105. Energy is conducted to the interior and center of the packed catalyst bed by metal structures 105 directly. The average temperature of the catalyst bed at each cross section is higher comparing with the conventional design, and the temperature distribution is also more uniform.

The shape, dimension, number of metal structures 105 and the installation locations are depending on the actual SMR reactor design and the SMR furnace operating conditions. The metal structures 105 are embedded in the catalyst bed 106. A greater number of metal structures 105 may be installed in the initial section of the reactor tube to quickly heat up the catalyst bed. A lesser number of metal structures 105 can be installed in the downstream to keep the temperature distribution more uniform.

Turning now to FIGS. 1, 2, and 3, an improved reactor process is illustrated. Note, in the interest of clarity, the same element numbers are consistently maintained throughout these figures. Reactor tube 101, which comprises an exterior 102 and an interior 103, with the interior 103 further comprising an inside surface 104. The interior 103 may be filled with a catalyst 106. A heat source Q is provided to the exterior 102 of the reactor tube 101. Reactant gas stream 107 is provided to the interior of the reactor tube. At least one heat transfer structure 105 is placed in thermal contact with the inside surface 104 of the reactor tube 101.

Heat source Q transfers heat 110 through reactor tube 101. Heat is then transferred 111 through heat transfer structure 105. Heat is then transferred from heat transfer structure 105 to the interior 103 of reactor tube 101. As the reactant gas stream 107 passes through the catalyst 106, the heat transferred from heat transfer structure 105 (along with heat transferring 115 from the inside surface) product gas stream 114 is produced.

Heat transfer structure 105 may have any shape which is achieves and retains thermal contact with the inside surface of the reactor tube, and which effectively transfers heat to the interior of the tube. One non-limiting example would be a spherical shape comprising two rings affixed to one another at right angles (as illustrated in FIG. 1). In a preferred embodiment, this spherical ring shape would be oriented such that one ring is in contact with the inside surface of the reactor tube along the entire circumference (as illustrated in FIGS. 2a and 2b).

In another embodiment, heat transfer structure 105 may have a tripod shape (as illustrated in FIGS. 2c and 2d). Such a shape may be planar when viewed radially (FIG. 2c) or may have a “fin” that may be oriented upstream or downstream (FIG. 2d), in order to better facilitate heat transfer.

In another embodiment, heat transfer structure 105 may have a cross-shape (as illustrated in FIGS. 2e and 2f). Such a shape may be planar when viewed radially (FIG. 2e) or may have a “fin” that may be oriented upstream or downstream (FIG. 2f), in order to better facilitate heat transfer. Care should be taken in such designs as the heat transfer structure 105 will experience thermal growth E_ir, in a radial direction and must be taken into account in order not to potentially damage the tube walls.

In another embodiment, heat transfer structure 105 may have a cross-shape or a tripod shape, or any suitable shape (illustrated for example by FIGS. 2g and 2h). In this embodiment, a fin of suitable shape (illustrated here as a triangle) may be utilized to allow thermal growth E_ia, in an axial direction and have less potential to damage the tube walls.

In one embodiment, two or more heat transfer structures 105 may be positioned along the length of reactor tube 101 (as illustrated in FIG. 3a)

The entrance end of the tube, wherein reactant gas stream 107 enters, will have a higher average tube wall temperature then the exit end of the tube, wherein the product gas stream 114 exits. In one embodiment, heat transfer structures 105 may be grouped into two or more sets. The first set S1, which may be nearer the entrance of the tube, may have an average spacing of L1, and the second set S2, which is downstream of S1, may have an average spacing of L2. Average spacing L1 may be closer together than average spacing L2. (as illustrated in FIG. 3b).

In one embodiment, two or more heat transfer structures 105 may be positioned only at the entrance end of reactor tube 101 (as illustrated in FIG. 3c)

EXAMPLE

Two computational fluid dynamics simulations were conducted. The first simulation was for a conventional reactor tube. The second simulation was for a reactor tube with 9 metal structures, in accordance with one embodiment of the present invention, installed. The chemical reaction is not considered. The catalyst bed is represented by alumina beads and fluid is nitrogen. The reactor tube has a length of 13.1 meters (43 ft), OD of 136.5 mm (5.37 inch) and ID of 105.7 mm (4.16 inch) respectively. The metal structures are installed at different locations. The first 6 metal structures are spaced 0.91 m evenly along the tube starting at 1.37 m from the inlet. The following 3 metal structures are spaced 1.22 m evenly. FIG. 4 illustrates the temperature profiles along the reactor centerline for both cases.

It should be noted that while the invention has been described in several different embodiment, it is obvious that some additional embodiments can be developed or added by the persons skilled in the art or familiar with the technology to further improve the invention without departing from the scope of this disclosure. For example, a portion of the compressed air from the compressed air combined cycle loop can be injected into the gas turbine and heated by the combustion of air and fuel to form a hot gas then expanded in the gas turbine to generate power.

Claims

1. An improved reactor process, comprising;

providing at least one reactor tube, said reactor tube comprising an exterior and an interior, said interior comprising an inside surface,

providing a heat source to the exterior of said at least one reactor tube,

providing a reactant gas stream to the interior of said at least one reactor tube,

placing at least one heat transfer structure in thermal contact with the inside surface of said at least one reactor tube, and

transferring heat from said heat source to at least a portion of said reactant gas stream at least partially through said at least one heat transfer structure, thereby producing a product gas stream.

2. The process of claim 1, further comprising a catalyst on the interior of said at least one reactor tube.

3. The process of claim 2, wherein said reactant gas stream comprises ethane and steam.

4. The process of claim 1, wherein said heat transfer structure thermally contacts the inside surface of said at least one reactor tube at two or more points.

5. The process of claim 1, wherein said heat transfer structure thermally contacts the inside surface of said at least one reactor tube at two or more points which are equally spaced along the circumference.

6. The process of claim 5, wherein said heat transfer structure thermally contacts the inside surface of said at least one reactor tube at three points which are equally spaced along the circumference.

7. The process of claim 5, wherein said heat transfer structure thermally contacts the inside surface of said at least one reactor tube at four points which are equally spaced along the circumference.

8. The process of claim 1, wherein said heat transfer structure thermally contacts the inside surface of said at least one reactor tube along an entire circumference.

9. The process of claim 1, wherein said heat transfer structure is formed from metal identical to that which forms said reactor tube.

10. The process of claim 1, wherein said heat transfer structure is formed from metal with a greater thermal conductivity than that of the tube metal.

11. The process of claim 1, wherein said heat transfer structure is formed from a high temperature metal.

12. The process of claim 1, wherein said heat transfer structure is formed from a metal with a lower linear coefficient of thermal expansion (αL) than that which forms the reactor tube.

13. The process of claim 1, wherein said heat transfer structure has a structure which transmits thermal expansion inward from said reactor tube, thereby minimizing hoop stress on said reactor tube.

14. The process of claim 12, wherein said structure is such that said thermal expansion is predominantly transmitted in an axial direction.

15. The process of claim 1, wherein at least two heat transfer structures are located along the length of said reactor tube.

16. The process of claim 1, wherein at least two heat transfer structures are located in a first section of said reactor tube.

17. The process of claim 16, wherein said first section is the section nearest the top of the reactor.

18. The process of claim 1, further comprising a first set and a second set of heat transfer structures sequentially located along the length of said reactor tube, wherein

said first set comprises at least three heat transfer structures separated by a first distance, and

said second set comprises at least three heat transfer structures separated by a second distance.

19. The process of claim 18, wherein said first set is upstream of said second set, and said first distance is less than said second distance.