JPS58484B2 - Start-up control method and device for shaft furnace for continuous sintering and reduction of steel powder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a start-up control method and apparatus for a shaft furnace for continuous sintering and reduction of copper powder.

Among steel powders, alloyed steel powders are often prepared mainly by the atomization method, but they cannot be applied to commercialization by powder metallurgy as they are, and finishing reduction is conventionally performed after rough reduction such as mill scale. It can only be made into a material for powder metallurgy after undergoing a sintering reduction process that corresponds to the above process.

However, copper powder alloyed mainly with strongly oxidizing elements such as Mn and Cr cannot be processed in the conventional final reduction process as described above.
Since it is not possible to produce copper powder with sufficiently low oxygen content, there is an urgent need to make it possible to perform sintering reduction suitable for atomized steel powder.

In order to solve this problem, the inventors previously filed a patent application in 1984-2.
In No. 6708, the basic development result that sintering self-reduction by high-frequency induction heating in a reduced pressure atmosphere after injecting carbon into steel powder, preheating sintering of the copper powder, and then sintering self-reduction by high-frequency induction heating in a reduced pressure atmosphere was suitably applied was carried out. It has already been disclosed that a vertical furnace or shaft furnace is particularly suitable.

The present invention focuses on the problems inherent in sinter reduction in a shaft furnace, especially the initial operation of a shaft furnace. An effective solution regarding the control method and device for the period from the start to normal operation is proposed below.

When starting up the shaft furnace, the raw steel powder charged into the preheating furnace from the cutting device is supported in the preheating tube while preventing it from flowing down, and is lowered at a constant speed to progress the sintering of the surface layer. Next, the raw material sintered as described above is sequentially sintered and reduced over the entire surface in an induction heating furnace, and the reduced cake that has passed through the induction heating furnace is lowered at a constant speed and cut into predetermined lengths. After completing this series of steps, the shaft furnace can enter steady operation.

A specific object of the present invention is to propose a control method and apparatus for carrying out the startup operation of such a shaft furnace extremely advantageously and efficiently.

FIG. 1 shows an example of a shaft furnace for carrying out the present invention.

In the figure, 1 indicates a preheating furnace, and 2 indicates an induction heating furnace, which are vertically arranged in that order as shown.

The preheating furnace 1 has a C.C.
It has a combustion chamber or a heating chamber 5 that performs external heating by combustion of gas or other fuel or resistance heating.

6 is iron skin. Although FIG. 1 shows an example in which a C gas furnace is used as the preheating furnace, the burner and exhaust gas flue are not shown.

The induction heating furnace 2 includes a one-turn secondary coil A9 in which an induction heating coil 7 is connected to a preheating tube 3 via a sliding flange joint 8.
An insulating inner cylinder 44 made of a porcelain tube is installed inside this secondary coil.

A two-stage raw material hopper 11 is placed at the top of the preheating furnace 1 via a cutting device 10.

1 The raw material steel powder is stored in the raw material hopper 11, and in the illustrated example, it is introduced into a constant volume of the slab feeder 12, and the stroke of the elevating filler 13 is used to timely detect the charging level of the raw material steel powder in the preheating tube 3. The raw steel powder is intermittently cut and charged into the preheating tube 3 by operating the slide feeder 12 accordingly.

A rising type leading dummy 14 is provided in the preheating tube 3 so as to deposit the first charge of the raw material steel powder.

The leading dummy 14 is made up of a dummy head 15 that fits relatively loosely near the lower end of the preheating tube 3, and a steel wool packing 16 superimposed on and fixed to the dummy head 15, which is held on a long elevating stem 17.

Although the elevating and lowering stem 17 is not shown, it is possible to control the lowering at a slow speed of several mm/min, for example, by means of a rope.

In the figure, reference numeral 18 denotes a Vinci roll located below the induction heating furnace 2 and supports the sintered reduction cake from the leading dummy 14 as it is produced, and 19 denotes a Vinci roll located further below the Vinci roll. A cutting device 20 cuts the sintered reduction cake into predetermined lengths in response to the operation of 18, and a cutting device 20 projects onto the falling path of the reduction cake after the leading dummy 14 reaches its lowering limit position and is cut. 21 is a discharge fixed guide, 22 is a chute for guiding the transfer of the cake;
2 is a packet elevator, 23 is a flapper valve, and 24 is a cooling chamber for the cut and sintered cake.

The shaft furnace is operated by first operating the slide feeder 12 in the illustrated raised position of the leading dummy 14 to cut out the raw material steel powder in the raw material hopper 11 into the preheating tube 3 of the preheating furnace 1 and charging it intermittently. After the slide feeder 12 is restored, the feeder 12 repeats the cutting and charging operation while reciprocating the feeler 13, whereby the raw steel powder is placed on the leading dummy 14 in the preheating tube 3. When a columnar deposit is formed by filling, the feeler 13 detects this in the middle of its stroke, and as a result, the slide feeder 12 temporarily stops, while the preheating furnace 1
Gas ignition takes place in the internal combustion chamber 5, and by this external heating, the columnar deposits supported on the leading dummy 14 are sequentially sintered inward in the radial direction from the outer periphery of the columnar deposits. There is a thickening of the shell-like sintered zone.

In such a preheating stage, the reduction reaction of FeO-based oxides proceeds advantageously in the vicinity of 1000°C, which corresponds to the preheating temperature range of Habo. However, even in this case, by making the degree of vacuum applied near the bottom of the preheating furnace slightly weaker than the degree of vacuum applied at the cutting side of the raw steel powder, the pressure difference between the top and bottom can be reduced to prevent the preheating. It is possible to advantageously prevent the raw material steel powder charged into the furnace from becoming a trigger for promoting the flow down.

The optimum preheating temperature is generally within the range of 780 to 1200°C, and is selected appropriately depending on the composition of the raw steel powder, the scale of the equipment, and other conditions, so that the cylindrical shell-shaped sintered region described above can self-retain. It is heated for a period of time necessary to support the weight of the raw steel powder further deposited inside and above the steel powder, and to eliminate the risk of the steel powder flowing down due to collapse.

According to a test in which the outer diameter of the columnar deposit was set to 160 mm, the wall thickness of the cylindrical shell-shaped sintered region was approximately 30 mm after heating for 1 to 3 hours at an ambient temperature of 1100 °C in a preheating furnace, and the inner unsintered part was The diameter was about 100 mm.

The columnar deposit containing this sintered region will be particularly referred to as a P cake.

After waiting for this P cake to be baked, the temperature of the preheating furnace 1 is lowered once.

This temperature drop amount is 6 when the preheating temperature is set to 1100℃.
It is about 00℃.

This temperature drop is caused by the thermal contraction that occurs in the preheating tube 3 made of heat-resistant steel, which causes radial tightening and compaction of the P cake, and when the preheating furnace is reheated, only the preheating tube 3 expands in advance, so that the P cake and There is a slight distance between it and the inner wall of the preheating tube 3, allowing the P cake to descend smoothly.

Once the P cake starts descending, it will never stick to the inner wall of the preheating tube again.

In addition, high-frequency induction heating is subsequently applied to the P cake that has started to descend in this way directly below the preheating furnace, and the heating temperature of the P cake is raised while gradually increasing the high-frequency input as described below. is still needed.

That is, the preheating furnace temperature is raised again to a predetermined preheating temperature of 1100° C., and the dummy head 15 of the leading dummy 14 is successively lowered to just below the heating zone of the induction heating furnace 2 while growing a cylindrical shell-shaped sintered region. During this time, the raw material steel powder charged subsequently is preheated, and a cylindrical shell-shaped sintered region is grown in the vertical direction.

Inside the P cake that sequentially extends downward inside the shaft furnace, there is a sintered-unsintered interface in the shape of a downwardly convex paraboloid whose bottom point is the upper end of the primary coil 7 in the induction heating furnace 2. ,
That is, a sintering front is formed.

After this sintering front reaches just above the heating zone of the induction heating furnace 2, the high frequency input is gradually increased to transform the P cake into a columnar sintered reduced body, hereinafter referred to as a cake.

Good results were obtained by gradually increasing the high frequency input using a step method in which the above-mentioned I-cake with an outer diameter of 160 mm was used in steps of about 2 KW at 10-minute intervals, and it took about an hour to reach a high number of KW. .

After that, the P cake generated in the preheating furnace 1 is successively advanced to transform into an I cake, and when its lower end reaches the Vinci roll 18, the support of the cake is transferred from the leading dummy 14 to the Vinci roll 18. let

FIG. 2 is a route map of this (1) cake support shoulder sump device, and 25, 26 are upper phototube switches and lower phototube switches 2, 7, which detect the predetermined lowering position of the elevating stem 17 and issue a signal; 28 and 29 respectively have a cylinder for advancing and retracting the shifting roll 18a of the vinyl roll 18 via the rod 18b, a cylinder for advancing and retreating the cutter blade 19a of the cutting device 19 via the rod 19b, and a cylinder for moving the chute 20 via the rod 20a. It is a cylinder that moves forward and backward.

However, the fact that the lower end of the I-cake has reached the vinyl roll 18 means that the lower end of the lifting stem 17 has reached the upper phototube switch 25.
A signal from the phototube switch 25 is input to the control circuit 30.

Therefore, the drive motor 31 of the leading dummy 14 is stopped for a certain period of time, and the wire winding/rewinding drum 32 connected to the elevating stem 17 and provided in the furnace bottom chamber is also stopped for a certain period of time.

Meanwhile, during this period, a signal manually applied to the switching valve 33 of the cylinder 27 energizes the solenoid 34 to cause fluid from the pump 35 to flow into the cylinder chamber 27a, and fluid in the cylinder chamber 27b to flow out to the reservoir 36. let

Therefore, the movable roll 18a moves forward and the fixed roll 1
■ Securely support the cake between 8c and 8c.

After the support of the I-cake by the Vinci roll 18 is completed,
That is, after the above-mentioned fixed stop time of the drive motor has elapsed, the drive motor 31 rapidly rotates to quickly retreat the lifting rod 17 to its lowering limit position, and by this retreat, the I-cake is supported by the vinyl roll 18 from the leading dummy 14. will be completely taken over.

When the leading dummy 14 reaches the lower limit position and crosses the lower phototube switch 26, an electrical signal is sent to the control circuit 37.
After that, the lowering of the lifting rod 17 is stopped by the drive motor 31.

As the leading dummy 14 descends, the hangar upper plate 38
The dummy head 15 and the steel wool gasket 16 left on the top are released by the cylinder 29, which is supplied with working fluid based on the operation of the lower phototube switch 26 and a signal from a control circuit (not shown), which pushes out the shooter 20, thereby forming a discharge guide. 21 and falls into the packet elevator 22.

A drive device (not shown) for the vinyl roll 18 is a shooter 20.
It is operated in conjunction with the pushing out of ■, and the cake is lowered at a constant speed.

Note that the descending speed is a device mechanism that can be variably set.

Furthermore, the flow path of the cylinder 28 of the cutting device 19 is switched based on the operation of the vinyl roll 18, and the I-cake lowered by the vinyl roll 18 is cut into predetermined dimensions and sent from the chute 20 and discharge guide 21 to the packet elevator 22. Fall inwards.

One cake that has entered the packet elevator 22 is charged into the cooling chamber 24 through a flapper valve 23 which is kept open during operation, and is cooled.

In the figure, 39 is a solenoid that operates the switching valve 33 in the opposite way to that described above, and 40 and 41 are rods 18b, respectively.
A limit switch that detects the backward movement of the switch valve 33 and issues a signal to stop the operation of the switching valve 33 to the neutral position, and the moving side roll 1.
This is a stopper that limits the advance of 8a beyond a predetermined amount.

Further, reference numerals 42 and 43 indicate limit switches for controlling the operation of the cutting device 19, respectively.

After performing a series of start-up controls for the shaft furnace as described above, a sintered reduction cake is continuously produced by steady operation.

Therefore, according to the present invention, the start-up of a shaft furnace for efficient sintering and reduction of steel powder can be performed easily, reliably, and extremely efficiently without causing any trouble.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a shaft furnace showing an embodiment of the present invention;
FIG. 2 is a route map showing an embodiment of the device of the present invention. DESCRIPTION OF SYMBOLS 1... Preheating furnace, 2... Induction heating furnace, 3... Preheating tube, 14... Leading dummy, 18... Vinci roll, 19
... Cutting device, 20... Shooter.

Claims (1)

[Claims] 1. The shaft furnace is constructed by vertically arranging a preheating furnace and an induction heating furnace. A leading dummy sealing the inner periphery of the preheating tube is used to seal the raw material steel powder to be loaded with carbon, which is sequentially cut and charged from the direction of the upper end of the lower end of the tube. The step of lowering the cylindrical sintered powder as it thickens, and the depressurization of the sintered region immediately below the almost parabolic sintering front of the unsintered powder interface within this cylindrical sintered region. The reduction cake obtained through the above reduction reaction is sequentially combined with the step of lowering the leading dummy according to the progress of the reduction reaction that occurs in each of the sintered particles by induction heating.
A shaft furnace for continuous sintering and reduction of copper powder, further comprising the step of supporting the guide dummy by operating pinch rolls in response to a detection signal of the lowering position of the leading dummy which has reached a predetermined lowering position below the furnace bottom. Starting control method. 2. The shaft furnace is constructed by vertically arranging a preheating furnace and an induction heating furnace. A leading dummy sealing the inner periphery of the preheating tube is used to seal the raw material steel powder, which is cut and charged sequentially from the section direction and filled with carbon, on the inner periphery of the preheating tube. a step of descending as the sinter thickens;
In response to the progress of the reduction reaction that occurs in each sintered particle by induction heating under reduced pressure on the sintering zone directly below the almost parabolic sintering front of the unsintered powder interface in this cylindrical shell-shaped sintering zone. The reduction cake obtained through the above-mentioned reduction reaction is removed by operating a pinch roll that responds to a detection signal of the lowering position of the leading dummy that has reached a predetermined lowering position below the furnace bottom. Continuous baking of copper powder characterized by further comprising the steps of: supporting the lead dummy as a shoulder; and pushing the chute onto the path of the reduction cake in response to a detection signal of the descending position of the leading dummy that has reached the descending limit position. Start-up control method for shaft furnace for reduction. 3 It goes up and down from the bottom of the shaft furnace, which is made up of a preheating furnace and an induction heating furnace arranged vertically, through the induction heating furnace and into the preheating tube of the preheating furnace, and at the lower end of the preheating tube, the upper end thereof. A leading dummy that seals the raw steel powder containing carbon, which is sequentially cut out from the direction and charged, is used to seal the inner periphery of the preheating tube. sintering by induction heating under reduced pressure on the sintered region immediately below the almost parabolic sintering front of the unsintered powder interface in this cylindrical shell-shaped sintered region. The reduction cake obtained through the above reduction reaction is sequentially combined with the step of lowering the leading dummy according to the progress of the reduction reaction occurring in each of the aggregated particles.
The process of supporting the lead dummy on its shoulder by operating pinch rolls that responds to the detection signal of the lowering position of the leading dummy that has reached the predetermined lowering position below the furnace bottom, and the process that responds to the detection signal of the lowering position of the leading dummy that has reached the lowering limit position. The reduction cake supported on the pinch rolls is cut to size by a cutting device that starts operating in response to the process of pushing the chute onto the path of the reduction cake and the operation of the pinch rolls that support the reduction cake from the leading dummy. 1. A method for controlling the start-up of a Nyaft furnace for continuous sintering and reduction of copper powder, comprising the step of cutting each time. 4. A leading dummy that moves up and down from the bottom of a shaft furnace in which a preheating furnace and an induction heating furnace are arranged vertically, through an induction power furnace and into the preheating tube of the preheating furnace; a pinch roll located below and supporting the reduction cake from the leading dummy in response to a detection signal of the position of the leading dummy which has reached a predetermined lowering position; a cutting device that operates in response to the operation of the cutting device, and a chute that is located further below the cutting device and that pushes out onto the falling path of the reduced cake in response to a detection signal of the position of the leading dummy that has reached the lowering limit position. A starting control device for a shaft furnace for continuous sintering and reduction of copper powder, characterized by comprising: