What is unreasonable is that the investment is large, the patent fee is expensive, and the flux and raw materials are ground first and then deeply dried, which requires additional energy consumption. Copper and sulfur produced by smelting furnace need to be crushed by water, dried and finely ground, and the working procedure is complicated. It is difficult to ensure the recovery rate of each process 100%, which will cause certain mechanical losses; The physical heat of hot and high-temperature matte is almost completely lost, and the water is dried after being crushed. In addition, a large number of water jackets in the furnace take away the heat of cooling water, and the utilization of heat energy is not reasonable. Water crushing copper matte needs a lot of water to wash, which increases the power consumption. Crushing and drying will increase the consumption of manpower and electricity. These are the important reasons why this technology has not been widely promoted for many years.
2.ISA process and Ausmelt process both belong to top-blown smelting series;
High-rise workshop should be built with top blowing, which has high noise, low oxygen concentration and large smoke. The top oxygen lance is12m long and needs to be replaced every three days to one week. The amount of stainless steel is large, the investment is large, and the operation is inconvenient. All of them use electric furnaces as dilution furnaces, and the copper content in slag is generally greater than 0.6%, which is not suitable for China.
3. Disadvantages of Mitsubishi method
Four furnaces (smelting furnace, dilution electric furnace, blowing furnace and anode furnace) are arranged by themselves. The melting furnace of the first process needs to be arranged at a higher floor position, and the construction cost is relatively high. Slag is diluted by electric furnace, and the copper content of slag reaches 0.6%~0.7%, which is much higher than the average grade of ore mined by most large copper mines in China, and the resources are not fully utilized.
4. The continuous blowing process in Noranda and Teniente is still in the industrial test stage.
Nolanda is side blowing, which requires manual drilling, and the labor intensity is very high, and the air leakage rate of the eye reaches 10%~ 15%. The noise is high, the operating conditions are poor and the smelting environment is not ideal. If you don't master it well, it will easily lead to foam slag spraying accidents.
To sum up, let's seek new smelting technology and find new ways through continuous exploration. Lead smelting and copper smelting with oxygen bottom blowing furnace were first developed by Shuikoushan, Hunan Province and China Nonferrous Engineering Design and Research Institute, and semi-industrial tests were carried out in Shuikoushan. First, it is used in lead smelting and its industrialization is successful. Later, Jiang, former vice president, chief engineer and national design master of China Nonferrous Engineering Design and Research Institute, used it in copper smelting and tried many times to cooperate, but no one wanted to eat the first crab. After many years, when the copper market in China and the international market was at its best, Cui Zhixiang, the chairman of Shandong Dongying Copper Group, found Jiang and proposed to smelt 200,000 tons of copper and gold in two phases. After many discussions and arguments, Cui Zhixiang and Master Jiang reached an agreement to jointly develop a new molten pool smelting process and industrial demonstration project of "making matte and grasping gold by oxygen bottom blowing". From the beginning of the project design to the production, Master Jiang made many in-depth field investigations, implemented Scientific Outlook on Development, and carefully reviewed every parameter and equipment operation data in the design. In order to "blow the new technology with oxygen", he worked hard day and night and respected the facts. From ignition and baking to debugging, it's really sweaty. The successful operation of oxygen bottom-blown furnace shows that all engineers and technicians and factory employees respect science and practice from design, construction to production, which is the foundation of winning every battle and the source of development. The whole process was smooth when the oxygen bottom blowing furnace was started. Master Jiang said happily, "This is the first step of innovation. There are still many problems to be solved step by step, and there is still a long way to go."
At present, the more advanced smelting process is feasible, and no flue gas escapes. As far as copper converter blowing is concerned, at present, more than 90% of the world adopts PS converter, which works intermittently, and the copper matte produced by smelting needs to be packed and transported in the workshop, which leads to the escape of sulfur dioxide flue gas at low altitude. In addition, it is difficult to completely seal the flue gas during converter feeding and blowing, and there are different degrees of escape phenomena, which makes the operating environment of PS converter blowing operation very bad. This is a worldwide problem faced by copper smelting today, and all countries are trying to solve this big problem. We should find a way to solve the problem from the source, work hard to cancel the converter and make a fuss about blowing the furnace.
At present, there are two kinds of continuous blowing processes used in foreign industrial production, which solve the problem of copper reverse transportation in the workshop. The capture rate of sulfur is more than 99.8%, which solves the low-altitude pollution of copper matte converting.
Among them, Mitsubishi process developed in Japan adopts top-blown furnace smelting, copper matte is precipitated by electric furnace, and slag is depleted, and then copper matte is continuously blown into crude copper by top-blown furnace. The three furnaces are connected by two chutes to realize continuous copper smelting. There are five such factories in the world, which is a continuous copper smelting process with less investment and low cost.
The other is the copper smelting process in kennecott Smelter, Utah, USA, which uses flash furnace smelting, slag beneficiation, copper matte water crushing, drying, grinding, and then blowing with flash furnace to make crude copper.
Although the above two continuous copper smelting processes have solved the environmental protection problems of blowing operation, they still have shortcomings and need further improvement.
Mitsubishi process consists of four self-flow furnaces (melting furnace, dilution furnace, blowing furnace and anode furnace). The melting furnace of the first process needs to be located on a higher floor, so the construction cost is relatively high. In addition, the slag of Mitsubishi process is diluted by electric furnace, and the copper content of the slag reaches 0.6%~0.8%, which is much higher than the average grade of most large copper mines in China, and the resources are not fully utilized. The disadvantage of flash continuous blowing is that matte needs to be crushed in water first, then dried and ground before blowing operation can be carried out. The process is complicated, the recovery rate of each process is difficult to guarantee 100%, and there is a small amount of mechanical loss. Moreover, the physical heat of liquid high-temperature matte is almost completely lost when it is crushed by water, and the drying and blowing process of solid matte requires an external heat source, so the utilization of heat energy is not reasonable. Water crushing of copper matte requires a lot of water, and drying and crushing increase labor and power consumption, which may be an important reason why this process has not been widely promoted for many years.
In addition, the continuous blowing processes in Noranda and Teniente are still in the industrial test stage.
Through the experiment of oxygen bottom blowing furnace, it is an important task for us to find an effective method to solve the low-altitude sulfur dioxide pollution caused by PS converter blowing in copper smelting, and to provide a new copper smelting process which is more advanced, shorter in process, less in investment, lower in cost, higher in recovery rate and better in comprehensive utilization than the existing continuous copper smelting processes in the world, such as Mitsubishi process and flash blowing process.
The essence of "continuous copper smelting with oxygen bottom blowing" invented by Jiang lies in drawing lessons from the self-flow configuration of Mitsubishi method, using the smelting mechanism and advantages of oxygen bottom blowing to connect the three processes of smelting, blowing and pyrometallurgical refining with three different bottom blowing furnaces, thus overcoming the shortcomings of converter blowing. In this way, the problem that 90% of the world's matte is still blown by converter and needs to be lifted in the workshop can be completely solved. The escape of sulfur dioxide and pollution in operation are effectively eliminated in the workshop, and the harm of low-altitude smoke in the workshop is eliminated. This not only saves cranes for converter production, but also cancels the large-area workshop and construction investment occupied by several converters, saving 1/3 expenses under the same conditions.
It is characterized in that high-grade copper matte is smelted in an oxygen bottom blowing furnace, and is blown into coarse copper in a bottom blowing furnace or a continuous blowing furnace developed in China. High iron slag is produced in the smelting process, and copper concentrate is selected from the slag to return to smelting, iron concentrate is selected for sale, and slag tailings are sold. The calcium slag produced in the blowing process is returned to smelting, and the flue gas is sent to produce sulfuric acid after purification. A method for smelt crude copper comprise that following steps:
1. After copper sulfide concentrate, other copper-containing materials and flux ingredients are granulated, they are added into an oxygen bottom-blown smelting furnace for smelting to produce high-grade copper matte and smelting slag. After the flue gas is cooled by a waste heat boiler to recover waste heat, it is sent to an electrostatic precipitator for purification and dust removal, and then sent to an acid-making workshop to produce sulfuric acid. Characterized in that:
(1) Adjust the oxygen supply ratio to produce high-grade matte. The grade of copper matte is controlled at 68%~70% to reduce the load of subsequent copper matte converting operation, and at the same time, less than 70% of copper matte is produced, and the copper content in smelting slag is at a low level, so that higher direct smelting output can be obtained. 2) High iron slag type is adopted for smelting. By adding flux, the iron oxide/silicon dioxide (weight ratio) of smelting slag is controlled between 2.0 and 2.2, which is higher than that of Mitsubishi process 1.4~ 1.6 and flash furnace 1.6~ 1.8 (slag type is slag dressing). The reason why the ratio of high iron to silicon can be used for slagging is because the reaction mechanism of bottom blowing smelting is that oxygen directly acts on copper matte, and copper matte acts as the carrier of oxygen to generate cuprous oxide, and cuprous oxide reacts with iron sulfide in concentrate to generate iron oxide. The oxygen potential of slagging reaction is low, so it is difficult to produce ferroferric oxide, so the slag can adopt a higher iron-silicon ratio. On the contrary, the reaction mechanism of Mitsubishi process or flash smelting process is that oxygen directly acts on the concentrate and iron sulfide directly reacts with oxygen, so the oxygen potential is high, the trend of generating ferroferric oxide is high, the proportion is high, the slag is sticky, and the melting degree of cuprous oxide in the slag increases, which is not conducive to the separation of slag and copper. Especially in Mitsubishi process, if the iron-silicon ratio is too high, the iron oxide in the slag will increase, and besides the copper content in the slag, there is also the danger of foam slag. Because of the low content of ferroferric oxide in oxygen bottom blowing smelting slag, high iron-silicon ratio can be used to make slag. Therefore, when smelting, the amount of timely addition is relatively small, the amount of smelting materials is reduced, the slag rate is low, the amount of materials for slag beneficiation is small, the energy consumption is correspondingly reduced, and the amount of copper lost with slag is correspondingly reduced.
2. Mineral processing of smelting slag
Smelting slag produced by bottom blowing furnace passes through slag ladle or slag pit, and is slowly cooled and then sent to mineral processing. The mineral processing technology includes crushing and grinding slag, flotation to select slag copper concentrate, and then selecting iron concentrate and tailings. The mineral processing of copper smelting slag has mature technology at home and abroad. Bottom blowing slag is similar to Noranda smelting slag. Daye treated Noranda smelting slag to produce copper concentrate and iron concentrate, and the tailings produced can be used for cement batching or brick making, realizing no waste residue in the smelter. The copper content of tailings is less than 0.35%, which can increase the total recovery rate of copper by 0.6%~0.7% compared with the electric furnace dilution process. The excellent index of copper content in depleted slag of electric furnace is 0.6%~0.7%. China's copper resources are extremely short, and the resources with copper content of about 0.42% in raw ore are still being mined. This technology uses mineral processing technology to recover residual copper from slag, with high copper recovery rate and full utilization of resources, which is in line with national conditions. What's more, the unit capital investment and operating cost of treating each ton of slag by mineral processing method are basically the same as those by electric furnace dilution method. Therefore, from the economic point of view, slag beneficiation is also more favorable.
3, copper matte blowing
Liquid high-temperature copper matte produced by the bottom-blown smelting furnace is continuously injected into the oxygen bottom-blown smelting furnace through the chute, and oxygen-enriched air is continuously fed from the bottom of the smelting furnace to continuously smelt high-grade copper matte. At the same time, flux limestone is continuously added into the furnace top opening for slagging through the silo and the metering belt feeder. (It is also possible to grind flux lime or limestone into powder without opening the top of the furnace, and send it into the furnace for slagging together with oxygen from the oxygen lance through the silo and the metering belt feeder. ) At one end of the furnace, the upper part is perforated to discharge smelting slag, and the lower part is perforated with a siphon device to discharge crude copper, as shown in Figure 2. Realize continuous addition of copper matte, continuous blowing, continuous addition of flux, continuous slagging and slag discharge, and continuous discharge of crude copper, and realize continuous blowing process. Its characteristics are as follows: 1) bottom blowing furnace is adopted. Under the condition that crude copper, matte and slag coexist, oxygen is transferred through crude copper. Therefore, the oxygen potential of crude copper is the highest, which can ensure that crude copper with lower sulfur content than other continuous smelting can be obtained, which is beneficial to remove V-group elements such As As, Sb and Bi and improve the quality of crude copper. At the same time, bottom blowing can reduce the generation of ferroferric oxide and prevent the precipitation of ferroferric oxide and the generation of foam slag. The low content of ferroferric oxide in slag will reduce the viscosity of slag, reduce the inclusion of cuprous oxide in slag, and make the copper content in slag lower than that of flash smelting and Mitsubishi smelting, which can be reduced to below 10%. (2) High-grade matte (containing 68%~70% copper) is used for smelting, so the smelting load is small and the smelting slag is less. By adjusting the oxygen-nitrogen ratio and oxygen supply pressure (the oxygen-nitrogen volume ratio can be adjusted within the range of 5:5 to 8:2, and the oxygen supply pressure can be adjusted within the range of 0.4 MPa to 0.8 MPa), the blowing reaction speed can be controlled, so that the blowing temperature can be controlled within the range of 1220℃ to 1250℃.
(3) Determine the type of slag blowing according to the composition of the concentrate: Generally speaking, the gangue of copper concentrate contains high iron, and there are few alkaline elements such as calcium and magnesium, so it is necessary to add flux calcium oxide when smelting. Iron-calcium slag is used, and the blown slag is returned to the smelting furnace after being crushed by water to replace the limestone flux needed for smelting. When copper concentrate with high calcium content is treated under special circumstances (limestone flux is not needed for smelting), quartz stone can also be added into the blowing furnace to make ferrosilicon slag, which is slowly cooled and sent to the slag selection workshop for treatment.
(4) According to the size of the bottom blowing furnace, the inclination of 1%~3% is maintained in the preparation, so that the coarse copper layer at the inlet end of matte is thinner, and the oxygen-enriched air sent by the spray gun can be directly sent to the matte layer for blowing reaction to prevent excessive cuprous oxide. One end of the coarse copper outlet can keep a thick coarse copper layer. In order to prevent the reverse equilibrium reaction with copper matte and improve the sulfur content of crude copper, some bottom permeable bricks are arranged at this end, and a small amount of oxygen-enriched air is sent into the crude copper layer slowly, so as to improve its oxygen potential and control the crude copper content to meet the standard, avoiding the need for re-desulfurization in anode furnace by Mitsubishi method and flash continuous blowing method, which leads to the need for special treatment of anode furnace flue gas, and solving the environmental protection problem.
(5) The bottom blowing furnace is continuously blown, and the furnace temperature is stable, which overcomes the shortcoming of excessive temperature fluctuation during the periodic operation of the converter, is beneficial to greatly improving the service life of the blowing furnace, reducing the consumption of refractory materials and maintenance workload, and thus reducing the cost of copper smelting. With continuous injection, the flue gas quantity and composition (sulfur dioxide content) are stable and balanced, and the furnace body does not need to rotate frequently, thus reducing the cost of copper smelting. Continuous blowing overcomes the shortcomings of large fluctuation of flue gas volume and flue gas composition during the periodic operation of converter, and can make use of acid production to reduce the investment of acid production equipment.
(6) A copper matte chute is provided from the smelting furnace to the blowing furnace, and the copper matte directly flows into the blowing furnace from the smelting furnace through the chute. A heat preservation burner is arranged on the connecting chute for heating and heat preservation to prevent copper matte from freezing in the chute. A ventilation hood is arranged at one end of the chute to eliminate the flue gas escaping from the heat preservation burner and the chute, and the flue gas is discharged after desulfurization. It solves the problems that when the converter runs periodically, matte is transported by trucks in the workshop, and a large amount of sulfur dioxide in matte escapes unorganized, resulting in serious low-altitude pollution of sulfur dioxide and deterioration of workshop operation.