FI63779C - FOERFARANDE FOER SUSPENSIONSMAELTNING AV FINFOERDELADE SULFID-ELLER SULFID- OCH OXIDMALMER ELLER -KONCENTRAT - Google Patents

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Jsr * w '"' utlAgcninosskrift 66779 C (45) ρ Α J i / '3 ^ (51) Kv.Hc? / Ma3 C 22 Β 5 / 14- // C 22 Β 15/00 SUOHI — FINLAND pi) ρκμκιιμι ^ -ρημμμι ^ 802591 (22) HtkemitpiWt - AnaBkninftdki l8.08.80 (23) Alkupllv · —GlMghttsdag l8.08.80 (41) Tullut lulklMkil - Whrtt offtnclig 19.02.82

Pmtitti- l> registry managed ................ .....

Patent · och registerstyrelsen ^ AmMun utiajd och utl. * Krifcen pubUrand 29.0U.83 (32) (33) (31) Requested «" right — Sugird prloriMt (71) Outokumpu Oy, Outokumpu, FI; Töölönkatu U, 00100 Helsinki 10,

Suomi-Finland (FI) (72) Risto Uolevi Saarinen, Espoo, Jorma Rikhard Myyri, Espoo,

Tarmo Kalevi Mäntymäki, Merstola, Finland-Finland (FI) (7U) Berggren Oy Ab (5U) Method for suspension smelting of finely divided sulphide or sulphide and oxide ores or concentrates This invention relates to a process for the slurry smelting of finely divided sulphide or sulphide and oxide ores or concentrates by feeding finely divided ore and concentrate and oxygen and / or oxygen-enriched air into the furnace gas space to oxidize and melt the sulphide ore or concentrate. and / or metal at the bottom of the furnace and dusty flue gases containing sulfur dioxide from the gas space of the furnace.

Suspension smelting of sulphide concentrates, based on Finnish patent 22,694, has become increasingly used around the world. It is known to be an economical, cost-effective and also environmentally friendly smelting method.

This so-called the flame smelting method is well known and described in many articles and conference publications (e.g. Bryk P., Ryselin J., Honkasalo J., Malmström R., Journal of Metals (1958) 6; Andersson B., Anjala Y., Mäntymäki T., 109th ΑΙΜΕ Annual Meeting, Las Vegas 1980).

Briefly, the method is as follows. The dried 2,63779 finely divided concentrate / circulating air dust and slag-forming substances and the air and / or oxygen mixture, preheated or cold, are introduced into the vertical reaction shaft of the flame melting furnace from top to bottom, whereby the oxidation reactions take place in suspension at high temperature. Under the influence of the heat of reaction and any additional fuel, most of the reaction products melt (with the exception of some slag components). In the case of copper concentrate, the following total reactions can be considered to take place in the reaction shaft: 2CuFeS2- * Cu2S + 2FeS + 1/2 S2

Cu 2 S + 1 1/2 O 2 -> Cu 2 O + SO 2

FeS2 - * FeS + 1/2 S2 1/2 S2 + 02 -SO2

FeS + 1 1/2 02 -> FeO + SO2 3FeO + 1/2 02 -> Fe3 ° 4

Other concentrates undergo similar reactions. The suspension falling from the reaction shaft enters the horizontal furnace part of the so-called to a lower furnace, or settler, with at least two but sometimes three different melt layers. The bottom can be a metal layer, most commonly blister copper, with either a stone layer on top or a slag layer directly on top. Most often, the bottom is a layer of stone and the top is a layer of slag. Most of the molten or solid particles in the suspension fall directly into the melt below the reaction shaft at approximately the slag drop temperature, the finest part continuing with the gases to the other end of the furnace. During the journey, the suspension settles into the lower furnace all the time. At its other end, the gases are led directly up to the so-called along the riser, from where they are further led to gas treatment equipment, a waste heat boiler and an electrostatic precipitator. Defrosting is usually performed as autogenously as possible, without external fuel. This is treated in the reaction space by preheating the air and / or enriching the oxygen.

The oxidation reactions that have begun in the reaction shaft are completed almost exclusively after the particles have fallen into the melt of the lower furnace. At the same time, the desired rock and / or metal and slag phases are formed. The following reactions are possible: 3 63779 and 3Fe304 (s) + FeS (I) ^ 10FeCKs) + SO2 (g)

Ib 3Fe304 (s) + FeS (l) --- »10FeO (s) + SO2 (g) II2FeO (s) + SiO2 (s) - ► 2Fe0-SiO2 III Cu2S (1) + Cu20 (l) - * 6Cu (1) + SC> 2 (g) IV 3Cu20 (l) + FeS (l)> 6Cu (l) + FeO (s) + SO2 (g) V Cu20 (l) + FeS (l) - * FeO + Cu2S (g)

In normal copper smelting, the most significant in terms of temperature economy is the combination of magnetite reduction and slag formation reactions (Ia + II or Ib + II). Other reactions occur to a small extent, so they are not very effective in terms of heat economy.

According to current practice, oil is burned both under the reaction shaft and along the bottom furnace to treat sub-furnace reactions and to compensate for heat losses. however, burning the oil increases the H 2 O content of the gas leaving the flame melting furnace, which is detrimental to the further processing of the gas. At the same time, the total amount of gas leaving the flame melting furnace increases because air is used for combustion. When the degree of oxygen enrichment is low, a large amount of preheated air has to be fed into the reaction shaft, whereby the total amount of gas leaving the flame melting furnace is large. Thus, the waste heat boiler and the electric filter after the riser must also be dimensioned to be large in size.

The resulting exhaust gases are, in accordance with practice, led to the production of liquid sulfur dioxide and sulfuric acid in a manner known per se. Only about one-fifth of the total amount of gas can be used for production, as the exhaust gases are rich in nitrogen, which should not be utilized in any way.

It is a primary object of the present invention to provide a method for efficiently capturing and removing large amounts of heat generated from slurry melting with oxygen or oxygen-enriched air from a furnace with flue gases.

It is a further object of the present invention to utilize the reaction gases formed in the slurry smelting of finely divided sulfide and / or oxide ores or concentrates so that the amount of gas fed to and from the slurry smelting unit can be substantially reduced at the same time. The main features of the invention appear from the appended claim 1.

When technical oxygen is used in the suspension smelting according to the prior art, excess heat is generated in the reaction shaft of the flame melting furnace without even additional fuel. Sulfur dioxide gas is well suited for trapping this excess heat because of its high heat content due to heteropolarity. The heat content of sulfur dioxide gas in the flame smelting according to the prior art at 1300 ° C is 66.2 MJ / kmol, while in the prior art flame smelting the heat content of the nitrogen as the main component of the exhaust gases is only 40.8 MJ / kmol at 1300 ° C.

In order to increase the sulfur dioxide content of the gases in the reaction shaft of the flame melting furnace, in a preferred embodiment of the invention, part of the exhaust gases is returned to the reaction shaft together with the primary oxygen. In this case, the sulfur dioxide content of the gases in the reaction shaft is already high at the time of feeding, which improves the binding of excess heat. In addition, the feed gas does not need to be preheated separately, because the exhaust gas from the recycle is fed at the temperature it is at when it leaves the electrostatic precipitator.

The use of technical oxygen substantially reduces the total amount of gas fed to the reaction shaft, because the main component of the prior art flame smelting, nitrogen, can only be fed with the gas from the recycle. Likewise, the total amount of gas leaving the flame melting furnace is reduced, because, for example, the bottom furnace of the flame melting furnace does not have to be fed with additional fuel by the recirculation method according to the invention, which would increase the total amount of flue gases. The elimination of the need for additional fuel also means a significant reduction in the water vapor content of the exhaust gas.

The heat bound to the flue gas of the flame melting furnace is recovered according to the prior art in a waste heat boiler. Due to the high sulfur dioxide content, the temperature of the gas entering the waste heat boiler is lower than in normal flame smelting, which is advantageous from the point of view of equipment technology.

5,63779

Due to the reduction in the total amount of gas, the suspension melt reaction gas recirculation process according to the invention reduces the waste heat boiler and electrostatic precipitator required in the process, which is advantageous from the point of view of the economy of suspension melting. By reducing the total amount of gas and the recycling method according to the invention, the suspension smelting process also becomes more environmentally friendly compared to normal flame smelting.

Despite the reduction in the total amount of gas, more and more economical liquid sulfur dioxide is generated from the exhaust gases of the recycling process according to the invention due to the high sulfur dioxide content in a manner known per se. For the production of liquid sulfur dioxide, the part of the total sulfur dioxide gas which exceeds the sulfur dioxide content of 8 vol · - ?, can be used. The final gas containing less than 8% by volume of sulfur dioxide / is used to produce sulfuric acid.

The process according to the invention for utilizing the reaction gases formed in the slurry smelting of finely divided sulphide and / or oxide ores or concentrates is illustrated by the accompanying figure, which shows the recirculation of the recycle gas according to the invention after removal from the slurry smelter to feed back to the slurry smelter.

The exhaust gases and oxidized air dust generated in the reaction shaft 1a of the flame melting furnace 1 and in the lower furnace Ib are led to the waste heat boiler 2, where the excess heat in the material is recovered. From the waste boiler 2, the gases and air dust go to an electrostatic precipitator 3, where solids are removed.

The gas leaving the electrostatic precipitator 3 is passed in a predetermined ratio partly to the production of liquid sulfur dioxide 5 and sulfuric acid 6, partly recycled 4 to be fed again to the flame melting furnace 1.

It is clear that SO 2 gas can also be introduced into the gas space of the furnace from some other source, e.g. a converter, but the most natural source of SO 2 is, of course, the flue gas obtained from the furnace itself.

63779 6

Example 1

The example considers the processing of a sulfide copper concentrate (25% Cu, 26% Fe, 29% S) by a flame smelting process utilizing the exhaust gas recirculation according to the invention.

Tables IA and IB summarize the heat and mass balance calculations for the flame melting furnace and the waste heat boiler and electric filter according to the example. Calculations have been performed per one rich-ton tonne fed.

The flame smelting of the sulphide copper concentrate is carried out using technical oxygen. The primary oxygen is fed to the reaction shaft of the flame melting furnace together with the recycle gas. The temperature of the recycle gas is then 320 ° C, which is higher than the preheating temperature of the feed gas of a normal flame melt (Tables 2A and 2B), so that the actual preheating of the feed gas using the recycle gas is not required. When technical oxygen is used, excess heat is generated autogenously in the reaction shaft of the flame melting furnace without additional fuel, which is well suited for scavenging with high recycle gas nitrogen, the heat content at 1240 ° C is only 38.7 MJ / kmol, or about 62% of the heat content of sulfur dioxide gas.

Using recycled gas reduces the temperature and total amount of gas leaving the flame melting furnace compared to normal flame melting. The decrease in temperature is due to the higher heat-binding capacity of sulfur dioxide, because the amounts of heat generated in the reaction space according to the example are higher compared to normal flame melting. The reduction in the total amount of air is almost entirely due to the fact that nitrogen enters the process only with the leakage air coming in at different stages.

As shown in Table IB, the gas leaving the flame melting furnace and entering the waste heat boiler contains 61.2% by volume of sulfur dioxide and only 24.8% by volume of nitrogen, while the corresponding values in normal flame smelting are 23% by volume of sulfur dioxide and 65.3% by volume of nitrogen. 63779 (Table 2B). At the same time, the amount of gas in the flame melting furnace has decreased due to the recycled gas: 25.31 kmol / ts - * 14.89 kmol / ts, i.e. in the recirculated gas system according to the example, the amount of gas is only 59% of normal flame smelting.

Reactions in a waste boiler consume some of the gaseous sulfur dioxide (0.24 kmol / ts) and oxygen (0.18 kmol / ts). In addition, when air enters the waste heat boiler and the electrostatic precipitator after the flame melting furnace according to the example, the proportion of nitrogen in the process gas increases. The final amount of gas coming from the electrostatic precipitator and going to further processing is thus as follows (compared to normal flame smelting):

Recycled gas Normal flame smelting LS kmol / ts tll-% kmol / ts vol.% SO2 8.87 47.6 5.56 19.1 C02 1.04 5.6 1.26 4.3 H 2 O 0.08 0.4 0.71 2.4 N2 6.97 37.4 19.81 68.2 O2 1.69 9.1 1.72 5.9 18.65 29.06 = 418 Nm3 / ts = 651 Nm3 / ts

Using recycled gas, the sulfur dioxide content of the final gas leaving the flame smelting process has increased by 19.1-47.6% by volume and the nitrogen content has decreased by 68.2-> 37.4% by volume compared to normal flame smelting. A significant reduction in the water vapor content using recycled gas is also to be noted. Water vapor increases the risk of corrosion by reacting with sulfur dioxide. In addition, the total amount of process gas using recycled gas is only 64% of the total amount of gas in a normal flame smelting. Thus, it is possible to reduce the equipment size of the waste heat boiler and electric filter required in the process.

Table IB also lists the molar amounts for recycled gas and gas for the production of liquid sulfur dioxide and sulfuric acid. The molar amounts are calculated directly from the recycled gas requirement specified in Table IA.

63779

A value of 0.595 obtained sufficiently for the recycle gas means that 37.3% of the total amount of exhaust gas obtained from the electrostatic precipitator goes to the recycle gas of the process according to the invention.

The rest of the exhaust gas is led to the production of liquid sulfur dioxide and sulfuric acid.

From the point of view of the production of liquid sulfur dioxide, an increase in the sulfur dioxide content of the exhaust gas (19.1-> 47.6% by volume) is advantageous, since a part of the gas exceeding 8% by volume can be used. Thus, in spite of the lower total amount of gas, more and more economically liquid sulfur dioxide can be produced in a known manner by means of the recycling system according to the invention.

The rest of the sulfur dioxide (<8% by volume) goes to the production of sulfuric acid. The following is a comparison of the amounts of gas used for the production of liquid sulfur dioxide and sulfuric acid and the amounts of product obtained by the recycling method according to the invention and by normal flame smelting:

Amount of recycled gas LS flame smelting using normal L0 in the exhaust gas Nm3 / ts 125 125

Amount of liquid SC 2 generated kg 297 206

Amount of sulfuric acid produced kg 92 226

The reduction in the amount of sulfuric acid generated compared to normal flame smelting is due to the fact that with the recirculation of the flue gas furnace exhaust gases according to the invention most of the sulfur dioxide can be fed to produce liquid sulfur dioxide while the total sulfur dioxide content remains constant.

Example 2

The example considers the processing of the sulphide copper concentrate mentioned in Example 1 by flame smelting utilizing the exhaust gas recycling according to the invention. Example 2 differs from Example 1 only in that during processing no additional gases mentioned in Example 1, e.g. leakage air, enter the flame melting furnace or the substantially associated waste heat boiler and electrostatic precipitator.

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Tables 3A and 3B summarize the material and temperature calculations of Example 2 per ton of copper concentrate fed.

The inert main component of normal flame smelting, nitrogen, is completely eliminated from the processing, because when flame smelting is carried out using technical oxygen, nitrogen enters the process only from additional gases fed to different points and not with the primary feed gas at all. In this example, these additional gases used in Example 1 do not come at all. Despite the omission of additional gases, the temperatures of the reaction products have not increased compared to Example 1.

Sufficient recycled gas gives a value of 1.01. This means that the recycled gas according to the invention is required for 101% of the exhaust gases from the process for the production of sulfur dioxide and sulfuric acid. Thus, more than half of the total amount of exhaust gases goes to the recycle bin. At the same time, the sulfur dioxide content of the gas fed to the reaction shaft of the flame melting furnace increases, which is advantageous from the point of view of the heat-binding capacity of the feed gas.

As can be seen from Table 3B, the sulfur dioxide content of the exhaust gas from the electrostatic precipitator has increased significantly due to the removal of nitrogen: 47.6 -> 85.5% by volume compared to the exhaust gas according to Example 1. Thus, the total amount of exhaust gas is also reduced: the total amount of exhaust gas is 70% of the amount according to Example 1 and only 45% of the total amount of exhaust gas from normal flame melting.

Despite the decrease in the total amount, the total amount of sulfur dioxide remains the same. Thus, as the concentration of sulfur dioxide increases, more and more economical liquid sulfur dioxide can be produced from the exhaust gas in a manner known per se. According to the example, 328 kg of liquid sulfur dioxide are produced per tonne of copper concentrate fed, which is 10% more than in Example 1 and up to 59% more than in normal flame smelting.

10 63779

Table IA

Flame smelting using recycled gas

Flame and temperature balance of the flame melting furnace

In 0 kg, kmol / ts ° C MJ / ts

The rich 1000 75 22

Aviation dust 94 75 1 O2 oxygen plant 9.06-0.63 = 8.43 25 0

Recycling gas -SO 2 x) 5.56x 320 74.5x -CO 2 x) 0.65x 320 8.3x -H 2 O x) 0.05x 320 0.5x -N 2 x> 4.37x 320 38.9x -O 2 *) 0 , 63 320 7

Air leakage

-N 2 x) 1.10 25 O

-02 *) 0.29 25 O

Reaction heat 2450 Total heat 2480 + 122.2x

Out

Stone 340 1270 306

Slag 500 1330 850

Oxidized lp 70 1240 74 SO 2 x) 5.8 + 5.56x 1240 364 + 349x CO2 x> 0.65 + 0.65x 1240 40 + 40x H 2 O x) 0.01 + 0.05x 1240 l + 2x N 2 x) 1.10 + 4.37x 1240 43 + 170x 02 x) 1.0 1240 41 Heat losses 500 Total heat 2219 + 561x

Recycled gas demand: 2480 + 122.8x = 2219 + 561x x = 0.595 63779 11

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Table 2A

Normal flame smelting Flame smelting furnace material and temperature balance In kg, kmolx / ts ° C MJ / ts

The rich 1000 75 22

Aviation dust 9 4 75 1 02 ~ oxygen plant x 5.86 225 36 02 air * 3.21 225 20 N2 * 12.10 225 73

Leakage air -N2 x 1.10 25 0

-02 x 0.29 25 O

H 2 O x 0.15 225 1

Reaction heat 2450 Total heat 2603

Out

Stone 340 1240 299

Slag 500 1330 850

Oxidized lp. 70 1300 80 SO2 * 5.80 1300 384 CO22 0.65 1300 42 N2 * 13.20 1300 539 H2O x 0.15 1300 8 02 x 1.00 1300 43 Heat loss 500 Total heat 2745 Oil: 40490 kJ / kg oil 11

Flue gases: 23894 _ "_ net heat of oil 16596 kJ / kg oil oil demand: (2745-2603) / 16.6 = 8.55 kg / ts 13: qm id m σ r- O 63779

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Table 3A

Flame smelting using recycled gas - no leakage air

Flame melting furnace material and temperature balance In kg, kmolx / ts ° C MJ / ts

The rich 1000 75 22

Air dust 94 75 1

O 2 oxygen plantx 9.06-0.27 25 O

Recycled gas -SO 2 x 5.56x 320 74.5x -CO 2 x 0.65x 320 8.3x -H 2 O x 0.05x 320 0.5 x -N 2 x -O 2 * 0.27 320 2

Reaction heat 2450 Total heat 2475 + 83.3x

Out

Stone 340 1270 306

Slag 500 1330 850

Oxidized lp. 70 1240 74 SO2 * 5.8 + 5.56x 1240 364 + 349x CO2 x 0.65 + 0.65x 1240 40 + 40x H2O XO, 01 + 0.05x 1240 l + 2x NX - 2 02 x 0.71 1240 29 Heat losses 500 Total heat 2164 + 391x

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Claims (4)

16 63779 A method for melting a suspension of finely divided sulphide or sulphide and oxide ores or concentrates by feeding finely ore or concentrate and oxygen and / or oxygen-enriched air into the furnace gas space to oxidize sulphide ore or concentrate and form a melt at the bottom of the furnace, removing molten slag and stone metal at the bottom of the furnace and dusty sulfur dioxide-containing flue gases from the gas space of the furnace, characterized in that sulfur dioxide gas is additionally fed to the furnace gas space to capture and dissipate the heat generated by oxidation with oxygen or oxygen-enriched air from the furnace with dusty flue gas flue gases. Method according to Claim 1, characterized in that a part of the flue gases containing sulfur dioxide is returned to the furnace after cooling and dust separation. Process according to Claim 1 or 2, characterized in that about 3 to 6 kmol of sulfur dioxide are fed to the furnace for each tonne of concentrate. A method according to claim 2, characterized in that about 40-50% by volume of the sulfur dioxide-containing flue gases removed therefrom are returned to the furnace.