Heat exchange – With first fluid holder or collector open to second fluid – Separate external discharge port for each fluid
Patent
1991-01-07
1992-07-21
Flanigan, Allen J.
Heat exchange
With first fluid holder or collector open to second fluid
Separate external discharge port for each fluid
432 16, 554591, 554592, F28C 314
Patent
active
051314622
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a heat exchanger of the type used for obtaining heat exchange of a pulverulent solid material and a gas. Such heat exchangers are used e.g. for preheating mineral raw material which is subsequently subjected to a burning process; the preheating being effected by use of the hot exit gases from the burning process.
Preheating of the pulverulent solid material may be carried out in a cyclone system consisting of several cylindric cyclones having a vertical or horizontal main axis and a conical bottom ending in an outlet for the solid material as it is known from e.g. chapter 20 of Duda: Cement-Data-Book, volume 1, ed. 3 (1985), Bauverlag GmBH, Wiesbaden und Berlin.
Prior art cyclones having a vertical axis are generally delimited at the top by a circular top plate or a circular opening in a downwards concave cyclone top part. A gas outlet pipe or a "central pipe" may extend through the plate or opening down into the cyclone cylinder. Solid material suspended in gas is supplied tangentially via a suspension inlet into the cylinder. Owing to the circulating movement of the gas therein the solid material is flung towards the vessel wall by the centrifugal force where it is stopped or subsequently slides down the wall onto the conical bottom and out through the material outlet while the gas leaves the vessel through the central pipe. Such cyclones are disclosed in i.a. patents Nos. FR 736.458, DE 1,913,305; SE 221,971; U.S. Pat. No. 3,740,865; U.S. Pat. No. 4,245,981, and DE 1,286,696. When used for heat exchange purposes, the heat exchange in cyclones of this type is effected counter-currently or co-currently in that the material during the heat exchange is circulated together with the gas flow in the cyclone. In order for the material to obtain the temperature desired for preheating prior to a burning process it is generally necessary to employ a plurality of such heat exchangers in series, typically four or five stages for preheating of e.g. cement raw material, thus causing this part of a kiln plant to have a considerable height of construction demanding an equally considerable consumption of construction materials.
In case of counter-current heat exchange, as it is known from i.a. GB-A-988,284 or from DK patent application No. 1600/85the centripetal travelling direction of the tangentially introduced gas is used counter to the centrifugal travelling direction of the material introduced into a cyclone having a horizontal axis and close to this axis in order to obtain an increased heat exchange effect as compared to cyclones having a vertical axis, and the use of horizontal counter-current cyclones in preheaters may contribute to delimit the construction height of the preheater. Horizontal cyclones, however, suffer from the drawback that, typically, their separation rates are smaller than those of conventional cyclones.
Therefore, it is an object of the present invention to provide a heat exchanger having a vertical main axis and operating according to the counter-current principle and which heat exchanger is sufficiently efficient as to heat exchange as well as to material separation to replace at least two of the hitherto used stages of a cyclone preheater and which thus offers constructional advantages similar to those of heat exchangers with a horizontal main axis.
According to the invention this object is achieved by a heat exchanger comprising a cylindrical central part having a downward tapering conical base, a concave upper part facing the central part and constituting the upper delimitation of the heat exchanger, a tangential gas inlet in the wall of the cylindric part, and an at least initially axially mounted gas outlet or central pipe said inlet and outlet contributing jointly to form a spiral gas flow inside the vessel, a heat resistant skirt mounted at the upper end of the gas outlet pipe and inclining downwardly at a given angle with the horrizontal plane, at least one material inlet mounted in the upper part of the vessel, and a material outlet at the lower part
REFERENCES:
patent: 2797077 (1957-06-01), Muller
patent: 3146998 (1964-09-01), Golucke et al.
patent: 3265775 (1966-08-01), Friedrich
patent: 3848550 (1974-11-01), Bowen
patent: 4221655 (1980-09-01), Nakayama et al.
patent: 4394138 (1983-08-01), Schilling
F. L. Smidth & Co. A/S
Flanigan Allen J.
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