FI58945C - SAETT ATT GENOMFOERA ENDOTERMA METALLURGICAL REDUCTION PROCESSER WITH HJAELP AV EN KONTINUERLIGT ARBETANDE MEKANISK UGN - Google Patents

Description

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(41) Tullut) «llklMksl - Bltvlt off« ntll | qj lantti. ) · R * klstwitiallltu · NlhtMtol, »**, j. kuLlulk * »pvm.- nitut och r * glfterttyr * lMn 'AntOktn titled och utUkrHten published 30.01.81 (32) (33) (31) Pyy« u «y · οι © ^ · μ» ~ »· (Μ prtoriwt 09.01 .73 O9.Ol.73 Sweden-Sweden (SE) 73002U0-U, 73002U1-2 (71) Granges Aktiebolag, 18, Gustav Adolfs torg, Stockholm, Sweden-Sweden (SE) (72) Karl Jonas Valter Svensson, Strossa, Sweden-Sweden (SE) (7U) Berggren Oy Ab (5U) Method for carrying out endothermic metallurgical reduction processes by means of a continuous mechanical furnace - Sätt att genomföra endothermic metallurgical reduction process with the use of continuous mechanical machining

The present invention relates to a method for carrying out heat-demanding processes, in particular metallurgical reduction reactions, by means of a continuously rotating mechanical furnace.

The invention enables continuous operation when carrying out a large number of processes which are currently difficult to carry out continuously, e.g. endothermic reduction reactions between e.g. solid, carbonaceous reducing agents and solid oxide-containing substances.

The method is thus well suited to the industrial performance of the so-called segregation process, in which copper or nickel compounds are reduced without melting their oxide ores in the form of metal granules so that they can then be separated from the side stone by foaming or, in the case of nickel, by magnetic separation. A particularly suitable method according to the invention is for the segregation of garnierite nickel ore.

Laboratory experiments have shown that the segregation method can be used to recover nickel from oxide ores. These experiments show that by mixing oxide nickel ore with CaCl 2 * 2H 2 O and coke, all finely divided, and then heating the mixture under a nitrogen atmosphere to about 1000 ° C and maintaining the mixture at this temperature for a suitable time, nickel and a small amount of iron are segregated into granules. in a form that can be separated from the side stone by foaming or magnetic enrichment. However, no industrially applicable method has been identified 2 58945. One difficulty in the industrial application of the segregation process is the maintenance of a suitable atmosphere in the furnace. The process seems to work best when maintaining an autogenous atmosphere, i. the gases evolved during the process alone are allowed to form the furnace atmosphere.

When segregating copper ores according to the so-called TORCO method, the problem of industrial application of the segregation process is solved by first preheating the ore to a sufficiently high temperature and then feeding it together with the reagents to a special furnace where the process takes place without heat input. This process is not suitable for nickel ore as it would require preheating to 1200-1300 ° C. However, it has been shown that preheating the ore above 900 ° C reduces the nickel yield in segregation, even more so the more the preheating temperature exceeds 900 ° C. However, completely independent of this fact, it is quite impossible to preheat the garnierite ore to 1200-1300 ° C, because the ore sinters strongly even when the temperature exceeds 1150 ° C.

It is an object of the present invention to make it possible to carry out a segregation process for nickel ores on an industrial scale under optimal conditions, in particular with regard to the furnace atmosphere, while providing extensive ore grinding. Grinding is necessary to release the ferronickel particles from the side rock so that they can then be mechanically separated.

This is achieved by continuously feeding the reaction components into a thermally insulated reaction vessel rotating about a horizontal axis, either at ambient temperature or preheated, and continuously withdrawing the resulting end products during feeding and taking out so as to substantially prevent air from entering the reaction space, and the process of the invention. is characterized in that the rotational speed of the furnace is lower than the speed at which the movement of the feed product closest to the furnace wall relative to this wall ceases, and that the furnace charge is heated to the reaction temperature only by the mechanical work of the furnace rotation. The furnace for carrying out the method according to the invention consists of a strong jacket inside which a heat-insulating layer is covered, which is covered by an inner liner resistant to heat, abrasion and etching of reaction gases, and inlet and outlet means provided with sealing means to prevent air from entering the furnace chamber.

3,58945

Provided that the ore is calcined at 700-800 ° C and then fed without cooling to a mechanical rotary kiln along with the necessary reagents, it will normally be calculated that 200-300 kWh per tonne of calcined ore must be fed to the kiln to perform the segregation process. This is half the amount of energy required to smelt hot, calcined ore in an electric furnace to produce ferronickel, which is the process currently commonly used to process garnierite ore.

The accompanying drawing shows examples of different procedures for carrying out the method according to the invention. Figure 1 shows an application example in which the goods entering a mechanical furnace are first preheated and possibly calcined in a second furnace. Figure 2 shows a similar embodiment, but in this case the goods leaving the mechanical furnace are cooled in air in a heat exchanger to be recovered. The preheated air is then used as combustion air in the first furnace. Figure 3 shows an embodiment in which the incoming goods are treated without preheating in a mechanical furnace. Figure 4 shows an application example in which preheating is performed by means of heat exchangers on both the supply and discharge side. On the discharge side, the exiting goods preheat the air, which is then used to preheat the input goods.

All figures show the same embodiment of a mechanical furnace equipped with different auxiliaries for carrying out the idea of the invention. The details which are common to the various figures are then given the same reference numerals.

As shown in the figure, the oven is in the form of a straight cylinder 1 with a horizontal axis 2 and slightly outwardly convex ends 3. It is slightly filled to half its volume with goods and grinding pieces 4. The goods are heated by the oven rotating about its horizontal axis.

The furnace consists of an outer, strong steel jacket 3 with a heat-insulating layer 6 inside and a heat-resistant lining 7 inside, which is a material very resistant to mechanical wear and otherwise tolerant of the conditions in the furnace, for example molten cast alumina or silicon carbide. Both ends have a central pin with a similarly central circular hole 8, 9, one of which is slightly larger than the other 9. Otherwise the oven is completely closed. From the smaller hole 9 the solids necessary for carrying out the reaction are fed in and from the larger hole 8 the solid reaction products 58945 are removed. In the event that one of the reaction components is a gas, it may be advantageous in certain circumstances to feed it in through the opening 8 and remove it from the opening 9. The supplied gas, together with any gas formed in the furnace, then flows countercurrent to the solid. Even when no gaseous components are fed to the furnace, it may be advantageous to remove the gases formed during the reaction through the hole 9.

The supply of solids to the furnace can suitably take place by means of a helical feeder 10 from a pocket 11 in which the feed mixture is stored.

Figures 1 and 2 show procedures suitable for performing a segregation process on gamierite-type nickel ores which - except that they contain at least 20% water as surface moisture - contain at least 10% chemically bound water. To remove this water, the ore is calcined - suitably after first pretreatment by partial drying, screening and crushing at -700-900 ° C, and then transferred warm, together with the necessary reagents, to a mechanical furnace.

Figures 1 and 2 thus require that the ore first preheat in a furnace 12 from which the goods fall into a pocket 11. Hot air is supplied to the furnace 12 by a fan 34 down the pipe 38. The spiral feeder 10 can then suitably be provided with a water-cooled shaft. Other components can also be fed into the pocket 11, which is better added after preheating - for example carbon and calcium chloride in the nickel segregation process - from a separate pocket 13 ·

In Fig. 3, it is required that a liquid component is also fed into the furnace, which takes place along a pipe 40 passed through the hollow shaft 41 of the helical conveyor. The liquid is pumped by a pump 42 from a tank 43 · The pipes 40 are sealed relative to the shaft by means of a sealing box 44. In the event that the gas supplied to and / or formed in the pump is to be discharged through the supply hole 9, it can in principle be done in the same way, i. through the hollow shaft 41 of the helical feeder. The pocket 11 according to Figures 3 and 4 is fed by a belt conveyor 45. The height of the surface in the pocket 1 is monitored by surface height meters 14, which may be e.g. of the gamma radiation type.

The oven body 1 is suitably mounted on bearings so-called. Hydrostatic bearings 15 on the feed side and the outlet side of the pins. The bearing pins, like the other parts of the furnace, are provided with a heat-insulating layer and a lining of refractory, wear-resistant material on the inside. The bearings are further cooled by the circulating oil which supports the bearing pin a. To facilitate the transport of the goods in and out through the pins, the inner surface of the liner may be formed to form a more or less uniform screw thread 16 to the pins.

As shown in Figures 1 and 4, the furnace outlet pin can open directly into the pocket 19. This pocket is completely closed, except for the degassing line 37. Numeral 31 denotes an exhaust gas purifier and collector connected to line 37. The height of the surface of the article is monitored and controlled by level gauges 20, which are of the gamma beam type, for example. Removal from the pocket can be performed with a tray or spiral type feeder 21.

Removal of warm goods in the pocket after the oven can be performed, for example, by a helical feeder or a tray feeder 21. In case it is important to protect the hot goods from oxidation, it is suitable to allow the goods to fall into the chute 22. As soon as the goods start to fall. in the longitudinal direction of the gutter. The amount of water in the jet is set so that the goods cool rapidly below 100 ° C without evaporation. Both the outer surface of the pocket and the spiral feeder shaft and housing can be water-cooled if required due to the temperature of the goods to be removed.

The volume of the furnace exhaust gases is usually small. However, it is suitable to provide the outlet pocket 19 with a dust chamber 36 into which most of the dust following the gases is allowed to settle. In the event that the furnace gases are removed through the supply opening 9, a similar device must be provided there as well.

According to another use of the method shown in Figures 2 and 4, the article is cooled indirectly before the pocket, and the heat thus recovered is used to preheat the combustion air of the preheating furnace (Figure 2) or to preheat the article fed to the furnace (Figure 4). Both cooling and preheating according to Figure 4 can each take place on their own drum with an inner 24 and an outer jacket 25 of heat-resistant material. The inner sheaths are fixedly attached to the outlet and feed pin, respectively, by a flange 26. The inner sheaths 24 are provided on the inside with threads 27 which carry the goods forward as the drum rotates. Between the two concentric sheaths 24, 25 of the drum there is a disc coil 28, the short sides of which are fixedly attached to the sheaths 24, 25, or at least seal against the sheath surfaces. Near the end of the outer jacket farther from the oven is the tread ring 29 · The tread ring 6 58945 rests on rollers 30. The outer jacket does not extend to the ends of the inner jacket but ends just before these. Sealing against the flanges 26, 32 is a stationary helical housing 33 at the inlet end of the cooling drum and at both the inlet and outlet ends of the preheating drum in Fig. 4. The first-mentioned housing is connected in used as combustion air. In Fig. 4 the same housing is connected by a cable 38 "to a corresponding housing 33 at the outlet end of the preheating drum. The housing at the supply end of this drum is connected to a second fan 39. Both fans 34, 39 suck air from both sheaths 24, 25. In Figure 4, the preheated air is sucked down the duct 38 "through the preheating drum and cools before it passes through the fan 39.

Both the inlet and outlet ends of the furnace have seals 35 which prevent air from entering the furnace or coming into contact with the hot reaction product. By keeping the surface of the article in both the previous pocket 11 of the oven and the pocket 19 after the oven at a certain height, the oven gases cannot penetrate out and the air cannot penetrate through the feeders 10, 21. The furnace gases are discharged along a gas discharge line, the pressure of which is maintained at such a level that the pressure in the reduction furnace remains approximately the same as in the ambient atmosphere.

The use of the oven can be arranged in many ways. One technically and economically good way is to operate it via large - or high-power - two large toothed rings attached to the inlet and / or outlet ends in the same flange connection with which the ends are attached to the jacket. The transmission of force to the gear rings then takes place in a known manner via the drive wheel, gearbox and motor.

Instead of attaching to the ends, the rack can be attached to bearing pins on the outside of the bearings. In this way, the diameter of the oven is not limited by the diameter of the ring gear.

A radically different way of rotating the furnace is to do it directly with a low frequency electric synchronous motor with a stator 17 surrounding the furnace casing and having a rotor 18 attached to the furnace casing, as shown in Figures 1, 2, 3 and 4. In this case, it is also conceivable that the motor is fitted to the furnace pin.

This direct use is particularly interesting at very high powers.

It also has the advantage that the oven speed can be varied at will. By adjusting the speed, the energy consumption per 7,58945 tons of goods passing through the oven can be adjusted while keeping the feed constant, which cannot be done with the operation described above without special drive motors.

In order for the oven to be cooled for decommissioning, maintenance or inspection, it must be possible to run it at a low speed of the order of 0.1 to 0.01 times the normal speed. Feeding a normal amount of unheated feed to the oven at this speed will cause the oven to cool relatively quickly. This can be achieved with the prior art on all actuators.

The furnace rotates at a speed lower than the so-called critical speed, above which the charge closest to the furnace wall ceases to move relative to the furnace wall.

At speeds below the critical speed, the charge receives strong movement due to the rotation of the furnace. By rolling the diameter and length of the furnace large enough and thermally insulating the furnace walls to a sufficient extent, it is possible to generate the heat necessary to carry out the process by the reaction mixture's own movement in the furnace. At the same time, the avalanche of goods causes it to mix efficiently and mechanically grind, i.e. grinds to a smaller size. Both of these factors facilitate the course of the chemical reaction.

Since the bulk density of the reaction mixture is usually low, it is most often advantageous to charge the furnace with a certain number of foreign grinding pieces. These must be able to withstand the atmosphere in the furnace and, in addition, be as heavy as possible, since the power consumption of the furnace and thus also the development of heat in the furnace charge are thus increased. The power consumption therefore increases as the number of grinding pieces increases until 50% of the furnace volume is filled with grinding pieces. However, since the residence time of the reaction mixture in the furnace is shortened as the grinding-piece filling increases, and this shortening may adversely affect the reaction, it is usually best to settle for less than 50% of the furnace volume. Also, a relatively small number of heavy grinders greatly increases the efficiency of the furnace because the power consumption increases relative to the product of the weight of the charge and the distance between the axis of rotation of the furnace and the center of gravity of the furnace, and the heavy grinders are primarily located far from the axis. A suitable grinding body material in the nickel segregation process is ferronickel, which is prepared, for example, by melting and casting the ferronickel powder obtained in the segregation process because it is stable in the corrosive atmosphere in the furnace. Another useful material is aluminum 8 58945 oxide. If grinding pieces are used, it is best to crush the ore from the outset as far as practicable, because then smaller grinding pieces can be used and these consume less of the inner lining.

Although the invention has been described above in connection with a segregation process, its use is by no means limited to this, but can be advantageously used in carrying out a number of other reactions. Examples of such reactions are as follows: t

PE 20. + 3C = 2Fe + 3CO (1)

CuO + C = Cu + CO (2) i

NiO + C = Ni + CO (3)

ZnO + C = ZÄ + CO (4)

The reactions according to Equations (1), (2) and (3) take place at such a temperature that melting of the commodity charge does not normally occur. In the reaction according to Equation (4), zinc is removed as a gas in a known manner, but the melting of the charge does not have to take place even then.

The invention also makes it possible to reduce off the major part of the iron content of titanium magnetite and ilmenite as a metallic powder which can be separated by a magnetic path. The non-magnetic residual product can then be used more economically than the original material to produce titanium oxide and possibly vanadium oxide. In order to make the iron particles large enough, additives such as borax, sodium carbonate, fluorine slag, phosphorus, sulfur, etc. can be used, which are known to have a positive effect.

In addition, this method offers a solution to one of the most serious environmental problems of today. It makes it possible to recover metals, nickel, zinc, iron and other metals directly from their sulphide concentrates, while at the same time binding sulfur as calcium sulphide. Examples of such a reaction are as follows: +

CuPeS2 + 2 CaO + 2 C = Cu + Pe + 2 CaS + 2 CO (5) f

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

PeS + CaO + C = Pe + CaS + CO (7)

ZnS + CaO + C = ZÄ + CaS + CO (8)

CaS can then be used in conjunction with NaCl, CO 2, water, and air to produce NaOO 2, S, and CaCl 2 according to a process of 9,58945 described in U.S. Bureau of Mines Report of Investigation 6928.

Examples of other reactions in which the process of the invention offers substantial advantages include the following: f

FeS2 = FeS + S (9) + 2 NaCl + H2SO4 = Na2SO1 + 2 HCl (10) Al2O3 · 2 SiO2 · 2 H2O + 4 (NHj |) 2SO2j = 2 (NHj,) AKSO],) 2 + t + 2 SiO2 + 6 NH3 + 5 H2O (11)

In reactions (9) to (11), it is of great importance that the gaseous products can be recovered in as pure and concentrated form as possible, which has proved impossible with previously known furnace structures. With the oven according to the invention, on the other hand, it works well.

Claims (4)

10 58945 1. A set of continuous genomic color transfer processors, in particular an endothermic metallurgical reduction reactor, and a color-insulated reaction core, which can be mechanically charged at a horizontal axis, at a temperature of the reaction reactor component. mätäs ut samt att in- och utmatningen sker sä att luftens tillträde account reaktionrummet väsentligen förhindras, kännetecknat därav, att ugnens rotationshastighet är ledgre än den vid vilken chargen närmast ugnsväggen slutar att röra sig relativt denat for reactive genomics, the genome is mechanically detached from the above rotation. 1. A method of continuously carrying out heat-demanding processes, in particular endothermic metallurgical reduction reactions, in a thermally insulated reaction vessel called a mechanical furnace rotating about a horizontal axis, in which the reaction components are fed continuously to the furnace and taking out in such a way as to substantially prevent air from entering the reaction space, characterized in that the rotational speed of the furnace is lower than the speed at which the feed closest to the furnace wall ceases relative to that wall and the furnace charge is heated to the reaction temperature only by mechanical means. by the rotational motion of the furnace applied to the new nip cartridge. 2. The invention is defined in claim 1, which is incorporated into the invention and claims to be included in the reaction to the reaction process. A method according to claim 1, characterized in that the incoming and outgoing goods are utilized to prevent air from entering the reaction process. 3. A patent according to claim 1, which is intended to account for the volume of the current volume, the volume of which is not significantly affected by the volume of the volume. A method according to claim 1, characterized in that heavy grinding pieces are added to the furnace charge up to a volume which is less than half of the volume available for circulation of the furnace charge. . Method according to one of Claims 1 to 3, characterized in that most of the hot products obtained from the reaction process are cooled, and that the heat thus recovered is used for preheating the incoming goods or combustion air in connection with the preheating of the goods. Method according to one of Claims 1 to 4, characterized in that the possible gaseous reaction components and / or the gases formed in the reaction are passed in the same direction as the solid reaction components through a mechanical furnace. Method according to one of Claims 1 to 1H, characterized in that the possible gaseous reaction components and / or the gases formed in the reaction are passed in the opposite direction to the solid reaction components through a mechanical furnace. Furnace for carrying out the method according to claim 1, comprising a lying, cylindrical furnace chamber (1) with slightly convex ends (3) outwards, provided with centrally located goods supply and discharge devices (9 »8) fitted with sealing means ( 10, 11, 23s 26, 35) to prevent air from entering the furnace chamber, characterized in that the furnace chamber (1) and the ends (3) consist of a strong steel sheath (5) »inside which a heat insulating layer (6) is arranged , covered by an inner liner resistant to heat, abrasion and corrosion of the reaction gases (7). Oven according to Claim 7, characterized in that the supply and / or discharge device (9, 8) comprises a hollow pin centrally located at the ends of the oven, with a feed screw (10) and an end remote from the oven chamber opening into a pocket (11). wherein the surface of the article is maintained at a minimum height by means of adjustment means (14) such that it acts sealingly with respect to the surrounding atmosphere. Oven according to Claim 7 or 8, characterized in that the outlet device (8) comprises a cooler for the outgoing goods which is in operative connection with a preheater for the incoming goods arranged in connection with the supply device (9). 4. The provisions of paragraphs 1 to 3 of this Regulation apply to the conditions of the reaction procedure,