Steel scrap preheating system based on continuous step negative pressure

Abstract

The utility model discloses a scrap steel preheating system based on continuous step negative pressure. The scrap steel preheating system comprises a horizontal preheating channel, a main pumping pipeline and a step negative pressure side pumping mechanism. A dynamic sealing feeding channel and a preheating medium inlet are formed in the two ends of the horizontal preheating channel respectively. And the main pumping pipeline is arranged on the horizontal preheating channel between the dynamic sealing feeding channel and the preheating medium inlet and is close to one side of the dynamic sealing feeding channel. And the stepped negative pressure side pumping mechanism is arranged at the lower part of the side wall of the horizontal preheating channel between the main pumping pipeline and the preheating medium inlet. Negative pressure increasing in a stepped mode in the flue gas flowing direction is formed at the bottom of a waste steel material layer through the stepped negative pressure side pumping mechanism, and high-temperature hot flue gas can move from top to bottom to penetrate through the waste steel material layer and horizontally move from right to left in the waste steel material layer. The contact area between the hot flue gas and the scrap steel is increased, the heat exchange effect is improved, the residence time of the flue gas in a scrap steel material layer is prolonged, the heat utilization efficiency of the hot flue gas is improved, and the temperature of a flue gas outlet is reduced. In addition, the device also has the characteristics of simple overall process flow, easiness in operation and control, no need of additionally increasing the occupied field, low investment cost, remarkable preheating and waste heat utilization effects and the like.

Description

Technical Field

[0001] The utility model relates to the technology of steel smelting, in particular to a scrap preheating system based on continuous stepped negative pressure, belonging to the technical field of scrap preheating in steel smelting. Background Technique

[0002] At present, the proportion of electric furnace steel in China is relatively low, only about 10%, and there is huge room for improvement. However, the cost of electric furnace steelmaking is relatively high, which restricts its development. The cost of electric furnace steel is affected by many factors such as scrap price, electricity price, and smelting energy consumption. All along, how to effectively reduce the energy consumption per ton of steelmaking and save smelting costs has been a problem that technical personnel in the metallurgical industry have been concerned about.

[0003] Using the high-temperature flue gas generated by the electric furnace to preheat the scrap and increase the temperature of the scrap entering the furnace can reduce the power consumption during the electric furnace smelting and shorten the smelting cycle. Theoretically, for every 100 °C increase in the scrap preheating temperature, 20 kWh / t of electric energy can be saved, and the energy-saving and consumption-reducing effect is remarkable. The horizontal continuous charging electric furnace uses the high-temperature flue gas in the horizontal preheating flue to preheat the scrap. The preheated scrap is continuously added into the furnace. During the smelting process, the furnace cover of the electric furnace is not opened, and the large steel retention operation is adopted in the furnace, which can realize the flat bath smelting, and the smelting efficiency is greatly improved. It is widely used in each steel plant. Its main process is: the scrap is loaded into the horizontal preheating channel and is sent into the electric furnace for melting from left to right by the mechanical conveying structure. The scrap continuously moves from left to right in the horizontal channel. At the same time, the high-temperature electric furnace flue gas moves from right to left. The high-temperature flue gas and the scrap move in opposite directions and exchange heat, and the scrap can be preheated from room temperature to a certain temperature.

[0004] Although the scrap preheating mechanism of the existing horizontal continuous charging electric furnace can play a certain preheating role for scrap, there are still deficiencies: 1) The flue gas outlet temperature is high and the scrap preheating efficiency is low; in the horizontal preheating channel, the high-temperature flue gas mainly passes through the upper part of the scrap layer in the channel, and the heat transfer method between the flue gas and the scrap is only radiative heat transfer. A large amount of heat carried by the high-temperature flue gas is not transferred to the scrap, resulting in a very low heat transfer efficiency between the high-temperature flue gas and the scrap, poor scrap preheating effect, and serious heat waste; moreover, the high flue gas outlet temperature leads to adverse effects such as burning of the cloth bag during subsequent flue gas treatment. 2) The temperature of the bottom scrap is low and the scrap melts slowly; the vertical thickness of the scrap in the horizontal preheating channel can reach about 800 mm. During the scrap preheating process, the upper scrap directly contacts the high-temperature flue gas and receives radiative heat transfer from the flue gas. The main way for the lower scrap to be heated is the heat conduction of the upper scrap; the penetration depth of the high-temperature flue gas in the scrap layer is insufficient and the residence time is also short, resulting in less convective heat transfer between the scrap and the flue gas; therefore, in actual operation, the temperature of the preheated scrap is uneven (higher at the top and lower at the bottom). The temperature of the scrap at a distance of 600-700 mm from the surface of the material layer is often <100 °C, greatly weakening the energy-saving effect of scrap preheating. And the low-temperature scrap is likely to condense with each other when entering the furnace, resulting in a greatly reduced melting speed of the scrap and an extended smelting cycle of the electric furnace. Summary of the Invention

[0005] In view of the problems in the prior art, such as low scrap preheating efficiency, poor preheating effect, and high flue gas outlet temperature during the preheating of scrap in the horizontal continuous charging channel, the present invention provides a scrap preheating system based on continuous stepped negative pressure. While the hot flue gas of the electric furnace conducts convective heat transfer to the scrap in the horizontal preheating channel, by adjusting the stepped negative pressure side extraction mechanism arranged at the lower part of the side wall of the horizontal preheating channel, a negative pressure that increases step by step along the flue gas flow direction is formed at the bottom of the scrap layer. Due to the action of the stepped negative pressure, on the one hand, the high-temperature hot flue gas can move from top to bottom through the scrap layer, increasing the contact area between the hot flue gas and the scrap and improving the heat transfer effect; on the other hand, the stepped negative pressure increasing along the flue gas flow direction can make the high-temperature hot flue gas move horizontally from right to left in the scrap layer, greatly extending the residence time of the flue gas in the scrap layer, improving the soaking and preheating effect on the scrap and the heat utilization efficiency of the hot flue gas, and reducing the flue gas outlet temperature.

[0006] To achieve the above technical objectives, the technical solutions adopted by the present invention are described as follows:

[0007] A scrap preheating system based on continuous stepped negative pressure, which includes a horizontal preheating channel, a main extraction pipeline, and a stepped negative pressure side extraction mechanism. One end of the horizontal preheating channel is provided with a dynamic sealing feeding channel, and the other end is provided with a preheating medium inlet. The main extraction pipeline is arranged on the horizontal preheating channel between the dynamic sealing feeding channel and the preheating medium inlet, and is close to the side of the dynamic sealing feeding channel. The stepped negative pressure side extraction mechanism is arranged at the lower part of the side wall of the horizontal preheating channel between the main extraction pipeline and the preheating medium inlet.

[0008] Preferably, the stepped negative pressure side extraction mechanism includes side extraction holes and side extraction pipes. A plurality of the side extraction holes are all opened at the lower part of the side wall of the horizontal preheating channel and are distributed along the length direction of the horizontal preheating channel. Each side extraction hole is independently connected to a side extraction pipe.

[0009] Preferably, side extraction holes are opened at the lower parts of the side walls on both sides of the horizontal preheating channel. Preferably, the side extraction holes on the side walls on both sides of the horizontal preheating channel are symmetrically arranged.

[0010] Preferably, according to the air flow direction, a ball valve (such as a manual ball valve or an electric ball valve), a temperature monitor, a pressure monitor, and a flow regulating valve are independently and sequentially arranged on each side extraction pipe.

[0011] Preferably, a section of side extraction hose is independently arranged on the pipe body of each side extraction pipe. Preferably, the side extraction hose is located between the temperature monitor and the pressure monitor.

[0012] Preferably, in the side wall body of the horizontal preheating channel, the hole channel of the side extraction hole extends obliquely upward from the outside to the inside. Preferably, while the hole channel of the side extraction hole extends obliquely upward from the outside to the inside, it also extends obliquely in the same direction as the material flow direction.

[0013] Preferably, in the vertical direction, the inclination angle of the hole channel of the side extraction hole is 5 - 70°, preferably 15 - 55°. In the horizontal direction, the inclination angle of the hole channel of the side extraction hole is 5 - 70°, preferably 15 - 55°.

[0014] Preferably, the aperture of the side extraction hole is 5 - 100 mm, preferably 10 - 80 mm, more preferably 20 - 50 mm.

[0015] Preferably, the side extraction hole is one of a round hole, a rectangular hole, a polygonal hole, and an oval hole, preferably a rectangular hole, more preferably a rectangular long hole.

[0016] Preferably, the aperture of the side extraction hole gradually decreases from the outside to the inside. Preferably, the outer aperture of the side extraction hole is 1.2 - 3 times its inner aperture.

[0017] Preferably, n side extraction holes are provided on the same side wall of the horizontal preheating channel. In the horizontal direction opposite to the material flow, the horizontal distance between the (n - 1)th side extraction hole and the nth side extraction hole is the same (i.e., the horizontal distance between any two adjacent side extraction holes is the same); the horizontal distance is 2 - 5 m, preferably 3 - 4 m.

[0018] Preferably, the horizontal distance from the first side extraction hole to the preheating medium inlet is 2 - 6 m, preferably 3 - 5 m.

[0019] Preferably, multiple rows of side extraction holes are provided on the same side wall of the horizontal preheating channel. The vertical distance from the lower edge of any side extraction hole in the lowermost row to the bottom end of the horizontal preheating channel is 20 - 200 mm, preferably 30 - 150 mm, more preferably 50 - 120 mm. The upper edge height of any side extraction hole in the uppermost row is not higher than two-thirds of the material layer height in the horizontal preheating channel. Preferably, in the vertical direction, the aperture of the side extraction holes in the upper row is smaller than that of the side extraction holes in the lower row, and the apertures of the side extraction holes at the same vertical height are the same.

[0020] Preferably, the system further includes a flue gas treatment unit, and the main extraction pipe and all the side extraction pipes are connected to the flue gas treatment unit.

[0021] Preferably, the flue gas treatment unit includes a heat exchanger, a dust collector, a suction fan, and a chimney connected in series in sequence.

[0022] Preferably, the system further includes a smelting electric furnace. The preheating medium inlet of the horizontal preheating channel is connected to the flue gas outlet of the smelting electric furnace 9.

[0023] Preferably, a hot flue gas temperature and pressure detector is also provided at the preheating medium inlet.

[0024] In the present utility model, within the horizontal preheating channel, scrap steel moves from left to right in the trough via a mechanical transmission device and finally flows into the smelting electric furnace. Most of the high-temperature flue gas generated by the smelting electric furnace (with a temperature generally about 1100 - 1300 °C) flows from right to left above the scrap steel, preheats the scrap steel below, and then is discharged through the main extraction pipeline. By opening a number of side extraction holes on both sides below the side walls of the horizontal preheating channel and using coordinated control with devices such as variable-frequency fans, valves, and pipelines, a stepped negative pressure with an increasing negative pressure from right to left (in the direction opposite to the material flow and the same as the flue gas flow) is formed at the positions of the number of side extraction holes. Through the action of the stepped negative pressure, on the one hand, when the high-temperature hot flue gas discharged from the electric furnace exchanges heat with the material in a countercurrent manner, it can also move from top to bottom and penetrate the scrap steel layer, thereby greatly increasing the contact heat exchange area between the flue gas and the scrap steel. On the other hand, the stepped negative pressure increasing from right to left can also make the high-temperature hot flue gas move horizontally from right to left in the scrap steel layer, greatly extending the residence time of the flue gas in the scrap steel layer and improving the contact heat exchange effect with the inner-layer material (changing from conductive heat exchange of the upper-layer material to direct contact heat exchange). Due to the increase in the contact area and the extension of the contact time between the high-temperature hot flue gas and the scrap steel, the heat exchange efficiency, that is, the effect, between the high-temperature hot flue gas and the scrap steel is enhanced, especially the contact convective heat exchange, enabling more heat carried by the high-temperature hot flue gas to be transferred to the scrap steel, while reducing the flue gas outlet temperature and also increasing the preheating temperature of the scrap steel. At the same time, the preheating effect of the bottom-layer scrap steel is also greatly improved and enhanced.

[0025] In the present utility model, the side extraction holes of the stepped negative pressure side extraction mechanism are arranged at the lower part of the side wall of the horizontal preheating channel between the main extraction pipeline and the preheating medium inlet. Generally, side extraction holes are opened at the lower parts of the side walls on both sides of the horizontal preheating channel, and the side extraction holes on both sides are symmetrically distributed. The side extraction holes are generally one of a round hole, a rectangular hole, a polygonal hole, and an oval hole. The aperture of the side extraction hole is 5 - 100 mm. It should be noted that the side extraction hole can be a single through-hole that independently penetrates the side wall of the horizontal preheating channel, or a collection of a number of air channels distributed within a certain range (as shown in Figure 5 ), and in this case, the aperture of the side extraction hole generally refers to the aperture of a single air channel. The design of the side extraction holes in the form of a combination of multiple air channels enables other air channels to continue to work while one or some of the air channels are blocked, thereby ensuring the stability of the working conditions.

[0026] Furthermore, to prevent clogging of the side extraction holes, the holes are designed to be tilted both vertically and horizontally from the outside to the inside (from the outside of the sidewall of the horizontal preheating channel to the inside). Specifically, the vertical inclination angle of the side extraction holes (extending downward) is 5-70° (preferably 15-55°); the horizontal inclination angle of the side extraction holes (extending toward the material flow) is 5-70° (preferably 15-55°). In other words, this dual-inclination facilitates the automatic shedding of dust, alleviating the problem of dust clogging at the extraction holes. Furthermore, the aperture gradually decreases from the outside to the inside (for example, the outer aperture diameter is 1.2-3 times the inner aperture diameter), further preventing material from clogging the side extraction holes' air inlet. Due to the variable diameter design, even if material enters the side extraction holes, the aperture gradually increases along the direction of the flue gas flow, making them less susceptible to clogging.

[0027] In the present invention, on the side extraction pipes connecting the side extraction holes, ball valves, temperature monitors, side extraction hoses, pressure monitors, and flow control valves are sequentially distributed along the flow direction of the airflow. Among them, the ball valve facilitates pipeline maintenance and replacement during the production process; the side extraction hose facilitates the dynamic connection between the material trough and the pipeline; the temperature monitor and pressure monitor are used to monitor the temperature and pressure in the pipeline, which are key monitoring parameters in the step negative pressure control process; the flow control valve is used to automatically control the flow rate in the pipeline, which is a key regulating device for achieving step negative pressure control. The flue gas in the side extraction hole pipes is merged into the main pipeline and then heat exchanged in the heat exchanger to reduce the flue gas temperature. The dust in the flue gas is then removed by the gravity dust collector. Finally, it is led out by the variable frequency exhaust fan and merged into the original main extraction pipeline of the factory building and discharged through the chimney.

[0028] In the present invention, n side extraction holes are provided on the same side wall of the horizontal preheating channel (symmetrically arranged on both sides). In the horizontal direction opposite to the material flow (i.e., from right to left), the horizontal spacing between the (n-1)th side extraction hole and the nth side extraction hole is the same, preferably 2-5 meters, more preferably 3-4 meters. The horizontal spacing between the first side extraction hole and the preheating medium inlet is 2-6 meters.

[0029] In the present invention, the negative pressure branch of each side extraction hole is important, so the negative pressure of the side extraction hole connected to it is independently controlled by each side extraction pipe. In actual working conditions, due to factors such as the thickness of the scrap steel layer, the porosity of the scrap steel, the size of the scrap steel, the gas flow rate, etc., the working conditions of each furnace may be different, and the side extraction negative pressure also needs to be changed accordingly, so as to better achieve the preheating effect, that is, the step negative pressure must be controlled more accurately. In the present invention, the control and adjustment method of the step negative pressure side extraction mechanism is specifically as follows: along the flow direction of the hot flue gas, n side extraction channels are provided on the lower part of the side wall of the horizontal preheating channel, and are numbered 1, 2, 3,..., (n-1), n in sequence. Then the side extraction negative pressure of each side extraction hole is:

[0030] P1=P0-(h-0.1)·△PP t (1).

[0031] P i =P (i-1) -L i ·△PP t (2)

[0032] In formulas (1) to (2), P0 is the air pressure at the flue gas inlet of the horizontal preheating channel, Pa. P1 is the side extraction pressure of the first extraction hole, Pa. i is the side extraction pressure of the i-th extraction hole, Pa, i is an integer from 2 to n. h is the thickness of the scrap steel layer, m. P t To adjust the pressure difference, the value is 10~200Pa (preferably 20~100Pa). △P is the pressure difference of the material layer, Pa. L i is the horizontal hole spacing between the i-th side extraction hole and the (i-1)-th side extraction hole, m.

[0033] Furthermore, the material layer pressure difference ΔP is specifically:

[0034] △P=4556·v·(1-ε) 2 / (d 2 ·ε 3 )+411.4v 2 (3).

[0035] In formula (3), ε is the porosity of the material layer, d is the equivalent diameter of the scrap steel, in meters, and v is the average velocity of the flue gas in the material layer, in meters per second.

[0036] Furthermore, the temperature of the flue gas extracted from the extraction holes on either side of the step negative pressure side extraction mechanism is detected in real time and recorded as Tc, °C. Then:

[0037] When 280℃≤Tc≤300℃, maintain the current operating conditions unchanged.

[0038] When Tc<280℃, increase the regulating pressure difference Pt value, and recalculate P1 to P according to Formulas (1) to (2). n value until all Tc ∈ [280, 300].

[0039] When Tc > 300 °C, reduce the regulating pressure difference P t value, and recalculate P1 to P according to Formulas (1) to (2). n value until all Tc ∈ [280, 300].

[0040] Furthermore, increase or decrease the regulating pressure difference P t value specifically as follows: Each time, increase or decrease the regulating pressure difference P t value by 1 to 15.

[0041] Preferably, when Tc < 280 °C or Tc > 300 °C, record (280 - Tc) or (Tc - 300) as ΔT, then there is:

[0042] When ΔT ≤ 50, each time adjust the regulating pressure difference P t value by increasing or decreasing 1 to 3.

[0043] When 50 < ΔT ≤ 150, each time adjust the regulating pressure difference P t value by increasing or decreasing 3 to 8.

[0044] When 150 < ΔT ≤ 300, each time adjust the regulating pressure difference P t value by increasing or decreasing 8 to 12.

[0045] When 300 < ΔT, each time adjust the regulating pressure difference P t value by increasing or decreasing 12 to 15.

[0046] In a preferred embodiment of the present invention: After the smelting electric furnace is started, high-temperature flue gas of about 1300 °C generated in the furnace enters the horizontal preheating channel through the preheating medium inlet, and a slight negative pressure is maintained at the preheating medium inlet, denoted as P0. Under the action of the main exhaust fan, the high-temperature hot flue gas passes over the scrap steel layer and then is discharged. At this time, start the fan of the bottom-side stepped negative-pressure side extraction mechanism and adjust the valves on each side extraction pipeline so that a gradually increasing negative pressure is generated from right to left at each side extraction hole. Due to the stepped negative pressure effect, part of the high-temperature flue gas penetrates the material layer from top to bottom and is discharged through the bottom-side side extraction pipeline. The specific pressure control process for each side extraction hole is as follows:

[0047] (1) Input each parameter, mainly including: the pressure at the preheating medium inlet, denoted as P0, the regulating pressure difference P t (for example, 20 Pa), the thickness of the scrap steel layer, denoted as h (for example, 0.8 m), and the horizontal hole spacing between the i-th side extraction hole and the (i - 1)-th side extraction hole, denoted as L i, the porosity of the material layer is denoted as ε, the equivalent diameter of the scrap steel is denoted as d, the average velocity of the flue gas in the material layer is denoted as v, and the pressure difference of the material layer is denoted as ∆P.

[0048] (2) According to the above formulas (1)-(3), adjust the power of the side extraction fan and the valve according to the pressure monitoring device, and accurately control the negative pressure of each bottom side extraction pipeline to achieve stepped negative pressure side bottom extraction.

[0049] (3) Detect the temperature of the flue gas extracted from each side extraction pipe according to the temperature monitor in each side extraction pipe at regular intervals. If the flue gas temperature Tc in any side extraction pipe > 300 °C, then reduce the adjusted pressure difference P t , the adjusted pressure difference P t ’ = P t - 5, and obtain the adjusted negative pressure of each side extraction pipeline according to the adjusted pressure difference P t ’. Then, adjust the fan power and valve according to the pressure monitoring device to achieve the adjusted stepped negative pressure side bottom extraction. This process is cyclically controlled until the flue gas temperature Tc in any side extraction pipe ≤ 300 °C.

[0050] If the flue gas temperature Tc in any side extraction pipe < 280 °C, then increase the adjusted pressure difference P t , the adjusted pressure difference P t ’ = P t + 5, and obtain the adjusted negative pressure of each side extraction pipeline according to the adjusted pressure difference P t ’. Then, adjust the fan power and valve according to the pressure monitoring device to achieve the adjusted stepped negative pressure side bottom extraction. This process is cyclically controlled until the flue gas temperature 280 °C ≤ Tc ≤ 300 °C in any bottom side extraction pipe.

[0051] In the present utility model, generally speaking, the scrap steel is horizontally transported from left to right into the smelting electric furnace in the horizontal preheating channel. While most of the high-temperature flue gas sweeps over the scrap steel material layer from right to left, under the action of the stepped negative pressure side extraction mechanism, the high-temperature flue gas can not only move vertically downward through the scrap steel material layer, increasing the contact area between the flue gas and the scrap steel, but also make the high-temperature flue gas move horizontally from right to left in the scrap steel material layer, greatly extending the residence time of the hot flue gas in the scrap steel material layer. Due to the increase in the contact area and the extension of the contact time between the high-temperature flue gas and the scrap steel, the heat transfer efficiency and effect between the high-temperature flue gas and the scrap steel are enhanced, especially the convective heat transfer, so that more heat carried by the high-temperature flue gas is transferred to the scrap steel, while reducing the flue gas temperature and also increasing the preheating temperature of the scrap steel, and the preheating temperature of the bottom-layer scrap steel is also effectively improved. By comprehensively comparing the average temperature of the scrap steel at the outlet of the preheating channel under different schemes (no extraction, equal negative pressure extraction, stepped negative pressure extraction), after adopting the side bottom stepped negative pressure extraction, the temperature of the scrap steel is significantly increased, and the average temperature of the scrap steel is increased by about 45% compared with the no extraction scheme, and the average temperature of the scrap steel is increased by about 21% compared with the equal negative pressure extraction scheme.

[0052] In the present utility model, the length of the horizontal preheating channel is 1 - 100 mm, preferably 5 - 80 m, and more preferably 10 - 50 m. The width of the horizontal preheating channel is 1 - 30 m, preferably 2 - 20 m, and more preferably 3 - 15 m. The height of the horizontal preheating channel is 0.3 - 10 m, preferably 0.5 - 8 m, and more preferably 0.8 - 5 m.

[0053] Compared with the prior art, the beneficial technical effects of the present utility model are as follows:

[0054] 1: In the present utility model, through the bottom stepped negative pressure side extraction mechanism, the high-temperature hot flue gas can not only move from top to bottom through the scrap layer, but also move horizontally from right to left in the scrap layer, which is very different from the movement direction of the flue gas under the condition of no air extraction or simple equal negative pressure air extraction. The stepped negative pressure air extraction increases the contact area between the flue gas and the scrap, prolongs the residence time of the flue gas in the scrap layer, strengthens the convective heat transfer between the high-temperature flue gas and the scrap, and improves the preheating effect of the scrap.

[0055] 2: The flue gas outlet temperature of the present utility model is significantly reduced, and adverse phenomena such as burning of cloth bags during subsequent flue gas treatment are effectively avoided; moreover, the temperature of the bottom-layer scrap is significantly increased. Compared with the condition of no air extraction, the preheating temperature of the bottom-layer scrap is increased by about 233%, the preheating temperature of the upper-layer scrap is increased by about 32%, the overall temperature of the scrap is increased by about 106%, the preheating temperature is greatly improved, the melting speed of the scrap after entering the furnace is accelerated, the electric furnace smelting cycle is shortened by about 7%, the power consumption is reduced by about 11%, the consumption of auxiliary materials is reduced, and the technical effects of cost reduction and efficiency improvement are achieved.

[0056] 3: The overall structure of the present utility model is simple, easy to operate and control, does not require additional increase in site occupation, has low input cost, and has remarkable preheating and waste heat utilization effects. It has excellent prospects for large-scale popularization and application and good social and economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 It is a schematic diagram of the overall structure of the system described in the present utility model.

[0058] Figure 2 It is a layout diagram of the symmetric side extraction pipes of the system described in the present utility model.

[0059] Figure 3 It is a horizontal cross-sectional view of the side extraction holes of the system described in the present utility model.

[0060] Figure 4 It is a vertical cross-sectional view of the side extraction holes of the system described in the present utility model.

[0061] Figure 5 It is a plan view of the side extraction holes when the system described in the present utility model has multiple air channels.

[0062] Reference numerals: 1: horizontal preheating channel; 101: dynamic sealing feed channel; 102: preheating medium inlet; 2: main extraction pipe; 3: stepped negative pressure side extraction mechanism; 301: side extraction hole; 302: side extraction pipe; 303: side extraction hose; 4: ball valve; 5: temperature monitor; 6: pressure monitor; 7: flow regulating valve; 8: flue gas treatment unit; 801: heat exchanger; 802: dust collector; 803: extraction fan; 804: chimney; 9: smelting electric furnace. Detailed implementation manners

[0063] The technical solutions of the present utility model will be illustrated by way of example below. The scope of protection claimed by the present utility model includes but is not limited to the following embodiments.

[0064] A scrap preheating system based on continuous stepped negative pressure, the system comprising a horizontal preheating channel 1, a main extraction pipe 2 and a stepped negative pressure side extraction mechanism 3. One end of the horizontal preheating channel 1 is provided with a dynamic sealing feed channel 101, and the other end is provided with a preheating medium inlet 102. The main extraction pipe 2 is arranged on the horizontal preheating channel 1 between the dynamic sealing feed channel 101 and the preheating medium inlet 102, and is close to the side of the dynamic sealing feed channel 101. The stepped negative pressure side extraction mechanism 3 is arranged at the lower part of the side wall of the horizontal preheating channel 1 between the main extraction pipe 2 and the preheating medium inlet 102.

[0065] Preferably, the stepped negative pressure side extraction mechanism 3 includes side extraction holes 301 and side extraction pipes 302. A plurality of the side extraction holes 301 are all opened at the lower part of the side wall of the horizontal preheating channel 1 and are distributed along the length direction of the horizontal preheating channel 1. Each side extraction hole 301 is independently connected to a side extraction pipe 302.

[0066] Preferably, side extraction holes 301 are opened at the lower parts of the side walls on both sides of the horizontal preheating channel 1. Preferably, the side extraction holes 301 on the side walls on both sides of the horizontal preheating channel 1 are symmetrically arranged.

[0067] Preferably, according to the flow direction of the air flow, a ball valve 4, a temperature monitor 5, a pressure monitor 6 and a flow regulating valve 7 are independently and sequentially arranged on each side extraction pipe 302.

[0068] Preferably, one section of side extraction hose 303 is independently arranged on the pipe body of each side extraction pipe 302. Preferably, the side extraction hose 303 is located between the temperature monitor 5 and the pressure monitor 6.

[0069] Preferably, in the side wall body of the horizontal preheating channel 1, the hole channel of the side extraction hole 301 extends obliquely upward from the outside to the inside. Preferably, while the hole channel of the side extraction hole 301 extends obliquely upward from the outside to the inside, it also extends obliquely in the direction of the material flow direction.

[0070] Preferably, in the vertical direction, the inclination angle of the orifice of the side extraction hole 301 is 5 to 70°, preferably 15 to 55°. In the horizontal direction, the inclination angle of the orifice of the side extraction hole 301 is 5 to 70°, preferably 15 to 55°.

[0071] Preferably, the aperture of the side extraction hole 301 is 5 to 100 mm, preferably 10 to 80 mm, more preferably 20 to 50 mm.

[0072] Preferably, the side extraction hole 301 is one of a round hole, a rectangular hole, a polygonal hole, and an oval hole, preferably a rectangular hole, more preferably a rectangular long hole.

[0073] Preferably, the aperture of the side extraction hole 301 gradually decreases from the outside to the inside. Preferably, the outer aperture of the side extraction hole 301 is 1.2 to 3 times its inner aperture.

[0074] Preferably, n side extraction holes 301 are provided on the same side wall of the horizontal preheating channel 1. In the horizontal direction opposite to the material flow, the horizontal distance between the (n - 1)th side extraction hole 301 and the nth side extraction hole 301 is the same. The horizontal distance is 2 to 5 m, preferably 3 to 4 m.

[0075] Preferably, the horizontal distance between the first side extraction hole 301 and the preheating medium inlet 102 is 2 to 6 m, preferably 3 to 5 m.

[0076] Preferably, multiple rows of side extraction holes 301 are provided on the same side wall of the horizontal preheating channel 1. The vertical distance from the lower edge of any one side extraction hole 301 in the lowermost row to the bottom end of the horizontal preheating channel 1 is 20 to 200 mm, preferably 30 to 150 mm, more preferably 50 to 120 mm. The upper edge height of any one side extraction hole 301 in the uppermost row is not higher than two-thirds of the material layer height in the horizontal preheating channel 1. Preferably, in the vertical direction, the aperture of the upper row of side extraction holes 301 is smaller than that of the lower row of side extraction holes 301, and the apertures of the side extraction holes 301 at the same vertical height are the same.

[0077] Preferably, the system further includes a flue gas treatment unit 8, and the main extraction pipe 2 and all the side extraction pipes 302 are connected to the flue gas treatment unit 8.

[0078] Preferably, the flue gas treatment unit 8 includes a heat exchanger 801, a dust collector 802, a draft fan 803, and a chimney 804 connected in series in sequence.

[0079] Preferably, the system further includes a smelting electric furnace 9. The preheating medium inlet 102 of the horizontal preheating channel 1 is connected to the flue gas outlet of the smelting electric furnace 9.

[0080] Preferably, a hot flue gas temperature and pressure detector is also provided at the preheating medium inlet 102. Embodiment 1

[0081] As Figures 1-5 shown, a scrap preheating system based on continuous stepped negative pressure includes a horizontal preheating channel 1, a main extraction pipe 2, and a stepped negative pressure side extraction mechanism 3. One end of the horizontal preheating channel 1 is provided with a dynamic seal feeding channel 101, and the other end is provided with a preheating medium inlet 102. The main extraction pipe 2 is arranged on the horizontal preheating channel 1 between the dynamic seal feeding channel 101 and the preheating medium inlet 102 and is close to the side of the dynamic seal feeding channel 101. The stepped negative pressure side extraction mechanism 3 is arranged at the lower part of the side wall of the horizontal preheating channel 1 between the main extraction pipe 2 and the preheating medium inlet 102. Embodiment 2

[0082] Repeat Embodiment 1, except that the stepped negative pressure side extraction mechanism 3 includes side extraction holes 301 and side extraction pipes 302. A plurality of the side extraction holes 301 are all opened at the lower part of the side wall of the horizontal preheating channel 1 and are distributed along the length direction of the horizontal preheating channel 1. Each side extraction hole 301 is independently connected to a side extraction pipe 302. Embodiment 3

[0083] Repeat Embodiment 2, except that side extraction holes 301 are opened at the lower parts of the side walls on both sides of the horizontal preheating channel 1. Embodiment 4

[0084] Repeat Embodiment 3, except that the side extraction holes 301 on the side walls on both sides of the horizontal preheating channel 1 are symmetrically arranged. Embodiment 5

[0085] Repeat Embodiment 4, except that according to the air flow direction, a ball valve 4, a temperature monitor 5, a pressure monitor 6, and a flow regulating valve 7 are independently and sequentially arranged on each side extraction pipe 302. Embodiment 6

[0086] Repeat Embodiment 5, except that a section of side extraction hose 303 is independently arranged on the pipe body of each side extraction pipe 302. Embodiment 7

[0087] Repeat Embodiment 6, except that the side extraction hose 303 is located between the temperature monitor 5 and the pressure monitor 6. Embodiment 8

[0088] Repeat Embodiment 7, except that in the side wall body of the horizontal preheating channel 1, the hole channel of the side extraction hole 301 extends obliquely upward from the outside to the inside. Embodiment 9

[0089] Repeat Example 8, except that while the duct of the side extraction hole 301 extends obliquely upward from outside to inside, it also extends obliquely in the same direction as the material flow direction. Example 10

[0090] Repeat Example 9, except that in the vertical direction, the inclination angle of the duct of the side extraction hole 301 is 30°. In the horizontal direction, the inclination angle of the duct of the side extraction hole 301 is 30°. Example 11

[0091] Repeat Example 10, except that the aperture of the side extraction hole 301 is 30 mm. Example 12

[0092] Repeat Example 11, except that the side extraction hole 301 is a rectangular hole. Example 13

[0093] Repeat Example 12, except that the aperture of the side extraction hole 301 gradually decreases from outside to inside. Example 14

[0094] Repeat Example 13, except that the outer aperture of the side extraction hole 301 is 1.5 times its inner aperture. Example 15

[0095] Repeat Example 14, except that n side extraction holes 301 are provided on the same side wall of the horizontal preheating channel 1, and in the horizontal direction opposite to the material flow, the horizontal spacing between the (n - 1)th side extraction hole 301 and the nth side extraction hole 301 is the same, specifically 3 m. Example 16

[0096] Repeat Example 15, except that the horizontal spacing between the first side extraction hole 301 and the preheating medium inlet 102 is 3.5 m. Example 17

[0097] Repeat Example 16, except that multiple rows of side extraction holes 301 are provided on the same side wall of the horizontal preheating channel 1, where the vertical spacing from the lower edge of any side extraction hole 301 in the bottom row to the bottom end of the horizontal preheating channel 1 is 100 mm. The upper edge height of any side extraction hole 301 in the top row is not higher than two-thirds of the material layer height in the horizontal preheating channel 1. Example 18

[0098] Repeat Example 17, except that in the vertical direction, the aperture of the upper row of side extraction holes 301 is smaller than that of the lower row of side extraction holes 301, and the apertures of the side extraction holes 301 at the same vertical height are the same. Example 19

[0099] Repeat Example 18, except that the system further includes a flue gas treatment unit 8, and the main extraction pipe 2 and all the side extraction pipes 302 are connected to the flue gas treatment unit 8. Example 20

[0100] Repeat Example 19, except that the flue gas treatment unit 8 includes a heat exchanger 801, a dust collector 802, a suction fan 803, and a chimney 804 that are arranged in series in sequence. Example 21

[0101] Repeat Example 20, except that the system further includes a smelting electric furnace 9. The preheating medium inlet 102 of the horizontal preheating channel 1 is connected to the flue gas outlet of the smelting electric furnace 9. Example 22

[0102] Repeat Example 21, except that a hot flue gas temperature and pressure detector is further provided at the preheating medium inlet 102.

Claims

1. A scrap preheating system based on continuous stepped negative pressure, characterized in that: The system includes a horizontal preheating channel (1), a main extraction pipeline (2), and a stepped negative-pressure side extraction mechanism (3); one end of the horizontal preheating channel (1) is provided with a dynamic-sealing feeding channel (101), and the other end is provided with a preheating medium inlet (102); the main extraction pipeline (2) is arranged on the horizontal preheating channel (1) between the dynamic-sealing feeding channel (101) and the preheating medium inlet (102), and is close to the side of the dynamic-sealing feeding channel (101); the stepped negative-pressure side extraction mechanism (3) is arranged at the lower part of the side wall of the horizontal preheating channel (1) between the main extraction pipeline (2) and the preheating medium inlet (102).

2. The scrap preheating system according to claim 1, wherein: The stepped negative-pressure side extraction mechanism (3) includes side extraction holes (301) and side extraction pipes (302); a plurality of the side extraction holes (301) are all opened at the lower part of the side wall of the horizontal preheating channel (1) and are distributed along the length direction of the horizontal preheating channel (1); each side extraction hole (301) is independently connected to a side extraction pipe (302).

3. The scrap preheating system according to claim 2, wherein: Side extraction holes (301) are opened at the lower parts of the side walls on both sides of the horizontal preheating channel (1).

4. The scrap preheating system according to claim 3, characterized in that: The side extraction holes (301) on the side walls on both sides of the horizontal preheating channel (1) are symmetrically arranged.

5. The scrap preheating system according to claim 2, wherein: According to the air flow direction, a ball valve (4), a temperature monitor (5), a pressure monitor (6), and a flow regulating valve (7) are independently and sequentially arranged on each side extraction pipe (302).

6. The scrap preheating system according to claim 5, wherein: A section of side extraction hose (303) is independently arranged on the pipe body of each side extraction pipe (302).

7. The scrap preheating system according to claim 6, wherein: The side extraction hose (303) is located between the temperature monitor (5) and the pressure monitor (6).

8. The scrap preheating system according to claim 2, wherein: In the side wall body of the horizontal preheating channel (1), the hole channel of the side extraction hole (301) extends obliquely upward from the outside to the inside.

9. The scrap preheating system according to claim 8, characterized in that: While the hole channel of the side extraction hole (301) extends obliquely upward from the outside to the inside, it also extends obliquely in the same direction as the material flow direction.

10. The scrap preheating system according to claim 9, characterized in that: In the vertical direction, the inclination angle of the hole channel of the side extraction hole (301) is 5 - 70°; in the horizontal direction, the inclination angle of the hole channel of the side extraction hole (301) is 5 - 70°.

11. The scrap preheating system according to claim 10, characterized in that: In the vertical direction, the inclination angle of the hole channel of the side extraction hole (301) is 15 - 55°; in the horizontal direction, the inclination angle of the hole channel of the side extraction hole (301) is 15 - 55°.

12. The scrap preheating system according to claim 2, characterized in that: The aperture of the side extraction hole (301) is 5 - 100 mm; and / or The side extraction hole (301) is one of a round hole, a rectangular hole, a polygonal hole, and an oval hole.

13. The scrap preheating system according to claim 12, characterized in that: The aperture of the side extraction hole (301) is 10 - 80 mm; and / or The side extraction hole (301) is a rectangular hole.

14. The scrap preheating system according to claim 13, wherein: The aperture of the side extraction hole (301) is 20 - 50 mm; and / or The side extraction hole (301) is a rectangular hole.

15. The scrap preheating system according to claim 12, wherein: The aperture of the side extraction hole (301) gradually decreases from the outside to the inside.

16. The scrap preheating system according to claim 15, wherein: The outer aperture of the side extraction hole (301) is 1.2 - 3 times its inner aperture.

17. The scrap preheating system according to claim 2, wherein: n side extraction holes (301) are arranged on the same side wall of the horizontal preheating channel (1), and in the horizontal direction opposite to the material flow, the horizontal distance between the (n - 1)th side extraction hole (301) and the nth side extraction hole (301) is the same.

18. The scrap preheating system according to claim 17, wherein: The horizontal distance between the (n - 1)th side extraction hole (301) and the nth side extraction hole (301) is 2 to 5 m.

19. The scrap preheating system according to claim 18, characterized in that: The horizontal distance between the (n - 1)th side extraction hole (301) and the nth side extraction hole (301) is 3 to 4 m.

20. The scrap preheating system according to claim 17, wherein: The horizontal distance from the first side extraction hole (301) to the preheating medium inlet (102) is 2 to 6 m.

21. The scrap preheating system according to claim 20, characterized in that: The horizontal distance from the first side extraction hole (301) to the preheating medium inlet (102) is 3 to 5 m.

22. The scrap preheating system according to claim 2, characterized in that: On the same side wall of the horizontal preheating channel (1), multiple rows of side extraction holes (301) are provided. The vertical distance from the lower edge of any one side extraction hole (301) in the lowermost row to the bottom end of the horizontal preheating channel (1) is 20 to 200 mm; the upper edge height of any one side extraction hole (301) in the uppermost row is not higher than two-thirds of the material layer height in the horizontal preheating channel (1).

23. The scrap preheating system according to claim 22, characterized in that: The vertical distance from the lower edge of any one side extraction hole (301) in the lowermost row to the bottom end of the horizontal preheating channel (1) is 30 to 150 mm.

24. The scrap preheating system according to claim 23, wherein: The vertical distance from the lower edge of any one side extraction hole (301) in the lowermost row to the bottom end of the horizontal preheating channel (1) is 50 to 120 mm.

25. The scrap preheating system according to claim 22, wherein: In the vertical direction, the aperture of the upper row of side extraction holes (301) is smaller than that of the lower row of side extraction holes (301), and the apertures of the side extraction holes (301) at the same vertical height are the same.

26. The scrap preheating system according to claim 2, wherein: The system further includes a flue gas treatment unit (8), and the main extraction pipe (2) and all the side extraction pipes (302) are communicated with the flue gas treatment unit (8).

27. The scrap preheating system according to claim 26, wherein: The flue gas treatment unit (8) includes a heat exchanger (801), a dust collector (802), a draft fan (803), and a chimney (804) that are arranged in series in sequence.

28. The scrap preheating system according to any one of claims 1-27, characterized in that: The system further includes a smelting electric furnace (9); the preheating medium inlet (102) of the horizontal preheating channel (1) is communicated with the flue gas outlet of the smelting electric furnace (9); and / or A hot flue gas temperature and pressure detector is further provided at the preheating medium inlet (102).

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