CN108302931B - The system of efficiency is improved in a kind of iron content zinc scrap concrete technique - Google Patents

Abstract

The invention discloses a system for improving oxidation reaction efficiency in the recovery process of waste containing iron and zinc, belonging to the technical field of metal recovery. This system includes burner, nozzle, kiln, pre-dust collector and heat exchanger. One end of the kiln is connected to the burner and nozzle, and the other end of the kiln is connected to the pre-dust collector. The air is heated by the burner and then enters the kiln. In the furnace; the pre-dust collector is provided with a heat exchanger, the heat exchanger and the nozzle are connected by an air duct, the exhaust gas in the kiln flows to the pre-dust collector to provide heat for the heat exchanger, and the outside air enters the heat exchanger Preheating, the preheated outside air flows through the air duct to the nozzle and then enters the kiln, and then flows to the pre-dust collector as part of the exhaust gas. The beneficial effect of the present invention is that the present invention preheats the external air through the waste heat of the exhaust gas through the heat exchanger, thereby realizing the maximum utilization of heat, and at the same time, the preheated external air has a better reaction effect than the cold air.

Description

A system for improving oxidation reaction efficiency in iron and zinc waste recycling process

technical field

The invention belongs to the technical field of metal recycling, and relates to a system for improving oxidation reaction efficiency in the recycling process of iron-zinc-containing waste.

Background technique

Rotary hearth furnace or rotary kiln roasting is a commonly used representative resource recovery process for iron and zinc waste. The above-mentioned process is to mix iron-zinc-containing waste with certain auxiliary raw materials, and then pre-process it, and then reduce and roast it in the reducing air above 1200°C, and then oxidize the volatilized zinc component next time, and use the coarse zinc oxide powder as the raw material. The form is recycled. This process consumes relatively little energy and is highly safe, making it the most widely used process worldwide. However, in order to produce high-temperature reducing air above 1200°C, it is necessary to use a heating burner as an additional heat source. The raw material of the heating burner includes LNG, LPG or other oils. Generally, LNG is the most widely used, and occupies a large proportion of the cost in the overall process operation, so it can affect the economy of resource utilization.

In order to solve the above problems, some use low-cost fuels, such as waste oil or marine C-grade fuel oil, or use high-efficiency blowtorches, but the effect is not very obvious, so it is necessary to conduct in-depth research on existing processes and introduce More energy-saving and environmentally friendly new technologies to solve the above problems.

At the high temperature of the rotary hearth furnace, the zinc oxide raw material undergoes reduction and a reaction occurs, and Zn(g) is generated, as shown in equation (1). Part of Zn remains in the furnace and is oxidized again to become fine ZnO powder, see equation (2). Moreover, while the zinc oxide is being reduced, the reduction reaction of other metal components is also going on, for example, ferric oxide is reduced by metallic iron, see equation (3).

ZnO(s)+CO(g)=Zn(g)+CO ₂ (g)--------------------------- --(1)

Zn(g)+1/2O ₂ (g)=ZnO(s)--------------------------------- ----(2)

Fe ₂ O ₃ (s)+3CO(g)=2Fe(s)+3CO ₂ (g)------------------(3)

The background of the development of this technology is that after the Zn component is separated, other metals will be reduced at the same time as the Zn component, and oxidation heat will be generated during the reoxidation process, which can be used as an alternative heat source for heating fuel in the furnace. to save energy. In order to ensure that the metal can be fully oxidized, it is necessary to increase the amount of air, but the newly added air is only to ensure that the metal is fully oxidized, and it is a targeted supply rather than an overall supply. This targeted air supply technology is more difficult ; and the newly added air has a lower temperature, which will reduce the overall temperature inside the rotary hearth furnace, and the preheated air will add additional energy loss, and the preheating of the tail gas after the reduction reaction has not been fully utilized, which will also cause energy loss. waste.

Contents of the invention

In view of this, the object of the present invention is to provide a system process that utilizes oxidation heat and waste heat of exhaust gas to preheat air and provide heat for the entire reduction reaction, thereby reducing fuel consumption and waste of heat energy.

In order to achieve the above object, the present invention provides the following technical solutions: including a burner, a nozzle, a kiln, a pre-dust collector and a heat exchanger, one end of the kiln is connected to the burner and the nozzle, and the other end of the kiln is connected to the pre-dust collector , the air enters the kiln after being heated by the burner; a heat exchanger is arranged on the pre-dust collector, and the heat exchanger and the nozzle are connected through an air duct, and the exhaust gas in the kiln flows to the pre-dust collector as a heat exchanger Provide heat, the outside air enters the heat exchanger for preheating, the preheated outside air flows through the air duct to the nozzle and then enters the kiln, and then flows to the pre-dust collector as part of the exhaust gas.

Further, the nozzle is provided with a hot air through hole, the inlet of the hot air through hole is arranged on the side of the nozzle and connected to the air duct, and the outlet of the hot air through hole is arranged at the bottom of the nozzle and inside the kiln.

Further, the nozzle is also provided with a powder through hole, the inlet of the powder through hole is arranged on the side of the nozzle, and the outlet of the powder through hole is arranged at the bottom of the nozzle and inside the kiln.

Further, the powder through hole is used for injecting iron filings powder or other material powders containing iron elements with a particle size of about 1 mm.

Further, the iron scrap powder or other iron-containing material powder is mixed with pure oxygen and injected into the kiln through the powder through hole.

Further, there are three hot air passage holes, and the three hot air passage holes share one inlet.

Further, the pre-dust collector is also provided with an exhaust gas treatment device.

Further, the kiln is provided with a metal feed port on one side, and a slag discharge port is provided at the bottom of the other side, and the flow direction of objects in the kiln is opposite to the gas flow direction.

Further, the kiln is a rotary kiln.

Further, the nozzle can be rotated by 45°-135° in the kiln.

The beneficial effect of the present invention is that: the present invention preheats the external air through the waste heat of the exhaust gas through the heat exchanger, thus realizing the maximum utilization of heat, and at the same time, the preheated external air has a better reaction effect than the cold air; the present invention The invention also increases the heat of oxidation by injecting iron filings and pure oxygen to provide heat for the chemical reaction in the kiln. In a word, the invention achieves a good effect of energy saving and environmental protection in the waste recovery process containing iron and zinc.

Description of drawings

In order to make the purpose, technical scheme and beneficial effect of the present invention clearer, the present invention provides the following drawings for illustration:

Fig. 1 is the overall process flow chart of the present invention;

Fig. 2 is a schematic view of the nozzle structure of the present invention;

Figure 3 is an illustration of the rotary effect of the rotary furnace and the nozzle;

Figure 4 is a comparison chart of the carbon reduction amount whether to inject outside air;

Figure 5 is a comparison chart of carbon reduction using cold air and hot air;

Figure 6 is a comparison chart of carbon reduction with or without injection of iron filings;

Fig. 7 is the figure of influence of oxygen purity on carbon reduction;

Figure 8 is a graph showing the influence of oxygen purity on carbon reduction when hot air and iron filings are injected;

1-burner; 2-nozzle; 3-kiln; 4-pre-dust collector; 5-heat exchanger; 6-air duct; 7-hot air hole; 8-powder hole; 9-tail gas treatment device; 10-metal feed port; 11-slag material discharge port.

Detailed ways

The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings; it should be understood that the preferred embodiments are only for illustrating the present invention, rather than limiting the protection scope of the present invention.

Accompanying drawing 1 is the overall process flow diagram of the present invention, as shown in Figure 1, a kind of method that improves oxidation reaction efficiency in the iron-zinc waste recycling process, comprises burner 1, nozzle 2, kiln furnace 3, preduster 4 and a heat exchanger 5, one end of the kiln 3 is connected to the burner 1 and the nozzle 2, and the other end of the kiln 3 is connected to the pre-dust collector 4, and the air enters the kiln 3 after being heated by the burner; The dust collector 4 is provided with a heat exchanger 5, and the heat exchanger 5 and the nozzle 2 are connected through an air duct 6. The hot air in the kiln 3 flows to the pre-dust collector 4 to provide heat for the heat exchanger 5, and the outside air enters the The heat exchanger 5 is preheated, and the preheated outside air flows through the air duct 6 to the nozzle 2 and then enters the kiln 3 , and then flows to the pre-dust collector 4 as part of the hot air.

The nozzle 2 is provided with a hot air through hole 7, the inlet of the hot air through hole 7 is arranged on the side of the nozzle 2 and connected with the air duct, and the outlet of the hot air through hole 7 is arranged at the bottom of the nozzle 2 and inside the kiln 3.

The nozzle is also provided with a powder through hole 8 , the inlet of the powder through hole 8 is arranged on the side of the nozzle 2 , and the outlet of the powder through hole 8 is arranged at the bottom of the nozzle 2 and inside the kiln 3 .

The powder through hole 8 is used for injecting iron filings powder or other material powders containing iron elements with a particle size of about 1 mm.

There are three hot air through holes 7, and the three hot air through holes 7 share one inlet.

The pre-dust collector 4 is also provided with an exhaust gas treatment device 9 .

A metal feed port 10 is provided above one side of the kiln 3 , and a slag discharge port 11 is provided below the other side. The flow direction of the solid inside the kiln 3 is opposite to the flow direction of the gas.

The nozzle 2 can be rotated by 45°-135° in the kiln 3 .

The present invention mainly utilizes the heat of oxidation generated by the oxidation of metal substances in the kiln to provide part of the heat required for the reaction in the kiln. In order to ensure that sufficient heat of oxidation can be generated, additional air is required to participate in the oxidation reaction. If the external cold air is added, the temperature in the entire kiln will drop, and if the external cold air is preheated, additional fuel will be consumed. At the same time, because the tail gas discharged from the kiln after the reaction has a relatively high temperature, if it is not utilized, it will cause loss and waste of heat energy. Therefore, the present invention discharges the tail gas into the pre-dust collector, and sets a heat exchanger in the dust collector to convert the heat of the tail gas into the heat of the outside air to preheat it, and then enters the kiln through the air duct and the nozzle. Inside. In this way, sufficient oxidation of metal substances can be achieved to generate oxidation heat, and at the same time, the heat of exhaust gas can be effectively used without consuming extra fuel to preheat the outside air.

Fig. 2 is a structural schematic diagram of the nozzle of the present invention, and the nozzle is provided with hot air through holes and powder through holes. The hot air through hole is set for injecting preheated air into the kiln; the powder through hole is set for injecting iron filings powder into the kiln. The reason for injecting iron powder is because if the iron content in the waste is very small or the reduction effect of metallic iron in the kiln is not good, resulting in a small amount of metallic iron, the oxidation heat generated by the oxidation of metallic iron is also very small , and this just fails to reach the purpose of the present invention. That is to say, the present invention can add oxidation heat by injecting a certain amount of iron filings powder or other material powders containing iron elements. At this time, the size of the iron filings powder is about 1 mm, and it is crushed into particles for use. If the particle size is too large, it will cause difficulty in injection, so it is better to use iron filings with a size of about 1mm. And, in addition to iron filings, a large amount of metallic iron sources can also be utilized. For example, the debris produced during the crushing process of metallic iron or the slag discharged from the above process can also be injected with magnetic components (containing iron) selected by magnetic force. The injection volume of all the above-mentioned iron-containing substances needs to be adjusted in consideration of the internal conditions of the kiln.

In addition, if the injected gas is pure oxygen, there will be a better effect, because in the air, the necessary pure oxygen (O ₂ ) for the actual oxidation reaction does not reach 21%, and oxygen deficiency is likely to occur. It may also affect the incomplete combustion of charcoal in the raw material. That is to say, adding pure oxygen (O ₂ ) will achieve a better effect. At the same time, because the content of _N2 charged in the furnace is reduced, the exhaust gas is reduced, and the effect of saving energy is also obtained.

The nozzle of the present invention has three hot air through holes, and the three hot air through holes share one opening, and the opening is connected to the air duct, but the outlets of the three hot air through holes are in different positions. In this way, the preheated outside air is injected at a certain angle or range.

Since the kiln is a rotary furnace, the position and angle of the charge can be changed at any time according to the rotation speed of the rotary furnace, the amount of the charge, the state of the attachment, and the situation in the furnace. At this time, if the injection nozzle is simply fixed, it is difficult to respond effectively according to the situation in the furnace. Figure 3 is an illustration of the rotary effect of the rotary furnace and the nozzle, because the air injection direction is not fixed in a specific direction, but continuously rotates within a certain angle (45-135°) and maintains continuous injection, which can not only improve oxidation Reaction efficiency, and, within a certain angle range, due to the continuous rotation, it can reduce the thermal deformation of the furnace body and reduce the formation of deposits on the furnace wall, so as to prolong the life of the injection nozzle and the furnace.

Example 1

The waste containing iron and zinc is used as the raw material, coke is used as the reducing agent, and the reduction reaction is carried out by using a rotary furnace. The raw material loaded is 20 tons/hr, the operating temperature is about 1200°C, and the temperature of the tail gas is about 800°C. At this time, preheated air above 300°C can be obtained by using the generated exhaust gas and using the heat exchanger installed on the pre-dust collector. The results of component analysis of the raw materials are shown in Table 1 below.

The composition analysis result (wt.%) of table 1 raw material

According to the composition ratio in the above table 1, the theoretical requirement is to inject 1.2 times the amount of air incrementally. Considering the actual operation situation, compare the reduction of charcoal.

In order to verify the effect of the nozzle, Figure 4 is a comparison chart of the amount of coke reduction with or without the injection of outside air. When no outside air is injected, the amount of coke reduction is 0, while the amount of coke reduction with injection of outside air is 560kg/h. Figure 5 is a comparison chart of coke reduction using cold air and hot air; according to 5, it can be clearly seen that the coke reduction is close to 560kg/h at the temperature of the injected air at 20°C, and the reduction of coke at 300°C The amount is close to 610kg/h. Combining Figure 4 and Figure 5, it can be seen that the oxidation effect of injecting cold air outside is better than that without injection, and the effect of injecting preheated outside air is better than injecting cold air.

In order to further improve the effect of coke reduction, iron filings and pure oxygen can be added. Table 2 shows the component contents of common carbon steel shavings used in this example. At this time, the injection volume of iron filings, considering the injection air volume, is uniformly used at 610kg/hr. The injected outside air is preheated air, and then observe the coke reduction results of whether iron filings or pure oxygen are injected, and whether iron filings and pure oxygen are injected at the same time.

Table 2 Composition content (wt%) of carbon steel shavings.

Figure 6 is a comparison chart of coke reduction with or without injection of iron filings under the condition of using preheated outside air. Compared with no use, an excellent energy reduction effect can be seen. Figure 7 shows the amount of coke reduction under different oxygen concentrations under the condition of using preheated outside air, that is to say, as the _O2 content increases, the amount of char used also decreases proportionally. Figure 8 shows that the preheated outside air was used at the same time, and iron filings and pure oxygen were injected at the same time. According to Figure 8, it can be seen that the difference in coke reduction under different oxygen concentrations is not very large, but the amount of coke usage still decreases proportionally ; And the reduction of coke has reached 722 ~ 757kg/h, which is obviously higher than that of non-injection and single injection. Therefore, injection of preheated outside air and simultaneous injection of iron filings and pure oxygen in a certain ratio can ensure excellent energy reduction effects in the recycling process of the above-mentioned iron-zinc-containing waste.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and equivalent technologies thereof, the present invention also intends to include these modifications and variations.

Claims (8)

1. A system for improving oxidation reaction efficiency in iron-zinc-containing waste recycling process, comprising burner, nozzle, kiln, pre-dust collector and heat exchanger, characterized in that: one end of the kiln is connected to the burner and Nozzle, the other end of the kiln is connected to the pre-dust collector, and the air enters the kiln after being heated by the burner; the pre-dust collector is equipped with a heat exchanger, and the heat exchanger and the nozzle are connected through an air duct, and the kiln The exhaust gas inside flows to the pre-dust collector to provide heat for the heat exchanger, and the outside air enters the heat exchanger for preheating. The preheated outside air flows through the air duct to the nozzle and then enters the kiln, and then flows to the pre-heating furnace as part of the exhaust gas. Dust collector; the nozzle is provided with a hot air through hole, the inlet of the hot air through hole is arranged on the side of the nozzle and connected with the air duct, the outlet of the hot air through hole is arranged at the bottom of the nozzle and is located inside the kiln; A powder through hole is also provided, the inlet of the powder through hole is arranged on the side of the nozzle, and the outlet of the powder through hole is arranged on the bottom of the nozzle and is located inside the kiln. 2. A system for improving oxidation reaction efficiency in a waste recovery process containing iron and zinc according to claim 1, characterized in that: said powder through hole is used for injecting iron filings powder with a particle size of about 1 mm or other iron filings powder containing Material powder of iron element. 3. A system for improving oxidation reaction efficiency in a recycling process of iron-zinc-containing waste according to claim 1, characterized in that: said iron filings powder or other material powders containing iron elements are mixed with pure oxygen and passed through together The powder is injected into the kiln through the holes. 4 . The method for improving oxidation reaction efficiency in the recycling process of iron-zinc-containing waste according to claim 1 , characterized in that: there are three hot air through holes, and the three hot air through holes share one inlet. 5. The system for improving the oxidation reaction efficiency in the recycling process of iron-zinc-containing waste according to claim 1, characterized in that: the pre-dust collector is also provided with a tail gas treatment device. 6. The system for improving oxidation reaction efficiency in a recycling process of iron-zinc-containing waste according to claim 1, characterized in that: a metal feed port is provided above one side of the kiln, and a metal feed port is provided below the other side Slag material outlet, the flow direction of objects in the kiln is opposite to the direction of gas flow. 7. A system for improving oxidation reaction efficiency in the recycling process of iron-zinc-containing waste according to claim 1, characterized in that: said kiln is a rotary kiln. 8. The system for improving oxidation reaction efficiency in the recovery process of iron-zinc-containing waste according to claim 1, characterized in that: the nozzle can be rotated by 45°-135° in the kiln.