Glass pipe heat exchanger

A heat exchanger particularly for cooling of hot smoke gases with aggresive components by clean gas to be heated, has side walls having two spaced ends, bottom walls arranged at the ends of the side walls, a plurality of glass pipes extending substantially parallel to each other and to the side walls and arranged so that a smoke gas passes through the glass pipes, while a clean gas passes transversely to the latter, and flow passages extending along the side walls in direction of glass pipes and arranged for guiding the smoke gas.

BACKGROUND OF THE INVENTION 
The present invention relates to a glass pipe heat exchanger, particularly 
for cooling of hot smoke gases with aggressive components. 
Heat exchangers of the above-mentioned general type are known in the art. 
The glass pipe heat exchangers with pipe bottoms and side walls of high 
corrosion-resistant steels, for example CrNi-steel with extremely high 
nickel content, are used in particular where smoke gas with extremely 
aggressive components must be cooled, whose chemical composition cannot be 
exactly determined in advance. The main field of application is garbage 
incinerating devices. They are also used for elimination of waste from the 
automobile industry. In both cases the chemical composition of the 
generated hot smoke gases are not known because of the constantly changing 
mixture of the materials to be burnt. The above-described glass pipe heat 
exchanger is charged with hot smoke gas through the glass pipes and guided 
at the exit via a washer with a subsequent droplet separator, whereas the 
glass pipes are loaded between the side walls and the bottom walls with 
cold clean gas. The clean gas which is thereby heated in the heat 
exchanger is finally supplied to the fire place. It has been noticed that 
despite all measures taken with respect to the gas passage and with 
respect to the material for the pipe bottoms and side walls, the side 
walls of the heat exchanger are subjected to corrosion after a relatively 
short operation time. 
The cause of this is exceeding of the dew point in the region of the side 
walls, inasmuch as the side walls encounter exclusively the clean gas 
which is considerably cooler than the smoke gas. As a result, the 
aggressive components in gas come into their full action. 
SUMMARY OF THE INVENTION 
Accordingly, it is an object of the present invention to provide a heat 
exchanger which avoids the disadvantages of the prior art. 
More particularly, it is an object of the present invention to provide a 
glass pipe heat exchanger which eliminates corrosion damage to its side 
walls over a longer operational time, as compared with the known heat 
exchangers. 
In keeping these objects and with others, which will become apparent 
therein after, one feature of the present invention recites, briefly 
stated, in a glass pipe heat exchanger having side and bottom walls and a 
plurality of glass pipes arranged so that a smoke gas passes through the 
glass pipes while a clean gas passes transverse to the latter, wherein 
means are provided for forming flow passages which extend along the side 
walls in direction of the glass pipes and are arranged for guiding the 
smoke gas. 
When the heat exchanger is designed in accordance to the present invention, 
the flow passages which extend along the side walls in direction of the 
glass pipes are now also charged with hot smoke gas. 
A portion of the smoke gas to flow through the glass pipes is preliminarily 
branched off and supplied through the flow passages. In this case the 
temperature level at the side walls can be retained so high that at no 
location does the excess of the mentioned dew-point take place and the 
corrosion damage is effectively prevented. Because of the inventive 
features, the temperature level at the side walls is guaranteed 
automatically by the hot smoke gas and thereby the heat exchanger is 
provided with a quasi integrated side wall heating without foreign energy. 
Although it is possible that along both side walls which are insulated from 
the surrounding atmosphere several flow passages can be provided one near 
the other, an advantageous embodiment of the invention resides in a 
construction in which the flow passages extend over the entire width of 
the side walls. In this case they can be subdivided by establishing 
inserts whose cross sections are selected so that they do not form 
noticeable flow resistance. 
In accordance with another feature of the invention, the flow passages are 
separated from a space in which the clean gas extends transversely to the 
glass pipes and around the latter, by intermediate walls of high 
corrosion-resistant sheet material. These features are especially 
advantageous when the glass pipe heat exchanger already in use must be 
subsequently converted in accordance to this invention. In this case it 
suffices, for example, to remove only pipe rows immediately adjacent to 
the side walls and to introduce the intermediate walls. Both, the side 
walls and the intermediate walls are retained by the hot smoke gas at the 
required temperature level. 
Finally, in accordance with a further advantageous feature of the present 
invention the inlet cross section of the flow passages is changeable. In a 
simple case, this can be accomplished by removal of the pipe bottom 
supporting the glass pipes in the region of the flow passages. By suitable 
formation of the supply openings, it can be taken care that the original 
ratio of the quantity of the smoke gas flowing through the glass pipes 
with consideration of the subsequent cooling, to the quantity of the clean 
gas flowing transversely of the heat exchanger is maintained.

A DESCRIPTION OF A PREFERRED EMBODYMENT 
A glass pipe heat exchanger in accordance to the present invention shown in 
FIGS. 1 and 2 is identified as a whole by reference numeral 1. The glass 
pipe heat exchanger 1 has an upper pipe bottom 2, a lower pipe bottom 3, 
and lateral walls 5 extending between the pipe walls 2 and 3. 
A plurality of glass pipes 4 extend between the pipe bottoms 2 and 3 
parallel to one another and are supported in the pipe bottoms. The side 
walls 5 are separated from the surrounding atmosphere by a heat insulation 
6 composed, for example, of mineral wool. The pipe bottoms 2 and 3 and 
side walls 5 are composed of a high corrosion-resistant material, for 
example a CrNi-steel with an extremely high nickel content. As can be seen 
from FIGS. 1 and 2 the heat exchanger 1 has passages 7 which extend along 
the side walls 5, and more particularly over the entire width B of the 
latter. The passages 7 extend in the direction of the glass pipes 4. They 
are limited by the side walls 5 of the glass pipe heat exchanger 1, on the 
one hand, and by intermediate walls 8 composed of CrNi-steel with 
extremely high nickel content, on the other hand. 
The end sides of the passages 7 are closed by inclined sheets 9 of the same 
material. The inclined position serves for improved flow guidance. In 
connection with this, it can be seen particularly from FIG. 1 that the 
glass pipes 4 in the passages 7 are removed. The passages 7 are 
substantially unobstructed passages without inserts in them. When it is 
necessary to provide elements for supporting the intermediate walls 8 
relative to the side walls 5, these elements can be arranged in the 
longitudinal direction of the glass pipes 4 and provided with a cross 
section which does not affect the gas flow in the passages 7. 
The heat exchanger 1 in accordance to the present invention, as shown in 
FIGS. 1 and 2, operates in the following manner: 
As indicated in FIG. 1, the hot smoke gas HR flows, for example, from above 
into a passage 11 of the glass pipe heat exchanger 1 and enter the glass 
pipes 4 which are offset from one another by gaps therebetween, on the one 
hand, and also enters via perforations 10 in the upper pipe bottom 2 shown 
in FIG. 2 the lateral flow passages 7, on the other hand. The smoke gas HR 
has at the entrance in the glass pipes 4 and the flow passages 7 a 
temperature, for example, equal to 300.degree. C. 
After leaving the glass pipe heat exchanger 1, the smoke gas HR cooled now 
to a temperature approximately 220.degree. C. is supplied via a discharge 
passage 12 to (not shown) a washer with a subsequent droplet separator 
where it is cooled to approximately 70.degree. C. 
The thus cooled clean gas RG is supplied, as can be seen from FIG. 2, via a 
passage 13 to the glass pipe heat exchanger 1 and flows between the upper 
and lower pipe bottoms 2 and 3 and the intermediate walls 8 around the 
glass pipes 4 to thereby cool the smoke gas HR inside the glass pipes 4. 
The clean gas RG is at the same time heated to a temperature of 
approximately 105.degree.-110.degree. C. and discharged via a discharge 
passage 14 to a (not shown) fire place. 
FIG. 3 shows that the inlet cross section of the lateral flow passages 7 
can be adjusted by exchanging of strips A having perforations 10 of 
differing dimensions. The strips A are displaceable in direction of the 
arrow Pf. 
It will be understood that each of the elements described above, or two or 
more together, may also find a useful application in other types of 
environments differing from the types described above. 
While the invention has been illustrated and described as embodied in a 
glass pipe heat exchanger, it is not intended to be limited to the details 
shown, since various modifications and structural changes may be made 
without departing in any way from the spirit of the present invention. 
Without further analysis, the foregoing will so fully reveal the gist of 
the present invention that others can, by applying current knowledge, 
readily adapt it for various applications without omitting features that, 
from the standpoint of prior art, fairly constitute essential 
characteristics of the generic of specific aspects of this invention. 
What is claimed as new and desired to be protected by Letters Patent is set 
forth in the appended claims.