US2031504A - Manufacture of sulphur dioxide - Google Patents

Description

Feb. 18, 1936. B, F, RHODlN 2,U31,5@4-

MANUFACTURE OF SULPHUR DIOXIDE Filed NOV. 18, 1931 Patented Feb. 18, 1936 UNITED STATES PATsr OFFICE MANUFACTURE OF SULPHUR DIOXIDE Munroe, Belleville, N.

Application November 18, 1931, Serial No. 575,732

8 Claims.

Special objects of the present invention are to obtain from pyrites in fine particles, a rich uniform grade of sulphur dioxide, S02, free so far as possible, of solids or diluents and to effect such operation in a commercially practical, economical manner and by apparatus of relatively simple nature.

The foregoing and other desirable objects are attained by novel process, and by certain novel features of construction, combinations and relation of parts, all as hereinafter described and claimed.

The drawing forming part of the specification illustrates an embodiment of the apparatus for carrying out the invention, but it is to be understood that the structure may be modified and changed asregards this present disclosure without departure from the true spirit and scope of the invention.

. Fig. 1 is a side elevation illustrating structure embodying the invention; Fig. 2 is an enlarged broken vertical sectional view of the roasting unit; Fig. 3 is an enlarged broken plan. and part sectional view of the magnetic isolator unit; Fig. 4 is a vertical sectional detail as on lined-4 of Fig. 3.

In Fig. 1, a bin for holding the moisture free pyrites is indicated at 5 and a screwconveyor is shown at 6 for lifting the pyritesuptto the mouth I of the roaster 8. As indicated in this view, the gas is drawn off from the roaster by means of a suction fan 9 connected by a conduit l0 with the lower portion of the roasterand a magnetic isolator l I is interposed in this conduit to strip the gas of any magnetic oxides carried off from the furnace.

The special construction of the furnace will be understood from Fig. 2. The screw conveyor is shown connected in air tight relation with the throat of the furnace. The material fro-m this conveyor is deposited directly on a power actuated vibrating screen I2, which sifts the material through a screen l3 of proper mesh in a fine shower into the feeding funnel Hi. This screening mechanism may be provided with a discharge I 5 for larger lumps, and preferably this discharge chute is trapped or provided with valves to prevent entry of air.

The air'for oxidation is admitted in the present disclosure in two separate streams, one inside and the other outside the funnel l4. Thus the furnace top is shown provided with air openings 16 over the funnel and a separate set of airopenings I? about the funnel. For the purpose of independently regulating such openings, a damper plate i8 is indicated rotatably centered on the top of the furnace about the inlet throat and an annular damper ring I9 is shown rotatably engaged about the head portion of the furnace surrounding the funnel, said air inlet regulating dampers being indicated as controllable by suitable operating connections or handles 20, 2i.

The lower end of the feeding-in funnel is shown formed as a burner ring 22, supplied with gas or other fuel forinitiating combustion.

The combustion chamber built of steel plate or other suitable material extends downwardly from the funnel and may be lined with firebrick or the like as indicated at 23, within the zone of greatest heat. The walls of this chamber are shown as corrugated vertically at 24 to provide additional area for heat extraction purposes and substantially the full length of the furnace is shown as water-jacketed at 25. The bottom of the furnace chamber is shown as coned downwardly and as provided at the center with a discharge outlet 25 for the oxides, which outlet, if desired, may be provided with a suitable plug cock, such as indicated at 21.

The oxides collecting in the bottom are utilized in the present disclosure as a dry seal by mounting above the bottom cone a deflector having a downwardly conical bottom 28, overstanding the furnace bottom and an upwardly conical portion 29, forming an inclined wall or shoulder for directing the oxides down into the reversely inclined annular discharge throat which leads to the central discharge outlet. From the upper inclined deflecting shoulder 23, a cylindrical deflecting wall 30 rises and from the top of this wall an inner wall 3| extends downwardly as a central well, contracted toward its lower end at 32 into a smaller discharge chute 33, opening into the upper conical portion of the discharge outlet 26.

In the present disclosure, the outer and inner walls 28, 3B and 3i, 33 of the trap forming deflector are connected to form a water space 34, here shown as connected at topand bottom by piping 35, 36, with the main water jacket, such piping preferably being so arranged as to insure adequate circulation to enable the deflector to properly cool the gas and the resulting oxides.

Over the top of the well 3!, a cap 31 is shown coned upwardly and protected from the direct heat by a suitable fire-brick lining or cover 38. This overstanding deflector extends down about the cylindrical portion 30 to near the bottom seal, so as to force the gases to travel downwardly to the bottom of the furnace and to make a sharp Cal turn, so as to deposit matter in suspension, before rising through the annular channel 39 between the outer and inner deflector walls 31, 30. The gases are then forced to pass from beneath the top of the cap 37 downwardly into the central well 3| and thence laterally out through the main gas conduit In. In making the sharp turn necessary to enter this lateral outlet, a further deposit of any matter in suspension is made in the funnel-shaped lower end of the central well, such deposited matter sealing the well at the bottom against entry of air.

The magnetic isolator I l in the gas flow line is shown as made up of two units disposed one in each of the two forks or branches of the flow line as indicated in Fig. 3. The flow through these branches is shown as controlled by switch valves 40, 4|, located at the entering and leaving ends of the same.

Each unit of the magnetic isolator is shown as consisting of alternately arranged overlapping magnetizable plates 42, 43, extending respectively downwardly from the roof and upwardly from the fioor of the unit, Fig. 4, and hinged doors 44 are shown closing these chambers at the bottom, which doors can be opened downwardly to discharge any accumulation.

Operation The pyrites are fed by the closed conveyor to the top of the roaster and are there screened and simply dropped into the top of the furnace, without any air. By proper control of the mechanical conveyor and the screening device, this feeding of the powdered material may be accurately governed and kept substantially uniform.

Air for oxidation enters about and mingles with the shower of pyrites through the top opening Hi, the amount being governed by damper l8; and a second stream of air enters about the funnel and about the primary mixture through the side openings I1, the amount of this latter flow being governed by damper l9. Desired quantitatively relationship between air and pyrites for production of a rich S02 gas can thus be accurately controlled. That part of the air admitted above the funnel as compared to that portion admitted below the funnel may be regulated to effect the most speedy and complete combustion. The funnel being relatively hot serves as a preheater for the two incoming streams of air. Combustion having been established by the gas ring 22, the mixture burns by itself in the combustion chamber and practically complete combustion is effected, rapidly and uniformly, because of the fact that the air is induced by the suction on the gas outlet line and so accompanies the entering powder, mingling with the same and travelling in the same direction. Pyrites entering the roaster as described, have a tendency to travel at a slower rate of speed than the air and this tendency aids separation of resultant solids and gases, enabling practically complete separation in the furnace and minimizing the carrying off in the gas of finely divided particles in suspension. The oxides are deflected by the fire cap of the central deflector and deposited in the annular seal in the bottom of the furnace, while the gases reverse direction and travel up beneath this cap, reversing direction at the top and then flowing outwardly at right angles through the gas flow pipe H The first reversal of flow tends to throw matter in suspension down into the main portion of the dry seal and the subsequent reversal and lateral flow tends to throw remaining matter in suspension down into the bottom of the central well, which communicates with and discharges into the main seal at 33.

The corrugated structure and water jacketing of the combustion chamber effects rapid cooling, so that the gases leaving the roaster and the oxides taken off at the bottom are relatively cool. The combustion may be controlled in part by regulating the suction exerted on the gas flow line and temperature may be governed by regulating the water cooling effect of the deflector which forms the seal and part of the gas flow line. By speedy flow through the critical temperature zone, the formation of trioxide is kept at a minimum and substantially pure sulphur dioxide is produced. The oxides formed and minute amounts of which may be carried off in suspension from the furnace chamber are of a magnetic nature and so are readily caught by the plates of the magnetic isolator units. After one unit has been in service for some time, the valves 40, 4|, may be thrown, as will be clear from Fig. 3, to switch flow from the fork containing that unit to the fork in which the other unit is located. Upon cutting off the magnetizing current in the first unit, the magnetic oxides will drop and may then be removed by way of the bottom doors of the unit. S02 delivered by the fan is ready for manufacture of sulphuric acid, but for production of bisulphite liquor vit is possible that removal by ordinary well-known means of such SO: as may be present, might be considered advisable before absorption in the towers. The water heated in the jacket and in the sealing deflector of the furnace may be used for various industrial purposes and the flow may be regulated to gain the desired cooling efiect in the furnace and the heat required for such industrial uses, so long as the latter does not conflict with the former. Various clean-out, sight or manhole covers may be provided in the furnace wherever desirable, such as indicated for example at 45, in Fig. 2. The oxides slide freely off the inclines of the deflector and furnace bottom and the feed rate and discharge rate may be regulated to maintain the desired seal at the furnace bottom.

By the present construction and particularly by taking in regulated quantities of air alongside of the pyrites and independently of the feeding in of the pyrites, substantially uniform and pure rich gas is produced and any small proportions of soilds carried over from the furnace are caught and removed in the magnetic isolator.

The apparatus is relatively simple, particularly 7 because of the fact that combustion and deposit of solids are all effected in the single furnace chamber in which the proportion of air to pyrites is accurately governed. The volume of air is preferably so regulated as to oppose formation of sulphur trioxide, but sufiicient oxygen is admitted to insure rapid complete combustionand immediate deposit of oxides. To magnetically precipitate or isolate any fine solids carried out of the furnace in the gas, it is necessary that the same possess magnetic properties. The iron oxides produced from pyrites in this furnace or flash roaster are non-magnetic above certain temperatures, but become magnetic upon reduction below certain temperatures. There is therefore provided in the illustration, Fig. 1, a water jacket or cooling chamber 46 about a portion of the gas out-flow pipe in advance of the magnetic isolator, which can be used if needed to bring the temperature of matter in suspension down to the point where the same will be attracted and held to the magnetic plates. This cooler also is of advantage in cooling the gas and lessening the work on the fan.

The process and apparatus disclosed, while at present considered preferable, may be modified in various ways within the true intent and scope of the claims and it should be understood further that the terms employed herein have been used in a descriptive rather than in a limiting sense, except possibily for such limitations as may be imposed by the state of the prior art.

What is claimed is:

1. Apparatus for production of sulphur dioxide from pyrites, comprising in combination with a furnace structure, a mechanical pyrites conveyor closed to admission of air and arranged to deliver pyrites into the top of the furnace, the upper portion of said furnace having controllable air inlets adjustable to regulate admission of air entirely independently of the pyrites feed, means for trapping the oxides and venting the gas from the bottom of the furnace structure and including a gas discharge line, means for applying suction to said gas discharge line to draw off the gas and to induce a supply of air into the top of the furnace in accordance with the regulation of the adjustment means aforesaid, said trapping means including a tubular water cooled deflector having gas passages about the same and external inclined surfaces for directing the oxides to form dry seals.

2. In apparatus of the character disclosed, a vertically arranged furnace structure, a feedingin funnel at the top of the furnace having a material inlet, a mechanical conveyor closed to admission of air and discharging into said material inlet of said funnel, a regulatable air inlet in the top of the funnel about said material inlet, a separately regulatable air inlet about the funnel, the furnace structure having a discharge for solids in the bottom of the same, deflecting means for trapping a seal of solids in the bottom of the furnace, deflecting means above said solids seal deflecting means for trapping out and for separating gases from the solids in the lower portion of the furnace and including a gas discharge conduit and means for applying suction to said conduit to withdraw the gas and to induce air for combustion into and about the'feeding-in funnel in accordance with the regulation at such points.

3. The process of oxidizing fine particles in suspension in a roaster having a throat opening into the combustion zone which comprises shaking the material through a screen in the form of fine particles into said throat separately from the air for oxidizing and supplying the air for oxidizing purposes to the combustion zone separately and independently of the supply of material by applying suction to a remote portion of the combustion zone and admitting a regulated quantityof free atmospheric air into the shower of particles shaken from the screen.

4.'Apparatus of the character disclosed, comprising in combination a roaster for pyrites or the like non-magnetic material, having an inlet for the material and adjacent free air inlets for the oxidizing air separate from the material inlet,

a gas ofitake extending from the roaster, means for exerting suction on said oiftake to induce air through said free air inlets, a cooling section in said offtake where the temperature is sufiiciently reduced for iron oxide particles in suspension in the gas to exhibit magnetic properties and a magnetic isolator acting on said portion of the ofitake.

5. In apparatus for the roasting of fine particles of pyrites in suspension, a furnace having an inlet funnel for the material to be roasted and separate and distinct main inlets for oxidizing agent, one opening inside said material inlet funnel and the other opening outside said inlet funnel, separate dampers for said inside and outside inlets and providing means for eifecting separate minute regulation of said inlets, said inlets being open to atmosphere to admit oxidizing air under the pull of suction and means for applying suction to the interior of the furnace.

6. In apparatus for the roasting of fine particles of pyrites in suspension, a furnace structure having an inlet for the material to be roasted, a water jacket for said furnace, a cooler in the furnace at a point removed from the material inlet and connections for eifecting circulation of cooling fluid between said water jacket of the furnace and said cooler.

'7. In apparatus for the roasting of fine particles of pyrites in suspension, the combination of a roasting furnace having a material inlet at the top, a solids removal outlet in the bottom and a gas outlet in the side, whereby the main solids will travel downwardly and may be removed at the bottom of the furnace and means for forcing gaseous and the remaining solids products to travel upwardly and again downwardly before reaching the side gas conduit, said latter means consisting in part of a sealing trap in communication with the downwardly flowing stream of the gaseous products.

8. In the roasting of pyrites or the like, the process which comprises entering the pyrites downwardly into a roaster under reduced atmospheric pressure without a supply of oxidizing air and entering air for oxidizing purposes at atmospheric pressure into the zone of reduced pressure in two separate streams, one a vertically downwardly flowing stream mixing at once with the entering pyrites and the other a lateral stream in the form of an annulus surrounding the entering stream of descending air and pyrites and minutely regulating said vertical and lateral air streams independently of each other and independently of the supply of pyrites to effect desired combinations with the latter in the zone of reduced atmospheric pressure.

BRODDE E. F. RHODIN.

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