Recycled raw material smelting
Containing the most common melting metallurgical apparatus renewable raw materials is copper blast furnace. The raw material process for processing low-grade tastes that is not suitable for the production of copper alloys is shown in Figure 1.
Figure 1 Flow chart of recycling copper-containing wall materials
The charge of the blast furnace is:
(1) Waste contaminated copper and its alloys, such as cutting head chip, the head plate, steel wire; industrial and household waste with copper and copper alloy parts; bimetallic scrap containing a large amount of iron, non-ferrous metals wherein Form of non-ferrous metals.
(2) slag and furnace body fragments obtained by producing copper-based alloys; return slag; lifting cladding; pre-made copper garbage blocks; molding sand, powder and other finely divided granules containing metal oxides and slag Form of non-ferrous metals.
Bimetallic, quartz and limestone are spiriting fluxes during smelting, and coke is a fuel and a reducing agent. The purpose of blast furnace smelting is to maximize the transfer of copper and tin into black copper (bronze) and to completely evaporate zinc as much as possible.
The reclaimed raw material is smelted in a blast furnace. The smelting process consumes 10-15% of coke by weight of the charge. The heat is released enough to melt the charge and overheat the smelting product, and to distill zinc, lead and other non-ferrous metals and their compounds. Into the gas phase. It is not required to create a strong reducing environment in the furnace because the charge contains mostly copper and other metals in a free or alloy state. Most of the oxides present in the charge are easily reduced.
According to the height of the blast, it can be divided into five areas to represent the physicochemical processes of each area. These processes determine the properties and distribution of the metal based on the smelting product.
The first zone is the reserve zone. The temperature of the furnace gas rising from the tuyere of the furnace is 400 to 600 °C. In this area, the charge is preheated to evaporate water, and the liquid phase first appears due to the melting of the metal lead and the solder, and the charge is prepared for the physicochemical change of the next process. The zinc vapor and carbon monoxide are burned on the surface of the furnace by the air sucked through the feed port. Therefore, the temperature of the exhaust gas is as high as 660 to 1000 °C.
In the second zone, the temperature of the furnace gas and the charge is in the range of 600 to 1000 °C. Carbonation decomposition, brass melting, partial zinc volatilization in copper-zinc alloys, and reduction of non-ferrous metals and iron oxides begin in this zone.
Copper oxides are most easily reduced by gaseous and solid reducing agents. In the equilibrium state of Cu 2 O+CO=2Cu+CO 2 reaction, the partial pressure values ​​of carbon monoxide in the obtained gas phase mixture are as follows:
Temperature (°C) 900 1050 1083
CO pressure (Pa) 2.79 9.04 11.31
The data listed shows that in the blast furnace reduction smelting conditions, the cuprous oxide can be reduced to metallic copper with any component of the furnace gas. Copper oxide is also easy to reduce. At a temperature of 445 ° C, the equilibrium gas mixture of CuO + CO → Cu + O 2 reaction contains 99% CuO 2 and 1% CO. Reduction of copper silicate and copper ferrite requires a higher concentration of carbon monoxide in the gas phase.
Free lead oxide is also easy to reduce.
Some of the lead in the recycled copper-containing material is present in the form of silicates and ferrites.
The lead oxide silicate is a fusible compound (melting temperature 727 to 772 ° C). Therefore, most of the lead is reduced from smelting. In the reaction for reducing lead from a liquid silicate compound at a temperature of 800 to 850 ° C, the equilibrium concentration of carbon monoxide is 3 to 6%. Although lead oxide reduction is relatively easy, it does not achieve complete reduction. Therefore, the slag always contains lead (II) oxide. The latter is constrained by the fusible, fluidized lead silicate that quickly passes through the blast furnace into the hearth. [next]
It is not particularly difficult to convert tin and tin-copper alloys or solders present in the charge to black copper.
The tin oxide reduction process is carried out step by step: SnO 2 →SnO→Sn. The reduction conditions for these oxides are virtually identical. Free stannous oxide (Sn 2 + ) is an unstable compound that disproportionates as follows:
2SnOâ†â†’SnO 2 +Sn (1)
The composition of the equilibrium gas phase mixture for the reduction of tin oxide with carbon monoxide has the following data:
Temperature (°C) 800 1000 1200
Content of CO in CO + CO 2 mixture (%) 20.9 8.0 4.0
The data listed demonstrates that the reduction of tin oxides to metallic tin is much more difficult than the reduction of copper and lead oxides to metallic copper and lead.
More difficult is the reduction of slag-forming tin oxide. The presence of stronger basic oxides such as CaO and FeO promotes the reduction of tin to black copper from the slag-forming tin oxide:
2SnO·SiO 2 +2CaO+2C(CO)=2Sn+2CaO·SiO 2 +2CO·(CO2) (2)
2SnO·SiO 2 +2FeO+2C(CO)= 2Sn+2FeO·SiO 2 +2CO·(CO2) (3)
It is meaningful to smelt the regenerated raw material containing tin in a blast furnace and to reduce the tin compound by means of the existing metal iron in the furnace:
2SnO·SiO 2 +2Fe=2Sn+2FeO·SiO 2 (4)
In the blast furnace smelting charge, a considerable portion of the zinc (25 to 30% of its total content) is zinc oxide. This is a compound that is difficult to reduce. Due to the low concentration of CO in the gas phase, the reaction
ZnO+CO=Zn+CO 2 (5)
The possibility of proceeding is small.
Zinc oxide is mainly reduced by metal iron during blast furnace smelting, and is carried out at temperatures above 1000 °C:
ZnO+Fe→Zn+FeO (6)
2ZnO·SiO 2 +2Fe=2Zn+2FeO·SiO 2 (7)
ZnO·Fe 2 O 3 +Fe+CO=Zn+3FeO+CO 2 (8)
Since zinc oxide is difficult to reduce and has high solubility in liquid slag, most of the zinc oxide introduced into the furnace is transferred to the slag.
In the third zone at a temperature of 1000-1300 ° C, the reduction process of the non-ferrous metal compound ends, and the charge is melted, and at the same time, black copper and slag, zinc and other volatile components (including lead oxide and stannous oxide) are formed. Continue to the gas phase.
In the fourth zone - the tuyere zone, the furnace temperature rose to around 1300 ~ 1400 °C. In the area close to the tuyere and slightly higher, the furnace is filled with red hot coke. The liquid smelt is filtered through the coke layer. Strong volatilization of volatile components occurs in the tuyere zone.
With the combustion of coke and the gasification of solid carbon, the necessary temperature dynamics and reducing environment are maintained in the furnace.
It must be noted that it is unreasonable to treat sulfur-containing materials in a blast furnace and to utilize carbon-containing coke. The presence of sulfur in the charge and fuel can result in the formation of matte, which is increased in lead and tin (PbS and SnS are volatile).
In the fifth zone (inner hearth), liquid smelt is collected, black copper is periodically discharged, and clarification and stratification of the melt components are performed. When there is an external clarifier, the smelted mixture product is continuously discharged from the furnace and finally stratified by density in the clarifier outside the furnace. The temperature in the hearth is 1200 to 1250 ° C, and the temperature is maintained by the helium entering the melt of the hearth.
The process of smelting recycled copper material in a blast furnace is characterized by the production of high zinc slag. The content of zinc oxide in the slag varies between 8% and 18%, usually between 9 and 12%. The content of the aluminum oxide in the slag is 5 to 13%, and the total content of the zinc oxide and the aluminum oxide is 20 to 30%. These slags are very different from the slags of other processes used in non-ferrous metallurgy. About 60% of the total zinc content in the slag is in the form of a silicate. The proportion of zinc present in the form of spinel (zinc spinel ZnO·Al 2 O 3 ) is 40%. The presence of refractory zinc spinel (melting point ≈ 1930 ° C) in the slag adversely affects the properties of the slag and causes black copper beads to be entrained in the slag. The slag should be alkaline. Because the content of zinc oxide is high, it is necessary to increase the content of ferrous oxide in the slag. When the amount of iron is insufficient, the content of calcium oxide is increased.
From the working practice of the blast furnace, the most suitable slag composition is: SiO 2 24 to 26%, FeO 35 to 40%, and CaO 8 to 12%. When slag is smelted with this component, the loss of copper is reduced and the volatilization of zinc is also satisfactory. In this case, the copper content in the slag does not exceed 0.9%.
In the blast furnace smelting, bimetal, quartz and limestone are used as fluxes. The iron in the bimetal ensures that the reduction of the non-ferrous metal from the oxide is more complete and produces a slag having a ferrous oxide content that is compliant.
Practice has proved that when the blast furnace is smelted, the optimum content of the material containing high ferrous oxide in the charge should be about 4%. In fact, the amount of bimetal provided is 2.5 to 3.0 times, which exceeds the need, produces iron tumors, increases the output of slag, and increases the consumption of coke. Removal of some bimetallic scrap from the blast furnace charge can help to improve the technical and economic indicators of the process. [next]
During smelting, free calcium oxide destroys the non-ferrous metal silicate and ferrous salts. Because calcium oxide is a strongly basic oxide, it displaces the non-ferrous metal oxide from the compound and promotes its reduction. In the treatment of copper-rich return materials (blowing and refining slag, copper-based alloy smelting slag, etc.), it is particularly necessary to add a flux because copper, zinc and lead are present in the form of slag.
The blast furnace smelting and regenerating copper-containing raw materials is usually made into black copper in a furnace with a small cross-sectional area (3 to 10 m 2 ) and a height from the tuyere axis to the top of the furnace of 4.5 to 6.0 m. A blast furnace with a cross-sectional area of ​​8.35 m 2 (1300 mm wide and 6065 mm long) was installed in a state-owned factory in the former Soviet Union (Fig. 2). The furnace is completely water jacketed with a total of 26 air outlets, each with a diameter of 130 mm. The water jacket of the furnace body, the throat and the flue are all connected to the vaporization cooler. The charge is loaded into the furnace from the feed port on the side wall of the blast furnace distributed at the top platform. The feeding port is covered with a water cooling furnace door, and the door is lifted by means of a cylinder. The most problem-solving is to use a ground feeder to charge. The load capacity of the machine is 4 tons, and the discharge time of one bucket is 35 seconds.
Figure 2 Blast furnace with electric heating hearth - clarifier
When the filling amount is lower than the mouth valve 2.0 to 2.5 meters, it should be fed into the furnace. The amount of each batch is 20 to 25 tons. Generally, coke, flux, slag and copper-zinc slag, brass scrap and chips are added first, followed by the addition of bimetal and other ingredients.
The melt in the hearth is placed in the electric heating bed through a water-cooling cylinder pipette, and three graphite electrodes having a diameter of 300 mm are placed in the front bed. These three electrodes are placed in the slag so that the front bed works like a resistance furnace. The power of the furnace transformer is 2000 kVA. The external electric heating front bed ensures a constant melt temperature, which can reduce the copper content in the slag slag, avoids stopping the furnace when black copper is released from the hearth, and reserves the required black copper for the normal operation of the converter process. The black copper is placed into the ladle from the front bed through the discharge port, and the slag continuously flows into the slag pot from the surface of the molten pool, and the electricity consumption per ton of the melt is 30 to 50 kW/hr, and the graphite electrode is consumed by 3 to 4 kg.
The process furnace gas was removed from the coarse dust and cooled to 250 ° C in an evaporatively cooled cyclone. The coarse dust as the return product is treated in the converter or returned to the blast furnace. However, neither solution is satisfactory. Coarse dust should be agglomerated and then sent to the blast furnace. Fine dust (which is a volatile of zinc and other volatile components) is used for dust collection by a bag filter (total dust collection area of ​​10,500 m 2 ). After dust collection, the dust content of the furnace gas does not exceed 0.04 g/ m3 .
The air pressure that is blasted into the furnace is 14.7 to 24.5 kPa, and in the tuyere area, the amount of blasting per 1 m 2 section in 1 minute is 50 to 70 m 3 . Under such a blasting system, the strengthening process of smelting is guaranteed, and the unit production capacity is up to 80-100 tons/( m2 ·day and night). [next]
When the blast furnace is smelted, the percentage of hand product yield of various products is as follows: black copper 30 to 33%, slag 53 to 57%, coarse dust 3 to 4%, fine dust 5 to 10%. The ingredients of various smelted products are listed in Table 1.
Table 1 Chemical composition of regenerated raw material smelting products (%)
Smelting products | Cu | Zn | Sn | Pb | Ni | SiO2 | CaO | FeO | Al2O3 |
Black copper | 82-87 | 5~8 | 1.2 to 2.2 | 1 to 2 | 0.5 to 1.5 | - | - | Fe=1.5 ~3.0 | - |
Rough dust | 10~15 | 25~30 | 0.2 to 0.3 | 3 to 4 | - | 15~20 | 2 to 3 | 10~12 | 3 to 5 |
Slag | 0.7 to 0.8 | 6 to 9 | 0.1 to 0.2 | 0.2 to 0.5 | 0.03~0.20 | 23~29 | 8~14 | 35～40 | 9~12 |
Return material | 1.4 to 4.0 | 5~8 | 0.2 to 0.5 | 0.2 to 0.6 | 0.05~0.20 | 20~26 | 8~14 | 33~38 | 5~10 |
Fine dust | 0.5 to 3.0 | 60 to 63 | 0.3 to 0.7 | 4~5 | - | - | - | - | Cl=1～2 |
Smelting results: 97.0~97.6% of the copper is recovered into the black copper; the copper which accounts for 1.8-2.2% of the total copper in the furnace is transferred to the slag, 0.2~0.4% of the copper is transferred to the fine dust; 45~55% of the zinc is fed with the furnace The gas is volatilized and recovered in the form of zinc oxide (commercial zinc oxide); 12 to 15% of the zinc remains in the black copper; 30 to 35% of the zinc is transferred to the slag. Zinc is taken away by the furnace gas and other losses are up to 15%; about 85% of the zinc entering the black copper is recovered as volatiles in the converter blowing. 60 to 65% of the lead is recovered in black copper, and the rest is roughly distributed between the slag and the smoke.
In the blast furnace smelting, a total of 65 to 70% of the tin is transferred to black copper, 25 to 30% of the tin enters the slag, and 2 to 4% of the tin enters the soot and the furnace gas. Black copper refining produces a tin-containing blowing slag in which most of the tin is enriched.
The tin-containing converter slag (containing 3.5 to 4.5% of tin), industrial and domestic waste copper and its alloys, bimetal scrap, and recycled raw material blast furnace smelted into black copper return slag is used as a raw material for the production of black bronze. In a blast furnace similar to smelting black copper, black bronze can be produced by a reduction smelting process using 16 to 18% coke. The slag and furnace fragments added to the blast furnace should be free of magnesium - chromium refractory inclusions and have a block size of no more than 250-300 mm.
Due to the fusibility of converter slag and various return slag. Therefore, a small amount of flux (limestone and quartz) is required for its treatment, and the amount is about 8% of the metal charge. The smelting results mainly depend on the blast system. When the blast is strengthened, the residence time of the charge in the blast furnace is shortened, resulting in incomplete reduction of oxides of tin and other non-ferrous metals, since the recovery of these metals into black bronze is reduced. When the air volume is insufficient, the production capacity of the equipment is also reduced. For a blast furnace with a tuyere cross-sectional area of ​​8.35 m2 , the most suitable gas consumption is 1 m 2 50-60 m 3 /min.
As described above, in addition to the tin-containing slag, there are scraps of copper and its alloys in the charge composition, wherein the amount of the alloy is 100 to 150% of the slag. Liquid copper is a good collector for tin, thus increasing the recovery of tin in bronze.
The blast furnace smelts the tin-containing material to obtain black bronze containing the following components: copper 80-85%, tin 5.5-6.5%, lead 4.5-5.0%, and zinc 2%. The recovery rate of various metals in bronze is 97-98% for copper wall, 65-70 for lead and 85% for tin. Nearly 12% of the tin is transferred to the slag and 3% of the tin is transferred to the gas phase. The slag composition is: 0.8 to 1.0% of copper, 0.4 to 0.6 of tin, and 0.4 to 0.5% of lead. Therefore, when the black copper wall or the bronze is smelted, the above materials are returned as a return material. After the obtained black bronze is refined into coarse bronze, it is used to produce recycled bronze in accordance with current standards.
The blast furnace reduction smelting process widely used in (former) Soviet and foreign companies is still the basic method for processing low-quality copper-containing recycled raw materials into black copper or bronze for a long time. The process is reformed with oxygen-enriched air and blast preheating to reduce expensive and in short supply of coke and increase metal recovery. [next]
The Ural Power Non-Ferrous Metallurgical Production Complex was developed and a reflow-type tubular hot-air metal heater was introduced at the Kirov Copper-making Company. The first set has been running smoothly since 1981.
The heating surface of the hot blast stove consists of 6 tubes of 45 mm diameter with a total heating area of ​​960 m 2 . The hot blast stove is guaranteed to be 6000 to 7000 m 3 /hr, and the thermal efficiency of the hot furnace is sufficiently high, about 80%. The air temperature entering the blast furnace tuyere reaches 250 to 280 °C.
Under the condition that the composition of the charged charge changes, the hot air can be used to stabilize the working system of the furnace, reduce the operation of the furnace itself (completely no need to clean the tuyere) and the operation of the electric heating front bed, so that the temperature of the top gas is reduced by 50-80. °C.
The use of preheated air can reduce the consumption of coke from 13 to 15% to 8.8 to 11%, and the unit productivity from 60 to 70 tons / m 2 · day and night to 90 to 100 tons / m 2 · day and night. Under the conditions of Kirov City Copper Refining Company, the use of preheated blast to strengthen the smelting and regenerating raw materials shows that the factor that further increases the productivity of the furnace is that the existing preparation and loading systems are backward and need to be fundamentally modified.
The use of oxygen-enriched blasts can also improve the technical and economic indicators of blast furnace smelting. When the oxygen-enriched air reaches 25%, the amount of smelting is increased by 15 to 20%, the consumption of coke is reduced by 10 to 15%, and the amount of dust is also reduced.
The potential to improve blast furnace smelting efficiency and increase furnace age is to improve the structure of the furnace, determine the optimum furnace type, and change the furnace, flue system and cyclone to gasification cooling. With gasification cooling, the furnace age can be increased by 1 to 1.5 times, not less than 2.5 years.
Now all the blast furnaces at the copper smelting company in Kirov have been converted to gasification cooling and the vertical furnace type has been determined.
Even in a blast furnace equipped with an electric heating front bed, when the copper-containing recycled raw material is smelted, a final slag containing a high amount of color metal can be obtained. The return of slag to black copper does not solve its processing problems. The most effective method for comprehensively treating the above slag is electrothermal method. This method can recover copper, tin, alloy lead, riser zinc and obtain waste that can be used as a fertilizer or to produce building materials.
In order to deal with the classified and unpolluted high-quality scrap copper and its alloys and cathode copper, many foreign companies have adopted blast furnaces developed by the US Smelting and Purification Company. The furnace works by preheating air to burn natural gas . The furnace was equipped with 31 burners arranged in four rows according to the height of the furnace. In the case of a small blast furnace phase (9 meters high, 1.75 meters upper diameter), its production capacity is 70-75 tons / hour.
According to the data of Ю.П.Kupuriakov and MC Scryal, the use of blast furnace to treat non-ferrous metal scrap can reduce fuel consumption by not less than 25% compared with shot furnace and induction furnace smelting. The blast furnace structure designed by Sue Recycling Non-Ferrous Metal Research and Design Institute for smelting waste aluminum has been semi-industrial tested.
(Former) Non-ferrous metallurgy in the Soviet Union uses a blast furnace to smelt cathode copper. The furnace is a furnace with a lined and sealed steel outer casing, and a furnace top chamber with a charging port and a smoke exhausting hole are arranged above the furnace. The furnace is equipped with burners for the combustion passages, distributed in the lining, and the consumption of natural gas and air must be limited to a small extent to prevent free oxygen from entering the furnace environment. In the latest modified blast furnace, a side combustion chamber is used as a fuel combustion device. This ensures an environment free of free oxygen in the furnace, which saves fuel and reduces the amount of harmful emissions.
The technical and economic indicators for blast furnace smelting are as follows:
Cathode copper smelting capacity (ton / hour) 40 ~ 80
Natural gas unit consumption ( m3 / ton) <50
Air consumption coefficient 0.90~0.95
Copper residue containing slag (%) 0.03
Refractory consumption (kg / ton cathode) 2.6
This equipment operates in 2 to 3 people.
(Before) The practice of the improvement and development of non-ferrous metallurgy outside the Soviet Union has proved that the conclusion that the use of blast furnace to treat high-quality non-ferrous metal scrap has broad prospects is correct.
At the same time, the technical characteristics of smelting mixed, contaminated, low-quality raw materials into black copper indicate that the recycling of a range of non-ferrous metals by this process is limited. However, smelting ensures a sufficiently high recovery of copper. Considering the characteristics of the raw materials and the content of tin in them, it can be considered that the distribution of copper in the smelted product is satisfactory, which is advantageous for the next extraction.
The zinc contained in the charge is actually refined into a semi-finished product----sublimation. This sublimate can be processed in a variety of process streams, including the production of dyes. Chlorine and fluorine have an adverse effect on the quality of the ascending compound. The content of the insulating material (polyvinyl chloride, fluoroplastic) of the polymer in the raw material is increased, resulting in substandard sublimate. The contaminated sublimate is gray and contains organic matter from the charge.
Nickel and cobalt mixed into the substandard raw materials, 70 to 80% enter the black copper, and the rest are slag. The next step in the treatment of black copper does not actually guarantee the recovery of nickel and cobalt. As noted above, nickel and cobalt have an adverse effect on the process of making cathode copper.
Therefore, the waste must be prepared and pre-sorted. This process, like the blast furnace reduction smelting, is unquestionable.
Wall-mounted Electric Fireplace
The wall-mounted Electric Fireplace can provide a relaxing ambiance for your living place with or without the heater. Adjustable temperature and flame settings allow you to customize the heat and colors of the flames according to your preference. You can operate the fireplace with the included remote control for convenience, and use the multi-stage timer turns the fireplace off automatically for safety.The surface of the electric fireplace is insulated, which is very safe for children or the elderly. Under the protection of the thermostat, the electric fireplace can be safely placed in the rooms of children or the elderly to warm up. You can easily install the wall-mounted fireplace with a screwdriver only. Just plug it in and enjoy!
Wall Mounted Fires, Wall Electric Fires, Wall Hanging Fireplace
Zhongshan Hangsam Electrical Appliance , https://www.grillfireplace.com