JPS6144160Y2 - - Google Patents

Description

[Detailed description of the invention] The invention is based on the method of directly energizing carbonaceous granules such as anthracite, petroleum coke, and metal oxide-carbon granules.
This invention relates to a vertical electric heating furnace for continuously heating to a high and uniform temperature.

As shown in the vertical cross-sectional view of Figure 1, the vertical electric heating furnace that is currently widely used includes a cylindrical iron furnace shell 1 lined with refractory material and an upper electrode 2 for directly applying electricity to the carbonaceous particles. and a lower electrode 3,
Carbonaceous particles are fed from the top of the furnace, heated while falling through the furnace under their own weight, and continuously discharged from the bottom of the furnace.

The physical properties of anthracite and coke vary significantly depending on the heating temperature, and when used as raw material aggregate for electrodes, products heated at a uniform temperature are required, and mixed granules of various oxides and carbon are required. When heating the material to cause a reduction and carbonization reaction, uniform heating to a predetermined temperature is required in order to prevent side reactions and complete the reaction.

However, even if the heating furnace described above is operated so that the distance between the electrodes is increased to minimize the temperature difference between the center of the furnace and the furnace wall, and the current flows in the direction of the furnace wall, the temperature at the center still reaches 2700℃. However, near the furnace wall, the temperature is only about 1500°C, and only a mixture of carbon particles heated over a wide range of 1500 to 2700°C can be obtained. Furthermore, due to the wide electrode spacing, a large amount of heat is radiated from the furnace body, resulting in low thermal efficiency and low power consumption.

In order to heat the carbonaceous granules to a uniform temperature, for example, rotary electric roasting furnaces and stirring electric heating furnaces have been devised in which the carbonaceous granules in the center and near the furnace walls are mixed in the furnace. The difference between the temperature and the mixing temperature is still large, and it is difficult to say that heating is uniform.

The present invention relates to the above-mentioned continuous vertical electric heating furnace, and provides a heating furnace that does not require a complicated mixing and stirring device and can heat carbonaceous particles continuously and uniformly with a small amount of electric power. It is something.

To explain the present invention based on the drawings, Fig. 2 shows the following:
In the longitudinal cross-sectional view, a cylindrical furnace shell 1 lined with a refractory material is provided with a cylindrical upper electrode 2 located on the central axis of the furnace, and a lower tubular electrode 3a opposed thereto. Although either carbonaceous or graphite electrodes can be used, artificial graphite electrodes are preferably used. Carbonaceous granules B are supplied from the top of the furnace, descend inside the furnace under their own weight, pass through a high-temperature uniform heating zone formed at the opening of the lower tubular electrode, and pass through the lower tubular electrode, which also serves as a carbonaceous granule discharge pipe. descending through the pipe of
After being cooled in the cooling cylinder 4, it is continuously discharged out of the furnace by a discharge device (not shown) provided at the bottom of the furnace. Around the upper end opening of the lower tubular electrode 3a,
A stationary layer 5 is formed depending on the outflow angle of the carbonaceous particles and protects the lining refractory. A high-temperature insulating material layer with higher electrical resistance than the carbonaceous particles is interposed between the stationary layer 5, the outer periphery of the lower tubular electrode, and the furnace wall to prevent heat radiation to the furnace shell, and to prevent the heat from radiating to the furnace shell. It is preferable to minimize the reactive current flowing into the side surfaces, and carbon black, charcoal, felt-like carbon fiber, porous carbon, silicon carbide, etc. are used as the high-temperature insulating material.

In the present invention, a soaking zone with the highest temperature is formed at the upper end opening of the lower tubular electrode 3a, and all of the carbonaceous particles are passed through this soaking zone and guided to the bottom of the furnace through the tube of the tubular electrode. The solid granules are uniformly heated to the maximum temperature. When heating,
The current, distance between electrodes, discharge rate of carbonaceous particles, etc. are adjusted to maintain a predetermined temperature.

In order to form a uniform heating zone with the highest temperature at the opening of the lower tubular electrode, it is necessary to arrange one set of the upper electrode and the lower tubular electrode along the central axis of the furnace, and there may be multiple upper electrodes. If the electrode is off the center axis, the symmetry inside the furnace will be lost and a uniform heating zone will not be formed. It is also necessary to bring the upper end opening of the lower tubular electrode closer to the upper and lower center of the furnace. That is, since the electrical resistance of the electrode is small, Joule heat is mainly generated between the upper and lower electrodes, and since the electrode has better heat transfer than the carbonaceous particles, the tip of the electrode tends to be lower than the nearby carbonaceous particles, and the highest temperature range Although heat is likely to be radiated directly from the furnace to the outside of the furnace through the lower tubular electrode,
The above-mentioned heat dissipation is prevented by making the lower tubular electrode sufficiently long, heating the lower tubular electrode with waste heat from the carbonaceous particles heated to the highest temperature, and keeping the tip of the electrode at a high temperature.

Next, the inner diameter of the upper end opening of the lower tubular electrode 3a is preferably in the range of 1 to 3 times the outer diameter of the upper electrode.
If it exceeds 3 times, the cross-sectional area of the current flowing through the carbonaceous particles increases, the heat generation density decreases, the highest temperature zone is not formed at the opening, and the temperature difference with the center of the furnace becomes large. If it is less than 1 times, the smooth flow of the carbonaceous particles will be inhibited, increasing the risk of blockage, and the reactive current flowing into the outer surface of the lower tubular electrode will increase, resulting in a decrease in thermal efficiency and a worsening of the power consumption rate.

Furthermore, the distance between the upper and lower electrodes should be 3 times or less than the outer diameter of the upper electrode, preferably 2.5 times or less; if it exceeds 3 times, the maximum temperature range will leave the lower tubular electrode opening and move upward, preventing the formation of a uniform heating zone. This is because the reactive current flowing into the outer surface of the lower tubular electrode is increased, and the amount of heat dissipated from the furnace wall is increased due to the expansion of the high temperature section.

Since the electric heating furnace according to the present invention has the above-described configuration, it is possible to achieve high temperature uniform heating of carbonaceous particles and a reduction in the electricity consumption rate due to high thermal efficiency.

It has the structure shown in Fig. 2 according to the present invention, the outer diameter of the upper electrode is 203 mm, the inner diameter of the lower tubular electrode is 350 mm, and the outer diameter is 450 mm.
mm, the distance between the upper and lower electrodes was 300 mm, and carbon black was filled between the outside of the lower tubular electrode and the furnace shell.
In the graphitization of petroleum coke and pitch coke using a 200kW electric heating furnace, good graphitized products were obtained. When we measured the temperature distribution of the graphitized product in comparison with the standard sample, we found that the discharge rate
For petroleum coke at 110Kg/hr, all
Within the range of 2500-2800℃ and the discharge rate is 130
Pitch coke when Kg/hr is 2200~2500
It is heated within the range of ℃, and the thermal efficiency is also
High values of 85% (petroleum coke) and 86% (petroleum coke) were obtained.

On the other hand, in the electric heating furnace shown in Figure 1, the outer diameter of both the upper and lower electrodes is
In a comparative example in which petroleum coke was graphitized using a 203 mm cylindrical electrode, graphitization did not proceed sufficiently, the temperature distribution was between 1400 and 2800 degrees Celsius, and the thermal efficiency was low at 59%. The electricity intensity is also the same as in the example.
Compared to 1650kWh (petroleum coke) and 1400kWh (pitch coke), the output was 1810kWh, demonstrating the excellent effectiveness of this invention.

The graphitized aggregate obtained by the electric heating furnace of the present invention exhibits excellent performance as a cathode for aluminum electrolytic furnaces, electrodes for ferroalloy manufacturing furnaces, block materials for blast furnace linings, etc. , mixed granules of metal oxide such as silica sand and carbon at 1700℃~
It is also extremely useful when uniformly heating to a predetermined temperature of 2400°C.

[Brief explanation of the drawing]

Figure 1 is a vertical cross-sectional view of a conventional vertical electric heating furnace.
FIG. 2 is a longitudinal sectional view of the vertical electric heating furnace according to the present invention. DESCRIPTION OF SYMBOLS 1... Iron furnace shell, 2... Upper electrode, 3... Lower electrode, 3a... Lower tubular electrode, 4... Cooling cylinder, 5
...Stationary layer.

Claims (1)

[Scope of utility model registration request] In a resistance heating type continuous vertical electric heating furnace, there is a set of upper cylindrical electrodes along the central axis of the furnace and a pipe whose inner diameter is 1 to 3 times the outer diameter of the upper cylindrical electrode and also serves as a discharge pipe for the material to be treated. A lower tubular electrode is provided, the distance between the two electrodes is within three times the outer diameter of the upper cylindrical electrode, and a high temperature insulation layer is interposed between the outer wall of the lower tubular electrode and the furnace shell. Vertical electric heating furnace.