JPS6023169B2 - How to clean the gas cooler of vacuum degassing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for washing agglomerated dust deposited in a gas cooler of a vacuum degassing apparatus for degassing molten steel or the like.

Conventionally, vacuum degassing treatment methods for molten steel and the like have been carried out as described below using the equipment system generally shown in FIG.

In the figure, the solid line indicates the system of the conventional method, where 1 is a ladle for storing molten steel to be processed, 2 is a vacuum tank for degassing (degassing tank), and 3 is a charging device for alloy added to molten steel. , 4
is a dust separator, 5 is a gas cooler, 6 is a vacuum exhaust system consisting of a multi-stage steam ejector (not shown), 7 is a vacuum gauge for operation, and 8 is an inert gas introduction for return pressure. It's a tube. In the degassing process, vacuum chamber 2
is evacuated and depressurized by a vacuum exhaust system 6, and the molten steel in the ladle 1 is degassed. Exhaust gas from the vacuum chamber passes through a gas cooler 5, if one is provided, and collects dust and
After the evaporated metal dust is sedimented and separated in the separator 4, it is discharged through a vacuum exhaust system. Degassing treatment is usually carried out under a vacuum close to -1k9/G, but once one heat treatment is completed, the operation of the vacuum evacuation system is stopped and inert gas is introduced into the cooling chamber through the inert gas introduction pipe 8 for repressurization. Gas is introduced and the pressure is restored to atmospheric pressure. This means that even if the operation of the vacuum evacuation system is stopped, there will still be 10 mo in the vacuum chamber.
This is because a low pressure of n or less is maintained, and the next step cannot be performed unless this pressure is restored to the same level as atmospheric pressure. As mentioned above, in the conventional method, the steam ejectors used in the vacuum evacuation system 6 are arranged in multiple stages due to the need to obtain a high degree of vacuum, which increases the volume of steam used as a power source. Since the capacity required of the ejector on the atmospheric side is large, normally a condenser (not shown) is installed in the degassing device to reduce the exhaust volume, but during degassing operation Since molten steel is subjected to vacuum treatment, evaporation of metal vapor that does not occur in the atmosphere occurs, especially Mn etc. with high vapor pressure evaporates, and when these are discharged to the vacuum evacuation system, they condense in the condenser. , it gets mixed into the cooling water of the condenser and leaks out.

The presence of this metal causes problems in the industrial treatment of cooling water. Therefore, in order to prevent the cooling water containing the metals from flowing out, a dust separator 4 is installed before the vacuum exhaust system 6 to coagulate and separate the dust generated in the vacuum tank (degassing tank) 2. However, in order to improve the dust collection efficiency, an indirect cooling type gas cooler 5 may be disposed within the dust separator 4.

(In this case, in terms of cooling effect, it is preferable to provide the separator inlet facing the dust that connects the vacuum chamber and the duct separator.) However, in the conventional method,
An operational vacuum gauge 7 was placed in the duct on the discharge side of the dust separator to measure the degree of vacuum, and the operation was carried out by assuming that the measured value was representative of the degassing effect of the degassing device. It is.

However, through detailed inspection of actual operations, the inventors of the present invention discovered that dust generated in the vacuum chamber during degassing treatment adheres and accumulates on the gas cooler, gradually increasing the resistance of the cooler, and causing this dust to accumulate. The accumulation greatly affects the pressure drop in the exhaust path, and despite the good vacuum indication from the operational vacuum gauge,
It was found that the degassing effect was reduced, and the reading on the operating vacuum gauge was not representative of the degassing effect. That is, the inventors of the present invention installed a test vacuum gauge 9 in a vacuum chamber, where pressure measurement was conventionally difficult due to the presence of evaporative gas.
(dotted line in Figure 1) and compared the vacuum level readings during degassing with the conventional operating vacuum gauge 7. It was discovered that even if the test vacuum gauge indicated the atmospheric pressure, the measured value fluctuated greatly, indicating the exact degree of vacuum in the vacuum chamber. The situation is as shown in Figure 2.According to conventional operational vacuum gauges, the vacuum level is seemingly stable at around 0.3 mbar, but a test vacuum gauge that accurately shows the pressure in the vacuum chamber According to the company, the degree of vacuum is approximately 1.5 to 5. It can be seen that the measured value of the conventional operational vacuum gauge does not accurately indicate the vacuum degree of the vacuum chamber, and that the degassing effect cannot be determined due to this. conventionally,
As long as the operating vacuum gauge indicates a stable low pressure,
Assuming that the degree of vacuum in the vacuum chamber was good, it can be said that sufficient measures were not taken to prevent deterioration of the degassing device due to increased resistance of the gas cooler. As mentioned above, fluctuations in the degree of vacuum in the vacuum chamber (and therefore fluctuations in the degassing effect)
The inventors of the present invention discovered that this was caused by an increase in resistance due to dust deposited on indirect gas coolers, and the inventors of the present invention then began research on a dust washing method. The company solved the difficult problem of having to clean gas coolers at high temperatures of around 1000 qo on the side and in a sealed structure of vacuum equipment, and invented a method for cleaning gas coolers without making any major additions to conventional equipment. .

The method of the present invention arranges a plurality of gas blowing nozzles facing the inlet side of the gas cooler, thereby eliminating the conventional dust
By blowing the inert gas that had been introduced into the gas cooler through the inlet pipe installed in the duct on the discharge side of the separator to restore the pressure in the degasser, the gas can be restored at the same time as the pressure in the degasser is restored. This method uses gas to refine the dust that has accumulated in the cooler.

An example of an apparatus for carrying out the method of the present invention is constructed as shown in FIG. 3, in which 1 is a ladle, 2 is a vacuum chamber, 4 is a dust separator, 5 is a gas cooler, ．． 1 is the vacuum exhaust system, 7 is the vacuum gauge for operation, 1 is the inert gas spray nozzle for spraying inert gas into the gas cooler, 11 is the spray gas piping, and 12 is the vacuum chamber when spraying the inert gas. It is a seal valve for closing.

The details of the arrangement of the gas cooler and the inert gas blowing nozzle are shown in FIG. 4, and one type of inert gas blowing nozzle is shown in FIG. A vertical multi-tube type gas cooler is preferable to a horizontal type because dust is relatively hard to adhere to and bottles can easily be washed away. In Figure 4, a is the side of the gas cooler, and b is The back side is shown, and in the figure, 13 is the gas cooler's supply and drainage duct, 14 is the cooling pipe,
15 is a duct that connects the vacuum chamber and the dust separator, and serves as a header part where the blowing gas piping 11 is branched and multiple inert gas blowing nozzles are attached; Only the inert gas blowing nozzle and the blowing gas piping are shown in b.

The inert gas blowing nozzle is placed at the front of the gas cooler (the side facing the vacuum chamber). In FIG. 5, reference numeral 16 indicates a header portion of the nozzle, and reference numeral 17 indicates a blowout pipe portion of the nozzle. Inert gas spray refinement is usually carried out after one heat of vacuum degassing treatment and when the degasser is repressurized in the conventional method, by spraying inert gas from the nozzle of the cooling pipe of the gas cooler. The dust accumulated in the cooling pipe is washed away (blown off) by the pressure of the gas, and the resistance of the cooler increased by the accumulation of dust is removed, and at the same time, the pressure in the degasser is restored.

According to the present invention, since the dust is easily washed off after each heat, the resistance of the gas cooler hardly increases, and the equipment can always be kept in the same state as when it was new. The results are also kept good on average.

When spraying with inert gas, a seal valve 12 at the outlet of the dust separator is installed to prevent dust from escaping into the vacuum.
Close. Note that gas cooler refinement with inert gas is normally performed after each heat, but it can be performed at any time during the degassing process if there is a need to remove resistance. It is possible to operate with a stable vacuum degree of the vacuum chamber close to the above value. Next, the improvement of resistance removal and degassing effect by carrying out the present invention will be explained with reference to examples.

A case where the vacuum degassing treatment was performed continuously for several heats without washing the dust of the gas cooler by the conventional method, and a case where the dust was washed every heat by the method of the present invention. A comparison was made between the vacuum degree of the vacuum chamber and the hydrogen content in lacquered steel after degassing treatment (indicating the degassing effect). The results are shown in FIG. In the figure, Ao and A indicate the degree of vacuum of the vacuum chamber according to the conventional method and the method of the present invention, respectively, and B. , B, respectively indicate the lower limit of the hydrogen content (tsubo m in the mold) in the port steel after degassing by the conventional method and the method of the present invention, and Co, C, similarly indicate the upper limit. The coordinate 1 on the horizontal axis indicates the first heat of the vacuum degassing process that started operation with the gas cooler in a new state, and the following heats are 2 to 2 in order.
Showing the 6th heat. As shown in Figure 6, according to the conventional method, the degree of vacuum in the vacuum chamber shows a tendency for the pressure to gradually increase as the degassing process is repeated, and the hydrogen in the molten steel after the degassing process shows a tendency to gradually increase. The content increases as the number of times increases at both the upper and lower limits (especially at the upper limit). On the other hand, when the gas cooler is cleaned every heat treatment using the method of the present invention, the degree of vacuum in the vacuum chamber is stable and good, with almost no difference from when using a new gas cooler. The hydrogen content in the molten steel after degassing treatment hardly changes from heat to heat, and even if there is an increase, it is extremely small, indicating that the degassing effect is superior to that of the conventional method. By carrying out the method of the invention,
The degree of vacuum, which used to be recorded at the upper limit of more than 2.5 hbar, can now be safely managed to 2.5 hbar or less, and the hydrogen content of molten steel after degassing treatment has also been reduced to 2.
．． 5-3. The one that recorded the end of the cape was 1. It reached a stable level at Cape Atomisaki. As described above, the gas cooler knee cleaning method of the present invention is a method that uses the inert gas for restoring the pressure of the degassing device at the end of dust cleaning, so it does not require the addition of large equipment, and it This is an extremely excellent method for keeping the degree of vacuum in the degassing device stable and good and maintaining a high degassing effect without increasing the cost.

[Brief explanation of the drawing]

Fig. 1 is a diagram schematically showing a conventional vacuum degassing method, Fig. 2 is a graph showing a comparison between the indicated value of a conventional operational vacuum gauge and the vacuum degree of the vacuum chamber indicated by a test vacuum gauge. Figure 3 is a diagram schematically showing the method of the present invention, Figure 4a is a layout diagram (side view) of the gas cooler and inert gas spray nozzle used in the method of the present invention, and b is the rear layout diagram. , FIG. 5 is a detailed view of the inert gas spray nozzle. FIG. 6 is a graph showing the relationship between the number of heats and molten steel hydrogen according to the method of the present invention. 1... Ladle, 2... Vacuum chamber, 3... Alloy charging device, 4... Dust separator,
5... Gas cooler, 6... Vacuum exhaust system, 7... Vacuum gauge for operation, 8... Gas introduction pipe for pressure recovery, 9... Test vacuum gauge, 10... Inert gas Spray nozzle, 11.
...Blow gas piping, 13...Cooler supply and drainage duct,
14...Cooling pipe. Figure 1 Figure 2 Figure 3 Figure 5 Figure 4 Figure 6

Claims (1)

[Claims] 1. When degassing molten steel, etc. using a vacuum degassing device consisting of a vacuum chamber, a dust separator, an indirect cooling type gas cooler installed in the dust separator, and a vacuum exhaust system, the above-mentioned gas and A plurality of inert gas spray nozzles are arranged facing the vacuum chamber exhaust inlet side of the cooler, and inert gas is applied to the gas cooler immediately after one heat of degassing treatment or during degassing treatment as necessary. 1. A method for cleaning a gas cooler of a vacuum degassing device, which comprises blowing gas to wash away dust that has coagulated and deposited on the gas cooler, and at the same time restoring the pressure in the vacuum degassing device.