阅读说明：本技术 一种外燃式废钢预热竖炉及其预热方法 (External combustion type scrap steel preheating shaft furnace and preheating method thereof ) 是由 孙中强 于 2021-09-18 设计创作，主要内容包括：本发明的一种外燃式废钢预热竖炉及其预热方法,属于冶金领域,竖炉包括外燃式燃烧炉、废钢预热竖炉和烟气活性炭处理系统；废钢预热竖炉内设有机械手,废钢预热竖炉侧壁设有下环形烟道和上环形烟道,下环形烟道和上环形烟道一侧通过支气管与废钢预热竖炉连接,另一侧通过管道与外燃式燃烧炉连接；废钢预热竖炉内包括有二次燃烧区。预热时,向废钢预热竖炉内分层加入废钢；外燃式燃烧炉产生烟气,经由下、上环形烟道通入废钢预热竖炉内,对废钢进行分层预热,获得预热后废钢与换热后烟气,废钢进行出钢操作。该设备及方法能够大幅提高热效率,减少碳排放,解决废钢预热过程烟气难治理难题,废钢预热烟气排放可以全部达标；同时减少废钢烧损。(The invention relates to an external combustion type scrap steel preheating shaft furnace and a preheating method thereof, belonging to the field of metallurgy, wherein the shaft furnace comprises an external combustion type combustion furnace, a scrap steel preheating shaft furnace and a flue gas activated carbon treatment system; a manipulator is arranged in the scrap steel preheating shaft furnace, a lower annular flue and an upper annular flue are arranged on the side wall of the scrap steel preheating shaft furnace, one side of the lower annular flue and one side of the upper annular flue are connected with the scrap steel preheating shaft furnace through a branch gas pipe, and the other side of the lower annular flue and the other side of the upper annular flue are connected with an external combustion type combustion furnace through a pipeline; the scrap steel preheating shaft furnace comprises a secondary combustion area. During preheating, adding the scrap steel into the scrap steel preheating shaft furnace in a layering manner; the smoke generated by the external combustion type combustion furnace is introduced into the scrap steel preheating shaft furnace through the lower annular flue and the upper annular flue, the scrap steel is preheated in layers, the preheated scrap steel and the smoke after heat exchange are obtained, and the scrap steel is subjected to steel tapping operation. The equipment and the method can greatly improve the thermal efficiency, reduce the carbon emission, solve the difficult problem of difficult treatment of the flue gas in the waste steel preheating process, and ensure that the waste steel preheating flue gas emission can completely reach the standard; meanwhile, the burning loss of the scrap steel is reduced.)

1. An external combustion type scrap preheating shaft furnace is characterized by comprising an external combustion type combustion furnace, a scrap preheating shaft furnace and a flue gas activated carbon treatment system; a manipulator is arranged in the scrap steel preheating shaft furnace, a lower annular flue and an upper annular flue are arranged on the side wall of the scrap steel preheating shaft furnace, one side of the lower annular flue and one side of the upper annular flue are connected with the scrap steel preheating shaft furnace through a branch gas pipe, and the other side of the lower annular flue and the other side of the upper annular flue are connected with an external combustion type combustion furnace through a pipeline; the scrap steel preheating shaft furnace is connected with a smoke activated carbon treatment system, and a secondary combustion area is included in the scrap steel preheating shaft furnace.

2. The external combustion type scrap preheating shaft furnace according to claim 1, wherein a plurality of said manipulators are provided.

3. The external combustion type scrap preheating shaft furnace according to claim 2, wherein 2 mechanical hands are arranged, and the mechanical hands sequentially comprise a first mechanical hand and a second mechanical hand from bottom to top, and are used for supporting and preheating scrap steel in a layered mode under the action of a furnace bottom discharge flap valve, and specifically comprise a first layer of scrap steel, a second layer of scrap steel and a third layer of scrap steel.

4. The external combustion scrap preheating shaft furnace according to claim 1, wherein:

a branch gas pipe communicated with the lower annular flue on the side wall of the scrap steel preheating shaft furnace is arranged at a position 300-500mm away from the furnace bottom;

the branch pipe of the side wall of the scrap steel preheating shaft furnace and the upper annular flue for communication is arranged at a position 200-400mm away from the first-layer manipulator, so that the manipulator is prevented from being damaged by high-temperature smoke.

5. The external combustion type scrap preheating shaft furnace according to claim 3, wherein the secondary combustion zone is arranged between the top of the first layer of scrap and the first layer of manipulator, and the secondary combustion zone is provided with combustion-supporting gas nozzles and a normally burning combustion lance.

6. The external combustion scrap preheating shaft furnace according to claim 1, wherein:

the scrap steel preheating shaft furnace is provided with a secondary combustion chamber, the secondary combustion chamber is arranged on a connecting pipeline between an external combustion type combustion furnace and an upper annular flue, the secondary combustion chamber is provided with a secondary combustion chamber combustion-supporting gas nozzle, and a refractory material valve is arranged in front of the secondary combustion chamber;

the feeding system is an isostatic pressure closed feeding system, and consists of a lower isostatic pressure chamber and an upper isostatic pressure chamber, wherein the lower isostatic pressure chamber and the upper isostatic pressure chamber sequentially comprise a feeding turnover sealing valve, a middle sealing turnover valve and an upper sealing plate from bottom to top;

the bottom of the scrap steel preheating shaft furnace is provided with a flap discharge valve and an isostatic pressing discharge system, and the flap discharge valve and the isostatic pressing discharge system comprise a discharge isostatic pressing chamber, wherein the upper part of the discharge isostatic pressing chamber is sealed by the flap discharge valve, and the side surface of the discharge isostatic pressing chamber is provided with a side sealing plate for taking a scrap steel groove; the heat-preservation scrap steel groove is arranged in the discharging isostatic pressing chamber and is used for containing preheated scrap steel;

the flue gas activated carbon treatment system consists of a pipeline reactor and a powder spraying device, wherein the powder spraying device is arranged at an inlet of the pipeline reactor, powder sprayed from the inlet is mixed with flue gas in a turbulent flow manner, and harmful gases such as sulfur, dioxin and benzopyrene in the flue gas are adsorbed and removed;

flue gas active carbon processing system connect gradually dust pelletizing system, draught fan and chimney, wherein:

the dust removal system removes the activated carbon and the dust which are absorbed and reacted by the pipeline reactor;

the induced draft fan provides power for whole flue gas waste heat utilization processing system, the induced draft fan motor is frequency modulation motor.

7. An external combustion type scrap preheating method using the external combustion type scrap preheating shaft furnace according to any one of claims 1 to 6, characterized by comprising the steps of:

(1) adding scrap steel into a scrap steel preheating shaft furnace through a feeding system in a layered manner;

(2) the external combustion type combustion furnace generates smoke, the smoke is introduced into the scrap steel preheating vertical furnace through the lower annular flue and the upper annular flue, scrap steel is preheated in a layered mode, preheated scrap steel and heat exchange smoke are obtained, and steel tapping operation is carried out on the scrap steel.

8. The external combustion type scrap preheating method according to claim 7, wherein in the step (1):

the process of adding the scrap steel comprises the following steps: opening the upper sealing plate, adding the scrap steel into the upper isostatic pressing chamber, closing the upper sealing plate, then opening the middle sealing flap valve, dropping the scrap steel into the lower isostatic pressing chamber, closing the middle sealing flap valve, opening the lower feeding flap valve to seal the flap valve when adding the scrap steel into the scrap steel preheating shaft furnace, and adding the scrap steel into the scrap steel preheating shaft furnace; the negative pressure of the upper area is large, and a double-layer isostatic pressing chamber is adopted, so that the influence on the induced air pressure of the system due to the pressure relief of the system can be avoided;

the adding amount of the single-layer scrap steel is determined by the subsequent application of the scrap steel, when the scrap steel is supplied for the smelting of the converter, the adding amount of the scrap steel of each layer is equal to the adding amount of the converter each time or is half of the adding amount of the converter added to each layer; when scrap steel is supplied to the electric arc furnace, the adding amount of the scrap steel is one half or one third of that of the scrap steel;

the first layer of scrap steel is supported by a furnace bottom discharging flap valve, the second layer of scrap steel is supported by a first layer of mechanical arm, the third layer of scrap steel is supported by a second layer of mechanical arm, and the like;

when the first layer of scrap steel is preheated to a softening state, the density of the scrap steel is increased, the air permeability is poor, and the smoke resistance is increased; in this state, no nitrogen oxides are produced by combustion.

9. The external combustion type scrap preheating method according to claim 7, wherein in the step (2):

the steel tapping process of the scrap steel comprises the following steps: opening a furnace bottom sealing flap valve for unloading, enabling the preheated high-temperature waste steel to fall into a heat-preservation waste steel groove of the isostatic pressing chamber, then closing the furnace bottom sealing flap valve, opening a side sealing plate of the isostatic pressing chamber, taking out the heat-preservation waste steel groove, closing the side sealing plate, and completing primary discharging; after the scrap steel is discharged, withdrawing the first layer of manipulator for discharging, recovering the discharged first layer of manipulator to a material receiving state, then discharging the material by the second layer of manipulator, recovering the discharged material by the second layer of manipulator to the material receiving state, and then feeding the material into the furnace by the upper feeding system;

the flue gas after heat exchange is treated to reach the standard and is discharged through a chimney.

Technical Field

The invention belongs to the field of metallurgy, and particularly relates to an external combustion type scrap steel preheating shaft furnace and a preheating method thereof.

Background

With the rapid development of the economy of China for many years, the quantity of the scrap steel generated in the society every year is larger and larger, and the scrap steel is solid waste and is also a resource. At present, two main processes for treating the solid waste exist. Firstly, melting and smelting in an electric furnace; and secondly, melting and smelting by using excess heat of the converter. Electric energy is consumed for electric furnace smelting, and the electric energy is secondary energy, so that the comprehensive emission is large. Because China is mainly thermal power generation at present. About 60% of the energy is wasted in thermoelectric conversion. The method is most reasonable when the waste heat of the existing converter is used for smelting the waste steel with more consumption. The waste heat utilization is energy-saving, the cost is low, the emission is less, and an electric furnace with large investment does not need to be built. But the residual heat quantity of the converter is limited, and the consumption of scrap steel is limited. In order to enable a converter to digest more scrap steel, the steel enterprises mostly adopt a scrap steel heating method at present, and the adopted processes comprise hot-metal ladle oxygen combustion gun heating and ladle oxygen combustion gun heating, and the heating method has a plurality of problems. The thermal efficiency is less than 40 percent; flue gas can not be well treated, and because the intermittent heating is adopted, the flue gas temperature change is very large, so that the flue gas can not be denitrated. The sulfur, dioxin and heavy metals in the flue gas can not be removed due to environmental restriction. Therefore, the method does not allow the process to exist once the environment protection management department is informed. At present, the scrap steel preheating device invented by Shijiazhuang huge scientific and technological resources Limited company only performs flue gas dust removal. And the patent also has problems in the steel scrap discharging link. On the basis of a primary energy shaft furnace scrap steel smelting technology, a shaft furnace scrap steel preheating process is developed. The above problems are solved.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provides an external combustion type scrap steel preheating shaft furnace and a preheating method thereof.

In order to achieve the purpose, the invention adopts the following technical scheme:

an external combustion type scrap preheating shaft furnace comprises an external combustion type combustion furnace 1, a scrap preheating shaft furnace 2 and a flue gas activated carbon treatment system 3; the scrap steel preheating shaft furnace 2 is internally provided with a manipulator 9 for supporting scrap steel.

The side wall of the scrap steel preheating shaft furnace 2 is provided with a lower annular flue 7 and an upper annular flue 8, one side of the lower annular flue 7 and one side of the upper annular flue 8 are connected with the scrap steel preheating shaft furnace 2 through a branch gas pipe, and the other side of the lower annular flue 7 and the other side of the upper annular flue 8 are connected with the external combustion type combustion furnace 1 through a pipeline.

The mechanical arm 9 is provided with a plurality of, preferably 2, sequentially comprises a first mechanical arm and a second mechanical arm from bottom to top, and has the combined action with a furnace bottom discharging flap valve for supporting and supporting scrap steel, preheating and discharging materials in a layered mode, and specifically comprises a first layer of scrap steel, a second layer of scrap steel and a third layer of scrap steel.

The height of the scrap preheating shaft furnace 2 depends on the type of the preheated scrap, the discharge frequency, the preheated flue gas temperature, the flue gas volume and the induced air pressure of an induced draft fan. The temperature of the exhaust gas is controlled below 200 ℃. The high heat efficiency of the exhaust temperature is low, and the selection of dust removing filter materials is not facilitated. Wherein, when:

the specific surface area of the scrap steel is large, the smoke resistance is large, the heat exchange efficiency is high, and the height of the shaft furnace is relatively low; on the contrary, the height of the shaft furnace is relatively higher;

the discharging frequency is high, the temperature difference gradient is large, and the height of the shaft furnace is relatively low; the flue gas temperature is high, the flue gas amount is large, the relatively large amount of heat is brought in, and the height of the shaft furnace is relatively high;

the induced air pressure of the induced draft fan is taken as an important factor for limiting the height of the shaft furnace, and the induced air capacity of the induced draft fan ensures that the flue gas of the external combustion furnace can be introduced into the shaft furnace.

And a branch gas pipe communicated with the lower annular flue 7 and on the side wall of the scrap steel preheating shaft furnace 2 is arranged at a position 300-500mm away from the furnace bottom so as to avoid the damage of high-temperature flue gas to furnace bottom equipment.

The branch pipe of the side wall of the scrap steel preheating shaft furnace 2 communicated with the upper annular flue 8 is arranged at a position 200-400mm away from the first-layer manipulator, so that the manipulator is prevented from being damaged by high-temperature smoke.

The scrap steel preheating shaft furnace 2 comprises a secondary combustion area, and the secondary combustion area 1 is arranged between the top of the first layer of scrap steel and the first layer of mechanical arm. The secondary combustion area is provided with a combustion-supporting gas nozzle 10, and a small-sized normal combustion gun 11 is arranged in the secondary combustion area and used for ignition.

The scrap steel preheating shaft furnace 2 is provided with a secondary combustion chamber 12, the secondary combustion chamber 12 is arranged on a connecting pipeline of the external combustion type combustion furnace 1 and the upper annular flue 8, the secondary combustion chamber 12 is provided with a secondary combustion chamber combustion-supporting gas nozzle 13, and a refractory material valve 14 is arranged in front of the secondary combustion chamber 12.

The scrap steel preheating shaft furnace is characterized in that a feeding system is arranged above the scrap steel preheating shaft furnace, the feeding system is an isostatic pressure closed feeding system 16, the isostatic pressure feeding system 16 consists of a lower isostatic pressure chamber and an upper isostatic pressure chamber, and the lower isostatic pressure chamber consists of a lower feeding turning plate sealing valve and a middle sealing turning plate valve. The upper isostatic pressing chamber consists of a middle sealing flap valve and an upper sealing plate, and the middle sealing flap valve is used as a shared sealing flap valve between the lower isostatic pressing chamber and the upper isostatic pressing chamber.

The bottom of the scrap steel preheating shaft furnace 2 is provided with a flap discharge valve 17 and an isostatic pressing discharge system 15, and the flap discharge valve 17 and the isostatic pressing discharge system comprise a discharge isostatic pressing chamber, wherein the upper part of the discharge isostatic pressing chamber is sealed by the flap discharge valve 17, and the side surface of the discharge isostatic pressing chamber is provided with a side sealing plate 18 for taking a scrap steel groove. The heat preservation scrap steel groove 19 is arranged in the discharging isostatic pressing chamber and used for containing preheated scrap steel.

The flue gas activated carbon treatment system 3 comprises a pipeline reactor and a powder spraying device, wherein the powder spraying device is arranged at an inlet of the pipeline reactor, powder sprayed from the inlet is mixed with flue gas in a turbulent flow manner, and harmful gases such as sulfur, dioxin, benzopyrene and the like in the flue gas are adsorbed and removed.

Flue gas active carbon processing system 3 connect gradually dust pelletizing system 4, draught fan 5 and chimney 6, wherein:

the dust removal system 4 removes the activated carbon and the dust which are absorbed and reacted by the pipeline reactor;

the draught fan 5 provides power for the whole flue gas waste heat utilization treatment system, and a motor of the draught fan is a frequency modulation motor.

An external combustion type scrap steel preheating method is carried out by adopting the external combustion type scrap steel preheating shaft furnace, and comprises the following steps:

(1) adding scrap steel into the scrap steel preheating shaft furnace 2 in layers through a feeding system;

(2) the external combustion type combustion furnace 1 generates flue gas, the flue gas is introduced into the scrap steel preheating shaft furnace 2 through the lower annular flue 7 and the upper annular flue 8, the scrap steel is preheated in a layered mode, preheated scrap steel and heat exchange flue gas are obtained, and steel tapping operation is carried out on the scrap steel.

In the step (1), the scrap steel adding process comprises the following steps: opening the upper sealing plate, adding the scrap steel into the upper isostatic pressing chamber, closing the upper sealing plate, then opening the middle sealing flap valve, dropping the scrap steel into the lower isostatic pressing chamber, closing the middle sealing flap valve, opening the lower feeding flap valve when adding the scrap steel into the scrap steel preheating shaft furnace 2, and adding the scrap steel into the scrap steel preheating shaft furnace 2. The negative pressure of the upper area is large, and the double-layer isostatic pressing chamber is adopted, so that the influence on the induced air pressure of the system due to the pressure relief of the system can be avoided.

In the step (1), the adding amount of the single-layer scrap steel is determined by the subsequent application of the scrap steel, when the scrap steel is supplied for converter smelting, the adding amount of the scrap steel of each layer is equal to the adding amount of the converter every time or is half of the adding amount of the converter every layer; when the electric arc furnace is supplied with scrap, one-half or one-third of the electric arc furnace is charged for convenient operation.

In the step (1), the first layer of scrap steel is supported by a furnace bottom discharging flap valve, the second layer of scrap steel is supported by a first layer of mechanical arm, the third layer of scrap steel is supported by a second layer of mechanical arm, and if a fourth layer of scrap steel is designed, the third layer of mechanical arm is designed to support the fourth layer of scrap steel.

In the step (1), when the first layer of scrap steel is preheated to a softening state, the density of the scrap steel is increased, the air permeability is deteriorated, the smoke resistance is increased, when the resistance is increased to a designed value, a refractory valve 14 of the secondary combustion chamber is opened, the smoke directly enters the second layer of scrap steel, and combustion-supporting gas is sprayed into the secondary combustion chamber 12 for secondary combustion before the smoke enters the upper annular flue 8. Because the surplus gas quantity is relatively small and the flue gas temperature is higher, the injected combustion-supporting gas can be combusted due to lower surplus coefficient. Such high temperature low oxygen combustion produces substantially no nitrogen oxides.

In the step (2), the steel tapping process of the scrap steel comprises the following steps: opening a furnace bottom sealing flap valve for unloading, enabling the preheated high-temperature waste steel to fall into a heat-preservation waste steel groove of the isostatic pressing chamber, then closing the furnace bottom sealing flap valve, opening a side sealing plate of the isostatic pressing chamber, taking out the heat-preservation waste steel groove, closing the side sealing plate, and completing primary discharging; and after the scrap steel is discharged, withdrawing the first layer of manipulator for discharging, recovering the first layer of manipulator after discharging to a material receiving state, then discharging the second layer of manipulator, recovering the second layer of manipulator for discharging to a material receiving state, and then feeding the material into the furnace by the upper feeding system.

In the step (2), the flue gas after heat exchange is treated to reach the standard and is discharged through a chimney, and the chimney is designed and manufactured according to the local environmental protection requirement.

The working principle of the invention is as follows:

the shaft furnace is the best heat transfer equipment in all industrial furnaces, so the shaft furnace is used as scrap steel preheating equipment in the invention. In order to reduce the oxidation of the waste steel caused by local unevenness, the invention selects an external combustion type combustion chamber, the hot flue gas after combustion is sent into the furnace, and the oxygen-fuel ratio of the external combustion type combustion chamber is less than 1, namely the gas is excessive, so that the high-temperature section in the preheating process is in the reducing atmosphere, and the oxidation of the high-temperature waste steel by the excessive oxygen is avoided. Air is blown into the upper 600-800 ℃ section of the shaft furnace for secondary combustion, so that the scrap steel is not easily oxidized at the temperature, and the fuel gas is easily combusted. Thus, atmospheric pollution and energy waste caused by gas escape can be avoided.

If the high-zinc light and thin material waste steel is preheated frequently, zinc steam enrichment can be caused in the furnace, so that the smoke is partially led out before secondary combustion for zinc recovery, and then the smoke after zinc recovery is sent back to the shaft furnace for continuous waste steel preheating.

Because the gas adopted by the external combustion type is excessively combusted, the reducing atmosphere is arranged in front of the secondary combustion section in the shaft furnace, and the nitrogen oxides are reduced by the reducing gas in the flue gas, so the nitrogen oxides in the flue gas are lower. Because the temperature of the scrap steel is lower, the oxidation of the scrap steel is less. In order to remove harmful gases such as sulfur, dioxin, benzopyrene and the like in the flue gas, an activated carbon spraying and blowing adsorption device is arranged at the rear part of the shaft furnace, and the harmful gases such as sulfur, dioxin, benzopyrene and the like are removed together. The sprayed activated carbon and the dust in the furnace are captured together in the dust remover. The activated carbon and the dust recovered by the dust remover can be sent to a blast furnace coal injection system and injected into the blast furnace along with the injected coal dust, so that resource utilization and harmless treatment are realized.

The invention has the beneficial effects that:

1. the heat efficiency is improved, and the carbon emission is reduced;

2. the problem of difficult management of waste steel preheating process flue gas is solved. The emission of waste steel preheating flue gas can reach the standard completely;

3. the burning loss of the scrap steel is reduced;

4. realizes the low-cost waste steel digestion. The thermal efficiency is much higher than that of an electric arc furnace;

5. a new way is explored for the converter to digest waste steel;

6. can greatly reduce the steel-making cost.

7. The technology is an auxiliary project for iron and steel smelting with remarkable economic and social benefits.

Drawings

FIG. 1 is a schematic structural view of an external combustion type scrap preheating shaft furnace apparatus according to embodiment 1 of the present invention; wherein:

the method comprises the following steps of 1-external combustion type combustion furnace, 2-scrap steel preheating shaft furnace, 3-smoke activated carbon treatment system, 4-dust removal system, 5-induced draft fan, 6-chimney, 7-lower annular flue, 8-upper annular flue, 9-mechanical arm, 10-combustion-supporting gas nozzle, 11-small-sized normal combustion burner, 12-secondary combustion chamber, 13-secondary combustion chamber combustion-supporting gas nozzle, 14-refractory valve, 15-isostatic pressing discharge system and 16-static pressing closed charging system. 17-flap discharge valve, 18-side closing plate and 19-heat preservation scrap steel groove.

Detailed Description

Example 1

A certain steel mill has one 100-ton oxygen top-blown converter, and because the designs of iron making, converter smelting and continuous casting are not matched, more scrap steel needs to be added to ensure that the produced molten steel is matched. Because the heat of molten iron is limited, 16-17 tons of scrap steel can be added into each furnace, namely about 15% of scrap steel is added, in order to increase the amount of the added scrap steel, an oxygen burning gun for preheating the scrap steel in a molten iron tank is arranged, the preheating is uneven, the burning loss of the scrap steel is large, the burning loss is 7% -8%, the energy utilization rate is only about 30%, and the adding amount of the scrap steel in each furnace is 20-23 tons after the molten iron tank is preheated. The adding proportion of the scrap steel is about 20 percent, so that the continuous casting low-drawing-speed production can be maintained reluctantly. Because the flue gas fluctuation is too large and the sealing is not good, only cyclone dust removal is carried out, and harmful gases such as sulfur, nitrate, dioxin and the like are not treated. When environmental protection is observed, the waste steel preheating equipment is shut down because the environmental protection emission exceeds the standard. In order to solve the problems, the external combustion type scrap preheating technical equipment is adopted, and the detailed structure of the external combustion type scrap preheating technical equipment is as described in the content part of the invention.

The method comprises the following specific implementation steps: the structure schematic diagram of the external combustion type scrap steel preheating shaft furnace device is shown in figure 1:

1. an external combustion type combustion furnace 1, a scrap steel preheating shaft furnace 2, a flue gas activated carbon treatment system 3, a dust removal system 4, an induced draft fan 5 and a chimney 6 are built;

2. converter gas is selected as the fuel gas of the external combustion furnace, and combustion-supporting gas is air rich in oxygen by 30%;

3. the external combustion type combustion furnace 1 is connected with a lower annular flue 7 and an upper annular flue 8 of the scrap steel preheating shaft furnace 2 through connecting pipelines. The upper annular flue and the lower annular flue are communicated with the interior of the shaft furnace through connecting branch gas pipes;

4. the scrap steel preheating shaft furnace is provided with a manipulator 9 for supporting scrap steel, layered preheating and discharging are carried out, and the maximum amount of scrap steel loaded in each layer is designed according to 35 tons. The first layer of scrap steel is supported by a furnace bottom discharging flap valve, the second layer of scrap steel is supported by a first layer of mechanical arm, and the third layer of scrap steel is supported by a second layer of mechanical arm. The smoke discharge temperature is designed according to 150 ℃, and is not more than 250 ℃ at most;

1. the distance between the lower annular flue 7 and a branch gas pipe communicated with the shaft furnace is selected to be 400 mm;

2. the upper annular flue 8 and the shaft furnace communicating branch pipe are arranged at a certain height of 300mm away from the first layer of manipulator;

3. and a secondary combustion area is arranged between the top of the first layer of scrap steel and the first layer of mechanical arm. A combustion-supporting gas nozzle 10 is arranged at a position far away from the manipulator, and a small-sized normal combustion gun 11 is arranged for ignition;

4. and a secondary combustion chamber 12 is arranged on a connecting pipeline of the external combustion furnace and the upper annular flue, and a combustion-supporting gas nozzle 13 is arranged in the secondary combustion chamber. A refractory valve 14 is provided in front of the secondary combustion chamber. When the first layer of scrap steel is preheated to a softening state, the density of the scrap steel is increased, the air permeability is deteriorated, and the smoke resistance is increased. When the resistance increases to the design value, the refractory valve 14 is opened to allow the flue gas to enter the second layer of scrap directly. Before the flue gas enters the upper annular flue 8, combustion-supporting gas is sprayed into the secondary combustion chamber 12 for secondary combustion. Because the surplus gas quantity is relatively small and the flue gas temperature is higher, the injected combustion-supporting gas can be combusted due to lower surplus coefficient. The high-temperature low-oxygen combustion basically does not generate nitrogen oxides, and the nitrogen oxides detected in the smoke discharge are less than 50Nmg/m³And meets the requirement of environmental protection.

5. The shaft furnace 2 is provided with an isostatic pressing discharging system 15, the upper part of the isostatic pressing chamber is sealed by a furnace bottom sealing flap valve, and the side surface of the isostatic pressing chamber is provided with a side sealing plate for taking a scrap steel groove. The heat-preservation scrap steel groove is placed in the isostatic pressing chamber to contain preheated scrap steel. When the shaft furnace discharges the waste steel, the furnace bottom sealing flap valve is opened to unload the waste steel, the preheated high-temperature waste steel falls into the heat-preservation waste steel groove of the isostatic pressing chamber, then the furnace bottom sealing flap valve is closed, the side sealing plate of the isostatic pressing chamber is opened, the heat-preservation waste steel groove is taken out, and the side sealing plate is closed. Finishing primary discharging;

6. after the scrap steel is discharged, withdrawing the first layer of manipulator for discharging, recovering the discharged first layer of manipulator to a material receiving state, then discharging the material by the second layer of manipulator, recovering the discharged material by the second layer of manipulator to the material receiving state, and then feeding the material into the furnace by the upper feeding system;

7. the upper charging system is provided with an isostatic closed charging system 16. The isostatic pressing charging system consists of a lower isostatic pressing chamber and an upper isostatic pressing chamber, and the lower isostatic pressing chamber and the upper isostatic pressing chamber are double-layer isostatic pressing chambers. The lower isostatic pressure chamber consists of a charging flap seal valve and a middle sealing flap valve. The upper isostatic pressure chamber consists of a middle sealing flap valve and an upper sealing plate. When adding the steel scrap, opening the upper sealing plate, adding the steel scrap into the upper isostatic pressure chamber, closing the upper sealing plate, then opening the middle sealing flap valve, dropping the steel scrap into the lower isostatic pressure chamber, closing the middle sealing flap valve, opening the feeding flap valve when adding the steel scrap into the shaft furnace, and adding the steel scrap into the shaft furnace. The negative pressure of the upper area is large, and a double-layer isostatic pressing chamber is adopted, so that the influence on the induced air pressure of the system due to the pressure relief of the system can be avoided;

8. the flue gas active carbon treatment system 3 consists of a pipeline reactor and powder spraying equipment. The powder gun is arranged at the inlet of the pipeline reactor. The pipeline reactor sprayed from the inlet is mixed with the flue gas in a turbulent flow manner, and harmful gases such as sulfur, dioxin, benzopyrene and the like in the flue gas are adsorbed and removed;

9. the dust remover 4 removes the activated carbon and the dust which are absorbed and reacted by the pipeline reactor;

10. and the draught fan 5 provides power for the whole flue gas waste heat utilization treatment system. The motor is a frequency modulation motor;

11. and the treated flue gas reaching the standard is discharged through a chimney. The chimney is designed and manufactured according to the local environmental protection requirement.

The system is normal in all in 7 months;

the heat efficiency of the system reaches 70%;

the average preheating temperature of the scrap steel is 850-950 ℃;

the charging amount of the scrap steel in each furnace is increased to 28-32 tons. The requirements of steel making and continuous casting are met;

the burning loss of the scrap steel is less than 2 percent. Far lower than the original 7% -8%;

the emission of sulfur, nitrate, dioxin and dust of the flue gas all reach the standard.