Similarly, when using hydrogen chloride gas as a chlorinating agent, it is also required to be high enough in the system. 
The ratio to prevent hydrolysis of the chloride can be achieved by increasing the partial pressure of hydrogen chloride and reducing the pressure of the water vapor. At the same time, the addition of a reducing agent at a certain temperature also makes it difficult to chlorinate an oxide which is difficult to be chlorinated with hydrogen chloride. Controlling a certain %HCl/%H 2 O ratio also achieves the purpose of selective chlorination.
In addition to the use of gaseous chlorinating agents, solid chlorinating agents such as sodium chloride and calcium chloride are often used in the industry. Their thermal stability is high, and no thermal dissociation occurs under the normal calcination temperature. The chlorination is mainly achieved by chlorine gas and hydrogen chloride gas obtained by decomposing other components. Tests showed that the silicon oxide, iron oxide, aluminum oxide, and other materials of sulfur dioxide in the gas phase, oxygen, water vapor, etc. can promote decomposition of the solid chlorinating agent. Its decomposition reaction is:
The relationship of ΔG°-T at the time of decomposition of the solid chlorinating agent is shown in Fig. 8. In the case of oxidative chlorination roasting, sodium chloride is mainly oxidatively decomposed. At lower temperatures, the effective component that promotes the decomposition of sodium chloride is sulfur dioxide in the furnace gas. Therefore, when the medium temperature chlorination roasting is carried out with sodium chloride, it is required that the charge contains a sufficient amount of sulfur, otherwise, an appropriate amount of pyrite should be added. In neutral and reducing atmospheres, sodium chloride is primarily hydrolyzed by water vapor, and other components can act as a promoter. Calcium chloride is often used as a chlorinating agent for chlorination. At this time, high sulfur content in the charge is harmful, which promotes early decomposition of calcium chloride and produces a relatively stable calcium sulfate. When chlorinated at high temperature, calcium chloride is mainly decomposed by oxygen and water vapor, and other components can promote its decomposition, and the decomposition product is mainly hydrogen chloride. Due to the chemical decomposition of the solid chlorinating agent, the action law of the gas chlorinating agent and the material component still has a guiding effect on the solid chlorinating agent.
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In addition to simple raw material containing metal oxides and sulfides, also often contain an amount of a metal complex compound, which is difficult to be chlorinated, but its stability decreases with increasing temperature, discharge temperature chlorination, many Complex metal compounds can still be chlorinated, and the addition of a reducing agent or gas to oxygen can also increase the chlorination effect.
The main factors affecting chlorination roasting are temperature, chlorinating agent type and concentration (dosage), gas phase composition, gas flow rate, material particle size, porosity, material chemical composition and mineral composition, and catalysis.
Currently, chlorination roasting process has been used to treat pyrite cinder, high-titanium slag, nickel-depleted ore, laterite ore poor tin, gold complex, complex bismuth lean ore. The calcination process can be carried out in a multi-hearth furnace, a shaft furnace, a rotary kiln or a boiling furnace.
Further, the chlorination process is one of the efficient isolation method is difficult in some mineral feedstock, which is a certain amount of carbonaceous reducing agent and a solid chlorinating agent in the feedstock is heated in neutral or weak reducing atmosphere, so that The useful components are chlorinated from the ore and simultaneously reduced to metal particles on the surface of the carbon particles, which are then enriched into concentrates by physical beneficiation. Segregation law since the advent of 1923 has been 60 years of history, at present, refractory oxide copper ore industrialized segregation, and segregation of lead, zinc, bismuth, antimony, tin, cobalt, nickel, gold, silver and other mineral raw materials is still in Experimental research phase.
It is generally believed that the separation of refractory copper oxide includes hydrogen chloride gas generated by hydrolysis of salt, chlorination and volatilization of copper oxide, and reduction of cuprous chloride by hydrogen and precipitation on the surface of carbon particles. Under the conditions of separation, hydrogen mainly comes from carbonaceous reducing agent contained in the cracking of volatile gas reaction of coal and water, the hydrogen adsorbed on the output surface of carbon particles, carbon particles become deposited copper segregation and the core development grew. Without carbon particles, the fine-grained metal copper reduced by hydrogen will spread over the surface of the gangue and furnace wall and is difficult to recover.
The main influencing factors of segregation are ore properties, temperature, reaction time, type and amount of chlorinating agent, type and amount of reducing agent, moisture content and industrial furnace type.
Tests show that various refractory copper oxide ore can be treated by segregation method. Copper sulfide minerals must be oxidized and calcined in advance. The sulfur content in the raw materials should be less than 0.3%. The calcium oxide produced by the decomposition of alkaline gangue will reduce the segregation of copper. Speed, the harmful effects of calcite are more than dolomite. The ore particle size depends mainly on the heating method of the charge, and can be coarser if used in a rotary kiln. The segregation temperature is related to the ore properties and heat exchange conditions. When the alkaline gangue is contained, the segregation temperature should generally be lower than the decomposition temperature. If the temperature is too high, the charge may be sticky or partially melted, which makes the operation difficult and makes it brittle and easy to grind. The easy-to-float copper is transformed into a dense, ductile, hard-to-float sheet of copper. The initial separation temperature of copper oxide is about 600 ° C, but the effective separation temperature is generally 700 to 800 ° C or slightly higher. The separation reaction time is related to factors such as the reaction temperature. Under the condition of no sintering, the temperature is appropriately increased, and the heat transfer of the heat can shorten the reaction time. When the other conditions are the same, the separation reaction time is appropriately increased to increase the recovery rate of copper. Sodium chloride is commonly used as a chlorinating agent in the industry, and the salt ratio is related to the thermal system, furnace type and ore properties. Under ideal conditions, it is only necessary to supplement the chlorides carried by the discharge and the flue gas. When the calcium and iron high raw materials are treated, the salt is higher than the silicon raw material, the salt ratio of the two stages is 0.1-1.0%, and the salt ratio of the one-stage rotary kiln is as high as 1.8-2.0%. The grain size of the salt has little effect. No fine grinding. Commonly used pulverized coal, coke powder or petroleum coke as reducing agent, the amount of which is related to the characteristics of reducing agent (type, volatile content, fixed carbon content, ash content and particle size composition), thermal system and raw material properties. The amount of the reducing agent isolated from the two stages is about 0.5 to 1.5%, and the length of the direct heating is about 3.5 to 4.0%. The particle size and volatile content of the reducing agent have a great influence on the characteristics of the isolated copper. Water vapor is a necessary condition for the hydrolysis of salt when leaving the plate. The water brought in by the raw material and the water produced by the separation process can ensure this condition, so no additional water is needed for the separation. Tests have shown that the moisture content in the gas phase up to 30% does not affect the segregation of copper, and helps to inhibit the chlorination of iron oxide minerals. There are two processes in the industry: segregation and two-stage separation. The former is a mixture of ore, chlorinating agent and reducing agent, which is heated, chlorinated and separated in the same equipment. The process is simple, the metal volatilization loss is small, but the heat utilization rate is low, and the amount of reducing agent and chlorinating agent is large. The atmosphere required for the isolation reaction is difficult to guarantee. The two-stage separation is to preheat the ore to the separation temperature, and then enter the separation chamber to mix with the chlorinating agent and the reducing agent to carry out chlorination volatilization and segregation. The advantage is that the reaction atmosphere is easy to ensure, the amount of the chlorinating agent and the reducing agent is small, and the furnace gas is used. The corrosion is small and the separation index is high, but the ore after heating is difficult to be uniformly mixed with the chlorinating agent and the reducing agent, the separation temperature is difficult to ensure, the separation reactor is difficult to seal, and the discharging device is complicated.
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