Magnesium reducing slag heat grading efficient utilization system

Abstract

The invention belongs to the technical field of magnesium smelting, and discloses a magnesium reducing slag heat grading efficient utilization system which comprises a magnesium reducing tank, and a magnesium slag outlet is sequentially connected with a high-temperature area heat exchanger and a low-temperature area heat exchanger. The hot water outlet end of the high-temperature area heat exchanger passes through the steam flash evaporator to generate hot steam to provide a power source for a steam jet pump of the vacuumizing system; the low-temperature area heat exchanger comprises a dividing wall type heat exchanger connected with the slag outlet, a heat exchange pipeline arranged in a circuitous mode is arranged in the dividing wall type heat exchanger, one end of the heat exchange pipeline is a cold air inlet end, the other end of the heat exchange pipeline is a hot air outlet end, and the hot air outlet end enters the combustor to conduct mixed preheating on fuel gas and cold air. The graded waste heat before and after phase change of the magnesium slag is recycled and reused in a magnesium reduction system, so that the efficient utilization of the waste heat of the reducing slag can be realized, the problem of single use of the traditional waste heat utilization of the reducing slag can be solved, and the magnesium smelting production organization can be flexible and adjustable.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of magnesium smelting, and particularly relates to a magnesium reduction slag heat grading efficient utilization system. BACKGROUND

[0002] The silicon thermal method is a current mainstream magnesium smelting process, and about 6 tons of magnesium reduction slag (referred to as magnesium reduction slag) are generated for each ton of original magnesium produced. The magnesium reduction slag discharged from the reduction tank has a temperature as high as 1150 DEG C and contains a large amount of heat. When the temperature of the magnesium reduction slag decreases to about 675 DEG C, the magnesium reduction slag will be converted from a beta phase to a gamma phase, and the volume will expand to be "powdered" from a spherical shape to a powder shape. The powder-shaped magnesium reduction slag with a certain thickness has a much lower thermal conductivity than the block-shaped magnesium reduction slag, and it is difficult to utilize the residual heat. The spherical (block) shape has a high temperature and a large heat transfer coefficient, and only a small heat exchange area and a very short heat exchange time are needed, the residual heat recovery effect is obvious, and the recovery cost is small. The powder shape has a low heat transfer coefficient, and a large heat exchange area and a longer heat exchange time are needed, and the residual heat recovery cost is increased.

[0003] However, the magnesium reduction slag residual heat recovery device does not distinguish the difference between the magnesium reduction slag before and after the phase change, and the heat exchange coefficient of the powder is conservatively used for design and calculation, resulting in an increased heat exchange surface of the residual heat recovery device, a heavy equipment, and an increased production cost. SUMMARY

[0004] The application aims to provide a magnesium reduction slag heat grading efficient utilization system, which is based on the obvious temperature difference of the magnesium reduction slag before and after the phase change, and the magnesium reduction slag is classified and recovered, and the recovered heat is applied to the magnesium reduction system again according to the characteristics, so that the efficient utilization of the residual heat of the reduction slag can be realized, the problem of single use of the traditional residual heat of the reduction slag can be solved, and the magnesium smelting production organization can be flexible and adjustable.

[0005] A magnesium reduction slag heat grading efficient utilization system, comprising a magnesium reduction tank, a magnesium crystallizer is installed at the top of the magnesium reduction tank, a vacuum extraction system is installed on the magnesium crystallizer, a burner is installed on the magnesium reduction tank, a magnesium slag discharge port is arranged at the bottom of the magnesium reduction tank, and a high-temperature zone heat exchanger and a low-temperature zone heat exchanger are sequentially connected to the magnesium slag discharge port, The high-temperature zone heat exchanger comprises a heat exchange box body, a stepped reciprocating paving mechanism is arranged in the heat exchange box body, an inlet port connected with the magnesium slag discharge port is arranged at the top end of the stepped reciprocating paving mechanism, an outlet port connected with the low-temperature zone heat exchanger is arranged at the bottom end of the stepped reciprocating paving mechanism, heat exchange pipelines are arranged in the heat exchange box body in a meandering manner, one end of the heat exchange pipeline is a cold water inlet end, the other end is a hot water outlet end, and hot steam generated after the hot water outlet end passes through a steam flash evaporator provides a power source for a steam jet pump of the vacuum extraction system; The low-temperature zone heat exchanger comprises a partition heat exchanger connected with the slag outlet, and the partition heat exchanger is internally provided with heat exchange pipelines arranged in a detour manner.

[0006] Preferably, the stepped reciprocating paving mechanism comprises a support frame, and driven paving plates and driving paving plates are alternately and sequentially stacked in the support frame from top to bottom, the bottoms of all the driven paving plates are connected through a driven shaft, and the bottoms of all the driving paving plates are connected through a driving shaft, that is, the movement of the driving shaft synchronously drives the reciprocating movement of all the driving paving plates, and the movement of the driven shaft synchronously drives the static or reciprocating movement of all the driven paving plates, and the relative movement of the driving paving plates and the driven paving plates pushes the spherical magnesium slag to roll into the slag outlet.

[0007] Preferably, a plurality of heat-permeable grids or heat-permeable through holes are uniformly arranged on the driving paving plates and the driven paving plates, the heat-permeable grids or heat-permeable through holes are smaller than the spherical magnesium slag, and the heat exchange pipelines in the heat exchange box are arranged in a detour manner around the stepped reciprocating paving mechanism.

[0008] Preferably, the stepped reciprocating paving mechanism further comprises a signal control unit and an execution control unit for controlling the movement of the driving shaft and the driven shaft, a temperature sensor for monitoring the temperature of the spherical magnesium slag after passing through the high-temperature zone heat exchanger is arranged in the slag outlet of the stepped reciprocating paving mechanism, the signal control unit judges whether the spherical magnesium slag generates phase change according to the stable information of the temperature sensor, and then controls the movement of the driving shaft and the driven shaft through the execution control unit to adjust the heat exchange time and the rolling speed of the spherical magnesium slag in the stepped reciprocating paving mechanism.

[0009] Preferably, the hot water outlet end generates hot steam with a temperature of 170 DEG C (6 kgf) or above after passing through the steam flash evaporator to provide a power source for the steam jet pump of the vacuum pumping system, that is, the temperature of the spherical magnesium slag after being cooled by the high-temperature zone heat exchanger is not lower than 250 DEG C, then the powdery magnesium slag after phase change enters the low-temperature zone heat exchanger, and the temperature of the powdery magnesium slag after being cooled by the low-temperature zone heat exchanger is controlled at about 150 DEG C.

[0010] Preferably, the bottom of the heat exchange box is a slope surface inclined to the slag outlet.

[0011] Preferably, an end cover is arranged at the slag inlet of the high-temperature zone heat exchanger.

[0012] The present application has the following beneficial effects: (1) according to the shape structure characteristics of the reduced magnesium slag and the phase change characteristics after cooling, the present application proposes to use the waste heat of the high-temperature spherical magnesium slag before phase change to generate hot steam to provide a power source for the steam jet pump of the vacuum pumping system, and the hot gas generated after the powdery magnesium slag after phase change is subjected to heat exchange enters the burner to mix and preheat the gas and the cold air.

[0013] (2) The high-temperature spherical magnesium slag rolls forward under the pushing action of the driven paving plate and the active paving plate, and quickly releases and transfers heat (one spherical magnesium slag thickness) to the cold water in the high-temperature heat exchange pipe. After being heated, the cold water enters the steam flash evaporator to generate stable high-temperature steam, which is used to drive the vacuum jet pump.

[0014] (3) The hot air after the low-temperature powdered magnesium slag heats the cold air through the heat exchanger in the low-temperature zone enters the burner to mix and preheat the fuel gas and cold air.

[0015] (4) The hot water outlet generates hot steam at a temperature of over 170°C after passing through the steam flash evaporator, which provides a power source for the steam jet pump of the vacuum system. At the same time, the temperature of the spherical magnesium slag after being cooled by the high-temperature heat exchanger is not lower than 250°C. Then, after phase change, the powdered magnesium slag enters the low-temperature heat exchanger. After being cooled by the low-temperature heat exchanger, the temperature is not higher than 150°C. This ensures the temperature required by the steam jet pump and makes full use of the waste heat of the powdered magnesium slag in the low-temperature zone.

[0016] (5) The staged waste heat recovery and reuse in magnesium reduction system before and after phase change of magnesium slag can be realized. This can not only realize the efficient use of waste heat of reduction slag, but also solve the problem of the single use of waste heat of traditional reduction slag. It can also make magnesium smelting production organization flexible and adjustable. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 This is a schematic diagram of the structure of the heat exchanger in the high-temperature zone and the heat exchanger in the low-temperature zone. Detailed Implementation

[0018] The present invention will now be further described with reference to the accompanying drawings.

[0019] like Figure 1 As shown, the present invention includes a magnesium reduction tank 13, a magnesium crystallizer 14 installed on the top of the magnesium reduction tank 13, a vacuum system 15 installed on the magnesium crystallizer 14, a burner 12 installed on the magnesium reduction tank 13, and a magnesium slag outlet 11 provided at the bottom of the magnesium reduction tank 13. The magnesium slag outlet 11 is sequentially connected to a high-temperature zone heat exchanger 2 and a low-temperature zone heat exchanger 3. The high-temperature zone heat exchanger 2 comprises a heat exchange box 28, a ladder-type reciprocating spreading mechanism is arranged in the heat exchange box 28, an inlet slag port 26 connected with the magnesium slag discharge port 11 is arranged at the top end of the ladder-type reciprocating spreading mechanism, an outlet slag port 213 connected with the low-temperature zone heat exchanger 3 is arranged at the bottom end of the ladder-type reciprocating spreading mechanism, and heat exchange pipelines 29 are arranged in the heat exchange box 28 in a meandering manner, one end of the heat exchange pipelines 29 is a cold water inlet end 212, the other end is a hot water outlet end 211, and hot steam generated after the hot water outlet end 211 passes through a steam flash evaporator 210 provides a power source for a steam jet pump of the vacuum pumping system 15. The low-temperature zone heat exchanger 3 comprises a partition wall type heat exchanger connected with the outlet slag port 213, heat exchange pipelines 32 are arranged in the partition wall type heat exchanger in a meandering manner, one end of the heat exchange pipelines 32 is a cold air inlet end 34, the other end is a hot air outlet end 35, and the hot air outlet end 35 enters the burner 12 to mix and preheat the fuel gas and the cold air.

[0020] As shown in Figure 1 and Figure 2 The ladder-type reciprocating spreading mechanism comprises a support frame, driven spreading plates 22 and driving spreading plates 24 are alternately and sequentially stacked in the support frame from top to bottom, the bottoms of all the driven spreading plates 22 are connected through a driven shaft 21, the bottoms of all the driving spreading plates 24 are connected through a driving shaft 25, the movement of the driving shaft 25 synchronously drives the reciprocating movement of all the driving spreading plates 24, the movement of the driven shaft 21 synchronously drives the static or reciprocating movement of all the driven spreading plates 22, and the relative movement of the driving spreading plates 24 and the driven spreading plates 22 pushes the spherical magnesium slag 27 to roll and fall into the outlet slag port 213.

[0021] In order to facilitate the heat dissipation and heat exchange of the spherical magnesium slag 27, a plurality of heat-permeable grids or heat-permeable through holes are uniformly arranged on the driving spreading plates 24 and the driven spreading plates 22, the size of the heat-permeable grids or heat-permeable through holes is smaller than the size of the spherical magnesium slag 26, and the heat exchange pipelines 29 in the heat exchange box 28 are arranged around the ladder-type reciprocating spreading mechanism or can also be arranged at the bottom and the top of the ladder-type reciprocating spreading mechanism.

[0022] The system further comprises a signal control unit and an execution control unit for controlling the movement of the driving shaft 25 and the driven shaft 21, a temperature sensor 214 for monitoring the temperature of the spherical magnesium slag 27 after passing through the high-temperature zone heat exchanger 2 is arranged in the outlet slag port 213 of the ladder-type reciprocating spreading mechanism, the signal control unit judges whether the spherical magnesium slag 27 is changed into the powdery magnesium slag 31 according to the stable information of the temperature sensor 214, and then controls the movement of the driving shaft 25 and the driven shaft 21 through the execution control unit to adjust the heat exchange time and the rolling speed of the spherical magnesium slag 27 in the ladder-type reciprocating spreading mechanism.

[0023] The hot water outlet end 211 generates hot steam of 170 DEG C (6 kgf) or above after passing through the steam flash evaporator 210 to provide power source for the steam jet pump of the vacuum pumping system; that is, the temperature of the spherical magnesium slag 27 after being cooled by the high-temperature zone heat exchanger 2 is not lower than 250 DEG C, and then the powder magnesium slag 31 after phase change enters the low-temperature zone heat exchanger 3, and the temperature of the powder magnesium slag 31 after being cooled by the low-temperature zone heat exchanger 3 is controlled at about 150 DEG C, such as 140 DEG C, 145 DEG C, 155 DEG C, 160 DEG C, etc., so that the temperature required by the steam jet pump is ensured, and the waste heat of the powder magnesium slag 31 in the low-temperature zone is fully utilized.

[0024] Meanwhile, the bottom of the heat exchange box 28 is provided as a slope surface 23 inclined to the slag outlet 213, and if the spherical magnesium slag 27 falls, it can also fall into the slag outlet 213 under the action of gravity. An end cover is arranged at the slag inlet 26 of the high-temperature zone heat exchanger 2, and when the spherical magnesium slag 27 in the reduction tank 13 is completely dropped, the end cover covers the slag inlet 26 in time.

[0025] In the working process of the present application, when the first magnesium reduction cycle in the magnesium reduction tank 13 is completed, the magnesium slag outlet 11 is opened, and the spherical magnesium slag 27 falls into the slag inlet 26 of the ladder type reciprocating paving mechanism, at this time, the spherical magnesium slag 27 is thinly and evenly paved on the driving paving plate 24 and the driven paving plate 22, so that the spherical magnesium slag 27 in the high-temperature state is fully cooled to quickly and efficiently exchange heat with the heat exchange pipeline 29, the cold water in the heat exchange pipeline 29 is quickly heated to boiling hot steam water, and then hot steam is generated after passing through the steam flash evaporator 210 to provide power source for the steam jet pump of the vacuum pumping system 15, and the process continues until the temperature of the spherical magnesium slag 27 is reduced to about 675 DEG C, at which time the spherical magnesium slag 27 is converted from beta phase to gamma phase, and the volume expands to be “powdered” from spherical shape to powder shape, and further until the temperature is reduced to about 250 DEG C to end the high-temperature zone heat exchange. After phase change to the powder magnesium slag 31, the powder magnesium slag 31 enters the low-temperature zone heat exchanger 3 to further exchange heat with the heat exchange pipeline 32, the cold air entering from the cold air inlet end 34 is heated and enters the burner 12 from the hot air outlet end 35 to mix and preheat the gas and the cold air, and after the low-temperature and high-temperature zone heat exchange is completed, the powder magnesium slag 31 is discharged from the bottom slag discharge port 33.

[0026] In the process, the temperature sensor 214 monitors the temperature of the spherical magnesium slag 27 after passing through the high-temperature zone heat exchanger 2 in real time, so as to judge whether the spherical magnesium slag 27 is phase changed to the powder magnesium slag 31, if the phase change temperature is not reached, the driving shaft 25 and the driven shaft 21 are slowed down to make the spherical magnesium slag 27 stay in the ladder type reciprocating paving mechanism for a long time to fully exchange heat, otherwise the driving shaft 25 and the driven shaft 21 are accelerated to make the spherical magnesium slag 27 quickly fall into the low-temperature zone heat exchanger 3 in the ladder type reciprocating paving mechanism to meet the respective needs of the high-temperature and low-temperature heat exchange.

[0027] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application, and are not intended to limit the same; although the present application has been described in detail with reference to the foregoing examples, those of ordinary skill in the art should understand that the technical solutions recorded in the foregoing examples can still be modified, or some of the technical features can be replaced by equivalents, but these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A high-efficiency system for the graded utilization of heat from magnesium reduction slag, comprising a magnesium reduction tank, a magnesium crystallizer installed at the top of the magnesium reduction tank, a vacuum system installed on the magnesium crystallizer, a burner installed on the magnesium reduction tank, and a magnesium slag discharge port at the bottom of the magnesium reduction tank, characterized in that, The magnesium slag outlet is sequentially connected to a high-temperature zone heat exchanger and a low-temperature zone heat exchanger. The high-temperature zone heat exchanger includes a heat exchange box, inside which is a stepped reciprocating paving mechanism. At the top of the stepped reciprocating paving mechanism is a slag inlet connected to the magnesium slag discharge port, and at the bottom of the stepped reciprocating paving mechanism is a slag outlet connected to the low-temperature zone heat exchanger. The heat exchange box is equipped with a meandering heat exchange pipe, one end of which is a cold water inlet and the other end is a hot water outlet. The hot water outlet passes through a steam flash evaporator to generate hot steam, which provides a power source for the steam jet pump of the vacuum system. The low-temperature zone heat exchanger includes a partitioned heat exchanger connected to the slag outlet. The partitioned heat exchanger is equipped with a meandering heat exchange pipe. One end of the heat exchange pipe is a cold air inlet, and the other end is a hot air outlet. The hot air outlet enters the burner to mix and preheat the fuel gas and cold air.

2. The magnesium reduction slag heat classification and high-efficiency utilization system according to claim 1, characterized in that, The stepped reciprocating paving mechanism includes a support frame, within which driven paving plates and active paving plates are alternately stacked from top to bottom. The bottom of all driven paving plates is connected by a driven shaft, and the bottom of all active paving plates is connected by an active shaft. That is, the movement of the active shaft synchronously drives all active paving plates to reciprocate, and the movement of the driven shaft synchronously drives all driven paving plates to remain stationary or reciprocate. Under the relative motion of the active and driven paving plates, the spherical magnesium slag rolls and falls into the slag outlet.

3. The magnesium reduction slag heat classification and high-efficiency utilization system according to claim 1 or 2, characterized in that, Multiple heat-permeable grids or heat-permeable holes are evenly distributed on the active paving plate and the driven paving plate. The size of the heat-permeable grids or heat-permeable holes is smaller than the size of the spherical magnesium slag. The heat exchange pipes inside the heat exchange box are arranged in a meandering manner around the stepped reciprocating paving mechanism.

4. The magnesium reduction slag heat classification and high-efficiency utilization system according to claim 1 or 2, characterized in that, It also includes a signal control unit and an execution control unit for controlling the movement of the drive shaft and the driven shaft. A temperature sensor is installed in the slag outlet of the stepped reciprocating paving mechanism to monitor the temperature of the spherical magnesia slag in real time after passing through the high-temperature heat exchanger. The signal control unit determines whether the spherical magnesia slag has undergone a phase change based on the stable information of the temperature sensor, and then controls the movement of the drive shaft and the driven shaft through the execution control unit to adjust the heat exchange time and rolling speed of the spherical magnesia slag in the stepped reciprocating paving mechanism.

5. The magnesium reduction slag heat classification and high-efficiency utilization system according to claim 4, characterized in that, After passing through the steam flash evaporator, the hot water outlet generates hot steam at a temperature of over 170°C, which provides a power source for the steam jet pump of the vacuum system. That is, the temperature of the spherical magnesium slag after passing through the high-temperature heat exchanger is not lower than 250°C. Then, after phase change, the powdered magnesium slag enters the low-temperature heat exchanger, and the temperature after passing through the low-temperature heat exchanger is controlled at around 150°C.

6. The magnesium reduction slag heat classification and high-efficiency utilization system according to claim 1 or 2, characterized in that, The bottom of the heat exchange box is a sloping surface that slopes towards the slag outlet.

7. The magnesium reduction slag heat classification and high-efficiency utilization system according to claim 1 or 2, characterized in that, An end cap is provided at the slag inlet of the heat exchanger in the high-temperature zone.

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