US2821461A - Method and apparatus for driving off volatile constituents from finely divided solidmatter - Google Patents

Description

Jan. 28, 1958 METHOD AND APPARATUS FOR DRIVING OFF VOLATILE s. A. AANNERUD' 2,821,461

CONSTITUENTS FROM FINELY DIVIDED sous MATTER 7 Filed se t. 2. 1950 i a $74 "$5 a I J 16 V 78 25 12 o (S02) 8 24 I 9W INVENTOR I SIGURD ARTHUR AANNERUD AfTORNEYS United METHOD AND APPARATUS FOR DRIVING OFF VOLATILE CONSTITUENTS FROM FINELY DI- VIDED SOLID MATTER Sigurd Arthur Aannerud, Thamshavn, Norway, assignor, by mesne assignments, to Pyror Limited, Pembroke, Bermuda, a corporation of Bermuda The invention relates to the extraction of constituents, particularly volatile constituents, from finely divided solid matter by counter-current heating with inert gas. In a treatment of this kind the heat economy is an important problem because the fine division, which is desirable to obtain a uniform and effective driving off, may involve a so high flow resistance of the charge that the gas can not be forced through it unless relatively small layer thicknesses are used, whereby the time of treatment may become so short that the gas only delivers a small part of its heat content to the charge, viz. it is necessary to use a great surplus of gas or a high excess temperature of the gas.

The present invention has for an object to remedy this and relates to a method and an apparatus for the said purpose which have as a main characterizing feature that the charge is passed downwards through a narrow shaft through which the gas is repeatedly forced transversely at constantly higher levels, namely at first in a cooling zone for calcine at which the gas is preheated by the latter, and thereafter in a heating zone into which the gas passes after having at first passed through a heating device so as to be heated to a higher temperature than the desired maximum temperature of the charge, and in which the gas together with increasing quantities of driven-off gas delivers heat to the charge.

Further features of the invention will appear from the following description of a convenient embodiment, reference being had to the drawing which illustrates an example of a calcining furnace particularly designed for driving off the loose sulphur atom of sulphur ore in particular, the reduction of Fe, S to FeS by heating with S in counter-current to temperatures below sintering temperature, for example to about 850 centigrades, such as it has for example been described for treating iron pyrites in my copending United States patent application Ser. No. 61,376, now U. S. Patent No. 2,653,905.

The drawing shows a vertical walled furnace 1 provided with a metallic casing 2. The furnace is assumed to be made with an elongated cross-section having its greatest cross-sectional dimension at right angles to the plane of the drawing, and the furnace space is formed by a narrow shaft 3 with parallel and plane vertical walls, viz. with elongated rectangular cross-section. At the top the walled shaft 3 is continued by a metallic casing 4 in the uppermost portion of the furnace.

Feeding takes place at the upper end where the casing 4 has an inlet with a connecting flange 5, permitting airtight connection of bags for example with sulphur ore. In the inlet there is also mounted a valve 6 to shut out the outer air when no charging takes place. At the bottom the shaft 3 is closed by a discharging device consisting of a rotating drum 7 which closes the lower end of the shaft while leaving a slot 8 and which by its rotation entrains calcine from the slot downwards into a collecting chamber 9 having an airtight closure in the form of a counter-weighted flap 10. Also the outlet under atent O M 2,821,461 Patented Jan. 28, 1958 the flap 10 has a flange 11 for airtight connection of containers for calcine, which for example is of importance in the process according to my said United States Patent No. 2,654,905, in which the material supplied to the leaching plant should be kept in an inert atmosphere.

or another inert gas, such as N is by means of a pump 12 forced into the furnace 1 at the bottom and, for passing the gas upwards through the furnace, in the latter at a short distance from the shaft 3 and alternately on either side thereof passages 13, 14 are provided in a lower zone and passages 15, 16, 17 in an upper zone. These passages extend stepwise upwards through the furnace and are provided with inlets to and outlets from the shaft in such positions that the outlet from one passage is directly opposite to the inlet to the next in each zone. These inlets and outlets are made in the form of grates with horizontal grate bars 18 which in crosssection are sloping downwards towards the shaft so as to prevent the charge from entering the passages. A similar inlet and outlet respectively are provided opposite to the outlet from the passage 14 and the inlet to passage 15 and are mutually connected by a passage 19 in which for example an electric heating element 20 has been inserted in airtight position.

The uppermost passage 17 leads into a space 21 in which the gas by means of horizontal walls is conducted in a labyrinth-like manner upwards around the casing 4 to an outlet at the upper end of the furnace, from which a conduit 22 is passed to the upper end of a cooler 23, provided at the bottom with a liquid seal 24 and with a conduit to the pump 12.

Due to the fact that in this manner the gas is forced through the shaft only in short paths and over the full width of the shaft it becomes possible to maintain the necessary circulation of the gas with a reasonable pumping power. In the areas of gas traversal within the lower zone the gas contacts the calcine which has been heated by gas that has passed along the heating element 20, in other words in this zone there occurs a cooling of the calcine while the gas is preheated. In the areas of traversal within the upper zone there will occur a successive heating of the charge and a consequent drivingoif of the loose sulphur atom of the ore by means of the hot gas, which enters from the passage 19 at a temperature somewhat above the desired maximum temperature of the charge and which thereby, While entraining the sulphur gas formed, undergoes a successive cooling. Thus, when entering the space 21 the gas mixture may have been brought down to a temperature which justifies the use of metallic shaft and guiding walls. Due to the consistency of the charge the flow resistance longitudinally of the shaft will be so high that practically no gas flow will take place from one traversing area to the next. However, the sections between the uppermost traversing area of the lower zone and the lowermost traversing area of the upper zone, i. e. the hottest section of the shaft, as well as the section extending from the lowermost traversing area of the lower zone to the outlet slot 8 are made somewhat longer than the remaining sections in order effectively to bar any direct passage of relatively cold gas to the heating zone of the shaft and escape of gas through the shaft outlet.

In the cooler 23 the entrained sulphur gas is condensed to liquid sulphur, which escapes through the liquid seal 24, while the S0 gas returns to the pump 12 through conduit 25, so that a constant circulation of S0; is maintained.

Though the invention has been specifically described as used for the treatment of sulphur ore with circulating 80,, this treatment may of course be carried out with any other, gas, such as nitrogen, which does not react with sulphur. vapor or calcine at the temperatures employed.

I claim:

A process for treating sulfur containing ore to drive off sulfur and recover the same as liquidsulfur which consists in passing said ore while in finely divided c'ondition continuously through a preheating zone, a heating zone, and a cooling zone, excluding air from the ore during its passage through said zones, flowing inert gas selected from the group consisting of sulfur dioxide and nitrogen counter-current to the flow of said ore, contacting said ore in the cooling zone with inert gas to extract heat from the treated ore by forcing inert gas transversely thereof stepwise and progressively upwards from the bottom of said cooling zone to the top, diverting the preheated gas from the ore and heating said gas to a temperature at which sulfur volatilizes, bringing the resultant heated gas into physical contact with the ore to be treated in the heating zone whereby sulfur is volatilized from the ore by forcing said heated gas transversely thereof stepwise and progressively upwards from the bottom of the heating zone to the top, thereafter separating the gas and the sulfur entrained therein from the heat-treated ore material, then conducting the sulfur laden heated gas into heat exchanging relationship with the ore as it passes through the preheating zone while maintaining said sulfur laden gases out of direct physical contact withthe ore entering said preheating zone whereby the ore is preheated by said sulfur laden gas without 4 causing condensation of sulfur, and recycling the gas from the gas exit end of the preheating zone to the gas inlet end of the cooling zone in a closed circuit with the gas being cooled to condense the sulfur therein as liquid sulfur.

References Cited in the file of this patent UNITED STATES PATENTS 1,473,723 Fogh Nov. 13, 1923 1,551,814 Dupuy Sept. 1, 1925 1,782,225 Bacon Nov. 18, 1930 1,895,284 Hay Ian. 24, 1933 1,925,027 Bollrnann et al Aug. 29, 1933 1,929,408 Bunce Oct. 10, 1933 1,963,282 Stimmel et al. June- 19, 1934 2,011,039 Crothers Aug. 13, 1935 2,031,801 Tyrer Feb. 25, 1936 2,068,842 Bradley Jan. 26, 1937 2,194,454 Greenawalt Mar. 19, 1940 2,302,841 Connolly Nov. 24, 1942 2,345,067 Osann Mar. 28, 1944 2,558,963 Klepetko et a1. July 3, 1951 FOREIGN PATENTS 343,048 Germany Oct. 27, 1921 13,165 Great Britain July 13, 1899 of 1898 147,117 Great Britain June 2, 1921

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