Patent Application
20120125567
The present invention relates to a heat exchange device for cooling a gas, comprising a channel and one or more heat exchange surfaces disposed in the channel, supported by a support structure.
Such heat exchangers are for example used in gasification processes for the production of synthetic gas, or syngas. In such a process, carbonaceous feedstock is partially oxidised in a reactor. Syngas leaving the reactor typically has a temperature of 1300-1600° C. The hot syngas is quenched to temperatures between 100-700° C. and is then transported to a coiled heat exchanger, generally comprising a number of parallel coiled tubes.
Support structures are used to support the heat exchange surfaces within the channel formed by the channel wall. Differences in thermal expansion of the various parts complicate possible support constructions. Sliding bearings can be used, allowing some degree of freedom of movement, but such bearings are difficult to realize and less reliable under the circumstances in such reactors.
U.S. Pat. No. 5,482,110 discloses a heat exchanger for cooling syngas from a partial combustion reactor comprising nested heat exchange surfaces carried by a support. Such a support structure may induce high local stress peaks.
It is an object of the present invention to provide a heat exchanger device with a robust support structure enabling reduction of loads caused by differences in thermal expansion by the various parts.
The object of the invention is achieved by a heat exchange device comprising:
The heat exchange surfaces can rest on the support structure, or the heat exchange surfaces can hang down from the support structure. The one or more heat exchange surfaces can be connected to the support structure, e.g., by welding joints. The support structure can be joined to the channel wall, or to a load bearing structure within the channel wall.
The device can for instance have a number of nested heat exchange surfaces of a closed geometry, e.g., of a cylindrical geometry, as is disclosed in U.S. Pat. No. 5,482,110. The heat exchange surfaces can be coaxially arranged or nested within the channel wall, which will typically be cylindrical. Optionally, the support structure can support a series of two or more bundles of nested heat exchange surfaces.
Generally, the fluid heat exchange medium is water, although any other type of aqueous or non-aqueous coolant can be used if so desired.
The support structure may for example have three or more arms, e.g., four or more arms to form a cross. If so desired a higher number of arms can be used.
The support structure can comprise a plurality of embedded parallel inner channels each being in open connection with one of the flow paths in the heat exchange surfaces. To equalize thermal expansion, the inner channels are preferably evenly distributed and equidistantly arranged. To this end, the inner channels may meander through the arm parts of the support structure. Since meandering inner channels are difficult to manufacture, the arm parts may be built of a number of sections each embedding parallel and equidistant inner channels making a single turn, e.g., of about 90 degrees. For example, each arm of the support structure may comprise:
The heat distribution with this configuration is such that differences in thermal expansion of the connected parts do not result in high mechanical stress loads.
The arms of the support structure can for example be formed as blocks or plates embedding inner channels operatively connected to the tubular parts. Alternatively, one or more of the arms of the support structure can wholly or partly be composed of tubular parts, optionally in combination with blocks or plates embedding inner channels operatively connected to the tubular parts.
If a larger number of heat exchange surfaces, or heat exchange surfaces of a higher weight, are to be supported, the height of the support structure can be increased. This way, the support structure can be made stronger without increasing the thickness of the support structure arms, which could result in undesirable high wall temperatures of the support structure.
The thickness of the arms of the support structure should be sufficient to give the support structure the required carrying capacity. Generally, a wall thickness of 5-20 mm at both sides of an inner channel balances sufficient strength with good heat dissipation capacity.
Particularly for the cooling of deposit-forming gases from pressure-loaded pyrolysis and gasification reactors it is desirable that the heat exchange surfaces are cleaned by rapping devices which can regularly be actuated during operation of the reactor. With the aid of, e.g., pneumatically operated rapping devices the individual heat exchange surfaces are accelerated to such an extent, that soot deposits and fouling are effectively removed. Cleaning by rapping can be done particularly effectively if all tubes of one heat exchange surface unit are rigidly connected to one constructive gastight unit, e.g., by constructing the heat exchange surfaces as a tube-stay-tube or fin-tube construction.
The heat exchange surfaces can be assembled as a plurality of nested heat exchange surfaces of a closed geometry whereby the inner heat exchange surface has a greater constructive height than the adjacent outer heat exchange surface so that each heat exchange surface can be rapped from the exterior without the need for penetrating any other heat exchange surfaces. Optionally, one or more deflectors arranged within the inner heat exchange surface of the nested set may be used to guide the hot gas flow towards the heat exchange surfaces, in order to cool all of the gas evenly.
The heat exchange device according to the present invention can for example be a section of a partial combustion reactor for the production of synthetic gas.
The invention is further explained under reference to the accompanying drawings. In the drawings:
The inner channel wall 3 encloses a set of four schematically represented nested coaxial heat exchange surfaces 5a, 5b, 5c, and 5d. In practice, two or more may be used—for example heat exchange surfaces 5a and 5b. Like the inner channel wall 3, the heat exchange surfaces 5a-d are built of parallel tubular lines. Optionally, the tubular lines of the heat exchange surfaces 5a-d can be helically wound.
The inner channel wall or membrane 3 defines a central channel 4a for hot gas flowing downwards along the heat exchange surfaces 5a-d towards a discharge. At the lower end of the inner channel wall 3, the cooled gas can enter the annular space 4b between the inner channel wall 3 and the outer wall 2. Coolant flowing through the pipe lines of inner channel wall 3 isolates the cool gas in the annular channel 4b from the hot gas in the central channel 4a.
The lower end 6 of each inner heat exchange surface 5b-d extends past the lower end 6 of the adjacent outer heat exchange surface 5a-c, respectively. This way, each individual heat exchange surface 5a-d can be cleaned individually by using rapper devices (not shown).
Four or more equidistantly arranged coolant discharge lines 7 are provided between the inner channel wall 3 and the outer channel wall 2, as schematically shown in
A horizontal support cross 20 has four arms 21 extending from a central crossing 22 to a corresponding coolant discharge line 7. The support cross 20 is shown in more detail in
Each arm 21 comprises a first and a second lower arm part 24, 25 respectively, and an upper arm part 26. In the first lower arm part 24, equidistantly arranged parallel flow paths 27 have a first part 27a extending upwardly to a first corner 27b and a second section 27c extending in the direction of the crossing section 22.
In the second lower arm part 25 are embedded equidistantly arranged parallel flow paths 28. Two of the four second lower arm parts 25 form a single block, while the other two are formed as separate parts at opposite sides of the block and under right angles with it and are welded to a central section of the block to form a cross, as shown in
In the upper arm part 26 are embedded equidistantly arranged parallel flow paths 29. Two of the four upper arm parts 26 form a block, while the other two upper arm parts 26 are formed as separate parts and are welded to the central section of the block to form a cross. The flow paths 29 in the upper arm parts 26 have a first vertical section 29a in line with the respective flow paths 28 in the second lower arm part 25 extending upwardly to a third corner 29b, and a second section 29c extending from the third corner 29b away from the crossing section 22.
Opposite to the side forming the crossing section 22, the upper arm parts 26 are joined to an extension part 30. These extension parts 30 are rectangular parts with equidistantly arranged inner channels 31 embedded in line with the horizontal channel sections 28c in the upper arm parts 26.
In this configuration, all parts of the support cross 20 are evenly cooled by the evenly distributed inner channels 27, 28, 29, 31 in arm parts 24, 25, 26, 30. As a result, the risk of mechanical stresses induced by differences in thermal expansion is substantially reduced.
The outer ends of inner channels 27, 28, 29, 31 in arm parts 24, 25, 26, 30 are surrounded by circular rims 35. The arm parts 24, 25, 26, 30 are welded together at these circular rims to form leaktight joints.
Blocks 32 (see
Inner channels 49a and 49b are embedded in the lower central section 44, having horizontal channel sections 49a connected at one end to the channel sections 47b in the lower main section 43, and to vertical channel sections 49b at their other end. The lower central section 44 is mirrored by the upper central section 45, which embeds inner channels 50a and 50b, with vertical sections 50a in line with the vertical inner channels sections 49b in lower central section 44. Horizontal channels sections 50b lead from the vertical channel sections 50a to the side of the upper central section 45 opposite the centre 22.
The upper main section 46 is made of three horizontal parallel pipe lines 51 operatively connected to the horizontal channel sections 50b in upper central section 45. The pipe lines 51 lead to an extension block 52 with three inner channels 53 connected to the pipe lines 51.
The outer ends of inner channels in arm parts 43, 44, 45 and the pipe lines 51 of upper main section 46 are surrounded by circular rims 54. The arm parts are welded together at these circular rims 54 to form leaktight joints.
| Number | Date | Country | Kind |
|---|---|---|---|
| 09165009.3 | Jul 2009 | EP | regional |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP10/59605 | 7/6/2010 | WO | 00 | 2/7/2012 |
