A vertical kiln for preheating raw materials of a fully enclosed submerged arc furnace and its working method

Abstract

The present invention relates to a shaft kiln for preheating raw materials of a fully enclosed submerged arc furnace and its working method. The shaft kiln includes a feeding bin, a top feeding pipe, a distributor, a shaft kiln body, a hot flue gas generating device, a low-temperature flue gas outlet pipe and a bottom discharging pipe. A plurality of top feeding pipes are arranged at the bottom of the feeding bin and are connected to a corresponding plurality of feeding ports at the top of the shaft kiln body through the distributor. The shaft kiln body is divided into a preheating section, a heating section and a soaking section from top to bottom. A heat exchange structure is arranged in the soaking section. The heat exchange structure is composed of an annular air duct, an outer heat exchanger, an inner heat exchanger and a middle heat exchanger which are arranged in sequence from outside to inside. The air inlet end of the annular air duct is communicated with the high-temperature flue gas outlet of the hot flue gas generating device. The present invention uses the gas recovered from the submerged arc furnace flue gas as fuel to generate high-temperature flue gas, which is introduced into the shaft kiln to preheat the raw materials of the submerged arc furnace, thereby reducing the power consumption of the submerged arc furnace and shortening the production cycle of the submerged arc furnace.

Description

Technical Field

[0001] The present invention relates to the technical field of submerged arc furnace smelting, and in particular to a shaft kiln for preheating raw materials of a fully enclosed submerged arc furnace and its working method. Background Art

[0002] A submerged arc furnace is also called an electric arc furnace or a resistance furnace. It is mainly used for reducing and smelting raw materials such as ores, carbonaceous reducing agents, and solvents. It mainly produces ferroalloys such as ferrosilicon, ferromanganese, ferrochrome, ferrotungsten, and silicomanganese alloy, and is an important industrial raw material in the metallurgical industry and chemical raw materials such as calcium carbide. Submerged arc furnaces can be divided into semi-closed submerged arc furnaces and fully enclosed submerged arc furnaces.

[0003] Currently, the main energy-saving method of a fully enclosed submerged arc furnace is to recover the waste heat of the submerged arc furnace flue gas. It does not consider the overall process chain of submerged arc furnace smelting. Although the amount of flue gas generated during the smelting process of a fully enclosed submerged arc furnace is small, there is gas with a high calorific value in it, and the utilization rate of this part of the gas is extremely low. A large amount of gas discharged not only pollutes the environment but also causes energy waste.

[0004] The flue gas of a fully enclosed submerged arc furnace has high physical sensible heat and chemical energy. The flue gas temperature is as high as over 850 °C, and the CO content in the flue gas accounts for about 60% - 80%. The present invention combines the raw material pretreatment process of the submerged arc furnace to realize the hierarchical utilization of the energy in the submerged arc furnace flue gas. The high-quality submerged arc furnace gas can not only be purified and used as clean gas in the factory area; for large-grained raw materials, through the shaft kiln described in the present invention, the gas can be recycled as fuel to preheat the raw materials entering the furnace, thereby improving the energy-saving effect of the submerged arc furnace. Summary of the Invention

[0005] The present invention provides a shaft kiln for preheating raw materials of a fully enclosed submerged arc furnace and its working method, which uses the gas recovered from the submerged arc furnace flue gas as fuel to generate high-temperature flue gas, and the high-temperature flue gas is introduced into the shaft kiln to preheat the raw materials of the submerged arc furnace, thereby reducing the power consumption of the submerged arc furnace and shortening the production cycle of the submerged arc furnace.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A vertical kiln for preheating raw materials of a fully enclosed submerged arc furnace, comprising a feeding bin, a top discharging pipe, a distributor, a vertical kiln body, a hot flue gas generating device, a low-temperature flue gas outlet pipe and a bottom discharging pipe; a plurality of top discharging pipes are arranged at the bottom of the feeding bin and are connected to a plurality of corresponding feeding ports at the top of the vertical kiln body through the distributor; the vertical kiln body is divided into a preheating section, a heating section and a soaking section from top to bottom; a heat exchange structure is arranged in the soaking section, and the heat exchange structure is composed of an annular air duct, an outer heat exchanger, an inner heat exchanger and a middle heat exchanger which are arranged in sequence from outside to inside; the air inlet end of the annular air duct is communicated with the high-temperature flue gas outlet of the hot flue gas generating device; the outer heat exchanger is of an annular structure, and a plurality of radial air outlet ports are arranged on the outer heat exchanger along the circumferential direction of the vertical kiln body; a plurality of inner heat exchangers are arranged at intervals along the circumferential direction of the vertical kiln body, and the space between two adjacent inner heat exchangers corresponds to the material dropping area below the distributor; the inner heat exchanger is provided with a radial air inlet channel communicated with a part of the radial air outlet ports of the outer heat exchanger, and the rest radial air outlet ports are directly communicated with the material dropping area; lateral air outlet ports are respectively arranged on both sides of the inner heat exchanger and are communicated with the radial air inlet channel; a bottom air inlet is arranged at the bottom of the middle heat exchanger, and a plurality of upper air outlet ports are arranged along the circumferential direction at the upper part of the middle heat exchanger. The bottom air inlet is communicated with the upper air outlet ports through a vertical air inlet channel; the bottom air inlet is communicated with the radial air inlet channels of some of the inner heat exchangers, and the radial air inlet channels of the rest inner heat exchangers are directly communicated with the inner space of the vertical kiln body; the upper air outlet ports of the middle heat exchanger are directly communicated with the inner space of the vertical kiln body; a low-temperature flue gas outlet pipe is further arranged at the top of the vertical kiln body, and a plurality of bottom discharging pipes are arranged at the bottom of the vertical kiln body.

[0008] A buffer bin is arranged above the feeding bin; a roller valve I is arranged at the connection part between the buffer bin and the feeding bin.

[0009] A charging hopper is arranged above the buffer bin; a roller valve II is arranged at the connection part between the charging hopper and the buffer bin.

[0010] There are two hot flue gas generating devices which are symmetrically arranged along the circumferential direction of the vertical kiln body. Two partition walls are arranged in the annular air duct to divide the annular air duct into two independent air supply channels, and each independent air supply channel is respectively connected to a hot flue gas generating device.

[0011] The hot flue gas generating device is a combustion chamber provided with a gas burner.

[0012] A conical section is arranged at one end of the radial air outlet port close to the annular flue, and the large end is outside and the small end is inside.

[0013] The lateral air outlet port is inclined downward and outward.

[0014] The upper air outlet port is inclined downward and outward.

[0015] The annular air duct, the outer heat exchanger, the inner heat exchanger and the middle heat exchanger are all built with refractory materials.

[0016] A working method for a shaft kiln for preheating raw materials of a fully enclosed submerged arc furnace, comprising the following steps:

[0017] 1) Materials enter the buffer bin from the feeding hopper through the roller valve II, then enter the feeding bin through the roller valve I, and finally are evenly distributed into the shaft kiln body by the distributor through multiple top discharging pipes; the materials preheated in the preheating section move downward, enter the heating section after being heated, and then enter the soaking section;

[0018] 2) The hot flue gas generating device uses the gas from the submerged arc furnace as fuel, and the high-temperature flue gas generated after combustion enters the annular air duct. A part of the high-temperature flue gas directly exchanges heat with the materials through the radial air outlet of the outer heat exchanger, and another part of the high-temperature flue gas enters the radial air inlet channel of the inner heat exchanger through the radial air outlet of the outer heat exchanger; a part of the high-temperature flue gas entering the radial air inlet channel exchanges heat with the materials through multiple lateral air outlets, and another part of the high-temperature flue gas enters the middle heat exchanger through the bottom air inlet; the high-temperature flue gas entering the middle heat exchanger exchanges heat with the materials through multiple upper air outlets after passing through the vertical air inlet channel; the low-temperature flue gas after exchanging heat with the materials is discharged from the low-temperature flue gas outlet pipe at the top of the shaft kiln body for subsequent purification treatment;

[0019] 3) The materials that meet the temperature requirements after heat exchange in the soaking section are discharged from the bottom discharging pipe and enter the submerged arc furnace as preheated raw materials.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] 1) Using the gas recovered from the flue gas of the submerged arc furnace as fuel to generate high-temperature flue gas, which is introduced into the shaft kiln to preheat the raw materials of the submerged arc furnace, thereby reducing the power consumption of the submerged arc furnace and shortening the production cycle of the submerged arc furnace;

[0022] 2) By arranging an annular flue, an outer heat exchanger, an inner heat exchanger and a middle heat exchanger in the preheating section of the shaft kiln, uniform heat exchange with the raw materials of the submerged arc furnace is achieved. Description of the Drawings

[0023] Figure 1 is a schematic structural diagram of a shaft kiln for preheating raw materials of a fully enclosed submerged arc furnace according to the present invention.

[0024] Figure 2 is Figure 1 an enlarged view of part A in

[0025] Figure 3 is Figure 1 a view taken along line B-B in

[0026] Figure 4 is Figure 3 a partial view of

[0027] In the figure: 1. Loading hopper; 2. Second roller valve; 3. Buffer bin; 4. First roller valve; 5. Feeding bin; 6. Top discharging pipe; 7. Distributor; 8. Vertical kiln body; 81. Preheating section; 82. Heating section; 83. Soaking section; 9. Heat exchange structure; 91. Annular flue; 92. Outer heat exchanger; 93. Inner heat exchanger; 94. Middle heat exchanger; 95. Radial air outlet; 96. Lateral air outlet; 97. Upper air outlet; 10. Hot flue gas generating device; 11. Bottom discharging pipe; 12. Low-temperature flue gas outlet pipe Specific embodiments

[0028] The specific embodiments of the present invention will be further described below in conjunction with the accompanying drawings:

[0029] As Figures 1-4 shown, a vertical kiln for preheating raw materials of a fully enclosed submerged arc furnace according to the present invention includes a feeding bin 5, a top discharging pipe 6, a distributor 7, a vertical kiln body 8, a hot flue gas generating device 10, a low-temperature flue gas outlet pipe 12 and a bottom discharging pipe 11; a plurality of top discharging pipes 6 are provided at the bottom of the feeding bin 5, and are connected to a plurality of corresponding feeding ports at the top of the vertical kiln body 8 through the distributor 7; the vertical kiln body 8 is divided into a preheating section, a heating section and a soaking section from top to bottom; a heat exchange structure 9 is provided in the soaking section, and the heat exchange structure 9 is composed of an annular air duct 91, an outer heat exchanger 92, an inner heat exchanger 93 and a middle heat exchanger 94 arranged in sequence from outside to inside; the air inlet end of the annular air duct 91 is communicated with the high-temperature flue gas outlet of the hot flue gas generating device 10; the outer heat exchanger 92 is of an annular structure, and a plurality of radial air outlets 95 are provided on it along the circumferential direction of the vertical kiln body 8; a plurality of inner heat exchangers 93 are arranged at intervals along the circumferential direction of the vertical kiln body 8, and the space between two adjacent inner heat exchangers 93 corresponds to the blanking area below the distributor 7; the inner heat exchanger 93 is provided with a radial air inlet channel communicated with a part of the radial air outlets 95 of the outer heat exchanger 92, and the remaining radial air outlets 95 are directly communicated with the blanking area; lateral air outlets 96 are respectively provided on both sides of the inner heat exchanger 93 and communicated with the radial air inlet channel; a bottom air inlet is provided at the bottom of the middle heat exchanger 94, and a plurality of upper air outlets 97 are provided along the circumferential direction at the upper part, and the bottom air inlet is communicated with the upper air outlets 97 through a vertical air inlet channel; the bottom air inlet is communicated with the radial air inlet channels of some inner heat exchangers, and the radial air inlet channels of the remaining inner heat exchangers are directly communicated with the internal space of the vertical kiln body 8; the upper air outlets 97 of the middle heat exchanger 94 are directly communicated with the internal space of the vertical kiln body 8; a low-temperature flue gas outlet pipe 12 is further provided at the top of the vertical kiln body 8, and a plurality of bottom discharging pipes 11 are provided at the bottom of the vertical kiln body 8.

[0030] A buffer bin 3 is provided above the feeding bin 5; a first roller valve 4 is provided at the connection between the buffer bin 3 and the feeding bin 5.

[0031] Above the buffer silo 3, a feeding hopper 1 is provided, and a roller valve two 2 is provided at the connection between the feeding hopper 1 and the buffer silo 3.

[0032] There are 2 heat flue gas generating devices 10, which are symmetrically arranged along the circumferential direction of the shaft kiln body 8. Two partition walls are provided in the annular air duct 91 to divide the annular air duct 91 into two independent air supply channels, and each independent air supply channel is respectively connected to a heat flue gas generating device 10.

[0033] The heat flue gas generating device 10 is a combustion chamber provided with a gas burner.

[0034] A conical section is provided at one end of the radial air outlet 95 close to the annular flue 91, with the large end outside and the small end inside.

[0035] The lateral air outlet 96 is inclined downward and outward.

[0036] The upper air outlet 97 is inclined downward and outward.

[0037] The annular air duct 91, the outer heat exchanger 92, the inner heat exchanger 93 and the middle heat exchanger 94 are all built with refractory materials.

[0038] A working method of a shaft kiln for preheating raw materials of a fully enclosed submerged arc furnace includes the following steps:

[0039] 1) Materials enter the buffer silo 3 from the feeding hopper 1 through the roller valve two 2, then enter the feeding silo 5 through the roller valve one 4, and finally are evenly distributed into the shaft kiln body 8 by the distributor 7 through multiple top feeding pipes 6; the materials preheated in the preheating section 81 move downward, and after being heated in the heating section 82, enter the soaking section 83;

[0040] 2) The heat flue gas generating device 10 uses submerged arc furnace gas as fuel, and the high-temperature flue gas generated after combustion enters the annular air duct 91. Part of the high-temperature flue gas directly exchanges heat with the materials through the radial air outlet 95 of the outer heat exchanger 92, and another part of the high-temperature flue gas enters the radial air inlet channel of the inner heat exchanger 93 through the radial air outlet 95 of the outer heat exchanger 92; part of the high-temperature flue gas entering the radial air inlet channel exchanges heat with the materials through multiple lateral air outlets 96, and another part of the high-temperature flue gas enters the middle heat exchanger 94 through the bottom air inlet; the high-temperature flue gas entering the middle heat exchanger 94 exchanges heat with the materials through multiple upper air outlets 97 after passing through the vertical air inlet channel; the low-temperature flue gas after exchanging heat with the materials is discharged from the low-temperature flue gas outlet pipe 12 at the top of the shaft kiln body 8 for subsequent purification treatment;

[0041] 3) The materials that meet the temperature requirements after heat exchange in the soaking section 83 are discharged from the bottom discharge pipe 11 and enter the submerged arc furnace as preheated raw materials.

[0042] In the shaft kiln for preheating the raw materials of a fully enclosed submerged arc furnace according to the present invention, the kiln shell of the shaft kiln body 8 is made of ordinary carbon steel and is supported by a section steel frame on the outside. A refractory lining is laid inside the kiln shell. The refractory lining adopts a trapezoidal structure with a smaller upper opening and a larger lower opening, which can prevent material accumulation and ensure good air permeability at the same time.

[0043] The shaft kiln described in the present invention is applicable to preheating the raw materials of the submerged arc furnace with a particle size of 10 - 100 mm, and the preheating temperature is 350 - 500 °C.

[0044] The shaft kiln described in the present invention adopts a double drum valve for sealing. Both the buffer bin 3 and the feeding bin 5 can store the raw materials of the submerged arc furnace. A variety of heat exchangers 92, 93, and 94 are arranged in the soaking section 83 of the shaft kiln body 8, so that the high-temperature flue gas and the raw materials of the submerged arc furnace can be fully and evenly heat-exchanged.

[0045] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and should be covered within the protection scope of the present invention.

Claims

1. A vertical kiln for preheating raw materials of a fully enclosed submerged arc furnace, characterized in that, It includes a feeding bin, a top discharging pipe, a distributor, a shaft kiln body, a hot flue gas generating device, a low-temperature flue gas outlet pipe and a bottom discharging pipe; a buffer bin is arranged above the feeding bin; a roller valve I is arranged at the connection between the buffer bin and the feeding bin; a feeding hopper is arranged above the buffer bin, and a roller valve II is arranged at the connection between the feeding hopper and the buffer bin; a plurality of top discharging pipes are arranged at the bottom of the feeding bin and are connected to a plurality of corresponding feeding ports at the top of the shaft kiln body through a distributor; the shaft kiln body is divided into a preheating section, a heating section and a soaking section from top to bottom; a heat exchange structure is arranged in the soaking section, and the heat exchange structure is composed of an annular air duct, an outer heat exchanger, an inner heat exchanger and a middle heat exchanger which are arranged in sequence from outside to inside; the air inlet end of the annular air duct is communicated with the high-temperature flue gas outlet of the hot flue gas generating device; the outer heat exchanger is of an annular structure, and a plurality of radial air outlets are arranged on it along the circumferential direction of the shaft kiln body; the inner heat exchangers are multiple and are arranged at intervals along the circumferential direction of the shaft kiln body, and the space between two adjacent inner heat exchangers corresponds to the blanking area below the distributor; the inner heat exchanger is provided with a radial air inlet channel communicated with a part of the radial air outlets of the outer heat exchanger, and the radial air outlets of the rest outer heat exchangers are directly communicated with the blanking area; the high-temperature flue gas generated after combustion enters the annular air duct, a part of the high-temperature flue gas directly exchanges heat with the materials through the radial air outlets of the outer heat exchanger, and the other part of the high-temperature flue gas enters the radial air inlet channel of the inner heat exchanger through the radial air outlets of the outer heat exchanger; lateral air outlets communicated with the radial air inlet channel are respectively arranged on both sides of the inner heat exchanger, and the lateral air outlets are inclined downward and outward; a bottom air inlet is arranged at the bottom of the middle heat exchanger, and a plurality of upper air outlets are arranged along the circumferential direction at the upper part. The bottom air inlet is communicated with the upper air outlets through a vertical air inlet channel, and the upper air outlets are inclined downward and outward; the bottom air inlet is communicated with the radial air inlet channels of part of the inner heat exchangers, and the radial air inlet channels of the rest inner heat exchangers are directly communicated with the internal space of the shaft kiln body; the upper air outlets of the middle heat exchanger are directly communicated with the internal space of the shaft kiln body; a low-temperature flue gas outlet pipe is also arranged at the top of the shaft kiln body, and a plurality of bottom discharging pipes are arranged at the bottom of the shaft kiln body.

2. The shaft kiln for preheating raw materials of a fully enclosed submerged arc furnace according to claim 1, characterized in that There are 2 hot flue gas generating devices which are symmetrically arranged along the circumferential direction of the shaft kiln body. 2 partition walls are arranged in the annular air duct to divide the annular air duct into 2 independent air supply channels, and each independent air supply channel is respectively connected to a hot flue gas generating device.

3. The shaft kiln for preheating raw materials of a fully enclosed submerged arc furnace according to claim 1 or 2, characterized in that, The hot flue gas generating device is a combustion chamber provided with a gas burner.

4. A shaft kiln for preheating raw materials of a fully enclosed submerged arc furnace according to claim 1, characterized in that, A conical section is arranged at one end of the radial air outlet close to the annular air duct, and the large end is outside and the small end is inside.

5. The shaft kiln for preheating raw materials of a fully enclosed submerged arc furnace according to claim 1, wherein, The annular air duct, the outer heat exchanger, the inner heat exchanger and the middle heat exchanger are all built with refractory materials.

6. The working method of a vertical kiln for preheating raw materials of a fully enclosed submerged arc furnace as described in claim 1, characterized in that, It includes the following steps: 1) The materials enter the buffer bin from the feeding hopper through the roller valve II, then enter the feeding bin through the roller valve I, and finally are evenly distributed into the shaft kiln body by the distributor through a plurality of top discharging pipes; the materials preheated in the preheating section move downward, are heated in the heating section and then enter the soaking section. 2) The hot flue gas generating device uses the blast furnace gas as fuel. The high-temperature flue gas generated after combustion enters the annular air duct. A part of the high-temperature flue gas directly exchanges heat with the materials through the radial air outlets of the outer heat exchanger, and another part of the high-temperature flue gas enters the radial air inlet channel of the inner heat exchanger through the radial air outlets of the outer heat exchanger; a part of the high-temperature flue gas entering the radial air inlet channel exchanges heat with the materials through multiple lateral air outlets, and another part of the high-temperature flue gas enters the middle heat exchanger through the bottom air inlet; the high-temperature flue gas entering the middle heat exchanger passes through the vertical air inlet channel and then exchanges heat with the materials through multiple upper air outlets; the low-temperature flue gas after exchanging heat with the materials is discharged through the low-temperature flue gas outlet pipe at the top of the shaft kiln body for subsequent purification treatment; 3) The materials that meet the temperature requirements after heat exchange in the soaking section are discharged through the bottom discharge pipe and enter the blast furnace as preheated raw materials.

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