A gas/liquid heat exchanger. Process gases leaving the heat-transfer elements of a heat-transfer-surface unit are guided through the displacement body that is associated with that unit. Feed water is introduced into the displacement body at the lower end thereof. After countercurrent heat-exchange flow relative to the process gas, the feed water is withdrawn from the upper end of the displacement body, and is introduced into a zone of downwardly flowing water.

BACKGROUND OF THE INVENTION 
The present invention relates to a gas/liquid heat exchanger having an 
upright pressure tank that includes a water chamber, at least one 
heat-transfer-surface unit, which is disposed in the water chamber and 
extends along the tank, a saturated steam chamber disposed above the water 
chamber, and built-in components that divide the water chamber into 
regions or zones of: water that flows upwardly along the 
heat-transfer-surface unit, water that flows downwardly, and calm water; 
each heat-transfer-surface unit includes a displacement body and 
heat-transfer-surface elements, especially helical heat-transfer-surface 
elements, that are disposed about the displacement body and have hot 
process gas under pressure flowing through them. 
A heat exchanger of this general type is disclosed in U.S. Pat. No. 
4,538,676, which belongs to the assignee of the present application. With 
this known heat exchanger, the exit temperature of the process gas as it 
leaves the pressure tank is always about 30.degree.-40.degree. C. greater 
than the saturated steam temperature. It is not possible to cool the 
process gas any further, because the temperature difference between the 
temperature of the steam/water mixture and the exit temperature of the 
process gas is already very small, and the efficiency of the heat-transfer 
surfaces is correspondingly low. After leaving the heat exchanger, the 
process gas is customarily rid of particulates in a wet scrubber, so that 
the heat content of the process gas supplied to the wet scrubber can no 
longer be relied upon for energy exploitation. 
It is therefore an object of the present invention to provide a gas liquid 
heat exchanger of the aforementioned general type with which it is 
possible to make greater utilization of the heat from the process gas; in 
other words, a heat exchanger that has an improved efficiency. 
A further object of the present invention is to reduce the size of the 
heat-transfer surfaces of the heat exchanger while maintaining the exit 
temperature of the process gases therefrom.

DESCRIPTION OF PREFERRED EMBODIMENTS 
Referring now to the drawings in detail, as can be seen from FIGS. 1 and 2, 
disposed centrally and coaxially within a tank 1 is a hexagonal 
displacement body 2. Provided opposite the corners of this displacement 
body 2 are wall units 3 that are connected to the tank 1. If necessary, 
the corners of the displacement body 2 can be connected to the wall units 
3 via planar wall units 4. 
Disposed in the compartments or cells 5 that surround the displacement body 
2, along an imaginary circle, are cylindrical displacement bodies 6 about 
which are disposed, in turn, coaxial heat-transfer-surface elements 7 that 
extend in a helical manner. Supplied to the heat-transfer-surface elements 
7, via feed lines 8, is hot process gas that is under pressure. 
The upper end 7a of the heat-transfer-surface element 7 is connected via a 
connecting line 9 to a widened or enlarged conduit 10 that extends 
downwardly through the interior of the displacement body 6 from above. The 
lower end of the conduit 10 is connected via a connecting line 11 to a gas 
outlet 12 via which the process gas is withdrawn from the tank 1. 
The lower end 6b of the displacement body 6 is connected to a supply line 
13 to which cold feed water is supplied via a ring conduit 14 and a 
water-supply line 15. 
The upper end 6a of the displacement body 6 is connected to a water outlet 
16 to which is connected a downwardly extending gravity or down pipe 17 
that extends into the wedge-shaped free space between the wall units 3 and 
the inner wall of the tank 1. 
The bottom end of the displacement body 2 is closed off by a plate 18, and 
the various heat-transfer-surface units are supported on a support 
structure 19 that is indicated only schematically and that in turn is 
connected to the inner wall of the tank 1. 
The tank 1, which is provided with a steam outlet 1a, is filled with water 
to the indicated level P. Disposed in the undulating region of the water 
level P is a calming device 20 for calming the surface of the water. 
During operation of the heat exchanger, a zone without liquid flow develops 
within the displacement body 2, while about the heat-transfer-surface 
units 7 a zone of upwardly directed flow develops, and in the wedges 
between the wall units 3 and the inner wall of the tank, zones of 
downwardly directed liquid flow develop. 
The feed water supplied by the line 15 is heated in a countercurrent flow 
by the process gas that is flowing downwardly in the conduit 10. The 
preheated feed water is introduced via the down pipes 17 into the 
downwardly directed liquid flow of the circulating water. In other words, 
as a result of the pump pressure that occurs in the line 15, a flow of the 
feed water is induced through the displacement bodies, and the preheated 
feed water that leaves the displacement bodies is introduced into the 
natural circulation in the tank. 
In order to be able to impart a helical course to the upwardly directed 
water flow within the displacement bodies 6, it is possible to provide 
appropriate guide elements 21, such as fins, at least in the lower portion 
of the annular gap that is provided between the conduit 10 and the 
displacement body. 
The embodiment illustrated in FIG. 3 differs from the embodiment of FIGS. 1 
and 2 in that instead of having an enlarged conduit 10, this embodiment is 
provided with a helical conduit 22 within the displacement body 6. 
The embodiment illustrated in FIG. 4 differs from the previous embodiments 
in that the displacement body 6 is supplied with the process gas rather 
than with feed water, while the feed water is guided within a line 23 that 
passes through the displacement body 6 from the bottom toward the top. 
With all of the inventive embodiments, the basic construction of the type 
of heat exchanger disclosed in the aforementioned U.S. Pat. No. 4,538,676 
can be maintained, with an increased utilization of heat, and/or a 
reduction in size of the individual heat-transfer-surface units and hence 
of the overall heat exchanger, being possible due to the feed water 
preheater that is integrated into the displacement body. 
The present inventive concept could also be used in conjunction with a heat 
exchanger of the type disclosed in applicant's German patent application P 
No. 36 02 935, filed Jan. 31, 1986, where a superheater is disposed 
downstream of the saturated-steam chamber above the calming device. 
The present invention is currently viewed as having primary application as 
a waste-heat tank following a pressure gasification, especially a partial 
oxidation. 
The present invention is, of course, in no way restricted to the specific 
disclosure of the specification and drawings, but also encompasses any 
modifications within the scope of the appended claims.