DK143168B - PROCEDURE FOR CONTINUOUS IMPLEMENTATION OF HEAT REQUIRED PROCESSES SEPCIEIELT ENDOTERMIC METALLURGICAL REDUCTION REACTIONS IN A HEAT-INSULATED REACTION CONTAINER - Google Patents

Description

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(11) PUBLICATION NOTICE 143168 DENMARK (B1) Int. Cl.3 F 27 B 7/02 UMmviMni \ C 22 B 5/00 § (21) Application No. 1 1 1/74 (22) Filed on 9 * J & n. 1974 (24) Living day vs. Jan 1974 (44) The application submitted and the submission document published on 6 July. 1 So]

DIRECTORATE OF

PATENT AND TRADEMARK (3 °) Priority requested from it

Jan 9 1973a 7300240, SE

Jan 9 1973a 730024-1, SE

(41) Aim. tllg. July 10. 197 ^ <71> GRAENGES SHARE COMPANY, 18 Gustav Adolfs torg, Stockholm, SE.

(72) Inventor: Karl Jonas Valter Svensson, 12 Grindvaegen, Strossa, SE.

(74) The clerk omits the proceedings:

The company Chas. Hude.

^^ HHæMnannHHæiHHMææH ^ Mi ^^ HHMHMMæænaææMMHæBM ^^^ æB ^ HHMM ^ ææi ^ æi ^ HMææææMi (54) Process for continuous conducting heat-demanding processes, especially endothermic metallurgical reduction reactions, in a heat insulated reaction reaction.

The present invention relates to a method for continuously carrying out heat-demanding processes, especially endothermic metallurgical reduction reactions, in a heat-insulated reaction vessel designed as a mechanical furnace that is rotated at a slower rate than that at which the charge closest to the furnace wall ends moving. relative thereto, in which method the incoming reaction components are continuously introduced into the furnace at ambient temperature or preheated, and the resulting reaction products are continuously discharged, the entry and exit being effected so as to prevent the air from entering the furnace space.

The invention enables continuous operation by carrying out a whole series of processes which today are difficult to carry out continuously, e.g. endothermic reduction reactions, such as between solid carbonaceous reducing agents and solid oxide materials.

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The process is thus suitable for industrial execution of the so-called segregation process in which copper or nickel contaminants are reduced without melting their oxide ore in the form of metallic grains of such size that they can later be separated from the ore by flotation or, when applies to nickel, even by magnetic separation. The process of the invention is particularly suitable for the segregation of garnieritic nickel ore.

Laboratory experiments have demonstrated the possibility of using the segregation method for the extraction of nickel from oxidic ores. These experiments show that by mixing oxide nickel ore with CaCl 2, 2 O and coke, all in finely divided form, then the mixture is heated in a nitrogen atmosphere to ca. 1000 ° C and keeping the mixture at this temperature for a suitable time, the nickel can be separated along with a small amount of the iron in the form of particles which can be separated from the ore by flotation or magnetic concentration.

However, no industrially applicable process has emerged. One difficulty in the industrial adaptation of the segregation process is the maintenance of the appropriate atmosphere in the furnace. The process seems to work best when maintaining an autogenous atmosphere, i.e. that the gases developed during the process alone will form the furnace atmosphere.

Copper ore segregation according to the so-called TORCO method solves the problem of how to use the segregation process industrially by first preheating the ore to a sufficiently high temperature and then introducing it together with the reagents in a special furnace room where the process takes place without heat supply . This process is not suitable for nickel ore as it would require preheating to 1200-1300 ° C. However, it has been found that preheating the ore above 900 ° C decreases the nickel yield by segregation, and this all the more the preheat temperature is brought to exceed 900 ° C. Apart from this, however, it is quite impossible to preheat garnish ore to 1200-1300 ° C, since a strong sintering of the ore takes place already when the temperature exceeds 1150 ° C.

The present invention aims to enable the process of conducting the nickel ore segregation process on an industrial scale under optimal conditions, especially with respect to the furnace atmosphere, while at the same time undertaking a far grinding of the ore. The grinding is necessary in order to be able to release the ferronicle particles from gaits so that they can later be separated mechanically.

This is achieved according to the invention in that the heating of the furnace charge to the temperature required to carry out the process is effected solely by the heat supplied to the furnace charge by the rotation of the furnace.

An oven for carrying out the method according to the invention may consist of a recumbent cylindrical oven chamber with outwardly projecting end bottoms, provided with centrally located supply and discharge devices for goods to and from the otherwise fully closed oven chamber, and the oven chamber and end pieces may consist of a strong casing with an internally disposed, heat-insulating layer, which is covered by a heat-resistant, durable and corrosion-resistant for the reaction gases, with the inlet and outlet devices provided with sealing means for preventing air access to the furnace chamber.

Assuming that ore is calcined at 700-900 ° C and then, without being cooled, introduced into the mechanical rotary kiln along with the necessary reagents, one can normally expect 200-300 kWh to be supplied to the furnace per hour. tons of calcined ore to carry out the segregation process. This is half the amount of energy that is used to melt the hot calcined ore in an electric furnace and produce ferro-nickel, which is currently the commonly used method of treating garnishe ore.

Examples of various embodiments of the practice of the method according to the invention are shown in the drawings, in which fig. 1 shows an exemplary embodiment in which the goods supplied to the mechanical furnace are first preheated and optionally calcined in another furnace; 2 shows a similar embodiment, but in this case outgoing goods are cooled from the mechanical furnace in a recuperative air heat exchanger. This preheated air is then used as combustion air in the first furnace, FIG. 3 shows an embodiment in which the incoming goods are processed without preheating in the mechanical furnace; FIG. an embodiment where the preheating is done by means of heat exchangers on the supply and discharge side. On the departure side, the outgoing goods preheat the air, which is then used to preheat the incoming goods.

In all the figures, one and the same embodiment of the mechanical furnace is provided with various auxiliary devices for carrying out the method according to the invention. Details common to the various figures have thus been given the same designations.

As shown in the figures, the furnace is in the form of a straight cylinder 1 with horizontal axis 2 and outwardly slightly raised end walls 3 · It is to slightly less than half the volume filled with goods and grinding elements. The heating of the goods takes place by rotating the furnace around its horizontal axis.

The stove consists of a strong steel sheath 5? within which there is a heat-insulating layer 6, and therein a heat-resistant 7 for high resistance to mechanical wear, and which, moreover, has good resistance under the conditions prevailing in the furnace, for example a melt-cast alumina or silicon carbide. In each of the end pieces there is a centrally located pin formed with an equally centrally located round opening 8, 9j where one opening 8 is somewhat larger than the other opening 9 · Otherwise the oven is completely closed. Through the smaller opening 9, the solids needed for the reaction are introduced and through the larger opening 8 the solid reaction products are withdrawn. In cases where a gas constitutes one of the reaction components, it may in some circumstances be advantageous to pass it through the aperture 8 and out through the aperture 9- The gas introduced then comes together with the gas possibly developed in the furnace to move in the gas. countercurrent to the fixed goods. Also, when no gaseous components are introduced into the furnace, it may be convenient to extract the gases formed by the reaction through the opening 9.

Suitably, the solid material can be supplied to the furnace by means of a feed auger 10 from a silo 11 in which the incoming goods mixture is stored.

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FIG. 1 and 2 illustrate methods convenient in carrying out the garnierite-type nickel ore segregation process which, in addition to containing at least 20% water as surface moisture, contains at least 10% chemically bonded water. To remove this water, the ore is suitably calcined, after being pre-treated by partial drying, sieving and crushing, at a temperature of 700-: 900oC and then transferred in hot state together with the necessary reagents to the mechanical furnace.

In Figs. 1 and 2, it is thus assumed that the ore is first preheated in a furnace 12, from which the goods fall into the silo 11. The furnace 12 is supplied with hot air by a fan 3 * + through a pipeline 38. The feed auger 10 can then be suitably made with water-cooled shaft. Other components may also be added to the silo 11 which is better added after the preheating, e.g. coal and calcium chloride in the nickel segregation process, from a separate silo 13.

In FIG. 3, it is provided that a liquid component is also supplied to the furnace, which is done through a pipe * + 0, which is passed through the hollow shaft of the feed auger at. The liquid is pumped with a pump k2 from the container k3 · The pipe cow seals against the shaft by means of a packing box kk. If the gas introduced and / or formed in the furnace is to be withdrawn through the inlet opening 9, this can be done in basically the same way, i.e. through the hollow shaft of the feed auger at.

The silo 1i in FIG. 3 and k are fed by a belt conveyor k5. The level in the silo 11 is checked with a level meter lk, e.g. of the gamma ray type.

The mounting of the furnace body 1 is suitably carried out by means of so-called hydrostatic bearings 15 on the inlet and outlet pins. In the same way as the furnace body, the bearing pins are otherwise provided with a heat-insulating layer and within this a lining of refractory, wear-resistant material. The bearings are also cooled by the circulating oil which carries the bearing pins. In order to facilitate the entry and exit of the goods through the pins, the inside of the liner may have been designed to form a more or less continuous screw thread 16 in the pins.

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As shown in FIG. 1 and 4, the discharge outlet of the furnace can directly flow into a silo 19. The silo is completely closed except for the gas outlet 37.

31 represents a gas cleaner and collector connected to the conduit 37. The goods level is controlled and controlled with level meters 20, e.g. of the gamma ray type. Departure from the silo may be effected by means of a cellular or screw-type feeding device 21.

For example, the discharge of the hot goods into the silo after the stove can be effected by means of a transport auger or a cell feeder 21. In case it is important to protect the hot goods from oxidation, it is convenient to drop the goods into a gutter 22 As soon as the goods have begun to fall, it is hit by a wide jet of water 23, which is directed parallel to the longitudinal direction of the gutter. The amount of water in the jet is adjusted so that the goods are quickly cooled to below 100 ° C without the vapors being annoying. Both the outside of the silo and the shaft and sheath of the transport auger can be water-cooled if necessary because of the temperature of the goods being carried.

The volume of the furnace gases is usually low. The silo 19 for the outgoing goods is suitably provided with a dust chamber 36, where the bulk of the dust supplied with the gases can settle. If the furnace gases are withdrawn through the supply opening 9, a corresponding device should also be found there.

In another way of carrying out the method shown in FIG. 2 and 4, the goods are cooled indirectly in front of the silo and the recovered heat is used to preheat combustion air to a previous preheater (Fig. 2) or to preheat the incoming goods to the furnace (Fig. 5). Both the cooling and preheating of FIG. 5 may be effected by means of each drum having an inner 25 and an outer sheath 25 of heat-resistant material. The inner sheaths are fixedly mounted on both the outlet and the access pins by means of a flange 26. The inner sheaths 25 are provided with screw threads 27j on the inside which carry goods forward by the rotation of the drum. In the space between the two concentric sheaths 25, 25 of the drum, there is a plate groove 28, the short sides of which are firmly connected to the sheaths 25, 25 or in each case sealing against the sheath surfaces. Near the end of the outer sheath, which is farthest away from the furnace, is a running ring 29. The running ring rests on rollers 30. The outer sheath does not extend all the way to the ends of the inner sheath, but ends somewhat before it. For sealing against the flanges 26, 32, a fixed helical housing 33 is provided at the supply end of the cooling drum and at both the supply and outlet ends of the preheating drum of FIG. * F. The former housing is shown in FIG. 2 connected to a fan 3 * + '? which through a conduit 38 'blows the preheated air into the preheater 12 where it is used as combustion air. In FIG. b, the same housing is connected to the corresponding housing 33 at the outlet end of the preheating drum by means of a pipeline 38 ". The housing located at the inlet end of this drum is connected to another fan 39 · Both fans 3 * +? 39 suck the air from the outlet end of the cooling drum to its entrance end through the helical space formed by the plate coil 28 and the two sheaths 2, 25. In FIG., the preheated air is sucked through the conduit 38 "through the preheating drum and cooled before passing the fan 39. at the outlet end there are seals 35 which prevent the air from entering the furnace or contacting the hot reaction product. By holding the goods in the silo 11 before the furnace and the goods in the silo 19 after the furnace above a certain level, the furnace gases are prevented from entering or the air enters through the feed devices 10, 21. The furnace gases are passed through a gas outlet where the pressure is kept at such a level that it is approximately the same in the reduction furnace as in the surrounding atmosphere.

The oven can be operated in several ways. A good way from a technical and economical point of view is to operate the furnace by means of one - or by large effects - two dental crowns, which are attached to the inlet and / or outlet end pieces in the same flange assemblies, by means of which the end pieces are attached to the casing . The transmission of the power to the gears is then done in a known manner by a drive or gear exchange and motor.

Instead of attaching the tooth rim to the end pieces, you can attach it to the bearing pins outside the bearings. In this way, the oven diameter is not limited by the diameter of the dental ring.

An entirely different way of operating the furnace is to do so directly by means of a low frequency electric synchronous motor whose stator 17 surrounds the furnace sheath and whose rotor 18 is attached thereto, as shown in FIG. 1 - * +.

It is also possible in this case that the engine is positioned on the stove pin. The direct operation is particularly interesting for very large effects. It also has the advantage that the oven speed can be varied as desired. With the help of the speed control the energy supplied per tons of goods passing through the furnace are regulated by constant feeding, which cannot be accomplished in the operation described previously without the use of special propulsion engines.

In order to be able to cool the furnace during shutdown, maintenance or inspection, it is necessary to be able to operate it at a low speed of the order of 0.1-0.01 of normal. By feeding at this rpm the furnace with a normal amount of non-preheated incoming goods, the oven is cooled relatively quickly. This can be accomplished by prior art in all drive devices.

The oven rotates at a speed lower than the so-called critical speed, above which the charge closest to the oven wall stops moving with the wall.

With a rpm which is below the critical, the charge gets a strong movement during the oven rotation. By making the oven diameter and length sufficiently large and insulating the walls of the oven sufficiently, it is possible to generate the heat needed for the process to be carried out by means of the reaction mixture's own movement inside the oven. At the same time, the commotion of the goods causes it to mix effectively and to disintegrate mechanically, i.e. that it is painted down. Both circumstances facilitate the course of the chemical reaction.

As the bulk weight of the reaction mixture is usually low, it is usually advantageous to add a certain amount of foreign paint to the furnace.

These must be resistant to the atmosphere prevailing in the oven and still consist of as heavy a material as possible as the power consumption of the oven and thus also the heat generation in the oven charge increases. Power consumption also increases with increased amount of paint bodies until $ 50 of the oven volume is filled with paint bodies. However, since the residence time of the reaction mixture in the furnace decreases as the loading with grinding elements increases and this decrease can adversely affect the reaction, it is generally best to settle for a grinding body lower than 50 $ of the volume of the furnace. Even a relatively small amount of heavy grinding elements greatly increases the power of the furnace, in that the power grows proportionally to the product of the weight of the load and the distance between the axis of rotation of the furnace and the center of gravity, and the heavy grinding bodies preferably occupy locations far from the axis of rotation. in the grinding bodies of the nickel segregation process are ferrous nickel produced e.g. by melting and casting the ferronicle powder obtained by the segregation process as this is stable in the corrosive atmosphere present in the furnace. Another useful material is alumina. If you use grinding bodies, it is best to crush the ore as far as possible from the beginning, as this is practically possible, since smaller grinding bodies can be used, and these wear less on the liner.

However, although the invention has now been described in connection with the segregation process, its use is by no means limited to it, but it can be used advantageously in carrying out a variety of other reactions. Examples of such are the following:

Fe203 + 3 C = 2 Fe + 3 ci (1) i

CuO + C = Cu + CO (2) t

NiO + C = Ni + CO (3) Ϊ i

ZnO + C = Zn + CO (* t)

Reactions according to formulas (1), (2) and (3) are carried out at such a temperature that there is usually no melting of the good batch. In the reaction of formula (V), the zinc will, in a known manner, go away in gaseous form, but there is no need for melting of the charge.

The invention also makes it possible to reduce the bulk of the iron content in tatanomagnetite and ilmenite in the form of a metallic powder which can be separated by magnetic means. The non-magnetic residual product can then be used more economically than the original material for the production of titanium oxide and, optionally, vanadium oxide. In order to obtain sufficient size of the iron particles, it is known that certain additives, such as borax, sodium carbonate, fluorspar, phosphorus, sulfur and others, act in a positive direction.

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The new approach also offers the solution of one of the most serious environmental problems of the time. It is possible, by this method, to extract copper, nickel, zinc, iron and others. metals directly by their sulphidic concentrates while bonding the sulfur as calcium sulphide.

Examples of such reactions are the following: *

CuFeS2 + 2 CaO + 2 C = Cu + Fe + 2 GaS + 2 CO (5) t

NiS + CaO + C = Ni + CaS + CO (6) f

FeS + CaO + C = Fe + CaS + CO (7) * ΐ

ZnS + CaO + C = Zn + CaS + CO (8)

CaS can then be used together with NaCl, CO2, water and air to prepare NaCO3, S and CaCl2 according to a process described in U.S. Pat. Bureau of Mines Report of Investigation 6928.

Examples of other reactions in which the process of the invention offers significant advantages are the following:

FeS2 = FeS + S (9) f 2 NaCl + H2S0i ^ = Na2S0 ^ + 2 HCl (10) A1203 ·: Si02 · 2 H2O + ^ (NH ^ SO ^ = 2 (ΝΗ ^) AKSO ^) 2 + 2 Si02 -1- 6 NH 2 + 7 h 2 O (11)

In reactions (9) - (11), it is of great importance that the gaseous products can be obtained in the most pure and concentrated form as possible, which has proved impossible in the furnace constructions used so far. On the other hand, the oven used in the process according to the invention goes well.